AJP - Heart Calcium Transients and Cell-Sarcomere
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Heart Circ Physiol 283: H650-H657, 2002; doi:10.1152/ajpheart.00043.2002
0363-6135/02 $5.00
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (23)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Raeburn, C. D.
Right arrow Articles by Meng, X.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Raeburn, C. D.
Right arrow Articles by Meng, X.
Vol. 283, Issue 2, H650-H657, August 2002

Neutralization of IL-18 attenuates lipopolysaccharide-induced myocardial dysfunction

Christopher D. Raeburn, Charles A. Dinarello, Michael A. Zimmerman, Casey M. Calkins, Benjamin J. Pomerantz, Robert C. McIntyre Jr., Alden H. Harken, and Xianzhong Meng

Department of Surgery, University of Colorado Health Sciences Center, Denver, Colorado 80262


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Tumor necrosis factor-alpha (TNF-alpha ) and interleukin-1beta (IL-1beta ) have been implicated in cardiac dysfunction during endotoxemia. Because IL-18 is a proinflammatory cytokine known to mediate the production of TNF-alpha and IL-1beta and to induce the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), we hypothesized that neutralization of IL-18 would attenuate lipopolysaccharide (LPS)-induced cardiac dysfunction. Mice (C57BL/6) were injected with LPS (0.5 mg/kg ip) or vehicle (normal saline), and left ventricular developed pressure (LVDP) was determined by the Langendorff technique. LVDP was depressed by 38% at 6 h after LPS. LPS-induced myocardial dysfunction was associated with increased myocardial levels of TNF-alpha and IL-1beta as well as increased expression of ICAM-1/VCAM-1. Pretreatment with neutralizing anti-mouse IL-18 antibody attenuated LPS-induced myocardial dysfunction (by 92%) and was associated with reduced myocardial IL-1beta production (65% reduction) and ICAM-1/VCAM-1 expression (50% and 35% reduction, respectively). However, myocardial TNF-alpha levels were not influenced by neutralization of IL-18. In conclusion, neutralization of IL-18 protects against LPS-induced myocardial dysfunction. IL-18 may mediate endotoxemic myocardial dysfunction through induction of and/or synergy with IL-1beta , ICAM-1, and VCAM-1.

tumor necrosis factor-alpha ; interleukin-18


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

LIPOPOLYSACCHARIDE (LPS) depresses intrinsic myocardial contractility (1, 31, 35) and is believed to be an important factor contributing to myocardial dysfunction during sepsis. LPS induces a cascade of proinflammatory cytokines, and tumor necrosis factor-alpha (TNF-alpha ) and interleukin-1beta (IL-1beta ) synergistically depress myocardial function (4, 9, 16, 30). Whereas TNF-alpha is involved in LPS-induced myocardial dysfunction, we (22) reported a temporal discordance between myocardial TNF-alpha levels and the contractile dysfunction that occurs during endotoxemia. After LPS, myocardial dysfunction did not occur until TNF-alpha levels had returned to baseline. These observations suggest that TNF-alpha may provide an essential early signal, but other cardiodepressant factors may more directly conspire to depress cardiac function. In addition to TNF-alpha and IL-1beta , we have observed an essential role for both vascular cell adhesion molecule-1 (VCAM-1) (34) and intercellular adhesion molecule-1 (ICAM-1) (unpublished data) in LPS-induced myocardial dysfunction.

IL-18 is a proinflammatory member of the IL-1 superfamily (42). Similar to IL-1beta , IL-18 is synthesized as an inactive precursor and is cleaved to its active form by caspase-1 (10, 13). IL-18 was initially recognized for its ability to induce interferon-gamma (IFN-gamma ) and its capacity to induce Th1 responses (23, 28). However, IL-18 was subsequently found to play an important role in LPS-induced hepatotoxicity (41), which stimulated further study of the role of this cytokine in sepsis. Elevated levels of IL-18 occur in the serum (5, 12, 27) and bronchoalveolar lavage fluid (18) of septic patients, and in vitro studies (17) indicate that LPS induces IL-18 secretion in human monocytes. LPS has also been shown to induce IL-18 in murine macrophages (37) and lungs (2). Myocardial production of IL-18 during endotoxemia has not been reported.

IL-18 activates nuclear factor (NF)-kappa B (19), which is a transcriptional regulator of many proinflammatory cytokines and cellular adhesion molecules. In vitro studies have shown that IL-18 increases the production of TNF-alpha and IL-1beta in murine macrophages (26) and human monocytes (33) and also induces the expression of ICAM-1 and VCAM-1 on endothelial cells (24, 43) and monocytes (15). In vivo studies have shown that neutralization (6, 25) or genetic absence (14) of IL-18 protects mice from lethal endotoxemia and from LPS-induced liver injury (6, 36, 41).

Specific blockade of IL-18 using IL-18 binding protein improves contractile function in human atrial strips after ischemia-reoxygenation (32). However, the specific role of IL-18 in myocardial dysfunction and the complex cascade of cytokines and cellular adhesion molecules induced by LPS is unknown. Therefore, in the present study, we sought to determine the role of IL-18 in LPS-induced myocardial dysfunction and to examine its role in myocardial TNF-alpha and IL-1beta production and ICAM-1/VCAM-1 expression during endotoxemia.


    METHODS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Materials. The IL-18 antiserum was obtained from New Zealand White rabbits immunized by intradermal injections of murine IL-18 (PeproTech; Rocky Hill, NJ) with Hunter's Titermax adjuvant. This antibody has been shown to inhibit LPS-induced IFN-gamma production in vivo (8) and to protect mice from lethal Escherichia coli endotoxemia (25). Murine IL-18, TNF-alpha , and IL-1beta enzyme-linked immunosorbent assay (ELISA) kits were purchased from R&D Systems (Minneapolis, MN). Rat anti-mouse VCAM-1 monoclonal antibody (MAb) (clone MVCAM.A429) was purchased from Endogen (Woburn, MA). Rat anti-mouse ICAM-1 MAb (clone KAT-1) and rat anti-mouse neutrophil p40 antigen MAb (clone 7/4) were purchased from Serotec (Oxford, UK). Rat IgG and Cy3-conjugated donkey anti-rat IgG were purchased from Jackson ImmunoResearch Laboratories (West Grove, PA). E. coli LPS (serotype 055:B5) and other chemicals were purchased from Sigma (St. Louis, MO).

Animals. Male C57BL/6 mice, B6.129 wild-type mice (B6), and TNF-alpha knockout (TNF-/-) mice, 20-25 g body wt, were purchased from Jackson Laboratory (Bar Harbor, ME). Animals were acclimated for 1 wk after delivery in a 12:12-h light-dark cycle room and maintained on a standard pellet diet before use. The experiments were approved by the Animal Care and Research Committee of the University of Colorado Health Sciences Center. Animals received humane care in compliance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publication No. 85-23, Revised 1985).

Experimental protocols. Mice were injected with either LPS (0.5 mg/kg ip) or vehicle (normal saline). We have previously monitored the hemodynamic response in rats to this dose of LPS and observed profound reduction in cardiac contractility with minimal influence on mean arterial pressure (MAP) (21). We confirmed this finding in anesthetized mice (n = 3) by cannulating the carotid artery and by monitoring MAP before and during endotoxemia. MAP remained constant throughout 6 h of endotoxemia, thus eliminating hypotensive shock as a potential confounding cause of myocardial dysfunction in this model of endotoxemia. In separate experiments, mice were injected with anti-IL-18 antibodies (200 µl ip) or normal rabbit serum (NRS) (200 µl ip) 30 min before LPS injection. A Limulus Amebocyte Lysate assay (BioWhittaker; Walkersville, MD) was performed to determine whether the anti-IL-18 antibody or NRS were contaminated by LPS. A minute but equivalent amount of LPS was detected in the anti-IL-18 antibody and NRS (0.088 and 0.089 ng/ml, respectively). At specific times after LPS, animals were anesthetized with ketamine (75 mg/kg ip; Phoenix Pharmaceutical; St. Joseph, MO) and xylazine (10 mg/kg ip; Fort Dodge Animal Health; Fort Dodge, IA), respectively, and simultaneously heparinized (2,000 U/kg; Elkins-Sinn; Cherry Hill, NJ). Hearts were then harvested and myocardial contractility was determined using the Langendorff technique. The time course of LPS-induced myocardial dysfunction in mice and measurement of maximal dysfunction at 6 h has been reported previously (34). Thus we examined cardiac dysfunction in this study at 6 h post-LPS.

To determine myocardial cytokine production and adhesion molecule expression, mice were injected with either LPS (0.5 mg/kg ip) or vehicle (normal saline) and hearts were harvested at 1, 2, 4, and 6 h after LPS. In separate experiments, mice were administered anti-IL-18 antibodies or NRS 30 min before LPS injection. Hearts were excised and divided in half transversely after the atria were removed. The apical portion was embedded in tissue-freezing media, frozen in dry ice-chilled isopentane, and stored at -70°C for immunofluorescent staining. The remainder of myocardium was placed into liquid nitrogen and stored at -70°C.

Isolated heart perfusion. Myocardial function was determined by an isovolumetric nonrecirculating Langendorff technique, as described previously (22). Isolated hearts were perfused with 37.0°C Krebs-Henseleit solution containing (in mmol/l) 11.0 glucose, 1.2 CaCl2, 4.7 KCl, 25 NaHCO3, 119 NaCl, 1.17 MgSO4, and 1.18 KH2PO4. Coronary perfusion pressure was maintained at 70 mmHg. The perfusion buffer was saturated with a gas mixture of 92.5% 02-7.5% CO2 to achieve a PO2 of 450 mmHg, PCO2 of 40 mmHg, and pH of 7.4. A balloon was constructed of ultrathin latex and tested to ensure that the balloon was of high compliance. A balloon was deemed to have an acceptable compliance if it did not show any positive pressure when filled with 25 µl of water. The balloon was inserted into the left ventricle via the left atrium and inflated with water (5-8 µl) to achieve a left ventricular end-diastolic pressure (LVEDP) of 10 mmHg. Pacing wires were attached to the right atrium and hearts were paced at 300 beats/min. Coronary flow was quantified by collecting the effluent from the pulmonary arteries as it dripped from the heart. Myocardial temperature was maintained at 37°C. Left ventricular developed pressure (LVDP), its maximum and minimum first derivatives over time (+dP/dt and -dP/dt, respectively), and LVEDP were continuously recorded by a computerized pressure amplifier-digitizer (MacLab version 8, ADInstruments; Cupertino, CA). After a 20-min equilibration period, LVDP and ±dP/dt were determined at varied LVEDP levels (10, 15, and 20 mmHg). The degree of reduction in LVDP and ±dP/dt in LPS-treated hearts, compared with saline controls, was not influenced by variation of LVEDP from 10 to 20 mmHg. Therefore, all data represented herein were obtained at a LVEDP of 10 mmHg.

Cytokine measurements. For cytokine measurements, the myocardial tissue was weighed and then suspended and homogenized 1:8 (wt/vol) in sterile phosphate-buffered saline (PBS) containing 0.5% Triton X-100 and a protease inhibitor cocktail (Sigma). Myocardial IL-18, TNF-alpha , and IL-1beta protein content was then determined by ELISA. The detection limits of the ELISA were (in pg/ml) 25.0 IL-18, 5.1 TNF-alpha , and 3.0 IL-1beta .

Immunofluorescent staining. Indirect immunofluorescent detection and localization of ICAM-1, VCAM-1, and neutrophils were performed as described previously (39). Transverse sections (5 µm thick) of ventricular myocardium were cut with a cryotome (International Equipment; Needham Heights, MA) and then dried at room temperature for 2 h. The sections were treated with a mixture of 30% methanol and 70% acetone at room temperature for 10 min and washed with PBS. The sections were then fixed in PBS-buffered 3% paraformaldehyde at room temperature for 10 min and washed with PBS. Each subsequent incubation was performed at room temperature. To block nonspecific binding sites, the sections were incubated for 30 min with 10% donkey serum in PBS. The sections were then incubated with a primary antibody [diluted 1:200 for ICAM-1 and VCAM-1 and 1:500 for neutrophils in PBS containing 1% bovine serum albumin (BSA)] for 60 min. After being washed three times with PBS, the sections were incubated for 45 min with Cy3-labeled donkey anti-rat IgG (1:250 dilution with PBS containing 1% BSA). After thorough washes with PBS, sections were counterstained with fluorescein-labeled wheat germ agglutinin (5 µg/ml, for cell surface staining) and bis-benzimide (2.5 µg/ml, for nuclear staining). The sections were mounted with aqueous antiquenching media. To ascertain the specificity of the primary antibody, adjacent sections were incubated with nonspecific rat IgG (diluted 1:200 in PBS containing 1% BSA) in replacement of the primary antibodies and then processed in identical conditions. Microscopic observation and photography were performed with a Leica DMRXA microscope.

Image quantitation. ICAM-1 and VCAM-1 images were quantitated with SlideBook version 2.6 software (Intelligent Imaging Innovations; Denver, CO). Eight random images were taken from each myocardial section. Imaging was performed at ×40 magnification (1,020 × 1,020 pixels/image). All images were taken while blinded to both the specimen and the Cy3 channel. Images were masked to exclude 95% of nonspecific fluorescence as determined from images of myocardium incubated with nonspecific rat IgG. Images were analyzed with the use of SlideBook to determine the mean area (µm2) and mean intensity and to calculate the integrated intensity (product of area and mean intensity).

Myocardial neutrophil number was determined by counting all nucleated cells with Cy3 fluorescence present on a myocardial section. The number of neutrophils per section was divided by the calculated area of the myocardial section and reported as the number of neutrophils per millimeter squared. This method of assessing tissue neutrophil accumulation has previously been shown to closely correlate with myeloperoxidase activity (40).

Statistical analysis. All data are expressed as means ± SE. Statistical significance of differences between groups was determined by analysis of variance and verified by a Bonferroni-Dunn post hoc test. Statistical analysis was performed using StatView version 5.0 (Abacus Concepts; Calabasas, CA).


    RESULTS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Effect of neutralization of IL-18 on LPS-induced myocardial dysfunction. We (22, 34) examined the time course of myocardial dysfunction in mice during endotoxemia and found the maximal depression in function to occur at 6 h after LPS. Therefore, to examine the role of IL-18 in LPS-induced myocardial dysfunction, hearts were studied at 6 h after LPS. Compared with saline controls, LVDP was reduced by 38% after LPS (36.3 ± 1.9 vs. 59.1 ± 2.7 mmHg, P < 0.001, Fig. 1). Pretreatment of mice 30 min before LPS with NRS had minimal influence on LPS-induced myocardial dysfunction; however, pretreatment with IL-18 neutralizing antibody nearly abrogated the dysfunction (Fig. 1). Coronary flow was not different between groups (data not shown).


View larger version (10K):
[in this window]
[in a new window]
  		Fig. 1.   Effect of anti-interleukin-18 (IL-18) on lipopolysaccharide (LPS)-induced myocardial dysfunction. Mice were injected with either vehicle (normal saline ip, n = 8) or Escherichia coli LPS (0.5 mg/kg ip, n = 8), and left ventricular developed pressure (LVDP) was determined at 6 h by isolated heart perfusion. In separate experiments, mice were pretreated with either normal rabbit serum (NRS; n = 5) or anti-IL-18 antibody (Anti-IL-18, n = 8) 30 min before LPS. Neutralization of IL-18 attenuated LPS-induced depression of LVDP.

Myocardial IL-18 content after LPS. To determine the effect of LPS on myocardial tissue IL-18 content, mice were injected intraperitoneally with either vehicle (saline) or LPS. Hearts were harvested at 2, 4, and 6 h after LPS and homogenized to determine myocardial IL-18 content by ELISA. Compared with vehicle control, a twofold increase in myocardial IL-18 content was observed at 4 h after LPS (Fig. 2).


View larger version (8K):
[in this window]
[in a new window]
  		Fig. 2.   Myocardial tissue content of IL-18 after LPS. Mice were injected with E. coli LPS (0.5 mg/kg ip). Hearts were homogenized at the time points indicated. Enzyme-linked immunosorbent assay (ELISA) was utilized to determine myocardial IL-18 content (n = 4-5 per group). LPS induced a twofold increase in myocardial IL-18 at 4 h.

To determine whether TNF-alpha was required for the LPS-induced increase in myocardial IL-18 levels, TNF-/- mice were also injected with LPS and compared with B6 mice. Similar to C57BL/6 mice, myocardial IL-18 levels of B6 mice were increased at 4 h after LPS compared with saline controls (3.4 ± 0.8 vs. 1.1 ± 0.2 pg/mg protein, Fig. 3). In saline controls, myocardial IL-18 levels were not different between TNF-/- and wild-type mice. However, 4 h after LPS, myocardial IL-18 levels were lower in TNF-/- compared with wild-type mice (1.9 ± 0.4 vs. 3.4 ± 0.8 pg/mg protein, Fig. 3). This difference was significant by post hoc Fisher's analysis but not by Bonferroni-Dunn. Whereas myocardial IL-18 levels in LPS-treated TNF-/- mice were increased slightly compared with saline controls, the increase did not reach statistical significance.


View larger version (10K):
[in this window]
[in a new window]
  		Fig. 3.   Effect of tumor necrosis factor-alpha (TNF-alpha ) knockout (TNF-/-) on LPS-induced myocardial IL-18 production. TNF-/- and wild-type (B6) mice were injected with either vehicle (normal saline, n = 3 per group) or E. coli LPS (0.5 mg/kg ip, n = 5-6 per group). Hearts were homogenized at 4 h and ELISA was utilized to determine myocardial IL-18 content. LPS induced a threefold increase in myocardial IL-18 in wild-type mice but did not significantly increase IL-18 levels in TNF-/- mice. After LPS, IL-18 levels were reduced in TNF-/- compared with wild-type mice (difference significant by Fisher's test but not by Bonferroni-Dunn test).

Effect of neutralization of IL-18 on LPS-induced myocardial TNF-alpha production. We then sought to determine whether protection against LPS-induced myocardial dysfunction afforded by neutralization of IL-18 is associated with attenuation in myocardial TNF-alpha content. TNF-alpha was below detection in vehicle-injected controls but reached peak levels at 1 h after LPS (7.7 ± 1.6 pg/mg protein). Pretreatment of mice 30 min before LPS with either NRS or neutralizing IL-18 antibody had no effect on myocardial TNF-alpha at 1 h (7.7 ± 2.4 and 6.4 ± 1.1 pg/mg protein, respectively) (Fig. 4). Plasma concentrations of TNF-alpha were below detection in vehicle-injected controls but were elevated at 1 h after LPS (2,855 ± 391 pg/ml). Pretreatment with either NRS or neutralizing IL-18 antibody did not reduce LPS-induced elevation in plasma TNF-alpha concentration (2,454 ± 269 and 2,288 ± 146 pg/ml, respectively).


View larger version (9K):
[in this window]
[in a new window]
  		Fig. 4.   Effect of anti-IL-18 on LPS-induced myocardial TNF-alpha production. Mice were injected with either vehicle (normal saline ip) or E. coli LPS (0.5 mg/kg ip). Hearts were homogenized at the time points indicated (n = 4-8 per group). In separate experiments, mice were pretreated with either NRS (n = 5) or anti-IL-18 (n = 7) 30 min before LPS. ELISA was utilized to determine myocardial TNF-alpha content. Neutralization of IL-18 did not influence LPS-induced myocardial TNF-alpha production.

Effect of neutralization of IL-18 on LPS-induced myocardial IL-1beta levels. To determine whether neutralization of IL-18 influences LPS-induced myocardial IL-1beta production, we first determined the time of maximal IL-1beta levels in the heart after LPS. Compared with control myocardium, LPS greatly increased myocardial IL-1beta content at 4 h (132.2 ± 7.5 vs. 2.7 ± 1.4 pg/mg protein, P < 0.001, Fig. 5). In contrast to TNF-alpha , pretreatment of mice with IL-18 neutralizing antibody attenuated LPS-induced myocardial IL-1beta production by 65% at 4 h (48.7 ± 3.5 pg/mg protein, P < 0.001, Fig. 5). Pretreatment of mice with NRS had no effect on myocardial IL-1beta production.


View larger version (10K):
[in this window]
[in a new window]
  		Fig. 5.   Effect of anti-IL-18 on LPS-induced myocardial IL-1beta content. Mice were injected with either vehicle (normal saline ip) or E. coli LPS (0.5 mg/kg ip). Hearts were homogenized at the time points indicated (n = 5-6 per group). In separate experiments, mice were pretreated with either NRS (n = 5) or anti-IL-18 (n = 6) 30 min before LPS. ELISA was utilized to determine myocardial IL-1beta content. Neutralization of IL-18 attenuated peak LPS-induced myocardial IL-1beta production by 65%.

Effect of neutralization of IL-18 on LPS-induced myocardial ICAM-1 and VCAM-1 protein expression. We previously observed that neutralization of either VCAM-1 (34) or ICAM-1 (unpublished data) attenuates LPS-induced myocardial dysfunction. Therefore, immunofluorescence was used to examine the effect of neutralization of IL-18 on the expression of these two adhesion molecules. At 6 h after LPS, the integrated intensity of myocardial ICAM-1 increased eightfold compared with vehicle control. Pretreatment of mice with neutralizing IL-18 antibody attenuated LPS-induced myocardial ICAM-1 expression by 50% (Fig. 6). Similarly, LPS induced a greater than fourfold increase in the integrated intensity of VCAM-1 compared with vehicle control, but neutralization of IL-18 attenuated VCAM-1 expression by 36% (Fig. 7). Pretreatment with NRS did not influence LPS-induced myocardial ICAM-1 or VCAM-1 expression.


View larger version (8K):
[in this window]
[in a new window]
  		Fig. 6.   Effect of anti-IL-18 on LPS-induced myocardial intercellular adhesion molecule (ICAM-1) protein expression. Mice were injected with either vehicle (normal saline ip, n = 5) or E. coli LPS (0.5 mg/kg ip, n = 6). In separate experiments, mice were pretreated with either NRS (n = 5) or anti-IL-18 (n = 8) 30 min before LPS. Indirect immunofluorescent staining was utilized to determine myocardial ICAM-1 protein expression at 6 h. ICAM-1 immunoreactivity is expressed as integrated intensity (the product of area and mean intensity). Neutralization of IL-18 attenuated by 50% the eightfold increase in ICAM-1 protein expression induced by LPS.



View larger version (8K):
[in this window]
[in a new window]
  		Fig. 7.   Effect of anti-IL-18 on LPS-induced myocardial vascular cell adhesion molecule (VCAM-1) protein expression. Mice were injected with either vehicle (normal saline, n = 5) or E. coli LPS (0.5 mg/kg ip, n = 6). In separate experiments, mice were pretreated with either NRS (n = 5) or anti-IL-18 (n = 8) 30 min before LPS. Indirect immunofluorescent staining was utilized to determine myocardial VCAM-1 protein expression at 6 h. VCAM-1 immunoreactivity is expressed as integrated intensity (the product of area and mean intensity). Neutralization of IL-18 attenuated by 36% the fourfold increase in VCAM-1 protein expression induced by LPS.

Effect of neutralization of IL-18 on LPS-induced myocardial neutrophil accumulation. LPS-induced injury in many organs is associated with the accumulation of neutrophils. We therefore investigated whether neutralization of IL-18 attenuates LPS-induced myocardial neutrophil accumulation. With the use of immunofluorescence, myocardial neutrophil number increased by fivefold at 6 h after LPS compared with vehicle control (13.3 ± 1.5 vs. 2.9 ± 1.5 neutrophils/mm2, P < 0.01). Pretreatment of mice with IL-18 neutralizing antibody attenuated LPS-induced myocardial neutrophil accumulation by 55% compared with pretreatment with NRS (Fig. 8).


View larger version (9K):
[in this window]
[in a new window]
  		Fig. 8.   Effect of anti-IL-18 on LPS-induced myocardial neutrophil number. Mice were injected with either vehicle (normal saline, n = 5) or E. coli LPS (0.5 mg/kg ip, n = 6). In separate experiments, mice were pretreated with either NRS (n = 5) or anti-IL-18 (n = 8) 30 min before LPS. Indirect immunofluorescent staining was used to determine myocardial neutrophil number at 6 h. Neutralization of IL-18 attenuated LPS-induced myocardial neutrophil accumulation by 55%.


    DISCUSSION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

In this study we observed that myocardial IL-18 content is increased by LPS and that LPS-induced myocardial dysfunction is attenuated by specific neutralization of endogenous IL-18. We also examined whether the protection against LPS-induced dysfunction provided by neutralization of IL-18 was associated with attenuation of other known cardiodepressant cytokines. Neutralization of IL-18 attenuated the increase in myocardial IL-1beta content. In addition, the ICAM-1/VCAM-1 protein expression that occurs during endotoxemia was also decreased by neutralization of IL-18. In contrast, neutralization of IL-18 had no influence on LPS-induced myocardial TNF-alpha production. Gene deletion of TNF-alpha attenuated the LPS-induced increase in myocardial IL-18 levels, which suggests that the cardiodepressive role of TNF-alpha during endotoxemia may be mediated via induction of IL-18. IL-18 may, in turn, be a direct cardiodepressant or may mediate endotoxemic myocardial dysfunction via induction of and/or synergy with IL-1beta , ICAM-1, and VCAM-1.

The IL-18 precursor is present in an inactive form, but after cleavage by caspase-1, biologically active IL-18 is released from cells (10, 13). Indeed, a basal level of IL-18 was detected in the myocardium of control mice with an ELISA that recognizes both pro-IL-18 and active IL-18. Whereas LPS induced a twofold increase in myocardial IL-18 content, the increase did not occur until 4 h after LPS; however, it is likely that some of the pro-IL-18 present in the myocardium was rapidly cleaved and secreted into the circulation as active IL-18 after LPS injection. Thus, although myocardial IL-18 content did not increase until 4 h after LPS, it is possible that an increase in the active form of IL-18 occurred earlier. The twofold increase in total myocardial tissue IL-18 observed in this study is similar to the degree of increase in lung and liver IL-18 content during endotoxemia reported by others (25).

Mice pretreated with NRS had similar LVDP compared with mice treated with LPS alone. In contrast, pretreatment with neutralizing antibody against IL-18 nearly completely abrogated LPS-induced myocardial dysfunction. Thus neutralization of IL-18 preserves myocardial function during endotoxemia. This finding is in agreement with other studies, which have demonstrated a protective effect of neutralization of IL-18 in LPS-induced hepatoxicity (6, 41), experimental colitis (38), postischemic acute renal failure (20), and ischemia-reoxygenation-induced myocardial contractile dysfunction (32). The results of this study suggest that IL-18 contributes as a significant cytokine in endotoxemic myocardial depression.

Neutralization of IL-18 attenuated LPS-induced myocardial dysfunction without reducing myocardial TNF-alpha production. Peak levels of myocardial IL-18 occurred at 4 h at which time TNF-alpha had returned to near baseline levels. Because the increase in myocardial IL-18 was delayed compared with myocardial TNF-alpha production, the increase in IL-18 could not be a signal for TNF-alpha production. Early activation of IL-18 is also unlikely a signal for TNF-alpha production because IL-18 neutralizing antibody was applied as a pretreatment. It is, however, not unexpected that neutralization of IL-18 protects against LPS-induced myocardial dysfunction without attenuating TNF-alpha because others have reported that neutralization of IL-18 protects against LPS-induced lung and liver (25, 36) injury without reducing tissue TNF-alpha levels. In addition, neutralization or genetic deficiency of IL-18 has also been reported to protect mice from lethal endotoxemia without reducing serum TNF-alpha levels (14, 26).

Meng et al. (22) reported a temporal discordance between myocardial TNF-alpha levels and contractile dysfunction during endotoxemia. After LPS, myocardial dysfunction did not occur until TNF-alpha levels had returned to baseline. Despite this observation, neutralization of TNF-alpha attenuated LPS-induced myocardial dysfunction. These data, as well as our current finding that neutralization of IL-18 attenuates LPS-induced myocardial dysfunction without attenuating myocardial TNF-alpha levels, suggest that the role of TNF-alpha in depressing myocardial function may lie in its induction of other downstream factors. This hypothesis was further examined by determining whether TNF-alpha was required for the LPS-induced increase in myocardial IL-18 levels. In TNF-/- mice, myocardial IL-18 levels were not significantly different between the saline control and LPS-treated groups. Compared with LPS-treated wild-type mice, myocardial IL-18 levels were decreased after LPS in TNF-/- mice. This suggests that TNF-alpha may regulate myocardial IL-18 production, and this may be a mechanism by which TNFalpha contributes to myocardial dysfunction during endotoxemia. Similarly, neutralization of TNF-alpha was reported (7) to attenuate the induction of IL-18 by the T cell mitogen concanavalin A (Con A), and the reduction in IL-18 protected mice from Con A-induced hepatoxicity. However, TNF-alpha appears not to be the sole factor regulating myocardial IL-18 production during endotoxemia because TNF-/- did not completely eliminate LPS-induced myocardial IL-18 production. Furthermore, we have not examined whether TNF-alpha influences the activation of caspase-1 and subsequent cleavage of IL-18 to its active form.

IL-1beta production reached peak levels at 4 h after LPS, which coincides with the increase in myocardial IL-18. Of considerable importance was the observation that neutralization of IL-18 reduced myocardial IL-1beta production. These findings suggest that IL-18, in part, regulates IL-1beta production during endotoxemia. We (22, 34) have reported that myocardial dysfunction during endotoxemia occurs at 4 h after LPS and that dysfunction is maximal at 6 h. IL-1beta is likely one of the direct myocardial depressive factors in endotoxemia. Indeed, several studies (4, 16, 29) demonstrate that IL-1beta depresses myocardial function. Moreover, in vitro studies (4, 16) have demonstrated that TNF-alpha and IL-1beta act synergistically to depress myocardial contractility. The results of the present in vivo study suggest that TNF-alpha may not be a direct cardiodepressant because myocardial TNF-alpha had returned to baseline at the time when myocardial dysfunction occurred. It is more likely that the importance of TNF-alpha is to act as an early signal during endotoxemia by inducing downstream cytokines rather than as a direct cardiodepressant. In contrast, both myocardial IL-18 and IL-1beta levels are elevated at 4 h after LPS. These factors may contribute directly to myocardial depression.

Transgenic mice that specifically overexpress myocardial TNF-alpha develop cardiac dysfunction (3); however, simultaneous ICAM-1 gene deletion in this TNF-alpha -transgenic mouse model markedly improves cardiac function (11). These data suggest that ICAM-1 is an important mediator of the cardiac dysfunction induced by TNF-alpha . Similarly, we (34) have reported that VCAM-1 is required for LPS-induced myocardial dysfunction. In the present study, neutralization of IL-18 attenuated LPS-induced myocardial ICAM-1 and VCAM-1 expression, which corroborates previous reports (15, 24, 43) of induction of the expression of these adhesion molecules by IL-18. Thus attenuation of ICAM-1 and VCAM-1 expression by neutralization of IL-18 may have contributed to the protection against LPS-induced myocardial dysfunction.

We (34) reported that LPS-induced myocardial neutrophil accumulation is temporally associated with cardiac dysfunction and that neutralization of VCAM-1 attenuates both LPS-induced myocardial neutrophil accumulation and dysfunction. Similarly, the attenuation of ICAM-1 and VCAM-1 expression by neutralization of IL-18 was associated with a reduction in myocardial neutrophil accumulation. Whereas it is tempting to speculate that the reduction in myocardial neutrophils may have contributed to protection against LPS-induced myocardial dysfunction, further investigation is necessary to determine the role of neutrophils in endotoxemic cardiodepression.

In conclusion, neutralization of IL-18 attenuates LPS-induced myocardial dysfunction without reducing myocardial TNF-alpha production. Whereas this study does not discount TNF-alpha as an important cytokine in LPS-induced myocardial dysfunction, it suggests that TNF-alpha is likely an early initiator and not a direct end effector of endotoxemic depression. This study does not suggest that IL-18 is the sole mediator of LPS-induced myocardial dysfunction but instead suggests that IL-18 plays an important role in this disorder likely via its induction of and/or synergy with IL-1beta , ICAM-1, and VCAM-1. A limitation of this study is that the model used examines the role of IL-18 in LPS-induced myocardial dysfunction (in the absence of live infection), and thus the results cannot be directly extrapolated to live infection, sepsis-induced myocardial dysfunction. Further investigation of the role of IL-18 in sepsis-induced myocardial dysfunction using an animal model of sepsis such as cecal ligation and puncture is warranted.


    ACKNOWLEDGEMENTS

The authors thank Lihua Ao for assistance in immunofluorescent staining of tissues and Sandor A. Falk for technical assistance in monitoring mean arterial pressures of mice during endotoxemia.


    FOOTNOTES

This study was supported in part by National Institute of General Medical Sciences Grants GM-49222 and GM-08315.

Address for reprint requests and other correspondence: C. D. Raeburn, Dept. of Surgery, Univ. of Colorado Health Sciences Center, 4200 E. Ninth Ave., Box C-320, Denver, CO 80262 (E-mail: christopher.raeburn{at}uchsc.edu).

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

10.1152/ajpheart.00043.2002

Received 20 January 2002; accepted in final form 24 April 2002.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Adams, HR, Baxter CR, and Parker JL. Reduction of intrinsic contractile reserves of the left ventricle by Escherichia coli endotoxin shock in guinea-pigs. J Mol Cell Cardiol 17: 575-585, 1985[ISI][Medline].

2.   Arndt, PG, Fantuzzi G, and Abraham E. Expression of interleukin-18 in the lung after endotoxemia or hemorrhage-induced acute lung injury. Am J Respir Cell Mol Biol 22: 708-713, 2000[Abstract/Free Full Text].

3.   Bryant, D, Becker L, Richardson J, Shelton J, Franco F, Peshock R, Thompson M, and Giroir B. Cardiac failure in transgenic mice with myocardial expression of tumor necrosis factor-alpha . Circulation 97: 1375-1381, 1998[Abstract/Free Full Text].

4.   Cain, BS, Meldrum DR, Dinarello CA, Meng X, Joo KS, Banerjee A, and Harken AH. Tumor necrosis factor-alpha and interleukin-1beta synergistically depress human myocardial function. Crit Care Med 27: 1309-1318, 1999[ISI][Medline].

5.   Endo, S, Inada K, Yamada Y, Wakabayashi G, Ishikura H, Tanaka T, and Sato S. Interleukin 18 (IL-18) levels in patients with sepsis. J Med 31: 15-20, 2000[ISI][Medline].

6.   Faggioni, R, Cattley RC, Guo J, Flores S, Brown H, Qi M, Yin S, Hill D, Scully S, Chen C, Brankow D, Lewis J, Baikalov C, Yamane H, Meng T, Martin F, Hu S, Boone T, and Senaldi G. IL-18-binding protein protects against lipopolysaccharide-induced lethality and prevents the development of Fas/Fas ligand-mediated models of liver disease in mice. J Immunol 167: 5913-5920, 2001[Abstract/Free Full Text].

7.   Faggioni, R, Jones-Carson J, Reed DA, Dinarello CA, Feingold KR, Grunfeld C, and Fantuzzi G. Leptin-deficient (ob/ob) mice are protected from T cell-mediated hepatotoxicity: role of tumor necrosis factor alpha  and IL-18. Proc Natl Acad Sci USA 97: 2367-2372, 2000[Abstract/Free Full Text].

8.   Fantuzzi, G, Puren AJ, Harding MW, Livingston DJ, and Dinarello CA. Interleukin-18 regulation of interferon gamma  production and cell proliferation as shown in interleukin-1beta -converting enzyme (caspase-1)-deficient mice. Blood 91: 2118-2125, 1998[Abstract/Free Full Text].

9.   Finkel, MS, Oddis CV, Jacob TD, Watkins SC, Hattler BG, and Simmons RL. Negative inotropic effects of cytokines on the heart mediated by nitric oxide. Science 257: 387-389, 1992[Abstract/Free Full Text].

10.   Ghayur, T, Banerjee S, Hugunin M, Butler D, Herzog L, Carter A, Quintal L, Sekut L, Talanian R, Paskind M, Wong W, Kamen R, Tracey D, and Allen H. Caspase-1 processes IFN-gamma -inducing factor and regulates LPS-induced IFN-gamma production. Nature 386: 619-623, 1997[Medline].

11.   Graciano, AL, Bryant DD, White DJ, Horton J, Bowles NE, and Giroir BP. Targeted disruption of ICAM-1, P-selectin genes improves cardiac function and survival in TNF-alpha transgenic mice. Am J Physiol Heart Circ Physiol 280: H1464-H1471, 2001[Abstract/Free Full Text].

12.   Grobmyer, SR, Lin E, Lowry SF, Rivadeneira DE, Potter S, Barie PS, and Nathan CF. Elevation of IL-18 in human sepsis. J Clin Immunol 20: 212-215, 2000[ISI][Medline].

13.   Gu, Y, Kuida K, Tsutsui H, Ku G, Hsiao K, Fleming MA, Hayashi N, Higashino K, Okamura H, Nakanishi K, Kurimoto M, Tanimoto T, Flavell RA, Sato V, Harding MW, Livingston DJ, and Su MS. Activation of interferon-gamma inducing factor mediated by interleukin-1beta -converting enzyme. Science 275: 206-209, 1997[Abstract/Free Full Text].

14.   Hochholzer, P, Lipford GB, Wagner H, Pfeffer K, and Heeg K. Role of interleukin-18 (IL-18) during lethal shock: decreased lipopolysaccharide sensitivity but normal superantigen reaction in IL-18-deficient mice. Infect Immun 68: 3502-3508, 2000[Abstract/Free Full Text].

15.   Kohka, H, Yoshino T, Iwagaki H, Sakuma I, Tanimoto T, Matsuo Y, Kurimoto M, Orita K, Akagi T, and Tanaka N. Interleukin-18/interferon-gamma -inducing factor, a novel cytokine, up-regulates ICAM-1 (CD54) expression in KG-1 cells. J Leukoc Biol 64: 519-527, 1998[Abstract].

16.   Kumar, A, Thota V, Dee L, Olson J, Uretz E, and Parrillo JE. Tumor necrosis factor alpha and interleukin 1beta are responsible for in vitro myocardial cell depression induced by human septic shock serum. J Exp Med 183: 949-958, 1996[Abstract/Free Full Text].

17.   Manigold, T, Bocker U, Traber P, Dong-Si T, Kurimoto M, Hanck C, Singer MV, and Rossol S. Lipopolysaccharide/endotoxin induces IL-18 via CD14 in human peripheral blood mononuclear cells in vitro. Cytokine 12: 1788-1792, 2000[ISI][Medline].

18.   Mathiak, G, Neville LF, Grass G, Boehm SA, Luebke T, Herzmann T, Kabir K, Rosendahl R, Schaefer U, Mueller C, Bohlen H, Wassermann K, and Hoelscher AH. Chemokines and interleukin-18 are up-regulated in bronchoalveolar lavage fluid but not in serum of septic surgical ICU patients. Shock 15: 176-180, 2001[ISI][Medline].

19.   Matsumoto, S, Tsuji-Takayama K, Aizawa Y, Koide K, Takeuchi M, Ohta T, and Kurimoto M. Interleukin-18 activates NF-kappa B in murine T helper type 1 cells. Biochem Biophys Res Commun 234: 454-457, 1997[ISI][Medline].

20.   Melnikov, VY, Ecder T, Fantuzzi G, Siegmund B, Lucia MS, Dinarello CA, Schrier RW, and Edelstein CL. Impaired IL-18 processing protects caspase-1-deficient mice from ischemic acute renal failure. J Clin Invest 107: 1145-1152, 2001[ISI][Medline].

21.   Meng, X, Ao L, Brown JM, Fullerton DA, Banerjee A, and Harken AH. Nitric oxide synthase is not involved in cardiac contractile dysfunction in a rat model of endotoxemia without shock. Shock 7: 111-118, 1997[ISI][Medline].

22.   Meng, X, Ao L, Meldrum DR, Cain BS, Shames BD, Selzman CH, Banerjee A, and Harken AH. TNF-alpha and myocardial depression in endotoxemic rats: temporal discordance of an obligatory relationship. Am J Physiol Regulatory Integrative Comp Physiol 275: R502-R508, 1998[Abstract/Free Full Text].

23.   Micallef, MJ, Ohtsuki T, Kohno K, Tanabe F, Ushio S, Namba M, Tanimoto T, Torigoe K, Fujii M, Ikeda M, Fukuda S, and Kurimoto M. Interferon-gamma -inducing factor enhances T helper 1 cytokine production by stimulated human T cells: synergism with interleukin-12 for interferon-gamma production. Eur J Immunol 26: 1647-1651, 1996[ISI][Medline].

24.   Morel, JC, Park CC, Woods JM, and Koch AE. A novel role for interleukin-18 in adhesion molecule induction through NFkappa B and phosphatidylinositol (PI) 3-kinase-dependent signal transduction pathways. J Biol Chem 276: 37069-37075, 2001[Abstract/Free Full Text].

25.   Netea, MG, Fantuzzi G, Kullberg BJ, Stuyt RJ, Pulido EJ, McIntyre RC, Jr, Joosten LA, Van der Meer JW, and Dinarello CA. Neutralization of IL-18 reduces neutrophil tissue accumulation and protects mice against lethal Escherichia coli and salmonella typhimurium endotoxemia. J Immunol 164: 2644-2649, 2000[Abstract/Free Full Text].

26.   Netea, MG, Kullberg BJ, Verschueren I, and Van der Meer JW. Interleukin-18 induces production of proinflammatory cytokines in mice: no intermediate role for the cytokines of the tumor necrosis factor family and interleukin-1beta . Eur J Immunol 30: 3057-3060, 2000[ISI][Medline].

27.   Novick, D, Schwartsburd B, Pinkus R, Suissa D, Belzer I, Sthoeger Z, Keane WF, Chvatchko Y, Kim SH, Fantuzzi G, Dinarello CA, and Rubinstein M. A novel IL-18BP ELISA shows elevated serum IL-18BP in sepsis and extensive decrease of free IL-18. Cytokine 14: 334-342, 2001[ISI][Medline].

28.   Okamura, H, Tsutsi H, Komatsu T, Yutsudo M, Hakura A, Tanimoto T, Torigoe K, Okura T, Nukada Y, Hattori K, Akita K, Namba M, Tanabe F, Konishi K, Fukuda S, and Kurimoto M. Cloning of a new cytokine that induces IFN-gamma production by T cells. Nature 378: 88-91, 1995[Medline].

29.   Oyama, J, Shimokawa H, Momii H, Cheng X, Fukuyama N, Arai Y, Egashira K, Nakazawa H, and Takeshita A. Role of nitric oxide and peroxynitrite in the cytokine-induced sustained myocardial dysfunction in dogs in vivo. J Clin Invest 101: 2207-2214, 1998[ISI][Medline].

30.   Pagani, FD, Baker LS, Hsi C, Knox M, Fink MP, and Visner MS. Left ventricular systolic and diastolic dysfunction after infusion of tumor necrosis factor-alpha in conscious dogs. J Clin Invest 90: 389-398, 1992[ISI][Medline].

31.   Parker, JL, and Adams HR. Development of myocardial dysfunction in endotoxin shock. Am J Physiol Heart Circ Physiol 248: H818-H826, 1985[Abstract/Free Full Text].

32.   Pomerantz, BJ, Reznikov LL, Harken AH, and Dinarello CA. Inhibition of caspase 1 reduces human myocardial ischemic dysfunction via inhibition of IL-18 and IL-1beta . Proc Natl Acad Sci USA 98: 2871-2876, 2001[Abstract/Free Full Text].

33.   Puren, AJ, Razeghi P, Fantuzzi G, and Dinarello CA. Interleukin-18 enhances lipopolysaccharide-induced interferon-gamma production in human whole blood cultures. J Infect Dis 178: 1830-1834, 1998[ISI][Medline].

34.   Raeburn, CD, Calkins CM, Zimmerman MA, Song Y, Ao L, Banerjee A, Meng X, and Harken AH. Vascular cell adhesion molecule-1 expression is obligatory for endotoxin-induced myocardial neutrophil accumulation and contractile dysfunction. Surgery 130: 319-325, 2001[ISI][Medline].

35.   Romanosky, AJ, Giaimo ME, Shepherd RE, and Burns AH. The effect of in vivo endotoxin on myocardial function in vitro. Circ Shock 19: 1-12, 1986[ISI][Medline].

36.   Sakao, Y, Takeda K, Tsutsui H, Kaisho T, Nomura F, Okamura H, Nakanishi K, and Akira S. IL-18-deficient mice are resistant to endotoxin-induced liver injury but highly susceptible to endotoxin shock. Int Immunol 11: 471-480, 1999[Abstract/Free Full Text].

37.   Seki, E, Tsutsui H, Nakano H, Tsuji N, Hoshino K, Adachi O, Adachi K, Futatsugi S, Kuida K, Takeuchi O, Okamura H, Fujimoto J, Akira S, and Nakanishi K. Lipopolysaccharide-induced IL-18 secretion from murine Kupffer cells independently of myeloid differentiation factor 88 that is critically involved in induction of production of IL-12 and IL-1beta . J Immunol 166: 2651-2657, 2001[Abstract/Free Full Text].

38.   Siegmund, B, Fantuzzi G, Rieder F, Gamboni-Robertson F, Lehr HA, Hartmann G, Dinarello CA, Endres S, and Eigler A. Neutralization of interleukin-18 reduces severity in murine colitis and intestinal IFN-gamma and TNF-alpha production. Am J Physiol Regulatory Integrative Comp Physiol 281: R1264-R1273, 2001[Abstract/Free Full Text].

39.   Song, Y, Ao L, Calkins CM, Raeburn CD, Harken AH, and Meng X. Differential cardiopulmonary recruitment of neutrophils during hemorrhagic shock: a role for ICAM-1? Shock 16: 444-448, 2001[ISI][Medline].

40.   Song, Y, Ao L, Raeburn CD, Calkins CM, Abraham E, Harken AH, and Meng X. A low level of TNF-alpha mediates hemorrhage-induced acute lung injury via p55 TNF receptor. Am J Physiol Lung Cell Mol Physiol 281: L677-L684, 2001[Abstract/Free Full Text].

41.   Tsutsui, H, Matsui K, Kawada N, Hyodo Y, Hayashi N, Okamura H, Higashino K, and Nakanishi K. IL-18 accounts for both TNF-alpha - and Fas ligand-mediated hepatotoxic pathways in endotoxin-induced liver injury in mice. J Immunol 159: 3961-3967, 1997[Abstract].

42.   Ushio, S, Namba M, Okura T, Hattori K, Nukada Y, Akita K, Tanabe F, Konishi K, Micallef M, Fujii M, Torigoe K, Tanimoto T, Fukuda S, Ikeda M, Okamura H, and Kurimoto M. Cloning of the cDNA for human IFN-gamma -inducing factor, expression in Escherichia coli, and studies on the biologic activities of the protein. J Immunol 156: 4274-4279, 1996[Abstract].

43.   Vidal-Vanaclocha, F, Fantuzzi G, Mendoza L, Fuentes AM, Anasagasti MJ, Martin J, Carrascal T, Walsh P, Reznikov LL, Kim SH, Novick D, Rubinstein M, and Dinarello CA. IL-18 regulates IL-1beta -dependent hepatic melanoma metastasis via vascular cell adhesion molecule-1. Proc Natl Acad Sci USA 97: 734-739, 2000[Abstract/Free Full Text].

Am J Physiol Heart Circ Physiol 283(2):H650-H657
0363-6135/02 $5.00 Copyright © 2002 the American Physiological Society


This article has been cited by other articles:


Home page
 Ann. Thorac. Surg.Home page
J. Cha, Z. Wang, L. Ao, N. Zou, C. A. Dinarello, A. Banerjee, D. A. Fullerton, and X. Meng
Cytokines link toll-like receptor 4 signaling to cardiac dysfunction after global myocardial ischemia.
Ann. Thorac. Surg., May 1, 2008; 85(5): 1678 - 1685.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Cell Physiol.Home page
X. Meng, L. Ao, Y. Song, A. Babu, X. Yang, M. Wang, M. J. Weyant, C. A. Dinarello, J. C. Cleveland Jr., and D. A. Fullerton
Expression of functional Toll-like receptors 2 and 4 in human aortic valve interstitial cells: potential roles in aortic valve inflammation and stenosis
Am J Physiol Cell Physiol, January 1, 2008; 294(1): C29 - C35.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Cell Mol. Bio.Home page
M. Divangahi, A. Demoule, G. Danialou, L. Yahiaoui, W. Bao, Z. Xing, and B. J. Petrof
Impact of IL-10 on Diaphragmatic Cytokine Expression and Contractility during Pseudomonas Infection
Am. J. Respir. Cell Mol. Biol., April 1, 2007; 36(4): 504 - 512.
[Abstract] [Full Text] [PDF]

Home page
 Cardiovasc ResHome page
J. H. Boyd, S. Mathur, Y. Wang, R. M. Bateman, and K. R. Walley
Toll-like receptor stimulation in cardiomyoctes decreases contractility and initiates an NF-{kappa}B dependent inflammatory response
Cardiovasc Res, December 1, 2006; 72(3): 384 - 393.
[Abstract] [Full Text] [PDF]

Home page
 CirculationHome page
P. Maffia, G. Grassia, P. Di Meglio, R. Carnuccio, L. Berrino, P. Garside, A. Ianaro, and A. Ialenti
Neutralization of Interleukin-18 Inhibits Neointimal Formation in a Rat Model of Vascular Injury
Circulation, August 1, 2006; 114(5): 430 - 437.
[Abstract] [Full Text] [PDF]

Home page
 Physiol. GenomicsHome page
S. Roy, S. Khanna, D. E. Kuhn, C. Rink, W. T. Williams, J. L. Zweier, and C. K. Sen
Transcriptome analysis of the ischemia-reperfused remodeling myocardium: temporal changes in inflammation and extracellular matrix
Physiol Genomics, May 16, 2006; 25(3): 364 - 374.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Heart Circ. Physiol.Home page
P. R. Woldbaek, J. B. Sande, T. A. Stromme, P. K. Lunde, S. Djurovic, T. Lyberg, G. Christensen, and T. Tonnessen
Daily administration of interleukin-18 causes myocardial dysfunction in healthy mice
Am J Physiol Heart Circ Physiol, August 1, 2005; 289(2): H708 - H714.
[Abstract] [Full Text] [PDF]

Home page
 Circ. Res.Home page
F. M. Syed, H. S. Hahn, A. Odley, Y. Guo, J. G. Vallejo, R. A. Lynch, D. L. Mann, R. Bolli, and G. W. Dorn II
Proapoptotic Effects of Caspase-1/Interleukin-Converting Enzyme Dominate in Myocardial Ischemia
Circ. Res., May 27, 2005; 96(10): 1103 - 1109.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
X. Meng, L. Ao, Y. Song, C. D. Raeburn, D. A. Fullerton, and A. H. Harken
Signaling for myocardial depression in hemorrhagic shock: roles of Toll-like receptor 4 and p55 TNF-{alpha} receptor
Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2005; 288(3): R600 - R606.
[Abstract] [Full Text] [PDF]

This Article