AJP - Heart Add DOIs to your references at manuscript stage!
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Heart Circ Physiol 294: H1298-H1303, 2008. First published January 11, 2008; doi:10.1152/ajpheart.00765.2007
0363-6135/08 $8.00
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
294/3/H1298    most recent
00765.2007v1
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 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 Google Scholar
Google Scholar
Right arrow Articles by Huang, S.
Right arrow Articles by Kem, D. C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Huang, S.
Right arrow Articles by Kem, D. C.

Proteasome inhibition 1 h following ischemia protects GRK2 and prevents malignant ventricular tachyarrhythmias and SCD in a model of myocardial infarction

Shijun Huang,1,2,* Eugene Patterson,* Xichun Yu,1,2 Marion W. Garrett,1 Isabel De Aos,2 and David C. Kem1,2

1Endocrinology Division and 2Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center and Oklahoma Veteran Affairs Medical Center, Oklahoma City, Oklahoma

Submitted 3 July 2007 ; accepted in final form 10 January 2008


   ABSTRACT
TOP
 ABSTRACT
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Arrhythmia-prone epicardial border zone (EBZ) tissues demonstrate decreased G protein-coupled receptor kinase-2 (GRK2) activity and increased sensitivity to isoproterenol 6–24 h after coronary artery ligation in the dog. We previously demonstrated that the ischemia-mediated decrease in GRK2 in cardiac ischemic tissue was largely blocked by proteasome blockade initiated 1 h before the onset of ischemia, and this was associated with significant cardioprotection against malignant ventricular tachyarrhythmias. For application to clinical circumstances, it is desirable to determine whether a clinical window exists following the onset of ischemia for such a protective effect. The treatment of six dogs with the selective proteasome inhibitor bortezomib 1 h after the surgical induction of left coronary artery ischemia provided 80% (EBZ) and 42% (infarct) protection (by immunoblot) against the loss of GRK2 at 24 h. There was no significant increase of heat shock protein 70(72) in the EBZ of bortezomib-treated animals compared with control. There was a striking absence of rapid (>300 beats/min) and very rapid (>360 beats/min) ventricular triplets that is highly predictive of sudden cardiac deaths (SCDs) during electrocardiogram monitoring of the first 24 h in the bortezomib-treated animals in contrast with nontreated infarcted animals. There were no SCDs in the 6 treated animals (0%) and five SCDs in the 14 control animals (36%). Assay of whole blood proteasome activity demonstrated the expected decrease over the 24-h observation period. These data support the concept that proteasome inhibition within a window of time following myocardial infarction may be of use in suppressing malignant tachyarrhythmias and SCD.

β-adrenergic receptor; G-protein receptor kinase; sudden cardiac death

SUDDEN CARDIAC DEATH (SCD) is related to recurrent ventricular tachyarrhythmias arising from a thin layer of surviving myocardium adjacent to the infarcted tissue (4, 11, 16, 17). Two peaks of SCD are observed in dogs; one is within 30 min and the second is during a period from 6–24 h following the production of a myocardial infarction by stepped coronary artery ligation (CAL). In the later period, SCD is generally characterized by episodic tachyarrhythmias triggering electrophysiological events, including sustained ventricular tachycardia (VT) and ventricular fibrillation (7, 13, 15–17). In the dog, these late tachyarrhythmias represent primarily sustained reentrant tachycardia from the epicardial border zone (EBZ) tissue (15).

We have reported a marked decrease in total G protein-coupled receptor kinase-2 (GRK2) activity in whole slices of canine EBZ tissue obtained during the subacute 6–24 h period after infarction, resulting in a loss of the ability of the EBZ tissue to become desensitized to β-adrenergic stimulation (23, 24). Subsequent studies demonstrated that pretreatment of the dog by either of two agents, a proteasome inhibitor (22) or a TNF-{alpha} sequestrant (23), protected against the loss of GRK2 expression and significantly diminished the ventricular ectopic activity. Although no deaths from SCD occurred in the two treated groups compared with the control animals, the relatively small n for each prevented the reduction in SCD from reaching significance in the separate studies.

In the present study, we have examined the effect of administering the proteasome inhibitor bortezomib 1 h after an induction of a myocardial infarction to determine whether a potential therapeutic window exists. In addition, we have examined the effect of bortezomib on the induction of heat shock protein 70(72) [Hsp70(72)], since this induction has previously been claimed to have pro- and antiapoptotic activity. One proposed antiapoptotic pathway was through the Hsp70(72)-mediated suppression of certain mitogen-activated protein kinases (MAPKs) (5, 6, 12). In contrast, the bortezomib-protected kinase GRK2 is presumably effective because it is not destroyed by the proteasome pathway and remains active in contradistinction to the previously reported effect of Hsp70(72) on the MAPKs. For this reason, we wished to determine whether, in fact, Hsp70(72) was induced in the EBZ at a time when GRK2 was exerting its protective effect.

These data indicate that 1) a window following CAL-induced ischemia does exist for protection against the development of monomorphic ventricular tachyarrhythmias and SCD with bortezomib and 2) Hsp70(72) is not induced in the EBZ tissue at a time when GRK2 activity retains its expected beneficial effect in minimizing the impact of catecholamines on electrophysiological activity in the ventricle.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Ischemic dog model. Twenty (14 control and 6 bortezomib treated) male dogs (30 to 45 lb) had a two-stage ligation of the left anterior descending coronary artery (LAD) below the first branch, as previously described (7, 8), during intravenous pentobarbital sodium (30 mg/kg) anesthesia. The minimal number of bortezomib-treated animals (n = 6) required to demonstrate significance had been experimentally determined by a previous study (22) and approved through overview by the Institutional Animal Care and Use Committee. Provision for an additional two animals was made in case circumstances such as an inadequate LAD system were present, but these extra animals were not needed. The last consecutively studied 14 control animals were used, including 6 new animals randomly intermixed with the study animals. In brief, a two-stage ligation of the coronary artery (a stenosis formed by ligating against and then removing a 20-gauge hypodermic needle, followed 15 min later by complete ligation of the artery) prevents or suppresses the initial lethal ventricular arrhythmias observed following abrupt coronary artery occlusion (7, 8). The dogs were given 0.4 mg/kg nalbuphine for postoperative analgesia and then allowed to awaken from anesthesia. A 24-h ambulatory ECG was obtained from leads on the thoracic surface. At 24 h after CAL, dogs were reanesthetized, a thoracotomy was performed, and the heart was removed and immersed in and perfused with ice-cold Tyrode buffer via the left main coronary artery. The outer 1.0 mm of EBZ tissue overlying the infarct was shaved by scalpel dissection. A cross section of the left ventricle was stained with triphenyltetrazolium chloride (TTZ; 0.1%) to determine the degree of viable and nonviable tissue. Remote site (RS) control tissue was obtained from a superior portion of the lateral left ventricle perfused via the left circumflex coronary artery. The infarct (Inf) sample was obtained from the middle of the region and characterized by darkened, reddish myocardium. The endocardial surface was also shaved, but owing to the thin nature of this tissue, it contained a significant amount of Inf tissue (22). The tissues were rapidly (within 10 min) divided into small aliquots and stored in liquid N2. The animal protocols were approved by the Institutional Animal Care and Use Committee and conform to the Helsinki International Guidelines for animal experimentation.

Bortezomib treatment. Six dogs were injected through a forepaw vein with 0.0875 mg/kg bortezomib (Velcade; Millennium Pharmaceuticals, Cambridge, MA). The other 14 dogs were injected with saline (control). The intravenous injection was given 1 h after LAD ligation. This dosage for dogs was based on previous studies of our laboratory and proteasome activity measurements (22). There are limited data available for dogs, but these studies (unpublished data; Millennium Pharmaceuticals) suggest a similar proteasome activity response to these dosages. No significant side effects of the injection dosage (i.e., hypotension or unusual tachycardia other than that associated with the ischemia) were observed in our study. Blood samples for the measurement of proteasome activity were obtained at 0, 1, 2, 4, 7, 12, and 24 h after LAD ligation.

Proteasome activity. Packed whole blood lysate proteasome activity was assayed in the pharmacology laboratory at Millennium Pharmaceuticals, as described (10). Whole blood lysate (20–100 µg of protein) was added to the cuvette. When the proteasome chymotryptic activity in the lysates was measured, the same assay buffer was used, except that the SDS concentration was 0.5 g/l. The signal was linear between 3 and 60 min. Measurement of the proteasome tryptic activity was performed in 60 µmol/l Bz-Val-Gly-Arg-7-amido-4-methylcoumarin (VGR-AMC) in 20 mmol/l HEPES, pH 8.0, containing 0.5 mmol/l EDTA and 10 ml/l DMSO. Enzyme units are expressed as picomoles AMC/s. Since bortezomib primarily inhibits chymotryptic but not tryptic activity of the proteasome, the ratio of chymotrypsin to trypsin activity provides a more sensitive and accurate estimate of bortezomib-induced proteasome inhibition (10).

Immunoblot analysis. GRK2 immunodetection was performed as previously described on detergent-solubilized extracts after immunoprecipitation (22). Hearts were homogenized in ice-cold radioimmunoprecipitation assay (RIPA) buffer containing 50 mM Tris (pH 8.0), 5 mM EDTA, 150 mM NaCl, 1% Nonidet P-40, 0.5% sodium deoxycholate, 0.1% SDS, 10 mM NaF, 5 mM EGTA, 10 mM sodium pyrophosphate, and 1 mM PMSF. GRK2 was immunoprecipitated from 1 ml of extract (250 µg) with 1.2 µg polyclonal anti-GRK2 antibody (Santa Cruz Biotechnology, Santa Cruz, CA) and 20 µl of a 50% slurry of protein A/G agarose conjugate agitated overnight at 4°C. Immune complexes were washed three times in ice-cold RIPA, resuspended in 25 µl of loading buffer, heated at 95°C for 5 min, and then electrophoresed and transferred to nitrocellulose. The GRK2 protein was detected using the monoclonal anti-GRK2 antibody (Upstate Biotechnology, Lake Placid, NY) and enhanced chemiluminescence (ECL; Amersham). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was detected by anti-GAPDH antibody (Sigma) and used as an internal control. Quantification was performed by densitometric scanning and using Image QuaNT software (Molecular Dynamics, Sunnyvale, CA). The relative expression levels of GRK2 were determined by normalization to the GAPDH values. A similar procedure was used to estimate Hsp70(72) using an antibody obtained from Stressgen (Division of Assay Designs, Ann Arbor, MI). Again, GAPDH was used as an internal control.

Statistics. Normalized immunoblot data were analyzed using a two-tailed nonparametric sign test. Other data are expressed as means ± SE. Normally distributed data were examined using a one-way ANOVA. Bonferroni multiple comparison test was used for posttest analysis. Significance was ascribed to P values of <0.05.


   RESULTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Each dog, following the two-stage ligation of the left anterior coronary artery, developed distinct Q waves on the anterior ECG leads. The cardiac tissue demonstrated a 1.0–1.5-mm surviving layer of myocardium on the epicardial surfaces of the Inf and a much thinner (0.2–0.5 mm) layer on the endocardial surface, as previously described (22). This was confirmed in each case by using a TTZ vital stain of a strip of tissue taken through the center of the infarct. Histological examination of the control RS, ischemic EBZ, and Inf tissues confirmed the expected changes 24 h after a transmural Inf.

The proteasome pathway has been implicated in the posttranscriptional degradation of GRK2 (18). We used the specific proteasome inhibitor bortezomib to determine whether blockade of this pathway might alter the frequency of malignant ventricular arrhythmias and the loss of GRK2 in this animal model. These animals were given bortezomib 0.0875 mg/kg iv 1 h after ligation of the LAD coronary artery. The effects of this infusion on whole blood cell proteasome activity (expressed as a chymotrypsin-to-trypsin activity ratio) are seen in Fig. 1. The proteasome activity in the whole blood of the dog was maximally suppressed at 1 h after infusion (2 h after LAD ligation) and gradually recovered to 50% of control at 24 h after ligation.


Figure 1
View larger version (18K):
[in this window]
[in a new window]

  		Fig. 1. Chymotrypsin-to-trypsin activity ratio in packed whole blood cells from bortezomib-treated dogs (n = 6) and saline-treated control dogs (n = 3) undergoing coronary artery ligation. Bortezomib was given 1 h after left anterior descending coronary artery (LAD) ligation with maximal suppression of proteasome activity observed 1 h after infusion (2 h after LAD ligation). *P < 0.001; **P < 0.05 compared with control dogs.

 
As previously reported, GRK2 expression after 24 h measured by immunoblot is significantly suppressed in both EBZ and Inf tissue taken from the saline control Inf animals (23, 24). Figure 2A demonstrates typical 24-h GRK2 expression in the various cardiac tissues in two dogs given either saline or bortezomib, respectively, 1 h after LAD ligation. Immunoblot analysis of unprecipitated GAPDH levels demonstrates equal amounts of the extracts. The cumulative data from cardiac tissues of six dogs are shown in Fig. 2B. Bortezomib treatment conferred remarkable protection against the expected loss in GRK2 expression in the EBZ tissue with the mean of levels in this region 80% of their nonischemic RS tissue. There was also a significant protection for GRK2 in the Inf tissue up to 42% of the RS. Saline-treated ligated animals demonstrated a significant decrease of GRK2 in the EBZ and Inf tissue compared with the RS control tissue.


Figure 2
View larger version (29K):
[in this window]
[in a new window]

  		Fig. 2. A: representative immunoblots of G protein-coupled receptor kinase 2 (GRK2) in tissue taken from a saline-treated 24-h LAD-ligated dog (left) and a bortezomib-treated ligated dog (right). GAPDH immunoblots were also performed to demonstrate equal tissue extracts. Dogs were treated with 0.0875 mg/kg bortezomib 1 h after LAD ligation. B: densitometry of GRK2 for remote site (RS), epicardial border zone (EBZ), and infarct (Inf) tissue from saline- and bortezomib-treated dogs was normalized to the GAPDH values. Data (means ± SE) are shown in B. When compared with saline controls, bortezomib treatment resulted in a significant protection for GRK2 in the EBZ (80% vs. 21% of the RS) and Inf (42% vs. 7% of the RS) tissue. *P < 0.01, n = 6.

 
Hsp70(72) values were estimated by immunoblot to examine the possibility of a relationship with the protection of GRK2. As a loading control, samples were probed with anti-GAPDH antibodies. As shown in Fig. 3, there was no significant difference of Hsp70(72) between the RS, EBZ, and Inf tissues of the control and bortezomib-treated animals (RS, treated vs. untreated, P = 0.27; EBZ, treated vs. untreated, P = 0.58; and Inf, treated vs. untreated, P = 0.37; treated, n = 6; untreated, n = 2).


Figure 3
View larger version (30K):
[in this window]
[in a new window]

  		Fig. 3. A: representative immunoblots of heat shock protein 70(72) [Hsp70(72)] in tissue taken from a saline-treated 24-h LAD-ligated dog (left) and a bortezomib-treated ligated dog (right). Equal protein loading was confirmed by GAPDH immunoblots. B: data were normalized to the GAPDH values and are shown as means ± SE. There was no significant difference in Hsp70(72) expression between the respective tissues in the bortezomib-treated (n = 6) and untreated (n = 2, P > 0.05) animals.

 
Holter ECG monitoring of the bortezomib-treated animals demonstrated a virtually complete absence of the very rapid triplets (≥360 beats/min) whose frequency is directly correlated with the occurrence of SCD in this animal model (Fig. 4) (15–17). This observation is in marked contrast to that observed in all survivors of the saline-treated (control) Inf animals (P < 0.05) and especially in those dying from SCD. This observation of a marked beneficial effect even extended to those rapid triplets with a somewhat slower rate of >300 beats/min (Fig. 5). When the analysis was extended to the most rapid triplet observed within a given hour (Fig. 6), there again was a marked diminution (P < 0.05) in this analysis. No bortezomib-treated animals died, whereas 5 of 14 control Inf animals died within the 24-h observation period. These data approached significance (bortezomib, 0 deaths of 6 dogs studied; and control, 5 deaths of 14 dogs studied; P = 0.06). When the data from our previously published study using the six animals pretreated 1 h before the induction of ischemia (22) and those treated 1 h after ligation are combined and compared with the 14 consecutive saline control animals, this difference reaches significance (combined deaths for the bortezomib, 0 deaths of 12 dogs studied; and control, 5 deaths of 14 dogs studied; P < 0.05).


Figure 4
View larger version (20K):
[in this window]
[in a new window]

  		Fig. 4. The incidence (means ± SE) of the very rapid (highest risk) ventricular triplets [all, ≥360 beats/min (bpm)] per hour for control (n = 14 dogs, 5 deaths) and bortezomib-pretreated (n = 6 dogs, 0 deaths) animals and those groups treated 1 h after LAD ligation (n = 6 dogs, 0 deaths). *Times of death of the 5 dogs in the control group. The saline control animals had a significantly greater number of triplets at the indicated time points (hours on the x-axis) (P < 0.05).

 

Figure 5
View larger version (21K):
[in this window]
[in a new window]

  		Fig. 5. The incidence (means ± SE) for all of the rapid triplets (all ≥300 beats/min) for the bortezomib and saline control groups. The saline control animals had a significantly greater number of total triplets at the indicated time points (hours on the x-axis) (P < 0.05). There was no significant difference between the bortezomib-pretreated animals and those given bortezomib 1 h after LAD ligation. n, Number of dogs. *Times of death of the 5 dogs in the control group.

 

Figure 6
View larger version (25K):
[in this window]
[in a new window]

  		Fig. 6. The mean intrinsic rate (beats/min) for the fastest ventricular triplet observed in each dog during each hour for the 4- to 24-h period following LAD ligation in control (n = 14 dogs) and bortezomib-pretreated (n = 6 dogs) animals and those treated 1 h after LAD ligation (n = 6 dogs). The saline control group consistently had faster triplets compared with the bortezomib groups at the indicated time points (hours on the x-axis) (P < 0.05), which would put them at greater risk for developing monomorphic ventricular tachycardia and subsequent ventricular fibrillation.

 

   DISCUSSION
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
The EBZ tissue represents an important site for the genesis of fatal sustained VT and SCD during the 5–24-h period following CAL in the dog (7, 13, 15–17). We have previously reported a rapid and consistent decrease in GRK2 expression and activity in the EBZ tissue overlying the myocardial Inf in a canine model (23, 24). This decrease was evident by 6 h after ligation of the LAD and persisted up to 96 h. These changes were associated with an increase in the percentage of high-affinity β-adrenergic receptors (β-ARs) in the EBZ tissue and a loss in the ability of this tissue to desensitize normally to β-agonist stimulation of adenylyl cyclase activity. These observations help clarify the pathophysiology of this model of SCD and have major clinical implications, since they provide a rationale for the increased propensity of this tissue for β-AR agonist-stimulated proarrhythmic early and delayed after depolarizations (4, 11, 16, 17). GRK2 serves as one of several mechanisms for inhibiting maximal and/or sustained β-AR signal transduction (2, 3, 9, 19). A marked deficiency of GRK2 as observed in the EBZ tissues might be expected to exaggerate the risk for an electrophysiological myocardial event, and our previous studies are consistent with this understanding. Such an acquired tissue hypersensitivity to adrenergic agonists appears to be one of several potential biochemical mechanisms placing myocardial tissue at risk for such events. The loss of a β-AR modulator would support the clinical effectiveness of β-blockers when these pharmaceutical agents are used for first-line prevention of fatal cardiac arrhythmias (21). We have previously demonstrated that acute pretreatment of this animal model with the β-blocker nadolol markedly suppresses the malignant tachyarrhythmias and has a beneficial effect in preventing SCD (14, 16).

The effects of the proteasome inhibitor bortezomib on both ventricular tachyarrhythmias and the tissue expression of GRK2 were dramatic even when given 1 h after the induction of ischemia. There was a marked preservation of GRK2 in both the ischemic and infarcted tissues in the six animals. These data provide evidence that a window exists for the protection against GRK2 loss after an induction of ischemia. Suppression of whole blood proteasome activity appeared to be consistent in this animal model. Although there is compartmentalization of bortezomib in the body with less movement into the central nervous system, eyes, and testes (1), the whole blood concentration appears to reflect those in the heart, liver, and vascular tissues (unpublished data; Millennium Pharmaceuticals). The preservation of GRK2 expression in the Inf was only slightly less than that previously observed in animals given bortezomib during the preligation (–1 h) period. These data support the limited, early access of collateral blood flow to this central region, which eventually becomes the Inf as seen at 24 h after ligation.

The effect of bortezomib in preserving GRK2 in the EBZ again was accompanied by a dramatic decrease in the very rapid (>360 beats/min) and rapid (>300 beats/min) ventricular triplets observed during Holter monitoring. The GRK2 protective effect of proteasome inhibition was of greater magnitude than that observed when a similar group of dogs was pretreated with a TNF-{alpha} sequestrant etanercept (Enbrel; Amgen, Thousand Oaks, CA) (23). This marked preservation of GRK2 expression is concurrent with the dramatic protection against malignant triplets, which are highly associated with the onset of fatal tachyarrhythmias in this model. These data support the probability that GRK2 translocation to endosomal structures and/or a marked activation of the proteasome proteolytic pathway (18) may combine to account for the marked diminution of GRK2 protein expression in this animal model of human SCD and lead to increased sensitivity of the tissues to autonomic activity.

Another highly selective proteasome inhibitor PS-519 has been demonstrated to reduce reperfusion injury when given to a pig model (20). The Pye et al. (20) study, however, was directed toward an entirely different set of cellular functions, resulting in the reperfusion activation of apoptosis and cellular injury. This benefit was attributed to the suppression of NF-{kappa}B activation and reduced myocardial inflammation and subsequent reperfusion injury. Others have noted that proteasome inhibition leads to a variable effect on cardiomyocytes and to other cell lines. Interestingly, there are reports of proteasome inhibition enhancing cell death by increasing MAPK JNK and p38 activity and, at the same time, inhibiting this same activity by an induction of Hsp70(72). This leaves the cells to respond to opposing effects that are beneficial or detrimental to protection against apoptosis (12).

Since their report of suppression of kinase activity was just the opposite of our extensive data regarding GRK2, we looked for concordant or discordant changes in Hsp70(72) in our model for SCD. We found no significant correlation of changes in Hsp70(72) between bortezomib-treated and -untreated animals. Since these data were obtained at 24 h, it is possible that the induction of Hsp70(72) might have occurred during the early hours after LAD ligation. Since the GRK2 was maintained over the full 24 h and ischemia persisted, it is likely that any early changes in Hsp70(72) that would be protective and were not sustained would have been associated with a loss of GRK2. Since the proteasome pathway has already been associated directly with GRK2 degradation (2, 18), it is unlikely that Hsp70(72) has any significant effect on the protection of GRK2 or its activity.

The present studies continue to support the concept that acute, selective inhibition of the 20S proteasome may be a useful tool for examining pathophysiological sequelae of myocardial ischemia. Although the association of GRK2 preservation with antecedent proteasome inhibition was of interest, the present studies now directly support the concept that bortezomib or another inhibitor of proteasome activity may protect against the onset of malignant tachyarrhythmias and consequent SCD.

In summary, our data using in vivo infarcted hearts has repetitively shown a rapid and marked decrease of GRK2 activity and protein expression in the EBZ and subendocardial tissues adjacent to the Inf. Preservation of GRK2 is observed in both EBZ and Inf tissue when proteasome activity is inhibited before or 1 h after the induction of ischemia. This suggests that protection of GRK2 expression and activity in the myocardium may provide an alternative or complementary means for decreasing the occurrence of postischemic SCD.


   GRANTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
This study was supported by the Oklahoma Center for the Advancement of Science and Technology (to D. C. Kem and S. Huang), the Department of Veteran Affairs Medical Center, Oklahoma City, OK (to D. C. Kem and E. Patterson), the Cardiac Arrhythmia Research Institute, the American Heart Association Heartland Affiliate (to X. Yu), and private grants from Mrs. Doris Travis, Mr. and Mrs. Stan Ward, and Dr. and Mrs. William Talley. Millennium Pharmaceuticals provided the bortezomib used for this study.


   FOOTNOTES
 

Address for reprint requests and other correspondence: D. C. Kem, Dept. of Medicine, WP1345, 920 Stanton Young Blvd., Oklahoma City, OK 73104 (e-mail: david-kem{at}ouhsc.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.

* S. Huang and E. Patterson contributed equally to this work. Back


   REFERENCES
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

  1. Adams J, Palombella VJ, Sausville EA, Johnson J, Destree A, Lazarus DD, Maas J, Pien CS, Prakash S, Elliott PJ. Proteasome inhibitors: a novel class of potent and effective antitumor agents. Cancer Res 59: 2615–2622, 1999.[Abstract/Free Full Text]
  2. Aragay AM, Ruiz-Gomez A, Penela P, Sarnago S, Elorza A, Jimenez-Sainz MC, Mayor F Jr. G protein-coupled receptor kinase 2 (GRK2): mechanisms of regulation and physiological functions. FEBS Lett 430: 37–40, 1998.[CrossRef][Web of Science][Medline]
  3. Bunemann M, Hosey MM. G-protein coupled receptor kinases as modulators of G-protein signalling. J Physiol 517: 5–23, 1999.[Abstract/Free Full Text]
  4. Dangman KH, Dresdner KP Jr, Zaim S. Automatic and triggered impulse initiation in canine subepicardial ventricular muscle cells from border zones of 24-hour transmural infarcts. New mechanisms for malignant cardiac arrhythmias? Circulation 78: 1020–1030, 1988.[Abstract/Free Full Text]
  5. Gabai VL, Meriin AB, Mosser DD, Caron AW, Rits S, Shifrin VI, Sherman MY. Hsp70 prevents activation of stress kinases. A novel pathway of cellular thermotolerance. J Biol Chem 272: 18033–18037, 1997.[Abstract/Free Full Text]
  6. Gabai VL, Meriin AB, Yaglom JA, Wei JY, Mosser DD, Sherman MY. Suppression of stress kinase JNK is involved in HSP72-mediated protection of myogenic cells from transient energy deprivation. HSP72 alleviates the stewss-induced inhibition of JNK dephosphorylation. J Biol Chem 275: 38088–38094, 2000.[Abstract/Free Full Text]
  7. Harris AS. Delayed development of ventricular ectopic rhythms following experimental coronary occlusion. Circulation 1: 1318–1328, 1950.[Web of Science][Medline]
  8. Harris AS, Estandia A, Tillotson RF. Ventricular ectopic rhythms and ventricular fibrillation following cardiac sympathectomy and coronary occlusion. Am J Physiol 165: 505–512, 1951.[Free Full Text]
  9. Krupnick JG, Benovic JL. The role of receptor kinases and arrestins in G protein-coupled receptor regulation. Annu Rev Pharmacol Toxicol 38: 289–319, 1998.[CrossRef][Web of Science][Medline]
  10. Lightcap ES, McCormack TA, Pien CS, Chau V, Adams J, Elliott PJ. Proteasome inhibition measurements: clinical application. Clin Chem 46: 673–683, 2000.[Abstract/Free Full Text]
  11. Mehra R, Zeiler RH, Gough WB, El-Sherif N. Reentrant ventricular arrhythmias in the late myocardial infarction period. 9. Electrophysiologic-anatomic correlation of reentrant circuits. Circulation 67: 11–24, 1983.[Abstract/Free Full Text]
  12. Meriin AB, Gabai VL, Yaglom J, Shifrin VI, Sherman MY. Proteasome inhibitors activate stress kinases and induce Hsp72. Diverse effects on apoptosis. J Biol Chem 273: 6373–6379, 1998.[Abstract/Free Full Text]
  13. Opitz CF, Mitchell GF, Pfeffer MA, Pfeffer JM. Arrhythmias and death after coronary artery occlusion in the rat. Continuous telemetric ECG monitoring in conscious, untethered rats. Circulation 92: 253–261, 1995.[Abstract/Free Full Text]
  14. Patterson E, Lucchesi BR. Antifibrillatory actions of nadolol. J Pharmacol Exp Ther 223: 144–152, 1982.[Free Full Text]
  15. Patterson E, Scherlag BJ, Lazzara R. Arrhythmias in the canine heart two to twenty-four hours after myocardial infarction. In: Electrophysiology and Pharmacology of the Heart, edited by Dangman KH and Miura DS. New York: Marcel Dekker, 1991, p. 301–330.
  16. Patterson E, Scherlag BJ, Lazzara R. Mechanism of prevention of sudden death by nadolol: differential actions on arrhythmia triggers and substrate after myocardial infarction in the dog. J Am Coll Cardiol 8: 1365–1372, 1986.[Abstract]
  17. Patterson E, Scherlag BJ, Lazzara R. Prevention of spontaneous sustained ventricular tachycardia in the postinfarction dog by left stellate ganglionectomy. J Cardiovasc Electrophysiol 2: 238–248, 1991.[CrossRef]
  18. Penela P, Ruiz-Gomez A, Castano JG, Mayor F Jr. Degradation of the G protein-coupled receptor kinase 2 by the proteasome pathway. J Biol Chem 273: 35238–35244, 1998.[Abstract/Free Full Text]
  19. Pitcher JA, Freedman NJ, Lefkowitz RJ. G protein-coupled receptor kinases. Annu Rev Biochem 67: 653–692, 1998.[CrossRef][Web of Science][Medline]
  20. Pye J, Ardeshirpour F, McCain A, Bellinger DA, Merricks E, Adams J, Elliott PJ, Pien C, Fischer TH, Baldwin AS Jr, Nichols TC. Proteasome inhibition ablates activation of NF-{kappa}B in myocardial reperfusion and reduces reperfusion injury. Am J Physiol Heart Circ Physiol 284: H919–H926, 2003.[Abstract/Free Full Text]
  21. Reiter MJ, Reiffel JA. Importance of beta blockade in the therapy of serious ventricular arrhythmias. Am J Cardiol 82: 9I–19I, 1998.[CrossRef][Web of Science][Medline]
  22. Yu X, Huang S, Patterson E, Garrett MW, Kaufman KM, Metcalf JP, Zhu M, Dunn ST, Kem DC. Proteasome degradation of GRK2 during ischemia and ventricular tachyarrhythmias in a canine model of myocardial infarction. Am J Physiol Heart Circ Physiol 289: H1960–H1967, 2005.[Abstract/Free Full Text]
  23. Yu X, Patterson E, Huang S, Garrett MW, Kem DC. Tumor necrosis factor alpha, rapid ventricular tachyarrhythmias, and infarct size in canine models of myocardial infarction. J Cardiovasc Pharmacol 45: 153–159, 2005.[CrossRef][Web of Science][Medline]
  24. Yu X, Zhang M, Kyker K, Patterson E, Benovic JL, Kem DC. Ischemic inactivation of G protein-coupled receptor kinase and altered desensitization of canine cardiac beta-adrenergic receptors. Circulation 102: 2535–2540, 2000.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Cardiovasc ResHome page
X. Yu and D. C. Kem
Proteasome inhibition during myocardial infarction
Cardiovasc Res, October 4, 2009; (2009) cvp309v2.
[Abstract] [Full Text] [PDF]

Home page
 Cardiovasc ResHome page
O. Tsukamoto, T. Minamino, and M. Kitakaze
Functional alterations of cardiac proteasomes under physiological and pathological conditions
Cardiovasc Res, September 4, 2009; (2009) cvp282v2.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
J. M. Huber, A. Tagwerker, D. Heininger, G. Mayer, A. R. Rosenkranz, and K. Eller
The proteasome inhibitor Bortezomib aggravates renal ischemia-reperfusion injury
Am J Physiol Renal Physiol, August 1, 2009; 297(2): F451 - F460.
[Abstract] [Full Text] [PDF]

Home page
 Cardiovasc ResHome page
A. Kloss, S. Meiners, A. Ludwig, and B. Dahlmann
Multiple cardiac proteasome subtypes differ in their susceptibility to proteasome inhibitors
Cardiovasc Res, July 31, 2009; (2009) cvp217v2.
[Abstract] [Full Text] [PDF]

Home page
 FASEB J.Home page
Z. P. Cai, Z. Shen, L. Van Kaer, and L. C. Becker
Ischemic preconditioning-induced cardioprotection is lost in mice with immunoproteasome subunit low molecular mass polypeptide-2 deficiency
FASEB J, December 1, 2008; 22(12): 4248 - 4257.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
294/3/H1298    most recent
00765.2007v1
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 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 Google Scholar
Google Scholar
Right arrow Articles by Huang, S.
Right arrow Articles by Kem, D. C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Huang, S.
Right arrow Articles by Kem, D. C.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online
Copyright © 2008 by the American Physiological Society.