We hypothesized that the interaction between tumor necrosis factor alpha (TNF)/nuclear factor-B (NFB) via activation of IKK may amplify one another resulting in the evolution of vascular disease and insulin resistance associated with diabetes. To test this hypothesis, endothelium-dependent (ACh) and -independent (SNP) vasodilation of isolated, pressurized coronary arterioles from mLepr^db (heterozygote, normal), Lepr^db (homozygote, diabetic) and Lepr^db mice null for TNF (db^TNF-/db^TNF-) were examined. Although dilation of vessels to SNP was not different between Lepr^db and mLepr^db mice, dilation to ACh was reduced in Lepr^db mice. The NFB antagonist, MG-132, or IKK inhibitor, sodium salicylate (NaSal), partially restored NO-mediated endothelium-dependent coronary arteriolar dilation in Lepr^db mice, but the responses in mLeprdb mice were unaffected. Protein expression of IKK and IKK were higher in Lepr^db than in mLepr^db mice; the expression of IKK, but not the expression of IKK, was attenuated by MG-132, the antioxidant apocynin, or in db^TNF-/db^TNF- mice. Lepr^db mice showed increased insulin resistance, but NaSal improved insulin sensitivity. Protein expression of TNF and NFB, and protein modification of p-IKK and p-JNK were greater in Lepr^db mice, but NaSal attenuated TNF, NFB, p-IKK and p-JNK in Lepr^db mice. The ratio of phosphorylated IRS-1 at Ser307 (p-IRS-1)/IRS-1 was elevated in Lepr^db compared with mLeprdb mice; both NaSal and JNK inhibitor SP600125 reduced p-IRS-1/IRS-1 in Lepr^db mice. MG-132 or neutralization of TNF reduced superoxide production in Lepr^db mice. In conclusion, our results indicate that the interaction between NFB and TNF signaling induces activation of IKK and amplifies oxidative stress, leading to endothelial dysfunction in type 2 diabetes.