Effect of PAR2 in regulating TNF-alpha and NAD(P)H oxidase in coronary arterioles in type 2 diabetic mice

Protease-activated receptor-2 (PAR2) is expressed in endothelial cells and mediates endothelium-dependent vasodilation. We hypothesized that PAR2 regulates tumor necrosis factor-alpha (TNF-alpha)-induced coronary arteriolar dysfunction in type 2 diabetic (db/db) mice. To test this, coronary arterioles from WT control, db/db, db/db mice treated with PAR2 antagonist FSLLRY-NH2 (db/db+FSLLRY-NH2) and db/db mice null for TNF (db(TNF-)/db(TNF-)) were isolated and pressurized (60 cmH(2)O) without flow. Although vasodilation to the endothelium-independent vasodilator sodium nitroprusside (SNP) was not different among WT, db/db, db/db+FSLLRY-NH2 and db(TNF-)/db(TNF-), endothelium-dependent acetylcholine (ACh)- and flow-mediated vasodilation were impaired in db/db mice but were enhanced in db(TNF-)/db(TNF-) mice and db/db mice treated with PAR2 antagonist. NOS inhibitor N-G-nitro-L-arginine-methyl ester (L-NAME) significantly reduced ACh-induced dilation in WT, db(TNF-)/db(TNF-) and db/db+FSLLRY-NH2, but did not alter the vasodilation in db/db mice. In contrast, cyclooxygenase (COX) inhibitor indomethacin (Indo) did not alter ACh-induced vasodilation in these four groups of mice. PAR2-activating peptide (PAR2-AP, 2-Furoyl-LIG-RLO-am)-induced dilation was higher in db/db mice than that in WT, db(TNF-)/db(TNF-) and db/db mice treated with PAR2 antagonist. These effects were abolished by denudation, or in the presence of L-NAME or Indo. Protein expressions of TNF-alpha, PAR2, gp91(phox) and p47(phox) in the heart and isolated coronary arterioles were higher in db/db mice compared to WT mice. Administration of PAR2 antagonist to db/db mice reduced protein expression of TNF-alpha, gp91(phox) and PAR2. Protein expression of gp91(phox) and p47(phox) was lower in db(TNF-)/db(TNF-) compared to db/db mice. These results indicate that PAR2 plays a pivotal role in endothelial dysfunction in type 2 diabetes by up-regulating the expression/production of TNF-alpha and activating NAD(P)H oxidase subunit p47(phox).