HIV Tat protein causes endothelial dysfunction in porcine coronary arteries

Purpose: Human immune deficiency virus (HIV) infection is often associated with chronic diseases, including atherosclerosis. However, the molecular mechanisms are largely unknown. We examined the effect of Tat protein, an HIV regulatory protein, on endothelial function in porcine coronary arteries. Methods: Porcine coronary arteries were dissected from nine pig hearts and cut into 5-mm ring segments, which were incubated as controls or with Tat protein (10 ^-7, 10 ^-9, 10 ^-11 mol/L) or Tat protein plus anti-Tat antibody, for 24 hours. Myography was performed with thromboxane A ₂ analog U46619 (10 ^-7 mol/L) for contraction and with graded doses of bradykinin (10 ^-8, 10 ^-7, and 10 ^-6 mol/L) or sodium nitroprusside (10 ^-5 mol/L) for relaxation. Endothelial nitric oxide synthase (eNOS) messenger RNA was determined with reverse transcriptase polymerase chain reaction (RT-PCR), and protein levels were determined with Western blot analysis. Immunoreactivity of eNOS of treated rings was also detected. Results: Endothelium-dependent vasorelaxation (10 ^-7 mol/L of bradykinin) was significantly reduced (46.41%) in pig coronary artery rings treated with 10 ^-7 mol/L of Tat protein, as compared with control arteries (P < .05). Arteries treated with Tat protein plus anti-Tat antibody relaxed similarly as control arteries. There were no differences in smooth muscle contractility (U46619) or endothelium-independent vasorelaxation (sodium nitroprusside) between control and Tat protein-treated groups. RT-PCR for eNOS mRNA showed reduction in eNOS levels for Tat-treated coronary artery rings by 73%, as compared with control vessels (P < .05). Tat protein-treated vessels demonstrated substantially less eNOS protein band intensity and immunoreactivity compared with control vessels. Conclusions: Tat protein significantly decreased endothelium-dependent vasorelaxation and eNOS mRNA and protein expression in endothelial cells of porcine coronary arteries. This study suggests that Tat protein-mediated endothelial dysfunction may be important in coronary heart disease in HIV-infected patients.