Nordihydroguaiaretic acid (NDGA) inhibits ritonavir-induced endothelial dysfunction in porcine pulmonary arteries

BACKGROUND HIV infection and treatment with highly active antiretroviral therapy (HAART) including HIV protease inhibitor ritonavir (RTV) have been associated with endothelial dysfunction and cardiovascular disease including pulmonary arterial hypertension. The objective of this study was to determine if nordihydroguaiaretic acid (NDGA), a natural herbal antioxidant found in the creosote bush Larrea tridentate, can protect vascular tissues against RTV-induced vascular injury. MATERIAL/METHODS Fresh porcine pulmonary artery (PA) rings were treated with a clinically relevant concentration of RTV (15 µmol/L) with or without NDGA for 24 hours, and then subjected to myograph analysis for vasomotor reactivity. Expression of endothelial nitric oxide synthase (eNOS) in both treated PA rings and human pulmonary artery endothelial cells (HPAECs) was analyzed by real-time PCR and immunohistochemistry. Oxidative stress levels were analyzed with the lucigenin-enhanced chemiluminescence and glutathione assay. RESULTS In response to bradykinin at 10-10 mol/L, RTV-treated PA rings showed a 39% reduction in endothelium-dependent vasorelaxation compared with the control vessels (P<0.05); when co-cultured with NDGA (1.75 or 3.50 µmol/L), the relaxation increased by 25% and 48%, respectively. RTV also decreased the maximal contraction and endothelium-independent vasorelaxation in RTV-treated vessels, while NDGA improved these vasomotor responses. In addition, treatment of RTV significantly decreased eNOS mRNA levels in both porcine PAs and HPAECs, and reduced eNOS immunoreactivity in porcine PAs, while NDGA significantly inhibited this effect of RTV. Furthermore, NDGA significantly blocked RTV-induced increase of superoxide anion in the PA rings and inhibited RTV-induced decrease of glutathione in HPAECs. CONCLUSIONS NDGA effectively inhibits the detrimental effects of HIV protease inhibitor RTV on vasomotor functions in porcine PAs. NDGA also blocks RTV-induced decrease of eNOS expression and increase of oxidative stress in both porcine PAs and HPAECs. This study may provide valuable information for the development of effective strategies for the prevention and treatment of HAART-associated cardiovascular complications.