Overexpression of mitochondrial antioxidant manganese superoxide dismutase (MnSOD) provides protection against AZT- or 3TC-induced endothelial dysfunction

Abstract

Nucleoside reverse transcriptase inhibitors (NRTIs) are considered the backbone of current combination therapies for HIV. These therapies have significantly decreased mortality and morbidity in HIV-infected patients, but some are associated with cardiovascular complications, including endothelial dysfunction, an early marker for atherosclerosis. Our prior studies demonstrated that co-treatment of cells with an antioxidant therapy reversed NRTI-induced endothelial injury. Thus, as a proof of concept that mitochondrially-targeted antioxidants may be useful in preventing NRTI toxicity, in the current study, mice overexpressing a mitochondrial antioxidant, manganese superoxide dismutase (MnSOD), were compared with wild-type (WT) mice. Mice were treated chronically with either zidovudine (AZT), lamivudine (3TC), or tenofovir (TDF) to determine whether overexpression of MnSOD protected them from endothelial dysfunction. Endothelial function was assessed using vessel reactivity experiments on thoracic aortas as well as measures of endothelium derived factors nitric oxide (NO), endothelin-1 (ET-1), and prostacyclin. Oxidative stress was evaluated as levels of plasma 8-isoprostane. Alterations in vessel reactivity, NO, and ET-1 in WT mice treated with AZT or 3TC were noted. Overexpression of MnSOD offered protection from decreases in vessel reactivity and increases in ET-1. These findings indicate that mitochondrial oxidative stress induced by AZT or 3TC plays a major role in mediating NRTI-induced endothelial dysfunction, and suggest that the use of targeted antioxidants administered in conjunction with NRTIs may attenuate these effects.

Keywords: Antioxidants; Atherosclerosis; Endothelial dysfunction; NRTI.

Figure 1

Plasma 8-isoprostane levels in wild-type (WT) and transgenic mice overexpressing MnSOD (MnSOD Tg). Mice were treated for 6-8 weeks with AZT (100 mg/kg/day), 3TC (50 mg/kg/day), or TDF (50 mg/kg/day) and plasma levels of 8-isoprostane were compared with controls. Data are means ± standard deviation. * Denotes significant difference (p < 0.05) from matched controls. # Indicates significant difference (p < 0.05) between treated MnSOD Tg and treated WT. n = 5/group.

Figure 2

Plasma nitrite levels in wild-type (WT) and transgenic mice overexpressing MnSOD (MnSOD Tg). Mice were treated for 6-8 weeks with AZT (100 mg/kg/day), 3TC (50 mg/kg/day), or TDF (50 mg/kg/day) and plasma nitrite levels were compared with controls. *P < 0.05 compared to matched controls. Data are means ± SD. #p < 0.05 between treated MnSOD Tg and treated WT. n = 5-7/group, as indicated within each bar.

Figure 3

Plasma 6-keto prostaglandin F1 levels in wild-type (WT) and transgenic mice overexpressing MnSOD (MnSOD Tg). Mice were treated for 6-8 weeks with AZT (100 mg/kg/day), 3TC (50 mg/kg/day), or TDF (50 mg/kg/day) and plasma 6-keto prostaglandin F1 levels were compared with controls. Data are means ± SD. *Significance (p < 0.05) compared to matched controls. #p < 0.05 between treated MnSOD Tg and treated WT. n = 5/group.

Figure 4

Plasma ET-1 levels in wild-type (WT) and transgenic mice overexpressing MnSOD (MnSOD Tg). Mice were treated for 6-8 weeks with AZT (100 mg/kg/day), 3TC (50 mg/kg/day), or TDF (50 mg/kg/day) and plasma ET-1 levels were compared with controls. Data are means ± SD. *Denotes significance (p < 0.05) compared to matched controls. # Indicates p < 0.05 between treated MnSOD Tg and treated WT. n = 5/group.

Figure 5

Endothelium-dependent vasorelaxation in wild-type (WT) and transgenic mice overexpressing MnSOD (MnSOD Tg). Mice were treated for 6-8 weeks with AZT (100 mg/kg/day), 3TC (50 mg/kg/day), or TDF (50 mg/kg/day) and endothelium-dependent vasorelaxation results were compared with controls. Data are means ± SD. *Denotes p < 0.05 compared to matched controls. #Indicates significant difference (p < 0.05) between treated MnSOD Tg and treated WT. n = 4-9/group, as indicated within each bar.