Oestrogen protects against Efavirenz-mediated endothelial cell dysfunction

Peter Keltie1, Jon Mabley2
1Brighton & Sussex Medical School, Brighton, East Sussex, United Kingdom, 2Brighton University, Brighton, East Sussex, United Kingdom

Highly Active Anti-Retroviral Therapy (HAART) has proved very successful in reducing morbidity and mortality associated with HIV infection. However, this extension of lifespan has revealed side effects associated with HAART including cardiovascular dysfunction with HIV patients on HAART becoming the fastest growing population with cardiovascular disease. Pre-menopausal women are have a lower incidence of cardiovascular disease as compared to men and this also applies to HIV infected women on HAART who have a lower incidence of cardiovascular side effects as compared to HIV infected men on HAART. Efavirenz, a non-nucleoside reverse transcriptase inhibitor, has been shown to cause endothelial cell dysfunction via increased oxidative stress causing DNA single strand breaks, over-activating the DNA repair enzyme poly (ADP-ribose) polymerase (PARP) with subsequent decrease in cellular levels of high energy phosphates and NAD.

The aim of this study was to examine whether oestrogen could protect against efavirenz-mediated endothelial cell function.

Thoracic aorta isolated from male Sprague-Dawley rats (180-220g) was cut into rings and exposed to the efavirenz (10 μM)±oestrogen (0.1 μM) ex vivo for 4h. Following this incubation the aortic rings were mounted in organ baths filled with warmed and oxygenated Krebs solution with isometric tension measured with isometric transducers and digitized using PowerLab. The contractile response (to phenylepherine) and relaxant response (to acetylcholine) was determined. Mouse endothelial cells were exposed to efavirenz (10 μM)±oestrogen (0.1 μM) for 4h prior to PARP activation being determined directly by measuring tritiated NAD incorporation into proteins.

Efavirenz-induced endothelial cell dysfunction was significantly (p<0.05 efavirenez alone vs. efavirenez plus oestrogen by analysis of variance with Bonferroni’s correction) reversed by oestrogen treatment. Efavirenz-mediated PARP activation in endothelial cells was also attenuated by oestrogen treatment. Aortic rings isolated from female Sprague-Dawley rats were found to be resistant to efavirenz-mediated dysfunction. Oestrogen’s protective effect was attenuated by BSO suggesting that oestrogens protection is via increased cellular glutathione reducing efavirenz-mediated oxidative stress and subsequent PARP activation.



In conclusion, oestrogen may be the protective factor that reduces HAART-mediated cardiovascular side effects in women.