abacavir and Atherosclerosis

: There is a long-lasting controversy surrounding an association between abacavir (ABC) and an increased risk of cardiovascular disease in HIV-positive patients. Although differing in their specifics, a number of published cohort studies and clinical trials support such an association, usually relating it to recent exposure to the drug, independently of traditional predisposing factors. However, other clinical trials have failed to reveal such a relation and have pointed to methodological differences to explain discrepancies. Significantly, the controversy has been fueled by the lack of a credible mechanism of action to justify the putative detrimental actions of ABC. There is a myriad of contradictory clinical indicators which are not clearly compatible with known profiles of either vascular physiopathology or pharmacological interference. However, basic research has recently hinted at altered homeostatic mechanisms, though this requires clinical validation. In particular, recurrent evidence - both clinical and experimental - relates ABC with vascular inflammation, a leading contributor to the atherosclerotic plaque and thrombosis. ABC's chemical structure is very close to that of endogenous purines (ATP, ADP and AMP), major paracrine signaling molecules capable of triggering prothrombotic and proinflammatory vascular programs. Other proposed mechanisms are a competitive inhibition of guanylyl cyclase in platelets and a subsequent decrease in cyclic guanosine monophosphate (cGMP). The present review aims to shed light on this complex subject by summarizing and critically evaluating all the available clinical data regarding a relationship between ABC and cardiovascular disease, and to put forward potential pharmacological explanations compatible with both the clinical scenario and experimental findings.

Topics: Anti-HIV Agents; Atherosclerosis; Cardiovascular Diseases; Dideoxynucleosides; HIV Infections; Humans; Vasculitis

Several reports have indicated that patients with low CD4+ cell count could be at a higher risk for arterial lesions or cardiovascular disease (CVD). Recently, current use of abacavir has been associated with an excess risk of CVD. High sensitivity-C-reactive protein and interleukin-6 levels were high for patients receiving the drug. These data lead to the hypothesis that alternative mechanisms may be at work other that those linked to lipid changes and "classic" risk factors for atheroma. Consequently, we investigated the ultrasound characteristics of carotid plaques in HIV-positive patients comparing the results with those obtained from patients affected by atherosclerosis and patients with arteritis. The study population included 110 HIV-positive patients and 91 HIV-negative patients (61 atherosclerotic patients and 30 with arteritis). All patients were subjected to ultrasonography of the epi-aortic vessels. When compared to atherosclerotic patients, there was a significantly higher proportion of HIV-positive patients with hypoechogenic and homogeneous lesions, uniform in their parietal and endoluminal portions with a smooth or slightly irregular surface. No significant differences were found between HIV-positive and arteritis patients. This ultrasonographic study confirms that inflammatory mechanisms could play a major role in the onset of vascular damage in HIV-1 positive patients.

Topics: Adult; Anti-HIV Agents; Arteritis; Atherosclerosis; C-Reactive Protein; Dideoxynucleosides; Female; HIV Infections; Humans; Interleukin-6; Male; Middle Aged; Ultrasonography