Publications

The transition from acute to chronic pain states might be the most important challenge in research to improve clinical treatment of debilitating pain. We describe a recently identified mechanism of neuronal plasticity in primary afferent nociceptive nerve fibers (nociceptors) by which an acute inflammatory insult or environmental stressor can trigger long-lasting hypersensitivity of nociceptors to inflammatory cytokines. This phenomenon, "hyperalgesic priming," depends on the epsilon isoform of protein kinase C (PKCepsilon) and a switch in intracellular signaling pathways that mediate cytokine-induced nociceptor hyperexcitability. We discuss the impact of this discovery on our understanding of, and ultimately our ability to treat, a variety of enigmatic and debilitating pain conditions, including those associated with repetitive injury, and generalized pain conditions, such as fibromyalgia.

BACKGROUND

HIV-infected patients have accelerated atherosclerosis. Abacavir has been associated with increased risk of cardiovascular events, for reasons that remain to be elucidated. As endothelial dysfunction is central to the pathogenesis of atherosclerosis, we tested the hypothesis that current treatment with abacavir is associated with impaired endothelial function.

METHODS

We studied a cohort of 61 antiretroviral-treated patients who had undetectable plasma HIV RNA levels. Endothelial function was assessed by measuring flow-mediated dilation (FMD) of the brachial artery. We compared FMD in patients treated with or without abacavir, while adjusting for traditional risk factors and HIV-specific characteristics.

RESULTS

The median age was 50 years (interquartile range 45-57). The median duration of HIV infection was 18 years, and the median CD4 cell count was 369 cells/microl. Thirty patients (49%) were receiving abacavir. Overall, the median FMD in the HIV-infected patients was low (3.5%; interquartile range 2.3-5.6%). The FMD was lower in the abacavir-treated patients than those not on abacavir (2.8 vs. 4.9%, P = 0.01). After adjustment for traditional risk factors, HIV-specific factors, and baseline brachial artery diameter, current abacavir use was independently associated with lower FMD (P = 0.017). Duration of therapy and CD4 cell count were not associated with reduced FMD.

CONCLUSION

Endothelial function, a central mechanism in atherosclerosis and a marker of cardiovascular risk, is impaired among antiretroviral-treated patients with undetectable viral loads. Current use of abacavir was independently associated with impaired endothelial function. This finding suggests that abnormal endothelial function may underlie the clinically observed increased risk in myocardial infarction among abacavir-treated patients.