[Pulmonary arterial hypertension related to HIV: is inflammation related to IL-6 the cornerstone?]

Vascular diseases have become the leading cause of mortality in the population treated for HIV infection. Pulmonary arterial hypertension (PAH) related to HIV (PAH-HIV), the fourth cause of PAH in France, has the same histological pattern as other PAH from the group 1 of Dana Point classification. But, conversely to idiopathic PAH in the general population, PAH-HIV is particular by its high frequency in HIV-infected population. This raises the question for the role of inflammation in the PAH-HIV pathophysiology. Its constant occurrence over the decades, despite introduction of combination antiretroviral therapy (CAT), does not preclude the hypothesis of an involvement of inflammation in the genesis of PAH-HIV. Indeed, it is well known that normalization of CD4+ by the CAT does not mean no inflammation. Especially, it persists an increased and continuous production of IL-6, a main cytokine in the genesis of PAH lesions. This inflammation mainly involves the endothelin-1 pathway, which has an action on endothelium and macrophages, leading to high production of IL-6. Moreover, plasmatic level of IL-6 has a prognostic value in PAH-HIV, independently from conventional (functional or hemodynamic) parameters. The use of endothelin receptor antagonist permits major effect on IL-6 production and dramatic effect on PAH in so-called "bosentan responders".