Human immunodeficiency virus (
HIV) infection is an independent risk factor for
cardiovascular disease. This risk is magnified by certain antiretrovirals, particularly the
protease inhibitor ritonavir, but the pathophysiology of this connection is unknown. We postulated that a major mechanism for antiretroviral-associated
cardiac disease is pathologic
fibrosis linked to platelet activation with release and activation of
transforming growth factor (TGF)-β1, and that these changes could be modeled in a murine system. We also sought to intervene utilizing inhaled
carbon monoxide (CO) as proof-of-concept for
therapeutics capable of regulating TGF-β1 signaling and
collagen autophagy. We demonstrate decreased cardiac function indices, including cardiac output, ejection fraction and stroke volume, and prominent cardiac
fibrosis, in mice exposed to pharmacological doses of
ritonavir. Cardiac output and
fibrosis correlated with plasma TGF-β1 levels. Mice with targeted deletion of TGF-β1 in megakaryocytes/platelets (PF4CreTgfb1flox/flox) were partially protected from
ritonavir-induced cardiac dysfunction and
fibrosis. Inhalation of low dose CO (250ppm), used as a surrogate for upregulation of inducible
heme oxygenase/endogenous CO pathways, suppressed
ritonavir-induced cardiac
fibrosis. This occurred in association with modulation of canonical (Smad2) and non-canonical (p38) TGF-β1 signaling pathways. In addition, CO treatment suppressed the M1 pro-inflammatory subset of macrophages and increased M2c regulatory cells in the hearts of RTV-exposed animals. The effects of CO were dependent upon autophagy as CO did not mitigate
ritonavir-induced
fibrosis in autophagy-deficient LC3-/- mice. These results suggest that platelet-derived TGF-β1 contributes to
ritonavir-associated cardiac dysfunction and
fibrosis, extending the relevance of our findings to other antiretrovirals that also activate platelets. The anti-fibrotic effects of CO are linked to alterations in TGF-β1 signaling and autophagy, suggesting a proof-of-concept for novel interventions in HIV/antiretroviral
therapy-mediated
cardiovascular disease.