LGR4 in HIV-associated atherosclerosis - PROJECT SUMMARY Atherosclerotic cardiovascular disease (ASCVD) is the second leading cause of non-AIDS-related mortality among people living with human immunodeficiency virus (HIV) (PLWH). The number of PLWH is continuously growing due to the viral suppression and life-extending benefits of available antiretroviral therapy (ART). However, the PLWH, even on effective ART with undetectable viral loads as well as elite HIV controllers who are ART-naïve and aviremic, exhibit sustained systemic inflammation and accelerated atherogenesis. Accumulated evidence suggests an important role of persistent macrophage (Mɸ) activation in controlled HIV- induced ASCVD and significant transcriptional heterogeneity among Mɸs within atherosclerotic lesions. Moreover, recent research indicates the involvement of Mɸ-derived extracellular vesicles in regulating neighboring non-HIV-infected Mɸ lipid metabolism, phenotype, foam cell formation, and atherogenesis. However, the precise molecular mechanisms linking controlled HIV infection to Mɸ activation and accelerated atherosclerosis remain poorly understood. Our preliminary experiments utilizing an experimental EcoHIV/NDK model, which mimics the physiological conditions of aviremic patients on effective ART, demonstrate increased atherosclerosis following infection. Furthermore, treatment with conditioned media (CM) collected from HIV- infected Mɸs induces expression of leucine-rich repeat-containing GPCR (LGR) 4 at both transcription and translational levels in non-infected murine primary Mɸs. Notably, Lgr4 upregulation induced by HIV-infected Mɸ CM was significantly higher than that promoted by oxidized LDL, a well-known atherogenic agent. Consistently, LGR4 levels are elevated in human atherosclerotic aortic segments compared with non-atherosclerotic tissue, and in atherosclerotic lesional Mɸs of EcoHIV-infected mice. Additionally, CM-treated Mɸs exhibit increased lipid accumulation (foam cell formation), augmented inflammation, and impaired efferocytosis. Nevertheless, the role of Mɸ Lgr4 in regulating HIV-regulated efferocytic potential, inflammation, and atherosclerosis is unknown. Based on these findings, we hypothesize that controlled HIV infection accelerates atherosclerosis via Mɸ LGR4- mediated signaling. This hypothesis will be tested with the two independent specific aims investigating whether (1) LGR4 mediates HIV-regulated Mɸ foam cell formation and efferocytic capacity, and (2) controlled HIV infection contributes to atherosclerosis via Mɸ LGR4-mediated signaling. Myeloid-cell specific Lgr4-deficient mice, an LGR4-signaling inhibitory peptide, unbiased single-cell RNA sequencing, and atherosclerotic lesion analysis will be employed to test the hypothesis. The successful completion of the proposed studies will provide novel insights into the mechanisms governing accelerated atherosclerosis in aviremic PLWH and identify novel therapeutic targets. To ensure the success of the proposed studies, we have assembled a multidisciplinary team comprising a collaborator and consultants, and are well-positioned to have all the required key resources.
