Murine transfer of a human gene variant associated with exceptional longevity displays senolytic effects both in immune compartment and endothelium of aged mice

Abstract

Abstract The persistence and accumulation of senescent cells has been shown to potentially play a role in the pathophysiology of age-related cardiovascular diseases. Indeed with time, a decline in immune efficacy, termed immunesenescence, and a deleterious secretory phenotype of senescent cells (SASP) generate that inflammatory background mainly mediating the elderly cardiovascular phenotype. Long Living Individuals (LLI) which delay aging, represent a model of positive biology and an exceptional resource to study and find a way to improve general public health. Previous studies from our group have shown that a human gene associated with exceptional longevity (LAV-BPIFB4) was able to block the atherosclerotic process in ApoE−/− mice by conferring the animals with a pro-resolving M2 macrophages profile. Furthermore, LAV-BPIFB4 promotes the recruitment of hematopoietic stem cells, reparative vascularization and frailty reduction. Here we sought to underpinn the role of LAV-BPIFB4 in counteracting the age-related remodeling of the immune responses. The effects of systemic adeno-associated viral vector-mediated LAV-BPIFB4 gene transfer on the immune dynamics in old mice have been investigated by an extensive flow cytometric approach in lymphoid tissues (bone marrow, spleen and peripheral blood). C57BL/6J mice were assigned to two age-matched experimental groups: a treatment group (AAV-LAV-BPIFB4; N=6 mice, aged 18–23 months and a control group (AAV-GFP; N=6 mice, aged 18–23 months. 30th and 60th day since the beginning of the infection, SA-beta Gal substrate has been used to identify CD45+ senescent cells in freshly isolated PBMC, splenocytes, bone marrow (BM)-derived cells. As expected, we monitored an increase in SA-betaGal activity in blood. This increase is most significant in CD11b+ myeloid cells, whithout affecting neither CD3+T neither NK1.1+Natural Killer (NK) cell compartment. Notably 30 days AAV-LAV-BPIFB4 infection and to a more the 60 days-treatment, resulted in a significant decrease in senescent pool of peripheral immune cells and a concomitant enrichment of senescent cells in spleen. Concomitantly, aorta from AAV-LAV treated mice showed significant reduction in SA-beta Gal positive area. Furthermore a LAV-BPIFB4 induction of pro-resolving M2 macrophages compared to control group was documented in the main haemocateretic organ. As consequence the senolytic effect of LAV-BPIFB4 gene-therapy well correlated with the rescue of proliferative index of splenocytes upon PHA stimulation, and their functional protective response to lipopolysaccharide (LPS) in term of IL-6 and TNF-alpha secretion. The restoration of a protective and balanced immune response finally reflected the reduction of senescent phenopype acquired by mouse aortic endothelial cells during the aging process in vivo. A better underpinning of the senolytic action of LAV-BPIFB4 may offer a valuable therapeutic tool to reverse aging phenotype causing most of cardiac diseases Funding Acknowledgement Type of funding source: Private company. Main funding source(s): Cariplo Foundation (n.2016-0874) to AAP and CV