P746Protective role of the longevity associated variant of BPIFB4 in chronic ischemia

Abstract

Abstract Background A rare Longevity Associated Variant (LAV) of the gene BPIFB4, whose protein product can be secreted, is recessively associated with extreme longevity, positively impacting the cardiovascular system and promoting therapeutic angiogenesis in an hindlimb ischemia model. Aim Aim of this work is to verify if LAV-BPIFB4 may temper the phenotype of chronic ischemia in humans, thus suggesting its therapeutic potential. Methods and results 39 hearts explanted from patients affected by end-stage ischemic heart disease were studied. Of these, 7 were homozygous for BPIFB4-LAV. Homozygous and non-homozygous patients did not differ in sex, age and in the prevalence of comorbidities or risk factors. However, the time elapsed from myocardial infarction to transplantation was significantly longer for LAV homozygous with respect to LAV heterozygous patients (159±95 vs 58±27 months, p=0.045). Histologically, while BPIFB4 levels did not differ in accordance with the genotype, the fraction of Tunel+and 53BP1+apoptotic and senescent myocytes was significantly lower in homozygous patients (1.2±0.4% vs 23.8±21.7%, p=0.026 and 31.5±6.7% vs 44.4±6.1%, p=0.031, respectively). Significantly lower levels of lipoperoxides and higher levels of Parkin were observed in homozygous hearts too. Next, we directly tested the role of BPIFB4 on PDGFRb+ NG2+Tbx18+cardiac pericytes/mural cells (PM) cultured from normal atria (PMnorm, n=10) and from ischemic failing hearts (PMfail, n=7). BPIFB4 gene transcript was significantly more expressed in PMnorm than PMfail. Silencing BPIFB4 expression in PMnorm significantly increased the proportion of senescent gH2AX+Ki67-cells (3.6±2.9% vs 13.6±9.5%, p=0.049). Conversely, addition of recombinant LAV BPIFB4 protein to PMfail cultures significantly reduced the rate of senescent cells (21.1±9.4% vs 6.0±4.8%, p=0.03), an effect that was not observed with the administration of WT BPIFB4. PMfail cultures exposed to LAV BPIFB4 significantly reversed alterations observed with pathology, such as the accumulation of both lipofuscins and of very elongated and interconnected mitochondria in the cell cytoplasm, as well as elevated mitochondrial superoxide anion levels. Finally, a larger fraction of PMnorm cells showed, with respect to PMfail, the nuclear translocation of vitamin D receptor (74.6±6.1% vs 50.1±14.4, p=0.04), coupled with a significant upregulation of its, longevity associated, target gene Klotho. Importantly, LAV BPIFB4 significantly increased the fraction of PMfail with vitamin D receptor nuclear localization (55.8±17.6% vs 85.1±8.2%, p=0.005). Conclusion LAV BPIFB4 could attenuate the progression of ischemic heart disease to heart failure. Part of its protective effect may be due to its ability to reduce mitochondrial oxidative stress and to revert the senescent phenotype of cardiac derived cells. Acknowledgement/Funding CARIPLO foundation