Fenótipo senescente em células mesenquimais no contexto da obesidade

Abstract

Obesity represents a highly prevalent chronic metabolic disease associated with the development of comorbidities that shorten lifespan. Loss of physiological homeostasis and organismal functional decline are central features of aging reflected on obesity, permeated by a low-grade chronic and systemic inflammatory state. Similarities between both processes suggest overlapped mechanisms driving their progression, being the central role of cellular senescence highlighted, alongside metabolic and morphological alterations. At the same time, it is observed the development of the senescence associated secretory phenotype (SASP), composed of pro-inflammatory, growth, and tissue remodeling factors, thus implicated on senescence spread and sustained chronic inflammation. Adipose tissue dysfunction is a hallmark of obesity related to functional decline of adipose-derived stem cells (ADSC) due to senescence. While ADSC play a key role in regulating tissue homeostasis, little is known regarding the mechanisms that modulate their premature senescence in the obesity context. In this sense, the present study aimed to evaluate cellular and molecular senescence-related characteristics on hADSC exposed to the plasma environment of individuals with obesity. To do so, hADSC cultures were treated for 10 to 18 days with medium supplemented with plasma from individuals with obesity (PO group), or with plasma from eutrophic individuals (PE group), or without plasma (control group). PO group presented a reduced proliferative index compared to the other groups, which was associated with cell cycle arrest in G2 and augmented expression of CDKN1A (p21) at 10 days of treatment, followed by augmented expression of CDKN2A (p16) at 18 days of treatment, denoting permanent cell cycle arrest. Furthermore, it was observed increased activity of the senescence-associated β-galactosidase (SA-β-gal) enzyme at the end of both timepoints, being demonstrated a positive correlation between its activity and TRF1 protein expression at 10 days of treatment. Considering the absence of differences in H2AX phosphorylation levels, a marker of DNA damage, we evaluated the activation of p38-MAPK, improved on PO group compared to the others. In line with this result, we demonstrated augmented activation of nuclear factor B (NF-B) on PO group, a target of p38-MAPK modulatory pathway, which in turn was associated with increased secretion of IL-6 and IL-8, SASP factors, at both time points. The data here presented reinforce the hypothesis that the inflammatory environment observed in obesity can evoke cellular alterations related to senescence phenotype establishment. We speculate that the establishment and perpetuation of cellular senescence in hADSC might be related to the activation of the p38-MAPK/NF-κB axis, thus related to the upregulation of SASP.