ROLE OF SIRTUIN 1 IN CD4+ T CELLS ACTIVATION AND DIFFERENTIATION IN A MURINE MODEL OF OBESITY AND TRANSPLANTATION

Author(s)

Omar Alberto Dominguez Amorocho

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2022-02-11

Examining board members

Niels Olsen Saraiva Câmara; Carlos José Escande Castro; Pablo José Fernández Marcos; João Santana da Silva

• Advisor: Niels Olsen Saraiva Câmara; Vinicius de Andrade Oliveira

Abstract

Histone deacetylases (HDACs) remove acetyl groups from lysine residues in different proteins, including histones. Sirtuins are members of class III HDACs and Sirtuin 1 (Sirt1) plays a role in cellular metabolism and immunological regulation. In obesity, the expression of Sirt1 is constitutively downregulated in most metabolic tissues. Recently, it has become evident the contribution of T cells to obesity. However, the importance of Sirt1 expression in T cells in the context of obesity has not been investigated. We hypothesized that Sirt1 in the context of obesity has an important role on CD4&#43 T cell polarization, not just from an epigenetic point of view, but by a metabolic modulation of the immune response and these modifications could also be involved in the progression of transplant rejection. Here, we evaluate the role of Sirt1 in the differentiation and activation of CD4&#43 T cells in an experimental model of obesity. Eight weeks old Sirt&#43/&#43 and CD4-Sirt1-/- animals were submitted to diet-induced obesity (DIO) or standard diet conditions for 12 weeks. Morphological, biochemical, metabolic, molecular and cell biology parameters were evaluated through and at the end of the DIO. After 12 weeks, DIO animals became obese and inflamed and showed a reduced activity of HDACs and a reduced expression of Sirt1, Sirt3, CD36 and PGC-1 expression in CD4&#43 T cells from lymph nodes, changes in the expression of these genes were observed also at different point times in peripheral blood. An increased frequency of Th1, Th17 and reduction of Treg cells in draining lymph nodes was also observed. CD4&#43 T cells also presented an increase in markers related to activation or exhaustion, such as KLRG-1 and PD-1 and a shift to a memory precursor phenotype (MPEC). We observed an increased glucose uptake in DIO animals compared to controls, especially in CD4-Sirt1-/- supporting increased glucose demand in T cells from DIO mice. In addition, an increased mitochondrial mass and mitochondrial superoxide production, an altered mitochondrial respiratory profile (in terms of proton leak, maximal and spare respiratory capacity) were observed in CD4&#43 T cells from obese animals. Conditional depletion of Sirt1 in CD4&#43 T cells increased the frequency of Th1 and Th17 cells, in the context of obesity, compared with the obtained results in Sirt1&#43/&#43 DIO animals. The bioenergetic profile of CD4&#43 T cells and glucose uptake also showed increased metabolic responses and glucose demand in DIO animals compared to controls. Regarding transplantation outcomes, no differences were observed between Sirt1+/+ and CD4-Sirt1-/- but an accelerated rejection rate was observed as a result of DIO. In conclusion, deletion of Sirt1 in CD4&#43 T cells aggravates the effect of obesity in the metabolic and functional profile of these cells. These data suggest a protective role of Sirt1 in CD4&#43 T cells in the context of metabolic disorders. All the procedures were evaluated and accepted by the ethical committees of the participant institutions and were performed according to the national and international regulations and guaranteeing the animal welfare. Ethics committee approval code: CEUA 9090200318 (AU)

• FAPESP's process: 17/16711-4 - Role of sirtuin 1 in CD4+ T cell activation and differentiation in obese transplanted engrafted animals
• Grantee: Omar Alberto Domínguez Amorocho
• Support Opportunities: Scholarships in Brazil - Doctorate