Adenosine from thermogenic adipocytes modulates macrophages phenotype in adipose tissue

• Grant number: 22/04296-0
• Support Opportunities: Scholarships in Brazil - Doctorate
• Effective date (Start): August 01, 2022
• Effective date (End): April 30, 2025
• Field of knowledge: Biological Sciences - Immunology - Cellular Immunology
• Principal Investigator: Luiz Osório Silveira Leiria
• Grantee: Nayara Pereira
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Brown adipocytes are known for their thermogenic potential, initiated by the activation of adrenergic receptors coupled to a G protein. The activation of these receptors in cells with high metabolic activity leads to an increase of intracellular cyclic AMP (cAMP), which, in excess, is pulled out of the cell by MRPs (Multidrug Resistance Proteins) channels. Extracellular cAMP/AMP can be converted to adenosine, an anti-inflammatory molecule important for activating thermogenesis. Although the production of adenosine by brown adipocytes has already been described, the mechanisms of production, as well as the effects of this molecule on macrophages present in thermogenic adipose tissue, are still unclear. In this sense, it is hypothesized that adenosine derived from extracellular cAMP from thermogenic adipocytes can modulate macrophages associated with brown adipose tissue, promoting a pro-thermogenic environment. To test the hypothesis, experiments will be developed to evaluate the efflux of nucleosides from thermogenic adipocytes, the pathways related to this phenomenon, and the consequent production of adenosine. For this, mass spectrometry techniques and enzyme inhibitors of the pathway will be used. A2a-/- (adenosine receptor knock-out) animals will be used to detect the influence of adenosine on macrophage phenotype and function. Modulation of macrophages (BMDM and/or peritoneal) by adenosine will be evaluated in assays with derived conditioned medium of brown adipocytes and co-culture with inserts, later analyzed by RT-PCR, functional assays, and immunofluorescence. Finally, the impact of adenosine-reprogrammed macrophages in healthy and obese LysMcreAdora2aflox and WT animal models induced thermogenesis will be evaluated. Parameters such as heat production capacity, glucose control, and systemic inflammation in both conditions will be tested. Given the evidence in the literature, we hope to observe that the production of adenosine by brown adipocytes has a modulating function on macrophages associated with brown adipose tissue, to directly contribute to the efficiency of thermogenic activity. (AU)