Metabolic Regulatory Pathways in Tolerogenic Bias Dendritic Cells

Author(s)

Thiago Andrade Patente

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2020-02-14

Examining board members

Jose Alexandre Marzagao Barbuto; Hugo Aguirre Armelin; Cristiane Naffah de Souza Breda; Pedro Manoel Mendes de Moraes Vieira

• Advisor: Jose Alexandre Marzagao Barbuto; Maria Lucia Cardillo Correa Giannella

Abstract

Type 1 diabetes mellitus (T1D) is an autoimmune disease in which dendritic cells (DC) play a relevant role. DC are antigen presenting cells, central to CD4&#43 T cell differentiation, including regulatory T cells (Tregs). When the environment provides tolerogenic signals, DC fail to induce T lymphocyte proliferation and are prone to induce tolerance. Different stimuli, such as retinoic acid (RA), dexamethasone (Dex) and vitamin D3 (VitD3), are capable of generating tolerogenic DC (tolDC). Immunogenic DC and tolDC differ in expression of costimulatory molecules, proinflammatory cytokine secretion, ability to generate suppressive T lymphocytes and metabolic profile. While immunogenic DC rely on glycolysis and anabolic metabolism to support their activity, the metabolic pathways involved in the induction of Treg by tolDC are less well defined. AMPK is a metabolic sensor known to antagonize anabolic signals, promoting catabolism and studies suggest that tolDC are characterized by a catabolic profile. However, the role of AMPK signaling in regulating tolDC metabolism and function has not been addressed. Moreover, the presence of VitD3 during mo-DC differentiation induces an initial glucose-dependent metabolic reprogramming. Thus, the present study had two main objectives: (1) as hyperglycemia is the main characteristic of T1D, we aimed to evaluate how glucose availability would impact the differentiation of mo-DC treated with VitD3 (VitD DC); (2) to investigate how and if AMPK could control the differentiation of tolDC induced by VitD3, RA and Dex. Metabolically, VitD3 differently modulates controls mo-DC and patients, inducing tolDC in patients in a glucose-independent manner. In controls, VitD3 induced increase in glycolysis and OXPHOS, which were, at least partially, reduced in hyperglycemia, as well as CD86 expression, TNF-a secretion and lymphostimulatory capacity. In diabetic patients, while VitD3 reduced both CD86 expression and TNF-a secretion in hyperglycemia, cell metabolism was not affected, suggesting that VitD3- induced metabolic reprogramming may not rely on glycolysis in patients. In the second part of the project, we confirmed that VitD3, Dex and RA induced functional tolDCs, since these tolDC induced suppressor CD4&#43 T cells. Metabolically, however, each tolDC exhibited a distinct phenotype: VitD-DC had increased glycolysis and OXPHOS, RA-DC had reduced spare respiratory capacity and Dex-DC had reduced glycolysis. ACC phosphorylation, a direct downstream target of AMPK, was increased in VitD-DC and RA-DC, suggesting increased AMPK activity. Consistently, AMPK silencing reverted the metabolic changes induced by VitD3 and RA, but not by Dex. When AMPK was silenced in human RA-DC, both ALDH activity (that was increased by RA treatment) and their tolerogenic capacity were lost. Mice with a deficiency in AMPK selectively in DC showed a reduction in ALDH activity and frequency of gut CD103&#43CD11b&#43 DC, considered to be the in vivo equivalent of RA-DC. This suggests that AMPK signaling is important for homeostasis of tolerogenic DC in the gut by promoting an anti-inflammatory status via regulation of ALDH activity specifically in CD103&#43CD11b&#43 DC. Taken together, these data point towards a key role for AMPK in regulating both the metabolic and tolerogenic properties of RA-DC and the homeostasis of the gut. (AU)

• FAPESP's process: 14/26437-9 - Glucose and glycated albumin effect over monocyte-induced dendritic cell (mo-DC) from heathy donors and type 1 diabetic patients.
• Grantee: Thiago Andrade Patente
• Support Opportunities: Scholarships in Brazil - Doctorate