Impact of infection-induced immunological scarring on the long-term host metabolic homeostasis

Abstract

The immune system deals with highly diverse infectious challenges in a manner that both promotes the control of invading agents and restores tissue homeostasis. At barrier tissues, sites of constant microbial exposure, tissue-specific immunity requires defined structural components that have immunologic and neuroendocrine detectors providing signal for the spatial segregation from the microbiota and infectious agents. This process ensures the maintenance of organ function and enables the balance between tolerance to environmental antigens and regulated protective immunity. These balanced processes are essential for the preservation of tissue integrity and function, and the microbiota plays an important role in this process. Inflammatory disorders affecting barrier sites are complex diseases that develop as a result of a breakdown in tissue homeostasis and the subsequent failure to regulate immunity against environmental or microbial antigens. In the past few years, metabolic disorders, such as obesity, diabetes, cardiovascular diseases and metabolic syndromes, have been included in the categories of complex diseases trigged by several endogenous and exogenous stressors. Indeed, it has been shown that there is an important crosstalk between the immune system and gut microorganisms during the development of obesity, metabolic syndromes and type 2 diabetes. However, the role of the microbiota and the functional impact of infections in such diseases are not fully understood. This is largely due to the complexity of the microbiota components and the bidirectional involvement of different host physiological systems in the maintenance of intestinal homeostasis, such as the immune and the neuroendocrine systems. For instance, the gut microbiota plays an essential role in nutrient absorption, changes in the diet impact the microbiota composition, and both microbiota and diet interfere with the function of the immune and endocrine systems. In this context, gastrointestinal infections can disturb homeostasis beyond the gut tissue, causing long-term consequences to distal sites and systems. Recently, we have shown that a single episode of acute gastrointestinal infection with Yersinia pseudotuberculosis can lead to the development of immunological scaring causing irreversible long-term consequences to tissue specific immunity. Notably, this immunological scar is characterized by the disruption of gut-immune system dialog, loss of compartmentalization of the microbiota and remodeling of the mesentery, including adipose tissue and associated lymphoid tissue. Since the intestinal tract and the associated lymphatic system are deeply affected in this context, we hypothesized that acute infections that promote mesentery remodeling could also impact the host metabolic homeostasis and trigger metabolic disorders. Therefore, in this project we will take advantage of the experimental of Yersinia-induced immunological scar to understand the crosstalk between microbiota-immune-neuroendocrine systems following acute infections in the development of metabolic disorders. The results obtained in this project will open a new framework to comprehend the pathogenesis of multifactorial / complex diseases triggered by infections at the barrier tissues. (AU)