Macrophages-common culprit in obesity and asthma

Abstract

Macrophages are essential innate immune cells that also regulate local metabolism. Endogenous or exogenous stimuli may polarize macrophages towards phenotypes that serve distinct innate immunological metabolic functions. IFNγ or lipopolysaccharide (LPS) polarizes macrophages towards the M1, or "classically activated" phenotype that participates in defense against intracellular pathogens. IL-4, IL-13, or chitin polarizes macrophages towards the M2, or "alternatively activated" phenotype, which defends against multicellular nematodes and fungi. Since macrophages polarize in local environments, M1 and M2 macrophages may coexist in different organs and may differentially affect asthma and obesity, two comorbid diseases where polarized macrophages contribute to their pathogenesis. While M1 macrophages are considered beneficial in asthma and contribute to the pathology of obesity, M2 macrophages contribute to the pathology of asthma, but limit metabolic syndrome associated with obesity. Here we discuss the roles for M1 and M2 macrophages in asthma and obesity, and propose a model by which M1-mediated inflammation in adipose tissue enhances M2-mediated inflammation in the asthmatic lung.

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