Exogenous Ubiquitin Differentially Modulates the Phenotype and Function of M1 and M2 Macrophages

TL;DR

Exogenous ubiquitin changes how M1 and M2 macrophages behave, reducing inflammation and possibly helping protect the heart after injury.

Contribution

This study reveals how exogenous ubiquitin differentially affects M1 and M2 macrophage function and signaling.

Findings

Exogenous ubiquitin reduced TNF-α and IL-10 secretion in M1 and M2 macrophages.

eUB altered macrophage migration, efferocytosis, and cytoskeletal structure in a polarization-dependent manner.

eUB modulated intracellular signaling by affecting STAT1, FAK, and STAT6 phosphorylation in macrophages.

Abstract

Background: Unresolved inflammation is a major predictor of heart failure following myocardial infarction. Exogenous ubiquitin (eUB) is shown to decrease inflammatory response and confer cardioprotection in mice 3 days post-ischemia/reperfusion (I/R) injury. Here, we hypothesized that eUB differentially modulates the phenotype and function of M1 and M2 macrophages. Methods and Results: Peritoneal macrophages, pretreated with UB for 30 min, were exposed to IFN-γ (M1 polarization) or IL-4 (M2 polarization) for 72 h. Cytokine/chemokine levels were measured in conditioned media, while cells were used for functional and biochemical assays. eUB reduced TNF-α secretion in M1, and TNF-α and IL-10 secretion in M2 macrophages. eUB induced cytoskeletal reorganization and reduced surface area in M1 macrophages. eUB enhanced M1 migration; however, it decreased M2 macrophage migration and efferocytosis. It decreased STAT1 and FAK phosphorylation in M1, while increasing STAT6 and FAK phosphorylation in M2 macrophages. Total protein ubiquitination remained unchanged. In non-activated macrophages, eUB altered morphology, suppressed IL-1β, IL-2, and IL-5 secretion, and enhanced efferocytosis. Conclusion: eUB modulates macrophage polarization, reduces pro-inflammatory cytokine secretion, and alters functional parameters and intracellular signaling. These effects may contribute to the cardioprotective potential of eUB 3 days post-I/R injury.

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