The NADPH Oxidase Nox4 Controls Macrophage Polarization in an NFκB-Dependent Manner

Abstract

The family of NADPH oxidases represents an important source of reactive oxygen species (ROS) within the cell. Nox4 is a special member of this family as it constitutively produces H2O2 and its loss promotes inflammation. A major cellular component of inflammation is the macrophage population, which can be divided into several subpopulations depending on their phenotype, with proinflammatory M(LPS+IFNγ) and wound-healing M(IL4+IL13) macrophages being extremes of the functional spectrum. Whether Nox4 is expressed in macrophages is discussed controversially. Here, we show that macrophages besides a high level of Nox2 indeed express Nox4. As Nox4 contributes to differentiation of many cells, we hypothesize that Nox4 plays a role in determining the polarization and the phenotype of macrophages. In bone marrow-derived monocytes, ex vivo treatment with LPS/IFNγ or IL4/IL13 results in polarization of the cells into M(LPS+IFNγ) or M(IL4+IL13) macrophages, respectively. In this ex vivo setting, Nox4 deficiency reduces M(IL4+IL13) polarization and forces M(LPS+IFNγ). Nox4-/- M(LPS+IFNγ)-polarized macrophages express more Nox2 and produce more superoxide anions than wild type M(LPS+IFNγ)-polarized macrophages. Mechanistically, Nox4 deficiency reduces STAT6 activation and promotes NFκB activity, with the latter being responsible for the higher level of Nox2 in Nox4-deficient M(LPS+IFNγ)-polarized macrophages. According to those findings, in vivo, in a murine inflammation-driven fibrosarcoma model, Nox4 deficiency forces the expression of proinflammatory genes and cytokines, accompanied by an increase in the number of proinflammatory Ly6C+ macrophages in the tumors. Collectively, the data obtained in this study suggest an anti-inflammatory role for Nox4 in macrophages. Nox4 deficiency results in less M(IL4+IL13) polarization and suppression of NFκB activity in monocytes.

Pharmacological inhibition of histone deacetylase reduces NADPH oxidase expression, oxidative stress and the progression of atherosclerotic lesions in hypercholesterolemic apolipoprotein E-deficient mice; potential implications for human atherosclerosis

“…Evidence exists that ROS production is enhanced in M1-like Mac compared to either resting or M2-like Mac [43]. Yet, the precise role and regulation of Nox expression in different Mac subsets is not entirely understood.…”

The Role of PARP1 in Monocyte and Macrophage Commitment and Specification: Future Perspectives and Limitations for the Treatment of Monocyte and Macrophage Relevant Diseases with PARP Inhibitors

“…However, in some cancer cell types, ADP-ribosylation emerged as an repressor of NOX1 and NOX4 since cell treatment with PJ34 resulted in upregulation of NOX1 and NOX4 mRNAs [ 114 ]. The latter enzyme plays a role in defining the macrophage phenotype and the direction of their polarization [ 115 ]. NOX4 promotes the development of anti-inflammatory phagocytes by the induction of STAT6 and, as a consequence, the reduction of NFκB activity.…”

Pan-Cancer Analysis Shows TP53 Mutations Modulate the Association of NOX4 with Genetic Programs of Cancer Progression and Clinical Outcome

“…We discovered a striking association between NOX2 and macrophage signatures that strongly suggests that the major source of NOX2 is derived from TAMs ( Figure 5 ). Although NOX2 is considered the primary source of ROS in macrophages, recent studies revealed that other less abundant NOX enzymes can affect the fate and function of macrophages, including DUOX1, NOX1 and NOX4 [ 42 , 43 , 44 ]. For example, studies with Nox1/Nox2 double-knockout mice suggest both oxidases support monocyte differentiation into macrophages [ 43 ].…”

“…For example, studies with Nox1/Nox2 double-knockout mice suggest both oxidases support monocyte differentiation into macrophages [ 43 ]. Furthermore, observations with Nox4 knock-out mice indicate the absence of Nox4 results in several proinflammatory phenotypes, including increased macrophage Nox2 expression and enhanced infiltration of proinflammatory macrophages in tumors of an induced fibrosarcoma model [ 44 ]. Taken together, we must consider that TAM and TAM-derived NOX2 are linked to the aforementioned genetic programs of cancer progression, and that this may, in part, involve a direct interplay between Nox2 and Nox4 within TAMs.…”