Here we show that iNOS-deficient mice display enhanced classically activated M1 macrophage polarization without major effects on alternatively activated M2 macrophages. eNOS and nNOS mutant mice show comparable M1 macrophage polarization compared with wild-type control mice. Addition of N6-(1-iminoethyl)-L-lysine dihydrochloride, an iNOS inhibitor, significantly enhances M1 macrophage polarization while S-nitroso-N-acetylpenicillamine, a NO donor, suppresses M1 macrophage polarization. NO derived from iNOS mediates nitration of tyrosine residues in IRF5 protein, leading to the suppression of IRF5-targeted M1 macrophage signature gene activation. Computational analyses corroborate a circuit that fine-tunes the expression of IL-12 by iNOS in macrophages, potentially enabling versatile responses based on changing microenvironments. Finally, studies of an experimental model of endotoxin shock show that iNOS deficiency results in more severe inflammation with an enhanced M1 macrophage activation phenotype. These results suggest that NO derived from iNOS in activated macrophages suppresses M1 macrophage polarization.

Diabetic nephropathy (DN) is a serious complication of diabetes. At its core, DN is a metabolic disorder which can also manifest itself in terms of local inflammation in the kidneys. Such inflammation can then drive the classical markers of fibrosis and structural remodeling. As a result, resolution of immune-mediated inflammation is critical towards achieving a cure for DN. Many immune cells play a part in DN, including key members of both the innate and adaptive immune systems. While these cells were classically understood to primarily function against pathogen insult, it has also become increasingly clear that they also serve a major role as internal sensors of damage. In fact, damage sensing may serve as the impetus for much of the inflammation that occurs in DN, in a vicious positive feedback cycle. Although direct targeting of these proinflammatory cells may be difficult, new approaches that focus on their metabolic profiles may be able to alleviate DN significantly, especially since dysregulation of the local metabolic environment may well be responsible for triggering inflammation to begin with. In this review, the authors consider the metabolic profile of several relevant immune types and discuss their respective roles.

Oleoylethanolamide, an endogenous PPAR-α ligand, attenuates liver fibrosis targeting hepatic stellate cells

Post-translational modifications have been identified to be of great importance in cancers and lysine acetylation, which can attract the multifunctional transcription factor BRD4, has been identified as a potential therapeutic target. In this paper, we identify that BRD4 has an important role in colorectal cancer; and that its inhibition substantially wipes out tumor cells. Treatment with inhibitor MS417 potently affects cancer cells, although such effects were not always outright necrosis or apoptosis. We report that BRD4 inhibition also limits distal metastasis by regulating several key proteins in the progression of epithelial-to-mesenchymal transition (EMT). This effect of BRD4 inhibitor is demonstrated via liver metastasis in animal model as well as migration and invasion experiments in vitro. Together, our results demonstrate a new application of BRD4 inhibitor that may be of clinical use by virtue of its ability to limit metastasis while also being tumorcidal.

The regulation of macrophage orientation pathological conditions is important but still incompletely understood. Here, we show that IL-10 and Rag1 double knockout mice spontaneously develop colitis with dominant M1 macrophage phenotype, suggesting that IL-10 regulates macrophage orientation in inflammation. We demonstrate that IL-10 stimulation induced miR-146b expression, and that the expression of miR-146b was impaired in IL-10 deficient macrophages. Our data show that miR-146b targets IRF5, resulting in the regulation of macrophage activation. Furthermore, miR-146b deficient mice developed intestinal inflammation with enhanced M1 macrophage polarization. Finally, miR-146b mimic treatment significantly suppresses M1 macrophage activation and ameliorates colitis development in vivo. Collectively, the results suggest that IL-10 dependent miR-146b plays an important role in the modulation of M1 macrophage orientation.

Reproducing the pathophysiology of human multiple sclerosis (MS) in animal models is critical to identifying mechanisms triggering demyelination and to developing early intervention strategies. Here, we aimed to model overactivated Wnt (wingless-related integration site) signaling previously shown in postmortem brain tissues of patients with MS by inducing experimental autoimmune encephalomyelitis (EAE) in Pdgfra ^CreER ;Apc ^fl/fl and Olig2 ^Cre ;Apc ^fl/fl mice. These mice have overactivated Wnt signaling in oligodendrocyte precursor cells (OPCs) because of a conditional knockout of the pathway repressor adenomatous polyposis coli (APC). Pdgfra ^CreER ;Apc ^fl/fl EAE mice exhibited increased expression of markers for Wnt activation such as Axis inhibition protein 2 (AXIN2) and Wnt inhibitory factor 1 (WIF1) in OPCs and showed exacerbated EAE progression in both the spinal cord and the brain. Genetic or antibody-mediated ablation of CC-chemokine ligand 4 (CCL4) prevented infiltration of CD4 ⁺ T cells and arrested disease progression in these mice. A characterization of CNS (central nervous system) immune cell clusters identified an augmented subpopulation of NK1.1 ⁺ CD11b ⁺ Gr-1 ⁺ cytotoxic macrophages in Pdgfra ^CreER ;Apc ^fl/fl EAE mice. Microinjection of this subpopulation of macrophages into the brains of wild-type C57/B6J mice was sufficient to induce demyelination. Ablation of CD4 ⁺ T cells prevented the effects of Wnt overactivation on demyelination and immune cell infiltration. Antagonizing chemokine receptor 5 (CCR5) using a European Medicines Agency–approved drug, maraviroc, reduced immune cell infiltration, alleviated demyelination, and attenuated EAE progression. We found an OPC-orchestrated immune cellular network that instigates early demyelination, provides insight into MS pathophysiology, and suggests avenues for early interventions.