Histidine‐rich glycoprotein promotes macrophage activation and inflammation in chronic liver disease

Abstract

Pathogen-and injury-related danger signals as well as cytokines released by immune cells influence the functional differentiation of macrophages in chronic inflammation. Recently, the liver-derived plasma protein, histidine-rich glycoprotein (HRG), was demonstrated, in mouse tumor models, to mediate the transition of alternatively activated (M2) to proinflammatory (M1) macrophages, which limit tumor growth and metastasis. We hypothesized that liver-derived HRG is a critical endogenous modulator of hepatic macrophage functionality and investigated its implications for liver inflammation and fibrosis by comparing C57BL/ 6N wild-type (WT) and Hrg 2/2 mice. In homeostatic conditions, hepatic macrophages were overall reduced and preferentially polarized toward the anti-inflammatory M2 subtype in Hrg 2/2 mice. Upon chronic liver damage induced by CCl 4 or methionine-choline-deficient (MCD) diet, liver injury and fibrosis were attenuated in Hrg 2/2 , compared to WT, mice. Macrophage populations were reduced and skewed toward M2 polarization in injured livers of Hrg 2/2 mice. Moreover, HRGdeficient mice showed significantly enhanced hepatic vascularization by micro-computed tomography and histology, corroborating proangiogenic activities of M2-polarized liver macrophages. Purified HRG protein induced, but HRG-deficient serum prevented, M1 macrophage differentiation in vitro. Accordingly, Hrg 2/2 mice transplanted with Hrg 1/1 bone marrow, but not Hrg 2/2 -transplanted Hrg 1/1 mice, remained protected from experimental steatohepatitis. Consistent with these findings, patients with chronic hepatitis C and nonalcoholic steatohepatitis significantly up-regulated hepatocytic HRG expression, which was associated with M1 polarization of adjacent macrophages. Conclusions: Liver-derived HRG, similar to alarmins, appears to be an endogenous molecular factor promoting polarization of hepatic macrophages toward the M1 phenotype, thereby promoting chronic liver injury and fibrosis progression, but limiting angiogenesis. Therefore, controlling tissue levels of HRG or PGF might be a promising strategy in chronic inflammatory liver diseases. (HEPATOLOGY 2016;63:1310-1324

Change in Chemical Composition of Simmental Crossbred Cattle Milk Improved its Physicochemical, Nutritional, and Processed Properties

“…Bartneck et al. () have found that His‐rich glycoprotein promoted macrophage activation and inflammation in mouse models. For example, His‐rich glycoprotein appears to be an endogenous molecular factor promoting the polarization of hepatic macrophages toward the proinflammatory phenotype.…”

Therapeutic inhibition of inflammatory monocyte recruitment reduces steatohepatitis and liver fibrosis

“…The NAFLD activity score was assessed by an expert pathologist (T. Longerich) who was blinded to the treatment group. Immunohistochemistry for F4/80 (Abcam) was performed on paraffin‐embedded liver sections and indirect immunofluorescence staining with collagen‐1 antibody (Novus Biologicals, Germany) on liver cryosections, both according to standard protocols . Hepatic leukocytes were analyzed by multicolor flow cytometry using an LSR‐Fortessa (BD Biosciences), as described …”

Receptor‐interacting protein kinase 3 mediates macrophage/monocyte activation in autoimmune hepatitis and regulates interleukin‐6 production

“…2,3 Persistent and excessive activation of macrophages results in pathological inflammation and fibrosis in chronic liver diseases. [4][5][6][7] Previous research suggests that activated macrophages are present in portal infiltrates and at sites of interface hepatitis in AIH. [8][9][10][11] Nonetheless, until now little has been known about the molecular mechanisms of macrophage activation in AIH.…”