CCL20 mediates lipopolysaccharide induced liver injury and is a potential driver of inflammation and fibrosis in alcoholic hepatitis

Abstract

Objective Chemokines are known to play an important role in the pathophysiology of alcoholic hepatitis (AH), a form of acute-on-chronic liver injury frequently mediated by gut derived lipopolysaccharide (LPS). In our study, we hypothesise that chemokine CCL20, one of the most upregulated chemokines in patients with AH, is implicated in the pathogenesis of AH by mediating LPS induced liver injury. Design CCL20 gene expression and serum levels and their correlation with disease severity were assessed in patients with AH. Cellular sources of CCL20 and its biological effects were evaluated in vitro and in vivo in chronic, acute and acute-on-chronic experimental models of carbon tetrachloride and LPS induced liver injury. RNA interference technology was used to knockdown CCL20 in vivo. Results CCL20 hepatic and serum levels were increased in patients with AH and correlated with the degree of fibrosis, portal hypertension, endotoxaemia, disease severity scores and short term mortality. Moreover, CCL20 expression was increased in animal models of liver injury and particularly under acute-on-chronic conditions. Macrophages and hepatic stellate cells (HSCs) were identified as the main CCL20 producing cell types. Silencing CCL20 in vivo reduced LPS induced aspartate aminotransferase and lactate dehydrogenase serum levels and hepatic proinflammatory and profibrogenic genes. CCL20 induced proinflammatory and profibrogenic effects in cultured primary HSCs. Conclusions Our results suggest that CCL20 upregulation is strongly associated with LPS and may not only represent a new potential biomarker to predict outcome in patients with AH but also an important mediator linking hepatic inflammation, injury and fibrosis in AH.

Roles for Chemokines in Liver Disease

“…101 CCL20, which binds to CCR6, may also serve as a mediator of inflammation and fibrosis in the setting of alcoholic liver disease. 102 Of note, in vivo knockdown of CCL20 reduced LPS-associated hepatic damage, suggesting its role as a mediator linking hepatic inflammation, injury, and fibrosis in alcoholic hepatitis. 102 Among CC chemokines, CCL2 has recently been suggested to play a role in alcohol-related damage, because its liver and plasma levels were associated with disease severity and with inflammation, including neutrophil infiltration, but not with steatosis, in patients with alcoholic liver disease.…”

“…102 Of note, in vivo knockdown of CCL20 reduced LPS-associated hepatic damage, suggesting its role as a mediator linking hepatic inflammation, injury, and fibrosis in alcoholic hepatitis. 102 Among CC chemokines, CCL2 has recently been suggested to play a role in alcohol-related damage, because its liver and plasma levels were associated with disease severity and with inflammation, including neutrophil infiltration, but not with steatosis, in patients with alcoholic liver disease. 103 Interestingly, polymorphisms in the CCL2 and CCR2 genes were more frequent in patients with severe disease.…”

“…17 Besides CX3CL1, injured hepatocytes strongly express the chemokine CCL20, 24 but HSCs and macrophages can also express CCL20. 102 In experimental fibrosis in mice, this favors the recruitment of gd T cells into injured liver, which limit inflammation and fibrosis by promoting HSC apoptosis. 24 The relevance of this mechanism for human fibrogenesis remains to be confirmed, because CCR6 has so far been associated with the positioning of (profibrogenic) IL-17-expressing T-helper cells in humans.…”

Cytokine Production and Signaling in Stellate Cells

“…Several factors stimulate the secretion of this group of cytokines, including molecules derived from Gram-negative or positive bacteria [82], adipokines such as resistin [83], or the core protein of HCV [84]. More recently, CCL20, the ligand of CCR6, has been identified as a chemokine secreted by HSCs [85]. CCL20 expression was increased in animal models of liver injury, and macrophages and HSCs were identified as the main cell types expressing CCL20.…”

Stellate Cells in Alcoholic Hepatitis

“…LPS also upregulates CCL20 chemokine production from HSC. In vivo silencing of CCL20 gene is shown to reduce hepatic pro-inflammatory and pro-fibrogenic gene levels, suggesting that CCL20 plays a role in hepatic inflammation, injury, and fibrosis [68]. Taken together, these data illustrate the critical crosstalk between the gut and liver, as well as the important TLR4-dependent cell-cell communication between HSC and Kupffer cells, in the progression of ALD [69].…”