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Tumor necrosis factor-?-mediated hepatocyte apoptosis stimulates fibrosis in the steatotic liver in mice.

ABSTRACT: Hepatocyte apoptosis has been implicated in the progression of nonalcoholic steatohepatitis. However, it is unclear whether the induction of tumor necrosis factor (TNF)-?-mediated hepatocyte apoptosis in the simple fatty liver triggers liver fibrosis. To address this question, high-fat diet-fed mice were repeatedly administered D-galactosamine, which increases the sensitivity of hepatocytes to TNF-?-mediated apoptosis. In mice treated with a high-fat diet plus D-galactosamine, hepatocyte apoptosis and liver fibrosis were induced, whereas both apoptosis and fibrosis were inhibited in these mice following gut sterilization with antimicrobials or knockout of TNF-?. Furthermore, liver fibrosis was diminished when hepatocyte apoptosis was inhibited by expressing a constitutively active inhibitor of nuclear factor ?B kinase subunit ?. Thus, hepatocyte apoptosis induced by intestinal dysbiosis or TNF-? up-regulation in the steatotic liver caused fibrosis. Organ fibrosis, including liver fibrosis, involves the interaction of cyclic adenosine monophosphate-response element-binding protein-binding protein (CBP) and ?-catenin. Here, hepatocyte-specific CBP-knockout mice showed reduced liver fibrosis accompanied by hepatocyte apoptosis diminution; notably, liver fibrosis was also decreased in mice in which CBP was specifically knocked out in collagen-producing cells because the activation of these cells was now suppressed. Conclusion: TNF-?-mediated hepatocyte apoptosis induced fibrosis in the steatotic liver, and inhibition of CBP/?-catenin signaling attenuated the liver fibrosis due to the reduction of hepatocyte apoptosis and suppression of the activation of collagen-producing cells. Thus, targeting CBP/?-catenin may represent a new therapeutic strategy for treating fibrosis in nonalcoholic steatohepatitis. (Hepatology Communications 2018;2:407-420).

SUBMITTER: Osawa Y

PROVIDER: S-EPMC5880193 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Tumor necrosis factor-α-mediated hepatocyte apoptosis stimulates fibrosis in the steatotic liver in mice.

Osawa Yosuke Y Kojika Ekumi E Hayashi Yukiko Y Kimura Masamichi M Nishikawa Koji K Yoshio Sachiyo S Doi Hiroyoshi H Kanto Tatsuya T Kimura Kiminori K

Hepatology communications 20180213 4

Hepatocyte apoptosis has been implicated in the progression of nonalcoholic steatohepatitis. However, it is unclear whether the induction of tumor necrosis factor (TNF)-α-mediated hepatocyte apoptosis in the simple fatty liver triggers liver fibrosis. To address this question, high-fat diet-fed mice were repeatedly administered D-galactosamine, which increases the sensitivity of hepatocytes to TNF-α-mediated apoptosis. In mice treated with a high-fat diet plus D-galactosamine, hepatocyte apoptos ...[more]

PMID: 29619419

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Project description:Although tumor necrosis factor (TNF) initially came to prominence because of its anti-tumor activity, most attention is now focused on its proinflammatory actions. TNF appears to play a critical role in both early and late events involved in inflammation, from localizing the noxious agent and amplifying the cellular and mediator responses at the local site and systemically, to editing (e.g., apoptosis) injured cells or effete immune cells and repairing inflammatory damage. We have generated mice deficient in TNF (TNF-/- mice) and have begun to examine the multiple functions attributed to TNF. TNF-/- mice develop normally and have no gross structural or morphological abnormalities. As predicted, they are highly susceptible to challenge with an infectious agent (Candida albicans), are resistant to the lethality of minute doses of lipopolysaccharide (LPS) following D-galactosamine treatment, have a deficiency in granuloma development, and do not form germinal centers after immunization. Phagocytic activity of macrophages appears relatively normal, as do T cell functions, as measured by proliferation, cytokine release, and cytotoxicity. B cell response to thymus-independent antigens is normal, but the Ig response to thymus-dependent antigen is reduced. Surprisingly, cytokine production induced by LPS appears essentially intact, with the exception of reduced colony-stimulating factor activity. Other unexpected findings coming from our initial analysis are as follows. (i) TNF has low toxicity in TNF-/- mice. (ii) TNF-/- mice show an anomalous late response to heat-killed Corynebacterium parvum. In contrast to the prompt response (granuloma formation, hepatosplenomegaly) and subsequent resolution phase in C. parvum-injected TNF+/+ mice, similarly treated TNF-/- mice show little or no initial response, but then develop a vigorous, disorganized inflammatory response leading to death. These results suggest that TNF has an essential homeostatic role in limiting the extent and duration of an inflammatory process-i.e., an anti-inflammatory function. (iii) In contrast to the expectation that TNF+/+ mice and TNF+/- mice would have identical phenotypes, TNF+/- mice showed increased susceptibility to high-dose LPS lethality, increased susceptibility to Candida challenge, and delayed resolution of the C. parvum-induced inflammatory process, indicating a strong gene dose requirement for different actions of TNF.

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Tumor necrosis factor-?-mediated hepatocyte apoptosis stimulates fibrosis in the steatotic liver in mice.

Publications

Tumor necrosis factor-α-mediated hepatocyte apoptosis stimulates fibrosis in the steatotic liver in mice.

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