Objective Mitochondrial dysfunction plays a dominant role in the pathogenesis of alcoholic liver disease (ALD); however, the underlying mechanisms remain to be fully understood. We previously found that hepatic activating transcription factor 4 (ATF4) activation was associated with mitochondrial dysfunction in ALD. This study aimed to investigate the function and mechanism of ATF4 in alcohol-induced hepatic mitochondrial dysfunction.
Design ATF4 activation was detected in the livers of patients with severe alcoholic hepatitis (AH). The role of ATF4 and mitochondrial transcription factor A (TFAM) in alcohol-induced liver damage was determined in hepatocyte-specific ATF4 knockout mice and liver-specific TFAM overexpression mice, respectively.
Results Hepatic PERK-eIF2α-ATF4 ER stress signalling was upregulated in patients with AH. Hepatocyte-specific ablation of ATF4 in mice ameliorated alcohol-induced steatohepatitis. ATF4 ablation also attenuated alcohol-impaired mitochondrial biogenesis and respiratory function along with the restoration of TFAM. Cell studies confirmed that TFAM expression was negatively regulated by ATF4. TFAM silencing in hepatoma cells abrogated the protective effects of ATF4 knockdown on ethanol-mediated mitochondrial dysfunction and cell death. Moreover, hepatocyte-specific TFAM overexpression in mice attenuated alcohol-induced mitochondrial dysfunction and liver damage. Mechanistic studies revealed that ATF4 repressed the transcription activity of nuclear respiratory factor 1 (NRF1), a key regulator of TFAM, through binding to its promoter region. Clinical relevance among ATF4 activation, NRF1–TFAM pathway disruption and mitochondrial dysfunction was validated in the livers of patients with AH.
Conclusion This study demonstrates that hepatic ATF4 plays a pathological role in alcohol-induced mitochondrial dysfunction and liver injury by disrupting the NRF1–TFAM pathway.
- alcoholic liver disease
- energy metabolism
Data availability statement
Data are available on reasonable request.
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Contributors LH and ZZ conceived and designed research; LH, HD, XS, WG, WeiZ, WenZ, RY, TL and ZZ performed experiments and data analysis. ARA and ZS collected human samples and acquired clinical data. All the authors participated in manuscript preparation.
Funding This research was supported by the National Institutes of Health grants R01AA018844 (ZZ), R01AA020212 (ZZ), R24AA025017 (ZS) and Postdoctoral Fellowship Award from the American Liver Foundation (LH).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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