Mitochondrial antiviral signaling protein enhances MASLD progression through the ERK/TNFα/NFκß pathway.

BACKGROUND AND AIMS: Mitochondrial antiviral signaling protein (MAVS) is a critical regulator that activates the host's innate immunity against RNA viruses, and its signaling pathway has been linked to the secretion of proinflammatory cytokines. However, the actions of MAVS on inflammatory pathways during the development of metabolic dysfunction-associated steatotic liver disease (MASLD) have been little studied. APPROACH AND RESULTS: Liver proteomic analysis of mice with genetically manipulated hepatic p63, a transcription factor that induces liver steatosis, revealed MAVS as a target downstream of p63. MAVS was thus further evaluated in liver samples from patients and in animal models with MASLD. Genetic inhibition of MAVS was performed in hepatocyte cell lines, primary hepatocytes, spheroids, and mice. MAVS expression is induced in the liver of both animal models and people with MASLD as compared with those without liver disease. Using genetic knockdown of MAVS in adult mice ameliorates diet-induced MASLD. In vitro, silencing MAVS blunts oleic and palmitic acid-induced lipid content, while its overexpression increases the lipid load in hepatocytes. Inhibiting hepatic MAVS reduces circulating levels of the proinflammatory cytokine TNFα and the hepatic expression of both TNFα and NFκß. Moreover, the inhibition of ERK abolished the activation of TNFα induced by MAVS. The posttranslational modification O -GlcNAcylation of MAVS is required to activate inflammation and to promote the high lipid content in hepatocytes. CONCLUSIONS: MAVS is involved in the development of steatosis, and its inhibition in previously damaged hepatocytes can ameliorate MASLD.

Definition and risk factors for chronicity following acute idiosyncratic drug-induced liver injury.

BACKGROUND & AIMS: Chronic outcome following acute idiosyncratic drug-induced liver injury (DILI) is not yet defined. This prospective, long-term follow-up study aimed to analyze time to liver enzyme resolutions to establish the best definition and risk factors of DILI chronicity. METHODS: 298 out of 850 patients in the Spanish DILI registry with no pre-existing disease affecting the liver and follow-up to resolution or ⩾1year were analyzed. Chronicity was defined as abnormal liver biochemistry, imaging test or histology one year after DILI recognition. RESULTS: Out of 298 patients enrolled 273 (92%) resolved ⩽1year from DILI recognition and 25 patients (8%) were chronic. Independent risk factors for chronicity were older age [OR: 1.06, p=0.011], dyslipidemia [OR: 4.26, p=0.04] and severe DILI [OR: 14.22, p=0.005]. Alanine aminotransferase (ALT), alkaline phosphatase (ALP) and total bilirubin (TB) median values were higher in the chronic group during follow-up. Values of ALP and TB >1.1 x upper limit of normal (xULN) and 2.8 xULN respectively, in the second month from DILI onset, were found to predict chronic DILI (p<0.001). Main drug classes involved in chronicity were statins (24%) and anti-infectives (24%). Histological examination in chronic patients demonstrated two cases with ductal lesion and seven with cirrhosis. CONCLUSIONS: One year is the best cut-off point to define chronic DILI or prolonged recovery, with risk factors being older age, dyslipidemia and severity of the acute episode. Statins are distinctly related to chronicity. ALP and TB values in the second month could help predict chronicity or very prolonged recovery. LAY SUMMARY: Drug-induced liver injury (DILI) patients who do not resolve their liver damage during the first year should be considered chronic DILI patients. Risk factors for DILI chronicity are older age, dyslipidemia and severity of the acute episode. Chronic DILI is not a very common condition; normally featuring mild liver profile abnormalities and not being an important clinical problem, with the exception of a small number of cases of early onset cirrhosis.

Neddylation orchestrates the complex transcriptional and posttranscriptional program that drives Schwann cell myelination.

Myelination is essential for neuronal function and health. In peripheral nerves, >100 causative mutations have been identified that cause Charcot-Marie-Tooth disease, a disorder that can affect myelin sheaths. Among these, a number of mutations are related to essential targets of the posttranslational modification neddylation, although how these lead to myelin defects is unclear. Here, we demonstrate that inhibiting neddylation leads to a notable absence of peripheral myelin and axonal loss both in developing and regenerating mouse nerves. Our data indicate that neddylation exerts a global influence on the complex transcriptional and posttranscriptional program by simultaneously regulating the expression and function of multiple essential myelination signals, including the master transcription factor EGR2 and the negative regulators c-Jun and Sox2, and inducing global secondary changes in downstream pathways, including the mTOR and YAP/TAZ signaling pathways. This places neddylation as a critical regulator of myelination and delineates the potential pathogenic mechanisms involved in CMT mutations related to neddylation.