Disordered lipid metabolism and inflammation, the hallmark features of metabolic dysfunction-associated steatohepatitis (MASH), present a significant therapeutic challenge even in the absence of obesity, making the discovery of novel pathogenic mechanisms and therapies imperative. Although Celastrol (Cel) markedly ameliorates high-fat diet (HFD)-induced obesity, whether and by what molecular basis it directly ameliorates hepatic inflammation and disordered lipid metabolism remains unclear. Here, using a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced MASH model, we demonstrate that Cel ameliorates steatohepatitis and identify CD36 in liver sinusoidal endothelial cells (LSECs)-the key gatekeepers of hepatic immunometabolic homeostasis-as the central mediator coordinating hepatic lipid transport and inflammatory responses. Elucidating the regulatory mechanism, we found that USP12 removes K48-linked ubiquitination from CD36 and stabilizes it in LSECs. Cel downregulates USP12, thereby promoting CD36 ubiquitination and subsequent degradation, which in turn attenuates chemokine-driven macrophage recruitment and suppresses pathological lipid transport. The clinical relevance of this axis is supported by the concurrent upregulation of both USP12 and CD36 in human livers with steatohepatitis. These findings reveal that LSEC heterogeneity orchestrates hepatic metabolism and inflammation via the USP12/CD36 axis, designating it a therapeutic target for interventions with agents such as Cel.

INTRODUCTION:Acute kidney injury (AKI) is characterized by a rapid decline in renal function, often associated with tubular cell death. Insulin-induced gene 1 (Insig1), a key regulator of cholesterol metabolism, has not been previously implicated in AKI pathogenesis. OBJECTIVES:This study examines the role of Insig1 in AKI and its underlying mechanisms. METHODS:We combined tubule-specific Insig1 knockout mice subjected to cisplatin or ischemia-reperfusion (I/R) injury with in vitro tubular cell models to define its role in AKI. Proteomics identified Insig1-interacting targets, and pathway inhibition validated the therapeutic potential in cisplatin-AKI mice. RESULTS:We observed significant downregulation of Insig1 in renal biopsies from AKI patients and in mouse models of cisplatin- or I/R-induced AKI. Conditional knockout of Insig1 in renal tubular epithelial cells markedly ameliorated kidney injury in these murine models. Mechanistically, Insig1 was found to interact with death-associated protein kinase 3 (Dapk3), a pro-apoptotic factor, thereby stabilizing Dapk3 protein levels. Knockdown of either Insig1 or Dapk3 in mouse renal tubular epithelial cells (mPTC) attenuated cisplatin-induced cell apoptosis, while their overexpression exacerbated cellular injury. Furthermore, pharmacological Dapk3 inhibition with HS148 recapitulated the renoprotective effects of Insig1 ablation in cisplatin-induced AKI mice. CONCLUSION:Our results unveil a novel Insig1/Dapk3 axis as a critical regulator of AKI progression, highlighting its potential as a therapeutic target in clinic.

The mode of electron transport in mitochondrial respiratory chain determines whether it generates energy or more reactive oxygen species (ROS), a key for cellular adaptation to diverse oxygen environments. However, the understanding of the mechanisms remains incomplete. Here, we find that NIMA-related kinase 7 (NEK7), targeted to mitochondria by its signal peptides, binds to succinate dehydrogenase complex iron sulfur subunit B (SDHB), stabilizing the spatial conformation of complex II and promoting forward electron transport. Deficiency of NEK7 in hepatocytes induces reverse electron transport (RET) and inhibits mitochondrial respiration, thereby promoting ROS generation, triggering spontaneous liver fibrosis and aggravating CCl4-induced liver fibrosis, which can be attenuated by RET inhibitors. More importantly, NEK7 overexpression effectively alleviates CCl4- and choline-deficient, high-fat diet-induced liver fibrosis. Overall, these findings highlight the pivotal role of NEK7 in orchestrating complex II and electron transport, providing new insights into the regulation of mitochondrial homeostasis and potential fibrosis treatments.

Acute kidney injury (AKI) is a globally recognized public health issue that lacks satisfactory therapeutic strategies. Deubiquitinase ubiquitin-specific protease 13 (USP13) regulates various pathophysiological processes via the deubiquitination of multiple substrates. However, its role in AKI remains unclear. To illustrate the role and underlying mechanism of USP13 in AKI, we subjected Usp13 knockdown mice, and mice treated with the USP13 inhibitor spautin-1, and mice with USP13 overexpression plasmids to cisplatin challenge. Renal tubular epithelial cell injury and mitochondrial disturbances were determined in vitro. Immunoprecipitation and deubiquitylation assays were performed to verify the interactions between USP13 and myeloid cell leukemia (MCL-1). We observed a significant decrease of USP13 expression in cisplatin-challenged AKI mice and renal tubular epithelial cells. Overexpression of USP13 alleviated kidney injury, whereas knockdown or inhibition of USP13 further exacerbated AKI. Mechanistically, USP13 downregulation resulted in increased degradation of MCL-1 which is a key regulator of cell survival and mitochondrial function, and the resultant MCL-1 reduction disrupted mitochondrial homeostasis and aggravated renal tubular epithelial cell injury and death, contributing to AKI progression. In conclusion, our findings demonstrated that inhibition of USP13 could exacerbate mitochondrial dysfunction and AKI through its effects on MCL-1, and USP13 may serve as a target for AKI prevention and treatment.

Cardiovascular disease (CVD) is reported to closely associate with the high mortality in patients with end-stage renal disease (ESRD), and endothelial damage induced by accumulated uremic toxins (mostly studied indoxyl sulfate [IS]) is the key pathological process, whose pathogenesis and therapeutic strategies remain incompletely understood. NIMA-related kinase 7 (NEK7) has been recognized as a novel mediator for NLRP3 inflammasome activation, which plays a crucial part in causing vascular endothelial injury. Here, we explored the potential functions and fundamental mechanisms of NEK7-mediated NLRP3 inflammasome activation in IS-induced endothelial injury. Expression of the NLRP3 inflammasome and its activation were markedly increased in IS-administered endothelium both in vivo and in vitro. Silencing NEK7, NLRP3, or caspase 1 significantly inhibited NLRP3 inflammasome activation, thereby alleviating IS-induced endothelial injury, as indicated by reduced inflammation and apoptosis in mouse arterial endothelial cells (MAECs). Furthermore, impaired endothelium in the aortas of both five-sixths nephrectomy mice and IS-injected mice with activated NLRP3 inflammasome, was either restored when conditional knockdown of NEK7 in endothelial cells or amplified upon NEK7 overexpression via hydrodynamic tail vein injection. Together, we validate that NEK7 promotes IS-induced endothelial injury by activating the NLRP3 inflammasome, which not only sheds lights on the underlying mechanisms of IS-mediated endothelial injury in ESRD, but also provides potential pharmacological target for the therapy of ESRD-related CVD.

Background & Aims:Acetaminophen (APAP)-induced acute liver injury (ALI) is a global health issue characterised by an incomplete understanding of its pathogenesis and unsatisfactory therapies. NEK7 plays critical roles in both cell cycle regulation and inflammation. In the present study, we investigated the role and mechanism of NEK7 in APAP-induced ALI.Methods:In mice with NEK7 overexpression (hydrodynamic tail vein injection of NEK7 plasmids), hepatocyte-specific NEK7 knockout (cKO), and inducible NEK7 knockout (iKO), an overdose of APAP was administered to induce ALI. Liver injury was determined by an analysis of serum liver enzymes, pathological changes, inflammatory cytokines, and metabonomic profiles. In vitro, hepatocyte damage was evaluated by an analysis of cell viability, the reactive oxygen species levels, and mitochondrial function in different cell lines. Hepatocyte proliferation and the cell cycle status were determined by Ki-67 staining, EdU staining, and the cyclin levels.Results:NEK7 was markedly downregulated in APAP-induced injured liver and damaged hepatocytes. NEK7 overexpression in the liver significantly alleviated APAP-induced liver injury, as shown by the restored liver function, reduced pathological injury, and decreased inflammation and oxidative stress, which was confirmed in a hepatocyte cell line. Moreover, both NEK7 cKO and iKO mice exhibited exacerbation of APAP-induced ALI. Finally, we determined that cyclin B1-mediated cell cycle progression could mediate the protective effect of NEK7 against APAP-induced ALI.Conclusions:Reduced NEK7 contributes to APAP-induced ALI, possibly by dysregulating cyclins and disturbing cell cycle progression.Lay summary:Acetaminophen-induced acute liver injury is one of the major global health issues, owing to its high incidence, potential severity, and limited therapeutic options. Our current understanding of its pathogenesis is incomplete. Herein, we have shown that reduced NEK7 (a protein with a key role in the cell cycle) exacerbates acetaminophen-induced acute liver injury. Hence, NEK7 could be a possible therapeutic target for the prevention or treatment of this condition.

Pregnane X receptor (PXR, NR1I2), a prototypical member of the nuclear receptor superfamily, has been implicated in various processes including metabolism, immune response, and inflammation. The immune system is made up of many interdependent parts, including lymphoid organs, cells, and cytokines, which play important roles in identifying, repelling, and eliminating pathogens and other foreign chemicals. An impaired immune system could contribute to various physical dysfunction, including severe infections, allergic diseases, autoimmune disorders, and other inflammatory diseases. Recent studies revealed the involvement of PXR in the pathogenesis of immune disorders and inflammatory responses. Thus, the aim of this work is to review and discuss the advances in research associated with PXR on immunity and inflammatory diseases and to provide insights into the development of therapeutic interventions of immune disorders and inflammatory diseases by targeting PXR.

Ubiquitin specific protease (USP)-13 is a deubiquitinase that removes ubiquitin from substrates to prevent protein degradation by the proteasome. Currently, the roles of USP13 in physiology and pathology have been reported. In physiology, USP13 is highly associated with cell cycle regulation, DNA damage repair, myoblast differentiation, quality control of the endoplasmic reticulum, and autophagy. In pathology, it has been reported that USP13 is important in the pathogenesis of infection, inflammation, idiopathic pulmonary fibrosis (IPF), neurodegenerative diseases, and cancers. This mini-review summarizes the most recent advances in USP13 studies involving its pathophysiological roles in different conditions and provides new insights into the prevention and treatment of relevant diseases, as well as further research on USP13.