Sex-Specific Regulation of Interferon-γ Cytotoxicity in Mouse Liver by Autophagy

Unveiling the hub genes associated with ochratoxin A-induced hepatotoxicity in broiler chickens

Ochratoxin A (OTA) widely exists in raw food and feed materials and can induce liver damage and toxicity. However, the mechanisms of OTA-induced hepatotoxicity were largely unknown. Thus, our study aimed to uncover the vital genes relevant to OTA-induced hepatotoxicity in broiler chickens. Gene expression data of chicken embryo primary hepatocytes (CEPHs) in OTA-treated and control groups were obtained from the GEO database. Totally 1407 differentially expressed genes (DEGs) were selected, of which 850 and 557 genes were up- and downregulated in OTA-treated CEPHs. Gene ontology (GO) enrichment revealed that the DEGs were in connection with various biological processes, such as signal transduction, extracellular matrix organization, axon guidance, cell division, cholesterol homeostasis, proteolysis, microtubule cytoskeleton organization, and chromosome segregation. Pathway enrichment showed that the DEGs were related to metabolic pathways, ferroptosis, calcium, FoxO, Wnt, cell cycle, apoptosis, calcium, and cell adhesion molecules signaling pathways. Furthermore, the hub genes, including CDK1, DLGAP5, KIF2C, VCL, ITGB3, and ZYX, were identified as hub genes potentially contributing to OTA-induced hepatotoxicity. Taken together, this study provides valuable insights into the mechanisms underlying OTA-induced hepatotoxicity in broiler chickens.

Differences in hepatocellular iron metabolism underlie sexual dimorphism in hepatocyte ferroptosis

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

The Liver in Hemophagocytic Lymphohistiocytosis: Not an Innocent Bystander

Hemophagocytic lymphohistiocytosis (HLH) is a rare multisystemic hyperinflammatory disease commonly associated with hepatic dysfunction. Liver injury is mediated by unchecked antigen presentation, hypercytokinemia, dysregulated cytotoxicity by natural killer and CD8 T cells, and disruption of intrinsic hepatic metabolic pathways. Over the past decade, there have been significant advances in diagnostics and expansion in therapeutic armamentarium for this disorder allowing for improved morbidity and mortality. This review discusses the clinical manifestations and pathogenesis of HLH hepatitis in both familial and secondary forms. It will review growing evidence that the intrinsic hepatic response to hypercytokinemia in HLH perpetuates disease progression and the novel therapeutic approaches for patients with HLH-hepatitis/liver failure.

Differences in Hepatocellular Iron Metabolism Underlie Sexual Dimorphism in Hepatocyte Ferroptosis

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe 2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe 2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

Essential Involvement of Neutrophil Elastase in Acute Acetaminophen Hepatotoxicity Using BALB/c Mice

Intense neutrophil infiltration into the liver is a characteristic of acetaminophen-induced acute liver injury. Neutrophil elastase is released by neutrophils during inflammation. To elucidate the involvement of neutrophil elastase in acetaminophen-induced liver injury, we investigated the efficacy of a potent and specific neutrophil elastase inhibitor, sivelestat, in mice with acetaminophen-induced acute liver injury. Intraperitoneal administration of 750 mg/kg of acetaminophen caused severe liver damage, such as elevated serum transaminase levels, centrilobular hepatic necrosis, and neutrophil infiltration, with approximately 50% mortality in BALB/c mice within 48 h of administration. However, in mice treated with sivelestat 30 min after the acetaminophen challenge, all mice survived, with reduced serum transaminase elevation and diminished hepatic necrosis. In addition, mice treated with sivelestat had reduced NOS-II expression and hepatic neutrophil infiltration after the acetaminophen challenge. Furthermore, treatment with sivelestat at 3 h after the acetaminophen challenge significantly improved survival. These findings indicate a new clinical application for sivelestat in the treatment of acetaminophen-induced liver failure through mechanisms involving the regulation of neutrophil migration and NO production.

Integrated regulation of stress responses, autophagy and survival by altered intracellular iron stores

Iron is a mineral essential for blood production and a variety of critical cellular functions. Altered iron metabolism has been increasingly observed in many diseases and disorders, but a comprehensive and mechanistic understanding of the cellular impact of impaired iron metabolism is still lacking. We examined the effects of iron overload or iron deficiency on cellular stress responses and autophagy which collectively regulate cell homeostasis and survival. Acute iron loading led to increased mitochondrial ROS (mtROS) production and damage, lipid peroxidation, impaired autophagic flux, and ferroptosis. Iron-induced mtROS overproduction is the mechanism of increased lipid peroxidation, impaired autophagy, and the induction of ferroptosis. Iron excess-induced ferroptosis was cell-type dependent and regulated by activating transcription factor 4 (ATF4). Upregulation of ATF4 mitigated iron-induced autophagic dysfunction and ferroptosis, whereas silencing of ATF4 expression impaired autophagy and resulted in increased mtROS production and ferroptosis. Employing autophagy-deficient hepatocytes and different autophagy inhibitors, we further showed that autophagic impairment sensitized cells to iron-induced ferroptosis. In contrast, iron deficiency activated the endoplasmic reticulum (ER) stress response, decreased autophagy, and induced apoptosis. Decreased autophagy associated with iron deficiency was due to ER stress, as reduction of ER stress by 4-phenylbutyric acid (4-PBA) improved autophagic flux. The mechanism of decreased autophagy in iron deficiency is a disruption in lysosomal biogenesis due to impaired posttranslational maturation of lysosomal membrane proteins. In conclusion, iron excess and iron deficiency cause different forms of cell stress and death in part through the common mechanism of impaired autophagic function.

Redundant Functions of ERK1 and ERK2 Maintain Mouse Liver Homeostasis Through Down-Regulation of Bile Acid Synthesis

Activation of extracellular signal-regulated kinase (ERK) 1/2 promotes hepatocyte proliferation in response to growth stimuli, but whether constitutive hepatocyte ERK1/2 signaling functions in liver physiology is unknown. To examine the role of ERK1/2 in hepatic homeostasis, the effects of a knockout of Erk1 and/or Erk2 in mouse liver were examined. The livers of mice with a global Erk1 knockout or a tamoxifen-inducible, hepatocyte-specific Erk2 knockout were normal. In contrast, Erk1/2 double-knockout mice developed hepatomegaly and hepatitis by serum transaminases, histology, terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick end-labeling, and assays of hepatic inflammation. Liver injury was associated with biochemical evidence of cholestasis with increased serum and hepatic bile acids and led to hepatic fibrosis and mortality. RNA sequencing and polymerase chain reaction analysis of double-knockout mouse livers revealed that the rate-limiting bile acid synthesis gene Cyp7a1 (cholesterol 7α-hydroxylase) was up-regulated in concert with decreased expression of the transcriptional repressor short heterodimer partner. Elevated bile acids were the mechanism of liver injury, as bile acid reduction by SC-435, an inhibitor of the ileal apical sodium-dependent bile acid transporter, prevented liver injury. Conclusion: Constitutive ERK1 and ERK2 signaling has a redundant but critical physiological function in the down-regulation of hepatic bile acid synthesis to maintain normal liver homeostasis.

Mouse liver injury induces hepatic macrophage FGF23 production

Fibroblast growth factor 23 (FGF23) is a bone marrow cell produced hormone that functions in the intestine and kidney to regulate phosphate homeostasis. Increased serum FGF23 is a well-established predictor of mortality in renal disease, but recent findings linking increased levels to hepatic and cardiac diseases have suggested that other organs are sources of FGF23 or targets of its effects. The potential ability of the liver to produce FGF23 in response to hepatocellular injury was therefore examined. Very low levels of Fgf23 mRNA and FGF23 protein were detected in normal mouse liver, but the amounts increased markedly during acute liver injury from the hepatotoxin carbon tetrachloride. Serum levels of intact FGF23 were elevated during liver injury from carbon tetrachloride. Chronic liver injury induced by a high fat diet or elevated bile acids also increased hepatic FGF23 levels. Stimulation of toll-like receptor (TLR) 4-driven inflammation by gut-derived lipopolysaccharide (LPS) underlies many forms of liver injury, and LPS induced Fgf23 in the liver as well as in other organs. The LPS-inducible cytokines IL-1β and TNF increased hepatic Fgf23 expression as did a TLR2 agonist Pam2CSK3. Analysis of Fgf23 expression and FGF23 secretion in different hepatic cell types involved in liver injury identified the resident liver macrophage or Kupffer cell as a source of hepatic FGF23. LPS and cytokines selectively induced the hormone in these cells but not in hepatocytes or hepatic stellate cells. FGF23 failed to exert any autocrine effect on the inflammatory state of Kupffer cells but did trigger proinflammatory activation of hepatocytes. During liver injury inflammatory factors induce Kupffer cell production of FGF23 that may have a paracrine proinflammatory effect on hepatocytes. Liver-produced FGF23 may have systemic hormonal effects as well that influence diseases in in other organs.

Study on the effect of active components of Schisandra chinensis on liver injury and its mechanisms in mice based on network pharmacology

The aim of this study was to analyze the active components of Schisandra chinensis on liver injury and its mechanism in mice by network pharmacology. The active components of S. chinensis were found through Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and their corresponding targets were predicted. The targets of liver injury were searched through Therapeutic Targets Database (TTD), DisGeNET and drugbank databases, and the Venn diagram was constructed to obtain the action targets. The "drug-active component-target" network and protein-protein interaction network (PPI) were constructed by using STRING database and Cytoscape software, and the key targets were further screened by the enrichment analysis of relevant KEGG pathways. Finally, a CCl4-induced mouse liver injury model was established to verify the efficacy and related targets of S. chinensis and clarify its mechanism. Eight active components and 56 related targets of S. chinensis were screened out based on their oral bioavailability (OB) and drug likeness (DL). Five targets of S. chinensis related to liver injury were found by using the Venn diagram. The key targets, namely Ptgs2 and Nos2 genes, were further screened out by constructing a PPI network, and Schisandrol B (SCB) was considered the key component most closely related to the liver injury in S. chinensis. The results indicate that SCB may play a role in the treatment of the CCl4-induced liver injury by down-regulating the expression of iNOS and COX-2, and regulating the expression of NF-κB and IL-17 signaling pathway to inhibit the expression of proinflammatory factors.