Glycogen synthase kinase 3β promotes liver innate immune activation by restraining AMP-activated protein kinase activation

ER stress promotes mitochondrial calcium overload and activates the ROS/NLRP3 axis to mediate fatty liver ischemic injury

BACKGROUND

Fatty livers are widely accepted as marginal donors for liver transplantation but are more susceptible to liver ischemia and reperfusion (IR) injury. Increased macrophage-related inflammation plays an important role in the aggravation of fatty liver IR injury. Here, we investigate the precise mechanism by which endoplasmic reticulum (ER) stress activates macrophage NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) signaling by regulating mitochondrial calcium overload in fatty liver IR.

METHODS

Control- and high-fat diet-fed mice were subjected to a partial liver IR model. The ER stress, mitochondrial calcium levels, and NLRP3 signaling pathway in macrophages were analyzed.

RESULTS

Liver steatosis exacerbated liver inflammation and IR injury and enhanced NLRP3 activation in macrophages. Myeloid NLRP3 deficiency attenuated intrahepatic inflammation and fatty liver injury following IR. Mechanistically, increased ER stress and mitochondrial calcium overload were observed in macrophages obtained from mouse fatty livers after IR. Suppression of ER stress by tauroursodeoxycholic acid effectively downregulated mitochondrial calcium accumulation and suppressed NLRP3 activation in macrophages, leading to decreased inflammatory IR injury in fatty livers. Moreover, Xestospongin-C-mediated inhibition of mitochondrial calcium influx decreased reactive oxygen species (ROS) expression in macrophages after IR. Scavenging of mitochondrial ROS by mito-TEMPO suppressed macrophage NLRP3 activation and IR injury in fatty livers, indicating that excessive mitochondrial ROS production was responsible for macrophage NLRP3 activation induced by mitochondrial calcium overload. Patients with fatty liver also exhibited upregulated activation of NLRP3 and the ER stress signaling pathway after IR.

CONCLUSIONS

Our findings suggest that ER stress promotes mitochondrial calcium overload to activate ROS/NLRP3 signaling pathways within macrophages during IR-stimulated inflammatory responses associated with fatty livers.

GSK3β: A ray of hope for the treatment of diabetic kidney disease

Diabetic kidney disease (DKD), a major microvascular complication of diabetes, is characterized by its complex pathogenesis, high risk of chronic renal failure, and lack of effective diagnosis and treatment methods. GSK3β (glycogen synthase kinase 3β), a highly conserved threonine/serine kinase, was found to activate glycogen synthase. As a key molecule of the glucose metabolism pathway, GSK3β participates in a variety of cellular activities and plays a pivotal role in multiple diseases. However, these effects are not only mediated by affecting glucose metabolism. This review elaborates on the role of GSK3β in DKD and its damage mechanism in different intrinsic renal cells. GSK3β is also a biomarker indicating the progression of DKD. Finally, the protective effects of GSK3β inhibitors on DKD are also discussed.

SNX10 promoted liver IR injury by facilitating macrophage M1 polarization via NLRP3 inflammasome activation

BACKGROUND

Liver ischemia reperfusion (IR) injury is a common cause of liver dysfunction in patients post liver partial resection and liver transplantation. However, the cellular defense mechanisms underlying IR are not well understood. Macrophage mediated sterile inflammation plays critical roles in liver IR injury. Sorting nexin (SNX) 10, a member of the SNX family which functions in regulation of endosomal sorting. This study aimed to explore the role of sorting nexin 10 (SNX10) during liver IR injury with a focus on regulating macrophage function.

METHODS

Both the gene and protein expression levels of SNX10 were analyzed in human specimens from 10 patients undergoing liver partial resection with ischemic insult and in a mouse model of liver IR. The in vivo effects of SNX10 in liver IR injury and sterile inflammation in mice were investigated. Bone marrow derived macrophages (BMDMs) were used to determine the role of SNX10 in modulating macrophage function in vitro.

RESULTS

Increased expression of SNX10 was observed both in human specimens and mice livers post IR. SNX10 knockdown alleviated IR induced sterile inflammation and liver damage in mice. SNX10 promoted M1 polarization of macrophage treated with LPS and facilitated inflammatory response by activating NLRP3 inflammasome.

CONCLUSIONS

We report for the first time that SNX10 is upregulated in IR-stressed livers. SNX10 activation aggravates liver IR injury and sterile inflammation by facilitating macrophage M1 polarization and inflammatory response suggesting SNX10 as a potential therapeutic target for liver IR injury.

Protective Effect of Monoterpene Isoespintanol in a Rat Model of Prediabetes Induced by Fructose

A high-fructose diet (HFD) induces murine alterations like those recorded in human prediabetes. Protective effects of isoespintanol (monoterpene isolated from Oxandra cf. xylopioides) on changes induced by HFD were evaluated. Animals were maintained for 21 days with a standard diet (C), 10% fructose (F), and F plus isoespintanol (FI, 10 mg/kg, i.p.). Glycemia, triglyceridemia, total and HDL-cholesterol, and insulin resistance index (IRX) were determined. Intraperitoneal glucose tolerance test (IGTT) was performed. In the liver, we measured glycogen, lipogenic gene expression (SREBP-1c, GPAT, FAS, and CPT1), oxidative stress (GSH and 3'-nitrotyrosine content), inflammation markers (iNOS, TNF-α, and PAI-1 gene expression; iNOS and COX-2 protein levels), p-eNOS, p-Akt, and p-GSK3β protein levels. Isoespintanol corrected enhanced triglycerides, lipogenic genes, and IRX, and reduced HDL-cholesterol induced by HFD. Increased liver glycogen and inflammatory markers and decreased GSH, p-Akt, and p-GSK3β measured in F rats were reversed by isoespintanol, and p-eNOS/e-NOS and iNOS/GADPH ratios were normalized. Isoespintanol restored glucose tolerance (IGTT) compared to F rats. These results demonstrate for the first time that isoespintanol prevents endocrine-metabolic alterations induced by HFD in prediabetic rats. These effects could be mediated by Akt/eNOS and Akt/GSK3β pathways, suggesting its possible use as a therapeutic tool for the prevention of diabetes at early stages of its development (prediabetes).

Limonin, a novel AMPK activator, protects against LPS-induced acute lung injury

AMP-activated protein kinase (AMPK) activation plays crucial roles in the treatment of many oxidative stress- and inflammation-induced diseases, including acute lung injury (ALI). Limonin is a naturally occurring tetracyclic triterpenoid extracted from the plants of Rutaceae and Meliaceae. Limonin also serves as an AMPK activator with anti-inflammatory and anti-oxidation effects. However, the potential beneficial effects of limonin on ALI and the possible mechanisms have never been disclosed till now. Here, the effects of limonin on lipopolysaccharide (LPS)-induced ALI in C57 BL/6 mice, plus bone marrow-derived macrophages (BMDM) stimulated with LPS to induce in vitro ALI model were investigated. Limonin significantly improved pulmonary function and alleviated lung pathological injury in LPS-induced mice. Meanwhile, limonin also markedly decreased inflammation and oxidative stress in lung tissues from LPS-treated mice. In vitro experiments also unveiled that limonin could decrease inflammation and oxidative stress in LPS-induced BMDM in a concentration-dependent manner. Mechanically, limonin could promote the activation of AMPKα and upregulate the expression of nuclear factor erythroid 2-related factor 2 (NRF2) in lung tissues and BMDM. Pharmacological inhibition of AMPKα by Compound C or AMPKα knockout could abolish the pulmonary protection from limonin during ALI. In conclusion, limonin mediates the activation of AMPKα/NRF2 pathway, providing an attractive therapeutic target for ALI in the future.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury

Aged livers have shown aggravated liver ischemia and reperfusion (IR) injury. Timely efferocytosis of apoptotic cells is a key mechanism for avoiding excessive inflammation and tissue injury. Here, we investigated the alteration of efferocytosis by aged macrophages and its role in regulating macrophage STING (stimulator of interferon genes) signaling and liver IR injury. Aged and young mice were subjected to liver partial IR model. Liver injury and inflammation were measured. Efferocytosis by aged macrophages and the underlying regulatory mechanism were analyzed as well. Aged macrophages exhibited impaired efferocytosis with decreased MerTK (c-mer proto-oncogene tyrosine kinase) activation, which was reversed by treatment of the MerTK CRISPR activation plasmid. Increased MerTK cleavage by ADAM17 (a disintegrin and metalloproteinase 17) due to enhanced ROS (reactive oxygen species) levels contributed to defective efferocytosis by aged macrophages. MerTK activation by suppressing ADAM17 or ROS improved aged macrophage efferocytosis, leading to reduced inflammatory liver injury. Moreover, increased apoptotic hepatocytes, DNA accumulation, and macrophage STING activation were observed in aged ischemic livers. Improvement in efferocytosis by aged macrophages via MerTK activation suppressed STING activation and inflammatory liver injury. Our study demonstrates that aging suppresses MerTK- mediated macrophage efferocytosis to promote macrophage STING activation and inflammatory liver IR injury, suggesting a new mechanism and potential therapy to promote inflammation resolution and efferocytosis in aged livers.

Chicken Glycogen Synthase Kinase 3β Suppresses Innate Immune Responses and Enhances Avian Leukosis Virus Replication in DF-1 Cells

Glycogen synthase kinase 3β (GSK3β) is a widely distributed multifunctional serine/threonine kinase. In mammals, GSK3β regulates important life activities such as proinflammatory response, anti-inflammatory response, immunity, and cancer development. However, the biological functions of chicken GSK3β (chGSK3β) are still unknown. In the present study, the full-length cDNA of chGSK3β was first cloned and analyzed. Absolute quantification of chicken chGSK3β in 1-day-old specific-pathogen-free birds has shown that it is widely expressed in all tissues, with the highest level in brain and the lowest level in pancreas. Overexpression of chGSK3β in DF-1 cells significantly decreased the gene expression levels of interferon beta (IFN-β), IFN regulatory factor 7 (IRF7), Toll-like receptor 3 (TLR3), melanoma differentiation-associated protein 5 (MDA5), MX-1, protein kinase R (PKR), and oligoadenylate synthase-like (OASL), while promoting the replication of avian leukosis virus subgroup J (ALV-J). Conversely, levels of most of the genes detected in this study were increased when chGSK3β expression was knocked down using small interfering RNA (siRNA), which also inhibited the replication of ALV-J. These results suggest that chGSK3β plays an important role in the antiviral innate immune response in DF-1 cells, and it will be valuable to carry out further studies on the biological functions of chGSK3β. IMPORTANCE GSK3β regulates many life activities in mammals. Recent studies revealed that chGSK3β was involved in regulating antiviral innate immunity in DF-1 cells and also could positively regulate ALV-J replication. These results provide new insights into the biofunction of chGSK3β and the virus-host interactions of ALV-J. In addition, this study provides a basis for further research on the function of GSK3 in poultry.

β-Hydroxybutyric acid upregulated by Suhuang antitussive capsule ameliorates cough variant asthma through GSK3β/AMPK-Nrf2 signal axis

ETHNOPHARMACOLOGICAL RELEVANCE

Cough variant asthma (CVA) is a chronic inflammatory disease characterized by cough as the main symptom. Suhuang antitussive capsule (Suhuang), one of traditional Chinese patent medicines, mainly treats CVA clinically. Previous studies have shown that Suhuang significantly improved CVA, post-infectious cough (PIC), sputum obstruction and airway remodeling. However, the effect of Suhuang on ovalbumin-induced (OVA-induced) metabolic abnormalities in CVA is unknown.

AIM OF THE STUDY

This study aimed to identify potential metabolites associated with efficacy of Suhuang in the treatment of CVA, and determined how Suhuang regulates metabolites, and differential metabolites reduce inflammation and oxidative stress.

MATERIALS AND METHODS

Rats were given 1 mg OVA/100 mg aluminum hydroxide in the 1st and 7th days by intraperitoneal injection and challenged by atomizing inhalation of 1% OVA saline solution after two weeks to establish the CVA model. Rats were intragastrically (i.g.) administrated with Suhuang at 1.4 g/kg and β-hydroxybutyric acid (β-HB) were given with different concentrations (87.5 and 175 mg/kg/day) by intraperitoneal injection for 2 weeks. After 26 days, GC-MS-based metabolomic approach was applied to observe metabolic changes and search differential metabolites. The number of coughs, coughs latencies, enzyme-linked immunosorbent assay (ELISA), histological analysis and quantitative-polymerase chain reaction (Q-PCR) were used to investigate the effects of Suhuang. Then β-HB on CVA rats, NLRP3 inflammasome and GSK3β/AMPK/Nrf2 signalling pathway were detected by western blotting.

RESULTS

The results showed that Suhuang treatment significantly enhanced the serum level of β-HB. Interestingly, exposure to exogenous β-HB was also protective against OVA-induced CVA. β-HB significantly reduced the number of coughs and lengthened coughs latencies, improved lung injury, reduced the secretion of various cytokines, and directly inhibited the NLRP3 inflammasome. In addition, β-HB increased the nuclear accumulation of Nrf2 by activating the GSK3β/AMPK signaling axis, and then inactivating the NF-κB signaling pathway, effectively protecting OVA-induced CVA from oxidative stress and inflammation.

CONCLUSIONS

The results of this study shows that β-HB can reduce inflammation and oxidative stress, the increased production of β-HB in serum might be the crucial factor for Suhuang to exert its effect in the treatment of CVA.

TRIM37 exacerbates hepatic ischemia/reperfusion injury by facilitating IKKγ translocation

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury is one of the major pathological processes associated with various liver surgeries. However, there is still a lack of strategies to protect against hepatic I/R injury because of the unknown underlying mechanism. The present study aimed to identify a potential strategy and provide a fundamental experimental basis for treating hepatic I/R injury.

METHOD

A classic 70% ischemia/reperfusion injury was established. Immunoprecipitation was used to identify direct interactions between proteins. The expression of proteins from different subcellular localizations was detected by Western blotting. Cell translocation was directly observed by immunofluorescence. HE, TUNEL and ELISA were performed for function tests.

RESULT

We report that tripartite motif containing 37 (TRIM37) aggravates hepatic I/R injury through the reinforcement of IKK-induced inflammation following dual patterns. Mechanistically, TRIM37 directly interacts with tumor necrosis factor receptor-associated factor 6 (TRAF6), inducing K63 ubiquitination and eventually leading to the phosphorylation of IKKβ. TRIM37 enhances the translocation of IKKγ, a regulatory subunit of the IKK complex, from the nucleus to the cytoplasm, thereby stabilizing the cytoplasmic IKK complex and prolonging the duration of inflammation. Inhibition of IKK rescued the function of TRIM37 in vivo and in vitro.

CONCLUSION

Collectively, the present study discloses some potential function of TRIM37 in hepatic I/R injury. Targeting TRIM37 might be potential for treatment against hepatic I/R injury.Targeting TRIM37 might be a potential treatment strategy against hepatic I/R injury.

Malic Enzyme 1 as a Novel Anti-Ferroptotic Regulator in Hepatic Ischemia/Reperfusion Injury

Ferroptosis has been linked to the pathogenesis of hepatic injury induced by ischemia/reperfusion (I/R). However, the mechanistic basis remains unclear. In this study, by using a mouse model of hepatic I/R injury, it is observed that glutathione (GSH) and cysteine depletion are associated with deficiency of the reducing power of nicotinamide adenine dinucleotide phosphate (NADPH). Genes involved in maintaining NADPH homeostasis are screened, and it is identified that I/R-induced hepatic ferroptosis is significantly associated with reduced expression and activity of NADP⁺ -dependent malic enzyme 1 (Me1). Mice with hepatocyte-specific Me1 gene deletion exhibit aggravated ferroptosis and liver injury under I/R treatment; while supplementation with L-malate, the substrate of ME1, restores NADPH and GSH levels and eventually inhibits I/R-induced hepatic ferroptosis and injury. A mechanistic study further reveals that downregulation of hepatic Me1 expression is largely mediated by the phosphatase and tensin homologue (PTEN)-dependent suppression of the mechanistic target of rapamycin/sterol regulatory element-binding protein 1 (mTOR/SREBP1) signaling pathway in hepatic I/R model. Finally, PTEN inhibitor, mTOR activator, or SREBP1 over-expression all increase hepatic NADPH, block ferroptosis, and protect liver against I/R injury. Taken together, the findings suggest that targeting ME1 may provide new therapeutic opportunities for I/R injury and other ferroptosis-related hepatic conditions.

GAS6 From CD200+ Adipose-Derived Stem Cells Mitigates Colonic Inflammation in a Macrophage-Dependent Manner

BACKGROUND AND AIMS

Stem cell therapy is a promising cell-based treatment modality for inflammatory bowel diseases [IBD], but its application is limited by the nature of cell heterogeneity.

METHODS

Single-cell RNA-sequencing was performed on the adipose-derived stem cells [ADSCs]. The in vitro immunomodulatory effect of ADSCs was evaluated by co-culturing with human CD4+ T cells or macrophages. The in vivo therapeutic value of ADSCs was assessed using a murine colitis model induced by dextran sulphate sodium [DSS] or 2,4,6-trinitrobenzene sulphonic acid [TNBS].

RESULTS

CD200+ ADSCs were identified as a novel subpopulation of ADSCs, based on gene ontology analysis of immunoregulatory functions. The immunoregulatory functions of these cells were further confirmed by co-culturing with CD4+ T cells or macrophages. Administration of CD200+ ADSCs effectively reduced intestinal inflammation in IBD mice models. Furthermore, we found CD200+ ADSCs-derived GAS6 exerted protective effects on experimental colitis by promoting macrophage M2 polarization via the Mer/PI3K/Akt/GSK3β signalling pathway.

CONCLUSIONS

This study uncovered the heterogeneity in ADSCs, in which CD200+ ADSCs presents as an alternative to conventional treatment of IBD.

Macrophage STING signaling promotes NK cell to suppress colorectal cancer liver metastasis via 4-1BBL/4-1BB co-stimulation

BACKGROUND AND AIMS

Macrophage innate immune response plays an important role in tumorigenesis. However, the role and mechanism of macrophage STING signaling in modulating tumor microenvironment to suppress tumor growth at secondary sites remains largely unclear.

METHODS

STING expression was assessed in liver samples from patients with colorectal cancer (CRC) liver metastasis. Global or myeloid stimulator of interferon gene (STING)-deficient mice, myeloid NOD-like receptor protein 3 (NLRP3)-deficient mice, and wild-type (WT) mice were subjected to a mouse model of CRC liver metastasis by intrasplenic injection of murine colon carcinoma cells (MC38). Liver non-parenchymal cells including macrophages and natural killer (NK) cells were isolated for flow cytometry analysis. Bone marrow-derived macrophages pretreated with MC38 were co-cultured with splenic NK cells for in vitro studies.

RESULTS

Significant activation of STING signaling were detected in adjacent and tumor tissues and intrahepatic macrophages. Global or myeloid STING-deficient mice had exacerbated CRC liver metastasis and shorten survival, with decreased intrahepatic infiltration and impaired antitumor function of NK cells. Depletion of NK cells in WT animals increased their metastatic burden, while no significant effects were observed in myeloid STING-deficient mice. STING activation contributed to the secretion of interleukin (IL)-18 and IL-1β by macrophages, which optimized antitumor activity of NK cells by promoting the expression of 4-1BBL in macrophages and 4-1BB in NK cells, respectively. Moreover, MC38 treatment activated macrophage NLRP3 signaling, which was inhibited by STING depletion. Myeloid NLRP3 deficiency increased tumor burden and suppressed activation of NK cells. NLRP3 activation by its agonist effectively suppressed CRC liver metastasis in myeloid SITNG-deficient mice.

CONCLUSIONS

We demonstrated that STING signaling promoted NLRP3-mediated IL-18 and IL-1β production of macrophages to optimize the antitumor function of NK cells via the co-stimulation signaling of 4-1BBL/4-1BB.

CoQ10 alleviates hepatic ischemia reperfusion injury via inhibiting NLRP3 activity and promoting Tregs infiltration

Hepatic ischemia-reperfusion injury (IRI) has been concerned as a main complication of liver surgery and transplantation. Previous studies show that reactive oxygen species (ROS) associated inflammation response and contribute to the liver damage during IRI. Coenzyme Q10 (CoQ10) has shown many beneficial effects on abrogating ROS production and ameliorating liver injury. This study found lower CoQ10 level in the process of liver IRI in a mouse model of hepatic IRI. Meanwhile, our results showed that CoQ10 administration significantly attenuate hepatic IRI proved by HE staining, serum ALT/AST. The NOD-like receptor protein 3 (NLRP3) inflammasome is activated by ROS which triggers the activation of inflammatory caspases. In this study, NLRP3 was significantly suppressed by CoQ10 while Foxp3 exhibited increased expression in liver. Furthermore, Kupffer cells (KCs) pretreated with CoQ10 under the condition of hypoxia and reoxygenation contributed to improved CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) ratio in co-culture system. Furthermore, NLRP3 inflammasome activator treatment in vivo resulted in higher expression of caspase-1 and NLRP3 and reduction of Tregs in liver, which reversed the protection of CoQ10 in the liver injury. Taken together, our study discovered that CoQ10 can suppress NLRP3 activity in KCs and improves Foxp3⁺ Tregs differentiation depending on M2 macrophage polarization of KCs to ameliorate hepatic IRI.

ATG2B upregulated in LPS-stimulated BMSCs-derived exosomes attenuates septic liver injury by inhibiting macrophage STING signaling

Pretreated mesenchymal stem cells (MSCs)-derived exosomes have shown great potential in the treatment of various inflammatory diseases. Recent evidence suggests that macrophage stimulator of interferon genes (STING) signal activation plays a critical role in sepsis and septic liver injury. Here, we aimed to investigate the role and effects of lipopolysaccharide (LPS)-pretreated bone marrow mesenchymal stem cells (BMSCs)-derived exosomes (L-Exo) on macrophage STING signaling in septic liver injury. Exosomes were collected from the BMSCs medium via ultracentrifugation. Liver injury, intrahepatic inflammation, and the activation of macrophage STING signaling were analyzed. Mitophagy and the release of mitochondrial DNA (mtDNA) into the cytosol were investigated. Through in vivo and in vitro experiments, L-Exo could markedly attenuate cecal ligation and puncture-induced septic liver injury and inhibit macrophage STING signaling. Mechanistically, L-Exo inhibited macrophage STING signaling by enhancing mitophagy and inhibiting the release of mtDNA into the cytosol. Furthermore, autophagy-related protein 2 homolog B (ATG2B) may be a major factor involved in this effect of L-Exo. These findings reveal that macrophage STING signaling plays an important role in septic liver injury and may be a therapeutic target. In addition, LPS pretreatment is an effective and promising approach for optimizing the therapeutic efficacy of MSCs-derived exosomes in septic liver injury, providing new strategies for treatment.

MLKL deficiency attenuated hepatocyte oxidative DNA damage by activating mitophagy to suppress macrophage cGAS-STING signaling during liver ischemia and reperfusion injury

Mixed-lineage kinase domain-like protein (MLKL)-mediated necroptosis has been implicated in aggravating liver ischemia and reperfusion (IR) injury. However, the precise role and mechanism of MLKL in regulating oxidative DNA damage of hepatocytes and subsequent activation of macrophage stimulator of interferon genes (STING) signaling remains unclear. In this study, we investigated the role of MLKL in regulating the interplay between hepatocyte injury and macrophage pro-inflammatory responses during liver IR injury. We found that IR increased MLKL expression in liver tissues of wild type (WT) mice. MLKL knockout (KO) attenuated liver IR injury and suppressed the activation of cGAS-STING signaling in intrahepatic macrophages, which was abrogated by STING activation with its agonist. Mechanistically, IR induced oxidative DNA damage in hepatocytes, leading to cGAS-STING activation in macrophages, which was suppressed by MLKL KO. Moreover, increased PTEN-induced kinase 1 (PINK1)-mediated mitophagy contributed to reduced oxidative DNA damage in hepatocytes and subsequent decreased activation of STING signaling in macrophages in MLKL KO mice. Our findings demonstrated a non-canonical role of MLKL in the pathogenesis of liver IR. MLKL deficiency significantly promoted PINK1-mediated mitophagy activation to inhibit oxidative DNA damage in hepatocytes, which in turn suppressed macrophage cGAS-STING activation and inflammatory liver IR injury.

Gsk3β regulates the resolution of liver ischemia/reperfusion injury via MerTK

Although glycogen synthase kinase β (Gsk3β) has been shown to regulate tissue inflammation, whether and how it regulates inflammation resolution versus inflammation activation is unclear. In a murine liver, partial warm ischemia/reperfusion injury (IRI) model, we found that Gsk3β inhibitory phosphorylation increased at both the early-activation and late-resolution stages of the disease. Myeloid Gsk3β deficiency not only alleviated liver injuries, it also facilitated the restoration of liver homeostasis. Depletion of Kupffer cells prior to the onset of liver ischemia diminished the differences between the WT and Gsk3β-KO mice in the activation of liver IRI. However, the resolution of liver IRI remained accelerated in Gsk3β-KO mice. In CD11b-DTR mice, Gsk3β-deficient BM-derived macrophages (BMMs) facilitated the resolution of liver IRI as compared with WT cells. Furthermore, Gsk3β deficiency promoted the reparative phenotype differentiation in vivo in liver-infiltrating macrophages and in vitro in BMMs. Gsk3 pharmacological inhibition promoted the resolution of liver IRI in WT, but not myeloid MerTK-deficient, mice. Thus, Gsk3β regulates liver IRI at both activation and resolution stages of the disease. Gsk3 inactivation enhances the proresolving function of liver-infiltrating macrophages in an MerTK-dependent manner.

Macrophage GSK3β-deficiency inhibits the progression of hepatocellular carcinoma and enhances the sensitivity of anti-PD1 immunotherapy

BACKGROUND

Glycogen synthase kinase 3β (GSK3β) was originally discovered to regulate glycogen synthesis and show a relationship to tumors. However, the biological functions of GSK3β in tumor-associated macrophages (TAMs) in cancers including hepatocellular carcinoma (HCC) remain unclear.

METHODS

The enrichment of GSK3β in tumor tissues was assessed by Gene Expression Omnibus (GEO) database. The in vitro and in vivo assays assisted in evaluating how GSK3β in TAMs affected HCC in terms of proliferation, invasion and migration. Immunofluorescence was used to assess GSK3β expression in TAMs in the anti-PD1 therapy non-responsive HCC group and the responsive group. Western blot and coimmunoprecipitation were performed to demonstrate the interaction between GSK3β and PD-L1. We carried out in vivo experiments in a C57BL/6 mouse model of HCC established through subcutaneous injection.

RESULTS

GEO single-cell RNA sequencing data suggested that GSK3β was highly enriched in TAMs of HCC. According to in vitro and in vivo experiments, reducing GSK3β in TAMs inhibits the cancer cell proliferation, invasion, and migration. The immunofluorescence and immunohistochemistry results confirmed that the GSK3β is significantly upregulated in TAMs of the anti-PD1 therapy non-responsive group in comparison with the responsive group. In vitro and in vivo experiments confirmed that reduced GSK3β in TAMs are capable of enhancing the sensitivity of anti-PD1 immunotherapy for HCC by decreasing PD-L1 ubiquitination. Mass spectrometry results suggested that high expression of CD14⁺GSK3β⁺ in the peripheral blood mononuclear cell (PBMC) can predict non-responsive to anti-PD1 treatment. Moreover, escitalopram is confirmed to act as GSK3β inhibitor that can increase the sensitivity of anti-PD1 immunotherapy for HCC.

CONCLUSIONS

This study revealed that macrophage GSK3β deficiency can inhibit the development of HCC by inhibiting the M2 phenotype and enhance the sensitivity of anti-PD1 immunotherapy for HCC by decreasing PD-L1 ubiquitination. The expression of CD14⁺GSK3β⁺ in PBMC can noninvasively predict anti-PD1 sensitivity in HCC patients, which provides novel strategies to predict anti-PD1 sensitivity, increase anti-PD1 therapeutic effect, and bring new hope for HCC patients.

Development and validation of a combined metabolism and immune prognostic model in lung adenocarcinoma

Background

Tumor metabolism and immune response can affect the biological behavior of tumor cells. There is an obvious relationship between glycolysis and immune response. However, the association between metabolism and immune response and prognosis in lung adenocarcinoma (LUAD) has not yet been examined in a comprehensive and detailed manner. The establishment of reliable models for predicting the prognosis of LUAD based on glycolysis ability and immune status is still highly anticipated.

Methods

The expression of genes were obtained from online databases, and the differentially expressed genes in LUAD tissues and adjacent tissues were identified. We used LUAD samples in The Cancer Genome Atlas (TCGA) database as training set and the Gene Expression Omnibus (GEO) databases as validation sets. The best predictive model was constructed using least absolute selection and shrinkage operator (LASSO) regression and Cox regression. The receiver operator characteristic (ROC) curve is used to verify the accuracy of the model. The expression status of the Glycolysis-related genes (GRGs) and the status of the immune cells in LUCD patients were further analyzed. The protein levels of the 3 identified genes were then tested in LUAD patients.

Results

We identified 3 GRGs and immune-related genes (i.e., fibroblast growth factor 2, hyaluronan-mediated motor receptor, and nuclear receptor 0B2) and constructed a stable comprehensive index of glycolysis and immunity (CIGI) prediction model. The validation results for this CIGI model were quite stable across different datasets and patient subgroups and the CIGI score can be included as an independent prognostic factor for LUAD patients. The area under the curve (AUC) values of 1-, 3- and 5-year of the finally established nomogram model are 0.767, 0.735 and 0.769. Further analysis showed that LUAD patients in the low-risk group had lower levels of glycolytic gene expression than those in the high-risk group and exhibited an immunosuppressed state. Finally, hyaluronan-mediated motor receptor may play a role in inhibiting cancer, while fibroblast growth factor 2 and nuclear receptor 0B2 may play roles in promoting cancer.

Conclusions

In this study, we established a new prognostic prediction model for LUAD patients that combines glycolysis ability and immune status.

Increased oxidative stress caused by impaired mitophagy aggravated liver ischemia and reperfusion injury in diabetic mice

AIMS/INTRODUCTION

Emerging evidence has suggested the detrimental role of oxidative stress in aggravating ischemia and reperfusion (IR) injury in diabetic livers. Interplay between oxidative stress and mitophagy has been shown. However, the role and mechanism of mitophagy in regulating oxidative stress and IR injury in diabetic livers remain unclear.

MATERIALS AND METHODS

Wild-type and db/db (DB) mice were subjected to a partial warm liver IR model. Liver injury, oxidative stress, mitophagy and related molecular pathways were analyzed.

RESULTS

Here, we found that increased liver IR injury was observed in DB mice, as evidenced by higher levels of serum alanine aminotransferase and serum aspartate, worsened liver architecture damage and more hepatocellular death. DB mice also showed increased mitochondrial oxidative stress. Mitochondrial reactive oxygen species scavenge alleviated liver IR injury in DB mice. Mechanistic analysis showed that 5' adenosine monophosphate-activated protein kinase-mediated mitophagy was suppressed in DB mice post-IR. Pharmacological activation of 5' adenosine monophosphate-activated protein kinase by its agonist effectively restored mitophagy activation, leading to decreased mitochondrial oxidative stress and attenuated liver IR injury in DB mice.

CONCLUSIONS

Our findings showed that diabetes increased oxidative stress to exacerbate liver IR injury by impairing 5' adenosine monophosphate-activated protein kinase-mediated mitophagy. Strategies targeting oxidative stress and mitophagy might provide a promising approach to ameliorate liver IR injury in diabetes patients.

Deoxyarbutin attenuates severe acute pancreatitis via the HtrA2/PGC-1α pathway

Severe acute pancreatitis (SAP) is an inflammatory disorder of the exocrine pancreas associated with high morbidity and mortality. SAP has been proven to trigger mitochondria dysfunction in the pancreas. We found that Deoxyarbutin (dA) recovered impaired mitochondrial function. High-temperature requirement protein A2 (HtrA2), a mitochondrial serine protease upstream of PGC-1α, is charge of quality control in mitochondrial homeostasis. The molecular docking study indicated that there was a potential interaction between dA and HtrA2. However, whether the protective effect of dA against SAP is regulated by HtrA2/PGC-1α remains unknown. Our study in vitro showed that dA significantly reduced the necrosis of primary acinar cells and reactive oxygen species (ROS) accumulation, recovered mitochondrial membrane potential (ΔΨm) and ATP exhaustion, while UCF-101 (HtrA2 inhibitor), and SR-18292 (PGC-1α inhibitor) eliminated the protective effect of dA. Moreover, HtrA2 siRNA transfection efficiently blocked the protective of dA on HtrA2/PGC-1α pathway in 266-6 acinar cells. Meanwhile, dA also decreased LC3II/I ration, as well as p62, and increased Parkin expression, while UCF-101 and Bafilomycin A1 (autophagy inhibitor) reversed the protective effect of dA. Our study in vivo confirmed that dA effectively alleviated severity of SAP by reducing pancreatic edema, plasma amylase, and lipase levels and improved the HtrA2/PGC-1α pathway. Therefore, this is the first study to identify that dA inhibits pancreatic injury caused by oxidative stress, mitochondrial dysfunction, and impaired autophagy in a HtrA2/PGC-1α dependent manner.

Targeting the Hepatic Microenvironment to Improve Ischemia/Reperfusion Injury: New Insights into the Immune and Metabolic Compartments

Hepatic ischemia/reperfusion injury (IRI) is mainly characterized by high activation of immune inflammatory responses and metabolic responses. Understanding the molecular and metabolic mechanisms underlying development of hepatic IRI is critical for developing effective therapies for hepatic IRI. Recent advances in research have improved our understanding of the pathogenesis of IRI. During IRI, hepatocyte injury and inflammatory responses are mediated by crosstalk between the immune cells and metabolic components. This crosstalk can be targeted to treat or reverse hepatic IRI. Thus, a deep understanding of hepatic microenvironment, especially the immune and metabolic responses, can reveal new therapeutic opportunities for hepatic IRI. In this review, we describe important cells in the liver microenvironment (especially non-parenchymal cells) that regulate immune inflammatory responses. The role of metabolic components in the diagnosis and prevention of hepatic IRI are discussed. Furthermore, recent updated therapeutic strategies based on the hepatic microenvironment, including immune cells and metabolic components, are highlighted.

Macrophage nuclear factor erythroid 2-related factor 2 deficiency promotes innate immune activation by tissue inhibitor of metalloproteinase 3-mediated RhoA/ROCK pathway in the ischemic liver

BACKGROUND AND AIMS

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of reactive oxygen species (ROS) and inflammation and has been implicated in both human and murine inflammatory disease models. We aimed to characterize the roles of macrophage-specific Nrf2 in liver ischemia/reperfusion injury (IRI).

APPROACH AND RESULTS

First, macrophage Nrf2 expression and liver injury in patients undergoing OLT or ischemia-related hepatectomy were analyzed. Subsequently, we created a myeloid-specific Nrf2-knockout (Nrf2M-KO ) strain to study the function and mechanism of macrophage Nrf2 in a murine liver IRI model. In human specimens, macrophage Nrf2 expression was significantly increased in liver tissues after transplantation or hepatectomy. Interestingly, lower Nrf2 expressions correlated with more severe liver injury postoperatively. In a mouse model, we found Nrf2M-KO mice showed worse hepatocellular damage than Nrf2-proficient controls based on serum biochemistry, pathology, ROS, and inflammation. In vitro, Nrf2 deficiency promoted innate immune activation and migration in macrophages on toll-like receptor (TLR) 4 stimulation. Microarray profiling showed Nrf2 deletion caused markedly lower transcriptional levels of tissue inhibitor of metalloproteinase 3 (Timp3). ChIP-seq, PCR, and luciferase reporter assay further demonstrated Nrf2 bound to the promoter region of Timp3. Moreover, a disintegrin and metalloproteinase (ADAM) 10/ROCK1 was specifically increased in Nrf2-deficient macrophages. Increasing Timp3 expression effectively inhibited ADAM10/ROCK1 expression and rescued the Nrf2M-KO -mediated inflammatory response on TLR4 stimulation in vitro. Importantly, Timp3 overexpression, recombinant Timp3 protein, or ROCK1 knockdown rescued Nrf2M-KO -related liver IRI by inhibiting macrophage activation.

CONCLUSIONS

In conclusion, macrophage Nrf2 mediates innate proinflammatory responses, attenuates liver IRI by binding to Timp3, and inhibits the RhoA/ROCK pathway, which provides a therapeutic target for clinical organ IRI.

Aging deteriorated liver Ischemia and reperfusion injury by suppressing Tribble's proteins 1 mediated macrophage polarization

Aggravated liver injury has been reported in aged ischemia/reperfusion-stressed livers; however, the mechanism of aged macrophage inflammatory regulation is not well understood. Here, we found that the adaptor protein TRIB1 plays a critical role in the differentiation of macrophages and the inflammatory response in the liver after ischemia/reperfusion injury. In the present study, we determined that aging promoted macrophage-mediated liver injury and that inflammation was mainly responsible for lower M2 polarization in liver transplantation-exposed humans post I/R. Young and aged mice were subjected to hepatic I/R modeling and showed that aging aggravated liver injury and suppressed macrophage TRIB1 protein expression and anti-inflammatory function in I/R-stressed livers. Restoration of TRIB1 is mediated by lentiviral infection-induced macrophage anti-inflammatory M2 polarization and alleviated hepatic I/R injury. Moreover, TRIB1 overexpression in macrophages facilitates M2 polarization and anti-inflammation by activating MEK1-ERK1/2 signaling under IL-4 stimulation. Taken together, our results demonstrated that aging promoted hepatic I/R injury by suppressing TRIB1-mediated MEK1-induced macrophage M2 polarization and anti-inflammatory function.

Defective mitophagy in aged macrophages promotes mitochondrial DNA cytosolic leakage to activate STING signaling during liver sterile inflammation

Macrophage‐stimulator of interferon genes (STING) signaling mediated sterile inflammation has been implicated in various age‐related diseases. However, whether and how macrophage mitochondrial DNA (mtDNA) regulates STING signaling in aged macrophages remains largely unknown. We found that hypoxia‐reoxygenation (HR) induced STING activation in macrophages by triggering the release of macrophage mtDNA into the cytosol. Aging promoted the cytosolic leakage of macrophage mtDNA and enhanced STING activation, which was abrogated upon mtDNA depletion or cyclic GMP‐AMP Synthase (cGAS) inhibition. Aged macrophages exhibited increased mitochondrial injury with impaired mitophagy. Mechanistically, a decline in the PTEN‐induced kinase 1 (PINK1)/Parkin‐mediated polyubiquitination of mitochondria was observed in aged macrophages. Pink1 overexpression reversed the inhibition of mitochondrial ubiquitination but failed to promote mitolysosome formation in the aged macrophages. Meanwhile, aging impaired lysosomal biogenesis and function in macrophages by modulating the mTOR/transcription factor EB (TFEB) signaling pathway, which could be reversed by Torin‐1 treatment. Consequently, Pink1 overexpression in combination with Torin‐1 treatment restored mitophagic flux and inhibited mtDNA/cGAS/STING activation in aged macrophages. Moreover, besides HR‐induced metabolic stress, other types of oxidative and hepatotoxic stresses inhibited mitophagy and promoted the cytosolic release of mtDNA to activate STING signaling in aged macrophages. STING deficiency protected aged mice against diverse types of sterile inflammatory liver injuries. Our findings suggest that aging impairs mitophagic flux to facilitate the leakage of macrophage mtDNA into the cytosol and promotes STING activation, and thereby provides a novel potential therapeutic target for sterile inflammatory liver injury in aged patients.

XBP1 deficiency promotes hepatocyte pyroptosis by impairing mitophagy to activate mtDNA-cGAS-STING signaling in macrophages during acute liver injury

Hepatocellular cell death and macrophage proinflammatory activation contribute to the pathology of various liver diseases, during which XBP1 plays an important role. However, the function and mechanism of XBP1 in thioacetamide (TAA)-induced acute liver injury (ALI) remains unknown. Here, we investigated the effects of XBP1 inhibition on promoting hepatocellular pyroptosis to activate macrophage STING signaling during ALI. While both TAA- and LPS-induced ALI triggered XBP1 activation in hepatocytes, hepatocyte-specific XBP1 knockout mice exhibited exacerbated ALI with increased hepatocellular pyroptosis and enhanced macrophage STING activation. Mechanistically, mtDNA released from TAA-stressed hepatocytes could be engulfed by macrophages, further inducing macrophage STING activation in a cGAS- and dose-dependent manner. XBP1 deficiency increased ROS production to promote hepatocellular pyroptosis by activating NLRP3/caspase-1/GSDMD signaling, which facilitated the extracellular release of mtDNA. Moreover, impaired mitophagy was found in XBP1 deficient hepatocytes, which was reversed by PINK1 overexpression. Mitophagy restoration also inhibited macrophage STING activation and ALI in XBP1 deficient mice. Activation of XBP1-mediated hepatocellular mitophagy and pyroptosis and macrophage STING signaling pathway were observed in human livers with ALI. Collectively, these findings demonstrate that XBP1 deficiency promotes hepatocyte pyroptosis by impairing mitophagy to activate mtDNA/cGAS/STING signaling of macrophages, providing potential therapeutic targets for ALI.

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XBP1 deficiency promoted hepatocellular pyroptosis and extracellular mtDNA release to enhance macrophage STING activation.

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XBP1 deficiency promoted ROS/NLRP3/caspase-1/GSDMD-mediated hepatocyte pyroptosis by impairing mitophagy.

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Hepatocellular mitophagy and pyroptosis and macrophage STING activation were detected in human livers with ALI.

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Hepatocyte-specific XBP1 deficiency aggravated TAA-induced ALI in mice.

GSK-3α/β Activity Negatively Regulates MMP-1/9 Expression to Suppress Mycobacterium tuberculosis Infection

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) infection is the deadliest infectious disease and a global health problem. Macrophages (Mφs) and neutrophils that can phagocytose Mtb represent the first line of immune response to infection. Glycogen synthase kinase-3α/β (GSK-3α/β) represents a regulatory switch in host immune responses. However, the efficacy and molecular mechanisms of how GSK-3α/β interacts with Mtb infection in Mφs remain undefined. Here, we demonstrated that Mtb infection downregulated GSK-3α/β activity and promoted matrix metalloproteinase-1 (MMP-1) and MMP-9 expressions in Mφs derived from acute monocytic human leukemia THP-1 cells (THP-1-Mφs). We confirmed the upregulation of MMP-9 expression in tissues of TB patients compared with patients of chronic inflammation (CI). In THP-1-Mφs and C57BL/6 mice, GSK-3α/β inhibitor SB216763 significantly increased MMP-1/9 production and facilitated Mtb load, while MMP inhibitors blocked MMP-1/9 expression and Mtb infection. Consistently, GSK-3α/β silencing significantly increased MMP-1/9 expression and Mtb infection, while overexpression of GSK-3α/β and constitutive activated GSK-3α/β mutants significantly reduced MMP-1/9 expression and Mtb infection in THP-1-Mφs. MMP-1/9 silencing reduced Mtb infection, while overexpression of MMP-1/9 promoted Mtb infection in THP-1-Mφs. We further found that GSK-3α/β inhibition increased Mtb infection and MMP-1/9 expression was blocked by ERK1/2 inhibitor. Additionally, we showed that protein kinase C-δ (PKC-δ) and mammalian target of rapamycin (mTOR) reduced GSK-3α/β activity and promoted MMP-1/9 production in Mtb-infected THP-1-Mφs. In conclusion, this study suggests that PKC-δ-mTOR axis suppresses GSK-3α/β activation with acceleration of MMP-1/9 expression through phospho-ERK1/2. These results reveal a novel immune escape mechanism of Mtb and a novel crosstalk between these critical signaling pathways in anti-TB immunity.

Kinases as Potential Therapeutic Targets for Anti-coronaviral Therapy

The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.

Plasma Cell-Free DNA Methylomics of Bipolar Disorder With and Without Rapid Cycling

Rapid cycling (RC) burdens bipolar disorder (BD) patients further by causing more severe disability and increased suicidality. Because diagnosing RC can be challenging, RC patients are at risk of rapid decline due to delayed suitable treatment. Here, we aimed to identify the differences in the circulating cell-free DNA (cfDNA) methylome between BD patients with and without RC. The cfDNA methylome could potentially be developed as a diagnostic test for BD RC. We extracted cfDNA from plasma samples of BD1 patients (46 RC and 47 non-RC). cfDNA methylation levels were measured by 850K Infinium MethylationEPIC array. Principal component analysis (PCA) was conducted to assess global differences in methylome. cfDNA methylation levels were compared between RC groups using a linear model adjusted for age and sex. PCA suggested differences in methylation profiles between RC groups (p = 0.039) although no significant differentially methylated probes (DMPs; q > 0.15) were found. The top four CpG sites which differed between groups at p < 1E-05 were located in CGGPB1, PEX10, NR0B2, and TP53I11. Gene set enrichment analysis (GSEA) on top DMPs (p < 0.05) showed significant enrichment of gene sets related to nervous system tissues, such as neurons, synapse, and glutamate neurotransmission. Other top notable gene sets were related to parathyroid regulation and calcium signaling. To conclude, our study demonstrated the feasibility of utilizing a microarray method to identify circulating cfDNA methylation sites associated with BD RC and found the top differentially methylated CpG sites were mostly related to the nervous system and the parathyroid.

Revisiting the Role of GSK3, A Modulator of Innate Immunity, in Idiopathic Inclusion Body Myositis

Idiopathic or sporadic inclusion body myositis (IBM) is the leading age-related (onset >50 years of age) autoimmune muscular pathology, resulting in significant debilitation in affected individuals. Once viewed as primarily a degenerative disorder, it is now evident that much like several other neuro-muscular degenerative disorders, IBM has a major autoinflammatory component resulting in chronic inflammation-induced muscle destruction. Thus, IBM is now considered primarily an inflammatory pathology. To date, there is no effective treatment for sporadic inclusion body myositis, and little is understood about the pathology at the molecular level, which would offer the best hopes of at least slowing down the degenerative process. Among the previously examined potential molecular players in IBM is glycogen synthase kinase (GSK)-3, whose role in promoting TAU phosphorylation and inclusion bodies in Alzheimer’s disease is well known. This review looks to re-examine the role of GSK3 in IBM, not strictly as a promoter of TAU and Abeta inclusions, but as a novel player in the innate immune system, discussing some of the recent roles discovered for this well-studied kinase in inflammatory-mediated pathology.

Inhibition of FSTL3 abates the proliferation and metastasis of renal cell carcinoma via the GSK-3β/β-catenin signaling pathway

Renal cell carcinoma (RCC) is a lethal malignancy of the genitourinary system. Follistatin-like 3 (FSTL3), which mediates cell differentiation and growth, acts as a biomarker of tumors and participates in cancer development and progression. Presently, the FSTL3’s functions in RCC were investigated. Quantitative reverse transcription PCR (qRT-PCR), Western Blot, and enzyme linked immunosorbent assay (ELISA) were conducted to verify FSTL3 expression in RCC tissues and cell lines. BrdU assay and CCK8 experiment were made to monitor cell proliferation. Transwell was implemented to examine the invasion of the cells. Flow cytometry analyzed cell apoptosis, and Western Blot evaluated the protein levels of E-cadherin, Twist, and Slug. In the meantime, the protein profiles of the GSK-3β, β-catenin, and TGF-β signaling pathways were ascertained. Moreover, the Xenograft tumor model was constructed in nude mice for measuring tumor growth in vivo. The statistics showed that FSTL3 presented an overexpression in RCC, and patients with a lower expression of FSTL3 manifested a better prognosis. Down-regulated FSTL3 hampered the proliferation, invasion, EMT, and tumor growth of RCC cells and caused cell apoptosis. On the contrary, FSTL3 overexpression enhanced the malignant behaviors of RCC cells. Furthermore, FSTL3 knockdown bolstered GSK-3β, suppressed β-catenin, and reduced BMP1-SMAD pathway activation. Inhibited β-catenin substantially mitigated FSTL3-mediated promoting functions in RCC. In short, FSTL3 functions as an oncogene in RCC by modulating the GSK-3β/β-catenin signaling pathway.

AICAR, an AMP-Activated Protein Kinase Activator, Ameliorates Acute Pancreatitis-Associated Liver Injury Partially Through Nrf2-Mediated Antioxidant Effects and Inhibition of NLRP3 Inflammasome Activation

Acute pancreatitis (AP) is a highly fatal acute inflammation and is often accompanied by multiple organ dysfunction syndrome (MODS). The liver, one of the most vulnerable extrapancreatic organs in AP, is the major organ involved in the evolution of the disease and correlates strongly with the occurrence of MODS. However, the etiology of pancreatitis-associated liver injury (PALI) has not been clarified and currently lacks an effective treatment. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) is a cell permeable nucleoside with pleiotropic effects on anti-inflammatory and antioxidant stress that binds with adenosine monophosphate protein kinase (AMPK) and induces AMPK activation. However, the role of AICAR in PALI remains elusive. Here, we show that activation of AMPK by AICAR, a direct AMPK agonist, significantly ameliorates sodium taurocholate-induced PALI in rats, whereas treatment of PALI rats with the AMPK antagonist Compound C profoundly exacerbates the degree of liver injury, suggesting that hepatic AMPK activation exerts an essential protective role in PALI. Mechanistically, AICAR induces AMPK activation, which in turn activates nuclear factor erythroid 2-related factor 2(Nrf2) -regulated hepatic antioxidant capacity and inhibits NLRP3 inflammasome-mediated pyrolysis, protecting rats from sodium taurocholate-induced PALI. In addition, Nrf2 deficiency strikingly weakens the beneficial effects of AICAR on alleviation of liver injury, oxidative stress and NLRP3 inflammasome activation in L-arginine-induced PALI mice. Thus, AICAR protects against PALI in rodents by triggering AMPK, which is mediated at least in part by Nrf2-modulated antioxidant effects and NLRP3 inflammasome activation.

Modulation of the Wound Healing through Noncoding RNA Interplay and GSK-3β/NF-κB Signaling Interaction

Diabetic foot ulcers are seriously endangering the physical and mental health of patients. Due to the long duration of inflammation, the treatment of nonhealing wounds in diabetes is one of the most prominent healthcare problems in the world. The nuclear factor kappa B (NF-κB) signaling pathway, a classical pathway that triggers inflammatory response, is regulated by many regulators, such as glycogen synthase kinase 3 beta (GSK-3β). Noncoding RNAs, a large class of molecules that regulate gene expression at the posttranscriptional or posttranslational level, play an important role in various stages of wound healing, especially in the stage of inflammation. Herein, we summarized the roles of noncoding RNAs in the NF-κB/GSK-3β signaling, which might provide new ideas for the treatment of diabetic wound healing.

Sevoflurane preconditioning protects experimental ischemic stroke by enhancing anti-inflammatory microglia/macrophages phenotype polarization through GSK-3β/Nrf2 pathway

Aims

Sevoflurane preconditioning (SPC) results in cerebral ischemic tolerance; however, the mechanism remains unclear. Promoting microglia/macrophages polarization from pro‐inflammatory state to anti‐inflammatory phenotype has been indicated as a potential treatment target against ischemic stroke. In this study, we aimed to assess the effect of SPC on microglia polarization after stroke and which signaling pathway was involved in this transition.

Methods

Mouse primary microglia with SPC were challenged by oxygen‐glucose deprivation (OGD) or lipopolysaccharide (LPS), and mice with SPC were subjected to middle cerebral artery occlusion (MCAO). Then, the mRNA and protein levels of pro‐inflammatory/anti‐inflammatory factors were analyzed. GSK‐3β phosphorylation and Nrf2 nuclear translocation were measured. The mRNA and protein expression of pro‐inflammatory/anti‐inflammatory factors, neurological scores, infarct volume, cellular apoptosis, the proportion of pro‐inflammatory/anti‐inflammatory microglia/macrophages, and the generation of super‐oxidants were examined after SPC or GSK‐3β inhibitor TDZD treatment with or without Nrf2 deficiency.

Results

Sevoflurane preconditioning promoted anti‐inflammatory and inhibited pro‐inflammatory microglia/macrophages phenotype both in vitro and in vivo. GSK‐3β phosphorylation at Ser9 was increased after SPC. Both SPC and TDZD administration enhanced Nrf2 nuclear translocation, reduced pro‐inflammatory microglia/macrophages markers expression, promoted anti‐inflammatory markers level, and elicited a neuroprotective effect. Nrf2 deficiency abolished the promoted anti‐inflammatory microglia/macrophages polarization and ischemic tolerance induced by TDZD treatment. The reduced percentage of pro‐inflammatory positive cells and super‐oxidants generation induced by SFC or TDZD was also reversed by Nrf2 knockdown.

Conclusions

Our results indicated that SPC exerts brain ischemic tolerance and promotes anti‐inflammatory microglia/macrophages polarization by GSK‐3β‐dependent Nrf2 activation, which provides a novel mechanism for SPC‐induced neuroprotection.

Fisetin mitigates hepatic ischemia-reperfusion injury by regulating GSK3β/AMPK/NLRP3 inflammasome pathway

BACKGROUND

Hepatic ischemia-reperfusion (I/R) injury (IRI) represents a crucial challenge in liver transplantation. Fisetin has anti-inflammatory, anti-aging and anti-oxidative properties. This study aimed to examine whether fisetin mitigates hepatic IRI and examine its underlying mechanisms.

METHODS

Sham or warm hepatic I/R operated mice were pretreated with fisetin (5, 10 or 20 mg/kg). Hepatic histological assessments, TUNEL assays and serum aminotransferase measurements were performed. An in vitro hypoxia/reoxygenation (H/R) model using RAW264.7 macrophages pretreated with fisetin (2.5, 5 or 10 µmol/L) was also used. Serum and cell supernatant concentrations of interleukin-1β (IL-1β), IL-18 and tumor necrosis factor-α (TNF-α) were determined by enzyme-linked immunosorbent assay (ELISA). Protein levels of p-GSK3β, p-AMPK and NLR family pyrin domain-containing 3 (NLRP3)-associated proteins were detected by Western blotting.

RESULTS

Compared with the I/R group, fisetin pretreatment reduced pathological liver damage, serum aminotransferase levels, serum concentrations of IL-1β, IL-18 and TNF-α in the murine IRI model. Fisetin also reduced the expression of NLRP3 inflammasome-associated proteins (NLRP3, cleaved caspase-1, IL-1β and IL-18) in I/R-operated liver. The experiments in vitro showed that fisetin decreased the release of IL-1β, IL-18 and TNF-α, and reduced the expression of NLRP3 inflammasome-associated proteins in H/R-treated RAW264.7 cells. Moreover, fisetin increased the expressions of p-GSK3β and p-AMPK in both models, indicating that its anti-inflammatory effects were dependent on GSK3β/AMPK signaling. The anti-inflammatory effects of fisetin were partially inhibited by the AMPK specific inhibitor compound C.

CONCLUSIONS

Fisetin showed protective effects against hepatic IRI, countering inflammatory responses through mediating the GSK3β/AMPK/NLRP3 inflammasome pathway.

The long and the small collide: LncRNAs and small heterodimer partner (SHP) in liver disease

Long non-coding RNAs (lncRNAs) are a large and diverse class of RNA molecules that are transcribed but not translated into proteins, with a length of more than 200 nucleotides. LncRNAs are involved in gene expression and regulation. The abnormal expression of lncRNAs is associated with disease pathogenesis. Small heterodimer partner (SHP, NR0B2) is a unique orphan nuclear receptor that plays a pivotal role in many biological processes by acting as a transcriptional repressor. In this review, we present the critical roles of SHP and summarize recent findings demonstrating the regulation between lncRNAs and SHP in liver disease.

The Orphan Nuclear Receptor Gene NR0B2 Is a Favorite Prognosis Factor Modulated by Multiple Cellular Signal Pathways in Human Liver Cancers

BACKGROUND

Liver cancer is a leading cause of cancer death worldwide, and novel prognostic factor is needed for early detection and therapeutic responsiveness monitoring. The orphan nuclear receptor NR0B2 was reported to suppress liver cancer development in a mouse model, and its expression levels were reduced in liver cancer tissues and cell lines due to hypermethylation within its promoter region. However, it is not clear if NR0B2 expression is associated with cancer survival or disease progression and how NR0B2 gene expression is regulated at the molecular level.

METHODS

Multiple cancer databases were utilized to explore NR0B2 gene expression profiles crossing a variety of human cancers, including liver cancers, on several publicly assessable bioinformatics platforms. NR0B2 gene expression with or without kinase inhibitor treatment was analyzed using the qPCR technique, and NR0B2 protein expression was assessed in western blot assays. Two human hepatocellular carcinoma cell lines HepG2 and Huh7, were used in these experiments. NR0B2 gene activation was evaluated using NR0B2 promoter-driven luciferase reporter assays.

RESULTS

NR0B2 gene is predominantly expressed in liver tissue crossing human major organs or tissues, but it is significantly downregulated in liver cancers. NR0B2 expression is mostly downregulated in most common cancers but also upregulated in a few intestinal cancers. NR0B2 gene expression significantly correlated with patient overall survival status in multiple human malignancies, including lung, kidney, breast, urinary bladder, thyroid, colon, and head-neck cancers, as well as liposarcoma and B-cell lymphoma. In liver cancer patients, higher NR0B2 expression is associated with favorite relapse-free and progression-free survival, especially in Asian male patients with viral infection history. In addition, NR0B2 expression negatively correlated with immune infiltration and PIK3CA and PIK3CG gene expression in liver cancer tissues. In HepG2 and Huh7 cells, NR0B2 expression at the transcription level was drastically reduced after MAPK inhibition but was significantly enhanced after PI3K inhibition.

CONCLUSION

NR0B2 gene expression is altered mainly in most human malignancies and significantly reduced in liver cancers. NR0B2 is a prognosis factor for patient survival in liver cancers. MAPK and PI3K oppositely modulate NR0B2 expression, and NR0B2 gene upregulation might serve as a therapeutic responsiveness factor in anti-PI3K therapy for liver cancer.

Proteome and Phosphoproteome Analyses Reveal the Kinase Regulatory Network Involved in Glycogen Synthesis Kinase 3β

Diabetic nephropathy is the most common chronic kidney disease in the world and the main cause of end-stage renal disease (ESRD). The structural integrity of podocytes is fundamental to the normal function of the glomerulus, and the role of glycogen synthase kinase 3β (GSK-3β) in podocytes is complicated. A thorough understanding of GSK-3β is crucial to understand the mechanism of diabetic nephropathy. To analyze the roles of GSK-3β in podocytes, GSK-3β knockdown lentivirus by clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR-associated protein (Cas)9 was applied to establish stable cell lines. Mass spectrometry was utilized to search for differentially expressed proteins. Consequently, we found 34 proteins with higher levels and 115 proteins with lower levels in GSk-3β knockdown cells than in control cells and identified 581 phosphosites with higher phosphorylation levels and 288 phosphosites with lower phosphorylation levels. We performed functional enrichment analysis of these proteins and phosphorylated proteins based on public databases. Enrichment analysis revealed that GSK-3β participates in the spliceosome, Hippo signaling pathway, actin binding, structural molecule activity, and other pathways. Then, we used motif analysis of phosphate sites to determine 89 conserved motifs based on 1,068 phosphoserine (pS) sites and 15 conserved motifs in view of 104 phosphothreonine (pT) sites. Additionally, protein–protein interaction network analysis was carried out using the STRING database. Cytoscape’s add-on Molecular Complex Detection (MCODE) was used to analyze key and core protein groups. In quantitative differential protein analysis, four MCODEs were obtained, and 22 MCODEs were obtained in the analysis of the phosphoproteome of differentially expressed proteins. Finally, we analyzed the kinase regulatory network in podocytes after GSK-3β knockdown and identified 299 protein kinases and 3,460 significantly changed phosphorylation modification sites on 1,574 proteins. These results will be valuable for further research on GSK-3β.

Lycopene alleviates hepatic ischemia reperfusion injury via the Nrf2/HO-1 pathway mediated NLRP3 inflammasome inhibition in Kupffer cells

Background

Lycopene is a naturally occurring carotenoid found in many fruits and vegetables, which has antioxidant effects. Although lycopene’s protective effect has been observed on ischemia reperfusion (IR) injury in different organs, the effect of lycopene on Kupffer cells (KCs) has not been clearly elucidated in IR-induced acute hepatic inflammatory injury.

Methods

Mice were administered with either olive oil (10 mL/kg body weight) as the control or lycopene (20 mg/kg body weight) by gavage for 2 weeks before undergoing hepatic IR injury.

Results

In this study, we observed that the levels of aspartate aminotransferases (AST), alanine aminotransferase (ALT), and the percentages of hepatocellular apoptosis in mice pretreated with lycopene were significantly lower than control mice. Lycopene inhibited F4/80+ macrophage and Ly6G+ neutrophil accumulation, which further decreased the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin 6 (IL-6). Interestingly, lycopene induced increased autophagy in KCs, which was evidenced by elevated autophagosomes and the increased protein level of LC3B. In these KCs, lycopene-induced upregulation of autophagy inhibited NOD-like receptor family pyrin domain-containing 3 protein (NLRP3) inflammasome activation, which was demonstrated by the reduced mRNA and protein levels of NLRP3, cleaved caspase-1, an apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and IL-1β. Furthermore, 3-methyladenine, an autophagy inhibitor, abolished lycopene’s inhibitory effect on the NLRP3 inflammasome in KCs, which led to increased hepatic IR injury. Intriguingly, we identified that the protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) were elevated in KCs isolated from IR-stressed mice pretreated with lycopene. Nrf2-siRNA or HO-1-siRNA could block the autophagy activation enhanced by lycopene in KCs, resulting in the activation of the NLRP3 inflammasome and aggravated hepatic IR injury.

Conclusions

Our findings demonstrated that lycopene promoted Nrf2/HO-1 pathway activation and further suppressed the NLRP3 inflammasome via enhancing KC autophagy, which alleviated hepatic IR injury.

TGR5/Cathepsin E signaling regulates macrophage innate immune activation in liver ischemia and reperfusion injury

The role and underlying mechanism of plasma membrane-bound G protein-coupled bile acid receptor (TGR5) in regulating macrophage innate immune activation during liver ischemia and reperfusion (IR) injury remains largely unclear. Here, we demonstrated that TGR5 depletion in myeloid cells aggravated liver injury with increased macrophage infiltration and enhanced inflammation in livers post-IR. While TGR5 deficiency enhanced mobility and proinflammatory M1 polarization of macrophages, TGR5 agonist enhanced the anti-inflammatory effect of TGR5 both in vivo and in vitro. Microarray profiling revealed that TGR5-deficient macrophages exhibited enhanced proinflammatory characteristics and cathepsin E (Cat E) was the most upregulated gene. Knockdown of Cat E abolished the enhanced mobility and shift of macrophage phenotypes induced by TGR5 depletion. Moreover, Cat E knockdown attenuated liver IR injury and liver inflammation in myeloid TGR5-deficient mice. In patients undergoing partial hepatectomy, IR stress promoted TGR5 activation of CD11b+ cells in peripheral blood mononuclear cells, correlating with the shift in macrophage M2 polarization. Ursodeoxycholic acid administration enhanced TGR5 activation and the trend in macrophage M2 polarization. Our results suggest that TGR5 attenuates proinflammatory immune activation by restraining macrophage migration and facilitating macrophage M2 polarization via suppression of Cat E and thereby protects against liver IR injury.

Macrophage Function and the Role of GSK3

Macrophages are present in nearly all vertebrate tissues, where they respond to a complex variety of regulatory signals to coordinate immune functions involved in tissue development, metabolism, homeostasis, and repair. Glycogen synthase kinase 3 (GSK3) is a ubiquitously expressed protein kinase that plays important roles in multiple pathways involved in cell metabolism. Dysregulation of GSK3 has been implicated in several prevalent metabolic disorders, and recent findings have highlighted the importance of GSK3 activity in the regulation of macrophages, especially with respect to the initiation of specific pathologies. This makes GSK3 a potential therapeutic target for the development of novel drugs to modulate immunometabolic responses. Here, we summarize recent findings that have contributed to our understanding of how GSK3 regulates macrophage function, and we discuss the role of GSK3 in the development of metabolic disorders and diseases.

TGR5 Regulates Macrophage Inflammation in Nonalcoholic Steatohepatitis by Modulating NLRP3 Inflammasome Activation

Nonalcoholic steatohepatitis (NASH) is a chronic liver disease associated with dysregulation of liver metabolism and inflammation. G-protein coupled bile acid receptor 1 (TGR5) is a cell surface receptor that is involved in multiple metabolic pathways. However, the functions of TGR5 in regulating macrophage innate immune activation in NASH remain unclear. Here, we found that TGR5 expression was decreased in liver tissues from humans and mice with NASH. Compared to wild type (WT) mice, TGR5-knockout (TGR5^−/−) mice exhibited exacerbated liver damage, increased levels of proinflammatory factors, and enhanced M1 macrophage polarization. Moreover, TGR5 deficiency facilitated M1 macrophage polarization by promoting NLRP3 inflammasome activation and caspase-1 cleavage. Taken together, our findings revealed that TGR5 signaling attenuated liver steatosis and inflammation and inhibited NLRP3-mediated M1 macrophage polarization in NASH.

Neuroprotection against cerebral ischemia/reperfusion by dietary phytochemical extracts from Tibetan turnip (Brassica rapa L.)

ETHNOPHARMACOLOGICAL RELEVANCE

The Tibetan turnip (Brassica rapa L.) has a wide array of medicine properties including heat-clearing, detoxifying and anti-hypoxia as listed in the famous centuries-old Tibetan medicine classic "The Four Medical Tantras". Evidence-based medicine also indicated the anti-hypoxic effect of turnips, suggesting a potential link to neuroprotective effect on ischemic stroke. This thereby enables turnips to serve as a novel nontoxic agent in related treatment.

AIM OF THE STUDY

This study aimed to investigate the neuroprotective effect and elucidate the mechanism of aqueous extract of turnip (AET) on cerebral ischemia/reperfusion.

MATERIALS AND METHODS

The experimental models of cerebral ischemia included transient middle cerebral artery occlusion/reperfusion (MCAO) in C57BL/6J mice and oxygen-glucose deprivation/reoxygenation (OGD/R) in HT-22 cells. Long-term effect of AET on infarct volume was evaluated by microtubule-associated protein 2 (MAP2) immunofluorescence 28 days after MCAO, and on neurofunctional outcomes determined by rotarod, grid walking, and cylinder tests in the meantime. Efficacy of AET was determined by the cell viability, the release of lactate dehydrogenase (LDH) and reactive oxygen species (ROS) in neurons. The underlying mechanism of AET rescued OGD/R cells were characterized by PI3K, Akt and mTOR expressions, which were further used to validate AET's role in the pathway.

RESULTS

AET can reduce cerebral infarct volume and ameliorate behavioral deficits of MCAO/R mice dose-dependently. In vitro experiment further demonstrated that suitable concentrations of AET inhibited ROS, LDH production and restored mitochondrial expression induced by OGD/R. AET pretreatment can reverse the OGD/R-induced decreased level of phosphorylation of PI3K, Akt, mTOR, whereas this effect was blocked in the LY294002 (PI3K inhibitor) treatment group.

CONCLUSIONS

AET improved the survival of OGD/R-injured HT-22 cells by activating the PI3K/Akt/mTOR pathway. Based on the results above, aqueous extract of turnip has a protective effect on focal cerebral ischemic injury.

Tumor-associated macrophages: potential therapeutic strategies and future prospects in cancer

Macrophages are the most important phagocytes in vivo. However, the tumor microenvironment can affect the function and polarization of macrophages and form tumor-associated macrophages (TAMs). Usually, the abundance of TAMs in tumors is closely associated with poor prognosis. Preclinical studies have identified important pathways regulating the infiltration and polarization of TAMs during tumor progression. Furthermore, potential therapeutic strategies targeting TAMs in tumors have been studied, including inhibition of macrophage recruitment to tumors, functional repolarization of TAMs toward an antitumor phenotype, and other therapeutic strategies that elicit macrophage-mediated extracellular phagocytosis and intracellular destruction of cancer cells. Therefore, with the increasing impact of tumor immunotherapy, new antitumor strategies to target TAMs are now being discussed.

Low density lipoprotein receptor related protein 6 (LRP6) protects heart against oxidative stress by the crosstalk of HSF1 and GSK3β

Low density lipoprotein receptor-related protein 6 (LRP6), a Wnt co-receptor, induces multiple functions in various organs. We recently reported cardiac specific LRP6 deficiency caused cardiac dysfunction in mice. Whether cardiomyocyte-expressed LRP6 protects hearts against ischemic stress is largely unknown. Here, we investigated the effects of cardiac LRP6 in response to ischemic reperfusion (I/R) injury. Tamoxifen inducible cardiac specific LRP6 overexpression mice were generated to build I/R model by occlusion of the left anterior descending (LAD) coronary artery for 40 min and subsequent release of specific time. Cardiac specific LRP6 overexpression significantly ameliorated myocardial I/R injury as characterized by the improved cardiac function, strain pattern and infarct area at 24 h after reperfusion. I/R induced-apoptosis and endoplasmic reticulum (ER) stress were greatly inhibited by LRP6 overexpression in cardiomyocytes. LRP6 overexpression enhanced the expression of heat shock transcription factor-1(HSF1) and heat shock proteins (HSPs), the level of p-glycogen synthase kinase 3β(GSK3β)(S9) and p-AMPK under I/R. HSF1 inhibitor deteriorated the apoptosis and decreased p-GSK3β(S9) level in LRP6 overexpressed -cardiomyocytes treated with H2O2. Si-HSF1 or overexpression of active GSK3β significantly attenuated the increased expression of HSF1 and p-AMPK, and the inhibition of apoptosis and ER stress induced by LRP6 overexpression in H2O2-treated cardiomyocytes. AMPK inhibitor suppressed the increase in p-GSK3β (S9) level but didn't alter HSF1 nucleus expression in LRP6 overexpressed-cardiomyocytes treated with H2O2. Active GSK3β, but not AMPK inhibitor, attenuated the inhibition of ubiquitination of HSF1 induced by LRP6-overexpressed-cardiomyocytes treated with H2O2. LRP6 overexpression increased interaction of HSF1 and GSK3β which may be involved in the reciprocal regulation under oxidative stress. In conclusion, cardiac LRP6 overexpression significantly inhibits cardiomyocyte apoptosis and ameliorates myocardial I/R injury by the crosstalk of HSF1 and GSK3β signaling.

Rspo1/Rspo3-LGR4 signaling inhibits hepatic cholesterol synthesis through the AMPKα-SREBP2 pathway

R-spondins (Rspos) are endogenous ligands of leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4). Rspos-LGR4 signaling plays important roles in embryogenesis, gastrointestinal homeostasis, and food intake. Here, we investigated the impacts of Rspos-LGR4 on hepatic cholesterol synthesis. Rspo1/3 and Lgr4 knockdown mice were used to investigate the impacts of Rspo1/3-LGR4 on hepatic cholesterol synthesis. AMPKα agonist, antagonist, and shRNA were used to explore the downstream targets of Rspos-LGR4 signaling. In our study, we reported that LGR4, Rspo1, and Rspo3 were highly expressed in hepatocytes and their expressions were sensitive to energy states. Rspo1 and Rspo3 reversed OA-induced cholesterol synthesis, accompanying with increased the phosphorylation of AMPKα Thr172, reduced SREBP2 nuclear translocation, and Srebf2 mRNA expression. Conversely, hepatic LGR4 knockdown increased hepatic cholesterol synthesis and decreased the phosphorylation of AMPKα both in vitro and in vivo. Activation or inhibition of AMPKα significantly abolished the effects of LGR4 deficiency or Rspos, respectively, on cholesterol synthesis. Knockdown of AMPKα1 or/and AMPKα2 repressed Rspos-induced inhibition on cholesterol synthesis. Our study indicates that Rspo1/Rspo3-LGR4 signaling in hepatocytes suppresses cholesterol synthesis via the AMPKα-SREBP2 pathway.

Aging aggravated liver ischemia and reperfusion injury by promoting STING-mediated NLRP3 activation in macrophages

Although aggravated liver injury has been reported in aged livers post‐ischemia and reperfusion (IR), the underlying mechanism of innate immune activation of aged macrophages is not well understood. Here, we investigated whether and how Stimulator of interferon genes (STING) signaling regulated macrophage proinflammatory activation and liver IR injury. Mice were subjected to hepatic IR in vivo. Macrophages isolated from IR‐stressed livers and bone marrow‐derived macrophages (BMDMs) from young and aged mice were used for in vitro studies. Enhanced nucleotide‐binding domain and leucine‐rich repeat containing protein 3 (NLRP3) activation was found in both livers and macrophages of aged mice post‐IR. NLRP3 knockdown in macrophages inhibited intrahepatic inflammation and liver injury in both young and aged mice. Interestingly, enhanced activation of the STING/ TANK‐binding kinase 1 (TBK1) signaling pathway was observed in aged macrophages post‐IR and mitochondria DNA (mtDNA) stimulation. STING suppression blocked over‐activation of NLRP3 signaling and excessive secretion of proinflammatory cytokines/chemokines in the mtDNA‐stimulated BMDMs from aged mice. More importantly, STING knockdown in macrophages abrogated the detrimental role of aging in aggravating liver IR injury and intrahepatic inflammation. Finally, peripheral blood from the recipients undergoing liver transplantation was collected and analyzed. The results showed that the elderly recipients had much higher levels of TNF‐α, IL‐6, IL‐1β, and IL‐18 post‐transplantation, indicating increased NLRP3 activation in lR‐stressed livers of elderly recipients. In summary, our study demonstrated that the STING‐NLRP3 axis was critical for the proinflammatory response of aged macrophages and would be a novel therapeutic target to reduce IR injury in elderly patients.

Isoform- and Cell Type-Specific Roles of Glycogen Synthase Kinase 3 N-Terminal Serine Phosphorylation in Liver Ischemia Reperfusion Injury

Glycogen synthase kinase 3 (Gsk3) α and β are both constitutively active and inhibited upon stimulation by N-terminal serine phosphorylation. Although roles of active Gsk3 in liver ischemia reperfusion injury (IRI) have been well appreciated, whether Gsk3 N-terminal serine phosphorylation has any functional significance in the disease process remains unclear. In a murine liver partial warm ischemia model, we studied Gsk3 N-terminal serine mutant knock-in (KI) mice and showed that liver IRI was decreased in Gsk3αS21A but increased in Gsk3βS9A mutant KI mice. Bone marrow chimeric experiments revealed that the Gsk3α, but not β, mutation in liver parenchyma protected from IRI, and both mutations in bone marrow-derived cells exacerbated liver injuries. Mechanistically, mutant Gsk3α protected hepatocytes from inflammatory (TNF-α) cell death by the activation of HIV-1 TAT-interactive protein 60 (TIP60)-mediated autophagy pathway. The pharmacological inhibition of TIP60 or autophagy diminished the protection of the Gsk3α mutant hepatocytes from inflammatory cell death in vitro and the Gsk3α mutant KI mice from liver IRI in vivo. Thus, Gsk3 N-terminal serine phosphorylation inhibits liver innate immune activation but suppresses hepatocyte autophagy in response to inflammation. Gsk3 αS21, but not βS9, mutation is sufficient to sustain Gsk4 activities in hepatocytes and protect livers from IRI via TIP60 activation.

Aging aggravated liver ischemia and reperfusion injury by promoting hepatocyte necroptosis in an endoplasmic reticulum stress-dependent manner

Background

Aggravated liver ischemia and reperfusion (IR) injury has been reported in aged mice. Although necroptosis inhibition showed no crucial effect on hepatic IR injury in young mice, whether and how necroptosis affects liver IR injury in aged mice remains unclear.

Methods

Young and aged mice were subjected to liver IR modeling. Liver injury, hepatocyte necroptosis and endoplasmic reticulum (ER) stress were analyzed in different groups.

Results

Significantly increased liver necroptosis was found in aged mice post IR compared with young mice. Necroptosis inhibition by necrostatin-1 (Nec-1) decreased hepatocyte necroptosis and liver injury post IR in aged mice, with no significant effects on young mice. Furthermore, IR induced ER stress in both young and aged mice, and enhanced ER stress was observed in aged mice post IR. Administration of 4-phenylbutyrate (4-PBA), an ER stress antagonist, alleviated liver IR injury in both young and aged mice. However, ER stress inhibition reduced hepatocyte necroptosis in aged mice but not in young mice.

Conclusions

Aging increased ER stress in IR-stressed hepatocytes, leading to aggravated necroptosis and liver IR injury. Our study demonstrated a novel mechanism of ER stress in the regulation of hepatocyte necroptosis in aged livers post IR, which would be a potential therapeutic target to reduce liver IR injury in elderly patients.

Histone deacetylase 6 inhibitor ACY1215 ameliorates mitochondrial dynamic and function injury in hepatocytes by activating AMPK signaling pathway in acute liver failure mice

Acute liver failure (ALF) is often accompanied by dynamic and functional disorders of mitochondria in hepatocytes. The histone deacetylase 6 inhibitor Rocilinostat (ACY1215) has a hepatoprotective effect. However, its protective effect on mitochondria of hepatocytes and its related mechanisms in ALF remain unknown. The purpose of the present study was to elucidate the protective effect of ACY1215 on mitochondrial of hepatocytes in ALF by regulating AMPK signaling pathway. LPS and D-Gal were used to induce ALF model in C57BL/6 mice. D-Gal and TNF-α were applied in L02 cells as model group. ACY1215 was administered to the mice or culture cells before the model' s establishment as ACY1215 group. The normal group in mice and L02 cells was not given any drug intervention. ACY1215 improves liver histological and functional changes in ALF model mice. Compared with normal group, the expression of p-AMPK and p-ACC proteins was decreased in model group. ACY1215 activated the AMPK signaling pathway with an increase of p-AMPK and p-ACC proteins level in model group. ACY1215 treatment decreased levels of mitochondrial fission proteins DRP1 and FIS1, and enhanced levels of mitochondrial fusion proteins MFN1, MFN2 and OPA1 in models. MtDNA copies in model group was decreased compared with normal group, but ACY1215 elevated the mtDNA copies in models. Mitochondrial respiratory electron transfer chain Complex I-III and citrate synthase (CS) activities in model group were decreased compared with normal group, but ACY1215 treatment enhanced these activities in model group. ACY1215 protects against dynamic disorders and dysfunction of mitochondria in hepatocytes in ALF by activating AMPK signaling pathway.

GSK-3-associated signaling is crucial to virus infection of cells

Signal transduction pathways play important roles in virus infection, replication, and associated pathogenesis. Some of the best understood cell signaling networks are crucial to virus infections such the mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K), protein kinase C (PKC), and the WNT/β-catenin pathways. Glycogen synthase kinase-3 (GSK-3) is a lesser known signaling molecule in the field of virus research. Interestingly, GSK-3 forms the crux of multiple cell signaling pathways. However, recent studies indicate that GSK-3 may perform key roles in the response to viral infection, replication and pathogenesis. The effects of activated or inactivated forms of GSK-3 on virus infection are still not yet clearly understood phenomenon. The comprehension of the molecular mechanisms underlying the regulation of GSK-3-associated signaling pathways in terms of different stages of virus replication could be important not only to understand the pathogenesis of virus, but also possibly leading to new therapeutic targets. This review will focus on recent advances in understanding the roles of GSK-3 on viral replication, pathogenesis and the immune responses.