Adropin protects against liver injury in nonalcoholic steatohepatitis via the Nrf2 mediated antioxidant capacity

Adropin and insulin resistance: Integration of endocrine, circadian, and stress signals regulating glucose metabolism

Dysregulation of hepatic glucose production (HGP) and glucose disposal leads to hyperglycemia and type 2 diabetes. Hyperglycemia results from the declining ability of insulin to reduce HGP and increase glucose disposal, as well as inadequate ß-cell compensation for insulin resistance. Hyperglucagonemia resulting from reduced suppression of glucagon secretion by insulin contributes to hyperglycemia by stimulating HGP. The actions of pancreatic hormones are normally complemented by peptides secreted by cells distributed throughout the body. This regulatory network has provided new therapeutics for obesity and type 2 diabetes (e.g., glucagon-like peptide 1). Other peptide hormones under investigation show promise in preclinical studies. Recent experiments using mice and nonhuman primates indicate the small secreted peptide hormone adropin regulates glucose metabolism. Here, recent expression profiling data indicating hepatic adropin expression increases with oxidative stress and declines with fasting or in the presence of hepatic insulin resistance and how adropin interacts with the pancreatic hormones, insulin, and glucagon to modulate glycemic control are discussed.

Exercise Intervention Mitigates Pathological Liver Changes in NAFLD Zebrafish by Activating SIRT1/AMPK/NRF2 Signaling

Non-alcoholic fatty liver disease (NAFLD) is a common disease that causes serious liver damage. Exercise is recognized as a non-pharmacological tool to improve the pathology of NAFLD. However, the antioxidative effects and mechanisms by which exercise ameliorates NAFLD remain unclear. The present study conducted exercise training on zebrafish during a 12-week high-fat feeding period to study the antioxidant effect of exercise on the liver. We found that swimming exercise decreased lipid accumulation and improved pathological changes in the liver of high-fat diet-fed zebrafish. Moreover, swimming alleviated NOX4-derived reactive oxygen species (ROS) overproduction and reduced methanedicarboxylic aldehyde (MDA) levels. We also examined the anti-apoptotic effects of swimming and found that it increased the expression of antiapoptotic factor bcl2 and decreased the expression of genes associated with apoptosis (caspase3, bax). Mechanistically, swimming intervention activated SIRT1/AMPK signaling-mediated lipid metabolism and inflammation as well as enhanced AKT and NRF2 activation and upregulated downstream antioxidant genes. In summary, exercise attenuates pathological changes in the liver induced by high-fat diets. The underlying mechanisms might be related to NRF2 and mediated by SIRT1/AMPK signaling.

A double-edged sword: The Kelch-like ECH-associated protein 1-nuclear factor erythroid-derived 2-related factor 2-antioxidant response element pathway targeted pharmacological modulation in nonalcoholic fatty liver disease

Nutraceuticals activating the Kelch-like epichlorohydrin (ECH)-associated protein 1 (Keap1)-nuclear factor erythroid-derived 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway are widely used for nonalcoholic fatty liver disease (NAFLD) because no specific drugs are approved yet. The pathology of NAFLD is summarized as the 'two-hit' hypothesis. The 'first hit' includes insulin resistance and lipid accumulation. Oxidative stress, lipid peroxidation, and inflammation are regarded as the 'second hit'. Now there is controversial evidence about the roles of the Keap1-Nrf2-ARE pathway and its activators in NAFLD. When the 'first hit' occurs, the hepatocyte-specific Nrf2 deficiency reduces insulin resistance and significantly attenuates lipid accumulation. However, when the 'second hit' occurs, Nrf2 activation reduces oxidative stress and combats inflammation. We reviewed the roles of the Keap1-Nrf2-ARE pathway as a double-edged sword in the development of NAFLD, its inhibitors as a novel therapeutic approach for early NAFLD, and the nutraceutical character of its activators.

Angelica Polysaccharide Antagonizes 5-FU-Induced Oxidative Stress Injury to Reduce Apoptosis in the Liver Through Nrf2 Pathway

Oxidative stress induced by chemotherapeutic agents causes hepatotoxicity. 5-Fluorouracil (5-FU) has been found to have a variety of side effects, but its toxic effect on the liver and the mechanism are still unclear. Angelica polysaccharide (ASP), the main active ingredient of Dang Gui, has antioxidative stress effects. In this study, we investigated the antagonistic effects of ASP on 5-FU-induced injury in the mouse liver and human normal liver cell line MIHA and the possible mechanism. Our results show that ASP inhibited 5-FU-induced the decrease in Bcl-2 protein and the increase in Bax protein. ASP alleviated 5-FU-induced the increase in alanine aminotransferase (ALT), triglyceride (TG), and aspartate aminotransferase (AST) content; hepatic steatosis; and liver fibrosis. ASP restored 5-FU-induced swelling of mitochondria and the endoplasmic reticulum. 5-FU promoted the expression of Keap1 and increased the binding to NF-E2-related factor 2 (Nrf2) to reduce the nuclear translocation of Nrf2, thereby weakening the transcriptional activity of Nrf2 to inhibit the expression of HO-1; reducing the activity of GSH, SOD, and CAT to increase ROS content; and aggravating DNA damage (indicated by the increase in 8-OHdG). However, ASP reversed these reactions. In conclusion, ASP attenuated the 5-FU-induced Nrf2 pathway barrier to reduce oxidative stress injury and thereby inhibit the disorder of lipid anabolism and apoptosis. The study provides a new protectant for reducing the hepatic toxicity caused by 5-FU and a novel target for treating the liver injury.

New Peptides as Potential Players in the Crosstalk Between the Brain and Obesity, Metabolic and Cardiovascular Diseases

According to the World Health Organization report published in 2016, 650 million people worldwide suffer from obesity, almost three times more than in 1975. Obesity is defined as excessive fat accumulation which may impair health with non-communicable diseases such as diabetes, cardiovascular diseases (hypertension, coronary artery disease, stroke), and some cancers. Despite medical advances, cardiovascular complications are still the leading causes of death arising from obesity. Excessive fat accumulation is caused by the imbalance between energy intake and expenditure. The pathogenesis of this process is complex and not fully understood, but current research is focused on the role of the complex crosstalk between the central nervous system (CNS), neuroendocrine and immune system including the autonomic nervous system, adipose tissue, digestive and cardiovascular systems. Additionally, special attention has been paid to newly discovered substances: neuropeptide 26RFa, preptin, and adropin. It was shown that the above peptides are synthesized both in numerous structures of the CNS and in many peripheral organs and tissues, such as the heart, adipose tissue, and the gastrointestinal tract. Recently, particular attention has been paid to the role of the presented peptides in the pathogenesis of obesity, metabolic and cardiovascular system diseases. This review summarizes the role of newly investigated peptides in the crosstalk between brain and peripheral organs in the pathogenesis of obesity, metabolic, and cardiovascular diseases.

Serum Adropin as a Potential Biomarker for Predicting the Development of Type 2 Diabetes Mellitus in Individuals With Metabolic Dysfunction-Associated Fatty Liver Disease

Background: Adropin, a peptide translated from the Energy Homeostasis Associated gene (ENHO), was mainly expressed in the liver and was a regulator in metabolic and energy homeostasis. This study aims to investigate the correlation between adropin and histological characteristics of the liver, and the clinical relevance of adropin in patients with metabolic dysfunction-associated fatty liver disease (MAFLD). Methods: A total of 62 subjects, including 32 healthy controls and 30 MAFLD patients, were enrolled in this case-control study. The MAFLD patients were further divided into two subgroups, including NGT-M group and T2DM-M group. Serum adropin levels, metabolic parameters and intrahepatic lipids, the liver ENHO mRNA expressions and histological characteristics were investigated. Results: MAFLD patients showed significantly lower circulating adropin compared with healthy controls (2.02 ± 2.92 vs. 5.52 ± 0.65 ng/mL, P < 0.0001). Subgroup analysis exhibited dramatically declined serum adropin levels in T2DM-M patients compared with NGT-M group (0.51 ± 0.73 vs. 4.00 ± 3.52 ng/mL, P < 0.001). H&E and Oil Red O staining show exacerbated steatohepatitis in T2DM-M patients in contrast with NGT-M group. Furthermore, serum adropin concentrations were negatively correlated with intrahepatic triglyceride (TG), total cholesterol (TC), and NAFLD activity score (NAS) (TG: r = -0.495; TC: r = -0.392; NAS: r = -0.451; all P < 0.05). Conclusions: MAFLD patients showed significantly lower adropin levels than the healthy controls, especially in T2DM patients. Adropin maybe a potential biomarker for predicting the development of MAFLD, especially in T2DM individuals.

Adropin Alleviates Myocardial Fibrosis in Diabetic Cardiomyopathy Rats: A Preliminary Study

Aim: Adropin (ADR) is a novel regulatory polypeptide and has important effects on energy metabolism in the heart. However, it is still unclear whether ADR can relieve ventricular remodeling in DCM. Therefore, this study was conducted to assess the effect of ADR on myocardial fibrosis in DCM rats.

Materials and Methods: Twenty Wistar rats were randomly assigned into four groups: healthy control group (CON), DCM model group (DCM), DCM model treated with ADR group (ADR) and DCM model treated with perindopril group (PER). Collagen volume fraction (CVF) and perivascular collagen area (PVCA) were calculated. Diastolic function was assessed by echocardiography. The mitochondrial membrane potential assay was conducted by Rhodamine 123 staining. The protein expression levels of Col I, Col III, Mitofusin-1, Mitofusin-2 and Drp1 were evaluated using western blot.

Results: Compared to CON group, CVF, PVCA and the relative protein expression of Col I, Col III and Drp1 increased in DCM group. And the relative expression of Mitofusin-1 and Mitofusin-2 proteins decreased. During our investigations, CVF, PVCA and the relative protein expression of Col I, Col III and Drp1 decreased in ADR treated rats compared to DCM group. The diastolic function was elevated in ADR group. The fluorescence of Rhodamine 123 and the expression of Mitofusin-1 and Mitofusin-2 also increased in ADR group.

Conclusion: Our study demonstrated that ADR could alleviate myocardial fibrosis and improve diastolic function in DCM rats. ADR may be a putative candidate for the treatment of DCM.

Quercetin as a protective agent for liver diseases: A comprehensive descriptive review of the molecular mechanism

Quercetin is the major representative of the flavonoid subgroup of flavones, with good pharmacological activities for the treatment of liver diseases, including liver steatosis, fatty hepatitis, liver fibrosis, and liver cancer. It can significantly influence the development of liver diseases via multiple targets and multiple pathways via antifat accumulation, anti-inflammatory, and antioxidant activity, as well as the inhibition of cellular apoptosis and proliferation. Despite extensive research on understanding the mechanism of quercetin in the treatment of liver diseases, there are still no targeted therapies available. Thus, we have comprehensively searched and summarized the different targets of quercetin in different stages of liver diseases and concluded that quercetin inhibited inflammation of the liver mainly through NF-κB/TLR/NLRP3, reduced PI3K/Nrf2-mediated oxidative stress, mTOR activation in autophagy, and inhibited the expression of apoptotic factors associated with the development of liver diseases. In addition, quercetin showed different mechanisms of action at different stages of liver diseases, including the regulation of PPAR, UCP, and PLIN2-related factors via brown fat activation in liver steatosis. The compound inhibited stromal ECM deposition at the liver fibrosis stage, affecting TGF1β, endoplasmic reticulum stress (ERs), and apoptosis. While at the final liver cancer stage, inhibiting cancer cell proliferation and spread via the hTERT, MEK1/ERK1/2, Notch, and Wnt/β-catenin-related signaling pathways. In conclusion, quercetin is an effective liver protectant. We hope to explore the pathogenesis of quercetin in different stages of liver diseases through the review, so as to provide more accurate targets and theoretical basis for further research of quercetin in the treatment of liver diseases.

Proteasome dysfunction under compromised redox metabolism dictates liver injury in NASH through ASK1/PPARγ binodal complementary modules

Incidence of hepatotoxicity following acute drug-induced proteasomal inhibition and development of chronic proteasome dysfunction in obesity and insulin resistance underscores the crucial importance of hepatic protein homeostasis albeit with an elusive molecular basis and therapeutic opportunities. Apart from lipotoxicity and endoplasmic reticulum (ER) stress, herein we report that hepatocytes are highly susceptible to proteasome-associated metabolic stress attune to altered redox homeostasis. Bortezomib-induced proteasomal inhibition caused severe hepatocellular injury independent of ER stress via proapoptotic Apoptosis Signal-regulating Kinase 1 (ASK1)- c-Jun N-terminal kinase (JNK1)- p38 signaling concomitant with inadequate peroxisome proliferator-activated receptor γ (PPARγ)- Nuclear factor erythroid 2-related factor 2 (Nrf2) -driven antioxidant response. Although inhibition of ASK1 rescued acute hepatotoxicity, hepatic depletion of PPARγ or its physiological activator pigment epithelium-derived factor (PEDF) further aggravated liver injury even under ASK1 inhibition, emphasizing that endogenous PPARγ driven antioxidant activity serves as a prerequisite for the favorable therapeutic outcome of ASK1 inhibition. Consequently, ASK1 inhibitor selonsertib and PPARγ agonist pioglitazone in pharmacological synergism ameliorated bortezomib-induced hepatotoxicity and significantly prolonged survival duration in mice. Moreover, we showed that proteasome dysfunction is associated with ASK1 activation and insufficient PPARγ/Nrf2-driven antioxidative response in a subset of human nonalcoholic steatohepatitis (NASH) patients and the preclinical NASH model. The latter remains highly responsive to the drug combination marked by revamped proteasomal activity and alleviated hallmarks of NASH such as steatosis, fibrosis, and hepatocellular death. We thus uncovered a pharmacologically amenable interdependent binodal molecular circuit underlying hepatic proteasomal dysfunction and associated oxidative injury.

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Acute proteasomal inhibition causes severe hepatocellular injury independent of ER stress.

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Proteasome dysfunction dictates metabolic stress and liver injury in NASH.

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ASK1 activation steers proteotoxic hepatocellular death under compromised PPARγ activity.

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Selonsertib and pioglitazone combination therapy prolong survival in proteotoxic hepatic failure.

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Combination therapy revamped proteasome activity and mitigate liver injury in NASH preclinical trial.

Exploration of the hepatoprotective effect and mechanism of magnesium isoglycyrrhizinate in mice with arsenic trioxide‑induced acute liver injury

Arsenic trioxide (ATO)-induced hepatotoxicity limits the therapeutic effect of acute myelogenous leukemia treatment. Magnesium isoglycyrrhizinate (MgIG) is a natural compound extracted from licorice and a hepatoprotective drug used in liver injury. It exhibits anti-oxidant, anti-inflammatory and anti-apoptotic properties. The aim of the present study was to identify the protective action and underlying mechanism of MgIG against ATO-induced hepatotoxicity. A total of 50 mice were randomly divided into five groups (n=10/group): Control; ATO; MgIG and high- and low-dose MgIG + ATO. Following continuous administration of ATO for 7 days, the relative weight of the liver, liver enzyme, histological data, antioxidant enzymes, pro-inflammatory cytokines, cell apoptosis and changes in Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 (Keap1-Nrf2) signaling pathway were observed. MgIG decreased liver injury, decreased the liver weight and liver index, inhibited oxidative stress and decreased the activity of glutathione, superoxide dismutase and catalase, production of reactive oxygen species and levels of pro-inflammatory cytokines, including IL-1β, IL-6 and TNF-α. Western blotting showed a decrease in Bax and caspase-3. There was decreased cleaved caspase-3 expression and increased Bcl-2 expression. MgIG notably activated ATO-mediated expression of Keap1 and Nrf2 in liver tissue. MgIG administration was an effective treatment to protect the liver from ATO-induced toxicity. MgIG maintained the level of Nrf2 in the liver and protected the antioxidative defense system to attenuate oxidative stress and prevent ATO-induced liver injury.

Serum Adropin Levels in Patients on Hemodialysis

Adropin is a novel pleotropic peptide involved in energy homeostasis, with possible contribution to cardiovascular protection through production of nitric oxide and subsequent blood pressure regulation. Given that patients undergoing hemodialysis (HD) are related with high cardiovascular risk, hyperlipidemia, chronic low-grade inflammation, and malnutrition the aim of our study was to investigate serum adropin levels in HD patients to evaluate possible associations with nutritional status and other relevant clinical and laboratory parameters. The study included 70 patients on HD and 60 healthy controls. Serum adropin levels were determined by an enzyme-linked immunosorbent assay in a commercially available diagnostic kit. Serum adropin levels were significantly lower in the HD group compared to the control group (2.20 ± 0.72 vs. 4.05 ± 0.93 ng/mL, p < 0.001). Moreover, there was a significant negative correlation with malnutrition-inflammation score (r = −0.476, p < 0.001), dialysis malnutrition score (r = −0.350, p = 0.003), HD duration (r = −0.305, p = 0.010), and high sensitivity C-reactive protein (hsCRP) (r = −0.646, p < 0.001). Additionally, there was a significant negative correlation between adropin levels and pre-dialysis systolic (r = −0.301, p = 0.011) and diastolic blood pressure (r = −0.299, p = 0.011). These results are implying that adropin is potentially involved in the pathophysiological mechanisms of chronic kidney disease (CKD)/HD and its complications. However, future larger scale longitudinal studies need to further address it.

Involvement of ABC transporters in the detoxification of non-substrate nanoparticles in lung and cervical cancer cells

This paper aimed to systemically investigate the role of adenosine triphosphate-binding cassette (ABC transporters) in the detoxification of non-substrate nanoparticles including titanium dioxide (n-TiO₂, 5-10 nm) and gold (AuNPs, 3 nm, 15 nm, and 80 nm, named as Au-3, Au-15 and Au-80) in human lung cancer (A549) and human cervical cancer (HeLa) cells. All these nanoparticles were of larger hydrophilic diameters than the channel sizes of ABC transporters, thus should not be the substrates of membrane proteins. After 24-h treatment, they induced significant cytotoxicity as reflected by the reduction in cell viability and glutathione (GSH) contents, as well as the increase in reactive oxygen species (ROS) level. At median-lethal concentrations (10 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for A549 cells; 20 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for Hela cells), all the nanoparticles significantly induced the gene expressions and activities of ABC transporters including P-glycoprotein (PGP) and multidrug resistance associated protein 1 (MRP1). Addition of transporter inhibitors enhanced the ROS levels produced by nanoparticles, but didn't alter their death-inducing effects and intracellular accumulations. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (NRF2) and pregnane X receptor (PXR) were proved to be important in the induction of ABC transporters by nanoparticles. After all, this paper revealed a damage-dependent modulation of ABC transporters by non-substrate nanoparticles. The up-regulated ABC transporters could help in reducing the oxidative stress produced by nanoparticles. Such information should be useful in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants or drugs.

Lupeol ameliorates LPS/D-GalN induced acute hepatic damage by suppressing inflammation and oxidative stress through TGFβ1-Nrf2 signal pathway

Acute hepatic damage is a severe condition characterized by inflammation and oxidative stress, which is a serious threat to people's life and health. But there are few effective treatments for acute liver injury. Therefore, safe and effective therapeutic approaches for preventing acute liver damage are urgently needed. Lupeol is a natural compound, which has significant antioxidant and anti-inflammatory properties in liver disease. However, the protective mechanism of lupeol against acute liver injury remains unclear. Here, zebrafish and mutant mice were utilized to investigate the protective effects of lupeol against lipopolysaccharide (LPS)/ D-galactosamine(D-GalN) -induced liver injury and the underlying mechanisms. We found that pretreatment with lupeol attenuated the LPS/D-GalN-induced liver injury by decreasing the infiltration of inflammatory cells and reducing pro-inflammatory cytokines. We also demonstrated that lupeol could protect injured liver from oxidative stress by downregulating the expression of TGFβ1 and upregulating Nrf2. Notably, our experimental results provided the support that lupeol effectively protected against LPS/D-GalN-induced acute liver injury via suppression of inflammation response and oxidative stress, which were largely dependent on the upregulation of the Nrf2 pathway via downregulating TGFβ1.

Exercise suppresses NLRP3 inflammasome activation in mice with diet-induced NASH: a plausible role of adropin

NLRP3 inflammasome activation, which can be triggered by reactive oxygen species (ROS), contributes to nonalcoholic steatohepatitis (NASH) progression. Exercise is an effective therapeutic strategy for NASH. However, whether exercise prevents NLRP3 activation in NASH has not been investigated. Here, we investigated the effect of exercise on NLRP3 inflammasome in mice with high-fat diet (HFD)-induced or methionine and choine-deficient (MCD) diet-induced NASH and explored whether adropin, a metabolic peptide hormone shown to inhibit inflammation, mediates an exercise-induced benefit against NLRP3 inflammasome activation. Exercise alleviated diet-induced hepatic steatosis, inflammation, and fibrosis. Importantly, exercise significantly reduced the expression of NLRP3 inflammasome components, decreased Caspase-1 enzymatic activity, normalized IL-1β production, and suppressed ROS overproduction in HFD-fed and MCD diet-fed mice. The exercise-elicited NLRP3 inflammasome inhibition was accompanied by increased adropin levels. Moreover, serum adropin levels were negatively correlated with serum IL-1β levels. We further explored the effect of adropin on the NLRP3 inflammasome in palmitic acid (PA)-treated hepatocytes and Kupffer cells. Although adropin treatment did not significantly decrease the levels of all inflammasome components, it reduced the active Caspase-1 level, decreased Caspase-1 activity and downregulated IL-1β expression in hepatocytes and Kupffer cells (KCs) treated with PA. Moreover, ROS levels in PA-stimulated hepatocytes and Kupffer cells were reduced upon adropin treatment. In summary, we demonstrated that the inhibitory effect of exercise on NLRP3 inflammasome activation was associated with adropin induction, resulting in NASH improvement.

Adropin as a potential mediator of the metabolic system-autonomic nervous system-chronobiology axis: Implementing a personalized signature-based platform for chronotherapy

Adropin is a peptide hormone, which plays a role in energy homeostasis and controls glucose and fatty acid metabolism. Its levels correlate with changes in carbohydrate-lipid metabolism, metabolic diseases, central nervous system function, endothelial function and cardiovascular disease. Both metabolic pathways and adropin are regulated by the circadian clocks. Here, we review the roles of the autonomic nervous system and circadian rhythms in regulating metabolic pathways and energy homeostasis. The beneficial effects of chronotherapy in various systems are discussed. We suggest a potential role for adropin as a mediator of the metabolic system-autonomic nervous system axis. We discuss the possibility of establishing an individualized adropin and circadian rhythm-based platform for implementing chronotherapy, and variability signatures for improving the efficacy of adropin-based therapies are discussed.

Oleoylethanolamide Protects Against Acute Liver Injury by Regulating Nrf-2/HO-1 and NLRP3 Pathways in Mice

Acute liver injury is a rapidly deteriorating clinical condition with markedly high morbidity and mortality. Oleoylethanolamide (OEA) is an endogenous lipid messenger with multiple bioactivities, and has therapeutic effects on various liver diseases. However, effects of OEA on acute liver injury remains unknown. In this study, effects and mechanisms of OEA in lipopolysaccharide (LPS)/d-galactosamine (D-Gal)-induced acute liver injury in mice were investigated. We found that OEA treatment significantly attenuated LPS/D-Gal-induced hepatocytes damage, reduced liver index (liver weight/body weight), decreased plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels. Moreover, mechanism study suggested that OEA pretreatment significantly reduced hepatic MDA levels, increased Superoxide dismutase (SOD) and Glutathione peroxidase (GSH-PX) activities via up-regulate Nrf-2 and HO-1 expression to exert anti-oxidation activity. Additionally, OEA markedly reduced the expression levels of Bax, Bcl-2 and cleaved caspase-3 to suppress hepatocyte apoptosis. Meanwhile, OEA remarkedly reduced the number of activated intrahepatic macrophages, and alleviated the mRNA expression of pro-inflammatory factors, including TNF-α, IL-6, MCP1 and RANTES. Furthermore, OEA obviously reduced the expression of IL-1β in liver and plasma through inhibit protein levels of NLRP3 and caspase-1, which indicated that OEA could suppress NLRP3 inflammasome pathway. We further determined the protein expression of PPAR-α in liver and found that OEA significantly increase hepatic PPAR-α expression. In addition, HO-1 inhibitor ZnPP blocked the therapeutic effects of OEA on LPS/D-Gal-induced liver damage and oxidative stress, suggesting crucial role of Nrf-2/HO-1 pathway in the protective effects of OEA in acute liver injury. Together, these findings demonstrated that OEA protect against the LPS/D-Gal-induced acute liver injury in mice through the inhibition of apoptosis, oxidative stress and inflammation, and its mechanisms might be associated with the Nrf-2/HO-1 and NLRP3 inflammasome signaling pathways.

Lower adropin expression is associated with oxidative stress and severity of nonalcoholic fatty liver disease

BACKGROUND & AIMS

Adropin has been reported to be involved in metabolic disorders, including nonalcoholic fatty liver disease (NAFLD). However, the clinical relevance of adropin expression to the histological severity of NAFLD is unclear. This study aimed to investigate adropin expression in biopsy-proven NAFLD patients.

METHODS

This case-control study enrolled a total of 109 participants, including 15 normal histological controls, 26 nonalcoholic fatty liver (NAFL), 21 nonalcoholic steatohepatitis (NASH) subjects and B-ultrasound NAFLD-free normal controls matched to the cases based on age and sex (the case:control ratio was 1:1). Liver biopsies were obtained and histological characteristics were assessed. Primary murine hepatocytes were isolated from C57BL/6J mice and incubated with doses of palmitate to induce oxidative stress.

RESULTS

The serum adropin level in NASH patients was 9.99 ± 5.51 ng/ml, significantly lower than that in B-ultrasound normal controls (22.70 ± 6.32 ng/ml), histological normal controls (21.93 ± 6.63 ng/ml) and NAFL patients (17.82 ± 6.90 ng/ml). Serum adropin levels were negatively correlated with the histological severity of NAFLD. The lower serum adropin level predicted NASH (area under the ROC curve: 87.1%). Adropin expression in serum and liver was also negatively associated with hepatic MDA and serum 8-iso-PGF2α levels. Furthermore, palmitate rather than oleate induced oxidative stress in a dose-dependent manner with a gradient decrease in adropin expression in primary murine hepatocytes. Adropin overexpression or treatment ameliorated palmitate-induced oxidative stress in hepatocytes.

CONCLUSIONS

Circulating adropin was inversely associated with the oxidative stress and histological severity of NAFLD. It may play an important role in the development of NAFLD.

Hsa_circ_0048179 attenuates free fatty acid-induced steatosis via hsa_circ_0048179/miR-188-3p/GPX4 signaling

Although circular RNAs (circRNAs) are known to play key roles in non-alcoholic fatty liver disease, much about their targets and mechanisms remains unknown. We therefore investigated the actions and mechanisms of hsa_circ_0048179 in an in vitro model of NAFLD. HepG2 cells were exposed to oleate/palmitate (2:1 ratio) for 24 h to induce intracellular lipid accumulation. Using CCK-8 assays, flow cytometry, fluorescence microscopy, western blotting, RT-qPCR, and Oil red O staining, we found that oleate/palmitate treatment reduced cell viability while increasing apoptosis and lipid accumulation in HepG2 cells. Levels of the antioxidant enzyme GPX4 were decreased in oleate/palmitate-treated HepG2 cells, and there were corresponding increases in reactive oxygen species and damage to mitochondrial cristae. Levels of hsa_circ_0048179 expression were also suppressed by oleate/palmitate treatment, and GPX4 levels were markedly increased in HepG2 cells following transfection with hsa_circ_0048179. Analysis of its mechanism revealed that hsa_circ_0048179 upregulated GPX4 levels by acting as a competitive “sponge” of miR-188-3p and that hsa_circ_0048179 attenuated oleate/palmitate-induced lipid accumulation in HepG2 cells by sponging miR-188-3p. Collectively, our findings suggest that hsa_circ_0048179 may play a key role in the pathogenesis of steatosis and may thus be a useful target for drug development.

Unique Novel Role of Adropin in a Gastric Ulcer in a Rotenone-Induced Rat Model of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, frequently associated with a gastric ulcer. We aimed to investigate the adropin neuroprotective/gastroprotective potential in the indomethacin (IND)-induced gastric ulcer in a rotenone-induced PD model. Rats were randomly divided into four groups: normal control group, rotenone/IND treated (PD /Ulcer) group, adropin treated PD/Ulcer group, and l-dopa/omeprazole (Om) treated PD/Ulcer group. There were ten rats selected for the normal control group. Striatal dopamine (DA), apoptosis/redox status, and motor/behavioral impairments were evaluated. Gastric oxidative stress, H⁺/K⁺-ATPase activity, prostaglandin E2, mucin content, and von Willebrand factor were measured. Gastric/striatal phosphatidylinositol 3-kinase (PI3K)/phosphorylated Akt and gastric vascular endothelial growth factor (VEGF)/striatal P53 immunoreactivities were checked. Striatal P53 upregulated modulator of apoptosis (Puma)/gastric vascular endothelial growth factor receptor-2 (Vegfr-2) expressions were evaluated. Adropin successfully restored striatal DA and attenuated rotenone-induced motor/behavior deficits along with strong gastroprotective potential, possibly through antioxidant activity via reduction in malondialdehyde level and upregulated superoxide dismutase, catalase activities, and serum ferric reducing antioxidant power. Adropin restored the delicate balance between the defective pro-survival PI3K/Akt/murine double minute 2 signals and apoptotic P53/Puma pathways. Adropin can be considered as a uniquely attractive therapeutic target in PD and its associated gastric ulcer.

Decreased Mitochondrial Function, Biogenesis, and Degradation in Peripheral Blood Mononuclear Cells from Amyotrophic Lateral Sclerosis Patients as a Potential Tool for Biomarker Research

Amyotrophic lateral sclerosis (ALS) is a multifactorial and progressive neurodegenerative disease of unknown etiology. Due to ALS’s unpredictable onset and progression rate, the search for biomarkers that allow the detection and tracking of its development and therapeutic efficacy would be of significant medical value. Considering that alterations of energy supply are one of ALS’s main hallmarks and that a correlation has been established between gene expression in human brain tissue and peripheral blood mononuclear cells (PBMCs), the present work investigates whether changes in mitochondrial function could be used to monitor ALS. To achieve this goal, PBMCs from ALS patients and control subjects were used; blood sampling is a quite non-invasive method and is cost-effective. Different parameters were evaluated, namely cytosolic calcium levels, mitochondrial membrane potential, oxidative stress, and metabolic compounds levels, as well as mitochondrial dynamics and degradation. Altogether, we observed lower mitochondrial calcium uptake/retention, mitochondria depolarization, and redox homeostasis deregulation, in addition to a decrease in critical metabolic genes, a diminishment in mitochondrial biogenesis, and an augmentation in mitochondrial fission and autophagy-related gene expression. All of these changes can contribute to the decreased ATP and pyruvate levels observed in ALS PBMCs. Our data indicate that PBMCs from ALS patients show a significant mitochondrial dysfunction, resembling several findings from ALS’ neural cells/models, which could be exploited as a powerful tool in ALS research. Our findings can also guide future studies on new pharmacological interventions for ALS since assessments of brain samples are challenging and represent a relevant limited strategy.

Hepatocyte expression of the micropeptide adropin regulates the liver fasting response and is enhanced by caloric restriction

The micropeptide adropin encoded by the clock-controlled energy homeostasis-associated gene is implicated in the regulation of glucose metabolism. However, its links to rhythms of nutrient intake, energy balance, and metabolic control remain poorly defined. Using surveys of Gene Expression Omnibus data sets, we confirm that fasting suppresses liver adropin expression in lean C57BL/6J (B6) mice. However, circadian rhythm data are inconsistent. In lean mice, caloric restriction (CR) induces bouts of compulsive binge feeding separated by prolonged fasting intervals, increasing NAD-dependent deacetylase sirtuin-1 signaling important for glucose and lipid metabolism regulation. CR up-regulates adropin expression and induces rhythms correlating with cellular stress-response pathways. Furthermore, adropin expression correlates positively with phosphoenolpyruvate carboxokinase-1 (Pck1) expression, suggesting a link with gluconeogenesis. Our previous data suggest that adropin suppresses gluconeogenesis in hepatocytes. Liver-specific adropin knockout (LAdrKO) mice exhibit increased glucose excursions following pyruvate injections, indicating increased gluconeogenesis. Gluconeogenesis is also increased in primary cultured hepatocytes derived from LAdrKO mice. Analysis of circulating insulin levels and liver expression of fasting-responsive cAMP-dependent protein kinase A (PKA) signaling pathways also suggests enhanced responses in LAdrKO mice during a glucagon tolerance test (250 µg/kg intraperitoneally). Fasting-associated changes in PKA signaling are attenuated in transgenic mice constitutively expressing adropin and in fasting mice treated acutely with adropin peptide. In summary, hepatic adropin expression is regulated by nutrient- and clock-dependent extrahepatic signals. CR induces pronounced postprandial peaks in hepatic adropin expression. Rhythms of hepatic adropin expression appear to link energy balance and cellular stress to the intracellular signal transduction pathways that drive the liver fasting response.

Adropin regulates hepatic glucose production via PP2A/AMPK pathway in insulin-resistant hepatocytes

Adropin as a secretory peptide has shown a protective role on the disorders of glucose and lipid metabolism. However, the role and mechanism of this peptide on the hepatic glucose production has remained unclear. Adropin knockout (KO) mice were generated to explore its effects on the enhanced hepatic glucose production in obesity. We found that compared to wild-type (WT) mice, adropin-KO mice developed the unbalanced enhanced hepatic glucose production in advance of the whole-body insulin resistance (IR) by high-fat diet (HFD). Mechanistically, adropin dissociated CREB-CRTC2 and FoxO1-PGC1α complex and reduced their binding to the promoters of G6Pase and PEPCK to decrease glucose production in IR. However, these effects were not observed in insulin-sensitive hepatocytes. Furthermore, in IR hepatocytes, dampened AMPK signaling was re-activated by adropin treatment via inhibition of PP2A. To further authenticate AMPK role in vivo, we administrated HFD-fed mice with AAV8-CA AMPKα and found that AMPK activation functionally restored the aberrant glucose production and IR induced by adropin-deficiency. This study provides evidence that adropin activates the AMPK pathway via inhibition of PP2A and decreases the liver glucose production in IR context. Therefore, adropin may represent a novel target for the prevention and treatment of diabetes.

Gentiopicroside Ameliorates Oxidative Stress and Lipid Accumulation through Nuclear Factor Erythroid 2-Related Factor 2 Activation

The activation of nuclear factor erythroid 2-related factor 2 (Nrf2) is closely related to the alleviation of nonalcoholic fatty liver disease (NAFLD) by regulating oxidative stress and lipid homeostasis. Gentiopicroside (GPS), an iridoid glycoside found in the Gentianaceae, possesses anti-inflammatory and antioxidant effects. However, the protective effects of GPS on lipid accumulation and oxidative damage have not been investigated thoroughly in free fatty acid- (FFA-) induced HepG2 cells and tyloxapol- (Ty-) induced hyperlipidemia mice. Cell counting kit-8 assays, Oil Red O staining, Western blotting analysis, extraction of nuclear and cytosolic proteins, and biochemical index assay were employed to explore the mechanisms by which GPS exerts a protective effect on FFA-induced HepG2 cells and Ty-induced hyperlipidemia mouse model. This paper demonstrates that GPS could effectively alleviate NAFLD by elevating cell viability, reducing fatty deposition, downregulating TG, and activating nucleus Nrf2 in FFA-induced HepG2 cells. Meanwhile, GPS significantly regulated the activation of phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway, Nrf2 antioxidant pathway, peroxisome proliferator-activated receptor α (PPARα), and GPS-inhibited sterol regulatory element-binding protein-1c (SREBP-1c) expression in FFA-stimulated lipid accumulation of HepG2 cells and Ty-treated mice. Interestingly, we highlight that PI3K/AKT inhibitor (LY294002) markedly increased the expression of Nrf2 antioxidant pathway, PPARα, and downregulated SREBP-1c in FFA-stimulated HepG2 cells. For these reasons, we found that the deletion of Nrf2 could lose the protective effects of GPS on the Nrf2 antioxidant pathway and PPARα activation and SREBP-1c inactivation in FFA-stimulated HepG2 cells and Ty-treated mice. GPS treatment had no effect on abnormal lipogenesis and antioxidant enzymes in Ty-induced Nrf2^−/− mice. This work gives a new explanation that GPS may be a useful therapeutic strategy for NAFLD through upregulation of the Nrf2 antioxidant pathway, which can alleviate oxidative damage and lipid accumulation.

Serum adropin levels are reduced in patients with inflammatory bowel diseases

Adropin is a novel peptide mostly associated with energy homeostasis and vascular protection. To our knowledge, there are no studies that investigated its relationship with inflammatory bowel diseases (IBD). The aim of this study was to compare serum adropin levels between 55 patients with IBD (30 Ulcerative colitis (UC) patients, 25 Crohn’s disease (CD) patients) and 50 age/gender matched controls. Furthermore, we explored adropin correlations with IBD severity scores, hsCRP, fecal calprotectin, fasting glucose and insulin levels. Serum adropin levels were significantly lower in patients with IBD in comparison with the control group (2.89 ± 0.94 vs 3.37 ± 0.60 ng/mL, P = 0.002), while there was no significant difference in comparison of UC patients with CD patients (P = 0.585). Furthermore, there was a negative correlation between adropin and fecal calprotectin (r = −0.303, P = 0.025), whereas in the total study population, we found a significant negative correlation with fasting glucose levels (r = −0.222, P = 0.023). A multivariable logistic regression showed that serum adropin was a significant predictor of positive IBD status when enumerated along with baseline characteristics (OR 0.455, 95% CI 0.251–0.823, P = 0.009). Our findings imply that adropin could be involved in complex pathophysiology of IBD, but further larger scale studies are needed to address these findings.

α-Lipoic acid induces Endoplasmic Reticulum stress-mediated apoptosis in hepatoma cells

Hepatocellular carcinoma (HCC) is the most common liver cancer and a major cause of adult death. The current treatments for HCC suffer from drug resistance and poor prognosis; therefore, novel therapeutic agents are urgently needed. Phytochemicals have been proposed to treat a range of cancers. Among them, α-lipoic acid (α-LA), a naturally synthesized antioxidant found in various dietary animal and plant sources, prevents oxidant-mediated cell death in normal cells while inducing apoptosis in several cancer cell lines. Previously, we demonstrated that the treatment of hepatoma cells with α-LA induced apoptosis, which was preceded by the generation of reactive oxygen species (ROS) and activation of the p53 protein, a known inducer of mitochondria-mediated apoptosis. Several studies have shown that ROS-induced apoptosis is associated with endoplasmic reticulum (ER) stress and Unfolded Protein Response (UPR) activation. Herein, we investigated if α-LA-induced apoptosis in hepatoma cell lines was ER stress- and UPR-mediated by gene expression profiling analyses. UPR and ER stress pathways were the most up-regulated after treatment with α-LA. This finding, which has been confirmed by expression analyses of ER- and UPR-associated proteins, provides a better understanding of the molecular mechanisms behind the anti-tumoral action of α-LA on hepatoma cells.

4,5-di-O-caffeoylquinic acid methyl ester isolated from Lonicera japonica Thunb. targets the Keap1/Nrf2 pathway to attenuate H2O2-induced liver oxidative damage in HepG2 cells

BACKGROUND

4,5-di-O-caffeoylquinic acid methyl ester (4,5-CQME) is a caffeoylquinic acid (CQA) isolated from Lonicera japonica Thunb., a traditional Chinese medicine. To date, the biological activity of 4,5-CQME has not been fully investigated.

PURPOSE

The aim of the current study was to explore the anti-oxidative activity and the underlying mechanism of 4,5-CQME.

METHODS

MTT assay was used to evaluate the cytoprotective effect of 4,5-CQME. DCFH-DA was used as a fluorescence probe to detect intracellular ROS. The mitochondrial membrane potential was detected using the fluorescent probe JC-1. MDA and GSH levels were measured using MDA and GSH commercial kits, respectively. Apoptosis assay was performed using the Annexin V-FITC/PI method. The functional mechanism of 4,5-CQME was investigated by analyzing relative signaling pathways through immunofluorescent staining, quantitative PCR and western blot analysis.

RESULTS

HepG2 cells were incubated with different concentrations of 4,5-CQME for 12 h before exposure to 500 μM H2O2 for 3 h. 4,5-CQME attenuated H2O2-induced oxidative damage and had a higher cytoprotective effect than 3-caffeoylquinic acid, 3-caffeoylquinic acid methyl ester, or 4,5-di-O-caffeoylquinic acid. 4,5-CQME also reduced ROS and MDA levels and rescued GSH depletion. Western blots demonstrated that 4,5-CQME decreased Bax/Bcl-2 and Bak levels. A mechanistic study confirmed that 4,5-CQME significantly suppressed H2O2-induced MAPKs phosphorylation but had little effect on MAPKs phosphorylation under normal conditions. By contrast, 4,5-CQME induced AKT phosphorylation in the presence or absence of H2O2. 4,5-CQME also regulated the Keap1/Nrf2 signaling pathway and enhanced both the mRNA and protein expressions of HO-1 and NQO1. The anti-oxidative effect of 4,5-CQME was greatly abolished by co-incubation with the Nrf2 inhibitor ML385 or PI3K inhibitor wortmannin.

CONCLUSIONS

Taken together, these results showed that 4,5-CQME offered significant protection against H2O2-induced oxidative stress, and its effect was in part due to the modulation of the Keap1/Nrf2 pathway.

CDKN2a/p16 Antagonizes Hepatic Stellate Cell Activation and Liver Fibrosis by Modulating ROS Levels

The lipid-storage hepatic stellate cells (HSC) play as pivotal role in liver fibrosis being able to trans-differentiate into myofibroblasts in response to various pro-fibrogenic stimuli. In the present study we investigated the role of CDKN2a/p16, a negative regulator of cell cycling, in HSC activation and the underlying mechanism. Levels of p16 were significantly down-regulated in activated HSCs isolated from mice induced to develop liver fibrosis compared to quiescent HSCs isolated from the control mice ex vivo. There was a similar decrease in p16 expression in cultured HSCs undergoing spontaneous activation or exposed to TGF-β treatment in vitro. More important, p16 down-regulation was observed to correlate with cirrhosis in humans. In a classic model of carbon tetrachloride (CCl₄) induced liver fibrosis, fibrogenesis was far more extensive in mice with p16 deficiency (KO) than the wild type (WT) littermates. Depletion of p16 in cultured HSCs promoted the synthesis of extracellular matrix (ECM) proteins. Mechanistically, p16 deficiency accelerated reactive oxygen species (ROS) generation in HSCs likely through the p38 MAPK signaling. P38 inhibition or ROS cleansing attenuated ECM production in p16 deficient HSCs. Taken together, our data unveil a previously unappreciated role for p16 in the regulation of HSC activation. Screening for small-molecule compounds that can boost p16 activity may yield novel therapeutic strategies against liver fibrosis.

Gegen Qinlian Decoction abates nonalcoholic steatohepatitis associated liver injuries via anti-oxidative stress and anti-inflammatory response involved inhibition of toll-like receptor 4 signaling pathways

Gegen Qilian Decoction (GGQLD) is a well-established classic Chinese medicine prescription in treating nonalcoholic steatohepatitis (NASH). However, the molecular mechanism of GGQLD action on NASH is still not clear. This study aimed to assess the anti-NASH effect of GGQLD, and to explore its molecular mechanisms in vivo and in vitro. In HFD-fed rats, GGQLD decreased significantly serum triglyceride (TG), cholesterol (CHO), total bile acid (TBA), low-density lipoprotein (LDL), free fatty acid (FFA) and lipopolysaccharide (LPS) levels, increased levels of differentially expressed proteins (DEPs) Ahcy, Gpx1, Mat1a, GNMT, and reduced the expression of ALDOB. In RAW264.7 macrophages, GGQLD reduced the expression levels of inflammatory factors TNF-α and IL-6 mRNA, and diminished NASH by increasing differentially expressed genes (DEGs) CBS, Mat1a, Hnf4α and Pparα to reduce oxidative stress or lipid metabolism. The results of DEGs verification also showed that GGQLD up-regulated expressions of Hnf4α, Pparα and Cbs genes. In HepG2 cells, GGQLD decreased IL-6 levels and intracellular TG content, and inhibited FFA-induced expression of toll-like receptor 4 (TLR4). In summary, GGQLD abates NASH associated liver injuries via anti-oxidative stress and anti-inflammatory response involved inhibition of TLR4 signal pathways. These findings provide new insights into the anti-NASH therapy by GGQLD.

A Review of Adropin as the Medium of Dialogue between Energy Regulation and Immune Regulation

Adropin is a secretory protein encoded by the energy balance gene and is closely associated with regulation of energy metabolism and insulin resistance. The clinical findings demonstrated its decreased expression in various inflammatory diseases, its negative correlation with the expression levels of inflammatory cytokines, and its potential anti-inflammatory effects. We speculate that adropin plays a pivotal regulatory role in immune cells and inflammatory factors. In this study, we reviewed the advances in researches concentrated on immunological effects of adropin.

Adropin as A Fat-Burning Hormone with Multiple Functions-Review of a Decade of Research

Adropin is a unique hormone encoded by the energy homeostasis-associated (Enho) gene. Adropin is produced in the liver and brain, and also in peripheral tissues such as in the heart and gastrointestinal tract. Furthermore, adropin is present in the circulatory system. A decade after its discovery, there is evidence that adropin may contribute to body weight regulation, glucose and lipid homeostasis, and cardiovascular system functions. In this review, we summarize and discuss the physiological, metabolic, and pathophysiological factors regulating Enho as well as adropin. Furthermore, we review the literature addressing the role of adropin in adiposity and type 2 diabetes. Finally, we elaborate on the role of adropin in the context of the cardiovascular system, liver diseases, and cancer.

The peptide hormone adropin regulates signal transduction pathways controlling hepatic glucose metabolism in a mouse model of diet-induced obesity

The peptide hormone adropin regulates energy metabolism in skeletal muscle and plays important roles in the regulation of metabolic homeostasis. Besides muscle, the liver has an essential role in regulating glucose homeostasis. Previous studies have reported that treatment of diet-induced obese (DIO) male mice with adropin34-76 (the putative secreted domain) reduces fasting blood glucose independently of body weight changes, suggesting that adropin suppresses glucose production in the liver. Here, we explored the molecular mechanisms underlying adropin's effects on hepatic glucose metabolism in DIO mice. Male DIO B6 mice maintained on a high-fat diet received five intraperitoneal injections of adropin34-76 (450 nmol/kg/injection) over a 48-h period. We found that adropin34-76 enhances major intracellular signaling activities in the liver that are involved in insulin-mediated regulation of glucose homeostasis. Moreover, treatment with adropin34-76 alleviated endoplasmic reticulum stress responses and reduced activity of c-Jun N-terminal kinase in the liver, explaining the enhanced activities of hepatic insulin signaling pathways observed with adropin34-76 treatment. Furthermore, adropin34-76 suppressed cAMP activated protein kinase A (PKA) activities, resulting in reduced phosphorylation of inositol trisphosphate receptor, which mediates endoplasmic reticulum calcium efflux, and of cAMP-responsive element-binding protein, a key transcription factor in hepatic regulation of glucose metabolism. Adropin34-76 directly affected liver metabolism, decreasing glucose production and reducing PKA-mediated phosphorylation in primary mouse hepatocytes in vitro Our findings indicate that major hepatic signaling pathways contribute to the improved glycemic control achieved with adropin34-76 treatment in situations of obesity.

Long non-coding RNA CHRF modulates the progression of cerebral ischemia/reperfusion injury via miR-126/SOX6 signaling pathway

Ischemic stroke remains as a major cause for disability and death in the world. Long non-coding RNA (lncRNA) cardiac hypertrophy-related factor (CHRF) has been suggested as a crucial modulator in cardiac injury and various human cancers. Nevertheless, its effects and mechanism on ischemic stroke remains unclear. In this study, we found that CHRF was significantly correlated with miR-126, and miR-126 expression was decreased in the ischemic core following ischemia, while CHRF expression was increased according to the in vivo and in vitro experiments. Additionally, miR-126 significantly reduced oxygen-glucose deprivation and reoxygenation (OGD/R)-triggered apoptosis using TUNEL and flow cytometry analysis. Moreover, CHRF played as a competing endogenous RNA (ceRNA) and competed with Sex-determining region Y box 6 (SOX6) to direct binding with miR-126, subsequently regulating ischemic neuronal death. CHRF knockdown in vivo markedly prevented ischemic damage and alleviated neurological dysfunctions. Thereby, these results revealed a new molecular mechanism of lncRNA CHRF through targeting miR-126/SOX6 signaling to modulate ischemic neuronal injury, providing solid evidence to develop promising therapeutic strategies against cerebral ischemic stroke.