Tumour necrosis factor-α promotes liver ischaemia-reperfusion injury through the PGC-1α/Mfn2 pathway

Inflammatory setting, therapeutic strategies targeting some pro-inflammatory cytokines and pathways in mitigating ischemia/reperfusion-induced hepatic injury: a comprehensive review

Ischemia/reperfusion injury (IRI) is a key determining agent in the pathophysiology of clinical organ dysfunction. It is characterized by an aseptic local inflammatory reaction due to a decrease in blood supply, hence deprivation of dependent oxygen and nutrients. In instances of liver transplantation, this injury may have irreversible implications, resulting in eventual organ rejection. The deterioration associated with IRI is affected by the hepatic health status and various factors such as alterations in metabolism, oxidative stress, and pro-inflammatory cytokines. The primary cause of inflammation is the initial immune response of pro-inflammatory cytokines, while Kupffer cells (KFCs) and neutrophil-produced chemokines also play a significant role. Upon reperfusion, the activation of inflammatory responses can elicit further cellular damage and organ dysfunction. This review discusses the interplay between chemokines, pro-inflammatory cytokines, and other inflammatory mediators that contribute to the damage to hepatocytes and liver failure in rats following IR. Furthermore, it delves into the impact of anti-inflammatory therapies in safeguarding against liver failure and hepatocellular damage in rats following IR. This review investigates the correlation between cytokine factors and liver dysfunction via examining databases, such as PubMed, Google Scholar, Science Direct, Egyptian Knowledge Bank (EKB), and Research Gate.

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

CircHIPK3 relieves vascular calcification via mediating SIRT1/PGC-1α/MFN2 pathway by interacting with FUS

BACKGROUND

Circular RNAs (circRNAs) have been reported to regulate the biological processes of human diseases. CircHIPK3 has been implicated in vascular calcification, but the downstream regulatory mechanisms remain unclear. Our study aimed to understand the regulatory function of circHIPK3 in vascular calcification.

METHODS

CircHIPK3 expression in atherosclerosis (AS) serum samples and vascular smooth muscle cells (VSMCs) calcification model was assessed by quantitative real-time polymerase chain reaction (qRT-PCR). The binding relationships between fused in sarcoma (FUS) and circHIPK3 or sirtuin 1 (SIRT1) were verified by RNA immunoprecipitation (RIP) assay and RNA pull-down assays. Alkaline phosphatase (ALP) activity and alizarin red staining assays were performed to evaluate the biological effect of β-glycerophosphate (β-GP) and circHIPK3 on calcium deposition. qRT-PCR and western blot assays were used to examine the effect of β-GP, circHIPK3, SIRT1, mitofusin 2 (MFN2), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) on VSMCs calcification and the expression of calcification-related proteins.

RESULTS

In AS serum samples and VSMCs calcification model, the expression of circHIPK3 was significantly reduced. CircHIPK3 overexpression inhibited ALP activity and calcium deposition in β-GP-induced VSMCs. Moreover, circHIPK3 could recruit FUS to further stabilize SIRT1 mRNA. CircHIPK3 promoted MFN2 expression to alleviate VSMCs calcification via activating SIRT1/PGC-1α signaling.

CONCLUSION

The positive regulation of circHIPK3/FUS/SIRT1/PGC-1α/MFN2 signaling pathway contributed to the alleviate VSMCs calcification, revealing a novel regulatory axis for vascular calcification.

Increased Ca2 + transport across the mitochondria-associated membranes by Mfn2 inhibiting endoplasmic reticulum stress in ischemia/reperfusion kidney injury

Renal ischemia/reperfusion (I/R) injury, which leads to acute kidney injury (AKI), is a major cause of morbidity and mortality in a variety of clinical situations. This study aimed to investigate the protective role of Mfn2 during renal I/R injury. Overexpression of Mfn2 in NRK-52E rat renal tubular epithelial cells and rats, then we constructed hypoxia reoxygenation (H/R) cells and I/R rat model. Apoptosis, ROS, ATP, Ca2+ levels in cells and rats, as well as renal tissue and functional injury in rats were detected respectively. Endoplasmic reticulum (ER) stress was further examined in cells and rats. The morphological changes of mitochondria-associated ER membranes (MAMs) were also detected. Mfn2 expression is reduced in H/R-treated NRK-52E cells and renal tissue of I/R rats. At the cellular level, overexpression of Mfn2 promoted cell proliferation, inhibited cell apoptosis, attenuated mitochondrial damage and Ca2+ overload, and ER stress. In addition, Mfn2 also restored the MAMs structure. In vivo experiments found that overexpression of Mfn2 could improve renal function and alleviate tissue injury. Concomitant with elevated Mfn2 expression in the kidney, reduced renal cell apoptosis, restored mitochondrial function, and reduced calcium overload. Finally, ER stress in rat kidney tissue was alleviated after overexpression of Mfn2. These results reveal that Mfn2 contributes to ER stress, mitochondrial function, and cell death in I/R injury, which provides a novel therapeutic target for AKI.

Hepatic ischemia-reperfusion syndrome and its effect on the cardiovascular system: The role of treprostinil, a synthetic prostacyclin analog

Hepatic ischemia-reperfusion syndrome has been the subject of intensive study and experimentation in recent decades since it is responsible for the outcome of several clinical entities, such as major hepatic resections and liver transplantation. In addition to the organ's post reperfusion injury, this syndrome appears to play a central role in the dysfunction of distant tissues and systems. Thus, continuous research should be directed toward finding effective therapeutic options to improve the outcome and reduce the postoperative morbidity and mortality rates. Treprostinil is a synthetic analog of prostaglandin I2, and its experimental administration has shown encouraging results. It has already been approved by the Food and Drug Administration in the United States for pulmonary arterial hypertension and has been used in liver transplantation, where preliminary encouraging results showed its safety and feasibility by using continuous intravenous administration at a dose of 5 ng/kg/min. Treprostinil improves renal and hepatic function, diminishes hepatic oxidative stress and lipid peroxidation, reduces hepatictoll-like receptor 9 and inflammation, inhibits hepatic apoptosis and restores hepatic adenosine triphosphate (ATP) levels and ATP synthases, which is necessary for functional maintenance of mitochondria. Treprostinil exhibits vasodilatory properties and antiplatelet activity and regulates proinflammatory cytokines; therefore, it can potentially minimize ischemia-reperfusion injury. Additionally, it may have beneficial effects on cardiovascular parameters, and much current research interest is concentrated on this compound.

Asiatic acid improves insulin secretion of cells in type 2 diabetes through TNF-/Mfn2 pathway

OBJECTIVES

To investigate the effects and molecular mechanisms of asiatic acid on β-cell function in type 2 diabetes mellitus (T2DM).

METHODS

The T2DM model was established by high fat diet and streptozotocin injection in ICR mice, and the effects of asiatic acid on glucose regulation were investigated in model mice. The islets were isolated from palmitic acid-treated diabetic mice. ELISA was used to detect the glucose-stimulated insulin secretion, tumor necrosis factor (TNF)-α and interleukin (IL)-6. ATP assay was applied to measure ATP production, and Western blotting was used to detect protein expression of mature β cell marker urocortin (Ucn) 3 and mitofusin (Mfn) 2. The regulatory effects of asiatic acid on glucose-stimulated insulin secretion (GSIS) and Ucn3 expression were also investigated after siRNA interference with Mfn2 or treatment with TNF-α.

RESULTS

Asiatic acid with the dose of 25 mg·kg－1·d－1 had the best glycemic control in T2DM mice and improved the homeostasis model assessment β index. Asiatic acid increased the expression of Mfn2 and Ucn3 protein and improved the GSIS function of diabetic β cells in vitro and in vivo (both P<0.05). Moreover, it improved the ATP production of islets of T2DM mice in vitro (P<0.05). Interfering Mfn2 with siRNA blocked the up-regulation of Ucn3 and GSIS induced by asiatic acid. Asiatic acid inhibited islet TNF-α content and increased Mfn2 and Ucn3 protein expression inhibited by TNF-α.

CONCLUSIONS

Asiatic acid improves β cell insulin secretion function in T2DM mice by maintaining the β cell maturity, which may be related to the TNF-α/Mfn2 pathway.

Mechanistic Understanding of D-Glucaric Acid to Support Liver Detoxification Essential to Muscle Health Using a Computational Systems Biology Approach

Liver and muscle health are intimately connected. Nutritional strategies that support liver detoxification are beneficial to muscle recovery. Computational-in silico-molecular systems' biology analysis of supplementation of calcium and potassium glucarate salts and their metabolite D-glucaric acid (GA) reveals their positive effect on mitigation of liver detoxification via four specific molecular pathways: (1) ROS production, (2) deconjugation, (3) apoptosis of hepatocytes, and (4) β-glucuronidase synthesis. GA improves liver detoxification by downregulating hepatocyte apoptosis, reducing glucuronide deconjugates levels, reducing ROS production, and inhibiting β-Glucuronidase enzyme that reduces re-absorption of toxins in hepatocytes. Results from this in silico study provide an integrative molecular mechanistic systems explanation for the mitigation of liver toxicity by GA.

PGC-1α participates in tumor chemoresistance by regulating glucose metabolism and mitochondrial function

Chemotherapy resistance is the main reason for the failure of cancer treatment. The mechanism of drug resistance is complex and diverse. In recent years, the role of glucose metabolism and mitochondrial function in cancer resistance has gathered considerable interest. The increase in metabolic plasticity of cancer cells' mitochondria and adaptive changes to the mitochondrial function are some of the mechanisms through which cancer cells resist chemotherapy. As a key molecule regulating the mitochondrial function and glucose metabolism, PGC-1α plays an indispensable role in cancer progression. However, the role of PGC-1α in chemotherapy resistance remains controversial. Here, we discuss the role of PGC-1α in glucose metabolism and mitochondrial function and present a comprehensive overview of PGC-1α in chemotherapy resistance.

Hepatoprotective Role of Carvedilol against Ischemic Hepatitis Associated with Acute Heart Failure via Targeting miRNA-17 and Mitochondrial Dynamics-Related Proteins: An In Vivo and In Silico Study

Acute heart failure (AHF) is one of the most common diseases in old age that can lead to mortality. Systemic hypoperfusion is associated with hepatic ischemia–reperfusion injury, which may be irreversible. Ischemic hepatitis due to AHF has been linked to the pathogenesis of liver damage. In the present study, we extensively investigated the role of mitochondrial dynamics-related proteins and their epigenetic regulation in ischemic liver injury following AHF and explored the possible hepatoprotective role of carvedilol. The biochemical analysis revealed that the ischemic liver injury following AHF significantly elevated the activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) enzymes, the level of total and direct bilirubin, and the expression of hepatic mitogen-activated protein kinase (MAPK), dynamin-1-like protein (DNM1L), and hepatic miRNA-17. At the same time, it significantly reduced the serum albumin level, the activity of hepatic superoxide dismutase (SOD), and the expression of mitochondrial peroxisome proliferator-activated receptor-1α (PGC-1α), and mitofusin 2 (Mtf2). The histological examination of the liver tissue revealed degenerated hepatocytes. Interestingly, administration of carvedilol either prior to or after isoprenaline-induced AHF significantly improved the liver function and reversed the deterioration effect of AHF-induced ischemic hepatitis, as demonstrated by biochemical, immunohistochemical, and histological analysis. Our results indicated that the hepatoprotective effect of carvedilol in ameliorating hepatic ischemic damage could be attributed to its ability to target the mitochondrial dynamics-related proteins (Mtf2, DNM1L and PGC-1α), but also their epigenetic regulator miRNA-17. To further explore the mode of action of carvedilol, we have investigated, in silico, the ability of carvedilol to target dynamin-1-like protein and mitochondrial dynamics protein (MID51). Our results revealed that carvedilol has a high binding affinity (−14.83 kcal/mol) toward the binding pocket of DNM1L protein. In conclusion, our study highlights the hepatoprotective pharmacological application of carvedilol to attenuate ischemic hepatitis associated with AHF.

Sulforaphane Exerts Beneficial Immunomodulatory Effects on Liver Tissue via a Nrf2 Pathway-Related Mechanism in a Murine Model of Hemorrhagic Shock and Resuscitation

Our research explores the immunomodulatory effects of sulforaphane (SFN), a well-known nuclear factor erythroid 2-related factor 2 (Nrf2) pathway agonist, on the sterile inflammation of and ischemia-reperfusion injuries to the liver after hemorrhagic shock (HS) followed by resuscitation (R). Male C57/BL6 wild-type and transgenic ARE-luc mice were exposed to mean arterial pressure-controlled HS. Fluid resuscitation was performed after 90 min of HS, and SFN was administrated intraperitoneally after that. The animals were sacrificed at 6 h, 24 h, and 72 h after resuscitation, and their livers were extracted to perform H&E staining and myeloperoxidase (MPO) activity analysis. The Kupffer cells were isolated for cytokines profile measurements and Nrf2 immunofluorescence staining. Further, the ARE-luc mice were used to assess hepatic Nrf2 activity in vivo. We identified that SFN-activated Kupffer cells’ Nrf2 pathway and modulated its cytokines expression, including TNF-α, MCP-1, KC/CXCL1, IL-6, and IL-10. Furthermore, SFN mitigated liver ischemia-reperfusion injury, as evidenced by the downregulation of the Suzuki score and the enhanced hepatic Nrf2 activity. The in vivo SFN treatment decreased neutrophils infiltration, as shown by the decreased MPO levels. Our study shows that SFN can decrease HS/R-induced hepatic ischemia-reperfusion injury and modulate the activity of Kupffer cells via an Nrf2-dependent pathway.

Nicotinamide riboside promotes Mfn2-mediated mitochondrial fusion in diabetic hearts through the SIRT1-PGC1α-PPARα pathway

Myocardial dysfunction is associated with an imbalance in mitochondrial fusion/fission dynamics in patients with diabetes. However, effective strategies to regulate mitochondrial dynamics in the diabetic heart are still lacking. Nicotinamide riboside (NR) supplementation ameliorated mitochondrial dysfunction and oxidative stress in both cardiovascular and aging-related diseases. This study investigated whether NR protects against diabetes-induced cardiac dysfunction by regulating mitochondrial fusion/fission and further explored the underlying mechanisms. Here, we showed an evident decrease in NAD⁺ (nicotinamide adenine dinucleotide) levels and mitochondrial fragmentation in the hearts of leptin receptor-deficient diabetic (db/db) mouse models. NR supplementation significantly increased NAD⁺ content in the diabetic hearts and promoted mitochondrial fusion by elevating Mfn2 level. Furthermore, NR-induced mitochondrial fusion suppressed mitochondrial H₂O₂ and O₂•^- production and reduced cardiomyocyte apoptosis in both db/db mice hearts and neonatal primary cardiomyocytes. Mechanistically, chromatin immunoprecipitation (ChIP) and luciferase reporter assay analyses revealed that PGC1α and PPARα interdependently regulated Mfn2 transcription by binding to its promoter region. NR treatment elevated NAD⁺ levels and activated SIRT1, resulting in the deacetylation of PGC1α and promoting the transcription of Mfn2. These findings suggested the promotion of mitochondrial fusion via oral supplementation of NR as a potential strategy for delaying cardiac complications in patients with diabetes.

Shen Qi Li Xin formula improves chronic heart failure through balancing mitochondrial fission and fusion via upregulation of PGC-1α

BACKGROUND

Our previous study proved that Shen Qi Li Xin formula (SQLXF) improved the heart function of chronic heart failure (CHF) patients, while the action mechanism remains unclear.

METHODS

H&E staining and TUNEL staining were performed to measure myocardial damages. Western blot was used to examine the expression of proteins. Moreover, CCK-8 assay and flow cytometry were used to measure cell viability and cell apoptosis, respectively. Concentrations of ATP and ROS in cells, and mitochondrial membrane potential (MMP) were detected to estimate oxidative stress.

RESULTS

In vivo, we found that SQLXF improved cardiac hemodynamic parameters, reduced LDH, CK-MB and BNP production, and attenuated myocardial damages in CHF rats. Besides, SQLXF promoted mitochondrial fusion-related proteins expression and inhibited fission-related proteins expression in CHF rats and oxygen glucose deprivation/reoxygenation (OGD/R)-induced cardiac myocytes (CMs). In vitro, our data show that certain dose of SQLXF inhibited OGD/R-induced CMs apoptosis, cell viability decreasing and oxidative stress.

CONCLUSION

Overall, certain dose of SQLXF could effectively improve the cardiac function of CHF rats through inhibition of CMs apoptosis via balancing mitochondrial fission and fusion. Our data proved a novel action mechanism of SQLXF in CHF improvement, and provided a reference for clinical.

Mitochondrial Dynamics and Liver Cancer

Simple Summary

Hepatocellular carcinoma is a leading cause of cancer-related death worldwide. Major risk factors in liver cancer development include chronic hepatitis B or C virus, autoimmune hepatitis, diabetes mellitus, alcohol abuse, and several metabolic diseases, among others. Standard therapy shows low efficacy, and there is an urgent need for novel therapies. Recent data permit to propose that proteins that control mitochondrial morphology through changes in mitochondrial fusion or mitochondrial fission, confer susceptibility or resistance to the development of liver cancer in mouse models. Here, we review the data that suggest mitochondrial dynamics to be involved in the development of liver tumors.

Abstract

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer. Due to its rising incidence and limited therapeutic options, HCC has become a leading cause of cancer-related death worldwide, accounting for 85% of all deaths due to primary liver cancers. Standard therapy for advanced-stage HCC is based on anti-angiogenic drugs such as sorafenib and, more recently, lenvatinib and regorafenib as a second line of treatment. The identification of novel therapeutic strategies is urgently required. Mitochondrial dynamics describes a group of processes that includes the movement of mitochondria along the cytoskeleton, the regulation of mitochondrial morphology and distribution, and connectivity mediated by tethering and fusion/fission events. In recent years, mitochondrial dynamic processes have emerged as key processes in the maintenance of liver mitochondrial homeostasis. In addition, some data are accumulating on the role played by mitochondrial dynamics during cancer development, and specifically on how such dynamics act directly on tumor cells or indirectly on cells responsible for tumor aggression and defense. Here, we review the data that suggest mitochondrial dynamics to be involved in the development of liver tumors.

Effect of mitochondrial quality control on the lycopene antagonizing DEHP-induced mitophagy in spermatogenic cells

Di(2-ethylhexyl) phthalate (DEHP) is a widespread environmental contaminant, which is mainly used as a plasticizer to improve the flexibility of products; however, its extensive use causes male reproductive damage. Lycopene (LYC) has a protective effect on male reproductive toxicity. Nevertheless, the underlying role of LYC in DEHP-induced spermatogenic cell damage remains unclear. Our study aimed to investigate the role of LYC in DEHP-induced spermatogenic cell damage and its underlying mechanism. Male ICR mice were treated with LYC (5 mg kg-1) and/or DEHP (500 mg kg-1 or 1000 mg kg-1) for 28 days. The results showed that LYC alleviated the DEHP-induced decrease in mitochondria volume density and mitochondrial membrane potential (ΔΨm). Subsequently, LYC prevented the DEHP-induced PGC-1α-mediated reduction in mitochondrial biogenesis in spermatogenic cells. LYC exhibited a potential preventive effect against DEHP-induced mitophagy caused by mitochondrial dynamics disorder in the spermatogenic cells. Meanwhile, LYC relieved DEHP-induced mitochondrial stress in the spermatogenic cells by activating UPRmt. These results proved that mitochondrial quality control may be related to the beneficial role of LYC in preventing DEHP-induced mitophagy in spermatogenic cells. This study provides new evidence of mitochondrial quality control as a target for LYC treatment, which can prevent DEHP-induced toxicity.

Effects of hypothermia on inflammatory cytokine expression in rat liver following asphyxial cardiac arrest

Hypothermic treatment is known to protect against cardiac arrest (CA) and improve survival rate. However, few studies have evaluated the CA-induced liver damage and the effects of hypothermia on this damage. Therefore, the aim of the present study was to determine possible protective effects of hypothermia on the liver after asphyxial CA. Rats were subjected to a 5-min asphyxial CA followed by return of spontaneous circulation (ROSC). The body temperature was controlled at 37±0.5˚C (normothermia group) or 33±0.5˚C (hypothermia group) for 4 h after ROSC. Livers were examined at 6, 12 h, 1 and 2 days after ROSC. Histopathological examination was performed by H&E staining. Alterations in the expression levels of pro-inflammatory (TNF-α and interleukin IL-2) and anti-inflammatory cytokines (IL-4 and IL-13) were investigated by immunohistochemistry. Sinusoidal dilatation and vacuolization were observed after asphyxial CA by histopathological examination. However, these CA-induced structural alterations were prevented by hypothermia. In immunohistochemical examination, the expression levels of pro-inflammatory cytokines were reduced in the hypothermia group compared with those in the normothermia group while the expression levels of anti-inflammatory cytokines were increased in the hypothermia group compared with those in the normothermia group. In conclusion, hypothermic treatment for 4 h following asphyxial CA in rats inhibited the increase of pro-inflammatory cytokines and stimulated the expression of anti-inflammatory cytokines compared with the normothermic group. The results of the present study suggested that hypothermic treatment after asphyxial CA reduced liver damage via the regulation of inflammation.

Overexpression of SERCA2a Alleviates Cardiac Microvascular Ischemic Injury by Suppressing Mfn2-Mediated ER/Mitochondrial Calcium Tethering

Our previous research has shown that type-2a Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) undergoes posttranscriptional oxidative modifications in cardiac microvascular endothelial cells (CMECs) in the context of excessive cardiac oxidative injury. However, whether SERCA2a inactivity induces cytosolic Ca²⁺ imbalance in mitochondrial homeostasis is far from clear. Mitofusin2 (Mfn2) is well known as an important protein involved in endoplasmic reticulum (ER)/mitochondrial Ca²⁺ tethering and the regulation of mitochondrial quality. Therefore, the aim of our study was to elucidate the specific mechanism of SERCA2a-mediated Ca²⁺ overload in the mitochondria via Mfn2 tethering and the survival rate of the heart under conditions of cardiac microvascular ischemic injury. In vitro, CMECs extracted from mice were subjected to 6 h of hypoxic injury to mimic ischemic heart injury. C57-WT and Mfn2^KO mice were subjected to a 1 h ischemia procedure via ligation of the left anterior descending branch to establish an in vivo cardiac ischemic injury model. TTC staining, immunohistochemistry and echocardiography were used to assess the myocardial infarct size, microvascular damage, and heart function. In vitro, ischemic injury induced irreversible oxidative modification of SERCA2a, including sulfonylation at cysteine 674 and nitration at tyrosine 294/295, and inactivation of SERCA2a, which initiated calcium overload. In addition, ischemic injury-triggered [Ca²⁺]c overload and subsequent [Ca²⁺]m overload led to mPTP opening and ΔΨm dissipation compared with the control. Furthermore, ablation of Mfn2 alleviated SERCA2a-induced mitochondrial calcium overload and subsequent mito-apoptosis in the context of CMEC hypoxic injury. In vivo, compared with that in wild-type mice, the myocardial infarct size in Mfn2^KO mice was significantly decreased. In addition, the findings revealed that Mfn2^KO mice had better heart contractile function, decreased myocardial infarction indicators, and improved mitochondrial morphology. Taken together, the results of our study suggested that SERCA2a-dependent [Ca²⁺]c overload led to mitochondrial dysfunction and activation of Mfn2-mediated [Ca²⁺]m overload. Overexpression of SERCA2a or ablation of Mfn2 expression mitigated mitochondrial morphological and functional damage by modifying the SERCA2a/Ca²⁺-Mfn2 pathway. Overall, these pathways are promising therapeutic targets for acute cardiac microvascular ischemic injury.

Macrophage Polarization and Liver Ischemia-Reperfusion Injury

Ischemia-reperfusion injury refers to organ damage caused by the previous insufficient supply of oxygen and nutrients and the involvement of metabolic by-products after blood flow is restored. Liver ischemia-reperfusion injury (IRI) has become a hot research in recent years, because it occurs in many clinical scenarios. After the introduction of liver transplantation and vascular control techniques in liver surgery, liver ischemia-reperfusion injury is considered to be an important factor affecting postoperative mortality and morbidity. As the largest immune organ in the human body, liver contain a lot of immune cells such as resident macrophages (Kupffer cells), dendritic cells, natural killer cells, and natural killer T cells which play a key role in ischemia-reperfusion injury. Among those, macrophage-mediated excessive inflammatory response is considered to be an important factor in liver ischemia-reperfusion injury. The prominent feature of liver injury is an increase in the number of macrophages in liver due to the infiltration of blood monocytes and differentiation into monocyte-derived macrophages. Liver macrophages can be divided into M1 macrophages which can promote inflammation progress and M2 macrophages that inhibit inflammation progress according to their different phenotypes and functions. Both of them can regulate liver aseptic inflammation, and play an important role in triggering, maintaining, and improving liver ischemia-reperfusion injury. This review summarizes studies of macrophage polarization on liver ischemia-reperfusion injury in recent years, to provide potential ideas for translation application in future clinical management.

The association between SNPs and hepatitis B virus related acute-on-chronic liver failure

OBJECTIVE

This study intended to investigate the association between ten single nucleotide polymorphisms (rs1143623, rs12692386, rs1799983, rs2297518, rs2910164, rs3129859, rs4251961, rs4846085, rs641738, rs873457) with susceptibility and prognosis of hepatitis B related acute-on-chronic liver failure (HBV-ACLF).

METHODS

This is a hospital-based case-control study included 274 patients with HBV-ACLF and 534 patients with chronic hepatitis B. The patients who were successfully followed were divided into the survival group and the death group according to the clinical outcome during the hospitalization and 90 days after discharge. The ten SNPs were genotyped in all subjects by using imLDR. Genotype, allele frequency, dominant model, recessive model and codominant model were constructed to investigate the association between single nucleotide polymorphisms with susceptibility and prognosis of HBV-ACLF.

RESULTS

The genotype distribution of rs1143623 was statistically different between the two groups (P = 0.04), but the allele frequency was not statistically significant (P = 0.44). GC and GG + CG genotypes at rs1143623 reduced the risk of HBV-ACLF. There were only two GG and GT genotypes in rs1799983 in our study, and the genotype and allele frequency were statistically different between the death group and the survival group (P = 0.027, P = 0.023). Patients with T allele may reduce the risk of death in patients with HBV-ACLF. The genotype and allele frequency of rs2297518 showed no significant difference. In dominant models, patients with GA + AA genotypes at rs2297518 had a reduced risk of death.

TLR4 knockout upregulates the expression of Mfn2 and PGC-1α in a high-fat diet and ischemia-reperfusion mice model of liver injury

AIMS

Patients with nonalcoholic fatty liver disease (NAFLD) have less tolerance to ischemia-reperfusion injury (IRI) of the liver than those with the healthy liver; hence have a higher incidence of severe complications after surgery. This study aimed to investigate the dynamics of the liver and mitochondrial damage and the impact of TLR4 knockout (TLR4KO) on Mfn2 expression in the composite model of NAFLD and IRI.

MAIN METHODS

We performed high-fat diet (HFD) feeding and ischemia reperfusion (IR) on wild type (WT) and TLR4 knockout TLR4KO mice.

KEY FINDINGS

The degree of structural and functional injuries to the liver and mitochondria (NAFLD and IRI) is greater than that caused by a single factor (NAFLD or IRI) or a simple superposition of both. The IL-6 and TNF-α expressions were significantly suppressed (P < .05), while PGC-1α and Mfn2 expressions were up-regulated considerably (P < .05) after TLR4KO. Furthermore, mitochondrial fusion increased, while ATP consumption and ROS production decreased significantly after TLR4KO (P < .05). The degree of reduction of compound injury by TLR4KO is more significant than the reduction degree of single factor injury. Also, TNF-α and IL-6 levels can be used predictive markers for mitochondrial damage and liver tolerance to NAFLD and IRI.

SIGNIFICANCE

TLR4KO upregulates the expression of Mfn2 and PGC-1α in the composite model of NAFLD and IRI. This pathway may be related to IL-6 and TNF-α. This evidence provides theoretical and experimental basis for the subsequent Toll-like receptor 4 (TLR4) receptor targeted therapy.

Rosiglitazone augments antioxidant response in the human trophoblast and prevents apoptosis†

Insufficient perfusion of the trophoblast by maternal blood is associated with an increased generation of reactive oxygen species and complications of the placenta. In this study, we first examined whether rosiglitazone, an agonist of the peroxisome proliferator-activated receptor-γ (PPARγ), protects the human trophoblast from oxidative injury by regulating key antioxidant proteins, catalase (CAT) and the superoxide dismutases (SOD1 and SOD2). In first trimester placental explants, localization of CAT was limited to cytotrophoblasts, whereas SOD1 was expressed in both the cyto- and syncytiotrophoblasts. In first trimester placental explants, hypoxia decreased the expression of both SOD1 and SOD2, and increased apoptosis. Treatment with rosiglitazone dose-dependently upregulated anti-oxidative CAT and SOD2, and rescued hypoxic injury in first trimester villous explants and JEG-3 cells, strongly suggesting the involvement of the PPARγ in regulating their expressions. Rosiglitazone facilitated transcription activity of PPARγ, and enhanced promotor binding, increased transcriptional activity at the CAT promoter, and elevated protein expression/activity. Treatment of hypoxic JEG-3 cells with rosiglitazone resulted in mitochondrial membrane potential increase and a reduction of caspase 9 and caspase 3 activity which is consistent with improved cell survival. To complement PPARγ activation data, we also utilized the antagonist (SR-202) and siRNA to suppress PPARγ expression and demonstrate the specific role of PPARγ in reducing ROS and oxidative stress. Ex vivo examination of term human placenta revealed lower expression of antioxidant proteins in pathologic compared to healthy placental tissues, which could be rescued by rosiglitazone, indicating that rosiglitazone can improve survival of the trophoblast under pathological conditions. These findings provide evidence that the PPARγ pathway directly influences cellular antioxidants production and the pathophysiology of placental oxidative stress.

Nobiletin ameliorates hepatic ischemia and reperfusion injury through the activation of SIRT-1/FOXO3a-mediated autophagy and mitochondrial biogenesis

Hepatic ischemia and reperfusion injury are characterized by impaired autophagy, mitochondrial dysfunction, and subsequent compromise of cellular homeostasis following hepatic surgery or transplantation. Nobiletin, a natural flavonoid, is a beneficial antioxidant that possesses anti-inflammatory and anti-cancer activities. We investigated the effect of nobiletin on hepatic IR injury and described the underlying mechanisms. C57BL/6 mice were subjected to 60 min of partial hepatic ischemia, treated with nobiletin (5 mg/kg) or vehicle at the start of reperfusion, and killed at 5 h of reperfusion. Hepatic ischemia and reperfusion increased hepatocellular oxidative damage, inflammation, and cell death, but these changes were alleviated upon nobiletin treatment. Nobiletin increased the expression of proteins that control autophagy, mitochondrial dynamics, and biogenesis. Specifically, the SIRT-1/FOXO3a and PGC-1α pathways were activated by nobiletin. IR-induced AKT activation was associated with FOXO3a phosphorylation, which resulted in a significant reduction in the nuclear FOXO3a levels and potentially attenuated autophagy-regulatory gene expression. Nobiletin increased FOXO3a expression and its nuclear translocation via the inhibition of AKT. Specific inhibition of SIRT-1 abolished the protective effect of nobiletin, causing decreased FOXO3a expression, followed by autophagy induction and decreased PGC-1α expression and mitochondrial dynamics. Taken together, our data indicate that SIRT-1 directly mediates the protective effect of nobiletin against hepatic ischemia and reperfusion injury. The activation of autophagy and mitochondrial function through the SIRT-1/FOXO3a and PGC-1α pathways indicate that nobiletin could have therapeutic potential for treating hepatic ischemia and reperfusion injury.

Nobiletin, an antioxidant found in citrus peel, may protect the liver from reperfusion injury, damage following blood flow interruption. When blood flow is restricted and then restored, as in transplant, surgery, or shock, cells are injured, largely due to damage to the cellular powerhouses, the mitochondria. Nobiletin is known to have many benefits, including anti-cancer and anti-inflammatory activities, but its mechanism of action is not well understood. Sang Won Park and Hwajin Kim, at the Gyeongsang National University School of Medicine, in Jinju, South Korea, and co-workers, investigated how nobiletin might protect the liver against interruption of blood flow. They found that nobiletin triggered cells to dismantle damaged mitochondria and produce new, functioning mitochondria, greatly reducing liver damage. These results illuminate how nobiletin works and may lead to better treatments for liver reperfusion injury.

RETRACTED: MicroRNA-497 promotes proliferation and inhibits apoptosis of cardiomyocytes through the downregulation of Mfn2 in a mouse model of myocardial ischemia-reperfusion injury

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concern was raised about the reliability of the images shown in Figure 1, and the Western blots in Figures 6C and 8E, which appear to contain similar features to those found in other publications, as detailed here: https://pubpeer.com/publications/5E5DF69C11DAD50FBE63CD4F95990F; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Additional concerns were raised over the provenance of the flow cytometry data in Figure 10C, that appear to contain repeating features. Furthermore, the myocardial infarct images in Figure 5A appear to actually show brain slices. Independent analysis also identified additional suspected image duplications within Figures 3A and 4. The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Dual Effect of Hepatic Macrophages on Liver Ischemia and Reperfusion Injury during Liver Transplantation

Ischemia-reperfusion injury (IRI) is a major complication in liver transplantation (LT) and it is closely related to the recovery of grafts' function. Researches has verified that both innate and adaptive immune system are involved in the development of IRI and Kupffer cell (KC), the resident macrophages in the liver, play a pivotal role both in triggering and sustaining the sterile inflammation. Damage-associated molecular patterns (DAMPs), released by the initial dead cell because of the ischemia insult, firstly activate the KC through pattern recognition receptors (PRRs) such as toll-like receptors. Activated KCs is the dominant players in the IRI as it can secret various pro-inflammatory cytokines to exacerbate the injury and recruit other types of immune cells from the circulation. On the other hand, KCs can also serve in a contrary way to ameliorate IRI by upregulating the anti-inflammatory factors. Moreover, new standpoint has been put forward that KCs and macrophages from the circulation may function in different way to influence the inflammation. Managements towards KCs are expected to be the effective way to improve the IRI.

Role of mitofusin 2 in the protective effect of breviscapine against hepatic ischemia/reperfusion injury in rats

The purpose of the present study was to investigate the effect of breviscapine injection on hepatic ischemia/reperfusion (I/R) injury in rats. To explore the relevance and discuss the underlying mechanism of mitofusin 2 (Mfn2) in hepatic I/R injury, 40 Sprague-Dawley male rats were randomly and equally divided into five groups (n=8 per group) as follows: Sham, I/R + normal saline 1 (NS1), I/R + breviscapine 1 (Bre1), I/R + NS2 and I/R + Bre2 groups. Groups 1 and 2 represented ischemia for 20 and 60 min, respectively. Breviscapine or normal saline was injected via the tail vein (single dose of 10 mg/kg) 1 h prior to surgery and immediately postoperatively. The classical model of hepatic I/R injury was used in the present study. The blood and liver samples of different groups were collected following reperfusion to observe serum transaminases and histopathological changes. Alterations in Mfn2, cytosolic cytochrome c and cleaved caspase-3 were additionally assessed. The results demonstrated that breviscapine improved liver function, based on histopathological analysis, and decreased levels of the liver enzymes aspartate and alanine aminotransferase in the I/R + Bre groups compared with the I/R + NS group (P<0.05). The expression of Mfn2 was significantly increased in the I/R + Bre groups (P<0.05), whereas the expression of caspase-3 and cytosolic cytochrome c protein was decreased in the I/R + Bre groups (P<0.05) compared with the I/R + NS group. These data provided substantial evidence that breviscapine treatment exerted a protective effect against damage induced by hepatic I/R. This protective effect was possibly due to its ability to inhibit I/R-induced apoptosis and promote the expression of Mfn2.

PGC1α: Friend or Foe in Cancer?

The PGC1 family (Peroxisome proliferator-activated receptor γ (PPARγ) coactivators) of transcriptional coactivators are considered master regulators of mitochondrial biogenesis and function. The PGC1α isoform is expressed especially in metabolically active tissues, such as the liver, kidneys and brain, and responds to energy-demanding situations. Given the altered and highly adaptable metabolism of tumor cells, it is of interest to investigate PGC1α in cancer. Both high and low levels of PGC1α expression have been reported to be associated with cancer and worse prognosis, and PGC1α has been attributed with oncogenic as well as tumor suppressive features. Early in carcinogenesis PGC1α may be downregulated due to a protective anticancer role, and low levels likely reflect a glycolytic phenotype. We suggest mechanisms of PGC1α downregulation and how these might be connected to the increased cancer risk that obesity is now known to entail. Later in tumor progression PGC1α is often upregulated and is reported to contribute to increased lipid and fatty acid metabolism and/or a tumor cell phenotype with an overall metabolic plasticity that likely supports drug resistance as well as metastasis. We conclude that in cancer PGC1α is neither friend nor foe, but rather the obedient servant reacting to metabolic and environmental cues to benefit the tumor cell.

Association between MFN2 gene polymorphisms and the risk and prognosis of acute liver failure: a case-control study in a Chinese population

This study aimed to determine the role of mitofusin 2 (MFN2) gene polymorphisms in the risk and prognosis of acute liver failure (ALF). A total of 298 blood samples were collected from 138 ALF patients (case group) and 160 healthy participants (control group). Coagulation function, glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), total bilirubin (TB), blood ammonia and lactic acid (LA) were measured. The predictive evaluation of MFN2 gene polymorphisms in the risk and prognosis of ALF patients was estimated using Kaplan-Meier survival analysis, haplotype analysis, binary logistic regression analysis and Cox regression analysis. Higher levels of GPT, GOT, TB, blood ammonia and LA were observed in ALF patients with the GG genotype of rs873457 or the TT genotype of rs4846085 than in those with the CC genotype of these two SNPs. The GTACAGC and GTGTGGC haplotypes were a protective factor and a risk factor for ALF, respectively. Blood ammonia and LA levels were independent risk factors and the CC genotype of rs873457 and the CC genotype of rs4846085 were protective factors for ALF. ALF patients with the GG genotype of rs873457 or the TT genotype of rs4846085 had a lower survival rate than those with other genotypes of these two SNPs. The rs4846085 and rs873457 polymorphisms were both independent factors affecting the prognosis of ALF patients. MFN2 gene polymorphisms (rs873457, rs2336384, rs1474868, rs4846085 and rs2236055) may be associated with ALF and the rs873457 and rs4846085 polymorphisms are correlated with the risk and prognosis of ALF.

Mitofusin 2 attenuates the histone acetylation at collagen IV promoter in diabetic nephropathy

Extracellular matrix (ECM) increase in diabetic nephropathy (DN) is closely related to mitochondrial dysfunction. The mechanism of protective function of mitofusin 2 (Mfn2) for mitochondria remains largely unknown. In this study, the molecular mechanisms for the effect of Mfn2 on mitochondria and subsequent collagen IV expression in DN were investigated. Ras-binding-deficient mitofusin 2 (Mfn2-Ras(Δ)) were overexpressed in rat glomerular mesangial cells, and then the cells were detected for mitochondrial morphology, cellular reactive oxygen species (ROS), mRNA and protein expression of collagen IV with advanced glycation end-product (AGE) stimulation. Preliminary results reveal that the mitochondrial dysfunction and the increased synthesis of collagen IV after AGE stimulation were reverted by Mfn2-Ras(Δ) overexpression. Bioinformatical computations were performed to search transcriptional factor motifs in the promoter region of collagen IV. Three specific regions for TFAP2A binding were identified, followed by validation with chromatin immunoprecipitation experiments. Knocking down TFAP2A significantly decreased the TF binding in the first two regions and the gene expression of collagen IV. Furthermore, results reveal that Mfn2-Ras(Δ) overexpression significantly mitigated TFAP2A binding and also reverted the histone acetylation at Regions 1 and 2 after AGE stimulation. In streptozotocin-induced diabetic rats, Mfn2-Ras(Δ) overexpression also ameliorated glomerular mesangial lesions with decreased collagen IV expression, accompanied by decreased acetylation and TFAP2A binding at Region 1. In conclusion, this study highlights the pathway by which mitochondria affect the histone acetylation of gene promoter and provides a new potential therapy approach for DN.

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

WISP1 mediates hepatic warm ischemia reperfusion injury via TLR4 signaling in mice

Wnt-induced secreted protein-1 (WISP1) is an extracellular matrix protein that has been reported in cancer researches. Our previous studies on WISP1 implied it could be a harmful mediator in septic mice. However, its role in liver ischemia reperfusion (I/R) injury is unknown. This study investigated the effects of WISP1 on liver I/R damage. Male C57BL/6 wild-type mice were used to undergo 60 min segmental (70%) ischemia. WISP1 expression was measured after indicated time points of reperfusion. Anti-WISP1 antibody was injected intraperitoneally to mice. Toll-like receptor 4 (TLR4) knockout mice and TIR-domain-containing adaptor inducing interferon-β (TRIF) knockout mice were adopted in this study. WISP1 was significantly enhanced after 6 h of reperfusion when compared with sham treated mice and significantly decreased either by TLR4 knockout mice or TRIF knockout mice. Anti-WISP1 antibody significantly decreased serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), pathological changes and pro-inflammatory cytokine levels in the mice following I/R. Furthermore, significantly increased serum transaminase levels were found in C57 wild-type mice treated with recombinant WISP1 protein, but not found in TLR4 knockout or TRIF knockout mice subjected to liver I/R. Taken together, WISP1 might contribute to hepatic ischemia reperfusion injury in mice and possibly depends on TLR4/TRIF signaling.

Molecular pathways in protecting the liver from ischaemia/reperfusion injury: a 2015 update

Ischaemia/reperfusion injury is an important cause of liver damage during surgical procedures such as hepatic resection and liver transplantation, and represents the main cause of graft dysfunction post-transplantation. Molecular processes occurring during hepatic ischaemia/reperfusion are diverse, and continuously include new and complex mechanisms. The present review aims to summarize the newest concepts and hypotheses regarding the pathophysiology of liver ischaemia/reperfusion, making clear distinction between situations of cold and warm ischaemia. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field are described.