Regulation of autophagy protects against liver injury in liver surgery-induced ischaemia/reperfusion

Transient ischaemia and reperfusion in liver tissue induce hepatic ischaemia/reperfusion (I/R) tissue injury and a profound inflammatory response in vivo. Hepatic I/R can be classified into warm I/R and cold I/R and is characterized by three main types of cell death, apoptosis, necrosis and autophagy, in rodents or patients following I/R. Warm I/R is observed in patients or animal models undergoing liver resection, haemorrhagic shock, trauma, cardiac arrest or hepatic sinusoidal obstruction syndrome when vascular occlusion inhibits normal blood perfusion in liver tissue. Cold I/R is a condition that affects only patients who have undergone liver transplantation (LT) and is caused by donated liver graft preservation in a hypothermic environment prior to entering a warm reperfusion phase. Under stress conditions, autophagy plays a critical role in promoting cell survival and maintaining liver homeostasis by generating new adenosine triphosphate (ATP) and organelle components after the degradation of macromolecules and organelles in liver tissue. This role of autophagy may contribute to the protection of hepatic I/R-induced liver injury; however, a considerable amount of evidence has shown that autophagy inhibition also protects against hepatic I/R injury by inhibiting autophagic cell death under specific circumstances. In this review, we comprehensively discuss current strategies and underlying mechanisms of autophagy regulation that alleviates I/R injury after liver resection and LT. Directed autophagy regulation can maintain liver homeostasis and improve liver function in individuals undergoing warm or cold I/R. In this way, autophagy regulation can contribute to improving the prognosis of patients undergoing liver resection or LT.     

Pre‐conditions for eliminating mitochondrial dysfunction and maintaining liver function after hepatic ischaemia reperfusion

The liver, the largest organ with multiple synthesis and secretion functions in mammals, consists of hepatocytes and Kupffer, stem, endothelial, stellate and other parenchymal cells. Because of early and extensive contact with the external environment, hepatic ischaemia reperfusion (IR) may result in mitochondrial dysfunction, autophagy and apoptosis of cells and tissues under various pathological conditions. Because the liver requires a high oxygen supply to maintain normal detoxification and synthesis functions, it is extremely susceptible to ischaemia and subsequent reperfusion with blood. Consequently, hepatic IR leads to acute or chronic liver failure and significantly increases the total rate of morbidity and mortality through multiple regulatory mechanisms. An increasing number of studies indicate that mitochondrial structure and function are impaired after hepatic IR, but that the health of liver tissues or liver grafts can be effectively rescued by attenuation of mitochondrial dysfunction. In this review, we mainly focus on the subsequent therapeutic interventions related to the conservation of mitochondrial function involved in mitigating hepatic IR injury and the potential mechanisms of protection. Because mitochondria are abundant in liver tissue, clarification of the regulatory mechanisms between mitochondrial dysfunction and hepatic IR should shed light on clinical therapies for alleviating hepatic IR‐induced injury.     

Involvement of kindlin‐2 in irisin’s protection against ischaemia reperfusion‐induced liver injury in high‐fat diet‐fed mice

Liver steatosis is associated with increased ischaemia reperfusion (I/R) injury. Our previous studies have shown that irisin, an exercise‐induced hormone, mitigates I/R injury via binding to αVβ5 integrin. However, the effect of irisin on I/R injury in steatotic liver remains unknown. Kindlin‐2 directly interacts with β integrin. We therefore suggest that irisin protects against I/R injury in steatotic liver via a kindlin‐2 dependent mechanism. To study this, hepatic steatosis was induced in male adult mice by feeding them with a 60% high‐fat diet (HFD). At 12 weeks after HFD feeding, the mice were subjected to liver ischaemia by occluding partial (70%) hepatic arterial/portal venous blood for 60 minutes, which was followed by 24 hours reperfusion. Our results showed HFD exaggerated I/R‐induced liver injury. Irisin (250 μg/kg) administration at the beginning of reperfusion attenuated liver injury, improved mitochondrial function, and reduced oxidative and endoplasmic reticulum stress in HFD‐fed mice. However, kindlin‐2 inhibition by RNAi eliminated irisin''s direct effects on cultured hepatocytes. In conclusion, irisin attenuates I/R injury in steatotic liver via a kindlin‐2 dependent mechanism.     

Mitochondrial Damage-Associated Molecular Patterns (MTDs) Are Released during Hepatic Ischemia Reperfusion and Induce Inflammatory Responses

Ischemia / reperfusion injury (IRI) during the course of liver transplantation enhances the immunogenicity of allografts and thus impacts overall graft outcome. This sterile inflammatory insult is known to activate innate immunity and propagate organ damage through the recognition of damage-associate molecular pattern (DAMP) molecules. The purpose of the present study was to investigate the role of mitochondrial DAMPs (MTDs) in the pathogenesis of hepatic IRI. Using in vitro models we observed that levels of MTDs were significantly higher in both transplantation-associated and warm IR, and that co-culture of MTDs with human and rat hepatocytes significantly increased cell death. MTDs were also released in an in vivo rat model of hepatic IRI and associated with increased secretion of inflammatory cytokines (TNF-α, IL-6, and IL-10) and increased liver injury compared to the sham group. Our results suggest that hepatic IR results in a significant increase of MTDs both in vitro and in vivo suggesting that MTDs may serve as a novel marker in hepatic IRI. Co-culture of MTDs with hepatocytes showed a decrease in cell viability in a concentration dependent manner, which indicates that MTDs is a toxic mediator participating in the pathogenesis of liver IR injury.     

Combined preconditioning and postconditioning provides synergistic protection against liver ischemic reperfusion injury

Hepatic Ischemia and Reperfusion Injury (IRI) is a major cause of liver damage during liver surgery and transplantation. Ischemic preconditioning and postconditioning are strategies that can reduce IRI. In this study, different combined types of pre- and postconditioning procedures were tested in a murine warm hepatic IRI model to evaluate their protective effects. Proanthocyanidins derived from grape seed was used before ischemia process as pharmacological preconditioning to combine with technical preconditioning and postconditioning. Three pathways related to IRI, including reactive oxygen species (ROS) generation, pro-inflammatory cytokines release and hypoxia responses were examined in hepatic IRI model. Individual and combined pre- and postconditioning protocols significantly reduce liver injury by decreasing the liver ROS and cytokine levels, as well as enhancing the hypoxia tolerance response. Our data also suggested that in addition to individual preconditioning or postconditioning, the combination of these two treatments could reduce liver ischemia/reperfusion injury more effectively by increasing the activity of ROS scavengers and antioxidants. The utilization of grape seed proanthocyanidins (GSP) could improve the oxidation resistance in combined pre- and postconditioning groups. The combined protocol also further increased the liver HIF-1 alpha protein level, but had no effect on pro-inflammatory cytokines release compared to solo treatment.     

Protective Effect of Grape Seed Proanthocyanidins against Liver Ischemic Reperfusion Injury: Particularly in Diet-Induced Obese Mice

Background: Hepatic ischemia and reperfusion injury (IRI) is a major complication in liver surgery, and hepatic steatosis is a primary factor aggravating cellular injury during IRI. Both pro-inflammatory cytokines and reactive oxygen species (ROS) are key mediators of hepatic IRI. Ischemic preconditioning (IpreC), remote ischemia preconditioning (RIPC) and ischemic postconditioning (IpostC) have offered protections on hepatic IRI, but all these methods have their own shortcomings. Grape seed proanthocyanidins (GSP) has a broad spectrum of pharmacological properties against oxidative stress. Thus, GSP has potential protective effects against hepatic IRI.Methods: C57BL/6 mice suffering 30mins hepatic ischemia process were sacrificed after 1h reperfusion to build murine warm hepatic IRI model. The mice were injected GSP intraperitoneally 10, 20, 40mg/kg/day for 3 weeks as pharmacological preconditioning. Obese mice fed with high-fat diet for 24 weeks before used. Three pathways related to IRI, including ROS elimination, pro-inflammatory cytokines release and hypoxia responses were examined.Results: Our data show that GSP could significantly reduce hepatic IRI by protecting hepatocyte function and increasing the activity of ROS scavengers, as well as decreasing cytokines levels. At the same time, GSP also enhance the hypoxia tolerance response. Combined GSP and postconditioning can provided synergistic protection. In the obese mice suffering hepatic IRI group, GSP was more effective than postconditioning on protecting liver against IRI, and the combined strategy was obviously superior to the solo treatment.Conclusion: GSP could protect liver against IRI: particularly in high-fat diet induced obese mice. GSP used as pharmacological preconditioning and combined with other protocols have huge potential to be used in clinical.     

Putative therapeutic impacts of cardiac CTRP9 in ischaemia/reperfusion injury

Recently, cytokines belonging to C1q/tumour necrosis factor‐related proteins (CTRPs) superfamily have attracted increasing attention due to multiple metabolic functions and desirable anti‐inflammatory effects. These various molecular effectors exhibit key roles upon the onset of cardiovascular diseases, making them novel adipo/cardiokines. This review article aimed to highlight recent findings correlated with therapeutic effects and additional mechanisms specific to the CTRP9, particularly in cardiac ischaemia/reperfusion injury (IRI). Besides, the network of the CTPR9 signalling pathway and its possible relationship with IRI were discussed. Together, the discovery of all involved underlying mechanisms could shed light to alleviate the pathological sequelae after the occurrence of IRI.     

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

Tumour necrosis factor (TNF)‐α has been considered to induce ischaemia‐reperfusion injury (IRI) of liver which is characterized by energy dysmetabolism. Peroxisome proliferator–activated receptor‐γ co‐activator (PGC)‐1α and mitofusion2 (Mfn2) are reported to be involved in the regulation of mitochondrial function. However, whether PGC‐1α and Mfn2 form a pathway that mediates liver IRI, and if so, what the underlying involvement is in that pathway remain unclear. In this study, L02 cells administered recombinant human TNF‐α had increased TNF‐α levels and resulted in down‐regulation of PGC‐1α and Mfn2 in a rat liver IRI model. This was associated with hepatic mitochondrial swelling, decreased adenosine triphosphate (ATP) production, and increased levels of reactive oxygen species (ROS) and alanine aminotransferase (ALT) activity as well as cell apoptosis. Inhibition of TNF‐α by neutralizing antibody reversed PGC‐1α and Mfn2 expression, and decreased hepatic injury and cell apoptosis both in cell culture and in animals. Treatment by rosiglitazone sustained PGC‐1α and Mfn2 expression both in IR livers, and L02 cells treated with TNF‐α as indicated by increased hepatic mitochondrial integrity and ATP production, reduced ROS and ALT activity as well as decreased cell apoptosis. Overexpression of Mfn2 by lentiviral‐Mfn2 transfection decreased hepatic injury in IR livers and L02 cells treated with TNF‐α. However, there was no up‐regulation of PGC‐1α. These findings suggest that PGC‐1α and Mfn2 constitute a regulatory pathway, and play a critical role in TNF‐α‐induced hepatic IRI. Inhibition of the TNF‐α or PGC‐1α/Mfn2 pathways may represent novel therapeutic interventions for hepatic IRI.     

Effect of temperature control upon a mouse model of partial hepatic ischaemia/reperfusion injury

In vivo models of hepatic ischaemia/reperfusion injury (IRI) are widely used to study both the mechanisms of hepatic ischaemic injury and to seek means of hepatic protection. Achieving high-quality reproducible data are essential if the results of multiple studies are to be compared and reconciled. This paper presents our findings concerning the effect of intraoperative thermoregulation upon signal to noise ratios of hepatic IRI experiments in mice. Four experiments were conducted, using three different strategies for core temperature maintenance. Animals underwent hepatic IRI and euthanized 24 h postoperatively for measurement of plasma alanine aminotransferase (ALT). Duration of ischaemia was used to adjust the severity of injury. Experiment 1 utilized a constant output heating system and resulted in rising postoperative ALTs following increasing durations of hepatic ischaemia. Experiment 2, using the same constant output heating system confirmed a difference between ischaemic and sham-operated animals. Experiment 3 used a thermostatically controlled heating system and resulted in highly variable results with a small, but statistically significant correlation between ALT levels and rectal temperature readings. Experiment 4 used a homeothermic warming system and demonstrated highly reproducible data from increasing durations of ischaemia. High-quality data from hepatic ischaemia/reperfusion models are dependent upon careful control of intraoperative temperature. The use of homeothermic warming systems is recommended and conversely, the use of thermostatically controlled warming mats is to be avoided in these models.     

Inhibition of TIM‐4 protects against cerebral ischaemia‐reperfusion injury

TIM‐4 plays an important role in ischaemia‐reperfusion injury of liver and kidney; however, the effects of TIM‐4 on cerebral ischaemia‐reperfusion injury (IRI) are unknown. The purpose of the present study was to investigate the potential role of TIM‐4 in experimental brain ischaemia‐reperfusion injury. In this study, cerebral ischaemia reperfusion was induced by transient middle cerebral artery occlusion (MCAO) for 1 hour in C57/BL6 mice. The TIM‐4 expression was detected in vivo or vitro by real‐time quantitative polymerase chain reaction, Western blot and flow cytometric analysis. In vivo, the administration of anti‐TIM‐4 antibodies significantly suppressed apoptosis, inhibited inflammatory cells and enhanced anti‐inflammatory responses. In vitro, activated microglia exhibited reduced cellular proliferation and induced IRI injury when co‐cultured with neurons; these effects were inhibited by anti‐TIM‐4 antibody treatment. Similarly, microglia transfected with TIM‐4 siRNA and stimulated by LPS + IFN‐γ alleviated the TIM‐4‐mediated damage to neurons. Collectively, our data indicate that the inhibition of TIM‐4 can improve the inflammatory response and exerts a protective effect in cerebral ischaemia‐reperfusion injury.     

Normothermic machine perfusion attenuates hepatic ischaemia-reperfusion injury by inhibiting CIRP-mediated oxidative stress and mitochondrial fission

Extracellular cold-inducible RNA-binding protein (CIRP) is a proinflammatory mediator that aggravates ischaemia-reperfusion injury (IRI). Normothermic machine perfusion (NMP) could effectively alleviate the IRI of the liver, but the underlying mechanism remains to be explored. We show that human DCD livers secreted a large amount of CIRP during static cold storage (CS), which is released into the circulation after reperfusion. The expression of CIRP was related to postoperative IL-6 levels and liver function. In a rat model, the CIRP expression was upregulated during warm ischaemia and cold storage. Then, rat DCD livers were preserved using CS, hypothermic oxygenated machine perfusion (HOPE) and NMP. C23, a CIRP inhibitor, was administrated in the HOPE group. Compared with CS, NMP significantly inhibited CIRP expression and decreased oxidative stress by downregulating NADPH oxidase and upregulating UCP2. NMP markedly inhibited the mitochondrial fission-related proteins Drp-1 and Fis-1. Further, NMP increased the mitochondrial biogenesis-related protein, TFAM. NMP significantly reduced inflammatory reactions and apoptosis after reperfusion, and NMP-preserved liver tissue had higher bile secretion and ICG metabolism compared to the CS group. Moreover, C23 administration attenuated IRI in the HOPE group. Additionally, HL-7702 cells were stimulated with rhCIRP and C23. High rhCIRP levels increased oxidative stress and apoptosis. In summary, NMP attenuates the IRI of DCD liver by inhibiting CIRP-mediated oxidative stress and mitochondrial fission.     

Liver damage and systemic inflammatory responses are exacerbated by the genetic deletion of CD39 in total hepatic ischemia

Liver ischemia reperfusion injury is associated with both local damage to the hepatic vasculature and systemic inflammatory responses. CD39 is the dominant vascular endothelial cell ectonucleotidase and rapidly hydrolyses both adenosine triphosphate (ATP) and adenosine diphosphate to adenosine monophosphate. These biochemical properties, in tandem with 5′-nucleotidases, generate adenosine and potentially illicit inflammatory vascular responses and thrombosis. We have evaluated the role of CD39 in total hepatic ischemia reperfusion injury (IRI). Wildtype mice, Cd39-hemizygous mice (+/−) and matched Cd39-null mice (−/−); (n = 25 per group) underwent 45 min of total warm ischemia with full inflow occlusion necessitating partial hepatectomy. Soluble nucleoside triphosphate diphosphohydrolase (NTPDases) or adenosine/amrinone were administered to wildtype (n = 6) and Cd39-null mice (n = 6) in order to study protective effects in vivo. Parameters of liver injury, systemic inflammation, hepatic ATP determinations by P³¹-NMR and parameters of lung injury were obtained. All wildtype mice survived up to 7 days with minimal biochemical disturbances and minor evidence for injury. In contrast, 64% of Cd39+/− and 84% of Cd39-null mice required euthanasia or died within 4 h post-reperfusion with liver damage and systemic inflammation associated with hypercytokinemia. Hepatic ATP depletion was pronounced in Cd39-null mice posthepatic IRI. Soluble NTPDase or adenosine administration protected Cd39-deficient mice from acute reperfusion injury. We conclude that CD39 is protective in hepatic IRI preventing local injury and systemic inflammation in an adenosine dependent manner. Our data indicate that vascular CD39 expression has an essential protective role in hepatic IRI.     

Renal Ischaemia Reperfusion Injury: A Mouse Model of Injury and Regeneration

Renal ischaemia reperfusion injury (IRI) is a common cause of acute kidney injury (AKI) in patients and occlusion of renal blood flow is unavoidable during renal transplantation. Experimental models that accurately and reproducibly recapitulate renal IRI are crucial in dissecting the pathophysiology of AKI and the development of novel therapeutic agents. Presented here is a mouse model of renal IRI that results in reproducible AKI. This is achieved by a midline laparotomy approach for the surgery with one incision allowing both a right nephrectomy that provides control tissue and clamping of the left renal pedicle to induce ischaemia of the left kidney. By careful monitoring of the clamp position and body temperature during the period of ischaemia this model achieves reproducible functional and structural injury. Mice sacrificed 24 hr following surgery demonstrate loss of renal function with elevation of the serum or plasma creatinine level as well as structural kidney damage with acute tubular necrosis evident. Renal function improves and the acute tissue injury resolves during the course of 7 days following renal IRI such that this model may be used to study renal regeneration. This model of renal IRI has been utilized to study the molecular and cellular pathophysiology of AKI as well as analysis of the subsequent renal regeneration.     

Early release of macrophage migration inhibitory factor after liver ischemia and reperfusion injury in rats

Macrophage migration inhibitory factor (MIF) is an important mediator of ischemia/reperfusion (I/R) injury in heart, brain and intestine. We previously demonstrated that MIF was released during warm/cold ischemia in vitro. However, the role of MIF in liver I/R injury remains unclear. We aimed to test the hypothesis that MIF acts as an early proinflammatory cytokine and could mediate the inflammatory injury in liver I/R. Rats (n = 6 per group) were subjected to 90 min warm ischemia followed by 0.5 h, 6 h and 24 h reperfusion, respectively to liver transplantation (LTx) after 6 h of cold ischemia followed by 24 h of reperfusion. The expression of MIF, its receptor (cluster of differentiation 74 (CD74)) and the downstream inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)) were analyzed. Peritoneal macrophages were cultured for 6 h alone or in the presence of effluent from cold-preserved livers or effluent depleted of MIF. Warm I/R increased hepatic MIF-mRNA and protein expression. MIF-protein was released into peripheral circulation in vivo with a maximum at 0.5 h after reperfusion. Induction of MIF-expression was associated with the expression of proinflammatory cytokines and its receptor in both models. MIF released by isolated cold preserved livers, induced TNF-α and IL-1β production by cultured peritoneal macrophages. Intrahepatic upregulation of MIF, release into systemic circulation and the associated upregulation of the proinflammatory mediators suggest a role of MIF in mediating the inflammatory response to I/R injury. Blocking experiments will help to elucidate its role as potential molecular target for preventing hepatic I/R injury.     

PGC‐1α protects from myocardial ischaemia‐reperfusion injury by regulating mitonuclear communication

The recovery of blood supply after a period of myocardial ischaemia does not restore the heart function and instead results in a serious dysfunction called myocardial ischaemia‐reperfusion injury (IRI), which involves several complex pathophysiological processes. Mitochondria have a wide range of functions in maintaining the cellular energy supply, cell signalling and programmed cell death. When mitochondrial function is insufficient or disordered, it may have adverse effects on myocardial ischaemia‐reperfusion and therefore mitochondrial dysfunction caused by oxidative stress a core molecular mechanism of IRI. Peroxisome proliferator‐activated receptor gamma co‐activator 1α (PGC‐1α) is an important antioxidant molecule found in mitochondria. However, its role in IRI has not yet been systematically summarized. In this review, we speculate the role of PGC‐1α as a key regulator of mitonuclear communication, which may interacts with nuclear factor, erythroid 2 like ‐1 and ‐2 (NRF‐1/2) to inhibit mitochondrial oxidative stress, promote the clearance of damaged mitochondria, enhance mitochondrial biogenesis, and reduce the burden of IRI.     

The uncoordinated-5 homolog B receptor affects hepatic ischemia reperfusion injury

Recent evidence has demonstrated additional roles for the neuronal guidance protein receptor UNC5B outside the nervous system. Given the fact that ischemia reperfusion injury (IRI) of the liver is a common source of liver dysfunction and the role of UNC5B during an acute inflammatory response we investigated the role of UNC5B on acute hepatic IRI. We report here that UNC5B(+/-) mice display reduced hepatic IRI and neutrophil (PMN) infiltration compared to WT controls. This correlated with serum levels of lactate dehydrogenase (LDH), aspartate- (AST) and alanine- (ALT) aminotransferase, the presence of PMN within ischemic hepatic tissue, and serum levels of inflammatory cytokines. Moreover, injection of an anti-UNC5B antibody resulted in a significant reduction of hepatic IR injury. This was associated with reduced parameters of liver injury (LDH, ALT, AST) and accumulation of PMN within the injured hepatic tissue. In conclusion our studies demonstrate a significant role for UNC5B in the development of hepatic IRI and identified UNC5B as a potential drug target to prevent liver dysfunction in the future.     

Lysine‐specific demethylase 1 aggravated oxidative stress and ferroptosis induced by renal ischemia and reperfusion injury through activation of TLR4/NOX4 pathway in mice

Acute kidney injury (AKI) is mainly caused by renal ischaemia reperfusion injury (IRI). Lots of evidence suggests that ferroptosis and oxidative stress play the vital role in renal IRI. However, the specific mechanism of renal IRI has not been fully elucidated. lysine‐specific demethylase 1 (LSD1) has been shown to regulate the pathogenesis of kidney disease. In this study, we firstly found that LSD1 was positively related to renal IRI. TCP, a classical LSD1 inhibitor, could alleviate tissue damage induced by renal IRI. Inhibition of LSD1 with either TCP or LSD1 knockdown could alleviate ferroptosis and oxidative stress caused by IRI both in vivo and in vitro. Furthermore, the results showed that suppression of LSD1 decreased the expression of TLR4/NOX4 pathway in HK‐2 cells subjected to H/R. With the si‐RNA against TLR4 or NOX4, it showed that the silence of TLR4/NOX4 reduced oxidative stress and ferroptosis in vitro. Moreover, to demonstrate the crucial role of TLR4/NOX4, TLR4 reduction, mediated by inhibition of LSD1, was compensated through delivering the adenovirus carrying TLR4 in vitro. The results showed that the compensation of TLR4 blunted the alleviation of oxidative stress and ferroptosis, induced by LSD1 inhibition. Further study showed that LSD1 activates TLR4/NOX4 pathway by reducing the enrichment of H3K9me2 in the TLR4 promoter region. In conclusion, our results demonstrated that LSD1 inhibition blocked ferroptosis and oxidative stress caused by renal IRI through the TLR4/NOX4 pathway, indicating that LSD1 could be a potential therapeutic target for renal IRI.     

The mitochondrial Ca2+ uptake regulator,MICU1, is involved in cold stress‐induced ferroptosis

Ferroptosis has recently attracted much interest because of its relevance to human diseases such as cancer and ischemia‐reperfusion injury. We have reported that prolonged severe cold stress induces lipid peroxidation‐dependent ferroptosis, but the upstream mechanism remains unknown. Here, using genome‐wide CRISPR screening, we found that a mitochondrial Ca²⁺ uptake regulator, mitochondrial calcium uptake 1 (MICU1), is required for generating lipid peroxide and subsequent ferroptosis under cold stress. Furthermore, the gatekeeping activity of MICU1 through mitochondrial calcium uniporter (MCU) is suggested to be indispensable for cold stress‐induced ferroptosis. MICU1 is required for mitochondrial Ca²⁺ increase, hyperpolarization of the mitochondrial membrane potential (MMP), and subsequent lipid peroxidation under cold stress. Collectively, these findings suggest that the MICU1‐dependent mitochondrial Ca²⁺ homeostasis‐MMP hyperpolarization axis is involved in cold stress‐induced lipid peroxidation and ferroptosis.     

Bone marrow‐derived mesenchymal stem cells enhance autophagy via PI3K/AKT signalling to reduce the severity of ischaemia/reperfusion‐induced lung injury

Autophagy, a type II programmed cell death, is essential for cell survival under stress, e.g. lung injury, and bone marrow‐derived mesenchymal stem cells (BM‐MSCs) have great potential for cell therapy. However, the mechanisms underlying the BM‐MSC activation of autophagy to provide a therapeutic effect in ischaemia/reperfusion‐induced lung injury (IRI) remain unclear. Thus, we investigate the activation of autophagy in IRI following transplantation with BM‐MSCs. Seventy mice were pre‐treated with BM‐MSCs before they underwent lung IRI surgery in vivo. Human pulmonary micro‐vascular endothelial cells (HPMVECs) were pre‐conditioned with BM‐MSCs by oxygen‐glucose deprivation/reoxygenation (OGD) in vitro. Expression markers for autophagy and the phosphoinositide 3‐kinase/protein kinase B (PI3K/Akt) signalling pathway were analysed. In IRI‐treated mice, administration of BM‐MSCs significantly attenuated lung injury and inflammation, and increased the level of autophagy. In OGD‐treated HPMVECs, co‐culture with BM‐MSCs attenuated endothelial permeability by decreasing the level of cell death and enhanced autophagic activation. Moreover, administration of BM‐MSCs decreased the level of PI3K class I and p‐Akt while the expression of PI3K class III was increased. Finally, BM‐MSCs‐induced autophagic activity was prevented using the inhibitor LY294002. Administration of BM‐MSCs attenuated lung injury by improving the autophagy level via the PI3K/Akt signalling pathway. These findings provide further understanding of the mechanisms related to BM‐MSCs and will help to develop new cell‐based therapeutic strategies in lung injury.