Isoflurane Preconditioning Alleviated Murine Liver Ischemia and Reperfusion Injury by Restoring AMPK/mTOR-Mediated Autophagy

Research progress on the role of mitochondria in the process of hepatic ischemia-reperfusion injury

During liver ischemia-reperfusion injury, existing mechanisms involved oxidative stress, calcium overload, and the activation of inflammatory responses involve mitochondrial injury. Mitochondrial autophagy, a process that maintains the normal physiological activity of mitochondria, promotes cellular metabolism, improves cellular function, and facilitates organelle renewal. Mitochondrial autophagy is involved in oxidative stress and apoptosis, of which the PINK1-Parkin pathway is a major regulatory pathway, and the deletion of PINK1 and Parkin increases mitochondrial damage, reactive oxygen species production, and inflammatory response, playing an important role in mitochondrial quality regulation. In addition, proper mitochondrial permeability translational cycle regulation can help maintain mitochondrial stability and mitigate hepatocyte death during ischemia-reperfusion injury. This mechanism is also closely related to oxidative stress, calcium overload, and the aforementioned autophagy pathway, all of which leads to the augmentation of the mitochondrial membrane permeability transition pore opening and cause apoptosis. Moreover, the release of mitochondrial DNA (mtDNA) due to oxidative stress further aggravates mitochondrial function impairment. Mitochondrial fission and fusion are non-negligible processes required to maintain the dynamic renewal of mitochondria and are essential to the dynamic stability of these organelles. The Bcl-2 protein family also plays an important regulatory role in the mitochondrial apoptosis signaling pathway. A series of complex mechanisms work together to cause hepatic ischemia-reperfusion injury (HIRI). This article reviews the role of mitochondria in HIRI, hoping to provide new therapeutic clues for alleviating HIRI in clinical practice.

Isoflurane, like sepsis, decreases CYP1A2 liver enzyme activity in intensive care patients: a clinical study and network model

PURPOSE

Liver function of intensive care patients is routinely monitored by static blood pathology. For specific indications, liver specific cytochrome activity may be measured by the commercially available maximum liver function capacity (LiMAx) test via quantification of the cytochrome P450 1A2 (CYP1A2) dependent C-methacetin metabolism. Sedation with the volatile anesthetic isoflurane was suspected to abrogate the correlation of LiMAx test with global liver function. We hypothesized that isoflurane has a CYP1A2-activity and LiMAx test result decreasing effect.

METHODS

In this monocentric, observational clinical study previously liver healthy intensive care patients, scheduled to be changed from propofol to isoflurane sedation, were enrolled. LiMAx testing was done before, during and after termination of isoflurane sedation.

RESULTS

The mean LiMAx value decreased during isoflurane sedation. Septic patients (n = 11) exhibited lower LiMAx values compared to non-septic patients (n = 11) at all time points. LiMAx values decreased with isoflurane from 140 ± 82 to 30 ± 34 µg kg-1 h-1 in the septic group and from 253 ± 92 to 147 ± 131 µg kg-1 h-1 in the non-septic group while laboratory markers did not imply significant hepatic impairment. Lactate increased during isoflurane inhalation without clinical consequence.

CONCLUSION

Sepsis and isoflurane have independently demonstrated an effect on reducing the hepatic CYP1A2-activity. A network model was constructed that could explain the mechanism through the influence of isoflurane on hypoxia inducible factor (HIF-1α) by upregulation of the hypoxia-inducible pathway and the downregulation of CYP1A2-activity via the ligand-inducible pathway. Thus, the increased anaerobic metabolism may result in lactate accumulation. The influence of isoflurane sedation on the validated correlation of global liver function with CYP1A2-activity measured by LiMAx testing needs to be investigated in more detail.

Autophagy in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is a major complication of liver resection or liver transplantation that can seriously affect patient's prognosis. There is currently no definitive and effective treatment strategy for HIRI. Autophagy is an intracellular self-digestion pathway initiated to remove damaged organelles and proteins, which maintains cell survival, differentiation, and homeostasis. Recent studies have shown that autophagy is involved in the regulation of HIRI. Numerous drugs and treatments can change the outcome of HIRI by controlling the pathways of autophagy. This review mainly discusses the occurrence and development of autophagy, the selection of experimental models for HIRI, and the specific regulatory pathways of autophagy in HIRI. Autophagy has considerable potential in the treatment of HIRI.

GluA1 Degradation by Autophagy Contributes to Circadian Rhythm Effects on Cerebral Ischemia Injury

The mechanisms of many diseases, including central nervous system disorders, are regulated by circadian rhythms. The development of brain disorders such as depression, autism, and stroke is strongly associated with circadian cycles. Previous studies have shown that cerebral infarct volume is smaller at night (active phase) than during the day (inactive phase) in ischemic stroke rodent models. However, the underlying mechanisms remain unclear. Increasing evidence suggests that glutamate systems and autophagy play important roles in the pathogenesis of stroke. Here, we report that GluA1 expression was decreased and autophagic activity was increased in active-phase male mouse models of stroke compared with the inactive-phase models. In the active-phase model, induction of autophagy decreased the infarct volume, whereas inhibition of autophagy increased the infarct volume. Meanwhile, GluA1 expression was decreased following activation of autophagy and increased following inhibition of autophagy. We used Tat-GluA1 to uncouple p62, an autophagic adapter, from GluA1 and found that this blocked the degradation of GluA1, an effect similar to that of inhibition of autophagy in the active-phase model. We also demonstrated that knock-out of the circadian rhythm gene Per1 abolished the circadian rhythmicity of the volume of infarction and also abolished GluA1 expression and autophagic activity in wild-type (WT) mice. Our results suggest an underlying mechanism by which the circadian rhythm participates in the autophagy-dependent regulation of GluA1 expression, which influences the volume of infarction in stroke.SIGNIFICANCE STATEMENT Circadian rhythms affect the pathophysiological mechanisms of disease. Previous studies suggested that circadian rhythms affect the infarct volume in stroke, but the underlying mechanisms remain largely unknown. Here, we demonstrate that the smaller infarct volume after middle cerebral artery occlusion/reperfusion (MCAO/R) during the active phase is related to lower GluA1 expression and activation of autophagy. The decrease in GluA1 expression during the active phase is mediated by the p62-GluA1 interaction, followed by direct autophagic degradation. In short, GluA1 is the substrate of autophagic degradation, which mainly occurs after MCAO/R during the active phase but not the inactive phase.

AMPK: The key to ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) refers to a syndrome in which tissue damage is further aggravated and organ function further deteriorates when blood flow is restored after a period of tissue ischemia. Acute myocardial infarction, stress ulcer, pancreatitis, intestinal ischemia, intermittent claudication, acute tubular necrosis, postshock liver failure, and multisystem organ failure are all related to reperfusion injury. AMP-activated protein kinase (AMPK) has been identified in multiple catabolic and anabolic signaling pathways. The functions of AMPK during health and diseases are intriguing but still need further research. Except for its conventional roles as an intracellular energy switch, emerging evidence reveals the critical role of AMPK in IRI as an energy-sensing signal molecule by regulating metabolism, autophagy, oxidative stress, inflammation, and other progressions. At the same time, drugs based on AMPK for the treatment of IRI are constantly being researched and applied in clinics. In this review, we summarize the mechanisms underlying the effects of AMPK in IRI and describe the AMPK-targeting drugs in treatment, hoping to increase the understanding of AMPK in IRI and provide new insights into future clinical treatment.

The Role of NLRP3 Inflammasome Activation Pathway of Hepatic Macrophages in Liver Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is considered an inherent component involved in liver transplantation, which induce early organ dysfunction and failure. And the accumulating evidences indicate that the activation of host innate immune system, especially hepatic macrophages, play a pivotal role in the progression of LIRI. Inflammasomes is a kind of intracellular multimolecular complexes that actively participate in the innate immune responses and proinflammatory signaling pathways. Among them, NLRP3 inflammasome is the best characterized and correspond to regulate caspase-1 activation and the secretion of proinflammatory cytokines in response to various pathogen-derived as well as danger-associated signals. Additionally, NLRP3 is highly expressed in hepatic macrophages, and the assembly of NLRP3 inflammasome could lead to LIRI, which makes it a promising therapeutic target. However, detailed mechanisms about NLRP3 inflammasome involving in the hepatic macrophages-related LIRI is rarely summarized. Here, we review the potential role of the NLRP3 inflammasome pathway of hepatic macrophages in LIRI, with highlights on currently available therapeutic options.

4.8% sevoflurane induces activation of autophagy in human neuroblastoma SH-SY5Y cells by the AMPK/mTOR signaling pathway

Prolonged sevoflurane exposure leads to neurotoxicity. Autophagy plays an important role in promoting cell survival in different conditions. However, the role and mechanism of autophagy in sevoflurane-induced neurotoxicity were not fully elucidated. We attempted to indicate whether sevoflurane could activate the AMP-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR)-mediated autophagy to attenuate anesthetics-induced neuronal injury in this study. Sevoflurane treatment significantly decreased the cell viability and induced apoptosis of SH-SY5Y cells. The expression level of Bcl-2 decreased, while that of Bax remarkably increased. Meanwhile, autophagy was activated by sevoflurane exposure as evidenced by increased expression levels of autophagy-related proteins (LC3-II and Atg5), decreased expression level of autophagic substrate P62, and increased autophagosomes and autolysosomes. Further autophagosomes and fewer autolysosomes were observed in the presence of Bafilomycin A1, an autolysosomes degradation inhibitor, suggesting that sevoflurane induced autophagic flux rather than inhibiting degradation of autophagy. Activation of autophagy by rapamycin partly reversed the sevoflurane-decreased cell viability. In contrast, inhibition of autophagy by 3-Methyladenine (3-MA) or Atg5-targeted small interfering RNA (siRNA) aggravated the sevoflurane-induced neurotoxicity. Further examination revealed that sevoflurane-induced autophagy was mediated by the AMPK/mTOR signaling pathway, with increased p-AMPK expression and decreased p-mTOR expression. Collectively, these results indicated that sevoflurane activates autophagy by regulating the AMPK/mTOR signaling pathway, which is protective against sevoflurane-induced damage in SH-SY5Y cells. Our results may assist clinicians to develop further promising therapeutic strategies for the neurotoxicity induced by inhaled anesthetics.

Short-term inhalation of isoflurane improves the outcomes of intraportal hepatocyte transplantation

Clinical hepatocyte transplantation (HTx) is only performed without general anesthesia, while inhalation anesthetics are usually used in animal experiments. We hypothesized that isoflurane may be a possible reason for the discrepancy between the results of animal experiments and the clinical outcomes of HTx. Syngeneic rat hepatocytes (1.0 × 10⁷) were transplanted to analbuminemic rats with (ISO group) and without (AW group) isoflurane. The serum albumin, AST, ALT, LDH levels and several inflammatory mediators were analyzed. Immunohistochemical staining and ex vivo imaging were also performed. The serum albumin levels of the ISO group were significantly higher in comparison to the AW group (p < 0.05). The serum AST, ALT, LDH levels of the ISO group were significantly suppressed in comparison to the AW group (p < 0.0001, respectively). The serum IL-1β, IL-10, IL-18, MCP-1, RNTES, Fractalkine and LIX levels were significantly suppressed in the ISO group. The ischemic regions of the recipient livers in the ISO group tended to be smaller than the AW group; however, the distribution of transplanted hepatocytes in the liver parenchyma was comparable between the two groups. Isoflurane may at least in part be a reason for the discrepancy between the results of animal experiments and the clinical outcomes of HTx.

Stellate Ganglion Block Improves the Proliferation and Function of Splenic CD4 + T Cells Through Inhibition of Posthemorrhagic Shock Mesenteric Lymph-Mediated Autophagy

Severe hemorrhagic shock leads to excessive inflammation and immune dysfunction, which results in high mortality related to mesenteric lymph return. A recent study showed that stellate ganglion block (SGB) increased the survival rate in rats suffering hemorrhagic shock. However, whether SGB ameliorates immune dysfunction induced by hemorrhagic shock remains unknown. The aim of the present study was to verify the favorable effects of SGB on the proliferation and function of splenic CD4 + T cells isolated from rats that underwent hemorrhagic shock and to investigate the mechanism related to the SGB interaction with autophagy and posthemorrhagic shock mesenteric lymph (PHSML). Male rats underwent SGB or sham SGB and conscious acute hemorrhage followed by resuscitation and multiple treatments. After 3 h of resuscitation, splenic CD4 + T cells were isolated to measure proliferation and cytokine production following stimulation with ConA in vitro. CD4 + T cells isolated from normal rats were treated with PHSML drained from SBG-treated rats, and proliferation, cytokine production, and autophagy biomarkers were detected. Hemorrhagic shock reduced CD4 + T cell proliferation and production of interleukin (IL)-2, IL-4, and tumor necrosis factor-α-induced protein 8-like 2 (TIPE2). SGB or administration of the autophagy inhibitor 3-methyladenine (3-MA) normalized these indicators. In contrast, administration of rapamycin (RAPA) autophagy agonist or intravenous injection of PHSML inhibited the beneficial effects of SGB on CD4 + T cells from hemorrhagic shocked rats. Furthermore, PHSML incubation decreased proliferation and cytokine production, increased LC3 II/I and Beclin-1 expression, and reduced p-PI3K and p-Akt expression in normal CD4 + T cells. These adverse effects of PHSML were also abolished by 3-MA administration, as well as incubation with PHSML obtained from SGB-treated rats. SGB improves splenic CD4 + T cell function following hemorrhagic shock, which is related to the inhibition of PHSML-mediated autophagy.

Isoquercitrin Upregulates Aldolase C Through Nrf2 to Ameliorate OGD/R-Induced Damage in SH-SY5Y Cells

Isoquercitrin (ISO), an extract from Chinese traditional herb, exhibits potent neuroprotective roles in various disease models. However, its role in stroke is not fully understood. We established oxygen-glucose deprivation and reoxygenation (OGD/R) model in SH-SY5Y cell to study the roles of ISO in stroke. In the experiment, the changes of LDH level and cell viability (MTT) were analyzed. Apoptotic cells stained with anti-Annexin V antibody and propidium iodide (PI) were detected by flow cytometry. The mRNA and protein level of aldolase C (ALDOC) and nuclear factor erythroid 2-related factor (Nrf2) was determined by real-time quantitative polymerase chain reaction (qPCR) and Western blotting assay, respectively. The localization of Nrf2 was investigated by immunofluorescent assay. OGD/R reduced cell viability via inducing cell apoptosis, while ISO treatment reduced the level of apoptosis in OGD/R-treated SH-SY5Y cells ISO rescued OGD/R-treated cells. Mechanistically, the expression of Nrf2 and ALDOC was upregulated upon ISO treatment, while knockdown of ALDOC diminished the activation of autophagy and hence inhibited ISO-mediated protective activity. We further demonstrated that ISO enhanced ALDOC transcription by promoting nuclear translocation of Nrf2, and suppression of Nrf2 decreased the expression of ALDOC. Our data revealed that ISO exhibited neuroprotective activity in OGD/R model through Nrf2-ALDOC-autopagy axis and highlighted the potential application of ISO in stroke treatment.

Imatinib protects against human beta-cell death via inhibition of mitochondrial respiration and activation of AMPK

The protein tyrosine kinase inhibitor imatinib is used in the treatment of various malignancies but may also promote beneficial effects in the treatment of diabetes. The aim of the present investigation was to characterize the mechanisms by which imatinib protects insulin producing cells. Treatment of non-obese diabetic (NOD) mice with imatinib resulted in increased beta-cell AMP-activated kinase (AMPK) phosphorylation. Imatinib activated AMPK also in vitro, resulting in decreased ribosomal protein S6 phosphorylation and protection against islet amyloid polypeptide (IAPP)-aggregation, thioredoxin interacting protein (TXNIP) up-regulation and beta-cell death. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) mimicked and compound C counteracted the effect of imatinib on beta-cell survival. Imatinib-induced AMPK activation was preceded by reduced glucose/pyruvate-dependent respiration, increased glycolysis rates, and a lowered ATP/AMP ratio. Imatinib augmented the fractional oxidation of fatty acids/malate, possibly via a direct interaction with the beta-oxidation enzyme enoyl coenzyme A hydratase, short chain, 1, mitochondrial (ECHS1). In non-beta cells, imatinib reduced respiratory chain complex I and II-mediated respiration and acyl-CoA carboxylase (ACC) phosphorylation, suggesting that mitochondrial effects of imatinib are not beta-cell specific. In conclusion, tyrosine kinase inhibitors modestly inhibit mitochondrial respiration, leading to AMPK activation and TXNIP down-regulation, which in turn protects against beta-cell death.

Fraxetin suppresses reactive oxygen species-dependent autophagy by the PI3K/Akt pathway to inhibit isoflurane-induced neurotoxicity in hippocampal neuronal cells

Isoflurane, a common volatile anesthetic, has been widely used to provide general anesthesia in operations. However, exposure to isoflurane may cause widespread neurotoxicity in the developing animal brain. Fraxetin, a natural coumarin derivative extracted from the bark of Fraxinus rhynchophylla, possesses versatile pharmacological properties including anti-oxidative, anti-inflammatory, and neuroprotective effects. However, the effect and action mechanism of fraxetin on neurotoxicity induced by isoflurane are unknown. Reactive oxygen species (ROS) generation, cell viability, lactate dehydrogenase (LDH) release, and apoptosis were estimated by 2',7'-dichlorofluorescin-diacetate (DCFH-DA) staining, MTT, LDH release, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) staining assays, respectively. The protein levels of light chain 3 (LC3)-I, LC3-II, p62, protein kinase B (Akt), and phosphorylated Akt (p-Akt) were detected by western blot analysis. Isoflurane induced ROS, LDH release, apoptosis, and autophagy, but inhibited the viability in HT22 cells, which were overturned by fraxetin or ROS scavenger N-acetyl-L-cysteine. Fraxetin suppressed isoflurane-induced PI3K/Akt inactivation in HT22 cells. PI3K/Akt inactivation by LY294002 resisted the effects of fraxetin on isoflurane-induced autophagy and autophagy-modulated neurotoxicity in HT22 cells. In conclusion, fraxetin suppressed ROS-dependent autophagy by activating the PI3K/Akt pathway to inhibit isoflurane-induced neurotoxicity in hippocampal neuronal cells.

Paclobutrazol exposure induces apoptosis and impairs autophagy in hepatocytes via the AMPK/mTOR signaling pathway

Paclobutrazol (PBZ), one of the most widely used plant growth retardants in vegetables, fruits, and traditional Chinese medicine ingredients, exposes people to adverse events. In this study, HepaRG hepatocytes were cultured and exposed to PBZ (360 μM) in vitro to determine its mechanism. Results showed that PBZ exposure inhibited cell viability in a time- and dose-dependent manner and increased the oxidative stress and apoptosis ratio in HepaRG cells. These data revealed that the adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) has an important role in PBZ-induced cell apoptosis, which is mediated by impaired autophagy and blocked by the AMPK activator. In conclusion, PBZ exposure induces apoptosis and impairs autophagy in hepatocytes via the AMPK/mTOR signaling pathway.

Astragaloside IV alleviates liver injury in type 2 diabetes due to promotion of AMPK/mTOR‑mediated autophagy

Diabetic liver injury is a serious complication of type 2 diabetes mellitus (T2DM), which is often irreversible in the later stage, and affects the quality of life. Autophagy serves an important role in the occurrence and development of diabetic liver injury. For example, it can improve insulin resistance (IR), dyslipidaemia, oxidative stress and inflammation. Astragaloside IV (AS-IV) is a natural saponin isolated from the plant Astragalus membranaceus, which has comprehensive pharmacological effects, such as anti-oxidation, anti-inflammation and anti-apoptosis properties, as well as can enhance immunity. However, whether AS-IV can alleviate diabetic liver injury in T2DM and its underlying mechanisms remain unknown. The present study used high-fat diets combined with low-dose streptozotocin to induce a diabetic liver injury model in T2DM rats to investigate whether AS-IV could alleviate diabetic liver injury and to identify its underlying mechanisms. The results demonstrated that AS-IV treatment could restore changes in food intake, water intake, urine volume and body weight, as well as improve liver function and glucose homeostasis in T2DM rats. Moreover, AS-IV treatment promoted suppressed autophagy in the liver of T2DM rats and improved IR, dyslipidaemia, oxidative stress and inflammation. In addition, AS-IV activated adenosine monophosphate-activated protein kinase (AMPK), which inhibited mTOR. Taken together, the present study suggested that AS-IV alleviated diabetic liver injury in T2DM rats, and its mechanism may be associated with the promotion of AMPK/mTOR-mediated autophagy, which further improved IR, dyslipidaemia, oxidative stress and inflammation. Thus, the regulation of autophagy may be an effective strategy to treat diabetic liver injury in T2DM.

Inhibiting ATP6V0D2 Aggravates Liver Ischemia-Reperfusion Injury by Promoting NLRP3 Activation via Impairing Autophagic Flux Independent of Notch1/Hes1

At present, liver ischemia-reperfusion (IR) injury is still a great challenge for clinical liver partial resection and liver transplantation. The innate immunity regulated by liver macrophages orchestrates the cascade of IR inflammation and acts as a bridge. As a specific macrophage subunit of vacuolar ATPase, ATP6V0D2 (V-ATPase D2 subunit) has been shown to promote the formation of autophagolysosome in vitro. Our research fills a gap which has existed in the study of inflammatory stress about the V-ATPase subunit ATP6V0D2 in liver macrophages. We first found that the expression of specific ATP6V0D2 in liver macrophages was upregulated with the induction of inflammatory cascade after liver IR surgery, and knockdown of ATP6V0D2 resulted in increased secretion of proinflammatory factors and chemokines, which enhanced activation of NLRP3 and aggravation of liver injury. Further studies found that the exacerbated activation of NLRP3 was related to the autophagic flux regulated by ATP6V0D2. Knocking down ATP6V0D2 impaired the formation of autophagolysosome and aggravated liver IR injury through nonspecific V-ATPase activation independent of V-ATPase-Notchl-Hesl signal axis. In general, we illustrated that the expression of ATP6V0D2 in liver macrophages was upregulated after liver IR, and by gradually promoting the formation of autophagolysosomes to increase autophagy flux to limit the activation of liver inflammation, this regulation is independent of the Notch1-Hes1 signal axis.

Sevoflurane preconditioning activates HGF/Met-mediated autophagy to attenuate hepatic ischemia-reperfusion injury in mice

Sevoflurane (SEV) preconditioning plays a protective effect against liver ischemia reperfusion (IR) injury, while the role of autophagy in SEV-mediated hepatoprotection and the precise mechanism is unclear. In the current study, mice were pretreated with SEV or autophagy inhibitor before liver IR injury. In vitro, primary rat hepatocytes were pretreated with SEV and then exposed to hypoxia/reoxygenation (H/R). Liver function was measured by biochemical and histopathological examinations, and markers associated with inflammation, oxidation, apoptosis and autophagy were subsequently measured. We found that SEV preconditioning dramatically reduced hepatic damage, alleviated cell inflammatory response, oxidative stress and apoptosis in mice suffering hepatic IR injury, whereas these protective effects were abolished by the autophagy inhibitor 3-MA. In addition, pretreatment with SEV markedly activated HGF/Met signaling pathway regulation. Besides, pretreatment with an hepatocyte growth factor (HGF) inhibitor or knocking down HGF expression significantly downregulated phosphorylated met (p-met) and autophagy levels, and abolished the protective effects of SEV against hepatic IR or hepatocyte H/R injury. Conversely, HGF overexpression efficiently increased the p-met and autophagy levels and strengthened the protective effects of SEV. These results indicated that sevoflurane preconditioning ameliorates hepatic IR injury by activating HGF/Met-mediated autophagy.

Eva1a inhibits NLRP3 activation to reduce liver ischemia-reperfusion injury via inducing autophagy in kupffer cells

Ischemia-reperfusion(IR) injury is one of the main complications of liver transplantation and partial hepatectomy. Innate immunity mediated by kupffer cells plays an important role in it. In this study, we focused on evaluating the intrinsic relationship between the autophagy induction of kupffer cells and the activation of NLRP3 inflammasomes caused by liver ischemia-reperfusion. Pre-depletion of kupffer cells can aggravate inflammation and tissue damage within 24 h after IR.Enhancing the autophagy of kupffer cells can inhibit the activation of NLRP3 caused by IR, and inhibiting autophagy can induce the secretion of IL1β dependent on NLRP3 activation.Eva1a is up-regulated by the inflammatory cascade activated by IR.Knockdown of Eva1a in vivo on the one hand will aggravate IR inflammation, increase the production of TNF-α, IL-1β and inhibit the secretion of IL-10.On the other hand, it will aggravate the liver histological damage. Knockout of Eva1a induces ASC activation and cleavage of caspase1 and IL1β in an NLRP3-dependent manner, which is closely related to the function of blocking Eva1a to promote autophagosome formation.We further found that knockdown of ATG16L1 will reverse the more formation of autophagosomes induced by overexpression of Eva1a, whereas knockdown of ATG16L1 did not further reduce the formation of autophagosomes inhibited by siEva1a. We also found that the addition of siATG7, siATG5 and siATG12 would reverse the IR autophagy of liver induced by overexpression of Eva1a, but inhibition of the Beclin1-Vps34 pathway did not significantly reverse the effect of overexpression of Eva1a.These prove that Eva1a and ATG16L1 may work together in the liver IR model to actively induce the formation of autophagosomes and be independent from the beclin1-vps34-induced autophagy pathway to limit the excessive activation of IR inflammation. Our study provides brand new insights into the mechanism of liver macrophages in the progression of inflammation in the context of liver ischemia-reperfusion injury.

Isoflurane activates AMP-activated protein kinase to inhibit proliferation, and promote apoptosis and autophagy in cervical carcinoma both in vitro and in vivo

OBJECTIVE

Isoflurane is an extensively used inhalational anesthesia, and its carcinogenic or anti-cancerous effect has been identified recently. However, the specific role of isoflurane in cervical cancer remains unclear.

AIM

This study aimed to investigate the function of isoflurane in cervical cancer as well as the underlying mechanism.

METHODS

After isoflurane treatment, HeLa cell viability, percentage of apoptotic cells, expression of active caspase-3/9 were examined by CCK-8 assay, Annexin V-FITC/PI double staining, and Western blot analysis, respectively. ROS generation, ratio of NAD⁺/NADH, and ATP level after isoflurane stimulation were determined using commercial assay kits. Afterwards, activation of AMPK and autophagy was assessed through Western blot analysis and immunofluorescence. Whether AMPK mediated the isoflurane-induced apoptosis and autophagy was explored by adding an AMPK inhibitor (Compound C). The in vivo function of isoflurane was finally investigated on a HeLa cell xenograft model.

RESULTS

Isoflurane inhibited cell viability and induced apoptosis evidenced by upregulation of active caspase-3/9 in HeLa cells. Oxidative stress was triggered by isoflurane, as isoflurane elevated ROS level, and lowered ratio of NAD⁺/NADH and ATP level. Further results showed isoflurane activated the AMPK/mTOR pathway and induced autophagy. In addition, inhibition of AMPK led to ameliorated effects of isoflurane on apoptosis and autophagy. In vivo experiments proved isoflurane could repress tumorigenesis, activate AMPK, and induce autophagy in Xenograft mouse.

CONCLUSIONS

Isoflurane activated AMPK to inhibit proliferation and promote apoptosis and autophagy both in vitro and in vivo.

Rapamycin improves renal injury induced by Iodixanol in diabetic rats by deactivating the mTOR/p70S6K signaling pathway

AIMS

To study how to effectively prevent or reduce renal injury caused by contrast agents in diabetic patients.

MAIN METHODS

Sprague Dawley (SD) rats were bred with a high-fat diet for eight weeks, then intraperitoneally injected with Streptozotocin (STZ) to prepare the diabetes model. Rats were treated with Iodixanol to prepare a contrast-induced acute kidney injury (CIAKI) model. Moreover, 3-methyladenine (3-MA), an autophagy inhibitor, was administrated to diabetic rats with or without Rapamycin treatment. Serum creatinine (SCr) and blood urea nitrogen (BUN) were examined using Biochemical detector. Kidney injury molecule-1 (KIM-1), N-acetyl-β-D-amino glycosidase (NAG) in urine, inflammatory and oxidative stress factors in serum were determined by ELISA. The expression level of ROS was quantified by immunofluorescence (IF). The protein expressions of Bax, BCl-2, LC3, Beclin1, mTOR and p70S6K in renal tissue were detected by Western blot.

KEY FINDINGS

Rapamycin was demonstrated to improve renal injury induced by Iodixanol diabetic rats, decrease the levels of SCr, BUN, KIM-1, NAG, improve renal functions, reduce inflammatory response and oxidative stress injury, down-regulate Bax, while up-regulate BCl-2 and inhibit apoptosis. Moreover, Rapamycin could inhibit the phosphorylation of mTOR/p70S6K pathway-associated proteins, activate autophagy and increase the levels of LC3 and Beclin1. After treatment with 3MA, an inhibitor of mTOR/p70S6K signaling pathway, the protective effects of Rapamycin on CIAKI were weakened.

SIGNIFICANCE

Rapamycin can alleviate renal injury induced by Iodixanol diabetic rats, and its regulatory mechanisms may be related to the regulation of mTOR/p70S6K signaling pathway and the activating autophagy.

Sevoflurane Preconditioning Confers Delayed Cardioprotection by Upregulating AMP-Activated Protein Kinase Levels to Restore Autophagic Flux in Ischemia-Reperfusion Rat Hearts

Background

Volatile anesthetic preconditioning confers delayed cardioprotection against ischemia/reperfusion injury (I/R). AMP-activated protein kinase (AMPK) takes part in autophagy activation. Furthermore, autophagic flux is thought to be impaired after I/R. We hypothesized that delayed cardioprotection can restore autophagic flux by activating AMPK.

Material/Methods

All male rat hearts underwent 30-min ischemia and 120-min reperfusion with or without sevoflurane exposure. AMPK inhibitor compound C (250 μg/kg, iv) was given at the reperfusion period. Autophagic flux blocker chloroquine (10 mg/kg, ip) was administrated 1 h before the experiment. Myocardial infarction, nicotinamide adenine dinucleotide (NAD⁺) content, and cytochrome c were measured. To evaluate autophagic flux, the markers of microtubule-associated protein 1 light chain 3 (LC3) I and II, P62 and Beclin 1, and lysosome-associated membrane protein-2 (LAMP 2) were analyzed.

Results

The delayed cardioprotection enhanced post-ischemic AMPK activation, reduced infarction, CK-MB level, NAD⁺ content loss and cytochrome c release, and compound C blocked these effects. Sevoflurane restored impaired autophagic flux through a lower ratio of LC3II/LC3I, downregulation of P62 and Beclin 1, and higher expression in LAMP 2. Consistently, compound C inhibited these changes of autophagy flux. Moreover, chloroquine pretreatment abolished sevoflurane-induced infarct size reduction, CK-MB level, NAD⁺ content loss, and cytochrome c release, with concomitant increase the ratios of LC3II/LC3I and levels of P62 and Beclin 1, but p-AMPK expression was not downregulated by chloroquine.

Conclusions

Sevoflurane exerts a delayed cardioprotective effects against myocardial injury in rats by activation of AMPK and restoration of I/R-impaired autophagic flux.

Diabetes induces hepatocyte pyroptosis by promoting oxidative stress-mediated NLRP3 inflammasome activation during liver ischaemia and reperfusion injury

Background

Although diabetes mellitus has been reported to aggravate liver ischaemia and reperfusion (IR) injury, the basic mechanism remains largely unknown. The object of the present study was to determine the role of oxidative stress and hepatocellular pyroptosis in liver IR injury in diabetic mice.

Methods

Db/db and C57BL/6 mice at 8 weeks of age were subjected to liver IR injury. Liver injury and hepatocyte cell death were analyzed. A NOD-like receptor family pyrin domain-containing 3 protein (NLRP3) inflammasome antagonist (CY09) and a reactive oxygen species (ROS) antagonist (N-Acetyl-L-cysteine, NAC) were used to determine the role of ROS-mediated hepatocellular pyroptosis in diabetic mice post-IR.

Results

Aggravated liver IR injury was found in db/db mice compared to C57BL/6 control mice, as demonstrated by increased serum alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) levels, liver architecture damage and Suzuki scores. Interestingly, IR induces the pyroptosis of hepatocytes in db/db mice, as evidenced by enhanced NLRP3 inflammasome activation, increased numbers of terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive hepatocytes and increased gene expression of interleukin-1β (IL-1β) and IL-18 in livers post-IR. The inhibitory effect of CY09, an NLRP3 antagonist, efficiently abrogated the exacerbation effects of diabetes on liver IR injury in db/db mice. Furthermore, increased ROS expression was detected in db/db mice compared to control mice after IR. ROS scavenging by NAC pretreatment markedly inhibited hepatocellular NLRP3 inflammasome activation and pyroptosis in the db/db mice post-IR, indicating that ROS play an essential role in mediating hepatocyte pyroptosis in the setting of diabetes mellitus.

Conclusions

Our results demonstrate that diabetes induces hepatocyte pyroptosis by promoting oxidative stress-mediated NLRP3 inflammasome activation during liver IR injury. Strategies targeting ROS and NLRP3 inflammasome activation would be beneficial for preventing liver IR injury in diabetic patients.

MSCs ameliorate hepatocellular apoptosis mediated by PINK1-dependent mitophagy in liver ischemia/reperfusion injury through AMPKα activation

Hepatocyte apoptosis is the main pathophysiological process underlying liver ischemia/reperfusion (I/R) injury. Mitochondrial abnormalities have a vital role in hepatocellular damage. The hepatoprotective effects of mesenchymal stem cells (MSCs) have been previously demonstrated. In this study, we aim to investigate the effect and potential mechanism of MSCs against liver I/R injury. Effects of MSCs were studied in mice liver I/R injury model and in a hypoxia/reoxygenation (H/R) model of L02 hepatocytes. The potential mechanisms of MSCs on these in vivo and in vitro I/R-induced hepatocellular apoptosis models were studies. Accompanied by the improvement of hepatic damage, MSCs exhibited capabilities of controlling mitochondrial quality, shown by reduced mitochondrial reactive oxygen species (mtROS) overproduction, decreased the accumulation of mitochondrial fragmentation, restored ATP generation and upregulated mitophagy. Furthermore, we descripted a potential mechanism of MSCs on upregulating mitophagy and found that the reduced Parkin and PINK1 expression and inactivated AMPKα pathway were observed in the liver tissue in I/R model. These effects were reversed by MSCs treatment. In vitro study showed that MSC-conditioned medium (MSC-CM) suppressed hepatocellular apoptosis and inhibited mtROS accumulation in the H/R environment. And these effects of MSC-CM were partially blocked after the cells were transfected with PINK1 siRNA or added with dorsomorphin. Collectively, our findings provide a novel pharmacological mechanism that MSCs exert hepatoprotective effect in liver I/R injury via upregulating PINK1-dependent mitophagy. In addition, this effect might be attributed to the modulation of AMPKα activation.

Inhibition of excessive mitophagy by N-acetyl-L-tryptophan confers hepatoprotection against Ischemia-Reperfusion injury in rats

In order to investigate the mechnism of hepatoprotective of N-acetyl-L-tryptophan (L-NAT) against ischemia-reperfusion (I/R) injury, the effects of L-NAT were investigated in hepatic ischemia-reperfusion injury (HIRI) models both in vitro and in vivo, which were made by BRL cells and Sprague-Dawley (SD) rats, respectively. The cell viability of hepatocyte was assessed by cell counting kit-8 (CCK-8) staining. The activation of autophagy was detected by electron microscopy (EM), quantitative real-time PCR (qRT-PCR), Western blotting and immunofluorescence. The activation of mitophagy was determined by the change of autophagy related protein, change of mitochondrial structure and function, co-location of autophagy protein and MitoTracker. Results showed that the morphological structures of hepatocytes were changed significantly after HIRI, and the cell viability of hydrogen peroxide (H₂O₂)-induced BRL cells was decreased. Autophagy markers Beclin1, microtubule associated protein 1 light chain 3-II (LC3-II) and autophagy related protein-7 (ATG-7) were highly expressed and the expression of SQSTM1 (P62) was decreased after HIRI, which suggested that autophagy of hepatocytes was activated after I/R. The reduction of ATP, mitochondrial DNA (mtDNA) and the mitochondrial transmembrane potential (ΔΨm) after H₂O₂-induced revealed that function of mitochondrial had also undergone significant changes. The increased expression of autophagy protein, destructure of mitochondria and mitochondrial dysfunction, the increased co-location of Beclin1 and MitoTracker induced by H₂O₂ implied the excessive mitophagy. The expression of the autophagy protein was increased by 3-Methyladenine (3-MA), providing another piece of evidence. Importantly, all changes were restored by L-NAT pretreament. In conclusion, the present findings demonstrate that excessive mitophagy involved in the process of HIRI and L-NAT may protect hepatocytes against HIRI by inhibiting activation of mitophagy and improving the structure and function of mitochondria.

Ischemic Postconditioning Alleviates Intestinal Ischemia-Reperfusion Injury by Enhancing Autophagy and Suppressing Oxidative Stress through the Akt/GSK-3β/Nrf2 Pathway in Mice

Aims

Ischemic postconditioning (IPO) has a strong protective effect against intestinal ischemia-reperfusion (IIR) injury that is partly related to autophagy. However, the precise mechanisms involved are unknown.

Methods

C57BL/6J mice were subjected to unilateral IIR with or without IPO. After 45 min ischemia and 120 min reperfusion, intestinal tissues and blood were collected for examination. HE staining and Chiu's score were used to evaluate pathologic injury. We test markers of intestinal barrier function and oxidative stress. Finally, we used WB to detect the expression of key proteins of autophagy and the Akt/GSK-3β/Nrf2 pathway.

Results

IPO significantly attenuated IIR injury. Expression levels of LC3 II/I, Beclin-1, and p62 were altered during IIR, indicating that IPO enhanced autophagy. IPO also activated Akt, inhibited GSK-3β/Nrf2 pathway.

Conclusion

Our study indicates that IPO can ameliorate IIR injury by evoking autophagy, activating Akt, inactivating GSK-3β, and activating Nrf2. These findings may provide novel insights for the alleviation of IIR injury.β/Nrf2 pathway.

Dexmedetomidine preconditioning alleviated murine liver ischemia and reperfusion injury by promoting macrophage M2 activation via PPARγ/STAT3 signaling

BACKGROUND

Although a protective role of dexmedetomidine in liver ischemia and reperfusion (IR) injury has been reported, the underlying mechanism remains to be determined. The aim of this study is to analyze the effects of dexmedetomidine on the regulation of macrophage innate immune activation during liver IR.

METHODS

Mice were randomly divided into dexmedetomidine preconditioning (DEX) and phosphate buffered saline vehicle control (VEH) groups. A murine 70% warm liver IR model was used, and liver injury and intrahepatic inflammation was compared between groups. Bone marrow-derived macrophages (BMDMs) were stimulated with LPS in the presence or absence of dexmedetomidine. The inflammatory cytokine production was measured, and the macrophage M1/M2 polarization was determined in different groups. The underlying mechanism of dexmedetomidine in regulating macrophage M2 activation was also analyzed.

RESULTS

Compared to mice observed in the control group, mice in the DEX group showed reduced liver injury and diminished proinflammatory immune responses in livers post IR. In vitro, dexmedetomidine pretreatment promoted BMDMs M2 activation, as evidenced by increased Arg1 and Mrc1 gene induction, decreased iNOS gene induction, inhibited phosphorated-signal transducer and activator of transcription 1 (p-STAT1) but enhanced p-STAT6 expression, much lower levels of proinflammatory TNF-α and IL-6, and higher levels of anti-inflammatory IL-10 cytokine secretion. Signaling pathway analysis revealed that peroxisome proliferator-activated receptor-γ (PPARγ)/ STAT3 activation was upregulated in BMDMs with dexmedetomidine pretreatment. Furthermore, PPARγ knockdown by siRNA not only inhibited STAT3 activation but also abrogated the promotion effects of macrophage M2 activation in BMDMs pretreated with dexmedetomidine. Finally, in vivo PPARγ inhibition in macrophages by siRNA significantly increased liver IR injury and intrahepatic inflammation in mice from the Dex group, with no significant effect in the VEH group.

CONCLUSIONS

Our results indicate that dexmedetomidine preconditioning inhibited intrahepatic proinflammatory innate immune activation by promoting macrophage M2 activation in a PPARγ/STAT3 dependent manner. Our results demonstrate a novel innate immune regulatory mechanism by dexmedetomidine preconditioning during liver IR injury.

The Upstream Pathway of mTOR-Mediated Autophagy in Liver Diseases

Autophagy, originally found in liver experiments, is a cellular process that degrades damaged organelle or protein aggregation. This process frees cells from various stress states is a cell survival mechanism under stress stimulation. It is now known that dysregulation of autophagy can cause many liver diseases. Therefore, how to properly regulate autophagy is the key to the treatment of liver injury. mechanistic target of rapamycin (mTOR)is the core hub regulating autophagy, which is subject to different upstream signaling pathways to regulate autophagy. This review summarizes three upstream pathways of mTOR: the phosphoinositide 3-kinase (PI3K)/protein kinase (AKT) signaling pathway, the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway, and the rat sarcoma (Ras)/rapidly accelerated fibrosarcoma (Raf)/mitogen-extracellular activated protein kinase kinase (MEK)/ extracellular-signal-regulated kinase (ERK) signaling pathway, specifically explored their role in liver fibrosis, hepatitis B, non-alcoholic fatty liver, liver cancer, hepatic ischemia reperfusion and other liver diseases through the regulation of mTOR-mediated autophagy. Moreover, we also analyzed the crosstalk between these three pathways, aiming to find new targets for the treatment of human liver disease based on autophagy.

Protective Role of mTOR in Liver Ischemia/Reperfusion Injury: Involvement of Inflammation and Autophagy

Liver ischemia/reperfusion (IR) injury is a common phenomenon after liver resection and transplantation, which often results in liver graft dysfunction such as delayed graft function and primary nonfunction. The mammalian target of rapamycin (mTOR) is an evolutionarily highly conserved serine/threonine protein kinase, which coordinates cell growth and metabolism through sensing environmental inputs under physiological or pathological conditions, involved in the pathophysiological process of IR injury. In this review, we mainly present current evidence of the beneficial role of mTOR in modulating inflammation and autophagy under liver IR to provide some evidence for the potential therapies for liver IR injury.

Combined ischemic and rapamycin preconditioning alleviated liver ischemia and reperfusion injury by restoring autophagy in aged mice

Old livers are more damaged by hepatic ischemia and reperfusion (IR) injury than young livers. The aim of this study was to investigate the effects of ischemic and rapamycin preconditioning on IR injury in old livers. Young (8-week-old) and aged (60-week-old) mice were subjected to IR or a sham control procedure. The aged mice were randomly divided into six groups: IR (CON), IR with ischemic preconditioning (IPC), IR with rapamycin preconditioning (RAPA), IR with combined ischemic and rapamycin preconditioning (IPC + RAPA), IR with 3-methyladenine (3-MA), IR with combined ischemic and rapamycin preconditioning with 3-MA pretreatment (IPC + RAPA+3-MA). Liver injury was evaluated 6 h after reperfusion. Hepatocellular autophagy induction was also analyzed by western blotting. The results revealed that aged mice had aggravated liver IR injury as compared to young mice. In aged mice following IR, IPC + RAPA but not IPC or RAPA alleviated liver injury, as evidenced by lower levels of serum ALT, improved preservation of liver architecture with lower Suzuki scores, and decreased caspase-3 activity compared with CON. In addition, western blot analysis revealed increased LC3B II but decreased p62 protein expression levels in the IPC + RAPA group, indicating that autophagic flux was restored by combined ischemic and rapamycin preconditioning. Furthermore, autophagy inhibition by the inhibitor 3-MA abrogated the protective role in the IPC + RAPA group, while no significant effects were observed in the CON group. In conclusions, our results demonstrated that combined ischemic and rapamycin preconditioning protected old livers against IR injury, which was likely attributed to restored autophagy activation.

Attenuating oxygen-glucose deprivation-caused autophagosome accumulation may be involved in sevoflurane postconditioning-induced protection in human neuron-like cells

Application of the commonly used volatile anesthetic sevoflurane after brain ischemia (sevoflurane postconditioning) attenuates ischemic brain injury. It is not known whether autophagy plays a role in this sevoflurane postconditioning-induced neuroprotection. Human SH-SY5Y cells were induced to become neuron-like cells. These cells were subjected to 1 h oxygen-glucose deprivation (OGD) and then exposed to sevoflurane for 1 h. Chloroquine, an inhibitor of autolysosomes, rapamycin, an autophagy inducer, or 3-methyladenine (3-MA), an autophagy inhibitor, were incubated with cells during OGD and sevoflurane exposure. OGD and the subsequent simulated reperfusion increased lactate dehydrogenase (LDH) release from the cells. This increase was dose-dependent inhibited by sevoflurane postconditioning. OGD increased the ratio of microtubule-associated protein 1 light chain 3 (LC3) II to LC3I and the expression of beclin-1 and p62. These increases were attenuated by sevoflurane. Sevoflurane alone did not have any effects on the expression of p62, beclin-1 and the ratio of LC3II to LC3I. Sevoflurane also enhanced the co-location of autophagosomes and lysosomes. Chloroquine increased the ratio of LC3II to LC3I, p62 and LDH release in cells subjected to OGD. Sevoflurane postconditioning attenuated OGD-induced inactivation of Akt and mechanistic target of rapamycin (mTOR). Inducing autophagosome generation by rapamycin attenuated sevoflurane postconditioning-reduced LDH release. Inhibition of autophagosome generation by 3-MA decreased OGD-induced LDH release. These results suggest that OGD increase autophagosome accumulation via increased formation of autophagosomes and reduced autophagosome clearance and that attenuation of OGD-induced autophagosome accumulation may contribute to sevoflurane postconditioning-induced cell protection.

Inhibition of glycogen synthase kinase 3β protects liver against ischemia/reperfusion injury by activating 5' adenosine monophosphate-activated protein kinase-mediated autophagy

AIM

Autophagy has been found to play an important role in hepatic ischemia/reperfusion (I/R) injury. Our previous study has also clarified that rictor deficiency aggravated hepatic I/R injury by suppressing autophagy. Here, we explore whether autophagy participates in glycogen synthase kinase 3β (GSK3β)-mediated cytoprotection in liver I/R.

METHODS

Mice were treated with SB216763 to inhibit GSK3β before being subjected to hepatic I/R. Liver injury was evaluated by liver and blood samples. Autophagy was measured by detecting expression of microtubule-associated protein 1 light chain-3B (LC3B) II and autophagy protein 5 (ATG-5), as well as the number of autophagosomes by transmission electron microscope. Primary hepatocytes pretreated with SB216763 for 2 h were subjected to hypoxia/reoxygenation to induce autophagy. The lactate dehydrogenase level was used to evaluate cell death and survival. Autophagy inhibitors and 5' adenosine monophosphate-activated protein kinase (AMPK) inhibitor were given in vivo or in vitro.

RESULTS

SB216763 significantly increased the number of autophagosomes and the protein levels of LC3B II and ATG-5 in liver I/R models, which was accompanied by a decline of hepatic necrosis and apoptosis. Consistent with the in vivo study, autophagy and cytoprotection were induced by the inhibition of GSK3β in the in vitro study. Moreover, pretreatment with autophagy inhibitors attenuated the cytoprotective role of autophagy in the GSK3β-treated liver I/R models. Further analysis showed that pretreatment with an AMPK inhibitor increased mammalian target of rapamycin (mTOR) activity, decreased autophagy, and abrogated GSK3β- mediated liver protection.

CONCLUSION

Autophagy was induced by GSK3β inhibition through the AMPK/mTOR pathway and could substantially ameliorate liver I/R injury. Therefore, our findings strongly renew the therapeutic value of the GSK3β/autophagy axis in hepatic I/R injury.

Novel therapeutic strategies for stroke: The role of autophagy

Autophagy is an important biological mechanism involved in the regulation of numerous fundamental cellular processes that are mainly associated with cellular growth and differentiation. Autophagic pathways are vital for maintaining cellular homeostasis by enhancing the turnover of nonfunctional proteins and organelles. Neuronal cells, like other eukaryotic cells, are dependent on autophagy for neuroprotection in response to stress, but can also induce cell death in cerebral ischemia. Recent studies have demonstrated that autophagy may induce neuroprotection following acute brain injury, including ischemic stroke. However in some special circumstances, activation of autophagy can induce cell death, playing a deleterious role in the etiology and progression of ischemic stroke. Currently, there are no therapeutic options against stroke that demonstrate efficient neuroprotective abilities. In the present work, we will review the significance of autophagy in the context of ischemic stroke by first outlining its role in ischemic neuronal death. We will also highlight the potential therapeutic applications of pharmacological modulators of autophagy, including some naturally occurring polyphenolic compounds that can target this catabolic process. Our findings provide renewed insight on the mechanism of action of autophagy in stroke together with potential neuroprotective compounds, which may partially exert their function through enhancing mitochondrial function and attenuating damaging autophagic processes.

Cellular stress and AMPK links metformin and diverse compounds with accelerated emergence from anesthesia and potential recovery from disorders of consciousness

The neural correlates of consciousness and the mechanisms by which general anesthesia (GA) modulate such correlates to induce loss of consciousness (LOC) has been described as one of the biggest mysteries of modern medicine. Several cellular targets and neural circuits have been identified that play a critical role in LOC induced by GA, including the GABAA receptor and ascending arousal nuclei located in the basal forebrain, hypothalamus, and brain stem. General anesthetics (GAs) including propofol and inhalational agents induce LOC in part by potentiating chloride influx through the GABAA receptor, leading to neural inhibition and LOC. Interestingly, nearly all GAs used clinically may also induce paradoxical excitation, a phenomenon in which GAs promote neuronal excitation at low doses before inducing unconsciousness. Additionally, emergence from GA, a passive process that occurs after anesthetic removal, is associated with lower anesthetic concentrations in the brain compared to doses associated with induction of GA. AMPK, an evolutionarily conserved kinase activated by cellular stress (e.g. increases in calcium [Ca2+] and/or reactive oxygen species [ROS], etc.) increases lifespan and healthspan in several model organisms. AMPK is located throughout the mammalian brain, including in neurons of the thalamus, hypothalamus, and striatum as well as in pyramidal neurons in the hippocampus and cortex. Increases in ROS and Ca2+ play critical roles in neuronal excitation and glutamate, the primary excitatory neurotransmitter in the human brain, activates AMPK in cortical neurons. Nearly every neurotransmitter released from ascending arousal circuits that promote wakefulness, arousal, and consciousness activates AMPK, including acetylcholine, histamine, orexin-A, dopamine, and norepinephrine. Several GAs that are commonly used to induce LOC in human patients also activate AMPK (e.g. propofol, sevoflurane, isoflurane, dexmedetomidine, ketamine, midazolam). Various compounds that accelerate emergence from anesthesia, thus mitigating problematic effects associated with delayed emergence such as delirium, also activate AMPK (e.g. nicotine, caffeine, forskolin, carbachol). GAs and neurotransmitters also act as preconditioning agents and the GABAA receptor inhibitor bicuculline, which reverses propofol anesthesia, also activates AMPK in cortical neurons. We propose the novel hypothesis that cellular stress-induced AMPK activation links wakefulness, arousal, and consciousness with paradoxical excitation and accelerated emergence from anesthesia. Because AMPK activators including metformin and nicotine promote proliferation and differentiation of neural stem cells located in the subventricular zone and the dentate gyrus, AMPK activation may also enhance brain repair and promote potential recovery from disorders of consciousness (i.e. minimally conscious state, vegetative state, coma).

Isoflurane Preconditioning Attenuates Brain Injury Induced by Electromagnetic Pulse via the TLR4/NFκB Signaling Pathway

Electromagnetic pulse (EMP) is a unique type of electromagnetic radiation, and EMP exposure causes a series of biological effects. The nervous system is sensitive to EMP. We studied the neuroprotective effects of isoflurane preconditioning against EMP exposure and used hematoxylin-eosin staining (HE) to observe the effects of electromagnetic pulse and isoflurane preconditioning on neurons. Inflammatory cytokines were detected by enzyme-linked immunosorbent assay (ELISA). Western blotting was used to detect the expression of caspase-3, CD11b, TLR4, and NFκBp65. We found that after EMP exposure, the number of abnormal neurons had increased, and the expression of caspase-3, CD11b, TLR4, and NFκBp65 had also increased. Isoflurane preconditioning can reverse the above phenomenon. Moreover, we found that isoflurane preconditioning can reduce neuronal apoptosis and improve cognitive impairment induced by EMP. These findings indicate that isoflurane preconditioning can protect neurons in the cerebral cortex from EMP exposure, alleviate the inflammatory reaction and cell apoptosis, and improve cognitive impairment induced by EMP. These effects may occur through the downregulation of the TLR4/NFκB signaling pathway and the inhibition of microglial activation.

Propofol inhibited autophagy through Ca2+/CaMKKβ/AMPK/mTOR pathway in OGD/R-induced neuron injury

Background

The neuroprotective role of propofol (PPF) in cerebral ischemia-reperfusion (I/R) has recently been highlighted. This study aimed to explore whether the neuroprotective mechanisms of PPF were linked to its regulation of Ca²⁺/CaMKKβ (calmodulin-dependent protein kinase kinase β)/AMPK (AMP-activated protein kinase)/mTOR (mammalian target of rapamycin)/autophagy pathway.

Methods

Cultured primary rat cerebral cortical neurons were treated with oxygen-glucose deprivation and re-oxygenation (OGD/R) to mimic cerebral I/R injury in vitro.

Results

Compared with the control neurons, OGD/R exposure successfully induced neuronal I/R injury. Furthermore, OGD/R exposure notably caused autophagy induction, reflected by augmented LC3-II/LC3-I ratio and Beclin 1 expression, decreased p62 expression, and increased LC3 puncta formation. Moreover, OGD/R exposure induced elevation of intracellular Ca²⁺ concentration ([Ca²⁺]i). However, PPF treatment significantly antagonized OGD/R-triggered cell injury, autophagy induction, and [Ca²⁺]i elevation. Further investigation revealed that both autophagy induction by rapamycin and [Ca²⁺]i elevation by the Ca²⁺ ionophore ionomycin significantly reversed the PPF-mediated amelioration of OGD/R-triggered cell injury. Importantly, ionomycin also significantly abrogated the PPF-mediated suppression of autophagy and CaMKKβ/AMPK/mTOR signaling in OGD/R-exposed neurons. Additionally, activation of CaMKKβ/AMPK/mTOR signaling abrogated the PPF-mediated autophagy suppression.

Conclusion

Our findings demonstrate that PPF antagonized OGD/R-triggered neuronal injury, which might be mediated, at least in part, via inhibition of autophagy through Ca²⁺/CaMKKβ/AMPK/mTOR pathway.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0054-1) contains supplementary material, which is available to authorized users.

Volatile Anesthetic Isoflurane Attenuates Liver Injury in Experimental Polymicrobial Sepsis Model

Volatile anesthetics are often administered to patients with sepsis for procedural anesthesia or sedation in intensive care units. Sepsis still carries significant morbidities and mortalities, and organ injuries pose major complications. Early liver dysfunction is associated with poor outcome mainly as a result of overwhelming neutrophil recruitment. Leukocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1) are major adhesion molecules on neutrophils and involved in neutrophil recruitment. We have previously showed that volatile anesthetic isoflurane inhibited LFA-1 and Mac-1. Here we studied the role of isoflurane, LFA-1 and Mac-1 on neutrophil recruitment to the liver and liver injury using experimental polymicrobial abdominal sepsis induced by cecal ligation and puncture (CLP) surgery. We used wild type (WT), LFA-1, Mac-1 and intercellular adhesion molecule-1 (ICAM-1) knockout (KO) mice. Following the induction of sepsis by CLP surgery, a group of mice were exposed to isoflurane for 2 hours. We found that Mac-1 and ICAM-1, but not LFA-1 were involved in neutrophil recruitment to liver. Isoflurane attenuated neutrophil recruitment and liver injury in WT and LFA-1 KO mice. Mac-1 KO mice had limited neutrophil recruitment and liver injury, both of which were not attenuated by isoflurane further, suggesting that isoflurane mitigated liver injury via Mac-1. Mac-1 colocalized with ICAM-1 and fibrinogen on liver tissues. In the presence of fibrinogen Mac-1 bound ICAM-1 significantly more, while LFA-1 bound less to ICAM-1, suggesting that Mac-1 used fibrinogen as a bridging molecule to bind ICAM-1. In conclusion, isoflurane exposure attenuated neutrophil recruitment and liver injury via Mac-1.

Transposable elements, placental development, and oocyte activation: Cellular stress and AMPK links jumping genes with the creation of human life

Transposable elements (TEs), also known as "jumping genes", are DNA sequences first described by Nobel laureate Barbara McClintock that comprise nearly half of the human genome and are able to transpose or move from one genomic location to another. As McClintock also noted that a genome "shock" or stress may induce TE activation and transposition, accumulating evidence suggests that cellular stress (e.g. mediated by increases in intracellular reactive oxygen species [ROS] and calcium [Ca2+], etc.) induces TE mobilization in several model organisms and L1s (a member of the retrotransposon class of TEs) are active and capable of retrotransposition in human oocytes, human sperm, and in human neural progenitor cells. Cellular stress also plays a critical role in human placental development, with cytotrophoblast (CTB) differentiation leading to the formation of the syncytiotrophoblast (STB), a cellular layer that facilitates nutrient and gas exchange between the mother and the fetus. Syncytin-1, a protein that promotes fusion of CTB cells and is necessary for STB formation, and its receptor is found in human sperm and human oocytes, respectively, and increases in ROS and Ca2+ promote trophoblast differentiation and syncytin-1 expression. Cellular stress is also essential in promoting human oocyte maturation and activation which, similar to TE mobilization, can be induced by compounds that increase intracellular Ca2+ and ROS levels. AMPK is a master metabolic regulator activated by increases in ROS, Ca2+, and/or an AMP(ADP)/ATP ratio increase, etc. as well as compounds that induce L1 mobilization in human cells. AMPK knockdown inhibits trophoblast differentiation and AMPK-activating compounds that promote L1 mobility also enhance trophoblast differentiation. Cellular stressors that induce TE mobilization (e.g. heat shock) also promote oocyte maturation in an AMPK-dependent manner and the antibiotic ionomycin activates AMPK, promotes TE activation, and induces human oocyte activation, producing normal, healthy children. Metformin promotes AMPK-dependent telomerase activation (critical for telomere maintenance) and induces activation of the endonuclease RAG1 (promotes DNA cleavage and transposition) via AMPK. Both RAG1 and telomerase are derived from TEs. It is our hypothesis that cellular stress and AMPK links TE activation and transposition with placental development and oocyte activation, facilitating both human genome evolution and the creation of all human life. We also propose the novel observation that various cellular stress-inducing compounds (e.g. metformin, resveratrol, etc.) may facilitate beneficial TE activation and transposition and enhance fertilization and embryological development through a common mechanism of AMPK activation.

Genipin alleviates vascular hyperpermeability following hemorrhagic shock by up-regulation of SIRT3/autophagy

Genipin (GP) is commonly used to treat cardiovascular diseases; however, the protective action of GP against vascular hyperpermeability (VH) has not been reported. We previously reported that intrinsic apoptotic signaling (IAS) is involved in VH following hemorrhagic shock (HS). GP inhibits apoptosis, but the specific mechanism remains unclear. In the present study, we observed that GP protects against HS-induced VH in vitro and in vivo. We report that this protective effect is related to the inhibition of IAS by up-regulation of autophagy via sirtuin 3 (SIRT3). The endothelial cell hyperpermeability induced by HS was enhanced by GP; this was attenuated by 3-methyladenine (3MA), a specific inhibitor of autophagy, indicating the involvement of autophagy. Consistent with these results, we found that 3MA reversed the effects of GP on up-regulation of autophagy, and also diminished the protective effect of GP against IAS activation following HS. Furthermore, knockout of SIRT3 inhibited GP-induced autophagy, indicating the requirement of SIRT3 in the regulation of autophagy by GP. In rats, GP improved HS-induced VH, which was repressed by 3MA and 3-(1H-1,2,3-triazol-4-yl)pyridine (3-TYP), a SIRT3 inhibitor. In conclusion, these findings suggest that autophagy plays a protective effect in VH following HS; the protective effect of autophagy is reinforced by GP, which protects against IAS and VH by up-regulating SIRT3.

Hydrogen sulfide and autophagy: A double edged sword

Hydrogen sulfide (H₂S) has been considered the third gaseous signaling molecule that plays important roles in a wide range of physiological and pathological conditions. However, there has been some controversy on the role of H₂S in autophagy. Recent studies indicate that a number of signaling pathways are involved in the pro-autophagy effect of H₂S, such as PI3K/Akt/mTOR, AMPK/mTOR, LKB1/STRAD/MO25, and miR-30c signaling pathways. On the other hand, there are many signaling pathways that play important roles in the anti-autophagy effect of H₂S, including SR-A, PI3K/SGK1/GSK3β, PI3K/AKT/mTOR, Nrf2-ROS-AMPK, AMPK/mTOR, and JNK1 signaling pathways. Novel H₂S-releasing donors/drugs could be designed and identified in order to increase the therapeutic effects by mediating autophagy in human diseases. In this review, the H₂S metabolism in mammals is summarized and the effects of signaling pathways in H₂S-mediated autophagy are further discussed.