Complete induction of autophagy is essential for cardioprotection in sepsis

Emerging roles of mitochondria and autophagy in liver injury during sepsis

Recent research indicates crucial roles of autophagy during sepsis. In animal models of sepsis induced by cecal ligation and puncture (CLP) or the systemic administration of lipopolysaccharides (LPS), autophagy is implicated in the activation and/or damage of various cells/organs, such as immune cells, heart, lung, kidney, and liver. Since sepsis is associated with an increased production of pro- as well as anti-inflammatory cytokines, it has long been considered that hypercytokinemia is a fetal immune response leading to multiple organ failure (MOF) and mortality of humans during sepsis. However, a recent paradigm illuminates the crucial roles of mitochondrial dysfunction as well as the perturbation of autophagy in the pathogenesis of sepsis. In the livers of animal models of sepsis, autophagy is involved in the elimination of damaged mitochondria to prevent the generation of mitochondrial ROS and the initiation of the mitochondrial apoptotic pathway. In addition, many reports now indicate that the role of autophagy is not restricted to the elimination of hazardous malfunctioning mitochondria within the cells; autophagy has been shown to be involved in the regulation of inflammasome activation and the release of cytokines as well as other inflammatory substances. In this review, we summarize recent literature describing the versatile role of autophagy and its possible implications in the pathogenesis of sepsis in the liver.

Rapamycin Protects Sepsis-Induced Cognitive Impairment in Mouse Hippocampus by Enhancing Autophagy

The purpose of this study is to test the hypothesis that the mammalian target of rapamycin (mTOR) signaling pathway might mediate neuroprotection in a mouse model of septic encephalopathy and also to identify the role of autophagy. Mice were subjected to cecal ligation and puncture (CLP) or a sham operation, and all 50 mice were randomly assigned to five groups: sham, CLP+ saline, CLP+ rapamycin (1, 5, 10 mg/kg) groups. Two weeks after the operation, Morris water maze was conducted for behavioral test; Nissl staining was used for observing glia infiltration; immunohistochemical staining and biochemical measures in hippocampi were performed to detect mTOR targets and autophagy indicators. Immunochemistry revealed significant loss of neurons and increased glia infiltration in hippocampus after CLP operation. Inhibition of mTOR by rapamycin rescued cognitive deficits caused by sepsis (p < 0.05). Rapamycin did not affect total mTOR targets, while phosphorylated mTOR targets (p-mTOR-Ser2448, p-p70S6k-Thr389, p-AKT-S473) decreased (p < 0.05) and autophagy indicators (LC3-II, Atg5, Atg7) were increased, and P62 was decreased in rapamycin-treated CLP mice compared with the untreated (p < 0.05) in hippocampus. Rapamycin improves learning after sepsis through enhancing autophagy and may be a potentially effective therapeutic agent for the treatment of sepsis-induced cognitive impairment.

Autophagy Primes Neutrophils for Neutrophil Extracellular Trap Formation during Sepsis

RATIONALE

Neutrophils are key effectors in the host's immune response to sepsis. Excessive stimulation or dysregulated neutrophil functions are believed to be responsible for sepsis pathogenesis. However, the mechanisms regulating functional plasticity of neutrophils during sepsis have not been fully determined.

OBJECTIVES

We investigated the role of autophagy in neutrophil functions during sepsis in patients with community-acquired pneumonia.

METHODS

Neutrophils were isolated from patients with sepsis and stimulated with phorbol 12-myristate 13-acetate (PMA). The levels of reactive oxygen species generation, neutrophil extracellular trap (NET) formation, and granule release, and the autophagic status were evaluated. The effect of neutrophil autophagy augmentation was further evaluated in a mouse model of sepsis.

MEASUREMENTS AND MAIN RESULTS

Neutrophils isolated from patients who survived sepsis showed an increase in autophagy induction, and were primed for NET formation in response to subsequent PMA stimulation. In contrast, neutrophils isolated from patients who did not survive sepsis showed dysregulated autophagy and a decreased response to PMA stimulation. The induction of autophagy primed healthy neutrophils for NET formation and vice versa. In a mouse model of sepsis, the augmentation of autophagy improved survival via a NET-dependent mechanism.

CONCLUSIONS

These results indicate that neutrophil autophagy primes neutrophils for increased NET formation, which is important for proper neutrophil effector functions during sepsis. Our study provides important insights into the role of autophagy in neutrophils during sepsis.

Association between genetic polymorphisms in the autophagy-related 5 gene promoter and the risk of sepsis

Previous studies demonstrated significant roles of autophagy in the pathogenesis of sepsis, but few studies focused on the effect of autophagy-related SNPs on sepsis susceptibility. In this present study, five polymorphisms of ATG5/ATG16L1 were investigated for the possible risk on sepsis in a Chinese Han population. Our results showed that ATG5 expression levels decreased with the severity of sepsis, and rs506027 T > C and rs510432 G > A were associated with sepsis progression and mortality. Moreover, the rs506027 TT and rs510432 GG carriers also exhibited increased expression levels of ATG5. Functional assays showed that ATG5 knockdown elevated the secretion of pro-inflammatory cytokines in THP-1 cells, and the extracted mononuclear cell of the risk C-A carriers exhibited decreased ATG5 expression levels, leading to enhanced releases of TNF-α and IL-1β under LPS stimulation in vitro. Furthermore, ATG5 T-G haplotype mutation showed higher promoter activities compared to C-A haplotype mutation, suggesting the effect of these SNPs on ATG5 gene transcription. Taken together, these results above indicated that these two ATG5 promoter polymorphisms may be functional and clinically significant for sepsis progression, underscoring its potentially therapeutic implications for sepsis and other inflammatory diseases.

Recovery from critical illness-induced organ failure: the role of autophagy

Autophagy is a catabolic process by which cells can dispose of damaged content and intracellular microorganisms. Recent evidence implicates autophagy as a crucial repair process necessary to recover from critical illness-induced organ failure. Withholding parenteral nutrition in the acute phase of critical illness activates autophagy and enhances recovery. Several registered drugs have autophagy-stimulating properties, but all lack specificity and none has been investigated in critically ill patients for this purpose.

Apigenin Alleviates Endotoxin-Induced Myocardial Toxicity by Modulating Inflammation, Oxidative Stress, and Autophagy

Apigenin, a component in daily diets, demonstrates antioxidant and anti-inflammatory properties. Here, we intended to explore the mechanism of apigenin-mediated endotoxin-induced myocardial injury and its role in the interplay among inflammation, oxidative stress, and autophagy. In our lipopolysaccharide- (LPS-) induced myocardial injury model, apigenin ameliorated cardiac injury (lactate dehydrogenase (LDH) and creatine kinase (CK)), cell death (TUNEL staining, DNA fragmentation, and PARP activity), and tissue damage (cardiac troponin I (cTnI) and cardiac myosin light chain-1 (cMLC1)) and improved cardiac function (ejection fraction (EF) and end diastolic left ventricular inner dimension (LVID)). Apigenin also alleviated endotoxin-induced myocardial injury by modulating oxidative stress (nitrotyrosine and protein carbonyl) and inflammatory cytokines (TNF-α, IL-1β, MIP-1α, and MIP-2) along with their master regulator NFκB. Apigenin modulated redox homeostasis, and its anti-inflammatory role might be associated with its ability to control autophagy. Autophagy (determined by LAMP1, ATG5, and p62), its transcriptional regulator transcription factor EB (TFEB), and downstream target genes including vacuolar protein sorting-associated protein 11 (Vps11) and microtubule-associated proteins 1A/1B light chain 3B (Map1lc3) were modulated by apigenin. Thus, our study demonstrated that apigenin may lead to potential development of new target in sepsis treatment or other myocardial oxidative and/or inflammation-induced injuries.

Delta opioid receptor agonist attenuates lipopolysaccharide-induced myocardial injury by regulating autophagy

BACKGROUND

Previous studies have described the protective effects of DADLE on myocardial injury in sepsis. Recently, autophagy has been shown to be an innate defense mechanism in sepsis-related myocardial injury. However, whether DADLE has an pro-autophagic effect is yet to be elucidated. The present study aimed to investigate the effect of DADLE on the regulation of autophagy during sepsis.

METHODS

Male mice were subjected to LPS or vehicle intraperitoneal injection. After LPS injection, mice received either DADLE, Naltrindole or vehicle. ELISA and JC-1 were used to evaluate the level cTnI and Mitochondrial membrane potential. Cardiac ultrastructural and autophagosomes were visualized by transmission electron microscopy. The relative protein levels were analyzed by Western blot.

RESULTS

The results showed that treatment with DADLE both immediately or 4 h after LPS intraperitoneal injection could improve the survival rate of mice with endotoxemic. DADLE could ease myocardium ultrastructure injury induced by LPS, this cardioprotective effect was also seen in increased MMP levels, and decreased cTnI levels. Through observation of transmission electron microscopy and Western blot we have discovered that the amount of autophagosome and the expression of autophagy related protein LC3II, Beclin1 were significantly increased with DADLE treatment. DADLE promoted LPS-induced autophagosome maturation as indicated by the increased LAMP-1 protein level and decreased SQSTM1/p62 protein level. The selective δ-opioid receptor antagonist Naltrindole play an opposite effects.

CONCLUSIONS

DADLE could improve the survival and protect myocardial dysfunction in mice with LPS-induced endotoxemia. This effect was related to the increase of autophagy.

Niclosamide attenuates inflammatory cytokines via the autophagy pathway leading to improved outcomes in renal ischemia/reperfusion injury

Renal ischemia/reperfusion (I/R) injury is a debilitating condition that leads to loss renal function and damage to kidney tissue in the majority of patients with acute kidney disease. Previous studies have indicated that autophagy serves a protective function in renal I/R injury. In the present study, the effect of the anthelmintic niclosamide in the regulation of inflammatory responses in kidney I/R was investigated. A total of 40 Sprague-Dawley rats were randomly divided into the following 5 groups (n=8 in each group): Sham group; renal I/R injury; renal I/R injury plus 3-methyladenine (3-MA) treatment (15 mg/kg); renal I/R injury plus niclosamide (25 mg/kg); and renal I/R injury plus rapamycin (10 mg/kg). The expression levels of autophagy-associated proteins in kidney samples obtained from rats with I/R injury were examined using reverse transcription-quantitative polymerase chain reaction and western blotting techniques. In addition, histopathological alterations, the expression of cytokines and renal function were evaluated. Treatment with niclosamide was associated with induction of autophagy and an overall improvement in renal function. There was an increased expression of autophagosome-associated proteins, suggesting a strong correlation between autophagy and improvement of renal function. The increased levels of anti-inflammatory cytokines and decreased levels of pro-inflammatory cytokines provided additional evidence that niclosamide may be effective for the treatment of renal I/R injury. Clinical studies are required to further validate the results of the present study.

Suppression of T Cell Autophagy Results in Decreased Viability and Function of T Cells Through Accelerated Apoptosis in a Murine Sepsis Model

Supplemental Digital Content is available in the text.

Objective:

While type 1 programmed cell death (apoptosis) of T cells leads to immunosuppression in sepsis, a crosstalk between apoptosis and autophagy (type 2 programmed cell death) has not been shown. The aim of this study is to elucidate the details of the interaction between autophagy and immunosuppression.

Design:

Laboratory investigation in the murine sepsis model.

Setting:

University laboratory.

Subjects:

Six- to 8-week-old male mice.

Interventions:

We investigated the kinetics of autophagy in T cells from spleen in a cecal ligation and puncture model with green fluorescent protein-microtubule-associated protein light chain 3 transgenic mice. We analyzed apoptosis, mitochondrial homeostasis and cytokine production in T cells, and survival rate after cecal ligation and puncture using T cell–specific autophagy-deficient mice.

Measurements and Main Results:

We observed an increase of autophagosomes, which was assessed by flow cytometry. However, an autophagy process in CD4⁺ T cells during sepsis was insufficient including the accumulation of p62. On the other hand, a blockade of autophagy accelerated T cell apoptosis compared with the control mice, augmenting the gene expression of Bcl-2-like 11 and programmed cell death 1. Furthermore, mitochondrial accumulation in T cells occurred via a blockade of autophagy during sepsis. In addition, interleukin-10 production in CD4⁺ T cells from the cecal ligation and puncture–operated knockout mice was markedly increased. Consequently, deficiency of autophagy in T cells significantly decreased the survival rate in the murine sepsis model.

Conclusions:

We demonstrated that blocking autophagy accelerated apoptosis and increased mortality in concordance with the insufficient autophagy process in CD4⁺ T cells in the murine sepsis model, suggesting that T cell autophagy plays a protective role against apoptosis and immunosuppression in sepsis.

Mitochondrial and endoplasmic reticulum dysfunction and related defense mechanisms in critical illness-induced multiple organ failure

Patients with critical illness-induced multiple organ failure suffer from a very high morbidity and mortality, despite major progress in intensive care. The pathogenesis of this condition is complex and incompletely understood. Inadequate tissue perfusion and an overwhelming inflammatory response with pronounced cellular damage have been suggested to play an important role, but interventions targeting these disturbances largely failed to improve patient outcome. Hence, new therapeutic perspectives are urgently needed. Cellular dysfunction, hallmarked by mitochondrial dysfunction and endoplasmic reticulum stress, is increasingly recognized as an important contributor to the development of organ failure in critical illness. Several cellular defense mechanisms are normally activated when the cell is in distress, but may fail or respond insufficiently to critical illness. This insight may open new therapeutic options by stimulating these cellular defense mechanisms. This review summarizes the current understanding of the role of mitochondrial dysfunction and endoplasmic reticulum stress in critical illness-induced multiple organ failure and gives an overview of the corresponding cellular defense mechanisms. Therapeutic perspectives based on these cellular defense mechanisms are discussed. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

TLR4 knockout attenuated high fat diet-induced cardiac dysfunction via NF-κB/JNK-dependent activation of autophagy

Obesity is commonly associated with a low grade systemic inflammation, which may contribute to the onset and development of myocardial remodeling and contractile dysfunction. Toll-like receptor 4 (TLR4) plays an important role in innate immunity and inflammation although its role in high fat diet-induced obesity cardiac dysfunction remains elusive. This study was designed to examine the effect of TLR4 ablation on high fat diet intake-induced cardiac anomalies, if any, and underlying mechanism(s) involved. Wild-type (WT) and TLR4 knockout mice were fed normal or high fat (60% calorie from fat) diet for 12weeks prior to assessment of mechanical and intracellular Ca²⁺ properties. The inflammatory signaling proteins (TLR4, NF-κB, and JNK) and autophagic markers (Atg5, Atg12, LC3B and p62) were evaluated. Our results revealed that high fat diet intake promoted obesity, marked decrease in fractional shortening, and cardiomyocyte contractile capacity with dampened intracellular Ca²⁺ release and clearance, elevated ROS generation and oxidative stress as measured by aconitase activity, the effects of which were significantly attenuated by TLR4 knockout. In addition, high fat intake downregulated levels of Atg5, Atg12 and LC3B, while increasing p62 accumulation. TLR4 knockout itself did not affect Atg5, Atg12, LC3B and p62 levels while it reconciled high fat diet intake-induced changes in autophagy. In addition, TLR4 knockout alleviated high fat diet-induced phosphorylation of IKKβ, JNK and mTOR. In vitro study revealed that palmitic acid suppressed cardiomyocyte contractile function, the effect of which was inhibited the TLR4 inhibitor CLI-095, the JNK inhibitor AS601245 or the NF-κB inhibitor Celastrol. Taken together, these data showed that TLR4 knockout ameliorated high fat diet-induced cardiac contractile and intracellular Ca²⁺ anomalies through inhibition of inflammation and ROS, possibly through a NF-κB/JNK-dependent activation of autophagy. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

Autophagy--A free meal in sickness-associated anorexia

Activation of the immune system is metabolically costly, yet a hallmark of an infection is a reduction in appetite with a subsequent reduction in metabolite provision. What is the functional value of decreasing nutrient intake when an infection imposes large demands on metabolic parameters? Here, we propose that sickness-associated anorexia (SAA) upregulates the ancient process of autophagy systemically, thereby profoundly controlling not only immune- but also nonimmune-competent cells. This allows an advanced impact on the resolution of an infection through direct pathogen killing, enhancement of epitope presentation and the contribution toward the clearance of noxious factors. By rendering a 'free meal,' autophagy is thus most fundamentally harnessed during an anorexic response in order to promote both host tolerance and resistance. These findings strongly suggest a reassessment of numerous SAA-related clinical applications and a re-evaluation of current efforts in patient care.

Ghrelin protects small intestinal epithelium against sepsis-induced injury by enhancing the autophagy of intestinal epithelial cells

BACKGROUND

Ghrelin is a hormone that protects against hypoxic injury of cardiac cells by inducing autophagy, but the role of autophagy in sepsis remains unclear. This study aimed to evaluate whether ghrelin could enhance autophagy in rats with intestinal sepsis.

METHODS

The cecal ligation and perforation (CLP) method was used to induce sepsis in Sprague-Dawley rats. The rats were assigned to four groups: normal group, sham-operated group, sepsis group, and Ghrelin-treated group. Sera and small intestinal tissues were collected from all groups. The sepsis was evaluated by histological analysis, and autophagy of small intestinal epithelial cells was assessed by electron microscopy, immunofluorescence, and biochemical methods.

RESULTS

The expression of autophagy-associated proteins such as LC3, Atg 7 and Beclin 1 increased by 8h post-CLP and declined to basal levels by 12h post-CLP. The expression of LC3, Atg 7 and Beclin 1 in Ghrelin-treated rats was higher than that in rats with sepsis. Furthermore, compared to rats with sepsis, Ghrelin-treated rats showed significantly reduced intestinal mucosa injury at 20h post-CLP.

CONCLUSION

Autophagy is induced in the early stages of sepsis. Ghrelin could enhance the autophagy of intestinal epithelial cells in rats with sepsis and protect the small intestinal epithelium against sepsis-induced injury.

Overexpression of Hypo-Phosphorylated IκBβ at Ser313 Protects the Heart against Sepsis

IκBβis an inhibitor of nuclear factor kappa B(NF-κB) and participates in the cardiac response to sepsis. However, the role of the hypo-phosphorylated form of IκBβ at Ser313, which can be detected during sepsis, is unknown. Here, we examined the effects of IκBβ with a mutation at Ser313→Ala313 on cardiac damage induced by sepsis. Transgenic (Tg) mice were generated to overexpress IκBβ, in which Ser-313 is replaced with alanine ubiquitously, in order to mimic the hypo-phosphorylated form of IκBβ. Survival analysis showed that Tg mice exhibited decreased inflammatory cytokine levels and decreased rates of mortality in comparison to wild type (WT) mice, after sepsis in a cecal-ligation and puncture model (CLP). Compared to WT septic mice, sepsis in Tg mice resulted in improved cardiac functions, lower levels of troponin I and decreased rates of cardiomyocyte apoptosis, compared to WT mice. The increased formation of autophagicvacuoles detected with electron microscopy demonstrated the enhancement of cardiac autophagy. This phenomenon was further confirmed by the differential expression of genes related to autophagy, such as LC3, Atg5, Beclin-1, and p62. The increased expression of Cathepsin L(Ctsl), a specific marker for mitochondrial stress response, may be associated with the beneficial effects of the hypo-phosphorylated form of IκBβ. Our observations suggest that the hypo-phosphorylated form of IκBβ at Ser313 is beneficial to the heart in sepsis through inhibition of apoptosisand enhancement of autophagy in mutated IκBβ transgenic mice.

Autophagy in sepsis: Degradation into exhaustion?

Autophagy is one of the innate immune defense mechanisms against microbial challenges. Previous in vitro and in vivo models of sepsis demonstrated that autophagy was activated initially in sepsis, followed by a subsequent phase of impairment. Autophagy modulation appears to be protective against multiple organ injuries in these murine sepsis models. This is achieved in part by preventing apoptosis, maintaining a balance between the productions of pro- and anti-inflammatory cytokines, and preserving mitochondrial functions. This article aims to discuss the role of autophagy in sepsis and the therapeutic potential of autophagy enhancers.

Endotoxemia Engages the RhoA Kinase Pathway to Impair Cardiac Function By Altering Cytoskeleton, Mitochondrial Fission, and Autophagy

AIMS

The RhoA/ROCK pathway controls crucial biological processes involved in cardiovascular pathophysiology, such as cytoskeleton dynamics, vascular smooth muscle contraction, and inflammation. In this work, we tested whether Rho kinase inhibition would beneficially impact cardiac cytoskeleton organization, bioenergetics, and autophagy in experimental endotoxemia induced by lipopolysaccharides (LPSs) in mice.

RESULTS

Fasudil, a potent ROCK inhibitor, prevented LPS-induced cardiac inflammation, oxidative stress, cytoskeleton disarray, and mitochondrial injury. ROCK inhibition prevented phosphorylation of cofilin and dynamin-related protein-1, which promotes stabilization-polymerization of F-actin and mediates mitochondrial fission, respectively. Pyr1, which exclusively alters actin dynamics, prevented LPS-induced myocardial dysfunction, suggesting that beneficial impact of ROCK inhibition was not mainly related to pleiotropic effects of fasudil on cardiac inflammation and oxidative stress. Fasudil reduced mitochondrial fragmentation, stimulated initiation of autophagy, and elicited cardioprotection in LPS heart. Mdivi-1, a potent mitochondria fission inhibitor, converted cardioprotective autophagy to an inefficient form due to cargo loading failure in which autophagic vacuoles fail to trap cytosolic cargo, despite their formation at enhanced rates and lysosomal elimination.

INNOVATION

In experimental endotoxemia, cardioprotection by RhoA/ROCK inhibition may be related to changes in actin cytoskeleton reorganization and mitochondrial homeostasis. Improvement of LPS-induced mitochondrial dysfunction by fasudil was attributed to inhibition of ROCK-dependent Drp1 phosphorylation and activation of autophagic processes that can limit mitochondrial fragmentation and enhance degradation of damaged mitochondria, respectively.

CONCLUSION

Fasudil prevented LPS-induced heart oxidative stress, abnormal F-actin distribution, and oxidative phosphorylation, which concur to improve cardiac contractile and bioenergetic function. We suggest that fasudil may represent a valuable therapy for patients with sepsis.

Rapamycin Inhibits Cardiac Hypertrophy by Promoting Autophagy via the MEK/ERK/Beclin-1 Pathway

Rapamycin, also known as sirolimus, is an antifungal agent and immunosuppressant drug used to prevent organ rejection in transplantation. However, little is known about the role of rapamycin in cardiac hypertrophy and the signaling pathways involved. Here, the effect of rapamycin was examined using phenylephrine (PE) induced cardiomyocyte hypertrophy in vitro and in a rat model of aortic banding (AB) - induced hypertrophy in vivo. Inhibition of MEK/ERK signaling reversed the effect of rapamycin on the up-regulation of LC3-II, Beclin-1 and Noxa, and the down-regulation of Mcl-1 and p62. Silencing of Noxa or Beclin-1 suppressed rapamycin-induced autophagy, and co-immunoprecipitation experiments showed that Noxa abolishes the inhibitory effect of Mcl-1 on Beclin-1, promoting autophagy. In vivo experiments showed that rapamycin decreased AB-induced cardiac hypertrophy in a MEK/ERK dependent manner. Taken together, our results indicate that rapamycin attenuates cardiac hypertrophy by promoting autophagy through a mechanism involving the modulation of Noxa and Beclin-1 expression by the MEK/ERK signaling pathway.

Clinical application: Restoration of immune homeostasis by autophagy as a potential therapeutic target in sepsis

Sepsis-induced lymphocyte and dendritic cell apoptosis contributes to immunosuppression, resulting in an inability to eradicate the primary infection and a propensity to acquire secondary infections. However, the inhibition of apoptosis may produce unexpected and undesirable consequences. Another cellular process, autophagy, is also activated in immune cells. There is increasing evidence to suggest that autophagy confers a protective effect in sepsis. The protective mechanisms underlying this effect include limiting apoptotic cell death and maintaining cellular homeostasis. Therefore, understanding the regulation of immune cell autophagy and apoptosis may provide insight into novel therapeutic strategies. The present review examined potential novel therapeutic strategies aimed at restoring immune homeostasis by inducing autophagy. The restoration of balance between apoptosis and autophagy may be a novel approach for improving sepsis-induced immunosuppression and decreasing susceptibility to sepsis.

Genipin alleviates sepsis-induced liver injury by restoring autophagy

BACKGROUND AND PURPOSE

Autophagy is an essential cytoprotective system that is rapidly activated in response to various stimuli including inflammation and microbial infection. Genipin, an aglycon of geniposide found in gardenia fruit, is well known to have anti-inflammatory, antibacterial and antioxidative properties. This study examined the protective mechanisms of genipin against sepsis, with particular focus on the autophagic signalling pathway.

EXPERIMENTAL APPROACH

Mice were subjected to sepsis by caecal ligation and puncture (CLP). Genipin (1, 2.5 and 5 mg·kg(-1) ) or vehicle (saline) was injected i.v. immediately (0 h) after CLP, and chloroquine (60 mg·kg(-1) ), an autophagy inhibitor, was injected i.p. 1 h before CLP. Blood and liver tissues were isolated 6 h after CLP.

KEY RESULTS

Genipin improved survival rate and decreased serum levels of aminotransferases and pro-inflammatory cytokines after CLP; effects abolished by chloroquine. The liver expression of autophagy-related protein (Atg)12-Atg5 conjugate increased after CLP, and this increase was enhanced by genipin. CLP decreased Atg3 protein liver expression, and genipin attenuated this decrease. CLP impaired autophagic flux, as indicated by increased liver expression of microtubule-associated protein-1 light chain 3-II and sequestosome-1/p62 protein; this impaired autophagic flux was restored by genipin, and chloroquine abolished this effect. Genipin also attenuated the decreased expression of lysosome-associated membrane protein-2 and Rab7 protein and increased expression of calpain 1 protein induced by CLP in the liver.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest that genipin protects against septic injury by restoring impaired autophagic flux. Therefore, genipin might be a potential therapeutic agent for the treatment of sepsis.

ß3-integrin inhibits lipopolysaccharide-induced autophagy in cardiomyocytes via the Akt signaling pathway

OBJECTIVE

To investigate the role of β 3 -integrin in lipopolysaccharide (LPS)-induced autophagy in cardiomyocytes and its underlying mechanism.

METHODS

β 3 -Integrin expression in cardiomyocytes was up- or downregulated by adenovirus transfection or cyclic arginine-glycine-aspartic acid (cRGD) peptide treatment before LPS stimulation. The expression of autophagy-associated proteins (LC3-II, Beclin-1 and Bcl-2) and the activation of Akt were determined using Western blotting. Autophagosomes and autophagic vacuoles were observed using monodansylcadaverine (MDC) dye and transmission electron microscopy, respectively.

RESULTS

Downregulation of β 3 -integrin with cRGD peptide resulted in enhanced LC3-II and Beclin-1 and decreased Bcl-2 expression. Low Beclin-1 levels were detected after LPS stimulation in adenovirus β 3 -integrin-transfected cardiomyocytes. There was no significant difference in LC3-II levels between control and adenovirus β 3 -integrin-transfected cardiomyocytes. Enhanced accumulation of MDC dye and autophagosomes, which were inhibited by β 3 -integrin overexpression, were detected after LPS treatment. The increased phosphorylation of Akt after LPS stimulation was inhibited by cRGD and enhanced by β 3 -integrin overexpression. Furthermore, the Akt inhibitor triciribine inhibited the negative effect of β 3 - integrin on autophagy, as shown by LC3-II and Beclin-1 upregulation.

CONCLUSIONS

β 3 -Integrin inhibits LPS-induced autophagy in cardiomyocytes. The inhibition of Akt signaling might be an important mechanism in this process.

The synthetic β-nitrostyrene derivative CYT-Rx20 induces breast cancer cell death and autophagy via ROS-mediated MEK/ERK pathway

The β-nitrostyrene family has been shown to suppress cancer cell proliferation and induce programmed cell death. However, mechanisms underlying β-nitrostyrenes remain less evaluated. Here, we synthesized a β-nitrostyrene derivative, CYT-Rx20, and characterized its anticancer effect and involving mechanisms in breast cancer. We found that CYT-Rx20 arrested breast cancer cells at G2/M phase and decreased cell viability by activating the caspase cascade, accompanying with increases of poly (ADP-ribose) polymerase (PARP) cleavage and γ-H2AX expression. On the other hand, up-regulation of Beclin-1, ATG5, and LC-3 was observed in CYT-Rx20-induced autophagy, which was evidently shown by transmission electron microscopy. In addition to these, CYT-Rx20-induced breast cancer cell death, intracellular reactive oxygen species (ROS) formation and expression of phospho-ERK1/2, Beclin-1, and LC-3 were significantly reversed in the presence of N-acetyl-l-cysteine (NAC), a thiol antioxidant. Furthermore, the cytotoxicity of CYT-Rx20 was enhanced by co-treatment with the autophagy inhibitor chloroquine or bafilomycin A1, suggesting that an incomplete autophagy process could deteriorate CYT-Rx20-induced cytotoxicity. In nude mice xenograft study, CYT-Rx20 significantly reduced orthotopic tumor growth. Immunohistochemical analysis revealed elevated expression of phospho-ERK1/2 and LC-3 in tumor tissues of the mice treated with CYT-Rx20. Together, we propose that CYT-Rx20 may have potential to be further developed into a β-nitrostyrene-based anticancer compound for the treatment of breast cancer.

Amiodarone as an autophagy promoter reduces liver injury and enhances liver regeneration and survival in mice after partial hepatectomy

The deregulation of autophagy is involved in liver regeneration. Here, we investigated the role of autophagy in the regulation of liver regeneration after partial hepatectomy (PHx) and the development of pharmacological interventions for improved liver regeneration after PHx. We show that autophagy was activated in the early stages of liver regeneration following 70% PHx in vivo. Moreover, amiodarone was associated with a significant enhancement of autophagy, liver growth, and hepatocyte proliferation, along with reduced liver injury and the termination of liver regeneration due to decreased transforming growth factor-β1 expression after 70% PHx. The promotion of autophagy appeared to selectively increase the removal of damaged mitochondria. We also found that Atg7 knockdown or pretreatment with chloroquine aggravated the liver injury associated with 70% PHx and reduced liver growth and hepatocyte proliferation. Finally, amiodarone improved liver regeneration, survival, and liver injury after 90% PHx. In conclusion, our results indicate that autophagy plays an important role in mouse liver regeneration and that modulating autophagy with amiodarone may be an effective method of improving liver regeneration, increasing survival, and ameliorating liver injury following PHx.

The Sick and the Weak: Neuropathies/Myopathies in the Critically Ill

Critical illness polyneuropathies (CIP) and myopathies (CIM) are common complications of critical illness. Several weakness syndromes are summarized under the term intensive care unit-acquired weakness (ICUAW). We propose a classification of different ICUAW forms (CIM, CIP, sepsis-induced, steroid-denervation myopathy) and pathophysiological mechanisms from clinical and animal model data. Triggers include sepsis, mechanical ventilation, muscle unloading, steroid treatment, or denervation. Some ICUAW forms require stringent diagnostic features; CIM is marked by membrane hypoexcitability, severe atrophy, preferential myosin loss, ultrastructural alterations, and inadequate autophagy activation while myopathies in pure sepsis do not reproduce marked myosin loss. Reduced membrane excitability results from depolarization and ion channel dysfunction. Mitochondrial dysfunction contributes to energy-dependent processes. Ubiquitin proteasome and calpain activation trigger muscle proteolysis and atrophy while protein synthesis is impaired. Myosin loss is more pronounced than actin loss in CIM. Protein quality control is altered by inadequate autophagy. Ca(2+) dysregulation is present through altered Ca(2+) homeostasis. We highlight clinical hallmarks, trigger factors, and potential mechanisms from human studies and animal models that allow separation of risk factors that may trigger distinct mechanisms contributing to weakness. During critical illness, altered inflammatory (cytokines) and metabolic pathways deteriorate muscle function. ICUAW prevention/treatment is limited, e.g., tight glycemic control, delaying nutrition, and early mobilization. Future challenges include identification of primary/secondary events during the time course of critical illness, the interplay between membrane excitability, bioenergetic failure and differential proteolysis, and finding new therapeutic targets by help of tailored animal models.

Regulation of autophagy by the nuclear factor κB signaling pathway in the hippocampus of rats with sepsis

BACKGROUND

Sepsis with brain dysfunction has contributed to an increase risk of morbidity and mortality. In its pathophysiology, both autophagy and nuclear factor κB (NF-κB) have been suggested to play important roles. Based on the fact that crosstalk between autophagy and NF-κB, two stress-response signaling pathways, has been detected in other pathophysiological processes, this study was undertaken to explore the process of autophagy in the hippocampus of septic rats and the role NF-κB plays in the regulation of autophagy during the process.

METHODS

Cecal ligation and puncture (CLP) or a sham operation was conducted on male Wistar rats. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of the NF-κB signaling pathway, or a vehicle control, was used to treat with the rats 2 h before the CLP operation. Hematoxylin-eosin staining and biological signal recording was used to measure the morphological and physiological signs of hippocampal dysfunction. An electron microscope was used to observe autophagosome formation and lysosome activation in the hippocampus after CLP. Western blotting and immune histochemistry were used to detect the hippocampus levels of NF-κB and essential proteins involved in formation of the autophagosome (microtubule-associated protein light chain 3 (LC3), Beclin1, Lamp-1, and Rab7).

RESULTS

Compared with sham-operated rats, the CLP rats showed decreasing mean arterial pressure (MAP), increasing heart rate (HR), and pathological histological changes. CLP rats exhibited not only increased vacuolization through electron micrographs but also increased LC3-II, decreased Beclin1, LAMP-1, and Rab7 through the immunofluorescence and Western blot. However, PDTC + CLP rats revealed that inhibition of the NF-κB signal axis by PDTC increased the levels of LC3-II, Beclin1, LAMP-1, and Rab7 and improved physiological function including blood pressure and heart rate.

CONCLUSIONS

The autophagy process during the hippocampus of CLP rats might be blocked by the activation of NF-κB signaling pathway. Inhibition of NF-κB signaling pathway could enhance the completion of autophagy with a neuroprotective function in septic brains.

Sinomenine hydrochloride protects against polymicrobial sepsis via autophagy

Sepsis, a systemic inflammatory response to infection, is the major cause of death in intensive care units (ICUs). The mortality rate of sepsis remains high even though the treatment and understanding of sepsis both continue to improve. Sinomenine (SIN) is a natural alkaloid extracted from Chinese medicinal plant Sinomenium acutum, and its hydrochloride salt (Sinomenine hydrochloride, SIN-HCl) is widely used to treat rheumatoid arthritis (RA). However, its role in sepsis remains unclear. In the present study, we investigated the role of SIN-HCl in sepsis induced by cecal ligation and puncture (CLP) in BALB/c mice and the corresponding mechanism. SIN-HCl treatment improved the survival of BALB/c mice that were subjected to CLP and reduced multiple organ dysfunction and the release of systemic inflammatory mediators. Autophagy activities were examined using Western blotting. The results showed that CLP-induced autophagy was elevated, and SIN-HCl treatment further strengthened the autophagy activity. Autophagy blocker 3-methyladenine (3-MA) was used to investigate the mechanism of SIN-HCl in vitro. Autophagy activities were determined by examining the autophagosome formation, which was shown as microtubule-associated protein light chain 3 (LC3) puncta with green immunofluorescence. SIN-HCl reduced lipopolysaccharide (LPS)-induced inflammatory cytokine release and increased autophagy in peritoneal macrophages (PM). 3-MA significantly decreased autophagosome formation induced by LPS and SIN-HCl. The decrease of inflammatory cytokines caused by SIN-HCl was partially aggravated by 3-MA treatment. Taken together, our results indicated that SIN-HCl could improve survival, reduce organ damage, and attenuate the release of inflammatory cytokines induced by CLP, at least in part through regulating autophagy activities.

Redox regulation of mitophagy in the lung during murine Staphylococcus aureus sepsis

Oxidative mitochondrial damage is closely linked to inflammation and cell death, but low levels of reactive oxygen and nitrogen species serve as signals that involve mitochondrial repair and resolution of inflammation. More specifically, cytoprotection relies on the elimination of damaged mitochondria by selective autophagy (mitophagy) during mitochondrial quality control. This aim of this study was to identify and localize mitophagy in the mouse lung as a potentially upregulatable redox response to Staphylococcus aureus sepsis. Fibrin clots loaded with S. aureus (1×10(7) CFU) were implanted abdominally into anesthetized C57BL/6 and B6.129X1-Nfe2l2tm1Ywk/J (Nrf2(-/-)) mice. At the time of implantation, mice were given vancomycin (6mg/kg) and fluid resuscitation. Mouse lungs were harvested at 0, 6, 24, and 48h for bronchoalveolar lavage (BAL), Western blot analysis, and qRT-PCR. To localize mitochondria with autophagy protein LC3, we used lung immunofluorescence staining in LC3-GFP transgenic mice. In C57BL/6 mice, sepsis-induced pulmonary inflammation was detected by significant increases in mRNA for the inflammatory markers IL-1β and TNF-α at 6 and 24h, respectively. BAL cell count and protein also increased. Sepsis suppressed lung Beclin-1 protein, but not mRNA, suggesting activation of canonical autophagy. Notably sepsis also increased the LC3-II autophagosome marker, as well as the lung׳s noncanonical autophagy pathway as evidenced by loss of p62, a redox-regulated scaffolding protein of the autophagosome. In LC3-GFP mouse lungs, immunofluorescence staining showed colocalization of LC3-II to mitochondria, mainly in type 2 epithelium and alveolar macrophages. In contrast, marked accumulation of p62, as well as attenuation of LC3-II in Nrf2-knockout mice supported an overall decrease in autophagic turnover. The downregulation of canonical autophagy during sepsis may contribute to lung inflammation, whereas the switch to noncanonical autophagy selectively removes damaged mitochondria and accompanies tissue repair and cell survival. Furthermore, mitophagy in the alveolar region appears to depend on activation of Nrf2. Thus, efforts to promote mitophagy may be a useful therapeutic adjunct for acute lung injury in sepsis.

T-cell autophagy deficiency increases mortality and suppresses immune responses after sepsis

BACKGROUND

Although the role of autophagy in sepsis has been characterized in several organs, its role in the adaptive immune system remains to be ascertained. This study aimed to investigate the role of autophagy in sepsis-induced T cell apoptosis and immunosuppression, using knockout mice with T cell specific deletion of autophagy essential gene Atg7.

METHODS AND RESULTS

Sepsis was induced in a cecal ligation and puncture (CLP) model, with T-cell-specific Atg7-knockout mice compared to control mice. Autophagic vacuoles examined by electron microscopy were decreased in the spleen after CLP. Autophagy proteins LC3-II and ATG7, and autophagosomes and autolysosomes stained by Cyto-ID Green and acridine orange were decreased in CD4+ and CD8+ splenocytes at 18 h and 24 h after CLP. This decrease in autophagy was associated with increased apoptosis of CD4+ and CD8+ after CLP. Moreover, mice lacking Atg7 in T lymphocytes showed an increase in sepsis-induced mortality, T cell apoptosis and loss of CD4+ and CD8+ T cells, in comparison to control mice. This was accompanied by suppressed cytokine production of Th1/Th2/Th17 by CD4+ T cells, reduced phagocytosis in macrophages and decreased bacterial clearance in the spleen after sepsis.

CONCLUSION

These results indicated that sepsis led to down-regulation of autophagy in T lymphocytes, which may result in enhanced apoptosis induction and decreased survival in sepsis. Autophagy may therefore play a protective role against sepsis-induced T lymphocyte apoptosis and immunosuppression.

Endoplasmic reticulum stress-mediated autophagy protects against lipopolysaccharide-induced apoptosis in HL-1 cardiomyocytes

Apoptosis of cardiomyocytes limits the contractile efficiency of the heart during sepsis. Prosurvival autophagy has been proposed as a novel mechanism to maintain normal heart function. Here, we demonstrated that autophagy was activated in lipopolysaccharide (LPS)-treated HL-1 cells, and it counteracted the LPS-induced apoptosis. We investigated further the mechanism by which LPS triggered autophagy in HL-1 cells. We discovered that endoplasmic reticulum (ER) stress played an important role in LPS-triggered autophagy. The ER activated a survival pathway through the ER-localized transmembrane protein PERK, which was essential for LPS-induced autophagy. Lipopolysaccharide increased expression of GRP78, phosphorylated PERK and phosphorylated eukaryotic initiation factor 2α. Similar results were observed after administration of tunicamycin, a well-known ER stressor. Most importantly, we found that 4-phenylbutyrate, an inhibitor of ER stress, suppressed LPS-activated autophagy in the presence of LPS in HL-1 cells. The same results were observed after small interfering RNA-mediated silencing of PERK protein. We also noticed that LPS-induced apoptosis appeared early, at 4 h. Our findings revealed that PERK, one arm of ER stress, facilitated survival of LPS-treated HL-1 cells by promoting autophagy, and could serve as a potential therapeutic strategy to alleviate septic myocardial dysfunction.

Sepsis-induced Cardiac Mitochondrial Damage and Potential Therapeutic Interventions in the Elderly

The incidence of sepsis and its attendant mortality risk are significantly increased with aging. Thus, severe sepsis in the elderly is likely to become an emerging concern in critical care units. Cardiac dysfunction is an important component of multi-organ failure after sepsis. In our laboratory, utilizing a pneumonia-related sepsis animal model, our research has been focused on the mechanisms underlying sepsis-induced cardiac failure. In this review, based on findings from others and ours, we discussed age-dependent decay in mitochondria and the role of mitochondrial reactive oxygen species (mtROS) in sepsis-induced cardiac inflammation and autophagy. Our recent discovery of a potential signal transduction pathway that triggers myocardial mitochondrial damage is also discussed. Because of the significance of mitochondria damage in the aging process and in sepsis pathogenesis, we hypothesize that specific enhancing mitochondrial antioxidant defense by mitochondria-targeted antioxidants (MTAs) may provide important therapeutic potential in treating elder sepsis patients. In this review, we summarized the categories of currently published MTA molecules and the results of preclinical evaluation of MTAs in sepsis and aging models.

Autophagy-related IRGM polymorphism is associated with mortality of patients with severe sepsis

OBJECTIVE

Autophagy is the regulated catabolic process for recycling damaged or unnecessary organelles, which plays crucial roles in cell survival during nutrient deficiency, and innate immune defense against pathogenic microorganisms. Autophagy has been also reported to be involved in various conditions including inflammatory diseases. IRGM (human immunity-related GTPase) has an important function in eliminating Mycobacterium tuberculosis from host cells via autophagy. We examined the association between genetic polymorphism and clinical course/outcome in severely septic patients.

METHODS

The study included 125 patients with severe sepsis/septic shock (SS) and 104 non-sepsis patients who were admitted to the intensive care unit (ICU) of Chiba University Hospital between October 2001 and September 2008 (discovery cohort) and 268 SS patients and 454 non-sepsis patients who were admitted to ICUs of five Japanese institutions including Chiba University Hospital between October 2008 and September 2012 (multi-center validation cohort). Three hundred forty seven healthy volunteers who consented to this study were also included. Genotyping was performed for a single-nucleotide polymorphism (SNP) within the coding region of IRGM, IRGM(+313) (rs10065172). Lipopolysaccharide challenge of whole blood from randomly selected healthy volunteers (n = 70) was performed for comparison of IRGM mRNA expression among different genotypes.

RESULTS

No significant difference in genotypic distributions (CC/CT/TT) at the IRGM(+313) locus was observed among the three subject groups (SS, non-sepsis, and healthy volunteers) in either cohort. When mortality were compared, no significant difference was observed in the non-sepsis group, while TT homozygotes exhibited a significantly higher mortality than the CC+CT genotype category in the SS group for both cohorts (P = 0.043, 0.037). Lipopolysaccharide challenge to whole blood showed a significant suppression of IRGM mRNA expression in TT compared with the CC+CT genotype category (P = 0.019).

CONCLUSIONS

The data suggest that the IRGM(+313), an autophagy-related polymorphic locus, influences outcome in severely septic patients, with the possible involvement of autophagy in sepsis exacerbation.

Complete activation of autophagic process attenuates liver injury and improves survival in septic mice

The accumulation of autophagosomes in the terminal step of the autophagic process has recently emerged as a potentially maladaptive process in the septic heart and lung. However, the role of autophagy in the septic liver has not been ascertained. This study was investigated by first examining the entire sequence of the autophagic process in the liver of septic mice. Second, a novel pharmacotherapeutic approach was utilized to treat sepsis with autophagy enhancer/inhibitor. Sepsis was induced by cecal ligation and puncture (CLP). C57BL/6 mice received autophagy enhancer carbamazepine (CBZ), autophagy inhibitor 3-methyladenine (inhibition of autophagosomal formation), or chloroquine (impairment of autophagosomal clearance). We found that the whole autophagic process was activated at 4 h after CLP; however, it did not proceed to completion during the 4- to 24-h time period, as indicated by accumulated autophagosomes and decreased autophagic flux. Carbamazepine, which induced complete activation of the autophagic process, improved CLP survival. This protective effect was also associated with decreased cell death, inflammatory responses, and hepatic injury. However, disruption of autophagosomal clearance with chloroquine abolished the above protective effects in CBZ-treated CLP mice. 3-Methyladenine, which resulted in inhibition of the autophagosomal formation, did not show any above beneficial effects in CLP mice. Impaired autophagosome-lysome fusion resulting in incomplete activation of autophagy may contribute to sepsis-induced liver injury. Treatment with CBZ may serve a protective role in the septic liver, possibly through the effect of complete activation of autophagic process.

Protective role of PARK2/Parkin in sepsis-induced cardiac contractile and mitochondrial dysfunction

Mitochondrial quality control plays a vital role in the maintenance of optimal mitochondrial function. However, its roles and regulation remain ill-defined in cardiac pathophysiology. Here, we tested the hypothesis that PARK2/Parkin, an E3-ligase recently described as being involved in the regulation of cardiac mitophagy, is important for (1) the maintenance of normal cardiac mitochondrial function; and (2) adequate recovery from sepsis, a condition known to induce reversible mitochondrial injury through poorly understood mechanisms. Investigations of mitochondrial and cardiac function were thus performed in wild-type and Park2-deficient mice at baseline and at 2 different times following administration of a sublethal dose of E. coli lipopolysaccharide (LPS). LPS injection induced cardiac and mitochondrial dysfunctions that were followed by complete recovery in wild-type mice. Recovery was associated with morphological and biochemical evidence of mitophagy, suggesting that this process is implicated in cardiac recovery from sepsis. Under baseline conditions, multiple cardiac mitochondrial dysfunctions were observed in Park2-deficient mice. These mild dysfunctions did not result in a visibly distinct cardiac phenotype. Importantly, Park2-deficient mice exhibited impaired recovery of cardiac contractility and constant degradation of mitochondrial metabolic functions. Interestingly, autophagic clearance of damaged mitochondria was still possible in the absence of PARK2 likely through compensatory mechanisms implicating PARK2-independent mitophagy and upregulation of macroautophagy. Together, these results thus provide evidence that in vivo, mitochondrial autophagy is activated during sepsis, and that compensation for a lack of PARK2 is only partial and/or that PARK2 exerts additional protective roles in mitochondria.

Augmenting autophagy to treat acute kidney injury during endotoxemia in mice

Objective

To determine that 1) an age-dependent loss of inducible autophagy underlies the failure to recover from AKI in older, adult animals during endotoxemia, and 2) pharmacologic induction of autophagy, even after established endotoxemia, is of therapeutic utility in facilitating renal recovery in aged mice.

Design

Murine model of endotoxemia and cecal ligation and puncture (CLP) induced acute kidney injury (AKI).

Setting

Academic research laboratory.

Subjects

C57Bl/6 mice of 8 (young) and 45 (adult) weeks of age.

Intervention

Lipopolysaccharide (1.5 mg/kg), Temsirolimus (5 mg/kg), AICAR (100 mg/kg). Measurements and Main Results: Herein we report that diminished autophagy underlies the failure to recover renal function in older adult mice utilizing a murine model of LPS-induced AKI. The administration of the mTOR inhibitor temsirolimus, even after established endotoxemia, induced autophagy and protected against the development of AKI.

Conclusions

These novel results demonstrate a role for autophagy in the context of LPS-induced AKI and support further investigation into like interventions that have potential to alter the natural history of disease.

Kinetics and protective role of autophagy in a mouse cecal ligation and puncture-induced sepsis

Introduction

It is not well understood whether the process of autophagy is accelerated or blocked in sepsis, and whether it is beneficial or harmful to the immune defense mechanism over a time course during sepsis. Our aim was to determine both the kinetics and the role of autophagy in sepsis.

Methods

We examined autophagosome and autolysosome formation in a cecal ligation and puncture (CLP) mouse model of sepsis (in C57BL/6N mice and GFP-LC3 transgenic mice), using western blotting, immunofluorescence, and electron microscopy. We also investigated the effect of chloroquine inhibition of autophagy on these processes.

Results

Autophagy, as demonstrated by increased LC3-II/LC3-I ratios, is induced in the liver, heart, and spleen over 24 h after CLP. In the liver, autophagosome formation peaks at 6 h and declines by 24 h. Immunofluorescent localization of GFP-LC3 dots (alone and with lysosome-associated membrane protein type 1 (LAMP1)), as well as electron microscopic examination, demonstrate that both autophagosomes and autolysosomes are increased after CLP, suggesting that intact autophagy mechanisms operate in the liver in this model. Furthermore, inhibition of autophagy process by chloroquine administration immediately after CLP resulted in elevated serum transaminase levels and a significant increase in mortality.

Conclusions

All autophagy-related processes are properly activated in the liver in a mouse model of sepsis; autophagy appears to play a protective role in septic animals.

Autophagy: a potential therapeutic target in lung diseases

Macroautophagy (hereafter referred to as autophagy) is an evolutionally conserved intracellular process to maintain cellular homeostasis by facilitating the turnover of protein aggregates, cellular debris, and damaged organelles. During autophagy, cytosolic constituents are engulfed into double-membrane-bound vesicles called "autophagosomes," which are subsequently delivered to the lysosome for degradation. Accumulated evidence suggests that autophagy is critically involved not only in the basal physiological states but also in the pathogenesis of various human diseases. Interestingly, a diverse variety of clinically approved drugs modulate autophagy to varying extents, although they are not currently utilized for the therapeutic purpose of manipulating autophagy. In this review, we highlight the functional roles of autophagy in lung diseases with focus on the recent progress of the potential therapeutic use of autophagy-modifying drugs in clinical medicine. The purpose of this review is to discuss the merits, and the pitfalls, of modulating autophagy as a therapeutic strategy in lung diseases.

Chronic Akt activation attenuated lipopolysaccharide-induced cardiac dysfunction via Akt/GSK3β-dependent inhibition of apoptosis and ER stress

Sepsis is characterized by systematic inflammation and contributes to cardiac dysfunction. This study was designed to examine the effect of protein kinase B (Akt) activation on lipopolysaccharide-induced cardiac anomalies and underlying mechanism(s) involved. Mechanical and intracellular Ca²⁺ properties were examined in myocardium from wild-type and transgenic mice with cardiac-specific chronic Akt overexpression following LPS (4 mg/kg, i.p.) challenge. Akt signaling cascade (Akt, phosphatase and tensin homologue deleted on chromosome ten, glycogen synthase kinase 3 beta), stress signal (extracellular-signal-regulated kinases, c-Jun N-terminal kinases, p38), apoptotic markers (Bcl-2 associated X protein, caspase-3/-9), endoplasmic reticulum (ER) stress markers (glucose-regulated protein 78, growth arrest and DNA damage induced gene-153, eukaryotic initiation factor 2α), inflammatory markers (tumor necrosis factor α, interleukin-1β, interleukin-6) and autophagic markers (Beclin-1, light chain 3B, autophagy-related gene 7 and sequestosome 1) were evaluated. Our results revealed that LPS induced marked decrease in ejection fraction, fractional shortening, cardiomyocyte contractile capacity with dampened intracellular Ca²⁺ release and clearance, elevated reactive oxygen species (ROS) generation and decreased glutathione and glutathione disulfide (GSH/GSSG) ratio, increased ERK, JNK, p38, GRP78, Gadd153, eIF2α, BAX, caspase-3 and -9, downregulated B cell lymphoma 2 (Bcl-2), the effects of which were significantly attenuated or obliterated by Akt activation. Akt activation itself did not affect cardiac contractile and intracellular Ca²⁺ properties, ROS production, oxidative stress, apoptosis and ER stress. In addition, LPS upregulated levels of Beclin-1, LC3B and Atg7, while suppressing p62 accumulation. Akt activation did not affect Beclin-1, LC3B, Atg7 and p62 in the presence or absence of LPS. Akt overexpression promoted phosphorylation of Akt and GSK3β. In vitro study using the GSK3β inhibitor SB216763 mimicked the response elicited by chronic Akt activation. Taken together, these data showed that Akt activation ameliorated LPS-induced cardiac contractile and intracellular Ca²⁺ anomalies through inhibition of apoptosis and ER stress, possibly involving an Akt/GSK3β-dependent mechanism.

Lc3 over-expression improves survival and attenuates lung injury through increasing autophagosomal clearance in septic mice

OBJECTIVE

To clarify the role of autophagy in sepsis-induced lung injury.

BACKGROUND

The role of autophagy as a protective or maladaptive response in lung cells during sepsis has not yet been determined. The lack of specificity of the autophagic process has driven the development of new approaches that assess autophagosomes from formation to fusion with lysosomes.

METHODS

Sepsis was induced by cecal ligation and puncture (CLP). The autophagic process was manipulated using the pharmacological inhibitors of the autophagy pathway. Green fluorescent protein (GFP)-microtubule-associated protein 1 light chain 3 (LC3) transgenic mice were further used to determine the role of autophagy.

RESULTS

The formation of autophagosomal protein LC3-II progressively accumulated in the lungs over 24 hours after CLP, with the Lc3 gene expression returning to baseline levels at 24 hours. Autophagosome-lysosome fusion, however, gradually decreased from 8 to 24 hours after CLP, suggesting impaired clearance of autophagosomes rather than upregulation of autophagy in the septic lung. In contrast, transgenic mice overexpressing the Lc3 gene exhibited increased clearance of autophagosomes and improved survival after CLP. This protective effect was also seen in decreased cell death, inflammatory responses, neutrophil accumulation, albumin leakage, and edema formation. However, blockade of autophagosome-lysosome fusion with bafilomycin A1 abolished the protective effects in transgenic mice. This indicates that Lc3 transgene attenuates lung injury/inflammation in sepsis, possibly through increasing the clearance of autophagosomes.

CONCLUSIONS

Autophagy in the septic lung represents a protective response. However, autophagy, by virtue of excessive autophagosome accumulation, may play a maladaptive role in the late stage of sepsis, leading to acute lung injury.

Insufficient autophagy contributes to mitochondrial dysfunction, organ failure, and adverse outcome in an animal model of critical illness

OBJECTIVE

Increasing evidence implicates mitochondrial dysfunction as an early, important event in the pathogenesis of critical illness-induced multiple organ failure. We previously demonstrated that prevention of hyperglycemia limits damage to mitochondria in vital organs, thereby reducing morbidity and mortality. We now hypothesize that inadequate activation of mitochondrial repair processes (clearance of damaged mitochondria by autophagy, mitochondrial fusion/fission, and biogenesis) may contribute to accumulation of mitochondrial damage, persistence of organ failure, and adverse outcome of critical illness.

DESIGN

Prospective, randomized studies in a critically ill rabbit model.

SETTING

University laboratory.

SUBJECTS

Three-month-old male rabbits.

INTERVENTIONS

We studied whether vital organ mitochondrial repair pathways are differentially affected in surviving and nonsurviving hyperglycemic critically ill animals in relation to mitochondrial and organ damage. Next, we investigated the impact of preventing hyperglycemia over time and of administering rapamycin as an autophagy activator.

MEASUREMENTS AND MAIN RESULTS

In both liver and kidney of hyperglycemic critically ill rabbits, we observed signs of insufficient autophagy, including accumulation of p62 and a concomitant decrease in the microtubule-associated protein light-chain-3-II/microtubule-associated protein light-chain-3-I ratio. The phenotype of insufficient autophagy was more pronounced in nonsurviving than in surviving animals. Molecular markers of insufficient autophagy correlated with impaired mitochondrial function and more severe organ damage. In contrast, key players in mitochondrial fusion/fission or biogenesis were not significantly different regarding survival status. Therefore, we focused on autophagy to study the impact of preventing hyperglycemia. Both after 3 and 7 days of illness, autophagy was better preserved in normoglycemic than in hyperglycemic rabbits, which correlated with improved mitochondrial function and less organ damage. Stimulation of autophagy in kidney with rapamycin correlated with protection of renal function.

CONCLUSIONS

Our findings put forward insufficient autophagy as a potentially important contributor to mitochondrial and organ damage in critical illness and open perspectives for therapies that activate autophagy during critical illness.

Enhancing autophagy with activated protein C and rapamycin protects against sepsis-induced acute lung injury

BACKGROUND

Autophagy plays distinct roles in apoptosis and the inflammatory process. Understanding the role of autophagy in sepsis-induced acute lung injury (ALI) may provide new insights into developing novel therapeutic strategies for this group of patients. The aim of this study was to investigate the regulation of autophagy in the septic lung and to use pharmacologic agents to modulate autophagy to study its functional significance.

METHODS

Mice were subjected to cecal ligation and puncture (CLP) or a sham operation. At 1 hour after CLP, mice were treated with vehicle, activated protein C (APC), rapamycin, or bafilomycin A1. Mice were humanely killed at 4 or 24 hours after the operation or were observed for ≤ 7 days.

RESULTS

CLP induced a systemic inflammatory response and significantly decreased survival. In lung tissue, increased leukocyte infiltration, inflammation, and apoptosis were observed. In contrast, autophagy was suppressed after CLP such that the expression of LC3II, Atg5, and Rab7 were downregulated. Rapamycin activated autophagy, limited the CLP-induced proinflammatory response, and downregulated apoptotic activity after CLP. The administration of APC after CLP had an effect similar to that of rapamycin. Both medications significantly improved survival 7 days after CLP.

CONCLUSION

The downregulation of autophagy may lead to systemic inflammation and ALI after sepsis. The direct or indirect modification of autophagy using rapamycin or APC, respectively, resulted in improved survival. Enhancing or restoring autophagy early after sepsis seems to be a potential strategy for the treatment of sepsis-induced ALI.

Cobalt protoporphyrin accelerates TFEB activation and lysosome reformation during LPS-induced septic insults in the rat heart

Lipopolysaccharide (LPS)-induced myocardial dysfunction is caused, at least in part, by mitochondrial dysfunction. Mitochondrial dysfunction and the oxidative damage associated with it are scavenged through various cellular defense systems such as autophagy to prevent harmful effects. Our recent study has demonstrated that cobalt protoporphyrin IX (CoPPIX), a potent inducer of heme oxygenase-1 (HO-1), ameliorates septic liver injuries by enhancing mitochondrial autophagy in rats. In our current study, we show that CoPPIX (5 mg/kg s.c.) not only accelerates the autophagic response but also promotes lysosome reformation in the rat heart treated with LPS (15 mg/kg i.p.). Lysosomal membrane-associated protein-2 (LAMP2), which is essential to the maintenance of lysosomal functions in the heart, is depleted transiently but restored rapidly during LPS administration in the rat. Activation of transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy, was also observed, indicating a hyper consumption and subsequent reformation of the lysosome to meet the increased demand for autophagosome cleaning. CoPPIX was found to promote these processes and tended to restore the LPS-induced suppression of cardiac performances whilst chloroquine (CQ; 20 mg/kg i.p.), an inhibitor of lysosomes and autophagic protein degradation, abrogates these beneficial effects. The cardioprotective effect of CoPPIX against LPS toxicity was also observed via decreased levels of cardiac releasing enzymes in the plasma. Taken together, our current data indicate that lysosome reformation mediated by TFEB may be involved in cardioprotection against LPS-induced septic insults, and serve as a novel mechanism by which CoPPIX protects the heart against oxidative stress.

Inflammaging: disturbed interplay between autophagy and inflammasomes

Inflammaging refers to a low-grade pro-inflammatory phenotype which accompanies aging in mammals. The aging process is associated with a decline in autophagic capacity which impairs cellular housekeeping, leading to protein aggregation and accumulation of dysfunctional mitochondria which provoke reactive oxygen species (ROS) production and oxidative stress. Recent studies have clearly indicated that the ROS production induced by damaged mitochondria can stimulate intracellular danger-sensing multiprotein platforms called inflammasomes. Nod-like receptor 3 (NLRP3) can be activated by many danger signals, e.g. ROS, cathepsin B released from destabilized lysosomes and aggregated proteins, all of which evoke cellular stress and are involved in the aging process. NLRP3 activation is also enhanced in many age-related diseases, e.g. atherosclerosis, obesity and type 2 diabetes. NLRP3 activates inflammatory caspases, mostly caspase-1, which cleave the inactive precursors of IL-1β and IL-18 and stimulate their secretion. Consequently, these cytokines provoke inflammatory responses and accelerate the aging process by inhibiting autophagy. In conclusion, inhibition of autophagic capacity with aging generates the inflammaging condition via the activation of inflammasomes, in particular NLRP3. We will provide here a perspective on the current research of the ROS-dependent activation of inflammasomes triggered by the decline in autophagic cleansing of dysfunctional mitochondria.

Structural changes of the heart during severe sepsis or septic shock

Cardiovascular dysfunction is common in severe sepsis or septic shock. Although functional alterations are often described, the elevated serum levels of cardiac proteins and autopsy findings of myocardial immune cell infiltration, edema, and damaged mitochondria suggest that structural changes to the heart during severe sepsis and septic shock may occur and may contribute to cardiac dysfunction. We explored the available literature on structural (versus functional) cardiac alterations during experimental and human endotoxemia and/or sepsis. Limited data suggest that the structural changes could be prevented, and myocardial function improved by (pre-)treatment with platelet-activating factor, cyclosporin A, glutamine, caffeine, simvastatin, or caspase inhibitors.

The decline of autophagy contributes to proximal tubular dysfunction during sepsis

Severe sepsis associated with overproduction of tumor necrosis factor α and reactive oxygen species leads to energy depletion and cellular damage. Both reactive oxygen species and damaged organelles induce autophagy for recycling nutrients to combat pathological stress. To study whether autophagy plays a beneficial role in the pathogenesis of renal failure during sepsis, rats were subjected to cecal ligation and puncture (CLP) or sham operation. Temporal relationship of autophagy and renal dysfunction were examined in vivo. The results showed that the level of lipidated microtubule-associated protein light chain 3 (LC3-II), a marker of autophagy, elevated transiently at 3 h but declined at 9 h until 18 h after CLP. Light chain 3 aggregation in renal tissue showed a similar trend to the change of LC3-II protein. High levels of blood urea nitrogen and creatinine as well as low tubular sodium reabsorption occurred at 18 h after CLP. The distribution of autophagy located primarily in angiotensin-converting enzyme-positive, which is concentrated in proximal tubule, but calbindin D28k (calcium-binding protein D28K, a marker of distal tubule)-negative cells in renal cortex. Therefore, NRK-52E (proximal tubule epithelial cell line) cells were used to further examine cell viability and DNA fragmentation after silencing or inducing autophagy. We found that knockdown of Atg7 (autophagy-related gene 7) exaggerates, whereas preincubation of rapamycin (an autophagy inducer) diminishes tumor necrosis factor α-induced cell death. These results suggest that the decline of sepsis-induced autophagy contributes to the proximal tubular dysfunction, and maintenance of sufficient autophagy prevents cell death. These data open prospects for therapies that activate autophagy during sepsis.

Early parenteral nutrition evokes a phenotype of autophagy deficiency in liver and skeletal muscle of critically ill rabbits

Muscular and hepatic abnormalities observed in artificially fed critically ill patients strikingly resemble the phenotype of autophagy-deficient mice. Autophagy is the only pathway to clear damaged organelles and large ubiquitinated proteins and aggregates. Fasting is its strongest physiological trigger. Severity of autophagy deficiency in critically ill patients correlated with the amount of infused amino acids. We hypothesized that impaired autophagy in critically ill patients could partly be evoked by early provision of parenteral nutrition enriched with amino acids in clinically used amounts. In a randomized laboratory investigation, we compared the effect of isocaloric moderate-dose iv feeding with fasting during illness on the previously studied markers of autophagy deficiency in skeletal muscle and liver. Critically ill rabbits were allocated to fasting or to iv nutrition (220 kcal/d, 921 kJ/d) supplemented with 50 kcal/d (209 kJ/d) of either glucose, amino acids, or lipids, while maintaining normoglycemia, and were compared with healthy controls. Fasted critically ill rabbits revealed weight loss and activation of autophagy. Feeding abolished these responses, with most impact of amino acid-enriched nutrition. Accumulation of p62 and ubiquitinated proteins in muscle and liver, indicative of insufficient autophagy, occurred with parenteral feeding enriched with amino acids and lipids. In liver, this was accompanied by fewer autophagosomes, fewer intact mitochondria, suppressed respiratory chain activity, and an increase in markers of liver damage. In muscle, early parenteral nutrition enriched with amino acids or lipids aggravated vacuolization of myofibers. In conclusion, early parenteral nutrition during critical illness evoked a phenotype of autophagy deficiency in liver and skeletal muscle.

Pharmacological targets in the renal peritubular microenvironment: implications for therapy for sepsis-induced acute kidney injury

One of the most frequent and serious complications to develop in septic patients is acute kidney injury (AKI), a disorder characterized by a rapid failure of the kidneys to adequately filter the blood, regulate ion and water balance, and generate urine. AKI greatly worsens the already poor prognosis of sepsis and increases cost of care. To date, therapies have been mostly supportive; consequently there has been little change in the mortality rates over the last decade. This is due, at least in part, to the delay in establishing clinical evidence of an infection and the associated presence of the systemic inflammatory response syndrome and thus, a delay in initiating therapy. A second reason is a lack of understanding regarding the mechanisms leading to renal injury, which has hindered the development of more targeted therapies. In this review, we summarize recent studies, which have examined the development of renal injury during sepsis and propose how changes in the peritubular capillary microenvironment lead to and then perpetuate microcirculatory failure and tubular epithelial cell injury. We also discuss a number of potential therapeutic targets in the renal peritubular microenvironment, which may prevent or lessen injury and/or promote recovery.