Permissive role of AMPK and autophagy in adiponectin deficiency-accentuated myocardial injury and inflammation in endotoxemia

MEGF9 prevents lipopolysaccharide-induced cardiac dysfunction through activating AMPK pathway

OBJECTIVE

Inflammation and oxidative damage play critical roles in the pathogenesis of sepsis-induced cardiac dysfunction. Multiple EGF-like domains 9 (MEGF9) is essential for cell homeostasis; however, its role and mechanism in sepsis-induced cardiac injury and impairment remain unclear.

METHODS

Adenoviral and adeno-associated viral vectors were applied to overexpress or knock down the expression of MEGF9 in vivo and in vitro. To stimulate septic injury, cardiomyocytes and mice were treated lipopolysaccharide (LPS). To clarify the necessity of AMP-activated protein kinase (AMPK), global AMPK knockout mice were used.

RESULTS

We found that MEGF9 expressions were reduced in cardiomyocytes and mice by LPS stimulation. Compared with negative controls, plasma MEGF9 levels were also decreased in septic patients, and negatively correlated with LPS-induced cardiac dysfunction. In addition, MEGF9 overexpression attenuated, while MEGF9 knockdown aggravated LPS-induced inflammation and oxidative damage in vivo and in vitro, thereby regulating LPS-induced cardiac injury and impairment. Mechanistic studies revealed that MEGF9 overexpression alleviated LPS-induced cardiac dysfunction through activating AMPK pathway.

CONCLUSION

We for the first time demonstrate that MEGF9 prevents LPS-related inflammation, oxidative damage and cardiac injury through activating AMPK pathway, and provide a proof-of-concept for the treatment of LPS-induced cardiac dysfunction by targeting MEGF9.

LIN28A-dependent lncRNA NEAT1 aggravates sepsis-induced acute respiratory distress syndrome through destabilizing ACE2 mRNA by RNA methylation

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a life-threatening and heterogeneous disorder leading to lung injury. To date, effective therapies for ARDS remain limited. Sepsis is a frequent inducer of ARDS. However, the precise mechanisms underlying sepsis-induced ARDS remain unclear.

METHODS

Here RNA methylation was detected by methylated RNA immunoprecipitation (MeRIP), RNA stability was determined by RNA decay assay while RNA antisense purification (RAP) was used to identify RNA-protein interaction. Besides, co-immunoprecipitation (Co-IP) was utilized to detect protein-protein interaction. Moreover, mice were injected with lipopolysaccharide (LPS) to establish sepsis-induced ARDS model in vivo.

RESULTS

This study revealed that long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) aggravated lung injury through suppressing angiotensin-converting enzyme 2 (ACE2) in sepsis-induced ARDS models in vitro and in vivo. Mechanistically, NEAT1 declined ACE2 mRNA stability through heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1) in lipopolysaccharide (LPS)-treated alveolar type II epithelial cells (AT-II cells). Besides, NEAT1 destabilized ACE2 mRNA depending on RNA methylation by forming methylated NEAT1/hnRNPA2B1/ACE2 mRNA complex in LPS-treated AT-II cells. Moreover, lin-28 homolog A (LIN28A) improved NEAT1 stability whereas insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) augmented NEAT1 destabilization by associating with LIN28A to disrupt the combination of LIN28A and NEAT1 in LPS-treated AT-II cells. Nevertheless, hnRNPA2B1 increased NEAT1 stability by blocking the interaction between LIN28A and IGF2BP3 in LPS-treated AT-II cells.

CONCLUSIONS

These findings uncover mechanisms of sepsis-triggering ARDS and provide promising therapeutic targets for sepsis-induced ARDS.

Melatonin: A potential protective multifaceted force for sepsis-induced cardiomyopathy

Sepsis is a life-threatening condition manifested by organ dysfunction caused by a dysregulated host response to infection. Lung, brain, liver, kidney, and heart are among the affected organs. Sepsis-induced cardiomyopathy is a common cause of death among septic patients. Sepsis-induced cardiomyopathy is characterized by an acute and reversible significant decline in biventricular both systolic and diastolic function. This is accompanied by left ventricular dilatation. The pathogenesis underlying sepsis-induced cardiomyopathy is multifactorial. Hence, targeting an individual pathway may not be effective in halting the extensive dysregulated immune response. Despite major advances in sepsis management strategies, no effective pharmacological strategies have been shown to treat or even reverse sepsis-induced cardiomyopathy. Melatonin, namely, N-acetyl-5-methoxytryptamine, is synthesized in the pineal gland of mammals and can also be produced in many cells and tissues. Melatonin has cardioprotective, neuroprotective, and anti-tumor activity. Several literature reviews have explored the role of melatonin in preventing sepsis-induced organ failure. Melatonin was found to act on different pathways that are involved in the pathogenesis of sepsis-induced cardiomyopathy. Through its antimicrobial, anti-inflammatory, and antioxidant activity, it offers a potential role in sepsis-induced cardiomyopathy. Its antioxidant activity is through free radical scavenging against reactive oxygen and nitrogen species and modulating the expression and activity of antioxidant enzymes. Melatonin anti-inflammatory activities control the overactive immune system and mitigate cytokine storm. Also, it mitigates mitochondrial dysfunction, a major mechanism involved in sepsis-induced cardiomyopathy, and thus controls apoptosis. Therefore, this review discusses melatonin as a promising drug for the management of sepsis-induced cardiomyopathy.

Phytochemicals targeting Alzheimer's disease via the AMP-activated protein kinase pathway, effects, and mechanisms of action

Alzheimer's disease (AD), characterized by cognitive dysfunction and other behavioral abnormalities, is a progressive neurodegenerative disease that occurs due to aging. Currently, effective drugs to mitigate or treat AD remain unavailable. AD is associated with several abnormalities in neuronal energy metabolism, such as decreased glucose uptake, mitochondrial dysfunction, and defects in cholesterol metabolism. Amp-activated protein kinase (AMPK) is an important serine/threonine protein kinase that regulates the energy status of cells. AMPK is widely present in eukaryotic cells and can sense and regulate energy metabolism to maintain energy supply and demand balance, making it a promising target for energy metabolism-based AD therapy. Therefore, this review aimed to discuss the molecular mechanism of AMPK in the pathogenesis of AD to provide a theoretical basis for the development of new anti-AD drugs. To review the mechanisms of phytochemicals in the treatment of AD via AMPK pathway regulation, we searched PubMed, Google Scholar, Web of Science, and Embase databases using specific keywords related to AD and phytochemicals in September 2023. Phytochemicals can activate AMPK or regulate the AMPK pathway to exert therapeutic effects in AD. The anti-AD mechanisms of these phytochemicals include inhibiting Aβ aggregation, preventing Tau hyperphosphorylation, inhibiting inflammatory response and glial activation, promoting autophagy, and suppressing anti-oxidative stress. Additionally, several AMPK-related pathways are involved in the anti-AD mechanism, including the AMPK/CaMKKβ/mTOR, AMPK/SIRT1/PGC-1α, AMPK/NF-κB/NLRP3, AMPK/mTOR, and PERK/eIF2α pathways. Notably, urolithin A, artemisinin, justicidin A, berberine, stigmasterol, arctigenin, and rutaecarpine are promising AMPK agonists with anti-AD effects. Several phytochemicals are effective AMPK agonists and may have potential applications in AD treatment. Overall, phytochemical-based drugs may overcome the barriers to the effective treatment of neurodegenerative diseases.

Exercise Improves Heart Function after Myocardial Infarction: The Merits of AMPK

BACKGROUND

AMPK is considered an important protein signaling pathway that has been shown to exert prominent cardioprotective effects on the pathophysiological mechanisms of numerous diseases. Following myocardial infarction, severe impairment of cardiac function occurs, leading to complications such as heart failure and arrhythmia. Therefore, protecting the heart and improving cardiac function are important therapeutic goals after myocardial infarction. Currently, there is substantial ongoing research on exercise-centered rehabilitation training, positioning exercise training as a significant nonpharmacological approach for preventing and treating numerous cardiovascular diseases.

OBJECTIVE

Previous studies have reported that exercise can activate AMPK phosphorylation and upregulate the AMPK signaling pathway to play a cardioprotective role in coronary artery disease, but the specific mechanism involved remains to be elucidated.

CONCLUSION

This review discusses the role and mechanism of the exercise-mediated AMPK pathway in improving postinfarction cardiac function through existing studies and describes the mechanism of exercise-induced myocardial repair of AMPK from multiple perspectives to formulate a reasonable and optimal exercise rehabilitation program for the prevention and treatment of myocardial infarction patients in the clinic.

Gramine improves sepsis-induced myocardial dysfunction by binding to NF-κB p105 and inhibiting its ubiquitination

BACKGROUND

Sepsis and its associated heart failure are among the leading causes of death. Gramine, a natural indole alkaloid, can be extracted from a wide variety of raw plants, and it exhibits therapeutic potential in pathological cardiac hypertrophy. However, the effect of gramine on inflammatory cardiomyopathy, particularly sepsis-induced myocardial injury, remains an unexplored area.

PURPOSE

To determine the role of gramine in sepsis-induced myocardial dysfunction and explore its underlying mechanism.

STUDY DESIGN AND METHODS

In mice, sepsis was established by intraperitoneally injecting lipopolysaccharide (LPS, 10 mg/kg). Subsequently, the effects of gramine administration (50 or 100 mg/kg) on LPS-triggered cardiac dysfunction in mice were investigated. For in vitro studies, isolated primary cardiomyocytes were used to assess the effect of gramine (25 or 50 µM) on LPS-induced apoptosis and inflammation. Additionally, molecular docking, co-immunoprecipitation and ubiquitination analyzes were conducted to explore the underlying mechanisms.

RESULTS

Gramine visibly ameliorated sepsis-induced cardiac dysfunction, inflammatory response, and mortality in vivo. Moreover, it significantly alleviated LPS-induced apoptotic and inflammatory responses in vitro. Furthermore, target prediction for gramine using the SuperPred website indicated that the nuclear factor NF-κB p105 subunit was one of the molecules ranked in priority order with a high model accuracy and a high probability score. Molecular docking studies demonstrated that gramine effectively docked to the death domain of NF-κB p105. Mechanistic studies revealed that gramine suppressed the processing of NF-κB p105 to p50 by inhibiting NF-κB p105 ubiquitination. Additionally, the protective effect of gramine on cardiac injury was almost abolished by overexpressing NF-κB p105.

CONCLUSION

Gramine is a promising bioactive small molecule for treating sepsis-induced myocardial dysfunction, which acts by docking to NF-κB p105 and inhibiting NF-κB p105 ubiquitination, thus preventing its processing to NF-κB p50. Therefore, gramine holds potential as a clinical drug for treating myocardial depression during sepsis.

Ischemia-induced cardiac dysfunction is exacerbated in adiponectin-knockout mice due to impaired autophagy flux

Strategies to enhance autophagy flux have been suggested to improve outcomes in cardiac ischemic models. We explored the role of adiponectin in mediating cardiac autophagy under ischemic conditions induced by permanent coronary artery ligation. We studied the molecular mechanisms underlying adiponectin's cardio-protective effects in adiponectin knockout (Ad-KO) compared with wild-type (WT) mice subjected to ischemia by coronary artery ligation and H9c2 cardiomyocyte cell line exposed to hypoxia. Systemic infusion of a cathepsin-B activatable near-infrared probe as a biomarker for autophagy and detection via noninvasive three-dimensional fluorescence molecular tomography combined with computerized tomography to quantitate temporal changes, indicated increased activity in the myocardium of WT mice after myocardial infarction which was attenuated in Ad-KO. Seven days of ischemia increased myocardial adiponectin accumulation and elevated ULK1/AMPK phosphorylation and autophagy assessed by Western blotting for LC3 and p62, an outcome not observed in Ad-KO mice. Cell death, assessed by TUNEL analysis and the ratio of Bcl-2:Bax, plus cardiac dysfunction, measured using echocardiography with strain analysis, were exacerbated in Ad-KO mice. Using cellular models, we observed that adiponectin stimulated autophagy flux in isolated primary adult cardiomyocytes and increased basal and hypoxia-induced autophagy in H9c2 cells. Real-time temporal analysis of caspase-3/7 activation and caspase-3 Western blot indicated that adiponectin suppressed activation by hypoxia. Hypoxia-induced mitochondrial reactive oxygen species production and cell death were also attenuated by adiponectin. Importantly, the ability of adiponectin to reduce caspase-3/7 activation and cell death was not observed in autophagy-deficient cells generated by CRISPR-mediated deletion of Atg7. Collectively, our data indicate that adiponectin acts in an autophagy-dependent manner to attenuate cardiomyocyte caspase-3/7 activation and cell death in response to hypoxia in vitro and ischemia in mice.

Recent progress in the role of endogenous metal ions in doxorubicin-induced cardiotoxicity

Doxorubicin is a widely used anticancer drug in clinical practice for the treatment of various human tumors. However, its administration is associated with cardiotoxicity. Administration of doxorubicin with low side effects for cancer treatment and prevention are, accordingly, urgently required. The human body harbors various endogenous metal ions that exert substantial influences. Consequently, extensive research has been conducted over several decades to investigate the potential of targeting endogenous metal ions to mitigate doxorubicin's side effects and impede tumor progression. In recent years, there has been a growing body of research indicating the potential efficacy of metal ion-associated therapeutic strategies in inhibiting doxorubicin-induced cardiotoxicity (DIC). These strategies offer a combination of favorable safety profiles and potential clinical utility. Alterations in intracellular levels of metal ions have been found to either facilitate or mitigate the development of DIC. For instance, ferroptosis, a cellular death mechanism, and metal ions such as copper, zinc, and calcium have been identified as significant contributors to DIC. This understanding can contribute to advancements in cancer treatment and provide valuable insights for mitigating the cardiotoxic effects of other therapeutic drugs. Furthermore, potential therapeutic strategies have been investigated to alleviate DIC in clinical settings. The ultimate goal is to improve the efficacy and safety of Dox and offer valuable insights for future research in this field.

Cardiac-specific overexpression of catalase attenuates lipopolysaccharide-induced cardiac anomalies through reconciliation of autophagy and ferroptosis

Lipopolysaccharide (LPS) from Gram-negative bacteria is a major contributor to cardiovascular failure, but the signaling mechanisms underlying its stress response are not fully understood. This study aimed to investigate the effect of the antioxidant enzyme catalase on LPS-induced cardiac abnormalities and the mechanisms involved, with particular focus on the interplay between autophagy, ferroptosis, and apoptosis. Cardiac-specific catalase (CAT) overexpression and wild-type (WT) mice were stimulated with LPS (6 mg/kg, intravenous injection), and cardiac morphology and function were evaluated. Oxidative stress, ferroptosis, apoptosis, and mitochondrial status were monitored, and survival curves were plotted based on the results of LPS stimulation. The results showed that, compared with WT mice, mice overexpressing catalase had a higher survival rate under LPS stimulation. Ultrasound echocardiography, cardiomyocyte characteristics, and Masson's trichrome staining showed that LPS inhibited cardiac function and caused cardiac fibrosis, while catalase alleviated these adverse effects. LPS increased apoptosis (TUNEL, caspase-3 activation, cleaved caspase-3), increased O₂^·- production, induced inflammation (TNF-α), autophagy, iron toxicity, and carbonyl damage, and significantly damaged mitochondria (mitochondrial membrane potential, mitochondrial proteins, and ultrastructure). These effects were significantly alleviated by catalase. Interestingly, the antioxidant N-acetylcysteine, autophagy inhibitor 3-methyladenine, and ferroptosis inhibitor lipostatin-1 all eliminated the LPS-induced contraction dysfunction and ferroptosis (using lipid peroxidation). Induction of ferroptosis could eliminate the cardioprotective effect of NAC. In conclusion, catalase rescues LPS-induced cardiac dysfunction by regulating oxidative stress, autophagy, ferroptosis, apoptosis, and mitochondrial damage in cardiomyocytes.

The role of adiponectin in cardiovascular disease

Cardiovascular disease (CVD) is a common disease that seriously threatens the health of human beings, especially middle-aged and elderly people over 50 years old. It has the characteristics of high prevalence, high disability rate and high mortality rate. Previous studies have shown that adiponectin has therapeutic effects on a variety of CVDs. As a key adipokine, adiponectin, is an abundant peptide-regulated hormone that is mainly released by adipocytes and cardiomyocytes, as well as endothelial and skeletal cells. Adiponectin can protect against CVD by improving lipid metabolism, protecting vascular endothelial cells and inhibiting foam cell formation and vascular smooth muscle cell proliferation. Further investigation of the molecular and cellular mechanisms underlying the adiponectin system may provide new ideas for the treatment of CVD. Herein, this review aims to describe the structure and function of adiponectin and adiponectin receptors, introduce the function of adiponectin in the protection of cardiovascular disease and analyze the potential use and clinical significance of this hormone in the protection and treatment of cardiovascular disease, which shows that adiponectin can be expected to become a new therapeutic target and biomarker for the diagnosis and treatment of CVD.

MRTF-A alleviates myocardial ischemia reperfusion injury by inhibiting the inflammatory response and inducing autophagy

Myocardin-related transcription factor A (MRTF-A) has an inhibitory effect on myocardial infarction; however, the mechanism is not clear. This study reveals the mechanism by which MRTF-A regulates autophagy to alleviate myocardial infarct-mediated inflammation, and the effect of silent information regulator 1 (SIRT1) on the myocardial protective effect of MRTF-A was also verified. MRTF-A significantly decreased cardiac damage induced by myocardial ischemia. In addition, MRTF-A decreased NLRP3 inflammasome activity, and significantly increased the expression of autophagy protein in myocardial ischemia tissue. Lipopolysaccharide (LPS) and 3-methyladenine (3-MA) eliminated the protective effects of MRTF-A. Furthermore, simultaneous overexpression of MRTF-A and SIRT1 effectively reduced the injury caused by myocardial ischemia; this was associated with downregulation of inflammatory factor proteins and when upregulation of autophagy-related proteins. Inhibition of SIRT1 activity partially suppressed these MRTF-A-induced cardioprotective effects. SIRT1 has a synergistic effect with MRTF-A to inhibit myocardial ischemia injury through reducing the inflammation response and inducing autophagy.

Research Progress on the Mechanism of Sepsis Induced Myocardial Injury

Sepsis is an abnormal condition with multiple organ dysfunctions caused by the uncontrolled infection response and one of the major diseases that seriously hang over global human health. Besides, sepsis is characterized by high morbidity and mortality, especially in intensive care unit (ICU). Among the numerous subsequent organ injuries of sepsis, myocardial injury is one of the most common complications and the main cause of death in septic patients. To better manage septic inpatients, it is necessary to understand the specific mechanisms of sepsis induced myocardial injury (SIMI). Therefore, this review will elucidate the pathophysiology of SIMI from the following certain mechanisms: apoptosis, mitochondrial damage, autophagy, excessive inflammatory response, oxidative stress and pyroptosis, and outline current therapeutic strategies and potential approaches in SIMI.

Silibinin protects against sepsis and septic myocardial injury in an NR1H3-dependent pathway

Cardiac dysfunction resulting from sepsis causes high morbidity and mortality. Silibinin (SIL) is a secondary metabolite isolated from the seed extract of the milk thistle plant with various properties, including anti-inflammatory, anti-fibrotic, and anti-oxidative activities. This study, for the first time, examined the effects and mechanisms of SIL pretreatment, posttreatment and in combination with classical antibiotics in septic myocardial injury. The survival rate, sepsis score, anal temperature, routine blood parameters, blood biochemical parameters, cardiac function indicators, pathological indicators of myocardial injury, NR1H3 signaling pathway, and several sepsis-related signaling pathways were detected 8 h following cecal ligation and puncture (CLP). Our results showed that SIL pretreatment showed a significant protective effect on sepsis and septic myocardial injury, which was explained by the attenuation of inflammation, inhibition of oxidative stress, improvement of mitochondrial function, regulation of endoplasmic reticulum stress (ERS), and activation of the NR1H3 pathway. SIL posttreatment and the combination of SIL and azithromycin (AZI) showed a certain therapeutic effect. RNA-seq detection further clarified the myocardial protective mechanisms of SIL. Taken together, this study provides a theoretical basis for the application strategy and combination of SIL in septic myocardial injury.

Evidence for the Benefits of Melatonin in Cardiovascular Disease

The pineal gland is a neuroendocrine gland which produces melatonin, a neuroendocrine hormone with critical physiological roles in the circadian rhythm and sleep-wake cycle. Melatonin has been shown to possess anti-oxidant activity and neuroprotective properties. Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.

Novel Insights Into the Potential Mechanisms of N6-Methyladenosine RNA Modification on Sepsis-Induced Cardiovascular Dysfunction: An Update Summary on Direct and Indirect Evidences

Sepsis is a life-threatening organ dysfunction caused by a host’s dysfunctional response to infection. As is known to all, septic heart disease occurs because pathogens invading the blood stimulate the activation of endothelial cells, causing a large number of white blood cells to accumulate and trigger an immune response. However, in severe sepsis, the hematopoietic system is inhibited, and there will also be a decline in white blood cells, at which time the autoimmune system will also be suppressed. During the immune response, a large number of inflammatory factors are released into cells to participate in the inflammatory process, which ultimately damages cardiac myocytes and leads to impaired cardiac function. N6-methyladenosine (m6A) is a common RNA modification in mRNA and non-coding RNA that affects RNA splicing, translation, stability, and epigenetic effects of some non-coding RNAs. A large number of emerging evidences demonstrated m6A modification had been involved in multiple biological processes, especially for sepsis and immune disorders. Unfortunately, there are limited results provided to analyze the association between m6A modification and sepsis-induced cardiovascular dysfunction (SICD). In this review, we firstly summarized current evidences on how m6A mediates the pathophysiological process in cardiac development and cardiomyopathy to emphasize the importance of RNA methylation in maintaining heart biogenesis and homeostasis. Then, we clarified the participants of m6A modification in extended inflammatory responses and immune system activation, which are the dominant and initial changes secondary to sepsis attack. After that, we deeply analyzed the top causes of SICD and identified the activation of inflammatory cytokines, endothelial cell dysfunction, and mitochondrial failure. Thus, the highlight of this review is that we systematically collected all the related potential mechanisms between m6A modification and SICD causes. Although there is lack of direct evidences on SICD, indirect evidences had been demonstrated case by case on every particular molecular mechanism and signal transduction, which require further explorations into the potential links among the listed mechanisms. This provides novel insights into the understanding of SICD.

Deletion of TLR4 attenuates lipopolysaccharide-induced acute liver injury by inhibiting inflammation and apoptosis

Septic acute liver injury is one of the leading causes of fatalities in patients with sepsis. Toll-like receptor 4 (TLR4) plays a vital role in response to lipopolysaccharide (LPS) challenge, but the mechanisms underlying TLR4 function in septic injury remains unclear. In this study, we investigated the role of TLR4 in LPS-induced acute liver injury (ALI) in mice with a focus on inflammation and apoptosis. Wild-type (WT) and TLR4-knockout (TLR4-/-) mice were challenged with LPS (4 mg/kg) for 6 h. TLR4 signaling cascade markers (TLR4, MyD88, and NF-κB), inflammatory markers (TNFα, IL-1β, and IL-6), and apoptotic markers (Bax, Bcl-2, and caspase 3) were evaluated. We showed that LPS challenge markedly increased the levels of serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST) and other liver pathological changes in WT mice. In addition, LPS challenge elevated the levels of liver carbonyl proteins and serum inflammatory cytokines, upregulated the expression of TLR4, MyD88, and phosphorylated NF-κB in liver tissues. Moreover, LPS challenge significantly increased hepatocyte apoptosis, caspase 3 activity, and Bax level while suppressing Bcl-2 expression in liver tissues. These pathological changes were greatly attenuated in TLR4-/- mice. Similar pathological responses were provoked in primary hepatic Kupffer cells isolated from WT and TLR4-/- mice following LPS (1 μg/mL, 6 h) challenge. In summary, these results demonstrate that silencing of TLR4 attenuates LPS-induced liver injury through inhibition of inflammation and apoptosis via TLR4/MyD88/NF-κB signaling pathway. TLR4 deletion confers hepatoprotection against ALI induced by LPS, possibly by repressing macrophage inflammation and apoptosis.

Hydrogen alleviates cell damage and acute lung injury in sepsis via PINK1/Parkin-mediated mitophagy

BACKGROUND

Multiple organ failure (MOF) is the main cause of early death in septic shock. Lungs are among the organs that are affected in MOF, resulting in acute lung injury. Inflammation is an important factor that causes immune cell dysfunction in the pathogenesis of sepsis. Autophagy is involved in the process of inflammation and also occurs in response to cell and tissue injury in several diseases. We previously demonstrated that hydrogen alleviated the inflammation-induced cell injury and organ damage in septic mice.

AIM

The focus of the present study was to elucidate whether mitophagy mediates the inflammatory response or oxidative injury in sepsis in vitro and in vivo. Furthermore, we evaluated the role of mitophagy in the protective effects of hydrogen against cell injury or organ dysfunction in sepsis.

METHOD

RAW 264.7 macrophages induced by lipopolysaccharide (LPS) were used as an in vitro model for inflammation, and cecal ligation and puncture (CLP)-induced acute lung injury mice were used as an in vivo model for sepsis. The key protein associated with mitophagy, PTEN-induced putative kinase 1 (PINK1), was knocked down by PINK1 shRNA transfection in RAW 264.7 macrophages or mice.

RESULTS

Hydrogen ameliorated cell injury and enhanced mitophagy in macrophages stimulated by LPS. PINK1 was required for the mitigation of the cell impairment in LPS-stimulated macrophages by hydrogen treatment. PINK1 knockdown abrogated the beneficial effects of hydrogen on mitophagy in LPS-stimulated macrophages. Hydrogen inhibited acute lung injury in CLP mice via activation of PINK1-mediated mitophagy.

CONCLUSION

These results suggest that PINK1-mediated mitophagy plays a key role in the protective effects of hydrogen against cell injury in LPS-induced inflammation and CLP-induced acute lung injury.

Liquiritin Attenuates Lipopolysaccharides-Induced Cardiomyocyte Injury via an AMP-Activated Protein Kinase-Dependent Signaling Pathway

Background: Liquiritin (LIQ) is a traditional Chinese medicine that has been reported to regulate inflammation, oxidative stress and cell apoptosis. However, the beneficial effects of LIQ in lipopolysaccharides (LPS)-induced septic cardiomyopathy (SCM) has not been reported. The primary goal of this study was to investigate the effects of LIQ in LPS-induced SCM model.

Methods: Mice were pre-treated with LIQ for 7 days before they were injected with LPS (10 mg/kg) for inducing SCM model. Echocardiographic analysis was used to evaluate cardiac function after 12 h of LPS injection. Thereafter, mice were sacrificed to collect hearts for molecular and histopathologic assays by RT-PCR, western-blots, immunohistochemical and terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) staining analysis respectively. AMPKα2 knockout (AMPKα2^−/−) mice were used to elucidate the mechanism of LIQ Neonatal rat cardiomyocytes (NRCMs) treated with or without LPS were used to further investigate the roles and mechanisms of LIQ in vitro experiments.

Results: LIQ administration attenuated LPS-induced mouse cardiac dysfunction and reduced mortality, based upon the restoration of EF, FS, LVEDs, heart rate, dp/dt max and dp/dt min deteriorated by LPS treatment. LIQ treatment also reduced mRNA expression of TNFα, IL-6 and IL-1β, inhibited inflammatory cell migration, suppressed cardiac oxidative stress and apoptosis, and improved metabolism. Mechanistically, LIQ enhanced the phosphorylation of AMP-activated protein kinase α2 (AMPKα2) and decreased the phosphorylation of mTORC1, IκBα and NFκB/p65. Importantly, the beneficial roles of LIQ were not observed in AMPKα2 knockout model, nor were they observed in vitro model after inhibiting AMPK activity with an AMPK inhibitor.

Conclusion: We have demonstrated that LIQ exerts its protective effects in an SCM model induced by LPS administration. LIQ reduced inflammation, oxidative stress, apoptosis and metabolic alterations via regulating AMPKα2 dependent signaling pathway. Thus, LIQ might be a potential treatment or adjuvant for SCM treatment.

AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAr) has been one of the most commonly used pharmacological modulators of AMPK activity. The majority of early studies on the role of AMPK, both in the physiological regulation of metabolism and in cancer pathogenesis, were based solely on the use of AICAr as an AMPK-activator. Even with more complex models of AMPK downregulation and knockout being introduced, AICAr remained a regular starting point for many studies focusing on AMPK biology. However, there is an increasing number of studies showing that numerous AICAr effects, previously attributed to AMPK activation, are in fact AMPK-independent. This review aims to give an overview of the present knowledge on AMPK-dependent and AMPK-independent effects of AICAr on metabolism, hypoxia, exercise, nucleotide synthesis, and cancer, calling for caution in the interpretation of AICAr-based studies in the context of understanding AMPK signaling pathway.

AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAr) has been one of the most commonly used pharmacological modulators of AMPK activity. The majority of early studies on the role of AMPK, both in the physiological regulation of metabolism and in cancer pathogenesis, were based solely on the use of AICAr as an AMPK-activator. Even with more complex models of AMPK downregulation and knockout being introduced, AICAr remained a regular starting point for many studies focusing on AMPK biology. However, there is an increasing number of studies showing that numerous AICAr effects, previously attributed to AMPK activation, are in fact AMPK-independent. This review aims to give an overview of the present knowledge on AMPK-dependent and AMPK-independent effects of AICAr on metabolism, hypoxia, exercise, nucleotide synthesis, and cancer, calling for caution in the interpretation of AICAr-based studies in the context of understanding AMPK signaling pathway.

Reduning injection and its effective constituent luteoloside protect against sepsis partly via inhibition of HMGB1/TLR4/NF-κB/MAPKs signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Reduning injection (RDN), a popular traditional Chinese medicine, formulated by three herbs (i.e., Artemisia carvifolia Buch.-Ham. ex Roxb., Lonicera japonica Thunb., and Gardenia jasminoides J. Ellis), has been widely used to treat upper respiratory infectious diseases in China.

AIM OF THE STUDY

To investigate the protective effect of RDN on both lipopolysaccharides (LPS)- and cecal ligation and puncture (CLP)-induced septic mice. To identify the potentially effective constituent, and to determine its protective effect and underlying mechanism in vivo and in vitro.

MATERIALS AND METHODS

Male C57BL/6 mice were used to establish septic model by tail intravenous injection of 4 mg/kg LPS or CLP surgery. After modeling, mice were administered by tail intravenous injection of RDN in the dose of 16 or 8 mL/kg/day. The mortality, histopathology, plasma levels of inflammatory cytokines were evaluated respectively. In addition, we screened the potentially effective substances of RDN against sepsis by detecting the nitric oxide (NO) production in LPS-stimulated Raw 264.7 cells and verified the effect of luteoloside in CLP-induced septic mice subsequently. Finally, the underlying mechanisms of RDN and luteoloside were investigated in the inflammatory model in vitro.

RESULTS

Administration of RDN significantly reduced the mortality and increased the survival rate in both LPS- and CLP-induced septic mice. Meanwhile, RDN reduced the release of inflammatory cytokines accompanied by alleviating the organs damage of lung, liver, and kidney in CLP-induced septic mice. Moreover, several components from Gardenia jasminoides J. Ellis extract (ZZ) or Lonicera japonica Thunb and Artemisia carvifolia Buch.-Ham. ex Roxb extract (JQ) as well as the constituents of luteoloside, quercetin, and caffeic acid were screened out to have obvious anti-inflammatory activity, which may be the potentially effective substances of RDN against sepsis. We further verified the protective role of luteoloside in CLP-induced septic mice. In addition, RDN and luteoloside significantly inhibited both the secretion and translocation of mobility group box (HMGB)1, and HMGB1-mediated activation of TLR4/NF-κB/MAPKs signaling pathways.

CONCLUSION

RDN and its effective constituent luteoloside exhibited a significant protective effect against sepsis, which were potential candidate drugs for treatment of sepsis. The mechanism of antisepsis partly was related to inhibition of HMGB1/TLR4/NF-κB/MAPKs signaling pathways. The results provide an evidence base for the follow-up clinical application of RDN in treatment of sepsis.

Cardamonin protects against lipopolysaccharide-induced myocardial contractile dysfunction in mice through Nrf2-regulated mechanism

In patients with sepsis, lipopolysaccharide (LPS) from the outer membrane of gram-negative bacteria triggers cardiac dysfunction and heart failure, but target therapy for septic cardiomyopathy remains unavailable. In this study we evaluated the beneficial effects of cardamonin (CAR), a flavone existing in Alpinia plant, on endotoxemia-induced cardiac dysfunction and the underlying mechanisms with focus on oxidative stress and apoptosis. Adult mice were exposed to LPS (4 mg/kg, i.p. for 6 h) prior to functional or biochemical assessments. CAR (20 mg/kg, p.o.) was administered to mice immediately prior to LPS challenge. We found that LPS challenge compromised cardiac contractile function, evidenced by compromised fractional shortening, peak shortening, maximal velocity of shortening/relengthening, enlarged LV end systolic diameter and prolonged relengthening in echocardiography, and induced apoptosis, overt oxidative stress (O2- production and reduced antioxidant defense) associated with inflammation, phosphorylation of NF-κB and cytosolic translocation of transcriptional factor Nrf2. These deteriorative effects were greatly attenuated or mitigated by CAR administration. However, H&E and Masson's trichrome staining analysis revealed that neither LPS challenge nor CAR administration significantly affected cardiomyocyte cross-sectional area and interstitial fibrosis. Mouse cardiomyocytes were treated with LPS (4 µg/mL) for 6 h in the absence or presence of CAR (10 μM) in vitro. We found that addition of CAR suppressed LPS-induced defect in cardiomyocyte shortening, which was nullified by the Nrf2 inhibitor ML-385 or the NF-κB activator prostratin. Taken together, our results suggest that CAR administration protects against LPS-induced cardiac contractile abnormality, oxidative stress, apoptosis, and inflammation through Nrf2- and NF-κB-dependent mechanism.

A novel Adiponectin receptor (AdipoR) involved in regulating cytokines production and apoptosis of haemocytes in oyster Crassostrea gigas

Adiponectin receptors (AdipoRs) comprise a seven-transmembrane domain-containing protein family, which specifically recognize adiponectin (APN) and play critical roles in the immunological and physiological processes in vertebrates. In the present study, a novel AdipoR is identified from oyster Crassostrea gigas (designated as CgAdipoR). The full-length cDNA of CgAdipoR is of 1209 bp encoding a polypeptide of 343 amino acids. There is an N-terminal domain, a Hly III domain, and a C-terminal domain in CgAdipoR. After the transfection of CgAdipoR, the level of intracellular Ca²⁺ into HEK293T cells increases significantly (1.36-fold, p < 0.05) after APN incubation. The mRNA transcripts of CgAdipoR are widely distributed in all the tested tissues, with the highest expression level in haemocytes (3.20-fold of that in hepatopancreas, p < 0.05). After lipopolysaccharide (LPS), Vibrio splendidus and polyinosinic-polycytidylic acid (poly (I:C)) stimulations, the mRNA expression of CgAdipoR in haemocytes is significantly up-regulated and reached the highest level at 24 h (15.07-fold, p < 0.01), 6 h (4.39-fold, p < 0.01) and 24 h (5.62-fold, p < 0.01) compared to control group, respectively. After CgAdipoR is interfered by specific CgAdipoR-dsRNA, the expression level of interleukins (CgIL17-1, CgIL17-2, CgIL17-3 and CgIL17-5) in haemocytes decreases significantly (p < 0.01) at 24 h post LPS stimulation, while the expression level of CgTNF-1 increases significantly (1.68-fold, p < 0.01), compared to that in the dsEGFP group. In CgAdipoR dsRNA-injected oysters, the mRNA expressions of anti-apoptotic B-cell lymphoma-2 (Bcl-2) in haemocytes significantly decreases at 24 h after LPS challenge, which is (0.58-fold, p < 0.05) of that in dsEGFP-injected oysters, while the apoptotic rate of haemocytes is significantly up-regulated (1.93-fold of that in dsEGFP group, p < 0.05). These results collectively suggest that CgAdipoR plays an important role in the immune response of oysters by regulating the expressions of inflammatory cytokines and haemocyte apoptosis.

Association between plasma adiponectin levels and left ventricular systolic dysfunction in sepsis patients

PURPOSE

As a well-known cardioprotective factor, the relevance of adiponectin (APN) to heart function following sepsis remains largely unknown. The present study evaluated the effects of plasma APN levels on heart function and 28-day mortality in sepsis patients.

MATERIALS AND METHODS

This was a prospective study that was performed with 98 patients with sepsis and 32 controls. Left ventricular systolic dysfunction (LVSD) was defined as a left ventricular ejection fraction (LVEF) ≤ 45% based on echocardiography. The effects of APN on the development of sepsis-related LVSD and prediction of 28-day mortality were evaluated.

RESULTS

Plasma APN levels significantly decreased in sepsis patients compared with controls, with rising severity of illness, and positively correlated with the LVEF and stroke volume index. Sepsis patients with LVSD had lower APN levels than patients without LVSD. According to the receiver operating characteristic curve, plasma APN levels had the comparable value in prediction of LVSD incidence than those conditional factors, including brain natriuretic peptide (BNP) and highly sensitive cardiac troponin T (hsTnT). Twenty-three of the 98 sepsis patients (23.47%) died at 28 days. Adiponectin levels were an independent predictive factor for 28-day mortality.

CONCLUSIONS

Low APN levels were associated with the incidence of LVSD and 28-day mortality in sepsis patients. Adiponectin may be a novel factor that may be useful for the diagnosis of LVSD.

Targeting AMP-Activated Protein Kinase in Aging-Related Cardiovascular Diseases

Aging is a pivotal risk factor for developing cardiovascular diseases (CVD) due to the lifelong exposure to various risk factors that may affect the heart and vasculature during aging. AMP-activated protein kinase (AMPK), a serine/threonine protein kinase, is a pivotal endogenous energy regulator that protects against various pathological alterations. In this report, we first introduced the protective mechanisms of AMPK signaling in myocardium, such as oxidative stress, apoptosis, inflammation, autophagy and inflammatory response. Next, we introduced the potential correlation between AMPK and cardiac aging. Then, we highlighted the roles of AMPK signaling in cardiovascular diseases, including myocardial ischemia, cardiomyopathy, and heart failure. Lastly, some potential directions and further perspectives were expanded. The information extends our understanding on the protective roles of AMPK in myocardial aging, which may contribute to the design of drug targets and sheds light on potential treatments of AMPK for aging-related CVD.

Autophagy is involved in the protective effect of p21 on LPS-induced cardiac dysfunction

p21 has emerged as an important protein involved in cardiovascular diseases, but its role remains controversial. Recently, p21 has been reported to mediate inflammatory responses. As inflammatory responses are a feature of sepsis, our study investigated whether p21 has a role in cardiac dysfunction induced by sepsis and analyzed the mechanisms involved. To establish a mouse sepsis model, p21 global knockout (p21KO) and C57BL/6J wild-type (WT) male mice were treated with 5 mg/kg LPS intraperitoneally for 6, 24, or 48 h. After LPS stimulation, the level of p21 had significantly increased in the WT mice and in cardiomyocytes. Cardiac dysfunction induced by LPS was markedly aggravated in p21KO mice relative to that of WT mice. Downregulation of p21 expression exacerbated the LPS-mediated inflammatory response, and it increased oxidative stress as well as mitochondrial damage in the heart and in cardiomyocytes. In contrast, overexpressing p21 attenuated the increase of TNFα and promoted the increase of SOD2. Moreover, p21 regulated the LPS-induced autophagy activation; that is, the increase in autophagy was impaired when p21 expression was decreased, whereas the increase was significant when p21 was overexpressed. The autophagy inducer rapamycin partially rescued the cardiac deterioration caused by p21 downregulation in the LPS-stimulated groups. In addition, p21 regulated the autophagy level by interacting with LC3B. These results revealed that p21 controls LPS-induced cardiac dysfunction by modulating inflammatory and oxidative stress, and it is partially dependent on regulating the autophagy level. This study is the first to show that p21 could interact with LC3B to promote autophagy for the improvement of cardiac function during sepsis.

MG-132 attenuates cardiac deterioration of viral myocarditis via AMPK pathway

BACKGROUND

Coxsackievirus B3 (CVB3) is the primary cause of infectious myocarditis. Aggressive immunological activation and apoptosis of myocytes contributes to progressive dysfunction of cardiac contraction and poor prognosis. MG-132, a proteasome inhibitor, regulates mitochondrial-mediated intrinsic myocardial apoptosis and downregulates NF-κB-mediated inflammation. Here, we determined whether AMPK pathway participates in MG-132-mediated myocardial protection in viral-induced myocarditis.

METHODS AND RESULTS

Acute viral myocarditis models were established by intraperitoneal inoculation of CVB3 in male BALB/c mice. Myocarditis and age-matched control mice were administered MG-132 and/or BML-275 dihydrochloride (BML) (AMPK antagonist) intraperitoneally daily from the day following CVB3 inoculation. MG-132 improved hemodynamics and inhibited the structural remodeling of the ventricle in mice with myocarditis, while BML largely blunted these effects. TUNEL staining and immunochemistry suggested that MG-132 exerts anti-apoptotic and anti-inflammatory effects against CVB3-induced myocardial injuries. BML attenuated the effects of MG-132 on anti-apoptosis and anti-inflammation.

CONCLUSION

MG-132 modulated apoptosis and inflammation, improved hemodynamics, and inhibited the structural remodeling of ventricles in a myocarditis mouse model via regulation of the AMPK signal pathway.

Activation of AMP-activated protein kinase during sepsis/inflammation improves survival by preserving cellular metabolic fitness

The purpose was to determine the role of AMPK activation in the renal metabolic response to sepsis, the development of sepsis-induced acute kidney injury (AKI) and on survival. In a prospective experimental study, 167 10- to 12-week-old C57BL/6 mice underwent cecal ligation and puncture (CLP) and human proximal tubule epithelial cells (TEC; HK2) were exposed to inflammatory mix (IM), a combination of lipopolysaccharide (LPS) and high mobility group box 1 (HMGB1). Renal/TEC metabolic fitness was assessed by monitoring the expression of drivers of oxidative phosphorylation (OXPHOS), the rates of utilization of OXPHOS/glycolysis in response to metabolic stress, and mitochondrial function by measuring O₂ consumption rates (OCR) and the membrane potential (Δψ_m ). Sepsis/IM resulted in AKI, increased mortality, and in renal AMPK activation 6-24 hours after CLP/IM. Pharmacologic activation of AMPK with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or metformin during sepsis improved the survival, while AMPK inhibition with Compound C increased mortality, impaired mitochondrial respiration, decreased OCR, and disrupted TEC metabolic fitness. AMPK-driven protection was associated with increased Sirt 3 expression and restoration of metabolic fitness. Renal AMPK activation in response to sepsis/IM is an adaptive mechanism that protects TEC, organs, and the host by preserving mitochondrial function and metabolic fitness likely through Sirt3 signaling.

CD74 knockout protects against LPS-induced myocardial contractile dysfunction through AMPK-Skp2-SUV39H1-mediated demethylation of BCLB

BACKGROUND AND PURPOSE

Lipopolysaccharides (LPS), an outer membrane component of Gram-negative bacteria, triggers myocardial anomalies in sepsis. Recent findings indicated a role for inflammatory cytokine MIF and its receptor, CD74, in septic organ injury, although little is known of the role of MIF-CD74 in septic cardiomyopathy.

EXPERIMENTAL APPROACH

This study evaluated the impact of CD74 ablation on endotoxaemia-induced cardiac anomalies. Echocardiographic, cardiomyocyte contractile and intracellular Ca2+ properties were examined.

KEY RESULTS

Our data revealed compromised cardiac function (lower fractional shortening, enlarged LV end systolic diameter, decreased peak shortening, maximal velocity of shortening/relengthening, prolonged duration of relengthening and intracellular Ca2+ mishandling) and ultrastructural derangement associated with inflammation, O2 - production, apoptosis, excess autophagy, phosphorylation of AMPK and JNK and dampened mTOR phosphorylation. These effects were attenuated or mitigated by CD74 knockout. LPS challenge also down-regulated Skp2, an F-box component of Skp1/Cullin/F-box protein-type ubiquitin ligase, while up-regulating that of SUV39H1 and H3K9 methylation of the Bcl2 protein BCLB. These effects were reversed by CD74 ablation. In vitro study revealed that LPS facilitated GFP-LC3B formation and cardiomyocyte defects. These effects were prevented by CD74 ablation. Interestingly, the AMPK activator AICAR, the autophagy inducer rapamycin and the demethylation inhibitor difenoconazole inhibited the effects of CD74 ablation against LPS-induced cardiac dysfunction, while the SUV39H1 inhibitor chaetocin or methylation inhibitor 5-AzaC ameliorated LPS-induced GFP-LC3B formation and cardiomyocyte contractile dysfunction.

CONCLUSION AND IMPLICATIONS

Our data suggested that CD74 ablation protected against LPS-induced cardiac anomalies, O2 - production, inflammation and apoptosis through suppression of autophagy in a Skp2-SUV39H1-mediated mechanism.

The Role of AMPK Activation for Cardioprotection in Doxorubicin-Induced Cardiotoxicity

Doxorubicin is a commonly used chemotherapeutic agent for the treatment of a range of cancers, but despite its success in improving cancer survival rates, doxorubicin is cardiotoxic and can lead to congestive heart failure. Therapeutic options for this patient group are limited to standard heart failure medications with the only drug specific for doxorubicin cardiotoxicity to reach FDA approval being dexrazoxane, an iron-chelating agent targeting oxidative stress. However, dexrazoxane has failed to live up to its expectations from preclinical studies while also bringing up concerns about its safety. Despite decades of research, the molecular mechanisms of doxorubicin cardiotoxicity are still poorly understood and oxidative stress is no longer considered to be the sole evil. Mitochondrial impairment, increased apoptosis, dysregulated autophagy and increased fibrosis have also been shown to be crucial players in doxorubicin cardiotoxicity. These cellular processes are all linked by one highly conserved intracellular kinase: adenosine monophosphate-activated protein kinase (AMPK). AMPK regulates mitochondrial biogenesis via PGC1α signalling, increases oxidative mitochondrial metabolism, decreases apoptosis through inhibition of mTOR signalling, increases autophagy through ULK1 and decreases fibrosis through inhibition of TGFβ signalling. AMPK therefore sits at the control point of many mechanisms shown to be involved in doxorubicin cardiotoxicity and cardiac AMPK signalling itself has been shown to be impaired by doxorubicin. In this review, we introduce different agents known to activate AMPK (metformin, statins, resveratrol, thiazolidinediones, AICAR, specific AMPK activators) as well as exercise and dietary restriction, and we discuss the existing evidence for their potential role in cardioprotection from doxorubicin cardiotoxicity.

Melatonin for the treatment of sepsis: the scientific rationale

Sepsis affects 30 million people worldwide, leading to 6 million deaths every year (WHO), and despite decades of research, novel initiatives are drastically needed. According to the current literature, oxidative imbalance and mitochondrial dysfunction are common features of septic patients that can cause multiorgan failure and death. Melatonin, alongside its traditionally accepted role as the master hormonal regulator of the circadian rhythm, is a promising adjunctive drug for sepsis through its anti-inflammatory, antiapoptotic and powerful antioxidant properties. Several animal models of sepsis have demonstrated that melatonin can prevent multiorgan dysfunction and improve survival through restoring mitochondrial electron transport chain (ETC) function, inhibiting nitric oxide synthesis and reducing cytokine production. The purpose of this article is to review the current evidence for the role of melatonin in sepsis, review its pharmacokinetic profile and virtual absence of side effects. While clinical data is limited, we propose the adjunctive use of melatonin is patients with severe sepsis and septic shock.

Proinflammatory Effect of Endothelial Microparticles Is Mitochondria Mediated and Modulated Through MAPKAPK2 (MAPK-Activated Protein Kinase 2) Leading to Attenuation of Cardiac Hypertrophy

Objective- This study investigates the functional significance of mitochondria present in endothelial microparticles (EMP) and how MK2 (MAPKAPK2 [MAPK-activated protein kinase 2]) governs EMP production and its physiological effect on cardiac hypertrophy. Approach and Results- Flow cytometric analysis, confocal imaging, oxygen consumption rate measurement through Seahorse were used to confirm the presence of functionally active mitochondria in nontreated EMP (EMP derived from untreated control cells), lipopolysaccharide, and oligomycin treatment increased mitochondrial reactive oxygen species activity in EMP (EMP derived from cells treated with lipopolysaccharide and EMP derived from cells treated with oligomycin, respectively). The dysfunctional mitochondria contained in EMP derived from cells treated with lipopolysaccharide and EMP derived from cells treated with oligomycin induced the expression of proinflammatory mediators in the target endothelial cells leading to the augmented adhesion of human monocytic cell line on EA.hy926 cells. Multiphoton real-time imaging detected the increased adherence of EMP derived from cells treated with oligomycin at the site of carotid artery injury as compared to EMP derived from untreated control cells. MK2 regulates EMP generation during inflammation by reducing E-selectin expression and regulating the cytoskeleton rearrangement through ROCK-2 (Rho-associated coiled-coil containing protein kinase 2) pathway. MK2-deficient EMP reduced the E-selectin and ICAM-1 (intracellular adhesion molecule-1) expression on target endothelial cells leading to reduced monocyte attachment and reduced cardiac hypertrophy in mice. Conclusions- MK2 promotes the proinflammatory effect of EMP mediated through dysfunctional mitochondria. MK2 modulates the inflammatory effect induced during cardiac hypertrophy through EMP.

The Protective Effects of Melatonin Against LPS-Induced Septic Myocardial Injury: A Potential Role of AMPK-Mediated Autophagy

Aim: Melatonin is an indolamine secreted by the pineal gland, as well as most of the organs and tissues. In addition to regulating circadian biology, studies have confirmed the multiple pharmacological effects of melatonin. Melatonin provides a strong defense against septic myocardial injury. However, the underlying mechanism has not been fully described. In this study, we investigated the protective effects of melatonin against lipopolysaccharide (LPS)-induced myocardial injury as well as the mechanisms involved. Methods: Mice were intraperitoneally injected with LPS to induce a septic myocardial injury model or an LPS shock model, depending on the dose of LPS. Melatonin was given (20 mg/kg/day, via intraperitoneal injection) for a week prior to LPS insult. 6 h after LPS injection, echocardiographic analysis, TUNEL staining, transmission electron microscopy (TEM), western blot, quantitative real-time PCR and ELISA were used to investigate the protective effects of melatonin against LPS induced myocardial injury. AMPK inhibitor, autophagy activator and inhibitor, siRNAs were used for further validation. Results: Survival test showed that melatonin significantly increased the survival rate after LPS-induced shock. In the sepsis model, melatonin markedly ameliorated myocardial dysfunction, decreased the release of inflammatory cytokines, activated AMP-activated protein kinase (AMPK), improved mitochondrial function, and activated autophagy. To confirm whether the protection of melatonin was mediated by AMPK and autophagy, Compound C, an AMPK inhibitor; 3-MA, an autophagy inhibitor; and Rapamycin (Rapa), an autophagy activator, were used in this study. AMPK inhibition down-regulated autophagy, abolished protection of melatonin, as indicated by significantly decreased cardiac function, increased inflammation and damaged mitochondrial function. Furthermore, autophagy inhibition by 3-MA significantly impaired the protective effects of melatonin, whereas autophagy activation by Rapa reversed LPS + Compound C induced myocardial injury. In addition, in vitro studies further confirmed the protection of melatonin against LPS-induced myocardial injury and the mechanisms involving AMPK-mediated autophagy signaling. Conclusions: In summary, our results demonstrated that melatonin protects against LPS-induced septic myocardial injury by activating AMPK mediated autophagy pathway.

PARP1 interacts with HMGB1 and promotes its nuclear export in pathological myocardial hypertrophy

High-mobility group box 1 (HMGB1) exhibits various functions according to its subcellular location, which is finely conditioned by diverse post-translational modifications, such as acetylation. The nuclear HMGB1 may prevent from cardiac hypertrophy, whereas its exogenous protein is proven to induce hypertrophic response. This present study sought to investigate the regulatory relationships between poly(ADP-ribose) polymerase 1 (PARP1) and HMGB1 in the process of pathological myocardial hypertrophy. Primary-cultured neonatal rat cardiomyocytes (NRCMs) were respectively incubated with three cardiac hypertrophic stimulants, including angiotensin II (Ang II), phenylephrine (PE), and isoproterenol (ISO), and cell surface area and the mRNA expression of hypertrophic biomarkers were measured. the catalytic activity of PARP1 was remarkably enhanced, meanwhile HMGB1 excluded from the nucleus. PARP1 overexpression by infecting with adenovirus PARP1 (Ad-PARP1) promoted the nuclear export of HMGB1, facilitated its secretion outside the cell, aggravated cardiomyocyte hypertrophy, which could be alleviated by HMGB1 overexpression. PE treatment led to the similar results, while that effect was widely depressed by PARP1 silencing or its specific inhibitor AG14361. Moreover, SD rats were intraperitoneally injected with 3-aminobenzamide (3AB, 20 mg/kg every day, a well-established PARP1 inhibitor) 7 days after abdominal aortic constriction (AAC) surgery for 6 weeks, echocardiography and morphometry of the hearts were measured. Pre-treatment of 3AB relieved AAC-caused the translocation of nuclear HMGB1 protein, cardiac hypertrophy, and heart dysfunction. Our research offers a novel evidence that PARP1 combines with HMGB1 and accelerates its translocation from nucleus to cytoplasm, and the course finally causes cardiac hypertrophy.

Mitochondrial ALDH2 protects against lipopolysaccharide-induced myocardial contractile dysfunction by suppression of ER stress and autophagy

Lipopolysaccharide (LPS), an essential component of outer membrane of the Gram-negative bacteria, plays a pivotal role in myocardial anomalies in sepsis. Recent evidence depicted an essential role for mitochondrial aldehyde dehydrogenase (ALDH2) in cardiac homeostasis. This study examined the effect of ALDH2 on endotoxemia-induced cardiac anomalies. Echocardiographic, cardiac contractile and intracellular Ca²⁺ properties were examined. Our results indicated that LPS impaired cardiac contractile function (reduced fractional shortening, LV end systolic diameter, peak shortening, maximal velocity of shortening/relengthening, prolonged relengthening duration, oxidation of SERCA, and intracellular Ca²⁺ mishandling), associated with ER stress, inflammation, O₂^- production, increased autophagy, CAMKKβ, phosphorylated AMPK and suppressed phosphorylation of mTOR, the effects of which were significantly attenuated or negated by ALDH2. LPS promoted early endosomal formation (as evidenced by RAB4 and RAB5a), apoptosis and necrosis (MTT and LDH) while decreasing late endosomal formation (RAB7 and RAB 9), the effects were reversed by ALDH2. In vitro study revealed that LPS-induced SERCA oxidation, autophagy and cardiac dysfunction were abrogated by ALDH2 activator Alda-1, the ER chaperone TUDCA, the autophagy inhibitor 3-MA, or the AMPK inhibitor Compound C. The beneficial effect of Alda-1 against LPS was nullified by AMPK activator AICAR or rapamycin. CAMKKβ inhibition failed to rescue LPS-induced ER stress. Tunicamycin-induced cardiomyocyte dysfunction was ameliorated by Alda-1 and autophagy inhibition, the effect of which was abolished by rapamycin. These data suggested that ALDH2 protected against LPS-induced cardiac anomalies via suppression of ER stress, autophagy in a CAMKKβ/AMPK/mTOR-dependent manner.

Adiponectin attenuates lipopolysaccharide-induced cell injury of H9c2 cells by regulating AMPK pathway

Adiponectin, an adipokine synthesized and secreted majorly by adipose tissue, is reported to exert cardioprotective properties via anti-inflammation and antiapoptosis. Lipopolysaccharide (LPS) is a common inflammation and apoptosis inducer of cardiomyocytes. However, few studies have reported the roles of adiponectin on LPS-induced inflammation as well as apoptosis of H9c2 cells, and the possible mechanisms of these effects. In the present study, we found that adiponectin significantly relieved LPS-induced cytotoxicity including decreased viability and elevated LDH release, inhibited LPS-triggered inflammation, which is evidenced by increases in release of TNF-α, IL-1β as well as IL-6, and attenuated the enhanced rates of apoptotic cells as well as increased caspase-3 activity caused by LPS in H9c2 cells. In addition, our data demonstrated that adiponectin upregulated AMP-activated protein kinase (AMPK) activation of H9c2 cells with or without LPS administration. Moreover, we found that blocking AMPK pathway by compound c attenuated the protective effects of adiponectin against the cytotoxicity, inflammatory response, and apoptosis of H9c2 cells resulted from LPS. Our observations bring novel insights for understanding the mediatory role of AMPK pathway implicated in the protective effects of adiponectin against LPS-induced cardiotoxicity.

Examining the Potential of Developing and Implementing Use of Adiponectin-Targeted Therapeutics for Metabolic and Cardiovascular Diseases

Cardiometabolic diseases encompass those affecting the heart and vasculature as well as other metabolic problems, such as insulin resistance, diabetes, and non-alcoholic fatty liver disease. These diseases tend to have common risk factors, one of which is impaired adiponectin action. This may be due to reduced bioavailability of the hormone or resistance to its effects on target tissues. A strong negative correlation between adiponectin levels and cardiometabolic diseases has been well-documented and research shown that adiponectin has cardioprotective, insulin sensitizing and direct beneficial metabolic effects. Thus, therapeutic approaches to enhance adiponectin action are widely considered to be desirable. The complexity of adiponectin structure and function has so far made progress in this area less than ideal. In this article we will review the effects and mechanism of action of adiponectin on cardiometabolic tissues, identify scenarios where enhancing adiponectin action would be of clinical value and finally discuss approaches via which this can be achieved.

Inflammation, Autophagy, and Apoptosis After Myocardial Infarction

Background

There is evidence for inflammation, autophagy, and apoptosis in the ischemic heart. Autophagy is a physiologic process for tissue survival. Apoptosis, on the other hand, is a mechanism that serves to clear the debris in the setting of tissue injury. The balance between autophagy and apoptosis may be important in cell survival and cardiac function.

Methods and Results

We examined the interplay of inflammation and myocyte autophagy and apoptosis during the ischemic process. We subjected mice to total left coronary artery ligation and studied these animals for up to 4 weeks. The inflammatory (tumor necrosis factor [TNF]‐α, monocyte chemoattractant protein‐1, interleukin‐6, and interleukin‐1β) and autophagic signals (light chain‐3 and beclin‐1) were strongest during the first week and then began to decline. However, the apoptotic signals peaked at week 2 after left coronary artery ligation, and the elevated levels persisted until the end of the fourth week. To elucidate the role of inflammation in the regulation of myocyte autophagy and apoptosis, we administered TNF‐α inhibitor (CAS1049741‐03‐8, Millipore, Burlington, MA) to the mice daily during the first week of myocardial infarction. Anti‐TNF‐α therapy reduced the levels of inflammatory cytokines and the inflammatory cell infiltration in and around the infarct area. However, cardiac function measured by echocardiography (fractional shortening and ejection fraction) worsened with anti‐TNF‐α therapy. More importantly, application of TNF‐α inhibitor markedly inhibited autophagy and promoted myocyte apoptosis in the border zone.

Conclusions

These observations suggest that inflammatory response may be protective in the early stage of the myocardial infarction through stimulation of myocyte autophagy. Anti‐inflammatory treatment early after coronary occlusion may have an adverse effect.

Reduced silent information regulator 1 signaling exacerbates sepsis-induced myocardial injury and mitigates the protective effect of a liver X receptor agonist

Myocardial injury and dysfunction are critical manifestations of sepsis. Previous studies have reported that liver X receptor (LXR) activation is protective during sepsis. However, whether LXR activation protects against septic heart injury and its underlying mechanisms remain elusive. This study was designed to determine the role of LXR activation in the septic heart with a focus on SIRT1 (silent information regulator 1) signaling. Male cardiac-specific SIRT1 knockout mice (SIRT1-/-) and their wild-type littermates were subjected to sepsis by cecal ligation and puncture (CLP) in the presence or absence of LXR agonist T0901317. The survival rate of mice was recorded during the 7-day period post CLP. Our results demonstrated that SIRT1-/- mice suffered from exacerbated mortality and myocardial injury in comparison with their wild-type littermates. Meanwhile, T0901317 treatment improved mice survival, accompanied by significant ameliorations of myocardial injury and dysfunction in wild-type mice but not in SIRT1-/- mice. Furthermore, the levels of myocardial inflammatory cytokines (TNF-α, IL-6, IL-1β, MCP-1, MPO and HMGB1), oxidative stress (ROS generation, MDA), endoplasmic-reticulum (ER) stress (protein levels of CHOP, GRP78, GRP94, IRE1α, and ATF6), and cardiac apoptosis following CLP were inhibited by T0901317 treatment in wild-type mice but not in SIRT1-/- mice. Mechanistically, T0901317 enhanced SIRT1 signaling and the subsequent deacetylation and activation of antioxidative FoxO1 and anti-ER stress HSF1, as well as the deacetylation and inhibition of pro-inflammatory NF-ΚB and pro-apoptotic P53, thereby alleviating sepsis-induced myocardial injury and dysfunction. Our data support the promise of LXR activation as an effective strategy for relieving heart septic injury.

Peripheral Neuropathy and Hindlimb Paralysis in a Mouse Model of Adipocyte-Specific Knockout of Lkb1

Brown adipose tissues (BAT) burn lipids to generate heat through uncoupled respiration, thus representing a powerful target to counteract lipid accumulation and obesity. The tumor suppressor liver kinase b1 (Lkb1) is a key regulator of cellular energy metabolism; and adipocyte-specific knockout of Lkb1 (Ad-Lkb1 KO) leads to the expansion of BAT, improvements in systemic metabolism and resistance to obesity in young mice. Here we report the unexpected finding that the Ad-Lkb1 KO mice develop hindlimb paralysis at mid-age. Gene expression analyses indicate that Lkb1 KO upregulates the expression of inflammatory cytokines in interscapular BAT and epineurial brown adipocytes surrounding the sciatic nerve. This is followed by peripheral neuropathy characterized by infiltration of macrophages into the sciatic nerve, axon degeneration, reduced nerve conductance, and hindlimb paralysis. Mechanistically, Lkb1 KO reduces AMPK phosphorylation and amplifies mammalian target-of-rapamycin (mTOR)-dependent inflammatory signaling specifically in BAT but not WAT. Importantly, pharmacological or genetic inhibition of mTOR ameliorates inflammation and prevents paralysis. These results demonstrate that BAT inflammation is linked to peripheral neuropathy.

The endotoxemia cardiac dysfunction is attenuated by AMPK/mTOR signaling pathway regulating autophagy

AMP-activated protein kinase (AMPK), an enzyme that plays a role in cellular energy homeostasis, modulates myocardial signaling in the heart. Myocardial dysfunction is a common complication of sepsis. Autophagy is involved in the aging related cardiac dysfunction. However, the role of AMPK in sepsis-induced cardiotoxicity has yet to be clarified, especially in aging. In this study, we explored the role of AMPK in lipopolysaccharide (LPS)-induced myocardial dysfunction and elucidated the potential mechanisms of AMPK/mTOR pathway regulating autophagy in young and aged mice. We harvested cardiac tissues by intraperitoneal injection of LPS treatment. The results by echocardiography, pathology, contractile and intracellular Ca²⁺ property as well as western blot analysis revealed that LPS induced remarkable cardiac dysfunction and cardiotoxicity in mice hearts and cardiomyocytes, which were more seriously in the aged mice. Western blot analysis indicated that the underlying mechanisms included inhibition autophagy mediated by AMPK/mTOR activation. LPS overtly promoted the expression of AMPK upstream regulator PP2A and PP2Cα. Pharmacological activation of AMPK improved cardiac function and upregulated cardiac autophagy induced by LPS in the aged mice. Collectively, our findings suggest that upregulation of autophagy by administration of AMPK could attenuate LPS-induced cardiotoxicity, which enhances our knowledge to explore new drugs and strategies for combating cardiac dysfunction induced by sepsis.

ADIPOQ/adiponectin induces cytotoxic autophagy in breast cancer cells through STK11/LKB1-mediated activation of the AMPK-ULK1 axis

ADIPOQ/adiponectin, an adipocytokine secreted by adipocytes in the breast tumor microenvironment, negatively regulates cancer cell growth hence increased levels of ADIPOQ/adiponectin are associated with decreased breast cancer growth. However, its mechanisms of action remain largely elusive. We report that ADIPOQ/adiponectin induces a robust accumulation of autophagosomes, increases MAP1LC3B-II/LC3B-II and decreases SQSTM1/p62 in breast cancer cells. ADIPOQ/adiponectin-treated cells and xenografts exhibit increased expression of autophagy-related proteins. LysoTracker Red-staining and tandem-mCherry-GFP-LC3B assay show that fusion of autophagosomes and lysosomes is augmented upon ADIPOQ/adiponectin treatment. ADIPOQ/adiponectin significantly inhibits breast cancer growth and induces apoptosis both in vitro and in vivo, and these events are preceded by macroautophagy/autophagy, which is integral for ADIPOQ/adiponectin-mediated cell death. Accordingly, blunting autophagosome formation, blocking autophagosome-lysosome fusion or genetic-knockout of BECN1/Beclin1 and ATG7 effectively impedes ADIPOQ/adiponectin induced growth-inhibition and apoptosis-induction. Mechanistic studies show that ADIPOQ/adiponectin reduces intracellular ATP levels and increases PRKAA1 phosphorylation leading to ULK1 activation. AMPK-inhibition abrogates ADIPOQ/adiponectin-induced ULK1-activation, LC3B-turnover and SQSTM1/p62-degradation while AMPK-activation potentiates ADIPOQ/adiponectin's effects. Further, ADIPOQ/adiponectin-mediated AMPK-activation and autophagy-induction are regulated by upstream master-kinase STK11/LKB1, which is a key node in antitumor function of ADIPOQ/adiponectin as STK11/LKB1-knockout abrogates ADIPOQ/adiponectin-mediated inhibition of breast tumorigenesis and molecular analyses of tumors corroborate in vitro mechanistic findings. ADIPOQ/adiponectin increases the efficacy of chemotherapeutic agents. Notably, high expression of ADIPOQ receptor ADIPOR2, ADIPOQ/adiponectin and BECN1 significantly correlates with increased overall survival in chemotherapy-treated breast cancer patients. Collectively, these data uncover that ADIPOQ/adiponectin induces autophagic cell death in breast cancer and provide in vitro and in vivo evidence for the integral role of STK11/LKB1-AMPK-ULK1 axis in ADIPOQ/adiponectin-mediated cytotoxic autophagy.

Monitoring p53 by MDM2 and MDMX is required for endocrine pancreas development and function in a spatio-temporal manner

Although p53 is not essential for normal embryonic development, it plays a pivotal role in many biological and pathological processes, including cell fate determination-dependent and independent events and diseases. The expression and activity of p53 largely depend on its two biological inhibitors, MDM2 and MDMX, which have been shown to form a complex in order to tightly control p53 to an undetectable level during early stages of embryonic development. However, more delicate studies using conditional gene-modification mouse models show that MDM2 and MDMX may function separately or synergistically on p53 regulation during later stages of embryonic development and adulthood in a cell and tissue-specific manner. Here, we report the role of the MDM2/MDMX-p53 pathway in pancreatic islet morphogenesis and functional maintenance, using mouse lines with specific deletion of MDM2 or MDMX in pancreatic endocrine progenitor cells. Interestingly, deletion of MDM2 results in defects of embryonic endocrine pancreas development, followed by neonatal hyperglycemia and lethality, by inducing pancreatic progenitor cell apoptosis and inhibiting cell proliferation. However, unlike MDM2-knockout animals, mice lacking MDMX in endocrine progenitor cells develop normally. But, surprisingly, the survival rate of adult MDMX-knockout mice drastically declines compared to control mice, as blockage of neonatal development of endocrine pancreas by inhibition of cell proliferation and subsequent islet dysfunction and hyperglycemia eventually lead to type 1 diabetes-like disease with advanced diabetic nephropathy. As expected, both MDM2 and MDMX deletion-caused pancreatic defects are completely rescued by loss of p53, verifying the crucial role of the MDM2 and/or MDMX in regulating p53 in a spatio-temporal manner during the development, functional maintenance, and related disease progress of endocrine pancreas. Also, our study suggests a possible mouse model of advanced diabetic nephropathy, which is complementary to other established diabetic models and perhaps useful for the development of anti-diabetes therapies.