Role of NLRP3 inflammasome in the pathogenesis of cardiovascular diseases

Melatonin Attenuates Cardiac Reperfusion Stress by Improving OPA1-Related Mitochondrial Fusion in a Yap-Hippo Pathway-Dependent Manner

The role of OPA1-related mitochondrial fusion in cardiac reperfusion stress has remained elusive. The aim of our study is to explore whether melatonin alleviates cardiac ischemia-reperfusion (IR) injury by modulating OPA1-related mitochondrial fusion. We found that melatonin reduced infarct area, sustained myocardial function, and suppressed cardiomyocyte death during cardiac reperfusion stress. Biological studies have revealed that IR-inhibited mitochondrial fusion was largely reversed by melatonin through upregulated OPA1 expression. Knocking down OPA1 abrogated the protective effects of melatonin on mitochondrial energy metabolism and mitochondrial apoptosis. In addition, we also found that melatonin modified OPA1 expression through the Yap–Hippo pathway; blockade of the Yap–Hippo pathway induced cardiomyocyte death and mitochondrial damage despite treatment with melatonin. Altogether, our data demonstrated that cardiac IR injury is closely associated with defective OPA1-related mitochondrial fusion. Melatonin supplementation enhances OPA1-related mitochondrial fusion by activating the Yap–Hippo pathway, ultimately reducing cardiac reperfusion stress.

NLRP3 inflammasome suppression improves longevity and prevents cardiac aging in male mice

While NLRP3‐inflammasome has been implicated in cardiovascular diseases, its role in physiological cardiac aging is largely unknown. During aging, many alterations occur in the organism, which are associated with progressive impairment of metabolic pathways related to insulin resistance, autophagy dysfunction, and inflammation. Here, we investigated the molecular mechanisms through which NLRP3 inhibition may attenuate cardiac aging. Ablation of NLRP3‐inflammasome protected mice from age‐related increased insulin sensitivity, reduced IGF‐1 and leptin/adiponectin ratio levels, and reduced cardiac damage with protection of the prolongation of the age‐dependent PR interval, which is associated with atrial fibrillation by cardiovascular aging and reduced telomere shortening. Furthermore, old NLRP3 KO mice showed an inhibition of the PI3K/AKT/mTOR pathway and autophagy improvement, compared with old wild mice and preserved Nampt‐mediated NAD⁺ levels with increased SIRT1 protein expression. These findings suggest that suppression of NLRP3 prevented many age‐associated changes in the heart, preserved cardiac function of aged mice and increased lifespan.

GLI1-mediated pulmonary artery smooth muscle cell pyroptosis contributes to hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is a clinically common malignant cardiovascular disease. Pyroptosis is a new form of inflammatory cell death that is involved in many disease processes. Glioma-associated oncogene family zinc finger 1 (GLI1) is a transcriptional activator that participates in many diseases, but its role has never been explored in inducing pyroptosis and the progress of PH. In this study, we used an animal model and cell molecular biology to determine the effect of GLI1 on chronic hypoxia-mediated PH progression and pulmonary artery smooth muscle cell (PASMC) pyroptosis. The major findings of the present study are as follows: Hypoxia induced aberrant expression of GLI1. The inhibition of GLI1 attenuated hypoxia-induced PH and PASMC pyroptosis. Meanwhile, GLI1 enhanced apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) expression by binding with its promoter. GLI1 may promote PASMC pyroptosis through ASC to affect the progression of PH. These findings may identify novel targets for molecular therapy of PH.

Calcium Pyrophosphate And Monosodium Urate Activate The NLRP3 Inflammasome Within Bladder Urothelium Via Reactive Oxygen Species And TXNIP

Objective

To investigate the in vitro activation of the NLRP3 inflammasome within bladder urothelium by stone-forming components. Further, to describe the contributions of reactive oxygen species (ROS) and thioredoxin-interacting protein (TXNIP), an important structural component of the inflammasome, to this activation.

Methods

Urothelial cells were harvested and incubated overnight. For agonist studies, cells were treated with varying concentrations of calcium pyrophosphate (CPPD) and monosodium urate (MSU). For inhibitor studies, cells were treated with either N-acetylcysteine (NAC) (1 hr) or Verapamil (4 hrs) prior to incubation with either CPPD (62.5 ug/mL) or MSU (1.25 ug/mL) for 24 hrs. Untreated controls were incubated with ATP (1.25 mM) for 1 hr to maximally stimulate NLRP3 inflammasome activity (measured as caspase-1 cleavage of the fluorogenic substrate Ac-YVAD-AFC). Results are reported as a percentage of maximum ATP response.

Results

CPPD and MSU activate caspase-1 in urothelial cells in a dose-dependent manner, reaching ~50% and ~25% of the ATP response, respectively. Pre-treatment with the general ROS scavenger NAC reduces this activation in a dose-dependent manner. Additionally, activation was suppressed through treatment with Verapamil, a known downregulator of TXNIP expression.

Conclusion

The stone components CPPD and MSU activate NLRP3 in an ROS and TXNIP-dependent manner in bladder urothelium. These findings demonstrate the importance of ROS and TXNIP, and suggest that targeting either may be a way to decrease stone-dependent NLRP3 inflammation within the bladder.

Cellular senescence induced by S100A9 in mesenchymal stromal cells through NLRP3 inflammasome activation

Bone marrow stromal cells from patients with myelodysplastic syndrome (MDS) display a senescence phenotype, but the underlying mechanism has not been elucidated. Pro-inflammatory signaling within the malignant clone and the bone marrow microenvironment has been identified as a key pathogenetic driver of MDS. Our study revealed that S100A9 is highly-expressed in lower-risk MDS. Moreover, normal primary mesenchymal stromal cells (MSCs) and the human stromal cell line HS-27a co-cultured with lower-risk MDS bone marrow mononuclear cells acquired a senescence phenotype. Exogenous supplemented S100A9 also induced cellular senescence in MSCs and HS-27a cells. Importantly, Toll-like receptor 4 (TLR4) inhibition or knockdown attenuated the cellular senescence induced by S100A9. Furthermore, we showed that S100A9 induces NLRP3 inflammasome formation, and IL-1β secretion; findings in samples from MDS patients further confirmed these thoughts. Moreover, ROS and IL-1β inhibition suppressed the cellular senescence induced by S100A9, whereas NLRP3 overexpression and exogenous IL-1β supplementation induces cellular senescence. Our study demonstrated that S100A9 promotes cellular senescence of bone marrow stromal cells via TLR4, NLRP3 inflammasome formation, and IL-1β secretion for its effects. Our findings deepen the understanding of the molecular mechanisms involved in MDS reprogramming of MSCs and indicated the essential role of S100A9 in tumor-environment interactions in bone marrow.

Mumefural Ameliorates Cognitive Impairment in Chronic Cerebral Hypoperfusion via Regulating the Septohippocampal Cholinergic System and Neuroinflammation

Chronic cerebral hypoperfusion (CCH) causes cognitive impairment and neurogenic inflammation by reducing blood flow. We previously showed that Fructus mume (F. mume) improves cognitive impairment and inhibits neuroinflammation in a CCH rat model. One of the components of F. mume, Mumefural (MF), is known to improve blood flow and inhibit platelet aggregation. Whether MF affects cerebral and cognitive function remains unclear. We investigated the effects of MF on cognitive impairment and neurological function-related protein expression in the rat CCH model, established by bilateral common carotid arterial occlusion (BCCAo). Three weeks after BCCAo, MF (20, 40, or 80 mg/kg) was orally administrated once a day for 42 days. Using Morris water maze assessment, MF treatment significantly improved cognitive impairment. MF treatment also inhibited cholinergic system dysfunction, attenuated choline acetyltransferase-positive cholinergic neuron loss, and regulated cholinergic system-related protein expressions in the basal forebrain and hippocampus. MF also inhibited myelin basic protein degradation and increased the hippocampal expression of synaptic markers and cognition-related proteins. Moreover, MF reduced neuroinflammation, inhibited gliosis, and attenuated the activation of P2X7 receptor, TLR4/MyD88, NLRP3, and NF-κB. This study indicates that MF ameliorates cognitive impairment in BCCAo rats by enhancing neurological function and inhibiting neuroinflammation.

The Mediterranean Diet And Cardioprotection: Historical Overview And Current Research

Ancient Greece was the cradle of the Mediterranean food tradition, characterized by the Mediterranean "eternal trinity" wheat - olive oil - wine, the very essence of the country's traditional agricultural and dietary regime, enriched by a culture of sharing and commensality. This food model, subsequently adopted and spread by the Romans, was rediscovered at the end of the Second World War by two American researchers, Leland Allbaugh and Ancel Keys. With the famous Seven Countries Study, Keys demonstrated for the first time that populations practicing a Mediterranean diet - such as the Greeks and southern Italians - showed low mortality rates from ischemic heart disease compared to the peoples of Northern Europe and North America. Since then, numerous subsequent epidemiological studies and randomized clinical trials have confirmed the beneficial effects of the Mediterranean diet both in primary and secondary prevention of cardiovascular diseases. This review will focus on the origins of the Mediterranean diet from its roots and its relationship to cardiovascular disease, with a brief overview of the nutritional mechanisms that influence atherosclerosis.

Metformin inhibited Nod-like receptor protein 3 inflammasomes activation and suppressed diabetes-accelerated atherosclerosis in apoE-/- mice

AIMS

The present study aimed to investigate the effect of metformin on diabetes-accelerated atherosclerosis and whether Nod-like receptor protein 3 (NLRP3) inflammasome is a target for metformin.

MATERIALS AND METHODS

ApoE^-/- male mice were divided randomly into control, streptozocin-induced diabetes mellitus and metformin groups. Metabolic parameters, atherosclerotic lesion, activation of NLRP3 inflammasomes and related signaling pathways were detected. THP-1-differentiated macrophages were used in in vitro experiments.

RESULTS

Compared with control mice, increased plasma lipids and proinflammatory interleukin-1β, aggravated macrophage infiltration into the atherosclerotic lesion, and accelerated development of atherosclerosis were observed in diabetic mice, which were associated with the activation of NLRP3 inflammasomes and dysregulation of thioredoxin-1 and thioredoxin-interacting protein. Treatment with metformin alleviated diabetes-induced metabolic disorders and atherosclerosis, as well as NLRP3 inflammasomes activation and dysregulation of thioredoxin-1/thioredoxin-interacting protein. In vitro experiments showed that high glucose induced the accumulation of reactive oxygen species and activated NLRP3 inflammasomes, which was significantly suppressed by treatment with metformin or antioxidant N-acetyl-L-cysteine. Moreover, Compound C, an inhibitor of adenosine 5'-monophosphate-activated protein kinase (AMPK), blocked the anti-inflammatory effect of metformin, indicating that metformin inhibited high glucose-induced NLRP3 inflammasomes activation through AMPK activation. Moreover, high glucose decreased thioredoxin-1 expression and increased thioredoxin-interacting protein expression, which was also reversed by metformin.

CONCLUSIONS

Metformin inhibited NLRP3 inflammasomes activation and suppressed diabetes-accelerated atherosclerosis in apoE^-/- mice, which at least partially through activation of AMPK and regulation of thioredoxin-1/thioredoxin-interacting protein.

MKP1 overexpression reduces TNF-α-induced cardiac injury via suppressing mitochondrial fragmentation and inhibiting the JNK-MIEF1 pathways

Mitochondrial stress has been acknowledged as the pathogenesis for tumor necrosis factor-α (TNF-α)-induced septic cardiomyopathy. Recently, MAP kinase phosphatase 1 (MKP1) downregulation and mitochondrial fragmentation modulate the mitochondrial stress via multiple molecular mechanisms. Thereby, the goal of our current work is to figure out the functional role of mitochondrial fragmentation in TNF-α-induced septic cardiomyopathy. Our results exhibited that MKP1 expression was significantly repressed in hearts treated by TNF-α. Overexpression of MKP1 sustained cardiac function and attenuated cardiomyocytes death in TNF-α-treated hearts. At the molecular levels, decreased MKP1 induced mitochondrial stress, as indicated by mitochondrial calcium overloading, mitochondrial oxidative stress, mitochondrial antioxidant downregulation, mitochondrial membrane potential reduction, mitochondrial bioenergetics suppression, mitochondrial proapoptotic factors liberation, and caspase-9 apoptotic pathway activation. To the end, we illustrated that MKP1-modulated mitochondrial stress via mitochondrial fragmentation; reactivation of mitochondrial fragmentation abolished the protective effect of MKP1 overexpression on mitochondrial function. Further, MKP1 affected mitochondrial division in a mechanism through the JNK-MIEF1 axis. Blockade of JNK pathway abolished the regulatory actions of MKP1 on mitochondrial division. Altogether, our results identify MKP1 as a novel cardioprotective factor in TNF-α-related septic cardiomyopathy via affecting mitochondrial division by the way of JNK-MIEF1 signaling pathway. Therefore, MKP1 expression, mitochondrial fragmentation modification, and JNK-MIEF1 pathway modulation may be considered as potential therapeutic targets for the treatment of cardiac injury induced by sepsis.

DPP-4 inhibition by linagliptin prevents cardiac dysfunction and inflammation by targeting the Nlrp3/ASC inflammasome

We compared the effects of linagliptin (Lina, a DPP4 inhibitor) and GLP-1 receptor activation by exenatide followed by exendin-4 in an infusion pump (EX) on infarct size (IS), post-infarction activation of the inflammasome and remodeling in wild-type (WT) and db/db diabetic mice. Mice underwent 30 min ischemia followed by 24 h reperfusion. IS was assessed by TTC. Additional mice underwent permanent coronary artery occlusion. Echocardiography was performed 2w after infarction. Activation of the inflammasome in the border zone of the infarction was assessed by rt-PCR and ELISA 2w after reperfusion. Further in vitro experiments were done using primary human cardiofibroblasts and cardiomyocytes exposed to simulated ischemia-reoxygenation. Lina and EX limited IS in both the WT and the db/db mice. Lina and EX equally improved ejection fraction in both the WT and the db/db mice. mRNA levels of ASC, NALP3, IL-1β, IL-6, Collagen-1, and Collagen-3 were higher in the db/db mice than in the WT mice. Infarction increased these levels in the WT and db/db mice. Lina more than EX attenuated the increase in ASC, NALP3, IL-1β, IL-6, Collagen-1 and Collagen-3, TNFα and IL-1β, and decreased apoptosis, especially in the db/db mice. In vitro experiments showed that Lina, but not EX, attenuated the increase in TLR4 expression, an effect that was dependent on p38 activation with downstream upregulation of Let-7i and miR-146b levels. Lina and EX had similar effects on IS and post-infarction function, but Lina attenuated the activation of the inflammasome and the upregulation of collagen-1 and collagen-3 more than direct GLP-1 receptor activation. This effect depends on p38 activation with downstream upregulation of miR-146b levels that suppresses TLR4 expression.

Vildagliptin inhibits high free fatty acid (FFA)-induced NLRP3 inflammasome activation in endothelial cells

Elevated free fatty acids (FFAs) are a risk factor for type 2 diabetes. Endothelial dysfunction induced by high levels of FFAs is one of the mechanisms related to the progression of diabetes. In clinical diabetes care, DPP-4 inhibitors have been shown to be effective in reducing glucose levels. In this study, we investigated the molecular mechanism of the clinically available DPP-4 inhibitor vildagliptin in the protection of FFA-induced endothelial dysfunction. Treatment of endothelial cells with vildagliptin inhibits FFA-induced cellular LDH release and generation of ROS. Vildagliptin also reverses FFA-induced reduced levels of GSH and elevated expression of the FFA-associated NAPHD oxidase protein NOX-4. Moreover, vildagliptin ameliorates the reduction in mitochondrial potential triggered by FFAs. Mechanistically, we show that vildagliptin suppresses FFA-induced expression of proteins of the NLRP3 inflammasome complex, including NLRP3, ASC, p20 and HMGB-1, and mitigates FFA-induced inactivation of the AMPK pathway. Consequently, vildagliptin inhibits production of two cytokines that are favored by NLRP3 inflammasome machinery: IL-1β and IL-18. Finally, we demonstrate that vildagliptin ameliorates FFA-induced reduced eNOS, indicating its protective role against endothelial dysfunction. Collectively, we conclude that the protective role of vildagliptin in endothelial cells is mediated via suppression of the AMPK-NLRP3 inflammasome-HMGB-1 axis pathway. These findings imply that the anti-diabetic drug vildagliptin possesses dual therapeutic applications in lowering glucose and improving vascular function.

Macrophage NLRP3 inflammasome activated by CVB3 capsid proteins contributes to the development of viral myocarditis

Viral myocarditis, mainly caused by enteroviruses specially coxsackievirus B3 (CVB3) infection, is a common clinical cardiovascular disease and characterized by cardiac massive inflammation. Our previous study showed that CVB3-induced myocardial NLRP3 contributed to the development of viral myocarditis. In this study, we found that beside of being up-regulated in myocardiocytes, NLPR3 was also obviously increased in the cardiac infiltrating macrophages. While whether this accumulated NLRP3 influences, macrophage inflammatory responses remains unknown. By adoptive transfer assays, we found that mice receiving NLRP3 up-regulated macrophages showed much more abundant cardiac IL-1β production and more severe myocardial inflammation, while those receiving NLRP3 down-regulated macrophages showed much less IL-1β production and milder myocarditis, indicating that NLRP3 up-regulated macrophages played a pathological role in CVB3-induced myocarditis. In addition, we further found that it was CVB3 capsid proteins VP1 (predominant) and VP2, but not viral RNAs, robustly triggered macrophage NLRP3 up-regulation and activation. Our study demonstrated macrophage NLRP3 inflammasome could be efficiently be activated by CVB3 capsid proteins, and contributed to the pathogenesis of viral myocarditis. It might provide some clues to the development of new therapeutic strategies based on macrophage NLRP3 modulation.

Electroacupuncture Alleviates Ischemic Brain Injury by Inhibiting the miR-223/NLRP3 Pathway

Background

Electroacupuncture (EA) has been commonly used to treat stroke in China. However, the underlying mechanism remains largely unknown. The present study investigated the neuroprotective effects of EA in middle cerebral artery occlusion (MCAO) rats and elucidated the possible anti-inflammatory mechanisms.

Material/Methods

In this study, modified neurological severity scoring (mNSS) was used to assess neurological deficits, and TTC staining and brain water content were measured to evaluate the degree of brain damage. HE staining, Nissl staining, and TUNEL staining were employed to evaluate apoptotic neuronal death. Molecular biological methods were used to measure the levels of miR-233, NLRP3, caspase-1, IL-1β, and IL-18 in the peri-infarct cortex.

Results

Our results showed that EA treatment significantly decreased the neurological deficit score and infarct volume of MCAO rats. The level of miR-223 was increased, while the levels of NLRP3, caspase-1, IL-1β, and IL-18 were decreased in the peri-infarct cortex of EA-treated MCAO rats. However, the neuroprotective effect of EA was partially blocked by antagomir-223.

Conclusions

These data suggest that EA treatment can alleviate neuroinflammation by inhibiting the miR-223/NLRP3 pathway, thus playing a neuroprotective role in MCAO in rats.

Pulegone inhibits inflammation via suppression of NLRP3 inflammasome and reducing cytokine production in mice

Context: Pulegone, a key compound in Schizonepeta essential oil, has been identified as an anti-inflammatory. However, its underlying molecular mechanisms on NLR family pyrin domain containing 3 (NLRP3) inflammasome have not been elucidated. Objective: Here, the modulatory effects of pulegone on NLRP3 inflammasome were investigated. Materials and methods: The C57BL/6J mice were randomly divided into five groups: Normal, Lipopolysaccharides (LPS), Dexamethasone (DEX, 5 mg/kg), Pulegone (0.095 and 0.190 g/kg) groups. All mice were challenged by LPS except for the Normal group. Results: A reduced expression of Interleukin-18 (IL-18), Interleukin-1β (IL-1β), Interleukin-5 (IL-5), Tumor necrosis factor-α (TNF-α), Interferon-gamma (IFN-γ), Monocyte chemoattratctant protein-1 (MCP-1), Macrophage inflammatory protein-1β (MIP-1β), Monocyte colony stimulating factor (M-CSF) and Granulocyte-macrophage colony stimulating factor (GM-CSF) in serum were detected in the pulegone groups as compared to the LPS group. In addition, a reduced mRNA and protein expression production of ASC, NLRP3, and Caspase-1 were detected in lungs after pulegone administration. Histological analysis results indicated that the histological changes of lungs caused by LPS were ameliorated by pulegone. Immunohistochemical study showed a decreased positive cell numbers of P2X7R in Pulegone (0.095 and 0.190 g/kg) groups. Conclusion: Pulegone exerts anti-inflammatory effects on LPS-induced sepsis mice via inhibition of the NLRP3 expression.

MicroRNAs as important regulators of the NLRP3 inflammasome

Inflammasomes are a group of cytosolic multi-protein signaling complexes that regulate maturation of the interleukin (IL)-1 family cytokines IL-1β and IL-18 through activation of inflammatory caspase-1. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome is the best characterized and consists of several key components that are assembled and activated in response to different endogenous and exogenous signals. The NLRP3 inflammasome is common to a number of human inflammatory diseases and its targeting may lead to novel anti-inflammatory therapy. NLRP3 inflammasome activation is tightly regulated by different mechanisms especially post-transcriptional modulation via microRNAs (miRNA). MicroRNAs are small endogenous noncoding RNAs that are 21-23 nucleotides in length and control the expression of various genes through binding to the 3'-untranslated regions of the respective mRNA and subsequent post-transcriptional regulation. MicroRNAs have recently been recognized as crucial regulators of the NLRP3 inflammasome. In this review, we summarize the current understanding of the role of miRNAs in the regulation of NLRP3 inflammasome complexes and their impact on the pathogenesis of inflammatory disease processes.

MicroRNA Post-transcriptional Regulation of the NLRP3 Inflammasome in Immunopathologies

Inflammation has a crucial role in protection against various pathogens. The inflammasome is an intracellular multiprotein signaling complex that is linked to pathogen sensing and initiation of the inflammatory response in physiological and pathological conditions. The most characterized inflammasome is the NLRP3 inflammasome, which is a known sensor of cell stress and is tightly regulated in resting cells. However, altered regulation of the NLRP3 inflammasome is found in several pathological conditions, including autoimmune disease and cancer. NLRP3 expression was shown to be post-transcriptionally regulated and multiple miRNA have been implicated in post-transcriptional regulation of the inflammasome. Therefore, in recent years, miRNA based post-transcriptional control of NLRP3 has become a focus of much research, especially as a potential therapeutic approach. In this review, we provide a summary of the recent investigations on the role of miRNA in the post-transcriptional control of the NLRP3 inflammasome, a key regulator of pro-inflammatory IL-1β and IL-18 cytokine production. Current approaches to targeting the inflammasome product were shown to be an effective treatment for diseases linked to NLRP3 overexpression. Although utilizing NLRP3 targeting miRNAs was shown to be a successful therapeutic approach in several animal models, their therapeutic application in patients remains to be determined.

Genetic ablation of TAZ induces HepG2 liver cancer cell apoptosis through activating the CaMKII/MIEF1 signaling pathway

Background and objective

Transcriptional coactivator with PDZ-binding motif (TAZ) has been found to be associated with tumor progression. Mitochondrial homeostasis regulates cancer cell viability and metastasis. However, the roles of TAZ and mitochondrial homeostasis in liver cancer viability have not been explored. The aim of our study was to investigate the influence of TAZ on HepG2 liver cancer cell apoptosis.

Materials and methods

HepG2 liver cancer cell was used in the present study, and shRNA against TAZ was transfected into HepG2 cell to knockdown TAZ expression. Mitochondrial function was analyzed using Western blotting, immunofluorescence assay, and flow cytometry. Pathway blocker was used to confirm the role of CaMKII pathway in TAZ-mediated cancer cell death.

Results

Our results indicated that TAZ deletion induced death in HepG2 cell via apoptosis. Biological analysis demonstrated that mitochondrial stress, including mitochondrial bioenergetics disorder, mitochondrial oxidative stress, and mitochondrial apoptosis, were activated by TAZ deletion. Furthermore, we found that TAZ affected mitochondrial stress by triggering mitochondrial elongation factor 1 (MIEF1)-related mitochondrial dysfunction. The loss of MIEF1 sustained mitochondrial function and promoted cancer cell survival. Molecular investigation illustrated that TAZ regulated MIEF1 expression via the CaMKII signaling pathway. Blockade of the CaMKII pathway prevented TAZ-mediated MIEF1 upregulation and improved cancer cell survival.

Conclusion

Taken together, our results highlight the key role of TAZ as a master regulator of HepG2 liver cancer cell viability via the modulation of MIEF1-related mitochondrial stress and the CaMKII signaling pathway. These findings define TAZ and MIEF1-related mitochondrial dysfunction as tumor suppressors that act by promoting cancer apoptosis via the CaMKII signaling pathway, with potential implications for new approaches to liver cancer therapy.

Yap-Hippo promotes A549 lung cancer cell death via modulating MIEF1-related mitochondrial stress and activating JNK pathway

Although the role of Yes-associated protein (Yap) has been described in the progression of lung cancer, the downstream effector of the Yap-Hippo pathway has not been identified. Accordingly, the aim of our study is to explore whether Yap modulates the activity of lung cancer by controlling mitochondrial elongation factor 1 (MIEF1)-related mitochondrial stress in a manner dependent on the JNK pathway. Cell viability was determined via MTT, LDH release and immunofluorescence assays. ATP production, the mitochondrial membrane potential, and caspase-9 activity were investigated to assess mitochondrial function. siRNA transfection and pathway blockers were used to observe the roles of MIEF1 and JNK in Yap-modulated cell viability in lung cancer cells in vitro. Yap deletion reduced cell viability in A549 and H358 lung cancer cells. At the molecular level, Yap deletion promoted mitochondrial dysfunction, as evidenced by the decreased mitochondrial potential, increased mitochondrial oxidative stress, augmented mitochondrial pro-apoptotic factor leakage and elevated caspase-9 activity. In addition, we found that Yap modulated mitochondrial stress via MIEF1 and that loss of MIEF1 abolished the regulatory actions of Yap on mitochondrial stress and cell viability. Besides, we provided evidence to support the necessary role of JNK in Yap-mediated MIEF1 upregulation. Inhibition of JNK abolished the promotive effect of Yap deletion on MIEF1 activation. Taken together, our results identified the JNK-MIEF1 pathway and mitochondrial stress as downstream effectors of Yap in lung cancer. This finding suggests a novel approach for the treatment of lung cancer in clinical practice.

Fish Oil Derived Omega 3 Fatty Acids Suppress Adipose NLRP3 Inflammasome Signaling in Human Obesity

CONTEXT

The NRLP3 inflammasome is a multiprotein danger-sensing complex that serves as a critical link between obesity-related adipose inflammation and insulin resistance and has been shown in animal models to be inhibited by fish oil-derived long chain omega-3 polyunsaturated fatty acids (n-3 PUFA).

OBJECTIVE

We conducted a clinical trial and in vitro experiments to test our hypothesis that n-3 PUFA suppress NLRP3 inflammasome in human obesity through downregulation of inflammasome gene expression in adipocytes and macrophages.

DESIGN

Placebo-controlled clinical trial and in vitro coculture experiments with primary human adipocytes (from biopsy specimens) and human THP-1 monocyte-derived macrophages treated with eicosapentaenoic acid (EPA) and/or docosahexaenoic acid (DHA) vs vehicle control.

SETTING

General community, research laboratory.

PATIENTS AND OTHER PARTICIPANTS

Obese (body mass index ≥ 30 kg/m2), nondiabetic males and females age 18 to 50. N = 25.

INTERVENTIONS

Clinical trial: Eight-week treatment with 4 g Lovaza (EPA and DHA) or placebo. Cells culture: EPA and/or DHA at 100 µg/mL or vehicle control in culture medium.

MAIN OUTCOME MEASURES

Adipose tissue or adipocyte/macrophage mRNA expression of IL-1β and IL-18 and circulating IL-18 levels.

RESULTS

Treatment of obese human subjects with fish oil supplements reduced expression of adipose inflammatory genes including inflammasome-associated IL-18 and IL-1β and circulating IL-18 levels. Both EPA and DHA reduced inflammasome gene expression in obese human adipose and human adipocyte and macrophages.

CONCLUSIONS

N-3 PUFA reduce NLRP3 inflammasome in human adipose through downregulation of gene expression in adipocytes and monocytes/macrophages and has potential as nutritional therapeutic agent in prevention of obesity-related inflammation.

Matrine has pro-apoptotic effects on liver cancer by triggering mitochondrial fission and activating Mst1-JNK signalling pathways

Mitochondrial homeostasis is closely associated with liver cancer progression via multiple mechanisms and is also a potential tumour-suppressive target in clinical practice. However, the role of mitochondrial fission in liver cancer cell viability has not been adequately investigated. Matrine, a type of alkaloid isolated from Sophoraflavescens, has been widely used to treat various types of cancer. However, the molecular effect of matrine on mitochondrial homeostasis is unclear. Therefore, the aim of the current study was to determine the role of mitochondrial fission in cell apoptosis, viability, migration and proliferation of HepG2 cells in vitro. The effect of matrine on mitochondrial fission and its mechanism were also explored. The results of our study showed that HepG2 cells treated with matrine had reduced viability, an increased apoptotic rate, a blunted migratory response, and impaired proliferation capacity. At the molecular level, matrine treatment activated mitochondrial fission, which promoted mitochondrial dysfunction, caused cellular oxidative stress, disrupted cellular energy metabolism and initiated cell apoptotic pathways. However, blockade of mitochondrial fission abolished the deleterious effects of matrine on HepG2 cells. Further, we demonstrated that the Mst1-JNK signalling axis was required for matrine-modulated mitochondrial fission. Matrine-mediated mitochondrial dysfunction was reversed by inhibiting Mst1-JNK pathways. Together, our results demonstrated that mitochondrial fission could be a potential upstream tumour-suppressive signal for liver cancer by modifying mitochondrial function and cell death. By contrast, matrine exerted an anticancer function in liver cancer by activating mitochondrial fission mediated by Mst1-JNK pathways.

Therapeutic effects of melatonin on cerebral ischemia reperfusion injury: Role of Yap-OPA1 signaling pathway and mitochondrial fusion

The role of OPA1-related mitochondrial fusion in brain reperfusion stress has remained elusive. The aim of our study is to explore whether melatonin alleviates cerebral IR injury by modulating OPA1-related mitochondrial fusion. We found that melatonin reduced infarct area and suppressed neuron death during reperfusion stress. Biological studies have revealed that IR-inhibited mitochondrial fusion was largely reversed by melatonin via upregulated OPA1 expression. Knocking down OPA1 abrogated the protective effects of melatonin on mitochondrial energy metabolism and mitochondrial apoptosis. In addition, we also found that melatonin modified OPA1 expression via the Yap-Hippo pathway; blockade of the Yap-Hippo pathway induced neuron death and mitochondrial damage despite treatment with melatonin. Altogether, our data demonstrated that cerebral IR injury is closely associated with defective OPA1-related mitochondrial fusion. Melatonin supplementation enhances OPA1-related mitochondrial fusion by activating the Yap-Hippo pathway, ultimately reducing brain reperfusion stress.

Dual Role of Triptolide in Interrupting the NLRP3 Inflammasome Pathway to Attenuate Cardiac Fibrosis

In a previous paper, we reported that triptolide (TP), a commonly used immunomodulator, could attenuate cardiac hypertrophy. This present study aimed to further explore the inhibition of cardiac fibrosis by TP and the possible mechanism from the perspective of the NOD-like receptor protein 3 (NLRP3) inflammasome. Hematoxylin-eosin and Masson’s staining, immunohistochemistry, and immunofluorescence were performed to observe cardiac fibrotic changes in mice and mouse cardiac fibroblasts (CFs). The Western blot, colocalization, and immunoprecipitation were applied to detect protein expression and interactions. Results suggested that TP dose-dependently inhibited cardiac fibrosis induced by isoproterenol and collagen production of CFs induced by angiotensin II. TP exhibited an antifibrotic effect via inhibiting activation of the NLRP3 inflammasome, which sequentially decreased IL-1β maturation, myeloid differentiation factor 88 (MyD88)-related phosphorylation of c-Jun N-terminal kinase (JNK), extracellular regulated protein kinase 1/2 (ERK1/2), and TGF-β1/Smad signaling, and ultimately resulted in less collagen production. Moreover, TP showed no antifibrotic effect in Nlrp3-knockout CFs. Notably, TP inhibited the expression of NLRP3 and apoptosis-associated speck-like proteins containing a caspase recruitment domain (ASC) as well as inflammasome assembly, by interrupting the NLRP3-ASC interaction to inhibit inflammasome activation. Finally, TP indeed inhibited the NLRP3-TGFβ1-Smad pathway in vivo. Conclusively, TP was found to play a dual role in interrupting the activation of the NLRP3 inflammasome to attenuate cardiac fibrosis.

Sepsis-related myocardial injury is associated with Mst1 upregulation, mitochondrial dysfunction and the Drp1/F-actin signaling pathway

LPS-induced septic cardiomyopathy has been found to be connected with mitochondrial stress through unknown mechanisms. Mitochondrial fission is an early event in mitochondrial dysfunction. The aim of our study was to determine the role and regulatory mechanism of mitochondrial fission in the progression of LPS-induced septic cardiomyopathy, with a particular focus on Mst1 and F-actin. Our data demonstrated that Mst1 expression was rapidly upregulated in LPS-treated hearts and that increased Mst1 promoted cardiomyocyte death by inducing mitochondrial stress. Mechanistically, elevated expression of Mst1 upregulated Drp1, and the latter initiated mitochondrial fission. Excessive mitochondrial fission caused mitochondrial oxidative injury, mitochondrial membrane potential reduction, mitochondrial proapoptotic element translocation into the cytoplasm/nucleus, mitochondrial energy dysfunction and mitochondrial apoptosis activation. Inhibition of mitochondrial fission sustained mitochondrial function and favored cardiomyocyte survival. Furthermore, we identified F-actin degradation as an apparent downstream event of mitochondrial fission activation in the context of LPS-induced septic cardiomyopathy. Stabilization of F-actin attenuated fission-mediated cardiomyocyte death. Altogether, our results define the Mst1/Drp1/mitochondrial fission/F-actin axis as a new signaling pathway that mediates LPS-related septic cardiomyopathy by inducing mitochondrial stress and cardiomyocyte death. Therefore, Mst1 expression, mitochondrial fission modification and F-actin stabilization may serve as potential therapeutic targets for sepsis-related myocardial injury.

Effects of melatonin on acute brain reperfusion stress: role of Hippo signaling pathway and MFN2-related mitochondrial protection

Acute brain reperfusion stress is associated with mitochondrial dysfunction through unknown mechanisms. Accordingly, there is no effective drug to control the development and progression of brain reperfusion stress currently. The aim of our investigation is to verify whether melatonin attenuates acute brain reperfusion stress via affecting mitochondrial function. Our studies demonstrated that melatonin treatment suppressed reperfusion-induced neuron death. At the molecular levels, melatonin treatment modulated mitochondrial homeostasis via activating mitochondrial fusion. At the stage of reperfusion, MFN2 expression was downregulated, contributing to mitochondrial fusion inhibition. Interestingly, MFN2-related mitochondrial fusion was reversed by melatonin. Loss of MFN2-related mitochondrial fusion abrogated the protective actions of melatonin on mitochondrial function. Mechanistically, melatonin sustained MFN2-related mitochondrial fusion via suppressing Mst1-Hippo pathway. Overexpression of Mst1 attenuated the beneficial effects of melatonin on mitochondrial fusion, evoking mitochondrial damage and neuron death in the setting of brain reperfusion stress. Taken together, our results confirmed the protective effects of melatonin on acute brain reperfusion stress. Melatonin treatment activated MFN2-related mitochondrial fusion via suppressing Mst1-Hippo pathway, finally sustaining mitochondrial function and reducing reperfusion-mediated cerebral injury.

Investigation of NF-κB-94ins/del ATTG and CARD8 (rs2043211) Gene Polymorphism in Acute Lymphoblastic Leukemia

NLRP3 inflammasome has been widely implicated in the development and progression of various hematological diseases. However, how NLRP3 inflammasome contributes to the pathogenesis and clinical features of acute lymphoblastic leukemia (ALL) is still unknown. Here, in ALL patients' bone marrow, we investigated the single-nucleotide polymorphisms (SNPs) and expression of NLRP3 inflammasome related genes, NF-κB, NLRP3, IL-1β, IL-18, Caspase-1, and ASC. A total of 308 ALL patients and 300 healthy participants were included in this study. D allele and DD genotype under codominant model of NF-κB-94ins/del ATTG were showed as a protective factor in susceptibility of ALL. As for CARD8 (rs2043211), AT/TT genotype under dominant model and TT genotype under codominant model greatly increased the ALL susceptibility. We further studied the relationship between NLRP3 inflammasome genetic polymorphisms and clinical relevance. The results showed that DD genotype of NF-κB-94 ins/del ATTG and AT/TT genotype of CARD8 (rs2043211) contributed to lower WBC count and T-cell immunophenotype, respectively. Moreover, we also found that AT and TT genotypes of CARD8 (rs2043211), GT and TT genotypes of IL-1β (rs16944), and TT genotype of IL-18 (rs1946518) were associated with higher mRNA expression of NLRP3 inflammasome related genes and secretion of downstream cytokines. In conclusion, NF-κB-94 ins/del ATTG and CARD8 (rs2043211) genotypes might serve as novel biomarkers and potential targets for ALL.

Matrine promotes liver cancer cell apoptosis by inhibiting mitophagy and PINK1/Parkin pathways

Matrine is a natural alkaloid isolated from the root and stem of the legume plant Sophora. Its anti-proliferative and pro-apoptotic effects on several types of cancer have been well-documented. However, the role of matrine in regulating mitochondrial homeostasis, particularly mitophagy in liver cancer apoptosis, remains uncertain. The aim of our study was to explore whether matrine promotes liver cancer cell apoptosis by modifying mitophagy. HepG2 cells were used in the study and treated with different doses of matrine. Cell viability and apoptosis were determined by MTT assay, TUNEL staining, western blotting, and LDH release assay. Mitophagy was monitored by immunofluorescence assay and western blotting. Mitochondrial function was assessed by immunofluorescence assay, ELISA, and western blotting. The results of our study indicated that matrine treatment dose-dependently reduced cell viability and increased the apoptotic rate of HepG2 cells. Functional studies demonstrated that matrine treatment induced mitochondrial dysfunction and activated mitochondrial apoptosis by inhibiting protective mitophagy. Re-activation of mitophagy abolished the pro-apoptotic effects of matrine on HepG2 cells. Molecular investigations further confirmed that matrine regulated mitophagy via the PINK1/Parkin pathways. Matrine blocked the PINK1/Parkin pathways and repressed mitophagy, whereas activation of the PINK1/Parkin pathways increased mitophagy activity and promoted HepG2 cell survival in the presence of matrine. Together, our data indicated that matrine promoted HepG2 cell apoptosis through a novel mechanism that acted via inhibiting mitophagy and the PINK1/Parkin pathways. This finding provides new insight into the molecular mechanism of matrine for treating liver cancer and offers a potential target to repress liver cancer progression by modulating mitophagy and the PINK1/Parkin pathways.

Excessive mitochondrial fragmentation triggered by erlotinib promotes pancreatic cancer PANC-1 cell apoptosis via activating the mROS-HtrA2/Omi pathways

Background

Mitochondrial fragmentation drastically regulates the viability of pancreatic cancer through a poorly understood mechanism. The present study used erlotinib to activate mitochondrial fragmentation and then investigated the downstream events that occurred in response to mitochondrial fragmentation.

Methods

Cell viability and apoptosis were determined via MTT assay, TUNEL staining and ELISA. Mitochondrial fragmentation was measured via an immunofluorescence assay and qPCR. siRNA transfection and pathway blockers were used to perform the loss-of-function assays.

Results

The results of our study demonstrated that erlotinib treatment mediated cell apoptosis in the PANC-1 pancreatic cancer cell line via evoking mitochondrial fragmentation. Mechanistically, erlotinib application increased mitochondrial fission and reduced mitochondrial fusion, triggering mitochondrial fragmentation. Subsequently, mitochondrial fragmentation caused the overproduction of mitochondrial ROS (mROS). Interestingly, excessive mROS induced cardiolipin oxidation and mPTP opening, finally facilitating HtrA2/Omi liberation from the mitochondria into the cytoplasm, where HtrA2/Omi activated caspase-9-dependent cell apoptosis. Notably, neutralization of mROS or knockdown of HtrA2/Omi attenuated erlotinib-mediated mitochondrial fragmentation and favored cancer cell survival.

Conclusions

Together, our results identified the mROS-HtrA2/Omi axis as a novel signaling pathway that is activated by mitochondrial fragmentation and that promotes PANC-1 pancreatic cancer cell mitochondrial apoptosis in the presence of erlotinib.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0665-1) contains supplementary material, which is available to authorized users.

Role and mechanism of the nod-like receptor family pyrin domain-containing 3 inflammasome in oral disease

OBJECTIVE

To summarize evidence and data from experimental studies regarding the role and mechanism of the Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome in the pathogenesis of several representative oral diseases.

MATERIALS AND METHODS

A literature search of PubMed and EBSCO was performed. The literature was searched using a combination of keywords, e.g., NLRP3 inflammasome, inflammation, microorganisms, oral inflammatory diseases, and oral immunological diseases.

RESULTS

The initiation and activation of the NLRP3 inflammasome are associated with the pathogenesis and progression of several representative oral diseases, including periodontitis, oral lichen planus, dental pulp disease, and oral cavity squamous cell carcinoma.

CONCLUSIONS

The NLRP3 inflammasome plays a crucial role in the progression of inflammatory and adaptive immune responses. The possible role of the NLRP3 inflammasome in several oral diseases, including not only periodontitis and pulpitis but also mucosal diseases and oral cavity squamous cell carcinoma, may involve the aberrant regulation of inflammatory and immune responses. Understanding the cellular and molecular biology of the NLRP3 inflammasome is necessary because the NLRP3 inflammasome may be a potential therapeutic target for the treatment and prevention of oral inflammatory and immunological diseases.

RETRACTED: DUSP1 alleviates cerebral ischaemia reperfusion injury via inactivating JNK-Mff pathways and repressing mitochondrial fission

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. The article titled “DUSP1 alleviates cerebral ischaemia reperfusion injury via inactivating JNK-Mff pathways and repressing mitochondrial fission” is a near duplicate of a previously published manuscript titled “DUSP1 alleviates cardiac ischemia/reperfusion injury by suppressing the Mff-required mitochondrial fission and Bnip3-related mitophagy via the JNK pathways. Redox Biology. 2018;14:576-587.”

Tanshinone IIA reduces SW837 colorectal cancer cell viability via the promotion of mitochondrial fission by activating JNK-Mff signaling pathways

Background

Mitochondrial homeostasis has been increasingly viewed as a potential target of cancer therapy, and mitochondrial fission is a novel regulator of mitochondrial function and apoptosis. The aim of our study was to determine the detailed role of mitochondrial fission in SW837 colorectal cancer cell viability, mobility and proliferation. In addition, the current study also investigated the therapeutic impact of Tanshinone IIA (Tan IIA), a type of anticancer adjuvant drug, on cancer mitochondrial homeostasis.

Results

The results of our data illustrated that Tan IIA promoted SW837 cell death, impaired cell migration and mediated cancer proliferation arrest in a dose-dependent manner. Functional investigation exhibited that Tan IIA treatment evoked mitochondrial injury, as witnessed by mitochondrial ROS overproduction, mitochondrial potential collapse, antioxidant factor downregulation, mitochondrial pro-apoptotic protein upregulation, and caspase-9-dependent apoptotic pathway activation. Furthermore, we confirmed that Tan IIA mediated mitochondrial damage by activating mitochondrial fission, and the inhibition of mitochondrial fission abrogated the proapoptotic effects of Tan IIA on SW837 cells. To this end, our results demonstrated that Tan IIA modulated mitochondrial fission via the JNK-Mff pathways. The blockade of the JNK-Mff axis inhibited Tan IIA-mediated mitochondrial fission and promoted the survival of SW837 cells.

Conclusions

Altogether, our results identified mitochondrial fission as a new potential target to control cancer viability, mobility and proliferation. Furthermore, our findings demonstrate that Tan IIA is an effective drug to treat colorectal cancer by activating JNK-Mff-mitochondrial fission pathways.

Electronic supplementary material

The online version of this article (10.1186/s12860-018-0174-z) contains supplementary material, which is available to authorized users.

Innate Immune Signaling in Nonalcoholic Fatty Liver Disease and Cardiovascular Diseases

The physiological significance of innate immune signaling lies primarily in its role in host defense against invading pathogens. It is becoming increasingly clear that innate immune signaling also modulates the development of metabolic diseases, especially nonalcoholic fatty liver disease and cardiovascular diseases, which are characterized by chronic, low-grade inflammation due to a disarrangement of innate immune signaling. Notably, recent studies indicate that in addition to regulating canonical innate immune-mediated inflammatory responses (or immune-dependent signaling-induced responses), molecules of the innate immune system regulate pathophysiological responses in multiple organs during metabolic disturbances (termed immune-independent signaling-induced responses), including the disruption of metabolic homeostasis, tissue repair, and cell survival. In addition, emerging evidence from the study of immunometabolism indicates that the systemic metabolic status may have profound effects on cellular immune function and phenotypes through the alteration of cell-intrinsic metabolism. We summarize how the innate immune system interacts with metabolic disturbances to trigger immune-dependent and immune-independent pathogenesis in the context of nonalcoholic fatty liver disease, as representative of metabolic diseases, and cardiovascular diseases.

Sirt3 attenuates post-infarction cardiac injury via inhibiting mitochondrial fission and normalization of AMPK-Drp1 pathways

Mitochondrial damage is involved in the pathogenesis of post-infarction cardiac injury. However, the upstream regulators of mitochondrial damage have not yet been identified. The aim of our study is to explore the role of Sirt3 in post-infarction cardiac injury with a particular focus on mitochondrial fission and AMPK-Drp1 pathways. Our results indicated that Sirt3 was downregulated in the progression of post-infarction cardiac injury. Overexpression of Sirt3 attenuated cardiac fibrosis, sustained myocardial function, inhibited the inflammatory response, and reduced cardiomyocyte death. Functional studies illustrated that chronic post-infarction cardiac injury was characterized by increased mitochondrial fission, which triggered mitochondrial oxidative stress, metabolic disorders, mitochondrial potential reduction and caspase-9 apoptosis in cardiomyocytes. However, Sirt3 overexpression attenuated mitochondrial fission and thus preserved mitochondrial homeostasis and cardiomyocyte viability. Furthermore, our results confirmed that Sirt3 repressed mitochondrial fission via normalizing AMPK-Drp1 pathways. Inhibition of AMPK activity re-activated Drp1 and thus abrogated the inhibitory effect of Sirt3 on mitochondrial fission. Altogether, our results indicate that Sirt3 enhancement could be an effective approach to retard the development of post-infarction cardiac injury via disrupting mitochondrial fission and normalizing the AMPK-Drp1 axis.

BI1 alleviates cardiac microvascular ischemia-reperfusion injury via modifying mitochondrial fission and inhibiting XO/ROS/F-actin pathways

Pathogenesis of cardiac microvascular ischemia-reperfusion (IR) injury is associated with excessive mitochondrial fission. However, the upstream mediator of mitochondrial fission remains obscure. Bax inhibitor 1 (BI1) is linked to multiple mitochondrial functions, and there have been no studies investigating the contribution of BI1 on mitochondrial fission in the setting of cardiac microvascular IR injury. This study was undertaken to establish the action of BI1 on the cardiac microvascular reperfusion injury and figure out whether BI1 sustained endothelial viability via inhibiting mitochondrial fission. Our observation indicated that BI1 was downregulated in reperfused hearts and overexpression of BI1 attenuated microvascular IR injury. Mechanistically, reperfusion injury elevated the levels of xanthine oxidase (XO), an effect that was followed by increased reactive oxygen species (ROS) production. Subsequently, oxidative stress mediated F-actin depolymerization and the latter promoted mitochondrial fission. Aberrant fission caused mitochondrial dysfunction and ultimately activated mitochondrial apoptosis in cardiac microvascular endothelial cells. By comparison, BI1 overexpression repressed XO expression and thus neutralized ROS, interrupting F-actin-mediated mitochondrial fission. The inhibitory effect of BI1 on mitochondrial fission sustained endothelial viability, reversed endothelial barrier integrity, attenuated the microvascular inflammation response, and maintained microcirculation patency. Altogether, we conclude that BI1 is essential in maintaining mitochondrial homeostasis and alleviating cardiac microvascular IR injury. Deregulated BI1 via the XO/ROS/F-actin pathways plays a causative role in the development of cardiac microvascular reperfusion injury.

NR4A1 Promotes Cerebral Ischemia Reperfusion Injury by Repressing Mfn2-Mediated Mitophagy and Inactivating the MAPK-ERK-CREB Signaling Pathway

Mitochondrial dysfunction has been acknowledged as the key pathogenic mechanism in cerebral ischemia-reperfusion (IR) injury. Mitophagy is the protective system used to sustain mitochondrial homeostasis. However, the upstream regulator of mitophagy in response to brain IR injury is not completely understood. Nuclear receptor subfamily 4 group A member 1 (NR4A1) has been found to be associated with mitochondrial protection in a number of diseases. The aim of our study is to explore the functional role of NR4A1 in cerebral IR injury, with a particular focus on its influence on mitophagy. Wild-type mice and NR4A1-knockout mice were used to generate cerebral IR injury in vivo. Mitochondrial function and mitophagy were detected via immunofluorescence assays and western blotting. Cellular apoptosis was determined via MTT assays, caspase-3 activity and western blotting. Our data revealed that NR4A1 was significantly increased in the reperfused brain tissues. Genetic ablation of NR4A1 reduced the cerebral infarction area and repressed neuronal apoptosis. The functional study demonstrated that NR4A1 modulated cerebral IR injury by inducing mitochondrial damage. Higher NR4A1 promoted mitochondrial potential reduction, evoked cellular oxidative stress, interrupted ATP generation, and initiated caspase-9-dependent apoptosis. Mechanistically, NR4A1 induced mitochondrial damage by disrupting Mfn2-mediated mitophagy. Knockdown of NR4A1 elevated Mfn2 expression and therefore reversed mitophagic activity, sending a prosurvival signal for mitochondria in the setting of cerebral IR injury. Further, we demonstrated that NR4A1 modulated Mfn2 expression via the MAPK-ERK-CREB signaling pathway. Blockade of the ERK pathway could abrogate the permissive effect of NR4A1 deletion on mitophagic activation, contributing to neuronal mitochondrial apoptosis. Overall, our results demonstrate that the pathogenesis of cerebral IR injury is closely associated with a drop in protective mitophagy due to increased NR4A1 through the MAPK-ERK-CREB signaling pathway.

TAZ inhibition promotes IL-2-induced apoptosis of hepatocellular carcinoma cells by activating the JNK/F-actin/mitochondrial fission pathway

Background

Cytokine-based cancer therapies have attracted a great deal of attention in recent years. Unfortunately, resistance to treatment limits the efficacy of these therapeutics. Therefore, the aim of our study was to explore the mechanism of IL-2-based therapy for hepatocellular carcinoma in an attempt to increase the efficiency of this treatment option.

Methods

HepG2 cells were treated with IL-2. Then, siRNA against TZA was used to transfected into HepG2 cells. Cellular apoptosis was measured via MTT assay, TUNEL assay and caspase-3 activity. Cellular proliferation was evaluated via EdU assay and western blotting. Cellular migration was detected via Transwell assay. Mitochondrial function was monitored by mitochondrial potential analysis, ROS staining, immunofluorescence and western blotting. Pathway blocker and activator were used to establish the role of JNK/F-actin/mitochondrial fission signaling pathway in HepG2 cells stress response.

Results

Our study found that IL-2 treatment significantly reduced the viability, mobility and proliferation of HepG2 cells in vitro. We also demonstrated that IL-2 treatment was accompanied by an increase in the expression of transcriptional co-activator with PDZ-binding motif (TAZ). Interestingly, genetic ablation of TAZ in the presence of IL-2 further promoted apoptosis, inhibited mobility, and arrested proliferation in HepG2 cells. At the molecular level, IL-2 administration activated excessive mitochondrial fission via the JNK/F-actin pathway; these effects were further enhanced by TAZ deletion. Mechanistically, TAZ knockdown further increased the expression of mitochondrial fission-related proteins such as Drp1, Mff and Fis. The augmented mitochondrial fission stimulated ROS overproduction, mediated redox imbalance, interrupted mitochondrial energy generation, reduced mitochondrial membrane potential, promoted leakage of the pro-apoptotic molecule cyt-c into the nucleus, and initiated caspase-9-related mitochondrial death. Further, we demonstrated that the anti-proliferative and anti-metastatic effects of IL-2 in HepG2 cells were enhanced by TAZ deletion, suggesting that IL-2 sensitizes HepG2 cells to IL-2-based cytokine therapy. However, JNK/F-actin pathway blockade could abrogate the inhibitory effects of TAZ deletion on HepG2 migration, proliferation and survival.

Conclusions

Taken together, our data indicate that the anti-tumor effects of IL-2-based therapies may be enhanced by TAZ deletion in a JNK/F-actin pathway-dependent manner. This finding provides a novel combinatorial therapeutic approach for treating hepatocellular carcinoma that might significantly increase the efficacy of cytokine-based therapies in a clinical setting.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0615-y) contains supplementary material, which is available to authorized users.

Important roles of the Ca2+-sensing receptor in vascular health and disease

Ca²⁺-sensing receptor (CaSR), a member of G protein-coupled receptor family, is widely expressed in the vascular system, including perivascular neurons, vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). When stimulated, CaSR can further increase the cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt) in two ways: intracellular Ca²⁺ release from endo/sarcoplasmic reticulum (ER/SR) and extracellular Ca²⁺ entry through Ca²⁺-permeable cation channels. In endothelium, increased Ca²⁺ subsequently activate nitric oxide synthase (NOS) and intermediate conductance Ca²⁺-activated K⁺ channels (IKCa), resulting in vasodilation through NOS-mediated NO release or membrane hyperpolarization. In VSMCs, CaSR-induced intracellular Ca²⁺ increase causes blood vessel constriction. CaSR activation predominantly induces vasorelaxation of whole vascular tissues through VECs-dependent mechanisms; however, CaSR-induced Ca²⁺ signaling in VSMCs may play a braking role in CaSR-mediated vasorelaxation. Emerging evidence reveals the importance of CaSR in the regulation of vascular tone and blood pressure. Here, we summarized recent advances in CaSR-mediated vascular reaction and the underlying mechanisms in different species, including humans. In addition, several studies have demonstrated that CaSR dysfunction may be associated with some fatal vascular diseases, such as pulmonary arterial hypertension, primary hypertension, diabetes, acute myocardial infarction and vascular calcification. With the advance of studies on CaSR in vascular health and disease, it is expected positive modulators or negative modulators of CaSR used for the treatment of specific diseases may be promising therapeutic options for the prevention and/or treatment of vascular diseases.

Therapeutic effect of Sirtuin 3 on ameliorating nonalcoholic fatty liver disease: The role of the ERK-CREB pathway and Bnip3-mediated mitophagy

Increased mitochondrial damage is related to the progression of a diet-induced nonalcoholic fatty liver disease. The aim of our study is to investigate the role of Sirtuin 3 (Sirt3) in treating nonalcoholic fatty liver disease with a focus on mitophagy and the ERK-CREB pathway. Our data indicated that Sirt3 was downregulated in liver tissue in response to chronic HFD treatment. Interestingly, re-introduction of Sirt3 protected hepatic function, attenuated liver fibrosis, alleviated the inflammatory response, and prevented hepatocyte apoptosis. Molecular investigations demonstrated that lipotoxicity was associated with an increase in mitochondrial apoptosis as evidenced by reduced mitochondrial potential, augmented ROS production, increased cyt-c leakage into the nucleus, and activated caspase-9 apoptotic signalling. Additionally, Sirt3 overexpression protected hepatocytes against mitochondrial apoptosis via promoting Bnip3-required mitophagy. Functional studies showed that Sirt3 reversed Bnip3 expression and mitophagy activity via the ERK-CREB signalling pathway. Blockade of the ERK-CREB axis repressed the promotive effects of Sirt3 on Bnip3 activation and mitophagy augmentation, finally negating the anti-apoptotic influences of Sirt3 on hepatocytes in the setting of high-fat-stress. Collectively, our data show that high-fat-mediated liver damage is associated with Sirt3 downregulation, which is followed by ERK-CREB pathway inactivation and Bnip3-mediated inhibition of mitophagy, causing hepatocytes to undergo mitochondria-dependent cell death. Based on this, strategies for enhancing Sirt3 activity and activating the ERK-CREB-Bnip3-mitophagy pathways could be used to treat nonalcoholic fatty liver disease.

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Sirt3 overexpression prevents diet-mediated fatty liver disease.

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Sirt3 blocks hepatocyte mitochondrial apoptosis in the setting of high-fat injury.

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Bnip3-mediated mitophagy protects mitochondria against high-fat-mediated damage.

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Sirt3 controls Bnip3-mediated mitophagy via the ERK-CREB signalling pathway.

ER-Mitochondria Microdomains in Cardiac Ischemia-Reperfusion Injury: A Fresh Perspective

The mitochondrial and endoplasmic reticulum (ER) homeostasis is pivotal to the maintenance of an array of physiological processes. The physical contact and association between ER and mitochondria, known as the ER–mitochondria microdomains or mitochondria-associated ER membrane (MAM), temporally and spatially regulates the mitochondria/ER structure and function. More evidence suggests a role for MAMs in energy production, cellular contraction and mobility, and normal extracellular signal transmission. In pathological states, such as cardiac ischemia–reperfusion (I/R injury), this ER–mitochondria microdomains may act to participate in the cellular redox imbalance, ER stress, mitochondrial injury, energy deletion, and programmed cell death. From a therapeutic perspective, a better understanding of the cellular and molecular mechanisms of the pathogenic ER–mitochondria contact should help to identify potential therapeutic target for cardiac I/R injury and other cardiovascular diseases and also pave the road to new treatment modalities pertinent for the treatment of reperfusion damage in clinical practice. This review will mainly focus on the possible signaling pathways involved in the regulation of the ER–mitochondria contact. In particular, we will summarize the downstream signaling modalities influenced by ER–mitochondria microdomains, for example, mitochondrial fission, mitophagy, calcium balance, oxidative stress, and programmed cell death in details.

Pyroptosis in pterygium pathogenesis

Pterygium is a common ocular disease characterized by proliferating fibrovascular tissue. Pyroptosis, a recently discovered programed cell death, is known to be associated with oxidative stress, one of the main causes of pterygia. Here, we aimed to study the role of pyroptosis in pterygium pathogenesis. The expression of nod-like receptor pyrins-3 (NLRP3), caspase-1, IL-18, and IL-1β was analyzed in 60 human pterygium tissues and 60 human conjunctival epithelium tissues using real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot analysis. Human conjunctival epithelial cells (HConECs) and human pterygium fibroblasts (HPFs) were primary cultured and the level of pyroptosis-associated factors was detected. Both cells were treated with H₂O₂, and cell lysis was detected by lactate dehydrogenase (LDH) release assay, the expression of the factors by qRT-PCR, Western blot analysis, and immunostaining. The downstream factors IL-18 and IL-1β were measured after inhibition of caspase-1 to confirm the caspase-1-dependent pyroptosis. α-SMA and E-cadherin were detected as indicators of pyroptosis-induced myofibroblast activation in HPFs. We discovered that the expression of the factors was significantly increased in pterygium and that caspase-1-dependent pyroptosis presents in both H₂O₂-treated HPFs and HConECs during which the expression of these factors was significantly elevated and the elevation of downstream factors IL-18 and IL-1β was restrained after caspase-1 inhibition. α-SMA increase and E-cadherin down-regulation were detected in H₂O₂-treated HPFs and the changes were reversed by caspase-1 inhibition. Pyroptosis displays a role in the pathological process of pterygium formation and progression. Pyroptosis appears to be an intriguing target to prevent pterygium pathogenesis.