Overexpression Of Mst1 Research Articles

Inhibiting endothelial cell Mst1 attenuates acute lung injury in mice.

Lung endothelium plays a pivotal role in the orchestration of inflammatory responses to acute pulmonary insults. Mammalian sterile 20-like kinase 1 (Mst1) is a serine/threonine kinase that has been shown to play an important role in the regulation of apoptosis, stress responses, and organ growth. This study investigated the role of Mst1 in lung endothelial activation and acute lung injury (ALI). We found that Mst1 was significantly activated in inflamed lung endothelial cells (ECs) and mouse lung tissues. Overexpression of Mst1 promoted nuclear factor κ-B (NF-κB) activation through promoting JNK and p38 activation in lung ECs. Inhibition of Mst1 by either its dominant negative form (DN-Mst1) or its pharmacological inhibitor markedly attenuated cytokine-induced expression of cytokines, chemokines, and adhesion molecules in lung ECs. Importantly, in a mouse model of lipopolysaccharide-induced (LPS-induced) ALI, both deletion of Mst1 in lung endothelium and treatment of WT mice with a pharmacological Mst1 inhibitor significantly protected mice from LPS-induced ALI. Together, our findings identified Mst1 kinase as a key regulator in controlling lung EC activation and suggest that therapeutic strategies aimed at inhibiting Mst1 activation might be effective in the prevention and treatment of inflammatory lung diseases.

Retracted] SFRP2 modulates non‑small cell lung cancer A549 cell apoptosis and metastasis by regulating mitochondrial fission via Wnt pathways.

Following the publication of this paper, it was drawn to the Editor's attention by a concerned reader that certain of the JC1‑stained cellular images shown in Fig. 2C on p. 1928 were strikingly similar to data that had already been published in different form in another article written by different authors at different research institutes [Yao S and Yan W: Overexpression of Mst1 reduces gastric cancer cell viability by repressing the AMPK‑Sirt3 pathway and activating mitochondrial fission. Onco Targets Ther 11: 8465‑8479, 2019]. Owing to the fact that the contentious data in the above article had already been published prior to its submission to Molecular Medicine Reports, the Editor has decided that this paper should be retracted from the Journal. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a satisfactory reply. The Editor apologizes to the readership for any inconvenience caused. [Molecular Medicine Reports 20: 1925‑1932, 2019; DOI: 10.3892/mmr.2019.10393].

Overexpression of Mst1 Reduces Gastric Cancer Cell Viability by Repressing the AMPK-Sirt3 Pathway and Activating Mitochondrial Fission [Retraction

[This retracts the article DOI: 10.2147/OTT.S180851.].

Abstract 15266: Inhibiting Endothelial Mammalian Sterile 20-Like Kinase 1 Attenuates Acute Lung Injury in Mice

Introduction: Lung endothelium plays a pivotal role in the orchestration of inflammatory and injury responses to acute pulmonary insults. Mammalian sterile 20-like kinase 1 (Mst1), a mammalian homolog of Hippo, is a serine/threonine kinase that is ubiquitously expressed in many tissues and has been shown to play an important role in the regulation of complex biological processes, such as apoptosis, oncogenesis and organ growth. While Mst1 is highly expressed in the lung, its role in the endothelial response to pulmonary insults is largely unknown. Hypothesis: Mst1 regulates inflammatory responses in acute lung injury. Methods: Mst1 activity was assessed in lung endothelium by western blot and immunofluorescent staining. EC activation was measured by nuclear factor kappa B (NF-κB) dependent luciferase assay and the electrophoresis mobility shift assay. Mst1 knockout mice and pharmacological inhibitor were employed to assess the effects of Mst1 on homeostatic and lipopolysaccharide (LPS)-induced endothelial inflammation. Results: In this study, we found that Mst1 activation, as determined by Mst1 phosphorylation and nuclear translocation, was significantly increased in lung ECs after exposure to tumor necrosis factor-alpha (TNF-α) and in lungs of LPS-instilled mice as compared to the vehicle control. Overexpression of either full length Mst1 or its kinase domain promoted NF-κB activation by approximately 6.5-fold and 8-fold, respectively, whereas overexpression of the dominant negative forms of Mst1 attenuated endothelial inflammatory responses to both TNF-α and interleukin-1β stimulation. Consistent with these observations, endothelial specific deletion of Mst1 markedly attenuated LPS-induced acute lung injury in mice. Furthermore, we found that treatment of wild-type mice with Mst1 specific pharmacological inhibitor significantly prevented LPS-induced lung injury. Conclusion: Our findings identified Mst1 kinase as a key regulator in promoting lung EC activation and vascular inflammation, and suggest that therapeutic strategies aimed at inhibiting Mst1 activation might be effective for preventing inflammatory vascular diseases of the lung.

MST1 mediates doxorubicin-induced cardiomyopathy by SIRT3 downregulation

Heart failure is a major side effect of doxorubicin (DOX) treatment in patients with cancer. However, the mechanisms underlying the development of DOX-induced heart failure need to be addressed. This study aims to test whether the serine/threonine kinase MST1, a major Hippo pathway component, contributes to the development of DOX-induced myocardial injury. C57BL/6J WT mice and mice with cardiomyocyte-specific dominant-negative MST1 (kinase-dead) overexpression received three weekly injections of DOX, reaching a final cumulative dose of 18 mg/kg. Echocardiographic, histological and biochemical analyses were performed six weeks after the first DOX administration. The effects of MST1 inhibition on DOX-induced cardiomyocyte injury were also tested in vitro. MST1 signaling was significantly activated in cardiomyocytes in response to DOX treatment in vitro and in vivo. Wild-type (WT) mice treated with DOX developed cardiac dysfunction and mitochondrial abnormalities. However, these detrimental effects were abolished in mice with cardiomyocyte-specific overexpression of dominant-negative MST1 (DN-MST1) or treated with XMU-MP-1, a specific MST1 inhibitor, indicating that MST1 inhibition attenuates DOX-induced cardiac dysfunction. DOX treatment led to a significant downregulation of cardiac levels of SIRT3, a deacetylase involved in mitochondrial protection, in WT mice, which was rescued by MST1 inhibition. Pharmacological inhibition of SIRT3 blunted the protective effects of MST1 inhibition, indicating that SIRT3 downregulation mediates the cytotoxic effects of MST1 activation in response to DOX treatment. Finally, we found a significant upregulation of MST1 and downregulation of SIRT3 levels in human myocardial tissue of cancer patients treated with DOX. In summary, MST1 contributes to DOX-induced cardiomyopathy through SIRT3 downregulation.

Evaluation of Coenzyme Q10 (CoQ10) Deficiency and Therapy in Mouse Models of Cardiomyopathy.

Mitochondrial dysfunction plays a key role in the development of heart failure, but targeted therapeutic interventions remain elusive. Previous studies have shown coenzyme Q10 (CoQ10) insufficiency in patients with heart disease with undefined mechanism and modest effectiveness of CoQ10 supplement therapy. Using 2 transgenic mouse models of cardiomyopathy owing to cardiac overexpression of Mst1 (Mst1-TG) or β 2 -adrenoceptor (β 2 AR-TG), we studied changes in cardiac CoQ10 content and alterations in CoQ10 biosynthesis genes. We also studied in Mst1-TG mice effects of CoQ10, delivered by oral or injection regimens, on both cardiac CoQ10 content and cardiomyopathy phenotypes. High performance liquid chromatography and RNA sequencing revealed in both models significant reduction in cardiac content of CoQ10 and downregulation of most genes encoding CoQ10 biosynthesis enzymes. Mst1-TG mice with 70% reduction in cardiac CoQ10 were treated with CoQ10 either by oral gavage or i.p. injection for 4-8 weeks. Oral regimens failed in increasing cardiac CoQ10 content, whereas injection regimen effectively restored the cardiac CoQ10 level in a time-dependent manner. However, CoQ10 restoration in Mst1-TG mice did not correct mitochondrial dysfunction measured by energy metabolism, downregulated expression of marker proteins, and oxidative stress nor to preserve cardiac contractile function. In conclusion, mouse models of cardiomyopathy exhibited myocardial CoQ10 deficiency likely due to suppressed endogenous synthesis of CoQ10. In contrast to ineffectiveness of oral administration, CoQ10 administration by injection regimen in cardiomyopathy mice restored cardiac CoQ10 content, which, however, failed in achieving detectable efficacy at molecular and global functional levels.

275 MST1 MEDIATES DOXORUBICIN-INDUCED CARDIOMYOPATHY BY SIRT3 DOWNREGULATION

Abstract Introduction Heart failure is a major side effect of doxorubicin (DOX) treatment in patients with cancer. However, the mechanisms underlying the development of DOX-induced cardiomyopathy (DCM) need to be addressed. Here, we demonstrate that the serine/threonine kinase MST1, a major Hippo pathway component, contributes to the development of DOX-induced myocardial injury. Hypothesis The inhibition of MST1 protects from DCM by preserving SIRT3 expression Methods C57BL/6J WT mice and mice with cardiomyocyte-specific dominant-negative MST1 (kinase-dead) overexpression received 3 weekly injections of DOX, reaching a final cumulative dose of 18 mg/kg. Echocardiographic, histological and biochemical analyses were performed 6 weeks after the first administration of DOX. Results MST1 signaling was significantly activated in cardiomyocytes in response to DOX treatment in vitro and in vivo. Wild-type (WT) mice treated with DOX had reduced fractional shortening (46,1±1,77 vs. 31,1±1,07, n=7-11) and mitochondrial abnormalities (3,7±0,93 vs. 10,2±1,5, n=12 microscopic fields from 3 independent samples). However, systolic dysfunction was abolished in mice with cardiomyocyte-specific overexpression of dominant-negative MST1 (DN-MST1) (31,1±1,07 vs. 46,3±1,13, n=11) or treated with the MST1 inhibitor ‘XMU-MP-1’ (37,5±1,8 vs. 46,6±1,87, n=8), indicating that MST1 inhibition attenuates DOX-induced cardiac dysfunction. Also, DOX treatment led to a significant downregulation of cardiac levels of SIRT3 (1±0,12 vs. 0,6±0,11, n=4), a deacetylase involved in mitochondrial protection, in WT mice, which was rescued by MST1 inhibition (0,6±0,11 vs. 1,3±0,04, n=4). Pharmacological inhibition of SIRT3 blunted the protective effects of MST1 inhibition (44,5±1,55 vs. 32,5±2,33, n=4), indicating that SIRT3 downregulation mediates the cytotoxic effects of MST1 activation in response to DOX treatment. Finally, we found a significant upregulation of MST1 levels in human myocardial tissue of cancer patients treated with DOX (1,5±0,23 vs. 2,4±0,12, N=81-123 cells from 3 different patients). Conclusion MST1 contributes to DOX-induced cardiomyopathy by promoting mitochondrial damage through SIRT3 downregulation in cardiomyocytes.

Abstract P2002: Mst1 Suppresses Pressure Overload-induced Cardiac Hypertrophy But Reduces Cardiac Function Through PERK Phosphorylation

Cardiac hypertrophy in response to hemodynamic overload is initially an adaptive mechanism to maintain normal cardiac function by reducing left ventricular (LV) wall stress. Conversely, insufficient hypertrophy could lead to elevated wall stress, causing increased cell death and cardiac dysfunction. The Hippo pathway plays an important role in determining organ size. Mammalian sterile 20-like kinase 1 (Mst1) is the key serine-threonine kinase in the Hippo pathway, controlling cell death, proliferation, and differentiation. Mice with cardiac-specific overexpression of Mst1 (Tg-Mst1) fail to develop compensatory hypertrophy despite LV dysfunction and dilation at baseline. To elucidate the mechanism through which Mst1 inhibits cardiac hypertrophy, pressure overload (PO) was imposed on WT and Tg-Mst1 mice by transverse aortic constriction (TAC). TAC-induced increases in LV weight/body weight were significantly suppressed in Tg-Mst1 mice (5.8 vs WT 5.1, p<0.05). LV ejection fraction (EF) after TAC was lower in Tg-Mst1 mice than in WT mice (40% vs WT 60%, p<0.01), consistent with the notion that Mst1 promotes PO-induced systolic dysfunction in part by inhibiting compensatory hypertrophy. Mst1 interacted with and induced phosphorylation of protein kinase RNA-like endoplasmic reticulum kinase (PERK). We generated knock-in mice expressing phosphorylation-resistant PERK (PERK-KI) and performed TAC on WT and PERK-KI mice. LVEF was preserved in PERK-KI mice compared to in WT mice (67% vs WT 46%, p<0.05) after 8 weeks of TAC. PO-induced increases in lung congestion were attenuated in PERK-KI mice compared to in WT mice (10 vs WT 11.5, p<0.05). Despite the improvement in cardiac function, cardiac hypertrophy was not attenuated in PERK-KI mice. These results suggest that phosphorylation of PERK by Mst1 is detrimental for the heart during PO, in part due to suppression of compensatory hypertrophy.

Melatonin attenuates manganese-induced mitochondrial fragmentation by suppressing the Mst1/JNK signaling pathway in primary mouse neurons

Manganese (Mn) toxicity is mainly caused by excessive Mn content in drinking water and occupational exposure. Moreover, overexposure to Mn can impair mental, cognitive, memory, and motor capacities. Although melatonin (Mel) can protect against Mn-induced neuronal damage and mitochondrial fragmentation, the underlying mechanism remains elusive. Here, we examined the related molecular mechanisms underlying Mel attenuating Mn-induced mitochondrial fragmentation through the mammalian sterile 20-like kinase-1 (Mst1)/JNK signaling path. To test the role of Mst1 in mitochondrial fragmentation, we treated mouse primary neurons overexpressing Mst1 with Mel and Mn stimulation. In normal neurons, 10 μM Mel reduced the effects of Mn (200 μM) on Mst1 expression at the mRNA and protein levels and on phosphorylation of JNK and Drp1, Drp1 mitochondrial translocation, and mitochondrial fragmentation. Conversely, overexpression of Mst1 hindered the protective effect of Mel (10 μM) against Mn-induced mitochondrial fragmentation. Anisomycin (ANI), an activator of JNK signaling, was similarly found to inhibit the protective effect of Mel on mitochondria, while Mst1 levels were not significantly changed. Thus, our results demonstrated that 10 μM Mel negatively regulated the Mst1-JNK pathway, thereby reducing excessive mitochondrial fission, maintaining the mitochondrial network, and alleviating Mn-induced mitochondrial dysfunction.

MST1 mediates neuronal loss and cognitive deficits: A novel therapeutic target for Alzheimer's disease.

Alzheimer's disease (AD) is the most prevalent form of dementia in the old adult and characterized by progressive cognitive decline and neuronal damage. The mammalian Ste20-like kinase1/2 (MST1/2) is a core component in Hippo signaling, which regulates neural stem cell proliferation, neuronal death and neuroinflammation. However, whether MST1/2 is involved in the occurrence and development of AD remains unknown. In this study we reported that the activity of MST1 was increased with Aβ accumulation in the hippocampus of 5xFAD mice. Overexpression of MST1 induced AD-like phenotype in normal mice and accelerated cognitive decline, synaptic plasticity damage and neuronal apoptosis in 2-month-old 5xFAD mice, but did not significantly affect Aβ levels. Mechanistically, MST1 associated with p53 and promoted neuronal apoptosis by phosphorylation and activation of p53, while p53 knockout largely reversed MST1-induced AD-like cognitive deficits. Importantly, either genetic knockdown or chemical inactivation of MST1 could significantly improve cognitive deficits and neuronal apoptosis in 7-month-old 5xFAD mice. Our results support the idea that MST1-mediated neuronal apoptosis is an essential mechanism of cognitive deficits and neuronal loss for AD, and manipulating the MST1 activity as a potential strategy will shed light on clinical treatment for AD or other diseases caused by neuronal injury.

Disruption of LTBP4 Inhibition-Induced TGFβ1 Activation Promoted Cell Proliferation and Metastasis in Skin Melanoma by Inhibiting the Activation of the Hippo-YAP1 Signaling Pathway.

Melanoma is a malignant tumor derived from melanocytes, which is the most fatal skin cancer. The present study aimed to explore and elucidate the candidate genes in melanoma and its underlying molecular mechanism. A total of 1,156 differentially expressed genes were obtained from the GSE46517 dataset of Gene Expression Omnibus database using the package “limma” in R. Based on two algorithms (LASSO and SVM-RFE), we obtained three candidate DEGs (LTBP4, CDHR1, and MARCKSL1). Among them, LTBP4 was identified as a diagnostic marker of melanoma (AUC = 0.985). Down-regulation of LTBP4 expression was identified in melanoma tissues and cells, which predicted poor prognosis of patients with melanoma. Cox analysis results discovered that LTBP4 with low expression was an independent prognostic factor for overall survival in patients with melanoma. LTBP4 inhibition reduced cell apoptosis and promoted cell proliferation and metastasis. These changes were correlated with the expression levels of caspase-3, Ki67 and E-cadherin. Further, as indicated by tumor formation study of nude mice, LTBP4 silencing improved the tumorigenic ability of melanoma cells. Knockdown of LTBP4 increased the percentage of active TGFβ1 secreted by melanoma cells. CTGF, Gyr61, and Birc5 expression levels were reduced, YAP1 phosphorylation was inhibited, and YAP1 was translocated from the cytoplasm to the nucleus in melanoma cells treated with TGF-β1. These effects were reversed by LTBP4 overexpression. As evidenced by immunofluorescent staining, Western blotting and luciferase reporter assay, LTBP4 overexpression activated the Hippo signaling pathway, which was characterized by the increased nuclear-cytoplasmic translocation of YAP1 and the enhanced phosphorylation of YAP1, MST1, and MOB1. In addition, the effects of LTBP4 overexpression on inhibiting CTGF, Cyr61 and Birc5 expression, promoting the apoptosis, and inhibiting the metastasis and proliferation of melanoma cells were reversed by the overexpression of YAP1 or MST1. In conclusion, the LTBP4-TGFβ1-Hippo-YAP1 axis is a critical pathway for the progression of skin melanoma.

MST1-knockdown protects against impairment of working memory via regulating neural activity in depression-like mice.

We reported that over-expression of MST1 induced the impairment of spatial memory via disturbing neural oscillation patterns in mice. Meanwhile, the P-MST1 is increased in the hippocampus after chronic unpredictable mild stress (CUMS). However, it is unclear if MST1 knockdown protects against stress-induced memory deficits via modulating neural activities. In the study, a CUMS mouse model was established and an intrahippocampal injection of AAV-shMST1 was used to knockdown MST1 in the hippocampus. The data showed that there were memory deficits with over-expressed P-MST1 level in CUMS mice. However, MST1 knockdown can significantly prevent the damages of CUMS-induced working memory and synaptic plasticity via regulating neural oscillation patterns. It suggests that MST1 down-regulation effectively protected against stress-induced behavioral dysfunctions. Moreover, as a more convenient way, neural oscillation analysis could provide some assistance for the auxiliary diagnosis and treatment of depression.

Retraction Note: 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.

Activation of Hippo signaling pathway mediates mitochondria dysfunction and dilated cardiomyopathy in mice.

Rationale: Mitochondrial dysfunction facilitates heart failure development forming a therapeutic target, but the mechanism involved remains unclear. We studied whether the Hippo signaling pathway mediates mitochondrial abnormalities that results in onset of dilated cardiomyopathy (DCM).Methods: Mice with DCM due to overexpression of Hippo pathway kinase Mst1 were studied. DCM phenotype was evident in adult animals but contractile dysfunction was identified as an early sign of DCM at 3 weeks postnatal. Electron microscopy, multi-omics and biochemical assays were employed.Results: In 3-week and adult DCM mouse hearts, cardiomyocyte mitochondria exhibited overt structural abnormalities, smaller size and greater number. RNA sequencing revealed comprehensive suppression of nuclear-DNA (nDNA) encoded gene-sets involved in mitochondria turnover and all aspects of metabolism. Changes in cardiotranscriptome were confirmed by lower protein levels of multiple mitochondrial proteins in DCM heart of both ages. Mitochondrial DNA-encoded genes were also downregulated; due apparently to repression of nDNA-encoded transcriptional factors. Lipidomics identified remodeling in cardiolipin acyl-chains, increased acylcarnitine content but lower coenzyme Q10 level. Mitochondrial dysfunction was featured by lower ATP content and elevated levels of lactate, branched-chain amino acids and reactive oxidative species. Mechanistically, inhibitory YAP-phosphorylation was enhanced, which was associated with attenuated binding of transcription factor TEAD1. Numerous suppressed mitochondrial genes were identified as YAP-targets.Conclusion: Hippo signaling activation mediates mitochondrial damage by repressing mitochondrial genes, which causally promotes the development of DCM. The Hippo pathway therefore represents a therapeutic target against mitochondrial dysfunction in cardiomyopathy.

Exosomal miR-199a-5p promotes hepatic lipid accumulation by modulating MST1 expression and fatty acid metabolism.

Non-alcoholic fatty liver disease (NAFLD) and its complications has become an expanding health problem worldwide with limited therapeutic approaches. The current study was aiming to identify novel microRNA in the regulation of hepatic lipid metabolism in NAFLD. Systematic screening of microRNA expression by high-throughput small RNA sequencing demonstrated that microRNA 199a-5p (miR-199a-5p) was significantly upregulated in high fat diet-induced steatosis mouse model, with the most abundant expression in adipose tissue. MST1 was further identified as the target gene for miR-199a with specific recognition at the 3' untranslated region with dural luciferase reporter assay. Delivery of miR-199a-5p with exosomes into mice aggravated liver lipid accumulation in hepatocytes, accompanied by down-regulation of hepatic MST1 expression and modulation of hepatic lipogenesis and lipolysis, includingSREBP-1c, AMPK signaling cascades andthe down-stream CPT1α and FASN.Conversely, administration of exosome containing anti-miR-199a-5p resulted in attenuated steotosis in mice fed on high fat diet. Importanly, miR-199a-5p-induced abnormal cellular lipid accumulation could be markedly reversed by overexpression of MST1. miR-199a-5p might be an essentail regulator for hepatic lipid metabolism, possibly through its interction with MST1 and the subsequent signaling cascade. Thus,miR-199a-5p mayserve as an important therapeutic target in the treatment of NAFLD.

Targeting mammalian serine/threonine-protein kinase 4 through Yes-associated protein/TEA domain transcription factor-mediated epithelial-mesenchymal transition ameliorates diabetic nephropathy orchestrated renal fibrosis

RationaleTubulointerstitial fibrosis, which is closely related to functional injury of the kidney, can be observed in advanced stages of diabetic nephropathy (DN). Mammalian serine/threonine-protein kinase 4 (MST1), a core component of the Hippo pathway that is involved in cellular proliferation and differentiation, plays a crucial role in the pathogenesis of multiple metabolic diseases, kidney diseases and cancer. MethodsIn type 1 and type 2 diabetic animals, as well as in human proximal tubular epithelial cells (HK-2), activation of MST1 was analyzed by immunohistochemistry and western blotting. In db/db mice, MST1 protein was knocked down or overexpressed by shRNA, and renal function, fibrosis, and downstream signaling were then investigated. RNA silencing and overexpression were performed by using an MST1 or YAP knockdown/expression lentivirus to investigate the regulation of MST1-mediated YAP/TEAD signaling pathways in the fibrosis process in HK-2 cells. Luciferase and coimmunoprecipitation (co-IP) assays were used to identify whether YAP directly regulated TEAD activation by forming a YAP-TEAD heterodimer, which ultimately leads to tubulointerstitial fibrosis. ResultsMST1 activation was significantly decreased in type 1 and type 2 diabetic nephropathy. Notably, the downregulation of MST1 activation was also observed in HK-2 cells in a glucose- and time-dependent manner. In vivo, downregulation of MST1 was sufficient to promote renal dysfunction and fibrosis in db/m mice, whereas overexpression of MST1 ameliorated diabetic nephropathy-induced renal fibrosis. Further mechanistic study demonstrated that activated YAP induced by MST1 inhibition directly upregulated TEAD activation by binding to TEAD and forming a YAP-TEAD heterodimer, resulting in the promotion of epithelial-mesenchymal transition (EMT) and fibrosis in renal tubular epithelial. ConclusionsMST1 activation represents a potential therapeutic strategy to treat or prevent the progression of diabetic nephropathy-induced renal fibrosis.

Suppressor of ras val-2 promotes inflammation-mediated oxidative stress and cell apoptosis in cardiomyocytes through activating Mst1-mROS signaling pathway

Context: Reperfusion injury after myocardial infarction is associated with inflammation response and oxidative stress.Aim: The aim of our study is to explore the influence of suppressor of ras val-2 (SRV2) on cardiomyocyte oxidative stress and inflammation response under hypoxia-reoxygenation (HR) injury.Methods: Cell viability was determined via MTT assay. qPCR and western blots were used to analyze the alterations of SRV2 and mammalian STE20-like protein kinases 1 (Mst1). ELISA and qPCR were used to verify the alterations of antioxidants and pro-inflammatory factors.Results: SRV2 was upregulated by HR injury in cardiomyocyte. Interestingly, loss of SRV2 attenuated HR injury-mediated cardiomyocyte damage through inhibiting cardiomyocyte apoptosis. At the molecular levels, SRV2 deletion reduced inflammation and oxidative stress induced by HR injury and thus promoted cardiomyocyte survival. Besides, SRV2 deletion inactivated the Mst1-mROS signaling pathway in cardiomyocyte and thus regulated the inflammation and oxidative stress. Interestingly, overexpression of Mst1 abolished the beneficial effects exerted by SRV2 deletion on HR-mediated cardiomyocyte death.Conclusions: SRV2 upregulation, induced by reperfusion injury, contributes to cardiomyocyte death through the Mst1-mROS signaling pathway.

Impact of Taurine on the proliferation and apoptosis of human cervical carcinoma cells and its mechanism.

Background:Cervical cancer has the fourth highest incidence and mortality rate of all cancers in women worldwide; it seriously harms their physical and mental health. The aim of this study was to observe the roles and preliminary mechanism of Taurine (Tau)-induced apoptosis in cervical cancer cells.Methods:Cells from the human cervical cancer cell line SiHa were transfected with the recombinant plasmid pEGFP-N1-MST1 (mammalian sterile 20-like kinase 1); then, the cell proliferation activity was analyzed by the MTT assay, cell apoptosis by flow cytometry, and the related protein levels by Western blotting.Results:Tau inhibited the proliferation of SiHa cells and induced apoptosis in these cells (the apoptotic rate was 21.95% in the Tau 160 mmol/L group and 30% in the Tau 320 mmol/L group), upregulated the expression of the MST1 (control, 0.53; Tau 40–320 mmol/L groups, 0.84–1.45) and Bax (control, 0.45; Tau 40–320 mmol/L groups, 0.64–1.51) proteins (P < 0.01), and downregulated the expression of Bcl-2 (control, 1.28, Tau 40–320 mmol/L groups, 0.93–0.47) (P < 0.01). The overexpression of MST1 promoted the apoptosis of SiHa cells, enhanced the apoptosis-inductive effects of Tau (P < 0.01), upregulated the expression of the proapoptotic proteins p73, p53, PUMA (p53 upregulated modulator of apoptosis), and caspase-3, and promoted the phosphorylation of YAP (Yes-associated protein).Conclusions: Tau inhibited the proliferation and induced the apoptosis of cervical cancer SiHa cells. The MST1 protein plays an important role in the Tau-induced apoptosis of cervical cancer cells.

RETRACTED: Overexpression of macrophage stimulating 1 enhances the anti-tumor effects of IL-24 in esophageal cancer via inhibiting ERK-Mfn2 signaling-dependent mitophagy

Although cytokine-based therapy is a promising tool to control the progression of esophageal cancer, low therapeutic responses largely compromise treatment efficacy through unidentified mechanisms. The goal of our study was to explore the roles of macrophage stimulating 1 (Mst1) and mitophagy in enhancing IL-24-based cytokine therapy in esophageal cancer. Our data demonstrated that IL-24 application promoted cancer death by inducing mitochondrial stress, as manifested by mitochondrial ROS overproduction, mitochondrial potential dissipation, cellular ATP deprivation and mitochondrial death activation. Overexpression of Mst1 enhanced IL-24-mediated mitochondrial damage and further augmented IL-24-induced death in esophageal cancer. Molecular investigations illustrated that the IL-24-activated mitochondrial response is accompanied by activation of mitophagy, a protective mechanism to attenuate mitochondrial damage. However, Mst1 overexpression inhibited mitophagy activity, which was achieved by inactivating the ERK-Mfn2 signaling pathway. The re-activation of mitophagy abolished the cancer-killing effects of Mst1 overexpression on esophageal cancer. Altogether, our data demonstrate that IL-24-related therapeutic resistance is associated with mitophagy activation. Mst1 overexpression inhibits mitophagy activity via suppressing the ERK-Mfn2 pathway, ultimately augmenting IL-24-inducd esophageal cancer death via enhanced mitochondrial stress.

Augmented Endothelial Specific Cationic Amino Acid Transporter‐1 Expression Prevents Renal Fibrosis and Inflammation and Loss of Renal Function in Heart Failure

INTRODUCTIONIt is now well established that impaired renal function associated with heart failure (HF) increases morbidity and mortality in HF patients. There are no effective treatments to rescue renal function in HF and the precise mechanisms that drive renal injury in HF remain elusive. Transport of L‐arginine via cationic amino acid transporter‐1 (CAT‐1) influences renal nitric oxide bioavailability. We hypothesised that impaired L‐arginine transport via CAT‐1 is central to the development of renal dysfunction in HF.METHODSAdult male 18–26 week old wild‐type mice (WT), transgenic mice with dilated cardiomyopathy (DCM) and double transgenic mice with DCM and endothelial‐specific overexpression of CAT1 (HFCAT‐1) were used (n=8 per group). Transgenic mice with dilated cardiomyopathy (DCM) have cardiac specific overexpression of Mammalian sterile 20‐like kinase‐1 (Mst1) which leads to apoptosis and DCM. The double transgenic HFCAT‐1 mouse model has endothelial specific overexpression of CAT1 driven by the Tie‐2 promotor and cardiac specific overexpression of Mst1. Cardiac and renal function were assessed via echocardiography and via calculating the albumin to creatinine ratio, respectively. Fibrosis was assessed via Masson's trichrome staining. Renal inflammation was assessed via expression of pro‐ and anti‐inflammatory gene expression. Plasma nitrate and nitrite levels were assessed via ELISA. Isolated renal cells from WT mice (n=3) were incubated with CAT1 antisense (2.5 μM) or its scrambled oligonucleotide for a period of 4‐h and then CAT1, collagen III and collagen IV expression were measured by PCR.RESULTSExpression of renal CAT1 was less in DCM mice (by 21%) compared to WT mice (P=0.04) and this was restored in HFCAT1 mice. Urinary albumin/creatinine ratio was greater in DCM mice (by 72%) compared to WT (P=0.04). Urinary albumin/creatinine ratio was normalized in HFCAT1 mice. Renal mRNA expression of Il6 was less in HFCAT‐1 mice than DCM mice (P=0.03). Renal mRNA expression of Il10 was 57% less in DCM mice than in WT mice and this was restored in HFCAT‐1 mice (P&lt;0.05). Renal mRNA expression of Pai1 was greater in DCM mice (by 42%), but not HFCAT‐1 mice, compared to WT mice (P=0.01). Tubulointerstitial and glomerular fibrosis were 89% and 76% greater respectively in DCM mice than in WT mice (P&lt;0.05). Tubulointerstitial and glomerular fibrosis were normalized in HFCAT‐1 mice. CAT1 antisense reduced the expression of CAT1 mRNA in isolated renal cells by 46% and collagen III expression in these cells was 8 fold greater compared to control. Ejection fraction was 33% less in DCM mice than in WT (P&lt;0.01) and this was not restored in HFCAT1 mice (P=0.24).CONCLUSIONRestoration of endothelial specific CAT1 expression normalizes renal inflammation and fibrosis and prevents the loss of GFR in experimental HF.Support or Funding InformationNHMRC Program grant (DK) and Baker Heart and Diabetes Institute Early Career Grant (NR)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.