Integrative analysis of the molecular signature of target genes involved in the antitumor effects of cantharidin on hepatocellular carcinoma.

BACKGROUND: Cantharidin (CTD) is the active ingredient of Chinese medicine, which has been traditionally used in multiple cancers treatment, especially in hepatocellular carcinoma (HCC). However, a comprehensive analysis of the CTD-related molecular mechanism is still necessary to understand its functions in HCC treatment. This study aimed to reveal the novel molecular targets and regulatory networks of CTD in HCC. METHODS: A model of H22 tumour-bearing mice was constructed, and the function of CTD in tumour growth was evaluated. An integrated approach of CTD associated transcriptional profiling and biological systems analysis was used to identify key regulators involved in antitumour pathways. The identified differential expression patterns were supported by the results of Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyse, and by protein-protein interaction (PPI) network construction. The relationships between gene expression and tumour immunity were evaluated using Tumour Immune Estimation Resource (TIMER). Prognostic value was analyzed with Kaplan-Meier plotter. RESULTS: In the present study, the therapeutic effect of CTD on HCC was evaluated in vivo. We obtained the CTD-related transcriptional profiles, systematically and intuitively illustrated its possible pharmacological mechanisms in HCC through multiple targets and signalling pathways. These results revealed that the CTD-related differentially expressed genes were involved in autophagy, transcription factors (TFs) related transcriptional regulation, fatty acid metabolism and immune response in HCC. We found that MAPT, TOP2A, CENPF and MEFV were hub genes of CTD targets involved in autophagy regulation. Totally, 14 TFs have been confirmed to be critical for transcriptional regulation, and 33 TF targets were identified as the hub genes in transcriptional mis-regulation pathway in cancer. These TFs were associated with the immune response and immune cell infiltration. In addition, the downregulated genes were significantly enriched in metabolic regulation pathways, especially fatty acid metabolism after CTD treatment. Furthermore, the network of CTD associated miRNAs with these fatty acid metabolism-related targets was constructed in HCC. CONCLUSIONS: Taken together, our results comprehensively elucidated that CTD could act on multiple targets in HCC therapy, affecting autophagy, transcriptional regulation, the immune response and fatty acid metabolism. Our results provide a foundation for the study of the molecular mechanistic of CTD and its clinical application in the treatment of HCC.

Nogo-B mediates endothelial oxidative stress and inflammation to promote coronary atherosclerosis in pressure-overloaded mouse hearts.

AIMS: Endothelial dysfunction plays a pivotal role in atherosclerosis, but the detailed mechanism remains incomplete understood. Nogo-B is an endoplasmic reticulum (ER)-localized protein mediating ER-mitochondrial morphology. We previously showed endothelial Nogo-B as a key regulator of endothelial function in the setting of hypertension. Here, we aim to further assess the role of Nogo-B in coronary atherosclerosis in ApoE-/- mice with pressure overload. METHODS AND RESULTS: We generated double knockout (DKO) mouse models of systemically or endothelium-specifically excising Nogo-A/B gene on an ApoE-/- background. After 7 weeks of transverse aortic constriction (TAC) surgery, compared to ApoE-/- mice DKO mice were resistant to the development of coronary atherosclerotic lesions and plaque rapture. Sustained elevation of Nogo-B and adhesion molecules (VCAM-1/ICAM-1), early markers of atherosclerosis, was identified in heart tissues and endothelial cells (ECs) isolated from TAC ApoE-/- mice, changes that were significantly repressed by Nogo-B deficiency. In cultured human umbilical vein endothelial cells (HUVECs) exposure to inflammatory cytokines (TNF-α, IL-1ß), Nogo-B was upregulated and activated reactive oxide species (ROS)-p38-p65 signaling axis. Mitofusin 2 (Mfn2) is a key protein tethering ER to mitochondria in ECs, and we showed that Nogo-B expression positively correlated with Mfn2 protein level. And Nogo-B deletion in ECs or in ApoE-/- mice reduced Mfn2 protein content and increased ER-mitochondria distance, reduced ER-mitochondrial Ca2+ transport and mitochondrial ROS generation, and prevented VCAM-1/ICAM-1 upregulation and EC dysfunction, eventually restrained atherosclerotic lesions development. CONCLUSION: Our study revealed that Nogo-B is a critical modulator in promoting endothelial dysfunction and consequent pathogenesis of coronary atherosclerosis in pressure overloaded hearts of ApoE-/- mice. Nogo-B may hold the promise to be a common therapeutic target in the setting of hypertension.

Cantharidin suppresses hepatocellular carcinoma development by regulating EZH2/H3K27me3-dependent cell cycle progression and antitumour immune response.

BACKGROUND: Cantharidin (CTD) is a major ingredient of cantharis (Mylabris phalerata Pallas) and has been used extensively in traditional Chinese medicines. It has been shown to exhibit anticancer activity in multiple types of cancer, especially hepatocellular carcinoma (HCC). However, there is no systematic study on the relationships among the regulatory networks of its targets in HCC therapy. We focused on histone epigenetic regulation and the influence of CTD on the immune response in HCC. METHODS: We performed a comprehensive analysis of novel CTD targets in HCC based on network pharmacology and RNA-seq approaches. The mRNA levels of target genes were analyzed by qRT-PCR, and the corresponding protein levels were confirmed using enzyme-linked immunosorbent assay (ELISA) and immunohistochemical staining (IHC). ChIP-seq data were visualized by IGV software. The associations of gene transcript levels with the cancer immune score and infiltration level were investigated using TIMER. In vivo, the H22 mouse model of hepatocellular carcinoma was established by treatment with CTD and 5-Fu. The immune cell proportions in the blood were elevated in model mice, as shown by flow cytometry. RESULTS: We identified 58 targets of CTD, which were involved in various pathways in cancer, including apoptosis, the cell cycle, EMT and immune pathways. Moreover, we found that 100 EMT-related genes were differentially expressed after CTD treatment in HCC cells. Interestingly, our results confirmed that the EZH2/H3K27me3 -related cell cycle pathway is a therapeutic target of CTD in antitumour. In addition, we evaluated the influence of CTD on the immune response. Our data showed that the significantly enriched gene sets were positively correlated with the chemokine biosynthetic and chemokine metabolic modules. The proportions of CD4+/CD8 + T cells and B cells were increased, but the proportion of Tregs was decreased after treatment with CTD in vivo. Moreover, we found that the expression of the inflammatory factor and immune checkpoint genes PD-1/PD-L1 was significantly reduced in the mouse model. CONCLUSION: We performed a novel integrated analysis of the potential role of CTD in HCC treatment. Our results provide innovative insight into the mechanism by which cantharidin exerts antitumour effects by regulating target genes expression to mediate apoptosis, EMT, cell cycle progression and the immune response in HCC. Based on the effect of CTD on the immune response, it can be used as a potential effective drug to activate antitumour immunity for the treatment of liver cancer.

WHSC1 is involved in DNA damage, cellular senescence and immune response in hepatocellular carcinoma progression.

Wolf-Hirschhorn syndrome candidate 1 (WHSC1) is a transcriptional regulatory protein that encodes a histone methyltransferase to control H3K36me2 modification. WHSC1 was upregulated and associated with poor prognosis in HCC. The elevated WHSC1 likely due to the alterations of DNA methylation or RNA modification. WHSC1 perhaps form a chromatin cross talk with H3K27me3 and DNA methylation to regulate transcription factors expression in HCC. Functional analysis indicated that WHSC1 was involved in DNA damage repair, cell cycle, cellular senescence and immune regulations. Furthermore, WHSC1 was associated with the infiltrating levels of B cell, CD4+, Tregs and macrophage cells. Therefore, our findings suggested that WHSC1 might function as a promotor regulator to affect the development and progression of HCC. Thus, WHSC1 could be a potential biomarker in predicting the prognosis and therapeutic target for patients with HCC.

AGEs-RAGE-KCa3.1 pathway mediates palmitic acid-induced migration of PBMCs from patients with type 2 diabetes.

Type 2 diabetes mellitus (T2DM) is characterized by chronic low-grade systemic inflammation. Tissue infiltration by monocyte migration contributes to the pathogenesis of vascular complications in T2DM. We studied the role of intermediate-conductance Ca2+-activated K+ (KCa3.1) channels in the palmitic acid (PA)-induced migration of peripheral blood mononuclear cells (PBMCs) from T2DM patients and the influence of advanced glycation endproducts (AGEs). A total of 49 T2DM patients and 33 healthy subjects was recruited into this study. Using flow cytometry and Western blotting analysis as well as cell migration assay, we found that there was a significant decrease in frequency of T lymphocytes and monocytes in CD45+ leukocyte population. PA at 100 µM stimulated migration of PBMCs from T2DM individuals, which was inhibited by the specific KCa3.1 channel blocker TRAM-34 (1 µM). The PBMC migration was positively correlated with glycosylated hemoglobin A1 chain (HbA1c) level of T2DM patients, an indicator of AGEs, and PBMCs with higher level of HbA1c showed upregulated expression of toll-like receptor (TLR) 2/4 and KCa3.1 channels. In THP-1 cells, AGEs at 200 µg/ml increased protein expression of TLR 2/4 and KCa3.1 channels, and were synergistically involved in PA-induced migration through receptors of AGEs (RAGE)-mediated KCa3.1 upregulation. In conclusion, in PBMCs of T2DM patients, AGEs promotes PA-induced migration via upregulation of TLR2/4 and KCa3.1 channels.

Mitochondrial damage in a Takotsubo syndrome-like mouse model mediated by activation of ß-adrenoceptor-Hippo signaling pathway.

Takotsubo syndrome (TTS) is characterized by short-term contractile dysfunction with its mechanism undefined. We showed that activation of cardiac Hippo pathway mediates mitochondrial dysfunction and that stimulation of ß-adrenoceptors (ßAR) activates Hippo pathway. Here, we investigated the role of ßAR-Hippo signaling in mediating mitochondrial dysfunction in isoproterenol (Iso)-induced TTS-like mouse model. Elderly postmenopausal female mice were administered with Iso (1.25 mg/kg/h for 23 h). Cardiac function was determined by serially echocardiography. At days 1 and 7 post-Iso exposure, mitochondrial ultrastructure and function were examined by electron microscopy and various assays. Alterations in cardiac Hippo pathway and effects of genetic inactivation of Hippo kinase (Mst1) on mitochondrial damage and dysfunction in the acute phase of TTS were investigated. Isoproterenol exposure induced acute increase in biomarkers of cardiac damage and ventricular contractile dysfunction and dilation. At day 1 post-Iso, we observed extensive abnormalities in mitochondrial ultrastructure, downregulation of mitochondrial marker proteins, and mitochondrial dysfunction evidenced by lower ATP content, increased lipid droplets, higher contents of lactate, and augmented reactive oxygen species (ROS). All changes were reversed by day 7. ßAR stimulation led to activation of cardiac Hippo pathway with enhanced expression of Hippo kinase Mst1 and inhibitory YAP phosphorylation, as well as reduced nuclear YAP-TEAD1 interaction. In mice with cardiac expression of inactive mutant Mst1 gene, acute mitochondrial damage and dysfunction were mitigated. Stimulation of cardiac ßAR activates Hippo pathway that mediates mitochondrial dysfunction with energy insufficiency and enhanced ROS, promoting acute but short-term ventricular dysfunction.NEW & NOTEWORTHY Takotsubo syndrome (TTS) is featured by activation of sympatho-ß-adrenoceptor (ßAR) system leading to acute loss of ventricular contractile performance. However, the molecular mechanism remains undefined. We demonstrated, in an isoproterenol-induced murine TTS-like model, extensive mitochondrial damage, metabolic dysfunction, and downregulated mitochondrial marker proteins, changes temporarily associated with cardiac dysfunction. Mechanistically, stimulation of ßAR activated Hippo signaling pathway and genetic inactivation of Mst1 kinase ameliorated mitochondrial damage and metabolic dysfunction at the acute phase of TTS.

Endothelial KCa3.1 and KCa2.3 Mediate S1P (Sphingosine-1-Phosphate)-Dependent Vasodilation and Blood Pressure Homeostasis.

BACKGROUND: S1P (sphingosine-1-phosphate) has been reported to possess vasodilatory properties, but the underlying pathways are largely unknown. METHODS: Isolated mouse mesenteric artery and endothelial cell models were used to determine S1P-induced vasodilation, intracellular calcium, membrane potentials, and calcium-activated potassium channels (KCa2.3 and KCa3.1 [endothelial small- and intermediate-conductance calcium-activated potassium channels]). Effect of deletion of endothelial S1PR1 (type 1 S1P receptor) on vasodilation and blood pressure was evaluated. RESULTS: Mesenteric arteries subjected to acute S1P stimulation displayed a dose-dependent vasodilation response, which was attenuated by blocking endothelial KCa2.3 or KCa3.1 channels. In cultured human umbilical vein endothelial cells, S1P stimulated immediate membrane potential hyperpolarization following activation of KCa2.3/KCa3.1 with elevated cytosolic Ca2+. Further, chronic S1P stimulation enhanced expression of KCa2.3 and KCa3.1 in human umbilical vein endothelial cells in dose- and time-dependent manners, which was abolished by disrupting either S1PR1-Ca2+ signaling or downstream Ca2+-activated calcineurin/NFAT (nuclear factor of activated T-cells) signaling. By combination of bioinformatics-based binding site prediction and chromatin immunoprecipitation assay, we revealed in human umbilical vein endothelial cells that chronic activation of S1P/S1PR1 promoted NFATc2 nuclear translocation and binding to promoter regions of KCa2.3 and KCa3.1 genes thus to upregulate transcription of these channels. Deletion of endothelial S1PR1 reduced expression of KCa2.3 and KCa3.1 in mesenteric arteries and exacerbated hypertension in mice with angiotensin II infusion. CONCLUSIONS: This study provides evidence for the mechanistic role of KCa2.3/KCa3.1-activated endothelium-dependent hyperpolarization in vasodilation and blood pressure homeostasis in response to S1P. This mechanistic demonstration would facilitate the development of new therapies for cardiovascular diseases associated with hypertension.

Hippo pathway activation mediates chemotherapy-induced anti-cancer effect and cardiomyopathy through causing mitochondrial damage and dysfunction.

Rationale: Chemotherapy is a common clinical strategy for cancer treatment. However, the accompanied cardiomyopathy renders cancer patients under risk of another life-threatening condition. Whereas Hippo pathway is known to play key roles in both cancerogenesis and heart disease, it remains unclear whether Hippo pathway activation mediates chemotherapy-induced cardiomyopathy. Methods and Results: In human breast cancer cells, doxorubicin (DOX) significantly induced upregulation of Hippo kinase Mst1, inhibitory phosphorylation of YAP, mitochondrial damage, reduced cell viability and increased apoptosis. Hippo pathway inactivation by Mst1-siRNA transfection effectively improved cell survival and mitigated mitochondrial damage and cell apoptosis. Another anti-cancer drug YAP inhibitor verteporfin also induced lower cancer cell viability, apoptosis and mitochondrial injury. Chronic treatment with DOX in vivo (4 mg/kg/week for 6 weeks) caused mitochondrial damage and dysfunction, oxidative stress and cardiac fibrosis, while acute DOX treatment (16 mg/kg single bolus) also induced myocardial oxidative stress and mitochondrial abnormalities. Chronic treatment with verteporfin (2 months) resulted in cardiomyopathy phenotypes comparable to that by chronic DOX regimen. In transgenic mice with cardiac overexpression of kinase-dead mutant Mst1 gene, these adverse cardiac effects of DOX were significantly attenuated relative to wild-type littermates. Conclusions: Anti-cancer action of both DOX and verteporfin is associated with Hippo pathway activation. Such action on cardiac Hippo pathway mediates mitochondrial damage and cardiomyopathy.

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

ABSTRACT: 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 ß 2 -adrenoceptor (ß 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.

YAP-galectin-3 signaling mediates endothelial dysfunction in angiotensin II-induced hypertension in mice.

BACKGROUND: Vascular endothelial dysfunction is regarded as an early event of hypertension. Galectin-3 (Gal-3) is known to participate in various pathological processes. Whilst previous studies showed that inhibition of Gal-3 effectively ameliorates angiotensin II (Ang II)-induced atherosclerosis or hypertension, it remains unclear whether Ang II regulates Gal-3 expression and actions in vascular endothelium. METHODS: Using techniques of molecular biology and myograph, we investigated Ang II-mediated changes in Gal-3 expression and activity in thoracic aortas and mesenteric arteries from wild-type and Gal-3 gene deleted (Gal-3-/-) mice and cultured endothelial cells. RESULTS: The serum level of Gal-3 was significantly higher in hypertensive patients or in mice with chronic Ang II-infusion. Ang II infusion to wild-type mice enhanced Gal-3 expression in the aortic and mesenteric arteries, elevated systolic blood pressure and impaired endothelium-dependent relaxation of the thoracic aortas and mesenteric arteries, changes that were abolished in Gal-3-/- mice. In human umbilical vein endothelial cells, Ang II significantly upregulated Gal-3 expression by promoting nuclear localization of Yes-associated protein (YAP) and its interaction with transcription factor Tead1 with enhanced YAP/Tead1 binding to Gal-3 gene promoter region. Furthermore, Gal-3 deletion augmented the bioavailability of nitric oxide, suppressed oxidative stress, and alleviated inflammation in the thoracic aorta of Ang II-infused mice or endothelial cells exposed to Ang II. CONCLUSIONS: Our results demonstrate for the first time that Ang II upregulates Gal-3 expression via increment in YAP nuclear localization in vascular endothelium, and that Gal-3 mediates endothelial dysfunction contributing to the development of hypertension.

SPATS2 is correlated with cell cycle progression and immune cells infiltration in hepatocellular carcinoma.

The spermatogenesis associated serine rich 2 (SPATS2) is a member of RNA-binding protein in which the abnormal expression is linked with carcinogenesis in serval types of cancer. However, there is no systematic study on the differential expression, prognostic significance, epigenetic regulation, immune infiltration of SPATS2 in hepatocellular carcinoma (HCC). In the present study, we investigated the expression, prognosis, epigenetic regulation, and immune cell infiltration of SPATS2 in HCC. We found that the elevated expression of SPATS2 was unfavorably associated with the clinical pathological stage and prognosis. Functional enrichment analysis revealed that SPATS2 is associated with cell cycle, apoptosis and cancer cell metastasis processes in HCC. Our results confirmed that knockdown of SPATS2 will affect cell cycle, apoptosis and invasion of HCC cell lines. Moreover, the expression of SPATS2 is upregulated by epigenetic regulation, including DNA methylation, m6A and histone modification in HCC. In addition, SPATS2 expression was positively correlated with immune cell infiltration or expression of immune related gene markers in HCC. Taken together, our data demonstrated that SPATS2 is associated with progression and immune infiltration, and could serve as a prognostic biomarker for HCC. In conclusion, these results highlight the potential of SPATS2 to be used as a therapeutic target for HCC.

Transcriptomic Analysis of Dysregulated Genes of the nDNA-mtDNA Axis in a Mouse Model of Dilated Cardiomyopathy.

Background: Mitochondrial dysfunction is implicated in the development of cardiomyopathy and heart failure. Transcription of mitochondrial DNA (mtDNA) encoded genes and subsequent protein synthesis are tightly regulated by nuclear DNA (nDNA) encoded proteins forming the nDNA-mtDNA axis. The scale of abnormalities in this axis in dilated cardiomyopathy (DCM) is unclear. We previously demonstrated, in a mouse DCM model with cardiac Mst1 overexpression, extensive downregulation of mitochondrial genes and mitochondrial dysfunction. Using the pre-acquired transcriptome sequencing database, we studied expression of gene sets of the nDNA-mtDNA axis. Methods: Using RNA-sequencing data from DCM hearts of mice at early and severe disease stages, transcriptome was performed for dysregulated nDNA-encoded gene sets that govern mtDNA transcription and in situ protein synthesis. To validate gene data, expression of a panel of proteins was determined by immunoblotting. Results: Relative to littermate controls, DCM hearts showed significant downregulation of all mtDNA encoded mRNAs, as well as mtDNA transcriptional activators. Downregulation was also evident for gene sets of mt-rRNA processing, aminoacyl-tRNA synthases, and mitoribosome subunits for in situ protein synthesis. Multiple downregulated genes belong to mitochondrial protein-importing machinery indicating compromised importing of proteins for mtDNA transcription and translation. Diverse changes were genes of mtRNA-binding proteins that govern maturation and stability of mtDNA-derived RNAs. Expression of mtDNA replicome genes was largely unchanged. These changes were similarly observed in mouse hearts at early and severe stages of DCM. Conclusion: Transcriptome revealed in our DCM model dysregulation of multiple gene sets of the nDNA-mtDNA axis, that is, expected to interfere with mtDNA transcription and in situ protein synthesis. Dysfunction of the nDNA-mtDNA axis might contribute to mitochondrial dysfunction and ultimately development of DCM.

Pathogenetic Link of Cardiac Rupture and Left Ventricular Thrombus Following Acute Myocardial Infarction: A Joint Preclinical and Clinical Study.

Background: Cardiac rupture (CR) and left ventricular thrombus (LVT) remain important complications of acute myocardial infarction (MI), and they are currently regarded as independent events. We explored the pathogenetic link between CR and LVT by investigating a murine model of MI with a high frequency of CR and in patients with acute MI. Methods: MI was induced in mice, the onset of CR was monitored, and the hearts of mice with or without fatal CR were histologically examined. Between 2015 and 2022, from patients admitted due to acute MI, the data of patients with CR or LVT were retrospectively collected and compared to uncomplicated patients (control). Results: A total of 75% of mice (n = 65) with MI developed CR 2-4 days after MI. A histological examination of CR hearts revealed the existence of platelet-rich intramural thrombi in the rupture tunnel, which was connected at the endocardial site to platelet-fibrin thrombi within an LVT. In CR or non-CR mouse hearts, LV blood clots often contained a portion of platelet-fibrin thrombi that adhered to the infarct wall. In non-CR hearts, sites of incomplete CR or erosion of the infarct wall were typically coated with platelet thrombi and dense inflammatory cells. Of 8,936 patients with acute MI, CR and LVT occurred in 102 (1.14%) and 130 (1.45%) patients, respectively, with three cases having both complications. CR accounted for 32.8% of in-hospital deaths. The majority of CR (95%) or LVT (63%, early LVT) occurred within 7 days. In comparison to the control or LVT-late groups, patients with CR or early LVT reported increased levels of cellular and biochemical markers for inflammation or cardiac injury. Conclusion: CR and LVT after MI are potentially linked in their pathogenesis. LVT occurring early after MI may be triggered by a thrombo-inflammatory response following wall rupture or endocardial erosion.

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.

Excess sarcoplasmic reticulum-mitochondria calcium transport induced by Sphingosine-1-phosphate contributes to cardiomyocyte hypertrophy.

Sphingosine-1-phosphate (S1P) has been shown to possess pro-hypertrophic properties in the heart, but the detailed molecular mechanism that underlies the pathological process is rarely explored. In the present study, we aim to explore the role of S1P-mediated intracellular Ca2+ signaling, with a focus on sarcoplasmic reticulum (SR)-mitochondria communication, in cardiomyocyte hypertrophy. Cultured neonatal rat ventricular myocytes (NRVMs) displayed significantly hypertrophic growth after treatment with 1 µmol/L S1P for 48 h, as indicated by the cell surface area or mRNA expressions of hypertrophic marker genes (ANP, BNP and ß-MHC). Importantly, mitochondrial Ca2+ and reactive oxygen species (ROS) levels were dramatically elevated upon S1P stimulation, and pharmacological blockage of which abolished NRVM hypertrophy. 0.5 Hz electrical pacing induced similar cytosolic Ca2+ kinetics to S1P stimulation, but unaffected the peak of mitochondrial [Ca2+]. With interference of the expression of type 2 inositol 1,4,5-trisphosphate receptors (IP3R2), which are unemployed in electrical paced Ca2+ activity but may be activated by S1P, alteration in mitochondrial Ca2+ as well as the hypertrophic effect in NRVMs under S1P stimulation were attenuated. The hypertrophic effect of S1P can also be abolished by pharmacological block of S1PR1 or Gi signaling. Collectively, our study highlights the mechanistic role of IP3R2-mediated excess SR-mitochondria Ca2+ transport in S1P-induced cardiomyocyte hypertrophy.

Stretch-induced sarcoplasmic reticulum calcium leak is causatively associated with atrial fibrillation in pressure-overloaded hearts.

AIMS: Despite numerous reports documenting an important role of hypertension in the development of atrial fibrillation (AF), the detailed mechanism underlying the pathological process remains incompletely understood. Here, we aim to test the hypothesis that diastolic sarcoplasmic reticulum (SR) Ca2+ leak in atrial myocytes, induced by mechanical stretch due to elevated pressure in the left atrium (LA), plays an essential role in the AF development in pressure-overloaded hearts. METHODS AND RESULTS: Isolated mouse atrial myocytes subjected to acute axial stretch displayed an immediate elevation of SR Ca2+ leak. Using a mouse model of transverse aortic constriction (TAC), the relation between stretch, SR Ca2+ leak, and AF susceptibility was further tested. At 36 h post-TAC, SR Ca2+ leak in cardiomyocytes from the LA (with haemodynamic stress), but not right atrium (without haemodynamic stress), significantly increased, which was further elevated at 4 weeks post-TAC. Accordingly, AF susceptibility to atrial burst pacing in the 4-week TAC mice were also significantly increased, which was unaffected by inhibition of atrial fibrosis or inflammation via deletion of galectin-3. Western blotting revealed that type 2 ryanodine receptor (RyR2) in left atrial myocytes of TAC mice was oxidized due to activation and up-regulation of Nox2 and Nox4. Direct rescue of dysfunctional RyR2 with dantrolene or rycal S107 reduced diastolic SR Ca2+ leak in left atrial myocytes and prevented atrial burst pacing stimulated AF. CONCLUSION: Our study demonstrated for the first time the increased SR Ca2+ leak mediated by enhanced oxidative stress in left atrial myocytes that is causatively associated with higher AF susceptibility in pressure-overloaded hearts.

AMPK upregulates KCa2.3 channels and ameliorates endothelial dysfunction in diet-induced obese mice.

The opening of endothelial small-conductance calcium-activated potassium channels (KCa2.3) is essential for endothelium-dependent hyperpolarization (EDH), which predominantly occurs in small resistance arteries. Adenosine monophosphate-activated protein kinase (AMPK), an important metabolic regulator, has been implicated in regulating endothelial nitric oxide synthase activity. However, it was unclear whether AMPK regulated endothelial KCa2.3-mediated EDH-type vasodilation. Using bioinformatics analysis and myograph system, we investigated the regulation by AMPK of KCa2.3 in human umbilical vein endothelial cells (HUVECs) or mouse second-order mesenteric resistance arteries. In HUVECs, AMPK activation either by activators (AICAR, A769662 and MK-8722) or expression of the constitutively active form of AMPK significantly upregulated KCa2.3 expression. Such effects were abolished by AMPK inhibitor (compound C) or AMPK α1-/α2-siRNA, extracellular-signal-regulated-kinase 5 (ERK5) inhibitor (ERK5-IN-1), and specific siRNA to myocyte-enhancer factor 2 (MEF2) or krüppel-like factor 2/4 (KLF2/4). KCa2.3 expression was significantly reduced in mesenteric resistance arteries in AMPKα2 knockout mice when compared with littermate control mice. Furthermore, in high-fat diet fed mice, 2-week treatment with AICAR restored endothelial KCa2.3 expression in mesenteric resistance arteries with improved endothelial dysfunction. Our results demonstrate that activation of AMPK upregulates KCa2.3 channel expression through the ERK5-MEF2-KLF2/4 signaling pathway in vascular endothelium, which contributes to benefits through KCa2.3-mediated EDH-type vasodilation in mesenteric resistance arteries.

Cardiac ß-adrenergic receptor activation mediates distinct and cell type-dependent changes in the expression and distribution of connexin 43.

Activation of the sympatho-ß-adrenergic receptors (ß-ARs) system is a hallmark of heart failure, leading to fibrosis and arrhythmias. Connexin 43 (Cx43) is the most abundant gap junctional protein in the myocardium. Current knowledge is limited regarding Cx43 remodelling in diverse cell types in the diseased myocardium and the underlying mechanism. We studied cell type-dependent changes in Cx43 remodelling due to ß-AR overactivation and molecular mechanisms involved. Mouse models of isoproterenol stimulation or transgenic cardiomyocyte overexpression of ß2 -AR were used, which exhibited cardiac fibrosis and up-regulated total Cx43 abundance. In both models, whereas Cx43 expression in cardiomyocytes was reduced and more laterally distributed, fibroblasts exhibited elevated Cx43 expression and enhanced gap junction communication. Mechanistically, activation of ß2 -AR in fibroblasts in vitro elevated Cx43 expression, which was abolished by the ß2 -antagonist ICI-118551 or protein kinase A inhibitor H-89, but simulated by the adenylyl cyclase activator forskolin. Our in vitro and in vivo data showed that ß-AR activation-induced production of IL-18 sequentially stimulated Cx43 expression in fibroblasts in a paracrine fashion. In summary, our findings demonstrate a pivotal role of ß-AR in mediating distinct and cell type-dependent changes in the expression and distribution of Cx43, leading to pathological gap junction remodelling in the myocardium.

Gal-3 (Galectin-3) and KCa3.1 Mediate Heterogeneous Cell Coupling and Myocardial Fibrogenesis Driven by ßAR (ß-Adrenoceptor) Activation.

Heart failure is associated with sympatho-ßAR (ß-adrenoceptor) activation and cardiac fibrosis. Gal-3 (galectin-3) and KCa3.1 channels that are upregulated in diverse cells of diseased heart are implicated in mediating myocardial inflammation and fibrosis. It remains unclear whether Gal-3 interacts with KCa3.1 leading to cardiac fibrosis in the setting of ßAR activation. We tested the effect of KCa3.1 blocker TRAM-34 on cardiac fibrosis and inflammation in cardiac-restricted ß2-TG (ß2AR overexpressed transgenic) mice and determined KCa3.1 expression in ß2-TG×Gal-3-/- mouse hearts. Mechanisms of KCa3.1 in mediating Gal-3 induced fibroblast activation were studied ex vivo. Expression of Gal-3 and KCa3.1 was elevated in ß2-TG hearts. Gal-3 gene deletion in ß2-TG mice decreased KCa3.1 expression in inflammatory cells but not in fibroblasts. Treatment of ß2-TG mice with TRAM-34 for 1 or 2 months significantly ameliorated cardiac inflammation and fibrosis and reduced Gal-3 level. In cultured fibroblasts, Gal-3 upregulated KCa3.1 expression and channel currents with enhanced membrane potential and Ca2+ entry through TRPV4 (transient receptor potential V4) and TRPC6 (transient receptor potential C6) channels leading to fibroblast activation. In conclusion, ßAR stimulation promotes Gal-3 production that upregulates KCa3.1 channels in noncardiomyocyte cells and activates KCa3.1 channels in fibroblasts leading to hyperpolarization of membrane potential and Ca2+ entry via TRP channels. Gal-3-KCa3.1 signaling mobilizes diverse cells facilitating regional inflammation and fibroblast activation and hence myocardial fibrosis.

KCa3.1 channel mediates inflammatory signaling of pancreatic ß cells and progression of type 2 diabetes mellitus.

Chronic islet inflammation is associated with development of type 2 diabetes mellitus (T2DM). Intermediate-conductance calcium-activated K+ (KCa3.1) channel plays an important role in inflammatory diseases. However, the role and regulation of KCa3.1 in pancreatic ß cells in progression of T2DM remain unclarified. In the present study, we evaluated the effect of the specific KCa3.1 channel blocker 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34) on diabetic phenotype in the db/db model. In diabetic mice, blockade of KCa3.1 significantly improved glucose tolerance, enhanced secretion of postprandial insulin level, and reduced loss of ß-cell mass through attenuating the expression and secretion of inflammatory mediators. Furthermore, in cultured pancreatic ß cells, exposure to high levels of glucose or palmitic acid significantly increased expression and current density of the KCa3.1 channel as well as secretion of proinflammatory chemokines, and the effects were similarly reversed by preincubation with TRAM-34 or a NF-κB inhibitor pyrrolidinedithiocarbamate. Additionally, expression of KCa3.1 in pancreas islet cells was up-regulated by activation of NF-κB with IL-1ß stimulation. In summary, up-regulated KCa3.1 due to activation of NF-κB pathway leads to pancreatic inflammation via expression and secretion of chemokines and cytokines by pancreatic ß cells, thereby facilitating progression of T2DM.-Pang, Z.-D., Wang, Y., Wang, X.-J., She, G., Ma, X.-Z., Song, Z., Zhao, L.-M., Wang, H.-F., Lai, B.-C., Gou, W., Du, X.-J., Deng, X.-L. KCa3.1 channel mediates inflammatory signaling of pancreatic ß cells and progression of type 2 diabetes mellitus.