Cardiac mesenchymal cells from diabetic mice are ineffective for cell therapy-mediated myocardial repair

Stem cell-based therapy in cardiac repair after myocardial infarction: Promise, challenges, and future directions

Stem cells represent an attractive resource for cardiac regeneration. However, the survival and function of transplanted stem cells is poor and remains a major challenge for the development of effective therapies. As two main cell types currently under investigation in heart repair, mesenchymal stromal cells (MSCs) indirectly support endogenous regenerative capacities after transplantation, while induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) functionally integrate into the damaged myocardium and directly contribute to the restoration of its pump function. These two cell types are exposed to a common microenvironment with many stressors in ischemic heart tissue. This review summarizes the research progress on the mechanisms and challenges of MSCs and iPSC-CMs in post-MI heart repair, introduces several randomized clinical trials with 3D-mapping-guided cell therapy, and outlines recent findings related to the factors that affect the survival and function of stem cells. We also discuss the future directions for optimization such as biomaterial utilization, cell combinations, and intravenous injection of engineered nucleus-free MSCs.

PU.1 inhibition does not attenuate cardiac function deterioration or fibrosis in a murine model of myocardial infarction

Activated cardiac fibroblasts are involved in both reparative wound healing and maladaptive cardiac fibrosis after myocardial infarction (MI). Recent evidence suggests that PU.1 inhibition can enable reprogramming of profibrotic fibroblasts to quiescent fibroblasts, leading to attenuation of pathologic fibrosis in several fibrosis models. The role of PU.1 in acute MI has not been tested. We designed a randomized, blinded study to evaluate whether DB1976, a PU.1 inhibitor, attenuates cardiac function deterioration and fibrosis in a murine model of MI. A total of 44 Ai9 periostin-Cre transgenic mice were subjected to 60 min of coronary occlusion followed by reperfusion. At 7 days after MI, 37 mice were randomly assigned to control (vehicle) or DB1976 treatment and followed for 2 weeks. Left ventricular ejection fraction (EF), assessed by echocardiography, did not differ between the two groups before or after treatment (final EF, 33.3 ± 1.0% in control group and 31.2 ± 1.3% in DB1976 group). Subgroup analysis of female and male mice showed the same results. There were no differences in cardiac scar (trichrome stain) and fibrosis (interstitial/perivascular collagen; picrosirius stain) between groups. Results from the per-protocol dataset (including mice with pre-treatment EF < 35% only) were consistent with the full dataset. In conclusion, this randomized, blinded study demonstrates that DB1976, a PU.1 inhibitor, does not attenuate cardiac functional deterioration or cardiac fibrosis in a mouse model of MI caused by coronary occlusion/reperfusion.

miR-133a-A Potential Target for Improving Cardiac Mitochondrial Health and Regeneration After Injury

ABSTRACT

The various roles of muscle secretory factors and myokines have been well studied, but in recent decades, the role of myocyte-specific microRNAs (myomiRs) has gained momentum. These myomiRs are known to play regulatory roles in muscle health in general, both skeletal muscle and cardiac muscle. In this review, we have focused on the significance of a myomiR termed miR-133a in cardiovascular health. The available literature supports the claim that miR-133a could be helpful in the healing process of muscle tissue after injury. The protective function could be due to its regulatory effect on muscle or stem cell mitochondrial function. In this review, we have shed light on the protective mechanisms offered by miR-133a. Most of the beneficial effects are due to the presence of miR-133a in circulation or tissue-specific expression. We have also reviewed the potential mechanisms by which miR-133a could interact with cell surface receptors and also transcriptional mechanisms by which they offer cardioprotection and regeneration. Understanding these mechanisms will help in finding an ideal strategy to repair cardiac tissue after injury.

Progressive stages of dysmetabolism are associated with impaired biological features of human cardiac stromal cells mediated by the oxidative state and autophagy

Cardiac stromal cells (CSCs) are the main players in fibrosis. Dysmetabolic conditions (metabolic syndrome—MetS, and type 2 diabetes mellitus—DM2) are strong pathogenetic contributors to cardiac fibrosis. Moreover, modulation of the oxidative state (OxSt) and autophagy is a fundamental function affecting the fibrotic commitment of CSCs, that are adversely modulated in MetS/DM2. We aimed to characterize CSCs from dysmetabolic patients, and to obtain a beneficial phenotypic setback from such fibrotic commitment by modulation of OxSt and autophagy. CSCs were isolated from 38 patients, stratified as MetS, DM2, or controls. Pharmacological modulation of OxSt and autophagy was obtained by treatment with trehalose and NOX4/NOX5 inhibitors (TREiNOX). Flow‐cytometry and real‐time quantitative polymerase chain reaction (RT‐qPCR) analyses showed significantly increased expression of myofibroblasts markers in MetS‐CSCs at baseline (GATA4, ACTA2, THY1/CD90) and after starvation (COL1A1, COL3A1). MetS‐ and DM2‐CSCs displayed a paracrine profile distinct from control cells, as evidenced by screening of 30 secreted cytokines, with a significant reduction in vascular endothelial growth factor (VEGF) and endoglin confirmed by enzyme‐linked immunoassay (ELISA). DM2‐CSCs showed significantly reduced support for endothelial cells in angiogenic assays, and significantly increased H₂O₂ release and NOX4/5 expression levels. Autophagy impairment after starvation (reduced ATG7 and LC3‐II proteins) was also detectable in DM2‐CSCs. TREiNOX treatment significantly reduced ACTA2, COL1A1, COL3A1, and NOX4 expression in both DM2‐ and MetS‐CSCs, as well as GATA4 and THY1/CD90 in DM2, all versus control cells. Moreover, TREiNOX significantly increased VEGF release by DM2‐CSCs, and VEGF and endoglin release by both MetS‐ and DM2‐CSCs, also recovering the angiogenic support to endothelial cells by DM2‐CSCs. In conclusion, DM2 and MetS worsen microenvironmental conditioning by CSCs. Appropriate modulation of autophagy and OxSt in human CSCs appears to restore these features, mostly in DM2‐CSCs, suggesting a novel strategy against cardiac fibrosis in dysmetabolic patients. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Transient Cell Cycle Induction in Cardiomyocytes to Treat Subacute Ischemic Heart Failure

Background: The regenerative capacity of the heart after myocardial infarction (MI) is limited. Our previous study showed that ectopic introduction of Cdk1/CyclinB1 and Cdk4/CyclinD1 complexes (4F) promotes cardiomyocyte proliferation in 15-20% of infected cardiomyocytes in vitro and in vivo and improves cardiac function after MI in mice.

Methods: Here, using temporal single-cell RNAseq we aimed to identify the necessary reprogramming stages during the forced cardiomyocyte proliferation with 4F on a single cell basis. Also, using rat and pig models of ischemic heart failure, we aimed to start the first preclinical testing to introduce 4F gene therapy as a candidate for the treatment of ischemia-induced heart failure.

Results: Temporal bulk and single-cell RNAseq and further biochemical validations of mature hiPS-CMs treated with either LacZ or 4F adenoviruses revealed full cell cycle reprogramming in 15% of the cardiomyocyte population at 48 h post-infection with 4F, which was mainly associated with sarcomere disassembly and metabolic reprogramming (n=3/timepoint/group). Transient overexpression of 4F, specifically in cardiomyocytes, was achieved using a polycistronic non-integrating lentivirus (NIL) encoding the 4F; each is driven by a TNNT2 promoter (TNNT2-4Fpolycistronic-NIL). TNNT2-4Fpolycistronic-NIL or control virus was injected intramyocardially one week after MI in rats (n=10/group) or pigs (n=6-7/group). Four weeks post-injection, TNNT2-4Fpolycistronic-NIL treated animals showed significant improvement in left ventricular ejection fraction and scar size compared with the control virus treated animals. At four months after treatment, rats that received TNNT2-4Fpolycistronic-NIL still showed a sustained improvement in cardiac function and no obvious development of cardiac arrhythmias or systemic tumorigenesis (n=10/group).

Conclusions: This study provides mechanistic insights into the process of forced cardiomyocyte proliferation and advances the clinical feasibility of this approach by minimizing the oncogenic potential of the cell cycle factors thanks to the use of a novel transient and cardiomyocyte-specific viral construct.

Single dose of synthetic microRNA-199a or microRNA-149 mimic does not improve cardiac function in a murine model of myocardial infarction

Intramyocardial injection of synthetic microRNAs (miRs) has recently been reported to be beneficial after myocardial infarction (MI). We conducted a randomized blinded study to evaluate the efficacy and reproducibility of this strategy in a mouse model of reperfused MI using rigorous methodology. Mice undergoing a 60-min coronary occlusion followed by reperfusion were randomly assigned to control miR, hsa-miR-199a-3p, hsa-miR-149-3p, or hsa-miR-149-5p mimic treatment. Intramyocardial injections of miRs were performed in the border zone right after reperfusion. At 8 weeks after MI, there were no significant differences in ejection fraction (EF) among groups (EF = 27.1 ± 0.4% in control group [n = 6] and 25.9 ± 0.5%, 26.0 ± 0.8%, and 26.6 ± 0.6% in hsa-miR-199a-3p, hsa-miR-149-3p, or hsa-miR-149-5p groups, respectively [n = 9 each]). Net change (delta) in EF at 8 weeks compared with day 3 after MI was - 4.1% in control and - 3.2%, - 2.4%, and - 0.4% in the miR-treated groups (P = NS). Assessment of cardiac function by hemodynamic studies (a method independent of echocardiography) confirmed that there was no difference in left ventricular systolic or diastolic function among groups. Consistent with the functional data, histological analysis showed no difference in scar size, cardiomyocyte area, capillary density, collagen content, or apoptosis among groups. In conclusion, this randomized, blinded study demonstrates that intramyocardial injection of a single dose of synthetic hsa-miR-199a-3p, hsa-miR-149-3p, or hsa-miR-149-5p mimic does not improve cardiac function or remodeling in a murine model of reperfused MI. The strategy of using synthetic miR mimics for cardiac repair after MI needs to be evaluated with rigorous preclinical studies before its potential clinical translation.

Diabetes induces dysregulation of microRNAs associated with survival, proliferation and self-renewal in cardiac progenitor cells

AIMS/HYPOTHESIS

Diabetes mellitus causes a progressive loss of functional efficacy in stem cells, including cardiac progenitor cells (CPCs). The underlying molecular mechanism is still not known. MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate genes at the post-transcriptional level. We aimed to determine if diabetes mellitus induces dysregulation of miRNAs in CPCs and to test if in vitro therapeutic modulation of miRNAs would improve the functions of diabetic CPCs.

METHODS

CPCs were isolated from a mouse model of type 2 diabetes (db/db), non-diabetic mice and human right atrial appendage heart tissue. Total RNA isolated from mouse CPCs was miRNA profiled using Nanostring analysis. Bioinformatic analysis was employed to predict the functional effects of altered miRNAs. MS analysis was applied to determine the targets, which were confirmed by western blot analysis. Finally, to assess the beneficial effects of therapeutic modulation of miRNAs in vitro and in vivo, prosurvival miR-30c-5p was overexpressed in mouse and human diabetic CPCs, and the functional consequences were determined by measuring the level of apoptotic cell death, cardiac function and mitochondrial membrane potential (MMP).

RESULTS

Among 599 miRNAs analysed in mouse CPCs via Nanostring analysis, 16 miRNAs showed significant dysregulation in the diabetic CPCs. Using bioinformatics tools and quantitative real-time PCR (qPCR) validation, four altered miRNAs (miR-30c-5p, miR-329-3p, miR-376c-3p and miR-495-3p) were identified to play an important role in cell proliferation and survival. Diabetes mellitus significantly downregulated miR-30c-5p, while it upregulated miR-329-3p, miR-376c-3p and miR-495-3p. MS analysis revealed proapoptotic voltage-dependent anion-selective channel 1 (VDAC1) as a direct target for miR-30c-5p, and cell cycle regulator, cyclin-dependent protein kinase 6 (CDK6), as the direct target for miR-329-3p, miR-376c-3p and miR-495-3p. Western blot analyses showed a marked increase in VDAC1 expression, while CDK6 expression was downregulated in diabetic CPCs. Finally, in vitro and in vivo overexpression of miR-30c-5p markedly reduced the apoptotic cell death and preserved MMP in diabetic CPCs via inhibition of VDAC1.

CONCLUSIONS/INTERPRETATION

Our results demonstrate that diabetes mellitus induces a marked dysregulation of miRNAs associated with stem cell survival, proliferation and differentiation, and that therapeutic overexpression of prosurvival miR-30c-5p reduced diabetes-induced cell death and loss of MMP in CPCs via the newly identified target for miR-30c-5p, VDAC1.

Cardiac Mesenchymal Cells Cultured at Physiologic Oxygen Tension Have Superior Therapeutic Efficacy in Heart Failure Caused by Myocardial Infarction

Stem/progenitor cells are usually cultured at atmospheric O₂ tension (21%); however, since physiologic O₂ tension in the heart is ∼5%, using 21% O₂ may cause oxidative stress and toxicity. Cardiac mesenchymal cells (CMCs), a newly discovered and promising type of progenitor cells, are effective in improving left ventricle (LV) function after myocardial infarction (MI). We have previously shown that, compared with 21% O₂, culture at 5% O₂ increases CMC proliferation, telomerase activity, telomere length, and resistance to severe hypoxia in vitro. However, it is unknown whether these beneficial effects of 5% O₂in vitro translate into greater therapeutic efficacy in vivo in the treatment of heart failure. Thus, murine CMCs were cultured at 21% or 5% O₂. Mice with heart failure caused by a 60-min coronary occlusion followed by 30 days of reperfusion received vehicle, 21% or 5% O₂ CMCs via echocardiography-guided intraventricular injection. After 35 days, the improvement in LV ejection fraction effected by 5% O₂ CMCs was > 3 times greater than that afforded by 21% O₂ CMCs (5.2 vs. 1.5 units, P < 0.01). Hemodynamic studies (Millar catheter) yielded similar results both for load-dependent (LV dP/dt) and load-independent (end-systolic elastance) indices. Thus, two independent approaches (echo and hemodynamics) demonstrated the therapeutic superiority of 5% O₂ CMCs. Further, 5% O₂ CMCs, but not 21% O₂ CMCs, significantly decreased scar size, increased viable myocardium, reduced LV hypertrophy and dilatation, and limited myocardial fibrosis both in the risk and non-infarcted regions. Taken together, these results show, for the first time, that culturing CMCs at physiologic (5%) O₂ tension provides superior therapeutic efficacy in promoting cardiac repair in vivo. This concept may enhance the therapeutic potential of CMCs. Further, culture at 5% O₂ enables greater numbers of cells to be produced in a shorter time, thereby reducing costs and effort and limiting cell senescence. Thus, the present study has potentially vast implications for the field of cell therapy.

Echocardiography-guided percutaneous left ventricular intracavitary injection as a cell delivery approach in infarcted mice

In the field of cell therapy for heart disease, a new paradigm of repeated dosing of cells has recently emerged. However, the lack of a repeatable cell delivery method in preclinical studies in rodents is a major obstacle to investigating this paradigm. We have established and standardized a method of echocardiography-guided percutaneous left ventricular intracavitary injection (echo-guided LV injection) as a cell delivery approach in infarcted mice. Here, we describe the method in detail and address several important issues regarding it. First, by integrating anatomical and echocardiographic considerations, we have established strategies to determine a safe anatomical window for injection in infarcted mice. Second, we summarize our experience with this method (734 injections). The overall survival rate was 91.4%. Third, we examined the efficacy of this cell delivery approach. Compared with vehicle treatment, cardiac mesenchymal cells (CMCs) delivered via this method improved cardiac function assessed both echocardiographically and hemodynamically. Furthermore, repeated injections of CMCs via this method yielded greater cardiac function improvement than single-dose administration. Echo-guided LV injection is a feasible, reproducible, relatively less invasive and effective delivery method for cell therapy in murine models of heart disease. It is an important approach that could move the field of cell therapy forward, especially with regard to repeated cell administrations.

Comparison of One and Three Intraventricular Injections of Cardiac Progenitor Cells in a Murine Model of Chronic Ischemic Cardiomyopathy

Repeated doses of c-kit⁺ cardiac progenitor cells (CPCs) are superior to a single dose in improving LV function in rats with old myocardial infarction (MI). However, this concept needs testing in different species to determine whether it is generalizable. We used a new murine model of chronic ischemic cardiomyopathy whose unique feature is that cell therapy was started late (3 months) after MI. Mice received three echo-guided intraventricular infusions, 5 weeks apart, of vehicle, CPCs × 1, or CPCs × 3. Echocardiography demonstrated that the single-dose group exhibited improved LV ejection fraction (EF) after the 1st infusion (CPCs), but not after the 2nd and 3rd (vehicle). In contrast, in the multiple-dose group LVEF continued to improve, so that the final value was greater than in vehicle or single-dose groups (P < 0.05). Hemodynamic studies showed that compared with vehicle, both preload-dependent and preload-independent functional parameters were significantly increased in the multiple-dose group but not in the single-dose group. Thus, two independent methods of functional assessment (echocardiography and hemodynamic studies) consistently demonstrated the superiority of three doses of CPCs vs. one dose. Compared with the single-dose group, the multiple-dose group exhibited less LV hypertrophy, as evidenced by a greater reduction in LV/body weight ratio and cardiomyocyte cross-sectional area. Furthermore, unlike the single dose, three CPC doses reduced myocardial inflammatory cells in the risk region. This is the first study of echo-guided intraventricular infusion of CPCs in mice with chronic ischemic cardiomyopathy. The results demonstrate that the beneficial effects of three CPC doses are greater than those of one dose, supporting the concept that multiple treatments are necessary to properly evaluate cell therapy. Our findings indicate that this concept applies not only to rat models but also to murine models. The generalizability of this strategy greatly enhances its importance and provides a rationale for large animal studies. Graphical abstract.

Mitochondrial quality control mechanisms as molecular targets in cardiac ischemiareperfusion injury

Mitochondrial damage is a critical contributor to cardiac ischemia/reperfusion (I/R) injury. Mitochondrial quality control (MQC) mechanisms, a series of adaptive responses that preserve mitochondrial structure and function, ensure cardiomyocyte survival and cardiac function after I/R injury. MQC includes mitochondrial fission, mitochondrial fusion, mitophagy and mitochondria-dependent cell death. The interplay among these responses is linked to pathological changes such as redox imbalance, calcium overload, energy metabolism disorder, signal transduction arrest, the mitochondrial unfolded protein response and endoplasmic reticulum stress. Excessive mitochondrial fission is an early marker of mitochondrial damage and cardiomyocyte death. Reduced mitochondrial fusion has been observed in stressed cardiomyocytes and correlates with mitochondrial dysfunction and cardiac depression. Mitophagy allows autophagosomes to selectively degrade poorly structured mitochondria, thus maintaining mitochondrial network fitness. Nevertheless, abnormal mitophagy is maladaptive and has been linked to cell death. Although mitochondria serve as the fuel source of the heart by continuously producing adenosine triphosphate, they also stimulate cardiomyocyte death by inducing apoptosis or necroptosis in the reperfused myocardium. Therefore, defects in MQC may determine the fate of cardiomyocytes. In this review, we summarize the regulatory mechanisms and pathological effects of MQC in myocardial I/R injury, highlighting potential targets for the clinical management of reperfusion.

Cardiac mesenchymal cells from failing and nonfailing hearts limit ventricular dilation when administered late after infarction

Although cell therapy-mediated cardiac repair offers promise for treatment/management of heart failure, lack of fundamental understanding of how cell therapy works limits its translational potential. In particular, whether reparative cells from failing hearts differ from cells derived from nonfailing hearts remains unexplored. Here, we assessed differences between cardiac mesenchymal cells (CMC) derived from failing (HF) versus nonfailing (Sham) hearts and whether the source of donor cells (i.e., from HF vs. Sham) limits reparative capacity, particularly when administered late after infarction. To determine the impact of the donor source of CMCs, we characterized the transcriptional profile of CMCs isolated from sham (Sham-CMC) and failing (HF-CMC) hearts. RNA-seq analysis revealed unique transcriptional signatures in Sham-CMC and HF-CMC, suggesting that the donor source impacts CMC. To determine whether the donor source affects reparative potential, C57BL6/J female mice were subjected to 60 min of regional myocardial ischemia and then reperfused for 35 days. In a randomized, controlled, and blinded fashion, vehicle, HF-CMC, or Sham-CMC were injected into the lumen of the left ventricle at 35 days post-MI. An additional 5 weeks later, cardiac function was assessed by echocardiography, which indicated that delayed administration of Sham-CMC and HF-CMC attenuated ventricular dilation. We also determined whether Sham-CMC and HF-CMC treatments affected ventricular histopathology. Our data indicate that the donor source (nonfailing vs. failing hearts) affects certain aspects of CMC, and these insights may have implications for future studies. Our data indicate that delayed administration of CMC limits ventricular dilation and that the source of CMC may influence their reparative actions.NEW & NOTEWORTHY Most preclinical studies have used only cells from healthy, nonfailing hearts. Whether donor condition (i.e., heart failure) impacts cells used for cell therapy is not known. We directly tested whether donor condition impacted the reparative effects of cardiac mesenchymal cells in a chronic model of myocardial infarction. Although cells from failing hearts differed in multiple aspects, they retained the potential to limit ventricular remodeling.

PTEN inhibition attenuates endothelial cell apoptosis in coronary heart disease via modulating the AMPK-CREB-Mfn2-mitophagy signaling pathway

Atherosclerosis (AS) is a major pathogenic factor in patients with cardiovascular diseases, and endothelial dysfunction (ED) plays a primary role in the occurrence and development of AS. In our study, we attempted to evaluate the role of phosphatase and tensin homolog (PTEN) in endothelial cell apoptosis under oxidized low-density lipoprotein (ox-LDL) stimulation and identify the associated mechanisms. The results of our study demonstrated that ox-LDL induced human umbilical vein endothelial cell (HUVEC) death via mitochondrial apoptosis, as evidenced by reduced mitochondrial potential, increased mitochondria permeability transition pore opening, cellular calcium overload, and caspase-9/-3 activation. In addition, ox-LDL also suppressed cellular energy production via downregulating the mitochondrial respiratory complex. Moreover, ox-LDL impaired HUVECs migration. Western blot analysis showed that PTEN expression was upregulated after exposure to ox-LDL and knockdown of PTEN could attenuate ox-LDL-mediated endothelial cell damage. Furthermore, we found that ox-LDL impaired mitophagy activity, whereas PTEN deletion could improve mitophagic flux and this effect relied on the activity of the AMP-activated protein kinase (AMPK)-cAMP-response element-binding protein (CREB)-Mitofusin-2 (Mfn2) axis. When the AMPK-CREB-Mfn2 pathway was inhibited, PTEN deletion-associated HUVECs protection was significantly reduced, suggesting that the AMPK-CREB-Mfn2-mitophagy axis is required for PTEN deletion-mediated endothelial cell survival under ox-LDL. Taken together, our results indicate that ox-LDL-induced endothelial cell damage is associated with PTEN overexpression, and inhibition of PTEN could promote endothelial survival via activating the AMPK-CREB-Mfn2-mitophagy signaling pathway.

Pak2 inhibition promotes resveratrol-mediated glioblastoma A172 cell apoptosis via modulating the AMPK-YAP signaling pathway

As a polyphenolic compound, resveratrol (Res) is widely present in a variety of plants. Previous studies have shown that Res can inhibit various tumors. However, its role in c remains largely unexplored. In the present study, we first demonstrated that Res inhibited cell viability and induced apoptosis of glioblastoma A172 cell. Further experiments showed that Res induced mitochondrial dysfunction and activated the activity of caspase-9. Functional studies have found that Res treatment is associated with an increase in the expression of Pak2. Interestingly, inhibition of Pak2 could further augment the proapoptotic effect of Res. Mechanistically, Pak2 inhibition induced reactive oxygen species overproduction, mitochondria-JNK pathway activation, and AMPK-YAP axis suppression. However, overexpression of YAP could abolish the anticancer effects of Res and Pak2 inhibition, suggesting a necessary role played by the AMPK-YAP pathway in regulating cancer-suppressive actions of Res and Pak2 inhibition. Altogether, our results indicated that Res in combination with Pak2 inhibition could further enhance the anticancer property of Res and this effect is mediated via the AMPK-YAP pathway.

Liraglutide reduces hyperglycemia-induced cardiomyocyte death through activating glucagon-like peptide 1 receptor and targeting AMPK pathway

Objective: Hyperglycemia-mediated cardiomyocyte damage is associated with inflammation and AMPK inactivation.Aim: The aim of our study is to explore the protective effects exerted by liraglutide on AMPK pathway and glucagon-like peptide 1 receptor in diabetic cardiomyopathy.Methods: Cardiomyocytes were treated with high-glucose stress and cardiomyocyte viability was determined via (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay. Besides, LDH release, immunofluorescence, and qPCR were used to verify the influence of liraglutide on hyperglycemia-treated cardiomyocytes.Results: Hyperglycemia treatment caused inflammation response and oxidative stress were significantly elevated in cardiomyocytes. This alteration could be reversed by liraglutide. Besides, cell viability was reduced whereas apoptosis was increased after exposure to high glucose treatment. However, liraglutide treatment could attenuate apoptosis and reverse cell viability in cardiomyocyte. Further, we found that AMPK pathway was also activated and glucagon-like peptide 1 receptor expression was increased in response to liraglutide treatment.Conclusions: Liraglutide could attenuate hyperglycemia-mediated cardiomyocyte damage through reversing AMPK pathway and upregulating glucagon-like peptide 1 receptor.

Resveratrol attenuates cerebral ischaemia reperfusion injury via modulating mitochondrial dynamics homeostasis and activating AMPK-Mfn1 pathway

The pathogenesis of cerebral ischaemia reperfusion injury (IRI) has not been fully described. Accordingly, there is little effective drug available for the treatment of cerebral IRI. The aim of our study was to explore the exact role played by Mfn1-mediated mitochondrial protection in cerebral IRI and evaluate the beneficial action of resveratrol on reperfused brain. Our study demonstrated that hypoxia-reoxygenation (HR) injury caused N2a cell apoptosis and this process was highly affected by mitochondrial dysfunction. Decreased mitochondrial membrane potential, increased mitochondrial oxidative stress, and an activated mitochondrial apoptosis pathway were noted in HR-treated N2a cells. Interestingly, resveratrol treatment could attenuate N2a cell apoptosis via sustaining mitochondrial homeostasis. Further, we found that resveratrol modulated mitochondrial performance via activating the Mfn1-related mitochondrial protective system. Knockdown of Mfn1 could abolish the beneficial effects of resveratrol on HR-treated N2a cells. Besides, we also report that resveratrol regulated Mfn1 expression via the AMPK pathway; inhibition of AMPK pathway also neutralized the anti-apoptotic effect of resveratrol on N2a cells in the setting of cerebral IRI. Taken together our results show that mitochondrial damage is closely associated with the progression of cerebral IRI. In addition we also demonstrate the protective action played by resveratrol on reperfused brain and show that this effect is achieved via activating the AMPK-Mfn1 pathway.

LATS2 promotes cardiomyocyte H9C2 cells apoptosis via the Prx3-Mfn2-mitophagy pathways

Context: The pathogenesis of cardiomyocyte death is closely associated with mitochondrial homeostasis via poorly understood mechanisms.Objective: The aim of our study is to explore the contribution of large tumor suppressor kinase 2 (LATS2) to the apoptosis of cardiomyocyte H9C2 cells.Materials and Methods: Adenovirus-mediated LATS2 overexpression was carried out in H9C2 cells. The cell viability and apoptosis rate were measured via an MTT assay, TUNEL staining, western blotting, an ELISA, and an LDH release assay. Mitophagy was quantified using immunofluorescence and western blotting.Results: The overexpression of LATS2 in H9C2 cells drastically promoted cell death. Molecular investigations showed that LATS2 overexpression was associated with mitochondrial injury, as evidenced by increased mitochondrial ROS production, reduced antioxidant factor levels, increased cyt-c liberation into the nucleus and activated mitochondrial caspase-9-dependent apoptotic pathway activity. Furthermore, our results demonstrated that LATS2-mediated mitochondrial malfunction by repressing mitophagy and that the reactivation of mitophagy could sustain mitochondrial integrity and homeostasis in response to LATS2 overexpression. Furthermore, we found that LATS2 inhibited mitophagy by inactivating the Prx3-Mfn2 axis. The reactivation of Prx3-Mfn2 pathways abrogated the LATS2-mediated inhibition of mitochondrial apoptosis in H9C2 cells.Conclusions: The overexpression of LATS2 induces mitochondrial stress by repressing protective mitophagy in a manner dependent on Prx3-Mfn2 pathways, thus reducing the survival of H9C2 cells.

Renal tubular cell death and inflammation response are regulated by the MAPK-ERK-CREB signaling pathway under hypoxia-reoxygenation injury

Context: Cell death and inflammation response have been found to the primary features of acute kidney injury.Objective: The aim of our study is to figure out the molecular mechanism by which hypoxia-reoxygenation injury affects the viability of tubular cell death.Materials and methods: HK2 cells were treated with hypoxia-reoxygenation injury in vitro. Pathway agonist was added into the medium of HK2 cell to activate MAPK-EEK-CREB axis.Results: Hypoxia-reoxygenation injury reduced HK2 cell viability and increased cell apoptosis rate in vitro. Besides, inflammation response has been found to be induced by hypoxia-reoxygenation injury in HK2 cells in vitro. In addition, MAPK-ERK-CREB pathway was deactivated during hypoxia-reoxygenation injury. Interestingly, activation of MAPK-ERK-CREB pathway could attenuate hypoxia-reoxygenation injury-mediated HK2 cell apoptosis and inflammation. Mechanistically, MAPK-ERK-CREB pathway activation upregulated the transcription of anti-apoptotic genes and reduced the levels of pro-apoptotic factors under hypoxia-reoxygenation injury.Conclusions: Our results report a novel signaling pathway responsible for acute kidney injury-related tubular cell death. Activation of MAPK-ERK-CREB signaling could protect tubular cell against hypoxia-reoxygenation-related cell apoptosis and inflammation response.

Sirt3 overexpression alleviates hyperglycemia-induced vascular inflammation through regulating redox balance, cell survival, and AMPK-mediated mitochondrial homeostasis

Context: Sirtuin-3 (Sirt3), a NAD-dependent deacetylase, has been reported to be involved in many biological processes.Objective: The present study aimed to investigate the effect and mechanism of Sirt3 on diabetic mice and human umbilical vein endothelial cells (HUVECs) under high glucose (HG) condition.Materials and methods: HUVECs were cultured under HG and inflammation pathway was determined via qPCR, western blots, and immunofluorescence.Results: Sirt3 expression was reduced in the progression of diabetic nephropathy. Overexpression of Sirt3 sustains renal function and retard the development of diabetic nephropathy. Mechanistically, Sirt3 overexpression attenuated hyperglycemia-mediated endothelial cells apoptosis in kidney. Besides, Sirt3 overexpression repressed oxidative injury and blocked caspase-9-related apoptosis pathway. Moreover, we found that Sirt3 overexpression was associated with AMPK activation and the latter elevates PGC1α-related mitochondrial protective system, especially mitochondrial autophagy. Loss of opa1 and/or inhibition of AMPK could depress mitochondrial autophagy and exacerbates mitochondrial function, finally contributing to the death of human renal mesangial cells.Conclusions: Our results demonstrated the beneficial effects of Sirt3 in the progression of diabetic nephropathy. Increased Sirt3-activated AMPK pathway, augments PGC1α-related mitochondrial protective system, sustained redox balance and closed caspase-9-involved apoptosis pathway in the setting of diabetic nephropathy.

Sirtuin 3 attenuates neuroinflammation-induced apoptosis in BV-2 microglia

In this study, we explored the upstream regulatory mechanisms underlying inflammation-induced mitochondrial dysfunction in microglial BV-2 cells. Our results demonstrate that Sirtuin 3 (Sirt3) expression was downregulated in response to LPS-induced neuroinflammation. In addition, overexpression of Sirt3 attenuated LPS-induced BV-2 cell death. Functional studies illustrated that Sirt3 overexpression promoted normal mitochondrial function and inhibited mitochondria-dependent apoptosis in LPS-treated BV-2 cells. At the molecular level, suppressor of ras val-2 (SRV2) promoted LPS-mediated mitochondrial damage by inducing mitochondrial fission. Sirt3 overexpression, which suppressed the transcription of SRV2 and thus suppressed mitochondrial fission, played an anti-apoptotic role in LPS-treated BV-2 cells. Furthermore, Sirt3 inhibited SRV2 expression via the Mst1-JNK pathway, and re-activation of this pathway abolished the protective effects of Sirt3 on mitochondrial damage and apoptosis. Taken together, our results indicate that Sirt3-induced, Mst1-JNK-SRV2 signaling pathway-dependent inhibition of mitochondrial fission protected against neuroinflammation-mediated cell damage in BV-2 microglia. Sirt3 might therefore be an effective treatment for neuroinflammation.

MKP1 reduces neuroinflammation via inhibiting endoplasmic reticulum stress and mitochondrial dysfunction

MAP kinase phosphatase 1 (MKP1) has been identified as an antiapoptotic protein via sustaining mitochondrial function. However, the role of MKP1 in neuroinflammation has not been fully understood. The aim of this study is to figure out the influence of MKP1 in lipopolysaccharide (LPS)-treated microglia BV-2 cells and investigate whether MKP1 reduces BV-2 cell death via modulating endoplasmic reticulum (ER) stress and mitochondrial dysfunction. The results of this study demonstrated that MKP1 was rapidly downregulated after exposure to LPS. However, the transfection of MKP1 adenovirus could reverse cell viability and attenuate LPS-mediated BV-2 cell apoptosis. Mechanistically, MKP1 overexpression alleviated ER stress and corrected LPS-induced calcium overloading. Besides, MKP1 adenovirus transfection also reversed mitochondrial bioenergetics, maintained mitochondrial membrane potential, and blocked mitochondria-initiated apoptosis signals. Furthermore, we found that MKP1 overexpression is associated with inactivation of mitogen-activated protein kinase-c-Jun N-terminal kinase (MAPK-JNK) pathway. Interestingly, the activation of MAPK-JNK pathway could abolish the protective effects of MKP1 on BV-2 cells survival and mitochondrial function in the presence of LPS. Altogether, our results identified MKP1 as a primary defender of neuroinflammation via modulating ER stress and mitochondrial function in a manner dependent on MAPK-JNK pathway. These findings may open a new window for the treatment of neuroinflammation in the clinical setting.

Therapeutic effects of bone mesenchymal stem cells on oral and maxillofacial defects: a novel signaling pathway involving miR-31/CXCR4/Akt axis

Context: Although bone mesenchymal stem cells (BMSCs) have been used for the treatment of oral and maxillofacial defects, the survival rate and limited proliferation reduces the therapeutic efficiency of BMSC.Objective: The aim of our study is to explore the role of miR-31 in regulating survival, proliferation, and migration of BMSC in vitro.Materials and methods: LPS was used in vitro to induce BMSC damage and then miR-31 was used to incubate with BMSC. Subsequently, BMSC proliferation, survival, and migration were determined via ELISA, qPCR, western blots, and immunofluorescence.Results: The expression of miR-31 was downregulated in response to LPS stress. Interestingly, supplementation of miR-31 could reverse the survival, proliferation and migration of BMSC under LPS. Mechanically, miR-31 treatment inhibited the activation of caspase, and thus promoted BMSC survival. Besides, miR-31 upregulated the genes related to cell proliferation, an effect that was followed by an increase in the levels of migratory factors. Further, we found that miR-31 treatment activated the CXCR4/Akt pathway and blockade of CXCR4/Akt could abolish the beneficial effects of miR-31 on BMSC proliferation, survival, and migration.Conclusions: miR-31 could increase the therapeutic efficiency of BMSC via the CXCR4/Akt pathway.

Tanshinone IIA attenuates cardiac microvascular ischemia-reperfusion injury via regulating the SIRT1-PGC1α-mitochondrial apoptosis pathway

Cardiac microvascular ischemia-reperfusion (IR) injury has been a neglected topic in recent decades. In the current study, we investigated the mechanism underlying microvascular IR injury, with a focus on mitochondrial homeostasis. We also explored the protective role of tanshinone IIA (Tan IIA) in microvascular protection in the context of IR injury. Through animal studies and cell experiments, we demonstrated that IR injury mediated microvascular wall destruction, lumen stenosis, perfusion defects, and cardiac microvascular endothelial cell (CMEC) apoptosis via inducing mitochondrial damage. In contrast, Tan IIA administration had the ability to sustain CMEC viability and microvascular homeostasis, finally attenuating microvascular IR injury. Function studies have confirmed that the SIRT1/PGC1α pathway is responsible for the microvascular protection from the Tan IIA treatment. SIRT1 activation by Tan IIA sustained the mitochondrial potential, alleviated the mitochondrial pro-apoptotic factor leakage, reduced the mPTP opening, and blocked mitochondrial apoptosis, providing a survival advantage for CMECs and preserving microvascular structure and function. By comparison, inhibiting SIRT1 abrogated the beneficial effects of Tan IIA on mitochondrial function, CMEC survival, and microvascular homeostasis. Collectively, this study indicated that Tan IIA should be considered a microvascular-protective drug that alleviates acute cardiac microcirculation IR injury via activating the SIRT1/PGC1α pathway and thereby blocking mitochondrial damage.

Pretreatment of bone mesenchymal stem cells with miR181-c facilitates craniofacial defect reconstruction via activating AMPK-Mfn1 signaling pathways

Context: Bone mesenchymal stem cells (BMSC)-based regenerative therapy is critical for the craniofacial defect reconstruction. However, oxidative stress micro-environment after transplantation limits the therapeutic efficiency of BMSC. The miR-181c has been found to be associated with cell survival and proliferation. Objective: Herein, we investigated whether prior miR-181c treatment promoted BMSC proliferation and survival under oxidative stress injury. Materials and methods: Cells were treated with hydrogen peroxide (H₂O₂) and then cell viability was determined via MTT assay, TUNEL staining and ELISA. Western blotting and immunofluorescence assay were used to detect those alterations of mitochondrial function. Results: H₂O₂ treatment reduced BMSC viability and this effect could be reversed via additional supplementation of miR181-c. Mechanistically, oxidative stress increased cell apoptosis, augmented caspase-3 activity, promoted reactive oxygen species (ROS) synthesis, impaired mitochondrial potential, and induced mitochondrial dynamics imbalance. However, miR-181c pretreatment reversed these effects of oxidative stress on BMSC. Moreover, miR-181c treatment improved BMSC proliferation, migration and paracrine, which are very important for craniofacial reconstruction. In addition, we identified that AMPK-Mfn1 axis was the direct targets of miR-181c in BMSC. Mfn1 silencing impaired the protective effects miR-181c on BMSC viability and proliferation under oxidative stress environment. Conclusions: Collectively, our results indicate that miR-181c participates in oxidative stress-mediated BMSC damage by modulating the AMPK-Mfn1 signaling pathway, suggesting miR-181c-AMPK-Mfn1 axis may serves as novel therapeutic targets to facilitate craniofacial defect reconstruction.

PTEN overexpression promotes glioblastoma death through triggering mitochondrial division and inactivating the Akt pathway

Objective: PTEN has been acknowledged as an anticancer factor in the progression of glioblastoma. Mitochondrial division has been found to be associated with cancer cell death. Objective: The aim of our study is to explore whether PTEN attenuates the development of glioblastoma by modulating mitochondrial division. Materials and methods: PTEN adenovirus was used to overexpress PTEN in U87 cells. Mitochondrial function was detected via western blot and immunofluorescence. Pathway blocker was used to inhibit the Akt activation. Results: The results of our study demonstrated that PTEN overexpression reduced cell viability by increasing cell apoptosis. At the molecular level, PTEN overexpression activated mitochondrial apoptosis by mediating mitochondrial dysfunction. Furthermore, we found that Drp1-related mitochondrial division was required for PTEN-mediated mitochondrial dysfunction and cell death. Finally, we found that PTEN modulated Drp1-related mitochondrial division via the Akt pathway; inactivation of Akt induced cell death, and mitochondrial damage, similar to the results obtained via PTEN overexpression. Conclusions: Taken together, our results clarify that the anticancer mechanism of PTEN in glioblastoma is dependent on the activation of Drp1-related mitochondrial division via Akt pathway modulation. This finding might provide new insight into the tumor-suppressive role played by PTEN in glioblastoma.

Ripk3 mediates cardiomyocyte necrosis through targeting mitochondria and the JNK-Bnip3 pathway under hypoxia-reoxygenation injury

Context: Cardiomyocyte necrosis following myocardial infarction drastically the progression of heart failure.Objective: In the current study, we explored the upstream mediator for cardiomyocytes necrosis induced by hypoxia-reoxygenation (HR) injury with a focus on mitochondrial function and JNK-Bnip3 pathway.Materials and methods: Cell necrosis was determined via MTT assay, TUNEL staining and PI staining. siRNA transfection was performed to inhibit Ripk3 activation in response to HR injury. Pathway blocker was applied to prevent JNK activation.Results: Ripk3 was rapidly increased in HR-treated cardiomyocytes and correlated with the necrosis of cardiomyocytes. Interestingly, silencing of Ripk3 attenuated HR-mediated cardiomyocytes necrosis. At the molecular levels, Ripk3 deletion sustained mitochondrial bioenergetics and stabilized mitochondrial glucose metabolism. Besides, Ripk3 deletion also reduced mitochondrial oxidative stress and inhibited mPTP opening. To the end, we found Ripk3 activation was along with JNK pathway activation and Bnip3 upregulation. Interestingly, blockade of JNK pathway abolished the harmful effects of HR injury on mitochondrial function, energy metabolism and redox balance. Moreover, overexpression of Bnip3 abrogated the protection action played by Ripk3 deletion on cardiomyocytes survival.Conclusions: Taken together, these data may identify Ripk3 upregulation, mitochondrial dysfunction and JNK-Bnip3 axis activation as the novel mechanisms underlying cardiomyocytes necrosis achieved by HR injury. Thereby, approaches targeted to the Ripk3-JNK-Bnip3-mitochondria cascade have the potential to ameliorate the progression of HR-related cardiomyocytes necrosis in the clinical practice.

Therapeutic contribution of melatonin to the treatment of septic cardiomyopathy: A novel mechanism linking Ripk3-modified mitochondrial performance and endoplasmic reticulum function

The basic pathophysiological mechanisms underlying septic cardiomyopathy have not yet been completely clarified. Disease-specific treatments are lacking, and care is still based on supportive modalities. The aim of our study was to assess the protective effects of melatonin on septic cardiomyopathy, with a focus on the interactions between receptor-interacting protein kinase 3 (Ripk3), the mitochondria, endoplasmic reticulum (ER) and cytoskeletal degradation in cardiomyocytes. Ripk3 expression was increased in heart samples challenged with LPS, followed by myocardial inflammation, cardiac dysfunction, myocardial breakdown and cardiomyocyte death. The melatonin treatment attenuated septic myocardial injury in a comparable manner to the genetic depletion of Ripk3. Molecular investigations revealed that Ripk3 intimately regulated mitochondrial function, ER stress, cytoskeletal homeostasis and cardioprotective signaling pathways. Melatonin-mediated inhibition of Ripk3 improved mitochondrial bioenergetics, reduced mitochondria-initiated oxidative damage, sustained mitochondrial dynamics, ameliorated ER stress, normalized calcium recycling, and activated cardioprotective signaling pathways (including AKT, ERK and AMPK) in cardiomyocytes. Interestingly, Ripk3 overexpression mediated resistance to melatonin therapy following the infection of LPS-treated hearts with an adenovirus expressing Ripk3. Altogether, our findings identify Ripk3 upregulation as a novel risk factor for the development of sepsis-related myocardial injury, and melatonin restores the physiological functions of the mitochondria, ER, contractile cytoskeleton and cardioprotective signaling pathways. Additionally, our data also reveal a new, potentially therapeutic mechanism by which melatonin protects the heart from sepsis-mediated dysfunction, possibly by targeting Ripk3.

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LPS-activated Ripk3 disturbs mitochondrial bioenergetics and promotes mitochondrial dynamics disorder.

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The inhibitory effect of melatonin on Ripk3 sustains heart function in LPS-mediated septic cardiomyopathy.

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LPS-mediated degradation of the cardiomyocyte contractile cytoskeleton could be reversed by melatonin.

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Melatonin modulates mitochondrial dynamics, ER stress, and cardioprotective signals by repressing Ripk3 expression.

Proinflammation effect of Mst1 promotes BV-2 cell death via augmenting Drp1-mediated mitochondrial fragmentation and activating the JNK pathway

Inflammation has been increasingly studied as part of the pathophysiology of neurodegenerative diseases. Mammalian Ste20-like kinase 1 (Mst1), a key factor of the Hippo pathway, is connected to cell death. Unfortunately, little study has been performed to detect the impact of Mst1 in neuroninflammation. The results indicated that Mst1 expression was upregulated because of LPS treatment. However, the loss of Mst1 sustained BV-2 cell viability and promoted cell survival in the presence of LPS treatment. Molecular investigation assay demonstrated that Mst1 deletion was followed by a drop in the levels of mitochondrial fission via repressing Drp1 expression. However, Drp1 adenovirus transfection reduced the protective impacts of Mst1 knockdown on mitochondrial stress and neuronal dysfunction. Finally, our results illuminated that Mst1 affected Drp1 content and mitochondrial fission in a JNK-dependent mechanism. Reactivation of the JNK axis inhibited Mst1 knockdown-mediated neuronal protection and mitochondrial homeostasis. Altogether, our results indicated that Mst1 upregulation and the activation of JNK-Drp1-mitochondrial fission pathway could be considered as the novel mechanism regulating the progression of neuroninflammation. This finding would pave a new road for the treatment of neurodegenerative diseases via modulating the Mst1-JNK-Drp1-mitochondrial fission axis.

Caveolin-1 knockdown increases the therapeutic sensitivity of lung cancer to cisplatin-induced apoptosis by repressing Parkin-related mitophagy and activating the ROCK1 pathway

Chemotherapy is the first-line treatment option for patients with lung cancer. However, therapeutic resistance occurs through an incompletely understood mechanism. Our research wants to investigate the influence of Caveolin-1 (Cav-1) on the therapeutic sensitivity of lung cancer in vitro. Results in this study demonstrated that Cav-1 levels were markedly inhibited in A549 lung cancer cells after exposure to cisplatin. Knockdown of caveolin further enhanced cisplatin-triggered cancer death in A549 cells. The functional investigation demonstrated that Cav-1 inhibition amplified the mitochondrial stress signaling induced by cisplatin, as evidenced by the mitochondrial reactive oxygen species burst, cellular metabolic disruption, mitochondrial membrane potential reduction, and mitochondrial caspase-9-related apoptosis activation. At the molecular level, cav-1 augmented cisplatin-mediated mitochondrial damage by inhibiting Parkin-related mitochondrial autophagy. Mitophagy activation effectively attenuated the promotive impact of Cav-1 knockdown on mitochondrial damage and cell death. Furthermore, our data indicated that Cav-1 affected Parkin-related mitophagy by activating the Rho-associated coiled-coil kinase 1 (ROCK1) pathway; inhibition of the ROCK1 axis prevented cav-1 knockdown-mediated cell death and mitochondrial damage. Taken together, our results provide ample data illuminate the necessary action exerted by Cav-1 on affecting cisplatin-related therapeutic resistance. Silencing of Cav-1 inhibited Parkin-related mitophagy, thus amplifying cisplatin-mediated mitochondrial apoptotic signaling. This finding identifies the Cav-1/ROCK1/Parkin/mitophagy axis as a potential target to overcome cisplatin-related resistance in lung cancer cells.

Inhibitory effect of melatonin on Mst1 ameliorates myocarditis through attenuating ER stress and mitochondrial dysfunction

Viral myocarditis has been found to be one of the leading causes of sudden death in young adults. However, no effective drugs have been developed to intervene the progression of myocarditis. Accordingly, the present study is carried out to explore the protective role played by melatonin in the setting of viral myocarditis with a focus on Mst1-Hippo pathway, mitochondrial dysfunction and ER stress. Cardiac function was determined via echocardiographic examination. Mitochondrial function and ER stress were detected via ELISA, western blots, and immunofluorescence. Our data demonstrated that virus injection induced cardiac dysfunction as evidenced by reduced contractile function in myocardium. Besides, LDH release assay and western blotting analysis demonstrated that cardiomyocyte death was activated by virus injection. Interestingly, melatonin treatment improved cardiac function and repressed virus-mediated cardiomyocyte apoptosis. At the molecular levels, mitochondrial dysfunction was induced by virus infection, as indicated by mitochondrial membrane potential reduction, mPTP opening rate elevation and caspase-9-related apoptosis activation. Besides, ER stress parameters were also elevated in virus-treated cardiomyocytes. Interestingly, melatonin treatment maintained mitochondrial dysfunction and repressed ER stress. To the end, we found that Mst1 was upregulated by virus infection; this effect was attenuated through supplementation with melatonin. However, Mst1 overexpression reduced the beneficial impact exerted by melatonin on cardiomyocyte viability, mitochondrial function and ER homeostasis. Our study illustrated that melatonin treatment attenuated viral myocarditis via sustaining cardiomyocyte viability, repressing mitochondrial dysfunction and inhibiting ER stress in a manner dependent on Mst1 inhibition.

Mst1 deletion reduces septic cardiomyopathy via activating Parkin-related mitophagy

Cardiomyocyte function and viability are highly modulated by mammalian Ste20-like kinase 1 (Mst1)-Hippo pathway and mitochondria. Mitophagy, a kind of mitochondrial autophagy, is a protective program to attenuate mitochondrial damage. However, the relationship between Mst1 and mitophagy in septic cardiomyopathy has not been explored. In the present study, Mst1 knockout mice were used in a lipopolysaccharide (LPS)-induced septic cardiomyopathy model. Mitophagy activity was measured via immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay. Pathway blocker and small interfering RNA were used to perform the loss-of-function assay. The results demonstrated that Mst1 was rapidly increased in response to LPS stress. Knockout of Mst1 attenuated LPS-mediated inflammation damage, reduced cardiomyocyte death, and improved cardiac function. At the molecular levels, LPS treatment activated mitochondrial damage, such as mitochondrial respiratory dysfunction, mitochondrial potential reduction, mitochondrial ATP depletion, and caspase family activation. Interestingly, in response to mitochondrial damage, Mst1 deletion activated mitophagy which attenuated LPS-mediated mitochondrial damage. However, inhibition of mitophagy via inhibiting parkin mitophagy abolished the protective influences of Mst1 deletion on mitochondrial homeostasis and cardiomyocyte viability. Overall, our results demonstrated that septic cardiomyopathy is linked to Mst1 upregulation which is followed by a drop in the protective mitophagy.

TrxR2 overexpression alleviates inflammation-mediated neuronal death via reducing the oxidative stress and activating the Akt-Parkin pathway

Neuronal death caused by inflammatory cytokine-mediated neuroinflammation is being extensively explored. Thioredoxin reductase (TrxR) 2 is a novel mediator of inflammation response. In the current study, we focus on the mechanisms of TrxR2 overexpression in inflammation-mediated neuronal death. LPS was used to induce neuroinflammation in N2a cells in vitro. Adenovirus-loaded TrxR2 was transfected into N2a cells to up-regulate TrxR2 expression. Then, cell viability was determined via MTT assay and TUNEL assay. Apoptosis was measured via western blotting and ELISA. Oxidative stress was detected via ELISA and flow cytometry. A pathway inhibitor was used to verify the role of the Akt-Parkin pathway in the LPS-mediated N2a cell death in the presence of TrxR2 overexpression. With the help of immunofluorescence assay and western blotting, we found that TrxR2 expression was significantly reduced in response to LPS treatment, and this effect was associated with N2a cell death via apoptosis. At the molecular level, TrxR2 overexpression elevated the activity of the Akt-Parkin pathway, as evidenced by the increased expression of p-Akt and Parkin. Interestingly, inhibition of the Akt-Parkin pathway abolished the regulatory effect of TrxR2 on LPS-treated N2a cells, as evidenced by the decreased cell viability and increased apoptotic ratio. Besides, TrxR2 overexpression also reduced oxidative stress, inflammation factor transcription and mitochondrial apoptosis. However, inhibition of Akt-Parkin axis abrogated the protective effects of TrxR2 on redox balance, mitochondrial performance and cell survival. LPS-mediated neuronal death was linked to a drop in TrxR2 overexpression and the inactivation of the Akt-Parkin pathway. Overexpression of TrxR2 sustained mitochondrial function, inhibited oxidative stress, repressed inflammation response, and blocked mitochondrial apoptosis, finally sending a pro-survival signal for the N2a cells in the setting of LPS-mediated inflammation environment.

Mst1 contributes to nasal epithelium inflammation via augmenting oxidative stress and mitochondrial dysfunction in a manner dependent on Nrf2 inhibition

Nasal epithelium inflammation plays an important role in transmitting and amplifying damage signals for the lower airway. However, the molecular basis of nasal epithelium inflammation damage has not been fully addressed. Mst1 is reported to modulate inflammation via multiple effects. Thus, the aim of our study is to understand the pathological mechanism underlying Mst1-related nasal epithelium inflammation in vitro. Our result indicated that Mst1 expression was rapidly increased in response to tumor necrosis factor-α (TNF-α) treatment in vitro and this effect was a dose-dependent manner. Interestingly, knockdown of Mst1 via transfecting small interfering RNA markedly reversed cell viability in the presence of TNF-α. Further, we found that Mst1 deficiency reduced cellular oxidative stress and attenuated mitochondrial dysfunction, as evidenced by reversed mitochondrial complex-I activity, decreased mitochondrial permeability transition pore opening rate, and stabilized mitochondrial membrane potential. Besides, we found that Nrf2 expression was increased after deletion of Mst1 whereas silencing of Nrf2 abolished the protective effects of Mst1 deletion on nasal epithelium survival and mitochondrial homeostasis. Moreover, Nrf2 overexpression also protected nasal epithelium against TNF-α-induced inflammation damage. Altogether, our data confirm that the Mst1 activation and Nrf2 downregulation seem to be the potential mechanisms responsible for the inflammation-mediated injury in nasal epithelium via mediating mitochondrial damage and cell oxidative stress.

Matrine promotes apoptosis in SW480 colorectal cancer cells via elevating MIEF1-related mitochondrial division in a manner dependent on LATS2-Hippo pathway

Matrine, an alkaloid compound isolated from Sophora flavescens Ait, has been shown to exert cancer-killing actions in a variety of tumors; however, its anticancer mechanism in colorectal cancer (CRC) is not clear. The goal of our study was to characterize the anticancer effects and molecular mechanisms of matrine in SW480 CRC cells in vitro. Matrine treatment reduced mitochondrial metabolic function and ATP levels, repressed mitochondrial membrane potential, evoked mitochondrial reactive oxygen species accumulation, and promoted cyt-c-related mitochondrial apoptosis activation. In addition, we found that matrine treatment activated mitochondrial fission through upregulating mitochondrial elongation factor 1 (MIEF1); silencing of MIEF1 prevented matrine-mediated mitochondrial damage and reversed the decrease in SW480 cell viability. Moreover, matrine treatment affected MIEF1 expression via the large tumor suppressor-2 (LATS2)-Hippo axis, and LATS2 deficiency suppressed the anticancer actions exerted by matrine on SW480 cancer cells. In summary, we show for the first time that matrine inhibits SW480 cell survival by activating MIEF1-related mitochondrial division via the LATS2-Hippo pathway. These findings explain the anticancer mechanisms of matrine in CRC and also identify the LATS2-MIEF1 signaling pathway as an effective target for the treatment of CRC.

Mitochonic acid-5 attenuates TNF-α-mediated neuronal inflammation via activating Parkin-related mitophagy and augmenting the AMPK-Sirt3 pathways

Mitochondrial dysfunction has been found to be associated with neuronal inflammation; however, no effective drug is available to attenuate neuroinflammation via sustaining mitochondrial function. In the current study, experiments were performed to understand the beneficial effects of mitochonic acid 5 (MA-5) on tumor necrosis factor-α (TNF-α)-mediated neuronal injury and mitochondrial damage. Our data illustrated that MA-5 pretreatment reduced inflammation response induced by TNF-α in CATH.a cells. Molecular investigations demonstrated that MA-5 pretreatment repressed oxidative stress, inhibited endoplasmic reticulum stress, sustained cellular energy metabolism, and blocked cell apoptosis induced by TNF-α stress. Further, we found that MA-5 treatment elevated the expression of Sirtuin 3 (Sirt3) and this effect was dependent on the activation of AMP-activated protein kinase (AMPK) pathway. Blockade of AMPK abolished the promotive action of MA-5 on Sirt3 and thus mediated mitochondrial damage and cell death. Besides, we also found that MA-5 treatment augmented Parkin-related mitophagy and increased mitophagy promoted CATH.a cells survival via improving mitochondrial function. Knockdown of Parkin abolished the beneficial action of MA-5 on mitochondrial homeostasis and CATH.a cell survival. Altogether, our results confirm that MA-5 is an effective drug to attenuate neuroinflammation via sustaining mitochondrial damage and promoting CATH.a cell survival. The protective action of MA-5 on neuronal damage is associated with Parkin-related mitophagy and the activation of AMPK-Sirt3 pathways.

Melatonin ameliorates endoplasmic reticulum stress in N2a neuroblastoma cell hypoxia-reoxygenation injury by activating the AMPK-Pak2 pathway

Endoplasmic reticulum (ER) stress has been identified as a primary factor involved in brain ischemia-reperfusion injury progression. p21-activated kinase 2 (Pak2) is a novel ER function regulator. The aim of our study is to explore the influence of Pak2 on ER stress and determine whether melatonin attenuates ER stress-mediated cell death by modulating Pak2 expression in vitro using N2a cells. The results of our study demonstrated that hypoxia-reoxygenation (HR) injury repressed the levels of Pak2, an effect that was accompanied by activation of ER stress. In addition, decreased Pak2 was associated with oxidative stress, calcium overload, and caspase-12-mediated apoptosis activation in HR-treated N2a cells. Interestingly, melatonin treatment reversed the decreased Pak2 expression under HR stress. Knockdown of Pak2 abolished the protective effects of melatonin on ER stress, oxidative stress, and caspase-12-related N2a cells death. Additionally, we found that Pak2 was regulated by melatonin via the AMPK pathway; inhibition of AMPK prevented melatonin-mediated Pak2 upregulation, a result that was accompanied by an increase in N2a cell death. Altogether, these results identify the AMPK-Pak2 axis as a new signaling pathway responsible for ER stress and N2a cell viability under HR injury. Modulation of the AMPK-Pak2 cascade via supplementation of melatonin might be considered an effective approach to attenuate reperfusion-mediated N2a cell damage via repression of ER stress.

Anti-tumor effect of LATS2 on liver cancer death: Role of DRP1-mediated mitochondrial division and the Wnt/β-catenin pathway

Large tumor suppressor 2 (LATS2), an important mediator of the cell apoptotic response pathway, has been linked to the progression of several cancers. Here, we described the molecular feature of LATS2 as a novel antitumor factor in liver cancer cells in vitro. Western blotting was used to detect the expression of LATS2 and its downstream factors. ELISA, immunofluorescence, and flow cytometry were used to evaluate the alterations of mitochondrial function in response to LATS2 overexpression. Adenovirus-loaded LATS2 and siRNA against DRP1 were transfected into liver cancer cells to overexpress LATS2 and knockdown DRP1 expression, respectively. The results of the present study demonstrated that overexpression of LATS2 was closely associated with more liver cancer cell death. Mechanistically, LATS2 overexpression increased the expression of DRP1, and DRP1 elevated mitochondrial division, an effect that was accompanied by mitochondrial dysfunction, including mitochondrial membrane potential reduction, mitochondrial respiratory complex downregulation, mitochondrial cyt-c release into the nucleus and mitochondrial oxidative injury. Moreover, LATS2 overexpression also initiated mitochondrial apoptosis, and this process was highly dependent on DRP1-related mitochondrial division. Molecular investigations demonstrated that LATS2 modulated DRP1 expression via the Wnt/β-catenin pathway. Inhibition of the Wnt/β-catenin pathway pregented LATS2-mediated DRP1 upregulation, ultimately sustaining mitochondrial function and cell viability in the presence of LATS2 overexpression. Altogether, the above data identify LATS2-Wnt/β-catenin/DRP1/mitochondrial division as a novel anticancer signaling pathway promoting cancer cell death, which might be an attractive therapeutic target for the treatment of hepatocellular carcinoma.

Nurr1 Promotes Lung Cancer Apoptosis Via Enhancing Mitochondrial Stress and p53-Drp1 Pathway

OBJECTIVE

Mitochondrial homeostasis is vital for the progression of lung cancer. Nurr1 has been identified as a novel mediator of mitochondrial homeostasis in several types of cancers. The aim of our study was to investigate whether Nurr1 modulates the viability of A549 lung cancer cells by inducing mitochondrial dysfunction, with a focus on the p53-Drp1 signaling pathway.

METHODS

western blotting, ELISA and immunofluorescence assay was used to verify the alterations of cell death. siRNA was used to determine the role of p53-Drp1 pathway in lung cancer death.

RESULTS

Nurr1 was downregulated in A549 lung cancer cells compared to normal pulmonary epithelial cells. Interestingly, overexpression of Nurr1 reduced the viability of A549 lung cancer cells by activating apoptosis and mitochondrial stress. At the molecular level, we provide data to support the regulatory effects of Nurr1 on the p53-Drp1 signaling pathway. Blockade of the p53-Drp1 signaling pathway abolished the proapoptotic action of Nurr1 on A549 cells and sustained mitochondrial homeostasis.

CONCLUSION

Taken together, our results depict the tumor-suppressive role played by Nurr1 in A549 lung cancer in vitro and show that the anticancer effects of Nurr1 are executed via triggering of mitochondrial dysfunction and activation of the p53-Drp1 signaling pathway.