Excess phosphate promotes SARS­CoV­2 N protein­induced NLRP3 inflammasome activation via the SCAP­SREBP2 signaling pathway.

Hyperphosphatemia or severe acute respiratory syndrome coronavirus 2 (SARS­CoV­2) infection can promote cardiovascular adverse events in patients with chronic kidney disease. Hyperphosphatemia is associated with elevated inflammation and sterol regulatory element binding protein 2 (SREBP2) activation, but the underlying mechanisms in SARS­CoV­2 that are related to cardiovascular disease remain unclear. The present study aimed to elucidate the role of excess inorganic phosphate (PI) in SARS­CoV­2 N protein­induced NLRP3 inflammasome activation and the underlying mechanisms in vascular smooth muscle cells (VSMCs). The expression levels of SARS­CoV­2 N protein, SREBP cleavage­activating protein (SCAP), mature N­terminal SREBP2, NLRP3, procaspase­1, cleaved caspase­1, IL­1ß and IL­18 were examined by western blotting. The expression levels of SREBP2, HMG­CoA reductase, HMGCS1, low density lipoprotein receptor, proprotein convertase subtilisin/kexin type 9 (PCSK9), SREBP1c, fatty acid synthase, stearyl coenzyme A desaturase 1, acetyl­CoA carboxylase α and ATP­citrate lyase were determined by reverse transcription­quantitative PCR. The translocation of SCAP or NLRP3 from the endoplasmic reticulum to the Golgi was detected by confocal microscopy. The results showed that excess PI promoted SCAP­SREBP and NLRP3 complex translocation to the Golgi, potentially leading to NLRP3 inflammasome activation and lipogenic gene expression. Furthermore, PI amplified SARS­CoV­2 N protein­induced inflammation via the SCAP­SREBP pathway, which facilitates NLRP3 inflammasome assembly and activation. Inhibition of phosphate uptake with phosphonoformate sodium alleviated NLRP3 inflammasome activation and reduced SREBP­mediated lipogenic gene expression in VSMCs stimulated with PI and with SARS­CoV­2 N protein overexpression. Inhibition of SREBP2 or small interfering RNA­induced silencing of SREBP2 effectively suppressed the effect of PI and SARS­CoV­2 N protein on NLRP3 inflammasome activation and lipogenic gene expression. In conclusion, the present study identified that PI amplified SARS­CoV­2 N protein­induced NLRP3 inflammasome activation and lipogenic gene expression via the SCAP­SREBP signaling pathway.

SARS-CoV-2 nucleocapsid protein promotes TMAO-induced NLRP3 inflammasome activation by SCAP-SREBP signaling pathway.

The sterol regulatory element-binding protein (SREBP) activation and cytokine level were significantly increased in coronavirus disease-19. The NLRP3 inflammasome is an amplifier for cellular inflammation. This study aimed to elucidate the modulatory effect of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP) on trimethylamine N-oxide (TMAO)-induced lipogenesis and NLRP3 inflammasome activation and the underlying mechanisms in vascular smooth muscle cells (VSMCs). Our data indicated that SARS-CoV-2 NP activates the dissociation of the SREBP cleavage activating protein (SCAP) from the endoplasmic reticulum, resulting in SREBP activation, increased lipogenic gene expression, and NLRP3 inflammasome activation. TMAO was applied to VSMC-induced NLRP3 inflammasome by promoting the SCAP-SREBP complex endoplasmic reticulum-to-Golgi translocation, which facilitates directly binding of SARS-CoV-2 NP to the NLRP3 protein for NLRP3 inflammasome assembly. SARS-CoV-2 NP amplified the TMAO-induced lipogenic gene expression and NLRP3 inflammasome. Knockdown of SCAP-SREBP2 can effectively reduce lipogenic gene expression and alleviate NLRP3 inflammasome-mediated systemic inflammation in VSMCs stimulated with TMAO and SARS-CoV-2 NP. These results reveal that SARS-CoV-2 NP amplified TMAO-induced lipogenesis and NLRP3 inflammasome activation via priming the SCAP-SREBP signaling pathway.

Hydrogen sulfide attenuates TMAO­induced macrophage inflammation through increased SIRT1 sulfhydration.

Chronic inflammation is a key factor that accelerates the progression of inflammatory vascular disease. Hydrogen sulfide (H2S) has potent anti­inflammatory effects; however, its underlying mechanism of action has not been fully elucidated. The present study aimed to investigate the potential effect of H2S on sirtuin 1 (SIRT1) sulfhydration in trimethylamine N­oxide (TMAO)­induced macrophage inflammation, and its underlying mechanism. Pro­inflammatory M1 cytokines (MCP­1, IL­1ß, and IL­6) and anti­inflammatory M2 cytokines (IL­4 and IL­10) were detected by RT­qPCR. CSE, p65 NF­κB, p­p65 NF­κB, IL­1ß, IL­6 and TNF­α levels were measured by Western blot. The results revealed that cystathionine γ­lyase protein expression was negatively associated with TMAO­induced inflammation. Sodium hydrosulfide (a donor of H2S) increased SIRT1 expression and inhibited the expression of inflammatory cytokines in TMAO­stimulated macrophages. Furthermore, nicotinamide, a SIRT1 inhibitor, antagonized the protective effect of H2S, which contributed to P65 NF­κB phosphorylation and upregulated the expression of inflammatory factors in macrophages. H2S ameliorated TMAO­induced activation of the NF­κB signaling pathway via SIRT1 sulfhydration. Moreover, the antagonistic effect of H2S on inflammatory activation was largely eliminated by the desulfhydration reagent dithiothreitol. These results indicated that H2S may prevent TMAO­induced macrophage inflammation by reducing P65 NF­κB phosphorylation via the upregulation and sulfhydration of SIRT1, suggesting that H2S may be used to treat inflammatory vascular diseases.

Sterol-resistant SCAP Overexpression in Vascular Smooth Muscle Cells Accelerates Atherosclerosis by Increasing Local Vascular Inflammation through Activation of the NLRP3 Inflammasome in Mice.

Atherosclerosis is a serious age-related pathology, and one of its hallmarks is the presence of chronic inflammation. Sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) is a cholesterol sensor that plays an essential role in regulating intracellular cholesterol homeostasis. Accordingly, dysregulation of the SCAP-SREBP pathway has been reported to be closely associated with an increased risk of obesity, hypercholesterolemia, and cardiovascular disease. In this study, we explored whether sterol-resistant SCAP (D443N mutation) in vascular smooth muscle cells (VSMCs) of mice promotes vascular inflammation and accelerates the occurrence and progression of atherosclerosis. We established a transgenic knock-in mouse model of atherosclerosis with an activating D443N mutation at the sterol-sensing domain of SCAP (SCAPD443N) by microinjection. Next, SCAPD443N/ApoE-/- mice were generated by crossing SCAPD443N mice with apolipoprotein E-/- (ApoE-/-) background mice. We found that sterol-resistant SCAP markedly amplified and accelerated the progression of atherosclerotic plaques in SCAPD443N/ApoE-/- mice compared with that in control ApoE-/- mice. Similarly, in SCAPD443N mice, aortic atherosclerotic plaques both appeared earlier and were greater in number than that in control SCAP+/+ mice, both of which were fed a Western diet for 12 or 24 weeks. Moreover, we observed that sterol-resistant SCAP significantly increased local inflammation and induced endothelial dysfunction in the aortas of SCAPD443N mice and SCAPD443N/ApoE-/- mice. In vitro, we also found that sterol-resistant SCAP overexpression in VSMCs increased the release of inflammatory cytokines and induced endothelial cell injury when both cell types were cocultured. Furthermore, we demonstrated that sterol-resistant SCAP overexpression in VSMCs promoted SCAP and NLRP3 inflammasome cotranslocation to the Golgi and increased the activation of the NLRP3 inflammasome pathway. These findings suggested that sterol-resistant SCAP in VSMCs of mice induced vascular inflammation and endothelial dysfunction, consequently accelerating atherosclerosis by activating the NLRP3 inflammasome pathway.

SCAP knockout in SM22α-Cre mice induces defective angiogenesis in the placental labyrinth.

The placental labyrinth is important for the exchange of nutrients and gases between the mother and the embryo in mice. This interface contains cells of both trophoblast and allantoic mesodermal origin that together produce maternal blood sinuses and placental blood vessels. However, the molecular mechanisms that take place during process of placental labyrinth development, especially concerning fetal capillaries, are not well understood. SREBP cleavage-activating protein (SCAP), a membrane protein, is required for the synthesis of fatty acids and cholesterol. Recently, when we crossed the offspring of the cross between smooth muscle 22 alpha (SM22α)- Cre recombinase (Cre) mice and SCAPloxp/loxp mice to research the function of SCAP in vascular smooth muscle cells (VSMCs) during certain pathological processes, we found that there were no resultant SM22α-Cre-specific SCAP knockout (KO) pups (SM22α-Cre+SCAPflox/flox; hereafter referred to as SCAP KO). Through anatomic studies of these embryos and placentas, we found that SCAP KO resulted in defective placental vessels and abnormal fetal morphology. Further immunohistochemical and immunocytochemical analyses suggested that SCAP is knocked out in the pericytes of the placental labyrinth. Compared to wildtype mice, SCAP KO placentas had abnormal vasculature in the labyrinth and lower levels of angiogenesis. By using RNA-seq and western blotting, we found that the expression of some genes and proteins in SCAP KO placentas was changed, including those related to pericyte/endothelial interactions genes and angiogenesis. Our results suggest that the proper organizational structure of the placental labyrinth depends on SCAP expression in pericytes.

FGF21 induces autophagy-mediated cholesterol efflux to inhibit atherogenesis via RACK1 up-regulation.

Fibroblast growth factor 21 (FGF21) acts as an anti-atherosclerotic agent. However, the specific mechanisms governing this regulatory activity are unclear. Autophagy is a highly conserved cell stress response which regulates atherosclerosis (AS) by reducing lipid droplet degradation in foam cells. We sought to assess whether FGF21 could inhibit AS by regulating cholesterol metabolism in foam cells via autophagy and to elucidate the underlying molecular mechanisms. In this study, ApoE-/- mice were fed a high-fat diet (HFD) with or without FGF21 and FGF21 + 3-Methyladenine (3MA) for 12 weeks. Our results showed that FGF21 inhibited AS in HFD-fed ApoE-/- mice, which was reversed by 3MA treatment. Moreover, FGF21 increased plaque RACK1 and autophagy-related protein (LC3 and beclin-1) expression in ApoE-/- mice, thus preventing AS. However, these proteins were inhibited by LV-RACK1 shRNA injection. Foam cell development is a crucial determinant of AS, and cholesterol efflux from foam cells represents an important defensive measure of AS. In this study, foam cells were treated with FGF21 for 24 hours after a pre-treatment with 3MA, ATG5 siRNA or RACK1 siRNA. Our results indicated that FGF21-induced autophagy promoted cholesterol efflux to reduce cholesterol accumulation in foam cells by up-regulating RACK1 expression. Interestingly, immunoprecipitation results showed that RACK1 was able to activate AMPK and interact with ATG5. Taken together, our results indicated that FGF21 induces autophagy to promote cholesterol efflux and reduce cholesterol accumulation in foam cells through RACK1-mediated AMPK activation and ATG5 interaction. These results provided new insights into the molecular mechanisms of FGF21 in the treatment of AS.

Fibroblast growth factor-21 alleviates hypoxia/reoxygenation injury in H9c2 cardiomyocytes by promoting autophagic flux.

Fibroblast growth factor (FGF)­21, a member of the family of FGFs, exhibits protective effects against myocardial ischemia and ischemia/reperfusion injury; it is also an enhancer of autophagy. However, the mechanisms underlying the protective role of FGF­21 against cardiomyocyte hypoxia/reoxygenation (H/R) injury remain unclear. The present study aimed to investigate the effect of FGF­21 on H9c2 cardiomyocyte injury induced by H/R and the mechanism associated with changes in autophagy. Cultured H9c2 cardiomyocytes subjected to hypoxia were treated with a vehicle or FGF­21 during reoxygenation. The viability of H9c2 rat cardiomyocytes was measured using Cell Counting Kit­8 and trypan blue exclusion assays. The contents of creatine kinase (CK) and creatine kinase isoenzymes (CK­MB), cardiac troponin I (cTnT), cardiac troponin T (cTnI) and lactate dehydrogenase (LDH) in culture medium were detected with a CK, CK­MB, cTnT, cTnI and LDH assay kits. The protein levels were examined by western blot analysis. Autophagic flux was detected by Ad­mCherry­GFP­LC3B autophagy fluorescent adenovirus reagent. The results indicated that FGF­21 alleviated H/R­induced H9c2 myocardial cell injury and enhanced autophagic flux during H/R, and that this effect was antagonized by co­treatment with 3­methyladenine, an autophagy inhibitor. Furthermore, FGF­21 increased the expression levels of Beclin­1 and Vps34 proteins, but not of mechanistic target of rapamycin. These data indicate that FGF­21 treatment limited H/R injury in H9c2 cardiomyocytes by promoting autophagic flux through upregulation of the expression levels of Beclin­1 and Vps34 proteins.

FGF21 protects human umbilical vein endothelial cells against high glucose-induced apoptosis via PI3K/Akt/Fox3a signaling pathway.

AIMS: Diabetic macroangiopathy is the main cause of morbidity and mortality in patients with diabetes. Endothelial cell injury is a pathological precondition for diabetic macroangiopathy. Fibroblast growth factor 21 (FGF21) is a key metabolic regulator which has recently been suggested to protect cardiac myocytes and vascular cells against oxidative stress-induced injury in vitro and vivo. In this study, we aimed to investigate the protective capacity of FGF21 in human umbilical vein endothelial cells (HUVECs) against high glucose (HG)-induced apoptosis via phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt)/FoxO3a pathway. METHODS: The cell viability was examined by CCK-8 assay, Intracellular ROS levels were measured by the detection of the fluorescent product formed by the oxidation of DCFH-DA, Apoptosis was analyzed using Hoechst 33258 nuclear staining and Flow Cytometry Analysis (FCA), the expression of protein were detected by Western blot. RESULTS: Results show that pretreating HUVECs with FGF21 before exposure to HG increases cell viability, while decreasing apoptosis and the generation of reactive oxygen species. Western blot analysis shows that HG reduces the phosphorylation of Akt and FoxO3a, and induces nuclear localization of FoxO3a. The effects were significantly reversed by FGF21 pre-treatment. Furthermore, the protective effects of FGF21 were prevented by PI3K/Akt inhibitor LY294002. CONCLUSIONS: Our data demonstrates that FGF21 protects HUVECs from HG-induced oxidative stress and apoptosis via the activation of PI3K/Akt/FoxO3a signaling pathway.

Role of PCSK9 in lipid metabolism and atherosclerosis.

Elevated plasma low-density lipoprotein cholesterol (LDL-C) is an important risk factor for cardiovascular diseases. Statins are the most widely used therapy for patients with hyperlipidemia. However, a significant residual cardiovascular risk remains in some patients even after maximally tolerated statin therapy. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a new pharmacologically therapeutic target for decreasing LDL-C. PCSK9 reduces LDL intake from circulation by enhancing LDLR degradation and preventing LDLR recirculation to the cell surface. Moreover, PCSK9 inhibitors have been approved for patients with either familial hypercholesterolemia or atherosclerotic cardiovascular disease, who require additional reduction of LDL-C. In addition, PCSK9 inhibition combined with statins has been used as a new approach to help reduce LDL-C levels in patients with either statin intolerance or unattainable LDL goal. This review will discuss the emerging anti-PCSK9 therapies in the regulation of cholesterol metabolism and atherosclerosis.

Molecular mechanisms of autophagy in cardiac ischemia/reperfusion injury (Review).

Autophagy is a maintenance process for recycling long-lived proteins and cytoplasmic organelles. The level of this process is enhanced during ischemia/reperfusion (I/R) injury. Autophagy can trigger survival signaling in myocardial ischemia, whereas defective autophagy during reperfusion is detrimental. Autophagy can be regulated through multiple signaling pathways in I/R, including Beclin­1/class III phosphatidylinositol­3 kinase (PI­3K), adenosine monophosphate activated protein kinase/mammalian target of rapamycin (mTOR), and PI­3K/protein kinase B/mTOR pathways, which consequently lead to different functions. Thus, autophagy has both protective and detrimental functions, which are determined by different signaling pathways and conditions. Targeting the activation of autophagy can be a promising new therapeutic strategy for treating cardiovascular disease.

Transforming growth factor ß1 promotes migration and invasion in HepG2 cells: Epithelial­to­mesenchymal transition via JAK/STAT3 signaling.

Transforming growth factor ß1 (TGFß1) is a cytokine with multiple functions. TGFß1 significantly induces migration and invasion of liver cancer cells. However, the molecular mechanisms underlying this effect remain unclear. Epithelial­to­mesenchymal transition (EMT) is crucial for the development of invasion and metastasis in human cancers. The aim of the present study was to determine whether TGFß1­induced EMT promoted migration and invasion in HepG2 cells. The underlying mechanism and the effect of EMT on HepG2 cells were also investigated. The results demonstrated that TGFß1 may induce EMT to promote migration and invasion of HepG2 cells, and this effect depends on activation of the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling pathway. JAK/STAT3 signaling is involved in human malignancies, including lung cancer, and is implicated in cell transformation, tumorigenicity, EMT and metastasis. In the present study, TGFß1 also activated JAK/STAT3 signaling in HepG2 cells and promoted Twist expression, but these events were abolished by treatment with the STAT3 inhibitor AG490. Additionally, Twist siRNA blocked TGFß1­induced EMT. Thus, TGFß1 was shown to induce EMT, thereby promoting the migration and invasion of HepG2 cells via JAK/STAT3/Twist signaling.

[Corrigendum] Insights into the pathogenesis of Mycoplasma pneumoniae (Review).

Following the publication of this review, an interested reader alerted us to the fact that a couple of figures had been reproduced from a pair of previous publications without proper acknowledgement of the original source/authors. Figs. 2 and 3, as featured in our review, had originally appeared (with only minor modifications) as Figs. 2 and 4, respectively, in the following articles: Rottem S: Interaction of mycoplasmas with host cells. Physiol Rev 83: 417-32, 2003; and Pilo P, Vilei EM, Peterhans E, Bonvin-Klotz L, Stoffel MH, Dobbelaere D and Frey J: A metabolic enzyme as a primary virulence factor of Mycoplasma mycoides subsp. mycoides small colony. J Bacteriol 187: 6824-6831, 2005. Permission to publish these figures was sought retrospectively from the publishers [The American Physiological Society (Fig. 2) and The American Society of Microbiology (Fig 3)]. Subsequently, Figs. 2 and 3 are reprinted in this Corrigendum, together with strap-lines that properly acknowledge the source articles. In addition, we omitted to explain that the glycerol metabolism causing injury in host cells refers to Mycoplasma mycoides subsp. mycoides. Consequently, this information has also been inserted into the corrected legend for Fig. 3 (opposite), with a pair of supporting references. We profusely apologize to the authors of the previous publications (Dr Joachim Frey and colleagues) for our having failed to include a proper acknowledgement of their figure, or to have credited their work appropriately. [the original article was published in the Molecular Medicine Reports 14: 4030-4036, 2016; DOI: 10.3892/mmr.2016.5765].

Inhibition of Hydrogen Peroxide-Induced Human Umbilical Vein Endothelial Cells Aging by Allicin Depends on Sirtuin1 Activation.

BACKGROUND The abnormal activity of Sirtuin 1 (Sirt1) is closely related to the aging of vascular endothelial cells. As a bioactive molecule, allicin has antioxidant, anti-inflammatory, and lipid-regulating mechanisms. However, few reports about the relationship of allicin and Sirt1 have been published. In this study, we aimed to elucidate the effect of allicin on Human Umbilical Vein Endothelial Cells (HUVECs) aging induced by hydrogen peroxide (H2O2) and the role of Sirt1 in this phenomenon. MATERIAL AND METHODS HUVEC were exposed to H2O2 to establish the aging model. The expression of protein and RNA were detected by Western blot and Reverse transcription-quantitative polymerase chain reaction. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to assess cell viability. Sirt1 enzyme activity assay was used to analyze enzymatic activity. Reactive oxygen species was detected by dichlorofluorescein diacetate (DCFH-DA). Cell aging was detected by Senescence ß-Galactosidase (SA-ß-gal) staining. RESULTS Results of this study revealed that pretreating HUVECs with 5 ng/mL allicin before exposure to H2O2 resulted in increased cell viability and reduced reactive oxygen species generation. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) analysis showed that H2O2 attenuated the phosphorylation and activation of Sirt1 and increased the expression of plasminogen activator inhibitor-1(PAI-1) protein. Moreover, H2O2 also promoted HUVEC aging. These effects were significantly alleviated by 5 ng/mL allicin co-treatment. Furthermore, the anti-aging effects of allicin were abolished by the Sirt1 inhibitor nicotinamide (NAM). CONCLUSIONS Overall, the results demonstrated that allicin protects HUVECs from H2O2-induced oxidative stress and aging via the activation of Sirt1.

Insights into the pathogenesis of Mycoplasma pneumoniae (Review).

Mycoplasma are the smallest prokaryotic microbes present in nature. These wall­less, malleable organisms can pass through cell filters, and grow and propagate under cell­free conditions in vitro. Of the pathogenic Mycoplasma Mycoplasma pneumoniae has been examined the most. In addition to primary atypical pneumonia and community­acquired pneumonia with predominantly respiratory symptoms, M. pneumoniae can also induce autoimmune hemolytic anemia and other diseases in the blood, cardiovascular system, gastrointestinal tract and skin, and can induce pericarditis, myocarditis, nephritis and meningitis. The pathogenesis of M. pneumoniae infection is complex and remains to be fully elucidated. The present review aimed to summarize several direct damage mechanisms, including adhesion damage, destruction of membrane fusion, nutrition depletion, invasive damage, toxic damage, inflammatory damage and immune damage. Further investigations are required for determining the detailed pathogenesis of M. pneumoniae.

Resveratrol inhibits doxorubicin-induced cardiotoxicity via sirtuin 1 activation in H9c2 cardiomyocytes.

Doxorubicin (DOX) is an efficient drug used in cancer therapy; however, it can induce severe cytotoxicity, which limits its clinical application. In the present study, the effects of resveratrol (RES) on sirtuin 1 (SIRT1) activation in mediating DOX-induced cytotoxicity in H9c2 cardiac cells was investigated. H9c2 cells were exposed to 5 µM DOX for 24 h to establish a model of DOX cardiotoxicity. Apoptosis of H9c2 cardiomyocytes was assessed using the MTT assay and Hoechst nuclear staining. The results demonstrated that pretreating H9c2 cells with RES prior to the exposure of DOX resulted in increased cell viability and a decreased quantity of apoptotic cells. Western blot analysis demonstrated that DOX decreased the expression level of SIRT1. These effects were significantly alleviated by co-treatment with RES. In addition, the results demonstrated that DOX administration amplified forkhead box O1 (FoxO1) and P53 expression levels in H9c2 cells. RES was also found to protect against DOX-induced increases of FoxO1 and P53 expression levels in H9c2 cells. Furthermore, the protective effects of RES were arrested by the SIRT1 inhibitor nicotinamide. In conclusion, the results demonstrated that RES protected H9c2 cells against DOX-induced injuries via SIRT1 activation.

Hydrogen sulfide protects H9c2 cardiac cells against doxorubicin-induced cytotoxicity through the PI3K/Akt/FoxO3a pathway.

Doxorubicin (DOX) is an efficient drug used in cancer therapy that also produces reactive oxygen species (ROS) that induces severe cytotoxicity, which limits its clinical application. Hydrogen sulfide (H2S), a novel gasotransmitter, has been shown to exert cardioprotective effects. The present study aimed to determine whether exogenous H2S protects H9c2 cardiac cells against DOX-induced cytotoxicity and whether these protective effects are mediated through the PI3K/Akt/FoxO3a pathway. The H9c2 cardiac cells were exposed to 5 µM DOX for 24 h to establish a model of DOX-induced cardiotoxicity. The results showed that the treatment of H9c2 cardiac cells with sodium hydrosulfide (NaHS) for 30 min prior to DOX exposure markedly attenuated the phosphorylation of Akt and FoxO3a. Notably, pre-treatment of the H9c2 cells with NaHS significantly attenuated the nuclear localization of FoxO3a as well as the apoptosis of H9c2 cells induced by DOX. The treatment of H9c2 cells with N-acetyl-L-cysteine (NAC), a scavenger of ROS, prior to DOX exposure, also markedly increased the phosphorylation of Akt and FoxO3a which was inhibited by DOX alone. Furthermore, pre-treatment with LY294002, a selective inhibitor of PI3K/Akt, reversed the protective effect of H2S against DOX-induced injury of cardiomyocytes, as demonstrated by an increased number of apoptotic cells, a decrease in cell viability and the reduced phosphorylation of Akt and FoxO3a. These findings suggested that exogenous H2S attenuates DOX-induced cytotoxic effects in H9c2 cardiac cells through the PI3K/Akt/FoxO3a pathway.

Curcumin mediates reversion of HGF-induced epithelial-mesenchymal transition via inhibition of c-Met expression in DU145 cells.

The hepatocyte growth factor (HGF)/c-Met signaling pathway results in cancer cell scattering and invasion, and has been reported to participate in several types of cancer, including prostate and colorectal cancer. The downstream phosphorylation cascade of HGF, particularly the mitogen-activated protein kinase and phosphoinositide 3-kinase/AKT signaling pathway, regulates epithelial-mesenchymal transition (EMT). However, the mechanism by which these signaling pathways govern EMT, and whether certain kinases are able to respond to specific EMT effectors, remains to be elucidated. In the present study, an increase in the levels of vimentin, rather than co-regulation of certain EMT marker proteins, was observed in response to HGF-induced EMT in DU145 prostate cancer cells. In addition, it was observed that curcumin abrogated HGF-induced DU145 cell scattering and invasion. Furthermore, curcumin was able to effectively inhibit the HGF-induced increase in the levels of vimentin by downregulating the expression of phosphorylated c-Met, extracellular signal-regulated kinase and Snail. In conclusion, the results of the present study demonstrated that curcumin was able to reverse HGF-induced EMT, possibly by inhibiting c-Met expression in DU145 prostate cancer cells.

PI3K/Akt/FoxO3a signaling mediates cardioprotection of FGF-2 against hydrogen peroxide-induced apoptosis in H9c2 cells.

Cardiovascular disease is a growing major global public health problem. Oxidative stress is regarded as one of the key regulators of pathological physiology, which eventually leads to cardiovascular disease. However, mechanisms by which FGF-2 rescues cells from oxidative stress damage in cardiovascular disease is not fully elucidated. Herein this study was designed to investigate the protective effects of FGF-2 in H2O2-induced apoptosis of H9c2 cardiomyocytes, as well as the possible signaling pathway involved. Apoptosis of H9c2 cardiomyocytes was induced by H2O2 and assessed using methyl thiazolyl tetrazolium assay, Hoechst, and TUNEL staining. Cells were pretreated with PI3K/Akt inhibitor LY294002 to investigate the possible PI3K/Akt pathways involved in the protection of FGF-2. The levels of p-Akt, p-FoxO3a, and Bim were detected by immunoblotting. Stimulation with H2O2 decreased the phosphorylation of Akt and FoxO3a, and induced nuclear localization of FoxO3a and apoptosis of H9c2 cells. These effects of H2O2 were abrogated by pretreatment with FGF-2. Furthermore, the protective effects of FGF-2 were abolished by PI3K/Akt inhibitor LY294002. In conclusion, our data suggest that FGF-2 protects against H2O2-induced apoptosis of H9c2 cardiomyocytes via activation of the PI3K/Akt/FoxO3a pathway.

Resveratrol protects cardiomyocytes from doxorubicin-induced apoptosis through the AMPK/P53 pathway.

Doxorubicin (DOX) is an efficient drug used in cancer therapy; however, it has severe cardiotoxic side effects. The aim of the present study was to investigate the effects of resveratrol on the adenosine monophosphate-activated protein kinase (AMPK)/P53 pathway in mediating DOX-induced cytotoxicity. H9c2 cells were exposed to 5 µM DOX for 24 h to establish a model of DOX-induced cardiotoxicity. DOX administration amplified P53 and B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) expression and decreased Bcl-2 expression in H9c2 cells. Resveratrol increased the cell viability and decreased the apoptotic rate. In addition, resveratrol markedly increased the phosphorylation of AMPK. Of note, resveratrol protected against DOX-induced increases of P53 and Bax and also prevented the downregulation of Bcl-2 in H9c2 cells. Furthermore, AMPK inhibitor Compound C abolished the protective effects of resveratrol. The results of the present study therefore indicated that resveratrol protected H9c2 cells from DOX-induced apoptosis via the AMPK/P53 pathway.