Atorvastatin prevents Angiotensin II induced myocardial hypertrophy in vitro via CCAAT/enhancer-binding protein β

Soluble epoxide hydrolase and TRPC3 channels jointly contribute to homocysteine-induced cardiac hypertrophy: Interrelation and regulation by C/EBPβ

OBJECTIVES

Studies in certain cardiac hypertrophy models suggested the individual role of soluble epoxide hydrolase (sEH) and canonical transient receptor potential 3 (TRPC3) channels, however, whether they jointly mediate hypertrophic process remains unexplored. Hyperhomocysteinemia promotes cardiac hypertrophy while the involvement of sEH and TRPC3 channels remains unknown. This study aimed to explore the role of, and interrelation between sEH and TRPC3 channels in homocysteine-induced cardiac hypertrophy.

METHODS

Rats were fed methionine-enriched diet to induce hyperhomocysteinemia. H9c2 cells and neonatal rat cardiomyocytes were incubated with homocysteine. Cardiac hypertrophy was evaluated by echocardiography, histological examination, immunofluorescence imaging, and expressions of hypertrophic markers. Epoxyeicosatrienoic acids (EETs) were determined by ELISA. TRPC3 current was recorded by patch-clamp. Gene promotor activity was measured using dual-luciferase reporter assay.

RESULTS

Inhibition of sEH by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) reduced ventricular mass, lowered the expression of hypertrophic markers, decreased interstitial collagen deposition, and improved cardiac function in hyperhomocysteinemic rats, associated with restoration of EETs levels in myocardium. TPPU or knockdown of sEH suppressed TRPC3 transcription and translation as well as TRPC3 current that were enhanced by homocysteine. Exogenous 11,12-EET inhibited homocysteine-induced TRPC3 expression and cellular hypertrophy. Silencing C/EBPβ attenuated, while overexpressing C/EBPβ promoted homocysteine-induced hypertrophy and expressions of sEH and TRPC3, resulting respectively from inhibition or activation of sEH and TRPC3 gene promoters.

CONCLUSIONS

sEH and TRPC3 channels jointly contribute to homocysteine-induced cardiac hypertrophy. Homocysteine transcriptionally activates sEH and TRPC3 genes through a common regulatory element C/EBPβ. sEH activation leads to an upregulation of TRPC3 channels via a 11,12-EET-dependent manner.

Atorvastatin attenuates cardiac hypertrophy through AMPK/miR-143-3p/Bcl2 axis

Atorvastatin is employed as a lipid lowering agent and its heart protective effect has been recently reported as well. However, the mechanism of atorvastatin in attenuating cardiac hypertrophy and inhibiting cardiac failure is unclear. In our study, cardiac hypertrophy was induced in rats using transverse aortic constriction (TAC) method and in cardiomyocytes using angiotensin II (Ang II). Atorvastatin significantly suppressed TAC-induced heart weight increase and cardiomyocytes apoptosis in rats. At a molecular level, we found that miR-143-3p was significantly up-regulated, and the up-regulation could be inhibited by atorvastatin via activating AMPK pathway. Furthermore, it was validated that Bcl2 was one of the target genes of miR-143-3p. Taken together, the data indicated that miR-143-3p aggravated cardiac hypertrophy by inducing cardiomyocytes apoptosis through inhibiting Bcl2 expression. This study demonstrated the effects of atorvastatin in attenuating cardiac hypertrophy and inhibiting cardiac failure, which is depending on Bcl2 expression via miR-143-3p inhibition by AMPK activation.

Klotho attenuates angiotensin II‑induced cardiotoxicity through suppression of necroptosis and oxidative stress

Hyperglycemia is known to lead to cardiac injury and inflammation through the reactive oxygen species (ROS)‑Toll‑like receptor 4 (TLR4)‑necroptosis pathway. Similarly, angiotensin II (Ang II) activates the TLR4‑nuclear factor κB (NF‑κB) p65 pathway, while the protein Klotho is known to inhibit this pathway, protecting cardiac cells from Ang II‑induced injury. However, there is currently a lack of data on whether necroptosis participates in Ang II‑induced cardiac injury and whether the Klotho protein has an effect on this process. The present study aimed to explore whether inhibition of the TLR4/NF‑κB p65 necroptosis pathway is involved in the Klotho protein‑mediated protection against the Ang II‑induced cardiac injury and inflammation. H9c2 cardiac cells were incubated with 0.01 mM Ang II. Western blotting was used to assess the expression of receptor‑interacting protein kinase 3 (RIP3), mixed‑lineage kinase domain‑like protein (MLKL), TLR4 and NF‑κB p65. The present study also assessed injury indexes: Inflammatory cytokine expression, mitochondrial membrane potential (ΔΨm), apoptosis, ROS production and cell viability. The expression of TLR4, phosphorylated (p)‑NF‑κB p65, RIP3 and MLKL were increased by incubation with Ang II in H9c2 cells. The pretreatment of H9c2 cells with necrostatin‑1 (Nec‑1, an inhibitor of necroptosis) or TAK‑242 (a small molecule inhibitor of TLR4) attenuated the upregulation of RIP3 and MLKL caused by Ang II. Klotho protein cotreatment also reversed the Ang II‑induced upregulation of TLR4, p‑NF‑κB p65, RIP3 and MLKL. Furthermore, Ang II decreased cell viability and upregulated the secretion of inflammatory cytokines, ΔΨm loss and ROS generation blocked by pretreatment with Nec‑1 or Klotho protein. Thus, it was determined that Klotho can attenuate the Ang II‑induced necroptosis of cardiomyocytes through the TLR4/NF‑κB p65 pathway, which suggests that Klotho could be a potential therapeutic drug against Ang II‑induced cardiotoxicity.

Metabolic impairment in response to early induction of C/EBPβ leads to compromised cardiac function during pathological hypertrophy

Chronic pressure overload-induced left ventricular hypertrophy in heart is preceded by a metabolic perturbation that prefers glucose over lipid as substrate for energy requirement. Here, we establish C/EBPβ (CCAAT/enhancer-binding protein β) as an early marker of the metabolic derangement that triggers the imbalance in fatty acid (FA) oxidation and glucose uptake with increased lipid accumulation in cardiomyocytes during pathological hypertrophy, leading to contractile dysfunction and endoplasmic reticulum (ER) stress. This is the first study that shows that myocardium-targeted C/EBPβ knockdown prevents the impaired cardiac function during cardiac hypertrophy led by maladaptive metabolic response with persistent hypertrophic stimuli, whereas its targeted overexpression in control increases lipid accumulation significantly compared to control hearts. A new observation from this study was the dual and opposite transcriptional regulation of the alpha and gamma isoforms of Peroxisomal proliferator activated receptors (PPARα and PPARγ) by C/EBPβ in hypertrophied cardiomyocytes. Before the functional and structural remodeling sets in the diseased myocardium, C/EBPβ aggravates lipid accumulation with the aid of the increased FA uptake involving induced PPARγ expression and decreased fatty acid oxidation (FAO) by suppressing PPARα expression. Glucose uptake into cardiomyocytes was greatly increased by C/EBPβ via PPARα suppression. The activation of mammalian target of rapamycin complex-1 (mTORC1) during increased workload in presence of glucose as the only substrate was prevented by C/EBPβ knockdown, thereby abating contractile dysfunction in cardiomyocytes. Our study thus suggests that C/EBPβ may be considered as a novel cellular marker for deranged metabolic milieu before the heart pathologically remodels itself during hypertrophy.

The long noncoding RNA LOC105374325 causes podocyte injury in individuals with focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a common kidney disease that results in nephrotic syndrome. FSGS arises from dysfunction and apoptosis of podocytes in the glomerulus of the kidney, leading to podocytopathy. The molecular mechanisms underlying podocyte apoptosis remain incompletely understood. Using an array of gene expression profiling, PCR, and in situ hybridization assay, we found here that the levels of the long noncoding RNA LOC105374325 were elevated in the renal podocytes of individuals with FSGS. We also observed that the microRNAs miR-34c and miR-196a/b down-regulated the expression of the apoptosis regulators BCL2-associated X, apoptosis regulator (Bax), and BCL2 antagonist/killer 1 (Bak) in podocytes. Competitive binding between LOC105374325 and miR-34c or miR-196a/b increased Bax and Bak levels and caused podocyte apoptosis. Of note, the mitogen-activated protein kinase P38 and the transcription factor CCAAT enhancer-binding protein β (C/EBPβ) up-regulated LOC105374325 expression. P38 inhibition or C/EBPβ silencing decreased LOC105374325 levels and inhibited apoptosis in adriamycin-treated podocytes. LOC105374325 overexpression decreased miR-34c and miR-196a/b levels, increased Bax and Bak levels, and induced proteinuria and focal segmental lesions in mice. In conclusion, activation of the P38/C/EBPβ pathway stimulates the expression of LOC105374325, which, in turn, increases Bax and Bak levels and causes apoptosis by competitively binding to miR-34c and miR-196a/b in the podocytes of individuals with FSGS.

Anti-hypertrophy effect of atorvastatin on myocardium depends on AMPK activation-induced miR-143-3p suppression via Foxo1

Left ventricular hypertrophy (LVH) is a pathological characteristic shared by distinct heart disorders. Atorvastatin is employed as a lipid lowering agent and its heart protection effect has been recently reported as well. Thus, the current study attempted to validate the anti-hypertrophy effect of atorvastatin as well as the associated mechanism. Hypertrophic feature was induced in rats using transverse aortic constriction (TAC) method and in cardiomyocytes using angiotensin II (Ang II). Then the animals and cells were treated with atorvastatin and the effect on cardiac weight and structure as well as cell viability, surface area, and apoptosis was assessed. The mechanism associated with the anti-hypertrophy effect of atorvastatin was further explored by focusing on the AMPK/Foxo1/miR-143-3p axis. The results showed that the administration of atorvastatin significantly suppressed TAC-induced heart weight increase and attenuated cardiac structure deteriorations in rats. In in vitro assays, atorvastatin increased cell viability, and reduced cell surface area and apoptosis in Ang II-treated H9c2 cells. At molecular level, atorvastatin activated AMPK, which further promoted Foxo1 activation and suppressed miR-143-3p level. The key role of AMPK during atorvastatin treatment was further validated by subjecting Ang II-treated H9c2 cells to co-incubation of atorvastatin and Compound C, which blocked the pro-survival and anti-hypertrophy effect of atorvastatin on H9c2 cells. The findings outlined in the current study confirmed the anti-hypertrophy effect of atorvastatin and provided a preliminary explanation on the mechanism associated with the treatment: the protective effect of atorvastatin on myocardium against hypertrophy depended on miR-143-3p inhibition via AMPK and Foxo1 activation.

Atorvastatin Attenuates Myocardial Hypertrophy Induced by Chronic Intermittent Hypoxia In Vitro Partly through miR-31/PKCε Pathway

Atorvastatin is proven to ameliorate cardiac hypertrophy induced by chronic intermittent hypoxia (CIH). However, little is known about the mechanism by which atorvastatin modulates CIH-induced cardiac hypertrophy, and whether specific hypertrophyrelated microRNAs are involved in the modulation. MiR-31 plays key roles in the development of cardiac hypertrophy induced by ischemia/hypoxia. This study examined whether miR-31 was involved in the protective role of atorvastatin against CIH-induced myocardial hypertrophy. H9c2 cells were subjected to 8-h intermittent hypoxia per day in the presence or absence of atorvastatin for 5 days. The size of cardiomyocytes, and the expression of caspase 3 and miR-31 were determined by Western blotting and RT-PCR, respectively. MiR-31 mimic or Ro 31-8220, a specific inhibitor of protein kinase C epsilon (PKCε), was used to determine the role of miR-31 in the anti-hypertrophic effect of atorvastatin on cardiomyocytes. PKCε in the cardiomyocytes with miR-31 upregulation or downregulation was detected using RT-PCR and Western blotting. The results showed that CIH induced obvious enlargement of cardiomyocytes, which was paralleled with increased atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and slow/beta cardiac myosin heavy-chain (MYH7) mRNA levels. All these changes were reversed by the treatment with atorvastatin. Meanwhile, miR-31 was increased by CIH in vitro. Of note, the atorvastatin pretreatment significantly increased the mRNA and protein expression of PKCe and decreased that of miR-31. Moreover, overexpression of miR-31 abolished the anti-hypertrophic effect of atorvastatin on cardiomyocytes. Upregulation and downregulation of miR-31 respectively decreased and increased the mRNA and protein expression of PKCε. These results suggest that atorvastatin provides the cardioprotective effects against CIH probably via up-regulating PKCε and down-regulating miR-31.