Macrophage fatty acid oxidation in atherosclerosis.

Atherosclerosis significantly contributes to the development of cardiovascular diseases (CVD) and is characterized by lipid retention and inflammation within the artery wall. Multiple immune cell types are implicated in the pathogenesis of atherosclerosis, macrophages play a central role as the primary source of inflammatory effectors in this pathogenic process. The metabolic influences of lipids on macrophage function and fatty acid ß-oxidation (FAO) have similarly drawn attention due to its relevance as an immunometabolic hub. This review discusses recent findings regarding the impact of mitochondrial-dependent FAO in the phenotype and function of macrophages, as well as transcriptional regulation of FAO within macrophages. Finally, the therapeutic strategy of macrophage FAO in atherosclerosis is highlighted.

LncRNA MIAT knockdown alleviates oxygen-glucose deprivation­induced cardiomyocyte injury by regulating JAK2/STAT3 pathway via miR-181a-5p.

BACKGROUND: Coronary artery disease (CAD) is a common heart disease with high incidence and mortality. Myocardial ischemia is the main type of CAD, which negatively affects health worldwide. The aim of the present study was to investigate the function and mechanism of myocardial infarction-associated transcript (MIAT) in myocardial ischemia. METHODS: Human cardiomyocytes (HCM) were treated with oxygen-glucose deprivation (OGD) to set the in vitro model and mouse myocardial ischemia/reperfusion (I/R) was set for in vivo model. Cell viability and apoptosis were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, flow cytometry, and immunofluorescence analysis. Inflammatory cytokines levels were detected by enzyme-linked immunosorbent assay. Gene and protein expressions were identified by quantitative real time-polymerase chain reaction or Western blotting. The interaction of MIAT, miR-181a-5p, and janus kinase 2 (JAK2) was identified by dual-luciferase report assay. Mouse heart tissues histopathological condition were observed by hematoxylin and eosin assays. RESULTS: Expression of MIAT and JAK2 were increased in OGD-treated HCM and mice of I/R model group, and miR-181a-5p was decreased. MIAT silencing could reverse the OGD treatment induced cell proliferation inhibition, cleaved caspase-3 and Bcl2-associated X (Bax) levels increased, while those of B-cell lymphoma-2 (Bcl-2) and mitochondria's cyt-C decreased. Besides, MIAT knockdown attenuated the OGD-induced increase of tumor necrosis factor-α, interleukin (IL)-1ß, and IL-6 levels. Moreover, MIAT targeted miR-181a-5p to enhance the expression of JAK2 and signal Transducer and Activator of Transcription 3 (STAT3), and miR-181a-5p overexpression promoted proliferation, whereas it inhibited apoptosis in OGD-induced cardiomyocytes. Furthermore, the regulatory effects of MIAT knockdown in cell proliferation, apoptosis, and inflammatory injury was reversed by inhibition of miR-181a-5p or overexpression of JAK2 in OGD-treated HCM. Knockdown of MIAT reduced myocardial injury caused by I/R treatment in vivo. CONCLUSION: MIAT knockdown inhibited apoptosis and inflammation by regulating JAK2/STAT3 signaling pathway via targeting miR-181a-5p in myocardial ischemia model. MIAT can be a possible therapeutic target for controlling the progression of myocardial ischemia.

Antioxidant defence system is responsible for the toxicological interactions of mixtures: A case study on PFOS and PFOA in Daphnia magna.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are two types of perfluorinated compounds (PFCs) frequently studied in recent years due to their potential for bioaccumulation and toxicity to humans. Usually, PFCs can co-exist in various environment. Therefore, over- or under-estimated risk assessments would result if antagonism or synergism occurred in mixture toxicity. In the present study, the acute and chronic toxicities of single and mixtures of PFOA and PFOS to Daphnia magna were investigated. PFOS was more toxic than PFOA, both in 48-h acute toxicity and 21-d chronic toxicity. In acute toxicity tests, mixture toxicities showed strong synergistic effects on mortality. The experimental EC50 of the mixture is 4.44 × 10-5 mol/L, whereas the predicted EC50 is 8.19 × 10-5 mol/L by Concentration Addition Model and 9.73 × 10-5 mol/L by Independent Action Model. In chronic toxicity tests, synergistic effects were also found in the aspects of offspring. The offspring rate is reduced significantly to 39.8% at the 9.61 × 10-7 mol/L of mixture, while, PFOS and PFOA do not have effects when they are tested individually at corresponding concentrations. To explore the potential mechanism of the synergistic effect, the interactions between PFCs and proteins, including acetylcholinesterase, superoxide dismutase, catalase, ecdysone receptor and glutathione-S-transferase, were investigated by the Molecular Docking. The docking results revealed that the driving forces for the binding of PFCs with proteins were predominantly hydrophobic and hydrogen-bonding interactions. Based on the binding models, we deduced that the potential mechanism of synergism is that PFOS and PFOA have similar binding modes with catalase and have different binding modes with superoxide dismutase. Overall, these data provide experimental evidence that there is strong synergism in acute and chronic toxicity of mixtures to D. magna and demonstrate that molecular structure of some components of the antioxidant defence system contributes to the synergistic interaction.

NFATc4 and myocardin synergistically up-regulate the expression of LTCC α1C in ET-1-induced cardiomyocyte hypertrophy.

AIMS: Dysregulation of Ca(2+) is a central cause of cardiac hypertrophy. The α1C subunit of L-type Ca(2+) channel (LTCC) is a pore-forming protein which is responsible for the voltage-dependent channel gating and channel selectivity for Ca(2+). Myocardin and nuclear factor of activated T-cells c4 (NFATc4) are two key transcription factors in cardiac hypertrophy. We aimed to investigate the underlying mechanism of the transcriptional regulation of LTCC α1C by myocardin and NFATc4 in hypertrophic cardiomyocytes. MAIN METHODS: Endothelin-1 (ET-1) was used to induce cardiomyocyte hypertrophy. Cyclosporin A (CSA) was used to block the activation of calcineurin/NFATc4 pathway in ET-1-treated cardiomyocytes and the expression of LTCC α1C were examined. Overexpression or RNAi interfering experiments were performed to investigate the effects of NFATc4 or myocardin on the transcriptional regulation of LTCC α1C. Interactions between NFATc4 and myocardin or the association of NFATc4 with myocardin promoter were assessed via Co-IP or ChIP assays respectively. KEY FINDINGS: In the present study, we found that ET-1 stimulated LTCC α1C transcription in neonatal rat cardiomyocytes partially via the activation of calcineurin/NFATc4 pathway. Overexpression of NFATc4 or myocardin promoted LTCC α1C expression in cardiomyocytes. Ca(2+) channel blocker verapamil or knockdown of α1C inhibited myocardin-induced cardiomyocyte hypertrophy. Further studies showed that NFATc4 interacted with myocardin to synergistically activate the expression of LTCC α1C, moreover, NFATc4 activated myocardin expression by binding to its promoter. SIGNIFICANCE: Our results suggest a novel mechanism of the transcriptional regulation of LTCC α1C by synergistic activities of NFATc4 and myocardin in ET-1-induced cardiomyocyte hypertrophy.

MicroRNA-29a-3p attenuates ET-1-induced hypertrophic responses in H9c2 cardiomyocytes.

Transcription factor nuclear factor of activated T cells c4 (NFATc4) is the best-characterized target for the development of cardiac hypertrophy. Aberrant microRNA-29 (miR-29) expression is involved in the development of cardiac fibrosis and congestive heart failure. However, whether miR-29 regulates hypertrophic processes is still not clear. In this study, we investigated the potential functions of miR-29a-3p in endothelin-1 (ET-1)-induced cardiomyocyte hypertrophy. We showed that miR-29a-3p was down-regulated in ET-1-treated H9c2 cardiomyocytes. Overexpression of miR-29a-3p significantly reduced ET-1-induced hypertrophic responses in H9c2 cardiomyocytes, which was accompanied by a decrease in NFATc4 expression. miR-29a-3p targeted directly to the 3'-UTR of NFATc4 mRNA and silenced NFATc4 expression. Our results indicate that miR-29a-3p inhibits ET-1-induced cardiomyocyte hypertrophy via inhibiting NFATc4 expression.

Protein kinase Cα inhibits myocardin-induced cardiomyocyte hypertrophy through the promotion of myocardin phosphorylation.

Myocardin plays a key role in the development of cardiac hypertrophy. However, the upstream signals that control the stability and transactivity of myocardin remain to be fully understood. The expression of protein kinase Cα (PKCα) also induces cardiac hypertrophy. An essential downstream molecule of PKCα, extracellular signal-regulated kinase 1/2, was reported to negatively regulate the activities of myocardin. But, the effect of cooperation between PKCα and myocardin and the potential molecular mechanism by which PKCα regulates myocardin-mediated cardiac hypertrophy are unclear. In this study, a luciferase assay was performed using H9C2 cells transfected with expression plasmids for PKCα and myocardin. Surprisingly, the results showed that PKCα inhibited the transcriptional activity of myocardin. PKCα inhibited myocardin-induced cardiomyocyte hypertrophy, demonstrated by the decrease in cell surface area and fetal gene expression, in cardiomyocyte cells overexpressing PKCα and myocardin. The potential mechanism underlying the inhibition effect of PKCα on the function of myocardin is further explored. PKCα directly promoted the basal phosphorylation of endogenous myocardin at serine and threonine residues. In myocardin-overexpressing cardiomyocyte cells, PKCα induced the excessive phosphorylation of myocardin, resulting in the degradation of myocardin and a transcriptional suppression of hypertrophic genes. These results demonstrated that PKCα inhibits myocardin-induced cardiomyocyte hypertrophy through the promotion of myocardin phosphorylation.

Ca²âº signal-induced cardiomyocyte hypertrophy through activation of myocardin.

Hypertrophic growth of cardiomyocytes in response to pressure overload is an important stage during the development of many cardiac diseases. Ca(2+) overload as well as subsequent activation of Ca(2+) signaling pathways has been reported to induce cardiac hypertrophy. Myocardin, a transcription cofactor of serum response factor (SRF), is a key transducer of hypertrophic signals. However, the direct role of myocardin in Ca(2+) signal-induced cardiomyocyte hypertrophy has not been explained clearly. In the present study, we discovered that embryonic rat heart-derived H9c2 cells responded to the stimulation of calcium ionophore A23187 with a cell surface area enlargement and an increased expression of cardiac hypertrophy marker genes. Increased Ca(2+) also induces an organization of sarcomeres in neonatal rat cardiomyocytes, as revealed by α-actinin staining. Increased Ca(2+) could upregulate the expression of myocardin. Knockdown of myocardin by shRNA attenuates hypertrophic responses triggered by increased intracellular Ca(2+), suggesting that Ca(2+) signals induce cardiomyocyte hypertrophy partly through activation of myocardin. Furthermore, A23187 treatment directly activates myocardin promoter, chelation of Ca(2+) by EGTA inhibits this activation and knockdown of myocardin expression using shRNA also abrogates A23187-induced ANF and SK-α-actin promoter activity. CSA (calcineurin inhibitor) and KN93 (CaMKII inhibitor) inhibit A23187-induced the increase in myocardin expression. These results suggest that myocardin plays a critical role in Ca(2+) signal-induced cardiomyocyte hypertrophy, which may serve as a novel mechanism that is important for cardiac hypertrophy.