The role of mAKAPβ in the process of cardiomyocyte hypertrophy induced by angiotensin II

Mechanism of Astragalus membranaceus (Huangqi, HQ) for treatment of heart failure based on network pharmacology and molecular docking

Heart failure is a leading cause of death in the elderly. Traditional Chinese medicine, a verified alternative therapeutic regimen, has been used to treat heart failure, which is less expensive and has fewer adverse effects. In this study, a total of 15 active ingredients of Astragalus membranaceus (Huangqi, HQ) were obtained; among them, Isorhamnetin, Quercetin, Calycosin, Formononetin, and Kaempferol were found to be linked to heart failure. Ang II significantly enlarged the cell size of cardiomyocytes, which could be partially reduced by Quercetin, Isorhamnetin, Calycosin, Kaempferol, or Formononetin. Ang II significantly up-regulated ANP, BNP, β-MHC, and CTGF expressions, whereas Quercetin, Isorhamnetin, Calycosin, Kaempferol or Formononetin treatment partially downregulated ANP, BNP, β-MHC and CTGF expressions. Five active ingredients of HQ attenuated inflammation in Ang II-induced cardiomyocytes by inhibiting the levels of TNF-α, IL-1β, IL-18 and IL-6. Molecular docking shows Isorhamnetin, Quercetin, Calycosin, Formononetin and Kaempferol can bind with its target protein ESR1 in a good bond by intermolecular force. Quercetin, Calycosin, Kaempferol or Formononetin treatment promoted the expression levels of ESR1 and phosphorylated ESR1 in Ang II-stimulated cardiomyocytes; however, Isorhamnetin treatment had no effect on ESR1 and phosphorylated ESR1 expression levels. In conclusion, our results comprehensively illustrated the bioactives, potential targets, and molecular mechanism of HQ against heart failure. Isorhamnetin, Quercetin, Calycosin, Formononetin and Kaempferol might be the primary active ingredients of HQ, dominating its cardioprotective effects against heart failure through regulating ESR1 expression, which provided a basis for the clinical application of HQ to regulate cardiac hypertrophy and heart failure.

Sclareol attenuates angiotensin II-induced cardiac remodeling and inflammation via inhibiting MAPK signaling

Chronic inflammation plays an important role in hypertensive heart failure. Suppressing angiotensin II (Ang II)-induced cardiac inflammation may contribute to the treatment of hypertension-associated heart failure. Sclareol, a natural product initially isolated from the leaves and flowers of Salvia sclarea, possesses antiinflammatory and immune-regulation activity in various systems. However, its effect on Ang II-induced cardiac remodeling remains unknown. In this study, we have explored the potential effects of sclareol on Ang II-induced heart failure. In vivo experiments were conducted in mice with Ang II-pump infusion for 28 days. Sclareol administration at 5 mg·kg-1 ·d-1 significantly reduced the expression of myocardial injury markers. Sclareol also exerts protective effects against Ang II-induced cardiac dysfunction in mice which is associated with alleviated cardiac inflammation and fibrosis. Transcriptome analysis revealed that inhibition of the Ang II-activated mitogen-activated protein kinase (MAPK) pathway contributed to the protective effect of sclareol. Sclareol inhibits Ang II-activated MAPKs pathway to reduce inflammatory response in mouse hearts and cultured cardiomyocytes. Blockage of MAPKs in cardiomyocytes abolished the antiinflammatory effects of sclareol. In conclusion, we show that sclareol protects hearts against Ang II-induced injuries through inhibiting MAPK-mediated inflammation, indicating the potential use of sclareol in the prevention of hypertensive heart failure.

A-Kinase Anchor Protein 95 Is Involved in ERK1/2-Elk-1 Signal Transduction in Colon Cancer

Objectives

To assess A-kinase anchor protein 95 (AKAP95), B-Raf, extracellular regulated protein kinases 1/2 (ERK1/2), and Elk-1 expression in colon cancer tissue, and characterize AKAP95 associations with B-Raf, ERK1/2, Elk-1, and colon cancer clinicopathological indices.

Methods

The immunohistochemistry streptavidin-perosidase (SP) method was used to determine protein expression levels in 64 colon cancer and 32 para-carcinoma tissue specimens.

Results

(1) Positive AKAP95 expression rates in colon cancer tissue were higher when compared with para-carcinoma tissue (92.19% vs. 59.38%, P < 0.05). Similar findings were determined for B-Raf (76.56% vs. 25%, P < 0.05), ERK1/2 (90.63% vs. 31.25%, P < 0.05), and Elk-1 levels (92.19% vs. 40.63%, P < 0.05). (2) No significant associations were identified between AKAP95, B-Raf, ERK1/2, and Elk-1 protein expression and degree of differentiation, histological type, and lymph node metastasis in colon cancer samples (P > 0.05); however, in The Cancer Genome Atlas and Gene Expression Omnibus datasets, AKAP95 was closely related to immune infiltration, and highly expressed AKAP95 was negatively associated with overall survival and relapse free survival rates in colon cancer patients. (3) Correlations were observed between AKAP95 and ERK1/2, AKAP95 and Elk-1, B-Raf and ERK1/2, B-Raf and Elk-1, and ERK1/2 and Elk-1 (all P < 0.05), but no correlation was observed between AKAP95 and B-Raf (P > 0.05).

Conclusions

AKAP95 may affect immune infiltration levels in colon cancer by participating in ERK1/2-Elk-1 signal transduction.

Liquiritin Attenuates Angiotensin II-Induced Cardiomyocyte Hypertrophy via ATE1/TAK1-JNK1/2 Pathway

Objective

To investigate the protective effect and mechanism of liquiritin (LIQ) on cardiomyocyte hypertrophy induced by angiotensin II (Ang II).

Methods

H9c2 cells were pretreated with LIQ before and after Ang II treatment. CCK8 assay was performed to evaluate cell viability. The cell surface area was measured by phalloidin staining. The mRNA expression of atrial and B-type natriuretic peptides (ANP and BNP, respectively) and β-myosin heavy chain (β-MHC) was determined by quantitative reverse transcription-polymerase chain reaction (RT-qPCR); the protein levels of arginyltransferase 1 (ATE1), transforming growth factor beta-activated kinase 1 (TAK1), phos-TAK1, c-Jun N-terminal kinases1/2 (JNK1/2), and phos-JNK1/2 were determined by Western blotting. After constructing the ATE1 overexpression cell models with the pcDNA3.1/ATE1, the abovementioned indicators were tested using the introduced methods.

Results

LIQ at a concentration of ≤30 μM was not cytotoxic to H9c2 cells before exposure to Ang II. The protective effect of LIQ was best observed at 30 μM after Ang II treatment. Phalloidin staining and RT-qPCR results indicated that the deposition of Ang II increased the cell surface area and levels of ANP, BNP, and β-MHC. On the other hand, Western blotting results showed that Ang II increased the ATE1 protein levels and TAK1 and JNK1/2 phosphorylation, which were significantly alleviated after LIQ treatment. LIQ also directly inhibited the ATE1 overexpression in H9c2 cells transfected with pcDNA3.1/ATE1 and further inhibited TAK1 and JNK1/2 phosphorylation.

Conclusion

LIQ can attenuate Ang II-induced cardiomyocyte hypertrophy by regulating the ATE1/TAK1-JNK1/2 pathway.

Celastrol Attenuates Angiotensin II-Induced Cardiac Remodeling by Targeting STAT3

RATIONALE

Excessive Ang II (angiotensin II) levels lead to a profibrotic and hypertrophic milieu that produces deleterious remodeling and dysfunction in hypertension-associated heart failure. Agents that disrupt Ang II-induced cardiac dysfunction may have clinical utility in the treatment of hypertension-associated heart failure.

OBJECTIVE

We have examined the potential effect of celastrol-a bioactive compound derived from the Celastraceae family-on Ang II-induced cardiac dysfunction.

METHODS AND RESULTS

In rat primary cardiomyocytes and H9C2 (rat cardiomyocyte-like H9C2) cells, celastrol attenuates Ang II-induced cellular hypertrophy and fibrotic responses. Proteome microarrays, surface plasmon resonance, competitive binding assays, and molecular simulation were used to identify the molecular target of celastrol. Our data showed that celastrol directly binds to and inhibits STAT (signal transducer and activator of transcription)-3 phosphorylation and nuclear translocation. Functional tests demonstrated that the protection of celastrol is afforded through targeting STAT3. Overexpression of STAT3 dampens the effect of celastrol by partially rescuing STAT3 activity. Finally, we investigated the in vivo effect of celastrol treatment in mice challenged with Ang II and in the transverse aortic constriction model. We show that celastrol administration protected heart function in Ang II-challenged and transverse aortic constriction-challenged mice by inhibiting cardiac fibrosis and hypertrophy.

CONCLUSIONS

Our studies show that celastrol inhibits Ang II-induced cardiac dysfunction by inhibiting STAT3 activity.

Effect of SKF‑96365 on cardiomyocyte hypertrophy induced by angiotensin II

Angiotensin II (Ang II) is an important bioactive peptide in the renin-angiotensin system, and it can contribute to cell proliferation and cardiac hypertrophy. Dysfunctions in transient receptor potential canonical (TRPC) channels are involved in many types of cardiovascular diseases. The aim of the present study was to investigate the role of the TRPC channel inhibitor SKF-96365 in cardiomyocyte hypertrophy induced by Ang II and the potential mechanisms of SKF-96365. H9c2 cells were treated with different concentrations of Ang II. The expression levels of cardiomyocyte hypertrophy markers and TRPC channel-related proteins were also determined. The morphology and surface area of the H9c2 cells, the expression of hypertrophic markers and TRPC channel-related proteins and the [³H] leucine incorporation rate were detected in the Ang II-treated H9c2 cells following treatment with the TRPC channel inhibitor SKF-96365. The intracellular Ca²⁺ concentration was tested by flow cytometry. The present results suggested that the surface area of H9c2 cells treated with Ang II was significantly increased compared with untreated H9c2 cells. The fluorescence intensity of α-actinin, the expression of hypertrophic markers and TRPC-related proteins, the [³H] leucine incorporation rate and the intracellular Ca²⁺ concentration were all markedly increased in the Ang II-treated H9c2 cells but decreased following SKF-96365 treatment. The present results suggested that Ang II induced cardiomyocyte hypertrophy in H9c2 cells and that the TRPC pathway may be involved in this process. Therefore, SKF-96365 can inhibit cardiomyocyte hypertrophy induced by Ang II by suppressing the TRPC pathway. The present results indicated that TRPC may be a therapeutic target for the development of novel drugs to treat cardiac hypertrophy.

mAKAPβ signalosomes - A nodal regulator of gene transcription associated with pathological cardiac remodeling

Striated myocytes compose about half of the cells of the heart, while contributing the majority of the heart's mass and volume. In response to increased demands for pumping power, including in diseases of pressure and volume overload, the contractile myocytes undergo non-mitotic growth, resulting in increased heart mass, i.e. cardiac hypertrophy. Myocyte hypertrophy is induced by a change in the gene expression program driven by the altered activity of transcription factors and co-repressor and co-activator chromatin-associated proteins. These gene regulatory proteins are subject to diverse post-translational modifications and serve as nuclear effectors for intracellular signal transduction pathways, including those controlled by cyclic nucleotides and calcium ion. Scaffold proteins contribute to the underlying architecture of intracellular signaling networks by targeting signaling enzymes to discrete intracellular compartments, providing specificity to the regulation of downstream effectors, including those regulating gene expression. Muscle A-kinase anchoring protein β (mAKAPβ) is a well-characterized scaffold protein that contributes to the regulation of pathological cardiac hypertrophy. In this review, we discuss the mechanisms how this prototypical scaffold protein organizes signalosomes responsible for the regulation of class IIa histone deacetylases and cardiac transcription factors such as NFAT, MEF2, and HIF-1α, as well as how this signalosome represents a novel therapeutic target for the prevention or treatment of heart failure.

Angiotensin II Causes Biphasic STAT3 Activation Through TLR4 to Initiate Cardiac Remodeling

Evidence indicates that Ang II (angiotensin II) activates STAT3 (signal transducer and activator of transcription 3) in cardiomyocytes. However, the mechanisms underlying STAT3 activation and downstream responses are not fully known. In this study, we show that Ang II caused biphasic STAT3 activation in cardiomyocytes. A rapid and early activation was mediated by direct association between TLR4 (toll-like receptor-4) and STAT3. This early activation increased IL-6 (interleukin-6) production, which in turn, induced the second STAT3 activation through the IL-6/gp130 (glycoprotein 130)/JAK2 (Janus-family tyrosine kinases 2) pathway, resulting in unregulated expression of genes for cardiac remodeling. Moreover, STAT3 inhibition or TLR4 knockout in mice protected against Ang II-induced hypertrophy, fibrosis, and cardiac functional deficits. Thus, Ang II-induced STAT3 activation in cardiomyocytes was biphasic, providing a sequential induction of IL-6 and myocardial remodeling genes, respectively. This work supports a novel mechanism on STAT3 activation in Ang II-induced cardiac dysfunction and remodeling.

G Protein-Coupled Estrogen Receptor 1 Inhibits Angiotensin II-Induced Cardiomyocyte Hypertrophy via the Regulation of PI3K-Akt-mTOR Signalling and Autophagy

Estrogen has been demonstrated to protect the heart against cardiac remodelling and heart failure in women. G protein-coupled estrogen receptor 1 (GPER1) is a recently discovered estrogen receptor (ER) that is expressed in various tissues. However, the mechanisms by which estrogen protects the heart, especially the roles played by ERs, are not clear. In this study, we explored the effect of GPER1 activation on angiotensin II (Ang II)-induced cardiomyocyte hypertrophy and the involved signalling pathways and mechanisms. Our data demonstrated that GPER1 is expressed in cardiomyocytes, a GPER1 agonist, G1, attenuated Ang II-induced cardiomyocyte hypertrophy and downregulated the mRNA expression levels of atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP). Bioinformatics analysis revealed that five proteins, including RAP1gap, might be the key proteins involved in the attenuation of Ang II-induced cardiomyocyte hypertrophy by GPER1. G1 increased the protein level of p-Akt, p-70S6K1 and p-mTOR but decreased p-4EBP1 expression. All these effects were inhibited by either G15 (a GPER1 antagonist) or MK2206 (an inhibitor of Akt). Autophagy analysis showed that the LC3II/LC3I ratio was increased in Ang II-treated cells, and the increase was inhibited by G1 treatment. The effect of G1 on autophagy was blocked by treatment with G15, rapamycin, and MK2206. These results suggest that GPER1 activation attenuates Ang II-induced cardiomyocyte hypertrophy by upregulating the PI3K-Akt-mTOR signalling pathway and inhibiting autophagy.

Role of PKA in the process of neonatal cardiomyocyte hypertrophy induced by urotensin II

The model of urotensin II (UII)-induced cardiomyocyte hypertrophy has been widely used in studies on hypertrophy. However, the molecular mechanisms responsible for UII-induced cardiomyocyte hypertrophy have not yet been fully elucidated. It has been demonstrated that cardiomyocyte hypertrophy induced by UII is associated with changes in the intracellular Ca2+ concentration. In the present study, we investigated whether the cAMP-dependent protein kinase A (PKA)‑mediated upregulation of the phosphorylation levels of phospholamban (PLN) at Ser16 contributes to UII-induced cardiomyocyte hypertrophy. After primary cultures of neonatal rat cardiomyocytes were exposed to UII for 48 h, cell size, protein/DNA contents and intracellular Ca2+ levels were detected. Western blot analysis was used to quantify the phosphorylated and total forms of PKA, PLN and the total amount of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA)2a. UII increased the cell size, the protein/DNA ratio and the intracellular Ca2+ levels, consistent with the characteristics of hypertrophic response. In addition, exposure to UII upregulated the phosphorylation levels of PKA, and the expression levels of its downstream proteins, PLN and SERCA2a. However, treatment with PKA inhibitor (KT-5720) reversed all these effects of UII. On the whole, our results suggest that UII induces cardiomyocyte hypertrophy through the PKA-mediated upregulation of PLN phosphorylation at Ser16, which provides a new experimental foundation for the prevention and/or treatment of cardiac hypertrophy.