Gene silencing of myofibrillogenesis regulator-1 by adenovirus-delivered small interfering RNA suppresses cardiac hypertrophy induced by angiotensin II in mice

Ca2+/Calmodulin-Dependent Protein Kinase II Regulation by Inhibitor of RIPK3 Protects against Cardiac Hypertrophy

The activity of Ca²⁺/calmodulin-dependent protein kinase II δ (CaMKII δ) is central to the mechanisms of cardiovascular diseases. Receptor-interacting protein kinase 3- (RIPK3-) mediated necroptosis has been reported to contribute to cardiac dysfunction. However, the potential protective role of inhibition of RIPK3, a regulator of CaMKII, on cardiac hypertrophy remains unclear. The present study is aimed at investigating how the RIPK3 inhibitor GSK'872 regulates CaMKII activity and exploring its effect on hypertrophic cardiomyopathy (HCM). Wild-type (WT) and RIPK3 gene knockout (RIPK3^−/−) mice were implanted subcutaneously with Alzet miniosmotic pumps (200 μL) and perfused with angiotensin II (AMP-AngII) to induce cardiac hypertrophy. After WT mice were induced by AngII for 72 hours, they were injected with GSK'872 with an intraperitoneal (IP) dose of 6 mg/kg once a day for two weeks. After this, they were physiologically examined for Echocardiography, myocardial injury, CaMKII activity, necroptosis, RIPK3 expression, mixed lineage kinase domain-like protein (MLKL) phosphorylation, and mitochondrial ultrastructure. The results indicated that deletion of the RIPK3 gene or administration of GSK'872 could reduce CaMKII activity, alleviate oxidative stress, reduce necroptosis, and reverse myocardial injury and cardiac dysfunction caused by AngII-induced cardiac hypertrophy in mice. The present study demonstrated that CaMKII activation and necroptosis augment cardiac hypertrophy in a RIPK3-dependent manner, which may provide therapeutic strategies for HCM. RIPK3 inhibitor GSK'872 has a protective effect on cardiac hypertrophy and could be an efficacious targeted medicine for HCM in clinical treatment.

Preliminary study on pathogenic mechanism of first Chinese family with PNKD

Background

The first Chinese family with paroxysmal non-kinesigenic dystonia (PNKD) was confirmed to harbour a PNKD mutation. However, the pathogenic mechanism of the PNKD-causing gene mutation was unclear.

Methods

Wild-type and mutant PNKD-L plasmids were prepared and transfected into the C6 cell line to study the distribution and stability of PNKD protein in C6 cells and its effect on the glutathione content. The blood and cerebrospinal fluid (CSF) of 3 PNKD patients and 3 healthy controls were collected. The differentially expressed proteins were identified using isobaric tags for relative and absolute quantitation. Furthermore, Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analyses were performed, and the protein–protein interaction network was constructed.

Results

Wild-type PNKD protein was mainly distributed in the membranes, whereas mutant PNKD protein was distributed throughout the C6 cells. After transfection with mutant PNKD-L plasmid, the glutathione content decreased significantly in C6 cells; the stability of the mutant PNKD protein was significantly low. There were 172 and 163 differentially expressed proteins in CSF and plasma, respectively, of PNKD patients and healthy controls. For these proteins, blood microparticle and complex activation (classical pathway) were the common GO enrichment term, and complex and coordination cascade pathway were the common KEGG enrichment pathway. Recombinant mothers against decapentaplegic homolog 4 (SMAD4) was one of the differentially expressed proteins; it exhibited a relationship with the aforementioned enrichment GO terms and KEGG pathway.

Conclusion

PNKD protein was mainly distributed in cell membranes. PNKD-L mutation affected subcellular localisation, PNKD protein stability, and glutathione content. SMAD4 was found to be a potential biomarker for PNKD diagnosis.

Silencing MR-1 Protects against Myocardial Injury Induced by Chronic Intermittent Hypoxia by Targeting Nrf2 through Antioxidant Stress and Anti-Inflammation Pathways

BACKGROUND

Patients with obstructive sleep apnea hypopnea syndrome (OSAHS) often have cardiac insufficiency mainly due to hypoxia/reperfusion injury caused by chronic intermittent hypoxia (CIH). Inflammation and oxidative stress are involved in the cardiovascular events of OSAHS patients. Studies have found that myofibrillation regulator-1 (MR-1) participates in the pathological process of OSAHS-induced myocardial injury, but the specific mechanism is still unclear.

METHODS

We used a CIH-induced rat model to simulate the process of OSAHS disease. Indices of myocardial injury, inflammation, and oxidative stress were detected using quantitative PCR and enzyme-linked immunosorbent assay (ELISA). After administration of adenoassociated viral vector (AAV) encoding silencing RNA against MR-1, we examined expression of the classic antioxidant stress pathway protein NF-E2-related factor 2 (Nrf2) using western blotting.

RESULTS

We found that levels of serum inflammatory factors tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-8 were increased, and we further observed disturbance of the oxidative stress system, in which the content of reactive oxygen species (ROS), superoxide dismutase (SOD), reduced glutathione (GSH), and malondialdehyde (MDA) was enhanced in CIH-induced rats. Subsequently, we detected that expression of Nrf2 and heme oxygenase-1 (HO-1) was slightly increased, while the expression of Kelch-like ECH-associated protein 1 (Keap-1) was significantly increased in the CIH model. Interestingly, after administration of silencing MR-1 AAV, the elevated levels of inflammatory factors were reduced, and the disordered oxidative stress system was corrected. Additionally, the expression of Nrf2 and HO-1 was distinctly increased, but the high expression of Keap-1 was decreased.

CONCLUSIONS

Our research results demonstrate that silencing MR-1 rescued the myocardium the injury from inflammatory and oxidative stress in CIH-induced rats by administration of the Nrf2 signaling pathway.

Cardiomyocyte calcineurin is required for the onset and progression of cardiac hypertrophy and fibrosis in adult mice

Previous studies have demonstrated that activation of calcineurin induces pathological cardiac hypertrophy (CH). In these studies, loss-of-function was mostly achieved by systemic administration of the calcineurin inhibitor cyclosporin A. The lack of conditional knockout models for calcineurin function has impeded progress toward defining the role of this protein during the onset and the development of CH in adults. Here, we exploited a mouse model of CH based on the infusion of a hypertensive dose of angiotensin II (AngII) to model the role of calcineurin in CH in adulthood. AngII-induced CH in adult mice was reduced by treatment with cyclosporin A, without affecting the associated increase in blood pressure, and also by induction of calcineurin deletion in adult mouse cardiomyocytes, indicating that cardiomyocyte calcineurin is required for AngII-induced CH. Surprisingly, cardiac-specific deletion of calcineurin, but not treatment of mice with cyclosporin A, significantly reduced AngII-induced cardiac fibrosis and apoptosis. Analysis of profibrotic genes revealed that AngII-induced expression of Tgfβ family members and Lox was not inhibited by cyclosporin A but was markedly reduced by cardiac-specific calcineurin deletion. These results show that AngII induces a direct, calcineurin-dependent prohypertrophic effect in cardiomyocytes, as well as a systemic hypertensive effect that is independent of calcineurin activity.

Silencing MR-1 attenuates atherosclerosis in ApoE-/- mice induced by angiotensin II through FAK-Akt-mTOR-NF-kappaB signaling pathway

Myofibrillogenesis regulator-1 (MR-1) is a novel protein involved in cellular proliferation, migration, inflammatory reaction and signal transduction. However, little information is available on the relationship between MR-1 expression and the progression of atherosclerosis. Here we report atheroprotective effects of silencing MR-1 in a model of Ang II-accelerated atherosclerosis, characterized by suppression focal adhesion kinase (FAK) and nuclear factor kappaB (NF-κB) signaling pathway, and atherosclerotic lesion macrophage content. In this model, administration of the siRNA-MR-1 substantially attenuated Ang II-accelerated atherosclerosis with stabilization of atherosclerotic plaques and inhibited FAK, Akt, mammalian target of rapamycin (mTOR) and NF-kB activation, which was associated with suppression of inflammatory factor and atherogenic gene expression in the artery. In vitro studies demonstrated similar changes in Ang II-treated vascular smooth muscle cells (VSMCs) and macrophages: siRNA-MR-1 inhibited the expression levels of proinflammatory factor. These studies uncover crucial proinflammatory mechanisms of Ang II and highlight actions of silencing MR-1 to inhibit Ang II signaling, which is atheroprotective.

Myofibrillogenesis regulator 1 (MR-1): a potential therapeutic target for cancer and PNKD

Human myofibrillogenesis regulator 1 (MR-1) is a functional gene also known as paroxysmal nonkinesigenic dyskinesia (PNKD). It is localised on human chromosome 2q35 and three different isomers, MR-1L, MR-1M and MR-1S, are formed by alternative splicing. MR-1S promotes cardiac hypertrophy and is closely related to cancer. MR-1S is overexpressed in haematologic and solid malignancies, such as hepatoma, breast cancer and chronic myelogenous leukaemia. MR-1S causes disordered cell differentiation, initiates malignant transformation and accelerates metastasis. MR-1S directly phosphorylates and activates the MEK-ERK-RSK pathway to accelerate cancer growth and facilitates metastasis by activating the MLC2-FAK-AKT pathway. Silencing MR-1 inhibits cancer cell proliferation and metastasis. MR-1S causes disordered cell differentiation, initiates malignant transformation and accelerates metastasis. MR-1 interacts with eukaryotic translation initiation factors and MRIP-1, which contains Ras GTPase, PH and zinc-containing ArfGap domains, as well as three ankyrin repeats. Mutations in the N-terminal region of MR-1L and MR-1S are the main causes of PNKD (a hereditary disease characterised by paroxysmal dystonic choreoathetosis) and targeting the mutated protein could provide symptomatic relief. These findings provide compelling evidence that MR-1 might be a diagnostic marker and therapeutic target for solid tumours, myelogenous leukaemia and PNKD.

Myofibrillogenesis regulator-1 attenuated hypoxia/reoxygenation-induced apoptosis by inhibiting the PERK/Nrf2 pathway in neonatal rat cardiomyocytes

The purpose of this study was to investigate the role of myofibrillogenesis regulator-1 (MR-1) in cardiomyocyte apoptosis induced by hypoxia/reoxygenation (H/R), through protein kinase R-like ER kinase (PERK)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. To address this aim, an H/R model of neonatal rat cardiomyocytes was used. MR-1 was overexpressed using an adenoviral vector system and knocked down using MR-1 specific siRNA. Apoptosis was assessed by using Annexin V/PI double staining, terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling assay, and the Bcl-2/Bax ratio. Western blotting was used to detect the protein levels of MR-1, glucose-regulated protein 78 (GRP78), total and phosphorylated PERK, Nrf2, activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), Bcl-2 and Bax. Immunofluorescence staining was used to assess the subcellular location of Nrf2. We found that H/R induced significant apoptosis in neonatal rat cardiomyocytes. MR-1 overexpression attenuated H/R-induced apoptosis, decreased GRP78 (P < 0.01) and CHOP expression (P < 0.05), and increased the Bcl-2/Bax ratio (P < 0.01). MR-1 overexpression suppressed H/R-induced PERK phosphorylation, Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). While MR-1 knockdown aggravated H/R-induced apoptosis, increased expression of GRP78 and CHOP (P < 0.05), and decreased the Bcl-2/Bax ratio (P < 0.01). MR-1 knockdown significantly increased H/R-induced PERK phosphorylation (P < 0.05), Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). These findings suggest that MR-1 alleviates H/R-induced cardiomyocyte apoptosis through inhibition of the PERK/Nrf2 pathway.

Interaction of the profilaggrin N-terminal domain with loricrin in human cultured keratinocytes and epidermis

The relationship between the two coexpressed differentiation markers, profilaggrin and loricrin, is not clear right now. In this study, we explored the interaction of profilaggrin N-terminal domain (PND) with loricrin in keratinocytes and epidermis. Confocal immunofluorescence microscopic analysis of human epidermis showed that PND colocalized with loricrin. Loricrin nucleofected into HaCaT cells colocalized with PND in the nucleus and cytoplasm. The PND localizes to both the nucleus and cytoplasm of epidermal granular layer cells. Nucleofected PND also colocalized with keratin 10 (K10) in the nucleus and cytoplasm. Immunoelectron microscopic analysis of human epidermis confirmed the findings in nucleofected keratinocytes. Yeast two-hybrid assays showed that the B domain of human and mouse PND interacted with loricrin. The glutathione S-transferase (GST) pull-down analysis using recombinant GST-PND revealed that PND interacted with loricrin and K10. Knockdown of PND in an organotypic skin culture model caused loss of filaggrin expression and a reduction in both the size and number of keratohyalin granules, as well as markedly reduced expression of loricrin. Considering that expression of PND is closely linked to keratinocyte terminal differentiation, we conclude that PND interacts with loricrin and K10 in vivo and that these interactions are likely to be relevant for cornified envelope assembly and subsequent epidermal barrier formation.