Herpud1 modulates hypertrophic signals independently of calmodulin nuclear translocation in rat myocardium-derived H9C2 cells.

In this study, we aimed to analyze the role of the Homocysteine-responsive endoplasmic reticulum-resident ubiquitin-like domain member 1 (Herpud1) gene in the development of cardiomyocyte hypertrophy in association with Calmodulin (CaM) nuclear translocation and cytosolic Ca2+ levels. To observe the mobilization of CaM in cardiomyocytes, we stably expressed eGFP-CaM in rat myocardium-derived H9C2 cells. These cells were then treated with Angiotensin II (Ang II), which stimulates a cardiac hypertrophic response, or dantrolene (DAN), which blocks the release of intracellular Ca2+. To observe intracellular Ca2+ in the presence of eGFP fluorescence, a Rohd-3 Ca2+ sensing dye was used. To examine the effect of suppressing Herpud1 expression, Herpud1 small interfering RNA (siRNA) were transfected into H9C2 cells. To examine whether hypertrophy induced by Ang II could be suppressed by Herpud1 overexpression, a Herpud1-expressing vector was introduced into H9C2 cells. CaM translocation was observed using eGFP fluorescence. Nuclear translocation of Nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4) and nuclear export of Histone deacetylase 4 (HDAC4) were also examined. First, Ang II induced H9C2 hypertrophy with nuclear translocation of CaM and elevation of cytosolic Ca2+, which were inhibited by DAN treatment. We also found that Herpud1 overexpression suppressed Ang II-induced cellular hypertrophy without preventing nuclear translocation of CaM or elevation of cytosolic Ca2+. Additionally, Herpud1 knockdown induced hypertrophy without the nuclear translocation of CaM, which was not inhibited by DAN treatment. Finally, Herpud1 overexpression suppressed Ang II-induced NFATc4 nuclear translocation but did not suppress Ang II-induced CaM nuclear translocation or HDAC4 nuclear export. Ultimately, this study lays the groundwork for elucidating the anti-hypertrophic effects of Herpud1 and the underlying mechanism of pathological hypertrophy.

Dantrolene reduces platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell proliferation and neointimal formation following vascular injury in mice.

Dantrolene is a ryanodine receptor blocker that is used clinically for treatment of malignant hyperthermia. This study was conducted using murine aortic vascular smooth muscle cells (MOVAS) and a mouse arterial injury model to investigate the inhibitory effect of dantrolene on smooth muscle cell proliferation and migration. We investigated whether dantrolene suppressed platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell proliferation and migration in vitro. The effect of dantrolene on smooth muscle phenotype was evaluated using immunostaining. In addition, smooth muscle cell proliferation and phenotype switching were tested by applying dantrolene around blood vessels using a mouse arterial injury model. Dantrolene inhibited PDGF-induced cell proliferation and migration of MOVAS. Dantrolene also inhibited the switch from contractile to synthetic phenotype both in vitro and in vivo. Dantrolene is effective at inhibiting vascular smooth muscle cell proliferation, migration, and neointimal formation following arterial injury in mice.

Endoplasmic reticulum stress promotes nuclear translocation of calmodulin, which activates phenotypic switching of vascular smooth muscle cells.

BACKGROUND AND AIMS: Increased endoplasmic reticulum (ER) stress is strongly associated with the phenotypic switching of vascular smooth muscle cells (VSMCs) in atherosclerosis. Depletion of the ER Ca2+ content is one of the leading causes of increased ER stress in VSMCs. The ryanodine receptor (RyR) is a major Ca2+ release channel in the sarcoplasmic reticulum membrane. Calmodulin (CaM), which binds to RyR (CaM-RyR), stabilizes the closed state of RyR in the resting state in normal cells. Defective CaM-RyR interactions can cause abnormal Ca2+ leakage through RyR, resulting in decreased Ca2+ content, indicating that defective CaM-RyR interactions may be a cause of increased ER stress. Herein, we used a mouse VSMCs to assess whether CaM-RyR plays a pivotal role in VSMCs phenotypic switching, which is caused by ER stress, and whether dantrolene, which enhances the binding affinity of CaM to RyR, affects VSMCs phenotypic switching. METHODS AND RESULTS: Tunicamycin was used to mimic ER stress in vitro. Tunicamycin-induced ER stress caused CaM to dissociate from the RyR and translocate to the nucleus, which stimulated phenotypic switching through the activation of MEF2 and KLF5. Dantrolene suppressed tunicamycin-induced apoptosis, ER stress (restoring ER Ca2+ content), and phenotypic switching of VSMCs. Suramin, which directly unbinds CaM from RyR, promoted nuclear CaM accumulation with parallel VSMCs phenotypic switching, and dantrolene prevented these effects. CONCLUSIONS: We observed that ER stress causes CaM translocation to the nucleus and drives the phenotypic switching of VSMCs. Thus, restoration of the binding affinity of CaM to RyR may be a therapeutic target for atherosclerosis.

TMEPAI, a transmembrane TGF-beta-inducible protein, sequesters Smad proteins from active participation in TGF-beta signaling.

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine of key importance for controlling embryogenesis and tissue homeostasis. How TGF-beta signals are attenuated and terminated is not well understood. Here, we show that TMEPAI, a direct target gene of TGF-beta signaling, antagonizes TGF-beta signaling by interfering with TGF-beta type I receptor (TbetaRI)-induced R-Smad phosphorylation. TMEPAI can directly interact with R-Smads via a Smad interaction motif. TMEPAI competes with Smad anchor for receptor activation for R-Smad binding, thereby sequestering R-Smads from TbetaRI kinase activation. In mammalian cells, ectopic expression of TMEPAI inhibited TGF-beta-dependent regulation of plasminogen activator inhibitor-1, JunB, cyclin-dependent kinase inhibitors, and c-myc expression, whereas specific knockdown of TMEPAI expression prolonged duration of TGF-beta-induced Smad2 and Smad3 phosphorylation and concomitantly potentiated cellular responsiveness to TGF-beta. Consistently, TMEPAI inhibits activin-mediated mesoderm formation in Xenopus embryos. Therefore, TMEPAI participates in a negative feedback loop to control the duration and intensity of TGF-beta/Smad signaling.

Periostin in allergic inflammation.

Periostin, an extracellular matrix protein belonging to the fasciclin family, has been shown to play a critical role in the process of remodeling during tissue/organ development or repair. Periostin functions as a matricellular protein in cell activation by binding to their receptors on cell surface, thereby exerting its biological activities. After we found that periostin is a downstream molecule of interleukin (IL)-4 and IL-13, signature cytokines of type 2 immune responses, we showed that periostin is a component of subepithelial fibrosis in bronchial asthma, the first formal proof that periostin is involved in allergic inflammation. Subsequently, a great deal of evidence has accumulated demonstrating the significance of periostin in allergic inflammation. It is of note that in skin tissues, periostin is critical for amplification and persistence of allergic inflammation by communicating between fibroblasts and keratinocytes. Furthermore, periostin has been applied to development of novel diagnostics or therapeutic agents for allergic diseases. Serum periostin can reflect local production of periostin in inflamed lesions induced by Th2-type immune responses and also can predict the efficacy of Th2 antagonists against bronchial asthma. Blocking the interaction between periostin and its receptor, αv integrin, or down-regulating the periostin expression shows improvement of periostin-induced inflammation in mouse models or in in vitro systems. It is hoped that diagnostics or therapeutic agents targeting periostin will be of practical use in the near future.

Periostin in Allergic Inflammation.

Periostin, an extracellular matrix protein belonging to the fasciclin family, has been shown to play a critical role in the process of remodeling during tissue/organ development or repair. Periostin functions as a matricellular protein in cell activation by binding to their receptors on cell surface, thereby exerting its biological activities. After we found that periostin is a downstream molecule of interleukin (IL)-4 and IL-13, signature cytokines of type 2 immune responses, we showed that periostin is a component of subepithelial fibrosis in bronchial asthma, the first formal proof that periostin is involved in allergic inflammation. Subsequently, a great deal of evidence has accumulated demonstrating the significance of periostin in allergic inflammation. It is of note that in skin tissues, periostin is critical for amplification and persistence of allergic inflammation by communicating between fibroblasts and keratinocytes. Furthermore, periostin has been applied to development of novel diagnostics or therapeutic agents for allergic diseases. Serum periostin can reflect local production of periostin in inflamed lesions induced by Th2-type immune responses and also can predict the efficacy of Th2 antagonists against bronchial asthma. Blocking the interaction between periostin and its receptor, αv integrin, or down-regulating the periostin expression shows improvement of periostin-induced inflammation in mouse models or in in vitro systems. It is hoped that diagnostics or therapeutic agents targeting periostin will be of practical use in the near future.

[Application of basic research to development of diagnostics and therapeutic agents against inflammatory diseases].

Biomarkers are generally important for the treatment of patients from the points of diagnosis of disease, assessment of cure, assessment of prognosis such as metastasis or recurrence, prevention of disease, and prediction of drug efficacy. Currently it is well accepted that allergic diseases such as bronchial asthma and atopic dermatitis are not single diseases, but syndromes encompassing different diseases entities. Therefore, it is important to cluster allergic disease patients to assess prognosis or the choice of therapeutic drugs, and useful biomarkers are required for these purposes. Periostin, an extracellular matrix protein, has recently emerged as a biomarker useful for clustering asthma patients. We further found that periostin plays an important role in allergic inflammation and based on this finding we are now developing therapeutic agents targeting periostin against allergic diseases. Since periostin is involved in the pathogenesis of various inflammatory diseases in addition to allergic diseases, such diagnostics and therapeutic agents can be applied to many inflammatory diseases. In this article, we describe the history of periostin research and our application of basic research to the development of diagnostics and therapeutic agents against inflammatory diseases.

Herpud1 suppress angiotensin II induced hypertrophy in cardiomyocytes.

Purpose: The purpose of this study was to analyze the role of homocysteine-responsive endoplasmic reticulum-resident ubiquitin-like domain member 1 (Herpud1) gene in the development of cardiomyocyte hypertrophy. Method: In order to examine the effect of suppressing Herpud1 expression, Herpud1 small interfering RNA (siRNA) was introduced into H9C2 cells, which are cell lines derived from rat myocardium, and the degree of Herpud1 protein expression and cell hypertrophy in the Herpud1 siRNA-transfected group and the control group was compared by immunostaining 48 h after Herrpud1 siRNA introduction. To examine whether hypertrophy induced by angiotensin II (Ang II) can be suppressed by the overexpression of Herpud1, the green fluorescent protein (GFP)-Herpud1 plasmid was introduced into H9C2 cells, and the degree of cell hypertrophy was examined in the GFP-Herpud1-and control groups for 48 h. Nuclear translocation of nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4), a transcription factor for hypertrophic genes, was also examined. Results: [1] Herpud1 siRNA-transfected cells showed decreased Herpud1 protein expression and hypertrophy formation compared to control cells [2]; Overexpression of Herpud1 suppresses Ang II-induced cell hypertrophy; and [3] Overexpression of Herpud1 inhibits nuclear translocation of NFATc4. Discussion: It was suggested that Herpud1 might be an anti-hypertrophic gene in Ang II induced cardiomyocytes hypertrophy.

Methylation of Smad6 by protein arginine N-methyltransferase 1.

Signal transduction pathways utilize posttranslational modifications to regulate the activity of their components in a temporal-spatial and efficient fashion. Arginine methylation is one of the posttranslational modifications that can result in monomethylated-, asymmetric dimethylated- and/or symmetric dimethylated-arginine residues in proteins. Here we demonstrate that inhibitory-Smads (Smad6 and Smad7), but not receptor-regulated- (R-)Smads and the common-partner Smad4, can be methylated by protein arginine N-methyltransferase (PRMT)1. Using mass-spectrometric analysis, we found that PRMT1 dimethylates arginine(74) (Arg(74)) in mouse Smad6. PRMT1 interacts with the N-terminal domain of Smad6 in which Arg(74) residue is located. Assays examined so far have shown no significant differences between the functions of Smad6 and those of methylation-defective Smad6 (Smad6R74A). Both wild-type and Smad6R74A were equally efficient in blocking BMP-induced growth arrest upon their ectopic expression in HS-72 mouse B-cell hybridoma cells.

Periostin controls keratinocyte proliferation and differentiation by interacting with the paracrine IL-1α/IL-6 loop.

Proliferation and differentiation of keratinocytes are normally well balanced, but this balance can be perturbed in wound healing and is dysregulated in pathological conditions such as atopic dermatitis. Epithelial-mesenchymal interaction affects this event via the cross-talk of cytokines and growth factors. Periostin, a matricellular protein, has an important role during reepithelialization in wound healing and is critical for hyperproliferation of keratinocytes in atopic dermatitis. Here we investigated how periostin regulates proliferation and differentiation of keratinocytes in the epithelial-mesenchymal interactions using a three-dimensional organotypic air-liquid interface coculture system. The release of IL-1α from keratinocytes and subsequent IL-6 production from fibroblasts were critical for keratinocyte proliferation and differentiation. Periostin secreted from fibroblasts was required for IL-1α-induced IL-6 production and enhanced IL-6 production by activation of the NF-κB pathway synergistically with IL-1α. Thus, the combination of an autocrine loop of periostin and a paracrine loop composed of IL-1α and IL-6 regulates keratinocyte proliferation and differentiation in the epithelial-mesenchymal interactions, and periostin tunes the magnitude of keratinocyte proliferation and differentiation by interacting with the paracrine IL-1α/IL-6 loop.