Epsti1 Regulates the Inflammatory Stage of Early Muscle Regeneration through STAT1-VCP Interaction.

During muscle regeneration, interferon-gamma (IFN-γ) coordinates inflammatory responses critical for activation of quiescent muscle stem cells upon injury via the Janus kinase (JAK) - signal transducer and activator of transcription 1 (STAT1) pathway. Dysregulation of JAK-STAT1 signaling results in impaired muscle regeneration, leading to muscle dysfunction or muscle atrophy. Until now, the underlying molecular mechanism of how JAK-STAT1 signaling resolves during muscle regeneration remains largely elusive. Here, we demonstrate that epithelial-stromal interaction 1 (Epsti1), an interferon response gene, has a crucial role in regulating the IFN-γ-JAK-STAT1 signaling at early stage of muscle regeneration. Epsti1-deficient mice exhibit impaired muscle regeneration with elevated inflammation response. In addition, Epsti1-deficient myoblasts display aberrant interferon responses. Epsti1 interacts with valosin-containing protein (VCP) and mediates the proteasomal degradation of IFN-γ-activated STAT1, likely contributing to dampening STAT1-mediated inflammation. In line with the notion, mice lacking Epsti1 exhibit exacerbated muscle atrophy accompanied by increased inflammatory response in cancer cachexia model. Our study suggests a crucial function of Epsti1 in the resolution of IFN-γ-JAK-STAT1 signaling through interaction with VCP which provides insights into the unexplored mechanism of crosstalk between inflammatory response and muscle regeneration.

Ginsenoside Rg5 promotes muscle regeneration via p38MAPK and Akt/mTOR signaling.

Background: Skeletal muscles play a key role in physical activity and energy metabolism. The loss of skeletal muscle mass can cause problems related to metabolism and physical activity. Studies are being conducted to prevent such diseases by increasing the mass and regeneration capacity of muscles. Ginsenoside Rg5 has been reported to exhibit a broad range of pharmacological activities. However, studies on the effects of Rg5 on muscle differentiation and growth are scarce. Methods: To investigate the effects of Rg5 on myogenesis, C2C12 myoblasts were induced to differentiate with Rg5, followed by immunoblotting, immunostaining, and qRT-PCR for myogenic markers and promyogenic signaling (p38MAPK). Immunoprecipitation confirmed that Rg5 increased the interaction between MyoD and E2A via p38MAPK. To investigate the effects of Rg5 on prevention of muscle mass loss, C2C12 myotubes were treated with dexamethasone to induce muscle atrophy. Immunoblotting, immunostaining, and qRT-PCR were performed for myogenic markers, Akt/mTOR signaling for protein synthesis, and atrophy-related genes (Atrogin-1 and MuRF1). Results: Rg5 promoted C2C12 myoblast differentiation through phosphorylation of p38MAPK and MyoD/E2A heterodimerization. Furthermore, Rg5 stimulated C2C12 myotube hypertrophy via phosphorylation of Akt/mTOR. Phosphorylation of Akt induces FoxO3a phosphorylation, which reduces the expression of Atrogin-1 and MuRF1. Conclusion: This study provides an understanding of how Rg5 promotes myogenesis and hypertrophy and prevents dexamethasone-induced muscle atrophy. The study is the first, to the best of our knowledge, to show that Rg5 promotes muscle regeneration and to suggest that Rg5 can be used for therapeutic intervention of muscle weakness and atrophy, including cancer cachexia.

Hornerin mediates phosphorylation of the polo-box domain in Plk1 by Chk1 to induce death in mitosis.

The centrosome assembles a bipolar spindle for faithful chromosome segregation during mitosis. To prevent the inheritance of DNA damage, the DNA damage response (DDR) triggers programmed spindle multipolarity and concomitant death in mitosis through a poorly understood mechanism. We identified hornerin, which forms a complex with checkpoint kinase 1 (Chk1) and polo-like kinase 1 (Plk1) to mediate phosphorylation at the polo-box domain (PBD) of Plk1, as the link between the DDR and death in mitosis. We demonstrate that hornerin mediates DDR-induced precocious centriole disengagement through a dichotomous mechanism that includes sequestration of Sgo1 and Plk1 in the cytoplasm through phosphorylation of the PBD in Plk1 by Chk1. Phosphorylation of the PBD in Plk1 abolishes the interaction with Sgo1 and phosphorylation-dependent Sgo1 translocation to the centrosome, leading to precocious centriole disengagement and spindle multipolarity. Mechanistically, hornerin traps phosphorylated Plk1 in the cytoplasm. Furthermore, PBD phosphorylation inactivates Plk1 and disrupts Cep192::Aurora A::Plk1 complex translocation to the centrosome and concurrent centrosome maturation. Remarkably, hornerin depletion leads to chemoresistance against DNA damaging agents by attenuating DDR-induced death in mitosis. These results reveal how the DDR eradicates mitotic cells harboring DNA damage to ensure genome integrity during cell division.

Ginsenoside Rg3 protects glucocorticoid­induced muscle atrophy in vitro through improving mitochondrial biogenesis and myotube growth.

Ginsenoside Rg3 (Rg3), amplified by iterative heating processing with fresh ginseng, has a broad range of pharmacological activities and improves mitochondrial biogenesis in skeletal muscle. However, thus far no study has examined how Rg3 affects myotube growth or muscle atrophy, to the best of the authors' knowledge. The present study was conducted to examine the myogenic effect of Rg3 on dexamethasone (DEX)­induced myotube atrophy and the underlying molecular mechanisms. Rg3 activated Akt/mammalian target of rapamycin signaling to prevent DEX­induced myotube atrophy thereby stimulating the expression of muscle­specific genes, including myosin heavy chain and myogenin, and suppressing muscle­specific ubiquitin ligases as demonstrated by immunoblotting and immunostaining assays. Furthermore, Rg3 efficiently prevented DEX­triggered mitochondrial dysfunction of myotubes through peroxisome proliferator­activated receptor­Î³ coactivator1α activities and its mitochondrial biogenetic transcription factors, nuclear respiratory factor­1 and mitochondrial transcription factor A. These were confirmed by immunoblotting, luciferase assays, RT­qPCR and mitochondrial analysis measuring the levels of ROS, ATP and membrane potential. By providing a mechanistic insight into the effect of Rg3 on myotube atrophy, the present study suggested that Rg3 has potential as a therapeutic or nutraceutical remedy to intervene in muscle aging or diseases including cancer cachexia.

Understanding of sarcopenia: from definition to therapeutic strategies.

Sarcopenia refers to the gradual loss of skeletal muscle mass and function along with aging and is a social burden due to growing healthcare cost associated with a super-aging society. Therefore, researchers have established guidelines and tests to diagnose sarcopenia. Several studies have been conducted actively to reveal the cause of sarcopenia and find an economic therapy to improve the quality of life in elderly individuals. Sarcopenia is caused by multiple factors such as reduced regenerative capacity, imbalance in protein turnover, alteration of fat and fibrotic composition in muscle, increased reactive oxygen species, dysfunction of mitochondria and increased inflammation. Based on these mechanisms, nonpharmacological and pharmacological strategies have been developed to prevent and treat sarcopenia. Although several studies are currently in progress, no treatment is available yet. This review presents the definition of sarcopenia and summarizes recent understanding on the detailed mechanisms, diagnostic criteria, and strategies for prevention and treatment.

Black ginseng activates Akt signaling, thereby enhancing myoblast differentiation and myotube growth.

BACKGROUND: Black ginseng (BG) has greatly enhanced pharmacological activities relative to white or red ginseng. However, the effect and molecular mechanism of BG on muscle growth has not yet been examined. In this study, we investigated whether BG could regulate myoblast differentiation and myotube hypertrophy. METHODS: BG-treated C2C12 myoblasts were differentiated, followed by immunoblotting for myogenic regulators, immunostaining for a muscle marker, myosin heavy chain or immunoprecipitation analysis for myogenic transcription factors. RESULTS: BG treatment of C2C12 cells resulted in the activation of Akt, thereby enhancing heterodimerization of MyoD and E proteins, which in turn promoted muscle-specific gene expression and myoblast differentiation. BG-treated myoblasts formed larger multinucleated myotubes with increased diameter and thickness, accompanied by enhanced Akt/mTOR/p70S6K activation. Furthermore, the BG treatment of human rhabdomyosarcoma cells restored myogenic differentiation. CONCLUSION: BG enhances myoblast differentiation and myotube hypertrophy by activating Akt/mTOR/p70S6k axis. Thus, our study demonstrates that BG has promising potential to treat or prevent muscle loss related to aging or other pathological conditions, such as diabetes.

Cyclosporine A induces nerve growth factor expression via activation of MAPK p38 and NFAT5.

PURPOSE: We investigated the effects of cyclosporine A (CsA) on the mechanism of nerve growth factor (NGF) expression using a cultured human corneal epithelial cell line (HCECL). METHODS: NGF transcription and production levels were assessed after treatment of cells with various concentrations of CsA. Activities of mitogen-activated protein kinase (MAPK), nuclear factor Kappa B (NF-κB), activator protein-1 (AP-1), and nuclear factor of activated T cells (NFATs) influenced by CsA were determined using a luciferase assay. The translocation activity of NFAT5 was assessed by confocal microscopy and Western immunoblotting after CsA treatment. Transcriptional activity of NGF was measured after pretreatment of cells with SB20429 (a p38 inhibitor) and NFAT5 small interfering RNA. RESULTS: NGF was induced after treatment with CsA, but not dexamethasone, in the HCECL. NGF expression was mediated via p38 phosphorylation and NFAT5 activation. Transcriptional activities of NF-κB, AP-1, and NFAT1 were not stimulated by CsA; however, nuclear translocation of NFAT5 was markedly upregulated by CsA. CsA-induced NGF production was markedly decreased on inhibition of NFAT5 or SB20429. CONCLUSIONS: CsA is a potent inducer of NGF in the HCECL. These results suggest that CsA mediates NGF expression through activation of p38 and NFAT5.

Complete remission in a patient with human herpes virus-8 negative multicentric Castleman disease using CHOP chemotherapy.

Multicentric Castleman disease (MCD) is a rare lymphoproliferative disorder. Although MCD pathogenesis is unclear, studies have suggested that human herpesvirus 8 (HHV-8) may be associated with the disorder. Recent reports have identified MCD cases without viral infection. A 43-year-old woman presented to our hospital for fever and myalgia of 6 months' duration. The complete blood count revealed an elevated leukocyte count (15.1x10(3)/microL) and a decreased hemoglobin level of 10.0 g/dL. The C-reactive protein level was elevated at 276.5 mg/L. Thoracic computed tomography (CT) scans revealed bilateral axillary lymphadenopathy. There was no evidence of HHV-8, human immunodeficiency virus (HIV), or Mycobacterium infection. Histologic evaluation of a lymph node biopsy from the left axilla yielded a diagnosis of MCD. Cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP) were administered for a total of 4 cycles. The patient's fever and lymphadenopathy resolved after the course of chemotherapy. She has been in complete remission for 24 months at this writing. As previously reported, this case report suggests that MCD can develop without viral infection. CHOP chemotherapy may be an effective treatment option for newly diagnosed MCD patients.

The Bone Morphogenesis Protein-2 (BMP-2) is associated with progression to metastatic disease in gastric cancer.

PURPOSE: Bone Morphogenetic Proteins (BMPs) are members of the TGF-beta superfamily and it has been demonstrated that BMPs enhance migration, invasion and metastasis. The purpose of this study was to identify the association between the serum BMP-2 level and the progression status of gastric cancer. MATERIALS AND METHODS: Fifty-five patients with metastatic gastric cancer (metastatic disease group), six patients with early gastric cancer without lymph node metastasis (the EGC group), and ten healthy control subjects were enrolled in this study. The serum BMP-2 level was quantified by use of a commercially available ELISA kit. In EGC group patients and patients with metastatic disease, whole blood was obtained before endoscopic mucosal resection and before the commencement of a scheduled cycle of systemic chemotherapy, respectively. RESULTS: No significant difference in the mean serum BMP-2 levels was observed between the control subjects and the EGC group patients (87.95 pg/ml for the control subjects and 84.50 pg/ml for the EGC group, p=1.0). However, the metastatic disease group patients had a significantly higher level of serum BMP (179.61 pg/ml) than the control subjects and EGC group patients (87.95 pg/ml for the control subjects and 84.50 pg/ml for the EGC group, p<0.0001). Moreover, the mean serum BMP-2 level from patients with a bone metastasis was significantly higher than the mean serum BMP-2 level from patients without a bone metastasis (204.73 pg/ml versus 173.33 pg/ml, p=0.021). CONCLUSIONS: BMP-2 seems to have a role in progression to metastatic disease in gastric cancer, especially in the late stage of tumorigenesis, including invasion and metastasis. BMP-2 may facilitate bone metastasis in gastric cancer. To confirm these findings, further studies are required with tissue specimens and the use of a cancer cell line.

Clinical factors related to suspected second primary lung cancer development in patients with head and neck cancer.

PURPOSE: The rate of second primary lung cancer development for patients with head and neck cancer (HNC) has been noted. The aim of our study was to evaluate the incidence and clinical features of suspected second primary lung cancer that developed in patients with primary HNC. MATERIALS AND METHODS: We conducted a retrospective study of 469 patients who were newly diagnosed with HNC at the Korea University Medical Center between January 2000 and December 2006. RESULTS: A total of 469 patients were included (389 men and 80 women). Eighteen patients (3.8%) had suspected second primary lung cancers. Statistically significant clinical variables for lung cancer development included the origin site for the primary HNC (oro-hypopharynx and larynx) (p=0.048), abnormal chest x-ray findings (p=0.027) and the histological HNC type (squamous cell carcinoma) (p=0.032). When the second primary lung cancers were combined with HNCs, the adjusted overall survival of patients with a second primary lung cancer was 16 months (p<0.001). CONCLUSIONS: Considering the relative risk factors for a second primary lung cancer developing in patients with HNC, advanced diagnostic tools, such as chest CT or PET CT scan, should be applied for the early detection of a second primary lung cancer.