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Myogenesis is a complex process that is regulated by a variety of factors. We have previously shown that vitamin C and mild endoplasmic reticulum stress synergistically enhance myogenesis. The present study evaluated the effects of vitamin C (ascorbic acid (AsA) and AsA 2-phosphate (AsAp)) and extracellular signal-regulated kinase (ERK) 1/2 pathway on myogenesis. Treatment with U0126, an inhibitor of MEK1/2 that phosphorylates and activates ERK1/2, during the differentiation, increased the mRNA levels of Myod and Myog with an increase in the protein level of myosin heavy chain (MYH)1/2. Treatment with AsA or AsAp alone had minimal effects on myogenesis in C2C12 cells. However, combination treatment with vitamin C and U0126 greatly enhanced myogenesis; the number of thick and long myotubes was increased, and the expression of MYH1/2 was also increased. PD98059, another MEK1/2 inhibitor, also enhanced myogenesis in combination with vitamin C. These results indicate that relief of endogenous ERK1/2 activity enhances vitamin C-mediated myogenesis, suggesting a functional interaction between endogenous ERK1/2 activity and vitamin C. In addition, inhibition of p38 mitogen-activated protein kinase repressed myogenesis in the presence of vitamin C. Thus, vitamin C is a conditional factor that modulates myogenesis. • Endogenous ERK1/2 activity negatively regulates myogenesis. • Inhibition of ERK activity greatly enhances vitamin C-stimulated myogenesis. • Inhibition of p38 MAP kinase represses myogenesis in the presence of vitamin C. • The role of endogenous JNK activity is similar to that of endogenous ERK1/2 activity. [ABSTRACT FROM AUTHOR]

Myogenesis is a complex process regulated by several factors. This study evaluated the functional interaction between vitamin C and a high dose of capsaicin (a potential endoplasmic reticulum (ER) stress inducer) on myogenesis. After the induction of differentiation, treatment with ascorbic acid or ascorbic acid phosphate (AsAp) alone had minimal effects on myogenesis in C2C12 cells. However, treatment with capsaicin (300 μM) in undifferentiated C2C12 cells increased the expression levels of genes related to ER stress as well as oxidative stress. Myogenesis was effectively enhanced in C2C12 cells treated with a combination of capsaicin (300 μM) for one day before differentiation stimulation and AsAp for four days post-differentiation; subsequently, thick and long myotubes formed, and the expression levels of myosin heavy chain (MYH) 1/2 and Myh1, Myh4, and Myh7 increased. Considering that mild ER stress stimulates myogenesis, AsAp may elicit myogenesis through the alleviation of oxidative stress-induced negative effects in capsaicin-pretreated cells. The enhanced expression of Myh1 and Myh4 coincided with the expression of Col1a1 , a type I collagen, suggesting that the fine-tuning of the myogenic cell microenvironment is responsible for efficient myogenesis. Our results indicate that vitamin C is a potential stimulator of myogenesis in cells, depending on the cell context. • High-dose capsaicin induces ER stress in undifferentiated myogenic cells. • Vitamin C enhances myogenesis in capsaicin-pretreated cells. • Modulation of extracellular matrix may be involved in vitamin C-induced myogenesis. [ABSTRACT FROM AUTHOR]

We demonstrated that castration enhanced the expression of uncoupling protein 1 (Ucp1), a thermogenic protein, in brown adipose tissue (BAT) and subcutaneous (sc) white adipose tissue (WAT) in male mice. Castration of male mice increased body temperature and reduced body weight gain compared with those of sham-operated mice. BAT Ucp1 mRNA expression in castrated male mice was significantly higher than that in sham-operated mice. Histologically, cells with multilocular fat droplets were observed in the castrated inguinal scWAT. Immunohistochemical staining revealed that these cells positively reacted with the anti -Ucp1 antibody. The Ucp1-positive area near the inguinal lymph node in the castrated WAT was extensive compared with that of the sham-operated WAT. Castration-induced Ucp1 up-regulation in scWAT was suppressed by high-fat diet feeding. These findings suggest that thermogenesis by BAT activation and scWAT browning contribute to castration-induced inhibition of body weight gain. However, considering that the effect of castration was blunted by high-fat diet consumption, thermogenesis stimulation in response to castration is inhibited by chronic over-nutrition. [ABSTRACT FROM AUTHOR]

Systemic iron balance is governed by the liver-derived peptide hormone hepcidin. The transcription of hepcidin is primarily regulated by the bone morphogenetic protein (BMP) and inflammatory cytokine pathways through the BMP-response element (BMP-RE) and STAT-binding site, respectively. In addition to these elements, we previously identified a TPA-responsive element (TRE) in the hepcidin promoter and showed that it mediated the transcriptional activation of hepcidin through activator protein (AP)-1 induced by serum. In the present study, we examined the role of TRE in the BMP-induced transcription of hepcidin in HepG2 liver cells. The serum treatment increased the basal transcription of hepcidin; however, responsiveness to the expression of ALK3(QD), a constitutively active BMP type I receptor, was unaffected. Consistent with these results, mutations in TRE in the hepcidin promoter decreased basal transcription, whereas responsiveness to the expression of ALK3(QD) remained unchanged. HepG2 cells significantly expressed AP-1 components in the basal state, whereas BMP did not up-regulate the expression of these components. The expression of c-fos enhanced the basal transcription of hepcidin as well as ALK3(QD)-mediated hepcidin transcription, whereas that of dominant-negative c-fos decreased hepcidin transcription. The results of the present study suggested that the cis -elements of the hepcidin promoter, BMP-RE and TRE, individually transmitted BMP-mediated and AP-1-mediated signals, respectively, whereas transcription was synergistically increased by the stimulation of BMP-RE and TRE. [ABSTRACT FROM AUTHOR]

We explored transcriptional regulation of mouse mast cell protease-9 (mMCP-9), which is implicated in inflammation of the jejunum during helminth infections and tissue remodeling of the uterus during pregnancy. Transcription was positively regulated by microphthalmia-associated transcription factor (MITF), a member of the basic helix-loop-helix–leucine zipper family that binds to the E-box, a CANNTG sequence. The most significant segment for positive regulation by MITF was nt −183 to −177 of the mMCP-9 promoter, CATCATG, which bound MITF-M. In addition, not only other MITF isoforms but also TFE3, another member of the family, activated mMCP-9 transcription through this nucleotide sequence inserted one base within the E-box. [Copyright &y& Elsevier]