Background: Hyperglycaemia promotes the proliferation of cardiac fibroblasts (CFs) and collagen synthesis in CFs. However, the molecular mechanism underlying the effects of HG on proliferation and collagen synthesis of CF, is not completely understood. Objectives: The objectives of the present study were to determine whether the STAT proteins has a functional role in high glucose-induced proliferation of CFs and collagen synthesis in vitro and whether the STAT signaling pathway and MAPK signaling pathway have synergetical effects on high glucose-mediated cardiac fibroblasts proliferation and collagen synthesis. Methods: Rat CFs were cultured in Dulbecco's modified Eagle's medium, supplemented with 5.5 or 25 mmol/L D-glucose, in the presence of absence of STAT1 inhibitor Fludarabine, STAT3 inhibitor S31-201 and ERK1/2 inhibitor PD98059. Proliferation were measured by the 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, the production of Type I and III collagen was evaluated using real-time quantitative RT-PCR and ELISA, and the phosphorylation expression of STAT1 and STAT3 were analyzed by Western blot. Results: High glucose treatment promoted the proliferation of cardiac fibroblasts and collagen types I and III synthesis. High glucose treatment induced STAT1 and STAT3 phosphorylation in cardiac fibroblasts, the mode and level of STAT1 and STAT3 phosphorylation were significantly different. Fludarabine and S31-201 could both inhibited high glucose stimulated proliferation of cardiac fibroblasts and collagen types I and III synthesis with different effects. Combination of Fludarabine and PD98059 or combination of S31-201 and PD98059 both exhibited stronger inhibitions on proliferation of cardiac fibroblasts and collagen types I synthesis, but the effects and functional modes are different. Conclusion: Both STAT1 and STAT3 mediate the proliferation of cardiac fibroblasts and collagen synthesis induced by high glucose. STAT1 and STAT3 both have synergetic effects with ERK1/2 on regulating proliferation of cardiac fibroblasts and collagen types I synthesis.

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To study the effect of tolvaptan on non-acute, non-hypovolemic hyponatremia in inappropriate secretion of antidiuretic hormone (SIADH) syndrome in Chinese patients. Hyponatremic SIADH patients received placebo (N = 18) or tolvaptan (N = 19) at an initial dose of 15 mg/day with further titration to 30 mg/day and 60 mg/day based on serum sodium concentrations. Randomized, double-blind, placebo-controlled trial. Primary endpoint was the change of the serum sodium from baseline to days 4 and 7. Analysis of covariance (ANCOVA) was used for statistical analysis. At day 4, average daily changes in serum sodium levels from baseline was 1.9 ± 2.9 mmol/L (1.9 ± 2.9 mEq/L) in the placebo group and 8.1 ± 3.6 mmol/L (8.1 ± 3.6 mEq/L) in the tolvaptan group; at day 7, the values were 2.5 ± 3.9 mmol/L (2.5 ± 3.9 mEq/L) and 8.6 ± 3.9 mmol/L (8.6 ± 3.9 mmEq/L) for the placebo and tolvaptan groups (ANCOVA, P < 0.001). At days 4 and 7, daily urine output and proportions of patients with normalized serum sodium were significantly superior in the tolvaptan group. The most common adverse events occurring in the tolvaptan group were dry mouth and thirst. Tolvaptan demonstrated superiority to placebo in the treatment of Chinese SIADH patients with hyponatremia by elevating serum sodium concentration with acceptable safety profile.

Runt-related transcription factor 2 (Runx2) and osterix are osteoblast-specific transcription factors essential for the development of osteoblastic cells and bone formation. PTH given intermittently has anabolic effects on bone; however, the exact role remains to be understood completely. The purpose of this study was both to investigate whether PTH regulates Runx2 as well as osterix expression and to identify the signaling used. Using RT-PCR, we confirmed that PTH (1-34) regulated Runx2 and osterix mRNA expression, in rat osteoblast-like cell line UMR 106, in a dose- and time-dependent manner. PTH in low concentrations stimulated both Runx2 and osterix mRNA expression while that in high concentrations did not. Forskolin, an adenylate cyclase activator, also enhanced Runx2 and osterix transcription, and the stimulatory effects of PTH and forskolin were blocked by the pre-treatment of the cells with H-89, a protein kinase A (PKA) inhibitor. In contrast, the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) had no effect on Runx2 transcription, but induced an increase in osterix mRNA level at the concentration of 500 nM at 12 h after treatment. Moreover, pre-treatment of the cells with calphostin C, a PKC-specific inhibitor, reduced the increase in osterix transcripts enhanced by PTH and PMA 12 h after treatment. However, these inhibitory effects were not sustained for longer terms. These observations demonstrate that PTH stimulates Runx2 and osterix expression in vitro, at least in part, at transcriptional level. Induction of Runx2 mRNA is mediated through the activation of cAMP/PKA signal transduction. In the case of osterix, although the increase in mRNA level is predominantly mediated via cAMP/PKA signaling, PKC activation might also be involved in this process.

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