Selective glucocorticoid receptor modulator compound A, in contrast to prednisolone, does not induce leptin or the leptin receptor in human osteoarthritis synovial fibroblasts.

OBJECTIVE: Glucocorticoids are powerful anti-inflammatory compounds that also induce the expression of leptin and leptin receptor (Ob-R) in synovial fibroblasts through TGF-ßsignalling and Smad1/5 phosphorylation. Compound A (CpdA), a selective glucocorticoid receptor agonist, reduces inflammation in murine arthritis models and does not induce diabetes or osteoporosis, thus offering an improved risk:benefit ratio in comparison with glucocorticoids. Due to the detrimental role of leptin in OA pathogenesis, we sought to determine whether CpdA also induced leptin and Ob-R protein expression as observed with prednisolone. METHODS: Human synovial fibroblasts and chondrocytes were isolated from the synovium and cartilage of OA patients after joint surgery. The cells were treated with prednisolone, TGF-ß1, TNF-α and/or CpdA. Levels of leptin, IL-6, IL-8, MMP-1 and MMP-3 were measured by ELISA and expression levels of Ob-R phospho-Smad1/5, phospho-Smad2, α-tubulin and glyceraldehyde 3-phosphate dehydrogenase were analysed by western blotting. RESULTS: CpdA, unlike prednisolone, did not induce leptin secretion or Ob-R protein expression in OA synovial fibroblasts. Moreover, CpdA decreased endogenous Ob-R expression and down-regulated prednisolone-induced leptin secretion and Ob-R expression. Mechanistically, CpdA, unlike prednisolone, did not induce Smad1/5 phosphorylation. CpdA, similarly to prednisolone, down-regulated endogenous and TNF-α-induced IL-6, IL-8, MMP-1 and MMP-3 protein secretion. The dissociative effect of CpdA was confirmed using chondrocytes with no induction of leptin secretion, but with a significant decrease in IL-6, IL-8, MMP-1 and MMP-3 protein secretion. CONCLUSION: CpdA, unlike prednisolone, did not induce leptin or Ob-R in human OA synovial fibroblasts, thereby demonstrating an improved risk:benefit ratio.

Endogenous BNP attenuates cardiomyocyte hypertrophy induced by Ang II via p38 MAPK/Smad signaling.

Previous studies suggest that B-type natriuretic peptide (BNP) exerts inhibitory effects on cardiac hypertrophy. Our studies have shown that long-term treatment of rats with BNP attenuated cardiac hypertrophy via down-regulation of TGF-ß1 and up-regulation of smad7. However, the mechanisms have not been fully elucidated. In the present study, we examined the role of endogenous BNP on cardiomyocyte hypertrophy and the related molecular mechanisms. Cardiomyocytes from neonatal rats were cultured and a cardiomyocyte hypertrophy model was established with angiotensin II (Ang II). The effects of blockade of endogenous BNP by its receptor antagonist, HS-142-1, on cell hypertrophy were investigated. Cardiomyocyte hypertrophy indices, including cell surface area, protein content and [3H] incorporation were measured. Smad and mitogen-activated protein kinase (MAPK) protein expressions were detected using Western blot analysis. We found that HS-142-1 increased Ang II-stimulated cardiomyocyte hypertrophy and Smad activation. In addition, the increase of cardiomyocyte hypertrophy and the activation of Smad caused by HS-142-1 were not altered by the ERK inhibitor, PD98059, but were decreased by the p38 MAPK inhibitor, SB203580. These results demonstrate that endogenous BNP attenuates cardiomyocyte hypertrophy, and this may be mediated through p38 MAPK/Smad, but not ERK/Smad signaling pathway.

Enhancement of bone morphogenetic protein-2 expression and bone formation by coumarin derivatives via p38 and ERK-dependent pathway in osteoblasts.

Osteoporosis is a reduction in skeletal mass due to an imbalance between bone resorption and bone formation. Bone morphogenetic protein (BMP) plays important roles in osteoblastic differentiation and bone formation. Therefore, components involved in BMP activation are good targets for the development of anti-osteoporosis drugs. In this study, imperatorin and bergapten, two coumarin derivatives, were shown to enhance alkaline phosphatase (ALP) activity, type I collagen synthesis and bone nodule formation in primary cultured osteoblasts. Imperatorin and bergapten increased mRNA levels of BMP-2 using quantitative RT-PCR, whereas the BMP-2 antagonist noggin attenuated the increase of ALP activity induced by imperatorin and bergapten, indicating that BMP-2 expression is required for the action of imperatorin and bergapten in osteoblastic maturation. Both imperatorin and bergapten enhanced the phosphorylation of SMAD (transcription factors activated by TGF-beta) 1/5/8, p38 and extracellular signal-regulated protein (ERK). Pretreatment of osteoblasts with p38 inhibitor (SB203580) or mitogen-activated protein kinase inhibitor (PD98059) or transfected with dominant negative mutant of p38 or ERK antagonized the elevation of BMP-2 expression and ALP activity induced by imperatorin and bergapten. Local administration of imperatorin or bergapten into the metaphysis of the tibia via the implantation of a needle cannula significantly increased the BMP-2 immunostaining and bone volume of secondary spongiosa in tibia. Taken together, our results provide evidence that coumarin derivatives increase BMP-2 expression and enhance bone formation in rat via the p38 and ERK-dependent signaling pathway.