4-Phenylbutyric acid presents therapeutic effect on osteoarthritis via inhibiting cell apoptosis and inflammatory response induced by endoplasmic reticulum stress.

Osteoarthritis (OA) is a common bone and joint disease with a wild range of risk factors, which is associated with endoplasmic reticulum (ER) stress. The aim of our study was to discuss the possible mechanism of ER stress associated with OA in vivo and explore novel therapeutic method against OA. OA-induced damages in cartilage tissues were evaluated by HE, Safranin O/fast green, and TUNEL staining. The inflammatory factors concentration and the expression of FAP, MMP2, MMP9, Bax, Bcl-2, CHOP, and GRP78 were evaluated by ELISA, real-time PCR, and Western blot analyses. As results, 4-phenylbutyric acid (4-PBA)-treated OA cartilage tissues presented alleviated tissue damage with less apoptotic cells and cytokine production in comparison with advanced-OA tissues. Downregulation of Bax/Bcl-2, CHOP, GRP78, inflammatory factors, and reactive oxygen species generation, and the increase of MMP level detected after 4-PBA treatment indicated an inhibitory effect of 4-PBA on cell apoptosis, inflammatory response, and ER stress in OA. In conclusion, we indicate that ER stress causes cell apoptosis and inflammatory response, resulting in the tissue damage within OA. At the same time, 4-PBA exhibited protective effect on cartilage cells against OA through the inhibition of ER stress.

ß­Ecdysterone promotes autophagy and inhibits apoptosis in osteoporotic rats.

Osteoporosis is an aging process of skeletal tissues with characteristics of reductions in bone mass and microarchitectural deterioration of bone tissue. The present study aimed to investigate the effects of glucocorticoid­induced osteoporosis on osteoblasts and to examine the roles of ß­ecdysterone (ß­Ecd) involved. In the present study, an in vivo model of osteoporosis was established through the subcutaneous implantation of prednisolone (PRED) into Sprague­Dawley rats, with or without a subcutaneous injection of ß­Ecd (5 or 10 mg/kg body weight). Expression of Beclin­1 and microtubule­associated protein 1A/1B­light chain 3I/II and apoptosis in lumbar vertebrae tissues was measured by immunofluorescence and TUNEL assays, respectively. Serum concentration of calcium and phosphorus, and the activity of tartrate­resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) were measured by biochemical assay. Reverse transcription­quantitative polymerase chain reaction and western blotting was used for detect the expression of related genes and proteins. PRED treatment inhibited bone formation by decreasing bone mineral density, and suppressing the expression of Runt­related transcription factor 2 and bone morphogenetic protein 2, while enhancing the activity of alkaline phosphatase, upregulating the expression of receptor activator of nuclear factor-κB ligand, and increasing the serum content of calcium, phosphorus and tartrate­resistant acid phosphatase in rats. Additionally, PRED was revealed to inhibit autophagy through the downregulation of Beclin­1, autophagy protein 5 and microtubule­associated protein 1A/1B­light chain 3I/II expression, whereas it induced the apoptosis, through the activation of caspase­3 and the suppression of apoptosis regulator BCL2 expression. Notably, the PRED­induced alterations in bone formation, autophagy and apoptosis were revealed to be attenuated by ß­Ecd administration. In conclusion, the findings of the present study suggested that ß­Ecd may be a promising candidate for the development of therapeutic strategies for the treatment of osteoporosis, through the induction of autophagy and the inhibition of apoptosis in vivo.