OBJECTIVE:The current study was to explore the effect of melatonin on osteoporosis and relevant mechanisms.MATERIALS AND METHODS:We performed micro-CT to detect bone microstructure and ELISA to detect the contents of osteocalcin (OCN) and bone alkaline phosphatase (BAP) in serum. Double fluorescence labeling of calcein and tetracycline and toluidine blue staining were used to determine morphological indexes of bone tissues. Alizarin red staining and Oil Red O staining were performed to recognize bone cells and adipocytes. RT-PCR was performed to determine the expression of osteoblast differentiation related genes.RESULTS:In the current study, data from micro-CT indicated that melatonin significantly increased the bone mass density (BMD), bone volume/tissue volume (BV/TV), trabecular number (Tb.N) and trabecular thickness (Tb.Th), and decreased the Structure Model Index (SMI) and trabecular Separation/Spacing (Tb.Sp) in elderly rats. Melatonin reduced calcium and phosphorus losses in urine and increased BAP and OCN levels in serum in elderly rats and increased bone formation rate (BFR) and bone mineralization rate (MAR) in elderly rats. Melatonin increased the number of osteoblasts in bone marrow and reduced the number of adipocytes in elderly rats. Melatonin also promoted the expression of osteogenic differentiation genes and suppressed the expression of adipogenic differentiation genes.CONCLUSIONS:WE suggest that melatonin could alleviate osteoporosis in aged rats' models probably by promoting osteoblast differentiation.

Ovarian aging has been associated with increased levels of reactive oxygen species and the deficiencies of antioxidant defense. The antioxidant peroxiredoxin 4 (Prdx4), as a member of Prdx protein family, controls cellular oxidative stress by reducing H2O2 levels. In previous studies, we provided evidence that Prdx4 was abundantly expressed in mouse and human ovaries and expression of Prdx4 in matured follicles was higher than that in immatured follicles. Accordingly, we speculated that Prdx4 expression could be associated with follicle development and it may be as a part of the antioxidative mechanism in follicular development. In this study, we demonstrated that Prdx4 was mainly expressed in the granulosa cells of mouse ovaries and the expression levels significantly increased along development of follicles. However, the expression levels of Prdx4 decreased when mice reached the aged stage (18 months old). Likewise a similar pattern that was observed in the mice study was also found in human ovaries where Prdx4 was expressed lower in premenopausal women than young women. Subsequent in vitro experiments indicated that Prdx4 mRNA and protein levels both increased with H2O2 in a concentrationdependent manner, but decreased rapidly with high concentration of H2O2, and the changes were closely related to cell proliferation. Taken together, these findings argue our understanding on the role of oxidative stress and antioxidant in follicular development and ovarian aging.

BackgroundThe development of antinociceptive tolerance following repetitive administration of opioid analgesics significantly hinders their clinical use. Evidence has accumulated indicating that microglia within the spinal cord play a critical role in morphine tolerance. The present study investigated the effects and possible mechanisms of a natural compound, paeoniflorin, in morphine tolerance via its specific inhibition of microglial activation.MethodsThe microglia cell line BV-2 was used. Cytokine expression was measured using quantitative polymerase chain reaction. Cell signalling was assayed by Western blot and immunohistochemistry. Nociception was assessed in Sprague-Dawley rats and CD-1 mice using Hargreaves' methods or the hot-plate test, respectively.Results(1) Morphine induces robust BV-2 cell activation, as evidenced by increased p38 mitogen-activated protein kinase (MAPK) phosphorylation, nuclear factor (NF)-B translocation and proinflammatory cytokine expression. These changes are inhibited by paeoniflorin. (2) Co-administration of paeoniflorin with morphine potentiates morphine antinociception by inhibiting p38 MAPK/NF-B signalling in the spinal cord. (3) Co-administration of paeoniflorin suppresses morphine-increased expression of toll-like receptor-4 both in BV-2 cells and within the spinal cord following chronic morphine treatment.ConclusionPaeoniflorin directly suppresses morphine-induced microglial activation and thus results in potentiation of morphine acute analgesia and attenuation of morphine chronic antinociceptive tolerance.

Evidence has accumulated indicating that microglia within the spinal cord play a critical role in morphine tolerance. The present study investigated the effects and possible mechanisms of 5′ adenosine monophosphate‐activated protein kinase (AMPK) activator resveratrol and AICAR to inhibit microglial activation and to limit the decrease in antinociceptive effects of morphine.