Yong Liang Zhang

LC, a novel estrone–rhein hybrid compound, concurrently stimulates osteoprotegerin and inhibits receptor activator of NF-κB ligand (RANKL) and interleukin-6 production by human osteoblastic cells

Estrogen analogues are promising drugs for postmenopausal osteoporosis, but because of their possible side effects such as increased risk of cancer, estrogens which exert their estrogenic effects selectively on bone are desired. It has been shown that rhein inhibits osteoclast formation and bone resorption activity and has an antitumor role in several types of cancers. Having found that rhein had high affinity for the bone mineral, we synthesized estrone-rhein hybrid compounds and confirmed that one of these hybrid compounds, LC, exhibited a selective profile in the bone and prevented bone loss but had no effect on endometrium growth in ovariectomized rats. However, the mechanisms underlying its actions on human bone cells have not been well defined. Here we show that LC concurrently stimulates osteoprotegerin (OPG) and inhibits receptor activator of nuclear factor-κB ligand (RANKL) and Interleukin-6 (IL-6) production by human osteoblastic MG-63 cells containing two estrogen receptor (ER) isotypes. Treatment with the ER antagonist ICI 182,780 abrogates the above actions of LC on osteoblast-derived cells. Using small interfering double-stranded RNAs (siRNA) technology, we further demonstrate that the effects of LC on IL-6 production are mediated by both ERα and ERβ but those on OPG and RANKL expression primarily by ERα. Furthermore, we also demonstrate that LC functions at least partially through activation of the classic estrogen response element (ERE) pathway as well as Ras/MEK/ERK and PI3K/Akt signaling. The effect of LC on bone is due to not only its estrogenic activity but also action of its rhein moiety. Also, this compound shows much weaker effect on breast epithelial cell growth than that of estrone. Therefore, using rhein for conjugating compounds is a promising method of effectively targeting estrogens to the bone.

Acute high-altitude hypoxic brain injury: Identification of ten differential proteins

Hypobaric hypoxia can cause severe brain damage and mitochondrial dysfunction, and is involved in hypoxic brain injury. However, little is currently known about the mechanisms responsible for mitochondrial dysfunction in hypobaric hypoxic brain damage. In this study, a rat model of hypobaric hypoxic brain injury was established to investigate the molecular mechanisms associated with mitochondrial dysfunction. As revealed by two-dimensional electrophoresis analysis, 16, 21, and 36 differential protein spots in cerebral mitochondria were observed at 6, 12, and 24 hours post-hypobaric hypoxia, respectively. Furthermore, ten protein spots selected from each hypobaric hypoxia subgroup were similarly regulated and were identified by mass spectrometry. These detected proteins included dihydropyrimidinase-related protein 2, creatine kinase B-type, isovaleryl-CoA dehydrogenase, elongation factor Ts, ATP synthase beta-subunit, 3-mercaptopyruvate sulfurtransferase, electron transfer flavoprotein alpha-subunit, Chain A of 2-enoyl-CoA hydratase, NADH dehydrogenase iron-sulfur protein 8 and tropomyosin beta chain. These ten proteins are all involved in the electron transport chain and the function of ATP synthase. Our findings indicate that hypobaric hypoxia can induce the differential expression of several cerebral mitochondrial proteins, which are involved in the regulation of mitochondrial energy production.

LC, a novel estrone-rhein hybrid compound, promotes proliferation and differentiation and protects against cell death in human osteoblastic MG-63 cells

Estrogen analogs are promising drugs for postmenopausal osteoporosis, but because of their possible side effects, estrogens which exert their estrogenic effects selectively on bone are desired. Based on our previous studies that rhein had high affinity for the bone mineral, we synthesized estrone-rhein hybrid compounds and confirmed that one of these hybrid compounds, LC, exhibited a selective profile in the bone and prevented bone loss but had no effect on endometrium growth in ovariectomized rats. However, the mechanisms underlying its actions on human bone cells have remained largely unknown. Here we show that LC increases proliferation and differentiation and opposes cisplatin-induced apoptosis in human osteoblastic MG-63 cells containing two estrogen receptor (ER) isoforms. LC promotes proliferation by altering cell cycle distribution whereas LC-mediated survival may be associated with up-regulation of X-linked inhibitor of apoptosis (XIAP) expression. Treatment with the ER antagonist ICI 182,780 abolishes the above actions of LC on osteoblast-derived cells. Using small interfering double-stranded RNAs technology, we further demonstrate that the effects of LC on proliferation and survival are mediated by both ERα and ERβ but those on differentiation primarily by ERα. Moreover, we demonstrate that LC may promote activation of the classic estrogen response element (ERE) pathway through increasing steroid receptor coactivator (SRC)-3 expression. Meanwhile, we find that regulation of osteoblastic proliferation and survival by LC involves Ras/MEK/ERK and PI3K/Akt signaling. Therefore, using rhein for conjugating compounds is a promising method of effectively targeting estrogens to the bone.

Daidzein increases OPG/RANKL ratio and suppresses IL-6 in MG-63 osteoblast cells.

Daidzein is a major dietary source of isoflavones found in Leguminosae, and belongs to the family of diphenolic compounds. The estrogenic effects of daidzein to prompt bone formation and prevent bone resorption have been observed in animal models and cultured cells. In our study, we studied the effects of daidzein, raloxifene and E2 on expression of the osteoblast-produced bone regulatory factors OPG, RANKL and IL-6 in human osteoblastic MG-63 cells. Results suggest that treatment with daidzein, raloxifene and E2 increased the levels of OPG and decreased those of RANKL and IL-6. The effects of daidzein on OPG and RANKL expression are mediated by both ERα and ERβ but those on IL-6 production primarily by ERα. Moreover, daidzein may promote activation of the classic estrogen response element (ERE) pathway through increasing ERα, ERβ and steroid hormone receptor coactivator (SRC)-1 expression. E2 was also able to enhance transcription derived from the ERE, while raloxifene has no effect on it. Raloxifene increased ERα protein and gene expression levels but had no effect on ERβ protein and gene expression at 0.1μM. E2 was found significantly increased the protein and mRNA levels of SRC-1, while raloxifene has no effect on it compared with control. This ability of daidzein to affect osteoblastic cells makes it a good candidate for the treatment of bone loss in postmenopausal women.

Protective Effect of Rosamultin against H2O2-Induced Oxidative Stress and Apoptosis in H9c2 Cardiomyocytes

Rosamultin is one of the main active compounds isolated from Potentilla anserina L., which belongs to a triterpene compound. Few studies have examined the effect of rosamultin on oxidative stress and its molecular mechanism. The aim of this present study was to elucidate the protective effect of rosamultin on H2O2-induced oxidative damage and apoptosis in H9c2 cardiomyocytes and its mechanism. The results showed that the pretreatment of rosamultin not only increased cell viability but also reduced the release of LDH and CK. Rosamultin inhibited a H2O2-induced decrease in SOD, CAT, and GSH-Px activities and an increase in MDA content. Meanwhile, ROS level, intracellular (Ca2+) fluorescence intensity, and apoptosis rate in the rosamultin pretreated group were markedly decreased compared with the model group. Rosamultin pretreatment significantly reversed the morphological changes and attenuated H2O2-induced apoptosis. Western blot analysis showed that rosamultin enhanced the expression of Bcl-2 and pCryAB and downregulated the expression of Bax, Cyt-c, Caspase-3, and Caspase-9 expression. Additionally, rosamultin might activate PI3K/Akt signal pathways and CryAB relative factors. Therefore, we suggest that rosamultin could have the potential for treating H2O2-induced oxidative stress injury through its antioxidant and antiapoptosis effect.