| Glucocorticoid-induced osteoporosis (GIOP) is the most common secondaryosteoporosis, and the essence is to reduce the ability of bone formation. Currently avariety of anti-osteoporosis drugs were used for clinical, but the most of them hadgeneral effect and toxicity. The study of anti-osteoporosis drugs, which have highefficacy and low toxicity, has became an urgent task in the drugs development ofmodern medicine.Ganoderma lucidum immunoregulatory protein (LZ-8) was isolated in1989, itbelongs to the fungal immunomodulatory protein family. LZ-8has been reported tobe effective in modulating immune function, inhibiting tumor growth, stimulatinginterleukin6(IL-6) and tumor necrosis factor (TNF-α) expressing, and so on.Recombinant LZ-8(rLZ-8) was cloned and expressed in Pichia pastoris, and the aimof the paper is to investigate whether rLZ-8has protective effect on GIOP.In the paper dexamethasone (2.5mg/kg intramuscularly) was given twice weeklyfrom the4thday to the end. At the final day, rats in each group were detected bonemineral content(BMC) and bone mineral density (BMD), the results showed that,compared with the saline group, the BMC and BMD of model group decreasedobviously (P＜0.01, P＜0.01), so the GIOP model was established successfully.60Wistar rats were randomly divided into six groups: Saline group, model group,positive drug group, rLZ-8low dosage group, rLZ-8middle dosage group and rLZ-8high dosage group. Each group had10rats. Rats of treatment groups were dosedintraperitoneally (i.p.) with rLZ-8(28μg/kg,56μg/kg,112μg/kg) or intragastrically(i.g.) with alendronate (1mg/kg) for48days, animals not receiving injections weregiven saline injections instead. Except the saline group, dexamethasone was giventwice weekly from the4thday to the end. After the last dosing rats were anesthetizedwith10%chloral hydrate, femur and serum samples and viscera were obtained duringautopsy, and all the samples were stored until used for assessment of biochemicalmarkers of bone turnover. Trabecular bone is a direct response to bone strength and stability, so in the study,after decalcification and other methods we observed the structure of trabecular boneof femur with the light microscope by using Hematoxylin and Eosin (H&E) staining.In the model group, the trabecular bone of femur were manifested with significantreduction and discontinuance, while the rats received rLZ-8shows different degreesof improvement. The result demonstrated that rLZ-8could protect the degeneration ofbone trabecular structure, which was caused by glucocorticoid(GCs).GCs could affect the bone metabolism, and also involve in the secretion of someinflammatory cytokines. Using rat sandwich enzyme-linked immunosorbent assay andcolorimetry method, we detected the serum of rats and got the following results.Compared with the saline group, levels of alkaline phosphatase (ALP) and P in serumincreased evidently (P＜0.01, P＜0.01), the content of Ca in serum decreased (P＜0.01), TNF-α and IL-6in serum up-regulated (P＜0.05, P＜0.05), while in the groupswith rLZ-8treatment, the phenomena were improved in different degrees. The datassuggest that rLZ-8could regulate metabolic disorders cased by GCs, and suppressexcessive secretion of inflammatory factors.To further study the mechanism of the protective effect of rLZ-8on GIOP, theprotein expression of osteoprotegerin (OPG) and receptor activator of nuclearfactor-κB ligand (RANKL) in the bone tissue, which has been obtained were assessedby Western blot. The results indicated that GCs effects the balance of bone resorptionand formation through the OPG/RANKL/RANK pathway, while rLZ-8could inhibitsthis process, and play a protective role.In a word, rLZ-8has a protective effect on rats with GIOP, and it would be apromising and effective therapy in treating osteoporosis. |
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