Luteolin Stimulates Proliferation and Inhibits Late Differentiation of Primary Rat Calvarial Osteoblast Induced by High-dose Dexamethasone via Sema3A /NRP1/Pleixin A1

Abstract

Background: Although Semaphorin 3A (Sema3A)/ Neuropilin-1(NRP1)/Plexin A1 is one of the important targets in bone metabolism, few studies are performed on this target in the glucocorticoids- induced osteoporosis. Luteolin is a chemical component of Honeysuckle and it has various bioactivities. The effect of Luteolin on the glucocorticoids-induced osteoporosis (primary osteoblasts model) remain unknown.

Objective: The aim of this study was to investigate the action of Sema3A/ NRP1/Plexin A1 in Luteolin- induced osteoprotection against high-dose Dexamethasone.

Methods: The effect of Luteolin on the proliferation, late differentiation, and apoptosis of primary osteoblasts model of glucocorticoids-induced osteoporosis in vitro as well as the expression of Sema3A/ NRP1/Plexin A1 are investigated by using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-Htetrazolium bromide, Cell Counting Kit-8, reverse transcription-quantitative real-time polymerase chain reaction, western bolting and so on.

Results: Suckling SD rats' calvarial osteoblasts were isolated and identified. The glucocorticoidsinduced primary osteoporosis cell model was established by 100 μM Dexamethasone in 48 h (P<0.01). Luteolin promotes osteoblasts either in physiological condition (without Dexamethasone) or pathological condition (with Dexamethasone) at 1 μM concentration for 48h (P<0.01). Luteolin partly reverses down-regulated expression of proliferation markers such as proliferating cell nuclear and CyclinD1. (P<0.01) Similarly, Luteolin partly reverses up-regulated expression of apoptosis markers such as Bax/B-cell lymphoma-2. (P<0.01) The expression of mRNA and protein of Sema3A/ NRP1/Plexin A1 decreased in model one which significantly increased in Luteolin protecting one. (P<0.05) Interestingly, the late differentiation marker such as osteocalcin and collagenase Ⅰ sharply decreased in Luteolin protecting group compared with model one. (P<0.01).

Conclusion: The thesis concludes that Luteolin promoted the proliferation of osteoblast and inhibited its apoptosis and late differentiation in this glucocorticoids-induced primary osteoporosis cell model. This function may be related to the expression of up-regulated Sema3A/NRP1/Plexin A1. Therefore, Luteolin may be a potential medicine for the glucocorticoids-induced osteoporosis.

Keywords: Osteoblast; dexamethasone; differentiation; luteolin; neuropilin-1; plexin A1; proliferation; semaphorin 3A.