AlCl₃ Inhibits OB Function By Down-regulating The BMP/Smad Signaling Pathway In Vitro

Neonatal rat calvarial osteoblasts(OB) were cultured to investigate the mechanism of aluminum on bone toxicity in vitro. OBs were cultured in DMEM medium and exposed to Al Cl3·6H2O in final concentration of 0 mg/mL(control group), 0.063 mg/mL(low-dose group G), 0.126 mg/mL(middle-dose group), and 0.252 mg/m L(high-dose group), respectively. Then m RNA expression levels of BMP-2, BMPR-ⅠA/Ⅱ, Runx2, Osterix, COL-I, ALP and BGP in OB,protein expression levels of BMP-2 and p-Smad1/5/8 in OBs, pBMPR-ⅠA in cytomembrane and protein expression levels of Runx2, Osterix,Smad1/5/8/4 in nucleus and cytoplasm of OB were examined. The result showed as follows:(1) The m RNA and protein expression levels of BMP-2 in OBs, the protein expression level of p-Smad1/5/8 in OBs, the mRNA expression levels of BMPR-ⅠA and BMPR-Ⅱ in OBs, the protein expression level of p BMPR-ⅠA in cytomembrane of OBs, the protein expression levels of Smad1/5/8/4 in nucleus and cytoplasm of OBs in Al-treated groups were significantly lower than those in CG(p<0.01). These results demonstrated that Al decreases OB function by inhibiting the BMP/Smad signaling pathway.(2) The mRNA and protein expression levels of Runx2 and Osterix in Al-treated groups were significantly lower than those in CG(P<0.01). The results demonstrated that Al inhibited the activity of nuclear transcription factors in OB.(3) The mRNA expression levels of COL-I, ALP and BGP in Al-treated groups were significantly lower than those in CG(P<0.01). The results demonstrated that Al inhibits OB function.These results indicated that Al inhibits the BMP/Smad signaling pathway and decreases the activity of nuclear transcription factors(Runx2 and Osterix), then down-regulates OB function to expressive the COL-I, ALP and BGP.