Diabetes mellitus adversely affects human bones and increases the risk of developing osteoporosis. In the present study, treatment with 30 mmol/l glucose was used to establish a high glucose (HG) cell model in vitro. Plasmids were used to overexpress the P2X purinoceptor 7 (P2X7) gene. Brilliant blue G and (4-benzoyl-benzoyl)-ATP were used as a P2X7 antagonist and agonist, respectively. Proliferation of osteogenic MC3T3-E1 cells and alkaline phosphatase (ALP) activity were determined using MTT and colorimetric assays, respectively. Alizarin Red S was used to assess calcification of MC3T3-E1 cells. Western blotting and reverse transcription-quantitative PCR were performed to determine protein and mRNA expression levels. The results demonstrated that HG inhibited MC3T3-E1 cell proliferation and P2X7 expression, reduced calcification, and downregulated the expression levels of ALP and osteocalcin (Ocn) in MC3T3-E1 cells. Overexpression of P2X7 in HG conditions increased calcification and proliferation, and upregulated the levels of ALP and Ocn in MC3T3-E1 cells. Inhibition of P2X7 downregulated the expressions of ALP and Ocn in MC3T3-E1 cells under HG conditions. Therefore, the present results indicated that HG caused damage to osteogenic MC3T3-E1 cells. Thus, P2X7 may be a regulatory factor that may be used to counteract the effects of HG on osteogenesis.

Abstract. Proflavin is one of the novel acridine derivatives that possess various pharmacological effects. Although numerous studies have been performed to investigate proflavin, its effects have not been investigated on the human osteosarcoma MG63 cell line. The core aim of the present study was to test the effects of proflavin on the viability of MG63 cells and the induction of apoptosis and autophagy in MG63 cells. The induction of apoptosis was examined by measuring the changes in the expression of the B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein mRNA and proteins. Apoptotic cell death was identified by the proteolytic cleavage of poly (adenosine diphosphate-ribose) polymerase and caspase-3 and caspase-9. In addition, the autophagic effects of proflavin were examined by the quantitation of the mRNA expression of autophagy protein 5 and Beclin 1, in addition to the identification of the accumulation of microtubule-associated protein 1 light chain 3-II. The present results revealed that proflavin inhibited the proliferation of MG63 cells in a dose-dependent manner. Proflavin-induced cell death was attributed to apoptosis and autophagy. Overall, the present results indicated that the antiseptic agent proflavin exerts anticancer potential through the synergistic activity of apoptosis and autophagy.