Effect of calcium ion regulating KLK4 expression on the growth of ameloblast

Objective To investigate the effect of calcium ions on the expression of kallikrein-4 (KLK4) and cell growth of ameloblast, and to provide an experimental basis for calcium ion promoting normal mineralization of enamel. Methods ALC cells were treated with 0, 2.0, 2.5, 3.0, and 3.5 mmol/L CaCl₂ for 24 and 48 h. KLK4 expression was analyzed by qRT-PCR and Western blot analysis. The viability of ALC cells was determined by using CCK-8. AnnexinV-FITC/PI dual staining combined with flow cytometry and Hoechst 33342 staining were used to detect the ALC cell cycle and cell apoptosis. The protein expression level of glucose-regulated protein 78 (GRP78) was measured by Western blot analysis. Results After 24 h of treatment with 2.5, 3.0, and 3.5 mmol/L CaCl₂, the expression of KLK4 mRNA was increased (<i>P</i>&lt;0.05), and after 24 h of treatment with 2.0, 2.5, 3.0, and 3.5 mmol/L CaCl₂, the expression of KLK4 protein was increased (<i>P</i>&lt;0.05). After 48 h of treatment with 3.0 mmol/L and 3.5 mmol/L CaCl₂, the expression of KLK4 mRNA and protein was increased (<i>P</i>&lt;0.05). Compared with the control group, the viability of ALC cells was increased after 24 and 48 h of treatment with 2.0, 2.5, and 3.0 mmol/L CaCl₂ (<i>P</i>&lt;0.05), and the highest cell viability was observed with 2.5 mmol/L CaCl₂. Hoechst 33342 staining results showed that 3.0 mmol/L and 3.5 mmol/L CaCl₂ may promote apoptosis in ALC cells. Flow cytometry showed that the proportion of G2/M phase cells and the apoptosis rate increased after 3.5 mmol /L CaCl₂ treatment for 24 h (<i>P</i>&lt;0.05), compared with the 0, 2.0, 2.5, and 3.0 mmol/L CaCl₂ groups. After 24 h of treatment with 3.0 mmol/L and 3.5 mmol/L CaCl₂, the expression of GRP78 protein was reduced (<i>P</i>&lt;0.05), and after 48 h of treatment with 2.5 mmol/L CaCl₂, the expression of GRP78 protein was reduced (<i>P</i>&lt;0.05). Conclusion Calcium ions can promote the increase of KLK4 expression and cell viability in ALC cells, but a higher concentration of calcium ions can block the G2/M phase of ALC cells, thus inducing apoptosis of ALC cells and reducing the expression of apoptosation-related protein GRP78.