Curcumin upregulates transforming growth factor-β1, its receptors, and vascular endothelial growth factor expressions in an in vitro human gingival fibroblast wound healing model

BACKGROUND

Curcumin accelerates healing of oral wounds; however, the responsible mechanisms remain underexplored. Our hypothesis is curcumin regulates the expression of wound healing-related genes in human gingival fibroblasts (hGFs). This study investigated whether curcumin regulates transforming growth factor (TGF)-β1, type I TGF-β receptor (TGF-βRI), type II TGF-β receptor (TGF-βRII), and vascular endothelial growth factor (VEGF) expression in unwounded hGFs and an in vitro hGF wound healing model.

METHODS

The cytotoxicity of curcumin was evaluated using the MTT assay. Unwounded hGFs were treated with non-cytotoxic concentrations of curcumin for 24 h. Gene expression was determined by quantitative polymerase chain reaction. Then, hGFs were treated with 1 µM curcumin in an in vitro wound healing model. PD98059 pretreatment was performed to determine whether extracellular signal-regulated kinase (ERK) signaling was required for regulation of gene expression by curcumin.

RESULTS

Curcumin at 0.1-20 µM caused no significant change in cell viability. In unwounded hGFs, curcumin had no significant effect on TGF-β1, TGF-βRI, TGF-βRII, or VEGF expression. Conversely, curcumin significantly upregulated the expression of these genes in the in vitro wound healing model. PD98059 significantly attenuated the curcumin-stimulated TGF-βRI, TGF-βRII, and VEGF expression, whereas it had no effect on TGF-β1 expression.

CONCLUSIONS

Curcumin upregulated TGF-β1, TGF-βRI, TGF-βRII, and VEGF expression in an in vitro hGF wound healing model. The ERK pathway is required for TGF-βRI, TGF-βRII, and VEGF induction by curcumin. Our findings support the development of curcumin as a therapeutic agent for gingival ulcers.

Curcumin Promotes Collagen Type I, Keratinocyte Growth Factor-1, and Epidermal Growth Factor Receptor Expressions in the In Vitro Wound Healing Model of Human Gingival Fibroblasts

OBJECTIVE

 Curcumin promotes oral wound healing; however, the underlying mechanism remains unknown. We hypothesized that curcumin may regulate gene expression in human gingival fibroblasts (hGFs). This study investigated the effect of curcumin on the expression of wound healing-related genes, collagen type I (COL1), keratinocyte growth factor (KGF)-1, and epidermal growth factor receptor (EGFR), in the in vitro wound healing model of hGFs, as well as the signaling pathway involved in the regulation of these genes by curcumin.

MATERIALS AND METHODS

 The hGFs were treated with curcumin in the unwounded condition and in the in vitro wound healing model (scratch assay). Gene expression was determined by quantitative polymerase chain reaction. PD98059 was used to elucidate whether extracellular signal regulated kinase (ERK) signaling is involved in the curcumin-regulated gene expression in hGFs. Cell migration was also analyzed by the scratch assay.

STATISTICAL ANALYSIS

 Data were analyzed by independent t-test or one-way analysis of variance (ANOVA) followed by Tukey's Honestly Significant Difference ( HSD) test.

RESULTS

 In unwounded hGFs, curcumin significantly increased KGF-1 and EGFR expressions but not COL1 mRNA expression. Interestingly, curcumin significantly upregulated COL1, KGF-1, and EGFR expressions in the in vitro wound healing model. Furthermore, PD98059 significantly decreased the curcumin-induced COL1 and EGFR expressions, but did not significantly affect KGF-1 upregulation by curcumin. However, hGF migration was not affected by curcumin treatment.

CONCLUSION

 Curcumin induced KGF-1 and EGFR expressions in unwounded hGFs. In the in vitro wound healing model, curcumin upregulated COL1 and EGFR expression via the ERK pathway and increased KGF-1 expression, possibly by an ERK-independent mechanism.