Effect of hypoxia on the proliferation and expressions of hypoxia-inducible factor-1α, vascular endothelial growth factor and matrix metalloproteinase-9 in keratinocytes obtained from oral lichen planus lesions

Abstract

To investigate the effect of hypoxia on the proliferation and expressions of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) in keratinocytes obtained from oral lichen planus (OLP) lesions. Hypoxia environment was induced by a airtight incubator. Five groups were included, normoxia control group, hypoxia control group (12, 24, 36, 48 h). The effect of different treatment time of hypoxia on cellular proliferation was determined with cell counting kit-8 (CCK-8). The mRNA and protein expressions of HIF-1α, VEGF and MMP-9 were analyzed respectively by quantitative real-time polymerase chain reaction with SYBR Green I and Western blotting. The growth activity of keratinocytes obtained from OLP lesions in the hypoxia groups (0.340±0.002, 0.415±0.006, 0.546±0.006) was reduced than that in control (0.431±0.001, 0.620±0.004, 1.022±0.005) (P < 0.01). The mRNA levels of VEGF (2.087±0.291, 3.189±0.573, 5.402±0.563) and MMP-9 (2.936±0.500, 4.083±0.300, 6.374±0.858) were elevated by hypoxia (P < 0.05). The protein levels of HIF- 1α (0.414±0.093, 0.751±0.056, 0.875±0.040), VEGF (0.393±0.046, 0.557±0.078, 0.767±0.045) and MMP-9 (0.250±0.053, 0.384±0.038, 0.611±0.092) were all remarkably elevated by hypoxia (P < 0.05). However, hypoxia had no effect on HIF-1α mRNA expression. The mRNA expression of HIF-1α after hypoxia exposure for 36 h (1.412±0.094) and 48 h (1.417±0.446) was higher than that of control group, however, there was no significant difference. A positive correlation was noted between HIF-1α and VEGF in protein level (r = 0.905, P = 0.000), and the same correlation found between HIF-1α and MMP-9 (r = 0.881, P = 0.000). Hypoxia conditions may inhibit the proliferation of keratinocytes obtained from OLP lesions. Hypoxia conditions can promote the protein expressions of HIF-1α and both the mRNA and protein expression of VEGF and MMP-9 in keratinocytes obtained from OLP lesions exposed to hypoxia. The relative high expression of HIF-1α may be involved in multiple aspects of OLP progression through the regulation of its downstream target genes.