Abstract
Hypoxia is a key trigger in the transformation of oral leukoplakia into oral cancer. However, it is still too early to determine the role of hypoxia in the development of oral leukoplakia. Prx1, an antioxidant protein, upregulated by hypoxia, regulates cellular autophagy in leukoplakia. This study aimed to understand the mechanisms by which hypoxia induces Prx1 expression during autophagy in oral leukoplakia. We used an experimental model of tongue epithelial hyperplasia induced by 4-nitroquinoline-1-oxide (4NQO) and dysplastic oral keratinocytes. Prx1 knockdown DOK cells, Leuk-1 cells and control cells were harvested, and cell proliferation was assayed using the Cell Counting Kit-8. Several hypoxia and autophagy-related proteins were examined using quantitative real-time polymerase chain reaction, immunohistochemistry, immunofluorescence, and western blotting in cells and mouse tongue tissues. In addition, the ultrastructure of the cells was observed by transmission electron microscopy. Hypoxia induces cell proliferation, autophagic vesicles and the expression of Prx1, BNIP3, LC3II/I and Beclin-1 in DOK and Leuk-1 cells. However, these effects were all attenuated by Prx1 knockdown. Histologically, 4NQO induced epithelial hyperplasia in the tongue mucosa. The expression of proliferation marker PCNA, autophagy-related proteins LC3B and Beclin-1, as well as HIF-1α/BNIP3 was significantly lower in the tongue tissues of Prx1flox/flox:Cre+ mice compared with Prx1flox/flox mice. In Prx1flox/flox:Cre+ mice, an increased expression of HIF-1α/BNIP3, LC3B and Beclin-1 was detected in epithelial hyperplasia tongue tissues compared to normal tissues. The current study suggests that Prx1 may promotes cell proliferation and autophagy in oral leukoplakia cells via the HIF-1α/BNIP3 pathway.