Premium
Specific inhibition of hypoxia inducible factor 1 exaggerates cell injury induced by in vitro ischemia through deteriorating cellular redox environment
Author(s) -
Guo Shuhong,
Miyake Minoru,
Liu Ke Jian,
Shi Honglian
Publication year - 2009
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2009.05877.x
Subject(s) - ischemia , hypoxia (environmental) , in vitro , redox , microbiology and biotechnology , chemistry , cell injury , pharmacology , neuroscience , biochemistry , biology , medicine , oxygen , apoptosis , organic chemistry
Hypoxia inducible factor 1 (HIF‐1) has been suggested to play a critical role in the fate of cells exposed to hypoxic stress. However, the mechanism of HIF‐1‐regulated cell survival is still not fully understood in ischemic conditions. Redox status is critical for decisions of cell survival, death and differentiation. We investigated the effects of inhibiting HIF‐1 on cellular redox status in SH‐SY5Y cells exposed to hypoxia or oxygen and glucose deprivation (OGD), coupled with cell death analyses. Our results demonstrated that inhibiting HIF‐1α expression by HIF‐1α specific small interfering RNA (siRNA) transfection increased reactive oxygen species generation, and transformed the cells to more oxidizing environments (low GSH/GSSG ratio, low NADPH level) under either hypoxic or OGD exposure. Cell death increased dramatically in the siRNA transfected cells, compared to non‐transfected cells after hypoxic/OGD exposures. In contrast, increasing HIF‐1α expression by desferrioxamine, a metal chelator and hydroxylase inhibitor, induced a more reducing environment (high GSH/GSSG ratio, high NADPH level) and reduced cell death. Further studies showed that HIF‐1 regulated not only glucose transporter‐1 expression, but also the key enzymes of the pentose phosphate pathway such as glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase. These enzymes are important in maintaining cellular redox homeostasis by generating NADPH, the primary reducing agent in cells. Moreover, catalase significantly decreased cell death in the siRNA‐transfected cells induced by hypoxia and OGD. These results suggest that maintenance of cellular redox status by HIF‐1 protects cells from hypoxia and ischemia mediated injuries.