Fig. 7.

Silencing hypoxia-inducible factor (HIF-1α) prevents intermittent hypoxia (IH)-induced increase in NADPH oxidase (NOX4) protein, mRNA, enzyme activity, and baseline insulin release in mouse insulinoma (MIN6) cells. A: MIN6 cells were exposed to increasing cycles of in vitro IH. Insulin release was measured in the media after terminating IH. Data were normalized to milligram (mg) of protein. B: representative immunoblot of HIF-1α and NOX4 along with tubulin protein. C: NOX4 mRNA; D: NOX enzyme activity in MIN6 cells treated with lentiviral short hairpin HIF-1 RNA (shRNA) targeted to HIF-1α or scrambled (scr) RNA and exposed to 60 cycles of IH (IH₆₀) or normoxia (N); E: insulin release in response to IH (normalized to mg protein); and F: insulin secretion responses to 30 mM KCl (normalized to 2mM KCl) in the media from MIN6 cells treated with lentiviral siRNA targeted to HIF-1α or scrambled (scr) RNA and exposed to IH₆₀ or normoxia (N). Data presented are means ± SE from five independent experiments. **P < 0.01; ns, Not significant (P value > 0.05).