Genetic engineering of the pancreatic β-cell line MIN6 to express bacterial globin proteins protects cells from nitrosative stress

Susceptibility of pancreatic β-cells to nitric oxide (NO) is a prime issue in type 1 diabetes mellitus. NO is produced by intraislet-resident macrophages or by the β-cells themselves after cytokine stimulation, leading to reduction of viability and apoptosis. We have previously demonstrated a potent NO detoxification activity of bacterial globin proteins. Unlike the mammalian counterparts, these proteins can possess an intramolecular reductase domain, which increases the catalytic NO turnover. Constitutive expression of either Ralstonia eutropha flavohemoglobin or Vitreoscilla hemoglobin increased the cellular viability of MIN6 β-cell cultures exposed to the NO donor sodium nitroprusside (SNP) maximally by 42.8% and 33.8%, respectively, relative to the wild-type MIN6 control. Addition of SNP to a final concentration of 100 IM induced caspase activity. Under these conditions, no significant induction of caspase activity was observed in the globin-protected cells, whereas in the parental MIN6 cells, caspase activity was increased by 57 ± 2%. Treatment of β-cells with a combination of interleukin-1β, interferon-I, and tumor necrosis factor-α stimulated the generation of NO in vivo, and the heterologous expression of globin proteins could protect β-cells to a small extent from the cytokine challenge.