Plasma from Type 2 Diabetes Patients Increase Monocyte‐Derived Superoxide Production via ER Stress‐NADPH Oxidase Pathway

Abstract

Recent evidence suggests that when human monocytes (THP-1 cells) were incubated with artificially made glucolipotoxic media to mimic the plasma composition of type 2 diabetes (T2D) patients, intracellular reactive oxygen species were increased via endoplasmic reticular (ER) stress. The extent to which these findings translate to patients with T2D remains unclear. First, we measured intracellular superoxide production (dihydroethidium fluorescence) in peripheral blood mononuclear cells from whole blood of T2D patients (N=6) and compared to healthy controls (CON; N=6). T2D patients exhibited greater basal intracellular superoxide (3.1±0.5 fold; P<0.05). Next, THP-1 cells were cultured with plasma from T2D patients or CON. The cells exposed to T2D plasma exhibited greater intracellular superoxide compared to CON (1.2±0.03 fold; P<0.05). Importantly, the increase in superoxide was eliminated by tauroursodeoxycholic acid (TUDCA; ER stress inhibitor) and gp91ds-tat (NADPH oxidase inhibitor) either alone or in combination. Lastly, when glucose (high: 25 mM or normal: 5.9 mM) alone was cultured with THP-1 cells, no increase in the monocyte-derived superoxide was found (P>0.05). Collectively, these data suggest that the ability of ER stress to induce human monocyte-derived superoxide in T2D appears to be mediated by NADPH oxidase. Moreover, hyperglycemia alone does not appear to be a primary contributor of elevated superoxide, suggesting that other potential triggers in plasma of T2D patients contribute to ER stress-induced NADPH oxidase activation in monocytes. Supported by MU CBIS pilot grant (NIH grant# P50AT006273) (SHD)