Exposure of colonic epithelial cells to oxidative and endoplasmic reticulum stress causes rapid potassium efflux and calcium influx
Shabala, L and Walker, EJ and Eklund, A and Randall-Demllo, S and Shabala, S and Guven, N and Cook, AL and Eri, RD, Exposure of colonic epithelial cells to oxidative and endoplasmic reticulum stress causes rapid potassium efflux and calcium influx, Cell Biochemistry and Function, 31, (7) pp. 603-611. ISSN 1099-0844 (2013) [Refereed Article]
Endoplasmic reticulum (ER) stress and oxidative stress have recently been linked to the pathogenesis of inflammatory bowel diseases. Under physiological conditions, intestinal epithelial cells are exposed to ER and oxidative stress affecting the cellular ionic homeostasis. However, these altered ion flux ‘signatures’ during these stress conditions are poorly characterized. We investigated the kinetics of K+, Ca2+ and H+ ion fluxes during ER and oxidative stress in a colonic epithelial cell line LS174T using a non-invasive microelectrode ion flux estimation technique. ER and oxidative stress were induced by cell exposure to tunicamycin (TM) and copper ascorbate (CuAsc), respectively, from 1 to 24 h. Dramatic K+ efflux was observed following acute ER stress with peak K+ efflux being 306 and 1387 nmolm-2s-1 for 10
and 50μgml-1, respectively (p<0.01). TM-dependent Ca2+ uptake was more prolonged with peak values of 085 and 268 nmolm-2s-1 for 10 and 50 mgml-1 TM, respectively (p<0.02). Ion homeostasis was also affected by the duration of ER stress. Increased duration of TM treatment from 0 to 18 h led to increases in both K+ efflux and Ca2+ uptake. While K+ changes were significantly higher at each time point tested, Ca2+ uptake was significantly higher only after prolonged treatment (18 h). CuAsc also led to an increased K+ efflux
and Ca2+ uptake. Functional assays to investigate the effect of inhibiting K+ efflux with tetraethylammonium resulted in increased cell viability. We conclude that ER/oxidative stress in colonic epithelial cells cause dramatic K+, Ca2+ and H+ ion flux changes, which may predispose this lineage to poor stress recovery reminiscent of that seen in inflammatory bowel diseases.
ER stress, inflammatory bowel disease, ion flux, oxidative stress, colonic epithelial cells