Hydrogen Sulfide as an allosteric modulator of ATP sensitive potassium channels in experimental colitis

Abstract

The ATP sensitive potassium channel (KATP) in mouse colonic smooth muscle cell is a complex containing a pore forming subunit (Kir6.1) and a sulfonyl urea receptor subunit (SUR2B). We used whole‐cell voltage‐clamp techniques to study the alterations in these channels in smooth muscle cells in experimental colitis. Colitis was induced in BALB/C mice following an intracolonic administration of trinitrobenzene sulfonic acid. KATP currents were measured at Vh −60 mV in high K+ external solution. The dose‐response to levcromakalim (LEV), a KATP channel opener, was significantly shifted to the left in the inflamed smooth muscle cells. Both the affinity and maximal currents induced by LEV were enhanced in inflammation. The EC50 in control was 6489 nM (n=10) and 423.4 nM (n=8) in inflamed colon while the maximal currents were 9.3 ± 1.1 pA/pF (60 μM) in control and 47.7 ± 16.8 pA/pF (3 μM) following inflammation. Similar to LEV, KATP currents activated by sodium hydrogen sulfide (NaHS) (10–1000 μM) were significantly greater in inflamed compared to controls. In control cells, pretreatment with 100 μM NaHS shifted the EC50 for LEV‐induced currents from 6489 nM (n=10) to 180.9 nM (n=8). These data suggest that NaHS can act as an allosteric modulator for LEV‐induced KATP currents. Decreased colonic motility may result from enhanced KATP activation by increased release of H2S in colitis. Supported by NIH DK046367.