NS6180, a new K(Ca) 3.1 channel inhibitor prevents T-cell activation and inflammation in a rat model of inflammatory bowel disease

Background and purpose: The K(Ca) 3.1 channel is a potential target for therapy of immune disease. We identified a compound from a new chemical class of K(Ca) 3.1 inhibitors and assessed in vitro and in vivo inhibition of immune responses.

Experimental approach: We characterized the benzothiazinone NS6180 (4-[[3-(trifluoromethyl)phenyl]methyl]-2H-1,4-benzothiazin-3(4H)-one) with respect to potency and molecular site of action on K(Ca) 3.1 channels, selectivity towards other targets, effects on T-cell activation as well as pharmacokinetics and inflammation control in colitis induced by 2,4-dinitrobenzene sulfonic acid, a rat model of inflammatory bowel disease (IBD).

Key results: NS6180 inhibited cloned human K(Ca) 3.1 channels (IC(50) = 9 nM) via T250 and V275, the same amino acid residues conferring sensitivity to triarylmethanes such as like TRAM-34. NS6180 inhibited endogenously expressed K(Ca) 3.1 channels in human, mouse and rat erythrocytes, with similar potencies (15-20 nM). NS6180 suppressed rat and mouse splenocyte proliferation at submicrolar concentrations and potently inhibited IL-2 and IFN-γ production, while exerting smaller effects on IL-4 and TNF-α and no effect on IL-17 production. Antibody staining showed K(Ca) 3.1 channels in healthy colon and strong up-regulation in association with infiltrating immune cells after induction of colitis. Despite poor plasma exposure, NS6180 (3 and 10 mg·kg(-1) b.i.d.) dampened colon inflammation and improved body weight gain as effectively as the standard IBD drug sulfasalazine (300 mg·kg(-1) q.d.).

Conclusions and implications: NS6180 represents a novel class of K(Ca) 3.1 channel inhibitors which inhibited experimental colitis, suggesting K(Ca) 3.1 channels as targets for pharmacological control of intestinal inflammation.