In Vitro: When applies to the media of ER stressed cultured cells, 4μ8C (IRE1 Inhibitor III) inhibits Xbp1 splicing in a concentration-dependent manner. 4μ8C dissociates slowly from IRE1, but ishout of inhibitor leads to rapid recovery of Xbp1 splicing in cells.The IRE1 endoribonuclease inhibitor 4μ8c prevents the splicing of the XBP1 mRNA in response to ER stress caused by mutant proinsulin production. The inositol-requiring enzyme 1α (IRE1α) is a serine-threonine kinase that plays crucial roles in activating the unfolded protein response. 4μ8C treatment dramatically inhibits IL-4 production by CD4+ T cells under Th0 conditions because both the IL-4 levels in the culture supernatant and the percentage of IL-4 positive cells are reduced by 4μ8C treatment. In addition, both IL-5 and IL-13 production are significantly reduced upon treatment with 4μ8C.
In Vivo: 4μ8c (IRE1 Inhibitor III) (i.p. injection; 10 mg/kg/day for 4 more weeks) leads to a significant reduction (45.2%) in atherosclerotic lesion area in en face aorta preparations. 4μ8c can effectively mitigate plaque development in mice. ?4μ8C (orally; 10, 50, or 100 mg/kg) suppresses passive cutaneous anaphylaxis (PCA) in mice (ED50 = 25.1 mg/kg). ?4μ8C reverses the ER stress-dependent loss of several known RIDD targets, with an EC50 of approximately 4 μM, approximating that of inhibition of XBP1 target gene activation.