Nuclear Factor-κB Is a Critical Mediator of Ste20-Like Proline-/Alanine-Rich Kinase Regulation in Intestinal Inflammation

Inflammatory bowel disease (IBD) is thought to result from commensal flora, aberrant cellular stress, and genetic factors. Here we show that the expression of colonic Ste20-like proline-/alanine-rich kinase (SPAK) that lacks a PAPA box and an F-α helix loop is increased in patients with IBD. The same effects were observed in a mouse model of dextran sodium sulfate-induced colitis and in Caco2-BBE cells treated with the pro-inflammatory cytokine tumor necrosis factor (TNF)-α. The 5′-flanking region of the SPAK gene contains two transcriptional start sites, three transcription factor Sp1-binding sites, and one transcription factor nuclear factor (NF)-κB-binding site, but no TATA elements. The NF-κB-binding site was essential for stimulated SPAK promoter activity by TNF-α, whereas the Sp1-binding sites were important for basal promoter activity. siRNA-induced knockdown of NF-κB, but not of Sp1, reduced TNF-α-induced SPAK expression. Nuclear run-on and mRNA decay assays demonstrated that TNF-α directly increased SPAK mRNA transcription without affecting SPAK mRNA stability. Furthermore, up-regulation of NF-κB expression and demethylation of the CpG islands induced by TNF-α also played roles in the up-regulation of SPAK expression. In conclusion, our data indicate that during inflammatory conditions, TNF-α is a key regulator of SPAK expression. The development of compounds that can either modulate or disrupt the activity of SPAK-mediated pathways is therefore important for the control and attenuation of downstream pathological responses, particularly in IBD.