GM-CSF is effective in the treatment of DSS colitis in a mechanism involving the 440c(+) pDC population.

Background & Aims-Regenerating (Reg) gene IV is predominantly expressed in the gastrointestinal (GI) cells and highly upregulated in many GI malignancies including colorectal cancer (CRC). Human CRC cells expressing higher levels of Reg IV are resistant to conventional therapies including irradiation (IR). However, underlying mechanism is not well defined.

Background The pathogenesis of inflammatory bowel disease (IBD) is associated with a dysregulated mucosal immune response. Certain stimulators of innate immunity (CpG DNA or GM-CSF) are reported to be anti-inflammatory in IBD. Toll-like receptor-7 (TLR7) is an important regulator of innate immunity and its activation plays a key role in induction of type I IFN. The present study tests the hypothesis that TLR7 agonists, Imiquimod have therapeutic efficacy in IBD. Methods Acute colitis was induced in Balb/c mice by giving 5% DSS in drinking water for 7 days. Mice were treated with Imiquimod either orally or topically, and its therapeutic effects on diseases activity were examined. Isolated mouse CD11c+ dendritic cells and human intestinal epithelial cells (HT29 & HCT116) were treated with Imiquimod (10 μg/ml) and their susceptibility to intracellular Salmonella typhimurium infection was assessed by gentamicin protection assay. Results Oral administration of Imiquimod induced type I IFN expression in the gastrointestinal mucosa and ameliorated DSS-induced acute colitis as assessed by clinical parameters, histology and mRNA expression of proinflammatory cytokines. Topical administration of Imiquimod also ameliorated DSS-colitis by inducing the expression of type I IFN in the colonic mucosa. However, no evidences for a systemic IFN response were observed. Imiquimod treatments to both CD11c+ and intestinal epithelial cells significantly increased expression of antimicrobial peptides (AMPs) and reduced survival of intracellular Salmonella typhimurium. Conclusions Imiquimod induces type I IFN and AMP to ameliorate DSS-induced acute colitis and prevents Salmonella survival. Therefore, Imiquimod treatments provide a new therapeutic approach for IBD patients.

Upregulation of regenerating gene 4 (Reg4) is observed in many human gastrointestinal malignancies including colorectal cancer (CRC). We previously reported a Reg4-mediated induction of epidermal growth factor receptor-Akt-AP1 signaling regulating CRC cell apoptosis. However, the role of Reg4 in the regulation of CRC cell division is poorly understood. This study tests the hypothesis that Reg4 induces Akt-GSK3β-β-Catenin-TCF-4 signaling to regulate CRC cell division. In vitro models of human CRC were used to determine the role of Reg4 in regulation of CRC cell division. Cell cycle studies demonstrated that Reg4 treatment significantly decreased CRC cell number in G1 phase and increased in G2 phase. Subsequently Reg4 significantly increased the mitotic index of CRC cells. As assessed by real-time RT-PCR and Western blot analyses, Reg4 significantly increased the expression of cell cycle regulatory genes Cyclin D1 and D3, and associated Cyclin-dependent kinases (CDK4 and CDK6). Reg4-mediated increase in these genes involved a pathway that included an induced Akt activity by increasing phosphorylation of Thr308 and Ser473, a reduced glycogen synthase kinase 3β(GSK-3β) activity by increasing phosphorylation of Ser9, an induced nuclear translocation of β-Catenin by decreasing phosphorylation of Ser33/37/Thr41, and an increased TCF-4 transcriptional activity. Furthermore, antagonism of Reg4-signaling using Reg4-specific mAbs (2H6 and 3E5) and Akt inhibitor significantly decreased, whereas agonism using GSK-3β antagonist (SB216763) significantly increased mitotic index and proliferation of CRC cells. These results identify Reg4 as a key regulator of the CRC cell division and proliferation, hence a potential target of human CRC treatment.

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