Protective effects of dietary curcumin in mouse model of chemically induced colitis are strain dependent.

BACKGROUND: Curcumin (diferulolylmethane) has been shown to have a protective role in mouse models of inflammatory bowel diseases (IBD) and to reduce the relapse rate in human ulcerative colitis (UC), thus making it a potentially viable supportive treatment option. Trinitrobenzene sulfonic acid (TNBS) colitis in NKT-deficient SJL/J mice has been described as Th1-mediated inflammation, whereas BALB/c mice are believed to exhibit a mixed Th1/Th2 response. METHODS: We therefore investigated the effect of dietary curcumin in colitis induced in these 2 strains. RESULTS: In the BALB/c mice, curcumin significantly increased survival, prevented weight loss, and normalized disease activity. In the SJL/J mice, curcumin demonstrated no protective effects. Genomewide microarray analysis of colonic gene expression was employed to define the differential effect of curcumin in these 2 strains. This analysis not only confirmed the disparate responses of the 2 strains to curcumin but also indicated different responses to TNBS. Curcumin inhibited proliferation of splenocytes from naive BALB/c mice but not SJL/J mice when nonspecifically stimulated in vitro with concanavalin A (ConA). Proliferation of CD4(+) splenocytes was inhibited in both strains, albeit with about a 2-fold higher IC(50) in SJL/J mice. Secretion of IL-4 and IL-5 by CD4(+) lymphocytes of BALB/c mice but not SJL/J mice was significantly augmented by ConA and reduced to control levels by curcumin. CONCLUSIONS: The efficacy of dietary curcumin in TNBS colitis varies in BALB/c and SJL/J mouse strains. Although the exact mechanism underlying these differences is unclear, the results suggest that the therapeutic value of dietary curcumin may differ depending on the nature of immune dysregulation in IBD.

Molecular mechanism of rat NHE3 gene promoter regulation by sodium butyrate.

Sodium butyrate (NaB) stimulates sodium and water absorption by inducing colonic Na(+)/H(+) exchange. NaB induces Na(+)/H(+) exchanger (NHE)3 activity and protein and mRNA expression both in vivo and in vitro. Our previously published observations indicated that this induction is Ser/Thr kinase dependent and that NaB-responsive elements were localized within -320/-34 bp of the rat NHE3 promoter. Here we further delineate the mechanism of NaB-mediated NHE3 gene transcription. Transient and stable transfection of Caco-2 cells with NHE3 gene reporter constructs identified Sp binding site SpB at position -58/-55 nt as critical for NaB-mediated induction. Gel mobility shift (GMSA) and DNA affinity precipitation assays indicated NaB-induced binding of Sp3 and decreased binding of Sp1 to SpB element. While no changes in expression of Sp1 or Sp3 were noted, NaB induced phosphorylation of Sp1 and acetylation of Sp3. Sp3 was a more potent inducer of NHE3 gene transcription, which suggested that change in balance, favoring binding of Sp3 to the SpB site, would result in significant increase in NHE3 promoter activity. Small interfering RNA studies in Caco-2 cells and data from NaB-treated SL2 cells used as a reconstitution model confirmed this hypothesis. In addition to the SpB site, which played a permissive role, an upstream novel butyrate response element located at -196/-175 nt was necessary for maximal induction. GMSA identified a protein-DNA complex with a -196/-175 nt probe; this interaction was not affected by NaB treatment, thus suggesting that in response to NaB Sp3 binding to site SpB precedes and results in recruitment of the putative factor to this upstream site.

Effects of Boswellia serrata in mouse models of chemically induced colitis.

Extracts from Boswellia serrata have been reported to have anti-inflammatory activity, primarily via boswellic acid-mediated inhibition of leukotriene synthesis. In three small clinical trials, boswellia was shown to improve symptoms of ulcerative colitis and Crohn's disease, and because of its alleged safety, boswellia was considered superior over mesalazine in terms of a benefit-risk evaluation. The goal of this study was to evaluate the effectiveness of boswellia extracts in controlled settings of dextran sulfate- or trinitrobenzene sulfonic acid-induced colitis in mice. Our results suggest that boswellia is ineffective in ameliorating colitis in these models. Moreover, individual boswellic acids were demonstrated to increase the basal and IL-1beta-stimulated NF-kappaB activity in intestinal epithelial cells in vitro as well as reverse proliferative effects of IL-1beta. We also observed hepatotoxic effect of boswellia with pronounced hepatomegaly and steatosis. Hepatotoxity and increased lipid accumulation in response to boswellia were further confirmed in vitro in HepG2 cells with fluorescent Nile red binding/resazurin reduction assay and by confocal microscopy. Microarray analyses of hepatic gene expression demonstrated dysregulation of a number of genes, including a large group of lipid metabolism-related genes, and detoxifying enzymes, a response consistent with that to hepatotoxic xenobiotics. In summary, boswellia does not ameliorate symptoms of colitis in chemically induced murine models and, in higher doses, may become hepatotoxic. Potential implications of prolonged and uncontrolled intake of boswellia as an herbal supplement in inflammatory bowel disease and other inflammatory conditions should be considered in future clinical trials with this botanical.