Green Tea Polyphenols and Sulfasalazine have Parallel Anti-Inflammatory Properties in Colitis Models

Abstract

Background: There is no cure for autoimmune chronic inflammatory bowel disease (IBD). IBD patients commonly use complementary and alternative medications of which the safety, efficacy, and interaction with standard-of-care therapies are not fully known. Thus the consequences can become life-threatening. Sulfasalazine commonly used in IBD, potentially has severe adverse effects, including infertility, pulmonary fibrosis, lack of response, and ultimately patients may require intestinal resection. We hypothesized that green tea polyphenols (GrTP, EGCG) and sulfasalazine have similar anti-inflammatory properties.

Methods: BALB/c mice received Dextran sodium sulfate (DSS) to induce colitis (ulcerative colitis model). Exposure of IL-10 deficient mice (BALB/c-background) to normal microbiota provoked enterocolitis (mimics Crohn's disease). Animals were treated with agents incorporated into daily diets. Control animals received sham treatment.

Results: DSS-treated animals developed severe bloody diarrhea and colitis (score 0-4, 3.2 ± 0.27). IL-10 deficient mice developed severe enterocolitis as manifested by diarrhea, rectal prolapse, and colonic lesions. Animals tolerated regimens (GrTP, EGCG, sulfasalazine) with no major side effects, and further developed less severe colitis. IL-10 deficient animals became moribund on high dose, while tolerated low and Mid doses with significant improved symptoms of enterocolitis. GrTP, EGCG, and sulfasalazine significantly ameliorated colonic damage and histological scores in treated animals in a similar manner (GrTP vs. DSS p < 0.05; EGCG, sulfasalazine vs. DSS p < 0.01). The inflammatory markers TNFα (3-fold), IL-6 (14-fold), and serum amyloid A (40-fold) increased in colitic animals and significantly decreased with treatment regiments. In contrast, circulatory leptin levels decreased in colitic animals (twofold). EGCG additionally reduced leptin levels (p < 0.01) while GrTP and sulfasalazine had no effect on leptin levels (p < 0.05). Hepatic and colonic antioxidants were significantly depleted in colitic animals and treatment regiments significantly restored antioxidants levels.

Conclusion: GrTP and EGCG improved antioxidants levels and attenuated severity of colitis analogous to sulfasalazine. Future studies will reveal whether polyphenols can become an alternative/additive therapy for IBD therapy in humans.

Keywords: EGCG; IBD; IL-10−/− mice; colitis; enterocolitis; polyphenols; sulfasalazine.

Figure 1

Percent body weight loss in DSS-induced colitis compared to the normal control animals. Colitic mice lost body weight and animals on High dose EGCG therapy showed the most weight loss. Mid and Low doses of EGCG had no effect on body weight. In contrast, GrTP and Sulfasalazine partially improved the body weight loss.

Figure 2

(A) DSS-induced colitic animals had increased secretion of inflammatory cytokine TNFα in blood circulation. EGCG therapy significantly prevented increased secretion (p < 0.05) and sulfasalazine normalized TNFα secretion. (B) Multifunctional cytokine, IL-6 was drastically increased in DSS-induced colitic animals. EGCG (p < 0.05) and sulfasalazine (p < 0.01) significantly reduced elevated level of this inflammatory marker in treated animals.

Figure 3

Circulating leptin level significantly decreased in DSS-induced colitic animals (p < 0.05) and EGCG further reduced the leptin levels (DSS vs. EGCG < 0.05), while GrTP and sulfasalazine had no significant effect on leptin levels (vs. DSS > 0.05).

Figure 4

Pathologic scores (zero-normal to four most severe) in colitic animals. DSS-induced severe colonic pathology. Low dose EGCG and sulfasalazine similarly attenuated pathological lesions (p < 0.01). To a lesser extent, GrTP (p < 0.05) ameliorated the colonic lesions.

Figure 5

IL-10 deficient mice when exposed to the normal colonic microbiota (Sham-Control) developed enterocolitis in conventional environment. (A) IL-10 deficient mice became anemic with low hematocrit (Sham-Control) and GrTP significantly improved hematocrit in treated animals. (B) IL-10 deficient mice had enlarged splenic tissue due to infiltration of inflammatory cells and GrTP significantly reduced the inflammatory response. (C) IL-10 deficient mice developed spontaneous enterocolitis and rectal prolapsed. GrTP significantly ameliorated the pathological scores.