Final Progress Report
Proposal No. IBD-0024R
Principal Investigator: Laura P. Hale, M.D., Ph.D.
Applicant Organization: Duke University (Durham, North Carolina, U.S.A.)
Project Title: Bromelain treatment of inflammatory bowel disease
Period of Award: December 1, 2003 - February 28, 2005
List of Significant Results (positive or negative)
1. Established that bromelain concentrations as low as 20 mg/ml are sufficient to remove bromelain-sensitive molecules from the surface of human and murine cells.
2. Established that orally administered bromelain retains its proteolytic activity throughout the murine gastrointestinal tract when administered in antacid (Maalox or NaHCO3).
3. Established that long-term oral bromelain treatment is non-toxic in mice at doses up to 1000 mg/kg/day.
4. Established that daily treatment with 5 mg bromelain significantly decreased both the incidence and severity of spontaneous colitis as well as the severity of established colitis in IL-10-/- mice.
5. Established that proteolytic activity is required for efficacy of bromelain as an anti-inflammatory agent in inflammatory bowel disease (IBD).
6. Developed expertise in the T cell transfer model of colitis (CD4+CD45RBhigh CD25- T effector cells into RAG-2-deficient mice).
7. Established that bromelain treatment in vitro decreases production of the pro-inflammatory cytokines and chemokines IFN-γ, MCP-1, G-CSF, and MIP-1b by human colon biopsies.
8. Developed assays to measure and standardize the activity of bromelain used in pre-clinical and clinical studies.
9. that delivery of bromelain as a concentrated bolus (rather than timed release) is the preferred method to prevent its inactivation and thus to maximize its proteolytic activity in vivo.
10. Established that exposure to piroxicam enhances intestinal epithelial apoptosis both in vitro and in vivo and facilitates adhesion and invasion of intestinal bacteria into mucosal tissues in vivo.
11. Established the normal composition and the spatial organization of the bacterial flora in murine intestine.
12. Established that mice with IBD develop intestinal biofilms and thus provide a good model for studying IBD-associated changes in bacterial-mucosal interactions that were first identified in human IBD tissues.
Lay Description of this Report
Bromelain is a mixture of protein-degrading enzymes that is purified from pineapple stems and sold by health food stores to “improve digestion.” We and others previously showed that bromelain affects the activation of lymphocytes. One published report described two patients whose ulcerative colitis was unresponsive to standard medical treatments, but went into remission after taking bromelain. The purpose of this project was to scientifically determine whether bromelain is beneficial in inflammatory bowel disease using a mouse model of colitis.
Most proteins in what we eat are simply digested and have no effects other than supplying nutrition. However, we found that bromelain is very stable within the gastrointestinal tract when given in antacids. Extracts of stool from bromelain-treated mice contain bromelain that can still degrade proteins. The activity of bromelain is most stable when bromelain is present at high concentrations. This means that giving the bromelain all at once in a large dose is better than using smaller doses throughout the day. We found that giving mice one dose of bromelain by mouth each day decreased the development of spontaneous colitis in IL-10 knockout mice. A similar dose of bromelain also greatly decreased the severity of colitis in IL-10 knockout mice with established moderate to severe colitis. The bromelain enzymes had to be active (that is, capable of degrading protein) in order to be beneficial. Bromelain treatment of colon biopsies that had been removed from patients with inflammatory bowel disease decreased their production of lymphocyte-activating substances. Taken together, these studies suggest that bromelain holds promise as a new type of treatment for patients with inflammatory bowel disease.
The active ingredients within bromelain derived from pineapple stem are similar to what is found in pineapple fruit, but are present in different proportions. Therefore, more study will be necessary to determine whether any benefits obtained by taking bromelain pills could also be obtained by eating pineapple fruit. Since bromelain enzymes are destroyed by heating but not freezing, any potential health benefit would be expected to occur only with fresh or frozen (but not canned) pineapple.