Bromelain is a well known anti-inflammatory compound derived from pineapple fruit and stem extract. It has been shown previously that bromelain decreases colonic inflammation in mice models of inflammatory disease. However the mechanism by which anti-inflammatory effect of bromelain is mediated, is unknown. In this study, we evaluated the effect of bromelain on intestinal inflammation using Lipopolysaccharide (LPS) treated human intestinal adenocarcinoma cell line (HT29 cells) as in vitro model system and Dextran Sulfate Sodium (DSS) induced mouse model of colitis as in vivo system. The expression of TLR4, PPARγ (an antagonist of TLR4), pro-inflammatory cytokines like TNFα and IL8 were evaluated in the in vitro model while in DSS induced mice model, several parameters of inflammation were examined after bromelain treatment. HT29 cells were challenged with 100 ng/ml LPS for 24 h and then treated with 20 μg/ml of pure bromelain for 24 h. Real-time PCR was carried out for quantifying relative expression of TLR4, PPARγ, IL8 and TNFα. Experimental colitis was induced in Swiss albino mice by adding 2% DSS in their drinking water for seven days followed by one day with water. Mice were co-treated with bromelain (100 mg/kg of body weight/day and 200 mg/kg of body weight/day) which was administered through oral gavage. Our in-vitro results demonstrated that LPS induced TLR4 mRNA expression decreases after bromelain treatment while that of PPARγ mRNA increases. In addition, mRNA expression of pro-inflammatory cytokines IL8 and TNFα also decreased significantly after bromelain treatment in LPS challenged HT29 cells. On the other hand, parameters of inflammation were significantly improved in DSS induced colitis model of mice after bromelain treatment. These results show that bromelain possibly negatively modulates expression of TLR4 and restricts NFκB activation to ameliorate inflammation during colitis.
Nirmal Verma#, Naresh Kumar Meena#, Ishani Majumdar and Jaishree Paul*
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