Modulation of colonic inflammation in Mdr1a-/- mice by green tea polyphenols and their effects on the colon transcriptome and proteome

This study tested the anti-inflammatory potential of a green tea extract rich in polyphenols (GrTP) in the colon of the multi-drug resistance targeted mutation (Mdr1a-/-) mouse model of IBD. A colonic histological injury score was determined for each mouse to establish the effect of GrTP on inflammation. Insights into mechanisms responsible for changes in inflammation were gained using transcriptome (microarray) and proteome (2-D gel electrophoresis and LCMS protein identification) analyses. A total of 24 male Mdr1a-/- mice purchased from Taconic (Hudson, NY, USA) at 4-5 weeks of age were used for this study. 12 mice were randomly assigned to each of two different dietary groups: control (AIN-76A powdered diet), or GrTP (AIN-76A + 0.6% green tea polyphenol). At 21 and 24 weeks of age, mice were euthanized and colon samples taken for histological and microarray analyses. The total histology score (HIS) in the colon was determined according to previously described criteria. Total RNA was isolated using TRIzol reagent. Colon RNA from four Mdr1a-/- mice on the GrTP diet (with low HIS) was compared with colon RNA from four Mdr1a-/- mice on the AIN-76A diet (with high HIS). All individual RNA samples were hybridized against a common reference RNA on separate slides. The reference RNA was prepared using equimolar RNA extracts from small intestine, colon, kidney and liver of normal healthy growing Swiss mice plus RNA extracts from Swiss mouse fetuses.