Estradiol Has Differential Effects on Acute Colonic Inflammation in the Presence and Absence of Estrogen Receptor [beta] Expression

Background Inflammatory bowel disease (IBD) increases the risk of developing colon cancer. This risk is higher in men compared to women, implicating a role for female hormones in the protection against this disease. Studies from our laboratory demonstrated that estradiol (E.sub.2) protects against inflammation-associated colon tumor formation when administered following chemical carcinogen and induction of chronic colitis. Aim This study seeks to better understand the effect of E.sub.2 on acute colitis in the presence and absence of estrogen receptor [beta] (ER[beta]). Methods Inflammation was induced by 2,4,6-trinitrobenzenesulfonic acid in wild-type (WT) and ER[beta] knockout (ER[beta]KO) mice implanted with a control or E.sub.2-containing pellet and killed 5 days later. Inflammation and injury were scored by a pathologist. Apoptosis and proliferation were assessed by immunohistochemistry. Cytokines were measured by multiplex analysis. Results E.sub.2 treatment reduced inflammation in the middle colon in WT mice and the distal colon in ER[beta]KO mice compared to control mice. WT mice had reduced IL-6, IL-12, IL-17, GM-CSF, IFN-[gamma], MCP-1, MIP-1[alpha], and TNF-[alpha], and ER[beta]KO had reduced IL-6 and IFN-[gamma] expression in response to E.sub.2. Injury scores were lower in E.sub.2-treated ER[beta]KO mice compared to control ER[beta]KO mice. ER[beta]KO mice had increased proliferation in the basal third of crypts in the distal colon and decreased apoptosis in the proximal colon. Conclusions These data suggest that E.sub.2 has differential protective effects against acute colitis in the presence or absence of ER[beta] and provide insight into how E.sub.2 may protect against IBD.