METHYLTRANSFERASE SMYD2 MODULATES THERAPEUTIC EFFECTS OF EPIDERMAL GROWTH FACTOR IN INFLAMMATORY BOWEL DISEASE

Abstract

Abstract BACKGROUND Inflammatory bowel disease (IBD) is a chronic and remitting inflammatory disorder of the gastrointestinal tract. A prior clinical trial demonstrated the ability of epidermal growth factor receptor (EGFR) ligand EGF to induce and maintain remission in ulcerative colitis. As a protein lysine methyltransferase, SET and MYND domain-containing protein 2 (SMYD2) regulates various cellular functions, including chromatin remodeling and tumorigenesis. A bioinformatic study has shown that EGFR might be a candidate for SMYD2-mediated methylation. In this research, we aimed to investigate whether SMYD2 depletion could synergize with EGFR-activating treatment to promote intestinal goblet cell regeneration in IBD. METHODS SMYD2 flox C57BL/6 (SMYD2fl/fl) and intestine epithelial cell-specific conditional knockout of SMYD2 (SMYD2ΔIEC) male mice (8 to10-week old) were given 3 cycles of DSS treatment, each cycle including 5 days of 2% DSS in drinking water followed by 16 days of normal drinking water. EGF (50 μg/kg/day) was administered via intraperitoneal injection once per day for 6 days during the third cycle of DSS treatment (from day 42 to 47 along with DSS administration). The disease activity index (DAI), including body weight loss, stool consistency and colorectal bleeding, was monitored and calculated daily. Histologic scoring was used to evaluate the extent of histopathologic change in middle colon tissue. Goblet cell differentiation and maturation was analyzed via Alcian Blue/periodic acid-Schiff (AB/PAS) staining and immunostaining. RESULTS EGF treatment significantly increased the number of goblet cells (AB/PAS staining positive cells) in both SMYD2fl/fl and SMYD2ΔIEC mice. However, in SMYD2ΔIEC mice, more mature goblet cells were observed. In contrast, in SMYD2fl/fl mice, most goblet cells were accumulated at the lower half of colon crypts with small mucin particles. As compared with SMYD2fl/fl mice receiving EGF treatment, SMYD2 depletion combined with EGF injection (6 days) failed to significantly improve body weight loss and DAI scoring during DSS treatment, as well as histologic scoring (including inflammatory cell infiltration and epithelial tissue damage). Immunostaining of goblet cell differentiation markers (including ATOH1, SPDEF and KLF4) revealed no significant difference between SMYD2fl/fl and SMYD2ΔIEC mice. CONCLUSION SMYD2 depletion combined with EGF treatment could promote goblet cell expansion and maturation in mouse DSS-induced chronic colitis. However, the mechanism by which SMYD2 depletion facilitates goblet cell maturation needs further investigation.