Effects Of Intestinal Flora Changes On Ulcerative Colitis In Mice

Objective: We will study the effects of fecal microbiota transplantation(FMT) on ulcerative colitis(UC) in mice. UC patients have increased occurrence of cardiovascular diseases and stroke. They also have decreased levels of total cholesterol and low-density lipoprotein cholesterol. We will study the method to measure cholesterol efflux rate of RAW 264.7 mouse macrophages and how it is affected by extracellular cholesterol levels and LPS.Methods: Littermates of BALB/c and C57BL/6J were randomized into groups and ulcerative colitis was induced by dextran sodium sulfate(DSS). Changes in body weight, survival rate, DAI scores and distal colon of mice in each group were studied. Major bacterial species in feces and inflammatory cytokines in colons were also studied. We optimized the labeling time and incubation time of BODIPY-cholesterol to measure the cholesterol efflux rate from RAW 264.7 cells. We also measured and compared cholesterol efflux rates after treating cells with cholesterol, LPS, human sera with abnormal high levels of cholesterol and human sera with normal levels of cholesterol.Results: C57BL/6J mice experienced more significant weight loss than BALB/c mice after DSS treatment. FMT caused reversal of DAI scores in BALB/c but not in C57BL/6J mice. In BALB/c mice, the effects of DSS are significant but reversible by FMT. FMT reduced colon inflammation that was paralleled by decreased inflammatory cytokine levels and altered bacterial microbiota. The best labeling time for BODIPY-cholesterol is between 2 and 8 hours. Cholesterol efflux rates were gradually decreased after the cells were incubated with increasing concentrations of cholesterol(0.1m M, 0.5m M, 2.5m M, P < 0.01). Treating cells with LPS also decreased cholesterol efflux rate(P < 0.05). Furthermore, we incubated cells with human sera with abnormally high levels of cholesterol or with normal levels of cholesterol. Cholesterol efflux rates in the former treatment group were lower than those in the latter group. Therefore, BODIPY-cholesterol can be used to measure cellular cholesterol efflux rate and to study the effects of extracellular cholesterol and LPS.Conclusions: FMT is effective in the mouse model of UC through its modulation on gut microbiota and the host immune system. BODIPY-cholesterol can be used to measure cellular cholesterol efflux rate and to study the effects of extracellular cholesterol and LPS.