| Objective To investigate the effect of NGF on DSS-induced acute ulcerative colitis, and explore possible mechanism NGF impact on the disease and ulcerative colitis in mice.Methods166-8weeks (18-20g) of SPF female Balb/c mice were freely drinking5%DSS distilled water7days, continue to drink distilled water in the next seven days, ELISA assay was used to detect intestinal tissue NGF levels change over time.40female SPF Balb/c mice were randomly divided into four subgroups:group A(normal control), group B(Model group or DSS Group), group C(DSS+Ad-NGF group, referred to as Ad-NGF group), and group D(DSS+Ad-0group, referred to as Ad-0group). Group A drank distilled water while other groups drank5%DSS distilled water.And all these groups ate the standard diet. On seventh day, four groups of mice were fasted for12hours,but not deprived of water. On eighth day, group A and B were anal perfused with100μL of0.9%normal saline for once, group C was anal injected with Ad-NGF and group D with Ad0100μL. On eighth day,group B,C and D changed to drink normal water until the fourteenth day. General condition, stool consistency, occult-gross bleeding and DAI of each mouse in each group were regularly daily recorded. Mice were killed on the fourteenth day and then colonic tissue was collected,the length of the colon measured. Part of the tissue was embedded in paraffin for pathological examination while part of the colon was placed in-80℃refrigerator for MPO and IL-10, IL-6, TNF-α, CGRP examination.Results The results show that the colonic tissue concentration of NGF increased gradually from day1to day5(0.095±0.032pg/g-0.32±0.24pg/g colonic tissue) and achieved a peek level of0.52±0.45pg/g colonic tissue on day6, then decreased gradually to control level on day7(0.09±0.04pg/g colonic tissue); while on day10, the concentration (0.06±0.023pg/g tissue) was lower than that of the control group. DAI and histology score increased significantly in DSS group (p＜0.01), but then decreased after intrarectal administration of Ad-NGF (p＜0.05), while no change was observed after Ad-0therapeutics. Ad-NGF (10.33±0.36cm) attenuated colonic length shortening in DSS group (control vs DSS:12.67±0.38cm vs7.98±0.15cm,p＜0.01)compared with Ad-0treatment(9.15±0.21cm).Similarly, NGF significantly inhibited DSS-induced inflammatory cytokines IL-6(DSS group vs Ad-NGF:304.57±3.19vs56.67±5.89, p<0.05, TNF-α (115.89±6.91,69.14±4.48, p＜0.05) increased, but promoted the secretion of IL-10 (65.34±6.44,160.73±6.42, p＜0.05), Ad-0had no such effect. NGF significantly inhibited MPO increased in DSS-induced colitis model, and Ad-NGF group concentration of MPO was much less than DSS group and Ad-0group (p＜0.05), no significant difference between DSS group and Ad-0group. DSS significantly inhibited the generation of intestinal tissue CGRP, and NGF supplementation significantly increased the levels of CGRP, but Ad-0had no such effect.Conclusions Our results suggest that intrarectal administration of NGF can inhibit the inflammatory injury of colitis induced by DSS in mice via inhibiting MPO activitity and secretion of inflammatory factors,meanwhile, increasing the secretion of IL-10and CGRP. NGF may be a good candidate for clinical treatment of ulcerative colitis. |
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