Role of colonic mast cell infiltration and nerve growth factor in visceral hypersensitivity of irritable bowel syndrome / 中华消化杂志

ABSTRACT

Objective To investigate the role of mucosal mast cells infiltration and degranulation with nerve growth factor (NGF)in development of visceral hypersensitivity in Sprague-Dawley (SD)rats. Methods The model of visceral hypersensitivity of irritable bowel syndrome (IBS)was established in 19 neonate SD rats with intestinal stimulation (rectalballon distention)on 8th,10th and 12th postnatal days. The other 19 neonate SD rats without colonic distention were assigned to the control group.After rats grew up (six to eight weeks old),the visceral sensitivity was tested by abdominal withdrawal reflex (AWR)in 10 rats of each group.Mast cell infiltration and degranulation were observed with toluidine blue staining in colon tissue slides.The NGF level of intestinal tissues was detected by enzyme-linked immunosorbent assay (ELISA)methods in the left nine rats of each group.The culture system of dorsal root ganglias (DRG)from the neonatal rats was set up.The changes of electrophysilogical characters of DRG stimulated with NGF (100 ng/mL)for four days were recorded with patch-clamp.Paired t test was performed for comparison between groups.Results The results of AWR indicated that neonatal colonic stimulation could significantly increase visceral sensitivity after growing up.Under 20,40 and 60 mmHg (1 mmHg=0.133 kPa)distention pressure,visceral sensitivity scores of visceral hypersensitivity rats and rats of control group were 1 .00±0.50 vs 1 .67 ±0.50,1 .89 ±0.31 vs 2.89 ±0.34 and 2.89 ±0.33 vs 3.89±0.33,the differences were statistically significant (t=-2.83,-6.00 and -6.00,all P <0.05 ). The results of master cells staining in tissue slides showed colonic master cells infiltration was obvious in rats with visceral hypersensitivity,and part of mast cells were degranulation.The result of ELISA demonstrated that NGF level of visceral hypersensitivity rats was significantly higher than that of control group ((11.07±3.06)pg/mg vs (2.38 ±1.88)pg/mg,t =-6.93,P <0.05).The results of electrophysilogical tests of primary cultured DRG indicated that compared with blank control growp,the action potential threshold of neuron in NGF 100 ng/mL group significantly decreased ((-18.0±2.1 )mV vs (-29.0 ± 2.5 )mV,t = 12.26,P <0.05)and discharge frequency increased ((5 .0± 1 .4 )/800 ms vs (12.0 ± 3.2)/800 ms,t=-8.40,P <0.05 ).Meanwhile,neuron voltage-gated K+ current density remarkably decreased,most were sustained delayed rectifier K+ current (I K )decreasing ((279.0 ±48.0)pA/pF vs (203.0±39.0)pA/pF,t=6.18,P <0.05).Conclusion Colonic stimulation in neonatal rats could cause intestinal master cells infiltration and degranulation,which induced changes of neuron electrophysilogical characters and resulted in visceral hypersensitivity after growing up.