Effects of intravenous infusion of bilirubin on the expression of phospho-p38 mitogen-activated protein kinase and the apoptosis in splenocytes of neonatal rats / 中华实用儿科临床杂志

ABSTRACT

Objective To explore the effects of bilirubin on myeloid differentiation factor phospho-p38 mitogen-activated protein kinase (p-p38MAPK) and apoptosis in splenocytes of neonatal rats.Methods Seven-day-old Sprague Dawley rats (clean grade),male or female,weighting 12.0-15.0 g,were randomly assigned to 6 groups.There were blank control group (Ⅰ),lipopolysaccharide (LPS) control group (Ⅱ),15 mg/kg bilirubin control (free-LPS) group (Ⅲ),15 mg/kg group (Ⅳa),30 mg/kg group (Ⅳb) and 50 mg/kg group (Ⅳc),and then subsequently divided into 2 h,5 h and 24 h subgroups in each groups.Some of the 200 newborn rats died amid the experiment,tinally,a total of 144 cases were involved in the analysis of results,and 8 rats in each subgroups.Newborn Sprague Dawley rats were administered at various doses of bilirubin (15 mg/kg,30 mg/kg and 50 mg/kg,respectively) intravenously; 1 h after injection,the rats were administered LPS intraperitoneally at a dose of 1 mg/kg;p-p38MAPK were detected by immunohistochemistry;Apoptosis in splenocytes was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling methods at 2 h 5 h and 24 h after the injection of bilirubin.Results 1.Expression of p-p38MAPK in each groupbilirubin in low-mid concentrations of range inhibited LPS-induced p38MAPK activation (qⅣa =20.93,10.37,respectively at 2 h,and 5 h,all P ＜ 0.01 ;qⅣ b =79.97,14.79,all P ＜ 0.01).The inhibition strengthened with increasing concentration of bilirubin.The effect was observed at 2 h,strengthened at 5 h,disappeared at 24 h.Bilirubin in the high concentrations of range stimulated the expression of p-p38MAPK (qⅣc =32.55,19.23,27.72,respectively at 2 h,5 h and 24 h,all P ＜0.01),observed at 5 h,reduced at 24 h.2.Effects of bilirubin on apoptosis in splenocytesLPS could increased the apoptosis index (AI) of splenocytes(q =54.62,P ＜ 0.01);The AI of splenocytes had no significant change in low concentrations of range of bilirubin (q =43.92,P ＞ 0.05).Low-mid concentration of bilirubin with LPS reduced the AI of splenocytes (q Ⅳ a =4.48,P ＜ 0.01 ;q Ⅳ b =2.07,P ＜ 0.05),while high concentration of bilirubin with LPS increased the AI of splenocytes (q =5.08,P ＜ 0.01).Conclusions Bilirubin in low-mid concentrations of range could inhibit the expression of LPS-induced p38MAPK,while bilirubin in high concentrations of range stimulated the expression.As the concentration of bilirubin elevated,its inhibition was prolonged.Bilirubin in high concentrations of range bilirubin could induce apoptosis in splenocytes.The immune dysfunction in neonatal hyperbilirubinemia may have something to do with the regulation of phosphorylation of p38MAPK and activation of apoptotic pathways.