Lonicera japonica-induced inhibition of interleukin-1 beta thermogenesis and E-type prostaglandin receptor-3 expression in the preoptic area of rabbits

Jun Dong; Rongbo Tu; Rui Pan; Xinhua Xie

摘要：BACKGROUND:It has been shown that interleukin-1β(IL-I β)can induce fever by activating vascular endothelial cells and macrophages of the supraoptic crest to generate prostaglandin E2,which binds with receptors of the thermo-sensitive hypothalamic neurons.Lonicera japonica is one of the medicinal plants used widely in Asia for its antipyretic properties.However,these mechanisms have not yet been intensively studied.OBJECTIVE:To investigate the antipyretic effect and mechanisms of Lonicera japonica on IL-1 β-induced febrile New Zealand rabbits by observing expression changes of E-type prostaglandin receptor-3 (EP3)mRNA in the preoptic anterior hypothalamus(POAH). DESIGN:A randomized controlled study. SETTING:Electrophysiological Laboratory at the Department of Pathophysiology,Medical College of Jinan University; Department of Orthopaedics,First Hospital Affiliated to Medical College of Jinan University. MATERIALS:The experiment was performed from April to December 2005,using a total of 32 New Zealand white rabbits of both sexes,weighing 1.5-2.0 kg.All the animal experiments were performed according to the internationally accepted ethical guidelines.Lonicera japonica injection was purchased from Huanghe pharmaceutical factory of Xi'an,China.IL-1 β was purchased from Sigma,USA.METHODS:A total of 32 rabbits were divided randomly into four groups:①Normal saline(NS)control group; ②Lonicerajaponica treatment group;③IL-1 β treatment group; and ④Lonicerajaponica plus IL-1 β treatment group.In the first 3 groups,the rabbits were given separate intravenous(I.v.)injections of 1 mL NS,1 mL l.Lonicera japonica,and 100 ng IL-1 β(dissolved in 0.9% NS without pyrogen).In the lonicera japonica plus IL-I βgroup each rabbit was given I.v.injections of l mL NS and,30 minutes later, 100 ng IL-I β. MAIN OUTCOME MEASURES:Colonic temperature of each rabbit was measured at 0,10,20,30,40,50, 60,and 70 minutes after injection and the maximum temperature rise( △ T)and the temperature response index after I hour(TRII)was calculated.Subsequently,in situ hybridization(ISH)was done with an ISH kit,EP3 mRNA expression in the POAH of all groups was measured(number of positive cells and average gray scale value).RESULTS:A total of 32 rabbits were included in the result analysis,without any loss.① △T and TRI1 : there was no significant difference between the Lonicerajaponica group and NS group(P＞0.05).The IL-1 β group was significantly greater compared to NS group(P＜0.01).The Lonicerajaponica plus IL-I β group was significantly less than the IL-1 β group(P＜0.05).② In the NS and Lonicera japonica groups,the EP3 mRNA expression was negative(no coloration)or only weakly positive(only a few brown yellow particles in the cytoplasm cells could not be identified).The number of positive cells and the average gray scale value were not significantly different between the two groups(P＞0.05).In the IL-I βgroup,the number of positive cells was remarkably higher and the average gray scale value was lower than the NS group(P＜0.01).In the Lonicera japonica plus IL-I βgroup,the number of positive cells was significantly less than the IL-1β group(P＜0.05).However,the average gray scale value was greater than the IL-1 β group(P＜0.05). CONCLUSION:Lonicera japonica has obvious antipyretie effects on IL-1 β-induced febrile rabbits and acts by inhibiting expression of EP3 mRNA in the POAH.