| Objective To study the effect of melatonin on enhancing anti-respiratory syncytial virus (RSV) activity of ribavirin and some mechanism; To study the effect of melatonin on immunity function of mice of viral pneumonia, which probably provide theoretical evidence for clinical diagnosis and treatment in the future.Methods①In vitro experiment, by microcytopathic inhibiting test, the anti-RSV effect on Hep-2 cell line of melatonin and ribavirin using respectively and combination was observed by MTT colorimetric assay, and calculate the 50% toxicity dose of ribavirin to Hep-2 cell, and the medicinal concentration when 50 percent of cytopathy in inhibition and the therapeutic index , the experiment is repeated in three times. The interaction of melatonin and ribavirin was estimated by q value provided by Jin Zhengjun,s method; to study the inhibition effect on RSV of ribavirin when the different time of MT administered.②In vivo experiment, mice model of viral pneumonia were established by administering RSV through nose. Blood was collected from the mouse eyeball and take the blood serum, to take the lung after Operating the chest, and takes the spleen aseptically. Observe the inhibition effect to the mice which has viral pneumonia; MTT method was used to observe the proliferation of lymphocytes induced by ConA and LPS. The function of antibody-forming cell was detected with quantitative haemolysis of SRBC. The method of MTT using YAC-1 as TC was applied to measure the activity of NK cell. The research observe the influence of melatonin to specificity immunity and non-specificity immunity function of the mouse with viral pneumonia; The level of IFN-γin serum was tested by ELISA; Pathological changes of mice lung were observed by microscopy.ResultsExperiments in vitro①The TD50 of melatonin and ribavirin for Hep-2 cells was 2655±235 and 3874±356mg/L respectively.②Ribavirin was effective in inhibiting RSV, and the effect was improved with its concentration increasing, and the IC50 of ribavirin for RSV was 280±46mg/L,and TI was 9.48±3.8.③The inhibition of MT and ribavirin used combined on RSV was significantly enhanced, the synergistic effect was observed when melatonin and ribavirin of the concentration of 25,50mg/L and 50,100,200mg/L combining together separately. All of the q values>1.15. Statistics results showed that there was interaction between two drugs. Melatonin can enhance the anti-RSV effect of Ribavirin.④The sensitiv ity of RSV to ribavirin was enhanced whether MT simultaneous working or the pretreatment, and MT pretreats 24h is more effective.Experiments in vivo①Ribavirin can significantly reduce the lung indice, the effective concentration is 17.5 mg.kg-1, the curative effect strengthen with the medicine dosage increasing.②Melatonin can significantly enhance the function of lymphocytes and the activity of NK cell and the function of antibody-forming cell , the rates of moderate and high dose group of melatonin were remarkable higher than that of model group( P<0.05).③The level of IFN-γsecretion was dramatically up-regulated in melatonin mice group.④Ribavirin can significantly lessen pulmonary histopathological change, and melatonin can enhance the antivirus activity of ribavirin. Conclusions①In vitro experiment, ribavirin can inhibit the cytopathic effect of RSV , and the effect was improved with its concentration increasing; melatonin can enhance the inhibition effect of ribavirin. The effect of antivirus of combined used is better than ribavirin used only.②In vivo experiment, Ribavirin is effective in inhibiting RSV and the effect is better when combined with melatonin.③melatonin can enhance the function of lymphocytes and the activity of NK cell. As well as the function of antibody-forming cell, Thus enhance the immunity of the body, and promote the activity of antivirus of ribavirin.
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