ABSTRACT
Objective To explore the effect of Melatonin(MT) on CD4+CD25+ regulatory T cell (CD4+CD25+Tr)and airway inflammation in asthmatic rat.Methods Thirty-two SD rats were randomly divided into 4 groups,8 rats in each group.Asthmatic group:rats were immunized on day 1 and 7 by intraperitoneal inject of mixture of ovalbumin(OVA) and aluminumhydroxide.From day 14,the animals were allenged with aerosolized OVA for 20 min per day for 7 consecutive days.MT group:OVA-sensitized rats were injected intraperitoneally with 0.1 mg/kg MT 30 min before each OVA challenge.Dexamethasone group:OVA-sensitized rats were injected intraperitoneally with 0.5 mg/kg Dexamethasone 30 min before each OVA challenge.Control group:OVA for inhalation and MT for intraperitoneal injection was replaced with saline.After the last challenge,peripheral blood was stained to count the percentage of eosinophil(EOS).Then the rats were lavaged and total leukocytes counts in bronchoalveolar lavage fluid(BALF) were performed after staining with Wright-Giemsa staining.The EOS counts around the airway was counted after the histological section of lung staining with hematoxylin and eosin staining.The serum level of immunoglobulin E(IgE) was detected by immunoenhancement.The change of CD4+CD25+Tr was assessed with flow cytometry.SPSS 10.0 software was applied to analyze data. Results In asthmatic rats,the CD4+CD25+ Tr/ CD4+T cells ratio had significant negative relationship with the EOS counts around the airway and the total leukocytes counts in BALF (r=-0.73 P0.05).There was a significant decrease in the percentage of the eosinophils in peripheral blood,the eosinophil counts around the airway,the total leukocytes counts in BALF and the serum level of IgE in MT group compared with asthmatic group (Pa