[Effects of dexamethasone on the expression of muscarinic receptor mRNA in asthmatic guinea pig airway smooth muscle and eosinophil infiltration in bronchoalveolar lavage fluid].
OBJECTIVE
To investigate the effect of dexamethasone on the expression of muscarinic receptor (MR) mRNA in smooth muscle and infiltration of eosinophils (Eos) in the airway of asthmatic guinea pigs.


METHODS
Thirty healthy guinea pigs were randomized into 3 equal groups, the control group, asthmatic group and dexamethasone therapy group. Asthma was induced in the latter 2 groups with the asthma-inducing agents and received treatments as indicated. Bronchial alveolar lavage fluid(BALF) were collected subsequently from the guinea pigs for examining the total cell number and cell classification, and histopathologic examination of the lung tissue was performed. Semi-quantitative analysis with reverse transcriptional- polymerase chain reaction (RT-PCR) was performed for M(2) and M(3) receptor mRNA in airway smooth muscle.


RESULTS
Compared with the control and the asthmatic group, the number of Eos in the BALF of dexamethasone therapy group was significantly lower (P<0.01). In spite of the presence of hyperemia and edema in the lung tissues of the dexamethasone therapy group, Eos infiltration was less severe than that in the asthmatic group. As found by RT-PCR, the quantity of M(2) receptor mRNA in the airway smooth muscle of the dexamethasone therapy group was significantly higher than those in both the control and asthmatic groups (P<0.01), and the quantity of M(3) receptor mRNA in the airway smooth muscle of dexamethasone therapy group was significantly higher than that in the asthmatic group, but did not significantly differ from that in the control group. The quantities of M(2) and M(3) receptor mRNAs in the control group were both significantly higher than that in asthmatic group (P<0.01).


CONCLUSIONS
The expression of M(2) receptor is increased in antigen- challenged guinea pigs, and that of M(3) receptor decreased. Dexamethasone can treat asthma by inhibiting inflammatory action involving Eos infiltration, regulating the expressions of M(2) and M(3) receptors and restoring the function of M(2) receptor.
Shi
Liang
L
Department of Respiratory Diseases, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China. shiliang188@163.com
Luo
Ya-ling
YL
Lai
Wen-yan
WY
Luo
Liang
L
D000818:Animals; D001249:Asthma / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D001980:Bronchi / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D003907:Dexamethasone / Q000494:pharmacology* / Q000627:therapeutic use; D004804:Eosinophils / Q000473:pathology*; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D010047:Ovalbumin; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011976:Receptors, Muscarinic / Q000096:biosynthesis* / Q000235:genetics
D012333:RNA, Messenger; D011976:Receptors, Muscarinic; D003907:Dexamethasone; D010047:Ovalbumin