Abstract:Objective Substance P (SP) is an important transmitter of non cholinergic excitatory nerves in the lung and can cause neurogenic inflammation in the airway of asthma. It is not know whether inhalation of glucocorticoids (GCs) can decrease the SP contents in lungs. This paper aims at studying the effect and molecule mechanism of GCs on the SP level. Methods Thirty guinea pigs were used to establish asthma models and were randomly assigned into a GCs treated asthma group and an Asthma group without treatment (n=15 each). The GCs treated asthma group received the beclomethasone dipropionate (BDP) aerosolized solution on the day before asthma inducement, on the day of inducement and 24 hrs after inducement. The SP contents in the plasma, brorchoalveolar lavage fluid (BALF) and lung tissues were detected by radioimmunoassay and the SP mRNA expression in the lung tissues was assayed by RT PCR technique 24 hrs after asthma inducement. Fifteen normal guinea pigs, which inhaled normal saline, were used as the Normal control group. Results The SP contents in the plasma, BALF and lung tissues (122±46 pg/ml, 90±39 pg/ml, 78±15 pg/g) in the Asthma group without treatment were significantly higher than those of the Normal control group (84±33 pg/ml, 32±21) pg/ml, and 42±12 pg/g respectively) and the GCs treated asthma group (50±13 pg/ml, 47±20 pg/ml and 40±13 pg/g respectively) (all P< 0.01 ). The plasma SP content in the GCs treated asthma group was lower than that of the Normal control group (P< 0.05 ), while the BALF and lung tissue SP contents did not differ from the Normal control group. The SP mRNA expression in the lung tissues in the Asthma group without treatment ( 1.0 ± 0.02 ) was significantly higher than that of the Normal Control group ( 0.2 ± 0.05 ) and the GCs treated asthma group ( 0.3 ± 0.06 )( both P< 0.01 ), and no significant difference was found between the GCs treated asthma group and the Normal control group. Conclusions Glucocorticoid can significantly down regulate SP mRNA expression and decrease the SP contents in plsma, BALF and lung tissues in asthmatic guinea pigs.
