ABSTRACT
Objective To evaluate the role of cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) signal transduction pathway in lidocaine-induced up-regulation of the expression of surfactant protein-A (SP-A) in rat alveolar epithelial type Ⅱ cells (AEC Ⅱ).Methods Healthy male Sprague-Dawley rats were sacrificed and AEC Ⅱ were isolated,purified and incubated in 24-well culture plates (100μd/hole) with density of 1 × 106/ml.After being incubated for 2 h,the culture medium was replaced with serum-free medium DMEM.The cells were randomly divided into 4 groups (n =48 each):control group (group C),forskolin (adenylate cyclase agonist) group (group F),lidocaine 200 μg/ml group (group L),and PKA inhibitor H89 + L group (group P+ L).Forskolin 10 μmol/ml was added to DMEM in group F.Lidocaine 200 μg/ml was added to DMEM in group L.H89 10μnol/ ml was added to DMEM and AEC Ⅱ were incubated for 10 min,and then lidocaine 200 μg/ml was added in group P + L.At 6,12 and 24 h of incubation (T1-3),cAMP content and PKA activity (using ELISA),and expression of SP-A mRNA (by real-time fluorescent quantitative PCR) and SP-A (by Western blot) were measured.Results Compared with group C,the expression of SP-A mRNA and SP-A was significantly upregulated,and cAMP level and PKA activity were increased at T1-3 in group F and at T2,3 in group L.Compared with group L,the expression of SP-A and SP-A mRNA was down-regulated,PKA activity was decreased,and no significant change was found in cAMP level at T1-3 in group P + L.Conclusion Lidocaine can up-regulate the expression of SP-A in AEC Ⅱ of rats through activating cAMP-PKA signal transduction pathway.