The relationship between PDE4 and AQP5 in lung tissue under inflammatory conditions: An experimental study

Objective: This study aimed to examine the relationship between Phosphodiesterase 4 (PDE4) and Aquaporin-5 (AQP5) under Lipopolysaccharide (LPS) induced-inflammatory condition. Methods: Inflammatory Acute lung injury (ALI) was induced by intratracheal LPS (5 mg/kg) administration. Rolipram (intraperitoneal) was used as PDE4 inhibiting agent at three different doses (1, 3 and 5 mg/kg) in rat groups. 24 h after LPS administration lung tissues obtained and following analyses performed. AQP5, Phosphodiesterase 4D (PDE4D), Cyclic adenosine monophosphate (cAMP) levels were evaluated for determination of the relationship between these parameters. Also Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), Nuclear factor kappa B (NF-κB), Mitogen-activated protein kinase (MAPK) levels were evaluated as ALI markers. Results: LPS-induced ALI resulted in increased PDE4 enzyme and inflammatory marker levels (IL-6, TNF-α, NF-κB and MAPK) and decreased AQP5 and cAMP levels. Inhibition of PDE4 enzyme to increase cAMP levels by Rolipram resulted in increased AQP5 expression and decreased inflammatory condition and in lung tissues. These results were supported by histopathological and immunhistochemical results. Conclusion: The fact that this study observed a decreases PDE4 expression and increases in AQP5 expression upon Rolipram administration might indicate a close relationship of these two parameters in inflammatory lung disease.