siRNA Targeting the Natriuretic Peptide Receptor-A Prevents Airway Inflammation in a Mouse Model of Allergic Asthma

Airway Inflammation in a Mouse Model of Allergic Asthma X. Wang, W. Xu, X. Kong, S. Shirley, R. Lockey, S. Mohapatra; University of South Florida, Tampa, FL, James A. Haley Veterans Hospital, Tampa, FL. RATIONALE: Atrial natriuretic peptide (ANP) is a human cardiovascular hormone that regulates blood pressure, volume and sodium/potassium balance. ANP also affects the immune system by promoting a Th2-type response. ANP binding to its receptor, NPRA, produces cyclic GMP (cGMP), which activates protein kinase (PKG) and modulates cell proliferation, apoptosis and inflammation. These experiments examined whether silencing NPRA expression in allergic mice by small interfering RNA (siRNA) can reduce allergen-induced airway inflammation. METHODS: siRNA for NPRA (siNPRA) were synthesized or cloned in pSilencer-1.0 vector. The inhibition of NPRA by siNPRA was verified in vitro by NPRA immunoblotting. For in vivo assays, Balb/c mice were sensitized and challenged with ovalbumin, then treated with chitosan siNPRA nanoparticles intranasally or transdermally. Cytokines from splenocyte cultures, eosinophils in bronchoalveolar lavage fluid (BALF) and lung histopathology were analyzed 4 days after siNPRA treatment. RESULTS: Splenocytes from siNPRA-treated mice showed reduced expression of IL-4, IL-10 and IFN-g. siNPRA also significantly decreased allergen-induced inflammatory lung damage and eosinophil infiltration compared to controls. CONCLUSIONS: The results suggest that ANP signaling via NPRA is involved in airway inflammation and that siRNA silencing of NPRA expression may provide an effective treatment for allergies and asthma. Supported by funds from the NIH (5R01-HL71101-01A2), VA Merit Award, Joy McCann Culverhouse and Mabel& Ellsworth Simmons Endowment. Funding: NIH