Akt activator SC79 stimulates antibacterial nitric oxide production from human nasal epithelial cells and increases macrophage phagocytosis in vitro

BackgroundThe role of the Akt serine/threonine kinase family in airway innate immunity is relatively unstudied compared with other pathways. Akt can phosphorylate and activate the endothelial nitric oxide synthase (eNOS) isoform expressed in airway epithelial ciliated cells. NO production by nasal epithelial cells often has antibacterial and antiviral effects. Increasing nasal epithelial NO production may be a useful anti-pathogen strategy for respiratory infections in diseases like chronic rhinosinusitis. We hypothesized that a small molecule Akt activator, SC79, might induce nasal epithelial cell NO production with bactericidal effects. MethodsWe tested the antibacterial-stimulatory effects of SC79 in primary nasal epithelial cells isolated from residual surgical material and grown at air-liquid interface. Because macrophages also use NO signaling to enhance phagocytosis, we also tested effects of SC79 in human macrophages differentiated from monocytes obtained from healthy apheresis donors. ResultsLive cell imaging of an NO-sensitive fluorescent dye revealed that SC79 induced dose-dependent NO production. Pharmacology and genetic knockdown revealed that this NO production is dependent on eNOS and Akt. The NO released into the airway surface liquid was sufficient to kill both lab and clinical strains of P. aeruginosa in a co-culture bacterial killing assay. SC79 enhanced bacterial phagocytosis in a NO-dependent and Akt-dependent manner. No overt toxicity (LDH release) or inflammatory effects (IL8 transcription) were observed in nasal cells or macrophages over 24 hrs. ConclusionsTogether, these data suggest that multiple innate immune pathways might be stimulated by SC79 delivered via topical nasal rinse or spray. Activating Akt using SC79 or another compound might have beneficial antipathogen effects in respiratory infections.