Absorption enhancement of a protein drug by nitric oxide donor: Effect on nasal absorption of human granulocyte colony-stimulating factor

The objective of this study was to evaluate the effect of a nitric oxide (N O) donor, S-nitroso-N-acetyl-DL-penicillamine (SNAP), on the nasal absorpti on of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in rabbits and to evaluate the irritation (cytotoxicity) potential of the NO d onor on the mucosal membrane using a cultured cell system (strain K B, huma n epidermoid carcinoma of the floor of the mouth). Significantly higher ser um G-CSF concentration and increased total leukocyte count in the periphera l blood were observed after coadministration of rhG-CSF (100 mu g/kg) with SNAP at various doses (0.3-3.3 mg/kg). The serum G-CSF concentration and th e increased total leukocyte count were markedly decreased by the presence o f the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazole-1-oxy l 3-oxide sodium salt (carboxy-PTIO), in combination with rhG-CSF and SNAP. However, no significant inhibitory effect of glutathione (peroxynitrite sc avenger) on the absorption-enhancing effect of SNAP was observed. These res ults suggest that carboxy-PTIO inhibits the absorption-enhancing effect of NO released From SNAP. We found that SNAP has, a very low potential for cyt otoxicity, as evaluated by the cell detachment assay, release of lactate de hydrogenase (LDH) from cultured cells and morphological observations of nas al tissue of rabbits. It is concluded that a NO donor such as SNAP is a pro mising absorption enhancer for nasal protein-drug delivery.