INTERFERON-GAMMA INCREASES CYTOPLASMIC MOTILITY OF ALVEOLAR MACROPHAGES VIA NITRIC OXIDE-DEPENDENT SIGNALING PATHWAYS

The effects of interferon-gamma (IFN-gamma) were investigated on cytoplasmic motility of alveolar macrophages (AM) from rat lungs in vitro. Cytoplasmic motility was examined by measuring remnant field strength from the cell surface of AM containing Fe3O4 particles, and the relaxation rate (lambda0; min-1), which is related to cytoplasmic motility, was determined. IFN-gamma caused an increase in lambda0 in a concentration-dependent fashion with the maximal effect at 1,000 U. DibutyryI cyclic GMP (db cyclic GMP; 10(-3) M) mimicked IFN-gamma-induced effects, but db cyclic AMP (10(-3) M) decreased lambda0. IFN-gamma (1,000 U)-induced increases in lambda0 were concentration-dependently inhibited by N(G)-monomethyl-L-arginine (L-NMMA) with complete inhibition of a concentration of 10(-4) M and were also completely inhibited by either methylene blue (10(-5) M) or KT 5823 (10(-5) M), a specific inhibitor of protein kinase G. IFN-gamma (1,000 U) caused significant nitrite (NO2-) production from the control values of 0.2 +/- 0.1 to 10.0 +/- 0.2 muM/24 h per 10(6) cells (P < 0.001, n = 10), and this increase in NO2- production by IFN-gamma (1,000 U) was completely inhibited by L-NMMA (10(-4) M). IFN-gamma caused a concentration-dependent increase in a filamentous-actin (F-actin) content with the maximal effect at 1,000 U. db cyclic GMP (10(-3) M) mimicked EFN-gamma induced effects on F-actin formation. These observations imply that IFN-gamma increases cytoplasmic motility of AM via nitric oxide (NO) production, NO-dependent signaling pathways, and transformation of F-actin from a globular-actin (G-actin).