A fundamental role for the nitric oxide-G-kinase signaling pathway in mediating intercellular Ca2+ waves in glia

Abstract

In this study, we highlight a role for the nitric oxide-cGMP-dependent protein kinase (NO-G-kinase) signaling pathway in glial intercellular Ca2+ wave initiation and propagation. Addition of the NO donor molsidomine (100- 500 μM) or puffing aqueous NO onto primary glial cell cultures evoked an increase in [Ca2+](i) in individual cells and also local intercellular Ca2+ waves, which persisted after removal of extracellular Ca2+. High concentrations of ryanodine (100-200 μM) and antagonists of the NO - G- kinase signaling pathway essentially abrogated the NO-induced increase in [Ca2+](i), indicating that NO mobilizes Ca2+ from a ryanodine receptor- linked store, via the NO-G-kinase signaling pathway. Addition of 10 μM nicardipine to cells resulted in a slowing of the molsidomine-induced rise in [Ca2+](i), and inhibition of Mn2+ quench of cytosolic fura-2 fluorescence mediated by a bolus application of 2 μM aqueous NO to cells, indicating that NO also induces Ca2+ influx in glia. Mechanical stress of individual glial cells resulted in an increase in intracellular NO in target and neighboring cells and intercellular Ca2+ waves, which were NO, cGMP, and G-kinase dependent, because incubating cells with nitric oxide synthase, guanylate cyclase, and G-kinase inhibitors, or NO scavengers, reduced Δ[Ca2+](i) and the rate of Ca2+ wave propagation in these cultures. Results from this study suggest that NO - G-kinase signaling is coupled to Ca2+ mobilization and influx in glial cells and that this pathway plays a fundamental role in the generation and propagation of intercellular Ca2+ waves in glia.