Involvement of Ca(2+) in globular adiponectin-induced reactive oxygen species.

Globular adiponectin (gAd) induces the generation of reactive oxygen species (ROS) and nitric oxide (NO) in the murine macrophage cell line RAW 264. We investigated the role of Ca(2+) in gAd-induced ROS and NO generation. Pretreatment with BAPTA-AM, a selective chelator of intracellular Ca(2+) (Ca(2+)), partially reduced gAd-induced generation of ROS and NO in gAd-treated RAW 264 cells. The lowest Ca(2+) occurred 30min after gAd treatment, after which Ca(2+) increased continually and exceeded the initial level. The mitochondrial Ca(2+) (Ca(2+)) detected by Rhod-2 fluorescence started to increase at 6h after gAd treatment. Pretreatment with a NAD(P)H oxidase inhibitor, diphenyleneiodonium, prevented the reduction of Ca(2+) in the early phase after gAd treatment. Calcium depletion by BAPTA-AM had no effect on the gAd-induced Ca(2+) oscillation. The administration of a specific calmodulin inhibitor, calmidazolium, significantly suppressed gAd-induced ROS and NO generation and NOS activity.