Flufenamic acid (FFA) is a nonsteroidal anti-inflammatory drug (NSAID). It has anti-inflammatory and antipyretic properties. In addition, it also modulates multiple channel activities. The mechanisms underlying the pharmacological actions of FFA are presently unclear. Given that AMP-activated protein kinase (AMPK) has both anti-inflammatory and channel-regulating functions, we examined whether FFA induces AMPK activation. 1) Exposure of several different types of cells to FFA resulted in an elevation of AMPKα phosphorylation at Thr-172. This effect of FFA was reproduced by functionally and structurally similar mefenamic acid, tolfenamic acid, niflumic acid and meclofenamic acid, but not by the inhibitors of cyclooxygenases, gap junctions and several membrane channels. 2) FFA-induced activation of AMPK was largely abolished by treatment of cells with BAPTA-AM (an intracellular Ca2+ chelator) or depletion of extracellular Ca2+, whereas it was mimicked by stimulation of cells with Ca2+ ionophore A23187 or ionomycin. 3) FFA triggered a rise in intracellular Ca2+, which was abolished by cyclosporine, a blocker of mitochondrial permeability transition pore. Cyclosporine also abolished FFA-induced activation of AMPK. 3) Inhibition of Ca2+/calmodulin-dependent kinase kinase β (CaMKKβ) with kinase inhibitors calphostin and STO-609 or downregulation of CaMKKβ with siRNA largely abrogated FFA-induced activation of AMPK. 4) FFA significantly suppressed NF-κB activity and iNOS expression triggered by IL-1β and TNFα. This suppression was also largely abrogated by STO-609. Taken together, we conclude that FFA induces AMPK activation through Ca2+-CaMKKβ pathway. Activation of AMPK is a presently unrecognized important mechanism underlying the pharmacological effects of FFA.
- calcium-activated potassium channels
- cellular transport
- ion channels
- nitric oxide synthase
- non-steroidal anti-inflammatory drugs (NSAIDs)
- Received April 14, 2011.
- Revision received June 26, 2011.
- Accepted July 13, 2011.
- The American Society for Pharmacology and Experimental Therapeutics