|Title||Niflumic acid inhibits chloride conductance of rat skeletal muscle by directly inhibiting the CLC-1 channel and by increasing intracellular calcium.|
|Publication Type||Journal Article|
|Year of Publication||2007|
|Authors||Liantonio A, Giannuzzi V, Picollo A, Babini E, Pusch M, D Camerino C|
|Journal||Br J Pharmacol|
|Date Published||2007 Jan|
|Keywords||Animals, Anti-Inflammatory Agents, Non-Steroidal, Calcium, Chloride Channels, Female, Humans, Intracellular Space, Male, Muscle Fibers, Skeletal, Muscle, Skeletal, Niflumic Acid, Oocytes, Patch-Clamp Techniques, Rats, Rats, Wistar, Xenopus laevis|
BACKGROUND AND PURPOSE: Given the crucial role of the skeletal muscle chloride conductance (gCl), supported by the voltage-gated chloride channel CLC-1, in controlling muscle excitability, the availability of ligands modulating CLC-1 are of potential medical as well as toxicological importance. Here, we focused our attention on niflumic acid (NFA), a molecule belonging to the fenamates group of non-steroidal anti-inflammatory drugs (NSAID).
EXPERIMENTAL APPROACH: Rat muscle Cl(-) conductance (gCl) and heterologously expressed CLC-1 currents were evaluated by means of current-clamp (using two-microelectrodes) and patch-clamp techniques, respectively. Fura-2 fluorescence was used to determine intracellular calcium concentration, [Ca(2+)](i), in native muscle fibres.
KEY RESULTS: NFA inhibited native gCl with an IC(50) of 42 muM and blocked CLC-1 by interacting with an intracellular binding site. Additionally, NFA increased basal [Ca(2+)](i) in myofibres by promoting a mitochondrial calcium efflux that was not dependent on cyclooxygenase or CLC-1. A structure-activity study revealed that the molecular conditions that mediate the two effects are different. Pretreatment with the Ca-dependent protein kinase C (PKC) inhibitor chelerythrine partially inhibited the NFA effect. Therefore, in addition to direct channel block, NFA also inhibits gCl indirectly by promoting PKC activation.
CONCLUSIONS AND IMPLICATIONS: These cellular effects of NFA on skeletal muscle demonstrate that it is possible to modify CLC-1 and consequently gCl directly by interacting with channel proteins and indirectly by interfering with the calcium-dependent regulation of the channel. The effect of NFA on mitochondrial calcium stores suggests that NSAIDs, widely used drugs, could have potentially dangerous side-effects.
|Alternate Journal||Br. J. Pharmacol.|
|PubMed Central ID||PMC2042903|
|Grant List||GGP04018 / / Telethon / Italy|