Time-dependent inhibition of G protein-coupled receptor signaling by local anesthetics.
BACKGROUND
Several beneficial effects of local anesthetics (LAs) were shown to be due to inhibition of G protein-coupled receptor signaling. Differences in exposure time might explain discrepancies in concentrations of LAs required to achieve these protective effects in vivo and in vitro (approximately 100-fold higher). Using Xenopus oocytes and human neutrophils, the authors studied time-dependent effects of LAs on G protein-coupled receptor signaling and characterized possible mechanisms and sites of action.


METHODS
Measurement of agonist-induced Ca2+-activated Cl currents, using a two-electrode voltage clamp technique, and determination of superoxide anion production by cytochrome c assay were used to assess the effects of LAs on G protein-coupled receptor signaling in oocytes and primed and activated human neutrophils, respectively. Antisense knockdown of G alpha q protein and inhibition of various proteins within the signaling pathway served for defining mechanisms and sites of action more specifically.


RESULTS
LAs attenuated G protein-coupled receptor signaling in both models in a time-dependent and reversible manner (lidocaine reduced lysophosphatidic acid signaling to 19 +/- 3% after 48 h and 25 +/- 2% after 6 h of control response in oocytes and human neutrophils, respectively). Whereas no effect was observed after extracellularly applied or intracellularly injected QX314, a lidocaine analog, using G alpha q-depleted oocytes, time-dependent inhibition also occurred after intracellular injection of QX314 into undepleted oocytes. Inhibition of phosphatases or protein kinases and agonist-independent G-protein stimulation, using guanosine 5'-O-3-thiotriphosphate or aluminum fluoride, did not affect time-dependent inhibition by LAs.


CONCLUSIONS
Inhibition of G protein-coupled receptor signaling by LAs was found to be time dependent and reversible. Critically requiring G alpha q-protein function, this effect is located downstream of guanosine diphosphate-guanosine triphosphate exchange and is not dependent on increased guanosine triphosphatase activity, phosphatases, or protein kinases.
Hollmann
Markus W
MW
Department of Anesthesiology and Intensive Care Medicine, University Hospital Heidelberg, Germany.
Herroeder
Susanne
S
Kurz
Katrin S
KS
Hoenemann
Christian W
CW
Struemper
Danja
D
Hahnenkamp
Klaus
K
Durieux
Marcel E
ME
D017607:Aluminum Compounds / Q000494:pharmacology; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D018118:Chloride Channels / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology; D010972:Platelet Activating Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011956:Receptors, Cell Surface / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014982:Xenopus laevis
D017607:Aluminum Compounds; D000779:Anesthetics, Local; D018118:Chloride Channels; D008246:Lysophospholipids; D010972:Platelet Activating Factor; D011956:Receptors, Cell Surface; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011493:Protein Kinase C; D010744:Phosphoric Monoester Hydrolases; D019204:GTP-Binding Proteins; C032881:lysophosphatidic acid; D005459:Fluorides; C032311:aluminum fluoride