title: Pseudomonas fluorescens lipopolysaccharide inhibits both delayed rectifier and transient A-type K+ channels of cultured rat cerebellar granule neurons.
abstract: Pseudomonas fluorescens is a Gram-negative bacillus closely related to the pathogen P. aeruginosa known to provoke infectious disorders in the central nervous system (CNS). The endotoxin lipopolysaccharide (LPS) expressed by the bacteria is the first infectious factor that can interact with the plasma membrane of host cells. In the present study, LPS extracted from P. fluorescens MF37 was examined for its actions on delayed rectifier and A-type K(+) channels, two of the main types of voltage-activated K(+) channels involved in the action potential firing. Current recordings were performed in cultured rat cerebellar granule neurons at days 7 or 8, using the whole-cell patch-clamp technique. A 3-h incubation with LPS (200 ng/ml) markedly depressed both the delayed rectifier (I(KV)) and transient A-type (I(A)) K(+) currents evoked by depolarizations above 0 and -40 mV, respectively. The percent decrease of I(KV) and I(A) ( approximately 30%) did not vary with membrane potential, suggesting that inhibition of both types of K(+) channels by LPS was voltage-insensitive. The endotoxin did neither modify the steady-state voltage-dependent activation properties of I(KV) and I(A) nor the steady-state inactivation of I(A). The present results suggest that, by inhibiting I(KV) and I(A), LPS applied extracellulary increases the action potential firing in cerebellar granule neurons. It is concluded that P. fluorescens MF37 may provoke in the CNS disorders associated with sever alterations of membrane ionic channel functions.
authors.affiliation: Laboratory of Cold Microbiology, UPRES 2123, University of Rouen, 55 Rue Saint Germain, 27000, Evreux, France.
authors.forename: Sana
authors.initials: S
authors.lastname: Mezghani-Abdelmoula
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chevalier
authors.forename: Olivier
authors.initials: O
authors.lastname: Lesouhaitier
authors.forename: Nicole
authors.initials: N
authors.lastname: Orange
authors.forename: Marc G J
authors.initials: MG
authors.lastname: Feuilloley
authors.forename: Lionel
authors.initials: L
authors.lastname: Cazin
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology* / Q000187:drug effects; D051668:Delayed Rectifier Potassium Channels; D004594:Electrophysiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects*; D024642:Potassium Channels, Voltage-Gated; D011551:Pseudomonas fluorescens / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D051668:Delayed Rectifier Potassium Channels; D008070:Lipopolysaccharides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated