Interleukin-1beta induces hyperpolarization and modulates synaptic inhibition in preoptic and anterior hypothalamic neurons.
Most of the inflammatory effects of the cytokine interleukin 1beta (IL-1beta) are mediated by induction of cyclooxygenase (COX)2 and the subsequent synthesis and release of prostaglandin E2. This transcription-dependent process takes 45-60 min, but IL-1beta, a well-characterized endogenous pyrogen also exerts faster neuronal actions in the preoptic area/anterior hypothalamus. Here, we have studied the fast (1-3 min) signaling by IL-1beta using whole-cell patch clamp recordings in preoptic area/anterior hypothalamus neurons. Exposure to IL-1beta (0.1-1 nM) hyperpolarized a subset ( approximately 20%) of preoptic area/anterior hypothalamus neurons, decreased their input resistance and reduced their firing rate. These effects were associated with an increased frequency of bicuculline-sensitive spontaneous inhibitory postsynaptic currents and putative miniature inhibitory postsynaptic currents, strongly suggesting a presynaptic mechanism of action. These effects require the type 1 interleukin 1 receptor (IL-1R1), and the adapter protein myeloid differentiation primary response protein (MyD88), since they were not observed in cultures obtained from IL-1R1 (-/-) or from MyD88 (-/-) mice. Ceramide, a second messenger of the IL-1R1-dependent fast signaling cascade, is produced by IL-1R1-MyD88-mediated activation of the neutral sphingomyelinase. C2-ceramide, its cell penetrating analog, also increased the frequency of miniature inhibitory postsynaptic currents in a subset of cells. Both IL-1beta and ceramide reduced the delayed rectifier and the A-type K(+) currents in preoptic area/anterior hypothalamus neurons. The latter effect may account in part for the increased spontaneous inhibitory postsynaptic current frequency as suggested by experiments with the A-type K(+) channel blockers 4-aminopyridine. Taken together our data suggest that IL-1beta inhibits the activity of preoptic area/anterior hypothalamus neurons by increasing the presynaptic release of GABA.
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Harold L. Dorris Neurological Research Center, Molecular and Integrative Neurosciences Department, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA. tabarean@scripps.edu
Korn
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Bartfai
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D000704:Analysis of Variance; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D007031:Hypothalamus / Q000166:cytology*; D053583:Interleukin-1beta / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000172:deficiency; D009433:Neural Inhibition / Q000187:drug effects* / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017472:Receptors, Interleukin-1 / Q000172:deficiency; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects* / Q000528:radiation effects; D013779:Tetrodotoxin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D053583:Interleukin-1beta; C507781:Myd88 protein, rat; D053594:Myeloid Differentiation Factor 88; C064769:N-acetylsphingosine; D026902:Potassium Channel Blockers; D017472:Receptors, Interleukin-1; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; D013110:Sphingosine; D001640:Bicuculline