mu-Opioid agonists inhibit the enhanced intracellular Ca(2+) responses in inflammatory activated astrocytes co-cultured with brain endothelial cells.
In order to imitate the in vivo situation with constituents from the blood-brain barrier, astrocytes from newborn rat cerebral cortex were co-cultured with adult rat brain microvascular endothelial cells. These astrocytes exhibited a morphologically differentiated appearance with long processes. 5-HT, synthetic mu-, delta- or kappa-opioid agonists, and the endogenous opioids endomorphin-1, beta-endorphin, and dynorphin induced higher Ca(2+) amplitudes and/or more Ca(2+) transients in these cells than in astrocytes in monoculture, as a sign of more developed signal transduction systems. Furthermore, stimulation of the co-cultured astrocytes with 5-HT generated a pronounced increase in intracellular Ca(2+) release in the presence of the inflammatory or pain mediating activators substance P, calcitonin gene-related peptide (CGRP), lipopolysaccharide (LPS), or leptin. These Ca(2+) responses were restored by opioids so that the delta- and kappa-opioid receptor agonists reduced the number of Ca(2+) transients elicited after incubation in substance P+CGRP or leptin, while the mu- and delta-opioid receptor agonists attenuated the Ca(2+) amplitudes elicited in the presence of LPS or leptin. In LPS treated co-cultured astrocytes the mu-opioid receptor antagonist naloxone attenuated not only the endomorphin-1, but also the 5-HT evoked Ca(2+) transients. These results suggest that opioids, especially mu-opioid agonists, play a role in the control of neuroinflammatory activity in astrocytes and that naloxone, in addition to its interaction with mu-opioid receptors, also may act through some binding site on astrocytes, other than the classical opioid receptor.
Hansson
E
E
Department of Clinical Neuroscience and Rehabilitation, The Sahlgrenska Academy, University of Gothenburg, 413 45 Gothenburg, Sweden. elisabeth.hansson@neuro.gu.se
Westerlund
A
A
Björklund
U
U
Olsson
T
T
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects*; D001921:Brain / Q000166:cytology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018920:Coculture Techniques / Q000379:methods; D042783:Endothelial Cells / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017450:Receptors, Opioid, mu / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology; D013997:Time Factors; D014841:von Willebrand Factor / Q000276:immunology / Q000378:metabolism
D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D005904:Glial Fibrillary Acidic Protein; D020738:Leptin; D008070:Lipopolysaccharides; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; C029417:Von Willebrand antigen; D014841:von Willebrand Factor; D012701:Serotonin; D013373:Substance P; D009270:Naloxone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D002118:Calcium