ABSTRACT
The plasticity of endothelin ETB receptor activity and the influence of pro-inflammatory cytokines was examined in cerebral artery. In fresh rat basilar artery, the selective ETB receptor agonist, sarafotoxin S6c, induced negligible contractions. However, after 1 day of organ culture, fully defined concentration-response curves were obtained in artery segments exposed to sarafotoxin S6c. Organ culture in the presence of either interleukin-1 beta or tumour necrosis factor-alpha, but not interleukin-2 or interleukin-6, further amplified the maximal contraction to sarafotoxin S6c. The plasticity of ETB receptor expression in cerebral arteries and sensitivity for pro-inflammatory cytokines, suggest a role in inflammatory cerebral diseases such as stroke.
Subject(s)
Cerebral Arteries/drug effects , Cerebral Arteries/physiology , Cytokines/pharmacology , Receptors, Endothelin/physiology , Vasoconstriction/drug effects , Vasoconstriction/physiology , Animals , Interleukin-1/pharmacology , Interleukin-2/pharmacology , Interleukin-6/pharmacology , Male , Organ Culture Techniques , Rats , Rats, Inbred WKY , Receptor, Endothelin B , Receptors, Endothelin/drug effects , Tumor Necrosis Factor-alpha/pharmacology , Vasoconstrictor Agents/pharmacology , Viper Venoms/pharmacologyABSTRACT
Segments of human temporal artery were placed in organ culture for up to 4 days and examined for endothelin ET(B) receptor activity in the presence and absence of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) by in vitro pharmacology and reverse transcriptase-polymerase chain reaction (RT-PCR). The contractile effect of prostaglandin F2alpha (used as a reference), was not significantly altered by culture or IL-1beta. However, the selective ET(B) agonist sarafotoxin S6c induced no contraction in fresh arteries, but marked contraction after culture. Both maximal contraction and potency to sarafotoxin S6c were increased in segments incubated with IL-1beta . The contraction was sensitive to BQ 788 (ET(B) antagonist), but not FR 139317 (ET(A) antagonist). Actinomycin D abolished the contraction, whereas only the cytokine-induced increase in contraction was inhibited by cycloheximide. ET(A) and ET(B) receptor mRNAs were detected in all arteries; predominantly for the ET(A) receptor in fresh arteries, and for the ET(B) receptor after culture. However, there was no change in the ET(A)/ET(B) receptor mRNA ratio after treatment with IL-1beta. This suggests de novo synthesis of contractile ET(B) receptors after organ culture and that IL- 1beta may further stimulate translation of the mRNA to active receptors. The results raise the possibility that contractile ET(B) receptors may be implicated in disease states with inflammatory processes.
Subject(s)
Interleukin-1/metabolism , Receptors, Endothelin/metabolism , Temporal Arteries/physiology , Vasomotor System/metabolism , Cycloheximide/pharmacology , Dactinomycin/pharmacology , Dinoprost/pharmacology , Humans , In Vitro Techniques , Interleukin-1/pharmacology , Muscle Contraction/drug effects , Receptor, Endothelin A , Receptor, Endothelin B , Receptors, Endothelin/drug effects , Receptors, Endothelin/genetics , Reverse Transcriptase Polymerase Chain Reaction , Temporal Arteries/drug effects , Vasoconstrictor Agents/pharmacology , Vasomotor System/drug effects , Viper Venoms/pharmacologyABSTRACT
Contractions induced by endothelin-1, endothelin-3 and the selective ETB agonist, sarafotoxin S6c, were studied in segments of human temporal artery. The results in fresh arteries were compared with those obtained after 1 or 4 days in organ culture, and with the specific ETA antagonist FR 139,317, the specific, mixed antagonist bosentan, or the specific ETB antagonist, BQ 788. Sarafotoxin S6c induced no contractile activity in fresh artery segments, but elicited marked contractions after culture. This contraction was only slightly inhibited by FR 139,317, but was abolished by BQ 788. Contractions induced by endothelin-1 were antagonized by FR 139,317 and bosentan, but not by BQ 788. Organ culture did not change the overall pattern, but all concentration-response curves were shifted leftwards. Contractions induced by endothelin-3 were abolished by all antagonists in fresh arteries, but some activity was restored after organ culture. Sensitivity to endothelin-3 was markedly increased. The results suggest a change in endothelin receptors during organ culture, resulting in a marked increase in contractile ETB activity, and possibly some increase in ETA activity. Such changes illustrate the complexity of endothelin responses in this vascular bed.
