Labuz Dominika, Berger Stephan, Mousa Shaaban A, Zöllner Christian, Rittner Heike L, Shaqura Mohammed A, Segovia-Silvestre Toni, Przewlocka Barbara, Stein Christoph, Machelska Halina
Klinik für Anaesthesiologie und Operative Intensivmedizin, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, D-12200 Berlin, Germany.
J Neurosci. 2006 Apr 19;26(16):4350-8. doi: 10.1523/JNEUROSCI.4349-05.2006.
Endomorphins (EMs) are endogenous selective mu-opioid receptor agonists. Their role in inflammatory pain has not been fully elucidated. Here we examine peripheral antinociception elicited by exogenously applied EM-1 and EM-2 and the contribution of EM-containing leukocytes to stress- and corticotropin-releasing factor (CRF)-induced antinociception. To this end, we applied behavioral (paw pressure) testing, radioligand binding, immunohistochemistry, and flow cytometry in rats with unilateral hindpaw inflammation induced with Freund's adjuvant. EMs injected directly into both hindpaws produced antinociception exclusively in inflamed paws. This was blocked by locally applied mu-receptor-selective (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2) but not kappa-receptor-selective (nor-binaltorphimine) antagonists. Delta-receptor antagonists (naltrindole and N,N-diallyl-Tyr-Aib-Aib-Phe-Leu) did not influence EM-1-induced but dose-dependently decreased EM-2-induced antinociception. Antibodies against beta-endorphin, methionine-enkephalin, or leucine-enkephalin did not significantly change EM-2-induced antinociception. Both EMs displaced binding of [3H]-[D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin to mu-receptors in dorsal root ganglia (DRG). Using [3H]-naltrindole or [(125)I]-[D-Pen2,5]-enkephalin, no detectable delta-binding was found in DRG of inflamed hindlimbs. Numerous beta-endorphin-containing and fewer EM-1- and EM-2-containing leukocytes were detected in subcutaneous tissue of inflamed paws. Leukocyte-depleting serum decreased the number of immigrating opioid-containing immune cells and attenuated swim stress- and CRF-induced antinociception in inflamed paws. Both forms of antinociception were strongly attenuated by anti-beta-endorphin and to a lesser degree by anti-EM-1 and anti-EM-2 antibodies injected into inflamed paws. Together, exogenously applied and immune cell-derived EMs alleviate prolonged inflammatory pain through selective activation of peripheral opioid receptors. Exogenous EM-2 in addition to mu-receptors also activates peripheral delta-receptors, which does not involve actions via other opioid peptides.
内吗啡肽（EMs）是内源性选择性μ-阿片受体激动剂。它们在炎性疼痛中的作用尚未完全阐明。在此，我们研究外源性应用的EM-1和EM-2所引发的外周抗伤害感受作用，以及含EM的白细胞在应激和促肾上腺皮质激素释放因子（CRF）诱导的抗伤害感受中的作用。为此，我们在弗氏佐剂诱导单侧后爪炎症的大鼠中进行了行为学（爪压力）测试、放射性配体结合实验、免疫组织化学和流式细胞术检测。直接注射到双侧后爪的EMs仅在发炎的爪子中产生抗伤害感受作用。这种作用被局部应用的μ受体选择性拮抗剂（D-苯丙氨酸-半胱氨酸-酪氨酸-D-色氨酸-鸟氨酸-苏氨酸-苯丙氨酸-苏氨酸-NH2）阻断，但未被κ受体选择性拮抗剂（去甲二丙诺啡）阻断。δ受体拮抗剂（纳曲吲哚和N，N-二烯丙基-酪氨酸-丙氨酸-丙氨酸-苯丙氨酸-亮氨酸）不影响EM-1诱导的抗伤害感受作用，但剂量依赖性地降低EM-2诱导的抗伤害感受作用。针对β-内啡肽、甲硫氨酸脑啡肽或亮氨酸脑啡肽的抗体并未显著改变EM-2诱导的抗伤害感受作用。两种EMs均可取代[3H]-[D-丙氨酸2，N-甲基-苯丙氨酸4，甘氨酸5-醇]脑啡肽与背根神经节（DRG）中μ受体的结合。使用[3H]-纳曲吲哚或[(125)I]-[D-青霉胺2，5]-脑啡肽，在发炎后肢的DRG中未检测到可检测到的δ结合。在发炎爪子的皮下组织中检测到大量含β-内啡肽的白细胞以及较少的含EM-1和EM-2的白细胞。消耗白细胞的血清减少了含阿片类物质的免疫细胞的迁移数量，并减弱了游泳应激和CRF诱导的发炎爪子的抗伤害感受作用。两种形式的抗伤害感受作用均被注入发炎爪子的抗β-内啡肽抗体强烈减弱，而被抗EM-1和抗EM-2抗体减弱的程度较小。总之，外源性应用的和免疫细胞衍生的EMs通过选择性激活外周阿片受体减轻持续性炎性疼痛。外源性EM-2除了激活μ受体外，还激活外周δ受体，这一过程不涉及其他阿片肽的作用。
