Goncalves Dos Santos Gilson, Li Ruihui, Ng Melissa Pui Een, Lemes Julia Borges Paes, Vieira Willians Fernando, Nagy Istvan, Tambeli Cláudia Herrera, Parada Carlos Amilcar
Pain Studies Lab - Department of Structural and Functional Biology, Institute of Biology, University of Campinas - UNICAMP, Campinas, Brazil.
Nociception Group, Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Imperial College London, London, UK.
Br J Pharmacol. 2020 Oct;177(20):4615-4626. doi: 10.1111/bph.15170. Epub 2020 Sep 6.
While dipyrone is a widely used analgesic, its mechanism of action is not completely understood. Recently, we have reported that the dipyrone metabolite 4-aminoantipyrine (4-AA) reduces PGE -induced pain-related behaviour through cannabinoid CB receptors. Here, we ascertained, in naive and PGE -induced "inflamed" conditions, both in vivo and in vitro, the molecular mechanisms involved in the 4-AA-induced analgesic effects.
The effect of local administration of 4-AA (160 μg per paw) on capsaicin (0.12 μg per paw) injection-induced pain-related behaviour and 4-AA's effect on 500-nM capsaicin-induced changes in intracellular calcium concentration ([Ca ] ) in cultured primary sensory neurons were assessed in vivo and in vitro, respectively.
4-AA reduced capsaicin-induced nociceptive behaviour in naive and inflamed conditions through CB receptors. 4-AA (100 μM) reduced capsaicin-induced increase in [Ca ] in a CB receptor-dependent manner, when PGE was not present. Following PGE application, 4-AA (1-50 μM) increased the [Ca ] . Although 4-AA activated both TRPV1 and TRPA1 channels, increased [Ca ] was mediated through TRPV1 channels. Activation of TRPV1 channels resulted in their desensitisation. Blocking CB receptors reduced both the excitatory and desensitising effects of 4-AA.
CB receptor-mediated inhibition of TRPV1 channels and TRPV1-mediated Ca -influx- and CB receptor-dependent desensitisation of TRPV1 channels contribute to the anti-nociceptive effect of 4-AA in naive and inflamed conditions respectively. Agonists active at both CB receptors and TRPV1 channels might be useful as analgesics, particularly in inflammatory conditions.
虽然安乃近是一种广泛使用的镇痛药，但其作用机制尚未完全明确。最近，我们报道安乃近代谢产物4-氨基安替比林（4-AA）通过大麻素CB受体减轻前列腺素E（PGE）诱导的疼痛相关行为。在此，我们在体内和体外分别确定了在未处理和PGE诱导的“炎症”条件下，4-AA诱导镇痛作用所涉及的分子机制。
分别在体内和体外评估局部注射4-AA（每只爪160μg）对辣椒素（每只爪0.12μg）注射诱导的疼痛相关行为的影响，以及4-AA对培养的初级感觉神经元中500 nM辣椒素诱导的细胞内钙浓度（[Ca]）变化的影响。
4-AA通过CB受体在未处理和炎症条件下减轻辣椒素诱导的伤害性感受行为。当不存在PGE时，4-AA（100μM）以CB受体依赖性方式减轻辣椒素诱导的[Ca]升高。应用PGE后，4-AA（1 - 50μM）使[Ca]升高。虽然4-AA激活了瞬时受体电位香草酸亚型1（TRPV1）和瞬时受体电位锚蛋白1（TRPA1）通道，但[Ca]升高是通过TRPV1通道介导的。TRPV1通道的激活导致其脱敏。阻断CB受体可降低4-AA的兴奋和脱敏作用。
CB受体介导的对TRPV1通道的抑制以及TRPV1介导的Ca内流和CB受体依赖性TRPV1通道脱敏分别导致4-AA在未处理和炎症条件下的抗伤害感受作用。对CB受体和TRPV1通道均有活性的激动剂可能作为镇痛药有用，特别是在炎症条件下。
