Vellani Vittorio, Petrosino Stefania, De Petrocellis Luciano, Valenti Marta, Prandini Massimiliano, Magherini Pier Cosimo, McNaughton Peter A, Di Marzo Vincenzo
Department of Biomedical Sciences, University of Modena and Reggio, Modena (MO), Italy.
Neuropharmacology. 2008 Dec;55(8):1274-9. doi: 10.1016/j.neuropharm.2008.01.010. Epub 2008 Feb 6.
N-arachidonoylethanolamine (anandamide, AEA), is a full agonist at both cannabinoid CB(1) receptors and "transient receptor potential vanilloid" type 1 (TRPV1) channels, and N-palmitoylethanolamine (PEA) potentiates these effects. In neurons of the rat dorsal root ganglia (DRG), TRPV1 is activated and/or sensitised by AEA as well as upon activation of protein kinases C (PKC) and A (PKA). We investigated here the effect on AEA levels of PKC and PKA activators in DRG neurons. AEA levels were significantly enhanced by both phorbol-miristoyl-acetate (PMA), a typical PKC activator, and forskolin (FSK), an adenylate cyclase stimulant, as well as by thrombin, which also activates PKC by stimulating protease-activated receptors (PARs). The levels of the other endocannabinoid and TRPV1-inactive compound, 2-arachidonoylglycerol (2-AG), were enhanced only by thrombin and to a lesser extent than AEA, whereas PEA was not affected by any of the treatments. Importantly, FSK- and PMA-induced elevation of AEA levels was not sensitive to intracellular Ca2+ chelation with BAPTA-acetoxymethyl (AM) ester. In human embryonic kidney (HEK-293) cells, which constitutively express PARs, thrombin, PMA and FSK elevated AEA levels, and the effects of the two former compounds were counteracted by the PKC inhibitor, RO318220, whereas the effect of FSK was reduced by the PKA inhibitor RpcAMPs. In conclusion, we report that AEA levels are stimulated by both PKC, either directly or after thrombin receptor activation, and PKA, possibly in a way independent from intracellular calcium. Since AEA activates TRPV1, these findings may suggest the existence of an amplificatory cascades on this receptor in sensory neurons.
N-花生四烯酰乙醇胺（花生四烯酸乙醇胺，AEA）是大麻素CB(1)受体和“瞬时受体电位香草酸”1型（TRPV1）通道的完全激动剂，N-棕榈酰乙醇胺（PEA）可增强这些作用。在大鼠背根神经节（DRG）神经元中，TRPV1可被AEA激活和/或致敏，也可在蛋白激酶C（PKC）和蛋白激酶A（PKA）激活时被激活和/或致敏。我们在此研究了DRG神经元中PKC和PKA激活剂对AEA水平的影响。典型的PKC激活剂佛波酯-肉豆蔻酸酯-乙酸酯（PMA）、腺苷酸环化酶刺激剂福斯高林（FSK）以及凝血酶（凝血酶也可通过刺激蛋白酶激活受体（PARs）激活PKC）均显著提高了AEA水平。另一种内源性大麻素及TRPV1非活性化合物2-花生四烯酸甘油酯（2-AG）的水平仅被凝血酶提高，且提高程度低于AEA，而PEA不受任何一种处理的影响。重要的是，FSK和PMA诱导的AEA水平升高对用BAPTA-乙酰氧基甲基（AM）酯进行的细胞内Ca2+螯合不敏感。在组成性表达PARs的人胚肾（HEK-293）细胞中，凝血酶、PMA和FSK提高了AEA水平，前两种化合物的作用被PKC抑制剂RO318220抵消，而FSK的作用被PKA抑制剂RpcAMPs减弱。总之，我们报告PKC直接或在凝血酶受体激活后以及PKA均可刺激AEA水平，可能是以一种独立于细胞内钙的方式。由于AEA激活TRPV1，这些发现可能提示感觉神经元中该受体上存在放大级联反应。
