Palomba Letizia, Silvestri Cristoforo, Imperatore Roberta, Morello Giovanna, Piscitelli Fabiana, Martella Andrea, Cristino Luigia, Di Marzo Vincenzo
From the Department of Biomolecular Sciences, University of Urbino "Carlo Bo", Urbino 61029, Italy and Endocannabinoid Research Group.
Endocannabinoid Research Group, Institute of Biomolecular Chemistry, Consiglio Nazionale delle Ricerche, Pozzuoli 80078, Italy.
J Biol Chem. 2015 May 29;290(22):13669-77. doi: 10.1074/jbc.M115.646885. Epub 2015 Apr 13.
The adipocyte-derived, anorectic hormone leptin was recently shown to owe part of its regulatory effects on appetite-regulating hypothalamic neuropeptides to the elevation of reactive oxygen species (ROS) levels in arcuate nucleus (ARC) neurons. Leptin is also known to exert a negative regulation on hypothalamic endocannabinoid levels and hence on cannabinoid CB1 receptor activity. Here we investigated the possibility of a negative regulation by CB1 receptors of leptin-mediated ROS formation in the ARC. Through pharmacological and molecular biology experiments we report data showing that leptin-induced ROS accumulation is 1) blunted by arachidonyl-2'-chloroethylamide (ACEA) in a CB1-dependent manner in both the mouse hypothalamic cell line mHypoE-N41 and ARC neuron primary cultures, 2) likewise blocked by a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, troglitazone, in a manner inhibited by T0070907, a PPAR-γ antagonist that also inhibited the ACEA effect on leptin, 3) blunted under conditions of increased endocannabinoid tone due to either pharmacological or genetic inhibition of endocannabinoid degradation in mHypoE-N41 and primary ARC neuronal cultures from MAGL(-/-) mice, respectively, and 4) associated with reduction of both PPAR-γ and catalase activity, which are reversed by both ACEA and troglitazone. We conclude that CB1 activation reverses leptin-induced ROS formation and hence possibly some of the ROS-mediated effects of the hormone by preventing PPAR-γ inhibition by leptin, with subsequent increase of catalase activity. This mechanism might underlie in part CB1 orexigenic actions under physiopathological conditions accompanied by elevated hypothalamic endocannabinoid levels.
脂肪细胞分泌的厌食激素瘦素最近被证明，其对调节食欲的下丘脑神经肽的部分调节作用，归因于弓状核（ARC）神经元中活性氧（ROS）水平的升高。已知瘦素还对下丘脑内源性大麻素水平以及大麻素CB1受体活性发挥负调节作用。在此，我们研究了CB1受体对ARC中瘦素介导的ROS形成进行负调节的可能性。通过药理学和分子生物学实验，我们报告的数据表明，瘦素诱导的ROS积累：1）在小鼠下丘脑细胞系mHypoE-N41和ARC神经元原代培养物中，花生四烯酰-2'-氯乙酰胺（ACEA）以CB1依赖性方式使其减弱；2）同样被过氧化物酶体增殖物激活受体-γ（PPAR-γ）激动剂曲格列酮阻断，且该阻断作用被PPAR-γ拮抗剂T0070907抑制，T0070907也抑制ACEA对瘦素的作用；3）在mHypoE-N41以及分别来自MAGL（-/-）小鼠的ARC神经元原代培养物中，由于对内源性大麻素降解的药理学或基因抑制导致内源性大麻素张力增加的条件下，瘦素诱导的ROS积累减弱；4）与PPAR-γ和过氧化氢酶活性的降低相关，而ACEA和曲格列酮均可使其逆转。我们得出结论，CB1激活可逆转瘦素诱导的ROS形成，从而可能逆转该激素的一些ROS介导的效应，其机制是通过防止瘦素对PPAR-γ的抑制，随后增加过氧化氢酶活性。在伴有下丘脑内源性大麻素水平升高的生理病理条件下，这一机制可能部分解释了CB1的促食欲作用。
