目的 探讨Nle4-D-Phe7-α-MSH(NDP-MSH)激活黑皮质素受体-3(Mc3r)在小鼠脑出血(intracerebral hemorrhage,ICH)后氧化应激和神经元凋亡中的作用.方法 170只小鼠按随机数字表法分为3组:Sham组(n=22)、ICH组(n=46)、ICH+NDP-MSH组(n=102),建立小鼠ICH模型.ICH后24h进行改良Garcia评分、Beam balance评分和脑含水量测定,双标免疫荧光检测小鼠脑血肿周围组织中Mc3r和Neun共定位,ELISA检测ICH小鼠血肿周围组织的MDA、SOD、CAT含量,Western blot检测脑组织中Mc3r、PKC、ERK1/2、Bcl-2、caspase-3的表达.结果 Mc3r在术后24h达到表达高峰,在神经元中广泛分布.NDP-MSH治疗后,改良的Garicia评分和Beam balance评分显著提高(P＜0.05),同侧基底神经节和皮层中的水肿显著降低(P＜0.05),ROS活性明显降低(P＜0.05).下调脑组织中Mc3r和PKC的表达后p-PKC,p-ERK1/2,Bcl-2的表达明显降低,c-caspase-3升高(P＜0.05).结论 NDP-MSH激活黑皮质素-3受体通过PKC/ERK信号通路改善小鼠脑出血后的氧化应激和神经元凋亡.

The melanocortin-4 receptor (MC4R),a hypothalamic master regulator of energy homeostasis and appetite,is a class A G-protein-coupled receptor and a prime target for the pharmacological treatment of obesity.Here,we present cryo-electron microscopy structures of MC4R-Gs-protein complexes with two drugs recently approved by the FDA,the peptide agonists NDP-α-MSH and setmelanotide,with 2.9 (A) and 2.6 (A) resolution.Together with signaling data from structure-derived MC4R mutants,the complex structures reveal the agonist-induced origin of transmembrane helix (TM) 6-regulated receptor activation.The ligand-binding modes of NDP-α-MSH,a high-affinity linear variant of the endogenous agonist α-MSH,and setmelanotide,a cyclic anti-obesity drug with biased signaling toward Gq/11,underline the key role of TM3 in ligand-specific interactions and of calcium ion as a ligand-adaptable cofactor.The agonist-specific TM3 interplay subsequently impacts receptor-Gs-protein interfaces at intracellular loop 2,which also regulates the G-protein coupling profile of this promiscuous receptor.Finally,our structures reveal mechanistic details of MC4R activation/inhibition,and provide important insights into the regulation of the receptor signaling profile which will facilitate the development of tailored anti-obesity drugs.