大麻素受体2与几种消化系统疾病

内源性大麻素系统包括内源性大麻素物质、特异性大麻素受体1(cannabinoid receptor 1,CB1)和CB2.内源性大麻素系统在胃肠道疾病、肝脏疾病、胰腺疾病和肿瘤的发生发展过程中扮演了众多的生理效应和病理生理角色.本文就内源性大麻素系统、CB2与肠易激综合征、炎症性肠病、胰腺炎、肝脏疾病及消化系肿瘤的关系等作一综述.     

血吸虫性肝纤维化小鼠肝组织中内源性大麻素1受体的表达

研究发现，内源性大麻素及其相应受体在肝纤维化、肝硬化的发生发展中起重要作用。本实验旨在研究血吸虫性肝纤维化时肝组织中内源性大麻素1（CB1）受体表达的变化情况，进一步阐明血吸虫性肝纤维化发病机制，为疾病治疗开辟新的途径。     

大麻素受体1在慢性乙型肝炎肝纤维化发生和发展中的作用

Sato等[1]和Teixeira Clerc等[2]先后发现大麻素受体1(CB1R)在慢性肝病发展过程中起着独特作用.为深入研究CB1R在慢性乙型肝炎(CHB)肝纤维化发生、发展过程中的作用,我们用免疫组织化学染色法检测肝组织中CB1R表达情况,分析CB1R半定量评分与纤维化分期、血清转化生长因子(TGF)β1、ALT以及HBV DNA水平等指标的相关性,为今后以CB1R为靶点进行抗肝纤维化治疗提供依据.     

氧化型低密度脂蛋白诱导巨噬细胞内源性大麻素系统激活

目的 探讨氧化型低密度脂蛋白刺激能否诱导巨噬细胞内源性大麻素系统激活.方法 体外常规培养RAW264.7小鼠巨噬细胞,加入氧化型低密度脂蛋白或溶媒孵育24 h,用高效液相色谱分析技术检测巨噬细胞内源性大麻素Anandamide和2-arachidonoylglycerol水平,以实时定量PCR技术和免疫印迹法对大麻素CB1、CB2受体和血小板活化因子受体mRNA和蛋白的表达进行分析.结果 内源性大麻素2-arachidonoylglycerol水平在6mg/L和12 mg/L氧化型低密度脂蛋白刺激时分别升高了2.4倍和4.8倍,而Anandamide水平无明显变化.3～12mg/L氧化型低密度脂蛋白刺激时,RAW264.7巨噬细胞大麻素CB1和CB2受体及血小板活化因子受体mRNA和蛋白的表达均明显上调(P＜0.01).结论 首次证实氧化型低密度脂蛋白通过激活血小板活化因子受体诱导巨噬细胞内源性大麻素系统激活,提示氧化型低密度脂蛋白致动脉粥样硬化过程中可能涉及该系统的激活.     

内源性大麻素系统心血管作用的研究进展

内源性大麻素系统在心血管系统中的作用涉及到血压、心率、心肌收缩力的调节等许多方面,在生理条件下主要通过刺激大麻素1受体(CB1受体)发挥降低血压和心脏抑制效果;在多种病理条件中也起了重要作用,包括通过CB1受体活化参与出血、内毒素和心源性休克、肝硬化伴随的低血压,降低高血压大鼠的血压;通过大麻素2受体(CB2受体)活化防止动脉粥样硬化进展,还能对缺血再灌注后的心肌起保护作用,但CB1受体和CB2受体谁在其中起主要作用尚不明确。对其机制的深入研究对研制新的药物,治疗心血管疾病有着深远意义。     

内源性大麻素调节去甲肾上腺素对肝星状细胞作用的研究

交感神经释放的神经递质对肝纤维化发展和促进肝纤维化时的损伤修复都有很重要的调节作用[1].有研究表明,内源性大麻素(anandamide,AZA)作为中枢神经系统中的神经调节因子,与其大麻素CB1、CB2受体对大脑中神经递质的释放起着重要的调节作用,但其对肝脏中神经递质释放的调节及协同神经递质对肝星状细胞(HSC)增殖、活化的调控国内外报道甚少.     

内源性大麻素系统与阻塞性睡眠呼吸暂停合并症

阻塞性睡眠呼吸暂停(obstructive sleep apnea,OSA)是以睡眠过程中反复的上气道狭窄甚至完全闭塞导致频繁发生呼吸暂停为特征的睡眠呼吸障碍性疾病,该疾病与白天嗜睡、肥胖、高血压、缺血性心脏病、心律失常等均有明显的相关性.内源性大麻素系统(endocannabinoid system,ECS)是新近发现的信号系统,由内源性大麻素(endogenous cannabinoids,EC),大麻素受体CB1、CB2及合成、降解EC的酶类共同组成.在体内,ECS有广泛的生理学作用.     

内源性大麻素样系统与肥胖

内源性大麻素样系统主要由内源性大麻素及其受体组成,后者分为CB1受体和CB2受体两种,激活后可引起摄食增加。与正常小鼠相比,CB1受体(-/-)小鼠的体重和脂肪明显减少,即使在致肥胖饮食条件下也不会发生肥胖或胰岛素抵抗。研究证实,CB1受体拮抗剂可通过中枢和外周两种机制抑制摄食并改善代谢;其中,利莫那班已进入Ⅲ期临床试验,可有效抑制食欲、减轻体重,并且尚未发现明显的副作用。     

替米沙坦对晚期血吸虫肝病患者肝纤维化程度和门静脉血流动力学的影响

肝纤维化是血吸虫病患者发病以及导致严重并发症的病理学基础,若能减轻乃至逆转肝纤维化,就能有效地改善血吸虫肝病患者的预后.阻断血管紧张素Ⅱ1型受体(angiotensinⅡtype 1 receptor,AT1R)后,代偿期肝硬化患者门静脉压力下降,血清肝纤维化指标水平亦降低[1].本研究采用AT1R拮抗剂替米沙坦治疗50例晚期血吸虫肝病患者,以期了解其对肝纤维化程度和门静脉血流动力学的影响,并探讨血清肝纤维化指标和门静脉血流动力学相关指标的相关性.     

大麻素受体1通过多种机制促进肝细胞癌的发生和进展

<正>【据《Hepatology》2015年5月报道】题:大麻素受体1通过多种机制促进肝细胞癌的发生和进展(作者Mukhopadhyay B等)肝细胞癌(HCC)的死亡率高且治疗方法有限。内源性大麻素与肝大麻素1受体相互作用(CB1Rs)诱导参与有丝分裂的细胞周期蛋白,包括叉头框M1,可促进再生的肝细胞增殖。由于该蛋白在肝癌组织中高表达,有助于其发生、发展过程,来自美国国立卫生研究院的Mukhopadhyay B等分析了小鼠及人类肝癌中内源性大麻素系统/CB1R。出生后二乙基亚硝胺诱导野生型小鼠8个月建立肝癌模型。观察连续磁共振成像,在CB1R(-/)小鼠或外周拮抗剂处理的野生型小鼠体内发现较少和较小的肿瘤全基因组转录组分析显     

Role of the endocannabinoid system in alcoholic liver disease

Alcohol abuse is a major cause of liver fibrosis and cirrhosis in developed countries. Alcoholic liver disease (ALD) is distinctively characterized by a pronounced inflammatory response due to elevated gut-derived endotoxin plasma levels, an augmented generation of oxidative stress with pericentral hepatic hypoxia and the formation of noxious ethanol metabolites (e.g. acetaldehyde or lipid oxidation products). These factors, based on a complex network of cytokine actions, together result in increased hepatocellular damage and activation of hepatic stellate cells, the key cell type of liver fibrogenesis. Recent studies suggest that the endocannabinoid system is a signaling system that also plays an important role in the pathogenesis of ALD. A study comparing chronic alcohol administration in cannabinoid receptor (CB) 1 or CB2 knockout versus wild-type mice revealed that CB1 signaling aggravated hepatic steatosis and fibrogenesis whereas CB2 protected the liver from ALD. These data suggested a protective role of CB2 (in contrast to CB1) in ALD. Similar results were found in global or hepatocyte-specific CB1 knockout mice that were resistant to ethanol-induced steatosis. Moreover, ethanol feeding upregulated the endocannabinoid 2-arachidonoyl glycerol and its biosynthetic enzyme diacylglycerol lipase-β selectively in hepatic stellate cells and subsequently increased expression of CB1 receptors in hepatocytes of wild-type mice leading to CB1-dependent hepatic steatosis by activation of lipogenic pathways. This ethanol-induced upregulation of CB1 receptors was partly dependent on the ethanol metabolite acetaldehyde. Thus, the hepatic endocannabinoid system offers emerging options for therapeutic exploitation not only for liver disease in general, but also for ALD.     

Peripheral cannabinoid receptor, CB2, regulates bone mass

The endogenous cannabinoids bind to and activate two G protein-coupled receptors, the predominantly central cannabinoid receptor type 1 (CB1) and peripheral cannabinoid receptor type 2 (CB2). Whereas CB1 mediates the cannabinoid psychotropic, analgesic, and orectic effects, CB2 has been implicated recently in the regulation of liver fibrosis and atherosclerosis. Here we show that CB2-deficient mice have a markedly accelerated age-related trabecular bone loss and cortical expansion, although cortical thickness remains unaltered. These changes are reminiscent of human osteoporosis and may result from differential regulation of trabecular and cortical bone remodeling. The CB2(-/-) phenotype is also characterized by increased activity of trabecular osteoblasts (bone-forming cells), increased osteoclast (the bone-resorbing cell) number, and a markedly decreased number of diaphyseal osteoblast precursors. CB2 is expressed in osteoblasts, osteocytes, and osteoclasts. A CB2-specific agonist that does not have any psychotropic effects enhances endocortical osteoblast number and activity and restrains trabecular osteoclastogenesis, apparently by inhibiting proliferation of osteoclast precursors and receptor activator of NF-kappaB ligand expression in bone marrow-derived osteoblasts/stromal cells. The same agonist attenuates ovariectomy-induced bone loss and markedly stimulates cortical thickness through the respective suppression of osteoclast number and stimulation of endocortical bone formation. These results demonstrate that the endocannabinoid system is essential for the maintenance of normal bone mass by osteoblastic and osteoclastic CB2 signaling. Hence, CB2 offers a molecular target for the diagnosis and treatment of osteoporosis, the most prevalent degenerative disease in developed countries.     

Endocannabinoids in liver disease

Endocannabinoids are lipid mediators of the same cannabinoid (CB) receptors that mediate the effects of marijuana. The endocannabinoid system (ECS) consists of CB receptors, endocannabinoids, and the enzymes involved in their biosynthesis and degradation, and it is present in both brain and peripheral tissues, including the liver. The hepatic ECS is activated in various liver diseases and contributes to the underlying pathologies. In patients with cirrhosis of various etiologies, the activation of vascular and cardiac CB(1) receptors by macrophage-derived and platelet-derived endocannabinoids contributes to the vasodilated state and cardiomyopathy, which can be reversed by CB(1) blockade. In mouse models of liver fibrosis, the activation of CB(1) receptors on hepatic stellate cells is fibrogenic, and CB(1) blockade slows the progression of fibrosis. Fatty liver induced by a high-fat diet or chronic alcohol feeding depends on the activation of peripheral receptors, including hepatic CB(1) receptors, which also contribute to insulin resistance and dyslipidemias. Although the documented therapeutic potential of CB(1) blockade is limited by neuropsychiatric side effects, these may be mitigated by using novel, peripherally restricted CB(1) antagonists.     

Increased anandamide induced relaxation in mesenteric arteries of cirrhotic rats: role of cannabinoid and vanilloid receptors

BACKGROUND AND AIMS: Anandamide is an endocannabinoid that evokes hypotension by interaction with peripheral cannabinoid CB1 receptors and with the perivascular transient receptor potential vanilloid type 1 protein (TRPV1). As anandamide has been implicated in the vasodilated state in advanced cirrhosis, the study investigated whether the mesenteric bed from cirrhotic rats has an altered and selective vasodilator response to anandamide. METHODS: We assessed vascular sensitivity to anandamide, mRNA and protein expression of cannabinoid CB1 receptor and TRPV1 receptor, and the topographical distribution of cannabinoid CB1 receptors in resistance mesenteric arteries of cirrhotic and control rats. RESULTS: Mesenteric vessels of cirrhotic animals displayed greater sensitivity to anandamide than control vessels. This vasodilator response was reverted by CB1 or TRPV1 receptor blockade, but not after endothelium denudation or nitric oxide inhibition. Anandamide had no effect on distal femoral arteries. CB1 and TRPV1 receptor protein was higher in cirrhotic than in control vessels. Neither CB1 mRNA nor protein was detected in femoral arteries. Immunochemistry showed that CB1 receptors were mainly in the adventitia and in the endothelial monolayer, with higher expression observed in vessels of cirrhotic rats than in controls. CONCLUSIONS: These results indicate that anandamide is a selective splanchnic vasodilator in cirrhosis which predominantly acts via interaction with two different types of receptors, CB1 and TRPV1 receptors, which are mainly located in perivascular sensory nerve terminals of the mesenteric resistance arteries of these animals.     

Implication of the endocannabinoid system in the locomotor hyperactivity associated with congenital hypothyroidism

Alterations in motor functions are well-characterized features observed in humans and experimental animals subjected to thyroid hormone dysfunctions during development. Here we show that congenitally hypothyroid rats display hyperactivity in the adult life. This phenotype was associated with a decreased content of cannabinoid receptor type 1 (CB(1)) mRNA in the striatum and a reduction in the number of binding sites in both striatum and projection areas. These findings suggest that hyperactivity may be the consequence of a thyroid hormone deficiency-induced removal of the endocannabinoid tone, normally acting as a brake for hyperactivity at the basal ganglia. In agreement with the decrease in CB(1) receptor gene expression, a lower cannabinoid response, measured by biochemical, genetic and behavioral parameters, was observed in the hypothyroid animals. Finally, both CB(1) receptor gene expression and the biochemical and behavioral dysfunctions found in the hypothyroid animals were improved after a thyroid hormone replacement treatment. Thus, the present study suggests that impairment in the endocannabinoid system can underlay the hyperactive phenotype associated with hypothyroidism.     

Mechanisms of CB1 receptor signaling: endocannabinoid modulation of synaptic strength

The CB1 cannabinoid receptor has attracted much recent interest because of the observation that CB1 receptor antagonists have efficacy in treating metabolic syndrome and obesity. CB1 receptors also mediate most of the psychotropic effects of Delta9-tetrahydrocannabinol (Delta9THC), the principal psychoactive component of cannabis. In addition, they are one component of an interesting and widespread paracrine signaling system, the endocannabinoid system. The endocannabinoid system is comprised of cannabinoid receptors, endogenous cannabinoids, and the metabolic pathways responsible for their synthesis and degradation. The details of the endocannabinoid system have been most thoroughly studied in the brain. Here it has been shown to be intimately involved in several forms of neuronal plasticity. That is, activation of CB1 receptors by endocannabinoids produces either short- or long-term changes in the efficacy of synaptic transmission. The behavioral consequences of these changes are many, but some of the most striking and relevant to the current symposium are those associated with endogenous reward and consumptive behavior.     

Impact of endocannabinoid system in modulation of cardiometabolic risk factors

Endocannabinoid system, the complex of specific cannabinoid receptors (CB1 and CB2 subtypes) and their endogenous agonistic ligands (endocannabinoids) plays, besides others, an important role in the central and peripheral regulation of food intake, fat accumulation, and lipid and glucose metabolism. Alterations of these functions are associated with endocannabinoid system hyperactivity. The cannabinoid receptor CB1 antagonist rimonabant normalizes the over activated endocannabinoid system which contributes to the regulation of energy homeostasis, and improves lipid and glucose metabolism--decreases body weight, waist circumference, intra-abdominal obesity and triglycerides, increases HDL-C, improves insulin sensitivity according to HOMA index. Results of the international multicentric clinical trials confirm that rimonabant is well tolerated and show antiatherogenic effects (increased adiponectin, decreased marker of inflammation CRP and improvement of LDL profile) as well as decreased percentage of subjects with NCEP/ATPIII (National Cholesterol Education Program Adult Treatment Panel III) defined metabolic syndrome. Thus, the CB1 cannabinoid receptor antagonist rimonabant is suggested to be a prospective drug decreasing cardiometabolic risk factors.     

The Role of Endocannabinoids System in Fatty Liver Disease and Therapeutic Potentials

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver morbidity and mortality with no proven effective therapy as of yet. Its prevalence is increasing globally in parallel with obesity and metabolic syndrome pandemic. The endocannabinoid (EC) system has been implicated in the pathogenesis of several diseases, including fatty liver diseases. This system refers to the cannabinoid receptors type 1 (CB1) and type 2 (CB2), with both their endogenous ligands and machinery dedicated to EC synthesis and degradation. There is accumulating evidence on the role CB1 as a key mediator of insulin resistance and liver lipogenesis in both animals and humans. On the other hand, CB2 receptors have been shown to promote inflammation with anti-fibrogenic properties. The pharmacological modulation of the EC system activity for the treatment of metabolic syndrome and NAFLD are promising yet premature. The initial limited success due to deleterious central nervous system side-effects are likely to be bypassed with the use of peripherally restricted drugs.     

Cannabinoid receptor 2 agonist ameliorates mesenteric angiogenesis and portosystemic collaterals in cirrhotic rats

Angiogenesis in liver cirrhosis leads to splanchnic hyperemia, increased portal inflow, and portosystemic collaterals formation, which may induce lethal complications, such as gastroesophageal variceal hemorrhage and hepatic encephalopathy. Cannabinoids (CBs) inhibit angiogenesis, but the relevant influences in cirrhosis are unknown. In this study, Spraque-Dawley rats received common bile duct ligation (BDL) to induce cirrhosis. BDL rats received vehicle, arachidonyl-2-chloroethylamide (cannabinoid receptor type 1 [CB(1) ] agonist), JWH-015 (cannabinoid receptor type 2 [CB(2) ] agonist), and AM630 (CB(2) antagonist) from days 35 to 42 days after BDL. On the 43rd day, hemodynamics, presence of CB receptors, severity of portosystemic shunting, mesenteric vascular density, vascular endothelial growth factor (VEGF), VEGFR-1, VEGFR-2, phospho-VEGFR-2, cyclooxygenase (COX)-1, COX-2, and endothelial nitric oxide synthase (eNOS) expressions as well as plasma VEGF levels were evaluated. Results showed that CB(1) and CB(2) receptors were present in left adrenal veins of sham rats, splenorenal shunts (the most prominent intra-abdominal shunts) of BDL rats, and mesentery of sham and BDL rats. CB(2) receptor was up-regulated in splenorenal shunts of BDL rats. Both acute and chronic JWH-015 treatment reduced portal pressure and superior mesenteric arterial blood flow. Compared with vehicle, JWH-015 significantly alleviated portosystemic shunting and mesenteric vascular density in BDL rats, but not in sham rats. The concomitant use of JWH-015 and AM630 abolished JWH-015 effects. JWH-133, another CB(2) agonist, mimicked the JWH-015 effects. JWH-015 decreased mesenteric COX-1, COX-2 messenger RNA expressions, and COX-1, COX-2, eNOS protein expressions. Furthermore, JWH-015 decreased intrahepatic angiogenesis and fibrosis. CONCLUSIONS: CB(2) agonist alleviates portal hypertension (PH), severity of portosystemic collaterals and mesenteric angiogenesis, intrahepatic angiogenesis, and fibrosis in cirrhotic rats. The mechanism is, at least partly, through COX and NOS down-regulation. CBs may be targeted in the control of PH and portosystemic collaterals.