Neuroimmunology Group, Functional and Systems Neurobiology Department, Cajal Institute, CSIC, 28002 Madrid, Spain.
J Neuroinflammation. 2011 Aug 18;8:102. doi: 10.1186/1742-2094-8-102.
VCAM-1 represents one of the most important adhesion molecule involved in the transmigration of blood leukocytes across the blood-brain barrier (BBB) that is an essential step in the pathogenesis of MS. Several evidences have suggested the potential therapeutic value of cannabinoids (CBs) in the treatment of MS and their experimental models. However, the effects of endocannabinoids on VCAM-1 regulation are poorly understood. In the present study we investigated the effects of anandamide (AEA) in the regulation of VCAM-1 expression induced by Theiler's virus (TMEV) infection of brain endothelial cells using in vitro and in vivo approaches.
i) in vitro: VCAM-1 was measured by ELISA in supernatants of brain endothelial cells infected with TMEV and subjected to AEA and/or cannabinoid receptors antagonist treatment. To evaluate the functional effect of VCAM-1 modulation we developed a blood brain barrier model based on a system of astrocytes and brain endothelial cells co-culture. ii) in vivo: CB(1) receptor deficient mice (Cnr1(-/-)) infected with TMEV were treated with the AEA uptake inhibitor UCM-707 for three days. VCAM-1 expression and microglial reactivity were evaluated by immunohistochemistry.
Anandamide-induced inhibition of VCAM-1 expression in brain endothelial cell cultures was mediated by activation of CB(1) receptors. The study of leukocyte transmigration confirmed the functional relevance of VCAM-1 inhibition by AEA. In vivo approaches also showed that the inhibition of AEA uptake reduced the expression of brain VCAM-1 in response to TMEV infection. Although a decreased expression of VCAM-1 by UCM-707 was observed in both, wild type and CB(1) receptor deficient mice (Cnr1(-/-)), the magnitude of VCAM-1 inhibition was significantly higher in the wild type mice. Interestingly, Cnr1(-/-) mice showed enhanced microglial reactivity and VCAM-1 expression following TMEV infection, indicating that the lack of CB(1) receptor exacerbated neuroinflammation.
Our results suggest that CB(1) receptor dependent VCAM-1 inhibition is a novel mechanism for AEA-reduced leukocyte transmigration and contribute to a better understanding of the mechanisms underlying the beneficial role of endocannabinoid system in the Theiler's virus model of MS.
VCAM-1 是血脑屏障（BBB）中白细胞迁移的最重要的黏附分子之一，是 MS 发病机制中的一个重要步骤。有几项证据表明大麻素（CBs）在 MS 及其实验模型的治疗中有潜在的治疗价值。然而，内源性大麻素对 VCAM-1 调节的影响还知之甚少。在本研究中，我们通过体外和体内方法研究了大麻素通过 Theiler 病毒（TMEV）感染脑内皮细胞对 VCAM-1 表达的调节作用。
i）体外：通过 ELISA 测量 TMEV 感染的脑内皮细胞上清液中的 VCAM-1，并进行 AE 和/或大麻素受体拮抗剂处理。为了评估 VCAM-1 调节的功能影响，我们开发了一种基于星形胶质细胞和脑内皮细胞共培养系统的血脑屏障模型。ii）体内：用 TMEV 感染的 CB1 受体缺陷小鼠（Cnr1(-/-)）用 AEA 摄取抑制剂 UCM-707 治疗三天。通过免疫组织化学评估 VCAM-1 表达和小胶质细胞反应性。
AEA 诱导的脑内皮细胞培养物中 VCAM-1 表达的抑制作用是通过激活 CB1 受体介导的。白细胞迁移的研究证实了 AEA 对 VCAM-1 抑制的功能相关性。体内方法还表明，抑制 AEA 摄取可降低 TMEV 感染时大脑 VCAM-1 的表达。尽管 UCM-707 在野生型和 CB1 受体缺陷型小鼠（Cnr1(-/-)）中均观察到 VCAM-1 表达减少，但野生型小鼠的 VCAM-1 抑制程度明显更高。有趣的是，TMEV 感染后 Cnr1(-/-) 小鼠的小胶质细胞反应性和 VCAM-1 表达增强，表明 CB1 受体缺失加剧了神经炎症。
我们的结果表明，CB1 受体依赖性 VCAM-1 抑制是 AEA 减少白细胞迁移的新机制，并有助于更好地理解内源性大麻素系统在 TMEV 诱导的 MS 模型中的有益作用的机制。
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