Toguri J T, Moxsom R, Szczesniak A M, Zhou J, Kelly M E M, Lehmann C
Department of Pharmacology, Dalhousie University, Halifax, NS, Canada.
Department of Anesthesia, Dalhousie University, Halifax, NS, Canada.
Clin Hemorheol Microcirc. 2015;61(2):237-49. doi: 10.3233/CH-151996.
Leukocyte adhesion to the endothelium and decreased microvascular blood flow causing microcirculatory dysfunction are hallmarks of systemic inflammation. We studied the impact of cannabinoid receptor activation on the iridial microcirculation, which is accessible non-invasively in vivo, in systemic inflammation induced by endotoxin challenge.
40 Lewis rats were used in the experiments. Endotoxemia was induced by 2 mg/kg i.v. lipopolysaccharide (LPS). Cannabinoid receptors (CBRs) were stimulated by i.v. administration of WIN 55212-2 (WIN; 1 mg/kg). CB1R antagonist (AM281; 2.5 mg/kg i.v.) or CB2R antagonist (AM630; 2.5 mg/kg i.v.) treatment prior to WIN was applied to identify the anti-inflammatory effects underlying each CBR subtype. Leukocyte-endothelial interactions were examined in rat iridial microvas culature by intravital microscopy at baseline and 1 and 2 h post-LPS. Additionally, systemic (mean arterial pressure, heart rate) and local (laser Doppler flow) hemodynamic variables were measured prior to and during cannabinoid treatments.
Endotoxemia resulted in severe inflammation as shown by significantly increased numbers of adherent leukocytes at 1 and 2 h observation time post-LPS challenge and decreased microcirculatory blood flow at 2 h within the iridial microcirculation. WIN treatment significantly reduced leukocyte adhesion in iridial microvessels with a diameter greater and less than 25 μm during endotoxemia (p < 0.05). Pre-treatment of animals by CB1R antagonist, AM281, did not affect WIN effects on LPS-induced leukocyte adhesion. When pre-treated with the CB2R antagonist, AM630, a reversal of the WIN-induced reduction in leukocyte adhesion was noticed in vessels with a diameter of less than 25 μm (p < 0.05). Cannabinoid treatment significantly increased the local iridial microcirculatory blood flow 2 hours after systemic LPS administration (p < 0.05).
Systemic administration of the CBR agonist, WIN, decreased leukocyte-adhesion and improved iridial microvascular blood flow. This effect is most likely mediated by CB2R activation. Our findings indicate that the iris microvasculature can serve as a model to study the microcirculation during systemic inflammation and help to identify potential therapies to treat microcirculatory dysfunction in diseases such as sepsis.
白细胞与内皮细胞的黏附以及微血管血流减少导致微循环功能障碍是全身炎症的标志。我们研究了大麻素受体激活对内毒素攻击诱导的全身炎症中虹膜微循环的影响，虹膜微循环在体内可通过非侵入性方式进行观察。
实验使用了40只Lewis大鼠。通过静脉注射2mg/kg脂多糖（LPS）诱导内毒素血症。通过静脉注射WIN 55212-2（WIN；1mg/kg）刺激大麻素受体（CBR）。在WIN给药前应用CB1R拮抗剂（AM281；2.5mg/kg静脉注射）或CB2R拮抗剂（AM630；2.5mg/kg静脉注射）以确定每种CBR亚型的抗炎作用。在基线以及LPS注射后1小时和2小时，通过活体显微镜检查大鼠虹膜微血管中的白细胞-内皮细胞相互作用。此外，在大麻素治疗前和治疗期间测量全身（平均动脉压、心率）和局部（激光多普勒血流）血流动力学变量。
内毒素血症导致严重炎症，表现为LPS攻击后1小时和2小时观察时间点黏附白细胞数量显著增加，以及虹膜微循环中2小时时微循环血流减少。WIN治疗显著降低了内毒素血症期间直径大于和小于25μm的虹膜微血管中的白细胞黏附（p<0.05）。用CB1R拮抗剂AM281对动物进行预处理不影响WIN对LPS诱导的白细胞黏附的作用。当用CB2R拮抗剂AM630预处理时，在直径小于25μm的血管中观察到WIN诱导的白细胞黏附减少的逆转（p<0.05）。大麻素治疗在全身给予LPS 2小时后显著增加了局部虹膜微循环血流（p<0.05）。
全身给予CBR激动剂WIN可减少白细胞黏附并改善虹膜微血管血流。这种作用很可能是由CB2R激活介导的。我们的研究结果表明虹膜微血管系统可作为研究全身炎症期间微循环的模型，并有助于确定治疗脓毒症等疾病中微循环功能障碍的潜在疗法。
