在大鼠和人类来源的形成血脑屏障(BBB)的脑微血管内皮细胞(BMEC)中研究了瞬时受体电位香草酸1-4(TRPV1-4)的表达和功能。在老鼠身上,通过qRT-PCR在大脑皮层中检测到Trpv1-4,脑微血管,和脑微血管内皮细胞[大鼠脑微血管内皮细胞(rPBMEC)]的原代培养物中。在分离的脑微血管和rPBMEC中发现相似的Trpv1-4表达谱,其顺序如下:Trpv4>Trpv2>Trpv3>Trpv1。在人类中,在BBB细胞系人脑微血管内皮细胞D3细胞(hCMEC/D3)和从成人和儿童脑切除术中分离的BMEC的原代培养物中检测到TRPV1-4[人脑微血管内皮细胞(hPBMEC)],显示在hCMEC/D3细胞和hPBMECs中相似的TRPV1-4表达谱如下:TRPV2>>TRPV4>TRPV1>TRPV3。Western印迹和免疫荧光实验证实,TRPV2和TRPV4是hCMEC/D3细胞中表达最多的TRPV亚型,质膜染色清晰。应用荧光染料Fluo-4AM酯来记录细胞内Ca2+水平。TRPV4功能活性在用特异性激动剂GSK1016790A刺激下介导Ca2+流入中得到证实(范围从3到1000nM,EC50为16.2±4.5nM),它被特定的TRPV4拮抗剂抑制,RN1734(30μM)。相比之下,TRPV1在hCMEC/D3细胞中被轻微激活,如高浓度(3μM)辣椒素诱导的弱Ca2流入所示。一种高效和特异性的TRPV1激动剂。通过与选择性有效的TRPV1拮抗剂辣椒素(20μM)共同处理,热诱导的Ca2内流不会改变,与通过qRT-PCR评估的TRPV1的低表达一致。我们目前的研究揭示了大鼠和人类之间的种间差异。TRPV1-4亚型表达的功能贡献在反映BBB完整性的大鼠和人组织中不相同。TRPV2在人中占主导地位,而TRPV4在大鼠中具有更大的作用。当在脑部疾病的大鼠模型中研究TRPV2或TRPV4的调节剂时,应考虑从基因表达角度的种间差异。
Transient receptor potential vanilloid 1-4 (TRPV1-4) expression and functionality were investigated in brain microvessel endothelial cells (BMEC) forming the blood-brain barrier (BBB) from rat and human origins. In rat, Trpv1-4 were detected by qRT-PCR in the brain cortex, brain microvessels, and in primary cultures of brain microvessel endothelial cells [rat brain microvessel endothelial cells (rPBMEC)]. A similar Trpv1-4 expression profile in isolated brain microvessels and rPBMEC was found with the following order: Trpv4 >
Trpv2 > Trpv3 > Trpv1. In human, TRPV1-4 were detected in the BBB cell line human cerebral microvessel endothelial cells D3 cells (hCMEC/D3) and in primary cultures of BMEC isolated from human adult and children brain resections [human brain microvascular endothelial cells (hPBMEC)], showing a similar TRPV1-4 expression profile in both hCMEC/D3 cells and hPBMECs as follow:
TRPV2 > > TRPV4 > TRPV1 > TRPV3. Western blotting and immunofluorescence experiments confirmed that
TRPV2 and TRPV4 are the most expressed TRPV isoforms in hCMEC/D3 cells with a clear staining at the plasma membrane. A fluorescent dye Fluo-4 AM ester was applied to record intracellular Ca2+ levels. TRPV4 functional activity was demonstrated in mediating Ca2+ influx under stimulation with the specific agonist GSK1016790A (ranging from 3 to 1000 nM, EC50 of 16.2 ± 4.5 nM), which was inhibited by the specific TRPV4 antagonist, RN1734 (30 μM). In contrast, TRPV1 was slightly activated in hCMEC/D3 cells as shown by the weak Ca2+ influx induced by capsaicin at a high concentration (3 μM), a highly potent and specific TRPV1 agonist. Heat-induced Ca2+ influx was not altered by co-treatment with a selective potent TRPV1 antagonist capsazepine (20 μM), in agreement with the low expression of TRPV1 as assessed by qRT-PCR. Our present
study reveals an interspecies difference between Rat and Human. Functional contributions of TRPV1-4 subtype expression were not identical in rat and human tissues reflective of BBB integrity.
TRPV2 was predominant in the human whereas TRPV4 had a larger role in the rat. This interspecies difference from a gene expression point of view should be taken into consideration when modulators of TRPV2 or TRPV4 are investigated in rat models of brain disorders.