Liu Limei, Liu Jian, Gao Yuansheng, Ng Chi Fai, Yu Xiaoxing, Dou Dou, Huang Yu
aDepartment of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, P.R. China bInstitute of Vascular Medicine, Li Ka Shing Institute of Health Sciences, School of Biomedical Sciences, Chinese University of Hong Kong cDepartment of Surgery, Chinese University of Hong Kong, Hong Kong, P.R. China *Limei Liu and Jian Liu contributed equally to the writing of this article.
J Hypertens. 2015 Apr;33(4):784-90; discussion 790. doi: 10.1097/HJH.0000000000000480.
Glucagon-like peptide-1 (GLP-1) exerts its actions via activating GLP-1 receptor (GLP-1R). Our previous study showed a reduced GLP-1R expression in spontaneously hypertensive rat (SHR) renal arteries. The present study investigated the mechanisms underlying GLP-1R downregulation in hypertension.
Intrarenal arteries of normotensive Wistar-Kyoto rat (WKY) and SHR were suspended in the myograph for force measurement. GLP-1R expression was evaluated by both immunofluorescence and western blotting. Protein kinase Cα (PKCα), PKCβ, PKCδ, and total PKC levels were assayed by western blotting.
Immunofluorescence revealed reduced GLP-1R level in SHR renal arteries compared with WKY renal arteries. GLP-1R agonist exendin-4 induced concentration-dependent relaxations in WKY arteries, which mainly depended on the presence of endothelium. GLP-1R antagonist exendin 9-39 inhibited this relaxation in WKY arteries, whereas the relaxations were significantly less in SHR arteries. Ex-vivo treatment with PKC inhibitor GFX, PKCα and PKCβ inhibitor Gö6976, and PKCβ inhibitor hispidin but not PKCδ inhibitor rottlerin improved the impaired relaxations and restored the diminished GLP-1R expression in SHR arteries. Furthermore, PKCβ level was greater in SHR than WKY arteries, with no difference in PKCα, PKCδ, or total PKC expressions between two rat strains. Treatment with PKC-activating agent phorbol-12-myristate-13-acetate attenuated exendin-4-induced relaxations and reduced GLP-1R expression in WKY arteries, which were reversed by GFX, Gö6976, or hispidin. More relevantly, immunofluorescence of human renal arteries also showed a reduced GLP-1R level in hypertensive patients.
The present results provide novel evidence that the reduced GLP-1R expression in SHR renal arteries is most likely mediated through PKCβ upregulation; the latter probably contributes to the impaired GLP-1R-mediated vasorelaxations in hypertension.
胰高血糖素样肽-1（GLP-1）通过激活GLP-1受体（GLP-1R）发挥作用。我们之前的研究表明，自发性高血压大鼠（SHR）肾动脉中GLP-1R表达降低。本研究探讨高血压中GLP-1R下调的机制。
将正常血压的Wistar-Kyoto大鼠（WKY）和SHR的肾内动脉悬挂于肌张力测定仪中进行张力测量。通过免疫荧光和蛋白质印迹法评估GLP-1R表达。通过蛋白质印迹法检测蛋白激酶Cα（PKCα）、PKCβ、PKCδ和总PKC水平。
免疫荧光显示，与WKY肾动脉相比，SHR肾动脉中GLP-1R水平降低。GLP-1R激动剂艾塞那肽-4在WKY动脉中诱导浓度依赖性舒张，这主要依赖于内皮的存在。GLP-1R拮抗剂艾塞那肽9-39抑制WKY动脉中的这种舒张，而SHR动脉中的舒张明显较弱。用PKC抑制剂GFX、PKCα和PKCβ抑制剂Gö6976以及PKCβ抑制剂漆黄素进行体外处理，但不用PKCδ抑制剂罗特勒素，可改善SHR动脉中受损的舒张并恢复降低的GLP-1R表达。此外，SHR动脉中的PKCβ水平高于WKY动脉，两种大鼠品系之间PKCα、PKCδ或总PKC表达无差异。用PKC激活剂佛波醇-12-肉豆蔻酸酯-13-乙酸酯处理可减弱艾塞那肽-4诱导的WKY动脉舒张并降低GLP-1R表达，GFX、Gö6976或漆黄素可逆转这种情况。更相关的是，人类肾动脉的免疫荧光也显示高血压患者中GLP-1R水平降低。
目前的结果提供了新的证据，表明SHR肾动脉中GLP-1R表达降低最可能是通过PKCβ上调介导的；后者可能导致高血压中GLP-1R介导的血管舒张受损。
