Translational and Experimental Medicine, Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV4 7AL, U.K.
Biosciences, Brunel University, Uxbridge UB8 3PH, U.K.
Clin Sci (Lond). 2018 Dec 13;132(24):2547-2564. doi: 10.1042/CS20180150. Print 2018 Dec 21.
Orexins/hypocretins exert cardiovascular effects which are centrally mediated. In the present study, we tested whether orexins and their receptors may also act in an autocrine/paracrine manner in the heart exerting direct effects. Quantitative reverse transcription-PCR (RT-PCR), immunohistochemical and Western blot analyses revealed that the rat heart expresses orexins and orexin receptors (OXR). In isolated rat cardiomyocytes, only orexin-B (OR-B) caused an increase in contractile shortening, independent of diastolic or systolic calcium levels. A specific orexin receptor-2 (OX2R) agonist ([Ala, d-Leu]-Orexin B) exerted similar effects as OR-B, whereas a specific orexin receptor-1 (OX1R) antagonist (SB-408124) did not alter the responsiveness of OR-B. Treatment of the same model with OR-B resulted in a dose-dependent increase in myosin light chain and troponin-I (TnI) phosphorylation. Following ischaemia/reperfusion in the isolated Langendorff perfused rat heart model, OR-B, but not OR-A, exerts a cardioprotective effect; mirrored in an model as well. Unlike OR-A, OR-B was also able to induce extracellular signal-regulated kinase (ERK) 1/2 (ERK1/2) and Akt phosphorylation in rat myocardial tissue and ERK1/2 phosphorylation in human heart samples. These findings were further corroborated in an rat model. In human subjects with heart failure, there is a significant negative correlation between the expression of OX2R and the severity of the disease clinical symptoms, as assessed by the New York Heart Association (NYHA) functional classification. Collectively, we provide evidence of a distinct orexin system in the heart that exerts a cardioprotective role via an OR-B/OX2R pathway.
食欲素/下丘脑分泌素对心血管系统有影响，这种影响是中枢介导的。在本研究中，我们检测了食欲素及其受体是否也能在心脏中以自分泌/旁分泌的方式发挥作用，从而产生直接作用。定量逆转录聚合酶链反应（RT-PCR）、免疫组织化学和 Western blot 分析显示，大鼠心脏表达食欲素和食欲素受体（OXR）。在分离的大鼠心肌细胞中，只有食欲素-B（OR-B）能独立于舒张期或收缩期钙水平增加收缩缩短。一种特定的食欲素受体-2（OX2R）激动剂（[Ala，d-Leu]-Orexin B）产生与 OR-B 相似的作用，而一种特定的食欲素受体-1（OX1R）拮抗剂（SB-408124）不会改变 OR-B 的反应性。用 OR-B 处理相同模型会导致肌球蛋白轻链和肌钙蛋白 I（TnI）磷酸化呈剂量依赖性增加。在分离的 Langendorff 灌注大鼠心脏模型中，OR-B 而非 OR-A 在缺血/再灌注后具有心脏保护作用；在 模型中也得到了印证。与 OR-A 不同，OR-B 还能够诱导大鼠心肌组织中细胞外信号调节激酶（ERK）1/2（ERK1/2）和 Akt 磷酸化，以及人心脏样本中 ERK1/2 磷酸化。这些发现也在 大鼠模型中得到了进一步证实。在心力衰竭的人类患者中，OX2R 的表达与疾病临床症状的严重程度呈显著负相关，这通过纽约心脏协会（NYHA）功能分类来评估。总之，我们提供了心脏中存在独特的食欲素系统的证据，该系统通过 OR-B/OX2R 途径发挥心脏保护作用。
