Ambrosino Paolo, Soldovieri Maria Virginia, De Maria Michela, Russo Claudio, Taglialatela Maurizio
Dept. of Medicine and Health Sciences, University of Molise, Campobasso, Italy.
Dept. of Medicine and Health Sciences, University of Molise, Campobasso, Italy; Dept. of Neuroscience, Section of Pharmacology, University of Naples Federico II, Naples, Italy.
Pharmacol Res. 2014 Sep;87:113-22. doi: 10.1016/j.phrs.2014.06.015. Epub 2014 Jul 8.
Transient receptor potential vanilloid type-1 (TRPV1) channels expressed in primary afferent neurons play a critical role in nociception triggered by endogenous and exogenous compounds. In the present study, the functional and biochemical interaction between TRPV1 channels and type-α peroxisome proliferator-activated receptors (PPARα) has been investigated. In TRPV1-expressing CHO cells, patch-clamp studies revealed that acute application of the PPARα agonists clofibrate (CLO; 0.1-100 μM), WY14643 (1-300 μM), or GW7647 (0.1-100 nM) activated TRPV1 currents in a concentration-dependent manner, with EC50s of 5.3 ± 0.8 μM, 13.0 ± 1.2 μM, and 12.7 ± 0.3 nM, respectively. The role of PPARα in these pharmacological responses was confirmed by the ability of the PPARα antagonist GW6471 (10 μM) to block CLO-, WY14643- and GW7647-induced TRPV1 activation, and by the observation that modulation of PPARα levels via siRNA-mediated suppression or PPARα over-expression affected TRPV1 channel activation by PPARα agonists accordingly. In cells cotransfected with PPARα and TRPV1, PPARα receptors were detected in TRPV1-immunoprecipitated fractions. When compared to capsaicin (CAP), TRPV1 currents activated by PPARα agonists showed a higher degree of acute desensitization and tachyphylaxis; moreover, GW7647, when pre-incubated at a concentration (1nM) unable to activate TRPV1 currents per se, desensitized CAP-induced TRPV1 currents. Finally, a sub-effective concentration of each PPARα agonist inhibited TRPV1-dependent bradykinin-induced [Ca(2+)]i transients in sensory neurons. Collectively, these results provide evidence for a PPARα-mediated pathway triggering TRPV1 channel activation and desensitization, and highlight a novel mechanism which might contribute to the analgesic effects shown by PPARα agonists in vivo.
表达于初级传入神经元的瞬时受体电位香草酸亚型1（TRPV1）通道在内源性和外源性化合物引发的伤害感受中起关键作用。在本研究中，对TRPV1通道与α型过氧化物酶体增殖物激活受体（PPARα）之间的功能和生化相互作用进行了研究。在表达TRPV1的CHO细胞中，膜片钳研究显示，急性应用PPARα激动剂氯贝丁酯（CLO；0.1 - 100 μM）、WY14643（1 - 300 μM）或GW7647（0.1 - 100 nM）可浓度依赖性激活TRPV1电流，其半数有效浓度（EC50）分别为5.3 ± 0.8 μM、13.0 ± 1.2 μM和12.7 ± 0.3 nM。PPARα拮抗剂GW6471（10 μM）能够阻断CLO、WY14643和GW7647诱导的TRPV1激活，以及通过观察到经由小干扰RNA（siRNA）介导的抑制或PPARα过表达对PPARα水平的调节相应地影响PPARα激动剂对TRPV1通道的激活，证实了PPARα在这些药理反应中的作用。在共转染PPARα和TRPV1的细胞中，在TRPV1免疫沉淀组分中检测到PPARα受体。与辣椒素（CAP）相比，PPARα激动剂激活的TRPV1电流表现出更高程度的急性脱敏和快速耐受；此外，GW7647在以本身无法激活TRPV1电流的浓度（1 nM）预孵育时，可使CAP诱导的TRPV1电流脱敏。最后，各PPARα激动剂的亚有效浓度抑制了感觉神经元中TRPV1依赖性缓激肽诱导的[Ca(2+)]i瞬变。总体而言，这些结果为PPARα介导的触发TRPV1通道激活和脱敏的途径提供了证据，并突出了一种可能有助于PPARα激动剂在体内显示镇痛作用的新机制。
