Cannabinoid CB1 receptors activation and genistein-induced estrogen ERα receptors activation suppress the ROS-induced hypersensitivity of rat vagal lung C-fiber afferents

• Main Authors: Chou-Ming Yeh, 葉周明
• Other Authors: Tien-Huan Hsu
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/02118340974445808173

博士 === 國立中興大學 === 獸醫學系暨研究所 === 105 === Vagal lung C-fibers (VLCFs) are widely distributed in the respiratory system and play the major chemosensors. Stimulation of VLCFs would induce airway reflexes, including cough, bronchoconstriction and mucus secretion. Certainly, VLCFs play protective roles in the respiratory system under normal physiological conditions. Reactive oxygen species (ROS), including H2O2, have been shown to induce hypersensitivity of VLCFs mainly through receptor potential ankyrin 1 (TRPA1) and P2X receptors. CBs exert anti-inflammatory effects by binding to specific CB receptors, designated CB1 and CB2. Genistein is a phytoestrogen that exerts anti-inflammatory and antioxidant effects by binding to two G-protein coupled receptors, ERα and ERβ. However, whether activation of CB receptors or ERs can suppress ROS-mediated VLCF hypersensitivity is unknown. To this end, the objectives of this proposal were to investigate 1) the effects of CBs agonists/antagonists perivagal treatment on the effects of VLCFs hyperactivity under the stimulation of ROS, and to delineate 2) the effects of genistein and ERs agonists/antagonists subcutaneous administration on the effects of VLCFs hyperactivity under the stimulation of ROS. We hope this proposal may clafify more details of the physiological properties of VLCFs and offer the therapeutic strategies of airway hypersensitiviy diseases. In the first study, aerosolized H2O2 (0.05%) was inhaled by anesthetized spontaneously breathing rats (n=304) to sensitize VLCFs, mimicking the raise of oxidative stress in the lungs under pathological conditions. Airway reflex reactivity to intravenous capsaicin was measured. Perivagal pretreatments with various types of agonists and antagonists were made to delineate the roles of the CB receptors. It demonstrated that aerosolized H2O2 induced an augmented apneic response to capsaicin, which was blocked by bilateral vagotomy or by perivagal capsaicin treatment, suggesting that the response is mediated through VLCFs. Moreover, perivagal treatment with HU210 (a non-selective CB agonist) or ACPA (a selective CB1 receptor agonist), attenuated this H2O2-induced VLCF hypersensitivity. In contrast, perivagal treatment with JWH133 (a CB2 receptor agonist) did not have the effects. The suppressive effects of HU210 and ACPA were prevented by an additional treatment with AM251 (a selective CB1 antagonist), but not with AM630 (a selective CB2 antagonist). Furthermore, perivagal treatment with a combination of ACPA, HC030031 (a TRPA1 receptor antagonist), and iso-PPADS (a P2X receptor antagonist) further attenuated the H2O2-induced VLCF hypersensitivity, as compared with treatment with a combination of HC030031 and iso-PPADS. In the second study, aerosolized H2O2 (0.05%) was inhaled by anesthetized spontaneously breathing rats (n = 248) to sensitize VLCFs. Subcutaneous injection of genistein, estrogen agonists and antagonists were done. Airway reflex induced by intravenous capsaicin was measured. Perivagal treatments with TRPA1 and P2X antagonists were made to investigate the roles of genistein and the ERs in VLCF hypersensitivity. Aerosolized H2O2 could induce an augmented apneic response to capsaicin, which was completely abolished by bilateral vagotomy or by perivagal capsaicin treatment, suggesting that the hyperactivity is mediated through VLCFs. Subcutaneous injection of genistein could attenuate the H2O2-induced VLCF hypersensitivity, but not affecting the sensitivity of VLCF to stimulants such as TRPA1 and P2X agonists. Furthermore, subcutaneous treatment with PPT (a selective ERα agonist), but not DPN (a ERβ agonist), could also attenuate this H2O2-induced VLCF hypersensitivity. The suppressive effects of genistein and PPT were prevented by an additional treatment with ICI 182,780 (a non-selective ER antagonist) or MPP (a selective ERα antagonist), but not with PHTPP (a selective ERβ antagonist). The reduction in the H2O2-mediated VLCF hypersensitivity caused by PPT alone was not statistically different from that produced by pretreatment with PPT and HC030031, or by PPT and iso-PPADS. The suppressive effect of HC030031 and iso-PPADS treatment in ROS-induced VLCF hypersensitiviey was similar to PPT, HC030031, and iso-PPADS treatment. These results indicated that activation of ERα receptors could suppress H2O2-induced VLCF hypersensitivity via the TRPA1 and P2X receptors mediated pathways. These results indicate that activation of CB1 receptors or genistein-induced ERα activation may suppress the ROS-mediated VLCF hypersensitivity and helpful in the treatment strategies of hypersensitive airway diseases.