Laboratory of Neurotoxicity and Psychopharmacology, Center of Natural and Exact Sciences, Federal University of Santa Maria, Santa Maria, RS, Brazil; Graduate Program in Biological Sciences: Biochemistry Toxicology, Federal University of Santa Maria, Santa Maria, RS, Brazil.
Laboratory of Neurotoxicity and Psychopharmacology, Center of Natural and Exact Sciences, Federal University of Santa Maria, Santa Maria, RS, Brazil.
Phytomedicine. 2019 Feb 15;54:248-258. doi: 10.1016/j.phymed.2018.09.201. Epub 2018 Sep 18.
Ionic channels such as the transient receptor potential ankyrin 1 (TRPA1) are essential for the detection and transmission of painful stimuli. In this sense, new TRPA1 antagonists have been searched as analgesics.
Preclinical studies support the antinociceptive activity of Tabernaemontana catharinensis ethyl acetate fraction (Eta), which has constituents previously identified as TRPA1 antagonists (gallic acid). It was verified for the first time the involvement of the TRPA1 on Eta's antinociceptive and anti-inflammatory effects in mice pain models.
It was evaluated the Eta's effect (0.01-100 mg/kg, oral route) on nociceptive (spontaneous nociception, mechanical and cold allodynia) and inflammatory (paw edema) parameters in pain models involved with TRPA1 activation.
Firstly, it was investigated the ability of Eta to act on TRPA1 or TRPV1 channels (Cainflux and binding assays in mice spinal cords). Next, it was evaluated the Eta's antinociceptive and anti-inflammatory effects after intraplantar injection of TRPA1 agonists (hydrogen peroxide, cinnamaldehyde or allyl isothiocyanate) in male Swiss mice (30-35 g). Moreover, the Eta's antinociceptive effects were evaluated on complete Freund's adjuvant (CFA)-induced chronic inflammatory pain (CIP), postoperative pain and on paclitaxel-induced peripheral neuropathy (PIPN). Oxidative parameters were evaluated in mice paw utilized for CFA induced-CIP model.
Eta inhibited the TRPA1 agonist-induced Ca influx [I= 72.4 ± 1.5%; IC= 0.023(0.004-0.125)µg/ml], but not TRPV1 agonist-induced, nor was able to displace [H]-resiniferatoxin (TRPV1 agonist) binding. Eta (0.1-100 mg/kg) inhibited the spontaneous nociception [ID= 0.043(0.002-0.723)mg/kg], mechanical [ID= 7.417(1.426-38.570)mg/kg] and cold allodynia, and edema development caused by TRPA1 agonists. Moreover, Eta (100 mg/kg) prevented and reversed the CFA-induced CIP (I= 55.8 ± 13.7%, I= 80.4 ± 5.1%, respectively) and postoperative pain (I= 88.0 ± 11.6%, I= 51.3 ± 14.9%, respectively), been also effective in reversing the acute (I= 94.4 ± 12.4%) and chronic (I= 86.8 ± 8.6%) PIPN. These effects seem to occur by TRPA1 channels pathway, and independently of TRPV1 or oxidative mechanisms.
Our results demonstrate that Eta-induced antinociception and anti-inflammatory effects occur by TRPA1 inhibition making possible the use of this preparation as a potential therapeutic agent to treat pathological pains.
瞬时受体电位锚蛋白 1（TRPA1）等离子通道对于疼痛刺激的检测和传递至关重要。从这个意义上说，人们一直在寻找新的 TRPA1 拮抗剂作为止痛药。
临床前研究支持 Tabernaemontana catharinensis 乙酸乙酯部分（Eta）的抗伤害作用，其成分先前被鉴定为 TRPA1 拮抗剂（没食子酸）。首次验证了 Eta 在小鼠疼痛模型中的抗伤害和抗炎作用涉及 TRPA1。
评估 Eta（0.01-100mg/kg，口服途径）对涉及 TRPA1 激活的疼痛模型中的伤害性（自发性疼痛、机械性和冷感觉过敏）和炎症（爪肿胀）参数的影响。
首先，研究了 Eta 对 TRPA1 或 TRPV1 通道（在小鼠脊髓中的 Cainflux 和结合测定）的作用。接下来，评估了 Eta 对 TRPA1 激动剂（过氧化氢、肉桂醛或丙烯基异硫氰酸酯）在雄性瑞士小鼠（30-35g）中皮下注射后的抗伤害和抗炎作用。此外，还评估了 Eta 对完全弗氏佐剂（CFA）诱导的慢性炎症性疼痛（CIP）、术后疼痛和紫杉醇诱导的周围神经病变（PIPN）的抗伤害作用。还评估了用于 CFA 诱导的 CIP 模型的小鼠爪中的氧化参数。
Eta 抑制了 TRPA1 激动剂诱导的 Ca2+内流[I=72.4±1.5%；IC=0.023（0.004-0.125）μg/ml]，但不能抑制 TRPV1 激动剂诱导的 Ca2+内流，也不能置换[H]-resiniferatoxin（TRPV1 激动剂）结合。Eta（0.1-100mg/kg）抑制自发性疼痛[ID=0.043（0.002-0.723）mg/kg]、机械性疼痛[ID=7.417（1.426-38.570）mg/kg]和冷感觉过敏，以及 TRPA1 激动剂引起的肿胀发展。此外，Eta（100mg/kg）预防和逆转了 CFA 诱导的 CIP（I=55.8±13.7%，I=80.4±5.1%）和术后疼痛（I=88.0±11.6%，I=51.3±14.9%），并有效逆转了急性（I=94.4±12.4%）和慢性（I=86.8±8.6%）PIPN。这些作用似乎是通过 TRPA1 通道途径发生的，并且独立于 TRPV1 或氧化机制。
我们的结果表明，Eta 诱导的抗伤害和抗炎作用是通过抑制 TRPA1 发生的，这使得这种制剂有可能作为治疗病理性疼痛的潜在治疗剂。
