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Objective:To evaluate the effect of gastrogin on AMP-activated protein kinase (AMPK)/transient receptor potential anchor protein 1 (TRPA1) signaling pathway in rats with neuropathic pain.Methods:Thirty-six SPF-grade healthy male Sprague-Dawley rats, aged 6-8 weeks, weighing 200-230 g, were divided into 3 groups ( n=12 each) using a random number table method: sham operation+ normal saline group (SHAM group), neuropathic pain+ normal saline group (NP group), and neuropathic pain+ gastrogin group (GAS group). Neuropathic pain was induced by chronic constrictive injury to sciatic nerve under 2% isoflurane anaesthesia. The sciatic nerve was only exposed but not ligated in SHAM group. Gastrogin 100 mg/kg was intraperitoneally injected for 14 consecutive days after developing the model in GAS group, while the equal volume of normal saline was given instead in SHAM and NP groups. The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 1 day before developing the model (T 0) and 1, 3, 5, 7, 10 and 14 days after developing the model (T 1-6). The rats were anesthetized and sacrificed following the measurement of pain thresholds at T 4 and T 6. The lumbar segment (L 4-6) of the spinal cord was removed for determination of TRPA1 mRNA expression (by quantitative real-time polymerase chain reaction), expression of TRPA1, AMPK and p-AMPK (by Western blot), expression of TRPA1 (by immunofluorescence staining) and expression of tumor necrosis-alpha(TNF-α), interleukin-1beta(IL-1β) and c-fos (by immunohistochemistry). Results:Compared with SHAM group, MWT and TWL were significantly decreased at T 1-6, the expression of TRPA1 mRNA, TRPA1, TNF-α, IL-1β and c-fos was up-regulated, the expression of p-AMPK was down-regulated ( P<0.05), and no significant change was found in AMPK expression in NP group ( P>0.05). Compared with NP group, MWT at T 3-6 and TWL at T 2-6 were significantly increased, the expression of TRPA1 mRNA, TRPA1, TNF-α, IL-1β and c-fos was down-regulated, and p-AMPK expression was up-regulated ( P<0.05), and no significant change was found in AMPK expression in GAS group ( P>0.05). Conclusions:The mechanism by which gastrogin reduces neuropathic pain may be related to modulating the expression of the AMPK/TRPA1 signaling pathway in rats.
ABSTRACT
Abstract Background Pain is an uncomfortable sensation in the body. Kaempferol is a flavonoid with antinociceptive effects. Transient receptor potential (TRP) channels have been characterized in the sensory system. Objective This study evaluated the central antinociceptive effect of Kaempferol and possible mechanisms of action of transient receptor potential cation channel subfamily V member 1 (TRPV1). Methods Capsaicin as a TRPV agonist (5 μg/μL, intracerebroventricular [ICV]) and capsazepine as its antagonist (10 μg/μL, icv) were used to test the analgesic effect of kaempferol (1.5 mg, ICV). Morphine (10 μg, ICV) was used as a positive control. The other groups were treated with a combination of kaempferol and capsaicin, kaempferol and capsazepine, and capsaicin and capsazepine. The cannula was implanted in the cerebroventricular area. The tail-flick, acetic acid, and formalin tests were used to assess analgesic activity.For evaluation of antiinflammatory effect, the formalin-induced rat pawedema was used. Results Kaempferol significantly decreased pain in the acute pain models, including the tail-flick and the first phase of the formalin test. In the late phase of the formalin test, as a valid model of nociception, capsazepine inhibited the antinociceptive effect of kaempferol. Conclusions Kaempferol has an analgesic effect in the acute pain model and can affect inflammatory pain. Also, the TRPV1 channel plays a role in the antinociceptive activity of kaempferol.
Resumo Antecedentes A dor é uma sensação desconfortável no corpo. Kaempferol é um flavonoide com efeitos antinociceptivos. Canais receptores de potencial transitório têm sido caracterizados no sistema sensorial. Objetivo Este estudo avaliou o efeito antinociceptivo central do kaempferol e os possíveis mecanismos de ação do TRPV1. Métodos Capsaicina como agonista de TRPV (5 μg/μL, intracerebroventricular [ICV]) e capsazepina como seu antagonista (10 μg/μL, icv) foram usados para testar o efeito analgésico do kaempferol (1,5 mg, ICV). A morfina (10 μg, ICV) foi usada como controle positivo. Os outros grupos foram tratados com uma combinação de kaempferol e capsaicina, kaempferol e capsazepina e capsaicina e capsazepina. A cânula foi implantada na área cerebroventricular. Os testes de movimento de cauda, ácido acético e formalina foram usados para avaliar a atividade analgésica. Para avaliação do efeito anti-inflamatório, foi utilizado o edema de pata de rato induzido por formalina. Resultados Kaempferol diminuiu significativamente a dor nos modelos de dor aguda, incluindo o movimento da cauda e a primeira fase do teste de formalina. Na fase tardia do teste da formalina, como modelo válido de nocicepção, a capsazepina inibiu o efeito antinociceptivo do kaempferol. Conclusões Kaempferol tem efeito analgésico no modelo de dor aguda e pode afetar a dor inflamatória. Além disso, o canal TRPV1 desempenha um papel na atividade antinociceptiva do kaempferol.
ABSTRACT
BACKGROUND/AIMS: Abdominal pain can be evoked or exacerbated after gastrointestinal cold stimulation in some patients with diarrhea-predominant irritable bowel syndrome (IBS-D), indicating a low temperature-induced sensitization of visceral perception. We investigated the role of vagal transient receptor potential ankyrin 1 (TRPA1, a cold-sensing ion channel) in cold-aggravated visceral mechanonociception in a stress-induced IBS animal model. METHODS: TRPA1 expression was examined in antral biopsies of healthy controls and IBS-D patients. Abdominal symptoms were assessed before and after warm or cold water intake. The visceromotor response (VMR) to colorectal distention (CRD) following intra-antral infusion of cold saline was measured in animals undergoing sham or chronic water avoidance stress. TRPA1 expression, extracellular signal-regulated protein kinase 1/2 (ERK1/2) phosphorylation, and neuronal calcium influx in vagal afferents were assessed. RESULTS: Compared to healthy controls, IBS-D patients displayed elevated antral TRPA1 expression, which was associated with symptom scores after cold (4°C) water intake. Intra-antral infusion of cold saline increased VMR to CRD in naive rats, an effect dependent on vagal afferents. In stressed rats, this effect was greatly enhanced. Functional blockade and gene deletion of TRPA1 abolished the cold effect on visceral nociception. TRPA1 expression in vagal (but not spinal) afferents increased after stress. Moreover, the cold-induced, TRPA1-dependent ERK1/2 activation and calcium influx in nodose neurons were more robust in stressed rats. CONCLUSIONS: Stress-exaggerated visceral mechanonociception after antral cold exposure may involve up-regulation of TRPA1 expression and function on vagal afferents. Our findings reveal a novel mechanism for abnormal gastrointestinal cold sensing in IBS.
Subject(s)
Animals , Humans , Rats , Abdominal Pain , Ankyrins , Biopsy , Calcium , Cold Temperature , Drinking , Gene Deletion , Irritable Bowel Syndrome , Models, Animal , Neurons , Nociception , Phosphorylation , Protein Kinases , Stress, Psychological , Up-Regulation , Vagus Nerve , Visceral Pain , WaterABSTRACT
Abstract Purpose: To investigate the specific molecular mechanisms and effects of curcumin derivative J147 on diabetic peripheral neuropathy (DPN). Methods: We constructed streptozotocin (STZ)-induced DPN rat models to detected mechanical withdrawal threshold (MWT) in vivo using Von Frey filaments. In vitro, we measured cell viability and apoptosis, adenosine 5'-monophosphate-activated protein kinase (AMPK) and transient receptor potential A1 (TRPA1) expression using MTT, flow cytometry, qRT-PCR and western blot. Then, TRPA1 expression level and calcium reaction level were assessed in agonist AICAR treated RSC96cells. Results: The results showed that J147reduced MWT in vivo, increased the mRNA and protein level of AMPK, reduced TRPA1 expression and calcium reaction level in AITCR treated RSC96 cells, and had no obvious effect on cell viability and apoptosis. Besides, AMPK negative regulated TRPA1 expression in RSC96 cells. Conclusions: J147 could ameliorate DPN via negative regulation AMPK on TRPA1 in vivo and in vitro. A curcumin derivative J147might be a new therapeutic potential for the treatment of DPN.