RESUMO
BACKGROUND: Although TRPA1, SP, histamine and 5-hydroxytryptamine (5-HT) have recognized contribution to nociceptive mechanisms, little is known about how they interact with each other to mediate inflammatory pain in vivo. In this study we evaluated whether TRPA1, SP, histamine and 5-HT interact, in an interdependent way, to induce nociception in vivo. METHODS AND RESULTS: The subcutaneous injection of the TRPA1 agonist allyl isothiocyanate (AITC) into the rat's hind paw induced a dose-dependent and short lasting behavioral nociceptive response that was blocked by the co-administration of the TRPA1 antagonist, HC030031, or by the pretreatment with antisense ODN against TRPA1. AITC-induced nociception was significantly decreased by the co-administration of selective antagonists for the NK1 receptor for substance P, the H1 receptor for histamine and the 5-HT1A or 3 receptors for 5-HT. Histamine- or 5-HT-induced nociception was decreased by the pretreatment with antisense ODN against TRPA1. These findings suggest that AITC-induced nociception depends on substance P, histamine and 5-HT, while histamine- or 5-HT-induced nociception depends on TRPA1. Most important, AITC interact in a synergistic way with histamine, 5-HT or substance P, since their combination at non-nociceptive doses induced a nociceptive response much higher than that expected by the sum of the effect of each one alone. This synergistic effect is dependent on the H1, 5-HT1A or 3 receptors. CONCLUSION: Together, these findings suggest a self-sustainable cycle around TRPA1, no matter where the cycle is initiated each step is achieved and even subeffective activation of more than one step results in a synergistic activation of the overall cycle.
Assuntos
Histamina/metabolismo , Dor/metabolismo , Serotonina/metabolismo , Substância P/metabolismo , Canais de Cátion TRPC/metabolismo , Acetanilidas/farmacologia , Animais , Antagonistas dos Receptores Histamínicos H1/farmacologia , Isotiocianatos , Masculino , Oligonucleotídeos Antissenso/farmacologia , Dor/induzido quimicamente , Piperazinas/farmacologia , Purinas/farmacologia , Pirilamina/farmacologia , Quinuclidinas/farmacologia , Ratos Wistar , Receptor 5-HT1A de Serotonina/metabolismo , Receptores Histamínicos H1/metabolismo , Receptores da Neurocinina-1/metabolismo , Receptores 5-HT3 de Serotonina/metabolismo , Antagonistas da Serotonina/farmacologia , Canal de Cátion TRPA1 , Canais de Cátion TRPC/agonistas , Canais de Cátion TRPC/antagonistas & inibidores , Canais de Cátion TRPC/genética , p-Metoxi-N-metilfenetilamina/farmacologiaRESUMO
OBJECTIVE: Gout is a common cause of inflammatory arthritis and is provoked by the accumulation of monosodium urate (MSU) crystals. However, the underlying mechanisms of the pain associated with acute attacks of gout are poorly understood. The aim of this study was to evaluate the role of transient receptor potential ankyrin 1 (TRPA-1) and TRPA-1 stimulants, such as H2 O2 , in a rodent model of MSU-induced inflammation. METHODS: MSU or H2 O2 was injected into the hind paws of rodents or applied in cultured sensory neurons, and the intracellular calcium response was measured in vitro. Inflammatory or nociceptive responses in vivo were evaluated using pharmacologic, genetic, or biochemical tools and methods. RESULTS: TRPA-1 antagonism, TRPA-1 gene deletion, or pretreatment of peptidergic TRP-expressing primary sensory neurons with capsaicin markedly decreased MSU-induced nociception and edema. In addition to these neurogenic effects, MSU increased H2 O2 levels in the injected tissue, an effect that was abolished by the H2 O2 -detoxifying enzyme catalase. H2 O2 , but not MSU, directly stimulated sensory neurons through the activation of TRPA-1. The nociceptive responses evoked by MSU or H2 O2 injection were attenuated by the reducing agent dithiothreitol. In addition, MSU injection increased the expression of TRPA-1 and TRP vanilloid channel 1 (TRPV-1) and also enhanced cellular infiltration and interleukin-1ß levels, and these effects were blocked by TRPA-1 antagonism. CONCLUSION: Our results suggest that MSU injection increases tissue H2 O2 , thereby stimulating TRPA-1 on sensory nerve endings to produce inflammation and nociception. TRPV-1, by a previously unknown mechanism, also contributes to these responses.
Assuntos
Dor Aguda/metabolismo , Artrite Gotosa/metabolismo , Peróxido de Hidrogênio/metabolismo , Inflamação/metabolismo , Canais de Cátion TRPC/metabolismo , Ácido Úrico/metabolismo , Acetanilidas/farmacologia , Dor Aguda/induzido quimicamente , Dor Aguda/tratamento farmacológico , Animais , Artrite Gotosa/induzido quimicamente , Artrite Gotosa/tratamento farmacológico , Modelos Animais de Doenças , Peróxido de Hidrogênio/farmacologia , Inflamação/induzido quimicamente , Inflamação/tratamento farmacológico , Masculino , Camundongos , Camundongos Knockout , Oxidantes/metabolismo , Oxidantes/farmacologia , Purinas/farmacologia , Ratos , Ratos Wistar , Células Receptoras Sensoriais/metabolismo , Canal de Cátion TRPA1 , Canais de Cátion TRPC/agonistas , Canais de Cátion TRPC/antagonistas & inibidores , Ácido Úrico/farmacologiaRESUMO
Abdominal pain is a frequent symptom of peritoneal cavity irritation, but little is known about the role of the receptors for irritant substances, transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), in this painful condition. Thus, we investigated the abdominal nociception caused by peritoneal stimulation with TRPV1 (capsaicin) and TRPA1 (allyl isothiocyanate, AITC) agonists and their mechanisms in rats. The intraperitoneal (i.p.) injection of either capsaicin or AITC (0.03-10 mg/kg) induced short-term (up to 20 min) and dose-dependent abdominal nociception, and also produced c-fos expression in spinal afferents of the dorsal horn. TRPV1 antagonism prevented (94 ± 4% inhibition) nociception induced by capsaicin but not by AITC. In contrast, the TRPA1 antagonism almost abolished AITC-induced nociception (95 ± 2% inhibition) without altering the capsaicin response. Moreover, nociception induced by either capsaicin or AITC was reduced by the desensitisation of TRPV1-positive sensory fibres with resiniferatoxin (73 ± 18 and 76 ± 15% inhibitions, respectively) and by the NK1 receptor antagonist aprepitant (56 ± 5 and 53 ± 8% inhibitions, respectively). Likewise, the i.p. injections of capsaicin or AITC increased the content of substance P in the peritoneal fluid. Nevertheless, neither the mast cell membrane stabiliser cromoglycate, nor the H1 antagonist promethazine, nor depletion of peritoneal macrophages affected abdominal nociception induced either by capsaicin or AITC. Accordingly, neither capsaicin nor AITC increased the histamine content in the peritoneal fluid or provoked peritoneal mast cell degranulation in vitro. Collectively, our findings suggest that TRPV1 and TRPA1 stimulation in the peritoneum produces abdominal nociception that is mediated by sensory fibres activation.
Assuntos
Nociceptividade , Peritônio/efeitos dos fármacos , Canais de Cátion TRPC/metabolismo , Canais de Cátion TRPV/metabolismo , Animais , Capsaicina/farmacologia , Trânsito Gastrointestinal/efeitos dos fármacos , Intestinos/efeitos dos fármacos , Intestinos/fisiologia , Isotiocianatos/farmacologia , Macrófagos/citologia , Macrófagos/efeitos dos fármacos , Masculino , Mastócitos/citologia , Mastócitos/efeitos dos fármacos , Nociceptividade/efeitos dos fármacos , Peritônio/imunologia , Peritônio/metabolismo , Peritônio/fisiologia , Ratos , Ratos Wistar , Receptores da Neurocinina-1/metabolismo , Substância P/farmacologia , Canal de Cátion TRPA1 , Canais de Cátion TRPC/agonistas , Canais de Cátion TRPV/agonistasRESUMO
The transient receptor potential ankyrin 1 (TRPA1) is expressed in peripheral and spinal terminals of sensory neurons, jointly to the vanilloid receptor (TRPV1). A relevant peripheral role of TRPA1 receptor has been implicated in a variety of processes, including the detection of noxious cold, and diverse painful stimulus, but the functional role of TRPA1 receptor in nociceptive transmission at spinal cord in vivo is poorly known. Therefore, the aim of this study was to evaluate whether the glutamatergic system is involved in the transmission of nociceptive stimulus induced for a TRPA1 agonist in the rat spinal cord. We observed that cinnamaldehyde, a TRPA1 agonist, on spinal cord synaptosomes leads to an increase in [Ca(2+)](i) and a rapid release of glutamate, but was not able to change the specific [(3)H]-glutamate binding. In addition, spinally administered cinnamaldehyde produced heat hyperalgesia and mechanical allodynia in rats. This behavior was reduced by the co-injection (i.t.) of camphor (TRPA1 antagonist) or MK-801 (N-methyl-D-aspartate (NMDA) receptor antagonist) to cinnamaldehyde. Besides, the pretreatment with resiniferatoxin (RTX), a potent TRPV1 agonist, abolished the cinnamaldehyde-induced heat hyperalgesia. Here, we showed that intrathecal RTX results in a decrease in TRPA1 and TRPV1 immunoreactivity in dorsal root ganglion. Collectively, our results demonstrate the pertinent participation of spinal TRPA1 in the possible enhancement of glutamatergic transmission of nociceptive signals leading to increase of the hypersensitivity, here observed as heat hyperalgesia. Then the modulation of spinal TRPA1 might be a valuable target in painful conditions associated with central pain hypersensitivity.