A Inosina como um modulador endógeno da dor: de coadjuvante a protagonista do sistema purinérgico
Carregando...
Arquivos
Data
2012-04-20
Autores
Nascimento, Francisney Pinto
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Santa Catarina
Resumo
A inosina é um nucleosídeo formado pela desaminação da adenosina pela ação da adenosina desaminase (ADA). A adenosina e a inosina possuem grande semelhança química, tendo como diferença um grupamento amina. Entre outras funções fisiológicas, a inosina apresenta atividade anti-inflamatória, neuroprotetora e cardiotônica. O objetivo deste trabalho foi avaliar o perfil antinociceptivo da inosina, avaliando seus mecanismos de ação e comparando seus efeitos aos causados pela adenosina. Foram utilizados camundongos das linhagens C57black/6, Swiss e ratos Wistar. A inosina e a adenosina (10 mg/kg, i.p.) reduziram a nocicepção induzida pela formalina, ambas com inibições de 44%. Quando coinjetada com a formalina, a inosina (20 μ g/sítio) apresentou efeito antinociceptivo na pata ipsilateral, mas não na pata contralateral. O DPCPX, um antagonista seletivo de receptores A1 de adenosina (A1R), quando injetado pela via i.t. (10 nmol/sítio) ou i.p. (0,1 mg/kg) preveniu a antinocicepção induzida pela inosina (10 mg/kg, i.p.). Porém, quando injetado localmente, o DPCPX (5μ g/sítio) não preveniu o efeito antinociceptivo local da inosina. A inosina administrada pelas vias i.t. (10 μ g/sítio) ou i.p. (10 mg/kg) não apresentou efeito antinociceptivo em animais nocaute para A1R, contudo, localmente (20 μ g/sítio, i.pl.) a inosina exerceu atividade antinociceptiva. Animais tratados com oligodeoxinucleotídeo antisentido para o A1R (AS-ODN-A1R) apresentaram redução da expressão do A1R, e foram insensíveis ao efeito antinociceptivo da inosina (10 mg/kg, i.p.). A inosina e a adenosina deslocaram o ligante radioativo [3H]DPCPX no ensaio de ligação específica para o A1R, com CI50 de 36 nM e 113 nM, respectivamente. A toxina pertussis, o CaCl2, os bloqueadores de canais de K+ caribdotoxina, glibenclamida, tetraetilamônio e 4-aminopiridina previniram o efeito antinociceptivo da inosina (10 mg/kg, i.p.) no teste da formalina. A inosina (10 mg/kg, i.p.) também reduziu a hiperalgesia induzida pelo PMA (0,1 nmol/pata) e pela bradicinina (3 nmol/pata), ativadores direto e indireto da PKC, respectivamente, mas não reduziu a hiperalgesia induzida pela PGE2 (10 nmol/pata) e forskolina (1 μ mol/pata), ambos ativadores indiretos da PKA. A inosina também reduziu a hiperalgesia mecânica induzida pelo CFA e pela ligação parcial do nervo ciático, além de reduzir os níveis de TNF-α na pata induzido pela injeção intraplantar de CFA. A inosina (10 mg/kg, i.p.) reduziu a dor espontânea induzida pela injeção intratecal de TNF-α (0,1 pg/sítio) e substância P (50 nmol/sítio), mas não a dor induzida pela IL1β (1 pg/sítio). A administração de deoxicoformicina (DCF, inibidor da adenosina desaminase, 50 mg/kg, i.p.) reduziu a antinocicepção induzida pela inosina no teste da formalina. As doses sub-ativas de forodesinea (FDS, inibidor da purina nucleosídeo fosforilase, 0,1 mg/kg, i.p) e inosina (3 mg/kg, i.p.) quando associadas induziram antinocicepção no teste da formalina. A inosina e a adenosina apresentaram efeito antinociceptivo até 2 horas após o tratamento no teste da formalina. Trinta minutos após a admnistração de adenosina (10 mg/kg, i.p.) ou inosina (10 mg/kg, i.p.), foi encontrado no plasma sanguíneo de camundongos apenas níveis elevados de inosina. Estes resultados demonstram que os A1R centrais estão envolvidos na antinocicepção da inosina, e que este envolvimento se dá pela ativação direta do receptor, sendo a inosina um ligante endógeno do A1R. A ativação dos canais de K+, redução dos níveis intracelulares de Ca2+ e a inibição da PKC são eventos que parecem estar envolvidos neste efeito. Ainda, a inosina reduz a hiperalgesia através da redução dos níveis de TNF-α. Finalmente, a inosina e a adenosina além de serem moléculas muito parecidas quimicamente, também possuem efeitos muito similares, sendo a inosina, um provável modulador endógeno da dor.
Inosine is formed from adenosine breakdown after deamination by adenosine deaminase (ADA) action. Adenosine and inosine have several structural and chemical similarities, being one amine group the only difference. Among other physiological functions, inosine has anti-inflammatory, neuroprotective and cardiotonic effects. The objective of this study was to evaluate the antinociceptive profile of inosine, to investigate its mechanisms of action and to evaluate and compare its effects with those caused by adenosine. Animals used were C57black/6 and swiss mice and Wistar rats. Inosine and adenosine (10 mg/kg, ip) reduced nociception induced by formalin, both which 44% of inhibition. When co-administered with formalin, inosine (20 μg / site) induced antinociceptive effect in the ipsilateral, but not in the contralateral paw. DPCPX, an antagonist of adenosine A1 receptor (A1R), when injected via i.t. (10 nmol / site) or i.p. (0.1 mg / kg) blocked the antinociceptive effect of inosine (10 mg / kg, ip). However, when injected peripherally, DPCPX (5μg/sítio) did not prevent the local antinociception induced by inosine. Using knockout animals for A1R, inosine by i.t. (10 mg / site) or i.p. (10 mg / kg) routes showed no antinociceptive effect. However, when injected locally (20 μg / site, i.pl.) inosine induced antinociceptive activity. Animals treated with antisense oligodeoxynucleotide (AS- ODN) for A1R showed a reduction of A1R expression, and abolished the inosine (10 mg / kg, ip) antinociception. Both inosine and adenosine displaced the radioactive ligand in the specific binding assay for the A1R, with maximum inhibition of 71 and 60%, respectively. Pertussis toxin, CaCl2, blockers of K+ channels such as caribdotoxin, glibenclamide, tetraethylammonium and 4- aminopyridine prevented the inosine antinociception. Inosine (10 mg / kg, ip) also decreased hyperalgesia induced by PMA (0.1 nmol / paw), and bradykinin (3 nmol / paw), direct and indirect PKC activators, respectively. However, inosine did not prevent hyperalgesia induced by PGE2 (10 nmol / paw) and forskolin (1 mmol / paw), both indirect PKA activators. Inosine also reduced the mechanical hyperalgesia induced by CFA and partial ligation of sciatic nerve. In addition, inosine reduced TNF-_ levels in the paw after intraplantar injection of CFA. Inosine (10 mg / kg ip) also reduced spontaneous pain induced by intrathecal injection of TNF-_ (0.1 pg / site) and Substance P (50 nmol / site), but did not reduce the pain induced by IL-1_ (1 pg / site). Administration of deoxycoformicin (DCF, 50 mg / kg ip) reduced inosine antinociception in the formalin test. Subactive doses of FDS (0.1 mg / kg, ip) and inosine (3 mg / kg, ip) when associated induced antinociception in the formalin test. Inosine and adenosine presented antinociceptive effect up to 2 hours after treatment in the formalin test. Thirty minutes after administration of adenosine (10 mg / kg, ip) or inosine (10 mg / kg, ip), only inosine elevated plasma levels were found. These results demonstrate that the central A1R are involved in antinociception induced by inosine, and this involvement occurs by direct activation of the receptor, being inosine an endogenous ligand of A1R. In addition, after activation of A1R, activation of K+ channels, reduction of intracellular Ca2+ levels and inhibition of PKC are events that are involved in this effect. Further, inosine reduces chronic hyperalgesia by reducing levels of TNF-_. Finally, adenosine and inosine are very similar molecules that also have very similar effects. Then, we suggest that inosine is an endogenous modulator of pain
Inosine is formed from adenosine breakdown after deamination by adenosine deaminase (ADA) action. Adenosine and inosine have several structural and chemical similarities, being one amine group the only difference. Among other physiological functions, inosine has anti-inflammatory, neuroprotective and cardiotonic effects. The objective of this study was to evaluate the antinociceptive profile of inosine, to investigate its mechanisms of action and to evaluate and compare its effects with those caused by adenosine. Animals used were C57black/6 and swiss mice and Wistar rats. Inosine and adenosine (10 mg/kg, ip) reduced nociception induced by formalin, both which 44% of inhibition. When co-administered with formalin, inosine (20 μg / site) induced antinociceptive effect in the ipsilateral, but not in the contralateral paw. DPCPX, an antagonist of adenosine A1 receptor (A1R), when injected via i.t. (10 nmol / site) or i.p. (0.1 mg / kg) blocked the antinociceptive effect of inosine (10 mg / kg, ip). However, when injected peripherally, DPCPX (5μg/sítio) did not prevent the local antinociception induced by inosine. Using knockout animals for A1R, inosine by i.t. (10 mg / site) or i.p. (10 mg / kg) routes showed no antinociceptive effect. However, when injected locally (20 μg / site, i.pl.) inosine induced antinociceptive activity. Animals treated with antisense oligodeoxynucleotide (AS- ODN) for A1R showed a reduction of A1R expression, and abolished the inosine (10 mg / kg, ip) antinociception. Both inosine and adenosine displaced the radioactive ligand in the specific binding assay for the A1R, with maximum inhibition of 71 and 60%, respectively. Pertussis toxin, CaCl2, blockers of K+ channels such as caribdotoxin, glibenclamide, tetraethylammonium and 4- aminopyridine prevented the inosine antinociception. Inosine (10 mg / kg, ip) also decreased hyperalgesia induced by PMA (0.1 nmol / paw), and bradykinin (3 nmol / paw), direct and indirect PKC activators, respectively. However, inosine did not prevent hyperalgesia induced by PGE2 (10 nmol / paw) and forskolin (1 mmol / paw), both indirect PKA activators. Inosine also reduced the mechanical hyperalgesia induced by CFA and partial ligation of sciatic nerve. In addition, inosine reduced TNF-_ levels in the paw after intraplantar injection of CFA. Inosine (10 mg / kg ip) also reduced spontaneous pain induced by intrathecal injection of TNF-_ (0.1 pg / site) and Substance P (50 nmol / site), but did not reduce the pain induced by IL-1_ (1 pg / site). Administration of deoxycoformicin (DCF, 50 mg / kg ip) reduced inosine antinociception in the formalin test. Subactive doses of FDS (0.1 mg / kg, ip) and inosine (3 mg / kg, ip) when associated induced antinociception in the formalin test. Inosine and adenosine presented antinociceptive effect up to 2 hours after treatment in the formalin test. Thirty minutes after administration of adenosine (10 mg / kg, ip) or inosine (10 mg / kg, ip), only inosine elevated plasma levels were found. These results demonstrate that the central A1R are involved in antinociception induced by inosine, and this involvement occurs by direct activation of the receptor, being inosine an endogenous ligand of A1R. In addition, after activation of A1R, activation of K+ channels, reduction of intracellular Ca2+ levels and inhibition of PKC are events that are involved in this effect. Further, inosine reduces chronic hyperalgesia by reducing levels of TNF-_. Finally, adenosine and inosine are very similar molecules that also have very similar effects. Then, we suggest that inosine is an endogenous modulator of pain
Descrição
Tese apresentada ao Programa de Pós-
graduação em Farmacologia da
Universidade Federal de Santa
Catarina para a obtenção do Grau de
Doutor em Farmacologia.
Orientador: Prof. Dr. Adair Roberto
Soares dos Santos
Palavras-chave
Inosina, Dor, Receptores de adenosina, Farmacologia
Citação
Nascimento, 2012.
NASCIMENTO, Francisney Pinto do. A Inosina como um modulador endógeno da dor: de coadjuvante a protagonista do sistema purinérgico. 2012. 217 p. Tese de Doutorado (Programa de Pós-graduação em Farmacologia) - Universidade Federal de Santa Catarina (UFSC), Florianópolis, 2012
NASCIMENTO, Francisney Pinto do. A Inosina como um modulador endógeno da dor: de coadjuvante a protagonista do sistema purinérgico. 2012. 217 p. Tese de Doutorado (Programa de Pós-graduação em Farmacologia) - Universidade Federal de Santa Catarina (UFSC), Florianópolis, 2012