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Efeito do tratamento com um quelante macrocíclico na atividade de enzimas inibidas por compostos de mercúrio em células de neuroblastoma
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Orientador(es)
Resumo(s)
O mercúrio (Hg) é um poluente global. Atualmente, os compostos mais relevantes no que toca à exposição humana são o metilmercúrio (MeHg) através do consumo de peixe, o vapor de mercúrio (Hg0v) proveniente das amálgamas dentárias e exposição ocupacional e o etilmercúrio (EtHg) presente em vacinas contendo timerosal (TM).
O Hg tem efeitos tóxicos a nível neurológico, cardiovascular, imunológico e renal, sendo no entanto o Sistema Nervoso Central (SNC) o principal órgão-alvo. Os compostos de Hg conseguem atravessar a placenta e são teratogénicos.
O Hg interfere com o estado redox intracelular, inibindo as enzimas do sistema da tiorredoxina – tiorredoxina redutase (TrxR) e tiorredoxina (Trx) – e diminuindo os níveis de GSH (sistema da glutationa).
O tratamento de intoxicações por Hg é feito recorrendo a agentes quelantes. No entanto, têm muitos efeitos secundários, baixa especificidade e eficácia controversa, pelo que a pesquisa de novos quelantes do Hg é de relevância toxicológica.
O 1-tia-4,7,10,13-tetraazaciclopentadecano ([15]anoN4S) já demonstrou ter atividade satisfatória enquanto quelante do Hg e do MeHg, com elevada estabilidade, nomeadamente em condições fisiológicas.
Neste trabalho, pretendeu-se avaliar a eficácia do [15]anoN4S enquanto quelante do Hg, por determinação da atividade da TrxR e da Trx e dos níveis de GSH, em células de neuroblastoma humano (SH-SY5Y) – um modelo do SNC – expostas a diferentes concentrações de Hg2+, MeHg e EtHg e co-expostas a [15]anoN4S.
A TrxR é mais sensível que a Trx, mas ambas foram inibidas de forma dose-dependente pelos compostos de Hg estudados, apresentando maior sensibilidade ao MeHg. Os níveis de GSH encontraram-se diminuídos aquando exposição ao MeHg ou ao EtHg. O [15]anoN4S não é capaz de recuperar a atividade da TrxR nem da Trx após exposição ao MeHg ou ao EtHg. No entanto, parece existir recuperação da atividade da Trx na exposição ao Hg2+. Os níveis de GSH são superiores quando as células são também expostas a [15]anoN4S, com aumentos mais significativos para exposição ao Hg2+.
Mercury (Hg) is a global pollutant. Currently, the most relevant sources of Hg exposure to humans are methylmercury (MeHg) through fish consumption, mercury vapor (Hg0v) from dental amalgams and occupational exposure and ethylmercury (EtHg), from thimerosal containing vaccines (TCV). Hg has toxic effects at the neurological, cardiovascular, immune and kidney level but the Central Nervous System (CNS) is the main target organ. Hg compounds can cross the placenta and exert teratogenic effects. Hg interferes with the intracellular redox state, inhibiting the enzymes of the thioredoxin system – thioredoxin reductase (TrxR) and thioredoxin (Trx) – and lowering GSH levels (glutathione system). The treatment of Hg poisoning is made using chelating agents. However, they have many side effects, low specificity and controversial effectiveness, so the search for new chelators of Hg is of toxicological relevance. The 1-thia-4,7,10,13-tetraazacyclopentadecane ([15]aneN4S) has been shown to have satisfactory activity as a chelating agent of Hg and MeHg with high stability, particularly under physiological conditions. In this work, we sought to evaluate the effectiveness of [15]aneN4S as a Hg chelator by determining TrxR and the Trx activity and GSH levels in human neuroblastoma cells (SH-SY5Y) – a CNS model – exposed to different concentrations of Hg2+, MeHg and EtHg and co-expoded to [15]aneN4S. TrxR is more sensitive than Trx, albeit both were inhibited by Hg compounds in a dose-dependent manner, with higher sensitivity to MeHg. GSH levels decreased when cells were exposed to MeHg or EtHg. The [15]aneN4S was not able to recover the activity of Trx or TrxR after exposure to MeHg or EtHg. However, there seems to be recovery of Trx from the same exposure to Hg2+. GSH levels are higher when SH-SY5Y cells are also exposed to [15]aneN4S, with more significant during exposure to Hg2+.
Mercury (Hg) is a global pollutant. Currently, the most relevant sources of Hg exposure to humans are methylmercury (MeHg) through fish consumption, mercury vapor (Hg0v) from dental amalgams and occupational exposure and ethylmercury (EtHg), from thimerosal containing vaccines (TCV). Hg has toxic effects at the neurological, cardiovascular, immune and kidney level but the Central Nervous System (CNS) is the main target organ. Hg compounds can cross the placenta and exert teratogenic effects. Hg interferes with the intracellular redox state, inhibiting the enzymes of the thioredoxin system – thioredoxin reductase (TrxR) and thioredoxin (Trx) – and lowering GSH levels (glutathione system). The treatment of Hg poisoning is made using chelating agents. However, they have many side effects, low specificity and controversial effectiveness, so the search for new chelators of Hg is of toxicological relevance. The 1-thia-4,7,10,13-tetraazacyclopentadecane ([15]aneN4S) has been shown to have satisfactory activity as a chelating agent of Hg and MeHg with high stability, particularly under physiological conditions. In this work, we sought to evaluate the effectiveness of [15]aneN4S as a Hg chelator by determining TrxR and the Trx activity and GSH levels in human neuroblastoma cells (SH-SY5Y) – a CNS model – exposed to different concentrations of Hg2+, MeHg and EtHg and co-expoded to [15]aneN4S. TrxR is more sensitive than Trx, albeit both were inhibited by Hg compounds in a dose-dependent manner, with higher sensitivity to MeHg. GSH levels decreased when cells were exposed to MeHg or EtHg. The [15]aneN4S was not able to recover the activity of Trx or TrxR after exposure to MeHg or EtHg. However, there seems to be recovery of Trx from the same exposure to Hg2+. GSH levels are higher when SH-SY5Y cells are also exposed to [15]aneN4S, with more significant during exposure to Hg2+.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2016
Palavras-chave
Compostos de mercúrio Neurotoxicidade Sistema da tiorredoxina Glutationa 1-tia-4,7,10,13-tetraazaciclopentadecano Mestrado Integrado - 2016