Avaliação da influência de polimorfismos do gene da metalotioneína MT2A sobre as concentrações de chumbo (Pb) no sangue, plasma e urina de trabalhadores expostos ao metal
Data
2020-05-28
Autores
Faria, Jéssica Ramalho 
Orientadores
Barcelos, Gustavo Rafael Mazzaron
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O chumbo (Pb) é o segundo elemento mais tóxico, atrás apenas do arsênio (As), e está presente em abundancia na crosta terrestre. O metal é utilizado principalmente na fabricação de baterias automotivas. A exposição ao Pb pode causar diversos efeitos nocivos à saúde tais como distúrbios gastrointestinais, neurológicos e no sistema antioxidante. Com o objetivo de minimizar os efeitos nocivos causados durante a jornada de trabalho o Ministério do trabalho classificou a exposição ao Pb inorgânico como insalubridade de grau máximo, além de estabelecer os biomarcadores de toxicidade, entretanto os valores limites estão desatualizados. Há grandes variações nas concentrações de biomarcadores de toxicidade associados à exposição ao chumbo (Pb), apesar de níveis semelhantes de exposição, hipoteticamente relacionados às diferenças genéticas nas enzimas que metabolizam o metal. Entretanto, pouco se sabe a respeito dos efeitos genéticos sobre o metabolismo e toxicidade induzida pelo Pb. As metalotioneínas (MTs) são proteínas de transporte e distribuição de metais essenciais tais como o zinco (Zn), cobre (Cu) e ferro (Fe); porém, devido a sua alta quantidade de grupamentos sulfidril, metais não essenciais podem ligar-se a ela, como o Pb, cádmio (Cd), dentre outros. Sendo assim, o objetivo do estudo foi avaliar o impacto de polimorfismos do tipo Single Nucleotide Polymorphisms (SNP) do gene MT2A (UTR-3 (3’-Untranslated Region), G → C; rs10636 e UTR-5 (5’-Untranslated Region), A→ G; rs28366003) sobre as concentrações de Pb no sangue (Pb-s), plasma (Pb-p) e urina (Pb-u), em 236 trabalhadores de fábricas de baterias automotivas expostos ao metal. As concentrações de Pb-s, Pb-p e Pb-u foram quantificadas por espectrometria de massa com plasma acoplado indutivamente (ICP-MS) e as genotipagens dos polimorfismos do gene MT2A foram realizadas através do método TaqMan, por meio do da Reação em Cadeia da Polimerase (RT-PCR) em Tempo Real. Para a avaliação do impacto dos polimorfismos sobre as concentrações do metal, regressões múltiplas foram aplicadas e ajustadas por idade, IMC, tempo de trabalho, tabagismo, álcool, além das concentrações de 15 elementos químicos (Al, Sr, Sn, Se, Sb, P, Mo, Mn, Mg, Co, As, Cu, P, Cd, Fe, Pb) e o valor de p≤0,050 foi considerado significativo. A idade média foi de 38 anos e o tempo de trabalho variou de 1 mês até 27 anos; concentrações de Pb-s, Pb-p e Pb-u foram de 21,1 ± 11,9 µg/dL, 0,60 ± 0,71 µg/dL e 38,9 ± 48,4 mg/g creatinina, respectivamente. Associações positivas entre tempo de trabalho e concentrações de Pb-s e Pb-p foram observadas, indicando que o período de exposição influência nas concentrações de Pb absorvido. Associações positivas entre os elementos Manganês (Mn) e Selênio (Se) no sangue e Magnésio (Mg) no plasma com as concentrações de Pb-s e Pb-p podem sugerir uma co-exposição a esses elementos durante a jornada de trabalho. Foi observado associação negativa entre os elementos Fe e As e as concentrações de Pb-s, o que pode sugerir uma competição entre os elementos na fase de absorção. Ainda, Cobre (Cu) e Antimônio (Sb) se mostram associados negativamente ao Pb-p. O alelo C do SNP rs10636 não impactou nas concentrações de Pb-s (β= -1,0; p= 0,65), Pb-p (β= 0,03; p= 0,71) e Pb-u (β= 0,09; p= 0,40) e o genótipo raro (AG) do SNP rs28366003 não influenciou nas concentrações de Pb-p (β= 0,09; p= 0,46) e Pb-u (β= 0,03; p= 0,84). Entretanto o genótipo raro (AG) está associado a maiores concentrações de Pb-s (β= 7,9; p=0,04), quando comparados com os indivíduos portadores do genótipo prevalente (AA). O resultado do estudo sugere que elementos químicos podem influenciar nas concentrações de Pb-s e Pb-p e que o SNP rs28366003 localizado na região promotora 5’UTR do gene MT2A pode impactar na toxicocinética e na toxicodinâmica do Pb.
Lead (Pb) is the second most toxic element, after arsenic only, and is present in abundance in the earth's crust. The metal is mainly used in the manufacture of automotive batteries. Exposure to Pb may cause a number of adverse effects to health, such as gastrointestinal, neurological and antioxidant disorders. In order to minimize the adverse effects caused during the workday, the Ministry of Labor has classified the exposure to inorganic Pb as unhealthy of maximum degree, in addition to establishing the toxicity biomarkers, however the limit values are out of date. There are wide variations in the concentrations of biomarkers and toxicity associated with lead (Pb) exposure, despite similar levels of exposure, hypothetically related to the genetic differences in the enzymes that metabolize the metal. However, little is known about the genetic effects on metabolism and toxicity induced by Pb. Metallothioneins (MTs) are transport and distribution proteins of essential metals such as zinc, copper and iron; however, due to its high amount of sulfhydryl groups, non-essential metals can bind to it, such as Pb, cadmium, among others. Therefore, the objective of this work was to evaluated the impact of polymorphisms (SNP) of MT2A genes (UTR-3 (3'-Untranslated Region), G → C; rs10636 and UTR-5 (5'- Untranslated Region), A → G; rs28366003) on Pb concentrations in blood (Pb-s), plasma (Pbp) and urine (Pb-u), in 236 workers of automotive battery factories exposed to the metal. The concentrations of Pb-s, Pb-p and Pb-u were quantified by ICP-MS and the genotyping of the MT2A were performed using the TaqMan method, using the Polymerase Chain Reaction (RTPCR) in Real Time To assess the impact of polymorphisms on metal concentrations, multiple regression were applied, corrected for age, BMI, working time, smoking, alcohol and other 15 chemical elements (Al, Sr, Sn, Se, Sb, P , Mo, Mn, Mg, Co, As, Cu, P, Cd, Fe, Pb) and the value of p≤0.050 was considered significant. The average age was 38 years and the working time ranged from 1 month to 27 years; Pb-s, Pb-p and Pb-u concentrations were 21.1 ± 11.9 µg/dL, 0.60 ± 0.71 µg/dL and 38.9 ± 48.4 µg/g creatinine, respectively. Positive associations between working time and Pb-s and Pb-p concentrations were observed, indicating that the exposure period influences the absorbed Pb concentrations. Positive associations between the elements Manganese (Mn) and Selenium (Se) in the blood and Magnesium (Mg) in the plasma and the concentrations of Pb-s and Pb-p may suggest a co-exposure to these elements during the working day. A negative association was observed between the elements Fe and As and the concentrations of Pb-s, which may suggest a competition between the elements in the absorption phase. Also, Cooper (Cu) and antimony (Sb) are negatively associated with Pb-p. The alele C allele of SNP rs10636 did not impact the concentrations of Pb-s (β = -1.0; p = 0.65), Pb-p (β = 0.03; p = 0.71) and Pb-u (β = 0.9; p = 0.40) and the rare (AG) genotype of SNP rs28366003 did not influence the concentrations of Pb-p (β = 0.09; p = 0.46) and Pb-u (β= 0.03; p= 0,84). However, the rare (AG) genotype is associated with higher concentrations of Pb-s (β=7.9; p=0.04), when compared to individuals carrying the prevalent (AA) genotype. The result of the study suggests that chemical elements can influence the concentrations of Pb-s and Pb-p and that the SNP rs28366003 located in the promoter region 5'UTR of the MT2A gene may impact on the toxicokinetics and toxicodynamics of the Pb.
Lead (Pb) is the second most toxic element, after arsenic only, and is present in abundance in the earth's crust. The metal is mainly used in the manufacture of automotive batteries. Exposure to Pb may cause a number of adverse effects to health, such as gastrointestinal, neurological and antioxidant disorders. In order to minimize the adverse effects caused during the workday, the Ministry of Labor has classified the exposure to inorganic Pb as unhealthy of maximum degree, in addition to establishing the toxicity biomarkers, however the limit values are out of date. There are wide variations in the concentrations of biomarkers and toxicity associated with lead (Pb) exposure, despite similar levels of exposure, hypothetically related to the genetic differences in the enzymes that metabolize the metal. However, little is known about the genetic effects on metabolism and toxicity induced by Pb. Metallothioneins (MTs) are transport and distribution proteins of essential metals such as zinc, copper and iron; however, due to its high amount of sulfhydryl groups, non-essential metals can bind to it, such as Pb, cadmium, among others. Therefore, the objective of this work was to evaluated the impact of polymorphisms (SNP) of MT2A genes (UTR-3 (3'-Untranslated Region), G → C; rs10636 and UTR-5 (5'- Untranslated Region), A → G; rs28366003) on Pb concentrations in blood (Pb-s), plasma (Pbp) and urine (Pb-u), in 236 workers of automotive battery factories exposed to the metal. The concentrations of Pb-s, Pb-p and Pb-u were quantified by ICP-MS and the genotyping of the MT2A were performed using the TaqMan method, using the Polymerase Chain Reaction (RTPCR) in Real Time To assess the impact of polymorphisms on metal concentrations, multiple regression were applied, corrected for age, BMI, working time, smoking, alcohol and other 15 chemical elements (Al, Sr, Sn, Se, Sb, P , Mo, Mn, Mg, Co, As, Cu, P, Cd, Fe, Pb) and the value of p≤0.050 was considered significant. The average age was 38 years and the working time ranged from 1 month to 27 years; Pb-s, Pb-p and Pb-u concentrations were 21.1 ± 11.9 µg/dL, 0.60 ± 0.71 µg/dL and 38.9 ± 48.4 µg/g creatinine, respectively. Positive associations between working time and Pb-s and Pb-p concentrations were observed, indicating that the exposure period influences the absorbed Pb concentrations. Positive associations between the elements Manganese (Mn) and Selenium (Se) in the blood and Magnesium (Mg) in the plasma and the concentrations of Pb-s and Pb-p may suggest a co-exposure to these elements during the working day. A negative association was observed between the elements Fe and As and the concentrations of Pb-s, which may suggest a competition between the elements in the absorption phase. Also, Cooper (Cu) and antimony (Sb) are negatively associated with Pb-p. The alele C allele of SNP rs10636 did not impact the concentrations of Pb-s (β = -1.0; p = 0.65), Pb-p (β = 0.03; p = 0.71) and Pb-u (β = 0.9; p = 0.40) and the rare (AG) genotype of SNP rs28366003 did not influence the concentrations of Pb-p (β = 0.09; p = 0.46) and Pb-u (β= 0.03; p= 0,84). However, the rare (AG) genotype is associated with higher concentrations of Pb-s (β=7.9; p=0.04), when compared to individuals carrying the prevalent (AA) genotype. The result of the study suggests that chemical elements can influence the concentrations of Pb-s and Pb-p and that the SNP rs28366003 located in the promoter region 5'UTR of the MT2A gene may impact on the toxicokinetics and toxicodynamics of the Pb.
Descrição
Citação
FARIA, Jéssica Ramalho. Avaliação da influência de polimorfismos do gene da metalotioneína MT2A sobre as concentrações de chumbo (Pb) no sangue, plasma e urina de trabalhadores expostos ao metal. 2020. 81 f. Dissertação (Mestrado Interdisciplinar em Ciências da Saúde) - Instituto de Saúde e Sociedade, Universidade Federal de São Paulo, Santos, 2020.