The Effect Of Mixing Methyl And Hydroxybenzoate On The Breeding Ability And Longevity Of Drosophila

Parabens are esters of p-hydroxybenzoic acid, including methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP) and so on. They are widely used as preservative substances in the foods, pharmaceuticals, and personal care products because of their no perceptible odor or taste, chemical stability, low toxicity, anti-microbial and so on. However, parabens are not absolutely safe for using. It was reported that parabens possess potential estrogenic activity, which are classified as an endocrine-disrupting chemicals that can affect growth, reproduction, and lifespan. In addition, parabens, more than one kind of ester, may accumulate in natural and human body environment due to its wide and long-time use in recent years. This shows that people may be exposed to a environment with mixtures of parabens. But now, most researches focus on the toxicity of individual paraben and a little is known for the toxicity of mixtures of parabens. Hence, It is greater realistic significance to investigate the mixed toxicity.The study was to investigate the effects of the mixture of MP and EP (Abbreviate: MP+EP) on the pre-adult growth, fecundity and lifespan in Drosophila melanogaster. When flies were exposed to control and low, moderate and high MP+EP diets (300 mg· L-1,700 mg-L-1, and 1000 mg-L-1) before emergence, the pre-adult growth and adult fecundity, JH and 20E contents, and the expression of genes related to growth and reproduction(EcR, Met, Gce, Foxo, and Shade) were tested; When adult flies were exposed to control and low, moderate and high MP+EP diets in their life, the survival rate, lifespan, SOD activites and MDA contents were measured. By MP+EP exposure in different periods of fruit flies, the study revealed that the toxic effect of mixed parabens on growth, reproduction, and lifespan from the aspects of endocrine regulation mechanism and the free radical theory of aging. The results showed:1. When flies were exposed to MP+EP before emergence, egg-papu and development time was delayed, the fresh weight of third instar larvae was decreased, and the adult fertility was decreased, especially in moderate-exposure and high-exposure groups (p<0.05 or p<0.01). But there was no significant difference in the percentage of pupation and eclosion among the control and MP+EP exposure groups. In addition, compared with individual EP, MP+EP had a additive toxic effect on larvae growth.2. When flies were exposed to MP+EP before emergence, moderate-exposure and high-exposure groups significantly increased JH, but decreased 20E in the third instar larvae. And MP+EP can also influence the hormone contents of adult flies. In female, moderate-exposure and high-exposure groups significantly increased JH contents at 1 d, decreased 20E contents at 3 d; In male, the JH contents were all decreased at 1 d and 3 d in moderate-exposure and high-exposure groups. In addition, the results also showed that MP+EP can disturbe the expression of genes related to growth and reproduction in flies. Firstly, MP+EP may upregulate or downregulate the expression of genes related hormone synthesis (Foxo and Shade), making the normal hormone levels imbalance; secondly, MP+EP, as an endocrine-disrupting chemicals, can induce or inhibit the expression of hormone receptors genes (EcR, Met and Gce), thereby disturbing the activity of hormone signaling pathways.3. When flies were exposed to MP+EP in adult life, the survival rate, mean lifespan, maximum lifespan, and medial death time was reduced. And MP+EP can increase SOD activities and decrease MDA levels. It was suggested that the effect of MP+EP on flies lifespan was related to its antioxidant capacity. Additionally, the toxicity of MP+EP was more than single EP in flies longevity.In sum, MP+EP may disorder flies JH and 20E balance and affect hormone signaling pathways, resulting in delaying the larvae growth and decreasing fecundity in adult. In addition, MP+EP can reduced the antioxidant abilities of fruit fly, leading to decreasing lifespan. The study revealed the effects of mixed parabens on Drosophila growth, fertility, and lifespan by MP+EP exposure in different period of flies, which will provide data for safety assessment of parabens.