Ecophysiology and pollution Flashcards
what is an endocrine disrupting chemical
an exogenous substance (from outside the body) pr mixture that alters function of the endocrine system and consequelnty causes adverse health effects in an intact organism or its progeny or populations
= EURPOEAN COMMISION 2012
outline the different mechanisms of endocrine disrupting chemical actions
1) direct binding to the hormone receptor
- Agnoistic effects = activation of receptors where chemicals bind and induce a biological responce
- Antagonistic effects = chemical bind and prevent the activation of receptors, blocking availability of endogenous hormones (within the body) aka antihormone effects
2) non-receptor mediated pathways = affects the concentration of hormones in the body
- modify the synthesis or metabolism of hormones e.g. production of steroids
- modify the number of hormone receptors = gene expression
- bind to modify the number of transport proteins in the blood
Provide an example of early evidence suggesting the negative effect of EDCs
Silent spring = Rachel Carson along with supporting papers
- linked the declining reproductive success in birds with the pesticide DDT
- Metabolite of DDT called DDE disrupted endocrine system and prostaglandin signalling in egg cell glands causing reduced calcium deposition in egg shells = thinner shells which couldn’t support embryo
- DDT bioaccumulates so birds of prey at top of food chain = largest effect
what are aquatic organisms at such as high risk from chemical contaminants
aquatic systems are a huge sink for the contamination of chemicals
- organisms are constantly bathed with contaminants
outline some sourced for aquatic chemical contaminants
- industrial
- products from mining e.g. metals
- sewage treatment effluent
- plastic pollution
- agricultural contaminants
- natural compounds such as pregnant cows releasing hormones into rivers or phytoestrogens from crop plants
how can chemicals disrupt sex steroids and reproduction
chemicals can mimic or inhibit sex steroid activity such as oestrogenic chemicals e.g.
1) Oestrogens and antioestrogens
oestrogen = EE2 = contraceptive pill chemical induces oestrogenic effects even in low concentrations as it is potent
antioestrogen = Bisphenol A = binds to oestrogen effector preventing oestrogenic response
2) Androgens and antiandrogens
androgens = bind to androgen receptors exerting masculine effects
anti= bind to and induces antagonistic effects
outline how they began to discover the problem of oestrogenic chemicals and why
1980/1990s began to release it was an issue= wasn’t directly killing individuals but impairing reproduction causing pop decline
why = due to feminisation of male fish discovered by cases of intersex gonads present in males (developing ovarian tissues in the testis)
associated also with
- vitellogenin production = stimulated by oestrogen
- reduced testosterone
- reduced sperm quality
altered reproductive behaviour
why and how is Vitellogenin an important biomarker for exposure to oestrogenic chemicals in fish
1) oestrogen enters the cell by diffusing and binds to oestrogen receptors
2) binds and moved into the nucleus, further binding to oestrogen responsive elements on DNA causing transcription of oestrogen responsive genes
3) Vitellogenin is one of these genes in which both male and female fish possess
4) therefore exposure of males to oestrogen will cause vitellogenin production providing good idea of oestorgenic chemicals
what did Sumpter and Joblin 1995 do in regards to investigating the effects of vitellogenin as a biomarker
They measured its gene expression and potrein levels to see how the amount of vitellogenin produced is responsive to different chemicals
they found
EE2 from the pill caused females and males to produce high concentrations of VG
also linked to other industrial chemicals
outline some papers which helped to build evidence about the effects of oestrogenic chemicals
1) Surveys of oestrogenic activity = Jule et al 1996
2) papers documenting sexual disruption in wild fish = Joblin et al., 1998
3) when roach become intersex it directly reduces fertility = Jobling et al ., 2002
how can oestrogenic chemical cause population level effects not just individual, outline some research
Kidd et al., 2007
North america has a series of experimental lakes, one of these laked was doses with synthetic oestrogen to see effects
found
1) collapse of ecosystem with some species being more sensitive than others
- fat head mino = 99% loss
- inverterbrates such as crustceans = increased as a result of food web effects
however papers also suggest that long term exposure could result in adaptations to oestrogenic chemicals = Hamilton et al. 2014
what are some ways of tackling the problem of oestrogenic chemical pollution
accumulation of research lead to development of oestorgen screens
- yeast cells have oestorgen receptors added to them to screen ostrogen actvity of different/ new chemicals to see if they activate receptors
= fed into the legislation in 2012 of banning nonylphenol due to evidence of reduced reproduction in rivers
how has past research lead to reduced oestrogenic chemical effects in aquatic systems
Environmental agency completed a survey in 2017 to compare to a survey in 1998-2000
found reduced environmetnal oestrogen exposure but still contiued impacts
= male roach feminisation still wid spread (60% of sites)
= male roach VTG has reduced but is still elevated
= severity fo intersex also decreased
outline some other chemicals which cause reproductive toxicity
1) Glyphosphate & roundup on zebra fish = Webster et al., 2013
= exposure causes changes in gene expression in reproductive sysems affects males (oxidative stress damaging developing sperm) and females (disrupts aromatase, less testosterone converted to oestrogen)
2) organophosphates in three spined stickle back sebire et al 2009
= pesticdes cause antiantogenic effects reducing secondary sexaul characeristics in males such as red colouring and production of spigen protein for nest bulding = decreased reproductibe success
what are some remaining challenges when it comes to EDC research
1) potential transgenerational effects = Brehm & Flaws, 2019
- found when exposing pregnant mammals with EDCs it affected parent, offspring ad the offspring’s developing gonads
2) mixture effects of chemicals not just individual e.g. synergism, interactions and independent action
