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Biomarkers for environmental toxicology
- 1. Biomarkers for environmental toxicology PRESENTED BY - MOHAMMAD ANAS DBT-JRF CSIR-IITR
- 2. Biomarkers : definition “A characterstic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacological responses to a therapeutic intervention” - NIH
- 3. Development of biomarkers Cherry red colour • CO poisoning Kayser- fliecher ring • Wilson’s disease Lead lines in gums • Pb toxicity Cholinesterase • Organophosphate poisoning
- 4. Biomarkers in toxicological studies Biomarker of Exposure Biomarker of Effect Biomarker of Susceptibility Eg. Methyl Hg Eg. Paraoxonase Eg. Metallothionein
- 5. Stages of toxic phenomenon and timing of three types of biomarkers Phase I: Exposure and Absorption Phase II: Distribution and metabolism Phase III: Interaction with endogenous macromolecules Phase IV: Early Subclinical changes Phase V : Clinical signs Biomarkers of susceptibility Biomarkers of effect (response) Biomarkers of exposure Aldridge, N. (2001) Stages in the induction of toxicology. Mechanisms and Concepts in Toxicology.
- 6. Requirements of a good biomarker in toxicological testing Biomarker requirements Easy chemical analysis Simplicity for sampling Ethically acceptable Relevancy Reflect a reversible change Validity
- 7. Some examples of biomarkers used in environmental toxicology Biomarkers 1- hydroxypyrene Blood Pb Methyl HgMetallothionein Cotinine
- 8. Metallothionein : biomarker for heavy metal contamination
- 9. Heavy Metals Non essential Ba, Li, Zr Less toxic Sn, Al Highly toxic Pb, Hg, Cd, As Essential Cu, Zn, Co, Cr, Mn, Fe On health effects basis Metal having atomic weight greater than sodium (23) and specific gravity (density) > 5gm/cm3 (Mukesh K. Raikwar et al.,2008)
- 10. Heavy metal toxicity in fishes • Loss of equilibrium • Increased operculum movement • Irregular vertical movements Cd, Pb, Hg and As – - Severe renal and nervous system damage - Gill damage Lamellar telanejctasis Lamellar necrosis Global Veterinaria 12 (2): 219-231, 2014 ISSN 1992-6197 © IDOSI Publications, 2014
- 11. Metallothionein • Synthesized in reponse to elevated heavy metal concentrations. • Strong affinity to bind many metal cations – As, Cd, Cu, Pb, and Hg • Reported in about 50 different aquatic invertebrates from 5 phyla. Nordberg, M., and Nordberg, G.F. (2000) Toxicological aspects of metallothionein.
- 12. 0 5 10 15 20 25 30 35 Rohu Katla Mrigel Umcontaminated Contaminated Gill Gill 0 5 10 15 20 25 30 35 40 45 50 Rohu Katla Mrigel Uncontaminated Contaminated Liver 0 5 10 15 20 25 30 35 Rohu Katla Mrigel Uncontaminated contaminated Muscle Heavy metal decreases total protein concentration in fishes Environmental Research, Engineering and Management, 2011.
- 13. Liver Muscle Muscle Gill Muscle Liver Gill 0 10 20 30 40 50 60 70 80 ROHU KATLA MRIGEL Uncontaminated Contaminated Muscle 0 5 10 15 20 25 30 ROHU KATLA MRIGEL Uncontaminated Contaminated Metallothioneinconc.µg/g Gill 0 50 100 150 200 250 ROHU KATLA MRIGEL Uncontaminated Contaminated Liver Heavy metal increases Metallothionein concentration in fishes Environmental Research, Engineering and Management, 2011.
- 14. Methyl mercury : A biomarker of exposure
- 15. Hg – in emissions (smoke) 50-75% from anthropogenic (human) sources Hg - Deposited on land and into water Methyl-mercury (MeHg) Bacteria Phytoplankton (algae) MeHg Zooplankton MeHg MeHg MeHg Small fish Large fish Me-Hg : Gets in the food web
- 16. Methyl-Hg poisoning • Methyl-Hg exposure causes neurotoxic effects- - Paraesthesia - Ataxia - Visual and hearing loss • Children more vulnerable to Me-Hg toxicity than adults. • Minimata disease in Japan. Jakubowski and Trzcinka-Ocho
- 17. Me-Hg as a biomarker of exposure • High levels of Hg acts as a biomarker of exposure to Methyl-Hg • Biological sample – Hair, nail, blood, urine • Normal Hg level - Non fish eating individuals - < 1 μg/g Fish eating individuals - > 30 μg/g • Mercury level in maternal hair - 70 μg/g ---- 30 % risk in children 10 – 20 μg/g ---- 5% risk in children • Detection by Atomic Absorption Spectroscopy. Jakubowski and Trzcinka-Ochocka, 2005
- 18. Summary • There is a need for combining data from multiple biomarkers. • Environmental toxicology has benefitted with the use of biomarkers. • Biomarkers range from very simple to complex ones. • Methyl-Hg and Metallothionein are some examples of biomarkers.
- 19. Future perspective • Biomarkers can provide valuable predictive tools in biomonitoring and ecological risk assessment. • Important role in the model for 21st Century Toxicology – “ Toxicity testing in the 21st Century : A Vision and Strategy.” -(NAS 2007) • Continued research in validation of biomarkers and use of highthroughput technology.
- 20. Acknowledgements • AcSIR 2015 batchmates • DBT
- 21. Thank You
Editor's Notes
- Measurement of biomarkers reflects time course of an injury and provide information on the molecular mechanism of toxicity.
- The earliest biomarkers date from a time before......
- Its role is evident at species level as mammals express higher level of paraxonase activities and are more resistant to the toxic effects of OP than birds and insects which express low levels of paraoxonase.
- Biomarker of effect are very useful for detecting these preclinical stages which might lead to decision making before adverse effects are declared in exposed .......
- It must be valid ie the capability to distinguish among diff levels of exposure is desirable. It must address the dose response relationship to support decisions before.....
- In fishes it is observed that external organs are damaged due to heavy metals exposure causing-------finally leading to death These figures depict gills of tilapia fish exposed in areas heavily polluted with........
- Metallothionein is normally present in aquatic invertebrates and its functions include detoxification of HM .Metallothionein is a low mol. Wt protein that binds heavy metals in aquatic organisms therefore it is considered as a strong biomarker of heavy metal pollution It has a normal function of detoxification of highly toxic heavy metals and it also plays role in providing metals to metalloenzymes but when there is heavy metal contamination the level of this protein increases and this increase ......... It is a cystein rich protein and the thiol groups in cystein are responsible for binding these heavy metals This fig shows metal sulfur clusters with Zn atoms drawn as black and Cd atoms as gray spheres.
- This study was done to determine the potential stress that fish species are facing in wastewater fed fishponds in east kolkata wetlands India major carps ...... Unpolluted sites were used as control Studies have shown that protein act as major macronutrient in fishes that control gain and loss of energy and heavy metals often results in decrease in total protein conc in fish tissues .
- The decrease in total protein conc in response to heavy metal conc was validated with the use of MT as a biomarker.
- Me-Hg is a hazardous env pollutant that bioaccumulates in marine food web. Coal burning......
- People who eat large amount of fishes can accumulate suffiecient amounts of Mehg to cause neurotoxic effects such as ---- ..........and may exhibit more severe clinical features eg ---- asymtomatic mothers gave birth to offsprings with congenital Minamata disease. These babies ......
- Various factors may influence biomarker response like age, gender etc so there is inter indiduality differences ................to develop a better understanding of biological and toxicological process.
- Biomarkers are anticipated to play important.......... as discussed by NAS in its report ...... Will help to advance furthur development of biomarkers and risk assessment.