Biomarkers for environmental

toxicologyPRESENTED BY -MOHAMMAD ANASDBT-JRFCSIR-IITR

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

Development of biomarkers

Cherry red colour• CO poisoning

Kayser- fliecher ring• Wilson’s disease

Lead lines in gums• Pb toxicity

Cholinesterase• Organophosphate poisoning

Biomarkers in toxicological studies

Biomarker of Exposure

Biomarker of Effect

Biomarker of Susceptibility

Eg. Methyl Hg Eg. Paraoxonase

Eg. Metallothionein

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.

Requirements of a good biomarker in toxicological testing

Biomarker requirements

Easy chemical analysis

Simplicity for sampling

Ethically acceptable

Relevancy

Reflect a reversible change

Validity

Some examples of biomarkers used in environmental toxicology

Biomarkers

1-hydroxypyrene

Blood Pb

Methyl HgMetallothionein

Cotinine

Metallothionein : biomarker for heavy metal contamination

Heavy Metals

Non essentialBa, Li, Zr

Less toxicSn, Al

Highly toxicPb, 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)

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

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.

Rohu Katla Mrigel0

5

10

15

20

25

30

35

Umcontaminated

Contaminated

GillGill

Rohu Katla Mrigel0

510

1520253035

404550

Uncontaminated

Contaminated

Liver

Rohu Katla Mrigel0

5

10

15

20

25

30

35

Uncontaminatedcontaminated

Muscle

Heavy metal decreases total protein concentration in fishes

Environmental Research, Engineering and Management, 2011.

Liver

MuscleMuscle

Gill

Muscle Liver Gill

ROHU KATLA MRIGEL0

10

20

30

40

50

60

70

80

Uncontaminated

Contaminated

Muscle

ROHU KATLA MRIGEL0

5

10

15

20

25

30

UncontaminatedContaminated

Met

allo

thio

nein

con

c. µ

g/g

ww Gill

ROHU KATLA MRIGEL0

50

100

150

200

250

UncontaminatedContaminated

Liver

Heavy metal increases Metallothionein concentration in fishes

Environmental Research, Engineering and Management, 2011.

Methyl mercury : A biomarker of exposure

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 fishLarge fish

Me-Hg : Gets in the food web

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-Ochocka, 2005

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

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.

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.

Acknowledgements

• AcSIR 2015 batchmates• DBT

Thank You