1212569_21823227.jpg logo_mu_cerne.gif 1212570_28446780.jpg logo_mu_cerne.gif Luděk Bláha, PřF MU, RECETOX www.recetox.cz BIOMARKERS AND TOXICITY MECHANISMS 10 – BIOMARKERS Introduction OPVK_MU_stred_2 1212569_21823227.jpg logo_mu_cerne.gif Definition and applications •- markers in biological systems with a sufficently long half-life which allow location where in the biological system change occur and to quantify the change. • •Various definitions and applications of „biomarkers“ –– Ecology / Geology -Human health and diseases -Toxicology (special focus in this class) 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers in ECOLOGY / GEOLOGY http://www.birmingham.ac.uk/Images/College-LES-only/GEES/staff-research/high-utility-biomarker-appl ications.jpg 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers in HUMAN HEALTH http://www.nature.com/nrd/journal/v12/n5/images/nrd3979-f1.jpg Examples of biomarker applications in human health: 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers in TOXICOLOGY -Identification of markers that inform/predict about long-term risks -Human: chronic health –e.g. early stages of liver steatosis, carcinogenesis -Ecotoxicology: early markers of ecotoxic effects - -BIOMARKER -change which occurs as a response to "stressors“ (xenobiotics, disease, temperature...) extending the adaptive response beyond the normal range - - -In vivo biomarkers: -changes measured in stressed organisms, i.e. in vivo ("classical biomarkers“ in toxicological research) - -In vitro biomarkers -in vitro testing characterizing potencies of xenobiotic to induce specific biological activity (or toxicity mechanism) -= biological potencies (markers of potential hazards) - - - 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers - classification •Categorization by US National Academy of Sciences • - Biomarkers of exposure • - Biomarkers of response or effect • - Biomarkers of susceptibility • •Continuum exists among biomarkers • Example: adducts of a toxicant bound to nucleotide ? biomarker of exposure (proof of toxicant) ? biomarker of response or effect (modified nucleotide = effect) • • 1212569_21823227.jpg logo_mu_cerne.gif Various biomarker types •Specific (selective) in vivo biomarkers ØBiomarkers selectively reflecting specific types (mechanisms) of toxicity •E.g. inhibition of AcCholE : exposure = organophosphates; effect = neurotoxicity • • + provides specific information • - multiple biomarkers need to be measured in parallel when searching for a cause of intoxication • • •Non-specific (non-selective) in vivo biomarkers ØBiomarkers of general stress •E.g. induction of Heat Shock Proteins (hsp) • • + general information about stress • - sensitive to many "stressors" (chemicals, temperature, salinity ...) • • 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers at different levels of biological organisation C:\Documents and Settings\Ludek Blaha\Dokumenty\katedra\vyuka\Biomarkery-Mechanismy\_SCAN_Gen&Apll_Toxicology\1842.jpg These BMs are mainly covered in our lecture 1212569_21823227.jpg logo_mu_cerne.gif Sampling biological materials for biomarker analyses •Non-destructive (non-invasive) –blood / haemolymph collection & analyses –skin, feather, hair, urine … –(life of the organism not affected) • •Destructive (invasive) –whole animal à research should follow 3R principles (Replacement, Reduction and Refinement) – à maximum use of the biological material –multiple biomarker evaluation • 1851 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers & Exposure • • • •h: homeostatic conditions •c: reversible stage •r: irreversible effects of pollutants - - •Various biomarker profiles - temporal changes–B2; B4 • • - repeated occurrence (B5) • - continuous increase (B1) • - increase with maximum (B3) • •: B1 + B3 are candidate biomarkers ! 1850 Biomarker intensity Health effect intensity Stressor / time Stressor / time 1212569_21823227.jpg logo_mu_cerne.gif Ideal biomarker http://www.jcancer.org/v01/p0150/jcav01p0150g01.jpg EXAMPLE - Paracetamol http://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Paracetamol_metabolism.svg/2000px-Paraceta mol_metabolism.svg.png EXAMPLE - Paracetamol • • • • • • (1)paracetamol (2)parent compound measurement - biomarker of exposure (3)activation to reactive metabolite (N-ac-p-benzoquinone, NAPQI) by CYP à reaction with GSH / measurement – levels of CYPs; levels of GSH – susceptibility (4)GSH-NAPQI conjugate – exposure, susceptibility (5)NAPQI-protein adducts à toxicity: exposure, effective dose (6)adaptations: GSH depletion, inhibition of protein synthesis – biomarkers of response (7)protein alkylation à degeneration of hepatocytes: necrosis à increase concentrations of bilirubin in plasma + inflammation - response / effect C:\Documents and Settings\Ludek Blaha\Dokumenty\katedra\vyuka\Biomarkery-Mechanismy\_SCAN_Gen&Apll_Toxicology\1843.jpg 1212569_21823227.jpg logo_mu_cerne.gif Biomarkers in toxicology – examples / overview (some are discussed in detail in following lectures) 1847