TOXICOLOGY FOR ENGLISH SPEAKING STUDENTS DEFINITION n THE STUDY ABOUT THE NATURE AND MECHANISMS OF CHEMICALS´ EFFECTS ON LIVING ORGANISMUS AND OTHER BIOLOGIC SYSTEMS n QUANTITATIVE ASSESSMENT OF THE SEVERITY AND FREQUENCY OF SUCH EFFECTS GOALS FOR PREVENTION n PROTECTION THE PUBLIC HEALTH n PROTECTION THE WORKERS n HEALTH PROMOTION n DEVELOPMENT OF SAFER CHEMICALS USED AS DRUGS, FOOD ADDITIVES, PESTICIDES, INDUSTRIAL CHEMICALS SORTS OF TOXICOLOGY n ANALYTICAL n CLINICAL n FORENSIC n OCCUPATIONAL n ENVIRONMENTAL n REGULATORY n CONVENTIONAL, … SCOPES OF TOXICOLOGY n MEDICINE: diagnosis, prevention, treatment n FOOD INDUSTRY: additives n AGRICULTURE: pesticides, growth regulators, animal food additives, veterinary drugs n INDUSTRY EPIDEMIES OF POISONING n POMPEII – VESUVE, SO[2 ]n SMOG REDUCTIVE (dust, CO, PAH): Donora, London n SMOG OXIDATIVE (O[3,] No[x,] CO[2] hydrocarbons): Los Angeles EPIDEMIES - continue n MINAMATA, NIIGATA, IRAQ, USA - METHYLMERCURY n ITAI-ITAI - CADMIUM n YUSHO, YUCHENG - PCBs n MITCHIGAN – PBBs n SEVESO – PCDD (TCDD) n BHOPALE - METHYLISOCYANATE ROUTES OF INTAKE n GASTROINTESTINAL TRACT n RESPIRATORY TRACT n SKIN n VAGINA, RECTUM, EAR, EYES n PARENTERAL APPLICATION BARRIERS n MUCOCILLIAL CLEARANCE n SKIN FILM (ACID AND FATTY) n PLACENTAL n CEREBRO-VASCULAR n RATE OF ABSORPTION TYPES OF UPTAKE n PASSIVE DIFUSSION n FILTRATION n CARRIER-MEDIATED TRANSPORT n ENGULFING BY THE CELLS BIOTRANSFORMATION n The main influencing factor: n WATER / LIPO – SOLUBILITY n WATER – SOLUBILE => EXCRETION WITHOUT METABOLISATION n POLARIC = > AFTER CONJUGATION n LIPO-SOLUBILE => 2 STEPS METABOLISM Ist STEP /PHASE n OXIDATION, REDUCTION, HYDROLYSIS n CATALYTIC MICROSOMAL ENZYMES n METABOLITES DEVELOPED BY OXIDATION ARE BOTH LESS AND MORE ACTIVE THAN THE MATERNAL COMPOUND n DUE TO OXYGEN / FREE RADICALS OXIDATIVE BIOTRANSFORMATION n MICROSOMAL ENZYMES – COMPLEX of n CYTOCHROM P450 n GENETIC DIFFERENCES IN GENOTYPE – GENETIC POLYMORPHISM CYTOCHROM P450 n ENVIRONMENTAL INFLUENCE ON FENOTYPE: n SOME DRUGS, DDT, PCBs, PCDDs, chemicals in VEGETABLES n CAN INDUCE THE RELEASE OF OXIDATIVE ENZYMES P450 CYTOCHROM P 450 – exampl. n CYP 1A1: lungs, placenta PAH n CYP 1A2: liver AFLATOXINS, NITROSAMINES n CYP 2A6: lungs, liver, … NITROSAMINES, NICOTINE CYP 1B1, 2C9,2C19, 2D6, 2E1, 3A… 2nd STEP / PHASE n CONJUGATION: n GLUCURONIDES FORMATION: the most important and common way, n Catalyzing enzymes: n UDP- GLUCURONYL TRANSPHERASEs: n Aliphatic and aromatic alcohols, amines, sulfhydryl compounds, … 2 nd STEP /PHASE n GLUTATHIONE FORMATION n Enzymes GLUTATHION-S-TRANSPHERASEs: n Polycyclic aromatic hydrocarbons n ACETYLATION: enzymes N-ACETYL TRANSPHERASEs: SLOW/FAST ACETYLATORS 2nd STEP /PHASE n SULPHATES FORMATION – enzymes SULPHOTRANSPHERASES n METHYLATION n GENETIC POLYMORPHISM: n „HAPPY“ / „UNHAPPY“ PEOPLE EXCRETION OF CHEMICALS n URINARY n BILIARY n EXPIRATED AIR n SALIVA n EVAPORATION n SKIN ADNEXES (HAIR, NAILS) n MOTHER´S MILK TESTs OF EXPOSURE n LEVELS OF THE SUBSTANCE or IT´S SPECIFIC METABOLITE: CO in the expirated air, cotinice, BaP DNA adducts n LEVELS OF NON-SPECIFIC METABOLITES: urinary glucuronides, thioethers TESTs OF EXPOSURE n ASSESSMENT OF THE ORGANISM´S RESPONSE: anemia in the Pb chronic exposure, Chromosomal aberations in the exposure to mutagens n ASSESSMENT OF THE INDIVIDUAL VULNERABILITY: genetic polymorphism in induction of microsomal enzymes, sexual /ethnic /age differences SPECTRUM OF EFFECTS n LOCAL x SYSTEMIC n REVERSIBLE x IRREVERSIBLE n IMMEDIATE x DELAYED n MORPHOLOGIC x FUNCTIONAL x BIOCHEMICAL n ALLERGIC x IDIOSYNCRATIC SPECTRUM OF EFFECTS n IRRITATION, INFLAMATION n TOXICITY (according to the target organ): hemato-, hepato-, neuro-, nephro-, cardio-, … n EMBRYOTOXICITY n TERRATOGENICITY n MUTAGENICITY n CARCINOGENICITY DIFFICULTIES IN RESEARCH n EXTRAPOLATION from the ANIMAL EXPERIMENTS to the HUMAN REALITY n DOSE – RESPONSE RELATIONSHIP n THE (upper) LIMITS FOR THE PHYSIOLOGIC RESPONSE n INTERACTION OF CHEMICALS IN MIXTURES ANTI-CHEMICAL DEFENSE n CONTINUAL EXCHANGE/REPLACEMENT OF DAMAGED CELLS n INDUCTION OF DETOXIFYING BIOTRANSFORMATION n ACTIVE EXCRETION OF HYDRO-SOLUBLE SUBSTANCES n DNA REPAIR IS THE NATURE SAFE? n DEFENSE HAS DEVELOPED IN THE EVOLUTION DUE TO EXPOSURE TO NATURAL CHEMICAL COMPOUNDS n ALL SURVIVE PLANTS HAVE DEVELOPED THEIR PROTECTION AGAINST THEIR NATURAL ENEMIES = NATURAL PESTICIDES NATURAL PESTICIDES n ARE CHEMICALY SIMILAR TO THOSE PRODUCED BY INDUSTRY n SOME OF THEM ARE STRONG TOXINS AND CARCINOGENS (botulotoxine, aflatoxine) n PLANTS CAN CHANGE both the CONCENTRATIONS and the SORT TOO MANY RHODENT CARCINOGENS n There were tested more than n 1000 INDUSTRIAL CHEMICALS and n 50 NATURAL CHEMICALS n In both groups, about n 50% are RHODENT CARCINOGENS EXPERIMENTAL TESTS n The MAXIMAL TOLERATED DOSES, and their fractions (1/2 1/4) ARE USED n WHICH MATHEMATIC MODEL OF EXTRAPOLATION FOR HUMAN EXPOSURE IS THE BEST? n LINEAR? EXPONENTIAL? n DOES THE SAFE TRESHOLD EXISTS? EPIDEMIOLOGIC/CLINIC STUDIES n ARE ONLY ACCEPTABLE FOR HUMAN RISK ASSESSMENT = > n CHEMICAL ACCIDENTS and DISASTERS ARE ASSESSED IN LONGITUDINAL PROSPECTIVE STUDIES n Also PROFESSIONAL EXPOSURES are the sources of IMPORTANT DATA CARCINOGENS´ CLASSIFICATION n CATEGORIES HUMAN / ANIMAL DATA n HUMAN C. 1A suffic. suffic./limited n PROBABLE 2A limited sufficient n POSSIBLE 2B inadeq. Suffic/limited n NO-CLASSIF. 3 absent inadeq/absen n NOT CARCIN.4 absent negative in 2 species CARCINOGENIC EFFECTS n OF CHEMICAL SUBSTANCES RISE THE MAJOR CONCERN OF RESEARCHES: n GENOTOXIC THEORY OF CARCINOGENESIS: INITIATION of DNA MUTAGENIC CHANGES – REPLICATION – PROMOTION – MANIFESTATION n EPIGENETIC (non-mutagenic) THEORY WHAT DO WE KNOW? n WE CAN MEASURE THE MUTAGENICITY (Ames´s test) AND RESPONSE (Chromosomal abberations, sister chromatide exchanges, DNA adducts…) n THERE ARE RELATIONSHIPS BETWEEN SHORT-TERM MARKERS and CANCER INCIDENCE n CELLs PROLIFERATION IS IMPORTANT WHAT WE DON´T KNOW? n WHICH MODEL FOR EXTRAPOLATION IS THE MOST PRECIOUS ? n WHICH IS THE ROLE OF NATURAL CHEMICALS and CONDITIONS ? n WHICH SIGNALS OF RESPONSE ON EXPOSURE ARE IMPORTANT FOR USE THEM TO ESTABLISH THE ACCEPTABLE LIMITS ? POLITICAL POINT OF VIEW: n TO KEEP LIMITS IN MORE DIFFICULT THAN TO ESTABLISH THEM n HOW MANY VULNERABLE PEOPLE WE WILL PROTECT BY THE LIMITS n CAN WE ACCEPT SOME SPECIFIC PROTECTION OF VULNERABLE PART OF POPULATION ENVIRONMENTAL HYSTERY n VERY OFTEN ENHANCES THE PUBLIC INTEREST ABOUT LOW-RISK FACTORS (sacharin, DDT, PBCs, Alar, …) n AND n OBSCURES / UNDERESTIMATES THE REAL RISKS (nutrition, smoking, poor hygiene, …) ALL CANCER MORTALITY: n ATTRIBUTIVE RISK IN LIFE STYLE n NUTRITION …………………… 35% n SMOKING ……………………… 30% n INFECTIOUS AGENTS …….. 10% n SEXUAL BEHAVIOUR ………. 7% n ALCOHOL ………………………. 4% n TOGETHER ……………………. 87% ALL CANCER MORTALITY n ATTRIBUTIVE RISK IN ENVIRONMENT n OCCUPATION …………………… 4% n MEDICAL TREATMENT ………. 3% n GEOPHYSICAL FACTORS ……. 3% n POLLUTED AIR, WATER …….. 2% n FOOD ADDITIVES/CONTAM. . <1% n TOGETHER ………………………. 13% CONCLUSSIONS n TOXICOLOGY IS DYNAMIC, EXCITATING SCIENCE n TOXICOLOGY CAN DISCOVER MANY MYSTERIOUS THINGS IN LIFE n TOXICOLOGY CAN REDUCE HUMAN CHEMOPHOBIA