1 985 63 CHRONIC RADIATION EXPOSURE AS AN ECOLOGICAL FACTOR: HYPERMETHYLATION AND GENETIC DIFFERENTIATION IN IRRADIATED SCOTS PINE POPULATIONS. GENETIC AND EPIGENETIC CHANGES WERE INVESTIGATED IN CHRONICALLY IRRADIATED SCOTS PINE (PINUS SYLVESTRIS L.) POPULATIONS FROM TERRITORIES THAT WERE HEAVILY CONTAMINATED BY RADIONUCLIDES AS RESULT OF THE CHERNOBYL NUCLEAR POWER PLANT ACCIDENT. IN COMPARISON TO THE REFERENCE SITE, THE GENETIC DIVERSITY REVEALED BY ELECTROPHORETIC MOBILITY OF AFLPS WAS FOUND TO BE SIGNIFICANTLY HIGHER AT THE RADIOACTIVELY CONTAMINATED AREAS. IN ADDITION, THE GENOME OF PINE TREES WAS SIGNIFICANTLY HYPERMETHYLATED AT 4 OF THE 7 AFFECTED SITES. 2018 2 6550 27 TRANSGENERATIONAL ACCUMULATION OF RADIATION DAMAGE IN SMALL MAMMALS CHRONICALLY EXPOSED TO CHERNOBYL FALLOUT. THE PURPOSE OF THIS INVESTIGATION HAS BEEN THE ANALYSIS OF THE LONG-TERM DEVELOPMENT OF BIOLOGICAL DAMAGE IN NATURAL POPULATIONS OF A MODEL MAMMALIAN SPECIES, THE BANK VOLE (CLETHRIONOMYS GLAREOLUS, SCHREBER), WHICH WERE CHRONICALLY EXPOSED TO LOW DOSES OF IONIZING RADIATION OVER 22 ANIMAL GENERATIONS WITHIN 10 YEARS FOLLOWING THE CHERNOBYL ACCIDENT. THE TIME COURSE OF THE BIOLOGICAL END-POINTS (CHROMOSOME ABERRATIONS IN BONE MARROW CELLS AND EMBRYONIC LETHALITY) WAS COMPARED WITH THE TIME COURSE OF THE WHOLE-BODY ABSORBED DOSE RATE FROM EXTERNAL AND INTERNAL EXPOSURE IN THE STUDIED POPULATIONS INHABITING MONITORING SITES IN BELARUS WITH DIFFERENT GROUND DEPOSITION OF RADIONUCLIDES. THE YIELD OF CHROMOSOME ABERRATIONS AND, IN LESSER DEGREE, EMBRYONIC LETHALITY WAS ASSOCIATED WITH THE RADIONUCLIDE CONTAMINATION OF THE MONITORING AREAS IN A DOSE-DEPENDENT MANNER. AS A MAIN FEATURE OF THE LONG-TERM DEVELOPMENT OF BIOLOGICAL DAMAGE UNDER LOW DOSE RATE IRRADIATION, PERMANENTLY ELEVATED LEVELS OF CHROMOSOME ABERRATIONS AND AN INCREASING FREQUENCY OF EMBRYONIC LETHALITY HAVE DEVELOPED OVER 22 ANIMAL GENERATIONS. THIS CONTRASTS WITH THE ASSUMPTION THAT THE BIOLOGICAL DAMAGE WOULD GRADUALLY DISAPPEAR SINCE IN THE SAME PERIOD OF TIME THE WHOLE-BODY ABSORBED DOSE RATE DECREASED EXPONENTIALLY WITH A HALF-VALUE TIME OF ABOUT 2.5-3 YEARS. FURTHERMORE, GRAVID FEMALES WERE CAPTURED, AND THEIR OFFSPRING, BORN AND GROWN UP UNDER CONTAMINATION-FREE LABORATORY CONDITIONS, SHOWED THE SAME ENHANCED LEVEL OF CHROMOSOME ABERRATIONS. THEREFORE THE AUTHORS SUGGEST THAT, ALONG WITH THE BIOLOGICAL DAMAGE ATTRIBUTABLE TO THE INDIVIDUAL EXPOSURE OF EACH ANIMAL, THE OBSERVED CELLULAR AND SYSTEMIC EFFECTS REFLECT THE TRANSGENERATIONAL TRANSMISSION AND ACCUMULATION, VIA GENETIC AND/OR EPIGENETIC PATHWAYS, OF DAMAGE ATTRIBUTABLE TO THE CHRONIC LOW-DOSE RATE EXPOSURE OF THE PRECEDING GENERATIONS OF ANIMALS. THEY ALSO SUGGEST THAT THE LEVEL OF THE ACCUMULATED TRANSMISSIBLE DAMAGE IN THE INVESTIGATED POPULATIONS WILL DECREASE IN FUTURE DUE TO THE FURTHER RECESSION OF THE CHRONIC EXPOSURE AND AS A CONSEQUENCE OF SELECTION PROCESSES. 2006 3 1115 33 COMPARATIVE ANALYSIS OF EPIGENETIC VARIABILITY IN TWO PINE SPECIES EXPOSED TO CHRONIC RADIATION IN THE CHERNOBYL AND FUKUSHIMA AFFECTED ZONES. COMPARATIVE ANALYSIS OF EPIGENETIC VARIABILITY IN TWO PINE SPECIES AFFECTED AS A RESULT OF THE CHERNOBYL AND FUKUSHIMA ACCIDENTS IS PRESENTED. THE ABSORBED DOSE RATE WITHIN THE AFFECTED CHERNOBYL SITES VARIES OVER A WIDER RANGE (1.5-24.6 MUGY/H) THAN WITHIN THE FUKUSHIMA SITES (3.5-6.5 MUGY/H). IT WAS SHOWN THAT CHRONIC IRRADIATION CAN CHANGE THE LEVEL OF WHOLE GENOME METHYLATION IN PINE POPULATIONS, BUT IN DIFFERENT WAYS. THE GENOMES OF JAPANESE RED PINES ARE HYPOMETHYLATED, AND THE DEGREE OF METHYLATION AND HYDROXYMETHYLATION DECREASES WITH AN INCREASE IN THE LEVEL OF RADIATION EXPOSURE. IN CONTRAST, THE PERCENTAGES OF GENOME METHYLATION AND HYDROXYMETHYLATION IN SCOTS PINE POPULATIONS EXCEED THE REFERENCE LEVELS. THE OBSERVED DISCREPANCY IN THE PATTERNS OF GENOME-WIDE DNA METHYLATION CAN BE ATTRIBUTED PARTLY TO THE DESIGN OF THE STUDY (DIFFERENCES IN THE CLIMATE, RADIATION DOSE, AGE AND SPECIES OF THE PINES) WHICH COULD AFFECT THE RESULTS. IN THE FRAME OF IRAP ANALYSIS, A LARGER NUMBER OF DIFFERENT BANDS WAS OBSERVED IN THE CHERNOBYL POPULATIONS COMPARED TO THE JAPANESE POPULATIONS. BOTH THE JAPANESE AND CHERNOBYL POPULATIONS ARE CHARACTERIZED BY SIGNIFICANT GENETIC VARIABILITY. HOWEVER, THE MAIN PART OF THIS VARIABILITY IS OBSERVED WITHIN POPULATIONS. THE DENDROGRAMS, BASED ON PRESENCE/ABSENCE OF IRAP FRAGMENTS AND NEI'S GENETIC DISTANCES, REVEALED SUBDIVISIONS OF THE CHERNOBYL AND JAPANESE POPULATIONS ACCORDING TO THE LEVEL OF RADIOACTIVE CONTAMINATION. ANALYSIS OF THE RESULTS PRESENTED WILL IMPROVE OUR UNDERSTANDING OF THE MECHANISMS UNDERLYING THE RESPONSES OF PINE TREES TO CHRONIC RADIATION EXPOSURE. 2023 4 3040 27 GENOME HYPERMETHYLATION IN PINUS SILVESTRIS OF CHERNOBYL--A MECHANISM FOR RADIATION ADAPTATION? ADAPTATION IS A COMPLEX PROCESS BY WHICH POPULATIONS OF ORGANISMS RESPOND TO LONG-TERM ENVIRONMENTAL STRESSES BY PERMANENT GENETIC CHANGE. HERE WE PRESENT DATA FROM THE NATURAL "OPEN-FIELD" RADIATION ADAPTATION EXPERIMENT AFTER THE CHERNOBYL ACCIDENT AND PROVIDE THE FIRST EVIDENCE OF THE INVOLVEMENT OF EPIGENETIC CHANGES IN ADAPTATION OF A EUKARYOTE-SCOTS PINE (PINUS SILVESTRIS), TO CHRONIC RADIATION EXPOSURE. WE HAVE EVALUATED GLOBAL GENOME METHYLATION OF CONTROL AND RADIATION-EXPOSED PINE TREES USING A METHOD BASED ON CLEAVAGE BY A METHYLATION-SENSITIVE HPAII RESTRICTION ENDONUCLEASE THAT LEAVES A 5' GUANINE OVERHANG AND SUBSEQUENT SINGLE NUCLEOTIDE EXTENSION WITH LABELED [3H] DCTP. WE HAVE FOUND THAT GENOMIC DNA OF EXPOSED PINE TREES WAS CONSIDERABLY HYPERMETHYLATED. MOREOVER, HYPERMETHYLATION APPEARED TO BE DEPENDENT UPON THE RADIATION DOSE ABSORBED BY THE TREES. SUCH HYPERMETHYLATION MAY BE VIEWED AS A DEFENSE STRATEGY OF PLANTS THAT PREVENTS GENOME INSTABILITY AND RESHUFFLING OF THE HEREDITARY MATERIAL, ALLOWING SURVIVAL IN AN EXTREME ENVIRONMENT. FURTHER STUDIES ARE CLEARLY NEEDED TO ANALYZE IN DETAIL THE INVOLVEMENT OF DNA METHYLATION AND OTHER EPIGENETIC MECHANISMS IN THE COMPLEX PROCESS OF RADIATION STRESS AND ADAPTIVE RESPONSE. 2003 5 6526 26 TRANSCRIPTIONAL CHANGES IN THE OVARIES OF PERCH FROM CHERNOBYL. FISH HAVE BEEN HIGHLY EXPOSED TO RADIATION IN FRESHWATER SYSTEMS AFTER THE CHERNOBYL NUCLEAR POWER PLANT (NPP) ACCIDENT IN 1986 AND IN FRESHWATER AND MARINE SYSTEMS AFTER THE MORE RECENT FUKUSHIMA NPP ACCIDENT IN 2011. IN THE YEARS AFTER THE ACCIDENT, THE RADIOACTIVITY LEVELS RAPIDLY DECLINED DUE TO RADIOACTIVE DECAY AND ENVIRONMENTAL PROCESSES, BUT CHRONIC LOWER DOSE EXPOSURES PERSISTED. TO GAIN INSIGHTS INTO THE LONG-TERM EFFECTS OF ENVIRONMENTAL LOW DOSE RADIATION ON FISH OVARIES DEVELOPMENT, A HIGH-THROUGHPUT TRANSCRIPTOMIC APPROACH INCLUDING A DE NOVO ASSEMBLY WAS APPLIED TO DIFFERENT GONAD PHENOTYPES OF FEMALE PERCH: DEVELOPED GONADS FROM REFERENCE LAKES, DEVELOPED/IRRADIATED FROM MEDIUM CONTAMINATED LAKE, AND BOTH DEVELOPED/IRRADIATED AND UNDEVELOPED FROM MORE HIGHLY CONTAMINATED LAKES. THIS IS THE MOST COMPREHENSIVE ANALYSIS TO DATE OF THE GENE RESPONSES IN WILDLIFE REPRODUCTIVE SYSTEM TO RADIATION. SOME GENE RESPONSES THAT WERE MODULATED IN IRRADIATED GONADS WERE FOUND TO BE INVOLVED IN BIOLOGICAL PROCESSES INCLUDING CELL DIFFERENTIATION AND PROLIFERATION (GGNB2, MOD5, RERGL), CYTOSKELETON ORGANIZATION (K1C18, MTPN), GONAD DEVELOPMENT (NELL2, TCP4), LIPID METABOLISM (LDAH, AT11B, NLTP), REPRODUCTION (CYB5, CYP17A, OVOS), DNA DAMAGE REPAIR (WDHD1, RAD51, HUS1), AND EPIGENETIC MECHANISMS (DMAP1). IDENTIFICATION OF THESE GENES PROVIDES A BETTER UNDERSTANDING OF THE UNDERLYING MOLECULAR MECHANISMS UNDERPINNING THE DEVELOPMENT OF THE GONAD PHENOTYPES OF WILD PERCH AND HOW FISH MAY RESPOND TO CHRONIC EXPOSURE TO RADIATION IN THEIR NATURAL ENVIRONMENT, THOUGH CAUSAL ATTRIBUTION OF GENE RESPONSES REMAINS UNCLEAR IN THE UNDEVELOPED GONADS. 2020 6 1511 20 DNA METHYLATION AND POTENTIAL MULTIGENERATIONAL EPIGENETIC EFFECTS LINKED TO URANIUM CHRONIC LOW-DOSE EXPOSURE IN GONADS OF MALES AND FEMALES RATS. INTRODUCTION: AN INCREASED HEALTH PROBLEM IN INDUSTRIALISED COUNTRIES IS THE CONTEMPORARY CONCERN OF PUBLIC AND SCIENTIFIC COMMUNITY AS WELL. THIS HAS BEEN ATTRIBUTED IN PART TO ACCUMULATED ENVIRONMENTAL POLLUTANTS ESPECIALLY RADIOACTIVE SUBSTANCES AND THE USE OF NUCLEAR POWER PLANTS WORLDWIDE. HOWEVER, THE OUTCOME OF CHRONIC EXPOSURE TO LOW DOSES OF A RADIONUCLIDE SUCH AS URANIUM REMAINS UNKNOWN. RECENTLY, A PARADIGM SHIFT IN THE PERCEPTION OF RISK OF RADIOTOXICOLOGY HAS EMERGED THROUGH INVESTIGATING THE POSSIBILITY OF TRANSMISSION OF BIOLOGICAL EFFECTS OVER GENERATIONS, IN PARTICULAR BY EPIGENETIC PATHWAYS. THESE PROCESSES ARE KNOWN FOR THEIR CRUCIAL ROLES ASSOCIATED WITH THE DEVELOPMENT OF SEVERAL DISEASES. OBJECTIVE: THE CURRENT WORK INVESTIGATES THE EPIGENETIC EFFECT OF CHRONIC EXPOSURE TO LOW DOSES OF URANIUM AND ITS INHERITANCE ACROSS GENERATIONS. MATERIALS AND METHODS TO TEST THIS PROPOSITION, A RODENT MULTIGENERATIONAL MODEL, MALES AND FEMALES, WERE EXPOSED TO A NON-TOXIC CONCENTRATION OF URANIUM (40MGL(-1) DRINKING WATER) FOR NINE MONTHS. THE URANIUM EFFECTS ON WERE EVALUATED OVER THREE GENERATIONS (F0, F1 AND F2) BY ANALYSING THE DNA METHYLATION PROFILE AND DNMT GENES EXPRESSION IN OVARIES AND TESTES TISSUES. RESULTS: HERE WE REPORT A SIGNIFICANT HYPERMETHYLATION OF TESTES DNA (P <0.005) WHEREAS OVARIES SHOWED HYPOMETHYLATED DNA (P <0.005). INTERESTINGLY, THIS DNA METHYLATION PROFILE WAS SIGNIFICANTLY MAINTAINED ACROSS GENERATIONS F0, F1 AND F2. FURTHERMORE, QPCR RESULTS OF BOTH TISSUES IMPLY A SIGNIFICANT CHANGE IN THE EXPRESSION OF DNA METHYLTRANSFERASE GENES (DNMT 1 AND DNMT3A/B) AS WELL. CONCLUSION: ALTOGETHER, OUR WORK DEMONSTRATES FOR THE FIRST TIME A SEX-DEPENDANCE AND INHERITANCE OF EPIGENETIC MARKS, DNA METHYLATION, AS A BIOLOGICAL RESPONSE TO THE EXPOSURE TO LOW DOSES OF URANIUM. HOWEVER, IT IS NOT CLEAR WHICH TYPE OF REPRODUCTIVE CELL TYPE IS MORE RESPONSIVE IN THIS CONTEXT. 2018 7 1835 29 EFFECTS OF NON-HUMAN SPECIES IRRADIATION AFTER THE CHERNOBYL NPP ACCIDENT. THE AREA AFFECTED BY THE CHERNOBYL NUCLEAR POWER PLANT ACCIDENT IN 1986 HAS BECOME A UNIQUE TEST SITE WHERE LONG-TERM ECOLOGICAL AND BIOLOGICAL CONSEQUENCES OF A DRASTIC CHANGE IN A RANGE OF ENVIRONMENTAL FACTORS AS WELL AS TRENDS AND INTENSITY OF SELECTION ARE STUDIED IN NATURAL SETTINGS. THE CONSEQUENCES OF THE CHERNOBYL ACCIDENT FOR BIOTA VARIED FROM AN ENHANCED RATE OF MUTAGENESIS TO DAMAGE AT THE ECOSYSTEM LEVEL. THE REVIEW COMPREHENSIVELY BRINGS TOGETHER KEY DATA OF THE LONG-TERM STUDIES OF BIOLOGICAL EFFECTS IN PLANTS AND ANIMALS INHABITING OVER 20 YEARS THE CHERNOBYL NPP ZONE. THE SEVERITY OF RADIATION EFFECTS WAS STRONGLY DEPENDENT ON THE DOSE RECEIVED IN THE EARLY PERIOD AFTER THE ACCIDENT. THE MOST EXPOSED PHYTOCENOSES AND SOIL ANIMALS' COMMUNITIES EXHIBITED DOSE DEPENDENT ALTERATIONS IN THE SPECIES COMPOSITION AND REDUCTION IN BIOLOGICAL DIVERSITY. ON THE OTHER HAND, NO DECREASE IN NUMBERS OR TAXONOMIC DIVERSITY OF SMALL MAMMALS EVEN IN THE MOST RADIOACTIVE HABITAT WAS SHOWN. IN A MAJORITY OF THE STUDIES, IN BOTH PLANT AND ANIMAL POPULATIONS FROM THE CHERNOBYL ZONE, IN THE FIRST YEARS AFTER THE ACCIDENT HIGH INCREASES IN MUTATION RATES WERE DOCUMENTED. IN MOST CASES THE DOSE-EFFECT RELATIONSHIPS WERE NONLINEAR AND THE MUTATION RATES PER UNIT DOSE WERE HIGHER AT LOW DOSES AND DOSE RATES. IN SUBSEQUENT YEARS A DECLINE IN THE RADIATION BACKGROUND RATE OCCURRED FASTER THAN REDUCTION IN THE MUTATION RATE. PLANT AND ANIMAL POPULATIONS HAVE SHOWN SIGNS OF ADAPTATION TO CHRONIC EXPOSURE. IN ADAPTATION TO THE ENHANCED LEVEL OF EXPOSURE AN ESSENTIAL ROLE OF EPIGENETIC MECHANISMS OF GENE EXPRESSION REGULATION WAS SHOWN. BASED ON THE CHERNOBYL NPP ACCIDENT STUDIES, IN THE PRESENT REVIEW ATTEMPTS WERE MADE TO ASSESS MINIMUM DOSES AT WHICH ECOLOGICAL AND BIOLOGICAL EFFECTS WERE OBSERVED. 2008 8 1325 19 DEPLETED URANIUM INDUCES SEX- AND TISSUE-SPECIFIC METHYLATION PATTERNS IN ADULT ZEBRAFISH. WE EXAMINED THE EFFECTS OF CHRONIC EXPOSURE TO DIFFERENT CONCENTRATIONS (2 AND 20 MUG L(-)(1)) OF ENVIRONMENTALLY RELEVANT WATERBORNE DEPLETED URANIUM (DU) ON THE DNA METHYLATION PATTERNS BOTH AT HPAII RESTRICTION SITES (5'-CCGG-3') AND ACROSS THE WHOLE GENOME IN THE ZEBRAFISH BRAIN, GONADS, AND EYES. WE FIRST IDENTIFIED SEX-DEPENDENT DIFFERENCES IN THE METHYLATION LEVEL OF HPAII SITES AFTER EXPOSURE. IN MALES, THESE EFFECTS WERE PRESENT AS EARLY AS 7 DAYS AFTER EXPOSURE TO 20 MUG L(-)(1) DU, AND WERE EVEN MORE PRONOUNCED IN THE BRAIN, GONADS, AND EYES AFTER 24 DAYS. HOWEVER, IN FEMALES, HYPOMETHYLATION WAS ONLY OBSERVED IN THE GONADS AFTER EXPOSURE TO 20 MUG L(-)(1) DU FOR 24 DAYS. SEX-SPECIFIC EFFECTS OF DU WERE ALSO APPARENT AT THE WHOLE-GENOME LEVEL, BECAUSE IN MALES, EXPOSURE TO 20 MUG L(-)(1) DU FOR 24 DAYS RESULTED IN CYTOSINE HYPERMETHYLATION IN THE BRAIN AND EYES AND HYPOMETHYLATION IN THE GONADS. IN CONTRAST, IN FEMALES, HYPERMETHYLATION WAS OBSERVED IN THE BRAIN AFTER EXPOSURE TO BOTH CONCENTRATIONS OF DU FOR 7 DAYS. BASED ON OUR CURRENT KNOWLEDGE OF URANIUM TOXICITY, SEVERAL HYPOTHESES ARE PROPOSED TO EXPLAIN THESE FINDINGS, INCLUDING THE INVOLVEMENT OF OXIDATIVE STRESS, ALTERATION OF DEMETHYLATION ENZYMES AND THE CALCIUM SIGNALING PATHWAY. THIS STUDY REPORTS, FOR THE FIRST TIME, THE SEX- AND TISSUE-SPECIFIC EPIGENETIC CHANGES THAT OCCUR IN A NONHUMAN ORGANISM AFTER EXPOSURE TO ENVIRONMENTALLY RELEVANT CONCENTRATIONS OF URANIUM, WHICH COULD INDUCE TRANSGENERATIONAL EPIGENETIC EFFECTS. 2016 9 5344 30 RADIOBIOLOGICAL FEATURES IN OFFSPRING OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER AFTER CHERNOBYL ACCIDENT. IN THEIR NATURAL HABITATS, POPULATIONS OF ORGANISMS ARE FACED WITH DIFFERENT LEVELS OF CHRONIC LOW-INTENSITY RADIATION, CAUSING A WIDE RANGE OF RADIOBIOLOGICAL EFFECTS (FROM RADIOSENSITIVITY TO RADIOADAPTIVE RESPONSE AND HORMESIS). IN THIS STUDY, SPECIMENS OF DROSOPHILA MELANOGASTER WERE SELECTED FROM TERRITORIES OF THE CHERNOBYL NUCLEAR POWER PLANT WITH DIFFERENT LEVELS OF RADIOACTIVE CONTAMINATION. THE ISOGENIC STOCKS DERIVED FROM THESE SPECIMENS REPRESENT THE GENETIC SYSTEMS OF CURRENT POPULATIONS AND MAKE IT POSSIBLE TO STUDY RADIORESISTANCE AND ITS MECHANISMS IN FUTURE GENERATIONS UNDER CONTROLLED LABORATORY CONDITIONS. PREVIOUS STUDIES HAVE SHOWN THAT TRANSGENERATIONAL RADIATION EFFECTS AT THE LEVEL OF LETHAL MUTATIONS AND SURVIVAL RATE ARE UNSTABLE AND DEPEND NOT ONLY ON THE LEVEL OF CHRONIC LOW-INTENSITY IRRADIATION, BUT ALSO ON OTHER FACTORS. A SINGLE ACUTE IRRADIATION EXPOSURE OF OFFSPRING WHOSE PARENTS INHABITED A SITE WITH A HIGHER LEVEL OF CHRONIC IRRADIATION MADE IT POSSIBLE TO REVEAL PRONOUNCED RADIORESISTANT FEATURES IN THE OFFSPRING. AND THE OFFSPRING WHOSE PARENTS WERE EXPOSED TO RADIATION LEVELS CLOSE TO THE NATURAL RADIATION BACKGROUND, ON THE CONTRARY, ACQUIRED RADIOSENSITIVE FEATURES. THEIR RESPONSE TO ACUTE EXPOSURE INCLUDES A HIGH-FREQUENCY OF LETHAL MUTATIONS AND A SHORT LIFESPAN. THE DIFFERENTIAL RESPONSE TO DIFFERENT LEVELS OF CHRONIC PARENTAL EXPOSURE IS CAUSED BY DIFFERENCES IN THE ACTIVITIES OF CERTAIN TRANSPOSONS THAT DESTABILIZE THE GENOME. OUR DATA CONTRIBUTE TO THE UNDERSTANDING OF GENETIC AND EPIGENETIC MECHANISMS (VIA TRANSPOSON ACTIVITY) OF THE EFFECT OF PARENTAL RADIATION EXPOSURE ON THE HEALTH AND ADAPTIVE POTENTIAL OF POPULATIONS AFFECTED BY THE TECHNOGENICALLY INCREASED RADIATION BACKGROUND. 2022 10 6777 17 [ASSOCIATION OF P-MOBILE ELEMENT ACTIVITY AND DNA METHYLATION PATTERN CHANGES IN THE CONDITIONS OF DROSOPHILA MELANOGASTER PROLONGED IRRADIATION]. ASSOCIATION OF THE RADIOSENSITIVITY AND EPIGENETIC PATTERN DNA CHANGES AT THE CONDITIONS OF PROLONGED IRRADIATION WAS INVESTIGATED. TWO LABORATORY DROSOPHILA MELANOGASTER STRAINS (CANTON-S AND RI) IRRADIATED FOR 20 GENERATIONS TO LOW DOSES RATE (1.2 X 10(-1), 0.8 X 10(-8) AND 0.12 X 10(-8) GY/S) WERE USED AS EXPERIMENTAL OBJECTS. DNA FOR THE ANALYSIS WAS EXTRACTED SEPARATELY FOR THE FLIES OF MALES AND FEMALES. RESTRICTION ENDONUCLEASES GLUL, GLAL WERE USED. RESTRICTION ANALYSIS HAS SHOWN THAT THERE ARE DIFFERENT DNA METHYLATED PATTERNS FOR MALES AND FEMALES AS FOR CONTROL AND EXPOSED VARIANTS. AT THE CHRONIC IRRADIATION THERE WAS THE DECLINE OF METHYLATION LEVEL AT THE ENZYMES GLUL, GLAL SITES RECOGNITION. 2010 11 6673 20 USE OF COMPUTER TV MORPHODENSITOMETRY TO STUDY EPIGENETIC CHANGES IN BLOOD LYMPHOCYTES FROM CHILDREN AFFECTED BY LOW-DOSE IRRADIATION. A NOVEL METHOD, COMPUTER TV MORPHODENSITOMETRY, WAS USED TO EVALUATE THE EFFECTS OF LOW-DOSE IRRADIATION ON PERIPHERAL BLOOD LYMPHOCYTES FROM CHILDREN AFFECTED BY THE CHERNOBYL DISASTER. THIS METHOD USES DIGITIZED IMAGES TO DETECT AND MEASURE CHANGES IN CHROMATIN SHAPE AND DENSITY AND TO PRODUCE TWO-DIMENSIONAL AND THREE-DIMENSIONAL PICTURES. IMAGES CAN THEN BE STORED TO CREATE A VIDEO ARCHIVE. THIS METHOD IS SENSITIVE ENOUGH TO OBSERVE SUBTLE CHANGES IN CHROMATIN STRUCTURE THAT PREVIOUSLY COULD BE DETECTED ONLY BY MORE DETAILED MOLECULAR ANALYSES. IN THIS STUDY, LYMPHOCYTE INTERPHASE NUCLEI IN DNA-STAINED BLOOD SMEARS FROM CHILDREN SUBJECTED TO CHRONIC LOW-DOSE IRRADIATION WERE EXAMINED BY COMPUTER TV MORPHODENSITOMETRY. PRELIMINARY DATA INDICATE THAT CIRCULATING LYMPHOCYTES FROM CHILDREN EXPOSED TO RADIATION MAY CONTAIN SIGNIFICANT ALTERATIONS IN THE STRUCTURE AND/OR DENSITY OF NUCLEAR CHROMATIN. 1997 12 1531 10 DNA METHYLATION DURING DEPLETED URANIUM-INDUCED LEUKEMIA. OBJECTIVES: THE RADIOACTIVE HEAVY METAL DEPLETED URANIUM (DU) IS USED IN KINETIC-ENERGY PENETRATORS IN MILITARY APPLICATIONS. THE OBJECTIVE OF THIS STUDY WAS TO DETERMINE INVOLVEMENT OF DNA METHYLATION IN DU-INDUCED LEUKEMIA. METHODS: METHYLATION WAS MEASURED BY DIRECT ANALYSIS OF 5-METHYLCYTOSINE CONTENT OF SPLEEN DNA IN DU LEUKEMIC MICE. RESULTS: SPLEEN HYPOMETHYLATION OCCURRED DURING DU-INDUCED LEUKEMOGENESIS (CHRONIC INTERNAL DU EXPOSURE). ABERRANT GENE TRANSCRIPTION WAS ALSO DETECTED. CONCLUSIONS: EPIGENETIC MECHANISMS ARE IMPLICATED IN DU-INDUCED LEUKEMIA. THESE DATA ARE EVIDENCE OF ABERRANT DNA HYPOMETHYLATION BEING ASSOCIATED WITH DU LEUKEMOGENESIS. 2009 13 1816 12 EFFECTS OF CHRONIC EXPOSURE TO BENZOPHENONE AND DICLOFENAC ON DNA METHYLATION LEVELS AND REPRODUCTIVE SUCCESS IN A MARINE COPEPOD. THE UV-FILTER BENZOPHENONE AND THE ANTI-INFLAMMATORY DICLOFENAC ARE COMMONLY DETECTED IN THE ENVIRONMENT. THE AIM OF THIS STUDY WAS TO ASSESS THE MULTIGENERATIONAL EFFECTS OF CHRONIC EXPOSURE TO LOW CONCENTRATIONS OF THESE CHEMICALS ON TOXICITY AND DNA METHYLATION LEVELS IN THE COPEPOD GLADIOFERENS PECTINATUS. ACUTE TOXICITY TESTS WERE CONDUCTED TO DETERMINE THE SENSITIVITY OF G. PECTINATUS TO THE CHEMICALS. ALL CHEMICALS IMPACTED BREEDING, HATCHING AND EGG VIABILITY. DICLOFENAC (1 MG.L(-1)) REDUCED THE NUMBER OF EGGS PER GRAVID FEMALE. BENZOPHENONE (0.5 MG.L(-1)) DECREASED EGG HATCHING SUCCESS. EXPOSURE TO THE REFERENCE TOXICANT COPPER (0.02 MG.L(-1)) LED TO UNSUCCESSFUL HATCHING. EFFECTS ON DNA METHYLATION WAS ESTIMATED BY THE PERCENTAGE OF 5- METHYLCYTOSINE. THE TREATMENTS RESULTED IN STRONG DIFFERENCES IN DNA METHYLATION WITH INCREASED METHYLATION IN THE EXPOSED ANIMALS. THE TWO CHEMICALS IMPACTED BOTH EGG VIABILITY AND THE INDUCTION OF DIFFERENTIAL DNA METHYLATION, SUGGESTING POTENTIAL INTRA- AND TRANS-GENERATIONAL EVOLUTIONARY EFFECTS. 2018 14 3620 13 IN VIVO AND IN VITRO GENOTOXIC AND EPIGENETIC EFFECTS OF TWO TYPES OF COLA BEVERAGES AND CAFFEINE: A MULTIASSAY APPROACH. THE AIM OF THIS WORK WAS TO ASSESS THE BIOLOGICAL AND FOOD SAFETY OF TWO DIFFERENT BEVERAGES: CLASSIC COCA COLA (CCC) AND CAFFEINE-FREE COCA COLA (CFCC). TO THIS END, WE DETERMINED THE GENOTOXICOLOGICAL AND BIOLOGICAL EFFECTS OF DIFFERENT DOSES OF LYOPHILISED CCC AND CFCC AND CAFFEINE (CAF), THE MAIN DISTINCTIVE CONSTITUENT. THEIR TOXIC/ANTITOXIC, GENOTOXIC/ANTIGENOTOXIC, AND CHRONIC TOXICITY (LIFESPAN ASSAY) EFFECTS WERE DETERMINED IN VIVO USING THE DROSOPHILA MODEL. THEIR CYTOTOXIC ACTIVITIES WERE DETERMINED USING THE HL-60 IN VITRO CANCER MODEL. IN ADDITION, CLASTOGENIC DNA TOXICITY WAS MEASURED USING INTERNUCLEOSOMAL FRAGMENTATION AND SCGE ASSAYS. THEIR EPIGENETIC EFFECTS WERE ASSESSED ON THE HL-60 METHYLATION STATUS USING SOME REPETITIVE ELEMENTS. THE EXPERIMENTAL RESULTS SHOWED A SLIGHT CHEMOPREVENTIVE EFFECT OF THE TWO COLA BEVERAGES AGAINST HL-60 LEUKAEMIA CELLS, PROBABLY MEDIATED BY NONAPOPTOTIC MECHANISMS. FINALLY, CCC AND CAF INDUCED A GLOBAL GENOME HYPOMETHYLATION EVALUATED IN LINE-1 AND ALU M1 REPETITIVE ELEMENTS. OVERALL, WE DEMONSTRATED FOR THE FIRST TIME THE SAFETY OF THIS FAMOUS BEVERAGE IN IN VIVO AND IN VITRO MODELS. 2016 15 1174 28 CONTRIBUTION OF TRANSPOSABLE ELEMENTS TO TRANSGENERATIONAL EFFECTS OF CHRONIC RADIOACTIVE EXPOSURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER LIVING FOR A LONG TIME IN THE ZONE OF THE CHERNOBYL NUCLEAR DISASTER. THE ACCIDENT AT THE CHERNOBYL NUCLEAR POWER PLANT (CHNPP) LED TO THE NEGATIVE IMPACT OF CHRONIC RADIOACTIVE CONTAMINATION ON POPULATIONS OF ORGANISMS ASSOCIATED WITH THE TRANSGENERATIONAL TRANSMISSION OF GENOME INSTABILITY. WHEN THE DESTABILIZATION OF GENOME, DIFFERENT GENETIC DAMAGES OCCUR, THE ACCUMULATION OF WHICH LEADS TO THE FORMATION OF MUTATIONS, MORPHOLOGICAL ANOMALIES, AND MORTALITY IN THE OFFSPRING. THE MECHANISMS UNDERLYING THE MANIFESTATION OF TRANSGENERATIONAL EVENTS IN THE OFFSPRING OF IRRADIATED PARENTS ARE NOT WELL UNDERSTOOD. IN THIS STUDY, FOR THE FIRST TIME, THE FEATURES OF THE INFLUENCE OF TRANSPOSABLE ELEMENTS (TES) ON THE LONG-TERM BIOLOGICAL CONSEQUENCES OF THE CHNPP ARE CONSIDERED. IN THIS WORK, SPECIMENS OF D. MELANOGASTER OBTAINED FROM NATURAL POPULATIONS IN 2007 IN THE AREAS OF THE CHNPP WITH HETEROGENEOUS RADIOACTIVE CONTAMINATION WERE STUDIED. THE DESCENDANTS FROM THESE POPULATIONS WERE MAINTAINED IN LABORATORY (INBRED) CONDITIONS FOR 160 GENERATIONS. A STABLE TRANSGENERATIONAL TRANSMISSION OF DOMINANT LETHAL MUTATIONS (DLMS) TO THE OFFSPRING OF ALL STUDIED POPULATIONS WAS SHOWN. THE DLM FREQUENCIES STRONGLY WERE CORRELATED WITH THE LEVEL OF SURVIVAL OF OFFSPRING. THE MEAN FREQUENCIES OF RECESSIVE SEX-LINKED LETHAL MUTATIONS VARIED AT THE LEVEL OF SPONTANEOUS POINT MUTATIONS. THE SIMULTANEOUS PRESENCE OF P, HOBO AND I ELEMENTS INDICATES THAT THE STUDIED POPULATIONS DO NOT HAVE A DEFINITE CYTOTYPE, THEIR PHENOTYPIC STATUS IS UNSTABLE. THE BEHAVIOR OF TES IN THE GENOMES OF OFFSPRING DEPENDS NOT ONLY ON PARENTAL EXPOSURE, BUT ALSO ON ORIGIN OF POPULATION, DISTANCE TO THE CHNPP, AND INBRED CONDITIONS. THE OBTAINED RESULTS CONFIRM THE HYPOTHESIS THAT TES ARE INVOLVED IN TRANSGENERATIONAL TRANSMISSION AND ACCUMULATION OF MUTATIONS BY THE OFFSPRING OF IRRADIATED PARENTS. THE TES PATTERN PRESENT IN THE CHERNOBYL GENOMES OF D. MELANOGASTER IS A PECULIAR OF EPIGENETIC MECHANISM FOR THE REGULATION OF PLASTICITY AND ADAPTATION OF POPULATIONS LIVING FOR MANY GENERATIONS UNDER CONDITIONS OF A TECHNOGENICALLY CAUSED RADIATION BACKGROUND. 2022 16 5342 20 RADIATION-INDUCED LATE EFFECTS IN TWO AFFECTED INDIVIDUALS OF THE LILO RADIATION ACCIDENT. RADIATION EXPOSURE LEADS TO A RISK FOR LONG-TERM DETERMINISTIC AND STOCHASTIC LATE EFFECTS. TWO INDIVIDUALS EXPOSED TO PROTRACTED PHOTON RADIATION IN THE RADIOLOGICAL ACCIDENT AT THE LILO MILITARY SITE IN GEORGIA IN 1997 RECEIVED FOLLOW-UP TREATMENT AND RESECTION OF SEVERAL CHRONIC RADIATION ULCERS IN THE BUNDESWEHR HOSPITAL ULM, GERMANY, IN 2003. MULTI-PARAMETER ANALYSIS REVEALED THAT SPERMATOGENETIC ARREST AND SERUM HORMONE LEVELS IN BOTH PATIENTS HAD RECOVERED COMPARED TO THE STATUS IN 1997. HOWEVER, WE OBSERVED A PERSISTENCE OF ALTERED T-CELL RATIOS, INCREASED ICAM1 AND BETA1-INTEGRIN EXPRESSION, AND ABERRANT BONE MARROW CELLS AND LYMPHOCYTES WITH SIGNIFICANTLY INCREASED TRANSLOCATIONS 6 YEARS AFTER THE ACCIDENT. THIS INVESTIGATION THUS IDENTIFIED ALTERED END POINTS STILL DETECTABLE YEARS AFTER THE ACCIDENT THAT SUGGEST PERSISTENT GENOMIC DAMAGE AS WELL AS EPIGENETIC EFFECTS IN THESE INDIVIDUALS, WHICH MAY BE ASSOCIATED WITH AN ELEVATED RISK FOR THE DEVELOPMENT OF FURTHER LATE EFFECTS. OUR OBSERVATIONS FURTHER SUGGEST THE DEVELOPMENT OF A CHRONIC RADIATION SYNDROME AND INDICATE FOLLOW-UP PARAMETERS IN RADIATION VICTIMS. 2007 17 903 15 CHRONIC EXPOSURE TO BISPHENOL A RESULTED IN ALTERATIONS OF REPRODUCTIVE FUNCTIONS VIA IMMUNE DEFENSE, OXIDATIVE DAMAGE AND DISRUPTION DNA/HISTONE METHYLATION IN MALE RARE MINNOW GOBIOCYPRIS RARUS. BISPHENOL A (BPA) IS A WIDELY USED CHEMICAL THAT REPRESENTS A REPRODUCTIVE HAZARD IN FISH. HOWEVER, THE MOLECULAR PATHWAYS MEDIATING REPRODUCTIVE TOXICITY UNDER CHRONIC BPA EXPOSURE REMAIN UNCLEAR. TO STUDY THE REPRODUCTIVE HAZARDS ASSOCIATED WITH CHRONIC BPA EXPOSURE, ADULT MALE RARE MINNOWS (GOBIOCYPRIS RARUS) WERE TREATED WITH 15 MUG L (-) (1) AND 225 MUG L (-) (1) BPA FOR 90 DAYS. RESULTS SHOWED THAT CHRONIC BPA TREATMENT INDUCED REPRODUCTIVE IMPAIRMENTS WITH DECREASED FERTILIZATION CAPACITY AND MOVEMENT TIME OF SPERM. TRANSCRIPTOME ANALYSIS INDICATED 1421 TRANSCRIPTS THAT WERE DIFFERENTIALLY EXPRESSED IN RESPONSE TO BPA EXPOSURE, WHICH ARE INVOLVED IN THE BIOLOGICAL PROCESS OF OXIDATIVE STRESS, IMMUNE RESPONSES AND DNA/HISTONE METHYLATION. BPA CAUSED THE OXIDATIVE STRESS VIA SIGNIFICANTLY INCREASING HYDROGEN PEROXIDE (H(2)O(2)) LEVELS AND INHIBITING THE ACTIVITIES OF ANTIOXIDANT-RELATED ENZYMES (CATALASE, CAT). BPA CAUSED AN INFLAMMATORY RESPONSE IN THE TESTES BY SIGNIFICANTLY INCREASING IL-1BETA LEVELS AND INDUCING INFILTRATION OF INFLAMMATORY CELLS. MOREOVER, EXPOSURE TO 15 MUG L (-) (1) BPA SIGNIFICANTLY DECREASED THE GENOMIC DNA METHYLATION LEVEL. THESE DATA REVEALED THAT CHRONIC BPA EXPOSURE HAD ADVERSE EFFECTS ON MALE REPRODUCTION. OXIDATIVE STRESS, INFLAMMATORY RESPONSE AND DNA/HISTONE METHYLATION MIGHT ACCOUNT FOR THE DECREASED SPERM QUALITY. 2021 18 6552 20 TRANSGENERATIONAL DNA METHYLATION CHANGES IN DAPHNIA MAGNA EXPOSED TO CHRONIC GAMMA IRRADIATION. OUR AIM WAS TO INVESTIGATE EPIGENETIC CHANGES IN DAPHNIA MAGNA AFTER A 25-DAY CHRONIC EXTERNAL GAMMA IRRADIATION (GENERATION F0 EXPOSED TO 6.5 MUGY.H(-1) OR 41.3 MGY.H(-1)) AND THEIR POTENTIAL INHERITANCE BY SUBSEQUENT RECOVERING GENERATIONS, NAMELY, F2 (EXPOSED AS GERMLINE CELLS IN F1 EMBRYOS) AND F3 (THE FIRST TRULY UNEXPOSED GENERATION). EFFECTS ON SURVIVAL, GROWTH, AND REPRODUCTION WERE OBSERVED AND DNA WAS EXTRACTED FOR WHOLE-GENOME BISULFITE SEQUENCING IN ALL GENERATIONS. RESULTS SHOWED EFFECTS ON REPRODUCTION IN F0 BUT NO EFFECT IN THE SUBSEQUENT GENERATIONS F1, F2, AND F3. IN CONTRAST, WE OBSERVED SIGNIFICANT METHYLATION CHANGES AT SPECIFIC CPG POSITIONS IN EVERY GENERATION INDEPENDENT OF DOSE RATE, WITH A MAJORITY OF HYPOMETHYLATION. SOME OF THESE CHANGES WERE SHARED BETWEEN DOSE RATES AND BETWEEN GENERATIONS. ASSOCIATED GENE FUNCTIONS INCLUDED GENE FAMILIES AND GENES THAT WERE PREVIOUSLY SHOWN TO PLAY ROLES DURING EXPOSURE TO IONIZING RADIATION. COMMON METHYLATION CHANGES DETECTED BETWEEN GENERATIONS F2 AND F3 CLEARLY SHOWED THAT EPIGENETIC MODIFICATIONS CAN BE TRANSMITTED TO UNEXPOSED GENERATIONS, MOST LIKELY THROUGH THE GERMLINE, WITH POTENTIAL IMPLICATIONS FOR ENVIRONMENTAL RISK. 2018 19 6555 23 TRANSGENERATIONAL EFFECTS OF GAMMA RADIATION DOSE AND DOSE RATE ON DROSOPHILA FLIES IRRADIATED AT AN EARLY EMBRYONAL STAGE. IONIZING RADIATION (IR) KILLS CELLS MAINLY THROUGH INDUCTION OF DNA DAMAGES AND THE SURVIVING CELLS MAY SUFFER FROM MUTATIONS. TRANSGENERATIONAL EFFECTS OF IR ARE WELL DOCUMENTED, BUT THE EXACT MECHANISMS UNDERLYING THEM ARE LESS WELL UNDERSTOOD; THEY INCLUDE INDUCTION OF MUTATIONS IN GERM CELLS AND EPIGENETIC INHERITANCE. PREVIOUSLY, EFFECTS IN THE OFFSPRING OF MICE AND ZEBRAFISH EXPOSED TO IR HAVE BEEN REPORTED. A FEW STUDIES ALSO SHOWED INDICATIONS OF TRANSGENERATIONAL EFFECTS OF RADIATION IN HUMANS, PARTICULARLY IN NUCLEAR POWER WORKERS. IN THE PRESENT PROJECT, SHORT- AND LONG-TERM EFFECTS OF LOW-DOSE-RATE (LDR; 50 AND 97 MGY/H) AND HIGH-DOSE-RATE (HDR; 23.4, 47.1 AND 495 GY/H) IR IN DROSOPHILA EMBRYOS WERE INVESTIGATED. THE EMBRYOS WERE IRRADIATED AT DIFFERENT DOSES AND DOSE RATES AND RADIOSENSITIVITY AT DIFFERENT DEVELOPMENTAL STAGES WAS INVESTIGATED. ALSO, THE SURVIVAL OF LARVAE, PUPAE AND ADULTS DEVELOPED FROM EMBRYOS IRRADIATED AT AN EARLY STAGE (30 MIN AFTER EGG LAYING) WERE STUDIED. THE LARVAL CRAWLING AND PUPATION HEIGHT ASSAYS WERE APPLIED TO INVESTIGATE RADIATION EFFECTS ON LARVAL LOCOMOTION AND PUPATION BEHAVIOR, RESPECTIVELY. IN PARALLEL, THE OFFSPRING FROM 3 GY IRRADIATED EARLY-STAGE EMBRYOS WERE FOLLOWED UP TO 12 GENERATIONS AND ABNORMAL PHENOTYPES WERE STUDIED. ACUTE EXPOSURE OF EMBRYOS AT DIFFERENT STAGES OF DEVELOPMENT SHOWED THAT THE EARLY STAGE EMBRYO IS THE MOST SENSITIVE. THE EFFECTS ON LARVAL LOCOMOTION SHOWED NO SIGNIFICANT DIFFERENCES BETWEEN THE DOSE RATES BUT A SIGNIFICANT DECREASE OF LOCOMOTION ACTIVITY ABOVE 7 GY WAS OBSERVED. THE RESULTS INDICATE THAT EMBRYOS EXPOSED TO THE LOW DOSE RATES HAVE SHORTER ECLOSION TIMES. AT THE SAME CUMULATIVE DOSE (1 UP TO 7 GY), HDR IS MORE EMBRYOTOXIC THAN LDR. WE ALSO FOUND A RADIATION-INDUCED DEPIGMENTATION ON MALES (A5 SEGMENT OF THE DORSAL ABDOMEN, A5PIG(-)) THAT CAN BE TRANSMITTED UP TO 12 GENERATIONS. THE PHENOMENON DOES NOT FOLLOW THE CLASSICAL MENDELIAN LAWS OF SEGREGATION. 2022 20 3657 21 INDUCTION AND RECOVERY OF CPG SITE SPECIFIC METHYLATION CHANGES IN HUMAN BRONCHIAL CELLS AFTER LONG-TERM EXPOSURE TO CARBON NANOTUBES AND ASBESTOS. INTRODUCTION: INHALATION OF ASBESTOS INDUCES LUNG CANCER VIA DIFFERENT CELLULAR MECHANISMS. TOGETHER WITH THE INCREASED PRODUCTION OF CARBON NANOTUBES (CNTS) GROWS THE CONCERN ABOUT ADVERSE EFFECTS ON THE LUNGS GIVEN THE SIMILARITIES WITH ASBESTOS. WHILE IT HAS BEEN ESTABLISHED THAT CNT AND ASBESTOS INDUCE EPIGENETIC ALTERATIONS, IT IS CURRENTLY NOT KNOWN WHETHER ALTERATIONS AT EPIGENETIC LEVEL REMAIN STABLE AFTER WITHDRAWAL OF THE EXPOSURE. IDENTIFICATION OF DNA METHYLATION CHANGES AFTER A LOW DOSE OF CNT AND ASBESTOS EXPOSURE AND RECOVERY CAN BE USEFUL TO DETERMINE THE FIBRE/PARTICLE TOXICITY AND ADVERSE OUTCOME. METHODS: HUMAN BRONCHIAL EPITHELIAL CELLS (16HBE) WERE TREATED WITH A LOW AND NON-CYTOTOXIC DOSE (0.25 MICROG/ML) OF MULTI-WALLED CARBON NANOTUBES (MWCNTS-NM400) OR SINGLE-WALLED CARBON NANOTUBES (SWCNTS-SRM2483) AND 0.05 MICROG/ML AMOSITE (BROWN) ASBESTOS FOR THE COURSE OF FOUR WEEKS (SUB-CHRONIC EXPOSURE). AFTER THIS TREATMENT, THE CELLS WERE FURTHER INCUBATED (WITHOUT PARTICLE/FIBRE) FOR TWO WEEKS, ALLOWING RECOVERY FROM THE EXPOSURE (RECOVERY PERIOD). NUCLEAR DEPOSITIONS OF THE CNTS WERE ASSESSED USING FEMTOSECOND PULSED LASER MICROSCOPY IN A LABEL-FREE MANNER. DNA METHYLATION ALTERATIONS WERE ANALYSED USING MICROARRAYS THAT ASSESS MORE THAN 850 THOUSAND CPG SITES IN THE WHOLE GENOME. RESULTS: AT NON-CYTOTOXIC DOSES, CNTS WERE NOTED TO BE INCORPORATED WITH IN THE NUCLEUS AFTER A FOUR WEEKS PERIOD. EXPOSURE TO MWCNTS INDUCED A SINGLE HYPOMETHYLATION AT A CPG SITE AND GENE PROMOTER REGION. NO CHANGE IN DNA METHYLATION WAS OBSERVED AFTER THE RECOVERY PERIOD FOR MWCNTS. EXPOSURE TO SWCNTS OR AMOSITE INDUCED HYPERMETHYLATION AT CPG SITES AFTER SUB-CHRONIC EXPOSURE WHICH MAY INVOLVE IN 'TRANSCRIPTION FACTOR ACTIVITY' AND 'SEQUENCE-SPECIFIC DNA BINDING' GENE ONTOLOGIES. AFTER THE RECOVERY PERIOD, HYPERMETHYLATION AND HYPOMETHYLATION WERE NOTED FOR BOTH SWCNTS AND AMOSITE. HIPPOCALCINLIKE 1 (HPCAL1), PROTEASE SERINE 3 (PRSS3), KALLIKREIN-RELATED PEPTIDASE 3 (KLK3), KRUPPEL LIKE FACTOR 3 (KLF3) GENES WERE HYPERMETHYLATED AT DIFFERENT TIME POINTS IN EITHER SWCNT-EXPOSED OR AMOSITE-EXPOSED CELLS. CONCLUSION: THESE RESULTS SUGGEST THAT THE SPECIFIC SWCNT (SRM2483) AND AMOSITE FIBRES STUDIED INDUCE HYPO- OR HYPERMETHYLATION ON CPG SITES IN DNA AFTER VERY LOW-DOSE EXPOSURE AND RECOVERY PERIOD. THIS EFFECT WAS NOT SEEN FOR THE STUDIED MWCNT (NM400). 2020