title: Long duration exposure to cadmium leads to increased cell survival, decreased DNA repair capacity, and genomic instability in mouse testicular Leydig cells.
abstract: Epidemiological and experimental studies have shown that cadmium is carcinogenic to human and experimental animals, however, the mechanism of cadmium-induced carcinogenesis is not clear. The aberrant expression of cell cycle and DNA repair genes resulting in increased cell proliferation and genomic instability are the characteristic features of cancer cells. The purpose of this study was to determine if exposure to cadmium can perturb cell proliferation/survival and causes genomic instability in TM3 cells, a mouse testicular Leydig cell line. The results of this study revealed that short-duration exposure to lower doses of cadmium significantly increase the growth of TM3 cells, whereas, higher doses are toxic and cause cell death. The long duration exposure to higher doses of cadmium, however, results in increased cell survival and acquisition of apoptotic resistance. Gene expression analysis by real-time PCR revealed increased expression of the anti-apoptotic gene Bcl-2, whereas decreased expression of pro-apoptotic gene Bax. Decreased expression of genes for maintenance of DNA methylation, DNMT1, and DNA repair, OGG1 and MYH, was also observed in cells exposed to cadmium for 24h. The random amplified polymorphic DNA (RAPD) assay revealed genomic instability in cells with chronic exposure to cadmium. The findings of this study indicate that mouse testicular Leydig cells adapt to chronic cadmium exposure by increasing cell survival through increased expression of Bcl-2, and decreased expression of Bax. The increased proliferation of cells with genomic instability may result in malignant transformation, and therefore, could be a viable mechanism for cadmium-induced cancers.
authors.affiliation: Department of Biology, Texas Southern University, 3100 Cleburne Avenue, Houston, TX 77004, United States. kamaleshwar28@gmail.com
authors.forename: Kamaleshwar P
authors.initials: KP
authors.lastname: Singh
authors.forename: Ragini
authors.initials: R
authors.lastname: Kumari
authors.forename: Christina
authors.initials: C
authors.lastname: Pevey
authors.forename: Desiree
authors.initials: D
authors.lastname: Jackson
authors.forename: James W
authors.initials: JW
authors.lastname: DuMond
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019256:Cadmium Chloride / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics; D045647:DNA Glycosylases / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D042822:Genomic Instability / Q000187:drug effects*; D007985:Leydig Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000235:genetics
chemical_list: D002273:Carcinogens; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; D045647:DNA Glycosylases; C485990:Ogg1 protein, mouse; D019256:Cadmium Chloride