Hexavalent Chromium Induces Infertility in Rats by Elevating Oxidative Stress, DNA Double-Strand Breaks, Microtubule Disruption, and Aberrant Segregation of Chromosomes in the Metaphase-II Oocytes
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Environmental and occupational exposure to hexavalent chromium, Cr(VI), causes female reproductive failures and infertility. Cr(VI) is used in more than 50 industries and is a group-A carcinogen, mutagenic and teratogenic, and a male and female reproductive toxicant. Our previous findings indicate that Cr(VI) causes follicular atresia, trophoblast cell apoptosis, and mitochondrial dysfunction in metaphase II (MII) oocytes. However, the integrated molecular mechanism of Cr(VI)-induced oocyte defects are not understood. The current study investigates the mechanism of Cr(VI) in causing meiotic disruption of MII oocytes, leading to infertility in superovulated rats. Postnatal day (PND)-22 rats were treated with potassium dichromate (1 and 5 ppm) in drinking water from PND 22-29 and superovulated. MII oocytes were analyzed by immunofluorescence, and images were captured by confocal microscopy and quantified by Image Pro Plus software. Our data showed that Cr(VI) increased microtubule misalignment, missegregation of chromosomes, a bulged and folded actin cap, oxidative DNA and protein damage, increased DNA double-strand break, and DNA repair protein RAD51. Cr(VI) also induced incomplete cytokinesis and delayed polar body extrusion. Our study indicates that exposure to environmentally relevant doses of Cr(VI) caused severe DNA damage, distorted oocyte cytoskeletal proteins, and caused oxidative DNA and protein damage leading to infertility.
