ANTIOXIDANT PROTECTIVE MECHANISMS IN OVARIAN FOLLICLES
Our research aims to elucidate the mechanisms by which toxicants and ionizing radiation disrupt reproductive function and to uncover protective mechanisms that prevent reproductive dysfunction. Reactive oxygen species are produced during normal ovarian function, and they may also be produced as a result of toxicant metabolism. Our earlier work demonstrated a role for reactive oxygen species in mediating spontaneous apoptosis in follicles deprived of hormonal support and apoptosis caused by exposure to ovarian toxicants. We discovered that reactive oxygen species increased in ovarian follicles cultured without gonadotropin support prior to any increase in endpoints of apoptosis and that follicle stimulating hormone stimulated synthesis of the antioxidant glutathione (GSH) and suppressed the rise in reactive oxygen species. We further showed that GSH depletion in cultured follicles reversed the protective, suppressive effect of follicle stimulating hormone on reactive oxygen species and on apoptosis. This work provides evidence that the protective effects of follicle stimulating hormone are mediated in part via upregulation of GSH synthesis. We also showed that increased generation of reactive oxygen species is an early event in the induction of apoptosis in cultured follicles or granulosa cells by dimethylbenzanthracene, a polycyclic aromatic hydrocarbon pollutant, and by the anticancer drug cyclophosphamide and ionizing radiation. Furthermore, depletion of GSH potentiated and supplementation of GSH prevented dimethylbenzanthracene, cyclophosphamide, and radiation-induced apoptosis in follicles and granulosa cells. Together these results demonstrate a critical role for GSH in preventing reactive oxygen species initiated apoptosis in ovarian follicles.
To study the roles of GSH in the ovary in vivo, we turned to a mouse model that is genetically deficient in GSH synthesis due to deletion of the modifier subunit of glutamate cysteine ligase (Gclm), the rate-limiting enzyme in GSH synthesis. We discovered that Gclm null female mice have very low ovarian GSH concentrations, resulting in poor oocyte quality, early preimplantation embryonic mortality with small litter sizes, and accelerated onset of ovarian senescence.
We also discovered that Gclm deficiency potentiates the transplacental gonadotoxicity of the environmental pollutant benzo[a]pyrene (BaP). Prenatal exposure to BaP destroyed ovarian germ cells, accelerated reproductive senescence, and caused epithelial ovarian cancer in the female offspring, and Gclm null females were more sensitive than Gclm wild type littermates. Prenatal BaP also impaired spermatogenesis in the male offspring and again Gclm deficient embryos were more sensitive than wild type embryos, but we found that the fetal testis is less sensitive than the fetal ovary to BaP toxicity. We are continuing to investigate the interactions between genetic deficiencies in antioxidant capacity and toxicant exposure in ovarian toxicity, reproductive aging and ovarian cancer.
Our newest project investigates the effects of charged particles, which are components of space radiation, on the ovary. We found that charged iron particles rapidly induced DNA strand breaks, oxidative lipid and protein damage, and apoptosis in ovarian follicles leading to dose-dependent depletion of ovarian follicles and premature ovarian failure. Our results show that the ovary is exquisitely sensitive to charged iron and oxygen particles, with complete depletion of the ovarian follicle reserve by doses of 0.5 Gy and development of ovarian tumors later in life. Ongoing studies are further investigating the mechanisms by which charged particles destroy ovarian follicles and cause ovarian tumors.
- Glutathione Deficiency Sensitizes Cultured Embryonic Mouse Ovaries to Benzo[a]pyrene-Induced Germ Cell Apoptosis. Lim J, Luderer U. Toxicology and Applied Pharmacology. 2018; In press.
- Charged Iron Particles Are Potent Inducers of Epithelial Ovarian Tumors. Mishra B, Lawson GW, Ripperdan R, Ortiz L, Luderer U. Mishra B, Lawson GW, Ripperdan R, Ortiz L, Luderer U. Radiation Research. 2018; in press.
- Very Low Doses of Heavy Oxygen Ion Radiation Induce Apoptosis in Ovarian Follicles, Causing Premature Ovarian Failure. Mishra B, Ripperdan R, Ortiz L, Luderer U. Reproduction. 2017; 154(2): 123-133.
- Ovarian Effects of Prenatal Exposure to Benzo[a]pyrene: Roles of Embryonic and Maternal Glutathione Status. Luderer U, Myers MB, Banda M, McKim KL, Ortiz L, Parsons BL. Reproductive Toxicology. 2017; 69: 187-195.
- Transitions in Pregnancy Planning in Women Recruited for a Large Prospective Cohort Study. Luderer U, Li T, Fine JP, Hamman RF, Stanford JB, Baker D. Human Reproduction. 2017; 32(6): 1325-1333.
- Associations between Urinary Biomarkers of Polycyclic Aromatic Hydrocarbon Exposure and Reproductive Function in Women. Luderer U, Christensen F, Johnson WO, She J, Ip HSI, Zhou J, Alvaran J, Krieg EF Jr, Kesner JS. Environment International. 2017; 100: 110-120.
- Spatial Characterization of Bioenergetics and Metabolism of Primordial to Preovulatory Follicles in Whole Ex Vivo Murine Ovary. Cinco R, Digman MA, Gratton R, Luderer U. Biology of Reproduction. 2016; 95(6): 129, 1-12.
- Exposure to Charged Iron Particles Typical of Space Radiation Induces Premature Ovarian Failure in Mice. Mishra B., Ortiz L, Luderer U. Human Reproduction. 2016; 31(8): 1816-26.
- Greater Sensitivity of the Mouse Fetal Ovary than the Fetal Testis to Benzo[a]pyrene-Induced Germ Cell Death. Lim J, Kong W, Lu M, Luderer U. Toxicological Sciences. 2016. 152(2): 372-81.
- Concepts and Challenges in Cancer Risk Prediction for the Space Radiation Environment. Barcellos-Hoff MH, Blakely E, Burma S, Fornace AJ, Gerson S, Hlatky L, Kirsch D, Luderer U, Shay J, Wang Y, Weil M. Life Sciences in Space Research. 2016; 6: 92-103.
- Glutamate Cysteine Ligase Modifier Subunit (Gclm) Null Mice Have Increased Ovarian Oxidative Stress and Accelerated Age-Related Ovarian Failure. Lim J, Nakamura BN, Mohar I, Kavanagh TJ, Luderer U. Endocrinology. 2015; 156(9):3329-3343.
- Luderer U. 2104. Ovarian Toxicity from Reactive Oxygen Species. In: G. Litwack (Ed in Chief), Vitamins and Hormones, Volume 94: 99-127, Endocrine Disrupters. Academic Press/Elsevier.
- In Utero Exposure to Benzo[a]pyrene Increases Adiposity and Causes Hepatic Steatosis in Female Mice, and Glutathione Deficiency Is Protective. Ortiz L, Nakamura BN, Li X, Blumberg B, Luderer U. Toxicology Letters. 2013; 223(2): 260-267. doi:10.1016/j.toxlet.2013.09.017 Reprinted in Toxicology Letters 230(2): 314-321, special issue “Environmental Contaminants and Target Organ Toxicities.”
- Glutathione-Deficient Mice have Increased Sensitivity to Transplacental Benzo[a]pyrene-Induced Premature Ovarian Failure and Ovarian Tumorigenesis.Lim J, Lawson GW, Nakamura BN, Ortiz L, Hur JA, Kavanagh TJ, Luderer U. Cancer Research. 2013; 73(2):1-10. DOI: 10.1158/0008-5472.CAN-12-3636
- Effects of Gestational and Lactational Exposure to Heptachlor Epoxide on Age at Puberty and Reproductive Function in Men and Women. Luderer U, Kesner JS, Fuller JM, Krieg EF Jr, Meadows JW, Tramma SL, Yang H, Baker D. Environmental Research. 2013; 121: 84-94. DOI: 10.1016/j.envres.2012.11.001
- Oxidative Damage Increases and Antioxidant Gene Expression Decreases with Aging in the Mouse Ovary. Lim J, Luderer U. Biology of Reproduction. 2011; 84: 775-782
- Increased sensitivity to testicular toxicity of transplacental benzo[a]pyrene exposure in male glutamate cysteine ligase modifier subunit knockout (Gclm-/-) mice. Nakamura BN, Mohar I, Lawson GW, Hoang YD, Cortés MM, Ortiz L, Patel R, Rau BA, McConnachie L, Kavanagh TJ, Luderer U. Toxicological Sciences. 2012; 126(1): 227-241. DOI: 10.1093/toxsci/kfs017.
- Roles of Reactive Oxygen Species and Antioxidants in Ovarian Toxicity. Devine PJ, Perreault SD, Luderer U. Biology of Reproduction. 2012; 86(2): 27, 1-10. DOI: 10.1095/biolreprod.111.095224
- Lack of Maternal Glutamate Cysteine Ligase Modifier Subunit (Gclm) Decreases Oocyte Glutathione Concentrations and Disrupts Preimplantation Development in Mice. Nakamura BN, Fielder TJ, Hoang YD, Lim J, McConnachie LA, Kavanagh TJ, Luderer U. Endocrinology. 2011; 152: 2806-2815
- Knockout of the Transcription Factor Nrf2 Disrupts Spermatogenesis in an Age-Dependent Manner. Nakamura BN, Lawson G, Chan JY, Banuelos J, Cortés MM, Hoang YD, Ortiz L, Rau BA, Luderer U. 2010, Free Radical Biology and Medicine. 49:1368-1379.
- Follicle-Stimulating Hormone and Estradiol Interact to Stimulate Glutathione Synthesis in Rat Ovarian Follicles and Granulosa Cells. Hoang YD, Nakamura BN, Luderer U. 2009 Biology of Reproduction. 81:636-646.
- Overexpression of Glutamate Cysteine Ligase Protects Human COV434 Granulosa Tumor Cells against Oxidative and Gamma-Radiation Induced Cell Death. Cortes-Wanstreet MM, Giedzinski E, Limoli CL, Luderer U. 2009 Mutagenesis 24:211-224
- Induction of Apoptosis by 9,10-Dimethyl-1,2-benzanthracene (DMBA) in Cultured Preovulatory Rat Follicles Is Preceded by a Rise in Reactive Oxygen Species and Is Prevented by Glutathione.Tsai-Turton M, Nakamura BN, Luderer U. Biology of Reproduction. 2007, 77: 442-451.
- Cyclophosphamide-Induced Apoptosis in COV434 Human Granulosa Cells Involves Oxidative Stress and Glutathione Depletion. Tsai-Turton M, Luong BT, Tan Y, Luderer U. Toxicological Sciences. 2007 98: 216-230.
- Opposing Effects of Glutathione Depletion and FSH on Reactive Oxygen Species and Apoptosis in Cultured Preovulatory Rat Follicles. Tsai-Turton M, Luderer U. Endocrinology. 2006, 147: 1224-1236.
- Minimal Ovarian Upregulation of Glutamate Cysteine Ligase Expression in Response to Suppression of Glutathione by Buthionine Sulfoximine. Hoang YD, Avakian AP, Luderer U. Reproductive Toxicology. 2006, 21:186-196.
- Gonadotropin Regulation of Glutamate Cysteine Ligase Catalytic and Modifier Subunit Expression in the Rat Ovary is Subunit and Follicle Stage-Specific. Tsai-Turton M, Luderer U. American Journal of Physiology Endocrinology and Metabolism. 2005, 289: E391-E402.
- Effects of Occupational Solvent Exposure on Reproductive Hormone Concentrations and Fecundability in Men. Luderer U, Bushley, A, Stover, BD, Bremner WJ, Faustman EM, Takaro TK, Checkoway H, Brodkin CA. American Journal of Industrial Medicine. 2004, 46:614-626
- Gestational and Lactational Exposure to Heptachlor Does Not Alter Reproductive System Development in Rats. Lawson G, Luderer U. Veterinary and Human Toxicology. 2004, 46:113-118.
- Effects of cyclophosphamide and buthionine sulfoximine on ovarian glutathione and apoptosis. Lopez SG, Luderer U. Free Radical Biology and Medicine. 2004, 36:1366-1377.