Milken Institute School of Public Health Poster Presentations (Marvin Center & Video)

Title

The Effects of Glyphosate on Rat Sperm Mitochondria

Document Type

Poster

Abstract Category

Environmental and Occupational Health

Keywords

sperm, glyphosate, mtDNA

Publication Date

Spring 5-1-2019

Abstract

Background: Glyphosate is one of the most widely used pesticides in the world, with over 750 products available, including Roundup®; however, there is ongoing controversy around glyphosate's ill health effects. It has been classified by the International Agency for Research on Cancer (IARC) as probably carcinogenic to humans. IARC also concluded that there was “strong” evidence for genotoxicity, both for “pure” glyphosate and for glyphosate formulations. In addition, there are questions about its role as an endocrine disruptor, its differential effects across the lifespan, and its possible impact on sperm health. Glyphosate-based propriety formulations, such as Roundup®, contain unknown additives which may exacerbate these outcomes. This is especially relevant in light of decreasing sperm counts in recent decades. Objectives: We sought to evaluate the impacts of these chemicals on sperm by assessing damage to mitochondrial DNA. This method was chosen because mitochondria produce the ATP that is essential for sustaining sperm motility and for successful fertilization. Both structural and functional alterations in mitochondria have been found in sperm with abnormal motility. In addition, mitochondrial DNA copy number is emerging as an important biomarker for sperm quality and fertility. Methods: Epididymal sperm samples were obtained from Sprague-Dawley rats (n=54) after humane euthanasia. Eighteen animals were prenatally exposed and then orally dosed with glyphosate, 18 animals were prenatally exposed and then orally dosed with Roundup®, and 18 animals served as controls. After weaning, 8 animals per group were treated for 6 weeks and the remaining 10 animals per group for 13 weeks before euthanasia. Mitochondrial and genomic DNA damage and mitochondrial copy number were determined after extraction of total DNA from frozen sperm. LA-qPCR was performed to determine mitochondrial and genomic damage, presented in lesions per 10kb. Real-time PCR was performed to determine mitochondrial copy number, which was used to normalize damage data. Results/Discussion: On average, 4.97 ng/µl of total DNA were extracted per sample. Mitochondrial copy number averaged 100.14 for controls, 95.94 for glyphosate samples, and 95.36 for Roundup® samples. Statistical comparisons using the Kruskal-Wallis tests of mtDNA damage will be presented. We will be analyzing sperm DNA damage in animals dosed with glyphosate compared to controls and in those dosed with Roundup® compared to both the controls and those dosed with glyphosate.

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Presented at Research Days 2019.

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The Effects of Glyphosate on Rat Sperm Mitochondria

Background: Glyphosate is one of the most widely used pesticides in the world, with over 750 products available, including Roundup®; however, there is ongoing controversy around glyphosate's ill health effects. It has been classified by the International Agency for Research on Cancer (IARC) as probably carcinogenic to humans. IARC also concluded that there was “strong” evidence for genotoxicity, both for “pure” glyphosate and for glyphosate formulations. In addition, there are questions about its role as an endocrine disruptor, its differential effects across the lifespan, and its possible impact on sperm health. Glyphosate-based propriety formulations, such as Roundup®, contain unknown additives which may exacerbate these outcomes. This is especially relevant in light of decreasing sperm counts in recent decades. Objectives: We sought to evaluate the impacts of these chemicals on sperm by assessing damage to mitochondrial DNA. This method was chosen because mitochondria produce the ATP that is essential for sustaining sperm motility and for successful fertilization. Both structural and functional alterations in mitochondria have been found in sperm with abnormal motility. In addition, mitochondrial DNA copy number is emerging as an important biomarker for sperm quality and fertility. Methods: Epididymal sperm samples were obtained from Sprague-Dawley rats (n=54) after humane euthanasia. Eighteen animals were prenatally exposed and then orally dosed with glyphosate, 18 animals were prenatally exposed and then orally dosed with Roundup®, and 18 animals served as controls. After weaning, 8 animals per group were treated for 6 weeks and the remaining 10 animals per group for 13 weeks before euthanasia. Mitochondrial and genomic DNA damage and mitochondrial copy number were determined after extraction of total DNA from frozen sperm. LA-qPCR was performed to determine mitochondrial and genomic damage, presented in lesions per 10kb. Real-time PCR was performed to determine mitochondrial copy number, which was used to normalize damage data. Results/Discussion: On average, 4.97 ng/µl of total DNA were extracted per sample. Mitochondrial copy number averaged 100.14 for controls, 95.94 for glyphosate samples, and 95.36 for Roundup® samples. Statistical comparisons using the Kruskal-Wallis tests of mtDNA damage will be presented. We will be analyzing sperm DNA damage in animals dosed with glyphosate compared to controls and in those dosed with Roundup® compared to both the controls and those dosed with glyphosate.