Endocrine disruption and cytotoxicity of Glyphosate and Roundup in human JAr cells in vitro

Dao H Ho ,Fiona Young ,Vicki Edwards ,Danielle J Glynn

doi:10.15761/iptg.1000114

Dao H Ho , Fiona Young + Show 2 more

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https://doi.org/10.15761/iptg.1000114

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Abstract

The toxicity of the active molecule in herbicides has been used to determine safe concentrations, because other components are considered inert. Roundup, which contains the active molecule Glyphosate, was described as an endocrine disrupter because non-cytotoxic concentrations inhibited progesterone synthesis in vitro. Human chorioplacental JAr cells synthesise progesterone, and increase synthesis when stimulated by chorionic gonadotrophin (hCG), or the transduction molecule cAMP. JAr cells were exposed to two Roundup formulations, and compared with the same concentrations of glyphosate ± cAMP, or ± hCG for 1, 4, 24, 48 or 72h. The surviving viable cells were quantified using an MTT assay, and progesterone was measured in an ELISA. hCG and cAMP stimulated progesterone synthesis by cells in vitro as expected. In contrast to previous reports, JAr cell death preceded decreased progesterone synthesis, and steroidogenesis was unaffected by low, non-cytotoxic concentrations of Roundup or glyphosate. Roundup was more cytotoxic than glyphosate alone; the 24h EC50 was 16mM for glyphosate, but 0.008mM when glyphosate was in a 7.2g/L Roundup formulation. Significant cytotoxicity was caused by glyphosate in Roundup (p<0.01) after 24h, and cytotoxicity was observed in vitro after exposure toa range of concentrations comparable to the Australian Drinking Water Guidelines. Endocrine disruption effects were secondary to cytotoxicity. Roundup was more cytotoxic than the same concentration of glyphosate alone, indicating that the other constituents of the herbicide are not inert. There is a compelling need to conduct in vivo studies to characterise the toxicity of glyphosate in a Roundup formulation, to facilitate re-evaluation of existing public health guidelines.

Highlights

Endocrine disrupting compounds (EDCs) are defined by the U.S Environmental Protection Agency (EPA) as being “exogenous agents that interfere with synthesis, secretion, transport, metabolism, binding action, or elimination of natural blood-borne hormones that are present in the body.”
Once cholesterol is inside the mitochondria it is rapidly converted to pregnenolone by cytochrome P450 cholesterol side chain cleavage enzyme (P450scc), and pregnenolone is converted to progesterone by 3β-hydroxysteroid dehydrogenase (3β-HSD) [4,5]
The cytochrome P450 aromatase enzyme (P450arom), which produces estradiol 17 beta (E2), appears to be modulated by xenobiotics such as Roundup [6,7,8]. Both steroidogenic acute regulatory protein (StAR) and P450arom are upregulated by activation of the luteinising hormone/chorionic gonadotrophin receptor (LH /CG), which has cyclic adenosine monophosphate as an intracellular transduction molecule

Summary

Introduction

Endocrine disrupting compounds (EDCs) are defined by the U.S Environmental Protection Agency (EPA) as being “exogenous agents that interfere with synthesis, secretion, transport, metabolism, binding action, or elimination of natural blood-borne hormones that are present in the body.” The US Endocrine Society noted that key mechanisms of action for endocrine disruption include perturbation of the enzymatic pathways involved in steroid biosynthesis [1].The rate limiting step of steroid hormone synthesis is the uptake of cholesterol from the outer to the inner mitochondrial membrane, a process mediated by the steroidogenic acute regulatory protein (StAR) [2,3]. The cytochrome P450 aromatase enzyme (P450arom), which produces estradiol 17 beta (E2), appears to be modulated by xenobiotics such as Roundup [6,7,8]. Both StAR and P450arom are upregulated by activation of the luteinising hormone/chorionic gonadotrophin receptor (LH /CG), which has cyclic adenosine monophosphate (cAMP) as an intracellular transduction molecule. The administration of a cAMP analogue, dibutrylc AMP, to the steroidogenic MA10 cell line in vitro upregulated StAR protein and stimulated a four-fold increase in synthesis of the steroid hormone progesterone [3]

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