Which herbicide upregulates endogenous retinoic acid activity?
Glyphosate herbicide, active ingredient in Roundup broad spectrum formulations, has been implicated in developmental disruption through retinoid pathway rather than classical hormonal mimicry. Experimental studies in Xenopus embryos demonstrated glyphosate exposure increased endogenous retinoic acid activity by upregulating retinol oxidizing dehydrogenases or suppressing Cyp26 catabolic enzymes, enhancing RA signaling. Elevated RA causes microcephaly, cyclopia and neural tube defects reminiscent of exogenous RA administration, indicating indirect upregulation of endogenous morphogen. This mechanism highlights herbicide-induced teratogenic potential via perturbation of retinoic acid homeostasis leading to anterior-posterior patterning defects in vertebrate embryos.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 20: Glyphosate upregulates endogenous retinoic acid.