Nucleic acid aptamers as interventions for developmental neurotoxicity - Lead (Pb) poisoning remains a pervasive public health problem in the U.S., causing neurotoxicity in children. Pb exposures are cumulative, and therapeutic elimination of Pb is not feasible for most affected people. Thus, prophylactic strategies are essential for protecting the health of exposed children. The neurotoxic effects of Pb are permanent, thereby adding significantly to the disease burden for affected children and communities. Therefore, there remains an urgent need for methods to protect children from cumulative lead exposure. Most Pb exposures are via ingestion from environmental sources including water, food, dust, or paint chips. A potential solution is to provide an effective prophylactic to protect individuals in high-risk environments from Pb ingestion. Aptamers are short stretches of nucleic acids (<100 nucleotide singlestranded DNA or RNA molecules) that bind specifically to a target molecule or ion. Pb-binding aptamers could be used to bind Pb in the gastrointestinal tract and thereby prevent absorption. However, the use of Pb-binding aptamers as prophylactics for Pb toxicity has not been previously reported. To assess the potential of an aptamer-based prophylactic strategy for Pb toxicity, we developed an in vivo Pb toxicity assay using the model organism C. elegans. Our recently published work (Anwar et al., 2024, New Biotechnol.) demonstrates that morphologic, behavioral, and reproductive phenotypes are adversely affected by Pb in our C. elegans model. Importantly, all three phenotypes are prevented in response to pre-exposure of the animals to Pb-binding aptamers. Our long-term goal is to develop highly efficient and cost-effective strategies for preventing Pb toxicity using aptamers. The objective of this R03 proposal is to determine the mechanism by which DNA and RNA aptamers protect C. elegans from neurotoxicity. We further seek to make initial an initial determination of the safety of aptamer-based Pb-chelation by performing toxicity assessments on the aptamers themselves. To attain our objective, we propose the following specific aims: Aim 1: Determine the mechanism of prophylactic effects of aptamers on developmental neurotoxicity caused by Pb. We will use our Pb-binding aptamers to specifically examine neurotoxicity in dopaminergic (DA) neurons in response to Pb, using the dat-1::GFP reporter system. Aim 2: Determine the mechanism of action and potential toxicity of Pb-binding aptamers. The mechanism of aptamer function will be investigated by measuring intracellular lead levels by atomic absorption spectroscopy. The role of complex secondary structures (G-quadruplexes, G4) that reportedly sequester lead ions will be assessed using competitive G4-binding small molecules. We will also critically assess the toxicity of the aptamers with survival, lifespan, and neurotoxicity assays. The proposed research addresses the lack of interventions for low level Pb poisoning in children, which is a clear public health gap.
