N,N' bis-(2-mercaptoethyl) isophthalamide induces developmental delay in Caenorhabditis elegans by promoting DAF-16 nuclear localization

Tao Ke; Félix Alexandre Antunes Soares; Abel Santamaría; Aaron B Bowman; Anatoly V Skalny; Michael Aschner

doi:10.1016/j.toxrep.2020.07.012

N,N' bis-(2-mercaptoethyl) isophthalamide induces developmental delay in Caenorhabditis elegans by promoting DAF-16 nuclear localization

Toxicol Rep. 2020 Jul 31:7:930-937. doi: 10.1016/j.toxrep.2020.07.012. eCollection 2020.

Authors

Tao Ke¹, Félix Alexandre Antunes Soares², Abel Santamaría³, Aaron B Bowman⁴, Anatoly V Skalny⁵, Michael Aschner¹

Affiliations

¹ Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, United States.
² Department of Biochemistry and Molecular Biology, Federal University of Santa Maria, Santa Maria, RS, Brazil.
³ Laboratorio de Aminoácidos Excitadores, Instituto Nacional de Neurología y Neurocirugía, 14269, Mexico City, Mexico.
⁴ School of Health Sciences, Purdue University, West Lafayette, IN 47907-2051, United States.
⁵ Yaroslavl State University, Sovetskaya St., 14, Yaroslavl 150000, Russia.

Abstract

N,N' bis-(2-mercaptoethyl) isophthalamide (NBMI) is a lipophilic thiol-containing agent that has high affinity for toxic metal ions, such as Hg²⁺, Pb²⁺, and Cd²⁺. Studies have shown that NBMI is a potent chelator of heavy metals, yet its potential toxicity in animals has yet to be determined. Using the model organism Caenorhabditis elegans (C. elegans), we show no significant change in worms' death rate or lifespan following NBMI treatment (10-1000 μM). However, NBMI treatment was associated with a significant developmental delay. To determine if the daf-2/age-1/daf-16 pathway is involved in NBMI toxicity, mRNA levels of these genes were assessed in worms treated with NBMI. Here, we found that while NBMI failed to significantly alter the expression of daf-16 or daf-2; age-1 was significantly downregulated by NBMI. Furthermore, NBMI significantly increased DAF-16 nuclear localization. Consistent with a role for this pathway in NBMI toxicity, the developmental arrest by NBMI was more prominent in the DAF-16 transgenic strain than in the wild type N2 strain. Moreover, in the mutant strains harboring null alleles of daf-16, NBMI had no effect on development. In addition, NBMI repressed the expression of detoxifying genes (skn-1, gst-4 and gcs-1). In summary, NBMI has a low developmental toxicity in the C. elegans model, and the nuclear translocation of DAF-16 is involved in the developmental effect of NBMI.

Keywords: C. elegans; Chelation; Developmental delay; Methylmercury.