Biology subjects

Serradimigni, R.

Publications and source records attributed to Serradimigni, R..

3 recordsLinked to original sources

bioRxiv2024

Embryonic exposures to flame retardant tetrabromobisphenol A (TBBPA) disrupts dorsoventral patterning in zebrafish

Tetrabromobisphenol A (TBBPA), a widely used flame retardant in commercial products such as synthetic textiles, plastics, and electronics poses potential toxicity risks through indoor exposure. This study aims to leverage zebrafish as a model to study TBBPA impacts on zebrafish dorsoventral patterning--a process that lays the foundation of an embryos axial determination and localization of specific tissues and organs. Zebrafish embryos were exposed to varying concentrations of TBBPA (0-10 {micro}M) at either 0.75- or 6-hours post-fertilization (hpf) and phenotyped at 8 or 24 hpf. Following this, whole-mount immunohistochemistry (IHC) was conducted out to quantify various proteins important in the BMP signaling pathway, epithelial-to-mesenchymal transition (EMT) and ectoderm and mesoderm germ layers. Importantly, these assessments were done at environmentally relevant concentrations ranging down to nM and pM levels. Our data showed a significant concentration-dependent increase in ventralization phenotypes, marked by enlarged blood island area, coupled with a disruption of the ventral-to-dorsal gradient of pSMAD protein levels, indicating BMP signaling disruptions. Perturbations in epithelial-to-mesenchymal transition (EMT), as evidenced by changes in E- and N-cadherin expression and Snail2 transcription factor levels, indicated impaired cell migration on TBBPA exposures. We then interrogated if TBBPA impacts germ layers and structures derived from specific germ layers. We observed significant concentration-dependent changes in levels of Sox2 and Sox10- both indicators of neural crest cell formation and differentiation from the ectoderm. We also observed a significant reduction of Tbx16- a marker of paraxial mesodermal cells. Collectively, both these data show TBBPA-induced impact on germ layers. Finally, we examined specific cell types derived from ectoderm and mesoderm and showed TBBPA-induced inhibition of cartilage development (derived from ectodermal neural crest cells) and blood cell development (derived from mesodermal cells). Our findings collectively demonstrate that TBBPA-induced disruptions in early developmental signaling and dorsoventral patterning may contribute to systemic toxicity in zebrafish embryos. Importantly, we see these disruptions at environmentally relevant concentrations, reinforcing the importance of continued interrogation of TBBPA in targeting early embryogenesis.

pharmacology and toxicology↗

bioRxiv2024

Assessing mechanisms driving phenol isopropylated phosphate (IPP)- induced larval photomotor response deficits in zebrafish

Phenol isopropylated phosphates (IPP) are an additive organophosphate flame retardant (OPFR) which has been extensively used in furniture, electronics, automobiles, plastics, and childrens products to slow down the spread of fire. The processing and distribution of IPP-containing products have been prohibited but its continuous leaching from end use products has retained the concern of its toxicity. The present study was designed to evaluate IPP-induced developmental toxicity using zebrafish embryos. We first conducted range finding experiments with embryonic zebrafish exposures to 0-200 M IPP from 6 to 120 h post fertilization and found significant morphological impacts like pericardial edema, yolk sac edema and spinal curvature at higher concentrations. For behavioral readouts, we performed larval photomotor response (LPR) assay at sublethal concentrations and observed hypoactive locomotory behavior in exposed larvae. Following this, relying on secondary analyses of our whole embryo mRNA-seq data, we conducted-1) retinoic acid receptor (RAR) signaling assay and 2) DNA methylation assays. In vitro assay for RA receptors indicate that IPP significantly inhibits RAR, but not RAR{beta} and RAR{gamma}. Whole-mount immunohistochemistry for 5-methylcytosine and global DNA methylation assay showed significant IPP-induced hypermethylation in situ. We conducted IPP co-exposure studies with a methylome modifier 5-azacytidine (Aza-c a methylation inhibitor) or retinoic acid signaling activators to assess if LPR phenotypes were mitigated by co-exposures. Data showed that Aza-c co-exposures partially reversed IPP-induced LPR hypoactivity and DNA hypermethylation, co-exposure with retinoic acid as well as AM580 (an RAR activator) were not able to reverse IPP-induced hypoactivity. Finally, based on RNA-seq data, we hypothesized that IPP affects the development of brain and eyes. Firstly, we performed global DNA methylation in brain and eyes, but did not find any significant effects. Then, we conducted mRNA sequencing on dissected brains and eyes, and found 2 and 135 differentially expressed genes, respectively. Gene ontology revealed that IPP affect phototransduction, voltage gated ion channels, synaptic and neurotransmitter signaling. Collectively, our data shows that IPP induces morphological abnormalities and disrupts larval photo motor response, potentially through methylomic regulation. Finally, we observed that IPP affects gene expression within the developing eye, establishing synaptic transmission, vision and muscle contraction as a potential causative factor for LPR responses.

pharmacology and toxicology↗

bioRxiv2024

Flame retardant tetrabromobisphenol A (TBBPA) disrupts histone acetylation during zebrafish maternal-to-zygotic transition

3,3,5.5-Tetrabromobisphenol A (TBBPA) is a widely used brominated flame-retardant utilized in the production of electronic devices and plastic paints. The objective of this study is to use zebrafish as a model and determine the effects of TBBPA exposure on early embryogenesis. We initiated TBBPA exposures (0, 10, 20 and 40M) at 0.75 h post fertilization (hpf) and monitored early developmental events such as cleavage, blastula and epiboly that encompass maternal-to-zygotic transition (MZT) and zygotic genome activation (ZGA). Our data revealed that TBBPA exposures induced onset of developmental delays by 3 hpf (blastula). By 5.5 hpf (epiboly), TBBPA-exposed (10-20 M) embryos showed concentration-dependent developmental lag by up to 3 stages or 100% mortality at 40 M. Embryos exposed to sublethal TBBPA concentrations from 0.75-6 hpf and raised in clean water to 120 hpf showed altered larval photomotor response (LPR), suggesting a compromised developmental health. To examine the genetic basis of TBBPA-induced delays, we conducted mRNA-sequencing on embryos exposed to 0 or 40 M TBBPA from 0.75 hpf to 2, 3.5 or 4.5 hpf. Read count data showed that while TBBPA exposures had no overall impacts on maternal or maternal-zygotic genes, collective read counts for zygotically activated genes were lower in TBBPA treatment at 4.5 hpf compared to time-matched controls, suggesting that TBBPA delays ZGA. Gene ontology assessments for both time- and stage-matched differentially expressed genes revealed TBBPA-induced inhibition of chromatin assembly- a process regulated by histone modifications. Since acetylation is the primary histone modification system operant during early ZGA, we immunostained embryos with an H3K27Ac antibody and demonstrated reduced acetylation in TBBPA-exposed embryos. Leveraging in silico molecular docking studies and in vitro assays, we also showed that TBBPA potentially binds to P300- a protein that catalyzes acetylation- and inhibits P300 activity. Finally, we co-exposed embryos to 20 M TBBPA and 50 M n-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benzamide (CTPB) -a histone acetyltransferase activator that promotes histone acetylation- and showed that TBBPA-CTPB co or pre-exposures significantly reversed TBBPA-only developmental delays, suggesting that TBBPA-induced phenotypes are indeed driven by repression of histone acetylation. Collectively, our work demonstrates that TBBPA disrupts ZGA and early developmental morphology, potentially by inhibiting histone acetylation. Future studies will focus on mechanisms of TBBPA-induced chromatin modifications.

pharmacology and toxicology↗