Impact of Acrylamide on Calcium Signaling and Cytoskeletal Filaments in Testes From F344 Rat

Abstract

Acrylamide (AA) at high exposure levels is neurotoxic, induces testicular toxicity, and increases dominant lethal mutations in rats. RNA-sequencing in testes was used to identify differentially expressed genes (DEG), explore AA-induced pathway perturbations that could contribute to AA-induced testicular toxicity and then used to derive a benchmark dose (BMD). Male F344/DuCrl rats were administered 0.0, 0.5, 1.5, 3.0, 6.0, or 12.0 mg AA/kg bw/d in drinking water for 5, 15, or 31 days. The experimental design used exposure levels that spanned and exceeded the exposure levels used in the rat dominant lethal, 2-generation reproductive toxicology, and cancer bioassays. The time of sample collection was based on previous studies that developed gene expressionbased BMD. At 12.0 mg/kg, there were 38, 33, and 65 DEG (P value <.005; fold change >1.5) in the testes after 5, 15, or 31 days of exposure, respectively. At 31 days, there was a dose-dependent increase in the number of DEG, and at 12.0 mg/kg/d the top three functional clusters affected by AA exposure were actin filament organization, response to calcium ion, and regulation of cell proliferation. The BMD lower 95% confidence limit using DEG ranged from 1.8 to 6.8 mg/kg compared to a no-observed-adverseeffect-level of 2.0 mg/kg/d for male reproductive toxicity. These results are consistent with the known effects of AA on calcium signaling and cytoskeletal actin filaments leading to neurotoxicity and suggest that AA can cause rat dominant lethal mutations by these same mechanisms leading to impaired chromosome segregation during cell division.

Mode of action-based risk assessment of genotoxic carcinogens

“…Instead, pronounced effects on calcium signalling and on cytoskeletal functions were observed in the thyroid, a tumour target organ in the male rat (Chepelev et al 2017). Under the same experimental conditions, evidence for a similar MOA being operative in rat testes has been reported (Recio et al 2017). In vivo mutagenicity studies using the Pig-a gene mutation assay and the micronucleus test in F344 rats and in B6C3F1 mice under similar conditions gave negative to equivocal results.…”

“…Several toxicogenomic studies on rats and mice exposed to AA in a time-and dose-dependent manner were conducted (Chepelev et al 2017(Chepelev et al , 2018Recio et al 2017). The group performed mRNA gene expression profiling to develop a MOA and to calculate transcriptional BMDLs for the most sensitive pathways, comparing these with data derived from traditional (apical) cancer studies.…”

“…(3) evidence is accumulating from toxicogenomic studies arguing for MOAs other than genotoxicity. This applies especially to the target organs of AA in rodent carcinogenicity studies, such as the thyroid, the testes, and the Harderian gland, where pronounced effects on calcium signalling and on cytoskeletal functions have been observed, but no compelling support for a genotoxic or hormonal MOA was found (Chepelev et al 2017(Chepelev et al , 2018Recio et al 2017).…”

Dietary Acrylamide and the Risks of Developing Cancer: Facts to Ponder

“…A recent study correlated calcium signaling and cytoskeletal filaments to genotoxic effects of AA in testes using F344 rats ( 53 ). Similar to this finding, existing literature implicates calcium signaling with several types of cancers ( 54 ).…”

Revisiting the evidence for genotoxicity of acrylamide (AA), key to risk assessment of dietary AA exposure

“…Several toxicogenomic studies in rodents exposed up to relatively high doses of AA were conducted and gene expression profiling was performed to approach elucidation of key MOA(s) (Chepelev et al 2017 , 2018 ; Recio et al 2017 ). They are of interest because they address potential MOAs in the main rodent target tissues of AA-induced neoplastic changes, the thyroid, the testes, and the Harderian gland.…”