Effect of thyroid hormone‐disrupting chemicals on swim bladder inflation and thyroid hormone‐related gene expression in Japanese medaka and zebrafish

Abstract

We compared the influence of thyroid hormone-disrupting chemicals (heptafluorobutanoic acid, PFBA and tris[1, phosphate, TDCPP) and thyroid hormone (3,3 0 ,5-triiodo-L-thyronine, T3) on swim bladder inflation and thyroid hormone-related gene expression in Japanese medaka and zebrafish. The swim bladder of most larvae had inflated at 4 h post hatching (hph) in Japanese medaka and at 48 hph in zebrafish in controls. In both fish species, the swim bladder inflation was inhibited in larvae exposed to PFBA (lowest observed effect concentration [LOEC] in medaka: 40 mg/L; in zebrafish: 80 mg/L), TDCPP (LOEC in medaka: 1 mg/L; in zebrafish: 0.5 mg/L), and T3 (no inhibition in Japanese medaka; LOEC in zebrafish: 7.5 μg/L). We also examined the influence of PFBA, TDCPP, and T3 on the expression of thyroid stimulating hormone subunit beta (tshβ) or thyroid hormone receptor alpha (trα) and beta (trβ). No changes were observed in the expression of genes after PFBA and TDCPP exposure; however, T3 exposure upregulated trα and trβ expression in both fish species. When the results were compared between Japanese medaka and zebrafish, swim bladder inflation in both species was found to be inhibited by exposure to thyroid hormone-disrupting chemicals. Our results show that inhibition of the swim bladder inflation at 4 hph in Japanese medaka and 48 hph in zebrafish is a potential indicator of thyroid hormone-disturbing activity of chemicals.

Effects of plasticizer diisobutyl adipate on the Japanese medaka (Oryzias latipes) endocrine system

“…According to Rehberger et al (2018), PTU exposure also reduced the number of follicles stained for T3. PTU exposure inhibited growth in Japanese medaka dose‐dependently, according to our earlier research (Horie, Nomura, Okamoto, et al, 2022). Growth inhibition was also induced by TDCs, such as perfluorooctane sulfonate (Du et al, 2009), tris(2‐butoxyethyl) phosphate (Zeng et al, 2018), and perfluorohexanoic acid (Zhang et al, 2022).…”

“…Swim bladder development and thyroid hormones are closely related. TDCs such as perfluorooctanoic acid (Godfrey et al, 2017(Godfrey et al, , 2019, tris[1,3-dichloro-2-propyl] phosphate (Godfrey et al, 2017;Horie, Nomura, Okamoto, et al, 2022), heptafluorobutanoic acid (Godfrey et al, 2017;Horie, Nomura, Okamoto, et al, 2022), and PTU (Horie et al, 2023;Stinckens et al, 2020) induced swim bladder noninflation in Japanese medaka and zebrafish. Furthermore, exposure to non-phthalate plasticizers such as DEHA (Horie, Nomura, Ramaswamy, et al, 2022a), ATBC (Horie, Yap, & Okamura, 2022), and DEHS (Horie, Nomura, Ramaswamy, et al, 2022b) also induced swim bladder non-inflation in Japanese medaka larvae.…”

“…The exposure period ranged from 4 haf to 1 day after hatching (1 dah). This exposure period was based on the results of our previous studies on the effects of chemicals on thyroid hormone‐related genes (Horie, Nomura, Okamoto, et al, 2022). At 1 dah, average hatching day, hatching rate, number of inflations of swim bladder, total body length, gene expression, and swimming behavior were observed.…”

Deiodinase 1 inhibition leading to increased mortality via reduced posterior swim bladder inflation

“…In the fathead minnow, the posterior chamber inflates around 6 dpf. In medaka, the swim bladder inflates around 2 hours post hatch (hatching occurs around 8 dpf) (Horie et al, 2022). Therefore this KE is only applicable to the embryonic life stage.…”

“…Interestingly, for those females that developed a swim bladder, exposure to methimazole and all halogenated chemicals with the exception of PFBA, resulted in larger swim bladders . Horie et al (2022) eludicated the timing of swim bladder inflation in medaka and compared effects on the swim bladder after exposure of zebrafish and medaka to PFBA and TDCPP. This KER is plausibly applicable across fish species with swim bladders, both physostomous and physoclistous.…”