Acute Exposure to a Common Organic UV Filter Does Not Alter the mRNA of Gonadal Estrogen or Growth Hormone Receptors in Mozambique Tilapia (Oreochromis mossambicus) In Vitro

Abstract

Background/objectives: Organic UV filters are chemical compounds that are commonly used in sunscreen products to absorb UV radiation from the Sun. To date, the filters have been detected in aquatic environments worldwide, as well as in aquatic organisms, including fish and coral. Hydroxy-4-methoxybenzophenone (BP-3) is a common organic UV filter and it is well documented to be among the filters that are detectable worldwide in water samples and aquatic organisms. Long-term exposure in vivo studies have demonstrated that high doses of BP-3 can cause endocrine-disrupting effects in aquatic organisms.

Methods: Using gonadal cell culture and quantitative RT-PCR, our study aimed to ascertain the effect of environmentally relevant doses of BP-3 (detected in aquatic systems) on the gene expression of reproductive targets, estrogen and growth hormone receptors (ERs and GHRs), in Mozambique tilapia (Oreochromis mossambicus) after an acute 24 h treatment.

Results/conclusions: Our study is the first to use an in vitro design to investigate the mechanism of the action of BP-3 on gonadal tissue in fish. Our results show that BP-3 does not induce gene regulation directly on the gonads of tilapia at doses that are comparable to what is detectable in aquatic environments after 24 h. We do verify, as seen in other teleost species, homologous regulation of ERβ in male tilapia gonadal tissue.

Keywords: Oreochromis mossambicus; bioaccumulation; endocrine disruptor; estrogen receptor; growth hormone receptor; oxybenzone; recreational waters; wastewater processing plant.

Figure 1

In vitro treatment of BP-3 for 24 h does not alter mRNA gene expression in tilapia (Oreochromis mossambicus) gonad tissue of (A) ERα, (B) ERβ, or (C) GHR. Gonadal tissue was cultured and treated with 0 µg/L, 0.1 µg/L, 1.0 µg/L, 10 µg/L, or 100 µg/L BP-3 for 24 h at 25 °C (n = 5 for each treatment group). Expression levels were determined by quantitative real-time PCR (qPCR) and are presented relative to the internal control gene (β-actin), with respect to control (mean ± SD).

Figure 2

In vitro treatment of 20 μg/L E2 causes increased mRNA gene expression of ERβ in tilapia (Oreochromis mossambicus) testes, but not ovaries. Gonadal tissue was cultured and treated with 20 μg/L E2 for 24 h at 25 °C and mRNA levels of (A) ERα, (B) ERβ, and (C) GRH were determined by quantitative real-time PCR (qPCR). Expression is presented relative to the internal control gene (β-actin), with respect to control (mean ± SD; * denotes statistical significance with t-test p < 0.05, n = 5).