U-shaped responses of fish zona pellucida protein and vitellogenin gene expression after octylphenol waterborne exposure.

GENOVESE, G; MAGGESE, M. C.; GUERREñO, MARIANA; TOWLE, D. W.; LO NOSTRO, F. L.

Milan

Congreso; SETAC Europe 21st Annual Meeting; 2011

SETAC

The endocrine disrupting chemicals have become ubiquitous in the environment and affect development and physiology by interfering with normal endocrine functions of human and wildlife. Octylphenol (OP) is a degradation product of alkylphenol ethoxylate surfactants (mainly used in industrial applications, agrochemicals, cleaners among others) which can mimic natural estrogens and cause reproductive impairments. Our previous results showed that in the cichlid fish Cichlasoma dimerus, zona pellucida proteins (ZP) that form the eggshell, and vitellogenin (VTG) the precursor of egg yolk, are both synthesized by the liver of mature females under estrogenic control but are normally not produced by males. The aim of the present study was to assess the effect of environmentally relevant concentrations of OP on ZP and VTG gene expression in C. dimerus males, which were exposed to 0.15, 1.5, 15, and 150  µg/L OP for 28 days. The expression of a putative housekeeping gene, Na+/K+-ATPase, was measured. Estrogenized female livers were used for the standard curve to normalize data. Exposure of male fish to OP caused down-regulation of Na+/K+-ATPase expression except for the lowest concentration of OP. However, exposition to 0.15 and 150 µg/L OP caused significant up-regulation of both forms of ZP (â, ã) and VTG while the other two concentrations of OP (1.5 and 15 µg/L) caused minor non-significant effects. These U-shaped dose-response curves or hormesis provide new evidences for the need of risk assessment of toxicants with a wider dose range. Conventional way of risk assessment of low dose might not be accurate by simple extrapolation based on the traditional theory of the threshold or linearity. It has been suggested that U-shaped responses appear as an over compensatory response to maintain homeostasis or take place by the combined contribution of different receptor subtypes with different affinity, accessibility or signaling cascade. Our preliminary data support the latter explanation. The endocrine disrupting chemicals have become ubiquitous in the environment and affect development and physiology by interfering with normal endocrine functions of human and wildlife. Octylphenol (OP) is a degradation product of alkylphenol ethoxylate surfactants (mainly used in industrial applications, agrochemicals, cleaners among others) which can mimic natural estrogens and cause reproductive impairments. Our previous results showed that in the cichlid fish Cichlasoma dimerus, zona pellucida proteins (ZP) that form the eggshell, and vitellogenin (VTG) the precursor of egg yolk, are both synthesized by the liver of mature females under estrogenic control but are normally not produced by males. The aim of the present study was to assess the effect of environmentally relevant concentrations of OP on ZP and VTG gene expression in C. dimerus males, which were exposed to 0.15, 1.5, 15, and 150  µg/L OP for 28 days. The expression of a putative housekeeping gene, Na+/K+-ATPase, was measured. Estrogenized female livers were used for the standard curve to normalize data. Exposure of male fish to OP caused down-regulation of Na+/K+-ATPase expression except for the lowest concentration of OP. However, exposition to 0.15 and 150 µg/L OP caused significant up-regulation of both forms of ZP (â, ã) and VTG while the other two concentrations of OP (1.5 and 15 µg/L) caused minor non-significant effects. These U-shaped dose-response curves or hormesis provide new evidences for the need of risk assessment of toxicants with a wider dose range. Conventional way of risk assessment of low dose might not be accurate by simple extrapolation based on the traditional theory of the threshold or linearity. It has been suggested that U-shaped responses appear as an over compensatory response to maintain homeostasis or take place by the combined contribution of different receptor subtypes with different affinity, accessibility or signaling cascade. Our preliminary data support the latter explanation.