Time-course recovery of estrogen-responsive genes of a cichlid fish exposed to waterborne octylphenol

GENOVESE, G.; REGUEIRA, M.; PIAZZA, Y.; TOWLE, D.; MAGGESE, M. C.; LO NOSTRO, F.

AQUATIC TOXICOLOGY

ELSEVIER SCIENCE BV

Año: 2012 vol. 114 p. 1 - 13

0166-445X

The aim of this study was to describe a time-course of estrogen-induced gene expression, corresponding plasma proteins and histological alterations after cessation of octylphenol (OP) exposure of Cichlasoma dimerus, to test differential responses of biomarkers suitable for environmental monitoring. Male fish were exposed to 150 µg/L OP for 28 days, and further transferred to OP-free water aquaria for 1, 3, 7, 14, 21 and 28 days. Blood and mucus samples were obtained in order to analyze vitellogenin (VTG) and zona pellucida (ZP) proteins; liver samples were used for gene expression, tissue damage of the liver, and further recovery of all the analyzed endpoints. Partial sequences of C. dimerus VTG and Na+/K+-ATPase (putative housekeeping gene) were obtained. Comparison with VTGs of several teleosts supports that the partial sequence obtained for C. dimerus belongs to VTGAb type. ZP and VTG expression was highly up-regulated by OP. Bands of 62, 52 y 50 kDa for ZP and 140, 103, 75 and 64 kDa for VTG, were detected after 28 days of OP exposure in plasma and mucus samples. After transference of treated fish to clean water, ZP bands in plasma disappeared rapidly (day 3), while VTG bands decreased gradually; no bands were detected on day 28 of recovery. Similarly, ZPB transcripts returned abruptly to background levels (day 3) sooner than ZPC (day 7) or VTG ones (day 14). Livers from OP treatment fish showed tissue disarrangement, hepatocytes with eccentric and euchromatic nuclei, and intense perinucleolar basophilia. After the recovery period, these changes were still evident though less pronounced; accounting for irreversibility of tissue damage or requirement of longer period of depuration. The present results confirm that for biochemical and molecular biomarkers such as induction of female proteins in male fish exposed to OP, complete recovery is achieved after adequate time of depuration (28 days). Male ZPB expression reflects recent exposure to estrogenic contaminants, while VTG may reveal past exposures. The combination of biomarkers with different temporal responses such as C. dimerus ZPs and VTG provides a more trustworthy interpretation of pollution status.