Sediment toxicity plays a fundamental role in the health of inland fish communities; however, the assessment of the hazard potential of contaminated sediments is not a common objective in environmental diagnostics or remediation. This study examined the potential of transcriptional endpoints investigated in zebrafish (Danio rerio) exposed to riverbed sediments in ecotoxicity testing. Embryo-larval 10-day tests were conducted on sediment samples collected from five sites (one upstream and four downstream of the city of Milan) along a polluted tributary of the Po River, the Lambro River. Sediment chemistry showed a progressive downstream deterioration in river quality, so that the final sampling site showed up to eight times higher concentrations of, for example, triclosan, galaxolide, PAH, PCB, BPA, Ni, and Pb, compared with the uppermost site. The embryo/larval tests showed widespread toxicity although the middle river sections evidenced worse effects, as evidenced by delayed embryo development, hatching rate, larval survival, and growth. At the mRNA transcript level, the genes encoding biotransformation enzymes (cyp1a, gst, ugt) showed increasing upregulations after exposure to sediment from further downstream sites. The genes involved in antioxidant responses (sod, gpx) suggested that more critical conditions may be present at downstream sites, but even upstream of Milan there seemed to be some level of oxidative stress. Indirect evidences of potential apoptotic activity (bcl2/bax < 1) in turn suggested the possibility of genotoxic effects. The genes encoding for estrogen receptors (erα, erβ1, erβ2) showed exposure to (xeno)estrogens with a progressive increase after exposure to sediments from downstream sites, paralleled by a corresponding downregulation of the ar gene, likely related to antiandrogenic compounds. Multiple levels of thyroid disruption were also evident particularly in downstream zebrafish, as for thyroid growth (nkx2.1), hormone synthesis and transport (tg, ttr, d2), and signal transduction (trα, trβ). The inhibition of the igf2 gene reasonably reflected larval growth inhibitions. Although none of the sediment chemicals could singly explain fish responses, principal component analysis suggested a good correlation between gene transcripts and the overall trend of contamination. Thus, the combined impacts from known and unknown covarying chemicals were proposed as the most probable explanation of fish responses. In summary, transcriptional endpoints applied to zebrafish embryo/larval test can provide sensitive, comprehensive, and timeliness information which may greatly enable the assessment of the hazard potential of sediments to fish, complementing morphological endpoints and being potentially predictive of longer studies.

中文翻译：

---

暴露于内分泌活跃河床沉积物的斑马鱼（斑马鱼）的胚胎/幼虫毒性和转录作用。

沉积物毒性对内陆鱼类群落的健康起着根本作用；然而，在环境诊断或修复中，评估受污染沉积物的潜在危害并不是一个共同的目标。这项研究检查了在生态毒性测试中暴露于河床沉积物的斑马鱼（斑马鱼）中转录终点的潜力。对沿波河（兰布罗河）受污染的五个支点（米兰市的一个上游和四个下游）收集的沉积物样本进行了幼虫期10天测试。沉积物化学显示河流质量在下游逐渐恶化，因此最终采样点的三氯生，galaxolide，PAH，PCB，BPA，Ni和Pb的浓度最高，是最高点的八倍。胚胎/幼虫试验显示出广泛的毒性，尽管中间河段显示出较差的影响，如延迟的胚胎发育，孵化率，幼虫存活和生长所证明。在mRNA转录水平上，编码生物转化酶（cyp1a，gst，ugt）的基因在暴露于来自其他下游位点的沉积物后显示出增加的上调。参与抗氧化反应的基因（sod，gpx）表明，下游部位可能存在更关键的条件，但即使在米兰上游，似乎也存在一定程度的氧化应激。潜在的凋亡活性的间接证据（bcl2 / bax <1）反过来提示了遗传毒性作用的可能性。编码雌激素受体的基因（erα，erβ1，erβ2）暴露于（异）雌激素后，暴露于下游位置的沉积物后逐渐增加，与此同时ar基因相应下调，这可能与抗雄激素化合物有关。甲状腺破坏的多个水平也很明显，尤其是在下游斑马鱼中，如甲状腺生长（nkx2.1），激素合成和运输（tg，ttr，d2）和信号转导（trα，trβ）。igf2基因的抑制作用合理地反映了幼虫的生长抑制作用。尽管没有一种沉积物化学物质可以单独解释鱼类的反应，但是主成分分析表明，基因转录物与总体污染趋势之间具有良好的相关性。因此，提出了来自已知和未知化学变质化学物质的综合影响，这是鱼类反应的最可能解释。