Proteomic and metabolomic analysis on the toxicological effects of Benzo[a]pyrene in pearl oyster Pinctada martensii

Highlights

• The high concentration of BaP (10 μg/L) mainly caused disturbances in osmotic regulation and energy metabolism in the digestive gland of P. martensii.

• Both concentrations of BaP (1 and 10 μg/L) induced significant proteome responses in energy metabolism, cytoskeleton, cell injury, oxidative stress and signal transduction.

Abstract

Benzo[a]pyrene (BaP) is one of the typical toxic polycyclic aromatic hydrocarbons (PAHs) that are widely present in marine environment. BaP has diverse toxic effects, including teratogenic, carcinogenic, mutagenic effects and so on, in various organisms. In this work, we focused on the differential proteomic and metabolomic responses in the digestive gland of pearl oyster Pinctada martensii exposed to two doses of BaP (1 and 10 μg/L). Metabolic responses revealed that the high dose of BaP (10 μg/L) mainly caused disturbances in osmotic regulation and energy metabolism in the digestive gland. Proteomic responses indicated that both doses of BaP induced disturbances in energy metabolism, cytoskeleton, cell injury, oxidative stress and signal transduction based on the differential proteomic biomarkers. Overall, these results demonstrated a number of potential biomarkers that were characterized by an integrated proteomic and metabolomic approach and provided a useful insight into the toxicological effects on pearl oyster P. martensii.

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in marine environments. The contaminations of PAHs in the marine environment can be derived from three main sources, including petrogenic, pyrogenic and diagenetic origin (Mostafa et al., 2009, Saha et al., 2009, Santacroce et al., 2015, Yim et al., 2014). Benzo[a]pyrene (BaP), a five-ring PAH, is one of the most discussed and studied members of PAHs, particularly because of its cytotoxic, mutagenic, and carcinogenic properties (Binelli et al., 2008, Juhasz and Naidu, 2000, Tung et al., 2014, Williams and Hubberstey, 2014). The previous researches demonstrated that BaP damaged DNA, effected aryl hydrocarbon receptor, nuclear protein, cytochrome (An et al., 2011, Pariseau et al., 2011; Yan et al., 2010). BaP can be metabolized to diverse exogenous metabolites, primarily the diol epoxides (Poirier and Beland, 1992). Akcha et al. (2000) measured enzymatic biomarker of BaP.

The traditional toxicological approaches focus on the measure of ordinary biomarkers, such as anti-oxidant enzymes activity or specifically expressed genes, to explore the toxic effects of environmental contaminants (Banni et al., 2014, Espinoza et al., 2012, Lozano et al., 2014). However, the use of single biomarkers related to contaminants may be limited by the lack of sensitivity and specificity (Campos et al., 2012). Therefore, a broad discovery of toxicological biomarkers at some levels, such as gene, protein and metabolite, can give a global view on the toxicological effects induced by the environmental contaminants in organisms (Ji et al., 2013a). Proteomics is an influential tool for describing complete proteomes at organelle, cell, organ or tissue levels. At the same time, it can also be used to compare proteomes under various environmental stresses (Ahsan et al., 2009, Lemos et al., 2010), to analyze the contaminant-induced toxicological effects and mechanisms (Wu et al., 2013a). Similar to proteomics, metabolomics can reveal the metabolic responses induced by pollutants through the comparative profiling of metabolomes in organisms (Ji et al., 2013b, Wu et al., 2005). Both proteomics and metabolomics are frequently used to describe the disturbance in metabolic pathways and corresponding enzymes and stress-responsive proteins induced by external stressors (Weckwerth, 2011, Wei et al., 2015a). It has a capability to better understand toxicological mechanisms of contaminants. Therefore, these two omics approaches could provide a potential view in environmental monitoring of environmental stressors, such as PAHs, using corresponding metabolite and protein biomarkers.

Bivalve mollusks are widely used as marine pollution bioindicators because of their sessile nature, filter-feeding habits and tolerance of pollutants (Campos et al., 2012, Ji et al., 2015a, Liu et al., 2014). The digestive gland tissue of mollusks is a significant digestive and immune organ in invertebrates functioning as innate immunity and detoxification (Canesi et al., 2010, Du et al., 2013). The pearl oyster Pinctada martensii is one of the most important commercial bivalve species widely distributed in tropic and subtropic marine coasts and is the main species for artificial pearl production (Shi et al., 2013). The pearl oyster can efficiently accumulate marine chemical compounds like PAHs due to its low metabolic rate and filter-feeding habit. Therefore, it can be used as a novel marine pollution indicator organism. To our knowledge, few studies have focused on the responses induced by PAHs as BaP in the pearl oyster P. martensii at protein and metabolite levels. In the present study, an integrated proteomic and metabolomic approach was used to elucidate the toxicological effects of BaP in P. martensii.