Benzo[a]pyrene Modulation of Acute Immunologic Responses in Red Sea Bream Pretreated with Lipopolysaccharide Jun Bo, Singaram Gopalakrishnan, Dan-Qing Fan, Harikrishnan Thilagam, Hai-Dong Qu, Nai Zhang, Fang-Yi Chen, Ke-Jian Wang State Key Laboratory of Marine Environmental Science, Department of Environmental Sciences and Engineering, College of Oceanography and Environmental Science, Xiamen University, Xiamen, Fujian 361005, People’s Republic of China Received 25 October 2011; revised 26 February 2012; accepted 27 February 2012 ABSTRACT: The effects of polycyclic aromatic hydrocarbons (PAHs) have been reported to modulate the immune response in aquatic animals, but the collected information of their effects on fish immunity is so far ambiguous. This study demonstrated that Benzo[a]pyrene (BaP) exposure altered the expression pat- tern of an antimicrobial peptide hepcidin (PM-hepc) gene and the activities of some immune-associated parameters in the lipopolysaccharide (LPS)-challenged red sea bream (Pagrus major). It was observed that LPS could increase respiratory burst, lysozyme and antibacterial activity in P. major . However when the P. major was exposed to different concentrations of BaP (1, 4, or 8 lgL 21 ) for 14 days and then chal- lenged with LPS there was no significant change in the lysozyme and antibacterial activity. It was further observed that LPS could induce the PM-hepc mRNA expression at 3, 6, and 12-h post-LPS challenge. However, when P. major was exposed first to BaP for 14 days and then challenged with LPS, the expres- sion of PM-hepc mRNA was delayed in the liver until 24 h and not significantly induced until 48 and 96 h. The mRNA expression pattern was completely different from that only with LPS challenge, showing that BaP exposure changed the PM-hepc mRNA expression pattern of fish with LPS challenge. This study demonstrated that BaP exposure can weaken or inhibit the induction of lysozyme and antibacterial activity in the LPS-challenged P. major; conversely BaP exposure could enhance the mRNA expression of PM- hepc gene, indicating that the effect of BaP has different modulatory mechanism on hepcidin genes and immune-associated parameters. # 2012 Wiley Periodicals, Inc. Environ Toxicol 00: 000–000, 2012. Keywords: Pagrus major; benzo[a]pyrene; immunomodulation; lipopolysaccharide; hepcidin INTRODUCTION The teleosts possess innate and acquired immunity even if they belong to the most primitive vertebrates. The teleosts mainly depend on the innate immune system because the acquired immune system is not perfectly developed. In higher vertebrates the immune system show high sensitivity to the xenobiotics present in the environment (Inadera, 2006) and the host immune system establishes different de- fensive means against the exogenous hazard such as induced production of antimicrobial peptide and generation of reactive oxygen species (ROS). It is worthwhile to note that ROS-mediated antimicrobial activity is powerful in host defense system but overproduction of ROS could be deleterious to the host homeostasis, thus its production must be tightly controlled by the host (Jiang et al., 2007; Lushchak, 2011). Though the studies revealed hemocyanin and hemoglobin could produce ROS in both invertebrates Correspondence to: K.-J. Wang; e-mail: wkjian@xmu.edu.cn Contract grant sponsor: Program for Changjiang Scholars and Innova- tive Research Team in University. Contract grant numbers: PCSIRT, IRT0941 Contract grant sponsor: National High Technology Research and Development Program of China. Contract grant number: 2007AA091406 Contract grant sponsor: Minjiang Scholar Program. Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/tox.21777  C 2012 Wiley Periodicals, Inc. 1