In vitro effects of arachidonic acid on immune functions of head kidney macrophages isolated from large yellow croaker (Larmichthys crocea)

The experiments were conducted to determine the effects of arachidonic acid (ARA) on macrophages isolated from large yellow croaker head kidney. After exposing to serum-free medium for 1 day, cultured cells were incubated in medium supplemented with graded levels of ARA (0, 5, 25, 100, 200 and 1000 mu M) in the form of fatty acid bovine serum albumin (FA-BSA) complex for 12 h, 24 h and 36 h, respectively. Cells treated with 0 mu M ARA (2% bovine serum albumin, BSA) were included as control at each incubation time. Following stimulation, cell viability, lipid peroxidation, secretory phopholipase A(2) (sPLA(2)) production and some immune parameters including phagocytosis, respiratory burst activity, prostaglandin E-2 (PGE(2)) and Interleukin 1 beta (IL-1 beta) production were examined. Results showed that cell viability decreased with prolonged exposure and increasing ARA concentration. Especially after 36 h, cell viability was significantly decreased by incubation with higher levels of ARA (200 and 1000 mu M) (P<0.01). In the meanwhile, higher levels of ARA (200 and 1000 mu M) caused a significant increase in the production of malondialdehyde (MDA) (P<0.05, P<0.01). Phagocytosis percentage (PP) values were significantly higher in treatments with 25 and 100 mu M ARA (P<0.05), but significantly lower in treatments with 1000 mu M ARA compared to the control group (P<0.01). Enhanced intracellular superoxide anion (O-2(-)) synthesis was found in cells treated with each level of ARA with an exception of 1000 mu M ARA (P>0.05). The significantly promoted production of sPLA(2) seemed to be irrelevant to increased ARA concentration, while PGE(2) production was significantly increased in an ARA dose dependent way (P<0.01). No pronounced effect on IL-1 beta production was observed between the control and ARA group, and levels of IL-1 beta in cell culture supernatant were fairly low (only approximately 6 pg/ml). These findings suggested that ARA could influence the immunity and physiological conditions of macrophages from head kidney of large yellow croaker in vitro. (C) 2011 Elsevier B.V. All rights reserved.