Effects of the antidepressant, fluoxetine, on immune parameters of the clam Venerupis philippinarum

Pharmaceuticals and personal care products (PPCPs) are a large group of substances used either by human for personal health and cosmetic reasons or by agribusiness to enhance growth or health of livestock. PPCPs are produced in large quantities and comprise numerous chemicals, including prescriptible drugs, veterinary drugs, diagnostic agents, fragrances, lotions, and cosmetics. Due to human activities, residues from both pharmaceutical manufacturing and hospitals, illicit drug use, veterinary drug use and agribusiness, large quantities of PPCPs enter aquatic environments. Among pharmaceuticals, fluoxetine (a selective serotonin reuptake inhibitor) is an antidepressant commonly used for the treatment of depression and other psychological disorders. Despite its wide use, there is lack of information about the effects of fluoxetine on bivalve immune parameters. In the present study, the effects of fluoxetine on some important immune parameters of the clam Venerupis philippinarum were evaluated for the first time. Clams (25 per concentration) were exposed for 7 days to differing fluoxetine concentrations (0, 1, 5, 25, 125, 625 mg/L), and haemolymph was collected from the anterior adductor muscle. Eight pools of haemolymph (from 3 bivalves each) were prepared for each experimental condition, and total haemocyte count (THC), Neutral Red uptake (NRU), lysozyme activity in cell-free haemolymph (CFH) and haemocyte proliferation were measured. A significant increase in THC values was observed in clams exposed to 25 mg/L, with respect to controls. NRU decreased significantly in haemocytes of clams exposed to 1 and 5 mg/L, compared with controls, whereas NRU returned to control values in clams exposed to the highest fluoxetine concentrations. Haemocyte proliferation increased significantly in animals exposed to 25, 125 and 625 mg/L, with respect to controls. Conversely, no significant alterations were observed in CFH lysozyme activity. Although preliminary, the results obtained demonstrate that fluoxetine affected markedly immune parameters in clams, even at environmentally realistic concentrations.