title: Manganese induced immune suppression of the lobster, Nephrops norvegicus.
abstract: Manganese (Mn) is one of the most abundant elements on earth, particularly in the soft bottom sediments of the oceans. As a micronutrient Mn is essential in the metabolic processes of organisms. However, at high concentrations the metal becomes a neurotoxin with well-documented effects. As a consequence of euthrophication, manganese is released from bottom sediments of coastal areas and the Norway lobsters, Nephrops norvegicus, can experience high levels of bioavailable Mn(2+). Here, we present the first report showing that Mn also affects several fundamental processes in the mobilisation and activation of immunoactive haemocytes. When N. norvegicus was exposed to a realistic [Mn(2+)] of 20 mg l(-1) for 10 days 24.1 microg ml(-1) was recorded in the haemolymph. At this concentration the total haemocyte count was reduced by ca. 60%. By using BrdU as a tracer for cell division, it was shown that the proliferation rate in the haematopoietic tissue did not increase, despite the haemocytepenia. A gene coding for a Runt-domain protein, known to be involved in maturation of immune active haemocytes in a variety of organisms, was identified also in haemocytes of N. norvegicus. The expression of this gene was >40% lower in the Mn-exposed lobsters as judged by using a cDNA probe and the in situ hybridisation technique. In response to non-self molecules, like lipopolysaccharide (LPS), the granular haemocytes of arthropods are known to degranulate and thereby release and activate the prophenoloxidase system, necessary for their immune defence. A degranulation assay, tested on isolated granular haemocytes, showed about 75% lower activity in the Mn-exposed lobsters than that for the unexposed. Furthermore, using an enzymatic assay, the activation per se of prophenoloxidase by LPS was found blocked in the Mn-exposed lobsters. Taken together, these results show that Mn exposure suppressed fundamental immune mechanisms of Norway lobsters. This identifies a potential harm that also exists for other organisms and should be considered when increasing the distribution of bioavailable Mn, as has been done through recently introduced applications of the metal.
authors.affiliation: Department of Marine Ecology, Göteborg University, Kristineberg Marine Research Station, SE-450 34 Fiskebäckskil, Sweden. bodil.hernroth@kmf.gu.se
authors.forename: Bodil
authors.initials: B
authors.lastname: Hernroth
authors.forename: Susanne P
authors.initials: SP
authors.lastname: Baden
authors.forename: Kristina
authors.initials: K
authors.lastname: Holm
authors.forename: Tove
authors.initials: T
authors.lastname: André
authors.forename: Irene
authors.initials: I
authors.lastname: Söderhäll
mesh_terms: D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D001772:Blood Cell Count; D001973:Bromodeoxyuridine; D049109:Cell Proliferation / Q000187:drug effects; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins; D005786:Gene Expression Regulation / Q000187:drug effects*; D006434:Hemocytes / Q000187:drug effects; D007108:Immune Tolerance / Q000187:drug effects*; D017403:In Situ Hybridization; D008070:Lipopolysaccharides; D020149:Manganese Poisoning / Q000276:immunology*; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000378:metabolism; D008121:Nephropidae / Q000276:immunology*; D009659:North Sea; D009687:Nuclear Proteins; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014157:Transcription Factors
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D009687:Nuclear Proteins; D014157:Transcription Factors; C080833:run protein, Drosophila; D014442:Monophenol Monooxygenase; D001973:Bromodeoxyuridine