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Manganese induced immune suppression of the lobster, Nephrops norvegicus
Hernroth, B.; Baden, S.P.; Holm, K.; Andre, T.; Söderhäll, I. (2004). Manganese induced immune suppression of the lobster, Nephrops norvegicus. Aquat. Toxicol. 70(3): 223-231. dx.doi.org/10.1016/j.aquatox.2004.09.004
In: Aquatic Toxicology. Elsevier Science: Tokyo; New York; London; Amsterdam. ISSN 0166-445X, more
Peer reviewed article  

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Keywords
    Arthropods; Arthropods; Immunology; Manganese; Nephrops norvegicus (Linnaeus, 1758) [WoRMS]; Marine

Authors  Top 
  • Hernroth, B.
  • Baden, S.P.
  • Holm, K.
  • Andre, T.
  • Söderhäll, I.

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 Mn2+. 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 [Mn2+] of 20 mg l-1 for 10 days 24.1 μg 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.

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