Manganese induced immune suppression of the lobster, Nephrops norvegicus

• 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 mug 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 c DNA 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 suppressiA 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.

Ämnesord

NATURVETENSKAP  -- Biologi -- Immunologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Immunology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Amino Acid Sequence

Analysis of Variance

Animals

Base Sequence

Blood Cell Count

Bromodeoxyuridine

Cell Proliferation/drug effects

Comparative Study

DNA Primers

DNA-Binding Proteins/genetics/metabolism

Drosophila Proteins

Gene Expression Regulation/*drug effects

Hemocytes/drug effects

Immune Tolerance/*drug effects

In Situ Hybridization

Lipopolysaccharides

Manganese Poisoning/*immunology

Molecular Sequence Data

Monophenol Monooxygenase/metabolism

Nephropidae/*immunology

North Sea

Nuclear Proteins

Research Support; Non-U.S. Gov't

Sequence Alignment

Sequence Analysis; DNA

Transcription Factors

manganese

Norway lobster

Nephrops norvegicus

arthropod

immunotoxicology

immune suppression

PROPHENOLOXIDASE-ACTIVATING SYSTEM

PACIFASTACUS-LENIUSCULUS

INSECT

IMMUNITY

ACCUMULATION

HYPOXIA

HEMOCYANIN

L.

RECOGNITION

PERFORMANCE

DISEASE

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