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Nitric oxide generation by hemocytes of the mussel Mytilus galloprovincialis
I Gourdon1, M C Guérin, J Torreilles
1UMR 5098, CP 80, Université Montpellier II, 2 place E. Bataillon, 34095-Montpellier Cédex 5, France.
Abstract:
The phagocytic activity of Mytilus galloprovincialis hemocytes is thought to be associated with NADPH-oxidase activity of the plasma membrane, thus producing superoxide anions. Few studies, however, have been devoted to nitric oxide release by these haemocytes. We investigated NO generation in M. galloprovincialis in order to understand its role in the defensive mechanisms of these organisms. The presence of NO-synthase-like enzymatic activity in protein homogenates from M. galloprovincialis hemocytes was revealed by the conversion of radiolabelled L-arginine to L-citrulline. We observed partial inhibition of the luminol-dependent chemiluminescence of stimulated M. galloprovincialis hemocytes by both NO-synthase inhibitors and superoxide dismutase, indicating that peroxynitrite (which results from the reaction between nitric oxide and superoxide anions) partially mediated this chemiluminescence. Furthermore, we confirmed the production of nitric oxide by M. galloprovincialis by highlighting the nitric oxide-synthase-dependence of the nitrate and nitrite production of stimulated hemocytes.
Insights
Mussel hemocytes generate nitric oxide (NO), contributing to their immune defense. This study confirms NO production and its role alongside superoxide anions in mussel immune responses.
Area of Science:
- Marine Biology
- Immunology
- Biochemistry
Background:
- Mussel hemocyte phagocytosis is linked to NADPH-oxidase and superoxide anion production.
- Nitric oxide (NO) release by hemocytes remains understudied in Mytilus galloprovincialis.
Purpose of the Study:
- Investigate nitric oxide (NO) generation in M. galloprovincialis hemocytes.
- Elucidate the role of NO in the defensive mechanisms of these marine organisms.
Main Methods:
- Assessed NO-synthase-like activity via radiolabelled L-arginine to L-citrulline conversion.
- Measured luminol-dependent chemiluminescence inhibition using NO-synthase inhibitors and superoxide dismutase.
- Confirmed NO production by measuring nitrate and nitrite levels, dependent on NO-synthase activity.
Main Results:
- Demonstrated NO-synthase-like enzymatic activity in M. galloprovincialis hemocyte homogenates.
- Showed that peroxynitrite, formed from NO and superoxide, partially mediates hemocyte chemiluminescence.
- Confirmed NO production by stimulated hemocytes, dependent on NO-synthase.
Conclusions:
- M. galloprovincialis hemocytes produce nitric oxide (NO).
- NO, in conjunction with superoxide anions, plays a role in the immune defense mechanisms of mussels.
- Peroxynitrite formation is implicated in the chemiluminescence response of stimulated hemocytes.