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Featured researches published by Arnaud Lacoste.


Applied and Environmental Microbiology | 2001

Stress and stress-induced neuroendocrine changes increase the susceptibility of juvenile oysters (Crassostrea gigas) to Vibrio splendidus

Arnaud Lacoste; Fabienne Jalabert; Shelagh K. Malham; Anne Cueff; Serge A. Poulet

ABSTRACT Oysters are permanently exposed to various microbes, and their defense system is continuously solicited to prevent accumulation of invading and pathogenic organisms. Therefore, impairment of the animals defense system usually results in mass mortalities in cultured oyster stocks or increased bacterial loads in food products intended for human consumption. In the present study, experiments were conducted to examine the effects of stress on the juvenile oysters resistance to the oyster pathogen Vibrio splendidus. Oysters (Crassostrea gigas) were challenged with a low dose of a pathogenic V. splendidus strain and subjected to a mechanical stress 3 days later. Both mortality andV.splendidus loads increased in stressed oysters, whereas they remained low in unstressed animals. Injection of noradrenaline or adrenocorticotropic hormone, two key components of the oyster neuroendocrine stress response system, also caused higher mortality and increased accumulation of V. splendidus in challenged oysters. These results suggest that the physiological changes imposed by stress, or stress hormones, influenced host-pathogen interactions in oysters and increased juvenile C. gigasvulnerability to Vibrio splendidus.


Developmental and Comparative Immunology | 2002

Stress-induced immune changes in the oyster Crassostrea gigas

Arnaud Lacoste; Shelagh K. Malham; Florence Gélébart; Anne Cueff; Serge A. Poulet

Information concerning the effect of stress on invertebrate immune functions are scarce. The present study investigated the consequences of a 15-min mechanical disturbance on immune parameters in oysters Crassostrea gigas. As indicated by noradrenaline and dopamine measurements, the mechanical disturbance caused a transient state of stress in oysters. The number of circulating hemocytes, the migratory and phagocytic activities and reactive oxygen species production of hemocytes were measured before, during and after application of the stressor. Results show that all immune functions were significantly downregulated during stress and a transient period of immunostimulation was observed 30-240 min after the end of the disturbance. Taken together, these results suggest that stress can exert a profound influence on oyster immune functions and they may explain why stress and the outbreak of disease are often linked in shellfish culture. Furthermore, the present study strongly suggests that checking the stress status of animals may be necessary to avoid biases when studying oyster immune responses in vivo.


Developmental and Comparative Immunology | 2001

Noradrenaline modulates hemocyte reactive oxygen species production via β-adrenergic receptors in the oyster Crassostrea gigas

Arnaud Lacoste; Shelagh K. Malham; Anne Cueff; Serge A. Poulet

Catecholamines (CA) are known to be present in the microenvironment of molluscan immunocytes. In the present study, experiments were conducted to determine the effects of noradrenaline (NA), the principal CA circulating in bivalve hemolymph, on the luminol-dependent chemiluminescence (CL) of oyster Crassostrea gigas hemocytes. Results show that NA had a dose-dependent inhibitory effect on the CL-response at the physiological concentration of 0.1 microM and above. The alpha-adrenoceptor agonist phenylephrine had no significant effect on the CL-response whereas the beta-adrenoceptor agonist isoproterenol mimicked the inhibitory effects of NA on the CL-response. The beta-adrenoceptor antagonist propanolol, but not the alpha-adrenoceptor antagonist prazosin, prevented the negative effects of NA on the CL-response. Taken together, these results show that beta-adrenergic receptors are present at the surface of oyster hemocytes and allow NA to down-regulate the CL-response.


Aquatic Living Resources | 2002

A first insight into stress-induced neuroendocrine and immune changes in the octopus Eledone cirrhosa

Shelagh K. Malham; Arnaud Lacoste; Florence Gélébart; Anne Cueff; Serge A. Poulet

A number of cephalopod species present substantial ecological and economical importance; however, data on the physiology of stress and on regulatory processes linking stress to immune defence against pathogens remain extremely scarce in these organisms. The present study examined the influence of a 5 min air exposure, a common perturbation associated with handling in aquaculture settings and fisheries, on neuroendocrine and immune parameters in the octopus Eledone cirrhosa. Measurements of circulating concentrations of noradrenaline and dopamine, two hormones that are released in the haemolymph during stress in bivalves and gastropods, showed that the 5 min air exposure represents a real stress to octopus. Indeed, blood levels of both hormones increased by about 2‐2.5-fold in stressed animals. Concomitantly, a significant decrease in the number of circulating haemocytes was observed, whereas haemocyte phagocytotic activity and superoxide anion production increased transiently between 5 and 60 min after the beginning of the stress. These results provide a first insight into the effects of stress on catecholamine levels and immune functions in cephalopods and suggest that stress and immunity may be associated in these organisms.


Marine Ecology Progress Series | 1997

The paradox of diatom-copepod interactions*

Syuhei Ban; Carolyn W. Burns; Jacques Castel; Yannick Chaudron; Epaminondas D. Christou; Rubén Escribano; Serena Fonda Umani; Stéphane Gasparini; Francisco GuerreroRuiz; Monica Hoffmeyer; Adrianna Ianora; Hyung-Ku Kang; Mohamed Laabir; Arnaud Lacoste; Antonio Miralto; Xiuren Ning; Serge A. Poulet; Valeriano Rodriguez; Jeffrey Runge; Junxian Shi; Michel Starr; Shin-ichi Uye; Yijun Wang


Journal of Experimental Zoology Part A: Comparative Experimental Biology | 2003

Evidence for a direct link between stress and immunity in the mollusc Haliotis tuberculata

Shelagh K. Malham; Arnaud Lacoste; Florence Gélébart; Anne Cueff; Serge A. Poulet


General and Comparative Endocrinology | 2001

Noradrenaline Modulates Oyster Hemocyte Phagocytosis via a β-Adrenergic Receptor–cAMP Signaling Pathway

Arnaud Lacoste; Shelagh K. Malham; Anne Cueff; Serge A. Poulet


General and Comparative Endocrinology | 2001

Stress-Induced Catecholamine Changes in the Hemolymph of the Oyster Crassostrea gigas

Arnaud Lacoste; Shelagh K. Malham; Anne Cueff; Serge A. Poulet


Journal of Cell Science | 2002

P35-sensitive caspases, MAP kinases and Rho modulate β-adrenergic induction of apoptosis in mollusc immune cells

Arnaud Lacoste; Anne Cueff; Serge A. Poulet


Journal of Cell Science | 2001

Noradrenaline and α-adrenergic signaling induce the hsp70 gene promoter in mollusc immune cells

Arnaud Lacoste; Marie-Cécile De Cian; Anne Cueff; Serge A. Poulet

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Yong Joo Kang

Pukyong National University

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Michel Starr

British Antarctic Survey

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Fabienne Jalabert

Centre national de la recherche scientifique

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