5-LOX expression in the brain tissue of stranded striped dolphins (stenella coeruleoalba) and bottlenose dolphins (tursiops truncatus), with or without infectious encephalitis/meningo-encephalitis.

INTRODUCTION Dolphin Morbillivirus (DMV), Toxoplasma gondii and Brucella ceti are regarded as pathogens of major concern for both free-ranging striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) (1). Although a more or less severe encephalitis/meningo-encephalitis is known to occur in striped dolphins and, to a lesser degree, in bottlenose dolphins infected by the aforementioned agents, very little information is available on the neuropathogenesis of brain lesions, including the neuronal and non-neuronal cells targeted during infection and the molecular mechanisms leading to neurodegeneration (2,3). MATERIALS & METHODS With this in mind, we investigated the Western blot (WB) expression of 5-lipoxygenase (5-LOX), a key-enzyme for mammalian infections, in the brain tissue from 11 striped dolphins and 5 bottlenose dolphins, with 3 of the striped dolphins and 2 of the bottlenose dolphins under study showing no morphologic evidence of central neuropathies. The remaining 8 striped dolphins and 2 additional bottlenose dolphins exhibited encephalitic/meningo-encephalitic lesions of various degree, associated with DMV (1 striped dolphin), T. gondii (5 striped dolphins and 2 bottlenose dolphins) and B. ceti (1 striped dolphin) infection, as well as with DMV-T. gondii coinfection (1 striped dolphin). The ImageJ software was used for densitometry imaging to analyze the intensity of WB bands. RESULTS All the 8 striped dolphins affected by encephalitis/meningo-encephalitis showed an intensity of 5-LOX WB bands which was more pronounced than that observed in the 3 dolphins without any morphologic evidence of brain lesions, with the most prominent band intensity being detected in the B. ceti-infected animal. The same was not true for T. gondii-infected as compared to T. gondii-uninfected bottlenose dolphins, 1 of which had the most consistent 5-LOX band intensity. Malacic areas, associated or not with cholesterol clefts, were seen scattered throughout this animal’s brain. DISCUSSION & CONCLUSIONS Based upon the results presented herein, the finding related to a higher expression of 5-LOX enzyme in the brain tissue of the 8 striped dolphins affected by infectious encephalitis/meningo-encephalitis appears to be of interest. The fact this was not paralleled by a simultaneous increase of 5-LOX expression in the brain from T. gondii-infected in comparison to T. gondii-uninfected bottlenose dolphins is also of concern, likely reflecting the mutual host-parasite adaptation of the latter (“inshore”) in comparison to the former (“offshore”) species (4). Since 5-LOX is a putative neurodegeneration biomarker in human patients (5) as well as in experimental animal models (6), further investigation on this challenging issue is needed. REFERENCES 1) Van Bressem M.-F., et al. (2009) - Dis. Aquat. Organ. 86, 143-157; 2) Di Guardo G. (2012) - Front. Microbiol. 3, 431; 3) Di Guardo G., Mazzariol S. (2013) - Emerg. Microbes Infect. 2(11), e74; 4) Di Guardo G., Mazzariol S. (2013) - Vet. Pathol. 50, 737; 5) Di Francesco A., et al. (2013) - J. Alzheimers Dis. 37, 3-8; 6) Chu J., et al. (2012) - Mol. Neurodegener. 7(1), 1. ACKNOWLEDGEMENTS We would like to thank the “Mediterranean Marine Mammals’ Tissue Bank” (University of Padua; Scientific coordinator: Prof. Bruno COZZI) for kindly providing us with part of the brain tissue samples investigated herein. This work was supported by a grant from the Italian Ministry for the Environment, in the framework of the Research Project entitled "Contaminanti ambientali e relativi effetti sul sistema nervoso centrale e sul sistema immunitario nei cetacei spiaggiati, le sentinelle del mare" (Scientific coordinator: Prof. Giovanni DI GUARDO).