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.

AIM OF THE STUDY 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). 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. With this in mind, we investigated the Western blot (WB) expression of 5-lipoxygenase (5-LOX), a key-enzyme for mammalian infections, within the brain tissue of 11 striped dolphins and 5 bottlenose dolphins stranded along the Italian coastline. MATERIAL & METHODS Three striped dolphins and 2 bottlenose dolphins showed no morphologic evidence of central neuropathies, while 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 co-infection (1 striped dolphin). 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. Nevertheless, malacic areas, associated or not with cholesterol clefts, were seen scattered throughout this animal’s brain. CONCLUSIONS In summary, we believe that the finding related to a higher expression of 5-LOX enzyme in the 8 striped dolphins affected by infectious encephalitis/meningo-encephalitis is of interest. The finding that 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. Since 5-LOX is a putative neurodegeneration biomarker both in human patients and in experimental animal models, further investigation on this challenging issue is warranted.