Preliminary biochemical characterization of toxins from the mucus of the freshwater stingray Paratrygon aiereba

Freshwater stingrays are venomous fish and live at the bottom of rivers and can be hidden in shallow pits that are excavated in sandy or muddy places. These animals are not aggressive, but because of these habits, the possibility of accidents is great, occurring when humans accidentally step on the dorsal part of these animals, who use the tail to defend themselves and deliver stings resulting in penetration of the sting in the body of the victim. These accidents occur mainly in the dry season in the northern region of the country when the rivers are shallower. Several cases of stinging accidents are described in the literature, and injuries caused by the stings of these animals are painful, difficult to heal, cause extensive necrosis, and sometimes systemic phenomena. These clinical manifestations are triggered by the action of the bioactive proteins present in the venom and mucus. Among the three riverine genera, Paratrygon, although presenting a wide geographic distribution and abundance in the Tocantins river, has no record of biochemical studies of the material secreted from the sting of the animal's back. The present work aims to make a preliminary biochemical characterization of the mucus of the Paratrygon aiereba streak. When comparing the epidermal mucus and P. aiereba venom samples, very similar protein profiles were observed. Through 12% SDS-PAGE gel electrophoresis, several components with molecular mass ranging from 8 to 100 KDa were identified in the mucus. Through the zymography, at least three proteins with gelatinolytic activities were visualized, and for the first time, caseinolytic activity was observed in the mucus. The data show important activity on phospholipids. A peptide with 4.907,8 Da, high conductivity and discrete antimicrobial activity for Gram negative bacteria Micrococus luteus was isolated with characteristics similar to a peptide - β- defensin. The results of this work point out the toxic potential of P. aiereba's epidermal mucus, which can aggravate the lesions caused by the venom of the animal. (author)