Oral treatment with a rattlesnake native polypeptide crotamine efficiently inhibits the tumor growth with no potential toxicity for the host animal and with suggestive positive effects on animal metabolic profile

Abstract

The efficacy of crotamine as antitumoral was first demonstrated by daily intraperitoneal (IP) injections of low doses of this toxin in an animal model bearing melanoma tumors. Significant inhibition of tumor growth and increased lifespan of mice bearing tumor was also noticed after 21 consecutive days of this daily IP administration of crotamine. However, due to the limited acceptance of treatments by IP route in clinical conditions, herein, we evaluated the antitumor effect of this native polypeptide employing the oral route. The efficacy of crotamine in inhibiting the melanoma growth in vivo, even after passing through the gastrointestinal tract of the animal, was confirmed here. In addition, biochemical biomarkers and also histopathological analysis showed both the absence of any potential toxic effects in tissues or organs of the animal in which the highest accumulation of crotamine is expected. Interestingly, a reduction of weight gain was observed mainly in animals with tumor treated with crotamine by IP route, but not by oral administration. Albeit, oral administered crotamine was able to significantly decrease the body weight gain of healthy animals without tumor. Taking advantage of this same experimental animal models receiving crotamine by oral route, it was possible to show metabolic changes as the increased capacity of glucose clearance, which was accompanied by a reduction of the total cholesterol, and by increased high-density lipoprotein levels, both observed mainly in the absence of tumor. Triglycerides and low-density lipoprotein were also significantly decreased, but only in the absence of tumor. Taken together, these data suggest a clear trend for metabolic positive effects and mischaracterize unhealthy condition of animals, with or without tumors, treated with crotamine for 21 days. In addition, this study confirmed the efficacy of crotamine administered by oral route as antitumor agent, which besides the additional advantage of administration convenience and decreased risk of toxic effects, allowed the serendipitous observation of several positive metabolic effects on treated animals.

Pharmacological characterization of crotamine effects on mice hind limb paralysis employing both ex vivo and in vivo assays: Insights into the involvement of voltage-gated ion channels in the crotamine action on skeletal muscles

“…We also hypothesize that the polysaccharide material that contacts the basement membrane of sarcolemma may also play a potential role in the effect observed for crotamine in skeletal muscle, as its affinity for proteoglycans present on cell membranes was largely studied and demonstrated by our group to explain the cytotoxic and antitumoral activity of crotamine [ 50 , 51 , 52 ]. In addition to its potential action on mitochondria, which are often numerous in striated skeletal muscle structure, the possible differential expression of proteoglycans in hind limbs and front paws skeletal muscles of an animal, may have equally the potential to explain the selective paralysis of mice hind limbs with no noticeable or important effects on mice front paws.…”

“…Interestingly, we finished observing only total paralysis onset (data in S2 Video ), for any dose of crotamine evaluated, and the minimum concentration/doses of crotamine necessary for this effect could not be determined here. But at this point, it is important to consider that even after 21 days of daily ip treatment with crotamine (1 μg/animal, which correspond to about 0.04 mg/kg of BW), we have never observed the hind limbs paralysis or any other noticeable change in the general behavior of treated animals [ 50 , 52 , 63 ]. It is also worth to mention that the mice hind limbs paralysis was not observed up to 2 h after administration by oral route of a single dose of 200 μg of crotamine (which corresponds to about 8 mg/kg of BW), or after a long term daily treatment by oral gavage with crotamine (10 μg/animal, which correspond to about 0.04 mg/kg of BW) [ 52 , 63 ].…”

Crotamine induces browning of adipose tissue and increases energy expenditure in mice

“…However, natural compounds isolated from venomous animals have been less studied in this field, and an unexplored collection of molecules with potential to counteract obesity and ameliorate its complications remains unexplored. Previous observations that crotamine inhibits weight gain in animal models of melanoma 24 , 26 led us to explore the potential effects of crotamine on metabolism.…”

“…Importantly, another group has demonstrated the ability of crotamine to induce insulin secretion in cultured pancreatic beta cells 25 . In the present study, the main objective was to investigate the metabolic effects of crotamine in healthy wild-type mice after 21 days of oral treatment, which was demonstrated by our laboratory to be an effective protocol for crotamine as an antitumor treatment agent 26 . Here, we found that crotamine induces the differentiation of brown adipocytes and stimulates basal energy expenditure, thereby reducing adiposity and improving glucose homeostasis.…”

Crotamine in Crotalus durissus: distribution according to subspecies and geographic origin, in captivity or nature

“…This toxin induces myonecrosis [24], paralysis and extension of hind legs, and spontaneous and irregular contractions in the diaphragm of rats, mice and rabbits [25] by acting on sodium and potassium channels [26,27]. More recently, it has been demonstrated that crotamine possesses antitumoral [28], cytotoxic [29], antibacterial [30][31][32], antileishmanial [33], anthelmintic [34] and antimalarial effects [35]; as well as induces platelet aggregation [32].…”