Propriedades anti-inflamatórias de proteases cisteínicas do látex da planta medicinal Calotropis procera (Ait.) R. Br. aplicadas ao controle de infecções por Salmonella

Abstract

Calotropis procera (Apocynaceae) is a medicinal plant by which its laticifer proteins have been reported as having important biological activities. In particular, a protein fraction rich in cysteine proteases (LPPII) was shown antinflammatory and capable to maintain blood clotting homeostasis in Salmonella-infected mice. In the present study, a murine model of systemic infection caused by Salmonella Typhimurium was used to evaluate the influence of LPPII on control of infection-induced inflammation. Preventive and curative treatment regimens were evaluated. In the preventive treatment schedule, experimental animals received LPPII (10mg/kg) intravenously (ev), whereas the control groups were administered with LPPII + IAA (10mg/kg), whose proteases were inactivated with Iodoacetamide, PBS intravenously or dexamethasone (0.5mg/animal) (ip). After 30 min, the animals were challenged with S. Typhimurium (105 CFU/mL) intraperitoneally (ip). After 6 hours of infection, the mice were submitted to euthanasia procedures and analyzes. In the curative treatment schedule, the animals were infected with S. Typhimurium (105 CFU/mL) (ip) and for two consecutive days were treated with LPPII (10mg/kg) or administered with LPII + IAA (10mg/kg), PBS intravenously or dexamethasone (ip). After 72 hours of infection, the groups were submitted to euthanasia procedures for sample collection and analysis. The results showed that, in the two treatment regimens, there was no bacterial clearance in the spleen, liver, peritoneal fluid and blood of the experimental animals when compared to the controls. The treatments with LPPII significantly reduced the amount of leukocytes in the peritoneal cavity of the animals in comparison to the LPPII + IAA and PBS control groups. The treatments also reduced gene expression of TNF-α, IL-12 and IFN-γ in animals receiving LPPII. Furthermore, there was no increase in survival of LPPII-treated and Salmonella-infected animals. Finally, peritoneal macrophages previously stimulated with LPS were exposed to an osmotin isolated from LPPII. It was observed that the treatments significantly reduced the IL-1 gene expression, but not TNF-α. We have shown that cysteine proteases present in the latex of C. procera are capable to decrease inflammation in the peritoneum of Salmonella Typhimurium-infected mice. Although the mechanisms involved in this effect are not fully elucidated, it has been demonstrated that an osmotin present in LPPII possesses anti-inflammatory potential and possible therapeutic relevance.