Caracterização dos efeitos da aveloz (euphorbia tirucalli linn) sobre a função renal de ratos wistar

Abstract

For many centuries, humanity has been attached to natural products, especially plants, to obtain relief and cure their illnesses. Over the years, knowledge about the properties of plants has been passed from generation, often ignoring the real effectiveness or toxicity of these plants. Euphorbia tirucalli is a plant of African origin, but it has widespread distribution and adaptation in the American continent, especially in Brazil. Its latex has already presented several therapeutic actions demonstrated in in vitro studies, therefore, there is a need for further studies in experimental animal models to demonstrate its therapeutic or toxic properties on different physiological systems. Thus, the aim this study was to characterize the Euphorbia tirucalli actions on the renal function of healthy Wistar rats and possible biomolecular mechanisms involved them. Wistar rats were divided into 2 groups: A control group that received distilled water (CT) and a group treated with E. tirucalli (ET) at a dose of 13.47 mg.Kg-1 for 15 days, both by gavage. The animals were weighed before and after 15 days of treatment. They were then anesthetized with sodium thiopental (50 mg.kg-1 i.p) and during the surgical process, femoral artery was catheterized for pressure measurement, femoral vein, for infusion of mannitol, inulin and paraminohippurate (PAH), as well as the bladder for urine collection. Tracheostomy was also performed for respiratory relief. Inulin and paraminohippurate clearances were performed to determine glomerular filtration rate (GFR), renal plasma flow (RPF), renal blood flow (RBF) and renal vascular resistance (RVR). Kidney cells were isolated and a tissue homogenate prepared for biochemical analysis. The reactive oxygen species (EROS) and nitrogen (ERNS) production, beside apoptosis were evaluated by flow cytometry. The animals showed no difference between their weights before and after treatments. The data indicate that there was no significant change in the values of GFR. However, significantly lower values of RPF (CT: 23.84±2.24 mL/min/Kg vs. ET: 17.51±2.24 mL/min/Kg) and RBF (CT: 39.13± 3.23 mL/min/Kg vs. ET: 27.73±3.63 mL/min/Kg), while higher values in the RVR of animals treated with E. tirucalli compared to the control group (CT: 4.178±0.36 a.u. vs. .ET: 6.354±0.59 a.u.) were observed. These data are supported by the increase in mean arterial pressure (MAP) of treated animals compared to controls (CT: 98.29 ±5.4 mmHg vs. ET: 119.0 ± 4.4 mmHg. Hematocrit data did not change with treatment. Renal hypertrophy index showed no significant difference between groups. Tissue homogenate analyzes showed a significantly higher quantification of Advanced Oxidation Protein Products (AOPP) in groups treated with E. tirucalli compared to the control group (CT:1785±366.3 µMol.L -1 vs ET:2774±231.2 µMol.L -1 ). Myeloperoxidase enzyme activity was significant increase in the treated group compared to the control group (CT:0.002±0.0002 a.u. vs ET: 0.0029±0.0002 a.u.), indicating that the ingestion of E. tirucalli latex promotes oxidative and inflammatory damage. ROS levels quantification showed that E. tirucalli treatment was significantly reduced superoxide anion levels (O2∙−) in the treated group compared to the control group (CT:156.7±15.86 MFI a.u. vs ET:95.78±20.31 MFI a.u.) evidenced by DHE-labeled kidney cells. On the other hand, there was no difference in H2O2 levels in the studied groups. Our data showed that among the RNS there was a significant increase in the nitric oxide (NO) levels verified by DAF labeled cells in the E. tirucalli treated group compared to the control (CT:1812±99.50 MFI a.u. vs ET:2737±249.6 MFI a.u.). Peroxynitrite (•ONOO-/•OH-) levels was also significant increase in E. tirucalli treated group compared to the control (CT:1176±90.45 MFI a.u. vs ET:1442±74.70 MFI a.u.). We also analyzed the apoptotic activity with Annexin-V and Propidium Iodide (PI) markers and a significant increase in renal cells labeled with Annexin V only was observed, indicating an initial apoptotic activity in renal cells from animals treated with E. tirucalli compared to the control group (CT:35.62 ± 3.05% vs ET:44.58 ± 1.82%). The results indicate that 15 days of E. tirucalli treatment are enough to alter the RVR in mechanisms that possibly involve increased oxidative stress and inflammatory activity. We believe that E. tirucalli, wich is rich in phorbol esters, would be responsible for the oxidative stress increase and together, both molecules have the ability to protein kinase C (PKC) activation, responsible for numerous transcription factors phosphorylating involved in inflammation and apoptosis phenomenon. Thus, it can be hypothesized that E. tirucalli use should be cautious because it causes functional and biomolecular changes in the renal tissue that can lead to future damage, which is especially worrying in patients who invariably use this plant.