Avaliação do efeito antilitiásico e nefroprotetor do sobrenadante etanólico do infuso de Costus spicatus (Jacq.) Sw

Abstract

Acute Kidney Injury (AKI) is a process of varied etiology, characterized by the abrupt loss of renal function. Nephrolithiasis, on the other hand, is the formation of stones originating from the precipitation of poorly soluble concentrated urine salts. With the intention of improving the scientific research and aiming to increase the knowledge about the nephropathies, several experimental models of diseases were developed, such as the glycerol-induced rhabdomyolysis model in animals and the in vitro crystallization by sodium oxalate precipitation, for studies related to nephrolithiasis. Used as substrates in the drug industry or in their popular and traditional use, plants represent an important and more accessible facet in the treatment of disease. Costus spicatus (Jacq.) Sw., commonly called "Cana do brejo" is popularly used for urinary tract diseases and as a diuretic and purifier. Therefore, the aim of this study was to investigate phytochemical and pharmacological effects of C. spicatus in an AKI model in male Wistars rats and upon an in vitro crystallization model for nephrolithiasis. The plant material was collected in Dourados-MS region, it was oven dried and ground, extraction was made with boiling water, followed by ethanol extraction, to obtain the ethanol-soluble fraction of C. spicatus (ESCS). To determine the phytochemical composition of ESCS, ultra-fast liquid chromatography coupled to a diode array detector and a mass spectrometer (LC-DAD-MS) was used. In vivo experiment used 48 Wistars rats, divided into six groups (n=8). During five days, three groups received ESCS administration (30, 100 and 300 mL/kg/day), another group received ascorbic acid (200 mg/kg) as positive control; two other groups received saline. Subsequent to treatment, the animals received an intramuscular injection of 25% glycerol (10 mL/kg). After AKI induction, blood pressure and renal reactivity were measured; serum samples were collected and the kidneys were excised for histopathological analysis and evaluation of the antioxidant potential, through the analysis of the enzymes catalase (CAT) and superoxide dismutase (SOD), as well as the levels of lipoperoxidation (LPO); 24-hour urine collections were performed at days 0, 3, 5 and 7. Others 25 animals were used to investigate the ESCS acute and prolonged diuretic activity (30, 100 and 300 mL/kg/day). To evaluate the antilithiatic effect, human urine samples were used, three samples received the addition of ESCS (0.05, 0.5 and 5 mg/mL) and underwent the crystallization process by precipitation of sodium oxalate concurrently with the control samples. After crystallization, the turbidity index (TI) was calculated and the number and size of crystals in each sample were estimated. The results show that 25 compounds were annotated from ESCS, and the main metabolite classes were flavonoids, steroidal saponin and organic acids. There was a significant reduction in urinary urea and creatinine excretion in the untreated AKI group and considerable histopathological damage (swelling, vacuolization, necrosis and inflammatory infiltrate). Animals with untreated AKI presented oliguria, ESCS prevented the occurrence of oliguria at different dosages. 30 mg/kg dose demonstrated a significant nephroprotection effect by increasing excretion of urea, creatinine, sodium, calcium and chlorine in the urine after AKI induction. 300 mg/kg dose presented the least severe histopathological lesions. Ascorbic acid had no nephroprotective effect on the analyzed parameters. A possible antioxidant action of ESCS was identified due to the increase in SOD (dose of 30 mg/kg) and CAT (doses of 100 and 300 mg kg) in kidneys samples. Results did not identify the plant's diuretic activity. ESCS was able to reduce significantly the calcium oxalate crystals area; it also reduces the proportion of the monohydrate crystals and decreases the aggregation of the crystals 24 hours later. In conclusion the 30 mg/kg dose of ESCS had a positive effect on urinary parameters, and the different doses prevented the occurrence of oliguria, in addition to demonstrating an antioxidant effect on the kidneys. C. spicatus had an antilithiatic action by significantly reducing the growth and aggregation of crystals (in vitro), in addition to hindering the formation of monohydrate crystals; which corroborates the popular use of the plant for urinary tract diseases.