Gloria E. Mendes

Acute kidney injury caused by bothrops snake venom.

Medically important venomous snakes in Latin America belong to the genus Bothrops, Crotalus, Lachesis and Micrurus. The Bothrops genus is responsible for the majority of accidents. The WHO globally estimates 2,500,000 poisonous snakebites and 125,000 deaths annually. In its last report in 2001, the Brazilian Ministry of Health accounted 359 deaths due to snakebites, of which the Bothrops genus was responsible for 185. Snake venoms cause local and systemic damage, including acute kidney injury, which is the most important cause of death among patients surviving the early effects of envenoming by the Crotalus and Bothrops genuses. Venom-induced acute kidney injury is a frequent complication of Bothrops snakebite, carrying relevant morbidity and mortality.

Loxosceles gaucho venom-induced acute kidney injury--in vivo and in vitro studies.

Background Accidents caused by Loxosceles spider may cause severe systemic reactions, including acute kidney injury (AKI). There are few experimental studies assessing Loxosceles venom effects on kidney function in vivo. Methodology/Principal Findings In order to test Loxosceles gaucho venom (LV) nephrotoxicity and to assess some of the possible mechanisms of renal injury, rats were studied up to 60 minutes after LV 0.24 mg/kg or saline IV injection (control). LV caused a sharp and significant drop in glomerular filtration rate, renal blood flow and urinary output and increased renal vascular resistance, without changing blood pressure. Venom infusion increased significantly serum creatine kinase and aspartate aminotransferase. In the LV group renal histology analysis found acute epithelial tubular cells degenerative changes, presence of cell debris and detached epithelial cells in tubular lumen without glomerular or vascular changes. Immunohistochemistry disclosed renal deposition of myoglobin and hemoglobin. LV did not cause injury to a suspension of fresh proximal tubules isolated from rats. Conclusions/Significance Loxosceles gaucho venom injection caused early AKI, which occurred without blood pressure variation. Changes in glomerular function occurred likely due to renal vasoconstriction and rhabdomyolysis. Direct nephrotoxicity could not be demonstrated in vitro. The development of a consistent model of Loxosceles venom-induced AKI and a better understanding of the mechanisms involved in the renal injury may allow more efficient ways to prevent or attenuate the systemic injury after Loxosceles bite.

Tacrolimus and nonsteroidal anti-inflammatory drugs: an association to be avoided.

Background: Tacrolimus (FK) and nonsteroidal anti-inflammatory drugs (NSAIDs) can cause acute nephrotoxicity. The expanding use of tacrolimus and the intense consumption of NSAIDS increase the chances of their simultaneous use. Methods: Rats receiving a nonselective COX inhibitor (diclofenac, D) and FK or a selective COX-2 inhibitor (rofecoxib, RO) and FK were treated with FK (2 mg/kg/day), D (10 mg/kg/day), RO (3 mg/kg/day), FK+D, FK+RO and vehicle for 7 days on low-salt diet. Results: Both associations significantly impaired glomerular filtration rate (GFR; 0.63 ± 0.06 ml/min/100 g in FK+D, 0.83 ± 0.06 ml/min/100 g in FK+RO) which did not occur with single drug therapy (0.98 ± 0.03 ml/min/100 g in D, 1.06 ± 0.04 ml/min/100 g in RO, 0.99 ± 0.05 ml/min/ 100 g in FK) or vehicle (1.10 ± 0.05 ml/min/100 g). GFR decrease was significantly higher with FK+D. GFR impairment occurred without RBF or RVR major changes. Mild tubular vacuolization and dilatation and acute degenerative changes were observed in tubular cells. FK+D animals showed a marked weight loss, not observed in the other groups. FK+NSAIDs association decreased FK blood levels (1.73 ± 0.3 ng/ml in FK+D, 1.8 ± 0.3 ng/ml in FK+RO, 3.2 ± 0.4 ng/ml in FK, p < 0.05). Conclusions: The association of FK and nonselective or COX-2 selective NSAIDs in salt-depleted animals caused a significant GFR impairment and decreased FK blood levels.

Ga-67 scintigraphy in the differential diagnosis between acute interstitial nephritis and acute tubular necrosis: an experimental study

BACKGROUND The differentiation between acute interstitial nephritis (AIN) and acute tubular necrosis (ATN) is crucial in patients with acute kidney injury. Gallium-67 citrate (Ga-67) has been used clinically in the differential diagnosis between these entities, but its efficacy is disputed. The aim of this study was to evaluate Ga-67 scintigraphy efficacy in the differentiation between experimental models of drug-induced AIN and ATN. METHODS Animals were divided into three groups: AIN (n = 8), ATN (n = 8) and control (NL, n = 10). The AIN group received intraperitoneal puromycin aminonucleoside (single dose, 150 mg/kg). The ATN group received a single intraperitoneal injection of cisplatin (6 mg/kg). The NL group did not receive active drugs. All of the animals were submitted to Ga-67 scintigraphy, serum creatinine (Cr) and urinary osmolality assessment, and blinded renal histology evaluation. RESULTS Renal Ga-67 uptake was strikingly more intense in the AIN group when compared to the ATN (P < 0.0001) and NL (P < 0.001) groups. The ATN group had increased Cr when compared to the NL group (P < 0.001) and lower urinary osmolality vs the NL (P < 0.001) and AIN (P < 0.01) groups. Renal histology showed severe acute tubular injury in the ATN group and intense interstitial inflammation in the AIN group, and was normal in control animals. CONCLUSION Ga-67 scintigraphy was extremely effective in the differentiation between experimental drug-induced ATN and AIN.

The Effects of So-Called ‘Forbidden Acupuncture Points’ on Pregnancy Outcome in Wistar Rats

Background: This study sought to determine if acupuncture in LI4 and SP6, or in sacral points could harm the pregnancy outcome in Wistar rats as is believed according to traditional knowledge. Methods: 48 pregnant Wistar rats were randomly divided into 4 groups: total control where the rats were left in cages without manipulation; anesthetized control where the rats were manipulated and anesthetized but did not received electroacupuncture; peripheral points and sacral points were the rats were anesthetized and received 4 acupuncture points – LI4-SP6 and BL27–28, respectively. The primary end point was embryonic loss after implantation, defined as (number of implantations – number of embryos in development) × 100 / number of implantations. Other evaluated parameters were fetal death, abortions, number of fetuses, and resorptions, resorption index (number of resorptions / total of implantations), maternal weight gain, and fetal weight. Results: There were no differences in embryonic loss after implantation (p = 0.45), fetal death (p = 1), abortions (p = 1), number of fetuses (p = 0.79), resorptions (p = 0.3), and resorption index (p = 0.45). There were differences in maternal weight gain and fetal weight, but they seemed unrelated to the treatment. Conclusions: We found no evidence that acupuncture in LI4-SP6 and sacral points could be harmful to the pregnancy outcome in Wistar rats.

Interaction of the Anti-Inflammatory Annexin A1 Protein and Tacrolimus Immunosuppressant in the Renal Function of Rats

Background: Tacrolimus (FK) is currently widely used in transplant immunosuppression and the treatment of autoimmune diseases. However, FK induces nephrotoxicity which is characterized by functional and structural renal injury. The ubiquitous protein annexin A1 (ANXA1) has potent anti-inflammatory effects and protects against ischemia/reperfusion injury. We investigated the effects of exogenous ANXA1 treatment in an experimental model of acute FK nephrotoxicity. Methods: Munich-Wistar rats received a low-salt diet for 1 week and were randomized to treatment with ANXA1 (Ac2-26 peptide 0.5 mg/kg/day s.c.), FK (6 mg/kg/day p.o.), association (FK+ANXA1) and vehicles (1 ml/kg/day) for 7 days. Results: FK induced a significant decrease in glomerular filtration rate and renal blood flow, and a significant increase in renal vascular resistance. In addition, FK caused extensive acute tubule-interstitial damage and an increase in anti-inflammatory ANXA1 expression in renal tissue. Exogenous ANXA1 treatment reduced FK-induced tubular dilatation and macrophage infiltration. For the first time, we observed that FK augmented ANXA1 expression in renal tissue. Conclusion: Exogenous ANXA1 treatment partially protected against FK-induced tubular injury and macrophage infiltration, and may be targeted in renal intervention strategies.

Could acupuncture at the so-called forbidden points be harmful to the health of pregnant Wistar rats?

Aim This study is the second report from a single experiment planned to determine if acupuncture at LI4 and SP6, or at the sacral points, could produce any harm in the pregnancy outcome of Wistar rats, as has been hypothesised in traditional knowledge. Here, we observe if these points can be harmful to the health of pregnant Wistar rats. Methods A total of 48 pregnant Wistar rats were randomly divided into 4 groups: total control, where rats were left in cages without manipulation; anesthetised control, where rats were manipulated and anesthetised but did not receive electroacupuncture; and peripheral point and sacral point groups, where rats were anesthetised and received 6 sessions of electroacupuncture at 4 acupuncture points: LI4 and SP6, and BL27 and BL28, respectively. In the 19th day of pregnancy the rats were killed and examined. The primary endpoints were levels of glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT) creatinine and histological changes of liver and kidney. Results There were no differences between the levels of biochemical parameters. No differences were also seen regarding the histopathological analysis. Conclusions We found no evidence that acupuncture at the LI4, SP6 and sacral points could be harmful to the Wistar rat dams.

Previous exposure to cigarette smoke aggravates experimental cyclosporine-induced nephrotoxicity.

Background/Aims: The effects of cigarette smoke (CS) on cyclosporine (CsA)-induced nephrotoxicity are poorly studied. This study aims to assess the effects of previous exposure to CS on CsA nephrotoxicity. Methods: Rats were either exposed to CS or sham (S) procedures for 10 min twice a day for 20 weeks. From the 16th to the 20th week, they received a low-salt diet. Beginning with the 17th week, they were given 2.5 mg/day CsA or vehicle (VH) for 3 weeks. The final groups were VH/CS, CsA/CS, VH/S, and CsA/S. On day 141, glomerular filtration rate (GFR), renal blood flow (RBF), renal vascular resistance (RVR), tubulointerstitial fibrosis, and CsA blood levels were measured and immunohistochemistry was analyzed for renal α-smooth muscle actin (SMA), nitrotyrosine, and vimentin. Results: CsA decrease in GFR was enhanced by CS exposure. CsA associated with CS induced higher periglomerular α-SMA and renal nitrotyrosine expression. CsA decreased RBF, but increased RVR, tubulointerstitial fibrosis, and α-SMA and renal vimentin expression. These changes and the CsA blood levels were not affected by CS exposure. Conclusion: CS aggravated the CsA-induced impairment of GFR and CS associated with CsA caused the development of periglomerular structural lesions and oxidative stress in a rat model of CsA nephrotoxicity.

Effect of Cyclosporine A on Glucose Interstitial Concentration in Renal Cortex and Medulla from Rats

Aim: To standardize microdialysis in rat kidneys and address cyclosporine A (CsA) effects on renal cortex and medulla interstitial glucose. Methods: Munich-Wistar rats were treated with vehicle or CsA (15 mg/kg/day) for 3 weeks. Glucose was assessed by spectrophotometry in dialysate samples from cortex, medulla and arterial plasma. Plasma insulin was measured by radioimmunoassay. Renal blood flow (RBF) was measured by Doppler ultrasound. Creatinine and urea were measured by spectrophotometry. Results: CsA significantly increased the plasma levels of urea and creatinine (1.5 ± 0.20 vs. 0.73 ± 0.03 mg/dl in controls, p < 0.05). Medullary glucose in control was 44% lower than arterial glucose (56 ± 6 vs. 101 ± 8 mg/dl, p < 0.05). At the same time, CsA increased arterial (163 ± 35 vs. 101 ± 8 mg/dl in controls, p < 0.05) and medullary interstitial glucose (100 ± 18 vs. 56 ± 6 mg/dl in controls, p < 0.05), but did not affect cortical glucose (114 ± 21 vs. 90 ± 11 mg/dl in controls). These changes occurred in the presence of a decreased plasma insulin level (2.7 ± 0.2 vs. 9.3 ± 0.4 µU/ml in controls, p < 0.05). The increment in medullary glucose in CsA group occurred despite a reduction in RBF (4.6 ± 0.8 vs. 6.5 ± 1.0 ml/min/kidney in controls, p < 0.05). Conclusions: Microdialysis was an adequate tool to investigate in vivo regulation of renal glucose metabolism. Renal glucose uptake was dependent on medullary cells and CsA treatment induced diabetogenic effects on renal medulla in situ.

Validation of an Experimental Model to Study Less Severe Chronic Renal Failure.

ABSTRACT Purpose: The 5/6 nephrectomy, mimics the stages of human chronic renal failure (CRF), but the procedure causes severe renal functional and morphological damage that could interfere with the evaluation of therapies for slowing the progression of the disease. This study summarizes the results of renal function, histology, and immunohistochemical findings in rats undergoing a 2/3 nephrectomy. Methods: The rats were distributed in groups according to the type of nephrectomy: CRF5/6: induced by a 5/6 renal mass reduction and CRF2/3: less severe CRF. The body weight and blood pressure were monitored, and the serum creatinine (SCr), creatinine clearance (CCr), urine osmolality, and 24-h proteinuria (PT24h) were measured. CRF progression was evaluated by the rate of decline of CCr (RCCr). Histology and immunohistochemistry were performed in the remnant kidneys. Statistical analysis was done by unpaired t-test, and a P-value < 0.05 was taken as a statistical significance. Results: Compared to the CRF5/6 group, the CRF2/3 model had a lower SCr, PT24h, CCr, and variations of the SCr from baseline. The disease progression was also significantly slower. The renal histopathological findings revealed fewer chronic lesions in rats with CRF2/3. Similarly, we observed less macrophage accumulation as well as lower proliferative activity and expression of fibronectin and a-smooth muscle-actin in the CRF2/3 model. Conclusions: The CRF2/3 model presented with a pattern of less severe CRF, functionally and morphologically, compared to the classical CRF5/6 model, and the CRF2/3 model may be useful for evaluating therapeutic interventions that target the early stages of CRF.