Ana Carolina de Bragança

N-acetylcysteine prevents pulmonary edema and acute kidney injury in rats with sepsis submitted to mechanical ventilation

Sepsis is a common cause of acute kidney injury (AKI) and acute lung injury. Oxidative stress plays as important role in such injury. The aim of this study was to evaluate the effects that the potent antioxidant N-acetylcysteine (NAC) has on renal and pulmonary function in rats with sepsis. Rats, treated or not with NAC (4.8 g/l in drinking water), underwent cecal ligation and puncture (CLP) 2 days after the initiation of NAC treatment, which was maintained throughout the study. At 24 h post-CLP, renal and pulmonary function were studied in four groups: control, control + NAC, CLP, and CLP + NAC. All animals were submitted to low-tidal-volume mechanical ventilation. We evaluated respiratory mechanics, the sodium cotransporters Na-K-2Cl (NKCC1) and the α-subunit of the epithelial sodium channel (α-ENaC), polymorphonuclear neutrophils, the edema index, oxidative stress (plasma thiobarbituric acid reactive substances and lung tissue 8-isoprostane), and glomerular filtration rate. The CLP rats developed AKI, which was ameliorated in the CLP + NAC rats. Sepsis-induced alterations in respiratory mechanics were also ameliorated by NAC. Edema indexes were lower in the CLP + NAC group, as was the wet-to-dry lung weight ratio. In CLP + NAC rats, α-ENaC expression was upregulated, whereas that of NKCC1 was downregulated, although the difference was not significant. In the CLP + NAC group, oxidative stress was significantly lower and survival rates were significantly higher than in the CLP group. The protective effects of NAC (against kidney and lung injury) are likely attributable to the decrease in oxidative stress, suggesting that NAC can be useful in the treatment of sepsis.

Sildenafil reduces polyuria in rats with lithium-induced NDI.

Lithium (Li)-treated patients often develop urinary concentrating defect and polyuria, a condition known as nephrogenic diabetes insipidus (NDI). In a rat model of Li-induced NDI, we studied the effect that sildenafil (Sil), a phosphodiesterase 5 (PDE5) inhibitor, has on renal expression of aquaporin-2 (AQP2), urea transporter UT-A1, Na(+)/H(+) exchanger 3 (NHE3), Na(+)-K(+)-2Cl(-) cotransporter (NKCC2), epithelial Na channel (ENaC; α-, β-, and γ-subunits), endothelial nitric oxide synthase (eNOS), and inducible nitric oxide synthase. We also evaluated cGMP levels in medullary collecting duct cells in suspension. For 4 wk, Wistar rats received Li (40 mmol/kg food) or no treatment (control), some receiving, in weeks 2-4, Sil (200 mg/kg food) or Li and Sil (Li+Sil). In Li+Sil rats, urine output and free water clearance were markedly lower, whereas urinary osmolality was higher, than in Li rats. The cGMP levels in the suspensions of medullary collecting duct cells were markedly higher in the Li+Sil and Sil groups than in the control and Li groups. Semiquantitative immunoblotting revealed the following: in Li+Sil rats, AQP2 expression was partially normalized, whereas that of UT-A1, γ-ENaC, and eNOS was completely normalized; and expression of NKCC2 and NHE3 was significantly higher in Li rats than in controls. Inulin clearance was normal in all groups. Mean arterial pressure and plasma arginine vasopressin did not differ among the groups. Sil completely reversed the Li-induced increase in renal vascular resistance. We conclude that, in experimental Li-induced NDI, Sil reduces polyuria, increases urinary osmolality, and decreases free water clearance via upregulation of renal AQP2 and UT-A1.

Hypertonic saline solution for prevention of renal dysfunction in patients with decompensated heart failure

BACKGROUND Renal dysfunction is associated with increased mortality in patients with decompensated heart failure. However, interventions targeted to prevention in this setting have been disappointing. We investigated the effects of hypertonic saline solution (HSS) for prevention of renal dysfunction in decompensated heart failure. METHODS In a double-blind randomized trial, patients with decompensated heart failure were assigned to receive three-day course of 100mL HSS (NaCl 7.5%) twice daily or placebo. Primary end point was an increase in serum creatinine of 0.3mg/dL or more. Main secondary end point was change in biomarkers of renal function, including serum levels of creatinine, cystatin C, neutrophil gelatinase-associated lipocalin-NGAL and the urinary excretion of aquaporin 2 (AQP2), urea transporter (UT-A1), and sodium/hydrogen exchanger 3 (NHE3). RESULTS Twenty-two patients were assigned to HSS and 12 to placebo. Primary end point occurred in two (10%) patients in HSS group and six (50%) in placebo group (relative risk 0.3; 95% CI 0.09-0.98; P=0.01). Relative to baseline, serum creatinine and cystatin C levels were lower in HSS as compared to placebo (P=0.004 and 0.03, respectively). NGAL level was not statistically different between groups, however the urinary expression of AQP2, UT-A1 and NHE3 was significantly higher in HSS than in placebo. CONCLUSIONS HSS administration attenuated heart failure-induced kidney dysfunction as indicated by improvement in both glomerular and tubular defects, a finding with important clinical implications. HSS modulated the expression of tubular proteins involved in regulation of water and electrolyte homeostasis.

Vitamin D Deficiency Aggravates Chronic Kidney Disease Progression after Ischemic Acute Kidney Injury

Background Despite a significant improvement in the management of chronic kidney disease (CKD), its incidence and prevalence has been increasing over the years. Progressive renal fibrosis is present in CKD and involves the participation of several cytokines, including Transforming growth factor-β1 (TGF-β1). Besides cardiovascular diseases and infections, several studies show that Vitamin D status has been considered as a non-traditional risk factor for the progression of CKD. Given the importance of vitamin D in the maintenance of essential physiological functions, we studied the events involved in the chronic kidney disease progression in rats submitted to ischemia/reperfusion injury under vitamin D deficiency (VDD). Methods Rats were randomized into four groups: Control; VDD; ischemia/reperfusion injury (IRI); and VDD+IRI. At the 62 day after sham or IRI surgery, we measured inulin clearance, biochemical variables and hemodynamic parameters. In kidney tissue, we performed immunoblotting to quantify expression of Klotho, TGF-β, and vitamin D receptor (VDR); gene expression to evaluate renin, angiotensinogen, and angiotensin-converting enzyme; and immunohistochemical staining for ED1 (macrophages), type IV collagen, fibronectin, vimentin, and α-smooth mucle actin. Histomorphometric studies were performed to evaluate fractional interstitial area. Results IRI animals presented renal hypertrophy, increased levels of mean blood pressure and plasma PTH. Furthermore, expansion of the interstitial area, increased infiltration of ED1 cells, increased expression of collagen IV, fibronectin, vimentin and α-actin, and reduced expression of Klotho protein were observed. VDD deficiency contributed to increased levels of plasma PTH as well as for important chronic tubulointerstitial changes (fibrosis, inflammatory infiltration, tubular dilation and atrophy), increased expression of TGF-β1 and decreased expression of VDR and Klotho protein observed in VDD+IRI animals. Conclusion Through inflammatory pathways and involvement of TGF-β1 growth factor, VDD could be considered as an aggravating factor for tubulointerstitial damage and fibrosis progression following acute kidney injury induced by ischemia/reperfusion.

Carbamazepine can induce kidney water absorption by increasing aquaporin 2 expression

BACKGROUND Carbamazepine (Carba) is an anticonvulsant and psychotropic drug used widely for the treatment of intellectual disability and severe pains, but the incidence of hyponatremia is a common related occurrence. This hyponatremia is frequently attributed to a SIADH induced by this drug. It is also known that Carba is used to decrease the urinary volume in Diabetes Insipidus (DI) because it has an antidiuretic effect. Lithium (Li) is one of the most important drugs used to treat bipolar mood disorders. However Li has the undesirable capacity to induce DI. Nowadays, the association of these drugs is used in the treatment of patients with psychiatric and neurological problems. METHODS In vivo and in vitro (microperfusion) experiments were developed to investigate the effect of Carba in the rat Inner Medullary Collecting Duct (IMCD). RESULTS The results revealed that Carba was able to stimulate the V2 vasopressin receptor-Protein G complex increasing the (Pf) and water absorption. In vivo studies showed that in rats with lithium-induced DI, Carba decreased the urinary volume and increased the urinary osmolality. AQP2 expression was increased both in normal IMCD incubated with Carba and in IMCD from lithium-induced DI after Carba addition to the diet, when compared with the control. CONCLUSION These results showed that the hyponatremia observed in patients using this anticonvulsant drug, at least in part, is due to the Carba capacity to increase IMCDs Pf and that the Lithium-Carbamazepine association is beneficial to the patient.

Vitamin D deficiency aggravates nephrotoxicity, hypertension and dyslipidemia caused by tenofovir: role of oxidative stress and renin-angiotensin system.

Vitamin D deficiency (VDD) is prevalent among HIV-infected individuals. Vitamin D has been associated with renal and cardiovascular diseases because of its effects on oxidative stress, lipid metabolism and renin-angiotensin-aldosterone system (RAAS). Tenofovir disoproxil fumarate (TDF), a widely used component of antiretroviral regimens for HIV treatment, can induce renal injury. The aim of this study was to investigate the effects of VDD on TDF-induced nephrotoxicity. Wistar rats were divided into four groups: control, receiving a standard diet for 60 days; VDD, receiving a vitamin D-free diet for 60 days; TDF, receiving a standard diet for 60 days with the addition of TDF (50 mg/kg food) for the last 30 days; and VDD+TDF receiving a vitamin D-free diet for 60 days with the addition of TDF for the last 30 days. TDF led to impaired renal function, hyperphosphaturia, hypophosphatemia, hypertension and increased renal vascular resistance due to downregulation of the sodium-phosphorus cotransporter and upregulation of angiotensin II and AT1 receptor. TDF also increased oxidative stress, as evidenced by higher TBARS and lower GSH levels, and induced dyslipidemia. Association of TDF and VDD aggravated renovascular effects and TDF-induced nephrotoxicity due to changes in the redox state and involvement of RAAS.

Rosiglitazone prevents sirolimus-induced hypomagnesemia, hypokalemia, and downregulation of NKCC2 protein expression

Sirolimus, an antiproliferative immunosuppressant, induces hypomagnesemia and hypokalemia. Rosiglitazone activates renal sodium- and water-reabsorptive pathways. We evaluated whether sirolimus induces renal wasting of magnesium and potassium, attempting to identify the tubule segments in which this occurs. We tested the hypothesis that reduced expression of the cotransporter NKCC2 forms the molecular basis of this effect and evaluated the possible association between increased urinary excretion of magnesium and renal expression of the epithelial Mg2+ channel TRPM6. We then analyzed whether rosiglitazone attenuates these sirolimus-induced tubular effects. Wistar rats were treated for 14 days with sirolimus (3 mg/kg body wt in drinking water), with or without rosiglitazone (92 mg/kg body wt in food). Protein abundance of NKCC2, aquaporin-2 (AQP2), and TRPM6 was assessed using immunoblotting. Sirolimus-treated animals presented no change in glomerular filtration rate, although there were marked decreases in plasma potassium and magnesium. Sirolimus treatment reduced expression of NKCC2, and this was accompanied by greater urinary excretion of sodium, potassium, and magnesium. In sirolimus-treated animals, AQP2 expression was reduced. Expression of TRPM6 was increased, which might represent a direct stimulatory effect of sirolimus or a compensatory response. The finding that rosiglitazone prevented or attenuated all sirolimus-induced renal tubular defects has potential clinical implications.

N-acetylcysteine attenuates renal alterations induced by senescence in the rat

The aim of this study was to evaluate the effects of N-acetylcysteine (NAC) on renal function, as well as on sodium and water transporters, in the kidneys of aged rats. Normal, 8-month-old male Wistar rats were treated (n=6) or not (n=6) with NAC (600 mg/L in drinking water) and followed for 16 months. At the end of the follow-up period, we determined inulin clearance, serum thiobarbituric acid reactive substances (TBARS), serum cholesterol, and urinary phosphate excretion. In addition, we performed immunohistochemical staining for p53 and for ED-1-positive cells (macrophages/monocytes), together with Western blotting of kidney tissue for NKCC2, aquaporin 2 (AQP2), urea transporter A1 (UT-A1) and Klotho protein. At baseline, the two groups were similar in terms of creatinine clearance, proteinuria, cholesterol, and TBARS. At the end of the follow-up period, NAC-treated rats presented greater inulin clearance and reduced proteinuria, as well as lower serum cholesterol, serum TBARS, and urinary phosphate excretion, in comparison with untreated rats. In addition, NAC-treated rats showed upregulated expression of NKCC2, AQP2, and UT-A1; elevated Klotho protein expression, low p53 expression, and few ED-1 positive cells. In conclusion, we attribute these beneficial effects of NAC (the significant improvements in inulin clearance and in the expression of NKCC2, AQP2, and UT-A1) to its ability to decrease oxidative stress, inhibit p53 expression, minimize kidney inflammation, and stimulate Klotho expression.

Vitamin D deficiency aggravates ischemic acute kidney injury in rats

Vitamin D deficiency (VDD) increases the risk of death in hospitalized patients. Renal ischemia/reperfusion injury (IRI) induces acute kidney injury (AKI), which activates cell cycle inhibitors, including p21, a cyclin‐dependent kinase inhibitor and genomic target of 25‐hydroxyvitamin D, which is in turn a potent immunomodulator with antiproliferative effects. In this study, we assess the impact of VDD in renal IRI. Wistar rats were divided into groups, each evaluated for 30 days: control (receiving a standard diet); VDD (receiving a vitamin D‐free diet); IRI (receiving a standard diet and subjected to 45‐min bilateral renal ischemia on day 28); and VDD + IRI (receiving a vitamin D‐free diet and subjected to 45‐min bilateral renal ischemia on day 28). At 48 h after IRI, animals were euthanized; blood, urine, and kidney tissue samples were collected. Compared with IRI rats, VDD + IRI rats showed a more severe decrease in glomerular filtration rate, greater urinary protein excretion, a higher kidney/body weight ratio and lower renal aquaporin 2 expression, as well as greater morphological damage, characterized by increased interstitial area and tubular necrosis. Our results suggest that the severity of tubular damage in IRI may be associated with downregulation of vitamin D receptors and p21. VDD increases renal inflammation, cell proliferation and cell injury in ischemic AKI.

PKC stimulated by glucagon decreases UT-A1 urea transporter expression in rat IMCD

It is well-known that glucagon increases fractional excretion of urea in rats after a protein intravenous infusion. This effect was investigated by using: (a) in vitro microperfusion technique to measure [14C]-urea permeability (Pu × 10−5cm/s) in inner medullary collecting ducts (IMCD) from normal rats in the presence of 10−7M of glucagon and in the absence of vasopressin and (b) immunoblot techniques to determine urea transporter expression in tubule suspension incubated with the same glucagon concentration. Seven groups of IMCDs (n = 47) were studied. Our results revealed that: (a) glucagon decreased urea reabsorption dose-dependently; (b) the glucagon antagonist des-His1-[Glu9], blocked the glucagon action but not vasopressin action; (c) the phorbol myristate acetate, decreased urea reabsorption but (d) staurosporin, restored its effect; e) staurosporin decreased glucagon action, and finally, (f) glucagon decreased UT-A1 expression. We can conclude that glucagon reduces UT-A1 expression via a glucagon receptor by stimulating PKC.