Renal ischemia-reperfusion leads to hypertension and changes in proximal tubule Na+ transport and renin-angiotensin-aldosterone system: Role of NADPH oxidase.

Acute renal injury (AKI) is a risk factor for the development of hypertension, which involves oxidative stress, changes in Na+ handling, and the intrarenal renin-angiotensin-aldosterone system (RAAS) as underlying mechanisms. We investigated in rats whether renal ischemia-reperfusion (IR) leads to changes in the proximal tubule ATP-dependent Na+ transport and the intrarenal content of RAAS components, as well as the role of NADPH oxidase. Rats weighing 300-350 g were submitted to AKI by bilateral IR (n = 25). After IR injury, the animals were followed up for 4 weeks. One part (n = 7) received daily treatment with the NADPH oxidase inhibitor apocynin (100 mg/kg, drinking water), while another part (n = 9) received apocynin 24 h before and after IR. One group was submitted to sham surgery (n = 8). Four weeks after IR, the rats presented elevated systolic blood pressure, as well as increased lipid peroxidation, NADPH oxidase activity, (Na++K+)ATPase activity, and upregulation of type 1 angiotensin II receptor in the renal cortex. On the other hand, there was a decrease in Na+-ATPase activity and downregulation of the isoforms 1 and 2 of the angiotensin-converting enzyme, type 2 angiotensin II receptor, and of the α and ε isoforms of protein kinase C. Most of these alterations was prevented by both apocynin treatment protocols. Thus, we conclude that AKI-induced by IR may induce changes in proximal tubule ATPases and RAAS components compatible with renal Na+ retention and hypertension. These data also indicate that the NADPH oxidase represents a key factor in the origin of these alterations.

Maternal endotoxemia induces renal collagen deposition in adult offspring: Role of NADPH oxidase/TGF-ß1/MMP-2 signaling pathway.

Maternal endotoxemia has been shown to increase renal collagen deposition in the offspring. Renal fibrosis is a hallmark of progressive chronic kidney disease. It was investigated whether maternal reactive oxygen species (ROS) leads to renal fibrosis or exacerbates unilateral ureteral obstruction (UUO)-induced renal fibrosis in the offspring of dams treated with lipopolysaccharide (LPS). Furthermore, it was studied the role of matrix metalloproteinases (MMPs) in these changes. Adults Wistar rats were obtained from dams submitted to LPS administration through the third part of gestation. To evaluate the role of maternal ROS, part of the dams received α-tocopherol simultaneously with LPS. Part of the offspring in each group was submitted to UUO at adulthood when sub-groups were treated with NADPH oxidase inhibitor, apocynin. Maternal LPS administration increased proteinuria, systolic arterial pressure and renal collagen deposition in adult offspring. LPS offspring rats also presented higher MMP-2 activity in parallel to a decreased renal cortical TIMP-2 content. These changes were correlated to increased amounts of TGF-ß1 and NOX2. Maternal α-tocopherol treatment prevented collagen deposition and reduced arterial pressure in adult offspring. α-Tocopherol also inhibited maternal endotoxemia-induced changes in TGF-ß1/NOX2/MMP-2 signaling. UUO led to increased collagen deposition in the contralateral kidneys of LPS offspring, which was correlated to increased NADPH oxidase activity and prevented by NADPH oxidase inhibition. In summary, maternal endotoxemia led to alterations in the TGF-ß1/NOX2/MMP-2 signaling pathway in renal tissue concomitant with collagen deposition, therefore contributing to hypertension in adult offspring.

NO mediates the effect of the synthetic natriuretic peptide NPCdc on kidney and aorta in nephrectomised rats.

NPCdc is a synthetic natriuretic peptide that was originally derived from another peptide, the NP2_Casca, isolated from Crotalus durissus cascavella venom. These molecules share 70% structural homology with natriuretic peptides obtained from different species, including humans. NP2_Casca induces vasorelaxation and increases nitric oxide levels independently of natriuretic peptide receptors A and B. This study aimed to investigate whether NPCdc-induced hypotension in control rats and rats with a reduced kidney mass is associated with effects on the glomerular filtration rate, NADPH oxidase activity and components downstream of natriuretic peptide receptor C (NPR-C). Anaesthetized Wistar rats that were subjected to a sham operation and 5/6 nephrectomy (5/6Nx) were infused with saline (vehicle) or NPCdc (7.5 µg/kg/min) for 70 min. The NPCdc treatment decreased the mean arterial pressure and NADPH oxidase activity while simultaneously increasing the glomerular filtration rate, fractional Na+ excretion and nitric oxide level. After 70 min, the levels of p-AKT Ser-473, p-eNOS Ser-1177, p-nNOS Ser-1417 and p-iNOSTyr-151 were not affected. However, p-ERK1/2 Thr-202/Tyr-204 levels were altered. Thus, nitric oxide and components of NPR-C signalling mediate the effects of NPCdc. The results suggest a potential therapeutic application of this peptide for cardiorenal syndrome.

Antioxidant and Antiulcerogenic Activity of the Dry Extract of Pods of Libidibia ferrea Mart. ex Tul. (Fabaceae).

Ethnomedicinal studies in the Amazon community and in the Northeast region of Brazil highlight the use of Libidibia ferrea fruits for the treatment of gastric problems. However, there are no data in the literature of this pharmacological activity. Thus, the aim of this paper is to provide a scientific basis for the use of the dry extract of L. ferrea pods (DELfp) for the treatment of peptic ulcers. Phytochemical characterization was performed by HPLC/MS. In vitro antioxidant activity was assessed using DPPH, ABTS, phosphomolybdenum, and superoxide radical scavenging activity. The gastroprotective activity, the ability to stimulate mucus production, the antisecretory activity, and the influence of -SH and NO compounds on the antiulcerogenic activity of DELfp were evaluated. The healing activity was determined by the acetic acid-induced chronic ulcer model. Anti-Helicobacter pylori activity was investigated. HPLC/MS results identified the presence of phenolic compounds, gallic acid and ellagic acid, in DELfp. The extract showed antioxidant activity in vitro. In ulcers induced by absolute ethanol and acidified ethanol, the ED50 values of DELfp were 113 and 185.7 mg/kg, respectively. DELfp (100, 200, and 400 mg/kg) inhibited indomethacin-induced lesions by 66.7, 69.6, and 65.8%, respectively. DELfp (200 mg/kg) reduced gastric secretion and H+ concentration in the gastric contents and showed to be independent of nitric oxide (NO) and dependent on sulfhydryl (-SH) compounds in the protection of the gastric mucosa. In the chronic ulcer model, DELfp reduced the area of the gastric lesion. DELfp also showed anti-H. pylori activity. In conclusion, DELfp showed antioxidant, gastroprotective, healing, and antiulcerogenic activities. The mechanism of these actions seems to be mediated by different pathways and involves the reduction of gastric secretion and H+ concentration, dependence on sulfhydryl compounds, and anti-H. pylori activity. All these actions support the medicinal use of this species in the management of peptic ulcers.

Alpha-Tocopherol during lactation and after weaning alters the programming effect of prenatal high salt intake on cardiac and renal functions of adult male offspring.

Maternal salt overload programs cardiovascular and renal alterations in the offspring. However, beneficial and harmful effects of high dose vitamin E supplementation have been described in humans and animals. We investigated the hypothesis as to whether cardiac and renal alterations can be programmed by gestational salt overload, and can become further modified during lactation and after weaning. Male Wistar rats were used, being the offspring of mothers that drank either tap water or 0.3 mol/L NaCl for 20 days before and during pregnancy. α-Tocopherol (0.35 g/kg) was administered to mothers daily during lactation or to their offspring for 3 weeks post-weaning. Systolic blood pressure (tcSBP) was measured in juvenile rats aged 210 days. The response of mean arterial pressure (MAP) and heart rate (HR) to intravenous infusion of angiotensin II (Ang II) was also examined. Left ventricle plasma membrane (PMCA) and sarcoplasmic reticulum Ca2+ -ATPase (SERCA) activities, and certain parameters of renal function, were measured. Maternal saline programmed for increased body mass and kidney mass/body mass ratio, increased tcSBP, increased mean arterial pressure and heart rate with anomalous response to infused Ang II. In the heart, saline increased PMCA and α-Tocopherol per se increased PMCA/SERCA. In the kidney, the most remarkable result was the silent saline programming of CrCl , which was sensitized for a sharp decrease after α-Tocopherol. In conclusion, the combination of maternal saline overload and high α-Tocopherol immediately after birth leads to simultaneous cardiovascular and renal alterations in the young offspring, like those encountered in type V cardiorenal syndrome.

Oxidative stress induced by prenatal LPS leads to endothelial dysfunction and renal haemodynamic changes through angiotensin II/NADPH oxidase pathway: Prevention by early treatment with α-tocopherol.

We investigated whether hypertension induced by maternal lipopolysaccharide (LPS) administration during gestation is linked to peripheral vascular and renal hemodynamic regulation, through angiotensin II → NADPH-oxidase signalling, and whether these changes are directly linked to intrauterine oxidative stress. Female Wistar rats were submitted to LPS, in the absence or presence of α-tocopherol during pregnancy. Malondialdehyde in placenta and in livers from dams and foetuses was enhanced by LPS. Tail-cuff systolic blood pressure (tcSBP) was elevated in the 16-week-old LPS offspring. Renal malondialdeyde and protein expression of NADPH oxidase isoform 2 were elevated in these animals at 20 weeks of age. Maternal α-tocopherol treatment prevented the elevation in malondialdehyde induced by LPS on placenta and livers from dams and foetuses, as well as prevented the elevation in tcSBP and the elevation in renal malondialdehyde in adult life. LPS offspring presented impairment of endothelium-dependent relaxation in aorta and mesenteric rings, which was blunted by angiotensin type 1 receptor (AT1R) blockade and NADPH oxidase inhibition. At age of 32 weeks, renal hemodynamic parameters were unchanged in anaesthetised LPS offspring, but angiotensin II infusion led to an increased glomerular filtration rate paralleled by filtration fraction elevation. The renal haemodynamic changes provoked by angiotensin II was prevented by early treatment with α-tocopherol and by late treatment with NADPH oxidase inhibitor. These results point to oxidative stress as a mediator of offspring hypertension programmed by maternal inflammation and to the angiotensin II → NADPH oxidase signalling pathway as accountable for vascular and renal dysfunctions that starts and maintains hypertension.

Perinatal α-tocopherol overload programs alterations in kidney development and renal angiotensin II signaling pathways at birth and at juvenile age: Mechanisms underlying the development of elevated blood pressure.

α-Tocopherol (α-Toc) overload increases the risk of dying in humans (E.R. Miller III et al. Meta-analysis: high-dosage vitamin E supplementation may increase all-cause mortality Ann Int Med. 142 (2005) 37-46), and overload during early development leads to elevation of blood pressure at adult life, but the mechanism(s) remains unknown. We hypothesized that α-Toc overload during organogenesis affects the renal renin angiotensin system (RAS) components and renal Na+ handling, culminating with late elevated blood pressure. Pregnant Wistar rats received α-Toc or the superoxide dismutase mimetic tempol throughout pregnancy. We evaluated components of the intrarenal renin angiotensin system in neonate and juvenile offspring: Ang II-positive cells, Ang II receptors (AT1 and AT2), linked protein kinases, O2- production, NADPH oxidase abundance, lipid peroxidation and activity of Na+-transporting ATPases. In juvenile offspring we followed the evolution of arterial blood pressure. Neonates from α-Toc and tempol mothers presented with accentuated retardment in tubular development, pronounced decrease in glomerular Ang II-positive cells and AT1/AT2 ratio, intense production of O2- and upregulation of the α, ε and λ PKC isoforms. α-Toc decreased or augmented the abundance of renal (Na++K+)ATPase depending on the age and α-Toc dose. In juvenile rats the number of Ang II-positive cells returned to control values as well as PKCα, but co-existing with marked upregulation in the activity of (Na++K+) and Na+-ATPase and elevated arterial pressure at 30 days. We conclude that the mechanisms of these alterations rely on selective targeting of renal RAS components through genic and pro-oxidant effects of the vitamin.

Renal molecular mechanisms underlying altered Na+ handling and genesis of hypertension during adulthood in prenatally undernourished rats.

In the present study, we investigated the development of hypertension in prenatally undernourished adult rats, including the mechanisms that culminate in dysfunctions of molecular signalling in the kidney. Dams were fed a low-protein multideficient diet throughout gestation with or without α-tocopherol during lactation. The time course of hypertension development followed in male offspring was correlated with alterations in proximal tubule Na+-ATPase activity, expression of angiotensin II (Ang II) receptors, and activity of protein kinases C and A. After the establishment of hypertension, Ang II levels, cyclo-oxygenase 2 (COX-2) and NADPH oxidase subunit expression, lipid peroxidation and macrophage infiltration were examined in renal tissue. Lipid peroxidation in undernourished rats, which was very intense at 60 d, decreased at 90 d and returned to control values by 150 d. During the prehypertensive phase, prenatally undernourished rats exhibited elevated renal Na+-ATPase activity, type 2 Ang II receptor down-regulation and altered protein kinase A:protein kinase C ratio. Stable late hypertension coexisted with highly elevated levels of Ang II-positive cells in the cortical tubulointerstitium, enhanced increase in the expression of p47phox (NADPH oxidase regulatory subunit), marked down-regulation of COX-2 expression, expanded plasma volume and decreased creatinine clearance. These alterations were reduced when the dams were given α-tocopherol during lactation. The offspring of well-nourished dams treated with α-tocopherol exhibited most of the alterations encountered in the offspring of undernourished dams not treated with α-tocopherol. Thus, alterations in proximal tubule Na+ transport, subcellular signalling pathways and reactive oxygen species handling in renal tissue underpin the development of hypertension.