Oxidative stress and nitric oxide in kidney function

J-shaped Association between Serum Uric Acid Levels and the Prevalence of a Reduced Kidney Function: A Cross-sectional Study Using Japanese Health Examination Data

Objective While an association between a reduced kidney function and hyperuricemia has been reported, its association with hypouricemia is not well understood. The present study therefore investigated this association. Methods Using a large Japanese health examination dataset, we performed a multivariable logistic regression analysis to assess the association between serum uric acid (SUA) levels and a reduced kidney function. The covariates included the age, body mass index, alcohol intake, and the presence of hypertension, dyslipidemia, or diabetes. Patients This study included 227,672 patients (104,854 men; 46.1%), and the analyses were performed separately for men and women. The patients were classified into 5 groups: hypouricemia (SUA ≤2.0 mg/dL) (1st) and four other (2nd-5th) groups with SUA levels of ≤2.0, 2.1-5.1, 5.2-5.9, 6.0-6.8, ≥6.9 mg/dL in men and ≤2.0, 2.1-3.7, 3.8-4.4, 4.5-5.1, ≥5.2 mg/dL in women, respectively. Results The characteristics of the study population were as follows: men, age 55.9±14.9 years old, SUA 5.9±1.3 mg/dL, estimated glomerular filtration rate (eGFR) 80.0±17.2 mL/min/1.73 m2, and a reduced kidney function (eGFR <60.0 mL/min/1.73 m2) 9.4%; women, age 57.3±15.0 years old, SUA 4.5±1.1 mg/dL, eGFR 81.2±18.0 mL/min/1.73 m2, and a reduced kidney function 9.4%. Compared with the 2nd group, the other 4 groups groups had a significantly higher prevalence of a reduced kidney function [odds ratio (OR), 2.58; 95% confidence interval (CI), 1.64-4.06 in men; OR, 1.66; 95% CI, 1.16-2.39 in women]. Conclusion The prevalence of a reduced kidney function was high in both men and women in the hypouricemia and high-SUA groups. SUA levels and the prevalence of a reduced kidney function showed a J-shaped association.

Critical roles of tubular mitochondrial ATP synthase dysfunction in maleic acid-induced acute kidney injury

Maleic acid (MA) induces renal tubular cell dysfunction directed to acute kidney injury (AKI). AKI is an increasing global health burden due to its association with mortality and morbidity. However, targeted therapy for AKI is lacking. Previously, we determined mitochondrial-associated proteins are MA-induced AKI affinity proteins. We hypothesized that mitochondrial dysfunction in tubular epithelial cells plays a critical role in AKI. In vivo and in vitro systems have been used to test this hypothesis. For the in vivo model, C57BL/6 mice were intraperitoneally injected with 400 mg/kg body weight MA. For the in vitro model, HK-2 human proximal tubular epithelial cells were treated with 2 mM or 5 mM MA for 24 h. AKI can be induced by administration of MA. In the mice injected with MA, the levels of blood urea nitrogen (BUN) and creatinine in the sera were significantly increased (p < 0.005). From the pathological analysis, MA-induced AKI aggravated renal tubular injuries, increased kidney injury molecule-1 (KIM-1) expression and caused renal tubular cell apoptosis. At the cellular level, mitochondrial dysfunction was found with increasing mitochondrial reactive oxygen species (ROS) (p < 0.001), uncoupled mitochondrial respiration with decreasing electron transfer system activity (p < 0.001), and decreasing ATP production (p < 0.05). Under transmission electron microscope (TEM) examination, the cristae formation of mitochondria was defective in MA-induced AKI. To unveil the potential target in mitochondria, gene expression analysis revealed a significantly lower level of ATPase6 (p < 0.001). Renal mitochondrial protein levels of ATP subunits 5A1 and 5C1 (p < 0.05) were significantly decreased, as confirmed by protein analysis. Our study demonstrated that dysfunction of mitochondria resulting from altered expression of ATP synthase in renal tubular cells is associated with MA-induced AKI. This finding provides a potential novel target to develop new strategies for better prevention and treatment of MA-induced AKI.

Recent Advances in Nanomaterials for the Treatment of Acute Kidney Injury

Acute kidney injury (AKI) is a serious clinical syndrome with high morbidity, elevated mortality, and poor prognosis, commonly considered a "sword of Damocles" for hospitalized patients, especially those in intensive care units. Oxidative stress, inflammation, and apoptosis, caused by the excessive production of reactive oxygen species (ROS), play a key role in AKI progression. Hence, the investigation of effective and safe antioxidants and inflammatory regulators to scavenge overexpressed ROS and regulate excessive inflammation has become a promising therapeutic option. However, the unique physiological structure and complex pathological alterations in the kidneys render traditional therapies ineffective, impeding the residence and efficacy of most antioxidant and anti-inflammatory small molecule drugs within the renal milieu. Recently, nanotherapeutic interventions have emerged as a promising and prospective strategy for AKI, overcoming traditional treatment dilemmas through alterations in size, shape, charge, and surface modifications. This Review succinctly summarizes the latest advancements in nanotherapeutic approaches for AKI, encompassing nanozymes, ROS scavenger nanomaterials, MSC-EVs, and nanomaterials loaded with antioxidants and inflammatory regulator. Following this, strategies aimed at enhancing biocompatibility and kidney targeting are introduced. Furthermore, a brief discussion on the current challenges and future prospects in this research field is presented, providing a comprehensive overview of the evolving landscape of nanotherapeutic interventions for AKI.

Monoterpene linalool restrains gentamicin-mediated acute kidney injury in rats by subsiding oxidative stress, apoptosis, and the NF-κB/iNOS/TNF-α/IL-1β pathway and regulating TGF-β

The clinical use of gentamicin (GM) is restricted by its nephrotoxic effects. This study aimed for the first time to elucidate the ameliorative effects of the monoterpene linalool (Lin) against GM-mediated acute kidney injury in rats. A total of thirty-two rats were subdivided into four equal groups: control (saline), Lin (100 mg/kg/day), GM (100 mg/kg/day), and GM + Lin (100 and 100 mg/kg/day). Lin and GM were intraperitoneally administered for 12 days. Our results illustrated that Lin ameliorated GM-mediated renal histopathological abnormalities and reduced serum urea and creatinine levels in rats exposed to GM. Lin treatment mitigated oxidative stress in nephrotoxic animals as manifested by reducing serum and renal levels of malondialdehyde and increasing the activities of serum and renal glutathione peroxidase and renal catalase. Moreover, Lin markedly inhibited GM-triggered inflammation by downregulating NF-κB, iNOS, TNF-α, and IL-1β and reducing renal myeloperoxidase activity and nitric oxide levels. Interestingly, Lin repressed GM-induced apoptosis, as reflected by a marked downregulation of Bax and caspase-3 expression, concurrent with the upregulation of Bcl2 expression. Finally, Lin administration led to a significant downregulation of TGF-β expression in nephrotoxic animals. In summary, Lin ameliorated GM-mediated nephrotoxicity in rats, at least through its antioxidant, anti-inflammatory, and anti-apoptotic activities and by modulating TGF-β.

Transient Receptor Vanilloid Subtype 4-Mediated Ca2+ Influx Promotes Glomerular Endothelial Inflammation in Sepsis-Associated Acute Kidney Injury

Sepsis-associated acute kidney injury (S-AKI) is a frequent complication in patients who are critically ill, which is often initiated by glomerular endothelial cell dysfunction. Although transient receptor vanilloid subtype 4 (TRPV4) ion channels are known to be permeable to Ca2+ and are widely expressed in the kidneys, the role of TRPV4 on glomerular endothelial inflammation in sepsis remains elusive. In the present study, we found that TRPV4 expression in mouse glomerular endothelial cells (MGECs) increased after lipopolysaccharide (LPS) stimulation or cecal ligation and puncture challenge, which increased intracellular Ca2+ in MGECs. Furthermore, the inhibition or knockdown of TRPV4 suppressed LPS-induced phosphorylation and translocation of inflammatory transcription factors NF-κB and IRF-3 in MGECs. Clamping intracellular Ca2+ mimicked LPS-induced responses observed in the absence of TRPV4. In vivo experiments showed that the pharmacologic blockade or knockdown of TRPV4 reduced glomerular endothelial inflammatory responses, increased survival rate, and improved renal function in cecal ligation and puncture-induced sepsis without altering renal cortical blood perfusion. Taken together, our results suggest that TRPV4 promotes glomerular endothelial inflammation in S-AKI and that its inhibition or knockdown alleviates glomerular endothelial inflammation by reducing Ca2+ overload and NF-κB/IRF-3 activation. These findings provide insights that may aid in the development of novel pharmacologic strategies for the treatment of S-AKI.

Shikonin Alleviates Gentamicin-Induced Renal Injury in Rats by Targeting Renal Endocytosis, SIRT1/Nrf2/HO-1, TLR-4/NF-κB/MAPK, and PI3K/Akt Cascades

Gentamicin causes kidney injury due to its accumulation in proximal tubule epithelial cells via the megalin/cubilin/CLC-5 complex. Recently, shikonin has been shown to have potential anti-inflammatory, antioxidant, antimicrobial, and chloride channel-inhibiting effects. The current study investigated the alleviation of gentamicin-induced renal injury by shikonin while preserving its bactericidal effect. Nine-week-old Wistar rats were administered 6.25, 12.5, and 25 mg/kg/day shikonin orally, one hour after the i.p. injection of 100 mg/kg/day gentamicin for seven days. Shikonin significantly and dose-dependently alleviated gentamicin-induced renal injury, as revealed by restoring normal kidney function and histological architecture. Furthermore, shikonin restored renal endocytic function, as indicated by suppressing the elevated renal megalin, cubilin, and CLC-5 and enhancing the reduced NHE3 levels and mRNA expressions induced by gentamicin. These potentials could be attributed to the modulation of the renal SIRT1/Nrf2/HO-1, TLR-4/NF-κB/MAPK, and PI3K/Akt cascades, which enhanced the renal antioxidant system and suppressed renal inflammation and apoptosis, as indicated by enhancements of SIRT1, Nrf2, HO-1, GSH, SOD, TAC, Iκb-α, Bcl-2, PI3K, and Akt levels and mRNA expressions, with reduction of TLR-4, NF-κB, MAPK, IL-1β, TNF-α, MDA, iNOS, NO, cytochrome c, caspase-3, Bax levels, and Bax/Bcl-2 ratio. Therefore, shikonin is a promising therapeutic agent for alleviating gentamicin-induced renal injury.

Composite biscuits from sandpaper and acha flour restore the altered activity of arginase, cholinergic, and purinergic enzymes in hypertensive-diabetic rats

Hypertension is one of the common co-morbidities in diabetes. Thus, the present study sought to study the effects of composite biscuits from the mixture of acha (Digitaria exilis) and sandpaper (Fiscus exasperata) leaf flours (ASLF) on mean arterial blood pressure (MABP), arginase, cholinergic, purinergic enzymatic cascade, and nitric oxide (NO) levels as well as oxidative status in streptozotocin (STZ)/L-N^G -nitro arginine methyl ester (L-NAME)-induced hypertensive/diabetic rats. Experimental rats were distributed randomly into 7 groups (n = 5). Group I-III rats were placed on the basal diet; IV-VII rats were placed on composite biscuits designated as A, B, C, and D respectively for 14 days. On the 13th day, the MABP of the experimental rats was monitored and recorded. Thereafter, the rats were sacrificed, tissues of interest were harvested, and homogenized. Subsequently, the activity of arginase cholinesterase and purinergic enzymes, as well as NO levels were evaluated in the experimental rats. However, hypertensive/diabetic rats placed on the formulated diet exhibited reduced MABP when compared with the untreated hypertensive/diabetic rats. Also, altered activity of arginase, cholinergic and purinergic were restored in diet-treated hypertensive/diabetic rats when compared with hypertensive/diabetic rats. Similarly, the NO level and antioxidant status of the treated hypertensive/diabetic rats were notably enhanced when compared with hypertensive/diabetic rats. It could be inferred that composite biscuits exhibited an ameliorative effect in hypertensive/diabetic states via their reductive effect on the MABP, arginase, cholinesterase, and purinergic enzymes and enhanced NO levels in hypertensive/diabetic rats. Meanwhile, the biscuit designated as D had seems better when their effects were compared holistically. PRACTICAL APPLICATIONS: Acha grains and sandpaper leaf have been used in the folklore for disease treatment. However, the production of composite biscuits from these naturally available recipes for the management of hypertensive diabetics proved therapeutic since their effect on hypertensive diabetic rats is positive. Therefore, the composite biscuit will offer nutraceutical benefits to both healthy and disease individuals.

Nitric Oxide Signalling in Descending Vasa Recta after Hypoxia/Re-Oxygenation

Reduced renal medullary oxygen supply is a key factor in the pathogenesis of acute kidney injury (AKI). As the medulla exclusively receives blood through descending vasa recta (DVR), dilating these microvessels after AKI may help in renoprotection by restoring renal medullary blood flow. We stimulated the NO-sGC-cGMP signalling pathway in DVR at three different levels before and after hypoxia/re-oxygenation (H/R). Rat DVR were isolated and perfused under isobaric conditions. The phosphodiesterase 5 (PDE5) inhibitor sildenafil (10⁻⁶ mol/L) impaired cGMP degradation and dilated DVR pre-constricted with angiotensin II (Ang II, 10⁻⁶ mol/L). Dilations by the soluble guanylyl cyclase (sGC) activator BAY 60-2770 as well as the nitric oxide donor sodium nitroprusside (SNP, 10⁻³ mol/L) were equally effective. Hypoxia (0.1% O₂) augmented DVR constriction by Ang II, thus potentially aggravating tissue hypoxia. H/R left DVR unresponsive to sildenafil, yet sGC activation by BAY 60-2770 effectively dilated DVR. Dilation to SNP under H/R is delayed. In conclusion, H/R renders PDE5 inhibition ineffective in dilating the crucial vessels supplying the area at risk for hypoxic damage. Stimulating sGC appears to be the most effective in restoring renal medullary blood flow after H/R and may prove to be the best target for maintaining oxygenation to this vulnerable area of the kidney.

The role of nitric oxide in sepsis-associated kidney injury

Sepsis is one of the leading causes of acute kidney injury (AKI), and several mechanisms including microcirculatory alterations, oxidative stress, and endothelial cell dysfunction are involved. Nitric oxide (NO) is one of the common elements to all these mechanisms. Although all three nitric oxide synthase (NOS) isoforms are constitutively expressed within the kidneys, they contribute in different ways to nitrergic signaling. While the endothelial (eNOS) and neuronal (nNOS) isoforms are likely to be the main sources of NO under basal conditions and participate in the regulation of renal hemodynamics, the inducible isoform (iNOS) is dramatically increased in conditions such as sepsis. The overexpression of iNOS in the renal cortex causes a shunting of blood to this region, with consequent medullary ischemia in sepsis. Differences in the vascular reactivity among different vascular beds may also help to explain renal failure in this condition. While most of the vessels present vasoplegia and do not respond to vasoconstrictors, renal microcirculation behaves differently from nonrenal vascular beds, displaying similar constrictor responses in control and septic conditions. The selective inhibition of iNOS, without affecting other isoforms, has been described as the ideal scenario. However, iNOS is also constitutively expressed in the kidneys and the NO produced by this isoform is important for immune defense. In this sense, instead of a direct iNOS inhibition, targeting the NO effectors such as guanylate cyclase, potassium channels, peroxynitrite, and S-nitrosothiols, may be a more interesting approach in sepsis-AKI and further investigation is warranted.

Renal Nano-drug delivery for acute kidney Injury: Current status and future perspectives

Acute kidney injury (AKI) causes considerable morbidity and mortality, particularly in the case of post-cardiac infarction or kidney transplantation; however, the site-specific accumulation of small molecule reno-protective agents for AKI has often proved ineffective due to dynamic fluid and solute excretion and non-selectivity, which impedes therapeutic efficacy. This article reviews the current status and future trajectories of renal nanomedicine research for AKI management from pharmacological and clinical perspectives, with a particular focus on appraising nanosized drug carrier (NDC) use for the delivery of reno-protective agents of different pharmacological classes and the effectiveness of NDCs in improving renal tissue targeting selectivity and efficacy of said agents. This review reveals the critical shift in the role of the small molecule reno-protective agents in AKI pharmacotherapy - from prophylaxis to treatment - when using NDCs for delivery to the kidney. We also highlight the need to identify the accumulation sites of NDCs carrying reno-protective agents in renal tissues during in vivo assessments and detail the less-explored pharmacological classes of reno-protective agents whose efficacies may be improved via NDC-based delivery. We conclude the paper by outlining the challenges and future perspectives of NDC-based reno-protective agent delivery for better clinical management of AKI.

Inflammation: improving understanding to prevent or ameliorate kidney diseases

Inflammatory processes are believed to play an important role in immune response to maintain tissue homeostasis by activating cellular signaling pathways and releasing inflammatory mediators in the injured tissue. Although acute inflammation can be considered protective, an uncontrolled inflammation may evolve to tissue damage, leading to chronic inflammatory diseases. Inflammation can be considered the major factor involved in the pathological progression of acute and chronic kidney diseases. Functional characteristics of this organ increase its vulnerability to developing various forms of injuries, including acute kidney injury (AKI) and chronic kidney disease (CKD). In view of translational research, several discoveries should be considered regarding the pathogenesis of the inflammatory process, which results in the validation of biomarkers for early detection of kidney diseases. Biomarkers enable the identification of proinflammatory mediators in kidney affections, based on laboratory research applied to clinical practice. Some inflammatory molecules can be useful biomarkers for the detection and diagnosis of kidney diseases, such as neutrophil gelatinase-associated lipocalin, kidney injury molecule-1 and interleukin 18.

Neuroprotective effects of insulin like growth factor-1 on engineered metal nanoparticles Ag, Cu and Al induced blood-brain barrier breakdown, edema formation, oxidative stress, upregulation of neuronal nitric oxide synthase and brain pathology

Military personnel are vulnerable to environmental or industrial exposure of engineered nanoparticles (NPs) from metals. Long-term exposure of NPs from various sources affect sensory-motor or cognitive brain functions. Thus, a possibility exists that chronic exposure of NPs affect blood-brain barrier (BBB) breakdown and brain pathology by inducing oxidative stress and/or nitric oxide production. This hypothesis was examined in the rat intoxicated with Ag, Cu or Al (50-60nm) nanoparticles (50mg/kg, i.p. once daily) for 7 days. In these NPs treated rats the BBB permeability, brain edema, neuronal nitric oxide synthase (nNOS) immunoreactivity and brain oxidants levels, e.g., myeloperoxidase (MP), malondialdehyde (MD) and glutathione (GT) was examined on the 8th day. Cu and Ag but not Al nanoparticles increased the MP and MD levels by twofold in the brain although, GT showed 50% decline. At this time increase in brain water content and BBB breakdown to protein tracers were seen in areas exhibiting nNOS positive neurons and cell injuries. Pretreatment with insulin like growth factor-1 (IGF-1) in high doses (1μg/kg, i.v. but not 0.5μg/kg daily for 7 days) together with NPs significantly reduced the oxidative stress, nNOS upregulation, BBB breakdown, edema formation and cell injuries. These novel observations demonstrate that (i) NPs depending on their metal constituent (Cu, Ag but not Al) induce oxidative stress and nNOS expression leading to BBB disruption, brain edema and cell damage, and (ii) IGF-1 depending on doses exerts powerful neuroprotection against nanoneurotoxicity, not reported earlier.

Betaine attenuates sodium arsenite-induced renal dysfunction in rats

Exposure to higher levels of arsenic is a serious threat affecting human health worldwide. We investigated the protective role of betaine (N,N,N-trimethylglycine) against sodium arsenite-induced renal dysfunction in rats. Sodium arsenite (5 mg/kg, oral) was given to rats for 4 weeks to induce nephrotoxicity. Betaine (125 and 250 mg/kg, oral) was administered in rats for 4 weeks along with sodium-arsenite feeding. Arsenic-induced renal dysfunction was demonstrated by measuring serum creatinine, creatinine clearance, urea, uric acid, potassium, fractional excretion of sodium, and microproteinuria. Oxidative stress in rat kidneys was determined by assaying thiobarbituric acid reactive substances, superoxide anion generation, and reduced glutathione levels. Furthermore, hydroxyproline assay was done to assess renal fibrosis in arsenic intoxicated rats. Hematoxylin-eosin and picrosirius red staining revealed pathological alterations in rat kidneys. Renal endothelial nitric oxide synthase (eNOS) expression was determined by immuno-histochemistry. Concurrent administration of betaine abrogated arsenic-induced renal biochemical and histological changes in rats. Betaine treatment significantly attenuated arsenic-induced decrease in renal eNOS expression. In conclusion, betaine is protective against sodium arsenite-induced renal dysfunction, which may be attributed to its anti-oxidant activity and modulation of renal eNOS expression in rat kidneys.

Agomelatine prevents gentamicin nephrotoxicity by attenuating oxidative stress and TLR-4 signaling, and upregulating PPARγ and SIRT1

Kidney injury is a relatively common complication of the use of aminoglycosides. Inflammation and oxidative stress play a key role in gentamicin (GM) nephrotoxicity. We investigated the protective effect of the melatonergic agonist agomelatine (AGM) on GM nephrotoxicity, emphasizing the involvement of TLR-4 signaling, SIRT1 and PPARγ. Rats received 25 mg/kg AGM for 15 days and 100 mg/kg GM for eight days starting at day 7. Elevated serum creatinine, urea and Kim-1 along with multiple histological alterations in the kidney were observed in GM-intoxicated rats. Malondialdehyde (MDA), TNF-α, IL-1β, nitric oxide (NO) and myeloperoxidase (MPO) were increased, and GSH, SOD and catalase were decreased in the kidney of GM-intoxicated rats. Treatment with AGM significantly ameliorated the kidney function biomarkers, prevented tissue injury, decreased inflammatory cytokines, MDA, NO and MPO, and boosted antioxidants. In addition, AGM suppressed the expression of TLR-4, NF-κB p65, p38 MAPK, ERK-1, VCAM-1 and iNOS, whereas upregulated SIRT1 and PPARγ in the kidney of GM-intoxicated rats. In conclusion, AGM prevented GM nephrotoxicity in rats by attenuating oxidative injury and inflammation. AGM suppressed TLR-4 signaling, enhanced antioxidants and upregulated SIRT1 and PPARγ in the kidney of GM-induced rats.

Potential protective roles of curcumin against cadmium-induced toxicity and oxidative stress

Curcumin, used as a spice and traditional medicine in India, exerts beneficial effects against several diseases, owing to its antioxidant, analgesic, and anti-inflammatory properties. Evidence indicates that curcumin might protect against heavy metal-induced organ toxicity by targeting biological pathways involved in anti-oxidation, anti-inflammation, and anti-tumorigenesis. Curcumin has received considerable attention owing to its therapeutic properties, and the mechanisms underlying some of its actions have been recently investigated. Cadmium (Cd) is a heavy metal found in the environment and used extensively in industries. Chronic Cd exposure induces damage to bones, liver, kidneys, lungs, testes, and the immune and cardiovascular systems. Because of its long half-life, exposure to even low Cd levels might be harmful. Cd-induced toxicity involves the overproduction of reactive oxygen species (ROS), resulting in oxidative stress and damage to essential biomolecules. Dietary antioxidants, such as chelating agents, display the potential to reduce Cd accumulation and metal-induced toxicity. Curcumin scavenges ROS and inhibits oxidative damage, thus resulting in many therapeutic properties. This review aims to address the effectiveness of curcumin against Cd-induced organ toxicity and presents evidence supporting the use of curcumin as a protective antioxidant.

D-Limonene Alleviates Acute Kidney Injury Following Gentamicin Administration in Rats: Role of NF-κB Pathway, Mitochondrial Apoptosis, Oxidative Stress, and PCNA

Clinical application of gentamicin (GM) is well known to be associated with the development of acute kidney injury (AKI). This study was the first to investigate the possible protective effects of D-limonene (D-lim) on AKI following GM administration in rats. 32 rats arranged in four groups (n = 8): (1) the control group received saline intraperitoneally (0.5 ml/day) and orally (0.5 ml/day), (2) the D-lim group received D-lim (100 mg/kg) orally and saline (0.5 ml/day) intraperitoneally, (3) the GM group received GM (100 mg/kg/day) intraperitoneally and saline (0.5 ml/day) orally, and (4) the treated group received intraperitoneal GM (100 mg/kg) and oral D-lim (100 mg/kg). All treatments were performed daily for 12 consecutive days. Results revealed that D-lim ameliorated GM-induced AKI, oxidative stress, mitochondrial apoptosis, and inflammation. D-lim showed nephroprotective effects as reflected by the decrease in serum urea and creatinine and improvement of renal histopathological changes. D-lim alleviated GM-induced oxidative stress by increasing the activities of renal catalase, serum and renal glutathione peroxidase, and renal superoxide dismutase and decreasing renal malondialdehyde and serum nitric oxide levels. Intriguingly, D-lim suppressed mitochondrial apoptosis by considerably downregulating Bax and caspase-3 (Casp-3) mRNA and protein expressions and markedly enhancing Bcl2 mRNA and protein expressions. Furthermore, D-lim significantly decreases GM-induced inflammatory response through downregulation of NF-κB, IL-6, and TNF-α mRNA and/or protein expressions and decrease in renal myeloperoxidase activity. Finally, D-lim remarkably downregulated PCNA protein expression in the treated group compared with the GM group. In brief, this study showed that D-lim alleviated AKI following GM administration in rats, partially through its antioxidant, anti-inflammatory, and antiapoptotic activities as well as downregulation of PCNA expression.

Protective Role of Nrf2 in Renal Disease

Chronic kidney disease (CKD) is one of the fastest-growing causes of death and is predicted to become by 2040 the fifth global cause of death. CKD is characterized by increased oxidative stress and chronic inflammation. However, therapies to slow or prevent CKD progression remain an unmet need. Nrf2 (nuclear factor erythroid 2-related factor 2) is a transcription factor that plays a key role in protection against oxidative stress and regulation of the inflammatory response. Consequently, the use of compounds targeting Nrf2 has generated growing interest for nephrologists. Pre-clinical and clinical studies have demonstrated that Nrf2-inducing strategies prevent CKD progression and protect from acute kidney injury (AKI). In this article, we review current knowledge on the protective mechanisms mediated by Nrf2 against kidney injury, novel therapeutic strategies to induce Nrf2 activation, and the status of ongoing clinical trials targeting Nrf2 in renal diseases.

Effect of dietary inclusion of pumpkin (Cucurbita pepo L) seed on nephrotoxicity occasioned by cisplatin in experimental rats

The study evaluated the effect of dietary inclusion of pumpkin (Cucurbita pepo L) seed (raw and roasted) on nephrotoxicity caused by cisplatin in rats. Rats were divided into control group, cisplatin-induced nephrotoxic untreated group, nephrotoxic-treated groups with Methimazole, dietary regimen containing raw pumpkin seed (5% and 10%) and roasted pumpkin seed (5% and 10%) for 14 days. Results acquired uncovered that cisplatin intoxication significantly increased (p ≤ .05) the levels of renal biomarkers, arginase activity, 8-hydroxy-21 -deoxy guanosine (8-OHdG), malondialdehyde (MDA), and reactive oxygen species (ROS) levels as well as significant decrease in functional sulfhydryl groups, nitric oxide levels, and antioxidant enzyme activities in rats' kidney when compared to the control group. These adverse changes, due to cisplatin inebriation in rodents, were in any case, forestalled by pre-treatment with pumpkin seed inclusive diet. This holds promise for the use of pumpkin seed as a food supplement in the management of nephrotoxic-related disorders. PRACTICAL APPLICATIONS: These results suggest that roasted pumpkin seed appears to be more nephroprotective than the raw pumpkin seed through regulations of arginase activity, enhancement in the antioxidant system, suppression of renal markers and lipid peroxidation. This holds p-omise for the use of roasted pumpkin seed as a food supplement in the management nephrotoxic-related disorders.

Nitric oxide delivery during cardiopulmonary bypass reduces acute kidney injury: A randomized trial

OBJECTIVE

Acute kidney injury (AKI) is a serious complication of cardiac surgery with cardiopulmonary bypass (CPB). The aim of this study was to evaluate the effects of nitric oxide (NO) supplementation to the CPB circuit on the development of cardiac surgery-associated AKI.

METHODS

This prospective randomized controlled study included 96 patients with moderate risk of renal complications who underwent elective cardiac surgery with CPB. The study protocol was registered at ClinicalTrials.gov (identifier NCT03527381). Patients were randomly allocated to either NO supplementation to the CPB bypass circuit (NO treatment group; n = 48) or usual care (control group; n = 48). In the NO treatment group, 40-ppm NO was administered during the entire CPB period. The primary outcome was the incidence of AKI.

RESULTS

NO treatment was associated with a significant decrease in AKI incidence (10 cases [20.8%] vs 20 cases [41.6%] in the control group; relative risk, 0.5; 95% confidence interval, 0.26-0.95; P = .023) and a higher median urine output during CPB (2.6 mL/kg/h [interquartile range (IQR), 2.1-5.08 mL/kg/h] vs 1.7 mL/kg/h [IQR, 0.80-2.50 mL/kg/h]; P = .0002). The median urinary neutrophil gelatinase-associated lipocalin level at 4 hours after surgery was significantly lower in the NO treatment group (1.12 ng/mL [IQR, 0.75-5.8 ng/mL] vs 4.62 ng/mL [IQR, 2.02-34.55 ng/mL]; P = .005). In the NO treatment group, concentrations of NO metabolites were significantly increased at 5 minutes postclamping, at 5 minutes after declamping, and at the end of the operation. Concentrations of proinflammatory and anti-inflammatory mediators and free plasma hemoglobin did not differ significantly between the 2 groups.

CONCLUSIONS

NO administration in patients at moderate risk of renal complications undergoing elective cardiac surgery with CPB was associated with a lower incidence of AKI.

Evaluation of the protective effect of edaravone on doxorubicin nephrotoxicity by [99mTc]DMSA renal scintigraphy and biochemical methods

To evaluate the nephroprotective effect of edaravone on doxorubicin-induced nephrotoxicity. In this experimental study, twenty-eight Wistar male rats were used. The rats were separated into 4 groups (n = 7); group І (control), rats were treated with saline (4 ml/kg) and group ІІ (doxorubicin), nephrotoxicity was induced by three doses of 18 mg/kg/i.p. doxorubicin, at a 24-h interval on the 12th, 13th, and 14th days. Group ІІІ (edaravone), rats were treated with edaravone (30 mg/kg/for 14 days), and group ІV (edaravone + doxorubicin), rats were treated with edaravone (30 mg/kg/for 14 days) and doxorubicin were injected (18 mg/kg/for 3 days; at a 24-h interval on the 12th, 13th, and 14th days). On the 15th day of the experiment, technetium-99m-labeled dimercaptosuccinic acid ([^99mTc]DMSA) uptake was obtained in both kidneys and biochemical parameters from serum and kidney tissue were measured. Doxorubicin led to nephrotoxicity through elevation of serum blood urea nitrogen (BUN), creatinine and tumor necrosis factor-α (TNF-α), nitric oxide (NO), and interleukin-6 (IL-6) in kidney tissue and decreased [^99mTc]DMSA uptake level in the kidney when compared with control group (p < 0.01). Pretreatment edaravone significantly decreased BUN and creatinine, also kidney tissue TNF-α, IL-6, NO, and increased [^99mTc]DMSA uptake level compared with the doxorubicin. Edaravone has a significant nephroprotective effect through the attenuation of oxidative stress and inflammatory markers during doxorubicin-induced nephrotoxicity in rats.

Oxidative stress as a potential target in acute kidney injury

Background

Acute kidney injury (AKI) is a major problem for health systems being directly related to short and long-term morbidity and mortality. In the last years, the incidence of AKI has been increasing. AKI and chronic kidney disease (CKD) are closely interconnected, with a growing rate of CKD linked to repeated and severe episodes of AKI. AKI and CKD can occur also secondary to imbalanced oxidative stress (OS) reactions, inflammation, and apoptosis. The kidney is particularly sensitive to OS. OS is known as a crucial pathogenetic factor in cellular damage, with a direct role in initiation, development, and progression of AKI. The aim of this review is to focus on the pathogenetic role of OS in AKI in order to gain a better understanding. We exposed the potential relationships between OS and the perturbation of renal function and we also presented the redox-dependent factors that can contribute to early kidney injury. In the last decades, promising advances have been made in understanding the pathophysiology of AKI and its consequences, but more studies are needed in order to develop new therapies that can address OS and oxidative damage in early stages of AKI.

Methods

We searched PubMed for relevant articles published up to May 2019. In this review we incorporated data from different types of studies, including observational and experimental, both in vivo and in vitro, studies that provided information about OS in the pathophysiology of AKI.

Results

The results show that OS plays a major key role in the initiation and development of AKI, providing the chance to find new targets that can be therapeutically addressed.

Discussion

Acute kidney injury represents a major health issue that is still not fully understood. Research in this area still provides new useful data that can help obtain a better management of the patient. OS represents a major focus point in many studies, and a better understanding of its implications in AKI might offer the chance to fight new therapeutic strategies.

Antioxidant modifications induced by the new metformin derivative HL156A regulate metabolic reprogramming in SAMP1/kl (-/-) mice

Aging is characterized by a reduced ability to defend against stress, an inability to maintain homeostasis, and an increased risk of disease. In this study, a metabolomics approach was used to identify novel metabolic pathways that are perturbed in a mouse model of accelerated aging (SAMP1/kl-/-) and to gain new insights into the metabolic associations of the metformin derivative HL156A. Extensive inflammation and calcification were observed in the tissues of the SAMP1/kl-/- mice with premature aging. In mouse embryonic fibroblasts (MEFs) obtained from SAMP1/kl-/- mice, we observed that HL156A induced FOXO1 expression through inhibition of the IGF-1/AKT/mTOR signaling pathways. Treatment of HL156A decreased reactive oxygen species production and enhanced mitochondrial transmembrane potential in SAMP1/kl-/- MEFs. A metabolomic profile analysis showed that HL156A increased the GSH/GSSG ratio in the kidneys of SAMP1/kl-/- mice (8-12 weeks old). In addition, treating SAMP1/kl-/- mice with HL156A (30 mg/kg) for 4 weeks improved survival and decreased the significant elevation of oxidized GSH (GSSG) that was observed in SAMP1/kl-/- mice. In histological sections, HL156A administered SAMP1/kl-/- mice exhibited a decrease in excessive calcification. Based on these findings, we conclude that the new metformin derivative HL156A may inhibit oxidative damage by inducing glutathione metabolism and antioxidant pathways.

Oxidative Stress and Renal Fibrosis: Mechanisms and Therapies

Oxidative stress results from the disruption of the redox system marked by a notable overproduction of reactive oxygen species. There are four major sources of reactive oxygen species, including NADPH oxidases, mitochondria, nitric oxide synthases, and xanthine oxidases. It is well known that renal abnormalities trigger the production of reactive oxygen species by diverse mechanisms under various pathologic stimuli, such as acute kidney injury, chronic kidney disease, nephrotic syndrome, and metabolic disturbances. Mutually, accumulating evidences have identified that oxidative stress plays an essential role in tubulointerstitial fibrosis by myofibroblast activation as well as in glomerulosclerosis by mesangial sclerosis, podocyte abnormality, and parietal epithelial cell injury. Given the involvement of oxidative stress in renal fibrosis, therapies targeting oxidative stress seem promising in renal fibrosis management. In this review, we sketch the updated knowledge of the mechanisms of oxidative stress generation during renal diseases, the pathogenic processes of oxidative stress elicited renal fibrosis and treatments targeting oxidative stress during tubulointerstitial fibrosis and glomerulosclerosis.

Pathologic Perspectives on Acute Tubular Injury Assessment in the Kidney Biopsy

The molecular mechanisms in acute tubular injury (ATI) are complex and enigmatic. Moreover, we currently lack validated tissue injury markers that can be integrated into the kidney biopsy analysis to guide nephrologists in their patient's management of AKI. Although recognizing the ATI lesion by light microscopy is fairly straightforward, the staging of tubular lesions in the context of clinical time course and etiologic mechanism currently is not adapted to the renal pathology practice. To the clinician, the exact time point when an ischemic or toxic injury has occurred often is not known and cannot be discerned from the review of the biopsy sample. Moreover, the assessment of the different types of organized necrosis as the underlying cell death mechanism, which can be targeted using specific inhibitors, has not yet reached clinical practice. The renal pathology laboratory is uniquely qualified to assess the time course and etiology of ATI using established analytic techniques, such as immunohistochemistry and electron microscopy. Recent advances in the understanding of pathophysiological mechanisms of ATI and the important role that certain types of tubular cell organelles play in different stages of the ATI lesions may allow differentiation of early versus late ATI. Furthermore, the determination of respective cell injury pathways may help to differentiate ischemic versus toxic etiology in a reliable fashion. In the future, such a kidney biopsy-based classification system of ATI could guide the nephrologist's management of patients in regard to treatment modality and drug choice.

Alteration in thiols homeostasis, protein and lipid peroxidation in renal tissue following subacute oral exposure of imidacloprid and arsenic in Wistar rats

The aim of present study was to assess whether No Observed Effect Level (NOEL) of imidacloprid (IMI) potentiates the arsenic induced renal toxicity at its maximum contaminant level in drinking water in Wistar rats. Significant elevation of lipid and protein oxidation with reduced level of total thiols and antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase, glutathione peroxidase and glutathione-s-transferase) in renal tissue may have contributed to increased renal plasma biomarkers (creatinine and blood urea nitrogen) following repeated exposure of IMI and arsenic alone and in-combination. The altered renal biomarkers in co-exposed groups corroborated with histopathological alterations in renal tissue. The observations indicated that altered thiol homeostasis in renal tissue may be associated with increased lipid and protein oxidation in IMI and arsenic administered rats. It is concluded that administration of IMI potentiate the arsenic induced renal damage in Wistar rats.

Reno-protective effects of ursodeoxycholic acid against gentamicin-induced nephrotoxicity through modulation of NF-κB, eNOS and caspase-3 expressions

Gentamicin (GNT) is a potent aminoglycoside antibiotic widely used to treat life-threatening bacterial infections. We aim to investigate the potential protective effect of ursodeoxycholic acid (UDCA) against GNT-induced nephrotoxicity. In this study, 24 male Wistar rats were used and randomly divided into four groups of six animals each. Control group received 0.5% carboxymethyl cellulose orally for 15 days, GNT group received GNT 100 mg/kg/day i.p. for 8 days, UDCA group received UDCA orally for 15 consecutive days at a dose of 60 mg/kg/day suspended in 0.5% carboxymethyl cellulose and UDCA-pretreated group received UDCA orally for 7 days then co-administered with GNT i.p. for 8 days at the same fore-mentioned doses. Serum levels of kidney function parameters (urea, creatinine, uric acid and albumin) were measured. Renal tissues were used to evaluate oxidative stress markers; malonaldehyde (MDA), reduced glutathione (GSH) and the anti-oxidant enzyme superoxide dismutase (SOD) activities and nuclear factor kappa light-chain enhancer of activated B cells (NF-κB) and kidney injury molecule-1 (KIM-1) mRNA levels. Immunohistochemical expression of endothelial nitric oxide synthase (eNOS) and caspase-3 and histological and ultrastructural examination were performed. Treatment with GNT increased the serum levels of renal function parameters and renal MDA, NF-κB and KIM-1 mRNA levels, while it decreased GSH and SOD activities. Marked immunohistochemical expression of caspase-3 was observed after GNT administration while it decreased eNOS expression. Histological and ultrastructural alterations were also evident in renal corpuscles and tubules. In contrast, pretreatment with UDCA reversed changes caused by GNT administration. These results suggest that UDCA ameliorates GNT-induced kidney injury via inhibition of oxidative stress, inflammation and apoptosis.

Risk assessment of environmental exposure to heavy metals in mothers and their respective infants

Exposure to heavy metals can cause renal injury, which has been well documented in occupational exposure. Studies of low exposure in the general population, however, are still scarce, particularly for vulnerable populations such as mothers and young children. This study evaluated exposure to heavy metals, and biomarkers of renal function and oxidative stress in 944 lactating mothers and their infants and investigated the role of the interaction between heavy metals and oxidative stress in altering renal function. Mother and infant urine samples were analyzed to measure mercury (Hg), cadmium (Cd), and lead (Pb) concentrations for determining body-burden exposure; N-acetyl-β-d-glucosaminidase (NAG), α₁-microglobulin (α₁-MG), albumin (ALB), and creatinine (Cr) concentrations for determining early renal injury; and 8-hydroxy-2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) concentrations for determining oxidative stress. The median concentrclearlyations in mothers presented as μg/g Cr (infants as μg/l) for Hg, Cd, and Pb were 0.695 (0.716), 0.322 (0.343), and 3.97 (5.306) respectively. The mothers and their infants had clearly been exposed to heavy metals and had levels higher than the reference values reported for the general populations of USA, Germany, and Canada. Multiple regression analyses clearly demonstrated associations between urinary heavy metals in quartiles and several renal and oxidative biomarkers in mothers and to a lesser extent their infants. ß coefficients for urinary excretions of MDA, 8-OHdG, ALB, α₁-MG, NAG, and Cr in mothers were high in the highest quartile of Hg (1.183-51.29μg/g Cr or 1.732-106.95μg/l), Cd (0.565-765.776μg/g Cr or 0.785-1347.0μg/l), and Pb (6.606-83.937μg/g Cr or 9.459-80.826μg/l), except Pb was not associated with ALB. Infants in the highest Pb quartile (9.293-263.098μg/l) had the highest ß coefficients of urinary excretion of MDA, 8-OHdG, ALB, NAG, and Cr. Significant increasing trend in biomarkers across the quartiles of the three metals was seen in both mothers and infants (p_trend <0.001). A receiver operating characteristic analysis supported the predictive abilities of the four renal biomarkers in discriminating between low versus high metal quartiles. The interaction between heavy metals and oxidative stress contributed to the high excretions of renal biomarkers, but the mechanism remains unclear. These findings add to the limited evidence that low exposure to heavy metals in the general population is associated with alterations in renal function that could eventually progress to renal damage if exposure continues and that children are more susceptible due to the immaturity of their body organs.

Protective Role for Antioxidants in Acute Kidney Disease

Acute kidney injury causes significant morbidity and mortality in the community and clinic. Various pathologies, including renal and cardiovascular disease, traumatic injury/rhabdomyolysis, sepsis, and nephrotoxicity, that cause acute kidney injury (AKI), induce general or regional decreases in renal blood flow. The ensuing renal hypoxia and ischemia promotes the formation of reactive oxygen species (ROS) such as superoxide radical anions, peroxides, and hydroxyl radicals, that can oxidatively damage biomolecules and membranes, and affect organelle function and induce renal tubule cell injury, inflammation, and vascular dysfunction. Acute kidney injury is associated with increased oxidative damage, and various endogenous and synthetic antioxidants that mitigate source and derived oxidants are beneficial in cell-based and animal studies. However, the benefit of synthetic antioxidant supplementation in human acute kidney injury and renal disease remains to be realized. The endogenous low-molecular weight, non-proteinaceous antioxidant, ascorbate (vitamin C), is a promising therapeutic in human renal injury in critical illness and nephrotoxicity. Ascorbate may exert significant protection by reducing reactive oxygen species and renal oxidative damage via its antioxidant activity, and/or by its non-antioxidant functions in maintaining hydroxylase and monooxygenase enzymes, and endothelium and vascular function. Ascorbate supplementation may be particularly important in renal injury patients with low vitamin C status.

Nitric oxide and asymmetric dimethyl arginine (ADMA) levels in an experimental hydronephrotic kidney caused by unilateral partial ureteral obstruction

Aim

Our aim is to measure asymmetric dimethyl arginine and nitric oxide levels in rats with induced unilateral acute ureteral obstruction to research the effects on the kidney.

Material and Methods

The study included 21 adolescent (average age 6 weeks) Sprague-Dawley male rats weighing between 240-290g divided at random into 3 groups. Group-1: Control group (n=6): underwent no procedures. Group-2: Sham group (n=6): underwent the same procedures as the experimental group without ureter and psoas muscle dissection. Group-3: Group with induced partial unilateral ureteral obstruction (n=9). All rats were sacrificed after 12 weeks. Superoxide dismutase enzyme activity and nitrite and nitrate salt levels were measured in renal tissue. Plasma nitrite-nitrate and ADMA levels were examined.

Results

In the experimental group histopathological changes observed included renal pelvis dilatation, flattened papillae, sclerotic glomerulus and fibrosis. In the experimental group tissue SOD and blood ADMA levels were higher than the control and sham groups (p<0.05) while tissue NO and plasma NO values were lower than in the sham and control groups (p<0.05).

Conclusion

Oxidative stress and disruption of NO synthesis play an important role in renal function and histopathological changes after obstructive renal disease. To prevent renal complications developing after obstructive nephropathy we believe that a new strategy may be research on reducing ADMA.

Curcumin inhibits adenosine deaminase and arginase activities in cadmium-induced renal toxicity in rat kidney

In this study, the effect of enzymes involved in degradation of renal adenosine and l-arginine was investigated in rats exposed to cadmium (Cd) and treated with curcumin, the principal active phytochemical in turmeric rhizome. Animals were divided into six groups (n = 6): saline/vehicle, saline/curcumin 12.5 mg/kg, saline/curcumin 25 mg/kg, Cd/vehicle, Cd/curcumin 12.5 mg/kg, and Cd/curcumin 25 mg/kg. The results of this study revealed that the activities of renal adenosine deaminase and arginase were significantly increased in Cd-treated rats when compared with the control (p < 0.05). However, co-treatment with curcumin inhibits the activities of these enzymes compared with Cd-treated rats. Furthermore, Cd intoxication increased the levels of some renal biomarkers (serum urea, creatinine, and electrolytes) and malondialdehyde level with a concomitant decrease in functional sulfhydryl group and nitric oxide (NO). However, co-treatment with curcumin at 12.5 mg/kg and 25 mg/kg, respectively, increases the nonenzymatic antioxidant status and NO in the kidney, with a concomitant decrease in the levels of malondialdehyde and renal biomarkers. Therefore, our results reinforce the importance of adenosine deaminase and arginase activities in Cd poisoning conditions and suggest some possible mechanisms of action by which curcumin prevent Cd-induced renal toxicity in rats.

Nephro-protective effect of a novel formulation of unopened coconut inflorescence sap powder on gentamicin induced renal damage by modulating oxidative stress and inflammatory markers

Fresh oyster white translucent sap obtained from the tender unopened inflorescence of coconut trees (Cocos nucifera) is identified to have great health benefits. Drug induced Nephrotoxicity is one of the major causes of renal damage in present generation. As a therapeutic agent, gentamicin imparts direct toxicity to kidney, resulting in acute tubular necrosis, glomerular and tubulointerstitial injury, haemodynamically mediated damage and obstructive nephropathy.There exists an increasing demand for safe and natural agents for the treatment and/or preventionofchronic nephrotoxicity and pathogenesis of kidney diseases. Our study shows the nephro protective/curing effect of a novel powder formulation of micronutrient enriched, unfermented coconut flower sap (CSP). The study was performed on adult male Wistar rats. The animals were grouped into three and treated separately with vehicle, gentamicin and gentamicin+CSP for 16days. Initially, gentamicin treatment significantly (p<0.05)reduced thelevels of antioxidant enzymes (SOD, CAT, GPx) and GSH and increased (p<0.05) the levels of creatinine, uric acid, urea, inflammatory markers (nitrite, IL-6, TNF- α, iNOS) and lipid peroxidation. Supplementation of coconut flower sap powder showed significant (p<0.05) reversal of all these biochemical parameters indicating an effective inhibition of the pathogenesis of nephrotoxicity and kidney disease.

Therapeutic insight into molsidomine, a nitric oxide donor in streptozotocin-induced diabetic nephropathy in rats

BACKGROUND

Diabetes-induced oxidative stress and hypertension play a major role in the development of nephropathy. Hence, the present study was undertaken to evaluate the protective effects of molsidomine, a nitric oxide donor in streptozotocin (STZ)-induced diabetic nephropathy (DN) in rats.

MATERIALS AND METHODS

Type 1 diabetes was induced through a single dose of STZ (52 mg/kg, i.p.) in male Wistar rats and then treated with molsidomine (5 and 10 mg/kg; p.o.) for 8 weeks. Physical parameters, vital and renal function test including blood glucose, albuminuria, blood urine nitrogen, serum creatinine, and kidney index were determined. Oxidative stress and lipid peroxidation were assessed in the kidney homogenate by means of antioxidant enzymes and malondialdehyde levels.

RESULTS

DN rats exhibited a significant renal dysfunction with a reduction in body weight, excessive oxidative stress, and pathological changes. Molsidomine treatment significantly improved vital sign, renal functions, and oxidative stress in DN rats in a dose-dependent manner. The protective effect of molsidomine was also substantiated by pathological changes in the architect of the kidney.

CONCLUSION

Molsidomine shows a significant beneficial effect in Type 1 DN in rats.

Organ protection during aortic cross-clamping

Open surgical repair of an aortic aneurysm requires aortic cross-clamping, resulting in temporary ischemia of all organs and tissues supplied by the aorta distal to the clamp. Major complications of open aneurysm repair due to aortic cross-clamping include renal ischemia-reperfusion injury and postoperative colonic ischemia in case of supra- and infrarenal aortic aneurysm repair. Ischemia-reperfusion injury results in excessive production of reactive oxygen species and in oxidative stress, which can lead to multiple organ failure. Several perioperative protective strategies have been suggested to preserve renal function during aortic cross-clamping, such as pharmacotherapy and therapeutic hypothermia of the kidneys. In this chapter, we will briefly discuss the pathophysiology of ischemia-reperfusion injury and the preventative measures that can be taken to avoid abdominal organ injury. Finally, techniques to minimize the risk of complications during and after open aneurysm repair will be presented.

Oxidative Stress Is Involved in the Renal Dysfunction Induced by Sinoaortic Denervation in Rats

The hypothesis that oxidative stress contributes to renal dysfunction in sinoaortically denervated (SAD) rats was investigated. Rats were sinoaortically denervated and received treatment with tempol (0.5 mmol/L in drinking water) for 8 weeks. Although the tempol treatment of the SAD rats had no significant effect on blood pressure or blood pressure viability, it significantly ameliorated the renal dysfunction as indicated by increases in renal blood flow (RBF) and the glomerular filtration rate (GFR) and reductions in plasma creatinine, blood urea nitrogen (BUN), the urine albumin excretion rate (UAE), and the glomerular sclerosis score (GSS). The SAD rats treated with tempol exhibited decreased plasma and renal malondialdehyde (MDA) levels and reduced renal formation of reactive oxygen species (ROS), superoxide (O₂^-), peroxynitrite (OONO^-) and 3-nitrotyrosine. Treatment with tempol suppressed the nuclear concentration of nuclear factor-kappaB (NF-κB) and reduced the renal levels of macrophage chemoattractant protein 1 (MCP-1) and interleukin-6 (IL-6). The tempol-treated SAD rats exhibited decreased renal advanced glycation end product (AGE) levels and decreased receptor for advanced glycation end products (RAGE) protein expression. The tempol treatment of the SAD rats restored mitochondrial adenosine triphosphate (ATP) formation, DNA content, membrane integrity and the renal oxygen consumption rate. Additionally, the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S epoxide transferase (GST), and catalase were decreased, and the activities of xanthin oxidase (XO) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase were enhanced in the kidneys of the SAD rats. In conclusion, our work firstly provided direct evidence that oxidative stress played an important role in the renal dysfunction of SAD rats.

Renal oxidative stress and renal CD8(+) T-cell infiltration in mercuric chloride-induced nephropathy in rats: role of angiotensin II

Mercuric chloride (HgCl2) induces kidney damage, in part, through oxidative stress. A role for angiotensin II (Ang II) in pro-inflammatory events in a model of acute HgCl2-induced nephropathy was reported. Ang II is a potent oxidative stress inducer; however, its role in oxidative/anti-oxidative events in HgCl2-induced nephropathy remains unknown. The aim of this study was to determine the role of Ang II in the oxidative stress and renal infiltration of CD8(+) T-cells after an acute HgCl2 intoxication. Three groups of Sprague Dawley rats were treated with a single subcutaneous dose of 2.5 mg/kg HgCl2: for 3 days prior to and for 4 days after that injection, rats in one group received Losartan (30 mg/kg), in another group Enalapril (30 mg/kg) or normal saline in the last group. Two other groups of drug-treated rats received saline in place of HgCl2. A final group of rats received saline in place of HgCl2 and the test drugs. All treatments were via gastric gavage. At 96 h after the vehicle/HgCl2 injection, blood and kidney samples were harvested. Renal sections were homogenized for measures of malondialdehyde (MDA), reduced glutathione (GSH) and catalase activity. Frozen sections were studied for the presence of superoxide anion ([Formula: see text]) and CD8(+) T-cells. HgCl2-treated rats had increased interstitial and tubular expression of [Formula: see text], high levels of MDA, normal catalase activity and GSH content, increased levels of interstitial CD8(+) T-cells and an increased percentage of necrotic tubules. Anti-Ang II treatments diminished the HgCl2-induced increases in interstitial [Formula: see text], CD8(+) T-cells and tubular damage and increased catalase and GSH expression above that due to HgCl2 alone; the HgCl2-induced high MDA levels were unaffected by the drugs. These data provide new information regarding the potential role of Ang II in the oxidative stress and renal CD8(+) T-cell infiltration that occur during HgCl2 nephropathy.

Distant effects of unilateral renal ischemia/reperfusion on contralateral kidney but not lung in rats: the roles of ROS and iNOS

Acute kidney injury is usually associated with distant organ dysfunction. The roles of inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) in this phenomenon were investigated following 2 h unilateral renal ischemia and 24 h reperfusion. There were 3 groups of rats subjected to either unilateral ischemia/reperfusion (UIR group), unilateral nephrectomy (UNX group), or sham operation. Two further groups were given α-tocopherol and aminoguanidine with UIR (treated-UIR group) and UNX (treated-UNX group). Plasma nitrite/nitrate and malondialdehyde were elevated only in the UIR group. Creatinine clearance and blood flow increased in non-ischemic kidney of the UIR, but not to the same extent as remnant kidney of the UNX group, while they had equal compensatory rises in absolute Na(+) and K(+) excretion and urine flow. Non-ischemic kidney of the treated-UIR group, but not remnant kidney of the treated-UNX group, showed more elevation in blood flow, whereas both kidneys had reductions in absolute Na(+) excretion and urine flow. Respiratory functional variable were not different between all groups. Therefore, 2 h unilateral renal ischemia and 24 h reperfusion did not affect lung but had distant effects on contralateral kidney partly mediated by ROS and NO-derived from iNOS to dampen compensatory increases in renal hemodynamics and to decrease tubular reabsorption.

Induced Pluripotent Stem Cell-Derived Conditioned Medium Attenuates Acute Kidney Injury by Downregulating the Oxidative Stress-Related Pathway in Ischemia-Reperfusion Rats

Teratoma-like formation addresses a critical safety concern for the potential utility of induced pluripotent stem cells (iPSCs). Therefore, therapy utilizing iPSC-derived conditioned medium (iPSC-CM) for acute kidney injury (AKI) has attracted substantial interest. A recent study showed that iPSC-CM effectively alleviated ventilator-induced lung injury in rats. It prompts us to assess the therapeutic effects of iPSC-CM on ischemic AKI. First, we assessed the changes in renal function and tubular cell apoptosis by intraperitoneal administration of iPSC-CM to ischemia-reperfusion (I/R) rats. Second, we explored the oxidative stress-related pathway in the apoptosis of renal tubular cells subjected to hypoxia-reoxygenation (H/R). Administration of iPSC-CM significantly improved renal function and protected tubular cells against apoptosis in rats with I/R-AKI, and the optimal effect was observed at the 50-fold concentrated iPSC-CM. iPSC-CM also mitigated the H/R-induced apoptosis of NRK-52E cells in vitro. Reactive oxygen species (ROS) production was augmented in kidneys following I/R and in NRK-52E cells subjected to H/R. Meanwhile, expressions of phosphorylated p38 MAPK, TNF-α, and cleaved caspase 3 and NF-κB activity were consistently increased in vivo and in vitro. Following administration of iPSC-CM, ROS production was abolished, and inflammatory cytokine expression was significantly suppressed. Annexin V-propidium iodide flow cytometry and in situ TUNEL assay further showed that iPSC-CM markedly attenuated H/R- or I/R-induced tubular cell apoptosis. Intriguingly, treatment with iPSC-CM significantly improved the survival of rats with I/R-induced AKI. iPSC-CM represents a favorable source of stem cell-based therapy and may serve as a potential therapeutic strategy for kidney repair in ischemic AKI.

Oxidative status in the macula densa modulates tubuloglomerular feedback responsiveness in angiotensin II-induced hypertension

AIM

Tubuloglomerular feedback (TGF) is an important mechanism in control of signal nephron glomerular filtration rate. The oxidative stress in the macula densa, primarily determined by the interactions between nitric oxide (NO) and superoxide (O2-), is essential in maintaining the TGF responsiveness. However, few studies examining the interactions between and amount of NO and O2- generated by the macula densa during normal and hypertensive states.

METHODS

In this study, we used isolated perfused juxtaglomerular apparatus to directly measure the amount and also studied the interactions between NO and O2- in macula densa in both physiological and slow pressor Angiotensin II (Ang II)-induced hypertensive mice.

RESULTS

We found that slow pressor Ang II at a dose of 600 ng kg(-1) min(-1) for two weeks increased mean arterial pressure by 26.1 ± 5.7 mmHg. TGF response increased from 3.4 ± 0.2 μm in control to 5.2 ± 0.2 μm in hypertensive mice. We first measured O2- generation by the macula densa and found it was undetectable in control mice. However, O2- generation by the macula densa increased to 21.4 ± 2.5 unit min(-1) in Ang II-induced hypertensive mice. We then measured NO generation and found that NO generation by the macula densa was 138.5 ± 9.3 unit min(-1) in control mice. The NO was undetectable in the macula densa in hypertensive mice infused with Ang II.

CONCLUSIONS

Under physiological conditions, TGF response is mainly controlled by the NO generated in the macula densa; in Ang II induced hypertension, the TGF response is mainly controlled by the O2- generated by the macula densa.

Endogenous flow-induced nitric oxide reduces superoxide-stimulated Na/H exchange activity via PKG in thick ascending limbs

Luminal flow stimulates endogenous nitric oxide (NO) and superoxide (O2 (-)) production by renal thick ascending limbs (TALs). The delicate balance between these two factors regulates Na transport in TALs; NO enhances natriuresis, whereas O2 (-) augments Na absorption. Endogenous, flow-stimulated O2 (-) enhances Na/H exchange (NHE). Flow-stimulated NO reduces flow-induced O2 (-), a process mediated by cGMP-dependent protein kinase (PKG). However, whether flow-stimulated, endogenously-produced NO diminishes O2 (-)-stimulated NHE activity and the signaling pathway involved are unknown. We hypothesized that flow-induced NO reduces the stimulation of NHE activity caused by flow-induced O2 (-) via PKG in TALs. Intracellular pH recovery after an acid load was measured as an indicator of NHE activity in isolated, perfused rat TALs. l-Arginine, the NO synthase substrate, decreased NHE activity by 34 ± 5% (n = 5; P < 0.04). The O2 (-) scavenger tempol decreased NHE activity by 46 ± 8% (n = 6; P < 0.004) in the absence of NO. In the presence of l-arginine, the inhibitory effect of tempol on NHE activity was reduced to -19 ± 6% (n = 6; P < 0.03). The soluble guanylate cyclase inhibitor LY-83583 blocked the effect of l-arginine thus restoring tempol's effect on NHE activity to -42 ± 4% (n = 6; P < 0.0005). The PKG inhibitor KT-5823 also inhibited l-arginine's effect on tempol-reduced NHE activity (-43 ± 5%; n = 5; P < 0.03). We conclude that flow-induced NO reduces the stimulatory effect of endogenous, flow-induced O2 (-) on NHE activity in TALs via an increase in cGMP and PKG activation.

Protective effects of methanolic extract form fruits of Lycium ruthenicum Murr on 2,2'-azobis (2-amidinopropane) dihydrochloride-induced oxidative stress in LLC-PK1 cells

Background:

Fruits of Lycium ruthenicum Murr is a health food and also used as a folk to treat heart disease, abnormal menstruation and menopause in Tibetan, China. However; whether L. ruthenicum Murr fruits methanolic extracts (LFME) protect LLC-PK1 porcine renal tubules cells from AAPH-induced oxidative damage has not been investigated.

Objective:

To investigate the protective effects of L. ruthenicum Murr fruits methanolic extracts (LFME) against 2, 2’- azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage in renal proximal tubule LLC-PK1 cells.

Materials and Methods:

LLC-PK1 cells were co-incubated with AAPH (1mM) and different concentrations of LFMW together for 24 h. Cell viability was determined by MTT assay. Total intercellular reactive oxygen species (ROS) levels and lipid peroxidation were measured using a fluorescent probe 2’, 7’-dichlorfluorescein-diacetate (DCFH-DA) and the TBA reactive substance (TBARS) assay, respectively. The endogenous antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-px) and intercellular glutathione (GSH) levels were determined using commercial assay kits according to the manufacturer's instructions.

Results:

LFME did not show a significant cytotoxic effect and increased the viability of LLC-PK1 cells in a concentration-dependent manner. LFME also decreased the total intercellular levels of ROS, reduced lipid peroxidation and increased the GSH levels as well as the activities of endogenous antioxidant enzymes to protect LLC-PK1 cells against AAPH-induced oxidative damage.

Conclusion:

The results from the present study indicated that LFME is an effective ROS scavenger to protect LLC-PK1 cells against AAPH-induced oxidative damage through decreasing ROS generation, reducing lipid peroxidation and up-regulation of endogenous GSH levels and antioxidant enzymes.

Protective role of the endothelial isoform of nitric oxide synthase in ANG II-induced inflammatory responses in the kidney

In the present study, we examine the hypothesis that the nitric oxide (NO) produced by endothelial NO synthase (eNOS) plays a protective role in the development of ANG II-induced hypertension and renal injury by minimizing oxidative stress and the inflammation induced by TNF-α. Systolic blood pressure (SBP) and renal injury responses to chronic infusions of ANG II (via implanted minipumps) were evaluated for 2 wk in wild-type (WT) and in eNOS knockout mice (KO) cotreated with or without a superoxide (O2(-)) scavenger, tempol (400 mg/l in the drinking water), or a TNF-α receptor blocker, etanercept (5 mg/kg/day ip). In study 1, when ANG II was given at a dose of 25 ng/min, it increased mean SBP in WT mice (Δ36 ± 3 mmHg; n = 7), and this effect was attenuated in mice pretreated with tempol (Δ24 ± 3 mmHg; n = 6). In KO mice (n = 9), this dose of ANG II resulted in severe renal injury associated with high mortality. To avoid this high mortality in KO, study 2 was conducted with a lower dose of ANG II (10 ng/min) that increased SBP slightly in WT (Δ17 ± 7 mmHg; n = 6) but exaggeratedly in KO (Δ48 ± 12 mmHg, n = 6) associated with severe renal injury. Cotreatment with either tempol (n = 6) or etanercept (n = 6) ameliorated the hypertensive, as well as the renal injury responses in KO compared with WT. These data demonstrate a protective role for eNOS activity in preventing renal inflammatory injury and hypertension induced by chronic increases in ANG II.

Evaluation of antihypertensive and antihyperlipidemic effects of bamboo shoot angiotensin converting enzyme inhibitory peptide in vivo

Cardiovascular protective functions of bamboo shoot angiotensin converting enzyme (ACE) inhibitory peptide (BSP) from bamboo shoot were evaluated, including antihypertensive effect on spontaneously hypertensive rats (SHRs) and antihyperlipidemic effect on high-fat-diet-induced rats. Thirty-day antihypertensive effects of BSP on SHRs were assayed. Asp-Tyr [10 mg/day kg body weight (BW)] and BSP (50 mg/day kg BW) significantly reduced ACE activity in lung at the same level (p < 0.05), while BSP (50 mg/day kg BW) reduced systolic blood pressure (SBP) more effectively for its phenolic compounds, such as ferulic acid and p-coumaric acid, which when combined with ACE inhibitor exert a synergistic effect. BSP could significantly reduce SBP, improve oxidant stress status (GSH-Px, SOD, TAC and MDA), and increase NO level in serum and NOS activity in kidney. BSP decreased total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-c) content and MDA level of hyperlipidemic rats, which might contribute to the ACE inhibitory capacity of Asp-Tyr and the fatty acid synthase inhibitory activity of phenolic compounds.

NFAT5 is activated by hypoxia: role in ischemia and reperfusion in the rat kidney

The current hypothesis postulates that NFAT5 activation in the kidney's inner medulla is due to hypertonicity, resulting in cell protection. Additionally, the renal medulla is hypoxic (10–18 mmHg); however there is no information about the effect of hypoxia on NFAT5. Using in vivo and in vitro models, we evaluated the effect of reducing the partial pressure of oxygen (PO₂) on NFAT5 activity. We found that 1) Anoxia increased NFAT5 expression and nuclear translocation in primary cultures of IMCD cells from rat kidney. 2) Anoxia increased transcriptional activity and nuclear translocation of NFAT5 in HEK293 cells. 3) The dose-response curve demonstrated that HIF-1α peaked at 2.5% and NFAT5 at 1% of O₂. 4) At 2.5% of O₂, the time-course curve of hypoxia demonstrated earlier induction of HIF-1α gene expression than NFAT5. 5) siRNA knockdown of NFAT5 increased the hypoxia-induced cell death. 6) siRNA knockdown of HIF-1α did not affect the NFAT5 induction by hypoxia. Additionally, HIF-1α was still induced by hypoxia even when NFAT5 was knocked down. 7) NFAT5 and HIF-1α expression were increased in kidney (cortex and medulla) from rats subjected to an experimental model of ischemia and reperfusion (I/R). 7) Experimental I/R increased the NFAT5-target gene aldose reductase (AR). 8) NFAT5 activators (ATM and PI3K) were induced in vitro (HEK293 cells) and in vivo (I/R kidneys) with the same timing of NFAT5. 8) Wortmannin, which inhibits ATM and PI3K, reduces hypoxia-induced NFAT5 transcriptional activation in HEK293 cells. These results demonstrate for the first time that NFAT5 is induced by hypoxia and could be a protective factor against ischemic damage.