Tyrosol attenuates ischemia-reperfusion-induced kidney injury via inhibition of inducible nitric oxide synthase

The effect of tyrosol on diclofenac sodium-induced acute nephrotoxicity in rats

Although diclofenac (DCF) is a nonsteroidal anti-inflammatory drug that is considered safe, its chronic use and overdose may show some toxic effects. The protective effect of tyrosol (Tyr) pretreatment against DCF-induced renal damage was investigated in this study. The 32 rats used in the study were randomly divided into four groups of eight rats each. According to the data obtained, it was determined that creatinine, urea, and blood urea nitrogen (BUN) levels increased in serum samples of the DCF group. Besides, the levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity decreased and the malondialdehyde (MDA) level increased in the kidney tissue. However, no change was observed in catalase (CAT) activity. Cyclooxygenase-2 (COX-2), nuclear factor kappa B (NF-κB), and tumor necrosis factor-alpha (Tnf-α) levels increased and nuclear factor erythroid 2-related factor 2 (Nrf-2) levels decreased. No change was detected in the level of interleukin 1 beta (IL-1β). When the DCF+Tyr group and the DCF group were compared, it was assessed that Tyr had a curative effect on all biochemical parameters. Also, kidney damages, such as degeneration and necrosis of tubular epithelium and congestion of veins, were obviated by treatment with tyrosol in histopathological examinations. It was determined that Tyr pretreatment provided a protective effect against nephrotoxicity induced by DCF with its anti-inflammatory and antioxidant properties.

HYAL1 deficiency attenuates lipopolysaccharide-triggered renal injury and endothelial glycocalyx breakdown in septic AKI in mice

BACKGROUND

Renal dysfunction and disruption of renal endothelial glycocalyx are two important events during septic acute kidney injury (AKI). Here, the role and mechanism of hyaluronidase 1 (HYAL1) in regulating renal injury and renal endothelial glycocalyx breakdown in septic AKI were explored for the first time.

METHODS

BALB/c mice were injected with lipopolysaccharide (LPS, 10 mg/kg) to induce AKI. HYAL1 was blocked in vivo using lentivirus-mediated short hairpin RNA targeting HYAL1 (LV-sh-HYAL1). Biochemical assays were performed to measure the levels and concentrations of biochemical parameters associated with AKI as well as levels of inflammatory cytokines. Renal pathological lesions were determined by hematoxylin-eosin (HE) staining. Cell apoptosis in the kidney was detected using terminal-deoxynucleoitidyl transferase-mediated nick end labeling (TUNEL) assay. Immunofluorescence and immunohistochemical (IHC) staining assays were used to examine the levels of hyaluronic acid in the kidney. The protein levels of adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling, endothelial glycocalyx, and autophagy-associated indicators were assessed by western blotting.

RESULTS

The knockdown of HYAL1 in LPS-subjected mice by LV-sh-HYAL1 significantly reduced renal inflammation, oxidative stress, apoptosis and kidney dysfunction in AKI, as well as alleviated renal endothelial glycocalyx disruption by preventing the release of hyaluronic acid to the bloodstream. Additionally, autophagy-related protein analysis indicated that knockdown of HYAL1 significantly enhanced autophagy in LPS mice. Furthermore, the beneficial actions of HYAL1 blockade were closely associated with the AMPK/mTOR signaling.

CONCLUSION

HYAL1 deficiency attenuates LPS-triggered renal injury and endothelial glycocalyx breakdown in septic AKI in mice.

A novel fluorescent probe for real-time imaging of thionitrous acid under inflammatory and oxidative conditions

Thionitrous acid (HSNO), a crosstalk intermediate of two crucial gasotransmitters nitric oxide and hydrogen sulfide, plays a critical role in redox regulation of cellular signaling and functions. However, real-time and facile detection of HSNO with high selectivity and sensitivity remains highly challenging. Herein we report a novel fluorescent probe (SNP-1) for HSNO detection. SNP-1 has a simple molecular structure, but showing strong fluorescence, a low detection limit, a broad linear detection range (from nanomolar to micromolar concentrations), ultrasensitivity, and high selectivity for HSNO in both aqueous media and cells. Benefiting from these unique features, SNP-1 could effectively visualize changes of HSNO levels in mouse models of acute ulcerative colitis and renal ischemia/reperfusion injury. Moreover, the good correlation between colonic HSNO levels and disease activity index demonstrated that HSNO is a promising new diagnostic agent for acute ulcerative colitis. Therefore, SNP-1 can serve as a useful fluorescent probe for precision detection of HSNO in various biological systems, thereby facilitating mechanistic studies, therapeutic assessment, and high-content drug screening for corresponding diseases.

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HSNO was the preferred intermediate to study crosstalk between H₂S and NO.

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HSNO displayed translational potential for diagnosis and assessment of diseases.

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SNP-1 displayed excellent fluorescence performance for HSNO detection.

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SNP-1 could effectively image HSNO in cells and mouse models.

5-Methyltetrahydrofolate Attenuates Oxidative Stress and Improves Kidney Function in Acute Kidney Injury through Activation of Nrf2 and Antioxidant Defense

Oxidative stress is a major mediator of adverse outcomes in acute kidney injury (AKI). Deficiency of micronutrients, such as folate, is common in AKI. Our previous study reported that AKI impaired kidney reabsorption of folate and decreased plasma folate level in rats. The present study investigated the effect of 5-methyltetrahydrofolate (5-MTHF), a biologically active form of folate/folic acid, on AKI-impaired kidney function and oxidative stress. Sprague-Dawley rats developed AKI after kidney ischemia (45 min) and reperfusion (24 h). Injection of 5-MTHF (3 µg/kg body weight) improved kidney function and attenuated oxidative stress with a restoration of glutathione and a reduction of lipid peroxidation in the kidney. Injection of 5-MTHF activated transcription factor Nrf2 and increased the expression of glutathione synthesizing enzymes, superoxide dismutase-1 and heme oxygenase-1 in the kidney. Simulated ischemia-reperfusion through hypoxia-reoxygenation increased oxidative stress in proximal tubular cells. Incubation of cells with 5-MTHF alleviated cell injury and increased antioxidant enzyme expression and intracellular glutathione levels. Inhibition of Nrf2 expression through siRNA transfection abolished the effect of 5-MTHF against oxidative stress. These results suggest that low-dose folic acid can improve kidney function through activation of Nrf2 and restoration of antioxidant defence. Micronutrient supplements may improve clinical outcomes in AKI.

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.

Ischemia-Reperfusion Injury Reduces Kidney Folate Transporter Expression and Plasma Folate Levels

Acute or chronic kidney disease can cause micronutrient deficiency. Patients with end-stage renal disease, kidney transplantation or on dialysis have reduced circulating levels of folate, an essential B vitamin. However, the molecular mechanism is not well understood. Reabsorption of folate in renal proximal tubules through folate transporters is an important process to prevent urinary loss of folate. The present study investigated the impact of acute kidney injury (AKI) on folate transporter expression and the underlying mechanism. AKI was induced in Sprague-Dawley rats that were subjected to kidney ischemia (45 min)-reperfusion (24 h). Both male and female rats displayed kidney injury and low plasma folate levels compared with sham-operated rats. The plasma folate levels were inversely correlated to plasma creatinine levels. There was a significant increase in neutrophil gelatinase-associated lipocalin (NGAL) and IL-6 mRNA expression in the kidneys of rats with ischemia-reperfusion, indicating kidney injury and increased inflammatory cytokine expression. Ischemia-reperfusion decreased mRNA and protein expression of folate transporters including folate receptor 1 (FOLR1) and reduced folate carrier (RFC); and inhibited transcription factor Sp1/DNA binding activity in the kidneys. Simulated ischemia-reperfusion through hypoxia-reoxygenation or Sp1 siRNA transfection in human proximal tubular cells inhibited folate transporter expression and reduced intracellular folate levels. These results suggest that ischemia-reperfusion injury downregulates renal folate transporter expression and decreases folate uptake by tubular cells, which may contribute to low folate status in AKI. In conclusion, ischemia-reperfusion injury can downregulate Sp1 mediated-folate transporter expression in tubular cells, which may reduce folate reabsorption and lead to low folate status.

Kidney Ischemia-Reperfusion Elicits Acute Liver Injury and Inflammatory Response

Ischemia-reperfusion (IR) is a common risk factor that causes acute kidney injury (AKI). AKI is associated with dysfunction of other organs also known as distant organ injury. The liver function is often compromised in patients with AKI and in animal models. However, the underlying mechanisms are not fully understood. Inflammatory response plays an important role in IR-induced tissue injury. Although increased proinflammatory cytokines have been detected in the kidney and the distant organs after renal IR, their original sources remain uncertain. In the present study, we investigated the acute effect of renal IR on hepatic inflammatory cytokine expression and the mechanism involved. Sprague-Dawley rats that were subjected to renal IR (ischemia for 45 min followed by reperfusion for 1 h or 6 h) had increased plasma levels of creatinine, urea, and transaminases, indicating kidney and liver injuries. There was a significant increase in the expression of proinflammatory cytokine mRNA (MCP-1, TNF-α, IL-6) in the kidney and liver in rats with renal IR. This was accompanied by a significant increase in proinflammatory cytokine protein levels in the plasma, kidney, and liver. Activation of a nuclear transcription factor kappa B (NF-κB) was detected in the liver after renal IR. The inflammatory foci and an increased myeloperoxidase (MPO) activity were detected in the liver after renal IR, indicating hepatic inflammatory response and leukocyte infiltration. These results suggest that renal IR can directly activate NF-κB and induce acute production of proinflammatory cytokines in the liver. Renal IR-induced hepatic inflammatory response may contribute to impaired liver function and systemic inflammation.

The Role of Oxidative Stress, Renal Inflammation, and Apoptosis in Post Ischemic Reperfusion Injury of Kidney Tissue: the Protective Effect of Dose-Dependent Boric Acid Administration

Ischemia/reperfusion (I/R) injury is associated with a strong inflammatory and oxidative stress response to hypoxia and reperfusion that impair organ function. We aimed to investigate the role of oxidative stress, renal inflammation, and apoptosis in the injury of the kidney tissue after ischemic reperfusion, and the protective effect of dose-dependent boric acid administration. For this purpose, 35 Sprague Dawley albino rats were divided into five groups of seven animals in each group: Sham, I/R and I/R + boric acid (BA) (i.p at doses of 50, 100, and 200 mg/kg). All animals underwent nephrectomy (the right kidney was removed) and were expected to recover for 15 days. After recovery, each animal received 45 min of ischemia. BA was injected intraperitoneally 10 min before reperfusion and a 24-h reperfusion procedure was performed. Sham group only underwent surgical stress procedure. In order to investigate the oxidative stress induced by I/R injury and antioxidant effects of different BA doses in the kidney tissue, TAS, TOS, MDA, SOD, CAT, and GSH levels were measured. DNA fragmentation, cytochrome C levels, caspase 3 activity were measured to determine apoptotic index in tissue. IL-6 and TNF-α levels were measured in the evaluation of inflammation. Hematoxylin-eosin and TUNEL staining was performed for histopathological examinations. As a result, increased oxidative stress, inflammation, and apoptosis after I/R were decreased with different doses of BA treatment. The application of high-dose BA was found to be lower in anti-apoptotic, anti-inflammatory, and antioxidant effects than in the low-dose groups.

Adalimumab mitigates ovarian ischemia-reperfusion injury in rats by regulating oxidative stress, apoptosis and resolution of inflammation

AIM

Ovarian torsion is a rare but an important reason of acute lower abdominal pain in women and associated with serious morbidity and mortality, if not treated promptly. The aim of this study was to evaluate the effects of an antitumor necrosis factor-α antibody on ovarian torsion in a rat model of ischemia-reperfusion (I/R) injury.

METHODS

Forty female Wistar Albino rats were used in the present study. The rats were randomly divided into four groups: group I (sham), group II (I/R), group III (I/R + isotonic saline) and group IV (I/R + adalimumab). The I/R model was induced by torsion of both ovaries. Immunohistochemical staining for interleukin-1β (IL-1β), nuclear factor-κB (NF-κB), and inducible nitric oxide synthase was performed. Tissue and serum oxidative stress markers in conjunction with apoptotic index (AI) with the terminal deoxynucleotidyl transferase dUTP nick end labeling method were also calculated.

RESULTS

Tissue total oxidant status, oxidative stress index and nitric oxide values were significantly decreased, and tissue total antioxidant status was found to be increased in group IV. Inflammation, vascular congestion and hemorrhagia were significantly lower in adalimumab-treated group. Serum oxidative stress markers and tissue malondialdehyde levels did not differ in study groups. The AI was significantly increased in groups 2 and 3. Adalimumab treatment significantly decreased the AI.

CONCLUSION

Adalimumab therapy in rats attenuated I/R induced ovarian injury, possibly suppressing inflammation, inhibiting oxidative stress, and altering apoptotic pathways.

Anti-Ischemic Activity of n-Tyrozol under Conditions of Repeated Transient Myocardial Ischemia in Rats

We studied anti-ischemic activity of n-tyrozol under conditions of repeated transient myocardial ischemia in rats caused by repeated (5×3 min) occlusion of the left coronary artery. n-Tyrozol administered intraperitoneally in a dose of 20 mg/kg daily over 4 days before the ischemia modeling (the last injection 15 min prior to the start of the experiment) produced a clear-cut anti-ischemic effect: it reduced ST elevation and promoted more complete recovery of ECG during reperfusion. During reperfusion periods, n-tyrozol significantly decreased the risk of ventricular fibrillation and shortened the duration of tachyarrhythmia episodes (ventricular tachycardia and fibrillation).

Supplementing diet with Manitoba lingonberry juice reduces kidney ischemia-reperfusion injury

BACKGROUND

Lingonberry (Vaccinium vitis-idaea L.) contains high levels of anthocyanins which are bioavailable in the kidney and may be protective against ischemia-reperfusion (IR)-induced acute kidney injury. This study investigated the effect of lingonberry juice on the IR-induced stress-activated signalling pathway and inflammatory response in the kidney.

RESULTS

Sprague-Dawley rats subjected to kidney IR had significantly impaired kidney function, with increased activation of the JNK signalling pathway and increased inflammatory response, measured using a multiplex panel containing an extensive array of inflammatory biomarkers. In rats fed 1 mL lingonberry juice daily for 3 weeks prior to IR, kidney function was protected and attenuation of inflammatory response and JNK signalling was reflected in the reduction of the measured biomarkers. In vitro results in cultured HK-2 cells confirmed that lingonberry anthocyanins reduced JNK signalling and inflammatory gene expression after IR.

CONCLUSION

This study shows, for the first time, that daily supplementation with lingonberry juice may protect against loss of kidney function induced by IR injury by modulating JNK signalling and inhibiting the subsequent inflammatory response. © 2017 Her Majesty the Queen in Right of Canada. Journal of the Science of Food and Agriculture © 2017 Society of Chemical Industry.

Downregulation of Glutathione Biosynthesis Contributes to Oxidative Stress and Liver Dysfunction in Acute Kidney Injury

Ischemia-reperfusion is a common cause for acute kidney injury and can lead to distant organ dysfunction. Glutathione is a major endogenous antioxidant and its depletion directly correlates to ischemia-reperfusion injury. The liver has high capacity for producing glutathione and is a key organ in modulating local and systemic redox balance. In the present study, we investigated the mechanism by which kidney ischemia-reperfusion led to glutathione depletion and oxidative stress. The left kidney of Sprague-Dawley rats was subjected to 45 min ischemia followed by 6 h reperfusion. Ischemia-reperfusion impaired kidney and liver function. This was accompanied by a decrease in glutathione levels in the liver and plasma and increased hepatic lipid peroxidation and plasma homocysteine levels. Ischemia-reperfusion caused a significant decrease in mRNA and protein levels of hepatic glutamate-cysteine ligase mediated through the inhibition of transcription factor Nrf2. Ischemia-reperfusion inhibited hepatic expression of cystathionine γ-lyase, an enzyme responsible for producing cysteine (an essential precursor for glutathione synthesis) through the transsulfuration pathway. These results suggest that inhibition of glutamate-cysteine ligase expression and downregulation of the transsulfuration pathway lead to reduced hepatic glutathione biosynthesis and elevation of plasma homocysteine levels, which, in turn, may contribute to oxidative stress and distant organ injury during renal ischemia-reperfusion.

Antineuroinflammatory and Antiproliferative Activities of Constituents from Tilia amurensis

As part of our ongoing search for bioactive constituents of natural Korean medicinal resources, we found in a preliminary study that the methanol (MeOH) extract from the trunks of Tilia amurensis RUPR. showed an inhibitory effect on nitric oxide (NO) production in an activated murine microglial cell line. A bioassay-guided fractionation and chemical investigation of the MeOH extract resulted in the isolation and identification of a new isoflavonoid glycoside, orobol 4'-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (1) and 16 known compounds (2-17). The structure of the new compound was determined by spectroscopic methods, i.e., one-dimensional (1D) and two-dimensional (2D)-NMR techniques and high resolution (HR)-MS, and chemical methods. The antineuroinflammatory activities of the isolated compounds were determined by measuring NO levels in the medium using murine microglial BV-2 cells. Among them, 12 compounds, including compound 1 (most active with an IC50 value of 23.42 µM), inhibited NO production in lipopolysaccharide-stimulated BV-2 cells. Moreover, compounds 1-4 showed moderate antiproliferative activities against the SK-MEL-2 cell line, with IC50 values ranging from 12.31 to 19.67 µM.

Tyrosol Attenuates High Fat Diet-Induced Hepatic Oxidative Stress: Potential Involvement of Cystathionine β-Synthase and Cystathionine γ-Lyase

The Mediterranean diet is known for its cardioprotective effects. Recently, its protective qualities have also been reported in patients with non-alcoholic fatty liver disease (NAFLD). Oxidative stress is one of the important factors responsible for the development and progression of NAFLD. Hydrogen sulfide (H2S), a multifaceted gasotransmitter, has emerged as a potential therapeutic target in NAFLD. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are major enzymes responsible for endogenous H2S synthesis. Since oxidative stress contributes to NAFLD pathogenesis, the objective of this study was to investigate the effect of tyrosol, a major compound in olive oil and white wine, on high fat diet-induced hepatic oxidative stress and the mechanisms involved. Mice (C57BL/6) were fed for 5 weeks with a control diet (10 % kcal fat), a high fat diet (60 % kcal fat, HFD) or a HFD supplemented with tyrosol. High fat diet feeding induced hepatic oxidative stress, as indicated by the significant increase in lipid peroxidation and NADPH oxidase activity. Tyrosol supplementation significantly increased hepatic CBS and CSE expression and H2S synthesis in high fat diet-fed mice. Such effects were associated with the attenuation of high fat diet-induced hepatic lipid peroxidation and the restoration of the redox equilibrium of the antioxidant glutathione. Tyrosol also inhibited palmitic acid-induced oxidative stress in hepatocytes (HepG2 cells). These results suggest that the antioxidant properties of tyrosol may be mediated through functional changes in CBS and CSE activity, which might contribute to the hepatoprotective effect of the Mediterranean diet.

Ascorbic acid improves renal microcirculatory oxygenation in a rat model of renal I/R injury

Background and objectives

Acute kidney injury (AKI) is a clinical condition associated with a degree of morbidity and mortality despite supportive care, and ischemia/reperfusion injury (I/R) is one of the main causes of AKI. The pathophysiology of I/R injury is a complex cascade of events including the release of free oxygen radicals followed by damage to proteins, lipids, mitochondria, and deranged tissue oxygenation. In this study, we investigated whether the antioxidant ascorbic acid would be able to largely prevent oxidative stress and consequently, reduce I/R-related injury to the kidneys in terms of oxygenation, inflammation, and renal failure.

Materials and methods

Rats were divided into three groups (n = 6/group): (1) a time control group; (2) a group subjected to renal ischemia for 60 min by high aortic occlusion followed by 2 h of reperfusion (I/R); and (3) a group subjected to I/R and treated with an i.v. 100 mg/kg bolus ascorbic acid 15 min before ischemia and continuous infusion of 50 mg/kg/hour for 2 h during reperfusion (I/R + AA). We measured renal tissue oxidative stress, microvascular oxygenation, renal oxygen delivery and consumption, and renal expression of inflammatory and injury markers.

Results

We demonstrated that aortic clamping and release resulted in increased oxidative stress and inflammation that was associated with a significant fall in systemic and renal hemodynamics and oxygenation parameters. The treatment of ascorbic acid completely abrogated oxidative stress and inflammatory parameters. However, it only partly improved microcirculatory oxygenation and was without any effect on anuria.

Conclusion

The ascorbic acid treatment partly improves microcirculatory oxygenation and prevents oxidative stress without restoring urine output in a severe I/R model of AKI.

Downregulation of cystathionine β-synthase and cystathionine γ-lyase expression stimulates inflammation in kidney ischemia-reperfusion injury

Inflammation plays a critical role in kidney ischemia-reperfusion injury but mechanisms of increased proinflammatory cytokine expression are not completely understood. Kidney has a high expression of cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) that can synthesize hydrogen sulfide. CBE and CSE are also responsible for the synthesis of cysteine, an essential precursor for glutathione, an antioxidant. Reduced hydrogen sulfide and glutathione production is associated with multiple organ injury. Although pro- and anti-inflammatory effects of hydrogen sulfide have been reported, its role in ischemia-reperfusion-induced inflammation in the kidney has not been well addressed. The aim of this study was to investigate the effect of CBS and CSE-mediated hydrogen sulfide and glutathione production on kidney inflammatory response and the mechanism involved. The left kidney of Sprague-Dawley rat was subjected to 45-min ischemia followed by reperfusion for 24 h. Ischemia-reperfusion caused a significant decrease in CBS and CSE mRNA and protein levels with a concomitant reduction of glutathione and hydrogen sulfide production in the kidney while the expression of proinflammatory cytokine expression (MCP-1, IL-6) was elevated. Hypoxia-reoxygenation of proximal tubular cells led to a decrease in CBS and CSE expression and an increase in proinflammatory cytokine expression. Supplementation of glutathione or hydrogen sulfide donor (NaHS) effectively attenuated cytokine expression in tubular cells. These results suggested that ischemia-reperfusion impaired CBS and CSE-mediated glutathione and hydrogen sulfide production in the kidney, which augmented the expression of proinflammatory cytokines. Regulation of CBS and CSE expression may be therapeutically relevant in alleviating ischemia-reperfusion-induced inflammation and improving kidney function.