Antioxidant and renoprotective effects of paricalcitol on experimental contrast-induced nephropathy model

Protective effect of paricalcitol in rat testicular damage induced by subchronic 1800 MHz radiofrequency radiation

In the present study, the possible protective effects of paricalcitol (P) were investigated in testicular damage because of 1800 MHz radiofrequency radiation (RFR) exposure. Male Sprague Dawley rats 8-10 weeks old (n = 28) were randomly divided into four groups as control (C) (n = 7), RFR (n = 7, 1800 MHz RFR 1 h/day for 30 days), P (n = 7, 0.2 μg/kg paricalcitol, 3 times a week for 30 days), and RFR + P (n = 7, 1800 MHz RFR 1 h/day for 30 days +0.2 μg/kg paricalcitol, 3 times a week for 30 days). Testicular tissue was evaluated with histological and biochemical methods. No statistically significant differences were detected between the groups in seminiferous tubule diameters and germinal epithelial thicknesses. While ultrastructural changes were observed in the seminiferous tubule and Leydig cells in the RFR group, these changes were decreased in the RFR + P group. It was found that the Johnsen Score, Ki67, and p63 immunoreactivity scores (IRS), superoxide dismutase (SOD), and catalase (CAT) activities in the RFR + P group were statistically increased as compared to the RFR group and the malondialdehyde (MDA) levels were decreased statistically and significantly. These results show that paricalcitol administration may have an ameliorative effect on testicular damage occurring because of 1800 MHz RFR exposure.

The Role of Vitamin D in SARS-CoV-2 Infection and Acute Kidney Injury

Vitamin D has been described as an essential nutrient and hormone, which can cause nuclear, non-genomic, and mitochondrial effects. Vitamin D not only controls the transcription of thousands of genes, directly or indirectly through the modulation of calcium fluxes, but it also influences the cell metabolism and maintenance specific nuclear programs. Given its broad spectrum of activity and multiple molecular targets, a deficiency of vitamin D can be involved in many pathologies. Vitamin D deficiency also influences mortality and multiple outcomes in chronic kidney disease (CKD). Active and native vitamin D serum levels are also decreased in critically ill patients and are associated with acute kidney injury (AKI) and in-hospital mortality. In addition to regulating calcium and phosphate homeostasis, vitamin D-related mechanisms regulate adaptive and innate immunity. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have a role in excessive proinflammatory cell recruitment and cytokine release, which contribute to alveolar and full-body endothelial damage. AKI is one of the most common extrapulmonary manifestations of severe coronavirus disease 2019 (COVID-19). There are also some correlations between the vitamin D level and COVID-19 severity via several pathways. Proper vitamin D supplementation may be an attractive therapeutic strategy for AKI and has the benefits of low cost and low risk of toxicity and side effects.

Narrative review of recent studies on the role of vitamin D in the prevention of cardiac and renal risk and additional considerations for COVID-19 vulnerability

The role of vitamin D in maintaining a healthy cardiovascular (CV) and the renal system has received increasing attention. Low vitamin D levels are associated with the incidence of hypertension, cardiac remodeling, and chronic congestive heart failure. Low vitamin D levels also influence renal disease progression and albuminuria deterioration. Moreover, recent research indicates that vitamin D deficiency can be a potential risk factor for coronavirus disease-19 (COVID-19) infection and poorer outcomes. Data are inconclusive as to whether supplementation with vitamin D agents reduces CV disease risk or COVID-19 severity. Conversely, in patients with kidney disease, vitamin D supplementation is associated with improved kidney function and albuminuria. This narrative review considers recent data on the effects of vitamin D on the CV and renal system, as well as its possible role regarding COVID-19 complications.

Ferrotoxicity and Its Amelioration by Calcitriol in Cultured Renal Cells

Globally, acute kidney injury (AKI) is associated with significant mortality and an enormous economic burden. Whereas iron is essential for metabolically active renal cells, it has the potential to cause renal cytotoxicity by promoting Fenton chemistry-based oxidative stress involving lipid peroxidation. In addition, 1,25-dihydroxyvitamin D3 (calcitriol), the active form of vitamin D, is reported to have an antioxidative role. In this study, we intended to demonstrate the impact of vitamin D on iron-mediated oxidant stress and cytotoxicity of Vero cells exposed to iohexol, a low osmolar iodine-containing contrast media in vitro. Cultured Vero cells were pretreated with 1,25-dihydroxyvitamin D3 dissolved in absolute ethanol (0.05%, 2.0 mM) at a dose of 1 mM for 6 hours. Subsequently, iohexol was added at a concentration of 100 mg iodine per mL and incubated for 3 hours. Total cellular iron content was analysed by a flame atomic absorption spectrophotometer at 372 nm. Lipid peroxidation was determined by TBARS (thiobarbituric acid reactive species) assay. Antioxidants including total thiol content were assessed by Ellman’s method, catalase by colorimetric method, and superoxide dismutase (SOD) by nitroblue tetrazolium assay. The cells were stained with DAPI (4 ${}^{\prime }$ ,6-diamidino-2-phenylindole), and the cytotoxicity was evaluated by viability assay (MTT assay). The results indicated that iohexol exposure caused a significant increase of the total iron content in Vero cells. A concomitant increase of lipid peroxidation and decrease of total thiol protein levels, catalase, and superoxide dismutase activity were observed along with decreased cell viability in comparison with the controls. Furthermore, these changes were significantly reversed when the cells were pretreated with vitamin D prior to incubation with iohexol. Our findings of this in vitro model of iohexol-induced renotoxicity lend further support to the nephrotoxic potential of iron and underpin the possible clinical utility of vitamin D for the treatment and prevention of AKI.

Ferrotoxicity and Its Amelioration by Calcitriol in Cultured Renal Cells

Globally, acute kidney injury (AKI) is associated with significant mortality and an enormous economic burden. Whereas iron is essential for metabolically active renal cells, it has the potential to cause renal cytotoxicity by promoting Fenton chemistry-based oxidative stress involving lipid peroxidation. In addition, 1,25-dihydroxyvitamin D3 (calcitriol), the active form of vitamin D, is reported to have an antioxidative role. In this study, we intended to demonstrate the impact of vitamin D on iron-mediated oxidant stress and cytotoxicity of Vero cells exposed to iohexol, a low osmolar iodine-containing contrast media in vitro. Cultured Vero cells were pretreated with 1,25-dihydroxyvitamin D3 dissolved in absolute ethanol (0.05%, 2.0 mM) at a dose of 1 mM for 6 hours. Subsequently, iohexol was added at a concentration of 100 mg iodine per mL and incubated for 3 hours. Total cellular iron content was analysed by a flame atomic absorption spectrophotometer at 372 nm. Lipid peroxidation was determined by TBARS (thiobarbituric acid reactive species) assay. Antioxidants including total thiol content were assessed by Ellman's method, catalase by colorimetric method, and superoxide dismutase (SOD) by nitroblue tetrazolium assay. The cells were stained with DAPI (4',6-diamidino-2-phenylindole), and the cytotoxicity was evaluated by viability assay (MTT assay). The results indicated that iohexol exposure caused a significant increase of the total iron content in Vero cells. A concomitant increase of lipid peroxidation and decrease of total thiol protein levels, catalase, and superoxide dismutase activity were observed along with decreased cell viability in comparison with the controls. Furthermore, these changes were significantly reversed when the cells were pretreated with vitamin D prior to incubation with iohexol. Our findings of this in vitro model of iohexol-induced renotoxicity lend further support to the nephrotoxic potential of iron and underpin the possible clinical utility of vitamin D for the treatment and prevention of AKI.

Paricalcitol Attenuates Contrast-Induced Acute Kidney Injury by Regulating Mitophagy and Senescence

Contrast-induced acute kidney injury (CI-AKI) is the third most common cause of hospital-acquired renal failure, with an incidence of 11%. However, the disease mechanism remains unclear, and no effective treatment is available. Paricalcitol has been reported to be effective in animal models of kidney injury. We hypothesized that paricalcitol could play a renoprotective role against CI-AKI. Rats were divided into control, paricalcitol, contrast, and paricalcitol-plus-contrast groups. We used a previously published protocol to produce CI-AKI. Paricalcitol (0.3 μg/kg) was administered intraperitoneally before 24 h and 30 min before indomethacin. We used HK-2 cells to evaluate the effects of paricalcitol on mitophagy and senescence. Ioversol triggered renal dysfunction, increasing blood urea nitrogen and serum creatinine. Significant tubular damage, increased 8-OHdG expression, and apoptosis were apparent. Ioversol injection induced high expression levels of the mitophagy markers Pink1, Parkin, and LC3 and the senescence markers β-galactosidase and p16INK4A. Paricalcitol pretreatment prevented renal dysfunction and reduced tissue damage by reducing both mitophagy and senescence. Cellular morphological changes were found, and expression of LC3B and HMGB1 was increased by ioversol in HK-2 cells. Paricalcitol countered these effects. This study showed that mitochondria might drive injury phenotypes in CI-AKI, and that paricalcitol protects against CI-AKI by decreasing mitochondrial damage.

Contrast-induced nephropathy and oxidative stress: mechanistic insights for better interventional approaches

Contrast-induced nephropathy (CIN) or contrast-induced acute kidney injury (CI-AKI) is an iatrogenic acute kidney injury observed after intravascular administration of contrast media for intravascular diagnostic procedures or therapeutic angiographic intervention. High risk patients including those with chronic kidney disease (CKD), diabetes mellitus with impaired renal function, congestive heart failure, intraarterial intervention, higher volume of contrast, volume depletion, old age, multiple myeloma, hypertension, and hyperuricemia had increased prevalence of CIN. Although CIN is reversible by itself, some patients suffer this condition without renal recovery leading to CKD or even end-stage renal disease which required long term renal replacement therapy. In addition, both CIN and CKD have been associated with increasing of mortality. Three pathophysiological mechanisms have been proposed including direct tubular toxicity, intrarenal vasoconstriction, and excessive production of reactive oxygen species (ROS), all of which lead to impaired renal function. Reports from basic and clinical studies showing potential preventive strategies for CIN pathophysiology including low- or iso-osmolar contrast media are summarized and discussed. In addition, reports on pharmacological interventions to reduce ROS and attenuate CIN are summarized, highlighting potential for use in clinical practice. Understanding this contributory mechanism could pave ways to improve therapeutic strategies in combating CIN.

Ferrotoxicity and its amelioration by endogenous vitamin D in experimental acute kidney injury

This work provides in-depth insights on catalytic iron-induced cytotoxicity and the resultant triggering of endogenous vitamin D synthesis in experimental acute kidney injury. Our results reveal significantly elevated levels of catalytic iron culminating in oxidant-mediated renal injury and a concomitant increase in 1,25-dihdyroxyvitamin D3 levels. Also, changes in other iron-related proteins including transferrin, ferritin, and hepcidin were observed both in the serum as well as in their mRNA expression. We consider all these findings vital since no connection between catalytic iron and vitamin D has been established so far. Furthermore, we believe that this work provides new and interesting results, with catalytic iron emerging as an important target in ameliorating renal cellular injury, possibly by timely administration of vitamin D. It also needs to be seen if these observations made in rats could be translated to humans by means of robust clinical trials.

Ferrotoxicity and its amelioration by endogenous vitamin D in experimental acute kidney injury

Acute kidney injury causes significant morbidity and mortality. This experimental animal study investigated the simultaneous impact of iron and vitamin D on acute kidney injury induced by iohexol, an iodinated, non-ionic monomeric radiocontrast agent in Wistar rats. Out of 36 healthy male Wistar rats, saline was injected into six control rats (group 1) and iohexol into the remaining 30 experimental rats (groups 2 to 6 comprising six rats each). Biochemical, renal histological changes, and gene expression of iron-regulating proteins and 1 α-hydroxylase were analyzed. Urinary neutrophil gelatinase-associated lipocalin (NGAL), serum creatinine, urine protein, serum and urine catalytic iron, 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, and tissue lipid peroxidation were assayed. Rats injected with iohexol showed elevated urinary NGAL (11.94 ± 6.79 ng/mL), serum creatinine (2.92 ± 0.91 mg/dL), and urinary protein levels (11.03 ± 9.68 mg/mg creatinine) together with histological evidence of tubular injury and iron accumulation. Gene expression of iron-regulating proteins and 1 α-hydroxylase was altered. Serum and urine catalytic iron levels were elevated (0.57 ± 0.17; 48.95 ± 29.13 µmol/L) compared to controls (0.49 ± 0.04; 20.7 ± 2.62 µmol/L, P < 0.001). Urine catalytic iron positively correlated with tissue peroxidation (r = 0.469, CI 0.122 to 0.667, P = 0.004) and urinary NGAL (r = 0.788, CI 0.620 to 0.887, P < 0.001). 25-hydroxyvitamin D3 (61.58 ± 9.60 ng/mL) and 1,25-dihydroxyvitamin D3 (50.44 ± 19.76 pg/mL) levels increased simultaneously. In a multivariate linear regression analysis, serum iron, urine catalytic iron, and tissue lipid peroxidation independently and positively predicted urinary NGAL, an acute kidney injury biomarker. This study highlights the nephrotoxic potential of catalytic iron besides demonstrating a concurrent induction of vitamin D endogenously for possible renoprotection in acute kidney injury.

Impact statement

This work provides in-depth insights on catalytic iron-induced cytotoxicity and the resultant triggering of endogenous vitamin D synthesis in experimental acute kidney injury. Our results reveal significantly elevated levels of catalytic iron culminating in oxidant-mediated renal injury and a concomitant increase in 1,25-dihdyroxyvitamin D3 levels. Also, changes in other iron-related proteins including transferrin, ferritin, and hepcidin were observed both in the serum as well as in their mRNA expression. We consider all these findings vital since no connection between catalytic iron and vitamin D has been established so far. Furthermore, we believe that this work provides new and interesting results, with catalytic iron emerging as an important target in ameliorating renal cellular injury, possibly by timely administration of vitamin D. It also needs to be seen if these observations made in rats could be translated to humans by means of robust clinical trials.

Evaluation of Renal Pathophysiological Processes Induced by an Iodinated Contrast Agent in a Diabetic Rabbit Model Using Intravoxel Incoherent Motion and Blood Oxygenation Level-Dependent Magnetic Resonance Imaging

OBJECTIVE

To examine the potential of intravoxel incoherent motion (IVIM) and blood oxygen level-dependent (BOLD) magnetic resonance imaging for detecting renal changes after iodinated contrast-induced acute kidney injury (CI-AKI) development in a diabetic rabbit model.

MATERIALS AND METHODS

Sixty-two rabbits were randomized into 2 groups: diabetic rabbits with the contrast agent (DCA) and healthy rabbits with the contrast agent (NCA). In each group, 6 rabbits underwent IVIM and BOLD imaging at 1 hour, 1 day, 2 days, 3 days, and 4 days after an iohexol injection while 5 rabbits were selected to undergo blood and histological examinations at these specific time points. Iohexol was administrated at a dose of 2.5 g I/kg of body weight. Further, the apparent transverse relaxation rate (R2*), average pure molecular diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) were calculated.

RESULTS

The D and f values of the renal cortex (CO) and outer medulla (OM) were significantly decreased compared to baseline values in the 2 groups 1 day after the iohexol injection (p < 0.05). A marked reduction in the D* values for both the CO and OM was also observed after 1 hour in each group (p < 0.05). In the OM, a persistent elevation of the R2* was detected for 4 days in the DCA group (p < 0.05). Histopathological changes were prominent, and the pathological features of CI-AKI aggravated in the DCA group until day 4. The D, f, and R2* values significantly correlated with the histological damage scores, hypoxia-inducible transcription factor-1α expression scores, and serum creatinine levels.

CONCLUSION

A combination of IVIM and BOLD imaging may serve as a noninvasive method for detecting and monitoring CI-AKI in the early stages in the diabetic kidney.

Investigating the Possible Protective Role of Direct Intra-arterial Administration of Mannitol and N-Acetylcysteine and Per Os Administration of Simvastatin Against Contrast-Induced Nephropathy: An Experimental Study in a Rabbit Model

PURPOSE

Contrast-induced nephropathy (CIN) is one of the leading causes of hospital-acquired acute kidney injury due to the use of iodinated contrast media in various interventional procedures like endovascular aneurysm repair. Its pathophysiology remains mostly unclear. The purpose of the present study was to comparatively study the possible protective role of direct intra-arterial administration of mannitol and acetylcysteine and per os administration of simvastatin in a histopathological level.

MATERIALS AND METHODS

In the present study, we administered iopromide directly in the infrarenal aorta of 24 New Zealand white rabbits after laparotomy. Animals were divided in four groups of six: G1 received iopromide with no protection, G2 iopromide with mannitol, G3 iopromide with acetylcysteine, and G4 iopromide with simvastatin. Renal function blood parameters were assessed prior to the administration, and in 48 h; histopathological evaluation of the kidneys was performed.

RESULTS

CIN was evident only in the no protection group G1. Moreover, G1 demonstrated significantly more severe lesions than groups G2, G3, and G4 regarding histopathological findings in glomeruli, vacuolization of tubular epithelial cells, tubular proteinaceous casts, and tubular necrosis. According to our results, intra-arterial administration of mannitol seems to be effective in protection against tubular necrosis.

CONCLUSION

In general, all three agents demonstrated a protective role in preventing the development of CIN, although it seems that there are various pathways that remain to be investigated further.

A novel simple experimental model for low-osmolar contrast-induced acute kidney injury using different definitions based on the levels of serum creatinine and cystatin C

Background

It remained lack of a kind of contrast-induced acute kidney injury (CI-AKI) model which was widely used in clinical practice and comparable to CI-AKI in humans.

Methods

Fifty Sprague-Dawley rats were divided into five groups of 10 rats each: (1) sham group (normal saline [NS] + NS); (2) NS plus low osmolality contrast medium (CM15) (NS + CM15); (3) furosemide (FM) plus NS (FM + NS); (4) FM + CM10; and (5) FM + CM15.We measured the levels of serum creatinine (SCr), cystatin C (cys-C) and histopathological scores of kidney tissues.

Results

SCr level in the FM + CM15 group were significantly increased after CM exposure compared with baseline levels (32.9 ± 4.57 vs. 158.7 ± 14.48 μmol/L, p < 0.001). Minor changes were found about the SCr levels between the pre- and post-exposure CM or NS treatment in the other groups. Additionally, the cys-C levels after CM exposure were increased compared with pretreatment levels in the FM + CM15 group (0.08 ± 0.03 vs. 0.18 ± 0.05 mg/L, p < 0.001). Minor changes were noted in the FM + NS group before and after NS administration. Only rats in the FM + CM15 group developed CI-AKI with the definitions of SCr or cys-C. Comparing to the FM + NS group, the histopathological scores were significantly increased in the FM + CM15 group.

Conclusions

A simple and reliable animal model for low osmolality contrast medium-induced AKI was established, which is similar to clinical CI-AKI based on different definitions for AKI.

Silymarin protects against radiocontrast-induced nephropathy in mice

Silymarin, an extract from Silybum marianum (milk thistle) containing a standardized mixture of flavonolignans that ameliorates some types of liver disease and, more recently, kidney damage, could be used for the ROS-scavenging effect of these antioxidants. Furthermore, contrast-induced nephropathy (CIN) is an iatrogenic impairment of renal function in patients subjected to angiographic procedures for which there is not yet a successful preventative treatment. Recent evidence has shown that this event is related to tubular/vascular injury activated mainly by oxidative stress. However, whether this bioavailable and pharmacologically safe extract protects against CIN is not clear. We proposed to evaluate the possible protective role of the antioxidant silymarin in an experimental model of CIN. Adult male Swiss mice were separated into 6 groups and pretreated orally with silymarin (50, 200 and 300 mg/kg), N-acetylcysteine (200 mg/kg) or vehicle for 5 days before the CIN and control groups. Renal function was analyzed by plasma creatinine, urea and cystatin C levels. Additionally, blood reactive oxygen species (ROS) were evaluated using ROS bioavailability, protein oxidation and DNA damage. Renal oxidative damage was evaluated using apoptosis/cell viability assays and histological analysis. We showed that silymarin preserved renal function and decreased systemic and renal oxidative damage (antigenotoxic and antiapoptotic properties, respectively) in a dose-dependent manner and was superior to conventional treatment with N-acetylcysteine. Histologically, silymarin treatment also had beneficial effects on renal glomerular and tubular injuries. Therefore, silymarin prophylaxis may be an interesting strategy for the prevention of CIN.

Rapamycin attenuates mitochondrial injury and renal tubular cell apoptosis in experimental contrast-induced acute kidney injury in rats

Reactive oxygen species (ROS) overproduction and renal tubular epithelial cell (TEC) apoptosis are key mechanisms of contrast-induced acute kidney injury (CI-AKI). Mitochondria are the main source of intracellular ROS. In the present study, the characteristics of mitophagy and the effects of rapamycin on contrast-induced abnormalities in oxidative stress, mitochondrial injury and mitophagy, TEC apoptosis and renal function were investigated in a CI-AKI rat model. Rats were divided into control group, CI-AKI group, and pretreatment groups (with rapamycin dose of 2 or 5 mg/kg). CI-AKI was induced by intraperitoneal injection of iohexol (12.25 g iodine/kg). Renal malondialdehyde (MDA) and catalase (CAT) were measured as oxidative markers. Light-chain 3 (LC3), P62, Beclin-1, PTEN-induced putative kinase (Pink1), and cytochrome c (Cyt c) expression were measured by Western blot. Mitochondrial membrane potential (ΔΨm) was determined by JC-1, colocalization of LC3-labeled autophagosomes with TOMM20-labeled mitochondria or LAMP2-labeled lysosomes was observed by fluorescence microscopy. Significantly increased serum creatinine (Scr), MDA and CAT, obvious mitochondrial injury including increase in cytosolic/mitochondrial Cyt c and decrease in ΔΨm, TEC apoptosis were induced by contrast administration. Contrast administration induced an increased expression of LC3II/I, Beclin-1, and Pink1 and decreased expression of P62. Rapamycin pretreatment induced overexpression of LC3II/I and Beclin-1. Moreover, LC3-labeled autophagosomes increasingly overlapped with TOMM20-labeled mitochondria and LAMP2-labeled lysosomes in CI-AKI, which was further enhanced by rapamycin administration. Contrast-induced Scr increase, oxidative stress, mitochondrial injury, TEC apoptosis, and necrosis were dose-dependently attenuated by rapamycin pretreatment. Rapamycin exerts renoprotective effects against CI-AKI by attenuating mitochondrial injury and oxidative stress, which might be associated with increasing mitophagy.

Application of noninvasive functional imaging to monitor the progressive changes in kidney diffusion and perfusion in contrast-induced acute kidney injury rats at 3.0 T

OBJECTIVES

Contrast-induced acute kidney injury is a prevalent cause of renal failure, and the noninvasive tools to monitor its progress are lacking. We applied intravoxel incoherent motion (IVIM) DWI to measure the progressive changes in kidney diffusion and perfusion of CI-AKI.

METHODS

Twenty-four rats received Iopromide (370 mg/ml, 1600 mg iodine/kg) to induce CI-AKI. IVIM DWI was performed on rats (n = 6) at 24 h prior to and 12, 24, 48, 72, and 96 h after the injection using a 3.0 T MRI scanner. The progressive changes in the diffusion (D) and perfusion parameters (D* and f) were studied in the cortex (CO), outer medulla (OM), and inner medulla (IM). For the histology group (n = 18), three rats were sacrificed at each time point.

RESULTS

In the CO, D reduced progressively from 24 to 48 h (P < 0.001) and increased starting from 72 h (P < 0.001). However, D decreased until to 72 h in the medulla (P < 0.001) and increased starting from 96 h (P < 0.001). D* decreased to the bottom at 24 h in the cortex and medulla (P = 0.037) and started to recover at 48 h (P = 0.007). f decreased in the cortex and medulla in an early stage (12 h) (P = 0.035) of CI-AKI and then ascended in the later stage (72 h) (P = 0.017). The H & E staining showed different degrees of serial pathological change including cloudy swelling, atrophy, even necrosis, and interstitial vasodilation of tubule epithelial cells and glomerulus cells.

CONCLUSION

Our study demonstrates the feasibility of using IVIM DWI to monitor the progress of CI-AKI, implying that IVIM DWI is a useful biomarker in the staging of CI-AKI.

Treatment combining aliskiren with paricalcitol is effective against progressive renal tubulointerstitial fibrosis via dual blockade of intrarenal renin

The aim of this study was to assess any potential additive effects of a treatment combining aliskiren with paricalcitol on reducing renal fibrosis. C57BL/6J mice were treated individually with aliskiren and/or paricalcitol until 7 days after initiation of unilateral ureteral obstruction (UUO).In obstructed kidneys of UUO mice, monotherapy with aliskiren or paricalcitol significantly attenuated interstitial fibrosis, collagen IV accumulation, and α-smooth muscle actin- and terminal deoxynucleotidyl transferase-mediated biotin nick end-labeling-positive cells. The combination treatment showed additive efficacy in inhibition of these parameters. Renal NADPH oxidase (Nox)1 and Nox2 were significantly decreased by aliskiren or paricalcitol alone or in combination, while renal Nox4 expression was significantly reduced by paricalcitol mono- or combination treatment. Increased levels of p-Erk and p-p38 MAPK, and NF-κB in UUO kidneys were also significantly reduced by either aliskiren or paricalcitol treatment alone or in combination. Aliskiren or paricalcitol monotherapy significantly reduced the expression of (pro)renin receptor in UUO kidneys. In addition, aliskiren tended to augment renin expression in UUO kidneys, but paricalcitol reduced its expression level. The combination treatment effectively blocked both (pro)renin receptor and renin expression induced by aliskiren, and resulted in a further reduction of the renal expression of angiotensin II AT1 receptor. Aliskiren failed to increase the expression of vitamin D receptor in UUO kidneys, but the combination treatment restored its expression level. Taken together, a treatment combining aliskiren with paricalcitol better inhibits UUO-induced renal injury. The mechanism of this synergy may involve more profound inhibition of the intrarenal renin-angiotensin system.

High phosphate induces a pro-inflammatory response by vascular smooth muscle cells and modulation by vitamin D derivatives

In chronic kidney disease patients, high phosphate (HP) levels are associated with cardiovascular disease, the major cause of morbidity and mortality. Since serum phosphate has been independently correlated with inflammation, the present study aimed to investigate an independent direct effect of HP as a pro-inflammatory factor in VSMCs. A possible modulatory effect of vitamin D (VitD) was also investigated. The study was performed in an in vitro model of human aortic smooth muscle cells (HASMCs). Incubation of cells in an HP (3.3 mM) medium caused an increased expression of the pro-inflammatory mediators intercellular adhesion molecule 1 (ICAM-1), interleukins (ILs) IL-1β, IL-6, IL-8 and tumour necrosis factor α (TNF-α) (not corroborated at the protein levels for ICAM-1), as well as an increase in reactive oxygen/nitrogen species (ROS/RNS) production. This was accompanied by the activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signalling as demonstrated by the increase in the nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells protein 65 (p65-NF-κΒ) assessed by Western blotting and confocal microscopy. Since all these events were attenuated by an antioxidant pre-incubation with the radical scavenger Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP), it is suggested that the inflammatory response is upstream mediated by the ROS/RNS-induced activation of NF-κΒ. Addition of paricalcitol (PC) 3·10−8 M to cells in HP prevented the phosphate induced ROS/RNS increase, the activation of NF-κΒ and the cytokine up-regulation. A bimodal effect was observed, however, for different calcitriol (CTR) concentrations, 10−10 and 10−12 M attenuated but 10−8 M stimulated this phosphate induced pro-oxidative and pro-inflammatory response. Therefore, these findings provide novel mechanisms whereby HP may directly favour vascular dysfunctions and new insights into the protective effects exerted by VitD derivatives.

Contrast-induced nephropathy: Basic concepts, pathophysiological implications and prevention strategies

Contrast-induced nephropathy (CIN) is reversible acute renal failure observed following administration of iodinated contrast media (CM) during angiographic or other medical procedures such as urography. There are various mechanisms through which CM develop their nephrotoxic effects, including oxidative stress and apoptosis. CIN is a real-life, albeit not very rare, entity. Exact pathophysiology remains obscure and no standard diagnostic criteria apply. The Acute Kidney Injury Network criteria was recently employed but its incidence/clinical significance warrants further clarification based on recent methodological advancements, because most published studies to date were contaminated by bias. The current study is a comprehensive review conducted to provide an overview of the basic concepts of CIN and summarize recent knowledge on its pathophysiology and the evidence supporting potential prevention strategies. CIN is expected to increase morbidity, hospital stay and mortality, while all patients scheduled to receive CM should undergo risk assessment for CIN and high-risk patients may be considered candidates for prevention strategies. The value of using compounds with antioxidant properties other than sodium bicarbonate, remains controversial, warranting further clinical investigation.

Application of BOLD MRI and DTI for the evaluation of renal effect related to viscosity of iodinated contrast agent in a rat model

PURPOSE

To evaluate the effects of viscosity of contrast agent (CA) on intrarenal oxygenation and diffusion as measured by blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) in a rat model.

MATERIALS AND METHODS

Radiocontrast iodixanol formulated in three viscosities were designated 270, 320, and 350 (mg iodine/mL). Sixty-three male Wistar rats were divided into four groups. Saline and iodixanol (4 g iodine/kg) were administered. MR images were acquired on a 3.0T scanner at baseline and at 1 hour, 24 hours, 48 hours, and 72 hours postinjection of solutions. BOLD-MRI was performed with a multiple gradient-recalled-echo sequence. The changes in R2*, apparent diffusion coefficient (ADC), fractional anisotropy (FA), histology, and hypoxia-inducible factor-1α (HIF-1α) immunoexpression were evaluated. The R2*, ADC, and FA values were normalized to baseline to calculate ΔR2*, ΔADC, and ΔFA.

RESULTS

Compared with baseline levels, distinct elevation of ΔR2* (P < 0.05) and obvious decrease in ΔADC (P < 0.01) and ΔFA (P < 0.05) were observed in all the anatomical compartments at 1 hour after administration of CA. The absolute values in ΔR2*, ΔADC, and ΔFA increased with increases in CA viscosity, and differed significantly between the CA groups in renal cortex (CO), outer stripe of outer medulla (OSOM), and inner stripe of outer medulla (ISOM) (all P < 0.05). A significant positive correlation was observed between ΔR2* and HIF-1α expression (P < 0.001, r = 0.75). Significant negative correlations were observed between ΔADC, ΔFA, and pathologies in CO, OSOM, ISOM (all P < 0.001, r = -0.68-0.87; all P < 0.001, r = -0.60-0.66).

CONCLUSION

The effect of CA viscosity on intrarenal oxygenation and diffusion was viscosity-dependent, and was identified using BOLD-MRI and DTI.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1320-1331.

Renalase protects against contrast-induced nephropathy in Sprague-Dawley rats

Background

Contrast-induced nephropathy (CIN) is the third leading cause of hospital-acquired acute renal failure. Oxidative stress, apoptosis and inflammation play crucial roles in CIN. Renalase is a newly discovered monoamine oxidase from the kidney. We hypothesize that renalase could protect against CIN through anti-oxidation, anti-inflammation and anti-apoptosis pathways.

Methods

We tested our hypothesis in vivo with a rat model of Ioversol-induced CIN and in vitro. Sprague-Dawley rats were divided into 4 groups (n = 6 per group): control group, Ioversol group (rats subjected to Ioversol-induced CIN), Ioversol plus vehicle group (CIN rats pretreated with vehicle) and Ioversol plus renalase group (CIN rats pretreated with 2 mg/kg recombinant renalase). HK2 cells were treated with Ioversol or H₂O₂.

Results

The results showed that pretreatment with renalase attenuated the deterioration of renal function, tubular necrosis, oxidative stress, apoptosis and inflammation (P<0.05). Furthermore, renalase protected HK2 cells against the cytotoxicity of Ioversol and suppressed Caspase-3 activity, oxidative stress and apoptosis induced by H₂O₂.

Conclusion

Recombinant renalase protected CIN in rats through anti-oxidation, anti-apoptosis and anti-inflammation mechanisms.

Effects of paricalcitol and aliskiren combination therapy on experimental diabetic nephropathy model in rats

BACKGROUND/AIMS

The aim of the present study was to investigate the effect of combination of aliskiren with paricalcitol on experimental diabetic nephropathy (DN) model in rats.

METHODS

Forty male Sprague Dawley rats were divided into 5 groups of 8 rats each, namely the control (Group C), diabetes (Group D), aliskiren (Group A), paricalcitol (Group P), and aliskiren plus paricalcitol (Group A+P) groups. Aliskiren was given by oral-gavage at a dose of 50 mg/kg/day once daily for 12 weeks. Paricalcitol was given by intraperitoneally at a dose of 0,4 µg/kg/three day of week for 12 weeks. Renal function parameters, oxidative stress biomarkers, mRNA expression of renin-angiotensin system parameters and kidney histology were determined.

RESULTS

Group A+P had lower mean albümin-to-creatinine ratio (ACR) (p=0.004) as well as higher creatinine clearance (CCr) (p<0.005) than the diabetic rats (Group D). Combination therapy significantly increased CCr (Group A+P vs. Group A, p<0.005; Group A+P vs. Group P, p=0.022) and reduced ACR (Group A+P vs. Group A, p=0.018; Group A+P vs. Group P, p<0.005) when compared to monotherapy. Serum malondialdehyde levels were significantly lower (p=0.004); glutathion levels (p=0.003), glutathion peroxidase (p=0.004) and superoxide dismutase (p<0.005) activities were significantly higher in group A+P than in group D. The mean scores of mRNA expression of renin (p<0.005), angiotensin II (p=0.012) and angiotensin type 1 receptor (p=0.018) in group A+P were significantly lower. Although combination therapy showed no additional effect on oxidative system, renin-angiotensin system and renal histology, aliskiren plus paricalcitol significantly decreased interstitial fibrosis volume when compared to monotherapy (Group A+P vs. Group A, p<0.005; Group A+P vs. Group P, p=0.002).

CONCLUSION

Our data seem to suggest a potential role of aliskiren plus paricalcitol acting synergystically for reducing the progression of diabetic nephropathy in an experimental rat model.

Sildenafil citrate for prophylaxis of nephropathy in an animal model of contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CIAKI) is one of the commonest complications associated with contrast media (CM). Although the exact etiology of CIAKI remains unclear, one hypothesis involves vasoconstriction of afferent arterioles resulting in renal ischemia. Increased renal blood flow, therefore, might represent an attractive target for the treatment of CIAKI. In this study we evaluated the protective effects of the phosphodiesterase type 5 (PDE5) inhibitor, sildenafil citrate, in a rabbit model of CIAKI. New Zealand white rabbits were used due to their susceptibility to CIAKI. To evaluate the effects of sildenafil, the drug was administered before CM infusion and repeatedly throughout the remainder of the experiment (6 mg/kg, p.o.). Animals were sacrificed after 48 hours and kidneys were prepared for histological evaluation. Intravenous administration of CM produced marked kidney injury. Serum creatinine concentrations were elevated within two hours of the infusion and remained elevated for the duration of the experiment. Histological evaluation of the kidneys revealed significant tubular necrosis. The effects of the CM were dose dependent. Treatment with sildenafil was associated with lesser degree of histological injury, attenuation in markers of acute kidney injury (48 hour creatinine 1.54±0.21 versus 4.42±1.31 mg/dl, p<0.05) and reduction in electrolyte derangement (percent change in serum K⁺ at 48 hours 2.55±3.80% versus 15.53±4.47%, p<0.05; serum Na⁺ at 48 hours −0.14±0.26% versus −1.97±1.29%, p = 0.20). The results suggest a possible role for PDE5 inhibitors in the treatment of CIAKI and warrant further evaluation to determine the exact mechanism of protection.

Benefical effects of lycopene against contrast medium-induced oxidative stress, inflammation, autophagy, and apoptosis in rat kidney

Currently, the number of imaging and interventional procedures that use contrast agents (CAs) is gradually increasing. Contrast-induced nephropathy (CIN) is the most important CA-related complication. Oxidative stress plays a significant role in its pathophysiology. Lycopene (LPN) is a natural substance with strong antioxidant capacity. The present study aimed to investigate the potential preventive effects of LPN against CIN. In total, 28 male Wistar albino rats were divided into 4 groups with 7 rats in each group; the groups include normal control group, LPN only group at a dose of 4 mg/kg/day for 10 days, CIN group by administering 10 mg/kg furosemide IM + 10 mg/kg indomethacin IP + 10 ml/kg iomeprol IV following 24-h dehydration, and CIN + LPN group. There were statistically significant increase in urea, creatinine, and malondialdehyde levels (p < 0.001, for all) but a significant decrease in glutathione, superoxide dismutase, catalase, and glutathione peroxidase levels (p < 0.001, for all) in the CIN group compared with the control group. On histological examination, a significant increase of infiltrated inflammatory cells and necrotic degenerative changes were observed in the CIN group and the immunohistochemical examination revealed a significant increase in inflammation (inducible nitric oxide synthase), autophagy (LC3/B), and apoptosis (cleaved caspase 3) in the CIN group compared with the control group (p < 0.05, for all). Significant improvements in these unfavorable parameters were observed with CIN + LPN group compared with the CIN only group. In conclusion, the favorable effects of LPN as an anti-inflammatory, antiautophagic, and antiapoptotic agent in an experimental model of CIN have been demonstrated.

The influence of selective vitamin D receptor activator paricalcitol on cardiovascular system and cardiorenal protection

The ubiquitous distribution of vitamin D receptors in the human body is responsible for the pleiotropic effects of vitamin D-receptor activation. We discuss the possible beneficial effects of a selective activator of vitamin D receptor, paricalcitol, on the cardiovascular system in chronic heart failure patients and chronic kidney patients, in light of new trials. Paricalcitol should provide additional clinical benefits over the standard treatment for chronic kidney and heart failure, especially in cases of cardiorenal syndrome.