A comparison of pathomolecular markers of fibrosis and morphology in kidney from autopsies of African Americans and whites

N-acetylcysteine delayed cadmium-induced chronic kidney injury by activating the sirtuin 1-P53 signaling pathway

With the development of modern industrial civilization, cadmium (Cd), a known nephrotoxic metal, has become a growing public safety issue due to its ability to induce various types of kidney disease. Maladaptive proximal tubule repair is a significant cause of Cd-induced chronic kidney disease (CKD), which is characterized by premature senescence and pro-fibrosis. Previously, we demonstrated that cadmium causes DNA damage and cycle arrest in renal tubular epithelial cells, which may be relevant to premature senescence regulated by sirtuin 1 (SIRT1). In this study, in vivo and in vitro studies were conducted to elucidate the role of SIRT1-mediated premature renal senescence in Cd-induced CKD. As oxidative stress is a significant cause of aging, we evaluated whether N-acetylcysteine (NAC) would inhibit Cd-induced premature aging and dysfunction in rat renal tubular epithelial cells. Cadmium induced premature renal senescence and fibrosis, and NAC inhibited premature renal senescence and fibrosis through the SIRT1-P53 pathway and delayed CKD progression. Overall, the results suggested that the SIRT1-P53 pathway mediates oxidative stress, premature renal senescence, and renal fibrosis during cadmium exposure, which may be a potential therapeutic target for Cd-induced CKD.

Effect of Erythropoietin on Postresuscitation Renal Function in a Swine Model of Ventricular Fibrillation

Purpose. To investigate the effect of EPO administration on postresuscitation renal function. Methods. Twenty-four female Landrace/Large-White piglets aged 10–15 weeks with average weight of 19 ± 2 kg were randomly assigned to 2 different groups of 12 subjects each. After the end of an 8-minute ventricular fibrillation, the control group (Group C) received saline as placebo, whereas the EPO group (Group E) received EPO 5000 U/kg. The animals were resuscitated according to the 2010 European Resuscitation Council Guidelines for Resuscitation. Results. Five animals (41.67%) from Group C and 11 animals (91.67%) from Group E achieved ROSC (p = 0.027). Eight animals (66.67%, 5 surviving and 3 nonsurviving) from Group C suffered severe kidney damage or AKI compared to animals from Group E, in which none of the swine had evidence of severe kidney damage or AKI (p = 0.001). There was a statistically significant difference in all tested biochemical markers between the two groups, as well as a positive correlation of creatinine with NGAL, L-FABP, and IL-18 (summed mean values' p = 0.049, 0.01, and 0.004, resp.). Conclusions. Administration of EPO protected swine from postresuscitation acute kidney injury.

Use of high-dose erythropoietin for repair after injury: A comparison of outcomes in heart and kidney

CONTEXT

There is a need to define the exact benefits and contraindications of use of high-dose recombinant human erythropoietin (EPO) for its non-hematopoietic function as a cytokine that enhances tissue repair after injury. This review compares the outcomes from use of EPO in the injured heart and kidney, two organs that are thought, traditionally, to have intrinsically-different repair mechanisms.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

Ongoing work by us on EPO protection of ischemia-reperfusion-injured kidneys indicated, first, that EPO acutely enhanced kidney repair via anti-apoptotic, pro-regenerative mechanisms, and second, that EPO may promote chronic fibrosis in the long term. Work by others on the ischaemia-injured heart has also indicated that EPO promotes repair. Although myocardial infarcts are made up mostly of necrotic tissue, many publications state EPO is anti-apoptotic in the heart, as well as promoting healing via cell differentiation and stimulation of granulation tissue. In the case of the heart, promotion of fibrosis may be advantageous where an infarct has destroyed a zone of cardiomyocytes, but if EPO stimulates progressive fibrosis in the heart, this may promote cardiac failure.

CONCLUSIONS

A major concern in relation to the use of EPO in a cytoprotective role is its stimulation of long-term inflammation and fibrosis. EPO usage for cytoprotection is undoubtedly advantageous, but it may need to be offset with an anti-inflammatory agent in some organs, like kidney and heart, where progression to chronic fibrosis after acute injury is often recorded.

Physiological stress increases renal injury in eNOS-knockout mice

African Americans have a fourfold greater likelihood of developing end-stage renal disease (ESRD) compared with Caucasians. It has been proposed that the increased prevalence may be explained by non-traditional factors such as environmental stress and psychosocial factors. In this study, we used infrequent running to exhaustion as a physiological stressor to mimic real life experiences, such walking up stairs when an elevator is malfunctioning or running to catch a bus, to study its effect on renal injury in a hypertensive mouse model (endothelial nitric oxide synthase-deficient mice; eNOS(-/-)). This model has previously been shown to have renal injury comparable to that observed in African Americans. The effect of physiological stress on renal injury was examined in the setting of low (0.12%), control (0.45%) and high (8%) dietary salt. Following bouts of physiological stress, eNOS(-/-) mice had significantly greater interstitial inflammation compared with unstressed eNOS(-/-) mice (two-way analysis of variance (2-ANOVA), Holm-Sidak; P<0.01). Interestingly, eNOS(-/-) mice on a high-salt diet had greater interstitial inflammation compared with similarly stressed eNOS(-/-) mice on a low- or control-salt diet (2-ANOVA, Holm-Sidak; P<0.03). These effects of stress were independent of systolic blood pressure (141±7, 143±4, and 158±8 vs. 141±4, 138±5, 150±4 mm Hg; end of study vs. baseline, respectively). There was no significant effect of stress or dietary salt on renal injury in control wild-type mice (eNOS(+)/(+)). These data demonstrate that physiological stress exacerbates the renal injury associated with hypertension and that high-salt compounds this effect of stress. These results provide support for the idea that psychosocial and environmental factors contribute to the increased prevalence of ESRD in hypertensive African Americans.

Soy protein prevents renal damage in a fructose-induced model of metabolic syndrome via inhibition of NF-kB in male rats

The study determines the effect of soy protein on inflammatory status and expression of nuclear factor-kappa B (NF-κB P(65)) and receptor for advanced glycation end products (RAGE) in a metabolic syndrome (MS) model. MS was induced in adult male rats by feeding them a high fructose diet (60 g/100 g diet). The rats were randomised into six groups by feeding one of the following semi-synthetic diets for 60 days: corn starch (60%) and casein (20%; CCD), fructose (60%) and casein (20%; FCD), fructose (60%) and soy protein (20%; FSD) or corn starch (60%) and soy protein (20%; CSD). The expression of NF-κB P(65), transforming growth factor-β1 (TGF-β1) and RAGE, histochemical localization of α-smooth muscle actin (α-SMA), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) assays, collagen deposition and ultrastructural analysis were performed. FCD rats displayed inflammatory changes and increased expression of growth factors and nuclear factors. FSD rats showed reduction in inflammation, fibrogenesis, collagen deposition, NF-κB activation and mitigated the ultrastructural changes. Soy protein prevents inflammation and early nephropathic changes in the MS model secondary to the attenuation of NF-κB activation.

Genistein modulates NF-κB-associated renal inflammation, fibrosis and podocyte abnormalities in fructose-fed rats

The study determines the effect of genistein on inflammatory status and expression of nuclear factor-kappa B (NF-κB p65), transforming growth factor-β1 (TGF-β1) and receptor for advanced glycation end products (RAGE) in kidney of fructose-fed rats. Adult male Wistar rats were fed a diet containing either starch or fructose as the source of carbohydrate. Fifteen days later, after confirming the development of insulin resistance in fructose-fed rats, the rats in each dietary group were divided into two and treated with either genistein (1 mg/kg/day) in 30% dimethylsulfoxide (DMSO) or 30% DMSO alone for the next 45 days. The expression of NF-κB P(65), TGF-β1 and RAGE, histochemical localization of α-smooth muscle actin (α-SMA), levels of tumour necrosis factor-α (TNF-α) and interleukin-6(IL-6) and ultrastructural analysis were performed at the end of the experimental period. Fructose-fed rats displayed inflammatory changes in kidney. Increased expression of TGF-β1 and RAGE in cytosol and NF-κB p65 in nuclear fraction were observed. α-SMA expression was higher in fructose-fed rat kidney. Proliferation of connective tissue was evident from increased collagen deposition in perivascular and intraglomerular regions. Administration of genistein to fructose-fed rats reduced inflammation, fibrogenesis and NF-κB activation. Genistein also mitigated the structural changes such as basement membrane thickening, reduction in podocyte number and loss of glomerular filtration barrier integrity. These findings suggest that genistein prevents inflammation, fibrosis and early nephropathic changes in fructose-fed insulin resistant rats secondary to the attenuation of NF-κB activation.

Texture analysis of liver fibrosis microscopic images: a study on the effect of biomarkers

Chronic hepatic injury results in liver fibrosis with eventual progression to irreversible cirrhosis. Liver fibrogenesis involves the activation of the quiescent hepatic stellate cell into an activated myofibroblast that is characterized by α-smooth muscle actin (α-SMA) expression and the production of collagens (types I and III). In the present study, rats were randomly divided into three groups: (i) control group, where rats were only treated with a vehicle; (ii) fibrosis group, where rats were treated with carbon tetrachloride (CCl(4)) to induce liver fibrosis; and (iii) silymarin group, where rats were protected with silymarin during CCl(4) treatment. Rats were sacrificed and sections of liver tissue were counterstained with hematoxylin and eosin and Masson's trichrome. Other sections were immunostained using collagens and α-SMA primary antibodies. Fibrosis was confirmed using serum marker measurements. Microscopic images of the stained sections were acquired and digitized. The Biomarker Index of Fibrosis (BIF) was calculated from the images by quantifying the percentage of stained fibers. Statistical methods of texture analysis (TA), namely co-occurrence and run-length matrices, were applied on the digital images followed by classification using agglomerative hierarchical clustering and linear discriminant analysis with cross validation. TA applied on different biomarkers was successful in discriminating between the groups, showing 100% sensitivity and specificity for classification between the control and fibrosis groups using any biomarker. Some classification attempts showed dependence on the biomarker used, especially for classification between the silymarin and fibrosis groups, which showed optimal results using Masson's trichrome. TA results were consistent with both BIF and serum marker measurements.

Effect of Astragalus membranaceus and Angelica sinensis combined with Enalapril in rats with obstructive uropathy

ACE inhibitors (ACEi) reduce renal tubulointerstitial fibrosis but are not completely effective. Combined extract of Astragalus membranaceus and Angelica sinensis (A&A) is a traditional antifibrotic agent in China. The present investigation aimed to determine whether an ACEi (Enalapril) and A&A together have a better antifibrotic effect in unilateral ureteral obstruction (UUO) than monotherapy with either agent. Male Sprague-Dawley rats (N = 4 per group) had either sham operation or UUO alone, with A&A (combined aqueous and ethanol extract equivalent to 2.1 g dried herbs), with Enalapril (in drinking water at 200 mg/mL) or with both treatments. Kidney and liver were collected for protein extraction or fixed for histologic stains, immunohistochemistry (IHC), microscopy. Enalapril or A&A individually were antifibrotic. Transforming growth factor-beta1, fibroblast activation, collagen deposition, macrophage accumulation and tubular cell apoptosis were all decreased. The combination of the two drugs was significantly more effective than Enalapril alone in reducing tumor necrosis factor-alpha, collagen accumulation, activation of fibroblasts, and tubular cell apoptosis. In conclusion, Enalapril with A&A significantly decreased tubulointerstitial fibrosis to a greater extent than treatment with Enalapril alone. Further studies focusing on the isolation of the active constituents of A&A and the clinical application of the combination of ACEi plus A&A are warranted to determine the value of this treatment in humans.

The effect of salt on renal damage in eNOS-deficient mice

African Americans have an increased incidence of end-stage renal disease and are characterized as having reduced bioavailability of nitric oxide and salt-sensitivity. We propose that endothelial nitric oxide synthase (eNOS) knockout mice (eNOS(-/-)) are a suitable model of hypertension-associated renal injury as seen in African Americans. Therefore, the purpose of this study was to determine whether older eNOS(-/-) mice have hypertension-associated renal injury and if dietary salt modulates this injury. Six-month-old eNOS(-/-) mice were placed on 0.12%, 0.45% or 8% NaCl diet for 8 weeks and blood pressure measured weekly; kidneys were collected for pathology evaluation and scoring at the end of the 8-week period. Mice deficient of eNOS were hypertensive at baseline compared with control mice in all three groups (128+/-3 vs. 112+/-3, P<0.05). Blood pressure was significantly elevated from baseline in eNOS(-/-) on 0.45 and 8% salt diets (P<0.02). The composite renal pathology scores for eNOS(-/-) mice were significantly greater than wild-type mice, indicating high salt intake exacerbates the injury (P<0.001 vs. normal salt diet). eNOS(-/-) mice may be used as a model of salt-induced and hypertension-associated renal injury as seen in African Americans.

An in vitro investigation of herbs traditionally used for kidney and urinary system disorders: potential therapeutic and toxic effects

AIM

Renal fibrosis is central to progression of most chronic renal pathologies. Antioxidants that protect the tubular epithelium and anti-fibrotics that induce apoptosis of pro-fibrotic myofibroblasts without adversely affecting tubular epithelium may slow progression of renal fibrosis, while toxic substances may exacerbate renal scarring. We investigated 47 herbs for their in vitro toxic or antioxidant effects on normal renal mammalian fibroblasts (NRK49F) and tubular epithelial cells (NRK52E) to determine their potential value as therapeutic agents in renal fibrosis involving oxidative stress.

METHODS

Herbs were chosen because of their traditional use in kidney or urinary system disorders, or because of recent published interest in their therapeutic or toxic potential in kidney disease. Extracts of herbs were made using a sequential multi-solvent extraction process. Each extract was analysed separately. Extraction solvents were ethyl acetate, methanol and 50% aqueous methanol. Cells were treated with extracts with/without oxidative stress (1.0 mM hydrogen peroxide). Cellular changes (apoptosis, necrosis, mitosis, transdifferentiation) were identified and quantified using defined criteria.

RESULTS

All extracts of Dioscorea villosa showed significant toxicity to both cell lines. At low concentrations (5-50 microg/mL) they induced epithelial to mesenchymal transdifferentiation, as demonstrated by increased immunohistochemistry staining for alpha-smooth muscle actin and transforming growth factor-beta1 in treated versus control cells. Angelica sinensis, Centella asiatica, Glycyrrhiza glabra, Scutellaria lateriflora, and Olea europaea demonstrated strong antioxidant effects in epithelial cells and/or apoptotic effects on fibroblasts.

CONCLUSION

This investigation has revealed renotoxicity of D. villosa and anti-fibrotic, oxidant potential of several herbal extracts, all of which require further study.