Stress associated proteins metallothionein, HO-1 and HSP 70 in human zero-hour biopsies of transplanted kidneys

TUNEL Assay: A Powerful Tool for Kidney Injury Evaluation

Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay is a long-established assay used to detect cell death-associated DNA fragmentation (3'-OH DNA termini) by endonucleases. Because these enzymes are particularly active in the kidney, TUNEL is widely used to identify and quantify DNA fragmentation and cell death in cultured kidney cells and animal and human kidneys resulting from toxic or hypoxic injury. The early characterization of TUNEL as an apoptotic assay has led to numerous misinterpretations of the mechanisms of kidney cell injury. Nevertheless, TUNEL is becoming increasingly popular for kidney injury assessment because it can be used universally in cultured and tissue cells and for all mechanisms of cell death. Furthermore, it is sensitive, accurate, quantitative, easily linked to particular cells or tissue compartments, and can be combined with immunohistochemistry to allow reliable identification of cell types or likely mechanisms of cell death. Traditionally, TUNEL analysis has been limited to the presence or absence of a TUNEL signal. However, additional information on the mechanism of cell death can be obtained from the analysis of TUNEL patterns.

α-Lipoic Acid Protects Against Ischemia-Reperfusion Injury in Simultaneous Kidney-Pancreas Transplantation

BACKGROUND

Multiple factors have been implicated in the process of ischemia-reperfusion injury (IRI) in organ transplantation. Among these factors, oxidative damage seems to initiate the injury. α-lipoic acid (ALA) is a potent antioxidant that is used in patients with diabetic polyneuropathy. The aim of the present study was to determine the effect of ALA in patients undergoing simultaneous kidney-pancreas transplant by evaluating the functional recovery of the graft and biochemical markers of IRI.

METHODS

Twenty-six patients were included in the following groups: (i) untreated control; (ii) donor and recipient (DR) ALA-treated, in which ALA was administered both to the deceased donor and to the recipients; and (iii) recipient ALA-treated group. The expression of inflammatory genes, as observed in biopsies taken at the end of surgery, as well as the serum cytokines, secretory leukocyte protease inhibitor, regenerating islet-derived protein 3β/pancreatitis-associated protein, amylase, lipase, glucose, and creatinine levels were quantified as markers of organ function.

RESULTS

The DR group showed high levels of TGFβ and low levels of C3 and TNFα in the kidneys, whereas high levels of C3 and heme oxygenase were identified in pancreas biopsies. Decreases in serum IL-8, IL-6, secretory leukocyte protease inhibitor, and regenerating islet-derived protein 3 β/pancreatitis-associated protein were observed after surgery in the DR group. Serum lipase and amylase were lower in the DR group than in the control and recipient groups. Early kidney dysfunction and clinical pancreatitis were higher in the control group than in either treatment group.

CONCLUSIONS

These results show that ALA preconditioning is capable of reducing inflammatory markers while decreasing early kidney dysfunction and clinical posttransplant pancreatitis.

Predictive biomarkers of renal allograft failure

BACKGROUND

Survival of renal allografts is limited by chronic allograft deterioration resulting from processes that are difficult to detect in their early stages, when therapeutic interventions would be most effective. Predictive biomarkers from easily accessible specimens, such as blood or urine, might improve early diagnosis of smoldering graft-damaging processes and help with the identification of patients at particularly high risk of sustained injury, thereby helping to tailor therapy and appropriate follow-up screening.

OBJECTIVE

This article reviews recently investigated biomarkers for the prediction of renal allograft failure, outlines the new '-omic' technologies as a potential source for the identification of new predictive biomarkers and judges the practical value of predictive biomarkers at the present timepoint.

METHODS

A literature search was performed using the medical database PubMed. No general restrictions (e.g., year of publication) were applied, but the focus was set on more recently published articles.

CONCLUSION

Despite a large number of interesting studies, none of the investigated candidate biomarkers is robustly established for widespread clinical use or able to replace biopsies for graft assessment.

Cytoprotection behind heme oxygenase-1 in renal diseases

Renal insults are considered a public health problem and are linked to increased rates of morbidity and mortality worldwide. The heme oxygenase (HO) system consists of evolutionary specialized machinery that degrades free heme and produces carbon monoxide, biliverdin and free iron. In this sense, the inducible isoform HO-1 seems to develop an important role and is widely studied. The reaction involved with the HO-1 molecule provides protection to injured tissue, directly by reducing the toxic heme molecule and indirectly by the release of its byproducts. The up regulation of HO-1 enzyme has largely been described as providing antioxidant, antiapoptotic, anti-inflammatory and immunomodulatory properties. Several works have explored the importance of HO-1 in renal diseases and they have provided consistent evidence that its overexpression has beneficial effects in such injuries. So, in this review we will focus on the role of HO-1 in kidney insults, exploring the protective effects of its up regulation and the enhanced deleterious effects of its inhibition or gene deletion.

Protein levels of heme oxygenase-1 during reperfusion in human kidney transplants with delayed graft function

INTRODUCTION

Delayed graft function (DGF) as a consequence of ischemia reperfusion injury (IRI) is associated with a decrease in long-term allograft survival. Heme oxygenase-1 (HO-1) is a stress responsive gene that is highly expressed in multiple pathological processes. The aim of our study was to analyze whether HO-1 protein levels in human kidney transplants during IRI correlate with the incidence of DGF.

METHODS

Kidney biopsies were obtained from 27 kidney allografts at two time points: at the end of cold storage and shortly after reperfusion. Samples were analyzed for HO-1 protein levels by Western blot.

RESULTS

Heme oxygenase-1 protein levels were significantly higher in post-reperfusion biopsies (39.4 vs. 13.7 arbitrary units, p = 0.001). In pre-reperfusion biopsies no association was observed between HO-1 protein levels and DGF. In post-reperfusion biopsies, higher levels of HO-1 protein were measured in kidneys with DGF (53.7 vs. 36.2 arbitrary units, p = 0.064). DGF kidneys showed a significantly higher increase from pre- to post-reperfusion in HO-1 protein (42.0 vs. 18.7 arbitrary units, p = 0.025).

CONCLUSION

Heme oxygenase-1 protein levels shortly after allograft reperfusion are closely related with initial graft function. Assessment thereof may be considered a valuable tool to predict DGF.

Influence of heme oxygenase-1 on microcirculation after kidney transplantation

BACKGROUND

Cytoprotective proteins, such as heme oxygenase-1 (HO-1), play a decisive role in ischemia-reperfusion injury during kidney transplantation. The aim of this study was to investigate the impact of heme oxygenase-1 on microcirculation and on ischemia-reperfusion injury in an isogenic kidney transplantation rat model.

MATERIALS AND METHODS

Seventy male Lewis rats were distributed into three groups. In Group 1(control), the kidneys were only mobilized. In Groups 2 and 3, bilateral nephrectomy was performed, and a kidney from another Lewis rat was orthotopically transplanted on the left side. The donor animals in Group 3 received preconditioning with the HO-1 inductor hemin. 24 h after reperfusion graft function and morphology were examined. Microcirculation was investigated by in vivo microscopy of the renal surface 1 h after reperfusion.

RESULTS

HO-1 preconditioning led to significantly lower serum creatinine and serum urea, as well as less histological damage and inducible nitric oxide synthase expression. Microcirculation was improved by a significant enlargement of the vascular diameter and an increase of the capillary flow.

CONCLUSIONS

Treatment with hemin improves microcirculation by induction of HO-1 and reduces ischemia-reperfusion injury after kidney transplantation. HO-1 induction was shown to be a promising approach in the preconditioning of donor kidneys.

Zinc dyshomeostasis in rats with aldosteronism. Response to spironolactone

Zinc is a structural constituent of many proteins, including Cu/Zn superoxide dismutase (SOD), an endogenous antioxidant enzyme. Hypozincemia has been found in patients hospitalized with congestive heart failure, where neurohormonal activation, including the renin-angiotensin-aldosterone system (RAAS), is expected and oxidative stress is present. This study was undertaken to elucidate potential pathophysiological mechanisms involved in Zn dyshomeostasis in aldosteronism. In rats receiving aldosterone/salt treatment (ALDOST) alone for 1 and 4 wk or in combination with spironolactone (Spiro), an ALDO receptor antagonist, we monitored 24-h urinary and fecal Zn excretion and tissue Zn levels in heart, liver, and skeletal muscle, together with tissue metallothionein (MT)-I, a Zn(2+)-binding protein, and Cu/Zn-SOD activities in plasma and tissues. When compared with unoperated, untreated, age-/sex-matched controls, urinary and, in particular, fecal Zn losses were markedly increased (P < 0.05) at days 7 and 28 of ALDOST, leading to hypozincemia and a fall (P < 0.05) in plasma Cu/Zn-SOD activity. Microscopic scars and perivascular fibrosis of intramural coronary arteries first appeared in the right and left ventricles at week 4 of ALDOST and were accompanied by increased (P < 0.05) tissue Zn, MT-I, and Cu/Zn-SOD activity, which were not found in uninjured liver or skeletal muscle. Spiro cotreatment prevented cardiac injury and Zn redistribution to the heart. Thus increased urinary and fecal Zn losses, together with their preferential translocation to sites of cardiac injury, where MT-I overexpression and increased Cu/Zn-SOD activity appeared, contribute to Zn dyshomeostasis in rats with aldosteronism, which were each prevented by Spiro. These findings may shed light on Zn dyshomeostasis found in patients with decompensated heart failure.