Abdulla K. Salahudeen

Progression of kidney disease in chronic renal transplant rejection

The rate of progression of renal insufficiency was quantitated from reciprocal of serum creatinine versus time plots in patients with clinical and histologic evidence of chronic renal transplant rejection. The plots were evaluated by the breakpoint test. This method identifies breakpoints in a linear plot and compares the statistical significance of the fit provided by two intersecting lines with that of a single straight line. The breakpoint test when applied to the 22 patients with a significant linear correlation between the reciprocal of serum creatinine versus time detected a change in the slope in 20 cases (90.9%) indicating the presence of a breakpoint. The average diastolic, systolic, and mean arterial pressures before the breakpoint were significantly correlated with the value of the serum creatinine at the time of the change of the slope (r = 0.45, P less than 0.05; r = 0.58, P less than 0.01; r = 0.56, P less than 0.05, respectively) demonstrating more severe hypertension in those patients with the more severe renal dysfunction. The slope after the breakpoint was significantly correlated with the mean diastolic blood pressure values after the breakpoint (r = 0.48, P less than 0.05) with higher pressures being found in those patients with faster rates of decline in renal function. Both before and after the breakpoint occurred, the rate of progression of the renal disease, as estimated by the reciprocal of serum creatinine versus time plot, was greater when the mean diastolic blood pressure was higher than 90 mmHg. In conclusion, the vast majority of patients with proven chronic rejection progress linearly although a change in the rate of progression was frequent. Higher levels of blood pressure correlate with greater rates of progression of renal insufficiency, and a faster progression associates with a diastolic blood pressure greater than 90 mmHg.

Apoptosis versus necrosis during cold storage and rewarming of human renal proximal tubular cells.

Background. A recent clinical study demonstrated that in renal allografts preserved in the cold apoptosis occurred soon after reperfusion. The mode of cell death during cold storage is generally considered necrotic. Whether apoptosis occurs as a part of cold storage is uncertain. The objective was to determine in human renal tubular cells whether apoptosis is specific for rewarming or it also occurs during cold storage and whether it could be modified. Methods and Results. Cold storage (4°C) of primary human renal proximal tubular epithelial (RPTE) in University of Wisconsin (UW) solution up to 48 hr caused a time-dependent increase in cell death measured by lactic dehydrogenase (LDH) release and vital dye exclusion methods. Transmission electron microscopy (TEM) demonstrated that cell death in the cold was necrotic, involving considerable mitochondrial disruption, and was not apoptotic. The TUNEL assay that provides a specific, quantitative measure for apoptosis showed no increase in TUNEL-positivity during flow cytometry of cells stored in cold: 37°C, 0.23±0.14%; 24 hr cold, 0.23±0.1%; 48 hr cold, 1.79±0.58%. Annexin-V staining, a sensitive method for detecting early apoptosis, similarly showed no increase in positively stained cells during cold storage. Addition of antioxidants 2-methyl aminochroman and deferoxamine to UW solution inhibited necrotic cell death and preserved mitochondrial structure. In contrast to cold storage alone, rewarming (37°C for 24 hr) of cold stored cells, however, resulted in significant apoptosis (TUNEL positive: 48 hr cold: 2±0.6%, 48 hr cold and 24 hr rewarming: 54±17%), which was confirmed by the TEM based on typical apoptotic features. Addition of 2-MAC and DFO significantly inhibited rewarming-induced apoptotic cell death (plus 2-MAC: 3±1%, plus DFO: 3±2%). Conclusion. Our study in human tubular cells provides evidence that cold storage per se does not result in apoptosis, but is primarily necrotic. However, rewarming is associated with significant apoptosis in the presence of ongoing necrosis, speculatively due to the activation of the apoptotic enzymic process of sublethally injured cells. Inclusion of antioxidants in the storage solution confers protection against both cold storage and rewarming-induced necrosis and apoptosis.

Cyclosporine nephrotoxicity: Attenuation by an antioxidant-inhibitor of lipid peroxidation in vitro and in vivo

The exact mechanisms by which cyclosporine (CsA) causes renal injury is not known. The possibility that reactive oxygen species (ROS) may play a role, since CsA induces renal microsomal lipid peroxidation and reduces glutathione levels, was investigated by examining whether administration of an antioxidant attenuates CsA-induced nephrotoxicity. One of three groups of uninephrectomized rats received vehicles, another CsA 25 mg/kg/day and the third, CsA plus antioxidant lazaroid (U-74389 G) 20 mg/kg/day, for 8 weeks. CsA-induced functional and structural derangements were accompanied by a significant induction of renal cortical lipid peroxidation (thiobarbituric acid reactive substances and conjugated diene). Administration of lazaroid significantly suppressed CsA-induced lipid peroxidation and provided significant functional and structural protection. That lazaroid affords renal functional protection against CsA in the rat was again demonstrable in a crossover study. To examine the relation between CsA nephrotoxicity and lipid peroxidation, cell culture studies were undertaken. CsA induced renal epithelial (LLC-PK1) cell injury (LDH release) as well as lipid peroxidation and degradation (prelabeled 3H arachidonic acid release). Lazaroid prevented CsA-induced cell injury and limited lipid alterations. These new findings--that an antioxidant inhibitor of lipid peroxidation limits CsA-induced renal toxicity in vitro and in vivo--suggest a pathogenic role for ROS-mediated lipid peroxidation in CsA-induced renal toxicity. Antioxidant therapy may minimize CsA-induced renal toxicity in humans.

Mechanism and prevention of cold storage-induced human renal tubular cell injury.

BACKGROUNDnThe recent observation that cold storage of kidneys and tubular cells causes marked increase in free radical-catalyzed F2-isoprostanes suggests that radicals might be formed during cold storage. As cold temperature is associated with reduced metabolic and enzymic activity, the notion that cold temperature causes free radical production appeared less tenable. The objective was, therefore, to seek direct evidence for the free radical production during the cold storage of human renal tubular cells, and to define the roles of extrinsic and intrinsic antioxidants in cold-induced cell injury.nnnMETHODSnHuman renal tubular cells were cold-stored at 4 degrees C for varying duration in University of Wisconsin solution and subjected to mRNA analysis, biochemical measurements, and cytoprotective studies.nnnRESULTSnCold storage caused a time-dependent reduction in glutathione levels, and an increase in the formation superoxide, hydrogen peroxide, and hydroxyl radicals. Cold-induced lactate dehydrogenase (LDH) release, ATP depletion, DNA damage, and membrane degradation were suppressed with the inclusion of antioxidant 2-methyl aminochroman or deferroxamine. The cells that were structurally protected with antioxidants were also intact functionally, as they had significantly improved cell proliferation. To examine the effect of cold on intrinsic antioxidant gene expression, antioxidant mRNA levels were analyzed using reverse transcription-polymerase chain reaction. The gene expression of mitochondrial Mn-superoxide dismutase (SOD), but not of cytosolic Cu,Zn-SOD or of glutathione peroxidase expression increased with cold exposure. The oxidant-sensitive gene heme oxygenase I increased slightly with 48-hr cold storage.nnnCONCLUSIONSnCold storage of human tubular cells causes marked increase in free radicals. These are likely of mitochondrial origin as there is a differential inducement of Mn-SOD gene, and are causal to cold-induced cell injury as extrinsic antioxidants abrogated the injury. Our findings support the strategy of adding antioxidants to preservation solutions or the strategy of pre-conditioning the organs to oxidative stress to minimize cold storage-induced organ damage.

Vitamin E inhibits renal mRNA expression of COX II, HO I, TGFβ, and osteopontin in the rat model of cyclosporine nephrotoxicity

Background. Ina rat model of cyclosporine (CsA) nephrotoxicity, vitamin E preserves renal function and reduces free radicals, vasoconstrictive thromboxanes, and tubulointerstitial fibrosis. We examined the effect of vitamin E on tubule gene expression in this model. Methods. In two of three groups, rats were treated with either CsA, or CsA plus vitamin E, whereas the control group received vehicles. We pooled purified tubules or whole kidney tissue in a novel manner to represent each treatment group, harvested RNA, and performed rigorously controlled qualitative reverse transcription-polymerase chain reaction. Results. Cyclooxygenase (COX) I mRNA was detectable in control animals, was increased by CsA, but was unchanged by vitamin E. COX II mRNA was detected in controls, was inhibited in the CsA group, and was further inhibited with vitamin E. Hemeoxygenase I and TGF-&bgr; and osteopontin mRNA were increased in the CsA-treated group and were inhibited by vitamin E. Conclusions. Our data support the involvement of free radicals, COX pathways, and pro-fibrotic genes in cyclosporine nephrotoxicity and suggest that the salutary effect of vitamin E involves the suppression of some of these genes.

Antioxidant lazaroid U-74006F improves renal function and reduces the expression of cytokines, inducible nitric oxide synthase, and mhc antigens in a syngeneic renal transplant model. Partial support for the response-to-injury hypothesis

In a recent study, antioxidant therapy at the time of renal transplantation in humans was associated with fewer rejection episodes and extended graft survival. A hypothesis generated by such studies and based on the response-to-injury model is that reducing the oxidative injury during transplantation may dampen certain cellular responses to injury that are important in triggering allograft rejection. To test whether ablation of oxidative injury would limit such responses, kidneys were transplanted between Wistar-Furth rats, with and without antioxidant 21-aminosteroid. 21-Aminosteroid was administered before kidney harvest and, again, before transplant reperfusion. The recipients left kidneys, removed to accommodate the donor kidneys, were used as normal control. The removal of the right kidneys contralateral to the transplant were delayed to day 4 to provide interim renal support. The transplanted kidneys were harvested on day 7. Administration of 21-aminosteroid was associated with better graft function and reduced lipid peroxidation. Compared with the normal control kidneys, the kidneys transplanted with vehicle had higher cytokine mRNA levels (measured by reverse transcriptase-polymerase chain reaction) for interleukin 2, interleukin 6, tumor necrosis factor-alpha, and interferon-gamma. The levels for these cytokines were reduced in kidneys transplanted with 21-aminosteroid. An increase in inducible nitric oxide synthase mRNA in the transplanted kidney was inhibited by 21-aminosteroid, as were the increase in class I and II MHC antigens. The new finding, that a reduction in transplantation-related oxidative injury in a syngeneic model is accompanied by a reduction in the expression of cytokines, MHC antigens, and inducible nitric oxide synthase, provides partial support for the response-to-injury hypothesis in the setting of renal transplantation. The data also demonstrate for the first time the efficacy of 21-aminosteroid to reduce lipid peroxidation and renal injury in kidneys transplanted after cold preservation.

Initiation Reactions of Lipid Peroxidation: A Raman Spectroscopic and Quantum-Mechanical Study

Near-infrared (NIR) Raman spectroscopy has been used to observe the spectrum changes of linolenic acid during the iron-dependent lipid peroxidation reactions. The intensity of several bands including those at 726, 977, 1264, 1658, and 3014 cm−1 decreased after lipid peroxidation. Other notable changes after lipid peroxidation include the appearance of a couple of new bands at 1165 and 1638 cm−1. The Raman spectrum change was suppressed by an antioxidant, 21-aminosteroid. Harmonic ab initio vibrational analysis was performed for two model structures: one for the pure linolenic acid and another for a peroxidation product. The calculations by the Hartree–Fock (HF) method and a density functional theory (DFT) indicate that a new band which appeared at 1638 cm−1 after lipid peroxidation is due to the rearrangement of skeletal double bonds.