Early risk factors contributing to the evolution of long-term allograft dysfunction

A comparison of the metabolic effects of continuous hypothermic perfusion or oxygenated persufflation during hypothermic storage of rat liver

The metabolic consequences of supplying oxygen by two different modes were investigated. The effects of hypothermic liver preservation after cold hypoxic flush (Group I), oxygenated vascular persufflation (Group II), and continuous oxygenated perfusion (Group III) were compared. Adenine nucleotides were measured to assess energetics, and 1H nuclear magnetic resonance spectroscopy was employed to investigate other metabolic pathways. Energetics were maintained by both modes of oxygenation at 24 h. The mitochondrial redox state is indicated by the ratio of acetoacetate (Ace) and beta-hydroxybutyrate (betaHb). The detection of only betaHb or Ace in the hypoxic flush and perfused livers, respectively, suggested that the mitochondria of these livers were hyperreduced and hyperoxidized, respectively. In contrast, both components of the redox couple were detected in the persufflated livers, suggesting that persufflation may be a simple and effective method of maintaining hepatic energetics long-term while maintaining a more normal mitochondrial redox state.

Effect of mycophenolate mofetil on nitric oxide production and inducible nitric oxide synthase gene expression during renal ischaemia-reperfusion injury

BACKGROUND

Recent animal data suggest that inducible nitric oxide synthase (iNOS) derived nitric oxide (NO) plays an important role in the pathogenesis of renal ischaemia-reperfusion injury (IRI) and that inhibition of iNOS ameliorates IRI. Mycophenolate mofetil (MMF), a lymphocyte selective anti-proliferative agent, has been shown to inhibit NO production in vitro. The aim of this study is to evaluate the effect of MMF on NO production and iNOS gene expression in vivo during renal IRI.

METHODS

Renal IRI was induced by clamping the left renal pedicle of male BALB/c mice for 30 min, followed by 15 min of reperfusion. The mice received placebo or MMF at 40, 80 or 120 mg/kg/day by oral gavage for 5 days before the operation. Sham-operated mice served as the operation control. The amount of NO produced and the level of iNOS gene expression in the kidney tissue during IRI was assessed by spin trapping electron paramagnetic resonance (EPR) spectroscopy and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) respectively.

RESULTS

In the sham-operated kidneys, only low levels of NO and iNOS mRNA were detected. In mice with renal IRI, the amount of NO detected was significantly increased, which was reduced in a dose dependent fashion by pre-treatment with MMF. Pre-treatment with MMF also substantially reduced iNOS gene expression in the kidney tissue.

CONCLUSIONS

We conclude that pre-treatment with MMF inhibits the production of NO and the induction of iNOS gene expression in the kidney during IRI. These results suggest that MMF might have the potential to ameliorate renal IRI.

Interleukin-17 antagonism inhibits acute but not chronic vascular rejection

BACKGROUND

Blocking the action of interleukin (IL) 17 with an IL-17 receptor (R):Fc fusion protein inhibits T-cell proliferative responses to alloantigens and prolongs vascularized heart graft survival. In this study, we examined whether IL-17 antagonism could suppress the development of chronic rejection.

METHODS

A 0.6-cm section of C57BL10 (H2b) thoracic aorta was transplanted to recipient C3H (H2k) abdominal aorta. IL-17R:Fc or control human immunoglobulin G was administered i.p. (500 microg/day) from days 0 to 6 or from days 0 to 29. Mice were killed on days 7 or 30. Grafts were examined histologically and stained for alpha-smooth muscle actin (alpha-smA). Antidonor mixed leukocyte reaction, cytotoxic T cell, and alloantibody responses were quantified.

RESULTS

On day 7, control grafts showed mononuclear cell (MNC) infiltration, pronounced endothelial damage, and apoptosis of intimal and medial cell compartments. By day 30, there was concentric intimal thickening, accumulation of alpha-smA+ cells, and collagen deposition. Patchy destruction of the elastic membranes and loss of alpha-smA expression in media were evident. IL-17R:Fc for 6 days decreased MNC infiltration in the intimal and medial compartments at day 7. The endothelium was preserved (completely or partially) in all grafts. The medial compartment showed normal alpha-smA expression. Irrespective of IL-17R:Fc treatment for either 6 days or continuously, allografts harvested at day 30 showed circumferential intimal thickening, with accumulation of alpha-smA+ cells and collagen deposition. There was no effect on circulating alloantibody levels.

CONCLUSIONS

These findings support a role for IL-17 in the immunopathogenesis of acute vascular rejection and demonstrate the potential of IL-17 antagonism for therapy. By contrast, IL-17 antagonism does not appear to prevent ensuing chronic graft vascular disease, in particular neointimal formation.

The use of the endothelin receptor antagonist, tezosentan, before or after renal ischemia protects renal function

BACKGROUND

Utilization of organs subjected to ischemia/reperfusion (I/R) injury could expand the donor pool. Endothelin (ET) is implicated in renal I/R injury. Therefore, our study compared the effectiveness of pre- and postischemic administration of the ET receptor antagonist, Tezosentan, in preserving renal function.

METHODS

In a rat model, a kidney was subjected to 45 min of ischemia along with a contralateral nephrectomy. After 24 hr of reperfusion, renal function was assessed by serum creatinine (Scr), inulin clearance (glomerular filtration rate; GFR), and histology. ET-1 peptide expression was localized using immunohistochemistry. Three groups were studied: I/R untreated (n=17), I/R pretreated (n=11), and I/R posttreated (n=13) with Tezosentan (15 mg/kg, i.v.).

RESULTS

Tezosentan significantly decreased (P<0.05) the rise in Scr from I/R injury (2.0+/-0.4 mg/dl, before and 2.9+/-0.4 mg/dl, after treatment) compared with untreated animals (4.2+/-0.4 mg/dl). GFR was significantly increased (P<0.05) from 0.13+/-0.03 ml/min (untreated animals) to 0.74+/-0.16 and 0.47+/-0.14 ml/min (pre- and posttreated animals). Untreated animals had significant cortical acute tubular necrosis, which was almost completely prevented by pretreatment with Tezosentan and markedly reduced by posttreatment. Increased ET-1 peptide expression was noted in the renal vasculature and in the cortical tubular epithelium of kidneys exposed to I/R.

CONCLUSIONS

The purpose of this study was to optimize the function of kidneys exposed to I/R injury. Pretreatment as well as posttreatment with Tezosentan successfully decreased Scr, increased GFR, and maintained renal architecture in kidneys after ischemia. Therefore, ET receptor antagonists may be useful to preserve renal function in the transplantation setting.

Mechanisms of chronic rejection

Chronic rejection remains the major obstacle to long-term allograft survival. Detailed understanding of putative etiologic risk factors, both antigen-dependent and -independent, is important for designing effective therapeutic strategies to ameliorate this process. Cell senescence may be an important factor in chronic rejection.

Decreased acute rejection in kidney transplant recipients is associated with decreased chronic rejection

OBJECTIVE

To determine whether a recent decrease in the rate of acute rejection after kidney transplantation was associated with a decrease in the rate of chronic rejection.

SUMMARY BACKGROUND DATA

Single-institution and multicenter retrospective analyses have identified acute rejection episodes as the major risk factor for chronic rejection after kidney transplantation. However, to date, no study has shown that a decrease in the rate of acute rejection leads to a decrease in the rate of chronic rejection.

METHODS

The authors studied patient populations who underwent transplants at a single center during two eras (1984-1987 and 1991-1994) to determine the rate of biopsy-proven acute rejection, the rate of biopsy-proven chronic rejection, and the graft half-life.

RESULTS

Recipients who underwent transplantation in era 2 had a decreased rate of biopsy-proven acute rejection compared with era 1 (p < 0.05). This decrease was associated with a decreased rate of biopsy-proven chronic rejection for both cadaver (p = 0.0001) and living donor (p = 0.08) recipients. A trend was observed toward increased graft half-life in era 2 (p = NS).

CONCLUSIONS

Development of immunosuppressive protocols that decrease the rate of acute rejection should lower the rate of chronic rejection and improve long-term graft survival.

Energy metabolism following prolonged hepatic cold preservation: benefits of interrupted hypoxia on the adenine nucleotide pool in rat liver

The ability of brief hypothermic reperfusion (HtR) to restore hepatic energy metabolism following periods of cold hypoxic preservation was studied in isolated rat livers after storage times of 5, 10, and 24 h. In addition, investigations were performed on the effects of HtR used to restore liver oxidative metabolism in the middle of a prolonged (24 h) hypoxic preservation period. A histidine-lactobionate-raffinose solution was used for the initial cold portal flush in all groups. Results showed that cold hypoxia for either 5 or 10 h yielded livers capable of similar recoveries of ATP, energy charge, and total adenine nucleotides, but that HtR after 24 h cold preservation resulted in reduced regeneration of ATP, a lower energy charge, and a fall in tissue adenine nucleotides. When livers were stored for 24 h but subjected to brief HtR after either 5 or 10 h before return to hypoxic storage, improved recoveries of the energy metabolites were seen over those recorded after 24 h hypoxia alone. The fact that these improvements were not due to an improved supply of adenine nucleotide precursors was demonstrated by studying groups which were given HtR with perfusate containing precursors of adenine nucleotides (adenosine, adenine, and inosine) after 24 h cold hypoxia. These data are consistent with the hypothesis that poor metabolic recovery after long-term hepatic cold preservation results more from decreased mitochondrial oxidative phosphorylation than from a lack of precursors for adenine nucleotide resynthesis. In addition, restoring oxidative metabolism at hypothermia for brief periods can to some extent protect final metabolic status after prolonged storage.

Ablating the ischemia-reperfusion injury in non-heart-beating donor kidneys

BACKGROUND

The objective of this study was to determine if allopurinol (AL) and/or trifluoperazine (TFP) added to the Belzer machine preservation solution (MPS) improves the function of non-heart-beating donor (NHBD) canine kidneys.

METHODS

Anesthetized canines underwent bilateral dissection of the renal vessels, obtaining baseline flow. After removing one kidney (heart-beating donor [HBD]), the dog was exsanguinated. After remaining in situ for 120 min (30-min warm ischemia time, 90-min cold ischemia time), the second kidney was removed (NHBD), flushed, biopsied, and weighed. The kidneys were machine-perfused separately for 20 hr, and pressure, flow, and resistance were measured serially. The kidneys were randomly assigned to a perfusate group (G): G1=MPS, G2=MPS+TFP, G3=MPS+AL, and G4=MPS+TFP+AL. Kidneys were implanted separately into a single recipient dog. Flow, resistance, and urine output were measured serially for 4 hr. Blood and urine samples and kidney biopsies were then obtained. All measurements were standardized to 100 g of kidney weight.

RESULTS

HBD kidneys functioned better than NHBD kidneys in all groups, as expected. Although perfusate G1 was the most effective solution for HBD kidneys, the TFP additive (perfusate G2) more effectively reversed the vasospastic effects of ischemia/reperfusion for NHBD than the MPS solution (G1) with or without other additives. In HBD kidneys, the addition of AL resulted in the best creatinine clearance; however, AL was less effective than MPS alone in NHBD kidneys. TFP+AL together were completely ineffective in preserving renal function, regardless of whether the kidneys were from HBD or NHBD.

CONCLUSIONS

MPS+TFP more effectively protected renal function against reperfusion injury in the NHBD than MPS alone, AL, or AL+TFP. AL exerts a salutary effect on creatinine clearance in HBD but not in the NHBD. The TFP and AL combination should not be used together with the MPS in machine preservation of kidneys.