Renal Allograft Rejection In Rats Research Articles

Changes and Significance of IL-17 in Acute Renal Allograft Rejection in Rats

To investigate the changes and significance of interleukin-17 (IL-17) in acute rejection following rat kidney transplantation. Using inbred Sprague Dawley rats as donors and Wistar rats as recipients, an acute rejection model of kidney transplantation was established to evaluate the effects of IL-17. Reverse transcription polymerase chain reaction and immunohistochemistry were used to detect IL-17. Compared with those in the normal control group, the rats in the allogeneic transplantation (ATX) group had different degrees of acute rejection 3, 5, and 7 days after operation, and the expression of IL-17 mRNA in the transplanted kidney was significantly increased (P < .05). In the ATX group, acute rejection was observed 7 days after operation, and the integrated optical density (IOD) value of IL-17 was significantly increased (P < .05). Compared with the normal control group, acute rejection occurred in varying degrees at 3, 5, and 7 days after operation in the ATX group, and the IOD value of IL-17 significantly increased (P < .05). IL-17 expression is increased in acute rejection after renal transplantation in rats. Other surgical factors in addition to acute rejection had no effect on IL-17 expression in rat kidney transplants. The immunosuppressant cyclosporin A was used to prevent the expression of IL-17 in rats with acute rejection.

Marrow Mesenchymal Stem Cells Effectively Reduce Histologic Changes in a Rat Model of Chronic Renal Allograft Rejection

BackgroundChronic allograft rejection remains as the leading cause of the chronic renal grafts loss post-transplantation. No therapy has been found really effective to prevent and treat chronic allograft rejection. Mesenchymal stem cells (MSCs) have characteristics of immunomodulation and are expected to be used for inducing graft immune tolerance in organ transplantation. We investigated the efficacy and safety of early infusion of donor-derived marrow MSCs in a rat model of chronic renal allograft rejection. MethodsOrthotopic kidney transplantations were performed in a rat strain combination of Sprague-Dawley (SD) → Wistar. The native right kidneys of recipient rats were kept intact as internal control of each graft. Twenty-three successfully transplanted recipient rats were divided into 3 groups: group 1 (the MSCs therapy group) (n = 8) and group 2 (the control group) (n = 8) both received a 10-day course of cyclosporine (CsA) (2 mg/kg intraperitoneally) to prevent initial acute rejection. MSCs (1 × 107) of first dosage and an additional dosage were injected into group 1 postoperative days (PODs) 0, 3, and 7. Group 2 received 0.9% saline solution in addition to CsA as the control group. Group 3 consisted of recipients (n = 7) receiving neither immunosuppression nor MSCs. Renal histopathology and immunohistochemistry of transforming growth factor β1 (TGF-β1) was examined at week 12. Safety of MSC infusion was determined by observing symptoms and signs after infusion and performing gross anatomy at week 12. ResultsAll the grafts of group 3 developed acute rejection and were rejected within 4 weeks. Bone marrow MSCs significantly decreased the severity of mononuclear cell interstitial inflammation, tubular atrophy, interstitial fibrosis, and vascular fibrous intimal thickening in renal grafts (P < .001). MSCs also greatly reduced the glomerulosclerosis rate of the transplanted kidneys of group 1 (P < .001). The TGF-ß1 expression of group 1 was weaker than that of group 2 (P = .043). There were no symptoms or signs of severe adverse side effects observed. ConclusionsEarly bone marrow MSCs infusion on PODs 0, 3, and 7 are effective and safe for chronic renal allograft rejection in rats. MSCs hold significant promise for clinical transplantation to treat chronic renal allograft rejection and prolong the renal graft survival.

Inhibition of histone methyltransferase EZH2 ameliorates early acute renal allograft rejection in rats.

BackgroundAlthough histone methyltransferases EZH2 has been proved to have significant regulatory effect on the immune rejection after hematopoietic stem cell transplantation, its role in solid-organ transplantation remains uncovered. In this study, we investigate whether histone methylation regulation can impact renal allograft rejection in rat models.ResultsAllogeneic rat renal transplantation model (Wistar to Lewis) was established, and the recipients were administrated with EZH2 inhibitor DZNep after transplantation. Renal allografts and peripheral blood were collected on day 5 after transplantation for histological examination and mechanism investigation. We found that inhibition of EZH2 by DZNep after transplantation significantly ameliorated acute rejection (AR), with decreased histological injury and reduced inflammatory infiltration in renal allografts. Attenuation of AR was due to the prohibited activation of alloreactive T cells, the subsequent impaired production of inflammatory cytokines, and also the elevated apoptosis of alloreactive T cells in both renal allografts and periphery. However, inhibition of EZH2 did not increase the regulatory T cells during the AR.ConclusionsDisruption of EZH2 by DZNep suppressed the immune responses of alloreactive T cells and ameliorated AR of renal allografts. This suggests a therapeutic potential of targeting histone methyltransferases EZH2 in treating allograft rejection after solid organ transplantation.

Attenuation of acute rat renal allograft rejection by apolipoprotein E-mimetic Peptide.

In addition to its well-described role in lipid metabolism, apolipoprotein E (ApoE) exerts immunomodulatory functions. A protective role of ApoE and ApoE-mimetic peptide (ApoE(133-149)) application was documented in several inflammatory disorders. In this study, we test the hypothesis that ApoE(133-149) promotes renal allograft survival. Dark Agouti, Brown Norway, and Fischer 344 kidneys were transplanted to Lewis rats to investigate fatal and reversible acute rejection. Apolipoprotein E expression was assessed in intravascular leukocytes of renal grafts, in graft tissue and in recipient blood plasma. Recipients of Brown Norway kidneys were treated with ApoE(133-149), and graft survival was monitored until day 100. Graft infiltration, cytokine, and chemokine production were analyzed. Intravascular graft leukocytes and renal tissue obtained from animals undergoing reversible acute rejection expressed increased levels of ApoE mRNA, whereas during fatal rejection, ApoE expression was reduced or remained unchanged. Animals treated with ApoE(133-149) showed prolonged allograft survival, which was associated with a reduced infiltration of CD8 and α/β T-cell receptor-expressing cells, diminished Granzyme B mRNA expression, and decreased caspase-3 activation. Endogenous ApoE overexpression and exogenous application of ApoE(133-149) seem to protect renal allografts from fatal acute rejection. This effect was associated with a reduced influx of cytotoxic T cells.

CD3-Mediated Contrast-Enhanced Sonography For Diagnosis of Rat Renal Allograft Rejection.

CD3-Mediated Contrast-Enhanced Sonography For Diagnosis of Rat Renal Allograft Rejection.

Macrophages Contribute to Cellular But Not Humoral Mechanisms of Acute Rejection in Rat Renal Allografts

Cells of the monocyte/macrophage lineage have been implicated as effectors in acute allograft rejection based on short-term depletion studies. However, the therapeutic potential of targeting monocyte/macrophages in acute rejection is unknown. We investigated the potential of a c-fms kinase inhibitor (fms-I) in acute renal allograft rejection. Lewis rats underwent bilateral nephrectomy and received an orthotopic Dark Agouti renal allograft. Recipients received fms-I or vehicle from the time of transplantation until being killed on day 5. Vehicle-treated rats developed severe allograft rejection with massive macrophage and T-cell infiltration. In contrast, fms-I substantially inhibited renal allograft dysfunction and structural damage with abrogation of macrophage and dendritic cell infiltration but had only a minor effect on the T-cell infiltrate. However, fms-I suppressed T-cell activation within the allograft, whereas systemic T- and B-cell activation was not affected. In a longer-term study to assess therapeutic potential, fms-I-treated rats developed severe antibody-mediated rejection on day 8 after transplantation. These transplants exhibited features of antibody-mediated rejection including capillaritis with thrombosis, acute tubular injury, IgG and C4d deposition, and neutrophil infiltration and activation. Interestingly, T-cell activation within these rejecting allografts remained suppressed, indicating separation of T-cell and antibody-mediated rejection. This study demonstrates the ability of c-fms kinase blockade to selectively deplete monocyte/macrophages in acute allograft rejection, although this did not result in significant prolongation of allograft survival. Furthermore, we identify contrasting roles for macrophages in cellular and humoral mechanisms of acute renal allograft rejection.

PET with 18F-FDG–Labeled T Lymphocytes for Diagnosis of Acute Rat Renal Allograft Rejection

We proposed small-animal PET with (18)F-FDG-labeled T lymphocytes as a new method for image-based diagnosis of acute allogeneic renal transplant rejection (AR) established in a rat model. One and 2 h after tail vein injection of 30 × 10(6) ex vivo (18)F-FDG-labeled human T cells into male 10-wk-old uninephrectomized, allogeneically transplanted rats (aTX; Lewis-brown Norway [LBN] to Lewis), whole-body radioactivity distribution was assessed in vivo by small-animal PET (postoperative day 4), and percentage injected dose (%ID) as a parameter of T-cell infiltration was assessed and compared between graft and native kidney. In vivo results were confirmed by autoradiography and staining of human CD3 after postmortem dissection. Syngeneically transplanted rats (sTX) (LBN to LBN), rats with ischemia-reperfusion injury (IRI) (45-min warm ischemia), and rats subjected to acute cyclosporine A (CSA) toxicity (50 mg/kg for 2 d intraperitoneally) served as controls. The accumulation of labeled cells was significantly elevated in allografts with AR (1.07 ± 0.28 %ID), compared with native control kidneys (0.49 ± 0.18 %ID) (P < 0.0001). No differences were found among native controls, sTX, CSA toxicity, and kidneys with IRI. In vivo uptake of (18)F-FDG cells measured in the PET scanner correlated with results obtained by autoradiography, histologic evaluation, and polymerase chain reaction. We proposed graft PET imaging using (18)F-FDG-labeled T cells as a new option to detect rat renal AR with a low dose of (18)F-FDG in a noninvasive, fast, and specific manner in rats.

Potential of Noninvasive Serial Assessment of Acute Renal Allograft Rejection by 18F-FDG PET to Monitor Treatment Efficiency

We propose (18)F-FDG PET as a method to monitor acute rejection of allogeneic renal transplants in a rat model. Allogeneically transplanted (aTX) rats (binephrectomized Lewis-brown Norway to Lewis) served as the renal transplant model. aTX rats treated with cyclosporine A (CSA) served as a therapy monitoring group. Healthy control rats, rats with acute CSA nephrotoxicity, rats with acute tubular necrosis, syngeneically transplanted (sTX) rats, and aTX rats treated with CSA since postoperative day 0 served as controls. After surgery, renal glucose metabolism was assessed in vivo serially up to postoperative day 7 by performing small-animal PET 3 h after intravenous injection of 30 MBq of (18)F-FDG. Mean radioactivity (cps/mm(3) of tissue) was measured and the percentage injected dose calculated. Results were confirmed by histologic, functional, and autoradiographic analysis. Renal (18)F-FDG uptake was significantly elevated at postoperative day 4 in aTX rats, when compared with control, sTX, acute tubular necrosis, or CSA-treated rats (P < 0.05). In vivo (18)F-FDG uptake correlated with the results of autoradiography and with inflammatory infiltrates observed on histologic examination. Notably, (18)F-FDG PET assessed the response to therapy 48 h earlier than the time at which serum creatinine decreased and when histologic examination still showed signs of allograft rejection. In aTX rats, the CSA-susceptible graft infiltrate was dominated by activated cytotoxic T cells and monocytes/macrophages. (18)F-FDG PET is an option to noninvasively assess early response to therapy in rat renal allograft rejection.

Prevention of renal allograft rejection without immune suppression: a model to revisit

Spectacular success in preventing renal allograft rejection in rats was obtained over 40 yr ago using only the reactants of the response: donor-type antigen and homologous antiserum directed against donor-type antigen. Tolerance was antigen specific and sustained by persistent antigen of the graft. The model has never been tested rigorously in a large species, though the rationale for why the procedures should work applies across species including humans. Confirming the results in a large species would have profound impact on research for treating multiple immune mediated diseases, in addition to providing a way for treating some transplant recipients. This is a propitious time to confirm the applicability to larger species. If successful, only the lack of imagination limits the potential impact.

Dimethylarginine metabolism during acute and chronic rejection of rat renal allografts

Background. Dimethylarginines are inhibitors of NO synthesis and are involved in the pathogenesis of vascular diseases. In this study, we ask the question if asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) levels change during fatal and reversible acute rejection, and contribute to the pathogenesis of chronic vasculopathy.Methods. The Dark Agouti to Lewis rat strain combination was used to investigate fatal acute rejection. Fischer 344 kidneys were transplanted to Lewis rats to study reversible acute rejection episode and the process of chronic rejection. Isograft recipients and untreated Lewis rats were used as controls. l-arginine derivatives were determined by HPLC, and ADMA-metabolizing enzymes were studied by quantitative RT–PCR and western blotting.Results. Renal transplantation transiently increased dimethylarginine levels independent of acute rejection. ADMA plasma levels did not importantly differ between recipients undergoing fatal or reversible acute rejection, whereas SDMA was even lower in recipients of Fisher 344 grafts. In comparison to isograft recipients, ADMA and SDMA levels were slightly elevated during reversible, but not during the process of chronic rejection. Increased dimethylarginine levels, however, did not block NO synthesis. Interestingly, protein methylation, but not ADMA degradation, was increased in allografts.Conclusions. Our data do not support the concept that renal allografts are protected from fatal rejection by dimethylarginines. Dimethylarginines may play a role in triggering chronic rejection, but a contribution to vascular remodelling itself is improbable. In contrast, differential arginine methylation of yet unknown proteins by PRMT1 may be involved in the pathogenesis of acute and chronic rejection.

Non-Invasive Imaging of Acute Renal Allograft Rejection in Rats Using Small Animal 18F-FDG-PET

BackgroundAt present, renal grafts are the most common solid organ transplants world-wide. Given the importance of renal transplantation and the limitation of available donor kidneys, detailed analysis of factors that affect transplant survival are important. Despite the introduction of new and effective immunosuppressive drugs, acute cellular graft rejection (AR) is still a major risk for graft survival. Nowadays, AR can only be definitively by renal biopsy. However, biopsies carry a risk of renal transplant injury and loss. Most important, they can not be performed in patients taking anticoagulant drugs.Methodology/Principal FindingsWe present a non-invasive, entirely image-based method to assess AR in an allogeneic rat renal transplantation model using small animal positron emission tomography (PET) and 18F-fluorodeoxyglucose (FDG). 3 h after i.v. injection of 30 MBq FDG into adult uni-nephrectomized, allogeneically transplanted rats, tissue radioactivity of renal parenchyma was assessed in vivo by a small animal PET-scanner (post operative day (POD) 1,2,4, and 7) and post mortem dissection. The mean radioactivity (cps/mm3 tissue) as well as the percent injected dose (%ID) was compared between graft and native reference kidney. Results were confirmed by histological and autoradiographic analysis. Healthy rats, rats with acute CSA nephrotoxicity, with acute tubular necrosis, and syngeneically transplanted rats served as controls. FDG-uptake was significantly elevated only in allogeneic grafts from POD 1 on when compared to the native kidney (%ID graft POD 1: 0.54±0.06; POD 2: 0.58±0.12; POD 4: 0.81±0.06; POD 7: 0.77±0.1; CTR: 0.22±0.01, n = 3–28). Renal FDG-uptake in vivo correlated with the results obtained by micro-autoradiography and the degree of inflammatory infiltrates observed in histology.Conclusions/SignificanceWe propose that graft FDG-PET imaging is a new option to non-invasively, specifically, early detect, and follow-up acute renal rejection. This method is potentially useful to improve post-transplant rejection monitoring.

Pivotal Advance: Up-regulation of acetylcholine synthesis and paracrine cholinergic signaling in intravascular transplant leukocytes during rejection of rat renal allografts

During acute rejection, large numbers of leukocytes accumulate in the blood vessels of experimental renal allografts. About 70% of them are activated, cytotoxic monocytes that appear to be involved in allograft destruction. ACh exerts anti-inflammatory effects upon monocytes/macrophages and has been proposed to be a key player in neuroimmunological interactions. Its short half-life, however, makes it unlikely that neuronal ACh affects blood leukocytes. Renal transplantation was performed in the allogeneic DA to LEW and in the isogeneic LEW to LEW rat strain combination. Intravascular leukocytes were harvested after 4 days, and the expression of CHT1, cChAT, pChAT, and nAChR subunits was investigated by RT-PCR, immunoblotting, and immunohistochemistry. Monocytes were identified by double-labeling with ED1-antibody, directed to a CD68-like antigen. ACh content was measured by HPLC. [Ca(2+)](i) was monitored by Fura-2. Intravascular graft leukocytes express CHT1 and cChAT mRNA and protein and pChAT protein. Their expression is strongly up-regulated in vivo during acute allograft rejection. Immunohistochemistry revealed CHT1, cChAT, and pChAT protein in ED1-positive monocytes. The ACh content of allograft intravascular leukocytes was sixfold higher than that of isografts. Intravascular leukocytes express nAChR subunits, and an ATP-induced increase in [Ca(2+)](i) was augmented in vitro by a nAChR inhibitor in allograft but not isograft leukocytes. Intravascular graft leukocytes, among them monocytes, up-regulate non-neuronal ACh synthesis and develop auto-/paracrine cholinergic attenuation of ATP signaling during acute allograft rejection.

The Effect of FK778 on Acute Rat Renal Allograft Rejection and Expression of Platelet-Derived Growth Factor and Transforming Growth Factor-Beta

Background Acute rejection is the single most important risk factor for the development of subsequent chronic allograft nephropathy (CAN). Both platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-β) are major mitogens mediating mesenchymal cell proliferation and epithelial to mesenchymal cell transition. Early posttransplant induction of these growth factors may start molecular mechanisms leading to CAN. A new promising immunosuppressive drug, FK778, is an analogue of the active metabolite of leflunamide, which inhibits de novo pyrimidine biosynthesis. Herein we investigated the effect of FK778 on acute rejection and on the expression of PDGF and TGF-β both alone and in combination with cyclosporine (CsA) or tacrolimus (Tac). Methods Kidney transplantations were performed from Dark Agouti (DA) to Wistar-Furth (WF) rats with syngeneic controls between DA rats. No immunosuppression was given to syngeneic grafts. Allografts were immunosuppressed with FK778 alone or in combination with CsA or Tac. Grafts were harvested on day 5 for histology and immunohistochemistry (PDGF-A, -B, PDGFR-α, -β, TGF-β1, and TGF-βR1). Results FK778 ameliorated the inflammatory response and reduced PDGF and TGF-β expression in a dose-dependent manner. It also showed synergy with calcineurin inhibitors, an effect that was stronger with Tac than with CsA. Conclusions Our results indicated that FK778 decreased PDGF and TGF-β expression early in acute rejection, suggesting it to be a promising therapy for CAN.

Peripheral Choline Acetyltransferase is Expressed by Monocytes and Upregulated During Renal Allograft Rejection in Rats

Acetylcholine (ACh) has been shown to modulate the function of mononuclear leukocytes, both by muscarinic and nicotinic ACh receptors. Acute stimulation of lymphocytes with ACh or muscarinic agonists enhances proinflammatory functions, whereas chronic application of the ACh agonist nicotine has an anti-inflammatory effect (Geng et al., 1996; Kawashima and Fujii, 2003). In macrophages, acute treatment with nicotine down-modulates effector functions (Wang et al., 2003, 2004). ACh regulating leukocytes might originate from the nervous system. However, once released, ACh is quickly degraded. Relevant concentrations occur only in the direct vicinity of nerve endings. Non-neuronal ACh acting in a paracrine or autocrine fashion is more likely to influence immune functions. Lymphocytes express all enzymes needed for ACh synthesis, including choline acetyltransferase (ChAT). In the rat, alternative splicing generates common ChAT and peripheral ChAT (pChAT). Up to now, ChAT expression by monocytes has not been demonstrated. We investigate pChAT in monocytes in an experimental model of acute renal allograft rejection. Inside the blood vessels of the transplant, huge numbers of activated, cytotoxic monocytes accumulate and probably contribute to graft destruction (Grau et al., 2001).

Peritransplant treatment with cobalt protoporphyrin attenuates chronic renal allograft rejection

Allogen-independent injury contributes to chronic rejection in renal allografts and heme oxygenase-1 (HO-1) has been shown to be protective in a number of settings. This study evaluated the effect of renal allograft recipient HO-1 up-regulation on chronic rejection in a rat model. Rat (F344 to Lewis) renal transplantation recipients were grouped: (i) cyclosporine (CsA) alone (0.75 mg/kg s.c. x 10 day; n = 5); (ii) CsA + low dose cobalt protoporphyrin (CoPP) an HO-1 inducer (0.5 mg/kg i.p. on days -5,0,5; n = 13) and (iii) CsA + high dose CoPP (5.0 mg/kg i.p. on days -5,0,5; n = 8). Renal function was assessed by serum creatinine levels on day 140. Histopathologic changes in allografts were graded. Morphometric analyses performed to objectively quantify the vascular changes and glomerulosclerosis. HO-1 expression quantified by Western blot and both HO-1 and endothelin (ET-1) localized using immunohistochemistry. Recipients treated with CsA + high dose CoPP had significantly decreased cortical scarring, vascular hyalinization and intimal thickness. They also had a significant, dose-dependent, reduction in luminal obliteration and glomerulosclerosis by morphometric analyses. This freedom from chronic rejection in recipients treated with CoPP translated into quiescent grafts at postoperative day 140 with immunostaining and Western blot demonstrating decreased level of HO-1 versus controls (P = 0.012). In summary, the peritransplant up-regulation of HO-1 in renal allograft recipients significantly attenuates chronic rejection in rat renal allografts by inhibiting transplant vasculopathy.

PG490-88, a new immunosuppressant, effectively prevents acute and chronic rejection in rat renal allografts

PG490-88 is a semisynthetic derivative of the novel compound PG490 (triptolide) purified from a Chinese herb. It has been shown to prolong acute allograft survival in multiple experimental organ transplant models. However, the effect of PG490-88 on prevention of acute and chronic renal allograft rejection has not been determined. Kidneys of ACI or F344 rats were transplanted into bilaterally nephrectomized LEW recipients as the acute or chronic allograft rejection models, respectively. Treatment of LEW recipients with PG490-88 significantly prolonged ACI kidney graft survival in a dose-dependent manner when compared with the untreated allograft controls. LEW recipients of F344 kidney grafts who received PG490-88 for 90 days with a brief course of low-dose FK506 showed normal serum creatinine levels and markedly reduced histological changes of chronic rejection at day 90 after transplantation. These results suggest that PG490-88 significantly prolongs kidney allograft survival in an acute rejection model and prevents chronic allograft rejection in rats.

Chemokine-binding viral protein M-T7 prevents chronic rejection in rat renal allografts.

M-T7 is a myxoma virus-encoded protein that has been found to bind and disrupt human chemokine gradients. This study examined whether purified M-T7 could prevent chronic rejection in a rat renal allograft model. Fisher F344 renal allografts were transplanted into Lewis rats. Recipients were randomly grouped into two groups: control animals treated with cyclosporine alone and animals treated with cyclosporine combined with low-, medium- and high-dose M-T7 viral protein. The survival rate was not significantly different between allograft groups. Renal allografts treated with high-dose M-T7 demonstrated a significant reduction in tubular atrophy, glomerular atrophy, vascular hyalinization, cortical scarring, and lymphocyte infiltration. Morphometric analyses demonstrated that the high-dose M-T7 group also showed a significantly decreased amount of glomerulosclerosis and transplant arteriosclerosis. These data demonstrate for the first time that the immunoregulatory viral protein M-T7 can effectively attenuate chronic rejection in rat renal allografts.

FK778, a powerful new immunosuppressant, effectively reduces functional and histologic changes of chronic rejection in rat renal allografts.

FK778 is a new derivative of the active leflunomide metabolite A77 1726. It effectively prevented acute allograft rejection in several experimental transplant models, and it is currently in phase II trials in human transplant recipients. In this study, we examined the effects of FK778 in a well-established model of chronic renal allograft rejection in the rat. Kidneys of Lewis (LEW) and F344 rats were orthotopically transplanted into bilaterally nephrectomized LEW recipients as the isograft and allograft control, respectively. Allograft recipients were orally administered FK778 at doses of 3 mg/kg per day, 10 mg/kg per day, and 20 mg/kg per day for 10 days. Blood and 24-hr urine samples were collected once a week after grafting for plasma creatinine, allo-specific antibodies, and proteinuria determination. Kidney grafts were harvested on the 90th day after transplantation and subjected to histologic, immunohistologic, and reverse transcriptase-polymerase chain reaction analysis. Histologic sections were semiquantitatively scored using criteria adapted from the Banff' classification for transplant pathologic conditions. Recipients treated with FK778 for 10 days exhibited a dose-dependent decrease in proteinuria and plasma creatinine for the entire 90-day period after transplantation when compared with the allograft control. FK778, at doses of 10 mg/kg per day and 20 mg/kg per day, remarkably reduced chronic histologic changes, including tubular atrophy, glomerulosclerosis, fibrointimal hyperplasia, and transplant glomerulopathy. In addition, FK778 treatment was associated with decreased intragraft mononuclear cell infiltration, serum allo-specific immunoglobulin (Ig)M and IgG antibody production, and intragraft transforming growth factor beta messenger RNA expression in those recipients surviving 90 days after transplantation when compared with the allograft control. FK778 effectively reduces functional and histologic chronic kidney allograft rejection in the rat.

Influence of acute selective endothelin-receptor-A blockade on renal hemodynamics in a rat model of chronic allograft rejection.

We have recently demonstrated up-regulation of renal endothelin (ET) synthesis in a rat model of chronic renal allograft rejection. Treatment with a selective ET-A receptor antagonist improved survival and reduced functional and morphological kidney damage. However, the underlying mechanisms have not yet been elucidated, as ET exhibits both hemodynamic and inflammatory properties. Therefore, in the present study we investigated acute hemodynamic effects of the selective ET-A receptor antagonist LU 302146 (LU) on chronic renal allograft rejection in rats. Experiments were performed in the Fisher-to-Lewis model of chronic renal allograft rejection. Lewis-to-Lewis isografts served as controls. After 2, 12, and 24 weeks, hemodynamic measurements were performed on anesthetized animals. Measurement of mean arterial pressure (MAP) was performed via a catheter in the femoral artery. Renal blood flow (RBF) was measured by an ultrasonic flow probe placed around the renal transplant artery. Medulla blood flow (MBF) and cortex blood flow (CBF) were determined with laser Doppler probes. Hemodynamic response upon intravenous bolus injection of LU (50 mg/kg) was investigated. The application of LU was followed by a decline in MAP that reached statistical significance only in isografts (ISOs) after 12 weeks and allografts (ALLOs) after 24 weeks. RBF slightly decreased in all groups; however, without reaching statistical significance. MBF showed a small increase in ALLO12 and ALLO24 whereas CBF slightly decreased in all groups. Acute ET-A receptor blockade does not induce important hemodynamic effects in kidneys undergoing chronic rejection. The lack of response to ET-A receptor blockade suggests that the beneficial effect of ET receptor antagonists in this model is likely to be due to improvement of renal morphology.

Induction of epidermal fatty acid binding protein in intravascular monocytes of renal allografts.

During acute rejection of rat renal allografts, numerous activated monocytes accumulate in the vasculature of the graft. These monocytes seem to be involved in allograft destruction. Proinflammatory and effector functions of monocytes and macrophages can be down-regulated by peroxisome proliferators, which are probably transported in the cytoplasm by fatty acid binding proteins (FABPs). We performed renal transplantation in rats in the Dark Agouti-to-Lewis strain combination. Intravascular graft leukocytes were harvested 4 days posttransplantation. Epidermal (E)-FABP mRNA and protein expression were investigated by reverse-transcriptase polymerase chain reaction and immunoblotting, respectively. E-FABP-expressing cells were identified by immunofluorescence. After allogeneic transplantation, intravascular graft leukocytes expressed E-FABP mRNA and protein. In isografts, significantly lower expression levels were observed. E-FABP protein was detected in monocytes expressing ED1 and in alphabeta-T-cell receptor positive T lymphocytes. E-FABP might regulate monocyte activation and may represent a promising target for a therapeutic intervention in allograft rejection.