The effect of acute rejection and cyclosporin A-treatment on induction of platelet-derived growth factor and its receptors during the development of chronic rat renal allograft rejection

A new lateral flow assay to detect sIL-2R during T-cell mediated rejection after kidney transplantation

Kidney is the most frequently transplanted among all solid organs worldwide. Kidney transplant recipients (KTRs) undergo regular follow-up examinations for the early detection of acute rejections. The gold standard for proving a T-cell mediated rejection (TCMR) is a biopsy of the renal graft often occurring as indication biopsy, in parallel to an increased serum creatinine that may indicate deterioration of renal transplant function. The goal of the current work was to establish a lateral flow assay (LFA) for diagnosing acute TCMR to avoid harmful, invasive biopsies. Soluble interleukin-2 (IL-2) receptor (sIl-2R) is a potential biomarker representing the α-subunit of the IL-2 receptor produced by activated T-cells, e.g., after allogen contact. To explore the diagnostic potential of sIL-2R as a biomarker for TCMR and borderline TCMR, plasma and urine samples were collected from three independent KTR cohorts with various distinct histopathological diagnostic findings according to BANFF (containing 112 rsp. 71 rsp. 61 KTRs). Samples were analyzed by a Luminex-based multiplex technique and cut off-ranges were determined. An LFA was established with two specific sIL-2R-antibodies immobilized on a nitrocellulose membrane. A significant association between TCMR, borderline TCMR and sIL-2R in plasma and between TCMR and sIL-2R in urine of KTRs was confirmed using the Mann-Whitney U test. The LFA was tested with sIL-2R-spiked buffer samples establishing a detection limit of 25 pM. The performance of the new LFA was confirmed by analyzing urine samples of the 2^nd and 3^rd patient cohort with 35 KTRs with biopsy proven TCMRs, 3 KTRs diagnosed with borderline TCMR, 1 mixed AMR/TCMR rsp. AMR/borderline TCMR and 13 control patients with a rejection-free kidney graft proven by protocol biopsies. The new point-of-care assay showed a specificity of 84.6% and sensitivity of 87.5%, and a superior estimated glomerular filtration rate (eGFR) at the time point of biopsy (specificity 30.8%, sensitivity 85%).

Epidermal growth factor inhibition, a novel pathway to prevent chronic allograft injury

BACKGROUND

Chronic allograft injury remains a major problem in clinical kidney transplantation and different growth factors participate in its development. Epidermal growth factor (EGF) affects cell proliferation and mitogenesis through its tyrosine kinase receptor. Erlotinib is an orally administered tyrosine kinase inhibitor used in clinical oncology to inhibit EGF signaling. We investigated its effect on the development of chronic allograft injury in an experimental kidney transplantation model.

METHODS

Kidney transplantations were performed between Dark Agouti and Wistar Furth rats. Recipients were immunosuppressed either with cyclosporine A (CsA, 1.5 mg/kg/day subcutaneously) or with CsA and erlotinib (10 mg/kg/day orally). Kidney grafts were harvested after 5 and 90 days for histology and immunohistochemistry. Aorta denudation model was used for the erlotinib dose response study to define the optimal dose for the transplantation study.

RESULTS

Epidermal growth factor expression was increased in CsA-treated allografts which developed intense chronic changes on day 90. Erlotinib ameliorated neointimal formation in the dose response study. In addition, erlotinib decreased chronic rejection changes and maintained better graft function in kidney transplantation model. Late posttransplant EGF and EGF receptor levels were reduced with erlotinib.

CONCLUSION

Based on these findings, EGF mediates in part the development of chronic allograft injury. Its inhibition with erlotinib prevents chronic rejection and maintains better allograft function. Therefore, EGF blocking by erlotinib provides a novel pathway to prevent chronic allograft injury.

Phosphodiesterase type 5 inhibition attenuates cyclosporine A induced nephrotoxicity in mice

We investigated the renal protective effects of phophodiesterase type 5 (PDE5) inhibitors in mice with cyclosporine A (CyA; a calcineurin phosphatase inhibitor) induced nephrotoxicity. Fifty male mice were divided into five groups of 10. Group 1 received no treatment, group 2 received only saline orally, group 3 received 30 mg/kg/day CyA by subcutaneous injection, group 4 received only 30 mg/kg/day vardenafil orally, and group 5 received 30 mg/kg/day CyA by subcutaneous injection and 30 mg/kg/day vardenafil orally. At 28 days, platelet-derived growth factor A (PDGF-A) and C (PDGF-C), transforming growth factor-beta 1 (TGF-β1), cyclo-oxygenase 1 and 2 (COX-1 and COX-2), and P glycoprotein (Pgp) expression levels were measured in the renal tissues. In addition, expressions of COX-1 and COX-2 genes were determined using real-time PCR. PDE5 inhibitor administration ameliorated decreased PDGF-A and C, TGF-β1, COX-1 and -2, and Pgp expression levels by modulation of cyclic guanosine monophosphate (cGMP) activity in kidneys. The relative expressions of COX-1 and COX-2 genes to GAPDH revealed that the maximum increase was obtained in the group treated with CyA and vardenafil for both COX-1 and COX-2 genes. Our study revealed that long term oral treatment with vardenafil protects kidneys from CyA induced nephrotoxicity. We showed that long term oral treatment with PDE5 prevents pathological kidney changes caused by CyA induced nephrotoxicity.

IF/TA-related metabolic changes--proteome analysis of rat renal allografts

BACKGROUND

Chronic allograft nephropathy, now more specifically termed interstitial fibrosis and tubular atrophy without evidence of any specific aetiology (IF/TA), is still an important cause of late graft loss. There is no effective therapy for IF/TA, in part due to the disease's multifactorial nature and its incompletely understood pathogenesis.

METHODS

We used a differential in-gel electrophoresis and mass spectrometry technique to study IF/TA in a renal transplantation model. Dark Agouti (DA) kidneys were allogeneically transplanted to Wistar-Furth (DA-WF, aTX) rats. Syngeneic grafts (DA-DA, sTX) served as controls. Nine weeks after transplantation, blood pressure, renal function and electrolytes were studied, in addition to real-time PCR, western blot analysis, histology and immunohistochemistry.

RESULTS

In contrast to sTX, the aTX developed IF/TA-dependent renal damage. Ten differentially regulated proteins were identified by 2D gel analysis and mass spectrometry, whereupon five proteins are mainly related to oxidative stress (aldo-keto reductase, peroxiredoxin-1, NAD(+)-dependent isocitrate dehydrogenase, iron-responsive element-binding protein-1 and serum albumin), two participate in cytoskeleton organization (l-plastin and ezrin) and three are assigned to metabolic functions (creatine kinase, ornithine aminotransferase and fructose-1,6-bisphosphatase).

CONCLUSION

The proteins related to IF/TA and involved in oxidative stress, cytoskeleton organization and metabolic functions may correspond with novel therapeutic targets.

Early short-term platelet-derived growth factor inhibition prevents the development of chronic allograft nephropathy in experimental rat kidney transplantation

Chronic allograft nephropathy (CAN) remains the primary reason for late allograft loss in kidney transplantation. Platelet-derived growth factor (PDGF) is a major mitogen mediating mesenchymal cell proliferation in CAN. When administered continuously the PDGF receptor tyrosine kinase inhibitor imatinib prevents the development of CAN and restores kidney function in experimental kidney transplantation. Herein we investigated whether early short-term imatinib treatment prevented CAN. Kidney transplantations were performed from DA to WF rats and syngenic controls were done between DA rats. Allograft recipients were immunosuppressed with cyclosporine (CsA; 1.5 mg/kg/d sc). One group of allografts was also treated with imatinib (10 mg/kg/d po). Serum creatinine levels were measured once a week. Grafts were harvested 90 days after transplantation for histology and immunohistochemistry (PDGF-AA, -BB, PDGFR-alpha, -beta). Histological changes were scored according to the Chronic Allograft Damage Index (CADI). Among syngenic grafts, no signs of CAN were observed, namely, CADI 0.3 +/- 0.2 (mean +/- SEM). Control allografts showed moderate to intense chronic changes, CADI 6.5 +/- 1.3. Early short-term imatinib treatment significantly prevented the development of CAN compared with control allografts. Only a few histological changes were seen, namely, CADI 3.3 +/- 1.4. Compared with control allografts PDGF ligand and receptor induction was significantly inhibited by imatinib to nearly the same level as in syngenic grafts. Creatinine values of imatinib-treated allografts were also lower than control allografts. Our results demonstrated that early short-term imatinib treatment significantly prevented CAN. This indicated that early PDGF induction has an important role in the pathogenesis of CAN.

Sirolimus attenuates chronic allograft nephropathy in an experimental rat kidney transplantation model

Chronic allograft nephropathy (CAN) is the primary reason for late allograft loss in kidney transplantation. The use of calcineurin inhibitors is suggested to be a risk factor for the development of CAN. Thus, calcineurin-inhibitor-free immunosuppressive protocols are needed to improve long-term graft outcome. Sirolimus affects the immune response by interfering with postreceptor interleukin-2 signaling. Safety profile of sirolimus is different from that of calcineurin inhibitors. We investigated the long-term effects of sirolimus on kidney allografts and fibrogenic growth factor expression and compared it to cyclosporine A. Kidney transplantations were performed from DA to WF rats and syngenic controls were done between DA rats. Allograft recipients were immunosuppressed daily with sirolimus 2 p.o. or CsA 1.5 mg/kg s.c. In addition, sirolimus-treated animals were treated with cyclosporine 1.5 mg/kg s.c. for the first 7 days after transplantation. Serum creatinine levels were measured once a week. Grafts were harvested 90 days after transplantation for histology and immunohistochemistry. Histological changes were scored according to the chronic allograft damage index (CADI). No signs of CAN were seen in syngenic grafts, CADI 0.8 +/- 0.2 (mean +/- SEM). In cyclosporine-treated allografts moderate to intense chronic changes were seen; CADI 10.3 +/- 0.6. Sirolimus significantly ameliorated the development of CAN compared to cyclosporine, CADI 3.0 +/- 0.5 (P < .05). Creatinine values of sirolimus-treated allografts were lower compared to the cyclosporine-treated allografts and were nearly similar to the syngenic grafts. Our results demonstrate that sirolimus attenuates the development of CAN and restores kidney function. Based on our findings, sirolimus improves the long-term kidney graft outcome.

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-beta) 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-beta 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-alpha, -beta, TGF-beta1, and TGF-betaR1).

RESULTS

FK778 ameliorated the inflammatory response and reduced PDGF and TGF-beta 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-beta expression early in acute rejection, suggesting it to be a promising therapy for CAN.

Mycophenolic acid inhibits mesangial cell activation through p38 MAPK inhibition

Mesangial cell (MC) proliferation and extracellular matrix (ECM) accumulation are major pathologic features of chronic renal disease including chronic allograft nephropathy (CAN). Mycophenolic acid (MPA), a potent immunosuppressant, has emerged as a treatment to prevent CAN because it inhibits MC proliferation and ECM synthesis, but the mechanism involved has not been clarified. The present study examined relative role of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK) activation in inhibitory effect of MPA on MC activation. Growth arrested and synchronized primary rat MC (passages 7-11) were stimulated by PDGF 10 ng/ml in the presence and absence of clinically attainable dose of MPA (0-10 microM). Cell proliferation was assessed by [(3)H]thymidine incorporation, fibronectin and the activation of ERK and p38 MAPK by Western blot analysis, and total collagen by [(3)H]proline incorporation. PDGF increased cell proliferation by 4.6-fold, fibronectin secretion by 3.2-fold, total collagen synthesis by 1.8-fold, and the activation of ERK and 38 MAPK by 5.6-fold and 3.1-fold, respectively, compared to control. MPA, at doses inhibiting PDGF-induced MC proliferation and ECM synthesis, effectively blocked p38 MAPK activation but reduced ERK activation by 23% at maximal concentration tested (10 microM). Exogenous guanosine partially reversed the inhibition of MPA on p38 MAPK activation. Inhibitor of ERK or p38 MAPK suppressed PDGF-induced MC proliferation and ECM synthesis. In conclusion, MPA inhibits p38 MAPK activation leading to inhibiting proliferation and ECM synthesis in MC. Guanosine reduction is partially responsible for inhibitory effect of MPA on p38 MAPK activation in MC.

Down-regulation of TGF-beta and VCAM-1 is associated with successful treatment of chronic rejection in rats

We measured the expression levels of transforming growth factor-beta (TGF-beta) and vascular cell adhesion molecule (VCAM-1) in rat kidney grafts undergoing chronic rejection and treated the rats with six different regimens in order to determine correlation between their expression levels and severity of chronic rejection. F344 or Lewis kidneys were transplanted into Lewis recipients to generate allograft or isograft groups, respectively. Graft recipients were treated with one of the following regimens: (1) untreated isograft, (2) untreated allograft, (3) tacrolimus (FK506), 1 mg/kg/d for 10 days, (4) triptolide (PG490-88), 0.5 mg/kg/d for 10 days, and (5) leflunomide analogue (FK778), 10 mg/kg/d for 10 days. Kidneys were harvested on day 90 after transplantation and subjected to histological analysis and gene expression analysis by real-time reverse transcriptase polymerase chain reaction (RT-PCR) for TGF-beta and VCAM-1. Gene expression values were compared to measurements of chronic rejection by linear regression analysis. Modified Banff score for transplant pathology show that chronic rejection was mild in the FK778 group, moderate in the PG490-88 group, and severe in the FK506 and allograft control groups. Overall, the expression levels of TGF-beta and VCAM-1 show high correlations with histological changes of chronic rejection. Suppression of the expression levels of TGF-beta and VCAM-1 is associated with the amelioration of chronic rejection by various drugs, suggesting that these molecules are important key molecules in chronic rejection.

Protective effects of PG490-88 on chronic allograft rejection by changing intragraft gene expression profiles

Our previous study showed that PG490-88 effectively ameliorated both functional and histological changes of chronic rejection in the rat. In this experiment, we investigated the intragraft gene expression profiles of PG490-88 under successful prevention of chronic rejection in rat kidney allografts. Kidneys of F344 rats were transplanted into bilaterally nephrectomized LEW recipients. Recipients with a brief course of low-dose FK506 (1 mg/kg per day for 10 days) were dosed with PG490-88 0.5 mg/kg per day, which was predetermined and defined as the effective dose of preventing chronic allograft rejection in this model, for 90 days after grafting. Kidney grafts were harvested on day 90 after transplantation and subjected to gene expression analysis by real-time RT-PCR. Overall, the expression levels of all genes tested were upregulated in the brief course of low-dose FK506 control. PG490-88 treatment exhibited significant inhibition of intragraft m RNA levels of iNOS, IL-6, and perforin and marginal downregulation of IL-2, IFNgamma, IRF-1, TNFalpha, and TGFbeta. There was no change in IL-10, granzyme B, and PDGFalpha, when compared to the brief course of low-dose FK506 control. These results suggested that downregulation of multiple intragraft gene expression by mainly suppression of iNOS, IL-6, and perforin might be responsible for successful prevention of chronic kidney allograft nephropathy by PG490-88 in rats.

Cytomegalovirus enhance expression of growth factors during the development of chronic allograft nephropathy in rats

Cytomegalovirus (CMV) accelerates chronic rejection (CRX) in a model of rat kidney allograft. In this model, the expressions of transforming growth factor beta 1 (TGF-beta), platelet-derived growth factor (PDGF)-AA, PDGF-BB and connective tissue growth factor (CTGF) were investigated with and without CMV. Transplantations were performed under immunosuppression. One group of animals was infected with CMV and the other was left uninfected. The grafts were harvested on days 3-60 after transplantation. Growth factor proteins were demonstrated by immunohistochemistry, and mRNAs by in situ hybridization. A significantly more intense and earlier endothelial TGF-beta (2.4 +/- 0.8 vs. 1.0 +/- 0.0; P < 0.05) and PDGF-AA (1.8 +/- 0.4 vs. 1.0 +/- 0.0; P < 0.05) expressions, confirmed by mRNA hybridization, occurred in the CMV group compared with the noninfected group. PDGF-BB appeared in a few inflammatory cells only. In addition CTGF appeared earlier and has more intense in the CMV group (2.5 +/- 0.6 vs. 1.2 +/- 0.5) and the number of CTGF mRNA-positive fibroblasts (57 +/- 9 vs. 3 +/- 4; P < 0.05) was significantly higher. Thus, CMV enhanced expression of TGF-beta1, PDGF-AA and CTGF during the development of CRX.

Relationships between HLA-A, -B, -DQ and -DR antigens and interstitial fibrosis in renal allografts

Although renal transplant recipients tend to exhibit similar clinical and immunological changes over time, some allograft biopsies show early IF. To evaluate the relationship between HLA antigens and IF in renal allografts, we reviewed for HLA-A, -B, -DQ, and -DR antigens in 88 renal transplant recipients. For each antigen type, we determined the numbers of patients who did and did not possess the antigen. We then determined the mean time to onset of IF for each of these two groups, and statistically compared the means. In the second part of the analysis, we divided the 88 patients into those who did and did not show IF at 6 months posttransplantation, and then calculated the prevalence of each antigen type in the IF (+) and IF (-) groups. This same procedure was repeated with the patients grouped according to presence of IF at 12 months posttransplantation. The patient groups with HLA-B8, -B27, -DQ2, -DQ5, -DQ6, -DQ7, -DR4, -DR13, and -DR15, respectively, had significantly shorter times to IF onset after transplantation than the corresponding groups without these antigens (p<0.05). The groups that were IF (+) at 6 and 12 months posttransplantation had significantly higher frequencies of HLA-B8, -B27, -DQ2, and -DR4 than the corresponding IF (-) groups at these two time points (p<0.05). The results indicated that any kidney recipient with these antigens is predisposed to developing diffuse IF in their graft relatively soon after transplantation. We conclude that although there are multiple etiological agents in the pathogenesis of interstitial fibrosis, one cannot exclude an HLA association in these cases.

Chronic allograft nephropathy is prevented by inhibition of platelet-derived growth factor receptor: tyrosine kinase inhibitors as a potential therapy

BACKGROUND

Chronic allograft nephropathy (CAN) is the primary reason for late allograft loss in kidney transplantation, and currently there is no treatment available for it. Platelet-derived growth factor (PDGF) is suggested to be a major mitogen mediating mesenchymal cell proliferation in CAN. It has been shown that PDGF is already induced at acute renal allograft rejection, indicating a link between acute rejection and subsequent development of CAN. However, the definite effect of PDGF on the pathogenesis of CAN is still unknown. We investigated the role of PDGF in CAN by inhibiting PDGF by imatinib (STI571), a selective PDGF receptor tyrosine kinase inhibitor.

METHODS

Kidney transplantations were performed from Dark Agouti (DA) to Wistar-Furth rats, and syngenic control transplantations were performed from DA to DA rats. All allograft recipients were immunosuppressed with cyclosporine A (1.5 mg/kg/day subcutaneously). One group of the animals was also treated with imatinib (10 mg/kg/day orally). Serum creatinine levels and cyclosporine A concentrations were measured once per week until the animals were killed. Grafts were harvested 5 and 90 days after transplantation for histology and immunohistochemistry.

RESULTS

Only very few histologic chronic changes, similar to syngenic grafts, were seen in imatinib-treated allografts compared with control allografts. Creatinine values of imatinib-treated allograft recipients and infiltration of inflammatory cells, PDGF ligand, and receptor induction were also at the same level as in syngenic grafts.

CONCLUSIONS

Our results demonstrate that imatinib prevents CAN almost completely, indicating that PDGF plays an important role in its pathogenesis. On the basis of our findings, imatinib could be a potential intervention in preventing CAN in clinical kidney transplantation.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

FK778 effectively reduces functional and histologic chronic kidney allograft rejection in the rat.