T lymphocytes and acute kidney injury: update.

The immune system is among the key pathogenic factors in acute kidney injury (AKI). Various immune cells, including dendritic cells, natural killer T cells, T and B lymphocytes, neutrophils and macrophages are involved. Conventional CD4+ lymphocytes are well established to participate in early injury, and CD4+CD25+FoxP3 regulatory T cells are protective and can accelerate repair. A newly identified kidney T cell receptor + CD4-CD8- (double-negative) T cell has complex functions, including potentially anti-inflammatory roles in AKI. In this mini review, we summarize the data on the role of lymphocytes in AKI and set the stage for further mechanistic studies as well as interventions to improve outcomes.

rPSGL-Ig for improvement of early liver allograft function: a double-blind, placebo-controlled, single-center phase II study.

The selectin antagonist known as recombinant P-selectin glycoprotein ligand IgG (rPSGL-Ig) blocks leukocyte adhesion and protects against transplantation ischemia reperfusion injury (IRI) in animal models. This randomized (1:1) single-center double-blind 47-patient phase 2 study with 6-month follow-up assessed rPSGL-Ig's safety and impact on early graft function at 1 mg/kg systemic dose with pretransplant allograft ex vivo treatment in deceased-donor liver transplant recipients. Safety was assessed in all patients, whereas efficacy was assessed in a prospectively defined per-protocol patient set (PP) by peak serum transaminase (TA) and bilirubin values, and normalization thereof. In PP patients, the incidence of poor early graft function (defined as peak TA >2500 U/L or bilirubin >10 mg/dL), average peak liver enzymes and bilirubin, normalization thereof and duration of primary and total hospitalization trended consistently lower in the rPSGL-Ig group compared to placebo. In patients with donor risk index above study-average, normalization of aspartate aminotransferase was significantly improved in the rPSGL-Ig group (p < 0.03). rPSGL-Ig treatment blunted postreperfusion induction versus placebo of IRI biomarker IP-10 (p < 0.1) and augmented cytoprotective IL-10 (p < 0.05). This is the first clinical trial of an adhesion molecule antagonist to demonstrate a beneficial effect on liver transplantation IRI and supported by therapeutic modulation of two hepatic IRI biomarkers.

AKI: an increasingly recognized risk factor for CKD development and progression.

Acute kidney injury (AKI) is an increasing health burden with high morbidity and mortality rates worldwide. AKI is a risk factor for chronic kidney disease (CKD) development and progression to end stage renal disease (ESRD). Rapid action is required to find treatment options for AKI, plus to anticipate the development of CKD and other complications. Therefore, it is essential to understand the pathophysiology of AKI to CKD transition. Over the last several years, research has revealed maladaptive repair to be an interplay of cell death, endothelial dysfunction, tubular epithelial cell senescence, inflammatory processes and more-terminating in fibrosis. Various pathological mechanisms have been discovered and reveal targets for potential interventions. Furthermore, there have been clinical efforts measures for AKI prevention and progression including the development of novel biomarkers and prediction models. In this review, we provide an overview of pathophysiological mechanisms involved in kidney fibrosis. Furthermore, we discuss research gaps and promising therapeutic approaches for AKI to CKD progression.

Subclinical rejection in stable positive crossmatch kidney transplant patients: incidence and correlations.

We reviewed 116 surveillance biopsies obtained approximately 1, 3, 6 and 12 months posttransplantation from 50 +XM live donor kidney transplant recipients to determine the frequency of subclinical cell-mediated rejection (CMR) and antibody-mediated rejection (AMR). Subclinical CMR was present in 39.7% of the biopsies at 1 month and >20% at all other time points. The presence of diffuse C4d on biopsies obtained at each time interval ranged from 20 to 30%. In every case, where histological and immunohistological findings were diagnostic for AMR, donor-specific antibody was found in the blood, challenging the long-held belief that low-level antibody could evade detection due to absorption on the graft. Among clinical factors, only recipient age was associated with subclinical CMR. Clinical factors associated with subclinical AMR were recipient age, positive cytotoxic crossmatch prior to desensitization and two mismatches of HLA DR 51, 52 and 53 alleles. Surveillance biopsies during the first year post-transplantation for these high-risk patients uncover clinically occult processes and phenotypes, which without intervention diminish allograft survival and function.

Acute kidney injury and lung dysfunction: a paradigm for remote organ effects of kidney disease?

An increasing body of evidence suggests that the deleterious effects of Acute Kidney Injury (AKI) on remote organ function could, at least in part, be due to loss of the normal balance of immune, inflammatory, and soluble mediator metabolism that attends injury of the tubular epithelium. Such dysregulation, acting at least in part on endothelium, leads to compromise of remote organ function. Kidney-lung interaction in the setting of AKI therefore constitutes not only a pressing clinical problem, but also an illuminating framework in which to consider possible mechanisms by which renal diseases exert such deleterious effects on patient outcomes, even when dialysis is provided.

Identification of the CD4(+) T cell as a major pathogenic factor in ischemic acute renal failure.

Leukocytes have been implicated in the pathogenesis of ischemic acute renal failure (ARF), but the roles of the individual cell types involved are largely unknown. Recent indirect evidence suggests that T cells may play an important role in a murine model of ARF. In the current study, we found that mice deficient in T cells (nu/nu mice) are both functionally and structurally protected from postischemic renal injury. Reconstitution of nu/nu mice with wild-type T cells restored postischemic injury. We then analyzed the contribution of the individual T cell subsets to postischemic injury and found that mice deficient in CD4(+) T cells, but not mice deficient in CD8(+) T cells, were significantly protected from ARF. Direct evidence for a pathophysiologic role of the CD4(+) T cell was obtained when reconstitution of CD4-deficient mice with wild-type CD4(+) T cells restored postischemic injury. In addition, adoptive transfers of CD4(+) T cells lacking either the costimulatory molecule CD28 or the ability to produce IFN-gamma were inadequate to restore injury phenotype. These results demonstrate that the CD4(+) T cell is an important mediator of ischemic ARF, and targeting this cell may yield novel therapies.

Genomic profiling of kidney ischemia-reperfusion reveals expression of specific alloimmunity-associated genes: Linking "immune" and "nonimmune" injury events.

Increased organ ischemia time leads to delayed graft function (DGF), increased acute rejection (AR), enhanced chronic allograft nephropathy (CAN), and reduced long-term allograft survival. The mechanisms by which IRI predisposes to AR and CAN are unknown. We hypothesized that gene expression profiling of ischemia-reperfusion injury (IRI)-affected kidney would identify how IRI predisposes to AR and CAN. Furthermore, we examined how current immunosuppressive drug molecular targets are altered by IRI. C57BL/6J mice were exposed to 30 (n = 3) or 60 (n = 3) minutes of bilateral kidney ischemia or sham surgery (n = 5). At 36 hour kidney tissue was collected and analyzed using Affymetrix 430MOEA (22626 genes) array and GC-RMA-SAM pipeline. Genes with the false discovery rate (q < 1%) and +/-50% fold change (FC) were considered affected by IRI. Genes coding for histocompatibility and antigen-presenting factors, calcineurin, and mammalian target of rapamycin (mTOR) pathway-associated proteins were selected using Gene Ontology (GO) analysis. GO analysis identified 10 and 17 alloimmunity-related genes affected by IRI induced by 30 and 60 minutes of ischemia, respectively, including Traf6 (FC = 2.99) and H2-D1 (FC = 2.58). We also detected significant IRI genomic responses in calcineurin and mTOR pathways represented by Fkbp5 (FC = 4.18) and Fkbp1a (FC = 2.0), and Eif4ebp1 (FC = 16.8) and Akt1 (FC = 3.64), respectively. These data demonstrated that IRI up-regulates expression of several alloimmunity-associated genes, which can in turn enhance alloimune responses. Our discovery of IRI-induced up-regulation of genes associated with calcineurin and mTOR pathways are consistent with clinical observations that FK506 and Rapamycin can alter the course of DGF. Further validation and dissection of these pathways can lead to novel approaches by which improved management of early "nonimmune" transplant events can decrease susceptibility to more classic "immune" changes and CAN.

Quantitative detection of promoter hypermethylation as a biomarker of acute kidney injury during transplantation.

Aberrant promoter hypermethylation, also known as epigenetics, is thought to be a promising biomarker approach to diagnose malignancies. Kidney repair after injury is a recapitulation of normal morphogenesis, with similarities to malignant transformation. We hypothesized that changes in urine epigenetics could be a biomarker approach during early kidney transplant injury and repair. We examined urine DNA for aberrant methylation of two gene promoters (DAPK and CALCA) by quantitative methylation-specific polymerase chain reaction from 13 deceased and 10 living donor kidney transplant recipients on postoperative day 2 and 65 healthy controls. Results were compared with clinical outcomes and to results of the kidney biopsy. Transplant recipients were significantly more likely to have aberrant hypermethylation of the CALCA gene promoter in urine than healthy controls (100% vs 31%; P < .0001). There was increased CALCA hypermethylation in the urine of deceased versus living donor transplants (21.60 +/- 12.5 vs 12.19 +/- 4.7; P = .04). Furthermore, there was a trend toward increased aberrant hypermethylation of urine CALCA in patients with biopsy-proven acute tubular necrosis versus acute rejection and slow or prompt graft function (mean: 20.40 +/- 6.9, 13.87 +/- 6.49, 17.17 +/- 13.4; P = .67). However, there was no difference of CALCA hypermethylation in urine of patients with delayed graft function versus those with slow or prompt graft function (16.9 +/- 6.2 vs 18.5 +/- 13.7, respectively; P = .5). There was no aberrant hypermethylation of DAPK in the urine of transplant patients. Urine epigenetics is a promising biomarker approach for acute ischemic injury in transplantation that merits future study.

IL-1 and TNF independent pathways mediate ICAM-1/VCAM-1 up-regulation in ischemia reperfusion injury.

In vitro studies have suggested that targeting interleukin (IL)-1 and tumor necrosis factor (TNF) can be used to regulate intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and potentially treat kidney inflammation. We therefore evaluated ICAM-1 and VCAM-1 regulation in knockout (KO) mice deficient in both IL-1 receptor 1 (R1) and TNF-R1 during renal ischemia reperfusion injury. ICAM-1 and VCAM-1 mRNA expression was measured with specific murine probes and Northern blotting (n =4/group). Protein expression was measured using immunohistochemistry. Serum creatinine (SCr), tubular histology, and neutrophil infiltration into postischemic kidneys were also quantified. ICAM-1 and VCAM-1 mRNA expression increased in both wild-type (WT) and KO mice at 2, 6, and 24 h. Protein expression of ICAM-1 and VCAM-1 was also increased at 24 h postischemia. SCr levels and tubular necrosis scores were comparable in WT and KO mice at 24 and 48 h. Neutrophil migration in KO mice was decreased at 24 h but comparable to WT at 48 h. These data demonstrate that IL-1 and TNF are not essential for postischemic increases in ICAM-1 and VCAM-1.

The effects of corticotropin and growth hormone releasing hormones on their respective secretory axes in chronic hemodialysis patients before and after correction of anemia with recombinant human erythropoietin.

Endocrine abnormalities in chronic hemodialysis patients are in part corrected by control of anemia with recombinant human erythropoietin (rHu-EPO). We further examined the role of rHu-EPO in select hormonal abnormalities thought to be anemia related as well as the GH-insulin-like growth factor 1 (GH-IGF-1) axis that is abnormal in hemodialysis patients. We studied responses to the administration of two hypothalamic hormones, GHRH and ovine corticotropin-releasing hormone (CRH), in five anemic male patients on chronic hemodialysis before and after correction of the anemia with rHu-EPO. For comparison, five age-matched normal male volunteers were tested once. Anemic patients on chronic hemodialysis had high basal GH concentrations, an exaggerated GH response to exogenous GHRH, increased levels of IGF-1, and elevated levels of IGF-1 binding protein-3 in comparison to controls. ACTH response to CRH was comparable in dialysis patients and normal controls, but the cortisol response to endogenous ACTH release was prolonged. The cortisol binding globulin was similar to the controls. After correction of anemia, the basal elevation of GH was no longer present, but the exaggerated response of GH to exogenous GHRH persisted. IGF-1 and IGF-1 binding protein-3 levels remained elevated. The ACTH response to CRH, which was normal before correction of the anemia, became exaggerated in terms of elevated levels. Nevertheless, the prolonged cortisol response persisted. It appears that correction of the anemia in hemodialysis patients with rHu-EPO can partly correct perturbations in the GH secretory axis but may lead to new abnormalities in the CRH-ACTH axis.

Role of leukocytes and leukocyte adhesion molecules in renal ischemic-reperfusion injury.

Renal ischemic-reperfusion injury (IRI) occurs frequently in transplanted as well as native kidneys. Effective treatment for this process is still elusive. Leukocytes and their products may be important in the pathogenesis of renal IRI, however their role is still controversial. Recently, adhesion receptors on leukocytes and their corresponding ligands have been identified. In the heart, considerable evidence supports the role of CD11/CD18, ICAM-1, and the selectin receptors in IRI. However, based on experimental studies in animal models, even though renal IRI appears to be ICAM-1 mediated, the role of the CD11/CD18 pathway appears to be minimal. In addition, the available evidence does not support the concept that L-selectin has significant involvement in renal IRI. In this review, the data and controversies regarding the role of leukocytes and leukocyte adhesion molecules in renal IRI are discussed.

Pathophysiologic role of selectins and their ligands in ischemia reperfusion injury.

Research findings are unveiling the potential role of leukocytes and leukocyte adhesion molecules such as selectins in ischemia-reperfusion injury (IRI). "Anti-adhesion" therapy using selectin blocking agents may represent a new approach to treatment of the many diverse clinical disorders in which ischemia-reperfusion occurs, including transplantation, reperfusion after thrombotic events and shock. In this paper we review the pathophysiology of IRI, the different types of selectins and selectin ligands, the clinical implications of selectin blockade in different organs with IRI, and new insights into mechanism of action.

Multiple primary malignancies in a renal transplant patient.

Organ transplantation and the use of immunosuppressive therapy has been associated with an increased incidence of malignancy. We report the case of a long-term renal transplant recipient who developed concomitant skin cancers, non-Hodgkin's lymphoma, and malignant fibrous histiocytoma. The development of three seemingly unrelated cancers in the same patient illustrates the favorable host environment in transplant patients for the development of malignancies.

Prominent and sustained up-regulation of gp130-signaling cytokines and the chemokine MIP-2 in murine renal ischemia-reperfusion injury.

Ischemia-reperfusion injury (IRI) is a major cause of renal dysfunction in both native kidneys and renal allografts. To broaden our understanding of the inflammatory mediators involved in IRI, we used multi-probe RNase protection assays to examine the expression of 26 different cytokine genes in a murine model of renal IRI. We observed that, in addition to up-regulation of IL-1beta and to a lesser extent TNF-alpha, IRI was associated with an intense and sustained up-regulation of three gp130-signaling cytokines, IL-6, IL-11, and leukemia inhibitory factor (LIF), as well as with up-regulation of the neutrophil chemotactic and activating mediator macrophage inflammatory protein (MIP)-2. Macrophage colony-stimulating factor (M-CSF) and monocyte chemoattractant protein (MCP)-1 were also moderately up-regulated after IRI, whereas mRNA levels of several other inflammatory mediators including IL-1alpha, IL-2, IL-4, interferon (IFN)-gamma, GM-CSF, and RANTES were minimally increased or remained undetectable. These findings identify MIP-2 as an attractive target for inhibition of leukocyte recruitment in renal IRI and also suggest a potentially novel role for gp130-mediated signals in IRI.

Genetic susceptibility to renal ischemia reperfusion injury revealed in a murine model.

BACKGROUND: The development of genetically engineered mice has led to increased use of mouse models to study renal ischemic reperfusion injury (IRI). We hypothesized that susceptibility to IRI could result from strain differences due to genetic factors. METHODS: Our study compared recovery subsequent to renal IRI in NIH Swiss, C57BL/6, and BALB/c mice. Serum creatinine (SCr) and blood urea nitrogen (BUN) levels were evaluated postischemia. We also conducted reverse transcriptase-polymerase chain reaction (RT-PCR) analyses of renal cytokines and adhesion molecules postischemia. RESULTS: At 48 hr postischemia, renal dysfunction in NIH Swiss mice was significantly reduced, compared with other groups (P<0.01). BUN measurements confirmed renal protection at 48 hr in the NIH Swiss group. RT-PCR analysis of mRNA postischemia demonstrated that, between strains, there was little difference in mRNA expression for renal cytokines and adhesion molecules. CONCLUSIONS: NIH Swiss mice appear to be resistant in susceptibility to renal IRI. Early expression of pro-inflammatory genes was not associated with resistance to IRI, thus genetic factors could be important in outcome after renal IRI.

Merkel cell carcinoma in a renal transplant patient: increased incidence?

The identification of malignancies associated with transplantation has led to enhanced vigilance and care in these patients, as well as insight into the pathogenesis of select malignancies. We report a case of Merkel cell carcinoma, an uncommon cutaneous malignancy of neuroendocrine origin, diagnosed in a 65-year-old Caucasian man 6 years after renal transplantation. While it is well known that transplant patients are at increased risk for squamous cell carcinomas of the skin, other types may also have an increased frequency. We suggest that Merkel cell carcinoma could have an increased incidence in the transplant population.

Alopecia in three women of Southeast Asian descent with chronic renal failure: possible association with erythropoietin use.

Recombinant human erythropoietin (Epo) has been used successfully to correct the anemia caused by chronic renal failure in patients undergoing dialysis, as well as the anemia associated with other conditions, including cancer therapy. Despite its benefits, it can be associated with adverse side effects. These include hypertension, headaches, increased seizure activity, clotted vascular access, and occasional thromboembolic events, such as myocardial infarction or stroke. We report a potentially new side effect associated with Epo of a cosmetic nature. Three Southeast Asian women with chronic renal failure developed diffuse, nearly total, hair loss during erythropoietin use. Two cases were strongly associated with Epo use, and a third had other intercurrent illnesses as well. Alopecia may be associated with Epo use in certain ethnic populations.

Possible molecular basis for changes in potassium handling in acute renal failure.

Renal potassium excretion is diminished in acute renal failure (ARF). The gastrointestinal tract can compensate for deficient renal potassium excretion in many patients with ARF. For both impaired renal potassium excretion and gastrointestinal compensation in ARF, little is known about the role of potassium channels. We hypothesized that specific changes in the expression of the secretory renal outer medullary potassium channel (ROMK), and the potassium channel regulator, channel-inducing factor (CHIF), in kidney and colon could contribute to changes in potassium handling. Sprague-Dawley rats underwent uninephrectomy and 35 minutes of renal ischemia, followed by varying periods of reperfusion. Renal function, serum and urine potassium levels, and aldosterone levels were measured. The expression of messenger RNA (mRNA) for ROMK and CHIF in the kidney and CHIF in the colon were measured by Northern blot hybridization. Serum creatinine level was increased at 24 hours and started to decline at 48 hours of renal ischemia reperfusion injury (IRI). Serum potassium level was increased at 24 hours, further elevated at 48 hours of IRI, and returned to normal at 7 days of IRI. Urine potassium level was reduced at 24 and 48 hours. Northern blot analysis indicated that the expression of ROMK1 mRNA in the cortex or medulla remained unchanged at 24 hours but profoundly decreased (by 70% to 80%) at 48 hours (n = 4; P < 0.01). The expression of CHIF mRNA in the kidney cortex or medulla decreased by 25% to 30% at 24 hours and 35% to 40% at 48 hours of IRI (n = 4; P < 0.05 for each group). CHIF mRNA expression in the distal colon was moderately increased at 24 hours (approximately twofold) and significantly enhanced at 48 hours (more than threefold; P < 0.01; n = 4) of IRI. Serum aldosterone level was increased approximately threefold at 48 hours of IRI (P < 0.01; n = 6). In conclusion, (1) suppression of ROMK and CHIF in the kidney may contribute to decreased renal potassium excretion in ARF; (2) enhanced expression of CHIF in the distal colon in IRI could be an adaptive response to increase potassium excretion in the colon and help modify hyperkalemia in ARF; and (3) increased aldosterone levels, as a response to hyperkalemia, could be upregulating colonic CHIF.

Acute renal failure from multiple myeloma precipitated by ACE inhibitors.

Renal failure in multiple myeloma can be precipitated during hemodynamic perturbances of renal blood flow, as seen secondary to volume depletion, radiocontrast dye, and nonsteroidal anti-inflammatory agents. We report two cases of acute renal failure that developed suddenly after initiation of angiotensin-converting enzyme (ACE) inhibitor, both with biopsy-proven cast nephropathy. ACE inhibitors may contribute to the intratubular light chain cast formation and acute "myeloma kidney" in susceptible patients.

Comparing methods for monitoring serum creatinine to predict late renal allograft failure.

Few studies have systematically investigated what changes in chronic renal allograft function best predict subsequent graft failure, when these changes occur, and whether they occur soon enough to allow possible intervention. We collected serum creatinine values (mean, 183 +/- 75 values/patient) measured over a maximum follow-up of 22 years in 101 consecutive renal transplant recipients (excluding creatinine levels from periods of acute rejection). We determined the dates of first decline in inverse creatinine (Delta1/Cr; < -20%, -30%, -40%, -50%, and -70%), declines in estimated creatinine clearance (CCr; <55, 45, 35, 25, and 15 mL/min), and declines in measured slope of 1/Cr over time. We used time-dependent covariates in Cox proportional hazards analyses to determine the relative effect of each renal function parameter on outcomes while adjusting for other risk factors. The best predictor of subsequent graft failure was Delta1/Cr. Delta1/Cr less than -40% first occurred at a median of 1.28 years after transplantation in 73 patients, and 67 patients went on to have graft failure a median of 3.28 years after Delta1/Cr less than -40%. The independent relative risk for graft failure attributable to Delta1/Cr less than -40% was 5.91 (95% confidence interval, 3.25 to 10.8; P < 0.0001). A decline in CCr, eg, less than 45 mL/min, also was a strong predictor of subsequent graft failure. Conversely, declines in allograft function estimated from slopes of 1/Cr were poor predictors of graft failure. In analysis limited to patients followed up for 2.5 years or less, Delta1/Cr continued to predict graft failure, suggesting that Delta1/Cr will be a useful predictor in populations with shorter follow-up. If confirmed in other populations, eg, patients treated with calcineurin inhibitors, this simple marker of chronic allograft dysfunction may prove to be a practical tool for defining patients at high risk for late graft failure.