Chronic Calcineurin Inhibitor Research Articles

Does Uromodulin Play a Role in Tacrolimus-Mediated Upregulation of the Sodium Chloride Cotransporter?

Background: Tacrolimus, a calcineurin inhibitor (CNI), is a medication commonly prescribed to prevent organ transplant rejection. However, chronic CNI use has several adverse effects, including hypertension. Recent studies have revealed that the renal sodium chloride cotransporter (NCC) mediates tacrolimus-induced hypertension. However, the mechanisms underlying NCC upregulation are not fully understood. Previous studies indicate that uromodulin plays a key role in renal ion channel regulation. As such, we hypothesize that uromodulin mediates tacrolimus induced NCC upregulation. Experimental Design: To test this hypothesis, male C57BL/6 mice received tacrolimus (10 mg/kg/day) or vehicle (ethanol/DMSO/saline) for 21 consecutive days via intraperitoneal injection. The impact of tacrolimus on systolic blood pressure (BP) was monitored by tail-cuff plethysmography. To examine uromodulin and NCC expression, kidneys were harvested and processed for immunohistochemistry. Results: Compared to the BP of vehicle-treated mice (120 mm Hg ± 4.252), mice administered tacrolimus had significant increases in BP (170 mm Hg ± 3.528). Furthermore, tacrolimus treatment increased phosphorylated NCC (pNCC) and uromodulin expression. Conclusions: These results indicate that tacrolimus-induced hypertension is accompanied by pNCC and uromodulin upregulation in distal convoluted tubules. Significance: Overall, these findings highlight uromodulin as a possible regulator of NCC. Funding: R21 DK119879, R01 DK-133698, R25DK07838. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Skin cancer in solid organ transplant recipients: still an open problem.

In the last two decades, the optimization of organ preservation and surgical techniques, and the personalized immunosuppression have reduced the rate of acute rejections and early post-transplant complications. However, long-term graft survival rates have not improved over time, and evidence suggest a role of chronic calcineurin inhibitor toxicity in this failure. Solid organ transplant recipients may develop chronic dysfunction/damage and several comorbidities, including post-transplant malignancies. Skin cancers, mostly non-melanoma skin cancers (squamous cell carcinoma and basal cell carcinoma), are the most common malignancies in Caucasian solid organ transplant recipients. Several factors, together with immunosuppression, may contribute to the susceptibility for skin cancers which, although often treatable, could be associated with a much higher mortality rate than in the general population. The rapid identification and treatment (including reduction of immunosuppression and early surgical treatments) have an important role to avoid an aggressive behavior of these malignancies. Organ transplant recipients with a history of skin cancer should be followed closely for developing new and metastatic lesions. Additionally, patient education on the daily use of sun-protective measures and the recognition of the early signs (self-diagnosis) of coetaneous malignancies are useful preventive measures. Finally, clinicians should make themselves aware of the problem and build, in every clinical follow-up center, collaborative network involving transplant clinicians, dermatologists and surgeons who should work together to easily identify and rapidly treat these complications. In this review, we discuss the current literature regarding the epidemiology, risk factors, diagnosis, preventive strategies and treatments of skin cancer in organ transplantation.

Multi‐omics analysis reveals regulatory mechanisms in chronic cyclosporine A‐induced nephrotoxicity studied a rat model

Chronic calcineurin inhibitor (CNI) nephrotoxicity is a major drawback in current immunosuppressive regimens. In the chronic setting, arteriolar hyalinosis, decreased glomerular filtration rate, interstitial fibrosis and tubular dedifferentiation are the major adverse side effects. Since CsA is still widely used in transplant recipients, particularly in posttransplant diabetes, mechanistic insights into nephrotoxic mechanisms are required. To identify regulatory mechanisms in CsA nephrotoxicity we used quantitative transcriptomic, proteomic and phosphoproteomic methods. We tested the hypothesis that tubulointerstitial pathomechanisms play a predominant role in chronic CNI nephropathy. Whole transciptome RNA‐seq as well as global proteomic and phosphoproteomic methodologies were performed on kidney extracts from normal Wistar rats receiving CsA (25mg/kg b.w./day) or vehicle for 3 weeks. Differentially expressed genes and proteins as well as their phosphorylation status were obtained. Products of interest were tested using Western blot, qPCR, and immunohistochemistry. CsA treatment stimulated genome‐wide alterations in rat kidney according to RNA‐seq data. We identified 342 transcripts upregulated (padj<0.05) which included Ribosome (padj<0,0001) and Oxidative phosphorylation (padj<0,0001) pathways, whereas 331 transcripts were downregulated, with enrichment in genes critical for amino acid metabolism. Data were controlled by the established upregulation of renin and downregulation of calbindin (pdaj<0,05) in global proteomics. KEGG pathway and GO analysis from proteomics largely corresponded to the RNA‐seq results. Upregulated proteins were further related to ECM‐receptor interaction and focal adhesion pathways (padj<0,05). Phosphoproteomics demonstrated functional phosphorylation of components from unfolded protein response pathways, indicating an activation of the integrated stress response upon CsA. Products were verified at the tissue‐ and cell level. In sum, using integrated ‐omics analysis in CsA nephrotoxicity proved to be a powerful approach. Chronic CsA treatment was associated with enhanced energy metabolism and activation of the unfolded protein‐response pathways. A tubulointerstitial focus has been demonstrated. Potential biomarker candidates have been obtained.

Tacrolimus induces ligand independent TGFβ receptor signaling to promote renal fibrosis

BackgroundAlthough calcineurin inhibitors (CNIs) such as tacrolimus and cyclosporin have dramatically improved the quality of patient care, long‐term therapy causes irreversible damage to the kidneys in the form of renal fibrosis. These morphologic changes ultimately lead to a decline in renal function and can progress to end‐stage renal failure. These detrimental outcomes present a critical need to identify the driving mechanisms by which CNIs cause renal damage.ObjectiveIt is well established that TGFb is a major contributor to CNI‐induced renal fibrosis. However, the underlying mechanisms remain unknown. The objectives of this study are to 1) investigate whether TGFb secretion is required to stimulate TGFb receptor signaling in a model of CNI‐induced renal fibrosis and 2) investigate whether calcineurin plays a critical role in regulating TGFb receptor activity.Experimental DesignTo examine the role of calcineurin inhibition in altered TGFb receptor signaling, wild type mice were treated with either vehicle (0.01% ethanol) or 10 mg/kg tacrolimus for 7 days. To confirm in vivo findings, wild‐type mouse renal cortical fibroblasts were treated with either vehicle (0.01% ethanol) or 1nM tacrolimus for 24 hours in the presence and absence of anti‐TGFb neutralizing antibodies. TGFb receptor expression and activation, TGFb receptor downstream signaling mediators, profibrotic markers and calcineurin activity were analyzed.ResultsFindings demonstrate that tacrolimus‐induced loss of calcineurin activity is accompanied with enhanced TGFb receptor activation and signaling. Notably, increasing concentrations of anti‐TGFb neutralizing antibodies failed to abolish aberrant TGFb signaling and increased expression of profibrotic markers.ConclusionsTogether, these results demonstrate that 1) CNIs promote ligand‐independent TGFb signaling and 2) calcineurin plays a functional role in regulating TGFb receptor activity.SignificanceThis study elucidates a direct pharmacological mechanism by which CNIs promote renal fibrosis and provides a physiological role of calcineurin in regulating TGFb receptor activity. Further insight into the role of calcineurin in regulating TGFb receptor activity could improve the long‐term outcomes of patients on chronic CNI therapy.

Calcineurin inhibitors and renal biopsy in children with idiopathic nephrotic syndrome.

Idiopathic nephrotic syndrome (NS) is common in children, and most patients respond to corticosteroid therapy. Patients who relapse may need additional immunosuppression with cyclophosphamide, mycophenolate mofetil, calcineurin inhibitors (CNI), or rituximab. Many such patients undergo protocol renal biopsies before and after the initiation of CNI therapy. The main objective of our study was to assess the role of protocol renal biopsies in the monitoring of CNI-induced nephrotoxicity in patients with steroid-dependent (SD)/frequent relapse (FR) NS. We did an Institutional Review Board (IRB)-approved retrospective chart review of patients who were diagnosed with NS at the Children's Hospital of Michigan from January 2000 to June 2019. Study inclusion criteria were a diagnosis of NS, age 1 - 21 years at initial diagnosis, SD/FR clinical course, patients with initial steroid resistance with renal biopsy showing minimal change disease, and renal biopsy before and after CNI initiation. The data is presented on 24 patients who met study inclusion criteria. Only 3 patients (12.5%) showed evidence of chronic CNI nephrotoxicity after a median treatment 66.5 months (range 12 - 153 months). Our study revealed that a baseline renal biopsy before starting CNI therapy for children with FR/SDNS is not necessary. A renal biopsy may be considered after 2 - 3 years of CNI administration in selected few cases in whom the diagnosis of CNI nephrotoxicity might help change the management.

Chimerism and tolerance: past, present and future strategies to prolong renal allograft survival.

Immunological factors are a major cause of kidney allograft loss. Calcineurin inhibitors (CNIs) have improved short-term kidney allograft survival; however, they in turn contribute to long-term kidney allograft loss from chronic CNI nephrotoxicity. Tolerance induction in transplantation can avoid the long-term adverse effects of immunosuppressive medications. This review aims to critically discuss recent efforts in inducing transplantation tolerance. Tolerance induction mediated by chimerism has shown some promise in minimizing or even complete withdrawal of immunosuppressive treatments in kidney allograft recipients. There has been a number of approaches as varied as the number of centres conducting these trials. However, they can be grouped into those mediated by transient microchimerism and those facilitated by more stable macro or full donor chimerism. The success rates in terms of long-term drug-free graft survival has been limited in microchimerism-mediated tolerance induction approaches. Mixed macrochimerism of less than 50% donor may be unstable with mostly the recipient's native immune system overpowering the donor chimeric status.Tolerance induction leading to chimerism has been limited to living donor kidney transplantation and additional long-term outcomes are required. Furthermore, immune monitoring after tolerance induction has faced a limitation in studying due to a lack of sufficient study participants and appropriate study controls. Tolerance induction is one of several strategies used to prolong kidney allograft survival, but it has not been routinely utilized in clinical practice. However, future applications from the trials to clinical practice remain limited to living donor kidney transplantation. Once further data regarding tolerance inductions exist and practicality becomes widely accepted, tolerance induction may shift the paradigm in the field of kidney transplantation to achieve the best possible outcome of 'One Organ for Life'.

Tacrolimus intrapatient variability in BK virus nephropathy and chronic calcineurin toxicity in kidney transplantation.

Intrapatient variability (IPV) in tacrolimus has been increasingly acknowledged as a risk factor for poor graft survival after kidney transplantation. Although past studies have mainly accounted for IPV in acute or chronic rejection states as due to underimmunosuppression, this is not yet clear. So far, tacrolimus IPV for BK virus-associated nephropathy (BKVN) and chronic calcineurin inhibitor toxicity (CNIT) has not been investigated. Here, we evaluated IPV in tacrolimus for BKVN and chronic CNIT, which are mainly considered as overimmunosuppression states. In this case-control study, kidney allograft biopsies conducted between 1998 and 2018 were included, with patients grouped by biopsy results as BKVN alone group, CNIT alone group, and normal graft function (control group). IPV was estimated as mean absolute deviation. Our study groups included 25 kidney transplant recipients with BKVN alone, 91 patients with CNIT alone, and 60 patients with normal 5-year graft survival (control group). In analyses of IPV in tacrolimus six months before graft biopsy, IPV was highest in the BKVN group (P = 0.001). The BKVN group also had the highest IPV in tacrolimus at 12 months after biopsy (P = 0.001), with all pairwise comparisons statistically different between groups. At 12 months after biopsy, five patients (20%) in the BKVN group and 10 patients (10.9%) in the CNIT group had graft loss. Among other risk factors, BKVN and chronic CNIT are consequences related to high IPV. Quantification of IVP for tacrolimus in clinical practice would help to optimize kidney transplant outcomes.

Diltiazem Böbrek Alıcılarında Greft Fonksiyonlarını İyileştirir mi?

Background: Acute and chronic calcineurin inhibitors (CNI) nephrotoxicity is a common concern in kidney transplant (KT) recipients. It is unclear whether diltiazem use can reduce CNI induced acute and chronic nephrotoxicity in (KT) recipients. In this study, we investigated the impact of diltiazem on 1 –year allograft survival and function.Materials and Methods: This single-center retrospective study included 312 kidney transplant recipients and donors. Diltiazem receiving and diltiazem-free recipients were compared for 1-year allograft survival and functions. Available allograft biopsies were investigated for the evidence pieces of CNI induced nephrotoxicity. Factors may have a potential impact on allograft functions were evaluated (cytomegalovirus and polyoma BK viremia positivity, acute rejection episodes, donors and recipients ages and body mass indexes). A statistical package program was used for data analysis. P<0.05 was assigned significant.Results: Seventy-three recipients in diltiazem arm and 239 in diltiazem-free arm were compared. In diltiazem and diltiazem-free arms, 1- year mortality, allograft survival rates and CNI induced nephrotoxicity incidences were 4.1% vs 3.8% (P=0.89), and 13.7% vs 7.1% (P=0.08), 18.8% vs 10.5% (P=0.27), respectively. However, 12-month estimated glomerular filtration rate was worse in diltiazem arm (62.75 ml/dk/1.73m2) compared to diltiazem-free group (73.19 ml/dk/1.73m2) (P=0.03). CNI toxicity had a weak impact on low eGFR in regression analysis (P=0.055 and 95% confidence interval).Conclusions: Despite diltiazem use allows to CNI dose reduction, it might have undesirable impacts on long-term allograft functions, which is the main target of the allograft care. Key Words: Allograft function, Diltiazem, Kidney transplantation

Proteomic Characterization of Urinary Extracellular Vesicles from Kidney-Transplanted Patients Treated with Calcineurin Inhibitors.

Use of immunosuppressive drugs is still unavoidable in kidney-transplanted patients. Since their discovery, calcineurin inhibitors (CNI) have been considered the first-line immunosuppressive agents, in spite of their known nephrotoxicity. Chronic CNI toxicity (CNIT) may lead to kidney fibrosis, a threatening scenario for graft survival. However, there is still controversy regarding CNIT diagnosis, monitoring and therapeutic management, and their specific effects at the molecular level are not fully known. Aiming to better characterize CNIT patients, in the present study, we collected urine from kidney-transplanted patients treated with CNI who (i) had a normal kidney function, (ii) suffered CNIT, or (iii) presented interstitial fibrosis and tubular atrophy (IFTA). Urinary extracellular vesicles (uEV) were enriched and the proteome was analyzed to get insight into changes happening during CNI. Members of the uroplakin and plakin families were significantly upregulated in the CNIT group, suggesting an important role in CNIT processes. Although biomarkers cannot be asserted from this single pilot study, our results evidence the potential of uEV as a source of non-invasive protein biomarkers for a better detection and monitoring of this renal alteration in kidney-transplanted patients.

Role of Klotho in Chronic Calcineurin Inhibitor Nephropathy.

Calcineurin inhibitors (CNIs) are the most popular immunosuppressants in organ transplantation, but nephrotoxicity is a major concern. The common mechanism underlying chronic CNI nephropathy is oxidative stress, and the process of chronic CNI nephropathy is similar to that of aging. Current studies provide evidence that antiaging Klotho protein plays an important role in protecting against oxidative stress, and its signaling is a target for preventing oxidative stress-induced aging process. In this review, we focus on the association between Klotho and oxidative stress and the protective mechanism of action of Klotho against oxidative stress in chronic CNI nephropathy. In addition, we discuss the delivery strategy for Klotho in CNI-induced nephropathy.

Infrequent tacrolimus-induced nephrotoxicity in French patients with steroid-dependent nephrotic syndrome.

Chronic nephrotoxicity with potentially irreversible lesions is a major concern regarding calcineurin inhibitor (CNI) treatment in children with severe forms of idiopathic nephrotic syndrome (INS). We retrospectively included all children on CNI for steroid-dependent INS with a duration of CNI treatment of more than 1year. Only patients in whom CNI could not be replaced by mycophenolate mofetil were included. All included patients underwent a kidney biopsy. All results were expressed as median and range. Twenty-one children (6 girls) were included. Age at disease onset was 49 (29-66) months and treatment duration on CNI was 30 (20-45) months. Age at kidney biopsy was 108 (78-170) months. Number of relapses was 7 (3-9) since disease onset. Serum creatinine level was transiently and moderately increased in two patients. Kidney biopsy revealed minimal change disease in 20/21 patients and focal segmental glomerulosclerosis in 1/21. Evidence for chronic CNI nephrotoxicity was found in one patient revealed by arteriolar hyalinosis and fibrosis in 50% of glomeruli. CNI-induced chronic nephrotoxicity was infrequent. In patients who require long-term and/or high-dose CNI treatment, kidney biopsies might be useful to exclude chronic CNI-induced lesions.

Introduction of everolimus in kidney transplant recipients at a late posttransplant stage.

This minireview focuses on the current knowledge about the introduction of everolimus (EVL), a mammalian target of rapamycin inhibitor, with calcineurin inhibitor (CNI) elimination or minimization in kidney transplant recipients at a late posttransplant stage. Within, we have summarized two major clinical trials, ASCERTAIN and APOLLO, and seven other retrospective or nonrandomized studies. In the open-label multicenter ASCERTAIN study, the estimated glomerular filtration rate (eGFR) at 24 mo after conversion was not significantly different between three groups-EVL with CNI elimination, CNI minimization and continued CNI unchanged-at a mean of 5.4 years after transplantation. However, recipients with baseline creatinine clearance higher than 50 mL/min had a greater increase in measured GFR after CNI elimination. In the open-label multicenter APOLLO study, adjusted eGFR within the on-treatment population was significantly higher in the EVL continuation group than in the CNI continuation group at 12 mo after conversion at a mean of 7 years posttransplantation. Other studies on recipients without adverse events and already having satisfactory renal function showed favorable graft function by EVL late-induction with CNI elimination or reduction. These studies showed that chronic allograft nephropathy, CNI nephrotoxicity, CNI arteriolopathy, cancer and viral infection (especially cytomegalovirus infection) may be good indications for late conversion to EVL.

Glomerular Abnormalities Associated with Chronic Calcineurin Inhibitor Nephrotoxicity in Late Renal Allograft Biopsies

Glomerular Abnormalities Associated with Chronic Calcineurin Inhibitor Nephrotoxicity in Late Renal Allograft Biopsies

Calcineurin inhibitors and nephrotoxicity in children.

Calcineurin inhibitors (CNIs) are commonly given to transplant recipients of kidneys and other solid organs and to patients with immune disorders, such as steroid-resistant nephrotic syndrome, steroid-dependent nephrotic syndrome, and frequent relapse nephrotic syndrome. Although CNIs remain the most effective available immunosuppressant agent, there is clinical concern regarding possible long-term nephrotoxicity. This concern is especially significant in children who have a longer life expectancy and greater growth rate. In this review, we analyzed the literatures to identify original articles that examined use of CNIs in children who received organ transplantation and nephropathy to assess the available evidence of their nephrotoxicity. PubMed, Elsevier, and Tompson ISI Web of Knowledge were searched for identifying relevant papers. Clinical research supports the presence of CNI-related nephrotoxicity. However, some researchers have questioned the prevalence and seriousness of chronic CNIs nephrotoxicity, especially because the pathological lesions typically associated with long-term CNI use are nonspecific. Many researchers have focused on early markers of CNI nephrotoxicity, and the methods that may help prevent and manage nephrotoxicity. Future research should focus on investigating early markers of CNI nephrotoxicity and strategies for improved immunosuppressant therapy, and developing alternative treatments. CNI-mediated nephrotoxicity should always be taken seriously in clinic.

Spectrum of renal allograft biopsy: A five-year experience at a tertiary care center of Eastern India

Renal allograft dysfunction (RAD) can have myriad causes and presentations. Allograft biopsy remains the gold standard for optimum management. This is a retrospective study carried out at a tertiary care institute from August 2011 to March 2016. Details of the renal allograft biopsy requisitions were recorded and analyzed. Two hundred and two patients had undergone kidney transplantation (KT) during the study period. One hundred and twenty-six had undergone renal biopsy for RAD. The acute asymptomatic rise of serum creatinine was the most common clinical presentation (47.61%) followed by chronic RAD (CRAD) (19.84%), proteinuria (15.87%), immediate graft dysfunction (10.31%), and persistent active urinary sediments (6.34%) in that order. The incidence of delayed graft function was 1.98%. The overall incidence of biopsy-proven rejection was 8.41% within oneyear and 8.91% beyond oneyear of transplant. Acute cellular rejection (ACR) [with or without antibody-mediated rejection (AMR)] was found in 65%; AMR was found in 40% and 15% had both ACR and AMR. Borderline acute cell-mediated rejection was found in 22.5% of biopsies. CRAD was due to chronic rejection and chronic calcineurin inhibitor toxicity in only about one-fourth of the cases. Incidence of glomerulo-nephritis was 10.89% and most of these occurred two years after KT. Renal allograft biopsy was associated with minor complications in 3.17% of cases. Clinical presentations do not reliably distinguish the various causes of RAD. Allograft biopsy is a mainstay in the diagnosis of RAD and is safe. Results of live donor first transplantation using complement-dependent cytotoxi-city crossmatch are comparable to those programs using newer methods like solid-phase assays. However, the direct comparison of these results with other studies may not be completely applicable.

Calcineurin inhibitor-induced complement system activation via ERK1/2 signalling is inhibited by SOCS-3 in human renal tubule cells.

One factor that significantly contributes to renal allograft loss is chronic calcineurin inhibitor (CNI) nephrotoxicity (CIN). Among other factors, the complement (C-) system has been proposed to be involved CIN development. Hence, we investigated the impact of CNIs on intracellular signalling and the effects on the C-system in human renal tubule cells. In a qPCR array, CNI treatment upregulated C-factors and downregulated SOCS-3 and the complement inhibitors CD46 and CD55. Additionally, ERK1/-2 was required for these regulations. Following knock-down and overexpression of SOCS-3, we found that SOCS-3 inhibits ERK1/-2 signalling. Finally, we assessed terminal complement complex formation, cell viability and apoptosis. Terminal complement complex formation was induced by CNIs. Cell viability was significantly decreased, whereas apoptosis was increased. Both effects were reversed under complement component-depleted conditions. In vivo, increased ERK1/-2 phosphorylation and SOCS-3 downregulation were observed at the time of transplantation in renal allograft patients who developed a progressive decline of renal function in the follow-up compared to stable patients. The progressive cohort also had lower total C3 levels, suggesting higher complement activity at baseline. In conclusion, our data suggest that SOCS-3 inhibits CNI-induced ERK1/-2 signalling, thereby blunting the negative control of C-system activation.

Immunosuppression Minimization and Avoidance Protocols: When Less Is Not More.

Kidney transplantation is well established as the best treatment option for end-stage kidney disease. It confers not only a better quality of life but also a significant survival advantage compared to dialysis. However, despite significant improvement in short-term kidney transplant graft survival over the past three decades, long-term graft survival remains suboptimal. Concerns about the possible contribution of chronic calcineurin inhibitor (CNI) nephrotoxicity to late allograft failure and other serious adverse effects of currently used immunosuppressive agents (especially corticosteroids) have led to increasing interest in developing regimens which may better preserve kidney allograft function and minimize other immunosuppression-related problems without increasing the risk of rejection. The availability of newer immunosuppressive agents has provided the opportunity to formulate such regimens. Approaches to this end include minimization, withdrawal, or avoidance of corticosteroids and CNIs. Currently, replacement of a CNI with a mammalian target of rapamycin inhibitor while continuing mycophenolate and discontinuation of corticosteroids within the first post-transplant week is being increasingly utilized. Belatacept-based, CNI-free immunosuppression is an emerging alternative approach to avoiding CNI-mediated nephrotoxicity. We also discuss the evolution, results, and pros and cons of corticosteroid- and CNI minimization protocols. Recent studies suggest that chronic alloimmune damage rather than chronic CNI nephrotoxicity is the major contributor to late kidney allograft failure. The implications of this finding for the use of CNI minimization protocols are also discussed.

Altitude and arteriolar hyalinosis after kidney transplantation.

The kidney is very susceptible to hypoxic injury. Calcineurin inhibitors (CNIs) induce vasoconstriction and might reduce renal tissue oxygenation. We aimed to investigate if the synergistic deleterious effects of CNI-treatment and hypoxia of high altitude living might accelerate the development of arteriolar hyalinosis in kidney allografts. We stratified all patients who received a kidney graft from 2000 to 2010 in our centre (n = 477) in three groups according to the residential elevation (below 400, between 400 to 600 and above 600 m above sea level) and we retrospectively re-evaluated all transplant biopsies performed during follow-up, specifically looking at the degree of arteriolar hyalinosis, the hallmark of chronic CNI nephrotoxicity. Living at high altitude was markedly associated with a higher degree of arteriolar hyalinosis (P < 0.001). Haemoglobin levels confirmed the functional relevance of different arterial oxygenation among the groups (P = 0.01). Thus, patients living at high altitude seem to be more susceptible to the development of arteriolar hyalinosis after kidney transplantation.

Granular swollen epithelial cells in the kidney allograft: A clinicopathological study with special emphasis on possible marker for kidney allograft aging.

To elucidate the clinicopathological significance of granular swollen epithelial cells (GSECs), which provides histological evidence in the diagnosis of mitochondrial nephropathy, but incidentally observed in renal allografts, we evaluated GSECs as a surrogate histological marker for kidney allograft aging, as previously reported for p16, p21, and β-galactosidase. We retrospectively reviewed 426 kidney allograft biopsy specimens diagnosed at our university from January 2009 to April 2015. The prevalence and density of GSECs were compared with an age-matched control group of 508 native kidney biopsies. GSECs were defined as swollen (>2 times larger than normal renal tubular cells) epithelial cells best observed using Masson trichrome staining. Morphometric analyses were performed using digital microscopy software. The prevalence of GSECs was 7.7% in allograft kidneys and 8.1% in native kidneys. GSECs in kidney allografts were predominantly detected in medullary renal tubules, but not in the Bowman's capsular epithelium or podocytes. GSECs were observed in the following cases; no remarkable changes, n = 11; interstitial fibrosis and tubular atrophy, n = 7; chronic calcineurin inhibitor toxicity, n = 5; antibody-mediated rejection, n = 3; T cell-mediated rejection grade IA, n = 1; and others, n = 6. Compared with control specimens, medullary density of GSECs in kidney allografts was significantly increased. The prevalence of GSECs slightly increased with post-transplant duration; however, this trend was not statistically significant. The present study does not provide pathological significance of GSEC in kidney allografts in terms of allograft aging, and warrant the further research with molecular approach.

Nox2 and Cyclosporine-Induced Renal Hypoxia.

We hypothesized that nicotinamide adenosine diphosphate oxidase 2 (Nox2) plays an important role in cyclosporine A (CsA)-induced chronic hypoxia. We tested this hypothesis in Fisher 344 rats, C57BL/6 J wild type and Nox2-/- mice, and in liver transplant recipients with chronic CsA nephrotoxicity. We used noninvasive molecular imaging (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging) and molecular diagnostic tools to assess intrarenal oxygenation and perfusion, and the molecular phenotype of CsA nephrotoxicity. We observed that chemical and genetic inhibition of Nox2 in rats and mice resulted in the prevention of CsA-induced hypoxia independent of regional perfusion (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging, pimonidazole, HIF-1α). Nicotinamide adenosine diphosphate oxidase 2 knockout was also associated with decreased oxidative stress (Nox2, HIF-1α, hydrogen peroxide, hydroxynonenal), and fibrogenesis (α-smooth muscle actin, picrosirius red, trichrome, vimentin). The molecular signature of chronic CsA nephrotoxicity using transcriptomic analyses demonstrated significant changes in 40 genes involved in injury repair, metabolism, and oxidative stress in Nox2-/- mice. Immunohistochemical analyses of kidney biopsies from liver transplant recipients with chronic CsA nephrotoxicity showed significantly greater Nox2, α-smooth muscle actin and picrosirius levels compared with controls. These studies suggest that Nox2 is a modulator of CsA-induced hypoxia upstream of HIF-1α and define the molecular characteristics that could be used for the diagnosis and monitoring of chronic calcineurin inhibitor nephrotoxicity.