Marian C. Clahsen-van Groningen

Optimum AT1 receptor-neprilysin inhibition has superior cardioprotective effects compared with AT1 receptor blockade alone in hypertensive rats

Neprilysin inhibitors prevent the breakdown of bradykinin and natriuretic peptides, promoting vasodilation and natriuresis. However, they also increase angiotensin II and endothelin-1. Here we studied the effects of a low and a high dose of the neprilysin inhibitor thiorphan on top of AT1 receptor blockade with irbesartan versus vehicle in TGR(mREN2)27 rats with high renin hypertension. Mean arterial blood pressure was unaffected by vehicle or thiorphan alone. Irbesartan lowered blood pressure, but after 7 days pressure started to increase again. Low- but not high-dose thiorphan prevented this rise. Only during exposure to low-dose thiorphan plus irbesartan did heart weight/body weight ratio, cardiac atrial natriuretic peptide expression, and myocyte size decrease significantly. Circulating endothelin-1 was not affected by low-dose thiorphan with or without irbesartan, but increased after treatment with high-dose thiorphan plus irbesartan. This endothelin-1 rise was accompanied by an increase in renal sodium-hydrogen exchanger 3 protein abundance, and an upregulation of constrictor vascular endothelin type B receptors. Consequently, the endothelin type B receptor antagonist BQ788 no longer enhanced endothelin-1-induced vasoconstriction (indicative of endothelin type B receptor-mediated vasodilation), but prevented it. Thus, optimal neprilysin inhibitor dosing reveals additional cardioprotective effects on top of AT1 receptor blockade in renin-dependent hypertension.

Greater Sensitivity of Blood Pressure Than Renal Toxicity to Tyrosine Kinase Receptor Inhibition with Sunitinib

Hypertension and renal injury are off-target effects of sunitinib, a tyrosine kinase receptor inhibitor used for the treatment of various tumor types. Importantly, these untoward effects are accompanied by activation of the endothelin system. Here, we set up a study to explore the dose dependency of these side effects. Normotensive Wistar Kyoto rats were exposed to 3 different doses of sunitinib or vehicle. After 8 days, rats were euthanized. Telemetrically measured blood pressure rose dose dependently, from 13 to 30 mm Hg. Proteinuria was present at all doses, but a rise in cystatin C occurred only at the intermediate and high doses. Compared with vehicle circulating endothelin-1 increased dose dependently, whereas 24-hour urinary endothelin excretion decreased. Light and electron microscopy revealed glomerular endotheliosis and ischemia with the intermediate and high doses of sunitinib but completely absent histological abnormalities with the low dose. Podocyte number per glomerular circumference did not change. Glomerular nephrin, Neph1, podocin, and endothelin-converting enzyme gene expression were downregulated in a dose-dependent manner. We conclude that the sunitinib-induced rise in blood pressure requires lower doses than its induction of renal function impairment and that functional changes in glomerular filtration barrier contribute to the occurrence of proteinuria, given the lack of histopathologic changes with the low dose of sunitinib.

A Randomized Controlled Clinical Trial Comparing Belatacept With Tacrolimus After De Novo Kidney Transplantation

Background Belatacept, an inhibitor of the CD28-CD80/86 costimulatory pathway, allows for calcineurin-inhibitor free immunosuppressive therapy in kidney transplantation but is associated with a higher acute rejection risk than ciclosporin. Thus far, no biomarker for belatacept-resistant rejection has been validated. In this randomized-controlled trial, acute rejection rate was compared between belatacept- and tacrolimus-treated patients and immunological biomarkers for acute rejection were investigated. Methods Forty kidney transplant recipients were 1:1 randomized to belatacept or tacrolimus combined with basiliximab, mycophenolate mofetil, and prednisolone. The 1-year incidence of biopsy-proven acute rejection was monitored. Potential biomarkers, namely, CD8+CD28−, CD4+CD57+PD1−, and CD8+CD28++ end-stage terminally differentiated memory T cells were measured pretransplantation and posttransplantation and correlated to rejection. Pharmacodynamic monitoring of belatacept was performed by measuring free CD86 on monocytes. Results The rejection incidence was higher in belatacept-treated than tacrolimus-treated patients: 55% versus 10% (P = 0.006). All 3 graft losses, due to rejection, occurred in the belatacept group. Although 4 of 5 belatacept-treated patients with greater than 35 cells CD8+CD28++ end-stage terminally differentiated memory T cells/&mgr;L rejected, median pretransplant values of the biomarkers did not differ between belatacept-treated rejectors and nonrejectors. In univariable Cox regressions, the studied cell subsets were not associated with rejection-risk. CD86 molecules on circulating monocytes in belatacept-treated patients were saturated at all timepoints. Conclusions Belatacept-based immunosuppressive therapy resulted in higher and more severe acute rejection compared with tacrolimus-based therapy. This trial did not identify cellular biomarkers predictive of rejection. In addition, the CD28-CD80/86 costimulatory pathway appeared to be sufficiently blocked by belatacept and did not predict rejection.

An Acute Cellular Rejection With Detrimental Outcome Occurring Under Belatacept-Based Immunosuppressive Therapy: An Immunological Analysis

Background Belatacept has been associated with an increased acute rejection rate after kidney transplantation. This case report sheds light on the possible immunological mechanisms underlying this phenomenon by analyzing the immunological mechanisms in patient serum, peripheral blood mononuclear cells, rejected kidney tissue, and graft infiltrating cells. Methods A 61-year-old woman treated with belatacept, who received her first kidney transplant from her husband was admitted with an acute, vascular rejection 56 days after transplantation which necessitated a transplantectomy. Histology and immunohistochemistry were performed on biopsy and explant tissue. CD86 expression on peripheral monocytes was assessed. Using Ficoll density methods, peripheral blood, and graft infiltrating lymphocytes were isolated and phenotyped. Results The explant showed a vascular rejection (Banff ACR grade III) and a perivascular infiltrate mostly consisting of T cells. No evidence for antibody-mediated rejection was found. In contrast to the peripheral blood monocytes, CD86 was still expressed by part of the mononuclear cells in the explant. Isolated graft cells were mostly CCR7−CD45RO+ effector memory CD4+ and CD8+ T cells (60-70%). CD28-positive as CD28-negative T cells were present in the explant, showing a great IFN-&ggr; production capacity and expressing granzyme B. Conclusions We postulate that this glucocorticoid-resistant cellular rejection occurring under belatacept was predominantly mediated by cytotoxic memory T cells, which are less susceptible to costimulatory blockade by belatacept, or resulted from incomplete CD80/86 blockade at the tissue level.

Effect of high salt diet on blood pressure and renal damage during vascular endothelial growth factor inhibition with sunitinib

BACKGROUND Antiangiogenic treatment with the multitargeted vascular endothelial growth factor (VEGF) receptor inhibitor sunitinib associates with a blood pressure (BP) rise and glomerular renal injury. Recent evidence indicates that VEGF derived from tubular cells is required for maintenance of the peritubular vasculature. In the present study, we focussed on tubular and glomerular pathology induced by sunitinib and explored whether a high salt (HS) diet augments the BP rise and renal abnormalities. METHODS Normotensive Wistar Kyoto (WKY) rats were exposed to a normal salt (NS) or HS diet for 2 weeks and subsequently for 8 days to sunitinib or vehicle administration after which the rats were euthanized and kidneys excised. Mean arterial pressure (MAP) was telemetrically measured. Urine was sampled for proteinuria and endothelinuria, and blood for measurement of endothelin-1, creatinine and cystatin C. RESULTS Compared with the NS diet, MAP rapidly rose by 27 ± 3 mmHg with the HS diet. On sunitinib, MAP rose further by 15 ± 1 with the NS and by 23 ± 4 mmHg with the HS diet (P < 0.05). The HS diet itself had no effect on proteinuria, endothelinuria or the plasma levels of endothelin-1, creatinine and cystatin C. Only with the HS diet, sunitinib administration massively increased proteinuria and endothelinuria and these two parameters were related (r = 0.50, P < 0.01). Likewise, renal glomerular pathology was enhanced during sunitinib with the HS diet, whereas tubulointerstitial injury or reduced peritubular capillary density did not occur. CONCLUSIONS An HS diet induces a marked BP rise in WKY rats and exacerbates both the magnitude of the BP rise and glomerular injury induced by sunitinib.

Primary polyomavirus infection, not reactivation, as the cause of trichodysplasia spinulosa in immunocompromised patients

Classic human polyomaviruses (JC and BK viruses) become pathogenic when reactivating from latency. For the rare skin disease trichodysplasia spinulosa, we show that manifestations of the causative polyomavirus (TSPyV) occur during primary infection of the immunosuppressed host. High TSPyV loads in blood and cerebrospinal fluid, sometimes coinciding with cerebral lesions and neuroendocrine symptoms, marked the acute phase of trichodysplasia spinulosa, whereas initiation and maturation of TSPyV seroresponses occurred in the convalescent phase. TSPyV genomes lacked the rearrangements typical for reactivating polyomaviruses. These findings demonstrate the clinical importance of primary infection with this rapidly expanding group of human viruses and explain the rarity of some novel polyomavirus-associated diseases.

CD4-positive T cells and M2 macrophages dominate the peritoneal infiltrate of patients with encapsulating peritoneal sclerosis

Background Encapsulating peritoneal sclerosis (EPS) is a severe complication of peritoneal dialysis (PD). Previously, it has been shown that infiltrating CD4-positive T cells and M2 macrophages are associated with several fibrotic conditions. Therefore, the characteristics of the peritoneal cell infiltrate in EPS may be of interest to understand EPS pathogenesis. In this study, we aim to elucidate the composition of the peritoneal cell infiltrate in EPS patients and relate the findings to clinical outcome. Study Design, Setting, and Participants We studied peritoneal membrane biopsies of 23 EPS patients and compared them to biopsies of 15 PD patients without EPS. The cellular infiltrate was characterized by immunohistochemistry to detect T cells(CD3-positive), CD4-positive (CD4+) and CD8-positive T cell subsets, B cells(CD20-positive), granulocytes(CD15-positive), macrophages(CD68-positive), M1(CD80-positive), and M2(CD163-positive) macrophages. Tissues were analysed using digital image analysis. Kaplan-Meier survival analysis was performed to investigate the survival in the different staining groups. Results The cellular infiltrate in EPS biopsies was dominated by mononuclear cells. For both CD3 and CD68, the median percentage of area stained was higher in biopsies of EPS as opposed to non-EPS patients (p<0.001). EPS biopsies showed a higher percentage of area stained for CD4 (1.29%(0.61-3.20)) compared to CD8 (0.71%(0.46-1.01), p = 0.04), while in the non-EPS group these cells were almost equally represented (respectively 0.28%(0.05-0.83) versus 0.22%(0.17-0.43), p = 0.97). The percentage of area stained for both CD80 and CD163 was higher in EPS than in non-EPS biopsies (p<0.001), with CD163+ cells being the most abundant phenotype. Virtually no CD20-positive and CD15-positive cells were present in biopsies of a subgroup of EPS patients. No relation was found between the composition of the mononuclear cell infiltrate and clinical outcome. Conclusions A characteristic mononuclear cell infiltrate consisting of CD4+ and CD163+ cells dominates the peritoneum of EPS patients. These findings suggest a role for both CD4+ T cells and M2 macrophages in the pathogenesis of EPS.

Encapsulating peritoneal sclerosis is associated with T-cell activation

BACKGROUND Encapsulating peritoneal sclerosis (EPS) is an excessive fibrotic response of the peritoneum that may occur after long-term peritoneal dialysis (PD). The underlying pathophysiology is poorly understood, but involvement of peritoneal inflammatory T helper 1 cells may be pivotal. METHODS Soluble interleukin-2 receptor alpha (sCD25) concentration was measured as a marker for T-cell activation in serum and ascites from EPS patients and various control patient groups. Peritoneal biopsies were stained for the presence of T cells, and T cells isolated from ascites of EPS patients were characterized in detail for differentiation status and cytokine expression. RESULTS Serum sCD25 concentrations are significantly and specifically increased in EPS patients compared with haemodialysis, PD and predialysis patients. Peritoneal effluent of stable PD patients contains very low levels of sCD25, while sCD25 levels in ascites of EPS patients are high and indicative of local production. In the years preceding the diagnosis of EPS, the serum sCD25 concentrations increased while remaining at stable levels in control PD patients. The peritoneum and ascites of EPS patients showed a significant influx of T cells with relatively increased numbers of CD4(+) T cells. These T cells were fully differentiated and displayed a T helper 1 cell type with a pro-inflammatory cytokine profile. CONCLUSIONS Increased serum sCD25 concentrations and peritoneal lymphocytosis in EPS patients indicate the involvement of activated T cells in the pathophysiology of excessive fibrosis.

Chronic-active antibody-mediated rejection with or without donor-specific antibodies has similar histomorphology and clinical outcome - a retrospective study

Chronic‐active antibody‐mediated rejection (c‐aABMR) is defined as histological evidence of chronic endothelial injury (cg), also known as transplant glomerulopathy, and either microvascular inflammation (MVI) or positivity for C4d. Importantly, the presence of donor‐specific antibodies (DSA) is currently still mandatory for the diagnosis of c‐aABMR. This retrospective study of 41 c‐aABMR patients investigates whether cases suspicious for c‐aABMR (DSA negative, n = 24) differ from cases of c‐aABMR (DSA positive, n = 17) with respect to renal histology, allograft function and long‐term graft survival. All included patients had progressive loss of allograft function and were diagnosed by for cause biopsy and scored according to the Banff ’15 criteria. In all DSApos cases, DSA were de novo and the majority was directed against HLA‐II being mostly anti‐HLA‐DQ antibodies. There were no statistically significant differences in clinical characteristics, decline in allograft function and renal allograft survival in cases with or without DSAs. All cases showed chronic histomorphological damage and inflammation, irrespective of the presence of DSA. Renal histology and clinical outcome of patients suspicious for c‐aABMR (DSAneg) do not significantly differ from patients with a diagnosis of c‐aABMR (DSApos). We believe that our study adds to the ongoing debate regarding the need for DSAs to be present for the diagnosis of c‐aABMR.

Donor genotype and intragraft expression of CYP3A5 reflect the response to steroid treatment during acute renal allograft rejection.

Background Glucocorticoid (GC)-refractory acute rejection (AR) is a risk factor for inferior renal allograft outcome. We investigated genetic predisposition to the response to steroid treatment of acute allograft rejection. Methods Single nucleotide polymorphisms of genes involved in GC signaling (GR, GLCCI1) and drug metabolism and transport (CYP3A5, ABCB1, and PXR) were analyzed in kidney transplant recipients (1995-2005, Leiden cohort, n = 153) treated with methylprednisolone. Significant associations were verified in a second cohort (Berlin cohort, n = 66). Results Patients who received a CYP3A5*1 allele expressing allograft had a lower risk of resistance to methylprednisolone during AR (odds ratio, 0.29; 95% confidence interval, 0.11-0.79; P = 0.016 in combined cohorts analysis). No differences were observed for GC signaling or other drug metabolism/transport-related genes. Both before transplantation (n = 69) and at time of AR (n = 88), tissue CYP3A5 mRNA expression was significantly higher in CYP3A5*1 allele expressing donor kidneys than in CYP3A5*3/*3 allografts (P < 0.00001). Moreover, steroid-responsive patients (n = 64) expressed significantly higher intragraft CYP3A5 mRNA levels compared to steroid-refractory patients (n = 42) in AR (P = 0.006). Conclusions CYP3A5 protein expression was detected in tubular epithelial cells and inflammatory cells within the grafts. Our findings show that steroid resistance during AR is associated with donor genotype and intragraft expression levels of CYP3A5.