Blockade of CD40-CD40 ligand protects against renal injury in chronic proteinuric renal disease

Efficacy and Safety of Bleselumab in Preventing the Recurrence of Primary Focal Segmental Glomerulosclerosis in Kidney Transplant Recipients: A Phase 2a, Randomized, Multicenter Study

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a common cause of end-stage kidney disease and frequently recurs after kidney transplantation. Recurrent FSGS (rFSGS) is associated with poor allograft and patient outcomes. Bleselumab, a fully human immunoglobulin G4 anti-CD40 antagonistic monoclonal antibody, disrupts CD40-related processes in FSGS, potentially preventing rFSGS.

METHODS

A phase 2a, randomized, multicenter, open-label study of adult recipients (aged ≥18 y) of a living or deceased donor kidney transplant with a history of biopsy-proven primary FSGS. The study assessed the efficacy of bleselumab combined with tacrolimus and corticosteroids as maintenance immunosuppression in the prevention of rFSGS >12 mo posttransplantation, versus standard of care (SOC) comprising tacrolimus, mycophenolate mofetil, and corticosteroids. All patients received basiliximab induction. The primary endpoint was rFSGS, defined as proteinuria (protein-creatinine ratio ≥3.0 g/g) with death, graft loss, or loss to follow-up imputed as rFSGS, through 3 mo posttransplant.

RESULTS

Sixty-three patients were followed for 12 mo posttransplantation. Relative decrease in rFSGS occurrence through 3 mo with bleselumab versus SOC was 40.7% (95% confidence interval, -89.8 to 26.8; P = 0.37; absolute decrease 12.7% [95% confidence interval, -34.5 to 9.0]). Central-blinded biopsy review found relative (absolute) decreases in rFSGS of 10.9% (3.9%), 17.0% (6.2%), and 20.5% (7.5%) at 3, 6, and 12 mo posttransplant, respectively; these differences were not statistically significant. Adverse events were similar for both treatments. No deaths occurred during the study.

CONCLUSIONS

In at-risk kidney transplant recipients, bleselumab numerically reduced proteinuria occurrence versus SOC, but no notable difference in occurrence of biopsy-proven rFSGS was observed.

Current understanding of the molecular mechanisms of circulating permeability factor in focal segmental glomerulosclerosis

The pathogenetic mechanisms underlying the onset and the post-transplant recurrence of primary focal segmental glomerulosclerosis (FSGS) are complex and remain yet to be fully elucidated. However, a growing body of evidence emphasizes the pivotal role of the immune system in both initiating and perpetuating the disease. Extensive investigations, encompassing both experimental models and patient studies, have implicated T cells, B cells, and complement as crucial actors in the pathogenesis of primary FSGS, with various molecules being proposed as potential "circulating factors" contributing to the disease and its recurrence post kidney-transplantation. In this review, we critically assessed the existing literature to identify essential pathways for a comprehensive characterization of the pathogenesis of FSGS. Recent discoveries have shed further light on the intricate interplay between these mechanisms. We present an overview of the current understanding of the engagement of distinct molecules and immune cells in FSGS pathogenesis while highlighting critical knowledge gaps that require attention. A thorough characterization of these intricate immune mechanisms holds the potential to identify noninvasive biomarkers that can accurately identify patients at high risk of post-transplant recurrence. Such knowledge can pave the way for the development of targeted and personalized therapeutic approaches in the management of FSGS.

State of the art in childhood nephrotic syndrome: concrete discoveries and unmet needs

Nephrotic syndrome (NS) is a clinical entity characterized by proteinuria, hypoalbuminemia, and peripheral edema. NS affects about 2-7 per 100,000 children aged below 18 years old yearly and is classified, based on the response to drugs, into steroid sensitive (SSNS), steroid dependent, (SDNS), multidrug dependent (MDNS), and multidrug resistant (MRNS). Forms of NS that are more difficult to treat are associated with a worse outcome with respect to renal function. In particular, MRNS commonly progresses to end stage renal failure requiring renal transplantation, with recurrence of the original disease in half of the cases. Histological presentations of NS may vary from minimal glomerular lesions (MCD) to focal segmental glomerulosclerosis (FSGS) and, of relevance, the histological patterns do not correlate with the response to treatments. Moreover, around half of MRNS cases are secondary to causative pathogenic variants in genes involved in maintaining the glomerular structure. The pathogenesis of NS is still poorly understood and therapeutic approaches are mostly based on clinical experience. Understanding of pathogenetic mechanisms of NS is one of the 'unmet needs' in nephrology and represents a significant challenge for the scientific community. The scope of the present review includes exploring relevant findings, identifying unmet needs, and reviewing therapeutic developments that characterize NS in the last decades. The main aim is to provide a basis for new perspectives and mechanistic studies in NS.

NCOA2 coordinates with the transcriptional KAT2B-NF-κB partner to trigger inflammation response in acute kidney injury

Dysregulation of multiple genes is an important risk factor for acute kidney injury (AKI). Numerous genes, such as proinflammatory cytokines, intracellular cell adhesion molecules (ICAMs), and nitric oxide synthases (NOSs), are implicated in AKI pathogenesis. However, the molecular mechanisms involved in the dysregulation of these genes are still obscure. Herein, we discovered that two subunits of NF-κB (p50 and p65) couple with lysine acetyltransferase 2B (KAT2B) and nuclear receptor coactivator 2 (NOCA2) to assemble a transcriptional complex in a LPS-induced mouse model of AKI. The NCOA2-KAT2B-NF-κB complex bound to the promoters of some NF-κB target genes, such as interleukin 1 beta (IL-1B), IL-6, tumor necrosis factor alpha (TNFA), ICAM1, vascular cell adhesion molecule 1 (VCAM1), cluster of differentiation 38 (CD38), CD40, CD80, and NOS2, and transactivated their expression. In vitro knockdown of components of the NCOA2-KAT2B-NF-κB complex or blockage of KAT2B by its inhibitors (5-chloro-2-(4-nitrophenyl)-3(2H)-isothiazolone [CNIT] and garcinol) significantly decreased the expression of these NF-κB target genes following LPS treatment. The administration of CNIT and garcinol significantly improved the in vivo outcomes of the AKI mice. Our findings reveal the underlying mechanism of NF-κB target upregulation in the pathogenesis of LPS-induced AKI and identify a new therapeutic strategy for AKI that involves targeting the NCOA2-KAT2B-NF-κB complex.

The role of the immune system in idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome (INS) in children is characterized by massive proteinuria and hypoalbuminemia and usually responds well to steroids. However, relapses are frequent, which can require multi-drug therapy with deleterious long-term side effects. In the last decades, different hypotheses on molecular mechanisms underlying INS have been proposed and several lines of evidences strongly indicate a crucial role of the immune system in the pathogenesis of non-genetic INS. INS is traditionally considered a T-cell-mediated disorder triggered by a circulating factor, which causes the impairment of the glomerular filtration barrier and subsequent proteinuria. Additionally, the imbalance between Th17/Tregs as well as Th2/Th1 has been implicated in the pathomechanism of INS. Interestingly, B-cells have gained attention, since rituximab, an anti-CD20 antibody demonstrated a good therapeutic response in the treatment of INS. Finally, recent findings indicate that even podocytes can act as antigen-presenting cells under inflammatory stimuli and play a direct role in activating cellular pathways that cause proteinuria. Even though our knowledge on the underlying mechanisms of INS is still incomplete, it became clear that instead of a traditionally implicated cell subset or one particular molecule as a causative factor for INS, a multi-step control system including soluble factors, immune cells, and podocytes is necessary to prevent the occurrence of INS. This present review aims to provide an overview of the current knowledge on this topic, since advances in our understanding of the immunopathogenesis of INS may help drive new tailored therapeutic approaches forward.

Therapeutic trials in adult FSGS: lessons learned and the road forward

Focal segmental glomerulosclerosis (FSGS) is not a specific disease entity but a lesion that primarily targets the podocyte. In a broad sense, the causes of the lesion can be divided into those triggered by a presumed circulating permeability factor, those that occur secondary to a process that might originate outside the kidneys, those caused by a genetic mutation in a podocyte or glomerular basement membrane protein, and those that arise through an as yet unidentifiable process, seemingly unrelated to a circulating permeability factor. A careful attempt to correctly stratify patients with FSGS based on their clinical presentation and pathological findings on kidney biopsy is essential for sound treatment decisions in individual patients. However, it is also essential for the rational design of therapeutic trials in FSGS. Greater recognition of the pathophysiology underlying podocyte stress and damage in FSGS will increase the likelihood that the cause of an FSGS lesion is properly identified and enable stratification of patients in future interventional trials. Such efforts will facilitate the identification of effective therapeutic agents.

Na/K-ATPase/src complex mediates regulation of CD40 in renal parenchyma

Background

Recent studies have highlighted a critical role for CD40 in the pathogenesis of renal injury and fibrosis. However, little is currently understood about the regulation of CD40 in this setting.

Methods

We use novel Na/K-ATPase cell lines and inhibitors in order to demonstrate the regulatory function of Na/K-ATPase with regards to CD40 expression and function. We utilize 5/6 partial nephrectomy as well as direct infusion of a Na/K-ATPase ligand to demonstrate this mechanism exists in vivo.

Results

We demonstrate that knockdown of the α1 isoform of Na/K-ATPase causes a reduction in CD40 while rescue of the α1 but not the α2 isoform restores CD40 expression in renal epithelial cells. Second, because the major functional difference between α1 and α2 is the ability of α1 to form a functional signaling complex with Src, we examined whether the Na/K-ATPase/Src complex is important for CD40 expression. We show that a gain-of-Src binding α2 mutant restores CD40 expression while loss-of-Src binding α1 reduces CD40 expression. Furthermore, loss of a functional Na/K-ATPase/Src complex also disrupts CD40 signaling. Importantly, we show that use of a specific Na/K-ATPase/Src complex antagonist, pNaKtide, can attenuate cardiotonic steroid (CTS)-induced induction of CD40 expression in vitro.

Conclusions

Because the Na/K-ATPase/Src complex is also a key player in the pathogenesis of renal injury and fibrosis, our new findings suggest that Na/K-ATPase and CD40 may comprise a pro-fibrotic feed-forward loop in the kidney and that pharmacological inhibition of this loop may be useful in the treatment of renal fibrosis.

Molecular and Cellular Mechanisms for Proteinuria in Minimal Change Disease

Minimal Change Disease (MCD) is a clinical condition characterized by acute nephrotic syndrome, no evident renal lesions at histology and good response to steroids. However, frequent recurrence of the disease requires additional therapies associated with steroids. Such multi-drug dependence and frequent relapses may cause disease evolution to focal and segmental glomerulosclerosis (FSGS) over time. The differences between the two conditions are not well defined, since molecular mechanisms may be shared by the two diseases. In some cases, genetic analysis can make it possible to distinguish MCD from FSGS; however, there are cases of overlap. Several hypotheses on mechanisms underlying MCD and potential molecular triggers have been proposed. Most studies were conducted on animal models of proteinuria that partially mimic MCD and may be useful to study glomerulosclerosis evolution; however, they do not demonstrate a clear-cut separation between MCD and FSGS. Puromycin Aminonucleoside and Adriamycin nephrosis are models of glomerular oxidative damage, characterized by loss of glomerular basement membrane polyanions resembling MCD at the onset and, at more advanced stages, by glomerulosclerosis resembling FSGS. Also Buffalo/Mna rats present initial lesions of MCD, subsequently evolving to FSGS; this mechanism of renal damage is clearer since this rat strain inherits the unique characteristic of overexpressing Th2 cytokines. In Lipopolysaccharide nephropathy, an immunological condition of renal toxicity linked to B7-1(CD80), mice develop transient proteinuria that lasts a few days. Overall, animal models are useful and necessary considering that they reproduce the evolution from MCD to FSGS that is, in part, due to persistence of proteinuria. The role of T/Treg/Bcells on human MCD has been discussed. Many cytokines, immunomodulatory mechanisms, and several molecules have been defined as a specific cause of proteinuria. However, the hypothesis of a single cell subset or molecule as cause of MCD is not supported by research and an interactive process seems more logical. The implication or interactive role of oxidants, Th2 cytokines, Th17, Tregs, B7-1(CD80), CD40/CD40L, c-Mip, TNF, uPA/suPAR, Angiopoietin-like 4 still awaits a definitive confirmation. Whole genome sequencing studies could help to define specific genetic features that justify a definition of MCD as a “clinical-pathology-genetic entity.”

Soluble CD40 ligand directly alters glomerular permeability and may act as a circulating permeability factor in FSGS

CD40/CD40 ligand (CD40L) dyad, a co-stimulatory bi-molecular complex involved in the adaptive immune response, has also potent pro-inflammatory actions in haematopoietic and non-haematopoietic cells. We describe here a novel role for soluble CD40L (sCD40L) as modifier of glomerular permselectivity directly acting on glomerular epithelial cells (GECs). We found that stimulation of CD40, constitutively expressed on GEC cell membrane, by the sCD40L rapidly induced redistribution and loss of nephrin in GECs, and increased albumin permeability in isolated rat glomeruli. Pre-treatment with inhibitors of CD40-CD40L interaction completely prevented these effects. Furthermore, in vivo injection of sCD40L induced a significant reduction of nephrin and podocin expression in mouse glomeruli, although no significant increase of urine protein/creatinine ratio was observed after in vivo injection. The same effects were induced by plasma factors partially purified from post-transplant plasma exchange eluates of patients with focal segmental glomerulosclerosis (FSGS), and were blocked by CD40-CD40L inhibitors. Moreover, 17 and 34 kDa sCD40L isoforms were detected in the same plasmapheresis eluates by Western blotting. Finally, the levels of sCD40Lwere significantly increased in serum of children both with steroid-sensitive and steroid-resistant nephrotic syndrome (NS), and in adult patients with biopsy-proven FSGS, compared to healthy subjects, but neither in children with congenital NS nor in patients with membranous nephropathy.

Our results demonstrate that sCD40L directly modifies nephrin and podocin distribution in GECs. Moreover, they suggest that sCD40L contained in plasmapheresis eluates from FSGS patients with post-transplant recurrence may contribute, presumably cooperating with other mediators, to FSGS pathogenesis by modulating glomerular permeability.

Clinical trials in minimal change disease

Minimal change disease (MCD) is a pathological condition characterized by subtle glomerular lesions causing massive and reversible proteinuria that is usually steroid sensitive. Recurrence of symptoms of active disease following successful treatment (including proteinuria, oedema and oliguria) and steroid toxicity requires the use of other drugs to attain or maintain remission. Unresolved MCD is considered the initial step in the pathological pathway leading to focal and segmental glomerulosclerosis (FSGS). Historically, cyclophosphamide, chlorambucil, mycophenolate and calcineurin inhibitors have been utilized with success in MCD; however, the chronic nature of the disease and the toxicity of long-term use of these medications has pushed the development of new therapies. Synthetic corticotropin (adrenocorticotropic hormone) and anti-CD20 monoclonal antibodies, for example, are currently under investigation in clinical trials. In addition, these new interventions have dramatically impacted our understanding of the mechanisms of the disease. Phase II-IV clinical trials targeting new mechanisms and/or molecules are in progress. The list is long and includes drugs blocking the adaptive immune system (abatacept and anti-CD40 antibodies), as well as retinoids and the sialic acid precursor N-acetyl-D-mannosamine (ManNAc), two agents that affect the sieving properties of the glomerular basement membrane. Other drugs are being tested against FSGS and, if successful, could also be utilized against MCD. Clinical trials currently in progress should furnish a proper solution to what appears to be a solvable problem.

Circulating CD40 and sCD40L Predict Changes in Renal Function in Subjects with Chronic Kidney Disease

Soluble CD40 ligand (sCD40L) has been implicated in the development of renal injury. The CD40 receptor exists in a soluble form, sCD40R, and has been shown to function as a competitive antagonist against CD40 activation. We analyzed whether plasma levels of sCD40L and sCD40R predict changes in renal function in an all-cause chronic kidney disease (CKD) cohort. Stratification of subjects based on sCD40L and sCD40R individually, as well as in combination, demonstrated that sCD40L was directly associated with declines in estimated glomerular filtration rate (eGFR). sCD40R was negatively associated with declines in eGFR. Baseline characteristics following stratification, including systolic blood pressure, history of diabetes mellitus or peripheral vascular disease, primary renal disease classification, and angiotensin converting enzyme inhibitor or angiotensin receptor blocker usage were not significantly different. High sCD40L and low sCD40R were both found to be independent predictors of a decline in eGFR at 1-year follow-up (−7.57%, p = 0.014; −6.39%, p = 0.044). Our data suggest that circulating levels of sCD40L and sCD40R are associated with changes in renal function in patients with CKD. The CD40 decoy receptor, sCD40R, may serve as a potential therapeutic target to attenuate renal function decline.

Identification of potential biomarkers and therapeutic targets for human IgA nephropathy and hypertensive nephropathy by bioinformatics analysis

In order to further elucidate the potential correlations and treatments of IgA nephropathy (IgAN) and hypertensive nephropathy (HT), bioinformatics analysis of IgAN and HT was performed. The mRNA expression profiles of human renal biopsy samples from patients with IgAN, patients with HT and pre‑transplant healthy living controls (LD) were downloaded from the Gene Expression Omnibus database. Then, the differentially expressed genes (DEGs) were identified and functions of DEGs were analyzed. Finally, the regulatory networks containing DEGs and related‑transcription factors (TFs) were constructed using Cytoscape software. When compared with the LD group, 134 and 188 DEGs were obtained in the IgAN and HT groups, respectively. A total of 39 genes were altered in the HT group when compared with the IgAN group. In addition, 66 genes were shared in the IgAN and HT groups when compared with the LD group, 6 of which [early growth response 1, activating transcription factor 3, nuclear receptor subfamily 4 group A member 2 (NR4A2), NR4A1, v‑maf avian musculoaponeurotic fibrosarcoma oncogene homolog F and Kruppel like factor 6] were identified as TFs. In addition, DEGs including interleukin (IL) 1 receptor antagonist, collagen type 4 α2 chain, IL8, FBJ murine osteosarcoma viral oncogene homolog and somatostatin were enriched in a number of inflammation‑associated biological processes, and DEGs including structural maintenance of chromosomes protein 3, v‑crk avian sarcoma virus CT10 oncogene homolog and myosin 6 were enriched in non‑inflammation‑associated biological processes. Therefore, the differentially expressed TF genes and the genes associated with inflammation may be effective as potential therapeutic targets for IgAN and HT.

Rituximab in Minimal Change Disease: Mechanisms of Action and Hypotheses for Future Studies

Treatment with rituximab, a monoclonal antibody against the B-lymphocyte surface protein CD20, leads to the depletion of B cells. Recently, rituximab was reported to effectively prevent relapses of glucocorticoid-dependent or frequently relapsing minimal change disease (MCD). MCD is thought to be T-cell mediated; how rituximab controls MCD is not understood. In this review, we summarize key clinical studies demonstrating the efficacy of rituximab in idiopathic nephrotic syndrome, mainly MCD. We then discuss immunological features of this disease and potential mechanisms of action of rituximab in its treatment based on what is known about the therapeutic action of rituximab in other immune-mediated disorders. We believe that studies aimed at understanding the mechanisms of action of rituximab in MCD will provide a novel approach to resolve the elusive immune pathophysiology of MCD.

Targeted disruption of Cd40 in a genetically hypertensive rat model attenuates renal fibrosis and proteinuria, independent of blood pressure

High blood pressure is a common cause of chronic kidney disease. Because CD40, a member of the tumor necrosis factor receptor family, has been linked to the progression of kidney disease in ischemic nephropathy, we studied the role of Cd40 in the development of hypertensive renal disease. The Cd40 gene was mutated in the Dahl S genetically hypertensive rat with renal disease by targeted-gene disruption using zinc-finger nuclease technology. These rats were then given low (0.3%) and high (2%) salt diets and compared. The resultant Cd40 mutants had significantly reduced levels of both urinary protein excretion (41.8 ± 3.1 mg/24 h vs. 103.7 ± 4.3 mg/24 h) and plasma creatinine (0.36 ± 0.05 mg/dl vs. 1.15 ± 0.19 mg/dl), with significantly higher creatinine clearance compared with the control S rats (3.04 ± 0.48 ml/min vs. 0.93 ± 0.15 ml/min), indicating renoprotection was conferred by mutation of the Cd40 locus. Furthermore, the Cd40 mutants had a significant attenuation in renal fibrosis, which persisted on the high salt diet. However, there was no difference in systolic blood pressure between the control and Cd40 mutant rats. Thus, these data serve as the first evidence for a direct link between Cd40 and hypertensive nephropathy. Hence, renal fibrosis is one of the underlying mechanisms by which Cd40 plays a crucial role in the development of hypertensive renal disease.

CD40 Generation 2.5 Antisense Oligonucleotide Treatment Attenuates Doxorubicin-induced Nephropathy and Kidney Inflammation

Preclinical and clinical data suggest CD40 activation contributes to renal inflammation and injury. We sought to test whether upregulation of CD40 in the kidney is a causative factor of renal pathology and if reduction of renal CD40 expression, using antisense oligonucleotides (ASOs) targeting CD40, would be beneficial in mouse models of glomerular injury and unilateral ureter obstruction. Administration of a Generation 2.5 CD40 ASO reduced CD40 mRNA and protein levels 75–90% in the kidney. CD40 ASO treatment mitigated functional, transcriptional, and pathological endpoints of doxorubicin-induced nephropathy. Experiments using an activating CD40 antibody revealed CD40 is primed in kidneys following doxorubicin injury or unilateral ureter obstruction and CD40 ASO treatment blunted CD40-dependent renal inflammation. Suborgan fractionation and imaging studies demonstrated CD40 in glomeruli before and after doxorubicin administration that becomes highly enriched within interstitial and glomerular foci following CD40 activation. Such foci were also sites of ASO distribution and activity and may be predominately comprised from myeloid cells as bone marrow CD40 deficiency sharply attenuated CD40 antibody responses. These studies suggest an important role of interstitial renal and/or glomerular CD40 to augment kidney injury and inflammation and demonstrate that ASO treatment could be an effective therapy in such disorders.

Costimulatory blockade: A novel approach to the treatment of glomerular disease?

Costimulatory pathways (Cluster of differentiation 28, tumor necrosis factor-related, adhesion and T Cell Ig- and mucin-domain molecules) regulating the interactions between receptors on the T cells and their ligands expressed on several cell types, have a key role in controlling many immunological and non immunological processes. Indeed, accumulating evidence indicate that these molecules are involved in the pathogenesis of numerous conditions, such as allograft rejection, atherosclerosis, rheumatoid arthritis, psoriasis and renal diseases, including glomerulonephritis. Primary or secondary (i.e., associated with infections, drugs or systemic diseases, such as systemic lupus erythematosus, diabetes, etc.) glomerulonephritis represent a group of heterogeneous diseases with different pathogenic mechanisms. Since costimulatory molecules, in particular CD80 and CD40, have been found to be expressed on podocytes in the course of different experimental and clinical glomerulonephritis, costimulation has been thought as a new therapeutic target for patients with glomerular diseases. However, although experimental data suggested that the blockade of costimulatory pathways is effective and safe in the prevention and treatment of glomerular diseases, clinical trials reported contrasting results. So, at this moment, there is not a strong evidence for the general use of costimulatory blockade as an alternative treatment strategy in patients with primary or secondary glomerulonephritis. Here, we critically discuss the current data and the main issues regarding the development of this innovative therapeutic approach.

A circulating antibody panel for pretransplant prediction of FSGS recurrence after kidney transplantation

Recurrence of focal segmental glomerulosclerosis (rFSGS) after kidney transplantation is a cause of accelerated graft loss. To evaluate pathogenic antibodies (Abs) in rFSGS, we processed 141 serum samples from 64 patients with and without primary rFSGS and 34 non-FSGS control patients transplanted at four hospitals. We screened about 9000 antigens in pretransplant sera and selected 10 Abs targeting glomerular antigens for enzyme-linked immunosorbent assay (ELISA) validation. A panel of seven Abs (CD40, PTPRO, CGB5, FAS, P2RY11, SNRPB2, and APOL2) could predict posttransplant FSGS recurrence with 92% accuracy. Pretransplant elevation of anti-CD40 Ab alone had the best correlation (78% accuracy) with rFSGS risk after transplantation. Epitope mapping of CD40 with customized peptide arrays and rFSGS sera demonstrated altered immunogenicity of the extracellular CD40 domain in rFSGS. Immunohistochemistry of CD40 demonstrated a differential expression in FSGS compared to non-FSGS controls. Anti-CD40 Abs purified from rFSGS patients were particularly pathogenic in human podocyte cultures. Injection of anti-CD40/rFSGS Ab enhanced suPAR (soluble urokinase receptor)-mediated proteinuria in wild-type mice, yet no sensitizing effect was noted in mice deficient in CD40 or in wild-type mice that received blocking Ab to CD40. In conclusion, a panel of seven Abs can help identify primary FSGS patients at high risk of recurrence before transplantation. Intrarenal CD40 (and possibly other specific glomerular antigens) is an important contributor to FSGS disease pathogenesis. Human trials of anti-CD40 therapies are warranted to evaluate their efficacy for preventing rFSGS and improving graft survival.

Adoptive transfer of bone marrow dendritic cells failed to localize in the renal cortex and to improve renal injury in adriamycin nephropathy

BACKGROUND AND AIMS

Murine bone marrow (BM) dendritic cells (DCs) can be modulated to be tolerogenic by cytokines, such as interleukin (IL)-10 and transforming growth factor (TGF)-β, and may play a regulatory role and sustain immune hemostasis in cognate kidney disease. However, it is unknown whether BM-DCs can be used to protect against renal injury in murine Adriamycin nephropathy (AN).

METHODS

In this study, by adoptive in vivo transfer of BM-DCs, including immature DCs, mature DCs (lipopolysaccharide-stimulated DCs) and BM regulatory DCs (IL-10/TGF-β-modified DCs, DCregs), we addressed the potential benefits of BM-DCs in chronic kidney disease.

RESULTS

We found that after adoptive transfer of DCregs, renal injury, including glomerulosclerosis, interstitial fibrosis and tubular atrophy, was not changed compared to AN controls. Correspondingly, renal functions measured by serum creatinine, 12-hour urine protein and creatinine clearance were also not improved by transfusion with DCregs compared to AN controls.

CONCLUSION

This study showed that the adoptive transfer of BM-DCs was unable to improve renal injury in an AN model, and this failure related to their inability to access the kidney.

Early growth response-1 (EGR-1) and nuclear factor of activated T cells (NFAT) cooperate to mediate CD40L expression in megakaryocytes and platelets

Increasing evidence implicates circulating platelets as mediators of chronic inflammatory and autoimmune diseases via the expression and release of CD40L, an important modulator of inflammation and adaptive immune responses traditionally associated with activated T cells. Emerging evidence suggests that platelet CD40L is dynamically regulated in several chronic inflammatory and autoimmune diseases and may mediate progression and secondary pathology associated with those disease states. The present study identifies NFATc2 as a key transcriptional modulator of CD40L expression in megakaryocytes and inflammatory activity of platelets. Furthermore, the current data show that EGR-1, a member of the early growth response family of zinc finger transcription factors, modulates NFATc2-dependent regulation of CD40L expression in megakaryocytes. Our novel demonstration that in vivo biochemical or genetic inhibition of NFATc2 activity in megakaryocyte diminishes platelet CD40L implicates the NFATc2/EGR-1 axis as a key regulatory pathway of inflammatory and immunomodulatory activity in platelets and represents a target for the development of therapeutics for the potential treatment of chronic inflammatory and autoimmune diseases.

Effect of CD40 and sCD40L on renal function and survival in patients with renal artery stenosis

Activation of the CD40 receptor on the proximal tubular epithelium of the kidney results in fibrosis and inflammation in experimental models of kidney injury. Soluble CD40 ligand is released by activated platelets. The role of CD40-soluble CD40 ligand in patients with ischemic renal disease is unknown. Plasma levels of CD40 and soluble CD40 ligand were measured by enzyme-linked immunosorbent assay in a single center cohort of 60 patients with renal artery stenosis recruited from Salford Royal Hospital, Manchester, United Kingdom. A natural log transformation of CD40 and soluble CD40 ligand was performed to normalize the data. Estimated glomerular filtration rate was used as the primary indicator of renal function. By univariate analysis, low baseline levels of circulating CD40 (R(2)=0.06; P<0.05) and baseline creatinine (R(2)=0.08; P=0.022) were associated with loss of kidney function at 1-year follow-up, whereas soluble CD40 ligand was not (R(2)=0.02; P=ns). In a multiple linear regression model, CD40 (P<0.02) and baseline creatinine (P<0.01) continued to be significantly associated with a decline in renal function (model R(2)=0.17; P<0.005). Baseline CD40 levels were somewhat lower in patients who died during follow-up (survivors, 7.3±0.9 pg/mL, n=48 versus nonsurvivors, 6.7±1.0 pg/mL, n=12; P=0.06). The CD40/soluble CD40 ligand signaling cascade may be a novel mechanism contributing to the development and progression of renal injury in patients with atherosclerotic renal artery stenosis.

Inhibition of calcium(2+)/calmodulin-dependent protein kinase type IV ameliorates experimental nephrotic syndrome

OBJECTIVE

Evidence has demonstrated that Ca(2+)/calmodulin-dependent protein kinase type IV (CaMKIV) contributes to altered cytokine production by promoting the production of inflammatory cytokines. This study aimed to explore the protective role and underlying mechanisms of CaMKIV inhibition in experimental nephrotic syndrome.

METHODS

BALB/c mice received single intravenous injections of adriamycin (10 mg/kg) then were sacrificed at two, four and six weeks. In the second study, treatment with KN-93, a CaMKIV inhibitor, or vehicle administered via intraperitoneal injection was started five days after adriamycin injection. Functional and pathologic parameters, the presence of inflammatory infiltration and the expressions of pro-inflammatory cytokines were assessed.

RESULTS

The CaMKIV protein expression levels were upregulated in the mice with adriamycin nephropathy, which was significantly inhibited by KN-93 (p<0.01). As compared with the vehicle-treated controls, KN-93 treatment resulted in marked suppression of proteinuria and serum creatinine at week 6 (p<0.01), but not at two weeks after induction of the disease. KN-93 inhibited glomerulosclerosis and the development of tubulointerstitial lesions. The renal alpha-smooth muscle actin (α-SMA) expression was also significantly suppressed by KN-93 treatment at week 6 (p<0.01). Moreover, KN-93 inhibited the renal monocyte chemoattractant protein-1 (MCP-1) expression, paralleled by a reduction in the interstitial infiltration of macrophages and T-cells (p<0.01).

CONCLUSION

Our findings suggest that activation of CaMKIV signaling is involved in the progression of glomerular diseases with a proteinuric state. Our data therefore justify the development of small molecule CaMKIV inhibitors for the treatment of clinical nephrotic syndrome.

A risk-analysis approach to the evaluation of analytical quality

BACKGROUND

Setting specifications for analytical quality is always difficult. The risk-management approach might be a way to do so. In this approach, the definition of the required analytical quality is based on the evaluation of patient risk. Risk derives from the probability of error and from the damage that such an error might cause.

METHODS

Eight Italian laboratories took part in this experiment. Measurements of glucose and total calcium were taken as examples. Analytical quality was evaluated using a specific ring trial with a frozen serum pool and by means of internal quality-control data. The total allowable error was defined according to biological variation specifications. The probability of error was extracted from the imprecision and comparative bias data of each laboratory. The damage caused by a wrong result was evaluated using the absolute probability judgment approach.

RESULTS

According to the iso-risk plots (standardized hyperboles on a graph where the x-axis represents damage and the y-axis represents probability) for glucose, all the laboratories were working with an analytical quality that guaranteed low risk for patients. On the contrary, for total calcium none of the laboratories exhibited sufficient quality to guarantee low risk for patients, the presence of bias being the most relevant problem.

CONCLUSIONS

The results seem to demonstrate the applicability of the risk approach to the analytical phase, indicating a new possible way to define analytical quality targets.

Platelet activation in patients with atherosclerotic renal artery stenosis undergoing stent revascularization

BACKGROUND AND OBJECTIVES

Soluble CD40 ligand (sCD40L) is a marker of platelet activation; whether platelet activation occurs in the setting of renal artery stenosis and stenting is unknown. Additionally, the effect of embolic protection devices and glycoprotein IIb/IIIa inhibitors on platelet activation during renal artery intervention is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma levels of sCD40L were measured in healthy controls, patients with atherosclerosis without renal stenosis, and patients with renal artery stenosis before, immediately after, and 24 hours after renal artery stenting.

RESULTS

Soluble CD40L levels were higher in renal artery stenosis patients than normal controls (347.5 ± 27.0 versus 65.2 ± 1.4 pg/ml, P < 0.001), but were similar to patients with atherosclerosis without renal artery stenosis. Platelet-rich emboli were captured in 26% (9 of 35) of embolic protection device patients, and in these patients sCD40L was elevated before the procedure. Embolic protection device use was associated with a nonsignificant increase in sCD40L, whereas sCD40L declined with abciximab after the procedure (324.9 ± 42.5 versus 188.7 ± 31.0 pg/ml, P = 0.003) and at 24 hours.

CONCLUSIONS

Atherosclerotic renal artery stenosis is associated with platelet activation, but this appears to be related to atherosclerosis, not renal artery stenosis specifically. Embolization of platelet-rich thrombi is common in renal artery stenting and is inhibited with abciximab.

Soluble CD40 ligand is elevated in type 1 diabetic nephropathy but not predictive of mortality, cardiovascular events or kidney function

Soluble CD40 ligand (sCD40L) derived from platelets mediates atherothrombosis, leading to proinflammatory and proatherosclerotic responses. We investigated the predictive value of plasma sCD40L for all-cause mortality, cardiovascular mortality and morbidity, progression towards end-stage renal disease (ESRD) and rate of decline in glomerular filtration rate (GFR) in patients with type 1 diabetes (T1DM) and nephropathy. The study was a prospective, observational follow-up study of 443 T1DM patients with diabetic nephropathy (274 men; age 42.1 ± 10.5 years [mean ± SD], duration of diabetes 28.3 ± 8.9 years, GFR 76 ± 33 ml/min/1.73 m2) and a control group of 421 patients with longstanding type 1 diabetes and persistent normoalbuminuria (232 men; age 45.4 ± 11.5 years, duration of diabetes 27.7 ± 10.1 years) at baseline. sCD40L was measured by ELISA. Plasma sCD40L levels were higher in patients with diabetic nephropathy compared to normoalbuminuric patients (median (range) 1.54 (0.02-13.38) vs. 1.30 (0.04-20.65) µg/L, respectively p = 0.004). The patients were followed for 8.1 (0.0-12.9) years (median (range)). Among normoalbuminuric patients, sCD40L levels did not predict all-cause mortality (p = 0.33) or combined fatal and non-fatal cardiovascular disease (CVD) (p = 0.27). Similarly, among patients with diabetic nephropathy, the covariate adjusted sCD40L levels did not predict all-cause mortality (p = 0.86) or risk of fatal and non-fatal CVD (p = 0.08). Furthermore, high levels of sCD40L did not predict development of ESRD (p = 0.85) nor rate of decline in GFR (p = 0.69). Plasma sCD40L is elevated in T1DM nephropathy but is not a predictor of all-cause mortality, cardiovascular mortality and morbidity or deterioration of kidney function

The CD40-CD154 co-stimulation pathway mediates innate immune injury in adriamycin nephrosis

BACKGROUND

Blockade of CD40-CD40 ligand (CD154) interactions protects against renal injury in adriamycin nephropathy (AN) in immunocompetent mice. To investigate whether this protection relied on adaptive or cognate immunity, we tested the effect of CD40-CD154 blockade in severe combined immunodeficient (SCID) mice.

METHODS

SCID mice were divided into three groups: normal, AN + hamster IgG (ADR+IgG group) and AN + anti-CD154 antibody (MR1) (ADR+MR1 group). AN was induced by tail vein injection of 5.2 mg/kg of adriamycin (ADR). Hamster IgG (control Ab) or MR1 was administered intraperitoneally on days 5, 7, 9 and 11 after ADR injection. Histological and functional data were collected 4 weeks after ADR injection. In vitro experiments tested the effect of soluble and cell-bound CD154 co-cultured with CD40-expressing cells [macrophages, mesangial cells and renal tubular epithelial cells (RTEC)].

RESULTS

All experimental animals developed nephropathy. Compared to the ADR+IgG group, ADR+MR1 animals had significantly less histological injury (glomerulosclerosis and tubular atrophy) and functional injury (creatinine clearance). Kidneys of ADR+MR1 animals had significantly less macrophage infiltration than those of ADR+IgG animals. Interestingly, expression of CD40 and CD41 (a platelet-specific marker) was significantly less in ADR+MR1 animals compared to ADR+IgG animals. In vitro, CD154 blockade significantly attenuated upregulation of CCL2 gene expression by RTEC stimulated by activated macrophage-conditioned medium. In contrast, platelet-induced upregulation of macrophage and mesangial cell proinflammatory cytokine gene expression were not CD154-dependent.

CONCLUSION

CD40-CD154 blockade has a significant innate renoprotective effect in ADR nephrosis. This is potentially due to inhibition of macrophage-derived soluble CD154.

C3a mediates epithelial-to-mesenchymal transition in proteinuric nephropathy

Tubulointerstitial inflammation and progressive fibrosis are common pathways that lead to kidney failure in proteinuric nephropathies. Activation of the complement system has been implicated in the development of tubulointerstitial injury in clinical and animal studies, but the mechanism by which complement induces kidney injury is not fully understood. Here, we studied the effect of complement on the phenotype of tubular epithelial cells. Tubular epithelial cells exposed to serum proteins adopted phenotypic and functional characteristics of mesenchymal cells. Expression of E-cadherin protein decreased and expression of both alpha-smooth muscle actin protein and collagen I mRNA increased. Exposure of the cells to the complement anaphylotoxin C3a induced similar features. Treating with a C3a receptor (C3aR) antagonist prevented both C3a- and serum-induced epithelial-to-mesenchymal transition. In the adriamycin-induced proteinuria model, C3aR-deficient mice demonstrated less injury, preserved renal function, and improved survival compared with wild-type mice. Furthermore, the kidneys of C3aR-deficient mice had significantly less interstitial collagen I and alpha-smooth muscle actin. In summary, the complement anaphylotoxin C3a is an important mediator of glomerular and tubulointerstitial injury and can induce tubular epithelial-to-mesenchymal transition.

Adriamycin alters glomerular endothelium to induce proteinuria

The pathophysiology underlying the nephrotic syndrome is becoming clear for several inherited podocytopathies; the mechanisms of injury that lead to the acquired forms of this disease are not well understood. We explored these mechanisms using the mouse model of adriamycin-induced proteinuria.We estimated the fractional clearances for FITC-Ficolls, albumin, and neutral albumin in cooled, isolated,perfused kidneys (cIPK) in situ. Treatment with adriamycin led to a significant increase in the fractional clearance of albumin and of Ficoll with radii larger than 20 A. Neutral albumin (33.4 A) and similarly sized Ficoll behaved similarly to each other. In addition, adriamycin led to a significant loss of charge density and size selectivity of the glomerular barrier. The thickness of the glomerular endothelial surface layer(i.e., or the glycocalyx) in adriamycin-treated animals was only 20% of that in normal animals. Finally,several proteoglycans were downregulated in isolated glomeruli. In summary, adriamycin thins the glomerular glycocalyx, perhaps by downregulating proteoglycan synthesis, and alters glomerular charge- and size selectivity. These data suggest that the glomerular endothelium may play a role in the pathogenesis of proteinuric renal diseases.

Increased concentrations of soluble CD40 ligand may help to identify type 1 diabetic adolescents and young adults at risk for developing persistent microalbuminuria

BACKGROUND

Recent studies on the pathogenesis of diabetic complications have demonstrated the important role of a number of aberrantly expressed molecules acting together in the development of early diabetic microvascular complications. Soluble CD40 ligand (sCD40L) is supposed to be one of the most likely candidates for both retinopathy and nephropathy.

METHODS

In January 1989, sCD40L was measured in 340 normoalbuminuric diabetic adolescents and young adults. Participants were examined at baseline and biannually thereafter. sCD40L was measured every 2 years during a 16-year follow-up period. sCD40L was also measured in parents.

RESULTS

Over 16 years, 32 out of 340 patients developed persistent microalbuminuria; no patient developed overt diabetic nephropathy. The risk of developing microalbuminuria was higher in children with increased sCD40L at the beginning of the study (using 6 ng/mL as the arbitrary cut-off value) (group A) compared with those with normal sCD40L (group B). Sex did not influence predictive value, sensitivity, or specificity. sCD40L was not significantly correlated with duration of diabetes. The percentage of offspring with both parents having sCD40L above the mean values was significantly higher in group A than in group B. The odds ratio (OR) for the occurrence of microalbuminuria after adjustment for confounding variables in patients with elevated baseline sCD40L was 4.2 (95% CI, 2.1-10.7).

CONCLUSIONS

Persistently increased sCD40L levels from the onset of diabetes might help to identify those normotensive and normoalbuminuric young patients at increased risk of developing incipient nephropathy later in life.

Inhibition of Jak/STAT signaling ameliorates mice experimental nephrotic syndrome

BACKGROUND/AIMS

This study investigated the role of JAK/STAT, an important pathway for cytokine signal transduction, in the progression of chronic glomerular diseases.

METHODS

BALB/c mice received a single intravenous injection of adriamycin (10 mg/kg) were sacrificed 2, 4 and 6 weeks later. In the second study, treatment with the selective JAK2 inhibitor AG490 (15 mg/kg, q.d., i.p.) or vehicle was started 5 days after adriamycin injection. Functional and pathologic markers, inflammatory infiltration, expression of pro-inflammatory cytokines and phosphorylation of JAK2/STATs were assessed.

RESULTS

JAK/STAT signaling was activated in adriamycin nephropathy. Phosphorylation of JAK2, STAT1 and STAT3 was significantly inhibited by AG490 (p <0.01). Compared to the vehicle-treated controls, AG490 treatment did not reduce proteinuria 2 weeks after induction of the disease, but resulted in significant decrease in proteinuria and serum creatinine at week 6 (p <0.05). Glomerulosclerosis, tubulointerstitial lesions and renal alpha-SMA expression were also significantly suppressed by AG490 treatment at week 6 (p < 0.01). In addition, AG490 inhibited the expression of MCP-1 mRNA, accompanied by reduced interstitial infiltration of macrophages and T cells (p <0.05).

CONCLUSIONS

This study suggests that activation of JAK/STAT signaling is involved in the progression of glomerular diseases with proteinuric state.

TGF-beta treatment modulates PD-L1 and CD40 expression in proximal renal tubular epithelial cells and enhances CD8 cytotoxic T-cell responses

BACKGROUND/AIM

TGF-beta expression is increased in immune-mediated and fibrotic renal diseases and modulates the tubulointerstitial T-cell response. We examined whether TGF-beta changes the expression of PD-L1 and CD40 in the renal proximal tubular epithelial cell (TEC), and whether the activation of CD8(+) cytotoxic T cells (CTLs) is influenced by TGF-beta treatment of TECs.

METHODS

Murine TECs were treated with TGF-beta or IFN-gamma. The expression of PD-L1 and CD40 was examined with RT-PCR and flow cytometry. To investigate if TGF-beta treatment influenced the antigen presentation capacity of TECs, OT-1 CTLs were co-incubated with TGF-beta-treated, OVA(257-264) peptide-pulsed congeneic TECs. The cytotoxicity of OT-1 CTLs was estimated by their capacity to produce IFN-gamma and their cytolytic activity.

RESULTS

TGF-beta treatment lead to a transition in morphology of renal TECs and downregulated the basal and the IFN-gamma-stimulated PD-L1 expression in TECs. Interestingly, TGF-beta treatment of TECs increased the constitutive and IFN-gamma-induced CD40 expression. In contrast to IFN-gamma which reduced the CTL activity, TGF-beta treatment of TECs elevated the OVA-specific CTL response.

CONCLUSION

Our data show that TGF-beta changed the cellular phenotype and the expression of PD-L1 and CD40 on TECs and enhanced the activity of OVA peptide-specific CD8(+) T cells. TGF-beta may thereby play an important role in the progression of renal tubulointerstitial damage in CD8(+) T-cell-mediated renal diseases.

Effect of 15d-PGJ2 on the expression of CD40 and RANTES induced by IFN-gamma and TNF-alpha on renal tubular epithelial cells (HK-2)

BACKGROUND/AIMS

Recent evidence shows that peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ameliorates a variety of inflammatory conditions. CD40 is a co-stimulatory molecule and its ligation induces production of different proinflammatory cytokines including RANTES (regulated upon activation, normal T cell expressed), which are considered as important factors in the initiation and maintenance of inflammatory response. The aim of this study was to investigate the effect of PPAR-gamma on CD40 and RANTES production on cultured human renal proximal tubular epithelial (HK-2) cells.

METHODS

HK-2 cells were maintained under defined in vitro conditions and treated with either PPAR-gamma agonist 15-deoxy-12,14-prostaglandin J2 (15d-PGJ2) or 15d-PGJ2 + PPAR-gamma antagonist GW9662, and then stimulated with a combination of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). The CD40 and RANTES levels were investigated.

RESULTS

HK-2 cells expressed low levels of CD40 and RANTES. Activation of HK-2 cells by combined treatment of TNF-alpha and IFN-gamma results in strong synergistic effects on the expression of CD40 and the secretion of RANTES. 15d-PGJ2 significantly decreased CD40 and RANTES expression and GW9662 partly abrogated the inhibition of 15d-PGJ2 on CD40 and RANTES.

CONCLUSION

15d-PGJ2 significantly decreased CD40 and RANTES expression in HK-2 cells, which were partially mediated by PPAR-gamma-dependent pathways. These results point to PPAR-gamma as a remarkable new target in the prevention of tubular inflammatory injury associated with renal disease.

Emergence of targeted immune therapies for systemic lupus

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease, characterised by flares of rampant inflammation that can threaten, in an unpredictable manner, almost any organ in the body. Current standard of care is largely empiric, involving the use of corticosteroids and toxic immune suppressive agents that are widely acknowledged to have unacceptable side effects for long-term use. Recently, there have been significant advances in understanding the nature of some fundamental immune imbalances underlying the complicated clinical manifestations of SLE. Nevertheless attempts to develop and test more targeted, and potentially safer immune-modulating drugs for lupus have encountered significant obstacles, due to the lack of validated biological markers for disease flare and remission, and difficulties in the clinical assessment of the heterogeneous patients. In support of renewed interest in drug development for lupus, large collaborative groups have formed, and efforts are underway to develop objective biomarkers for SLE as well as to improve the standardisation and reproducibility of clinical outcome measures in multi-centre trials.

CD40L proinflammatory and profibrotic effects on proximal tubular epithelial cells: role of NF-kappaB and lyn

Chronic allograft nephropathy (CAN) is the main cause of renal graft loss, but its pathogenic mechanisms are still unclear. Immune system activation has been suggested as a key event in the development of CAN. CD40 is a co-stimulatory protein whose expression is upregulated in proximal tubular epithelial cells (PTEC) in acute rejection. This receptor interacts with CD40L, expressed by activated T cells. CD40L induces the production by PTEC of different proinflammatory cytokines, but very little is known of its profibrotic effects. The aim of this study was to investigate the effect of CD40/CD40L interaction on PTEC expression of plasminogen activator inhibitor-1 (PAI-1), a powerful profibrotic mediator, and monocyte chemoattractant protein-1 (MCP-1), a proinflammatory cytokine, and to investigate the signaling pathways that lead to these effects. Soluble CD40L induced a time-dependent increase in both PAI-1 and MCP-1 gene expression and protein production in PTEC. CD40 cross-linking on PTEC caused TNF-R-associated factors 2 and 6 membrane translocation. This event led to NF-kappaB activation, through the NF-kappaB-inducing kinase, and to a significant increase in the phosphorylation of lyn, a src-related tyrosine kinase. Lyn, upon phosphorylation, became strictly associated with caveolin-1, a scaffolding protein enriched in caveolae. Lyn inhibition did not have any effect on CD40L-induced NF-kappaB activation and MCP-1 expression but abolished PAI-1 induction. On the contrary, NF-kappaB inhibition significantly reduced only MCP-1 expression. In conclusion, CD40L could play a key role in the pathogenesis of CAN through PAI-1 induction. CD40L profibrotic and proinflammatory effects are mediated by different signaling pathways, suggesting that drugs that inhibit inflammation may not be equally effective in reducing fibrosis.

Activation of mesangial cells by platelets in systemic lupus erythematosus via a CD154-dependent induction of CD40

BACKGROUND

Platelets are potential contributors to glomerular injury via the release of chemotactic and/or mitogenic mediators upon activation or through direct CD154/CD40-dependent interaction with cell components of the glomerulus. We examined whether platelets could activate mesangial cells and the potential role of the platelet-associated CD154.

METHODS

Thrombin-activated platelets from systemic lupus erythematosus (SLE) patients or from disease or healthy controls were grown with human mesangial cells in the presence or not of a neutralizing anti-CD154 antibody either in contact or in a noncontact setting, the platelets and mesangial cells being separated by a pore size semipermeable membrane. The induction of mesangial cell surface antigens was assayed by flow cytometry. The quantification of mesangial cell proliferation was performed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and the production of transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor (PDGF) and soluble CD40 were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Activated platelets from patients with SLE could induce an up-regulation of the expression of CD40 on mesangial cells with a concomitant release of soluble CD40. This induction required a direct contact between platelets and mesangial cells and was dependent upon the platelet-associated CD154. Pathologic consequences of the up-regulation of CD40 were a CD40-dependent stimulation of the proliferation of mesangial cells and a CD40-dependent increased production of TGF-beta1 by these cells.

CONCLUSION

Platelets from patients with SLE can activate mesangial cells through CD40/CD154 interactions, leading to an induction of proliferation of the mesangial cells and an enhanced production of TGF-beta1, a profibrotic cytokine.

[Platelet-associated CD154: a new interface in haemostasis and in the inflammatory reaction]

Blood platelets play a crucial part in the blood clotting process by forming the platelet plug. Recent evidence indicates that they are likely to play a key role in the inflammatory reaction via CD154/CD40 interactions. CD40 was known to be widely expressed, for instance on cells of the vasculature including endothelial cells, smooth muscle cells and macrophages. It was also known that the triggering of CD40 on these cells led to the acquisition of an activated pro-inflammatory and pro-coagulant phenotype. It was subsequently shown that platelets express CD154 which is cryptic in unstimulated platelets but is expressed at the platelet surface upon platelet activation. When expressed at the platelet surface and exposed to CD40-expressing vascular cells, the platelet-associated CD154 triggers a variety of pro-inflammatory and pro-coagulant responses including induction of adhesion receptors, release of cytokines and chemokines, induction of tissue factor and of metalloproteinases. Platelet-associated CD154 is also involved in platelet/platelet interactions during platelet aggregation. Furthermore, in vivo models have emphasized the critical role of the platelet-associated CD154 in the progression of atherosclerotic disease and in the stabilization of arterial thrombi. Recent data show that CD40-bearing cells involved in fibrosis such as hepatic stellate cells and glomerular mesangial cells also respond to platelet-associated CD154, thus suggesting a new mechanism by which platelets may be instrumental in the inflammatory diseases of the liver or the kidney. Finally, platelet-associated CD154 has been shown to have immune competence both in vitro and in vivo, observations that open new fields of research on the potential implications of platelets in the immune response and auto-immune diseases.

Macrophages and progressive tubulointerstitial disease

Macrophages and progressive tubulointerstitial disease. In chronic renal disease, tubulointerstitial inflammation and injury is associated with infiltrating macrophages. As a consequence of primary injury, proteinuria, chronic hypoxia, and glomerular-derived cytokines may all differentially modulate the expression of factors that promote macrophage recruitment. In addition to adhesion molecules and chemokines, products of complement system and renin-angiotensin system activation may direct this process. Once present at interstitial sites, macrophages interact with resident cells and extracellular matrix to generate a proinflammatory microenvironment that amplifies tissues injury and promotes scarring. There is now increasing evidence for the efficacy of interventions directed against factors that recruit, activate, or are produced by macrophages. A detailed understanding of the biology of this area may lead to the further development of therapies that will improve the outcome of renal disease.

SGK1 as a determinant of kidney function and salt intake in response to mineralocorticoid excess

Mineralocorticoids modify salt balance by both stimulating salt intake and inhibiting salt loss. Renal salt retention is accomplished by upregulation of reabsorption, an effect partially mediated by serum- and glucocorticoid-inducible kinase 1 (SGK1). The present study explored the contribution of SGK1 to the regulation of renal function, salt intake, and blood pressure during mineralocorticoid excess. DOCA/1% NaCl treatment increased blood pressure and creatinine clearance to a similar extent in SGK1-deficient sgk1−/−and wild-type sgk1+/+mice but led to more pronounced increase of proteinuria in sgk1+/+mice (by 474 ± 89%) than in sgk1−/−mice (by 154 ± 31%). DOCA/1% NaCl treatment led to significant increase of kidney weight (by 24%) and to hypokalemia (from 3.9 ± 0.1 to 2.7 ± 0.1 mmol/l) only in sgk1+/+mice. The treatment enhanced renal Na+excretion significantly more in sgk1+/+mice (from 3 ± 1 to 134 ± 32 μmol·24 h−1·g body wt−1) than in sgk1−/−mice (from 4 ± 1 to 49 ± 8 μmol·24 h−1·g body wt−1), pointing to SGK1-dependent stimulation of salt intake. With access to two drinking bottles containing 1% NaCl or water, DOCA treatment did not significantly affect water intake in either genotype but increased 1% NaCl intake in sgk1+/+mice (within 9 days from 3.5 ± 0.9 to 16.5 ± 2.4 ml/day) consistent with DOCA-induced salt appetite. This response was significantly attenuated in sgk1−/−mice (from 2.6 ± 0.6 to 5.9 ± 0.9 ml/day). Thus SGK1 contributes to the stimulation of salt intake, kidney growth, proteinuria, and renal K+excretion during mineralocorticoid excess.

CD40: A Mediator of Pro- and Anti-Inflammatory Signals in Renal Tubular Epithelial Cells

Infiltration of immune cells into the renal interstitium is characteristic of chronic inflammatory kidney diseases. CD4+ T cells and platelets express CD40 ligand (CD40L) and are reported to mediate proinflammatory events in renal proximal tubular epithelial cells (RPTEC) via interaction with CD40. In other cell types, CD40 signals can also induce protective genes. Here, human RPTEC were treated with sCD40L to ligate CD40, and a significant increase in the generation of proinflammatory reactive oxygen species was found; however, CD40-activated cells did not undergo apoptosis. This suggests that CD40 signals may simultaneously induce antiapoptotic genes for cytoprotection of RPTEC. Heme oxygenase-1 (HO-1) expressed in RPTEC serves as a protective gene, but it is not known whether it is regulated by CD40. Next, RPTEC were transiently transfected with a full-length HO-1 promoter-luciferase construct and were treated with sCD40L. CD40 ligation was found to significantly increase HO-1 promoter activity. By electrophoretic mobility shift assay, it was confirmed that CD40 signaling induced the transcriptional activation of HO-1 through the binding of NF-kappaB to its promoter. By Western blot analysis, a marked increase in HO-1 protein expression following CD40 ligation was also found. These observations are of clinical significance because it was found that CD40 and HO-1 are induced in expression in vivo in inflamed rejecting kidney biopsies and co-expressed in renal tubules. Therefore, ligation of CD40 in RPTEC promotes both inflammatory and anti-inflammatory processes. Regulating the balance between these two events may be of importance in the prevention of tubular injury associated with renal disease.

The role of tubulointerstitial inflammation

BACKGROUND

Exploration of the role of tubulointerstitial inflammation in experimental chronic renal disease (CRD) is an essential step to understanding and finding new treatments for human CRD. Adriamycin nephrosis (AN) is an experimental analogue of human focal glomerular sclerosis and tubulointerstitial inflammation.

METHODS

Using murine and rat AN, we have systematically investigated the pathogenic roles of chemokines, costimulatory molecules, and inflammatory cells, such as macrophages and effector and regulatory T lymphocytes. The profile of humoral and cellular mediators was studied in vitro and in vivo. The pathogenic significance of various factors was investigated by DNA vaccination, leukocyte reconstitution and depletion, retroviral transduction, and blockade with monoclonal antibodies.

RESULTS

Renal cortical and tubular cell CC-chemokines, including MCP-1, RANTES, and MIP-1alpha, were up-regulated via mediation of NFkappaB, and contributed to disease by attracting inflammatory cells into the interstitium. The role of these chemokines was confirmed by DNA vaccination. CD40-CD40L costimulation signals were involved in expansion and activation of the inflammatory infiltrate, whereas PD-1 signals were inhibitory, and CD28-B7 appeared to have a neutral effect. Macrophage and CD8+ T cells were shown to be effectors of injury, whereas CD4+CD25+ and gammadelta T cells acted as regulatory cells. FoxP3 transduction was able to convert naive T cells to CD4+CD25+ regulatory T cells.

CONCLUSION

There is a broad range of humoral and cellular factors involved in the pathogenesis of experimental CRD, some of which are potential targets for treatment of human CRD.

Challenges in bringing the bench to bedside in drug development for sle

It is now widely accepted that the current standard of care for systemic lupus erythematosus (SLE) patients is inadequate. There has not been a new medication approved for this disease in thirty years. Attempts to develop and test new drugs have been ongoing since the mid-1990s, but have encountered formidable obstacles. Current models for lupus pathogenesis have provided a theoretical framework for understanding how heterogeneous genetic defects might combine in various ways to increase susceptibility to SLE in different individuals, and could have important implications for new drug development. With the current burst of drug discovery and increased public awareness of SLE, the impetus to overcome these obstacles has never been greater.

The CD40/CD40L costimulatory pathway in inflammatory bowel disease

The CD154-CD40 ligand pair interaction plays a central role in both induction of the immune response and in immune effector functions. Indeed, many animal disease models and human autoimmune diseases have demonstrated a central role for CD154 expression. The expression of CD154 is very tightly regulated by the immune system through a number of non-redundant overlapping mechanisms that ensure its limited initial induction, along with its temporal maintenance and rapid elimination from the cell surface, and its functional neutralization by the release of soluble CD40. In this review, we discuss the current state of understanding of CD154 regulation during the activation of the immune system and describe numerous strategic mechanisms by which modulation of CD154-CD40 interactions may be applied to treat autoimmune disease.