Potential and Uncertainties of RejectClass in Acute Kidney Graft Dysfunction: An Independent Validation Study

BACKGROUND

Kidney graft rejections are classified based on the Banff classification. The RejectClass algorithm, initially derived from a cohort comprising mostly protocol biopsies, identifies data-driven phenotypes of acute rejection and chronic pathology using Banff lesion scores. It also provides composite scores for inflammation activity and chronicity. This study independently evaluates the performance of RejectClass in a cohort consisting entirely of indication biopsies.

METHODS

We retrospectively applied RejectClass to 441 patients from the German TRABIO (TRAnsplant BIOpsies) cohort who had received indication biopsies. The primary endpoint was death-censored graft failure during 2 y of follow-up.

RESULTS

The application of RejectClass to our cohort demonstrated moderately comparable phenotypic features with the derivation cohort, and most clusters indicated an elevated risk of graft loss. However, the reproduction of all phenotypes and the associated risks of graft failure, as depicted in the original studies, was not fully accomplished. In contrast, adjusted Cox proportional hazards analyses substantiated that both the inflammation score and the chronicity score are independently associated with graft loss, exhibiting hazard ratios of 1.7 (95% confidence interval, 1.2-2.3; P = 0.002) and 2.2 (95% confidence interval, 1.8-2.6; P < 0.001), respectively, per 0.25-point increment (scale: 0.0-1.0).

CONCLUSIONS

The composite inflammation and chronicity scores may already have direct utility in quantitatively assessing the disease stage. Further refinement and validation of RejectClass clusters are necessary to achieve more reliable and accurate phenotyping of rejection.

Inhibition of the renal apical sodium dependent bile acid transporter prevents cholemic nephropathy in mice with obstructive cholestasis

BACKGROUND & AIMS

Cholemic nephropathy (CN) is a severe complication of cholestatic liver diseases for which there is no specific treatment. We revisited its pathophysiology with the aim of identifying novel therapeutic strategies.

METHODS

Cholestasis was induced by bile duct ligation (BDL) in mice. Bile flux in kidneys and livers was visualized by intravital imaging, supported by MALDI mass spectrometry imaging and liquid chromatography-tandem mass spectrometry. The effect of AS0369, a systemically bioavailable apical sodium-dependent bile acid transporter (ASBT) inhibitor, was evaluated by intravital imaging, RNA-sequencing, histological, blood, and urine analyses. Translational relevance was assessed in kidney biopsies from patients with CN, mice with a humanized bile acid (BA) spectrum, and via analysis of serum BAs and KIM-1 (kidney injury molecule 1) in patients with liver disease and hyperbilirubinemia.

RESULTS

Proximal tubular epithelial cells (TECs) reabsorbed and enriched BAs, leading to oxidative stress and death of proximal TECs, casts in distal tubules and collecting ducts, peritubular capillary leakiness, and glomerular cysts. Renal ASBT inhibition by AS0369 blocked BA uptake into TECs and prevented kidney injury up to 6 weeks after BDL. Similar results were obtained in mice with humanized BA composition. In patients with advanced liver disease, serum BAs were the main determinant of KIM-1 levels. ASBT expression in TECs was preserved in biopsies from patients with CN, further highlighting the translational potential of targeting ASBT to treat CN.

CONCLUSIONS

BA enrichment in proximal TECs followed by oxidative stress and cell death is a key early event in CN. Inhibiting renal ASBT and consequently BA enrichment in TECs prevents CN and systemically decreases BA concentrations.

IMPACT AND IMPLICATIONS

Cholemic nephropathy (CN) is a severe complication of cholestasis and an unmet clinical need. We demonstrate that CN is triggered by the renal accumulation of bile acids (BAs) that are considerably increased in the systemic blood. Specifically, the proximal tubular epithelial cells of the kidney take up BAs via the apical sodium-dependent bile acid transporter (ASBT). We developed a therapeutic compound that blocks ASBT in the kidneys, prevents BA overload in tubular epithelial cells, and almost completely abolished all disease hallmarks in a CN mouse model. Renal ASBT inhibition represents a potential therapeutic strategy for patients with CN.

Single Nucleotide Polymorphisms Associated with AA-Amyloidosis in Siamese and Oriental Shorthair Cats

AA-amyloidosis in Siamese and Oriental shorthair cats is a lethal condition in which amyloid deposits accumulate systemically, especially in the liver and the thyroid gland. The age at death of affected cats varies between one and seven years. A previous study indicated a complex mode of inheritance involving a major locus. In the present study, we performed a multi-locus genome-wide association study (GWAS) using five methods (mrMLM, FASTmrMLM, FASTmrEMMA, pLARmEB and ISIS EM-BLASSO) to identify variants associated with AA-amyloidosis in Siamese/Oriental cats. We genotyped 20 affected mixed Siamese/Oriental cats from a cattery and 48 healthy controls from the same breeds using the Illumina Infinium Feline 63 K iSelect DNA array. The multi-locus GWAS revealed eight significantly associated single nucleotide polymorphisms (SNPs) on FCA A1, D1, D2 and D3. The genomic regions harboring these SNPs contain 55 genes, of which 3 are associated with amyloidosis in humans or mice. One of these genes is SAA1, which encodes for a member of the Serum Amyloid A family, the precursor protein of Amyloid A, and a mutation in the promotor of this gene causes hereditary AA-amyloidosis in humans. These results provide novel knowledge regarding the complex genetic background of hereditary AA-amyloidosis in Siamese/Oriental cats and, therefore, contribute to future genomic studies of this disease in cats.

High Macrophage Densities in Native Kidney Biopsies Correlate With Renal Dysfunction and Promote ESRD

Introduction

Macrophages and monocytes are main players in innate immunity. The relevance of mononuclear phagocyte infiltrates on clinical outcomes remains to be determined in native kidney diseases.

Methods

Our cross-sectional study included 324 patients with diagnostic renal biopsies comprising 17 disease entities and normal renal tissues for comparison. All samples were stained for CD68⁺ macrophages. Selected groups were further subtyped for CD14⁺ monocytes and CD163⁺ alternatively activated macrophages. Using precise pixel-based digital measurements, we quantified cell densities as positively stained areas in renal cortex and medulla as well as whole renal tissue. Laboratory and clinical data of all cases at the time of biopsy and additional follow-up data in 158 cases were accessible.

Results

Biopsies with renal disease consistently revealed higher CD68⁺-macrophage densities and CD163⁺-macrophage densities in cortex and medulla compared to controls. High macrophage densities correlated with impaired renal function at biopsy and at follow-up in all diseases and in diseases analyzed separately. High cortical CD68⁺-macrophage densities preceded shorter renal survival, defined as requirement of permanent dialysis. CD14⁺ monocyte densities showed no difference compared to controls and did not correlate with renal function.

Conclusion

Precise quantification of macrophage densities in renal biopsies may contribute to risk stratification to identify patients with high risk for end-stage renal disease (ESRD) and might be a promising therapeutic target in renal disease.

Amyloidogenicity assessment of transthyretin gene variants

Objective

Hereditary transthyretin‐mediated amyloidosis is a treatable condition caused by amyloidogenic variants in the transthyretin‐gene resulting in severe peripheral neuropathy or cardiomyopathy. Only about a third of over 130 known variants are clearly pathogenic, most are classified as variants of uncertain significance. A clear delineation of these into pathogenic or non‐pathogenic is highly desirable but hampered by low frequency and penetrance. We thus sought to characterize their amylogenic potential by an unbiased in vitro approach.

Methods

Thioflavin T and turbidity assays were used to compare the potential of mammalian cell expressed wt‐transthyretin and 12 variant proteins (either variants of uncertain significance, benign, pathogenic) to aggregate and produce amyloid fibrils in vitro. As proof of principle, the assays were applied to transthyretin‐Ala65Val, a variant that was newly detected in a family with peripheral neuropathy and amyloid deposits in biopsies. In silico analysis was performed to compare the position of the benign and pathogenic variants.

Results

Transthyretin‐Ala65Val showed a significantly higher amyloidogenic potential than wt‐transthyretin, in both turbidity‐ and Thioflavin T‐assays, comparable to known pathogenic variants. The other eight tested variants did not show an increased amyloidogenic potential. In silico structural analysis further confirmed differences between pathogenic and benign variants in position and interactions.

Interpretation

We propose a biochemical approach to assess amyloidogenic potential of transthyretin variants. As exemplified by transthyretin‐Ala65Val, data of three assays together with histopathology clearly demonstrates its amyloidogenicity.

Long-term B cell depletion associates with regeneration of kidney function

Background

Chronic kidney disease (CKD) is a common condition that increases mortality and the risk of cardiovascular and other morbidities regardless of underlying renal condition. Chronic inflammation promotes renal fibrosis. Recently, renal B cell infiltrates were described in chronic kidney disease of various etiologies beyond autoimmunity.

Methods

We here investigated B cells and indicators of tertiary lymphoid structure formation in human renal biopsies. Renal function was studied during long‐term B cell depletion in human patients with membranous nephropathy and with CKD of unknown origin.

Results

Cytokine profiles of tertiary lymphoid structure formation were detected in human renal interstitium in a range of kidney diseases. Complex B cell structures consistent with tertiary lymphoid organ formation were evident in human membranous nephropathy. Here, B cell density did not significantly associate with proteinuria severity, but with worse excretory renal function. Proteinuria responses mostly occurred within the first 6 months of B cell depletion. In contrast, recovery of excretory kidney function was observed only after 18 months of continuous therapy, consistent with a structural process. Renal tertiary lymphatic structures were also detected in the absence of autoimmune kidney disease. To start to address whether B cell depletion may affect CKD in a broader population, we assessed kidney function in neurologic patients with CKD of unknown origin. In this cohort, eGFR significantly increased within 24 months of B cell depletion.

Conclusion

Long‐term B cell depletion associated with significant improvement of excretory kidney function in human CKD. Kinetics and mechanisms of renal B cell aggregation should be investigated further to stratify the impact of B cells and their aggregates as therapeutic targets.

Rare germline variants in the E-cadherin gene CDH1 are associated with the risk of brain tumors of neuroepithelial and epithelial origin

The genetic basis of brain tumor development is poorly understood. Here, leukocyte DNA of 21 patients from 15 families with ≥ 2 glioma cases each was analyzed by whole-genome or targeted sequencing. As a result, we identified two families with rare germline variants, p.(A592T) or p.(A817V), in the E-cadherin gene CDH1 that co-segregate with the tumor phenotype, consisting primarily of oligodendrogliomas, WHO grade II/III, IDH-mutant, 1p/19q-codeleted (ODs). Rare CDH1 variants, previously shown to predispose to gastric and breast cancer, were significantly overrepresented in these glioma families (13.3%) versus controls (1.7%). In 68 individuals from 28 gastric cancer families with pathogenic CDH1 germline variants, brain tumors, including a pituitary adenoma, were observed in three cases (4.4%), a significantly higher prevalence than in the general population (0.2%). Furthermore, rare CDH1 variants were identified in tumor DNA of 6/99 (6%) ODs. CDH1 expression was detected in undifferentiated and differentiating oligodendroglial cells isolated from rat brain. Functional studies using CRISPR/Cas9-mediated knock-in or stably transfected cell models demonstrated that the identified CDH1 germline variants affect cell membrane expression, cell migration and aggregation. E-cadherin ectodomain containing variant p.(A592T) had an increased intramolecular flexibility in a molecular dynamics simulation model. E-cadherin harboring intracellular variant p.(A817V) showed reduced β-catenin binding resulting in increased cytosolic and nuclear β-catenin levels reverted by treatment with the MAPK interacting serine/threonine kinase 1 inhibitor CGP 57380. Our data provide evidence for a role of deactivating CDH1 variants in the risk and tumorigenesis of neuroepithelial and epithelial brain tumors, particularly ODs, possibly via WNT/β-catenin signaling.

Targeting muscle-enriched long non-coding RNA H19 reverses pathological cardiac hypertrophy

AIMS

Pathological cardiac remodelling and subsequent heart failure represents an unmet clinical need. Long non-coding RNAs (lncRNAs) are emerging as crucial molecular orchestrators of disease processes, including that of heart diseases. Here, we report on the powerful therapeutic potential of the conserved lncRNA H19 in the treatment of pathological cardiac hypertrophy.

METHOD AND RESULTS

Pressure overload-induced left ventricular cardiac remodelling revealed an up-regulation of H19 in the early phase but strong sustained repression upon reaching the decompensated phase of heart failure. The translational potential of H19 is highlighted by its repression in a large animal (pig) model of left ventricular hypertrophy, in diseased human heart samples, in human stem cell-derived cardiomyocytes and in human engineered heart tissue in response to afterload enhancement. Pressure overload-induced cardiac hypertrophy in H19 knock-out mice was aggravated compared to wild-type mice. In contrast, vector-based, cardiomyocyte-directed gene therapy using murine and human H19 strongly attenuated heart failure even when cardiac hypertrophy was already established. Mechanistically, using microarray, gene set enrichment analyses and Chromatin ImmunoPrecipitation DNA-Sequencing, we identified a link between H19 and pro-hypertrophic nuclear factor of activated T cells (NFAT) signalling. H19 physically interacts with the polycomb repressive complex 2 to suppress H3K27 tri-methylation of the anti-hypertrophic Tescalcin locus which in turn leads to reduced NFAT expression and activity.

CONCLUSION

H19 is highly conserved and down-regulated in failing hearts from mice, pigs and humans. H19 gene therapy prevents and reverses experimental pressure-overload-induced heart failure. H19 acts as an anti-hypertrophic lncRNA and represents a promising therapeutic target to combat pathological cardiac remodelling.

Intragraft gene expression in native kidney BK virus nephropathy versus T cell-mediated rejection: Prospects for molecular diagnosis and risk prediction

Novel tools are needed to improve diagnostic accuracy and risk prediction in BK virus nephropathy (BKVN). We assessed the utility of intragraft gene expression testing for these purposes. Eight hundred genes were measured in 110 archival samples, including a discovery cohort of native kidney BKVN (n = 5) vs pure T cell-mediated rejection (TCMR; n = 10). Five polyomavirus genes and seven immune-related genes (five associated with BKVN and two associated with TCMR) were significantly differentially expressed between these entities (FDR < 0.05). These three sets of genes were further evaluated in samples representing a spectrum of BK infection (n = 25), followed by a multicenter validation cohort of allograft BKVN (n = 60) vs TCMR (n = 10). Polyomavirus 5-gene set expression reliably distinguished BKVN from TCMR (validation cohort AUC = 0.992), but the immune gene sets demonstrated suboptimal diagnostic performance (AUC ≤ 0.720). Within the validation cohort, no significant differences in index biopsy gene expression were identified between BKVN patients demonstrating resolution (n = 35), persistent infection (n = 14) or de novo rejection (n = 11) 6 months following a standardized reduction in immunosuppression. These results suggest that, while intragraft polyomavirus gene expression may be useful as an ancillary diagnostic for BKVN, assessment for concurrent TCMR and prediction of clinical outcome may not be feasible with current molecular tools.

Complex segregation analysis of familial amyloidosis in Oriental shorthair cats

Amyloidosis in Siamese/Oriental cats is a lethal condition with variable age of clinical onset. There is no sex predisposition and clinical signs of disease usually become apparent by 1-7 years of age. In the terminal stages, the liver is enlarged and pale, and contains parenchymal hemorrhages. In the present study, pedigree data from 17 cats with clinical signs consistent with amyloidosis underwent genetic analysis. Necropsy and histopathological data were available for 10 of the 17 cats. Necropsy findings included pale, fragile and enlarged livers with capsular ruptures and parenchymal hemorrhages, and sanguineous effusions in the abdominal cavity. Congo red staining with birefringence confirmed systemic amyloidosis mostly involving the liver and thyroid gland. In four of the 10 cases, protein deposits were classified as amyloid A protein (AA-amyloid) by immunostaining. Pedigree data for all 17 affected cats indicated a familial trait. Animal threshold model analysis demonstrated that the heritability for amyloidosis was 0.56 ± 0.09 (standard error). Complex segregation analysis was used for statistical comparisons among models to determine environmental or sex dependent effects, and Mendelian, polygenic, or mixed Mendelian and polygenic inheritance patterns. A mixed model with a Mendelian and polygenic component provided the best fit to the data and thus was most likely. All other models of inheritance were rejected due to their insufficient ability to explain segregation of amyloidosis. In conclusion, we found evidence for a complex genetic basis for amyloidosis in Oriental shorthair cats.

The role of protocol biopsies after pediatric kidney transplantation

Data on protocol biopsies (PBs) after pediatric kidney transplantation are rare.We evaluated 6-month post-transplantation renal function in 86 children after PB as observational study. Patients were divided into 3 groups:Glomerular filtration rate (GFR) and delta GFR were determined.PBs 6 months post-kidney transplantation did not influence the clinical course in stable pediatric patients and are therefore of questionable value. Decreased kidney function may however be stabilized by therapeutic intervention according to results of PB.

Characterizing renal involvement in Hermansky-Pudlak Syndrome in a zebrafish model

Hermansky-Pudlak Syndrome (HPS) is a rare disease caused by mutations in the genes coding for various HPS proteins. HPS proteins are part of multi-subunit complexes involved in the biogenesis of organelles from the lysosomal-endosomal-system. In humans, this syndrome is characterized by the presence of albinism, platelet dysfunction and pulmonary fibrosis. The renal component to the disease remains unstudied and untreated in patients with HPS. Here we demonstrate that in humans, HPS proteins have a high renal expression with active transcription of HPS1, 3, 4 and 5 in human podocyte cell culture, suggesting that impaired function of HPS proteins could directly impact renal function. Therefore, we developed a zebrafish model to study the renal involvement of HPS proteins in proteinuric kidney disease. Remarkably, knockdown of HPS genes in zebrafish causes glomerular injury with edema, proteinuria and structural changes of the glomerular filtration barrier. Moreover, reduced expression of HPS proteins in zebrafish recapitulates other important disease hallmarks, like hypopigmentation and accumulation of intracellular debris characteristic of lysosomal disorders. In conclusion, we present a valid zebrafish model that highlights the previously underestimated relevance of renal disease in HPS. This draws attention to the therapeutic options available to manage this component of the syndrome.

Kidney injury enhances renal G-CSF expression and modulates granulopoiesis and human neutrophil CD177 in vivo

Kidney injury significantly increases overall mortality. Neutrophilic granulocytes (neutrophils) are the most abundant human blood leukocytes. They are characterized by a high turnover rate, chiefly controlled by granulocyte colony stimulating factor (G‐CSF). The role of kidney injury and uremia in regulation of granulopoiesis has not been reported. Kidney transplantation, which inherently causes ischemia–reperfusion injury of the graft, elevated human neutrophil expression of the surface glycoprotein CD177. CD177 is among the most G‐CSF‐responsive neutrophil genes and reversibly increased on neutrophils of healthy donors who received recombinant G‐CSF. In kidney graft recipients, a transient rise in neutrophil CD177 correlated with renal tubular epithelial G‐CSF expression. In contrast, CD177 was unaltered in patients with chronic renal impairment and independent of renal replacement therapy. Under controlled conditions of experimental ischemia–reperfusion and unilateral ureteral obstruction injuries in mice, renal G‐CSF mRNA and protein expression significantly increased and systemic neutrophilia developed. Human renal tubular epithelial cell G‐CSF expression was promoted by hypoxia and proinflammatory cytokine interleukin 17A in vitro. Clinically, recipients of ABO blood group‐incompatible kidney grafts developed a larger rise in neutrophil CD177. Their grafts are characterized by complement C4d deposition on the renal endothelium, even in the absence of rejection. Indeed, complement activation, but not hypoxia, induced primary human endothelial cell G‐CSF expression. Our data demonstrate that kidney injury induces renal G‐CSF expression and modulates granulopoiesis. They delineate differential G‐CSF regulation in renal epithelium and endothelium. Altered granulopoiesis may contribute to the systemic impact of kidney injury.

Kidney graft survival of >25 years: a single center report including associated graft biopsy results

Only few centers have reported their observations on patients with very long-term kidney graft survival of more than 25 years. Eighty-six subjects were identified in our center with graft survival of >25 years. Donor age was 31.3 ± 18.5 years. Mean duration of transplantation was 30.3 ± 3.6 years. At last follow-up, the cystatin C clearance was 47 ± 23 ml/min. Transplant biopsies for cause were performed in 30 subjects at a median of 28.4 years (19.1-40.3) after transplantation. Acute or chronic active T cell-mediated rejection was present in five cases and histological characteristics of acute or chronic active humoral rejection in eight cases. More than 80% of biopsies had inflammatory infiltrates in nonatrophic or atrophic cortical areas. The number of HLA mismatches were higher in biopsied subjects (3.0 ± 1.8 vs. 2.2 ± 1.7 without biopsy). Immunosuppressive therapy was adapted in most biopsied subjects; impaired graft function and proteinuria was unchanged at last follow-up. Sixty percent of all subjects had hyperparathyroidism (iPTH of the whole group: 132 ± 157 pg/ml), which was predominantly secondary, as judged by serum calcium and graft function. Young donor age was certainly a prerequisite of longterm graft survival. Nonetheless, inflammation or rejection in most biopsied patients suggests an important role of alloreactivity even in this late course.

Prognostic relevance of topoisomerase II α and minichromosome maintenance protein 6 expression in colorectal cancer

BACKGROUND

Despite rising incidence rates of colorectal malignancies, only a few prognostic tools have been implemented in proven clinical routine. Cell division and proliferation play a significant role in malignancies. In terms of colorectal cancer, the impact of proliferation associated proteins is controversially debated. The aim of our study was to examine the expression of topoisomerase II α and minichromosome maintenance protein 6 and to correlate these findings with the clinical data.

METHODS

Tissue samples of 619 patients in total were stained using the antibodies Ki-S4 and Ki-MCM6 targeting topoisomerase II α as well as minichromosome maintenance protein 6. The median rate of proliferation was correlated with clinical and follow up data.

RESULTS

The expression rate of minichromosome maintenance protein 6 is significantly higher than the proportion of topoisomerase II α in tumour cells (p < 0.001). A high expression of both proteins coincides with a beneficial outcome for the patient, indicating a favourable prognostic marker (p < 0.001 and p = 0.008).

CONCLUSIONS

We have demonstrated that high expression rates of proliferative markers is linked to a beneficial patient outcome. According to the general opinion, a high expression rate correlates with a poor patient outcome. In this study, we were able to refute this assertion.

Podocyte-Specific Sialylation-Deficient Mice Serve as a Model for Human FSGS

BACKGROUND

The etiology of steroid-resistant nephrotic syndrome, which manifests as FSGS, is not completely understood. Aberrant glycosylation is an often underestimated factor for pathologic processes, and structural changes in the glomerular endothelial glycocalyx have been correlated with models of nephrotic syndrome. Glycans are frequently capped by sialic acid (Sia), and sialylation's crucial role for kidney function is well known. Human podocytes are highly sialylated; however, sialylation's role in podocyte homeostasis remains unclear.

METHODS

We generated a podocyte-specific sialylation-deficient mouse model (PCmas^-/- ) by targeting CMP-Sia synthetase, and used histologic and ultrastructural analysis to decipher the phenotype. We applied CRISPR/Cas9 technology to generate immortalized sialylation-deficient podocytes (asialo-podocytes) for functional studies.

RESULTS

Progressive loss of sialylation in PCmas^-/- mice resulted in onset of proteinuria around postnatal day 28, accompanied by foot process effacement and loss of slit diaphragms. Podocyte injury led to severe glomerular defects, including expanded capillary lumen, mesangial hypercellularity, synechiae formation, and podocyte loss. In vivo, loss of sialylation resulted in mislocalization of slit diaphragm components, whereas podocalyxin localization was preserved. In vitro, asialo-podocytes were viable, able to proliferate and differentiate, but showed impaired adhesion to collagen IV.

CONCLUSIONS

Loss of cell-surface sialylation in mice resulted in disturbance of podocyte homeostasis and FSGS development. Impaired podocyte adhesion to the glomerular basement membrane most likely contributed to disease development. Our data support the notion that loss of sialylation might be part of the complex process causing FSGS. Sialylation, such as through a Sia supplementation therapy, might provide a new therapeutic strategy to cure or delay FSGS and potentially other glomerulopathies.

[Diagnosis and treatment of kidney involvement in plasma cell diseases : Renal involvement in multiple myeloma and monoclonal gammopathies]

BACKGROUND

Kidney involvement is a common complication in patients with plasma cell diseases.

OBJECTIVE

This article outlines the spectrum of renal involvement in plasma cell dyscrasia and describes diagnostic and therapeutic measures to guide clinical management.

MATERIAL AND METHODS

Evaluation and discussion of the current literature as well as existing guidelines and recommendations of professional societies.

RESULTS

The clinical manifestations of renal involvement in plasma cell disorders are heterogeneous and range from acute cast nephropathy in multiple myeloma to rare forms of glomerulonephritis. The term monoclonal gammopathy of renal significance (MGRS) was introduced to describe kidney involvement caused by monoclonal gammopathy but without evidence for underlying malignancy. Light chain cast nephropathy is the most common renal manifestation in multiple myeloma, whereas monoclonal immunoglobulin deposition disease (MIDD) and renal light chain (AL) amyloidosis can be found in multiple myeloma and MGRS. Decisive is the extended hematological diagnostics in order to exclude the presence of a hematological neoplasm. The treatment of renal involvement in monoclonal gammopathies involves the reduction of the plasma cell clone with cytoreductive treatment. The reduction of the monoclonal protein in serum is prognostically relevant for the renal response to treatment. In the case of histological evidence of a light chain cast nephropathy, high cut-off dialysis is recommended to reduce the free light chains in serum.

CONCLUSION

The spectrum of renal manifestations in plasma cell dyscrasia has been expanded, particularly since the introduction of the term MGRS. Diagnostic and therapeutic management remain an interdisciplinary challenge.

Distinct morphological features of acute tubular injury in renal allografts correlate with clinical outcome

Acute tubular injury (ATI) is common in renal allografts and is related to inferior long-term allograft function. However, it is unknown which of the morphological features of ATI can predict outcome and how they should be graded. Here, we examine features of ATI systematically in protocol biopsies and biopsies for cause to define the most predictive features. Analyses included 521 protocol biopsies taken at 6 wk, 3 mo, and 6 mo after transplantation and 141 biopsies for cause from 204 patients. Features of ATI included brush border loss, tubular epithelial lucency, flattening, pyknosis, nuclei loss, and luminal debris, each graded semiquantitatively. Additional immunohistochemical stainings were performed for markers of cell injury (neutrophil gelatinase-associated lipocalin), cell death [cleaved caspase-3, fatty acid-coenzyme A ligase 4 (FACL4)], and proliferation (K_i-67). Interobserver reliability was good for pyknosis, flattening, and brush border loss and poor for lucency, nuclei loss, and luminal debris. In protocol biopsies between 6 wk and 6 mo, the degree of ATI remained virtually unchanged. Biopsies for cause had generally higher injury scores. Deceased donor source, delayed graft function, ganciclovir/valganciclovir treatment, and urinary tract infection correlated with ATI. The degree of pyknosis, flattening, and brush border loss correlated best with impaired allograft function. FACL4 expression was observed in areas of ATI. Only patients with K_i-67 expression showed stable or improved allograft function in the longitudinal assessment. Reliable assessment of ATI is possible by semiquantitative grading of tubular epithelial cell brush border loss, flattening, and pyknosis. Examination of K_i-67 expression can help determine the potential for recovery from this damage.

Loss of Kynurenine 3-Mono-oxygenase Causes Proteinuria

Changes in metabolite levels of the kynurenine pathway have been observed in patients with CKD, suggesting involvement of this pathway in disease pathogenesis. Our recent genetic analysis in the mouse identified the kynurenine 3-mono-oxygenase (KMO) gene (Kmo) as a candidate gene associated with albuminuria. This study investigated this association in more detail. We compared KMO abundance in the glomeruli of mice and humans under normal and diabetic conditions, observing a decrease in glomerular KMO expression with diabetes. Knockdown of kmo expression in zebrafish and genetic deletion of Kmo in mice each led to a proteinuria phenotype. We observed pronounced podocyte foot process effacement on long stretches of the filtration barrier in the zebrafish knockdown model and mild podocyte foot process effacement in the mouse model, whereas all other structures within the kidney remained unremarkable. These data establish the candidacy of KMO as a causal factor for changes in the kidney leading to proteinuria and indicate a functional role for KMO and metabolites of the tryptophan pathway in podocytes.

TRPC6 G757D Loss-of-Function Mutation Associates with FSGS

FSGS is a CKD with heavy proteinuria that eventually progresses to ESRD. Hereditary forms of FSGS have been linked to mutations in the transient receptor potential cation channel, subfamily C, member 6 (TRPC6) gene encoding a nonselective cation channel. Most of these TRPC6 mutations cause a gain-of-function phenotype, leading to calcium-triggered podocyte cell death, but the underlying molecular mechanisms are unclear. We studied the molecular effect of disease-related mutations using tridimensional in silico modeling of tetrameric TRPC6. Our results indicated that G757 is localized in a domain forming a TRPC6-TRPC6 interface and predicted that the amino acid exchange G757D causes local steric hindrance and disruption of the channel complex. Notably, functional characterization of model interface domain mutants suggested a loss-of-function phenotype. We then characterized 19 human FSGS-related TRPC6 mutations, the majority of which caused gain-of-function mutations. However, five mutations (N125S, L395A, G757D, L780P, and R895L) caused a loss-of-function phenotype. Coexpression of wild-type TRPC6 and TRPC6 G757D, mimicking heterozygosity observed in patients, revealed a dominant negative effect of TRPC6 G757D. Our comprehensive analysis of human disease-causing TRPC6 mutations reveals loss of TRPC6 function as an additional concept of hereditary FSGS and provides molecular insights into the mechanism responsible for the loss-of-function phenotype of TRPC6 G757D in humans.

Diffusion-Weighted imaging and diffusion tensor imaging detect delayed graft function and correlate with allograft fibrosis in patients early after kidney transplantation

PURPOSE

To combine diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) for detection of allograft dysfunction in patients early after kidney transplantation and to correlate diffusion parameters with renal function and renal histology of allograft biopsies.

MATERIALS AND METHODS

Between day 4 and 11 after kidney transplantation 33 patients with initial graft function and 31 patients with delayed graft function (DGF) were examined with a 1.5T magnetic resonance imaging (MRI) scanner. DTI and DWI sequences were acquired and fractional anisotropy (FA), apparent diffusion coefficient (ADCmono), pure diffusion (ADCdiff ), and the perfusion fraction (Fp) were calculated. Kidney biopsies in 26 patients were analyzed for allograft pathology, ie, acute tubular injury, inflammation, edema, renal fibrosis, and rejection. Histological results were correlated with MRI parameters.

RESULTS

In the renal medulla FA (0.25 ± 0.06 vs. 0.29 ± 0.06, P < 0.01) and ADCmono (1.73 ± 0.13*10(-3) vs. 1.93 ± 0.16*10(-3) mm(2) /s, P < 0.001) were significantly reduced in DGF patients compared with patients with initial function. For ADCdiff and Fp similar reductions were observed. FA and ADCmono significantly correlated with renal function (r = 0.53 and r = 0.57, P < 0.001) and were inversely correlated with the amount of renal fibrosis (r = -0.63 and r = -0.65, P < 0.05).

CONCLUSION

Combined DTI and DWI detected allograft dysfunction early after kidney transplantation and correlated with allograft fibrosis. J. Magn. Reson. Imaging 2016;44:112-121.

[Transplant Surgeon Meets Nephrologist: Important Nephrological Aspects Before and After Kidney or Liver Transplantation]

In cases of chronic renal insufficiency, successful kidney transplantation is the method of choice to restore patients' health, well-being and physical fitness. The interdisciplinary collaboration of nephrologists and transplant surgeons has always been a prerequisite for the successful pre-, peri- and post-transplant care of renal transplant patients. The same holds true for liver transplant patients. Here the nephrologist is often involved in cases requiring pre- or post-transplant dialysis as well as in decision making for combined liver-kidney transplantation. This review focuses on nephrological aspects in patient care before and after kidney and liver transplantation.

[A 58-year-old patient with temporal headache, jaw claudication and B symptoms]

CASE REPORT

We report the case of a patient with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis with involvement of the temporal artery, presenting with clinical manifestations of giant cell arteritis and temporal arteritis, such as temporal headache, jaw claudication, weight loss, night sweats and increased inflammatory parameters. The ultrasound scan showed a typical halo sign of the temporal artery.

DIAGNOSTICS

In the case of further atypical organ symptoms, e.g. hematuria and proteinuria, detailed differential diagnostic investigations are essential to clarify the situation. Histological findings from the affected organs play a decisive role.

CONCLUSION

An involvement of the temporal artery due to ANCA-associated vasculitis is extremely rare and may mimic giant cell arteritis. The exact diagnosis of ANCA-associated vasculitis is, however, important because this leads to a different approach concerning therapy and prognosis.

Identification and characterization of a defective CYP3A4 genotype in a kidney transplant patient with severely diminished tacrolimus clearance

Cytochrome P450 3A4 (CYP3A4) is a major drug-metabolizing enzyme that is widely investigated. So far, no homozygous inactive variant has been described. We report on a 19-year-old kidney transplant patient suffering from Alport syndrome, who experienced unexpected high tacrolimus plasma trough levels during immunosuppressant therapy. Because nonadherence, liver failure, or drug-drug interactions could be excluded, we hypothesized a diminished metabolism of the drug caused by mutations in the main detoxification enzyme, CYP3A4. Exome sequencing revealed a novel single-nucleotide polymorphism (c.802C>T) resulting in a premature stop codon in CYP3A4 exon 5. Accordingly, no CYP3A4 protein could be detected in kidney biopsy tissue, and there was lack of expression in HepG2 cells transiently transfected with the mutated CYP3A4. In addition, the patient harbored inactive CYP3A5*3, resulting in loss of function of the entire CYP3A locus, explaining the deteriorated tacrolimus clearance. This is, to our knowledge, the first case of a complete failure of CYP3A4 in humans.

The RIP1-kinase inhibitor necrostatin-1 prevents osmotic nephrosis and contrast-induced AKI in mice

The pathophysiology of contrast-induced AKI (CIAKI) is incompletely understood due to the lack of an appropriate in vivo model that demonstrates reduced kidney function before administration of radiocontrast media (RCM). Here, we examine the effects of CIAKI in vitro and introduce a murine ischemia/reperfusion injury (IRI)-based approach that allows induction of CIAKI by a single intravenous application of standard RCM after injury for in vivo studies. Whereas murine renal tubular cells and freshly isolated renal tubules rapidly absorbed RCM, plasma membrane integrity and cell viability remained preserved in vitro and ex vivo, indicating that RCM do not induce apoptosis or regulated necrosis of renal tubular cells. In vivo, the IRI-based CIAKI model exhibited typical features of clinical CIAKI, including RCM-induced osmotic nephrosis and increased serum levels of urea and creatinine that were not altered by inhibition of apoptosis. Direct evaluation of renal morphology by intravital microscopy revealed dilation of renal tubules and peritubular capillaries within 20 minutes of RCM application in uninjured mice and similar, but less dramatic, responses after IRI pretreatment. Necrostatin-1 (Nec-1), a specific inhibitor of the receptor-interacting protein 1 (RIP1) kinase domain, prevented osmotic nephrosis and CIAKI, whereas an inactive Nec-1 derivate (Nec-1i) or the pan-caspase inhibitor zVAD did not. In addition, Nec-1 prevented RCM-induced dilation of peritubular capillaries, suggesting a novel role unrelated to cell death for the RIP1 kinase domain in the regulation of microvascular hemodynamics and pathophysiology of CIAKI.

Adverse results of a decellularized tissue-engineered pulmonary valve in humans assessed with magnetic resonance imaging

OBJECTIVES

Matrix P® and Matrix P plus® tissue-engineered pulmonary valves (TEPV) were offered as an improvement for pulmonary valve replacement (PVR) because of recellularization by host cells. The high frequency of graft failure gave reason to evaluate the underlying morphological substrate using magnetic resonance imaging (MRI) and histology.

METHODS

Between June 2006 and August 2008, 17 Matrix P® and 10 Matrix P plus® TEPVs were implanted in 26 patients with a median age of 12.4 (range: 0.8-38.7, interquartile range: 6.1-18.1) years. The grafts were studied by MRI, and underwent histological examination when explantation was required.

RESULTS

Surgical (n = 13) or transcatheter (n = 1) TEPV replacement because of graft failure was needed in 14 cases (52%) 19 (0.5-53) months after implantation. MRI detected significant TEPV stenosis with mild insufficiency (V(max) = 3.7 ± (standard deviation) 0.5 m/s, regurgitant fraction (RGF) = 10 ± 3%) and stenosis with moderate-to-severe insufficiency (V(max) = 3.5 ± 0.8 m/s, RGF = 38 ± 10%) in 6 patients, respectively, and severe insufficiency (RGF = 40%) in 1 patient. In patients with graft failure, MRI showed hyperenhancement and TEPV wall thickening. Histology revealed severe inflammation, increased fibrous tissue and foreign-body reaction against valve leaflets and fascial tissue, while TEPV endothelialization was not detected in any case.

CONCLUSIONS

The high frequency of Matrix P® and Matrix P plus® graft failure can be related to inflammation and fibrosis revealed by MRI and histology. Our results do not support the use of these valves for PVR and suggest careful follow-up examinations, including MRI for early detection of graft inflammation and fibrosis.

[Histological findings in bilateral asymmetrical vasoproliferative retinal tumor]

We present a case of a bilateral vasoproliferative tumor of the retina in a young man. The first symptom was visual impairment due to vitreous hemorrhage. The right eye showed small tumors which were successfully treated by repeated cryocoagulation, photocoagulation and bevazicumab injection. The tumor in the left eye was larger and eventually led to a painful secondary glaucoma. After enucleation, this tumor was examined histologically and immunohistochemically. The clinical and histological differential diagnoses and therapeutic options are discussed.

Dichotomy between RIP1- and RIP3-mediated necroptosis in tumor necrosis factor-α-induced shock

Tumor necrosis factor receptor (TNFR) signaling may result in survival, apoptosis or programmed necrosis. The latter is called necroptosis if the receptor-interacting protein 1 (RIP1) inhibitor necrostatin-1 (Nec-1) or genetic knockout of RIP3 prevents it. In the lethal mouse model of TNFα-mediated shock, addition of the pan-caspase inhibitor zVAD-fmk (zVAD) accelerates time to death. Here, we demonstrate that RIP3-deficient mice are protected markedly from TNFα-mediated shock in the presence and absence of caspase inhibition. We further show that the fusion protein TAT-crmA, previously demonstrated to inhibit apoptosis, also prevents necroptosis in L929, HT29 and FADD-deficient Jurkat cells. In contrast to RIP3-deficient mice, blocking necroptosis by Nec-1 or TAT-crmA did not protect from TNFα/zVAD-mediated shock, but further accelerated time to death. Even in the absence of caspase inhibition, Nec-1 application led to similar kinetics. Depletion of macrophages, natural killer (NK) cells, granulocytes or genetic deficiency for T lymphocytes did not influence this model. Because RIP3-deficient mice are known to be protected from cerulein-induced pancreatitis (CIP), we applied Nec-1 and TAT-crmA in this model and demonstrated the deterioration of pancreatic damage upon addition of these substances. These data highlight the importance of separating genetic RIP3 deficiency from RIP1 inhibition by Nec-1 application in vivo and challenge the current definition of necroptosis.

Chronic portal vein thrombosis: transcapsular hepatic collateral vessels and communicating ectopic varices

PURPOSE

To assess patients with chronic portal vein thrombosis (PVT) with respect to transcapsular collateral veins, the communication between these veins and ectopic varices, and the cause of PVT.

MATERIALS AND METHODS

This study was approved by the institutional review committees, and written informed consent was obtained. From November 2003 to March 2008, 145 consecutive patients with chronic PVT due to a variety of causes were assessed for transcapsular collaterals and ectopic varices with ultrasonography (US). Analysis of contingency tables was performed with the Fisher exact test.

RESULTS

Transcapsular collaterals were detected in 15 (10.3%) of 145 patients with chronic PVT. They were restricted to patients with a history of hepatobilary surgery, severe pancreatitis, or abdominal surgery (n = 21) and were not detected in patients with liver cirrhosis, systemic coagulopathy, extrahepatic malignancy, idiopathic PVT, chronic pancreatitis, or infectious or inflammatory diseases (n = 124) (P < .001). Ectopic varices were infrequent in 70 patients with liver cirrhosis (n = 2, 3%) but were common in 14 patients with PVT after hepatobiliary surgery (n = 9, 64%) (P < .001, odds ratio = 21.4). Direct communication between transcapsular collaterals and ectopic varices was visible in all nine patients in this cohort. In eight of these patients, ectopic varices were found to be the bleeding source in gastrointestinal hemorrhage.

CONCLUSION

Transcapsular collaterals frequently occur in patients with chronic PVT due to hepatobilary surgery or necrotizing pancreatitis. They are associated with ectopic varices; therefore, awareness of transcapsular collaterals in this patient subgroup will help to localize ectopic varices as potential bleeding source.

Gene Expression in Macrophage-Rich Inflammatory Cell Infiltrates in Human Atherosclerotic Lesions as Studied by Laser Microdissection and DNA Array

OBJECTIVE

Inflammatory cells play an important role in atherogenesis. However, more information is needed about their gene expression profiles in human lesions.

METHODS AND RESULTS

We used laser microdissection (LMD) to isolate macrophage-rich shoulder areas from human lesions. Gene expression profiles in isolated cells were analyzed by cDNA array and compared with expression patterns in normal intima and THP-1 macrophages. Upregulation of 72 genes was detected with LMD and included 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, interferon regulatory factor-5 (IRF-5), colony stimulating factor (CSF) receptors, CD11a/CD18 integrins, interleukin receptors, CD43, calmodulin, nitric oxide synthase (NOS), and extracellular superoxide dismutase (SOD). Several of these changes were also present in PMA-stimulated THP-1 macrophages in vitro. On the other hand, expression of several genes, such as VEGF, tissue factor pathway inhibitor 2, and apolipoproteins C-I and C-II, decreased.

CONCLUSIONS

Overexpression of HMG-CoA reductase in macrophage-rich lesion areas may explain some beneficial effects of statins, which can also modulate increased expression of CD11a/CD18 and CD43 found in microdissected cells. We also found increased expression of CSF receptors, IRF-5, and interleukin receptors, which could become useful therapeutic targets for the treatment of atherosclerotic diseases.

Changes in gene expression in atherosclerotic plaques analyzed using DNA array

A better understanding of atherogenesis at the level of gene expression could lead to the identification of new therapeutic strategies for vascular diseases. With DNA array technology, it is possible to identify multiple, simultaneous changes in gene expression in small tissue samples from atherosclerotic arteries. We analyzed gene expression in normal arteries and in immunohistologically characterized human advanced atherosclerotic lesions using an array of 18376 cDNA fragments. The array method was first validated by detecting a group of genes (n=17) that were already known to be connected to atherogenesis. These genes included e.g. Apolipoprotein E, CD68, TIMP and phospholipase D. Next we detected 75 differentially expressed genes that were previously not connected to atherogenesis. A subgroup of genes involved in cell signaling and proliferation was selected for further analyzes with in situ hybridization and RT-PCR which confirmed array results by showing induction in advanced lesions of Janus kinase 1 (JAK-1) which is an important signaling molecule in activated macrophages; VEGF receptor-2 which mediates angiogenic and vasculoprotective effects of VEGF; and an unknown gene, which mapped on chromosome 19. It is concluded that DNA array technology enables fast screening of gene expression in small samples of atherosclerotic lesions. The technique will be useful for the identification of new factors, such as JAK-1 and VEGF receptor-2, which may play an important role in atherogenesis.

Angiogenesis, vascular endothelial growth factor and platelet-derived growth factor-BB expression, iron deposition, and oxidation-specific epitopes in stented human coronary arteries

Pathogenesis of in-stent restenosis remains poorly understood because information from human histopathologic studies is scarce. We used an improved saw-grinding and cutting method on methacrylate-embedded samples containing metal stents, which allows in situ hybridization and immunohistochemical analysis of in-stent restenosis. Twenty-one samples were collected 3 hours to 3 years after stenting from 6 patients aged 36 to 81 years. Except in very early samples collected within hours after the stent deployment, neovascularization was present in all segments studied. At advanced stages, extensive neovascularization was located mainly at the luminal side of the stent struts and was only rarely accompanied by inflammatory cells. The neovessels colocalized with vascular endothelial growth factor (VEGF)-A mRNA and protein expression as well as with iron deposits and oxidation-specific epitopes, which imply the presence of chronic oxidative stress. VEGF-A expression was detected in the same areas containing macrophages, endothelial cells, and, to a lesser extent, smooth muscle cells, which also showed platelet-derived growth factor-BB expression. We conclude that in-stent restenosis features neovascularization, VEGF-A and platelet-derived growth factor-BB expression, and iron deposition, which is most probably derived from microhemorrhages. These mechanisms may play an important role in the development of neointimal thickening and could provide useful targets for the prevention and treatment of in-stent restenosis.

Renal handling of human apolipoprotein(a) and its fragments in the rat

The sites and mechanisms of the catabolism of atherogenic lipoprotein(a) (Lp(a)) are not well understood. Lp(a) is increased in patients with end-stage renal disease, suggesting a renal catabolism of Lp(a). To gain a better insight into renal handling of Lp(a), we established a heterologous rat model to study the renal catabolism of human Lp(a). Pure human Lp(a) was injected into Wistar rats, and animals were sacrificed at different time points (30 minutes to 24 hours). Intact Lp(a) was cleared from the circulation of injected rats with a half-life time of 14.5 hours. Strong intracellular immunostaining for apolipoprotein(a) (apo(a)) was observed in the cytoplasm of proximal tubular cells after 4, 8, and 24 hours. Apolipoprotein B (apoB) was colocalized with glomerular apo(a) 1 to 8 hours after Lp(a) injection, but renal capillaries and tubules remained negative. No relevant amounts of apo(a) fragments were found in the plasma of rats after injection of Lp(a). During all urine collection periods, apo(a) fragments with molecular weights of 50 to 160 kd were detected in the urine, however. Our results show that human Lp(a) injected into rats accumulates intracellularly in the rat kidney, and apo(a) fragments are excreted in the urine. The kidney apparently plays a major role in fragmentation of Lp(a). Despite the fact that rodents lack endogenous Lp(a), rats injected with human Lp(a) may provide a useful heterologous animal model to study the renal metabolism of Lp(a) further.

Increased NADH-oxidase-mediated superoxide production in the early stages of atherosclerosis: evidence for involvement of the renin-angiotensin system

BACKGROUND

Angiotensin II activates NAD(P)H-dependent oxidases via AT1-receptor stimulation, the most important vascular source of superoxide (O2*-). The AT1 receptor is upregulated in vitro by low-density lipoprotein. The present study was designed to test whether hypercholesterolemia is associated with increased NAD(P)H-dependent vascular O2*- production and whether AT1-receptor blockade may inhibit this oxidase and in parallel improve endothelial dysfunction.

METHODS AND RESULTS

Vascular responses were determined by isometric tension studies, and relative rates of vascular O2*- production were determined by use of chemiluminescence with lucigenin, a cypridina luciferin analogue, and electron spin resonance studies. AT1-receptor mRNA was quantified by Northern analysis, and AT1-receptor density was measured by radioligand binding assays. Hypercholesterolemia was associated with impaired endothelium-dependent vasodilation and increased O2*- production in intact vessels. In vessel homogenates, we found a significant activation of NADH-driven O2*- production in both models of hyperlipidemia. Treatment of cholesterol-fed animals with the AT1-receptor antagonist Bay 10-6734 improved endothelial dysfunction, normalized vascular O2*- and NADH-oxidase activity, decreased macrophage infiltration, and reduced early plaque formation. In the setting of hypercholesterolemia, the aortic AT1 receptor mRNA was upregulated to 166+/-11%, accompanied by a comparable increase in AT1-receptor density.

CONCLUSIONS

Hypercholesterolemia is associated with AT1-receptor upregulation, endothelial dysfunction, and increased NADH-dependent vascular O2*- production. The improvement of endothelial dysfunction, inhibition of the oxidase, and reduction of early plaque formation by an AT1-receptor antagonist suggests a crucial role of angiotensin II-mediated O2*- production in the early stage of atherosclerosis.

Increased NAD(P)H oxidase-mediated superoxide production in renovascular hypertension: evidence for an involvement of protein kinase C

BACKGROUND

Angiotensin II infusion has been shown to cause hypertension and endothelial dysfunction and to increase superoxide (O-.2) production in vascular tissue, mainly via an activation of nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-dependent oxidase, the most significant O-.2 source in endothelial and/or smooth muscle cells. With these studies, we sought to determine whether endothelial dysfunction in renovascular hypertension is secondary to an activation of these oxidases.

METHODS

Endothelial function in aortas from rats with two kidney-one clip (2K-1C) hypertension and age-matched controls was assessed using isometric tension studies in organ chambers. Changes in vascular O-.2 production were measured using lucigenin-enhanced chemiluminescence and electron spin resonance spectroscopy.

RESULTS

In hypertensive animals, relaxation to endothelium-dependent (acetylcholine) and endothelium-independent nitrovasodilators (nitroglycerin) was impaired. Constriction to a direct activator of protein kinase C (PKC) phorbol ester 12,13 dibutyrate (PDBu) was enhanced, and vascular O-.2 was significantly increased compared with controls. Vascular O-.2 was normalized by the PKC inhibitor calphostin C, by the inhibitor of flavin-dependent oxidases, diphenylene iodonium, and recombinant heparin-binding superoxide dismutase, whereas inhibitors of the xanthine oxidase (oxypurinol), nitric oxide synthase (NG-nitro-l-arginine) and mitochondrial NADH dehydrogenase (rotenone) were ineffective. Studies of vascular homogenates demonstrated that the major source of O-.2 was a NAD(P)H-dependent oxidase. Incubation of intact tissue with PDBu markedly increased O-. 2, the increase being significantly stronger in vessels from hypertensive animals as compared with vessels from controls. Endothelial dysfunction was improved by preincubation of vascular tissue with superoxide dismutase and calphostin C.

CONCLUSIONS

We therefore conclude that renovascular hypertension in 2K-1C rats is associated with increased vascular O-.2 leading to impaired vasodilator responses to endogenous and exogenous nitrovasodilators. Increased vascular O-.2 is likely secondary to a PKC-mediated activation of a membrane-associated NAD(P)H-dependent oxidase.

Survival and cardiovascular pathology of heterozygous Watanabe heritable hyperlipidaemic rabbits treated with pravastatin and probucol on a low-cholesterol (0.03%)-enriched diet

This study was aimed at determining the effects of a combined pravastatin and probucol regimen on survival and vascular pathology of heterozygous Watanabe heritable hyperlipidaemic (WHHL) rabbits fed a low-cholesterol (0.03%)-enriched diet. Pravastatin monotherapy preceded the combined treatment. In animals receiving pravastatin and the enriched diet (verum group; n = 6), mean total serum cholesterol levels were consistently lowered at a dosage of 5 mg/kg pravastatin and with the combined treatment. Survival was increased (median 45 vs 25 months), while coronary atherosclerosis was less obstructive and altered to a more fibrous type than in controls (n = 8). The extent of aortic lesions, as determined by the relative plaque volume, was not related to survival in either group. However, aortic plaque types in verum group animals revealed less severe stages with a different composition and architecture, with a lower relative content of macrophage-derived foam cells and necrosis and a higher relative content of extracellular matrix. There was also a thicker fibrous cap than in control animals of similar age. Our data reveal a beneficial effect on survival of heterozygous WHHL rabbits when lipid-lowering and antioxidative treatment are combined. This appears to be due both to reduced coronary atherosclerosis and to a different, more stable type of atherosclerotic disease in this animal model.

[Atherosclerosis. Formal pathogenesis, classification and functional significance]

Atherosclerosis and its complications determine the majority of deaths in the western world, followed by malignant tumors. The present work introduces a classification of stages of atherosclerotic disease based on relevant pathogenic and therapeutic concepts, elaborated by H. Stary. At the present, we are able to relate different lesion types to a time course and partly to interferences between participating cell populations as well as to special pathogenic stimuli. From the therapeutic view, this knowledge is fundamental for preventive as well as interventional strategies like gene therapy. Distinct atherosclerotic plaques reveal a different composition and architecture, which may account for the variable risk for further complications of lesions showing the same size and degree of stenosis. In combination with an advanced clinical and diagnostic characterization of atherosclerotic lesions, the present concept might contribute to a better and differential therapy of atherosclerosis.