Sudden Death in High School Athletes: A Case Series Examining the Influence of Sickle Cell Trait.

ABSTRACT: Athletes with sickle cell trait (SCT) have up to a 37-fold increased risk of exercise-related death. Exertional collapse associated with sickle cell trait (ECAST) is uncommon but can lead to exercise-related death due to exertional sickling. We present a case series of fatal ECAST in high school athletes aged 14 to 16 years. All 3 athletes experienced collapse during practice sessions with muscle pain or weakness. Upon evaluation at the hospital, the athletes had a significant metabolic acidosis that did not respond as expected to fluid resuscitation. Admitting diagnoses for the athletes included exertional heat stroke or dehydration. All 3 athletes had profound rhabdomyolysis leading to acute renal failure, worsening metabolic acidosis, and hyperkalemia. They rapidly progressed to disseminated intravascular coagulation, multiorgan system failure, and death. The autopsies of all 3 athletes showed extensive sickle cell vaso-occlusion involving the spleen liver, and muscles. Final clinical and pathologic diagnosis supported ECAST with fatal exertional rhabdomyolysis. Exertional collapse associated with sickle cell trait is an uncommon but potentially deadly condition that is often underrecognized or misdiagnosed as exertional heat stroke. The development of ECAST is thought to be multifactorial with exercise intensity, recent illness, and exercising conditions (ie, heat and altitude). Prevention should be the primary goal for athletes with SCT through exercise modification, education of precipitation factors, and cessation of exercise with recent illness. Athletes with suspected ECAST should undergo aggressive resuscitation with a low threshold for early transfer to a tertiary care facility for further management and potential hemodialysis.

Segmental Sclerosis and Extracapillary Hypercellularity Predict Diabetic ESRD.

Pathogenetic markers of diabetic kidney disease (DKD) progression to ESRD are lacking. We characterized the prognostic value of histologic findings in DKD for time to ESRD in native kidney specimens from biopsies performed from 1995 to 2011 with diabetic glomerulosclerosis as the only glomerular disease diagnosis (n=109). Biopsy specimens were analyzed according to standard methods, including determination of diabetic nephropathy class, as defined by the Renal Pathology Society. Clinical data were extracted from electronic medical records. We used competing risk models, with death as the competing risk, to estimate subdistribution hazard ratios (HRs) for ESRD. All multivariable models included age, sex, black race, baseline eGFR, and baseline proteinuria. Pathologic characteristics achieving P<0.1 were added into successively complex models. ESRD occurred in 56% of patients, and 26% of patients died before reaching ESRD. In univariate analyses, diabetic nephropathy class was not statistically significant in predicting time to ESRD. The final multivariable model (n=106) showed a borderline association between mild mesangial expansion and decreased risk for ESRD (subdistribution HR, 0.64; 95% confidence interval, 0.40 to 1.00). Poor prognostic factors in the final model included segmental sclerosis and extracapillary hypercellularity (subdistribution HR, 2.04; 95% confidence interval, 1.36 to 3.05; and subdistribution HR, 2.21; 95% confidence interval, 1.19 to 4.11, respectively). In conclusion, we identified segmental sclerosis and extracapillary hypercellularity as novel, poor prognostic indicators of time from DKD to ESRD. Whether these indicators represent a distinct pathogenetic phenotype of DKD will require a large study with a broad spectrum of disease severity.

Glomerular C4d deposits can mark structural capillary wall remodelling in thrombotic microangiopathy and transplant glomerulopathy: C4d beyond active antibody-mediated injury: a retrospective study.

Peritubular capillary C4d (ptc-C4d) usually marks active antibody-mediated rejection, while pseudolinear glomerular capillary C4d (GBM-C4d) is of undetermined diagnostic significance, especially when seen in isolation without concurrent ptc-C4d. We correlated GBM-C4d with structural GBM abnormalities and active antibody-mediated rejection in 319 renal transplant and 35 control native kidney biopsies. In kidney transplants, ptc-C4d was associated with GBM-C4d in 97% by immunofluorescence microscopy (IF) and 61% by immunohistochemistry (IHC; P < 0.001). Transplant glomerulopathy correlated with GBM-C4d (P < 0.001) and presented with isolated GBM-C4d lacking ptc-C4d in 69% by IF and 40% by IHC. Strong isolated GBM-C4d was found post year-1 in repeat biopsies with transplant glomerulopathy. GBM-C4d staining intensity correlated with Banff cg scores (rs = 0.45, P < 0.001). Stepwise exclusion and multivariate logistic regression corrected for active antibody-mediated rejection showed significant correlations between GBM duplication and GBM-C4d (P = 0.001). Native control biopsies with thrombotic microangiopathies demonstrated GBM-C4d in 92% (IF, P < 0.001) and 35% (IHC). In conclusion, pseudolinear GBM-C4d staining can reflect two phenomena: (i) structural GBM changes with duplication in native and transplant kidneys or (ii) active antibody-mediated rejection typically accompanied by ptc-C4d. While ptc-C4d is a dynamic 'etiologic' marker for active antibody-mediated rejection, isolated strong GBM-C4d can highlight architectural glomerular remodelling.

Renal Survival in Patients with Collapsing Compared with Not Otherwise Specified FSGS.

BACKGROUND AND OBJECTIVES: Idiopathic collapsing FSGS has historically been associated with poor renal outcomes. Minimal clinical data exist on the efficacy of immunosuppressive therapy. Our study sought to provide a comprehensive description of renal survival in patients with collapsing and not otherwise specified FSGS after controlling for factors affecting renal prognosis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We performed a retrospective analysis of an inception cohort study of patients diagnosed between 1989 and 2012. All potential patients with collapsing FSGS fulfilling the inclusion criteria were identified and compared with patients with not otherwise specified FSGS (approximately 1:2 ratio) on the basis of biopsy report and record availability. Time to ESRD was analyzed using Cox proportional hazards models. RESULTS: In total, 187 patients were studied (61 collapsing and 126 not otherwise specified), with a mean follow-up of 96 months. At baseline, patients with collapsing FSGS had higher median proteinuria (12.2 [5.6-14.8] versus 4.4 [2.3-8.1] g/d, respectively; P<0.001), lower median albuminemia (2.4 [1.9-3.0] versus 2.9 [1.8-3.7] g/dl, respectively; P=0.12), and lower median eGFR (48 [26-73] versus 60 [42-92] ml/min per 1.73 m2, respectively; P=0.01) than patients with not otherwise specified FSGS. The proportion of patients with remission of proteinuria was similar in patients with collapsing FSGS and patients with not otherwise specified FSGS (65.7% [23 of 35] versus 63.2% [72 of 114], respectively; P=0.84). The overall renal outcome (ESRD defined as eGFR<15 ml/min per 1.73 m2, dialysis, or transplantation) of patients with collapsing FSGS was not poorer than that of patients with not otherwise specified FSGS in multivariate analyses after adjusting for baseline characteristics and immunotherapy (hazard ratio, 1.78; 95% confidence interval, 0.92 to 3.45). CONCLUSIONS: Compared with not otherwise specified FSGS, idiopathic collapsing FSGS presented with more severe nephrotic syndrome and lower eGFR but had a similar renal survival after controlling for exposure to immunosuppressive treatment. These results highlight the importance of early diagnosis and institution of immunosuppressive therapy in patients with collapsing FSGS.

The Application of Digital Pathology to Improve Accuracy in Glomerular Enumeration in Renal Biopsies.

BACKGROUND: In renal biopsy reporting, quantitative measurements, such as glomerular number and percentage of globally sclerotic glomeruli, is central to diagnostic accuracy and prognosis. The aim of this study is to determine the number of glomeruli and percent globally sclerotic in renal biopsies by means of registration of serial tissue sections and manual enumeration, compared to the numbers in pathology reports from routine light microscopic assessment. DESIGN: We reviewed 277 biopsies from the Nephrotic Syndrome Study Network (NEPTUNE) digital pathology repository, enumerating 9,379 glomeruli by means of whole slide imaging. Glomerular number and the percentage of globally sclerotic glomeruli are values routinely recorded in the official renal biopsy pathology report from the 25 participating centers. Two general trends in reporting were noted: total number per biopsy or average number per level/section. Both of these approaches were assessed for their accuracy in comparison to the analogous numbers of annotated glomeruli on WSI. RESULTS: The number of glomeruli annotated was consistently higher than those reported (p<0.001); this difference was proportional to the number of glomeruli. In contrast, percent globally sclerotic were similar when calculated on total glomeruli, but greater in FSGS when calculated on average number of glomeruli (p<0.01). The difference in percent globally sclerotic between annotated and those recorded in pathology reports was significant when global sclerosis is greater than 40%. CONCLUSIONS: Although glass slides were not available for direct comparison to whole slide image annotation, this study indicates that routine manual light microscopy assessment of number of glomeruli is inaccurate, and the magnitude of this error is proportional to the total number of glomeruli.

Reproducibility of the NEPTUNE descriptor-based scoring system on whole-slide images and histologic and ultrastructural digital images.

The multicenter Nephrotic Syndrome Study Network (NEPTUNE) digital pathology scoring system employs a novel and comprehensive methodology to document pathologic features from whole-slide images, immunofluorescence and ultrastructural digital images. To estimate inter- and intra-reader concordance of this descriptor-based approach, data from 12 pathologists (eight NEPTUNE and four non-NEPTUNE) with experience from training to 30 years were collected. A descriptor reference manual was generated and a webinar-based protocol for consensus/cross-training implemented. Intra-reader concordance for 51 glomerular descriptors was evaluated on jpeg images by seven NEPTUNE pathologists scoring 131 glomeruli three times (Tests I, II, and III), each test following a consensus webinar review. Inter-reader concordance of glomerular descriptors was evaluated in 315 glomeruli by all pathologists; interstitial fibrosis and tubular atrophy (244 cases, whole-slide images) and four ultrastructural podocyte descriptors (178 cases, jpeg images) were evaluated once by six and five pathologists, respectively. Cohen's kappa for inter-reader concordance for 48/51 glomerular descriptors with sufficient observations was moderate (0.40

Treatment with Glucocorticoids or Calcineurin Inhibitors in Primary FSGS.

BACKGROUND AND OBJECTIVES: In primary FSGS, calcineurin inhibitors have primarily been studied in patients deemed resistant to glucocorticoid therapy. Few data are available about their use early in the treatment of FSGS. We sought to estimate the association between choice of therapy and ESRD in primary FSGS. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We used an inception cohort of patients diagnosed with primary FSGS by kidney biopsy between 1980 and 2012. Factors associated with initiation of therapy were identified using logistic regression. Time-dependent Cox models were performed to compare time to ESRD between different therapies. RESULTS: In total, 458 patients were studied (173 treated with glucocorticoids alone, 90 treated with calcineurin inhibitors with or without glucocorticoids, 12 treated with other agents, and 183 not treated with immunosuppressives). Tip lesion variant, absence of severe renal dysfunction (eGFR≥30 ml/min per 1.73 m(2)), and hypoalbuminemia were associated with a higher likelihood of exposure to any immunosuppressive therapy. Only tip lesion was associated with initiation of glucocorticoids alone over calcineurin inhibitors. With adjusted Cox regression, immunosuppressive therapy with glucocorticoids and/or calcineurin inhibitors was associated with better renal survival than no immunosuppression (hazard ratio, 0.49; 95% confidence interval, 0.28 to 0.86). Calcineurin inhibitors with or without glucocorticoids were not significantly associated with a lower likelihood of ESRD compared with glucocorticoids alone (hazard ratio, 0.42; 95% confidence interval, 0.15 to 1.18). CONCLUSIONS: The use of immunosuppressive therapy with calcineurin inhibitors and/or glucocorticoids as part of the early immunosuppressive regimen in primary FSGS was associated with improved renal outcome, but the superiority of calcineurin inhibitors over glucocorticoids alone remained unproven.

Phenotypic heterogeneity in females with X-linked Alport syndrome.

AIMS: X-linked Alport syndrome (AS) is a monogenic inherited disorder of type IV collagen, a structural protein in the kidney and cochlea. Males typically exhibit a severe phenotype with end-stage renal disease (ESRD) and/or deafness by early adulthood. Because of the presence of two X chromosomes, females often have a less severe phenotype and hence the diagnosis of AS is often not considered. Herein, we present a case of an adolescent girl with proteinuria and hematuria in the setting of a strong family history of AL. CASE REPORT: The mother and maternal aunt of the proband had both presented with dipstick positive hematuria and proteinuria at age 8 years. These girls were not evaluated by nephrology until mid-adolescence when they had worsening creatinine levels. Kidney biopsy in the younger sister demonstrated segmental glomerulosclerosis with segmental thinning and lamination of the glomerular basement membrane, consistent with AS. Kidney biopsy in the older sister was performed just prior to the need for renal replacement therapy and showed only global glomerulosclerosis. Both sisters were transplanted by the age of 20 years. Their mother subsequently developed ESRD at age 53 years. With the advent of genetic testing, the proband and her family were brought in for evaluation. It had been assumed this family of AS had autosomal dominant transmission, however, genetic testing of the proband was positive for a splice site mutation of COL4A5 located on the X-chromosome. Sequencing of genes COL4A3, COL4A4, and COL4A6 were negative for mutation. CONCLUSIONS: The current case report demonstrates the importance of considering skewed X-inactivation in females who exhibit signs or symptoms of Xlinked disorders.

Low TGFß1 expression prevents and high expression exacerbates diabetic nephropathy in mice.

Nephropathy develops in many but not all patients with long-standing type 1 diabetes. Substantial efforts to identify genotypic differences explaining this differential susceptibility have been made, with limited success. Here, we show that the expression of the transforming growth factor ß1 gene (Tgfb1) affects the development of diabetic nephropathy in mice. To do this we genetically varied Tgfb1 expression in five steps, 10%, 60%, 100%, 150%, and 300% of normal, in mice with type 1 diabetes caused by the Akita mutation in the insulin gene (Ins2(Akita)). Although plasma glucose levels were not affected by Tgfb1 genotype, many features of diabetic nephropathy (mesangial expansion, elevated plasma creatinine and urea, decreased creatinine clearance and albuminuria) were progressively ameliorated as Tgfb1 expression decreased and were progressively exacerbated when expression was increased. The diabetic 10% hypomorphs had comparable creatinine clearance and albumin excretion to wild-type mice and no harmful changes in renal morphology. The diabetic 300% hypermorphs had ∼1/3 the creatinine clearance of wild-type mice, >20× their albumin excretion, ∼3× thicker glomerular basement membranes and severe podocyte effacement, matching human diabetic nephropathy. Switching Tgfb1 expression from low to high in the tubules of the hypomorphs increased their albumin excretion more than 10-fold but creatinine clearance remained high. Switching Tgfb1 expression from low to high in the podocytes markedly decreased creatinine clearance, but minimally increased albumin excretion. Decreasing expression of Tgfb1 could be a promising option for preventing loss of renal function in diabetes.

Palladin is upregulated in kidney disease and contributes to epithelial cell migration after injury.

Recovery from acute kidney injury involving tubular epithelial cells requires proliferation and migration of healthy cells to the area of injury. In this study, we show that palladin, a previously characterized cytoskeletal protein, is upregulated in injured tubules and suggest that one of its functions during repair is to facilitate migration of remaining cells to the affected site. In a mouse model of anti-neutrophilic cytoplasmic antibody involving both tubular and glomerular disease, palladin is upregulated in injured tubular cells, crescents and capillary cells with angiitis. In human biopsies of kidneys from patients with other kidney diseases, palladin is also upregulated in crescents and injured tubules. In LLC-PK1 cells, a porcine proximal tubule cell line, stress induced by transforming growth factor-ß1 (TGF-ß1) leads to palladin upregulation. Knockdown of palladin in LLC-PK1 does not disrupt cell morphology but does lead to a defect in cell migration. Furthermore, TGF-ß1 induced increase in the 75 kDa palladin isoform occurs in both the nucleus and the cytoplasm. These data suggest that palladin expression is induced in injured cells and contributes to proper migration of cells in proximal tubules, possibly by regulation of gene expression as part of the healing process after acute injury.

Cathelicidin antimicrobial peptide as a serologic marker and potential pathogenic factor in antineutrophil cytoplasmic antibody-associated vasculitis.

Antineutrophil cytoplasmic antibodies are associated with pauci-immune small-vessel vasculitis and crescentic glomerulonephritis. Cathelicidin LL37 is the human member of a family of antimicrobial peptides that are released from activated neutrophils and monocytes at sites of acute inflammation. Zhang and colleagues evaluated serum levels of cathelicidin LL37 and interferon-alpha in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and glomerulonephritis. Increased levels of cathelicidin LL37 and interferon-alpha were associated with AAV patients, particularly those with glomerular crescent formation. Cathelicidin LL37 may also be involved in the pathogenesis of AAV and thus could be a target for novel therapy. Cathelicidin LL37 is a promising new biomarker for active AAV, including aggressive crescentic glomerulonephritis, and may prove to be both a prognostic marker and a guide for treatment.

Predictors of treatment outcomes in ANCA-associated vasculitis with severe kidney failure.

BACKGROUND AND OBJECTIVES: In ANCA-associated GN, severe renal dysfunction portends a poor prognosis for renal recovery and patient survival. This study evaluated the prognostic factors affecting renal and patient outcomes in patients presenting with severe kidney failure to guide immunosuppressive therapy. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This study retrospectively evaluated clinical and histopathologic characteristics of 155 patients who underwent biopsy between October 1985 and February 2011 (median eGFR at presentation, 7.1 ml/min per 1.73 m(2); 87% required hemodialysis), all treated with immunosuppressive medications. Three outcomes of interest were measured: patient survival, renal survival, and treatment response (defined as dialysis-free survival without active vasculitis by 4 months after biopsy). Competing risk, Cox, and logistic regression analyses were conducted for each outcome measure. RESULTS: Within 4 months after biopsy, treatment response was attained in 51% of patients, 35% remained on dialysis, and 14% died. In a competing risk analysis, estimated cumulative incidence rates of ESRD and disease-related mortality were 26% and 17% at 1 year and 32% and 28% at 5 years, respectively. Cyclophosphamide therapy and treatment response by 4 months were independently associated with patient and renal survival, adjusting for the percentage of normal glomeruli, histopathologic chronicity index score, and baseline clinical characteristics. Only 5% of patients still dialysis dependent at 4 months subsequently recovered renal function. Low chronicity index score (odds ratio [OR], 1.16; 95% confidence interval [95% CI], 1.04 to 1.30, per unit decrease) and baseline eGFR>10 ml/min per 1.73 m(2) (OR, 2.77; 95% CI, 1.09 to 7.01) were significantly associated with treatment response by 4 months. Among cyclophosphamide-treated patients, the likelihood of treatment response was >14% even with highest chronicity index score and eGFR<10 ml/min per 1.73 m(2). CONCLUSIONS: Although low baseline renal function and severe renal scarring are associated with lower treatment response rate, no "futility" threshold could be identified. Conversely, continued immunosuppressive therapy beyond 4 months is unlikely to benefit patients who remain dialysis dependent.

Digital pathology evaluation in the multicenter Nephrotic Syndrome Study Network (NEPTUNE).

Pathology consensus review for clinical trials and disease classification has historically been performed by manual light microscopy with sequential section review by study pathologists, or multi-headed microscope review. Limitations of this approach include high intra- and inter-reader variability, costs, and delays for slide mailing and consensus reviews. To improve this, the Nephrotic Syndrome Study Network (NEPTUNE) is systematically applying digital pathology review in a multicenter study using renal biopsy whole slide imaging (WSI) for observation-based data collection. Study pathology materials are acquired, scanned, uploaded, and stored in a web-based information system that is accessed through a web-browser interface. Quality control includes metadata and image quality review. Initially, digital slides are annotated, with each glomerulus identified, given a unique number, and maintained in all levels until the glomerulus disappears or sections end. The software allows viewing and annotation of multiple slide sections concurrently. Analysis utilizes "descriptors" for patterns of injury, rather than diagnoses, in renal parenchymal compartments. This multidimensional representation via WSI, allows more accurate glomerular counting and identification of all lesions in each glomerulus, with data available in a searchable database. The use of WSI brings about efficiency critical to pathology review in a clinical trial setting, including independent review by multiple pathologists, improved intraobserver and interobserver reproducibility, efficiencies and risk reduction in slide circulation and mailing, centralized management of data integrity and slide images for current or future studies, and web-based consensus meetings. The overall effect is improved incorporation of pathology review in a budget neutral approach.

Diagnostic significance of peritubular capillary basement membrane multilaminations in kidney allografts: old concepts revisited.

BACKGROUND: Injury to peritubular capillaries and capillary basement membrane multilamination (PTCL) is a hallmark of antibody-mediated chronic renal allograft rejection. However, the predictive diagnostic value of PTCL is incompletely studied. METHODS: We analyzed the diagnostic significance of PTCL and propose diagnostic strategies. We evaluated 360 diagnostic native and 187 transplant kidney specimens by electron microscopy (terminology: PTCL-C, severe; PTCL subgroup C3, very severe multilamination; see Materials and Methods for definitions). RESULTS: PTCL was not pathognomonic for any specific disease. PTCL-C/C3 was rare in native kidneys (C, 6%; C3, 1%), associated mainly with late thrombotic microangiopathy (C: 78%; C3: 11% of cases). In allografts, PTCL-C/C3 was significantly more common, especially in specimens more than 24 months after transplantation (C, 47%; C3, 31%). PTCL-C/C3 was found in acute (C, 20%; C3, 7%) and chronic T-cell rejection (C, 67%; C3, 29%), calcineurin inhibitor toxicity (C, 36%; C3, 18%), or C4d(+) specimens (C, 61%; C3, 50%) with odds ratios between 4 and 36. PTCL-C3 was more predominant in cases with antibody-mediated injury. Highest odds ratios (81-117) for PTCL-C/C3 were noted in combined injuries, that is, mixed chronic T-cell and concurrent chronic antibody-mediated rejection. Positive predictive values of PTCL-C and C3 are the following: all rejection types, 89% and 93%; all Banff chronic rejection types, 69% and 71%; and chronic presumptive antibody rejection, 37% and 49%, respectively. Corresponding negative predictive values of C and C3 for different Banff rejection categories are between 50% and 94%. CONCLUSIONS: The presence of PTCL-C3 is a helpful adjunct finding to diagnose rejection-induced tissue injury but cannot precisely predict the Banff rejection category. Conversely, the absence of PTCL-C3 is helpful in excluding chronic, Banff category II antibody-mediated rejection.

Pathogenesis of antineutrophil cytoplasmic autoantibody vasculitis.

PURPOSE OF REVIEW: Antineutrophil cytoplasmic autoantibodies (ANCAs) are associated with vasculitis. Current therapy involves administration of toxic therapy that is not optimally effective. This review will summarize evidence for the pathogenicity of ANCAs, which will suggest possible strategies for improving treatment. RECENT FINDINGS: Pauci-immune small vessel vasculitis is associated with antibodies against myeloperoxidase (MPO-ANCA) and proteinase 3 (PR3-ANCA). One research group has reported a high frequency of autoantibodies against lysosomal-associated membrane protein 2 (LAMP-2) in patients with MPO-ANCA or PR3-ANCA. Epigenetic dysregulation appears to be the basis for increased MPO and PR3 neutrophil gene expression in ANCA disease. Release of neutrophil extracellular traps may be involved in initiating the ANCA autoimmune response and causing vessel injury. Generation of C5a by alternative pathway activation is involved in pathogenesis in mouse models. Intervention strategies in mice that target antigens, antibodies and inflammatory signaling pathways may translate into novel therapies. Animal models of LAMP-ANCA and PR3-ANCA disease have been proposed. Molecular mimicry and responses to complementary peptides may be initiating events for ANCAs. T cells, including regulatory T cells, have been implicated in the origin and modulation of the ANCAs, as well as in the induction of tissue injury. SUMMARY: Our basic understanding of the origins and pathogenesis of ANCA disease is advancing. This deeper understanding already has spawned novel therapies that are being investigated in clinical trials. This brief review shows that there are more questions than answers, and new questions are emerging faster than existing questions are being answered.

Experimental models of vasculitis and glomerulonephritis induced by antineutrophil cytoplasmic autoantibodies.

Antineutrophil cytoplasmic autoantibodies (ANCA) are closely associated with systemic small vessel vasculitis characterized by segmental vessel wall necrotizing inflammation and a paucity of immunoglobulin deposition. Clinically, in vitro and experimental animal model observations indicate a direct pathogenic role for ANCA. This review focuses on the results of experiments utilizing a mouse model of ANCA disease induced by transfer of mouse anti-MPO IgG or anti-MPO lymphocytes into recipient mice, which causes small vessel vasculitis and glomerulonephritis that closely mimics human disease. Evidence for the following conclusion about this model, and by implication about human ANCA disease, will be summarized as follows: (1) anti-MPO IgG is sufficient even in the absence of functional T cells to cause disease and anti-MPO T lymphocytes are not sufficient to cause acute injury; (2) neutrophils are required; (3) ANCA antigens in bone marrow-derived cells are sufficient targets; (4) increased circulating pro-inflammatory cytokines and microbial products exacerbate disease, and concurrent viral infection exacerbates and modulates the phenotype of disease; (5) Fcγ receptor engagement is required for disease induction, and Fcγ receptor repertoire modulates the phenotype of disease, especially pulmonary disease; (6) activation of the alternative pathway of complement is required, complement is activated by factors released by neutrophils stimulated by ANCA IgG and engagement of C5a receptors is a primary event in complement-mediated amplification; and (7) genetic background has a marked influence on the severity and outcome of disease, and modified gene expression in bone marrow-derived cells is the primary basis for genetically determined differences in disease susceptibility. Investigations using this animal model of ANCA disease have provided important insights into the cellular, molecular and genetic factors involved in the pathogenesis of ANCA disease which are likely to lead to the identification of improved markers of disease activity and response to therapy, as well as more effective and less toxic therapies.

Lack of both bradykinin B1 and B2 receptors enhances nephropathy, neuropathy, and bone mineral loss in Akita diabetic mice.

An insertion polymorphism of the angiotensin-I converting enzyme gene (ACE) is common in humans and the higher expressing allele is associated with an increased risk of diabetic complications. The ACE polymorphism does not significantly affect blood pressure or angiotensin II levels, suggesting that the kallikrein-kinin system partly mediates the effects of the polymorphism. We have therefore explored the influence of lack of both bradykinin receptors (B1R and B2R) on diabetic nephropathy, neuropathy, and osteopathy in male mice heterozygous for the Akita diabetogenic mutation in the insulin 2 gene (Ins2). We find that all of the detrimental phenotypes observed in Akita diabetes are enhanced by lack of both B1R and B2R, including urinary albumin excretion, glomerulosclerosis, glomerular basement membrane thickening, mitochondrial DNA deletions, reduction of nerve conduction velocities and of heat sensation, and bone mineral loss. Absence of the bradykinin receptors also enhances the diabetes-associated increases in plasma thiobarbituric acid-reactive substances, mitochondrial DNA deletions, and renal expression of fibrogenic genes, including transforming growth factor beta1, connective tissue growth factor, and endothelin-1. Thus, lack of B1R and B2R exacerbates diabetic complications. The enhanced renal injury in diabetic mice caused by lack of B1R and B2R may be mediated by a combination of increases in oxidative stress, mitochondrial DNA damage and over expression of fibrogenic genes.