Regulation der Sphingosinkinase 1 und 2 und der neutralen Ceramidase in renalen Mesangiumzellen der Ratte

In den letzten Jahren gewann die Erforschung des Sphingolipidstoffwechsels in den verschiedensten Zellsystemen immer mehr an Bedeutung, da es sich zeigte, dass einige Sphingolipidspezies, vor allem Ceramid und Sphingosin-1-Phosphat, als wichtige intra- und extrazelluläre Botenstoffe wirken und bei einer Vielzahl unterschiedlicher zellulärer Antworten, wie Apoptose, Proliferation und Migration, eine wichtige Rolle spielen. Während Ceramid eher pro-apoptotisch und wachstumshemmend wirkt, begünstigt Sphingosin-1-Phosphat als „Gegenspieler“ eher die Proliferation und das Zellwachstum. Ceramid kann relativ schnell in Sphingosin-1-Phosphat umgewandelt werden durch die Wirkung zweier Enzymklassen, den Ceramidasen und den Sphingosinkinasen. Konsequenterweise ist die Regulation dieser Enzyme von entscheidender Bedeutung für das zelluläre Gleichgewicht zwischen Ceramid und Sphingosin-1-Phosphat. Im Rahmen dieser Dissertation wurde die Wirkung von extrazellulären Nukleotiden, die ebenfalls als Regulatoren zahlreicher zellulärer Antworten, wie z.B. Proliferation und Migration, bekannt sind und über entsprechende Oberflächenrezeptoren, die Purinrezeptoren, wirken, auf die Aktivität besonders der Sphingosinkinasen 1 und 2 näher untersucht. Es sollte geklärt werden, ob die Sphingosinkinasen an einigen durch extrazelluläre Nukleotide induzierbaren zellulären Antworten, in diesem Falle der Migration und der Proliferation von Zellen, beteiligt sind. Als Zellsystem wurden Nierenmesangiumzellen verwendet, da diese Zellen bei verschiedenen entzündlichen Nierenerkrankungen (Glomerulonephritiden) eine wichtige Rolle spielen. Es konnte in dieser Arbeit gezeigt werden, dass extrazelluläre Nukleotide die Aktivität der Sphingosinkinase 1 in den Mesangiumzellen stimulieren können. Zu beobachten ist dabei eine biphasische Aktivitätssteigerung der Sphingosinkinase 1. Die erste Aktivitätssteigerung nach einer Kurzzeitstimulation ist dabei auf eine Phosphorylierung des Enzyms zurückzuführen, während die zweite Aktivitätssteigerung mit einer Aktivierung des Sphingosinkinase 1-Promotors, einer verstärkten mRNA-Expression und einer de novo Proteinsynthese zu erklären ist. Diese Induktion kann durch die Verwendung von Hemmstoffen des PKC- und MAPK-Signalweges, sowie durch Verwendung eines Transkriptions- (Actinomycin D) oder eines Translationsinhibitors (Cycloheximid) blockiert werden. Die Halbwertszeit der mRNA der Sphingosinkinase 1 in den Mesangiumzellen konnte auf ca. 20 Minuten bestimmt werden. Im Gegensatz dazu ist die Sphingosinkinase 2 nicht durch ATP aktivierbar, wohl aber durch diverse Abbauprodukte von ATP, wie AMP und Adenosin, sowie durch UTP und seine Abbauprodukten UDP und UMP. Die neutrale Ceramidase kann nicht durch ATP und UTP aktiviert werden, wohl aber durch P2X7-Rezeptoragonisten (Bz-ATP, αβ-Me-ATP, γS-ATP) und TPA. In einem zweiten Schritt wurde die Rolle der Sphingosinkinasen und der neutralen Ceramidase bei der durch extrazelluläre Nukleotide induzierten Migration und Proliferation untersucht. Es zeigte sich mit Hilfe von genspezifischer siRNA zur Depletion der Sphingosinkinasen und der neutralen Ceramidase, sowie durch Verwendung von Kinase-Hemmstoffen und damit einhergehend der Inhibierung der Signalwege und mit Hilfe von verschiedenen Zelllinien isoliert aus Wildtyp-, SPHK 1-überexprimierenden und mSPHK1-defizienten Mäusen, dass die Aktivierung der Sphingosinkinase 1 durch extrazelluläre Nukleotide von entscheidender Bedeutung für die Migrationsfähigkeit der Zellen ist, jedoch keinen signifikanten Einfluss auf die Proliferationsrate der Mesangiumzellen hat. Auch die Aktivität der neutralen Ceramidase ist von entscheidender Bedeutung für die Migrationsfähigkeit der Zellen. Durch Depletion der neutralen Ceramidase scheint Ceramid in den Zellen zu akkumulieren, was die Proliferationsrate reduziert. Für die Proliferation der Mesangiumzellen könnte die Sphingosinkinase 2 als negativer Regulator fungieren, wie die Experimente mit der genspezifischen siRNA unter UTP-Stimulation gezeigt haben. Für die Migration der Mesangiumzellen gilt darüber hinaus, dass auch das Produkt der Sphingosinkinase 1, Sphingosin-1-Phosphat, in der Lage ist, die Migration zu stimulieren. Im Gegensatz dazu spielt Sphingosin-1-Phosphat für die Induktion der Proliferation der hier verwendeten Zellen keine wesentliche Rolle. Zusammenfassend zeigen die Daten, dass die Sphingosinkinase 1 und vorgeschaltet auch die neutrale Ceramidase bei der Migration von Mesangiumzellen eine zentrale Rolle spielen und damit als therapeutische Angriffspunkte bei der Behandlung von Krankheiten, die durch eine vermehrte Migration gekennzeichnet sind, in Frage kommen.

Analyse der Wirkung des Naturstoffes Oxacyclododecindion in einem chronisch-inflammatorischen Krankheitsmodell

Die medikamentöse Standardtherapie entzündlich-rheumatischer Erkrankungen wie der rheumatoider Arthritis (RA) und des systemischen Lupus erythematodes (SLE) sind oft unzureichend und erlauben keine nebenwirkungsarme beziehungsweise -freie Behandlung. Daher ist es von großem Interesse für diese Indikationsgebiete, wirkungsvolle Substanzen zu entwickeln, die für eine Langzeittherapie geeignet sind. Naturstoffe wie Oxacyclododecindion (Oxa) können dabei als mögliche Leitstruktur dienen. Oxa wurde bereits in in-vitro Untersuchungen als ein potenter Inhibitor der Expression von proinflammatorischen und profibrotischen Genen identifiziert. rnZiel dieser Arbeit war es in in-vivo Modellen der RA und des SLEs das therapeutische Potential des Naturstoffes Oxa aufzuklären. Da eine Etablierung der Kollagen-induzierten Arthritis im untersuchten murinen RA-Modell, dem HLA-DR4.AE° Stamm, nicht möglich war, wurden die Untersuchungen ausschließlich im MRL Faslpr Mausstamm, einem anerkannten SLE-Modell durchgeführt. MRL Faslpr Mäuse entwickeln wie SLE-Patienten unter anderem eine schwerwiegende Glomerulonephritis. rnIn den Nieren weiblicher MRL Faslpr Mäuse konnte die Oxa-Behandlung die Expression zahlreicher proinflammatorischer Mediatoren beeinflussen, die in Zusammenhang mit der Pathogenese des humanen SLE gebracht werden. So reduziert der Naturstoff die Expression von Zytokinen wie TNFα, IFNγ und IL6 als auch Chemokinen wie CCL2, CSF-1 und RANTES auf mRNA- und Proteinebene. Dabei war die Wirkung von Oxa in den in-vivo Analysen ähnlich gut wie die des potenten Glukokortikoids Dexamethason. Die Reduktion chemotaktischer Moleküle durch die Oxa-Behandlung führte nachweislich zu einer reduzierten Akkumulation von Immunzellen. Die anti-inflammatorischen und immunmodulatorischen Effekte von Oxa waren so ausgeprägt, dass klinisch-pathologische Marker der Glomerulonephritis, wie die Ablagerung von Immunkomplexen, die vermehrte Bildung von Kollagenfasern und die Ausscheidung von Proteinen im Urin gemildert wurden. Weiterführende Untersuchungen im SLE Modell konnten neue Zielmoleküle von Oxa identifizieren, wie KIM1 und zahlreiche SLE-assoziierte microRNAs (miR 19a, 29c und 369). Diese Befunde legen nahe, dass Oxa eine vielversprechende anti-entzündliche und -fibrotische Verbindung darstellt. rnDie Entschlüsselung des Wirkmechanismus von Oxa steht erst am Anfang. Die Analysen im Rahmen dieser Arbeit zeigten jedoch, dass Oxa einen Einfluss auf die Phosphorylierung und somit Aktivierung der p38 MAPK sowie auf die mRNA-Stabilität von proinflammatorischen Zytokinen wie TNFα zu haben scheint.rn

Reversal of established lupus nephritis and prolonged survival of New Zealand black x New Zealand white mice treated with the topoisomerase I inhibitor irinotecan

Systemic lupus erythematosus is a chronic autoimmune disorder that predominantly affects women of childbearing age. Lupus-associated glomerulonephritis is a major cause of mortality in these patients. Current treatment protocols for systemic lupus erythematosus include cyclophosphamide, prednisolone, azathioprine, and mycophenolate mofetil. However, in mice none of these agents alone or in combination were shown to reverse established proteinuria. Using New Zealand Black x New Zealand White F1 mice, we report that administration of the topoisomerase I inhibitor irinotecan from week 13 completely prevented the onset of proteinuria and prolonged survival up to at least 90 wk without detectable side effects. Furthermore, application of irinotecan to mice with established lupus nephritis, as indicated by grade 3+ (> or =300 mg/dl) and grade 4+ (> or =2000 mg/dl) proteinuria and, according to a median age of 35 wk, resulted in remission rates of 75% and 55%, respectively. Survival was significantly prolonged with 73 wk (grade 3+ and 4+ combined) versus 40 wk for control animals. Although total IgG and anti-dsDNA Abs in the serum and mesangial IgG deposits in the kidneys were not reduced in irinotecan-treated mice, subendothelial immune deposits were considerably diminished, suggesting a prevention of glomerular basement membrane disruption. This effect was accompanied by increased rates of ssDNA breaks and inhibition of renal cell apoptosis being different to what is known about irinotecan in anticancer therapy. In conclusion, our data provide evidence that irinotecan might represent an entirely new strategy for the treatment of systemic lupus erythematosus.

Dialysis and Renal Transplantation in HIV-Infected Patients: a European Survey

OBJECTIVES:: To determine prevalence and characteristics of end-stage renal diseases (ESRD) [dialysis and renal transplantation (RT)] among European HIV-infected patients. METHODS:: Cross-sectional multicenter survey of EuroSIDA clinics during 2008. RESULTS:: Prevalence of ESRD was 0.5%. Of 122 patients with ESRD 96 were on dialysis and 26 had received a RT. Median age was 47 years, 73% were males and 43% were black. Median duration of HIV infection was 11 years. Thirty-three percent had prior AIDS; 91% were receiving antiretrovirals; and 88% had undetectable viral load. Median CD4T-cell count was 341 cells per cubic millimetre; 20.5% had hepatitis C coinfection. Most frequent causes of ESRD were HIV-associated nephropathy (46%) and other glomerulonephritis (28%). Hemodialysis (93%) was the most common dialysis modality; 34% of patients were on the RT waiting list. A poor HIV control was the reason for exclusion from RT waiting list in 22.4% of cases. All the RT recipients were all alive at the time of the survey. Acute rejection was reported in 8 patients (30%). Functioning graft was present in 21 (80%). CONCLUSIONS:: This is the first multinational cross-sectional study of ESRD among European HIV population. Low prevalence of ESRD was found. Two-thirds of patients were excluded from RT for non-HIV/AIDS-related pathologies. Most patients had a functioning graft despite a high acute rejection rate.

Structural modification of DNA--a therapeutic option in SLE?

Systemic lupus erythematosus (SLE) is an autoimmune disease that affects multiple organs, with glomerulonephritis representing a frequent and serious manifestation. SLE is characterized by the presence of various autoantibodies, including anti-DNA antibodies that occur in approximately 70% of patients with SLE and which contribute to disease pathogenesis. Consequently, immunosuppressive therapies are applied in the treatment of SLE to reduce autoantibody levels. However, increasing evidence suggests that DNA--especially double--stranded DNA-constitutes an important pathogenic factor that is able to activate inflammatory responses by itself in autoimmune diseases. Therefore, modifying the structure of DNA to reduce its pathogenicity might be a more targeted approach for the treatment of SLE than immunosuppression. This article presents information in support of this strategy, and discusses the potential methods of DNA structure manipulation--in light of data obtained from mouse models of SLE--including topoisomerase I inhibition, administration of DNase I, or modification of histones using heparin or histone deacetylase inhibitors.

Coxsackie B viruses and the kidney--a neglected topic

Coxsackie B viruses types 1-6 (CVB1-6) occur worldwide and cause a broad spectrum of diseases, including myocarditis and aseptic meningitis. Although renal damage due to CVB has been suspected since the 1950s, these agents are only rarely searched for in today's clinical nephrological practice. Nevertheless, CVB can infect mesangial cells. Furthermore, infections with these viruses lead to a histological picture resembling mesangioproliferative glomerulonephritis and IgA-nephropathy in mice. In the present article, we provide an overview of this largely neglected topic, and of the slowly and steadily increasing evidence suggesting a link between coxsackieviral infections and kidney diseases.

Targeting the sphingosine kinase/sphingosine 1-phosphate pathway to treat chronic inflammatory kidney diseases

Chronic kidney diseases including glomerulonephritis are often accompanied by acute or chronic inflammation that leads to an increase in extracellular matrix (ECM) production and subsequent glomerulosclerosis. Glomerulonephritis is one of the leading causes for end-stage renal failure with high morbidity and mortality, and there are still only a limited number of drugs for treatment available. In this MiniReview, we discuss the possibility of targeting sphingolipids, specifically the sphingosine kinase 1 (SphK1) and sphingosine 1-phosphate (S1P) pathway, as new therapeutic strategy for the treatment of glomerulonephritis, as this pathway was demonstrated to be dysregulated under disease conditions. Sphingosine 1-phosphate is a multifunctional signalling molecule, which was shown to influence several hallmarks of glomerulonephritis including mesangial cell proliferation, renal inflammation and fibrosis. Most importantly, the site of action of S1P determines the final effect on disease progression. Concerning renal fibrosis, extracellular S1P acts pro-fibrotic via activation of cell surface S1P receptors, whereas intracellular S1P was shown to attenuate the fibrotic response. Interference with S1P signalling by treatment with FTY720, an S1P receptor modulator, resulted in beneficial effects in various animal models of chronic kidney diseases. Also, sonepcizumab, a monoclonal anti-S1P antibody that neutralizes extracellular S1P, and a S1P-degrading recombinant S1P lyase are promising new strategies for the treatment of glomerulonephritis. In summary, especially due to the bifunctionality of S1P, the SphK1/S1P pathway provides multiple target sites for the treatment of chronic kidney diseases.

Low dose irinotecan improves advanced lupus nephritis in mice potentially by changing DNA relaxation and anti–double-stranded DNA binding

Objective Albeit clear advances in the treatment of SLE, many patients still present with refractory lupus nephritis requiring new treatment strategies for this disease. Here we determined whether reduced doses of the topoisomerase I inhibitor irinotecan, which is known as chemotherapeutic agent, were able to suppress SLE in NZB/W F1 mice. We further evaluated the potential mechanism how irinotecan influenced the course of SLE. Methods NZB/W F1 mice were treated with low dose irinotecan either from week 24 of age or from established glomerulonephritis defined by a proteinuria ≥grade 3+. Binding of anti-dsDNA antibodies was measured by ELISA; and DNA relaxation was visualized by gel electrophoresis. Results Significantly reduced irinotecan dosages improved lupus nephritis and prolonged survival in NZB/W F1 mice. The lowest dose successfully used for the treatment of established murine lupus nephritis was more than 50 times lower than the dose usually applied for chemotherapy in humans. As a mechanism, low dose irinotecan reduced B cell activity; however, the levels of B cell activity in irinotecan-treated mice were similar to those in Balb/c mice of the same age suggesting that irinotecan did not induce a clear immunosuppression. In addition, incubation of double-stranded (ds) DNA with topoisomerase I increased binding of murine and human anti-dsDNA antibodies showing for the first time that relaxed DNA is more susceptible to anti-dsDNA antibody binding. This effect was reversed by addition of the topoisomerase I inhibitor camptothecin. Conclusion Our results propose topoisomerase I inhibitors as a novel and targeted therapy for SLE. © 2014 American College of Rheumatology.

IgA-Nephropathie und Purpura Schönlein-Henoch - ein breites Spektrum

IgA nephropathy is the most common glomerulonephritis in Europe. The disease has been discovered in 1968 in Paris by Jean Berger at the Necker-Children's Hospital. Diagnosis is made by kidney biopsy and requires the presence of mesangial deposits of IgA. This form of glomerulonephritis can be seen in children and adults. In childhood, it most frequently presents within the context of Schoenlein-Henoch purpura. In adulthood, the most common form is limited to the kidney. Schoenlein-Henoch purpura can be seen in adults and manifests as a very aggressive vasculitis, usually in the context of a specific drug intake. The underlying pathophysiological concept today is an insufficient glycosylation of the IgA1 hinge region triggering the formation of autoantibodies against this site. Therapeutic options for the disease are limited. Important is optimal blood pressure control. Selected patients will profit from steroid therapy.

Vaccination of cattle with the N terminus of LppQ of Mycoplasma mycoides subsp. mycoides results in type III immune complex disease upon experimental infection.

Contagious bovine pleuropneumonia (CBPP) is a serious respiratory disease of cattle caused by Mycoplasma mycoides subsp. mycoides. Current vaccines against CBPP induce short-lived immunity and can cause severe postvaccine reactions. Previous studies have identified the N terminus of the transmembrane lipoprotein Q (LppQ-N') of M. mycoides subsp. mycoides as the major antigen and a possible virulence factor. We therefore immunized cattle with purified recombinant LppQ-N' formulated in Freund's adjuvant and challenged them with M. mycoides subsp. mycoides. Vaccinated animals showed a strong seroconversion to LppQ, but they exhibited significantly enhanced postchallenge glomerulonephritis compared to the placebo group (P = 0.021). Glomerulonephritis was characterized by features that suggested the development of antigen-antibody immune complexes. Clinical signs and gross pathological scores did not significantly differ between vaccinated and placebo groups. These findings reveal for the first time the pathogenesis of enhanced disease as a result of antibodies against LppQ during challenge and also argue against inclusion of LppQ-N' in a future subunit vaccine for CBPP.

Cetoacidosis inducida por corticoides y gatifloxacina en una mujer joven no diabética

Objetivo: Comunicar un caso de cetoacidosis inducida por corticoides y gatifloxacina y discutir los mecanismos de esta inusual y seria complicación. Caso clínico: Mujer de 32 años, ingresa por neumonía adquirida en la comunidad de 5 días de evolución. Antecedentes: AR probable diagnosticada 4 meses antes tratada con metotrexate y corticoides intermitente. Examen físico: regular estado general, IMC 21, Tº 38ºC, FR 32/min, derrame pleural derecho, FC 96/min, PA 110/70, artralgias sin artritis. Exámenes complementarios: Hto 23%, GB 16300/mm3, VSG 96mm/1ºh, glucemia 0.90mg/dl, función hepática y amilasa normales, uremia 1.19g/l, creatinina 19mg/l. Hemocultivos (2) y esputo positivos para Neumococo penicilina-sensible. La neumonía responde a gatifloxacina. Deteriora la función renal hasta la anuria con acidosis metabólica. Se interpreta como glomerulonefritis lúpica rápidamente progresiva por proteinuria de 2g/24hs, FR (+) 1/1280, FAN (+) 1/320 homogéneo, Anti ADN (+) , complemento bajo: C3 29.4mg/dl y C4 10mg/dl, Ac anti Ro, La, Scl70, RNP y anticardiolipinas positivos. Se indica metilprednisolona EV (3 bolos 1g), complicándose con hiperglucemias de >6 g/l y cetoacidosis con cetonuria (+); Ac anti ICA y antiGAD negativos con HbA1C 5.2%. Es tratada en UTI (insulina y hemodiálisis). La paciente mejora, se desciende la dosis de corticoides, con normalización de la glucemia sin tratamiento hipoglucemiante. Comentarios 1) La presencia de HbA1C nomal, Ac anti ICA y GAD negativos permite descartar con razonable grado de certeza una diabetes tipo1 asociada al lupus. 2) El desarrollo de la cetoacidosis durante el tratamiento con corticoides y gatifloxacina y su resolución posterior avalan el rol etiológico de los mismos. 3) La cetoacidosis puede explicarse por estimulación de la gluconeogénesis y la insulinoresistencia a nivel de receptor y post-receptor generada por los fármacos potenciado por el estado inflamatorio relacionado con el lupus y la sepsis.

Endocarditis infecciosa : significado de la disfunción renal

Objetivo: Determinar la significación clínica y pronóstica de la disfunción renal en pacientes con Endocarditis Infecciosa (EI) Material y método: Estudio protocolizado, descriptivo, observacional y transversal de pacientes con EI diagnosticados según criterios de Duke. Se realizó un análisis comparativo entre los pacientes con EI sin (Grupo Sin) y con Disfunción Renal (Grupo DR), que se definió en base a uremia > 0.60 g/l y/o creatininemia > 1.5 mg/dl y/o hematuria o proteinuria. Fueron analizados en EPI info 6.04. Resultados: De un total de 110 EI incluidas, 58 (52.7%) presentaron DR principalmente secundaria a glomerulonefritis (n 22), sepsis (n 14), insuficiencia renal crónica (n 5), insuficiencia cardíaca, nefropatía diabética y nefrotoxicidad (n 4 cada una) y embólica (n 1). No hubo diferencias en la permanencia media hospitalaria (32 DS±23.3 vs 26.32 DS±17.28 días), el sexo (masculino: 60.3 vs 71.25%) y la demora diagnóstica (5.5 (DS±7.23) vs. 5.4 (DS±7.64 días)(pNS). La edad media fue mayor en el grupo DR en el LS (49.62 DS±15.71 vs 43.53 DS±17.94 años). El Grupo DR tuvo mas frecuentemente EI Definida (87.9 vs 67.3%) (p=0.0089) y no hubo diferencias en la localización Mitral (48.3 vs 48.1%) y Aórtica (44.8 vs 34.6%). La valvulopatía degenerativa se presentó en el LS en DR (34.5 VS 19.6%)(p=0.07). No hubo diferencias en la presencia de comórbidas (62.1 vs 71.2%) (pNS) pero la enfermedad últimamente fatal ocurrió mas frecuentemente en DR (51.4 vs 21.6%)(p=0.05). Al ingreso sólo la presencia de rales pulmonares (53.4 vs 32.7%) y púrpura cutánea (27.6 vs 13.5%) fueron más frecuentes en DR (p=0.05). La sepsis no controlada (34.5 vs 15.7%), insuficiencia cardíaca (51.7 vs 32.7%), encefalopatía (50 vs 27.5%), shock séptico (24.1 vs 7.8%) y fallo multiorgánico (34.5 vs 3.9%) fueron complicaciones más frecuentes en DR (p<0.05). La fiebre persistente se encontró en el LS en el grupo de DR (48.3 vs 32.7%)(p=0.09). No hubo diferencias en el hallazgo de vegetaciones por ecocardiografía (83.3 vs 75.6%). La anemia (Hb<9 mg/dl) (31.86 DS±53.41 vs 35.21 DS±7.85)(p=0.009), hipergammaglobulinemia (58.5 vs 29.8)(p=0.006) e hiperglucemia (36.1 vs 18.5)(p=0.03) se asociaron a DR. En el grupo con DR fue mas común la EI con cultivos negativos (31.5 vs 0%)(p=0.001) y el predominio de las infecciones por S. aureus Meticilino Resistente (MRSA)(21.6 vs 2.7%) (p=0.02). No hubo diferencias en la indicación de cirugía (31 vs 36.5%). La mortalidad hospitalaria fue significativamente mayor en DR (51.7 vs 25%)(p=0.0041)(OR 3.2, IC95%1.42-7.24). Conclusión: En los pacientes con EI la disfunción renal resultó ser un indicador de desarrollo de complicaciones infecciosas y cardíacas, de infección por MRSA y de mortalidad cruda hospitalaria.-

Prevention of development of autoimmune disease in BXSB mice by mixed bone marrow transplantation

Transplantations of fully allogeneic, autoimmune-resistant T-cell-depleted marrow (TCDM) plus syngeneic, autoimmune-prone TCDM into lethally irradiated BXSB mice were carried out to investigate the ability of the mixed bone marrow transplantation (BMT) to prevent development of autoimmune disease and, at the same time, to reconstitute fully the immunity functions of heavily irradiated BXSB recipients. Male BXSB mice were engrafted with mixed TCDM from both allogeneic, autoimmune-resistant BALB/c mice and syngeneic, autoimmune-prone BXSB mice. BMT with mixed TCDM from both resistant and susceptible strains of mice (mixed BMT) prolonged the median life span and inhibited development of glomerulonephritis in BXSB mice. BMT with mixed TCDM also prevented the formation of anti-DNA antibodies that is typically observed in male mice of this strain. Moreover, mixed BMT reconstituted primary antibody production in BXSB recipients, so that no annoying immunodeficiencies that are regularly observed in fully allogeneic chimeras were present in the recipient of the mixed TCDM. These findings indicate that transplanting allogeneic, autoimmune-resistant TCDM plus syngeneic, autoimmune-prone TCDM into lethally irradiated BXSB mice prevents development of autoimmune disease in this strain of mice. In addition, this dual BMT reconstitutes the immunity functions and avoids the immunodeficiencies that occur regularly in fully allogeneic chimeras after total-body irradiation.

The solution structure of the N-terminal domain of α2-macroglobulin receptor-associated protein

The three-dimensional structure of the N-terminal domain (residues 18–112) of α2-macroglobulin receptor-associated protein (RAP) has been determined by NMR spectroscopy. The structure consists of three helices composed of residues 23–34, 39–65, and 73–88. The three helices are arranged in an up-down-up antiparallel topology. The C-terminal 20 residues were shown not to be in a well defined conformation. A structural model for the binding of RAP to the family of low-density lipoprotein receptors is proposed. It defines a role in binding for both the unordered C terminus and the structural scaffold of the core structure. Pathogenic epitopes for the rat disease Heymann nephritis, an experimental model of human membranous glomerulonephritis, have been identified in RAP and in the large endocytic receptor gp330/megalin. Here we provide the three-dimensional structure of the pathogenic epitope in RAP. The amino acid residues known to form the epitope are in a helix–loop–helix conformation, and from the structure it is possible to rationalize the published results obtained from studies of fragments of the N-terminal domain.

Complete genome sequence of an M1 strain of Streptococcus pyogenes

The 1,852,442-bp sequence of an M1 strain of Streptococcus pyogenes, a Gram-positive pathogen, has been determined and contains 1,752 predicted protein-encoding genes. Approximately one-third of these genes have no identifiable function, with the remainder falling into previously characterized categories of known microbial function. Consistent with the observation that S. pyogenes is responsible for a wider variety of human disease than any other bacterial species, more than 40 putative virulence-associated genes have been identified. Additional genes have been identified that encode proteins likely associated with microbial “molecular mimicry” of host characteristics and involved in rheumatic fever or acute glomerulonephritis. The complete or partial sequence of four different bacteriophage genomes is also present, with each containing genes for one or more previously undiscovered superantigen-like proteins. These prophage-associated genes encode at least six potential virulence factors, emphasizing the importance of bacteriophages in horizontal gene transfer and a possible mechanism for generating new strains with increased pathogenic potential.