Biomedical subjects

Novella Calvaresi

Publications and source records attributed to Novella Calvaresi.

9 recordsLinked to original sources

PubMed2006

Glomerular activation of the lectin pathway of complement in IgA nephropathy is associated with more severe renal disease.

IgA nephropathy (IgAN) is characterized by glomerular co-deposition of IgA and complement components. Earlier studies showed that IgA activates the alternative pathway of complement, whereas more recent data also indicate activation of the lectin pathway. The lectin pathway can be activated by binding of mannose-binding lectin (MBL) and ficolins to carbohydrate ligands, followed by activation of MBL-associated serine proteases and C4. This study examined the potential role of the lectin pathway in IgAN. Renal biopsies of patients with IgAN (n=60) showed mesangial deposition of IgA1 but not IgA2. Glomerular deposition of MBL was observed in 15 (25%) of 60 cases with IgAN and showed a mesangial pattern. All MBL-positive case, but none of the MBL-negative cases showed glomerular co-deposition of L-ficolin, MBL-associated serine proteases, and C4d. Glomerular deposition of MBL and L-ficolin was associated with more pronounced histologic damage, as evidenced by increased mesangial proliferation, extracapillary proliferation, glomerular sclerosis, and interstitial infiltration, as well as with significantly more proteinuria. Patients who had IgAN with or without glomerular MBL deposition did not show significant differences in serum levels of MBL, L-ficolin, or IgA or in the size distribution of circulating IgA. Furthermore, in vitro experiments showed clear binding of MBL to polymeric but not monomeric patient IgA, without a significant difference between both groups. Together, these findings strongly point to a role for the lectin pathway of complement in glomerular complement activation in IgAN and suggest a contribution for both MBL and L-ficolin in the progression of the disease.

Adult↗

PubMed2006

Glomerular podocytes contain neuron-like functional synaptic vesicles.

Although patients with chronic renal failure are increasing worldwide, many aspects of kidney biology remain to be elucidated. Recent research has uncovered several molecular properties of the glomerular filtration barrier, in which podocytes, highly differentiated, ramified cells that enwrap the glomerular basement membrane, have been reported to be mainly responsible for filter's selectivity. We previously described that podocytes express Rab3A, a GTPase restricted to cell types that are capable of highly regulated exocytosis, such as neuronal cells. Here, we first demonstrate by a proteomic study that Rab3A in podocytes coimmmunoprecipitates with molecules once thought to be synapse specific. We then show that podocytes possess structures resembling synaptic vesicles, which contain glutamate, coexpress Rab3A and synaptotagmin 1, and undergo spontaneous and stimulated exocytosis and recycling, with glutamate release. Finally, from the results of a cDNA microarray study, we describe the presence of a series of neuron- and synapse-specific molecules in normal human glomeruli and confirm the glomerular protein expression of both metabotropic and ionotropic glutamate receptors. These data point toward a synaptic-like mechanism of communication among glomerular cells, which perfectly fits with the molecular composition of the glomerular filter and puts in perspective several previous observations, proposing a different working hypothesis for understanding glomerular signaling dynamics.

Animals↗

PubMed2006

Glutamate AMPA receptors change in motor neurons of SOD1G93A transgenic mice and their inhibition by a noncompetitive antagonist ameliorates the progression of amytrophic lateral sclerosis-like disease.

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder involving the selective degeneration of motor neurons. In a small proportion of patients, ALS is caused by mutations in copper/zinc superoxide dismutase (SOD1), and mice overexpressing SOD1(G93A) mutant develop a syndrome that closely resembles the human disease. Excitotoxicity mediated by glutamate AMPA receptors has been suggested to be implicated in the selective susceptibility of motor neurons occurring in ALS. In SOD1(G93A) mice, we found that levels of GluR2 AMPA subunit, which plays a pivotal role in the maintenance of calcium impermeability of AMPA receptors, are decreased in spinal motor neurons before symptom onset in concomitance with a modest increase of GluR3 expression, a calcium-permeable AMPA subunit. This effect can result in a higher number of calcium-permeable AMPA receptors on motor neurons of SOD1(G93A) mice, predisposing these cells to be injured by AMPA-mediated glutamate firing. In support of this, we showed that treatment with a new noncompetitive AMPA antagonist, ZK 187638, partially protected motor neurons, improved motor function, and prolonged the survival of SOD1(G93A) mice.

Amyotrophic Lateral Sclerosis↗

PubMed2005

Functional consequences of integrin-linked kinase activation in podocyte damage.

BACKGROUND: The delicate foot process architecture of glomerular podocytes critically depends on integrin mediated cell-glomerular basement membrane (GBM) interaction. Integrin signaling via the integrin-linked kinase (ILK) is activated in podocyte damage and associated with considerable podocyte phenotype alterations. ILK has been shown to regulate cell fate via nuclear interaction of beta-catenin with lymphoid enhancer factor (LEF-1) transcription factors. The aim of this study was to elucidate the molecular mechanisms of ILK dependant phenotype regulation in podocytes. METHODS: ILK function was evaluated in conditionally immortalized murine glomerular epithelial cells using overexpression of ILK and a small molecule ILK inhibitor in puromycin/adriamycin-induced podocyte damage in vitro and in vivo. RESULTS: Kinase active, but not mutant ILK induced translocation of beta-catenin to the cell nucleus, de novo expression of LEF-1, and nuclear colocalization of beta-catenin and LEF-1. The role of ILK signaling in podocyte damage was evaluated using puromycin, an agent known to cause selective proteinuria and to increase ILK activity. The small molecular ILK inhibitor MC-5 blocked puromycin-induced nuclear translocation of beta-catenin, podocyte detachment, cell proliferation, and repression of the slit membrane molecules P-cadherin and CD2ap. In vivo activation of the beta-catenin pathway could be shown by nuclear colocalization of beta-catenin with WT-1 in adriamycin nephropathy. CONCLUSION: ILK regulates podocyte cell matrix interaction, proliferation, and slit membrane gene expression in podocyte damage. As this pathway is amendable to pharmacologic intervention, further detailed studies of in vivo ILK function in glomerular disease appear justified.

Active Transport, Cell Nucleus↗

PubMed2004

Induction of B7-1 in podocytes is associated with nephrotic syndrome.

Kidney podocytes and their slit diaphragms form the final barrier to urinary protein loss. This explains why podocyte injury is typically associated with nephrotic syndrome. The present study uncovered an unanticipated novel role for costimulatory molecule B7-1 in podocytes as an inducible modifier of glomerular permselectivity. B7-1 in podocytes was found in genetic, drug-induced, immune-mediated, and bacterial toxin-induced experimental kidney diseases with nephrotic syndrome. The clinical significance of our results is underscored by the observation that podocyte expression of B7-1 correlated with the severity of human lupus nephritis. In vivo, exposure to low-dose LPS rapidly upregulates B7-1 in podocytes of WT and SCID mice, leading to nephrotic-range proteinuria. Mice lacking B7-1 are protected from LPS-induced nephrotic syndrome, suggesting a link between podocyte B7-1 expression and proteinuria. LPS signaling through toll-like receptor-4 reorganized the podocyte actin cytoskeleton in vitro, and activation of B7-1 in cultured podocytes led to reorganization of vital slit diaphragm proteins. In summary, upregulation of B7-1 in podocytes may contribute to the pathogenesis of proteinuria by disrupting the glomerular filter and provides a novel molecular target to tackle proteinuric kidney diseases. Our findings suggest a novel function for B7-1 in danger signaling by nonimmune cells.

Actins↗

PubMed2003

The densitometric physical fractionator for counting neuronal populations: application to a mouse model of familial amyotrophic lateral sclerosis.

The method of the 'densitometric physical fractionator' presented here realizes an accurate and reproducible stereological quantification, not requiring a motorized or controlled z-axis, of cell populations. It includes a special software for the calibration of the optics alignment of the microscope and a semi-automatic procedure that integrates specific densitometric functions for image analysis, to identify the reference volume and the particle profiles. This improves the identification of the cells significantly, reduces variability in the subjective choice of the particles by the operators, and allows a consistent saving of time during the analysis. The method is proved to be unbiased and the accuracy and reproducibility of the results has been validated through intra- and inter-operator analyses. Furthermore, it has been applied to calculate the loss of spinal motor neurons during pathology progression in transgenic mice for superoxide-dismutase Cu/Zn dependent (SOD1) mutants, a model of amyotrophic lateral sclerosis (ALS).

Amyotrophic Lateral Sclerosis↗

PubMed2003

Kif1Bbeta isoform is enriched in motor neurons but does not change in a mouse model of amyotrophic lateral sclerosis.

The kinesin superfamily motor protein Kif1B is expressed in two isoforms, Kif1Balpha and Kif1Bbeta, with distinct cargo-binding domains. We examined the mRNA distribution of the two isoforms in adjacent sections of brain and spinal cord of adult mice using in situ hybridization analysis. Kif1Bbeta mRNA is enriched in several regions of brain and spinal cord. Its levels are four to five times higher than that of the alpha isoform, which was barely detectable. The highest mRNA levels of Kif1Bbeta were found in the cortex, hippocampus, cerebellum and the grey matter of the spinal cord. At the cellular level the highest signal was found in motor neurons in the motor nuclei of medulla oblongata and the ventral horn of spinal cord. Because expression of other Kif genes is altered in amyotrophic lateral sclerosis (ALS) models, we examined the expression level of Kif1Bbeta mRNA in the spinal cord of transgenic mice carrying the SOD1G93A mutation, a model of familial ALS, at presymptomatic and early stages of the disease. No changes were observed in Kif1Bbeta mRNA in motor neurons or in other regions of the spinal cord. These findings indicate that Kif1Balpha, which modulates the transport of mitochondria, may play a major role in tissues other than the central nervous system. Instead Kif1Bbeta, responsible for the transport of synaptic vesicle precursors, seems to play an important role in the nervous system, particularly in the lower motor neurons. The absence of changes of Kif1Bbeta mRNA in transgenic SOD1G93A mice suggests that other molecular mechanisms may play a role in the disruption of axonal transport occurring in the motor neurons of these mice.

Amyotrophic Lateral Sclerosis↗

PubMed2002

Expression of glutamate receptor subtypes in the spinal cord of control and mnd mice, a model of motor neuron disorder.

We studied the expression and distribution of glutamate receptor subtypes in the spinal cord of mnd mice, a model of motor neuron disorders and neuronal ceroid lipofuscinosis, and control mice using immunocytochemistry and in situ hybridization. The constitutive subunit of the NMDA ionotropic glutamate receptor, NMDAR1, was expressed in all neurons of the grey matter and was not modified in the spinal cord of mnd mice in either its normal or phosphorylated form. The immunoreactivity of GluR2, but not its mRNA, was increased mainly in the substantia gelatinosa both in presymptomatic and in 8-month-old symptomatic mice, suggesting compensatory changes aimed at reducing the Ca2+ permeability of the receptor channel. In spinal cord of mnd mice, mRNA, and protein levels of GluR3 were low only at the symptomatic stage, possibly as a consequence of motor neuron dysfunction. This was not due to motoneuron degeneration, because the number of choline acetyltransferase (ChAT) immunopositive lumbar motor neurons and the ChAT activity in the spinal cord and hind leg muscles of symptomatic mnd mice were no different from control mice. GluR4 mRNA was increased throughout the grey matter, presumably in relation to the marked microglia activation reported in the grey matter of the lumbar spinal cord in mnd mice. These changes in ionotropic glutamate receptors may alter glutamatergic neurotransmission and play some role in the pathology of mnd mice.

Animals↗

PubMedDate not supplied

CD20-positive infiltrates in human membranous glomerulonephritis.

Membranous glomerulonephritis (MGN), histologically defined by subepithelial immune deposits, is the most common cause of nephrotic syndrome in Caucasian adults. The current hypothesis of the underlying disease mechanism postulates production of antibodies against podocyte-derived antigens. Respective antigens could be demonstrated in different animal models and recently in human neonatal MGN. Further support for this hypothesis was generated by the response of human MGN to therapeutic B cell depletion by rituximab. However, the role of B cells in this disease is not well defined. In this study, the interstitial expression of CD20 mRNA was determined in 31 MGN patients and controls (tumor nephrectomies (n = 4), minimal change disease (MCD, n = 10) and focal segmental glomerulosclerosis (n = 6)). CD20 mRNA expression was significantly higher in MGN patients compared to controls. By immunohistochemistry, a focal or diffuse interstitial B cell infiltration could be detected in MGN patients (n = 63), which was absent or minimal in patients with MCD (n = 11). These data suggest an involvement of B cells in the pathogenesis of MGN, possibly as antigen-presenting cells. Further studies should investigate the potential to predict the response to therapeutic B cell depletion by intrarenal CD20 quantification, a potential diagnostic basis for the selection of a specific therapy currently evolving for renal disease.

Antigens, CD20↗