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A Remuzzi

Publications and source records attributed to A Remuzzi.

At least 19 recordsLinked to original sources
PubMed1996

Cyclosporine enhances leukocyte adhesion to vascular endothelium under physiologic flow conditions.

We investigated the effect of cyclosporine (CyA) on leukocyte adhesion to endothelium under flow conditions. Confluent human umbilical vein endothelial cells (HUVECs) were incubated for 24 hours with CyA (1, 5, and 10 micromol/L) and then exposed to a total human leukocyte suspension in a parallel plate flow chamber under laminar flow (1.5 dynes/cm2. Human umbilical vein endothelial cells stimulated with interleukin-1beta (20 U/mL) were used as a positive control. Adherent cells were measured by digital image analysis. Results showed that CyA dose-dependently increased the number of leukocytes adhering to HUVECs compared with control cells. Leukocyte adhesion markedly increased on HUVECs incubated with interleukin-lbeta, one of the most potent inducers of endothelial cell adhesiveness. Exposure of endothelial cells to CyA did not affect the number of rolling leukocytes, which was similar to control values. To examine the role of adhesion molecules in CyA-induced leukocyte adhesion, HUVECs were incubated with monoclonal antibodies against intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and E-selectin before adhesion assay. Functional blocking of ICAM-1, VCAM-1, and E-selectin on endothelial cells significantly inhibited CyA (10 micromol/L)-induced leukocyte adhesion. Confocal fluorescence microscopy studies showed that CyA induced an increase in the endothelial surface expression of ICAM-1, VCAM-1, and E-selectin. Pretreatment of leukocytes with the platelet activating factor receptor antagonist L659,989 significantly reduced the number of leukocytes adhering to CyA-treated HUVECs. We suggest that CyA enhances leukocyte adhesion to endothelium by upregulating adhesive proteins on endothelial surface membrane. Blocking leukocyte receptor for platelet-activating factor partially prevents adhesion, suggesting a role for endothelial cell-associated platelet-activating factor in the interaction between leukocytes and CyA-treated endothelium.

Cell Adhesion↗
PubMed1996

Angiotensin II modulates glomerular capillary permselectivity in rat isolated perfused kidney.

Studies in experimental animals and humans have documented that inhibition of the renin-angiotensin system by angiotensin-converting enzyme inhibitors reduces urinary protein excretion rate and retards the development of renal injury. Here we sought to investigate whether angiotensin II (All) modified the size-selective properties to macromolecules of the glomerular capillary barrier in isolated perfused rat kidney preparation. Compared with basal values, continuous All infusion into the renal artery at the rate of 3 or 8 ng/min, but not at 0.6 ng/min, induced a progressive and significant increase in urinary protein excretion rate. Evaluation of the sieving properties of the glomerular barrier by fractional clearance of polydisperse Ficoll showed that All significantly enhanced the filtration of tracer molecules of radil > or = 34A. All-induced changes in urinary protein excretion rate and in Ficoll fractional clearance were completely prevented by pretreatment with the specific All Type 1 receptor antagonist SR 47436.

Angiotensin II↗
PubMed1995

Verotoxin-1 promotes leukocyte adhesion to cultured endothelial cells under physiologic flow conditions.

Hemolytic uremic syndrome (HUS), which is the most common cause of acute renal failure in infants and small children, is caused by verotoxin (VT)-producing Escherichia coli infection. Endothelial injury determines microvascular thrombosis and evidence is available from recent studies that suggests that leukocyte activation participates in endothelial damage. We studied here the effect of VT-1 on leukocyte adhesion to vascular endothelium under physiologic flow conditions. Human umbilical vein endothelial cells (HUVECs) were incubated for 24 hours with VT-1 (0.1, 1, and 10 pmol/L) and then exposed to a total leukocyte suspension in a parallel plate flow chamber under laminar flow conditions (1.5 dynes/cm2). Adherent cells were counted by digital image processing. Results showed that VT-1 dose-dependently increased the number of adhering leukocytes to HUVECs as compared with unstimulated cells. The adhesive response elicited by VT-1 was comparable to that of interleukin-1 beta (IL-1 beta), one of the most potent inducers of endothelial cell adhesiveness. Exposure of HUVECs to VT-1 did not affect the number of rolling leukocytes, which was similar to that of control values. To examine the role of adhesion molecules in VT-1-induced leukocyte adhesion, HUVECs were incubated with mouse monoclonal antibodies against E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) before adhesion assay. Functional blocking of E-selectin, ICAM-1, and VCAM-1 on endothelial cells significantly inhibited VT-1-induced increase in leukocyte adhesion. In some experiments, before VT-1 incubation, HUVECs were pretreated for 24 hours with tumor necrosis factor alpha (TNF alpha; 100 U/mL), which is known to increase VT receptor expression on HUVECs. The number of adhering leukocytes on HUVECs exposed to TNF alpha and VT-1 significantly increased as compared with HUVECs incubated with VT-1 and TNF alpha alone. These results suggest that VT-1 modulates leukocyte-endothelium interaction, thus increasing leukocyte adhesion and upregulating adhesive proteins on endothelial surface membrane.

Animals↗
PubMed1995

Fluid shear stress modulates surface expression of adhesion molecules by endothelial cells.

We investigated the effect of hemodynamic shear forces on the expression of adhesive molecules, E-selectin, and intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells (HUVEC) exposed to laminar (8 dynes/cm2) or turbulent shear stress (8.6 dynes/cm2 average), or to a static condition. Laminar flow induced a significant time-dependent increase in the surface expression of ICAM-1, as documented by flow cytometry studies. Endothelial cell surface expression of ICAM-1 in supernatants of HUVEC exposed to laminar flow was not modified, excluding the possibility that HUVEC exposed to laminar flow synthetize factors that upregulate ICAM-1. The effect of laminar flow was specific for ICAM-1, while E-selectin expression was not modulated by the flow condition. Turbulent flow did not affect surface expression of either E-selectin or ICAM-1. To evaluate the functional significance of the laminar-flow-induced increase in ICAM-1 expression, we studied the dynamic interaction of total leukocyte suspension with HUVEC exposed to laminar flow (8 dynes/cm2 for 6 hours) in a parallel-plate flow chamber or to static condition. Leukocyte adhesion to HUVEC pre-exposed to flow was significantly enhanced, compared with HUVEC maintained in static condition (233 +/- 67 v 43 +/- 16 leukocytes/mm2, respectively), and comparable with that of interleukin-1 beta treated HUVEC. Mouse monoclonal antibody anti-ICAM-1 completely blocked flow-induced upregulation of leukocyte adhesion. Interleukin-1 beta, which upregulated E-selectin expression, caused leukocyte rolling on HUVEC that was significantly lower on flow-conditioned HUVEC and almost absent on untreated static endothelial cells. Thus, laminar flow directly and selectively upregulates ICAM-1 expression on the surface of endothelial cells and promotes leukocyte adhesion. These data are relevant to the current understanding of basic mechanisms that govern local inflammatory reactions and tissue injury.

Antibodies, Monoclonal↗
PubMed1995

Numerical analysis of blood flow in reconstructed glomerular capillary segments.

Poiseuille's formula is conventionally used to calculate hydraulic resistance of blood capillaries. This law, however, applies to tubes with constant diameter and straight axis. Since blood capillaries, especially in the glomerular microcirculation, are far from having these features, we wanted to estimate the effect of the shape of glomerular capillary segments on the calculation of their hydraulic resistance in comparison to the values obtained with Poiseuille's formula. We studied blood flow through capillary segments of a reconstructed glomerular network from a normal Munich-Wistar rat. Geometrical parameters of capillary segments derived from serial section reconstruction of the glomerulus were used to perform numerical analysis of blood flow. Non-Newtonian properties of blood were simulated by calculating apparent blood viscosity as a function of local rheological parameters for each capillary segment. The numerically calculated hydraulic resistances were always higher than those given by the Poiseuille equation (from 22 to 99%), and this was attributed to the geometrical complexity of the reconstructed vessels. We also performed simulations of the blood flow and filtration along the glomerular network using a previously developed theoretical model that considers the topographical organization of the network structure and dimensions of individual capillary segments. Considering higher hydraulic resistances (as estimated with the numerical analysis) we found that the calculated ultrafiltration coefficient did not change appreciably, but the total network pressure drop and the fraction of filtering surface area at filtration equilibrium were higher than previously estimated.

Animals↗
PubMed1995

Direct podocyte damage in the single nephron leads to albuminuria in vivo.

The hypothesis that detachment of podocytes leads to albuminuria was tested by studying the single nephron albuminuria in vivo after injecting a saponin solution (0.6 mg/ml) in Bowman's space of superficial glomeruli, which produces selective damage of the podocytes, in female Munich-Wistar-Frömter rats. Animals were subsequently installed under a fluorescence microscope, a purified fluoresceinated rat albumin solution was intravenously injected and the passage of the fluorescent albumin was followed through the microscope. Of the 47 glomeruli injected with the saponin solution (in 6 animals) 46 became fluorescent within seconds with the fluorescence progressing from Bowman's space into the proximal tubule and then in the rest of the tubule. In superficial non-injected and control-injected glomeruli weak fluorescence could be detected only in the glomerular tuft and the peritubular capillaries. Tubuli injected with the saponin solution remained indistinguishable from non-injected tubuli. Electron microscopic study of the saponin-injected glomeruli confirmed the selective removal of podocytes. Immunogold electron microscopy confirmed that the intact albumin molecule effectively passed the glomerular capillary wall at the site where podocyte detachment had occurred. It is concluded that selective removal of podocytes at the single nephron level leads to albuminuria in vivo, and therefore podocytes play a crucial role in regulating the permeability of the glomerular capillary wall.

Albumins↗
PubMed1995

ACE inhibition prevents renal failure and death in uninephrectomized MWF/Ztm rats.

Many studies have consistently documented that angiotensin converting enzyme (ACE) inhibitors prevent proteinuria and glomerulosclerosis in progressive renal disease, but very few data are available on whether they also prevent renal failure and death. The mechanisms of the beneficial effect of ACE inhibition are only partially understood. Recent data suggest that angiotensin II modulates renal synthesis of endothelin-1, a vasoactive peptide implicated in the process of renal injury. Here we investigated in a long-term study whether ACE inhibition ameliorated renal function in uninephrectomized (UNx) male MWF/Ztm rats. Three groups of rats at nine weeks of age underwent UNx or sham-operation. Nephrectomized animals were left untreated or treated with the ACE inhibitor lisinopril in drinking water. In untreated UNx animals systolic blood pressure, serum creatinine, urinary protein and renal synthesis of endothelin-1, evaluated by its urinary excretion, were significantly increased, as compared with control animals with two kidneys. End-stage renal failure developed in all untreated UNx rats that died within 9 to 14 months from UNx. ACE inhibitor significantly reduced systolic blood pressure, completely prevented proteinuria and renal function deterioration, and reduced endothelin-1 excretion. All UNx rats treated with lisinopril were alive 14 months after UNx. These results show that ACE inhibition prevents end-stage renal failure induced by UNx in male MWF/Ztm, and that the beneficial effects of angiotensin II inhibition in this model are related to modulation of renal synthesis of endothelin-1.

Aging↗
PubMed1995

Three-dimensional analysis of glomerular morphology in patients with subtotal nephrectomy.

Previous studies documented that single section examination of kidney tissue underestimates glomerulosclerosis and that three-dimensional examination of glomerular morphology improves recognition of the incidence and distribution of sclerotic changes within the glomerular capillary tuft. We have adopted this technique to evaluate the true frequency and the spatial extent of glomerulosclerosis in patients who were subjected to extensive renal mass reduction. We re-evaluated four kidney biopsies of patients with a solitary kidney who had undergone partial nephrectomy for renal-cell carcinoma. Histopathological examination aimed at detection of glomerular sclerotic lesions was performed on serial sections (from 75 to 93 serial sections for each biopsy, 3 microns thick) together with three-dimensional morphometric analysis of glomerular tuft and sclerotic areas using a computer-based image processing system. Results were compared with observations based on more conventional single section evaluation of the same biopsies. Among 65 glomeruli examined by three-dimensional morphometric analysis, only 8% were normal, 42% revealed segmental sclerosis and 51% global sclerosis. These results confirmed that single section evaluation grossly overestimates the number of normal glomeruli (37% vs. 8%, respectively), since the majority of glomeruli classified as normal are indeed affected by sclerotic changes in areas typically out of the section plane. The three-dimensional distribution of sclerosis is characterized by the appearance of multi-focal areas affecting a small capillary tuft volume (< 10%) which ultimately propagate to the entire capillary tuft. Despite the maintenance of renal function, at the time of biopsy in patients with extensive ablation of renal mass, the incidence of glomerulosclerosis affects almost the entire glomerular population.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗
PubMed1995

Mathematical description of transport of water and macromolecules through the glomerular capillary wall.

Glomerular diseases are associated with changes in glomerular membrane permeability properties that alter filtration rate of plasma water and barrier function of the capillary wall. To estimate intrinsic permeability properties that regulate transmembrane transport of water and macromolecules, theoretical analysis of renal clearance of tracer molecules can be used. The development of adequate theoretical models is required to achieve sufficient accuracy to simulate complicated biological processes. Current research in this area is aimed at improving and validating the presently available models in order to characterize the nature of permeability changes associated with pathological conditions. This is a key step in understanding the pathophysiological nature of glomerular diseases and in the development of effective treatments.

Animals↗
PubMed1995

PAF mediates neutrophil adhesion to thrombin or TNF-stimulated endothelial cells under shear stress.

Platelet-activating factor (PAF) is known to modulate polymorphonuclear leukocyte (PMN) adhesion to endothelial cells cultured under static conditions and activated by thrombin. In contrast, there are no data on the role of PAF in PMN adhesion to cells exposed to flow conditions and activated by stimuli other than thrombin. Here we used the PAF receptor antagonist L-659,989 to evaluate PMN adhesion to human umbilical vein endothelial cells (HUVEC) in basal conditions or upon challenge with thrombin or tumor necrosis factor-alpha (TNF-alpha). Experiments were performed under dynamic flow using a parallel-plate flow chamber and a computer-based image analysis system. Rolling and adhesion of PMNs to endothelial cells significantly increased upon stimulation with thrombin. Thrombin-stimulated HUVEC also synthesized higher amounts of PAF than untreated cells. Pretreatment of PMNs with L-659,989 significantly reduced their rolling and adhesion to thrombin-activated HUVEC. Stimulation of HUVEC with TNF-alpha significantly increased the number of rolling and adherent PMNs as compared with untreated cells. Adhesion of PMNs to and migration across TNF-alpha-stimulated HUVEC were reduced by L-659,989, whereas cell rolling was unchanged. We conclude that PAF mediates leukocyte interaction under flow conditions with HUVEC activated by inflammatory stimuli.

Cell Adhesion↗
PubMed1995

Capillary network structure does not affect theoretical analysis of glomerular size selectivity.

Anatomical studies have demonstrated that the glomerular capillaries are complex and heterogeneous networks. Conventional models of glomerular size selectivity, however, are based on the assumption of simplified geometries. We developed a theoretical model of glomerular size-selective function based on the geometric data obtained in a previous reconstruction of a glomerular network from a normal Munich-Wistar rat. This heterogeneous model was compared with the homogeneous model conventionally used to calculate membrane selective parameters from the fractional clearance of two test solutes, neutral dextran and Ficoll. For both models we assumed a hypothetical log-normal distribution of pore sizes and calculated optimal membrane pore-size parameters using previously published values of fractional clearances. The difference between the sieving coefficients calculated with the two models was negligible, never exceeding 5.5%. Since the homogeneous model does not consider the pressure drop along the glomerular capillary, we also computed fractional clearances with the homogeneous model, assuming the same pressure drop as in the heterogeneous one. The differences in computed fractional clearances using the homogeneous model with and without a pressure drop were less than 1.2%. We concluded that models based on identical capillary networks can therefore be used for interpreting sieving coefficients for macromolecules.

Animals↗
PubMed1995

Nitric oxide synthesis by cultured endothelial cells is modulated by flow conditions.

In the present study, we examined the hypothesis that dynamic characteristics of flow modulate the production of vasoactive mediators, namely nitric oxide (NO) and endothelin-1 (ET-1), by human umbilical vein endothelial cells (HUVECs). Cells were exposed for 6 hours in a cone-and-plate apparatus to different types of flow: steady laminar, with shear stresses of 2, 8, and 12 dyne/cm2, pulsatile laminar, with shear stress from 8.2 to 16.6 dyne/cm2 and a frequency of 2 Hz; periodic laminar, with square wave cycles of 15 minutes and shear stress from 2 to 8 dyne/cm2, and turbulent, with shear stress of 8 dyne/cm2 on average. A second culture dish was kept in a normal incubator as a static control for each experiment. Laminar flow induced synthesis of NO by HUVECs that was dependent on shear-stress magnitude. Laminar shear stress at 8 dyne/cm2 also upregulated the level of NO synthase mRNA. As observed with steady laminar flow, pulsatile flow also induced an increase in NO release by endothelial cells. When HUVECs were subjected to step-change increases of laminar shear, a further increase of NO synthesis was observed, compared with steady laminar shear of the same magnitude. Turbulent flow did not upregulate NO synthase mRNA or increase NO release. Both laminar and turbulent shear stress reduced, although not significantly, ET-1 mRNA and ET-1 production compared with the static condition. These results indicate that local blood flow conditions modulate the production of vasoactive substances by endothelial cells. This may affect vascular cell functions such as nonthrombogenicity, regulation of blood flow, and vascular tone.

Amino Acid Oxidoreductases↗
PubMed1995

The effects of nonsteroidal anti-inflammatory drugs on glomerular filtration of proteins and their therapeutic utility.

Cyclooxygenase inhibitors have long been used in experimental studies as well as in clinical practice to reduce urinary protein excretion in proteinuric renal diseases. However, the mechanisms by which this treatment limits glomerular filtration of proteins are not fully elucidated. We will review the cellular and molecular mechanisms that regulate glomerular permselectivity and the experimental observations available on the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on these glomerular functions. The effects of NSAIDs on glomerular microcirculation will also be analyzed in comparison with another class of drugs used to lower proteinuria in nephrotic patients, the angiotensin converting enzyme inhibitors. Finally, we will analyze the relationship between urinary prostaglandins and thromboxane A2 and discuss the effects of modulating these hormones on glomerular functions.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Clinical coagulation laboratory and oral anticoagulant therapy treatment. Instrumentation and methodology.

To assess the organization and the quality of care of an anticoagulation clinic, the structure, the process of laboratory control and the clinical outcome in our Center are described. 1068 patients under control in 1994 (M/F 572/496; median age 63 range 6-91 ys., 74% in long-term prophylaxis) were evaluated. The clinic was run twice weekly by a physician, two nurses and a technician; management for emergencies was always warranted. Prothrombin time was carried out with a sensitive thromboplastin (ISI < 1.1) and a computer program provided calculation and graphical representation of INR, comparison with therapeutic range, automatic dosage prescription and print out. Laboratory quality of therapy was assessed by three different techniques: 'cumulative INR', 'last check in file' and 'linear change', yielding respectively 69% of laboratory controls, 71% of patients and 80% of days within the therapeutic range. The rate of thrombosis, major and total bleeding were respectively 0.2%, 0.2% and 12.5%. An anticoagulation clinic represents an effective organizational model for the management of patients taking oral anticoagulants.

Administration, Oral↗
PubMed1994

Dissociation between antiproteinuric and antihypertensive effect of angiotensin converting enzyme inhibitors in rats.

To clarify whether angiotensin converting enzyme (ACE) inhibitors prevent progressive renal injury directly by their antihypertensive effect we administered the ACE inhibitor lisinopril to male MWF/Ztm rats as a single daily dose that lowered blood pressure for only 9 of 24 h. We investigated the effects of this treatment in short- and long-term studies and compared them with another antihypertensive drug, the calcium channel blocker nitrendipine, given to partially control blood pressure as done with the ACE inhibitor. In untreated animals systemic hypertension, proteinuria, and glomerulosclerosis developed spontaneously with age, and lisinopril reduced systemic hypertension and prevented proteinuria and glomerular lesions. Nitrendipine, despite similar blood pressure control, was ineffective in preventing both proteinuria and glomerulosclerosis. After 2 mo of treatment glomerular capillary pressure was significantly reduced by lisinopril and slightly but significantly increased by nitrendipine, compared with untreated controls. The ultrafiltration coefficient was significantly higher in lisinopril than in controls and not significantly changed by nitrendipine. With both drugs, however, glomerular hemodynamic effects were observed only at a few hours after administration and were abolished before the next administration. No significant changes in glomerular tuft volume were observed in treated and untreated animals after 2 and 6 mo of observation. Thus ACE inhibitor, despite only partial control of systemic blood pressure, effectively prevented proteinuria and glomerular injury. Comparable blood pressure control obtained with a calcium channel blocker was not associated with renal protection. These results suggest that ACE inhibitors could protect glomerular microcirculation by a mechanism that is not directly related to their antihypertensive action.

Alpha-Globulins↗
PubMed1994

Effects of angiotensin-converting enzyme inhibition on glomerular capillary wall ultrastructure in MWF/Ztm rats.

Previous studies have documented that treatment with angiotensin-converting enzyme (ACE) inhibitors prevents spontaneous proteinuria and enhances the glomerular ultrafiltration coefficient in male MWF/Ztm rats. The aim of this study was to study whether these beneficial effects of ACE inhibitors on glomerular capillary wall function are derived from the preservation of its ultrastructure. Conventional morphometrical analysis of kidney tissue, by light and electron microscopy, was used to quantify glomerular structural changes in the male MWF/Ztm rats treated with the ACE inhibitor cilazapril for 2 and 6 months and in age-matched untreated controls. At the end of the observation periods, both systolic blood pressure and urinary protein excretion were significantly reduced in treated animals as compared with controls. Glomerular volume increased significantly with time but was comparable in control and in treated rats. Surface area available for filtration (measured as peripheral capillary wall) was comparable in control and in treated animals at the same time and increased significantly with time only in treated rats. Mesangial volume was significantly higher in cilazapril-treated animals than in controls after 2 months of treatment and was comparable after 6 months. ACE inhibitor treatment did not induce significant ultrastructural changes such as basement membrane thickness, configuration of epithelial podocytes, and the width and the frequency of the epithelial slit diaphragms. These results indicate that the previously observed increase in the glomerular ultrafiltration coefficient by an ACE inhibitor in these animals is not the consequence of changes in filtering surface area but likely reflects an increase in membrane hydraulic permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗