[Pathogenic factors in diabetic nephropathy. Where do we come from and where are we headed?].
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Biomedical subjects
Publications and source records attributed to J Egido.
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BACKGROUND: Several epidemiological studies have demonstrated the beneficial effect of red wine intake in reducing total and cardiovascular mortality. This effect has been attributed in part to its antioxidant properties. Because the monocytes/macrophages and the nuclear transcription factor kappaB (NF-kappaB) are implicated in the pathogenesis of atherosclerotic lesions, we examined the effect of red wine intake on the activation of NF-kappaB in peripheral blood mononuclear cells. METHODS AND RESULTS: Sixteen healthy volunteers were studied 3 times each: after a moderate dose, a low dose, and no wine with a fat-enriched breakfast. Lipid profile and NF-kappaB activation (electrophoretic mobility shift assay) were examined in blood samples taken before and 3, 6, and 9 hours after wine intake. In addition, mononuclear cells were incubated with VLDL in the presence of some antioxidants (quercetin and alpha-tocopherol succinate) contained in red wine to study their effects on NF-kappaB activation. Subjects receiving a fat-enriched breakfast had increased NF-kappaB activation in peripheral blood mononuclear cells coinciding with the augmentation in total triglycerides and chylomicrons. Red wine intake prevented NF-kappaB activity even though it induced a certain increase in serum lipids, particularly VLDL, that did not increase after the fat ingestion alone. However, another form of alcohol intake (vodka) did not modify the NF-kappaB activation provided by postprandial lipemia. In cultured mononuclear cells, isolated human VLDL caused NF-kappaB activation in a time-dependent manner that did not occur in the presence of the red wine antioxidants quercetin and alpha-tocopherol. CONCLUSIONS: Our results provide a new potential mechanism to explain the beneficial effects of red wine intake in the reduction of cardiovascular mortality.
Apoptosis is an active form of cell death that, in balance with mitosis, regulates cell number. Cell number abnormalities are a frequent feature of renal disease. We now review current concepts on the molecular regulation of apoptotic cell death, including the influence of survival and lethal factors from the extracellular microenvironment as well as the role of intracellular regulators of apoptosis, such as death receptors, proapoptotic and antiapoptotic bcl2-related proteins, the mitochondria and caspases. In addition the role of apoptosis in the genesis, persistence and progression and remodeling and resolution of renal injury is discussed. Information on the expression and function of apoptosis regulatory proteins in specific renal syndromes is summarized. Finally, future perspectives in research and clinical intervention are discussed.
Nuclear factor-kappaB (NF-kappaB) regulates many genes involved in vascular physiopathology. We have previously observed in vivo NF-kappaB activation in injured vessels that diminished by angiotensin-converting enzyme inhibition. In the present work, we investigated the effect of angiotensin II (Ang II) on NF-kappaB activity in rat vascular smooth muscle cells, evaluating the molecular mechanisms and the specific receptor subtype involved. Ang II increased NF-kappaB DNA binding (5-fold, 10(-)(9) mol/L at 1 hour; electrophoretic mobility shift assay), nuclear translocation of p50/p65 subunits, and cytosolic inhibitor kappaBalpha (IkappaBalpha) degradation. Ang II elicited NF-kappaB-mediated transcription (transfection of a reporter gene) and expression of NF-kappaB-related genes (monocyte chemoattractant protein-1 and angiotensinogen). AT(1) (DUP753) and AT(2) (PD123319 and CGP42112) receptor antagonists inhibited Ang II-induced NF-kappaB DNA binding in a dose-dependent manner ( approximately 85% for each one; 10(-)(5) mol/L at 1 hour). The AT(2) agonist p-aminophenylalanine(6)-Ang II augmented NF-kappaB binding (4.6-fold, 10(-)(9) mol/L at 1 hour), p65 nuclear levels, and transcription of an NF-kappaB reporter gene. AT(1) antagonist markedly inhibited NF-kappaB-mediated transcription and gene expression. Some differences between AT(1)/AT(2) intracellular signals were found. Antioxidants and ceramide inhibitors, but not protein kinase C inhibitors, diminished NF-kappaB activation elicited by both Ang II and the AT(2) agonist, while tyrosine kinase inhibitors only decreased Ang II-induced NF-kappaB activity. Our results demonstrate that Ang II activates NF-kappaB via AT(1) and AT(2), although NF-kappaB-mediated transcription occurred mainly through AT(1). Both receptors share some signaling pathways (oxygen radicals and ceramide); however, tyrosine kinases only participate in AT(1)/NF-kappaB responses. These data provide novel insights into Ang II actions, suggesting a potential implication of the AT(2) in the pathobiology of vascular cells.
Most human nephritis is due to glomerular deposition and/or formation of immune complexes (IC). In cultured mesangial cells, Fc receptor stimulation induces proliferation, matrix synthesis, and release of several mediators implicated in the initiation and progression of glomerular injury. Since Ig Fc fragments in vitro modified these phenomena, we studied the effects of systemic administration of IgG Fc fragments on the evolution of experimental IC nephritis. Fc fragment injection (1 mg/day i.p.) to rats with ongoing nephritis (proteinuria 20-50 mg/24 h vs 9 +/- 0.2 mg/24 h in controls) markedly ameliorates proteinuria, renal function, and morphological renal lesions. This was accompanied by a reduction in the renal synthesis of chemokines (monocyte chemoattractant protein-1, IFN-inducible protein-10, and cytokine-induced neutrophil chemoattractant-1), matrix proteins, and growth factors (platelet-derived growth factor, and TGF-beta), and in the activity of transcription factors. The treatment did not affect the glomerular deposition of IgG IC and complement C1q. In contrast, a decrease in the renal expression and production of C3 was observed without changes in serum complement levels. In vitro, very low complement consumption and no C3b covalent interaction were observed with Fc fragments, confirming that they did not modify systemic complement activity. These results indicate that the administration of Fc fragments prevents the development of glomerular damage in an aggressive model of proliferative glomerulonephritis through mechanisms involving a reduced local generation of complement, chemokines and growth factors. Modulation of IC-mesangial cell interaction by Fc fragment administration could represent a new approach to the treatment of severe immune nephritis.
OBJECTIVE: To study the effects of cyclosporin A (CSA) in a model of rheumatoid arthritis (RA) and the activation of growth factors related to pannus development at the site of injury. METHODS: Antigen arthritis was induced in the knees of 14 New Zealand rabbits, and the animals were randomized into 2 therapeutic groups: CSA at 10 mg/kg/day and CSA solvent. After 3 weeks of treatment, the rabbits were killed, and synovial tissues were obtained and compared with healthy specimens with regard to histopathologic lesions, deposition of transforming growth factor beta (TGFbeta) and collagens, and messenger RNA expression of platelet-derived growth factor B (PDGF-B) and TGFbeta. The effect of CSA on the expression of TGFbeta and PDGF-B was also examined in cultured synovial cells. RESULTS: CSA administration alleviated the histologic damage and avoided the overdeposition of matrix elements in the injured tissue. It was also able to normalize the enhanced expression of TGFbeta and PDGF-B observed in the untreated rabbits. Despite this modulation found in vivo, CSA up-regulated in a dose-dependent manner the gene expression of both trophic factors by healthy cultured synovial cells. CONCLUSION: The present study shows that continuous administration of CSA prevents the development of chronic synovitis in an experimental model of RA. As reported in other cell types, CSA promoted TGFbeta transcription by synovial cells in vitro, but failed to display a profibrogenic effect in the inflamed environment.
The vascular extracellular matrix is responsible for the mechanical properties of the vessel wall and is also involved in biologic processes such as cellular adhesion, regulation, and proliferation. Thus, an adequate balance of its components is necessary for the normal functioning of the vasculature. Vascular disorders affect this balance, and this plays a key role in their pathophysiology. Atherogenesis is accompanied by an increase in matrix deposition in response to low-density lipoprotein accumulation. However, this matrix, mainly collagen, also has a protective role by forming a fibrous cap around the lipid core, avoiding contact with blood. A decrease in the amount of collagen will weaken the cap and make it prone to rupture, leading to thrombosis and acute coronary syndromes. In hypertension, the increase in matrix deposition results in vascular stiffness and cardiac dysfunction. In this paper, we discuss the relevance of matrix regulation in these conditions.
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BACKGROUND: Monocyte infiltration is a common feature of renal diseases. Angiotensin II (Ang II) participates in inflammatory cell infiltration in the kidney. However, the influence of other peptides of the renin-angiotensin system, such as the N-terminal Ang II degradation product Ang III, has not been addressed. METHODS: In cultured renal and mononuclear cells, we investigated whether Ang III is involved in monocyte recruitment through the regulation of the chemokine, monocyte chemoattractant protein-1 (MCP-1; Northern blot, Western blot, immunofluorescence, and chemotaxis), and the activation of transcription factors, nuclear factor kappaB (NF-kappaB) and activating protein-1 (AP-1; electrophoretic mobility shift assay). RESULTS: In cultured rat mesangial and mononuclear cells, Ang III increased MCP-1 gene expression and protein levels. Supernatants from Ang III-treated mesangial cells showed increased chemoattractant activity for monocytes, which was partially inhibited by the addition of anti-MCP-1 antibody. Ang III elicited a rapid NF-kappaB activation (8-fold, after 30 min), showing a kinetics and intensity similar to that observed with Ang II and tumor necrosis factor-alpha. The maximal NF-kappaB activation was correlated with nuclear translocation of p50 and p65 subunits and disappearance of cytosolic IkappaB. Ang III also activated AP-1 (5-fold, after 18 h), while SP-1 was unchanged. Two NF-kappaB inhibitors abolished the Ang III-induced MCP-1 mRNA expression, suggesting that overexpression of this chemokine is mediated, at least in part, by NF-kappaB activation. CONCLUSIONS: Ang III activates the transcription factors NF-kappaB and AP-1 and increases the expression of related genes, such as MCP-1. Our study describes a novel and potent proinflammatory action of this Ang degradation product, expanding the present view of the renin-angiotensin system.
UNLABELLED: Overexpression of chemokines, fibrogenic cytokines, and myofibroblasts in human membranous nephropathy. BACKGROUND: Proteinuria plays a central role in the progression of glomerular disease, and there is growing evidence suggesting that it may determine tubular cell activation with release of chemokines and fibrogenic factors, leading to interstitial inflammatory reaction. However, most studies on this subject have been performed in experimental models, and the experience in human kidney biopsies has been scarce. We analyzed the tissue sections of patients with idiopathic membranous nephropathy (IMN), a noninflammatory glomerular disease that may follow a progressive disease with heavy persistent proteinuria, interstitial cell infiltration, and decline of renal function. METHODS: Paraffin-embedded biopsy specimens from 25 patients with IMN (13 progressive and 12 nonprogressive) were retrospectively studied by immunohistochemistry [monocyte chemoattractant protein-1 (MCP-1), regulated on activation normal T-cell expressed and secreted chemokine (RANTES), osteopontin (OPN), platelet-derived growth factor-BB (PD-GF-BB)] and in situ hybridization [MCP-1, RANTES, PDGF-BB, transforming growth factor-beta1 (TGF-beta1)]. Moreover, we studied the presence of myofibroblasts, which were identified by the expression of alpha-smooth muscle actin (alpha-SMA), the monocytes/macrophages (CD68-positive cells), and T-cell infiltration (CD4+ and CD8+ cells). All of the patients were nephrotic and without treatment at time of the biopsy. RESULTS: A strong up-regulation of MCP-1, RANTES, and OPN expression was observed, mainly in tubular epithelial cells, with a significant major intensity in the progressive IMN patients. A strong correlation between the mRNA expression and the corresponding protein was noted. The presence of these chemokines and OPN was associated with interstitial cell infiltration. TGF-beta and PDGF were also up-regulated, mainly in tubular epithelial cells, with a stronger expression in the progressive IMN, and an association with the presence of myofibroblasts was found. CONCLUSIONS: Patients with severe proteinuria and progressive IMN have an overexpression in tubular epithelial cells of the chemokines MCP-1, RANTES, and OPN and the profibrogenic cytokines PDGF-BB and TGF-beta. Because this up-regulation was associated with an interstitial accumulation of mononuclear cells and an increase in myofibroblastic activity, it is suggested that those mediators are potential predictors of progression in IMN. Finally, based on experimental data and the findings of this article, we speculate that severe proteinuria is the main factor responsible for the up-regulation of these factors in tubular epithelial cells.
BACKGROUND: While tubular cell death is a characteristic of acute renal failure (ARF), the molecular mechanisms that modulate this cell death are unclear. Cell fate in acute renal failure hinges on a balance of survival and mortality factors in a changing environment. We further explored this issue by studying selected cell death-related proteins in experimental renal failure. METHOD: The expression of genes that promote (c-myc, Bax, BclxS) or protect (Bcl2, BclxL) from cell death was studied by Northern blot, Western blot, and immunohistochemistry in murine kidneys following ARF induced by folic acid or in renal tubular epithelial cells (MCT) stressed in culture. RESULTS: Renal mRNA levels encoding for c-myc and BclxL were elevated in ARF while the Bcl2/Bax ratio was decreased (Bcl2 decreased and Bax increased; P < 0.05). Protein levels of BclxL increased and Bcl2 protein decreased. Expression of tumor necrosis factor (TNF-alpha), a mediator of ARF, was also increased. Immunohistochemistry further demonstrated that BclxL was increased in some tubuli and absent in others, while Bcl2 expression decreased diffusely. Bax staining was also patchy among tubuli and individual cells in the tubular wall and lumen. As a relative deficit of survival factors is present in ARF, MCT epithelium were deprived of serum survival factors. This resulted in apoptosis, decreased Bcl2/Bax and BclxL/Bax ratios (P < 0.05) and sensitization to TNF-alpha-induced apoptosis (P < 0.05). The latter was prevented by enforced overexpression of BclxL (P < 0.01). TNF-alpha increased the mRNA levels encoding for c-myc and decreased BclxL expression. Neither MCT cells nor the kidney expressed BclxS. CONCLUSIONS: A relative deficit of survival factors likely contributes to changes in levels of BclxL and Bax in ARF. These deficits predispose to cell death induced by persistent lethal factors such as TNF-alpha that is increased in ARF and a potential source of increased c-myc, a downstream facilitator of cell death. These findings implicate members of the Bcl2 family of proteins as regulators of tubular cell death in ARF and single them out as potential therapeutic targets.
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Cardiovascular mortality, mainly due to the rupture of unstable atherosclerotic plaques, is reduced by 3-hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Inflammatory cells, attracted to the vascular lesion by chemokines, have been implicated in the process of the plaque rupture. In cultured vascular smooth muscle cells (VSMC) and U937 mononuclear cells we have studied the effect of Atorvastatin (Atv) on nuclear factor kappaB (NF-kappaB) activity, an inducer of the mRNA expression of chemokines such as interferon-inducible protein 10 (IP-10) and monocyte chemoattractant protein 1 (MCP-1). Angiotensin II (Ang II) and tumor necrosis factor alpha (TNF-alpha) increased NF-kappaB activity in VSMC (2 and 5-fold, respectively). Preincubation of cells with 10(-7) mol/l Atv diminished this activation (44 and 53%). The inhibition was reversed by mevalonate, farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP), but not by other isoprenoids. Coinciding with the NF-kappaB activation in VSMC, there was a diminution of cytoplasmic IkappaB levels that was recovered by pretreatment with Atv. Ang II and TNF-alpha induced the expression of IP-10 (1.5 and 3.4-fold) and MCP-1 (2.4 and 4-fold) in VSMC. Atv reduced this overexpression around 38 and 35% (IP-10), and 54 and 39% (MCP-1), respectively. Our results strongly suggest that Atv, through the inhibition of NF-kappaB activity and chemokine gene expression, could reduce the inflammation within the atherosclerotic lesion and play a role in the stabilization of the lesion.
BACKGROUND: Transcriptional activities of genes require intermediary regulators (nuclear factors) that bind to specific segments of nuclear DNA. A method to localize in situ the distribution of these factors using nonradioactive oligonucleotides in paraffin wax-embedded tissues is described. The distribution of two nuclear factors, activated protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB), was studied in two experimental models of immune complex glomerulonephritis in rats and atherosclerosis in rabbits. METHODS: Sections were fixed with 0.2% paraformaldehyde and were digested with pepsin A. Oligonucleotides containing the consensus sequence of NF-kappaB and AP-1 were 3'-labeled with digoxigenin. The preparations were incubated with the labeled probes (4 degreesC, overnight). After washing, the sections were incubated with an antidigoxigenin antibody conjugated with alkaline phosphatase, and the color reaction was developed. In addition, this method was combined with standard immunohistochemistry to identify the cell-type-specific localization of these DNA-binding factors. RESULTS: Kidney sections from rats with immune complex nephritis showed positive nuclear staining for AP-1 in the nuclei of several glomerular and tubulointerstitial cells. Arteries from rabbits with focal atherosclerosis presented nuclear staining for NF-kappaB in the neointima and media. The nuclear staining was highly specific, as assessed by several negative controls. In addition, Southwestern histochemistry in rabbits, followed by immunohistochemistry, demonstrated that the NF-kappaB activity was present in the area occupied by macrophages and smooth muscle cells. CONCLUSION: These results show a novel method of in situ transcription factors detection using nonradioactive probes in paraffin wax-embedded tissues, which allows a simultaneous visualization of the cell-type-specific localization of these nuclear factors.
BACKGROUND: PTHrP, which appears to act as a growth/differentiation factor in a variety of tissues, is present in the kidney; however, its role is unclear. METHODS: The expression of PTHrP and the PTH/PTHrP receptor were investigated by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry in the remnant kidney of uninephrectomized (UNX) rats after protein overloading [1 g/day of bovine serum albumin (BSA)]. RESULTS: Compared with UNX-control rats, proteinuria in BSA-overloaded animals was detected within the first 24 hours and increased during the entire study period (28 days). Kidney examination by light microscopy showed no significant renal lesions at day 1 of BSA treatment, whereas at days 8 and 28, tubular lesions, infiltration of mononuclear cells, and mesangial expansion were observed. PTHrP mRNA expression in the renal cortex was already increased at day 1 (fourfold) and plateaued between days 8 and 28 (12- and 15-fold, respectively) in BSA-overloaded animals compared with UNX-control rats. At day 8, immunohistochemical analysis with two different anti-PTHrP antibodies showed a dramatic increase of PTHrP staining in the damaged proximal and distal tubules from BSA-overloaded rats with respect to UNX-control rats. Moreover, intense PTHrP immunostaining was also observed in glomerular mesangial and endothelial cells in BSA-overloaded rats, but not in the UNX-control rats. A reciprocal decrease of PTH/PTHrP receptor mRNA and immunostaining, without significant changes in the cellular localization (proximal and distal tubule, and glomerular mesangial and epithelial cells) of the PTH/PTHrP receptor positivity was found to occur in the renal cortex of BSA-overloaded rats. At day 8, coinciding with the up-regulation of PTHrP, an increase in the angiotensin converting enzyme and preproendothelin-1 gene expression was observed in the renal cortex of BSA-overloaded rats compared with UNX-control rats. CONCLUSIONS: These results indicate that PTHrP can be added to the group of genes that are up-regulated in proximal tubular cells in response to intense proteinuria. Our results, together with previous findings, suggest that the vasoactive hormones angiotensin II and endothelin-1 could participate in the PTHrP production in the renal cortex of BSA-overloaded rats. Further experiments are required to clarify the mechanisms of PTHrP up-regulation and its possible role in the response to renal damage in this animal model.
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BACKGROUND: The phospholipid platelet-activating factor (PAF) participates in the pathogenesis of renal ischemia/reperfusion injury, and in vitro, it induces synthesis of extracellular matrix proteins by mesangial and tubular epithelial cells. This study investigated the long-term effects of the potent orally active PAF antagonist UR-12670 in warm ischemic uninephrectomized rats, which was given according to different therapeutic schedules. METHODS: Uninephrectomized male Sprague-Dawley rats were divided into five groups and were followed for 52 weeks: rats without ischemia (SK); ischemic kidney for 60 minutes (SIK); ischemic kidney and UR-12670 from 0 to the 7th day (UR 0-7); ischemic kidney and UR-12670 from day 0 to 52 weeks (UR 0-E); and ischemic kidney and UR-12670 from day 8 to week 52 (UR 8-E). Two more groups (ischemic and UR treated) served to evaluate the UR-12670-protective effect on ischemic acute renal failure at one week. RESULTS: UR-12670 administration exerted functional and morphological protection against post-ischemic acute renal failure. The ischemic untreated (SIK) group developed progressive proteinuria from week 12. The onset of proteinuria in ischemic UR-12670-treated groups was delayed to the 24th week, and it was significantly lower than in SIK group throughout the study. Only SIK and ischemic-treated UR 0-7 rats presented with chronic renal failure, as shown by creatinine, creatinine clearance, glomerular filtration rate (GFR), and renal plasma flow (GFR 52 weeks: SK, 2525 +/- 267; SIK, 992 +/- 149; UR 0-7, 1551 +/- 385 microliter/min). Kidneys from the short-term treated group (UR 0-7) showed a reduction of glomerulosclerosis (SK, 14.4 +/- 3.7; SIK, 75.7 +/- 7.7; UR 0-7, 41. 5 +/- 8.5%) and vascular myointimal hyperplasia, but the tubulointerstitial damage (tubulointerstitial score: SK, 0.2 +/- 0. 2; SIK, 4.4 +/- 0.5; UR 0-7, 3.7 +/- 0.7) was similar to that in the ischemic untreated group. Long-term ischemic treated rats (UR 0-E, UR 8-E) did not develop chronic renal failure (GFR: UR 0-E, 2059 +/- 314; UR 8-E, 2410 +/- 208 microliter/min). In these groups, glomerulosclerosis (UR 0-E, 32.8 +/- 5.8; UR 8-E, 24.3 +/- 3.0%), tubulointerstitial damage (tubulointerstitial score: UR 0-E, 2.1 +/- 0.5; UR 8-E, 1.9 +/- 0.3) and vascular myointimal hyperplasia were significantly lower than in the ischemic untreated group. By in situ hybridization, an increase of transforming growth factor-beta1 mRNA expression in glomerular and tubular cells was observed in ischemic untreated and ischemic treated UR 0-7 rats. UR-12670 long-term treated rats showed a clear reduction of transforming growth factor-beta1 mRNA-positive glomerular cells. CONCLUSION: The chronic administration of the PAF antagonist UR-12670 attenuates the long-term effects of ischemia-reperfusion injury in uninephrectomized rats. The beneficial effect of this agent, even when given beyond the initial ischemia/reperfusion injury, suggests that PAF plays a role in the mechanisms of progression to late renal damage in this model.