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Biomedical subjects

Alberto Ortiz

Publications and source records attributed to Alberto Ortiz.

30 records · Page 2Linked to original sources
PubMed2003

Renal expression of angiotensin type 2 (AT2) receptors during kidney damage.

BACKGROUND: Activation of the renin angiotensin system has been described in pathologic conditions, including kidney damage. Angiotensin II (Ang II) acts through two receptors, AT1 and AT2. Most of the known actions of Ang II, including vasoconstriction and fibrosis, are due to AT1 activation. Recent data suggest that AT2 participates in the regulation of cell growth and renal inflammatory infiltration. Therefore, we investigated the renal expression of AT2 receptors in several models of renal injury. METHODS: Investigations were done in the following experimental models of kidney damage: systemic infusion of Ang II (inflammation), folic acid nephropathy (tubular cell death), and protein overload proteinuria. AT2 expression was determined by immunohistochemistry (protein) and reverse transcription-polymerase chain reaction (RT-PCR) (gene). RESULTS: In control animals, low levels of renal expression of AT2 were found. Ang II infusion resulted in an up-regulation of AT2 in tubular cells and de novo AT2 expression in glomeruli and vessels, associated with the presence of inflammatory cells. Acute tubular injury induced by folic acid was characterized by AT2 overexpression and apoptosis in tubular cells. Protein overload caused heavy proteinuria and tubular AT2 up-regulation. CONCLUSION: AT2 is re-expressed in pathologic conditions of kidney damage, such as inflammation, apoptosis, and proteinuria, suggesting a potential role of this receptor during renal injury.

Angiotensin II↗
PubMed2003

Intracellular mechanisms of cyclosporin A-induced tubular cell apoptosis.

Tubular cell apoptosis contributes to the pathogenesis of renal injury. However, the intracellular pathways that are active in tubular epithelium are poorly understood. The lethal pathways activated by cyclosporin A (CsA), a nephrotoxin that induces caspase-dependent apoptosis in tubular epithelium, were explored. Fas expression, caspase activation, and mitochondrial injury were assessed by Western blot, flow cytometry, and microscopy in cultured murine tubular epithelial cells exposed to CsA. The influence of FasL antagonists, Bax antisense oligodeoxynucleotides, and caspase inhibitors on cell survival was explored. Tubular cells constitutively express FasL. CsA increased the expression of Fas. However, Fas had no role in CsA-induced apoptosis, as CsA did not sensitize to FasL-induced apoptosis, caspase-8 activity was not increased, and neither blocking anti-FasL antibodies nor caspase-8 inhibition prevented CsA-induced apoptosis. Apoptosis induced by CsA is associated with the translocation of Bax to the mitochondria and Bax antisense oligodeoxynucleotides protected from CsA-induced apoptosis. CsA promoted a caspase-independent release of cytochrome c and Smac/Diablo from mitochondria. CsA also led to a caspase-dependent loss of mitochondrial membrane potential. Caspase-2, caspase-3, and caspase-9 were activated, and specific caspase inhibitor prevented apoptosis and increased long-term survival. Evidence for endoplasmic reticulum stress, such as induction of GADD153, was also uncovered. However, endoplasmic reticulum-specific caspase-12 was not activated. CsA induces changes in several apoptotic pathways. However, the main lethal apoptotic pathway in CsA-exposed tubular epithelial cells involves mitochondrial injury.

Animals↗
PubMed2002

Role of endogenous vascular endothelial growth factor in tubular cell protection against acute cyclosporine toxicity.

BACKGROUND: Recent studies have shown that exogenous administration of vascular endothelial growth factor (VEGF) is protective against cyclosporine A (CsA) renal toxicity. No data are available, however, on the possible role of endogenous VEGF. Our objective was to examine whether endogenous VEGF has a significant role in the renal response against CsA toxicity. METHODS: In vivo, we used high-dose (50-150 mg/kg/day) CsA +/- specific goat anti-mouse VEGF blocking monoclonal antibody (alpha-VEGF) in mice. In vitro, we exposed mouse tubular cells (MCT) to CsA +/- alpha-VEGF. RESULTS: alpha-VEGF markedly enhanced CsA renal toxicity, inducing severe tubular damage and increased blood urea nitrogen. In animals treated with CsA + alpha-VEGF, damage progressed to generalized tubular injury (histology) and apoptosis (terminal deoxynucleotide transferase-mediated dUTP nick-end labeling) with associated anemia and reticulocytosis (18 days of treatment). CsA + alpha-VEGF treatments strikingly increased tubular VEGF and Bcl-xL proteins. In vitro, autocrine production of VEGF by MCT was identified by Western blot. Of specific interest, CsA toxicity in MCT increased significantly in the presence of alpha-VEGF. CONCLUSIONS: Endogenous VEGF has a relevant role in the renal tubular defense against CsA toxicity. Blockade of the VEGF effect by alpha-VEGF results in clear-cut intensification of the tubular injury and appearance of regenerative anemia in the CsA + alpha-VEGF-treated animals. The occurrence of both in vivo and in vitro effects of VEGF blockade provides evidence of a direct protective effect of VEGF on the tubular cell.

Acute Disease↗
PubMed2001

Acceleration of neutrophil apoptosis by glucose-containing peritoneal dialysis solutions: role of caspases.

Commercial, glucose-containing peritoneal dialysis (PD) solutions have deleterious effects on leukocytes and mesothelial cells that contribute to an impaired peritoneal defense. However, the molecular mechanisms of these deleterious effects are poorly understood. The effect of PD solutions on neutrophil viability, the molecular mechanisms of cell death, its functional consequences, and the possibilities for pharmacologic modulation have now been studied. The effect of newly available, bicarbonate-buffered PD solutions were further investigated. Lactate-buffered, glucose-containing PD solutions increased the apoptosis rate of cultured neutrophils (control media versus 4.25% glucose PD solution: 31 +/- 3% versus 52 +/- 3% apoptosis at 24 h, P < 0.001). Bicarbonate-buffered, 4.25% glucose-containing PD solutions with low concentration of glucose degradation products did not increase the rate of apoptosis. Apoptosis induced by lactate-buffered, 4.25% glucose PD solutions was not related to hyperosmolality or acidic pH and was not reproduced by increasing the glucose concentration by the addition of glucose to a commercial, lactate-buffered fluid. Neutrophil apoptosis was associated with caspase-3 activation. Inhibition of caspase-3 by the use of the caspase-3 inhibitor acetyl-Asp-Glu-Val-Asp-fmk or the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone (zVAD-fmk) prevented features of apoptosis, such as morphologic changes, internucleosomal DNA degradation, and the appearance of hypodiploid cells and increased the number of viable, trypan blue-excluding neutrophils. Furthermore, zVAD-fmk increased neutrophil phagocytosis of bacteria. However, the caspase-1 inhibitor acetyl-Tyr-Val-Ala-Asp-aldehyde did not prevent cell death. These data suggest that unidentified components in commercial, lactate-buffered, high-glucose PD fluid accelerate the rate of neutrophil apoptosis. Glucose degradation products may be such unidentified components. Acceleration of neutrophil apoptosis may contribute to the impaired local defense system of patients undergoing PD.

Apoptosis↗
PubMed2000

Proapoptotic Fas ligand is expressed by normal kidney tubular epithelium and injured glomeruli.

Fas ligand (FasL) is a cell membrane cytokine that can promote apoptosis through activation of Fas receptors. Fas receptor activation induces glomerular cell apoptosis in vivo and participates in tubular cell death during acute renal failure. However, there is little information on the expression of FasL in the kidney. This study reports that FasL mRNA and protein are present in normal mouse and rat kidney. In situ hybridization and immunohistochemistry showed that proximal tubular epithelium is the main site of FasL expression in the normal kidney. In addition, increased total kidney FasL mRNA and de novo FasL protein expression by glomerular cells were observed in two different models of glomerular injury : rat immune-complex proliferative glumerulonephritis and murine lupus nephritis. Both full-length and soluble FasL were increased in the kidneys of the mice with nephritis. Cultured murine proximal tubular epithelial MCT cells and primary cultures of murine tubular epithelial cells expressed FasL mRNA and protein. Tubular epithelium-derived FasL induced apoptosis in Fassensitive lymphoid cell lines but not in Fas-resistant lymphoid cell lines. By contrast, MCT cells grown in the presence of the survival factors of serum were resistant to FasL, and only became partially sensitive to apoptosis induced by high concentrations (100 ng/ml) of FasL upon serum deprivation. However, MCT cells stimulated with inflammatory mediators (tumor necrosis factor-alpha, interferon-gamma, and lipopolysaccharide) increased cell surface Fas expression and were sensitized to apoptosis induced by FasL (FasL 55 +/- 5% versus control 8.3 +/- 4.1% apoptotic cells at 24 h, P < 0.05). Cytokine-primed primary cultures of tubular epithelial cells also acquired sensitivity to FasL-induced apoptosis. These results suggest that FasL expression by intrinsic renal cells may play a role in cell homeostasis in the normal kidney and during renal injury.

Animals↗
PubMedDate not supplied

Long-term blood pressure control prevents oxidative renal injury.

Arterial hypertension is a leading contributor to the progression of chronic renal disease. Short-term studies had addressed the role of oxidative stress in hypertensive nephropathy. We have now studied oxidative stress and caspase activation in a long-term model of hypertensive renal injury. Nontreated spontaneously hypertensive rats with uninephrectomy displayed severe arterial hypertension over a 36-week follow-up. Uncontrolled high blood pressure in the context of modest renal mass reduction resulted in significant histological renal injury. Blood pressure control by the angiotensin-converting enzyme (ACE) inhibitor, quinapril, or the AT1 receptor antagonist, losartan, decreased the degree of renal injury. Hypertensive renal injury was associated with evidence of activation of the apoptotic pathway (increased activation of caspase-3) and local renal (increased staining for 4-hydroxy-2-nonenal) and systemic [increased serum levels of 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha)] lipid oxidation when compared with normotensive control rats. In addition, severe hypertension decreased the renal antioxidant defenses, as exemplified by decreased expression of Cu/Zn superoxide dismutase. Treatment with quinapril or losartan decreased caspase-3 activation, 4-hydroxy-2-nonenal staining, and 8-iso-PGF2alpha levels and increased Cu/Zn superoxide dismutase expression. These results suggest that hypertension-associated oxidative stress and its consequences may be decreased by either ACE inhibition or AT1 receptor antagonist, emphasizing the role of angiotensin II in hypertensive renal damage.

Angiotensin II Type 1 Receptor Blockers↗
PubMedDate not supplied

Peritoneal dialysis retardation of progression of advanced renal failure.

OBJECTIVES: The rate of decline of residual renal function is slower in peritoneal dialysis (PD) than in hemodialysis. However, it is unclear which and whether either of the two techniques modifies the natural course of renal failure. We tested whether PD influences the natural course of the progression of chronic renal failure in humans. DESIGN: Retrospective review of clinical charts. SETTING: Tertiary-care center. PATIENTS: Fourteen patients were selected from the 36 patients that were treated with PD in our center from January 1997 to June 2000, applying the following criteria: predialysis follow-up longer than 12 months, renal creatinine clearance 20 mL/minute or more at the start of predialysis follow-up, follow-up while on PD longer than 6 months, and renal creatinine clearance above 0 mL/minute at the start of PD. MAIN OUTCOME MEASURE: Residual renal function calculated as renal creatinine clearance obtained from 24-hour urine samples. RESULTS: A lower mean rate of decline of residual renal function was observed during PD than during the predialysis period (-0.06 +/- 0.16 vs -0.94 +/- 0.74 mL/min/month, p < 0.0005). The rate of decline in renal creatinine clearance was faster in every patient during the predialysis period than during his or her time on PD. CONCLUSIONS: These preliminary data support the hypothesis that PD may contribute to the slowing of the natural progression of renal disease in humans, as it does in rodents. Prospective studies involving a larger number of patients are needed to settle the question.

Adult↗
PubMedDate not supplied

Inhibition of caspases improves bacterial clearance in experimental peritonitis.

BACKGROUND: Inhibition of caspases improves the antibacterial capacity of leukocytes cultured with peritoneal dialysis solutions, and improves the prognosis of septic, polymicrobial experimental peritonitis. OBJECTIVE: To test whether inhibition of caspases alters the evolution of peritonitis in the presence of peritoneal dialysis solution. DESIGN: 32 mice were assigned to therapy with either the pan-caspase inhibitor zVAD or vehicle for 48 hours following infection with Staphylococcus aureus, in the presence of lactate-buffered, 4.25% glucose peritoneal dialysis solution. 16 mice received vehicle in phosphate-buffered saline. MAIN OUTCOME MEASURE: Number of bacteria recovered from the peritoneum at 48 hours. RESULTS: Peritoneal dialysis solution accelerated leukocyte apoptosis. zVAD decreased the number of apoptotic peritoneal leukocytes and the number of bacteria recovered from the peritoneum at 48 hours (zVAD 2.8 +/- 0.3 vs vehicle 3.9 +/- 0.2 log colony forming units of S. aureus, p = 0.007). CONCLUSIONS: Inhibition of caspases accelerates peritoneal bacterial clearance in the presence of peritoneal dialysis solutions in vivo in the experimental setting. Inhibition of caspases should be explored as a mean to accelerate recovery following peritonitis in the clinical setting.

Amino Acid Chloromethyl Ketones↗
PubMedDate not supplied

Oral protein-energy supplements in peritoneal dialysis: a multicenter study.

BACKGROUND: Protein-energy malnutrition is prevalent in peritoneal dialysis (PD) patients and is associated with increased morbidity and mortality. OBJECTIVE: To evaluate the impact of prophylactic treatment with an oral protein-energy supplement (Protenplus; Fresenius AG, Bad Homburg, Germany) on nutritional parameters in patients starting PD. DESIGN: Prospective, multicenter, randomized study of group A patients (Protenplus, n = 35) and group B (controls, n = 30), with evaluations at baseline and at 6 and 12 months. STATISTICAL METHODS: Efficacy of factors by linear mixed model analysis for repeated measurements, chi-square, t-test, and Mann-Whitney test. OUTCOME PARAMETERS: Patient compliance, serum albumin, and other nutritional parameters. RESULTS: No significant differences were found at baseline evaluation. During follow-up, a significant number of group A patients abandoned intake of the supplement due to non-compliance (n = 7) or side effects (n = 8) (chi2 p < 0.01). Patients with lower residual renal function were less likely to comply. The mixed model in the "intention to treat" analysis showed a significant increase related to supplement intake only in total lymphocyte count in group A. The "as treated" analysis of the 29 patients who fulfilled the study (9 in group A, 20 in group B) disclosed that belonging to group A constituted an independent factor for increased lymphocyte count (p < 0.001), body weight (p < 0.03), tricipital skinfold thickness (p < 0.01), middle-arm muscle circumference (p < 0.025), lean body mass (LBM) (p < 0.002), creatinine LBM related to body surface area (p < 0.001), and creatinine generation rate (p < 0.002). However, these data may have been biased by the high rate of noncompliance in group A. CONCLUSIONS: Protenplus proved to be unsuitable as a long term, oral protein-energy supplement in PD patients due to a high rate of noncompliance and intolerance, primarily among patients with lower residual renal function. The question of whether other products, better-tolerated as nutritional supplements, could compensate for daily protein peritoneal losses in long-term PD remains open.

Adolescent↗