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Biomedical subjects

Pedro Aljama

Publications and source records attributed to Pedro Aljama.

26 records · Page 2Linked to original sources
PubMed2002

Massive telomere loss is an early event of DNA damage-induced apoptosis.

Chromosomal stability and cell viability require a proficient telomeric end-capping function. In particular, telomere dysfunction because of either critical telomere shortening or because of mutation of telomere-binding proteins results in increased apoptosis and/or cell arrest. Here, we show that, in turn, DNA damage-induced apoptosis results in a dramatic telomere loss. In particular, using flow cytometry for simultaneous detection of telomere length and apoptosis, we show that cells undergoing apoptosis upon DNA damage also exhibit a rapid and dramatic loss of telomeric sequences. This telomere loss occurs at early stages of apoptosis, because it does not require caspase-3 activation, and it is induced by loss of the mitochondrial membrane potential (Deltapsi(m)) and production of reactive oxygen species. These observations suggest a direct effect of mitochondrial dysfunction on telomeres.

Apoptosis↗
PubMed2002

Cell apoptosis and hemodialysis-induced inflammation.

Hemodialysis patients exhibit a defective immune response leading to an increased susceptibility of infections and neoplasms. Far from being helpful, dialytic therapy per se also may be responsible for this acquired immunodeficiency. Dialysis membranes and bacterial products present in dialysis water may trigger and even perpetuate an abnormal mononuclear cell activation. Upon contact with cellulosic dialysis membranes, monocytes display an increased expression of surface markers of cell activation, such as adhesion molecules CD18, CD49, CD54 and the lipopolysaccharide (LPS) ligand (CD14). Moreover, proinflammatory cytokines as IL-1beta and TNF-alpha are released both in vivo and in vitro when monocytes are exposed to cellulosic membranes. Of special interest is the fact that end-stage renal disease patients undergoing hemodialysis exhibit an increased mononuclear cell apoptosis. This apoptosis is directly related to the degree of biocompatibility of the dialysis membrane. Apoptosis is activated when monocytes enter in contact with the cellulosic dialysis membrane through cell surface receptors linked to G-proteins. In early steps of apoptosis signaling, pertussis toxin-sensitive G proteins are coupled to protein kinase C (PKC)-dependent phosphorylative mechanisms. Furthermore, recent evidence support that the execution phase of apoptosis is mediated by a caspase-3 dependent pathway. Finally, very recent available data support that monocytes subjected to repeated activation suffer a process of accelerated senescence, as demonstrated by the senescent phenotype (CD14 and CD32) expressed and their shortened telomeric length. This senescent profile may generage a defective cellular response in acute stress situations, explaining (at least in part) the altered immune response observed in hemodialysis patients.

Acute-Phase Reaction↗
PubMed2002

Caspase-3-dependent pathway mediates apoptosis of human mononuclear cells induced by cellulosic haemodialysis membranes.

BACKGROUND: Mononuclear cells from patients dialysed with cellulosic membranes undergo rapid apoptosis in vitro. The aim of the present study was to determine whether the apoptosis associated with cellulosic haemodialysis membrane shares similar features with the spontaneous apoptosis described in normal monocytes. Thus, we determined whether apoptosis is dependent on caspase-3 activity and is inhibited by lipopolysaccharide (LPS), which are two features of spontaneous apoptosis in normal monocytes. METHODS: We examined mononuclear cells from healthy subjects and from 14 end-stage renal failure patients on haemodialysis with cellulosic membranes (n=7) and non-cellulosic membranes (n=7). Isolated mononuclear cells were cultured for 48 h. To determine the effect of haemodialysis membrane exposure on caspase-3 activity, on mononuclear apoptosis, or both, cells from healthy subjects were cultured in mini-dialysers with the same membrane types that were used in the haemodialysis patients. Caspase-3 active form was determined by flow cytometric analysis using anti-human-active caspase-3 antibodies. The effect of LPS and Ac-DEVD-CHO, a specific inhibitor of active caspase-3, was also evaluated. Cell apoptosis was assessed by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling method. RESULTS: After 48 h of culture, the percentage of mononuclear cells expressing the active form of caspase-3 was greater in patients dialysed with cellulosic membranes than in patients using non-cellulosic membranes and in healthy subjects. This increase in caspase-3 activity was associated with a high rate of apoptosis, which was prevented by Ac-DEVD-CHO, an inhibitor of caspase-3 activity. LPS decreased both apoptosis and caspase-3 activity in mononuclear cells from patients dialysed with cellulosic membranes. Finally, in cells from healthy subjects, both caspase-3 activation and apoptosis were induced after incubation with cellulosic membranes. In contrast, the active form of caspase-3 was not increased in cells cultured with non-cellulosic membranes and was significantly lower than with cellulosic membranes. CONCLUSION: These findings suggest that the apoptosis of mononuclear cells induced by cellulosic haemodialysis membranes occurs through a pathway that is similar to the spontaneous apoptosis of normal monocytes. They additionally suggest that LPS regulates the proteolytic activation of caspase-3.

Adult↗
PubMed2002

The effect of LPS, uraemia, and haemodialysis membrane exposure on CD14 expression in mononuclear cells and its relation to apoptosis.

BACKGROUND: Both uraemia and bioincompatible haemodialysis membranes induce mononuclear cell apoptosis. Recent reports demonstrate that spontaneous apoptosis in normal monocytes is associated with the down-regulation of CD14 molecules, whereas LPS which prevents the down-regulation of CD14 favours monocyte survival. The aim of the present study was to evaluate a possible association between mononuclear cell apoptosis and low expression of CD14 molecules. This study also investigated whether LPS affects mononuclear cell CD14 expression and the apoptosis induced by uraemia and exposure to Cuprophan (CU) membrane. METHODS: The study was performed in vitro examining the effects of CU membrane and LPS on mononuclear cells from normal subjects and from end-stage renal failure patients. Cells were analysed by flow cytometry with fluorescent monoclonal antibodies to determine CD14 expression and with Annexin-V labelling to determine apoptosis. RESULTS: In mononuclear cells from uraemic patients cultured for 48 h, there was a subset of cells with low CD14 expression; this subset of cells was not observed in normal monocytes cultured for the same period of time. Cells with low CD14 expression were also observed when normal or uraemic mononuclear cells were cultured in the presence of CU membrane. Simultaneous measurement of apoptosis and CD14 expression revealed that cells with low CD14 expression underwent apoptosis. The addition of LPS to the medium markedly reduced the number of mononuclear cells with low CD14 expression and also reduced the rate of apoptosis in these cells. CONCLUSION: Our data suggest that mononuclear cell apoptosis induced by uraemia and the CU membrane is associated with low CD14 expression. Furthermore, LPS prevented the decrease in CD14 and reduced the rate of apoptosis.

Adult↗
PubMed2000

Effect of uremia and dialysis modality on mononuclear cell apoptosis.

The aim of this study was to evaluate the effect of both uremia itself and hemodialysis (HD) membranes on the induction of apoptosis. Four groups of subjects were evaluated: 21 nondialyzed (Non-D) patients, 10 continuous ambulatory peritoneal dialysis (CAPD) patients, and 53 HD patients who were on hemophan, cuprophan, cellulose acetate, AN69, and polysulfone; control subjects were nine healthy volunteers. Circulating mononuclear cells were obtained before dialysis and cultured for 48 h. Mean percentage of apoptosis was analyzed by a FACScan flow cytometer using Annexin V-FITC. Cell apoptosis was increased in Non-D patients (11.5 +/- 5.5%) compared with control subjects (2.1 +/- 0.7%, P < 0.001) and CAPD patients (7. 0 +/- 5.8%, P < 0.05). In patients on HD with cuprophan, apoptosis was higher than in control subjects and Non-D and CAPD patients. In Non-D patients, apoptosis was inversely correlated with renal creatinine clearance (r = -0.62, P = 0.003). Cell apoptosis was higher in hemophan than the other HD membranes. In seven patients on hemophan, switching to polysulfone resulted in decreased apoptosis (P < 0.01). Mononuclear cell circulation through mini-dialyzers made of different types of membranes (cuprophan, hemophan, cellulose acetate, AN69, and polysulfone) prouced a significant increase in apoptosis. However, there was a marked difference in the percentage of apoptosis induced by these five membranes, being significantly increased in hemophan and cuprohan compared with the other three membranes. Similar results were obtained when whole blood from healthy donors was circulated through the mini-dialyzers, showing that mononuclear cell apoptosis was increased in hemophan and cuprophan compared with polysulfone. In conclusion, uremia and membrane characteristics may independently affect the mononuclear cell apoptosis.

Adult↗
PubMedDate not supplied

Anemia management and treatment response in patients on hemodialysis: the MAR study.

BACKGROUND: Anemia management guidelines describe the importance of anemia as a risk factor in hemodialysis and the need for clinical prospective studies focused on this role of anemia. Response to treatment with iron and epoetin is multifactorial, and results are still far from the targets set by the guidelines. The Morbidity and Mortality Anemia Renal study (MAR) is a multicenter prospective cohort study of hemodialysis (HD), designed to assess the burden of anemia on morbidity and mortality. We report here a cross-sectional analysis of the management of anemia, and response-to-treatment factors. METHODS: A total of 1,710 patients were included (60% male, mean age 64.4 +/- 13.6 years, mean 16.2 +/- 11.1 months on HD) with a high comorbidity (hypertension 75.8%, diabetes 25.9%, heart failure 13.9% and coronary disease 16.7%) and a mean Charlson Index of 6.5 +/- 2.3. RESULTS: There were 28.7% of patients who had started epoetin before end-stage renal disease (pre-ESRD), 81.4% of patients displayed Hb <11 g/dL when initiating HD with a mean Hb of 9.7 g/dL. Only 67.9% of prevalent HD patients attained a hemoglobin (Hb) level above 11 g/dL, 89.5% achieved a ferritin level above 100 ng/mL, 76.7% a transferrin saturation index (TSI) above 20%, and 61.1% met all 3 objectives. The multivariate analysis identified the following risk factors for Hb <11g/dL: low albumin (odds ratio, OR = 1.75), HD efficacy below objectives (OR = 1.44) and female sex (OR = 1.36), corrected for comorbidity, epoetin treatment, transfusion, surgery or hospital admission. CONCLUSIONS: As compared with previous surveys, we found an improved but still inadequate anemia management in Spanish HD patients. Our results are comparable with those of Euro-DOPPS. Several modifiable factors related to a lower Hb concentration were assessed. On behalf of the MAR Study Group.

Aged↗