Impaired calcium regulation in subcortical vascular encephalopathy

Alzheimer's disease-like alterations in peripheral cells from presenilin-1 transgenic mice

Many cases of early-onset inherited Alzheimer's disease (AD) are caused by mutations in the presenilin-1 (PS1) gene. Expression of PS1 mutations in cell culture systems and in primary neurons from transgenic mice increases their vulnerability to cell death. Interestingly, enhanced vulnerability to cell death has also been demonstrated for peripheral lymphocytes from AD patients. We now report that lymphocytes from PS1 mutant transgenic mice show a similar hypersensitivity to cell death as do peripheral cells from AD patients and several cell culture systems expressing PS1 mutations. The cell death-enhancing action of mutant PS1 was associated with increased production of reactive oxygen species and altered calcium regulation, but not with changes of mitochondrial cytochrome c. Our study further emphasizes the pathogenic role of mutant PS1 and may provide the fundamental basis for new efforts to close the gap between studies using neuronal cell lines transfected with mutant PS1, neurons from transgenic animals, and peripheral cells from AD patients.

Impaired lymphocyte calcium metabolism in end-stage renal disease: enhanced influx, decreased efflux, and reduced response to mitogen

Lymphocytes from patients with end-stage renal disease (ESRD) exhibit elevated cytosolic calcium concentration ((Ca2+)i), but the mechanisms responsible for this elevated (Ca2+)i have not been entirely elucidated. In addition, lymphocyte proliferative responses to mitogenic stimuli are suppressed in patients with ESRD. The objectives of the study were as follows: (1) to measure calcium influx and efflux in lymphocytes from patients with ESRD; (2) to measure the effect of the calcium regulator parathyroid hormone (PTH) on lymphocyte (Ca2+)i; (3) to measure cytosolic calcium signal in patients' lymphocytes after mitogenic stimulation. The three study groups were as follows: healthy subjects (control), patients with chronic renal failure (CRF) before the beginning of regular dialysis treatment, and patients undergoing regular hemodialysis (HD) treatment. Peripheral blood lymphocytes were tested in vitro for (Ca2+)i, Ca2+ influx, and membrane calcium-adenosine triphosphatase (CaATPase) activity. Cytosolic Ca2+ signals were traced after stimulations by PTH and by phytohemagglutinin (PHA). Baseline (Ca2+)i was significantly elevated in both ESRD groups. Ca2+ influx was enhanced and CaATPase activity was reduced in both ESRD groups. PTH caused a (Ca2+)i increase in normal cells in a dose-dependent manner. PHA caused a (Ca2+)i elevation, with a Ca2+ signal in both groups of patients with ESRD that was significantly smaller than that in the control group. These findings suggest that the high (Ca2+)i found in lymphocytes from patients with ESRD is the result of enhanced Ca2+ influx concomitant with reduced Ca2+ extrusion, as reflected by reduced CaATPase activity. The patients' elevated serum PTH levels may have contributed to the high (Ca2+]i. The impaired cytosolic (Ca2+)i response to PHA may explain in part the suppressed lymphocyte proliferative response to PHA in patients with ESRD.

Changes of intracellular calcium regulation in Alzheimer's disease and vascular dementia

Free intracellular calcium ([Ca2+]i) represents probably the most important intracellular messenger for many signal transduction pathways. Due to this crucial role of [Ca2+]i, it has been assumed that alterations of [Ca2+]i are critically involved in brain aging and in the pathophysiology of Alzheimer's disease (AD). This hypothesis is corroborated by several studies demonstrating changes of [Ca2+]i in peripheral cells from AD patients. However, the findings are still controversial. Using blood lymphocytes and neutrophils as two different peripheral model systems, we evaluated several parameters of intracellular Ca2+ regulation in a very large group of AD patients and non-demented controls. We found no major difference in Ca2+ homeostasis, since neither the basal [Ca2+]i, nor the activation-induced Ca2+ responses differed among neutrophils or lymphocytes from aged controls and AD patients. However, we observed a delayed Ca2+ response of AD lymphocytes after phytohemagglutinin (PHA) stimulation indicating an impaired function of Ca2+ influx-controlling mechanisms. Furthermore, we studied whether differences exist in Ca2+ regulation between lymphocytes from patients with vascular dementia and AD patients, to define AD-specific alterations and to distinguish between the two dementia groups and non-demented control subjects respectively. First evidences indicate that Ca2+ mobilization in lymphocytes is specifically impaired in lymphocytes from patients with vascular dementia.