Blocking of acidosis-mediated apoptosis by a reduction of lactate dehydrogenase activity through antisense mRNA expression.

Lactic acid produced from the cells is a potential cause of extra- and intracellular acidification. Due to scarce technical tools, lactic acid that leads to acidification could not be reduced and direct evidence of the relationship between metabolic lactate and apoptosis has not yet been elucidated. In this study, we designed a cellular pH regulation system in CHO cells by a reduction of lactate dehydrogenase (LDH) activity through LDH antisense mRNA expression. This inhibited lactate production and, therefore, acidification of the cytosol. Under HCO3(-)-buffered growth conditions, both the parent CHO cells and the engineered CHO cells maintained their extracellular pH and intracellular pH fairly well. However, upon acidification of the cytosol, only the parent CHO cells underwent apoptosis under HCO3(-)-free conditions. In fact, we observed a number of apoptosis-related events only in control cells, including mitochondrial dysfunction, cytochrome c release, and an increase in caspase-3 enzymatic activity.     

Specific regional differences of in vitro beta-endorphin metabolism in schizophrenics

Incubation of beta-endorphin (beta-E; 25 microM) with twice-washed brain membrane homogenates leads to the formation of several biologically active peptide fragments which have been shown to be present in the brain. Based on clinical studies, some of these endorphin fragments have been shown to be active in patients with neuropsychiatric disease states. We studied the regional specificity of beta-E metabolism in frontal cortex versus putamen from sex and age matched controls versus subjects with a diagnosis of schizophrenia. The present study demonstrates that cortical tissue has a lower rate of gamma-endorphin production from beta-E and a similar rate of des-tyrosine-gamma-endorphin production. Significant differences were noted in the production of other active fragments (beta-E (1-16, 2-16, 6-21)). These results support the hypothesis that there is a regional specificity of beta-E metabolism in the brain, and these differences may have important functional consequences to secreted peptides and important clinical consequences in schizophrenia.     

Promotion and inhibition of vesicle fusion by polylysine

Polylysine induced rapid aggregation of large unilamellar vesicles composed of phosphatidylcholine-cardiolipin (1:1 molar ratio) but not their fusion. Application of the terbium-dipicolinic acid fusion assay showed that addition of polylysine at nanomolar concentrations enabled a significant lowering of the Ca2+ threshold concentration for vesicle fusion from 9 to 1 mM. Analysis of the kinetics of fusion with a mass-action kinetic model showed that polylysine enhanced significantly the rate of aggregation but affected only slightly the rate of fusion per se. Maximal enhancement of overall fusion rates occurred at a charge ratio (polylysine/cardiolipin) of about 0.5. At larger polylysine concentrations, e.g., at charge ratios greater than 3, polylysine inhibited vesicle fusion.