Differential in vitro metabolism of β-endorphin in schizophrenia

Biologically active peptide fragments derived from the proteolytic cleavage of β-endorphin (βE) have been shown to be present in the brain. Based on clinical results using some of these fragments in neuropsychiatric disease studies we investigated the in vitro metabolism of βE by twice-washed membrane homogenates of postmortem putamen from sex and age matched controls versus subjects with a diagnosis of schizophrenia. The present study demonstrates that frozen (−80°C) postmortem human tissues are viable for these studies and that metabolism in control tissue proceeds similarly to fresh tissues. Furthermore, a significant increase in the formation of the putative neuroleptic-like peptide fragment desenkephalin-γ-endorphin in postmortem schizophrenic putamen versus controls was shown. A significant decrease in the formation of βE 6–21 was also reported. These data suggest that an approach using postmortem human brain is possible in studying β-endorphin catabolism and is therefore applicable to other neuropeptide systems.     

Regulation of beta-adrenergic responses during in vitro differentiation of mouse erythroleukemia cells

Dimethyl sulfoxide (DMSO)-induced erythroid differentiation of Friend mouse erythroleukemia (MEL) cells is associated with a marked transient modulation of catecholamine sensitivity. Within 24 h after induction and well before the onset of hemoglobin synthesis, we observed a 3-fold increase in beta-receptor density and a more than 10-fold increase in receptor-coupled cAMP formation. During the following 4 days, in parallel with the development of normoblast-like cells, receptor numbers returned to preinduction levels while catecholamine-dependent cAMP formation remained significantly elevated. Simultaneously, the apparent potency of the beta-adrenoceptor agonist isoprenaline increased 10-fold. Improved receptor-cyclase coupling is probably due to a major shift in the expression of Gi and Gs regulatory proteins. Bacterial toxin-mediated ADP-ribosylation of membrane proteins suggests that the dominating species in native cells is Gi (Gsa:Gia = 1.7). By contrast, Gs predominates in differentiated cells (Gsa:Gia = 1.8:1). Receptor-independent forskolin-stimulated cAMP formation showed a pronounced, albeit transient, decrease during differentiation. We suggest that these changes in cellular cAMP responses may be important for transient positive or negative cooperative interactions between hormones and growth factors in the course of erythroid cell development.     

TGF-β1 induces efficient differentiation of human cardiomyocyte progenitor cells into functional cardiomyocytes in vitro

The adult mammalian heart has limited regenerative capacity and was generally considered to contain no dividing cells. Recently, however, a resident population of progenitor cells has been identified, which could represent a new source of cardiomyocytes. Here, we describe the efficient isolation and propagation of human cardiomyocyte progenitor cells (hCMPCs) from fetal heart and patient biopsies. Establishment of hCMPC cultures was remarkably reproducible, with over 70% of adult atrial biopsies resulting in robustly expanding cell populations. Following the addition of transforming growth factor β, almost all cells differentiated into spontaneously beating myocytes with characteristic cross striations. hCMPC-derived cardiomyocytes showed gap-junctional communication and action potentials of maturing cardiomyocytes. These are the first cells isolated from human heart that proliferate and form functional cardiomyocytes without requiring coculture with neonatal myocytes. Their scalability and homogeneity are unique and provide an excellent basis for developing physiological, pharmacological, and toxicological assays on human heart cells in vitro.     

N-2 methylated quaternary derivatives of β-carboline-3-carboxylates inhibit acetylcholinesterase in vitro

Alkyl β-carboline-3-carboxylate derivatives (e.g. β-CCM and β-CCB), known to interact with the central benzodiazepine receptor, were quaternized at the N-2 position using methyl iodide. The products strongly inhibited acetylcholinesterase in vitro and displayed affinities for muscarinic receptors in the micromolar range.     

Characterization of in vitro proteolytic processing of β-endorphin by reversed-phase HPLC

In vitro, central and peripheral proteolytic processing of β-endorphin by membrane-bound enzymes results in the formation of specific active fragments that have been recently shown to function in behavior, intestinal motility and in the central control of urinary bladder activity. A high resolution, reversed phase high performance liquid chromatography system capable of separating 28 β-endorphin related fragments simultaneously was used to study the time-course processing of β-endorphin by membrane associated peptidases in the brain and regions of the small intestine. The hypothesis we tested was that a homeostatic balance between α- and γ-type endorphins exists in these tissues. The results of the study show that the rate and quantity of fragments produced between the mucosa and nerve-muscle regions of the small intestine are significantly different. Metabolic rates, pattern, and the ratio of α/γ-type endorphins in the brain were very similar to the nerve-muscle region of the small intestine. This suggests that β-endorphin processing to active fragments is occurring at the nerves of the small intestine and that a specific and similar balance of α/γ-type endorphin exists in the brain and gastrointestinal system at neutral pH.     

Cell-surface changes during in vitro differentiation of pluripotent embryonal carcinoma cells

When aggregates of HM-1 embryonal carcinoma (EC) cells were exposed to 10(-6) M retinoic acid for 2 days and cultured in medium lacking retinoic acid, they differentiated to nerve cells, endoderm cells, and myoblasts. Cells 2 days after initial exposure to retinoic acid were not significantly different from the parental EC cells, as judged by cell-surface architecture and by reactivity to lectins. On the fourth day, the surface of the aggregates was covered with two kinds of cells distinguishable from the parental cells. The round cells with short villi seemed to be precursors to endoderm cells. Receptors for Dolichos biflorus agglutinin (DBA) newly appeared and receptors for peanut agglutinin (PNA) were still expressed on their surfaces. The other cells, which were round cells with a few processes, might be precursors to nerve cells. PNA receptors had disappeared from their surfaces, and DBA receptors were not expressed. On the sixth day of differentiation, possible precursors to myoblasts were detected; they were flat cells with smooth surfaces. These cells lacked cell-surface receptors for the two lectins, while the precursor cells and the myoblasts excreted intercellular fibers reacting with PNA. HM-1 cells synthesized much embryoglycan, the structure of which was similar to that of the glycan isolated from quasinullipotent F9 cells. The only difference was that the glycan from HM-1 cells lacked DBA binding sites. Synthesis of fucosylated embryoglycan mainly decreased between the second and fourth day of differentiation. As above, cell-surface changes occurred mainly between the second and fourth day. The period seems to be important in determining the fate of the cells, since endoderm cells were scarcely seen among differentiated cells which had been continuously exposed to 10(-6) M retinoic acid during the period.     

Differentiation of prospective mouse pancreatic islet cells during development in vitro and during regeneration

The pancreatic islets of mouse embryos are comprised of four different endocrine cell types and of cells containing a hormone (i.e., glucagon) and a catecholamine enzyme (tyrosine hydroxylase, TH) which appear sequentially during development in vivo. The presence of TH in glucagon cells, however, is transient, since adult pancreatic A cells do not express the enzyme. In this study we sought to determine whether the endocrine precursor cells are primed to differentiate and express catecholamine enzymes during their maturation following a predetermined sequence or whether these processes are regulated by environmental cues. To answer this question, we used immunocytochemical procedures to examine the differentiation of pancreatic rudiments removed from E11 mouse embryos and maintained in culture and of pancreases that regenerated in vitro from E11 pancreatic ducts. We found that although all the endocrine cell types differentiate in the gland in culture, the sequence of their appearance is different from that in vivo, suggesting that the timing of differentiation may be regulated by environmental factors. We also found that, in vitro, the pancreas contains TH-glucagon cells, indicating that the expression of the enzyme by pancreatic A cells is independent of factors present in vivo. Moreover, the fact that the TH-glucagon cells also differentiate during pancreatic regeneration suggests that the expression of the enzyme may be a characteristic stage of endocrine cell precursors during maturation.     

A mechanism for heterogeneous endothelial responses to flow in vivo and in vitro

Exposure of endothelium to a nominally uniform flow field in vivo and in vitrofrequently results in a heterogeneous distribution of individual cell responses. Extremes in response levels are often noted in neighboring cells. Such variations are important for the spatial interpretation of vascular responses to flow and for an understanding of mechanotransduction mechanisms at the level of single cells. We propose that variations of local forces defined by the cell surface geometry contribute to these differences. Atomic force microscopy measurements of cell surface topography in living endothelium both in vitro and in situ combined with computational fluid dynamics demonstrated large cell-to-cell variations in the distribution of flow-generated shear stresses at the endothelial luminal surface. The distribution of forces throughout the surface of individual cells of the monolayer was also found to vary considerably and to be defined by the surface geometry. We conclude that the endothelial three-dimensional surface geometry defines the detailed distribution of shear stresses and gradients at the single cell level, and that there are large variations in force magnitude and distribution between neighboring cells. The measurements support a topographic basis for differential endothelial responses to flow observed in vivo and in vitro. Included in these studies are the first preliminary measurements of the living endothelial cell surface in an intact artery.     

Cloning, expression, purification, distribution and kinetics characterization of the bacterial β-galactosidase fused to the cytoplasmic transduction peptide in vitro and in vivo

Cytoplasmic transduction peptide (CTP) offers exciting therapeutic opportunities for the treatment of many diseases caused by cytoplasmic functional molecules. It can transduce large, biologically active proteins into the cytoplasmic compartment of several mammalian cells. However, other intriguing features of CTP, including its activity in vitro, and distribution and tissue infiltration abilities in vivo, remain to be explored. The present study was initiated to (1) further confirm the cytoplasmic localization preference and the enzymatic activity of the transduced CTP-β-gal in vitro and (2) examine the kinetics and tissue distribution of the CTP-β-gal fusion protein in mice. A CTP-β-gal fusion protein was expressed in Escherichia coli and either transduced into BaF3-BCR/ABL cells or administered intravenously into female Balb/C mice at a dose of 100 μg per mouse. Its localization in BaF3-BCR/ABL cells was evaluated by immunocytochemistry and in situ X-gal staining, and its distribution in various tissues was analyzed both by in situ X-gal staining and quantitative enzymatic activity assay. β-Galactosidase enzyme activity was observed in BaF3-BCR/ABL cells and in all tissues tested, with peak activity occurring at 15 min in most tissues and at 24 h in brain. These data will not only allow rational selection of delivery schedules for therapeutic CTP, but will also aid the use of CTP fusion protein transduction in the development of protein therapeutics targeting the cytoplasmic compartment both in vitro and in vivo.     

Phagocytosis by carp granulocytes; in vivo and in vitro observations

The phagocytic ability of carp (Cyprinus carpio L.) granulocytes was evaluated in vivo and in vitro. In suspensions of head kidney cells, neutrophil granulocytes incorporated both latex beads and coccidian merozoites. In intestinal tissues from carp with a Goussia carpelli infection, all granulocyte cell types (neutrophils and cells of the basophilic-eosinophilic complex) phagocytosed cell detritus and coccidian developmental stages, mainly merozoites.     

3,5,3′,5′-Tetrachlorobiphenyl is a weak oestrogen agonist in vitro and in vivo

Polychlorinated biphenyls (PCBs) are widespread, persistent environmental contaminants of which some congeners can act as endocrine disrupters. Previous work has shown that 3,4,3′,4′-tetrachlorobiphenyl (PCB77) can act as an oestrogen with actions mediated through the oestrogen receptor. Here, oestrogenic actions have been assessed for two further tetrachlorobiphenyl isomers. Assays of oestrogenic action have involved (1) ligand regulation of oestrogen-sensitive gene expression; (2) ligand regulation of cell growth in oestrogen-dependent human breast cancer cell lines MCF7 McGrath and ZR-75-1; and (3) ligand activity in the immature mouse uterine weight bioassay in vivo. These results demonstrate that 3,5,3′,5′-tetrachlorobiphenyl (PCB 80) can be considered to be a weak oestrogen agonist, but the 2,5,2′,5′-congener (PCB 52) revealed no oestrogenic properties in any of these assays. Implications of these results are discussed in relation to structure-activity predictions for environmental oestogens.     

Tyrphostin-induced differentiation of mouse erythroleukemia cells

Inhibitors of protein-tyrosine kinases (TPKs) from the tyrphostins family induce terminal erythroid differentiation of mouse erythroleukemia (MEL) cells. The most potent tyrphostin was found to be AG-568 which was therefore investigated in more detail. Just prior to differentiation the inhibition of tyrosine phosphorylation of a pp⁹⁷ protein band was noted. We also found that AG-568 treatment induces the appearance of a putative differentiation factor which could induce tyrphostin-independent differentiation in untreated cells. Our study suggests that the inhibition of tyrosine phosphorylation by AG-568 leads to the production of differentiating factor(s) which induce the MEL cells to differentiate.     

Dihydrotestosterone and estradiol-17β mutually neutralize their inhibitory effects on human vascular smooth muscle cell growth in vitro

We reported previously that high concentrations of either estradiol-17β (E₂) or dihydrotestosterone (DHT) inhibit growth of human cultured vascular smooth muscle cells (VSMC), mediated by cell membrane receptors and MAP-kinase–kinase activity (MEK). We now tested whether the presence of the opposite gender's dominant sex hormone modifies these effects. We incubated VSMC with various concentrations of E₂ and DHT or protein bound hormones (E₂–BSA or T–BSA), alone or in various combinations. High concentration of E₂ or E₂–BSA inhibited VSMC growth and stimulated MEK. In the presence of 3 nM DHT, high concentration of E₂ no longer inhibited ³[H] thymidine incorporation or increased MEK. Moreover, when high DHT concentration (300 nM) was added to VSMC exposed to high E₂, VSMC growth actually increased without change in MEK. DHT at 300 nM suppressed VSMC growth and increased MEK while 0.3 nM E₂ had only marginal effect on this interaction, and 30 nM E₂ reversed the inhibitory effect of DHT on cell growth. The inhibitory effects of both E₂ and DHT on VSMC cell growth and the stimulation of MEK was apparently mediated by cell membrane receptors, as it persisted when bovine serum albumin (BSA)-bound hormones were used. Further, inhibition of VSMC growth induced by E₂–BSA was reversed in the presence of T–BSA and vice versa. These results suggest that while female and male sex hormones affect VSMC growth similarly, they interfere in a dose-, hormone- and MEK-dependent manner with each other's effect.     

Regulation of β-amyloid stimulated proinflammatory responses by peroxisome proliferator-activated receptor α

Amyloid deposition within the brains of Alzheimer's Disease patients results in the activation of microglial cells and the induction of a local inflammatory response. The interaction of microglia or monocytes with β-amyloid (Aβ) fibrils elicits the activation a complex tyrosine kinase-based signal transduction cascade leading to stimulation of multiple independent signaling pathways and ultimately to changes in proinflammatory gene expression. The Aβ-stimulated expression of proinflammatory genes in myeloid lineage cells is antagonized by the action of a family of ligand-activated nuclear hormone receptors, the peroxisome proliferator-activated receptors (PPARs). We report that THP-1 monocytes express predominantly PPARγ isoform and lower levels of PPARα and PPARδ isoforms. PPAR mRNA levels are not affected by differentiation of the cells into a macrophage phenotype, nor are they altered following exposure to the classical immune stimulus, lipopolysaccharide. Previous studies have found that PPARγ agonists act broadly to inhibit inflammatory responses. The present study explored the action of the PPARα isoform and found that PPARα agonists inhibited the Aβ-stimulated expression of TNFα and IL-6 reporter genes in a dose-dependent manner. Moreover, the PPARα agonist WY14643 inhibited macrophage differentiation and COX-2 gene expression. However, the PPARα agonists failed to inhibit Aβ-stimulated elaboration of neurotoxic factors by THP-1 cells. These findings demonstrate that PPARα acts to suppress a diverse array of inflammatory responses in monocytes.