Apoptosis in the monkey small intestinal epithelium: structural and functional alterations in the mitochondria

Investigating lipid headgroup composition within epithelial membranes: a systematic review

Membrane lipid composition is often quoted within the literature, but with very little insight into how or why these compositions vary when compared to other biological membranes. One prominent area that lacks understanding in terms of rationale for lipid variability is the human gastro-intestinal tract (GIT). We have carried out a comprehensive systematic literature search to ascertain the key lipid components of epithelial membranes, with a particular focus on addressing the human GIT and to use compositional data to understand structural aspects of biological membranes. Both bacterial outer membranes and the human erythrocyte membrane were used as a comparison for the mammalian [epithelial] membranes and to understand variations in lipid presence. We show that phosphatidylcholine (PC) lipid types tend to dominate (33%) with phosphatidylethanolamines (PE) and cholesterol having very similar abundances (25 and 23% respectively). This systematic review presents a detailed insight into lipid headgroup composition and roles in various membrane types, with a summary of the distinction between the major lipid bilayer forming lipids and how peripheral lipids regulate charge and fluidity. The variety of lipids present in biological membranes is discussed and rationalised in terms function as well as cellular position.

Stimulatory effect of components of rose flowers on catalytic activity and mRNA expression of superoxide dismutase and catalase in erythrocytes

In the present study, two antioxidant components (polysaccharopeptide complex P(1-a) and condensed tannin P(1-b)) from rose (Rosa rugosa) flowers were each incubated with mouse erythrocytes to investigate their effect on erythrocyte superoxide dismutase (SOD), and catalase (CAT) activities. It was found that the activities of Cu, Zn-SOD and CAT were markedly increased after incubation for 3h with rose flower fractions at the concentration of 500μg/ml. Similar changes were also observed in the erythrocyte gene expression of SOD and CAT. These results show that P(1-a) and P(1-b) are effective antioxidants that increase the activity and the gene expression of SOD and CAT in mouse erythrocytes.

Bcl-2 prevents abnormal mitochondrial proliferation during etoposide-induced apoptosis

At the late stage of etoposide-induced apoptosis in HL-60 cells, marked by condensation of chromatin, mitochondria increase in numbers. There is also a drastic increase in mitochondrial DNA content. This increase in mitochondrial numbers and DNA content is an indicator of mitochondrial proliferation during apoptosis. These proliferating mitochondria exhibit abnormal morphology and are impaired, which is demonstrated by decrease in mitochondrial membrane potential and ATP content. The described apoptosis-induced abnormal mitochondrial proliferation was inhibited by overexpression of Bcl-2 protein, which also diminishes mitochondrial impairment. The increase in mitochondrial DNA levels correlated with elevated expression of one of the regulators of mitochondrial DNA replication, mtSSB. Our data suggest that proliferation of mitochondria may be an integral part of a cascade of apoptotic events.

Structure, molecular evolution, and gene expression of primate superoxide dismutases

Mn- and Cu,Zn-superoxide dismutase (SOD) cDNAs of eight primate species, Pan troglodytes, Pongo pygmaeus, Hylobates lar, Macaca fuscata, Macaca fascicularis, Macaca mulatta, Cebus apella, and Callithrix jacchus, were cloned. The whole protein-coding sequences were covered, comparing 198 and 153 (or 154) amino acids, for Mn- and Cu,Zn-SODs, respectively. Residues forming metal ligands were completely conserved in the two primate SODs and nucleotide/amino acid substitutions were more frequent in Cu,Zn-SODs than in Mn-SODs. Molecular evolutionary analyses showed Mn-SOD to have evolved at a constant rate and its phylogenetic tree well reflected primate phylogeny. Cu,Zn-SOD was shown to have evolved differently between primate lineages. The significant high ratio of a non-synonymous/synonymous rate was found in the lineage leading to great apes and humans, showing that this lineage underwent positive Darwinian selection. Southern hybridization suggested that the genes for primate Mn- and Cu,Zn-SOD exist as single copies. Northern analysis in various Japanese monkey tissues showed Mn- and Cu,Zn-SOD expression to be high in the liver, kidneys, and adrenal glands.

Decreased cardiolipin synthesis corresponds with cytochrome c release in palmitate-induced cardiomyocyte apoptosis

Apoptosis has been identified recently as a component of many cardiac pathologies. However, the potential triggers of programmed cell death in the heart and the involvement of specific metabolic pathway(s) are less well characterized. Detachment of cytochrome c from the mitochondrial inner membrane is a necessary first step for cytochrome c release into the cytosol and initiation of apoptosis. The saturated long chain fatty acid, palmitate, induces apoptosis in rat neonatal cardiomyocytes and diminishes content of the mitochondrial anionic phospholipid, cardiolipin. These changes are accompanied by 1) acyl chain saturation of phosphatidic acid and phosphatidylglycerol, 2) large increases in the levels of these two phospholipids, and 3) a decline in cardiolipin synthesis. Although cardiolipin synthase activity is unchanged, saturated phosphatidylglycerol is a poor substrate for this enzyme. Under these conditions, decreased cardiolipin synthesis and release of cytochrome c are directly and significantly correlated. The results suggest that phosphatidylglycerol saturation and subsequent decreases in cardiolipin affect the association of cytochrome c with the inner mitochondrial membrane, directly influencing the pathway to cytochrome c release and subsequent apoptosis.

Thrombopoietin and the TPO receptorduring platelet storage

BACKGROUND

For most cells, the addition of a specific growth factor has improved cellular viability by preventing programmed cell death (apoptosis). To determine whether the platelet-specific hematopoietic growth factor thrombopoietin (TPO) might improve platelet viability, endogenous TPO and the platelet TPO receptor were analyzed during storage, and the effect of recombinant TPO on platelet viability was assessed.

STUDY DESIGN AND METHODS

During platelet storage, TPO stability was assessed by SDS-PAGE, TPO receptor function was measured, and the platelet TPO receptor was characterized by a (125)I-rHuTPO competitive-binding assay. A recombinant TPO, pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), was added to platelet concentrates during storage, and its effect on pH, LDH, and metabolic activity was determined.

RESULTS

During storage, the molecular weight and concentration of endogenous TPO (125 +/- 19 pg/mL) and exogenous TPO (5720 +/- 140 pg/mL) were constant for 12 days; the number (33 +/- 4), binding affinity (149 +/- 33 pM), and function of the platelet TPO receptors were constant for 7 days. Metabolic activity measured with the MTT and MTS assays closely correlated with changes in the pH and LDH. The addition of PEG-rHuMGDF did not alter the pH, LDH, or metabolic activity of platelets during storage, but it did increase by 65 percent the uptake of (35)S-methionine into platelets. Finally, platelet concentrates obtained from donors treated with PEG-rHuMGDF retained normal metabolic activity for 12 days, as compared with 5 to 6 days for normal platelet concentrates.

CONCLUSIONS

TPO and its platelet receptor are present in normal amounts and have normal function during platelet storage. The addition of recombinant TPO increased platelet methionine transport but did not alter platelet viability during storage. Other means to prevent apoptosis during platelet storage should be considered, and the measurement of platelet metabolic activity by MTT and MTS assays may assist this effort.

Apoptosis in the intestinal epithelium: its relevance in normal and pathophysiological conditions

Apoptosis is now recognized as an important process responsible for maintenance of the cellular balance between proliferation and death. Apoptosis is distinct from necrosis in that it is a programmed form of cell death and occurs without any accompanying inflammation. This form of cell death can be induced by a wide range of cellular signals, which leads to activation of cell death machinery within the cell and is characterized by distinct morphological changes. Apoptosis is especially relevant in the gastrointestinal tract, as the mammalian intestinal mucosa undergoes a process of continual cell turnover that is essential for maintenance of normal function. Cell proliferation is confined to the crypts, while differentiation occurs during a rapid, orderly migration up to the villus. The differentiated enterocytes, which make up the majority of the cells, then undergo a process of programmed cell death (apoptosis). Although apoptosis is essential for the maintenance of normal gut epithelial function, dysregulated apoptosis is seen in a number of pathological conditions in the gastrointestinal tract. The cellular mechanisms regulating this tightly regimented process have not been clearly defined and this topic represents an area of active investigation as delineation of this process will lead to a better understanding of normal gut mucosal growth.