Glucose-induced regulation of novel iron transporters in vascular endothelial cell dysfunction

Increased iron indices have been associated with the development of diabetes and its complications. In the present study, we have investigated the glucose-induced alteration of iron transporters, divalent metal transporter-1 (DMT-1), iron regulated transporter protein-1 (IREG-1), and transferrin receptor (TfR), in endothelial cell iron accumulation and oxidative stress. Cells were exposed to high glucose levels and subjected to gene expression, protein expression, iron measurement and assessment of oxidative stress. Our results show, for the first time, expression of DMT-1 and IREG-1 in vascular endothelial cells. Our data further indicates upregulation of DMT-1 and IREG-1 mRNA and protein in response to high levels of glucose. TfR, however, exhibited a modest decrease in response to high levels of glucose. Increased expression of DMT-1 and IREG-1 was associated with iron accumulation and oxidative stress. Furthermore, our results show differential expression of iron transporters with treatment of high glucose-exposed cells with two different iron chelators. In conclusion, our study suggests that glucose-induced alteration of iron transporters may arbitrate iron accumulation and oxidative stress in endothelial cells.     

Digestive enzyme patterns and evaluation of protease classes in Catla catla (family: Cyprinidae) during early developmental stages

Digestive enzymes of Catla catla were studied during ontogenic development. Specific amylase activity was 0.12+/-0.01 mg maltose mg protein(-1) h(-1) in fish 4 days after hatching (DAH) and reached a maximum on (0.41+/-0.12 mg maltose mg protein(-1) h(-1)) 34 DAH. Total protease activity was minimum (123.2+/-16.5 mU mg protein(-1) min(-1)) on day-8 and reached its highest level (2713+/-147.2 mU mg protein(-1) min(-1)) on day-32. Trypsin activity showed constant increasing trend from day-16 onwards and was maximum on day-34 (118.1+/-7.09 mU mg protein(-1) min(-1)). Highest chymotrypsin activity was found on day-32 (1789.0+/-111.7 mU mg protein(-1) min(-1)). Lipase activity was detected in 4 DAH catla. Lipase activity increased steadily from day-22 onwards. SDS-PAGE of crude enzyme extracts showed that high molecular mass bands (41.8-127.8 kDa) appeared during the early stages followed by low molecular mass bands (17.8-37.2 kDa). The number of protease activity bands in substrate SDS-PAGE increased with age of fish. During ontogenesis of carp, soybean trypsin inhibitor (SBTI), PMSF and TLCK inhibited 75.5+/-1.19% to 92.8+/-0.85%, 53.3+/-9.47% to 90.5+/-2.6% and 39.8+/-3.8% to 84.7+/-1.54% of total protease activity, respectively. There was only 2.58+/-0.66% to 10.21+/-0.09% inhibition of protease activity with EDTA. SBTI and PMSF inhibited 8 and 4 activity bands, respectively. TLCK, a specific trypsin inhibitor, inhibited four trypsin-like enzymes in carp during ontogenesis.     

There's more to life than neurotransmission: the regulation of exocytosis by synaptotagmin VII

Among the 16 known vertebrate synaptotagmins, only Syt I, IV and VII are also present in C. elegans and Drosophila, suggesting that these isoforms play especially important roles in vivo. Extensive evidence indicates that Syt I is a synaptic vesicle Ca(2+) sensor essential for rapid neurotransmitter release. It has been suggested that the ubiquitously expressed Syt VII also regulates synaptic vesicle exocytosis, despite its presence in several tissues in addition to the brain. Here, we discuss recent genetic and biochemical evidence that does not support this view. Syt VII null mutants do not have a neurological phenotype, and the protein is found on the membrane of lysosomes and some non-synaptic secretory granules, where it regulates Ca(2+)-triggered exocytosis and plasma membrane repair.     

The importance of calcium influx, calpain and calmodulin for the activation of CaCo-2 cell death pathways by Clostridium perfringens enterotoxin

CaCo-2 cells exhibit apoptosis when treated with low doses of Clostridium perfringens enterotoxin (CPE), but develop oncosis when treated with high CPE doses. This study reports that the presence of extracellular Ca(2+) in treatment buffers is important for normal activation of both those cell death pathways in CPE-treated CaCo-2 cells. Normal development of CPE-induced cell death pathway effects, such as morphologic damage, DNA fragmentation, caspase activation, mitochondrial membrane depolarization and cytochrome c release, was strongly inhibited when CaCo-2 cells were CPE-treated in Ca(2+)-free buffers. When treatment buffers contained Ca(2+), CPE caused a rapid increase in CaCo-2 cell Ca(2+) levels, apparently because of increased Ca(2+) influx through a CPE pore. High CPE doses caused massive changes in cellular Ca(2+) levels that appear responsible for activating oncosis, whereas low CPE doses caused less perturbations in cellular Ca(2+) levels that appear responsible for activating apoptosis. Both CPE-induced apoptosis and oncosis were found to be calmodulin- and calpain-dependent processes. As Ca(2+) levels present in the intestinal lumen resemble those of Ca(2+)-containing treatment buffers used in this study, perturbations in cellular Ca(2+) levels and calpain/calmodulin-dependent processes are also probably important for inducing enterocyte cell death during CPE-mediated gastrointestinal disease.     

Synthesis of novel peptide nucleic acid-peptide chimera for non-invasive imaging of cancer

A chelator-peptide-PNA-peptide chimera specific for KRAS has been prepared by continuous solid phase coupling with a C-terminal insulin-like growth factor 1 (IGF1) ligand, D(cys-ser-lys-cys), and N-terminal bis(S-benzoyl thioglycoloyl) diaminopropanoate chelator for radionuclide labeling. The probe was purified by RP-HPLC and characterized by MALDI-TOF mass spectroscopy. The probe was labeled with 99mTc and 64Cu. Both labeled probes accumulated in human pancreatic cancer xenografts in immunocompromised mice. Control experiments with mismatch chimeras and control xenografts will be necessary to determine the specificity of this molecular diagnostic strategy.     

Inhibition of rat brain mitochondrial electron transport chain activity by dopamine oxidation products during extended in vitro incubation: implications for Parkinson's disease

Several studies on mitochondrial functions following brief exposure (5-15 min) to dopamine (DA) in vitro have produced extremely variable results. In contrast, this study demonstrates that a prolonged exposure (up to 2 h) of disrupted or lysed mitochondria to DA (0.1-0.4 mM) causes a remarkable and dose-dependent inhibition of complex I and complex IV activities. The inhibition of complex I and complex IV activities is not prevented by the antioxidant enzyme catalase (0.05 mg/ml) or the metal-chelator diethylenetriaminepentaacetic acid (0.1 mM) or the hydroxyl radical scavengers like mannitol (20 mM) and dimethyl sulphoxide (20 mM) indicating the non-involvement of *OH radicals and Fenton's chemistry in this process. However, reduced glutathione (5 mM), a quinone scavenger, almost completely abolishes the DA effect on mitochondrial complex I and complex IV activities, while tyrosinase (250 units/ml) which catalyses the conversion of DA to quinone products dramatically enhances the former effect. The results suggest the predominant involvement of quinone products instead of reactive oxygen radicals in long-term DA-mediated inactivation of complex I and complex IV. This is further indicated from the fact that significant amount of quinones and quinoprotein adducts (covalent adducts of reactive quinones with protein thiols) are formed during incubation of mitochondria with DA. Monoamine oxidase A (MAO-A) inhibitor clorgyline also provides variable but significant protection against DA induced inactivation of complex I and complex IV activities, presumably again through inhibition of quinoprotein formation. Mitochondrial ability to reduce tetrazolium dye 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) in presence of a respiratory substrate like succinate (10 mM) is also reduced by nearly 85% following 2 h incubation with 0.4 mM DA. This effect of DA on mitochondrial function is also dose-dependent and presumably mediated by quinone products of DA oxidation. The mitochondrial dysfunction induced by dopamine during extended periods of incubation as reported here have important implications in the context of dopaminergic neuronal death in Parkinson's disease (PD).     

p38 MAP kinase regulates rapid matrix metalloproteinase-9 release from eosinophils

Eosinophils constitutively produce and store matrix metalloproteinase-9 (MMP-9), a protease implicated in tissue remodeling observed in asthma. In this study, we examined the rapid release of stored MMP-9 from eosinophils following stimulation with either tumor necrosis factor-alpha (TNF-alpha or the bacterial product fMLP. TNF-alpha induced rapid and robust pro-MMP-9 release from eosinophils. MMP-9 could be detected in the cell-free supernatant as early as 15min after stimulation. Rapid MMP-9 release was similarly induced by fMLP. TNF-alpha stimulation activated the mitogen-activated protein (MAP) kinases p38 MAP kinase and extracellular signal-regulated kinase-2 (Erk-2) at times and concentrations similar to that observed for MMP-9 release. Using pharmacological inhibitors, we found that TNF-alpha-stimulated MMP-9 release was mediated by p38 MAP kinase, but not Erk-1/2. Signaling through p38 MAP kinase may represent a universal mechanism for MMP-9 release from eosinophils, as fMLP-induced MMP-9 release was also regulated by p38 MAP kinase.     

Crystal structures of HbA2 and HbE and modeling of hemoglobin delta 4: interpretation of the thermal stability and the antisickling effect of HbA2 and identification of the ferrocyanide binding site in Hb

Hemoglobin A(2) (alpha(2)delta(2)) is an important hemoglobin variant which is a minor component (2-3%) in the circulating red blood cells, and its elevated concentration in beta-thalassemia is a useful clinical diagnostic. In beta-thalassemia major, where there is beta-chain production failure, HbA(2) acts as the predominant oxygen deliverer. HbA(2) has two more important features. (1) It is more resistant to thermal denaturation than HbA, and (2) it inhibits the polymerization of deoxy sickle hemoglobin (HbS). Hemoglobin E (E26K(beta)), formed as a result of the splice site mutation on exon 1 of the beta-globin gene, is another important hemoglobin variant which is known to be unstable at high temperatures. Both heterozygous HbE (HbAE) and homozygous HbE (HbEE) are benign disorders, but when HbE combines with beta-thalassemia, it causes E/beta-thalassemia which has severe clinical consequences. In this paper, we present the crystal structures of HbA(2) and HbE at 2.20 and 1.74 A resolution, respectively, in their R2 states, which have been used here to provide the probable explanations of the thermal stability and instability of HbA(2) and HbE. Using the coordinates of R2 state HbA(2), we modeled the structure of T state HbA(2) which allowed us to address the structural basis of the antisickling property of HbA(2). Using the coordinates of the delta-chain of HbA(2) (R2 state), we also modeled the structure of hemoglobin homotetramer delta(4) that occurs in the case of rare HbH disease. From the differences in intersubunit contacts among beta(4), gamma(4), and delta(4), we formed a hypothesis regarding the possible tetramerization pathway of delta(4). The crystal structure of a ferrocyanide-bound HbA(2) at 1.88 A resolution is also presented here, which throws light on the location and the mode of binding of ferrocyanide anion with hemoglobin, predominantly using the residues involved in DPG binding. The pH dependence of ferrocyanide binding with hemoglobin has also been investigated.