Cyclophosphamide-impaired regulation of hepatic heme metabolism

Summary Im male rats hepatic cytochromes b₅ and P-450 were reduced at different times after treatment with cyclophosphamide (CP) (200 mg/kg i.p. for 3 days). In contrast, microsomal heme did not change until 48 h after the last dose of CP, leading to accumulation of heme in a non-cytochromal form. Parallel to the above changes the heme metabolism showed derangement: -aminolaevulinate synthase, the rate-limiting enzyme in heme synthesis, was depressed and heme oxygenase, the enzyme which catalyzes the oxidative degradation of heme, was increased.     

The effect of hypoxia on hepatic cytochromes and heme turnover in rats in vivo

We evaluated the effect of hypoxia (7% v/v) on hepatic heme turnover in vivo and microsomal heme protein content in male Sprague-Dawley rats. Hepatic heme protein turnover, measured as 14CO-production during continuous infusion of 5-14C-aminolevulinic acid, a precursor of nonerythrogenic heme, was decreased 60% during hypoxia and returned to control levels promptly after reoxygenation. Hepatic cytochrome P-450 content was decreased in hypoxic and 24-h reoxygenated animals. We conclude that normobaric hypoxia decreases hepatic cytochrome P-450 which could contribute to decreased drug metabolism in hypoxia. This decrease is probably due to heme oxygenase-independent breakdown of hepatic heme.     

The effect of hypoxia on hepatic cytochromes and heme turnover in rats in vivo

Summary We evaluated the effect of hypoxia (7% v/v) on hepatic heme turnover in vivo and microsomal heme protein content in male Sprague-Dawley rats. Hepatic heme protein turnover, measured as¹⁴CO-production during continuous infusion of 5-¹⁴C-aminolevulinic acid, a precursor of nonerythrogenic heme, was decreased 60% during hypoxia and returned to control levels promptly after reoxygenation. Hepatic cytochrome P-450 content was decreased in hypoxic and 24-h reoxygenated animals. We conclude that normobaric hypoxia decreases hepatic cytochrome P-450 which could contribute to decreased drug metabolism in hypoxia. This decrease is probably due to heme oxygenase-independent breakdown of hepatic heme.     

Die Rolle von Glukose im Erholungsprozess des Muskels

Summary It is well known that after exhausting muscle work glucose (or saccharose) leads to quick recovery in man. Experiments on rats have shown that in adult animals 50% of all creatine is present as creatine-phosphate (CP). In old animals above 22 months, only about 25% is present as CP. Diets with a 50% glucose content lead in old animals, in rest, to 50% CP in the muscle. Also after exhausting work on glucose diet the restitution is so complete that about 50% CP is present. The main reservoir of energy for the restitution of muscle, ADP ATP, comes from the breakdown of CP. The problem may be discussed whether high glucose diet may be damaging insulin production by exhaustion.     

Chlorpromazine causes vesicle population changes in the monoaminergic synapse of the rat caudate nucleus.

The population of monoaminergic synaptic vesicles in the rat caudate nucleus remained unchanged or slightly decreased 3 h after chlorpromazine (CP) administration, and clearly increased after 24 h. The diameter of synaptic vesicles became smaller when the vesicles increased. These findings suggest that CP causes presynaptic blocking in part of its actions and leads to a condition in which neural transmission is inactive. In the control animals, population of the vesicles tended to fluctuate following the circadian rhythm.     

Chlorpromazine causes vesicle population changes in the monoaminergic synapse of the rat caudate nucleus

Summary The population of monoaminergic synaptic vesicles in the rat caudate nucleus remained unchanged or slightly decreased 3 h after chlorpromazine (CP) administration, and clearly increased after 24 h. The diameter of synaptic vesicles became smaller when the vesicles increased. These findings suggest that CP causes presynaptic blocking in part of its actions and leads to a condition in which neural transmission is inactive. In the control animals, population of the vesicles tended to fluctuate following the circadian rhythm.     

Choroid plexus implants rescue Alzheimer’s disease-like pathologies by modulating amyloid-β degradation

The choroid plexuses (CP) release numerous biologically active enzymes and neurotrophic factors, and contain a subpopulation of neural progenitor cells providing the capacity to proliferate and differentiate into other types of cells. These characteristics make CP epithelial cells (CPECs) excellent candidates for cell therapy aiming at restoring brain tissue in neurodegenerative illnesses, including Alzheimer’s disease (AD). In the present study, using in vitro approaches, we demonstrated that CP were able to diminish amyloid-β (Aβ) levels in cell cultures, reducing Aβ-induced neurotoxicity. For in vivo studies, CPECs were transplanted into the brain of the APP/PS1 murine model of AD that exhibits advanced Aβ accumulation and memory impairment. Brain examination after cell implantation revealed a significant reduction in brain Aβ deposits, hyperphosphorylation of tau, and astrocytic reactivity. Remarkably, the transplantation of CPECs was accompanied by a total behavioral recovery in APP/PS1 mice, improving spatial and non-spatial memory. These findings reinforce the neuroprotective potential of CPECs and the use of cell therapies as useful tools in AD.     

Cimetidine induces hepatic heme oxygenase activity without altering hepatic heme catabolism

Cimetidine inhibits oxidative drug metabolism; it is not known whether this drug alters the catabolic fate of hepatic heme. We therefore investigated hepatic heme turnover both by a 14CO breath test and directly by labeling the heme pool. Neither acute (150 mg/kg i.p.) nor chronic (150 mg/kg i.p. bid for 3 days) cimetidine administration significantly affected hepatic heme turnover. Chronic, but not acute, cimetidine significantly (p less than 0.025) increased heme oxygenase activity. Cimetidine inhibited heme oxygenase activity in vitro at concentrations achieved in vivo.     

Cimetidine induces hepatic heme oxygenase activity without altering hepatic heme catabolism

Summary Cimetidine inhibits oxidative drug metabolism; it is not known whether this drug alters the catabolic fate of hepatic heme. We therefore investigated hepatic heme turnover both by a¹⁴CO breath test and directly by labeling the heme pool. Neither acute (150 mg/kg i.p.) nor chronic (150 mg/kg i.p. bid for 3 days) cimetidine administration significantly affected hepatic heme turnover. Chronic, but not acute, cimetidine significantly (p<0.025) increased heme oxygenase activity. Cimetidine inhibited heme oxygenase activity in vitro at concentrations achieved in vivo.     

Microarray-based identification of differentially expressed growth- and metastasis-associated genes in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis. To improve diagnosis and treatment, key mechanisms of deregulated molecular functions have to be identified. Using microarray analysis, the expression patterns of 5600 human genes were assessed in PDAC by comparison with the normal pancreas and chronic pancreatitis (CP). The expression of 467 of 5600 genes was increased in PDAC in comparison to the normal pancreas, and the expression of 120 of these genes was not increased in CP. In addition, 341 of 5600 genes were expressed at decreased levels in PDAC tissues, of which 96 were decreased in comparison to both normal and CP tissues. Thus, a total of 808 of 5600 human genes were differentially expressed in pancreatic cancer. The identification of a large panel of altered genes in PDAC will stimulate additional studies that will lead to improved understanding of the molecular mechanisms underlying pancreatic malignant growth.     

Targeting Nrf-2 is a promising intervention approach for the prevention of ethanol-induced liver disease

Alcoholic liver disease (ALD) remains to be a worldwide health problem. It is generally accepted that oxidative stress plays critical roles in the pathogenesis of ALD, and antioxidant therapy represents a logical strategy for the prevention and treatment of ALD. Nuclear factor erythroid-derived 2-like 2 (NFE2L2 or Nrf-2) is essential for the antioxidant responsive element (ARE)-mediated induction of endogenous antioxidant enzymes such as heme oxygenase 1 (HO-1) and glutamate–cysteine ligase [GCL, the rate-limiting enzyme in the synthesis of glutathione (GSH)]. Activation of Nrf-2 pathway by genetic manipulation or pharmacological agents has been demonstrated to provide protection against ALD, which suggests that targeting Nrf-2 may be a promising approach for the prevention and treatment of ALD. Herein, we review the relevant literature about the potential hepatoprotective roles of Nrf-2 activation against ALD.     

Turning points in the evolution of peroxidase–catalase superfamily: molecular phylogeny of hybrid heme peroxidases

Heme peroxidases and catalases are key enzymes of hydrogen peroxide metabolism and signaling. Here, the reconstruction of the molecular evolution of the peroxidase–catalase superfamily (annotated in pfam as PF00141) based on experimentally verified as well as numerous newly available genomic sequences is presented. The robust phylogenetic tree of this large enzyme superfamily was obtained from 490 full-length protein sequences. Besides already well-known families of heme b peroxidases arranged in three main structural classes, completely new (hybrid type) peroxidase families are described being located at the border of these classes as well as forming (so far missing) links between them. Hybrid-type A peroxidases represent a minor eukaryotic subfamily from Excavates, Stramenopiles and Rhizaria sharing enzymatic and structural features of ascorbate and cytochrome c peroxidases. Hybrid-type B peroxidases are shown to be spread exclusively among various fungi and evolved in parallel with peroxidases in land plants. In some ascomycetous hybrid-type B peroxidases, the peroxidase domain is fused to a carbohydrate binding (WSC) domain. Both here described hybrid-type peroxidase families represent important turning points in the complex evolution of the whole peroxidase–catalase superfamily. We present and discuss their phylogeny, sequence signatures and putative biological function.     

Scapharca dimeric hemoglobin: A new mechanism of information transfer between globin chains

The homodimeric hemoglobin component present in the red cells of the bivalve molluscScapharca inaequivalvis, HbI, is endowed with high cooperativity in ligand binding. This behaviour is in contrast with that of vertebrate hemoglobins in which cooperativity is associated with a tetrameric assembly and the presence of two types of chain. Analysis of the aminoacid sequence and immunological data suggested that the assembly of HbI differed from that characteristic of vertebrate hemoglobins and hence that cooperativity had an unusual structural basis. Indeed the X-ray structures of the carbonmonoxy and deoxy derivatives at 2.4 resolution showed that in HbI the heme carrying E and F helices are not exposed to solvent as in the vertebrate hemoglobin tetramer, but form the subunit interface and bring the two heme groups practically in direct contact through a network of hydrogen bonds. Ligand binding brings about marked structural changes that are limited to the heme environment, whereas quaternary changes are only minor. The structural changes in the heme environment result in alterations in the network of interactions between the heme groups which lead to changes in ligand affinity. In HbI therefore cooperativity in ligand binding is achieved through direct heme-heme communication as opposed to the long range information transfer operative in the vertebrate hemoglobin tetramer.     

Studies onxHaynaldoticum sardoum Meletti et Onnis metabolism during seed life-span: α-amylase and glutamate decarboxylase activity

Summary Embryo GAD activity and -amylase in the endosperm of 2 different physiological lines (CP; CV) ofxHaynaldoticum sardoum Meletti et Onnis were evaluated and different stages of seed ripening and progressively older seeds were examined. Results concerning GAD activity during ripening show differences between CP and CV seeds, the former being more active. In the ageing seeds, the GAD remains constant (CP is twice as much as CV) up to 4th year and greatly decreases at the 5th. The -amylase activity is fairly constant during ripening in CV endosperm and increases in CP: at the fully-ripe stage, both show similar values. During seed ageing, the activity decreases progressively in CV endosperm while, in CP, values are greater but fairly constant. The results are discussed in connection with dormancy and the different physiological ageing of seeds.This work was supported by a grant from the Consiglio Nazionale delle Ricerche (Rome, Italy).Acknowledgments. The authors wish to thank Mr F. Saviozzi, Mr V. Sbrana and Mr R. Bertini for their expert technical assistance.     

Endocrine and exocrine pancreatic function after camostate-induced growth of the organ

It is well known that oral administration of camostate induces hyperplasia and hypertrophy of the rat pancreas. It is not clear, however, whether pancreatic hormone and enzyme secretion are affected by camostate treatment.In rats, daily administration of 200 mg camostate/kg b. wt for 14 days significantly increased pancreatic weight and pancreatic content of DNA, protein, amylase, lipase, trypsin and chymotrypsin, as well as the amount of insulin, glucagon and somatostatin. In the intact animal, blood glucose levels and serum concentrations of insulin and glucagon in response to an oral glucose load were not impaired after camostate treatment. In the isolated perfused pancreas, however, insulin and glucagon secretions were reduced, whereas somatostatin release was not affected. The volume of pancreatic juice produced by the unstimulated isolated perfused organ, as well as protein and enzyme secretion, were increased after camostate treatment. Likewise, the isolated perfused pancreas from camostate-treated rats secreted a larger volume of pancreatic juice and more protein in response to cholecystokinin (CCK), while enzyme secretion was affected in a non-parallel manner: amylase release was markedly reduced, lipase release was unchanged, and release of trypsin and chymotrypsin was increased.     

Neuroglobin,seven years after

Neuroglobin is expressed in vertebrates brain and belongs to a branch of the globin family that diverged early in evolution. Sequence conservation suggests a relevant role in the nervous system, with tight structural restraints. Experiments in vivo and in vitro showed increased hypoxic stress damage upon repressing neuroglobin biosynthesis and improved recovery following overexpression. Neuroglobin shows internal heme hexacoordination, which controls oxygen affinity and kinetics. Neuroglobin concentration, oxygen affinity and enhanced autooxidation question a role in oxygen delivery; thus it was proposed that the neuroprotective effect might be due to radical scavenging or activation of protection mechanisms. Neuroglobin's structure shows a peculiar internal cavity of very large size. Binding of heme ligands is associated to a conformational change involving the heme that "slides" into the pre-existing cavity and makes the sixth coordination position available. These features may pave the way to an understanding of neuroprotection by neuroglobin.     

Heme structure in cooperative and noncooperative hemoglobins: study by resonant Raman diffusion]

The modifications of heme sites of hemoglobin, which should occur upon apoprotein alterations (responsible for variations of oxygen affinity), have been examined by Resonnant Raman scattering. The oxygenated (R) and deoxygenated (T) shape of apoprotein do not modify the heme states. The spectral differences between these forms are essentially due to the presence or the absence of the sixth ligand.     

Fetal calf serum alters cyclic adenosine 3',5'-monophosphate's effect on heme synthesis in vitro.

An investigation of the effect of cAMP on heme synthesis of rat bone marrow cells revealed that at 10(-2) M this cyclic nucleotide inhibits heme synthesis and that optimum stimulation occurs at 10(-4) M. Some unidentified constituent of fetal calf serum in the culture medium modifies the direction and degree of cAMP's effect.     

Acid phosphatase activity of small intestine of mice after exposure to different doses of gamma rays

Summary Effect of whole-body radiation at 3 different dose levels on the activity of acid phosphatase was studied in the small intestine of Swiss albino mice. In all the 3 exposure groups the enzyme activity increased significantly at 24 h after irradiation; the time at which the maximum histological damage was seen. With the beginning of recovery the enzyme tended to decrease and gradually approached control values.