Protective effects of hsp70 in inflammation

Inflammation results from the recruitement to a given tissue or organ and the activation of leucocytes, among which the monocytes-macrophages play a major role. These phagocytic cells produce high levels of reactive oxygen species (ROS) as well as cytokines. Whereas both ROS and cytokines have the potential to regulate the expression of heat shock (HS)/stress proteins (HSP), it appears that these proteins in turn have the ability to protect cells and tissues from the deleterious effects of inflammation. The mechanisms by which such protection occurs include prevention of ROS-induced DNA strand breaks and lipid peroxidation as well as protection from mitochondrial structure and function. In vivo, HS protects organs against a number of lesions associated with the increased production of ROS and/or cytokines. In an animal model for adult respiratory distress syndrome, an acute pulmonary inflammatory condition, HS completely prevented mortality. HSP (hsp70 in particular) may also exert protective effects in the immune system by contributing to the processing and presentation of bacterial and tumoral antigens. The analysis of the expression of hsp70 may prove of diagnostic and prognostic value in inflammatory conditions and therapeutical applications are being considered.     

dNTP pools imbalance as a signal to initiate apoptosis

Fidelity in DNA synthesis and repair is largely dependent on a balanced supply of deoxynucleotide triphosphate (dNTP) pools. Results from different groups have shown that alterations in dNTP supply result in DNA fragmentation and cell death with characteristics of apoptosis. We have recently shown that in apoptosis driven by deprivation of interleukin-3 (IL-3) in a murine hemopoietic cell line, there is a rapid imbalance in the availability of dNTP that precedes DNA fragmentation. In these cells, dNTP pool balance is closely coupled to the function of the salvage pathway of dNTP synthesis. Apoptosis, induced by treatment of these cells with drugs that inhibit the de novo dNTP synthesis, is prevented when dNTP precursors are supplied through the salvage pathway. IL-3 regulates thymidine kinase activity, suggesting that alterations in dNTP metabolism after IL-3 deprivation could be a relevant event in the commitment of hemopoietic cells to apoptosis.     

5-Bromodeoxyuridine inhibition of the transformation of Rous sarcoma virus-infected chicken cells]

The transformation of Rous-Sarcoma-Virus-infected synchronized Chicken cells is prevented when 5-bromodeoxyuridine is added for 3 hrs. at time of the peak of the first S phase following infection. Virus progeny is normally released. The inhibitory effect of BrdU is reversed by simultaneous addition of thymidine, but not by that of deoxyuridine. Hence, the inhibition of the transformation seems to result from the incorporation of the analogue into the nuclear DNA.     

Endothelial injury by nicotine and its prevention

Summary Nicotine administered i.v. or p.o. in doses above 0.0125 mg/kg to the rat caused a highly significant increase in circulating anuclear carcasses of endothelial cells estimated by an original method. This effect of nicotine was completely prevented by a prior oral administration of the flavonoids hydroxyethylrutosides (HR) or Mono-7-HR.Acknowledgment. Both flavonoid preparations were kindly supplied by Zyma SA, Nyon Switzerland.     

Mitochondrial permeability transition triggers the release of mtDNA fragments

Fragments of mitochondrial DNA are released from mitochondria upon opening of the mitochondrial permeability transition pore. Cyclosporin A, an inhibitor of pore opening, completely prevented the release of mitochondrial fragments. Induction of mitochondrial permeability transition and subsequent release of the fragments of mitochondrial DNA could be one cause of genomic instability in the cell.Received 22 September 2004; received after revision 11 October 2004; accepted 18 October 2004M. Patrushev, V. Kasymov and V. Patrusheva contributed equally to this work.     

The effect of chloroquine upon the developing lens

Summary Applied to the developing lens of the 14-day-old chick embryo, in organ culture conditions, chloquine prevented the elongation of the primary lens fibres, destroyed the equatorial ones and provoked vacuolisation and/or destruction in the epithelial cells.This work was supported by a grant from the office of the Chief Scientist, Ministry of Health, Israel     

DNA repair nucleases

Stability of DNA largely depends on accuracy of repair mechanisms, which remove structural anomalies induced by exogenous and endogenous agents or introduced by DNA metabolism, such as replication. Most repair mechanisms include nucleolytic processing of DNA, where nucleases cleave a phosphodiester bond between a deoxyribose and a phosphate residue, thereby producing 5-terminal phosphate and 3-terminal hydroxyl groups. Exonucleases hydrolyse nucleotides from either the 5 or 3 end of DNA, while endonucleases incise internal sites of DNA. Flap endonucleases cleave DNA flap structures at or near the junction between single-stranded and double-stranded regions. DNA nucleases play a crucial role in mismatch repair, nucleotide excision repair, base excision repair and double-strand break repair. In addition, nucleolytic repair functions are required during replication to remove misincorporated nucleotides, Okazaki fragments and 3 tails that may be formed after repair of stalled replication forks.Received 12 June 2003; received after revision 29 July 2003; accepted 16 September 2003     

Protein assemblies with palindromic structure motifs

Symmetric DNA sequence motifs allow the formation of palindromic protein/DNA complexes. Although symmetric protein sequence motifs are less common, recent structural discoveries have unraveled a few protein/protein complexes with palindromic symmetry. Remarkably, symmetric protein/protein complexes can be generated either by adjacent or remote sequence motifs, which may be repeated or inverted. This contribution reflects and comments on recent findings of palindromic protein/protein complexes. Received 14 May 2008; received after revision 21 June 2008; accepted 14 July 2008     

Surface receptors and functional interactions of human natural killer cells: from bench to the clinic

The past 10years have witnessed dramatic progress in our understanding of how natural killer (NK) cells function and their role in innate immunity. Thanks to an array of inhibitory receptors specific for different HLA class I molecules, human NK cells can sense the decrease or loss of even single alleles at the cell surface. This represents a typical condition of a potential danger, i.e. the presence of tumor or virally infected cells. NK cell triggering and lysis of these cells is mediated by several activating receptors and coreceptors that have recently been identified and cloned. While normal cells are usually resistant to NK-mediated attack, a remarkable exception is represented by dendritic cells (DCs). In their immature form they are susceptible to NK-mediated lysis because of the expression of low levels of surface HLA class I molecules. The process of DC maturation (mDCs) is characterized by the surface expression of high levels of HLA class I molecules. Accordingly, mDCs become resistant to NK cells. A recent major breakthrough highlighted the role played by donor NK cells in allogenic bone marrow transplantation to cure acute myeloid leukemias. Alloreactive NK cells derived from donor hematopoietic precursors not only prevented leukemic relapses, but also prevented graft rejection and graft-versus-host disease.Received 12 March 2003; received after revision 18 April 2003; accepted 30 April 2003     

The effects on thermoregulation of intracerebroventricular injections of L-aspartic acid in the sheep

Summary L-Aspartic acid was injected into a lateral cerebral ventricle of the sheep at ambient temperatures between 0° and 40°C. Doses of 100 or 500 nmoles·kg^–1 caused a rise in heat production and/or a decrease in heat loss; rectal temperature rose. Atropine sulphate attenuated or prevented these effects.     

The effect of chloroquine upon the developing lens

Applied to the developing lens of the 14-day-old chick embryo, in organ culture conditions, chloroquine prevented the elongation of the primary lens fibres, destroyed the equatorial ones and provoked vacuolisation and/or destruction in the epithelial cells.     

Functions of disordered regions in mammalian early base excision repair proteins

Reactive oxygen species, generated endogenously and induced as a toxic response, produce several dozen oxidized or modified bases and/or single-strand breaks in mammalian and other genomes. These lesions are predominantly repaired via the conserved base excision repair (BER) pathway. BER is initiated with excision of oxidized or modified bases by DNA glycosylases leading to formation of abasic (AP) site or strand break at the lesion site. Structural analysis by experimental and modeling approaches shows the presence of a disordered segment commonly localized at the N- or C-terminus as a characteristic signature of mammalian DNA glycosylases which is absent in their bacterial prototypes. Recent studies on unstructured regions in DNA metabolizing proteins have indicated their essential role in interaction with other proteins and target DNA recognition. In this review, we have discussed the unique presence of disordered segments in human DNA glycosylases, and AP endonuclease involved in the processing of glycosylase products, and their critical role in regulating repair functions. These disordered segments also include sites for posttranslational modifications and nuclear localization signal. The teleological basis for their structural flexibility is discussed.     

Ureteral contractions induced by rat urine in vitro: Probable involvement of renal kallikrein

Summary Rat urine, even at a 110 final dilution in Tyrode's solution, stimulates contraction of the ureteral musculature in vitro. This effect can be ascribed to the presence of kallikrein or a kallikrein-like enzyme in urine. Isometric contractions of ureters were prevented by previous addition of aprotinin to the organ bath. Urine also lost its activity after inactivation of enzymes by heat or acid treatment.Acknowledgments. Aprotinin (Trasylol^®) was kindly supplied by Baypropharm, Köln, W.-Germany. This work was supported by the German Research Foundation (SFB 90).     

Effects of thyroxine on the reproductive organs and growth of young chickens

Summary Male chicks of an egg-laying strain were injected with 0, 1, 2 or 4 g/100g b. wt thyroxine s. c. daily from 7 to 12 weeks of age. Increasing dose suppressed testicular development and puberty was completely blocked by the highest level. Live weight gain was enhanced by thyroxine treatment. Similar treatment of females prevented normal development of the ovaries at puberty.     

Posttranslational modification of mammalian AP endonuclease (APE1)

A key issue in studying mammalian DNA base excision repair is how its component proteins respond to a plethora of cell-signaling mediators invoked by DNA damage and stress-inducing agents such as reactive oxygen species, and how the actions of individual BER proteins are attributed to cell survival or apoptotic/necrotic death. This article reviews the past and recent progress on posttranslational modification (PTM) of mammalian apurinic/apyrimidinic (AP) endonuclease 1 (APE1).     

Bacillus thuringiensis δ-endotoxin: Evidence that toxin acts at the surface of susceptible cells

Summary Enzymically activated -endotoxin ofBacillus thuringiensis covalently bound to Sephadex beads, has the same effect on insect cells in tissue culture as free toxin. The effect is prevented by antitoxin antibody and heat denaturation and is not due to a nonspecific protein effect, the beads, or toxin released from the beads. The toxin, therefore, probably acts at the cell surface.     

Monoaminoguanidine prevents sorbitol accumulation, nonenzymatic protein glycosylation and development of kidney lesions in diabetic rats

Monoaminoguanidine administration (25 mg/kg b.wt, i.p. for 14 weeks) to alloxan diabetic rats (blood glucose greater than or equal to 250 mg/dl) decreased the nonenzymatic protein glycosylation and sorbitol levels. It prevented development of Armanni-Ebstein tubular lesions, pathological changes in the glomerular capillary tufts and glomerular basement membrane thickening in the kidney.     

β-phenylethyl isothiocyanate-mediated apoptosis in hepatoma HepG2 cells

-Phenylethyl isothiocyanate (PEITC) is a promising chemoprotective compound that is routinely consumed in the diet as its glucosinolate precursor. Previous studies have shown that PEITC can inhibit phase I enzymes and induce phase II detoxification enzymes along with apoptosis in vitro. The detailed mechanisms involved in the apoptotic cascade, however, have not been elucidated. In the present study, we demonstrate that PEITC can induce apoptosis in hepatoma HepG2 cells in a concentration- and time-dependant manner as determined by TUNEL positive and SubG1 population analysis. Caspase-3-like activity and poly(ADP-ribosyl)polymerase cleavage increased during treatment with 20 µM PEITC; high concentrations, however, induced necrosis. Pre-treatment with Z-VAD-FMK and the caspase-3-specific inhibitor Ac-DEVD-CHO prevented PEITC-induced apoptosis, as determined by caspase-3-like activity and DNA fragmentation. Additional investigations also showed that at concentrations of 5-C10 µM PEITC, DNA synthesis was inhibited and G2/M phase cell cycle arrest occurred, correlating with an alteration in cyclin B1 and p34^cdc2 protein levels. Furthermore, we also demonstrate a concentration- and time-dependant burst of superoxide (O₂^-) in PEITC-treated cells. However, pre- and co-treatment with the free radical scavengers Trolox, ascorbate, mannitol, uric acid and the superoxide mimetic manganese (III) tetrakis (N-methyl-2-pyridyl) porphyrin failed to prevent PEITC-mediated apoptosis. Taken together, these results suggest that PEITC potently induces apoptosis and cell cycle arrest in HepG2 cells and that the generation of reactive oxygen species appears to be a secondary effect.Received 23 December 2002; accepted 22 April 2003