Poly(adenosine dephosphate ribose) metabolism and regulation of myocardial cell growth by oxygen

Burn and smoke injury activates poly(ADP-ribose)polymerase in circulating leukocytes

The nuclear enzyme poly(ADP-ribose)polymerase (PARP) plays a significant role in the pathogenesis of various forms of critical illness. DNA strand breaks induced by oxidative and nitrative stress trigger the activation of PARP, and PARP, in turn, mediates cell death and promotes proinflammatory responses. Until recently, most studies focused on the role of PARP in solid organs such as heart, liver, and kidney. We investigated the effect of burn and smoke inhalation on the levels of poly(ADP-ribosylated) proteins in circulating sheep leukocytes ex vivo. Adult female merino sheep were subjected to burn injury (2× 20% each flank, 3 degrees) and smoke inhalation injury (insufflated with a total of 48 breaths of cotton smoke) under deep anesthesia. Arterial and venous blood was collected at baseline, immediately after the injury and 1 to 24 h after the injury. Leukocytes were isolated with the Histopaque method. The levels of poly(ADP-ribosyl)ated proteins were determined by Western blotting. The amount of reactive oxygen species was quantified by the OxyBlot method. To examine whether PARP activation continues to increase ex vivo in the leukocytes, blood samples were incubated at room temperature or at 37°C for 3 h with or without the PARP inhibitor PJ34. To investigate whether the plasma of burn/smoke animals may trigger PARP activation, burn/smoke plasma was incubated with control leukocytes in vitro. The results show that burn and smoke injury induced a marked PARP activation in circulating leukocytes. The activity was the highest immediately after injury and at 1 h and decreased gradually over time. Incubation of whole blood at 37°C for 3 h significantly increased poly(ADP-ribose) levels, indicative of the presence of an ongoing cell activation process. In conclusion, PARP activity is elevated in leukocytes after burn and smoke inhalation injury, and the response parallels the time course of reactive oxygen species generation in these cells.

Detection of poly(ADP-ribose) synthetase activity in alveolar macrophages of rats exposed to nitrogen dioxide and ozone

The toxic effects of nitrogen dioxide (NO2) and ozone (O3) are mediated through the formation of free radicals, which can cause DNA strand breaks. The present study demonstrates that exposure to NO2 and O3 causes a stimulation of poly(ADP-ribose) (polyADPR) synthetase in alveolar macrophages of rats. Three-month-old male Sprague-Dawley rats, specific pathogen free, were exposed to either 1.2 ppm NO2 or 0.3 ppm O3 alone or a combination of these 2 oxidants continuously for 3 days. The control group was exposed to filtered room air. To evaluate whether exposure to these two oxidants (NO2 and O3) caused DNA damage to lung cells, the activity of polyADPR synthetase was measured. Cellular DNA repair is dependent upon the formation of poly(ADP-ribose) polymerase, which is catalyzed by polyADPR synthetase. PolyADPR synthetase is known to be activated in response of DNA damage. The results showed that the enzyme activity was stimulated after exposure to O3 or exposure to NO2 + O3. Ozone exposure caused a 25% increase in the enzyme activity as compared to the control. Combined exposure to NO2 + O3 showed a 53% increase in the enzyme activity. These results were statistically significant as compared to the control and NO(2) exposure groups. Other parameters such as total cell count, cell viability, and differential cell count were also determined. The stimulation of polyADPR synthetase activity after O3 exposure or NO2 + O3 exposure reflects a response to lung cellular DNA repair, which may be used as an indicator for assessing DNA damage caused by oxidant injury.

Poly(ADP-ribose) synthetase activity during bleomycin-induced lung fibrosis in hamsters

Bleomycin damages cellular DNA and is a potent inducer of pulmonary fibrosis. It has been shown to act through a superoxide-mediated mechanism. We are interested in determining the biochemical mechanisms involved in fibrosis and in this preliminary study we have examined the temporal relationship between early biochemical events associated with DNA damage and fibrosis, in lungs of hamsters after administration of 0.75 unit of bleomycin. The activities of poly(ADP-ribose) synthetase, an enzyme associated with DNA repair, inducible superoxide dismutase (SOD) and prolyl hydroxylase as well as the tissue levels of NAD+ and hydroxyproline in the lung were determined. All three enzyme activities expressed as per milligram DNA or per lung, increased upon bleomycin treatment over the saline-administered controls. Lung poly(ADP-ribose) synthetase activity which is sensitive to DNA breaks, increased first (24% over control in 1 day, P less than 0.0001), attained the maximum value on the 5th day (952% over control, P less than 0.0001), and started to decline thereafter and approached near the control value on 14th day. Bleomycin treatment induced a rapid change in the level of lung NAD+. After 1 day the level of NAD+ was reduced by 42% compared to the control (P less than 0.001), further declined to 65% (P less than 0.001) on the 3rd day, and stayed at that level until the 7th day. On the 14th day, however, the NAD+ level was still lower (29%, P less than 0.05) but approaching the value in the control animals. The activity of prolyl hydroxylase showed significant increase on the 3rd day (50% over control, P less than 0.0001) after bleomycin administration. The enzyme activity continued to increase until the end of the experiment (490% of control, P less than 0.0001, on Day 14). The content of undialyzable hydroxyproline, a marker for collagen, was also increased significantly in the lung tissue on the 3rd day (30% over control, P less than 0.05), continued to increase and reached the highest level on the 14th day (71% over control, P less than 0.001). A significant increase in the activity of SOD (19% over control, P less than 0.001) was seen on the 5th day which continued to increase and attained the highest value on Day 14 (115% over control, P less than 0.0001).(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulation of poly(ADP-ribose) synthetase activity in the lungs of mice exposed to a low level of ozone

Toxic effects of O3 are mediated through the formation of free radicals, which can cause DNA strand breaks. Cellular DNA repair is dependent upon the formation of poly(ADP-ribose) (polyADPR) catalyzed by polyADPR synthetase. In order to evaluate whether O3 exposure inflicted DNA damage in lung tissue, we measured the activity of polyADPR synthetase (known to be activated in response to DNA damage) in mouse lungs after exposure to 0.45 ppm (882 micrograms/m3) O3 for up to 7 days. The enzyme activity was stimulated with O3 exposure relative to unexposed controls, showing a 20% (P less than 0.05) increase at Day 5 and 42% (P less than 0.001) at Day 7 of O3 exposure. In addition, the activity of superoxide dismutase (SOD), known to be stimulated in response to production of superoxide anion (.O2-), was measured as an indicator of free radical involvement. Relative to unexposed controls, the SOD activity in exposed animal lungs increased to the peak level at Day 5 (48%, P less than 0.001) and then declined at Day 7 of O3 exposure but was still higher than controls (17%, P less than 0.05). When animals, after 5 days of O3 exposure, were allowed to recover in filtered room air, the activities of both enzymes declined to their respective control values in 6 days. These results suggest a possible temporal relationship between O3 injury and the activities of polyADPR synthetase and a free radical scavenging enzyme, SOD. The stimulation of polyADPR synthetase activity with O3 exposure, reflecting a response to lung cellular DNA repair, may be a sensitive indicator for assessing DNA damage in oxidant injury.

Ca2+, Mg2+ and (adenosine diphosphate ribose)n in cellular response to irradiation

A model of cellular response to irradiation involving adenosine diphosphate ribosylation (ADP-ribosylation) is proposed. Its main assumptions are (a) control of accessibility of sites for ADP-ribosylation in chromatin by free Ca2+/Mg2+ ratio; and (b) regulation of the Ca2+/Mg2+ ratio by factors affecting intracellular free Ca2+ concentration; the regulation would be mediated by mitochondria. The model seeks to explain the mechanism of action of radiomodifiers such as caffeine, local anaesthetics, polyamines and 2,4-dinitrophenol.

Development and regression of increased ventricular mass

This report deals with increased cardiac mass in the light of the following variables: normal ventricular growth (embryo, fetus, neonate and child), the response to work loads (hemodynamic stress) and hypoxia, the cell responses of hyperplasia (increase in cell number), hypertrophy (increase in cell size) and the type of cell (muscle or connective tissue), the age or maturity of the myocardium at the time the hemodynamic or hypoxic stress is imposed, and the biochemistry, ultrastructure and functional morphology (modeling) of the ventricles in response to volume or pressure overload. The desirable physiologic adaptations to work loads are characterized, and the transition from physiologic to pathologic states is examined, comparing and contrasting increased ventricular mass in patients and in trained athletes. Regression of increased ventricular mass is then discussed, first at the cell level (hypertrophy/hyperplasia; muscle cell/connective tissue cell), then at the organ level. The requirements for maintaining or establishing normal ventricular function after removal of overload are reviewed, together with such variables as the type and duration of preoperative hemodynamic stress, the right versus the left ventricle and the relative rates of contractile protein synthesis and degradation.

Oxygen enhances fusion of cultured chick embryo myoblasts

Fusion of mononucleate myoblasts to form multinucleated myotubes increases when skeletal muscle cells are grown in progressively higher oxygen concentrations (5%, 20%, and 40% oxygen). At four days of growth fusion of myoblasts (as expressed by the percent of all muscle nuclei that are located in myotubes) is 57 +/- 2% in 5% oxygen, 68 +/- 1% in 20% oxygen, and 78 +/- 2% in 40% oxygen (P less than 0.001). However, at a concentration of 40%, oxygen depresses the rate of cell division and thereby affects the number of myoblasts available for fusion. Thus, oxygen concentration significantly modifies growth of skeletal muscle in vitro. Its net effect on myotube formation results from the interaction of its separate effects to enhance cell fusion and to depress cell proliferation.

Unusual levels of (ADP-ribose)n and DNA synthesis in ataxia telangiectasia cells following gamma-ray irradiation

Poly (ADP-ribose) polymerase is a eukaryotic chromosomal enzyme which utilizes the ADP-ribose moiety of NAD to synthesize the nucleic acid homopolymer (ADP-ribose)n (ref. 1). The precise function of (ADP-ribose)n has not been fully established although it does covalently modify chromosomal proteins by ADP-ribosylation. Here we demonstrate that gamma-ray irradiation of lymphoblastoid cells from normal subjects results in depressed DNA synthesis and increased (ADP-ribose)n synthesis. Irradiation of lymphoblastoid cells from patients with the autosomal recessive disease ataxia telangiectasia (AT), however, failed to depress DNA synthesis and did not elevate (ADP-ribose)n levels. We have confirmed that (ADP-ribose)n is synthesized in response to DNA damage and we propose that this polymer may function in the recovery from DNA damage by suppressing DNA synthesis.

Adenosine diphosphate ribose transferase from baby-hamster kidney cells (BHK-21/C13). Characterization of the reaction and product

Some properties of ADP-ribose transferase, and its reaction product, from BHK-21/C13 cells are described. Enzyme activity was found almost exclusively in nuclei (90%), with the remaining 10% located in the cytosolic fraction. The nuclear enzyme is chromatin-bound and requires bivalent cations, preferably Mg2+, a pH of 8.0 and a temperature of 25 degrees C for optimal activity. Chromatin preparations incorporated radioactivity from [14C]NAD+ into acid-insoluble material for about 60 min. Kinetics for substrate NAD+ utilization were not of Michaelis--Menten type; biphasic kinetics were shown from a double-reciprocal plot (1/reaction velocity against 1/[NAD+]) and from a 'Hofstee' plot (reaction velocity/[NAD+] against reaction velocity). The transferase is unstable in the absence of Mg2+ ions. It is inhibited by thymidine, nicotinamide and nicotinamide analogues, but not by ATP, which stimulates it at concentrations of 5 mM and above. The enzyme requires thiol groups for activity; it is readily inhibited by N-ethylmaleimide at 0.5 mM. The product of the reaction is stable under acid conditions at temperatures up to 25 degrees C, but it is hydrolysed by HClO4 at 70 degrees C. It is resistant to NaOH, but is cleaved from its attachment to protein with alkali into trichloroacetic acid-insoluble and -soluble components. On the basis of Cs2SO4- density-gradient analysis under denaturing conditions (gradients included urea and guanidinium hydrochloride), and analysis of the reaction product directly on hydroxyapatite, we conclude that most of the radioactive ADP-ribose residues are firmly bound to protein, presumably in covalent linkage. Hydroxyapatite-chromatographic analysis of ADP-ribose residues released from protein by alkaline digestion showed a spectrum of molecular sizes including mono-, oligo- and poly-(ADP-ribose), when chromatin was incubated initially with [14C]NAD+ for 10 min and then for a further 30 min after addition of excess non-radioactive NAD+, only about 10% of the radioactive mono-(ADP-ribose) could be 'chased' into longer-chain molecules. Hydroxyapatite analysis was also used to show that, whereas all ADP-ribose residues were released from protein with NaOH, only 50% of them were susceptible to hydroxylamine. These hydroxylamine-sensitive residues included all size classes, although mono-(ADP-ribose) predominated. Finally, there was an approximately equal distribution of ADP-ribose incorporated into HCl-soluble proteins (including the histones) and HCl-insoluble proteins (including the non-histone proteins) when chromatin was incubated with NAD+ up to 0.5 mM, but at higher NAD+ concentrations more ADP-ribose was incorporated into the HCl-soluble fraction (82% at 4.0 mM-NAD+).

Characterisation of poly(ADP-Rib) polymerase activity in nuclei from the slime mould Dictyostelium discoideum

Nuclei isolated from D. discoideum and incubated in vitro with 3H-NAD synthesise poly(ADP-Rib). The optimum incubation conditions for the poly(ADP-Rib) polymerase were determined. The Km of the enzyme is 18 microM NAD and it is inhibited by nicotinamide. Most of the poly(ADP-Rib) synthesised is attached to nuclear proteins.