Protective Effect Of Pretreatment Research Articles

Attenuation of N-methyl-N′-nitro-N-nitrosoguanidine induced genotoxicity and oxidative stress by tomato and garlic combination

The protective effect of pretreatment with tomato and garlic against N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)-induced genotoxicity and oxidative stress was investigated in male Swiss mice. In vivo bone marrow micronucleus test was performed to assess the antigenotoxic effect of tomato and garlic. Oxidative stress was monitored by estimating the extent of lipid peroxidation and the status of the glutathione redox cycle antioxidants. Increased frequency of bone marrow micronuclei with enhanced lipid peroxidation was associated with compromised antioxidant defenses in MNNG treated animals. Although pretreatment with tomato and garlic significantly reduced the frequencies of MNNG-induced bone marrow micronuclei, the combination of tomato and garlic exerted a greater protective effect. This was associated with modulation of lipid peroxidation as well as reduced glutathione (GSH) and the GSH-dependent enzymes glutathione peroxidase (GPx) and glutathione-S-transferase (GST). These findings suggest that a diet containing even low levels of different naturally occurring compounds is effective in exerting antigenotoxic effects by modulating oxidative stress.

SUR2A C-terminal fragments reduce KATP currents and ischaemic tolerance of rat cardiac myocytes.

C-terminal fragments of the sulphonylurea receptor SUR2A can alter the functional expression of cloned ATP-sensitive K(+) channels (K(ATP)). To investigate the protective role of K(ATP) channels during metabolic stress we transfected SUR2A fragments into adult rat cardiac myocytes. A fragment comprising residues 1294-1358, the A-fragment, reduced sarcolemmal K(ATP) currents by over 85% after 2 days (pinacidil-activated current densities were: vector alone 7.04 +/- 1.22; and A-fragment 0.94 +/- 0.07 pA pF(-1), n= 6,6, P < 0.001). An inactive fragment (1358-1545, current density 6.30 +/- 0.85 pA pF(-1), n= 6) was used as a control. During metabolic inhibition (CN and iodoacetate) of isolated myocytes stimulated at 1 Hz, the A-fragment delayed action potential shortening and contractile failure, but accelerated rigor contraction and increased Ca(2+) loading. On reperfusion, A-fragment-transfected cells also showed increased intracellular Ca(2+) and the proportion of cells recovering contractile function was reduced from 40.0 to 9.5% (P < 0.01). The protective effect of pretreatment with 2,4-dinitrophenol, measured from increased functional recovery and reduced Ca(2+) loading, was abolished by the A-fragment. Our data are consistent with a role for K(ATP) channels in causing action potential failure and reduced Ca(2+) loading during metabolic stress, and with a major role in protection by preconditioning. The effects of the A-fragment may arise entirely from reduced expression of the sarcolemmal K(ATP) channel, but we also discuss the possibility of mitochondrial effects.

Protective effect of melatonin against nodularin-induced oxidative stress.

Nodularin is a hepatotoxin from a cyanobacterium, Nodularia spumigena, that inhibits protein phosphatases 1 and 2 and posseses tumor-promoting activity. The aim of this paper was to examine whether nodularin is able to induce oxidative stress in mouse liver tissue and whether melatonin (protective compound against oxidative damage) could supress the activity of nodularin. We studied the effect of nodularin (1, 5, and 10 microg/kg body weight) and melatonin (5, 10, and 15 mg/kg body weight) administration on the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in mouse liver. Intraperitoneal treatment of mice with nodularin per 7 days decreased the activities of all estimated enzymes in a dose-dependent manner. Intraperitoneal treatment of animals with melatonin per 7 days increased the activities of SOD, CAT, and GSH-Px and this effect was concentration-dependent. Co-treatment (nodularin 5 microg/kg body weight + melatonin 5, 10, and 15 mg/kg body weight per 7 days) and post-treatment with melatonin (nodularin 5 microg/kg body weight per 7 days + melatonin 5, 10, and 15 mg/kg body weight per next 7 days) increased the activities of SOD, CAT, and GSH-Px in comparison to the nodularin group. No significant differences from the nodularin group were noted in the group after pre-treatment with melatonin. In conclusion, these findings suggest that oxidative damage may be involved in the toxicity of nodularin. Moreover, co-treatment and post-treatment with 10 and 15 mg/kg body weight of melatonin may protect against nodularin-induced oxidative stress. There was no protective effect of pre-treatment with melatonin.

Protective effect of pretreatment with low-dose lipopolysaccharide on D-galactosamine-induced acute liver failure.

The effect of low-dose lipopolysaccharide (LPS) induced nitric oxide (NO) on liver damage and survival in rats with acute liver failure caused by a lethal dose of D-galactosamine (D-gal) was studied. Ninety percent of control animals died within 4 days after D-gal injection, but pretreatment with low-dose LPS significantly decreased mortality to 5%. There was marked elevation in serum aspartate aminotransferase and alanine aminotransferase levels 24 h after D-gal injection. These aminotransferases were significantly improved in low-dose LPS pretreated rats 24 h after the administration of D-gal. NG-Nitro-L-arginine-methyl ester, but not NG-nitro-D-arginine-methyl ester, reversed this cytoprotection. Pretreatment with low-dose LPS prevents experimental liver failure induced by D-gal through activation of endogenous NO synthesis.

Effects of trimetazidine in ethanol‐ and acetic acid‐induced colitis: oxidant/anti‐oxidant status

There is overwhelming evidence in favour of a significant role of reactive oxygen metabolites (ROM) in the pathophysiology of inflammatory bowel disease (IBD) in man and in experimental animal models. This study was undertaken to investigate the possible protective effects of pretreatment with trimetazidine (TMZ) on the oxidant-anti-oxidant balance in ethanol- and acetic acid-induced colonic damage in rats. TMZ was chosen because of its various cytoprotective features (preserving cellular ATP levels, limiting intracellular acidosis and limiting inorganic phosphate, Na(+) and Ca(2+) accumulation) and anti-oxy characteristics which were previously reported. A total of 80 rats were randomized into eight major groups each consisting of 10 animals. Animals in groups 1, 2 and 3 served as models of ethanol-induced colitis (0.25 ml of 30% (v/v) ethanol), while group 4 served as their control. Animals in groups 5, 6 and 7 served as models of acetic acid-induced colitis (1 ml of 4% (v/v) acetic acid), while group 8 served as their control. TMZ was administered 5 mg/kg by intrarectal (i.r.) and intraperitoneal (i.p.) routes to groups 1, 2, 5 and 6. Intraperitoneal administration of TMZ was used in order to evaluate its systemic effect while i.r. administration was used to determine its local effect. After decapitation, colon mucosa samples were obtained and evaluated macroscopically and microscopically. Myeloperoxidase (MPO) activities as markers for inflammation, malondialdehyde (MDA) levels as markers for oxidant stress and reduced glutathione (GSH) and oxidized glutathione (GSSG) levels as markers for anti-oxidant status were determined. Acute colitis was observed in macroscopic and microscopic evaluation in ethanol- and acetic acid-administered groups compared with controls (P = 0.000). The macroscopic and microscopic scores in colitis groups were correlated with MPO activities (r = 0.5365, P = 0.000 and r = 0.5499, P = 0.000, respectively). MDA and GSSG levels in the acetic acid-induced colitis group were higher compared with ethanol-induced colitis group (P < 0.008 and P < 0.005, respectively), while GSH levels were significantly lower (P < 0.05). While TMZ pretreatment did not improve the oxidant state, it preserved the GSH levels significantly (P < 0.05). In conclusion, ethanol- and acetic acid-induced colitis models are appropriate experimental colitis models which in many ways manifest the characteristics seen in tissue injury related to colitis in humans. Of these two, the acetic acid-induced colitis model proved more suitable than the ethanol model for investigating the alterations in long-term and in more severe tissue injury. While TMZ pretreatment via i.p. or i.r. route did not improve the oxidative-inflammative state in either of these models, it did contribute significantly to the preservation of the anti-oxidant pool via the conservation of intracellular GSH levels. This conserving effect of TMZ was substantially more pronounced in the i.p. route compared with the i.r. route. Based on our results, we conclude that the 'GSH-preservation' role of TMZ can be the mode of action it manifests as an anti-oxy compound.

This Month in ANESTHESIOLOGY

This Month in ANESTHESIOLOGY

Protective effects of extracted human-liver RNA, a known interferon inducer, against radiation-induced cytogenetic damage in male mice

Cells in vitro or in vivo pre-exposed to low-dose radiation (LDR) or low concentrations of chemical mutagens became more resistant to large-dose radiation-induced DNA or chromosome damage. This was known as radio-adaptive response, for which the exact mechanism was unclear. However, multiple cellular and molecular responses to LDR have been documented, for instance, the induction of some cytokines such as interferon (IFN). Adminstration of exogenous IFN to cultured cells or mice showed marked radio-protection. In the present study, we investigated the in vivo radio-protective effects of extracted human liver RNA (HL-RNA), a known IFN inducer, indirectly to determine the radio-protective action of endogenous IFN. First, mice were administered with 6.25 mg/kg HL-RNA at different times before exposure to radiation and the 24 h pretreatment offered the optimal protective action for HL-RNA on cytogenetic effects in bone marrow cells. When the mice were treated with different concentrations of HL-RNA for 24 h, a wide dose-range (25–100 mg/kg) of HL-RNA resulted in a marked protection from X-ray-induced chromosome aberrations in both bone marrow cells and germ cells. In subsequent experiments, a protective effect of pretreatment with 25 mg/kg HL-RNA for 24 h was also found for radiation-induced micronuclei in polychromatic erythrocytes (PCE), and inhibition of DNA repair ability (unscheduled DNA synthesis, UDS). These results demonstrated that HL-RNA, an IFN inducer, is able to offer significant cytogenetic protection from radiation, implying indirectly that the induction of IFN by LDR may also play a protective role as one of the mechanisms in the induction of the cytogenetic adaptive response.

Transforming growth factors-β protect primary rat hippocampal neuronal cultures from degeneration induced by β-amyloid peptide

Treatment of primary rat embryo hippocampal neuronal cultures with 10 −5 M β-amyloid peptide fragment 25–35 (AβP) for 24 h resulted in a 60% decrese in cell viability as determined by MTT incorporation. When these cells were treated with 0.1–10 ng/ml of either transforming growth factor-β (TGF-β) 1, 2 or 3 for 24 h before exposure to AβP, there was a 2.9-, 1.9-, and 3.2-fold increase in cell survival, respectively, compared to cells treated with AβP alone. The viability of cells treated with AβP and 0.1–10 ng/ml TGF-β was comparable to that of cells not treated with AβP. The protective effects were less pronounced at lower TGF-β concentrations. The protective effects of pretreatment with TGF-β were less striking in mouse CCL-N-2a and human SK-N-SH neuroblastoma cell lines. When all cells were treated with TGF-β for 24 h following a 24 h exposure to AβP, there was a trend toward increased cell viability which was less significant than pretreatment with TGFs-β. An isoform-specific TGF-β SELISA showed that primary hippocampal neuronal cultures and the neuroblastoma cell lines secrete all 3 TGF-β isoforms. Based on our results, we propose that the increased expression of TGF-β observed in brains of patients with Alzheimer's disease may offer some degree of neuroprotection.

Dehydroepiandrosterone protects mice inoculated with West Nile virus and exposed to cold stress.

The protective effect of pretreatment with dehydroepiandrosterone (DHEA) on stress-enhanced viral encephalitis was studied in mice exposed to cold following inoculation with West Nile virus (WNV). Exposure of WNV-inoculated mice to cold water (1 +/- 0.5 degrees C, 5 minutes/day for 8 days) resulted in a mortality rate of 83% as compared to 50% in nonstressed mice (p < 0.05). The effect of cold stress was more pronounced when mice were inoculated with WN-25, a noninvasive neurovirulent variant of WNV. Mice infected with WN-25 showed no mortality, whereas cold stressed mice inoculated with the same virus had a mortality rate of 67% (p < 0.05). The administration of DHEA (serial injections of 10-20 mg/kg with or without a loading dose of 1 gm/kg) resulted in a significant reduction in the mortality rate of stressed mice inoculated with either virus (p < 0.05). Virus levels in the blood and brain of the DHEA-treated mice, were significantly lower than in the control groups. DHEA also prevented the involution of lymphoid organs in stressed mice. The present study provides direct evidence of the protective effects of DHEA as an "anti-stress" agent. Its ability to prevent mortality associated with WNV or WN-25, and involution of lymphoid organs caused by stress-induced immunosuppression, supports the notion that its activity is based on the modulation of the host response.

Effect of preinduction of metallothionein on paraquat toxicity in mice.

The effect of pretreatment with metallothionein (MT)-inducing metals (Zn, Cu, Bi, Co, Cd or Hg) on paraquat (PQ) toxicity was investigated in mice. PQ lethality was remarkably reduced by pretreatment with the above MT-inducing metals. The protective effect of pretreatment with these metals on PQ lethality was significantly correlated with MT levels in the lung, a target tissue of PQ toxicity, in mice administered MT-inducing metals, but not with MT in the liver or kidney. The increase in pulmonary lipid peroxidation in mice treated with PQ was significantly inhibited by Zn pretreatment. Zn was the most effective of the MT-inducing metals used in this experiment in protecting mice against PQ lethality. Of those monitored, the only pulmonary free radical scavenging factor increased by Zn pretreatment was MT. Other free radical scavenging factors (activities of superoxide dismutase, glutathione peroxidase and catalase, and concentration of non-protein thiols level) were not influenced by Zn treatment. These results indicate that the induction of pulmonary MT protects against the lethality and lung toxicity of PQ. Pulmonary MT may scavenge free radicals produced by PQ, thereby protecting against lethal pulmonary toxicity.

Protective effect of pretreatment with tetrandrine in ischemic-reperfused rat heart

Protective effect of pretreatment with tetrandrine in ischemic-reperfused rat heart

Tolerance to lead-induced porphyrin metabolic disorders following lead pretreatment in mice

The protective effect of pretreatment with lead on lead-induced toxicity was investigated in mice, using some biological parameters such as urinary excretion of δ-aminolevulinic acid (ALA) and coproporphyrin, accumulation of erythrocyte protoporphyrin and inhibition of erythrocyte (5-aminolevulinic acid dehydratase; these are useful indicators for evaluating the effects on health of lead. It was demonstrated that pretreatment with a single intraperitoneal dose of 2 mg Pb kg , 7 days prior to the challenge dose, prevents in part the increasing excretion of urinary ALA induced by a challenge exposure to lead (200 ppm) in the drinking water for 7 days.

Protective effects of pretreatment with intracoronary nifedipine on myocardial ischemia and dysfunction

To assess whether pretreatment with intracoronary nifedipine protects the myocardium against acute ischemia induced by coronary occlusion, 18 patients were studied during coronary angioplasty of the left anterior coronary artery. After a control occlusion of 60 seconds, 0.1 mg nifedipine was injected and occlusion was repeated for 60 seconds. Before and during the occlusion period, pulmonary capillary pressure was measured and the intracoronary epicardial ECG was recorded. After intracoronary administration of nifedipine, the onset of the rise in diastolic filling pressure was delayed from 23 to 38 seconds (p less than 0.01) and the changes at 60 seconds of occlusion were reduced from 14 to 11 mmHg (p less than 0.05). Nifedipine delayed the appearance of ischemic ST-segment elevation in the intracoronary ECG from 11 to 21 seconds (p less than 0.01) and diminished the changes at 60 seconds of occlusion from 1.8 to 1.2 mV (p less than 0.05). These findings suggest that pretreatment with intracoronary nifedipine protects the myocardium against some of the mechanical and electrocardiographic consequences of regional ischemia during acute coronary occlusion.

Protective effects of pretreatment with superoxide dismutase, catalase and oxypurinol on tubular damage caused by transient ischaemia

The effect of 60 min of ischaemia on glomerular and tubular functions (osmolar clearance, fractional Na+ excretion, K+ clearance, concentrating ability) after different periods of time was studied in New Zealand White rabbits. Pronounced changes in both glomerular and tubular functions were observed immediately on reperfusion and after 48 h. One week after ischaemia the functions appeared to be normalized. Mannitol is routinely used in clinical kidney transplantation due to its hyperosmolar effects and its ability to scavenge the hydroxyl radical. In the present study the possible additive protective effect against ischaemia-reperfusion damage of a combined pretreatment with mannitol and oxygen free radical scavengers or mannitol and a xanthine oxidase inhibitor was examined. Oxypurinol was chosen as the xanthine oxidase inhibitor due to its direct inhibitory effect. Concerning glomerular function, no protective effect of the combined pretreatment compared with mannitol alone was observed. However, concerning the tubular function tests combined pretreatment with either mannitol-superoxide dismutase-catalase or mannitol-oxypurinol turned out to be superior compared with that of mannitol alone.

Renal function during reperfusion after warm ischaemia in rabbits: an experimental study on the possible protective effects of pretreatment with oxygen radical scavengers or lidoflazine

Survival and renal function were studied after 60 min of renal ischaemia and contralateral nephrectomy in four groups of French loop rabbits. One group served as untreated control animals. The other groups were pretreated with superoxide dismutase (SOD) and catalase, lidoflazine or a buffered albumin solution containing mannitol, L-methionine and MgCl2. Six out of nine rabbits died during the 14-day follow-up period in the untreated control group, while the corresponding figure in each of the three treatment groups was one out of nine. Five of the rabbits that died exhibited azotaemia or hyperpotassaemia that could explain the death, while four died of non-renal related causes. In the surviving animals, no differences in serum creatinine, potassium and sodium concentration or urinary output of osmoles was observed between the four groups. The increase in serum creatinine of the French loop rabbits observed after 60 min of ischaemia was considerably less pronounced than the corresponding increase observed in New Zealand White rabbits, indicating that the kidneys of the former strain are more tolerant to ischaemia. A cardiomyodepressant factor could be demonstrated in the venous effluent from previously ischaemic kidneys. This release could not be prevented by pretreatment with SOD and catalase.

Protective effect of pretreatment with intracoronary nisoldipine on ischemic myocardium during coronary occlusion: I. Amende, G. Herrmann, R. Simon, P. Lichtlen. Hannover Medical School, Hannover, West Germany

Protective effect of pretreatment with intracoronary nisoldipine on ischemic myocardium during coronary occlusion: I. Amende, G. Herrmann, R. Simon, P. Lichtlen. Hannover Medical School, Hannover, West Germany

Protective effect of pretreatment with the calcium antagonist anipamil on the ischemic-reperfused rat myocardium: A phosphorus-31 nuclear magnetic resonance study

To assess whether the prophylactic administration of anipamil, a new calcium antagonist, protects the heart against the effects of ischemia and reperfusion, rats were injected intraperitoneally twice daily for 5 days with 5 mg/kg body weight of this drug. The heart was then isolated and perfused by the Langendorff technique. Phosphorus-31 nuclear magnetic resonance spectroscopy was used to monitor myocardial energy metabolism and intracellular pH during control perfusion and 30 min of total ischemia (37 °C), followed by 30 min of reperfusion.Pretreatment with anipamil altered neither left ventricular developed pressure under normoxic conditions nor the rate and extent of depletion of adenosine triphosphate (ATP) and creatine phosphate during ischemia. Intracellular acidification, however, was attenuated.On reperfusion, hearts from anipamil-pretreated animals recovered significantly better than untreated hearts with respect to replenishment of ATP and creatine phosphate stores, restitution of low levels of intracellular inorganic phosphate and recovery of left ventricular function and coronary flow. Intracellular pH recovered rapidly to preischemic levels, whereas in untreated hearts a complex intracellular inorganic phosphate peak indicated the existence of areas of different pH within the myocardium.It is concluded that anipamil pretreatment protects the heart against some of the deleterious effects of ischemia and reperfusion. Because this protection occurred in the absence of a negative inotropic effect during normoxia, it cannot be attributed to an energy-sparing effect during ischemia. Therefore, alternative mechanisms of action are to be considered.

Drug-concentration dependent sensitivity to lysis by antibody and complement, of adriamycin- or mitomycin-treated murine lymphoma cells

Murine lymphoma cells (RDM4) were pretreated in culture, with Adriamycin (ADM) and with Mitomycin C (Mit C), at different concentrations, for 20 h and carefully washed. In a first series of experiments, they were labelled with 51Cr and used as target to the lytic action of alloantiserum and complement (Ab+c), as appraised by the specific 51Cr release test. It was found that exposures of the prospective target cells to high drug concentrations (e.g. 32 μg/ml of ADM or 20 μg/ml of Mit C) enhanced their susceptibility to Ab + c killing, whereas exposures to low concentrations (i.e. 0.1 μg/ml of ADM, or 1 μg/ml of Mit C) protected them from Ab + c mediated lysis. In a second experimental series, similarly treated RDM4 were pulsed with 3H-TdR after their exposure to Ab + c. In this case the cytotoxic effect was appraised as “inhibition” of isotope incorporation. Using the second criterion, the protective action of pretreatment with low drug concentrations was confirmed, and was particularly clearcut in the case of ADM. The protective effect of pretreatment with low concentration of ADM (0.1 μg) was also confirmed in vivo, with the “Winn assay”.

A co-cultivation system as a model for in vitro studies of modulating effects of naturally occurring indoles on the genotoxicity of model compounds

An in vitro model system, consisting of primary chick embryo hepatocytes as the metabolizing system co-cultured with V79 Chinese hamster cells as the target cells for the SCE assay, was used to study the modulating effects of naturally occurring indoles on the genotoxicity of benzo[ a]pyrene (B[ a]P) and N-nitrosodimethylamine (NDMA). At 25 μg/ml, indole-3-carbinol (I3C) induced ethoxyresorufin- O-deethylase (ERROD) activity 3.9-fold and ethoxycoumarin- O-deethylase (ETCO) activity 2-fold. Indole-3-acetonitrile (I3A; 35 μg/ml) induced ERROD activity 1.6-fold and ETCO activity 2-fold. Pretreatment with I3C resulted in a 20–40% decrease in genotoxicity for both B[ a]P and NDMA. Pretreatment with I3A resulted in a similar decrease in genotoxicity for B[ a]P, whereas no decrease was observed for NDMA. When a microsomal fraction prepared from I3C-pretreated hepatocytes was used, no decrease in B[ a]P-induced genotoxicity was found; in contrast, use of an S-9 fraction prepared from the same cells resulted in a 45% decrease. Exposure of cells to B[ a]P after pretreatment with I3C for suboptimal times also resulted in a significant decrease in genotoxic activity. The data indicate that the protective effects of pretreatment with the indoles, observed in this study, are not directly correlated with induction of cytochrome P-450-associated enzymes. Instead they seem to be more the result of a changed balance in the enzyme systems involved in the indole biotransformation process and point to an essential role of conjugating enzyme systems.

FUNCTIONAL ANALYSIS OF PROTEINS ON THE THYLAKOID MEMBRANE——EFFECTS OF Mg 2+ AND BSA ON THE TRYPSIN-INDUCED CHLOROPHYLL a FLUORESCENCE AND THYLAKOID MEMBRANE SURFACE CHARGE CHANGES IN SPINACH CHLOROPLASTS

Trypsin digestion of spinach chloroplasts not only inhibits light-induced variable fluorescence yield (△F/F_0) but also abolishes Mg~(2+) stimulating effect on △F/F_0. If chloroplasts are incubated by Mg~(2+) prior to trypsin digestion, Mg~(2+) stimulating ability remains unchanged whereas the enzyme-induced △F/F_0 decline itself is not affected. The protective effect of pretreatment of chloroplasts with Mg~(2+) against trypsin closely correlated with alteration of the net negative charge on the outer surface of the thylakoid membrane by Mg~(2+). In contrast to this, addition of BSA to the chloroplast digested with trypsin significantly recovers the light-induced variable fluorescence yield but it does not influence Mg~(2+)-induced variable fluorescence change. The recovery effect of BSA incubation is not dependent upon Mg~(2+) concentration. Also, BSA does not alter the net negative charge on the outer surface of the thylakoid membrane.These results demonstrate the existence of two independent proteins or polypeptides on the outer surface of the thylakoid membrane which play an important role for the functional integrity of excitation energy distribution between PS-Ⅱ and PS-Ⅰ. Different mechanisms involved in the Chl a fluorescence change are considered in this context.