Hydralazine stimulates production of oxygen free radicals in Eagle's medium and cultured fibroblasts

Reactive oxygen species and cytotoxicity in rainbow trout hepatocytes: effects of medium and incubation time

This study evaluated the effects of exposure medium and culture age on intracellular reactive oxygen species (ROS) development and cytotoxicity in fish hepatocytes following exposure to copper (Cu). ROS was quantified using the fluorescent probes DHR 123 and CM-H2DCFDA following exposure to Cu in Leibovitz' medium (L-15) or Tris-buffered saline (TBS). Similarly, culture age effects were investigated using 1-, 2- and 4-day-old cultured hepatocytes by exposing them to Cu in TBS. The exposure in L-15 resulted in significantly higher ROS compared to TBS using CM-H2DCFDA, but not DHR 123. The age of the primary cultures significantly affected the development of ROS for both probes. None of the exposures caused cytotoxicity in the hepatocytes. The results showed that both factors may affect responses to stressors, and suggested that the use of a simple medium such as TBS may be preferable for some applications. It is also preferable to use 1-day-old primary hepatocyte cultures.

Acrolein scavenging: a potential novel mechanism of attenuating oxidative stress following spinal cord injury

It has long been established that oxidative stress plays a critical role in the pathophysiology of spinal cord injury, and represents an important target of therapeutic intervention following the initial trauma. However, free radical scavengers have been largely ineffective in clinical trials, and as such a novel target to attenuate oxidative stress is highly warranted. In addition to free radicals, peroxidation of lipid membranes following spinal cord injury (SCI) produces reactive aldehydes such as acrolein. Acrolein is capable of depleting endogenous antioxidants such as glutathione, generating free radicals, promoting oxidative stress, and damaging proteins and DNA. Acrolein has a significantly longer half-life than the transient free radicals, and thus may represent a potentially better target of therapeutic intervention to attenuate oxidative stress. There is growing evidence, from our lab and others, to suggest that reactive aldehydes such as acrolein play a critical role in oxidative stress and SCI. The focus of this review is to summarize the cellular and biochemical mechanisms of acrolein-induced membrane damage, mitochondrial injury, oxidative stress, cell death, and functional loss. Evidence will also be presented to suggest that acrolein scavenging may be a novel means of therapeutic intervention to attenuate oxidative stress and improve recovery following traumatic SCI.

Hydralazine inhibits compression and acrolein-mediated injuries in ex vivo spinal cord

We have previously shown that acrolein, a lipid peroxidation byproduct, is significantly increased following spinal cord injury in vivo, and that exposure to neuronal cells results in oxidative stress, mitochondrial dysfunction, increased membrane permeability, impaired axonal conductivity, and eventually cell death. Acrolein thus may be a key player in the pathogenesis of spinal cord injury, where lipid peroxidation is known to be involved. The current study demonstrates that the acrolein scavenger hydralazine protects against not only acrolein-mediated injury, but also compression in guinea pig spinal cord ex vivo. Specifically, hydralazine (500 mumol/L to 1 mmol/L) can significantly alleviate acrolein (100-500 mumol/L)-induced superoxide production, glutathione depletion, mitochondrial dysfunction, loss of membrane integrity, and reduced compound action potential conduction. Additionally, 500 mumol/L hydralazine significantly attenuated compression-mediated membrane disruptions at 2 and 3 h following injury. This was consistent with our findings that acrolein-lys adducts were increased following compression injury ex vivo, an effect that was prevented by hydralazine treatment. These findings provide further evidence for the role of acrolein in spinal cord injury, and suggest that acrolein-scavenging drugs such as hydralazine may represent a novel therapy to effectively reduce oxidative stress in disorders such as spinal cord injury and neurodegenerative diseases, where oxidative stress is known to play a role.

Use of spectroscopic probes for detection of reactive oxygen species

The detection and quantitation of reactive oxygen species (ROS) receives a great deal of interest because of their importance in a wide range of physiological and pathogenic events. Probe-assisted spectroscopy (electron spin resonance, spectrophotometry, fluorescence and luminescence) is the main tool for this application. This review discusses the properties of spectroscopic probes most commonly used for ROS detection and highlights their limitations in cellular systems. These include poor stability of some probes and/or products that may be subjected to cellular metabolism and lack of specificity in their reactions with oxidants or reductants. Additional problems often arise from undesired reactions of the probes and from their non-homogeneous distribution in the studied system, production of ROS by the probes themselves, perturbation of the systems under investigation by the probes, and artifacts due to the presence of ROS in the reaction medium. The limits imposed by these difficulties on the precise evaluation of the amounts and rates of formation of ROS are discussed critically.

Evaluation of hydralazine and procainamide effects on fibroblast membrane fluidity

In this study the membrane fluidity of fibroblasts under different pharmacological treatment was investigated. Two drugs, hydralazine and procainamide, were used to treat the immortalized mouse NIH 3T3 and hamster B14 fibroblasts. Membrane lipid dynamics was measured by fluorescence spectroscopy and electron spin resonance techniques. Two kinds of fluorescent probes (TMA-DPH and 12-(9-anthroyloxy)-stearic acid (12-AS)) and two spin labels (5-doxylstearic acid (5-DS) and 12-doxylstearic acid (12-DS)) were used to monitor fluidity in the upper polar and in the hydrophobic core regions of the lipid bilayer. The drugs influenced the membrane hydrophobic core, of which hydralazine induced fluidization and procainamide increased the rigidity. The membrane fluidity at the surface of the lipid bilayer was not modified by the drugs which indicates that both drugs intercalated mainly into the inner core of the cell membrane.

Light-dependent generation of reactive oxygen species in cell culture media

Cell culture media (RPMI 1640, Dulbecco's Minimal Essential Medium and yeast extract-peptone-glucose medium) were found to oxidize dichlorodihydrofluorescein diacetate and dihydrorhodamine 123, and to generate spin adduct of 5,5'-dimethyl-1-pyrroline N-oxide, which indicates formation of reactive oxygen species (ROS). The production of ROS was light dependent. The main component of the media responsible for the generation of ROS was riboflavin, but tryptophan, tyrosine, pyridoxine, and folic acid enhanced the effect of riboflavin. These observations point to exposure of cells to ROS under in vitro culture conditions.

Studies on the mutagenic activity of hydralazine and dihydralazine in Salmonella typhimurium strains differing in expression of antioxidant genes

The mutagenic activity of two antihypertensive drugs, hydralazine and dihydralazine was investigated in oxyR- proficient (TA104) and -deficient (TA4125) Salmonella typhimurium strains showing different ability to induce proteins involved in protection of the cells against oxidative damage. The results of the Ames test demonstrated that dihydralazine, in contrast to hydralazine, was mutagenic for oxyR- strain at concentrations that were nonmutagenic for oxyR+ strain. The scavenger of superoxide anion, superoxide dismutase decreased in both strains the number of revertants induced by dihydralazine but not by hydralazine. The results may suggest that active oxygen species generated by dihydralazine contribute to its mutagenicity.

Antihypertensive drug therapy and antioxidant enzyme mRNA levels in spontaneously hypertensive (SHR) rats

Previous studies have shown that chronic treatment of SHR (spontaneously hypertensive) rats with the antihypertensive drugs captopril, hydralazine and terazosin results in changes in the specific activities of the antioxidant enzymes glutathione peroxidase, catalase and Cu/Zn superoxide dismutase in liver and myocardium. In order to determine if these changes were caused by alterations in the levels of the mRNAs for these enzymes, the tissue levels of the antioxidant enzyme mRNAs have been measured. In myocardium, all three drug treatments increased Cu/Zn superoxide dismutase mRNA but decreased glutathione peroxidase mRNA levels, and in liver, all three drugs changed glutathione peroxidase mRNA levels. In comparison to untreated SHR animals, the levels of all three mRNAs were altered in the myocardium, but not in the liver, of normotensive WKY rats. Comparisons of mRNA levels with tissue enzyme specific activities suggest that tissue antioxidant enzyme expression is, in most cases, regulated by antihypertensive drugs through transcriptional control mechanisms.

Changes in DNA supercoiling in fibroblasts cultured in the presence of hydralazine

We have analyzed changes in the supercoiling of nucleoid DNA of murine fibroblasts cultured in the presence of hydralazine. The entire DNA attached to the nuclear matrix was extracted from the cells and sedimented in neutral sucrose density gradients containing ethidium bromide. Nucleoids from cells treated with hydralazine responded to increasing ethidium bromide concentrations in a different way than those from control cultures. That is, supercoiled loops of DNA unwound with lower concentrations of ethidium bromide sedimented less rapidly than those of control cells, indicating that hydralazine reduced the degree of DNA supercoiling. Also, nucleoids from the drug-treated cells resisted the transition from relaxed to positive supercoiling at higher concentrations of ethidium bromide. Changes in nucleoid DNA supercoiling correlated directly with the dose of hydralazine in the fibroblast culture.

Hydralazine, but not captopril, decreases free radical production and apoptosis in neurons and thymocytes

The effects of captopril and hydralazine, two commonly used antihypertensive drugs, on free radical generation and the onset of apoptosis in neuron and thymocyte preparations from 10-12 day old rats have been studied. Apoptosis was induced in neurons by kainate or N-methyl-D-aspartate and in thymocytes by heat shock. Intracellular free radical production was measured by 2',7'-dichlorofluorescein fluorescence, and apoptotic cells were detected by cell staining with fluorescein-labelled annexin V. Captopril was found to have no effect on intracellular free radical generation and also had no significant effect on the early stages of apoptosis in neurons and thymocytes. In contrast, hydralazine was found to decrease free radical generation in both neurons and thymocytes, and it also significantly decreased the numbers of apoptotic cells when neurons and thymocytes were stimulated for apoptosis. Hydralazine had a greater effect on decreasing free radical generation in neurons than in thymocytes, but it had a more pronounced effect on decreasing apoptosis in thymocytes compared to neurons, suggesting that apoptosis, under our experimental conditions, may not solely be triggered by free radical generation. These results contrast with earlier reports that captopril is a free radical scavenger and can decrease apoptosis in T-lymphocytes and cardiomyocytes, and the results obtained with hydralazine are in apparent disagreement with earlier reports that this drug is a free radical generator and can cause intracellular damage suggestive of enhanced free radical formation.

Suppression of the hydrazine-induced formation of megamitochondria in the rat liver by coenzyme Q10

The effects of coenzyme Q10 (CoQ10) on the hydrazine-induced changes in the structure of mitochondria and those in antioxidant systems of the liver were investigated using rats as experimental animals. Animals were placed on a powdered diet containing 1.0% hydrazine for 7-8 days in the presence or absence of the combined treatment with CoQ10. Results obtained were as follows: (a) treatment of animals with CoQ10 prevented the hydrazine-induced formation of megamitochondria in the liver; (b) changes observed in the liver of the hydrazine-treated animals in comparison to the control were increases in the contents of alpha-tocopherol and CoQ analogs, increases in the levels of lipid peroxidation, decreases in the level of reduced glutathione with increases in that of oxidized glutathione, and increases in the ratio of unsaturated to saturated fatty acids in phospholipid domains of mitochondrial membranes; and (c) administration of CoQ10 to hydrazine-treated animals suppressed enhanced lipid peroxidation and improved lowered adenosine diphosphate/O ratios of mitochondria. The present data suggest that CoQ10 suppresses the hydrazine-induced formation of megamitochondria by scavenging free radicals generated from hydrazine and its metabolites.