Peroxynitrite may be involved in bladder damage caused by cyclophosphamide in rats

Could Mesna and Celery Seed Cotherapy Modulate Oxidative Stress and Inflammation of the Urinary Bladder Induced by Ifosfamide in Rabbits?

Background

Ifosfamide (IFS) has potential complications such as nephropathy and hemorrhagic cystitis (HC). Although mesna can prevent IFS-induced cystitis by direct binding and neutralization of acrolein, HC symptoms have still been observed clinically in most of these cases. Celery is a powerful healing vegetable that has antioxidant, anti-inflammatory, and anticancer effects. The current study evaluated the synergistic effects of mesna and celery seed on IFS-induced HC in rabbits.

Methods

Twenty male rabbits (four groups) were administered distilled water, IFS, mesna, and mesna+celery seed cotherapy (MCC) for three weeks. The serum and urinary bladder of experimental rabbits underwent biochemical (TNF-α, MDA, iNOS, SOD, GPx, and CAT), histopathological and ultrastructural investigations to evaluate the structural changes of the urinary bladder (UB).

Results

IFS injection resulted in severe cystitis with a remarkable increase in the scale of hematuria, elevations of TNF-α, MDA, and iNOS activity, and reduced activity of SOD, GPx, and CAT antioxidants. Additionally, the structure of UB exhibited evident mucosal edema and ulceration. In contrast, the MCC regimen group revealed partial synergistic improvement of all mentioned parameters.

Conclusion

IFS induced cystitis by releasing acrolein, which exerted a significant role in the pathogenesis of HC. In contrast, the MCC intake partially ameliorated the UB damage through its antioxidant and anti-inflammatory effects.

Conventional Chemotherapy Nephrotoxicity

Conventional chemotherapies remain the mainstay of treatment for many malignancies. Kidney complications of these therapies are not infrequent and may have serious implications for future kidney function, cancer treatment options, eligibility for clinical trials, and overall survival. Kidney adverse effects may include acute kidney injury (via tubular injury, tubulointerstitial nephritis, glomerular disease and thrombotic microangiopathy), long-term kidney function loss and CKD, and electrolyte disturbances. In this review, we summarize the kidney complications of conventional forms of chemotherapy and, where possible, provide estimates of incidence, and identify risk factors and strategies for kidney risk mitigation. In addition, we provide recommendations regarding kidney dose modifications, recognizing that these adjustments may be limited by available supporting pharmacokinetic and clinical outcomes data. We discuss management strategies for kidney adverse effects associated with these therapies with drug-specific recommendations. We focus on frequently used anticancer agents with established kidney complications, including platinum-based chemotherapies (cisplatin, carboplatin, oxaliplatin), cyclophosphamide, gemcitabine, ifosfamide, methotrexate and pemetrexed, among others.

Review of Advances in Uroprotective Agents for Cyclophosphamide- and Ifosfamide-induced Hemorrhagic Cystitis

Cyclophosphamide and ifosfamide are widely used drugs for malignancies and rheumatologic conditions. One of the most significant adverse reactions to these drugs is hemorrhagic cystitis. Mesna is the most widely used uroprotective agent that acts to neutralize the caustic metabolite, acrolein, responsible for induction of hemorrhagic cystitis. However, mesna is not a perfect alternative, and studies since its discovery have investigated the use of alternative drugs and adjuncts to increase mesna's efficacy. This review details some of the recent work into novel uroprotective agents for drug-induced hemorrhagic cystitis.

Prevention of cyclophosphamide-induced hemorrhagic cystitis by resveratrol: a comparative experimental study with mesna

PURPOSE

Hemorrhagic cystitis (HC) is the most common urotoxic side effect of cyclophosphamide (CP). The aim of this study was to compare the classical efficacy of mesna (2-mercaptoethane sulfonate sodium) with three different doses of resveratrol (RES) on cyclophosphamide-induced HC in rats.

METHODS

Forty-six male Sprague-Dawley rats were divided into six groups. Group 1 served as a negative control (sham). Five groups received a single dose of cyclophosphamide (150 mg/kg) intraperitoneally at the same time. Groups 2, 3, 4, 5, and 6 received only CP, CP + 20 mg/kg RES, CP + 40 mg/kg RES, CP + 80 mg/kg RES, and CP + classical protocol of three doses of mesna (30 mg/kg three times), respectively. Antioxidants, cytokines, and malondialdehyde levels were measured in all groups. In addition, histopathological alterations in tissues were examined.

RESULTS

CP administration induced severe HC with marked edema, hemorrhage, and inflammation in group 2. RES 20 mg/kg showed meaningful protection against bladder damage compared to the control group. It was seen that RES 40 mg/kg gave weaker protection but RES 80 mg/kg was not found to be effective.

CONCLUSION

In conclusion, marked bladder protection was found in 20 and 40 mg/kg RES applications compared to the control group, but this protection was weaker than with mesna.

Urothelial signaling

The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

Similarities and differences of hyperbaric oxygen and medical ozone applications

Hyperbaric oxygen (HBO) treatment is based on the principle of having the patient breath 100% oxygen in an environment above atmospheric pressure. Ozone (O(3)) is a colourless gas with a specific odour and consists of three oxygen atoms. The classical scientific understanding is that the world has become a place suitable for life for aerobic organisms with the increasing oxygen in the atmosphere billions of years ago. The formation of ozone after oxygen has then protected aerobic creatures from harmful rays. We now use these two gases for treatment purposes. It is noteworthy that the oxygen and ozone molecules that are formed by the same atom in different numbers are used for similar medical indications. We will try to emphasize the similarities and differences of HBO and medical ozone applications in this article.

Protective effect of aminoguanidine against cyclophosphamide-induced oxidative stress and renal damage in rats

BACKGROUND

Cyclophosphamide (CP) is widely used in the treatment of tumors and B-cell malignant disease, such as lymphoma, myeloma, chronic lymphocytic leukemia, and Waldenstrom's macroglobulinemia. Renal damage is one of the dose-limiting side effects of CP. Oxidative stress is reported to play important roles in CP-induced renal damage.

AIM

To find out whether aminoguanidine (AG) protects against CP-induced oxidative stress and renal damage.

METHOD

Renal damage was induced in the rats by administration of a single injection of CP at a dose of 150 mg/kg body weight intraperitoneally. For the AG pretreatment studies, the rats were injected intraperitoneally with AG at a dose of 200 mg/kg body weight 1 hour before administration of CP. The control rats received AG or saline alone. All the rats were killed 16 hours after the administration of CP or saline. The kidneys were used for histological examination by light microscopy and biochemical assays--malondialdehyde, protein carbonyl content, reduced glutathione (GSH), and the activities of antioxidant enzymes including glutathione peroxidase (GPx), glutathione S transferase (GSTase), catalase, glutathione reductase, and myeloperoxidase (MPO), a marker of neutrophil infiltration.

RESULTS

Pretreatment with AG attenuated CP-induced renal damage histologically. Pretreatment with AG prevented CP-induced lipid peroxidation, protein oxidation, depletion of reduced GSH, and loss of activities of the antioxidant enzymes including GPx, catalase, and GSTase and also MPO activity.

CONCLUSION

The results of the present study reveal that AG can prevent CP-induced renal damage by inhibiting oxidative stress. Thus, AG may be useful for prevention of the nephrotoxicity of CP.

Epigenetic perturbations in the pathogenesis of mustard toxicity; hypothesis and preliminary results

Among the most readily available chemical warfare agents, sulfur mustard (SM), also known as mustard gas, has been the most widely used chemical weapon. SM causes debilitating effects that can leave an exposed individual incapacitated for days to months; therefore delayed SM toxicity is of much greater importance than its ability to cause lethality. Although not fully understood, acute toxicity of SM is related to reactive oxygen and nitrogen species, oxidative stress, DNA damage, poly(ADP-ribose) polymerase (PARP) activation and energy depletion within the affected cell. Therefore several antioxidants and PARP inhibitors show beneficial effects against acute SM toxicity. The delayed toxicity of SM however, currently has no clear mechanistic explanation. One third of the 100,000 Iranian casualties are still suffering from the detrimental effects of SM in spite of the extensive treatment. We, therefore, made an attempt whether epigenetic aberrations may contribute to pathogenesis of mustard poisoning. Preliminary evidence reveals that mechlorethamine (a nitrogen mustard derivative) exposure may not only cause oxidative stress, DNA damage, but epigenetic perturbations as well. Epigenetic refers to the study of changes that influence the phenotype without causing alteration of the genotype. It involves changes in the properties of a cell that are inherited but do not involve a change in DNA sequence. It is now known that in addition to mutations, epimutations contribute to a variety of human diseases. Under light of preliminary results, the current hypothesis will focus on epigenetic regulations to clarify mustard toxicity and the use of drugs to correct possible epigenetic defects.

Acute and delayed sulfur mustard toxicity; novel mechanisms and future studies

Sulfur mustard (SM), also known as mustard gas, has been the most widely used chemical weapon. The toxicity of SM as an incapacitating agent is of much greater importance than its ability to cause lethality. Acute toxicity of SM is related to reactive oxygen and nitrogen species, DNA damage, poly(ADP-ribose) polymerase activation and energy depletion within the affected cell. Therefore melatonin shows beneficial effects against acute SM toxicity in a variety of manner. It scavenges most of the oxygen- and nitrogen-based reactants, inhibits inducible nitric oxide synthase, repairs DNA damage and restores cellular energy depletion. The delayed toxicity of SM however, currently has no mechanistic explanation. We propose that epigenetic aberrations may be responsible for delayed detrimental effects of mustard poisoning. Epigenetic refers to the study of changes that influence the phenotype without causing alteration of the genotype. It involves changes in the properties of a cell that are inherited but do not involve a change in DNA sequence. It is now known that in addition to genetic mutations, epimutations can also involve in the pathogenesis of a variety of human diseases. Several actions of melatonin are now delineated by epigenetic actions including modulation of histone acetylation and DNA methylation. Future studies are warranted to clarify whether epigenetic mechanisms are involved in pathogenesis of delayed sulfur mustard toxicity and melatonin alleviates delayed toxicity of this warfare agent.

Use of chemoprotectants in chemotherapy and radiation therapy: the challenges of selecting an appropriate agent

Chemoprotection refers to the protection from the toxicity of one chemical by the intervention of another. Conflicting preclinical and clinical reports make it difficult to either ignore or accept the use of chemoprotectants during cancer chemotherapy or radiotherapy. The selection of anticancer drugs depends on the type and stage of cancer development. However, very little attention has been paid to the selection of chemoprotectants. The answer to the use of chemoprotectants during cancer therapy lies in their appropriate selection in a case-specific and/or issue-specific manner. The need of the hour is to find better answers on the rationality of chemoprotectants selection during cancer therapy using cutting-edge science. In this commentary, we have presented few examples to justify our view-points.

Urothelial signaling

The urinary bladder "mucosa" or innermost portion of the bladder is composed of transitional epithelium, basement membrane, and the lamina propria. This chapter reviews the specialized anatomy of the bladder epithelium (urothelium) and speculates on possible communication mechanisms from urothelial cells to various cell types within the bladder wall. For example, beyond serving as a simple barrier, there is growing evidence that the urinary bladder urothelium exhibits specialized sensory properties and plays a key role in the detection and transmission of both physiological and nociceptive stimuli. Findings from a number of studies suggest that the urothelium exhibits both "sensor" (expressing receptors/ion channels capable of responding to thermal, mechanical, and chemical stimuli) and "transducer" (ability to release chemicals) properties. Thus, urothelial cells exhibit the ability to sense changes in their extracellular environment including the ability to respond to chemical, mechanical, and thermal stimuli that may communicate the state of the urothelial environment to the underlying nervous and muscular systems.

Effects of the compounds MV8608 and MV8612 obtained from Mandevilla velutina in the model of hemorrhagic cystitis induced by cyclophosphamide in rats

Hemorrhagic cystitis (HC) is a common side effect observed in patients under chemotherapy with cyclophosphamide (CYP). The urotoxic side effects of CYP are attributed to the metabolic compound acrolein, and can be partially prevented by the uroprotector agent 2-mercaptoethene sulfate (Mesna). The present study analyzed the anti-inflammatory and the antinociceptive effects of compounds MV8608 and MV8612 obtained from Mandevilla velutina in the rat model of CYP-induced HC. Male Wistar rats were used (six to eight per group, 220-250 g). HC was induced by a single administration of CYP (100 mg/kg, ip). Three behavioral parameters--breathing rate, closing of the eyes, and specific posture--were used as nociception indexes, and scored at different time intervals (15-180 min) after cystitis induction. As inflammatory parameters, hemorrhage presence, edema formation, and bladder weight were determined at 24 h after CYP administration. The neutrophil migration was assessed by means of myeloperoxidase (MPO activity), 4 h after cystitis induction. As expected, Mesna treatment was able to reduce in a significant manner all the inflammatory and the nociceptive parameters induced by CYP. Of note, the administration of MV8608 significantly inhibited the hemorrhage formation and the neutrophil recruitment, while the MV8612 treatment markedly reduced the bladder weight, without interfering with neutrophil influx. Interestingly, the treatment with either MV8608 or MV8612 markedly reduced the nociceptive responses. The present results clearly indicate that MV8608 and MV8612 might represent important alternatives to prevent side effects, especially the nociception, following chemotherapy with CYP.

Effect of melatonin on the expression of Nrf2 and NF-kappaB during cyclophosphamide-induced urinary bladder injury in rat

Urotoxicity is one of the major problems associated with cyclophosphamide (CP) chemotherapy in cancer patients. Melatonin is a potent antioxidant and reduces CP-induced urotoxicity. However, the molecular mechanisms of protection offered by melatonin are not yet clear. The present study investigated the role of nuclear erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (NF-kappaB) on melatonin-mediated protection against CP-induced urotoxicity. CP was administered intraperitoneally at the dose of 150 mg/kg to induce urotoxicity in male Sprague-Dawley rats. Melatonin treatment (10 mg/kg) was initiated 3 days before and continued for 1 day after the CP administration. Melatonin treatment reduced the CP-induced oxidative stress and DNA damage in the urinary bladder as observed by abrogation in thiobarbituric acid-reactive substances and glutathione levels as well as comet and modified comet assay parameters. Melatonin treatment reduced the bladder damage and apoptosis as observed by histological analysis and TUNEL assay. Melatonin increased the expression of transcription factor Nrf2 as well as associated phase-II enzymes NADPH: quinone oxidoreductase-1 and heme oxygenase-1. Further melatonin treatment reduced the expression of transcription factor NF-kappaB. The results of the present study provide evidence that melatonin treatment favorably alters Nrf2 and NF-kappaB expression and, this appears to be at least in part responsible for observed protection against CP-induced urotoxicity.

Molecular, genetic and epigenetic pathways of peroxynitrite-induced cellular toxicity

Oxidative stress plays a key role in the pathogenesis of cancer and many metabolic diseases; therefore, an effective antioxidant therapy would be of great importance in these circumstances. Nevertheless, convincing randomized clinical trials revealed that antioxidant supplementations were not associated with significant reduction in incidence of cancer, chronic diseases and all-cause mortality. As oxidation of essential molecules continues, it turns to nitro-oxidative stress because of the involvement of nitric oxide in pathogenesis processes. Peroxynitrite damages via several distinctive mechanisms; first, it has direct toxic effects on all biomolecules and causes lipid peroxidation, protein oxidation and DNA damage. The second mechanism involves the induction of several transcription factors leading to cytokine-induced chronic inflammation. Finally, it causes epigenetic perturbations that exaggerate nuclear factor kappa-B mediated inflammatory gene expression. Lessons-learned from the treatment of several chronic disorders including pulmonary diseases suggest that, chronic inflammation and glucocorticoid resistance are regulated by prolonged peroxynitrite production.

Proanthocyanidin protects intestine and remote organs against mesenteric ischemia/reperfusion injury

BACKGROUND

Intestinal ischemia/reperfusion (IR) induces a systemic inflammatory response and releases harmful substances that may affect the function and integrity of distant organs such as lung, liver, and kidney. We conducted this study to find out if proanthocyanidins (PA) has protective effects against mesenteric IR injury and mesenteric IR-induced intestinal and distant organ injury.

MATERIALS AND METHODS

Thirty-two Sprague-Dawley rats were divided into four groups: control, control + PA, IR, IR + PA. The IR and IR + PA groups were subjected to mesenteric arterial ischemia for 60 min and reperfusion for 6 h. The Control + PA and IR + PA groups were administered PA (100 mg/kg/day via oral gavage) for 7 days prior to injury insult. We collected ileal and distant organ tissues, such as pulmonary, hepatic, and kidney specimens to measure tissue levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), and nitrite plus nitrate (NO(x)), and we then evaluated histological changes.

RESULTS

In the IR group, significant increases in MDA and NO(x) levels and significant increases in SOD and GPx activities of intestine, liver, kidney, and lung were observed. The MDA and NO(x) levels were significantly lower, as were the SOD and GPx activities in the IR + PA group than that in the IR group. Although the intestine and distant organs damage scores were significantly higher in the IR group, these injuries were prevented by PA in the IR + PA group.

CONCLUSIONS

This study demonstrates that PA has a significant effect in the protection of the intestine and the remote organs against mesenteric IR injury.

A refocus on the bladder as the originator of storage lower urinary tract symptoms: a systematic review of the latest literature

CONTEXT

The focus of clinical understanding and management of male storage lower urinary tract symptoms (LUTS) has shifted from the prostate to the bladder. This is mirrored by an increasing body of experimental evidence suggesting that the bladder is the central organ in the pathogenesis of LUTS.

OBJECTIVE

A systematic review of the literature available on pathophysiologic aspects of storage LUTS.

EVIDENCE ACQUISITION

Medline was searched for the period ending December 2008 for studies on human and animal tissue exploring possible functional and structural alterations underlying bladder dysfunction. Further studies were chosen on the basis of manual searches of reference lists and review papers.

EVIDENCE SYNTHESIS

Numerous recent publications on LUTS pathophysiology were identified. They were grouped into studies exploring abnormalities on urothelial/suburothelial, muscular, or central levels.

CONCLUSIONS

Studies revealed both structural and functional alterations in bladders from patients with LUTS symptoms or animals with experimentally induced bladder dysfunction. In particular, the urothelium and the suburothelial space, containing afferent nerve fibres and interstitial cells, have been found to form a functional unit that is essential in the process of bladder function. Various imbalances within this suburothelial complex have been identified as significant contributors to the generation of storage LUTS, along with potential abnormalities of central function.

Benefit of Satureja khuzestanica in subchronically rat model of cyclophosphamide-induced hemorrhagic cystitis

Cyclophosphamide (CP) as a widely used antineoplastic drug causes hemorrhagic cystitis (HC) mainly via induction of oxidative stress. Regarding established antioxidant potential of Satureja khuzestanica (Lamiaceae) essential oil (SKEO), we aimed to investigate its protective effects in a subchronic rat model of CP-induced HC. CP (6mg/kg/day) and SKEO (225mg/kg/day) were administered alone or in combination by gavage for 28 days. Histopathological changes were investigated by light microscopy. Plasma samples were assayed for lipid peroxidation and total antioxidant power as biomarkers of toxic stress. In the CP-treated animals, irregular mucus layer, severe hemorrhage and edema, infiltration of inflammatory cells, and accumulation of mast cells were observed. In the CP+SKEO group, a relatively normal urothelial topography with decreased number of mucosal mast cells and inflammatory cells were observed. Increased lipid peroxidation along with decreased total antioxidant capacity resulting from CP treatment was significantly recovered by SKEO co-treatment. It is concluded that SKEO protects rats from CP-induced HC by reduction of free radical-induced toxic stress. It is strongly recommended to examine SKEO in the clinic to approve its benefit in patients undertaking CP.

Nitrosative stress, protein tyrosine nitration, PARP activation and NAD depletion in the kidneys of rats after single dose of cyclophosphamide

OBJECTIVES

Cyclophosphamide (CP) and its structural analogue ifosfamide are highly effective cytostatic drugs. While both cyclophosphamide and ifosfamide have severe urotoxic side effects, only ifosfamide is thought to be nephrotoxic. The nephrotoxicity of CP in generally overlooked because of normal plasma creatinine levels. Therefore, little information is available regarding the pathogenic mechanism of renal damage by CP. In the present study, we investigated the role of nitrosative stress in CP-induced renal damage.

METHODS

The experimental rats received a single i.p. of 150 mg/kg body weight CP in saline and were killed 6 h or 16 h later. The control rats received saline. The kidneys were used for histological and biochemical analysis. Nitrotyrosine and poly (ADP-ribose) polymerase (PARP) were localized immunohistochemically as indicators of protein nitration and DNA damage, respectively. Nitrite, NAD and superoxide dismutase (SOD) activity were assayed in the kidney homogenates.

RESULTS

The nitrite level in the kidneys of CP-treated rats was elevated twofold. The kidneys of CP-treated rats stained strongly for nitrotyrosine as well as for PARP. Significant decrease in oxidized NAD levels was also observed in the kidneys of CP-treated rats. The activity of the peroxynitrite sensitive enzyme SOD was significantly reduced in the kidneys of CP-treated rats.

CONCLUSION

The results of the present study reveal that nitrosative stress may play an important role in CP-induced renal damage. It is suggested that protein nitration, PARP activation and NAD +/- depletion may play a critical role in the pathogenesis of cyclophosphamide induced renal damage.

Aminoguanidine, selective nitric oxide synthase inhibitor, ameliorates cyclophosphamide-induced hemorrhagic cystitis by inhibiting protein nitration and PARS activation

OBJECTIVES

To elucidate the mechanism by which aminoguanidine (AG) protects against cyclophosphamide (CP)-induced hemorrhagic cystitis.

METHODS

Hemorrhagic cystitis was induced in the rats by administration of a single injection of CP at a dose of 150 mg/kg body weight intraperitoneally. For the AG pretreatment studies, the rats were injected intraperitoneally with AG at a dose of 200 mg/kg body weight 1 hour before administration of CP. The control rats received AG or saline alone. All the rats were killed 16 hours after the administration of CP or saline.

RESULTS

Pretreatment with AG ameliorated CP-induced bladder damage. Pretreatment with AG prevented CP-induced elevation in nitrate levels, nitration of protein tyrosine, poly (adenosine diphosphate ribose) polymerase (PARP) activation, and restored the activity of superoxide dismutase, the peroxynitrite-sensitive enzyme. The results of the present study have confirmed that AG is effective in preventing CP-induced cystitis and have also demonstrated that the protective effect is from its ability to inhibit nitric oxide-induced protein nitration and poly (adenosine diphosphate ribose) polymerase activation.

CONCLUSIONS

AG can prevent CP-induced urotoxicity and lead to better tolerance of the drug. Thus, a more efficient and comfortable therapy can be achieved for patients in need of CP treatment. AG appears to be a promising drug for the prevention of the urotoxicity of CP.

Ameliorative effects of proanthocyanidin on renal ischemia/reperfusion injury

INTRODUCTION

Several natural products have been reported to have beneficial effects on ischemia/reperfusion (I/R) injury, particularly from a preventative perspective. Therefore, this study was designed to investigate the efficiency of proanthocyanidin (PA), a natural product derived from grape seed, on renal dysfunction and injury induced by I/R of rat kidney.

MATERIALS AND METHODS

Twenty-four male Sprague-Dawley rats were divided into three groups: sham-operated, I/R, I/R+PA. Rats were given PA (100 mg/kg/day peroral) 7 days prior to I/R. All rats except sham-operated underwent 60 min of bilateral renal ischemia followed by 6 h of reperfusion. After reperfusion, kidneys and blood were obtained for evaluation. Superoxide dismutase, glutathione peroxidase, malondialdehyde, protein carbonyl content, and nitrite/nitrate level (NO(x)) were determined in the renal tissue. Serum creatinine (S(Cr)), blood urea nitrogen (BUN), and aspartate aminotransferase (AST) were determined in the blood. Additionally, renal sections were used for histological grade of renal injury.

RESULTS

PA significantly reduced the I/R-induced increases in S(Cr), BUN, and AST. In addition, PA markedly reduced elevated oxidative stress product, restored decreased antioxidant enzymes, and attenuated histological alterations. Moreover, PA attenuated the tissue NO(x), levels indicating reduced NO production.

CONCLUSIONS

The pretreatment of rats with PA reduced the renal dysfunction and morphological changes, ameliorated cellular injury, and restored renal antioxidant enzymes caused by renal I/R.

Protein nitration, PARP activation and NAD+ depletion may play a critical role in the pathogenesis of cyclophosphamide-induced hemorrhagic cystitis in the rat

OBJECTIVES

Hemorrhagic cystitis (HC) is a major dose-limiting side effect of cyclophosphamide (CP). The mechanism by which CP induces cystitis is not clear. Recent studies demonstrate that nitric oxide; (peroxynitrite) is involved in bladder damage caused by CP. However, the molecular targets of peroxynitrite are not known. The present study is aimed at investigating whether proteins and DNA are molecular targets of peroxynitrite using a rat model.

METHODS

The experimental rats received a single i.p. injection of 150 mg kg(-1) body weight CP in saline and killed 6 or 16 h later. The control rats received saline. The bladders were used for histological and biochemical analysis. Nitrotyrosine and poly-(ADP-ribose) polymerase (PARP) were localized immunohistochemically as indicators of protein nitration and DNA damage, respectively. Nitrite, malondialdehyde, protein thiol and superoxide dismutase (SOD) activity were assayed in the bladder.

RESULTS

Hematuria and urinary bladder edema was observed in the CP-treated rats and histologically, moderate to severe damage to the urinary bladder was observed. The bladders of CP-treated rats stained strongly for nitrotyrosine as well as for PARP. Significant decrease in oxidized NAD levels was observed in the bladders of CP-treated rats 16 h following treatment with CP. Protein thiol was depleted and the activity of the peroxynitrite sensitive enzyme SOD was significantly reduced in the bladders of CP-treated rats.

CONCLUSION

The results of the present study reveal that protein nitration, PARP activation and NAD+ depletion may play a critical role in the pathogenesis of CP-induced hemorrhagic cystitis. Based on the results we propose a mechanism for CP-induced cystitis.

Melatonin: an established antioxidant worthy of use in clinical trials

Oxidative stress plays a key role in the pathogenesis of aging and many metabolic diseases; therefore, an effective antioxidant therapy would be of great importance in these circumstances. Nutritional, environmental, and chemical factors can induce the overproduction of the superoxide anion radical in both the cytosol and mitochondria. This is the first and key event that leads to the activation of pathways involved in the development of several metabolic diseases that are related to oxidative stress. As oxidation of essential molecules continues, it turns to nitrooxidative stress because of the involvement of nitric oxide in pathogenic processes. Once peroxynitrite forms, it damages via two distinctive mechanisms. First, it has direct toxic effects leading to lipid peroxidation, protein oxidation, and DNA damage. This mechanism involves the induction of several transcription factors leading to cytokine-induced chronic inflammation. Classic antioxidants, including vitamins A, C, and E, have often failed to exhibit beneficial effects in metabolic diseases and aging. Melatonin is a multifunctional indolamine that counteracts virtually all pathophysiologic steps and displays significant beneficial actions against peroxynitrite-induced cellular toxicity. This protection is related to melatonin's antioxidative and antiinflammatory properties. Melatonin has the capability of scavenging both oxygen- and nitrogen-based reactants, including those formed from peroxynitrite, and blocking transcriptional factors, which induce proinflammatory cytokines. Accumulating evidence suggests that this nontoxic indolamine may be useful either as a sole treatment or in conjunction with other treatments for inhibiting the biohazardous actions of nitrooxidative stress.

Erdosteine and ebselen as useful agents in intestinal ischemia/reperfusion injury

BACKGROUND

Reactive oxygen and nitrogen species generated during reperfusion of the tissue are characteristic of ischemia/reperfusion (I/R) injury. The purpose of the present study was to investigate whether erdosteine and ebselen, molecules with antioxidant properties and peroxynitrite scavenging capability, respectively, can reduce oxidative stress and histological damage in the rat small bowel subjected to mesenteric I/R injury.

MATERIALS AND METHODS

Forty Sprague-Dawley rats were divided into five groups equally: sham, I/R, I/R plus erdosteine, I/R plus ebselen, and I/R plus erdosteine and ebselen. Intestinal ischemia for 45 min and reperfusion for 3 d were carried out. Ileal specimens were obtained to determine the tissue levels of malondialdehide (MDA), protein carbonyl content (PCC), superoxide dismutase (SOD), glutathione peroxidase (GPx), nitrite/nitrate (NO(x)) level and histological changes.

RESULTS

Intestinal I/R resulted in increased tissue MDA, PCC, and NO(x) levels and decreased SOD and GPx activities. Both erdosteine and ebselen alone significantly decreased MDA, PCC, and NO(x) levels and increased antioxidant enzymes activities, but all values were different from control. These changes almost returned to control values in the group treated with erdostein and ebselen. Histopathologically, the intestinal injury in rats treated with erdosteine and ebselen as well as combination were less than I/R group.

CONCLUSIONS

Both erdosteine and ebselen were able to attenuate I/R injury of the intestine via inhibition of lipid peroxidation and protein oxidation, maintenance of antioxidant, and free radical scavenger properties. Nevertheless, combination treatment showed more promising results, suggesting that scavenging peroxynitrite nearby antioxidant activity is important in preventing intestinal I/R injury.

Establishing the use of melatonin as an adjuvant therapeutic against paraquat-induced lung toxicity in rats

It is well known that the intake of paraquat (PQ) causes severe tissue injury leading to numerous fatalities. Considering that the main target for PQ toxicity is the lung and involves the production of reactive oxygen and nitrogen species, transcription factors and inflammatory cytokines, it may be hypothesized that the combination of a potent antiinflammatory and antioxidant agent may counteract more of PQ's effects than an antiinflammatory agent alone. For this purpose, combination of dexamethasone (Dex) and melatonin (Mel) was compared with Dex alone. A total of 40 male Wistar albino rats were divided into four groups as control, PQ, Dex only, and Dex plus Mel. The animals were given intraperitoneally a toxic dose of 19 mg/kg PQ dissolved in 1 ml saline. Control animals were injected with the same amount of saline only. A dose of 1 mg/kg Dex was administered 2 hrs after PQ administration. In the combination treatment group, 20 mg/kg Mel was given with Dex. All drugs were given every 12 hrs for a total of six doses. Five animals in PQ group and three animals in Dex only group died by the end of the study. No deaths occurred in the Dex+Mel group. Dex exerted improvements in several oxidative and antioxidative parameters. However, combination treatment provided beneficial effects against PQ toxicity far greater than Dex alone. This difference was also apparent when tissues were histologically compared. In conclusion, Mel exhibited strong additive beneficial effects with Dex and can be considered as a safe treatment modality against PQ toxicity.

Effects of poly(ADP-ribose) polymerase inhibition in bladder damage caused by cyclophosphamide in rats

It was previously shown that nitric oxide produced by inducible nitric oxide synthase (iNOS) and peroxynitrite are responsible for cyclophosphamide (CP)-induced cystitis. Since endogenous production of peroxynitrite is known to lead to poly(ADP-ribose) polymerase (PARP) activation, in this study, the aim was to evaluate whether the PARP activation pathway is also included in the pathogenesis of CP-induced bladder ulceration in rats. A total of 48 male albino Wistar rats were divided into 5 groups. Group 1 served as control and was given 2 ml saline; four groups received a single dose of CP (200 mg/kg) with the same time intervals. Group 2 received CP only; Group 3, selective iNOS inhibitor 1400W (20 mg/kg); Group 4, peroxynitrite scavenger ebselen (30 mg/kg); and Group 5, PARP inhibitor 3-aminobenzamide (20 mg/kg). CP injection resulted in severe cystitis with continuous macroscopic hemorrhage, strong edema, inflammation, and ulceration. Moreover, bladder iNOS activation and urine nitrite-nitrate levels were dramatically increased. Histologically, 1400W protected bladder against CP damage and decreased urine nitrite-nitrate levels and bladder iNOS induction. Ebselen has shown similar histologic results with 1400W without changing urinary nitrite-nitrate level and iNOS activity. Furthermore in the 3-aminobenzamide group, beneficial effects had also occurred including decreased ulceration. These results suggest that PARP activation involves pathogenesis of CP-induced bladder ulceration. Furthermore, PARP is not only important for ulceration but also for bladder edema, hemorrhage, and inflammation because of broken uroepithelial cellular integrity.

Effect of melatonin on apoptosis, proliferation and differentiation of urothelial cells after cyclophosphamide treatment

Melatonin was recently shown to have protective effects against cyclophosphamide (CP)-induced hemorrhagic cystitis (HC) by diminishing bladder oxidative stress. HC is accompanied by destruction of the bladder urothelium and followed by apoptosis and rapid regeneration via proliferation and differentiation of urothelial cells, reaching complete restoration of normal urothelium in three weeks. Therefore, the effect of melatonin on apoptosis, proliferation and differentiation of urothelial cells, during destruction and regeneration of the urothelium three-weeks after a single dose CP treatment, was studied. F344 male rats were injected intraperitoneally with saline (control group) or melatonin (Mel group) or a single dose of CP (100 mg/kg; CP group) or melatonin (10 mg/kg) with CP (Mel + CP group). Melatonin co-treatment with CP significantly reduced apoptosis and increased proliferation of urothelial cells at day 1 and thus prevented extensive loss of cells from the urothelium. However, proliferation indices at days 4 and 7 after melatonin and CP co-treatment suddenly dropped and therefore the development of hyperplasia was prevented. Melatonin co-treatment with CP also resulted in earlier differentiation of superficial urothelial cells. Melatonin seems to have protective effect against CP-induced urothelial damage and a favorable impact on regeneration and restoration of normal urothelium, since it reduces the number of apoptotic and proliferating urothelial cells and results in their earlier differentiation.

Alpha-tocopherol, beta-carotene and melatonin administration protects cyclophosphamide-induced oxidative damage to bladder tissue in rats

Cyclophosphamide (CP) has potential urotoxicity such as hemorrhagic cystitis (HC). 2-Mercaptoethane sulfonate (mesna) has been widely used as an effective agent against CP-induced cystitis, but significant HC has still been encountered clinically. In recent studies, mesna was shown to be more effective if combined with antioxidants. The purpose of this study was to evaluate the effects of antioxidants, alpha-tocopherol, beta-carotene and melatonin on CP-induced bladder damage in rats, even if used without mesna administration. Male Sprague-Dawley rats weighing 180-210 g were divided into 5 groups. Four groups received a single dose of CP (100 mg/kg) intraperitoneally with the same time intervals. Group 2 received CP only, group 3 received beta-carotene (40 mg/kg/day), group 4 received alpha-tocopherol (40 mg/kg/day) and group 5 received melatonin (10 mg/kg/day) both before and the day after CP injection. Group 1 served as control. Bladder histopathology, as well as malondialdehyde (MDA) and iNOS levels, and excretion of nitrite-nitrates (NO(x)) in urine were evaluated. CP injection resulted in severe histological changes and macroscopic hematuria. alpha-Tocopherol and melatonin showed meaningful protection against bladder damage. Protection by beta-carotene was also significant but weaker. MDA levels increased significantly with CP injection and all antioxidants ameliorated this increase in bladder tissue. CP also elevated the NO(x) level in urine and iNOS activity in bladder. Only melatonin was able to decrease these parameters. In conclusion, there is no doubt that oxidants have a role in the pathogenesis of CP-cystitis. Antioxidants, especially melatonin and alpha-tocopherol, may help to ameliorate bladder damage induced by CP.

Melatonin alleviates lung damage induced by the chemical warfare agent nitrogen mustard

The cytotoxic mechanism of mustards has not been fully elucidated; recently, we reported that reactive oxygen species, nitric oxide [produced by inducible nitric oxide synthase (iNOS)] and peroxynitrite are involved in the pathogenesis and responsible for mustard-induced toxicity. Melatonin, a potent antioxidant molecule, acts as an iNOS inhibitor and a peroxynitrite scavenger. Using the prototypic nitrogen mustard (mechlorethamine/HN2) as a model and based on its known cytotoxic mechanisms, the present study was performed to test melatonin for its capability in protecting the lungs of injured male Wistar rats. Lung mustard toxicity was induced via an intratracheally injection of HN2 (0.5mg/kg) dissolved in saline (100microl). Control animals were injected the same amount of saline only. Melatonin was administered intraperitoneally with two different doses (20mg/kg or 40mg/kg) beginning 1h before HN2 application and continued every 12h for six replications. Forty-eight hours after the last melatonin injection, the animals were sacrificed and their lungs were taken for further assay, i.e., malondialdehyde (MDA) levels, and superoxide dismutase (SOD), glutathione peroxidase (GPx) and iNOS activity. Additionally their urine was collected for nitrite-nitrate (NO(x)) analysis. HN2 injection caused increased iNOS activity and MDA levels in lung tissue and NO(x) values in urine; lung GPx activity was significantly depressed. Melatonin restored all of these oxidative and nitrosative stress markers in a dose-dependent manner. In conclusion, the results of study provide evidence that melatonin may have the ability to reduce mustard-induced toxicity in the lungs.

Mechanisms of disease: involvement of the urothelium in bladder dysfunction

Although the urinary bladder urothelium has classically been thought of as a passive barrier to ions and solutes, a number of novel properties have been recently attributed to urothelial cells. Studies have revealed that the urothelium is involved in sensory mechanisms (i.e. the ability to express a number of sensor molecules or respond to thermal, mechanical and chemical stimuli) and can release chemical mediators. Localization of afferent nerves next to the urothelium suggests that urothelial cells could be targets for neurotransmitters released from bladder nerves or that chemicals released by urothelial cells could alter afferent nerve excitability. Taken together, these and other findings highlighted in this article suggest a sensory function for the urothelium. Elucidation of mechanisms that influence urothelial function might provide insights into the pathology of bladder dysfunction.

Pathophysiological aspects of cyclophosphamide and ifosfamide induced hemorrhagic cystitis; implication of reactive oxygen and nitrogen species as well as PARP activation

Cyclophosphamide (CP) and ifosfamide (IF) are widely used antineoplastic agents, but their side-effect of hemorrhagic cystitis (HC) is still encountered as an important problem. Acrolein is the main molecule responsible of this side-effect and mesna (2-mercaptoethane sulfonate) is the commonly used preventive agent. Mesna binds acrolein and prevent its direct contact with uroepithelium. Current knowledge provides information about the pathophysiological mechanism of HC: several transcription factors and cytokines, free radicals and non-radical reactive molecules, as well as poly(adenosine diphosphate-ribose) polymerase (PARP) activation are now known to take part in its pathogenesis. There is no doubt that HC is an inflammatory process, including when caused by CP. Thus, many cytokines such as tumor necrosis factor (TNF) and the interleukin (IL) family and transcription factors such as nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) also play a role in its pathogenesis. When these molecular factors are taken into account, pathogenesis of CP-induced bladder toxicity can be summarized in three steps: (1) acrolein rapidly enters into the uroepithelial cells; (2) it then activates intracellular reactive oxygen species and nitric oxide production (directly or through NF-kappaB and AP-1) leading to peroxynitrite production; (3) finally, the increased peroxynitrite level damages lipids (lipid peroxidation), proteins (protein oxidation) and DNA (strand breaks) leading to activation of PARP, a DNA repair enzyme. DNA damage causes PARP overactivation, resulting in the depletion of oxidized nicotinamide-adenine dinucleotide and adenosine triphosphate, and consequently in necrotic cell death. For more effective prevention against HC, all pathophysiological mechanisms must be taken into consideration.

Lung toxicity of nitrogen mustard may be mediated by nitric oxide and peroxynitrite in rats

Nitric oxide (NO) has previously been shown to be responsible for nitrogen mustard (NM)-induced tissue toxicity. Excessive amounts of NO are known to be able to produce peroxynitrite, an important reactive nitrogen compound, by reacting with superoxide. Previous studies reported that NO synthase inhibitors are able to prevent NM toxicity. The aim of this study was to evaluate whether peroxynitrite is also responsible for NM-induced lung tissue damage in rats. Wistar rats were divided into four groups. NM was injected intratracheally and was treated with the selective inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine (AG) (intraperitoneal) or the peroxynitrite scavenger ebselen (intragastric). Control animals were exposed to saline only. NM injection caused both oxidative and nitrosative stress, reflected by dramatically increased levels of the lipid peroxidation end product malondialdehyde (MDA), iNOS activation and urine nitrite-nitrate (NOx) values. Histopathological evaluation demonstrated lung damage with NM exposure. AG blocked iNOS activation and decreased urine NOx levels, and resulted in less histopathological changes in the lung. Although the histopathological outcome was found to be similar to AG, ebselen did not change urinary NOx or lung iNOS levels. Furthermore, ebselen was more able than AG to protect against MDA accumulation. In conclusion, the ability of ebselen to prevent against lung damage without blocking NO synthesis suggests that peroxynitrites may have an important role in the pathogenesis of NM toxicity in addition to NO.

Amifostine and glutathione prevent ifosfamide- and acrolein-induced hemorrhagic cystitis

INTRODUCTION

Ifosfamide (IFS) is an antineoplastic alkylating agent whose major side effect is hemorrhagic cystitis (HC). This toxicity is attributed to the renal excretion of acrolein (ACR), a highly urotoxic IFS metabolite. Despite the clinical use of mesna to prevent HC, a significant percent ( approximately 33%) of patients present with at last one feature of HC, mainly hematuria.

AIM

To investigate the use of two antioxidants-amifostine and glutathione-for the prevention of experimental IFS- and ACR-induced HC.

MATERIALS AND METHODS

Male Swiss mice were treated intraperitoneal (i.p.) with saline (control), glutathione (125, 250 or 500 mg/kg) or amifostine (25, 50 or 100 mg/kg), and 30 min later they received a single i.p. injection of IFS at a dose of 400 mg/kg. To investigate the systemic effects of the antioxidants on ACR-induced HC, the animals were treated with saline, amifostine (50 mg/kg, i.p.) or glutathione (500 mg/kg, i.p.), and 30 min afterward with 75 mug ACR intravesically (i.ve.). In another set of experiments, the antioxidants were injected directly into the bladder, where the mice received a single i.ve injection of ACR (75 mug) plus amifostine (1.5 mg/kg) or glutathione (2 mg/kg). HC was measured 3 h after IFS or ACR injection according to bladder wet weight, macroscopic (edema and hemorrhage) and microscopic changes, i.e., edema, hemorrhage, cellular infiltration, fibrin deposition and urothelial desquamation.

RESULTS

Pretreatments with amifostine or glutathione prevented IFS-induced HC in a dose-dependent manner. Furthermore, ACR-induced HC was also prevented by systemic (i.p.) or local (i.ve.) pretreatment with glutathione or amifostine. The greatest protective effect was seen with local amifostine treatment (2 mg/kg i.ve.) (P < 0.05).

CONCLUSIONS

Glutathione and amifostine show a beneficial effect in experimental IFS- and ACR-induced HC. Thus, they should be investigated as an alternative treatment to prevent HC observed in patients undergoing IFS treatment.

Molecular targets against mustard toxicity: implication of cell surface receptors, peroxynitrite production, and PARP activation

Despite many years of research into chemical warfare agents, cytotoxic mechanisms induced by mustards are not well understood. Reactive oxygen and nitrogen species (ROS and RNS) are likely to be involved in chemical warfare agents induced toxicity. These species lead to lipid peroxidation, protein oxidation, and DNA injury, and trigger many pathophysiological processes that harm the organism. In this article, several steps of pathophysiological mechanisms and possible ways of protection against chemical warfare agents have been discussed. In summary, pathogenesis of mustard toxicity is explained by three steps: (1) mustard binds target cell surface receptor, (2) activates intracellular ROS and RNS leading to peroxynitrite (ONOO(-)) production, and (3) the increased ONOO(-) level damages organic molecules (lipids, proteins, and DNA) leading to poly(adenosine diphosphate-ribose) polymerase (PARP) activation. Therefore, protection against mustard toxicity could also be performed in these ways: (1) blocking of cell surface receptor, (2) inhibiting the ONOO(-) production or scavenging the ONOO(-) produced, and (3) inhibiting the PARP, activated by ONOO(-) and hydroxyl radical (OH(*)) induced DNA damage. As conclusion, to be really effective, treatment against mustards must take all molecular mechanisms of cytotoxicity into account. Combination of several individual potent agents, each blocking one of the toxic mechanisms induced by mustards, would be interesting. Therefore, variations of combination of cell membrane receptor blockers, antioxidants, nitric oxide synthase inhibitors, ONOO(-) scavengers, and PARP inhibitors should be investigated.