Growth and methanogenesis by Methanosarcina strain 227 on acetate and methanol

Methanosarcina strain 227 exhibited exponential growth on sodium acetate in the absence of added H(2). Under these conditions, rates of methanogenesis were limited by concentrations of acetate below 0.05 M. One mole of methane was formed per mole of acetate consumed. Additional evidence from radioactive labeling studies indicated that sufficient energy for growth was obtained by the decarboxylation of acetate. Diauxic growth and sequential methanogenesis from methanol followed by acetate occurred in the presence of mixtures of methanol and acetate. Detailed studies showed that methanol-grown cells did not metabolize acetate in the presence of methanol, although acetate-grown cells did metabolize methanol and acetate simultaneously before shifting to methanol. Acetate catabolism appeared to be regulated in response to the presence of better metabolizable substrates such as methanol or H(2)-CO(2) by a mechanism resembling catabolite repression. Inhibition of methanogenesis from acetate by 2-bromoethanesulfonate, an analog of coenzyme M, was reversed by addition of coenzyme M. Labeling studies also showed that methanol may lie on the acetate pathway. These results suggested that methanogenesis from acetate, methanol, and H(2)-CO(2) may have some steps in common, as originally proposed by Barker. Studies with various inhibitors, together with molar growth yield data, suggest a role for electron transport mechanisms in energy metabolism during methanogenesis from methanol, acetate, and H(2)-CO(2).

Specificity and biological distribution of coenzyme M (2-mercaptoethanesulfonic acid)

The specificity of the growth requirement of Methanobacterium ruminantium strain M1 for a new coenzyme, 2-mercaptoethanesulfonic acid (HS--CoM), was examined. A variety of derivatives, analogs, and potential biosynthetic precursors of coenzyme M were tested; only a restricted range of thioether, thioester, and thiocarbonate derivatives of the cofactor were found to replace the HS--CoM requirement. Bromoethanesulfonic acid (BrCH2CH2SO3-), a halogenated analog of HS--CoM, potently inhibited the growth response. No coenzyme was detectable in a wide range of nonmethanogenic eucaryotic tissues and procaryotic organisms. However, all methanogens available in pure culture exhibited high levels of coenzyme M which ranged from 0.3 to 16 nmol/mg of dry weight.

Ifosfamide/mesna. A review of its antineoplastic activity, pharmacokinetic properties and therapeutic efficacy in cancer

Ifosfamide is an oxazaphosphorine alkylating agent with a broad spectrum of antineoplastic activity. It is a prodrug metabolised in the liver by cytochrome P450 mixed-function oxidase enzymes to isofosforamide mustard, the active alkylating compound. Mesna, a uroprotective thiol agent, is routinely administered concomitantly with ifosfamide, and has almost eliminated ifosfamide-induced haemorrhagic cystitis and has reduced nephron toxicity. Therapeutic studies, mostly noncomparative in nature, have demonstrated the efficacy of ifosfamide/mesna alone, or more commonly as a component of combination regimens, in a variety of cancers. In patients with relapsed or refractory disseminated nonseminomatous testicular cancer, a salvage regimen of ifosfamide/mesna, cisplatin and either etoposide or vinblastine produced complete response in approximately one-quarter of patients. As a component of both induction and salvage chemotherapeutic regimens, ifosfamide/mesna has produced favourable response rates in small cell lung cancer, paediatric solid tumours, non-Hodgkin's and Hodgkin's lymphoma, and ovarian cancer. Induction therapy with ifosfamide/mesna-containing chemotherapeutic regimens has been encouraging in non-small cell lung cancer, adult soft-tissue sarcomas, and as neoadjuvant therapy in advanced cervical cancer. As salvage therapy, ifosfamide/mesna-containing combinations have a palliative role in advanced breast cancer and advanced cervical cancer. Ifosfamide/mesna can elicit responses in patients refractory to numerous other antineoplastic drugs, including cyclophosphamide. With administration of concomitant mesna to protect against ifosfamide-induced urotoxicity, the principal dose-limiting toxicity of ifosfamide is myelosuppression; leucopenia is generally more severe than thrombocytopenia. Reversible CNS adverse effects ranging from mild somnolence and confusion to severe encephalopathy and coma can occur in approximately 10 to 20% of patients after intravenous infusion, and the incidence of neurotoxicity may be increased to 50% after oral administration because of differences in the preferential route of metabolism between the 2 routes of administration. Other adverse effects of ifosfamide include nephrotoxicity, alopecia, and nausea/vomiting. In general, intravenously administered mesna is associated with a low incidence of adverse effects; however, gastrointestinal disturbances are common following oral administration. Thus, ifosfamide/mesna is an important and worthwhile addition to the currently available range of chemotherapeutic agents. It has a broad spectrum of antineoplastic activity and causes less marked myelosuppression than many other cytotoxic agents. At present, the role of ifosfamide/mesna in refractory germ cell testicular cancer is clearly defined; however, its overall place in the treatment of other forms of cancer awaits delineation in future well-controlled comparative studies.

Radioprotectants: current status and new directions

The ability to prevent radiotherapy-induced toxicity without affecting antitumor efficacy has the potential to enhance the therapeutic benefit for cancer patients without increasing their risk of serious adverse effects. Among the currently available cytoprotective agents capable of protecting normal tissue against damage caused by either chemo- or radiotherapy, only amifostine has been shown in clinical trials to reduce radiation-induced toxicity. Most notably, it reduces the incidence of xerostomia, which is a clinically significant long-term toxicity arising in patients undergoing irradiation of head and neck cancers. In vitro studies with the active metabolite of amifostine (WR-1065) have shown it to prevent both radiation-induced cell death and radiation-induced mutagenesis. The potential of this agent to prevent secondary tumors, as well as other radiation-induced toxicities is now the focus of ongoing research. Among other novel approaches to radioprotection being explored are methods to increase levels of the antioxidant mitochondrial enzyme manganese superoxide dismutase (MnSOD). In addition, the use of epoetin alfa, alone or in combination with cytoprotectants (e.g., amifostine), to treat radiation-induced anemia is also being investigated. The objective of developing newer cytoprotective therapies is to improve the therapeutic ratio by reducing the acute and chronic toxicities associated with more intensive and more effective anticancer therapies.

Synaptic-like microvesicles of neuroendocrine cells originate from a novel compartment that is continuous with the plasma membrane and devoid of transferrin receptor

We have characterized the compartment from which synaptic-like microvesicles (SLMVs), the neuroendocrine counterpart of neuronal synaptic vesicles, originate. For this purpose we have exploited the previous observation that newly synthesized synaptophysin, a membrane marker of synaptic vesicles and SLMVs, is delivered to the latter organelles via the plasma membrane and an internal compartment. Specifically, synaptophysin was labeled by cell surface biotinylation of unstimulated PC12 cells at 18 degrees C, a condition which blocked the appearance of biotinylated synaptophysin in SLMVs and in which there appeared to be no significant exocytosis of SLMVs. The majority of synaptophysin labeled at 18 degrees C with the membrane-impermeant, cleavable sulfo-NHS-SS-biotin was still accessible to extracellularly added MesNa, a 150-D membrane-impermeant thiol-reducing agent, but not to the 68,000-D protein avidin. The SLMVs generated upon reversal of the temperature to 37 degrees C originated exclusively from the membranes containing the MesNa-accessible rather than the MesNa-protected population of synaptophysin molecules. Biogenesis of SLMVs from MesNa-accessible membranes was also observed after a short (2 min) biotinylation of synaptophysin at 37 degrees C followed by chase. In contrast to synaptophysin, transferrin receptor biotinylated at 18 degrees or 37 degrees C became rapidly inaccessible to MesNa. Immunofluorescence and immunogold electron microscopy of PC12 cells revealed, in addition to the previously described perinuclear endosome in which synaptophysin and transferrin receptor are colocalized, a sub-plasmalemmal tubulocisternal membrane system distinct from caveolin-positive caveolae that contained synaptophysin but little, if any, transferrin receptor. The latter synaptophysin was selectively visualized upon digitonin permeabilization and quantitatively extracted, despite paraformaldehyde fixation, by Triton X-100. Synaptophysin biotinylated at 18 degrees C was present in these subplasmalemmal membranes. We conclude that SLMVs originate from a novel compartment that is connected to the plasma membrane via a narrow membrane continuity and lacks transferrin receptor.

Prevention of isophosphamide-induced urothelial toxicity with 2-mercaptoethane sulphonate sodium (mesnum) in patients with advanced carcinoma

In 8 patients receiving intravenous isophosphamide 2 g/m2 at 2-week intervals for advanced bronchogenic carcinoma the protective effect of 2-mercaptoethane sulphonate sodium (mesnum) against isophosphamide-induced urothelial toxicity was tested in a single-blind crossover trial. With isophosphamide alone, 7 of the 8 patients developed either haematuria or symptoms of bladder irritation; when mesnum was given in addition, only 1 patient had microhaematuria and frequency, and this was in association with a urinary-tract infection. 5 patients then received fifteen courses of isophosphamide in increasing doses of 4 to 8 g/m2 i.v. with mesnum. In contrast to previous experience with isophosphamide at this high dosage, frank haematuria was never seen, microhaematuria was seen after only three courses, and mild dysuria after only one course. Pharmacokinetic studies showed that mesnum did not interfere with the metabolism of isophosphoramide or its active anti-tumour metabolite, isophosphoramide mustard. Mesnum therefore enhances the therapeutic ratio of isophosphamide and may thereby increase its clinical efficacy.

Studies on the urotoxicity of oxazaphosphorine cytostatics and its prevention--III. Profile of action of sodium 2-mercaptoethane sulfonate (mesna)

Mesna is a pharmacologically unremarkable, physiologically largely inert and almost totally non-toxic thio compound. It is rapidly eliminated renally and only slightly permeates into tissues. It has been shown experimentally that the bladder damage inducible in the rat by administration of oxazaphosphorine cytostatics can be successfully prevented by quite small doses of mesna. The detoxifying action of mesna is limited to the kidneys and the efferent urinary tract. The systemic effects of the oxazaphosphorines, however, remain unaffected. This applies particularly to the curative oncocidal efficacy of these compounds. It has also been shown experimentally that mesna does not affect the curative effects of other cytostatic drugs (doxorubicin, BCNU, methotrexate, vincristine). The efficacy of the cardiac glycoside proscillaridin is also not impaired by mesna.

Coenzyme M derivatives and their effects on methane formation from carbon dioxide and methanol by cell extracts of Methanosarcina barkeri

Extracts of Methanosarcina barkeri reduced methanol and CO2 to CH4 in the presence of H2 and converted methanol stoichiometrically into CH4 and CO2 in the absence of H2. In dialyzed cell-free extracts these reactions were stimulated by 2-mercaptoethanesulfonic acid (coenzyme M) and some derivatives (acetyl and formylcoenzyme M and the oxidized form of coenzyme M), which could be converted to coenzyme M by enzyme systems present in the extracts. Methylcoenzyme M could not be used in these systems.

Delayed radioprotection by NFkappaB-mediated induction of Sod2 (MnSOD) in SA-NH tumor cells after exposure to clinically used thiol-containing drugs

The ability of thiol-containing reducing agents to activate transcription factors leading to changes in gene expression and enzyme activities provides an additional mechanism to potentially protect against radiation-induced cell killing. Manganese superoxide dismutase (Sod2) is one such gene whose expression levels have been shown to be elevated after exposure to the thiol compounds WR-1065 and N-acetyl-L-cysteine (NAC), resulting in an increase in radiation resistance. To further characterize this effect, SA-NH sarcoma cells, both wild-type and a clone stably transfected with a plasmid containing an IkappaBalpha gene mutated at serines 32 and 36, which prevents the inducible phosphorylation of these residues and the subsequent activation of NFkappaB (SA-NH+mIkappaBalpha1), were grown to confluence and then exposed to amifostine's free thiol WR-1065 at a concentration of 4 mM for 30 min. Effects of thiol exposure on NFKB activation in SA-NH+mIkappaBalpha1 cells were determined by a gel shift assay, and changes in Sod2 protein levels in these cells 24 h after exposure to 40 microM or 4 mM WR-1065 were measured by Western blot analysis and compared with wild-type cells exposed to the NFkappaB inhibitor BAY 11-7082. Changes in radiation response, measured immediately after thiol exposure or 24 h later, were determined using a colony-forming assay and were correlated with NFKB activation and Sod2 protein levels. The effects of captopril, mesna and NAC, each at a dose of 4 mM, on radiation response were also determined and contrasted with those of WR-1065. Only WR-1065 and captopril protected SA-NH cells when present during irradiation, i.e. 1.57 and 1.31 times increase in survival at 2 Gy, respectively. All four thiols were protective if irradiation with 2 Gy occurred 24 h later; i.e. increases in survival of 1.40, 1.22, 1.35, and 1.25 times were found for WR-1065, captopril, mesna and NAC, respectively. This delayed radioprotective effect correlated with elevated Sod2 protein levels in wild-type SA-NH tumor cells but was not observed in SA-NH+mIkappaBalpha1 cells, indicating that interference with thiol-induced NFKB activation abrogates this delayed radioprotective effect. Because the delayed radioprotective effect is readily demonstrable at a radiation dose of 2 Gy 24 h after exposure to clinically approved thiol-containing drugs such as amifostine, captopril, mesna and NAC, it suggests a new potential concern regarding the issue of tumor protection and the use of these agents in cancer therapy.

Detoxification of urotoxic oxazaphosphorines by sulfhydryl compounds

Urotoxic side effects, especially hemorrhagic cystitis, have so far been a limiting factor in the therapeutic use of cyclophosphamide (Endoxan), ifosfamide (Holoxan), and trofosfamide (Ixoten). The uroprotective agent mesna (Uromitexan) allows regional detoxification in the kidney and the urinary tract, and thus clinical prevention of the urotoxic side effects of the above cytostatics. The uroprotective mechanism of mesna is based on the formation of nontoxic additive compounds with acrolein and 4-hydroxy-metabolites. In the body, mesna is rapidly transformed into its biologically inert disulfide. After glomerular filtration mesna disulfide is rapidly reduced by reacting with the glutathion system and elimination in the urine as a free thiol compound, further detoxifying the aggressive oxazaphosphorine metabolites.

A model of hemorrhagic cystitis induced with acrolein in mice

Acrolein is a urinary metabolite of cyclophosphamide and ifosfamide, which has been reported to be the causative agent of hemorrhagic cystitis induced by these compounds. A direct cytotoxic effect of acrolein, however, has not yet been demonstrated. In the present study, the effects of intravesical injection of acrolein and mesna, the classical acrolein chemical inhibitor, were evaluated. Male Swiss mice weighing 25 to 35 g (N = 6 per group) received saline or acrolein (25, 75, 225 microg) intravesically 3, 6, 12, and 24 h before sacrifice for evaluation of bladder wet weight, macroscopic and histopathological changes by Gray's criteria, and 3 and 24 h for assessment of increase in vascular permeability. In other animals, mesna was administered intravesically (2 mg) or systemically (80 mg/kg) 1 h before acrolein. Intravesical administration of acrolein induced a dose- and time-dependent increase in vascular permeability and bladder wet weight (within 3 h: 2.2- and 21-fold increases in bladder wet weight and Evans blue dye exuded, respectively, at doses of 75 microg/bladder), as confirmed by Gray's criteria. Pretreatment with mesna (2-mercaptoethanesulfonic acid), which interacts with acrolein resulting in an inactive compound, inhibited all changes induced by acrolein. Our results are the first demonstration that intravesical administration of acrolein induces hemorrhagic cystitis. This model of acrolein-induced hemorrhagic cystitis in mice may be an important tool for the evaluation of the mechanism by which acrolein induces bladder lesion, as well as for investigation of new uroprotective drugs.

Evidence of a new dechlorinated ochratoxin A derivative formed in opossum kidney cell cultures after pretreatment by modulators of glutathione pathways: correlation with DNA-adduct formation

Ochratoxin A (OTA), a nephrotoxic mycotoxin probably implicated in human Balkan endemic nephropathy and associated urothelial tumors, induces renal carcinomas in rodents and nephrotoxicity in pigs. OTA induces DNA-adduct formation, but the structure of the adducts and their role in nephrotoxicity and carcinogenicity have only partly been elucidated. In vivo, 2-mercaptoethane sulfonate (MESNA) protects rats against OTA-induced nephrotoxicity but not against carcinogenicity, indicating two different mechanisms leading to nephrotoxicity or carcinogenicity. To better understand how DNA-adduct could be generated, opossum kidney cells (OK) have been treated by OTA alone or in presence of several compounds such as MESNA or N-acetylcysteine (another agent that, like MESNA, reduces oxidative stress by increasing of free thiols in kidney), buthionine sulfoximine (BSO) (an inhibitor of glutathione-synthase), and alpha amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid (ACIVICIN) (an inhibitor of gamma glutamyl transpeptidase). Cytotoxicity of OTA on OK cells was evaluated by applying the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. None of the listed agents diminished OTA cytotoxicity significantly; ACIVICIN even increases OTA cytotoxicity. In contrast, analysis of the HPLC profiles of OTA metabolites produced during these incubations indicated that the pattern, the quantity of metabolites, and the nature of the derivatives were modulated by these agents. Ochratoxin B (OTB), open-ring ochratoxin A (OP-OA), 4 hydroxylated OTA, 10 hydroxylated OTA, OTA without phenylalanine, OTB without phenylalanine, and a dechlorinated OTA metabolite could be identified by nano-ESI-IT-MS.

Toxicity of ifosfamide and its metabolite chloroacetaldehyde in cultured renal tubule cells

Renal injury is a common side effect of the chemotherapeutic agent ifosfamide. Current evidence suggests that the ifosfamide metabolite chloroacetaldehyde may contribute to this nephrotoxicity. The present study examined the effects of ifosfamide and chloroacetaldehyde on rabbit proximal renal tubule cells in primary culture. The ability of the uroprotectant medication sodium 2-mercaptoethanesulfonate (mesna) to prevent chloroacetaldehyde-induced renal cell injury was also assessed. Chloroacetaldehyde (12.5-150 microM) produced dose-dependent declines in neutral red dye uptake, ATP levels, glutathione content, and cell growth. Coadministration of mesna prevented chloroacetaldehyde toxicity while pretreatment of cells with the glutathione-depleting agent buthionine sulfoximine enhanced the toxicity of chloroacetaldehyde. Ifosfamide (1000-10,000 microM) toxicity was detected only at concentrations of 4000 microM or greater. Analysis of media collected from ifosfamide-treated cell cultures revealed the presence of several ifosfamide metabolites, demonstrating that renal proximal tubule cells are capable of biotransforming this chemotherapeutic agent. This primary renal cell culture system should prove useful in studying the cause and prevention of ifosfamide nephrotoxicity.

Mesna: a novel renoprotective antioxidant in ischaemic acute renal failure

BACKGROUND

Reactive oxygen species (ROS) play a key role in renal ischaemia-reperfusion injury. After establishing the in vitro anti-oxidative potential of mesna, a sulfhydryl-containing compound, its effect on kidney function and morphology in a rat model of ischaemic acute renal failure (ARF) was examined.

METHODS

Mesna (180 mg/kg) was administered at different time points relative to ischaemia and/or reperfusion onset. Kidney function was assessed by glomerular filtration rate (GFR) and fractional sodium excretion (FE(Na)) before a 45-min period of unilateral renal artery clamping and following 90 min of reperfusion. Mesna was administered by bolus, 30 min before the induction of ischaemia, 5 min before ischaemia, 5 min before reperfusion, and 5 min after the onset of reperfusion.

RESULTS

Mesna improved function of the ischaemic kidney at each administration. When mesna was administered 5 min before the onset of reperfusion, GFR reached 90-100% of its pre ischaemic value and FE(Na) was improved by 75%. The beneficial effect of mesna was also demonstrated by light and electron microscopy. Kidneys treated with mesna 5 min before reperfusion resembled ischaemic non-reperfused kidneys and showed subtle morphological and ultrastructural changes compared with ischaemic-reperfused kidneys. Mesna had no haemodynamic effect on renal blood flow and did not induce any osmotic diuresis.

CONCLUSIONS

We suggest that mesna acts as an antioxidant. Its antioxidant potential together with optimal protection achieved when administered 5 min before reperfusion, supports the conclusion that mesna scavenges ROS generated at the onset of reperfusion, thus diminishing reperfusion injury and organ damage.

Protective effects of MESNA (2-mercaptoethane sulphonate) against acetaminophen-induced hepatorenal oxidative damage in mice

Acetaminophen, a widely used analgesic and antipyretic, is known to cause hepatic and renal injury in humans and experimental animals when administered in high doses. It was reported that these toxic effects of acetaminophen are due to oxidative reactions that take place during its metabolism. In this study we aimed to investigate the possible beneficial effect of 2-mercaptoethane sulphonate (MESNA), an antioxidant agent, against acetaminophen toxicity in mice. Balb-c mice were injected i.p. with: vehicle (the control group); a single dose of 150 mg kg(-1) MESNA (MES group); a single dose of 900 mg kg(-1) i.p. acetaminophen (AA4h and AA24h groups); and MESNA, at a dose of 150 mg kg(-1) after acetaminophen injection (AA4h-MES and AA24h-MES groups). The MESNA injection was repeated once more 12 h after the first injection in the AA24h-MES group. Blood urea nitrogen, serum creatinine, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in blood and glutathione (GSH) and malondialdehyde (MDA) levels, myeloperoxidase (MPO) activity and collagen contents in liver and kidney tissues were measured. Tissues also were examined microscopically. Blood urea nitrogen and serum creatinine, which were increased significantly (P < 0.001) following acetaminophen treatment were decreased significantly (P < 0.05-0.001) after treatment with MESNA. The ALT and AST levels were also increased significantly (P < 0.001) after acetaminophen treatment but were not reduced with MESNA. Acetaminophen treatment caused a significant (P < 0.05-0.001) decrease in GSH levels whereas MDA levels and MPO activity were increased in both tissues. These changes were reversed by MESNA treatment. Collagen contents of the liver and kidney tissues were increased by acetaminophen treatment (P < 0.001) and reversed back to the control levels with MESNA. Our results imply that acetaminophen causes oxidative damage in hepatic and renal tissues and that MESNA, via its antioxidant effects, protects these tissues. Therefore, its therapeutic role as a 'tissue injury-limiting agent' must be elucidated further in drug-induced oxidative damage.

Comparative toxicity of ifosfamide metabolites and protective effect of mesna and amifostine in cultured renal tubule cells

Renal injury is a common side effect of the chemotherapeutic agent ifosfamide. Current evidence suggests that the ifosfamide metabolite chloroacetaldehyde contributes to this nephrotoxicity. The present study examined the effects of chloroacetaldehyde and acrolein, another ifosfamide metabolite, on rabbit proximal renal tubule cells in primary culture. The ability of the uroprotectant medications sodium 2-mercaptoethanesulfonate (mesna) and amifostine to prevent chloroacetaldehyde- and acrolein-induced renal cell injury was also assessed. Chloroacetaldehyde and acrolein (25-200 M) produced dose-dependent declines in neutral red dye uptake, glucose transport and glutathione content. Chloroacetaldehyde was a more potent toxin than acrolein. Pretreatment of cells with the glutathione-depleting agent buthionine sulfoximine enhanced the toxicity of both chloroacetaldehyde and acrolein while co-administration of mesna or amifostine prevented metabolite toxicity. These results support the hypothesis that chloroacetaldehyde is responsible for ifosfamide-induced nephrotoxicity. The protective effect of mesna and amifostine in vitro contrasts with clinical experience showing that these medications do not eliminate ifosfamide nephrotoxicity.

Enhancement of cytotoxicity of hydrogen peroxide by hyperthermia in chinese hamster ovary cells: role of antioxidant defenses

Regional hyperthermia has potential for human cancer treatment, particularly in combination with systemic chemotherapy or radiotherapy. The mechanisms involved in heat-induced cell killing are currently unknown. Hyperthermia may increase oxidative stress in cells, and thus, oxidative stress could have a role in the mechanism of cell death. We use hydrogen peroxide as a model oxidant to improve understanding of interactions between heat and oxidative stress. Heat increased cytotoxicity of hydrogen peroxide in Chinese hamster ovary cells. Altered levels of cellular antioxidants should create an imbalance between prooxidant and antioxidant systems, thus modifying cytotoxic responses to heat and to oxidants. We determine the involvement of the two cellular antioxidant defenses against peroxides, catalase and the glutathione redox cycle, in cellular sensitivity to heat, to hydrogen peroxide, and to heat combined with the oxidant. Defense systems were either inhibited or increased. For inhibition studies, intracellular glutathione was diminished to less than 15% of its initial level by treatment with L-buthionine sulfoximine (1 mM, 24 h). Inhibition of catalase was achieved with 3-amino-1,2,4-triazole (20 mM, 2 h), which caused a 80% decrease in endogenous enzyme activity. To increase antioxidants, cells were pretreated with the thiol-containing reducing agents, N-acetyl-L-cysteine, 2-oxo-4-thiazolidine carboxylate, and 2-mercaptoethane sulfonate. These compounds increased intracellular glutathione levels by 30%. Catalase activity was increased by addition of exogenous enzyme to cells. We show that levels of glutathione and catalase affect cellular cytotoxic responses to heat and hydrogen peroxide, either used separately or in combination. These findings are relevant to mechanisms of cell killing at elevated temperatures and suggest the involvement of oxidative stress.

BNP7787, a novel protector against platinum-related toxicities, does not affect the efficacy of cisplatin or carboplatin in human tumour xenografts

BNP7787 (2',2'-dithio-bis-ethane sulphonate sodium), a water-soluble disulphide, is chemically and mechanistically different from other sulphur-containing chemoprotective agents. Presently, BNP7787 is under investigation for its protective properties with regard to the side-effects of platinum compounds. In this study, we evaluated BNP7787, mesna and amifostine for their effects on the antitumour activity of platinum compounds. Continuous exposure to BNP7787 did not affect the antiproliferative effects of cisplatin or carboplatin, but the efficacy of both compounds was reduced in the presence of mesna in vitro in two human ovarian cancer cell lines. BNP7787 or amifostine combined with cisplatin or carboplatin given in standard schedules for the treatment of nude mice bearing well-established OVCAR-3 xenografts did not interfere with platinum-induced inhibition of tumour growth. Of interest, BNP7787 or amifostine co-administered with carboplatin was significantly more effective than carboplatin alone (P<0.01). In the presence of amifostine, doses of cisplatin and carboplatin could be safely increased by factors of 1.6 and 1.5, respectively. Unlike in a previous study of BNP7787 in tumour-bearing rats, BNP7787 did not protect against additional weight loss following treatment with higher doses of cisplatin in OVCAR-3-bearing mice. Pharmacokinetics of (mixed) disulphides including BNP7787 and extractable mesna in deproteinised plasma revealed a rapid disappearance of BNP7787 and an AUC(5-60) value of mesna 9-fold lower than that calculated after an equivalent dose of mesna by weight. We can conclude that BNP7787 does not interfere with the antitumour activity of platinum compounds in vitro and in vivo. Clinical trials are underway to evaluate the protection of normal tissues by BNP7787 when combined with cisplatin.

Protective Effect of MESNA (2-Mercaptoethane Sulfonate) Against Hepatic Ischemia/Reperfusion Injury in Rats

PURPOSE

Reoxygenation of ischemic tissue generates various reactive oxygen metabolites (ROMs), which have a deleterious effect on various cellular functions. We evaluated the possible protective effect of 2-mercaptoethane sulfonate (MESNA) on hepatic ischemia/reperfusion (I/R) injury.

METHODS

Wistar albino rats were subjected to 45-min hepatic ischemia, followed by 60-min reperfusion. 2-Mercaptoethane sulfonate, 150 mg/kg, or saline was given intraperitoneally (i.p.) twice, 15 min before ischemia and immediately before reperfusioin. We measured serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels to assess liver function. Liver tissue samples were taken to measure the levels of malondialdehyde (MDA), an end-product of lipid peroxidation; glutathione (GSH), a key antioxidant; and myeloperoxidase (MPO) activity, as an indirect index of neutrophil infiltration. We also measured hepatic collagen content, as a fibrosis marker.

RESULTS

Plasma ALT and AST levels were higher in the I/R group than in the control group, but this increase was significantly decreased by MESNA treatment. Hepatic GSH levels, which were significantly depressed by I/R, increased back to the control levels in the MESNA-treated I/R group. Increases in tissue MDA levels and MPO activity caused by I/R injury decreased back to the control levels after MESNA treatment. Similarly, the increased hepatic collagen content in the I/R group decreased to the level of the control group after MESNA treatment.

CONCLUSION

The fact that MESNA alleviated I/R-induced injury of the liver and improved hepatic structure and function suggests that its antioxidant and oxidant scavenging properties may be of therapeutic value in protecting the liver against oxidative injury caused by I/R.

The effect of sodium 2-mercapto-ethane sulphonate and hypertonic saline aerosols on bronchial clearance in chronic bronchitis

1 The efficacy of a mucolytic agent, 2-mercapto-ethane sulphonate, administered in the form of an aerosol was evaluated in a group of eleven patients with chronic bronchitis in a controlled, double-blind, crossover study. 2 Saline aerosol isotonic (1.21M, 7.1%) to the drug was used as a placebo. 3 Approximately 1 ml drug/placebo was inhaled by the patients twice a day for 3 days and a final dose was given on the mornings of the drug/placebo trial runs. 4 There was no improvement in this group of patients in lung function or subjective well being attributable to the drug. 5 The viscosity of sputum, dry macromolecular weight and N-acetyl neuraminic acid/fucose ratio remained unaltered throughout the study. 6 An enhancement of tracheobronchial clearance was obtained following the administration of either placebo (31%) or drug aerosols (24%) Statistical significance (P less than 0.01) was only achieved for the placebo and was attributed to an increase in sputum volume.

Prophylaxis with mesna prevents oxidative stress induced by ischemia reperfusion in the intestine via inhibition of nuclear factor-kappaB activation

BACKGROUND AND AIM

Mesna (2-mercaptoethane-sulfonate) has been shown to attenuate oxidative injury induced by ischemia reperfusion (I/R) in the kidneys, the liver, and the intestine; however, its mechanism of action has not been fully elucidated. We sought to determine a prophylactic administration schedule of mesna that would confer optimal antioxidant protection on the intestinal mucosa following I/R and to investigate whether mesna's action is mediated via inhibition of nuclear factor-kappaB (NF-kappaB) activity.

METHODS

Wistar rats were subjected to one of the following: (a) induction of 30 min ischemia followed by 60 min reperfusion (I30/R60) of the intestine, (b) pretreatment with intraperitoneal or oral mesna at various time- and dose- administration schedules plus I30/R60, (c) sham operation, (d) no operation (controls), or (e) oral mesna alone. At the end of the reperfusion period or at various time points after mesna alone administration, the oxidative state of the intestinal mucosa was assessed in terms of glutathione to glutathione disulfide ratio, malondialdehyde concentration, and superoxide dismutase activity. In addition, NF-kappaB activity in the intestinal mucosa was assessed immunohistochemically in the oral mesna plus I/R and in the oral mesna alone groups.

RESULTS

Sham operation caused mild stress, while I/R caused substantial oxidative stress in the intestinal mucosa. Mesna pretreatment had an antioxidant effect which varied from attenuation to prevention of oxidative stress. Over the two routes of administration, the oral proved to be more effective and had a time- and dose- dependent effect. The antioxidant action of mesna was not related to enhancement of the intestinal mucosa oxidative state. Furthermore, I/R induced NF-kappaB activation in the intestinal mucosa which was inhibited by mesna pretreatment. In the absence of oxidative damage, mesna led to downregulation of activated NF-kappaB.

CONCLUSIONS

Prophylaxis with mesna prevents oxidative stress induced by I/R in the intestine via inhibition of NF-kappaB activation.