Misonidazole neurotoxicity in mice decreased by administration with pyridoxine

Scopoletin Induced Metabolomic Profile Disturbances in Zebrafish Embryos

Scopoletin, a typical example of a coumarin compound, exists in several Artemisia species and other plant genera. However, the systemic metabolic effects induced by scopoletin remain unclear. In the present study, we evaluated the metabolic profiles in scopoletin-exposed zebrafish embryos using UHPLC-Q-Obitrap-HRMS combined with multivariate analysis. Compared with the control group, 33 metabolites in scopoletin group were significantly upregulated, while 27 metabolites were significantly downregulated. Importantly, scopoletin exposure affected metabolites mainly involved in phosphonate and phosphinate metabolism, vitamin B6 metabolism, histidine metabolism, sphingolipid metabolism, and folate biosynthesis. These results suggested that scopoletin exposure to zebrafish embryos exhibited marked metabolic disturbance. This study provides a perspective of metabolic impacts and the underlying mechanism associated with scopoletin exposure.

A Systematic Review of the Benefit of B-Vitamins as a Complementary Treatment in Cancer Patients

B-vitamins act as enzymatic co-factors in immune functions, therefore they are considered to reduce chemotherapy-induced side effects in cancer patients. We conducted a systematic search, screening five electronic databases (Embase, Cochrane, PsychInfo, CINAHL and Medline) to find studies on the effectiveness and potential harm of B-vitamin therapy on cancer patients. Out of the 7465 search results, 11 RCTs about vitamin B6, B12 and B-vitamins in combination were included in this systematic review. A total of 1546 patients with diverse types of cancer were evaluated. Overall, most studies were of acceptable quality and reported consistent results. Studies examining the effectiveness of vitamin B6 reported that there is no significant impact on decreasing the incidence and severity of chemotherapy-induced side effects (e.g., hand-foot syndrome), the necessity of chemotherapy dose-modifications or improving patients' quality of life, tumor response/progression, and overall survival. Two studies reported that vitamin B12 could be effective in the alleviation of symptoms resulting from chemotherapy; it might decrease motor, sensory and pain symptoms of peripheral neuropathy. However, a combination of B vitamins may not reduce the incidence of chemotherapy-induced peripheral neuropathy. All in all, the evidence on B-vitamins in cancer patients is low and supplementation cannot be recommended.

Hypoxia-responsive block copolymer radiosensitizers as anticancer drug nanocarriers for enhanced chemoradiotherapy of bulky solid tumors

Radiosensitizers play an important role in the clinical radiotherapy of hypoxic solid tumors to improve therapeutic efficacy. However, the in vivo performance of clinically used small-molecule radiosensitizers is commonly compromised by low bioavailability in hypoxic tumor regions. Herein, amphiphilic block copolymer radiosensitizers are prepared from clinically approved poly(ethylene glycol)-block-poly(l-glutamic acid) (PEG-b-PLG) and metronidazole (MN) to obtain MN-grafted PEG-b-PLG (PEG-b-P(LG-g-MN)) via condensation reaction, which can self-assemble into core-shell micelles as nanoparticle-formulated radiosensitizers in aqueous solution. The radiosensitizers are demonstrated to possess significantly higher sensitization enhancement ratio (SER) of 2.18 and potent in vivo tumor ablation capability upon exposure to electron beam irradiation compared with clinically used sodium glycididazole (GS) with SER of 1.32. Moreover, after optimizing the ratios of carboxyl and MN groups, PEG-b-P(LG-g-MN) micelles can be used to encapsulate doxorubicin (DOX@HMs) efficiently. Hypoxia-responsive structural transformation of MN into hydrophilic aminoimidazole triggers fast DOX release from DOX@HMs. After intravenous injection of DOX@HMs, potent ablation capability against bulky solid tumors (∼500 mm³) is realized at a low radiation dose (4 Gy) via enhanced chemoradiotherapy. Therefore, the developed novel amphiphilic block copolymer radiosensitizers can be concurrently used as high-efficiency radiosensitizers and hypoxia-responsive DOX nanocarriers for enhanced chemoradiotherapy.

Neurophysiologic studies of patients with Crohn's disease on long-term treatment with metronidazole

Fifty-three patients with Crohn's disease were chosen for this study. They were divided into three groups: the first group (19 patients) was treated with metronidazole and had been receiving the drug for at least 1 year; the second group (13 patients) had previously had the same type of long-term treatment but had been off the drug for at least 3 months before entering the study; the third group (21 patients) had never received treatment with metronidazole. The maximum daily dose of metronidazole used was 800 mg. All patients were examined with a broad set of neurophysiologic investigations devised to reveal signs of peripheral neuropathy. No significant difference was found between the three groups. The conclusion was that a daily dose of metronidazole not exceeding 800 mg is well tolerated by patients with Crohn's disease with regard to objective signs of neurotoxicity. A few patients from all three groups showed a raised perception threshold for changes of temperature in the feet (as compared with the department's normal standard). The results of the test were almost identical in the three groups and thus not connected with the metronidazole treatment. During the study, patients were asked about subjective neurologic symptoms such as tingling and numbness. A few patients from all three groups reported such paresthesias from time to time, but they were of a transient nature, not perpetual, and, in patients taking metronidazole, not aggravated despite continuing treatment with unchanged dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Irradiation of primary thalamic and brainstem tumors in a pediatric population. A 33-year experience

A retrospective analysis of 70 pediatric patients (less than 16 years of age) with histologically proven or presumed primary neoplasms of the thalamus, hypothalamus, and brainstem, treated with combined surgery and postoperative radiotherapy or radiotherapy alone at the Washington University Medical Center from January 1950 through December 1983, is reported. Overall survival for all patients at 5 and 10 years was 34.9% and 32.7%, respectively. Follow-up of the 22 surviving patients ranged from 3.0 to 20.0 years (median, 10.6 years). Statistical analysis of multiple prognostic factors was performed. Prognostic factors found by single variate analysis to significantly influence survival were primary site of disease, extent of surgery, race, cranial nerve paresis at diagnosis, and dose of radiation. Factors evaluated but found to be insignificant were age at diagnosis, duration of symptoms before diagnosis, sex, and volume irradiated. Multivariate analysis revealed that only total radiation dose and race were of prognostic significance.

Comparative distribution of misonidazole and its amine metabolite in female Swiss Webster mice

The distribution of misonidazole and its terminal reduction product 1-(2-amino-1-imidazolyl)-3-methoxy-2-propanol (miso-amine) were compared in female Swiss Webster mice to determine if either misonidazole or miso-amine is distributed to peripheral nerves. Female Swiss Webster mice received a 100 mg/kg (5 microCi/mumole) i.p. dose of either 3H-misonidazole or 3H-miso-amine and the distribution of radioactivity was determined in various tissues including sciatic nerves and other myelinated nerves. Urine from misonidazole treated animals contained both miso-amine and misonidazole (8.4 and 20.4%, respectively, of the total radioactivity in the urine). Misonidazole produced higher initial tissue concentrations of radioactivity than did miso-amine. The relative tissue concentrations of radioactivity produced by misonidazole or miso-amine were similar, although not identical, 48 hours after administration of the drugs. Both sciatic and other myelinated nerves were found to retain radioactivity following the administration of either misonidazole or miso-amine.

Hypoxic cell radiosensitizers: expectations and progress in drug development

When misonidazole (MISO) was introduced into clinical trials there were great expectations that the cure rate of many tumors would be dramatically increased. The lack of efficacy of MISO discouraged further studies with hypoxic cell sensitizers. In recent years superior sensitizers SR 2508 and RO-03-8799 have been introduced into the clinic. SR 2508 is less neurotoxic than MISO, allowing more than three times the total amount of drug to be administered. Furthermore, based on the analysis of a patient's plasma pharmacokinetic profile, neurotoxicity may be largely avoidable. RO-03-8799 is superior in that it produces a higher sensitizer enhancement ratio than MISO for the same administered dose. Unlike with MISO and SR 2508, the dose of RO-03-8799 that can be administered is limited by acute toxicity with no cumulative toxicity having yet been encountered. The lack of overlapping toxicities of RO-03-8799 and SR 2508 may permit their simultaneous use with radiation thereby further increasing the utility of this class of compounds. Study design has improved and the expected clinical benefit from sensitizers has been clarified. Sensitizers, like particle radiation therapy and hyperthermia will, if successful, effect the rate of local tumor control, but cannot improve the cure rate of patients with preexisting metastatic disease. Taking into account the need to optimize reoxygenation, the various reasons for tumor radioresistance other than hypoxia, and the lower oxygen and sensitizer enhancement ratios at 200 cGy per fraction, it is likely that sensitizers will provide some clinical benefit for patients with selected tumor types. Future trials with sensitizers may not only provide clinical benefit but may help answer the question as to the role of hypoxia in clinical radiotherapy.

Pharmacology and toxicology of sensitizers: mechanism studies

Nitroimidazoles are being studied extensively as hypoxic cell radiosensitizers. Besides their ability to selectively sensitize hypoxic cells to radiation, which depends on the parent compound, nitroimidazoles have a variety of other effects in vitro, in vivo and clinically which appear to require reductive metabolism. These other effects include direct cytotoxicity to hypoxic cells, mutagenicity and antimicrobial effects. As a first step to suggesting possible mechanisms for these other biological effects, a summary has been made of the known oxidative and reductive products of the two most widely studied radiosensitizers, metronidazole and misonidazole. Focussing on reductive products, it is clear that a great variety exists which are or may be reactive with biological molecules. Knowledge about the reduction chemistry of nitroimidazoles is new and far from complete. As a second step to suggesting possible mechanisms for these biological effects, it is important to view the problem in terms of the in vivo situation where distribution and sites of metabolism of the drug and its reduction products will be important factors. Variables such as levels of tissue oxygenation and nitroreductase activity will be important to assess. Combining basic information about the reduction chemistry of nitroimidazoles with knowledge about the pharmacology of drugs and their reduced products should allow a better assessment of mechanism of action as well as a better implementation of these drugs clinically.

The effect of vitamin B6 on the neurotoxicity and pharmacology of desmethylmisonidazole and misonidazole: clinical and laboratory studies

The clinical usefulness of misonidazole (MISO) and desmethylmisonidazole (DMM) is severely limited by neurotoxicity. Based on theoretical considerations and on laboratory data suggesting that pyridoxine (PN) decreased MISO toxicity in mice, we attempted to ameliorate the clinical neuropathy of DMM using oral PN. Pharmacokinetic analysis suggested interaction of PN and DMM but no protection against neuropathy was observed. Serial experiments with C3H and BALB/c mice were done using various forms of vitamin B6 (PN, pyridoxal, pyridoxal phosphate) administered orally and i.p. and the nonspecific adsorbing agent activated charcoal. No consistent protection was observed. A slower rate of drug delivery (dose/day) allowed a larger cumulative dose of MISO to be given, a result paradoxical to that seen in the clinic. Dexamethasone did not alter MISO toxicity in mice, contrary to the clinical findings. We conclude that vitamin B6 is not useful in preventing clinical neurotoxicity of MISO or DMM. Furthermore, this mouse model of neurotoxicity assessment has produced results inconsistent with those seen clinically.

The current status of drug development of hypoxic cell radiosensitizers and their potential role in gynecologic oncology

Both laboratory and clinical data suggest that hypoxia contributes to the failure of radiotherapy to achieve local control of bulky gynecologic tumors. As part of a Phase I trial of hypoxic cell radiosensitizers, 19 women at Stanford University with advanced (n = 6) or recurrent (n = 13) pelvic neoplasms were treated with radiotherapy plus desmethylmisonidazole. Complete or partial response occurred in 42% of patients with some patients achieving local control for over 1 year. It is unknown if the sensitizer added to the results of radiotherapy alone. A Phase I trial of a theoretically superior sensitizer, SR-2508, is soon to begin. It is anticipated that the dose-limiting neurotoxicity seen with misonidazole and desmethylmisonidazole will either be eliminated or will occur at a much higher total dose of drug. Many patients with gynecologic tumors could potentially benefit from participation in the new drug trials.