Relationship between oral mucositis and high-dose methotrexate therapy in pediatric acute lymphoblastic leukemia.

OBJECTIVE: Oral mucositis is a major toxicity in the high-dose methotrexate (HD-MTX) treatment for children with acute lymphoblastic leukemia (ALL). The first aim of this study was to evaluate the relationship between the MTX serum concentration and occurrence of oral mucositis in pediatric ALL patients. The second aim was to clarify the relationship between MTX exposure and epidermal keratinocyte cell injury using an in vitro study. METHODS: 49 patients were treated according to the Japan Association of Childhood Leukemia Study (JACLS) ALL-HR02 protocol. This protocol involves HD-MTX treatment (3 g/m2 for 24-h i.v. infusion). The MTX serum concentrations were measured by a fluorescence polarization immunoassay. The relationship between oral mucositis and MTX serum concentrations 48 and 72 h after administration was determined. The cell toxicity of MTX for human epidermal keratinocytes was analyzed by using a cell viability assay (WST-1 assay). In addition, pharmacokinetic evaluation for clearance, AUC extrapolated from 48 h to infinity (AUC48h-inf) and elimination half-life (t1/2b) were done using the 1-compartmental models. RESULTS: Oral mucositis occurred in 24 patients (49.0%), in whom 20 patients (83.3% in oral mucositis group) showed WHO severity Grade 1 or 2. Only 4 patients (16.7% in oral mucositis group) showed Grade 3 severity. 22 patients (44.9%) had oral mucositis in the group with a concentration under 10-6 M 48 h after MTX administration. There was no significant deference among the cell viabilities in the concentrations of 10-6 M, 10-5 M and 10-4 M 48 h after the MTX exposure. However, the cell viability obtained 24 h after the MTX exposure was significantly different from the respective cell viability 48, 72 and 96 h after the MTX exposure. In the group with oral mucositis, the clearance decreased significantly (p = 0.042), and the t1/2b (p = 0.025) and AUC48h- yen (p = 0.025) increased significantly compared with the non-symptom group. CONCLUSIONS: It seems that there is no significant relationship between the serum MTX concentration and oral mucositis. This in vitro study has demonstrated that the cell injury was related to the duration of MTX exposure rather than a high MTX concentration.

Involvement of de novo ceramide synthesis in radiocontrast-induced renal tubular cell injury.

We reported previously that various radiocontrast media cause apoptosis in porcine proximal tubular (LLC-PK(1)) cells, in which reduction in B-cell lymphoma (Bcl)-2 expression and caspase-3 activation are implicated. In the present study, we investigated a role for ceramide in radiocontrast media-induced apoptosis in renal tubular cells. LLC-PK(1) cells were exposed to radiocontrast media for 30 min, followed by incubation for 24 h in normal medium. Cell viability was assessed by 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt assay, while apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling stain. Immunofluorescent stains were performed using antibodies against phosphorylated Akt (pAkt) and cAMP response element binding protein (CREB) (pCREB), and ceramide. The mRNA expression and protein content of Bcl-2 were determined by reverse transcriptase-polymerase chain reaction and enzyme immunoassay, respectively. In vivo model of contrast-induced renal injury was induced in mice with unilateral renal occlusion. The cell injury induced by the nonionic radiocontrast medium ioversol was reversed by inhibiting de novo ceramide synthesis with fumonisin B(1) (FB(1)) and L-cycloserine, but not by suppressing sphingomyelin breakdown with D609. FB(1) reversed ioversol-induced decrease in the immunoreactivities of pAkt and pCREB, reduction in Bcl-2 expression and caspase-3 activation. Like ioversol, C2 ceramide and the Akt inhibitor Src homology-6 induced apoptosis by reducing pAkt and pCREB-like immunoreactivities, lowering Bcl-2 expression and enhancing caspase-3 activity. Indeed, various radiocontrast media, excluding iodixanol which showed the least nephrotoxicity, enhanced ceramide-like immunoreactivity. The role for de novo ceramide synthesis was also shown in the in vivo model of radiocontrast nephropathy. We demonstrated here for the first time that the enhancement of de novo ceramide synthesis contributes to radiocontrast nephropathy.

Contrast medium-induced pulmonary vascular hyperpermeability is aggravated in a rat climacterium model.

UNLABELLED: Tominaga K, Kataoka Y, Sendo T, et al. Contrast medium-induced pulmonary vascular hyperpermeability is aggravated in a rat climacterium model. Invest Radiol 2001;36:131-135. RATIONALE AND OBJECTIVES: To test whether climacterium influences adverse pulmonary reactions to contrast media, the authors investigated the effect of ioxaglate on pulmonary vascular permeability in ovariectomized rats as a climacterium model. METHODS: From 7 days after surgery, ovariectomized rats were treated with estradiol valerate or vehicle once per week for 3 weeks. At 28 days after surgery, ioxaglate, an ionic contrast medium, was intravenously injected at 1.5 mL/min in rats. Pulmonary vascular permeability was evaluated by measuring the amount of Evans blue dye in the lung tissue. RESULTS: Ioxaglate dose-dependently increased pulmonary vascular permeability in sham-operated and ovariectomized rats. Ovariectomized rats showed a 2.6-fold increased aggravation of vascular permeability by ioxaglate 4 g I/kg compared with sham-operated rats. Estradiol valerate (0.2-5.0 mg/kg) dose-dependently blocked ioxaglate-increased vascular permeability in ovariectomized rats. CONCLUSIONS: These findings suggest that climacterium is included, at least in part, in the risk factors for contrast-induced adverse pulmonary reactions, and this risk is lowered by estrogen replacement therapy.

Effects of rifampicin and phenobarbital on the fate of isoniazid and hydrazine in vivo in rats.

After the intraperitoneal (i.p.) administration of isoniazid (INH) to male Wistar rats, the liver and plasma levels of hydrazine (Hz) and acetylhydrazine (AcHz), which are hazardous metabolites of INH and well known as mutagens, carcinogens and hepatotoxins, were determined by gas chromatography-mass spectrometry (GC-MS). The levels of Hz in rifampicin (RMP)- or phenobarbital (PB)-pretreated groups were lower than those in the control group, while the amount of AcHz was scarcely altered. In each of the pretreated groups a pronounced increase in the oxidative elimination rate of Hz was observed. These results are of important toxicological significance in INH therapy with RMP, since an active intermediate of Hz seems to be a hepatotoxin.