Metabolomic analyses of body fluids after subchronic manganese inhalation in rhesus monkeys.

Neurotoxicity is linked with high-dose manganese inhalation. There are few biomarkers that correlate with manganese exposure. Blood manganese concentrations depend upon the magnitude and duration of the manganese exposure and inconsistently reflect manganese exposure concentrations. The objective of this study was to search for novel biomarkers of manganese exposure in the urine and blood obtained from rhesus monkeys following subchronic manganese sulfate (MnSO(4)) inhalation. Liquid chromatography-mass spectrometry was used to identify putative biomarkers. Juvenile rhesus monkeys were exposed 5 days/week to airborne MnSO(4) at 0, 0.06, 0.3, or 1.5 mg Mn/m(3) for 65 exposure days or 1.5 mg Mn/m(3) for 15 or 33 days. Monkeys exposed to MnSO(4) at >or= 0.06 mg Mn/m(3) developed increased brain manganese concentrations. A total of 1097 parent peaks were identified in whole blood and 2462 peaks in urine. Principal component analysis was performed on a subset of 113 peaks that were found to be significantly changed following subchronic manganese exposure. Using the Nearest Centroid analysis, the subset of 113 significantly perturbed components predicted globus pallidus manganese concentrations with 72.9% accuracy for all subchronically exposed monkeys. Using the five confirmed components, the prediction rate for high brain manganese levels remained > 70%. Three of the five identified components, guanosine, disaccharides, and phenylpyruvate, were significantly correlated with brain manganese levels. In all, 27 metabolites with statistically significant expression differences were structurally confirmed by MS-MS methods. Biochemical changes identified in manganese-exposed monkeys included endpoints relate to oxidative stress (e.g., oxidized glutathione) and neurotransmission (aminobutyrate, glutamine, phenylalanine).

Relative efficacy of chelating agents on excretion and tissue distribution of manganese in mice.

The effect of repeated parenteral administration of a number of structurally diverse chelating agents on the excretion and tissue distribution of manganese was assessed in mice following 4 weeks of manganese exposure. Males Swiss mice received s.c. injections of manganese(II) chloride tetrahydrate (8.9 mg Mn kg-1 body wt.) for 4 weeks (5 days per week). After the end of this exposure period, cyclohexanediaminetetraacetic acid (CDTA), ethyleneglycol-bis-(beta-aminoethylether)-N,N-tetraacetic acid (EGTA), N-(2-hydroxyethyl)ethylenediamine triacetic acid (HEDTA), isonicotinyl hydrazine (INH), L-dopa, sodium 4.5-dihydroxy-1.3-benzenedisulphonate (Tiron), p-aminosalicylic acid (PAS) or 0.9% saline (control group) were given i.p. for five consecutive days. The doses of the chelators were approximately equal to one-eighth of their respective LD50 values. Urine and faeces were daily collected for 5 days. Twenty-four hours after the final chelator injection, mice were killed and manganese concentrations were determined in various tissues. Although CDTA, EGTA and HEDTA significantly enhanced the elimination of manganese into urine, none of the chelators increased faecal excretion. Tissue concentrations of manganese were significantly reduced only by CDTA. According to these results, among the compounds tested only CDTA would mobilize effectively manganese in manganese-loaded mice.