Insights into the mechanisms of ifosfamide encephalopathy: drug metabolites have agonistic effects on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors and induce cellular acidification in mouse cortical neurons.
ABSTRACT Therapeutic value of the alkylating agent ifosfamide has been limited by major side effects including encephalopathy. Although the underlying biochemical processes of the neurotoxic side effects are still unclear, they could be attributed to metabolites rather than to ifosfamide itself. In the present study, the effects of selected ifosfamide metabolites on indices of neuronal activity have been investigated, in particular for S-carboxymethylcysteine (SCMC) and thiodiglycolic acid (TDGA). Because of structural similarities of SCMC with glutamate, the Ca(2+)(i) response of single mouse cortical neurons to SCMC and TDGA was investigated. SCMC, but not TDGA, evoked a robust increase in Ca(2+)(i) concentration that could be abolished by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), but only partly diminished by the N-methyl-D-aspartate receptor antagonist 10,11-dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK=801). Cyclothiazide (CYZ), used to prevent AMPA/kainate receptor desensitization, potentiated the response to SCMC. Because activation of AMPA/kainate receptors is known to induce proton influx, the intracellular pH (pH(i)) response to SCMC was investigated. SCMC caused a concentration-dependent acidification that was amplified by CYZ. Since H(+)/monocarboxylate transporter (MCT) activity leads to similar cellular acidification, we tested its potential involvement in the pH(i) response. Application of the lactate transport inhibitor quercetin diminished the pH(i) response to SCMC and TDGA by 43 and 51%, respectively, indicating that these compounds may be substrates of MCTs. Taken together, this study indicates that hitherto apparently inert ifosfamide metabolites, in particular SCMC, activate AMPA/kainate receptors and induce cellular acidification. Both processes could provide the biochemical basis of the observed ifosfamide-associated encephalopathy.
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ABSTRACT: The oxazaphosphorines (cyclophosphamide, ifosfamide and trofosfamide) are widely used in clinical practice for their antitumor and immunomodulatory activities. However, their use is associated with toxicities. The metabolism of oxazaphosphorines involves cytochrome P450 biotransformations, leading to highly reactive metabolites such as acrolein and chloroacetaldehyde responsible for urotoxicity, neurotoxicity and nephrotoxicity. While the mechanisms behind these toxicities remain under investigation, some advances have been made, as exemplified by the use of mesna to limit acrolein related urotoxicity. This review highlights potential strategies for limiting side effects commonly associated with the oxazaphosphorine drugs, through pharmacological or medicinal chemistry-based approaches. The readers will gain a comprehensive review of these approaches to treatment in terms of: i) pharmacology: use of antidotes and modification of metabolism through inhibition/induction of CYP enzymes or use of gene therapy; and ii) medicinal chemistry: the design of new drugs to target cancer cells and avoid CYP biotransformation with pre-activated prodrugs or with side-chain substituted analogues. An increased knowledge of oxazaphosphorines' metabolism and toxicity may allow the development of new anticancer drugs combined with drug delivery systems to circumvent drug toxicity, providing increased tumoral specificity and greater anticancer activity.Expert Opinion on Drug Metabolism & Toxicology 05/2010; 6(8):919-38. · 2.94 Impact Factor
Article: Neurological toxicity of ifosfamide.[Show abstract] [Hide abstract]
ABSTRACT: Ifosfamide is an alkylating agent with well-demonstrated efficacy against a large number of malignant diseases. With cyclophosphamide it shares a toxicity profile characterized by myelosuppression and urotoxicity, but ifosfamide has additionally disclosed adverse neurological effects. Ifosfamide-related central nervous system toxicity is characterized by metabolic encephalopathy of varying severity. Symptoms have been reported in 5-30% of all patients treated with ifosfamide. The mechanism of ifosfamide-related central nervous system toxicity has not been fully elucidated, although the symptoms have most often been noted when the drug is given at high doses or administered orally. The neurotoxicity is generally self-limiting and reversible between 48 and 72 h after discontinuation of ifosfamide, although fatal sequelae have been reported. Therapeutic options are now available.Oncology 02/2003; 65 Suppl 2:11-6. · 2.17 Impact Factor
- Current Organic Chemistry 09/2011; 15(17):3029-3042. · 3.04 Impact Factor