Altered expression of methylenetetrahydrofolate reductase modifies response to methotrexate in mice.

Basak Celtikci, Daniel Leclerc, Andrea K Lawrance, Liyuan Deng, Hana C Friedman, Natalia I Krupenko, Sergey A Krupenko, Stepan Melnyk, S Jill James, Alan C Peterson, Rima Rozen
Author Information
  1. Basak Celtikci: Departments of Human Genetics and Pediatrics, McGill University Health Centre, Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.

Abstract

OBJECTIVE: Folates provide one-carbon units for nucleotide synthesis and methylation reactions. A common polymorphism (677C-->T) in methylenetetrahydrofolate reductase (MTHFR) encodes an enzyme with reduced activity. Response to the antifolate methotrexate (MTX) may be modified in 677TT individuals because MTHFR converts nonmethylated folates, used for thymidine and purine synthesis, to 5-methyltetrahydrofolate, used in homocysteine remethylation to methionine. To study potential interactions between MTHFR activity and MTX, we examined the impact of decreased and increased MTHFR expression on MTX response in mice.
METHODS: Mthfr-deficient (Mthfr and Mthfr) and wild-type (Mthfr) mice were injected with MTX or saline and assessed for hematological parameters (hematocrit, hemoglobin, red, and white blood cell numbers), plasma homocysteine, nephrotoxicity, hepatotoxicity, and splenic 2'-deoxyuridine 5'-triphosphate/2'-deoxythymidine 5'-triphosphate ratios. MTHFR-overexpressing transgenic mice (MTHFR-Tg) were generated, metabolites and folate distributions were measured, and response to MTX was assessed.
RESULTS: MTX-treated Mthfr and Mthfr mice displayed hyperhomocysteinemia and decreased hematocrit, hemoglobin, and red blood cell numbers compared with wild-type animals. Mthfr mice also showed increased nephrotoxicity and hepatotoxicity. MTHFR-Tg mice were generated and confirmed to have increased levels of MTHFR with altered distributions of folate and thiols in a tissue-specific manner. After MTX treatment, MTHFR-Tg mice exhibited the same decreases in hematological parameters as Mthfr-deficient mice, and significantly decreased thymidine synthesis (higher 2'-deoxyuridine 5'-triphosphate/2'-deoxythymidine 5'-triphosphate ratios) compared with wild-type mice, but they were protected from MTX-induced hyperhomocysteinemia.
CONCLUSION: Underexpression and overexpression of Mthfr/MTHFR increase MTX-induced myelosuppression but have distinct effects on plasma homocysteine and nephrotoxicity. Pharmacogenetic analysis of polymorphisms in folate-dependent enzymes may be useful in optimization of MTX therapy.

Grants

  1. NIH DK54388/NIDDK NIH HHS

MeSH Term

Animals
Cells, Cultured
Female
Gene Expression
Homocysteine
Immunosuppression Therapy
Immunosuppressive Agents
Kidney Diseases
Male
Methotrexate
Methylenetetrahydrofolate Reductase (NADPH2)
Mice
Mice, Inbred BALB C
Mice, Inbred C57BL
Mice, Knockout
Models, Biological
Polymorphism, Single Nucleotide

Chemicals

Immunosuppressive Agents
Homocysteine
Methylenetetrahydrofolate Reductase (NADPH2)
Methotrexate

Word Cloud

Created with Highcharts 10.0.0miceMTXMthfrMTHFRsynthesishomocysteinedecreasedincreasedresponsewild-typenephrotoxicityMTHFR-TgmethylenetetrahydrofolatereductaseactivitymethotrexatemayusedthymidineexpressionMthfr-deficientassessedhematologicalparametershematocrithemoglobinredbloodcellnumbersplasmahepatotoxicity2'-deoxyuridine5'-triphosphate/2'-deoxythymidine5'-triphosphateratiosgeneratedfolatedistributionshyperhomocysteinemiacomparedMTX-inducedOBJECTIVE:Folatesprovideone-carbonunitsnucleotidemethylationreactionscommonpolymorphism677C-->TencodesenzymereducedResponseantifolatemodified677TTindividualsconvertsnonmethylatedfolatespurine5-methyltetrahydrofolateremethylationmethioninestudypotentialinteractionsexaminedimpactMETHODS:injectedsalinewhitesplenicMTHFR-overexpressingtransgenicmetabolitesmeasuredRESULTS:MTX-treateddisplayedanimalsalsoshowedconfirmedlevelsalteredthiolstissue-specificmannertreatmentexhibiteddecreasessignificantlyhigherprotectedCONCLUSION:UnderexpressionoverexpressionMthfr/MTHFRincreasemyelosuppressiondistincteffectsPharmacogeneticanalysispolymorphismsfolate-dependentenzymesusefuloptimizationtherapyAlteredmodifies

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