Human trisomy 21 fibroblasts rescue methotrexate toxic effect after treatment with 5‐methyl‐tetrahydrofolate and 5‐formyl‐tetrahydrofolate

Abstract

Trisomy 21 causes Down syndrome (DS), the most common human genetic disorder and the leading genetic cause of intellectual disability. The alteration of one‐carbon metabolism was described as the possible metabolic cause of the intellectual disability development in subjects with DS. One of the biochemical pathways involved in the one‐carbon group transfer is the folate cycle. The cytotoxic drug methotrexate (MTX) is a folic acid (FA) analogue which inhibits the activity of dihydrofolate reductase enzyme involved in the one‐carbon metabolic cycle. Trisomy 21 cells are more sensitive to the MTX effect than euploid cells, and in 1986 Jérôme Lejeune and Coll. demonstrated that MTX was twice as toxic in trisomy 21 lymphocytes than in control cells. In the present work, the rescue effect on MTX toxicity mediated by FA and some of its derivatives, tetrahydrofolate (THF), 5‐formyl‐THF, and 5‐methyl‐THF, in both normal and trisomy 21 skin fibroblast cells, was evaluated. A statistically significant rescue effect was obtained by 5‐formyl‐THF, 5‐methyl‐THF, and their combination, administered together with MTX. In conclusion, trisomy 21 fibroblast cell lines showed a good response to the rescue effects of 5‐formyl‐THF and 5‐methyl‐THF on the MTX toxicity almost as normal cell lines.

One-carbon pathway and cognitive skills in children with Down syndrome

“…These results reinforce the idea that DS might be a metabolic disease due to the presence of biochemical alterations of fundamental pathways like the folate cycle, Hcy-Met cycle and Hcy trans-sulfuration 14 . Different studies show how Hcy and vitamin B12 could be involved in cognitive development.…”

The transcriptome profile of human trisomy 21 blood cells

“…The given hypothesis that the one-carbon pathway might be involved in the manifestation of the main symptoms in DS [ 14 ], and the experimental confirmation that T21 lymphocytes are more sensitive to the methotrexate effect than normal control cells [ 35 ] led us to analyse the expression profiles of the main genes encoding for the key enzymes of the one-carbon pathway. Expression values were selected for genes implicated in the one-carbon metabolic process (Gene Ontology, GO:0006730) and the folic acid-containing compound metabolic process (GO:0006760) [ 36 ]. Among 37 genes for which a T21 vs normal control expression ratio was available (derived by expression values detected in at least two samples in both pools), the global mean expression ratio is 1.22 (with a standard deviation of 0.69), and 22 genes are over-expressed and 15 under-expressed (Supplementary Table 5 ).…”

“…There is no GO category directly linked to the one-carbon pathway, probably because the global mean expression ratio of genes involved in it is 1.21 with only a few genes with T21/normal expression ratio ≥1.30 (the chosen cut-off for over-expressed genes in the functional enrichment analysis). However, the over-expression of genes like GART (21q22.1, gene expression ratio=1.58), encoding for phosphoribosylglycinamide formyltransferase, phosphoribosylglycinamide synthetase, phosphoribosylaminoimidazole synthetase and SLC46A1 (17q11.2, gene expression ratio=1.67) and encoding for solute carrier family 46 member 1, and SLC19A1 (21q22.3, gene expression ratio=3.50), encoding for the solute carrier family 19 member 1, provides interesting hints about the hypothesis regarding the alteration of the one-carbon pathway in the manifestation of ID in DS [ 35 , 36 ]. Indeed, the first is a key enzyme of the folic acid cycle necessary to convert tetrahydrofolate (THF) to 10-formyl-THF and 5,10-methenyl-THF to THF; the second is the main carrier of folates and antifolates in the nervous system, and the third is the ubiquitously expressed form of folate carriers [ 36 ].…”

“…However, the over-expression of genes like GART (21q22.1, gene expression ratio=1.58), encoding for phosphoribosylglycinamide formyltransferase, phosphoribosylglycinamide synthetase, phosphoribosylaminoimidazole synthetase and SLC46A1 (17q11.2, gene expression ratio=1.67) and encoding for solute carrier family 46 member 1, and SLC19A1 (21q22.3, gene expression ratio=3.50), encoding for the solute carrier family 19 member 1, provides interesting hints about the hypothesis regarding the alteration of the one-carbon pathway in the manifestation of ID in DS [ 35 , 36 ]. Indeed, the first is a key enzyme of the folic acid cycle necessary to convert tetrahydrofolate (THF) to 10-formyl-THF and 5,10-methenyl-THF to THF; the second is the main carrier of folates and antifolates in the nervous system, and the third is the ubiquitously expressed form of folate carriers [ 36 ]. A recent study [ 50 ] about the transcriptome profile of the whole heart already showed that a coherence at a quantitative level between the transcriptome model and the ratio of gene products found at precise relative amounts in that tissue exists.…”

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“…Recognizing that whole blood folate levels represent a composite measure of folate content in both the plasma and circulating blood cells, predominately made up of RBCs, we measured total folate concentrations in the plasma (Figure 1B) and circulating erythrocytes (RBCs) (Figure 1C). In contrast to whole blood folate levels, median [IQR] plasma folate levels were found to be 13% higher in the children with DS (48 [29,69] 2A) and 21% lower RBC concentrations of 5,10-MeTHF (53 [33,78] vs 67 [36,102] nmol/L, Figure 2B) compared to the control group. However, only RBC concentrations of 5mTHF achieved statistical significance (p=0.0021).…”