Physiological levels of folic acid reveal purine alterations in Lesch-Nyhan disease

Abstract

Lesch-Nyhan disease (LND), caused by a deficient salvage purine pathway, is characterized by severe neurological manifestations and uric acid overproduction. However, uric acid is not responsible for brain dysfunction, and it has been suggested that purine nucleotide depletion, or accumulation of other toxic purine intermediates, could be more relevant. Here we show that purine alterations in LND fibroblasts depend on the level of folic acid in the culture media. Thus, physiological levels of folic acid induce accumulation of 5-aminoimidazole-4-carboxamide riboside 5′-monophosphate (ZMP), an intermediary of de novo purine biosynthetic pathway, and depletion of ATP. Additionally, Z-nucleotide derivatives (AICAr, AICA) are detected at high levels in the urine of patients with LND and its variants (hypoxanthine-guanine phosphoribosyltransferase [HGprt]-related neurological dysfunction and HGprt-related hyperuricemia), and the ratio of AICAr/AICA is significantly increased in patients with neurological problems (LND and HGprt-related neurological dysfunction). Moreover, AICAr is present in the cerebrospinal fluid of patients with LND, but not in control individuals. We hypothesize that purine alterations detected in LND fibroblasts may also occur in the brain of patients with LND.

Folic Acid Protects against Hyperuricemia in C57BL/6J Mice via Ameliorating Gut–Kidney Axis Dysfunction

“…Of note, PICRUSt analysis also revealed that folic acid reversed the disrupted purine metabolism in HUA mice. Accordingly, it was speculated that folic acid treatment affected the abundance of Lactobacillus by interfering with the utilization of purine . On the contrary, folic acid increased the relative abundance of Lactococcus and Muribaculaceae bacteria, which proved to be involved in the improvement of intestinal barrier function. , Generally, ecological imbalance in the intestinal flora also induces fluctuations in metabolites such as SCFAs, which provide a beneficial systematic physiological effect on the host health .…”

AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review

“…The Lesch-Nyhan results from a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), so that the activity of the salvage pathway is diminished and the de novo pathway of purine nucleotide synthesis accelerated, leading to an accumulation of ZMP or AICAR [ 96 ]. Recent studies reported an increase in the levels of AICAr, which normally arises from dephosphorylation of ZMP, in urine and cerebrospinal fluid of patients with deficiency of HGPRT [ 97 ], suggesting that the accumulation of ZMP may be the cause of neurological abnormalities, similar to the toxicity of ZMP accumulation in yeast [ 98 ]. Yeast is a good experimental system to study the effects of AICAr that are AMPK-independent as the yeast AMPK orthologue SNF1 is activated by ADP rather than AMP, and genes strongly regulated by Snf1p are not identical to AICAr-regulated transcription.…”

HGprt deficiency disrupts dopaminergic circuit development in a genetic mouse model of Lesch–Nyhan disease

“…However, this could not be confirmed in multiple patient-derived HGprt-deficient cell types in culture [ 64 ] or in HGprt-deficient knockout mice [ 65 ] for a long time. Only recently it has been reported that fibroblasts from LND patients do show ATP depletion and accumulation of 5-aminoimidazole-4-carboxamide riboside 5′-monophosphate (ZMP, an intermediary of the de novo purine biosynthetic pathway) when the culture medium has physiological levels of folic acid instead of typically artificially high levels as commonly used in cell studies [ 66 ]. The presence of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAr, a ZMP derivative) in urine and cerebrospinal fluid of LND patients, but not in control individuals [ 66 ], as well as an increased AICAr content of HGprt deficient mouse brains compared to controls [ 67 ] suggest that similar metabolic aberrations may occur in both humans and mice in vivo.…”

“…A more specific mechanism could be that increased AICAr alters sonic hedgehog (SHH) and Wnt/β-catenin pathway gene expression, as has been shown in human embryonic carcinoma cell line NT2/D1 during neural differentiation [ 69 ], thereby providing a mechanistic connection between the purinergic derangement due to HGprt dysfunction, the irregularities in RG-L morphology and subsequent abnormal proliferation and migration of DA progenitors as discussed above. Additional studies are required to establish the exact HGprt-dependent neurodevelopmental mechanism that causes brain dysfunction in LND, as well as to investigate the possible therapeutic effect of folic acid to correct the purinergic abnormalities observed in HGprt-deficient cell models [ 66 ].…”

“…Future studies should therefore focus on the potential reversibility of the early aberrations of dopaminergic maldevelopment, as well as the timing of such intervention, e.g. by gene therapy to prevent the dopaminergic midbrain maldevelopment demonstrated here, by administering levodopa very early before symptoms emerge to prevent unfavorable neuroplastic processes, or perhaps by administering supplements such as folic acid that may prevent pathogenic purinergic metabolic derangements [ 66 ].…”