Effect of hypoxia on purine metabolism of human skeletal muscle cells

Abstract

Mammals experience some degree of hypoxia during their lifetime. In response to hypoxic challenge, mammalian cells orchestrate specific responses at transcriptional and posttranslational level which lead to changes in the purine metabolites in order to cope with threatening conditions. The aim of this study was to evaluate the response of the enzymes involved in the purine metabolism of human muscle cells to hypoxic conditions. Muscle cells in culture were exposed to hypoxia and the enzymatic activity of inosine monophosphate dehydrogenase (IMPDH), xanthine oxidase (XO), purine nucleoside phosphorylase (PNP) and hypoxanthine guanine phosphoribosyl transferase (HGPRT) as well as their transcript expression were quantified under normoxic and hypoxic conditions. Purine metabolite (hypoxanthine (HX), xanthine (X), uric acid (UA), inosine monophosphate (IMP), inosine, nicotinamide adenine dinucleotide (NAD+), adenosine, adenosine monophosphate (AMP), adenosine diphosphate (ADP), adenosine triphosphate (ATP), guanosine diphosphate (GDP) and guanosine triphosphate (GTP)) concentrations were also quantified. Significant reduction of IMPDH activity and HX and IMP concentrations (p < 0.05) were observed after hypoxia, suggesting a decrease of de novo synthesis of purines. After hypoxia a global reduction of transcripts was observed, suggesting a reduction of the metabolic machinery of purine metabolism to new steady states that balance ATP demand and ATP supply pathways.