Tag: inducible nitric oxide synthase

Dysregulation of tetrahydrobiopterin metabolism in myalgic encephalomyelitis/chronic fatigue syndrome by pentose phosphate pathway

Abstract:

Background: Tetrahydrobiopterin (BH4) and its oxidized derivative dihydrobiopterin (BH2) were found to be strongly elevated in ME/CFS patients with orthostatic intolerance (ME + OI).

Objective: However, the molecular mechanism of biopterin biogenesis is poorly understood in ME + OI subjects. Here, we report that the activation of the non-oxidative pentose phosphate pathway (PPP) plays a critical role in the biogenesis of biopterins (BH4 and BH2) in ME + OI subjects.

Research design and results: Microarray-based gene screening followed by real-time PCR-based validation, ELISA assay, and finally enzyme kinetic studies of glucose-6-phosphate dehydrogenase (G6PDH), transaldolase (TALDO1), and transketolase (TK) enzymes revealed that the augmentation of anaerobic PPP is critical in the regulations of biopterins. To further investigate, we devised a novel cell culture strategy to induce non-oxidative PPP by treating human microglial cells with ribose-5-phosphate (R5P) under a hypoxic condition of 85%N2/10%CO2/5%O2 followed by the analysis of biopterin metabolism via ELISA, immunoblot, and dual immunocytochemical analyses. Moreover, the siRNA knocking down of the taldo1 gene strongly inhibited the bioavailability of phosphoribosyl pyrophosphate (PRPP), reduced the expressions of purine biosynthetic enzymes, attenuated GTP cyclohydrolase 1 (GTPCH1), and suppressed subsequent production of BH4 and its metabolic conversion to BH2 in R5P-treated and hypoxia-induced C20 human microglia cells. These results confirmed that the activation of non-oxidative PPP is indeed required for the upregulation of both BH4 and BH2 via the purine biosynthetic pathway. To test the functional role of ME + OI plasma-derived biopterins, exogenously added plasma samples of ME + OI plasma with high BH4 upregulated inducible nitric oxide synthase (iNOS) and nitric oxide (NO) in human microglial cells indicating that the non-oxidative PPP-induced-biopterins could stimulate inflammatory response in ME + OI patients.

Conclusion: Taken together, our current research highlights that the induction of non-oxidative PPP regulates the biogenesis of biopterins contributing to ME/CFS pathogenesis.

Source: Bulbule S, Gottschalk CG, Drosen ME, Peterson D, Arnold LA, Roy A. Dysregulation of tetrahydrobiopterin metabolism in myalgic encephalomyelitis/chronic fatigue syndrome by pentose phosphate pathway. J Cent Nerv Syst Dis. 2024 Aug 19;16:11795735241271675. doi: 10.1177/11795735241271675. PMID: 39161795; PMCID: PMC11331476. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11331476/ (Full text)

Role of polymorphisms of inducible nitric oxide synthase and endothelial nitric oxide synthase in idiopathic environmental intolerances

Abstract:

Oxidative stress and inflammation play a pathogenetic role in idiopathic environmental intolerances (IEI), namely, multiple chemical sensitivity (MCS), fibromyalgia (FM), and chronic fatigue syndrome (CFS). Given the reported association of nitric oxide synthase (NOS) gene polymorphisms with inflammatory disorders, we aimed to investigate the distribution of NOS2A -2.5 kb (CCTTT) n as well as Ser608Leu and NOS3 -786T>C variants and their correlation with nitrite/nitrate levels, in a study cohort including 170 MCS, 108 suspected MCS (SMCS), 89 FM/CFS, and 196 healthy subjects.

Patients and controls had similar distributions of NOS2A Ser608Leu and NOS3 -786T>C polymorphisms. Interestingly, the NOS3 -786TT genotype was associated with increased nitrite/nitrate levels only in IEI patients. We also found that the NOS2A -2.5 kb (CCTTT)11 allele represents a genetic determinant for FM/CFS, and the (CCTTT)16 allele discriminates MCS from SMCS patients. Instead, the (CCTTT)8 allele reduces by three-, six-, and tenfold, respectively, the risk for MCS, SMCS, and FM/CFS. Moreover, a short number of (CCTTT) repeats is associated with higher concentrations of nitrites/nitrates. Here, we first demonstrate that NOS3 -786T>C variant affects nitrite/nitrate levels in IEI patients and that screening for NOS2A -2.5 kb (CCTTT) n polymorphism may be useful for differential diagnosis of various IEI.

 

Source: De Luca C, Gugliandolo A, Calabrò C, Currò M, Ientile R, Raskovic D, Korkina L, Caccamo D. Role of polymorphisms of inducible nitric oxide synthase and endothelial nitric oxide synthase in idiopathic environmental intolerances. Mediators Inflamm. 2015;2015:245308. doi: 10.1155/2015/245308. Epub 2015 Mar 24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387900/ (Full article)