Inflammation-induced reactive nitrogen species cause proteasomal degradation of dimeric peroxiredoxin-1 in a mouse macrophage cell line

Abstract

Peroxiredoxin 1 (PRDX1) is an antioxidant enzyme that, when secreted, can act as a proinflammatory signal. Here we studied the regulation of intracellular PRDX1 by lipopolysaccharide (LPS) and interferon-gamma (IFNγ) in the RAW 264.7 mouse macrophage cell line. While LPS or IFNγ alone did not affect PRDX1 protein levels, their combination led to an almost complete loss of the PRDX1 dimer. This was likely mediated by the increased production of nitric oxide (NO) as it was reversed by the NO synthase inhibitor ʟ-Nmethylarginine (ʟ-NMMA), while a NO-releasing agent decreased PRDX1 levels. Inhibition of the proteasome with MG132 also prevented the loss of the PRDX1 dimer, suggesting that the decrease is due to a NO-activated proteasomal degradation pathway.By contrast with the decrease in protein levels, LPS increased PRDX1 mRNA and this effect was amplified by IFNγ. Two other Nrf2 target genes, thioredoxin reductase (TXNRD1) and heme oxygenase (HMOX1), were also induced by LPS but IFNγ did not increase their expression further. This study shows that inflammation differentially regulates PRDX1 at the levels of protein stability and gene expression, and that NO plays a key role in this mechanism.

Release of redox enzymes and micro-RNAs in extracellular vesicles, during infection and inflammation

“…Interestingly, combined treatment with IFN-gamma and LPS further reduces PRDX1 intracellular levels due to the activation of proteasomal degradation [46]. The loss of a peroxide-detoxifying enzymes due to the combination of increased degradation and vesicular release could make the intracellular environment more oxidizing (Figure 3), perphaps facilitating the killing of intracellular pathogens [46].…”