Hydrogen peroxide signaling via its transformation to a stereospecific alkyl hydroperoxide that escapes reductive inactivation

Abstract

During systemic inflammation, indoleamine 2,3-dioxygenase 1 (IDO1) becomes expressed in endothelial cells where it uses hydrogen peroxide (H2O2) to oxidize L-tryptophan to the tricyclic hydroperoxide, cis-WOOH, that then relaxes arteries via oxidation of protein kinase G 1α. Here we show that arterial glutathione peroxidases and peroxiredoxins that rapidly eliminate H2O2, have little impact on relaxation of IDO1-expressing arteries, and that purified IDO1 forms cis-WOOH in the presence of peroxiredoxin 2. cis-WOOH oxidizes protein thiols in a selective and stereospecific manner. Compared with its epimer trans-WOOH and H2O2, cis-WOOH reacts slower with the major arterial forms of glutathione peroxidases and peroxiredoxins while it reacts more readily with its target, protein kinase G 1α. Our results indicate a paradigm of redox signaling by H2O2 via its enzymatic conversion to an amino acid-derived hydroperoxide that ‘escapes’ effective reductive inactivation to engage in selective oxidative activation of key target proteins.

How abundant are superoxide and hydrogen peroxide in the vasculature lumen, how far can they reach?

“…Because Prdx2 reduces most of the H 2 O 2 in human erythrocytes [ 23 , 65 , 71 ], H 2 O 2 influx rates in excess of ≈2 μM s −1 — corresponding to ≈80 nM plasma H 2 O 2 — should extensively oxidize this protein. However, Prdx2 is modestly oxidized in erythrocytes, even under lipopolysaccharide-induced endotoxemia, which strongly stimulates H 2 O 2 production by circulating phagocytes [ 72 , 73 ]. Therefore, H 2 O 2 in blood plasma does not reach the 100 nM range systemically.…”

Macrophages: shapes and functions

“…The formation of the active NADPH oxidase leads to an increase in oxygen consumption, which is referred to as “oxidative burst”. This creates superoxide anion radical ( ) in the lumen of the phagolysosome, which is converted into H 2 O 2 by superoxide dismutase (SOD) [ 59 ]. Further reactions lead to the formation of toxic ROS, including and from H 2 O 2 .…”

Exploring functional and structural features of chemically related natural prenylated hydroquinone and benzoic acid from Piper crassinervium (Piperaceae) on bacterial peroxiredoxin inhibition

“…We expressed and purified the HsPrx2 and used the heterologous Trx system from S. cerevisiae (ScTrx1 and ScTrxR1) (S7E-S7G Fig) to perform the peroxidase activity assays by NADPH oxidation assay, as described previously by Truzzi and coworkers [35]. The need for the heterologous yeast system lies in the fact that human TrxR is a seleno protein able to decompose hydroperoxides [47,48], and the use of the human Trx system would make the results unreliable. The NADPH oxidation assay was performed using the same experimental conditions applied to the Prx bacterial isoforms, and the results revealed that compound C2 was not able to inhibit the human isoform HsPrx efficiently, since only a very slight decrease in peroxidase activity was detected (Fig 5A , Table 3).…”