Inhibition of the phospholipase A2 activity of peroxiredoxin 6 prevents lung damage with exposure to hyperoxia

Abstract

Lung injury associated with hyperoxia reflects in part the secondary effects of pulmonary inflammation and the associated production of reactive oxygen species due to activation of NADPH oxidase, type 2 (NOX2). Activation of NOX2 requires the phospholipase A2 (PLA2) activity of peroxiredoxin 6 (Prdx6). Therefore, we evaluated whether blocking Prdx6 PLA2 activity using the inhibitor MJ33 would be protective in a mouse model of acute lung injury resulting from hyperoxic exposure. Mice were treated with an intraperitoneal injection of MJ33 (2.5 nmol/g body weight) at the start of exposure (zero time) and at 48 h during continuous exposure to 100% O2 for 80 h. Treatment with MJ33 reduced the number of neutrophils and the protein content in the fluid obtained by bronchoalveolar lavage, inhibited the increase in lipid peroxidation products in lung tissue, decreased the number of apoptotic cells in the lung, and decreased the perivascular edema associated with the 80 h exposure to hyperoxia. Thus, blocking Prdx6 PLA2 activity by MJ33 significantly protected lungs against damage from hyperoxia, presumably by preventing the activation of NOX2 and the amplification of lung injury associated with inflammation. These findings demonstrate that MJ33, a potent inhibitor of Prdx6 PLA2 activity, can protect mouse lungs against the manifestations of acute lung injury due to oxidative stress.

Peroxiredoxin 6 (Prdx6) supports NADPH oxidase1 (Nox1)-based superoxide generation and cell migration

“…Similar results were obtained in Prdx6-deficient, differentiated PLB-985 myeloid cells, where reconstitution with the PLA 2 activity of Prdx6 was necessary for maximal oxidase activity of Nox2 in response to the bacterial peptide formyl-methionylleucyl-phenylalanine (fMLF), but not PMA [24]. Other experiments showed acute lung injury caused by ischemia-reperfusion, LPS or hyperoxia exposure was prevented by blocking Nox2 activation by using the transition state analogue inhibitor of Prdx6 PLA 2 activity (MJ33), which does not affect the antioxidant (peroxidase) function of Prdx6 [52] [53] [54]. Thus, despite the well-established role of Prdx6 in antioxidant defense, the paradox of how Prdx6 promotes oxidative stress in the context of acute lung injury was explained on the basis of its independent phospholipase function, which activates Nox2.…”

Mutation of Serine 32 to Threonine in Peroxiredoxin 6 Preserves Its Structure and Enzymatic Function but Abolishes Its Trafficking to Lamellar Bodies

“…Lung Morphology-Lungs were excised from wild type (WT) or S32T mutant mice, cleared of blood, and fixed by perfusion through the pulmonary artery with 4% paraformaldehyde (30,31). Tissue samples for routine morphology were processed by the Pathology Core of The Children's Hospital of Philadelphia (Abramson Research Center, Philadelphia) and stained with hematoxylin and eosin (H&E).…”

The phospholipase A2 activity of peroxiredoxin 6 [S]

“…Although the inhibition of aiPLA 2 activity may reduce the ability of Prdx6 to repair peroxidized cell membranes, repair through reduction of phospholipid hydroperoxides, i.e., the PHGPx activity of Prdx6, would be unaffected. Thus, inhibition of aiPLA 2 activity by administration of MJ33 led to a marked reduction of lung injury including the extent of lipid peroxidation in mouse models of ALI associated with the intratracheal administration of bacterial lipopolysaccharide (LPS), ischemia-reperfusion injury, or exposure to hyperoxia (19,86,119,120).…”