Identification of Small Peptides that Inhibit NADPH Oxidase (Nox2) Activation.

Aron Fisher,Chandra Dodia,Sheldon Feinstein

doi:10.3390/antiox7120181

Abstract

Nicotinamide adenine phosphate (NADPH) oxidase type 2 (Nox2), a major source of reactive oxygen species in lungs, plays an important role in tissue damage associated with acute inflammatory diseases. The phospholipase A2 (PLA2) activity of peroxiredoxin 6 (Prdx6), called aiPLA2, is required for Nox2 activation through its role in the cellular generation of Rac, a key cytosolic component of the activation cascade. Lung surfactant protein A (SP-A) binds to Prdx6, inhibits its aiPLA2 activity, and prevents activation of Nox2. Based on protein docking software, we previously identified a 16 amino acid (aa) peptide derived from rat SP-A as the Prdx6 binding motif. We now identify the minimal effective sequences of rat/mouse and human SP-A as 9-aa sequences that we have called PLA2-inhibitory peptide (PIP).These sequences are PIP-1, rat/mouse; PIP-2, human; and PIP-3, a hybrid of PIPs 1&2. aiPLA2 activity in vitro was inhibited by 50% with ~7–10 µg PIP/µg Prdx6. Inhibition of the aiPLA2 activity and Nox2 activation of lungs in vivo was similar for intratracheal (IT) and intravenous (IV) administration of PIP-2, but required its incorporation into liposomes as a delivery vehicle; tissue ½ time for decrease of the in vivo inhibition of aiPLA2 activity after PIP-2 administration was ~50 h. These properties suggest that PIP-2 could be an effective therapeutic agent to prevent tissue injury associated with lung inflammation.

Highlights

The term ‘reactive oxygen species’, abbreviated as ROS, comprises superoxide anion (O2 − ), a free radical, and the non-radical H2 O2, along with other chemically reactive compounds derived from the metabolism of molecular O2
We identified a 16 amino acid peptide sequence in surfactant protein A (SP-A) that binds to peroxiredoxin 6 (Prdx6) and inhibits its aiPLA2 activity [26]
We previously identified a 16 amino acid peptide corresponding to the amino acids at positions 83 to 99 of the carbohydrate-recognition domain (CRD) of rat SP-A; these aa are located at positions 102–118 in the SP-A monomer

Summary

Introduction

The term ‘reactive oxygen species’, abbreviated as ROS, comprises superoxide anion (O2 − ), a free radical, and the non-radical H2 O2 , along with other chemically reactive compounds derived from the metabolism of molecular O2. ROS are generated normally during cellular metabolism by a variety of enzymatic as well as non-enzymatic pathways. The seven-member family of NADPH oxidases (Nox) and related dual oxidases (Duox) are the only enzymes that are known to generate. The first of the NOX/Duox family of enzymes to be described, is expressed widely in tissues with especially high levels in polymorphonuclear leukocytes (PMN). Intracellular Nox is inactive in the resting state but can be activated by a complex and tightly controlled pathway [3]. Control of activation is critical since the uncontrolled production of ROS can lead to oxidative damage to tissues

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