Novel variants in the PRDX6 Gene and the risk of Acute Lung Injury following major trauma

<p>Abstract</p> <p>Background</p> <p>Peroxiredoxin 6 (<it>PRDX6</it>) is involved in redox regulation of the cell and is thought to be protective against oxidant injury. Little is known about genetic variation within the PRDX6 gene and its association with acute lung injury (ALI). In this study we sequenced the <it>PRDX6 </it>gene to uncover common variants, and tested association with ALI following major trauma.</p> <p>Methods</p> <p>To examine the extent of variation in the <it>PRDX6 </it>gene, we performed direct sequencing of the 5' UTR, exons, introns and the 3' UTR in 25 African American cases and controls and 23 European American cases and controls (selected from a cohort study of major trauma), which uncovered 80 SNPs. <it>In silico </it>modeling was performed using Patrocles and Transcriptional Element Search System (TESS). Thirty seven novel and tagging SNPs were tested for association with ALI compared with ICU at-risk controls who did not develop ALI in a cohort study of 259 African American and 254 European American subjects that had been admitted to the ICU with major trauma.</p> <p>Results</p> <p>Resequencing of critically ill subjects demonstrated 43 novel SNPs not previously reported. Coding regions demonstrated no detectable variation, indicating conservation of the protein. Block haplotype analyses reveal that recombination rates within the gene seem low in both Caucasians and African Americans. Several novel SNPs appeared to have the potential for functional consequence using <it>in silico </it>modeling. Chi²analysis of ALI incidence and genotype showed no significant association between the SNPs in this study and ALI. Haplotype analysis did not reveal any association beyond single SNP analyses.</p> <p>Conclusions</p> <p>This study revealed novel SNPs within the <it>PRDX6 </it>gene and its 5' and 3' flanking regions via direct sequencing. There was no association found between these SNPs and ALI, possibly due to a low sample size, which was limited to detection of relative risks of 1.93 and above. Future studies may focus on the role of <it>PRDX6 </it>genetic variation in other diseases, where oxidative stress is suspected.</p

Mouse Models of Genetically Altered Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) has been shown to have three enzymatic activities: peroxidase, phospholipase A2 (PLA2) and acyl transferase. The peroxidase activity is unusual, as it is capable of reducing phospholipid hydroperoxides (as well as hydrogen peroxide and short chain organic peroxides). Knockout and overexpressing mice have been produced that demonstrate the effect that eliminating or overproducing Prdx6 has on the animals&#8217; physiology. In addition, mutations in various amino acids of Prdx6 have been identified that interfere with different enzymatic functions as well as protein transport. These mutations were originally characterized biochemically; subsequently, several knock-in mouse strains have been produced, each containing one mutation. These mice include the S32T knock-in that affects protein transport, the C47S knock-in that inactivates the peroxidase enzymatic activity, the D140A knock-in that inactivates the PLA2 enzymatic activity and the H26A knock-in that inactivates the peroxidase and blocks binding to phospholipids. This review summarizes the properties of these mice based upon studies conducted with the knockout, overexpressing and knock-in mice and the effect of the genetic changes on the biochemistry and physiology of these mice. The availability of these mice is also briefly discussed

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

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&amp;2. aiPLA2 activity in vitro was inhibited by 50% with ~7&#8315;10 &#181;g PIP/&#181;g 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 &#189; 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

Correction: Fisher, Aron B., et al. A Peptide Inhibitor of NADPH Oxidase (NOX2) Activation Markedly Decreases Mouse Lung Injury and Mortality Following Administration of Lipopolysaccharide (LPS). Int. J. Mol. Sci. 2019, 20, 2395

The authors wish to make the following corrections to our previously published paper [...

Advancing age increases sperm chromatin damage and impairs fertility in peroxiredoxin 6 null mice

Due to socioeconomic factors, more couples are choosing to delay conception than ever. Increasing average maternal and paternal age in developed countries over the past 40 years has raised the question of how aging affects reproductive success of males and females. Since oxidative stress in the male reproductive tract increases with age, we investigated the impact of advanced paternal age on the integrity of sperm nucleus and reproductive success of males by using a Prdx6−/− mouse model. We compared sperm motility, cytoplasmic droplet retention sperm chromatin quality and reproductive outcomes of young (2-month-old), adult (8-month-old), and old (20-month-old) Prdx6−/− males with their age-matched wild type (WT) controls. Absence of PRDX6 caused age-dependent impairment of sperm motility and sperm maturation and increased sperm DNA fragmentation and oxidation as well as decreased sperm DNA compaction and protamination. Litter size, total number of litters and total number of pups per male were significantly lower in Prdx6−/− males compared to WT controls. These abnormal reproductive outcomes were severely affected by age in Prdx6−/− males. In conclusion, the advanced paternal age affects sperm chromatin integrity and fertility more severely in the absence of PRDX6, suggesting a protective role of PRDX6 in age-associated decline in the sperm quality and fertility in mice. Keywords: PRDX6, Paternal age, Sperm chromatin, Oxidative stress, Male infertility, Reactive oxygen specie

A Peptide Inhibitor of NADPH Oxidase (NOX2) Activation Markedly Decreases Mouse Lung Injury and Mortality Following Administration of Lipopolysaccharide (LPS)

We have previously derived three related peptides, based on a nine-amino acid sequence in human or rat/mouse surfactant protein A, that inhibit the phospholipase A2 activity of peroxiredoxin 6 (Prdx6) and prevent the activation of lung NADPH oxidase (type 2). The present study evaluated the effect of these Prdx6-inhibitory peptides (PIP) in a mouse (C57Bl/6) model of acute lung injury following lipopolysaccharide (LPS) administration. All three peptides (PIP-1, 2 and 3) similarly inhibited the production of reactive O2 species (ROS) in isolated mouse lungs as detected by the oxidation of Amplex red. PIP-2 inhibited both the increased phospholipase A2 activity of Prdx6 and lung reactive oxygen species (ROS) production following treatment of mice with intratracheal LPS (5 &#181;g/g body wt.). Pre-treatment of mice with PIP-2 prevented LPS-mediated lung injury while treatment with PIP-2 at 12 or 16 h after LPS administration led to reversal of lung injury when evaluated 12 or 8 h later, respectively. With a higher dose of LPS (15 &#181;g/g body wt.), mortality was 100% at 48 h in untreated mice but only 28% in mice that were treated at 12&#8211;24 h intervals, with PIP-2 beginning at 12 h after LPS administration. Treatment with PIP-2 also markedly decreased mortality after intraperitoneal LPS (15 &#181;g/g body wt.), used as a model of sepsis. This study shows the dramatic effectiveness of a peptide inhibitor of Prdx6 against lung injury and mouse mortality in LPS models. We propose that the PIP nonapeptides may be a useful modality to prevent or to treat human ALI