The Role of Peroxiredoxins in the Regulation of Sepsis

Extracellular peroxiredoxin 6 released from alveolar epithelial cells as a DAMP drives macrophage activation and inflammatory exacerbation in acute lung injury

Acute respiratory distress syndrome (ARDS) is featured with acute lung inflammatory injury. Our prospective study found that higher levels of peroxiredoxin 6(PRDX6) were detected in bronchoalveolar lavage (BAL) fluid from ARDS patients. Elevated PRDX6 was also correlated with monocytic activation and poor prognosis in ARDS patients. To investigate the origin of extracellular PRDX6, we conducted in vitro and in vivo experiments, demonstrating that PRDX6 can be actively released from alveolar epithelial cells under stress conditions. Our study demonstrated that it could be released from injured lung epithelial cells into the bronchoalveolar interstitial space in mice with acute lung injury and in vitro experiments. Moreover, exogenous PRDX6 was shown to activate the TLR4/NF-κB signalling pathway and induce M1 polarization of macrophages. Notably, the inflammatory effects of PRDX6 were mitigated by specific inhibition of the TLR4 (Toll-like receptor 4)-MD2 (Myeloid differentiation factor 2) complex. Using molecular docking simulations and in vitro binding assays, we confirmed a direct interaction between PRDX6 and MD2, further supporting its role as a damage-associated molecular patterns (DAMP) in ARDS. Our findings suggest that extracellular PRDX6 in bronchoalveolar lavage fluid could be a new DAMP factor in ALI, providing new insights into the pathogenesis of secondary hit in ALI/ARDS and highlighting PRDX6 as a potential therapeutic target for mitigating lung inflammation.

Peroxiredoxin 1-Toll-like receptor 4-p65 axis inhibits receptor activator of nuclear factor kappa-B ligand-mediated osteoclast differentiation

Peroxiredoxin 1 (PRDX1), an intracellular antioxidant enzyme, has emerged as a regulator of inflammatory responses via Toll-like receptor 4 (TLR4) signaling. Despite this, the mechanistic details of the PRDX1-TLR4 axis and its impact on osteoclast differentiation remain elusive. Here, we show that PRDX1 suppresses RANKL-induced osteoclast differentiation. Utilizing pharmacological inhibitors, we reveal that PRDX1 inhibits osteoclastogenesis through both TLR4/TRIF and TLR4/MyD88 pathways. Transcriptome analysis revealed PRDX1-mediated alterations in gene expression, particularly upregulating serum amyloid A3 (Saa3) and aconitate decarboxylase 1 (Acod1). Mechanistically, PRDX1-TLR4 signaling activates p65, promoting Saa3 and Acod1 expression while inhibiting Nfatc1, a master regulator of osteoclastogenesis. Remarkably, PRDX1 redirects p65 binding from Nfatc1 to Saa3 and Acod1 promoters, thereby suppressing osteoclast formation. Structural analysis showed that a monomeric PRDX1 mutant with enhanced TLR4 binding exhibited the potent inhibition of osteoclast differentiation. These findings reveal the PRDX1-TLR4 axis's role in inhibiting osteoclastogenesis, offering potential therapeutic insights for bone disorders.

Oxidative Stress in Sepsis: A Focus on Cardiac Pathology

This study aims to analyze post-mortem human cardiac specimens, to verify and evaluate the existence or extent of oxidative stress in subjects whose cause of death has been traced to sepsis, through immunohistological oxidative/nitrosative stress markers. Indeed, in the present study, i-NOS, NOX2, and nitrotyrosine markers were higher expressed in the septic death group when compared to the control group, associated with also a significant increase in 8-OHdG, highlighting the pivotal role of oxidative stress in septic etiopathogenesis. In particular, 70% of cardiomyocyte nuclei from septic death specimens showed positivity for 8-OHdG. Furthermore, intense and massive NOX2-positive myocyte immunoreaction was noticed in the septic group, as nitrotyrosine immunostaining intense reaction was found in the cardiac cells. These results demonstrated a correlation between oxidative and nitrosative stress imbalance and the pathophysiology of cardiac dysfunction documented in cases of sepsis. Therefore, subsequent studies will focus on the expression of oxidative stress markers in other organs and tissues, as well as on the involvement of the intracellular pattern of apoptosis, to better clarify the complex pathogenesis of multi-organ failure, leading to support the rationale for including therapies targeting redox abnormalities in the management of septic patients.