Increased formation of neutrophil extracellular traps induced by autophagy and identification of autophagy-related biomarkers in systemic lupus erythematosus.

Abnormal death of neutrophils and the subsequent ineffective clearance of cell fragments result in production of autoantigens that can lead to systemic lupus erythematosus (SLE). Excessive formation of neutrophil extracellular traps (NETs) can trigger the synthesis of pro-inflammatory cytokines such as type I interferons, leading to tissue damage and immune dysfunction in SLE patients. In this study, we found that a decrease in neutrophil counts in the peripheral blood was correlated with clinical parameters in SLE patients. Patients with low neutrophil counts had high renal activity index and chronicity index scores. NET formation and neutrophil autophagy in SLE patients were increased. The autophagy inhibitor hydroxychloroquine was shown to restrict NET formation. Using comprehensive bioinformatics analysis, we found that the expression of the autophagy-related gene, hypoxia-inducible factor 1A (HIF1A), was enhanced in peripheral neutrophils and in the renal glomeruli in SLE patients. Targeting HIF1A could be a potential therapeutic approach for SLE.

NIX Mediates Mitophagy in Spinal Cord Injury in Rats by Interacting with LC3.

Excessive mitophagy plays a role in neuronal death in spinal cord injury (SCI), its molecular regulation remains largely unknown. The present study aims to determine the role of NIX, a member of a unique subfamily of death-inducing mitochondrial proteins, in the regulation of mitophagy in SCI. Here we show that NIX is highly upregulated in SCI and hypoxia, and localized to mitochondria. The mitochondria-bound NIX interacts with autophagosome-localized LC3 (Microtubule-associated protein 1 light chain 3) to form a mitochondria-NIX-LC3-autophagosome complex, resulting in excessive mitophagy in SCI. Downregulation of NIX by RNA interference restores the function of mitochondria in spinal cord neurons under hypoxia. Importantly, inhibition of NIX improves recovery of locomotor function in rats after SCI. The present study demonstrates that NIX interacts with LC3 to activate excessive mitophagy in SCI. Inhibition of NIX is therefore likely a neuroprotective strategy.

Interferon-α activates interleukin-1 receptor-associated kinase 1 to induce regulatory T-cell apoptosis in patients with systemic lupus erythematosus.

Impaired regulatory T-cell (Treg) responses and upregulated interleukin-1 receptor-associated kinase 1 (IRAK1) expression are associated with the development of human systemic lupus erythematosus (SLE). Here, we show that the levels of upregulated IRAK1 expression in circulating Tregs are correlated with the percentages of apoptotic Tregs, Systemic Lupus Erythematosus Disease Activity Index scores, and serum complement C3 levels in SLE patients. High levels of plasma interferon (IFN)-α in SLE patients induced IRAK1 phosphorylation to trigger Treg apoptosis, which was mitigated by IRAK1 inhibitor (IRAK-Inh) treatment. Bioinformatics indicated that IRAK1 activation was related to the IFN-α/ß and mitogen-activated protein kinase (MAPK) signaling in Tregs and IFN-α treatment induced the p38 and MAPK/ERK kinase 3/6 phosphorylation, which was attenuated by IRAK-Inh in Tregs. Treatment with IRAK-Inh effectively alleviated renal injury and promoted the survival of lupus-prone B6.MRL-Faslpr /Nju mice. Therefore, IFN-α induced IRAK1 activation to promote Treg apoptosis, contributing to the pathogenesis of SLE and IFN-α/IRAK1 may be therapeutic targets for SLE.

Bcl-2/E1B-19KD-Interacting Protein 3/Light Chain 3 Interaction Induces Mitophagy in Spinal Cord Injury in Rats Both In Vivo and In Vitro.

Autophagy and mitophagy have been shown to occur in spinal cord injury (SCI). Bcl-2/E1B-19KD-interacting protein 3 (BNIP3) and its homologue, NIX, have been implicated in the regulation of mitophagy. The aim of this work was to characterize the mechanisms and role of BNIP3 in SCI-associated mitophagy. Our data showed that BNIP3, targeted to mitochondria, interacted with microtubule-associated protein 1A/1B-light chain 3 (LC3), which is targeted to autophagosomes, thus forming a mitochondria-BNIP3-LC3-autophagosome complex and resulting in mitophagy. Downregulation of BNIP3 by RNA interference strengthened the mitochondrial function and decreased cell death in spinal cord neurons under hypoxia. Particularly, BNIP3 knockdown significantly improved neurological recovery and the number of neuronal nuclei-positive cells post-SCI in rats. The present study demonstrated that BNIP3 interacts with LC3 to induce mitophagy, whereas its inhibition provided protective neuronal effects in SCI rat models both in vivo and in vitro.

Interleukin-1 receptor associated kinase 1 is a potential therapeutic target of anti-inflammatory therapy for systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease and currently has no effective therapy. The genome-wide analyses indicate that interleukin-1 receptor associated kinase 1 (IRAK1) is associated with the susceptibility of SLE in humans. In the present study, we identified that IRAK1 was overexpressed and hyper-activated in splenic mononuclear cells from B6.MRL-Faslpr/Nju (B6.lpr) mice and peripheral blood mononuclear cells (PBMCs) from SLE patients. Intraperitoneal treatment with a small molecular inhibitor of IRAK1 (IRAK1/4 inhibitor or IRAK-Inh) significantly mitigated inflammatory responses and renal injury in B6.lpr mice. IRAK-Inh treatment or knockdown of IRAK1 by specific siRNA decreased the relative levels of NF-κBp65 phosphorylation in human PBMCs from SLE patients. Therefore, IRAK1 may be a potential target for anti-inflammatory therapy for SLE and other inflammatory diseases.

Induction of neuronal mitophagy in acute spinal cord injury in rats.

Autophagy and up-regulation of autophagy-associated proteins microtubule-associated protein 1 light chain 3 (LC3) and Beclin-1 have been shown to occur in spinal cord injury (SCI). Bcl-2/E1B-19 K-interacting protein 3 (BNIP3) and Nip-like protein X (NIX, also known as BNIP3L) are mitochondrial BH3-only proteins that are implicated in mitophagy. In this study, we show that mitophagy is activated in the injured neurons, and hypoxia-inducible proteins BNIP3, NIX, and p53 are upregulated after SCI. Numerous autophagosomes containing damaged mitochondria (mitophagosomes) were found in the injured neurons 24 h after SCI in rats by transmission electron microscopy; mitophagy, therefore, had occurred. Hypoxia-inducible proteins BNIP3, NIX, and p53 were upregulated in spinal cord neurons in both a rat model of SCI and cultured primary spinal neurons exposed to hypoxia. BNIP3 and NIX were transcriptionally regulated mainly by hypoxia-inducible factor-1α as well as p53 in cultured spinal cord neurons. This study provides direct morphological and biochemical evidence for mitophagy in the damaged neural tissue after SCI.