FUNDC1 Regulates Autophagy by Inhibiting ROS-NLRP3 Signaling to Avoid Apoptosis in the Lung in a Lipopolysaccharide-Induced Mouse Model

Mechanism and role of mitophagy in the development of severe infection

Mitochondria produce adenosine triphosphate and potentially contribute to proinflammatory responses and cell death. Mitophagy, as a conservative phenomenon, scavenges waste mitochondria and their components in the cell. Recent studies suggest that severe infections develop alongside mitochondrial dysfunction and mitophagy abnormalities. Restoring mitophagy protects against excessive inflammation and multiple organ failure in sepsis. Here, we review the normal mitophagy process, its interaction with invading microorganisms and the immune system, and summarize the mechanism of mitophagy dysfunction during severe infection. We highlight critical role of normal mitophagy in preventing severe infection.

LncRNA THRIL, transcriptionally activated by AP-1 and stabilized by METTL14-mediated m6A modification, accelerates LPS-evoked acute injury in alveolar epithelial cells

Acute lung injury (ALI) and its extreme manifestation, acute respiratory distress syndrome (ARDS), are life-threatening diseases in intensive care units. LncRNA THRIL plays a crucial role in regulating the inflammatory response; however, the potential function of THRIL in ALI/ARDS and the associated mechanism remain unclear. In our study, we found that THRIL was upregulated in the serum of ALI/ARDS patients, and its increased expression was positively correlated with the inflammatory cytokines IL-17. In LPS-induced A549 cells, knockdown of THRIL inhibited the release of the proinflammatory cytokines TNF-α, IL-1β, IL-17, and IL-6, decreased the number of monodansylcadaverine-positive cells and LC3-II with immunofluorescence staining, decreased the expression of autophagy marker ATG7 and Beclin1, and increased expression of p62. Mechanistically, the transcription factor AP-1 bound directly to the THRIL promoter region and activated its transcription by c-Jun upon LPS exposure. Moreover, m6A modification of THRIL was increased in LPS-treated A549 cells, and METTL14 knockdown significantly abolished m6A modification and reduced stabilization of THRIL mRNA. In conclusion, our findings reveal that THRIL, transcriptionally activated by AP-1 and modified by METTL14-mediated m6A modification, induces autophagy in LPS-treated A549 cells, suggesting the potential application of THRIL for ALI/ARDS therapy.

Role of mitochondrial stress and the NLRP3 inflammasome in lung diseases

BACKGROUND

As an organelle essential for intracellular energy supply, mitochondria are involved in intracellular metabolism and inflammation, and cell death. The interaction of mitochondria with the NLRP3 inflammasome in the development of lung diseases has been extensively studied. However, the exact mechanism by which mitochondria mediate the activation of the NLRP3 inflammasome and trigger lung disease is still unclear.

METHODS

The literatures related to mitochondrial stress, NLRP3 inflammasome and lung diseases were searched in PubMed.

RESULTS

This review aims to provide new insights into the recently discovered mitochondrial regulation of the NLRP3 inflammasome in lung diseases. It also describes the crucial roles of mitochondrial autophagy, long noncoding RNA, micro RNA, altered mitochondrial membrane potential, cell membrane receptors, and ion channels in mitochondrial stress and regulation of the NLRP3 inflammasome, in addition to the reduction of mitochondrial stress by nuclear factor erythroid 2-related factor 2 (Nrf2). The effective components of potential drugs for the treatment of lung diseases under this mechanism are also summarized.

CONCLUSION

This review provides a resource for the discovery of new therapeutic mechanisms and suggests ideas for the development of new therapeutic drugs, thus promoting the rapid treatment of lung diseases.

NLRX1 increases human retinal pigment epithelial autophagy and reduces H2O2-induced oxidative stress and inflammation by suppressing FUNDC1 phosphorylation and NLRP3 activation

BACKGROUND

Age-related macular degeneration (AMD) is a leading cause of impaired vision as well as some earlier effects, such as reading and face recognition. Oxidative damage and inflammation of retinal pigment epithelial (RPE) cells are major causes of AMD. Additionally, autophagy in RPE cells can lead to cellular homeostasis under oxidative stress. Nucleotide-binding oligomerization domain (NOD)-like receptor X1 (NLRX1) is a mysterious modulator of the immune system function which inhibits inflammatory response, attenuates reactive oxygen species (ROS) production, and regulates autophagy. This study attempted to explore the role of NLRX1 in oxidative stress, inflammation, and autophagy in AMD.

METHODS

An in vitro model of AMD was built in human retinal pigment epithelial cell line 19 (ARPE-19) treated with H₂O₂. The cell viability, NLRX1 expressions, levels of superoxide dismutase (SOD), glutathione (GHS), and ROS, concentrations of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-6, and monocyte chemoattractant protein-1 (MCP-1), expressions of NLRX1, p62, LC3-II/LC3-I, FUNDC1, and NOD-like receptor protein 3 (NLRP3) inflammasome were expounded by cell counting kit-8, colorimetric, enzyme-linked immunosorbent serologic assay (ELISA), and Western blot assay.

RESULTS

H₂O₂ treatment notably reduced the relative protein expression of NLRX1. Meanwhile, H₂O₂ incubation decreased cell viability, diminished SOD and GSH concentrations, accompanied with the increased level of ROS, enhanced IL-1β, TNF-α, IL-6, and MCP-1 concentrations, and aggrandized the relative protein expression of p62 with reduced LC3-II/LC3-I ratio. Moreover, these results were further promoted with knockdown of NLRX1 and reversed with overexpression. Mechanically, silencing of NLRX1 further observably enhanced the relative levels of -phosphorylated FUNDC1/FUNDC1, and NLRP3 inflammasome-related proteins, while overexpression of NLRX1 exhibited inverse results in the H₂O₂-induced ARPE-19 cells.

CONCLUSION

NLRX1 suppressed H₂O₂-induced oxidative stress and inflammation, and facilitated autophagy by suppressing FUNDC1 phosphorylation and NLRP3 activation in ARPE-19 cells.

The Therapeutic Effect of Phosphopeptide P140 Attenuates Inflammation Induced by Uric Acid Crystals in Gout Arthritis Mouse Model

Gout is a painful form of inflammatory arthritis characterized by the deposition of monosodium urate (MSU) crystals in the joints. The aim of this study was to investigate the effect of peptide P140 on the inflammatory responses in crystal-induced mouse models of gout and cell models including MSU-treated human cells. Injection of MSU crystals into the knee joint of mice induced neutrophil influx and inflammatory hypernociception. Injection of MSU crystals subcutaneously into the hind paw induced edema and increased pro-inflammatory cytokines levels. Treatment with P140 effectively reduced hypernociception, the neutrophil influx, and pro-inflammatory cytokine levels in these experimental models. Furthermore, P140 modulated neutrophils chemotaxis in vitro and increased apoptosis pathways through augmented caspase 3 activity and reduced NFκB phosphorylation. Moreover, P140 increased the production of the pro-resolving mediator annexin A1 and decreased the expression of the autophagy-related ATG5-ATG12 complex and HSPA8 chaperone protein. Overall, these findings suggest that P140 exerts a significant beneficial effect in a neutrophilic inflammation observed in the model of gout that can be of special interest in the design of new therapeutic strategies.

The multi-faced role of FUNDC1 in mitochondrial events and human diseases

Mitophagy plays a vital role in the selective elimination of dysfunctional and unwanted mitochondria. As a receptor of mitophagy, FUN14 domain containing 1 (FUNDC1) is attracting considerably critical attention. FUNDC1 is involved in the mitochondria fission, the clearance of unfolded protein, iron metabolism in mitochondria, and the crosstalk between mitochondria and endoplasmic reticulum besides mitophagy. Studies have demonstrated that FUNDC1 is associated with the progression of ischemic disease, cancer, and metabolic disease. In this review, we systematically examine the recent advancements in FUNDC1 and the implications of this protein in health and disease.

The Emerging Role of FUNDC1-Mediated Mitophagy in Cardiovascular Diseases

Mitochondria are highly dynamic organelles and play essential role in ATP synthase, ROS production, innate immunity, and apoptosis. Mitochondria quality control is critical for maintaining the cellular function in response to cellular stress, growth, and differentiation Signals. Damaged or unwanted mitochondria are selectively removed by mitophagy, which is a crucial determinant of cell viability. Mitochondria-associated Endoplasmic Reticulum Membranes (MAMs) are the cellular structures that connect the ER and mitochondria and are involved in calcium signaling, lipid transfer, mitochondrial dynamic, and mitophagy. Abnormal mitochondrial quality induced by mitophagy impairment and MAMs dysfunction is associated with many diseases, including cardiovascular diseases (CVDs), metabolic syndrome, and neurodegenerative diseases. As a mitophagy receptor, FUNDC1 plays pivotal role in mitochondrial quality control through regulation of mitophagy and MAMs and is closely related to the occurrence of several types of CVDs. This review covers the regulation mechanism of FUNDC1-mediated mitophagy and MAMs formation, with a particular focus on its role in CVDs.