The APPL1-Rab5 axis restricts NLRP3 inflammasome activation through early endosomal-dependent mitophagy in macrophages

Mitochondrial dynamics and metabolism in macrophages for cardiovascular disease: A review

BACKGROUND

Mitochondria regulate macrophage function, affecting cardiovascular diseases like atherosclerosis and heart failure. Their dynamics interact with macrophage cell death mechanisms, including apoptosis and necroptosis.

PURPOSE

This review explores how mitochondrial dynamics and metabolism influence macrophage inflammation and cell death in CVDs, highlighting therapeutic targets for enhancing macrophage resilience and reducing CVD pathology, while examining molecular pathways and pharmacological agents involved.

STUDY DESIGN

This is a narrative review that integrates findings from various studies on mitochondrial dynamics and metabolism in macrophages, their interactions with the endoplasmic reticulum (ER) and Golgi apparatus, and their implications for CVDs. The review also considers the potential therapeutic effects of pharmacological agents on these pathways.

METHODS

The review utilizes a comprehensive literature search to identify relevant studies on mitochondrial dynamics and metabolism in macrophages, their role in CVDs, and the effects of pharmacological agents on these pathways. The selected studies are analyzed and synthesized to provide insights into the complex relationships between mitochondria, the ER, and Golgi apparatus, and their implications for macrophage function and fate.

RESULTS

The review reveals that mitochondrial metabolism intertwines with cellular architecture and function, particularly through its intricate interactions with the ER and Golgi apparatus. Mitochondrial-associated membranes (MAMs) facilitate Ca2+ transfer from the ER to mitochondria, maintaining mitochondrial homeostasis during ER stress. The Golgi apparatus transports proteins crucial for inflammatory signaling, contributing to immune responses. Inflammation-induced metabolic reprogramming in macrophages, characterized by a shift from oxidative phosphorylation to glycolysis, underscores the multifaceted role of mitochondrial metabolism in regulating immune cell polarization and inflammatory outcomes. Notably, mitochondrial dysfunction, marked by heightened reactive oxygen species generation, fuels inflammatory cascades and promotes cell death, exacerbating CVD pathology. However, pharmacological agents such as Metformin, Nitazoxanide, and Galanin emerge as potential therapeutic modulators of these pathways, offering avenues for mitigating CVD progression.

CONCLUSION

This review highlights mitochondrial dynamics and metabolism in macrophage inflammation and cell death in CVDs, suggesting therapeutic targets to improve macrophage resilience and reduce pathology, with new pharmacological agents offering treatment opportunities.

TBK1 and IKKε prevent premature cell death by limiting the activity of both RIPK1 and NLRP3 death pathways

The loss of TBK1, or both TBK1 and the related kinase IKKε, results in uncontrolled cell death-driven inflammation. Here, we show that the pathway leading to cell death depends on the nature of the activating signal. Previous models suggest that in steady state, TBK1/IKKε-deficient cells die slowly and spontaneously predominantly by uncontrolled tumor necrosis factor-RIPK1-driven death. However, upon infection of cells that express the NLRP3 inflammasome, (e.g., macrophages), with pathogens that activate this pathway (e.g., Listeria monocytogenes), TBK1/IKKε-deficient cells die rapidly, prematurely, and exclusively by enhanced NLRP3-driven pyroptosis. Even infection with the RIPK1-activating pathogen, Yersinia pseudotuberculosis, results in enhanced RIPK1-caspase-8 activation and enhanced secondary NLRP3 activation. Mechanistically, TBK1/IKKε control endosomal traffic, and their loss disrupts endosomal homeostasis, thereby signaling cell stress. This results in premature NLRP3 activation even upon sensing "signal 2" alone, without the obligatory "signal 1." Collectively, TBK1/IKKε emerge as a central brake in limiting death-induced inflammation by both RIPK1 and NLRP3 death-inducing pathways.

Exploring the therapeutic potential of HAPC in COVID-19-induced acute lung injury

BACKGROUND

Acute lung injury (ALI) is one of the critical complications of coronavirus disease 2019 (COVID-19), which significantly impacts the survival of patients.

PURPOSE

In this study, we screened COVID-19-related target genes and identified and optimized potential drugs targeting these genes for the treatment of COVID-19.

STUDY DESIGN

In this study, bioinformatic analyses were conducted and subsequently identified and optimized potential drugs targeting these genes for the treatment of COVID-19 were carried out.

METHODS

Firstly, we analyzed the targets gene in patients with COVID-19 using single-cell data analysis. We performed structural modifications on Chicoric acid (CA) and combined it with hyaluronic acid to enhance the targeted activity towards Cluster of differentiation 44 (CD44). Poly (sodium-p styrenesulfonate) (PSS) was used to form a PSS-coated CA+hyaluronic acid nanocomplex (HA-P). Subsequently, Lactobacillus murinus conidia cell wall (CW) was encapsulated to prepare PSS-coated CA + hyaluronic acid + Lactobacillus murinus conidia cell wall (HAPC) nanocomplexes.

RESULTS

The expression of APPL1 expression in macrophage of COVID-19 patients was up-regulation. CA was found to bind to the APPL1 protein and inhibit its ubiquitination. HAPC effectively targeted ALI through the highly efficient interaction between CD44 and Hyaluronic acid (HA). HAPC alleviated the symptoms of ALI and restored epithelial function in mice with ALI. HAPC induced the Adaptor protein containing a pH domain, PTB domain and leucine zipper motif 1 (APPL1)/ liver kinase B1 (LKB1)/ AMP-activated protein kinase (AMPK) pathway by inactivating the NOD - like receptor protein 3 (NLRP3) pathway in ALI. CA interacted with the APPL1 protein and prevented its ubiquitination. HAPC facilitated the interaction between APPL1 and LKB1 to induce the AMPK/NLRP3 pathway. It promoted the formation of LKB1 at GLU-67, ARG-72, ARG-314, ASP-316, and GLN-312 and APPL1 at ARG-106, ASP-115, LYS-124, ASN-119, and GLU-120.

CONCLUSION

Altogether, HAPC nanocomplexes exerted anti-inflammatory effects on ALI by promoting the interaction between APPL1 and LKB1 to induce the AMPK/NLRP3 pathway, and may be one new therapeutic strategie for ALI.

Nepetin limits NLRP3 inflammasome activation and alleviates NLRP3-driven inflammatory diseases via PINK1-dependent mitophagy

The NLRP3 inflammasome plays a pivotal role in the progression of inflammatory diseases. Mitochondrial damage, oxidative stress and mitochondrial DNA (mtDNA) leak are the key upstream factors for NLRP3 inflammasome activation. Nepetin (Nep), a naturally occurring flavonoid found with anti-inflammatory properties; however, whether it can affect the NLRP3 inflammasome activation and its precise anti-inflammatory mechanism remains unclear. In this study, we demonstrated that Nep enhances PINK1-mediated ubiquitin phosphorylation, which promotes mitophagy and subsequently inhibits NLRP3 inflammasome activation and pyroptosis in macrophages. The administration of Nep to macrophages alleviated of mitochondrial damage, reduced mitochondrial superoxide production, restored mitochondrial membrane potential and prevented the mtDNA leakage. These findings provide compelling evidence for the antioxidant effect of Nep. Furthermore, the pivotal function of mitophagy in the NLRP3 inflammasome inhibitory impact of Nep was substantiated through the utilisation of mitophagy inhibitors and siRNA techniques. Notably, Nep increased survival and reduced organ damage in mice with systemic inflammation by inhibiting NLRP3 inflammasome activation. In addition, Nep suppressed NLRP3 inflammasome activation in obese mice, which led to reduced white adipose and liver inflammation, thereby ameliorating insulin resistance. In conclusion, our findings suggest that Nep is a potent NLRP3 inflammasome inhibitor and a promising candidate for the development of anti-inflammatory therapies.

Protective Effects of Mdivi-1 on Cognition Disturbance Following Sepsis in Mice via Alleviating Microglia Activation and Polarization

BACKGROUND

Neuroinflammation is one of the essential pathogeneses of cognitive damage suffering from sepsis-associated encephalopathy (SAE). Lots of evidences showed the microglia presented mitochondrial fragmentation during SAE. This study investigated the protective effects and novel mechanisms of inhibiting microglia mitochondrial fragmentation via mitochondrial division inhibitor 1 (Mdivi-1) on cognitive damage in SAE.

METHODS

The SAE model was performed by cecal ligation and puncture (CLP), and Mdivi-1 was administrated via intraperitoneal injection. Morris water maze was performed to assess cognitive function. Mitochondrial morphology was observed by electron microscope or MitoTracker staining. The qRT-PCR, immunofluorescence staining, and western blots were used to detect the inflammatory factors and protein content, respectively. Flow cytometry was used to detect the polarization of hippocampal microglia. Bioinformatics analysis was used to verify hypotheses.

RESULTS

Mdivi-1 administration alleviated sepsis-induced mitochondrial fragmentation, microglia activation, polarization, and cognitive damage. The mechanisms study showed neuroinflammation and oxidative stress were suppressed via NF-κB and Keap1/Nrf2/HO-1 pathways following Mdivi-1 administration; meanwhile, pyroptosis in microglia was reduced, which was associated with enhanced autophagosome formation via p62 elevation following Mdivi-1 administration.

CONCLUSION

Inhibition of microglia mitochondrial fragmentation is beneficial to SAE cognitive disturbance, the mechanisms are related to alleviating neuroinflammation, oxidative stress, and pyroptosis.

Revealing the dance of NLRP3: spatiotemporal patterns in inflammasome activation

The nucleotide-binding domain, leucine-rich repeat, and pyrin domain containing-protein 3 (NLRP3) inflammasome is a multiprotein complex that plays a critical role in the innate immune response to both infections and sterile stressors. Dysregulated NLRP3 activation has been implicated in a variety of autoimmune and inflammatory diseases, including cryopyrin-associated periodic fever syndromes, diabetes, atherosclerosis, Alzheimer's disease, inflammatory bowel disease, and cancer. Consequently, fine-tuning NLRP3 activity holds significant therapeutic potential. Studies have implicated several organelles, including mitochondria, lysosomes, the endoplasmic reticulum (ER), the Golgi apparatus, endosomes, and the centrosome, in NLRP3 localization and inflammasome assembly. However, reports of conflict and many factors regulating interactions between NLRP3 and subcellular organelles remain unknown. This review synthesizes the current understanding of NLRP3 spatiotemporal dynamics, focusing on recent literature that elucidates the roles of subcellular localization and organelle stress in NLRP3 signaling and its crosstalk with other innate immune pathways converging at these organelles.

Endosomal traffic disorders: a driving force behind neurodegenerative diseases

Endosomes are crucial sites for intracellular material sorting and transportation. Endosomal transport is a critical process involved in the selective uptake, processing, and intracellular transport of substances. The equilibrium between endocytosis and circulation mediated by the endosome-centered transport pathway plays a significant role in cell homeostasis, signal transduction, and immune response. In recent years, there have been hints linking endosomal transport abnormalities to neurodegenerative diseases, including Alzheimer's disease. Nonetheless, the related mechanisms remain unclear. Here, we provide an overview of endosomal-centered transport pathways and highlight potential physiological processes regulated by these pathways, with a particular focus on the correlation of endosomal trafficking disorders with common pathological features of neurodegenerative diseases. Additionally, we summarize potential therapeutic agents targeting endosomal trafficking for the treatment of neurodegenerative diseases.

Loss of O6-methylguanine DNA methyltransferase (MGMT) in macrophages alters responses to TLR3 stimulation and enhances DNA double-strand breaks and mitophagy

O6-methylguanine-DNA methyltransferase (MGMT) is a DNA damage repair enzyme. The roles of this enzyme in immune cells remain unclear. In this study, we explored the roles of MGMT in bone marrow-derived murine macrophages (BMMs) via the use of MGMT knockout (KO) mice. Loss of MGMT altered the response to TLR3 agonists (poly (I:C)), such as dampening the production of TNFα and IL-6. Increased DNA double-strand breaks (DSBs) were observed in MGMT-KO macrophages but did not result in increased cell death. MGMT localized to both nuclei and mitochondria at increasing levels during poly (I:C) stimulation. MGMT deficiency increased the production of mitochondrial reactive oxygen species (mtROS), which was correlated with increased mitophagy. The underlying mechanism involves mediation through activation of the AMPKα pathway. Taken together, our findings reveal the roles of MGMT in macrophages in regulating the response to TLR3, which links DSBs to mtROS and mitophagy via the AMPKα pathway. These roles may have consequences for the inflammatory response and chronic inflammation.

Bergapten attenuates hemorrhagic shock induced multi-organ injury by inhibiting NLRP3 inflammasome activation and pyroptosis

OBJECTIVES

Treatment of hemorrhagic shock (HS) induced multi-organ injury remains a challenge. Bergapten (BeG) is a bioactive coumarin-derived compound, and previous articles have suggested that BeG may serve as a prospective therapeutic modality for HS. This study was designed to investigate the efficacy of BeG in the treatment of HS and its underlying mechanisms.

METHODS

In this research, we established a rat model of HS, following which we assessed the protective effects of BeG on HS induced multi-organ injury. Subsequently, we scrutinized the activation of NLRP3 inflammasomes and pyroptosis in damaged organs. Additionally, we conducted examinations of AMPK and the downstream mitophagy pathway in damaged organs. Finally, we established a hypoxia/reoxygenation (H/R) model in HK-2 cells to simulate the in vitro HS process. Following AMPK inhibition with compound C, we evaluated the levels of mitophagy and cellular pyroptosis in BeG-treated HK-2 cells subjected to H/R.

RESULTS

BeG treatment alleviated HS induced multi-organ injury. Subsequent analyses indicated that the therapeutic effects of BeG were related to the attenuation of NLRP3 inflammasome activation and pyroptosis. Additionally, we found BeG treatment stimulated the phosphorylation of AMPK, thereby enhancing mitophagy. Lastly, we found that the inhibition of AMPK in vitro attenuates BeG's enhancement of mitophagy and its suppression of pyroptosis.

CONCLUSION

Our research indicates that BeG has the potential to alleviate multi-organ injury induced by HS. The protective effect of BeG is likely associated with its promotion of mitophagy through AMPK activation, thereby inhibiting NLRP3 inflammasome-mediated pyroptosis.

MDM2 induces pro-inflammatory and glycolytic responses in M1 macrophages by integrating iNOS-nitric oxide and HIF-1α pathways in mice

M1 macrophages induce protective immunity against infection, but also contribute to metabolic and inflammatory diseases. Here we show that the E3 ubiquitin ligase, MDM2, promotes the glycolytic and inflammatory activities of M1 macrophage by increasing the production of IL-1β, MCP-1 and nitric oxide (NO). Mechanistically, MDM2 triggers the ubiquitination and degradation of E3 ligase, SPSB2, to stabilize iNOS and increases production of NO, which s-nitrosylates and activates HIF-1α for triggering the glycolytic and pro-inflammatory programs in M1 macrophages. Myeloid-specific haplodeletion of MDM2 in mice not only blunts LPS-induced endotoxemia and NO production, but also alleviates obesity-induced adipose tissue-resident macrophage inflammation. By contrast, MDM2 haplodeletion induces higher mortality, tissue damage and bacterial burden, and also suppresses M1 macrophage response, in the cecal ligation and puncture-induced sepsis mouse model. Our findings thus identify MDM2 as an activator of glycolytic and inflammatory responses in M1 macrophages by connecting the iNOS-NO and HIF-1α pathways.

Cell life-or-death events in osteoporosis: All roads lead to mitochondrial dynamics

Mitochondria exhibit heterogeneous shapes and networks within and among cell types and tissues, also in normal or osteoporotic bone tissues with complex cell types. This dynamic characteristic is determined by the high plasticity provided by mitochondrial dynamics and is stemmed from responding to the survival and functional requirements of various bone cells in a specific microenvironments. In contrast, mitochondrial dysfunction, induced by dysregulation of mitochondrial dynamics, may act as a trigger of cell death signals, including common apoptosis and other forms of programmed cell death (PCD). These PCD processes consisting of tightly structured cascade gene expression events, can further influence the bone remodeling by facilitating the death of various bone cells. Mitochondrial dynamics, therefore, drive the bone cells to stand at the crossroads of life and death by integrating external signals and altering metabolism, shape, and signal-response properties of mitochondria. This implies that targeting mitochondrial dynamics displays significant potential in treatment of osteoporosis. Considerable effort has been made in osteoporosis to emphasize the parallel roles of mitochondria in regulating energy metabolism, calcium signal transduction, oxidative stress, inflammation, and cell death. However, the emerging field of mitochondrial dynamics-related PCD is not well understood. Herein, to bridge the gap, we outline the latest knowledge on mitochondrial dynamics regulating bone cell life or death during normal bone remodeling and osteoporosis.

EGFR-MEK1/2 cascade negatively regulates bactericidal function of bone marrow macrophages in mice with Staphylococcus aureus osteomyelitis

The ability of Staphylococcus aureus (S. aureus) to survive within macrophages is a critical strategy for immune evasion, contributing to the pathogenesis and progression of osteomyelitis. However, the underlying mechanisms remain poorly characterized. This study discovered that inhibiting the MEK1/2 pathway reduced bacterial load and mitigated bone destruction in a mouse model of S. aureus osteomyelitis. Histological staining revealed increased phosphorylated MEK1/2 levels in bone marrow macrophages surrounding abscess in the mouse model of S. aureus osteomyelitis. Activation of MEK1/2 pathway and its roles in impairing macrophage bactericidal function were confirmed in primary mouse bone marrow-derived macrophages (BMDMs). Transcriptome analysis and in vitro experiments demonstrated that S. aureus activates the MEK1/2 pathway through EGFR signaling. Moreover, we found that excessive activation of EGFR-MEK1/2 cascade downregulates mitochondrial reactive oxygen species (mtROS) levels by suppressing Chek2 expression, thereby impairing macrophage bactericidal function. Furthermore, pharmacological inhibition of EGFR signaling prevented upregulation of phosphorylated MEK1/2 and restored Chek2 expression in macrophages, significantly enhancing S. aureus clearance and improving bone microstructure in vivo. These findings highlight the critical role of the EGFR-MEK1/2 cascade in host immune defense against S. aureus, suggesting that S. aureus may reduce mtROS levels by overactivating the EGFR-MEK1/2 cascade, thereby suppressing macrophage bactericidal function. Therefore, combining EGFR-MEK1/2 pathway blockade with antibiotics could represent an effective therapeutic approach for the treatment of S. aureus osteomyelitis.

Syringic acid suppresses Cutibacterium acnes-induced inflammation in human keratinocytes via regulating the NLRP3/caspase-1/IL-1β signaling axis by activating PPARγ/Nrf2-antioxidant pathway

BACKGROUND

Our previous studies have demonstrated a strong relationship betweenCutibacterium acnes(C. acnes), oxidative stress, and acne inflammation. Syringic acid (SA) is a plant widely used for its antimicrobial, anti-inflammatory, and antioxidant activities, but lacking data on acne. This study aims to investigate the effect and mechanism of SA on acne inflammation induced by C. acnes in vitro and in vivo.

METHODS

After using the SA to expose HaCaT keratinocytes, we reevaluated the effect of the SA on cell viability, cell apoptosis, ROS, CAT, SOD, and other inflammatory variables in the heat-killed C. acnes-treated HaCaT cells. Next, to induce mice with acne inflammation, ICR mice were given an intradermal injection of live C. acnes into their right ears. The effect of SA on this inflammation was then examined. Moreover, we explored the mechanism of SA on PPARγ/Nrf2 and NLRP3/caspase-1/IL-1β pathways by ELISA, immunofluorescence microscopy, and western blot assay.

RESULTS

Heat-killed C. acnes triggered remarkable cell apoptosis, ROS production, interleukin (IL)-1β, IL-18, IL-6, and TNF-α release, reduced SOD and CAT activity, and upregulated the expression of proteins in HaCaT cells, including up-regulating IL-1β, PPARγ, Nrf2, HO-1, NQO1, NLRP3, and caspase-1, whereas SA inhibited these effects by partially impairing PPARγ activation. In addition, PPARγ silencing decreased C. acnes-induced IL-1β secretion and the production of intracellular ROS, down-regulating the expression of Nrf2. Nrf2 activator (SFN) enhanced anti-inflammatory activity through antioxidant mechanisms, boosting intracellular ROS production, reducing SOD and CAT activity, and promoting the increase in ROS, HO-1, NQO1, and IL-1β levels, while PPARγ inhibitor (GW662) effectively inhibited this effect in heat-killed C. acnes-treated cells. Finally, SA also exhibited notable improvements in ear redness, swelling, and the expression of PPARγ, NLRP3, and IL-1β in vivo.

CONCLUSIONS

SA inhibited C. acnes-induced inflammation via regulating the NLRP3/caspase-1/IL-1β signaling axis by activating the PPARγ/Nrf2-antioxidant pathway, suggesting a new treatment possibility for acne vulgaris.

Macrophage migration inhibitory factor (MIF) suppresses mitophagy through disturbing the protein interaction of PINK1-Parkin in sepsis-associated acute kidney injury

Damage to renal tubular epithelial cells (RTECs) signaled the onset and progression of sepsis-associated acute kidney injury (SA-AKI). Recent research on mitochondria has revealed that mitophagy plays a crucial physiological role in alleviating injury to RTECs and it is suppressed progressively by the inflammation response in SA-AKI. However, the mechanism by which inflammation influences mitophagy remains poorly understood. We examined how macrophage migration inhibitory factor (MIF), a pro-inflammatory protein, influences the PINK1-Parkin pathway of mitophagy by studying protein-protein interactions when MIF was inhibited or overexpressed. Surprisingly, elevated levels of MIF were found to directly bind to PINK1, disrupting its interaction with Parkin. This interference hindered the recruitment of Parkin to mitochondria and impeded the initiation of mitophagy. Furthermore, this outcome led to significant apoptosis of RTECs, which could, however, be reversed by an MIF inhibitor ISO-1 and/or a new mitophagy activator T0467. These findings highlight the detrimental impact of MIF on renal damage through its disruption of the interaction between PINK1 and Parkin, and the therapeutic potential of ISO-1 and T0467 in mitigating SA-AKI. This study offers a fresh perspective on treating SA-AKI by targeting MIF and mitophagy.

NLRP3 inflammasome: a key player in the pathogenesis of life-style disorders

Proinflammatory cytokines and chemokines play a crucial role in regulating the inflammatory response, which is essential for the proper functioning of our immune system. When infections or threats to the body's defense mechanisms are detected, the innate immune system takes the lead. However, an excessive inflammatory response can lead to the production of high concentrations of cytotoxic molecules, resulting in tissue damage. Inflammasomes are significant contributors to innate immunity, and one of the most extensively studied inflammasome complexes is NOD-like receptor 3 (NLRP3). NLRP3 has a wide range of recognition mechanisms that streamline immune activation and eliminate pathogens. These cytosolic multiprotein complexes are composed of effector, adaptor, and sensor proteins, which are crucial for identifying intracellular bacterial breakdown products and initiating an innate immune cascade. To understand the diverse behavior of NLRP3 activation and its significance in the development of lifestyle-related diseases, one must delve into the study of the immune response and apoptosis mediated by the release of proinflammatory cytokines. In this review, we briefly explore the immune response in the context of lifestyle associated disorders such as obesity, hyperlipidemia, diabetes, chronic respiratory disease, oral disease, and cardiovascular disease.

SLC7A11-ROS/αKG-AMPK axis regulates liver inflammation through mitophagy and impairs liver fibrosis and NASH progression

The changes of inflammation and metabolism are two features in nonalcoholic steatohepatitis (NASH). However, how they interact to regulate NASH progression remains largely unknown. Our works have demonstrated the importance of solute carrier family 7 member 11 (SLC7A11) in inflammation and metabolism. Nevertheless, whether SLC7A11 regulates NASH progression through mediating inflammation and metabolism is unclear. In this study, we found that SLC7A11 expression was increased in liver samples from patients with NASH. Upregulated SLC7A11 level was also detected in two murine NASH models. Functional studies showed that SLC7A11 knockdown or knockout had augmented steatohepatitis with suppression of inflammatory markers in mice. However, overexpression of SLC7A11 dramatically alleviated diet-induced NASH pathogenesis. Mechanically, SLC7A11 decreased reactive oxygen species (ROS) level and promoted α-ketoglutarate (αKG)/prolyl hydroxylase (PHD) activity, which activated AMPK pathway. Furthermore, SLC7A11 impaired expression of NLRP3 inflammasome components through AMPK-mitophagy axis. IL-1β release through NLRP3 inflammasome recruited myeloid cells and promoted hepatic stellate cells (HSCs) activation, which contributed to the progression of liver injury and fibrosis. Anti-IL-1β and anakinra might attenuate the hepatic inflammatory response evoked by SLC7A11 knockdown. Moreover, the upregulation of SLC7A11 in NASH was contributed by lipid overload-induced JNK-c-Jun pathway. In conclusions, SLC7A11 acts as a protective factor in controlling the development of NASH. Upregulation of SLC7A11 is protective by regulating oxidation, αKG and energy metabolism, decreasing inflammation and fibrosis.

Metabolic control of mitophagy

Mitochondrial dysfunction is a major hallmark of ageing and related chronic disorders. Controlled removal of damaged mitochondria by the autophagic machinery, a process known as mitophagy, is vital for mitochondrial homeostasis and cell survival. The central role of mitochondria in cellular metabolism places mitochondrial removal at the interface of key metabolic pathways affecting the biosynthesis or catabolism of acetyl-coenzyme A, nicotinamide adenine dinucleotide, polyamines, as well as fatty acids and amino acids. Molecular switches that integrate the metabolic status of the cell, like AMP-dependent protein kinase, protein kinase A, mechanistic target of rapamycin and sirtuins, have also emerged as important regulators of mitophagy. In this review, we discuss how metabolic regulation intersects with mitophagy. We place special emphasis on the metabolic regulatory circuits that may be therapeutically targeted to delay ageing and mitochondria-associated chronic diseases. Moreover, we identify outstanding knowledge gaps, such as the ill-defined distinction between basal and damage-induced mitophagy, which must be resolved to boost progress in this area.

Tissue-resident macrophages exacerbate lung injury after remote sterile damage

Remote organ injury, which is a common secondary complication of sterile tissue damage, is a major cause of poor prognosis and is difficult to manage. Here, we report the critical role of tissue-resident macrophages in lung injury after trauma or stroke through the inflammatory response. We found that depleting tissue-resident macrophages rather than disrupting the recruitment of monocyte-derived macrophages attenuated lung injury after trauma or stroke. Our findings revealed that the release of circulating alarmins from sites of distant sterile tissue damage triggered an inflammatory response in lung-resident macrophages by binding to receptor for advanced glycation end products (RAGE) on the membrane, which activated epidermal growth factor receptor (EGFR). Mechanistically, ligand-activated RAGE triggered EGFR activation through an interaction, leading to Rab5-mediated RAGE internalization and EGFR phosphorylation, which subsequently recruited and activated P38; this, in turn, promoted RAGE translation and trafficking to the plasma membrane to increase the cellular response to RAGE ligands, consequently exacerbating inflammation. Our study also showed that the loss of RAGE or EGFR expression by adoptive transfer of macrophages, blocking the function of RAGE with a neutralizing antibody, or pharmacological inhibition of EGFR activation in macrophages could protect against trauma- or stroke-induced remote lung injury. Therefore, our study revealed that targeting the RAGE-EGFR signaling pathway in tissue-resident macrophages is a potential therapeutic approach for treating secondary complications of sterile damage.

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.

Assessment of pathogenicity and functional characterization of APPL1 gene mutations in diabetic patients

BACKGROUND

Adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 (APPL1) plays a crucial role in regulating insulin signaling and glucose metabolism. Mutations in the APPL1 gene have been associated with the development of maturity-onset diabetes of the young type 14 (MODY14). Currently, only two mutations [c.1655T>A (p.Leu552*) and c.281G>A p.(Asp94Asn)] have been identified in association with this disease. Given the limited understanding of MODY14, it is imperative to identify additional cases and carry out comprehensive research on MODY14 and APPL1 mutations.

AIM

To assess the pathogenicity of APPL1 gene mutations in diabetic patients and to characterize the functional role of the APPL1 domain.

METHODS

Patients exhibiting clinical signs and a medical history suggestive of MODY were screened for the study. Whole exome sequencing was performed on the patients as well as their family members. The pathogenicity of the identified APPL1 variants was predicted on the basis of bioinformatics analysis. In addition, the pathogenicity of the novel APPL1 variant was preliminarily evaluated through in vitro functional experiments. Finally, the impact of these variants on APPL1 protein expression and the insulin pathway were assessed, and the potential mechanism underlying the interaction between the APPL1 protein and the insulin receptor was further explored.

RESULTS

A total of five novel mutations were identified, including four missense mutations (Asp632Tyr, Arg633His, Arg532Gln, and Ile642Met) and one intronic mutation (1153-16A>T). Pathogenicity prediction analysis revealed that the Arg532Gln was pathogenic across all predictions. The Asp632Tyr and Arg633His variants also had pathogenicity based on MutationTaster. In addition, multiple alignment of amino acid sequences showed that the Arg532Gln, Asp632Tyr, and Arg633His variants were conserved across different species. Moreover, in in vitro functional experiments, both the c.1894G>T (at Asp632Tyr) and c.1595G>A (at Arg532Gln) mutations were found to downregulate the expression of APPL1 on both protein and mRNA levels, indicating their pathogenic nature. Therefore, based on the patient's clinical and family history, combined with the results from bioinformatics analysis and functional experiment, the c.1894G>T (at Asp632Tyr) and c.1595G>A (at Arg532Gln) mutations were classified as pathogenic mutations. Importantly, all these mutations were located within the phosphotyrosine-binding domain of APPL1, which plays a critical role in the insulin sensitization effect.

CONCLUSION

This study provided new insights into the pathogenicity of APPL1 gene mutations in diabetes and revealed a potential target for the diagnosis and treatment of the disease.

The mechanosensitive ion channel ASIC2 mediates both proprioceptive sensing and spinal alignment

By translating mechanical forces into molecular signals, proprioceptive neurons provide the CNS with information on muscle length and tension, which is necessary to control posture and movement. However, the identities of the molecular players that mediate proprioceptive sensing are largely unknown. Here, we confirm the expression of the mechanosensitive ion channel ASIC2 in proprioceptive sensory neurons. By combining in vivo proprioception-related functional tests with ex vivo electrophysiological analyses of muscle spindles, we showed that mice lacking Asic2 display impairments in muscle spindle responses to stretch and motor coordination tasks. Finally, analysis of skeletons of Asic2 loss-of-function mice revealed a specific effect on spinal alignment. Overall, we identify ASIC2 as a key component in proprioceptive sensing and a regulator of spine alignment.

The Role of Histone Deacetylases in NLRP3 Inflammasomesmediated Epilepsy

Epilepsy is one of the most common brain disorders that not only causes death worldwide, but also affects the daily lives of patients. Previous studies have revealed that inflammation plays an important role in the pathophysiology of epilepsy. Activation of inflammasomes can promote neuroinflammation by boosting the maturation of caspase-1 and the secretion of various inflammatory effectors, including chemokines, interleukins, and tumor necrosis factors. With the in-depth research on the mechanism of inflammasomes in the development of epilepsy, it has been discovered that NLRP3 inflammasomes may induce epilepsy by mediating neuronal inflammatory injury, neuronal loss and blood-brain barrier dysfunction. Therefore, blocking the activation of the NLRP3 inflammasomes may be a new epilepsy treatment strategy. However, the drugs that specifically block NLRP3 inflammasomes assembly has not been approved for clinical use. In this review, the mechanism of how HDACs, an inflammatory regulator, regulates the activation of NLRP3 inflammasome is summarized. It helps to explore the mechanism of the HDAC inhibitors inhibiting brain inflammatory damage so as to provide a potential therapeutic strategy for controlling the development of epilepsy.

Astragulus embranaceus (Fisch.) Bge-Dioscorea opposita Thunb herb pair ameliorates sarcopenia in senile type 2 diabetes mellitus through Rab5a/mTOR-mediated mitochondrial dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Astragulus embranaceus (Fisch.) Bge (Huangqi) and Dioscorea opposita Thunb (Shanyao) are one of the most widely accepted herb pairs in traditional Chinese medicine prescriptions for treating sarcopenia. However, the mechanisms underlying the combination of these herbs for anti-sarcopenia treatment are not yet fully understood.

AIM OF THE STUDY

To investigate the potential effect of the Astragulus embranaceus (Fisch.) Bge and Dioscorea opposita Thunb herb pair (Ast-Dio) on sarcopenia in mice that have been induced with senile type 2 diabetes mellitus, as well as to explore the underlying mechanisms related to the Rab5a/mTOR signaling pathway and mitochondrial quality control.

MATERIALS AND METHODS

Network pharmacology was utilized to identify the main active ingredients of Ast-Dio and potential therapeutic targets for sarcopenia. Gene Ontology function and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were conducted to explore the underlying mechanisms of Ast-Dio in treating sarcopenia. The high-performance liquid chromatography method coupled with triple-quadrupole tandem mass spectrometry was developed to quantify the major constituents of Ast-Dio. Male C57/BL6 mice, aged 12 months, induced with type 2 diabetes mellitus via streptozotocin were divided into three groups for 8 weeks: the model group, Ast-Dio treatment group (7.8 g/kg), and metformin treatment group (100 mg/kg). Normal control groups included mice aged 3 and 12 months, respectively. The study monitored changes in fasting blood glucose levels, grip strength, and body weight during 8 weeks of intragastric administration. Liver and kidney function in mice was evaluated by measuring the levels of serum creatinine, alanine transaminase, and aspartate transaminase. Skeletal muscle mass condition was evaluated by muscle weight, and hematoxylin and eosin staining. Protein and mRNA expressions related to muscle atrophy, mitochondrial quality control, and the Rab5a/mTOR signaling pathway were detected using immunofluorescence staining, immunohistochemical staining, Western blotting, and quantitative real-time polymerase chain reaction. In addition, transmission electron microscopy was employed to investigate the condition of mitochondria in the groups.

RESULTS

Through the prediction analysis of network pharmacology, we identified mTOR as one of the primary targets for Ast-Dio therapy of sarcopenia. Gene Ontology functional enrichment analysis revealed that mitochondrial control quality is crucial in the treatment of sarcopenia with Ast-Dio. Our findings showed that senile type 2 diabetes mellitus induced muscle mass loss and a reduction in grip strength, both of which were dramatically restored by Ast-Dio treatment. Notably, Ast-Dio increased Myogenin expression while decreasing Atrogin-1 and MuRF-1 expression. Additionally, Ast-Dio activated Rab5a/mTOR and its downstream effector AMPK. Moreover, Ast-Dio modulated mitochondrial quality control by decreasing Mitofusin-2 expression while increasing the expression of TFAM, PGC-1α, and MFF.

CONCLUSIONS

Our results suggest that Ast-Dio treatment may alleviate sarcopenia in mice with senile type 2 diabetes mellitus through its effects on the Rab5a/mTOR pathway and mitochondrial quality control.

The pathogenesis and potential therapeutic targets in sepsis

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

MafB regulates NLRP3 inflammasome activation by sustaining p62 expression in macrophages

Activation of the NLRP3 inflammasome is a two-step process: the priming and the activating. The priming step involves the induction of NLRP3 and pro-IL-1β, while the activating step leads to the full inflammasome activation triggered by a NLRP3 activator. Although mechanisms underlying the NLRP3 inflammasome activation have been increasingly clear, the regulation of this process remains incompletely understood. In this study, we find that LPS and Pseudomonas aeruginosa cause a rapid downregulation in MafB transcription in macrophages, which leads to a quick decline in the level of MafB protein because MafB is short-lived and constantly degraded by the ubiquitin/proteasome system. We find that MafB knockdown or knockout markedly enhances the NLRP3, but not the NLRP1, NLRC4, or AIM2, inflammasome activation in macrophages. Conversely, pharmacological induction of MafB diminishes the NLRP3 inflammasome activation. Mechanistically, we find that MafB sustains the expression of p62, a key mediator of autophagy/mitophagy. We find that MafB inhibits mitochondrial damage, and mitochondrial ROS production and DNA cytoplasmic release. Furthermore, we find that myeloid MafB deficient mice demonstrate increased systemic and lung IL-1β production in response to LPS treatment and P. aeruginosa infection and deficient lung P. aeruginosa clearance in vivo. In conclusion, our study demonstrates that MafB is an important negative regulator of the NLRP3 inflammasome. Our findings suggest that strategies elevating MafB may be effective to treat immune disorders due to excessive activation of the NLRP3 inflammasome.

Reactive oxygen species trigger inflammasome activation after intracellular microbial interaction

The intracellular production of reactive oxygen species (ROS), composed of oxygen-reduced molecules, is important not only because of their lethal effects on microorganisms but also due to their potential inflammatory and metabolic regulation properties. The ROS pro-inflammatory properties are associated with the second signal to inflammasome activation, leading to cleaving pro-IL-1β and pro-IL18 before their secretion, as well as gasdermin-D, leading to pyroptosis. Some microorganisms can modulate NLRP3 and AIM-2 inflammasomes through ROS production: whilst Mycobacterium bovis, Mycobacterium kansasii, Francisella novicida, Brucella abortus, Listeria monocytogenes, Influenza virus, Syncytial respiratory virus, Porcine reproductive and respiratory syndrome virus, SARS-CoV, Mayaro virus, Leishmania amazonensis and Plasmodium sp. enhance inflammasome assembly, Hepatitis B virus, Mycobacterium marinum, Mycobacterium tuberculosis, Francisella tularensis and Leishmania sp. disrupt it. This process represents a recent cornerstone in our knowledge of the immunology of intracellular pathogens, which is reviewed in this mini-review.

Application and value of hydrogen sulfide modulated autophagy in sepsis

Sepsis is is anabnormalhost immune responsecausedbyinfection. Antibiotics, anti-viral drugs, and vasoactive drugs have always been used in the traditional treatment of sepsis, but there are no specific and effective drugs in clinical practice. Autophagy is a highly conservative process in biological evolution, and plays an important role in maintaining intracellular homeostasis and cellular self-renewal. Autophagy can remove and degrade misfolding proteins and damaged organelles in cells, providing materials for cell repair and self-renewal. Hydrogen sulfide (H2S) is a colorless gas that smells likerotteneggs. It is the third endogenous gas signal molecule discovered after nitric oxide and carbon monoxide and has become a research hotspot in recent years. H2S has a variety of biological functions and plays an important role in various physiological and pathological processes. Thereisgrowingevidencethat H2S can regulate autophagy. The intervention of autophagy is a promising therapeutic strategy to improve sepsis organ damage. This article reviews the organ protection of autophagy in sepsis and the role of H2S in regulating autophagy in sepsis, revealing that H2S intervention with autophagy may be a a worthy target in sepsis treatment.

Bergapten inhibits NLRP3 inflammasome activation and pyroptosis via promoting mitophagy

Inhibition of NLRP3 inflammasome activation produces potent therapeutic effects in a wide array of inflammatory diseases. Bergapten (BeG), a furocoumarin phytohormone present in many herbal medicines and fruits, exibits anti-inflammatory activity. In this study we characterized the therapeutic potential of BeG against bacterial infection and inflammation-related disorders, and elucidated the underlying mechanisms. We showed that pre-treatment with BeG (20 μM) effectively inhibited NLRP3 inflammasome activation in both lipopolysaccharides (LPS)-primed J774A.1 cells and bone marrow-derived macrophages (BMDMs), evidenced by attenuated cleaved caspase-1 and mature IL-1β release, as well as reduced ASC speck formation and subsequent gasdermin D (GSDMD)-mediated pyroptosis. Transcriptome analysis revealed that BeG regulated the expression of genes involved in mitochondrial and reactive oxygen species (ROS) metabolism in BMDMs. Moreover, BeG treatment reversed the diminished mitochondrial activity and ROS production after NLRP3 activation, and elevated the expression of LC3-II and enhanced the co-localization of LC3 with mitochondria. Treatment with 3-methyladenine (3-MA, 5 mM) reversed the inhibitory effects of BeG on IL-1β, cleaved caspase-1 and LDH release, GSDMD-N formation as well as ROS production. In mouse model of Escherichia coli-induced sepsis and mouse model of Citrobacter rodentium-induced intestinal inflammation, pre-treatment with BeG (50 mg/kg) significantly ameliorated tissue inflammation and injury. In conclusion, BeG inhibits NLRP3 inflammasome activation and pyroptosis by promoting mitophagy and maintaining mitochondrial homeostasis. These results suggest BeG as a promising drug candidate for the treatment of bacterial infection and inflammation-related disorders.

Mitochondrial DNA Release in Innate Immune Signaling

According to the endosymbiotic theory, most of the DNA of the original bacterial endosymbiont has been lost or transferred to the nucleus, leaving a much smaller (∼16 kb in mammals), circular molecule that is the present-day mitochondrial DNA (mtDNA). The ability of mtDNA to escape mitochondria and integrate into the nuclear genome was discovered in budding yeast, along with genes that regulate this process. Mitochondria have emerged as key regulators of innate immunity, and it is now recognized that mtDNA released into the cytoplasm, outside of the cell, or into circulation activates multiple innate immune signaling pathways. Here, we first review the mechanisms through which mtDNA is released into the cytoplasm, including several inducible mitochondrial pores and defective mitophagy or autophagy. Next, we cover how the different forms of released mtDNA activate specific innate immune nucleic acid sensors and inflammasomes. Finally, we discuss how intracellular and extracellular mtDNA release, including circulating cell-free mtDNA that promotes systemic inflammation, are implicated in human diseases, bacterial and viral infections, senescence and aging.

Prediction of Prostate Cancer Biochemical and Clinical Recurrence Is Improved by IHC-Assisted Grading Using Appl1, Sortilin and Syndecan-1

Gleason scoring is used within a five-tier risk stratification system to guide therapeutic decisions for patients with prostate cancer. This study aimed to compare the predictive performance of routine H&E or biomarker-assisted ISUP (International Society of Urological Pathology) grade grouping for assessing the risk of biochemical recurrence (BCR) and clinical recurrence (CR) in patients with prostate cancer. This retrospective study was an assessment of 114 men with prostate cancer who provided radical prostatectomy samples to the Australian Prostate Cancer Bioresource between 2006 and 2014. The prediction of CR was the primary outcome (median time to CR 79.8 months), and BCR was assessed as a secondary outcome (median time to BCR 41.7 months). The associations of (1) H&E ISUP grade groups and (2) modified ISUP grade groups informed by the Appl1, Sortilin and Syndecan-1 immunohistochemistry (IHC) labelling were modelled with BCR and CR using Cox proportional hazard approaches. IHC-assisted grading was more predictive than H&E for BCR (C-statistic 0.63 vs. 0.59) and CR (C-statistic 0.71 vs. 0.66). On adjusted analysis, IHC-assisted ISUP grading was independently associated with both outcome measures. IHC-assisted ISUP grading using the biomarker panel was an independent predictor of individual BCR and CR. Prospective studies are needed to further validate this biomarker technology and to define BCR and CR associations in real-world cohorts.

Novel Histopathological Biomarkers in Prostate Cancer: Implications and Perspectives

Prostate cancer (PCa) is the second most frequently diagnosed cancer in men. Despite the significant progress in cancer diagnosis and treatment over the last few years, the approach to disease detection and therapy still does not include histopathological biomarkers. The dissemination of PCa is strictly related to the creation of a premetastatic niche, which can be detected by altered levels of specific biomarkers. To date, the risk factors for biochemical recurrence include lymph node status, prostate-specific antigen (PSA), PSA density (PSAD), body mass index (BMI), pathological Gleason score, seminal vesicle invasion, extraprostatic extension, and intraductal carcinoma. In the future, biomarkers might represent another prognostic factor, as discussed in many studies. In this review, we focus on histopathological biomarkers (particularly CD169 macrophages, neuropilin-1, cofilin-1, interleukin-17, signal transducer and activator of transcription protein 3 (STAT3), LIM domain kinase 1 (LIMK1), CD15, AMACR, prostate-specific membrane antigen (PSMA), Appl1, Sortilin, Syndecan-1, and p63) and their potential application in decision making regarding the prognosis and treatment of PCa patients. We refer to studies that found a correlation between the levels of biomarkers and tumor characteristics as well as clinical outcomes. We also hypothesize about the potential use of histopathological markers as a target for novel immunotherapeutic drugs or targeted radionuclide therapy, which may be used as adjuvant therapy in the future.

The Role of Rab Proteins in Mitophagy: Insights into Neurodegenerative Diseases

Mitochondrial dysfunction and vesicular trafficking alterations have been implicated in the pathogenesis of several neurodegenerative diseases. It has become clear that pathogenetic pathways leading to neurodegeneration are often interconnected. Indeed, growing evidence suggests a concerted contribution of impaired mitophagy and vesicles formation in the dysregulation of neuronal homeostasis, contributing to neuronal cell death. Among the molecular factors involved in the trafficking of vesicles, Ras analog in brain (Rab) proteins seem to play a central role in mitochondrial quality checking and disposal through both canonical PINK1/Parkin-mediated mitophagy and novel alternative pathways. In turn, the lack of proper elimination of dysfunctional mitochondria has emerged as a possible causative/early event in some neurodegenerative diseases. Here, we provide an overview of major findings in recent years highlighting the role of Rab proteins in dysfunctional mitochondrial dynamics and mitophagy, which are characteristic of neurodegenerative diseases. A further effort should be made in the coming years to clarify the sequential order of events and the molecular factors involved in the different processes. A clear cause-effect view of the pathogenetic pathways may help in understanding the molecular basis of neurodegeneration.

ADAM10-a "multitasker" in sepsis: focus on its posttranslational target

BACKGROUND

Sepsis has a complex pathogenesis in which the uncontrolled systemic inflammatory response triggered by infection leads to vascular barrier disruption, microcirculation dysfunction and multiple organ dysfunction syndrome. Numerous recent studies reveal that a disintegrin and metalloproteinase 10 (ADAM10) acts as a "molecular scissor" playing a pivotal role in the inflammatory response during sepsis by regulating proteolysis by cleaving various membrane protein substrates, including proinflammatory cytokines, cadherins and Notch, which are involved in intercellular communication. ADAM10 can also act as the cellular receptor for Staphylococcus aureus α-toxin, leading to lethal sepsis. However, its substrate-specific modulation and precise targets in sepsis have not yet to be elucidated.

METHODS

We performed a computer-based online search using PubMed and Google Scholar for published articles concerning ADAM10 and sepsis.

CONCLUSIONS

In this review, we focus on the functions of ADAM10 in sepsis-related complex endothelium-immune cell interactions and microcirculation dysfunction through the diversity of its substrates and its enzymatic activity. In addition, we highlight the posttranslational mechanisms of ADAM10 at specific subcellular sites, or in multimolecular complexes, which will provide the insight to intervene in the pathophysiological process of sepsis caused by ADAM10 dysregulation.

Role of the regulation of mesenchymal stem cells on macrophages in sepsis

Sepsis is a common clinical critical disease with high mortality. The excessive release of cytokines from macrophages is the main cause of out-of-control immune response in sepsis. Mesenchymal stem cells (MSCs) are thought to be useful in adjunctive therapy of sepsis and related diseases, due to their function in immune regulation, anti-inflammatory, antibacterial, and tissue regeneration. Also there have been several successful cases in clinical treatment. Some previous studies have shown that MSCs regulate the function of macrophages through secreting cytokines and extracellular vesicles, or transferring mitochondria directly to target cells, which affects the progress of sepsis. Here, we review the regulation of MSCs on macrophages in sepsis, mainly focus on the regulation ways. We hope that will help to understand the immunological mechanism and also provide some clues for the clinical application of MSCs in the biotherapy of sepsis.

NMDAR-dependent synaptic potentiation via APPL1 signaling is required for the accessibility of a prefrontal neuronal assembly in retrieving fear extinction

BACKGROUND

The ventromedial prefrontal cortex (vmPFC) has been viewed as a locus to store and recall extinction memory. However, the synaptic and cellular mechanisms underlying this process remain elusive.

METHODS

We combined transgenic mice, electrophysiological recording, activity-dependent cell labeling, and chemogenetic manipulation to analyze the role of adaptor protein APPL1 in the vmPFC for fear extinction retrieval.

RESULTS

We found that both constitutive and conditional APPL1 knockout decreases NMDA receptor (NMDAR) function in the vmPFC and impairs fear extinction retrieval. Moreover, APPL1 undergoes nuclear translocation during extinction retrieval. Blocking APPL1 nucleocytoplasmic translocation reduces NMDAR currents and disrupts extinction retrieval. We further identified a prefrontal neuronal ensemble that is both necessary and sufficient for the storage of extinction memory. Inducible APPL1 knockout in this ensemble abolishes NMDAR-dependent synaptic potentiation and disrupts extinction retrieval, while simultaneously chemogenetic activation of this ensemble rescues the impaired behaviors.

CONCLUSIONS

Therefore, our results indicate that a prefrontal neuronal ensemble stores extinction memory, and APPL1 signaling supports these neurons to retrieve extinction memory via controlling NMDAR-dependent potentiation.

Chemical mimetics of the N-degron pathway alleviate systemic inflammation by activating mitophagy and immunometabolic remodeling

The Arg/N-degron pathway, which is involved in the degradation of proteins bearing an N-terminal signal peptide, is connected to p62/SQSTM1-mediated autophagy. However, the impact of the molecular link between the N-degron and autophagy pathways is largely unknown in the context of systemic inflammation. Here, we show that chemical mimetics of the N-degron Nt-Arg pathway (p62 ligands) decreased mortality in sepsis and inhibited pathological inflammation by activating mitophagy and immunometabolic remodeling. The p62 ligands alleviated systemic inflammation in a mouse model of lipopolysaccharide (LPS)-induced septic shock and in the cecal ligation and puncture model of sepsis. In macrophages, the p62 ligand attenuated the production of proinflammatory cytokines and chemokines in response to various innate immune stimuli. Mechanistically, the p62 ligand augmented LPS-induced mitophagy and inhibited the production of mitochondrial reactive oxygen species in macrophages. The p62 ligand-mediated anti-inflammatory, antioxidative, and mitophagy-activating effects depended on p62. In parallel, the p62 ligand significantly downregulated the LPS-induced upregulation of aerobic glycolysis and lactate production. Together, our findings demonstrate that p62 ligands play a critical role in the regulation of inflammatory responses by orchestrating mitophagy and immunometabolic remodeling.

Aberrant protein expression of Appl1, Sortilin and Syndecan-1 during the biological progression of prostate cancer

Diagnosis and assessment of patients with prostate cancer is dependent on accurate interpretation and grading of histopathology. However, morphology does not necessarily reflect the complex biological changes occurring in prostate cancer disease progression, and current biomarkers have demonstrated limited clinical utility in patient assessment. This study aimed to develop biomarkers that accurately define prostate cancer biology by distinguishing specific pathological features that enable reliable interpretation of pathology for accurate Gleason grading of patients. Online gene expression databases were interrogated and a pathogenic pathway for prostate cancer was identified. The protein expression of key genes in the pathway, including adaptor protein containing a pleckstrin homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif 1 (Appl1), Sortilin and Syndecan-1, was examined by immunohistochemistry (IHC) in a pilot study of 29 patients with prostate cancer, using monoclonal antibodies designed against unique epitopes. Appl1, Sortilin, and Syndecan-1 expression was first assessed in a tissue microarray cohort of 112 patient samples, demonstrating that the monoclonal antibodies clearly illustrate gland morphologies. To determine the impact of a novel IHC-assisted interpretation (the utility of Appl1, Sortilin, and Syndecan-1 labelling as a panel) of Gleason grading, versus standard haematoxylin and eosin (H&E) Gleason grade assignment, a radical prostatectomy sample cohort comprising 114 patients was assessed. In comparison to H&E, the utility of the biomarker panel reduced subjectivity in interpretation of prostate cancer tissue morphology and improved the reliability of pathology assessment, resulting in Gleason grade redistribution for 41% of patient samples. Importantly, for equivocal IHC-assisted labelling and H&E staining results, the cancer morphology interpretation could be more accurately applied upon re-review of the H&E tissue sections. This study addresses a key issue in the field of prostate cancer pathology by presenting a novel combination of three biomarkers and has the potential to transform clinical pathology practice by standardising the interpretation of the tissue morphology.

Ononin alleviates DSS-induced colitis through inhibiting NLRP3 inflammasome via triggering mitophagy

BACKGROUND

Ononin, a flavonoid isolated from Astragalus membranaceus root, is the active ingredient of A. membranaceus and has potential anti-inflammatory properties, but its effect on colitis is unclear.

AIMS

This study aimed to explore the anticolitis effect of Ononin by establishing a colitis model in mice induced by dextran sulfate sodium (DSS).

METHODS

Male C57BL/6 mice were provided DSS, then treated with Ononin (10, 20, 40 mg/kg) or 5-ASA (40 mg/kg). The colitis symptoms were observed, the disease activity index (DAI) score were recorded daily, and colonic inflammation was evaluted by histopathological scoring. The expression of cytokines, inflammatory mediators, and mitophagy/NLRP3 inflammasome-related proteins were measured.

RESULTS

Ononin significantly alleviated weight loss and colon shortening in mice with colitis (p < .01). Moreover, Ononin decreased the production of inflammatory cytokines and mediators associated with colitis (p < .05). In addition, Ononin inhibited macrophages infiltration and reduced caspase-1 activation in colitis mice. Caspase-1 activation is closely related to the NLRP3 inflammasome. Therefore, we investigated the effect of Ononin on NLRP3 inflammasome in vitro. The relevant results confirmed that Ononin inhibited NLRP3 inflammasome activation and inhibited mitochondrial damage (p < .05). Further studies revealed that Ononin inhibited mitochondrial damage through triggering mitophagy (p < .05).

CONCLUSION

Ononin alleviates DSS-induced colitis by activating mitophagy to inhibit NLRP3 inflammasome.

Relevance of the pyroptosis-related inflammasome drug targets in the Chuanxiong to improve diabetic nephropathy

Background

A chronic inflammatory disease caused by disturbances in metabolism, diabetic nephropathy (DN) is a chronic inflammatory disease. Pyroptosis is a novel form of programmed cell death in many inflammation-related diseases, including DN. Therefore, pyroptosis could be a promising target for DN therapy.

Methods

To get the components and pharmacodynamic targets of Chuanxiong, we identified by searching TCMID, TCMSP, ETCM and HERB databases. Then, from the Molecular Signatures Database (MSigDB) and Gene Ontology (GO) database, pyroptosis genes were collected. Identification of critical genes in DN by bioinformatics analysis and then using the ConsensusClusterPlus package to divide the express data of diff genes into some subgroups with different levels of pyroptosis; the WGCNA machine algorithm was used to simulate the mechanism Chuanxiong improving DN.

Results

In this study, we found DHCR24, ANXA1, HMOX1, CDH13, ALDH1A1, LTF, CHI3L1, CACNB2, and MTHFD2 interacted with the diff genes of DN. We used GSE96804 as a validation set to evaluate the changes of APIP, CASP6, CHMP2B, CYCS, DPP8, and TP53 in four different cell proapoptotic states. WGCNA analysis showed that DHCR24, CHI3L1, and CACNB2 had significant changes in different cell proapoptotic levels. In the experimental stage, we also confirmed that the active ingredients of Chuanxiong could improve the inflammatory state and the levels of pyroptosis under high glucose.

Conclusion

The improvement of DN by Chuanxiong is related to the change of pyroptosis.

Engineered Extracellular Vesicles with SHP2 High Expression Promote Mitophagy for Alzheimer's Disease Treatment

Mitochondrial dysfunction is a fundamental pathological feature of Alzheimer's disease (AD). However, toxicity and poor brain enrichment of existing mitophagy inducers limit their further applications. In this study, a platform for AD therapy is developed using nanosized mesenchymal-stem-cells-derived extracellular vesicles with tyrosine phosphatase-2 (SHP2) high-expression (MSC-EVs-SHP2). The high blood-brain barrier penetration ability of MSC-EVs-SHP2 is demonstrated in AD-mice, facilitating SHP2 delivery to the brain. In addition, MSC-EVs-SHP2 significantly induces mitophagy of neuronal cells, which alleviates mitochondrial damage-mediated apoptosis and NLRP3 inflammasome activation. Mitophagy further diminishes neuronal cells apoptosis and neuroinflammation, culminating with rescued synaptic loss and cognitive decline in an AD mouse model. The EV-engineering technology provides a potential platform for effective AD therapy by inducing mitophagy.

Dynamin-Related Protein 1 Is Involved in Mitochondrial Damage, Defective Mitophagy, and NLRP3 Inflammasome Activation Induced by MSU Crystals

Excessive generation of reactive oxygen species (ROS) has great impacts on MSU crystal-induced inflammation. Drp1-dependent mitochondrial fission is closely associated with mitochondrial ROS levels. However, whether Drp1 signaling contributes to MSU crystal-induced inflammation remains unclear. Mice bone marrow-derived macrophages (BMDMs) were primed with LPS and then stimulated with MSU suspensions for 12 h. The protein levels associated with mitochondrial dynamics, oxidative stress, and mitophagy were detected by Western blot. BMDMs were loaded with MitoTracker Green probe to detect mitochondrial morphology. To measure mitochondrial reactive oxygen species (ROS) and total ROS levels, cells were loaded, respectively, with MitoSOX and DHE probes. The effects of Mito-TEMPO, an antioxidant that targets the mitochondria or DRP1 inhibitor (Mdivi-1) on MSU crystal-induced peritonitis and arthritis mouse models, were evaluated. Our study revealed that MSU crystal stimulation resulted in elevation of mitochondrial fragmentation of BMDMs. Treatment with Mito-TEMPO or Drp1 knockdown significantly ameliorated the mitochondrial damage induced by MSU crystals. BMDMs exposure to MSU crystals increased the expression of auto/mitophagy marker proteins and promoted the fusion of mitophagosomes with lysosomes, leading to accumulation of mitolysosomes. Drp1 knockdown alleviated defective mitophagy and activation of the NLRP3 inflammasome in MSU crystal-treated BMDMs. This study indicates that there is crosstalk between mitochondrial ROS and Drp1 signaling in MSU crystal-induced inflammation. Drp1 signaling is involved in MSU crystal-induced mitochondrial damage, impaired mitophagy and NLRP3 inflammasome activation.

Mitochondrial VDAC1: A Potential Therapeutic Target of Inflammation-Related Diseases and Clinical Opportunities

The multifunctional protein, voltage-dependent anion channel 1 (VDAC1), is located on the mitochondrial outer membrane. It is a pivotal protein that maintains mitochondrial function to power cellular bioactivities via energy generation. VDAC1 is involved in regulating energy production, mitochondrial oxidase stress, Ca²⁺ transportation, substance metabolism, apoptosis, mitochondrial autophagy (mitophagy), and many other functions. VDAC1 malfunction is associated with mitochondrial disorders that affect inflammatory responses, resulting in an up-regulation of the body’s defensive response to stress stimulation. Overresponses to inflammation may cause chronic diseases. Mitochondrial DNA (mtDNA) acts as a danger signal that can further trigger native immune system activities after its secretion. VDAC1 mediates the release of mtDNA into the cytoplasm to enhance cytokine levels by activating immune responses. VDAC1 regulates mitochondrial Ca²⁺ transportation, lipid metabolism and mitophagy, which are involved in inflammation-related disease pathogenesis. Many scientists have suggested approaches to deal with inflammation overresponse issues via specific targeting therapies. Due to the broad functionality of VDAC1, it may become a useful target for therapy in inflammation-related diseases. The mechanisms of VDAC1 and its role in inflammation require further exploration. We comprehensively and systematically summarized the role of VDAC1 in the inflammatory response, and hope that our research will lead to novel therapeutic strategies that target VDAC1 in order to treat inflammation-related disorders.

Irisin Promotes Osteogenesis by Modulating Oxidative Stress and Mitophagy through SIRT3 Signaling under Diabetic Conditions

Advanced glycation end products (AGEs) accumulate in the bone tissue of patients with diabetes mellitus, resulting in oxidative stress, poor bone healing, or regeneration. Irisin, a novel exercise-induced myokine, is involved in the regulation of bone metabolism. However, the effects of irisin on adipose-derived stem cell (ASC) osteogenic differentiation and bone healing under diabetic conditions remain poorly understood. ASCs were obtained from inguinal fat of Sprague-Dawley rats and treated with different concentrations of AGEs and irisin. Cell proliferation, apoptosis, and osteogenic differentiation abilities of ASCs were detected. To explore the regulatory role of sirtuin 3 (SIRT3), ASCs were transfected with lentivirus-mediated SIRT3 overexpression or knockdown vectors. Next, we investigated mitochondrial functions, mitophagy, and mitochondrial biogenesis in different groups. Moreover, SOD2 acetylation and potential signaling pathways were assessed. Additionally, a diabetic rat model was used to evaluate the effect of irisin on bone healing in calvarial critical-sized defects (CSDs) in vivo. Our results showed that irisin incubation mitigated the inhibitory effects of AGEs on ASCs by increasing cell viability and promoting osteogenesis. Moreover, irisin modulated mitochondrial membrane potential, intracellular ROS levels, mitochondrial O₂^·− status, ATP generation, complex I and IV activities, mitophagy, and mitochondrial biogenesis via a SIRT3-mediated pathway under AGEs exposure. Furthermore, in calvarial CSDs of diabetic rats, transplantation of gels encapsulating irisin-pretreated ASCs along with irisin largely enhanced bone healing. These findings suggest that irisin attenuates AGE-induced ASC dysfunction through SIRT3-mediated maintenance of oxidative stress homeostasis and regulation of mitophagy and mitochondrial biogenesis. Thus, our studies shed new light on the role of irisin in promoting the ASC osteogenesis and targeting SIRT3 as a novel therapeutic intervention strategy for bone regeneration under diabetic conditions.

Impairment of APPL1/Myoferlin facilitates adipogenic differentiation of mesenchymal stem cells by blocking autophagy flux in osteoporosis

An imbalance of human mesenchymal stem cells (hMSCs) adipogenic and osteogenic differentiation is crucial in the pathogenesis of osteoporosis, and elucidation of the underlying mechanism is urgently needed. APPL1, an adaptor protein of the adiponectin receptor, was recently shown to be closely related to bone mass. However, the role of APPL1 in the imbalance of hMSC differentiation in osteoporosis is unclear. Therefore, we aimed to explore the mechanisms by which APPL1 alters hMSCs adipogenic differentiation in osteoporosis. Here, we found that APPL1 expression was downregulated in elderly patients with osteoporosis and in mouse osteoporosis model. APPL1 negatively regulated hMSC adipogenic differentiation in vivo and in vitro. Mechanistically, by enhancing ubiquitination-mediated Myoferlin degradation, downregulated APPL1 expression increased the risk of lysosome dysfunction during hMSCs adipogenic differentiation. Lysosomal dysfunction inhibited autophagy flux by suppressing autophagosome degradation and promoted hMSC differentiation towards the adipocyte lineage. Our findings suggest that APPL1/Myoferlin downregulation promoted hMSCs adipogenic differentiation by inhibiting autophagy flux, further impairing the balance of hMSCs adipogenic and osteogenic differentiation in osteoporosis; the APPL1/ Myoferlin axis may be a promising diagnostic and therapeutic target for osteoporosis.

Hormesis and Oxidative Distress: Pathophysiology of Reactive Oxygen Species and the Open Question of Antioxidant Modulation and Supplementation

Alterations of redox homeostasis leads to a condition of resilience known as hormesis that is due to the activation of redox-sensitive pathways stimulating cell proliferation, growth, differentiation, and angiogenesis. Instead, supraphysiological production of reactive oxygen species (ROS) exceeds antioxidant defence and leads to oxidative distress. This condition induces damage to biomolecules and is responsible or co-responsible for the onset of several chronic pathologies. Thus, a dietary antioxidant supplementation has been proposed in order to prevent aging, cardiovascular and degenerative diseases as well as carcinogenesis. However, this approach has failed to demonstrate efficacy, often leading to harmful side effects, in particular in patients affected by cancer. In this latter case, an approach based on endogenous antioxidant depletion, leading to ROS overproduction, has shown an interesting potential for enhancing susceptibility of patients to anticancer therapies. Therefore, a deep investigation of molecular pathways involved in redox balance is crucial in order to identify new molecular targets useful for the development of more effective therapeutic approaches. The review herein provides an overview of the pathophysiological role of ROS and focuses the attention on positive and negative aspects of antioxidant modulation with the intent to find new insights for a successful clinical application.

A new role of the early endosome in restricting NLRP3 inflammasome via mitophagy

NLRP3 (NLR family pyrin domain containing 3) inflammasome is a potent mediator of inflammation due to its ability to produce the pro-inflammatory cytokines IL1B (interleukin 1 beta) and IL18 in response to numerous danger signals and pathogens. Mitophagy, a selective form of autophagy, restricts NLRP3 inflammasome activation by limiting the mitochondrial-derived danger signals. Here, we demonstrated that the adaptor protein APPL1 together with its interaction partner RAB5 in early endosomes negatively regulate NLRP3 inflammasome activation via induction of mitophagy in macrophages. Hematopoietic-deletion of Appl1 exacerbates systemic NLRP3 inflammasome activation in rodent models under obese or septic conditions. Our study identified a new regulatory network between early endosomes and mitochondria in control of NLRP3 inflammasome activation.