UCP2-induced fatty acid synthase promotes NLRP3 inflammasome activation during sepsis

Metabolic reprogramming of the inflammatory response in the nervous system: the crossover between inflammation and metabolism

Metabolism is a fundamental process by which biochemicals are broken down to produce energy (catabolism) or used to build macromolecules (anabolism). Metabolism has received renewed attention as a mechanism that generates molecules that modulate multiple cellular responses. This was first identified in cancer cells as the Warburg effect, but it is also present in immunocompetent cells. Studies have revealed a bidirectional influence of cellular metabolism and immune cell function, highlighting the significance of metabolic reprogramming in immune cell activation and effector functions. Metabolic processes such as glycolysis, oxidative phosphorylation, and fatty acid oxidation have been shown to undergo dynamic changes during immune cell response, facilitating the energetic and biosynthetic demands. This review aims to provide a better understanding of the metabolic reprogramming that occurs in different immune cells upon activation, with a special focus on central nervous system disorders. Understanding the metabolic changes of the immune response not only provides insights into the fundamental mechanisms that regulate immune cell function but also opens new approaches for therapeutic strategies aimed at manipulating the immune system.

The palmitoylation of gasdermin D directs its membrane translocation and pore formation during pyroptosis

Plasma membrane perforation elicited by caspase cleavage of the gasdermin D (GSDMD) N-terminal domain (GSDMD-NT) triggers pyroptosis. The mechanisms underlying GSDMD membrane translocation and pore formation are not fully understood. Here, using a proteomic approach, we identified fatty acid synthase (FASN) as a GSDMD-binding partner. S-palmitoylation of GSDMD at Cys191/Cys192 (human/mouse), catalyzed by palmitoyl acyltransferases ZDHHC5 and ZDHHC9 and facilitated by reactive oxygen species (ROS), directly mediated membrane translocation of GSDMD-NT but not full-length GSDMD (GSDMD-FL). Palmitoylation of GSDMD-FL could be induced before inflammasome activation by stimuli such as lipopolysaccharide (LPS), consequently serving as an essential molecular event in macrophage priming. Inhibition of GSDMD palmitoylation suppressed macrophage pyroptosis and IL-1β release, mitigated organ damage, and enhanced the survival of septic mice. Thus, GSDMD-NT palmitoylation is a key regulatory mechanism controlling GSDMD membrane localization and activation, which may offer an additional target for modulating immune activity in infectious and inflammatory diseases.

Advances in Metabolic Regulation of Macrophage Polarization State

Macrophages are significant immune-related cells that are essential for tissue growth, homeostasis maintenance, pathogen resistance, and damage healing. The studies on the metabolic control of macrophage polarization state in recent years and the influence of polarization status on the development and incidence of associated disorders are expounded upon in this article. Firstly, we reviewed the origin and classification of macrophages, with particular attention paid to how the tricarboxylic acid cycle and the three primary metabolites affect macrophage polarization. The primary metabolic hub that controls macrophage polarization is the tricarboxylic acid cycle. Finally, we reviewed the polarization state of macrophages influences the onset and progression of cancers, inflammatory disorders, and other illnesses.

Acetyl-CoA synthetase 2 induces pyroptosis and inflammation of renal epithelial tubular cells in sepsis-induced acute kidney injury by upregulating the KLF5/NF-κB pathway

BACKGROUND

Pyroptosis of the renal tubular epithelial cells (RTECs) and interstitial inflammation are central pathological characteristics of acute kidney injury (AKI). Pyroptosis acts as a pro-inflammatory form of programmed cell death and is mainly dependent on activation of the NLRP3 inflammasome. Previous studies revealed that acetyl-CoA synthetase 2 (ACSS2) promotes inflammation during metabolic stress suggesting that ACSS2 might regulate pyroptosis and inflammatory responses of RTECs in AKI.

METHODS AND RESULTS

The expression of ACSS2 was found to be significantly increased in the renal epithelial cells of mice with lipopolysaccharide (LPS)-induced AKI. Pharmacological and genetic strategies demonstrated that ACSS2 regulated NLRP3-mediated caspase-1 activation and pyroptosis through the stimulation of the KLF5/NF-κB pathway in RTECs. The deletion of ACSS2 attenuated renal tubular pathological injury and inflammatory cell infiltration in an LPS-induced mouse model, and ACSS2-deficient mice displayed impaired NLRP3 activation-mediated pyroptosis and decreased IL-1β production in response to the LPS challenge. In HK-2 cells, ACSS2 deficiency suppressed NLRP3-mediated caspase-1 activation and pyroptosis through the downregulation of the KLF5/NF-κB pathway. The KLF5 inhibitor ML264 suppressed NF-κB activity and NLRP3-mediated caspase-1 activation, thus protecting HK-2 cells from LPS-induced pyroptosis.

CONCLUSION

Our results suggested that ACSS2 regulates activation of the NLRP3 inflammasome and pyroptosis by inducing the KLF5/NF-κB pathway in RTECs. These results identified ACSS2 as a potential therapeutic target in AKI.

A New Strategy for Targeting UCP2 to Modulate Glycolytic Reprogramming as a Treatment for Sepsis A New Strategy for Targeting UCP2

Sepsis is a severe and life-threatening disease caused by infection, characterized by a dysregulated immune response. Unfortunately, effective treatment strategies for sepsis are still lacking. The intricate interplay between metabolism and the immune system limits the treatment options for sepsis. During sepsis, there is a profound shift in cellular energy metabolism, which triggers a metabolic reprogramming of immune cells. This metabolic alteration impairs immune responses, giving rise to excessive inflammation and immune suppression. Recent research has demonstrated that UCP2 not only serves as a critical target in sepsis but also functions as a key metabolic switch involved in immune cell-mediated inflammatory responses. However, the regulatory mechanisms underlying this modulation are complex. This article focuses on UCP2 as a target and discusses metabolic reprogramming during sepsis and the complex regulatory mechanisms between different stages of inflammation. Our research indicates that overexpression of UCP2 reduces the Warburg effect, restores mitochondrial function, and improves the prognosis of sepsis. This discovery aims to provide a promising approach to address the significant challenges associated with metabolic dysfunction and immune paralysis.

The involvement of the mitochondrial membrane in drug delivery

Treatment effectiveness and biosafety are critical for disease therapy. Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. To further enhance the precision of disease treatment, future research should shift focus from targeted cellular delivery to targeted subcellular delivery. As the cellular powerhouses, mitochondria play an indispensable role in cell growth and regulation and are closely involved in many diseases (e.g., cancer, cardiovascular, and neurodegenerative diseases). The double-layer membrane wrapped on the surface of mitochondria not only maintains the stability of their internal environment but also plays a crucial role in fundamental biological processes, such as energy generation, metabolite transport, and information communication. A growing body of evidence suggests that various diseases are tightly related to mitochondrial imbalance. Moreover, mitochondria-targeted strategies hold great potential to decrease therapeutic threshold dosage, minimize side effects, and promote the development of precision medicine. Herein, we introduce the structure and function of mitochondrial membranes, summarize and discuss the important role of mitochondrial membrane-targeting materials in disease diagnosis/treatment, and expound the advantages of mitochondrial membrane-assisted drug delivery for disease diagnosis, treatment, and biosafety. This review helps readers understand mitochondria-targeted therapies and promotes the application of mitochondrial membranes in drug delivery. STATEMENT OF SIGNIFICANCE: Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. Compared to cell-targeted treatment, targeting of mitochondria for drug delivery offers higher efficiency and improved biosafety and will promote the development of precision medicine. As a natural material, the mitochondrial membrane exhibits excellent biocompatibility and can serve as a carrier for mitochondria-targeted delivery. This review provides an overview of the structure and function of mitochondrial membranes and explores the potential benefits of utilizing mitochondrial membrane-assisted drug delivery for disease treatment and biosafety. The aim of this review is to enhance readers' comprehension of mitochondrial targeted therapy and to advance the utilization of mitochondrial membrane in drug delivery.

Emerging nanomaterials targeting macrophage adapted to abnormal metabolism in cancer and atherosclerosis therapy (Review)

Macrophages, as highly heterogeneous and plastic immune cells, occupy a pivotal role in both pro‑inflammatory (M1) and anti‑inflammatory (M2) responses. While M1‑type macrophages secrete pro‑inflammatory factors to initiate and sustain inflammation, M2‑type macrophages promote inflammation regression and uphold tissue homeostasis. These distinct phenotypic transitions in macrophages are closely linked to significant alterations in cellular metabolism, encompassing key response pathways such as glycolysis, pentose phosphate pathway, oxidative phosphorylation, lipid metabolism, amino acid metabolism, the tricarboxylic acid cycle and iron metabolism. These metabolic adaptations enable macrophages to adapt their activities in response to varying disease microenvironments. Therefore, the present review focused primarily on elucidating the intricate metabolic pathways that underlie macrophage functionality. Subsequently, it offers a comprehensive overview of the current state‑of‑the‑art nanomaterials, highlighting their promising potential in modulating macrophage metabolism to effectively hinder disease progression in both cancer and atherosclerosis.

The implications of FASN in immune cell biology and related diseases

Fatty acid metabolism, particularly fatty acid synthesis, is a very important cellular physiological process in which nutrients are used for energy storage and biofilm synthesis. As a key enzyme in the fatty acid metabolism, fatty acid synthase (FASN) is receiving increasing attention. Although previous studies on FASN have mainly focused on various malignancies, many studies have recently reported that FASN regulates the survival, differentiation, and function of various immune cells, and subsequently participates in the occurrence and development of immune-related diseases. However, few studies to date systematically summarized the function and molecular mechanisms of FASN in immune cell biology and related diseases. In this review, we discuss the regulatory effect of FASN on immune cells, and the progress in research on the implications of FASN in immune-related diseases. Understanding the function of FASN in immune cell biology and related diseases can offer insights into novel treatment strategies for clinical diseases.

Dual-specificity phosphatase 5-mediated fatty acid oxidation promotes Mycobacterium bovis BCG -induced inflammatory responses

Mycobacterium tuberculosis (Mtb) reprograms FAs metabolism of macrophages during infection and affects inflammatory reaction eventually, however, the mechanism remains poorly understood. Here we show that Mycobacterium bovis (BCG) induces DUSP5 expression through TLR2-MAPKs signaling pathway and promotes fatty acid oxidation (FAO). Silencing DUSP5 by adeno-associated virus vector (AAV) ameliorates lung injury and DUSP5 knockdown reduces the expression of IL-1β, IL-6 and inactivated NF-κB signaling in BCG-infected macrophages. Of note, DUSP5 specific siRNA increases the content of free fatty acids (FFAs) and triglyceride (TG), but represses the expression of FAO associated enzymes such as CPT1A and PPARα, suggesting DUSP5 mediated FAO during BCG infection. Moreover, Inhibiting FAO by pharmacological manner suppresses IL-1β, IL-6, TNF-α expression and relieves lung damage. Taken together, our data indicates DUSP5 mediates FAO reprogramming and promotes inflammatory response to BCG infection.

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.

Theaflavin mitigates acute gouty peritonitis and septic organ injury in mice by suppressing NLRP3 inflammasome assembly

Activation of NLR family pyrin domain-containing 3 (NLRP3) inflammasome plays important role in defending against infections, but its aberrant activation is causally linked to many inflammatory diseases, thus being a therapeutic target for these diseases. Theaflavin, one major ingredient of black tea, exhibits potent anti-inflammatory and anti-oxidative activities. In this study, we investigated the therapeutic effects of theaflavin against NLRP3 inflammasome activation in macrophages in vitro and in animal models of related diseases. We showed that theaflavin (50, 100, 200 μM) dose-dependently inhibited NLRP3 inflammasome activation in LPS-primed macrophages stimulated with ATP, nigericin or monosodium urate crystals (MSU), evidenced by reduced release of caspase-1p10 and mature interleukin-1β (IL-1β). Theaflavin treatment also inhibited pyroptosis as shown by decreased generation of N-terminal fragment of gasdermin D (GSDMD-NT) and propidium iodide incorporation. Consistent with these, theaflavin treatment suppressed ASC speck formation and oligomerization in macrophages stimulated with ATP or nigericin, suggesting reduced inflammasome assembly. We revealed that theaflavin-induced inhibition on NLRP3 inflammasome assembly and pyroptosis resulted from ameliorated mitochondrial dysfunction and reduced mitochondrial ROS production, thereby suppressing interaction between NLRP3 and NEK7 downstream of ROS. Moreover, we showed that oral administration of theaflavin significantly attenuated MSU-induced mouse peritonitis and improved the survival of mice with bacterial sepsis. Consistently, theaflavin administration significantly reduced serum levels of inflammatory cytokines including IL-1β and attenuated liver inflammation and renal injury of mice with sepsis, concomitant with reduced generation of caspase-1p10 and GSDMD-NT in the liver and kidney. Together, we demonstrate that theaflavin suppresses NLRP3 inflammasome activation and pyroptosis by protecting mitochondrial function, thus mitigating acute gouty peritonitis and bacterial sepsis in mice, highlighting a potential application in treating NLRP3 inflammasome-related diseases.

Pitfalls of Mitochondrial Redox Signaling Research

Redox signaling from mitochondria (mt) to the cytosol and plasma membrane (PM) has been scarcely reported, such as in the case of hypoxic cell adaptation or (2-oxo-) 2-keto-isocaproate (KIC) β-like-oxidation stimulating insulin secretion in pancreatic β-cells. Mutual redox state influence between mitochondrial major compartments, the matrix and the intracristal space, and the cytosol is therefore derived theoretically in this article to predict possible conditions, when mt-to-cytosol and mt-to-PM signals may occur, as well as conditions in which the cytosolic redox signaling is not overwhelmed by the mitochondrial antioxidant capacity. Possible peroxiredoxin 3 participation in mt-to-cytosol redox signaling is discussed, as well as another specific case, whereby mitochondrial superoxide release is diminished, whereas the matrix MnSOD is activated. As a result, the enhanced conversion to H2O2 allows H2O2 diffusion into the cytosol, where it could be a predominant component of the H2O2 release. In both of these ways, mt-to-cytosol and mt-to-PM signals may be realized. Finally, the use of redox-sensitive probes is discussed, which disturb redox equilibria, and hence add a surplus redox-buffering to the compartment, where they are localized. Specifically, when attempts to quantify net H2O2 fluxes are to be made, this should be taken into account.

ATP-citrate lyase controls endothelial gluco-lipogenic metabolism and vascular inflammation in sepsis-associated organ injury

Sepsis involves endothelial cell (EC) dysfunction, which contributes to multiple organ failure. To improve therapeutic prospects, elucidating molecular mechanisms of vascular dysfunction is of the essence. ATP-citrate lyase (ACLY) directs glucose metabolic fluxes to de novo lipogenesis by generating acetyl-Co-enzyme A (acetyl-CoA), which facilitates transcriptional priming via protein acetylation. It is well illustrated that ACLY participates in promoting cancer metastasis and fatty liver diseases. Its biological functions in ECs during sepsis remain unclear. We found that plasma levels of ACLY were increased in septic patients and were positively correlated with interleukin (IL)-6, soluble E-selectin (sE-selectin), soluble vascular cell adhesion molecule 1 (sVCAM-1), and lactate levels. ACLY inhibition significantly ameliorated lipopolysaccharide challenge-induced EC proinflammatory response in vitro and organ injury in vivo. The metabolomic analysis revealed that ACLY blockade fostered ECs a quiescent status by reducing the levels of glycolytic and lipogenic metabolites. Mechanistically, ACLY promoted forkhead box O1 (FoxO1) and histone H3 acetylation, thereby increasing the transcription of c-Myc (MYC) to facilitate the expression of proinflammatory and gluco-lipogenic genes. Our findings revealed that ACLY promoted EC gluco-lipogenic metabolism and proinflammatory response through acetylation-mediated MYC transcription, suggesting ACLY as the potential therapeutic target for treating sepsis-associated EC dysfunction and organ injury.

Mitochondrial control of innate immune responses

Mitochondria are versatile organelles and essential components of numerous biological processes such as energy metabolism, signal transduction, and cell fate determination. In recent years, their critical roles in innate immunity have come to the forefront, highlighting impacts on pathogenic defense, tissue homeostasis, and degenerative diseases. This review offers an in-depth and comprehensive examination of the multifaceted mechanisms underlying the interactions between mitochondria and innate immune responses. We will delve into the roles of healthy mitochondria as platforms for signalosome assembly, the release of mitochondrial components as signaling messengers, and the regulation of signaling via mitophagy, particularly to cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling and inflammasomes. Furthermore, the review will explore the impacts of mitochondrial proteins and metabolites on modulating innate immune responses, the polarization of innate immune cells, and their implications on infectious and inflammatory diseases.

The NLRP3 inflammasome: role in the pathobiology of chronic pain

Chronic pain is not only one of the most common health problems, it is often challenging to treat adequately. Chronic pain has a high prevalence globally, affecting approximately 20% of the adult population. Chronic inflammatory pain and neuropathic (nerve) pain conditions are areas of large unmet medical need because analgesic/adjuvant agents recommended for alleviation of these types of chronic pain often lack efficacy and/or they produce dose-limiting side effects. Recent work has implicated the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome in the pathobiology of chronic pain, especially neuropathic and inflammatory pain conditions. NLRP3 is activated by damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). This in turn leads to recruitment and activation of caspase-1 an enzyme that cleaves the inactive IL-1β and IL-18 precursors to their respective mature pro-inflammatory cytokines (IL-1β and IL-18) for release into the cellular milieu. Caspase-1 also cleaves the pyroptosis-inducing factor, gasdermin D, that leads to oligomerization of its N-terminal fragment to form pores in the host cell membrane. This then results in cellular swelling, lysis and release of cytoplasmic contents in an inflammatory form of cell death, termed pyroptosis. The ultimate outcome may lead to the development of neuropathic pain and/or chronic inflammatory pain. In this review, we address a role for NLRP3 inflammasome activation in the pathogenesis of various chronic pain conditions.

A Lipid Perspective on Regulated Pyroptosis

Pyroptosis is a novel pro-inflammatory cell programmed death dependent on Gasdermin (GSMD) family-mediated membrane pore formation and subsequent cell lysis, accompanied by the release of inflammatory factors and expanding inflammation in multiple tissues. All of these processes have impacts on a variety of metabolic disorders. Dysregulation of lipid metabolism is one of the most prominent metabolic alterations in many diseases, including the liver, cardiovascular system, and autoimmune diseases. Lipid metabolism produces many bioactive lipid molecules, which are important triggers and endogenous regulators of pyroptosis. Bioactive lipid molecules promote pyroptosis through intrinsic pathways involving reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, lysosomal disruption, and the expression of related molecules. Pyroptosis can also be regulated during the processes of lipid metabolism, including lipid uptake and transport, de novo synthesis, lipid storage, and lipid peroxidation. Taken together, understanding the correlation between lipid molecules such as cholesterol and fatty acids and pyroptosis during metabolic processes can help to gain insight into the pathogenesis of many diseases and develop effective strategies from the perspective of pyroptosis.

UCP2 deficiency impairs podocyte autophagy in diabetic nephropathy

OBJECTIVE

Podocytes have been indicated to be a critical factor for the development of diabetic kidney disease. Podocyte loss leads to irreversible glomerular injury and proteinuria in animal models. As terminal differentiated cells, autophagy is crucial for maintaining podocyte homeostasis. Previous studies have shown that Uncoupling proteins 2 (UCP2) regulate fatty acid metabolism, mitochondrial calcium uptake and reactive oxygen species (ROS) production. This study aimed to investigate whether UCP2 promote autophagy in podocyte and further explore the regulation mechanism of UCP2.

METHODS

For podocyte-specific UCP2-KO mice, we cross bred UCP2f^l/fl mouse strain with the podocin-Cre mice. Diabetic mice were obtained by daily intraperitoneally injections of 40 mg/kg streptozotocin for 3 days. After 6 weeks, mice were scarified, and kidney tissues were analyzed by histological stain, Western blot, Immunofluorescence, and immunohistochemistry. Also, urine samples were collected for protein quantification. For in vitro study, podocytes were primary cultured from UCP2f^l/fl mouse or transfected with adeno-associated virus (AAV)-UCP2.

RESULTS

Diabetic kidney showed elevated expression of UCP2 and specific ablation of UCP2 in podocyte aggravates diabetes-induced albuminuria and glomerulopathy. UCP2 protects hyperglycemia-induced podocyte injury by promoting autophagy in vivo and in vitro. Rapamycin treatment significantly ameliorates streptozotocin (STZ)-induced podocyte injury in UCP2^-/- mice.

CONCLUSION

UCP2 expression in podocyte increased under diabetic condition and appeared to be an initial compensatory response. UCP2 deficiency in podocyte impaired autophagy and exacerbates podocyte injury and proteinuria in diabetic nephropathy.

The NLRP3 inflammasome: activation and regulation

The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome is a cytoplasmic supramolecular complex that is activated in response to cellular perturbations triggered by infection and sterile injury. Assembly of the NLRP3 inflammasome leads to activation of caspase-1, which induces the maturation and release of interleukin-1β (IL-1β) and IL-18, as well as cleavage of gasdermin D (GSDMD), which promotes a lytic form of cell death. Production of IL-1β via NLRP3 can contribute to the pathogenesis of inflammatory disease, whereas aberrant IL-1β secretion through inherited NLRP3 mutations causes autoinflammatory disorders. In this review, we discuss recent developments in the structure of the NLRP3 inflammasome, and the cellular processes and signaling events controlling its assembly and activation.

The role of immunometabolism in macrophage polarization and its impact on acute lung injury/acute respiratory distress syndrome

Lung macrophages constitute the first line of defense against airborne particles and microbes and are key to maintaining pulmonary immune homeostasis. There is increasing evidence suggesting that macrophages also participate in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), including the modulation of inflammatory responses and the repair of damaged lung tissues. The diversity of their functions may be attributed to their polarized states. Classically activated or inflammatory (M1) macrophages and alternatively activated or anti-inflammatory (M2) macrophages are the two main polarized macrophage phenotypes. The precise regulatory mechanism of macrophage polarization is a complex process that is not completely understood. A growing body of literature on immunometabolism has demonstrated the essential role of immunometabolism and its metabolic intermediates in macrophage polarization. In this review, we summarize macrophage polarization phenotypes, the role of immunometabolism, and its metabolic intermediates in macrophage polarization and ALI/ARDS, which may represent a new target and therapeutic direction.

Inhibition of fatty acid synthase protects obese mice from acute lung injury via ameliorating lung endothelial dysfunction

BACKGROUND

Obesity has been identified as a risk factor for acute lung injury/acute respiratory distress syndrome (ALI/ARDS). However, the underlying mechanisms remain elusive. This study aimed to investigate the role of fatty acid synthase (FASN) in lipopolysaccharide (LPS)-induced ALI under obesity.

METHODS

A high-fat diet-induced obese (DIO) mouse model was established and lean mice fed with regular chow diet were served as controls. LPS was intratracheally instilled to reproduce ALI in mice. In vitro, primary mouse lung endothelial cells (MLECs), treated by palmitic acid (PA) or co-cultured with 3T3-L1 adipocytes, were exposed to LPS. Chemical inhibitor C75 or shRNA targeting FASN was used for in vivo and in vitro loss-of-function studies for FASN.

RESULTS

After LPS instillation, the protein levels of FASN in freshly isolated lung endothelial cells from DIO mice were significantly higher than those from lean mice. MLECs undergoing metabolic stress exhibited increased levels of FASN, decreased levels of VE-cadherin with increased p38 MAPK phosphorylation and NLRP3 expression, mitochondrial dysfunction, and impaired endothelial barrier compared with the control MLECs when exposed to LPS. However, these effects were attenuated by FASN inhibition with C75 or corresponding shRNA. In vivo, LPS-induced ALI, C75 pretreatment remarkably alleviated LPS-induced overproduction of lung inflammatory cytokines TNF-α, IL-6, and IL-1β, and lung vascular hyperpermeability in DIO mice as evidenced by increased VE-cadherin expression in lung endothelial cells and decreased lung vascular leakage.

CONCLUSIONS

Taken together, FASN inhibition alleviated the exacerbation of LPS-induced lung injury under obesity via rescuing lung endothelial dysfunction. Therefore, targeting FASN may be a potential therapeutic target for ameliorating LPS-induced ALI in obese individuals.

The platelet pannexin 1-IL-1β axis orchestrates pancreatic ductal adenocarcinoma invasion and metastasis

We aimed to investigate the protumor mechanisms of platelets in pancreatic ductal adenocarcinoma (PDAC). Serum samples were collected from 656 PDAC patients and 3105 healthy people, and a Panx1 knockout tumor model and an adoptive platelet transfusion mouse model were established. We showed that the blood platelet counts were not significantly different between stage III/IV and stage I/II patients, while the number of the CD41+/CD62P+ platelets was significantly elevated in stage III/IV patients, indicating that CD41+/CD62P+ platelets are associated with a poor prognosis. Further analysis showed that a high level of CD41+/CD62P+ platelets was significantly correlated with microvascular invasion (P = 0.002), advanced 8th edition AJCC stage (P < 0.001), and a high CA19-9 level (P = 0.027) and independently predicted a poor prognosis for resectable I/II PDAC. Furthermore, we found significantly higher Panx1 expression in CD41+/CD62P+ platelets than in CD41+/CD62P- platelets in PDAC patients. Mechanistically, Panx1 was able to enhance IL-1β secretion in CD41+/CD62P+ platelets by phosphorylating p38 MAPK and consequently promoted the invasion and metastasis of PDAC cells. Finally, we synthesized a novel compound named PC63435 by the ligation of carbenoxolone (a Panx1 inhibitor) and PSGL-1 (a CD62P ligand). PC63435 specifically bound to CD41+/CD62P+ platelets, then blocked the Panx1/IL-1β pathway and reduced the proportion of CD41+/CD62P+ platelets, which suppressed PDAC tumor invasion and metastasis in vivo. These results demonstrated that the Panx1/IL-1β axis in CD41+/CD62P+ platelets enhanced PDAC cell malignancy and that this axis may be a promising target for PDAC therapy.

Metabolic Reprogramming and Its Regulatory Mechanism in Sepsis-Mediated Inflammation

Sepsis is a systemic inflammatory disease caused by an infection that can lead to multiple organ failure. Sepsis alters energy metabolism, leading to metabolic reprogramming of immune cells, which consequently disrupts innate and adaptive immune responses, triggering hyperinflammation and immunosuppression. This review summarizes metabolic reprogramming and its regulatory mechanism in sepsis-induced hyperinflammation and immunosuppression, highlights the significance and intricacies of immune cell metabolic reprogramming, and emphasizes the pivotal role of mitochondria in metabolic regulation and treatment of sepsis. This review provides an up-to-date overview of the relevant literature to inform future research directions in understanding the regulation of sepsis immunometabolism. Metabolic reprogramming has great promise as a new target for sepsis treatment in the future.

Palmitoylation of gasdermin D directs its membrane translocation and pore formation in pyroptosis

Gasdermin D (GSDMD)-mediated macrophage pyroptosis plays a critical role in inflammation and host defense. Plasma membrane perforation elicited by caspase-cleaved GSDMD N-terminal domain (GSDMD-NT) triggers membrane rupture and subsequent pyroptotic cell death, resulting in release of pro-inflammatory IL-1β and IL-18. However, the biological processes leading to its membrane translocation and pore formation are not fully understood. Here, using a proteomics approach, we identified fatty acid synthase (FASN) as a GSDMD-binding partner and demonstrated that post-translational palmitoylation of GSDMD at Cys191/Cys192 (human/mouse) led to membrane translocation of GSDMD-NT but not full-length GSDMD. GSDMD lipidation, mediated by palmitoyl acyltransferases ZDHHC5/9 and facilitated by LPS-induced reactive oxygen species (ROS), was essential for GSDMD pore-forming activity and pyroptosis. Inhibition of GSDMD palmitoylation with palmitate analog 2-bromopalmitate or a cell permeable GSDMD-specific competing peptide suppressed pyroptosis and IL-1β release in macrophages, mitigated organ damage, and extended the survival of septic mice. Collectively, we establish GSDMD-NT palmitoylation as a key regulatory mechanism controlling GSDMD membrane localization and activation, providing a novel target for modulating immune activity in infectious and inflammatory diseases.

One Sentence Summary

LPS-induced palmitoylation at Cys191/Cys192 is required for GSDMD membrane translocation and its pore-forming activity in macrophages.

Role of Damage-Associated Molecular Patterns (DAMPS) in the Postoperative Period after Colorectal Surgery

Anastomotic leakage (AL) is a defect of the intestinal wall at the anastomotic site and is one of the most severe complications in colorectal surgery. Previous studies have shown that the immune system response plays a significant role in the development of AL. In recent years, DAMPs (damage-associated molecular patterns) have been identified as cellular compounds with the ability to activate the immune system. The NLRP3 inflammasome plays an important role in the inflammatory responses which are mediated by DAMPs such as ATP, HSP proteins or uric acid crystals, when found in extracellular environments. Recent publications suggest that systemic concentration of DAMPs in patients with colorectal surgery may determine the inflammatory process and have a role in the occurrence of AL and other post-surgery complications. This review provides valuable knowledge about the current evidence supporting this hypothesis and highlights the possible role of these compounds in postoperative processes, which could open a new path to explore new strategies to prevent possible post-surgical complications.

NLRP3 inflammasome in neurodegenerative disease

Neurodegenerative diseases are characterized by a dysregulated neuro-glial microenvironment, culminating in functional deficits resulting from neuronal cell death. Inflammation is a hallmark of the neurodegenerative microenvironment and despite a critical role in tissue homeostasis, increasing evidence suggests that chronic inflammatory insult can contribute to progressive neuronal loss. Inflammation has been studied in the context of neurodegenerative disorders for decades but few anti-inflammatory treatments have advanced to clinical use. This is likely due to the related challenges of predicting and mitigating off-target effects impacting the normal immune response while detecting inflammatory signatures that are specific to the progression of neurological disorders. Inflammasomes are pro-inflammatory cytosolic pattern recognition receptors functioning in the innate immune system. Compelling pre-clinical data has prompted an intense interest in the role of the NLR family pyrin domain containing 3 (NLRP3) inflammasome in neurodegenerative disease. NLRP3 is typically inactive but can respond to sterile triggers commonly associated with neurodegenerative disorders including protein misfolding and aggregation, mitochondrial and oxidative stress, and exposure to disease-associated environmental toxicants. Clear evidence of enhanced NLRP3 inflammasome activity in common neurodegenerative diseases has coincided with rapid advancement of novel small molecule therapeutics making the NLRP3 inflammasome an attractive target for near-term interventional studies. In this review, we highlight evidence from model systems and patients indicating inflammasome activity in neurodegenerative disease associated with the NLRP3 inflammasome's ability to recognize pathologic forms of amyloid-β, tau, and α-synuclein. We discuss inflammasome-driven pyroptotic processes highlighting the potential utility of evaluating extracellular inflammasome-related proteins in the context of biomarker discovery. We complete the report by pointing out gaps in our understanding of intracellular modifiers of inflammasome activity and mechanisms regulating the resolution of inflammasome activation. The literature review and perspectives provide a conceptual platform for continued analysis of inflammation in neurodegenerative diseases through the study of inflammasomes and pyroptosis, mechanisms of inflammation and cell death now recognized to function in multiple highly prevalent neurological disorders.

Pyruvate dehydrogenase kinase supports macrophage NLRP3 inflammasome activation during acute inflammation

Activating the macrophage NLRP3 inflammasome can promote excessive inflammation with severe cell and tissue damage and organ dysfunction. Here, we show that pharmacological or genetic inhibition of pyruvate dehydrogenase kinase (PDHK) significantly attenuates NLRP3 inflammasome activation in murine and human macrophages and septic mice by lowering caspase-1 cleavage and interleukin-1β (IL-1β) secretion. Inhibiting PDHK reverses NLRP3 inflammasome-induced metabolic reprogramming, enhances autophagy, promotes mitochondrial fusion over fission, preserves crista ultrastructure, and attenuates mitochondrial reactive oxygen species (ROS) production. The suppressive effect of PDHK inhibition on the NLRP3 inflammasome is independent of its canonical role as a pyruvate dehydrogenase regulator. Our study suggestsa non-canonical role of mitochondrial PDHK in promoting mitochondrial stress and supporting NLRP3 inflammasome activation during acute inflammation.

Recombinant human angiotensin-converting enzyme 2 plays a protective role in mice with sepsis-induced cardiac dysfunction through multiple signaling pathways dependent on converting angiotensin II to angiotensin 1-7

Background

Sepsis-induced cardiac dysfunction (SICD) is a common complication of sepsis and contributes to mortality and the complexity of management in patients with sepsis. Recombinant human angiotensin-converting enzyme 2 (rhACE2) has been reported to protect the heart from injury and dysfunction in conditions which involve increased angiotensin II (Ang II). In this study, we aimed to detect the effects of rhACE2 on SICD.

Methods

A SICD model was developed in male C57/B6 mice by lipopolysaccharide (LPS) intraperitoneal injection. When cardiac dysfunction was confirmed by echocardiography 3 hours after LPS administration, mice were treated with either saline, rhACE2, or rhACE2 + A779. All mice received echocardiographic examination at 6 hours after LPS injection and then were sacrificed for serum and myocardial tissues collection. Angiotensin, cardiac troponin I (cTnI), and inflammatory markers in serum were measured. Histopathology features were examined by hematoxylin and eosin (HE) and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining to evaluate structure injury and cell pyroptosis rate in heart tissue respectively. Pyroptosis-related proteins and signaling pathways involved in nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation in heart tissue were investigated by western blot (WB).

Results

RhACE2 relieved myocardial injury and improved cardiac function in mice with SICD accompanied by decrease of Ang II and increase of angiotensin 1-7 (Ang 1-7) in serum. RhACE2 diminished activation of NLRP3 inflammasome, inflammatory response, and cell pyroptosis induced by LPS. In addition, rhACE2 partly inhibited activation of nuclear factor κB (NF-κB), the p38 mitogen-activated protein kinase (MAPK) pathway, and promoted activation of the AMP-activated protein kinase-α1 (AMPK-α1) pathway in heart tissue. Administration of A779 offset the inhibitive effects of rhACE2 on NLRP3 expression and protective role on cardiac injury and dysfunction in mice with SICD.

Conclusions

RhACE2 plays a protective role in SICD, ameliorating cardiac injury and dysfunction through NF-κB, p38 MAPK, and the AMPK-α1/NLRP3 inflammasome pathway dependent on converting Ang II to Ang 1-7.

Investigation of He's Yang Chao recipe against oxidative stress-related mitophagy and pyroptosis to improve ovarian function

BACKGROUND

Primary ovarian insufficiency (POI) is a common gynecological disease with serious ramifications including low pregnancy rate and low estrogen symptoms. Traditional Chinese medicine is regarded as an effective treatment for POI. However, the therapeutic mechanism of it is unclear.

METHODS

In this study, a mouse model of primary ovarian insufficiency was established by intraperitoneal injection of cyclophosphamide (CTX) and He's Yang Chao Recipe (HSYC) concentrate was used for intragastric administration. Serum hormone levels (Anti-Müllerian Hormone, Estradiol, Progesterone, Luteinizing Hormone and Follicle Stimulating Hormone) and Oxidative Stress (OS) related products, superoxide dismutase (SOD), GSH-Px, and malondialdehyde (MDA) were measured by enzyme-linked immunosorbent assay. Pathological changes in ovarian tissue were evaluated by hematoxylin and eosin staining, and flow cytometry was used to determine reactive oxygen species content and mitochondrial membrane potential levels in granulosa cells. Mitochondrial distribution and morphology were investigated using immunofluorescence staining. The level of mitophagy was evaluated by LC3 immunofluorescence staining and autophagosome counts using electron microscopy. Western blotting and qPCR were used to detect the expression of proteins and genes related to mitophagy and the NLRP3 inflammasome.

RESULTS

After HSYC treatment, the ovarian damage was milder than in the CTX group. Compared with the CTX group; SOD, GSH-Px, and the total antioxidant capacity were significantly increased, while MDA and ROS were decreased in the HSYC treatment groups. Furthermore, mitochondrial distribution and membrane potential levels were improved after HSYC treatment compared to the CTX group. After the HSYC treatment, the LC3 fluorescent intensity and autophagosome counts were decreased. Similarly, mitophagy related markers PINK1, Parkin, LC3, and Beclin1 were decreased, while p62 was significantly increased, compared with the CTX groups. The mRNA and protein expression of NLRP3 inflammasome, NLRP3, caspase-1, GSDMD, IL-18, and IL-1β were significantly decreased in the HSYC treatment groups.

CONCLUSION

This is the first study in molecular mechanisms underlying HSYC against granulosa cell injury in POI. HSYC protects ovaries from CTX-induced ovarian damage and oxidative stress. HSYC enhanced ovarian function in mice with primary ovarian insufficiency by inhibiting PINK1-Parkin mitophagy and NLRP3 inflammasome activation.

The NLRP3 inflammasome: regulation by metabolic signals

Macrophages undergo profound metabolic reprogramming upon sensing infectious and sterile stimuli. This metabolic shift supports and regulates essential innate immune functions, including activation of the NLRP3 inflammasome. Within distinct metabolic networks, key enzymes play pivotal roles to control flux restraining detrimental inflammasome signaling. However, depending on the metabolic cues, specific enzymes and metabolites result in inflammasome activation outcomes which contrast other metabolic steps in the pathway. We posit that understanding which metabolic steps commit to discrete inflammasome fates will broaden our understanding of metabolic checkpoints to maintain homeostasis and offer better therapeutic options in human disease.

UCP2 as a Cancer Target through Energy Metabolism and Oxidative Stress Control

Despite numerous therapies, cancer remains one of the leading causes of death worldwide due to the lack of markers for early detection and response to treatment in many patients. Technological advances in tumor screening and renewed interest in energy metabolism have allowed us to identify new cellular players in order to develop personalized treatments. Among the metabolic actors, the mitochondrial transporter uncoupling protein 2 (UCP2), whose expression is increased in many cancers, has been identified as an interesting target in tumor metabolic reprogramming. Over the past decade, a better understanding of its biochemical and physiological functions has established a role for UCP2 in (1) protecting cells from oxidative stress, (2) regulating tumor progression through changes in glycolytic, oxidative and calcium metabolism, and (3) increasing antitumor immunity in the tumor microenvironment to limit cancer development. With these pleiotropic roles, UCP2 can be considered as a potential tumor biomarker that may be interesting to target positively or negatively, depending on the type, metabolic status and stage of tumors, in combination with conventional chemotherapy or immunotherapy to control tumor development and increase response to treatment. This review provides an overview of the latest published science linking mitochondrial UCP2 activity to the tumor context.

Mechanosensing in macrophages and dendritic cells in steady-state and disease

Macrophages and dendritic cells are myeloid cells that play critical roles in immune responses. Macrophages help to maintain homeostasis through tissue regeneration and the clearance of dead cells, but also mediate inflammatory processes against invading pathogens. As the most potent antigen-presenting cells, dendritic cells are important in connecting innate to adaptive immune responses via activation of T cells, and inducing tolerance under physiological conditions. While it is known that macrophages and dendritic cells respond to biochemical cues in the microenvironment, the role of extracellular mechanical stimuli is becoming increasingly apparent. Immune cell mechanotransduction is an emerging field, where accumulating evidence suggests a role for extracellular physical cues coming from tissue stiffness in promoting immune cell recruitment, activation, metabolism and inflammatory function. Additionally, many diseases such as pulmonary fibrosis, cardiovascular disease, cancer, and cirrhosis are associated with changes to the tissue biophysical environment. This review will discuss current knowledge about the effects of biophysical cues including matrix stiffness, topography, and mechanical forces on macrophage and dendritic cell behavior under steady-state and pathophysiological conditions. In addition, we will also provide insight on molecular mediators and signaling pathways important in macrophage and dendritic cell mechanotransduction.

Autophagy Mediates Escherichia Coli-Induced Cellular Inflammatory Injury by Regulating Calcium Mobilization, Mitochondrial Dysfunction, and Endoplasmic Reticulum Stress

Bovine endometritis is a reproductive disorder that is induced by mucus or purulent inflammation of the uterine mucosa. However, the intracellular control chain during inflammatory injury remains unclear. In the present study, we found that E. coli activated the inflammatory response through the assembly of the NLRP3 inflammasome and activation of the NF-κB p65 subunit in primary bovine endometrial epithelial cells (bEECs). Infection with E. coli also led to an abnormal increase in cytoplasmic calcium and mitochondrial dysfunction. Additionally, live-cell imaging of calcium reporters indicated that the increase in cytosolic calcium mainly was caused by the release of Ca²⁺ ions stored in the ER and mitochondria, which was independent of extracellular calcium. Cytoplasmic calcium regulates mitochondrial respiratory chain transmission, DNA replication, and biogenesis. Pretreatment with NAC, BAPTA-AM, or 2-APB reduced the expression of IL-1β and IL-18. Moreover, ERS was involved in the regulation of bovine endometritis and cytosolic calcium was an important factor for regulating ERS in E. coli-induced inflammation. Finally, activation of autophagy inhibited the release of IL-1β and IL-18, cytochrome c, ATP, ERS-related proteins, and cytoplasmic calcium. Collectively, our findings demonstrate that autophagy mediated E. coli-induced cellular inflammatory injury by regulating cytoplasmic calcium, mitochondrial dysfunction, and ERS.

A Global Picture of Molecular Changes Associated to LPS Treatment in THP-1 Derived Human Macrophages by Fourier Transform Infrared Microspectroscopy

Macrophages are among the first immune cells involved in the initiation of the inflammatory response to protect the host from pathogens. THP-1 derived macrophages (TDM) are used as a model to study the pro-inflammatory effects of lipopolysaccharide (LPS) exposure. Intact TDM cells were analysed by Fourier transform infrared (FTIR) microspectroscopy, supported by multivariate analysis, to obtain a snapshot of the molecular events sparked by LPS stimulation in macrophage-like cells. This spectroscopic analysis enabled the untargeted identification of the most significant spectral components affected by the treatment, ascribable mainly to lipid, protein, and sulfated sugar bands, thus stressing the fundamental role of these classes of molecules in inflammation and in immune response. Our study, therefore, shows that FTIR microspectroscopy enabled the identification of spectroscopic markers of LPS stimulation and has the potential to become a tool to assess those global biochemical changes related to inflammatory and anti-inflammatory stimuli of synthetic and natural immunomodulators different from LPS.

UCP2 silencing restrains leukemia cell proliferation through glutamine metabolic remodeling

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy derived from early T cell progenitors. Since relapsed T-ALL is associated with a poor prognosis improving initial treatment of patients is essential to avoid resistant selection of T-ALL. During initiation, development, metastasis and even in response to chemotherapy, tumor cells face strong metabolic challenges. In this study, we identify mitochondrial UnCoupling Protein 2 (UCP2) as a tricarboxylic acid (TCA) cycle metabolite transporter controlling glutamine metabolism associated with T-ALL cell proliferation. In T-ALL cell lines, we show that UCP2 expression is controlled by glutamine metabolism and is essential for their proliferation. Our data show that T-ALL cell lines differ in their substrate dependency and their energetic metabolism (glycolysis and oxidative). Thus, while UCP2 silencing decreases cell proliferation in all leukemia cells, it also alters mitochondrial respiration of T-ALL cells relying on glutamine-dependent oxidative metabolism by rewiring their cellular metabolism to glycolysis. In this context, the function of UCP2 in the metabolite export of malate enables appropriate TCA cycle to provide building blocks such as lipids for cell growth and mitochondrial respiration. Therefore, interfering with UCP2 function can be considered as an interesting strategy to decrease metabolic efficiency and proliferation rate of leukemia cells.

Progressive Host-Directed Strategies to Potentiate BCG Vaccination Against Tuberculosis

The pursuit to improve the TB control program comprising one approved vaccine, M. bovis Bacille Calmette-Guerin (BCG) has directed researchers to explore progressive approaches to halt the eternal TB pandemic. Mycobacterium tuberculosis (M.tb) was first identified as the causative agent of TB in 1882 by Dr. Robert Koch. However, TB has plagued living beings since ancient times and continues to endure as an eternal scourge ravaging even with existing chemoprophylaxis and preventive therapy. We have scientifically come a long way since then, but despite accessibility to the standard antimycobacterial antibiotics and prophylactic vaccine, almost one-fourth of humankind is infected latently with M.tb. Existing therapeutics fail to control TB, due to the upsurge of drug-resistant strains and increasing incidents of co-infections in immune-compromised individuals. Unresponsiveness to established antibiotics leaves patients with no therapeutic possibilities. Hence the search for an efficacious TB immunization strategy is a global health priority. Researchers are paving the course for efficient vaccination strategies with the radically advanced operation of core principles of protective immune responses against M.tb. In this review; we have reassessed the progression of the TB vaccination program comprising BCG immunization in children and potential stratagems to reinforce BCG-induced protection in adults.

Role of succinic acid in the regulation of sepsis

Sepsis is a life-threatening disease characterized by a defensive response to damage. The immune response in patients with sepsis is overenhanced in the early stages and suppressed in the later stages, leading to poor prognosis. Metabolic reprogramming and epigenetic changes play a role in sepsis. Metabolic intermediates such as elevated succinic acid levels are significantly altered in patients with sepsis. Succinic acid, a metabolic intermediate of the tricarboxylic acid cycle, participates in energy supply and plays a role in metabolic reprogramming. Simultaneously, as an epigenetic regulator, it participates in gene transcription, translation, and post-translational modifications. It also participates in the inflammatory response, hypoxia, and the production of reactive oxygen species via endocrine and paracrine pathways. In this review, we have discussed the effects of succinic acid on sepsis and its therapeutic potential.

Metabolic Reprogramming Induces Macrophage Polarization in the Tumor Microenvironment

Macrophages are one of the most important cells in the innate immune system, they are converted into two distinct subtypes with completely different molecular phenotypes and functional features under different stimuli of the microenvironment: M1 macrophages induced by IFN-γ/lipopolysaccharides(LPS) and M2 macrophages induced by IL-4/IL-10/IL-13. Tumor-associated macrophages (TAMs) differentiate from macrophages through various factors in the tumor microenvironment (TME). TAMs have the phenotype and function of M2 macrophages and are capable of secreting multiple cytokines to promote tumor progression. Both tumor cells and macrophages can meet the energy needs for rapid cell growth and proliferation through metabolic reprogramming, so a comprehensive understanding of pro-tumor and antitumor metabolic switches in TAM is essential to understanding immune escape mechanisms. This paper focuses on the functions of relevant signaling pathways and cytokines during macrophage polarization and metabolic reprogramming, and briefly discusses the effects of different microenvironments and macrophage pathogenicity, in addition to describing the research progress of inhibitory drugs for certain metabolic and polarized signaling pathways.

miR-155 down-regulation protects the heart from hypoxic damage by activating fructose metabolism in cardiac fibroblasts

INTRODUCTION

Hypoxia-inducible factor (HIF)1α has been shown to be activated and induces a glycolytic shift under hypoxic condition, however, little attention was paid to the role of HIF1α-actuated fructolysis in hypoxia-induced heart injury.

OBJECTIVES

In this study, we aim to explore the molecular mechanisms of miR-155-mediated fructose metabolism in hypoxic cardiac fibroblasts (CFs).

METHODS

Immunostaining, western blot and quantitative real-time reverse transcription PCR (qRT-PCR) were performed to detect the expression of glucose transporter 5 (GLUT5), ketohexokinase (KHK)-A and KHK-C in miR-155^-/- and miR-155^wt CFs under normoxia or hypoxia. A microarray analysis of circRNAs was performed to identify circHIF1α. Then CoIP, RIP and mass spectrometry analysis were performed and identified SKIV2L2 (MTR4) and transformer 2 alpha (TRA2A), a member of the transformer 2 homolog family. pAd-SKIV2L2 was administrated after coronary artery ligation to investigate whether SKIV2L2 can provide a protective effect on the infarcted heart.

RESULTS

When both miR-155^-/- and miR-155^wt CFs were exposed to hypoxia for 24 h, these two cells exhibited an increased glycolysis and decreased glycogen synthesis, and the expression of KHK-A and KHK-C, the central fructose-metabolizing enzyme, was upregulated. Mechanistically, miR-155 deletion in CFs enhanced SKIV2L2 expression and its interaction with TRA2A, which suppresses the alternative splicing of HIF1α pre-mRNA to form circHIF1α, and then decreased circHIF1α contributed to the activation of fructose metabolism through increasing the production of the KHK-C isoform. Finally, exogenous delivery of SKIV2L2 reduced myocardial damage in the infarcted heart.

CONCLUSION

In this study, we demonstrated that miR-155 deletion facilitates the activation of fructose metabolism in hypoxic CFs through regulating alternative splicing of HIF1α pre-mRNA and thus circHIF1ɑ formation.

Reprogramming Macrophage Metabolism and its Effect on NLRP3 Inflammasome Activation in Sepsis

Sepsis, the most common life-threatening multi-organ dysfunction syndrome secondary to infection, lacks specific therapeutic strategy due to the limited understanding of underlying mechanisms. It is currently believed that inflammasomes play critical roles in the development of sepsis, among which NLRP3 inflammasome is involved to most extent. Recent studies have revealed that dramatic reprogramming of macrophage metabolism is commonly occurred in sepsis, and this dysregulation is closely related with the activation of NLRP3 inflammasome. In view of the fact that increasing evidence demonstrates the mechanism of metabolism reprogramming regulating NLRP3 activation in macrophages, the key enzymes and metabolites participated in this regulation should be clearer for better interpreting the relationship of NLRP3 inflammasome and sepsis. In this review, we thus summarized the detail mechanism of the metabolic reprogramming process and its important role in the NLRP3 inflammasome activation of macrophages in sepsis. This mechanism summarization will reveal the applicational potential of metabolic regulatory molecules in the treatment of sepsis.

Dichloroacetate improves systemic energy balance and feeding behavior during sepsis

Sepsis is a life-threatening organ dysfunction caused by dysregulated host response to an infection. The metabolic aberrations associated with sepsis underly an acute and organism-wide hyperinflammatory response and multiple organ dysfunction; however, crosstalk between systemic metabolomic alterations and metabolic reprogramming at organ levels remains unknown. We analyzed substrate utilization by the respiratory exchange ratio, energy expenditure, metabolomic screening, and transcriptional profiling in a cecal ligation and puncture model to show that sepsis increases circulating free fatty acids and acylcarnitines but decreases levels of amino acids and carbohydrates, leading to a drastic shift in systemic fuel preference. Comparative analysis of previously published metabolomics from septic liver indicated a positive correlation with hepatic and plasma metabolites during sepsis. In particular, glycine deficiency was a common abnormality of the plasma and liver during sepsis. Interrogation of the hepatic transcriptome in septic mice suggested that the septic liver may contribute to systemic glycine deficiency by downregulating genes involved in glycine synthesis. Interestingly, intraperitoneal injection of the pyruvate dehydrogenase kinase (PDK) inhibitor dichloroacetate reversed sepsis-induced anorexia, energy imbalance, inflammation, dyslipidemia, hypoglycemia, and glycine deficiency. Collectively, our data indicated that PDK inhibition rescued systemic energy imbalance and metabolic dysfunction in sepsis partly through restoration of hepatic fuel metabolism.

The crosstalk between NLRP3 inflammasome and gut microbiome in atherosclerosis

Atherosclerosis (AS) is chronic pathological process based on the inflammatory reaction associated with factors including vascular endothelial dysfunction, inflammation, and autoimmunity. Inflammasomes are known to be at the core of the inflammatory response. As a pattern recognition receptor of innate immunity, the NLRP3 inflammasome mediates the secretion of inflammatory factors by activating the Caspase-1, which is important for maintaining the immune system and regulating the gut microbiome, and participates in the occurrence and development of AS. The intestinal microecology is composed of a large number of complex structures of gut microbiota and its metabolites, which play an important role in AS. The gut microbiota and its metabolites regulate the activation of the NLRP3 inflammasome. Targeting the NLRP3 inflammasome and regulating intestinal microecology represent a new direction for the treatment of AS. This paper systematically reviews the interaction between the NLRP3 inflammasome and gut microbiome in AS, strategies for targeting the NLRP3 inflammasome and gut microbiome for the treatment of AS, and provides new ideas for the research and development of drugs for the treatment of AS.

QKI deficiency in macrophages protects mice against JEV infection by regulating cell migration and antiviral response

Japanese encephalitis (JE) is a major reason to cause viral encephalitis, with 50% patients suffering from severe neuro-inflammation and permanent neural injury. Effective anti-viral treatment is urgently needed. Here, we found RNA binding protein quaking (QKI) was involved in the progression of JE by regulating migration and anti-viral response of macrophages. After JE virus (JEV) infection, QKI-deficient mice had lower viral loads in the brain and fewer neurological symptoms. In comparison with control mice, proinflammatory cytokines in the brain of QKI-deficient animals revealed distinct patterns, with lower levels of IL-6 (interleukin-6) and IFN-β (interferon-β) at the early stage but higher levels at the end of JE. Then we found infiltration of CCR2 positive ((C-C motif) receptor 2) peripheral macrophages and CCR2 expression on macrophages were inhibited in QKI-deficient mice, while the expression of CCR2 ligands was not changed. Bioinformatical analysis showed that a QRE (quaking response element) located on 3'UTR (untranslated region) of Ccr2. We further verified that QKI was able to interact with Ccr2 mRNA and regulate its degradation in vitro. Additionally, since the IFN-β production was increased in QKI-ablation mice after JEV infection, the anti-viral response was analyzed. Results in QKI-silenced N9 cells showed that the expression of RIG-I (retinoic acid-inducible gene-I) and TBK1 (TANK binding kinase 1) was increased, thus further inducing IRF3 (interferon regulatory factor 3) phosphorylation and interferon activation. Overall, these results revealed QKI mediated the anti-viral process via interfering migration of macrophages to CNS (central nervous system) and enhancing RIG-I/IRF3/IFN-β pathway to restrict virus dissemination.

Caffeine Citrate Protects Against Sepsis-Associated Encephalopathy and Inhibits the UCP2/NLRP3 Axis in Astrocytes

Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction without overt central nervous system infection. Caffeine citrate has therapeutic effect on different brain diseases, while its role in SAE remains unclear. The expression levels of interleukin (IL)-18 and IL-1β were upregulated in the cerebrospinal fluid of the subjects. In this study, a rat model of SAE was established by cecal ligation and puncture. Caffeine citrate inhibited SAE-induced neuronal apoptosis and astrocytic activation, decreased reactive oxygen species (ROS) generation, and elevated mitochondrial membrane potential (MMP) level in the cerebral cortex. In vitro, primary astrocytes were isolated from rat cerebral cortex and incubated with lipopolysaccharide (LPS) and interferon-γ (IFN-γ). Caffeine citrate reduced ROS and MMP levels and mitochondrial complex enzyme activities in LPS plus IFN-γ-induced astrocytes. Moreover, caffeine citrate inhibited the activation of nucleotide-binding and oligomerization domain (NOD)-like receptor (NLRP3) inflammasome and decreased the production of IL-1β and IL-18 in vivo and in vitro. Notably, caffeine citrate promoted UCP2 expression in astrocytes. The neuroprotective role of UCP2 has been reported in several experimental brain diseases. These results suggest that caffeine citrate inhibits neuronal apoptosis, astrocytic activation, mitochondrial dysfunction in rat cerebral cortex, thereby alleviating SAE. The protection of caffeine citrate against SAE may be achieved by the UCP2-mediated NLRP3 pathway inhibition in astrocytes.

Pathways Related to NLRP3 Inflammasome Activation Induced by Gold Nanorods

The widespread and increasing use of engineered nanomaterials (ENM) increases the risk of human exposure, generating concern that ENM may provoke adverse health effects. In this respect, their physicochemical characteristics are critical. The immune system may respond to ENM through inflammatory reactions. The NLRP3 inflammasome responds to a wide range of ENM, and its activation is associated with various inflammatory diseases. Recently, anisotropic ENM have become of increasing interest, but knowledge of their effects on the immune system is still limited. The objective of the study was to compare the effects of gold ENM of different shapes on NLRP3 inflammasome activation and related signalling pathways. Differentiated THP-1 cells (wildtype, ASC- or NLRP3-deficient), were exposed to PEGylated gold nanorods, nanostars, and nanospheres, and, thus, also different surface chemistries, to assess NLRP3 inflammasome activation. Next, the exposed cells were subjected to gene expression analysis. Nanorods, but not nanostars or nanospheres, showed NLRP3 inflammasome activation. ASC- or NLRP3-deficient cells did not show this effect. Gene Set Enrichment Analysis revealed that gold nanorod-induced NLRP3 inflammasome activation was accompanied by downregulated sterol/cholesterol biosynthesis, oxidative phosphorylation, and purinergic receptor signalling. At the level of individual genes, downregulation of Paraoxonase-2, a protein that controls oxidative stress, was most notable. In conclusion, the shape and surface chemistry of gold nanoparticles determine NLRP3 inflammasome activation. Future studies should include particle uptake and intracellular localization.

Activation of UCP2 by anethole trithione suppresses neuroinflammation after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating disease, in which neuroinflammation substantially contributes to brain injury. Uncoupling protein 2 (UCP2) is a member of the mitochondrial anion carrier family, which uncouples oxidative phosphorylation from ATP synthesis by facilitating proton leak across the mitochondrial inner membrane. UCP2 has been reported to modulate inflammation. In this study we investigated whether and how UCP2 modulated neuroinflammation through microglia/macrophages following ICH in vitro and in vivo. We used an in vitro neuroinflammation model in murine BV2 microglia to mimic microglial activation following ICH. ICH in vivo model was established in mice through collagenase infusion into the left striatum. ICH mice were treated with anetholetrithione (ADT, 50 mg· kg^-1 ·d^-1, ip) or the classical protonophoric uncoupler FCCP (injected into hemorrhagic striatum). We showed that the expression and mitochondrial location of microglial UCP2 were not changed in both in vitro and in vivo ICH models. Knockdown of UCP2 exacerbated neuroinflammation in BV2 microglia and mouse ICH models, suggesting that endogenous UCP2 inhibited neuroinflammation and therefore played a protective role following ICH. ADT enhanced mitochondrial ROS production thus inducing mitochondrial uncoupling and activating UCP2 in microglia. ADT robustly suppressed neuroinflammation, attenuated brain edema and improved neurological deficits following ICH, and these effects were countered by striatal knockdown of UCP2. ADT enhanced AMP-activated protein kinase (AMPK) activation in the hemorrhagic brain, which was abrogated by striatal knockdown of UCP2. Moreover, striatal knockdown of AMPK abolished the suppression of neuroinflammation by ADT following ICH. On the other hand, FCCP-induced mitochondrial uncoupling was independent of UCP2 in microglia; and striatal knockdown of UCP2 did not abrogate the suppression of neuroinflammation by FCCP in ICH mice. In conclusion, the uncoupling activity is essential for suppression of neuroinflammation by UCP2. We prove for the first time the concept that activators of endogenous UCP2 such as anetholetrithione are a new class of uncouplers with translational significance.

Inflammasome Activation and Pyroptosis via a Lipid-regulated SIRT1-p53-ASC Axis in Macrophages From Male Mice and Humans

Obesity-linked diabetes is associated with accumulation of proinflammatory macrophages into adipose tissue leading to inflammasome activation and pyroptotic secretion of interleukin (IL)-1β and IL-18. Targeting fatty acid binding protein 4 (FABP4) uncouples obesity from inflammation, attenuates characteristics of type 2 diabetes and is mechanistically linked to the cellular accumulation of monounsaturated fatty acids in macrophages. Herein we show that pharmacologic inhibition or genetic deletion of FABP4 activates silent mating type information regulation 2 homolog 1 (SIRT1) and deacetylates its downstream targets p53 and signal transducer and activator of transcription 3 (STAT3). Pharmacologic inhibition of fatty acid synthase or stearoyl-coenzyme A desaturase inhibits, whereas exogenous addition of C16:1 or C18:1 but not their saturated acyl chain counterparts, activates SIRT1 and p53/STAT3 signaling and IL-1β/IL-18 release. Expression of the p53 target gene ASC [apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (CARD)] required for assembly of the NLR family pyrin domain containing 3 (NLRP3) inflammasome is downregulated in FABP4 null mice and macrophage cell lines leading to loss of procaspase 1 activation and pyroptosis. Concomitant with loss of ASC expression in FABP4-/- macrophages, inflammasome activation, gasdermin D processing, and functional activation of pyroptosis are all diminished in FABP4 null macrophages but can be rescued by silencing SIRT1 or exogenous expression of ASC. Taken together, these results reveal a novel lipid-regulated pathway linking to SIRT1-p53-ASC signaling and activation of inflammasome action and pyroptosis.