Reactive Oxygen Species in Macrophages: Sources and Targets

Ecotoxicological evaluation of chitosan biopolymer films particles in adult zebrafish (Danio rerio): A comparative study with polystyrene microplastics

To mitigate the environmental impact of microplastics (MPs), the scientific community has innovated sustainable and biodegradable polymers as viable alternatives to traditional plastics. Chitosan, the deacetylated form of chitin, stands as one of the most thoroughly investigated biopolymers and has garnered significant interest due to its versatile applications in both medical and cosmetic fields. Nevertheless, there is still a knowledge gap regarding the impact that chitosan biopolymer films (CBPF) may generate in aquatic organisms. In light of the foregoing, this study aimed to assess and compare the potential effects of CBPF on the gastrointestinal tract, gills, brain, and liver of Danio rerio against those induced by MPs. The findings revealed that both CBPF and MPs induced changes in the levels of oxidative stress biomarkers across all organs. However, it is essential to note that our star plots illustrate a tendency for CBPF to activate antioxidant enzymes and for MPs to produce oxidative damage. Regarding gene expression, our findings indicate that MPs led to an up-regulation in the expression of genes associated with apoptotic response (p53, casp3, cas9, bax, and bcl2) in all fish organs. Meanwhile, CBPF produced the same effect in genes related to antioxidant response (nrf1 and nrf2). Overall, our histological observations substantiated these effects, revealing the presence of plastic particles and tissue alterations in the gills and gastrointestinal tract of fish subjected to MPs. From these results, it can be concluded that CBPF does not represent a risk to fish after long exposure.

Tramadol suppresses growth of orthotopic liver tumors via promoting M1 macrophage polarization in the tumor microenvironment

Tumor-associated macrophages (TAMs) are major infiltrating immune cells in liver cancer. They are polarized to anti-tumor M1 type or tumor-supporting M2 type in a dynamic changing state. Tramadol, a synthetic opioid, exhibits tumor-suppressing effect in several cancers, but whether it plays a role in TAMs polarization is uncertain. In the present study, the potential influence of tramadol on TAMs polarization was explored in liver cancer. An orthotopic murine Hepa 1-6 liver cancer model was constructed. The potential function of tramadol was evaluated by cell viability assay, EdU incorporation assay, flow cytometry, immunofluorescence, quantitative real-time polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay (ELISA) assay, T cell proliferation and suppression assays and western blot. We found that tramadol suppressed proliferation and tumor formation of murine Hepa 1-6 cells in vitro and in vivo. Tramadol reprogramed the immune microenvironment to favor M1 macrophage polarization in orthotopic Hepa 1-6 tumors. Moreover, tramadol facilitated M1 macrophage polarization and inhibited M2 macrophage polarization of bone marrow-derived macrophages (BMDMs) and human THP-1 macrophages in vitro. Furthermore, tramadol-treated BMDMs promoted proliferation and activation of splenic CD4+ and CD8+ T cells. Tramadol induced cellular ROS production and mitochondrial dysfunction of BMDMs. Finally, tramadol activated NF-κB signaling in BMDMs and THP-1 macrophages, while inhibition of NF-κB signaling by JSH-23 attenuated the influence of tramadol on macrophage polarization. In conclusion, these data elucidated a novel anti-tumor mechanism of tramadol in liver cancer. Tramadol might be a promising treatment strategy for liver cancer patients.

Cell-homing and immunomodulatory composite hydrogels for effective wound healing with neovascularization

Wound healing in cases of excessive inflammation poses a significant challenge due to compromised neovascularization. Here, we propose a multi-functional composite hydrogel engineered to overcome such conditions through recruitment and activation of macrophages with adapted degradation of the hydrogel. The composite hydrogel (G-TSrP) is created by combining gelatin methacryloyl (GelMA) and nanoparticles (TSrP) composed of tannic acid (TA) and Sr2+. These nanoparticles are prepared using a one-step mineralization process assisted by metal-phenolic network formation. G-TSrP exhibits the ability to eliminate reactive oxygen species and direct polarization of macrophages toward M2 phenotype. It has been observed that the liberation of TA and Sr2+ from G-TSrP actively facilitate the recruitment and up-regulation of the expression of extracellular matrix remodeling genes of macrophages, and thereby, coordinate in vivo adapted degradation of the G-TSrP. Most significantly, G-TSrP accelerates angiogenesis despite the TA's inhibitory properties, which are counteracted by the released Sr2+. Moreover, G-TSrP enhances wound closure under inflammation and promotes normal tissue formation with strong vessel growth. Genetic analysis confirms macrophage-mediated wound healing by the composite hydrogel. Collectively, these findings pave the way for the development of biomaterials that promote wound healing by creating regenerative environment.

Lipopolysaccharide pretreatment increases the sensitivity of the TRPV1 channel and promotes an anti-inflammatory phenotype of capsaicin-activated macrophages

BACKGROUND

The transient receptor potential vanilloid 1 (TRPV1) is well-established in neuronal function, yet its role in immune reactions remains enigmatic. The conflicting data on its inflammatory role, suggesting both pro-inflammatory and anti-inflammatory effects upon TRPV1 stimulation in immune cells, adds complexity. To unravel TRPV1 immunomodulatory mechanisms, we investigated how the TRPV1 agonist capsaicin influences lipopolysaccharide (LPS)-induced pro-inflammatory macrophage phenotypes.

RESULTS

Changes in the surface molecules, cytokine production, and signaling cascades linked to the phenotype of M1 or M2 macrophages of the J774 macrophage cell line and bone marrow-derived macrophages, treated with capsaicin before or after the LPS-induced inflammatory reaction were determined. The functional capacity of macrophages was also assessed by infecting the stimulated macrophages with the intracellular parasite Leishmania mexicana.

CONCLUSION

Our findings reveal that TRPV1 activation yields distinct macrophage responses influenced by the inflammatory context. LPS pre-treatment followed by capsaicin activation prompted increased calcium influx, accompanied by a shift toward an anti-inflammatory M2b-like polarization state.

Schwann cell TRPA1 elicits reserpine-induced fibromyalgia pain in mice

BACKGROUND AND PURPOSE

Fibromyalgia is a complex clinical disorder with an unknown aetiology, characterized by generalized pain and co-morbid symptoms such as anxiety and depression. An imbalance of oxidants and antioxidants is proposed to play a pivotal role in the pathogenesis of fibromyalgia symptoms. However, the precise mechanisms by which oxidative stress contributes to fibromyalgia-induced pain remain unclear. The transient receptor potential ankyrin 1 (TRPA1) channel, known as both a pain sensor and an oxidative stress sensor, has been implicated in various painful conditions.

EXPERIMENTAL APPROACH

The feed-forward mechanism that implicates reactive oxygen species (ROS) driven by TRPA1 was investigated in a reserpine-induced fibromyalgia model in C57BL/6J mice employing pharmacological interventions and genetic approaches.

KEY RESULTS

Reserpine-treated mice developed pain-like behaviours (mechanical/cold hypersensitivity) and early anxiety-depressive-like disorders, accompanied by increased levels of oxidative stress markers in the sciatic nerve tissues. These effects were not observed upon pharmacological blockade or global genetic deletion of the TRPA1 channel and macrophage depletion. Furthermore, we demonstrated that selective silencing of TRPA1 in Schwann cells reduced reserpine-induced neuroinflammation (NADPH oxidase 1-dependent ROS generation and macrophage increase in the sciatic nerve) and attenuated fibromyalgia-like behaviours.

CONCLUSION AND IMPLICATIONS

Activated Schwann cells expressing TRPA1 promote an intracellular pathway culminating in the release of ROS and recruitment of macrophages in the mouse sciatic nerve. These cellular and molecular events sustain mechanical and cold hypersensitivity in the reserpine-evoked fibromyalgia model. Targeting TRPA1 channels on Schwann cells could offer a novel therapeutic approach for managing fibromyalgia-related behaviours.

Ferruginous components of particulate matters in subway environments, α-Fe2O3 or Fe3O4, exacerbates allergies

The respiratory effects of particulate matter (PM) in subway station platforms or tunnels have attracted considerable research attention. However, no studies have characterized the effects of subway PM on allergic immune responses. In this study, iron oxide (α-Fe2O3 and Fe3O4) particles-the main components of subway PM-were intratracheally administered to BALB/c mice where ovalbumin (OVA) induced allergic pulmonary inflammation. Iron oxide particles enhanced OVA-induced eosinophil recruitment around the bronchi and mucus production from airway epithelium. The concentrations of type 2 cytokines, namely, interleukin (IL)-5 and IL-13, in bronchial alveolar lavage fluids were increased by iron oxide particles. Iron oxide particles also increased the number of type 2 innate lymphoid cells and CD86+ cells in the lung. Moreover, phagocytosis of particles in lung cells was confirmed by Raman spectroscopy. In a subsequent in vitro study, bone marrow-derived antigen-presenting cells (APCs) isolated from NC/Nga mice were exposed to iron oxide particles and OVA. They were also exposed to outdoor ambient PM: Vehicle Exhaust Particulates (VEP) and Urban Aerosols (UA) as references. Iron oxide particles promoted the release of lactate dehydrogenase, C-X-C motif chemokine ligand 1 and IL-1α from APCs, which tended to be stronger than those of VEP. These results suggest that iron oxide particles enhance antigen presentation in the lungs, promoting allergic immune response in mice; iron oxide particles-induced death and inflammatory response of APCs can contribute to allergy exacerbation. Although iron oxide particles do not contain various compounds like VEP, iron oxide alone may have sufficient influence.

Metabolomic analysis reveals macrophage metabolic reprogramming and polarization under different nutritional cues

BACKGROUND AND AIMS

Obesity-induced chronic inflammation and metabolic abnormalities are highly relevant to the functional dysregulation of macrophages, especially under obese conditions. Hyperglycemia and hyperlipidemia, central to obesity, directly alter macrophage activity. However, the impacts of different nutritional cues on the intricate metabolic networks in macrophages remain unclear.

MATERIALS AND METHODS

In this study, we employed metabolomic approaches to examine the metabolic responses of macrophages to high glucose, high fat and their coexistence, aiming to delineate the molecular mechanisms of nutritional factors on macrophage activation and obesity-related diseases from a metabolic perspective.

RESULTS

Our findings revealed that different nutritional conditions could reprogram key metabolism in macrophages. Additionally, we identified a metabolite derived from macrophages, Long-Chain Phosphatidylcholine (LPC), which exerts beneficial effects on obese mice. It ameliorates the obesity phenotype and improves glucose metabolism profiles. This discovery suggests that LPC has a significant therapeutic potential in the context of obesity-induced metabolic dysfunctions. Our study unveils the metabolic phenotype of macrophages in high-fat and high-sugar environments and uncovers a macrophage-derived metabolite that significantly ameliorates the obesity phenotype.

CONCLUSION

This finding reveals a potential dialogue mechanism between macrophages and adipocytes, shedding light on the complex interplay of immune and metabolic systems in obesity. This discovery not only enhances our understanding of obesity's underlying mechanisms but also opens up new avenues for therapeutic interventions targeting macrophage-adipocyte interactions.

2,4'-Dihydroxybenzophenone: A Promising Anti-Inflammatory Agent Targeting Toll-like Receptor 4/Myeloid Differentiation Factor 2-Mediated Mitochondrial Reactive Oxygen Species Production during Lipopolysaccharide-Induced Systemic Inflammation

The biochemical properties of 2,4'-dihydroxybenzophenone (DHP) have not been extensively studied. Therefore, this study aimed to investigate whether DHP could alleviate inflammatory responses induced by lipopolysaccharide (LPS) and endotoxemia. The results indicated that DHP effectively reduced mortality and morphological abnormalities, restored heart rate, and mitigated macrophage and neutrophil recruitment to inflammatory sites in LPS-microinjected zebrafish larvae. Additionally, the expression of pro-inflammatory mediators, including inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), and interleukin-12 (IL-12), was significantly reduced in the presence of DHP. In RAW 264.7 macrophages, DHP inhibited the LPS-induced inflammatory response by downregulating pro-inflammatory mediators and decreasing the expression of myeloid differentiation primary response 88 (MyD88), phosphorylation of IL-1 receptor-associated protein kinase-4 (p-IRAK4), and nuclear factor-κB (NF-κB). Molecular docking analysis demonstrated that DHP occupies the hydrophobic pocket of myeloid differentiation factor 2 (MD2) and blocks the dimerization of Toll-like receptor 4 (TLR4). A molecular dynamics simulation confirmed that DHP stably bound to the hydrophobic pocket of MD2. Furthermore, the DHP treatment inhibited mitochondrial reactive oxygen species (mtROS) production during the LPS-induced inflammatory response in both RAW 264.7 macrophages and zebrafish larvae, which was accompanied by stabilizing mitochondrial membrane potential. In conclusion, our study highlights the therapeutic potential of DHP in alleviating LPS-induced inflammation and endotoxemia. The findings suggest that DHP exerts its anti-inflammatory effects by inhibiting the TLR4/MD2 signaling pathway and reducing the level of mtROS production. These results contribute to a better understanding of the biochemical properties of DHP and support its further exploration as a potential therapeutic agent for inflammatory conditions and endotoxemia.

Monocyte to macrophage differentiation and changes in cellular redox homeostasis promote cell type-specific HIV latency reactivation

HIV latency regulation in monocytes and macrophages can vary according to signals directing differentiation, polarization, and function. To investigate these processes, we generated an HIV latency model in THP-1 monocytes and showed differential levels of HIV reactivation among clonal populations. Monocyte-to-macrophage differentiation of HIV-infected primary human CD14+ and THP-1 cells induced HIV reactivation and showed that virus production increased concomitant with macrophage differentiation. We applied the HIV-infected THP-1 monocyte-to-macrophage (MLat) model to assess the biological mechanisms regulating HIV latency dynamics during monocyte-to-macrophage differentiation. We pinpointed protein kinase C signaling pathway activation and Cyclin T1 upregulation as inherent differentiation mechanisms that regulate HIV latency reactivation. Macrophage polarization regulated latency, revealing proinflammatory M1 macrophages suppressed HIV reactivation while anti-inflammatory M2 macrophages promoted HIV reactivation. Because macrophages rely on reactive-oxygen species (ROS) to exert numerous cellular functions, we disrupted redox pathways and found that inhibitors of the thioredoxin (Trx) system acted as latency-promoting agents in T-cells and monocytes, but opposingly acted as latency-reversing agents in macrophages. We explored this mechanism with Auranofin, a clinical candidate for reducing HIV reservoirs, and demonstrated Trx reductase inhibition led to ROS induced NF-κB activity, which promoted HIV reactivation in macrophages, but not in T-cells and monocytes. Collectively, cell type-specific differences in HIV latency regulation could pose a barrier to HIV eradication strategies.

Enhancement of Bone Tissue Regeneration with Multi-Functional Nanoparticles by Coordination of Immune, Osteogenic, and Angiogenic Responses

Inorganic nanoparticles are promising materials for bone tissue engineering due to their chemical resemblance to the native bone structure. However, most studies are unable to capture the entirety of the defective environment, providing limited bone regenerative abilities. Hence, this study aims to develop a multifunctional nanoparticle to collectively control the defective bone niche, including immune, angiogenic, and osteogenic systems. The nanoparticles, self-assembled by biomimetic mineralization and tannic acid (TA)-mediated metal-polyphenol network (MPN), are released sustainably after the incorporation within a gelatin cryogel. The released nanoparticles display a reduction in M1 macrophages by means of reactive oxygen species (ROS) elimination. Consequently, osteoclast maturation is also reduced, which is observed by the minimal formation of multinucleated cells (0.4%). Furthermore, the proportion of M2 macrophages, osteogenic differentiation, and angiogenic potential are consistently increased by the effects of magnesium from the nanoparticles. This orchestrated control of multiple systems influences the in vivo vascularized bone regeneration in which 80% of the critical-sized bone defect is regenerated with new bones with mature lamellar structure and arteriole-scale micro-vessels. Altogether, this study emphasizes the importance of the coordinated modulation of immune, osteogenic, and angiogenic systems at the bone defect site for robust bone regeneration.

Taenia solium cysticerci's extracellular vesicles Attenuate the AKT/mTORC1 pathway for Alleviating DSS-induced colitis in a murine model

The excretory-secretory proteome plays a pivotal role in both intercellular communication during disease progression and immune escape mechanisms of various pathogens including cestode parasites like Taenia solium. The cysticerci of T. solium causes infection in the central nervous system known as neurocysticercosis (NCC), which affects a significant population in developing countries. Extracellular vesicles (EVs) are 30-150-nm-sized particles and constitute a significant part of the secretome. However, the role of EV in NCC pathogenesis remains undetermined. Here, for the first time, we report that EV from T. solium larvae is abundant in metabolites that can negatively regulate PI3K/AKT pathway, efficiently internalized by macrophages to induce AKT and mTOR degradation through auto-lysosomal route with a prominent increase in the ubiquitination of both proteins. This results in less ROS production and diminished bacterial killing capability among EV-treated macrophages. Due to this, both macro-autophagy and caspase-linked apoptosis are upregulated, with a reduction of the autophagy substrate sequestome 1. In summary, we report that T. solium EV from viable cysts attenuates the AKT-mTOR pathway thereby promoting apoptosis in macrophages, and this may exert immunosuppression during an early viable stage of the parasite in NCC, which is primarily asymptomatic. Further investigation on EV-mediated immune suppression revealed that the EV can protect the mice from DSS-induced colitis and improve colon architecture. These findings shed light on the previously unknown role of T. solium EV and the therapeutic role of their immune suppression potential.

Plasma-liquid interactions in the presence of organic matter-A perspective

As investigations in the biomedical applications of plasma advance, a demand for describing safe and efficacious delivery of plasma is emerging. It is quite clear that not all plasmas are "equal" for all applications. This Perspective discusses limitations of the existing parameters used to define plasma in context of the need for the "right plasma" at the "right dose" for each "disease system." The validity of results extrapolated from in vitro studies to preclinical and clinical applications is discussed. We make a case for studying the whole system as a single unit, in situ. Furthermore, we argue that while plasma-generated chemical species are the proposed key effectors in biological systems, the contribution of physical effectors (electric fields, surface charging, dielectric properties of target, changes in gap electric fields, etc.) must not be ignored.

Hypotensive drugs mitigate the high-sodium diet-induced pro-inflammatory activation of mouse macrophages in vivo

Nowadays, there is an increasing emphasis on the need to alleviate the chronic inflammatory response to effectively treat hypertension. However, there are still gaps in our understanding on how to achieve this. Therefore, research on interaction of antihypertensive drugs with the immune system is extremely interesting, since their therapeutic effect could partly result from amelioration of hypertension-related inflammation, in which macrophages seem to play a pivotal role. Thus, current comprehensive studies have investigated the impact of repeatedly administered hypotensive drugs (captopril, olmesartan, propranolol, carvedilol, amlodipine, verapamil) on macrophage functions in the innate and adaptive immunity, as well as if drug-induced effects are affected by a high-sodium diet (HSD), one of the key environmental risk factors of hypertension. Although the assayed medications increased the generation of reactive oxygen and nitrogen intermediates by macrophages from standard fed donors, they reversed HSD-induced enhancing effects on macrophage oxidative burst and secretion of pro-inflammatory cytokines. On the other hand, some drugs increased macrophage phagocytic activity and the expression of surface markers involved in antigen presentation, which translated into enhanced macrophage ability to activate B cells for antibody production. Moreover, the assayed medications augmented macrophage function and the effector phase of contact hypersensitivity reaction, but suppressed the sensitization phase of cell-mediated hypersensitivity under HSD conditions. Our current findings contribute to the recognition of mechanisms, by which excessive sodium intake affects macrophage immune activity in hypertensive individuals, and provide evidence that the assayed medications mitigate most of the HSD-induced adverse effects, suggesting their additional protective therapeutic activity.

Exploring Anti-Fibrotic Effects of Adipose-Derived Stem Cells: Transcriptome Analysis upon Fibrotic, Inflammatory, and Hypoxic Conditioning

Autologous fat transfers show promise in treating fibrotic skin diseases, reversing scarring and stiffness, and improving quality of life. Adipose-derived stem cells (ADSCs) within these grafts are believed to be crucial for this effect, particularly their secreted factors, though the specific mechanisms remain unclear. This study investigates transcriptomic changes in ADSCs after in vitro fibrotic, inflammatory, and hypoxic conditioning. High-throughput gene expression assays were conducted on ADSCs exposed to IL1-β, TGF-β1, and hypoxia and in media with fetal bovine serum (FBS). Flow cytometry characterized the ADSCs. RNA-Seq analysis revealed distinct gene expression patterns between the conditions. FBS upregulated pathways were related to the cell cycle, replication, wound healing, and ossification. IL1-β induced immunomodulatory pathways, including granulocyte chemotaxis and cytokine production. TGF-β1 treatment upregulated wound healing and muscle tissue development pathways. Hypoxia led to the downregulation of mitochondria and cellular activity.

Dynamics of cellular plasticity in non-alcoholic steatohepatitis (NASH)

Non-alcoholic steatohepatitis (NASH) is a pathogenic stage of the broader non-alcoholic fatty liver disease (NAFLD). Histological presentation of NASH includes hepatocyte ballooning, macrophage polarization, ductular reaction, and hepatic stellate cell (HSCs) activation. At a cellular level, a heterogenous population of cells such as hepatocytes, macrophages, cholangiocytes, and HSCs undergo dramatic intra-cellular changes in response to extracellular triggers, which are termed "cellular plasticity. This dynamic switch in the cellular structure and function of hepatic parenchymal and non-parenchymal cells and their crosstalk culminates in the perpetuation of inflammation and fibrosis in NASH. This review presents an overview of our current understanding of cellular plasticity in NASH and its molecular mechanisms, along with possible targeting to develop cell-specific NASH therapies.

Bioactive Nanofiber-Hydrogel Composite Regulates Regenerative Microenvironment for Skeletal Muscle Regeneration after Volumetric Muscle Loss

Volumetric muscle loss (VML) is a severe form of muscle trauma that exceeds the regenerative capacity of skeletal muscle tissue, leading to substantial functional impairment. The abnormal immune response and excessive reactive oxygen species (ROS) accumulation hinder muscle regeneration following VML. Here, an interfacial cross-linked hydrogel-poly(ε-caprolactone) nanofiber composite, that incorporates both biophysical and biochemical cues to modulate the immune and ROS microenvironment for enhanced VML repair, is engineered. The interfacial cross-linking is achieved through a Michael addition between catechol and thiol groups. The resultant composite exhibits enhanced mechanical strength without sacrificing porosity. Moreover, it mitigates oxidative stress and promotes macrophage polarization toward a pro-regenerative phenotype, both in vitro and in a mouse VML model. 4 weeks post-implantation, mice implanted with the composite show improved grip strength and walking performance, along with increased muscle fiber diameter, enhanced angiogenesis, and more nerve innervation compared to control mice. Collectively, these results suggest that the interfacial cross-linked nanofiber-hydrogel composite could serve as a cell-free and drug-free strategy for augmenting muscle regeneration by modulating the oxidative stress and immune microenvironment at the VML site.

Nanoparticles with intermediate hydrophobicity polarize macrophages to plaque-specific Mox phenotype via Nrf2 and HO-1 activation

Mox macrophages were identified recently and are closely associated with atherosclerosis. Considering the potential health risks and the impact on macrophage modulation, this study investigated the Mox polarization of macrophages induced by nanoparticles (NPs) with tunable hydrophobicity. One nanoparticle (C4NP) with intermediate hydrophobicity efficiently upregulated the mRNA expression of Mox-related genes including HO-1, Srxn1, Txnrd1, Gsr, Vegf and Cox-2 through increased accumulation of Nrf2 at a nontoxic concentration in both resting and LPS-challenged macrophages. Additionally, C4NP impaired phagocytic capacity by 20% and significantly increased the secretion of cytokines, including TNFα, IL-6 and IL-10. Mechanistic studies indicated that intracellular reactive oxygen species (ROS) were elevated by 1.5-fold and 2.6-fold in resting and LPS-challenged macrophages respectively. Phosphorylated p62 was increased by 2.5-fold in resting macrophages and maintained a high level in LPS-challenged ones, both of which partially accounted for the significant accumulation of Nrf2 and HO-1. Notably, C4NP depolarized mitochondrial membrane potential by more than 50% and switched macrophages from oxidative phosphorylation-based aerobic metabolism to glycolysis for energy supply. Overall, this study reveals a novel molecular mechanism potentially involving ROS-Nrf2-p62 signaling in mediating macrophage Mox polarization, holding promise in ensuring safer and more efficient use of nanomaterials.

ROS signaling in innate immunity via oxidative protein modifications

The innate immune response represents the first-line of defense against invading pathogens. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been implicated in various aspects of innate immune function, which involves respiratory bursts and inflammasome activation. These reactive species widely distributed within the cellular environment are short-lived intermediates that play a vital role in cellular signaling and proliferation and are likely to depend on their subcellular site of formation. NADPH oxidase complex of phagocytes is known to generate superoxide anion radical (O2 •-) that functions as a precursor for antimicrobial hydrogen peroxide (H2O2) production, and H2O2 is utilized by myeloperoxidase (MPO) to generate hypochlorous acid (HOCl) that mediates pathogen killing. H2O2 modulates the expression of redox-responsive transcriptional factors, namely NF-kB, NRF2, and HIF-1, thereby mediating redox-based epigenetic modification. Survival and function of immune cells are under redox control and depend on intracellular and extracellular levels of ROS/RNS. The current review focuses on redox factors involved in the activation of immune response and the role of ROS in oxidative modification of proteins in macrophage polarization and neutrophil function.

Host and microbial regulation of mitochondrial reactive oxygen species during mycobacterial infections

Mycobacteria, including Mycobacterium tuberculosis (Mtb) and non-tuberculous mycobacteria (NTM), pose challenges in treatment due to their increased resistance to antibiotics. Following infection, mycobacteria and their components trigger robust innate and inflammatory immune responses intricately associated with the modulation of mitochondrial functions, including oxidative phosphorylation (OXPHOS) and metabolism. Certainly, mitochondrial reactive oxygen species (mtROS) are an inevitable by-product of OXPHOS and function as a bactericidal weapon; however, an excessive accumulation of mtROS are linked to pathological inflammation and necroptotic cell death during mycobacterial infection. Despite previous studies outlining various host pathways involved in regulating mtROS levels during antimicrobial responses in mycobacterial infection, our understanding of the precise mechanisms orchestrating the fine regulation of this response remains limited. Emerging evidence suggests that mycobacterial proteins play a role in targeting the mitochondria of the host, indicating the potential influence of microbial factors on mitochondrial functions within host cells. In this review, we provide an overview of how both host and Mtb factors influence mtROS generation during infection. A comprehensive study of host and microbial factors that target mtROS will shed light on innovative approaches for effectively managing drug-resistant mycobacterial infections.

Adaptor molecules mediate negative regulation of macrophage inflammatory pathways: a closer look

Macrophages play a central role in initiating, maintaining, and terminating inflammation. For that, macrophages respond to various external stimuli in changing environments through signaling pathways that are tightly regulated and interconnected. This process involves, among others, autoregulatory loops that activate and deactivate macrophages through various cytokines, stimulants, and other chemical mediators. Adaptor proteins play an indispensable role in facilitating various inflammatory signals. These proteins are dynamic and flexible modulators of immune cell signaling and act as molecular bridges between cell surface receptors and intracellular effector molecules. They are involved in regulating physiological inflammation and also contribute significantly to the development of chronic inflammatory processes. This is at least partly due to their involvement in the activation and deactivation of macrophages, leading to changes in the macrophages' activation/phenotype. This review provides a comprehensive overview of the 20 adaptor molecules and proteins that act as negative regulators of inflammation in macrophages and effectively suppress inflammatory signaling pathways. We emphasize the functional role of adaptors in signal transduction in macrophages and their influence on the phenotypic transition of macrophages from pro-inflammatory M1-like states to anti-inflammatory M2-like phenotypes. This endeavor mainly aims at highlighting and orchestrating the intricate dynamics of adaptor molecules by elucidating the associated key roles along with respective domains and opening avenues for therapeutic and investigative purposes in clinical practice.

Double cross-linked graphene oxide hydrogel for promoting healing of diabetic ulcers

This study explores the synthesis and characterization of a novel double cross-linked hydrogel composed of polyvinyl alcohol (PVA), sodium alginate (SA), graphene oxide (GO), and glutathione (GSH), henceforth referred to as PVA/SA/GO/GSH. This innovative hydrogel system incorporates two distinct types of cross-linking networks and is meticulously engineered to exhibit sensitivity to high glucose and/or reactive oxygen species (ROS) environments. A sequential approach was adopted in the hydrogel formation. The initial phase involved the absorption of GSH onto GO, which was subsequently functionalized with boric acid and polyethylene glycol derivatives via a bio-orthogonal click reaction. This stage constituted the formation of the first chemically cross-linked network. Subsequently, freeze-thaw cycles were utilized to induce a secondary cross-linking process involving PVA and SA, thereby forming the second physically cross-linked network. The resultant PVA/SA/GO/GSH hydrogel retained the advantageous hydrogel properties such as superior water retention capacity and elasticity, and additionally exhibited the ability to responsively release GSH under changes in glucose concentration and/or ROS levels. This feature finds particular relevance in the therapeutic management of diabetic ulcers. Preliminary in vitro evaluation affirmed the hydrogel's biocompatibility and its potential to promote cell migration, inhibit apoptosis, and exhibit antibacterial properties. Further in vivo studies demonstrated that the PVA/SA/GO/GSH hydrogel could facilitate the healing of diabetic ulcer sites by mitigating oxidative stress and regulating glucose levels. Thus, the developed PVA/SA/GO/GSH hydrogel emerges as a promising candidate for diabetic ulcer treatment, owing to its specific bio-responsive traits and therapeutic efficacy.

Comprehensive proteomics of monocytes indicates oxidative imbalance functionally related to inflammatory response in chronic kidney disease-related atherosclerosis

Atherosclerosis-induced cardiovascular events are the leading cause of mortality in chronic kidney disease (CKD) patients. Monocytes are involved in the formation of atherosclerotic plaques and mediate in the overproduction of ROS, promoting inflammation and oxidative stress. However, the relationship between monocytes, inflammation, and oxidative status in CKD-associated atherosclerosis has not been thoroughly investigated. Monocytes and plasma derived from two groups of CKD patients with varying degrees of atherosclerosis and two groups of patients with cardiovascular disease (CVD) and non-CKD atherosclerosis were analyzed. This study was designed to perform a comprehensive proteomic analysis of monocytes in combination with functional bioinformatics. In addition, a targeted investigation of oxidative stress- and inflammatory-related factors to explore CKD-associated atherosclerosis was applied. Dysregulation of proteins involved in lipid oxidation, cell survival, ROS synthesis and metabolism, and inflammatory responses has been revealed. The characteristic disturbances in the monocyte proteome changed with the progression of CKD. A closer examination of oxidative stress's triggers, mediators, and effects on protein and lipid levels showed alterations in the oxidative imbalance between CKD and CVD. CKD monocytes demonstrated a significant increase of oxidized glutathione without changing the level of its reduced form. Evaluation of enzymatic antioxidants, sources of ROS, and modifications caused by ROS also revealed significant alterations between the study groups. In CKD, inflammation and oxidative imbalance correlated and drove each other. However, in CVD, oxidative stress-related factors were associated with each other but not to inflammatory proteins. Moreover, lipid abnormalities were more specific to classical CVD and unrelated to CKD. Such a comprehensive characterization of monocytes and oxidative stress in CKD and CVD patients has never been presented so far. Obtained results support the involvement of distinct mechanisms underlying the acceleration of atherosclerotic and non-atherosclerotic CKD.

Radical-Generating Activity, Phagocytosis, and Mechanical Properties of Four Phenotypes of Human Macrophages

Macrophages are the major players and orchestrators of inflammatory response. Expressed proteins and secreted cytokines have been well studied for two polar macrophage phenotypes-pro-inflammatory M1 and anti-inflammatory regenerative M2, but little is known about how the polarization modulates macrophage functions. In this study, we used biochemical and biophysical methods to compare the functional activity and mechanical properties of activated human macrophages differentiated from monocyte with GM-CSF (M0_GM) and M-CSF (M0_M) and polarized into M1 and M2 phenotypes, respectively. Unlike GM-CSF, which generates dormant cells with low activity, M-CSF confers functional activity on macrophages. M0_M and M2 macrophages had very similar functional characteristics-high reactive oxygen species (ROS) production level, and higher phagocytosis and survival compared to M1, while M1 macrophages showed the highest radical-generating activity but the lowest phagocytosis and survival among all phenotypes. All phenotypes decreased their height upon activation, but only M1 and M2 cells increased in stiffness, which can indicate a decrease in the migration ability of these cells and changes in their interactions with other cells. Our results demonstrated that while mechanical properties differ between M0 and polarized cells, all four phenotypes of monocyte-derived macrophages differ in their functional activities, namely in cytokine secretion, ROS production, and phagocytosis. Within the broad continuum of human macrophages obtained in experimental models and existing in vivo, there is a diversity of phenotypes with varying combinations of both markers and functional activities.

Mitochondrial Regulation of Macrophages in Innate Immunity and Diverse Roles of Macrophages During Cochlear Inflammation

Macrophages are essential components of the innate immune system and constitute a non-specific first line of host defense against pathogens and inflammation. Mitochondria regulate macrophage activation and innate immune responses in various inflammatory diseases, including cochlear inflammation. The distribution, number, and morphological characteristics of cochlear macrophages change significantly across different inner ear regions under various pathological conditions, including noise exposure, ototoxicity, and age-related degeneration. However, the exact mechanism underlying the role of mitochondria in macrophages in auditory function remains unclear. Here, we summarize the major factors and mitochondrial signaling pathways (e.g., metabolism, mitochondrial reactive oxygen species, mitochondrial DNA, and the inflammasome) that influence macrophage activation in the innate immune response. In particular, we focus on the properties of cochlear macrophages, activated signaling pathways, and the secretion of inflammatory cytokines after acoustic injury. We hope this review will provide new perspectives and a basis for future research on cochlear inflammation.

Effect of triggering receptor expressed on myeloid cells 2-associated alterations on lipid metabolism in macrophages in the development of non-alcoholic fatty liver disease

BACKGROUND AND AIM

Triggering receptor expressed on myeloid cells 2 (TREM2) plays crucial roles in metabolic homeostasis and inflammatory response. Altered metabolic function in macrophages could modulate their activation and immune phenotype. The present study aimed to investigate the expression of TREM2 in non-alcoholic fatty liver disease (NAFLD) and to clarify the underlying mechanism of TREM2 on macrophages lipid metabolism and oxidative stress.

METHODS

Hepatic TREM2 expression and its relationship with NAFLD progression were analyzed in patients with NAFLD and mice fed a high-fat diet. Lipid metabolism and oxidative stress were investigated in macrophages from NAFLD mice or stimulated with saturated fatty acids. Knockdown and overexpression of TREM2 were further explored.

RESULTS

Triggering receptor expressed on myeloid cells 2+ macrophages were increased along with NAFLD development, characterized by aggravated steatosis and liver damage in humans and mice. TREM2 expression was upregulated and lipid metabolism was changed in macrophages from NAFLD mice or metabolically activated by saturated fatty acid in vitro, as demonstrated by increased lipid uptake and catabolism, but reduced de novo synthesis of fatty acids (FAs). Regulation of TREM2 expression in lipid-laden macrophages reprogrammed lipid metabolism, especially the fatty acid oxidation capacity of mitochondria. TREM2 knockdown promoted oxidative stress by aggravating FAs deposition in mitochondria. Intervention of mitochondrial FAs transport in lipid-laden macrophages alleviated FA deposition and reactive oxygen species production induced by TREM2 knockdown.

CONCLUSIONS

Triggering receptor expressed on myeloid cells 2 expression was associated with the lipid metabolic profile and reactive oxygen species production in macrophages. High expression of TREM2 in macrophages may protect the liver from oxidative stress in NAFLD.

Defining and targeting macrophage heterogeneity in the mammary gland and breast cancer

INTRODUCTION

Macrophages are innate immune cells that are associated with extensive phenotypic and functional plasticity and contribute to normal development, tissue homeostasis, and diseases such as cancer. In this review, we discuss the heterogeneity of tissue resident macrophages in the normal mammary gland and tumor-associated macrophages in breast cancer. Tissue resident macrophages are required for mammary gland development, where they have been implicated in promoting extracellular matrix remodeling, apoptotic clearance, and cellular crosstalk. In the context of cancer, tumor-associated macrophages are key drivers of growth and metastasis via their ability to promote matrix remodeling, angiogenesis, lymphangiogenesis, and immunosuppression.

METHOD

We identified and summarized studies in Pubmed that describe the phenotypic and functional heterogeneity of macrophages and the implications of targeting individual subsets, specifically in the context of mammary gland development and breast cancer. We also identified and summarized recent studies using single-cell RNA sequencing to identify and describe macrophage subsets in human breast cancer samples.

RESULTS

Advances in single-cell RNA sequencing technologies have yielded nuances in macrophage heterogeneity, with numerous macrophage subsets identified in both the normal mammary gland and breast cancer tissue. Macrophage subsets contribute to mammary gland development and breast cancer progression in differing ways, and emerging studies highlight a role for spatial localization in modulating their phenotype and function.

CONCLUSION

Understanding macrophage heterogeneity and the unique functions of each subset in both normal mammary gland development and breast cancer progression may lead to more promising targets for the treatment of breast cancer.

Crucial physicochemical factors mediating mitochondrial toxicity of nanoparticles at noncytotoxic concentration

Nanomaterials have been extensively applied in multiple industries, among which silver nanoparticles (AgNPs), silicon dioxide nanoparticles (SiNPs), and gold nanoparticles (AuNPs) have become representative of widely consumed NPs. Limited knowledge is available regarding the subcellular responses of NPs with different physicochemical properties, i.e. material type and size, under the noncytotoxic concentrations. Macrophages are important sensitive cells exposed to NPs, and mitochondria are sensitive organelles that respond at the subcellular level. Herein, we found that sublethal concentrations of AgNPs and SiNPs, not AuNPs, decreased the mitochondrial membrane potential (MMP) and tubular mitochondria, and further resulted in an increase of ROS level and a decrease of ATP generation. AgNPs and SiNPs can also disturb mitochondrial dynamics manifested as increasing Mfn2 expression and decreasing Drp1 expression. Further assessments for mitochondrial function showed that AgNPs and SiNPs exposure led to a decrease in the gene expressions related to complex I (Ndufa8 and Ndufs2), complex III (Uqcrc2 and Uqcrfs1), complex IV (Cox6b1), and activity of complex I, suggesting their potential roles in impairing cellular respiration. In terms of the effects of NPs with different sizes, stronger toxicity was observed in smaller-sized nanoparticles. Among the above mitochondrial changes, we identified that ROS, ATP, MMP, tubular mitochondria, and expression of Drp1 were relatively sensitive indicators in subcellular response to NPs. With the above sensitive indicators, the comparison of heterogeneity between material type and size of the NPs showed that material type occupied a main influence on subcellular mitochondrial effects. Our finding provided important data on the potential subcellular risks of NPs, and indicated the vital role of material type for a better understanding of the nanomaterial biological safety.

Progranulin-deficient macrophages cause cardiotoxicity under hypoxic conditions

Myocardial infarction (MI) induces structural and electrical cardiac remodeling in response to ischemic insult, causing lethal arrhythmias and sudden death. Progranulin (PGRN) is a glycoprotein mainly expressed in macrophages that modulates the immune responses. In this study, we investigated the direct influence of PGRN knockout (Grn-/-) macrophages on post-MI pathophysiology. An MI mouse model was established by ligating the left coronary artery for RNA sequencing and electrocardiographic analysis. Bone marrow-derived macrophages (BMDMs) were injected into mice and supernatant was collected for the measurement of reactive oxygen species (ROS) levels and extracellular flux analysis. Administration of Grn-/- BMDMs prolonged the QT intervals in the MI mouse model. Moreover, genes highly expressed in macrophages were upregulated in Grn-/- heart after MI. Post-hypoxic supernatant of Grn-/- BMDMs increased the oxygen-glucose deprivation-induced cardiomyocyte death. Grn-/- BMDMs exhibited increased ROS production, oxygen consumption, and extracellular acidification under hypoxia and inflammatory conditions. These findings suggest that PGRN deficiency causes cardiotoxicity via secretory components of macrophages that exhibit metabolic abnormalities under hypoxia.

Research progress on mitochondria regulating tumor immunity

Tumor cells adapt their metabolism to meet the demands for energy and biosynthesis. Mitochondria, pivotal organelles in the metabolic reprogramming of tumor cells, contribute to tumorigenesis and cancer progression significantly through various dysfunctions in both tumor and immune cells. Alterations in mitochondrial dynamics and metabolic signaling pathways exert crucial regulatory influence on the activation, proliferation, and differentiation of immune cells. The tumor microenvironment orchestrates the activation and functionality of tumor-infiltrating immune cells by reprogramming mitochondrial metabolism and inducing shifts in mitochondrial dynamics, thereby facilitating the establishment of a tumor immunosuppressive microenvironment. Stress-induced leakage of mitochondrial DNA contributes multifaceted regulatory effects on anti-tumor immune responses and the immunosuppressive microenvironment by activating multiple natural immune signals, including cGAS-STING, TLR9, and NLRP3. Moreover, mitochondrial DNA-mediated immunogenic cell death emerges as a promising avenue for anti-tumor immunotherapy. Additionally, mitochondrial reactive oxygen species, a crucial factor in tumorigenesis, drives the formation of tumor immunosuppressive microenvironment by changing the composition of immune cells within the tumor microenvironment. This review focuses on the intrinsic relationship between mitochondrial biology and anti-tumor immune responses from multiple angles. We explore the core role of mitochondria in the dynamic interplay between the tumor and the host to facilitate the development of targeted mitochondrial strategies for anti-tumor immunotherapy.

Single-cell transcriptomics reveals ferrimagnetic vortex iron oxide nanoring-mediated mild magnetic hyperthermia exerts antitumor effects by alleviating macrophage suppression in breast cancer

The potential of Ferrimagnetic vortex iron oxide nanoring-mediated mild magnetic hyperthermia (FVIO-MHT) in solid tumor therapy has been demonstrated. However, the impact of FVIO-MHT on the tumor microenvironment (TME) remains unclear. This study utilized single-cell transcriptome sequencing to examine the alterations in the TME in response to FVIO-MHT in breast cancer. The results revealed the cellular composition within the tumor microenvironment (TME) was primarily modified due to a decrease in tumor cells and an increased infiltration of myeloid cells. Subsequently, an enhancement in active oxygen (ROS) metabolism was observed, indicating oxidative damage to tumor cells. Interestingly, FVIO-MHT reprogrammed the macrophages' phenotypes, as evidenced by alterations in the transcriptome characteristics associated with both classic and alternative activated phenotypes. And an elevated level of ROS generation and oxidative phosphorylation suggested that activated phagocytosis and inflammation occurred in macrophages. Additionally, cell-cell communication analysis revealed that FVIO-MHT attenuated the suppression between tumor cells and macrophages by inhibiting phagocytic checkpoint and macrophage migration inhibitory factor signaling pathways. Inhibition of B2m, an anti-phagocytosis checkpoint, could promote macrophage-mediated phagocytosis and significantly inhibit tumor growth. These data emphasize FVIO-MHT may promote the antitumor capabilities of macrophages by alleviating the suppression between tumor cells and macrophages.

Protective Role of MAVS Signaling for Murine Lipopolysaccharide-Induced Acute Kidney Injury

Despite treatment advances, acute kidney injury (AKI)-related mortality rates are still high in hospitalized adults, often due to sepsis. Sepsis and AKI could synergistically worsen the outcomes of critically ill patients. TLR4 signaling and mitochondrial antiviral signaling protein (MAVS) signaling are innate immune responses essential in kidney diseases, but their involvement in sepsis-associated AKI (SA-AKI) remains unclear. We studied the role of MAVS in kidney injury related to the TLR4 signaling pathway using a murine LPS-induced AKI model in wild-type and MAVS-knockout mice. We confirmed the importance of M1 macrophage in SA-AKI through in vivo assessment of inflammatory responses. The TLR4 signaling pathway was upregulated in activated bone marrow-derived macrophages, in which MAVS helped maintain the LPS-suppressed TLR4 mRNA level. MAVS regulated redox homeostasis via NADPH oxidase Nox2 and mitochondrial reverse electron transport in macrophages to alleviate the TLR4 signaling response to LPS. Hypoxia-inducible factor 1α (HIF-1α) and AP-1 were key regulators of TLR4 transcription and connected MAVS-dependent reactive oxygen species signaling with the TLR4 pathway. Inhibition of succinate dehydrogenase could partly reduce inflammation in LPS-treated bone marrow-derived macrophages without MAVS. These findings highlight the renoprotective role of MAVS in LPS-induced AKI by regulating reactive oxygen species generation-related genes and maintaining redox balance. Controlling redox homeostasis through MAVS signaling may be a promising therapy for SA-AKI.

Chronic Kidney Disease Interplay with Comorbidities and Carbohydrate Metabolism: A Review

Chronic kidney disease (CKD) poses a global health challenge, engendering various physiological and metabolic shifts that significantly impact health and escalate the susceptibility to severe illnesses. This comprehensive review delves into the intricate complexities of CKD, scrutinizing its influence on cellular growth homeostasis, hormonal equilibrium, wasting, malnutrition, and its interconnectedness with inflammation, oxidative stress, and cardiovascular diseases. Exploring the genetic, birth-related, and comorbidity factors associated with CKD, alongside considerations of metabolic disturbances, anemia, and malnutrition, the review elucidates how CKD orchestrates cellular growth control. A pivotal focus lies on the nexus between CKD and insulin resistance, where debates persist regarding its chronological relationship with impaired kidney function. The prevalence of insulin abnormalities in CKD is emphasized, contributing to glucose intolerance and raising questions about its role as a precursor or consequence. Moreover, the review sheds light on disruptions in the growth hormone and insulin-like growth factor axis in CKD, underscoring the heightened vulnerability to illness and mortality in cases of severe growth retardation. Wasting, a prevalent concern affecting up to 75% of end-stage renal disease (ESRD) patients, is analyzed, elucidating the manifestations of cachexia and its impact on appetite, energy expenditure, and protein reserves. Taste disturbances in CKD, affecting sour, umami, and salty tastes, are explored for their implications on food palatability and nutritional status. Independent of age and gender, these taste alterations have the potential to sway dietary choices, further complicating the management of CKD. The intricate interplay between CKD, inflammation, oxidative stress, and cardiovascular diseases is unraveled, emphasizing the profound repercussions on overall health. Additionally, the review extends its analysis to CKD's broader impact on cognitive function, emotional well-being, taste perception, and endothelial dysfunction. Concluding with an emphasis on dietary interventions as crucial components in CKD management, this comprehensive review navigates the multifaceted dimensions of CKD, providing a nuanced understanding essential for developing targeted therapeutic strategies.

Fever-Range Hyperthermia Promotes Macrophage Polarization towards Regulatory Phenotype M2b

Fever-range hyperthermia (FRH) is utilized in chronic disease treatment and serves as a model for fever's thermal component investigation. Macrophages, highly susceptible to heat, play a pivotal role in various functions determined by their polarization state. However, it is not well recognized whether this process can be modulated by FRH. To address this, we used two different macrophage cell lines that were treated with FRH. Next, to define macrophage phenotype, we examined their functional surface markers CD80 and CD163, intracellular markers such as inducible nitric oxide synthase (iNOS), arginase-1 (Arg-1), and the expression of interleukin-10 (IL-10) and tumor necrosis factor α (TNF-α). Additionally, in FRH-treated cells, we analyzed an expression of Toll-like receptor 4 (TLR-4) and its role in macrophage polarization. We also checked whether FRH can switch the polarization of macrophages in pro-inflammatory condition triggered by lipopolysaccharide (LPS). FRH induced M2-like polarization, evident in increased CD163, IL-10, and Arg-1 expression. Notably, elevated COX-2, TNF-α, and TLR-4 indicated potential pro-inflammatory properties, suggesting polarization towards the M2b phenotype. Additionally, FRH shifted lipopolysaccharide (LPS)-induced M1 polarization to an M2-like phenotype, reducing antimicrobial molecules (ROS and NO). In summary, FRH emerged as a modulator favoring M2-like macrophage polarization, even under pro-inflammatory conditions, showcasing its potential therapeutic relevance.

Water-extractable polysaccharide fraction PNE-P1 from Pinus koraiensis pine nut: Structural features and immunostimulatory activity

The polysaccharide fraction PNE-P1 was isolated from hot water extract (PNE) of the defatted meal of pine nuts (Pinus koraiensis) using DEAE-cellulose column chromatography. This fraction had three components of molecular masses 1251, 616, and 303 g/mol consisting mainly of arabinose, xylose, and galacturonic acid at a molar ratio of 2:1.6:1. Structural analysis with FTIR/Raman, methylation and GC-MS, and NMR revealed that PNE-P1 is a cell wall polysaccharide complex including arabinan, heteroxylan, homogalacturonan (HM) and rhamnogalacturonan I (RG-I) parts. Being nontoxic to RAW 264.7 macrophages in the concentration range of 10-200 μg/mL, PNE-P1 promoted proliferation of these cells, significantly induced the secretion of proinflammatory cytokines (TNF-α and IL-6) and chemokines (RANTES and MIP-1α) and enhanced the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and nitric oxide (NO). PNE-P1 also markedly induced macrophage-mediated phagocytosis of apoptotic Jurkat T cells. These results demonstrate that pine nuts Pinus koraiensis contain a complex of water-soluble plant cell wall polysaccharides, which can stimulate innate immunity by potentiating macrophage function.

Immune checkpoint inhibitors in bone metastasis: Clinical challenges, toxicities, and mechanisms

Immune checkpoint inhibitors (ICIs) have revolutionized the field of anti-cancer therapy over the last decade; they provide durable clinical responses against tumors by inhibiting immune checkpoint proteins that canonically regulate the T cell-mediated immune response. Despite their success in many primary tumors and soft tissue metastases, ICIs function poorly in patients with bone metastases, and these patients do not have the same survival benefit as patients with the same primary tumor type (e.g., non-small cell lung cancer [NSCLC], urothelial, renal cell carcinoma [RCC], etc.) that has not metastasized to the bone. Additionally, immune-related adverse events including rheumatologic and musculoskeletal toxicities, bone loss, and increased fracture risk develop after treatment with ICIs. There are few preclinical studies that investigate the interplay of the immune system in bone metastases; however, the current literature suggests a role for CD8+ T cells and myeloid cell subsets in bone homeostasis. As such, this review focuses on findings from the clinical and pre-clinical studies that have investigated immune checkpoint blockade in the bone metastatic setting and highlights the need for more comprehensive investigations into the relationship between immune cell subsets, ICIs, and the bone-tumor microenvironment.

Modulation of Innate Immune Memory Dynamics by Subcellular Reactive Oxygen Species

Significance: Innate immune cells adopt distinct memory states during the pathogenesis of acute and chronic inflammatory diseases. Intracellular generations of reactive oxygen species (ROS) play key roles during the programming dynamics of innate immune cells such as monocytes and macrophages. Recent Advances: ROS modulate the adaptation of innate leukocytes to varying intensities and durations of inflammatory signals, facilitate fundamental reprogramming dynamics such as priming, tolerance, and exhaustion, in addition to fundamental processes of proliferation, differentiation, phagocytosis, chemotaxis, as well as expression of pro- and anti-inflammatory mediators. ROS can be generated at distinct subcellular compartments including cellular membrane, mitochondria, and peroxisome. Complex inflammatory signals may finely regulate ROS generation within distinct subcellular compartments, which in turn may differentially facilitate innate memory dynamics. Critical Issues: Complex inflammatory signals with varying strengths and durations may differentially trigger ROS generation at peroxisome, mitochondria, and other subcellular organelles. Peroxisomal or mitochondrial ROS may facilitate the assembly of distinct signaling platforms involved in the programming of memory innate leukocytes. Despite the emerging connection of subcellular ROS with innate immune memory, underlying mechanisms are still not well defined. Future Directions: Recent important discoveries linking subcellular ROS and innate memory as critically reviewed here hold novel translational relevance related to acute and chronic inflammatory diseases. Capitalizing on these novel findings, future systems studies that use next-generation single-cell dynamic analyses in response to complex inflammatory environments are urgently needed to comprehensively decipher the programming dynamics of innate immune memory, finely modulated by subcellular ROS. Antioxid. Redox Signal. 39, 1027-1038.

Biomimetic nanoplatform with anti-inflammation and neuroprotective effects for repairing spinal cord injury in mice

Regeneration in the therapeutics of spinal cord injury (SCI) remains a challenge caused by the hyperinflammation microenvironment. Nanomaterials-based treatment strategies for diseases with excellent therapeutic efficacy are actively pursued. Here, we develop biodegradable poly (lactic-co-glycolic acid) nanoparticles (PLGA) obtained by loading celastrol (pCel) for SCI thrapy. Cel, as an antioxidant drug, facilitated reactive oxygen species (ROS) scavenging, and decreased the generation of pro-inflammatory cytokines. To facilitate its administration, pCel is formulated into microspheres by oil-in-water (O/W) emulsion/solvent evaporation technique. The constructed pCel can induced polarization of macrophages and obviously improved lipopolysaccharide (LPS) and interferon-γ (IFN-γ)-induced mitochondrial dysfunction, and increased neurite length in PC12 cells and primary neurons. In vivo experiments revealed that pCel regulated the phenotypic polarization of macrophages, prevented the release of pro-inflammatory cytokines, promoted myelin regeneration and inhibited scar tissue formation, and further improve motor function. These findings indicated that the neuroprotective effect of this artificial biodegradable nanoplatform is benefit for the therapy of SCI. This research opens an exciting perspective for the application of SCI treatment and supports the clinical significance of pCel.

Basic Mechanisms of Immunometabolites in Shaping the Immune Response

BACKGROUND

Innate immune cells play a crucial role in responding to microbial infections, but their improper activation can also drive inflammatory disease. For this reason, their activation state is governed by a multitude of factors, including the metabolic state of the cell and, more specifically, the individual metabolites which accumulate intracellularly and extracellularly. This relationship is bidirectional, as innate immune cell activation by pathogen-associated molecular patterns causes critical changes in cellular metabolism.

SUMMARY

In this review, we describe the emergence of various "immunometabolites." We outline the general characteristics of these immunometabolites, the conditions under which they accumulate, and their subsequent impact on immune cells. We delve into well-studied metabolites of recent years, such as succinate and itaconate, as well as newly emerging immunometabolites, such as methylglyoxal.

KEY MESSAGES

We hope that this review may be used as a framework for further studies dissecting the mechanisms by which immunometabolites regulate the immune system and provide an outlook to harnessing these mechanisms in the treatment of inflammatory diseases.

Carbon Dots' Potential in Wound Healing: Inducing M2 Macrophage Polarization and Demonstrating Antibacterial Properties for Accelerated Recovery

Bacterial infections and persistent inflammation can impede the intrinsic healing process of wounds. To combat this issue, researchers have delved into the potential use of carbon dots (CDs) in the regulation of inflammation and counteract infections. These CDs were synthesized using a microwave-assisted hydrothermal process and have demonstrated outstanding antibacterial and antibiofilm properties against Gram-positive and Gram-negative bacteria. Additionally, CDs displayed biocompatibility at therapeutic concentrations and the ability to specifically target mitochondria. CD treatment effectively nullified lipopolysaccharide-triggered reactive oxygen species production by macrophages, while simultaneously promoting macrophage polarization toward an anti-inflammatory phenotype (M2), leading to a reduction in inflammation and an acceleration in wound healing. In vitro scratch assays also revealed that CDs facilitated the tissue-repairing process by stimulating epithelial cell migration during reepithelialization. In vivo studies using CDs topically applied to lipopolysaccharide (LPS)-stimulated wounds in C57/BL6 mice demonstrated significant improvements in wound healing due to enhanced fibroblast proliferation, angiogenesis, and collagen deposition. Crucially, histological investigations showed no indications of systemic toxicity in vital organs. Collectively, the application of CDs has shown immense potential in speeding up the wound-healing process by regulating inflammation, preventing bacterial infections, and promoting tissue repair. These results suggest that further clinical translation of CDs should be considered.

Autofluorescence imaging of endogenous metabolic cofactors in response to cytokine stimulation of classically activated macrophages

BACKGROUND

Macrophages are one of the most prevalent subsets of immune cells within the tumor microenvironment and perform a range of functions depending on the cytokines and chemokines released by surrounding cells and tissues. Recent research has revealed that macrophages can exhibit a spectrum of phenotypes, making them highly plastic due to their ability to alter their physiology in response to environmental cues. Recent advances in examining heterogeneous macrophage populations include optical metabolic imaging, such as fluorescence lifetime imaging (FLIM), and multiphoton microscopy. However, the method of detection for these systems is reliant upon the coenzymes NAD(P)H and FAD, which can be affected by factors other than cytoplasmic metabolic changes. In this study, we seek to validate these optical measures of metabolism by comparing optical results to more standard methods of evaluating cellular metabolism, such as extracellular flux assays and the presence of metabolic intermediates.

METHODS

Here, we used autofluorescence imaging of endogenous metabolic co-factors via multiphoton microscopy and FLIM in conjunction with oxygen consumption rate and extracellular acidification rate through Seahorse extracellular flux assays to detect changes in cellular metabolism in quiescent and classically activated macrophages in response to cytokine stimulation.

RESULTS

Based on our Seahorse XFP flux analysis, M0 and M1 macrophages exhibit comparable trends in oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Autofluorescence imaging of M0 and M1 macrophages was not only able to show acute changes in the optical redox ratio from pre-differentiation (0 hours) to 72 hours post-cytokine differentiation (M0: 0.320 to 0.258 and M1: 0.316 to 0.386), mean NADH lifetime (M0: 1.272 ns to 1.379 ns and M1: 1.265 ns to 1.206 ns), and A1/A2 ratio (M0: 3.452 to ~ 4 and M1: 3.537 to 4.529) but could also detect heterogeneity within each macrophage population.

CONCLUSIONS

Overall, the findings of this study suggest that autofluorescence metabolic imaging could be a reliable technique for longitudinal tracking of immune cell metabolism during activation post-cytokine stimulation.

Intracellular bacterial eradication using a novel peptide in vitro

AIM

To determine the effect of a novel antimicrobial peptide (AMP; OP145) and cell-penetrating peptide (Octa-arginine/R8) conjugate on the killing of intracellular Enterococcus faecalis, compared to OP145 and an antibiotic combination recommended for regenerative endodontic procedures.

METHODOLOGY

The biocompatible concentrations of OP145 and OP145-R8 were determined by assessing their cytotoxicity against human macrophages and red blood cells. Spatiotemporal internalization of the peptides into macrophages was investigated qualitatively and quantitatively by confocal laser scanning microscopy and flow cytometry respectively. Killing of extracellular and intracellular E. faecalis OG1RF by the peptides was determined by counting the colony-forming units (CFU). Intracellular antibacterial activity of the peptides was compared to a double antibiotic combination. Confocal microscopy was used to confirm the intracellular bacterial eradication. Significant differences between the different test groups were analysed using one-way analysis of variance. p < .05 was considered to be statistically significant.

RESULTS

Peptides at a concentration of 7.5 μmol/L were chosen for subsequent experiments based on the results of the alamarBlue™ cell viability assay and haemolytic assay. OP145-R8 selectively internalized into lysosomal compartments and the cytosol of macrophages. Conjugation with R8 improved the internalization of OP145 into macrophages in a temporal manner (70.53% at 1 h to 77.13% at 2 h), while no temporal increase was observed for OP145 alone (60.53% at 1 h with no increase at 2 h). OP145-R8 demonstrated significantly greater extracellular and intracellular antibacterial activity compared to OP145 at all investigated time-points and concentrations (p < .05). OP145-R8 at 7.5 μmol/L eradicated intracellular E. faecalis after 2 h (3.5 log reduction compared to the control; p < .05), while the antibiotics could not reduce more than 0.5 log CFU compared to the control (p > .05). Confocal microscopy showed complete absence of E. faecalis within the OP145-R8 treated macrophages.

CONCLUSIONS

The results of this study demonstrated that the conjugation of an AMP OP145 to a cell-penetrating peptide R8 eradicated extracellular and intracellular E. faecalis OG1RF without toxic effects on the host cells.

The Roles of NFR2-Regulated Oxidative Stress and Mitochondrial Quality Control in Chronic Liver Diseases

Chronic liver disease (CLD) affects a significant portion of the global population, leading to a substantial number of deaths each year. Distinct forms like non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (ALD), though they have different etiologies, highlight shared pathologies rooted in oxidative stress. Central to liver metabolism, mitochondria are essential for ATP production, gluconeogenesis, fatty acid oxidation, and heme synthesis. However, in diseases like NAFLD, ALD, and liver fibrosis, mitochondrial function is compromised by inflammatory cytokines, hepatotoxins, and metabolic irregularities. This dysfunction, especially electron leakage, exacerbates the production of reactive oxygen species (ROS), augmenting liver damage. Amidst this, nuclear factor erythroid 2-related factor 2 (NRF2) emerges as a cellular protector. It not only counters oxidative stress by regulating antioxidant genes but also maintains mitochondrial health by overseeing autophagy and biogenesis. The synergy between NRF2 modulation and mitochondrial function introduces new therapeutic potentials for CLD, focusing on preserving mitochondrial integrity against oxidative threats. This review delves into the intricate role of oxidative stress in CLD, shedding light on innovative strategies for its prevention and treatment, especially through the modulation of the NRF2 and mitochondrial pathways.

The Intersection between Bacterial Metabolism and Innate Immunity

BACKGROUND

The innate immune system is the first line of defense against microbial pathogens and is essential for maintaining good health. If pathogens breach innate barriers, the likelihood of infection is significantly increased. Many bacterial pathogens pose a threat to human health on account of their ability to evade innate immunity and survive in growth-restricted environments. These pathogens have evolved sophisticated strategies to obtain nutrients as well as manipulate innate immune responses, resulting in disease or chronic infection.

SUMMARY

The relationship between bacterial metabolism and innate immunity is complex. Although aspects of bacterial metabolism can be beneficial to the host, particularly those related to the microbiota and barrier integrity, others can be harmful. Several bacterial pathogens harness metabolism to evade immune responses and persist during infection. The study of these adaptive traits provides insight into the roles of microbial metabolism in pathogenesis that extend beyond energy balance. This review considers recent studies on bacterial metabolic pathways that promote infection by circumventing several facets of the innate immune system. We also discuss relationships between innate immunity and antibiotics and highlight future directions for research in this field.

KEY MESSAGES

Pathogenic bacteria have a remarkable capacity to harness metabolism to manipulate immune responses and promote pathogenesis. While we are beginning to understand the multifaceted and complex metabolic adaptations that occur during infection, there is still much to uncover with future research.

Material matters: exploring the interplay between natural biomaterials and host immune system

Biomaterials are widely used for various medical purposes, for instance, implants, tissue engineering, medical devices, and drug delivery systems. Natural biomaterials can be obtained from proteins, carbohydrates, and cell-specific sources. However, when these biomaterials are introduced into the body, they trigger an immune response which may lead to rejection and failure of the implanted device or tissue. The immune system recognizes natural biomaterials as foreign substances and triggers the activation of several immune cells, for instance, macrophages, dendritic cells, and T cells. These cells release pro-inflammatory cytokines and chemokines, which recruit other immune cells to the implantation site. The activation of the immune system can lead to an inflammatory response, which can be beneficial or detrimental, depending on the type of natural biomaterial and the extent of the immune response. These biomaterials can also influence the immune response by modulating the behavior of immune cells. For example, biomaterials with specific surface properties, such as charge and hydrophobicity, can affect the activation and differentiation of immune cells. Additionally, biomaterials can be engineered to release immunomodulatory factors, such as anti-inflammatory cytokines, to promote a tolerogenic immune response. In conclusion, the interaction between biomaterials and the body's immune system is an intricate procedure with potential consequences for the effectiveness of therapeutics and medical devices. A better understanding of this interplay can help to design biomaterials that promote favorable immune responses and minimize adverse reactions.

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.

Suppression of Pro-Inflammatory M1 Polarization of LPS-Stimulated RAW 264.7 Macrophage Cells by Fucoxanthin-Rich Sargassum hemiphyllum

Macrophages play an important role in managing the onset and progression of chronic inflammatory diseases. The primary objective of this study is to explore the antioxidant potential and anti-inflammatory properties of Sargassum hemiphyllum ethanol extract (SHE) and its fraction. SHE and its five constituent fractions were assessed for overall antioxidant capabilities and inhibitory effects on LPS-induced inflammation by modulating macrophages polarization in both RAW 264.7 macrophages and bone-marrow-derived macrophages (BMDM). Among the organic solvent fractions of SHE, the ethyl acetate fraction displayed the highest total phenolic content and total antioxidant capacity. Notably, the n-hexane (Hex) fraction showed the most substantial suppression of LPS-induced tumor necrosis factor α secretion in BMDM among the five fractions of SHE. The SHE and Hex fraction significantly reduced the heightened expression of pro-inflammatory cytokines and inflammation-inducible enzymes induced by LPS in RAW 264.7 macrophages. In particular, the SHE and Hex fraction inhibited M1 macrophage polarization by reducing the mRNA expression of M1 macrophage markers in macrophages that were polarized toward the M1 phenotype. Furthermore, the SHE and Hex fraction attenuated the induction in nuclear factor E2-related factor 2 and its target genes, which was accompanied by an alteration in antioxidant gene expression in M1-polarized BMDM. The findings suggest that both SHE and its Hex fraction exhibit inhibitory effects on LPS-triggered inflammation and oxidative stress by modulating the polarization of M1 macrophages within macrophage populations.

NAT10 regulates the LPS-induced inflammatory response via the NOX2-ROS-NF-κB pathway in macrophages

Periodontitis is a chronic osteolytic inflammatory disease resulting from complex dynamic interactions among bacterial pathogens and the host immune response. Macrophages play a vital role in the pathogenesis of periodontitis by triggering periodontal inflammation and inducing periodontium destruction. N-Acetyltransferase 10 (NAT10) is an acetyltransferase that has been shown to catalyse N4-acetylcytidine (ac4C) mRNA modification and is related to cellular pathophysiological processes, including the inflammatory immune response. Nevertheless, whether NAT10 regulates the inflammatory response of macrophages in periodontitis remains unclear. In this study, the expression of NAT10 in macrophages was found to decrease during LPS-induced inflammation. NAT10 knockdown significantly reduced the generation of inflammatory factors, while NAT10 overexpression had the opposite effect. RNA sequencing revealed that the differentially expressed genes were enriched in the NF-κB signalling pathway and oxidative stress. Both the NF-κB inhibitor Bay11-7082 and the ROS scavenger N-acetyl-L-cysteine (NAC) could reverse the upregulation of inflammatory factors. NAC inhibited the phosphorylation of NF-κB, but Bay11-7082 had no effect on the production of ROS in NAT10-overexpressing cells, suggesting that NAT10 activated the LPS-induced NF-κB signalling pathway by regulating ROS generation. Furthermore, the expression and stability of Nox2 was promoted after NAT10 overexpression, indicating that Nox2 may be a potential target of NAT10. In vivo, the NAT10 inhibitor Remodelin reduced macrophage infiltration and bone resorption in ligature-induced periodontitis mice. In summary, these results showed that NAT10 accelerated LPS-induced inflammation via the NOX2-ROS-NF-κB pathway in macrophages and that its inhibitor Remodelin might be of potential therapeutic significance in periodontitis treatment.

Metabolic reprogramming in inflammatory microglia indicates a potential way of targeting inflammation in Alzheimer's disease

Microglia activation drives the pro-inflammatory activity in the early stages of Alzheimer's disease (AD). However, the mechanistic basis is elusive, and the hypothesis of targeting microglia to prevent AD onset is little explored. Here, we demonstrated that upon LPS exposure, microglia shift towards an energetic phenotype characterised by high glycolysis and high mitochondrial respiration with dysfunction. Although the activity of electron transport chain (ETC) complexes is boosted by LPS, this is mostly devoted to the generation of reactive oxygen species. We showed that by inhibiting succinate dehydrogenase (SDH) with dimethyl malonate (DMM), it is possible to modulate the LPS-induced metabolic rewiring, facilitating an anti-inflammatory phenotype. DMM improves mitochondrial function in a direct way and by reducing LPS-induced mitochondrial biogenesis. Moreover, the block of SDH with DMM inhibits the recruitment of hypoxia inducible-factor 1 α (HIF-1α), which mediates the induction of glycolysis and cytokine expression. Similar bioenergetic alterations were observed in the microglia isolated from AD mice (3xTg-AD), which present high levels of circulating LPS and brain toll-like receptor4 (TLR4). Moreover, this well-established model of AD was used to show a potential effect of SDH inhibition in vivo as DMM administration abrogated brain inflammation and modulated the microglia metabolic alterations of 3xTg-AD mice. The RNA-sequencing analysis from a public dataset confirmed the consistent transcription of genes encoding for ETC subunits in the microglia of AD mice (5xFAD). In conclusion, TLR4 activation promotes metabolic changes and the pro-inflammatory activity in microglia, and SDH might represent a promising therapeutic target to prevent AD development.

Interplay between Immune and Bacterial Cells on a Biomimetic Nanostructured Surface: A "Race for the Surface" Study

Biomaterial-associated infection is an ever-increasing risk with devasting consequences for patients. Considerable research has been undertaken to address this issue by imparting antibacterial properties to the surface of biomedical implants. One approach that generated much interest over recent years was the generation of bioinspired bactericidal nanostructures. In the present report, we have investigated the interplay between macrophages and bacteria on antibacterial nanostructured surfaces to determine the outcome of the so-called "race for the surface". Our results showed that macrophages can indeed outcompete Staphylococcus aureus via multiple mechanisms. The early generation of reactive oxygen species by macrophages, downregulation of bacterial virulence gene expression, and the bactericidal nature of the nanostructured surface itself collectively acted to help the macrophage to win the race. This study highlights the potential of nanostructured surfaces to reduce infection rates and improve the long-term success of biomedical implants. This work can also serve as guidance to others to investigate in vitro host-bacteria interactions on other candidate antibacterial surfaces.

Genome-scale modeling predicts metabolic differences between macrophage subtypes in colorectal cancer

Colorectal cancer (CRC) shows high incidence and mortality, partly due to the tumor microenvironment (TME), which is viewed as an active promoter of disease progression. Macrophages are among the most abundant cells in the TME. These immune cells are generally categorized as M1, with inflammatory and anti-cancer properties, or M2, which promote tumor proliferation and survival. Although the M1/M2 subclassification scheme is strongly influenced by metabolism, the metabolic divergence between the subtypes remains poorly understood. Therefore, we generated a suite of computational models that characterize the M1- and M2-specific metabolic states. Our models show key differences between the M1 and M2 metabolic networks and capabilities. We leverage the models to identify metabolic perturbations that cause the metabolic state of M2 macrophages to more closely resemble M1 cells. Overall, this work increases understanding of macrophage metabolism in CRC and elucidates strategies to promote the metabolic state of anti-tumor macrophages.