Macrophage-mediated Inflammatory Responses Research Articles

Multifunctional Prosthesis Surface: Modification of Titanium with Cinnamaldehyde-Loaded Hierarchical Titanium Dioxide Nanotubes.

Orthopedic prostheses are the ultimate therapeutic solution for various end-stage orthopedic conditions. However, aseptic loosening and pyogenic infections remain as primary complications associated with these devices. In this study, a hierarchical titanium dioxide (TiO2) nanotube drug delivery system loaded with cinnamaldehyde for the surface modification of titanium implants, is constructed. These specially designed dual-layer TiO2 nanotubes enhance material reactivity and provide an extensive drug-loading platform within a short time. The introduction of cinnamaldehyde enhances the bone integration performance of the scaffold (simultaneously promoting bone formation and inhibiting bone resorption), anti-inflammatory capacity, and antibacterial properties. In vitro experiments have demonstrated that this system promoted osteogenesis by upregulating both Wnt/β-catenin and MAPK signaling pathways. Furthermore, it inhibits osteoclast formation, suppresses macrophage-mediated inflammatory responses, and impedes the proliferation of Staphylococcus aureus and Escherichia coli. In vivo experiments shows that this material enhances bone integration in a rat model of femoral defects. In addition, it effectively enhances the antibacterial and anti-inflammatory properties in a subcutaneous implant in a rat model. This study provides a straightforward and highly effective surface modification strategy for orthopedic Ti implants.

Induction of MTHFD2 in Macrophages Inhibits Reactive Oxygen Species-mediated NF-κB Activation and Protects against Inflammatory Responses.

The one-carbon metabolism enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is critical for cancer cell proliferation and immune cell phenotypes, but whether it can contribute to macrophage inflammatory responses remains unclear. In this study, we show that MTHFD2 was upregulated by LPS in murine macrophages upon activation of the TLR4-MyD88-IKKα/β-NF-κB signaling pathway. MTHFD2 significantly attenuated LPS-induced macrophage proinflammatory cytokine production through its enzymatic activity. Notably, ablation of myeloid MTHFD2 rendered mice more sensitive to septic shock and CCl4-induced acute hepatitis. Mechanistically, MTHFD2 restrained IKKα/β-NF-κB activation and macrophage inflammatory phenotype by scavenging reactive oxygen species through the generation of NADPH. Our study reveals MTHFD2 as a "self-control" mechanism in macrophage-mediated inflammatory responses.

Mechanical gated ion channel Piezo1: Function, and role in macrophage inflammatory response.

Macrophages are present in many mechanically active tissues and are often subjected to varying degrees of mechanical stimulation. Macrophages play a crucial role in resisting pathogen invasion and maintaining tissue homeostasis. Piezo-type mechanosensitive channel component 1 (Piezo1) is the main cation channel involved in the rapid response to mechanical stimuli in mammals. This channel plays a crucial role in controlling blood pressure and motor performance and regulates urinary osmotic pressure and epithelial cell proliferation and division. In recent years, numerous studies have shown that in macrophages, Piezo1 not only plays a role in regulating the aforementioned physiological processes but also participates in multiple pathological processes such as inflammation and cancer. In this review, we summarize the research progress on Piezo1-mediated regulation of macrophage-mediated inflammatory responses through downstream signalling pathways and the aerobic glycolysis pathway.

Extracellular vesicles: A promising therapy against SARS-CoV-2 infection

Extracellular vesicles: A promising therapy against SARS-CoV-2 infection

Histone demethylase KDM5B licenses macrophage-mediated inflammatory responses by repressing Nfkbia transcription.

Macrophages play a critical role in the immune homeostasis and host defense against invading pathogens. However, uncontrolled activation of inflammatory macrophages leads to tissue injury and even fuels autoimmunity. Hence the molecular mechanisms underlying macrophage activation need to be further elucidated. The effects of epigenetic modifications on the function of immune cells draw increasing attention. Here, we demonstrated that lysine-specific demethylase 5B (KDM5B), a classical transcriptional repressor in stem cell development and cancer, was required for the full activation of NF-κB signaling cascade and pro-inflammatory cytokine production in macrophages. KDM5B deficiency or inhibitor treatment protected mice from immunologic injury in both collagen-induced arthritis (CIA) model and endotoxin shock model. Genome-wide analysis of KDM5B-binding peaks identified that KDM5B was selectively recruited to the promoter of Nfkbia, the gene encoding IκBα, in activated macrophages. KDM5B mediated the H3K4me3 modification erasing and decreased chromatin accessibility of Nfkbia gene locus, coordinating the elaborate suppression of IκBα expression and the enhanced NF-κB-mediated macrophage activation. Our finding identifies the indispensable role of KDM5B in macrophage-mediated inflammatory responses and provides a candidate therapeutic target for autoimmune and inflammatory disorders.

Type I Cystatin Derived from Fasciola gigantica Suppresses Macrophage-Mediated Inflammatory Responses

There is an inverse relationship between the high incidence of helminth infection and the low incidence of inflammatory disease. Hence, it may be that helminth molecules have anti-inflammatory effects. Helminth cystatins are being extensively studied for anti-inflammatory potential. Therefore, in this study, the recombinant type I cystatin (stefin-1) of Fasciola gigantica (rFgCyst) was verified to have LPS-activated anti-inflammatory potential, including in human THP-1-derived macrophages and RAW 264.7 murine macrophages. The results from the MTT assay suggest that rFgCyst did not alter cell viability; moreover, it exerted anti-inflammatory activity by decreasing the production of proinflammatory cytokines and mediators, including IL-1β, IL-6, IL-8, TNF-α, iNOS, and COX-2 at the gene transcription and protein expression levels, as determined by qRT-PCR and Western blot analysis, respectively. Further, the secretion levels of IL-1β, IL-6, and TNF-α determined by ELISA and the NO production level determined by the Griess test were decreased. Furthermore, in Western blot analysis, the anti-inflammatory effects involved the downregulation of pIKKα/β, pIκBα, and pNF-κB in the NF-κB signaling pathway, hence reducing the translocation from the cytosol into the nucleus of pNF-κB, which subsequently turned on the gene of proinflammatory molecules. Therefore, cystatin type 1 of F. gigantica is a potential candidate for inflammatory disease treatment.

Mangiferin Ameliorates Obesity-Associated Inflammation and Autophagy in High-Fat-Diet-Fed Mice: In Silico and In Vivo Approaches

Obesity-induced insulin resistance is the fundamental cause of metabolic syndrome. Accordingly, we evaluated the effect of mangiferin (MGF) on obesity and glucose metabolism focusing on inflammatory response and autophagy. First, an in silico study was conducted to analyze the mechanism of MGF in insulin resistance. Second, an in vivo experiment was conducted by administering MGF to C57BL/6 mice with high-fat-diet (HFD)-induced metabolic disorders. The in silico analysis revealed that MGF showed a high binding affinity with macrophage-related inflammatory cytokines and autophagy proteins. In the in vivo study, mice were divided into three groups: normal chow, HFD, and HFD + MGF 150 mg/kg. MGF administration to obese mice significantly improved the body weight, insulin-sensitive organs weights, glucose and lipid metabolism, fat accumulation in the liver, and adipocyte size compared to HFD alone. MGF significantly reduced the macrophages in adipose tissue and Kupffer cells, inhibited the gene expression ratio of tumor necrosis factor-α and F4/80 in adipose tissue, reduced the necrosis factor kappa B gene, and elevated autophagy-related gene 7 and fibroblast growth factor 21 gene expressions in the liver. Thus, MGF exerted a therapeutic effect on metabolic diseases by improving glucose and lipid metabolism through inhibition of the macrophage-mediated inflammatory responses and activation of autophagy.

Methyltransferase like 7B is upregulated in sepsis and modulates lipopolysaccharide-induced inflammatory response and macrophage polarization

ABSTRACT Macrophages play a critical role in the regulation of the inflammatory responses in sepsis. Methyltransferase like 7B (METTL7B) has been implicated in several pathophysiological conditions. Nevertheless, the potential engagement of METTL7B in sepsis remains to be elucidated. In this study, we retrieved transcriptomic profile data of septic patients and healthy donors and compared the expression level of METTL7B between septic patients and healthy controls. We also collected septic patient samples to analyze METTL7B expression via RT-qPCR. Murine bone marrow-derived macrophages (BMDMs) were isolated and treated with incremental doses of LPS as an in vitro cell model. METTL7B was overexpressed or knocked down in BMDMs, and lipopolysaccharide (LPS)-mediated inflammatory cytokines production and macrophage polarization were evaluated. We found that METTL7B was upregulated in the blood and peripheral blood mononuclear cells (PBMC) of septic patients, which also showed a significant diagnostic potential for sepsis. In BMDMs, METTL7B was induced in a time and dose-dependent manner by LPS. Modulating the expression level of METTL7B could regulate LPS-mediated inflammatory cytokines production and macrophage polarization. The functional role of METTL7B was also validated in a septic mouse model. Our findings indicate that METTL7B is implicated in the immunopathogenesis of sepsis through modulating macrophage-mediated inflammatory responses. METTL7B may serve as a potential diagnostic and therapeutic target for sepsis.

Metabolic Reprogramming Mediates Macrophage Polarization After Myocardial Infarction

BackgroundMacrophages play a critical role in left ventricular (LV) remodeling after myocardial infarction (MI), and limiting macrophage‐mediated inflammatory responses while enhancing reparative roles is a promising therapeutic strategy. Monocyte‐derived M1 macrophages mediate the early inflammatory response, while M2 macrophages mediate the later wound healing and scar formation phase. Metabolic reprogramming from glycolysis to mitochondrial oxidative phosphorylation mediates M1 to M2 polarization. We hypothesized that metabolic reprogramming occurs in macrophages over the course of post‐MI remodeling, and that blocking macrophage glycolysis attenuates post‐MI inflammation.MethodsMI was induced in adult (16‐20 week old) male C57BL/6J mice by permanent ligation of the left coronary artery for 1, 3, or 7 days, and cardiac function was assessed by echocardiography. Macrophages were extracted from the LV infarct area by immunomagnetic sorting. Macrophage metabolic flux was assessed by Extracellular Flux Analysis (Seahorse); upon glucose administration, glycolysis was measured by extracellular acidification rate (ECAR) while glucose oxidation was measured by oxygen consumption (OCR). Leukocyte subtypes (neutrophils, monocytes, resident macrophages) were assessed by flow cytometry. Real‐time PCR was used to assess gene expression by relative mRNA levels. To specifically block macrophage glycolysis, LysMCre mice were crossed with mice floxed for Slc2a1, the major macrophage glucose transporter, to generate macrophage‐Slc2a1 null mice.ResultsMI led to LV contractile dysfunction (decreased ejection fraction; days 1, 3, and 7 versus day 0), thinning of the infarct wall (days 1, 3, and 7) and non‐infarct wall (day 7), and dilation (increased internal diameter at diastole and end‐diastolic volume; day 7). At day 1, increased neutrophils (Ly6G+) and monocytes (Ly6Chi) were observed in the infarcted LV; at day 7, neutrophils and monocytes returned to baseline levels and the majority of macrophages were resident M2 subtype (Ly6Clow versus day 1). Day 1 macrophages showed elevated glycolysis (ECAR versus day 0) and increased mRNA levels of the M1 marker Il1b (versus day 3 and 7); day 3 macrophages showed increased glycolysis (ECAR versus day 0) and decreased glucose oxidation (versus day 0); day 7 macrophages showed decreased glycolysis (ECAR versus day 1 and 3) and increased glucose oxidation (OCR versus day 1 and 3), and increased Slc2a1 mRNA, Krebs cycle genes (Pdha1, Idh1/2, Sdha/bmRNA), pentose phosphate pathway genes (G6pd2/x, Pgd, Rpia, Taldo1 mRNA), and Il10 (M2 marker) mRNA. In macrophage‐Slc2a1 null mice, macrophage glycolysis was decreased and glucose oxidation increased at day 3, and infarct levels of Il1b were decreased compared to floxed controls.ConclusionsOur results indicate that time‐dependent macrophage metabolic reprogramming occurs over the MI remodeling process, and that blocking macrophage glycolysis may be a promising strategy for limiting post‐MI inflammation and adverse remodeling.

Effects of Volatile Anaesthetics and Iron Dextran on Chronic Inflammation and Antioxidant Defense System in Rats

Iron, as an essential microelement, is involved in cell proliferation, metabolism, and differentiation. It also modulates the fate and function of macrophages in hematopoiesis and macrophage-mediated inflammatory responses. On the other hand, anesthetics can affect the inflammatory process by modulating the response to stress or the functions of immune cells. The aim of this paper is to understand how excessive iron intake alters physiological, functional characteristics of peripheral tissues and whether different anesthetics can alter cell metabolism regarding oxidative stress (OS) and inflammation through regulation of macrophage polarization. Y59 rats were injected intraperitoneally with iron dextran solution at a dose of 50 mg/kg or were exposed to inhaled anesthetics sevoflurane and isoflurane and their combination for 28 days every other day. The results show that the use of anesthetics reduces the rat’s organ weight and increases OS in peripheral tissues, leading to M1 macrophage polarization. Excessive iron intake leads to increased OS, inflammation, and an increased ratio of IL-12/IL-10 cytokines to the M1 macrophage phenotype. Iron, in combination with sevoflurane, has a protective effect in tissues showing the M2 phenotype of macrophages. The combination of iron dextran and isoflurane in rats leads to an increase in the erythropoiesis process made possible through the induction of hypoxia.

Regulation of macrophage-associated inflammatory responses by species-specific lactoferricin peptides.

Inflammation is the body's response to injury or infection and is important for healing and eliminating pathogens; however, prolonged inflammation is damaging and may lead to the development of chronic inflammatory disorders. Recently, there has been interest in exploiting antimicrobial peptides (AMPs) that exhibit immunoregulatory activities to treat inflammatory diseases. In this study, we investigated the immunomodulatory effects of lactoferrin-derived lactoferricin AMPs from three different species (bovine, mouse, and human) with subtle differences in their amino acid sequences that alter their antimicrobial action; to our knowledge, no other studies have compared their immunomodulatory effects. Macrophages, key players in the induction and propagation of inflammation, were used to investigate the effects of species-specific lactoferricin peptides on inflammatory processes. Bovine lactoferricin was the only one of the three peptides studied that downregulated lipopolysaccharide (LPS)-induced pro-inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-6, in both human and mouse macrophages. Lactoferricin regulated inflammation through targeting LPS-activated nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) signaling pathways. Although the immunoregulatory role of lactoferricin during an inflammatory response in vivo is yet to be elucidated, further investigation with the use of animal models is warranted by the current findings. The ability of lactoferricin, especially that of bovine origin, to downregulate macrophage-mediated inflammatory responses suggests potential for the development of this peptide as a novel immunotherapeutic agent in the treatment of chronic inflammatory conditions.

Syk promotes phagocytosis by inducing reactive oxygen species generation and suppressing SOCS1 in macrophage-mediated inflammatory responses.

ObjectiveInflammation, a vital innate immune response against infection and injury, is mediated by macrophages. Spleen tyrosine kinase (Syk) regulates inflammatory responses in macrophages; however, its role and underlying mechanisms are uncertain.Materials and MethodsIn this study, overexpression and knockout (KO) cell preparations, phagocytosis analysis, confocal microscopy, reactive oxygen species (ROS) determination, mRNA analysis, and immunoprecipitation/western blotting analyses were used to investigate the role of Syk in phagocytosis and its underlying mechanisms in macrophages during inflammatory responses.ResultsSyk inhibition by Syk KO, Syk-specific small interfering RNA (siSyk), and a selective Syk inhibitor (piceatannol) significantly reduced the phagocytic activity of RAW264.7 cells. Syk inhibition also decreased cytochrome c generation by inhibiting ROS-generating enzymes in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and ROS scavenging suppressed the phagocytic activity of RAW264.7 cells. LPS induced the tyrosine nitration (N-Tyr) of suppressor of cytokine signaling 1 (SOCS1) through Syk-induced ROS generation in RAW264.7 cells. On the other hand, ROS scavenging suppressed the N-Tyr of SOCS1 and phagocytosis. Moreover, SOCS1 overexpression decreased phagocytic activity, and SOCS1 inhibition increased the phagocytic activity of RAW264.7 cells.ConclusionThese results suggest that Syk plays a critical role in the phagocytic activity of macrophages by inducing ROS generation and suppressing SOCS1 through SOCS1 nitration during inflammatory responses.

Syk-MyD88 Axis Is a Critical Determinant of Inflammatory-Response in Activated Macrophages.

BackgroundInflammation, a vital immune response to infection and injury, is mediated by macrophage activation. While spleen tyrosine kinase (Syk) and myeloid differentiation primary response 88 (MyD88) are reportedly involved in inflammatory responses in macrophages, their roles and underlying mechanisms are largely unknown.MethodsHere, the role of the MyD88-Syk axis and the mechanism by which Syk and MyD88 cooperate during macrophage-mediated inflammatory responses are explored using knockout conditions of these proteins and mutation strategy as well as flowcytometric and immunoblotting analyses.ResultsSyk rapidly activates the nuclear factor-kappa B (NF-κB) signaling pathway in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and the activation of the NF-κB signaling pathway is abolished in Syk−/− RAW264.7 cells. MyD88 activates Syk and Syk-induced activation of NF-κB signaling pathway in LPS-stimulated RAW264.7 cells but Syk-induced inflammatory responses are significantly inhibited in MyD88−/− RAW264.7 cells. MyD88 interacts with Syk through the tyrosine 58 residue (Y58) in the hemi-immunoreceptor tyrosine-based activation motif (ITAM) of MyD88, leading to Syk activation and Syk-induced activation of the NF-κB signaling pathway. Src activates MyD88 by phosphorylation at Y58 via the Src kinase domain. In addition, Ras-related C3 botulinum toxin substrate 1 (Rac1) activation and Rac1-induced formation of filamentous actin (F actin) activate Src in LPS-stimulated RAW264.7 cells.ConclusionsThese results suggest that the MyD88-Syk axis is a critical player in macrophage-mediated inflammatory responses, and its function is promoted by an upstream Src kinase activated by Rac1-generated filamentous actin (F-actin).

Aspartate Metabolism Facilitates IL-1β Production in Inflammatory Macrophages.

Increasing evidence support that cellular amino acid metabolism shapes the fate of immune cells; however, whether aspartate metabolism dictates macrophage function is still enigmatic. Here, we found that the metabolites in aspartate metabolism are depleted in lipopolysaccharide (LPS) plus interferon gamma (IFN-γ)-stimulated macrophages. Aspartate promotes interleukin-1β (IL-1β) secretion in M1 macrophages. Mechanistically, aspartate boosts the activation of hypoxia-inducible factor-1α (HIF-1α) and inflammasome and increases the levels of metabolites in aspartate metabolism, such as asparagine. Interestingly, asparagine also accelerates the activation of cellular signaling pathways and promotes the production of inflammatory cytokines from macrophages. Moreover, aspartate supplementation augments the macrophage-mediated inflammatory responses in mice and piglets. These results uncover a previously uncharacterized role for aspartate metabolism in directing M1 macrophage polarization.

Disulfiram-loaded lactoferrin nanoparticles for treating inflammatory diseases.

Sepsis is a dysregulated immune response to infection and potentially leads to life-threatening organ dysfunction, which is often seen in serious Covid-19 patients. Disulfiram (DSF), an old drug that has been used to treat alcohol addiction for decades, has recently been identified as a potent inhibitor of the gasdermin D (GSDMD)-induced pore formation that causes pyroptosis and inflammatory cytokine release. Therefore, DSF represents a promising therapeutic for the treatment of inflammatory disorders. Lactoferrin (LF) is a multifunctional glycoprotein with potent antibacterial and anti-inflammatory activities that acts by neutralizing circulating endotoxins and activating cellular responses. In addition, LF has been well exploited as a drug nanocarrier and targeting ligands. In this study, we developed a DSF-LF nanoparticulate system (DSF-LF NP) for combining the immunosuppressive activities of both DSF and LF. DSF-LF NPs could effectively block pyroptosis and inflammatory cytokine release from macrophages. Treatment with DSF-LF NPs showed remarkable therapeutic effects on lipopolysaccharide (LPS)-induced sepsis. In addition, this therapeutic strategy was also applied to treat ulcerative colitis (UC), and substantial treatment efficacy was achieved in a murine colitis model. The underlying mode of action of these DSF-LF-NPs may contribute to efficiently suppressing macrophage-mediated inflammatory responses and ameliorating the complications caused by sepsis and UC. As macrophage pyroptosis plays a pivotal role in inflammation, this safe and effective biomimetic nanomedicine may offer a versatile therapeutic strategy for treating various inflammatory diseases by repurposing DSF.

Pharmacological activation of SIRT1 by metformin prevented trauma-induced heterotopic ossification through inhibiting macrophage mediated inflammation

Trauma-induced heterotopic ossification (HO) is the aberrant extra-skeletal bone formation that severely incapacitates patient's daily life. Inflammation is the first stage of this progression, becoming an appealing target of early therapeutic intervention. Metformin, a widely used antidiabetic drug, also poses the therapeutic potential to modulate various inflammatory-related diseases. Therefore, this study aimed to investigate the preventive effect of metformin on trauma-induced HO progression, and unveil the underlying molecular mechanisms. A murine burn/tenotomy model was established to mimic trauma-induced HO in vivo. The anti-inflammation and anti-ossification effects of metformin were evaluated by histological staining and micro-CT. The inhibitory effects of metformin on macrophages activation in vitro were examined by ELISA and qRT-PCR. The underlying molecular mechanisms were further explored by immunofluorescence staining and western-blotting in vivo. Increased macrophages infiltration and inflammatory responses were found at early stage during HO progression. However, metformin dose-dependently attenuated the macrophage-mediated inflammatory responses both in vivo and vitro, which might account for the inhibitory effect of metformin on chondrogenesis and HO formation after trauma. Furthermore, elevated SIRT1 expression and decreased NF-κB p65 acetylation were found in the beneficial effects of metformin. Moreover, similar preventive effects were also found in SRT1720 HCI, a specific SIRT1 activator, while were remarkably reversed after the administration of EX527 (a specific SIRT1 inhibitor) with metformin. Taken together, our results provide a novel evidence that metformin can effectively attenuate trauma-induced HO by mitigating macrophage inflammatory responses through inhibiting NF-κB signaling via SIRT1-dependent mechanisms, which favors future therapeutic investigations for trauma-related disease.

Olea europaea Suppresses Inflammation by Targeting TAK1-Mediated MAP Kinase Activation.

Possessing a variety of medicinal functions, Olea europaea L. is widely cultivated across the world. However, the anti-inflammatory mechanism of Olea europaea is not yet fully elucidated. In this study, how the methanol extract of the leaves of Olea europaea (Oe-ME) can suppress in vitro inflammatory responses was examined in terms of the identification of the target protein. RAW264.7 and HEK293T cells were used to study macrophage-mediated inflammatory responses and to validate the target protein using PCR, immunoblotting, nuclear fraction, overexpression, and cellular thermal shift assay (CETSA) under fixed conditions. Oe-ME treatment inhibited the mRNA expression levels of cyclooxygenase (COX)-2, matrix metallopeptidase (MMP)-9, and intercellular adhesion molecule-1 (ICAM-1) in activated RAW264.7 cells. Oe-ME diminished the activation of activator protein (AP)-1 and the phosphorylation of its upstream signaling cascades, including extracellular signal regulated kinase (ERK), mitogen-activated protein kinase kinase 1/2 (MEK1/2), c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase kinase 3/6 (MKK3/6), p38, MKK7, and transforming growth factor-β-activated kinase 1 (TAK1), in stimulated-RAW264.7 cells. Overexpression and CETSA were carried out to verify that TAK1 is the target of Oe-ME. Our results suggest that the anti-inflammatory effect of Oe-ME could be attributed to its control of posttranslational modification and transcription of TAK1.

Neutrophil-Macrophage Imbalance Drives the Development of Renal Scarring during Experimental Pyelonephritis.

In children, the acute pyelonephritis that can result from urinary tract infections (UTIs), which commonly ascend from the bladder to the kidney, is a growing concern because it poses a risk of renal scarring and irreversible loss of kidney function. To date, the cellular mechanisms underlying acute pyelonephritis-driven renal scarring remain unknown. We used a preclinical model of uropathogenic Escherichia coli-induced acute pyelonephritis to determine the contribution of neutrophils and monocytes to resolution of the condition and the subsequent development of kidney fibrosis. We used cell-specific monoclonal antibodies to eliminate neutrophils, monocytes, or both. Bacterial ascent and the cell dynamics of phagocytic cells were assessed by biophotonic imaging and flow cytometry, respectively. We used quantitative RT-PCR and histopathologic analyses to evaluate inflammation and renal scarring. We found that neutrophils are critical to control bacterial ascent, which is in line with previous studies suggesting a protective role for neutrophils during a UTI, whereas monocyte-derived macrophages orchestrate a strong, but ineffective, inflammatory response against uropathogenic, E. coli-induced, acute pyelonephritis. Experimental neutropenia during acute pyelonephritis resulted in a compensatory increase in the number of monocytes and heightened macrophage-dependent inflammation in the kidney. Exacerbated macrophage-mediated inflammatory responses promoted renal scarring and compromised renal function, as indicated by elevated serum creatinine, BUN, and potassium. These findings reveal a previously unappreciated outcome for neutrophil-macrophage imbalance in promoting host susceptibility to acute pyelonephritis and the development of permanent renal damage. This suggests targeting dysregulated macrophage responses might be a therapeutic tool to prevent renal scarring during acute pyelonephritis.

Glycogen metabolism regulates macrophage-mediated acute inflammatory responses

Our current understanding of how sugar metabolism affects inflammatory pathways in macrophages is incomplete. Here, we show that glycogen metabolism is an important event that controls macrophage-mediated inflammatory responses. IFN-γ/LPS treatment stimulates macrophages to synthesize glycogen, which is then channeled through glycogenolysis to generate G6P and further through the pentose phosphate pathway to yield abundant NADPH, ensuring high levels of reduced glutathione for inflammatory macrophage survival. Meanwhile, glycogen metabolism also increases UDPG levels and the receptor P2Y14 in macrophages. The UDPG/P2Y14 signaling pathway not only upregulates the expression of STAT1 via activating RARβ but also promotes STAT1 phosphorylation by downregulating phosphatase TC45. Blockade of this glycogen metabolic pathway disrupts acute inflammatory responses in multiple mouse models. Glycogen metabolism also regulates inflammatory responses in patients with sepsis. These findings show that glycogen metabolism in macrophages is an important regulator and indicate strategies that might be used to treat acute inflammatory diseases.

MgO Nanoparticles Protect against Titanium Particle-Induced Osteolysis in a Mouse Model Because of Their Positive Immunomodulatory Effect.

Aseptic prosthetic loosening (APL) often leads to the failure of prostheses. It is inseparable from wear-particle-induced macrophage-mediated inflammatory responses and osteolysis. Mg2+ is a metal ion with excellent anti-inflammatory properties. Herein, Mg2+ was introduced into a nanomedicine (MgO nanoparticles (MNPs)) to protect against APL. MNPs could be phagocytized by macrophages and gradually degraded intracellularly. Following MNPs treatment, lipopolysaccharide (LPS)-activated macrophages polarized into deeper M1 phenotype at 6 h but then switched to the M2 phenotype at 48 h. Furthermore, the MNPs suppressed the titanium (Ti) particle-induced osteoclastogenesis and osteolysis in vivo. However, the MNPs exhibited no impact on the receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis and even inhibited osteogenesis in vitro. The contrary results between the in vitro and in vivo experiments imply that macrophages are the key factor in the inhibited osteoclastogenesis in vivo because the pathogenic process of APL is mainly attributed to macrophages, osteoblasts, and osteoclasts. Accordingly, an indirect coculture system was designed that considers the immunomodulatory effect of macrophages. RANKL-induced osteoclastogenesis was significantly inhibited under the influence of MNPs in the indirect coculture system. Taken together, the MNPs inhibited the inflammatory responses of macrophages provoked by the Ti particles and thus regulated the expressions of RANKL and OPG in osteoblasts to suppress osteoclastogenesis. The target cell of MNPs was macrophages but not osteoclasts, indicating the importance of the immunomodulatory effect of macrophages. These results collectively demonstrated that MNPs can prevent APL and other osteolysis-related diseases.