Bone marrow-derived macrophages from aged rats are more responsive to inflammatory stimuli

Biodegradable Zn-2Cu-0.5Zr alloy promotes the bone repair of senile osteoporotic fractures via the immune-modulation of macrophages

Delayed bone-healing of senile osteoporotic fractures remains a clinical challenge due to the alterations caused by aging in bone and immune systems. The novel biomaterials that address the deficiencies in both skeletal cells and immune systems are required to effectively treat the bone injuries of older patients. Zinc (Zn) has shown promise as a biodegradable material for use in orthopedic implants. To address the bone-healing deficiencies in elderly patients with bone injuries, we developed a biodegradable Zn-based alloy (Zn-2Cu-0.5Zr) with enhanced mechanical properties, including a yield strength of 198.7 MPa and ultimate tensile strength of 217.6 MPa, surpassing those of pure Zn and Zn-2Cu alloys. Cytotoxicity tests conducted on bone marrow mesenchymal stem cells (BMSCs) and MC3T3-E1 cells demonstrated that the extracts from Zn-2Cu-0.5Zr alloy exhibited no observable cytotoxic effects. Furthermore, the extracts of Zn-2Cu-0.5Zr alloy exhibited significant anti-inflammatory effects through regulation of inflammation-related cytokine production and modulation of macrophage polarization. The improved immune-osteo microenvironment subsequently contributed to osteogenic differentiation of BMSCs. The potential therapeutic application of Zn-2Cu-0.5Zr in senile osteoporotic fracture was tested using a rat model of age-related osteoporosis. The Zn-2Cu-0.5Zr alloy met the requirements for load-bearing applications and accelerated the healing process in a tibial fracture in aged rats. The imaging and histological analyses showed that it could accelerate the bone-repair process and promote the fracture healing in senile osteoporotic rats. These findings suggest that the novel Zn-2Cu-0.5Zr alloy holds potential for influencing the immunomodulatory function of macrophages and facilitating bone repair in elderly individuals with osteoporosis.

TPG-functionalized PLGA/PCL nanofiber membrane facilitates periodontal tissue regeneration by modulating macrophages polarization via suppressing PI3K/AKT and NF-κB signaling pathways

Traditional fibrous membranes employed in guided tissue regeneration (GTR) in the treatment of periodontitis have limitations of bioactive and immunomodulatory properties. We fabricated a novel nTPG/PLGA/PCL fibrous membrane by electrospinning which exhibit excellent hydrophilicity, mechanical properties and biocompatibility. In addition, we investigated its regulatory effect on polarization of macrophages and facilitating the regeneration of periodontal tissue both in vivo and in vitro. These findings showed the 0.5%TPG/PLGA/PCL may inhibit the polarization of RAW 264.7 into M1 phenotype by suppressing the PI3K/AKT and NF-κB signaling pathways. Furthermore, it directly up-regulated the expression of cementoblastic differentiation markers (CEMP-1 and CAP) in periodontal ligament stem cells (hPDLSCs), and indirectly up-regulated the expression of cementoblastic (CEMP-1 and CAP) and osteoblastic (ALP, RUNX2, COL-1, and OCN) differentiation markers by inhibiting the polarization of M1 macrophage. Upon implantation into a periodontal bone defect rats model, histological assessment revealed that the 0.5%TPG/PLGA/PCL membrane could regenerate oriented collagen fibers and structurally intact epithelium. Micro-CT (BV/TV) and the expression of immunohistochemical markers (OCN, RUNX-2, COL-1, and BMP-2) ultimately exhibited satisfactory regeneration of alveolar bone, periodontal ligament. Overall, 0.5%TPG/PLGA/PCL did not only directly promote osteogenic effects on hPDLSCs, but also indirectly facilitated cementoblastic and osteogenic differentiation through its immunomodulatory effects on macrophages. These findings provide a novel perspective for the development of materials for periodontal tissue regeneration.

Exosomes derived from M2 macrophages prevent steroid-induced osteonecrosis of the femoral head by modulating inflammation, promoting bone formation and inhibiting bone resorption

Inflammatory reactions are involved in the development of steroid-induced osteonecrosis of the femoral head(ONFH). Studies have explored the therapeutic efficacy of inhibiting inflammatory reactions in steroid-induced ONFH and revealed that inhibiting inflammation may be a new strategy for preventing the development of steroid-induced ONFH. Exosomes derived from M2 macrophages(M2-Exos) display anti-inflammatory properties. This study aimed to examine the preventive effect of M2-Exos on early-stage steroid-induced ONFH and explore the underlying mechanisms involved. In vitro, we explored the effect of M2-Exos on the proliferation and osteogenic differentiation of bone marrow-derived mesenchymal stem cells(BMMSCs). In vivo, we investigated the role of M2-Exos on inflammation, osteoclastogenesis, osteogenesis and angiogenesis in an early-stage rat model of steroid-induced ONFH. We found that M2-Exos promoted the proliferation and osteogenic differentiation of BMMSCs. Additionally, M2-Exos effectively attenuated the osteonecrotic changes, inhibited the expression of proinflammatory mediators, promoted osteogenesis and angiogenesis, reduced osteoclastogenesis, and regulated the polarization of M1/M2 macrophages in steroid-induced ONFH. Taken together, our data suggest that M2-Exos are effective at preventing steroid-induced ONFH. These findings may be helpful for providing a potential strategy to prevent the development of steroid-induced ONFH.

Spray-dried pH-sensitive chitosan microparticles loaded with Mycobacterium bovis BCG intended for supporting treatment of Helicobacter pylori infection

Gram-negative spiral-shaped Helicobacter pylori (Hp) bacteria induce the development of different gastric disorders. The growing resistance of Hp to antibiotics prompts to search for new therapeutic formulations. A promising candidate is Mycobacterium bovis BCG (BCG) with immunomodulatory properties. Biodegradable mucoadhesive chitosan is a good carrier for delivering BCG mycobacteria to the gastric mucosal environment. This study aimed to show whether BCG bacilli are able to increase the phagocytic activity of Cavia porcellus-guinea pig macrophages derived from the bone marrow towards fluorescently labeled Escherichia coli. Furthermore, to encapsulate live BCG bacilli, in spray-dried chitosan microparticles (CHI-MPs), and assess the pH-dependent release of mycobacteria in pH conditions mimicking gastric (acidic) or gut (alkaline) milieu. Microparticles (MPs) were made of chitosan and coated with Pluronic F-127-(Plur) or N-Acetyl-D-Glucosamine-(GlcNAc) to increase the MPs resistance to low pH or to increase anti-Hp effect, respectively. Spray-drying method was used for microencapsulation of live BCG. The biosafety of tested CHI-MPs has been confirmed using cell models in vitro and the model of guinea pig in vivo. The CHI-MPs loaded with BCG released live mycobacteria at pH 3.0 (CHI-GlcNAc-MPs) or pH 8.0. (CHI-Plur-MPs). The CHI-MPs loaded with live BCG can be used for per os inoculation of Cavia porcellus to check the effectiveness of delivered mycobacteria in increasing anti-H. pylori host response.

Biomimetic Therapeutics for Bone Regeneration: A Perspective on Antiaging Strategies

Advances in modern medicine and the significant reduction in infant mortality have steadily increased the population's lifespan. As more and more people in the world grow older, incidence of chronic, noncommunicable disease is anticipated to drastically increase. Recent studies have shown that improving the health of the aging population is anticipated to provide the most cost-effective and impactful improvement in quality of life during aging-driven disease. In bone, aging is tightly linked to increased risk of fracture, and markedly decreased regenerative potential, deeming it critical to develop therapeutics to improve aging-driven bone regeneration. Biomimetics offer a cost-effective method in regenerative therapeutics for bone, where there are numerous innovations improving outcomes in young models, but adapting biomimetics to aged models is still a challenge. Chronic inflammation, accumulation of reactive oxygen species, and cellular senescence are among three of the more unique challenges facing aging-induced defect repair. This review dissects many of the innovative biomimetic approaches research groups have taken to tackle these challenges, and discusses the further uncertainties that need to be addressed to push the field further. Through these research innovations, it can be noted that biomimetic therapeutics hold great potential for the future of aging-complicated defect repair.

Lenvatinib Mitigates Transarterial Embolization-Induced Polarization of Tumor-Associated Macrophages in a Rat Hepatocellular Carcinoma Model

PURPOSE

To investigate the effect of transarterial embolization (TAE) on macrophage polarization and the modulatory effect of lenvatinib when used in combination with TAE in a rat hepatocellular carcinoma model.

MATERIALS AND METHODS

A N1S1-bearing orthotopic rat model was subjected to TAE and administered 5 mg/kg of lenvatinib. CD8+, CD68+, and CD206+ cells were examined in 4 groups: sham (n = 5), lenvatinib (n = 5), TAE (n = 5), and combination of TAE and lenvatinib (n = 5). Transcriptome analysis was performed to assess gene expression related to macrophage polarization in the sham, TAE, and combination groups. An in vitro coculture experiment with bone marrow-derived macrophages was performed to identify lenvatinib target in macrophage polarization.

RESULTS

There were no significant differences in the number of CD8+ and CD68+ cells among the 4 groups. Tumor-associated macrophage positivity for CD206 was significantly higher in the TAE group (58.1 ± 20.9) than in the sham (11.2 ± 14.3; P < .001) and combination (27.1 ± 19.7; P = .003) groups. In the transcriptome analysis, compared with the genes in the sham group, 5 macrophage polarization-related genes, including St6gal1, were upregulated by more than 1.5 fold in the TAE group and downregulated by more than 1.5 fold in the combination group. The coculture experiment showed that lenvatinib did not affect macrophages but affected N1S1 cells, leading to macrophage polarization.

CONCLUSIONS

TAE-induced M2 macrophage polarization. Lenvatinib administration with TAE could reprogram macrophage polarization, improving tumor immune microenvironment.

A TLR4 Agonist Induces Osteosarcoma Regression by Inducing an Antitumor Immune Response and Reprogramming M2 Macrophages to M1 Macrophages

Osteosarcoma (OsA) has limited treatment options and stagnant 5-year survival rates. Its immune microenvironment is characterized by a predominance of tumor-associated macrophages (TAMs), whose role in OsA progression remain unclear. Nevertheless, immunotherapies aiming to modulate macrophages activation and polarization could be of interest for OsA treatment. In this study, the antitumor effect of a liposome-encapsulated chemically detoxified lipopolysaccharide (Lipo-MP-LPS) was evaluated as a therapeutic approach for OsA. Lipo-MP-LPS is a toll-like receptor 4 (TLR4) agonist sufficiently safe and soluble to be IV administered at effective doses. Lipo-MP-LPS exhibited a significant antitumor response, with tumor regression in 50% of treated animals and delayed tumor progression in the remaining 50%. The agent inhibited tumor growth by 75%, surpassing the efficacy of other immunotherapies tested in OsA. Lipo-MP-LPS modulated OsA's immune microenvironment by favoring the transition of M2 macrophages to M1 phenotype, creating a proinflammatory milieu and facilitating T-cell recruitment and antitumor immune response. Overall, the study demonstrates the potent antitumor effect of Lipo-MP-LPS as monotherapy in an OsA immunocompetent model. Reprogramming macrophages and altering the immune microenvironment likely contribute to the observed tumor control. These findings support the concept of immunomodulatory approaches for the treatment of highly resistant tumors like OsA.

Bone regeneration in inflammation with aging and cell-based immunomodulatory therapy

Aging of the global population increases the incidence of osteoporosis and associated fragility fractures, significantly impacting patient quality of life and healthcare costs. The acute inflammatory reaction is essential to initiate healing after injury. However, aging is associated with "inflammaging", referring to the presence of systemic low-level chronic inflammation. Chronic inflammation impairs the initiation of bone regeneration in elderly patients. This review examines current knowledge of the bone regeneration process and potential immunomodulatory therapies to facilitate bone healing in inflammaging.Aged macrophages show increased sensitivity and responsiveness to inflammatory signals. While M1 macrophages are activated during the acute inflammatory response, proper resolution of the inflammatory phase involves repolarizing pro-inflammatory M1 macrophages to an anti-inflammatory M2 phenotype associated with tissue regeneration. In aging, persistent chronic inflammation resulting from the failure of M1 to M2 repolarization leads to increased osteoclast activation and decreased osteoblast formation, thus increasing bone resorption and decreasing bone formation during healing.Inflammaging can impair the ability of stem cells to support bone regeneration and contributes to the decline in bone mass and strength that occurs with aging. Therefore, modulating inflammaging is a promising approach for improving bone health in the aging population. Mesenchymal stem cells (MSCs) possess immunomodulatory properties that may benefit bone regeneration in inflammation. Preconditioning MSCs with pro-inflammatory cytokines affects MSCs' secretory profile and osteogenic ability. MSCs cultured under hypoxic conditions show increased proliferation rates and secretion of growth factors. Resolution of inflammation via local delivery of anti-inflammatory cytokines is also a potential therapy for bone regeneration in inflammaging. Scaffolds containing anti-inflammatory cytokines, unaltered MSCs, and genetically modified MSCs can also have therapeutic potential. MSC exosomes can increase the migration of MSCs to the fracture site and enhance osteogenic differentiation and angiogenesis.In conclusion, inflammaging can impair the proper initiation of bone regeneration in the elderly. Modulating inflammaging is a promising approach for improving compromised bone healing in the aging population.

Stereocomplexed microparticles loaded with Salvia cadmica Boiss. extracts for enhancement of immune response towards Helicobacter pylori

Controlled delivery of therapeutic substance gives numerous advantages (prevents degradation, improves uptake, sustains concentration, lowers side effects). To encapsulate Salvia cadmica extracts (root or aerial part), enriched with polyphenols with immunomodulatory activity, in stereocomplexed microparticles (sc-PLA), for using them to enhance the immune response towards gastric pathogen Helicobacter pylori. Microparticles were made of biodegradable poly(lactic acid) (PLA) and poly(D-lactic acid) (PDLA). Their stereocomplexation was used to form microspheres and enhance the stability of the obtained particles in acidic/basic pH. The release of Salvia cadmica extracts was done in different pH (5.5, 7.4 and 8.0). The obtained polymers are safe in vitro and in vivo (guinea pig model). The sc-PLA microparticles release of S. cadmica extracts in pH 5.5, 7.4, and 8.0. S. cadmica extracts enhanced the phagocytic activity of guinea pig bone marrow-derived macrophages, which was diminished by H. pylori, and neutralized H. pylori driven enhanced production of tumor necrosis factor (TNF)-α and interleukin (IL)-10. The sc-PLA encapsulated S. cadmica extracts can be recommended for further in vivo study in guinea pigs infected with H. pylori to confirm their ability to improve an immune response towards this pathogen.

S1P lyase inhibition prevents lung injury following high pressure-controlled mechanical ventilation in aging mice

Ventilator-induced Lung Injury (VILI) is characterized by hypoxia, inflammatory cytokine influx, loss of alveolar barrier integrity, and decreased lung compliance. Aging influences lung structure and function and is a predictive factor in the severity of VILI; however, the mechanisms of aging that influence the progression or increased susceptibility remain unknown. Aging impacts immune system function and may increase inflammation in healthy individuals. Recent studies suggest that the bioactive sphingolipid mediator sphingosine-1-phosphate (S1P) and the enzyme that degrades it S1P lyase (SPL) may be involved in lung pathologies including acute lung injury. It is unknown whether aging influences S1P and SPL expression that have been implicated in lung inflammation, injury, and cell apoptosis. We hypothesized that aging and injurious mechanical ventilation synergistically impair S1P levels and enhance S1P lyase (SPL) expression that amplifies alveolar barrier damage and diminishes pulmonary function. Young (2-3 mo) and old (20-25 mo) C57BL/6 mice were mechanically ventilated for 2 h using pressure-controlled mechanical ventilation (PCMV) at 45 cmH2O and 35 cmH2O, respectively. We assessed the impact of aging and PCMV on several indications of acute lung injury, immune cell recruitment, S1P levels and SPL activity. Furthermore, we evaluated the protective effects of inhibiting SPL by tetrahydroxybutylimidazol (THI) administration on the negative outcomes associated with aging and mechanical injury. PCMV exacerbated lung injury in old mice and increased neutrophil influx that was further exacerbated due to aging. SPL expression increased in the young and old ventilated mice and the old nonventilated group. THI treatment reduced several of the indicators of lung injury and resulted in elevated S1P levels in lung tissue and plasma from mice that were injured from mechanical ventilation. CD80 and CD206 activation markers of alveolar and interstitial macrophages were also influenced by THI. SPL inhibition may be a viable therapeutic approach for patients requiring mechanical ventilation by preventing or regulating the exaggerated inflammatory response and reducing lung injury.

Interleukin-17 Promotes the Infiltration of CD8+ T Cells into the Brain in a Mouse Model for Alzheimer's Disease

BACKGROUND

Interleukin-17 (IL-17) family cytokines play critical roles in inflammation and pathogen resistance. Inflammation in the central nervous system, denoted as neuroinflammation, promotes the onset and progression of Alzheimer's disease (AD). Previous studies showed that IL-17A neutralizing antibody treatment alleviated Amyloid β (Aβ) burden in rodent models of AD, while overexpression of IL-17A in mouse lateral ventricles rescued part of the AD pathology. However, the involvement of IL-17 in AD and its mechanism of action remain largely unknown.

METHODS

To investigate the role of IL-17 in AD, we crossed mice lacking the common receptor of IL-17 signaling (IL-17RA knockout mice) to the APP/PS1 mouse model of AD. We then analyzed the composition of immune cells and cytokines/chemokines during different phases of AD pathology, and interrogated the underlying mechanism by which IL-17 may regulate immune cell infiltration into AD brains.

RESULTS

Ablation of IL-17RA in APP/PS1 mice decreased infiltration of CD8+ T cells and myeloid cells to mouse brain. IL-17 was able to promote the production of myeloid- and T cell-attracting chemokines CXCL1 and CXCL9/10 in primary glial cells. We also observed that IL-17 is upregulated in the late stage of AD development, and ectopic expression of IL-17 via adenoviral infection to the cortex trended towards worsened cognition in APP/PS1 mice, suggesting a pathogenic role of excessive IL-17 in AD.

CONCLUSION

Our data show that IL-17 signaling promotes neuroinflammation in AD by accelerating the infiltration of CD8+ T lymphocytes and Gr1+ CD11b+ myeloid cells.

Inhibition of autophagy in microglia and macrophages exacerbates innate immune responses and worsens brain injury outcomes

Excessive and prolonged neuroinflammation following traumatic brain injury (TBI) contributes to long-term tissue damage and poor functional outcomes. However, the mechanisms contributing to exacerbated inflammatory responses after brain injury remain poorly understood. Our previous work showed that macroautophagy/autophagy flux is inhibited in neurons following TBI in mice and contributes to neuronal cell death. In the present study, we demonstrate that autophagy is also inhibited in activated microglia and infiltrating macrophages, and that this potentiates injury-induced neuroinflammatory responses. Macrophage/microglia-specific knockout of the essential autophagy gene Becn1 led to overall increase in neuroinflammation after TBI. In particular, we observed excessive activation of the innate immune responses, including both the type-I interferon and inflammasome pathways. Defects in microglial and macrophage autophagy following injury were associated with decreased phagocytic clearance of danger/damage-associated molecular patterns (DAMP) responsible for activation of the cellular innate immune responses. Our data also demonstrated a role for precision autophagy in targeting and degradation of innate immune pathways components, such as the NLRP3 inflammasome. Finally, inhibition of microglial/macrophage autophagy led to increased neurodegeneration and worse long-term cognitive outcomes after TBI. Conversely, increasing autophagy by treatment with rapamycin decreased inflammation and improved outcomes in wild-type mice after TBI. Overall, our work demonstrates that inhibition of autophagy in microglia and infiltrating macrophages contributes to excessive neuroinflammation following brain injury and in the long term may prevent resolution of inflammation and tissue regeneration.Abbreviations: Becn1/BECN1, beclin 1, autophagy related; CCI, controlled cortical impact; Cybb/CYBB/NOX2: cytochrome b-245, beta polypeptide; DAMP, danger/damage-associated molecular patterns; Il1b/IL1B/Il-1β, interleukin 1 beta; LAP, LC3-associated phagocytosis; Map1lc3b/MAP1LC3/LC3, microtubule-associated protein 1 light chain 3 beta; Mefv/MEFV/TRIM20: Mediterranean fever; Nos2/NOS2/iNOS: nitric oxide synthase 2, inducible; Nlrp3/NLRP3, NLR family, pyrin domain containing 3; Sqstm1/SQSTM1/p62, sequestosome 1; TBI, traumatic brain injury; Tnf/TNF/TNF-α, tumor necrosis factor; Ulk1/ULK1, unc-51 like kinase 1.

The crosstalk between macrophages and bone marrow mesenchymal stem cells in bone healing

Bone injury plagues millions of patients worldwide every year, and it demands a heavy portion of expense from the public medical insurance system. At present, orthopedists think that autologous bone transplantation is the gold standard for treating large-scale bone defects. However, this method has significant limitations, which means that parts of patients cannot obtain a satisfactory prognosis. Therefore, a basic study on new therapeutic methods is urgently needed. The in-depth research on crosstalk between macrophages (Mϕs) and bone marrow mesenchymal stem cells (BMSCs) suggests that there is a close relationship between inflammation and regeneration. The in-depth understanding of the crosstalk between Mϕs and BMSCs is helpful to amplify the efficacy of stem cell-based treatment for bone injury. Only in the suitable inflammatory microenvironment can the damaged tissues containing stem cells obtain satisfactory healing outcomes. The excessive tissue inflammation and lack of stem cells make the transplantation of biomaterials necessary. We can expect that the crosstalk between Mϕs and BMSCs and biomaterials will become the mainstream to explore new methods for bone injury in the future. This review mainly summarizes the research on the crosstalk between Mϕs and BMSCs and also briefly describes the effects of biomaterials and aging on cell transplantation therapy.

Microbiota-microglia connections in age-related cognition decline

Aging is an inevitable process that all individuals experience, of which the extent differs among individuals. It has been recognized as the risk factor of neurodegenerative diseases by affecting gut microbiota compositions, microglia, and cognition abilities. Aging‐induced changes in gut microbiota compositions have a critical role in orchestrating the morphology and functions of microglia through the gut‐brain axis. Gut microbiota communicates with microglia by its secreted metabolites and neurotransmitters. This is highly associated with age‐related cognitive declines. Here, we review the main composition of microbiota in the aged individuals, outline the changes of the brain in age‐related cognitive decline from a neuroinflammation perspective, especially the changes of morphology and functions of microglia, discuss the crosstalk between microbiota and microglia in the aged brain and further highlight the role of microbiota‐microglia connections in neurodegenerative diseases (Alzheimer's disease and Parkinson's disease).

Role of collagen regulators in cancer treatment: A comprehensive review

Abstract:

Collagen is the most important structural protein and also a main component of extra-cellular matrix (ECM). It plays a role in tumor progression. Collagen can be regulated by altering it’s biosynthesis pathway through various signaling pathways, receptors and genes. Activity of cancer cells can also be regulated by other ECM components like metalloproteinases, hyaluronic acid, fibronectin and so on. Hypoxia is also one of the condition which leads to cancer progression by stimulating the expression of procollagen lysine as a collagen crosslinker, which increases the size of collagen fibres promoting cancer spread. The collagen content in cancerous cells leads to resistance in chemotherapy. So, to reduce this resistance, some of the collagen regulating therapies are introduced, which include inhibiting its biosynthesis, disturbing cancer cell signaling pathway, mediating ECM components and directly utilizing collagenase. This study is an effort to compile the strategies reported to control the collagen level and different collagen inhibitors reported so far. More research is needed in this area, growing understandings of collagen’s structural features and its role in cancer progression will aid in the advancement of newer chemotherapies.

Aging Leads to Increased Monocytes and Macrophages With Altered CSF-1 Receptor Expression and Earlier Tumor-Associated Macrophage Expansion in Murine Mesothelioma

Increased cancer incidence occurs with the emergence of immunosenescence, highlighting the indispensability of the immune system in preventing cancer and its dysregulation with aging. Tumor-associated macrophages (TAMs) are often present in high numbers and are associated with poor clinical outcomes in solid cancers, including mesothelioma. Monocytes and macrophages from the bone marrow and spleen can respond to tumor-derived factors, such as CSF-1, and initiation of the CSF-1R signaling cascade results in their proliferation, differentiation, and migration to the tumor. Age-related changes occur in monocytes and macrophages in terms of numbers and function, which in turn can impact tumor initiation and progression. Whether this is due to changes in CSF-1R expression with aging is currently unknown and was investigated in this study. We examined monocytes and macrophages in the bone marrow and spleen during healthy aging in young (3–4 months) and elderly (20–24 months) female C57BL/6J mice. Additionally, changes to these tissues and in TAMs were examined during AE17 mesothelioma tumor growth. Healthy aging resulted in an expansion of Ly6C^high monocytes and macrophages in the bone marrow and spleen. CSF-1R expression levels were reduced in elderly splenic macrophages only, suggesting differences in CSF-1R signaling between both cell type and tissue site. In tumor-bearing mice, Ly6C^high monocytes increased with tumor growth in the spleen in the elderly and increased intracellular CSF-1R expression occurred in bone marrow Ly6C^high monocytes in elderly mice bearing large tumors. Age-related changes to bone marrow and splenic Ly6C^high monocytes were reflected in the tumor, where we observed increased Ly6C^high TAMs earlier and expansion of Ly6C^low TAMs later during AE17 tumor growth in the elderly compared to young mice. F4/80^high TAMs increased with tumor growth in both young and elderly mice and were the largest subset of TAMs in the tumor. Together, this suggests there may be a faster transition of Ly6C^high towards F4/80^high TAMs with aging. Amongst TAM subsets, expression of CSF-1R was lowest in F4/80^high TAMs, however Ly6C^low TAMs had higher intracellular CSF-1R expression. This suggests downstream CSF-1R signaling may vary between macrophage subsets, which can have implications towards CSF-1R blockade therapies targeting macrophages in cancer.

Exploring Sex-Related Differences in Microglia May Be a Game-Changer in Precision Medicine

One area of microglial biology that has been relatively neglected until recently is sex differences and this is in spite of the fact that sex is a risk factor in several diseases that are characterized by neuroinflammation and, by extension, microglial activation. Why these sex differences exist is not known but the panoply of differences extend to microglial number, genotype and phenotype. Significantly, several of these sex-related differences are also evident in health and change during life emphasizing the dynamic and plastic nature of microglia. This review will consider how age impacts on sex-related differences in microglia and ask whether the advancement of personalized medicine demands that a greater focus is placed on studying sex-related differences in microglia in Alzheimer's disease, Parkinson's disease and models of inflammatory stress and trauma in order to make true progress in dealing with these conditions.

Palmitic Acid and Oleic Acid Differently Modulate TLR2-Mediated Inflammatory Responses in Microglia and Macrophages

The relationship between systemic immunity and neuroinflammation is widely recognised. Infiltration of peripheral immune cells to the CNS during certain chronic inflammatory states contributes significantly to neuropathology. Obesity and its co-morbidities are primary risk factors for neuroinflammatory and neurodegenerative conditions, including Alzheimer’s disease (AD). Dietary fats are among the most proinflammatory components of the obesogenic diet and play a prominent role in the low-grade systemic inflammation associated with the obese state. Saturated fatty acid (SFA) is largely implicated in the negative consequences of obesity, while the health benefits of monounsaturated fatty acid (MUFA) are widely acknowledged. The current study sought to explore whether SFA and MUFA differently modulate inflammatory responses in the brain, compared with peripheral immune cells. Moreover, we assessed the neuroinflammatory impact of high-fat-induced obesity and hypothesised that a MUFA-rich diet might mitigate inflammation despite obesogenic conditions. Toll-like receptor (TLR)2 mediates the inflammation associated with both obesity and AD. Using the TLR2 agonist lipoteichoic acid (LTA), we report that pre-exposure to either palmitic acid (PA) or oleic acid (OA) attenuated cytokine secretion from microglia, but heightened sensitivity to nitric oxide (NO) production. The reduction in cytokine secretion was mirrored in LTA-stimulated macrophages following exposure to PA only, while effects on NO were restricted to OA, highlighting important cell-specific differences. An obesogenic diet over 12 weeks did not induce prominent inflammatory changes in either cortex or hippocampus, irrespective of fat composition. However, we reveal a clear disparity in the effects of MUFA under obesogenic and non-obesogenic conditions.

Inspiration for the prevention and treatment of neuropsychiatric disorders: New insight from the bone-brain-axis

Bone is the main supporting structure of the body and the main organ involved in body movement and calcium and phosphorus metabolism. Recent studies have shown that bone is also a potential new endocrine organ that participates in the physiological and pathophysiological processes of the cardiovascular, digestive, and endocrine systems through various bioactive cytokines secreted by bone cells and bone marrow. Bone-derived active cytokines can also directly act on the central nervous system and regulate brain function and individual behavior. The bidirectional regulation of the bone-brain axis has gradually attracted attention in the field of neuroscience. This paper reviews the regulatory effects of bone-derived active cytokines and bone-derived cells on individual brain function and brain diseases, as well as the occurrence and development of related neuropsychiatric diseases. The central regulatory mechanism function is briefly introduced, which will broaden the scope for mechanistic research and help establish prevention and treatment strategies for neuropsychiatric diseases based on the bone-brain axis.

Immunoporosis: Role of Innate Immune Cells in Osteoporosis

Osteoporosis or porous bone disorder is the result of an imbalance in an otherwise highly balanced physiological process known as 'bone remodeling'. The immune system is intricately involved in bone physiology as well as pathologies. Inflammatory diseases are often correlated with osteoporosis. Inflammatory mediators such as reactive oxygen species (ROS), and pro-inflammatory cytokines and chemokines directly or indirectly act on the bone cells and play a role in the pathogenesis of osteoporosis. Recently, Srivastava et al. (Srivastava RK, Dar HY, Mishra PK. Immunoporosis: Immunology of Osteoporosis-Role of T Cells. Frontiers in immunology. 2018;9:657) have coined the term "immunoporosis" to emphasize the role of immune cells in the pathology of osteoporosis. Accumulated pieces of evidence suggest both innate and adaptive immune cells contribute to osteoporosis. However, innate cells are the major effectors of inflammation. They sense various triggers to inflammation such as pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), cellular stress, etc., thus producing pro-inflammatory mediators that play a critical role in the pathogenesis of osteoporosis. In this review, we have discussed the role of the innate immune cells in great detail and divided these cells into different sections in a systemic manner. In the beginning, we talked about cells of the myeloid lineage, including macrophages, monocytes, and dendritic cells. This group of cells explicitly influences the skeletal system by the action of production of pro-inflammatory cytokines and can transdifferentiate into osteoclast. Other cells of the myeloid lineage, such as neutrophils, eosinophils, and mast cells, largely impact osteoporosis via the production of pro-inflammatory cytokines. Further, we talked about the cells of the lymphoid lineage, including natural killer cells and innate lymphoid cells, which share innate-like properties and play a role in osteoporosis. In addition to various innate immune cells, we also discussed the impact of classical pro-inflammatory cytokines on osteoporosis. We also highlighted the studies regarding the impact of physiological and metabolic changes in the body, which results in chronic inflammatory conditions such as ageing, ultimately triggering osteoporosis.

Aging and the immune response in diabetic peripheral neuropathy

A large proportion of older individuals with diabetes go on to develop diabetic peripheral neuropathy (DPN). DPN is associated with an increase in inflammatory cells within the peripheral nerve, activation of nuclear factor kappa-light-chain-enhancer of activated B cells and receptors for advanced glycation end products/advanced glycation end products pathways, aberrant cytokine expression, oxidative stress, ischemia, as well as pro-inflammatory changes in the bone marrow; all processes that may be exacerbated with age. We review the immunological features of DPN and discuss whether age-related changes in relevant immunological areas may contribute to age being a risk factor for DPN.

Donepezil Ameliorates Pulmonary Arterial Hypertension by Inhibiting M2-Macrophage Activation

Background: The beneficial effects of parasympathetic stimulation in pulmonary arterial hypertension (PAH) have been reported. However, the specific mechanism has not been completely clarified. Donepezil, an oral cholinesterase inhibitor, enhances parasympathetic activity by inhibiting acetylcholinesterase, whose therapeutic effects in PAH and its mechanism deserve to be investigated. Methods: The PAH model was established by a single intraperitoneal injection of monocrotaline (MCT, 50 mg/kg) in adult male Sprague-Dawley rats. Donepezil was administered via intraperitoneal injection daily after 1 week of MCT administration. At the end of the study, PAH status was confirmed by echocardiography and hemodynamic measurement. Testing for acetylcholinesterase activity and cholinergic receptor expression was used to evaluate parasympathetic activity. Indicators of pulmonary arterial remodeling and right ventricular (RV) dysfunction were assayed. The proliferative and apoptotic ability of pulmonary arterial smooth muscle cells (PASMCs), inflammatory reaction, macrophage infiltration in the lung, and activation of bone marrow-derived macrophages (BMDMs) were also tested. PASMCs from the MCT-treated rats were co-cultured with the supernatant of BMDMs treated with donepezil, and then, the proliferation and apoptosis of PASMCs were evaluated. Results: Donepezil treatment effectively enhanced parasympathetic activity. Furthermore, it markedly reduced mean pulmonary arterial pressure and RV systolic pressure in the MCT-treated rats, as well as reversed pulmonary arterial remodeling and RV dysfunction. Donepezil also reduced the proliferation and promoted the apoptosis of PASMCs in the MCT-treated rats. In addition, it suppressed the inflammatory response and macrophage activation in both lung tissue and BMDMs in the model rats. More importantly, donepezil reduced the proliferation and promoted the apoptosis of PASMCs by suppressing M2-macrophage activation. Conclusion: Donepezil could prevent pulmonary vascular and RV remodeling, thereby reversing PAH progression. Moreover, enhancement of the parasympathetic activity could reduce the proliferation and promote the apoptosis of PASMCs in PAH by suppressing M2-macrophage activation.

Macrophage Immunometabolism and Inflammaging: Roles of Mitochondrial Dysfunction, Cellular Senescence, CD38, and NAD

Aging is a complex process that involves dysfunction on multiple levels, all of which seem to converge on inflammation. Macrophages are intimately involved in initiating and resolving inflammation, and their dysregulation with age is a primary contributor to inflammaging—a state of chronic, low-grade inflammation that develops during aging. Among the age-related changes that occur to macrophages are a heightened state of basal inflammation and diminished or hyperactive inflammatory responses, which seem to be driven by metabolic-dependent epigenetic changes. In this review article we provide a brief overview of mitochondrial functions and age-related changes that occur to macrophages, with an emphasis on how the inflammaging environment, senescence, and NAD decline can affect their metabolism, promote dysregulation, and contribute to inflammaging and age-related pathologies.

Exercise-induced re-programming of age-related metabolic changes in microglia is accompanied by a reduction in senescent cells

Microglial activation and neuroinflammatory changes are characteristic of the aged brain and contribute to age-related cognitive impairment. Exercise improves cognitive function in aged animals, perhaps because of a modulatory effect on microglial activation. Recent evidence indicates that inflammatory microglia are glycolytic, driven by an increase in 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), an enzyme that is described as the master regulator of glycolysis. Here we investigated whether microglia from aged animals exhibited a glycolytic signature and whether exercise exerted a modulatory effect on this metabolic profile. Young (4 month-old) and aged (18 month-old) mice were trained for 10 days on a treadmill. One day before sacrifice, animals were assessed in the novel object recognition and the object displacement tests. Animals were sacrificed after the last bout of exercise, microglial cells were isolated, cultured for 5 days and assessed for metabolic profile. Performance in both behavioural tests was impaired in sedentary aged animals and exercise attenuated this age-related effect. A significant increase in glycolysis, glycolytic capacity and PFKFB3 was observed in microglia from aged animals and exercise ameliorated these effects, while it also increased the phagocytic capacity of cells. The senescent markers, β-galactosidase and p16^INK4A, were increased in microglia from sedentary aged mice, and expression of these markers was significantly decreased by exercise. The data demonstrate that the exercise-related improved cognition is orchestrated by a normalization of the metabolic profile and functionality of microglia.

Preadipocyte secretory factors differentially modulate murine macrophage functions during aging which are reversed by the application of phytochemical EGCG

The present study aimed at evaluating the role of senescent cell microenvironment as an extrinsic causal factor for altered age-associated macrophage functions, and that whether such changes could be ameliorated by the application of tea catechin epigallocatechin gallate (EGCG). To ascertain this, we analyzed the impact of secretory metabolites of proliferating (P) and senescent (S) preadipocyte cells on the induction of phenotypic and functional characteristics associated with aging in macrophages isolated from young (YM) and old (OM) C57BL/6J mice. The role of EGCG as alleviator of preadipocyte media-induced senescence and inflamm-aging was evaluated in OM. Results revealed strong age-related dysregulation in macrophage functions as evident by decreased CD11b expression, enhanced expression of cytokines (IL-6/TNF-α/IL-1β/IL-10) and cell cycle inhibitors p53/p21^WAF1/p16^Ink4a, as well as augmentation of M2 phenotype (Arg1/Msr1/Mrc1) and SA-β-gal activity. Ex vivo exposure of macrophages (YM and OM) to secretory factors of preadipocytes induced differential effects, and treatment with S culture media largely showed an augmentation of senescent phenotype, particularly in the YM. Pretreatment with EGCG (10 µM) to OM caused a dramatic reversal of both age-associated and preadipocyte media-induced changes as evident from upregulation of CD11b and ROS levels, inhibition of inflammatory makers, attenuation of p53/p21^WAF1/p16^Ink4a expression and SA-β-gal activity. Our results indicate vital role of adipose tissue-mediated extrinsic factors in shaping macrophage phenotype and functions during aging. It is also apparent that EGCG is a promising candidate in developing preventive therapies aimed at alleviating macrophage inflamm-aging and senescence that may help curb incidences of inflammatory disorders in elderly.

Effect of Aging on the Macrophage Response to Titanium Particles

Macrophage-mediated inflammatory reaction to implant wear particles drives bone loss around total joint replacements (TJR). Although most TJR recipients are elderly, studies linking wear particle-activated macrophages and peri-implant osteolysis have not taken into account the multiple effects that aging has on the innate immune system and, in particular, on macrophages. To address this, we compared the wear particle responses of bone marrow macrophages obtained from young (2-month) and aged (18-month) mice. Macrophages were polarized to M0, M1, or M2 phenotypes in vitro, challenged with titanium particles, and their inflammatory response was characterized at multiple time points by quantitative reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, age-dependent changes in activation of transcription factor nuclear factor-κB were analyzed by a lentiviral vector-based luciferase reporter system. The particle stimulation experiment was further repeated using human primary macrophages isolated from blood donors of different ages. We found that the pro-inflammatory responses were generally higher in macrophages obtained from young mice, but differences between the age groups remained small and of uncertain biological significance. Noteworthily, M2 polarization effectively suppressed the particle-induced inflammation in both young and aged macrophages. These results suggest that aging of the innate immune system per se plays no significant role in the response of macrophages to titanium particles, whereas induction of M2 polarization appears a promising strategy to limit macrophage-mediated inflammation regardless of age. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:405-416, 2020.

The role of the immune system in driving neuroinflammation

Neuroinflammation is now recognised as an important contributory factor in the progression of Alzheimer’s disease and probably also in the early stages of the disease. It is likely that this derives largely from aberrant activation of microglia, the resident mononuclear phagocytes of the brain. These cells are responsible for physiological immune surveillance and clearance of pathogens in the central nervous system, but evidence indicates that in Alzheimer’s disease, microglial function is compromised, and this contributes to the pathology. It is unclear what factors cause the inappropriate activation of the microglia in Alzheimer’s disease, but one contributor may be infiltrating peripheral immune cells and these include macrophages and T cells. It has been suggested that both cell types modulate the phenotype of microglia, highlighting the importance of crosstalk between the innate and adaptive immune system in Alzheimer’s disease. This review outlines our current knowledge of how cells of the peripheral immune system, specifically macrophages and T cells, may modulate microglial phenotype in the context of Alzheimer’s disease and considers the impact on their function, especially phagocytic capacity.

Investigation of Antibacterial and Antiinflammatory Activities of Proanthocyanidins from Pelargonium sidoides DC Root Extract

The study explores antibacterial, antiinflammatory and cytoprotective capacity of Pelargonium sidoides DC root extract (PSRE) and proanthocyanidin fraction from PSRE (PACN) under conditions characteristic for periodontal disease. Following previous finding that PACN exerts stronger suppression of Porphyromonas gingivalis compared to the effect on commensal Streptococcus salivarius, the current work continues antibacterial investigation on Staphylococcus aureus, Staphylococcus epidermidis, Aggregatibacter actinomycetemcomitans and Escherichia coli. PSRE and PACN are also studied for their ability to prevent gingival fibroblast cell death in the presence of bacteria or bacterial lipopolysaccharide (LPS), to block LPS- or LPS + IFNγ-induced release of inflammatory mediators, gene expression and surface antigen presentation. Both PSRE and PACN were more efficient in suppressing Staphylococcus and Aggregatibacter compared to Escherichia, prevented A. actinomycetemcomitans- and LPS-induced death of fibroblasts, decreased LPS-induced release of interleukin-8 and prostaglandin E2 from fibroblasts and IL-6 from leukocytes, blocked expression of IL-1β, iNOS, and surface presentation of CD80 and CD86 in LPS + IFNγ-treated macrophages, and IL-1β and COX-2 expression in LPS-treated leukocytes. None of the investigated substances affected either the level of secretion or expression of TNFα. In conclusion, PSRE, and especially PACN, possess strong antibacterial, antiinflammatory and gingival tissue protecting properties under periodontitis-mimicking conditions and are suggestable candidates for treatment of the disease.

Effect of Systemic Inflammation on Rat Attentional Function and Neuroinflammation: Possible Protective Role for Food Restriction

Background: Aging is characterized by subtle cognitive decline, which correlates with increased peripheral inflammation. Acute activation of the peripheral immune system, via lipopolysaccharide (LPS) injection, elicits deficits in hippocampal-dependent spatial memory. Little is known concerning the effect of chronic inflammation on prefrontal cortex (PFC)-dependent vigilance. We examined the impact of repeated LPS injections in young and middle-age rats on the 5-choice serial reaction time task (5-CSRTT), expecting repeated LPS treatment to induce attentional deficits with greater disruption in middle-age. Methods: Male Fischer-344 rats, 4- and 12-months-old, were food restricted and trained on the 5-CSRTT. Once rats reached criterion, they were injected with LPS (1 mg/kg, i.p.) weekly for 4 weeks and testing started 48 h after each injection. To examine the possibility that mild food restriction inherent to the behavioral task influenced inflammation markers, a second group of food-restricted or ad-lib-fed rats was assessed for cytokine changes 48 h after one injection. Results: Performing LPS-treated rats exhibited a sickness response, manifesting as reduced initiated and completed trials during the first week but recovered by the second week of testing. After the first week, LPS-treated rats continued to exhibit longer response latencies, despite no change in food retrieval latency, suggestive of LPS-induced cognitive slowing. Similarly, LPS-induced impairment of attention was observed as increased omissions with heightened cognitive demand and increased age. Repeated LPS-treatment increased the level of PFC IL-1α, and PFC IL-6 was marginally higher in middle-age rats. No effect of age or treatment was observed for plasma cytokines in performing rats. Histological examination of microglia indicated increased colocalization of Iba1+ and CD68+ cells from middle-age relative to young rats. Examination of food restriction demonstrated an attenuation of age- and LPS-related increases in plasma cytokine levels. Conclusions: Systemic inflammation, induced through LPS treatment, impaired attentional function, which was independent of sickness and exacerbated by increased cognitive demand and increased age. Additional studies revealed that food restriction, associated with the task, attenuated markers of neuroinflammation and plasma cytokines. The results emphasize the need for improved methods for modeling low-level chronic systemic inflammation to effectively examine its impact on attention during aging.

Controlled M1-to-M2 transition of aged macrophages by calcium phosphate coatings

Older adults suffer from weakened and delayed bone healing due to age-related alterations in bone cells and in the immune system. Given the interaction between the immune system and skeletal cells, therapies that address deficiencies in both the skeletal and the immune system are required to effectively treat bone injuries of older patients. The sequence of macrophage activation observed in healthy tissue repair involves a transition from a pro-inflammatory state followed by a pro-reparative state. In older patients, inflammation is slower to resolve and impedes healing. The goal of this study was to design a novel drug delivery system for temporal guidance of the polarization of macrophages using bone grafting materials. A biomimetic calcium phosphate coating (bCaP) physically and temporally separated the pro-inflammatory stimulus interferon-gamma (IFNγ) from the pro-reparative stimulus simvastatin (SIMV). Effective doses were identified using a human monocyte line (THP-1) and testing culminated with bone marrow macrophages obtained from old mice. Sequential M1-to-M2 activation was achieved with both cell types. These results suggest that this novel immunomodulatory drug delivery system holds potential for controlling macrophage activation in bones of older patients.

Iron accumulation in microglia triggers a cascade of events that leads to altered metabolism and compromised function in APP/PS1 mice

Among the changes that typify Alzheimer's disease (AD) are neuroinflammation and microglial activation, amyloid deposition perhaps resulting from compromised microglial function and iron accumulation. Data from Genome Wide Association Studies (GWAS) identified a number of gene variants that endow a significant risk of developing AD and several of these encode proteins expressed in microglia and proteins that are implicated in the immune response. This suggests that neuroinflammation and the accompanying microglial activation are likely to contribute to the pathogenesis of the disease. The trigger(s) leading to these changes remain to be identified. In this study, we set out to examine the link between the inflammatory, metabolic and iron-retentive signature of microglia in vitro and in transgenic mice that overexpress the amyloid precursor protein (APP) and presenilin 1 (PS1; APP/PS1 mice), a commonly used animal model of AD. Stimulation of cultured microglia with interferon (IFN)γ and amyloid-β (Aβ) induced an inflammatory phenotype and switched the metabolic profile and iron handling of microglia so that the cells became glycolytic and iron retentive, and the phagocytic and chemotactic function of the cells was reduced. Analysis of APP/PS1 mice by magnetic resonance imaging (MRI) revealed genotype-related hypointense areas in the hippocampus consistent with iron deposition, and immunohistochemical analysis indicated that the iron accumulated in microglia, particularly in microglia that decorated Aβ deposits. Isolated microglia prepared from APP/PS1 mice were characterized by a switch to a glycolytic and iron-retentive phenotype and phagocytosis of Aβ was reduced in these cells. This evidence suggests that the switch to glycolysis in microglia may kick-start a cascade of events that ultimately leads to microglial dysfunction and Aβ accumulation.

Advanced glycation end products-related modulation of cathepsin L and NF-κB signalling effectors in retinal pigment epithelium lead to augmented response to TNFα

The retinal pigment epithelium (RPE) plays a central role in neuroretinal homoeostasis throughout life. Altered proteolysis and inflammatory processes involving RPE contribute to the pathophysiology of age‐related macular degeneration (AMD), but the link between these remains elusive. We report for the first time the effect of advanced glycation end products (AGE)—known to accumulate on the ageing RPE's underlying Bruch's membrane in situ—on both key lysosomal cathepsins and NF‐κB signalling in RPE. Cathepsin L activity and NF‐κB effector levels decreased significantly following 2‐week AGE exposure. Chemical cathepsin L inhibition also decreased total p65 protein levels, indicating that AGE‐related change of NF‐κB effectors in RPE cells may be modulated by cathepsin L. However, upon TNFα stimulation, AGE‐exposed cells had significantly higher ratio of phospho‐p65(Ser536)/total p65 compared to non‐AGEd controls, with an even higher fold increase than in the presence of cathepsin L inhibition alone. Increased proportion of active p65 indicates an AGE‐related activation of NF‐κB signalling in a higher proportion of cells and/or an enhanced response to TNFα. Thus, NF‐κB signalling modulation in the AGEd environment, partially regulated via cathepsin L, is employed by RPE cells as a protective (para‐inflammatory) mechanism but renders them more responsive to pro‐inflammatory stimuli.

Microglial immune response is impaired against the neurotropic fungus Lomentospora prolificans

Lomentospora (Scedosporium) prolificans is an opportunistic pathogen capable of causing invasive infections in immunocompromised patients. The fungus is able to disseminate via the bloodstream finally arriving at the central nervous system producing neurological symptoms and, in many cases, patient death. In this context, microglial cells, which are the resident immune cells in the central nervous system, may play an important role in these infections. However, this aspect of anti-L. prolificans immunity has been poorly researched to date. Thus, the interactions and activity of microglial cells against L. prolificans were analysed, and the results show that there was a remarkable impairment in their performance regarding phagocytosis, the development of oxidative burst, and in the production of pro-inflammatory cytokines, compared with macrophages. Interestingly, L. prolificans displays great growth also when challenged with immune cells, even when inside them. We also proved that microglial phagocytosis of the fungus is highly dependent on mannose receptor and especially on dectin-1. Taken together, these data provide evidence for an impaired microglial response against L. prolificans and contribute to understanding the pathobiology of its neurotropism.

Inflammatory microglia are glycolytic and iron retentive and typify the microglia in APP/PS1 mice

Microglia, like macrophages, can adopt inflammatory and anti-inflammatory phenotypes depending on the stimulus. In macrophages, the evidence indicates that these phenotypes have different metabolic profiles with lipopolysaccharide (LPS)- or interferon-γ (IFNγ)-stimulated inflammatory cells switching to glycolysis as their main source of ATP and interleukin-4 (IL-4)-stimulated cells utilizing oxidative phosphorylation. There is a paucity of information regarding the metabolic signatures of inflammatory and anti-inflammatory microglia. Here, we polarized primary microglia with IFNγ and show that the characteristic increases in tumor necrosis factor-α (TNFα) and nitric oxide synthase 2 (NOS2) were accompanied by increased glycolysis and an increase in the expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB)3, an enzyme that plays a significant role in driving glycolysis. These changes were associated with increased expression of ferritin and retention of iron in microglia. Significantly, retention of iron in microglia increased TNFα expression and also increased glycolysis suggesting that increased intracellular iron concentration may drive the metabolic and/or inflammatory changes. Analysis of microglia prepared from wildtype mice and from transgenic mice that overexpress amyloid precursor protein (APP) and presenilin 1 (PS1; APP/PS1) revealed genotype-related increases in glycolysis, accompanied by increased PFKFB3, and an increase in the expression of ferritin. The data indicate a distinct metabolic signature of inflammatory microglia from APP/PS1 mice that are also distinguishable by their iron handling profiles.

Differential Expression of Human Peripheral Mononuclear Cells Phenotype Markers in Type 2 Diabetic Patients and Type 2 Diabetic Patients on Metformin

Background: Although peripheral blood mononuclear cells (PBMC) have been demonstrated to be in a pro-inflammatory state in obesity and type 2 Diabetes Mellitus (T2DM), characterization of circulating PBMC phenotypes in the obese and T2DM and the effect of Metformin on these phenotypes in humans is still ill-defined and remains to be determined. Methods: Thirty normal healthy adult volunteers of normal weight, 30 obese subjects, 20 obese newly diagnosed diabetics and 30 obese diabetics on Metformin were recruited for the study. Fasting blood samples were collected and PBMC were isolated from whole blood. Polarization markers (CD86, IL-6, TNFα, iNOS, CD36, CD11c, CD169, CD206, CD163, CD68, CD11b, CD16, and CD14) were measured by RT-qPCR. Gene expression fold changes were calculated using the 2^-ΔΔCT method for RT-qPCR. Results: Obesity and T2DM are associated an increased CD68 marker in PBMC. mRNA expression of CD11b, CD11c, CD169, and CD163 were significantly reduced in PBMC from T2DM subjects whereas CD11c was significantly inhibited in PBMC from obese subjects. On the other hand, macrophage M1-like phenotype was observed in T2DM circulation as demonstrated by increased mRNA expression of CD16, IL-6, iNOS, TNFα, and CD36. There were no significant changes in CD14 and CD86 in the obese and T2DM when compared to the lean subjects. Metformin treatment in T2DM reverted CD11c, CD169, IL-6, iNOS, TNFα, and CD36 to levels comparable to lean subjects. CD206 mRNA expression was significantly upregulated in PBMC of T2DM while Metformin treatment inhibited CD206 expression levels. Conclusions: These data support the notion that PBMC in circulation in T2DM express different pattern of phenotypic markers than the patterns typically present in M1 and M2 like cells. These phenotypic markers could be representative of metabolically activated macrophages (MMe)-like cells. Metformin, on the other hand, reduces MMe-like cells in circulation.

Role of infiltrating monocytes/macrophages in acute and chronic neuroinflammation: Effects on cognition, learning and affective behaviour

Peripheral macrophages have limited capacity to gain access to the brain parenchyma under normal physiological conditions. However, accumulating evidence indicates that significant trafficking to the central nervous systems occurs in response to injury or infection and is also apparent under chronic neuroinflammatory conditions. The role of infiltrating macrophages in neuronal function is unclear and confounded by the similarity in morphology and phenotype adopted by both activated macrophages and microglia. Furthermore, the ability of macrophages/microglia to adopt both pro- and anti-inflammatory activation states, along with the fact that these cells display heterogenous expression of molecules associated with both states, has made it difficult to discover their impact upon neuronal injury and cognitive processes. The ability of macrophages to exert a neuroprotective role is influenced by the microenvironment they encounter upon tissue invasion. Upon encountering an inflammatory microenvironment, macrophage polarisation is driven towards a pro-inflammatory (M1) phenotype, a state associated with reduced capacity for restorative processes such as the removal of debris, and enhanced production of pro-inflammatory mediators such as TNFα, IL-1β and NADPH oxidase. Prolonged production of these inflammatory mediators has been shown to affect neuronal function and health. Thus, macrophage polarisation may be dictated by the inflammatory queues these cells are exposed to upon migration and their subsequent impact on neuronal function may be determined by their ability to resolve the underlying inflammation.

Human β-defensin 3 inhibits periodontitis development by suppressing inflammatory responses in macrophages

Human β-defensin 3 (hBD3) is a cationic peptide with immunomodulatory effects on both innate and acquired immune responses. Periodontitis, an inflammatory disease that extends deep into periodontal tissues, causes the loss of supporting structures around the tooth. The present study assessed the effects of hBD3 as a monotherapy for periodontitis in mice and explored its potential mechanism. In vivo, hBD3 inhibited the levels of tumour necrosis factor (TNF)-α, interleukin-6, and matrix metalloprotease-9 in periodontium exposed to Porphyromonas gingivalis (P.g) in a mouse periodontitis model; reduced osteoclast formation and lower alveolar bone loss were also observed. In addition, hBD3 was related to the expression of polarization signature molecules in circulating monocytes. In vitro, hBD3 notably suppressed the production of TNF-α and interleukin-6 in RAW 264.7 cells stimulated by the lipopolysaccharide of P.g. Moreover, hBD3 attenuated polarization of RAW 264.7 cells into the M1 phenotype, with reduced activation of nuclear factor-κB signal transduction. In conclusion, hBD3 exhibits potent anti-periodontitis properties both in vitro and in vivo, and this effect may be correlated to inhibition of the nuclear factor-κB pathway and macrophage polarization.

Alcohol, aging, and innate immunity

The global population is aging: in 2010, 8% of the population was older than 65 y, and that is expected to double to 16% by 2050. With advanced age comes a heightened prevalence of chronic diseases. Moreover, elderly humans fair worse after acute diseases, namely infection, leading to higher rates of infection-mediated mortality. Advanced age alters many aspects of both the innate and adaptive immune systems, leading to impaired responses to primary infection and poor development of immunologic memory. An often overlooked, yet increasingly common, behavior in older individuals is alcohol consumption. In fact, it has been estimated that >40% of older adults consume alcohol, and evidence reveals that >10% of this group is drinking more than the recommended limit by the National Institute on Alcohol Abuse and Alcoholism. Alcohol consumption, at any level, alters host immune responses, including changes in the number, phenotype, and function of innate and adaptive immune cells. Thus, understanding the effect of alcohol ingestion on the immune system of older individuals, who are already less capable of combating infection, merits further study. However, there is currently almost nothing known about how drinking alters innate immunity in older subjects, despite innate immune cells being critical for host defense, resolution of inflammation, and maintenance of immune homeostasis. Here, we review the effects of aging and alcohol consumption on innate immune cells independently and highlight the few studies that have examined the effects of alcohol ingestion in aged individuals.

Inflammation, ageing, and bone regeneration

Bone healing involves complex biological pathways and interactions among various cell types and microenvironments. Among them, the monocyte–macrophage–osteoclast lineage and the mesenchymal stem cell–osteoblast lineage are critical, in addition to an initial inflammatory microenvironment. These cellular interactions induce the necessary inflammatory milieu and provide the cells for bone regeneration and immune modulation. Increasing age is accompanied with a rise in the basal state of inflammation, potentially impairing osteogenesis.

The translational potential of this article: Translational research has shown multiple interactions between inflammation, ageing, and bone regeneration. This review presents recent, relevant considerations regarding the effects of inflammation and ageing on bone healing.

Programmed death (PD)-1 attenuates macrophage activation and brain inflammation via regulation of fibrinogen-like protein 2 (Fgl-2) after intracerebral hemorrhage in mice

Neuroinflammation plays an important role in the recovery of brain injury in ICH. Macrophage is the major executor in the neuroinflammation and initiates neurological defects. Programmed death 1 (PD-1) delivers inhibitory signals that regulate the balance between T cell activation, tolerance, and immunopathology. PD-1 expression by macrophages plays a pathologic role in the innate inflammatory response. However, the exact role of PD-1 on inflammatory responses following ICH has not been well identified. In this experiment, PD-1 KO (PD-1 -/-) ICH mice and Wild-type (WT) ICH mice were caused by intracranial injection of type IV collagenase. The level of macrophage activation, inflammatory cytokines and fibrinogen-like protein 2 (Fgl-2) were detected using immunofluorescence staining and ELISA assays. In addition, brain edema and neurological scores of ICH mice were also measured. Our data demonstrated that ICH promoted PD-1 expression of macrophage and enhanced inflammatory cytokines and Fgl-2 concentrations. PD-1 -/- mice exhibited significantly higher expression of the inflammatory cytokines which initiate Fgl-2, than did their wild-type (WT) littermates. As a result, macrophage activation, cerebral edema and neurological deficit scores of PD-1 -/- mice were higher. In conclusion, our data demonstrate that PD-1 plays a vital role in brain inflammation via regulation of Fgl-2 after ICH, and that manipulation of PD-1 might be a promising therapeutical target in ICH.

Targeting innate immunity for neurodegenerative disorders of the central nervous system

Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview of physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia and astrocyte cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article. Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer's disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview on physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article.

Aging Affects Bone Marrow Macrophage Polarization: Relevance to Bone Healing

Macrophages are an important component of the inflammatory cascade by initiating and modulating the processes leading to tissue regeneration and bone healing. Depending on the local environment, macrophages can be polarized into M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotypes. In order to assess the effects of aging on macrophage function, bone marrow macrophage polarization using primary bone marrow macrophages (BMMs) from young (8 weeks old) and aged (72 weeks old) wild-type male C57BL/6J mice was analyzed. Fluorescence-activated cell sorting (FACS) analysis (CD11b, iNOS, CD206), qRT-PCR (iNOS, TNF-α, CD206, Arginase 1), and ELISA (TNF-α, IL-1ra) were performed to compare the M1 and M2 phenotypic markers in young and aged mouse macrophages. Once M1 and M2 macrophage phenotypes were confirmed, the results showed that TNF-α mRNA was significantly upregulated in aged M1s after interferon gamma (INF-γ) exposure. Arginase 1 and CD206 mRNA expression were still upregulated with IL4 stimulation in aged macrophages, but to a lesser extend than those from younger animals. TNF-α secretion was also significantly increased in aged M1s compared to young M1s, following lipopolysaccharide (LPS) exposure. However, the IL-1ra secretion did not increase accordingly in aged mice. The results demonstrate that, compared to younger animals, aging of bone marrow derived macrophages increases the resting levels of oxidative stress, and the ratios of pro- to anti-inflammatory markers. These age-related changes in macrophage polarization may explain in part the attenuated response to adverse stimuli and delay in processes such as fracture healing seen in the elderly.

LAY SUMMARY

Bone healing is a complex process that involves both biological and mechanical factors. Macrophages are key cells that regulate the events involved in bone healing, especially the initial inflammatory phase. In this biological cascade of events, macrophages present as different functional phenotypes including uncommitted (M0), pro-inflammatory (M1), and anti-inflammatory (M2), a process called macrophage polarization. A clear understanding of the effects of aging on macrophage polarization is critical to modulating adverse events such as fractures, atraumatic bone loss, and tissue regeneration in an aging population.

Aging, inflammation, stem cells, and bone healing

Complex interactions among cells of the monocyte-macrophage-osteoclast lineage and the mesenchymal stem cell-osteoblast lineage play a major role in the pathophysiology of bone healing. Whereas the former lineage directs inflammatory events and bone resorption, the latter represents a source of cells for bone regeneration and immune modulation. Both of these lineages are affected by increasing age, which is associated with higher baseline levels of inflammatory mediators, and a significant reduction in osteogenic capabilities. Given the above, fracture healing, osteoporosis, and other related events in the elderly present numerous challenges, which potentially could be aided by new therapeutic approaches to modulate both inflammation and bone regeneration.

Macrophage depletion reduced brain injury following middle cerebral artery occlusion in mice

Background

Macrophages are involved in demyelination in many brain diseases. However, the role of macrophages in the recovery phase of the ischemic brain is unknown. The present study aims to explore the role of macrophages in the ischemic brain injury and tissue repair following a 90-min transient middle cerebral artery occlusion in mice.

Methods

Clodronate liposomes were injected into mice to deplete periphery macrophages. These mice subsequently underwent middle cerebral artery occlusion. F4/80⁺ and CD68⁺ cells were examined in the mouse spleen and brain to confirm macrophage depletion at 14 days after middle cerebral artery occlusion. Modified neurological severity scores were used to evaluate the behavioral function between 1 and 14 days after middle cerebral artery occlusion. MBP, Iba1, and CD31 immunostaining were performed to determine myelin lesion, microglia activation, and microvessel density.

Results

Clodronate liposomes depleted 80 % of the macrophages in the mouse spleen and reduced macrophage infiltration in the mouse brain. Macrophage depletion reduced the myelin damage in the ipsilateral striatum and microglia activation in both the ipsilateral cortex and striatum, enhanced the microvessel density in the peri-infarct region, attenuated brain atrophy, and promoted neurological recovery following middle cerebral artery occlusion.

Conclusions

Our results suggested that macrophage depletion is a potential intervention that can promote tissue repair and remodeling after brain ischemia, reduce demyelination and microglia activation, and enhance focal microvessel density.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0504-z) contains supplementary material, which is available to authorized users.