Complexity of danger: the diverse nature of damage-associated molecular patterns

Resolution of inflammation in oral diseases

The resolution of inflammation is an essential endogenous process that protects host tissues from an exaggerated chronic inflammatory response. Multiple interactions between host cells and resident oral microbiome regulate the protective functions that lead to inflammation in the oral cavity. Failure of appropriate regulation of inflammation can lead to chronic inflammatory diseases that result from an imbalance between pro-inflammatory and pro-resolution mediators. Thus, failure of the host to resolve inflammation can be considered an essential pathological mechanism for progression from the late stages of acute inflammation to a chronic inflammatory response. Specialized pro-resolving mediators (SPMs), which are essential polyunsaturated fatty acid (PUFA)-derived autacoid mediators, aid in regulating the endogenous inflammation resolving process by stimulating immune cell-mediated clearance of apoptotic polymorphonuclear neutrophils, cellular debris, and microbes, restricting further neutrophil tissue infiltration, and counter-regulating pro-inflammatory cytokine production. The SPM superfamily contains four specialized lipid mediator families: lipoxins, resolvins, protectins, and maresins that can activate resolution pathways. Understanding the crosstalk between resolution signals in the tissue response to injury has therapeutic application potential for preventing, maintaining, and regenerating chronically damaged tissues. Here, we discuss the fundamental concepts of resolution as an active biochemical process, novel concepts demonstrating the role of resolution mediators in tissue regeneration in periodontal and pulpal diseases, and future directions for therapeutic applications with particular emphasis on periodontal therapy.

Anti-nucleolin aptamer, iSN04, inhibits the inflammatory responses in C2C12 myoblasts by modulating the β-catenin/NF-κB signaling pathway

A myogenetic oligodeoxynucleotide, iSN04, is the 18-base single-stranded DNA that acts as an anti-nucleolin aptamer. iSN04 has been reported to restore myogenic differentiation by suppressing inflammatory responses in myoblasts isolated from patients with diabetes or healthy myoblasts exposed to cancer-releasing factors. Thus, iSN04 is expected to be a nucleic acid drug for the muscle wasting associated with chronic diseases. The present study investigated the anti-inflammatory mechanism of iSN04 in the murine myoblast cell line C2C12. Tumor necrosis factor-α (TNF-α) or Toll-like receptor (TLR) ligands (Pam₃CSK₄ and FSL-1) induced nuclear translocation and transcriptional activity of nuclear factor-κB (NF-κB), resulting in upregulated expression of TNF-α and interleukin-6. Pre-treatment with iSN04 significantly suppressed these inflammatory responses by inhibiting the nuclear accumulation of β-catenin induced by TNF-α or TLR ligands. These results demonstrate that antagonizing nucleolin with iSN04 downregulates the inflammatory effect mediated by the β-catenin/NF-κB signaling pathway in C2C12 cells. In addition, the anti-inflammatory effects of iSN04 were also observed in the rat smooth muscle cell line A10 and the murine adipocyte-like fibroblast cell line 3T3-L1, suggesting that iSN04 may be useful in preventing inflammation induced by metabolic disorders.

Narrative review of systemic inflammatory response mechanisms in cardiac surgery and immunomodulatory role of anesthetic agents

Although surgical techniques and perioperative care have made significant advances, perioperative mortality in cardiac surgery remains relatively high. Single- or multiple-organ failure remains the leading cause of postoperative mortality. Systemic inflammatory response syndrome (SIRS) is a common trigger for organ injury or dysfunction in surgical patients. Cardiac surgery involves major surgical dissection, the use of cardiopulmonary bypass (CPB), and frequent blood transfusions. Ischemia-reperfusion injury and contact activation from CPB are among the major triggers for SIRS. Blood transfusion can also induce proinflammatory responses. Here, we review the immunological mechanisms of organ injury and the role of anesthetic regimens in cardiac surgery.

The neuroimmune system - Where aging and excess alcohol intersect

As the percentage of the global population over age 65 grows, and with it a subpopulation of individuals with alcohol use disorder (AUD), understanding the effect of alcohol on the aged brain is of utmost importance. Neuroinflammation is implicated in both natural aging as well as alcohol use, and its role in alterations to brain morphology and function may be exacerbated in aging individuals who drink alcohol to excess. The neuroimmune response to alcohol in aging is complex. The few studies investigating this issue have reported heightened basal activity and either hypo- or hyper-reactivity to an alcohol challenge. This review of preclinical research will first introduce key players of the immune system, then explore changes in neuroimmune function with aging or alcohol alone, with discussion of vulnerable brain regions, changes in cytokines, and varied reactions of microglia and astrocytes. We will then consider different levels of alcohol exposure, relevant animal models of AUD, and neuroimmune activation by alcohol across the lifespan. By identifying key findings, challenges, and targets for future research, we hope to bring more attention and resources to this underexplored area of inquiry.

Emerging adjuvants for intradermal vaccination

The majority of vaccines have been delivered into the muscular tissue. Skin contains large amounts of antigen-presenting cells and has been recognized as a more immunogenic site for vaccine delivery. Intradermal delivery has been approved to improve influenza vaccine efficacy and spare influenza vaccine doses. In response to the recent monkeypox outbreak, intradermal delivery has been also approved to stretch the limited monkeypox vaccine doses to immunize more people at risk. Incorporation of vaccine adjuvants is promising to further increase intradermal vaccine efficacy and spare more vaccine doses. Yet, intradermal vaccination is associated with more significant local reactions than intramuscular vaccination. Thus, adjuvants suitable to boost intradermal vaccination need to have a good local safety without inducing overt local reactions. This review introduces currently approved adjuvants in licensed human vaccines and their relative reactogenicity for intradermal delivery and then introduces emerging chemical and physical adjuvants with a good local safety to boost intradermal vaccination. The rational to develop physical adjuvants, the types of physical adjuvants, and the unique advantages of physical adjuvants to boost intradermal vaccination are also introduced in this review.

From Co-Infections to Autoimmune Disease via Hyperactivated Innate Immunity: COVID-19 Autoimmune Coagulopathies, Autoimmune Myocarditis and Multisystem Inflammatory Syndrome in Children

Neutrophilia and the production of neutrophil extracellular traps (NETs) are two of many measures of increased inflammation in severe COVID-19 that also accompany its autoimmune complications, including coagulopathies, myocarditis and multisystem inflammatory syndrome in children (MIS-C). This paper integrates currently disparate measures of innate hyperactivation in severe COVID-19 and its autoimmune complications, and relates these to SARS-CoV-2 activation of innate immunity. Aggregated data include activation of Toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD) receptors, NOD leucine-rich repeat and pyrin-domain-containing receptors (NLRPs), retinoic acid-inducible gene I (RIG-I) and melanoma-differentiation-associated gene 5 (MDA-5). SARS-CoV-2 mainly activates the virus-associated innate receptors TLR3, TLR7, TLR8, NLRP3, RIG-1 and MDA-5. Severe COVID-19, however, is characterized by additional activation of TLR1, TLR2, TLR4, TLR5, TLR6, NOD1 and NOD2, which are primarily responsive to bacterial antigens. The innate activation patterns in autoimmune coagulopathies, myocarditis and Kawasaki disease, or MIS-C, mimic those of severe COVID-19 rather than SARS-CoV-2 alone suggesting that autoimmunity follows combined SARS-CoV-2-bacterial infections. Viral and bacterial receptors are known to synergize to produce the increased inflammation required to support autoimmune disease pathology. Additional studies demonstrate that anti-bacterial antibodies are also required to account for known autoantigen targets in COVID-19 autoimmune complications.

Synapse Dysfunctions in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory disease of the central nervous system (CNS) affecting nearly three million humans worldwide. In MS, cells of an auto-reactive immune system invade the brain and cause neuroinflammation. Neuroinflammation triggers a complex, multi-faceted harmful process not only in the white matter but also in the grey matter of the brain. In the grey matter, neuroinflammation causes synapse dysfunctions. Synapse dysfunctions in MS occur early and independent from white matter demyelination and are likely correlates of cognitive and mental symptoms in MS. Disturbed synapse/glia interactions and elevated neuroinflammatory signals play a central role. Glutamatergic excitotoxic synapse damage emerges as a major mechanism. We review synapse/glia communication under normal conditions and summarize how this communication becomes malfunctional during neuroinflammation in MS. We discuss mechanisms of how disturbed glia/synapse communication can lead to synapse dysfunctions, signaling dysbalance, and neurodegeneration in MS.

Elucidating the Focal Immunomodulatory Clues Influencing Mesenchymal Stem Cells in the Milieu of Intervertebral Disc Degeneration

The intervertebral discs (IVDs) are a relatively mobile joint that interconnects vertebrae of the spine. Intervertebral disc degeneration (IVDD) is one of the leading causes of low back pain, which is most often related to patient morbidity as well as high medical costs. Patients with chronic IVDD often need surgery that may sometimes lead to biomechanical complications as well as augmented degeneration of the adjacent segments. Moreover, treatment modalities like rigid intervertebral fusion, dynamic instrumentation, as well as other surgical interventions are still controversial. Mesenchymal stem cells (MSCs) have exhibited to have immunomodulatory functions and the ability to differentiate into cartilage, making these cells possibly an epitome for IVD regeneration. Transplanted MSCs were able to repair IVDD back to the normal disc milieu via the activation of the generation of extracellular matrix (ECM) proteins such as aggrecan, proteoglycans and collagen types I and II. IVD milieu clues like, periostin, cluster of differentiation, tumor necrosis factor alpha, interleukins, chemokines, transforming growth factor beta, reactive oxygen species, toll-like receptors, tyrosine protein kinase receptor and disialoganglioside, exosomes are capable of influencing the MSCs during treatment of IVDD. ECM microenvironment clues above have potentials as biomarkers as well as accurate molecular targets for therapeutic intervention in IVDD.

Inflammation and damage-associated molecular patterns in major psychiatric disorders

BACKGROUND

Emerging evidence indicates that inflammation plays an important role as a mechanism underlying mental disorders. However, most of the research on inflammatory mechanisms focuses on serum levels of interleukins and very few studies have investigated molecules that initiate and expand innate immune pathways such as damage-associated molecular patterns (DAMPs).

OBJECTIVES

This study investigated the levels of DAMPs among patients diagnosed with major depressive disorder (MDD), bipolar disorder (BD) I and II, schizophrenia (SCZ), and generalized anxiety disorder (GAD). We quantified serum levels of heat shock proteins (HSPs) 70 and 60 and of S100 calcium-binding protein B (S100B).

METHODS

Serum levels of HSP70, HSP60, and S100B were assessed in a sample of participants with psychiatric disorders (n = 191) and a control group (CT) (n = 59) using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum HSP70 concentrations were significantly higher in the MDD group compared to the CT, SCZ, and BD groups. The GAD group had higher concentrations of HSP70 than the SCZ group. Exploring associations with medications, lithium (p = 0.003) and clozapine (p = 0.028) were associated with lower HSP70 levels. Approximately 64% of the sample had DAMPs levels below the limits of detection indicated by the respective ELISA kit.

CONCLUSION

This was the first study to assess DAMPs levels in a transdiagnostic sample. Our preliminary findings suggest that HSP70 may be associated with MDD pathophysiology. Medications such as lithium and clozapine were associated with lower HSP70 levels in BD and SCZ groups, respectively. Therefore, it is worth mentioning that all participants were medicated and many psychotropic drugs exert an anti-inflammatory effect, possibly reducing the signs of inflammation.

Comparative tissue proteomics reveals unique action mechanisms of vaccine adjuvants

Radiofrequency adjuvant (RFA) was recently developed to boost influenza vaccination without the safety concerns of chemical adjuvants due to their physical nature. Yet, the action mechanisms of RFA remain largely unknown. Omics techniques offer new opportunities to identify molecular mechanisms of RFA. This study utilized comparative tissue proteomics to explore molecular mechanisms of the physical RFA. Comparison of RFA and chemical adjuvant (Alum, AddaVax, MPL, MPL/Alum)-induced tissue proteome changes identified 14 exclusively induced proteins by RFA, among which heat shock protein (HSP) 70 was selected for further analysis due to its known immune-modulating functions. RFA showed much weakened ability to boost ovalbumin and pandemic influenza vaccination in HSP70 knockout than wild-type mice, hinting crucial roles of HSP70 in RFA effects. This study supports comparative tissue proteomics to be an effective tool to study molecular mechanisms of vaccine adjuvants.

Prx4 acts as DAMP in shrimp, enhancing bacterial resistance via the toll pathway and prophenoloxidase activation

Peroxiredoxin (Prx), an antioxidant enzyme family, has been identified as immune modulating damage-associated molecular patterns (DAMPs) in mammals but not in shrimp. Acute non-lethal heat shock (NLHS) that enhances shrimp Penaeus vannamei resistance to Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (VP_AHPND). Among the five P. vannamei Prxs (LvPrx) isoforms, LvPrx4, the most abundant in unchallenged shrimp hemocytes that was upregulated in hemocytes following NLHS treatment, is of great interest. The escalation of the LvPrx4 monomer in hemolymph of NLHS treated shrimp indicates that it probably acts as DAMP. This study revealed that pre-challenge with rLvPrx4 could prolong VP_AHPND-infected shrimp survival, increase prophenoloxidase (proPO) activity and promote Toll pathway-related genes expression mediated by Toll-like receptor (TLR) 1 and 2. The presented findings elucidated the molecular mechanism of LvPrx4 monomer as DAMP in NLHS-induced VP_AHPND resistance by inducing the TLR1/2 signaling pathway and the proPO activating system.

Effective adjuvantation of nanograms of influenza vaccine and induction of cross-protective immunity by physical radiofrequency adjuvant

Novel adjuvants are highly demanded to aid in development of improved or new vaccines against existing or emerging infectious diseases. Considering commonly used Alum and MF59 adjuvants induce tissue stress and release of endogenous danger signals to mediate their adjuvant effects, physical modalities may be used to induce tissue stress and endogenous danger signal release to enhance vaccine-induced immune responses. Furthermore, physical adjuvants are less likely to induce significant systemic adverse reactions due to their localized effects. Recently we found non-invasive radiofrequency (RF) pretreatment of the skin could significantly enhance intradermal vaccine-induced immune responses in murine models that included pandemic influenza vaccine, pre-pandemic vaccine, and influenza internal antigen vaccine. It remained to be explored whether the physical RF adjuvant (RFA) could be used to boost seasonal influenza vaccination, spare vaccine doses, and induce cross-protective immunity. This study found the physical RFA could significantly enhance seasonal influenza vaccine-induced immune responses against each viral strain and robustly enhance low-dose (nanograms) H3N2 vaccine-induced immune responses and protection in murine models. RFA also induced cross-protective immunity against heterologous and heterosubtypic influenza viruses. Further studies found heat shock protein 70 (inducible endogenous danger signal) and myeloid differentiation primary response 88 adaptor played a crucial role in dose-sparing effects of RFA. These data strongly support further development of the physical RFA to boost influenza vaccination.

Hematologic dysfunction in cancer: Mechanisms, effects on antitumor immunity, and roles in disease progression

With the major advances in cancer immunology and immunotherapy, it is critical to consider that most immune cells are short-lived and need to be continuously replenished from hematopoietic stem and progenitor cells. Hematologic abnormalities are prevalent in cancer patients, and many ground-breaking studies over the past decade provide insights into their underlying cellular and molecular mechanisms. Such studies demonstrate that the dysfunction of hematopoiesis is more than a side-effect of cancer pathology, but an important systemic feature of cancer disease. Here we review these many advances, covering the cancer-associated phenotypes of hematopoietic stem and progenitor cells, the dysfunction of myelopoiesis and erythropoiesis, the importance of extramedullary hematopoiesis in cancer disease, and the developmental origins of tumor associated macrophages. We address the roles of many secreted mediators, signaling pathways, and transcriptional and epigenetic mechanisms that mediate such hematopoietic dysfunction. Furthermore, we discuss the important contribution of the hematopoietic dysfunction to cancer immunosuppression, the possible avenues for therapeutic intervention, and highlight the unanswered questions and directions for future work. Overall, hematopoietic dysfunction is established as an active component of the cancer disease mechanisms and an important target for therapeutic intervention.

Recent progress and perspectives on the relationship between hyperuricemia and periodontitis

Periodontitis is one of the most prevalent diseases in oral cavity, which could not merely lead to the destruction of supporting or surrounding tooth structures but also affect the whole-body health such as the digestive and nervous systems. Epidemiological investigations suggested that in some developed countries, more than 45% or even 50% population were suffering from periodontitis. However, the prevalence increases with age remarkably and it is investigated that a high prevalence (>50%) is affecting the elderly who is over 65 years old. There is an increasing interest in the direct and indirect relationships between periodontitis and hyperuricemia. Currently, hyperuricemia has become the second major metabolic disease in modern society and the prevalence of hyperuricemia among adult males and females was 21.7% and 14.4% respectively. As an inflammatory disease associated with various systemic diseases, periodontitis may have certain connections with hyperuricemia. Partial existing research announced that hyperuricemia could act as an inhibitory factor for periodontitis, while other scholars presented that a high uric acid (UA) level was more likely to aggravate inflammatory immune response and lead to more serious tissue destruction. This article provides a detailed and comprehensive overview of the relationship underlying hyperuricemia and periodontitis in the molecular mechanisms. Given the impact of hyperuricemia, this review could provide insight into its comorbidities.

MSCs interaction with the host lung microenvironment: An overlooked aspect?

Mesenchymal stromal cells (MSCs) were identified more than 50 years ago, and research advances have promoted the translation of pre-clinical studies into clinical settings in several diseases. However, we are only starting to uncover the local factors that regulate cell phenotype, cell function, and cell viability across tissues following administration in different diseases. Advances in pre-clinical and translational studies suggest that the host environment, especially inflammatory active environments, plays a significant role in directing the infused MSCs towards different phenotypes with different functions. This can significantly effect their therapeutic efficacy. One way to study this interaction between the host environment and the infused cells is to expose MSCs ex vivo to patient samples such as serum or bronchoalveolar lavage fluid. Using this approach, it has been demonstrated that MSCs are very sensitive to different host factors such as pathogens, inflammatory cytokines, and extra cellular matrix properties. By understanding how different local host factors effect MSC function it will open possibilities to select specific patient sub-groups that are more likely to respond to this type of treatment and will also open possibilities to prime the local host environment to increase viability and to enrich for a specific MSC phenotype. Here, we aim to review the current understanding of the interaction of MSCs with the host microenvironment. To narrow the scope of this mini review, the focus will be on the pulmonary microenvironment, with a specific focus on the diseases acute respiratory distress syndrome (ARDS) and cystic fibrosis (CF).

Inflammatory Mechanism of Brucella Infection in Placental Trophoblast Cells

Brucellosis is a severe zoonotic infectious disease caused by the infection of the Brucella, which is widespread and causes considerable economic losses in underdeveloped areas. Brucella is a facultative intracellular bacteria whose main target cells for infection are macrophages, placental trophoblast cells and dendritic cells. The main clinical signs of Brucella infection in livestock are reproductive disorders and abortion. At present, the pathogenesis of placentitis or abortion caused by Brucella in livestock is not fully understood, and further research on the effect of Brucella on placental development is still necessary. This review will mainly introduce the research progress of Brucella infection of placental trophoblast cells as well as the inflammatory response caused by it, explaining the molecular regulation mechanism of Brucella leading to reproductive system disorders and abortion, and also to provide the scientific basis for revealing the pathogenesis and infection mechanism of Brucella.

Early effects of LPS-induced neuroinflammation on the rat hippocampal glycolytic pathway

Neuroinflammation is a common feature during the development of neurological disorders and neurodegenerative diseases, where glial cells, such as microglia and astrocytes, play key roles in the activation and maintenance of inflammatory responses in the central nervous system. Neuroinflammation is now known to involve a neurometabolic shift, in addition to an increase in energy consumption. We used two approaches (in vivo and ex vivo) to evaluate the effects of lipopolysaccharide (LPS)-induced neuroinflammation on neurometabolic reprogramming, and on the modulation of the glycolytic pathway during the neuroinflammatory response. For this, we investigated inflammatory cytokines and receptors in the rat hippocampus, as well as markers of glial reactivity. Mitochondrial respirometry and the glycolytic pathway were evaluated by multiple parameters, including enzymatic activity, gene expression and regulation by protein kinases. Metabolic (e.g., metformin, 3PO, oxamic acid, fluorocitrate) and inflammatory (e.g., minocycline, MCC950, arundic acid) inhibitors were used in ex vivo hippocampal slices. The induction of early inflammatory changes by LPS (both in vivo and ex vivo) enhanced glycolytic parameters, such as glucose uptake, PFK1 activity and lactate release. This increased glucose consumption was independent of the energy expenditure for glutamate uptake, which was in fact diverted for the maintenance of the immune response. Accordingly, inhibitors of the glycolytic pathway and Krebs cycle reverted neuroinflammation (reducing IL-1β and S100B) and the changes in glycolytic parameters induced by LPS in acute hippocampal slices. Moreover, the inhibition of S100B, a protein predominantly synthesized and secreted by astrocytes, inhibition of microglia activation and abrogation of NLRP3 inflammasome assembly confirmed the role of neuroinflammation in the upregulation of glycolysis in the hippocampus. Our data indicate a neurometabolic glycolytic shift, induced by inflammatory activation, as well as a central and integrative role of astrocytes, and suggest that interference in the control of neurometabolism may be a promising strategy for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

TAK-242 treatment and its effect on mechanical properties and gene expression associated with IVD degeneration in SPARC-null mice

PURPOSE

Intervertebral disc (IVD) degeneration is accompanied by mechanical and gene expression changes to IVDs. SPARC-null mice display accelerated IVD degeneration, and treatment with (toll-like receptor 4 (TLR4) inhibitor) TAK-242 decreases proinflammatory cytokines and pain. This study examined if chronic TAK-242 treatment impacts mechanical properties and gene expression associated with IVD degeneration in SPARC-null mice.

METHODS

Male and female SPARC-null and WT mice aged 7-9 months were given intraperitoneal injections with TAK-242 or an equivalent saline vehicle for 8 weeks (3x/per week, M-W-F). L2-L5 spinal segments were tested in cyclic axial tension and compression. Gene expression analysis (RT-qPCR) was performed on male IVD tissues using Qiagen RT2 PCR arrays.

RESULTS

SPARC-null mice had decreased NZ length (p = 0.001) and increased NZ stiffness (p < 0.001) compared to WT mice. NZ length was not impacted by TAK-242 treatment (p = 0.967) despite increased hysteresis energy (p = 0.024). Tensile stiffness was greater in SPARC-null mice (p = 0.018), and compressive (p < 0.001) stiffness was reduced from TAK-242 treatment in WT but not SPARC-null mice (p = 0.391). Gene expression analysis found upregulation of 13 ECM and 5 inflammatory genes in SPARC-null mice, and downregulation of 2 inflammatory genes after TAK-242 treatment.

CONCLUSIONS

TAK-242 had limited impacts on SPARC-null mechanical properties and did not attenuate NZ mechanical changes associated with IVD degeneration. Expression analysis revealed an increase in ECM and inflammatory gene expression in SPARCnull mice with a reduction in inflammatory expression due to TAK-242 treatment. This study provides insight into the role of TLR4 in SPARC-null mediated IVD degeneration.

Composition and regulation of the immune microenvironment of salivary gland in Sjögren’s syndrome

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized by exocrine gland dysfunction and inflammation. Patients often have dry mouth and dry eye symptoms, which seriously affect their lives. Improving dry mouth and eye symptoms has become a common demand from patients. For this reason, researchers have conducted many studies on external secretory glands. In this paper, we summarize recent studies on the salivary glands of pSS patients from the perspective of the immune microenvironment. These studies showed that hypoxia, senescence, and chronic inflammation are the essential characteristics of the salivary gland immune microenvironment. In the SG of pSS, genes related to lymphocyte chemotaxis, antigen presentation, and lymphocyte activation are upregulated. Interferon (IFN)-related genes, DNA methylation, sRNA downregulation, and mitochondrial-related differentially expressed genes are also involved in forming the immune microenvironment of pSS, while multiple signaling pathways are involved in regulation. We further elucidated the regulation of the salivary gland immune microenvironment in pSS and relevant, targeted treatments.

Bifurcation of signalling in human innate immune pathways to NF-kB and IRF family activation

The human innate immune response can be activated through a wide range of stimuli. This multi-faceted system can be triggered by a range of immunostimulants including pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). These stimuli drive intracellular signalling pathways that branch off downstream to activate several distinct transcription factors. The two most impactful of which in innate immune outcomes are the NF-κB and the IRF family members. Both transcription factor families play defining roles in driving inflammation as well as the antiviral response. Pathways leading to their simultaneous activation share common upstream components but eventually distinct regulators which directly facilitate their activation. This review will discuss the current state of knowledge about what is known about how these pathways bifurcate to activate NF-κB and IRF family members.

Modulating macrophage polarization for the enhancement of fracture healing, a systematic review

Background

All fracture repairs start with the innate immune system with the inflammatory response known as the inflammatory stage guided and driven by the secretion of chemokine by the ruptured tissue, followed by the sequential recruitment of neutrophils, monocytes and macrophages. These innate immune cells would infiltrate the fracture site and secrete inflammatory cytokines to stimulate recruitment of more immune cells to arrive at the fracture site coordinating subsequent stages of the repair process. In which, subsidence of pro-inflammatory M1 macrophage and transformation to anti-inflammatory M2 macrophages promotes osteogenesis that marks the start of the anabolic endochondral stage.

Methods

Literature search was performed on Pubmed, Embase, and Web of Science databases (last accessed 15th April 2021) using “macrophage AND fracture”. Review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline.

Results

Eleven pre-clinical animal studies out of 429 articles were included in this systematic review according to our inclusion and exclusion criteria. All of which investigated interventions targeting to modulate the acute inflammatory response and macrophage polarization as evident by various markers in association with fracture healing outcomes.

Conclusion

This systematic review summarizes attempts to modulate the innate immune response with focuses on promoting macrophage polarization from M1 to M2 phenotype targeting the enhancement of fracture injury repair. Methods used to achieve the goal may include applications of damage-associated molecular pattern (DAMP), pathogen-associated molecular pattern (PAMP) or mechanical stimulation that hold high translational potentials for clinical application in the near future.

Expression of the pro-inflammatory P2Y14 receptor in the non-vasectomized and vasectomized human epididymis

BACKGROUND

Vasectomy causes spermatozoa accumulation in the epididymis, which may cause epididymitis. Inflammation is triggered by alert molecules released following tissue stress or injury. These include UDP-glucose, which activates the pro-inflammatory P2Y14 receptor (P2Y14), and induces immune cell recruitment. However, little is known about P2Y14 in the epididymis and its potential activation following vasectomy.

OBJECTIVES

(i) to localize P2Y14 in the human excurrent duct; and (ii) to examine the effect of vasectomy on P2Y14 protein and P2RY14 mRNA content, the production of selected cytokines and chemokines, and immune cell recruitment in the epididymis.

MATERIAL AND METHODS

in situ hybridization, qRT-PCR, western blotting, immunohistochemistry and immunofluorescence were performed in banked human epididymis samples.

RESULTS

P2RY14 mRNA and P2Y14 protein were detected in epithelial cells in the efferent duct, epididymis and vas deferens in non-vasectomized men. Keratin 5 (KRT5)-positive basal cells were strongly labeled for P2Y14 in all epididymal segments. A progressive apical localization was detected in principal cells (negative for the proton pump V-ATPase) from the corpus to the cauda. A subset of V-ATPase-positive clear cells also showed strong P2Y14 labeling. Vasectomy induced an increase in P2RY14 mRNA in the corpus and cauda, and stronger apical labeling in principal cells in the corpus. CXCL10 mRNA increased in the cauda and CCL2 mRNA decreased in the corpus of vasectomized versus non-vasectomized men. No change in IL-8 and IL-1β mRNA was detected. Numerous CD45⁺ leukocytes were detected in the interstitium of the corpus and cauda following vasectomy, while only a few were seen in non-vasectomized men. Several CD45⁺ leukocytes, some of which containing spermatozoa, were detected in the corpus lumen following vasectomy.

DISCUSSION AND CONCLUSION

Our study indicates that vasectomy-induced spermatozoa congestion may lead to an inflamed-prone local environment characterized by potential activation of P2Y14 and recruitment of immune cells in the epididymis. This article is protected by copyright. All rights reserved.

The Influence of Heparan Sulfate on Breast Amyloidosis and the Toxicity of the Pre-fibrils Formed by β-casein

Heparan sulfate (HS) as a mediator is usually involved in both inflammation and fibrosis. Besides, pre-fibrils are the intermediates of amyloid fibrils that usually cause cell death and tissue damage, like the amyloid-β in Alzheimer's disease, α-synuclein in Parkinson disease and islet amyloid polypeptide in type II diabetes mellitus. However, the related study was involved rarely in breast. Therefore, the combing technologies including hematoxylin-eosin staining and thioflavin S staining were used to investigate the influence of HS on breast amyloidosis. To further study the toxicity of the pre-fibrils formed by β-casein on the HC11 cells and the breast mammary gland, the combing technologies including pentamer formyl thiophene acetic acid fluorescence analysis, MTT assay, Annexin V/PI staining and hematoxylin-eosin staining were performed. The results demonstrated that HS, acted as an endogenous molecule, induced the inflammation and amyloid fibril formation at the same time, and there was a close relationship between inflammation and fibrosis of breast. In addition, the pre-fibrils formed by β-casein were toxic because they induced the death and apoptosis of HC11 cells, as well as the inflammation of mammary gland of rats. Therefore, the early examination and identify of the pre-fibrils in the breast were worth considering to prevent the disease development, and it was interesting to explore the HS mimetics to impair the breast amyloidosis and attenuate the inflammatory response in the future.

Damage associated molecular patterns and neutrophil extracellular traps in acute pancreatitis

Previous researches have emphasized a trypsin-centered theory of acute pancreatitis (AP) for more than a century. With additional studies into the pathogenesis of AP, new mechanisms have been explored. Among them, the role of immune response bears great importance. Pro-inflammatory substances, especially damage-associated molecular patterns (DAMPs), play an essential role in activating, signaling, and steering inflammation. Meanwhile, activated neutrophils attach great importance to the immune defense by forming neutrophil extracellular traps (NETs), which cause ductal obstruction, premature trypsinogen activation, and modulate inflammation. In this review, we discuss the latest advances in understanding the pathological role of DAMPs and NETs in AP and shed light on the flexible crosstalk between these vital inflammatory mediators. We, then highlight the potentially promising treatment for AP targeting DAMPs and NETs, with a focus on novel insights into the mechanism, diagnosis, and management of AP.

Mitochondrial Damage-Associated Molecular Patterns Content in Extracellular Vesicles Promotes Early Inflammation in Neurodegenerative Disorders

Neuroinflammation is a common hallmark in different neurodegenerative conditions that share neuronal dysfunction and a progressive loss of a selectively vulnerable brain cell population. Alongside ageing and genetics, inflammation, oxidative stress and mitochondrial dysfunction are considered key risk factors. Microglia are considered immune sentinels of the central nervous system capable of initiating an innate and adaptive immune response. Nevertheless, the pathological mechanisms underlying the initiation and spread of inflammation in the brain are still poorly described. Recently, a new mechanism of intercellular signalling mediated by small extracellular vesicles (EVs) has been identified. EVs are nanosized particles (30-150 nm) with a bilipid membrane that carries cell-specific bioactive cargos that participate in physiological or pathological processes. Damage-associated molecular patterns (DAMPs) are cellular components recognised by the immune receptors of microglia, inducing or aggravating neuroinflammation in neurodegenerative disorders. Diverse evidence links mitochondrial dysfunction and inflammation mediated by mitochondrial-DAMPs (mtDAMPs) such as mitochondrial DNA, mitochondrial transcription factor A (TFAM) and cardiolipin, among others. Mitochondrial-derived vesicles (MDVs) are a subtype of EVs produced after mild damage to mitochondria and, upon fusion with multivesicular bodies are released as EVs to the extracellular space. MDVs are particularly enriched in mtDAMPs which can induce an immune response and the release of pro-inflammatory cytokines. Importantly, growing evidence supports the association between mitochondrial dysfunction, EV release and inflammation. Here, we describe the role of extracellular vesicles-associated mtDAMPS in physiological conditions and as neuroinflammation activators contributing to neurodegenerative disorders.

Inflammatory gene expression during acute high‐altitude exposure

Abstract

The molecular signalling pathways that regulate inflammation and the response to hypoxia share significant crosstalk and appear to play major roles in high‐altitude acclimatization and adaptation. Several studies demonstrate increases in circulating candidate inflammatory markers during acute high‐altitude exposure, but significant gaps remain in our understanding of how inflammation and immune function change at high altitude and whether these responses contribute to high‐altitude pathologies, such as acute mountain sickness. To address this, we took an unbiased transcriptomic approach, including RNA sequencing and direct digital mRNA detection with NanoString, to identify changes in the inflammatory profile of peripheral blood throughout 3 days of high‐altitude acclimatization in healthy sea‐level residents (n = 15; five women). Several inflammation‐related genes were upregulated on the first day of high‐altitude exposure, including a large increase in HMGB1 (high mobility group box 1), a damage‐associated molecular pattern (DAMP) molecule that amplifies immune responses during tissue injury. Differentially expressed genes on the first and third days of acclimatization were enriched for several inflammatory pathways, including nuclear factor‐κB and Toll‐like receptor (TLR) signalling. Indeed, both TLR4 and LY96, which encodes the lipopolysaccharide binding protein (MD‐2), were upregulated at high altitude. Finally, FASLG and SMAD7 were associated with acute mountain sickness scores and peripheral oxygen saturation levels on the first day at high altitude, suggesting a potential role of immune regulation in response to high‐altitude hypoxia. These results indicate that acute high‐altitude exposure upregulates inflammatory signalling pathways and might sensitize the TLR4 signalling pathway to subsequent inflammatory stimuli.

Key points

Inflammation plays a crucial role in the physiological response to hypoxia.

High‐altitude hypoxia exposure causes alterations in the inflammatory profile that might play an adaptive or maladaptive role in acclimatization.

In this study, we characterized changes in the inflammatory profile following acute high‐altitude exposure.

We report upregulation of novel inflammation‐related genes in the first 3 days of high‐altitude exposure, which might play a role in immune system sensitization.

These results provide insight into how hypoxia‐induced inflammation might contribute to high‐altitude pathologies and exacerbate inflammatory responses in critical illnesses associated with hypoxaemia.

The Role of KEAP1-NRF2 System in Atopic Dermatitis and Psoriasis

The Kelch-like erythroid cell-derived protein with cap‘n’collar homology-associated protein 1 (KEAP1)-nuclear factor erythroid-2-related factor 2 (NRF2) system, a thiol-based sensor-effector apparatus, exerts antioxidative and anti-inflammatory effects and maintains skin homeostasis. Thus, NRF2 activation appears to be a promising treatment option for various skin diseases. However, NRF2-mediated defense responses may deteriorate skin inflammation in a context-dependent manner. Atopic dermatitis (AD) and psoriasis are two common chronic inflammatory skin diseases caused by a defective skin barrier, dysregulated immune responses, genetic predispositions, and environmental factors. This review focuses on the role of the KEAP1-NRF2 system in the pathophysiology of AD and psoriasis and the therapeutic approaches that utilize this system.

Proteoglycans in Toll-like receptor responses and innate immunity

The extracellular matrix (ECM) is an active and dynamic feature of tissues that not only provides gross structure but also plays key roles in cellular responses. The ever-changing microenvironment responds dynamically to cellular and external signals, and in turn influences cell fate, tissue development, and response to environmental injury or microbial invasion. It is therefore paramount to understand how the ECM components interact with each other, the environment and cells, and how they mediate their effects. Among the ECM components that have recently garnered increased attention, proteoglycans (PGs) deserve special note. Recent evidence strongly suggests that they play a crucial role both in health maintenance and disease development. In particular, proteoglycans dictate whether homeostasis or cell death will result from a given injury, by triggering and modulating activation of the innate immune system, via a conserved array of receptors that recognize exogenous (infectious) or endogenous (tissue damage) molecular patterns. Innate immune activation by proteoglycans has important implications for the understanding of cell-matrix interactions in health and disease. In this review, we will summarize the current state of knowledge of innate immune signaling by proteoglycans, discuss the implications, and explore future directions to define progress in this area of extracellular matrix biology.

Fibronectin Functions as a Selective Agonist for Distinct Toll-like Receptors in Triple-Negative Breast Cancer

The microenvironment of tumors is characterized by structural changes in the fibronectin matrix, which include increased deposition of the EDA isoform of fibronectin and the unfolding of the fibronectin Type III domains. The impact of these structural changes on tumor progression is not well understood. The fibronectin EDA (FnEDA) domain and the partially unfolded first Type III domain of fibronectin (FnIII-1c) have been identified as endogenous damage-associated molecular pattern molecules (DAMPs), which induce innate immune responses by serving as agonists for Toll-Like Receptors (TLRs). Using two triple-negative breast cancer (TNBC) cell lines MDA-MB-468 and MDA-MB-231, we show that FnEDA and FnIII-1c induce the pro-tumorigenic cytokine, IL-8, by serving as agonists for TLR5 and TLR2, the canonical receptors for bacterial flagellin and lipoprotein, respectively. We also find that FnIII-1c is not recognized by MDA-MB-468 cells but is recognized by MDA-MB-231 cells, suggesting a cell type rather than ligand specific utilization of TLRs. As IL-8 plays a major role in the progression of TNBC, these studies suggest that tumor-induced structural changes in the fibronectin matrix promote an inflammatory microenvironment conducive to metastatic progression.

Astragaloside IV attenuate MI-induced myocardial fibrosis and cardiac remodeling by inhibiting ROS/caspase-1/GSDMD signaling pathway

Astragalus membranaceus is a traditional Chinese medicine and has been widely used in treating cardiovascular diseases (CVDs), such as asthma, edema, and chest tightness. Astragaloside IV (AS-IV), one of the major active components extracted from Astragalus membranaceus, has a series of pharmacological effects, including inhibiting inflammation, regulating energy metabolism, reducing oxidative stress and apoptosis. However, the effect of AS-IV on myocardial infarction (MI) and the underlying molecular mechanism remains unclear. The purpose of our study is to investigate the effects of AS-IV on MI-induced myocardial fibrosis and cardiac remodeling and to elucidate its underlying mechanisms. MI was induced by ligation of the left anterior descending (LAD) coronary artery. Echocardiography was used to evaluate cardiac function in mice. Pathological changes in cardiac tissues were analyzed with hematoxylin and eosin (H&E) staining, Masson staining, and wheat germ agglutinin (WGA) staining. Immunohistochemistry was used to detect the expression of fibrosis and inflammation-related proteins. Immunofluorescence and flow cytometry were used to detect ROS level. The expressions of α-SMA, Collagen I, NLRP3, cleaved cas-1, cleaved IL-18, cleaved IL-β, GSDMD-N, and cleaved caspase-1 were examined using western blot. The results of cardiac ultrasound showed that AS-IV could improve poor ventricular remodeling, myocardial pathological staining showed that AS-IV could significantly reduce the myocardial fibrosis and myocardial hypertrophy, ROS levels were also significantly reduced, and the protein expression of NLRP3/Caspase-1/GSDMD signaling pathway was remarkably decreased in the AS-IV group. Furthermore, immunohistochemical staining results showed that the expression of myocardial macrophages and neutrophils in AS-IV group decreased significantly, to further investigate whether the reduction of myocardial pyroptosis by AS-IV is related to the regulation of macrophages, in vitro, AS-IV was selected to stimulate bone marrow-derived macrophages (BMDMs). Our findings indicated that AS-IV protective effect of the heart might be related to the reduction of macrophage pyroptosis. These results demonstrate that AS-IV alleviated MI-induced myocardial fibrosis and cardiac remodeling by suppressing ROS/Caspase-1/GSDMD signaling pathway, AS-IV should be further studied in the future.

The Big Picture of Neurodegeneration: A Meta Study to Extract the Essential Evidence on Neurodegenerative Diseases in a Network-Based Approach

The common features of all neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Amyotrophic Lateral Sclerosis (ALS), and Huntington's disease, are the accumulation of aggregated and misfolded proteins and the progressive loss of neurons, leading to cognitive decline and locomotive dysfunction. Still, they differ in their ultimate manifestation, the affected brain region, and the kind of proteinopathy. In the last decades, a vast number of processes have been described as associated with neurodegenerative diseases, making it increasingly harder to keep an overview of the big picture forming from all those data. In this meta-study, we analyzed genomic, transcriptomic, proteomic, and epigenomic data of the aforementioned diseases using the data of 234 studies in a network-based approach to study significant general coherences but also specific processes in individual diseases or omics levels. In the analysis part, we focus on only some of the emerging findings, but trust that the meta-study provided here will be a valuable resource for various other researchers focusing on specific processes or genes contributing to the development of neurodegeneration.

Single-Cell RNA-Sequencing: Astrocyte and Microglial Heterogeneity in Health and Disease

Astrocytes and microglia are non-neuronal cells that maintain homeostasis within the central nervous system via their capacity to regulate neuronal transmission and prune synapses. Both astrocytes and microglia can undergo morphological and transcriptomic changes in response to infection with human immunodeficiency virus (HIV). While both astrocytes and microglia can be infected with HIV, HIV viral proteins in the local environment can interact with and activate these cells. Given that both astrocytes and microglia play critical roles in maintaining neuronal function, it will be critical to have an understanding of their heterogeneity and to identify genes and mechanisms that modulate their responses to HIV. Heterogeneity may include a depletion or increase in one or more astrocyte or microglial subtypes in different regions of the brain or spine as well as the gain or loss of a specific function. Single-cell RNA sequencing (scRNA-seq) has emerged as a powerful tool that can be used to characterise these changes within a given population. The use of this method facilitates the identification of subtypes and changes in cellular transcriptomes that develop in response to activation and various disease processes. In this review, we will examine recent studies that have used scRNA-seq to explore astrocyte and microglial heterogeneity in neurodegenerative diseases including Alzheimer’s disease and amyotrophic lateral sclerosis as well as in response to HIV infection. A careful review of these studies will expand our current understanding of cellular heterogeneity at homeostasis and in response to specific disease states.

Haptoglobin Induces a Specific Proteomic Profile and a Mature-Associated Phenotype on Primary Human Monocyte-Derived Dendritic Cells

Damage-associated molecular patterns (DAMPs) play a critical role in dendritic cells (DCs) ability to trigger a specific and efficient adaptive immune response for different physiological and pathological scenarios. We have previously identified constitutive DAMPs (HMGB1 and Calreticulin) as well as new putative inducible DAMPs such as Haptoglobin (HP), from a therapeutically used heat shock-conditioned melanoma cell lysate (called TRIMEL). Remarkably, HP was shown to be the most abundant protein in the proteomic profile of heat shock-conditioned TRIMEL samples. However, its relative contribution to the observed DCs phenotype has not been fully elucidated. Human DCs were generated from monocytes isolated from PBMC of melanoma patients and healthy donors. DC lineage was induced with rhIL-4 and rhGM-CSF. After additional stimulation with HP, the proteome of these HP-stimulated cells was characterized. In addition, DCs were phenotypically characterized by flow cytometry for canonical maturation markers and cytokine production. Finally, in vitro transmigration capacity was assessed using Transwell plates. Our results showed that the stimulation with HP was associated with the presence of exclusive and higher relative abundance of specific immune-; energy production-; lipid biosynthesis-; and DAMPs-related proteins. Importantly, HP stimulation enhanced the expression of specific DC maturation markers and pro-inflammatory and Th1-associated cytokines, and an in vitro transmigration of primary human DCs. Taken together, these data suggest that HP can be considered as a new inducible DAMP with an important role in in vitro DC activation for cancer immunotherapy.

Programmed cell death detection methods: a systematic review and a categorical comparison

Programmed cell death is considered a key player in a variety of cellular processes that helps to regulate tissue growth, embryogenesis, cell turnover, immune response, and other biological processes. Among different types of cell death, apoptosis has been studied widely, especially in the field of cancer research to understand and analyse cellular mechanisms, and signaling pathways that control cell cycle arrest. Hallmarks of different types of cell death have been identified by following the patterns and events through microscopy. Identified biomarkers have also supported drug development to induce cell death in cancerous cells. There are various serological and microscopic techniques with advantages and limitations, that are available and are being utilized to detect and study the mechanism of cell death. The complexity of the mechanism and difficulties in distinguishing among different types of programmed cell death make it challenging to carry out the interventions and delay its progression. In this review, mechanisms of different forms of programmed cell death along with their conventional and unconventional methods of detection of have been critically reviewed systematically and categorized on the basis of morphological hallmarks and biomarkers to understand the principle, mechanism, application, advantages and disadvantages of each method. Furthermore, a very comprehensive comparative analysis has been drawn to highlight the most efficient and effective methods of detection of programmed cell death, helping researchers to make a reliable and prudent selection among the available methods of cell death assay. Conclusively, how programmed cell death detection methods can be improved and can provide information about distinctive stages of cell death detection have been discussed.

Antioxidant, Anti-Inflammatory and Cytotoxic Activity of Phenolic Compound Family Extracted from Raspberries (Rubus idaeus): A General Review

Raspberries (Rubus idaeus) possess a wide phenolic family profile; this serves the role of self-protection for the plant. Interest in these compounds have significantly increased, since they have been classified as nutraceuticals due to the positive health effects provided to consumers. Extensive chemical, in vitro and in vivo studies have been performed to prove and validate these benefits and their possible applications as an aid when treating several chronic degenerative diseases, characterized by oxidative stress and an inflammatory response. While many diseases could be co-adjuvanted by the intake of these phenolic compounds, this review will mainly discuss their effects on cancer. Anthocyanins and ellagitannins are known to provide a major antioxidant capacity in raspberries. The aim of this review is to summarize the current knowledge concerning the phenolic compound family of raspberries, and topics discussed include their characterization, biosynthesis, bioavailability, cytotoxicity, antioxidant and anti-inflammatory activities.

Toll-like receptors and damage-associated molecular patterns in the pathogenesis of heart transplant rejection

Significant strides have been made in our understanding of the immune system and its role in cardiac transplant rejection. Despite the growing knowledge of immune responses, the mortality rate following cardiac transplantation remains grim. Related to procedural and pathological complications, toll-like receptor (TLR) and damage-associated molecular pattern (DAMP) signaling is the most direct and earliest interface between tissue integration and the innate immune response. This in turn can activate an adaptive immune response that further damages myocardial tissue. Furthermore, relevant literature on the status of DAMPs in the context of heart-transplantation remains limited, warranting further attention in clinical and translational research. This review aims to critically appraise the perspectives, advances, and challenges on DAMP-mediated innate immune response in the immune-mediated rejection of cardiac transplantation. Detailed analysis of the influence of TLR and DAMP signaling in mounting the immune response against the transplanted heart holds promise for improving outcomes through early detection and prevention of varied forms of organ rejection.

Basic mechanisms in cardiogenic shock: part 1-definition and pathophysiology

Cardiogenic shock mortality rates remain high despite significant advances in cardiovascular medicine and the widespread uptake of mechanical circulatory support systems. Except for early invasive angiography and percutaneous coronary intervention of the infarct-related artery, the most widely used therapeutic measures are based on low-quality evidence. The grim prognosis and lack of high-quality data warrant further action. Part 1 of this two-part educational review defines cardiogenic shock and discusses current treatment strategies. In addition, we summarize current knowledge on basic mechanisms in the pathophysiology of cardiogenic shock, focusing on inflammation and microvascular disturbances, which may ultimately be translated into diagnostic or therapeutic approaches to improve the outcome of our patients.

The Novel Role of Metabolism-Associated Molecular Patterns in Sepsis

Sepsis, a life-threatening organ dysfunction, is not caused by direct damage of pathogens and their toxins but by the host’s severe immune and metabolic dysfunction caused by the damage when the host confronts infection. Previous views focused on the damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs), including metabolic proinflammatory factors in sepsis. Recently, new concepts have been proposed to group free fatty acids (FFAs), glucose, advanced glycation end products (AGEs), cholesterol, mitochondrial DNA (mtDNA), oxidized phospholipids (OxPLs), ceramides, and uric acid into metabolism-associated molecular patterns (MAMPs). The concept of MAMPs will bring new guidance to the research and potential treatments of sepsis. Nowadays, sepsis is regarded as closely related to metabolic disorders, and MAMPs play an important role in the pathogenesis and development of sepsis. According to this view, we have explained MAMPs and their possible roles in the pathogenesis of sepsis. Next, we have further explained the specific functions of different types of MAMPs in the metabolic process and their interactional relationship with sepsis. Finally, the therapeutic prospects of MAMPs in sepsis have been summarized.

From hurdle to springboard: The macrophage as target in biomaterial-based bone regeneration strategies

The past decade has seen a growing appreciation for the role of the innate immune response in mediating repair and biomaterial directed tissue regeneration. The long-held view of the host immune/inflammatory response as an obstacle limiting stem cell regenerative activity, has given way to a fresh appreciation of the pivotal role the macrophage plays in orchestrating the resolution of inflammation and launching the process of remodelling and repair. In the context of bone, work over the past decade has established an essential coordinating role for macrophages in supporting bone repair and sustaining biomaterial driven osteogenesis. In this review evidence for the role of the macrophage in bone regeneration and repair is surveyed before discussing recent biomaterial and drug-delivery based approaches that target macrophage modulation with the goal of accelerating and enhancing bone tissue regeneration.

The cross-talk between soluble "Find me" and "Keep out" signals as an initial step in regulating efferocytosis

The rapid clearance of apoptotic cells (ACs), known as efferocytosis, prompts the inhibition of inflammatory responses and autoimmunity and maintains homeostatic cell turnover by controlling the release of intracellular contents. The fast clearance of ACs requires professional and nonprofessional phagocytic cells that can accurately and promptly recognize ACs and migrate towards them. Cells undergoing apoptosis alarm their presence by releasing special soluble chemotactic factors, such as lactoferrin, that act as "Find me," "Keep out," or "Stay away" signals to recruit phagocytic cells, such as macrophages or prevent granulocyte migration. Efferocytosis effectively serves to prevent damage-associated molecular pattern release and secondary necrosis and inhibit inflammation/autoimmunity at the very first step. Since less attention has been given to the cross-talk and balance of "Find me" and "Keep out" signals released from ACs in efferocytosis, we set out to investigate the current knowledge of the roles of "Find me" and "Keep out" signals in the efferocytosis process.

Pentachlorophenol mediated regulation of DAMPs and inflammation: In vitro study

Pentachlorophenol (PCP) was once widely employed organochlorine pesticide and wood preservative in United States. Due to its toxicity, the U.S. Environmental Protection Agency classified it as a restricted-use pesticide and established as a liver carcinogen. Earlier reports have indicated increased production of inflammatory mediators like IL-1β and TNF-α by immune cells, including NK cells, lymphocytes, or monocytes, on PCP exposure. Yet, there is little to no knowledge regarding the molecular mechanisms affected by acute and chronic exposure to PCP in humans. Considering this, we examined PCP-induced inflammation and downstream signaling in-(a) human lung adenocarcinoma cells (A549) with type II alveolar epithelial characteristics; and (b) human liver carcinoma cells (HepG2). We treated A549 and HepG2 cells with 1 μM and 10 μM of PCP for 24 h duration. We observed a significant induction of cytokine/chemokine production (IL-1β, IL-6, TNF-α, IL-8, CCL2, and CCL5) in PCP-treated- HepG2 and A549 cells. The mRNA expression analyses showed upregulated levels of danger associated molecular patterns (DAMPs)-HMGB1 and heat shock protein 70 (Hsp70); and TLR-4 receptor in PCP-challenged cells. Increased expression of transcription factors-NF-kB and STAT3 provide further insights into PCP-induced molecular mechanisms. Interestingly, antibody mediated blocking of DAMPs abrogated PCP-mediated transcriptional induction of cytokines/chemokines and transcription factors in HepG2 and A549 cells. Overall, our findings demonstrate important role of DAMPs in PCP-induced inflammatory responses.

Waterborne Human Pathogenic Viruses in Complex Microbial Communities: Environmental Implication on Virus Infectivity, Persistence, and Disinfection

Waterborne human pathogenic viruses challenge global health and economy. Viruses were long believed to transmit among hosts as individual, free particles. However, recent evidence indicates that viruses also transmit in populations, so-called en bloc transmission, by either interacting with coexisting bacteria, free-living amoebas, and other higher organisms through endosymbiosis and surface binding, or by being clustered inside membrane-bound vesicles or simply self-aggregating with themselves. En bloc transmission of viruses and virus-microbiome interactions could enable viruses to enhance their infectivity, increase environmental persistence, and resist inactivation from disinfection. Overlooking this type of transmission and virus-microbiome interactions may underestimate the environmental and public health risks of the viruses. We herein provide a critical perspective on waterborne human pathogenic viruses in complex microbial communities to elucidate the environmental implication of virus-microbiome interactions on virus infectivity, persistence, and disinfection. This perspective also provides insights on advancing disinfection and sanitation guidelines and regulations to protect the public health.

Tenascin-C is a driver of inflammation in the DSS model of colitis

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Increased tenascin-C staining appeared to predominantly occur in damaged ulcerated areas.

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Tenascin-C knock-out mice were partly protected from DSS induced colitis.

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Mice deficient in tenascin-C had areas of + ve EpCAM staining indicating that crypt and epithelial integrity was maintained.

Inflammatory Bowel Disease (IBD) is a grouping of chronic inflammatory disorders of the gut. Tenascin-C is a pro-inflammatory, extracellular matrix protein found upregulated in IBD patients and whilst a pathological driver of chronic inflammation, its precise role in the etiology of IBD is unknown. To study tenascin-C’s role in colitis pathology we investigated its expression in a murine model of IBD. Wild-type (WT) or tenascin-C knockout (KO) male mice were left untreated or treated with dextran sodium sulphate (DSS) in their drinking water. Tenascin-C was upregulated at the mRNA level in the colitic distal colon of day eight DSS treated mice, coinciding with significant increases in gross and histological pathology. Immunohistochemistry localized this increase in tenascin-C to areas of inflammation and ulceration in the mucosa. Tenascin-C KO mice exhibited reduced gross pathology in comparison. These differences also extended to the histopathological level where reduced colonic inflammation and tissue damage were found in KO compared to WT mice. Furthermore, the severity of the distal colon lesions were less in the KO mice after 17 days of recovery from DSS treatment. This study demonstrates a role for tenascin-C as a driver of inflammatory pathology in a murine model of IBD and thus suggests neutralizing its pro-inflammatory activity could be explored as a therapeutic strategy for treating IBD.

Proteostasis Perturbations and Their Roles in Causing Sterile Inflammation and Autoinflammatory Diseases

Proteostasis, a portmanteau of the words protein and homeostasis, refers to the ability of eukaryotic cells to maintain a stable proteome by acting on protein synthesis, quality control and/or degradation. Over the last two decades, an increasing number of disorders caused by proteostasis perturbations have been identified. Depending on their molecular etiology, such diseases may be classified into ribosomopathies, proteinopathies and proteasomopathies. Strikingly, most—if not all—of these syndromes exhibit an autoinflammatory component, implying a direct cause-and-effect relationship between proteostasis disruption and the initiation of innate immune responses. In this review, we provide a comprehensive overview of the molecular pathogenesis of these disorders and summarize current knowledge of the various mechanisms by which impaired proteostasis promotes autoinflammation. We particularly focus our discussion on the notion of how cells sense and integrate proteostasis perturbations as danger signals in the context of autoinflammatory diseases to provide insights into the complex and multiple facets of sterile inflammation.

Monocytes augment inflammatory responses in human aortic valve interstitial cells via β2-integrin/ICAM-1-mediated signaling

OBJECTIVE

Inflammatory infiltration in aortic valves promotes calcific aortic valve disease (CAVD) progression. While soluble extracellular matrix (ECM) proteins induce inflammatory responses in aortic valve interstitial cells (AVICs), the impact of monocytes on AVIC inflammatory responses is unknown. We tested the hypothesis that monocytes enhance AVIC inflammatory responses to soluble ECM protein in this study.

METHODS

Human AVICs isolated from normal aortic valves were cocultured with monocytes and stimulated with soluble ECM protein (matrilin-2). ICAM-1 and IL-6 productions were assessed. YAP and NF-κB phosphorylation were analyzed. Recombinant CD18, neutralizing antibodies against β₂-integrin or ICAM-1, and inhibitor of YAP or NF-κB were applied.

RESULTS

AVIC expression of ICAM-1 and IL-6 was markedly enhanced by the presence of monocytes, although matrilin-2 did not affect monocyte production of ICAM-1 or IL-6. Matrilin-2 up-regulated the expression of monocyte β₂-integrin and AVIC ICAM-1, leading to monocyte-AVIC adhesion. Neutralizing β₂-integrin or ICAM-1 in coculture suppressed monocyte adhesion to AVICs and the expression of ICAM-1 and IL-6. Recombinant CD18 enhanced the matrilin-2-induced ICAM-1 and IL-6 expression in AVIC monoculture. Further, stimulation of coculture with matrilin-2 induced greater YAP and NF-κB phosphorylation. Inhibiting either YAP or NF-κB markedly suppressed the inflammatory response to matrilin-2 in coculture.

CONCLUSION

Monocyte β₂-integrin interacts with AVIC ICAM-1 to augment AVIC inflammatory responses to soluble matrilin-2 through enhancing the activation of YAP and NF-κB signaling pathways. Infiltrated monocytes may promote valvular inflammation through cell-cell interaction with AVICs to enhance their sensitivity to damage-associated molecular patterns.

Anti-inflammatory effects of mesenchymal stem cell-conditioned media inhibited macrophages activation in vitro

The immunomodulatory effects of mesenchymal stem cells (MSCs) on macrophages have been reported, however, the underlying mechanism remains unknown. Therefore, this study aimed to investigate the anti-inflammatory effects of MSCs on lipopolysaccharide (LPS)-stimulated macrophages and the subsequent downregulation of their inflammatory mediators. Macrophages were treated with conditioned media from MSCs, without a subsequent change of MSCs responding to the inflammation state. This study also evaluated whether the interleukin (IL) 4 stimulation of MSCs can improve their anti-inflammatory effects. Results demonstrated that the MSC-conditioned medium (MSC-CM) stimulated with IL4 significantly inhibited inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression of LPS-activated macrophages. MSC-CM treatment inhibited the mRNA transcription of the cytokines IL1β and IL6, the chemokines C–C motif ligand (CCL) 2, CCL3, CCL4, and CCL5, and the chemokine receptors CCR2 and CCR5, in LPS-stimulated macrophages. As revealed through western blot and immunofluorescence analyses, the phosphorylation of p38, JNK, and ERK MAPKs, as well as phosphorylation of NF-κB in stimulated macrophages, were also inhibited by the MSC-CM. Further, more potent anti-inflammatory effects were observed with the IL4-stimulated cells, compared with those observed with the non-stimulated cells. The MSC-CM demonstrated a potent anti-inflammatory effect on LPS-activated macrophages, while the IL4 stimulation improved this effect. These findings indicate that MSCs could exert anti-inflammatory effects on macrophages, and may be considered as a therapeutic agent in inflammation treatment.

The Pseudomonas aeruginosa Type III Secretion System Exoenzyme Effector ExoU Induces Mitochondrial Damage in a Murine Bone Marrow-Derived Macrophage Infection Model

Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen that causes nosocomial pneumonia, urinary tract infections, and bacteremia. A hallmark of P. aeruginosa pathogenesis is disruption of host cell function by the type III secretion system (T3SS) and its cognate exoenzyme effectors. The T3SS effector ExoU is phospholipase A2 (PLA2) that targets the host cell plasmalemmal membrane to induce cytolysis and is an important virulence factor that mediates immune avoidance. In addition, ExoU has been shown to subvert the host inflammatory response in a noncytolytic manner. In primary bone marrow-derived macrophages (BMDMs), P. aeruginosa infection is sensed by the nucleotide-binding domain containing leucine-rich repeats-like receptor 4 (NLRC4) inflammasome, which triggers caspase-1 activation and inflammation. ExoU transiently inhibits NLRC4 inflammasome-mediated activation of caspase-1 and its downstream target, interleukin 1β (IL-1β), to suppress activation of inflammation. In the present study, we sought to identify additional noncytolytic virulence functions for ExoU and discovered an unexpected association between ExoU, host mitochondria, and NLRC4. We show that infection of BMDMs with P. aeruginosa strains expressing ExoU elicited mitochondrial oxidative stress. In addition, mitochondria and mitochondrion-associated membrane fractions enriched from infected cells exhibited evidence of autophagy activation, indicative of damage. The observation that ExoU elicited mitochondrial stress and damage suggested that ExoU may also associate with mitochondria during infection. Indeed, ExoU phospholipase A2 enzymatic activity was present in enriched mitochondria and mitochondrion-associated membrane fractions isolated from P. aeruginosa-infected BMDMs. Intriguingly, enriched mitochondria and mitochondrion-associated membrane fractions isolated from infected Nlrc4 homozygous knockout BMDMs displayed significantly lower levels of ExoU enzyme activity, suggesting that NLRC4 plays a role in the ExoU-mitochondrion association. These observations prompted us to assay enriched mitochondria and mitochondrion-associated membrane fractions for NLRC4, caspase-1, and IL-1β. NLRC4 and pro-caspase-1 were detected in enriched mitochondria and mitochondrion-associated membrane fractions isolated from noninfected BMDMs, and active caspase-1 and active IL-1β were detected in response to P. aeruginosa infection. Interestingly, ExoU inhibited mitochondrion-associated caspase-1 and IL-1β activation. The implications of ExoU-mediated effects on mitochondria and the NLRC4 inflammasome during P. aeruginosa infection are discussed.

An alternative downstream translation start site in the non-TIR adaptor Scimp enables selective amplification of CpG DNA responses in mouse macrophages

Toll-like receptor (TLR) signaling relies on Toll/interleukin-1 receptor homology (TIR) domain-containing adaptor proteins that recruit downstream signaling molecules to generate tailored immune responses. In addition, the palmitoylated transmembrane adaptor protein family member Scimp acts as a non-TIR-containing adaptor protein in macrophages, scaffolding the Src family kinase Lyn to enable TLR phosphorylation and proinflammatory signaling responses. Here we report the existence of a smaller, naturally occurring translational variant of Scimp (Scimp TV1), which is generated through leaky scanning and translation at a downstream methionine. Scimp TV1 also scaffolds Lyn, but in contrast to full-length Scimp, it is basally rather than lipopolysaccharide (LPS)-inducibly phosphorylated. Macrophages from mice that selectively express Scimp TV1, but not full-length Scimp, have impaired sustained LPS-inducible cytokine responses. Furthermore, in granulocyte macrophage colony-stimulating factor-derived myeloid cells that express high levels of Scimp, selective overexpression of Scimp TV1 enhances CpG DNA-inducible cytokine production. Unlike full-length Scimp that localizes to the cell surface and filopodia, Scimp TV1 accumulates in intracellular compartments, particularly the Golgi. Moreover, this variant of Scimp is not inducibly phosphorylated in response to CpG DNA, suggesting that it may act via an indirect mechanism to enhance TLR9 responses. Our findings thus reveal the use of alternative translation start sites as a previously unrecognized mechanism for diversifying TLR responses in the innate immune system.

Regulation of the immune response to contact sensitizers by Nrf2

The skin is frequently exposed to chemical stress by organic chemicals or metal ions that can directly or indirectly challenge its immune components and may lead to T cell-mediated delayed type hypersensitivity reactions. The disruption of the skin's homeostasis by exposure to contact sensitizers can trigger an inflammatory immune response that results in eczema and allergic contact dermatitis. The recognition of these chemicals depends on Pattern Recognition Receptors expression on sentinel skin cells, mainly the innate resident immune cells orchestrating the skin's immune response and involving both oxidative and inflammatory pathways. The main driver of these both pathways is the Nrf2/Keap1 pathway, a major ubiquitous regulator of cellular oxidative and electrophilic stress, activated in various innate immune cells of the skin, including keratinocytes and epidermal Langerhans cells in the epidermis and dermal dendritic cells in the dermis. Nrf2 also shows a strong protective capacity by down-regulating inflammatory pathways. In this review, the important role of Nrf2 in the regulation of the immune response to contact sensitizers will be discussed and highlighted. This article is protected by copyright. All rights reserved.