Neutrophil migration in infection and wound repair: going forward in reverse

Cellular and Molecular Events of Wound Healing and the Potential of Silver Based Nanoformulations as Wound Healing Agents

Chronic wounds are a silent epidemic threatening the lives of many people worldwide. They are associated with social, health care and economic burdens and can lead to death if left untreated. The treatment of chronic wounds is very challenging as it may not be fully effective and may be associated with various adverse effects. New wound healing agents that are potentially more effective are being discovered continuously to combat these chronic wounds. These agents include silver nanoformulations which can contain nanoparticles or nanocomposites. To be effective, the discovered agents need to have good wound healing properties which will enhance their effectiveness in the different stages of wound healing. This review will focus on the process of wound healing and describe the properties of silver nanoformulations that contribute to wound healing.

Innate Immune Responses to Sporothrix schenckii: Recognition and Elimination

Sporothrix schenckii (S. schenckii), a ubiquitous thermally dimorphic fungus, is the etiological agent of sporotrichosis, affecting immunocompromised and immunocompetent individuals. Despite current antifungal regimens, sporotrichosis results in prolonged treatment and significant mortality rates in the immunosuppressed population. The innate immune system forms the host's first and primary line of defense against S. schenckii, which has a bi-layered cell wall structure. Many components act as pathogen-associated molecular patterns (PAMPs) in pathogen-host interactions. PAMPs are recognized by pattern recognition receptors (PRRs) such as toll-like receptors, C-type lectin receptors, and complement receptors, triggering innate immune cells such as neutrophils, macrophages, and dendritic cells to phagocytize or produce mediators, contributing to S. schenckii elimination. The ultrastructure of S. schenckii and pathogen-host interactions, including PRRs and innate immune cells, are summarized in this review, promoting a better understanding of the innate immune response to S. schenckii and aiding in the development of protective and therapeutic strategies to combat sporotrichosis.

Metabolic regulation of type 2 immune response during tissue repair and regeneration

Type 2 immune responses are mediated by the cytokines interleukin (IL)-4, IL-5, IL-10, and IL-13 and associated cell types, including T helper (Th)2 cells, group 2 innate lymphoid cells (ILC2s), basophils, mast cells, eosinophils, and IL-4- and IL-13-activated macrophages. It can suppress type 1-driven autoimmune diseases, promote antihelminth immunity, maintain cellular metabolic homeostasis, and modulate tissue repair pathways following injury. However, when type 2 immune responses become dysregulated, they can be a significant pathogenesis of many allergic and fibrotic diseases. As such, there is an intense interest in studying the pathways that modulate type 2 immune response so as to identify strategies of targeting and controlling these responses for tissue healing. Herein, we review recent literature on the metabolic regulation of immune cells initiating type 2 immunity and immune cells involved in the effector phase, and talk about how metabolic regulation of immune cell subsets contribute to tissue repair. At last, we discuss whether these findings can provide a novel prospect for regenerative medicine.

Suppression of innate immunity by the vaccinia virus protein N1 promotes skin microbiota expansion and increased immune infiltration following vaccination

Vaccinia virus (VACV) protein N1 is an intracellular immunomodulator that contributes to virus virulence via inhibition of NF-κB. Intradermal infection with a VACV lacking gene N1L (vΔN1) results in smaller skin lesions than infection with wild-type virus (WT VACV), but the impact of N1 deletion on the local microbiota as well as the innate and cellular immune responses in infected ear tissue is mostly uncharacterized. Here, we analysed the bacterial burden and host immune response at the site of infection and report that the presence of protein N1 correlated with enhanced expansion of skin microbiota, even before lesion development. Furthermore, early after infection (days 1-3), prior to lesion development, the levels of inflammatory mediators were higher in vΔN1-infected tissue compared to WT VACV infection. In contrast, infiltration of ear tissue with myeloid and lymphoid cells was greater after WT VACV infection and there was significantly greater secondary bacterial infection that correlated with greater lesion size. We conclude that a more robust innate immune response to vΔN1 infection leads to better control of virus replication, less bacterial growth and hence an overall reduction of tissue damage and lesion size. This analysis shows the potent impact of a single viral immunomodulator on the host immune response and the pathophysiology of VACV infection in the skin.

Distinct stimulus-dependent neutrophil dynamics revealed by real-time imaging of intestinal mucosa after acute injury

Clinical symptoms in many inflammatory diseases of the intestine are directly related to neutrophil (PMN) migration across colonic mucosa and into the intestinal lumen, yet in-vivo studies detailing this process are lacking. Using real-time intravital microscopy and a new distal colon loop model, we report distinct PMN migratory dynamics in response to several models of acute colonic injury. PMNs exhibited rapid swarming responses after mechanically induced intestinal wounds. Similar numbers of PMNs infiltrated colonic mucosa after wounding in germ-free mice, suggesting microbiota-independent mechanisms. By contrast, acute mucosal injury secondary to either a treatment of mice with dextran sodium sulfate or an IL-10 receptor blockade model of colitis resulted in lamina propria infiltration with PMNs that were largely immotile. Biopsy wounding of colonic mucosa in DSS-treated mice did not result in enhanced PMN swarming however, intraluminal application of the neutrophil chemoattractant LTB₄ under such conditions resulted in enhanced transepithelial migration of PMNs. Analyses of PMNs that had migrated into the colonic lumen revealed that the majority of PMNs were directly recruited from the circulation and not from the immotile pool in the mucosa. Decreased PMN motility parallels upregulation of the receptor CXCR4 and apoptosis. Similarly, increased expression of CXCR4 on human PMNs was observed in colonic biopsies from people with active ulcerative colitis. This new approach adds an important tool to investigate mechanisms regulating PMN migration across mucosa within the distal intestine and will provide new insights for developing future anti-inflammatory and pro-repair therapies.

Micro-Nanocarriers Based Drug Delivery Technology for Blood-Brain Barrier Crossing and Brain Tumor Targeting Therapy

The greatest obstacle to using drugs to treat brain tumors is the blood-brain barrier (BBB), making it difficult for conventional drug molecules to enter the brain. Therefore, how to safely and effectively penetrate the BBB to achieve targeted drug delivery to brain tumors has been a challenging research problem. With the intensive research in micro- and nanotechnology in recent years, nano drug-targeted delivery technologies have shown great potential to overcome this challenge, such as inorganic nanocarriers, organic polymer-carriers, liposomes, and biobased carriers, which can be designed in different sizes, shapes, and surface functional groups to enhance their ability to penetrate the BBB and targeted drug delivery for brain tumors. In this review, the composition and overcoming patterns of the BBB are detailed, and then the hot research topics of drug delivery carriers for brain tumors in recent years are summarized, and their mechanisms of action on the BBB and the factors affecting drug delivery are described in detail, and the effectiveness of targeted therapy for brain tumors is evaluated. Finally, the challenges and dilemmas in developing brain tumor drug delivery systems are discussed, which will be promising in the future for targeted drug delivery to brain tumors based on micro-nanocarriers technology.

Autoimmunity, cancer and COVID-19 abnormally activate wound healing pathways: critical role of inflammation

Recent evidence indicates that targeting IL-6 provides broad therapeutic approaches to several diseases. In patients with cancer, autoimmune diseases, severe respiratory infections [e.g. coronavirus disease 2019 (COVID-19)] and wound healing, IL-6 plays a critical role in modulating the systemic and local microenvironment. Elevated serum levels of IL-6 interfere with the systemic immune response and are associated with disease progression and prognosis. As already noted, monoclonal antibodies blocking either IL-6 or binding of IL-6 to receptors have been used/tested successfully in the treatment of rheumatoid arthritis, many cancer types, and COVID-19. Therefore, in the present review, we compare the impact of IL-6 and anti-IL-6 therapy to demonstrate common (pathological) features of the studied diseases such as formation of granulation tissue with the presence of myofibroblasts and deposition of new extracellular matrix. We also discuss abnormal activation of other wound-healing-related pathways that have been implicated in autoimmune disorders, cancer or COVID-19.

Surgery-mediated tumor-promoting effects on the immune microenvironment

Surgical resection continues to be the mainstay treatment for solid cancers even though chemotherapy and immunotherapy have significantly improved patient overall survival and progression-free survival. Numerous studies have shown that surgery induces the dissemination of circulating tumor cells (CTCs) and that the resultant inflammatory response promotes occult tumor growth and the metastatic process by forming a supportive tumor microenvironment (TME). Surgery-induced platelet activation is one of the initial responses to a wound and the formation of fibrin clots can provide the scaffold for recruited inflammatory cells. Activated platelets can also shield CTCs to protect them from blood shear forces and promote CTCs evasion of immune destruction. Similarly, neutrophils are recruited to the fibrin clot and enhance cancer metastatic dissemination and progression by forming neutrophil extracellular traps (NETs). Activated macrophages are also recruited to surgical sites to facilitate the metastatic spread. More importantly, the body's response to surgical insult results in the recruitment and expansion of immunosuppressive cell populations (i.e. myeloid-derived suppressor cells and regulatory T cells) and in the suppression of natural killer (NK) cells that contribute to postoperative cancer recurrence and metastasis. In this review, we seek to provide an overview of the pro-tumorigenic mechanisms resulting from surgery's impact on these cells in the TME. Further understanding of these events will allow for the development of perioperative therapeutic strategies to prevent surgery-associated metastasis.

Helicobacter pylori-infected human neutrophils exhibit impaired chemotaxis and a uropod retraction defect

Helicobacter pylori is a major human pathogen that colonizes the gastric mucosa and plays a causative role in development of peptic ulcers and gastric cancer. Neutrophils are heavily infected with this organism in vivo and play a prominent role in tissue destruction and disease. Recently, we demonstrated that H. pylori exploits neutrophil plasticity as part of its virulence strategy eliciting N1-like subtype differentiation that is notable for profound nuclear hypersegmentation. We undertook this study to test the hypothesis that hypersegmentation may enhance neutrophil migratory capacity. However, EZ-TAXIScan™ video imaging revealed a previously unappreciated and progressive chemotaxis defect that was apparent prior to hypersegmentation onset. Cell speed and directionality were significantly impaired to fMLF as well as C5a and IL-8. Infected cells oriented normally in chemotactic gradients, but speed and direction were impaired because of a uropod retraction defect that led to cell elongation, nuclear lobe trapping in the contracted rear and progressive narrowing of the leading edge. In contrast, chemotactic receptor abundance, adhesion, phagocytosis and other aspects of cell function were unchanged. At the molecular level, H. pylori phenocopied the effects of Blebbistatin as indicated by aberrant accumulation of F-actin and actin spikes at the uropod together with enhanced ROCKII-mediated phosphorylation of myosin IIA regulatory light chains at S19. At the same time, RhoA and ROCKII disappeared from the cell rear and accumulated at the leading edge whereas myosin IIA was enriched at both cell poles. These data suggest that H. pylori inhibits the dynamic changes in myosin IIA contractility and front-to-back polarity that are essential for chemotaxis. Taken together, our data advance understanding of PMN plasticity and H. pylori pathogenesis.

Mechanotransduction in skin wound healing and scar formation: Potential therapeutic targets for controlling hypertrophic scarring

Hypertrophic scarring (HTS) is a major source of morbidity after cutaneous injury. Recent studies indicate that mechanical force significantly impacts wound healing and skin regeneration which opens up a new direction to combat scarring. Hence, a thorough understanding of the underlying mechanisms is essential in the development of efficacious scar therapeutics. This review provides an overview of the current understanding of the mechanotransduction signaling pathways in scar formation and some strategies that offload mechanical forces in the wounded region for scar prevention and treatment.

In vitro neutrophil migration is associated with inhaled corticosteroid treatment and serum cytokines in pediatric asthma

Background: Different asthma phenotypes are driven by molecular endotypes. A Th1-high phenotype is linked to severe, therapy-refractory asthma, subclinical infections and neutrophil inflammation. Previously, we found neutrophil granulocytes (NGs) from asthmatics exhibit decreased chemotaxis towards leukotriene B4 (LTB₄), a chemoattractant involved in inflammation response. We hypothesized that this pattern is driven by asthma in general and aggravated in a Th1-high phenotype.

Methods: NGs from asthmatic nd healthy children were stimulated with 10 nM LTB₄/100 nM N-formylmethionine-leucyl-phenylalanine and neutrophil migration was documented following our prior SiMA (simplified migration assay) workflow, capturing morphologic and dynamic parameters from single-cell tracking in the images. Demographic, clinical and serum cytokine data were determined in the ALLIANCE cohort.

Results: A reduced chemotactic response towards LTB₄ was confirmed in asthmatic donors regardless of inhaled corticosteroid (ICS) treatment. By contrast, only NGs from ICS-treated asthmatic children migrate similarly to controls with the exception of Th1-high donors, whose NGs presented a reduced and less directed migration towards the chemokines. ICS-treated and Th1-high asthmatic donors present an altered surface receptor profile, which partly correlates with migration.

Conclusions: Neutrophil migration in vitro may be affected by ICS-therapy or a Th1-high phenotype. This may be explained by alteration of receptor expression and could be used as a tool to monitor asthma treatment.

Neutrophils in Intestinal Inflammation: What We Know and What We Could Expect for the Near Future

Neutrophils are short-lived cells that play a crucial role in inflammation. As in other tissues, these polymorphonuclear phagocytes are involved in the intestinal inflammatory response, on the one hand, contributing to the activation and recruitment of other immune cells, but on the other hand, facilitating intestinal mucosa repair by releasing mediators that aid in the resolution of inflammation. Even though these responses are helpful in physiological conditions, excessive recruitment of activated neutrophils in the gut correlates with increased mucosal damage and severe symptoms in patients with inflammatory bowel disease (IBD) and pre-clinical models of colitis. Thus, there is growing interest in controlling their biology to generate novel therapeutic approaches capable of reducing exacerbated intestinal inflammation. However, the beneficial and harmful effects of neutrophils on intestinal inflammation are still controversial. With this review, we summarise and discuss the most updated literature showing how neutrophils (and neutrophil extracellular traps) contribute to developing and resolving intestinal inflammation and their putative use as therapeutic targets.

A Host-Directed Approach to the Detection of Infection in Hard-to-Heal Wounds

Wound infection is traditionally defined primarily by visual clinical signs, and secondarily by microbiological analysis of wound samples. However, these approaches have serious limitations in determining wound infection status, particularly in early phases or complex, chronic, hard-to-heal wounds. Early or predictive patient-derived biomarkers of wound infection would enable more timely and appropriate intervention. The observation that immune activation is one of the earliest responses to pathogen activity suggests that immune markers may indicate wound infection earlier and more reliably than by investigating potential pathogens themselves. One of the earliest immune responses is that of the innate immune cells (neutrophils) that are recruited to sites of infection by signals associated with cell damage. During acute infection, the neutrophils produce oxygen radicals and enzymes that either directly or indirectly destroy invading pathogens. These granular enzymes vary with cell type but include elastase, myeloperoxidase, lysozyme, and cathepsin G. Various clinical studies have demonstrated that collectively, these enzymes, are sensitive and reliable markers of both early-onset phases and established infections. The detection of innate immune cell enzymes in hard-to-heal wounds at point of care offers a new, simple, and effective approach to determining wound infection status and may offer significant advantages over uncertainties associated with clinical judgement, and the questionable value of wound microbiology. Additionally, by facilitating the detection of early wound infection, prompt, local wound hygiene interventions will likely enhance infection resolution and wound healing, reduce the requirement for systemic antibiotic therapy, and support antimicrobial stewardship initiatives in wound care.

The potential of functionalized dressing releasing flavonoids facilitates scar-free healing

Scars are pathological marks left after an injury heals that inflict physical and psychological harm, especially the great threat to development and aesthetics posed by oral and maxillofacial scars. The differential expression of genes such as transforming growth factor-β, local adherent plaque kinase, and yes-related transcriptional regulators at infancy or the oral mucosa is thought to be the reason of scarless regenerative capacity after tissue defects. Currently, tissue engineering products for defect repair frequently overlook the management of postoperative scars, and inhibitors of important genes alone have negative consequences for the organism. Natural flavonoids have hemostatic, anti-inflammatory, antioxidant, and antibacterial properties, which promote wound healing and have anti-scar properties by interfering with the transmission of key signaling pathways involved in scar formation. The combination of flavonoid-rich drug dressings provides a platform for clinical translation of compounds that aid in drug disintegration, prolonged release, and targeted delivery. Therefore, we present a review of the mechanisms and effects of flavonoids in promoting scar-free regeneration and the application of flavonoid-laden dressings.

Evaluating polymeric biomaterials to improve next generation wound dressing design

Wound healing is a dynamic series of interconnected events with the ultimate goal of promoting neotissue formation and restoration of anatomical function. Yet, the complexity of wound healing can often result in development of complex, chronic wounds, which currently results in a significant strain and burden to our healthcare system. The advancement of new and effective wound care therapies remains a critical issue, with the current therapeutic modalities often remaining inadequate. Notably, the field of tissue engineering has grown significantly in the last several years, in part, due to the diverse properties and applications of polymeric biomaterials. The interdisciplinary cohesion of the chemical, biological, physical, and material sciences is pertinent to advancing our current understanding of biomaterials and generating new wound care modalities. However, there is still room for closing the gap between the clinical and material science realms in order to more effectively develop novel wound care therapies that aid in the treatment of complex wounds. Thus, in this review, we discuss key material science principles in the context of polymeric biomaterials, provide a clinical breadth to discuss how these properties affect wound dressing design, and the role of polymeric biomaterials in the innovation and design of the next generation of wound dressings.

The clinical relevance of neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio in chronic obstructive pulmonary disease with lung cancer

Background

Chronic obstructive pulmonary disease (COPD) coexisting with lung cancer is associated with severe mortality and a worse prognosis. Inflammation plays an important role in common pathogenic pathways and disease progression. However, a few studies have identified the clinical value of the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in COPD with lung cancer, which are systemic inflammatory response markers in the blood. This study aimed to determine the association of the NLR or PLR with clinical characteristics and whether NLR or PLR can be diagnostic markers for COPD with lung cancer.

Methods

Between 2015 and 2021, we conducted a retrospective analysis of 236 COPD patients with lung cancer and 500 patients without lung cancer (control group). Clinical information, blood routine examination, and spirometry results were collected and analyzed. The receiver operating characteristic (ROC) curve was used to identify the best cutoff point of NLR or PLR. Multivariate logistic regression analysis was performed to evaluate the association of NLR or PLR with the diagnosis and prognosis of COPD with lung cancer.

Results

Compared to patients in the COPD-only group, patients in the lung cancer group had a higher percentage of current smoking and emphysema, and it was found that NLR or PLR was significantly higher in the lung cancer group. Multivariate analysis showed that age, smoking status, FEV1%pred, emphysema, NLR, and PLR were independent risk factors for lung cancer development in COPD. Furthermore, the high level of NLR or PLR was associated with age over 70 years old, current smoking status, and ineligible surgery treatment. The level of PLR or NLR markedly increased with hypercoagulation status, the severity of airflow limitation, and advanced progression of lung cancer. Additionally, the ROC analysis also revealed that elevated NLR or PLR was an independent predictor of COPD in lung cancer patients, TNM stages IIIB–IV at first diagnosis in lung cancer, and ineligible surgery in lung cancer patients.

Conclusion

Increased NLR or PLR values might be an important and easily measurable inflammation biomarker to predict the diagnosis and severity of lung cancer with COPD.

CXC Chemokines in the Pathogenesis of Pulmonary Disease and Pharmacological Relevance

Chemokines and their receptors play important roles in the pathophysiology of many diseases by regulating the cellular migration of major inflammatory and immune players. The CXC motif chemokine subfamily is the second largest family, and it is further subdivided into ELR motif CXC (ELR+) and non-ELR motif (ELR-) CXC chemokines, which are effective chemoattractants for neutrophils and lymphocytes/monocytes, respectively. These chemokines and their receptors are expected to have a significant impact on a wide range of lung diseases, many of which have inflammatory or immunological underpinnings. As a result, manipulations of this subfamily of chemokines and their receptors using small molecular agents and other means have been explored for potential therapeutic benefit in the setting of several lung pathologies. Furthermore, encouraging preclinical data has necessitated the progression of a few of these drugs into clinical trials in order to make the most effective use of interventions in the development of viable targeted therapeutics. The current review presents the understanding of the roles of CXC ligands (CXCLs) and their cognate receptors (CXCRs) in the pathogenesis of several lung diseases such as allergic rhinitis, COPD, lung fibrosis, lung cancer, pneumonia, and tuberculosis. The potential therapeutic benefits of pharmacological or other CXCL/CXCR axis manipulations are also discussed.

Development of a standardized and validated flow cytometry approach for monitoring of innate myeloid immune cells in human blood

Innate myeloid cell (IMC) populations form an essential part of innate immunity. Flow cytometric (FCM) monitoring of IMCs in peripheral blood (PB) has great clinical potential for disease monitoring due to their role in maintenance of tissue homeostasis and ability to sense micro-environmental changes, such as inflammatory processes and tissue damage. However, the lack of standardized and validated approaches has hampered broad clinical implementation. For accurate identification and separation of IMC populations, 62 antibodies against 44 different proteins were evaluated. In multiple rounds of EuroFlow-based design-testing-evaluation-redesign, finally 16 antibodies were selected for their non-redundancy and separation power. Accordingly, two antibody combinations were designed for fast, sensitive, and reproducible FCM monitoring of IMC populations in PB in clinical settings (11-color; 13 antibodies) and translational research (14-color; 16 antibodies). Performance of pre-analytical and analytical variables among different instruments, together with optimized post-analytical data analysis and reference values were assessed. Overall, 265 blood samples were used for design and validation of the antibody combinations and in vitro functional assays, as well as for assessing the impact of sample preparation procedures and conditions. The two (11- and 14-color) antibody combinations allowed for robust and sensitive detection of 19 and 23 IMC populations, respectively. Highly reproducible identification and enumeration of IMC populations was achieved, independently of anticoagulant, type of FCM instrument and center, particularly when database/software-guided automated (vs. manual “expert-based”) gating was used. Whereas no significant changes were observed in identification of IMC populations for up to 24h delayed sample processing, a significant impact was observed in their absolute counts after >12h delay. Therefore, accurate identification and quantitation of IMC populations requires sample processing on the same day. Significantly different counts were observed in PB for multiple IMC populations according to age and sex. Consequently, PB samples from 116 healthy donors (8-69 years) were used for collecting age and sex related reference values for all IMC populations. In summary, the two antibody combinations and FCM approach allow for rapid, standardized, automated and reproducible identification of 19 and 23 IMC populations in PB, suited for monitoring of innate immune responses in clinical and translational research settings.

Transcriptomics of circulating neutrophils in dairy cows with subclinical hypocalcemia

Hypocalcemia is closely associated with inflammatory diseases in dairy cows. Recent research has underscored the key role of calcium in the adaptations of the innate immune system during this period. The main objective in the present study was to compare the transcriptome profiles and analyze differences in the expression of neutrophil (PMNL) immune function-related genes and calcium binding-related genes in hypocalcemic cows. At 2 days postpartum, a concentration >2.10 mmol Ca2+/L was used to classify cows as controls (CON), and a concentration <2.00 mmol Ca2+/L used to classify cows as low-calcium (LCAL) (n = 8 in each group). A routine medical examination was conducted by the attending veterinarian to ensure there were no other complications and that the blood β-hydroxybutyrate was <1.2 mmol/L. Blood was collected from the tail vein (20 mL) to isolate PMNL, and 5 cows in each group were used for RNA sequencing and statistical analysis of gene expression differences. Transcriptome RNA-seq sequencing analysis was via omicsstudio using the R package edgeR. GO and KEGG enrichment analysis were used for bioinformatics. The remaining 3 cows in each group were used for validation of RNA sequencing data via quantitative PCR, which confirmed the observed responses. Compared with CON, 158 genes in LCAL were significantly up-regulated and 296 genes were down-regulated. The downregulation of Interleukin-12 (CXCL12), Tubulin beta chain (TUBB1), L1 cell adhesion molecule (L1CAM), and Myeloperoxidase (MPO) indicated a decrease in immune function of PMNL in LCAL cows. The decreased expression of calcium-binding pathway-related genes in PMNL of LCAL cows indicated a decrease in immune function of PMNL likely related to calcium ions. For example, cartilage acid protein 1 (CRTAC1) and calcium/calmodulin-dependent kinase 4 (CAMK4) were significantly reduced in LCAL cows. The upregulation of Cyclin dependent kinase inhibitor 1A (CDKN1A), Perforin 1 (PRF1), and Homeodomain interacting protein kinase 3 (HIPK3) indicated that LCAL led to greater cell apoptosis and senescence. Overall, the analyses indicated that the reduction in PMNL immune function during hypocalcemia is associated with downregulation of intracellular Ca2+ related genes and upregulation of genes controlling apoptosis and senescence. Together, these alterations contribute to an immunosuppressive state during the transition period.

A New Product of Bilirubin Degradation by H2O2 and Its Formation in Activated Neutrophils and in an Inflammatory Mouse Model

Bilirubin (BR) is a tetrapyrrolic compound stemming from heme catabolism with diverse physiological functions. It can be oxidized by H₂O₂ to form several degradation products, some of which have been detected in vivo and may contribute to the pathogenesis of certain diseases. However, the oxidative degradation of BR is complex and the conditions that BR degradation occurs pathophysiologically remain obscure. Neutrophils are known to generate large amounts of reactive oxygen species, including H₂O₂, upon activation and they are mobilized to inflammatory sites; therefore, we hypothesized that activated neutrophils could cause BR degradation, which could occur at inflammatory sites. In the present study, we investigated BR degradation by H₂O₂ and identified hematinic acid (BHP1) and a new product BHP2, whose structure was characterized as 2,5-diformyl-4-methyl-1H-pyrrole-3-propanoic acid. An LC-MS/MS method for the quantitation of the two compounds was then established. Using the LC-MS/MS method, we observed the concentration-dependent formation of BHP1 and BHP2 in mouse neutrophils incubated with 10 and 30 μM of BR with the yields being 16 ± 3.2 and 31 ± 5.9 pmol/10⁶ cells for BHP1, and 25 ± 4.4 and 71 ± 26 pmol/10⁶ cells for BHP2, respectively. After adding phorbol 12-myristate 13-acetate, a neutrophil agonist, to 30 μM of BR-treated cells, the BHP1 yield increased to 43 ± 6.6 pmol/10⁶ cells, whereas the BHP2 one decreased to 47 ± 9.2 pmol/10⁶ cells. The two products were also detected in hemorrhagic skins of mice with dermal inflammation and hemorrhage at levels of 4.5 ± 1.9 and 0.18 ± 0.10 nmol/g tissue, respectively, which were significantly higher than those in the non-hemorrhagic skins. BHP2 was neurotoxic starting at 0.10 μM but BHP1 was not, as assessed using Caenorhabditis elegans as the animal model. Neutrophil-mediated BR degradation may be a universally pathophysiological process in inflammation and can be particularly important under pathological conditions concerning hemorrhage.

TREM-1 is required for enhanced OpZ-induced superoxide generation following priming

Inflammatory agents, microbial products, or stromal factors pre-activate or prime neutrophils to respond to activating stimuli in a rapid and aggressive manner. Primed neutrophils exhibit enhanced chemotaxis, phagocytosis, and respiratory burst when stimulated by secondary activating stimuli. We previously reported that Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) mediates neutrophil effector functions such as increased superoxide generation, transepithelial migration, and chemotaxis. However, it is unclear whether TREM-1 is required for the process of priming itself or for primed responses to subsequent stimulation. To investigate this, we utilized in vitro and in vivo differentiated neutrophils that were primed with TNF-α and then stimulated with the particulate agonist, opsonized zymosan (OpZ). Bone marrow progenitors isolated from WT and Trem-1-/- mice were transduced with estrogen regulated Homeobox8 (ER-Hoxb8) fusion transcription factor and differentiated in vitro into neutrophils following estrogen depletion. The resulting neutrophils expressed high levels of TREM-1 and resembled mature in vivo differentiated neutrophils. The effects of priming on phagocytosis and oxidative burst were determined. Phagocytosis did not require TREM-1 and was not altered by priming. In contrast, priming significantly enhanced OpZ-induced oxygen consumption and superoxide production in WT but not Trem-1-/- neutrophils indicating that TREM-1 is required for primed oxidative burst. TREM-1-dependent effects were not mediated during the process of priming itself as priming enhanced degranulation, ICAM-1 shedding, and IL-1ß release to the same extent in WT and Trem-1-/- neutrophils. Thus, TREM-1 plays a critical role in primed phagocytic respiratory burst and mediates its effects following priming.

Usage of Nanoparticles to Alter Neutrophils' Function for Therapy

Neutrophils, the most abundant white blood cells in the human body, are important immune cells responsible for the innate immune response. Neutrophils can migrate to inflammatory areas, such as tumor sites and infection sites, because of chemotaxis. Neutrophil-based nanomaterials, such as neutrophil-nanomaterial composites and neutrophil membrane-based nanomaterials, can help the drug or imaging agent gather in the inflammatory area with the help of chemotaxis. In addition, some nanomaterials can interfere with the function of neutrophils to treat tissue damage caused by excessive local accumulation of neutrophils. This review focuses on the interaction between nanomaterials and neutrophils as well as the applications of neutrophil-based nanomaterials and neutrophil-interfering nanomaterials.

Unique characteristics of lung-resident neutrophils are maintained by PGE2/PKA/Tgm2-mediated signaling

Lung-resident neutrophils need to be tightly regulated to avoid degranulation- and cytokine-associated damage to fragile alveolar structures that can lead to fatal outcomes. Here we show that lung neutrophils (LNs) express distinct surface proteins and genes that distinguish LNs from bone marrow and blood neutrophils. Functionally, LNs show impaired migratory activity toward chemoattractants and produce high levels of interleukin-6 (IL-6) at steady state and low levels of tumor necrosis factor-α in response to lipopolysaccharide (LPS) challenge. Treating bone marrow neutrophils with bronchoalveolar lavage fluid or prostaglandin E2 induces LN-associated characteristics, including the expression of transglutaminase 2 (Tgm2) and reduced production of inflammatory cytokines upon LPS challenge. Neutrophils from Tgm2-/- mice release high levels of inflammatory cytokines in response to LPS. Lung damage is significantly exacerbated in Tgm2-/- mice in an LPS-induced acute respiratory distress syndrome model. Collectively, we demonstrate that prostaglandin E2 is a key factor for the generation of LNs with unique immune suppressive characteristics, acting through protein kinase A and Tgm2, and LNs play essential roles in protection of the lungs against pathogenic inflammation.

Link of sorafenib resistance with the tumor microenvironment in hepatocellular carcinoma: Mechanistic insights

Sorafenib, a multi-kinase inhibitor with antiangiogenic, antiproliferative, and proapoptotic properties, is the first-line treatment for patients with late-stage hepatocellular carcinoma (HCC). However, the therapeutic effect remains limited due to sorafenib resistance. Only about 30% of HCC patients respond well to the treatment, and the resistance almost inevitably happens within 6 months. Thus, it is critical to elucidate the underlying mechanisms and identify effective approaches to improve the therapeutic outcome. According to recent studies, tumor microenvironment (TME) and immune escape play critical roles in tumor occurrence, metastasis and anti-cancer drug resistance. The relevant mechanisms were focusing on hypoxia, tumor-associated immune-suppressive cells, and immunosuppressive molecules. In this review, we focus on sorafenib resistance and its relationship with liver cancer immune microenvironment, highlighting the importance of breaking sorafenib resistance in HCC.

Inflammation-mediated matrix remodeling of extracellular matrix-mimicking biomaterials in tissue engineering and regenerative medicine

Extracellular matrix (ECM)-mimicking biomaterials are considered effective tissue-engineered scaffolds for regenerative medicine because of their biocompatibility, biodegradability, and bioactivity. ECM-mimicking biomaterials preserve natural microstructures and matrix-related bioactive components and undergo continuous matrix remodeling upon transplantation. The interaction between host immune cells and transplanted ECM-mimicking biomaterials has attracted considerable attention in recent years. Transplantation of biomaterials may initiate injuries and early pro-inflammation reactions characterized by infiltration of neutrophils and M1 macrophages. Pro-inflammation reactions may lead to degradation of the transplanted biomaterial and drive the matrix into a fetal-like state. ECM degradation leads to the release of matrix-related bioactive components that act as signals for cell migration, proliferation, and differentiation. In late stages, pro-inflammatory cells fade away, and anti-inflammatory cells emerge, which involves macrophage polarization to the M2 phenotype and leukocyte activation to T helper 2 (Th2) cells. These anti-inflammatory cells interact with each other to facilitate matrix deposition and tissue reconstruction. Deposited ECM molecules serve as vital components of the mature tissue and influence tissue homeostasis. However, dysregulation of matrix remodeling results in several pathological conditions, such as aggressive inflammation, difficult healing, and non-functional fibrosis. In this review, we summarize the characteristics of inflammatory responses in matrix remodeling after transplantation of ECM-mimicking biomaterials. Additionally, we discuss the intrinsic linkages between matrix remodeling and tissue regeneration. STATEMENT OF SIGNIFICANCE: Extracellular matrix (ECM)-mimicking biomaterials are effectively used as scaffolds in tissue engineering and regenerative medicine. However, dysregulation of matrix remodeling can cause various pathological conditions. Here, the review describes the characteristics of inflammatory responses in matrix remodeling after transplantation of ECM-mimicking biomaterials. Additionally, we discuss the intrinsic linkages between matrix remodeling and tissue regeneration. We believe that understanding host immune responses to matrix remodeling of transplanted biomaterials is important for directing effective tissue regeneration of ECM-mimicking biomaterials. Considering the close relationship between immune response and matrix remodeling results, we highlight the need for studies of the effects of clinical characteristics on matrix remodeling of transplanted biomaterials.

NLRC3 deficiency promotes cutaneous wound healing due to the inhibition of p53 signaling

Cutaneous wound healing is a complicated process that is characterized by an initial inflammatory phase followed by a proliferative phase. NLRC3 plays important roles in innate immunity, inflammatory regulation and tumor cell growth. However, the function of NLRC3 in wound healing remains unclear. Here, we investigated the function of NLRC3 in acute cutaneous wound healing using Nlrc3 gene knockout (Nlrc3^-/-) mice. Our results demonstrated that skin wound repair in Nlrc3^-/- mice was significantly accelerated compared with that in wild-type (WT) mice. NLRC3 deficiency promoted the inflammatory and proliferative phases in wounds enhanced the inflammatory response and increased re-epithelialization and granulation tissue formation, and these phenotypes were primarily ascribed to regulatory effects on p53 signaling. Mechanistically, we uncovered novel crosstalk between NLRC3 and p53 signaling and revealed that NLRC3 could mediate the ubiquitination and degradation of p53 in an Hsp90-dependent manner. In conclusion, our study suggests that NLRC3 is a critical negative regulator of the inflammatory response and cell proliferation during wound healing and that blocking NLRC3 may represent a potential approach for accelerating wound healing.

Macrophage Phenotypes in Normal and Diabetic Wound Healing and Therapeutic Interventions

Macrophage differentiation and polarization are essential players in the success of the wound-healing process. Acute simple wounds progress from inflammation to proliferation/regeneration and, finally, to remodeling. In injured skin, macrophages either reside in the epithelium or are recruited from monocytes. Their main role is supported by their plasticity, which allows them to adopt different phenotypic states, such as the M1-inflammatory state, in which they produce TNF and NO, and the M2-reparative state, in which they resolve inflammation and exhibit a reparative function. Reparative macrophages are an essential source of growth factors such as TGF-β and VEGF and are not found in nonhealing wounds. This review discusses the differences between macrophage phenotypes in vitro and in vivo, how macrophages originate, and how they cross-communicate with other cellular components in a wound. This review also highlights the dysregulation of macrophages that occurs in nonhealing versus overhealing wounds and fibrosis. Then, the therapeutic manipulation of macrophages is presented as an attractive strategy for promoting healing through the secretion of growth factors for angiogenesis, keratinocyte migration, and collagen production. Finally, Hoxa3 overexpression is discussed as an example of the therapeutic repolarization of macrophages to the normal maturation state and phenotype with better healing outcomes.

Distinct impact of IgG subclass on autoantibody pathogenicity in different IgG4-mediated diseases

IgG4 is the least potent human IgG subclass for the FcγR-mediated antibody effector function. Paradoxically, IgG4 is also the dominant IgG subclass of pathogenic autoantibodies in IgG4-mediated diseases. Here, we show that the IgG subclass and Fc-FcγR interaction have a distinct impact on the pathogenic function of autoantibodies in different IgG4-mediated diseases in mouse models. While IgG4 and its weak Fc-FcγR interaction have an ameliorative role in the pathogenicity of anti-ADAMTS13 autoantibodies isolated from thrombotic thrombocytopenic purpura (TTP) patients, they have an unexpected exacerbating effect on anti-Dsg1 autoantibody pathogenicity in pemphigus foliaceus (PF) models. Strikingly, a non-pathogenic anti-Dsg1 antibody variant optimized for FcγR-mediated effector function can attenuate the skin lesions induced by pathogenic anti-Dsg1 antibodies by promoting the clearance of dead keratinocytes. These studies suggest that IgG effector function contributes to the clearance of autoantibody-Ag complexes, which is harmful in TTP, but beneficial in PF and may provide new therapeutic opportunity.

IsoLGs (Isolevuglandins) Drive Neutrophil Migration in Hypertension and Are Essential for the Formation of Neutrophil Extracellular Traps

BACKGROUND

IsoLGs (isolevuglandins) are electrophilic products of lipid peroxidation formed in the presence of reactive oxygen species. IsoLGs contribute to hypertension by an unknown mechanism. Studies have shown that reactive oxygen species production drives the formation of neutrophil extracellular traps (NETs) and that NETs accumulate within the aorta and kidneys of patients with hypertension. The purpose of this study was to determine the role of isoLGs in neutrophil migration and NET formation (NETosis) in hypertension.

METHODS

Mice were treated with Ang II (angiotensin II) and the specific isoLG scavenger 2-hydroxybenzylamine and examined for tissue neutrophil and NET accumulation by single-cell sequencing and flow cytometry. Isolated human neutrophils were studied to determine the role of isoLGs in NETosis and neutrophil chromatin expansion by immunofluorescence and live cell confocal microscopy.

RESULTS

Single-cell sequencing performed on sham, Ang II, and Ang II+2-hydroxybenzylamine treated mice revealed neutrophils as a primary target of 2-hydroxybenzylamine. Peripheral neutrophil migration, aortic NET accumulation, and renal NET accumulation is blocked with 2-hydroxybenzylamine treatment. In isolated human neutrophils, isoLGs accumulate during NETosis and scavenging of isoLGs prevents NETosis. IsoLGs drive neutrophil chromatin expansion during NETosis and disrupt nucleosome structure.

CONCLUSIONS

These observations identified a critical role of isoLGs in neutrophil migration and NETosis in hypertension and provide a potential therapy for NET-associated diseases including hypertension and associated end organ damage.

Nanobiotechnology: Applications in Chronic Wound Healing

Wounds occur when skin integrity is broken and the skin is damaged. With progressive changes in the disease spectrum, the acute wounds caused by mechanical trauma have been become less common, while chronic wounds triggered with aging, diabetes and infection have become more frequent. Chronic wounds now affect more than 6 million people in the United States, amounting to 10 billion dollars in annual expenditure. However, the treatment of chronic wounds is associated with numerous challenges. Traditional remedies for chronic wounds include skin grafting, flap transplantation, negative-pressure wound therapy, and gauze dressing, all of which can cause tissue damage or activity limitations. Nanobiotechnology — which comprises a diverse array of technologies derived from engineering, chemistry, and biology — is now being applied in biomedical practice. Here, we review the design, application, and clinical trials for nanotechnology-based therapies for chronic wound healing, highlighting the clinical potential of nanobiotechnology in such treatments. By summarizing previous nanobiotechnology studies, we lay the foundation for future wound care via a nanotech-based multifunctional smart system.

Neutrophils in malaria: A double-edged sword role

Neutrophils are the most abundant leukocytes in human peripheral blood. They form the first line of defense against invading foreign pathogens and might play a crucial role in malaria. According to World Health Organization (WHO), malaria is a globally significant disease caused by protozoan parasites from the Plasmodium genus, and it’s responsible for 627,000 deaths in 2020. Neutrophils participate in the defense response against the malaria parasite via phagocytosis and reactive oxygen species (ROS) production. Neutrophils might also be involved in the pathogenesis of malaria by the release of toxic granules and the release of neutrophil extracellular traps (NETs). Intriguingly, malaria parasites inhibit the anti-microbial function of neutrophils, thus making malaria patients more susceptible to secondary opportunistic Salmonella infections. In this review, we will provide a summary of the role of neutrophils during malaria infection, some contradicting mouse model neutrophil data and neutrophil-related mechanisms involved in malaria patients’ susceptibility to bacterial infection.

Optically Manipulated Neutrophils as Native Microcrafts In Vivo

As the first line of host defense against invading pathogens, neutrophils have an inherent phagocytosis capability for the elimination of foreign agents and target loading upon activation, as well as the ability to transmigrate across blood vessels to the infected tissue, making them natural candidates to execute various medical tasks in vivo. However, most of the existing neutrophil-based strategies rely on their spontaneous chemotactic motion, lacking in effective activation, rapid migration, and high navigation precision. Here, we report an optically manipulated neutrophil microcraft in vivo through the organic integration of endogenous neutrophils and scanning optical tweezers, functioning as a native biological material and wireless remote controller, respectively. The neutrophil microcrafts can be remotely activated by light and then navigated to the target position along a designated route, followed by the fulfillment of its task in vivo, such as active intercellular connection, targeted delivery of nanomedicine, and precise elimination of cell debris, free from the extra construction or modification of the native neutrophils. On the basis of the innate immunologic function of neutrophils and intelligent optical manipulation, the proposed neutrophil microcraft might provide new insight for the construction of native medical microdevices for drug delivery and precise treatment of inflammatory diseases.

Infection With Escherichia Coli Pathotypes Is Associated With Biomarkers of Gut Enteropathy and Nutritional Status Among Malnourished Children in Bangladesh

Escherichia coli (E. coli) pathotypes are the most common cause of diarrhea, especially in developing countries. Environmental Enteric Dysfunction (EED) is presumed to be the result of infection with one or more pathotypes and can affect intestinal health and childhood growth. We sought to investigate the association of E. coli pathotypes infection with biomarkers of EED and nutritional status among slum-dwelling malnourished children in Bangladesh. This study comprised a total of 1050 stunted and at risk of stunting children. TaqMan Array Card assays were used to determine the presence of E. coli pathotypes in feces. Prevalence of infection with EAEC was highest (68.8%) in this cohort of children, followed by EPEC (55.9%), ETEC (44%), Shigella/EIEC (19.4%) and STEC (3.2%). The levels of myeloperoxidase and calprotectin were significantly higher in EAEC (P=0.02 and P=0.04), EPEC (P=0.02 and P=0.03) and Shigella/EIEC (P=0.05 and P=0.02) positive participants while, only calprotectin was significantly higher in ETEC (P=0.01) positive participants. Reg1B was significantly higher in participants with EAEC (P=0.004) while, neopterin levels were significantly lower in ETEC (P=0.003) and Shigella/EIEC (P=0.003) positive cases. A significant positive relationship was observed between EAEC and fecal levels of Reg1B (β = 0.28; 95% CI = 0.12, 0.43; p-value<0.001). Besides, ETEC was found to be positively and significantly associated with the levels of calprotectin (β = 0.14; 95 percent CI = 0.01, 0.26; p-value=0.037) and negatively with neopterin (β = -0.16; 95% CI = -0.30, -0.02; p-value=0.021). On the other hand, infection with EPEC was found to be negatively associated with length-for-age (β = -0.12; 95% CI = -0.22, -0.03; p-value=0.011) and weight-for-age (β = -0.11; 95% CI = -0.22, -0.01; p-value=0.037). The study findings suggest that infection with certain E. coli pathotypes (EAEC and ETEC) influences gut health and EPEC is associated with linear growth and underweight in Bangladeshi children.

The effect of reparixin on survival in patients at high risk for in-hospital mortality: a meta-analysis of randomized trials

Introduction

A great number of anti-inflammatory drugs have been suggested in the treatment of SARS-CoV-2 infection. Reparixin, a non-competitive allosteric inhibitor of the CXCL8 (IL-8) receptors C-X-C chemokine receptor type 1 (CXCR1) and C-X-C chemokine receptor type 2 (CXCR2), has already been tried out as a treatment in different critical settings. Due to the contrasting existing literature, we decided to perform the present meta-analysis of randomized controlled trials (RCTs) to investigate the effect of the use of reparixin on survival in patients at high risk for in-hospital mortality.

Methods

We created a search strategy to include any human RCTs performed with reparixin utilization in patients at high risk for in-hospital mortality, excluding oncological patients. Two trained, independent authors searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) for appropriate studies. Furthermore, references of review articles and included RCTs were screened to identify more studies. No language restrictions were enforced. To assess the risk of bias of included trials, the Revised Cochrane risk-of-bias tool for randomized trials (RoB 2) was used.

Results

Overall, six studies were included and involved 406 patients (220 received reparixin and 186 received the comparator). The all-cause mortality in the reparixin group was significantly lower than that in the control group [5/220 (2.3%) in the reparixin group vs. 12/186 (6.5%) in the control group, odds ratio = 0.33 (95% confidence interval 0.12 to 0.96), p-value for effect 0.04, p for heterogeneity 0.20, I2 = 36%]. In addition, no difference in the rate of pneumonia, sepsis, or non-serious infections was shown between the two groups.

Conclusion

Our meta-analysis of randomized trials suggests that short-term inhibition of CXCL8 activity improved survival in patients at high risk for in-hospital mortality without increasing the risk of infection.

Meta-analysis registration

PROSPERO, identifier CRD42021254467.

Endoplasmic reticulum stress in innate immune cells - a significant contribution to non-alcoholic fatty liver disease

Liver disease and its complications affect millions of people worldwide. NAFLD (non-alcoholic fatty liver disease) is the liver disease associated with metabolic dysfunction and consists of four stages: steatosis with or without mild inflammation (NAFLD), non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. With increased necroinflammation and progression of liver fibrosis, NAFLD may progress to cirrhosis or even hepatocellular carcinoma. Although the underlying mechanisms have not been clearly elucidated in detail, what is clear is that complex immune responses are involved in the pathogenesis of NASH, activation of the innate immune system is critically involved in triggering and amplifying hepatic inflammation and fibrosis in NAFLD/NASH. Additionally, disruption of endoplasmic reticulum (ER) homeostasis in cells, also known as ER stress, triggers the unfolded protein response (UPR) which has been shown to be involved to inflammation and apoptosis. To further develop the prevention and treatment of NAFLD/NASH, it is imperative to clarify the relationship between NAFLD/NASH and innate immune cells and ER stress. As such, this review focuses on innate immune cells and their ER stress in the occurrence of NAFLD and the progression of cirrhosis.

Risk factors associated with 30-day complications following lower extremity sarcoma surgery: A national surgical quality improvement project analysis

BACKGROUND

Our study aims to identify risk factors associated with complications in lower extremity (LE) sarcoma surgery, as well as the prevalence and complications associated with concurrent plastic surgery procedures (CPSP).

METHODS

ACS-NSQIP database was accessed to identify patients treated for LE sarcoma (2010-2019). Patient demographics, preoperative lab, comorbidities, tumor type, location, principle procedure, and presence/characteristics of CPSPs were recorded. Thirty-day soft tissue complications were analyzed. Bivariate and multivariate logistic regression was performed on IBM SPSS.™ RESULTS: Nine hundred eighteen patients were included (483 males and 435 females), average age and body mass index (BMI) of 57 and 27.4 kg/m,² respectively. Comorbidities included smoking (13.9%, 128), hypertension (37.3%, 342), and insulin-dependent diabetes (3.7%, 34). Preoperative lab values included albumin <3.5 (6.8%, 63), hematocrit <30% (8.2%, 75), and platelet count <150 000 (5.9%, 54). Thirty-day soft tissue complication rate was 5.7% (52 of 918). On multivariate logistic regression, increased age (p = 0.039), higher BMI (p = 0.017), and longer operative times (p = 0.002) were significant risk factors independently associated with soft tissue complications.

CONCLUSIONS

Soft tissue complications within 30 days occur in 6% of patients. Graft procedures carry a 20% risk of complications. Risk factors independently associated with complications include increased age, increased BMI, and longer operative times.

FcᵧRIIb protects from reperfusion injury by controlling antibody and type I IFN-mediated tissue injury and death

Intestinal ischemia and reperfusion (I/R) is accompanied by an exacerbated inflammatory response characterized by deposition of IgG, release of inflammatory mediators, and intense neutrophil influx in the small intestine, resulting in severe tissue injury and death. We hypothesized that FcᵧRIIb activation by deposited IgG could inhibit tissue damage during I/R. Our results showed that I/R induction led to the deposition of IgG in intestinal tissue during the reperfusion phase. Death upon I/R occurred earlier and was more frequent in FcᵧRIIb^-/- than WT mice. The higher lethality rate was associated with greater tissue injury and bacterial translocation to other organs. FcᵧRIIb^-/- mice presented changes in the amount and repertoire of circulating IgG, leading to increased IgG deposition in intestinal tissue upon reperfusion in these mice. Depletion of intestinal microbiota prevented antibody deposition and tissue damage in FcᵧRIIb^-/- mice submitted to I/R. We also observed increased production of ROS on neutrophils harvested from the intestines of FcᵧRIIb^-/- mice submitted to I/R. In contrast, FcᵧRIII^-/- mice presented reduced tissue damage and neutrophil influx after reperfusion injury, a phenotype reversed by FcᵧRIIb blockade. In addition, we observed reduced IFN-β expression in the intestines of FcᵧRIII^-/- mice after I/R, a phenotype that was also reverted by blocking FcᵧRIIb. IFNAR^-/- mice submitted to I/R presented reduced lethality and TNF release. Altogether our results demonstrate that antibody deposition triggers FcᵧRIIb to control IFN-β and IFNAR activation and subsequent TNF release, tailoring tissue damage, and death induced by reperfusion injury.

Targeted trapping of endogenous endothelial progenitor cells for myocardial ischemic injury repair through neutrophil-mediated SPIO nanoparticle-conjugated CD34 antibody delivery and imaging

Endothelia progenitor cell (EPC)-based revascularization therapies have shown promise for the treatment of myocardial ischemic injury. However, applications and efficacy are limited by the relatively inefficient recruitment of endogenous EPCs to the ischemic area, while implantation of exogenous EPCs carries the risk of tumorigenicity. In this study, we developed a therapeutic protocol that relies on the capacity of neutrophils (NEs) to target lesions and release preloaded EPC-binding molecules for high efficiency capture. Neutrophils were loaded with superparamagnetic iron oxide nanoparticles conjugated to an antibody against the EPC surface marker CD34 (SPIO-antiCD34/NEs), and the therapeutic efficacy in ischemic mouse heart following SPIO-antiCD34/NEs injection was monitored by SPIO-enhanced magnetic resonance imaging (MRI). These SPIO-antiCD34/NEs exhibited unimpaired cell viability, superoxide generation, and chemotaxis in vitro as well as satisfactory biocompatibility in vivo. In a mouse model of acute myocardial infarction (MI), SPIO-antiCD34 accumulation could be observed 0.5 h after intravenous injection of SPIO-antiCD34/NEs. Moreover, the degree of CD133⁺ EPC accumulation at MI sites was three-fold higher than in control MI model mice, while ensuing microvessel density was roughly two-fold higher than controls and left ventricular ejection fraction was > 50%. Therapeutic cell biodistribution, MI site targeting, and treatment effects were confirmed by SPIO-enhanced MRI. This study offers a new strategy to improve the endogenous EPC-based myocardial ischemic injury repair through NEs mediated SPIO nanoparticle conjugated CD34 antibody delivery and imaging. STATEMENT OF SIGNIFICANCE: The efficacy of endogenous endothelial progenitor cell (EPC)-based cardiovascular repair therapy for ischemic heart damage is limited by relatively low EPC accumulation at the target site. We have developed a method to improve EPC capture by exploiting the strong targeting ability of neutrophils (NEs) to ischemic inflammatory foci and the capacity of these treated cells to release of preloaded cargo with EPC-binding affinity. Briefly, NEs were loaded with superparamagnetic iron oxide nanoparticles conjugated to an antibody against the EPC surface protein CD34 (SPIO-antiCD34). Thus, we explored sites targeting with nanocomposites cargo for non-invasive EPCs interception and therapy tracking. We demonstrate that SPIO-antiCD34 released from NEs can effectively capture endogenous EPCs and thereby promote heart revascularization and functional recovery in mice. Moreover, the entire process can be monitored by SPIO-enhanced magnetic resonance imaging including therapeutic cell biodistribution, myocardial infarction site targeting, and tissue repair.

Opportunities presented by zebrafish larval models to study neutrophil function in tissues

Appropriate neutrophil function is essential for innate immune defence and to avoid inflammatory pathology. Neutrophils can adapt their responses according to their environment and recently, the existence of multiple distinct neutrophil populations has been confirmed in both health and disease. However, the study of neutrophil functions in their tissue environment has remained challenging, and for instance, the relationship between neutrophil maturity and function is not fully understood. Many neutrophil morphological and functional features are highly conserved between mammals and non-mammalian vertebrates. This enables the use of the transparent and genetically tractable zebrafish larvae to study neutrophil biology. We review data on the development and function of zebrafish larval neutrophils and advances zebrafish have brought to studies of neutrophil biology. In addition, we discuss opportunities and aspects to be considered when using the larval zebrafish model to further enhance our understanding of neutrophil function in health and disease.

The Dynamic Contribution of Neutrophils in the Chronic Respiratory Diseases

Asthma, chronic obstructive pulmonary disease, and idiopathic pulmonary fibrosis are representative chronic respiratory diseases (CRDs). Although they differ in terms of disease presentation, they are all thought to arise from unresolved inflammation. Neutrophils are not only the first responders to acute inflammation, but they also help resolve the inflammation. Notably, emerging clinical studies show that CRDs are associated with systemic and local elevation of neutrophils. Moreover, murine studies suggest that airway-infiltrating neutrophils not only help initiate airway inflammation but also prolong the inflammation. Given this background, this review describes neutrophil-mediated immune responses in CRDs and summarizes the completed, ongoing, and potential clinical trials that test the therapeutic value of targeting neutrophils in CRDs. The review also clarifies the importance of understanding how neutrophils interact with other immune cells and how these interactions contribute to chronic inflammation in specific CRDs. This information may help identify future therapeutic strategies for CRDs.

Hybrid Biomaterial Initiates Refractory Wound Healing via Inducing Transiently Heightened Inflammatory Responses

Inflammation plays a crucial role in triggering regeneration, while inadequate or chronic inflammation hinders the regenerative process, resulting in refractory wounds. Inspired by the ideal regeneration mode in lower vertebrates and the human oral mucosa, realigning dysregulated inflammation to a heightened and acute response provides a promising option for refractory wound therapy. Neutrophils play important roles in inflammation initiation and resolution. Here, a hybrid biomaterial is used to stimulate transiently heightened inflammatory responses by precise tempospatial regulation of neutrophil recruitment and apoptosis. The hybrid biomaterial (Gel@fMLP/SiO₂ -FasL) is constructed by loading of formyl-met-leu-phe (fMLP) and FasL-conjugated silica nanoparticles (SiO₂ -FasL) into a pH-responsive hydrogel matrix. This composition enables burst release of fMLP to rapidly recruit neutrophils for heightened inflammation initiation. After neutrophils act to produce acids, the pH-responsive hydrogel degrades to expose SiO₂ -FasL, which induces activated neutrophils apoptosis via FasL-Fas signaling triggering timely inflammation resolution. Apoptotic neutrophils are subsequently cleared by macrophages, and this efferocytosis activates key signalings to promote macrophage anti-inflammatory phenotypic transformation to drive regeneration. Ultimately, Gel@fMLP/SiO₂ -FasL successfully promotes tissue regeneration by manipulating inflammation in critical-sized calvarial bone defects and diabetic cutaneous wound models. This work provides a new strategy for refractory wound therapy via inducing transiently heightened inflammatory responses.

Insight into the role of DPP-4 in fibrotic wound healing

Wound healing is a complex and long-term process consisting of hemostasis, inflammation, proliferation, and maturation/remodeling. These four stages overlap and influence each other; they affect wound healing in different ways, and if they do not function perfectly, they may cause scarring, proliferative scarring and keloid formation. A therapeutic target affecting wound healing in multiple ways will help the healing process proceed more effectively. DPP-4/CD26 is a multifunctional dimorphic glycoprotein widely distributed on the surface of a variety of cells, including fibroblasts and keratin-forming cells. It has been found to affect periwound inflammation, re-epithelialization, extracellular matrix secretion and skin fibrosis and is a potential target for promoting wound healing and inhibiting scar formation. After presenting a brief introduction of the wound healing process and DPP-4/CD26, this paper summarizes the effects of DPP-4/CD26 on cells involved in different stages of wound healing and discusses the feasibility of DPP-4/CD26 as a multifunctional target for the treatment of wound healing and inhibition of scar formation.

m6A demethylase ALKBH5 is required for antibacterial innate defense by intrinsic motivation of neutrophil migration

Neutrophil migration into the site of infection is necessary for antibacterial innate defense, whereas impaired neutrophil migration may result in excessive inflammation and even sepsis. The neutrophil migration directed by extracellular signals such as chemokines has been extensively studied, yet the intrinsic mechanism for determining neutrophil ability to migrate needs further investigation. N⁶-methyladenosine (m⁶A) RNA modification is important in immunity and inflammation, and our preliminary data indicate downregulation of RNA m⁶A demethylase alkB homolog 5 (ALKBH5) in neutrophils during bacterial infection. Whether m⁶A modification and ALKBH5 might intrinsically modulate neutrophil innate response remain unknown. Here we report that ALKBH5 is required for antibacterial innate defense by enhancing intrinsic ability of neutrophil migration. We found that deficiency of ALKBH5 increased mortality of mice with polymicrobial sepsis induced by cecal ligation and puncture (CLP), and Alkbh5-deficient CLP mice exhibited higher bacterial burden and massive proinflammatory cytokine production in the peritoneal cavity and blood because of less neutrophil migration. Alkbh5-deficient neutrophils had lower CXCR2 expression, thus exhibiting impaired migration toward chemokine CXCL2. Mechanistically, ALKBH5-mediated m⁶A demethylation empowered neutrophils with high migration capability through altering the RNA decay, consequently regulating protein expression of its targets, neutrophil migration-related molecules, including increased expression of neutrophil migration-promoting CXCR2 and NLRP12, but decreased expression of neutrophil migration-suppressive PTGER4, TNC, and WNK1. Our findings reveal a previously unknown role of ALKBH5 in imprinting migration-promoting transcriptome signatures in neutrophils and intrinsically promoting neutrophil migration for antibacterial defense, highlighting the potential application of targeting neutrophil m⁶A modification in controlling bacterial infections.

Integrins are double-edged swords in pulmonary infectious diseases

Integrins are an important family of adhesion molecules that are widely distributed on immune cells in the lungs. Of note, accumulating evidences have shown that integrins are double-edged swords in pulmonary infectious diseases. On one hand, integrins promote the migration of immune cells to remove the invaded pathogens in the infected lungs. However, on the other hand, integrins also act as the targets for pathogens to escape from host immune system, which is a potential factor leading to further tissue damage. Thus, the innovative therapeutic strategies based on integrins has inspired well-founded hopes to treat pulmonary infectious diseases. In this review, we illustrate the involvement of integrins in pulmonary infectious diseases, and further discuss the innovative therapeutic targets based on integrins.

Polydopamine Biomaterials for Skin Regeneration

Designing biomaterials capable of biomimicking wound healing and skin regeneration has been receiving increasing attention recently. Some biopolymers behave similarly to the extracellular matrix (ECM), supporting biointerfacial adhesion and intrinsic cellular interactions. Polydopamine (PDA) is a natural bioadhesive and bioactive polymer that endows high chemical versatility, making it an exciting candidate for a wide range of biomedical applications. Moreover, biomaterials based on PDA and its derivatives have near-infrared (NIR) absorption, excellent biocompatibility, intrinsic antioxidative activity, antibacterial activity, and cell affinity. PDA can regulate cell behavior by controlling signal transduction pathways. It governs the focal adhesion behavior of cells at the biomaterials interface. These features make melanin-like PDA a fascinating biomaterial for wound healing and skin regeneration. This paper overviews PDA-based biomaterials' synthesis, properties, and interactions with biological entities. Furthermore, the utilization of PDA nano- and microstructures as a constituent of wound-dressing formulations is highlighted.

Neutrophil phenotypes and functions in cancer: A consensus statement

Neutrophils are the first responders to infection and inflammation and are thus a critical component of innate immune defense. Understanding the behavior of neutrophils as they act within various inflammatory contexts has provided insights into their role in sterile and infectious diseases; however, the field of neutrophils in cancer is comparatively young. Here, we summarize key concepts and current knowledge gaps related to the diverse roles of neutrophils throughout cancer progression. We discuss sources of neutrophil heterogeneity in cancer and provide recommendations on nomenclature for neutrophil states that are distinct in maturation and activation. We address discrepancies in the literature that highlight a need for technical standards that ought to be considered between laboratories. Finally, we review emerging questions in neutrophil biology and innate immunity in cancer. Overall, we emphasize that neutrophils are a more diverse population than previously appreciated and that their role in cancer may present novel unexplored opportunities to treat cancer.