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

Single-cell analysis with childhood and adult systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE), a heterogeneous and chronic autoimmune disease, exhibit unique changes in the complex composition and transcriptional signatures of peripheral blood mononuclear cells (PBMCs). While the mechanism of pathogenesis for both childhood-onset SLE (cSLE) and adult-onset SLE (aSLE) remains unclear, cSLE patients are considered more unpredictable and dangerous than aSLE patients. In this study, we analysed single-cell RNA sequencing data (scRNA-seq) to profile the PBMC clusters of cSLE/aSLE patients and matched healthy donors and compared the PBMC composition and transcriptional variations between the two groups. Our analysis revealed that the PBMC composition and transcriptional variations in cSLE patients were similar to those in aSLE patients. Comparative single-cell transcriptome analysis between healthy donors and SLE patients revealed IFITM3, ISG15, IFI16 and LY6E as potential therapeutic targets for both aSLE and cSLE patients. Additionally, we observed that the percentage of pre-B cells (CD34-) was increased in cSLE patients, while the percentage of neutrophil cells was upregulated in aSLE patients. Notably, we found decreased expression of TPM2 in cSLE patients, and similarly, TMEM150B, IQSEC2, CHN2, LRP8 and USP46 were significantly downregulated in neutrophil cells from aSLE patients. Overall, our study highlights the differences in complex PBMC composition and transcriptional profiles between cSLE and aSLE patients, providing potential biomarkers that could aid in diagnosing SLE.

Design Strategy of Microneedle Systems for Skin Wound Healing: Based on the Structure of Tips and Therapeutic Methodologies

The skin, being the largest organ of the human body, is susceptible to damage resulting in wounds that are vulnerable to pathogenic attacks and fail to provide effective protection for internal tissues. Therefore, it is crucial to expedite wound healing. In recent years, microneedles have garnered significant attention as an innovative drug delivery system owing to their noninvasive and painless administration, simplified application process, precise control over drug release, and versatile loading capabilities. Consequently, they hold immense potential for the treatment of skin wound. This review presents a comprehensive design strategy for the microneedle system in promoting skin wound healing. First, the process of skin wound healing and the characteristics of specific wounds are elucidated. The design strategies for microneedles are subsequently presented and classified based on their structural and therapeutic methodologies. Finally, a succinct recapitulation of the previously discussed points and a prospective analysis are provided.

Polygenic TB control and the sequence of innate/adaptive immune responses to infection: MHC-II alleles determine the size of the S100A8/9-producing neutrophil population

Among several quantitative trait loci involved in tuberculosis (TB) control in mice, one was mapped within the chromosome 17 segment occupied by the H2 complex and another within the chromosome 3 segment comprising the S100A8/9 genes, which encode neutrophil inflammatory factor S100A8/9. Previously, we developed a panel of H2-congenic mouse strains differing by small segments of the major histocompatibility complex Class II (MHC-II) region from TB-susceptible H2j mice transferred onto the genetic background of the TB-resistant C57BL/6 (H2b) strain. Susceptible B6.I-9.3 mice differ from B6 progenitors by the alleles of their only classical MHC-II H2-Aβ gene. The goals of the present study were to: (i) comprehensively characterise the differences in TB-related phenotypes between mice of the two strains and (ii) decipher interactions between the H2-Aβ and S100A8/9 genes. Here, we describe the dynamics of TB-related phenotypes differentiating B6.I-9.3 and B6 mice (colony forming units counts, histopathology, lung immune cell infiltration and cytokine profiles). We show that disproportionally diminished CD4+ T-cell population, an enlarged S100A8/9-positive neutrophil population and higher S100A8/9 serum levels in B6.I-9.3 mice collectively form the 'susceptible' phenotype before infection. An increase in IL-17 and a decrease in intrferon-gamma production by CD4+ T-cells in these mice provide a mechanistic explanation of this phenotype. Using F2 segregation analysis, we show that the number of S100A8/9-producing neutrophils in lungs and spleens and the proportion of Th17 CD4+ T-cells in lungs are significantly lower in the presence of the MHC-II dominant 'resistant' b allele compared to the recessive 'susceptible' j/j genotype. This provides direct genetic evidence that MHC-II-regulated CD4+ T-cell landscapes determine neutrophil abundance before infection, an important pathogenic factor in TB immunity.

Tagetes erecta L.: A traditional medicine effective in inflammatory process treatment

ETHNOPHARMACOLOGICAL RELEVANCE

Tagetes erecta L. (Asteraceae), popularly known as Aztec Marigold, is used in folk medicine to treat several ailments including inflammatory processes. Despite its historical use, the specific mechanisms through which it may modulate inflammation, particularly its effects on neutrophils and macrophages activation, have not yet been completely investigated.

AIM OF THE STUDY

This study aimed to elucidate the anti-inflammatory mechanism of the hydroalcoholic extract obtained from T. erecta flowers, focusing on its role in the regulation of neutrophil and macrophage functions.

MATERIAL AND METHODS

The production of TNF, IL-6, CXCL-1, IL-1β, IL-10 (ELISA) and NO (Griess reaction), adhesion molecule expression (CD62L, CD49d and CD18, flow cytometry), and chemotaxis were analyzed in vitro using oyster glycogen-recruited peritoneal neutrophils or macrophages (RAW 264.7) stimulated with lipopolysaccharide (LPS) and treated with the extract (1, 10 or 100 μg/mL). The resolution of inflammation was accessed by efferocytosis assay. The in vivo anti-inflammatory activity was investigated using carrageenan-induced inflammation in the subcutaneous tissue of male Swiss mice orally treated with the T. erecta extract (30, 100 or 300 mg/kg). The leukocyte influx (optical microscopy), secretion of chemical mediators (TNF, IL-6 and IL-1β, ELISA) and protein exudation (Bradford reaction) were quantified in the inflamed exudate.

RESULTS

In vitro studies demonstrated that the extract inhibited neutrophil chemotaxis and reduced the production and/or release of cytokines (TNF, IL-1β, CXCL1, and IL-6) as well as nitric oxide (NO) by neutrophils and macrophages when stimulated with LPS. Neutrophils treated with LPS and incubated with the extract showed an increase in CD62L expression, which leads to the impairment of neutrophil adhesion. The extract also enhanced efferocytosis of apoptotic neutrophils by macrophages, which was accompanied by increased IL-10 secretion and decreased TNF levels. In vivo studies yielded similar results, showing reduction in neutrophil migration, protein exudation, and cytokine release (TNF, IL-6, and IL-1β).

CONCLUSIONS

Together, the data herein obtained shows that T. erecta flower extract has anti-inflammatory effects by regulating inflammatory mediators, limiting neutrophil migration, and promoting efferocytosis. The in vivo results suggest that an herbal medicine made with T. erecta could represent an interesting pharmacological tool for the treatment of acute inflammatory condition.

In vitro vascularized liver tumor model based on a microfluidic inverse opal scaffold for immune cell recruitment investigation

Liver cancer, characterized as a kind of malignant tumor within the digestive system, poses great health harm, and immune escape stands out as an important reason for its occurrence and development. Chemokines, pivotal in guiding immune cells' migration, is necessary to initiate and deliver an effective anti-tumor immune response. Therefore, understanding the chemotactic environment and identifying chemokines that regulate recruitment of immune cells to the tumor microenvironment (TME) are critical to improve current immunotherapy interventions. Herein, we report a well-defined inverse opal scaffold generated with a microfluidic emulsion template for the construction of a vascularized liver tumor model, offering insights into immune cells' recruitment. Due to the excellent 3D porous morphology of the inverse opal scaffold, human hepatocellular carcinoma cells can aggregate in the pores of the scaffold to form uniform multicellular tumor spheroids. More attractively, the vascularized liver tumor model can be achieved by constructing a 3D co-culture system involving endothelial cells and hepatocellular carcinoma cells. The results demonstrate that the 3D co-cultured tumor cells increase the neutrophil chemokines remarkably and recruit neutrophils to tumor tissues, then promote tumor progression. This approach opens a feasible avenue for realizing a vascularized liver tumor model with a reliable immune microenvironment close to that of a solid tumor of liver cancer.

Macrophage and Neutrophil Dysfunction in Diabetic Wounds

Significance: The incidence of diabetes continues to rise throughout the world in an alarming rate. Diabetic patients often develop diabetic foot ulcers (DFUs), many of which do not heal. Non-healing DFUs are a major cause of hospitalization, amputation, and increased morbidity. Understanding the underlying mechanisms of impaired healing in DFU is crucial for its management. Recent Advances: This review focuses on the recent advancements on macrophages and neutrophils in diabetic wounds and DFUs. In particular, we discuss diabetes-induced dysregulations and dysfunctions of macrophages and neutrophils . Critical Issues: It is well established that diabetic wounds are characterized by stalled inflammation that results in impaired healing. Recent findings in the field suggest that dysregulation of macrophages and neutrophils plays a critical role in impaired healing in DFUs. The delineation of mechanisms that restore macrophage and neutrophil function in diabetic wound healing is the focus of intense investigation. Future Directions: The breadth of recently generated knowledge on the activity of macrophages and neutrophils in diabetic wound healing is impressive. Experimental models have delineated pathways that hold promise for the treatment of diabetic wounds and DFUs. These pathways may be useful targets for further clinical investigation.

Foxp3+ Treg control allergic skin inflammation by restricting IFN-γ-driven neutrophilic infiltration and NETosis

BACKGROUND

Atopic dermatitis (AD), a chronic inflammatory skin disease with T cell activation as a key feature, in which Th2 cell-mediated responses play a pivotal role. Regulatory T cells (Treg) are central immune cells that restrict autoimmunity and inflammation in the body. Patients with immune dysregulation, polyendocrinopathy, or enteropathy X-linked syndrome, an immune disease characterized by a deficiency in Treg, develop skin inflammation and allergic disorders, indicating that Treg play a crucial role in the development of allergic skin inflammation.

OBJECTIVE

we investigated the underlying mechanisms by which Treg control cutaneous allergic inflammation.

METHODS

An allergic skin inflammation mouse model was constructed using MC903, and Treg-depleted mouse model was constructed using diphtheria toxin. Neutralization of IFN-γ was constructed using anti-mouse-IFN-γ mouse antibody. Neutrophil infiltration was analyzed by flow cytometry and immunohistochemistry. Neutrophil extracellular traps (NETs), a process called NETosis, were detected using immunofluorescence. In vitro neutrophil stimulation and immunocytochemistry was conducted to demonstrate the effect of IFN-γ on NETosis.

RESULTS

The depletion of Foxp3+ Treg led to significantly exacerbated AD-like skin inflammation, including increased recruitment of neutrophils and expression of Th1 cytokine IFN-γ. Neutrophil infiltrating in skin of Treg-depleted mice released more NETs than wild type. Neutralization of IFN-γ abolished neutrophil infiltration and NETosis in Treg-depleted mice. Neutrophils stimulated with IFN-γ were more prone to release NETs in vitro. Finally, Foxp3+ Treg control cutaneous allergic inflammation by regulating IFN-γ-driven neutrophilic infiltration and NETosis.

CONCLUSION

Our results highlight the previously underestimated Treg-IFN-γ-neutrophil inflammatory axis.

Modulating the immune system towards a functional chronic wound healing: A biomaterials and Nanomedicine perspective

Chronic non-healing wounds persist as a substantial burden for healthcare systems, influenced by factors such as aging, diabetes, and obesity. In contrast to the traditionally pro-regenerative emphasis of therapies, the recognition of the immune system integral role in wound healing has significantly grown, instigating an approach shift towards immunological processes. Thus, this review explores the wound healing process, highlighting the engagement of the immune system, and delving into the behaviors of innate and adaptive immune cells in chronic wound scenarios. Moreover, the article investigates biomaterial-based strategies for the modulation of the immune system, elucidating how the adjustment of their physicochemical properties or their synergistic combination with other agents such as drugs, proteins or mesenchymal stromal cells can effectively modulate the behaviors of different immune cells. Finally this review explores various strategies based on synthetic and biological nanostructures, including extracellular vesicles, to finely tune the immune system as natural immunomodulators or therapeutic nanocarriers with promising biophysical properties.

PTP1B phosphatase dampens iPSC-derived neutrophil motility and antimicrobial function

Neutrophils are rapidly recruited to sites of infection and are critical for pathogen clearance. Therapeutic use of primary neutrophils has been limited, as they have a short lifespan and are not amenable to genetic manipulation. Human induced pluripotent stem cells (iPSCs) can provide a robust source of neutrophils for infusion and are genetically tractable. However, current work has indicated that dampened intracellular signaling limits iPSC-derived neutrophil (iNeutrophil) cellular activation and antimicrobial response. Here, we show that protein tyrosine phosphatase 1B (PTP1B) inhibits intracellular signaling and dampens iNeutrophil effector function. Deletion of the PTP1B phosphatase increased PI3K and ERK signaling and was associated with increased F-actin polymerization, cell migration, and phagocytosis. In contrast, other effector functions like NETosis and reactive oxygen species production were reduced. PTP1B-deficient neutrophils were more responsive to Aspergillus fumigatus and displayed rapid recruitment and control of hyphal growth. Accordingly, depletion of PTP1B increased production of inflammatory factors including the neutrophil chemokine interleukin-8. Taken together, these findings suggest that PTP1B limits iNeutrophil motility and antimicrobial function.

Impaired neutrophil migration underpins host susceptibility to infectious colitis

Citrobacter rodentium models infection with enteropathogenic Escherichia coli and ulcerative colitis (UC). While C57BL/6 (C57) mice recover, C3H/HeN (C3H) mice succumb to infection, partially due to increased colonic neutrophil elastase activity, also seen in UC patients; however, the underlying cause was unknown. Here, we found that bone marrow, blood, and colonic C57 neutrophils expressed (CD)11bHi and reached the infected colonic lumen, where they underwent productive NETosis. In contrast, while the number of C3H neutrophils increased in the bone marrow, blood, and colon, they remained CD11bLo and got trapped in the submucosa, away from C. rodentium, where they underwent harmful NETosis. CD11bLo neutrophils in C3H mice infected with CRi9, which triggers expression of neutrophil chemoattractants, reached the colonization site, resulting in host survival. UC patient neutrophils also displayed decreased levels of the activation/differentiation markers CD16/CXCR4. These results, suggesting that neutrophil malfunction contributes to exacerbated colitis, provide insight for future therapeutic prospects.

G-protein-coupled receptor 84 regulates acute inflammation in normal and diabetic skin wounds

Lipids have emerged as potent regulators of immune cell function. In the skin, adipocyte lipolysis increases the local pool of free fatty acids and is essential for coordinating early macrophage inflammation following injury. Here, we investigate G-protein-coupled receptor 84 (GPR84), a medium-chain fatty acid (MCFA) receptor, for its potential to propagate pro-inflammatory signaling after skin injury. GPR84 signaling was identified as a key component of regulating myeloid cell numbers and subsequent tissue repair through in vivo administration of a pharmacological antagonist and the MCFA decanoic acid. We found that impaired injury-induced dermal adipocyte lipolysis is a hallmark of diabetes, and lipidomic analysis demonstrated that MCFAs are significantly reduced in diabetic murine wounds. Furthermore, local administration of decanoic acid rescued myeloid cell numbers and tissue repair during diabetic wound healing. Thus, GPR84 is a readily targetable lipid signaling pathway for manipulating injury-induced tissue inflammation with beneficial effects on acute diabetic healing.

Placental neutrophil reverse trans-migration and maternal serum neutrophil extracellular trap expression in HIV infection co-morbid pre-eclampsia in women of African ancestry

Neutrophil extracellular traps (NETs) and placental neutrophil reverse transmigration (r-TM) are implicated in the pathogenesis of pre-eclampsia (PE). However, the role of the comorbidity of PE and human immunodeficiency virus (HIV) infection in placental neutrophil r-TM and serum NETs remains unknown. Human placental tissue (n = 160) and serum (n = 80) samples were obtained post-ethical approval and divided by pregnancy type and HIV status and across the study population. Immunohistochemistry and morphometry were performed to localize and quantify junctional adhesion molecule-C (JAM-C) expression as an inverse marker of neutrophil r-TM within placental villi. An enzyme-linked immunosorbent assay (ELISA) was performed to quantify the concentration of citrullinated histone H3 (cit-H3) as a marker of NETs. GraphPad Prism (version 8.0.2) was used to compare the results, and a p value of p < 0.05 was considered statistically significant. The localization of JAM-C was observed on the syncytiotrophoblasts (STBs) and endothelial cells of placental villi. The immunoexpression of JAM-C was elevated in PE vs. normotensive (N) placentae. In the exchange villi, JAM-C immunoexpression was higher in the N+ve vs. N-ve group. However, in PE comorbid HIV infection, JAM-C expression was lower in the PE+ve vs. PE-ve group. Citrullinated histone-H3 concentration was lower in the N+ve vs. N-ve group but elevated in early-onset PE (EOPE)+ve vs. late-onset PE (LOPE)+ve group. These results indicate that PE and HIV-infected placentae individually express elevated JAM-C, manifesting in less neutrophil r-TM. However, in exchange villi of PE comorbid with HIV infection reduced JAM-C enhances neutrophil r-TM, thus supporting the synergistic effect of PE comorbid with HIV.

Neutrophil immune profile guides spinal cord regeneration in zebrafish

Spinal cord injury triggers a strong innate inflammatory response in both non-regenerative mammals and regenerative zebrafish. Neutrophils are the first immune population to be recruited to the injury site. Yet, their role in the repair process, particularly in a regenerative context, remains largely unknown. Here, we show that, following rapid recruitment to the injured spinal cord, neutrophils mostly reverse migrate throughout the zebrafish body. In addition, promoting neutrophil inflammation resolution by inhibiting Cxcr4 boosts cellular and functional regeneration. Neutrophil-specific RNA-seq analysis reveals an enhanced activation state that correlates with a transient increase in tnf-α expression in macrophage/microglia populations. Conversely, blocking neutrophil recruitment through Cxcr1/2 inhibition diminishes the presence of macrophage/microglia at the injury site and impairs spinal cord regeneration. Altogether, these findings provide new insights into the role of neutrophils in spinal cord regeneration, emphasizing the significant impact of their immune profile on the outcome of the repair process.

Characteristics of Neutrophil Migration and Function in Acute Inflammation Induced by Zymosan and Carrageenan in the Mice Air Pouch Model

Deciphering the complex and redundant process of acute inflammation remains challenging. The failure of numerous clinical trials assessing anti-inflammation agents which had promising preclinical effects inevitably questions the validity of current animal models of inflammation. This study aimed to better understand the process of immune inflammatory response and to select more suitable models to evaluate the effect of potential anti-inflammatory drugs. Zymosan and λ-carrageenan are the most used representatives of particulate and soluble irritants that trigger acute inflammation in the air pouch inflammation model. When zymosan was used, the number of exudate cells first increased at 4 h-8 h, followed by a drop at 12 h-24 h. While, the changes in number of leukocytes in peripheral blood and proportion of neutrophils in bone marrow have the opposite trend. Meanwhile, neutrophils released neutrophil extracellular traps (NETs) to clean zymosan particles. In contrast, the cell migration response to carrageenan increased during 4 h to 24 h, no obvious NETs were observed, and the number of leukocytes in peripheral blood increased and the proportion of neutrophils in bone marrow decreased slightly. This study indicated that although both zymosan and carrageenan are sterile irritants, the characteristics of the inflammatory response induced by each other were different. In the acute phase of inflammation, zymosan-stimulated neutrophils were mobilized, recruited, and engulfed, and then died by NETs. Carrageenan stimulated the production of cytokines/chemokines by neutrophils or macrophages, but did not lead to an obvious death by releasing NETs.

Chemerin attracts neutrophil reverse migration by interacting with C-C motif chemokine receptor-like 2

Neutrophil reverse migration (rM) is a recently identified phenomenon in which neutrophils migrate away from the inflammatory site back into the vasculature following initial infiltration, which involved in the resolution of loci inflammatory response or dissemination of inflammation. Present study was aimed to explore the mechanisms in neutrophil rM. By scRNA-seq on the white blood cells in acute lung injury model, we found rM-ed neutrophils exhibited increased gene expression of C-C motif chemokine receptor-like 2 (Ccrl2), an atypical chemokine receptor. Furthermore, an air pouch model was established to directly track rM-ed neutrophils in vivo. Air pouches were generated by 3 ml filtered sterile air injected subcutaneously for 3 days, and then LPS (2 mg/kg) was injected into the pouches to mimic the inflammatory state. For the rM-ed neutrophil tracking system, cell tracker CMFDA were injected into the air pouch to stain the inflammatory loci cells, and after 6 h, stained cells in blood were regarded as the rM-ed neutrophil. Based on this tracking system, we confirmed that rM-ed neutrophils showed increased CCRL2. We also found that the concentrations of the CCRL2 ligand chemerin in plasma was increased in the late stage. Neutralizing chemerin decreased the rM-ed neutrophil ratio in the blood. These results suggest that circulating chemerin attracts neutrophils to leave inflammatory sites by interacting with CCRL2, which might involve in the dissemination of inflammation.

Tracing Immunological Interaction in Trimethylamine N-Oxide Hydrogel-Derived Zwitterionic Microenvironment During Promoted Diabetic Wound Regeneration

The diabetic wound healing is challenging due to the sabotaged delicate balance of immune regulation via an undetermined pathophysiological mechanism, so it is crucial to decipher multicellular signatures underlying diabetic wound healing and seek therapeutic strategies. Here, this work develops a strategy using novel trimethylamine N-oxide (TMAO)-derived zwitterionic hydrogel to promote diabetic wound healing, and explore the multi-cellular ecosystem around zwitterionic hydrogel, mapping out an overview of different cells in the zwitterionic microenvironment by single-cell RNA sequencing. The diverse cellular heterogeneity is revealed, highlighting the critical role of macrophage and neutrophils in managing diabetic wound healing. It is found that polyzwitterionic hydrogel can upregulate Ccl3+ macrophages and downregulate S100a9+ neutrophils and facilitate their interactions compared with polyanionic and polycationic hydrogels, validating the underlying effect of zwitterionic microenvironment on the activation of adaptive immune system. Moreover, zwitterionic hydrogel inhibits the formation of neutrophil extracellular traps (NETs) and promotes angiogenesis, thus improving diabetic wound healing. These findings expand the horizons of the sophisticated orchestration of immune systems in zwitterion-directed diabetic wound repair and uncover new strategies of novel immunoregulatory biomaterials.

Artificial Neutrophils Against Vascular Graft Infection

Efficient neutrophil migration to infection sites plays a vital role in the body's defense against bacterial infections and natural immune responses. Neutrophils have a short lifespan and cannot be mass-cultured in vitro. Therefore, developing more stable artificial neutrophils (AN) in a controllable manner has become a research focus. However, existing AN lack chemotaxis, which is the ability to migrate toward high-signal-concentration positions in a dynamic blood- flow environment. Supplying AN with chemotaxis is key to designing AN that are more similar to natural neutrophils in terms of morphology and function. In this study, micrometer-sized, spherical, biocompatible AN are developed. These AN consist of zeolitic imidazolate framework-8 nanoparticles encapsulating two enzymes, coacervate droplet frameworks, and outer phospholipid bilayers carrying enzymes. The AN exhibit responsiveness to elevated hydrogen peroxide levels at inflammation sites, actively chemotaxing toward these sites along concentration gradients. They also demonstrate effective combat against Staphylococcus aureus infections. The capabilities of the AN are further validated through in vitro experiments and in vivo evaluations using vascular graft infection models. This study replicates natural neutrophils in terms of chemical composition, functionality, and physiological impact. It introduces new ideas for advancing the development of advanced artificial cells.

Neutrophil Extracellular Traps: A Crucial Factor in Post-Surgical Abdominal Adhesion Formation

Post-surgical abdominal adhesions, although poorly understood, are highly prevalent. The molecular processes underlying their formation remain elusive. This review aims to assess the relationship between neutrophil extracellular traps (NETs) and the generation of postoperative peritoneal adhesions and to discuss methods for mitigating peritoneal adhesions. A keyword or medical subject heading (MeSH) search for all original articles and reviews was performed in PubMed and Google Scholar. It included studies assessing peritoneal adhesion reformation after abdominal surgery from 2003 to 2023. After assessing for eligibility, the selected articles were evaluated using the Critical Appraisal Skills Programme checklist for qualitative research. The search yielded 127 full-text articles for assessment of eligibility, of which 7 studies met our criteria and were subjected to a detailed quality review using the Critical Appraisal Skills Programme (CASP) checklist. The selected studies offer a comprehensive analysis of adhesion pathogenesis with a special focus on the role of neutrophil extracellular traps (NETs) in the development of peritoneal adhesions. Current interventional strategies are examined, including the use of mechanical barriers, advances in regenerative medicine, and targeted molecular therapies. In particular, this review emphasizes the potential of NET-targeted interventions as promising strategies to mitigate postoperative adhesion development. Evidence suggests that in addition to their role in innate defense against infections and autoimmune diseases, NETs also play a crucial role in the formation of peritoneal adhesions after surgery. Therefore, therapeutic strategies that target NETs are emerging as significant considerations for researchers. Continued research is vital to fully elucidate the relationship between NETs and post-surgical adhesion formation to develop effective treatments.

Neutrophil Migration Is Mediated by VLA-6 in the Inflamed Adipose Tissue

Adipose tissue, well known for its endocrine function, plays an immunological role in the body. The inflamed adipose tissue under LPS-induced systemic inflammation is characterized by the dominance of pro-inflammatory immune cells, particularly neutrophils. Although migration of macrophages toward damaged or dead adipocytes to form a crown-like structure in inflamed adipose tissue has been revealed, the neutrophilic interaction with adipocytes or the extracellular matrix remains unknown. Here, we demonstrated the involvement of adhesion molecules, particularly integrin α6β1, of neutrophils in adipocytes or the extracellular matrix of inflamed adipose tissue interaction. These results suggest that disrupting the adhesion between adipose tissue components and neutrophils may govern the accumulation of excessive neutrophils in inflamed tissues, a prerequisite in developing anti-inflammatory therapeutics by inhibiting inflammatory immune cells.

Advancing chemokine research: the molecular function of CXCL8

CXCL8 and other chemokines have been implicated in tissue inflammation and are attractive candidates for therapeutic targeting to treat human disease.

A Pilot Study to Investigate Peripheral Low-Level Chronic LPS Injection as a Model of Neutrophil Activation in the Periphery and Brain in Mice

Lipopolysaccharide-induced (LPS) inflammation is used as model to understand the role of inflammation in brain diseases. However, no studies have assessed the ability of peripheral low-level chronic LPS to induce neutrophil activation in the periphery and brain. Subclinical levels of LPS were injected intraperitoneally into mice to investigate its impacts on neutrophil frequency and activation. Neutrophil activation, as measured by CD11b expression, was higher in LPS-injected mice compared to saline-injected mice after 4 weeks but not 8 weeks of injections. Neutrophil frequency and activation increased in the periphery 4-12 h and 4-8 h after the fourth and final injection, respectively. Increased levels of G-CSF, TNFa, IL-6, and CXCL2 were observed in the plasma along with increased neutrophil elastase, a marker of neutrophil extracellular traps, peaking 4 h following the final injection. Neutrophil activation was increased in the brain of LPS-injected mice when compared to saline-injected mice 4-8 h after the final injection. These results indicate that subclinical levels of peripheral LPS induces neutrophil activation in the periphery and brain. This model of chronic low-level systemic inflammation could be used to understand how neutrophils may act as mediators of the periphery-brain axis of inflammation with age and/or in mouse models of neurodegenerative or neuroinflammatory disease.

An opportunistic pathogen under stress: how Group B Streptococcus responds to cytotoxic reactive species and conditions of metal ion imbalance to survive

Group B Streptococcus (GBS; also known as Streptococcus agalactiae) is an opportunistic bacterial pathogen that causes sepsis, meningitis, pneumonia, and skin and soft tissue infections in neonates and healthy or immunocompromised adults. GBS is well-adapted to survive in humans due to a plethora of virulence mechanisms that afford responses to support bacterial survival in dynamic host environments. These mechanisms and responses include counteraction of cell death from exposure to excess metal ions that can cause mismetallation and cytotoxicity, and strategies to combat molecules such as reactive oxygen and nitrogen species that are generated as part of innate host defence. Cytotoxicity from reactive molecules can stem from damage to proteins, DNA, and membrane lipids, potentially leading to bacterial cell death inside phagocytic cells or within extracellular spaces within the host. Deciphering the ways in which GBS responds to the stress of cytotoxic reactive molecules within the host will benefit the development of novel therapeutic and preventative strategies to manage the burden of GBS disease. This review summarizes knowledge of GBS carriage in humans and the mechanisms used by the bacteria to circumvent killing by these important elements of host immune defence: oxidative stress, nitrosative stress, and stress from metal ion intoxication/mismetallation.

IRG1/ACOD1 Promotes Neutrophil Reverse Migration and Alleviates Local Inflammation

Polymorphonuclear neutrophil (PMN) infiltration at inflammatory site plays a critical role in inflammation. PMN reverse migration (rM) describes the phenomenon that PMNs migrate away from inflammatory site back into the vasculature, and its role within inflammatory scenarios remains to be fully determined. This study aimed to investigate the mechanism underlying PMN rM and its role in inflammation. First, we demonstrated PMN rM in a mouse model of LPS-induced acute lung inflammation. By single-cell RNA sequencing (scRNA-seq), we demonstrated that reverse migrated (rM-ed) PMNs in blood expressed high level of immuneresponsive gene 1 (Irg1), the encoding gene of cis-aconitate decarboxylase (ACOD1). Using a mouse air pouch model, which enables us to directly track rM-ed PMNs in vivo, we detected higher expression of ACOD1 in the rM-ed PMNs in circulation. Furthermore, mice with Irg1 knockout exhibited decreased PMN rM and higher levels of inflammatory cytokine in inflammatory site. Mechanistically, we found that itaconate, the product of ACOD1 catalyzation, decreased PMN ICAM-1 expression at the inflammation site. Furthermore, inflammatory site showed a high level of shed CD11a, the ligand of ICAM-1. Neutralization of either ICAM-1 or CD11a leading to increased PMN rM. These findings suggest that the binding of ICAM-1 and shed CD11a serves as a retaining force to hold PMNs in the site of inflammation, and ACOD1-decreased PMN surface expression of ICAM-1 weakens the retaining force, so promoting PMNs to leave the inflammatory site. These results indicate a regulatory role of IRG1 in PMN rM and subsequent contributions to inflammation resolution.

What can we learn about fish neutrophil and macrophage response to immune challenge from studies in zebrafish

Fish rely, to a high degree, on the innate immune system to protect them against the constant exposure to potential pathogenic invasion from the surrounding water during homeostasis and injury. Zebrafish larvae have emerged as an outstanding model organism for immunity. The cellular component of zebrafish innate immunity is similar to the mammalian innate immune system and has a high degree of sophistication due to the needs of living in an aquatic environment from early embryonic stages of life. Innate immune cells (leukocytes), including neutrophils and macrophages, have major roles in protecting zebrafish against pathogens, as well as being essential for proper wound healing and regeneration. Zebrafish larvae are visually transparent, with unprecedented in vivo microscopy opportunities that, in combination with transgenic immune reporter lines, have permitted visualisation of the functions of these cells when zebrafish are exposed to bacterial, viral and parasitic infections, as well as during injury and healing. Recent findings indicate that leukocytes are even more complex than previously anticipated and are essential for inflammation, infection control, and subsequent wound healing and regeneration.

Co-administration of L-Ascorbic Acid and α-Tocopherol Alleviates Arsenic-Induced Immunotoxicities in the Thymus and Spleen by Dwindling Oxidative Stress-Induced Inflammation

Herein, we investigated whether L-ascorbic acid (L-AA) and α-tocopherol (α-T) co-administration has the potential to alleviate arsenic-induced immunotoxicities in the thymus, spleen, and circulating leukocytes. Forty-eight adult male Wistar rats were randomly divided into four groups before the treatment: group I (control); group II (sodium arsenite, 3 mg/kg/day/rat); group III (sodium arsenite + L-AA (200 mg/kg/day/rat) and α-T (400 mg/kg/day/rat)); group IV (L-AA and α-T). The result showed that sodium arsenite exposure (consecutive 30 days) caused weight reduction, structural alterations in the thymus and spleen, accompanied by a decrease in thymocyte and splenocyte count. Decreased superoxide dismutase and catalase activity, increased malondialdehyde and protein-carbonyl content, reduced Nrf2 and Bcl2 expression, and increased p-ERK, NF-kβ, Bax, and cleaved-caspase-3 expression were also observed in the thymus and spleen of arsenic-exposed rats. Enhanced plasma ACTH and corticosterone, ROS-induced apoptosis of lymphocytes were also observed. L-AA and α-T co-administration has the potential to abrogate the deleterious impact of arsenic on the thymus, spleen, and circulating lymphocytes. Whole transcriptome analysis of leukocytes revealed that arsenic treatment augmented the expression of Itga4, Itgam, and MMP9 genes, which might help in transient migration of the leukocytes through the endothelial cell layer. Co-administration with L-AA and α-T maintained Itga4, Itgam, and MMP9 gene expression within leukocytes at a lower level.

Integrative bioinformatics and experimental validation of hub genetic markers in acne vulgaris: Toward personalized diagnostic and therapeutic strategies

BACKGROUND

Acne vulgaris is a widespread chronic inflammatory dermatological condition. The precise molecular and genetic mechanisms of its pathogenesis remain incompletely understood. This research synthesizes existing databases, targeting a comprehensive exploration of core genetic markers.

METHODS

Gene expression datasets (GSE6475, GSE108110, and GSE53795) were retrieved from the GEO. Differentially expressed genes (DEGs) were identified using the limma package. Enrichment analyses were conducted using GSVA for pathway assessment and clusterProfiler for GO and KEGG analyses. PPI networks and immune cell infiltration were analyzed using the STRING database and ssGSEA, respectively. We investigated the correlation between hub gene biomarkers and immune cell infiltration using Spearman's rank analysis. ROC curve analysis validated the hub genes' diagnostic accuracy. miRNet, TarBase v8.0, and ChEA3 identified miRNA/transcription factor-gene interactions, while DrugBank delineated drug-gene interactions. Experiments utilized HaCaT cells stimulated with Propionibacterium acnes, treated with retinoic acid and methotrexate, and evaluated using RT-qPCR, ELISA, western blot, lentiviral transduction, CCK-8, wound-healing, and transwell assays.

RESULTS

There were 104 genes with consistent differences across the three datasets of paired acne and normal skin. Functional analyses emphasized the significant enrichment of these DEGs in immune-related pathways. PPI network analysis pinpointed hub genes PTPRC, CXCL8, ITGB2, and MMP9 as central players in acne pathogenesis. Elevated levels of specific immune cell infiltration in acne lesions corroborated the inflammatory nature of the disease. ROC curve analysis identified the acne diagnostic potential of four hub genes. Key miRNAs, particularly hsa-mir-124-3p, and central transcription factors like TFEC were noted as significant regulators. In vitro validation using HaCaT cells confirmed the upregulation of hub genes following Propionibacterium acnes exposure, while CXCL8 knockdown reduced pro-inflammatory cytokines, cell proliferation, and migration. DrugBank insights led to the exploration of retinoic acid and methotrexate, both of which mitigated gene expression upsurge and inflammatory mediator secretion.

CONCLUSION

This comprehensive study elucidated pivotal genes associated with acne pathogenesis, notably PTPRC, CXCL8, ITGB2, and MMP9. The findings underscore potential biomarkers, therapeutic targets, and the therapeutic potential of agents like retinoic acid and methotrexate. The congruence between bioinformatics and experimental validations suggests promising avenues for personalized acne treatments.

Immune cells in skin inflammation, wound healing, and skin cancer

Given the self-evident importance of cutaneous immunity in the maintenance of body-surface homeostasis, disturbance of the steady-state skin is inextricably intertwined with dysfunction in cutaneous immunity. It is often overlooked by people that skin, well-known as a solid physical barrier, is also a strong immunological barrier, considering the abundant presence of immune cells including lymphocytes, granulocytes, dendritic cells, and macrophages. What's more, humoral immune components including cytokines, immunoglobulins, and antimicrobial peptides are also rich in the skin. This review centers on skin inflammation (acute and chronic, infection and aseptic inflammation), wound healing, and skin cancer to elucidate the elaborate network of immune cells in skin diseases.

Neutrophils secrete exosome-associated DNA to resolve sterile acute inflammation

Acute inflammation, characterized by a rapid influx of neutrophils, is a protective response that can lead to chronic inflammatory diseases when left unresolved. Secretion of LTB 4 -containing exosomes is required for effective neutrophil infiltration during inflammation. In this study, we show that neutrophils release nuclear DNA in a non-lytic, rapid, and repetitive manner, via a mechanism distinct from suicidal NET release and cell death. The packaging of nuclear DNA occurs in the lumen of nuclear envelope (NE)-derived multivesicular bodies (MVBs) that harbor the LTB 4 synthesizing machinery and is mediated by the lamin B receptor (LBR) and chromatin decondensation. Disruption of secreted exosome-associated DNA (SEAD) in a model of sterile inflammation in mouse skin amplifies and prolongs the presence of neutrophils, impeding the onset of resolution. Together, these findings advance our understanding of neutrophil functions during inflammation and the physiological significance of NETs, with implications for novel treatments for inflammatory disorders.

Hesperidin - loaded PVA/alginate hydrogel: targeting NFκB/iNOS/COX-2/TNF-α inflammatory signaling pathway

Introduction

Skin injuries represent a prevalent form of physical trauma, necessitating effective therapeutic strategies to expedite the wound healing process. Hesperidin, a bioflavonoid naturally occurring in citrus fruits, exhibits a range of pharmacological attributes, including antimicrobial, antioxidant, anti-inflammatory, anticoagulant, and analgesic properties. The main objective of the study was to formulate a hydrogel with the intention of addressing skin conditions, particularly wound healing.

Methods

This research introduces a methodology for the fabrication of a membrane composed of a Polyvinyl alcohol - Sodium Alginate (PVA/A) blend, along with the inclusion of an anti-inflammatory agent, Hesperidin (H), which exhibits promising wound healing capabilities. A uniform layer of a homogeneous solution comprising PVA/A was cast. The process of crosslinking and the enhancement of hydrogel characteristics were achieved through the application of gamma irradiation at a dosage of 30 kGy. The membrane was immersed in a Hesperidin (H) solution, facilitating the permeation and absorption of the drug. The resultant system is designed to deliver H in a controlled and sustained manner, which is crucial for promoting efficient wound healing. The obtained PVA/AH hydrogel was evaluated for cytotoxicity, antioxidant and free radical scavenging activities, anti-inflammatory and membrane stability effect. In addition, its action on oxidative stress, and inflammatory markers was evaluated on BJ-1 human normal skin cell line.

Results and Discussion

We determined the effect of radical scavenging activity PVA/A (49 %) and PVA/AH (87%), the inhibition of Human red blood cell membrane hemolysis by PVA/AH (81.97 and 84.34 %), hypotonicity (83.68 and 76.48 %) and protein denaturation (83.17 and 85.8 %) as compared to 250 μg/ml diclofenac (Dic.) and aspirin (Asp.), respectively. Furthermore, gene expression analysis revealed an increased expression of genes associated with anti-oxidant and anti-inflammatory properties and downregulated TNFα, NFκB, iNOS, and COX2 by 67, 52, 58 and 60%, respectively, by PVA/AH hydrogel compared to LPS-stimulated BJ-1 cells. The advantages associated with Hesperidin can be ascribed to its antioxidant and anti-inflammatory attributes. The incorporation of Hesperidin into hydrogels offers promise for the development of a novel, secure, and efficient strategy for wound healing. This innovative approach holds potential as a solution for wound healing, capitalizing on the collaborative qualities of PVA/AH and gamma irradiation, which can be combined to establish a drug delivery platform for Hesperidin.

CLEC-1 Restrains Acute Inflammatory Response and Recruitment of Neutrophils following Tissue Injury

The inflammatory response is a key mechanism for the elimination of injurious agents but must be tightly controlled to prevent additional tissue damage and progression to persistent inflammation. C-type lectin receptors expressed mostly by myeloid cells play a crucial role in the regulation of inflammation by recognizing molecular patterns released by injured tissues. We recently showed that the C-type lectin receptor CLEC-1 is able to recognize necrotic cells. However, its role in the acute inflammatory response following tissue damage had not yet been investigated. We show in this study, in a mouse model of liver injury induced by acetaminophen intoxication, that Clec1a deficiency enhances the acute immune response with increased expression of Il1b, Tnfa, and Cxcl2 and higher infiltration of activated neutrophils into the injured organ. Furthermore, we demonstrate that Clec1a deficiency exacerbates tissue damage via CXCL2-dependent neutrophil infiltration. In contrast, we observed that the lack of CLEC-1 limits CCL2 expression and the accumulation, beyond the peak of injury, of monocyte-derived macrophages. Mechanistically, we found that Clec1a-deficient dendritic cells increase the expression of Il1b, Tnfa, and Cxcl2 in response to necrotic cells, but decrease the expression of Ccl2. Interestingly, treatment with an anti-human CLEC-1 antagonist mAb recapitulates the exacerbation of acute immunopathology observed by genetic loss of Clec1a in a preclinical humanized mouse model. To conclude, our results demonstrate that CLEC-1 is a death receptor limiting the acute inflammatory response following injury and represents a therapeutic target to modulate immunity.

CXCR2 perturbation promotes Staphylococcus aureus implant-associated infection

Introduction. Staphylococcus aureus is the leading cause of acute medical implant infections, representing a significant modern medical concern. The success of S. aureus as a pathogen in these cases resides in its arsenal of virulence factors, resistance to multiple antimicrobials, mechanisms of immune modulation, and ability to rapidly form biofilms associated with implant surfaces. S. aureus device-associated, biofilm-mediated infections are often persistent and notoriously difficult to treat, skewing innate immune responses to promote chronic reoccurring infections. While relatively little is known of the role neutrophils play in response to acute S. aureus biofilm infections, these effector cells must be efficiently recruited to sites of infection via directed chemotaxis. Here we investigate the effects of modulating CXC chemokine receptor 2 (CXCR2) activity, predominantly expressed on neutrophils, during S. aureus implant-associated infection.Hypothesis. We hypothesize that modulation of CXCR2 expression and/or signalling activities during S. aureus infection, and thus neutrophil recruitment, extravasation and antimicrobial activity, will affect infection control and bacterial burdens in a mouse model of implant-associated infection.Aim. This investigation aims to elucidate the impact of altered CXCR2 activity during S. aureus biofilm-mediated infection that may help develop a framework for an effective novel strategy to prevent morbidity and mortality associated with implant infections.Methodology. To examine the role of CXCR2 during S. aureus implant infection, we employed a mouse model of indwelling subcutaneous catheter infection using a community-associated methicillin-resistant S. aureus (MRSA) strain. To assess the role of CXCR2 induction or inhibition during infection, treatment groups received daily intraperitoneal doses of either Lipocalin-2 (Lcn2) or AZD5069, respectively. At the end of the study, catheters and surrounding soft tissues were analysed for bacterial burdens and dissemination, and Cxcr2 transcription within the implant-associated tissues was quantified.Results. Mice treated with Lcn2 developed higher bacterial burdens within the soft tissue surrounding the implant site, which was associated with increased Cxcr2 expression. AZD5069 treatment also resulted in increased implant- and tissues-associated bacterial titres, as well as enhanced Cxcr2 expression.Conclusion. Our results demonstrate that CXCR2 plays an essential role in regulating the severity of S. aureus implant-associated infections. Interestingly, however, perturbation of CXCR2 expression or signalling both resulted in enhanced Cxcr2 transcription and elevated implant-associated bacterial burdens. Thus, CXCR2 appears finely tuned to efficiently recruit effector cells and mediate control of S. aureus biofilm-mediated infection.

Cellular and molecular mechanisms of skin wound healing

Wound healing is a complex process that involves the coordinated actions of many different tissues and cell lineages. It requires tight orchestration of cell migration, proliferation, matrix deposition and remodelling, alongside inflammation and angiogenesis. Whereas small skin wounds heal in days, larger injuries resulting from trauma, acute illness or major surgery can take several weeks to heal, generally leaving behind a fibrotic scar that can impact tissue function. Development of therapeutics to prevent scarring and successfully repair chronic wounds requires a fuller knowledge of the cellular and molecular mechanisms driving wound healing. In this Review, we discuss the current understanding of the different phases of wound healing, from clot formation through re-epithelialization, angiogenesis and subsequent scar deposition. We highlight the contribution of different cell types to skin repair, with emphasis on how both innate and adaptive immune cells in the wound inflammatory response influence classically studied wound cell lineages, including keratinocytes, fibroblasts and endothelial cells, but also some of the less-studied cell lineages such as adipocytes, melanocytes and cutaneous nerves. Finally, we discuss newer approaches and research directions that have the potential to further our understanding of the mechanisms underpinning tissue repair.

Macrophages coordinate immune response to laser-induced injury via extracellular traps

BACKGROUND

Retinal degeneration results from disruptions in retinal homeostasis due to injury, disease, or aging and triggers peripheral leukocyte infiltration. Effective immune responses rely on coordinated actions of resident microglia and recruited macrophages, critical for tissue remodeling and repair. However, these phagocytes also contribute to chronic inflammation in degenerated retinas, yet the precise coordination of immune response to retinal damage remains elusive. Recent investigations have demonstrated that phagocytic cells can produce extracellular traps (ETs), which are a source of self-antigens that alter the immune response, which can potentially lead to tissue injury.

METHODS

Innovations in experimental systems facilitate real-time exploration of immune cell interactions and dynamic responses. We integrated in vivo imaging with ultrastructural analysis, transcriptomics, pharmacological treatments, and knockout mice to elucidate the role of phagocytes and their modulation of the local inflammatory response through extracellular traps (ETs). Deciphering these mechanisms is essential for developing novel and enhanced immunotherapeutic approaches that can redirect a specific maladaptive immune response towards favorable wound healing in the retina.

RESULTS

Our findings underscore the pivotal role of innate immune cells, especially macrophages/monocytes, in regulating retinal repair and inflammation. The absence of neutrophil and macrophage infiltration aids parenchymal integrity restoration, while their depletion, particularly macrophages/monocytes, impedes vascular recovery. We demonstrate that macrophages/monocytes, when recruited in the retina, release chromatin and granular proteins, forming ETs. Furthermore, the pharmacological inhibition of ETosis support retinal and vascular repair, surpassing the effects of blocking innate immune cell recruitment. Simultaneously, the absence of ETosis reshapes the inflammatory response, causing neutrophils, helper, and cytotoxic T-cells to be restricted primarily in the superficial capillary plexus instead of reaching the damaged photoreceptor layer.

CONCLUSIONS

Our data offer novel insights into innate immunity's role in responding to retinal damage and potentially help developing innovative immunotherapeutic approaches that can shift the immune response from maladaptive to beneficial for retinal regeneration.

An amphibian-derived cathelicidin accelerates cutaneous wound healing through its main regulatory effect on phagocytes

Cathelicidins are an important family of antimicrobial peptides (AMPs) involved in the innate immunity in vertebrates. The mammalian cathelicidins have been well characterized, but the relationship between structure and function in amphibian cathelicidins is still not well understood. In this study, a novel 29-residue cathelicidin antimicrobial peptide (BugaCATH) was identified from the skin of Bufo gargarizans. Unlike other AMPs, BugaCATH does not display any direct antimicrobial effects in vitro. However, it effectively promotes full-thickness wound repair in mice. Following injury, BugaCATH initiates and expedites the inflammatory stage by recruiting neutrophils and macrophages to the wound site. BugaCATH not only regulates neutrophil phagocytic activity but also stimulates the generation of cytokines (TNF-α, IL-6, and IL-1β) and chemokines (CXCL1, CXCL2, CCL2, and CCL3) in macrophages and in mice. Furthermore, it promotes macrophage M2 polarization that facilitates the conversion from a pro-inflammatory macrophage-dominated wound environment to an anti-inflammatory one during the mid to late stages, which is crucial for reducing inflammation and effective wound repair. The MAPK (ERK, JNK, and p38) and NF-κB-NLRP3 signaling pathways are involved in the activity. Moreover, BugaCATH directly enhances the migration of keratinocytes and vascular endothelial cells without affecting their proliferation. Notably, BugaCATH significantly improves the proliferation of keratinocytes and endothelial cells in the presence of macrophages. The current study revealed that in addition to proliferation of keratinocytes and endothelial cells, BugaCATH possesses the ability to modulate inflammatory processes during skin injury through its regulatory effect on phagocytes. The combination of these capabilities makes BugaCATH a potent candidate for skin wound therapy.

Immunomodulatory hydrogels for skin wound healing: cellular targets and design strategy

Skin wounds significantly impact the global health care system and represent a significant burden on the economy and society due to their complicated dynamic healing processes, wherein a series of immune events are required to coordinate normal and sequential healing phases, involving multiple immunoregulatory cells such as neutrophils, macrophages, keratinocytes, and fibroblasts, since dysfunction of these cells may impede skin wound healing presenting persisting inflammation, impaired vascularization, and excessive collagen deposition. Therefore, cellular target-based immunomodulation is promising to promote wound healing as cells are the smallest unit of life in immune response. Recently, immunomodulatory hydrogels have become an attractive avenue to promote skin wound healing. However, a detailed and comprehensive review of cellular targets and related hydrogel design strategies remains lacking. In this review, the roles of the main immunoregulatory cells participating in skin wound healing are first discussed, and then we highlight the cellular targets and state-of-the-art design strategies for immunomodulatory hydrogels based on immunoregulatory cells that cover defect, infected, diabetic, burn and tumor wounds and related scar healing. Finally, we discuss the barriers that need to be addressed and future prospects to boost the development and prosperity of immunomodulatory hydrogels.

Facile process ofHibiscusmucilage polymer formulation usingHibiscus rosa-sinensisleaves to treat second-degree burn and excision wounds

Mucilage is a sticky substance found in various plants and microorganisms and is made up of proteins and polysaccharides. Mucilage fromHibiscus rosa sinensisisis a complex polysaccharide traditionally used to treat different skin diseases. In our study, we fabricated mucilage polymer fromHibiscus rosa sinensisleaves and evaluated its potential application in second-degree burns and excision wounds. The physical properties of Hibiscus mucilage (HM) polymer were demonstrated by using Ultraviolet-visible absorption spectroscopy, x-ray diffraction, Fourier transform infrared spectroscopy, dynamic light scattering, Scanning electron microscopy, Brunauer-Emmett-Tellerand, Swelling ratio. The human cell lines WI-38, and HaCaT have been used forin-vitroexperiments like MTT, scratch wound, BrdU, ROS scavenging assays, and western blot analysis. The results of the MTT, scratch-wound, and BrdU assay indicated that the HM polymer is nontoxic in nature and also enhances both the properties of cellular migration and proliferation, respectively. On the other hand, the result of the ROS scavenging assay suggested that HM polymer enhances the antioxidant activity of cells while the western blot analysis designated that the HM polymer treatment caused downregulation of the pro-inflammatory cytokine IFN-γand upregulation of the pAkt (Serine 473) protein, and TGF-β1 signaling pathway. Therefore, allin-vitroexperimental studies recommended that HM polymer is biocompatible and has antioxidant and anti-inflammatory effects. In thein vivoexperiment, second-degree burns and excision wounds were created on the dorsal surface of male BALB/c mice. After the sixth day of HM polymer treatment have developed new tissue, hair follicles, blood vessels,α-SMA, and Collagen type-1 fiber on the burn and excision wound area while the 11th day of HM polymer treatment cured the wound area significantly. Therefore, it could be contemplated that HM polymer is a potential agent for treating different wounds in the near future.

Non-canonical G protein signaling

The original paradigm of classical - also referred to as canonical - cellular signal transduction of heterotrimeric G proteins (G protein) is defined by a hierarchical, orthograde interaction of three players: the agonist-activated G protein-coupled receptor (GPCR), which activates the transducing G protein, that in turn regulates its intracellular effectors. This receptor-transducer-effector concept was extended by the identification of regulators and adapters such as the regulators of G protein signaling (RGS), receptor kinases like βARK, or GPCR-interacting arrestin adapters that are integrated into this canonical signaling process at different levels to enable fine-tuning. Finally, the identification of atypical signaling mechanisms of classical regulators, together with the discovery of novel modulators, added a new and fascinating dimension to the cellular G protein signal transduction. This heterogeneous group of accessory G protein modulators was coined "activators of G protein signaling" (AGS) proteins and plays distinct roles in canonical and non-canonical G protein signaling pathways. AGS proteins contribute to the control of essential cellular functions such as cell development and division, intracellular transport processes, secretion, autophagy or cell movements. As such, they are involved in numerous biological processes that are crucial for diseases, like diabetes mellitus, cancer, and stroke, which represent major health burdens. Although the identification of a large number of non-canonical G protein signaling pathways has broadened the spectrum of this cellular communication system, their underlying mechanisms, functions, and biological effects are poorly understood. In this review, we highlight and discuss atypical G protein-dependent signaling mechanisms with a focus on inhibitory G proteins (Gi) involved in canonical and non-canonical signal transduction, review recent developments and open questions, address the potential of new approaches for targeted pharmacological interventions.

Beyond host defense and tissue injury: the emerging role of neutrophils in tissue repair

Neutrophils, the most abundant immune cells in human blood, play a fundamental role in host defense against invading pathogens and tissue injury. Neutrophils carry potentially lethal weaponry to the affected site. Inadvertent and perpetual neutrophil activation could lead to nonresolving inflammation and tissue damage, a unifying mechanism of many common diseases. The prevailing view emphasizes the dichotomy of their function, host defense versus tissue damage. However, tissue injury may also persist during neutropenia, which is associated with disease severity and poor outcome. Numerous studies highlight neutrophil phenotypic heterogeneity and functional versatility, indicating that neutrophils play more complex roles than previously thought. Emerging evidence indicates that neutrophils actively orchestrate resolution of inflammation and tissue repair and facilitate return to homeostasis. Thus, neutrophils mobilize multiple mechanisms to limit the inflammatory reaction, assure debris removal, matrix remodeling, cytokine scavenging, macrophage reprogramming, and angiogenesis. In this review, we will summarize the homeostatic and tissue-reparative functions and mechanisms of neutrophils across organs. We will also discuss how the healing power of neutrophils might be harnessed to develop novel resolution and repair-promoting therapies while maintaining their defense functions.

Targeting neutrophils: Mechanism and advances in cancer therapy

BACKGROUND

Cancer is a thorny problem which cannot be conquered by mankind at present and recent researchers have put their focus on tumor microenviroment. Neutrophils, the prominent leukocytes in peripheral blood that accumulate in tumours, serves as frontline cells in response to tumour progression owing to the rapid development of micro biotechnology. Hence, targeted therapy with these neutrophils has made targeting treatment a promising field in cancer therapy.

MAIN BODY

We broadly summarise some studies on the phenotypes and functions of tumour-associated neutrophils as well as the unique web-like products of neutrophils that play a role in cancer progression-neutrophil extracellular traps-and the interactions between neutrophils and the tumour microenvironment. Moreover, several targeted neutrophils therapeutic studies have made some progress and provided potential strategies for the treatment of cancer.

CONCLUSION

This review aims to offer a holistic perspective on therapeutic interventions targeting neutrophils to further inspire more researches on cancer therapies.

Learning how to find targets in the micro-world: the case of intermittent active Brownian particles

Finding the best strategy to minimize the time needed to find a given target is a crucial task both in nature and in reaching decisive technological advances. By considering learning agents able to switch their dynamics between standard and active Brownian motion, here we focus on developing effective target-search behavioral policies for microswimmers navigating a homogeneous environment and searching for targets of unknown position. We exploit projective simulation, a reinforcement learning algorithm, to acquire an efficient stochastic policy represented by the probability of switching the phase, i.e. the navigation mode, in response to the type and the duration of the current phase. Our findings reveal that the target-search efficiency increases with the particle's self-propulsion during the active phase and that, while the optimal duration of the passive case decreases monotonically with the activity, the optimal duration of the active phase displays a non-monotonic behavior.

Comparative transcriptomics coupled to developmental grading via transgenic zebrafish reporter strains identifies conserved features in neutrophil maturation

Neutrophils are evolutionarily conserved innate immune cells playing pivotal roles in host defense. Zebrafish models have contributed substantially to our understanding of neutrophil functions but similarities to human neutrophil maturation have not been systematically characterized, which limits their applicability to studying human disease. Here we show, by generating and analysing transgenic zebrafish strains representing distinct neutrophil differentiation stages, a high-resolution transcriptional profile of neutrophil maturation. We link gene expression at each stage to characteristic transcription factors, including C/ebp-β, which is important for late neutrophil maturation. Cross-species comparison of zebrafish, mouse, and human samples confirms high molecular similarity of immature stages and discriminates zebrafish-specific from pan-species gene signatures. Applying the pan-species neutrophil maturation signature to RNA-sequencing data from human neuroblastoma patients reveals association between metastatic tumor cell infiltration in the bone marrow and an overall increase in mature neutrophils. Our detailed neutrophil maturation atlas thus provides a valuable resource for studying neutrophil function at different stages across species in health and disease.

The Construction of Three-Layered Biomimetic Arterial Graft Balances Biomechanics and Biocompatibility for Dynamic Biological Reconstruction

The process of reconstructing an arterial graft is a complex and dynamic process that is subject to the influence of various mechanical factors, including tissue regeneration and blood pressure. The attainment of favorable remodeling outcomes is contingent upon the biocompatibility and biomechanical properties of the arterial graft. A promising strategy involves the emulation of the three-layer structure of the native artery, wherein the inner layer is composed of polycaprolactone (PCL) fibers aligned with blood flow, exhibiting excellent biocompatibility that fosters endothelial cell growth and effectively prevents platelet adhesion. The middle layer, consisting of PCL and polyurethane (PU), offers mechanical support and stability by forming a contractile smooth muscle ring and antiexpansion PU network. The outer layer, composed of PCL fibers with an irregular arrangement, promotes the growth of nerves and pericytes for long-term vascular function. Prioritizing the reconstruction of the inner and outer layers establishes a stable environment for intermediate smooth muscle growth. Our three-layer arterial graft is designed to provide the blood vessel with mechanical support and stability through nondegradable PU, while the incorporation of degradable PCL generates potential spaces for tissue ingrowth, thereby transforming our graft into a living implant.

Cisplatin Toxicity Causes Neutrophil-Mediated Inflammation in Zebrafish Larvae

Cisplatin is an antineoplastic agent used to treat various tumors. In mammals, it can cause nephrotoxicity, tissue damage, and inflammation. The release of inflammatory mediators leads to the recruitment and infiltration of immune cells, particularly neutrophils, at the site of inflammation. Cisplatin is often used as an inducer of acute kidney injury (AKI) in experimental models, including zebrafish (Danio rerio), due to its accumulation in kidney cells. Current protocols in larval zebrafish focus on studying its effect as an AKI inducer but ignore other systematic outcomes. In this study, cisplatin was added directly to the embryonic medium to assess its toxicity and impact on systemic inflammation using locomotor activity analysis, qPCR, microscopy, and flow cytometry. Our data showed that larvae exposed to cisplatin at 7 days post-fertilization (dpf) displayed dose-dependent mortality and morphological changes, leading to a decrease in locomotion speed at 9 dpf. The expression of pro-inflammatory cytokines such as interleukin (il)-12, il6, and il8 increased after 48 h of cisplatin exposure. Furthermore, while a decrease in the number of neutrophils was observed in the glomerular region of the pronephros, there was an increase in neutrophils throughout the entire animal after 48 h of cisplatin exposure. We demonstrate that cisplatin can have systemic effects in zebrafish larvae, including morphological and locomotory defects, increased inflammatory cytokines, and migration of neutrophils from the hematopoietic niche to other parts of the body. Therefore, this protocol can be used to induce systemic inflammation in zebrafish larvae for studying new therapies or mechanisms of action involving neutrophils.

Resistin - A Plausible Therapeutic Target in the Pathogenesis of Psoriasis

Resistin, a cytokine hormone predominantly secreted by adipose tissue, is elevated in various metabolic disorders such as obesity, type 2 diabetes, and cardiovascular disease. In addition to its involvement in metabolic regulation, resistin has been implicated in the pathogenesis of psoriasis, a chronic inflammatory skin disorder. Numerous studies have reported increased resistin levels in psoriatic skin lesions, suggesting a possible association between resistin and psoriasis. Recent studies have suggested the potential involvement of resistin in the development and progression of certain cancers. Resistin is overexpressed in breast, colorectal, and gastric cancers. This suggests that it may play a role in the development of these cancers, possibly by inducing inflammation and cell growth. The link between resistin and cancer raises the possibility of shared underlying mechanisms driving the pathogenesis of psoriasis. Chronic inflammation, one such mechanism, is a hallmark of psoriasis and cancer. Further research is needed to fully understand the relationship between resistin and psoriasis. Identifying potential therapeutic targets is crucial for effective management of psoriasis. By doing so, we may be able to develop more effective treatment options for individuals living with psoriasis and ultimately improve their quality of life. Ultimately, a more comprehensive understanding of the mechanisms underlying the impact of resistin on psoriasis is essential for advancing our knowledge and finding new ways to treat and manage this challenging condition.

Reduced Bioactive Microbial Products (Pathogen-Associated Molecular Patterns) Contribute to Dysregulated Immune Responses and Impaired Healing in Infected Wounds in Mice with Diabetes

Diabetic chronic ulcers are plagued with persistent nonresolving inflammation. However, diabetic wound environment early after injury suffers from inadequate inflammatory responses due to reductions in proinflammatory cytokines levels. Diabetic neutrophils have known impairments in bactericidal functions. We hypothesized that reduced bacterial killing by diabetic neutrophils, due to their bactericidal functional impairments, results in reduced bioactive bacterial products, known as pathogen-associated molecular patterns, which in turn contribute to reduced signaling through toll-like receptors, leading to inadequate production of proinflammatory cytokines in infected diabetic wound early after injury. We tested our hypothesis in db/db type 2 obese diabetic mouse wound infection model with Pseudomonas aeruginosa. Our data indicate that despite substantially higher levels of infection, toll-like receptor 4-mediated signaling is reduced in diabetic wounds early after injury owing to reduced bioactive levels of lipopolysaccharide. We further demonstrate that topical treatment with lipopolysaccharide enhances toll-like receptor 4 signaling, increases proinflammatory cytokine production, restores leukocyte trafficking, reduces infection burden, and stimulates healing in diabetic wounds. We posit that lipopolysaccharide may be a viable therapeutic option for the treatment of diabetic foot ulcers if it is applied topically after the surgical debridement process, which is intended to reset chronic ulcers into acute fresh wounds.

Identification the Low Oxidative Stress Subtype of Periodontitis

OBJECTIVE

The aim of this research was to identify the low oxidative stress-related genes expression (L-OS) subtype in patients with periodontitis.

METHODS

Microarray data (MA) were retrieved from the Gene Expression Omnibus database. The different oxidative stress (OS) subtypes of periodontitis were identified by K-means clustering analysis and gene set variation analysis (GSVA). Differentially expressed genes (DEGs) (|Log fold change (FC)| >1, q < 0.05) amongst the OS subtypes and healthy controls (HCs) were identified by Limma R package. The genomic feature of L-OS subtype and corresponding medicines were evaluated and visualised with Drug-Gene Interaction Database and cytoscape-v3.7.2 software (Pearson correlation coefficient > 0.4). Finally, the LASSO-Logistic regression model was adopted to evaluate and predict patients' OS phenotype in routine clinical practice.

RESULTS

The 241 periodontitis samples and 69 HCs were included. Thirty-three DEGs between the L-OS and high oxidative stress-related genes expression (H-OS) subtypes and 96 DEGs, including 8 transcription factors, between L-OS subtype and HCs were identified, respectively. Then, the network of TFs-Genes-Drugs was constructed to determine genomic feature of L-OS subtype. Finally, a 4-gene signature formula and the cutoff value were identified by ML with LASSO model to predict patients' classification.

CONCLUSIONS

For the first time, we identified L-OS subtype of periodontitis and evaluated its genomic feature with MA.

An in silico modeling approach to understanding the dynamics of the post-burn immune response

Introduction

Burns are characterized by a massive and prolonged acute inflammation, which persists for up to months after the initial trauma. Due to the complexity of the inflammatory process, Predicting the dynamics of wound healing process can be challenging for burn injuries. The aim of this study was to develop simulation models for the post-burn immune response based on (pre)clinical data.

Methods

The simulation domain was separated into blood and tissue compartments. Each of these compartments contained solutes and cell agents. Solutes comprise pro-inflammatory cytokines, anti-inflammatory cytokines and inflammation triggering factors. The solutes diffuse around the domain based on their concentration profiles. The cells include mast cells, neutrophils, and macrophages, and were modeled as independent agents. The cells are motile and exhibit chemotaxis based on concentrations gradients of the solutes. In addition, the cells secrete various solutes that in turn alter the dynamics and responses of the burn wound system.

Results

We developed an Glazier-Graner-Hogeweg method-based model (GGH) to capture the complexities associated with the dynamics of inflammation after burn injuries, including changes in cell counts and cytokine levels. Through simulations from day 0 - 4 post-burn, we successfully identified key factors influencing the acute inflammatory response, i.e., the initial number of endothelial cells, the chemotaxis threshold, and the level of chemoattractants.

Conclusion

Our findings highlight the pivotal role of the initial endothelial cell count as a key parameter for intensity of inflammation and progression of acute inflammation, 0 - 4 days post-burn.

In Vitro Neutrophil-Bacteria Assay in Whole Blood Microenvironments with Single-Cell Confinement

Blood is a common medium through which invasive bacterial infections disseminate in the human body. In vitro neutrophil-bacteria assays allow flexible mechanistic studies and screening of interventional strategies. In standard neutrophil-bacteria assays, both the immune cells and microorganisms are typically interrogated in an exogenous, homogeneous, bulk fluid environment (e.g., culture media or bacterial broth in microtiter plates), lacking the relevant physicochemical factors in the heterogenous blood-tissue microenvironment (e.g., capillary bed) with single-cell confinement. Here we present an in vitro neutrophil-bacteria assay by leveraging an open microfluidic model known as "μ-Blood" that supports sub-microliter liquid microchannels with single-cell confinement. In this study we compare the exogenous and endogenous fluids including neutrophils in RPMI (standard suspension cell culture media) and whole blood in response to Staphylococcus aureus ( S. aureus , a gram-positive, non-motile bacterium) in phosphate buffered saline (PBS), Mueller Hinton Broth (MHB), and human serum. Our results reveal a significant disparity between the exogenous and endogenous fluid microenvironments in the growth kinetics of bacteria, the spontaneous generation of capillary (i.e., Marangoni) flow, and the outcome of neutrophil intervention on the spreading bacteria.

Neutrophils in Physiology and Pathology

Infections, cardiovascular disease, and cancer are major causes of disease and death worldwide. Neutrophils are inescapably associated with each of these health concerns, by either protecting from, instigating, or aggravating their impact on the host. However, each of these disorders has a very different etiology, and understanding how neutrophils contribute to each of them requires understanding the intricacies of this immune cell type, including their immune and nonimmune contributions to physiology and pathology. Here, we review some of these intricacies, from basic concepts in neutrophil biology, such as their production and acquisition of functional diversity, to the variety of mechanisms by which they contribute to preventing or aggravating infections, cardiovascular events, and cancer. We also review poorly explored aspects of how neutrophils promote health by favoring tissue repair and discuss how discoveries about their basic biology inform the development of new therapeutic strategies.

Direct measurement of dynamic attractant gradients reveals breakdown of the Patlak-Keller-Segel chemotaxis model

Chemotactic bacteria not only navigate chemical gradients, but also shape their environments by consuming and secreting attractants. Investigating how these processes influence the dynamics of bacterial populations has been challenging because of a lack of experimental methods for measuring spatial profiles of chemoattractants in real time. Here, we use a fluorescent sensor for aspartate to directly measure bacterially generated chemoattractant gradients during collective migration. Our measurements show that the standard Patlak-Keller-Segel model for collective chemotactic bacterial migration breaks down at high cell densities. To address this, we propose modifications to the model that consider the impact of cell density on bacterial chemotaxis and attractant consumption. With these changes, the model explains our experimental data across all cell densities, offering insight into chemotactic dynamics. Our findings highlight the significance of considering cell density effects on bacterial behavior, and the potential for fluorescent metabolite sensors to shed light on the complex emergent dynamics of bacterial communities.