WASP integrates substrate topology and cell polarity to guide neutrophil migration

To control their movement, cells need to coordinate actin assembly with the geometric features of their substrate. Here, we uncover a role for the actin regulator WASP in the 3D migration of neutrophils. We show that WASP responds to substrate topology by enriching to sites of inward, substrate-induced membrane deformation. Superresolution imaging reveals that WASP preferentially enriches to the necks of these substrate-induced invaginations, a distribution that could support substrate pinching. WASP facilitates recruitment of the Arp2/3 complex to these sites, stimulating local actin assembly that couples substrate features with the cytoskeleton. Surprisingly, WASP only enriches to membrane deformations in the front half of the cell, within a permissive zone set by WASP’s front-biased regulator Cdc42. While WASP KO cells exhibit relatively normal migration on flat substrates, they are defective at topology-directed migration. Our data suggest that WASP integrates substrate topology with cell polarity by selectively polymerizing actin around substrate-induced membrane deformations in the front half of the cell.

Molecular Characterization and Functional Analysis of the Nattectin-like Toxin from the Venomous Fish Thalassophryne maculosa

TmC4-47.2 is a toxin with myotoxic activity found in the venom of Thalassophryne maculosa, a venomous fish commonly found in Latin America whose envenomation produces an injury characterized by delayed neutrophil migration, production of major pro-inflammatory cytokines, and necrosis at the wound site, as well as a specific systemic immune response. However, there are few studies on the protein structure and functions associated with it. Here, the toxin was identified from the crude venom by chromatography and protein purification systems. TmC4-47.2 shows high homology with the Nattectin from Thalassophryne nattereri venom, with 6 cysteines and QPD domain for binding to galactose. We confirm its hemagglutinating and microbicide abilities independent of carbohydrate binding, supporting its classification as a nattectin-like lectin. After performing the characterization of TmC4-47.2, we verified its ability to induce an increase in the rolling and adherence of leukocytes in cremaster post-capillary venules dependent on the α5β1 integrin. Finally, we could observe the inflammatory activity of TmC4-47.2 through the production of IL-6 and eotaxin in the peritoneal cavity with sustained recruitment of eosinophils and neutrophils up to 24 h. Together, our study characterized a nattectin-like protein from T. maculosa, pointing to its role as a molecule involved in the carbohydrate-independent agglutination response and modulation of eosinophilic and neutrophilic inflammation.

Secreted MbovP0145 Promotes IL-8 Expression through Its Interactive β-Actin and MAPK Activation and Contributes to Neutrophil Migration

Mycoplasma bovis (M. bovis) is an important pathogen of cattle responsible for huge economic losses in the dairy and beef industries worldwide. The proteins secreted by M. bovis are mainly related to its adhesion, invasion, virulence, and intracellular survival and play a role in mycoplasma–host interactions. In our previous study, we found MbovP0145, a secreted protein present in the M. bovis secretome, but little is known about its function. In this study, we assessed the inflammatory characteristics and underlined mechanism of this inflammation of recombinant MbovP0145 (rMbovP0145). For this, bovine lung epithelial cells (EBL) were stimulated by rMbovP0145 to see the IL-8 production in a time- and dose-dependent manner. We observed that rMbovP0145 increased the production of IL-8 via ERK1/2 and P38 pathway activation. Further, the effect of the M. bovis ΔMbov_0145 mutant and its complementary strain on IL-8 mRNA expression was also confirmed. A pulldown assay of the GST-tagged MbovP0145 protein with mass spectrometry demonstrated that β-actin could specifically interact with rMbovP0145 to mediate the IL-8 signaling. As knockdown of β-actin expression with RNA interference in EBL cells decreased the mRNA expression of IL-8 and the phosphorylated ERK1/2 and P38 proteins, whereas disrupted actin polymerization by cytochalasin D led to a significantly higher IL-8 expression and MAPK phosphorylation in rMbovP0145-stimulated cells. Compared to M. bovis HB0801 and its complementary strain, the culture supernatant of EBL cells infected with the M. bovis ΔMbov_0145 mutant induced less neutrophil migration to the lower chamber in a transwell system. In conclusion, MbovP0145 promoted IL-8 expression by interacting with β-actin through activation of the MAPK pathway, thus contributing to neutrophil migration.

IL-17 Exacerbates Experimental Autoimmune Prostatitis via CXCL1/CXCL2-Mediated Neutrophil Infiltration

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a poorly understood disease. Accumulating evidence suggests that autoimmune dysfunction is involved in the development of CP/CPPS. IL-17 is associated with the occurrence and development of several chronic autoimmune inflammatory diseases. However, the molecular mechanisms underlying the role of IL-17 in CP/CPPS remain unclear. Herein, we first confirmed that IL-17 was increased in the prostate tissues of experimental autoimmune prostatitis (EAP) mice. Corresponding to the increase of IL-17 in the prostate of EAP, neutrophil infiltration and the levels of CXCL1 and CXCL2 (CXC chemokine ligands 1 and 2) were also increased. Treatment of EAP mice with IL-17-neutralizing monoclonal antibody (mAb) resulted in a decreased number of infiltrated neutrophils, as well as the CXCL1 and CXCL2 level. Depletion of neutrophil by anti-Ly6G antibodies ameliorated inflammatory changes and hyperalgesia caused by EAP. Fucoidan, which could potently inhibit neutrophil migration, could also ameliorate the manifestations of EAP. Our finding suggested that IL-17 promoted the production of CXCL1 and CXCL2, which subsequently triggered neutrophil chemotaxis to prostate tissues. And fucoidan might be a potential drug for the therapy of EAP by the effectively inhibiting on neutrophil infiltration.

Receptor-binding domain of SARS-CoV-2 contribution to the neutrophil activation during 100 nm particle-induced immune response in conduction airway mucosa of mice

BACKGROUND: Airborne pathogens such as virus particles undergo elimination from the respiratory tract by mucociliary clearance and phagocytosis by immune cells. The data about phagocytic cell type infiltration and stimuli that attract phagocytic cells to conducting airway are required for the anti-virus immune response mechanism understanding and the treatment strategy development. AIM: To detect the role of the receptor-binding domain of SARS-CoV-2 in neutrophil immune response activation in conducting airway mucosa after 100 nm particles application. MATERIALS AND METHODS: C57BL/6 mice received an oropharyngeal application of fluorescent 100 nm particles suspended in the receptor-binding domain of SARS-CoV-2 solution. 24 hours after, conducting airways of mice were dissected and subjected for immunohistochemistry as whole-mounts. Three-dimensional images of conducting airway regions were obtained using confocal microscopy. Quantitative image analysis was performed to estimate the ingestion activity of neutrophils in conducting airway mucosa. RESULTS: Neutrophil migration to conducting airway mucosa was detected in case of the application of particles in receptor-binding domain solution, but not in phosphate buffer or bovine serum albumin solution. Receptor-binding domain solution alone also induced neutrophil migration to conducting airway mucosa. Infiltrating conducting airway wall mucosa neutrophils contributed to particles internalization. CONCLUSIONS: The receptor-binding domain of SARS-CoV-2 can activate the neutrophil-mediated response in conducting airway mucosa.

Exosome-Mediated eCIRP Release From Macrophages to Induce Inflammation in Sepsis

Extracellular cold-inducible RNA-binding protein (eCIRP) is an important damage-associated molecular pattern (DAMP). Despite our understanding of the potentially harmful effects of eCIRP in sepsis, how eCIRP is released from cells remains elusive. Exosomes are endosome-derived extracellular vesicles, which carry proteins, lipids, and nucleic acids to facilitate intercellular communication and several extracellular functions. We hypothesized that eCIRP is released via exosomes to induce inflammation in sepsis. Exosomes isolated from the supernatants of LPS-treated macrophage culture and serum of endotoxemia and polymicrobial sepsis mice showed high purity, as revealed by their unique median sizes ranging between 70 and 126 nm in diameter. eCIRP levels of the exosomes were significantly increased after LPS treatment in the supernatants of macrophage culture, mouse serum, and cecal ligation and puncture (CLP)-induced sepsis mouse serum. Protease protection assay demonstrated the majority of eCIRP was present on the surface of exosomes. Treatment of WT macrophages and mice with exosomes isolated from LPS-treated WT mice serum increased TNFα and IL-6 production. However, treatment with CIRP−/- mice serum exosomes significantly decreased these levels compared with WT exosome-treated conditions. CIRP−/- mice serum exosomes significantly decreased neutrophil migration in vitro compared with WT exosomes. Treatment of mice with serum exosomes isolated from CIRP−/- mice significantly reduced neutrophil infiltration into the peritoneal cavity. Our data suggest that eCIRP can be released via exosomes to induce cytokine production and neutrophil migration. Thus, exosomal eCIRP could be a potential target to inhibit inflammation.

Healing effects of Solanum nigrum fruit extract on second-degree burn wounds and its antibacterial activity against common pathogens of burn infection

Aims: Solanum nigrum (S. nigrum) is a species of flowering plant from the Solanaceae family and one of the indigenous plants of Eurasia. Given the biological activities of this plant, like antimicrobial, antioxidant, and anti-inflammatory ones, this study assessed its effects on the healing process of second-degree burn wounds in rats. We also evaluated its antibacterial activity against common pathogens of burn wound infection (i.e., Pseudomonas aeruginosa, Staphylococcus aureus, and Acinetobacter baumanni). Methods: S. nigrum fruit extract was prepared by percolation and reflux methods. The extract was applied for the treatment of animal models with second-degree burn wounds. Parameters of wound healing and maturation, including collagen deposition, epithelialization, reduction of neutrophil migration, and angiogenesis, were evaluated. The antimicrobial activity of S. nigrum fruit extract against common pathogens of burn wound infection was assessed by the agar well diffusion method via measurement of zones of microbial growth inhibition. Results: Histological analysis showed a significant reduction in neutrophil migration by the 20% hydroalcoholic extract vs. control group (normal saline). In addition, we found that the 20% hydroalcoholic extract was more efficient than silver sulfadiazine in augmenting collagen deposition. S. nigrum hydro alcoholic extract also showed an inhibitory effect on S. aureus. Conclusion: S. nigrum 20% hydroalcoholic extract improved some of the wound healing parameters such as collagen deposition and inflammation. It also shows an inhibitory effect on S. aureus. So, it may have therapeutic effects on burns.

RORA regulates neutrophil migration and activation in zebrafish

Neutrophil migration and activation are essential for defense against pathogens. However, this process may also lead to collateral tissue injury. We used microRNA overexpression as a platform and discovered protein-coding genes that regulate neutrophil migration. Here we show that miR-99 decreased the chemotaxis of zebrafish neutrophils and human neutrophil-like cells. In zebrafish neutrophils, miR-99 directly targets the transcriptional factor RAR-related orphan receptor alpha (roraa). Inhibiting RORα, but not the closely related RORγ, reduced chemotaxis of zebrafish and primary human neutrophils without causing cell death, and increased susceptibility of zebrafish to bacterial infection. Expressing a dominant-negative form of Rorα or disrupting the roraa locus specifically in zebrafish neutrophils reduced cell migration. At the transcriptional level, RORα regulates transmembrane signaling receptor activity and protein phosphorylation pathways. Our results, therefore, reveal previously unknown functions of miR- 99 and RORα in regulating neutrophil migration and anti-microbial defense.

Inhibition of Prostaglandin F2α Receptors Exaggerates HCl-Induced Lung Inflammation in Mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe respiratory disorders that are caused by aspiration, sepsis, trauma, and pneumonia. A clinical feature of ALI/ARDS is the acute onset of severe hypoxemia, and the mortality rate, which is estimated at 38–50%, remains high. Although prostaglandins (PGs) are detected in the bronchoalveolar lavage fluid of patients with ALI/ARDS, the role of PGF2α in ALI remains unclear. We aimed to clarify the role of PGF2α/PGF2α receptor (FP) signaling in acid-induced ALI using an FP receptor antagonist, AL8810. Intratracheal injection of hydrochloric acid (HCl) increased neutrophil migration into the lungs, leading to respiratory dysfunction. Pre-administration of AL8810 further increased these features. Moreover, pre-treatment with AL8810 enhanced the HCl-induced expression of pro-inflammatory cytokines and neutrophil migratory factors in the lungs. Administration of HCl decreased the gene expression of lung surfactant proteins, which was further reduced by co-administration of AL8810. Administration of AL8810 also increased lung edema and reduced mRNA expression of epithelial sodium channel in the lungs, indicating that AL8810 reduced fluid clearance. Furthermore, AL8810 also increased lipopolysaccharide-induced expression of adhesion molecules such as intracellular adhesion molecule-1 and E-selectin in human umbilical vein endothelial cells. These results indicate that inhibition of FP receptors by AL8810 exacerbated HCl-induced ALI.

Plasma obtained following murine hindlimb ischemic conditioning protects against oxidative stress in zebrafish models through activation of nrf2a and downregulation of duox

Ischemia/reperfusion of organ systems in trauma patients with resuscitated hemorrhagic shock (HSR) contributes to tissue injury and organ dysfunction. Previous studies using a murine model of HSR showed that remote ischemic preconditioning (RIC) protected against organ injury and that the plasma was able to prevent neutrophil migration in a zebrafish tailfin-cut inflammation model. In this study, we hypothesized that RIC plasma inhibits neutrophil function through a decrease in reactive oxygen species (ROS) production via the upregulation of the transcription factor Nrf2 and downstream antioxidative genes. Plasma from mice subjected to RIC (4 cycles of 5-min hindlimb ischemia/reperfusion) was microinjected into zebrafish. The results show that RIC plasma caused a reduction of ROS generation in response to tail injury. In addition, RIC plasma protected the fish larvae in the survival studies when exposed to either H2O2 or LPS. Oxidative stress PCR Array showed that RIC plasma treatment led to upregulation of antioxidative related genes including hsp70, hmox1a, nqo1 as well as downregulation of duox, the producer of H2O2. To explore the role of nrf2 in RIC, RIC plasma from Nrf2 KO mice were injected to the zebrafish and showed no inhibitory effect on neutrophil migration. Moreover, knockdown of nrf2a attenuated the anti-inflammatory and protective effect of RIC plasma. The downregulation of duox and upregulation of hmox1a were confirmed to require the activation of nrf2a. Therefore, we show that the protective effect of RIC may be related to the elaboration of humoral factors which counter injury-induced ROS generation in a nrf2-dependent fashion.