Synthetic silica fibers of different length, diameter and shape: synthesis and interaction with rat (NR8383) and human (THP-1) macrophages in vitro, including chemotaxis and gene expression profile.

BACKGROUND: Inhalation of biopersistent fibers like asbestos can cause strong chronic inflammatory effects, often resulting in fibrosis or even cancer. The interplay between fiber shape, fiber size and the resulting biological effects is still poorly understood due to the lack of reference materials. RESULTS: We investigated how length, diameter, aspect ratio, and shape of synthetic silica fibers influence inflammatory effects at doses up to 250 µg cm-2. Silica nanofibers were prepared with different diameter and shape. Straight (length ca. 6 to 8 µm, thickness ca. 0.25 to 0.35 µm, aspect ratio ca. 17:1 to 32:1) and curly fibers (length ca. 9 µm, thickness ca. 0.13 µm, radius of curvature ca. 0.5 µm, aspect ratio ca. 70:1) were dispersed in water with no apparent change in the fiber shape during up to 28 days. Upon immersion in aqueous saline (DPBS), the fibers released about 5 wt% silica after 7 days irrespectively of their shape. The uptake of the fibers by macrophages (human THP-1 and rat NR8383) was studied by scanning electron microscopy and confocal laser scanning microscopy. Some fibers were completely taken up whereas others were only partially internalized, leading to visual damage of the cell wall. The biological effects were assessed by determining cell toxicity, particle-induced chemotaxis, and the induction of gene expression of inflammatory mediators. CONCLUSIONS: Straight fibers were only slightly cytotoxic and caused weak cell migration, regardless of their thickness, while the curly fibers were more toxic and caused significantly stronger chemotaxis. Curly fibers also had the strongest effect on the expression of cytokines and chemokines. This may be due to the different aspect ratio or its twisted shape.

Bortezomib restrains M2 polarization and reduces CXCL16-associated CXCR6+CD4 T cell chemotaxis in bleomycin-induced pulmonary fibrosis.

BACKGROUND: The development of pulmonary fibrosis involves a cascade of events, in which inflammation mediated by immune cells plays a pivotal role. Chemotherapeutic drugs have been shown to have dual effects on fibrosis, with bleomycin exacerbating pulmonary fibrosis and bortezomib alleviating tissue fibrotic processes. Understanding the intricate interplay between chemotherapeutic drugs, immune responses, and pulmonary fibrosis is likely to serve as the foundation for crafting tailored therapeutic strategies. METHODS: A model of bleomycin-induced pulmonary fibrosis was established, followed by treatment with bortezomib. Tissue samples were collected for analysis of immune cell subsets and functional assessment by flow cytometry and in vitro cell experiments. Additionally, multi-omics analysis was conducted to further elucidate the expression of chemokines and chemokine receptors, as well as the characteristics of cell populations. RESULTS: Here, we observed that the expression of CXCL16 and CXCR6 was elevated in the lung tissue of a pulmonary fibrosis model. In the context of pulmonary fibrosis or TGF-ß1 stimulation in vitro, macrophages exhibited an M2-polarized phenotype and secreted more CXCL16 than those of the control group. Moreover, flow cytometry revealed increased expression levels of CD69 and CXCR6 in pulmonary CD4 T cells during fibrosis progression. The administration of bortezomib alleviated bleomycin-induced pulmonary fibrosis, accompanied by reduced ratio of M2-polarized macrophages and decreased accumulation of CD4 T cells expressing CXCR6. CONCLUSIONS: Our findings provide insights into the key immune players involved in bleomycin-induced pulmonary fibrosis and offer preclinical evidence supporting the repurposing strategy and combination approaches to reduce lung fibrosis.

Open-Top Patterned Hydrogel-Laden 3D Glioma Cell Cultures for Creation of Dynamic Chemotactic Gradients to Direct Cell Migration.

The laminar flow profiles in microfluidic systems coupled to rapid diffusion at flow streamlines have been widely utilized to create well-controlled chemical gradients in cell cultures for spatially directing cell migration. However, within hydrogel-based closed microfluidic systems of limited depth (≤0.1 mm), the biomechanical cues for the cell culture are dominated by cell interactions with channel surfaces rather than with the hydrogel microenvironment. Also, leaching of poly(dimethylsiloxane) (PDMS) constituents in closed systems and the adsorption of small molecules to PDMS alter chemotactic profiles. To address these limitations, we present the patterning and integration of a PDMS-free open fluidic system, wherein the cell-laden hydrogel directly adjoins longitudinal channels that are designed to create chemotactic gradients across the 3D culture width, while maintaining uniformity across its ∼1 mm depth to enhance cell-biomaterial interactions. This hydrogel-based open fluidic system is assessed for its ability to direct migration of U87 glioma cells using a hybrid hydrogel that includes hyaluronic acid (HA) to mimic the brain tumor microenvironment and gelatin methacrylate (GelMA) to offer the adhesion motifs for promoting cell migration. Chemotactic gradients to induce cell migration across the hydrogel width are assessed using the chemokine CXCL12, and its inhibition by AMD3100 is validated. This open-top hydrogel-based fluidic system to deliver chemoattractant cues over square-centimeter-scale areas and millimeter-scale depths can potentially serve as a robust screening platform to assess emerging glioma models and chemotherapeutic agents to eradicate them.

Targeting myeloid chemotaxis to reverse prostate cancer therapy resistance.

Inflammation is a hallmark of cancer1. In patients with cancer, peripheral blood myeloid expansion, indicated by a high neutrophil-to-lymphocyte ratio, associates with shorter survival and treatment resistance across malignancies and therapeutic modalities2-5. Whether myeloid inflammation drives progression of prostate cancer in humans remain unclear. Here we show that inhibition of myeloid chemotaxis can reduce tumour-elicited myeloid inflammation and reverse therapy resistance in a subset of patients with metastatic castration-resistant prostate cancer (CRPC). We show that a higher blood neutrophil-to-lymphocyte ratio reflects tumour myeloid infiltration and tumour expression of senescence-associated mRNA species, including those that encode myeloid-chemoattracting CXCR2 ligands. To determine whether myeloid cells fuel resistance to androgen receptor signalling inhibitors, and whether inhibiting CXCR2 to block myeloid chemotaxis reverses this, we conducted an investigator-initiated, proof-of-concept clinical trial of a CXCR2 inhibitor (AZD5069) plus enzalutamide in patients with metastatic CRPC that is resistant to androgen receptor signalling inhibitors. This combination was well tolerated without dose-limiting toxicity and it decreased circulating neutrophil levels, reduced intratumour CD11b+HLA-DRloCD15+CD14- myeloid cell infiltration and imparted durable clinical benefit with biochemical and radiological responses in a subset of patients with metastatic CRPC. This study provides clinical evidence that senescence-associated myeloid inflammation can fuel metastatic CRPC progression and resistance to androgen receptor blockade. Targeting myeloid chemotaxis merits broader evaluation in other cancers.

Pamoic acid is an inhibitor of HMGB1·CXCL12 elicited chemotaxis and reduces inflammation in murine models of Pseudomonas aeruginosa pneumonia.

BACKGROUND: High-mobility group box 1 protein (HMGB1) is an ubiquitous nuclear protein that once released in the extracellular space acts as a Damage Associated Molecular Pattern and promotes inflammation. HMGB1 is significantly elevated during Pseudomonas aeruginosa infections and has a clinical relevance in respiratory diseases such as Cystic Fibrosis (CF). Salicylates are HMGB1 inhibitors. To address pharmacological inhibition of HMGB1 with small molecules, we explored the therapeutic potential of pamoic acid (PAM), a salicylate with limited ability to cross epithelial barriers. METHODS: PAM binding to HMGB1 and CXCL12 was tested by Nuclear Magnetic Resonance Spectroscopy using chemical shift perturbation methods, and inhibition of HMGB1·CXCL12-dependent chemotaxis was investigated by cell migration experiments. Aerosol delivery of PAM, with single or repeated administrations, was tested in murine models of acute and chronic P. aeruginosa pulmonary infection in C57Bl/6NCrlBR mice. PAM efficacy was evaluated by read-outs including weight loss, bacterial load and inflammatory response in lung and bronco-alveolar lavage fluid. RESULTS: Our data and three-dimensional models show that PAM is a direct ligand of both HMGB1 and CXCL12. We also showed that PAM is able to interfere with heterocomplex formation and the related chemotaxis in vitro. Importantly, PAM treatment by aerosol was effective in reducing acute and chronic airway murine inflammation and damage induced by P. aeruginosa. The results indicated that PAM reduces leukocyte recruitment in the airways, in particular neutrophils, suggesting an impaired in vivo chemotaxis. This was associated with decreased myeloperoxidase and neutrophil elastase levels. Modestly increased bacterial burdens were recorded with single administration of PAM in acute infection; however, repeated administration in chronic infection did not affect bacterial burdens, indicating that the interference of PAM with the immune system has a limited risk of pulmonary exacerbation. CONCLUSIONS: This work established the efficacy of treating inflammation in chronic respiratory diseases, including bacterial infections, by topical delivery in the lung of PAM, an inhibitor of HMGB1.

Artemisinin inhibits neutrophil and macrophage chemotaxis, cytokine production and NET release.

Immune cell chemotaxis to the sites of pathogen invasion is critical for fighting infection, but in life-threatening conditions such as sepsis and Covid-19, excess activation of the innate immune system is thought to cause a damaging invasion of immune cells into tissues and a consequent excessive release of cytokines, chemokines and neutrophil extracellular traps (NETs). In these circumstances, tempering excessive activation of the innate immune system may, paradoxically, promote recovery. Here we identify the antimalarial compound artemisinin as a potent and selective inhibitor of neutrophil and macrophage chemotaxis induced by a range of chemotactic agents. Artemisinin released calcium from intracellular stores in a similar way to thapsigargin, a known inhibitor of the Sarco/Endoplasmic Reticulum Calcium ATPase pump (SERCA), but unlike thapsigargin, artemisinin blocks only the SERCA3 isoform. Inhibition of SERCA3 by artemisinin was irreversible and was inhibited by iron chelation, suggesting iron-catalysed alkylation of a specific cysteine residue in SERCA3 as the mechanism by which artemisinin inhibits neutrophil motility. In murine infection models, artemisinin potently suppressed neutrophil invasion into both peritoneum and lung in vivo and inhibited the release of cytokines/chemokines and NETs. This work suggests that artemisinin may have value as a therapy in conditions such as sepsis and Covid-19 in which over-activation of the innate immune system causes tissue injury that can lead to death.

Influence of glucose on swarming and quorum sensing of Dickeya solani.

Dickeya solani is a pathogen most frequently responsible for infecting potato plants in Europe. As in the case of most plant pathogens, its ability to colonize and invade the host depends on chemotaxis and motility. The coordinated movement of Dickeya over solid surfaces is governed by a quorum sensing mechanism. In D. solani motility is regulated by ExpI-ExpR proteins, homologous to luxI-luxR system from Vibrio fisheri, in which N-acyl-homoserine lactones (AHLs) serve as signaling molecules. Moreover, in many Gram-negative bacteria motility is coupled with central metabolism via carbon catabolite repression. This enables them to reach more nutrient-efficient niches. The aim of this study was to analyze the swarming motility of D. solani depending on the volume of the medium in the cultivation plate and glucose content. We show that the ability of this bacterium to move is strictly dependent on both these factors. Moreover, we analyze the production of AHLs and show that the quorum sensing mechanism in D. solani is also influenced by the availability of glucose in the medium and that the distribution of these signaling molecules are different depending on the volume of the medium in the plate.

Isoflurane attenuates sepsis-associated lung injury.

Acute lung injury is one of major complications associated with sepsis, responsible for morbidity and mortality. Patients who suffer from acute lung injury often require respiratory support under sedations, and it would be important to know the role of sedatives in lung injury. We examined volatile anesthetic isoflurane, which is commonly used in surgical setting, but also used as an alternative sedative in intensive care settings in European countries and Canada. We found that isoflurane exposure attenuated neutrophil recruitment to the lungs in mice suffering from experimental polymicrobial abdominal sepsis. We found that isoflurane attenuated one of major neutrophil chemoattractants LTB4 mediated response via its receptor BLT1 in neutrophils. Furthermore, we have shown that isoflurane directly bound to BLT1 by a competition assay using newly developed labeled BLT1 antagonist, suggesting that isoflurane would be a BLT1 antagonist.

Mimic Nature Using Chemotaxis of Ionic Liquid Microdroplets for Drug Delivery Purposes.

Due to the growing prevalence of incurable diseases, such as cancer, worldwide, nowadays, the development of smart drug delivery systems is an inevitable necessity. Chemotaxis-driven movement of ionic liquid microdroplets containing therapeutic compounds is a well-known example of a smart drug delivery system. This review aims to classify, summarize, and compare ionic liquid-based chemotaxis systems in an easily understandable article. Chemotaxis is the basis of the movement of cells and microorganisms in biological environments, which is the cause of many vital biochemical and biological processes. This review attempts to summarize the available literature on single-component biomimetic and self-propelling microdroplet systems based on ionic liquids, which exhibit chemotaxis and spontaneously move in a determined direction by an external gradient, particularly a chemical change. It also aims to review artificial ionic liquid-based chemotaxis systems that can be used as drug carriers for medical purposes. The various ionic liquids used for this purpose are discussed, and different forms of chemical gradients and mechanisms that cause movement in microfluidic channels will be reviewed.

Transcriptional regulation of chemokine network by biologic monotherapy in ileum of patients with Crohn's disease.

BACKGROUND: Crohn's disease (CD) exacerbation is marked by an intense cellular trafficking. We set out to determine the specific impact of biologic therapies on regulating chemokine network gene expression in healthy, mildly and severely inflamed tissue of CD patients. METHODS: Twenty CD patients on biologics (adalimumab, ustekinumab, vedolizumab) or untreated undergoing colonoscopy due to clinical symptoms of flare. Healthy, mildly and severely inflamed ileum biopsies from each patient were collected. Chemokines and receptors gene expression was analyzed and a STRING analysis for functional enrichment was performed. RESULTS: The chemokine network exhibited wide transcriptional differences among tissues in active untreated patients, whereas all biologic treatments reduced these differences and homogenized their transcriptional activity. In mildly inflamed tissue, all treatments showed gene upregulation while ustekinumab additionally maintained the downregulation of genes such as CCL2, CCL3, CCL17 or CCL23, involved in T cell chemotaxis, inflammatory monocyte and NK trafficking. In severely inflamed tissue, all treatments shared a downregulatory effect on chemokines controlling T cell response (i.e. CXCL16, CXCR3). Adalimumab and vedolizumab significantly reduced the expression of genes promoting antigen presentation by DCs and the initiation of leukocyte extravasation (i.e. CXCL12, CCL25, CCR7). Ustekinumab significantly reduced genes positively regulating Th1 cytokine production and IL-8 mediated signaling (i.e. IL1B, XCL1, CXCR1, CXCR2). CONCLUSION: Biologic therapies differentially target the chemokine network gene expression profile in the ileal tissue of active CD patients. These results may contribute to better understanding cell homing and to defining future personalized therapeutic strategies for CD patients.

P17 induces chemotaxis and differentiation of monocytes via MRGPRX2-mediated mast cell-line activation.

BACKGROUND: P17, a peptide isolated from Tetramorium bicarinatum ant venom, is known to induce an alternative phenotype of human monocyte-derived macrophages via activation of an unknown G protein-coupled receptor (GPCR). OBJECTIVE: We sought to investigate the mechanism of action and the immunomodulatory effects of P17 mediated through MRGPRX2 (Mas-related G protein-coupled receptor X2). METHODS: To identify the GPCR for P17, we screened 314 GPCRs. Upon identification of MRGPRX2, a battery of in silico, in vitro, ex vivo, and in vivo assays along with the receptor mutation studies were performed. In particular, to investigate the immunomodulatory actions, we used ß-hexosaminidase release assay, cytokine releases, quantification of mRNA expression, cell migration and differentiation assays, immunohistochemical labeling, hematoxylin and eosin, and immunofluorescence staining. RESULTS: P17 activated MRGPRX2 in a dose-dependent manner in ß-arrestin recruitment assay. In LAD2 cells, P17 induced calcium and ß-hexosaminidase release. Quercetin- and short hairpin RNA-mediated knockdown of MRGPRX2 reduced P17-evoked ß-hexosaminidase release. In silico and in vitro mutagenesis studies showed that residue Lys8 of P17 formed a cation-π interaction with the Phe172 of MRGPRX2 and [Ala8]P17 lost its activity partially. P17 activated LAD2 cells to recruit THP-1 and human monocytes in Transwell migration assay, whereas MRGPRX2-impaired LAD2 cells cannot. In addition, P17-treated LAD2 cells stimulated differentiation of THP-1 and human monocytes, as indicated by the enhanced expression of macrophage markers cluster of differentiation 11b and TNF-α by quantitative RT-PCR. Immunohistochemical and immunofluorescent staining suggested monocyte recruitment in mice ears injected with P17. CONCLUSIONS: Our data provide novel structural information regarding the interaction of P17 with MRGPRX2 and intracellular pathways for its immunomodulatory action.

A chemorepellent inhibits local Ras activation to inhibit pseudopod formation to bias cell movement away from the chemorepellent.

The ability of cells to sense chemical gradients is essential during development, morphogenesis, and immune responses. Although much is known about chemoattraction, chemorepulsion remains poorly understood. Proliferating Dictyostelium cells secrete a chemorepellent protein called AprA. AprA prevents pseudopod formation at the region of the cell closest to the source of AprA, causing the random movement of cells to be biased away from the AprA. Activation of Ras proteins in a localized sector of a cell cortex helps to induce pseudopod formation, and Ras proteins are needed for AprA chemorepulsion. Here we show that AprA locally inhibits Ras cortical activation through the G protein-coupled receptor GrlH, the G protein subunits Gß and Gα8, Ras protein RasG, protein kinase B, the p21-activated kinase PakD, and the extracellular signal-regulated kinase Erk1. Diffusion calculations and experiments indicate that in a colony of cells, high extracellular concentrations of AprA in the center can globally inhibit Ras activation, while a gradient of AprA that naturally forms at the edge of the colony allows cells to activate Ras at sectors of the cell other than the sector of the cell closest to the center of the colony, effectively inducing both repulsion from the colony and cell differentiation. Together, these results suggest that a pathway that inhibits local Ras activation can mediate chemorepulsion.

Simultaneous recording of behavioral and neural responses of free-moving nematodes C. elegans.

To reveal the neural mechanisms that control animal behavior, it is necessary to link the neural responses to behavioral changes and interpret them. We have developed a protocol to simultaneously record the behavior and neural activity of freely moving C. elegans by combining a microfluidic device and a tracking stage. Here we detail the protocol for the experiment, with an example of behavioral and neural responses of nematodes to salt concentration changes. For complete details on the use and execution of this protocol, please refer to Sato et al. (2021).

Discovery of (Z)-1-(3-((1H-Pyrrol-2-yl)methylene)-2-oxoindolin-6-yl)-3-(isoxazol-3-yl)urea Derivatives as Novel and Orally Highly Effective CSF-1R Inhibitors for Potential Colorectal Cancer Immunotherapy.

Inhibiting the polarization or survival of tumor-associated macrophages through blocking CSF-1/CSF-1R signal transduction has become a promising strategy for cancer immunotherapy. Herein, a series of (Z)-1-(3-((1H-pyrrol-2-yl)methylene)-2-oxoindolin-6-yl)-3-(isoxazol-3-yl)urea derivatives were designed, synthesized, and evaluated as novel and orally highly effective CSF-1R inhibitors for colorectal cancer immunotherapy. Among these derivatives, compound 21 was found to possess excellent CSF-1R inhibitory activity (IC50 = 2.1 nM) and potent antiproliferative activity against colorectal cancer cells. Compound 21 inhibited the progression of colorectal cancer by suppressing the migration of macrophages, reprograming M2-like macrophages to the M1 phenotype, and enhancing the antitumor immunity. More importantly, compound 21, as a single agent, showed significantly superior in vivo anticolorectal cancer efficacy over PLX3397, highlighting a promising candidate for the immunotherapy of colorectal cancer.

Pharmacological modulation of fish-induced depth selection in D. magna: the role of cholinergic and GABAergic signalling.

Animal behaviour is closely related to individual fitness, which allows animals to choose suitable mates or avoid predation. The central nervous system regulates many aspects of animal behaviour responses. Therefore, behavioural responses can be especially sensitive to compounds with a neurodevelopmental or neurofunctional mode of action. Phototactic behavioural changes against fish in the freshwater crustacean Daphnia magna have been the subject of many ecological investigations. The aim of this study was to identify which neurotransmitter systems modulate phototactic behaviour to fish kairomones. We used a positive phototactic D. magna clone (P132,85) that shows marked negative phototactism after exposure to fish kairomones. Treatments included up to 16 known agonists and antagonists of the serotonergic, cholinergic, dopaminergic, histaminergic, glutamatergic and GABAergic systems. It was hypothesized that many neurological signalling pathways may modulate D. magna phototactic behaviour to fish kairomones. A new custom-designed device with vertically oriented chambers was used, and changes in the preferred areas (bottom, middle, and upper areas) were analysed using groups of animals after 24 h of exposure to the selected substance(s). The results indicated that agonists of the muscarinic acetylcholine and GABAA receptors and their equi-effective mixture ameliorated the negative phototactic response to fish kairomones, whereas antagonists and their mixtures increased the negative phototactism to fish kairomones. Interestingly, inhibition of the muscarinic acetylcholine receptor abolished positive phototaxis, thus inducing the phototactic response to fish kairomones. Analysis of the profile of neurotransmitters and their related metabolites showed that the D. magna behavioural responses induced by fish depend on changes in the levels of acetylcholine, dopamine and GABA.

A mathematical model for Escherichia coli chemotaxis to competing stimuli.

Chemotactic bacteria sense and respond to temporal and spatial gradients of chemical cues in their surroundings. This phenomenon plays a critical role in many microbial processes such as groundwater bioremediation, microbially enhanced oil recovery, nitrogen fixation in legumes, and pathogenesis of the disease. Chemical heterogeneity in these natural systems may produce numerous competing signals from various directions. Predicting the migration behavior of bacterial populations under such conditions is necessary for designing effective treatment schemes. In this study, experimental studies and mathematical models are reported for the chemotactic response of Escherichia coli to a combination of attractant (α-methylaspartate) and repellent (NiCl2 ), which bind to the same transmembrane receptor complex. The model describes the binding of chemoeffectors and phosphorylation of the kinase in the signal transduction mechanism. Chemotactic parameters of E. coli (signaling efficiency σ , stimuli sensitivity coefficient γ , and repellent sensitivity coefficient κ ) were determined by fitting the model with experimental results for individual stimuli. Interestingly, our model naturally identifies NiCl2 as a repellent for κ>1 . The model is capable of describing quantitatively the response to the individual attractant and repellent, and correctly predicts the change in direction of bacterial population migration for competing stimuli with a twofold increase in repellent concentration.

A humanized monoclonal antibody against the endothelial chemokine CCL21 for the diagnosis and treatment of inflammatory bowel disease.

Chemokines are small proteins that promote leukocyte migration during development, infection, and inflammation. We and others isolated the unique chemokine CCL21, a potent chemo-attractant for naïve T-cells, naïve B-cells, and immature dendritic cells. CCL21 has a 37 amino acid carboxy terminal extension that is distinct from the rest of the chemokine family, which is thought to anchor it to venule endothelium where the amino terminus can interact with its cognate receptor, CCR7. We and others have reported that venule endothelium expressing CCL21 plays a crucial role in attracting naïve immune cells to sites of antigen presentation. In this study we generated a series of monoclonal antibodies to the amino terminus of CCL21 in an attempt to generate an antibody that blocked the interaction of CCL21 with its receptor CCR7. We found one humanized clone that blocked naïve T-cell migration towards CCL21, while memory effector T-cells were less affected. Using this monoclonal antibody, we also demonstrated that CCL21 is expressed in the mucosal venule endothelium of the large majority of inflammatory bowel diseases (IBD), including Crohn's disease, ulcerative colitis, and also in celiac disease. This expression correlated with active IBD in 5 of 6 cases, whereas none of 6 normal bowel biopsies had CCL21 expression. This study raises the possibility that this monoclonal antibody could be used to diagnose initial or recurrent of IBD. Significantly, this antibody could also be used for therapeutic intervention in IBD by selectively interfering with recruitment of naïve immune effector cells to sites of antigen presentation, without harming overall memory immunity.

Lysophosphatidylglucoside is a GPR55 -mediated chemotactic molecule for human monocytes and macrophages.

Neutrophils undergo spontaneous apoptosis within 24-48 h after leaving bone marrow. Apoptotic neutrophils are subsequently phagocytosed and cleared by macrophages, thereby maintaining neutrophil homeostasis. Previous studies have demonstrated involvement of lysophosphatidylglucoside (lysoPtdGlc), a degradation product of PtdGlc, in modality-specific repulsive guidance of spinal sensory axons, via its specific receptor GPR55. In the present study, using human monocytic cell line THP-1 as a model, we demonstrated that lysoPtdGlc induces monocyte/macrophage migration with typical bell-haped curve and a peak at concentration 10-9 M. Lysophosphatidylinositol (lysoPtdIns), a known GPR55 ligand, induced migration at higher concentration (10-7 M). LysoPtdGlc-treated cells had a polarized shape, whereas lysoPtdIns-treated cells had a spherical shape. In EZ-TAXIScan (chemotaxis) assay, lysoPtdGlc induced chemotactic migration activity of THP-1 cells, while lysoPtdIns induced random migration activity. GPR55 antagonist ML193 inhibited lysoPtdGlc-induced THP-1 cell migration, whereas lysoPtdIns-induced migration was inhibited by CB2-receptor inverse agonist. SiRNA experiments showed that GPR55 mediated lysoPtdGlc-induced migration, while lysoPtdIns-induced migration was mediated by CB2 receptor. Our findings, taken together, suggest that lysoPtdGlc functions as a chemotactic molecule for human monocytes/macrophages via GPR55 receptor, while lysoPtdIns induces random migration activity via CB2 receptor.

LRG1 facilitates corneal fibrotic response by inducing neutrophil chemotaxis via Stat3 signaling in alkali-burned mouse corneas.

Leucine-rich α-2-glycoprotein-1 (LRG1) is a novel profibrotic factor that modulates transforming growth factor-ß (TGF-ß) signaling. However, its role in the corneal fibrotic response remains unknown. In the present study, we found that the LRG1 level increased in alkali-burned mouse corneas. In the LRG1-treated alkali-burned corneas, there were higher fibrogenic protein expression and neutrophil infiltration. LRG1 promoted neutrophil chemotaxis and CXCL-1 secretion. Conversely, LRG1-specific siRNA reduced fibrogenic protein expression and neutrophil infiltration in the alkali-burned corneas. The clearance of neutrophils effectively attenuated the LRG1-enhanced corneal fibrotic response, whereas the presence of neutrophils enhanced the effect of LRG1 on the fibrotic response in cultured TKE2 cells. In addition, the topical application of LRG1 elevated interleukin-6 (IL-6) and p-Stat3 levels in the corneal epithelium and in isolated neutrophils. The clearance of neutrophils inhibited the expression of p-Stat3 and IL-6 promoted by LRG1 in alkali-burned corneas. Moreover, neutrophils significantly increased the production of IL-6 and p-Stat3 promoted by LRG1 in TKE2 cells. Furthermore, the inhibition of Stat3 signaling by S3I-201 decreased neutrophil infiltration and alleviated the LRG1-enhanced corneal fibrotic response in the alkali-burned corneas. S3I-201 also reduced LRG1 or neutrophil-induced fibrotic response in TKE2 cells. In conclusion, LRG1 promotes the corneal fibrotic response by stimulating neutrophil infiltration via the modulation of the IL-6/Stat3 signaling pathway. Therefore, LRG1 could be targeted as a promising therapeutic strategy for patients with corneal fibrosis.

Three-dimensional stochastic simulation of chemoattractant-mediated excitability in cells.

During the last decade, a consensus has emerged that the stochastic triggering of an excitable system drives pseudopod formation and subsequent migration of amoeboid cells. The presence of chemoattractant stimuli alters the threshold for triggering this activity and can bias the direction of migration. Though noise plays an important role in these behaviors, mathematical models have typically ignored its origin and merely introduced it as an external signal into a series of reaction-diffusion equations. Here we consider a more realistic description based on a reaction-diffusion master equation formalism to implement these networks. In this scheme, noise arises naturally from a stochastic description of the various reaction and diffusion terms. Working on a three-dimensional geometry in which separate compartments are divided into a tetrahedral mesh, we implement a modular description of the system, consisting of G-protein coupled receptor signaling (GPCR), a local excitation-global inhibition mechanism (LEGI), and signal transduction excitable network (STEN). Our models implement detailed biochemical descriptions whenever this information is available, such as in the GPCR and G-protein interactions. In contrast, where the biochemical entities are less certain, such as the LEGI mechanism, we consider various possible schemes and highlight the differences between them. Our simulations show that even when the LEGI mechanism displays perfect adaptation in terms of the mean level of proteins, the variance shows a dose-dependence. This differs between the various models considered, suggesting a possible means for determining experimentally among the various potential networks. Overall, our simulations recreate temporal and spatial patterns observed experimentally in both wild-type and perturbed cells, providing further evidence for the excitable system paradigm. Moreover, because of the overall importance and ubiquity of the modules we consider, including GPCR signaling and adaptation, our results will be of interest beyond the field of directed migration.