Macrophage Recruitment In Response Research Articles

Sonic Hedgehog acts as a macrophage chemoattractant during regeneration of the gastric epithelium

Sonic Hedgehog (Shh), secreted from gastric parietal cells, contributes to the regeneration of the epithelium. The recruitment of macrophages plays a central role in the regenerative process. The mechanism that regulates macrophage recruitment in response to gastric injury is largely unknown. Here we tested the hypothesis that Shh stimulates macrophage chemotaxis to the injured epithelium and contributes to gastric regeneration. A mouse model expressing a myeloid cell-specific deletion of Smoothened (LysMcre/+;Smof/f) was generated using transgenic mice bearing loxP sites flanking the Smo gene (Smo loxP) and mice expressing a Cre recombinase transgene from the Lysozyme M locus (LysMCre). Acetic acid injury was induced in the stomachs of both control and LysMcre/+;Smof/f (SmoKO) mice and gastric epithelial regeneration and macrophage recruitment analyzed over a period of 7 days post-injury. Bone marrow-derived macrophages (BM-Mø) were collected from control and SmoKO mice. Human-derived gastric organoid/macrophage co-cultures were established, and macrophage chemotaxis measured. Compared to control mice, SmoKO animals exhibited inhibition of ulcer repair and normal epithelial regeneration, which correlated with decreased macrophage infiltration at the site of injury. Bone marrow chimera experiments using SmoKO donor cells showed that control chimera mice transplanted with SmoKO bone marrow donor cells exhibited a loss of ulcer repair, and transplantation of control bone marrow donor cells to SmoKO mice rescued epithelial cell regeneration. Histamine-stimulated Shh secretion in human organoid/macrophage co-cultures resulted in macrophage migration toward the gastric epithelium, a response that was blocked with Smo inhibitor Vismodegib. Shh-induced macrophage migration was mediated by AKT signaling. In conclusion, Shh signaling acts as a macrophage chemoattractant via a Smo-dependent mechanism during gastric epithelial regeneration in response to injury.

Modulation of Epidermal γδ T Cell Functionality by Obesity due to Acute versus Chronic TNF-α Reception

Abstract Epidermal γδ T cells exhibit functional plasticity with roles varying from wound healing to tumor cell lysis. Activation of epidermal γδ T cells occurs via the γδ TCR along with costimulation, suggesting that costimulatory ligand expression regulates functional outcome. Data from our lab indicates that the cytokine milieu adds an additional pressure on epidermal γδ T cells to mediate or inhibit a particular functionality. Previous work from our lab shows that obesity impairs epidermal γδ T cell wound repair function in a TNF-α dependent manner. Here we identify TNF-α as a modulator of epidermal γδ T cell function in wound repair or cellular lysis depending on reception of acute or chronic signals. TNF-α signals through two receptors, tumor necrosis factor receptor 1 and 2 (TNFR1 and TNFR2), thus the signaling dynamics are complex and induce varied responses including apoptosis, survival and inflammation. We show that epidermal γδ T cells exhibit low TNFR1 and TNFR2 expression prior to TCR activation. Even with low TNFR expression epidermal γδ T cells produce cytokines and chemokines involved in inflammation and macrophage recruitment in response to acute TNF-α signals without TCR activation. During TCR activation or IL-2 stimulation epidermal γδ T cells to upregulate TNFR2 indicating a reliance on TNFR2 signaling during activation. Alternatively, chronic TNF-α stimulation, similar to levels in obese patients, induces a reduction in epidermal γδ T cell cytotoxicity, proliferation and viability. Normal function is restored with IL-2 addition suggesting the inhibition is not permanent, but instead can be modulated. These studies provide potential targets for regulating epidermal γδ T cell functions such as wound repair and tumor lysis.

Sonic Hedgehog Acts as a Macrophage Chemoattractant During Gastric Epithelial Regeneration in Response to Injury

Background/HypothesisHedgehog (Hh) signaling not only plays a crucial role in embryonic development, but also controls gastric physiological events including epithelial cell differentiation, regeneration and acid secretion. Sonic Hedgehog (Shh), is secreted from gastric parietal cells in response to injury and contributes to the regeneration of the injured epithelium. Following injury, the recruitment of macrophages plays crucial role both in the regenerative process. The mechanism that regulates macrophage recruitment in response to injury is largely unknown. Thus, here we tested the hypothesis thatShh stimulates macrophage chemotaxis to the injured epithelium and contributes to gastric regeneration.MethodsA mouse model expressing a myeloid cell‐specific deletion of Smoothened (LysMCre/SmoKO) was generated using transgenic mice bearing loxP sites flanking exon 1 of the Smo gene (Smo loxP) and mice expressing a Cre recombinase transgene from the Lysozyme M locus (LysMCre). Acetic acid injury was induced in the stomachs of both control and KO mice and gastric epithelial regeneration and macrophage recruitment analyzed over a period of 7 days post‐injury. Bone marrow‐derived macrophages (BM‐Mø) were collected from control and KO mice. Migration of BM‐Mø was performed using ibidi μ‐Slide Chemotaxis chambers in response to recombinant murine Shh (rmShh). Murine‐ and human‐derived gastric organoid/macrophage co‐cultures were established and macrophage chemotaxis measured.Results1) LysMCre/SmoKO mice exhibit loss of macrophage recruitment and epithelial regeneration in response to injury: Compared to control mice, KO animals exhibited loss of ulcer repair and normal epithelial regeneration, that correlated with decreased macrophage infiltration at the site of injury. 2) In vitro, macrophages from LysMCre/SmoKO mice or organoid/macrophage co‐cultures treated with Vismodegib lose chemotaxis: Forward migration index, a measure of directed movement, was significantly elevated in control BM‐Mø migrating towards rmShh compared to media control. In contrast, Smo‐deficient BM‐Mø did not migrate towards rmShh. While control BM‐Mø migrated toward chemokine CCL2, this chemotactic response was not observed using Smo‐deficient BM‐Mø. In murine‐derived gastric organoid/BM‐Mø co‐cultures, epithelial Shh, stimulated with histamine, correlated with macrophage migration toward the organoid. This response was lost in organoid/BM‐Mø co‐cultures derived from KO mice. Human‐derived organoid/macrophage co‐cultures stimulated with histamine resulted in Shh secretion and macrophage migration toward the gastric organoid, a response that was blocked with Smo‐inhibitor Vismodegib.ConclusionsShh signaling acts as a macrophage chemoattractant via a Smo‐dependent mechanism during gastric epithelial regeneration in response to injury.Support or Funding InformationNIH (NIDDK) 5R01DK083402‐08 grant (YZ)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

AMP-activated protein kinase regulates glycocalyx impairment and macrophage recruitment in response to low shear stress.

Low shear stress (LSS) increases degradation of the endothelial glycocalyx, leading to production of endothelial inflammation and atherosclerosis. However, the underlying mechanisms of how LSS diminishes the endothelial glycocalyx remain unclear. We showed that LSS inactivated AMPK, enhanced Na+-H+ exchanger (NHE)1 activity, and induced glycocalyx degradation. Activation of AMPK prevented LSS-induced NHE1 activity and endothelial glycocalyx impairment. We further identified hyaluronidase 2 (HYAL2) as a mediator of endothelial glycocalyx impairment in HUVECs exposed to LSS. Inactivation of AMPK by LSS up-regulates the activity of HYAL2, which acts downstream of NHE1. We characterized a left common carotid artery partial ligation (PL) model of LSS in C57BL/6 mice. The results showed decreased expression of hyaluronan (HA) in the endothelial glycocalyx and decreased thickness of the endothelial glycocalyx in PL mice. Pharmacological activation of AMPK by ampkinone not only attenuated glycocalyx impairment due to HA degradation but also blocked vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 expression increase and macrophage recruitment in the endothelia of PL mice. Our results revealed that AMPK dephosphorylation induced by LSS activates NHE1 and HYAL2 to promote HA degradation and glycocalyx injury, which may contribute to endothelial inflammatory reaction and macrophage recruitment.-Zhang, J., Kong, X., Wang, Z., Gao, X., Ge, Z., Gu, Y., Ye, P., Chao, Y., Zhu, L., Li, X., Chen, S. AMP-activated protein kinase regulates glycocalyx impairment and macrophage recruitment in response to low shear stress.

Protease activated receptor-1 regulates macrophage-mediated cellular senescence: a risk for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a destructive disease in part resulting from premature or mature cellular aging. Protease-activated receptor-1 (PAR-1) recently emerged as a critical component in the context of fibrotic lung diseases. Therefore, we aimed to study the role of macrophages in PAR-1-mediated idiopathic pulmonary fibrosis. The number of macrophages were significantly reduced in lungs of PAR-1 antagonist (P1pal-12) treated animals upon bleomycin instillation. In line with these data, PAR-1 stimulation increased monocyte / macrophage recruitment in response to epithelium injury in in vitro trans-well assays. Moreover, macrophages induced fibroblasts migration, differentiation and secretion of collagen, which were inhibited in the presence of TGF-β receptor inhibitors. Interestingly, these profibrotic effects were partially inhibited by treatment with the PAR-1 inhibitor P1pal-12. Using shRNA mediated PAR-1 knock down in fibroblasts, we demonstrate that fibroblast PAR-1 contributes to TGF-β activation and production. Finally, we show that the macrophage-dependent induction of PAR-1 driven TGF-β activation was mediated by FXa. Our data identify novel mechanisms by which PAR-1 stimulation on different cell types can contribute to IPF and identify macrophages as key players in PAR-1 dependent development of this devastating disease. IPF may result from cellular senescence mediated by macrophages in the lung.

S100A10 regulates plasminogen-dependent macrophage invasion

AbstractThe plasminogen activation system plays an integral role in the migration of macrophages in response to an inflammatory stimulus, and the binding of plasminogen to its cell-surface receptor initiates this process. Although previous studies from our laboratory have shown the importance of the plasminogen receptor S100A10 in cancer cell plasmin production, the potential role of this protein in macrophage migration has not been investigated. Using thioglycollate to induce a peritoneal inflammatory response, we demonstrate, for the first time, that compared with wild-type (WT) mice, macrophage migration across the peritoneal membrane into the peritoneal cavity in S100A10-deficient (S100A10−/−) mice was decreased by up to 53% at 24, 48, and 72 hours. Furthermore, the number of S100A10-deficient macrophages that infiltrated Matrigel plugs was reduced by 8-fold compared with their WT counterpart in vivo. Compared with WT macrophages, macrophages from S100A10−/− mice demonstrated a 50% reduction in plasmin-dependent invasion across a Matrigel barrier and a 45% reduction in plasmin generation in vitro. This loss in plasmin-dependent invasion was in part the result of a decreased generation of plasmin and a decreased activation of pro-MMP-9 by S100A10-deficient macrophages. This study establishes a direct involvement of S100A10 in macrophage recruitment in response to inflammatory stimuli.

Importance of CXC Chemokine Receptor 2 in Alveolar Neutrophil and Exudate Macrophage Recruitment in Response to Pneumococcal Lung Infection

Sustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury. CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. Whether or not the abundant neutrophil recruitment observed in severe pneumonia is essential for protective immunity against Streptococcus pneumoniae infections is incompletely defined. Here we show that CXCR2 deficiency severely perturbs the recruitment of both neutrophils and exudate macrophages associated with a massive bacterial outgrowth in distal airspaces after infection with S. pneumoniae, resulting in 100% mortality in knockout (KO) mice within 3 days. Moreover, irradiated wild-type mice reconstituted with increasing amounts of CXCR2 KO bone marrow (10, 25, 50, and 75% KO) have correspondingly decreased numbers of both neutrophils and exudate macrophages, which is associated with a stepwise increase in bacterial burden and a reciprocal stepwise decrease in survival in S. pneumoniae-induced pulmonary infection. Finally, application of the CXCR2 antagonist SB-225002 resulted in decreased alveolar neutrophil and exudate macrophage recruitment in mice along with increased lung bacterial loads after infection with S. pneumoniae. Together, these data show that CXC chemokine receptor 2 serves a previously unrecognized nonredundant role in the regulation of both neutrophil and exudate macrophage recruitment to the lung in response to S. pneumoniae infection. In addition, we demonstrate that a threshold level of 10 to 25% of reduced neutrophil recruitment is sufficient to cause increased mortality in mice infected with S. pneumoniae.

Importance of CXC chemokine receptor 2 in alveolar neutrophil and exudate macrophage recruitment in response to pneumococcal lung infection

Importance of CXC chemokine receptor 2 in alveolar neutrophil and exudate macrophage recruitment in response to pneumococcal lung infection

Importance of CXC chemokine receptor 2 in alveolar neutrophil and exudates macrophage recruitment in response to pneumococcal lung infection

Aims: Sustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury. CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. Whether the abundant neutrophil recruitment observed in severe pneumonia is essential for protective immunity against Streptococcus pneumoniae is poorly defined. Results: Here we show that CXCR2 KO compared to wild-type mice have a severely reduced recruitment of neutrophils and exudate macrophages that is associated with a massive bacterial outgrowth in distal airspaces after infection with S. pneumoniae, resulting in 100% mortality within three days. Furthermore, irradiated wild-type mice reconstituted with increasing amounts of CXCR2 KO bone marrow (10–25–50–75% KO) have correspondingly decreased numbers of both neutrophil and exudates macrophage recruitment that is associated with a step-wise increase in bacterial burden and a reciprocal step-wise decrease in survival in S. pneumoniae induced pulmonary infection. Summary: These data show that CXC chemokine receptor 2 serves a previously unrecognized non-redundant role in the regulation of both neutrophil and exudate macrophage recruitment to the lung in response to S. pneumoniae infection.

Adiponectin is required for enhancement of CCL2 expression in adipose tissue during Listeria monocytogenes infection

Obesity is an important background of metabolic syndrome progression. Our previous study demonstrated that chemokine CCL2 expression was suppressed in liver of obese mice that were highly susceptible to Listeria monocytogenes infection. We investigated the role of adiponectin in CCL2 expression in obese mice after L. monocytogenes infection. When leptin-deficient obese ob/ob mice were infected intraperitoneally with L. monocytogenes, the elimination of bacteria from spleen, liver, mesenteric lymph nodes and adipose tissue was inhibited in ob/ob mice compared with their heterozygote littermates, ob/? mice. CCL2 expression in the adipose tissue of ob/? mice was enhanced by L. monocytogenes infection, different from ob/ob mice. Similarly, adiponectin expression was not observed in the adipose tissue of ob/ob mice. When mouse adipocyte 3T3-F442A-derived adipocytes were infected with L. monocytogenes, CCL2 expression was transiently up-regulated, following up-regulation of adiponectin expression. Up-regulation of CCL2 in adipocytes by L. monocytogenes infection was suppressed by knocked-down of adiponectin expression and supplementation of recombinant adiponectin partially recovered CCL2 expression. These results suggest that adiponectin is required for appropriate expression of CCL2 that is important for macrophage recruitment in response to bacterial infection.

Effects of PARP-1 deficiency on airway inflammatory cell recruitment in response to LPS or TNF: differential effects on CXCR2 ligands and Duffy Antigen Receptor for Chemokines.

We reported that PARP-1 exhibits differential roles in expression of inflammatory factors. Here, we show that PARP-1 deletion was associated with a significant reduction in inflammatory cell recruitment to mouse airways upon intratracheal administration of LPS. However, PARP-1 deletion exerted little effect in response to TNF exposure. LPS induced massive neutrophilia and moderate recruitment of macrophages, and TNF induced recruitment of primarily macrophages with smaller numbers of neutrophils in the lungs. Following either exposure, macrophage recruitment was blocked severely in PARP-1(-/-) mice, and this was associated with a marked reduction in MCP-1 and MIP-1alpha. This association was corroborated partly by macrophage recruitment in response to intratracheal administration of MCP-1 in PARP-1(-/-) mice. Surprisingly, although neutrophil recruitment was reduced significantly in LPS-treated PARP-1(-/-) mice, neutrophil numbers increased in TNF-treated mice, suggesting that PARP-1 deletion may promote a macrophagic-to-neutrophilic shift in the inflammatory response upon TNF exposure. Neutrophil-specific chemokines mKC and MIP-2 were reduced significantly in lungs of LPS-treated but only partially reduced in TNF-treated PARP-1(-/-) mice. Furthermore, the MIP-2 antagonist abrogated the shift to a neutrophilic response in TNF-exposed PARP-1(-/-) mice. Although CXCR2 expression increased in response to either stimulus in PARP-1(+/+) mice, the DARC increased only in lungs of TNF-treated PARP-1(+/+) mice; both receptors were reduced to basal levels in treated PARP-1(-/-) mice. Our results show that the balance of pro-neutrophilic or pro-macrophagic stimulatory factors and the differential influence of PARP-1 on these factors are critical determinants for the nature of the airway inflammatory response.

L-Type Calcium Channel Blockers Exert an Antiinflammatory Effect by Suppressing Expression of Plasminogen Receptors on Macrophages

L-type Ca(2+) channel (LTCC) blockers, represented by amlodipine and verapamil, are widely used antihypertensive drugs that also have antiinflammatory activities. Plasminogen (Plg) is an important mediator of macrophage recruitment, and this role depends on its interaction with Plg receptors (Plg-Rs). Plg-Rs include histone 2B, alpha-enolase, annexin 2, and p11, all proteins which lack signal sequences for cell surface export. When human or murine monocytoid cells were induced to differentiate into macrophages, their Plg binding and Plg-R expression increased by 4-fold. These changes were suppressed by pretreatment with verapamil and amlodipine. Expression of the Ca(v)1.2 LTCC pore subunit was induced in differentiated macrophages, and siRNA against this subunit suppressed the upregulation of Plg binding and Plg-Rs. In vivo, amlodipine and verapamil suppressed peritoneal macrophage recruitment in response to thioglycollate by >60% at doses that did not affect blood pressure. In drug-treated animals, macrophages migrated into but not through the peritoneal membrane tissue and showed reduced surface expression of Plg-Rs. These findings demonstrate that Plg-R expression on macrophages is dependent on Ca(v)1.2 LTCC subunit expression. Suppression of Plg-Rs may contribute to the antiinflammatory effects of the widely used LTCC blockers.

Histone H2B as a functionally important plasminogen receptor on macrophages

AbstractPlasminogen (Plg) facilitates inflammatory cell recruitment, a function that depends upon its binding to Plg receptors (Plg-Rs). However, the Plg-Rs that are critical for cell migration are not well defined. Three previously characterized Plg-Rs (α-enolase, annexin 2, and p11) and a recently identified Plg-R (histone H2B [H2B]) were assessed for their contribution to Plg binding and function on macrophages. Two murine macrophage cell lines (RAW 264.7 and J774A.1) and mouse peritoneal macrophages induced by thioglycollate were analyzed. All 4 Plg-Rs were present on the surface of these cells and showed enhanced expression on the thioglycollate-induced macrophages compared with peripheral blood monocytes. Using blocking Fab fragments to each Plg-R, H2B supported approximately 50% of the Plg binding capacity, whereas the other Plg-Rs contributed less than 25%. Anti-H2B Fab also demonstrated a major role of this Plg-R in plasmin generation and matrix invasion. When mice were treated intravenously with anti-H2B Fab, peritoneal macrophage recruitment in response to thioglycollate was reduced by approximately 45% at 24, 48, and 72 hours, with no effect on blood monocyte levels. Taken together, these data suggest that multiple Plg-Rs do contribute to Plg binding to macrophages, and among these, H2B plays a very prominent and functionally important role.

CD44 Regulates Macrophage Recruitment to the Lung in Lipopolysaccharide-Induced Airway Disease

LPS from bacteria is ubiquitous in the environment and can cause airway disease and modify allergic asthma. Identification of gene products that modulate the biologic response to inhaled LPS will improve our understanding of inflammatory airways disease. Previous work has identified quantitative trait loci for the response to inhaled LPS on chromosomes 2 and 11. In these regions, 28 genes had altered RNA expression after inhalation of LPS, including CD44, which was associated with differences in both TNF-alpha levels and neutrophil recruitment into the lung. It has previously been shown that CD44 can modulate macrophage recruitment in response to Mycobacterium tuberculosis, as well as clearance of neutrophils after lung injury with both bleomycin and live Escherichia coli bacteria. In this study, we demonstrate that the biologic response to inhaled LPS is modified by CD44. Macrophages failed to be recruited to the lungs of CD44-deficient animals at all time points after LPS exposure. CD44-deficient macrophages showed reduced motility in a Transwell migration assay, reduced ability to secrete the proinflammatory cytokine TNF-alpha, reduced in vivo migration in response to monocyte chemotactic protein-1, and diminished adhesion to vascular endothelia in the presence of TNF-alpha. In addition, CD44-deficient animals had 150% fewer neutrophils at 24 h and 50% greater neutrophils 48 h after LPS exposure. These results support the role of CD44 in modulating the biologic response to inhaled LPS.

Adriamycin promotes macrophage dysfunction in mice

Impaired wound healing contributes to the morbidity and mortality associated with adriamycin chemotherapy. Macrophages are essential for tissue repair and loss of macrophage function leads to impaired wound healing. We recently showed that adriamycin is a potent inducer of thiol oxidation and cell injury in cultured macrophages (FASEB J. 19:1866–1868; 2005). Here we tested the hypothesis that adriamycin also promotes oxidative stress and macrophage dysfunction in vivo. We treated FVB mice twice a week either with low doses of adriamycin (4 mg/kg) or with the same volume of saline by tail vein injection for a total of 8 injections. Wound healing was significantly delayed in adriamycin-treated mice. The number of resident peritoneal macrophages was decreased by 30% and macrophage recruitment in response to thiogycolate stimulation was decreased by 46% in mice treated with adriamycin. LPS-induced TNFα and IL-1β secretion from macrophages of adriamycin-treated mice was decreased by 28.7 and 29.5%, respectively, compared to macrophages isolated from saline-injected mice. Peritoneal macrophages isolated from adriamycin-treated mice also showed increased formation of reactive oxygen species and enhanced protein-S-glutathionylation. In summary, our results show that low cumulative doses of adriamycin are sufficient both to promote sustained thiol oxidative stress and macrophage dysfunction in vivo and to delay tissue repair, suggesting that macrophage dysfunction contributes to impaired wound healing associated with adriamycin chemotherapy.

Gammaherpesvirus-Induced Lung Pathology Is Altered in the Absence of Macrophages

The purpose of this study was to examine the lung pathogenesis of murine gammaherpesvirus (MHV-68) infection in mice that lack CC chemokine receptor CCR2, an important receptor for macrophage recruitment to sites of inflammation. BALB/c and CCR2(-/-) mice were inoculated intranasally (i.n.) with MHV-68 and samples were collected during acute infection (6 dpi) and following viral clearance (12 dpi). Immunohistochemistry was used to determine which cells types responded to MHV-68 infection in the lungs. Lung pathology in infected BALB/c mice was characterized by a mixed inflammatory cell infiltrate, necrosis, and increased alveolar macrophages by 12 dpi. Immunohistochemistry showed intense positive staining for macrophages. CCR2(-/-) mice showed greater inflammation in the lungs at 12 dpi than did BALB/c mice, with more necrosis and diffuse neutrophil infiltrates in the alveoli. Immunohistochemistry demonstrated much less macrophage infiltration in the CCR2(-/-) mice than in the BALB/c mice. These studies show that CCR2 is involved in macrophage recruitment in response to MHV-68 infection and illustrates how impairments in macrophage function affect the normal inflammatory response to this viral infection.