Rapamycin inhibits lipopolysaccharide induction of granulocyte-colony stimulating factor and inducible nitric oxide synthase expression in macrophages by reducing the levels of octamer-binding factor-2

An altered sputum macrophage transcriptome contributes to the neutrophilic asthma endotype

Background

Neutrophilic asthma (NA) is a clinically important asthma phenotype, the cellular and molecular basis of which is not completely understood. Airway macrophages are long‐lived immune cells that exert important homeostatic and inflammatory functions which are dysregulated in asthma. Unique transcriptomic programmes reflect varied macrophage phenotypes in vitro. We aimed to determine whether airway macrophages are transcriptomically altered in NA.

Methods

We performed RNASeq analysis on flow cytometry‐isolated sputum macrophages comparing NA (n = 7) and non‐neutrophilic asthma (NNA, n = 13). qPCR validation of RNASeq results was performed (NA n = 13, NNA n = 23). Pathway analysis (PANTHER, STRING) of differentially expressed genes (DEGs) was performed. Gene set variation analysis (GSVA) was used to test for enrichment of NA macrophage transcriptomic signatures in whole sputum microarray (cohort 1 ‐ controls n = 16, NA n = 29, NNA n = 37; cohort 2 U‐BIOPRED ‐ controls n = 16, NA n = 47, NNA n = 57).

Results

Flow cytometry‐sorting significantly enriched sputum macrophages (99.4% post‐sort, 44.9% pre‐sort, p < .05). RNASeq analysis confirmed macrophage purity and identified DEGs in NA macrophages. Selected DEGs (SLAMF7, DYSF, GPR183, CSF3, PI3, CCR7, all p < .05 NA vs. NNA) were confirmed by qPCR. Pathway analysis of NA macrophage DEGs was consistent with responses to bacteria, contribution to neutrophil recruitment and increased expression of phagocytosis and efferocytosis factors. GSVA demonstrated neutrophilic macrophage gene signatures were significantly enriched in whole sputum microarray in NA vs. NNA and controls in both cohorts.

Conclusions

We demonstrate a pathophysiologically relevant sputum macrophage transcriptomic programme in NA. The finding that there is transcriptional activation of inflammatory programmes in cell types other than neutrophils supports the concept of NA as a specific endotype.

Induction of OCT2 contributes to regulate the gene expression program in human neutrophils activated via TLR8

The transcription factors (TFs) that regulate inducible genes in activated neutrophils are not yet completely characterized. Herein, we show that the genomic distribution of the histone modification H3K27Ac, as well as PU.1 and C/EBPβ, two myeloid-lineage-determining TFs (LDTFs), significantly changes in human neutrophils treated with R848, a ligand of Toll-like receptor 8 (TLR8). Interestingly, differentially acetylated and LDTF-marked regions reveal an over-representation of OCT-binding motifs that are selectively bound by OCT2/POU2F2. Analysis of OCT2 genomic distribution in primary neutrophils and of OCT2-depletion in HL-60-differentiated neutrophils proves the requirement for OCT2 in contributing to promote, along with nuclear factor κB (NF-κB) and activator protein 1 (AP-1), the TLR8-induced gene expression program in neutrophils. Altogether, our data demonstrate that neutrophils, upon activation via TLR8, profoundly reprogram their chromatin status, ultimately displaying cell-specific, prolonged transcriptome changes. Data also show an unexpected role for OCT2 in amplifying the transcriptional response to TLR8-mediated activation.

Nutrient availability contributes to a graded refractory period for regeneration in Xenopus tropicalis

Xenopus tadpoles are a unique model for regeneration in that they exhibit two distinct phases of age-specific regenerative competence. In Xenopus laevis, young tadpoles fully regenerate following major injuries such as tail transection, then transiently lose regenerative competence during the "refractory period" from stages 45-47. Regenerative competence is then regained in older tadpoles before being permanently lost during metamorphosis. Here we show that a similar refractory period exists in X. tropicalis. Notably, tadpoles lose regenerative competence gradually in X. tropicalis, with full regenerative competence lost at stage 47. We find that the refractory period coincides closely with depletion of maternal yolk stores and the onset of independent feeding, and so we hypothesized that it might be caused in part by nutrient stress. In support of this hypothesis, we find that cell proliferation declines throughout the tail as the refractory period approaches. When we block nutrient mobilization by inhibiting mTOR signaling, we find that tadpole growth and regeneration are reduced, while yolk stores persist. Finally, we are able to restore regenerative competence and cell proliferation during the refractory period by abundantly feeding tadpoles. Our study argues that nutrient stress contributes to lack of regenerative competence and introduces the X. tropicalis refractory period as a valuable new model for interrogating how metabolic constraints inform regeneration.

Physalactone and 4β-Hydroxywithanolide E Isolated from Physalis peruviana Inhibit LPS-Induced Expression of COX-2 and iNOS Accompanied by Abatement of Akt and STAT1

In previous studies, withanolides isolated from Physalis peruviana were found to exhibit anti-inflammatory potential by suppressing nitrite production induced by lipopolysaccharide (LPS) treatment. Currently, we selected two of the most potent compounds, 4β-hydroxywithanolide E (1) and physalactone (2), to examine the underlying mechanism of action. With LPS-stimulated RAW 264.7 cells in culture, the compounds inhibited the mRNA and protein expression of iNOS and COX-2. To determine which upstream signaling proteins were involved in these effects, phosphorylation levels of three mitogen-activated protein kinases (MAPKs) including ERK1/2, JNK1/2, and p38, were examined, but found unaffected. Similarly, the degradation of IκBα was not attenuated by the compounds. However, phosphorylation of Akt at the Ser-473 residue was inhibited, as was the phosphorylation of STAT1. Interestingly, the compounds also reduced the protein level of total STAT1, possibly by ubiquitin-dependent protein degradation. In sum, these results indicate the potential of 1 and 2 to mediate anti-inflammatory effects through the unexpected mechanism of inhibiting the transcription of iNOS and COX-2 via Akt- and STAT1-related signaling pathways.

L5-LDL from ST-elevation myocardial infarction patients induces IL-1β production via LOX-1 and NLRP3 inflammasome activation in macrophages

L5-LDL, the most electronegative LDL associated with major cardiovascular risks, significantly rises in patients with ST-segment elevation myocardial infarction (STEMI). The inflammatory nature of atherosclerotic vascular diseases has prompted us to investigate whether L5-LDL induces the production of inflammatory cytokines, especially vascular ischemia-related interleukin (IL)-1β, in the pathogenesis of STEMI. Clinical data showed that plasma levels of L5-LDL and IL-1β were higher in the STEMI patients than in the controls (P < 0.05). In THP-1-derived human macrophages, L5-LDL significantly increased the levels of both IL-1β and cleaved caspase-1, indicating the activation of NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasomes by L5-LDL. Knockdown of NLRP3 and its adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC) resulted in decreased L5-LDL-induced IL-1β. Furthermore, knock down of the lectin-type oxidized LDL receptor (LOX-1) in THP-1 cells attenuated L5-LDL-induced activation of NF-κB and caspase-1, leading to subsequent inhibition of IL-1β in macrophages. Furthermore, blockade LOX-1 with neutralizing antibody also inhibited L5-LDL-induced IL-1β in human peripheral blood mononuclear cell-derived macrophages. In conclusion, L5-LDL induces IL-1β production in macrophages by activation of NF-κB and caspase-1 through the LOX-1-dependent pathway. This study represents the evidence linking L5-LDL and the inflammatory cytokine IL-1β in STEMI, and identifies L5-LDL as a novel therapeutic target in acute myocardial infarction.

NEW & NOTEWORTHY

This study represents the evidence linking L5-LDL and the inflammatory cytokine IL-1β in ST-segment elevation myocardial infarction (STEMI). We elucidate the molecular mechanism underlying L5-LDL-induced production of IL-1β in macrophages. The results showed that L5-LDL induced activation of caspase-1 and NF-κB through the lectin-type oxidized LDL receptor (LOX-1)-dependent pathway, leading to the production of IL-1β.

Acetylation impacts Fli-1-driven regulation of granulocyte colony stimulating factor

Fli-1 has emerged as a critical regulator of inflammatory mediators, including MCP-1, CCL5, and IL-6. The cytokine, granulocyte colony stimulating factor (G-CSF) regulates neutrophil precursor maturation and survival, and activates mature neutrophils. Previously, a significant decrease in neutrophil infiltration into the kidneys of Fli-1^+/- lupus-prone mice was observed. In this study, a significant decrease in G-CSF protein expression was detected in stimulated murine and human endothelial cells when expression of Fli-1 was inhibited. The murine G-CSF promoter contains numerous putative Fli-1 binding sites and several regions within the proximal promoter are significantly enriched for Fli-1 binding. Transient transfection assays indicate that Fli-1 drives transcription from the G-CSF promoter and mutation of the Fli-1 DNA binding domain resulted in a 94% loss of transcriptional activation. Mutation of a known acetylation site, led to a significant increase in G-CSF promoter activation. The histone acetyltransferases p300/CBP and p300/CBP associated factor (PCAF) significantly decrease Fli-1 specific activation of the G-CSF promoter. Thus, acetylation appears to be an important mechanism behind Fli-1 driven activation of the G-CSF promoter. These results further support the theory that Fli-1 plays a major role in the regulation of several inflammatory mediators, ultimately affecting inflammatory disease pathogenesis.

Viral inhibitors of NKG2D ligands for tumor surveillance

INTRODUCTION

Natural Killer cells (NK) are key for the innate immune response against tumors and viral infections. Several viral proteins evade host immune response and target the NK cell receptor NKG2D and its ligands. Areas covered: This review aimed to describe the viruses and their proteins that interfere with the NKG2D receptor and their ligands, and how these interactions lead to immune evasion, host protection, and tissue damage from acute and chronic viral infections. Expert opinion: The study of viral proteins has already impacted the field of oncology. A prime example is the HBV vaccine and the development of antiviral drugs for HIV, Hepatitis C, and the family of Herpesviridae viruses. The NKG2D system seems to be a rational therapeutic target. Nevertheless, an effective cytotoxic response by NK cells is mediated by a network of activating and inhibitory receptors, the integration of which determines if the NK cell becomes cytotoxic or permissive. Immunotherapeutic agents that increase the antitumor lytic activity of NK cells through modulating activation and inhibitory signaling of NK cells are being developed. Nevertheless, more research is needed to dissect the integrative mechanism of NK cells function to fully exploit their antitumor and antiviral effector mechanisms.

mTOR masters monocytic myeloid-derived suppressor cells in mice with allografts or tumors

CD11b(+) Gr1(+) myeloid-derived suppressor cells (MDSCs) play critical roles in controlling the processes of tumors, infections, autoimmunity and graft rejection. Immunosuppressive drug rapamycin (RPM), targeting on the key cellular metabolism molecule mTOR, is currently used in clinics to treat patients with allo-grafts, autoimmune diseases and tumors. However, the effect of RPM on MDSCs has not been studied. RPM significantly decreases the cell number and the immunosuppressive ability on T cells of CD11b(+) Ly6C(high) monocytic MDSCs (M-MDSCs) in both allo-grafts-transplanted and tumor-bearing mice respectively. Mice with a myeloid-specific deletion of mTOR have poor M-MDSCs after grafting with allo-skin tissue or a tumor. Grafting of allo-skin or tumors significantly activates glycolysis pathways in myeloid precursor cells in bone marrow, which is inhibited by RPM or mTOR deletion. 2-deoxyglucose (2-DG), an inhibitor of the glycolytic pathway, inhibits M-MDSC differentiation from precursors, while enhancing glycolysis by metformin significantly rescues the RPM-caused deficiency of M-MDSCs. Therefore, we offer evidence supporting that mTOR is an intrinsic factor essential for the differentiation and immunosuppressive function of M-MDSCs and that these metabolism-relevant medicines may impact MDSCs-mediated immunosuppression or immune tolerance induction, which is of considerable clinical importance in treating graft rejection, autoimmune diseases and cancers.

SB203580 increases G-CSF production via a stem-loop destabilizing element in the 3' untranslated region in macrophages independently of its effect on p38 MAPK activity

Background

Granulocyte-colony stimulating factor (G-CSF) is a major regulator of the production and survival of neutrophils. Regulation of G-CSF expression is complex and occurs at both transcription and post-transcription levels. Two distinct types of cis-acting elements in the 3’ untranslated region (3’UTR) of G-CSF mRNA have been identified as destabilizing elements; these consist of adenylate uridylate-rich elements (AUREs) and a stem–loop destabilizing element (SLDE). Regulation of the stability of mRNA by p38 mitogen-activated protein kinase (MAPK) has been indicated to be linked to AUREs in the 3’UTR. However, whether p38 MAPK is involved in the regulation of the stability of G-CSF mRNA has not been elucidated. This study investigated the effect of SB203580, an inhibitor of p38 MAPK, on the lipopolysaccharide-induced G-CSF expression in macrophages at the post-transcription level.

Results

Our study showed surprising results that SB203580 augmented the lipopolysaccharide-induced increase in the G-CSF mRNA levels in RAW264.7 mouse macrophages, mouse bone marrow-derived macrophages and in THP-1 human macrophages. This effect was also seen in p38α MAPK knockdown RAW264.7 cells, showing that it was not due to inhibition of p38 MAPK activity. In the presence of actinomycin D, the decay of G-CSF mRNA was slower in SB203580-treated cells than in control cells, showing that SB203580 increased the stability of G-CSF mRNA. Reporter genes containing luciferase with or without the 3’UTR of G-CSF were constructed and transfected into RAW264.7 cells and the results showed that the presence of the 3’UTR reduced the luciferase mRNA levels and luciferase activity. Furthermore, SB203580 increased the luciferase mRNA levels and activity in RAW264.7 cells transfected with the luciferase reporter containing the 3’UTR, but not in cells transfected with the luciferase reporter without the 3’UTR. Mutations of the highly conserved SLDE in the 3’UTR abolished these effects, showing that the SLDE was essential for the SB203580-induced increase in the stability of mRNA.

Conclusions

SB203580 increases G-CSF expression in macrophages by increasing the stability of G-CSF mRNA via its 3’UTR, and the effect was not due to its inhibition of p38 MAPK activity. The results of this study also highlight a potential target for boosting endogenous production of G-CSF during neutropenia.

YC-1 induces lipid droplet formation in RAW 264.7 macrophages

BACKGROUND

3-(5'-Hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) is a potential anticancer drug that may activate soluble guanylyl cyclase (sGC) and increase the level of cyclic guanosine monophosphate (cGMP). The aim of this study was to explore the effects of YC-1 on lipid droplet accumulation and foam cell formation in macrophages.

RESULTS

Human-oxidized low density lipoprotein (ox-LDL) was used to induce accumulation of lipid droplets in a murine macrophage cell line, RAW 264.7. Oil red O staining showed that treatment with 20 μM YC-1 for 24 h increased the area of intracellular lipid droplets in macrophages. The results of high content screening (HCS) with the AdipoRed™ assay further revealed that YC-1 enhanced ox-LDL-induced foam cell formation. This was evidenced by an increase in the total area of lipid droplets and the mean fluorescence intensity per cell. Inhibition of cGMP-dependent protein kinase (PKG) using KT5823 significantly reduced YC-1-enhanced lipid droplet formation in ox-LDL-induced macrophage foam cells.

CONCLUSION

YC-1 induces lipid droplet formation in macrophages, possibly through the sGC/cGMP/PKG signaling pathway. This chemical should be tested with caution in future clinical trials.

Preferential production of G-CSF by a protein-like Lactobacillus rhamnosus GR-1 secretory factor through activating TLR2-dependent signaling events without activation of JNKs

Background

Different species and strains of probiotic bacteria confer distinct immunological responses on immune cells. Lactobacillus rhamnosus GR-1 (GR-1) is a probiotic bacterial strain found in both the intestinal and urogenital tracts, and has immunomodulatory effects on several cell types including macrophages. However, detailed immunological responses and the signaling mechanism involved in the response are largely unknown.

Results

We examined the production of GR-1-induced cytokines/chemokines and signaling events in macrophages. Among 84 cytokines and chemokines examined, GR-1 discretely induced granulocyte colony-stimulating factor (G-CSF) mRNA at highest levels (>60-fold) without inducing other cytokines such as IL-1α, IL-1β, IL-6 and TNF-α (<5-fold). The toll-like receptor (TLR) 2/6-agonist PAM₂CSK₄, TLR2/1-agonist PAM₃CSK₄ and TLR4-agonist lipopolysaccharide induced all of these inflammatory cytokines at high levels (>50-fold). The TLR2 ligand lipoteichoic acid activated all mitogen-activated kinases, Akt and NF-κB; whereas, GR-1 selectively activated extracellular regulated kinases and p38, NF-κB and Akt, but not c-Jun N-terminal kinases (JNKs) in a TLR2-dependent manner. Using specific inhibitors, we demonstrated that lack of JNKs activation by GR-1 caused inefficient production of pro-inflammatory cytokines but not G-CSF production. A secreted heat-labile protein-like molecule, 30–100 kDa in size, induced the preferential production of G-CSF.

Conclusion

This study elucidated unique signaling events triggered by GR-1, resulting in selective production of the immunomodulatory cytokine G-CSF in macrophages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0578-2) contains supplementary material, which is available to authorized users.

LPS-Induced G-CSF Expression in Macrophages Is Mediated by ERK2, but Not ERK1

Granulocyte colony-stimulating factor (G-CSF) selectively stimulates proliferation and differentiation of neutrophil progenitors which play important roles in host defense against infectious agents. However, persistent G-CSF production often leads to neutrophilia and excessive inflammatory reactions. There is therefore a need to understand the mechanism regulating G-CSF expression. In this study, we showed that U0126, a MEK1/2 inhibitor, decreases lipopolysaccharide (LPS)-stimulated G-CSF promoter activity, mRNA expression and protein secretion. Using short hairpin RNA knockdown, we demonstrated that ERK2, and not ERK1, involves in LPS-induced G-CSF expression, but not LPS-regulated expression of TNF-α. Reporter assays showed that ERK2 and C/EBPβ synergistically activate G-CSF promoter activity. Further chromatin immunoprecipitation (ChIP) assays revealed that U0126 inhibits LPS-induced binding of NF-κB (p50/p65) and C/EBPβ to the G-CSF promoter, but not their nuclear protein levels. Knockdown of ERK2 inhibits LPS-induced accessibility of the G-CSF promoter region to DNase I, suggesting that chromatin remodeling may occur. These findings clarify that ERK2, rather than ERK1, mediates LPS-induced G-CSF expression in macrophages by remodeling chromatin, and stimulates C/EBPβ-dependent activation of the G-CSF promoter. This study provides a potential target for regulating G-CSF expression.

Mechanistic target of rapamycin inhibition extends cellular lifespan in dendritic cells by preserving mitochondrial function

TLR-mediated activation of dendritic cells (DCs) is associated with a metabolic transition in which mitochondrial oxidative phosphorylation is inhibited by endogenously synthesized NO and the cells become committed to glucose and aerobic glycolysis for survival. We show that inhibition of mechanistic target of rapamycin (mTOR) extends the lifespan of TLR-activated DCs by inhibiting the induction of NO production, thereby allowing the cells to continue to use their mitochondria to generate ATP, and allowing them the flexibility to use fatty acids or glucose as nutrients to fuel core metabolism. These data provide novel mechanistic insights into how mTOR modulates DC metabolism and cellular longevity following TLR activation and provide an explanation for previous findings that mTOR inhibition enhances the efficacy of DCs in autologous vaccination.

Inhibitory effect of a callophycin A derivative on iNOS expression via inhibition of Akt in lipopolysaccharide-stimulated RAW 264.7 cells

In previous studies, (R)-2-isobutyl 3-methyl 3,4-dihydro-1H-pyrido[3,4-b]indole-2,3(9H)-dicarboxylate (1), a callophycin A derivative, was found to strongly inhibit nitrite production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, while (R)- or (S)-callophycin A showed only weak inhibition. We currently report additional studies to define the mechanisms underlying the inhibitory action of 1. Expression of inducible nitric oxide synthase (iNOS) was reduced at both protein and mRNA levels. Major upstream signaling molecules and transcription factors regulating iNOS expression were examined, but it was found that 1 did not affect the phosphorylated and total protein levels of p38 mitogen-activated protein kinase (p38 MAPK), Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), and signal transducer and activator of transcription 1 (STAT1), nor did it mediate the degradation of the inhibitor of nuclear factor-κB α-isoform (IκBα). However, starting at early time points, 1 consistently inhibited the phosphorylation of protein kinase B/Akt at serine 473. In addition, 1 suppressed the protein expression of octamer-binding transcription factor-2 (Oct-2) and the expression of microRNA 155 (miR-155). In sum, compound 1 inhibits LPS-induced nitrite production by a unique and complex mechanism. Reduction of iNOS expression is accompanied by inhibition of Akt activation, Oct-2 protein expression, and miR-155 expression.

FJU-C4, a new 2-pyridone compound, attenuates lipopolysaccharide-induced systemic inflammation via p38MAPK and NF-κB in mice

Despite advances in antibiotic therapy and intensive care, the mortality caused by systemic inflammatory response syndrome and severe sepsis remains high. The use of anti-inflammatory agents to attenuate inflammatory response during acute systemic inflammatory reactions may improve survival rates. Here we show that a newly synthesized 2-pyridone compound (FJU-C4) can suppress the expression of late inflammatory mediators such as iNOS and COX-2 in murine macrophages. The pro-inflammatory cytokines, including TNFα, IL-1β, and IL-6, were dose-dependently suppressed by FJU-C4 both in mRNA and protein levels. In addition, the expression of TNFα was inhibited from as early as 2 hours after exposure to LPS stimulation. The production of mature pro-inflammatory cytokines was also suppressed by pretreatment with FJU-C4 in either cell culture medium or mice serum when stimulated by LPS. FJU-C4 prolongs mouse survival and prevents mouse death from LPS-induced systemic inflammation when the dose of FJU-C4 is over 5 mg/kg. The activities of ERK, JNK, and p38MAPK were induced by LPS stimulation on murine macrophage cell line, but only p38MAPK signaling was dramatically suppressed by pretreatment with the FJU-C4 compound in a dose-dependent manner. NF-κB activation also was suppressed by FJU-C4 compound. These findings suggest that the FJU-C4 compound may act as a promising therapeutic agent against inflammatory diseases by inhibiting the p38MAPK and NF-κB signaling pathway.

Extracellular signal-regulated kinase 2 mediates the expression of granulocyte colony-stimulating factor in invasive cancer cells

Granulocyte colony-stimulating factor (G-CSF) affects granulopoiesis and is important for mobilizing neutrophils into blood circulation. Due to the hematopoietic properties of G-CSF, it has been widely used to clinically treat chemotherapy-induced neutropenia. However, G-CSF can promote tumors by inhibiting innate and adaptive immunity and enhancing angiogenesis and neoplastic growth. Most G-CSF-producing tumors are associated with a poor prognosis. This indicates that G-CSF promotes cancer progression. Thus, identifying regulatory molecules involved in tumor-derived G-CSF expression may provide therapeutic targets for cancer treatment. This study identified considerable G-CSF expression in malignant breast, lung and oral cancer cells. However, G-CSF expression was barely detectable in non-invasive cell lines. Expression of G-CSF mRNA and protein increased during exposure to tumor necrosis factor-α (TNF-α). Treatment with U0126 (a mitogen-activated protein kinase inhibitor) drastically reduced basal levels of G-CSF and TNF-α-induced G-CSF in aggressive cancer cells. This study also showed that knockdown of extracellular signal-regulated kinase (ERK) 2 by shRNA was necessary and sufficient to eliminate the expression of tumor-derived G-CSF. This did not apply to ERK1. Therefore, ERK2 (but not ERK1) is responsible for the transcriptional regulation of tumor-derived G-CSF. The results indicate the pharmaceutical value of specific ERK2 inhibitors in treating patients with G-CSF-producing tumors.

Role of macrophages in mobilization of hematopoietic progenitor cells from bone marrow after hemorrhagic shock

The release of hematopoietic progenitor cells (HPCs) from bone marrow (BM) is under tight homeostatic control. Under stress conditions, HPCs migrate from BM and egress into circulation to participate in immune response, wound repair, or tissue regeneration. Hemorrhagic shock with resuscitation (HS/R), resulting from severe trauma and major surgery, promotes HPC mobilization from BM, which, in turn, affects post-HS immune responses. In this study, we investigated the mechanism of HS/R regulation of HPC mobilization from BM. Using a mouse HS/R model, we demonstrate that the endogenous alarmin molecule high-mobility group box 1 mediates HS/R-induced granulocyte colony-stimulating factor secretion from macrophages (Mϕ in a RAGE [receptor for advanced glycation end products] signaling-dependent manner. Secreted granulocyte colony-stimulating factor, in turn, induces HPC egress from BM. We also show that activation of β-adrenergic receptors on Mϕ by catecholamine mediates the HS/R-induced release of high-mobility group box 1. These data indicate that HS/R, a global ischemia-reperfusion stimulus, regulates HPC mobilization through a series of interacting pathways that include neuroendocrine and innate immune systems, in which Mϕ play a central role.

Inhibition by rapamycin of the lipoteichoic acid-induced granulocyte-colony stimulating factor expression in mouse macrophages

Granulocyte-colony stimulating factor (G-CSF) is a cytokine which involves in anti-inflammation and inflammation as well. Rapamycin is an inhibitor of mTOR which also plays a role in innate immunity. This study investigated the effect of rapamycin on the lipoteichoic acid (LTA)-induced expression of G-CSF in macrophages and its underlying mechanism. Our data show that LTA induced G-CSF expression in RAW264.7 and bone marrow-derived macrophages and that this effect was inhibited by rapamycin. Analysis of the G-CSF 5' flanking sequence revealed that the -283 to +35 fragment, which contains CSF and octamer elements, was required for maximal promoter activity in response to LTA stimulation. Western blot analyses of proteins that bind to the CSF and octamer element show that LTA increased protein levels of NF-κB, C/EBPβ and Oct-2, and that rapamycin inhibited the LTA-induced increase in Oct-2 protein levels, but not the others. Knockdown of Oct-2 by RNA interference resulted in a decrease in LTA-induced G-CSF mRNA levels. Moreover, forced expression of Oct-2 by transfection with the pCG-Oct-2 plasmid overcame the inhibitory effect of rapamycin on the LTA-induced increase in G-CSF mRNA levels and promoter activity. This study demonstrates that rapamycin reduces G-CSF expression in LTA-treated macrophages by inhibiting Oct-2 expression.