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

The role of granulocyte colony‑stimulating factor in breast cancer development: A review

Granulocyte-colony-stimulating factor (G-CSF) is a member of the hematopoietic growth factor family that primarily affects the neutrophil lineage. G-CSF serves as a powerful mobilizer of peripheral blood stem cells and recombinant human G-CSF (rhG-CSF) has been used to treat granulocytopenia and neutropenia after chemotherapy for cancer patients. However, recent studies have found that G-CSF plays an important role in cancer progression. G-CSF expression is increased in different types of cancer cells, such as lung cancer, gastric cancer, colorectal cancer, invasive bladder carcinoma, glioma and breast cancer. However, it is unclear whether treatment with G-CSF has an adverse effect. The current review provides an overview of G-CSF in malignant breast cancer development and the data presented in this review are expected to provide new ideas for cancer therapy.

Polydatin reduces Staphylococcus aureus lipoteichoic acid-induced injury by attenuating reactive oxygen species generation and TLR2-NFκB signalling

Staphylococcus aureus (S. aureus) causes severe inflammation in various infectious diseases, leading to high mortality. The clinical application of antibiotics has gained a significant curative effect. However, it has led to the emergence of various resistant bacteria. Therefore, in this study, we investigated the protective effect of polydatin (PD), a traditional Chinese medicine extract, on S. aureus lipoteichoic acid (LTA)-induced injury in vitro and in vivo. First, a significant improvement in the pathological conditions of PD in vivo was observed, suggesting that PD had a certain protective effect on LTA-induced injury in a mouse model. To further explore the underlying mechanisms of this protective effect of PD, LTA-induced murine macrophages were used in this study. The results have shown that PD could reduce the NF-κB p65, and IκBα phosphorylation levels increased by LTA, resulting in a decrease in the transcription of pro-inflammatory factors, such as TNF-α, IL-1β and IL-6. However, LTA can not only activate NF-κB through the recognition of TLR2 but also increase the level of intracellular reactive oxygen species (ROS), thereby activating NF-κB signalling. We also detected high levels of ROS that activate caspases 9 and 3 to induce apoptosis. In addition, using a specific NF-κB inhibitor that could attenuate apoptosis, namely NF-κB p65, acted as a pro-apoptotic transcription factor in LTA-induced murine macrophages. However, PD could inhibit the generation of ROS and NF-κB p65 activation, suggesting that PD suppressed LTA-induced injury by attenuating ROS generation and TLR2-NFκB signalling.

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.

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.

Carbonic anhydrase IX promotes myeloid-derived suppressor cell mobilization and establishment of a metastatic niche by stimulating G-CSF production

The mobilization of bone marrow-derived cells (BMDC) to distant tissues before the arrival of disseminated tumor cells has been shown preclinically to facilitate metastasis through the establishment of metastatic niches. Primary tumor hypoxia has been demonstrated to play a pivotal role in the production of chemokines and cytokines responsible for the mobilization of these BMDCs, especially in breast cancer. Carbonic anhydrase IX (CAIX, CA9) expression is highly upregulated in hypoxic breast cancer cells through the action of hypoxia-inducible factor-1 (HIF1). Preclinical evidence has demonstrated that CAIX is required for breast tumor growth and metastasis; however, the mechanism by which CAIX exerts its prometastatic function is not well understood. Here, we show that CAIX is indispensable for the production of granulocyte colony-stimulating factor (G-CSF) by hypoxic breast cancer cells and tumors in an orthotopic model. Furthermore, we demonstrate that tumor-expressed CAIX is required for the G-CSF-driven mobilization of granulocytic myeloid-derived suppressor cells (MDSC) to the breast cancer lung metastatic niche. We also determined that CAIX expression is required for the activation of NF-κB in hypoxic breast cancer cells and constitutive activation of the NF-κB pathway in CAIX-depleted cells restored G-CSF secretion. Together, these findings identify a novel hypoxia-induced CAIX-NF-κB-G-CSF cellular signaling axis culminating in the mobilization of granulocytic MDSCs to the breast cancer lung metastatic niche.

Multiple effects of Escherichia coli Nissle 1917 on growth, biofilm formation, and inflammation cytokines profile of Clostridium perfringens type A strain CP4

Clostridium perfringens is an important Gram-positive pathogen responsible for food poisoning, necrotic enteritis, gas gangrene, and even death. Escherichia coli Nissle 1917 (EcN) is a well-characterized probiotic strain with demonstrated benefits. In this study, we evaluated the effects of EcN on growth, toxin production, biofilm formation, and inflammatory cytokine responses of C. perfringens. In vitro co-culture experiments demonstrated that EcN inhibited growth, gas production, and toxin production (α-toxin and NetB) of C. perfringens in a dose-dependent manner. The growth inhibition effect was not observed when C. perfringens was incubated with EcN cell-free supernatants (CFSE), suggesting that growth inhibition was caused by nutrition competition during co-incubation. In vitro studies demonstrated that pre-incubation with EcN did not inhibit C. perfringens attachment to Caco-2 cells, but did reduce C. perfringens total number, toxin production, and cytotoxicity after 24 h. The similar growth inhibition results were also observed during the formation of C. perfringens biofilm. Finally, pre-incubation of EcN with RAW264.7 cells significantly decreased the production of inflammatory cytokines caused by the introduction of C. perfringens. Our results indicate that EcN can inhibit many of the pathological effects of C. perfringens in vitro conditions.

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.