Curcumin, a compound with anti-inflammatory and anti-oxidant properties, down-regulates chemokine expression in bone marrow stromal cells.

Chemotactic cytokines or chemokines play an important role in the regulation of myelopoiesis. Since the production of chemokines and colony stimulating factors (CSFs) by bone marrow stromal cells requires inflammatory conditions, we investigated the effect of curcumin, an agent with anti-inflammatory and anti-oxidant activities, on the expression of monocyte chemoattractant protein-1 (MCP-1 or MCP-1/JE) and interferon inducible protein-10kD (IP-10) in mouse bone marrow stromal cell line +/+-1.LDA11. Both chemokines are readily expressed in stromal cells after stimulation with pro-inflammatory interleukin-1alpha (IL-1alpha), interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and endotoxin lipopolysaccharide (LPS). Curcumin attenuates the levels of MCP-1/JE and IP-10 mRNA expression by all of these stimulatory agents. A detailed analysis of the regulatory effects of curcumin on chemokine expression by IL-1alpha was performed. Curcumin inhibits both chemokine mRNAs in a dose- and time-dependent manner. The suppressive effect of curcumin on both mRNAs is reversible with complete recovery from suppression within 24 hours after removal of curcumin. The suppression of mRNA by curcumin is dependent on de novo synthesis of an intermediary protein(s), since suppression is abrogated by concomitant treatment with cycloheximide (CHX). Destabilization of mRNA transcripts is not the mechanism by which curcumin lowers the levels of mRNA; however, transcripts formed in the presence of curcumin are more stable, as indicated by their slower degradation kinetics. Run-on transcriptional assays demonstrate that curcumin inhibits the transcriptional activity of both genes. Finally, the attenuation of chemokine gene expression is associated with decreased production of chemotactic activity. Together, these findings indicate that while curcumin may post-transcriptionally stabilize mRNA transcripts formed in its presence, the overall reduction in mRNA levels by curcumin is mediated by inhibition of the transcription of chemokine genes.

IL-4 upregulates IL-1-induced chemokine gene expression in bone marrow stromal cells by enhancing NF-kB activation.

Bone marrow stromal cells play a critical role in the proliferation and differentiation of hematopoietic stem and progenitor cells by secreting numerous hematopoietic growth factors and colony-stimulating factors (CSFs). We have previously reported that monocyte chemotactic protein-1 (MCP-1 or MCP-1/JE) and interferon-inducible protein 10 KD (IP-10) are both induced in murine bone marrow stromal cell line +/(+)-1.LDA11 upon stimulation with various inflammatory agents, including IL-1 alpha, IFN-gamma, TNF-alpha, or LPS. In addition, the expression of MCP-1/JE and IP-10 mRNA by these inducers is potentiated by IL-4 and TGF-beta 1. In the present study we have investigated the mechanism of IL-4-mediated upregulation of MCP-1/JE gene expression. Our results of nuclear run-on experiments show that IL-4 enhances the IL-1-induced transcription of MCP-1/JE gene. Because the transcription of genes is regulated by DNA binding nuclear factors and binding sites for transcription factors AP-1 and SP-1, and NF-kB in the enhancer region of MCP-1/JE have been demonstrated, we examined the effect of IL-4 on the levels of these factors in stromal cells stimulated with IL-1. Whereas AP-1 and SP-1 are constitutively expressed in stromal cells, NF-kB is detected only after stimulation with IL-1. Furthermore, while unable to induce the activation of NF-kB alone, IL-4 enhanced the activation of NF-kB by IL-1. Taken together, these data suggest that upregulation of NF-kB may be the mechanism by which IL-4 increases the transcription of MCP-1/JE gene resulting in overabundance of the chemokine mRNA.

Chemokine gene expression in bone marrow stromal cells: downregulation with sodium salicylate.

Chemotactic cytokines, chemokines, have been shown to influence the proliferation of hematopoietic progenitor cells. Thus, regulation of chemokine production by bone marrow accessory cells is a critical aspect of stromal cell regulation of hematopoiesis. We have previously reported that monocyte chemotactic protein-1 (MCP-1 or MCP-1/JE) and interferon inducible protein 10 kD (IP-10) are both induced in murine bone marrow stromal cells +/(+)-1.LDA11 after stimulation with the inflammatory agents interleukin-1 alpha (IL-1 alpha), interferon-gamma (IFN-gamma), or lipopolysaccharide (LPS). In the present study, we have investigated the effect of sodium salicylate, an antiinflammatory agent, on the IL-1 alpha-induced expression of MCP-1/JE and IP-10 genes in stromal cells. Sodium salicylate attenuates the levels of MCP-1/JE and IP-10 mRNA in a concentration- and time-dependent manner. The suppression of MCP-1/JE mRNA is reversible, whereas IP-10 mRNA expression is more or less irreversibly affected as its recovery from the effect of sodium salicylate is slow and partial. Sodium salicylate-mediated suppression of mRNA expression is attributable neither to de novo synthesis of intermediary protein(s) nor to the destabilization of mature mRNA transcripts. On the other hand, sodium salicylate downregulates the transcriptional activity of both genes. Furthermore, IL-1 alpha induces activation of transcription factor nuclear factor (NF)-kB, and sodium salicylate suppresses it in a dose-dependent manner. We conclude that while posttranscriptional events remain unaffected, inhibition of NF-kB activation by sodium salicylate may account for the suppression of chemokine gene expression at the transcriptional level.

Induction of chemokine mRNA in bone marrow stromal cells: modulation by TGF-beta 1 and IL-4.

Bone marrow stromal cells produce cytokines that are essential for the proliferation and differentiation of hematopoietic stem and progenitor cells. Thus, regulation of cytokine production by bone marrow accessory cells is a critical aspect of stromal cell regulation of hematopoiesis. We have investigated the effect of two cytokines that have been demonstrated to modulate factor production by non-marrow accessory cells (i.e., transforming growth factor-beta 1 [TGF-beta 1] and interleukin-4 [IL-4]) on the induced expression of cytokine mRNA in a bone marrow-derived, cloned, murine stromal cell line +/+/-.LDA11. We showed that +/+/-.LDA11 cells can be induced with lipopolysaccharide (LPS), IL-1 alpha, or interferon-gamma (IFN-gamma) to express mRNA for monocyte chemoattractant protein-1 (MCP-1/JE), IFN-inducible protein-10 (IP-10), stem cell factor (SCF), and macrophage colony-stimulating factor (M-CSF) but not for IL-1 alpha, IL-3, or tumor necrosis factor-alpha (TNF-alpha). The expression of MCP-1/JE and IP-10 mRNA by these inducers was potentiated by TGF-beta 1 and IL-4. The augmentation by TGF-beta 1 of both mRNAs induced with IL-1 alpha was maximum when applied to the cells concurrently with the inducer; the IFN-gamma-induced expression of mRNAs was augmented even if the addition of TGF-beta 1 was delayed. Similarly, IL-4 potentiation of both mRNAs by either inducer progressively increased as the time between exposure to the inducer and exposure to IL-4 increased. Neither modulator altered the time course of mRNA expression by either inducer. TGF-beta 1- and IL-4-mediated augmentation of MCP-1/JE mRNA by IL-1 alpha or IFN-gamma was partially reversed by cycloheximide (CHX), whereas potentiation of IP-10 by either modulator remained unaffected. Increase in the stability of mRNA transcripts by TGF-beta 1 or IL-4 does not appear to play a role in the enhanced accumulation of mRNA in the presence of the modulators. These findings support a role for TGF-beta 1 and IL-4 as critical regulatory molecules in production of MCP-1 and IP-10 chemokines by stromal cells.

Transforming growth factor beta-1 (TGF-beta 1) potentiates IL1 alpha-induced IL6 mRNA and cytokine protein production in a human astrocytoma cell line.

We analyzed the response of human astrocytoma cell line U373-MG to various cytokines by measuring the production of interleukin-6 (IL6) mRNA and cytokine protein. Interferon gamma (IFN gamma), transforming growth factor beta 1 (TGF-beta 1), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-colony-stimulating factor (G-CSF) did not induce IL6 mRNA production; however, IL6 mRNA expression and protein production was strongly induced by IL1 alpha and to a lesser extent by IFN alpha. The IL6 mRNA expression induced by IL1 alpha was potentiated by TGF-beta 1 and IFN alpha and slightly decreased by IFN gamma. The potentiation of cytokine mRNA accumulation by TGF-beta 1 was both time- and concentration-dependent. Induction of IL6 mRNA by IL1 alpha was optimally potentiated either if U373-MG cells were pretreated with TGF-beta 1 or if TGF-beta 1 was added within 30 min after stimulation with IL1 alpha. The potentiation of IL6 mRNA by TGF-beta 1 required de novo synthesis of an intermediate protein since treatment with cycloheximide abrogated the amount of mRNA enhanced by TGF-beta 1 without affecting IL1 alpha-driven mRNA production. Nuclear run-on analyses demonstrated increased transcriptional activity of the IL6 gene when stimulated with IL1 alpha in the presence of TGF-beta 1. However, actinomycin-D pulse chase experiments showed that TGF-beta 1 did not increase the stability of IL6 mRNA. Thus, in concert, the results demonstrate that TGF-beta 1 potentiates IL6 production in astrocytoma cells by promoting the transcriptional activity of the IL6 gene and requires coexpression of new proteins. Since cytokines can provide potent mitogenic signals to tumor cells, the results presented here further suggest that the antitumor effect of combination cytokine therapy might partly depend on heterotypic interactions between tumor cells and cytokines.