Publications by authors named "Rosa Ba��os"

2 Publications

  • Page 1 of 1

6-Methylprednisolone down-regulates IRAK-M in human and murine osteoclasts and boosts bone-resorbing activity: a putative mechanism for corticoid-induced osteoporosis.

J Leukoc Biol 2007 Sep 18;82(3):700-9. Epub 2007 Jun 18.

Research Unit, La Paz Hospital, Madrid 28046, Spain.

Osteoclasts are large, multinucleated cells, which originate from the fusion of macrophages. They play a central role in bone development and remodeling via the resorption of bone and are thus important mediators of bone loss, which leads to osteoporosis. IL-1R-associated kinase (IRAK)-M is a pseudokinase, which acts as a negative modulator of innate immune responses mediated by TLRs and IL-1R. Recently, it has been reported that IRAK-M also participates in the control of macrophage differentiation into osteoclasts. In addition, it was shown that IRAK-M knockout mice develop a strong osteoporosis phenotype, suggesting that down-regulation of this molecule activates osteoclast-mediated bone resorption. We studied the effect of the osteoporosis-inducing glucocorticoid, 6-methylprednisolone (6-MP), on IRAK-M expression in osteoclasts. Our results showed that osteoclasts, derived from THP-1 and RAW cells as well as human blood monocytes, differentiated into osteoclasts, express high levels of IRAK-M at mRNA and protein levels. In addition, 6-MP down-regulates IRAK-M expression, which correlates with an increased activation of bone resorption. These findings suggest a mechanism of corticosteroid-induced osteoporosis and open new avenues for treating this endemic disease of Western societies.
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September 2007

Tumor cells deactivate human monocytes by up-regulating IL-1 receptor associated kinase-M expression via CD44 and TLR4.

J Immunol 2005 Mar;174(5):3032-40

Research Unit, Department of Surgical Research, La Paz Hospital, Madrid, Spain.

Although blood monocytes possess significant cytotoxic activity against tumor cells, tumor-infiltrating monocytes are commonly deactivated in cancer patients. Monocytes pre-exposed to tumor cells show significantly decreased expression levels of TNF-alpha, IL-12p40, and IL-1R-associated kinase (IRAK)-1. Activation of the Ser/Thr kinase IRAK-1 is an important event in several inflammatory processes. By contrast, another IRAK family member, IRAK-M, negatively regulates this pathway, and is up-regulated in cultures of endotoxin-tolerant monocytes and in monocytes from septic patients within the timeframe of tolerance. In this study, we show that IRAK-M expression is enhanced at the mRNA and protein level in human monocytes cultured in the presence of tumor cells. IRAK-M was induced in monocytes upon coculturing with different tumor cells, as well as by fixed tumor cells and medium supplemented with the supernatant from tumor cell cultures. Moreover, blood monocytes from patients with chronic myeloid leukemia and patients with metastasis also overexpressed IRAK-M. Low concentrations of hyaluronan, a cell surface glycosaminoglycan released by tumor cells, also up-regulated IRAK-M. The induction of IRAK-M by hyaluronan and tumor cells was abolished by incubation with anti-CD44 or anti-TLR4 blocking Abs. Furthermore, down-regulation of IRAK-M expression by small interfering RNAs specific for IRAK-M reinstates both TNF-alpha mRNA expression and protein production in human monocytes re-exposed to a tumor cell line. Altogether, our findings indicate that deactivation of human monocytes in the presence of tumor cells involves IRAK-M up-regulation, and this effect appears to be mediated by hyaluronan through the engagement of CD44 and TLR4.
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March 2005