FBXW7α attenuates inflammatory signalling by downregulating C/EBPδ and its target gene Tlr4.

Toll-like receptor 4 (Tlr4) has a pivotal role in innate immune responses, and the transcription factor CCAAT/enhancer binding protein delta (C/EBPδ, Cebpd) is a Tlr4-induced gene. Here we identify a positive feedback loop in which C/EBPδ activates Tlr4 gene expression in macrophages and tumour cells. In addition, we discovered a negative feedback loop whereby the tumour suppressor FBXW7α (FBW7, Cdc4), whose gene expression is inhibited by C/EBPδ, targets C/EBPδ for degradation when C/EBPδ is phosphorylated by GSK-3β. Consequently, FBXW7α suppresses Tlr4 expression and responses to the ligand lipopolysaccharide. FBXW7α depletion alone is sufficient to augment pro-inflammatory signalling in vivo. Moreover, as inflammatory pathways are known to modulate tumour biology, Cebpd null mammary tumours, which have reduced metastatic potential, show altered expression of inflammation-associated genes. Together, these findings reveal a role for C/EBPδ upstream of Tlr4 signalling and uncover a function for FBXW7α as an attenuator of inflammatory signalling.

Protection from lethal gram-negative bacterial sepsis by targeting Toll-like receptor 4.

Toll-like receptor 4 (TLR4), the signal-transducing molecule of the LPS receptor complex, plays a fundamental role in the sensing of LPS from gram-negative bacteria. Activation of TLR4 signaling pathways by LPS is a critical upstream event in the pathogenesis of gram-negative sepsis, making TLR4 an attractive target for novel antisepsis therapy. To validate the concept of TLR4-targeted treatment strategies in gram-negative sepsis, we first showed that TLR4(-/-) and myeloid differentiation primary response gene 88 (MyD88)(-/-) mice were fully resistant to Escherichia coli-induced septic shock, whereas TLR2(-/-) and wild-type mice rapidly died of fulminant sepsis. Neutralizing anti-TLR4 antibodies were then generated using a soluble chimeric fusion protein composed of the N-terminal domain of mouse TLR4 (amino acids 1-334) and the Fc portion of human IgG1. Anti-TLR4 antibodies inhibited intracellular signaling, markedly reduced cytokine production, and protected mice from lethal endotoxic shock and E. coli sepsis when administered in a prophylactic and therapeutic manner up to 13 h after the onset of bacterial sepsis. These experimental data provide strong support for the concept of TLR4-targeted therapy for gram-negative sepsis.

Molecular and functional characterization of a novel cardiac-specific human tropomyosin isoform.

BACKGROUND: Tropomyosin (TM), an essential actin-binding protein, is central to the control of calcium-regulated striated muscle contraction. Although TPM1alpha (also called alpha-TM) is the predominant TM isoform in human hearts, the precise TM isoform composition remains unclear. METHODS AND RESULTS: In this study, we quantified for the first time the levels of striated muscle TM isoforms in human heart, including a novel isoform called TPM1kappa. By developing a TPM1kappa-specific antibody, we found that the TPM1kappa protein is expressed and incorporated into organized myofibrils in hearts and that its level is increased in human dilated cardiomyopathy and heart failure. To investigate the role of TPM1kappa in sarcomeric function, we generated transgenic mice overexpressing cardiac-specific TPM1kappa. Incorporation of increased levels of TPM1kappa protein in myofilaments leads to dilated cardiomyopathy. Physiological alterations include decreased fractional shortening, systolic and diastolic dysfunction, and decreased myofilament calcium sensitivity with no change in maximum developed tension. Additional biophysical studies demonstrate less structural stability and weaker actin-binding affinity of TPM1kappa compared with TPM1alpha. CONCLUSIONS: This functional analysis of TPM1kappa provides a possible mechanism for the consequences of the TM isoform switch observed in dilated cardiomyopathy and heart failure patients.

The dexamethasone-induced inhibition of proliferation, migration, and invasion in glioma cell lines is antagonized by macrophage migration inhibitory factor (MIF) and can be enhanced by specific MIF inhibitors.

Glioblastomas (GBMs) are the most frequent and malignant brain tumors in adults. Glucocorticoids (GCs) are routinely used in the treatment of GBMs for their capacity to reduce the tumor-associated edema. Few in vitro studies have suggested that GCs inhibit the migration and invasion of GBM cells through the induction of MAPK phosphatase 1 (MKP-1). Macrophage migration inhibitory factor (MIF), an endogenous GC antagonist is up-regulated in GBMs. Recently, MIF has been involved in tumor growth and migration/invasion and specific MIF inhibitors have been developed on their capacity to block its enzymatic tautomerase activity site. In this study, we characterized several glioma cell lines for their MIF production. U373 MG cells were selected for their very low endogenous levels of MIF. We showed that dexamethasone inhibits the migration and invasion of U373 MG cells, through a glucocorticoid receptor (GR)- dependent inhibition of the ERK1/2 MAPK pathway. Oppositely, we found that exogenous MIF increases U373 MG migration and invasion through the stimulation of the ERK1/2 MAP kinase pathway and that this activation is CD74 independent. Finally, we used the Hs 683 glioma cells that are resistant to GCs and produce high levels of endogenous MIF, and showed that the specific MIF inhibitor ISO-1 could restore dexamethasone sensitivity in these cells. Collectively, our results indicate an intricate pathway between MIF expression and GC resistance. They suggest that MIF inhibitors could increase the response of GBMs to corticotherapy.

Feasibility of a knowledge translation CME program: courriels Cochrane.

INTRODUCTION: Systematic literature reviews provide best evidence, but are underused by clinicians. Thus, integrating Cochrane reviews into continuing medical education (CME) is challenging. We designed a pilot CME program where summaries of Cochrane reviews (Courriels Cochrane) were disseminated by e-mail. Program participants automatically received CME credit for each Courriel Cochrane they rated. The feasibility of this program is reported (delivery, participation, and participant evaluation). METHOD: We recruited French-speaking physicians through the Canadian Medical Association. Program delivery and participation were documented. Participants rated the informational value of Courriels Cochrane using the Information Assessment Method (IAM), which documented their reflective learning (relevance, cognitive impact, use for a patient, expected health benefits). IAM responses were aggregated and analyzed. RESULTS: The program was delivered as planned. Thirty Courriels Cochrane were delivered to 985 physicians, and 127 (12.9%) completed at least one IAM questionnaire. Out of 1109 Courriels Cochrane ratings, 973 (87.7%) conta-ined 1 or more types of positive cognitive impact, while 835 (75.3%) were clinically relevant. Participants reported the use of information for a patient and expected health benefits in 595 (53.7%) and 569 (51.3%) ratings, respectively. DISCUSSION: Program delivery required partnering with 5 organizations. Participants valued Courriels Cochrane. IAM ratings documented their reflective learning. The aggregation of IAM ratings documented 3 levels of CME outcomes: participation, learning, and performance. This evaluation study demonstrates the feasibility of the Courriels Cochrane as an approach to further disseminate Cochrane systematic literature reviews to clinicians and document self-reported knowledge translation associated with Cochrane reviews.