Translocation of the IL-1 receptor to focal adhesions is regulated through the C-terminal end of the cytoplasmic domain

A Comprehensive View of the Neurotoxicity Mechanisms of Cocaine and Ethanol

Substance use disorder is an emerging problem concerning to human health, causing severe side effects, including neurotoxicity. The use of illegal drugs and the misuse of prescription or over-the-counter drugs are growing in this century, being one of the major public health problems. Ethanol and cocaine are one of the most frequently used drugs and, according to the National Institute on Drug Abuse, their concurrent consumption is one of the major causes for emergency hospital room visits. These molecules act in the brain through different mechanisms, altering the nervous system function. Researchers have focused the attention not just in the mechanism of action of these drugs, but also in the mechanism by which they damage the nervous tissue (neurotoxicity). Therefore, the goal of the present review is to provide a global perspective about the mechanisms of the neurotoxicity of cocaine and ethanol.

IL-1alpha and IL-1beta have different effects on formation and activity of large osteoclasts

Interleukin 1 (IL-1) is a proinflammatory cytokine upregulated in conditions such as rheumatoid arthritis and periodontal disease. Both isoforms, IL-1alpha and IL-1beta, have been shown to activate osteoclasts (OCs), the cells responsible for resorbing bone. Inflammatory conditions are also characterized by increased bone loss and by the presence of large OCs (10+ nuclei). We and others have previously shown that large OCs are more likely to be resorbing compared to small OCs (2-5 nuclei). Moreover, large OCs express higher levels of the IL-1 activating receptor IL-1RI, integrins alphav and beta3, RANK, and TNFR1, while small OCs have higher levels of the decoy receptor IL-1RII. We hypothesized that IL-1 would have different effects on large and small OCs due to these distinct receptor expression patterns. To test this hypothesis, RAW 264.7 cells were differentiated into populations of small and large OCs and treated with IL-1alpha or IL-1beta (1 and 10 ng/ml). In the presence of sRANKL, both IL-1alpha and IL-1beta increased total OC number and resorptive activity of large OCs. IL-1alpha stimulated formation of large OCs and increased the number of resorption pits, while IL-1beta changed the morphology of large OCs and integrin-beta3 phosphorylation. No effects were seen in small OCs in response to either IL-1 isoform. These results demonstrate that IL-1 predominantly affects large OCs. The dissimilarity of responses to IL-1alpha and IL-1beta suggests that these isoforms activate different signaling pathways within the two OC populations.

Involvement of TLR4/type I IL-1 receptor signaling in the induction of inflammatory mediators and cell death induced by ethanol in cultured astrocytes

Activated astroglial cells are implicated in neuropathogenesis of many infectious and inflammatory diseases of the brain. A number of inflammatory mediators and cytokines have been proposed to play a key role in glial cell-related brain damage. Cytokine production seems to be initiated by signaling through TLR4/type I IL-1R (IL-1RI) in response to their ligands, LPS and IL-1beta, playing vital roles in innate host defense against infections, inflammation, injury, and stress. We have shown that glial cells are stimulated by ethanol, up-regulating cytokines and inflammatory mediators associated with TLR4 and IL-1RI signaling pathways in brain, suggesting that ethanol may contribute to brain damage via inflammation. We explore the possibility that ethanol, in the absence of LPS or IL-1beta, triggers signaling pathways and inflammatory mediators through TLR4 and/or IL-1RI activation in astrocytes. We show in this study that ethanol, at physiologically relevant concentrations, is capable of inducing rapid phosphorylation within 10 min of IL-1R-associated kinase, ERK1/2, stress-activated protein kinase/JNK, and p38 MAPK in astrocytes. Then an activation of NF-kappaB and AP-1 occurs after 30 min of ethanol treatment along with an up-regulation of inducible NO synthase and cyclooxygenase-2 expression. Finally, we note an increase in cell death after 3 h of treatment. Furthermore, by using either anti-TLR4- or anti-IL-1RI-neutralizing Abs, before and during ethanol treatment, we inhibit ethanol-induced signaling events, including NF-kappaB and AP-1 activation, inducible NO synthase, and cyclooxygenase-2 up-regulation and astrocyte death. In summary, these findings indicate that both TLR4 and IL-1RI activation occur upon ethanol treatment, and suggest that signaling through these receptors mediates ethanol-induced inflammatory events in astrocytes and brain.

Signal transduction pathways activated by the IL-1 receptor/toll-like receptor superfamily

Toll-like receptors (TLRs) are an important point of first contact between host and microbe, and once activated generate signals which culminate in the induction of genes important for host defence. TLRs respond to different microbial products, and the signalling pathways activated are very similar to that generated by the pro-inflammatory cytokine interleukin-1 (IL-1). This is because the Type I IL-1 receptor and TLRs are highly homologous in their cytosolic portions, possessing a Toll/IL-1 receptor (TIR) domain. Signals triggered include the important transcription factor NF-kappa B and two MAP kinases, p38 and Jun N-terminal kinase. Receptor-proximal proteins involved include the adapter MyD88, IRAK, IRAK-2, Tollip, TRAF6 and TAK-1. These latter two proteins need to be ubiquitinated in order to be active. Differences between signals generated by TLRs are emerging, with TLR-4 signalling requiring an additional adapter termed MyD88-adapter-like (Mal), which may regulate the expression of genes specific for the response required to eliminate infection by Gram-negative bacteria. Future studies on TLR signalling may reveal hitherto unsuspected specificities in the innate immune response to infection.

Ras participates in the activation of p38 MAPK by interleukin-1 by associating with IRAK, IRAK2, TRAF6, and TAK-1

Interleukin-1 (IL-1) activates p38 MAP kinase via the small G protein Ras, and this activity can be down-regulated by another small G protein Rap. Here we have further investigated the role of Ras and Rap in p38 MAPK activation by IL-1. Transient transfection of cells with constitutively active forms of the known IL-1 signaling components MyD88, IRAK, and TRAF-6, or the upstream kinases MKK6 and MKK3, activated p38 MAPK. Dominant negative forms of these were found to inhibit activation of p38 MAPK by IL-1. Dominant negative RasN17 blocked the effect of the active forms of all but MKK3 and MKK6, indicating that Ras lies downstream of TRAF-6 but upstream of MKK3 and MKK6 on the pathway. Furthermore, the activation of p38 MAPK caused by overexpressing active RasVHa could not be inhibited using dominant negative mutants of MyD88, IRAK, or IRAK-2, or TRAF6, but could be inhibited by dominant negative MKK3 or MKK6. In the same manner, the inhibitory effect of Rap on the activation of p38 by IL-1 occurred at a point downstream of MyD88, IRAK, and TRAF6, since the activation of p38 MAPK by these components was inhibited by overexpressing active Rap1AV12, while neither MKK3 nor MKK6 were affected. Active RasVHa associated with IRAK, IRAK2, and TRAF6, but not MyD88. In addition we found a role for TAK-1 in the activation of p38 MAPK by IL-1, with TAK-1 also associating with active Ras. Our study suggests that upon activation Ras becomes associated with IRAK, Traf-6, and TAK-1, possibly aiding the assembly of this multiprotein signaling complex required for p38 MAPK activation by IL-1.