I?B? is expressed in mast cells

Down-regulation of heat shock protein HSP90ab1 in radiation-damaged lung cells other than mast cells

Ionizing radiation (IR) leads to fibrosing alveolitis (FA) after a lag period of several weeks to months. In a rat model, FA starts at 8 weeks after IR. Before that, at 5.5 weeks after IR, the transcription factors Sp1 (stimulating protein 1) and AP-1 (activator protein 1) are inactivated. To find genes/proteins that were down-regulated at that time, differentially expressed genes were identified in a subtractive cDNA library and verified by quantitative RT-PCR (reverse transcriptase polymerase chain reaction), western blotting and immunohistochemistry (IH). The mRNA of the molecular chaperone HSP90AB1 (heat shock protein 90 kDa alpha, class B member 1) was down-regulated 5.5 weeks after IR. Later, when FA manifested, HSP90ab1 protein was down-regulated by more than 90% in lung cells with the exception of mast cells. In most mast cells of the normal lung, both HSP90ab1 and HSP70, another major HSP, show a very low level of expression. HSP70 was massively up-regulated in all mast cells three months after irradiation whereas HSP90AB1 was up-regulated only in a portion of mast cells. The strong changes in the expression of central molecular chaperones may contribute to the well-known disturbance of cellular functions in radiation-damaged lung tissue.

Ribozyme-mediated targeting of IkappaBgamma inhibits melanoma invasion and metastasis

IkappaBgamma is one member of a family of proteins that can inhibit the nuclear localization of nuclear factor-kappaB. However, the other specific functions of IkappaBgamma are still poorly understood, and its effects on tumor metastasis have not yet been characterized. We examined the consequences of targeting IkappaBgamma in melanoma cells using a hammerhead ribozyme. We developed stable transformant B16-F10 melanoma cell lines that express a ribozyme that targets mouse IkappaBgamma (IkappaBgamma-144-Rz). Tail-vein injection of B16-F10 cells that stably express IkappaBgamma-144-Rz into mice resulted in a significant reduction of the metastatic potential of these cells. IkappaBgamma-144-Rz-expressing B16 cells were shown to have increased transcriptional activity of nuclear factor-kappaB. We then showed that IkappaBgamma-144-Rz-expressing cells demonstrated both reduced invasion and increased apoptosis, suggesting the existence of pathways through which IkappaBgamma promotes melanoma metastasis. Using gene expression profiling, we identified a differentially expressed gene set that is regulated by the stable suppression of IkappaBgamma that may participate in mediating its anti-metastatic effects; we also confirmed the altered expression levels of several of these genes by quantitative real time polymerase chain reaction. Plasmid-mediated expression of IkappaBgamma-144-Rz produced a significant inhibition of the metastatic progression of B16-F10 cells to the lung and resulted in significant anti-invasive and pro-apoptotic effects on murine Lewis lung carcinoma cells. Our results suggest a novel role for IkappaBgamma in promoting the metastatic progression of melanoma.

Expression of the immunomodulator IL-10 in type I pneumocytes of the rat: alterations of IL-10 expression in radiation-induced lung damage

Fibrosing alveolitis is a disease with inflammatory, proliferative, and fibrotic components. In different models, it has been shown that the cytokine interleukin-10 (IL-10) plays a conflicting role in inflammation-associated fibrotic processes, inasmuch as it is an anti-inflammatory cytokine but also a TH2 cytokine with inherent pro-fibrotic effects. IL-10 is produced primarily by inflammatory cells. In this report, we show in a rat model of radiation-induced fibrosing alveolitis that IL-10 is also produced by type I alveolar epithelial cells in both normal and fibrotic lungs. The total amount of IL-10 in the lung is increased after irradiation, but type I pneumoyctes contain less IL-10. The R3/1 permanent type I pneumocyte cell line also contains IL-10, which is reduced after irradiation. Whereas in the normal lung, the entire alveolar surface is covered by IL-10-producing pneumocytes, this continuity is interrupted in fibrotic lungs, because type I pneumocytes lack full differentiation and thus full spreading over the alveolar surface. The exposure of the IL-10-negative epithelial basal membrane may allow for an easier attachment of inflammatory cells such as alveolar macrophages. These cells have the potential to act in a pro-inflammatory way by tumor necrosis factor alpha and also in a pro-fibrotic way by activating TH2 cytokines.

Influence of mizolastine on antigen-induced activation of signalling pathways in murine mast cells

BACKGROUND

There is accumulating evidence that some antihistamines can interrupt intermediate signalling events that regulate cell function. The effect of mizolastine on both the generation and release process of many cytokines in mast cells further implies that the inhibition by mizolastine may target signalling pathways.

AIM

To observe the influence of mizolastine on antigen-induced activation of signalling pathways in murine mast cells.

METHODS

Western blot analysis and enzyme assay were performed. Immunoblots were prepared from whole cell lysates and probed with antibodies against Fyn, Akt, ERK, p38, phospho-Fyn, phospho-Akt, phospho-ERK and phospho-p38, respectively.

RESULTS

Our study showed that signalling molecules such as IP3, Fyn, p38 and ERK were enhanced when mast cells were stimulated by antigen, and that this was not inhibited by treatment with mizolastine. Mizolastine at concentrations from 10(-9) to 10(-5) mol/L could inhibit activation of the PI3K kinase downstream signalling molecule Akt to antigen stimulation. The study also demonstrated that mizolastine exerted inhibitory ability on protein kinase C (PKC) activation in a dose-dependent manner.

CONCLUSION

PKC-mediated phosphorylation of Akt can be blocked by mizolastine. There may be a PKC-independent pathway effectively activating MAPK pathways in mast cells in response to antigen induction, which cannot be affected by mizolastine.