| 1. |
- Öberg, Fredrik, et al.
(författare)
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Herbal melanin activates TLR4/NF-kappaB signaling pathway
- 2009
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Ingår i: Phytomedicine. - : Elsevier BV. - 0944-7113 .- 1618-095X. ; 16:5, s. 477-84
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Tidskriftsartikel (refereegranskat)abstract
- Expression of many pro-inflammatory cytokines is controlled by the NF-kappaB signaling pathway. NF-kappaB is induced by LPS through activation of TLR4. Melanins extracted from fungal, plant and human sources modulate cytokine production and activate NF-kappaB pathway. We showed that a herbal melanin (HM) from Nigella sativa L. modulates cytokine production and suggested it as a ligand for TLR4. In this study we investigated the possibility that the HM-induced cytokine production is via an NF-kappaB signaling pathway. We found that HM induced the degradation of IkappaBalpha, a key step in the activation of NF-kappaB. Moreover, addition of IkappaB kinase (IKK) specific inhibitors effectively inhibited the observed HM-induced production of IL-8 and IL-6 by TLR4-transfected HEK293 cells and THP-1 cells. Our results have also shown that HM induced cleavage of caspase 8, and that this cleavage was partially abrogated by IKK inhibitors. We suggest that HM can modulate the inflammatory response by inducing IL-8 and IL-6 production via TLR4-dependent activation of the NF-kappaB signaling pathway.
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| 2. |
- Dimberg, Anna, et al.
(författare)
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Inhibition of monocytic differentiation by phosphorylation-deficient Stat1 is associated with impaired expression of Stat2, ICSBP/IRF8 and C/EBP epsilon
- 2006
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Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 0300-9475 .- 1365-3083. ; 64:3, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- Monocytic differentiation is coordinated through the ordered activation of multiple signalling pathways, controlling transcription of specific subsets of genes that regulate the development of the mature phenotype. To identify key transcription factors involved in this process, we used the human monoblastic U-937 cell line as a model of monocytic differentiation. U-937 cells can be differentiated by treatment with all-trans retinoic acid (ATRA) and 1,25 alpha-dihydroxycholecalciferol (VitD3), resulting in G(0)/G(1)-arrested cells expressing monocytic surface markers. We have previously shown that ATRA-induced differentiation and cell cycle arrest specifically requires Stat1 activation, through phosphorylation of tyrosine 701 and serine 727. In this report, we used U-937 cells expressing phosphorylation-deficient mutants of Stat1 (Stat1Y701F and Stat1S727A) to determine myeloid-specific transcription factors that are activated downstream of Stat1 during induced monocytic differentiation. We demonstrate that ATRA-induced upregulation of Stat2, ICSBP/IRF8 and C/EBP epsilon, key transcription factors linked to myelomonocytic differentiation, is selectively impaired in cells expressing mutant Stat1. In contrast, ATRA-induced expression of PU.1, C/EBP alpha, C/EBP beta and IRF-1 was unaffected. Taken together, our data suggest that ATRA-induced regulation of Stat2, ICSBP and C/EBP epsilon is dependent on active Stat1, and that a failure to correctly regulate these transcription factors is associated with the inhibition of monocytic differentiation.
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| 3. |
- Dimberg, Lina, et al.
(författare)
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Ectopic and IFN-induced expression of Fas overcomes resistance to Fas-mediated apoptosis in multiple myeloma cells.
- 2005
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020.
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Tidskriftsartikel (refereegranskat)abstract
- Multiple myeloma (MM) is an as yet incurable B cell malignancy. Increased survival in vitro is a hallmark of MM cells, implying that a therapeutic potential may lie in circumventing anti-apoptotic signals. We have previously reported that interferons (IFNs) sensitize MM cells to Fas/CD95-mediated apoptosis (1). In the present study, we explore the mechanism underlying this effect. In a wide screening of apoptosis-related genes, Apo2L/TRAIL and Fas were identified as IFN-targets. Sensitization to Fas-mediated apoptosis by IFNs was not affected by blocking Apo2L/TRAIL, suggesting that Apo2L/TRAIL is not a key mediator in this process. In contrast, we found that an elevated Fas expression was functionally linked to increased susceptibility to Fas-mediated apoptosis. This was further supported by the finding that IFN-treatment enhanced Fas-mediated caspase-8 activation, one of the earliest signaling events down-stream receptor activation. In addition, IFN treatment attenuated the IL-6 dependent activation of Stat3, interfering with a known survival-pathway in MM that has previously been linked with resistance to Fas-mediated apoptosis. Taken together, our results show that IFN-induced up-regulation of Fas sensitizes MM cells to Fas-mediated apoptosis and suggest that attenuation of Stat3 activation may be a potentially important event in this process.
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| 4. |
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| 5. |
- Fryknäs, Mårten, et al.
(författare)
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STAT1 signaling is associated with acquired crossresistance to doxorubicin and radiation in myeloma cell lines
- 2007
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 120:1, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- The myeloma cell line RPMI 8226/S and its doxorubicin resistant subline 8226/Dox40 were used as models to explore the potential importance of the STAT1 signaling pathway in drug and radiation resistance. The 40-fold doxorubicin resistant subline 8226/Dox40 was found to be crossresistant to single doses of 4 and 8 Gy of radiation. A genome-wide mRNA expression study comparing the 8226/Dox40 cell line to its parental line was performed to identify the underlying molecular mechanisms. Seventeen of the top 50 overexpressed genes have previously been implicated in the STAT1 signaling pathway. STAT1 was over expressed both at the mRNA and protein level. Moreover, analyses of nuclear extracts showed higher abundance of phosphorylated STAT1 (Tyr 701) in the resistant subline. Preexposure of the crossresistant cells to the STAT1 inhibiting drug fludarabine reduced expression of overexpressed genes and enhanced the effects of both doxorubicin and radiation. These results show that resistance to doxorubicin and radiation is associated with increased STAT1 signaling and can be modulated by fludarabine. The data support further development of therapies combining fludarabine and radiation.
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| 6. |
- Kårehed, Karin, et al.
(författare)
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IFN-gamma-induced upregulation of Fc gamma-receptor-I during activation of monocytic cells requires the PKR and NF kappa B pathways
- 2007
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Ingår i: Molecular Immunology. - : Elsevier BV. - 0161-5890 .- 1872-9142. ; 44:4, s. 615-624
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Tidskriftsartikel (refereegranskat)abstract
- Interferon (IFN)-gamma is a potent activator of macrophages, increasing the cells capacity to perform specific functions during inflammation and immune response. In this report we use IFN-gamma-induced upregulation of the high affinity receptor for IgG (Fc gamma RI/CD64) in the human monocytic cell line U-937 as a model for monocytic activation. We show that upregulation of Fc gamma RI is dependent on signals mediated by the dsRNA-dependent kinase PKR, and the transcription factor NF kappa B. silencing of PKR expression by siRNA or inhibition of PKR by 2-aminopurine (2-AP) potently blocks the IFN-gamma-induced transcriptional activation of the Fc gamma RI promoter. We find that the serine 727 phosphorylation of Stat1, required for full IFN-gamma-induced Fc gamma RI promoter activity, is dependent on PKR. We further show that IFN-gamma induction of Fc gamma RI upregulation is dependent on the NF kappa B pathway, as evidenced by inhibition of NF kappa B using a phosphorylation defective I kappa B alpha (S32A/S36A) mutant, or inhibiting the IKB-kinase (IKK) by treatment with BMS345541. Our results suggest that IFN-gamma-induced increase of Fc gamma RI expression requires the integration of two signalling events: PKR-dependent Stat1 serine 727 phosphorylation, and activation of NF kappa B.
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| 7. |
- Kårehed, Karin, 1972-
(författare)
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Signal Transduction in Malignant Cells – Transformation, Activation and Differentiation
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- All aspects of cell life are regulated by signal transduction mechanisms. This thesis describes the regulatory roles of a few key signal transduction molecules involved in three major biological responses. The studied pathways include platelet derived growth factor (PDGF)-BB induced transformation of murine fibroblasts, interferon (IFN)-γ stimulated monocyte activation and all-trans retinoic acid (ATRA) induced myeloid differentiation.We found that intact phosphoinositide 3OH-kinase (PI3K) activity is essential in the signaling pathway that leads to the morphological alterations and migration pattern characteristic of PDGF-BB transformed NIH/sis and NIH/COL1A1 fibroblasts. Furthermore, our data indicated that the small Rho-GTPase, Rac1 is the predominant mediator of these signals downstream of PI3K.The study of the IFN-γ induced activation of monocytic U-937 cells showed that upregulation of the high affinity receptor for IgG (FcγRI) is dependent on the coordination of several regulatory events: the PKR-mediated serine 727 phosphorylation of Stat1, the expression of the hematopoietic lineage specific transcription factor PU.I, and the activation of the NFκB pathway.ATRA-induced differentiation and cell cycle arrest are impaired in U-937 sublines expressing phosphorylation deficient Stat1 (Stat1Y701F and Stat1S727A). The findings in paper III indicated that the expression pattern of the myeloid specific transcription factors Stat2, ICSBP and c/EBPε was altered in the sublines and that intact Stat1 activation is critical for maintaining the balance of the transcriptional network during ATRA induced terminal differentiation.Finally, ATRA-induced differentiation and growth arrest were blocked by treatment with the IKKα/β inhibitor BMS345541 or by ectopic expression of the NFκB super repressor IκBα (S32A/S36A). The fact that IκB(AA) sublines differentiated normally in response to vitamin D3, showed that NFκB inhibition specifically affected ATRA induced responses. Notably we suggest that the activity of the NFκB pathway may interfere with the differentiation process via a direct effect on the RAR/RXR mediated transcription.
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| 8. |
- Larsson, Maria, et al.
(författare)
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Bad odors stick better than good ones : Olfactory qualities and odor recognition
- 2009
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Ingår i: Experimental psychology (Göttingen). - : Hogrefe & Huber Publishers. - 1618-3169 .- 2190-5142. ; 56:6, s. 375-380
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Tidskriftsartikel (refereegranskat)abstract
- The influences of perceived odor qualities on the retention of olfactory information across the adult lifespan were examined. Young (19–36 years), young-old (60–74 years), and old (75–91 years) adults (n = 202) rated a set of unfamiliar odors across a series of perceptual dimensions (i.e., pleasantness, intensity, and irritability) at encoding. The overall results indicated that memory for unpleasant olfactory information was better than that for pleasant odors across the lifespan. Also, participants showed better retention for odors perceived with high intensity and irritability than for odors rated with low or medium scores. Interestingly, the old adults showed selective beneficial memory effects for odors rated as highly irritable. To the extent that perceptions of high irritability reflect an activation of the trigeminal sensory system, this finding suggests that older adults may use trigeminal components in odor information to compensate for age-related impairments in olfactory memory.
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| 9. |
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| 10. |
- Nyblom, Anna Maria, 1975, et al.
(författare)
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Exceptional overproduction of a functional human membrane protein
- 2007
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Ingår i: Protein Expression and Purification. - : Elsevier BV. - 1046-5928 .- 1096-0279. ; 56:1, s. 110-120
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic-especially human-membrane protein overproduction remains a major challenge in biochemistry. Heterologously overproduced and purified proteins provide a starting point for further biochemical, biophysical and structural studies, and the lack of sufficient quantities of functional membrane proteins is frequently a bottleneck hindering this. Here, we report exceptionally high production levels of a correctly folded and crystallisable recombinant human integral membrane protein in its active form; human aquaporin 1 (hAQP1) has been heterologously produced in the membranes of the methylotrophic yeast Pichia pastoris. After solubilisation and a two step purification procedure, at least 90 mg hAQP1 per liter of culture is obtained. Water channel activity of this purified hAQP was verified by reconstitution into proteoliposomes and performing stopped-flow vesicle shrinkage measurements. Mass spectrometry confirmed the identity of hAQPI in crude membrane preparations, and also from purified protein reconstituted into proteoliposomes. Furthermore, crystallisation screens yielded diffraction quality crystals of untagged recombinant hAQP1. This study illustrates the power of the yeast P. pastoris as a host to produce exceptionally high yields of a functionally active, human integral membrane protein for subsequent functional and structural characterization. (c) 2007 Elsevier Inc. All rights reserved.
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