| 1. |
- Franklin, Bernardo S., et al.
(författare)
-
Malaria primes the innate immune response due to interferon-gamma induced enhancement of toll-like receptor expression and function
- 2009
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 106:14, s. 5789-5794
-
Tidskriftsartikel (refereegranskat)abstract
- Malaria-induced sepsis is associated with an intense proinflammatory cytokinemia for which the underlying mechanisms are poorly understood. It has been demonstrated that experimental infection of humans with Plasmodium falciparum primes Toll-like receptor (TLR)-mediated proinflammatory responses. Nevertheless, the relevance of this phenomenon during natural infection and, more importantly, the mechanisms by which malaria mediates TLR hyperresponsiveness are unclear. Here we show that TLR responses are boosted in febrile patients during natural infection with P. falciparum. Microarray analyses demonstrated that an extraordinary percentage of the up-regulated genes, including genes involving TLR signaling, had sites for IFN-inducible transcription factors. To further define the mechanism involved in malaria-mediated "priming,'' we infected mice with Plasmodium chabaudi. The human data were remarkably predictive of what we observed in the rodent malaria model. Malaria-induced priming of TLR responses correlated with increased expression of TLR mRNA in a TLR9-, MyD88-, and IFN gamma-dependent manner. Acutely infected WT mice were highly susceptible to LPS-induced lethality while TLR9(-/-), IL12(-/-) and to a greater extent, IFN gamma(-/-) mice were protected. Our data provide unprecedented evidence that TLR9 and MyD88 are essential to initiate IL12 and IFN gamma responses and favor host hyperresponsiveness to TLR agonists resulting in overproduction of proinflammatory cytokines and the sepsis-like symptoms of acute malaria.
|
|
| 2. |
- Diczfalusy, Ulf, et al.
(författare)
-
Marked upregulation of cholesterol 25-hydroxylase expression by lipopolysaccharide
- 2009
-
Ingår i: Journal of Lipid Research. - 1539-7262 .- 0022-2275. ; 50:11, s. 2258-2264
-
Tidskriftsartikel (refereegranskat)abstract
- During screening of genes upregulated by lipopolysaccharide (LPS; endotoxin) treatment of bone marrow-derived mouse macrophages, it was unexpectedly found that cholesterol 25-hydroxylase (Ch25h) was strongly upregulated. Treatment of macrophages with 10 ng/ml of LPS for 2 h resulted in a 35-fold increase in the expression of Ch25h. In contrast, LPS treatment did not increase the expression of Cyp27a1 or Cyp7b1. The increased Ch25h expression was found to be independent of Myeloid differentiation protein 88 signaling but dependent on Toll-like receptor 4 signaling. LPS treatment of macrophages caused a 6- to 7-fold increase in cellular 25-hydroxycholesterol concentration. When macrophages were treated with increasing concentrations of 25-hydroxycholesterol, a dose-dependent release of CCL5 into the culture medium was observed. Intravenous injection of LPS in eight healthy volunteers resulted in an increase in plasma 25-hydroxycholesterol concentration. The possibility is discussed that 25-hydroxycholesterol may have a role in the inflammatory response, in addition to its more established role in the regulation of cholesterol homeostasis.-Diczfalusy, U., K. E. Olofsson, A- M. Carlsson, M. Gong, D. T. Golenbock, O. Rooyackers, U. Flaring, and H. Bjorkbacka. Marked upregulation of cholesterol 25-hydroxylase expression by lipopolysaccharide. J. Lipids Res. 2009. 50: 2258-2264.
|
|
| 3. |
- Meng, Jianmin, et al.
(författare)
-
Genome-Wide Expression Profiling and Mutagenesis Studies Reveal that Lipopolysaccharide Responsiveness Appears To Be Absolutely Dependent on TLR4 and MD-2 Expression and Is Dependent upon Intermolecular Ionic Interactions
- 2011
-
Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 187:7, s. 3683-3693
-
Tidskriftsartikel (refereegranskat)abstract
- Lipid A (a hexaacylated 1,4' bisphosphate) is a potent immune stimulant for TLR4/MD-2. Upon lipid A ligation, the TLR4/MD-2 complex dimerizes and initiates signal transduction. Historically, studies also suggested the existence of TLR4/MD-2-independent LPS signaling. In this article, we define the role of TLR4 and MD-2 in LPS signaling by using genome-wide expression profiling in TLR4- and MD-2-deficient macrophages after stimulation with peptidoglycan-free LPS and synthetic Escherichia coli lipid A. Of the 1396 genes significantly induced or repressed by any one of the treatments in the wild-type macrophages, none was present in the TLR4-or MD-2-deficient macrophages, confirming that the TLR4/MD-2 complex is the only receptor for endotoxin and that both are required for responses to LPS. Using a molecular genetics approach, we investigated the mechanism of TLR4/MD-2 activation by combining the known crystal structure of TLR4/MD-2 with computer modeling. According to our murine TLR4/MD-2-activation model, the two phosphates on lipid A were predicted to interact extensively with the two positively charged patches on mouse TLR4. When either positive patch was abolished by mutagenesis into Ala, the responses to LPS and lipid A were nearly abrogated. However, the MyD88-dependent and -independent pathways were impaired to the same extent, indicating that the adjuvant activity of monophosphorylated lipid A most likely arises from its decreased potential to induce an active receptor complex and not more downstream signaling events. Hence, we concluded that ionic interactions between lipid A and TLR4 are essential for optimal LPS receptor activation. The Journal of Immunology, 2011, 187: 3683-3693.
|
|
