NAD+-dependent SIRT1 deacetylase participates in epigenetic reprogramming during endotoxin tolerance.
ABSTRACT Gene-selective epigenetic reprogramming and shifts in cellular bioenergetics develop when Toll-like receptors (TLR) recognize and respond to systemic life-threatening infections. Using a human monocyte cell model of endotoxin tolerance and human leukocytes from acute systemic inflammation with sepsis, we report that energy sensor sirtuin 1 (SIRT1) coordinates the epigenetic and bioenergy shifts. After TLR4 signaling, SIRT1 rapidly accumulated at the promoters of TNF-α and IL-1β, but not IκBα; SIRT1 promoter binding was dependent on its co-factor, NAD(+). During this initial process, SIRT1 deacetylated RelA/p65 lysine 310 and nucleosomal histone H4 lysine 16 to promote termination of NFκB-dependent transcription. SIRT1 then remained promoter bound and recruited de novo induced RelB, which directed assembly of the mature transcription repressor complex that generates endotoxin tolerance. SIRT1 also promoted de novo expression of RelB. During sustained endotoxin tolerance, nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme for endogenous production of NAD(+), and SIRT1 expression increased. The elevation of SIRT1 required protein stabilization and enhanced translation. To support the coordination of bioenergetics in human sepsis, we observed elevated NAD(+) levels concomitant with SIRT1 and RelB accumulation at the TNF-α promoter of endotoxin tolerant sepsis blood leukocytes. We conclude that TLR4 stimulation and human sepsis activate pathways that couple NAD(+) and its sensor SIRT1 with epigenetic reprogramming.
Article: Inference of molecular phylogeny of Sarcocystis felis (Sarcocystidae) from cats based on nuclear-encoded ribosomal gene sequences.[show abstract] [hide abstract]
ABSTRACT: The phylogenetic position of four clinical isolates of Sarcocystis felis was assessed using ssurRNA and ITS1 gene sequences in the context of a wide array of other Sarcocystis sp. Phylogenetic reconstructions using neighbour-joining and maximum parsimony methods generated identical tree topologies with strong support values at each node. High ssurRNA sequence similarity (> or =99%) and the resulting phylogeny demonstrated that S. felis and S. neurona are significantly closely related to each other. The two Sarcocystis formed a monophyletic group distinct from the other Sarcocystis sp., irrespective of the alignment algorithms or tree-building method used. The absolute (100%) identity of ssurRNA sequences of sarcocysts and sporocysts obtained from one cat raised the question regarding the cat's role as a potential intermediate host besides its known role as a definitive host of S. felis. On the other hand, S. felis sarcocyst DNA sequence was found to be quite dissimilar over the ITS1 region when compared to S. neurona. These findings indicated that using sequences from two different genetic loci provided a stronger comparative basis than would have been possible using either one.Journal of the Egyptian Society of Parasitology 08/2006; 36(2):441-53.
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ABSTRACT: Decolonization may be defined as treatment to eradicate Staphylococcus aureus or methicillin-resistant S aureus (MRSA) carriage. Potential benefits of decolonization include decreased risk of subsequent staphylococcal infection and prevention of staphylococcal transmission to reduce endemic rates of infection or manage outbreaks. This article reviews available data regarding various proposed treatment regimens for eradicating staphylococcal carriage and the effectiveness of decolonization for infection prevention and as an infection control measure.Infectious disease clinics of North America 04/2009; 23(1):133-51. · 2.29 Impact Factor
Article: Endotoxin tolerance disrupts chromatin remodeling and NF-kappaB transactivation at the IL-1beta promoter.[show abstract] [hide abstract]
ABSTRACT: The NF-kappaB family plays a crucial role in the pathogenesis of highly lethal septicemia by modulating transcription of many innate and adaptive immunity genes. Two phases of NF-kappaB activation occur: cytosolic activation and nuclear transactivation. Septicemia with multiorgan failure is associated with chronic activation of cytosolic NF-kappaB with translocation and accumulation of increased levels of nuclear p65 in blood leukocytes. Paradoxically, NF-kappaB-dependent transcription of many proinflammatory genes responding to bacterial LPS endotoxin (LPS) is persistently repressed during septicemia; this phenomenon of LPS tolerance is associated with immunosuppression and poor prognosis. This report suggests an explanation for this paradox. Using an in vitro human leukocyte model and chromatin immunoprecipitation assays, we find that both the cytosolic activation and nuclear transactivation phases of NF-kappaB occur in LPS responsive THP-1 promonocytes with recruitment and binding of NF-kappaB p65 at the IL-1beta promoter. However, transcriptionally repressed LPS-tolerant THP-1 cells do not bind NF-kappaB p65 at the IL-1beta promoter, despite cytosolic activation and accumulation of p65 in the nucleus. In contrast, NF-kappaB p50, which also accumulates in the nucleus, constitutively binds to the IL-1beta promoter NF-kappaB site in both LPS-responsive and LPS-tolerant cells. The level of p65 binding correlates with a binary shift in nucleosome remodeling between histone H3 phosphorylation at serine 10 and methylation of histone H3 at lysine 9. We conclude that LPS tolerance disrupts the transactivating stage of NF-kappaB p65 and altered nucleosome remodeling at the IL-1beta promoter in human leukocytes.The Journal of Immunology 08/2005; 175(1):461-8. · 5.79 Impact Factor