Predictors of abnormalities on magnetic resonance cholangiopancreatography: is there a role when the biliary tree is normal on previous imaging?

BACKGROUND: There is limited evidence supporting the use of magnetic resonance cholangiopancreatography (MRCP) if the biliary tree is within normal limits on ultrasound scan (US) or computed tomography (CT). The aim of this study was to assess the role of MRCP in the absence of a dilated biliary system on index imaging. METHODS: A retrospective observational study of consecutive MRCP investigations (n=427) was performed between October 2010 and June 2013 at a single district general hospital. Data collected included patient demographics, clinical presentation, liver function tests (LFTs) and radiological presence of stones. Binary logistic regression and chi-square test were performed using SPSS v23. RESULTS: We included 358 cases, 65% female (n=231) and 35% male (n=127), with a mean age of 60 years. Of these, 63% presented with abdominal pain (n=225), with 20% having concurrent deranged LFTs (n=44) and 8% jaundice (n=18). Index imaging demonstrated a dilated biliary system >6 mm in 68% (n=245). Alkaline phosphatase (ALP) elevation was an independent positive predictor for an abnormal MRCP (P=0.003). Abnormal index imaging, ALP and clinical jaundice were all significantly associated with a positive MRCP (P<0.001, P=0.028, P=0.018). CONCLUSIONS: It is efficacious to proceed to MRCP with abnormal findings on index imaging, clinical jaundice or elevated ALP. An MRCP scan should be strongly considered in the context of elevated ALP and normal US/CT biliary system.

IkappaB kinase alpha-mediated derepression of SMRT potentiates acetylation of RelA/p65 by p300.

Over the last several years, significant progress has been made in identifying chromatin-regulated events that govern NF-kappaB transcription. Using either laminin attachment or tumor necrosis factor alpha as a physiological stimulus of NF-kappaB activation, we demonstrate that IkappaB kinase alpha (IKKalpha) is recruited to chromatin in distinct phases. In the initial phase, IKKalpha is responsible for derepressing the silencing mediator for retinoic acid and thyroid hormone receptor (SMRT)-histone deacetylase 3 (HDAC3) corepressor complex from the p50 homodimer. However, in the latter phase, chromatin-bound IKKalpha coordinates the simultaneous phosphorylation of RelA/p65(S536) and SMRT(S2410) as detected by chromatin immunoprecipitation (ChIP) assays. Although phosphorylated SMRT remains bound to the active p50-RelA/p65 heterodimer of NF-kappaB, derepression of SMRT is evidenced by the loss of chromatin-associated HDAC3 activity. ChIP and re-ChIP analysis demonstrates that phosphorylation of RelA/p65(S536) and SMRT(S2410) occurs prior to acetylation of RelA/p65 at K310. Moreover, IKKalpha-induced phosphorylation of RelA/p65(S536) displaces corepressor activity, allowing p300-mediated acetylation of RelA/p65. Introduction of nonphosphorylatable mutants of RelA/p65 and SMRT proteins or the inhibition of IKK activity results in active repression of NF-kappaB promoters by tethering the SMRT-HDAC3 complex. Similar to phosphorylation within the Rel homology domain of RelA/p65, which governs an exchange of HDAC1 for CBP/p300 acetyltransferases, we demonstrate that phosphorylation within the transactivation domain of RelA/p65(S536) displaces SMRT-HDAC3 repressor activity, allowing p300 to acetylate RelA/p65.

Modulation of NF-kappaB-dependent transcription and cell survival by the SIRT1 deacetylase.

NF-kappaB is responsible for upregulating gene products that control cell survival. In this study, we demonstrate that SIRT1, a nicotinamide adenosine dinucleotide-dependent histone deacetylase, regulates the transcriptional activity of NF-kappaB. SIRT1, the mammalian ortholog of the yeast SIR2 (Silencing Information Regulator) and a member of the Sirtuin family, has been implicated in modulating transcriptional silencing and cell survival. SIRT1 physically interacts with the RelA/p65 subunit of NF-kappaB and inhibits transcription by deacetylating RelA/p65 at lysine 310. Treatment of cells with resveratrol, a small-molecule agonist of Sirtuin activity, potentiates chromatin-associated SIRT1 protein on the cIAP-2 promoter region, an effect that correlates with a loss of NF-kappaB-regulated gene expression and sensitization of cells to TNFalpha-induced apoptosis. While SIRT1 is capable of protecting cells from p53-induced apoptosis, our work provides evidence that SIRT1 activity augments apoptosis in response to TNFalpha by the ability of the deacetylase to inhibit the transactivation potential of the RelA/p65 protein.