Geranylgeranyltransferase type I (GGTase-I) deficiency hyperactivates macrophages and induces erosive arthritis in mice

RHO family proteins are important for the function of inflammatory cells. They are modified with a 20-carbon geranylgeranyl lipid in a process catalyzed by protein geranylgeranyltransferase type I (GGTase-I). Geranylgeranylation is viewed as essential for the membrane targeting and activity of RHO proteins. Consequently, inhibiting GGTase-I to interfere with RHO protein activity has been proposed as a strategy to treat inflammatory disorders. However, here we show that mice lacking GGTase-I in macrophages develop severe joint inflammation resembling erosive rheumatoid arthritis. The disease was initiated by the GGTase-I-deficient macrophages and was transplantable and reversible in bone marrow transplantation experiments. The cells accumulated high levels of active GTP-bound RAC1, CDC42, and RHOA, and RAC1 remained associated with the plasma membrane. Moreover, GGTase-I deficiency activated p38 and NF-κB and increased the production of proinflammatory cytokines. The results challenge the view that geranylgeranylation is essential for the activity and localization of RHO family proteins and suggest that reduced geranylgeranylation in macrophages can initiate erosive arthritis.     

Capillary electrophoresis-based sirtuin assay using non-peptide substrates

Sirtuins are NAD(+)-dependent class III histone deacetylases, which catalyze the deacetylation of acetyl-lysine residues of histones and other protein substrates yielding the deacetylated protein, nicotinamide and 2'-O-acetyl-ADP-ribose. Two lysine amide derivatives containing dansyl (Dns) or 7-dimethylaminocoumarin (DMAC) residues, i.e. Dns-K(Ac)-NH(2) and DMAC-K(Ac)-NH(2), were synthesized and evaluated as substrates for human sirtuin 1. A CZE method with field amplified sample injection and a MEKC method with sweeping were established and validated for monitoring the deacetylation process of Dns-K(Ac)-NH(2) and DMAC-K(Ac)-NH(2), respectively. Deacetylation by sirtuin 1 was demonstrated for both of the substrates. The Michaelis-Menten constants, K(m), were 88.0μM for Dns-K(Ac)-NH(2) and 42.9μM for DMAC-K(Ac)-NH(2). The applicability of the methods was demonstrated using known sirtuin inhibitors. Resveratrol did not activate sirtuin 1 using the present CE-based enzyme assay. The results indicated that the lysine derivatives can be used in sirtuin assays instead of peptide substrates.     

Reactive hypertrophy of an accessory spleen mimicking tumour recurrence of metastatic renal cell carcinoma

De novo occurrence of an accessory spleen after splenectomy is worth noting for two reasons. First, it is known that splenectomy can cause reactive hypertrophy of initially inactive and macroscopically invisible splenic tissue. Second, it can mimic tumour recurrence in situations in which splenectomy has been performed for oncological reasons. This might cause difficulties in differential diagnosis and the clinical decision for reoperation. We report the case of a patient with suspected recurrence of renal cell carcinoma after total pancreatectomy and splenectomy for metastatic renal cell carcinoma, which finally revealed an accessory spleen as the morphological correlate of the newly diagnosed mass in the left retroperitoneum.     

Prognostic significance of Dicer expression in ovarian cancer—link to global microRNA changes and oestrogen receptor expression

MicroRNA (miRNA) deregulation is a hallmark of human cancer. However, the mechanisms underlying miRNA alteration and the specific role of proteins involved in miRNA processing remains to be elucidated. Dicer is a key enzyme in the miRNA processing pathway that is essential for the production of mature miRNAs from their precursors. We tested the hypothesis that Dicer has biological and clinical relevance in ovarian cancer, using a range of methods including in vitro manipulation of Dicer expression. We observed down‐regulation of Dicer in a subgroup of ovarian carcinomas, and found that decreased Dicer expression correlates significantly with reduced patient survival in serous cancers and advanced disease stages. Moreover, microarray and functional analysis suggest that reduced Dicer expression is connected with a global down‐regulation of the microRNAome and with gene expression changes, particularly reduced expression of oestrogen receptor (ER) mRNA and protein in tumour tissue and in cell culture. Our data suggest a common mechanism for miRNAs changes by alterations in the basic machinery controlling miRNA biogenesis, of which Dicer is a central enzyme. These alterations of miRNA processing are of prognostic value and may play a role in the molecular pathogenesis of ovarian carcinoma and, possibly, other tumours. Knowledge of these molecular pathways may help toward new targeted therapeutic approaches for ovarian cancer. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Tracheal rupture after orotracheal intubation in intensive care

We report a case of an iatrogenic tracheal rupture following an endotracheal intubation. The 78-year-old patient was admitted to the intensive care unit because of an acute respiratory failure related to a severe nosocomial pneumonia occurring 21 days after an abdominal aorta surgery. His main antecedent was a cigarette smoke-induced chronic obstructive pulmonary disease. Immediately after being intubated, a traumatic tracheobronchial rupture was suspected because of the sudden appearance of cervicothoracic subcutaneous emphysema. A thoracic computed tomography with multiplanar reformations confirmed the diagnosis and the evolution was unfortunately rapidly unfavourable. Risk factors, clinical and radiological aspects, and management of this rare but serious complication of endotracheal intubation will be discussed.