Hypertonic induction of COX-2 in collecting duct cells by reactive oxygen species of mitochondrial origin

Our previous studies have documented MAPK mediation of the hypertonicity-induced stimulation of COX-2 expression in cultured renal medullary epithelial cells. The present study extends this observation by examining the role of reactive oxygen species (ROSs). ROS levels, determined using dichlorodihydrofluorescence diacetate and cytochrome c, were rapidly and significantly increased following exposure of mIMCD-K2 cells to media made hypertonic by adding NaCl. Hypertonic treatment (550 mosmol/kg) for 16 h induced a 5.6-fold increase in COX-2 protein levels and comparable increases in prostaglandin E(2) release, both of which were completely abolished by the NADPH oxidase inhibitor diphenyleneiodonium (25-50 microM). The general antioxidant N-acetyl-l-cysteine (6 mM), and the superoxide dismutase mimetic TEMPO (2.0 mm) reduced COX-2 levels by 75.6 and 79.8%, respectively. Exposure of mIMCD-K2 cells to exogenous O(2)(-.) generated by the xanthine/xanthine oxidase system mimicked the effect of hypertonicity on COX-2 expression and prostaglandin E(2) release. The increases in phosphorylation of ERK1/2 and p38 were detected 20 min following the hypertonic treatment and were both prevented by N-acetyl-l-cysteine. The increases in ROSs in response to hypertonic treatment were completely blocked by any one of the mitochondrial inhibitors tested, such as rotenone, thenoyltrifluoroacetone, or carbonyl cyanide m-chlorophenylhydrazone, associated with remarkable inhibition of COX-2 expression. In contrast, the increases in ROSs were not significantly altered in IMCD cells deficient in either gp91(phox) or p47(phox), nor were the increases in COX-2 expression. We conclude that ROSs derived from mitochondria, but not NADPH oxidase, mediate the hypertonicity-induced phosphorylation of MAPK and the stimulation of COX-2 expression.     

The prevalence of plasmid‐mediated quinolone resistance determinants among clinical isolates of ESBL or AmpC‐producing Escherichia coli from Chinese pediatric patients

Three kinds of PMQR determinants (qnr genes, aac(6’)‐Ib‐cr, and qepA) have been discovered and shown to be widely distributed among clinical isolates. To characterize the prevalence of PMQR determinants in ESBL or AmpC‐producing E. coli clinical isolates in Chinese children, a total of 292 ESBL or AmpC‐producing E. coli clinical isolates collected from five children's hospitals in China from 2005 to 2006 were screened for PMQR determinants by PCR. Twenty (6.8%) of the 292 isolates were positive for PMQR determinants. A total of 12 (4.1%) isolates were positive for qnr genes, comprising three positive for qnrA (1.0%), three for qnrB (1.0%), and six for qnrS (2.1%). Twenty‐four (8.2%) isolates were positive for aac(6’)‐Ib, of which 10 (3.4% of 292) had the –cr variant. There was no qepA gene detected in the isolates. Conjugation revealed that qnr, aac(6’)‐Ib‐cr, and ESBL‐encoding genes were transferred together.     

Functional dichotomy between OX40 and 4-1BB in modulating effector CD8 T cell responses

Members of the TNFR family are thought to deliver costimulatory signals to T cells and modulate their function and survival. In this study, we compare the role of two closely related TNFR family molecules, OX40 and 4-1BB, in generating effector CD8 T cells to Ag delivered by adenovirus. OX40 and 4-1BB were both induced on responding naive CD8 T cells, but 4-1BB exhibited faster and more sustained kinetics than OX40. OX40-deficient CD8 T cells initially expanded normally; however, their accumulation and survival at late times in the primary response was significantly impaired. In contrast, 4-1BB-deficient CD8 T cells displayed hyperresponsiveness, expanding more than wild-type cells. The 4-1BB-deficient CD8 T cells also showed enhanced maturation attributes, whereas OX40-deficient CD8 T cells had multiple defects in the expression of effector cell surface markers, the synthesis of cytokines, and in cytotoxic activity. These results suggest that, in contrast to current ideas, OX40 and 4-1BB can have a clear functional dichotomy in modulating effector CD8 T cell responses. OX40 can positively regulate effector function and late accumulation/survival, whereas 4-1BB can initially operate in a negative manner to limit primary CD8 responses.     

Mutations in isocitrate dehydrogenase 2 accelerate glioma cell migration via matrix metalloproteinase-2 and 9

The gene encoding isocitrate dehydrogenase (IDH) is somatically mutated predominantly in secondary glioblastoma multiforme. Glioma-specific mutations in IDH1 always produced a single amino acid substitution at R132, but mutations in IDH2 were exclusively at R172 which was the analogous site to R132 in IDH1. Mutations of IDH1 and IDH2 led to simultaneous loss and gain of activities in the production of α-ketoglutarate and 2-hydroxyglutarate, respectively. Matrix metalloproteinases (MMPs) are zinc-dependent endoproteinases involved in the degradation of the extracellular matrix. The exact role of IDH2 mutant on MMPs activity and cell migration has not been fully studied. Here, we show that in response to IDH2 mutations, low levels of α-ketoglutarate increased the stabilization of HIF-1α which can contribute to tumor growth. Moreover, mutant IDH2-induced HIF-1α improved the secretion levels of pro-MMP-2 and pro-MMP-9 as well as the conversion from pro-MMP-2 to its active form, giving C6 glioma cells a higher migration potential. The HIF-1α pathway is probably a critical pathway for release of MMPs in the glioma cancer harboring IDH mutant.     

Distinct urinary metabolic profile of human colorectal cancer

A full spectrum of metabolic aberrations that are directly linked to colorectal cancer (CRC) at early curable stages is critical for developing and deploying molecular diagnostic and therapeutic approaches that will significantly improve patient survival. We have recently reported a urinary metabonomic profiling study on CRC subjects (n = 60) and health controls (n = 63), in which a panel of urinary metabolite markers was identified. Here, we report a second urinary metabonomic study on a larger cohort of CRC (n = 101) and healthy subjects (n = 103), using gas chromatography time-of-flight mass spectrometry and ultra performance liquid chromatography quadrupole time-of-flight mass spectrometry. Consistent with our previous findings, we observed a number of dysregulated metabolic pathways, such as glycolysis, TCA cycle, urea cycle, pyrimidine metabolism, tryptophan metabolism, polyamine metabolism, as well as gut microbial-host co-metabolism in CRC subjects. Our findings confirm distinct urinary metabolic footprints of CRC patients characterized by altered levels of metabolites derived from gut microbial-host co-metabolism. A panel of metabolite markers composed of citrate, hippurate, p-cresol, 2-aminobutyrate, myristate, putrescine, and kynurenate was selected, which was able to discriminate CRC subjects from their healthy counterparts. A receiver operating characteristic curve (ROC) analysis of these markers resulted in an area under the receiver operating characteristic curve (AUC) of 0.993 and 0.998 for the training set and the testing set, respectively. These potential metabolite markers provide a novel and promising molecular diagnostic approach for the early detection of CRC.     

Serum metabolic signatures of fulminant type 1 diabetes

Fulminant type 1 diabetes (FT1DM) is a relatively new clinical entity featured by acute destruction of pancreatic beta cells. Clinical consequences of FT1DM could be fatal when timely medications are not provided, suggesting the particular importance of rapid and accurate diagnosis. Here we report a serum metabonomics study of FT1DM patients, together with healthy control subjects (NC), type 2 diabetes (T2DM), classic type 1 diabetes (T1DM), and diabetic ketoacidosis (DKA) patients, with the aim of discovering metabolic markers associated with FT1DM. A total of 79 subjects were enrolled (22 NC, 22 T1DM, 22 T2DM, 8 DKA and 5 FT1DM) and the serum metabolic profiling of fasting blood samples was performed using gas chromatography time-of-flight mass spectrometry (GC-TOFMS) coupled with multivariate and univariate statistical analyses. Serum metabolites differentially expressed in FT1DM relative to NC, or to T2DM, T1DM and DKA were identified. Three metabolite markers, 5-oxoproline, glutamate, and homocysteine, were significantly altered among FT1DM, T2DM, T1DM, and DKA. In addition, the three metabolite markers, 5-oxoproline, glutamate, and homocysteine, presented similar patterns of distribution across groups. The results showed that the metabolic signatures of FT1DM identified in this study could be of potential clinical significance for the accurate diagnosis of FT1DM.