No abstract

Differences in the composition of the gut microbial community have been associated with diseases such as obesity, Crohn's disease, ulcerative colitis and colorectal cancer (CRC). We used 454 titanium pyrosequencing of the V1-V2 region of the 16S rRNA gene to characterize adherent bacterial communities in mucosal biopsy samples from 33 subjects with adenomas and 38 subjects without adenomas (controls). Biopsy samples from subjects with adenomas had greater numbers of bacteria from 87 taxa than controls; only 5 taxa were more abundant in control samples. The magnitude of the differences in the distal gut microbiota between patients with adenomas and controls was more pronounced than that of any other clinical parameters including obesity, diet or family history of CRC. This suggests that sequence analysis of the microbiota could be used to identify patients at risk for developing adenomas.

These studies provide evidence that cystic fibrosis transmembrane conductance regulator (CFTR) potentiates and accelerates regulatory volume decrease (RVD) following hypotonic challenge by an autocrine mechanism involving ATP release and signaling. In wild-type CFTR-expressing cells, CFTR augments constitutive ATP release and enhances ATP release stimulated by hypotonic challenge. CFTR itself does not appear to conduct ATP. Instead, ATP is released by a separate channel, whose activity is potentiated by CFTR. Blockade of ATP release by ion channel blocking drugs, gadolinium chloride (Gd 3؉ ) and 4,4-diisothiocyanatostilbene-2,2di-sulfonic acid (DIDS), attenuated the effects of CFTR on acceleration and potentiation of RVD. These results support a key role for extracellular ATP and autocrine and paracrine purinergic signaling in the regulation of membrane ion permeability and suggest that CFTR potentiates ATP release by stimulating a separate ATP channel to strengthen autocrine control of cell volume regulation.ATP and its metabolites function as potent autocrine and paracrine agonists that act within tissues to control cell function through activation of P2 purinergic receptors (1-3) expressed by all cells and tissues. Purinergic agonists are essential for many specialized physiological functions (1-10). In cystic fibrosis (CF), 1 ATP and a related triphosphate nucleotide, UTP, stimulate epithelial chloride (Cl Ϫ ) channels alternative to CFTR via purinergic receptors (11-16). Supraphysiological concentrations of ATP also stimulate CFTR (17). Metabolites of ATP can also act as Cl Ϫ secretagogues (15,16,18). Despite the diverse roles of purinergic signaling, the cellular mechanisms that govern ATP release are not fully defined. CFTR and related ATP-binding cassette (ABC) transporters such as mdr-1 or P-glycoprotein have been implicated as facilitators of ATP release in some cell models (14, 19 -24), while other laboratories have failed to show evidence of CFTRfacilitated ATP conduction or release (25-30).Release of ATP via a conductive pathway has been implicated as an essential autocrine regulator of cell volume in rat hepatoma cells (5). Moreover, ABC transporters have been shown to modulate volume-sensitive Cl Ϫ channels and cell volume (31-34). As such, we tested the hypotheses that CFTR facilitates ATP release under constitutive and hypotonic conditions for autocrine control of cell volume regulation. These hypotheses were also based on the fact that airway surface liquid on CF epithelia is hypertonic with respect to NaCl (35) and/or reduced in volume (36) or both (37, 38) when compared with non-CF epithelia. These airway surface liquid composition abnormalities may reflect an inability of CF epithelial cells to sense changes in external mucosal environment and/or an inability of CF cells to regulate their own cell volume.To this end, complimentary observations using a variety of techniques suggest that expression of CFTR enhances ATP release and modulates the dynamic relationship between cell volume, puriner...

High grade glioma cells derived from patient biopsies express an amiloride-sensitive sodium conductance that has properties attributed to the human brain sodium channel family, also known as acid-sensing ion channels (ASICs). This amiloride-sensitive conductance was not detected in cells obtained from normal brain tissue or low grade or benign tumors. Differential gene profiling data showed that ASIC1 and ASIC2 mRNA were present in normal and low grade tumor cells. Although ASIC1 was present in all of the high grade glial cells examined, ASIC2 mRNA was detected in less than half. The main purpose of our work was to examine the molecular mechanisms that may underlie the constitutively activated sodium currents present in high grade glioma cells. Our results show that 1) gain-of-function mutations of ASIC1 were not present in a number of freshly resected and cultured high grade gliomas, 2) syntaxin 1A inhibited ASIC currents only when ASIC1 and ASIC2 were co-expressed, and 3) the inhibition of ASIC currents by syntaxin 1A had an absolute requirement for either ␥-or ␦-hENaC. Transfection of cultured cells originally derived from high grade gliomas (U87-MG and SK-MG1) with ASIC2 abolished basal amiloride-sensitive sodium conductance; this inhibition was reversed by dialysis of the cell interior with Munc-18, a syntaxinbinding protein that typically blocks the interaction of syntaxin with other proteins. Thus, syntaxin 1A cannot inhibit Na ؉ permeability in the absence of adequate plasma membrane ASIC2 expression, accounting for the observed functional expression of amiloride-sensitive currents in high grade glioma cells.

The human gut is home to a complex and diverse microbiota that contributes to the overall homeostasis of the host. Increasingly, the intestinal microbiota is recognized as an important player in human illness such as colorectal cancer (CRC), inflammatory bowel diseases, and obesity. CRC in itself is one of the major causes of cancer mortality in the Western world. The mechanisms by which bacteria contribute to CRC are complex and not fully understood, but increasing evidence suggests a link between the intestinal microbiota and CRC as well as diet and inflammation, which are believed to play a role in carcinogenesis. It is thought that the gut microbiota interact with dietary factors to promote chronic inflammation and CRC through direct influence on host cell physiology, cellular homeostasis, energy regulation, and/or metabolism of xenobiotics. This review provides an overview on the role of commensal gut microbiota in the development of human CRC and explores its association with diet and inflammation.