Epidermal growth factor upregulates serotonin transporter in human intestinal epithelial cells via transcriptional mechanisms.

Serotonin transporter (SERT) regulates extracellular availability of serotonin and is a potential pharmacological target for gastrointestinal disorders. A decrease in SERT has been implicated in intestinal inflammatory and diarrheal disorders. However, little is known regarding regulation of SERT in the intestine. Epidermal growth factor (EGF) is known to influence intestinal electrolyte and nutrient transport processes and has protective effects on intestinal mucosa. Whether EGF regulates SERT in the human intestine is not known. The present studies examined the regulation of SERT by EGF, utilizing Caco-2 cells grown on Transwell inserts as an in vitro model. Treatment with EGF from the basolateral side (10 ng/ml, 24 h) significantly stimulated SERT activity (∼2-fold, P < 0.01) and mRNA levels compared with control. EGF increased the activities of the two alternate promoter constructs for human SERT gene: SERT promoter 1 (hSERTp1, upstream of exon 1a) and SERT promoter 2 (hSERTp2, upstream of exon 2). Inhibition of EGF receptor (EGFR) tyrosine kinase activity by PD168393 (1 nM) blocked the stimulatory effects of EGF on SERT promoters. Progressive deletions of the SERT promoter indicated that the putative EGF-responsive elements are present in the -672/-472 region of the hSERTp1 and regions spanning -1195/-738 and -152/+123 of hSERTp2. EGF markedly increased the binding of Caco-2 nuclear proteins to the potential AP-1 cis-elements present in EGF-responsive regions of hSERTp1 and p2. Overexpression of c-jun but not c-fos specifically transactivated hSERTp2, with no effects on hSERTp1. Our findings define novel mechanisms of transcriptional regulation of SERT by EGF via EGFR at the promoter level that may contribute to the beneficial effects of EGF in gut disorders.

Small pulmonary nodule management: a survey of the members of the Society of Thoracic Radiology with comparison to the Fleischner Society guidelines.

PURPOSE: We surveyed the members of the Society of Thoracic Radiology regarding their interpretation of and management decision for small pulmonary nodules on computed tomography. We then compared their responses with the published guidelines set forth by the Fleischner Society. MATERIALS AND METHODS: A survey consisting of 13 case scenarios in which small pulmonary nodules were encountered on computed tomography examination was electronically mailed to 625 members of the Society of Thoracic Radiology. Statistical analysis was performed to determine associations between responses, years of experience, location in an endemic region of granulomatous disease, and setting of practice. To assess the relationship between recommendation (defined as appropriate or not appropriate based on the Fleischner Society guidelines) and the characteristics of the radiologist, univariate analyses were first carried out. Characteristics with evidence of association with recommendation (defined as P<0.10) were included in the multiple-variable analysis. Multiple-variable logistic regression was used to assess the simultaneous effects of reader characteristics on recommendation. A backward selection process was used applying a significance level of 0.05. This analysis was carried out for each question. RESULTS: One hundred and eighty-one surveys were completed (29%). Overall, 27% of the participants had made the appropriate recommendation based on the Fleischner Society guidelines. There was an overall trend for over-management in the various clinical scenarios. Radiologists who had been in practice for longer periods of time were less likely to select the appropriate management, as were radiologists who practiced outside the United States. In addition, in certain scenarios, radiologists in endemic areas were less likely to over-manage than their counterparts in nonendemic regions. CONCLUSIONS: Among responding members of the Society of Thoracic Radiology, there was poor adherence to the published guidelines set forth by the Fleischner Society.

Enteropathogenic Escherichia coli infection inhibits intestinal serotonin transporter function and expression.

BACKGROUND & AIMS: Serotonin transporter (SERT) plays a critical role in regulating serotonin (5-hydroxytryptamine [5-HT]) availability in the gut. Elevated 5-HT levels are associated with diarrheal conditions such as irritable bowel syndrome and enteric infections. Whether alteration in SERT activity contributes to the pathophysiology of diarrhea induced by the food-borne pathogen enteropathogenic Escherichia coli (EPEC) is not known. The present studies examined the effects of EPEC infection on SERT activity and expression in intestinal epithelial cells and elucidated the underlying mechanisms. METHODS: Caco-2 cells as a model of human intestinal epithelia and EPEC-infected C57BL/6J mouse model of infection were utilized. SERT activity was measured as Na(+) and Cl(-) dependent (3)[H] 5-HT uptake. SERT expression was measured by real-time quantitative reverse-transcription polymerase chain reaction, Western blotting, and immunofluorescence studies. RESULTS: Infection of Caco-2 cells with EPEC for 30-120 minutes decreased apical SERT activity (P < .001) in a type 3 secretion system dependent manner and via involvement of protein tyrosine phosphatases. EPEC infection decreased V(max) of the transporter; whereas cell surface biotinylation studies revealed no alteration in the cellular or plasma membrane content of SERT in Caco-2 cells. EPEC infection of mice (24 hours) reduced SERT immunostaining with a corresponding decrease in SERT messenger RNA levels, 5-HT uptake, and mucosal 5-HT content in the small intestine. CONCLUSIONS: Our results demonstrate inhibition of SERT by EPEC and define the mechanisms underlying these effects. These data may aid in the development of a novel pharmacotherapy to modulate the serotonergic system in treatment of infectious diarrheal diseases.

Serotonin modifies cytoskeleton and brush-border membrane architecture in human intestinal epithelial cells.

Serotonin or 5-hydroxytryptamine (5-HT) influences numerous functions in the gastrointestinal tract. We previously demonstrated that 5-HT treatment of Caco-2 cells inhibited Na(+)/H(+) exchangers (NHE) and Cl(-)/OH(-) exchange activities via distinct signaling mechanisms. Since regulation of several ion transporters such as NHE3 is influenced by intact cytoskeleton, we hypothesized that 5-HT modifies actin cytoskeleton and/or brush-border membrane architecture via involvement of signaling pathways. Ultrastructural analysis showed that 5-HT (0.1 muM, 1 h) treatment of Caco-2 cells caused the apical membrane to assume a convex dome shape that was associated with shortening of microvilli. To examine whether these cellular architecture changes are cytoskeleton driven, we analyzed actin cytoskeleton by fluorescence microscopy. 5-HT induced basal stress fibers with prominent cortical actin filaments via 5-HT3 and 5-HT4 receptor subtypes. This induction was partially attenuated by chelation of intracellular Ca(2+) and PKCalpha inhibition (Go6976). In vitro assays revealed that PKCalpha interacted with actin and this association was increased by 5-HT. Our data provide novel evidence that 5-HT-induced signaling via 5-HT3/4 receptor subtypes to cause Ca(2+) and PKCalpha-dependent regulation of actin cytoskeleton may play an important role in modulation of ion transporters that contribute to pathophysiology of diarrheal conditions associated with elevated levels of 5-HT.

Urine electrolyte, mineral, and protein excretion in NHERF-2 and NHERF-1 null mice.

The adaptor proteins sodium/hydrogen exchanger regulatory factor (NHERF)-1 and NHERF-2 have overlapping tissue distribution in renal cells and overlapping specificity in their binding to renal transporters and other proteins. To compare the kidney-specific differences in the function of these adaptor proteins, NHERF-1 and NHERF-2 null mice were compared with wild-type control mice. In NHERF-2 null mice, the renal proximal tubule abundance and distribution of NHERF-1 and NHERF-3 were not different from those in wild-type animals. The glomerular expression of podocalyxin and ZO-1 also did not differ. NHERF-1 null mice had increased urinary excretion of phosphate, calcium, and uric acid compared with wild-type control and NHERF-2 null mice. Because of the association between NHERF-2 and podocalyxin in glomeruli and ClC-5 in the renal proximal tubule, the urinary excretion of protein was determined. There were no differences in the urinary excretion of protein or low-molecular-weight proteins between wild-type control, NHERF-1(-/-), and NHERF-2(-/-) mice. These studies indicate that the increased urinary excretion of phosphate and uric acid are specific to NHERF-1 null mice and highlight the fact that predictions about the role of adaptor proteins such as the NHERF proteins obtained from studies of model cell systems must be confirmed in whole animals.

Sarcoidosis of gastrointestinal tract: a rare disease.

Gastrointestinal (GI) tract sarcoidosis is an uncommon form of sarcoidosis. The GI tract can be involved as an isolated disease as a part of systemic sarcoidosis. Clinical manifestations of esophageal, gastric, small bowel, colon, and appendicular sarcoidosis are discussed in this review. The differential diagnosis of GI sarcoidosis is extensive. Other granulomatous diseases of the GI tract, like tuberculosis, fungal infections, parasitic diseases, inflammatory bowel disease, and Whipple's disease, should be excluded before making the diagnosis of GI sarcoidosis. Corticosteroid therapy is effective in treatment of GI sarcoidosis. Surgical intervention may be necessary in patients with bowel obstruction, perforation, or massive hemorrhage.

Erlotinib-associated acute pneumonitis: report of two cases.

Two cases of erlotinib-associated acute pneumonitis are described. The first patient was started on erlotinib treatment for metastatic non-small cell lung cancer. The second patient was treated with erlotinib for metastatic adenocarcinoma of unknown origin. Both patients developed dyspnea and hypoxemia five to six days after initiation of erlotinib treatment. In both cases, computed tomography scan of the chest showed extensive bilateral ground-glass infiltrates consistent with pneumonitis. In both patients, acute pneumonitis resulted in respiratory failure requiring intubation and mechanical ventilation. Diffuse alveolar hemorrhage was excluded by bronchoscopy in both cases. Bronchoalveolar lavage cultures were negative. Erlotinib treatment was stopped and both patients were treated with corticosteroids. The first patient improved gradually and finally was discharged to a rehabilitation centre, but unfortunately the second patient died of Klebsiella sepsis. Naranjo causality scale in both cases suggested a probable association between erlotinib and pneumonitis. Literature on erlotinib-associated pneumonitis is sparse. The clinical presentation and radiographic findings of erlotinib-associated acute pneumonitis are described.

JunD stabilization results in inhibition of normal intestinal epithelial cell growth through P21 after polyamine depletion.

BACKGROUND & AIMS: Normal intestinal mucosal growth requires cellular polyamines that regulate expression of various genes involved in cell proliferation, growth arrest, and apoptosis. We have recently shown that growth inhibition after polyamine depletion is associated with an increase in JunD/AP-1 activity in normal intestinal epithelial cells (IEC-6 line). The current study tests the hypothesis that polyamine depletion-induced JunD/activator protein 1 (AP-1) activity results from the activation of junD gene expression and plays a critical role in regulation of intestinal epithelial cell growth. METHODS: The junD gene transcription was examined by nuclear run-on assays, and messenger RNA (mRNA) stability was measured by determination of JunD mRNA half-life. Functions of JunD were investigated by using JunD antisense oligodeoxyribonucleotides and transient transfection with the junD-expressing vector. RESULTS: Depletion of cellular polyamines by DL-alpha-difluoromethylornithine (DFMO) induced levels of JunD mRNA and protein, which was associated with an increase in G(1) phase growth arrest. Polyamine depletion did not increase the rate of junD gene transcription but significantly increased the stability of JunD mRNA. Decreasing JunD protein by using JunD antisense oligomers promoted cell growth in polyamine-deficient cells. Growth arrest following polyamine depletion also was accompanied by increases in both p21 expression and its promoter activity. Treatment with JunD antisense oligomers inhibited the p21 promoter and prevented the increase in p21 expression in the presence of DFMO. Ectopic expression of the wild-type junD increased p21-promoter activity and inhibited epithelial cell growth. CONCLUSIONS: Polyamines negatively regulate junD gene expression posttranscriptionally, and increased JunD/AP-1 inhibits intestinal epithelial cell proliferation at least partially through the activation of p21 promoter.