Bilateral multifocal renal oncocytoma--a case report and literature review.

A case of bilateral multifocal renal oncocytoma is reported. The incidence, diagnosis and management of such tumors is discussed.

Endogenous corticosteroids modulate Clostridium difficile toxin A-induced enteritis in rats.

We examined the role of glucocorticoids in acute inflammatory diarrhea mediated by Clostridium difficile toxin A. Toxin A (5 microg) or buffer was injected in rat ileal loops, and intestinal responses were measured after 30 min to 4 h. Ileal toxin A administration increased plasma glucocorticoids after 1 h, at which time the toxin-stimulated secretion was not significant. Administration of the glucocorticoid analog dexamethasone inhibited toxin A-induced intestinal secretion and inflammation and downregulated toxin A-mediated increase of macrophage inflammatory protein-2. Adrenalectomy followed by replacement with glucocorticoids at various doses suggested that intestinal responses to toxin A were related to circulating levels of glucocorticoids. Administration of the glucocorticoid receptor antagonist RU-486 enhanced toxin A-mediated intestinal secretion and inflammation. We conclude that C. difficile toxin A causes increased secretion of endogenous glucocorticoids, which diminish the intestinal secretory and inflammatory effects of toxin A.

Neurotensin is a proinflammatory neuropeptide in colonic inflammation.

The neuropeptide neurotensin mediates several intestinal functions, including chloride secretion, motility, and cellular growth. However, whether this peptide participates in intestinal inflammation is not known. Toxin A, an enterotoxin from Clostridium difficile, mediates pseudomembranous colitis in humans. In animal models, toxin A causes an acute inflammatory response characterized by activation of sensory neurons and intestinal nerves and immune cells of the lamina propria. Here we show that neurotensin and its receptor are elevated in the rat colonic mucosa following toxin A administration. Pretreatment of rats with the neurotensin receptor antagonist SR-48, 692 inhibits toxin A-induced changes in colonic secretion, mucosal permeability, and histologic damage. Exposure of colonic explants to toxin A or neurotensin causes mast cell degranulation, which is inhibited by SR-48,692. Because substance P was previously shown to mediate mast cell activation, we examined whether substance P is involved in neurotensin-induced mast cell degranulation. Our results show that neurotensin-induced mast cell degranulation in colonic explants is inhibited by the substance P (neurokinin-1) receptor antagonist CP-96,345, indicating that colonic mast activation in response to neurotensin involves release of substance P. We conclude that neurotensin plays a key role in the pathogenesis of C. difficile-induced colonic inflammation and mast cell activation.

Participation of reactive oxygen metabolites in Clostridium difficile toxin A-induced enteritis in rats.

Reactive oxygen metabolites (ROMs) contribute to the pathophysiology of intestinal inflammation. Our aim was to ascertain the involvement of ROMs in experimental ileitis in rats produced by toxin A of Clostridium difficile. Intraluminal toxin A caused a significant increase in hydroxyl radical and hydrogen peroxide production by ileal microsomes starting 1 h following toxin exposure and peaking at 2-3 h, and this was inhibited by pretreatment with DMSO, a ROM scavenger, or superoxide dismutase (SOD), which inactivates ROMs. In contrast, mucosal xanthine oxidase increased only slightly after toxin A exposure, and allopurinol, an inhibitor of xanthine oxidase, had no effect on toxin A-associated intestinal responses. Induction of neutropenia resulted in reduction of toxin-mediated free radical formation, fluid secretion, and permeability. The enterotoxic effects of C. difficile toxin A were associated with increased ROM release in ileal tissues, and the ROM inhibitors DMSO and SOD inhibited these effects. This suggests that ROMs released during toxin A enteritis are released primarily from neutrophils invading the inflamed bowel segment.

BCL-2 expression and inhibin-A in adrenal neoplasms: a comparative study.

Differential diagnosis between adrenal cortical and adrenal medullary lesions may be difficult in many cases. Different immunohistochemical, histochemical tools as well as ultrastructural diagnostic techniques have been employed to aid in differentiating between these lesions. Recently, both inhibin-A and BCL-2 have been shown to stain selectively adrenal cortical tissue and its derived neoplasms but not adrenal medulla or pheochromocytomas. In this study we compared the staining reactions of inhibin-A and BCL-2 in cases of adrenal cortical adenomas and carcinomas as well as pheochromocytomas. We found that both inhibin-A and BCL-2 stained cortical derived tissues, but not medullary derived tissues. Staining intensity for inhibin-A was significantly weaker than for BCL-2. We found that fixation techniques may influence the staining reactivity, as some cases did not immunoreact with any of the antibodies. We conclude that both inhibin-A, and, preferentially, BCL-2 are useful additions to a staining protocol to help in the differential diagnosis of cortical and medullary neoplasms.

Colonic mucin release in response to immobilization stress is mast cell dependent.

We recently reported that immobilization stress increased colonic motility, mucin, and prostaglandin E2 (PGE2) release and mucosal mast cell degranulation in rat colon [Proc. Natl. Acad. Sci. USA 93: 12611-12615, 1996; Am. J. Physiol. 271 (Gastrointest. Liver Physiol. 34): G884-G892, 1996]. To directly assess the contribution of mast cells, we compared colonic responses to stress in mast cell-deficient KitW/KitW-v and normal(+/+) mice. Mucin and PGE2 release were measured in colonic explants cultured from KitW/KitW-v and (+/+) mice 30 min after immobilization stress. We found that stress stimulated colonic mucin release (1.8-fold), goblet cell depletion (3-fold), and PGE2 (2.3-fold) release in (+/+) but not mast cell-deficient KitW/KitW-v mice. However, mast cell-deficient mice that had their mast cell population reconstituted by injection of bone marrow-derived mast cells from (+/+) mice had colonic responses to stress similar to those of normal (+/+) mice. In contrast, colonic transit changes in response to stress, estimated by fecal output, were similar between KitW/KitW-v and normal (+/+) mice. We conclude that mast cells regulate colonic mucin and PGE2 release but not colonic transit changes in response to immobilization stress.

Clostridium difficile toxin A stimulates macrophage-inflammatory protein-2 production in rat intestinal epithelial cells.

Neutrophil infiltration of the colonic mucosa is a hallmark of Clostridium difficile toxin A-mediated enterocolitis. Macrophage-inflammatory protein-2 (MIP-2) is a potent neutrophil chemoattractant secreted by rat macrophages and epithelial cells in response to inflammatory stimuli. In this work, we report that administration of toxin A into rat ileal loops increased mucosal levels of MIP-2 before the onset of fluid secretion and mucosal neutrophil infiltration. Administration of rabbit anti-MIP-2 IgG, but not control IgG, reduced toxin A-mediated secretion (by 58%), mucosal permeability (by 80%), and myeloperoxidase activity (by 85%). Immunohistochemical analysis demonstrated increased MIP-2 expression in intestinal epithelial and lamina propria cells 1 h after toxin A administration. Intestinal epithelial cells purified from toxin A-exposed ileal loops also showed increased MIP-2 mRNA expression and MIP-2 protein release that was inhibited by pretreatment of rats with the transcriptional inhibitor actinomycin D. These results indicate that C. difficile toxin A induces MIP-2 release from intestinal epithelial cells and that MIP-2 contributes to neutrophil mucosal influx during toxin A enteritis.

Neurokinin-1 (NK-1) receptor is required in Clostridium difficile- induced enteritis.

Toxin A, a 308,000-Mr enterotoxin from Clostridium difficile, mediates antibiotic-associated diarrhea and colitis in humans. Injection of toxin A into animal intestine triggers an acute inflammatory response characterized by activation of sensory neurons and immune cells of the intestinal lamina propria, including mast cells and macrophages, and migration of circulating neutrophils in the involved intestinal segment. In this study we show that mice genetically deficient in the neurokinin-1 receptor are protected from the secretory and inflammatory changes as well as from epithelial cell damage induced by toxin A. The protective effect of neurokinin-1R deletion correlates with diminished intestinal levels of the cytokine TNF-alpha and its mRNA and the leukocyte enzyme myeloperoxidase. These results demonstrate a major requirement for substance P receptors in the pathogenesis of acute inflammatory diarrhea.

CGRP upregulation in dorsal root ganglia and ileal mucosa during Clostridium difficile toxin A-induced enteritis.

We have previously reported that pretreatment of rats with capsaicin (an agent that ablates sensory neurons) or CP-96345 (a substance P receptor antagonist) dramatically inhibits fluid secretion and intestinal inflammation in ileal loops exposed to Clostridium difficile toxin A. The aim of this study was to determine whether calcitonin gene-related peptide (CGRP), a neuropeptide also found in sensory afferent neurons, participates in the enterotoxic effects of toxin A. Administration of toxin A was also found to increase CGRP content in dorsal root ganglia and ileal mucosa 60 min after toxin exposure. Furthermore, immunohistochemical studies demonstrated increased neuronal staining for CGRP 2 h after toxin A treatment. Pretreatment of rats with CGRP-(8-37), a specific CGRP antagonist, before instillation of toxin A into ileal loops significantly inhibited toxin-mediated fluid secretion (by 48%), mannitol permeability (by 83%), and histological damage. We conclude that CGRP, like substance P, contributes to the secretory and inflammatory effects of toxin A via increased production of this peptide from intestinal nerves, including primary sensory afferent neurons.

IL-11 inhibits Clostridium difficile toxin A enterotoxicity in rat ileum.

Interleukin-11 (IL-11) is a stromal cell-derived cytokine with several biological activities against hematopoietic cells. Recent results indicated that IL-11 reduced mucosal damage in animal models of colitis. This study aimed to explore the action of recombinant human IL-11 (rhIL-11) on the intestinal effects of Clostridium difficile toxin A, an inflammatory enterotoxin, and cholera toxin, a noninflammatory enterotoxin in rat ileum. We administered rhIL-11 subcutaneously to rats before injection of toxin A into ileal loops and measured fluid secretion, epithelial permeability to mannitol, histopathological damage, and release of rat mast cell protease II (RMCP II) from intestinal mast cells and of tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) from lamina propria macrophages. rhIL-11 (50-1,000 micrograms/kg) inhibited toxin A but not cholera toxin-mediated secretion and permeability in a dose-dependent fashion and reduced toxin A-induced epithelial cell damage. Rats treated with rhIL-11 also showed reduced RMCP II, TNF-alpha, and MIP-2 release in response to toxin A. Exposure of rat peripheral monocytes in vitro to rhIL-11 (1 microgram/ml) inhibited lipopolysaccharide and toxin A-mediated increases in TNF-alpha mRNA and protein levels. We conclude that rhIL-11 blocks the intestinal effects of C. difficile toxin A, possibly by inhibiting release of inflammatory mediators from mucosal mast cells and intestinal macrophages.

Comparison of topoisomerase II alpha and MIB-1 expression in uterine cervical squamous lesions.

The aim of this study was to assess the role of MIB-1 in the classification of cervical squamous lesions and to compare it with a novel proliferation marker, topoisomerase II alpha (TP II alpha). We classified 46 archival uterine cervical cases into 6 groups: normal (n = 3); human papillomavirus (n = 15); mild (n = 10), moderate (n = 7), and severe (n = 6) cervical intra-epithelial neoplasia; and invasive carcinoma (n = 5). The formalin-fixed, paraffin-embedded tissue sections were stained with monoclonal antibodies to Ki-67 (MIB-1) and TP II alpha with a standard streptavidin immunohistochemical technique, with antigen retrieval to assess enzyme presence. The results were based on nuclear staining and percentage of positivity. We found that the mean percentage of positive nuclei increased from normal through increasing grades of dysplasia to its maximal level in invasive carcinoma. The level of positive nuclei in the epithelium also generally increased from basal to full thickness with progression of the lesions. The correlation between the percentage of nuclei positive for both antibodies with the use of linear regression was close, with an r value of 0.85. Our conclusions were that MIB-1 is an adjunct in the classification of squamous lesions of the uterine cervix and that TP II alpha is a useful proliferation marker in this setting.

Topoisomerase II alpha expression in normal, inflammatory, and neoplastic conditions of the gastric and colonic mucosa.

Topoisomerase II alpha (TP) excises and reconnects double-stranded super-coiled DNA during the replicative cell cycle. We studied the localization of TP and Ki-67 in inflammatory and neoplastic mucosal lesions of the stomach and of TP in similar conditions of the colon. TP expression was correlated with tumor stage, grade, and survival time in the colonic tumors to evaluate its potential utility as a predictive marker for clinical outcome. Forty-three sections of chronic gastritis, lesions indefinite for dysplasia, low- and high-grade dysplasia, and gastric adenocarcinomas were immunostained with antibody against TP and Ki-67. For the colon, 71 sections of normal mucosa, chronic colitis, hyperplastic polyps, adenomas, and carcinomas were examined; fresh tissue was analyzed by flow cytometry. Expression of TP in non-neoplastic gastric mucosa was maximal in neck/foveolar cells and focal in surface and deep gland cells. Increased surface and deep gland positivity was found in low-grade dysplasia and a diffuse distribution of positive cells in high-grade dysplasia and carcinoma. The Ki-67 staining pattern was similar. TP in non-neoplastic colon was restricted to the lower crypt zone; it was greatly expanded in the surface/upper crypt region in adenomas and was diffuse in carcinomas. Flow cytometric analysis revealed TP expression mainly in the S and G2/M phase, with higher labeling index in tumors. There was no correlation of TP with stage, grade, or survival times in the colonic tumors. Staining for TP and Ki-67 might help in the distinction of inflammatory and neoplastic lesions of the stomach and colon.

Increased substance P responses in dorsal root ganglia and intestinal macrophages during Clostridium difficile toxin A enteritis in rats.

Previously we reported that pretreatment of rats with the substance P (SP) antagonist CP-96,345 inhibits the enterotoxic responses following administration of toxin A from Clostridium difficile into ileal loops, indicating that SP participates in the intestinal responses to this toxin. We now report that injection of toxin A into rat ileum causes a rapid increase in SP content in lumbar dorsal root ganglia (DRG) and mucosal scrapings 30-60 min after toxin A administration. Toxin A-mediated fluid secretion, mannitol permeability, and ileal histologic damage is significantly increased only after 2 hr. Toxin A also causes an increase in the abundance of SP mRNA in lumbar DRG and ileal mucosa as measured by reverse transcription-PCR. Lamina propria macrophages (LPMs) obtained from toxin A-injected loops release greater amounts of tumor necrosis factor alpha (TNFalpha) and SP as compared with LPMs isolated from buffer-injected loops (P < 0.01). Pretreatment of rats with the SP antagonist CP-96,345 inhibits toxin A-mediated TNFalpha release from isolated LPMs, whereas an inactive enantiomer (CP-96,344) of the SP antagonist has no effect. LPMs obtained from toxin A-injected ileal loops incubated in vitro with SP (10(-8) to 10(-9) M) show enhanced TNFalpha secretion, whereas LPMs isolated from buffer-injected loops do not respond to SP. In addition, LPMs obtained from toxin A-injected ileal loops incubated in vitro with CP-96,345 showed a diminished TNFalpha release. Our results indicate that activated LPMs secrete SP during toxin A enteritis that can lead to secretion of cytokines, suggesting an autocrine/paracrine regulation of cytokine secretion by SP from LPMs during intestinal inflammation.

Saccharomyces boulardii protease inhibits Clostridium difficile toxin A effects in the rat ileum.

Saccharomyces boulardii, a nonpathogenic yeast, is effective in treating some patients with Clostridium difficile diarrhea and colitis. We have previously reported that S. boulardii inhibits rat ileal secretion in response to C. difficile toxin A possibly by releasing a protease that digests the intestinal receptor for this toxin (C. Pothoulakis, C. P. Kelly, M. A. Joshi, N. Gao, C. J. O'Keane, I. Castagliuolo, and J. T. LaMont, Gastroenterology 104: 1108-1115, 1993). The aim of this study was to purify and characterize this protease. S. boulardii protease was partially purified by gel filtration on Sephadex G-50 and octyl-Sepharose. The effect of S. boulardii protease on rat ileal secretion, epithelial permeability, and morphology in response to toxin A was examined in rat ileal loops in vivo. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified S. boulardii protease revealed a major band at 54 kDa. Pretreatment of rat ileal brush border (BB) membranes with partially purified protease reduced specific toxin A receptor binding (by 26%). Partially purified protease digested the toxin A molecule and significantly reduced its binding to BB membranes in vitro (by 42%). Preincubation of toxin A with S. boulardii protease inhibited ileal secretion (46% inhibition, P < 0.01), mannitol permeability (74% inhibition, P < 0.01), and histologic damage caused by toxin A. Thus, S. boulardii protease inhibits the intestinal effects of C. difficile toxin A by proteolysis of the toxin and inhibition of toxin A binding to its BB receptor. Our results may be relevant to the mechanism by which S. boulardii exerts its protective effects in C. difficile infection in humans.

Acute stress causes mucin release from rat colon: role of corticotropin releasing factor and mast cells.

We determined the effects of immobilization stress on rat colonic mucus release and mast cell degranulation and examined whether corticotropin releasing factor (CRF) was involved in these responses. After 30-min immobilization, rats were killed, colonic mucosal explants were cultured, and levels of rat mast cell protease II (RMCP II) and prostaglandin E2 (PGE2) were measured. Mucin release from explants was assayed by incorporation of [3H]glucosamine into colonic mucin and by histological evaluation of goblet cell depletion. Stress caused significant increases of colonic RMCP II, PGE2, and mucin release and fecal pellet output and caused an approximately 10-fold increase in colonic mucosal levels of cyclooxygenase-2 (COX-2) mRNA. These stress-associated changes were reproduced by intravenous or intracerebral injection of CRF in conscious, nonstressed rats. Pretreatment of rats with the CRF antagonist alpha-helical-CRF9-41, hexamethonium, atropine, or bretylium, or the mast cell stabilizer lodoxamide inhibited stress-induced release of RMCP II, PGE2, and mucin, whereas indomethacin prevented mucin release but not mast cell degranulation. Hexamethonium and CP-96,345, a substance P antagonist, inhibited fecal pellet output caused by stress. We conclude that CRF released during immobilization stress increases colonic transit via a neuronal pathway and stimulates colonic mucin secretion via activation of neurons and mast cells.

A neurotensin antagonist, SR 48692, inhibits colonic responses to immobilization stress in rats.

We previously reported that short-term immobilization stress of rats causes increased colonic mucin release, goblet cell depletion, prostaglandin E2 secretion, and colonic mast cell activation, as well as increased colonic motility. The purpose of this study was to investigate whether neurotensin (NT), a peptide expressed in both brain and digestive tract, participates in these responses. Rats were pretreated with SR 48692 (1 mg/kg, i.p.), an NT antagonist, 15 min before immobilization (30 min). The administration of the antagonist significantly inhibited stress-mediated secretion of colonic mucin, prostaglandin E2, and a product of rat mast cells, rat mast cell protease II (P < 0.05), but did not alter the increase in fecal pellet output caused by immobilization stress. Immobilization stress also resulted in a quantifiable decrease in the abundance of NT receptor mRNA in rat colon compared with that in colonic tissues from nonimmobilized rats as measured by densitometric analysis of in situ hybridization studies (P < 0.03). We conclude that the peptide NT is involved in colonic goblet cell release and mucosal mast cell activation after immobilization stress.

A receptor decoy inhibits the enterotoxic effects of Clostridium difficile toxin A in rat ileum.

BACKGROUND & AIMS: Clostridium difficile toxin A causes secretion and intestinal inflammation in rodents by binding to a specific trisaccharide Gal alpha 1-3Gal beta 1-4 GlcNAc on enterocyte receptors. The purpose of this study was to explore the ability of Synsorb 90 (Synsorb Biotech Inc., Calgary, Alberta, Canada), and inert support carrying this trisaccharide, to bind toxin A in vitro and to inhibit its enterotoxic effects in vivo. METHODS: Binding of [3H]toxin A to Synsorb 90, Synsorb 83 (beta-mannose attached), and Chromosorb P (inert support with no sugar attached) (Synsorb Biotech Inc.) was measured. The inhibitory effects of these compounds on toxin A-mediated fluid secretion, mannitol permeability, and histological damage were measured in ileal loops in vivo. RESULTS: Toxin A showed specific binding to Synsorb 90, bearing the specific trisaccharide that binds toxin A, but not to Synsorb 83 or to Chromosorb P. Pretreatment of rats with Synsorb 90 by gavage (200 mg/kg body wt), but no Synsorb 83 or Chromosorb P at the same doses, dramatically reduced toxin A-associated fluid secretion and permeability. CONCLUSIONS: An immobilized toxin A receptor sequesters toxin A in the intestinal lumen and inhibits its effects of ileal mucosa. These results suggest a potential use for this agent in treating patients with C. difficile colitis.

Rabbit sucrase-isomaltase contains a functional intestinal receptor for Clostridium difficile toxin A.

The intestinal effects of Clostridium difficile toxin A are inidated by toxin binding to luminal enterocyte receptors. We reported previously that the rabbit ileal brush border (BB) receptor is a glycoprotein with an alpha-d-galactose containing trisaccharide in the toxin-binding domain (1991. J. Clin. Invest. 88:119-125). In this study we characterized the rabbit ileal BB receptor for this toxin. Purified toxin receptor peptides of 19 and 24 amino acids showed 100% homology with rabbit sucrase-isomaltase (SI). Guinea pig receptor antiserum reacted in Western blots with rabbit SI and with the purified toxin receptor. Antireceptor IgG blocked in vitro binding of toxin A to rabbit ileal villus cell BB. Furthermore, anti-SI IgG inhibited toxin A-induced secretion (by 78.1%, P < 0.01), intestinal permeability (by 80.8%, P < 0.01), and histologic injury (P < 0.01) in rabbit ileal loops in vivo. Chinese hamster ovary cells transfected with SI cDNA showed increased intracellular calcium increase in response to native toxin (holotoxin) or to a recombinant 873-amino acid peptide representing the receptor binding domain of toxin A. These data suggest that toxin A binds specifically to carbohydrate domains on rabbit ileal SI, and that such binding is relevant to signal transduction mechanisms that mediate in vitro and in vivo toxicity.

A human antibody binds to alpha-galactose receptors and mimics the effects of Clostridium difficile toxin A in rat colon.

BACKGROUND & AIMS: Nearly all human sera contain an immunoglobulin G antibody (antigalactose) that binds the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc expressed on cells from most mammals but not humans. Because the Clostridium difficile toxin A receptor in rodents contains this trisaccharide, the aim of this study was to examine whether antigalactose could mimic the enterotoxic effects of toxin A and bind to receptors containing this trisaccharide. METHODS: Fluid secretion, [3H]-mannitol permeability, and release of rat mast cell protease II and prostaglandin E2 were measured after luminal exposure of rat colon to either purified human anti-galactose, control immunoglobulin G, toxin A, or buffer. RESULTS: Toxin A (5 micrograms) and antigalactose (250 micrograms) but not control immunoglobulin (250 micrograms) stimulated colonic fluid secretion and caused increased mannitol permeability and rat mast cell protease II release. Antigalactose and toxin A and, to a lesser degree, control immunoglobulin G also stimulated release of prostaglandin E2, but only toxin A produced acute inflammation of rat colonic mucosa. Antigalactose and toxin A bound specifically to a single class of colonic brush border receptors with dissociation constants of 10(-6) mol/L and 5.4 x 10(-8) mol/L, respectively. CONCLUSIONS: Fluid secretion, increased permeability, and mast cell activation occur in rat colon when toxin A or human antigalactose immunoglobulin G bind to receptors bearing the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc.