Ball in the Wall: Mesenteric Fibromatosis-a Rare Case Report.

INTRODUCTION: Mesenteric fibromatosis-desmoid tumor of mesentery is a rare benign soft tissue tumor of mesentery. On CT, it mimics gastrointestinal stromal tumor (GIST). CASE REPORT: A 44-year-old female with small intestinal mass, preoperatively diagnosed radiologically and pathologically as GIST. CONCLUSION: Mesenteric fibromatosis is a rare tumor often mistaken for GIST. Histopathology and immunohistochemistry is the key as management of both the tumors differs.

Calcium accentuates injury induced by ethanol in human gastric cells.

The mechanism(s) whereby ethanol induces cellular injury remains poorly understood. Furthermore, the role of calcium in gastric mucosal injury under in vitro conditions is poorly defined. The major objectives of this study were to (1) define the temporal relationship between intracellular calcium accumulation induced by ethanol and cellular injury, (2) characterize the mechanism(s) whereby ethanol increases cellular calcium content, and (3) determine whether calcium removal would attenuate ethanol-induced cellular injury. Human gastric cells (AGS) were used for all experiments. Sustained intracellular calcium accumulation induced by ethanol, but not transient changes, preceded and directly correlated with cellular injury. Cells exposed to damaging concentrations of ethanol demonstrated an initial calcium surge that appeared to be a consequence of inositol 1,4,5-triphosphate (IP3) generation and subsequent internal store release followed by a sustained plateau resulting from extracellular calcium influx through store-operated calcium channels. Finally, both morphologic (cellular injury) and functional (clearance of bovine serum albumin) changes induced by ethanol were significantly attenuated when extracellular Ca(+&plus) influx was prevented, and further decreased when intracellular Ca(++) stores were depleted. These data indicate that calcium plays a significant role in cellular injury induced by ethanol.

Nonsteroidal anti-inflammatory drugs attenuate epidermal growth factor-induced proliferation independent of prostaglandin synthesis inhibition.

BACKGROUND: The mechanism(s) whereby nonsteroidal anti-inflammatory drugs (NSAIDs) attenuate colorectal tumor growth remains poorly understood. This study determined if NSAIDs decreased epidermal growth factor (EGF)-induced proliferation in human colonic tumor (Caco-2) cells and whether this process involved the inhibition of prostaglandin (PG) synthesis. METHODS: Caco-2 cells were serum-starved (48 h) and subsequently treated (48 h) with either serum-free media or EGF (10 ng/ml) +/- physiologic and noninjurious (as determined by LDH release) concentrations of aspirin, indomethacin, and ibuprofen. PG synthesis was measured by EIA. Proliferation was quantitated with two assays: cellular protein and nucleic acid content. RESULTS: NSAID treatment did not inhibit growth in cells treated with only serum-free media. Cells exposed to EGF demonstrated a significant increase in PGE2, protein, and nucleic acid. Levels of other eicosanoids (PGI2, TXA2) were minimal both before and after EGF treatment. Despite varying degrees of PGE2 inhibition, each NSAID group equally attenuated EGF-induced protein and nucleic acid synthesis. The correlation between PGE2 levels and protein (R2 = 0.56) or nucleic acid (R2 = 0.54) was poor. Finally, the addition of a physiologically appropriate concentration of exogenous PGE2 failed to reverse NSAID-induced growth inhibition. CONCLUSION: These data suggest that NSAIDs, independent of PG synthesis inhibition, attenuate EGF-induced proliferation in Caco-2 cells. This may provide one explanation for how NSAIDs limit colonic neoplasia.

Prostaglandins protect human intestinal cells against ethanol injury by stabilizing microtubules: role of protein kinase C and enhanced calcium efflux.

Prostaglandins (PG) protect gastrointestinal cells against damage induced by ethanol (EtOH) and other noxious agents, a process termed cytoprotection. The present study investigated the relationships between microtubule (MT) stability, protein kinase C (PKC) activation, and calcium efflux as a possible mechanism of PG's protective action using a human colonic cell line (Caco-2) exposed to known damaging concentrations of EtOH (7.5% and 10%). Preincubation of Caco-2 cells with 16,16-dimethyl-PGE2 (PG, 2.6 microM) significantly increased PKC activity in these cells. Pretreatment of Caco-2 cells with 50 microM OAG (a synthetic diacylglycerol and PKC activator) or 30 nM TPA (a direct PKC activator) prior to exposure to 7.5% or 10% EtOH for 5 min significantly reduced cell injury, as determined by trypan blue exclusion, and increased MT stability, as confirmed by confocal microscopy. Pretreatment of Caco-2 cells with 4 alpha-PDD (an inactive phorbol ester, 20 nM) failed to prevent cell injury and disruption of the MT cytoskeleton. Preincubation with staurosporine (a PKC inhibitor, 3 nM) abolished the protective effects of PG in cells exposed to 7.5% and 10% EtOH. Incubation of Caco-2 cells with A23187 (a Ca2+ ionophore), similar to 10% EtOH, caused a significant reduction in cell viability and MT stability. Preincubation with A23187 in combination with PG or OAG prior to subsequent exposure to EtOH significantly abolished the protective effects of PG or OAG pretreatment. Finally, pretreatment with OAG, TPA, or PG resulted in significant increases in calcium-45 efflux, which correlated with increased stability of the MT cytoskeleton. These data suggest that PG possesses direct protective effects against EtOH injury in Caco-2 cells and may act by stabilizing MT through the PKC signal transduction pathway and/or stimulation of calcium efflux from the cells.

Indomethacin increases susceptibility to injury in human gastric cells independent of PG synthesis inhibition.

Indomethacin and other nonsteroidal anti-inflammatory drugs are commonly used to indirectly deduce the possible role of PGs in a process being studied. The objective of this study was to determine if indomethacin, at concentrations comparable to plasma and tissue levels obtained in humans taking therapeutic doses, predisposes human gastric cells to injury through inhibition of PGs or acts through an alternate mechanism. The role of intracellular Ca2+ in this damaging process was also assessed. Indomethacin pretreatment, although by itself nondamaging, was associated with elevated intracellular Ca2+ concentrations and an increased cellular permeability, an effect that was dependent on extracellular Ca2+. Furthermore, indomethacin pretreatment significantly predisposed AGS cells to injury induced by two dissimilar agents (deoxycholate and A-23187), both of which are associated with intracellular Ca2+ accumulation. The addition of exogenous PGs did not reverse the predisposition to injury induced by indomethacin. The observed effects of indomethacin were dependent on concentration and not on ability to inhibit PG synthesis. Similar effects were not observed with equipotent concentrations of ibuprofen or aspirin. Finally, the exacerbation of deoxycholate-induced injury induced by indomethacin was not observed when extracellular Ca2+ was removed. Indomethacin, by disturbing intracellular Ca2+ homeostasis, predisposes human gastric cells to injury through mechanisms independent of PG synthesis. The current study suggests that data resulting from studies employing only indomethacin as a PG synthesis inhibitor should be interpreted with caution.

Role of calcium in adaptive cytoprotection and cell injury induced by deoxycholate in human gastric cells.

We have developed an in vitro model of adaptive cytoprotection induced by deoxycholate (DC) in human gastric cells and have shown that pretreatment with a low concentration of DC (mild irritant, 50 microM) significantly attenuates injury induced by a damaging concentration of DC (250 microM). This study was undertaken to assess the effect of the mild irritant on changes in intracellular Ca2+ and to determine if these perturbations account for its protective action. Protection conferred by the mild irritant was lost when any of its effects on intracellular Ca2+ were prevented: internal Ca2+ store release via phospholipase C and inositol 1,4, 5-trisphosphate sustained Ca2+ influx through store-operated Ca2+ channels or eventual Ca2+ efflux. We also investigated the relationship between Ca2+ accumulation and cellular injury induced by damaging concentrations of DC. In cells exposed to high concentrations of DC, sustained Ca2+ accumulation as a result of extracellular Ca2+ influx, but not transient changes in intracellular Ca2+ content, appeared to precede and induce cellular injury. We propose that the mild irritant disrupts normal Ca2+ homeostasis and that this perturbation elicits a cellular response (involving active Ca2+ efflux) that subsequently provides a protective action by limiting the magnitude of intracellular Ca2+ accumulation.

Adaptive cytoprotection induced by ethanol in human intestinal cells: role of prostaglandins and calcium homeostasis.

OBJECTIVE: To determine whether adaptive cytoprotection exists in human intestinal cells under in vitro conditions and what role, if any, endogenous prostaglandins or calcium may play in mediating this protective response. SUMMARY BACKGROUND DATA: Adaptive cytoprotection can be defined as that process whereby the administration of a low concentration of a damaging agent, termed a "mild irritant," which by itself is not injurious, can attenuate gastrointestinal mucosal injury subsequently induced by the application of higher concentrations of the same or other necrotizing agents. Despite substantial investigation, the mediator or mediators of adaptive cytoprotection remain poorly understood. METHODS: Postconfluent Caco-2 cells were used in all experiments. Cellular death was quantitated using a dual-component fluorescent assay. Changes in intracellular calcium concentration were quantitated by measuring fluorescent signal changes of the single wavelength calcium indicator (Fluo-3). Finally, prostaglandin E2 release into the media was quantitated by radioimmunoassay. RESULTS: Pretreatment of Caco-2 cells with low concentrations of ethanol (mild irritant) significantly attenuated injury induced by higher damaging concentrations of ethanol. The protection conferred by the mild irritant was directly dependent on both the concentration of the irritant used and the duration of exposure and was abrogated when cells were pretreated with an endogenous prostaglandin inhibitor (indomethacin) or if the mild irritant was administered in calcium-free media. Cells exposed to ethanol had a significant and concentration-dependent increase in intracellular calcium concentration, an effect that was highly related to cellular injury. Pretreatment with a mild irritant significantly decreased intracellular calcium increases induced by not only ethanol but also by a calcium ionophore (A23187). Cells treated with low concentrations of ethanol demonstrated no significant elevation in prostaglandin E2 release. CONCLUSIONS: Adaptive cytoprotection induced by ethanol exists in human colonocytes under in vitro conditions independent of mucosal blood flow, neural innervation, or circulating humoral factors. The authors' data suggest that this response does not require endogenous prostaglandin synthesis but may involve processes whereby intracellular calcium accumulation is prevented.

Adaptive cytoprotection against deoxycholate-induced injury in human gastric cells in vitro: is there a role for endogenous prostaglandins?

The majority of previous work investigating adaptive cytoprotection has involved in vivo studies, which have suggested that this protective response is in large part mediated by endogenous prostaglandins (PGs). The aim of this study was to investigate adaptive cytoprotection under in vitro conditions in human gastric cells and to better delineate the role of endogenous PGs in this protective response. AGS cells (a human gastric carcinoma cell line) were characterized morphologically and subsequently used for all experiments. Sodium deoxycholate was used as both the mild irritant and the damaging agent, and cell injury was quantified using both a commercial viability/cytotoxicity kit as well as transepithelial permeability studies. Finally, endogenous PG synthesis in response to varying concentrations of deoxycholate was determined. AGS cells were determined to be morphologically similar to gastric mucous cells. Pretreatment of cells with low-dose deoxycholate significantly attenuated injury upon subsequent exposure to damaging concentrations of deoxycholate, and this protection was determined to be dependent upon both concentration and duration of mild irritant exposure. Preincubation of AGS cells with indomethacin reversed protection induced by mild irritant pretreatment and also significantly increased cellular susceptibility to injury. Results of the permeability studies closely paralleled those assessing cell mortality. While deoxycholate exposure increased PG synthesis, the concentrations required were much higher than those needed to initiate protection. Adaptive cytoprotection exists in AGS cells under in vitro conditions independent of intact blood flow, neural innervation, or circulating humoral mediators. While this protection is reversed by indomethacin, it appears that this reversal results from increased cellular injury secondary to diminished basal PGs, rather than inhibition of endogenous PG synthesis.

The effect of trinitrobenzene sulfonic acid on gut-derived smooth muscle cell arachidonic acid metabolism: role of endogenous prostanoids.

The contribution of smooth muscle cells as a potential source of eicosanoid production during inflammatory states remains to be elucidated. We investigated the effect of trinitrobenzene sulfonic acid (TNB), a known pro-inflammatory agent, on jejunal smooth muscle cell eicosanoid production. Human gut-derived smooth muscle cells (HISM) were incubated with TNB for 1 hour. Additionally, some cells were preincubated with either dimethylthiourea, or indomethacin for 1 hour before exposure to identical concentrations of TNB. Incubation with TNB led to significant increases in PGE(2) and 6-keto PGF-1(alpha) release, but not leukotriene B(4) release; responses which were both inhibited by dimethylthiourea and indomethacin treatment. Our results suggest that gutderived smooth muscle cells may represent an important source of proinflammatory prostanoids but not leukotrienes during inflammatory states of the intestine. The inhibition of prostanoid activity by thiourea may be mediated by suppression of cyclooxygenase activity in this cell line.

The effect of an interleukin receptor antagonist (IL-1ra) on colonocyte eicosanoid release.

We investigated whether an interleukin 1 receptor antagonist (IL-1ra) altered cellular release of prostanoids and leukotrienes in a transformed colonic cell line (CACO-2) in the presence of proinflammatory stimuli. Cellular inflammation was induced by treatment with lipopolysaccharide (LPS) or the cytokine, interleukin 1 beta (IL-1(beta)). In a separate set of experiments, cells were pretreated with IL-1ra prior to exposure to LPS or IL-1(beta). Prostaglandin E(2) and leukotriene B(4) (LTB(4)) levels were quantified by ELISA assays. Both LPS and IL-1(beta) exposure were noted to stimulate cellular PGE(2) release, a response which was significantly inhibited by IL-1ra treatment. Either stimulant when administered alone failed to stimulate release of LTB(4). When administered after IL-1ra pretreatment however, both stimuli caused a significant increase in LTB(4) release. These results suggest that a cytokine receptor antagonist can selectively influence eicosanoid production in this cell line. Furthermore, this study suggests that a IL-1ra may have a future clinical role in the treatment of inflammatory disorders of the colon which are intimately linked to enhanced eicosanoid synthesis.

Lysophosphatidylcholine-stimulated protein and glycoprotein production by human gallbladder mucosal cells.

It has been demonstrated in experimental cholecystitis in cats produced by lysophosphatidylcholine that the development of inflammation is associated with the exsorption of a large amount of protein into the gallbladder lumen. It was subsequently demonstrated that in feline experimental cholecystitis the protein produced was albumin and that its production was decreased by vesicular transport inhibitors, suggesting an active secretory process. In the present study, the effect of lysophosphatidylcholine on protein production by fresh, isolated human gallbladder mucosal cells was evaluated. Isolated gallbladder mucosal cells were incubated with [14C]leucine for 24 hr in tissue culture medium. The cells readily incorporated the radioactive label into cellular protein, a process inhibited by cycloheximide. Exposure of the cells to lysophosphatidylcholine for 1 hr in buffer solution resulted in loss of intracellular protein into the buffer solution. Exposure of the cells for 1 hr prior to lysophosphatidylcholine administration to vesicular transport inhibitors, colchicine, and cytochalasin B and to 4 degrees C culture conditions failed to alter the lysophosphatidylcholine-produced passage of the 14C label extracellularly. SDS-PAGE evaluation of the protein produced demonstrated that human gallbladder mucosal cells continuously produced a 66-kDa protein that was not increased by increasing concentration of lysophosphatidylcholine and a 14-kDa protein that increased with increasing concentrations of lysophosphatidylcholine. Employing Western blotting with specific antibodies, the 66-kDa protein was demonstrated to not be albumin but a 66-kDa glycoprotein, and the 14-kDa protein was demonstrated to contain phospholipase A2. Human gallbladder mucosal cells produced a protein and glycoprotein in response to lysophosphatidylcholine by a mechanism not related to vesicular transport.

Gallbladder mucosal protein secretion during development of experimental cholecystitis.

The development of experimental cholecystitis produced by lysophosphatidylcholine is associated with reversal of the normal absorptive characteristics of gallbladder mucosa, resulting in the intraluminal accumulation of water, glycoprotein, and protein. The purpose of the present study was to attempt to ascertain if the protein leaks into the lumen because of the cytolytic properties of lysophosphatidylcholine or if it is due to an active secretory process and to characterize the protein produced. Experiments were performed on anesthetized cats undergoing gallbladder perfusion with and without lysophosphatidylcholine. The amount of protein in the perfusate was measured and albumin clearance from blood to gallbladder lumen was calculated with and without the administration of vesicular transport inhibitors. In separate experiments, control and lysophosphatidylcholine (LPC) produced gallbladder perfusates were collected and the protein subjected to SDS-PAGE to ascertain the nature of the protein secreted. Inhibitors of both microtubular and microfilament activity decreased the protein accumulation and clearance produced by lysophosphatidylcholine. Gallbladder white blood cell accumulation and inflammation as evaluated by beta-glucuronidase and prostaglandin E levels were not significantly altered by cytochalasin or colchicine administration. Lysophosphatidylcholine also produced significant increases in perfusate LDH levels. The protein produced was primarily a 66-kDa protein. Transfer of the protein to a nitrocellulose membrane and immunoblotting with anti-albumin antibody demonstrated that the protein was albumin. The results suggest that during the development of cholecystitis, lysophosphatidylcholine produces albumin accumulation in the gallbladder primarily by inducing an active secretory process resulting in gallbladder distension.

Evidence for a colonic PAF receptor.

We sought to determine the effect of exogenously administered platelet-activating factor (PAF) on eicosanoid release from the left colon of the rabbit. Using an isolated buffer-perfused rabbit left colon preparation, 1.0- or 5.0-micrograms doses of PAF were infused into the inferior mesenteric artery. Effluents from the inferior mesenteric vein and colonic lumen were collected and the concentrations of the eicosanoids, prostaglandin E, 6-ketoprostaglandin F1 alpha, thromboxane B2, and leukotriene B4 (LTB4), were measured by ELISA. During PAF infusion there was a significant increase of all prostanoids, but not LTB4 into the venous effluent and colonic luminal perfusate when compared to control experiments. Additional studies were performed by pretreating the colons with the PAF antagonists WEB-2170 or alprazolam prior to PAF infusion. Both venous and luminal effluent prostanoid release was effectively blocked by WEB-2170, but not by alprazolam. Colons pretreated with WEB-2170 prior to PAF had markedly diminished tissue injury when compared to colons treated with PAF alone. Inhibition of PAF-stimulated prostanoid release by WEB-2170 suggests that a PAF-sensitive receptor is present in rabbit colonic tissue which may induce eicosanoid-mediated tissue injury.

Platelet-activating factor mediates trinitrobenzene induced dysmotility in the left colon.

We investigated whether TNB alters colonic tissue levels of PAF at the expense of changes in colonic motility in the isolated perfused rabbit left colon. Colonic inflammation was induced by the intracolonic administration of 0.25 ml of 50% ethanol containing 30 mg of trinitrobenzene. Strain gauge transducers were sewn onto the serosal surface of the colon to evaluate colonic motility. TNB administration increased tissue levels of PAF and increased the average force of each colonic contraction. Pretreatment with the PAF receptor antagonist WEB-2170 prior to TNB infusion decreased tissue concentrations of PAF and ameliorated the altered motility parameters seen with TNB alone. These results suggest that PAF is stimulated by TNB and may participate in colonic dysmotility during inflammatory states.

The effect of lysolecithin on prostanoid and platelet-activating factor formation by human gall-bladder mucosal cells.

It has been demonstrated that lysolecithin (lysophosphatidyl choline, LPC) produces experimental cholecystitis in cats mediated by arachidonic acid metabolites. LPC is a cytolytic agent that has been postulated as a contributing factor in the development of cholecystitis in humans. The purpose of this research was to evaluate the effect of LPC on human gall-bladder mucosal cell phospholipase A(2) and cyclooxygenase activity. Gall-bladder mucosal cells were isolated from the gall-bladders of patients undergoing routine cholecystectomy. Fresh, isolated cells were maintained in tissue culture and stimulated with varying doses of LPC. Platelet-activating factor concentration was quantitated as an index of phospholipase A(2) activity and prostanoids were measured as an index of cyclooxygenase activity. Also, the effect of LPC on cyclooxygenase 1 and 2 expression in microsomal protein was evaluated. LPC caused dose related increases in 6-keto-PGF(1alpha) and PAF produced by human gall-bladder mucosal cells. Exposure of human gall-bladder mucosal cells to LPC failed to elicit expression of constitutive cyclooxygenase-1, while the expression of inducible cyclooxygenase-2 was increased. The results of this study indicate that LPC induces the formation of prostanoids and PAF by human gall-bladder mucosal cells, suggesting that this substance may promote the development of gall-bladder inflammation.

Platelet-activating factor mediates trinitrobenzene induced colitis.

Platelet-activating factor (PAF) is an endogenous phospholipid which may be an important mediator of shock and inflammation. Recent evidence suggests that PAF plays a role in the development of ischemic colitis and inflammatory bowel disease. Its effects are mediated by second messengers, including the arachidonic acid metabolites. Using an ex vivo isolated left colon rabbit perfusion model, our aims were to determine whether exogenously administered trinitrobenzene sulfonic acid (TNB), which produces experimental colitis, stimulates both PAF and eicosanoid release in the colon, and if so, whether this effect can be blocked by a PAF antagonist. Colonic inflammation was induced by the intracolonic administration of 0.25 ml of 50% ethanol containing 30 mg of TNB. Tissue and perfusate concentrations of the eicosanoids, [prostaglandin E (PGE2), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2), leukotriene B4 (LTB4)] and the autocoid PAF were measured by ELISA. During TNB infusion there was a significant increase in tissue levels of PAF compared to control colons. Additional studies performed pretreating the colons with the PAF receptor antagonist WEB-2170 prior to TNB infusion blocked PAF release. TNB stimulated release of luminal eicosanoids except LTB4 and suppressed release of tissue prostanoids. Pretreatment with WEB-2170 prior to TNB inhibited luminal eicosanoids, and inhibited PGE2 and prostacyclin, but not TX tissue suppression. Inhibition of TNB-stimulated PAF release by WEB-2170 suggests that PAF may play a role in TNB-induced colitis and this phenomenon may mediate tissue injury.

The effect of Clostridium difficile toxin on colonocyte prostanoid activity.

Antibiotic-associated colitis is caused by Clostridium difficile toxin. However, the pathophysiology of this entity is poorly understood. The aim of this study was to determine the effects of C. difficile toxin on colonocyte cyclooxygenase and phospholipase A2 (PLA2) activity. A transformed colonocyte cell line (Caco-2) was grown to confluency on 6 well plates. The cells were stimulated with graded concentrations of C. difficile toxin. In separate experiments, the cells were pretreated for one hour prior to stimulation with the cyclooxygenase inhibitor, indomethacin, or the glucocorticoid, dexamethasone. The culture media was collected one hour following C. difficile stimulation. Prostaglandin E2 (PGE2), 6-keto prostaglandin F1 alpha (6KPGF), thromboxane B2 (TxB2) and leukotriene B4 (LTB4) levels were determined in the media by an ELISA. Platelet activating factor (PAF) concentration was determined by a RIA. C. difficile toxin stimulated PGE2 and 6KPGF levels in a dose dependent fashion but failed to stimulate TxB2, LTB4 or PAF. Prostanoid production was inhibited by indomethacin dose dependently but was not inhibited by dexamethasone. The presence of indomethacin resulted in production of PAF. Our results show that the effects of C. difficile toxin on colonocytes are mediated by cyclooxygenase activity. The increase in PAF formation associated with indomethacin administration suggests that the prostanoids modulate PLA2 activity and inhibit PAF formation.

Studies on the etiology of acute acalculous cholecystitis: the effect of lipopolysaccharide on human gallbladder mucosal cells.

Previous studies in animals have shown that lipopolysaccharide produces experimental cholecystitis possibly through a platelet-activating factor-prostanoid mediated process. In this study it was intended to evaluate the effect of LPS on primary cultures of human gallbladder mucosal cells. Gallbladder mucosal cells were isolated from gallbladders removed during routine cholecystectomies or other operations. The cells were cultured for 24 h before treatment. Unstimulated cells produced low levels of prostanoids and significant basal levels of PAF. LPS produced stimulation of eicosanoid and PAF secretion. The increased prostanoid formation was not enhanced when LPS and PAF were administered together. Prostanoid synthesis was inhibited by the administration of a cyclooxygenase inhibitor while administration of a PAF receptor antagonist significantly increased prostanoid formation, suggesting that increased PAF levels function as a negative control mechanism to decrease prostanoid synthesis. The results suggest that endotoxemia may produce a cascade of inflammatory processes in human gallbladder mucosal cells resulting in the development of acute acalculous cholecystitis.

Effect of platelet-activating factor and its antagonists on colonic dysmotility and tissue levels of colonic neuropeptides.

We investigated whether platelet-activating factor (PAF) alters colonic tissue levels of substance P and vasoactive intestinal peptide (VIP), two neuropeptides that regulate colonic motility. Left colons were harvested from NZ White Rabbits and underwent vascular perfusion via the inferior mesenteric artery. Strain gauge transducers were sewn onto the serosal surface of the colon to evaluate colonic motility. Colons were perfused with either buffered saline alone or with 5.0 x 10(-5) M PAF. PAF administration increased tissue VIP and substance P levels and decreased the force of colonic contractions. Pretreatment with WEB-2170 or alprazolam decreased concentrations of both tissue neuropeptides, and decreased the force of colonic contractions and minute motility index. These results suggest that both VIP and substance P are stimulated by PAF and may participate in colonic dysmotility during inflammatory states.

The production of experimental cholecystitis by endotoxin.

Acute acalculous cholecystitis (AAC) is a severe inflammatory disorder of the gallbladder. It occurs primarily in patients acutely ill from other disorders and is related to sepsis and shock. We previously found that platelet-activating factor (PAF), a phospholipid autacoid purported to be a mediator of the shock response, produced AAC. This study was performed to determine the effect of intravenous lipopolysaccharide (LPS) on feline gallbladders. Anesthetized cats underwent LPS administration with and without administration of a cyclooxygenase inhibitor and PAF antagonist. Gallbladder inflammation was evaluated by quantitation of luminal water transport and tissue myeloperoxidase levels. In an attempt to understand the mechanisms of the response, gallbladder perfusate and tissue prostanoid and PAF levels were quantitated as were serum PAF levels. LPS administration resulted in alteration of the normal absorptive pattern of the gallbladder mucosa to exsorption of fluid into the gallbladder lumen, increased tissue myeloperoxidase levels and increased serum PAF levels. This was associated with increased gallbladder tissue and perfusate prostanoid levels and increased perfusate PAF levels. Indomethacin prevented the pro-inflammatory changes in the gallbladder produced by LPS. The PAF antagonist, alprazolam, increased gallbladder prostanoid production when administered alone and with LPS. The administration of LPS resulted in the production of acute changes in the gallbladder consistent with cholecystitis. These changes being prevented by a cyclooxygenase inhibitor suggests that development of AAC may be related to the release of systemic and local pro-inflammatory substances.