Effects of endotoxin and dexamethasone on group I and II phospholipase A2 in rat ileum and stomach

Alterations in the epithelial stem cell compartment could contribute to permanent changes in the mucosa of patients with ulcerative colitis

OBJECTIVE

UC is a chronic inflammatory disease of the colonic mucosa. Growing evidence supports a role for epithelial cell defects in driving pathology. Moreover, long-lasting changes in the epithelial barrier have been reported in quiescent UC. Our aim was to investigate whether epithelial cell defects could originate from changes in the epithelial compartment imprinted by the disease.

DESIGN

Epithelial organoid cultures (EpOCs) were expanded ex vivo from the intestinal crypts of non-IBD controls and patients with UC. EpOCs were induced to differentiate (d-EpOCs), and the total RNA was extracted for microarray and quantitative real-time PCR (qPCR) analyses. Whole intestinal samples were used to determine mRNA expression by qPCR, or protein localisation by immunostaining.

RESULTS

EpOCs from patients with UC maintained self-renewal potential and the capability to give rise to differentiated epithelial cell lineages comparable with control EpOCs. Nonetheless, a group of genes was differentially regulated in the EpOCs and d-EpOCs of patients with UC, including genes associated with antimicrobial defence (ie, LYZ, PLA2G2A), with secretory (ie, ZG16, CLCA1) and absorptive (ie, AQP8, MUC12) functions, and with a gastric phenotype (ie, ANXA10, CLDN18 and LYZ). A high rate of concordance was found in the expression profiles of the organoid cultures and whole colonic tissues from patients with UC.

CONCLUSIONS

Permanent changes in the colonic epithelium of patients with UC could be promoted by alterations imprinted in the stem cell compartment. These changes may contribute to perpetuation of the disease.

Recombinant TsP53 modulates intestinal epithelial barrier integrity via upregulation of ZO‑1 in LPS‑induced septic mice

Tight junctions (TJs) are a critical component in maintaining the intestinal mucosal barrier function and gastrointestinal health of animals. Gut barrier dysfunction contributes to the initiation and development of sepsis which induces an uncontrollable systemic inflammatory response and gives rise to life‑threatening clinical conditions. Excretory‑secretary antigens from Trichimella spiralis (T. spiralis) have been reported to protect from sepsis in a mouse model, however the mechanism remains to be elucidated. Mice were treated with recombinant T. spiralis 53‑kDa glycoprotein (rTsP53) at 2 or 6 h following lipopolysaccharide (LPS) injection. Survival rate, serum systemic inflammation, Chiu's score, D‑lactic acid (D‑LA) and diamine oxidase (DAO) as intestinal injured biomarkers, bacterial translocation and growth in peritoneal fluid (PF) and mesenteric lymph nodes (MLN), intestinal tight junction structure and protein zona occludens (ZO)‑1 expression were investigated. In LPS‑induced septic mice, rTsP53 was demonstrated to protract the survival and inhibit serum systemic inflammatory response, and then, allayed morphological alteration, decreased the release of D‑LA and DAO from intestines. Furthermore, LPS‑induced intestinal permeability, bacterial translocation and growth in PF, MLN and vital organs were significantly suppressed by rTsP53 treatment. Notably, rTsP53 treatment markedly improved the intestinal tight junction damaged in sepsis via promoting ZO‑1 expression. These results demonstrated that rTsP53 ameliorated LPS‑induced intestinal injury and is a potential protective agent for treatment of sepsis.

A Mechanistic Basis for the Beneficial Effects of Caloric Restriction On Longevity and Disease: Consequences for the Interpretation of Rodent Toxicity Studies

Caloric restriction in rodents has been repeatedly shown to increase life span while reducing the severity and retarding the onset of both spontaneous and chemically induced neoplasms. These effects of caloric restriction are associated with a spectrum of biochemical and physiological changes that characterize the organism's adaptation to reduced caloric intake and provide the mechanistic basis for caloric restriction's effect on longevity. Here, we review evidence suggesting that the primary adaptation appears to be a rhythmic hypercorticism in the absence of elevated adrenocorticotropin (ACTH) levels. This characteristic hypercorticism evokes a spectrum of responses, including reduced body temperature and increased metabolic efficiency, decreased mitogenic response coupled with increased rates of apoptosis, reduced inflammatory response, reduced oxidative damage to proteins and DNA, reduced reproductive capacity, and altered drug-metabolizing enzyme expression. The net effect of these changes is to (1) decrease growth and metabolism in peripheral tissues to spare energy for central functions, and (2) increase the organism's capacity to withstand stress and chemical toxicity. Thus, caloric restriction research has uncovered an evolutionary mechanism that provides rodents with an adaptive advantage in conditions of fluctuating food supply. During periods of abundance, body growth and fecundity are favored over endurance and longevity. Conversely, during periods of famine, reproductive performance and growth are sacrificed to ensure survival of individuals to breed in better times. This phenomena can be observed in rodent populations that are used in toxicity testing. Improvements over the last 30 years in animal husbandry and nutrition, coupled with selective breeding for growth and fecundity, have resulted in several strains now exhibiting larger animals with reduced survival and increased incidence of background lesions. The mechanistic data from caloric restriction studies suggest that these large animals will also be more susceptible to chemically induced toxicity. This creates a problem in comparing tests performed on animals of different weights and comparing data generated today with the historical database. The rational use of caloric restriction to control body weight to within preset guidelines is a possible way of alleviating this problem.

Pathophysiology of LPS-induced gastrointestinal injury in the rat: role of secretory phospholipase A2

A hydrophobic layer of phosphatidylcholine (PC) overlies and protects the surface of the gastrointestinal (GI) tract, contributing to barrier integrity. During critical illness such as sepsis, gut barrier integrity is compromised, which could be related to degradation of PC. The purpose of this study was to investigate a role for luminal (secretory) phospholipase A2 (sPLA(2)) in LPS-induced GI injury. Rats were treated with LPS (5 mg/kg) or saline for 0.5, 1, 3, and 5 h. The gastric and ileal luminal contents were collected for determination of sPLA(2) activity, and the luminal lipids were analyzed using thin layer chromatography for lyso-PC content. The GI permeability was assessed in vivo with fluorescein-isothiocyanate dextran 4000 and rats were tested with or without a specific sPLA(2) inhibitor. LPS induced significant increases in sPLA(2) activity and lyso-PC content in the gastric and ileal lumens at 5 h. In addition, LPS treated rats showed a significant increase in GI permeability to fluorescein-isothiocyanate dextran in both the stomach and ileum at 5 h, which was prevented by pretreatment with the sPLA(2) inhibitor. In response to LPS, sPLA(2) activity increases in the GI tract lumen where it may degrade the extracellular protective phospholipid layer and membranes, producing injurious lyso-PC and increased GI permeability. Pretreatment with an orally active sPLA(2) inhibitor blocks the LPS-induced increase in GI permeability, and may suggest a new approach to fortify the GI mucosal barrier and prevent complications from endotoxin in trauma and other patients.

Increased gene expression of novel cytosolic and secretory phospholipase A(2) types in human airway epithelial cells induced by tumor necrosis factor-alpha and IFN-gamma

Phospholipase A(2) (PLA(2)) is a growing family of enzymes that may play a major role in inflammation. We investigated the effect of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) on the gene expression of 19 different PLA(2) types (IB, IIA, IID, IIE, IIF, III, IVA, IVB, IVC, V, VIA, VIB, VIIA, VIIB, VIIIA, VIIIB, X, XII, and XIII) in human bronchoepithelial (BEAS-2B) and nasal epithelial (RPMI 2650) cells. The cells were stimulated with TNF-alpha or IFN-gamma for different lengths of time (1, 4, 18, and 48 h), and the mRNA levels of the different PLA(2) types were determined by reverse transcriptase-PCR (RT-PCR) and normalized to those of the housekeeping gene, GAPDH. In both cell lines, TNF-alpha increased the expression of PLA(2) IVA and IVC, and IFN-gamma increased the expression of PLA(2) IIA and IID. No influence on the gene expression of PLA(2)-activating protein (PLAP) was noted on cytokine stimulation. These findings indicate that TNF-alpha and IFN-gamma induce gene expression of two novel cytosolic and secretory PLA(2) types (IVC and IID, respectively) in human airway epithelial cells. The possibility that these PLA(2) types are involved in cytokine-mediated inflammation in the respiratory tract is inferred.

Role of gut flora on intestinal group II phospholipase A2 activity and intestinal injury in shock

We previously showed that group II phospholipase A2 (PLA2-II), a secretory, bactericidal, and proinflammatory protein in intestinal crypts, is upregulated after lipopolysaccharide (LPS) and platelet-activating factor (PAF) challenge. Here we examined whether germ-free environment (GF) or antibiotic treatment (ABX) affects the pathophysiological responses and intestinal PLA2-II activity after PAF (1.5 microg/kg) or LPS (8 mg/kg) injection. We found that LPS and PAF induced hypotension and mild intestinal injury in conventionally fed (CN) rats; these changes were milder in ABX rats, whereas GF rats showed no intestinal injury. PLA2-II enzyme activity was detected in normal rat small intestine; the basal level was not diminished in ABX or GF rats. PAF and LPS caused an increase in PLA2-II activity, which was abrogated in GF and ABX rats. Recolonization of GF rats by enteral contamination restituted their PLA2-II response to PAF and LPS and susceptibility to bowel injury. We conclude that PAF- and LPS-induced increases in PLA2-II activity are dependent on gut bacteria, and ABX and GF rats are less susceptible to LPS-induced injury than CN rats.

Presence of group IIa secretory phospholipase A2 in mast cells and macrophages in normal human ileal submucosa and in Crohn's disease

Secretory group IIa phospholipase A2 (PLA2-II) is an important regulator of proinflammatory lipid mediator production and may play a role in ileal inflammation in Crohn's disease. The enzyme has previously only been detected in epithelial Paneth cells. However, one characteristic feature of Crohn's disease is the transmural inflammation. Full thickness ileal sections from nine patients with Crohn's disease, and histologically normal sections from patients with colonic cancer (n=7) and chronic severe constipation (n=1) as controls, were used in this study. PLA2-II-positive cells were detected by immunofluorescence and in situ hybridization. Metachromatic staining and esterase staining were used to identify mast cells and macrophages, respectively. It was shown that mast cells and macrophages in the ileal submucosa in both patients and controls showed positive PLA2-II staining. The number of PLA2-II-labeled cells that did not react with metachromasia, e.g. macrophages, was significantly greater in inflamed Crohn's disease compared to controls. This is, to our knowledge, the first study that has described the presence in healthy, while presence and upregulation of PLA2-II-positive cells in inflamed human ileal submucosa. Our findings suggest a proinflammatory potential for secretory PLA2-II in submucosa, while proinflammatory stimulation of mast cells and macrophages in vitro has shown that the enzyme is responsible for delayed prostaglandin formation.

Aldosterone alters the phospholipid composition of rat colonocytes

Previous studies have shown that aldosterone treatment of amphibian epithelial cells results not only in stimulation of Na(+) absorption but also in changes in phospholipid composition which are necessary for the mineralocorticoid action of aldosterone. The present study was designed to investigate the effect of aldosterone on phospholipids of mammalian epithelia. Phospholipid and fatty acid composition was examined in colonic epithelium (mineralocorticoid target tissue) and thymus (non-mineralocorticoid but glucocorticoid target tissue) of rats which had received aldosterone or vehicle by a miniosmotic pump for 7 days. Aldosterone increased the mass of colonic phospholipids relative to cellular proteins with concomitant changes in the percentage distribution of fatty acids, whereas the relative distribution of membrane phospholipds was not changed. Phosphatidylcholine increased the content of polyunsaturated and decreased that of monounsaturated fatty acids, which predominantly reflected the accretion of arachidonic and a decrease in oleic and palmitoleic acids. Within the phosphatidylethanolamine subclass, pretreatment of rats with aldosterone decreased the content of monounsaturated fatty acids (predominantly oleic and palmitoleic acid) and of n-3 fatty acids, and increased the content of saturated fatty acids (palmitic acid). The saturated-to-nonsaturated fatty acid ratio also significantly increased after aldosterone treatment. No changes in thymic phospholipids were seen. The results are consistent with the contention that aldosterone specifically modulates phospholipid concentration and metabolism in mineralocorticoid target tissue. The changes in phospholipid content and its fatty acid composition during the fully developed effect of aldosterone may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.

The role of phospholipase A2 in calcium-ionophore-mediated injury to rat gastric mucosal cells

Although transient increases in intracellular Ca2+ ([Ca2+]i) underlie a number of important physiological processes, sustained elevations in [Ca2+]i mediate damage to a number of tissues and cell types including gastric mucosal cells. Increases in [Ca2+]i can activate phospholipid hydrolysis via increases in phospholipase A2 (PLA2) activity and subsequent cell injury. In the present study we have examined whether [Ca2+]i-induced gastric cellular injury is mediated by PLA2 activation. Gastric mucosal cells were harvested from rat stomachs after pronase digestion. Cell integrity was assessed using trypan blue dye exclusion and release of lysozomal enzymes. PLA2 activity was estimated colorimetrically by determination of thiol release from the substrate, arachidonyl thio-PC. In these studies calcium ionophore A23187 (3-25 microM) resulted in an increase in cell injury. The damage produced by A23187 (12.5 microM) was inhibited by preincubation of cells with the PLA2 inhibitor, quinacrine (1-100 microM). Quinacrine did not reduce ethanol (10% w/v) mediated-cell damage. Similarly Ca2+ ionophore A23187 treatment resulted in a concentration-dependent increase in PLA2 activity in gastric cells. The increase in PLA2 activity was attenuated if cells were incubated in Ca2+-depleted medium containing EGTA (4 mM). Furthermore lysophospholipids generated by PLA2 (lysophosphatidylethanolamine and lysophosphatidylcholine; 100 microM) also increased the degree of cell injury. Pretreatment of cells with the PAF antagonist WEB 2086 (10(-6) and 10(-5) M), the leukotriene synthase inhibitor 5,6-dehydroarachidonic acid (10 microM), or the thromboxane synthase inhibitor furegrelate (1 microM) decrease A23187-mediated cell injury. These data suggest that Ca2+ ionophore-mediated increases in [Ca2+]i result in gastric cell injury and this effect is mediated in part by PLA2 activation and subsequent release of free fatty acids and lysophosphatides.

Mice lacking secretory phospholipase A2 show altered apoptosis and differentiation with Helicobacter felis infection

BACKGROUND & AIMS

Infection with Helicobacter pylori uniformly leads to a chronic superficial gastritis that may progress to atrophic gastritis, a premalignant process. A mouse model of Helicobacter felis infection was used to study possible genetic determinants of the response to infection.

METHODS

Three inbred mouse strains with known secretory phospholipase A2 (sPLA2) genotypes [BALB/c (+/+), C3H/HeJ (+/+), and C57BL/6 (-/-)] were orally infected with H. felis and examined longitudinally using routine histology, immunocytochemistry, electron microscopy, proliferating cell nuclear antigen, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, and Northern and Western blot studies.

RESULTS

Only the C57BL/6 strain showed increased gastric fundic proliferation and apoptosis in response to infection. In addition, the C57BL/6 mouse showed a marked loss of parietal and chief cells, along with a marked expansion of an aberrant gastric mucous cell lineage that stained positive for spasmolytic polypeptide. In contrast, no significant change in these cell types was observed in BALB/c and C3H/HeJ strains. Increased expression of sPLA2 was observed in BALB/c and C3H/HeJ after H. felis infection, whereas sPLA2 expression was absent in C57BL/6 mice.

CONCLUSIONS

H. felis infection leads to increased apoptosis and altered cellular differentiation in the C57BL/6 mouse, a strain that lacks gastric sPLA2 expression. Because sPLA2 has been identified recently as the MOM1 (modifier of MIN) locus that influences polyp formation in the colon, these studies suggest that sPLA2 may also influence the gastric epithelial response to Helicobacter infection.

Caloric restriction as a mechanism mediating resistance to environmental disease

It has been observed that susceptibility to many degenerative diseases increases concurrently with industrialization and rising living standards. Although epidemiologic studies suggest that specific environmental and dietary factors may be important, caloric intake alone (as reflected in body size) may account for much of the differential risk observed among diverse human populations. It has been suggested from animal studies that caloric intake may be the primary effector for many hormonal, metabolic, physiologic, and behavioral responses that coordinate reproductive strategy to apparent availability of food. When caloric intake is excessive, particularly at critical developmental stages, physiologic priorities are set for body growth and fecundity rather than for endurance and longevity. The converse occurs during periods of famine, thus increasing the probability that sufficient individuals survive to restore the population when conditions improve. Calorically restricted rodents have significantly longer reproductive and total life spans than their ad libitum-fed controls and exhibit a spectrum of biochemical and physiologic alterations that characterize their adaptation to reduced intake. These include reduced stature, hypercorticism in the absence of elevated adrenocorticotropic hormone levels, increased metabolic efficiency, decreased mitogenic response coupled with increased rates of apoptosis, reduced inflammatory response, induction of stress proteins and DNA repair enzymes, altered drug-metabolizing enzyme expression, and modified cell-mediated immune function. The overall profile of these changes is one of improved defense against environmental stress. This has been suggested as the mechanistic basis for the protective effects of low body weight on radiation and chemically induced cancers in experimental animals. It may also explain the significantly higher thresholds of acute toxicity observed when calorically restricted rodents are exposed to certain test compounds.

Mechanisms of acute vasodilator response to bacterial lipopolysaccharide in the rat coronary microcirculation

1. In this study the mechanisms of the acute vasodilator action of bacterial lipopolysaccharide (LPS) were investigated in the rat Langendorff perfused heart. 2. Infusion of LPS (5 microg ml(-1)) caused a rapid and sustained fall in coronary perfusion pressure (PP) of 59 +/- 4 mmHg (n = 12) and a biphasic increase in NO levels determined in the coronary effluent by chemiluminescent detection. Both the fall in PP and the increase in NO release were completely abolished (n = 3) by pretreatment of hearts with the NO synthase inhibitor L-NAME (50 microM). 3. LPS-induced vasodilatation was markedly attenuated to 5 +/- 4 mmHg (n 3) by pretreatment of hearts with the B2 kinin receptor antagonist Hoe-140 (100 nM). 4. Vasodilator responses to LPS were also blocked by brief pretreatment with mepacrine (0.5 microM, n = 3) or nordihydroguaiaretic acid (0.1 microM, n = 4) and markedly attenuated by WEB 2086 (3 microM, n = 4). 5. Thirty minutes pretreatment of hearts with dexamethasone (1 nM), but not progesterone (1 microM), significantly modified responses to LPS. The action of dexamethasone was time-dependent, having no effect when applied either simultaneously with or pre-perfused for 5 min before the administration of LPS but inhibiting the response to LPS by 91 +/- 1% (n = 4) when pre-perfused for 15 min. The inhibition caused by dexamethasone was blocked by 15 min pretreatment with the glucocorticoid receptor antagonist RU-486 (100 nM) or by 2 min pre-perfusion of a 1:200 dilution of LCPS1, a selective antilipocortin 1 (LC1) neutralizing antibody. 6. Treatment with the protein synthesis inhibitor, cycloheximide (10 microM, for 15 min) selectively blunted LPS-induced vasodilatation, reducing the latter to 3 +/- 5 mmHg (n = 3), while having no effect on vasodilator responses to either bradykinin or sodium nitroprusside. 7. These results indicate that LPS-induced vasodilatation in the rat heart is dependent on activation of kinin B2 receptors and synthesis of NO. In addition, phospholipase A2 (PLA2) is activated by LPS resulting in the release of platelet-activating factor (PAF) and lipoxygenase but not cyclo-oxygenase products. These effects are dependent on de novo synthesis of an intermediate protein which remains to be identified.

Serum phospholipases A2 in patients undergoing panproctocolectomy because of severe ulcerative colitis

A major role has been proposed for group II phospholipase A2 in the pathogenesis of local and generalised inflammatory reactions. Elevated catalytic activity and mass concentrations of this enzyme have been found in serum and tissue samples of the colon in patients with active ulcerative colitis. The cellular source(s) of group II phospholipase A2 in the blood circulation is (are) unknown. In the current prospective study, we investigated the mass concentration of group II phospholipase A2 and the catalytic activity concentration of phospholipase A2 in serial serum samples of 15 consecutive patients who underwent a standard panproctocolectomy operation for severe ulcerative colitis. Both the catalytic activity concentrations of phospholipase A2 and the mass concentrations of group II phospholipase A2 increased rapidly in serum samples to maximum values on the first postoperative day and then decreased (p = 0.002 and p < 0.001, respectively) in patients who recovered uneventfully. Three patients had postoperative complications that further increased the enzyme concentrations at the time of respective complications. The pattern of group II phospholipase A2 mass concentration profiles was similar to the profiles of C-reactive protein. The results show that the removal of the large bowel does not eliminate the potential to secrete group II phospholipase A2 into the blood circulation in these patients. Secretion of group II phospholipase A2 into the circulation after surgery seems to be a normal host response to a major abdominal operation and postoperative complications. Consequently, we conclude that the large bowel is not an important source of group II phospholipase A2 in sera of patients with ulcerative colitis. The results also support the assumptions that the catalytic activity of phospholipase A2 in serum is attributable to group II phospholipase A2 and that this enzyme is an acute phase protein.

Cyclooxygenase-1 and cyclooxygenase-2 gene expression in human colorectal adenocarcinomas and in azoxymethane induced colonic tumours in rats

Increased prostaglandin E2 synthesis is considered important in both human and experimental colon carcinogenesis. It is not known, however, which cyclooxygenase isoenzyme is involved. The aim of this study was to compare the content of mRNA for cyclooxygenase-1 and cyclooxygenase-2 in colorectal cancers with the content in normal colonic specimens. Fifteen human colorectal adenocarcinomas, 35 azoxymethane induced colonic tumours from rats, and specimens of normal colon were analysed by reverse transcription and polymerase chain reaction (RT-PCR). It was found that cyclooxygenase-1 and cyclooxygenase-2 mRNA were increased in azoxymethane induced colonic tumours, compared with specimens taken adjacent to the tumours or from the macroscopically normal intestine distant from the tumours. Cyclooxygenase-1 and cyclooxygenase-2 mRNA were increased in specimens from the macroscopically normal intestine of azoxymethane treated animals, compared with colonic specimens from saline treated rats. Cyclooxygenase-2 mRNA, but not cyclooxygenase-1 mRNA, was increased in human colorectal cancers, compared with the adjacent mucosa or macroscopically normal mucosa distant from the tumours. The results suggest that cyclooxygenase-2 is involved in the increased prostaglandin E2 synthesis in colonic cancers, and that activation of this isoenzyme is an early event in colon carcinogenesis. However, cyclooxygenase-1 may also be involved, at least in experimental colon carcinogenesis.

Cytosolic phospholipase A2 and cyclooxygenase-2 mediate release and metabolism of arachidonic acid in tumor necrosis factor-alpha-primed cultured intestinal epithelial cells (INT 407)

BACKGROUND

We have recently reported that tumor necrosis factor-alpha (TNF-alpha), a pro-inflammatory cytokine that has been suggested to play a role in the pathogenesis of inflammatory bowel disease, potentiates phospholipase A2 (PLA2)-stimulated arachidonic acid (AA) release and prostaglandin E2 (PGE2) formation in cultured intestinal epithelial cells (INT 407). The aim of the present study was to investigate which particular isoforms of PLA2 and cyclooxygenase (COX) are involved in these processes.

METHODS

Cells were labeled with 14C-AA or 14C-oleic acid, and the amounts of released fatty acid and PGE2 were analyzed by thin-layer chromatography. mRNA was analyzed by reverse transcription and polymerase chain reaction.

RESULTS

The cells contained mainly mRNA for cytosolic PLA2 (cPLA2) and only trace amounts of mRNA for group I and II PLA2. TNF-alpha potentiated the release of 14C-AA but not of 14C-oleic acid. The TNF-alpha-potentiated PGE2 release was reduced after inhibition of cellular COX activity or mRNA synthesis. TNF-alpha increased the amounts of mRNA for COX-2 but not for COX-1.

CONCLUSIONS

The results point to the possibility that TNF-alpha may modulate the intestinal mucosal content of biologically active AA metabolites by priming cPLA2- and COX-2-mediated processes in the epithelial cells.

Phospholipase A2 gene expression and activity in histologically normal ileal mucosa and in Crohn's ileitis

Increased activity of phospholipase A2 (PLA2) in the ileal mucosa may contribute to the inflammation in Crohn's disease. The results of this study showed that (a) three months after ileocolonic resection for Crohn's disease the neoterminal ileal mucosa showed endoscopically new inflammation and had higher PLA2 activity than at the time of the operation (n = 8); no such findings were seen in controls (n = 7), (b) histologically normal ileal mucosa (n = 3) contained mRNA for three isoforms of PLA2 (PLA2-I, PLA2-II, and cPLA2), but the amounts of PLA2-II mRNA clearly exceeded the amounts of mRNA for PLA2-I and cPLA2, (c) ileal mucosa from Crohn's patients (n = 2) contained higher values of PLA2-II mRNA than ileal mucosa from two controls, (d) ileal mucosa from Crohn's patients (n = 4) showed increased PLA2-II mRNA three months after ileocolonic resection. In conclusion, these results show that the predominating PLA2 mRNA in the human ileal mucosa is type II PLA2, and the increased synthesis of PLA2-II might be responsible for the increased PLA2 activity found in the ileal mucosa accompanying recurrent ileal inflammation in Crohn's disease.