Mucosal Cell Injury Research Articles

Mucositis associated with stem cell transplantation: current status and innovative approaches to management

Treatment-related morbidity, and in some cases, mortality, associated with autologous and allogeneic bone marrow transplantation has decreased in the past decade largely due to the use of blood stem cells combined with hematopoietic growth factors. However, these procedures remain morbid, with several series documenting regimen-related injury to the oral mucous membranes, the worst form of toxicity from a patient perspective. The pathophysiology of transplant-related mucositis is related to two major events: direct mucosal basal cell injury leading to atrophy and ulcerations, and local infections that can become systemic, the latter of which are exacerbated by the severe neutropenia accompanying high-dose chemotherapy. Recent investigational agents designed to interfere with these two aspects of mucositis have been developed and are showing promise in early clinical trials. In particular, keratinocyte growth factor (KGF) and interleukin-11 appear active. They increase basal cell proliferation, prevent apoptosis due to the preparative regimen, and appear to ameliorate the mucositis seen with high-dose chemotherapy regimens. Oral, nonabsorbable anti-infective agents are also being tested in an attempt to prevent both local and systemic infections. Devoid of significant side-effects, KGF is now in large phase 2 trials that, if positive, will be a significant advance in promoting less morbid transplants by reducing pain and the risk of secondary infections and thus may reduce supportive care costs.

Helicobacter pylori induces apoptosis in gastric epithelial cells through inducible nitric oxide.

Gastric mucosal injury by Helicobacter pylori has been suggested to be mediated by various cytokines induced by this organism. Nitric oxide (NO) is an important effector molecule involved in immune regulation and defence. To clarify the mechanisms by which H. pylori induces gastric mucosal cell injury, we examined whether H. pylori induces gastric epithelial death via NO production. Cytotoxic and non-cytotoxic strains of H. pylori were used. The death of MKN45 cells caused by H. pylori was examined by the 3-(4,5-dimethyl-thiazole-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. Aminoguanidine was used to inhibit inducible nitric oxide synthase (iNOS) activity. Expression of iNOS mRNA was determined by the reverse transcriptase-polymerase chain reaction and the DNA fragmentation analysis was performed by using agarose gel electrophoresis. The MTT assay revealed that neither viable H. pylori nor other components of the microorganism induced cell death. Both preincubation of MKN45 cells with interferon-gamma for 6 h and coculture with TNF-alpha significantly increased the cytotoxicity of H. pylori. Both cytotoxic and non-cytotoxic strains of H. pylori induced cell death. Expression of iNOS mRNA was observed in MKN45 cells at 6, 8 and 12 h after H. pylori inoculation. The cytotoxicity of H. pylori was inhibited by aminoguanidine and DNA fragmentation analysis showed that H. pylori induced apoptosis. These findings suggested that viable H. pylori induces apoptosis of gastric epithelial cells via nitric oxide. Our study indicated that iNOS expression plays an important role in gastric cell injury.

Helicobacter pylori-induced gastric mucosal cell injury is mediated by inducible nitric oxide syntase

Helicobacter pylori-induced gastric mucosal cell injury is mediated by inducible nitric oxide syntase

Free radical-scavenging activity of Crassostera gigas extract (JCOE)

In the present study, we evaluate the free radical-scavenging activity of JCOE (Japan clinic oyster extract), a powder extracted from Crassostera gigas by a spin-trapping method using electron paramagnetic resonance (EPR), and also estimate the protective effect against gastric mucosal cell injury induced by hydrogen peroxide. The EPR study demonstrated that JCOE directly scavenged superoxide radical as well as hydroxyl radical in a concentration-dependent manner. After exposure to hydrogen peroxide for 4 h in Hank's balanced buffered solution, cell viability of rat gastric mucosal cells (RGM-1) was measured by modified MTT assay. Hydrogen peroxide-induced injury was not reversed by 1-h preincubation with 100 to 1,000 micrograms/mL JCOE solution which has high reactivity to hydroxyl radicals, indicating that the active ingredients, including taurine of JCOE on scavenging action of hydroxyl radical, did not penetrate cell membranes easily. Twenty-four hour pretreatment with the JCOE solution significantly reversed the decrease in cell viability induced by hydrogen peroxide, indicating the possibility that JCOE solution may stimulate the endogenous eliminating system against hydrogen peroxide.

Serotonin (5-HT): An enteroendocrine marker of rejection after small bowel allotransplantation in the pig

The histopathologic findings of mucosal epithelial cell injury in acute and chronic rejection in small bowel transplantation are well known. Several studies have been done on the pig either as autotransplantation, allotrans-plantation, orthotopic, or enterotopic transplantation, with or without immunosuppression. Very few investigations on the enteroendocrine system have been done. In particular, none have been done on rejection in pigs after intestinal transplantation. On the other hand, changes in the enteroendocrine markers (somatostatin and chromogranin A) have been examined in detail after auxiliary small bowel transplantation in dogs without immunosuppression, showing no apparent changes on the 7th postoperative day, even if in a severe rejection status. Recent studies on rats have evaluated the presence of serotonin after small bowel allotransplantation with different times of preservation, and after reperfusion. The authors concluded that the number of serotonin-positive cells decreased with a preservation time of more than 1 hour in Ringer lactate at 4°C. We too have examined the modifications of argentaffin as well as serotonin-positive cells in the harvested small bowel of pigs perfused with Belzer solution (4°C) and preserved in Ringer lactate at 4°C, after preservation and reperfusion in the combined liver-small bowel allotransplantation. We noticed that the argentaffin and serotonin cells were preserved up to 20 hours and that after reperfusion the most important injury was due to the disappearance of these cells from the crypts. In this study, we studied the modifications of the intestinal enterochromaffin cells after combined liver-small bowel and small bowel alone allotransplantation in pigs, with the aim of evaluating a correlation with rejection.

Studies on gastric mucosal cell injury induced by Helicobacter pylori.

The cause of gastric cell injury induced by Helicobacter pylori was investigated in vitro using gastric mucosal cells derived from male Japanese white rabbits. To evaluate the contribution of the potent urease activity of H. pylori to gastric mucosal cell injury, the supernatant of the H. pylori bacterial pellet, solubilized with N-octyl-glucoside, was added to the gastric mucosal cell suspension. Cell injury was assessed by lactate dehydrogenase (LDH) release into the extracellular fluid. Treatment of cells with H. pylori extracts together with urea resulted in high levels of LDH release, suggesting definite gastric mucosal cell injury, and elevation of ammonia concentration was also observed. In contrast, incubation with H. pylori extracts alone or urea solution alone did not result in increased LDH release or elevated ammonia concentrations. The degree of LDH release from gastric mucosal cells due to H. pylori extracts in the presence of urea was similar to that induced by administration of the same amount of exogenous ammonia. The addition of acetohydroxamic acid, a potent specific urease inhibitor, remarkably inhibited ammonia production, the elevation of pH of extracellular fluid, and LDH release in a dose-dependent manner. These results suggest that ammonia produced by potent urease activity of H. pylori in the presence of urea plays an important role in the pathogenesis of gastric mucosal cell injury.

Dry air-induced mucosal cell injury and bronchovascular leakage in canine peripheral airways.

The purpose of this study was to examine the relationship between hyperpnea-induced mucosal injury, bronchovascular hyperpermeability, and airway reactivity. Hyperpnea-induced bronchoconstriction was assessed by measuring peripheral airway resistance (Rp) in anesthetized mechanically ventilated male mongrel dogs. Either colloidal carbon or monastral blue was used to localize bronchovascular leakage after a 5-min exposure to either a 1000 ml/min dry, 2000 ml/min wet, or 2000 ml/min dry air challenge. Morphometric analyses of cross-sectioned bronchi revealed that hyperpnea with dry air stimulated goblet cell degranulation, damaged the bronchial mucosa, and increased bronchovascular permeability. Exposure to only a 2000 ml/min dry air challenge produced marked mucosal injury when compared with control. Regardless of treatment, bronchial vessels lying below normal mucosa characterized by goblet/ciliated cell (G/C) ratios > or = 0.3 did not leak. A G/C transition zone between 0 and 0.3 separated normal from damaged mucosa. Within this zone, vascular permeability was inversely correlated with G/C ratio. In addition, airflow-induced changes in Rp were inversely related to G/C ratio and positively correlated with bronchovascular leakage. Although these correlations are consistent with the speculation that bronchovascular leakage and edema formation are responsible for the dry air-induced changes in Rp, it is equally plausible that bronchovascular leakage is not the cause of but occurs in concert with airway narrowing to protect cells in the bronchial mucosa from excessive losses of heat and water.

Rebamipide, a novel antiulcer agent, attenuates Helicobacter pylori induced gastric mucosal cell injury associated with neutrophil derived oxidants.

The effect of rebamipide, a novel antiulcer compound, on Helicobacter pylori activated neutrophil dependent in vitro gastric epithelial cell injury was investigated. Luminol dependent chemiluminescence (ChL), which detects toxic oxidants from neutrophils exhibited a 12-fold increase when the bacterial suspension of H pylori was added to the isolated human neutrophils. This change was significantly attenuated by rebamipide at a concentration less than 1 mM, showing that rebamipide may inhibit oxidant production from H pylori elicited neutrophils. To assess whether rebamipide attenuates gastric mucosal injury, we tested its inhibitory action on H pylori induced gastric mucosal damage associated with neutrophils in vitro. Rabbit gastric mucosal cells were monolayered in culture wells and coincubated with human neutrophils and H pylori, and the cytotoxicity index was then calculated. Cultured gastric cells were significantly damaged when they were incubated with human neutrophils activated by H pylori. This cellular damage was attenuated by rebamipide in a dose-dependent manner. Furthermore, spectrophotometrical measurement showed that rebamipide (1 mM) inhibits urease activity by 21.7%. As monochloramine (an oxidant yielded by reaction of neutrophil derived chlorinated oxidant and ammonia) is proposed as an important toxic molecule in this model, the current findings suggest that the preventive effect of rebamipide on H pylori elicited neutrophil induced gastric mucosal injury may result from its inhibitory actions on the neutrophilic oxidative burst as well as H pylori derived urease activity.

Glutamine Preserves Gut Glutathione Levels during Intestinal Ischemia/Reperfusion

Intestinal ischemia/reperfusion (I/R) causes formation of reactive oxygen intermediates (ROI) which lead to mucosal cell injury. Glutathione (GSH), an ROI scavenger, protects tissues from ROI-mediated cell injury. Since GSH biosynthesis is partially dependent on glutamine (Gln) levels, we tested the hypothesis that intravenous Gln infusion will assist in maintaining mucosal cell GSH levels and decrease membrane lipid peroxidation during intestinal I/R. The external jugular vein of male Sprague-Dawley rats was cannulated and infused with normal saline (NS) at 2 cc/hr. After 3 days, matched pairs of rats received either NS alone or NS + 3% Gln for an additional 24 hr. Next, mucosal GSH levels were measured after a sham I/R in 6 rats and after either 30 or 60 min of ischemia/60 min of reperfusion in a group of 8 and 12 rats, respectively. Finally, conjugated diene (CD), a byproduct of membrane lipid peroxidation, was measured following 60 min of ischemia/60 min of reperfusion in a separate group of 12 rats. Control rats had the highest GSH levels and there was no difference between NS vs NS + 3% Gln rats (2.50 ± 0.48 vs 2.50 ± 0.43, P = NS). With 30 and 60 min of ischemia/60 min of reperfusion, GSH levels were significantly lower in NS-infused rats compared to those in NS + 3% Gln-infused rats (30 min: 1.54 ± 0.14 vs 1.80 ± 0.16, P < 0.05; 60 min: 1.27 ± 0.15 vs 1.52 ± 0.20, P < 0.04). In addition, CD levels were lower in NS + 3% Gln-infused rats compared to those in NS alone-infused rats (5.58 ± 0.87 vs 7.94 ± 0.55, P < 0.04). In conclusion, Gln supplementation partially maintains gut GSH levels during bowel I/R, which in turn lessens I/R-induced cell membrane lipid peroxidation.

Effect of Local Acid-Base Status on Gastric Mucosal Blood Flow and Surface Cell Injury by Bile Acid

Topical application of 5 m M sodium taurocholate (5 TC, pH 1.2) to canine gastric mucosa results in luminal hydrogen ion (H +) loss and surface epithelial cell (SEC) injury. However, gross mucosal injury does not occur because of a protective increase in gastric mucosal blood flow (GMBF). The mechanism of this blood flow response is unknown. To test the hypothesis that mucosal acid-base status influences mucosal blood flow and surface cell injury, three groups of dogs with vascularized chambered gastric mucosae were studied during two sequential 30-min periods. Mucosae were exposed during period 1 to topical acidified isotonic saline (ATS, pH 1.2), and during period II to topical 5 TC. During both periods, group A ( n = 5) received close intraarterial (ia) NaCl (0,15 M), group B ( n = 5) close ia HCO 3 (0.32 M), and group C ( n = 4) close ia HCl (0.2 N ). Parameters evaluated during both ATS and 5 TC periods included the luminal accumulation of DNA (DNAE, a sensitive marker of SEC exfoliation), luminal H + loss, and GMBF measured using radiolabeled microspheres. Gastric venous pH was also measured. It was found that, compared to the NaCl group, the HCO 3 group had no increase in GMBF after 5 TC exposure. Simultaneously, however, SEC loss was reduced by 48%, 604 ± 72 with NaCl versus 314 ± 59 μg/30 min DNA with HCO 3, P < 0.025. Infusion of ia HCl generated a large increase in GMBF without an increase in SEC injury compared to ia NaCl. Thus, mucosal acid-base status is an important modulator of mucosal blood flow which is itself critically important to gastric mucosal protection during bile acid induced injury.

The mechanisms of aspirin-induced gastric mucosal injury.

We examined changes in intracellular pH with the fluorescent probe BCECF after treatment with aspirin (ASA) in gastric mucosal cells isolated from guinea pigs at various extracellular, pH levels. The cytotoxic activities of ASA and the intracellular trapping of ASA at various extracellular pH levels were also examined by colorimetric MTT assay and counting the influx of [14C](carboxyl-14C)-ASA. Under acid extracellular pH, ASA reduced intracellular pH in gastric mucosal cells and exhibited cytotoxicity. Intracellular trapping of ASA was also observed only under acidic extracellular conditions. The present study suggests that ASA causes gastric mucosal cell injury in vitro by reducing intracellular pH, resulting from intracellular trapping of ASA under acidic extracellular conditions.

Helicobacter pylori-associated ammonia production enhances neutrophil-dependent gastric mucosal cell injury.

The role of neutrophil and its chlorinated oxidant were investigated in Helicobacter pylori-induced gastric mucosal injury in vitro. Luminol-dependent chemiluminescence (ChL) was used to detect neutrophil-derived oxidants. ChL activity was significantly elevated when neutrophils were incubated in H. pylori, indicating that H. pylori actually elicits oxidative burst of neutrophils. To assess whether H. pylori-activated neutrophils exert the cytotoxicity for gastric mucosal cells, rabbit gastric mucosal cell was monolayered in culture wells and labeled with a fluorescence dye, 2',7'-bis(2-carboxyethyl)-5(6)carboxy-fluorescein, which is retained in the intracellular space as long as the cell membrane is intact. Labeled cells were coincubated with neutrophils and H. pylori. We inferred from the cytotoxicity index (specific %cytotoxicity), which was calculated from fluorometrical measurements of supernatant and lysate, that the mucosal cells were significantly damaged by H. pylori-activated neutrophils. This injury was largely attenuated by eliminating urea from the incubation mixture or by acetohydroxamic acid, a potent urease inhibitor. Additionally, the scavengers of neutrophil-derived oxidants, including taurine, methionine, and catalase, also attenuated this injury. Cultured mucosal cells that were exposed to the solution containing monochloramine (an oxidant yielded by reaction of hypochlorous acid and ammonia) were highly damaged compared with cells exposed to hypochlorous acid or hydrogen peroxide at physiological concentrations. These data suggest that H. pylori-activated neutrophils promote gastric mucosal cell injury and that monochloramine plays a unique and important role in this process.

Effects of neutrophil-derived oxidants on intestinal permeability, electrolyte transport, and epithelial cell viability

There are several pathophysiologic conditions in which intestinal inflammation is associated with enhanced mucosal permeability, fluid loss, and epithelial cell injury. The objective of this study was to determine the effects of polymorphonuclear leukocyte (PMN)-derived oxidants on ileal mucosal permeability in vivo as well as electrolyte transport and epithelial cell viability in vitro. Using blood-to-lumen clearance of [51Cr]EDTA as a measure of mucosal permeability, we found that luminal perfusion with hydrogen peroxide (H2O2), hypochlorous acid (HOCl), or monochloramine (NH2Cl) produced a dose-dependent increase in mucosal permeability. Perfusion with 0.1 mM, 0.5 mM, and 1.0 mM oxidant produced a 2 +/- 1, 5 +/- 2, and 11 +/- 5-fold increase in mucosal permeability for H2O2, a 2 +/- 1, 8 +/- 3, and 36 +/- 12-fold increase for HOCl, and a 3 +/- 1, 11 +/- 2, and 30 +/- 7-fold increase for NH2Cl. Taurine monochloramine (TauNHCl) was ineffective in enhancing the blood-to-lumen clearance of [51Cr]EDTA. Furthermore, 0.01 mM and 0.1 mM NH2Cl and H2O2 produced significant increases in short-circuit current across rat ileum in vitro, whereas HOCl and TauNHCl were without effect. Tissue resistance and potential difference were not altered, suggesting that NH2Cl, HOCl, and H2O2 were not cytotoxic under these conditions. Cultured intestinal epithelial cells exposed to NH2Cl and HOCl were injured in a dose-dependent manner in vitro, whereas H2O2 and Tau NHCl were nontoxic. Taken together, our data suggest that PMN-derived oxidants may mediate the enhanced mucosal permeability, electrolyte transport, and epithelial cell injury associated with acute inflammation of the bowel.

Vascular injury in acute gastric mucosal damage. Mediatory role of leukotrienes.

Recent investigations indicate that microvascular injury, leading to increased vascular permeability and capillary stasis, precede the development of chemically induced hemorrhagic mucosal lesions in the stomach. The vascular damage is more amenable to protection by prostaglandins and sulfhydryls than the diffuse surface mucosal cell injury. The vascular and mucosal lesions may be the result of direct toxicity of damaging agents (eg, ethanol, HCl, NaOH) and the release of vasoactive amines and leukotrienes. We review here our recent studies performed in rats indicating that intraarterial infusion of LTC4 or LTD4 in the stomach caused vascular injury as revealed by monastral blue. Infusion of leukotrienes alone caused no hemorrhagic mucosal lesions but aggravated the damage caused by 25, 50, or 100% ethanol and 0.2 N HCl given intragastrically. The ethanol-induced mucosal lesions were slightly diminished by the lipoxygenase inhibitor L-651,392 and markedly decreased by eicosapentaenoic acid, which competes with arachiconic acid as a substrate for 5-lipoxygenase. These results are discussed and correlated with biochemical results from other laboratories demonstrating increased levels of leukotrienes in the gastric mucosa after administration of ethanol and decreased release following pretreatment with prostaglandins or sulfhydryl-related agents. New data thus support a mediatory role for leukotrienes in the pathogenesis of vascular injury and mucosal lesions in the stomach.

Basic mechanisms of gastrointestinal mucosal cell injury and protection

Basic mechanisms of gastrointestinal mucosal cell injury and protection

Basic mechanisms of gastrointestinal mucosal cell injury and protection

Basic mechanisms of gastrointestinal mucosal cell injury and protection

Basic Mechanisms of Gastrointestinal Mucosal Cell Injury and Protection

Basic Mechanisms of Gastrointestinal Mucosal Cell Injury and Protection

Basic Mechanisms of Gastrointestinal Mucosal Cell Injury and Protection

Basic Mechanisms of Gastrointestinal Mucosal Cell Injury and Protection

Dinitrochlorobenzene-induced colitis in the guinea-pig: studies of colonic lamina propria lymphocytes.

Dinitrochlorobenzene-induced colitis in guinea-pigs may be immunologically mediated: animals must be presensitised to dinitrochlorobenzene to develop colitis, sensitivity can be passively transferred by lymphocytes and the injury can be mitigated by immunosuppression. In this study, we examined lamina propria lymphocytes isolated from colons of animals with dinitrochlorobenzene-induced colitis, and appropriate controls. Lamina propria lymphocytes from colitis animals have a greater percentage of rabbit erythrocyte-rosetting cells (T cells) (20.1 +/- 3.0 vs 2.3 +/- 0.8, p less than .01) and a greater capacity to mediate mitogen-induced cellular cytotoxicity with phytohaemagglutinin than lamina propria lymphocytes from normal colon (% specific cytoxicity = 29.4 +/- 8.7 vs 5.0 +/- 4.5, P less than .005). There was no difference in the percentage of rosetting cells or cytotoxicity index of spleen or mesenteric lymph node lymphocytes between the colitis animals and controls. These data suggest that there are changes in the distribution and functional characteristics of lamina propria lymphocytes which correlate with mucosal cell injury in the dinitrochlorobenzene-colitis model.