Expression of adhesion molecules and leukocyte recruitment into gastric mucosa following ischemia-reperfusion

Administration of angiotensin II in the paraventricular nucleus protects gastric mucosa from ischemia-reperfusion injury

Our previous study demonstrated that electrical stimulation of the hypothalamic paraventricular nucleus (PVN) protects against gastric ischemia-reperfusion (GI-R) injury, but it is still unknown whether angiotensin II (Ang II) in the PVN plays a role in the development of GI-R. The purpose of this study was to investigate the effect of Ang II in the PVN on GI-R injury. GI-R injury was induced in rats by clamping the celiac artery for 30 min, and then reperfusing for 30 min, 1 h, 3 h, 6 h or 24 h, respectively. A cannula was inserted into the unilateral PVN for microinjection of Ang II. The extent of gastric mucosal damage was determined by gross and histological methods. We found that microinjection of pharmacological doses of Ang II (3, 30, and 300 ng) into the PVN dose-dependently inhibited GI-R injury, and that Ang II (30 ng) markedly attenuated GI-R injury at 1 h and 3 h after reperfusion. The effect of Ang II was prevented by pretreatment with the Ang II AT1 receptor antagonist losartan (5 microg) into the lateral cerebral ventricle. Furthermore, the protective effect of Ang II on GI-R injury was abolished by propranolol (1 mg/kg, i.v.) or disconnection of the nerves innervating the adrenal glands, was augmented by sympathectomy or phentolamine (1 mg/kg, i.v.), and was not affected by subdiaphragmatic vagotomy or atropine (1 mg/kg, i.v.). These results indicate that the PVN is a responsive site for central Ang II-induced protection against GI-R injury. The central effects of Ang II are mediated by AT1 receptors in the PVN, and the peripheral effects by a sympathetic-adrenal gland/beta-adrenoceptor pathway.

Extracellular signal-regulated kinase pathways may mediate the protective effect of electrical stimulation of the paraventricular nucleus against ischaemia-reperfusion injury of the gastric mucosa

1. The aim of the present study was to elucidate the role of the extracellular signal-regulated kinase (ERK) pathway in mediating the effects of electrical stimulation of the paraventricular nucleus (PVN) on apoptosis and proliferation induced by gastric ischaemia-reperfusion injury (GI/RI). 2. To investigate the effects of electrical stimulation of the hypothalamic PVN on gastric mucosal apoptosis and proliferation in response to ischaemia-reperfusion (I/R), we used a GI/RI model by clamping the coeliac artery for 30 min and then reperfusing the artery for 30 min or 1, 3 or 6 h. We used immunohistochemistry and western blotting to investigate the expression, activation and distribution of ERKs and the dynamic changes in their downstream cellular factors Bcl-2 and Bax at different times subsequent to electrical stimulation of the PVN in the I/R-injured gastric mucosa. 3. Electrical stimulation of the PVN markedly attenuated GI/RI at 30 min and 1 and 3 h after reperfusion. Electrical stimulation decreased gastric mucosal apoptosis, increased gastric mucosal proliferation and promoted the expression and activation of phosphorylated (p)-ERK1/2 30 min after reperfusion. Electrical stimulation increased the expression of Bcl-2 and decreased the expression of Bax at 30 min and 1 and 3 h after reperfusion. In contrast, inhibition of ERK1/2 activity by the specific upstream mitogen-activated protein kinase kinase inhibitor PD98059 produced similar effects at 1 h after reperfusion in rats subjected to I/R with or without electrical stimulation of the PVN. Administration of PD98059 aggravated gastric mucosal injury, increased apoptosis, decreased proliferation in gastric mucosal cells, decreased the expression and activity of p-ERK1/2 and Bcl-2 expression and increased Bax expression. 4. These results indicate that the PVN protects against GI/RI and that this protection is associated with the inhibition of cellular apoptosis and the promotion of proliferation in the gastric mucosa, probably by activating the ERK pathway.

Leucocyte-endothelial interactions in health and disease

The emigration of leucocytes into the tissue as a crucial step in the response to inflammatory signals has been acknowledged for more than 100 years. The endothelium does not only represent a mechanical barrier between blood and tissue, the circulatory system also connects different organ systems with each other, thus allowing the communication between remote systems. Leukocytes can function as messengers and messages at the same time. Failure or dysregulation of leucocyte-endothelial communication can severely affect the integrity of the organism. The interaction between leucocytes and the vascular endothelium has been recognised as an attractive target for the therapy of numerous disorders and diseases, including excessive inflammatory responses and autoimmune diseases, both associated with enormous consequences for patients and the health care system. There is promising evidence that the success rate of such treatments will increase as the understanding of the molecular mechanisms keeps improving. This chapter reviews the current knowledge about leucocyte-endothelial interaction. It will also display examples of both physiological and dysregulated leucocyte-endothelial interactions and identify potential therapeutical approaches.

Effects of hypothalamic paraventricular nuclei on apoptosis and proliferation of gastric mucosal cells induced by ischemia/reperfusion in rats

AIM: To investigate the effects of electrical stimulation of hypothalamic paraventricular nuclei (PVN) on gastric mucosal cellular apoptosis and proliferation induced by gastric ischemia/reperfusion (I/R) injury.

METHODS: For different experimental purposes, stimulating electrode plantation or electrolytic destruction of the PVN was applied, then the animals’ GI/R injury model was established by clamping the celiac artery for 30 min and allowing reperfusing the artery for 30 min, 1 h, 3 h or 6 h respectively. Then histological, immunohistochemistry methods were used to assess the gastric mucosal damage index, the gastric mucosal cellular apoptosis and proliferation at different times.

RESULTS: The electrical stimulation of PVN significantly attenuated the GI/R injury at 30 min, 1 h and 3 h after reperfusion. The electrical stimulation of PVN decreased gastric mucosal apoptosis and increased gastric mucosal proliferation. The electrolytic destruction of the PVN could eliminate the protective effects of electrical stimulation of PVN on GI/R injury. These results indicated that the PVN participated in the regulation of GI/R injury as a specific area in the brain, exerting protective effects against the GI/R injury, and the protection was associated with the inhibition of cellular apoptosis and the promotion of gastric mucosal proliferation.

CONCLUSION: Stimulating PVN significantly inhibits the gastric mucosal cellular apoptosis and promots gastric mucosal cellular proliferation. This may explain the protective mechanisms of electrical stimulation of PVN against GI/R injury.

Fundamental and distinct roles of P-selectin and LFA-1 in ischemia/reperfusion-induced leukocyte-endothelium interactions in the mouse colon

OBJECTIVE

To study the adhesive mechanisms underlying ischemia/reperfusion (I/R)-induced leukocyte-endothelium interactions in the colon.

SUMMARY BACKGROUND DATA

Leukocyte recruitment is a key feature in I/R-induced tissue injury, but the mechanisms regulating leukocyte rolling and adhesion in the colon are not known. The authors recently developed a new model to study the molecular mechanisms of I/R-provoked leukocyte-endothelium interactions in the colon microcirculation using inverted intravital fluorescence microscopy.

METHODS

The superior mesenteric artery was occluded for 30 minutes and leukocyte responses were analyzed after 120 minutes of reperfusion in colonic venules in mice. The adhesive mechanisms underlying I/R-induced leukocyte rolling and adhesion were investigated using monoclonal antibodies against L-, E- and P-selectin, and CD11a gene-targeted mice were used to examine the role of lymphocyte function antigen-1 (LFA-1, CD11a/CD18).

RESULTS

Reperfusion provoked a clear-cut increase in leukocyte rolling and adhesion in colonic venules compared to negative controls. Both P- and E-selectin mRNA were expressed in the colon after this I/R insult. Pretreatment with an anti-P-selectin antibody reduced leukocyte rolling and adhesion by 88% and 85%, respectively, whereas antibodies against L- and E-selectin had no effect. Moreover, I/R-induced leukocyte adhesion in LFA-1-deficient mice was reduced by more than 95%.

CONCLUSIONS

This study provides evidence that leukocyte rolling is exclusively and nonredundantly mediated by P-selectin and that firm adhesion is supported by LFA-1 in I/R-induced leukocyte recruitment in the colon. Taken together, both P-selectin and LFA-1 may be important targets to control pathologic inflammation in I/R-induced tissue injury in the colon.

Neuroregulative mechanism of hypothalamic paraventricular nucleus on gastric ischemia-reperfusion injury in rats

A rat model of gastric ischemia-reperfusion injury (GI-RI) was established by clamping the celiac artery for 30 min and allowing reperfusion for 1 h, on which the regulatory effect of the paraventricular nucleus (PVN) and its neural mechanisms were investigated. The results were: 1. Electrical stimulation of the PVN obviously attenuated the GI-RI. Microinjection of L-glutamic acid into PVN produced an effect similar to that of PVN stimulation. 2. Electrolytic ablation of the PVN aggravated the GI-RI. 3. Nucleus tractus solitarius (NTS) ablation could eliminate the protective effect of electrical stimulation of PVN on GI-RI. 4. Hypophysectomy did not alter the effect of electrical stimulation of PVN. 5. Vagotomy or sympathectomy both could increase the effect of PVN stimulation on GI-RI. These results indicate that the PVN participates in the development of GI-RI as a specific area in the CNS, exerting protective effects on the GI-RI. The NTS and vagus and sympathetic nerve may be involved in the regulative mechanism of PVN on GI-RI, but the PVN mechanism here is independent of the PVN-hypophyseal pathway.

Liver dysfunction elicited by gut ischemia-reperfusion

Gut ischemia and reperfusion (I/R) has been implicated as a prime mechanism in the pathogenesis of multiple organ failure and in initiating remote organ failure. Although it has long been known that gut I/R elicits liver dysfunction, only recently has the kinetics of leukocyte accumulation in the hepatic microcirculation and mechanisms of the liver injury after gut I/R been investigated. These studies reveal that the magnitude of gut I/R-induced liver injury depends on the duration of ischemic period and animal species. Gut I/R-induced accumulation of leukocytes, both neutrophils and lymphocytes, in the liver results in an oxidative stress in proximity to non-perfused sinusoid that contributes to subsequent hepatocellular injury. The gut I/R-induced leukosequestration in the liver is mediated by adhesion molecules that are induced by different cytokines, endotoxin, and oxidants. Kupffer cells also play an important role in the gut I/R-induced leukosequestration and liver injury. Nitric oxide and anti-oxidants such as superoxide dismutase protect the liver against the deleterious effects of gut I/R. Furthermore, agents such as ethanol can alter the hepatic responses to gut I/R. The results of these studies provide novel information and potential therapeutic strategies for reducing the liver dysfunction and multiple organ failure induced by gut I/R.

Leukocyte adherence contributes to disruption of the blood-brain barrier during activation of mast cells

The goal of this study was to examine the role of leukocytes in disruption of the blood-brain barrier during activation of mast cells using compound 48/80. We examined the pial microcirculation in rats using intravital fluorescence microscopy. Permeability of the blood-brain barrier (clearance of fluorescent-labeled dextran; molecular weight 10000 daltons; FITC-dextran-10 K) was determined while suffusing with vehicle or compound 48/80 (10 or 25 microg/ml). During superfusion with vehicle (saline), clearance of FITC-dextran-10 K from pial vessels was modest and remained relatively constant during the experimental period (0.52+/-0.05 ml/sx10(-6) at 80 min). In addition, diameter of pial arterioles remained constant (32+/-5 microm) while suffusing with vehicle. In contrast, topical application of compound 48/80 produced marked disruption of the blood-brain barrier to FITC-dextran-10 K. For example, suffusion with compound 48/80 (25 microg/ml) increased clearance of FITC-dextran-10 K about 4-fold to 2.26+/-0.25 ml/sx10(-6) at 80 min. In addition, superfusion with compound 48/80 (25 microg/ml) constricted pial arterioles by 26+/-9% at 80 min. To determine a potential role for leukocyte adhesion to endothelium in disruption of the blood-brain barrier during suffusion with compound 48/80, we examined permeability during suffusion with compound 48/80 (25 microg/ml) in the presence of WT.3 (2 mg/kg i.v.), a monoclonal antibody directed against the functional epitope of the leukocyte adhesive glycoprotein (CD18; LFA-1beta). We found that infusion of WT.3 markedly attenuated disruption of the blood-brain barrier to FITC-dextran-10 K in response to compound 48/80. The clearance of FITC-dextran-10 K during superfusion with compound 48/80 in the presence of WT.3 was 1.29+/-0.14 ml/sx10(-6) at 80 min (P<0.05). Thus, the findings of the present study suggest that application of compound 48/80, to degranulate mast cells, activates the adhesion of leukocytes to cerebral venular endothelium which contributes to disruption of the blood-brain barrier.

Activation of genes for superoxide dismutase, interleukin-1beta, tumor necrosis factor-alpha, and intercellular adhesion molecule-1 during healing of ischemia-reperfusion-induced gastric injury

BACKGROUND

Ischemia followed by reperfusion (I/R) induces gastric lesions, probably due to excessive formation of free radicals, but the role of the scavenger of these radicals, proinflammatory cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), in the healing of these lesions has not been extensively studied. It is also unknown whether expression of intercellular adhesion molecule-1 (ICAM-1), which mediates neutrophil-induced injury and neutrophil infiltration, is involved in the recovery from I/R lesions.

METHODS

I/R lesions were induced in Wistar rats by applying a small clamp to the celiac artery for 30 min (ischemia phase), followed by the removal of the clamp for 60 min (reperfusion phase). The influence of I/R on gastric secretion was also tested in rats equipped with a gastric fistula (GF) without or with the exposure to a standard period of I/R. Two series of rats (A and B) were used to determine the effects of exogenous and endogenous superoxide dismutase SOD (series A) and allopurinol, a xanthine oxidase inhibitor (series B), on the mucosal recovery from the gastric lesions induced by I/R. The animals were killed immediately after the exposure to I/R (0 h) and at 3 h, 24 h, or 3, 5, or 10 days after this I/R, the area of gastric lesions being measured by planimetry, and the gastric blood flow (GBF) determined by the H2 gas clearance method. Blood was withdrawn for measurement of plasma IL-1beta and TNF-alpha levels with enzyme-linked immunosorbent assay, and plasma gastrin with radioimmunoassay. Biopsy samples of oxyntic mucosa were taken for the assessment of SOD, IL-1beta, TNF-alpha, and ICAM-1 mRNAs by reverse-transcription polymerase chain reaction and Southern blot.

RESULTS

Exposure to I/R resulted in acute gastric erosions, with the maximal increase of the area of these lesions observed 3 h after the end of I/R. This effect was accompanied by a decrease in the GBF, a significant increase in blood free radicals and plasma gastrin increments, and almost complete suppression of gastric secretion. Starting 24 h after I/R, the gastric superficial lesions progressed into deeper ulcers that healed progressively within 10 days, and this was accompanied by gradual restoration of the gastric secretion and the GBF. Treatment with SOD and allopurinol accelerated significantly the healing of I/R erosions, and this effect was accompanied by a significant increase in the GBF and the attenuation of blood free radicals. At 0, 3, and 12 h after I/R a significant decrease in SOD mRNA was observed, whereas expression of TNF-alpha, IL-1beta, and ICAM-1 showed a progressive increase starting immediately after I/R, reaching a maximum on day 3. The plasma level of TNF-alpha and IL-1beta started to increase on day 3 and peaked on day 5 after I/R, being still significantly higher at day 10 than that measured in the vehicle-treated control gastric mucosa. On day 10 the gastric ulcers were almost completely healed, and a decrease in the expression for TNF-alpha, IL-1beta, and ICAM-1 mRNA and an increase in the expression of SOD mRNA were observed.

CONCLUSIONS

1) exposure to I/R produces gastric lesions mediated by the excessive formation of free radicals, resulting in suppression of both gastric microcirculation and secretory activity of the stomach; 2) SOD and allopurinol accelerate the healing of I/R lesions, probably due to suppression of oxygen free radicals and improvement of gastric microcirculation; and 3) the upregulation of SOD mRNA, with subsequent increase in the SOD production and local release of IL-1beta and TNF-alpha, may activate ICAM-1 expression and neutrophil infiltration, which appear to play an important role in the progression of I/R-induced acute gastric erosions into chronic ulcers.

Circulating neutrophil CD18 receptor expression and ischemic flap neutrophil infiltration in a guinea pig model

This article demonstrates a correlation between circulating neutrophil CD18 expression, neutrophil infiltration, and varying periods of ischemia induced in guinea pig island skin flaps. Fifty adult female Hartley guinea pigs were equally separated into a control group, a sham group, and ischemic groups of 2, 4, and 10 hours. All, except those in the control group, had single guinea pig island flank skin flaps raised. Systemic neutrophil surface receptor (CD18) expression was analyzed with monoclonal antibodies, and flap skin biopsy specimens were analyzed for neutrophil infiltration. The results show that neutrophil counts and receptor detection increase as flap ischemia increases. However, a trend toward declining receptor expression was observed in the 10-hour ischemic group. In conclusion, systemic neutrophil adhesion receptor upregulation is correlated with cutaneous flap neutrophil infiltration and ischemia-reperfusion injury in a guinea pig model. A trend toward declining receptor expression with advanced ischemia was observed.

Circulating Neutrophil CD18 Receptor Expression and Ischemic Flap Neutrophil Infiltration in a Guinea Pig Model

This article demonstrates a correlation between circulating neutrophil CD18 expression, neutrophil infiltration, and varying periods of ischemia induced in guinea pig island skin flaps. Fifty adult female Hartley guinea pigs were equally separated into a control group, a sham group, and ischemic groups of 2, 4, and 10 hours. All, except those in the control group, had single guinea pig island flank skin flaps raised. Systemic neutrophil surface receptor (CD18) expression was analyzed with monoclonal antibodies, and flap skin biopsy specimens were analyzed for neutrophil infiltration. The results show that neutrophil counts and receptor detection increase as flap ischemia increases. However, a trend toward declining receptor expression was observed in the 10-hour ischemic group. In conclusion, systemic neutrophil adhesion receptor upregulation is correlated with cutaneous flap neutrophil infiltration and ischemia-reperfusion injury in a guinea pig model. A trend toward declining receptor expression with advanced ischemia was observed.

Gene therapy in transplantation

Facilitation of solid organ and cell transplantation depends on metabolic and immunologic factors that can be manipulated ex vivo and in vivo using gene transfer technology. Vectors have been developed which can optimally transfer relevant genes to various tissues and organs. Interventions aimed at promoting tissue preservation before transplantation, prevention of oxidative stress and immunological rejection have recently become attractive options using viral and nonviral gene delivery vehicles. Further understanding of the mechanisms involved in tolerance induction as well as the facilitation of xenogeneic engraftment have made possible a variety of avenues that can be exploited using gene transfer technology.

Systemic neutrophil intrinsic 5-lipoxygenase activity and CD18 receptor expression linked to reperfusion injury

OBJECTIVE

To determine if systemic neutrophil intrinsic 5-lipoxygenase (5-LO) inhibition correlates with decreased expression of surface adhesion molecules and attenuation of ischemia-reperfusion (i/r) injury in guinea pig island skin flaps.

METHODS

Eighty-one adult female Hartley guinea pigs were divided into one control group, three 2-hour ischemia groups, and four 10-hour ischemia groups. Island dorsal skin flaps were developed (except in the control group), and 2 hours before reperfusion, zileutin (a 5-LO inhibitor) or vehicle was administered orally. Postreperfusion systemic neutrophil receptor expression, neutrophil flap infiltration, and flap survival were measured. Neutrophils from whole blood were analyzed for CD18 containing surface receptor expression using monoclonal antibodies and cell associated fluorescence. Neutrophil infiltration into a distal centimeter squared of flap tissue was assessed using myeloperoxidase antibodies, and flap survival was determined within 7 days postoperatively.

RESULTS

Flaps in the treated 2- and 10-hour ischemic groups survived totally intact, while the untreated 10-hour ischemic flaps underwent total necrosis. A significant main effect of the drug was detected using analysis of variance (ANOVA) (P =.0001). Surface receptor detection and neutrophil infiltration were significantly increased in the untreated animals.

CONCLUSIONS

Zileuton, a 5-LO inhibitor, reduces adhesion receptor expression on systemic neutrophils and attenuates i/r injury. Systemic neutrophil intrinsic 5-LO activity and CD18 receptor expression are linked to reperfusion injury and may be fundamental events in its pathogenesis.

The role of endogenous acid in the development of acute gastric ulcer induced by ischemia-reperfusion in the rat

We investigated the role of endogenous gastric acid in the development of gastric ulcer from erosion induced by ischemia-reperfusion of the celiac artery in the rat. A half-hour clamping of the celiac artery (ischemia) caused acute gastric erosions 1 hour after reperfusion and such acute injuries progressed to ulcers 48-72 hours after reperfusion without any necrotizing agents. Gastric acid secretion decreased immediately after ischemia and didn't recover until 12 hours after reperfusion. Intraperitoneal administrations of cimetidine (100 mg/kg, every 12 hours) or omeprazole (30 mg/kg, every 24 hours) were started at 1, 6, or 12 hours after reperfusion. When administrations were started 1 hour after reperfusion, both drugs significantly decreased the total damaged area and prevented the progression of gastric erosions to ulcers. However, administrations started 6 or 12 hours after reperfusion failed to inhibit the total damaged area and to prevent ulcer formation. These results suggest that endogenous gastric acid may play an important role in the progression of gastric erosions to ulcers although ischemia itself reduces acid secretion. Furthermore, treatment with anti-acid-secretory drugs in the early stage of mucosal damage may be important for the prevention of ulcer.