Effects of intestinal ischemia-reperfusion on major conduit arteries

Etanercept restores vasocontractile sensitivity affected by mesenteric ischemia reperfusion

BACKGROUND

The aim of the study is to evaluate in vivo and in vitro effects of etanercept, a soluble tumor necrosis factor receptor, on the contractile responses of superior mesenteric artery in an experimental mesenteric ischemia and reperfusion model.

MATERIAL AND METHODS

After obtaining animal ethics committee approval, 24 Sprague-Dawley rats were allocated to three groups. Control group (Gr C, n = 6) underwent a sham operation, whereas ischemia/reperfusion and treatment groups underwent 90 min ischemia and 24-h reperfusion (Gr I/R, n = 12; Gr I/R+E, n = 6). The treatment group received 5 mg/kg etanercept intravenously at the beginning of reperfusion. At the end of reperfusion, all animals were sacrificed, and third branch of superior mesenteric artery was dissected for evaluation of contractile responses. In vitro effects of etanercept on vasocontractile responses were also evaluated. The excised ileums were analyzed under light microscope. Two-way analysis of variance following Bonferroni post hoc test was used for evaluation of contractile responses.

RESULTS

Endothelin-1 and phenylephrine-mediated vasocontractile sensitivity were found increased in Gr I/R when compared with Gr C. Both intravenous administration and organ bath incubation of etanercept decreased the sensitivity of contractile agents for Gr I/R. Mucosal injury, lamina propria disintegration, and denuded villous tips were observed in Gr I/R, whereas the epithelial injury and the subepithelial edema were found to be milder in Gr I/R+E.

CONCLUSIONS

Etanercept can be a promising agent in mesenteric ischemic reperfusion injury as it does not only inhibit inflammation by blocking tumor necrosis factor-α in circulation but also restores vascular contractility during reflow. These findings support an unexplained recuperative effect of drug beyond its anti-inflammatory effects.

Increased endothelin-1 vasoconstriction in mesenteric resistance arteries after superior mesenteric ischaemia-reperfusion

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) plays an important role in the maintenance of vascular tone. We aimed to evaluate the influence of superior mesenteric artery (SMA) ischaemia-reperfusion (I/R) on mesenteric resistance artery vasomotor function and the mechanism involved in the changes in vascular responses to ET-1.

EXPERIMENTAL APPROACH

SMA from male Sprague-Dawley rats was occluded (90 min) and following reperfusion (24h), mesenteric resistance arteries were dissected. Vascular reactivity was studied using wire myography. Protein and mRNA expression, superoxide anion (O(2) (•-) ) production and ET-1 plasma concentration were evaluated by immunofluorescence, real-time quantitative PCR, ethidium fluorescence and elisa, respectively.

KEY RESULTS

I/R increased ET-1 plasma concentration, ET-1-mediated vasoconstriction and ET(B) mRNA expression, and down-regulated ET(A) mRNA expression. Immunofluorescence confirmed mRNA results and revealed an increase in ET(B) receptors in the mesenteric resistance artery media layer after I/R. Therefore, the ET(B) receptor agonist sarafotoxin-6 induced a contraction that was inhibited by the ET(B) receptor antagonist BQ788 only in vessels, with and without endothelium, from I/R rats. Furthermore, BQ788 potentiated ET-1 vasoconstriction only in sham rats. Endothelium removal in rings from I/R rats unmasked the inhibition of ET-1 vasoconstriction by BQ788. Endothelium removal, N(ω) -nitro-L-arginine methyl ester and superoxide dismutase abolished the differences in ET-1 vasoconstriction between sham and I/R rats. We also found that I/R down-regulates endothelial NOS mRNA expression and concomitantly enhanced O(2) (•-) production by increasing NADPH oxidase 1 (NOX-1) and p(47phox) mRNA.

CONCLUSIONS AND IMPLICATIONS

Mesenteric I/R potentiated the ET-1-mediated vasoconstriction by a mechanism that involves up-regulation of muscular ET(B) receptors and decrease in NO bioavailability.

Vascular relaxation of canine visceral arteries after ischemia by means of supraceliac aortic cross-clamping followed by reperfusion

BACKGROUND

The supraceliac aortic cross-clamping can be an option to save patients with hipovolemic shock due to abdominal trauma. However, this maneuver is associated with ischemia/reperfusion (I/R) injury strongly related to oxidative stress and reduction of nitric oxide bioavailability. Moreover, several studies demonstrated impairment in relaxation after I/R, but the time course of I/R necessary to induce vascular dysfunction is still controversial. We investigated whether 60 minutes of ischemia followed by 30 minutes of reperfusion do not change the relaxation of visceral arteries nor the plasma and renal levels of malondialdehyde (MDA) and nitrite plus nitrate (NOx).

METHODS

Male mongrel dogs (n = 27) were randomly allocated in one of the three groups: sham (no clamping, n = 9), ischemia (supraceliac aortic cross-clamping for 60 minutes, n = 9), and I/R (60 minutes of ischemia followed by reperfusion for 30 minutes, n = 9). Relaxation of visceral arteries (celiac trunk, renal and superior mesenteric arteries) was studied in organ chambers. MDA and NOx concentrations were determined using a commercially available kit and an ozone-based chemiluminescence assay, respectively.

RESULTS

Both acetylcholine and calcium ionophore caused relaxation in endothelium-intact rings and no statistical differences were observed among the three groups. Sodium nitroprusside promoted relaxation in endothelium-denuded rings, and there were no inter-group statistical differences. Both plasma and renal concentrations of MDA and NOx showed no significant difference among the groups.

CONCLUSION

Supraceliac aortic cross-clamping for 60 minutes alone and followed by 30 minutes of reperfusion did not impair relaxation of canine visceral arteries nor evoke biochemical alterations in plasma or renal tissue.

Influence of physical preconditioning on the responsiveness of rat pulmonary artery after pulmonary ischemia/reperfusion

The aim of this work was to evaluate the effect of physical preconditioning in the responsiveness of rat pulmonary rings submitted to lung ischemia/reperfusion (IR). Wistar rats were divided into three groups: Sedentary sham-operated (SD/SHAM); sedentary submitted to ischemia/reperfusion (SD/IR) and trained submitted to ischemia/reperfusion (TR/IR) animals. Exercise training consisted in sessions of 60 min/day running sessions, 5 days/week for 8 weeks. Left pulmonary IR was performed by occluding for 90 min and reperfusing for 120 min. After that, pulmonary arteries were isolated and concentration-response curves to acetylcholine (ACh), histamine (HIST), sodium nitroprusside (SNP), phenylephrine and U46619 were obtained. Neither potency (-log EC(50)) nor maximal responses (E(max)) were modified for ACh and HIST in all groups. On the other hand, the potency for SNP was significantly increased in TR/IR group (8.23+/-0.06) compared to SD/IR group (7.85+/-0.04). Contractile responses mediated by a-adrenergic receptor were markedly decreased in IR groups (SD/IR: 6.75+/-0.06 and TR/IR: 6.62+/-0.04) compared to SD/SHAM (7.33+/-0.05). No changes were seen for the U46619 in all groups. In conclusion, the present study shows that exercise training has no protective actions in the local blood vessel where the IR process takes place.

[Oxidative alterations, total antioxidant status and nitric oxide study in rats submitted to ischemia and reperfusion of hind limbs]

PURPOSE

To verify the effect of the ischemia time on the oxidative alterations, total antioxidant status and the nitric oxide, in the muscle, kidney and plasma, in rats submitted to ischemia and reperfusion of hind limbs.

METHODS

Forty male rats were randomized in four groups with ten animals each. Laparotomy, abdominal aorta infra ejuxta renal isolation. Groups 1 and 3 (sham), passage of the polipropilen 7.0 monofilamentary thread aorta around without bending it and waiting time of 1 hour to group 1 and 6 hours to group 3. Withdrawal of the thread, waiting time of 15 minutes, euthanasia and material collection. Groups 2 and 4 (experiments), ligation of abdominal aorta with the same thread and ischemia of 1 hour in the group 2 and 6 hours to the group 4. Withdrawal of the thread and reperfusion for 15 minutes. Euthanasia and blood collection by flowing; withdrawal of the left hind limb muscle and of the left kidney. The parameters evaluated were: malondialdehyde, total antioxidant status and the nitric oxide.

RESULTS

The "T" Student test and the MANN-WHITNEY test have been used as nonparametrics tests and the rejection level have been fixed in 0.05 or 5%. There were significative alterations of the malondialdehyde in the kidney. The total antioxidant status has been shoun significative alterations in the kidney, muscle and plasma. Although the nitric oxide has been altered in the plasma only.

CONCLUSION

The ischemia time changing has provoked significative alterations of malondialdehyde, total antioxidant status and nitric oxide.

Candida albicans and Streptococcus salivarius modulate IL-6, IL-8, and TNF-alpha expression and secretion by engineered human oral mucosa cells

We investigated the involvement of oral epithelial cells via two cytokines (IL-6 and TNF-alpha) and one chemokine (IL-8) in local defences against live yeast (Candida albicans) and bacteria (Streptococcus salivarius) using an engineered human oral mucosa model. We report that the yeast changed from the blastospore to the hyphal form and induced significant tissue disorganization at later contact periods (24 and 48 h) compared to the bacteria. However, this effect did not reduce the viability or total number of epithelial cells. Gene activation analyses revealed that IL-6, IL-8 and TNF-alpha mRNA levels rose in tissues in contact with live C. albicans or S. salivarius. Gene activation was followed by an upregulation of protein secretion. IL-6 levels were higher after contact with C. albicans than with S. salivarius. IL-8 levels after contact with S. salivarius were higher than with C. albicans. Our study suggests that S. salivarius is more efficient at inducing proinflammatory mediator release than C. albicans. These results provide additional evidence for the contribution of oral epithelial cells to the inflammatory response against fungi and bacteria.