Mechanisms of oxidant-mediated microvascular injury following reperfusion of the ischemic intestine

Total salvianolic acid improves ischemia-reperfusion-induced microcirculatory disturbance in rat mesentery

AIM: To investigate the effect of total salvianolic acid (TSA) on ischemia-reperfusion (I/R)-induced rat mesenteric microcirculatory dysfunctions.

METHODS: Male Wistar rats were randomly distributed into 5 groups (n = 6 each): Sham group and I/R group (infused with saline), TSA group, TSA + I/R group and I/R + TSA group (infused with TSA, 5 mg/kg per hour). Mesenteric I/R were conducted by a ligation of the mesenteric artery and vein (10 min) and subsequent release of the occlusion. TSA was continuously infused either starting from 10 min before the ischemia or 10 min after reperfusion. Changes in mesenteric microcirculatory variables, including diameter of venule, velocity of red blood cells in venule, leukocyte adhesion, free radicals released from venule, albumin leakage and mast cell degranulation, were observed through an inverted intravital microscope. Meanwhile, the expression of adhesion molecules CD11b/CD18 on neutrophils was evaluated by flow cytometry. Ultrastructural evidence of mesenteric venules damage was assessed after microcirculation observation.

RESULTS: I/R led to multiple responses in mesenteric post-capillary venules, including a significant increase in the adhesion of leukocytes, production of oxygen radicals in the venular wall, albumin efflux and enhanced mast cell degranulation in vivo. All the I/R-induced manifestations were significantly reduced by pre- or post-treatment with TSA, with the exception that the I/R-induced increase in mast cell degranulation was inhibited only by pre-treatment with TSA. Moreover, pre- or post-treatment with TSA significantly attenuated the expression of CD11b/CD18 on neutrophils, reducing the increase in the number of caveolae in the endothelial cells of mesentery post-capillary venules induced by I/R.

CONCLUSION: The results demonstrated that TSA protects from and ameliorates the microcirculation disturbance induced by I/R, which was associated with TSA inhibiting the production of oxygen-free radicals in the venular wall and the expression of CD11b/CD18 on neutrophils.

Potential of 3,4-dihydroxy-phenyl lactic acid for ameliorating ischemia-reperfusion-induced microvascular disturbance in rat mesentery

This study intended to examine the effect of 3,4-dihydroxy-phenyl lactic acid (DLA), a major ingredient of Salvia miltiorrhiza, on ischemia-reperfusion (I/R)-induced rat mesenteric microcirculatory injury. DLA (5 mg.kg(-1).h(-1)), superoxide dismutase (SOD, 12,000 U.kg(-1).h(-1)), or catalase (CAT, 20 mg/kg) was continuously infused either starting from 10 min before the ischemia or 10 min after the initiation of reperfusion. The venule diameter, number of adherent leukocytes, FITC-albumin leakage, dihydrorhodamine 123 fluorescence, and mast cell degranulation were determined using an intravital microscope. The production of hydrogen peroxide (H(2)O(2)) and the expression of adhesion molecules CD11b/CD18 in neutrophils were evaluated by in vitro experiments. The results showed that pretreatment with DLA significantly reduced peroxide production in and leukocyte adhesion to venular wall, albumin leakage, and mast cell degranulation induced by I/R. The DLA posttreatment exerted an ameliorating effect on I/R-induced disorders as well, characterized by inhibiting further increase in peroxide production in venular wall and albumin leakage and diminishing the number of leukocytes that had adhered to the venular wall. In vitro experiments revealed that treatment with DLA significantly attenuated TNF-alpha plus fMLP-evoked production of H(2)O(2) and the H(2)O(2)-elicited expression of CD11b/CD18 on neutrophils. SOD and CAT manifested similarly but with the exception that either SOD or CAT were unable to retrieve the adherent leukocytes if administrated after initiation of reperfusion and to depress the H(2)O(2)-induced expression of CD11b/CD18 on neutrophils. It is concluded that DLA protects from and ameliorates the I/R-induced microcirculatory disturbance by interfering with both peroxide production and adhesion molecule expression.

Pathophysiology of gastrointestinal mucosal permeability

The intestinal mucosa is composed of multiple barriers to the lumen-to-blood transport of solutes, including the unstirred water and mucous layers, the apical and basolateral cell membranes of the epithelial cell, the paracellular junctions, the interstitial matrix, and the capillary and lymphatic endothelia. The epithelial barrier appears effectively to restrict the movement of solutes with a radius as low as 3 A, yet it also permits limited permeation by molecules as large as albumin (36 A radius). There is evidence to suggest that the restrictive properties of the gastrointestinal mucosa are significantly altered under various physiological and pathological conditions, and measurement of plasma (or luminal) clearances of water-soluble molecules has proved to be a popular method for studying intestinal permeability. The aim of this review is to discuss the concept of the plasma clearance method, methodological aspects of the technique, factors that influence plasma-to-lumen clearance measurements (e.g. solute size, blood flow, and permeability of the epithelial cell barrier), and advantages and disadvantages of the clearance method. Finally, application of the clearance technique to the study of ischaemia/reperfusion-, ethanol-, and FMLP-induced mucosal injury will be described.