Iloprost reduces leukocyte adhesion in skeletal muscle venules following ischaemia in a rat model of femorodistal bypass

Attenuation of changes in capillary fine structure and leukocyte adhesion improves muscle performance following chronic ischaemia in rats

Acute ischaemia-reperfusion disrupts capillary fine structure and increases leukocyte adhesion in postcapillary venules. We determined whether chronic muscle ischaemia has similar consequences, and whether it is possible to ameliorate its effect on muscle performance. Following ischaemia (unilateral ligation, common iliac artery) rat hindlimb muscles were examined without other intervention or following treatment with an xanthine oxidase inhibitor (allopurinol), a Na(+)/H(+) exchange blocker (amiloride), or an oxygen free radical scavenger (vitamin E). No significant leukocyte adhesion or rolling, nor changes in capillary fine structure were observed 3 days postsurgery, when limb use was limited. However, leukocyte rolling and adhesion almost trebled by 7 days (P < 0.001), when normal gait was largely restored. Capillary fine structure was disturbed over a similar time course, e.g. relative endothelial volume (control 46%, 7 days 61%; P < 0.05), that resolved by 5 weeks. Where activity was increased by mild electrical stimulation 3 days after ligation muscles showed enhanced capillary swelling (endothelial volume 66% versus 50%, P < 0.005), but improved fatigue index (52% versus 16%, P < 0.001) as a result of greater blood flow. Muscle fatigue after ligation was related to the extent of contraction-induced hyperaemia (R(2) = 0.725), but not capillary swelling. Amiloride, and to a lesser extent allopurinol but not vitamin E, significantly decreased leukocyte rolling and adhesion, as well as capillary endothelial swelling. We conclude that increased activity of ischaemic muscles on recovery is likely to accentuate acidosis accompanying changes in microcirculation and contribute to enhanced muscle fatigue, whereas formation of oxygen free radicals may be attenuated by endogenous protective mechanisms.

The ILAILL study: iloprost as adjuvant to surgery for acute ischemia of lower limbs: a randomized, placebo-controlled, double-blind study by the italian society for vascular and endovascular surgery

SUMMARY BACKGROUND DATA

High rate of complications has been reported following revascularization for acute limb ischemia (ALI). No adjuvant pharmacologic treatment, apart from anticoagulation and standard perioperative care, has been shown clinically effective.

OBJECTIVE

Aim of this study was to evaluate the effects of the prostacyclin analog iloprost as adjuvant to surgery for ALI.

METHODS

A total of 300 patients were randomly assigned to receive perioperative iloprost (intra-arterial, intraoperative bolus of 3000 ng, plus intravenous infusion of 0.5-2.0 ng/kg/min for 6 hours/day for 4-7 days following surgery), or placebo. The primary endpoint was the combined incidence of death and amputation at 3-month follow-up. Secondary endpoints were the incidence of each single major complication, total event rate, symptomatology, and tolerability.

RESULTS

The combined incidence of death and amputation was 19.9% in the placebo and 14.1% in the iloprost group (relative risk, 1.56; 95% confidence interval, 0.89-2.75, P = 0.12, Cox regression analysis). A statistically significant lower mortality (4.7%) was reported in patients receiving iloprost, compared with controls (10.6%; relative risk, 2.61; 95% confidence interval, 1.07-6.37, P = 0.03). The overall incidence of fatal plus major cardiovascular events was 33.1% and 22.8% in placebo and iloprost groups, respectively (relative risk, 1.61; 95% confidence interval, 1.04-2.49, P = 0.03). No serious adverse reactions occurred after iloprost administration, nor differences in the incidence of bleeding or hypotension between treatment groups.

CONCLUSIONS

Although at lower levels than previously reported, our results confirm the severity of ALI. Iloprost as adjuvant to surgery significantly reduced mortality and overall major event rate. Further data are needed to support this finding, and to face a still open medical issue.

ICAM-1 expression and leukocyte behavior in the microcirculation of chronically ischemic rat skeletal muscles

In muscle microcirculation, short periods of ischemia followed by reperfusion are known to upregulate leukocyte and endothelial adhesion molecules, but little is known about leukocyte adherence and ICAM-1 expression during chronic ischemia or any likely effect of muscle activity which is recommended in chronic ischemia due to peripheral arterial disease. Leukocyte rolling and stationary adhesion were observed in post-capillary venules in ischemic and contralateral rat extensor digitorum longus (EDL) muscles 3 and 7 days after unilateral ligation of the common iliac artery and in 3-day ischemic EDLs that were electrically stimulated on days 1 and 2 post-ligation (7 x 15 min per day). ICAM-1 was localized immunohistochemically to venular vessels in all muscles. Following ligation, use of the ischemic leg was observed to be restricted for the first 3 days, returning to normal by 7 days. After 3 days, leukocyte rolling/adherence and ICAM-1 expression were no different in ischemic than control muscles, but all were increased in contralateral muscles. In ischemic muscles, electrical stimulation doubled the numbers of rolling leukocytes and upregulated ICAM-1 expression. After 7 days, increased muscle activity as a result of natural movement also resulted in greater ICAM-1 expression, a 4- to 5-fold increase in rolling leukocyte numbers and a 3-fold increase in stationary adherent leukocytes. Chronic ischemia thus increases ICAM-1 and leukocyte adherence in muscle microcirculation only when combined with contractile activity. Post-capillary venular endothelium may be modified by muscle acidosis when contractions are performed under low flow conditions or by changes in rheological (shear force) factors.

The influence of prostaglandins on leukocyte-endothelium interactions in rabbit mesenteric venules

Contradictory results have been reported concerning the effects of prostaglandins (PGs) on leukocyte-endothelium interactions. Therefore, we investigated the in vivo effects of PGE1, PGE2, Iloprost (a stable PGI2-analogue), and also of a combination of these PGs on leukocyte rolling and FMLP-induced leukocyte adhesion in venules of rabbit mesentery. This preparation was used because of its low level of vasoactivity, eliminating hemodynamic effects on leukocyte-endothelium interactions. The mesentery was superfused with PGs or vehicle. After 30 min FMLP was added to the PG-solution for 15 min, whereupon the tissue was superfused with the PG-solution alone for another 30 min. Neither the PGs nor the cocktail influenced leukocyte rolling. During FMLP administration leukocyte adhesion increased and leukocyte rolling decreased; adhesion was highest in the presence of PGE2. The FMLP-induced decrease in leukocyte rolling was similar in all groups. After FMLP administration had been stopped the number of adherent cells almost returned to baseline and the level of leukocyte rolling increased, the baseline level being reached only in the presence of PGE2. In conclusion, these findings indicate that the effects of PGs on leukocyte-endothelium interactions are limited.

Guanylyl cyclase inhibition reduces contractility and decreases cGMP and cAMP in isolated rat hearts

OBJECTIVE

Several studies have shown that increasing cGMP in the heart reduces contractility, however, decreasing basal cGMP levels have also been shown in some studies to reduce contractility. This study was designed to evaluate the hypothesis that decreasing basal levels of cGMP decreases ventricular contractility, and that this depressed function is associated with a decrease in cAMP.

METHODS

Using paced, constant flow, buffer-perfused rat hearts, we determined the effects of intracoronary infusions of the guanylyl cyclase inhibitor, LY83583 (10(-5) M), on ventricular function, oxygen consumption, and ventricular content of cGMP and cAMP. These experiments were conducted in the absence and presence of isoproterenol (ISO) to increase baseline left ventricular developed pressure (LVDP) and cAMP.

RESULTS

LY83583, infused for 25 min, decreased LVDP by 44 +/- 3 (SE), 77 +/- 20 and 120 +/- 38 mmHg, in control, 10(-9) M, and 10(-8) M ISO-stimulated hearts, respectively. Regardless of the level of ISO stimulation, LY83583 reduced LVDP to the same sub-basal level. Oxygen consumption also decreased, but proportionately less than LVDP. ISO increased cAMP without changing cGMP. LY83583 decreased cGMP by about 25% at all levels of ISO, and decreased cAMP by 22% in the 10(-8) M ISO-stimulated group.

CONCLUSION

Guanylyl cyclase inhibition by LY83583 decreased cGMP, cAMP and ventricular contractility. However, LY83583 depression of contractility was not always associated with a reduction in cAMP, suggesting that LY83583 can depress contractility by both cAMP-dependent and independent mechanisms.

Pharmacokinetics and pharmacodynamics of intra-graft iloprost in femorodistal bypass surgery

Intra-graft injection of the prostacyclin analogue, iloprost, was performed at the end of femorodistal bypass procedures in 12 patients with severe peripheral arterial occlusive disease. Iloprost plasma levels were measured and compared with changes in haemodynamics. There was a high initial iloprost plasma level (mean 625 pg/ml) which dropped to a mean of 50 pg/ml after 15 min. This correlated with an immediate reduction in systolic blood pressure which had returned to pretreatment levels after 15 min. In contrast, the vascular resistance distal to the graft showed a reduction after 5 min which was maintained for at least 20 min after iloprost injection and the mean blood flow through the graft increased steadily throughout the same period of measurement. The study showed an effect of iloprost on blood pressure which correlated with plasma levels, but the time course of the changes in distal vascular resistance and graft blood flow demonstrated an effect more prolonged than the half-life of iloprost.

Changes in neutrophil rheology after acute ischemia and reperfusion in the rat hindlimb

Neutrophils may contribute to the pathogenesis of ischemia-reperfusion injury by impairing microcirculatory flow and causing tissue damage. In this study neutrophil deformability and activation were studied after acute ischemia and reperfusion of the rat hindlimb. A cell transit analyzer with 8 microm pore filters was used to measure the flow resistance of individual neutrophils isolated from arterial blood drawn 30 seconds and 5 minutes after reperfusion, after 2 hours of femoral or iliac artery occlusion, in anesthetized rats. Femoral occlusion followed by 30 seconds of reperfusion resulted in a 16% rise in mean pore transit time, and iliac occlusion caused a 31% increase. Neutrophil activation (percentage of cells with nonspherical shape) rose from 6% to 23% (femoral occlusion) or from 7% to 29% (iliac occlusion). By 5 minutes of reperfusion, transit times, but not shape change, had almost returned to preischemic levels. Sham-occluded rats had no significant change in neutrophil behavior. Plasma isolated from rats after 30 seconds of reperfusion after 2 hours of iliac occlusion caused a 27% increase in mean transit time when incubated with nonautologous neutrophils, while activation rose from 32% to 55%. Thus plasma factor(s) released after ischemia and reperfusion of rat hindlimb caused transient rheologic alteration of circulating neutrophils, which may contribute to local or disseminated vascular occlusion and tissue injury.