The HMG-CoA reductase inhibitor simvastatin activates the protein kinase Akt and promotes angiogenesis in normocholesterolemic animals.

Recent studies suggest that statins can function to protect the vasculature in a manner that is independent of their lipid-lowering activity. We show here that statins rapidly activate the protein kinase Akt/PKB in endothelial cells. Accordingly, simvastatin enhanced phosphorylation of the endogenous Akt substrate endothelial nitric oxide synthase (eNOS), inhibited apoptosis and accelerated vascular structure formation in vitro in an Akt-dependent manner. Similar to vascular endothelial growth factor (VEGF) treatment, both simvastatin administration and enhanced Akt signaling in the endothelium promoted angiogenesis in ischemic limbs of normocholesterolemic rabbits. Therefore, activation of Akt represents a mechanism that can account for some of the beneficial side effects of statins, including the promotion of new blood vessel growth.

Role of platelet-activating factor-acether in mediating guinea pig anaphylaxis.

The pathophysiology of anaphylaxis is very complex, and the sequelae of events are not fully explained in terms of the effects of histamine and peptide leukotrienes alone. Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine, PAF-acether) has been detected in animals undergoing anaphylaxis. Injection of synthetic PAF-acether induces similar effects, including bronchoconstriction, respiratory arrest, systemic hypotension, neutropenia, and thrombocytopenia. The results reported here demonstrate that the histamine- and leukotriene-independent component of guinea pig anaphylaxis in vivo and in isolated lung parenchymal strips in vitro is mediated by PAF-acether. However, PAF-acether is not responsible for the anaphylaxis-induced thrombocytopenia.

In vivo neutralization of P-selectin protects feline heart and endothelium in myocardial ischemia and reperfusion injury.

The cardioprotective effects of an mAb to P-selectin designated mAb PB1.3 was examined in a feline model of myocardial ischemia (MI) and reperfusion. PB1.3 (1 mg/kg), administered after 80 min of ischemia (i.e., 10 min before reperfusion), significantly attenuated myocardial necrosis compared to a non-blocking mAb (NBP1.6) for P-selectin (15 +/- 3 vs 35 +/- 3% of area at risk, P < 0.01). Moreover, endothelial release of endothelium derived relaxing factor, as assessed by relaxation to acetylcholine, was also significantly preserved in ischemic-reperfused coronary arteries isolated from cats treated with mAb PB1.3 compared to mAb NBP1.6 (67 +/- 6 vs 11 +/- 3, P < 0.01). This endothelial preservation was directly related to reduced endothelial adherence of PMNs in ischemic-reperfused coronary arteries. Immunohistochemical localization of P-selectin was significantly upregulated in the cytoplasm of endothelial cells that lined coronary arteries and veins after 90 min of ischemia and 20 min of reperfusion. The principal site of intracytoplasmic expression was in venous vessels. mAb PB1.3 significantly decreased (P < 0.01) adherence of unstimulated PMNs to thrombin and histamine stimulated endothelial cells in a concentration-dependent manner in vitro. These results demonstrate that PMN adherence to endothelium by P-selectin is an important early consequence of reperfusion injury, and a specific monoclonal antibody to P-selectin exerts significant endothelial preservation and cardioprotection in myocardial ischemia and reperfusion.

Peroxynitrite inhibits leukocyte-endothelial cell interactions and protects against ischemia-reperfusion injury in rats.

Peroxynitrite (ONOO-) anion, formed by the interaction of superoxide with nitric oxide (NO), has previously been implicated as a cytotoxic agent. However, the effects of this free radical species on neutrophil (PMN)-endothelial cell interactions is largely unknown. We investigated the direct actions of ONOO- on PMN adhesion to endothelial cells in vitro and in vivo, as well as the effects of ONOO- on PMN-mediated myocardial ischemia-reperfusion injury. In vitro, peroxynitrite (100-1,000 nM) inhibited the adhesion of rat PMNs to the endothelium of isolated thrombin- or H2O2-stimulated rat mesenteric artery (P < 0.01 vs. thrombin or H2O2 alone). In vivo, in the rat mesentery, thrombin (0.5 U/ml) or N(G)-nitro-L-arginine-methyl ester (50 microM) significantly increased venular leukocyte rolling and adherence, which were also significantly (P < 0.01) attenuated by ONOO (800 nM) accompanied by reduced P-selectin expression on the endothelial cell surface. Isolated perfused rat hearts were subjected to global ischemia and reperfusion with rat PMNs (10(8) cells), which resulted in profound cardiac depression (i.e., a marked reduction in left ventricular developed pressure and maximal rate of development of left ventricular pressure). Infusion of ONOO- reversed the myocardial contractile dysfunction of ischemic-reperfused rat hearts to near baseline levels, and markedly attenuated the accumulation of PMNs in the postischemic heart. The present study provides strong evidence that nanomolar concentrations of ONOO- both inhibit leukocyte-endothelial cell interactions and exert cytoprotective effects in myocardial ischemia-reperfusion injury. Furthermore, our results suggest that the inhibition of P-selectin expression by peroxynitrite is a key mechanism of the modulatory actions of ONOO- on leukocyte-endothelial cell interactions.

Statin therapy and myocardial no-reflow.

HMG-CoA reductase inhibitors (statins) have now become one of the most powerful pharmacological strategies in the treatment of cardiovascular diseases. Originally, the cardioprotective effects of statins were thought to be mediated through lipid lowering actions. However, it has now become increasingly clear that the beneficial effects of statins are not related to the lipid lowering effects, but rather to a number of pleiotropic actions. Of particular interest, statins have been shown to increase bioavailability of nitric oxide and protect against vascular inflammation and cardiac cell death in a number of cardiovascular disease states. In this present issue of the British Journal of Pharmacology, Zhao and colleagues provide a novel mechanism of action for statins with the observation that simvastatin reduces myocardial 'no-reflow' after ischemia and reperfusion by activating the mitochondrial K(ATP) channel. The findings of the present study have very profound implications for the treatment of cardiovascular disease. This commentary discusses the implications of these findings and how they relate to the established cardioprotective actions of statins.

Myocardial ischemia/reperfusion injury in NADPH oxidase-deficient mice.

Previous studies have suggested that oxygen-derived free radicals are involved in the pathophysiology of myocardial ischemia/reperfusion (MI/R) injury. Specifically, neutrophils have been shown to mediate postischemic ventricular arrhythmias and myocardial necrosis. We hypothesized that MI/R injury would be reduced in the absence (-/-) of NADPH oxidase. Heterozygous control mice (n=23) and NADPH oxidase(-/-) mice (n=24) were subjected to 30 minutes of coronary artery occlusion and 24 hours of reperfusion. Myocardial area at risk per left ventricle was similar in heterozygous control hearts (55+/-3%) and NADPH oxidase(-/-) hearts (61+/-4%). Contrary to our hypothesis, the size of infarct area at risk was similar in the heterozygous control mice (42+/-4%) and NADPH oxidase(-/-) mice (34+/-5%) (P=not significant). In addition, echocardiographic examination of both groups revealed that left ventricle fractional shortening was similar in NADPH oxidase(-/-) mice (n=8; 27+/-2.5%) and heterozygous control mice (n=10; 23.3+/-3. 3%) after MI/R. Superoxide production, as detected by cytochrome c reduction, was significantly impaired (P<0.01) in NADPH oxidase(-/-) mice (n=6) compared with heterozygous mice (n=7) (0.04+/-0.03 versus 2.2+/-0.08 nmol O(2).min(-1).10(6) cells(-1)). Intravital microscopy of the inflamed mesenteric microcirculation demonstrated that leukocyte rolling and adhesion were unaffected by the absence of NADPH oxidase. Oyster glycogen-stimulated neutrophil transmigration into the peritoneum was also similar in both the heterozygous control mice and NADPH oxidase(-/-) mice (P:=not significant). These findings suggest that NADPH oxidase does not contribute to the development of myocardial injury and dysfunction after MI/R.

Simvastatin preserves the ischemic-reperfused myocardium in normocholesterolemic rat hearts.

BACKGROUND: Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac contractile dysfunction as well as cardiomyocyte injury. These deleterious effects are due in large part to endothelial dysfunction leading to the upregulation of cell adhesion molecules and subsequent neutrophil-endothelium interaction. At clinically relevant doses, simvastatin, an HMG-CoA reductase inhibitor, has been shown to lower serum cholesterol levels and normalize endothelial cell function. We wanted to test the effects of simvastatin on neutrophil-mediated cardiac dysfunction in a controlled model of myocardial ischemia-reperfusion. METHODS AND RESULTS: This study examines the effects of simvastatin in a neutrophil-dependent isolated perfused rat heart model of ischemia (I) (20 minutes) and reperfusion (R) (45 minutes) injury. Administration of simvastatin 25 micrograms/rat improved coronary flow and preserved left ventricular developed pressure (LVDP) and dP/dtmax, indexes of cardiac contractile function. Final LVDP was 95+/-5 mm Hg in I/R hearts perfused with PMNs and simvastatin, compared with 49+/-4 mm Hg in PMN-perfused I/R hearts receiving only vehicle (P<0.001). In addition, simvastatin significantly reduced PMN accumulation in the ischemic myocardium (P<0.01). In PMN-perfused rat hearts after I/R, simvastatin also significantly attenuated P-selectin expression, CD18 upregulation in rat PMNs, and PMN adherence to rat vascular endothelium. Significant, although less potent, effects were obtained with pravastatin. CONCLUSIONS: These results provide evidence that HMG-CoA reductase inhibitors are potent and effective cardioprotective agents that inhibit leukocyte-endothelial cell interactions and preserve cardiac contractile function and coronary perfusion after myocardial ischemia and reperfusion. Moreover, these effects are unrelated to the cholesterol-lowering action of this agent and appear to be mediated by enhanced endothelial release of NO.

Simvastatin exerts both anti-inflammatory and cardioprotective effects in apolipoprotein E-deficient mice.

BACKGROUND: Simvastatin attenuates ischemia and reperfusion in normocholesterolemic animals by stabilizing endothelial nitric oxide synthase activity and inhibiting neutrophil-mediated injury. Because endothelial dysfunction is a detrimental effect of hypercholesterolemia, we examined whether short-term treatment with simvastatin could inhibit leukocyte-endothelium interaction and attenuate myocardial ischemia-reperfusion injury in apoE-deficient (apoE(-/-)) mice fed a high-cholesterol diet. METHODS AND RESULTS: We studied leukocyte-endothelium interactions in apoE(-/-) mice fed a normal or a high-cholesterol diet after short-term (ie, 18 hours) simvastatin treatment. We also studied simvastatin treatment in myocardial ischemia-reperfusion injury by subjecting apoE(-/-) mice to 30 minutes of ischemia and 24 hours of reperfusion. ApoE(-/-) mice fed a high-cholesterol diet exhibited higher blood cholesterol levels, which were not affected by short-term simvastatin treatment. However, the increased leukocyte rolling and adherence that occurred in cholesterol-fed apoE(-/-) mice (P<0.001 versus control diet) were significantly attenuated by simvastatin treatment (P<0.01 versus vehicle). Cholesterol-fed apoE(-/-) mice subjected to myocardial ischemia-reperfusion also experienced increased myocardial necrosis (P<0.01 versus control diet), which was significantly attenuated by simvastatin (P<0.01 versus vehicle). Simvastatin therapy also significantly increased vascular nitric oxide production in apoE(-/-) mice. CONCLUSIONS: Simvastatin attenuates leukocyte-endothelial cell interactions and ameliorates ischemic injury in hypercholesterolemic mice independently of lipid-lowering actions.

An anti-CD18 antibody limits infarct size and preserves left ventricular function in dogs with ischemia and 48-hour reperfusion.

OBJECTIVES: This study investigated whether an antibody against neutrophil adhesion protein CD18 could limit myocardial infarct size and preserve left ventricular function after prolonged reperfusion in a canine model. BACKGROUND: Myocardial reperfusion injury is mediated in part by accumulation of activated neutrophils. Although antibodies against CD18 have been shown to reduce neutrophil influx and infarct size after ischemia and 3 to 4 h of reperfusion, it is unknown whether protection is sustained beyond this time or whether there is meaningful preservation of ventricular function. METHODS: Dogs undergoing 90-min circumflex coronary artery occlusion and 48-h reperfusion were randomized to receive 1 mg/kg bodyweight of R15.7 (an anti-CD18 antibody, n = 12) or saline (control, n =12) 10 min before reperfusion. Contrast left ventriculography was used to measure left ventricular ejection fraction and regional chord shortening at baseline, during occlusion and at 48 h. Microspheres injected during occlusion were used to measure collateral flow and risk region size. Postmortem infarct size was measured with triphenyltetrazolium chloride. RESULTS: In the dose administered, R15.7 bound to neutrophils in vivo, with >85% saturation of CD18 for >24 h, with sustained antibody excess in the plasma. R15.7 significantly reduced infarct size after adjusting for the effect of collateral flow (p = 0.0002, analysis of covariance). In a subgroup of dogs with collateral flow <30% of nonischemic flow, infarct size was reduced from 34.6 +/- 3.9% (mean +/- SE) of the region at risk in the control group to 19.5 +/- 3.3% in the antibody group (p = 0.008). Ejection fraction and regional chord shortening did not differ between the two groups at baseline or during occlusion, but after 48-h reperfusion, ejection fraction and inferior wall regional cord shortening (representing the infarct zone) were both higher in the R15.7 group than the control group (43.6 +/- 2.9% vs. 28.5 +/- 1.8%, p < 0.01; 2.55 +/- 0.29% vs. 1.06 +/- 0.18%, p < 0.05). CONCLUSIONS: A single injection of an anti-CD18 antibody given before reperfusion can limit myocardial infarct size by nearly 50% and preserve global and regional left ventricular function after 48 h of reperfusion.

Pretreatment with simvastatin attenuates myocardial dysfunction after ischemia and chronic reperfusion.

We have previously demonstrated that simvastatin attenuates myocardial cell necrosis after acute myocardial ischemia and reperfusion via induction of endothelial cell NO synthase. However, it remains unknown whether the cardioprotective effects of statins can persist after extended periods of reperfusion. Furthermore, it is unknown whether simvastatin therapy can attenuate postischemic cardiac dysfunction. Pretreatment with simvastatin attenuated myocardial injury after 30 minutes of myocardial ischemia and 24 hours of reperfusion. However, the protective effects are not recognized unless simvastatin is given at least 3 hours before myocardial ischemia. Subsequently, we pretreated mice with vehicle or simvastatin and subjected the mice to 30 minutes of myocardial ischemia and 6 months of reperfusion. Myocardial infarct size (percentage of left ventricle) was significantly reduced by 51% in the simvastatin-treated group compared with the vehicle-treated group. Left ventricular diastolic and systolic dilatation was significantly (P<0.05) reduced in simvastatin-treated mice compared with vehicle-treated mice. Additionally, the decrement in fractional shortening after 6 months of reperfusion was minimized in simvastatin-treated mice (P=NS versus baseline) compared with vehicle-treated mice (P<0.05 versus baseline). Left ventricular end-diastolic pressure was significantly (P<0.01) elevated in vehicle-treated mice (21+/-4 mm Hg) but not simvastatin-treated mice (5+/-2 mm Hg) compared with baseline values. These data demonstrate that simvastatin treatment before myocardial ischemia attenuates infarct size and preserves myocardial function after chronic reperfusion in mice.

Quantification of neutrophil migration following myocardial ischemia and reperfusion in cats and dogs.

Endothelial cell dysfunction and cardiac myocyte injury resulting from ischemia and reperfusion have been associated with accumulation of neutrophils in the myocardium. To determine whether the accumulation is related primarily to intravascular sequestration or extravascular infiltration of neutrophils during the early period of reperfusion, we morphometrically quantified the tissue distribution of neutrophils in cats and dogs. At the end of the reperfusion period, the base of the heart was cross-clamped to preserve neutrophil location at the moment of death. Point-counting methods were used to determine the distribution of neutrophils inside and outside coronary arterioles and venules (< or = 100 microns in diameter) as well as coronary capillaries 5-10 microns in diameter in 0.5-microns-thick, plastic-embedded sections. Ischemia-reperfusion resulted in a threefold increase in neutrophil number in the lumen of arterioles and venules at 60 min of reperfusion and up to a sevenfold increase at 270 min of reperfusion (P < .05) compared to time-matched control nonischemic hearts. The ratio of intravascular neutrophils in venules to arterioles was 2:1. Intracapillary neutrophils increased, but not significantly, at 60 min of reperfusion. At 270 min of reperfusion, intracapillary neutrophils increased 11-fold (P < .05). The percentage of total neutrophils that accumulated outside arterioles and venules in cat hearts was 8% at 60 min of reperfusion (not significant, NS) and 28% at 270 min of reperfusion (P < .05). In dog hearts, the percentages were 26% (NS) and 44% (P < .05), respectively. The percentage of total neutrophils that accumulated outside capillaries was < 6% in both cat and dog hearts (NS). The combination of rapid intravascular sequestration, delayed extravascular infiltration, and low incidence of neutrophil-cardiac myocyte contact in situ in these two species suggests that neutrophil-mediated cardiac myocyte injury during early reperfusion may initially depend on diffusion of inflammatory mediators and subsequently require direct contact between neutrophils and cardiac myocytes.

Monoclonal antibody to ICAM-1 preserves postischemic blood flow and reduces infarct size after ischemia-reperfusion in rabbit.

Neutrophils are pivotal in the pathogenesis of reperfusion injury leading to myocardial infarction. Firm adhesion of PMN to endothelium may be initiated by the interaction between constitutively expressed intercellular adhesion molecule-1 (ICAM-1) on endothelium and beta2 integrin (CD11b/CD18) on neutrophils. We tested the hypothesis that a monoclonal antibody (mAb RR1/1) against ICAM-1 would preserve postischemic myocardial blood flow and attenuate myocardial injury in an anesthetized rabbit model of coronary occlusion and reperfusion. Either mAb RR1/1 or isotypematched control mAb (R3.1) was injected 10 min before reperfusion. Postischemic myocardial blood flow in the area at risk (Ar) and necrotic area was significantly improved with mAb RR1/1 treatment compared with vehicle and mAb R3.1 during the reperfusion period. RR1/1 had no effect on nonischemic zone blood flow. The Ar as a percent of left ventricle was comparable between groups. Infarct size (TTC) as a percent of Ar was significantly reduced by mAb RR1/1 compared with saline vehicle and mAb R3.1. Plasma creatine kinase activity confirmed the reduction of infarct size in mAb RR1/1 group. In in vitro studies, 40 microg/mL mAb RR1/l, which approximates the plasma concentration of 2 mg/kg mAb RR1/1, markedly inhibited platelet-activating factor-stimulated neutrophil adherence to rabbit aortic endothelium. We conclude that blockade of ICAM-1 during reperfusion reduces postischemic perfusion defects and attenuates the progression of myocardial injury leading to necrosis. This cardioprotection by mAb RR1/1 may be due to inhibition of neutrophil adhesion to the coronary endothelium.

The role of nitric oxide and cell adhesion molecules on the microcirculation in ischaemia-reperfusion.

The microcirculation undergoes a profound degree of endothelial dysfunction within minutes (i.e., 2.5 to 5 min) following reperfusion of ischaemic vasculature. This has been documented in the coronary and mesenteric microcirculation. The endothelial dysfunction is characterized by a loss in basal and agonist-mediated nitric oxide (NO) produced by the vascular endothelium. The loss of NO results in upregulation of cell adhesion molecules (CAMs) particularly P-selectin 10-20 min following reperfusion. Thus, CAM upregulation renders the endothelium sticky, and a marked degree of leukocyte adherence (particularly neutrophils) occurs 20 min following reperfusion. This enhanced involvement of neutrophils leads to neutrophil infiltration into the underlying tissue (e.g., myocardium) within 2-3 h of reperfusion. The infiltration of neutrophils leads to reperfusion injury (i.e., necrosis) which is significant at 3 h but becomes profound at 4.5 h following reperfusion. Cardiac necrosis can be significantly attenuated by treatment with NO, an organic NO donor, L-arginine, or specific blockers of CAMs given just prior to reperfusion. This approach is a promising one for a variety of types of reperfusion injury.

Modulation of leukocyte-endothelial interactions by reactive metabolites of oxygen and nitrogen: relevance to ischemic heart disease.

Ischemia and reperfusion (I/R) are thought to play an important role in the pathophysiology of ischemic diseases of the heart. It is now well appreciated that leukocyte-endothelial cell interactions are important determinants for I/R-induced microvascular injury and dysfunction. There is a growing body of experimental data to suggest that reactive metabolites of oxygen and nitrogen are important physiological modulators of leukocyte-endothelial cell interactions. A number of investigators have demonstrated that I/R enhances oxidant production within the microcirculation resulting in increases in leukocyte adhesion and transendothelial cell migration. Several other studies have shown that exogenous nitric oxide (NO) donors may attenuate leukocyte and platelet adhesion and/or aggregation in a number of different inflammatory conditions including I/R. The objective of this review is to discuss the physiological chemistry of reactive metabolites of oxygen and nitrogen with special attention given to those interactions that may modulate leukocyte-endothelial cell interactions, provide an overview of the evidence implicating reactive metabolites of oxygen and nitrogen as modulators of leukocyte-endothelial cell interactions in vivo, and discuss how these mechanisms may be involved in the pathophysiology of ischemic heart disease.

Increased disease activity in eNOS-deficient mice in experimental colitis.

Oral dextran sodium sulfate (DSS, 3%) produces experimental colitis with many features of human inflammatory bowel disease (IBD), (leukocyte extravasation, cachexia, and histopathology). Previous studies suggest that the inducible nitric oxide synthase (iNOS) in blood cells or in the endothelium contribute to this injury. However, until now no study has been performed to directly evaluate the role of endothelial nitric oxide synthase (eNOS) in IBD. We compared disease activity in wild-type (eNOS+/+) and eNOS-deficient (eNOS-/-) mice in the DSS model of colitis. Administration of DSS induced weight loss, stool blood, and overt histopathology in both mouse strains. Disease activity was dramatically increased in eNOS-/- mice compared to wild types. Histologically, eNOS-deficient mice had greater leukocyte infiltration, gut injury, and expressed higher levels of the mucosal addressin, MAdCAM-1. These results demonstrate that eNOS plays an important role in limiting injury to the intestine during experimental colitis and altered eNOS content and/or activity may contribute to human IBD.

Role of nitric oxide in the regulation of acute and chronic inflammation.

Recent studies by a number of different laboratories have implicated nitric oxide (NO) as an important modulator of a variety of acute and chronic inflammatory disorders. A hallmark of inflammation is the adhesion of leukocytes to post-capillary venular endothelium and the infiltration of leukocytes into the tissue interstitium. Leukocyte adhesion and infiltration is known to be dependent on interaction of the leukocytes with the endothelial cell surface via a class of glycoproteins collectively known as endothelial cell adhesion molecules (ECAMs). Several recent studies suggest that NO may modulate cytokine-induced ECAM expression in cultured endothelial cells in vitro by regulating the activation of nuclear transcription factor kappa B (NF-kappaB). This discussion reviews some of the more recent studies that assess the role of the different NOS isoforms on the inflammatory response in vivo.

Oxidative stress and cardiac disease.

Reactive oxygen species (ROS) are formed at an accelerated rate in postischemic myocardium. Cardiac myocytes, endothelial cells, and infiltrating neutrophils contribute to this ROS production. Exposure of these cellular components of the myocardium to exogenous ROS can lead to cellular dysfunction and necrosis. While it remains uncertain whether ROS contribute to the pathogenesis of myocardial infarction, there is strong support for ROS as mediators of the reversible ventricular dysfunction (stunning) that often accompanies reperfusion of the ischemic myocardium. The therapeutic potential of free radical-directed drugs in cardiac disease has not been fully realized.

Levels of expression of P-selectin, E-selectin, and intercellular adhesion molecule-1 in coronary atherectomy specimens from patients with stable and unstable angina pectoris.

Unstable angina occurs when atherosclerotic plaque ruptures. Recent evidence suggests a role for inflammation in this process. Leukocyte-endothelial cell interactions are important in inflammation and are regulated by cell adhesion molecules. This study was designed to examine the vascular expression of cell adhesion molecules and cytokines in patients with unstable angina. Directional coronary atherectomy was performed in patients with unstable and stable angina. Expression of the cell adhesion molecules P-selectin, E-selectin, and intercellular adhesion molecule-1 in the tissue obtained was examined using immunohistochemistry. In addition, expression of the cytokines tumor necrosis factor-alpha and interleukin-1beta, which participate in the regulation of cell adhesion molecule expression, was also examined. Atherectomy specimens had significantly greater P-selectin expression from patients with unstable angina than from patients with stable angina. P-selectin expression was observed primarily on endothelial cells. There were no differences in any of the other factors between patients with unstable and stable angina. In addition, other clinical and angiographic variables were not associated with differential expression of any of the cell adhesion molecules or cytokines. These results indicate a possible role for P-selectin in the process of unstable angina.

Age-related differences in response to neutrophil-mediated reperfusion injury in the neonatal piglet heart.

BACKGROUND: Neonatal hearts have altered adhesion molecule interactions in response to ischemia-reperfusion. How this affects myocardial function is unknown. METHODS: Isolated, buffer perfused 0- to 2-day (newborn) and 2-week piglet hearts were first subjected to 20-minute global, normothermic ischemia, followed by 45 minutes of reperfusion during which 150 x 10(6) newborn or 2-week neutrophils were infused. In some hearts, an antibody to SLe(x) (CSLEX-1) was infused with neutrophils during reperfusion. Hemodynamic variables, including left ventricular developed pressure (LVDP), were recorded at timed intervals. Neutrophil CD-18, L-selectin, and SLe(x) contents were measured by flow cytometry. RESULTS: Full recovery of LVDP was observed in newborn hearts receiving newborn or 2-week-old neutrophils. Recovery of LVDP was depressed (p < 0.01, ANOVA) in 2-week-old hearts receiving 2-week old, not newborn, neutrophils. Infusion of CSLEX-1 in 2-week-old hearts restored LVDP to baseline. Whereas flow cytometry showed higher (p < 0.01, Student's t test) CD-18 and L-selectin expression on newborn versus 2-week-old neutrophils, newborn neutrophils expressed lower (p < 0.01) SLe(x) levels. CONCLUSIONS: Initial "loose" neutrophil-endothelial selectin interactions are a necessary prelude to "firm" adhesion and reperfusion injury. Operations performed soon after birth may be better tolerated than when surgery is delayed; anti-SLe(x) preparations may prove beneficial when performing cardiac procedures on older infants.

Novel mechanism of action of a prostacyclin enhancing agent in haemorrhagic shock.

Prostacyclin (PGI2) is a potent vasodilator, an inhibitor of platelet aggregation, and a membrane stabilizing agent with beneficial effects in ischemia and shock. We studied defibrotide, a new agent which enhances PGI2 release from vascular tissue, to determine its effects in a murine model of hemorrhagic shock. Hemorrhaged rats treated with defibrotide maintained post-reinfusion mean arterial blood pressure (MABP) at significantly higher values compared to rats receiving the vehicle (final MABP, 100 +/- 3 vs. 69 +/- 7 mm Hg, p less than 0.01). Defibrotide attenuated the release of the lysosomal hydrolase cathepsin D (p less than 0.02), and the plasma accumulation of free amino-nitrogen groups (p less than 0.02). The plasma activity of a myocardial depressant factor (MDF) was significantly lower in defibrotide treated shocked rats than in the vehicle group (29 +/- 4 vs. 61 +/- 8 U/ml, p less than 0.01). Moreover, plasma i6-keto-PGF1 alpha concentrations increased 3-fold above haemorrhaged rats receiving only the vehicle. This, as well as the improved MABP, was abolished by indomethacin. Additionally, defibrotide exerts an anti-proteolytic action in pancreatic homogenates, and a lysosomal stabilizing effect in large granule fractions of rat liver homogenates. Moreover, defibrotide enhanced the recovery from norepinephrine induced vasoconstriction in rat aortic rings having an intact endothelium (p less than 0.01 from vehicle), and augmented the release of i6-keto-PGF1 alpha, the stable metabolite of PGI2, from isolated rat aortae. Our results indicate that enhancement of endogenous vascular PGI2 release coupled with direct, or PGI2 mediated antiproteolytic and membrane stabilizing actions may be important physiological mechanisms counteracting the deleterious effects of hemorrhagic shock.