Multiple selectin blockade with a small molecule inhibitor downregulates liver chemokine expression and neutrophil infiltration after hemorrhagic shock.

BACKGROUND: The purpose of this study was to investigate the regulatory effect of a small molecule selectin inhibitor in the liver by examining the functional, structural, and survival response of animals subjected to hemorrhagic shock and to determine the liver infiltration of neutrophils and the regulation of chemokine expression. Selectins play an important role in the development of the lesions associated with ischemia/reperfusion and hemorrhagic shock. Blocking individually the selectin family of adhesion molecules with monoclonal antibodies has resulted in better organ function and survival. To our knowledge, there are no studies demonstrating the beneficial effect of multiple selectin blockade with a small molecule inhibitor under conditions of hemorrhagic shock. METHODS: Forty-eight Sprague-Dawley rats were subjected to hemorrhagic shock. Three groups of animals were included (n = 16/group), i.e., the sham, control, and treated groups, which received a small molecule selectin inhibitor (TBC-1269) at 25 mg/kg body weight after the bleeding began. The following parameters were evaluated: fluid requirements during resuscitation, liver injury tests (aspartate aminotransferase, alanine aminotransferase), liver histology and myeloperoxidase, and macrophage inflammatory protein-2 mRNA and cytokine-induced neutrophil chemoattractant mRNA in liver tissue, and animal survival at 3 days. Statistical analysis included Student's t test and analysis of variance when indicated. RESULTS: Significant improvement in liver function and histology was noted in the treated group. Survival was also improved, although it is not known whether liver failure was the most proximate cause of lethality. Infiltration of neutrophils, measured by tissue myeloperoxidase, was significantly decreased in livers of treated animals. No significant changes were noted in fluid requirements. The small molecule selectin inhibitor group showed a down-regulating effect on liver macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant mRNA expression associated with less accumulation of neutrophils in the liver. CONCLUSION: This study supports the role that selectins play in the pathogenesis of hemorrhagic shock. The mechanism of protection seen after multiple selectin blockade (TBC-1269) centered, in part, around the infiltration of liver neutrophils, probably dependent on the induction of macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant mRNA expression in liver tissue.

Postischemic function and protein kinase C signal transduction.

BACKGROUND: The protective effects of myocardial preconditioning may occur by way of multiple mechanisms, with G-protein-mediated protein kinase C (PKC) translocation as a final common pathway. In this study we investigate the pharmacologic induction of preconditioning, by PKC translocation, using PKC agonists/antagonists to reveal its effects on contractile function after myocardial ischemia. METHODS: Langendorff-perfused rabbit hearts received: (1) control; (2) dimethyl sulfoxide (vehicle); (3) acetylcholine (0.55 mmol/L; PKC agonist); (4) 1,2-s,n-dioctanoylglycerol (DOG; 22 mmol/L; PKC agonist); (5) chelerythrine (0.8 mmol/L; PKC antagonist); or (6) DOG-chelerythrine followed by a 2-hour ischemic period, using modified St. Thomas cardioplegia and a 45-minute reperfusion period. The period of ischemia was chosen so as to allow for improvement by appropriate agonists. To observe metabolic changes, tissue nucleotides and nucleosides were measured. Membrane and cytosolic fractions of PKC were determined by an anti-PKC antibody directed against the PKC delta isozyme. Lactate levels and myocardial pH were measured. RESULTS: The PKC agonists DOG and acetylcholine showed the greatest recovery of developed pressure (68% +/- 2%, 60% +/- 9%, respectively). Although pH, lactate, and nucleotide levels were similar between groups at all times, myocyte PKC translocation demonstrated 25% of PKC delta isoforms on cell membrane sites during baseline, which shifted to 67% delta 17% with unprotected ischemia. DOG mimicked this shift with 58% delta 12% of PKC delta isoforms on membranes, which was also blocked by chelerythrine to 35% +/- 7%. CONCLUSIONS: These data demonstrate that PKC translocation results in improved postischemic function, not by alteration of energetics or metabolism, and deserves further investigation.

Reperfusion adequacy and functional recovery.

Ischemic myocardium undergoes many physiologic changes, including alterations in contractile function, histologic condition, and oxygen utilization. Reperfusion of ischemic myocardium may reverse some of these changes; however, the level of reperfusion needed for adequate functional recovery, as opposed to myocyte salvage, remains controversial. This study examines the effects of varying levels of reperfusion following ischemia on functional parameters of recovery. Isolated rabbit hearts were subjected to global ischemia at 37 degrees C for 10, 20, or 45 min. The hearts were reperfused at either mean normal baseline pressure (80 mm Hg), one half baseline (40 mm Hg), or one fourth baseline (20 mm Hg). With reperfusion, although all hearts retained the compensatory metabolic ability to upregulate oxygen extraction, reduction of reperfusion pressure resulted in depression of contractility and myocardial oxygen consumption, especially with low-pressure reperfusion. These findings suggest that all levels of reperfusion are not equal for optimal myocardial functional recovery. As minimal reperfusion may result in persistent stunning of myocardium, other means of enhancing reperfusion, such as percutaneous transluminal coronary angioplasty or coronary artery bypass grafting, should be considered.

Perfluorocarbon supplementation and postischemic cardiac function.

BACKGROUND: During induced ischemia for cardiac surgery inefficient anaerobic energy mechanisms predominate. Sustaining aerobic metabolism with perfluorocarbon-supplemented blood cardioplegia theoretically could lead to improved postischemic recovery. Therefore we studied functional recovery after myocardial ischemia, comparing perflubron (C8F17Br) supplemented blood cardioplegia to standard blood cardioplegia. METHODS: Nineteen dogs underwent 15 minutes of 37 degrees C global ischemia on cardiopulmonary bypass, followed by 90 minutes of cardioplegic arrest by use of blood cardioplegia with or without perflubron and then 30 minutes of 37 degrees C reperfusion. During ischemia myocardial oxygen tension, temperature, and pH were measured. Postischemic left ventricular recovery was assessed by means of preload recruitable stroke work, exponential end-diastolic stress-strain regression, and preservation of adenosine triphosphate and energy charge. RESULTS: The addition of perflubron, a new shorter half-life, lecithin-emulsified perfluorocarbon, provided superior myocardial protection when compared with standard blood cardioplegia. This benefit was evidenced by significantly increased recovery of preload recruitable stroke work slope (71% +/- 8% versus 42% +/- 9%), decreased myocardial edema, and enhanced end ischemic myocardial oxygen and pH levels. CONCLUSIONS: The reliable oxygen delivery system and endothelial-preserving properties of the perfluorocarbons may prove to be an invaluable asset in addition to standard blood cardioplegia in the preservation of postischemic ventricular function. These data support the further investigation of perfluorocarbon-enriched blood cardioplegia.

Early complications and long-term survival in severely obese coronary bypass patients.

Our objective was to describe the short-term morbidity of coronary artery bypass operations and the effect of surgery plus aggressive cardiac rehabilitation on the long-term prognosis of severely obese patients with coronary artery disease. We investigated an inception cohort of 28 consecutive severely obese patients with three-vessel coronary disease followed on average for 51 months. The patients' age, preoperative and postoperative weight, risk factors, and cholesterol were measured. We performed coronary artery bypass surgery, then began aggressive cardiac rehabilitation programs. We recorded intraoperative data, perioperative deaths, complications, readmissions, and lengths of stay. Also, New York Heart classifications and use of anti-anginal or cholesterol-lowering medications were noted. All patients were followed up. Despite high morbidity, long-term function and survival of severely obese CABG patients compares favorably with that of average patients. However, aggressive behavior modification fails to alter their postoperative weight or risk profile, placing them at risk for both second CABG procedures and continued obesity-related disease occurrences.

The regional effect of retrograde cardioplegia in areas of evolving ischemia.

Retrograde cardioplegia (RCP) is often used for myocardial protection during coronary bypass grafting, but the regional effect of RCP in areas of evolving ischemia is unknown. We examined the functional and metabolic indices of regional myocardial preservation following acute coronary occlusion with evolving ischemia in a canine model. Following the institution of 37 degrees C cardiopulmonary bypass in 14 dogs, the left anterior descending artery (LAD) was occluded for 15 min. The hearts were then subjected to 90 min of cardioplegic arrest (12 degrees C, 15 mL/kg every 30 min). Seven had antegrade cardioplegia (ACP) alone, while seven had ACP until arrest, then RCP. No topical cooling was used. The LAD occlusion was released after the first bolus of cardioplegia. Regional temperature and pH were measured in the LAD and circumflex (nonischemic) distributions. After 90 min of ischemia and 30 min of reperfusion, all dogs were weaned from bypass. Postischemic function was determined globally by the return of developed pressure (%dP/dt) and regionally by ultrasonic wall crystals. End-ischemic ATP preservation in the LAD distribution was assessed by HPLC (mm ATP/mg protein). Results show that regional functional and metabolic indices were better maintained with RCP in the ischemic LAD distribution. Although only moderate reduction of global function was seen with ACP, the severe reduction noted in LAD regional wall motion with ACP reflects poor regional protection that can be significantly improved in evolving ischemia with RCP.