Mycoplasma pneumoniae induces airway epithelial cell expression of MUC5AC in asthma.

As excess mucin expression can contribute to the exacerbation of asthma, the present authors hypothesised that Mycoplasma pneumoniae significantly induces MUC5AC (the major airway mucin) expression in airway epithelial cells isolated directly from asthmatic subjects. A total of 11 subjects with asthma and six normal controls underwent bronchoscopy with airway brushing. Epithelial cells were cultured at an air-liquid interface and incubated with and without M. pneumoniae for 48 h, and in the presence and absence of nuclear factor (NF)-kappaB and a toll-like receptor (TLR)2 inhibitor. Quantitative PCR was performed for MUC5AC and TLR2 mRNA. MUC5AC protein and total protein were determined by ELISA. M. pneumoniae exposure significantly increased MUC5AC mRNA and protein expression after 48 h in epithelial cells isolated from asthmatic, but not from normal control subjects, at all concentrations as compared to unexposed cells. TLR2 mRNA expression was significantly increased in asthmatic epithelial cells at 4 h compared with unexposed cells. NF-kappaB and TLR2 inhibition reduced MUC5AC expression to the level of the unexposed control in both groups. Mycoplasma pneumoniae exposure significantly increased MUC5AC mRNA and protein expression preferentially in airway epithelial cells isolated from asthmatic subjects. The toll-like receptor 2 pathway may be involved in this process.

Zileuton: clinical implications of 5-Lipoxygenase inhibition in severe airway disease.

The 5-Lipoxygenase pathway results in the formation of leukotrienes, including leukotriene B(4) (LTB(4)), 5-oxo-6E,8Z,11Z,14Z-eicosatetranoic acid and the cysteinyl leukotrienes (LTC(4), LTD(4) and LTE(4)) and activates all four leukotriene receptors, BLT1, BLT2, cysLT(1) and cysLT(2). Zileuton is the only commercially available inhibitor of the 5-Lipoxygenase pathway. In a number of clinical trials, zileuton has been shown to improve airway function and inflammation, asthma symptom control and quality of life in asthmatics. Given the important role that leukotrienes play in airway inflammation, zileuton provides an additional therapeutic option in the management of chronic, persistent asthma, particularly those asthmatics with more severe disease. In addition, zileuton has shown promise in a number of other conditions, including upper airway inflammatory conditions, dermatological disease and chronic obstructive pulmonary disease. The development of new formulations, including a controlled release tablet formulation for b.i.d. dosing and an intravenous preparation for acute asthma exacerbations may enhance clinical utility and expand therapeutic indications.

Tricyclic antidepressants directly depress human myocardial mechanical function independent of effects on the conduction system.

OBJECTIVES: To measure the effect of tricyclic antidepressant drugs (TCAs) on human myocardial contractility. METHODS: Human atrial tissue was obtained during cardiac bypass surgery. The tissue was harvested, suspended in a Tyrode buffer at 37 degrees C, and perfused with a 95%/5% oxygen-carbon dioxide mixture. Developed force was continuously measured using a force transducer and recorded by computer. After an equilibration period, escalating doses of amitriptyline or desipramine were added to the bath. All strips were exposed to the following five concentrations of each drug: 0 (control) 0.4, 4, 40, and 400 microM. The results for each experiment were expressed as the difference between the developed force measured prior to the addition of each concentration of drug and the developed force measured after a 30-minute exposure to the drug. RESULTS: Desipramine decreased the developed force by 27%, 49%, and 74% at concentrations of 0.4, 40, and 400 microM, respectively. Amitriptyline decreased the developed force by 38% at the 40-microM concentration and by 89% at the 400-microM concentration. Untreated strips retained 94% of baseline developed force at 150 minutes. CONCLUSIONS: Tricyclic antidepressants depress human myocardial function in a dose-dependent fashion independent of the effects on the cardiac conduction system. While previous work has demonstrated the effect of therapies for the reversal of impaired cardiac conduction following TCA poisoning, to the best of the authors' knowledge, no reports have documented the effects of therapy on direct myocardial depression. Additional therapies targeted at reversing the direct cardiodepressive effects of TCA may improve outcome following TCA poisoning.

Attenuation of verapamil-induced myocardial toxicity in an ex-vivo rat model using a verapamil-specific ovine immunoglobin.

OBJECTIVE: To determine whether an ovine verapamil-specific immunoglobin G (V-IgG) attenuates verapamil toxicity in an ex-vivo rat left ventricular papillary muscle model. METHODS: The authors dissected left ventricular papillary muscle strips from male Sprague-Dawley rats (350-410 g) and suspended them in an oxygen-perfused Tyrode buffer bath at 37.5 degrees C. Muscle strips equilibrated for 90 minutes under electrical stimulation of 1 Hz. Resting and developed tension (mg) were monitored continuously. A concentration-response trial was performed with verapamil concentrations ranging from 31 to 1,020 nM; 510 nM produced consistent reduction in developed tension. A trial of V-IgG was then conducted by administering the following treatments to papillary muscle strips in a randomized manner: V-IgG + 510 nM verapamil, nonspecific ovine IgG (N-IgG) + 510 nM verapamil (protein control), and 510 nM verapamil alone. Immunoglobin G was administered in equimolar concentrations to verapamil. Attenuation was expressed as inhibition of the verapamil-induced reduction of developed tension. RESULTS: The V-IgG comparative trial indicated the V-IgG + verapamil treatment had a mean reduction in developed tension of 14.1% (SD +/- 12.2) compared with 36.2% (SD +/- 14.9) for N-IgG + verapamil and 34.9% (SD +/- 8.1) for verapamil alone (p < 0.05). There was no difference between the two control groups. CONCLUSION: Verapamil-specific IgG attenuated verapamil-induced reduction of developed tension in an ex-vivo rat model.

Calcium neutralizes fluoride bioavailability in a lethal model of fluoride poisoning.

OBJECTIVES: Acute systemic fluoride poisoning can result in systemic hypocalcemia, cardiac dysrhythmias, and cardiovascular collapse. Topical and intraarterial therapy with calcium or magnesium salts reduces dermal injury from fluoride burns. The mechanism of these therapies is to bind and inactivate the fluoride ion. The purpose of this study is to evaluate the effect of calcium and magnesium to decrease the bioavailability of fluoride in a lethal model of fluoride poisoning. METHODS: In preliminary studies, we determined that fluoride 3.6 mM/kg intraperitoneally in the form of sodium fluoride was uniformly and rapidly fatal in a mouse model. Using this fluoride dose, we performed a controlled, randomized, blinded study of low- and high-dose calcium chloride (1.8 and 3.6 mM/kg intraperitoneally, respectively) and magnesium sulfate (3.6 mM/kg intraperitoneally) to decrease the bioavailability of the fluoride ion. After injection with sodium fluoride, animals were immediately treated with injections of sodium chloride (control), calcium chloride (low- or high-dose), or magnesium sulfate. The major outcome was 6-hour survival using a Cox Proportional Hazard model. RESULTS: All untreated animals died within 60 minutes. Using a Cox Proportional Hazard model, each 1.8 mM/kg dose of calcium chloride administered reduced the risk of death by 33%. Magnesium sulfate treatment was not associated with a hazard reduction. CONCLUSION: Calcium chloride administered simultaneously with sodium fluoride reduces the bioavailability of fluoride poisoning in a mouse model. The equivalent dose of magnesium sulfate does not significantly decrease fluoride bioavailability.

Rude unhinging of the machinery of life: metabolic approaches to hemorrhagic shock.

In 1862, Samuel Gross described shock as the "rude unhinging" of the machinery of life. As noted above, adequate oxygen delivery and metabolism are essential to the maintenance of cellular energy stores. Failure of adequate tissue oxygen delivery and utilization during shock can lead to organ dysfunction and death. Hemorrhagic shock after trauma can result in inherent mitochondrial dysfunction as manifested by decoupling. This pathologic condition has been recently termed cytopathic hypoxia. Since mitochondria are the ultimate consumer of oxygen in cells, mitochondria might indeed be the machinery of life rudely unhinged by shock. Yet, therapeutic strategies have been recently developed to support mitochondrial function in shock and related states. If these therapeutic interventions directed towards organelle and cellular resuscitation are proven to enhance human organ function and improve survival, then these strategies could augment current therapeutic regimens directed exclusively towards hemodynamic and ventilatory homeostasis.

Bench to bedside: tumor necrosis factor-alpha: from inflammation to resuscitation.

Proinflammatory mediators such as tumor necrosis factor-alpha (TNF) have been implicated in the pathophysiology in a number of acute disease states. Tumor necrosis factor-alpha can contribute to cell death, apoptosis, and organ dysfunction. Tumor necrosis factor-alpha can be generated with sepsis or ischemia-reperfusion by activation of cell mitogen-activated protein kinases and nuclear factor kappa B, leading to TNF production. A number of strategies to modulate TNF have been recently explored, including factors directed toward mitogen-activated protein kinases, TNF transcription, anti-inflammatory ligands, heat shock proteins, and TNF-binding proteins. However, TNF may also play an important role in the adaptive response to injury and inflammation. Control of the deleterious effects of TNF and other proinflammatory cytokines represents a realistic goal for clinical emergency medicine. The purpose of this article is to provide a background of relevance to emergency medicine academicians on the production and regulation of TNF, the acute effects of TNF on pathophysiology, and the rationale for therapeutic interventions directed toward TNF and the clinical experience with these strategies.

Hyperkalemia and ionized hypocalcemia during cardiac arrest and resuscitation: possible culprits for postcountershock arrhythmias?

STUDY OBJECTIVE: Early countershock of ventricular fibrillation (VF) has been shown to improve immediate and long-term outcome of out-of-hospital cardiac arrest. However, studies indicate that countershock of prolonged VF most commonly results in asystole or a nonperfusing bradyarrhythmia (pulseless electrical activity [PEA]), which rarely respond to current therapy. The cause of these postcountershock rhythm disturbances is not well understood but may be related to electrical injury of the globally ischemic myocardium or to local metabolic abnormalities that impair impulse formation and cardiac contraction. The purpose of this study was to evaluate changes in serum potassium and free calcium homeostasis during cardiac arrest and advanced cardiac life support (ACLS) interventions. METHODS: After sedation, intubation, anesthesia, and instrumentation, VF was induced in 13 dogs. After 7.5 minutes of VF, animals were immediately countershocked, standard closed-chest CPR was initiated, and epinephrine was administered (1 mg in repeated doses if necessary). RESULTS: Ten animals could not be resuscitated despite 20 minutes of ACLS interventions. In these animals, a progressive increase in serum potassium was observed from the onset of ACLS to the termination of resuscitation efforts (4.3+/-.6 to 6.0+/-.8 mEq/L, P<.01). A significant increase was observed within 10 minutes of beginning ACLS measures. This was accompanied by a decrease in ionized calcium concentration over the same period (4.95+/-.40 to 3.44 mg/dL, P<.01). The decrease in ionized calcium was significant within 5 minutes of ACLS interventions. Nine of these 10 animals had either postcountershock asystole or PEA at the termination of resuscitative efforts. The increase in potassium was not related to acidemia. Successfully resuscitated animals did not demonstrate these electrolyte changes. CONCLUSION: Ionized hypocalcemia and hyperkalemia occur during prolonged resuscitative efforts and may be related to dysfunctional transcellular ionic transport mechanisms. These cations play important roles in cardiac electrical and contractile activity and may play a role in refractory postcountershock rhythm disturbances.

Clinical implications of hemoglobin as a nitric oxide carrier.

Hemoglobin is perhaps the most intensively studied of the biologically important molecules. Much is known of its structure, its function, and its regulation. In addition to well-characterized processes of oxygen, carbon dioxide, and carbon monoxide transport, new data suggest a key role of hemoglobin as a carrier of nitric oxide. In this review, we describe the basis of this interaction, as well as its clinical relevance to such problems as acute respiratory distress syndrome, percutaneous transluminal coronary angioplasty, and transplant allograft survival.

Ischemic preconditioning attenuates functional, metabolic, and morphologic injury from ischemic acute renal failure in the rat.

Ischemic preconditioning has been shown to ameliorate injury due to subsequent ischemia in several organs. However, relatively little is known about preconditioning and the kidney. To address this, rats were randomized to control (C, N = 14), 2 min of ischemic preconditioning (P2 N = 10), 3 periods of 2 min of ischemia separated by 5 min periods of reflow (P2,3 N = 7), or three 5 min periods of ischemia separated by 5 min of reflow (P5,3 N = 6) prior to 45 min of bilateral renal ischemia followed by 24 hours of reperfusion. We observed a lower serum creatinine after 24 hours of reflow in P2, P2, 3 but not P5, 3 rats compared with C. Histology was examined in the C and P2, 3 groups and demonstrated less severe injury in the P2, 3 group. To gain insight into the mechanism by which preconditioning ameliorated ischemic injury, we performed near IR spectroscopy and 31P NMR spectroscopy. Based on near IR spectroscopy, the P2, 3 group had closer coupling of cytochrome aa3 redox state with that of hemoglobin during reflow. In the 31P NMR studies, the changes in ATP and pHi were similar during ischemia, but the P2, 3 group recovered ATP and pHi faster than C. These data suggest that ischemic preconditioning may ameliorate ischemic renal injury as assessed by functional, metabolic and morphological methods. The mechanism(s) by which this occurs requires additional study.

Hemoglobin-based oxygen carriers: development and clinical potential.

This article addresses issues involved in the development of hemoglobin-based oxygen carriers and provides a focused overview of the 4 hemoglobin-based oxygen carriers with emergency medicine application currently in clinical trials.

Hemodynamic effects of repeated doses of epinephrine after prolonged cardiac arrest and CPR: preliminary observations in an animal model.

STUDY PURPOSE: To assess the hemodynamic response to repeated doses of epinephrine (EPI) in an animal model of prolonged cardiac arrest and CPR. DESIGN: Basic laboratory investigation. Fourteen canines were subjected to electrically induced ventricular fibrillation (VF) followed by 7.5 min of VF without CPR. INTERVENTIONS: After 7.5 min of VF, manual closed-chest CPR (80-100 compressions per minute, compression to ventilation ratio 8:1) was initiated. Countershocks were performed, recommended advanced cardiac life support drugs were given, and CPR was continued until restoration of spontaneous circulation (ROSC) or for 20 min. Epinephrine, 1 mg (approximately 0.04 mg kg(-1)), was administered when indicated and at recommended time intervals. METHODS: Aortic and right atrial pressures were measured with micromanometer catheters before and after EPI, and CPR coronary perfusion pressure (CPP) was calculated (CPR diastolic aortic to right atrial pressure difference). Survival was defined as maintenance of ROSC for 30 min. RESULTS: Countershocks after 7.5 min resulted in asystole in ten animals and persistant VF in four. In those animals successfully resuscitated (n = 3), the change in CPP was 21 +/- 11 mm Hg after the first dose of EPI. Only one animal required a second dose of EPI. The majority of the study group (n = 11) could not be resuscitated. The increase in CPP after EPI averaged only 3 +/- 2 mm Hg and subsequent doses produced no significant effect on CPP (2 +/- 4 mm Hg). CONCLUSIONS: The hemodynamic response to the first dose of EPI determines if the critical CPP needed for ROSC and survival will occur. Repeat doses of EPI do not appear to improve CPP to a degree to affect clinically meaningful measures of outcome, i.e., successful countershock and survival.

Mitochondrial oxidative phosphorylation thermodynamic efficiencies reflect physiological organ roles.

Mitochondria cannot maximize energy production, efficiency, and the cellular ATP phosphorylation potential all at the same time. The theoretical and observed determinations of coupling of oxidative phosphorylation in mitochondria from rat liver, heart, and brain were compared using classical and nonequilibrium thermodynamic measures. Additionally, the optimal thermodynamic efficiency and flow ratios were determined for control of the two energy-converting complexes of the respiratory chain: complex I (NADH), which reflects the integrated cellular pathway, and complex II (FADH2), the predominantly tricarboxylic acid (TCA) cycle pathway. For all three organs, the cellular respiratory pathway was more tightly coupled than the TCA pathway and resulted in a greater optimal efficiency. Liver mitochondria are the most thermodynamically efficient at ATP production using oxidative phosphorylation. Heart and brain mitochondrial systems utilize more oxygen, but can produce ATP at a faster rate than liver systems. Per the theory of economic degrees of coupling, isolated rat liver mitochondrial systems are designed for the economic production of ATP for use in cellular processes. In the brain, the mitochondrial TCA cycle pathway promotes the maximal maintenance of the cellular energy state for cellular viability, whereas in the heart the TCA cycle pathway maximizes the production of ATP. The coupling of oxidative phosphorylation not only can be expected to change with substrate availability but may also reflect an ontogenetic response of mitochondria to fit specific organ roles in the rat.

Development of new methods to assess the outcomes of emergency care.

This article provides information supporting the need for new outcome measures in emergency care. It also addresses the use of these measures in emergency care, the impact of emergency care, identification of at-risk groups, new approaches to measuring patient satisfaction, quality of life, and cost-effectiveness, and the related unique implications for emergency medicine.

Postischemic administration of succinate reverses the impairment of oxidative phosphorylation after cardiac ischemia and reperfusion injury.

BACKGROUND: Ischemia and reperfusion (IR) can lead to impaired myocardial mechanical function and inhibition of key metabolic enzyme systems after IR. In this study, we sought to identify the postischemic lesion in oxidative phosphorylation and hypothesized that selective substrate repletion would restore mitochondrial metabolic function during reperfusion. METHODS AND RESULTS: Isolated rat hearts were subjected to global ischemia (25 minutes; 37 degrees C) and reperfusion (40 minutes). Left ventricular developed pressure (LVDP) and the cytochrome a,a3 redox state (near infrared spectroscopy) were continuously monitored. Oxygen consumption was measured for the NADH (mitochondrial complex I) and FADH2 (complex II) pathways in both the resting and maximal ADP-stimulated states. Myocellular oxidative phosphorylation capacity was measured using an NADPH-linked assay specific for mitochondrial ATPase. The hearts were randomized to either succinate (200 micromol/L) or control for the first 5 minutes of reperfusion after ischemia. IR in the control group resulted in an impairment of NADH (complex I) oxidative phosphorylation capacity (1.4+/-0.4 versus control 3.9+/-0.6 nmol ATP/min/mg) and depressed LVDP (49+/-3% of baseline; P<.05). The oxidative phosphorylation capacity for the succinate-using FADH2 pathway remained intact (2.6+/-0.3 versus 2.4+/-0.4). Postischemic succinate administration enhanced LVDP recovery after IR (89+/-8% of baseline; P<.05). Diminished electron transport resulted in depletion of electrons from cytochrome a,a3 during ischemia and early reperfusion, which was reversed by providing succinate as substrate. CONCLUSIONS: Cardiac ischemia and reperfusion results in a defect at mitochondrial complex I but not complex II. Cytochrome a,a3 undergoes anomalous oxidation during ischemia. Postischemic administration of succinate infusion restores the cytochrome a,a3 redox state balance and myocardial function after IR.