Binding to cysteinyl-leukotriene receptors

Feasibility of lung cancer hyperthermia using breathable perfluorochemical (PFC) liquids. Part I: Convective hyperthermia

Clinical studies have shown that hyperthermia in combination with radiotherapy and/or chemotherapy may be effective in the treatment of advanced cancer. No method of lung hyperthermia, however, has been accepted as standard or superior. This investigation sought to demonstrate in animals the thermal and physiologic feasibility of lung hyperthermia induced using heated breathable perfluorochemical (PFC) liquids, a method termed liquid-filled lung convective hyperthermia (LCHT). The ability to use LCHT is rooted in the development of both PFC liquid ventilation, now in clinical development with the PFC perflubron (LiquiVent), and a PFC blood substitute also in late Phase III trials (Oxygent). As LCHT background, the PFC technologies and biology are first reviewed. The physical properties of a variety of PFCs were evaluated for LCHT and it was concluded that more than one liquid is suitable based on such properties. Using total liquid ventilation type devices, LCHT was shown to deliver successfully localized (lobar) lung heating in sheep, and bilateral whole lung heating and whole-body hyperthermia in rabbits, cats and lambs. During LCHT, lung parenchymal temperatures were uniform (<1 degree C) across heated regions. In addition, based on patterns relating lung tissue temperatures to inspiratory and expiratory PFC liquid temperatures in the endotracheal tube, LCHT may minimize invasive thermometry requirements in the lung. Based on acute experiments, it was concluded that LCHT appears feasible and may simplify lung hyperthermia. It was recommended that potentially synergistic combinations of LCHT with other whole-body hyperthermia or local heating modalities, and with chemotherapeutic lung drug delivery, also be explored in the future.

Determination of structure and transcriptional regulation of CYSLTR1 and an association study with asthma and rhinitis

Pharmacologic studies have revealed that cysteinyl leukotrienes (CYSLTs) act through two receptors, cysteinyl leukotriene receptor 1 (CYSLTR1) and CYSLTR2. CYSLTR1 antagonists are widely used to treat asthma and rhinitis. In this study, we characterized the genomic structure and transcriptional regulation of CYSLTR1 and examined associations between CYSLTR1 polymorphisms and asthma/rhinitis. The experiment of rapid amplification of cDNA end revealed that CYSLTR1 contains three exons and that the entire open reading frame is located in exon 3. Reverse transcriptase-polymerase chain reaction showed that there were multiple splice variants of CYSLTR1 and that the transcript expression patterns differed from tissues and cell types. The promoter region of CYSLTR1 is from -665 to -30 bp relative to the transcription start site. We identified four polymorphisms (c.-618-434T/C, c.-618-275C/A, c.-618-136G/A, and 927C/T), and transmission disequilibrium tests revealed that none of these polymorphisms was associated with the development of asthma/rhinitis. However, the TCG and CAA haplotypes in the promoter region caused different transcriptional activity. Our findings indicate that CYSLTR1 polymorphisms are not likely to be involved in the development of asthma/rhinitis, but it is possible that these polymorphisms could influence drug responses in individuals with atopic diseases.

An advanced expiratory circuit for the recovery of perfluorocarbon liquid from non-saturated perfluorocarbon vapour during partial liquid ventilation: an experimental model

Background

The loss of perfluorocarbon (PFC) vapour in the expired gases during partial liquid ventilation should be minimized both to prevent perfluorocarbon vapour entering the atmosphere and to re-use the recovered PFC liquid.

Using a substantially modified design of our previously described condenser, we aimed to determine how much perfluorocarbon liquid could be recovered from gases containing PFC and water vapour, at concentrations found during partial liquid ventilation, and to determine if the amount recovered differed with background flow rate (at flow rates suitable for use in neonates).

Methods

The expiratory line of a standard ventilator circuit set-up was mimicked, with the addition of two condensers. Perfluorocarbon (30 mL of FC-77) and water vapour, at concentrations found during partial liquid ventilation, were passed through the circuit at a number of flow rates and the percentage recovery of the liquids measured.

Results

From 14.2 mL (47%) to 27.3 mL (91%) of the infused 30 mL of FC-77 was recovered at the flow rates studied. Significantly higher FC-77 recovery was obtained at lower flow rates (ANOVA with Bonferroni's multiple comparison test, p < 0.0001). As a percentage of the theoretical maximum recovery, 64 to 95% of the FC-77 was recovered. Statistically significantly less FC-77 was recovered at 5 Lmin^-1 (ANOVA with Bonferroni's multiple comparison test, p < 0.0001). Amounts of perfluorocarbon vapour recovered were 47%, 50%, 81% and 91% at flow rates of 10, 5, 2 and 1 Lmin^-1, respectively.

Conclusion

Using two condensers in series 47% to 91% of perfluorocarbon liquid can be recovered, from gases containing perfluorocarbon and water vapour, at concentrations found during partial liquid ventilation.

A prototype of a liquid ventilator using a novel hollow-fiber oxygenator in a rabbit model

OBJECTIVE

A functional total liquid ventilator should be simple in design to minimize operating errors and have a low priming volume to minimize the amount of perfluorocarbon needed. Closed system circuits using a membrane oxygenator have partially met these requirements but have high resistance to perfluorocarbon flow and high priming volume. To further this goal, a single piston prototype ventilator with a low priming volume and a new high-efficiency hollow-fiber oxygenator in a circuit with a check valve flow control system was developed.

DESIGN

Prospective, controlled animal laboratory study.

SETTING

Research facility at a university medical center.

SUBJECTS

Seven anesthetized, paralyzed, normal New Zealand rabbits

INTERVENTIONS

The prototype oxygenator, consisting of cross-wound silicone hollow fibers with a surface area of 1.5 m2 with a priming volume of 190 mL, was tested in a bench-top model followed by an in vivo rabbit model. Total liquid ventilation was performed for 3 hrs with 20 mL.kg(-1) initial fill volume, 17.5-20 mL.kg(-1) tidal volume, respiratory rate of 5 breaths/min, inspiratory/expiratory ratio 1:2, and countercurrent sweep gas of 100% oxygen.

MEASUREMENTS AND MAIN RESULTS

Bench top experiments demonstrated 66-81% elimination of CO2 and 0.64-0.76 mL.min(-1) loss of perfluorocarbon across the fibers. No significant changes in PaCO2 and PaO2 were observed. Dynamic airway pressures were in a safe range in which ventilator lung injury or airway closure was unlikely (3.6 +/- 0.5 and -7.8 +/- 0.3 cm H2O, respectively, for mean peak inspiratory pressure and mean end expiratory pressure). No leakage of perfluorocarbon was noted in the new silicone fiber gas exchange device. Estimated in vivo perfluorocarbon loss from the device was 1.2 mL.min(-1).

CONCLUSIONS

These data demonstrate the ability of this novel single-piston, nonporous hollow silicone fiber oxygenator to adequately support gas exchange, allowing successful performance of total liquid ventilation.

A novel expiratory circuit for recovery of perfluorocarbon liquid during partial liquid ventilation

OBJECTIVE

To determine whether perfluorocarbon liquid can be condensed from gases containing perfluorocarbon vapour and whether the amount recovered varies with background flow rate.

DESIGN AND SETTING

Bench-top experimental study in a neonatal laboratory.

INTERVENTIONS

The expiratory limb of a standard ventilator circuit set-up was mimicked, with the addition of a chilled water jacket (Liebig) condenser. Perfluorocarbon vapour was passed through the circuit at a number of flow rates.

MEASUREMENTS AND RESULTS

Perfluorocarbon vapour was passed through the circuit and the percentage recovery of liquid measured. More than 60% of the perfluorocarbon vapour was recovered at all flow rates (1, 2, 5 and 10 l/min), with significantly higher recovery obtained (up to 74%) at low flow rates (1 l/min).

CONCLUSIONS

Using a simple condenser, more than 60% of perfluorocarbon liquid can be recovered without altering the function of an expiratory limb of a ventilator circuit.

Cysteinyl leukotriene receptors

Cysteinyl leukotrienes (CysLTs) are important inflammatory mediators in asthma and allergic disorders. Two types of CysLT receptors, CysLT(1) and CysLT(2), which were originally defined pharmacologically based on their sensitivity to CysLT(1) specific antagonists, are responsible for most of the known CysLT biological actions. The regulation of CysLT receptor expression and signaling in disease processes is largely unclear. Recent molecular cloning of both receptor subtypes from several different species will greatly facilitate future research in understanding CysLT signal transduction mechanisms. Expression of the relatively better-studied CysLT(1) is verified in lung tissues and peripheral blood cells. Elucidating how this receptor mediates airway inflammation will deepen our understanding of asthma etiology. On the other hand, detection of CysLT(2) in the heart, brain, and adrenal glands will inject new excitement into the search for novel CysLT functions. This review summarizes receptor cloning, ligand binding, expression, signaling, and functions in an effort to bridge early pharmacological studies to future studies at the molecular level.

Support of respiratory failure in the pediatric surgical patient

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances in the understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for supporting children and adults with severe respiratory failure. This review will focus on recent laboratory and clinical data regarding the techniques of lung protective ventilator strategies, inhaled nitric oxide, liquid ventilation, and extracorporeal life support (ECLS, ECMO). Some of these modalities are commonplace, while others may have much to offer the pediatric clinician if their benefit is clearly demonstrated in future clinical trials.

Levels of cysteinyl leukotriene receptor mRNA in human peripheral leucocytes: significantly higher expression of cysteinyl leukotriene receptor 2 mRNA in eosinophils

BACKGROUND

Cysteinyl leukotrienes (CysLTs) have been implicated as important contributors in the pathophysiology of asthma and their biological effects are mediated by at least two distinct G-protein-coupled receptors. cDNA sequences of cysteinyl leukotriene receptor 1 (CysLTR1) and cysteinyl leukotriene receptor 2 (CysLTR2) have recently been elucidated.

OBJECTIVES

Our aim is to explore gene expression and the comparative expression of CysLTR1 mRNA and CysLTR2 mRNA in human peripheral blood leucocytes.

METHODS

Gene expression of CysLTR1 and CysLTR2 mRNAs in human peripheral blood eosinophils, neutrophils, monocytes and T lymphocytes has been measured by competitive reverse transcription-polymerase chain reactions using RNA or DNA competitors.

RESULTS

(a) When cellular levels of CysLTR1 mRNA were normalized to those of G3PDH mRNA, the relative concentration of CysLTR1 mRNA in eosinophils (43.8 +/- 37.2, n = 29) was significantly higher than that in neutrophils (18.7 +/- 23.3, n = 11), monocytes (0.93 +/- 1.1, n = 10) and T lymphocytes (3.4 +/- 2.4, n = 11). (b) When measured using each DNA competitor, mRNAs for both types of CysLTR coexisted in each type of leucocyte. The ratio of CysLTR1 mRNA to CysLTR2 mRNA was significantly lower in eosinophils (0.65 +/- 0.42, n = 12) than in neutrophils (6.9 +/- 4.9, n = 12), monocytes (1.8 +/- 0.9, n = 10) and T lymphocytes (4.5 +/- 5.7, n = 10). (c) Human umbilical vein endothelial cells expressed CysLTR2 mRNA, but not CysLTR1 mRNA.

CONCLUSION

These studies reveal that CysLTR1 mRNA and, in particular, CysLTR2 mRNA are abundantly expressed at high levels in eosinophils, raising the possibility that CysLTR2 may have an important physiological role in eosinophils and a CysLTR2 antagonist may be a good target for preventing signal transduction by CysLTs in eosinophils.

The action of cysteinyl-leukotrienes on intracellular calcium mobilization in human detrusor myocytes

OBJECTIVE

To investigate the presence of leukotriene D4 receptors in fura-2-loaded human detrusor smooth muscle cells (DSMCs) by examining the ability of leukotriene D4 to raise intracellular-free Ca2+ concentration ([Ca2+]i), to determine the origin of the leukotriene D4-mediated rise in [Ca2+]i and to investigate whether the specific leukotriene D4 receptor antagonist montelukast inhibits the Ca2+ response induced by leukotriene D4.

MATERIALS AND METHODS

Detrusor muscle biopsies were obtained from patients with benign noninvasive bladder diseases undergoing cystoscopy. DSMCs were isolated using an explant technique and maintained in culture. Only primary cultures or cells passaged up to three times were used for experiments. DSMCs were characterized with immunohistochemical staining and their identity confirmed by transmission electron microscopy. [Ca2+]i was measured in single DSMCs using the Ca2+ probe fura-2 and fluorescence-ratio microscopy.

RESULTS

Immunohistochemical staining showed that 80-99% of the cells were positive for smooth muscle alpha-actin. The ultrastructural features of the cultured cells were those of smooth muscle cells and showed no differentiation in a fibroblastic or myofibroblastic direction. Leukotriene D4 increased the level of [Ca2+]i in a dose-dependent manner. Calcium was mobilized almost exclusively from intracellular Ca2+ stores. There was a dose-dependent inhibition of the increase in [Ca2+]i by montelukast.

CONCLUSION

The present study is the first to show the presence of specific leukotriene D4 receptors in human detrusor myocytes. This may have implications for a potential pathophysiological role of leukotriene D4 in patients with interstitial cystitis and other functional or inflammatory bladder disorders.

Roles of prostaglandins and leukotrienes in acute inflammation caused by bacterial infection

Prostanoids, including prostaglandins and thromboxanes, are generated by the phospholipase A2/cyclooxygenase pathway, and leukotrienes are generated by the 5-lipoxygenase pathway from arachidonic acid. At physiological concentrations, vasodilator prostaglandins enhance the vascular permeability effects of histamine and bradykinin, and leukotrienes are important mediators of leukocyte accumulation during acute inflammation. On the other hand, prostaglandin metabolites such as cyclopentenone prostaglandins contribute to the resolution of acute inflammation through inhibition of nuclear factor-kappaB activation. Thus, arachidonic acid oxygenation products mediate diverse effects that induce and resolve acute inflammation caused by bacterial infection.

Role of ventilation strategy on perfluorochemical evaporation from the lungs

To study the effect of ventilation strategy on perfluorochemical (PFC) elimination profile (evaporative loss profile; E(L)), 6 ml/kg of perflubron were instilled into anesthetized normal rabbits. The strategy was to maintain minute ventilation (VE, in ml/min) in three groups: VE(L) (low-range VE, 208 +/- 2), VE(M) (midrange VE, 250 +/- 9), and VE(H) (high-range VE, 293 +/- 1) over 4 h. In three other groups, respiratory rate (RR, breaths/min) was controlled at 20, 30, or 50 with a constant VE and adjusted tidal volume. PFC content in the expired gas was measured, and E(L) was calculated. There was a significant VE- and time-dependent effect on E(L.) Initially, percent PFC saturation and loss rate decreased in the VE(H) > VE(M) > VE(L) groups, but by 3 h the lower percent PFC saturation resulted in a loss rate such that VE(H) < VE(M) < VE(L) at 4 h. For the groups at constant VE, there was a significant time effect on E(L) but no RR effect. In conclusion, E(L) profile is dependent on VE with little effect of the RR-tidal volume combination. Thus measurement of E(L) and VE should be considered for the replacement dosing schemes during partial liquid ventilation.