Synthesis and release of platelet-activating factor and eicosanoids in human endothelial cells induced by different agonists

Endothelial cells in allograft rejection

In organ transplantation, blood borne cells and macromolecules (e.g., antibodies) of the host immune system are brought into direct contact with the endothelial cell lining of graft vessels. In this location, graft endothelial cells play several roles in allograft rejection, including the initiation of rejection responses by presentation of alloantigen to circulating T cells; the development of inflammation and thrombosis; and as targets of injury and agents of repair.

Endothelial cells in allograft rejection

In organ transplantation, blood borne cells and macromolecules (e.g., antibodies) of the host immune system are brought into direct contact with the endothelial cell lining of graft vessels. In this location, graft endothelial cells play several roles in allograft rejection, including the initiation of rejection responses by presentation of alloantigen to circulating T cells; the development of inflammation and thrombosis; and as targets of injury and agents of repair.

IL-4 primes human endothelial cells for secondary responses to histamine

Interleukin-4 (IL-4) is a multifunctional cytokine, which is involved in numerous disease states, including atopic asthma. IL-4 not only induces direct responses in cells but can also prime for secondary responses to stimuli. Little is known about the priming effects of IL-4 on endothelial cells; therefore, we chose to examine the ability of IL-4 to prime endothelial cells for platelet-activating factor (PAF) synthesis and prostaglandin E(2) (PGE(2)) release. IL-4 alone did not enhance PAF synthesis or PGE(2) release; however, pretreatment with IL-4 primed for PAF synthesis and PGE(2) release in response to subsequent stimulation with histamine. In contrast, tumor necrosis factor alpha (TNF-alpha), oncostatin M (OSM), and IL-1beta did not prime endothelial cells for PAF synthesis in response to histamine. The priming effects of IL-4 occurred without any detectable changes in the requirement for signaling pathways upstream of PGE(2) release. IL-4 treatment increased the expression of mRNA for histamine receptor 1 (HR1) and shifted the inhibition curve for pyrilamine, a specific HR1 antagonist. In addition, the dose-response curve for histamine-induced elevations in intracellular calcium was shifted following IL-4 stimulation. Together, these data indicate that HR1 is up-regulated in IL-4-stimulated human umbilical vein endothelial cells (HUVEC) and suggest that this up-regulation may contribute to the enhanced responsiveness of IL-4-stimulated HUVEC to histamine.

Perindopril augments ecto-ATP diphosphohydrolase activity and enhances endothelial anti-platelet function in human umbilical vein endothelial cells

OBJECTIVES

Recent clinical trials have demonstrated that angiotensin-converting enzyme inhibitors (ACEIs) reduce thrombotic events by unknown mechanisms in patients with atherosclerotic cardiovascular diseases.

DESIGN

We studied the in-vitro effects of perindopril, an ACEI, on the ability of human umbilical vein endothelial cells (HUVEC) to inhibit platelet aggregation.

METHODS

Platelet aggregation in the presence of HUVEC and endothelial surface expression and activities of ecto-ATP diphosphohydrolase (ecto-ADPase), CD39, were determined. The capability of HUVEC to release prostacyclin and nitric oxide (NO) was also investigated.

RESULTS

Perindoprilat (an active metabolite of perindopril) significantly enhanced the surface expression and activities of ecto-ADPase and prostacyclin release, resulting in enhancement of ability to inhibit platelet aggregation by HUVEC. These effects of perindoprilat were also observed in HUVEC activated by tumour necrosis factor (TNF)-alpha, which increased the expression of intracellular adhesion molecule-1 (ICAM-1), CD54, and, despite up-regulation of prostacyclin release, attenuated endothelial anti-platelet properties by decreasing ecto-ADPase activity. Perindoprilat partially restored this capability, but failed to reduce enhanced expression of ICAM-1. By contrast, the role of NO as a platelet inhibitor appeared minimal in HUVEC. Candesartan, an angiotensin II receptor (AT(1)) blocker, did not affect endothelial anti-platelet property.

CONCLUSIONS

Perindoprilat was found to augment endothelial capability to inhibit platelet aggregation by increasing ecto-ADPase activity and prostacyclin release in HUVEC. This beneficial effect of perindoprilat appeared to be preserved in the activated cells exposed to TNF-alpha, although no evidence was found to support that it could reverse the inflammation process induced by cytokines.

Effect of sevoflurane on human neutrophil apoptosis

BACKGROUND AND OBJECTIVE

Both chronic occupational exposure to volatile anaesthetic agents and acute in vitro exposure of neutrophils to isoflurane have been shown to inhibit the rate of apoptosis of human neutrophils. It is possible that inhibition of neutrophil apoptosis arises through delaying mitochondrial membrane potential collapse. We assessed mitochondrial depolarization and apoptosis in unexposed neutrophils and neutrophils exposed to sevoflurane in vivo.

METHODS

A total of 20 mL venous blood was withdrawn pre- and postinduction of anaesthesia, the neutrophils isolated and maintained in culture. At 1, 12 and 24 h in culture, the percentage of neutrophil apoptosis was assessed by dual staining with annexin V-FITC and propidium iodide. Mitochondrial depolarization was measured using the dual emission styryl dye JC-1.

RESULTS

Apoptosis was significantly inhibited in neutrophils exposed to sevoflurane in vivo at 24 (exposed: 38 (12)% versus control: 28 (11)%, P = 0.001), but not at 1 or 12 h, in culture. Mitochondrial depolarization was not delayed in neutrophils exposed to sevoflurane.

CONCLUSIONS

The most important findings are that sevoflurane inhibits neutrophil apoptosis in vivo and that inhibition is not mediated primarily by an effect on mitochondrial depolarization.

Opioid-induced respiratory depression is associated with increased tidal volume variability

BACKGROUND AND OBJECTIVE

mu-agonistic opioids cause concentration-dependent hypoventilation and increased irregularity of breathing. The aim was to quantify opioid-induced irregularity of breathing and to investigate its time-course during and after an opioid infusion, and its ability to predict the severity of respiratory depression.

METHODS

Twenty-three patients breathing spontaneously via a continuous positive airway pressure (CPAP) mask received an intravenous (i.v.) infusion of alfentanil (2.3 microg kg(-1) min(-1), 14 patients) or pirinitramide (piritramide) (17.9 microg kg(-1) min(-1), nine patients) until either a cumulative dose of 70 microg kg(-1) for alfentanil or 500 microg kg(-1) for pirinitramide had been achieved or the infusion had to be stopped for safety reasons. Tidal volumes (VT) and minute ventilation were measured with an anaesthesia workstation. For every 20 breaths, the quartile coefficient was calculated (Qeff20V(T)).

RESULTS

Both the decrease of minute volume and the increase of Qeff20V(T) during and after opioid infusion were highly significant (P < 0.001, ANOVA). Patients in which the alfentanil infusion had to be terminated prematurely had lower minute volumes (P = 0.002, t-test) and higher Qeff20V(T) (P = 0.034, t-test) than those who received the complete dose. Changes in the regularity of breathing measured as Qeff20V(T) parallel those of minute ventilation during and after opioid infusion.

CONCLUSIONS

Opioids cause a more complicated disturbance of the control of respiration than a mere resetting to higher PCO2. Furthermore, Qeff20V(T) appears to predict the severity of opioid-induced respiratory depression.

Intravenous patient-controlled analgesia after thoracotomy: a comparison of morphine with tramadol

BACKGROUND AND OBJECTIVE

This study examined the quality of analgesia together with the side-effects produced by tramadol compared with morphine using intravenous patient-controlled analgesia during the first 24 h after thoracotomy.

METHODS

Forty-four patients scheduled for thoracotomy were included in the study. Morphine 0.3 mg kg(-1) was given interpleurally 20 min before a standard general anaesthetic. In the postanaesthetic care unit, the patients were randomly allocated to one of two groups to self-administer tramadol or morphine using a patient-controlled analgesia device throughout a 24 h period. The patient-controlled analgesia device was programmed to deliver tramadol 20 mg as an intravenous bolus or morphine 2 mg with a lockout time of 10 min.

RESULTS

Mean cumulative morphine and tramadol consumption were 48.13 +/- 30.23 and 493.5 +/- 191.5 mg, respectively. There was no difference in the quality of analgesia between groups. Five (26.3%) patients in the tramadol group and seven (33%) in the morphine group had nausea, and three of the latter patients vomited. The incidence rate of vomiting with tramadol was 5.2%. All vital signs were within safe ranges. Sedation was less in the tramadol group, but not statistically significant.

CONCLUSIONS

In this clinical setting, which includes interpleural morphine pre-emptively, postoperative analgesia provided by tramadol was similar to that of morphine at rest and during deep inspiration. Side-effects were slight and comparable between the patients receiving morphine and tramadol.

Neural nets and prediction of the recovery rate from neuromuscular block

BACKGROUND AND OBJECTIVE

The aim was to train artificial neural nets to predict the recovery of a neuromuscular block during general anaesthesia. It was assumed that the initial/early neuromuscular recovery data with the simultaneously measured physical variables as inputs into a well-trained back-propagation neural net would enable the net to predict a rough estimate of the remaining recovery time.

METHODS

Spontaneous recovery from neuromuscular block (electrically evoked electromyographic train-of-four responses) were recorded with the following variables known to affect the block: multiple minimum alveolar concentration, end-tidal CO2 concentration, and peripheral and central temperature.

RESULTS

The mean prediction errors, mean absolute prediction errors, root-mean-squared prediction errors and correlation coefficients of all the nets were significantly better than those of average-based predictions used in the study. The root-mean-squared prediction error of the net - employing minimum alveolar concentrations from the whole recovery period (the recovery time from E2/E1 = 0.30 to E4/E1 = 0.75; E1 = first response of train-of-four, E2 = second response of train-of-four, etc.)--were significantly smaller than those of other nets, or the same net employing minimum alveolar concentrations only from the initial recovery period (from E2/E1 = 0.30 to E4/E1 = 0.25).

CONCLUSIONS

Neural nets could predict individual recovery times from the neuromuscular block significantly better than the average-based method used here, which was supposed to be more accurate than guesses by any clinician. The minimum alveolar concentration was the only monitored variable that influenced the recovery rate, but it did not aid neural net prediction.

Sevoflurane but not isoflurane can reduce prostacyclin production of endothelial cells

BACKGROUND AND OBJECTIVE

Little is known about the interaction of newer volatile anaesthetics with endothelial eicosanoid production. Sevoflurane may possibly reduce prostacyclin formation. Thus, we compared the influences of sevoflurane and isoflurane on endothelial prostacyclin production.

METHODS

Production of prostacyclin of human umbilical vein endothelial cells was measured by the ELISA technique under basal conditions and after stimulation with calcium ionophore A 23187 10 micromol or histamine 0.1 micromol in the absence and presence of 1 and 2 minimal alveolar concentrations (MAC) of sevoflurane or isoflurane.

RESULTS

The basal production of prostacyclin was unaffected by the volatile anaesthetics. Stimulation of endothelial cells increased prostacyclin formation 3-5-fold. Sevoflurane at 2 MAC, but not at 1 MAC, could reduce stimulated prostacyclin production by about half (P < 0.05). Isoflurane had no inhibitory effect. Inhibition of cyclo-oxygenase function by acetylsalicylic acid abolished the induced burst of prostacyclin formation completely.

CONCLUSIONS

Sevoflurane, but not isoflurane, can reduce stimulated endothelial prostacyclin production in a concentration-dependent manner. Because at least 2 MAC of sevoflurane were required, this effect should be of minor importance under clinical conditions of balanced anaesthesia.

Adsorption of sufentanil to epidural filters and catheters

BACKGROUND AND OBJECTIVE

Stable drug concentrations must be administered to provide adequate patient-controlled epidural analgesia. This study investigated the stability of sufentanil after the epidural delivery system had been flushed with solutions containing the drug.

METHODS

Sufentanil citrate, 5 microg mL(-1) was injected through an epidural catheter system into a glass container. The concentrations of the drug leaving the system, in 1 mL aliquots (1-5 mL) were measured using high-performance liquid chromatography. In the same manner, sufentanil samples were analysed after flushing the filter, as well as after priming the filter and catheter.

RESULTS

ANOVA for repeated measurements demonstrated that sufentanil concentrations remained constant as long as the catheter had been adequately flushed. However, the concentration of sufentanil in the solution exiting the filter was reduced significantly. Hardly any sufentanil could be detected (0.09 +/- 0.01 microg mL(-1), P < 0.001) in the first 1 mL aliquot (probe) leaving the filter. Altogether, 3 mL sufentanil solution was needed to pass through the filter before the baseline values were restored (P > 0.05). The greatest decrease occurred when the whole epidural delivery apparatus (catheter and filter) was primed; to regain baseline values, as much as 4 mL solution was needed to flush the system.

CONCLUSIONS

Sufentanil citrate is adsorbed by the materials used to manufacture systems (catheters, filters) used in epidural anaesthesia. Hence, the epidural catheter system should be primed with sufentanil before connecting it to the patient so as to deliver reliable concentrations.

Nitrous oxide/oxygen mixture and the prevention of pain during injection of propofol

BACKGROUND AND OBJECTIVE

The incidence of pain associated with the injection of propofol still remains a problem. This study sought to examine the analgesic effects of inhaled nitrous oxide in oxygen on the prevention of propofol injection pain.

METHODS

Nitrous oxide in oxygen was compared with a lidocaine (20 mg)-propofol mixture and with propofol alone (control) in a prospective, randomized, observer-blinded study. ASA I and II patients (n = 135) scheduled for elective surgical procedures were studied. A standard propofol injection technique and scoring system to measure the pain on injection was used.

RESULTS

Demographic variables were similar between the study groups. Without analgesia (control) 26 of 45 patients (58%) reported pain on injection compared with 11 of 45 patients (24%) in both the nitrous oxide (95% CI: 14-52%, P = 0.001) and lidocaine groups (95% CI: 14-52%, P = 0.001).

CONCLUSIONS

The inhalation of a nitrous oxide/oxygen mixture significantly reduces the incidence of pain during propofol injection. This therapeutic stratagem was as effective as a lidocaine-propofol mixture.

Effects of repeated anaesthesia on central cholinergic function in the rat cerebral cortex

BACKGROUND AND OBJECTIVE

General anaesthesia may contribute to postoperative cognitive decline in the elderly. The aim was to determine the effects of repeated pentobarbital anaesthesia throughout life on central cholinergic function in the rat.

METHODS

Young Lewis rats were randomly allocated to two groups. The anaesthesia group (n = 15) was anaesthetized with pentobarbital 20 mg kg(-1) intraperitoneally at 6, 8.5, 11, 13.5, 16, 18.5, 21 and 23.5 months of age. The control group (n = 12) was treated identically, apart from the anaesthesia. At 26 months of age, the animals were killed and the brain dissected and stored for analysis. Central cholinergic function in the cortex and hippocampus was assessed by measuring [3H]-epibatidine and [125I]alpha-bungarotoxin binding to nicotinic receptors and choline acetyltransferase (ChAT) activity.

RESULTS

Tissue from nine rats in the anaesthesia group and eight in the control group was available for analysis. There was a significant reduction in alpha-bungarotoxin binding in the anaesthetized compared with the control group in the superior cortex (P < 0.0002) and molecular cortex (P < 0.04). There were no significant differences between the groups for epibatidine binding or ChAT.

CONCLUSIONS

Repeated anaesthesia in rat reduces central nicotinic cholinergic binding in the cortex. The findings may have implications for postoperative cognitive function studies.

Induced arterial hypotension for interventional thoracic aortic stent-graft placement: impact on intracranial haemodynamics and cognitive function

BACKGROUND AND OBJECTIVE

The study investigated the impact of induced arterial hypotension for the facilitation of endovascular stent-graft placement in patients with thoracic aortic aneurysm on cerebral blood flow velocity and neurological/neurocognitive outcome.

METHODS

In 27 ASA III patients, cerebral blood flow velocity was recorded during induced arterial hypotension for endovascular stent-graft placement using transcranial Doppler sonography and the Folstein Mini Mental State Examination and the National Institute of Health Stroke Scale were performed before and after the intervention.

RESULTS

Mean arterial pressure was decreased <50 mmHg, and in 22 patients it was <40 mmHg. Diastolic cerebral blood flow velocity decreased by 59%. Postoperatively, six of 21 patients exhibited changes in the Folstein Mini Mental State Examination and four of these six patients in the National Institute of Health Stroke Scale as indices of new-found neurocognitive dysfunction, but there were no signs of stroke. Loss of the diastolic blood flow profile was detected in two of six patients with new-found neurocognitive dysfunctions and in 18 of 21 patients with no new-found neurocognitive dysfunction. Changes in the Folstein Mini Mental State Examination on postoperative day 1 were correlated to the pre-procedural Folstein Mini Mental State Examination, but not to the time spent with a mean arterial pressure <50 mmHg, <40 mmHg or with a loss of diastolic blood flow profile.

CONCLUSIONS

Transcranial Doppler sonography visualizes the individual effect of induced hypotension and the period of intracranial circulatory arrest during aortic stent-graft placement. However, transient new-found neurocognitive dysfunctions occur independently of the transcranial Doppler data, and are in close correlation to the neurocognitive state before the procedure. The results suggest that induced arterial hypotension is not the major factor for postoperative new-found neurocognitive dysfunction.

Gastric mucosal-to-end-tidal PCO2 difference during major abdominal surgery: influence of the arterial-to-end-tidal PCO2 difference?

BACKGROUND AND OBJECTIVE

Because gastric mucosal PCO2 must be referenced to arterial values via a gastric-to-arterial PCO2 gap (Pg-aCO2), the gastric-to-end-tidal PCO2 difference (Pg-ETCO2) may be proposed as a surrogate method to monitor Pg-aCO2. However, the influence of arterial-to-end-tidal PCO2 (Pa-ETCO2) on its value remains unknown. Pa-ETCO2 may be enhanced by a low cardiac output and subsequent reduced perfusion of the lungs. This study was designed to compare such gaps observed during abdominal surgery in patients with or without preoperative cardiac dysfunction.

METHODS

Haemodynamic, metabolic and tonometric variables were measured in seven patients with Crohn's disease and in five patients with chronic heart failure scheduled for abdominal surgery. Data were collected before skin incision (T0); at extractor placement (T1), 30 (T2) and 60 (T3) min later; at organ extraction (T4), 30 (T5) and 60 (T6) min later, and at the end of surgery (T7).

RESULTS

Gradients appeared larger in the cardiac group. The difference was significant for Pg-ETCO2 during the whole study period, while it was only reached at T1-T2 for Pa-ETCO2 and at T5-T6 for Pg-aCO2. Gaps did not change significantly over the peroperative time points in either group. No major haemodynamic variations were registered in either group.

CONCLUSIONS

In patients with preoperative chronic heart failure, Pg-ETCO2 remained constant throughout a major general surgical procedure and was only moderately influenced by the Pa-ETCO2 gap. In these patients, Pg-ETCO2 may be used as a reliable index of gastrointestinal perfusion after control of PaCO2.

Ondansetron disintegrating tablets of 8 mg twice a day for 3 days did not reduce the incidence of nausea or vomiting after laparoscopic surgery

BACKGROUND AND OBJECTIVE

Although many antiemetic drugs are available for intravenous use in the hospital setting, few are available after patient discharge. Consequently, nausea and vomiting are frequent complaints from patients at home after ambulatory surgery. We tested the hypothesis that the new 8 mg ondansetron disintegrating tablets will decrease the rate of nausea and vomiting at home after laparoscopic surgery.

METHODS

Ninety-six patients were studied in a randomized double-blind study. Starting the first evening after operation and continuing every 12 h for 3 days, patients received either placebo or ondansetron 8 mg disintegrating tablets orally. The patients returned a questionnaire about postoperative nausea and vomiting, other side-effects, e.g. dizziness, headache, nightmare, anxiety and pain, as well as their overall satisfaction at 24 and 72 h after completion of surgery.

RESULTS

The rates of nausea and vomiting were similar in the two groups, both during the first 24 h (28 versus 48%, placebo and ondansetron, respectively (ns) and during the 24-72 h (21 versus 35% (ns)). The incidence rate of vomiting was 8% (placebo) versus 12% (ondansetron) during the first 24 h (ns) and 9 versus 13% respectively in the 24-72 h (ns). No difference between groups was observed in overall satisfaction, incidence of postoperative pain or other side-effects.

CONCLUSIONS

The use of ondansetron disintegrating tablets of 8 mg twice a day for 3 days did not reduce the incidence of nausea and vomiting in patients undergoing outpatient laparoscopic surgery.

Effects of xenon on mesenteric blood flow

BACKGROUND AND OBJECTIVE

The effects of xenon on mesenteric vascular resistance have not been investigated. Because human beings anaesthetized with xenon show good cardiovascular stability, we believed that the agent would have little or no effect on vascular resistance in the splanchnic bed. We determined the effects of different inhaled xenon concentrations on mesenteric blood flow and mesenteric oxygen consumption in pigs sedated with intravenous propofol.

METHODS

Twenty-three minipigs were instrumented with transit time flow probes around the pulmonary and superior mesenteric arteries as well as with pulmonary artery and portal venous catheters. A 14 h recovery was allowed followed by recordings of baseline values. Xenon was then randomly administered in 0.30, 0.50, and 0.70 end-tidal fractions.

RESULTS

The administration of xenon resulted in an 8% (not dose dependent) decrease in mean arterial pressure (from 99 +/- 15 to 91 +/- 19 mmHg; P < 0.05), a 20% decrease in calculated systemic oxygen consumption (from 0.23 +/- 0.07 to 0.19 +/- 0.04L min(-1); P < 0.01), a 20% reduction in mesenteric oxygen delivery (from 41 +/- 12 to 33 +/- 11 mL min; P < 0.001), a 37% reduction in mesentericmetabolic rate of oxygen (from 11.3 +/- 3.6 to 7.1 +/- 3.2 mL min(-1); P < 0.01) and an 8% decrease in mesenteric artery blood flow (0.22 +/- 0.07 to 0.20 +/- 0.07 L min(-1); P < 0.05) in a dose-dependent fashion. Heart rate, cardiac output, systemic vascular resistance, mesenteric vascular resistance, mesenteric oxygen extraction fraction and portal lactate concentration were not significantly altered by xenon.

CONCLUSIONS

Xenon inhalation in the propofol-sedated pig had no measurable effects on mesenteric vascular resistance. This finding may partly explain the well-known cardiovascular stability observed in patients anaesthetized with xenon. Although mesenteric artery blood flow and mesenteric oxygen delivery decreased during xenon administration, unchanged mesenteric oxygen extraction fraction and portal lactate suggest that metabolic regulation of the splanchnic circulation remained unaltered.

Dopamine stabilizes milrinone-induced changes in heart rate and arterial pressure during anaesthesia with isoflurane

BACKGROUND AND OBJECTIVE

Phosphodiesterase-III inhibitors and dobutamine effectively improve cardiac function in patients with cardiac failure, but they are limited by possible hypotensive effects. We tested the hypothesis that dopamine contributes to stabilizing milrinone-induced haemodynamic changes.

METHODS

Nine patients undergoing major surgery were anaesthetized using nitrous oxide and oxygen supplemented with isoflurane 1-2%. After baseline haemodynamics were recorded, milrinone (25 or 50 microg kg(-1)) was administered over 10min, followed by a continuous infusion (0.5 microg kg(-1) min(-1). The second set of haemodynamic values was measured 50 min after beginning the continuous infusion of milrinone. Dopamine (4 microg kg(-1) min(-1)) was then administered with milrinone.

RESULTS

Milrinone significantly increased the heart rate from 81 +/- 8 to 102 +/- 16beats min(-1), but it decreased the mean arterial pressure from 83 +/- 10 to 66 +/- 10 mmHg and systemic vascular resistance (P < 0.05 for each). The pulmonary capillary wedge pressure, cardiac index and pulmonary vascular resistance did not change significantly. The addition of dopamine to the milrinone infusion significantly decreased the heart rate (94 +/- 12 beats min(-1)) and increased the mean arterial pressure (82 +/- 11 mmHg). Dopamine and milrinone, but not milrinone alone, significantly increased the cardiac index and the rate-pressure product.

CONCLUSIONS

The combination regimen of milrinone and dopamine improved cardiac function, and changes in heart rate and mean arterial pressure induced by milrinone were attenuated by dopamine. The results suggest that a combination regimen of milrinone and dopamine rather than milrinone alone should be used to maintain arterial pressure.

Endothelial cell activation following moderate traumatic brain injury

Traumatic brain injury (TBI) initiates a cascade of acute and chronic injury responses which include disturbances in the cerebrovasculature that may result in the activation of the microvascular endothelial development of a dysfunction endothelium. The present study examines endothelial cell (EC) activation in a percussion model of moderate TBI. The criteria for endothelial activation used in these studies was surface expression of a number of markers collectively termed endothelial activation antigens. Temporal induction of the major histocompatibility (MHC) class II molecules, E-selectin (CD62E), vascular cell adhesion molecule (VACM-1) (CD106) as well as altered expression of constitutively expressed intercellular adhesion molecule-1 (ICAM-1) (CD54), the glucose transporter protein (glut-1), the transferrin receptor (tfR) (CD71), and MHC class I molecules was examined at various times following impact. Induction of E-selectin and increased expression of ICAM-1 was seen by 2 h post-impact (PI) and was sustained through 24 h PI. Decreased expression of immunologically reactive glut-1 and tfR was observed by 2-4 h PI and remained low up to 24 h PI. No induction of VCAM-1, MHC class II molecules or altered constitutive expression or MHC class I molecules was seen. Changes in EC activation were observed predominantly at the site of impact and were diminished temporarily. These results indicate that mild concussive injury to the brain results in activation of the endothelium.

Hemodynamic effects of platelet-activating factor in nonpregnant and pregnant sheep

The present study was designed to assess the dose-related effects of platelet-activating factor (PAF) on systemic, renal, and uterine hemodynamics in nonpregnant sheep and to evaluate how pregnancy might alter these responses. Nonpregnant and pregnant (110 +/- 5 days gestation) ewes were instrumented for conscious measurements of maternal mean arterial pressure (MAP), renal blood flow (RBF), uterine blood flow (UBF), hematocrit, and urinary protein concentration. After recovery, dose-response curves to PAF were generated by systemic infusion at 10, 30, and 100 ng. kg(-1). min(-1) (15 min/dose) into the maternal femoral vein. The above parameters were measured, and renal and uterine vascular resistances (RVR and UVR, respectively) were calculated. In pregnant sheep, PAF increased MAP, RVR, UVR, and urinary protein concentration. We also observed increases in hematocrit, indicative of reduced blood volume secondary to increased systemic microvascular protein permeability. These responses were similar in nonpregnant sheep, with the exception of UVR in nonpregnant ewes being decreased (and thus UBF was increased), whereas in pregnant sheep, UVR was increased, which resulted in decreased UBF. This suggests that pregnancy alters the mechanism of action of PAF within the uterine vasculature in a way that can reduce UBF and thereby potentially compromise placental perfusion.

TNF-alpha and IL-1alpha induce heme oxygenase-1 via protein kinase C, Ca2+, and phospholipase A2 in endothelial cells

Heme oxygenase-1 (HO-1), an enzyme important in protection against oxidant stress, is induced in human vascular endothelial cells by the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1alpha (IL-1alpha). However, the signaling mediators that regulate the induction are not known. This study examined the involvement of protein kinase C (PKC), phospholipase A2 (PLA2), calcium, and oxidants in cytokine induction of HO-1. Acute exposure to the PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated HO-1 mRNA. However, prolonged exposure, which downregulates most PKC isoforms, blocked induction of HO-1 mRNA by IL-1alpha and TNF-alpha. Additionally, the phosphatase inhibitors okadaic acid and calyculin enhanced cytokine induction of HO-1. Mepacrine, a PLA2 inhibitor, prevented HO-1 induction by cytokine, suggesting a role for arachidonate, the product of PLA2 hydrolysis of phospholipids, in HO-1 expression. The intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) blocked cytokine induction of HO-1. Paradoxically, the calcium ionophore A-23187 prevented HO-1 induction by cytokine but not by PMA. Finally, the oxidant scavenger N-acetylcysteine inhibited HO-1 induction by cytokines. These results demonstrate that TNF-alpha and IL-1alpha induction of HO-1 requires PKC-mediated phosphorylation and PLA2 activation as well as oxidant generation.

T-Cell Receptor Signaling Pathway Exerts a Negative Control on Thrombin-Mediated Increase in [Ca2+]i and p38 MAPK Activation in Jurkat T Cells: Implication of the Tyrosine Kinase p56Lck

Activation of the mitogen-activated protein kinase (Erk) and c-Jun terminal kinase is a well-documented mechanism for the seven transmembrane spanning receptors. We have previously shown that thrombin stimulation of the T-leukemic cell line Jurkat induced a transient increase in [Ca2+]i and tyrosine phosphorylation of several cellular proteins. Here, we have analyzed p42-44 MAPK, JNK and p38 MAPK activation using Jurkat T-cell lines deficient in either the tyrosine kinase p56Lck (JCaM1) or the tyrosine phosphatase CD45 (J45.01). Our results demonstrate that p56Lck and CD45 exert a negative control on thrombin-induced p38 MAPK activation and [Ca2+]i release in Jurkat cells. Thrombin receptor expression was identical on the different cell lines as assessed by FACS analysis. Tyrosine phosphorylation of p38 MAPK was drastically increased after thrombin stimulation of JCaM1 or J45.01 cells, as compared with parental cells (JE6.1). P42-44 MAPK and JNK activity also enhanced after thrombin treatment of JE6.1 and JCaM1 cell lines, whereas basal kinase activity was higher in J45.01 cells and was not further stimulated by thrombin. Thrombin and thrombin receptor agonist peptide-induced [Ca2+]imobilization paralleled p38 MAPK activation in JCaM1 and J45.01 cells. Moreover, reconstitution of J45.01 and JCaM1 cell lines with either CD45 or Lck is accompanied by restoration of a normal thrombin-induced [Ca2+]i response and p38MAPK phosphorylation. These data show that a component of the T-cell receptor signaling pathway exerts a negative control on thrombin-induced responses in Jurkat T cells. Accordingly, we found that thrombin enhanced tyrosine phosphorylation of p56Lck and decreased p56Lck kinase activity in J45.01 cells. Our results are consistent with a negative role for p56Lck on thrombin-induced [Ca2+]i release and p38 MAPK activation in Jurkat T-cell lines.

T-Cell Receptor Signaling Pathway Exerts a Negative Control on Thrombin-Mediated Increase in [Ca2+]i and p38 MAPK Activation in Jurkat T Cells: Implication of the Tyrosine Kinase p56Lck

Activation of the mitogen-activated protein kinase (Erk) and c-Jun terminal kinase is a well-documented mechanism for the seven transmembrane spanning receptors. We have previously shown that thrombin stimulation of the T-leukemic cell line Jurkat induced a transient increase in [Ca2+]i and tyrosine phosphorylation of several cellular proteins. Here, we have analyzed p42-44 MAPK, JNK and p38 MAPK activation using Jurkat T-cell lines deficient in either the tyrosine kinase p56Lck (JCaM1) or the tyrosine phosphatase CD45 (J45.01). Our results demonstrate that p56Lck and CD45 exert a negative control on thrombin-induced p38 MAPK activation and [Ca2+]i release in Jurkat cells. Thrombin receptor expression was identical on the different cell lines as assessed by FACS analysis. Tyrosine phosphorylation of p38 MAPK was drastically increased after thrombin stimulation of JCaM1 or J45.01 cells, as compared with parental cells (JE6.1). P42-44 MAPK and JNK activity also enhanced after thrombin treatment of JE6.1 and JCaM1 cell lines, whereas basal kinase activity was higher in J45.01 cells and was not further stimulated by thrombin. Thrombin and thrombin receptor agonist peptide-induced [Ca2+]imobilization paralleled p38 MAPK activation in JCaM1 and J45.01 cells. Moreover, reconstitution of J45.01 and JCaM1 cell lines with either CD45 or Lck is accompanied by restoration of a normal thrombin-induced [Ca2+]i response and p38MAPK phosphorylation. These data show that a component of the T-cell receptor signaling pathway exerts a negative control on thrombin-induced responses in Jurkat T cells. Accordingly, we found that thrombin enhanced tyrosine phosphorylation of p56Lck and decreased p56Lck kinase activity in J45.01 cells. Our results are consistent with a negative role for p56Lck on thrombin-induced [Ca2+]i release and p38 MAPK activation in Jurkat T-cell lines.

Expression of cytokine receptors in the placenta in term and preterm labour

Elevated uterine concentrations of interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumour-necrosis factor-alpha (TNF-alpha) are suspected to cause increased prostaglandin release from gestational tissues, but little information is available about the expression pattern of cytokine receptors in these tissues. In this study, cytokine receptor positive cells in frozen tissue sections of placentae (n=70) and fetal membranes (n=50) were identified by immunohistological staining with monoclonal antibodies specific for IL-6 receptor, TNF receptors I and II, and IL-1 receptor I. Both subunits of the IL-6 receptor (gp130 and gp80) as well as TNF receptors I and II were expressed by fetal endothelial cells within placental villi, while IL-1-receptor I was detected exclusively in stromal cells of the maternal decidua. The IL-1 receptor I and TNF receptors I and II were expressed in both uterine quiescence and labour, irrespective of gestational age. Immunoreactivity of the gp130 subunit of the IL-6 receptor was found also throughout pregnancy, while the appearance of the gp80 subunit correlated with the presence of term and preterm labour. In case of preterm labour, expression of the gp80 subunit was predominantly detected in the absence of intrauterine infection. Therefore, it is concluded that the de novo expression of the gp80 subunit and consequently the appearance of entire IL-6 receptors in the placenta is associated with spontaneously occurring labour at term and also with preterm occurring labour in the absence of inrauterine infection.

Studies of the nature of the binding by albumin of platelet-activating factor released from cells

This report confirms that human umbilical vein endothelial cells activated by A23187 produce platelet-activating factor (PAF) (22.4 +/- 9.9 ng/10(6) cells/h; mean +/- S.E.). A proportion of the PAF produced (56%) was released by cells into the medium. The PAF released, however, was not detected without prior organic extraction, and the method of organic extraction was critical for detection. Extraction with 80% ethanol was not successful, but a modified methanol/chloroform extraction method was. These observations may explain some of the conflicting reports in the literature on release of PAF by activated endothelial cells. The requirements for organic extraction may reflect the nature of cell-released PAF's binding by albumin; it was observed that PAF added to identical media could be detected in a bioassay without the requirement for extraction. Such PAF was also readily degraded by PAF-acetylhydrolase added to media, while PAF released from cells was resistant to such degradation, suggesting that it was released in a "protected" configuration. Stimulation of cells was performed in media with albumin as the only extracellular macromolecule. Limited proteolytic digestion of the albumin with trypsin and pepsin showed that PAF released by cells was located exclusively between amino acids 240 and 386 (domain II), while no synthetic PAF added to media was located on this region. These results are identical to those described for the release of PAF by the early embryo. Albumin exposed to embryos had a higher thiol concentration (0.77 +/- 0.04 micromol of thiol/micromol of albumin; mean +/- S.E.) than control media to which an equivalent amount of synthetic PAF was added (0.59 +/- 0.02 micromol of thiol/micromol of albumin) (measured with Ellman's reagent). Furthermore, albumin from conditioned media was more susceptible to reduction by 10 mM dithiothreitol than control albumin, as assessed by its mobility on PAGE. The protected configuration of released PAF was caused by cell-dependent conformational changes to albumin involving cysteine-cysteine disulfide bonds. Partial reduction with dithiothreitol of albumin exposed to cells resulted in released PAF being able to be detected directly in a bioassay without the requirement for prior organic extraction.

Platelet-activating factor biosynthesis induced by various stimuli in human HaCaT keratinocytes

Platelet-activating factor (PAF) is a potent inflammatory mediator that is thought to play a role in cutaneous inflammation. These studies used mass spectrometry to examine the molecular species of PAF precursor glycerophosphocholine lipids (GPC) as well as the biosynthesis of PAF and other sn-2 acetyl-GPC in a human keratinocyte-derived cell line (HaCaT keratinocytes). Approximately 28% of HaCaT keratinocyte GPC consisted of 1-alkyl species, and the relative amounts of the sn-1 alkyl constituents of the PAF precursor 1-alkyl-2-acyl-GPC were as follows: hexadecyl > octadecenyl > octadecyl. Ionophore (A23187)-stimulated HaCaT keratinocytes synthesized both PAF (1-hexadecyl, 1-octadecenyl, and 1-octadecyl species) and less potent 1-acyl analogs (1-palmitoyl, 1-oleoyl, and 1-stearoyl species). PAF production was rapid and maximal by 10 min. The major species of sn-2acetyl-GPC at 2.5 min were 1-hexadecyl-2-acetyl-GPC (2.2 ng/10(6) cells) and 1-palmitoyl-2-acetyl-GPC (2.4 ng/10(6) cells). HaCaT keratinocytes also synthesized PAF and 1-acyl PAF analogs when stimulated with the peptide growth factor endothelin-1 and the nonhydrolyzable PAF receptor agonist carbamyl-PAF. Both 1-hexadecyl-2- acetyl-GPC and 1-palmitoyl-2-acetyl-GPC stimulated intracellular calcium mobilization in HaCaT cells, indicating that these sn-2 acetyl-GPC act in autocrine fashion. These studies revealed that the human keratinocyte-derived cell line HaCaT can synthesize significant amounts of PAF and 1-acyl analogs in vitro from both nonspecific (A23187) and specific (endothelin-1, carbamyl-PAF) stimulation, suggesting a role for this inflammatory lipid mediator in keratinocyte pathophysiology.