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K Messmer

Publications and source records attributed to K Messmer.

At least 19 recordsLinked to original sources
PubMed1995

Investigating the origin of cyclic changes in limb volume using mercury-in-silastic strain gauge plethysmography in man.

1. Vasomotion, a phenomen frequently observed in skeletal muscle microcirculation, has been observed under physiological conditions and found enhanced during critical reduction of tissue perfusion due to hypoxic hypoxia, haemorrhage and local hypotension. We used a computer assisted non-invasive plethysmographic method to investigate periodic changes of limb volume (volumotion), which we previously found in critically ill patients. The current study was designed to investigate the origin of volumotion. 2. Simultaneous recordings of limb circumference of both calves were obtained. In patients with peripheral vascular disease and patients with minor surgery the cross-correlation with spontaneous breathing was investigated. In patients who had undergone major abdominal or vascular surgery we analysed for cross-correlations between MSG plethysmography signals of both legs and changes in central venous, arterial and ventilation pressures. In this group the effects of positive-pressure ventilation and positive end-expiratory pressure (PEEP) were also studied. 3. No ventilation-related volumotion was observed during spontaneous breathing. During positive-pressure ventilation a ventilation-related peak was found in the Fourier transform in agreement with the ventilation frequency applied. The amplitude of ventilation-related volumotion decreased significantly after a pressure cuff applied to the thigh was inflated above central venous pressure. We observed a significant increase in the amplitude of ventilation-related volumotion when PEEP was applied. 4. Ventilation-related volumotion showed significant cross-correlation between both legs. Slow wave volumotion (0.5-7 cycles min-1) was frequently observed, but always appeared unilaterally. Whilst we looked for correlations between slow wave volumotion and changes in central venous pressure and arterial blood pressure, respectively, significant cross-correlation with the MSG plethysmography recordings was only observed at the frequency of the positive-pressure ventilation. 5. The fact that periodic changes of limb circumference matching the frequency of the positive-pressure ventilation were detectable with the MSG plethysmography system demonstrates that small volume changes (less than 0.02 ml (100 ml tissue)-1) can be assessed using this system. As slow wave volumotion was observed unilaterally and revealed no correlation either with breathing, ventilation or arterial and central venous pressure, we suggest that slow wave volumotion is a local event most likely reflecting arteriolar vasomotion.

Aged↗
PubMed1995

Angiogenesis and vascularization of murine pancreatic islet isografts.

Although the microvascular endothelium has been identified as the primary target site for the initiation of pancreatic islet graft rejection, little is known of the microvascular and cellular mechanisms involved, partly due to the lack of adequate models. Herein, we present a model for the in vivo assessment of the microcirculation of pancreatic islet grafts in mice. Isolated islets of Langerhans from immunocompetent hairless mice and immunoincompetent athymic nude mice were transplanted syngeneically into a specially designed dorsal skinfold chamber mounted on nondiabetic recipients. The islets' microcirculation was visualized by means of intravital fluorescence microscopy, and microcirculatory parameters were quantitatively analysed over a period of 14 days in the awake animal. Between day 2 and 4 after transplantation 84% (31/37; hairless mice) and 69% (36/52; nude mice) of the islet grafts revealed capillary sprouts and formation of new microvessels. On day 6, these sprouts were found interconnected, and red blood cell movement within the newly formed microvascular network was observed. The process of angiogenesis and revascularization was completed within 10 days after transplantation yielding a glomerulus-like network of capillaries as known for pancreatic islets in situ. Functional capillary density of the islet grafts ranged between 650 and 700 cm-1 in both hairless and nude mice. Within the islets' microvessels neither accumulation of leukocytes nor leukocyte-endothelial cell interaction was observed, indicating the lack of rejection and inflammation in these syngeneic islet grafts. We propose that this model provides a wide spectrum of promising experimental approaches for the study of microcirculatory and cellular mechanisms in free pancreatic islet transplantation.

Animals↗
PubMed1995

Leukocytes contribute to hepatic ischemia/reperfusion injury via intercellular adhesion molecule-1-mediated venular adherence.

BACKGROUND: Leukocytes are suggested to modulate ischemia/reperfusion injury via membrane receptor-controlled interaction with the microvascular endothelium. METHODS: With the use of intravital fluorescence microscopy we investigated the role of the intercellular adhesion molecule-1 (ICAM-1) in a rat model of hepatic reperfusion injury with a neutralizing monoclonal antibody (anti-ICAM-1). RESULTS: Sixty minutes of left lobar ischemia and reperfusion (isotype-matched immunoglobulin G1 control antibody) caused leukostasis in sinusoids (240 +/- 15 cells per liver lobule), leukocyte adherence in postsinusoidal venules (679 +/- 76 cells per mm2 endothelial surface of postsinusoidal venules), nutritive perfusion failure (15% +/- 2% nonperfused sinusoids), excretory dysfunction (bile flow, 1.2 +/- 0.3 microliters.min-1.gm-1), and loss of hepatocellular integrity (serum aspartate aminotransferase, 1353 +/- 317 units.L-1; serum alanine aminotransferase, 1055 +/- 265 units.L-1). Anti-ICAM-1 did not affect sinusoidal leukostasis; however, it effectively inhibited postischemic leukocyte adherence to the venular endothelial lining (217 +/- 38 cells/mm2, p < 0.01). Concomitantly, hepatic reperfusion injury, including sinusoidal perfusion (6% +/- 1% nonperfused sinusoids, p < 0.01), excretory function (bile flow, 1.8 +/- 0.1 microliters.min-1.gm-1, p < 0.05), and hepatocellular integrity (aspartate aminotransferase, 480 +/- 108 units.L-1; alanine aminotransferase, 447 +/- 80 units.L-1, p < 0.05), was significantly ameliorated by anti-ICAM-1. CONCLUSIONS: These findings prove in vivo the pivotal role of ICAM-1 in leukocyte-dependent manifestation of postischemic liver damage.

Animals↗
PubMed1995

Effects of inhaled prostacyclin as compared with inhaled nitric oxide on right ventricular performance in hypoxic pulmonary vasoconstriction.

OBJECTIVE: Recently, inhalation of prostacyclin (PGI2) has been shown to cause selective pulmonary vasodilation. However, the effects of inhaled PGI2 on right ventricular (RV) performance are still unknown and therefore were compared with those of inhaled nitric oxide (NO). DESIGN: Reported measurements design. SETTING: Animal research laboratory. ANIMALS: Six anesthetized, ventilated dogs (28 +/- 2 kg). INTERVENTIONS: Pulmonary hypertension was induced by decreasing FIO2 to 0.09-0.11 ('hypoxic pulmonary vasoconstriction', HPV). Subsequently, a single dose of either NO (50 ppm) or PGI2-aerosol (0.9 +/- 0.3 ng/kg/min) was randomly added to the inspired gas. MEASUREMENTS AND MAIN RESULTS: Measurements were performed before induction of HPV and 10 minutes after application and withdrawal of each drug. Central hemodynamics, global RV function, and local RV function (n = 5, sonomicrometry) were assessed. HPV resulted in an increase of pulmonary artery pressure (PAP), pulmonary vascular resistance (PVR), RV stroke work, right coronary artery flow, maximal rate of RV pressure increase (RV dP/dtmax), and maximal velocity of shortening of contractile elements (Vmax). In contrast, RV ejection fraction, RV end-diastolic volume, RV end-diastolic fiber length, and systolic fiber shortening were unchanged. Both PGI2-aerosol and NO attenuated the HPV-induced increase in PAP and PVR without affecting arterial pressure. NO, but not PGI2, resulted in an increase of RV ejection fraction from 42 to 46% (p < 0.05). Right coronary flow dropped from 29 to 21 mL/min during PGI2 (p < 0.05). RV stroke work, RV dP/dtmax, and Vmax decreased subsequent to both NO and PGI2, whereas local RV function was not affected. CONCLUSIONS: In pulmonary hypertension induced by HPV, PGI2-aerosol and inhaled NO reduced RV afterload and, hence, RV oxygen demand, with only minor changes of stroke volume and cardiac output, indicating an improvement of overall efficiency of RV contraction. RV ejection fraction increased on NO, but not with PGI2. This might be explained by the fact that the reduction of pulmonary vascular resistance during PGI2 amounted to only 65% of the effect of NO. In summary, both inhaled NO and PGI2-aerosol showed beneficial effects on RV performance and may prove helpful in the treatment of acute pulmonary hypertension.

Administration, Inhalation↗
PubMed1995

Hypertonic saline dextran does not increase cardiac contractile function during small volume resuscitation from hemorrhagic shock in anesthetized pigs.

Small volumes of hypertonic saline dextran (10% of shed blood volume [SBV] restore cardiac output (CO) and increase arterial pressure in hemorrhagic shock. Besides rapid expansion of plasma volume, a positive inotropic effect has been proposed as an additional mechanism for the immediate onset of the cardiovascular response. This study compares the effects of 7.2% saline/10% dextran 60 (HSDex, n = 8) and normal saline (NS; n = 6) on central hemodynamics and cardiac contractility assessed by end-systolic elastance (Ees; conductance technique) and segmental preload recruitable stroke work (sPRSW; sonomicrometry). In anesthetized open chest pigs (28 +/- 1 kg, mean +/- SEM) shock was induced by blood withdrawal (40% of blood volume) to maintain mean arterial pressure (MAP) at 45 mm Hg for 75 min. Resuscitation was started by bolus infusion (2 min) of either HSDex (10% of SBV) or the identical sodium load of NS (80% of SBV); 30 min later both groups received 6% dextran (10% of SBV). Hemorrhagic shock reduced CO (-45%) and left ventricular end-diastolic volume (Ved; -70%) while Ees increased (NS:2.2 +/- 0.4 to 7.5 +/- 1.8 mm Hg/mL, P < 0.05; HSDex: 1.9 +/- 0.2 to 9.1 +/- 2.6 mm Hg/mL, P = 0.085). Within 5 min after infusion of either solution CO returned to baseline values and MAP (NS +55%, HSDex +64%) and Ved (+100%) increased. Neither HSDex nor NS increased Ees above shock levels (NS, 8.7 +/- 4.9 mm Hg/mL; HSDex, 7.3 +/- 2.6 mm Hg/mL) and no group differences occurred in other measurements of contractility (dP/dt40,sPRSW). Plasma osmolality increased to 328 +/- 3 mOsmol/kg with HSDex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Does colloid-induced plasma hyperviscosity in haemodilution jeopardize perfusion and oxygenation of vital organs?

BACKGROUND AND METHODS: The infusion of dextran solutions is associated with haemodilution and, under some conditions, with a slight increase in plasma viscosity. To clarify the compound effects of simultaneous haemodilution and plasma viscosity increases on macro- and microhaemodynamics, we investigated the changes in arterial perfusion (radiolabelled microspheres, 15 microns ø) and oxygenation (tissue Po2) of vital organs using an animal model of plasma hyperviscosity. In nine splenectomized beagles plasma viscosity was increased step by step from 1.06 (baseline) to 2.14, and 2.99 mPa.s by infusion of small amounts (4% of total blood volume) of an ultra-high-molecular-weight dextran (50% w/v, mw: 500,000). RESULTS: Despite the significant increase in plasma viscosity, cardiac output as well as specific organ blood flows in heart, brain, liver, and muscle rose steadily with each step of viscosity, while the haematocrit declined from 0.31 to 0.24 and 0.20, respectively. Medians of tissue Po2 in liver peaked at a viscosity of 2 mPa.s and returned to baseline values at 3 mPa.s, whereas in non-working skeletal muscle Po2 values were maximal at 3 mPa.s. CONCLUSION: These results indicate that the impact of plasma viscosity on the rheological properties of whole blood is completely offset by the concomitant reduction of haematocrit. Thus, the comparatively minor changes in plasma viscosity observed after prolonged use of clinical dextrans and other colloids in no way compromise the perfusion and oxygenation of vital organs.

Animals↗
PubMed1995

Prostacyclin aerosol and inhaled nitric oxide fail to reverse pulmonary vasoconstriction induced by thromboxane analogue in dogs.

Inhalation of either prostacyclin (PGI2) as an aerosol or nitric oxide (NO) has been shown to elicit selective pulmonary vasodilation during hypoxic pulmonary vasoconstriction in dogs. Hypoxia may produce cardiovascular changes confounding interpretation of drug effects. Therefore, we investigated the effects of PGI2-aerosol and inhaled NO (50 p.p.m.) on pulmonary pressure-flow relationships (P/Q plots) during thromboxane analogue (U46619) induced pulmonary vasoconstriction. In eight anaesthetized dogs infusion of U46619 (0.33 +/- 0.18 micrograms kg-1 min-1) increased the slope (3.5 +/- 1.1 to 8.4 +/- 1.7 mmHg L-1 min-1, P < 0.001) and the intercept (4.4 +/- 2.3 to 10.2 +/- 4.6 mmHg, P < 0.01) of P/Q plots indicating pulmonary vasoconstriction. Inhalation of both aerosolized PGI2 solution (10 micrograms mL-1) and NO (50 p.p.m.) reduced neither the slope nor the intercept of the P/Q plots. Increasing the concentration of the aerosolized PGI2 solution to 50 micrograms mL-1 (n = 3) did not enhance the effect on pulmonary circulation but systemic vascular resistance fell by 23%. Oxygenation and intrapulmonary shunt remained unchanged during both PGI2-aerosol and inhaled NO. The failure of PGI2-aerosol to induce pulmonary vasodilation indicates that during aerosolization PGI2-concentrations at receptor sites on pulmonary vessels were insufficient to surmount U46619 induced vasoconstriction; this notion is supported by unchanged arterial plasma concentrations of the PGI2 degradation product 6-keto-PGF1 alpha. Considering that NO inhaled at comparable concentrations in sheep reversed U46619 induced pulmonary vasoconstriction, species differences may account for the failure of both PGI2-aerosol and NO to dilate pulmonary vessels in dogs.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

In vitro effects of oxidized low density lipoprotein on CD11b/CD18 and L-selectin presentation on neutrophils and monocytes with relevance for the in vivo situation.

Oxidized LDL (oxLDL) has been identified as a potent stimulus of leukocyte adhesion to endothelium, a hallmark of early atherogenesis. A cytofluorometric study was performed to further characterize the mechanisms by which oxLDL stimulates the rapid adhesion of leukocytes to endothelium in vitro and in vivo. Incubation (30 minutes at 37 C) of whole blood (diluted with buffered saline to 1 x 10(6) leukocytes/ml) with oxLDL (0.85 mg LDL cholesterol/ml; oxidized by 7.5 mumol/L Cu2+ for 18 hours) but not native LDL stimulated the upregulation of CD11b/CD18 adhesion receptors on neutrophils (anti-leu-15 binding: 178 +/- 16% of baseline, P < 0.01, means +/- SD of n = 10 experiments) and on monocytes (169 +/- 34% of baseline, P < 0.01). This phenomenon was almost entirely inhibited by n-butanol or the vasoactive drug pentoxifylline (PTX), which also significantly reduced oxLDL-induced leukocyte adhesion to venular and arteriolar endothelium, as assessed by intravital microscopy on the dorsal skinfold chamber in hamsters (venules: 49 +/- 19 versus 120 +/- 34 cells/mm2, P < 0.05; arterioles: 9 +/- 4 versus 52 +/- 7 cells/mm2, P < 0.01) 30 minutes after intravenous injection of oxLDL (4 mg/kg body weight; means +/- SD of n = 7 hamsters per group). Butanol and PTX also significantly reduced the upregulation of CD11b/CD18 by f-methionyl-leucyl-phenylalanine (fMLP) and platelet-activating factor (PAF) but not by phorbol myristate acetate (PMA). Whereas fMLP and PAF stimulate leukocytes via binding to specific cell surface receptors and triggering complex signal transduction pathways, PMA bypasses these pathways and directly activates intracellular protein kinase C. By analogy, we propose that oxLDL upregulates CD11b/CD18 through its previously documented ability to stimulate the generation of second messengers. The effect of n-butanol and PTX on receptor presentation cannot be explained by changes in plasma membrane fluidity, as both agents failed to reverse the decrease in plasma membrane fluidity of neutrophils after stimulation with oxLDL, as assessed by fluorescence anisotropy measurement of the membrane marker diphenylhexatriene. Incubation of isolated neutrophils but not of whole blood with oxLDL resulted in a significant loss of L-selectin from the neutrophil surface (anti-TQ-1 binding: 40 +/- 13% of baseline, P < 0.01). A significant loss of this adhesion receptor on neutrophils and monocytes was also observed after stimulation of isolated neutrophils and whole blood with fMLP, PAF, and PMA.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Butanol↗
PubMed1994

7.2% NaCl/10% dextran 60 versus 20% mannitol for treatment of intracranial hypertension.

Severe head injury is frequently associated with extracranial injuries causing hemorrhagic hypotension. Volume replacement with isotonic fluids not only is therapeutically of limited efficacy but may aggravate posttraumatic brain edema. On the other side, hypertonic/hyperoncotic saline/dextran solution (HHS) shown to restore cardiovascular function in hemorrhagic shock instantaneously, was found to decrease intracranial pressure in experimental head injury. Currently the therapeutic efficacy of HHS and mannitol on ICP was compared at 24 hrs after a focal cerebral lesion and inflation of an epidural balloon in rabbits. Both solutions given at an equimolar dose rapidly lowered the ICP. After the first injection, ICP reduction was longer maintained with mannitol (189 +/- 27 min) as compared to HHS (98 +/- 14 min), while no difference in duration of lowering ICP was found after the second injection. Due to its blood pressure effects, HHS afforded a higher cerebral perfusion pressure than mannitol. In animals with HHS, the water content of the traumatized hemisphere was increased while the contralateral hemisphere was dehydrated. With mannitol, no differences in water content were found between the injured and uninjured hemisphere. The efficiency of HHS in hemorrhagic shock and intracranial hypertension render the fluid mixture particularly promising in patients with polytrauma in combination with head injury.

Animals↗
PubMed1994

Visualization of nutritive perfusion following tourniquet ischemia in arterial pattern skin flaps: effect of vasoactive medication.

We present an experimental model that makes it possible to investigate the effects of global ischemia and reperfusion on microvascular perfusion and viability of ill-proportioned (poorly designed) arterial pattern skin flaps in hairless mice. Skin flaps were created on the ears of hairless mice by dissecting two of three nutritional vessel bundles at the ear base. Under these nonischemic conditions, 19 percent of the total flap area went on to necrose (as a result of poor flap design). Global ischemia was induced to the flap tissue for 6 hours with a tourniquet clamp directly after flap incision. The extension of perfused tissue area and flap viability were assessed at the microcirculatory level by intravital video microscopy at 1, 3, 6, and 18 hours and 7 days after reperfusion in animals treated with either normal saline (control) or the vasoactive drug buflomedil hydrochloride (3 mg/kg of body weight per day, i.v., starting 4 hours prior to flap creation and continued at daily intervals until the end of the experiments). In untreated animals (n = 18), 1 hour after clamp release we observed reperfusion of 39.55 percent (38.5/44.9) of total flap area. Reperfusion remained unchanged within the following 5 hours. Within the next 12 hours, reperfused flap area was dramatically reduced to 21.9 percent (15.1/58.4). Seven days thereafter, only 18.8 percent (10.9/42.2) of total flap area remained viable. In contrast, we found in buflomedil-treated animals (n = 18) that 57.3 percent (53.5/62.9) of the total flap tissue was reperfused within the first hour after clamp release (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Hypertonic hydroxyethyl starch restores hepatic microvascular perfusion in hemorrhagic shock.

The influence of small-volume resuscitation (hypertonic saline-10% hydroxyethyl starch, HS/HES) on liver microcirculation (intravital fluorescence microscopy) was studied in a nonheparinized hemorrhagic shock model [mean arterial pressure (MAP) 40 mmHg for 1 h] in rats. Resuscitation was performed with Ringer lactate (RL, 4-fold shed volume/20 min; n = 7), 10% hydroxyethyl starch 200/0.6 (HES, shed volume/5 min; n = 6), or 7.2% NaCl-10% hydroxyethyl starch 200/0.6 (HS/HES, 10% shed volume/2 min; n = 7). One hour after resuscitation, MAP increased in all groups, but it did not return to preshock values (P < 0.05). HES (16 +/- 2% nonperfused sinusoids) and HS/HES (14 +/- 2% nonperfused sinusoids), but not RL (24 +/- 2% nonperfused sinusoids), reduced (P < 0.05) shock-induced sinusoidal perfusion failure (28 +/- 3%) with restoration of leukocyte velocity in sinusoids (S) and postsinusoidal venules (V). Shock-induced stasis/adherence of leukocytes was further increased (P < 0.05) after resuscitation with RL (S, 38 +/- 6%; V, 55 +/- 20%) and HES (S, 31 +/- 8%; V, 23 +/- 14%). In contrast, resuscitation with HS/HES prevented increased leukocyte stasis in sinusoids (-4 +/- 4%) as well as adherence to endothelial lining of postsinusoidal venules (-5 +/- 10%). We conclude that replacement of only 10% of actual blood loss by means of small-volume resuscitation (HS/HES) can restore hepatic microvascular perfusion and prevent reperfusion-induced leukocyte stasis/adherence.

Animals↗
PubMed1994

Leukocyte rolling in venules of striated muscle and skin is mediated by P-selectin, not by L-selectin.

Leukocyte rolling in post-capillary venules is mediated by adhesion molecules of the selectin family expressed on both leukocytes (L-selectin) and endothelial cells (E- and P-selectin). With the use of intravital fluorescence microscopy, the effects of antibodies against these selectins were analyzed in the skinfold chamber model of BALB/c mice and the ear model of homozygous hairless mice (hr/hr) that permit chronic observation of striated muscle and skin microcirculation in awake animals, respectively. Mice were injected intravenously with monoclonal antibodies (MAb) to murine L-selectin and E-selectin and affinity-purified polyclonal antibodies to P-selectin. The antibodies, which are known to block cell adhesion, were tested by immunoprecipitation to selectively bind to L-, E-, or P-selectin. Leukocyte rolling was a constant finding in both microcirculation models in the absence of inflammatory stimuli. In both models, injection of anti-P-selectin antibodies completely prevented baseline leukocyte rolling over an observation period of 2 h (P < 0.01 vs. baseline), while no effects were seen after administration of either anti-L-selectin or anti-E-selectin MAb. Treatment with the isotype-matched control antibodies did not affect leukocyte rolling in either model. We conclude that leukocyte rolling in postcapillary venules of murine striated muscle and skin is a physiological process mediated via P-selectin, whereas L- and E-selectin appear not to play a significant role under these circumstances.

Animals↗
PubMed1994

Is sodium acetate dextran superior to sodium chloride dextran for small volume resuscitation from traumatic hemorrhagic shock?

Small volumes (4 mL/kg body weight (bw)) of hypertonic sodium chloride dextran effectively restore cardiac output and nutritional blood flow and increase arterial pressure in severe hemorrhagic shock. It has been suggested that the chloride anion be replaced with acetate to provide a solution that avoids the risk of hyperchloremia and has the advantage of supplying a buffering base to optimize hypertonic resuscitation. This study compares the effects of hypertonic sodium chloride dextran solution (7.2% NaCl/10% dextran 60 [NaCl-Dx]; n = 7) with sodium acetate dextran (10.4% Na-Ac/10% dextran 60 [NaAc-Dx]; n = 6) on hemodynamic, oxygen transport, and metabolic variables. Both solutions had the identical osmolality (2400 mOsmol/kg). Dogs (16.9 +/- 1.9 kg) were anesthetized and mechanically ventilated. Shock was induced by exteriorization of intestine and blood withdrawal (50% of blood volume) to maintain mean arterial blood pressure (MAP) at 40 mm Hg for 75 min. Thereafter, resuscitation was performed either with NaCl-Dx (4 mL/kg over 2 min) or NaAc-Dx (4 mL/kg over 4 min). During hypertonic resuscitation, there was a short-lasting decrease in MAP, which was more pronounced in the NaAc-Dx group (delta MAP -7.3 +/- 2.5 mm Hg). Cardiac index and oxygen consumption were normalized within 5 min after resuscitation with both solutions. In NaAc-Dx-treated animals, MAP remained at lower values as compared to NaCl-Dx-treated dogs at 5 and 30 min after resuscitation (52 +/- 3 vs 74 +/- 6, and 61 +/- 7 vs 79 +/- 12 mm Hg; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1994

P-selectin mediates the interaction of circulating leukocytes with platelets and microvascular endothelium in response to oxidized lipoprotein in vivo.

BACKGROUND: Oxidized low density lipoprotein (oxLDL) has been demonstrated to stimulate leukocyte/endothelium interaction, an early feature of atherogenesis. Using the skinfold chamber model for intravital microscopy in hamsters and mice, we have shown that oxLDL-induced leukocyte adhesion to microvascular endothelium shares many characteristics with leukocyte adhesion during inflammation and ischemia/reperfusion, including the involvement of beta 2 integrin adhesion molecules. In light of the two-step model of leukocyte adhesion, we have examined the contribution of P-selectin to oxLDL-induced leukocyte/endothelium interaction. P-selectin is an inducible adhesion molecule on platelets and endothelium, mediating the initial steps of leukocyte margination and rolling along the endothelial lining, as well as of aggregate formation between platelets and leukocytes. EXPERIMENTAL DESIGN: For our studies, we used the dorsal skinfold chamber model for intravital fluorescence microscopy on awake Syrian golden hamsters. Hamsters were treated 10 minutes before oxLDL-injection (oxidized by Cu2+, 4 mg/kg body weight, intravenously) with blocking antibodies to P-selectin (2 mg/kg body weight intravenously, N = 7). RESULTS: In seven control animals (pretreated with an irrelevant IgG antibody), oxLDL injection elicited leukocyte rolling and adhesion on both venular and arteriolar endothelium, and also the formation of aggregates tumbling down the microvessels and firmly adhering to the microvascular endothelium. The aggregates consisted of leukocytes and activated, dendritic platelets, as assessed by scanning electron microscopy of the buffy coat isolated by density gradient centrifugation of whole blood taken from hamsters 15 minutes after injection of oxLDL. Leukocyte adhesion to venular and arteriolar endothelium, as well as the formation of leukocyte/platelet aggregates were significantly reduced by pretreatment of the animals with anti-P-selectin antibodies. CONCLUSIONS: These data emphasize the similarities between leukocyte adhesion in response to oxLDL and in other pathophysiologic conditions, identifying P-selectin as a crucial player in the interaction between leukocytes and microvascular endothelium as well as in the formation of circulating leukocyte/platelet aggregates.

Animals↗