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Introduction. Thermal preconditioning has previously been shown to attenuate ischemia-reperfusion induced injuries, possible due to increased expression of heat shock proteins (HSP). The model of thermal preconditioning used, however, was not clinically relevant as preconditioning was to 41°C, leading to cellular damage. Our aim was thus to establish a novel and clinically applicable method of preconditioning. Materials and Methods. Twenty-six male Sprague-Dawley rats were split into three groups (nine control, nine ischemia-reperfusion, and eight preconditioned followed by ischemia-reperfusion). To precondition the animals, they were anesthetized and, using a water bath, their core temperature was raised by 1°C for 15 min once a day for five successive days. I/R injury consisted of 30 min of aortic cross-clamping followed by 120 min of reperfusion; control animals had a laparotomy only. Indicators of lung injury were tissue myeloperoxidase, broncho-alveolar lavage protein concentration, and tissue edema. Tissue heat shock protein expression was detected by Western blot analysis. Results. Lower torso ischemia-reperfusion causes significant lung injury versus control, with raised levels of myeloperoxidase 4.53 iu/g to 7.88 iu/g (P < 0.05), raised B.A.L. protein concentration 419 μg/ml to 684 μg/ml (P < 0.05) and altered wet dry ratio 4.63 to 5.50. Clinically relevant thermal preconditioning attenuates all of these parameters back to control levels: myeloperoxidase 3.87 iu/g (P < 0.05 vs I/R), B.A.L. to 284 μg/ml (P < 0.01 vs I/R) and wet dry ratio to 4.44 (P < 0.05 vs I/R). Western blot demonstrated increased expression of H.S.P. 72 in the preconditioned group versus control and I/R alone. Western blot demonstrated increased expression of HSP72 in the preconditioned group vs control and I/R alone. Conclusions. We conclude that clinically applicable thermal preconditioning can attenuate ischemia-reperfusion induced lung injury, possibly through increased expression of HSP72.

Objectives to elicit whether pre-treatment with pravastatin will prevent or ameliorate the acute lung injury that occurs following lower torso ischaemia–reperfusion (IR) in an experimental animal model. Materials and methods male Sprague–Dawley rats were randomised into three groups (n=7/group). The control group underwent a sham laparotomy and aortic dissection. The second group underwent infrarenal aortic cross clamping for 30 min followed by reperfusion for 120 min. The third group pre-treated with pravastatin sodium (0.4 mg/kg/day over 5 days) were again subjected to an ischaemia–reperfusion (IR) injury. The parameters used to assess lung injury included: Wet to dry lung weight ratio (W:D), myeloperoxidase activity (MPO), protein concentration (BALprot) and neutrophil count (BAL PMN) of bronchoaveolar lavage fluid. Western blotting was used to determine the expression of constitutive endothelial nitric oxide synthase (ecNOS) within lung tissue. Results IR causes an acute lung injury as indicated by statistically significant differences in W:D lung weight ratios, MPO activity, neutrophil count and BALprotein concentration in the IR group over that of controls. Pre-treatment with pravastatin attenuated this neutrophil infiltration and microvascular leakage. The pravastatin group showed a marked increased expression of ecNOS over that of the IR group and controls. Conclusion this data indicates that pre-treatment with pravastatin protects against ischaemia–reperfusion induced lung injury in an experimental animal model. We believe that its mechanism of action involves an upregulation of ecNOS, which increases basal expression of nitric oxide providing protective effects on the pulmonary circulation against microvascular injury.

An early event in endotoxin-induced tissue injury is adhesion and migration of leukocytes through the endothelium. This is a three-stage process, initially low-grade selectin-mediated adhesion, seen as a decrease in rolling velocity, followed by integrin-mediated adhesion and transmigration. Thermotolerance has been shown to reduce tissue injury and mortality induced by endotoxin. The aim of this study was to investigate the effect of thermotolerance on leukocyte-endothelial interactions. Intravital video microscopy was used to examine hemodynamic parameters, leukocyte rolling, adhesion, and migration in rat mesenteric postcapillary venules. Sprague-Dawley rats were randomized into control, lipopolysaccharide (LPS), and thermotolerance + LPS groups. Thermotolerance was induced 18 h prior to administration of LPS by elevating core body temperature to 41 + 0.5 degrees C for 15 min. LPS (055:B5 15 mg/kg) was administered via the jugular vein after baseline recording. Leukocyte rolling velocity and the number of adherent and migrated leukocytes were measured by intravital microscopy at baseline 0 min and 10, 30, 60, and 90 min after LPS administration. Heat shock protein 72 (HSP72) expression in tissues was determined by Western immunoblotting. The results indicated that LPS administration significantly decreased leukocyte rolling velocity during endotoxemia and increased leukocyte adhesion (10.3 +/- 1.67, 13.2 +/- 1.40, and 10.0 +/- 1.57/100 microm) and migration (5.7 +/- 1.02 and 8.3 +/- 1.76/field) at 30, 60, and 90 min after LPS injection (P0.01 vs baseline and control group). Thermotolerance maintained leukocyte rolling velocity and significantly reduced leukocyte adhesion (5.7 +/- 0.88 and 4.0 +/- 0.68/100 microm) and migration (2.8 +/- 0.32 and 3.0 +/- 0.68/field) at 30 and 60 min after LPS administration (P0.01 and 0.05 vs LPS group). Expression of HSP72 was induced in mesentery, gut, and lung by thermotolerance. This study indicates that thermotolerance attenuated LPS-induced microvascular injury by decreasing leukocyte-endothelial adhesion and migration.

Background. Adhesion of polymorphonuclear leukocytes (PMN) to endothelial cells and subsequent transendothelial migration are an early key events in the inflammatory response and play an important part in the pathogenesis of septic shock, contributing to vascular and tissue injury. Taurine (2-aminoethanesulfonic acid) is a sulphur-containing β amino acid. It is a known antioxidant, possesses antimicrobial properties, and has previously been shown to be protective to the endothelium both in vivo and in vitro. The aim of this study was to determine if pretreatment with taurinewould attenuate the lipopolysaccharide (LPS)-induced increase in leukocyte-endothelial interactions and microvascular permeability during endotoxemia. Materials and methods. Male Sprague-Dawley rats (300–350 g) were randomized into three groups: (1) Control, (2) LPS, and (3) LPS + Taurine groups. Taurine was administered orally as a 4% solution. Endotoxemia was induced using Escherichia Coli endotoxin (Serotype 0.55 B5)—15 mg/kg via a slow intravenous infusion. Using mesenteric postcapillary venules (28–32-μm diameter) the number of adherent and migrated leukocytes and their rolling velocity were measured by intravital microscopy at baseline and subsequently at 10, 30, 60, and 90 min post administration of LPS. Results. Following administration of LPS there was a reduction in leukocyte rolling velocity at 30, 60 and 90 min. This was accompanied by a significant increase in the number of adherent leukocytes at 10, 30, 60 and 90 min. Transendothelial migration was significantly increased at 90 min. Taurine significantly attenuated the LPS-induced reduction in leukocyte rolling velocity at 10 and 30 min and the number of adherent leukocytes at all time points. Taurine also attenuated the LPS-induced increase in transendothelial migration at 90 min. Conclusions. These results demonstrate that taurine ameliorates endotoxin-induced leukocyte-endothelial cell interactions associated with sepsis, thereby suggesting that taurine may have a therapeutic role in the preventionof endothelial damage in sepsis.

Background: The therapeutic efficacy of interleukin-2 (IL-2) has been limited by a dose-dependent vascular leak syndrome. This may be related to neutrophil-mediated endothelial injury. Taurine has been shown to decrease this injury in vitro. This study investigates the role of taurine in preventing IL-2-induced lung injury, and the role of neutrophil-endothelial interactions in mediating this injury. Methods:Study 1: Sprague-Dawley rats (n = 12/groups) were randomised to controls, IL-2-treated (1 × 106 units), and IL-2-treated with taurine (4% solution, orally for 48 h prior to IL-2 therapy). Lung injury was measured by extravascular lung water (wet/dry weight) and bronchoalveolar lavage protein concentration. Neutrophil infiltration was evaluated by measuring myeloperoxidase activity and bronchoalveolar lavage neutrophil concentration. Study 2: Rats (n = 10/group) were randomised into the same groups as study 1. Neutrophil-endothelial interactions in mesenteric vessels were assessed by intravital microscopy at half-hourly intervals. Results: Taurine reduced IL-2-induced acute lung injury as reflected by a decrease in wet-to-dry lung weight ratio from 7.2 ± 0.5 in the IL-2 group to 4.7 ± 0.3 in the taurine group (p < 0.05), and a decrease in bronchoalveolar neutrophil concentration from 823 ± 19.5 in the IL-2 group to 538 ± 18 in the taurine group (p < 0.05). Intravital microscopy demonstrated that IL-2 increased leucocyte adhesion and migration in mesenteric vessels, and that this was significantly reduced by taurine. Conclusion: These data suggest that taurine prevents IL-2-induced tissue injury in part by decreasing neutrophil-endothelial interactions.

Background Ischaemia–reperfusion injury is mediated by neutrophil–endothelial interaction. Induction of heat shock proteins attenuates neutrophil–endothelial interactions. The aim of this study was to determine whether thermal preconditioning could have a protective effect on neutrophil-mediated lung injury in an animal model of lower torso ischaemia–reperfusion. Methods Sprague-Dawley rats were randomized into: control, ischaemia–reperfusion, and ischaemia–reperfusion preconditioned with hyperthermia groups. Ischaemia–reperfusion injury was induced by infrarenal aortic clamping for 30 min and reperfusion for 120 min. Thermotolerance was induced by raising the core body temperature to 40·5–41·5°C for 15 min, 18 h before ischaemia–reperfusion. Wet:dry lung (W:D) weight ratio, bronchoalveolar lavage protein (BALprot) concentration, tissue myeloperoxidase (MPO) activity and bronchoalveolar lavage polymorphonuclear neutrophil (BAL PMN) count were measured. Heat shock protein 72 (hsp72) expression in lung, intestine and mesentery was measured using Western immunoblotting. Results Ischaemia–reperfusion resulted in a significant increase in tissue oedema (W:D weight ratio) and BALprot concentration. In addition there was a marked increase in tissue neutrophil infiltration (MPO activity, BAL PMN concentration). Preconditioning with hyperthemia resulted in increased expression of hsp72 and significantly reduced tissue oedema and neutrophil infiltration. Conclusion Thermal preconditioning protects against neutrophil-mediated ischaemia–reperfusion-induced lung injury, possibly by increasing the expression of heat shock proteins.

Lower torso revascularisation following ischaemia results in a systemic inflammatory response. Endothelial barrier function is disrupted by neutrophil-derived proteases and oxidants. Taurine, an amino acid found in large quantities in neutrophils, is a powerful endogeneous anti-oxidant. The aims of this study were to investigate the systemic effects of reperfusion following lower limb revascularisation and to evaluate the role of taurine administration in preventing this injury. A rat model of aortic occlusion (30 min) followed by 2 h of reperfusion was used. Animals were randomised to one of three groups ( n = 10 per group): control; ischaemia reperfusion untreated (IR) and taurine-treated. Taurine (4% solution) was administrated orally for 48 h prior to the experiment. Neutrophil infiltration and microvascular permeability were assessed by measuring tissue myeloperoxidase activity and wet/dry weights respectively in lung, liver, kidney, and in cardiac and skeletal muscle. Statistical analysis was by means of analysis of variance (ANOVA). Reperfusion resulted in pulmonary and renal microvascular injury as assessed by organ oedema. Hepatic tissue, skeletal and cardiac muscle were unaffected by lower limb revascularisation. Taurine was effective in preventing neutrophil-mediated pulmonary but not renal microvascular injury. These data suggest that, whilst reperfusion-induced pulmonary injury is predominantly neutrophilmediated, agents other than neutrophil-derived oxidative metabolites, capable of independently causing organ injury through direct endothelial damage, are produced during reperfusion.

The aim of this study was to determine whether glyceryl trinitrate (GTN) has a protective effect on neutrophil- mediated lung injury in a model of aortic occlusion (30 min) and reperfusion (120 min). Sprague-Dawley rats were randomized into control (n = 11), ischaemia-reperfusion (IR) (n = 12), and IR treated with GTN (2 μg kg−1 min−1) during reperfusion (n = 10). Myeloperoxidase (MPO) activity measured pulmonary neutrophil influx. Pulmonary endothelial permeability was measured by wet:dry weight ratio, bronchoalveolar lavage (BAL) protein and neutrophil counts. Neutrophil superoxide release was measured by flow cytometry in a further IR versus GTN experiment (n = 6 in each group). The significant increase in MPO activity produced by IR to a level of 7·99 units g−1 was prevented by GTN which reduced the level to 4·73 units g−1. The increase in pulmonary microvascular leakage after reperfusion was also prevented by GTN: BAL protein without GTN was 992 μg ml−1 and with GTN 579 μg ml−1; BAL neutrophil count without GTN was 3219 cells mm−3 and with GTN 820 cells mm−3; the wet:dry lung weight ratio without GTN was 3·8 and with GTN 3·3. Neutrophil superoxide release increased significantly after 40 min of reperfusion in the untreated IR group (P < 0·05). This increase was prevented in the GTN-treated group. GTN administration had no effect on plasma thromboxane production during revascularization. These data suggest that GTN administration during the reperfusion phase has the potential to decrease pulmonary microvascular injury.

This study evaluated the effect of varying the synthesis of nitric oxide with sodium nitroprusside or N-nitro-L-arginine methyl ester (L-NAME) in a pancreatitis-lung injury model. Rats (n = 45) were randomized to control or caerulein-induced pancreatitis groups, treated with saline, sodium nitroprusside (0·4 μg/kg) or l-NAME (10 mg/kg). Myeloperoxidase activity was used as a measure of neutrophil infiltration. Wet to dry (W:D) lung weight and bronchoalveolar lavage (BAL) protein concentrations were used to assess vascular leakage. Pancreatitis was shown to induce pulmonary neutrophil influx: mean(s.e.m.) myeloperoxidase activity 6·79(0·5) units/g in caerulein-treated animals versus 2·08(0·5) units/g in controls (P < 0·001). Animals with pancreatitis showed increased microvascular leakage compared with controls (mean(s.e.m.) W:D lung weight 7·01(0·5) versus 2·85(0·2), P < 0·001; BAL protein concentration 2539(222) versus 347(32) μg/ml, P < 0·001). Compared with the saline-treated pancreatitis group, these changes were reduced by sodium nitroprusside (mean(s.e.m.) myeloperoxidase activity to 2·5(0·4) units/g, P < 0·001; W:D lung weight to 3·8(0·37), P < 0·001; BAL protein concentration 1389(182) μg/ml, P < 0·05). L-NAME exacerbated the pancreatitis-induced pulmonary oedema (W:D lung weight increased to 11·96(0·6), P < 0·001), protein leakage (BAL protein concentration rose to 3707(309) μg/ml, P < 0·05) and neutrophil infiltration (myeloperoxidase activity increased to 9·01(0·3) units/g, P < 0·05). These data suggest that, in vivo, nitric oxide inhibits pancreatitis-induced lung injury, possibly in part by inhibiting pulmonary neutrophil influx.

Background To avoid ischemic necrosis, compartment syndrome is a surgical emergency treated with decompression once identified. A potentially lethal, oxidant-driven reperfusion injury occurs after decompression. N-acetylcysteine is an antioxidant with the potential to attenuate the reperfusion injury. Questions/purposes We asked whether N-acetylcysteine could preserve striated muscle contractility and modify neutrophil infiltration and activation after simulated compartment syndrome release. Materials and Methods Fifty-seven rats were randomized to control, simulated compartment syndrome, and simulated compartment syndrome plus N-acetylcysteine groups. We isolated the rodent cremaster muscle on its neurovascular pedicle and placed it in a pressure chamber. Chamber pressure was elevated above critical closing pressure for 3 hours to simulate compartment syndrome. Experiments were concluded at three times: 1 hour, 24 hours, and 7 days after decompression of compartment syndrome. We assessed twitch and tetanic contractile function and tissue myeloperoxidase activity. Ten additional rats were randomized to control and N-acetylcysteine administration after which neutrophil respiratory burst activity was assessed. Results The simulated compartment syndrome decreased muscle contractility and increased muscle tissue myeloperoxidase activity compared with controls. Treatment with N-acetylcysteine preserved twitch and tetanic contractility. N-acetylcysteine did not alter neutrophil infiltration (myeloperoxidase activity) acutely but did reduce infiltration at 24 hours, even when given after decompression. N-acetylcysteine reduced neutrophil respiratory burst activity. Conclusion N-acetylcysteine administration before or after simulated compartment syndrome preserved striated muscle contractility, apparently by attenuating neutrophil activation and the resultant oxidant injury. Clinical Relevance Our data suggest a potential role for N-acetylcysteine in the attenuation of muscle injury after release of compartment syndrome and possibly in the prophylaxis of compartment syndrome.

Background The aim of this study was to investigate whether inhibition of hydroxymethylglutaryl co-enzyme A reductase attenuates leucocyte–endothelial cell interactions and alters expression of endothelial constitutive nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) following exposure to endotoxin. Methods Male Sprague–Dawley rats were randomized into control, lipopolysaccharide (LPS) and pravastatin + LPS groups (seven per group). Pravastatin sodium was gavaged at 0·4 mg per kg per day for 5 days, after which LPS 15 mg/kg was administered via the jugular vein. Intravital microscopy was used to determine leucocyte–endothelial cell interactions. Results Following the administration of LPS there was a significant reduction in leucocyte rolling velocity at 10 min (mean(s.e.m.) 69(3) versus 102(6) per cent of baseline value; P = 0·041), an increase in the number of adherent leucocytes at 10 min (4·5(0·5) versus 2·8(0·3) per 100 µm; P = 0·044) and an increase in the number of leucocytes undergoing transendothelial migration at 30 min (4·2(0·4) versus 1·7(0·4) per field; P = 0·008) compared with controls. Pretreatment with pravastatin significantly attenuated LPS-induced leucocyte–endothelial cell interactions (rolling velocity 89(6) per cent at 10 min, P = 0·038; adherent leucocytes 3·0(0·5) per 100 µm at 10 min, P = 0·038; migrating leucocytes 1·9(0·5) per field at 30 min, P = 0·001). This endothelial protection was associated with maintenance of ecNOS and reduced iNOS expression within mesenteric tissues. Conclusion These data show that pravastatin produces anti-inflammatory effects in response to injurious stimuli by attenuation of leucocyte–endothelial cell interactions.

We have previously demonstrated that clinically applicable thermal preconditioning induces heat shock protein 72 (HSP72) and protects against a subsequent ischemia-reperfusion (I/R) injury in an animal model. A core component of I/R injuries is the interaction between activated leukocytes and endothelial cells. We hypothesized that the effects of clinically applicable thermal preconditioning are mediated through attenuation of this leukocyte-endothelial (L-E) interaction.Twenty-one male Sprague Dawley rats were divided into control, I/R, and preconditioning plus I/R groups. Preconditioning was done under general anesthesia and the animals' temperature raised by 1 degrees C for 15 minutes in a water bath. This was repeated once a day for 5 successive days. I/R injury was caused by occlusion of the superior mesenteric artery for 10 minutes followed by 1 hour of reperfusion. L-E interactions were analyzed using intravital microscopy of a mesenteric vessel in vivo. L-E interactions were determined using leukocyte velocity (which decreases as cells interact), and number of adherent and migrated leukocytes. HSP72 was assessed by Western blot.Ischemia-reperfusion caused a decrease in leukocyte rolling velocity at all timepoints (p0.05 versus controls). Preconditioning attenuated the effects of I/R, and leukocyte rolling velocity was significantly improved versus I/R (p0.05) to levels similar to those in controls. Similarly, the number of adherent and migrating leukocytes increased significantly (p0.05) after I/R versus control at all time points, and preconditioning attenuated these to control levels, (p0.05 versus I/R) at both the 30- and 60-minute postischemia time points. Upregulation of HSP72 was demonstrated on Western blot.These results demonstrate that the benefit of clinically applicable thermal preconditioning is at least partially because of an immunomodulatory role in attenuating leukocyte-endothelial interactions associated with an increased expression of HSP 72.

Objectives: intimal hyperplasia (IH) is a major cause of re-stenosis post-vascular intervention. Induction of heat shock proteins (HSPs), by thermal pre-conditioning, reduces IH. Our aim was to investigate the effect of the pharmacological HSP inducer herbimycin A on IH in the rat carotid balloon injury model. Materials and Methods: thirty male Sprague–Dawley rats were randomized into three groups. All groups underwent balloon injury to the left carotid artery. Stress proteins were induced 18 h pre-operatively by heat shock or herbimycin A. Two weeks post-operatively, animals were sacrificed and carotid intima/media area ratio (I/M ratio) calculated using computerized planimetry. Neo-intimal proliferation was assessed immunohistochemically with PCNA (proliferating cell nuclear antigen). Western blot and immunohistochemistry for arterial HSP70 and HSP27 were performed. Results: heat stress and herbimycin significantly reduced the I/M ratio (p < 0.05 vs balloon injury alone). Neo-intimal proliferation was significantly reduced in the heat stress and herbimycin groups (p < 0.05 vs balloon injury alone). Heat stress induced arterial HSP70 and HSP27. Herbimycin A increased arterial HSP27. Conclusion: herbimycin A significantly attenuates IH after balloon injury. HSP27 may be the HSP involved in mediating this response. Pharmacological inducers of HSPs may have a therapeutic role to play in preventing re-stenosis post-vascular intervention.Eur J Vasc Endovasc Surg 25, 40–47 (2003)

Background. Respiratory complications continue to be a major cause of morbidity and mortality following major vascular surgery. The recent UK Small Aneurysm Trial cited preoperative respiratory function as the major predictor of outcome following elective aortic surgery. Aim. The aim of this study was to investigate the effect of aortic clamping and revascularization on diaphragmatic muscle function in a small animal model and to evaluate the role of preoperative treatment with recombinant human growth hormone (rhGH) in preventing diaphragmatic muscle dysfunction. Methods. Male Sprague-Dawley rats (n = 18) were randomized into one of three groups: control (n = 6) underwent laparotomy only; IR (n = 6) had a laparotomy with infrarenal cross-clamping for 30 min followed by lower torso revascularization for 2 h; IR + rhGH (n = 6) were treated with rhGH (Genotropin 0.3 IU/kg/day) for 5 days before laparotomy and aortic cross-clamping for 30 min followed by lower torso revascularization for 2 h. Diaphragmatic muscle contractile function was assessed ex vivo using electrical field stimulation in a tissue bath. Results. Two hours of IR injury resulted in a significant impairment in diaphragmatic twitch (Control, 242.01 + 38.45 g; IR, 108.55 + 7.15 g). This impairment was prevented by pretreatment with rhGH (rhGH, 319.14 + 30.71 g; P < 0.01). Tetanic function was also significantly impaired by ischemia reperfusion injury (control, 605 + 77.63 g; IR, 228.12 + 14.38 g). Again, pretreatment with rhGH prevented this deterioration (IR + rhGH, 704.39 + 45.69 g; P < 0.05) compared with controls. Conclusion. The results of this study suggest that preoperative administration of rhGH may have a role in preventing the diaphragmatic dysfunction associated with infrarenal aortic cross-clamping and revascularization.

Ischemia/reperfusion (I/R) results in endothelial dysfunction, seen as loss of endothelium-dependent vasodilatation. In prolonged ischemia, this can result in marked vasospasm or no reflow in the microvasculature. Thermotolerance (T) attenuates I/R-induced microvascular injury. The aim of this study was to investigate the effect of thermotolerance on I/R-induced vasomotor changes and "no reflow." Sprague-Dawley rats were randomized into an ischemia/reperfusion group (I/R group) and a group in which thermotolerance (41 + 0.5 degrees C for 15 min 18 h prior to I/R) was induced (T + I/R group). IR injury was established by occlusion of the superior mesenteric and celiac vascular pedicle for 30 min, followed by 60 min of reperfusion. Vasomotor function [arteriolar constriction:dilatation (C:D) ratio] measured by response to acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) and "no-reflow" phenomenon were determined in mesenteric arterioles by intravital microscopy. Data are expressed as means +/- SEM and were analyzed using ANOVA and chi(2) test. I/R caused a significant decrease in endothelium-dependent vasodilatation (C:D = 1.37+/-0.31 in IR group vs. 2.06+/-0.20 in baseline, P0.01) and no reflow in arterioles in 16 of 28 unheated rats. Endothelium-independent dilatation was not altered by I/R. Thermotolerance attenuated this impairment of endothelium-dependent dilatation (P0.01 vs. IR; C:D = 1.95+/-0.19) and reduced no-reflow phenomenon to 4 of 16 rats (P0.05 vs. IR). This study demonstrated that thermotolerance preserves endothelial vasomotor function and markedly reduces "no reflow" in arterioles.

To assess the efficacy of the cytoprotective B-amino acid taurine in prevention of skeletal muscle dysfunction secondary to ischaemia-reperfusion (IR) injury.Randomised controlled animal study.Biomedical research laboratory, teaching hospital, Republic of Ireland.96 Sprague Dawley rats.Rats were randomised into three groups (n = 24/group): control (sham); ischaemia-reperfusion (untreated); and ischaemia-reperfusion + taurine. A further 24 rats were given taurine alone. The rat cremaster skeletal muscle model of four hours of ischaemia followed by reperfusion was used. Taurine 4%wt/vol was given in the animals' water throughout the experiment, beginning 48 hours before the ischaemia was initiated.8 rats were killed from each group and muscle contractile function was assessed using electrical field stimulation in a tissue bath at 24 hrs, 48 hrs and 7 days.Ischaemia followed by 24 hours, 48 hours or 7 days of reperfusion resulted in significant reduction in both muscle twitch and tetanic contractile function (p0.05). This was reversed by taurine, which resulted in significant preservation of twitch and tetanic contractility at all time points including one week of reperfusion (p0.05). There was no difference in muscle function between muscle treated with taurine after ischaemia-reperfusion and control muscle, with the same operation but without ischaemia, from 48 hours onwards.These data show that pharmaceutical use of the endogenous amino acid taurine, unlike many-other agents, protects electrophysiological function in skeletal muscle against both early and late ischaemia-reperfusion injury.

Objectives: to determine whether pharmacological induction of heat shock proteins (HSPs) by herbimycin-A (a tyrosine-kinase inhibitor) would protect against neutrophil-mediated lung injury in an animal model of lower torso ischaemia-reperfusion. Materials and methods: Sprague-Dawley rats were randomised into three groups: the control group underwent midline laparotomy only; the ischaemia-reperfusion (IR) group underwent laparotomy and clamping of the infrarenal abdominal aorta for 30 min followed by 2 h of reperfusion; the third group (HerbIR) was pretreated with herbimycin-A 18 h prior to IR insult. Wet to dry lung weight ratio (W:D), bronchoalveolar lavage protein concentration (BALprot), tissue myeloperoxidase activity (MPO) and bronchoalveolar lavage neutrophil count (BALPMN) were measured. Heat shock protein 72 (HSP72) expression in lung, intestine, mesentery and liver was measured using Western immunoblotting. Results: IR resulted in acute lung injury with tissue oedema (W:D) and neutrophil infiltration (PMO, BALPMN). Herbimycin-A, in vivo, induced HSP expression and attenuated neutrophil infiltration (MPO, BALPMN). Conclusion: these data indicate that herbimycin-A protects against ischaemia-reperfusion induced pulmonary neutrophil infiltration, possibly by increasing the expression of heat shock proteins.

Leukocyte-endothelial interaction is a pivotal step in the pathogenesis of ischemia-reperfusion (I/R) injury. Exposure of cells to a subcritical heat stress may protect cells from subsequent I/R injury, through induction of a 72-kDa heat shock protein (HSP72). The aim of this study was to investigate the effect of thermotolerance on leukocyte adherence and migration during an I/R period in rat mesenteric postcapillary venules. Sprague-Dawley rats were randomized into control (sham I/R), I/R, and thermotolerance+I/R groups. Thermotolerance was induced 18 hr prior to I/R, which was in turn established by occlusion of the superior mesenteric vascular pedicle for 10 mins, followed by 60 mins of reperfusion. The blood flow, leukocyte rolling velocity, and the number of adherent and migrated leukocytes in postcapillary venules were measured by intravital microscopy. I/R significantly decreased the rolling velocity of leukocytes; increased the number of adherent leukocytes at 10, 30, and 60 mins after reperfusion; and also increased the number of migrated leukocytes at 60 mins after reperfusion. Thermotolerance induction expression of HSP72 in pulmonary, intestinal, and mesenteric tissues was determined by Western immunoblotting. Thermotolerance significantly prevented the I/R-induced decrease in rolling velocity of leukocytes, the increase in the number of adherent leukocytes at 30 and 60 mins, and the increase in the number of migrated leukocytes at 60 mins. This results suggest that thermotolerance attenuates I/R injury by modulating leukocyte-endothelial interaction in vivo, possibly by increasing tissue expression of HSP72.

Aortic occlusion and revascularization (I-R) may lead to lung injury dependent on activated neutrophil adherence. Nitric oxide (NO) inhibits neutrophil adherence to endothelial cells. We studied the effect of increasing or decreasing NO levels with sodium nitroprusside (SNP) or N-nitro-L-arginine methyl ester (L-NAME) in an I-R lung injury model of 30 min ischemia followed by 120 min reperfusion. Sprague-Dawley rats (10/group) were randomized to controls, I-R, I-R treated with L-NAME (10 mg/ml/hr), and I-R treated with SNP (0.2 mg/ml/hr). Myeloperoxidase activity (MPO) was used as a measure of pulmonary neutrophil influx. Pulmonary endothelial permeability was measured by wet:dry weight ratio and bronchoalveolar lavage protein (BAL prot) and neutrophil counts (BAL PMN). Aortic occlusion and revascularization led to significant increases in pulmonary neutrophil influx (6.1 +/- 0.1 MPO u/g vs 3.05 +/- 0.4 MPO u/g in the control group, P < 0.001) and microvascular leakage; BAL prot (347 +/- 32 mg/ml in controls vs 454 +/- 16 mg/ml in the I-R group, P < 0.05); and BAL PMN (0.7 +/- 0.05 in controls vs 1.8 +/- 0.07 PMN/ml in the I-R group, P < 0.001). These changes were exacerbated further by administration of L-NAME (MPO = 8.9 +/- 0.7; BAL prot = 581 +/- 40 mg/ml; BAL PMN = 2.7 +/- 0.16 PMN/ml). Sodium nitroprusside therapy attenuated the I-R-induced lung injury (3.5 +/- 0.4 MPO u/g, P < 0.05 vs I-R; BAL prot = 330 +/- 61 mg/ml; BAL PMN = 0.9 +/- 0.1 PMN/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Ischaemic nerve injury has been suggested as the mechanism for post-tourniquet limb paralysis. As hypothermia has been shown to prolong ischaemia time in many tissues, we tested the hypothesis that cold protection would reduce tourniquet induced neural injury. In 16 male Wistar rats a tourniquet was applied to the right hind limb for 3 h. In eight rats both hind limbs were maintained at room temperature (27 degrees C) while the limb temperature was decreased to 4 degrees C by application of cold polyglycol gel packs in the remaining eight animals. Motor nerve conduction velocity (MNCV) and the amplitude of muscle motor units (AMMU) in response to nerve stimulation were measured at 0 h, 1 h and 1 week post-tourniquet release. Application of the tourniquet for 3 h abolished nerve conduction in all animals. Hypothermia resulted in a significant improvement in AMMU (5.8 +/- vs. 0.6 +/- 0.4 mv, p less than 0.05) at 1 h and in MNCV (26.6 +/- 1.6 vs. 8.1 +/- 4.4 ms-1, p less than 0.05) and AMMU (18.5 +/- 2.0 vs. 9.7 +/- 4.5 mv, p less than 0.05) at 1 week. Hypothermia without ischaemia also reduced MNCV (44.2 +/- 9.4 vs. 74.3 +/- 8.9 ms-1, p less than 0.05) and AMMU (28.1 +/- 2.8 vs. 36.3 +/- 8.4 mv, N.S.). These data indicate that hypothermia reduces normal MNCV and protects nerve function during tourniquet ischaemia. These results support the ischaemic hypothesis for post-tourniquet nerve injury. Cold protection may have clinical applications for surgical procedures performed with tourniquet ischaemia.