C.J. Kelly

Taurine and Vitamin C Modify Monocyte and Endothelial Dysfunction in Young Smokers

Background—Endothelial dysfunction initiated by monocyte-endothelial interactions has previously been observed in many vasculopathies, including chronic cigarette smoking. Taurine, a semiessential amino acid, and vitamin C, a naturally occurring antioxidant, have previously been shown to have endothelial protective effects when exposed to proinflammatory insults. Therefore, we hypothesized that taurine and vitamin C would restore endothelial function in young smokers by modifying monocyte-endothelial interactions. Methods and Results—Endothelial-dependent vasodilatation was assessed in vivo using duplex ultrasonography, and monocyte-endothelial interactions were assessed in vitro using endothelial cell culture (human umbilical vein endothelial cells [HUVECs]) with monocyte-conditioned medium (MCM). Endothelial-dependent vasodilatation was significantly impaired in young smokers compared with nonsmokers. Pretreatment of young smokers for 5 days with 2 g/d vitamin C and, more significantly, with 1.5 g/d taurine attenuated this response. MCM taken from smokers impaired the release of nitric oxide and increased the levels of endothelin-1 release from HUVECs. When HUVECs were cultured with MCM from smokers who had been treated with taurine, the levels of nitric oxide and endothelin-1 returned toward control levels. This was attributed to an upregulation in endothelial nitric oxide synthase expression. Conclusions—These observations suggest that taurine supplementation has a beneficial impact on macrovascular endothelial function, and an investigation of its effect on altered endothelial function in dyslipidemic states is warranted.

Clinically relevant thermal preconditioning attenuates ischemia-reperfusion injury

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 degrees 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 degrees 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 microg/ml to 684 microg/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 microg/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.

Plasma factors augment neutrophil and endothelial cell activation during aortic surgery

Lung injury following reperfusion results from endothelial damage caused by release of cytotoxic products by activated neutrophils (PMN) in the pulmonary microvasculature. This process is facilitated by the release of pro-inflammatory cytokines and arachidonic metabolites following the outset of reperfusion. This study aimed to evaluate the effect of plasma obtained before and after revascularisation on neutrophil and endothelial cell activation. Plasma (IR-plasma) was obtained from venous blood samples taken before and during aortic cross-clamping, and 5, 40 and 60 min following clamp removal in seven patients undergoing elective infrarenal aortic aneurysm resection. PMN from healthy volunteers (n = 5) were incubated with these plasma samples or with fMLP (N-formylmethionyl-leucyl-phenylalanine) as positive control for 30 min and assessed flow-cytometrically for CD11b expression. Human endothelial cells (ECV-304) were incubated with IR plasma for 2, 4 and 6 h or with tumour necrosis factor (TNF) (20 ng/ml) as positive control and assessed for ICAM-1 expression. Incubation with IR plasma resulted in a significant increase from pre-clamp in PMN CD11b expression. A similar trend was seen in endothelial cell ICAM-1 expression following 2 h incubation. These results indicate that reperfusion-induced endothelial dysfunction may be mediated by plasma factors released upon revascularisation which facilitate neutrophil-endothelial interaction through up-regulation of adhesion receptor expression.

Effect of intravenous taurine on endotoxin-induced acute lung injury in sheep.

OBJECTIVE To find out if pretreatment with taurine would reduce the severity of endotoxin-induced acute lung injury in a large animal model. DESIGN Randomised controlled study under licence from the Department of Health. SETTING Department of Surgical Research, Ireland. ANIMALS 15 male Suffolk sheep. INTERVENTIONS Vascular catheters were placed in the femoral artery and vein and a Swan-Ganz catheter in the external jugular vein under general anaesthetic. Animals were randomized into three groups: control with measurements taken at baseline and half hourly up to 90 minutes; endotoxin, given Escherichia coli endotoxin intravenously after baseline measurements and taurine given 300 mg/kg 1 hour before endotoxin was given. MAIN OUTCOME MEASURES Mean systemic arterial pressure, mean pulmonary arterial pressure, arterial oxygen tension (PO2), pulmonary myeloperoxidase activity, and neutrophil respiratory burst activity. RESULTS Endotoxin induced a severe lung injury characterised by a decrease in mean systemic blood pressure and an increase in pulmonary artery pressure, hypoxia, and an increase in pulmonary myeloperoxidase activity. Pretreatment with intravenous taurine significantly reduced these haemodynamic changes. It reduced pulmonary myeloperoxidase activity and peripheral neutropenia and increased neutrophil respiratory burst activity. CONCLUSIONS This data suggest that taurine may have a therapeutic role in preventing the lung injury seen in endotoxaemia.

Arginine supplementation improves histone and acute-phase protein synthesis during gram-negative sepsis in the rat.

Mechanisms of nutrient alteration of hepatic protein synthesis during sepsis are unclear. In vitro, arginine downregulates endotoxin-stimulated hepatocyte protein synthesis but in vivo effects are unknown. This study evaluated the effects of supplemental arginine or glycine on fibrinogen (acute-phase protein), histone, albumin, and liver protein synthesis after Gram-negative sepsis in the rat. Adult rats (225 g, n=36) were randomized to receive isonitrogenous isocaloric total parenteral nutrition supplemented with 264 mg of N per kilogram per day as either arginine or glycine. On day 5, each group was further randomized to control or sepsis. Sepsis was induced by injection of 8 x 10(7) Escherichia coli per 100 g body weight, and then a continuous infusion of [1-14C] leucine was started. The rats were sacrificed 4 hours later. The fractional protein synthesis rates (percent per day) of histone, fibrinogen, albumin, and liver were determined. Supplemental arginine led to significantly increased histone (p < 0.05, analysis of variance) and fibrinogen (p < 0.01, analysis of variance) synthesis in the septic rats compared with all other groups. Histone and albumin synthesis were also significantly increased (p < 0.05) in the arginine-supplemented control group compared with the glycine-supplemented control group. Arginine supplementation during sepsis significantly increased (p < 0.05) albumin and liver protein synthesis compared with controls. Histones which are involved in DNA synthesis and are rich in arginine may play a role in the host response to stress and sepsis. These in vivo results appear to contradict hepatocyte-Kupffer cell coculture studies perhaps because of the hormonal and cytokine responses to nutrient substrate and acute septicemia.

Concurrent colorectal malignancy and abdominal aortic aneurysm: a multicentre experience and review of the literature.

OBJECTIVES There is lack of consensus regarding concurrent vs. staged approaches, and the prioritisation of staged procedures in cases presenting with colorectal carcinoma (CRC) and abdominal aortic aneurysm (AAA) synchronously. We aim to present our experience, review the literature on this therapeutic dilemma and examine the role of endovascular aortic repair (EVAR). DESIGN, MATERIALS AND METHODS An observational study of the experience of two centres and a systematic review of the published literature. RESULTS Twenty-four patients were identified from the prospective databases of two tertiary referral centres between 2001 and 2006. Intervention for both malignancy and aneurysm was performed in 13 patients. In 10 patients, cancer resection was performed initially and was followed by open aneurysm repair (n=3) or EVAR (n=7). Two patients (AAA diameters: 7.0 and 8.0cm) underwent EVAR prior to colonic resection. One patient was selected for synchronous surgery. There were no interval AAA ruptures, graft infection or postoperative mortalities. Literature review identified 269 such cases; of these 101 were treated by combined surgery. In staged surgery, there were nine interval aneurysmal ruptures and one aortic graft infection. CONCLUSIONS In our experience, staged management can be undertaken, without interval aneurysmal rupture. EVAR has an evolving role in preventing delay in CRC management, in high-risk patients, and during combined intervention.

Ruptured abdominal aortic aneurysm — Can treatment costs and outcomes be predicted by using clinical or physiological parameters?

Mortality rates for patients undergoing surgery for ruptured abdominal aortic aneurysm (RAAA) remain high. The high cost of providing care for these patients mandates that proposed treatment protocols be evaluated for their cost-effectiveness. This study assessed costs related to outcome in different groups of patients with RAAA. From July 1987 to December 1993, 140 patients underwent emergency surgery for RAAA. Complete data on preoperative haemodynamic status, blood transfusion requirements, intensive care unit (ICU) stay and other hospital costs was available for 94 patients. Seventy-seven males (mean age 71.6(6)) and 17 females (mean age 77.2(6)) underwent surgery. Known risk factors including age (< or > 70 years), shock on admission (systolic blood pressure (BP) < or > 90 mm Hg), sex, and acute renal failure were analysed. For the purpose of comparison, costs (Pounds) were assessed by the ESRI (Economic and Social Research Institute of Ireland) based on 1992 prices. The overall survival rate was 48%: 53% among males and 24% among females (p < 0.05, Chi-squared test). In addition to having a significantly worse outcome than males, female patients with RAAA also had longer hospital and ICU stays and this was reflected in significantly greater expenditure. Similarly, male patients > 70 years old presenting with haemodynamic instability had significantly longer hospital and ICU stays than younger male patients. The average cost per RAAA survival (12,945 Pounds) in this series is not prohibitive, and the greater cost in high risk groups should not discourage intervention.

Differential effects of lower limb revascularisation on organ injury and the role of the amino acid taurine

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 neutrophil-mediated, agents other than neutrophil-derived oxidative metabolites, capable of independently causing organ injury through direct endothelial damage, are produced during reperfusion.

Regional hypothermia protects against tourniquet neuropathy

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.

Osteoprotegerin is higher in peripheral arterial disease regardless of glycaemic status.

INTRODUCTION Peripheral arterial disease (PAD) and type 2 diabetes mellitus (DM) are both associated with excessive vascular calcification and elevated levels of inflammatory markers IL-6 and hsCRP. The recently identified Osteoprotegerin(OPG)/RANKL/TRAIL pathway has been implicated in vascular calcification, but data on levels in PAD and effect of co-existent DM are lacking. MATERIALS AND METHODS 4 groups of patients were recruited - 26 with PAD and DM, 35 with DM alone, 22 with PAD alone, and 21 healthy individuals. Serum OPG, RANKL, TRAIL, hsCRP and IL-6 were measured using commercial ELISA assays. Presence and severity of PAD was defined using ankle brachial index (ABI). RESULTS Serum OPG (7.4±0.3 vs.5.8±0.2 pmol/l, p<0.0001), TRAIL (95.5±5.2 ng/ml vs. 76.2±4.4 ng/ml, p=0.006), hsCRP (2.6±0.3 vs. 1.8±0.3 mg/l, p=0.048), and IL-6 (4.1±0.4 vs. 2.9±0.4 pg/ml, p=0.06) were higher in patients with PAD. There was no difference in RANKL. Only OPG was significantly higher in PAD and DM (7.2±0.3 pmol/l) and PAD alone (7.7±0.4 pmol/l) compared to DM only (5.8±0.3 pmol/l) and healthy controls (5.6±0.4 pmol/l), p<0.01, but OPG was no higher in those with DM plus PAD versus those with PAD alone (p<0.3). Only OPG was associated with PAD severity, correlating negatively with ABI (r=-0.26, p=0.03), independent of age, gender, glycaemic status, hsCRP and IL-6. CONCLUSIONS PAD is associated with higher serum OPG, regardless of the co-existence of DM. This finding, in addition to its correlation with severity of PAD, suggests that OPG may be a novel marker for the presence and severity of PAD, possibly by reflecting the degree of underlying vascular calcification.