Ischaemia-reperfusion injury impairs tissue plasminogen activator release in man

Chuanzhitongluo capsule ameliorates microcirculatory dysfunction in rats: Efficacy evaluation and metabolic profiles

Background: Ischemic stroke is a leading cause of mortality and disability worldwide. Microcirculatory dysfunction is the foremost hindrance for a good clinical prognosis in ischemic stroke patients. Clinical researches show that Chuanzhitongluo capsule (CZTL) has a curative effect during the recovery period of ischemic stroke, which contributes to a good prognosis. However, it is not known whether CZTL treats ischemic stroke by ameliorating microcirculation dysfunction.

Objective: In this study, we investigated the influence of CZTL on microcirculation and its underlying mechanism.

Methods: A rat model of acute microcirculatory dysfunction was established by stimuli of adrenaline and ice water. The microcirculatory damage in model rats and the efficacy of CZTL were assessed by detecting laser speckle contrast imaging, coagulation function, hemorheology, vasomotor factor and microcirculation function. The potential mechanism of CZTL action was explored by the untargeted metabolomic analysis based on ultra-performance liquid chromatography-quadrupole-time of flight-mass spectrometry.

Results: Laser speckle contrast imaging showed that model rats suffered low perfusion in ears, feet and tails, and CZTL treatment increased microcirculatory blood flow. Coagulation function detection results showed that CZTL diminished the reduction of thrombin time, prothrombin time, activated partial thromboplastin time and the elevated fibrinogen level caused by acute microcirculatory dysfunction. Furthermore, CZTL could recover the increased blood viscosity as well as the abnormal vasomotor and microcirculation function in rats with acute microcirculatory dysfunction. Metabolomics analysis indicated that CZTL might regulate sphingolipid metabolism and arachidonic acid metabolism to exert protective effects on microcirculation.

Conclusion: These results elucidated that CZTL was highly effective against microcirculatory dysfunction and its potential mechanisms related with the modulation of sphingolipid and arachidonic acid metabolic pathways. The present study provided a new perspective on the clinical application of CZTL, and it contribute to explore novel therapeutic drug against microcirculatory dysfunction.

Influence of ischemia-reperfusion injury on endothelial function in men and women with similar serum estradiol concentrations

Prior data suggest that, relative to the early follicular phase, women in the late follicular phase are protected against endothelial ischemia-reperfusion (I/R) injury when estradiol concentrations are highest. In addition, endothelial I/R injury is consistently observed in men with naturally low endogenous estradiol concentrations that are similar to those of women in the early follicular phase. Therefore, the purpose of this study was to determine whether the vasodeleterious effect of I/R injury differs between women in the early follicular phase of the menstrual cycle and age-matched men. We tested the hypothesis that I/R injury would attenuate endothelium-dependent vasodilation to the same extent in women and age-matched men with similar circulating estradiol concentrations. Endothelium-dependent vasodilation was assessed via brachial artery flow-mediated dilation (duplex ultrasound) in young healthy men (n = 22) and women (n = 12) before (pre-I/R) and immediately after (post-I/R) I/R injury, which was induced via 20 min of arm circulatory arrest followed by 20-min reperfusion. Serum estradiol concentrations did not differ between sexes (men 115.0 ± 33.9 pg·mL^-1 vs. women 90.5 ± 40.8 pg·mL^-1; P = 0.2). The magnitude by which I/R injury attenuated endothelium-dependent vasodilation did not differ between men (pre-I/R 5.4 ± 2.4% vs. post-I/R 3.0 ± 2.7%) and women (pre-I/R 6.1 ± 2.8% vs. post-I/R 3.7 ± 2.7%; P = 0.9). Our data demonstrate that I/R injury similarly reduces endothelial function in women in the early follicular phase of the menstrual cycle and age-matched men with similar estradiol concentrations.

Fibrinolysis and Remote Ischemic Conditioning: Mechanisms and Treatment Perspectives in Stroke

Stroke is a leading cause of death and disability. Intravenous thrombolysis and mechanical thrombectomy have greatly improved outcomes in acute ischemic stroke (AIS). However, only a minority of patients receive reperfusion therapies, highlighting the need for novel neuroprotective therapies. Remote ischemic conditioning (RIC), consisting of brief, intermittent extremity occlusion and reperfusion induced with an inflatable cuff, is a potential neuroprotective therapy in acute stroke. The objective of this narrative review is to describe the effect of RIC on endogenous fibrinolysis and, from this perspective, investigate the potential of RIC in the prevention and treatment of stroke. A systematic literature search was performed in PubMed, and human studies in English were included. Seven studies had investigated the effect of RIC on fibrinolysis in humans. Long-term daily administration of RIC increased endogenous fibrinolysis, whereas a single RIC treatment did not acutely influence endogenous fibrinolysis. Fifteen studies had investigated the effect of RIC as a neuroprotective therapy in the prevention and treatment of stroke. Long-term RIC administration proved effective in reducing new cerebral vascular lesions in patients with established cerebrovascular disease. In patients with acute stroke, RIC was safe and feasible, though its clinical efficacy as a neuroprotectant is yet unproven. In conclusion, a single RIC treatment does not affect fibrinolysis in the acute phase, whereas long-term RIC administration may increase endogenous fibrinolysis. Increased endogenous fibrinolysis is unlikely to be the mediator of the acute neuroprotective effect of RIC in stroke patients, whereas it may partly explain the reduced stroke recurrence associated with long-term RIC treatment.

Effect of remote ischaemic conditioning on platelet reactivity and endogenous fibrinolysis in ST-elevation myocardial infarction: a substudy of the CONDI-2/ERIC-PPCI randomized controlled trial

AIMS

Remote ischaemic conditioning (RIC) has been shown to reduce myocardial infarct size in animal models of myocardial infarction. Platelet thrombus formation is a critical determinant of outcome in ST-segment elevation myocardial infarction (STEMI). Whether the beneficial effects of RIC are related to thrombotic parameters is unclear.

METHODS AND RESULTS

In a substudy of the Effect of Remote Ischaemic Conditioning on clinical outcomes in STEMI patients undergoing Primary Percutaneous Coronary Intervention (ERIC-PPCI) trial, we assessed the effect of RIC on thrombotic status. Patients presenting with STEMI were randomized to immediate RIC consisting of an automated autoRIC™ cuff on the upper arm inflated to 200 mmHg for 5 min and deflated for 5 min for four cycles (n = 53) or sham (n = 47). Venous blood was tested at presentation, discharge (48 h) and 6-8 weeks, to assess platelet reactivity, coagulation, and endogenous fibrinolysis using the Global Thrombosis Test and thromboelastography. Baseline thrombotic status was similar in the two groups. At discharge, there was some evidence that the time to in vitro thrombotic occlusion under high shear stress was longer with RIC compared to sham (454 ± 105 s vs. 403 ± 105 s; mean difference 50.1 s; 95% confidence interval 93.7-6.4, P = 0.025), but this was no longer apparent at 6-8 weeks. There was no difference in clot formation or endogenous fibrinolysis between the study arms at any time point.

CONCLUSION

RIC may reduce platelet reactivity in the first 48 h post-STEMI. Further research is needed to delineate mechanisms through which RIC may reduce platelet reactivity, and whether it may improve outcomes in patients with persistent high on-treatment platelet reactivity.

Effect of remote ischemic preconditioning on hemostasis and fibrinolysis in head and neck cancer surgery: A randomized controlled trial

Introduction

The aim of this randomized controlled trial was to investigate if remote ischemic preconditioning (RIPC) reduced platelet aggregation and increased fibrinolysis in cancer patients undergoing surgery and thereby reduced the risk of thrombosis.

Materials and methods

Head and neck cancer patients undergoing tumor resection and microsurgical reconstruction were randomized 1:1 to RIPC or sham intervention. RIPC was administered intraoperatively with an inflatable tourniquet by four cycles of 5-min upper extremity occlusion and 5-min reperfusion. The primary endpoint was collagen-induced platelet aggregation measured with Multiplate as area-under-the-curve on the first postoperative day. Secondary endpoints were markers of primary hemostasis, secondary hemostasis, and fibrinolysis. Clinical data on thromboembolic and bleeding complications were prospectively collected at 30-day follow-up. An intention-to-treat analysis was performed.

Results

Sixty patients were randomized to RIPC (n = 30) or sham intervention (n = 30). No patients were lost to follow-up. The relative mean [95% confidence interval] collagen-induced platelet aggregation was 1.26 [1.11;1.40] in the RIPC group and 1.17 [1.07;1.27] in the sham group on the first postoperative day reported as ratios compared with baseline (P = 0.30). Median (interquartile range) 50% fibrin clot lysis time was 517 (417–660) sec in the RIPC group and 614 (468–779) sec in the sham group (P = 0.25). The postoperative pulmonary embolism rate did not differ between groups (P = 1.0).

Conclusions

RIPC did not influence hemostasis and fibrinolysis in head and neck cancer patients undergoing surgery. RIPC did not reduce the rate of thromboembolic complications.

Tissue conservation for transplantation

Pathophysiological changes that occur during ischemia and subsequent reperfusion cause damage to tissues procured for transplantation and also affect long-term allograft function and survival. The proper preservation of organs before transplantation is a must to limit these injuries as much as possible. For decades, static cold storage has been the gold standard for organ preservation, with mechanical perfusion developing as a promising alternative only recently. The current literature points to the need of developing dedicated preservation protocols for every organ, which in combination with other interventions such as ischemic preconditioning and therapeutic additives offer the possibility of improving organ preservation and extending it to multiple times its current duration. This review strives to present an overview of the current body of knowledge with regard to the preservation of organs and tissues destined for transplantation.

Role of the plasma cascade systems in ischemia/reperfusion injury of bone

Ischemia/reperfusion (I/R) injury has been extensively studied in organs such as heart, brain, liver, kidney, and lung. As a vascularized organ, bone is known to be susceptible to I/R injury too, but the respective mechanisms are not well understood to date. We therefore hypothesized that, similar to other organs, plasma cascade-induced inflammation also plays a role in bone I/R injury. Reperfusion injury in rat tibia was induced by unilateral clamping of the femoral artery and additional use of a tourniquet, while keeping the femoral vein patent to prevent venous congestion. Rats were subjected to 4h ischemia and 24h reperfusion. Deposition of complement fragment C3b/c and fibrin as well as expression of tissue factor (TF), tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), and E-selectin was detected by immunohistochemistry. In plasma, the levels of high mobility group box1 (HMGB1) were measured by ELISA. The total level of complement in serum was assessed by the CH50 test. Our results show that deposition of C3b/c was significantly increased with respect to healthy controls in cortical bone as well as in marrow of reperfused limbs. C3b/c deposition was also increased in cortical bone, but not in bone marrow, of contralateral limbs. Deposition of fibrin, as well as expression of PAI-1, was significantly increased in bone after ischemia and reperfusion, whereas expression of tPA was reduced. These differences were most prominent in vessels of bone, both in marrow and cortical bone, and both in reperfused and contralateral limbs. However, PAI-1, was only increased in vessels of reperfused cortical bone and there were no significant changes in expression of E-selectin. With respect to solid bone tissue, a significant increase of C3b/c and fibrin deposition was shown in osteocytes, and for fibrin also in the bone matrix, in both contralateral and reperfused cortical bone compared with normal healthy controls. A slight expression of TF was visible in osteocytes of the normal healthy control group, while TF was not present in the experimental groups. Moreover, CH50 values in serum decreased over time and HMGB1 was significantly increased in plasma of animals at the end of reperfusion. We conclude that ischemia and reperfusion of bone leads to activation of the complement and coagulation systems and a downregulation of the fibrinolytic cascade. In the acute phase, a vascular inflammation induced by activation of the plasma cascade systems also occurs in the bone. This is similar to I/R injury of other vascularized organs and tissues.

Effect of long-term remote ischaemic conditioning on platelet function and fibrinolysis in patients with chronic ischaemic heart failure

INTRODUCTION

Remote ischaemic conditioning (RIC) protects against ischaemia-reperfusion injury through cellular protective pathways, but may also modulate haemostasis. We aimed to investigate the effect of long-term RIC on platelet function and fibrinolysis in patients with chronic ischaemic heart failure (CIHF).

MATERIAL AND METHODS

In a prospective, outcome-assessor blinded, paired study, 16 patients with CIHF and 21 age- and gender-matched controls without ischaemic heart disease (IHD) were treated with RIC once daily for 28±4days. RIC was performed as four cycles of 5min upper arm ischaemia and reperfusion. We evaluated collagen and arachidonic acid induced platelet aggregation (Multiplate® Analyzer), platelet turnover (Sysmex® XE-5000), platelet activation (plasma soluble-platelet-selectin) and fibrinolysis (clot lysis time, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1)). We compared blood samples assessed at baseline and following long-term RIC.

RESULTS

Long-term RIC did not affect platelet aggregation, turnover or activation or PAI-1 in any study groups. Long-term RIC did not affect fibrin clot lysis time in patients with CIHF but reduced fibrin clot lysis time in matched controls without IHD (median: 773s (interquartile range: 689-936) vs. 658s (618-823), p=0.03). t-PA was increased following long-term RIC in CIHF patients (2.5 (1.7-3.4) vs. 2.9 (1.8-4.0), p=0.03) and in matched controls without IHD (1.5 (1.3-1.9) vs. 1.6 (1.4-2.3), p=0.03).

CONCLUSIONS

While long-term RIC did not affect collagen or arachidonic acid induced platelet aggregation, platelet turnover or sP-selectin, fibrinolysis was increased although most consistently in matched controls without IHD. This finding suggests that RIC may stimulate fibrinolysis potentially reducing the risk of thrombosis.

Human Second Window Pre-Conditioning and Post-Conditioning by Nitrite Is Influenced by a Common Polymorphism in Mitochondrial Aldehyde Dehydrogenase

Pre-conditioning is an exciting physiological phenomenon that, despite great efforts, has so far resisted translation to mainstream clinical medicine. Many potential triggers (e.g., ischemia of the organ in question or a remote organ, many different drugs) have been investigated, but recent work has implicated activation of mitochondrial aldehyde dehydrogenase (ALDH2) as central to the process. A genetic polymorphism, known as ALDH2*2, is common worldwide (present in up to 40% of Han Chinese people) and produces a functionally different enzyme. The authors used a variety of protocols in the human ischemic forearm model, in participants with both enzyme types, to assess cytoprotection with low-dose sodium nitrite and attempt to further elucidate the role of ALDH2.

Remote Limb Ischemic Conditioning at Two Cuff Inflation Pressures Yields Learning Enhancements in Healthy Adults

The authors tested whether 2 doses of remote limb ischemic conditioning (RLIC), induced via blood pressure cuff inflation, enhanced motor and cognitive learning to an equal extent, and explored a panel of blood biomarkers of RLIC. Thirty-two young adults were randomized to 3 groups and underwent a 7-day protocol of RLIC/sham followed by motor and cognitive training, with follow-up. Both RLIC groups had greater motor learning and a trend toward greater cognitive learning compared with the sham group. RLIC at the lower inflation pressure was as effective as RLIC with the higher inflation pressure. No significant candidate blood biomarkers were found. RLIC could be a well-tolerated method to enhance learning and improve rehabilitation outcomes in people with neurological conditions.

Rotigaptide protects the myocardium and arterial vasculature from ischaemia reperfusion injury

AIM

Ischaemia-reperfusion injury (IRI) causes impaired endothelial function and is a major component of the adverse effects of reperfusion following myocardial infarction. Rotigaptide increases gap junction conductance via connexin-43. We tested the hypothesis that rotigaptide reduces experimental myocardial infarction size and ameliorates endothelial IRI in humans.

METHODS

Myocardial infarction study: porcine myocardial infarction was achieved by catheter-induced occlusion of the left anterior descending artery. In a randomized double-blind study, rotigaptide (n = 9) or placebo (n = 10) was administered intravenously as a 10 min bolus prior to reperfusion and continuously during 2 h of reperfusion. Myocardial infarction size (IS) was assessed as proportion of the area at risk (AAR). Human translational study: forearm IRI was induced in the presence or absence of intra-arterial rotigaptide. In a randomized double-blind study, forearm arterial blood flow was measured at rest and during intra-arterial infusion of acetylcholine (5-20 μg min(-1) ; n = 11) or sodium nitroprusside (2-8 mg min(-1) ; n = 10) before and after intra-arterial infusion of placebo or rotigaptide, and again following IRI.

RESULTS

Myocardial infarction study: Rotigaptide treatment was associated with a reduction of infarct size (IS/AAR[%]: 18.7 ± 4.1 [rotigaptide] vs. 43.6 ± 4.2 [placebo], P = 0.006). Human translational study: Endothelium-dependent vasodilatation to acetylcholine was attenuated after ischaemia-reperfusion in the presence of placebo (P = 0.007), but not in the presence of rotigaptide (P = NS). Endothelium-independent vasodilatation evoked by sodium nitroprusside was unaffected by IRI or rotigaptide (P = NS).

CONCLUSIONS

Rotigaptide reduces myocardial infarction size in a porcine model and protects from IRI-related endothelial dysfunction in man. Rotigaptide may have therapeutic potential in the treatment of myocardial infarction.

Remote ischemic conditioning

In remote ischemic conditioning (RIC), brief, reversible episodes of ischemia with reperfusion in one vascular bed, tissue, or organ confer a global protective phenotype and render remote tissues and organs resistant to ischemia/reperfusion injury. The peripheral stimulus can be chemical, mechanical, or electrical and involves activation of peripheral sensory nerves. The signal transfer to the heart or other organs is through neuronal and humoral communications. Protection can be transferred, even across species, with plasma-derived dialysate and involves nitric oxide, stromal derived factor-1α, microribonucleic acid-144, but also other, not yet identified factors. Intracardiac signal transduction involves: adenosine, bradykinin, cytokines, and chemokines, which activate specific receptors; intracellular kinases; and mitochondrial function. RIC by repeated brief inflation/deflation of a blood pressure cuff protects against endothelial dysfunction and myocardial injury in percutaneous coronary interventions, coronary artery bypass grafting, and reperfused acute myocardial infarction. RIC is safe and effective, noninvasive, easily feasible, and inexpensive.

Repeated daily dosing with sildenafil provides sustained protection from endothelial dysfunction caused by ischemia and reperfusion: a human in vivo study

Sildenafil and nitroglycerin (GTN) are effective pharmacological preconditioning agents, protecting from the adverse effects of ischemia and reperfusion (I/R). The objective of the present study was to determine whether repeated, daily administration of sildenafil or GTN provides sustained preconditioning from I/R in the human forearm vasculature. Thirty-six healthy volunteers participated in this investigator-blind, randomized, placebo-controlled trial. Subjects received transdermal GTN (0.6 mg/h, 2 h/day), sildenafil (50 mg once daily), or placebo. Twenty-four hours after the first dose of medication, subjects underwent an assessment of flow-mediated dilation (FMD) before and after I/R (15 min of upper arm ischemia followed by 15 min of reperfusion). Subjects continued their study medication for 7 days, at which point FMD measurements were repeated before and after I/R. Venous blood samples were obtained for the determination of myeloperoxidase, P-selectin, and myoglobin before and after each I/R episode. Twenty-four hours after the first dose, both sildenafil and GTN (but not placebo) provided protection from the adverse effects of I/R. After 7 days of repeated daily doses and 24 h after the last dose, FMD was significantly blunted after I/R in placebo- and GTN-treated groups. In contrast, repeated daily administration of sildenafil provided continued protection from the adverse effects of I/R on endothelial function. There was no significant change in plasma levels of myeloperoxidase, P-selectin, or myoglobin at any time point. In conclusion, the present study establishes, for the first time in humans, that sildenafil, but not GTN, provides sustained pharmacological preconditioning of the endothelium and protection from adverse I/R effects on vascular function.

Biomarkers for ischemic preconditioning: finding the responders

Ischemic preconditioning is emerging as an innovative and novel cytoprotective strategy to counter ischemic vascular disease. At the root of the preconditioning response is the upregulation of endogenous defense systems to achieve ischemic tolerance. Identifying suitable biomarkers to show that a preconditioning response has been induced remains a translational research priority. Preconditioning leads to a widespread genomic and proteonomic response with important effects on hemostatic, endothelial, and inflammatory systems. The present article summarizes the relevant preclinical studies defining the mechanisms of preconditioning, reviews how the human preconditioning response has been investigated, and which of these bioresponses could serve as a suitable biomarker. Human preconditioning studies have investigated the effects of preconditioning on coagulation, endothelial factors, and inflammatory mediators as well as on genetic expression and tissue blood flow imaging. A biomarker for preconditioning would significantly contribute to define the optimal preconditioning stimulus and the extent to which such a response can be elicited in humans and greatly aid in dose selection in the design of phase II trials. Given the manifold biologic effects of preconditioning a panel of multiple serum biomarkers or genomic assessments of upstream regulators may most accurately reflect the full spectrum of a preconditioning response.

Hypercoagulation Assessed by Thromboelastography is Neither Related to Infarct Size nor to Clinical Outcome After Primary Percutaneous Coronary Intervention

Objectives:

We investigated the relationship between coagulation assessed by thromboelastography (TEG) and myocardial damage in ST-segment elevation myocardial infarction (STEMI).

Methods:

We measured platelet activity with TEG-maximum amplitude (TEG-MA) in 233 patients undergoing urgent percutaneous coronary intervention (PCI). Infarct size and myocardial salvage index were evaluated using cardiac magnetic resonance, and the relation of these parameters to posttreatment coagulation was examined retrospectively. Adverse events were adjudicated and related to the coagulation status during the index event.

Results:

Hypercoagulation was found in 82 (35.2%) patients and was neither correlated to infarct size nor correlated to myocardial salvage index ( P = .28 and .65, respectively) or clinical adverse events. Patients who experienced an adverse event during follow-up had a slightly higher TEG-MA value than patients with an event-free follow-up, but this was not statistically significant (68.1 vs 67.3, P = .44).

Conclusions:

The TEG-MA does not appear to be a sensitive predictor of reperfusion success and prognosis in urgent PCI for STEMI.

Prolonged low flow reduces reactive hyperemia and augments low flow mediated constriction in the brachial artery independent of the menstrual cycle

Non-invasive forearm ischemia-reperfusion injury and low flow induced vascular dysfunction models provide methods to evaluate vascular function. The role of oestrogen, an endogenous anti-oxidant on recovery from ischemia-reperfusion injury has not been evaluated nor has the impact of prolonged low flow on vascular function been established. Eight healthy women (33±10 yr) attended the lab during the follicular, ovulatory and mid-luteal phases of their menstrual cycles. After 30 minutes of rest, brachial artery vascular function was assessed by ultrasound measurements of diameter changes during 5 minutes of forearm ischemia and 3 minutes after. Subsequently, a 20-minute forearm ischemia period was completed. Further, vascular function assessments were completed 15, 30 and 45 minutes into recovery. Flow-mediated dilation, low-flow-mediated constriction, and reactive hyperaemia proximal to the area of ischemia were determined. Flow-mediated dilation was reduced at 15 minutes of recovery but recovered at 30 and 45 minutes (PRE: 7.1±1.0%, POST15∶4.5±0.6%, POST30∶5. 5±0.7% POST45∶5.9±0.4%, p<0.01). Conversely, low-flow mediated constriction increased (PRE: −1.3±0.4%, POST15: −3.3±0.6%, POST30: −2.5±0.5% POST45: −1.5±0.12%, p<0.01). Reactive hyperaemia was reduced throughout recovery (p<0.05). Data were unaffected by menstrual phase. Prolonged low flow altered vascular function and may relate as much to increased vasoconstriction as with decreased vasodilation. Reductions in anterograde shear and greater retrograde shear likely modulate the brachial artery response, but the reduced total shear also plays an important role. The data suggest substantial alterations in vascular function proximal to areas of ischemia with potential clinical implications following reperfusion.