Ischemia-reperfusion: mechanisms of microvascular dysfunction and the influence of risk factors for cardiovascular disease

Goal-directed colloid versus crystalloid therapy and microcirculatory blood flow following ischemia/reperfusion

OBJECTIVE

Ischemia/reperfusion can impair microcirculatory blood flow. It remains unknown whether colloids are superior to crystalloids for restoration of microcirculatory blood flow during ischemia/reperfusion injury. We tested the hypothesis that goal-directed colloid - compared to crystalloid - therapy improves small intestinal, renal, and hepatic microcirculatory blood flow in pigs with ischemia/reperfusion injury.

METHODS

This was a randomized trial in 32 pigs. We induced ischemia/reperfusion by supra-celiac aortic-cross-clamping. Pigs were randomized to receive either goal-directed isooncotic hydroxyethyl-starch colloid or balanced isotonic crystalloid therapy. Microcirculatory blood flow was measured using Laser-Speckle-Contrast-Imaging. The primary outcome was small intestinal, renal, and hepatic microcirculatory blood flow 4.5 h after ischemia/reperfusion. Secondary outcomes included small intestinal, renal, and hepatic histopathological damage, macrohemodynamic and metabolic variables, as well as specific biomarkers of tissue injury, renal, and hepatic function and injury, and endothelial barrier function.

RESULTS

Small intestinal microcirculatory blood flow was higher in pigs assigned to isooncotic hydroxyethyl-starch colloid therapy than in pigs assigned to balanced isotonic crystalloid therapy (768.7 (677.2-860.1) vs. 595.6 (496.3-694.8) arbitrary units, p = .007). There were no important differences in renal (509.7 (427.2-592.1) vs. 442.1 (361.2-523.0) arbitrary units, p = .286) and hepatic (604.7 (507.7-701.8) vs. 548.7 (444.0-653.3) arbitrary units, p = .376) microcirculatory blood flow between groups. Pigs assigned to colloid - compared to crystalloid - therapy also had less small intestinal, but not renal and hepatic, histopathological damage.

CONCLUSIONS

Goal-directed isooncotic hydroxyethyl-starch colloid - compared to balanced isotonic crystalloid - therapy improved small intestinal, but not renal and hepatic, microcirculatory blood flow in pigs with ischemia/reperfusion injury. Whether colloid therapy improves small intestinal microcirculatory blood flow in patients with ischemia/reperfusion needs to be investigated in clinical trials.

Clinical Significance of Elevated Xanthine Dehydrogenase Levels and Hyperuricemia in Patients with Sepsis

Patient outcomes for severe sepsis and septic shock remain poor. Excessive oxidative stress accelerates organ dysfunction in severe acute illnesses. Uric acid (UA) is the most abundant antioxidant. We hypothesized that UA and related molecules, which play a critical role in antioxidant activity, might be markers of oxidative stress in sepsis. The study aimed to clarify the clinical significance of UA and the relationship between UA, molecules related to UA, and outcomes by measuring blood UA, xanthine dehydrogenase (XDH), and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels over time. Blood UA levels in septic patients were correlated with the SOFA score (ρ = 0.36, p < 0.0001) and blood XDH levels (ρ = 0.27, p < 0.0001). Blood XDH levels were correlated with the SOFA score (ρ = 0.59, p < 0.0001) and blood 8-OHdG levels (ρ = -0.32, p < 0.0001). Blood XDH levels were persistently high in fatal cases. Blood XDH level (OR 8.84, 95% CI: 1.42-91.2, p = 0.018) was an independent factor of poor outcomes. The cutoff of blood XDH level was 1.38 ng/mL (sensitivity 92.8%, specificity 61.9%), and those 1.38 ng/mL or higher were associated with a significantly reduced survival rate (blood XDH level > 1.38 ng/mL: 23.7%, blood XDH level < 1.38 ng/mL: 96.3%, respectively, p = 0.0007). Elevated UA levels due to elevated blood XDH levels in sepsis cases may reduce oxidative stress. Countermeasures against increased oxidative stress in sepsis may provide new therapeutic strategies.

Natural compounds regulate the PI3K/Akt/GSK3β pathway in myocardial ischemia-reperfusion injury

The PI3K/Akt/GSK3β pathway is crucial in regulating cardiomyocyte growth and survival. It has been shown that activation of this pathway alleviates the negative impact of ischemia-reperfusion. Glycogen synthase kinase-3 (GSK3β) induces apoptosis through stimulation of transcription factors, and its phosphorylation has been suggested as a new therapeutic target for myocardial ischemia-reperfusion injury (MIRI). GSK3β regulatory role is mediated by the reperfusion injury salvage kinase (RISK) pathway, and its inhibition by Akt activation blocks mitochondrial permeability transition pore (mPTP) opening and enhances myocardial survival. The present article discusses the involvement of the PI3K/Akt/GSK3β pathway in cardioprotective effects of natural products against MIRI.Abbreviations: Akt: protein kinase B; AMPK: AMP-activated protein kinase; ATP: adenosine triphosphate; Bad: bcl2-associated agonist of cell death; Bax: bcl2-associated x protein; Bcl-2: B-cell lymphoma 2; CK-MB: Creatine kinase-MB; CRP: C-reactive-protein; cTnI: cardiac troponin I; EGCG: Epigallocatechin-3-gallate; Enos: endothelial nitric oxide synthase; ER: endoplasmic reticulum; ERK ½: extracellular signal‑regulated protein kinase ½; GSK3β: glycogen synthase kinase-3; GSRd: Ginsenoside Rd; GSH: glutathione; GSSG: glutathione disulfide; HO-1: heme oxygenase-1; HR: hypoxia/reoxygenation; HSYA: Hydroxysafflor Yellow A; ICAM-1: Intercellular Adhesion Molecule 1; IKK-b: IκB kinase; IL: interleukin; IPoC: Ischemic postconditioning; IRI: ischemia-reperfusion injury; JNK: c-Jun N-terminal kinase; Keap1: kelch-like ECH-associated protein- 1; LDH: lactate dehydrogenase; LVEDP: left ventricular end diastolic pressure; LVP: left ventricle pressure; LVSP: left ventricular systolic pressure; MAPK: mitogen-activated protein kinase; MDA: malondialdehyde; MIRI: myocardial ischemia-reperfusion injury; MnSOD: manganese superoxide dismutase; mPTP: mitochondrial permeability transition pore; mtHKII: mitochondria-bound hexokinase II; Nrf-1: nuclear respiratory factor 1; Nrf2: nuclear factor erythroid 2-related factor; NO: nitric oxide; PGC-1α: peroxisome proliferator‑activated receptor γ coactivator‑1α; PI3K: phosphoinositide 3-kinases; RISK: reperfusion injury salvage kinase; ROS: reactive oxygen species; RSV: Resveratrol; SOD: superoxide dismutase; TFAM: transcription factor A mitochondrial; TNF-α: tumor necrosis factor-alpha; VEGF-B: vascular endothelial growth factor B.

Neutrophil dynamics and inflammaging in acute ischemic stroke: A transcriptomic review

Stroke is among the leading causes of death and disability worldwide. Restoring blood flow through recanalization is currently the only acute treatment for cerebral ischemia. Unfortunately, many patients that achieve a complete recanalization fail to regain functional independence. Recent studies indicate that activation of peripheral immune cells, particularly neutrophils, may contribute to microcirculatory failure and futile recanalization. Stroke primarily affects the elderly population, and mortality after endovascular therapies is associated with advanced age. Previous analyses of differential gene expression across injury status and age identify ischemic stroke as a complex age-related disease. It also suggests robust interactions between stroke injury, aging, and inflammation on a cellular and molecular level. Understanding such interactions is crucial in developing effective protective treatments. The global stroke burden will continue to increase with a rapidly aging human population. Unfortunately, the mechanisms of age-dependent vulnerability are poorly defined. In this review, we will discuss how neutrophil-specific gene expression patterns may contribute to poor treatment responses in stroke patients. We will also discuss age-related transcriptional changes that may contribute to poor clinical outcomes and greater susceptibility to cerebrovascular diseases.

Capillaroscopic Evidence of Microvascular Damage in Volleyball Players

Volleyball players experience repetitive stress that involves their hands and, in particular, their fingers. Literature reports that repetitive trauma can lead to local vascular abnormalities, such as reduced capillarization and lower resting blood flow. These anomalies could be related to the presence of dysfunctional endothelium. The aim of this study is to correlate the capillaroscopic findings by nailfold video capillaroscopy (NVC) to volleyball practice in order to early detect possible anomalies and perform an adequate follow-up to avoid damages that could negatively affect sport practice and the players' health status. In this study, 38 subjects were enrolled, 19 volleyball players and 19 healthy non-players as a comparison group. In almost all the players, we found capillaroscopic alterations of the "aspecific pattern" type without substantial gender differences. We may assume that the repeated traumas involving players' fingers can negatively modify their microcirculation. Based on these observations, it could be a desirable clinical practice to screen professional volleyball players with NVC in order to implement preventive strategies aimed at protecting the health of athletes.

Suppressing Pyroptosis Augments Post-Transplant Survival of Stem Cells and Cardiac Function Following Ischemic Injury

The acute demise of stem cells following transplantation significantly compromises the efficacy of stem cell-based cell therapeutics for infarcted hearts. As the stem cells transplanted into the damaged heart are readily exposed to the hostile environment, it can be assumed that the acute death of the transplanted stem cells is also inflicted by the same environmental cues that caused massive death of the host cardiac cells. Pyroptosis, a highly inflammatory form of programmed cell death, has been added to the list of important cell death mechanisms in the damaged heart. However, unlike the well-established cell death mechanisms such as necrosis or apoptosis, the exact role and significance of pyroptosis in the acute death of transplanted stem cells have not been explored in depth. In the present study, we found that M1 macrophages mediate the pyroptosis in the ischemia/reperfusion (I/R) injured hearts and identified miRNA-762 as an important regulator of interleukin 1β production and subsequent pyroptosis. Delivery of exogenous miRNA-762 prior to transplantation significantly increased the post-transplant survival of stem cells and also significantly ameliorated cardiac fibrosis and heart functions following I/R injury. Our data strongly suggest that suppressing pyroptosis can be an effective adjuvant strategy to enhance the efficacy of stem cell-based therapeutics for diseased hearts.

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.

The use of pulse pressure variation for predicting impairment of microcirculatory blood flow

Dynamic parameters of preload have been widely recommended to guide fluid therapy based on the principle of fluid responsiveness and with regard to cardiac output. An equally important aspect is however to also avoid volume-overload. This accounts particularly when capillary leakage is present and volume-overload will promote impairment of microcirculatory blood flow. The aim of this study was to evaluate, whether an impairment of intestinal microcirculation caused by volume-load potentially can be predicted using pulse pressure variation in an experimental model of ischemia/reperfusion injury. The study was designed as a prospective explorative large animal pilot study. The study was performed in 8 anesthetized domestic pigs (German landrace). Ischemia/reperfusion was induced during aortic surgery. 6 h after ischemia/reperfusion-injury measurements were performed during 4 consecutive volume-loading-steps, each consisting of 6 ml kg⁻¹ bodyweight⁻¹. Mean microcirculatory blood flow (mean Flux) of the ileum was measured using direct laser-speckle-contrast-imaging. Receiver operating characteristic analysis was performed to determine the ability of pulse pressure variation to predict a decrease in microcirculation. A reduction of ≥ 10% mean Flux was considered a relevant decrease. After ischemia–reperfusion, volume-loading-steps led to a significant increase of cardiac output as well as mean arterial pressure, while pulse pressure variation and mean Flux were significantly reduced (Pairwise comparison ischemia/reperfusion-injury vs. volume loading step no. 4): cardiac output (l min⁻¹) 1.68 (1.02–2.35) versus 2.84 (2.15–3.53), p = 0.002, mean arterial pressure (mmHg) 29.89 (21.65–38.12) versus 52.34 (43.55–61.14), p < 0.001, pulse pressure variation (%) 24.84 (17.45–32.22) versus 9.59 (1.68–17.49), p = 0.004, mean Flux (p.u.) 414.95 (295.18–534.72) versus 327.21 (206.95–447.48), p = 0.006. Receiver operating characteristic analysis revealed an area under the curve of 0.88 (CI 95% 0.73–1.00; p value < 0.001) for pulse pressure variation for predicting a decrease of microcirculatory blood flow. The results of our study show that pulse pressure variation does have the potential to predict decreases of intestinal microcirculatory blood flow due to volume-load after ischemia/reperfusion-injury. This should encourage further translational research and might help to prevent microcirculatory impairment due to excessive fluid resuscitation and to guide fluid therapy in the future.

Hyperoxia After Return of Spontaneous Circulation in Cardiac Arrest Patients

Current guidelines emphasize the use of 100% oxygen during cardiopulmonary resuscitation after cardiac arrest. When patients are ventilated for variable periods after return of spontaneous circulation (ROSC), hyperoxia causes increased morbidity and mortality by overproduction of reactive oxygen species. Various patient, volunteer, and animal studies have shown the harmful effects of hyperoxia. This mini-review article aims to expand the potential clinical spectrum of hyperoxia on individual organ systems leading to organ dysfunction. A framework to achieve and maintain normoxia after ROSC is proposed. Despite the harmful considerations of hyperoxia in critically ill patients, additional safety studies including dose-effect, level and onset of the reactive oxygen species effect, and safe hyperoxia applicability period after ROSC, need to be performed in various animal and human models to further elucidate the role of oxygen therapy after cardiac arrest.

The multifaceted role of ischemia/reperfusion in sickle cell anemia

Sickle cell anemia is a unique disease dominated by hemolytic anemia and vaso-occlusive events. The latter trigger a version of ischemia/reperfusion (I/R) pathobiology that is singular in its origin, cyclicity, complexity, instability, perpetuity, and breadth of clinical consequences. Specific clinical features are probably attributable to local I/R injury (e.g., stroke syndromes) or remote organ injury (e.g., acute chest syndrome) or the systematization of inflammation (e.g., multifocal arteriopathy). Indeed, by fashioning an underlying template of endothelial dysfunction and vulnerability, the robust inflammatory systematization no doubt contributes to all sickle pathology. In this Review, we highlight I/R-targeting therapeutics shown to improve microvascular blood flow in sickle transgenic mice undergoing I/R, and we suggest how such insights might be translated into human therapeutic strategies.

A review of myocardial ischaemia/reperfusion injury: Pathophysiology, experimental models, biomarkers, genetics and pharmacological treatment

Cardiovascular diseases are known to be the most fatal diseases worldwide. Ischaemia/reperfusion (I/R) injury is at the centre of the pathology of the most common cardiovascular diseases. According to the World Health Organization estimates, ischaemic heart disease is the leading global cause of death, causing more than 9 million deaths in 2016. After cardiovascular events, thrombolysis, percutaneous transluminal coronary angioplasty or coronary bypass surgery are applied as treatment. However, after restoring coronary blood flow, myocardial I/R injury may occur. It is known that this damage occurs due to many pathophysiological mechanisms, especially increasing reactive oxygen types. Besides causing cardiomyocyte death through multiple mechanisms, it may be an important reason for affecting other cell types such as platelets, fibroblasts, endothelial and smooth muscle cells and immune cells. Also, polymorphonuclear leukocytes are associated with myocardial I/R damage during reperfusion. This damage may be insufficient in patients with co-morbidity, as it is demonstrated that it can be prevented by various endogenous antioxidant systems. In this context, the resulting data suggest that optimal cardioprotection may require a combination of additional or synergistic multi-target treatments. In this review, we discussed the pathophysiology, experimental models, biomarkers, treatment and its relationship with genetics in myocardial I/R injury. SIGNIFICANCE OF THE STUDY: This review summarized current information on myocardial ischaemia/reperfusion injury (pathophysiology, experimental models, biomarkers, genetics and pharmacological therapy) for researchers and reveals guiding data for researchers, especially in the field of cardiovascular system and pharmacology.

TRAF1 Exacerbates Myocardial Ischemia Reperfusion Injury via ASK1-JNK/p38 Signaling

Background After acute myocardial infarction, the recovery of ischemic myocardial blood flow may cause myocardial reperfusion injury, which reduces the efficacy of myocardial reperfusion. Ways to reduce and prevent myocardial ischemia/reperfusion (I/R) injury are of great clinical significance in the treatment of patients with acute myocardial infarction. TRAF1 (tumor necrosis factor receptor-associated factor 1) is an important adapter protein that is implicated in molecular events regulating immunity, inflammation, and cell death. Little is known about the role and impact of TRAF1 in myocardial I/R injury. Methods and Results TRAF1 expression is markedly induced in wild-type mice and cardiomyocytes after I/R or hypoxia/reoxygenation stimulation. I/R models were established in TRAF1 knockout mice and wild type mice (n=10 per group). We demonstrated that TRAF1 deficiency protects against myocardial I/R-induced loss of heat function, inflammation, and cardiomyocyte death. In addition, overexpression of TRAF1 in primary cardiomyocytes promotes hypoxia/reoxygenation-induced inflammation and apoptosis in vitro. Mechanistically, TRAF1 promotes myocardial I/R injury through regulating ASK1 (apoptosis signal-regulating kinase 1)-mediated JNK/p38 (c-Jun N-terminal kinase/p38) MAPK (mitogen-activated protein kinase) cascades. Conclusions Our results indicated that TRAF1 aggravates the development of myocardial I/R injury by enhancing the activation of ASK1-mediated JNK/p38 cascades. Targeting the TRAF1-ASK1-JNK/p38 pathway provide feasible therapies for cardiac I/R injury.

Reactive species-induced microvascular dysfunction in ischemia/reperfusion

Vascular endothelial cells line the inner surface of the entire cardiovascular system as a single layer and are involved in an impressive array of functions, ranging from the regulation of vascular tone in resistance arteries and arterioles, modulation of microvascular barrier function in capillaries and postcapillary venules, and control of proinflammatory and prothrombotic processes, which occur in all segments of the vascular tree but can be especially prominent in postcapillary venules. When tissues are subjected to ischemia/reperfusion (I/R), the endothelium of resistance arteries and arterioles, capillaries, and postcapillary venules become dysfunctional, resulting in impaired endothelium-dependent vasodilator and enhanced endothelium-dependent vasoconstrictor responses along with increased vulnerability to thrombus formation, enhanced fluid filtration and protein extravasation, and increased blood-to-interstitium trafficking of leukocytes in these functionally distinct segments of the microcirculation. The number of capillaries open to flow upon reperfusion also declines as a result of I/R, which impairs nutritive perfusion. All of these pathologic microvascular events involve the formation of reactive species (RS) derived from molecular oxygen and/or nitric oxide. In addition to these effects, I/R-induced RS activate NLRP3 inflammasomes, alter connexin/pannexin signaling, provoke mitochondrial fission, and cause release of microvesicles in endothelial cells, resulting in deranged function in arterioles, capillaries, and venules. It is now apparent that this microvascular dysfunction is an important determinant of the severity of injury sustained by parenchymal cells in ischemic tissues, as well as being predictive of clinical outcome after reperfusion therapy. On the other hand, RS production at signaling levels promotes ischemic angiogenesis, mediates flow-induced dilation in patients with coronary artery disease, and instigates the activation of cell survival programs by conditioning stimuli that render tissues resistant to the deleterious effects of prolonged I/R. These topics will be reviewed in this article.

Effects of pycnogenol on ischemia/reperfusion-induced inflammatory and oxidative brain injury in rats

BACKGROUND

Ischemia/reperfusion (I/R) injury results from the onset of re-circulation following a perfusion deterioration period in the tissues, resulting in more damage than that caused by perfusion deterioration. This study aimed to determine the effects of pycnogenol on I/R injury in rat brain tissues.

METHODS

Eighteen albino Wistar rats were divided into three groups: I/R injury (IR, n = 6) group; I/R injury + pycnogenol (IR + P, n = 6) group; and sham group (SG, n = 6). After 30 min of transient ischemia, 24 h of reperfusion was achieved in the IR and IR + P groups. Surgical dissection, except for transient ischemia, was performed in SG. Next, histopathological and biochemical investigations were performed on brain tissues. Malondialdehyde (MDA), reduced glutathione (GSH), and glutathione peroxidase (GPO) were analyzed as oxidative stress markers; IL-1β and TNF-α were analyzed as inflammatory stress markers in biochemical tests.

RESULTS

Histopathological examination revealed normal morphology in SG and diffuse cortex damage with edema, vasopathology, and inflammatory cell infiltration in the IR group. The IR + P group showed less cortex damage, edema, and vasopathology than the IR group. The MDA, IL-1β, and TNF-α levels were significantly higher in the IR group than those in the SG group. The values of same markers for the IR + P group were significantly lower than the IR group. The GSH and GPO levels were significantly decreased with IR damage, but PYC treatment showed significant improvement in the levels.

CONCLUSION

This study showed that the administration of pycnogenol ameliorated brain damage after I/R injury by reducing oxidative and inflammatory damage in the rat brain.

Volume Based Resuscitation and Intestinal Microcirculation after Ischaemia/Reperfusion Injury: Results of an Exploratory Aortic Clamping Study in Pigs

OBJECTIVES

In the presence of ischaemia/reperfusion (I/R) induced endothelial injury, volume administration may not correlate with increased microcirculation. The aim of this study was to evaluate intestinal microcirculation after standardised sequential volume loading in an animal model of I/R injury following supracoeliac aortic clamping.

METHODS

This was a prospective exploratory pilot animal study. Intestinal I/R injury was induced in eight pigs during experimental thoraco-abdominal aortic repair. After 6 h of I/R, microcirculatory blood flow (mFlux, measured in the ileum using direct laser speckle contrast imaging) and macrohaemodynamic parameters (using trans-cardiopulmonary thermodilution) were measured and measurements were repeated after each of four sequential volume loading steps (VLS1 - 4). Each load was administered over 5 min followed by another 5 min for equilibration.

RESULTS

All animals survived until after VLS4. After 6 h of I/R cardiac output (CO) (p < .001) and mFlux (p < .001) had both decreased. CO increased again after VLS1 (p < .001) and VLS2 (p = .036), whereas mFlux did not change. In contrast, mFlux further decreased after VLS3 (p < .01) and VLS4 (p < .001), whereas CO did not change anymore. Extravascular lung water continued to increase after VLS2 (p = .046) and VLS4 (p = .049).

CONCLUSIONS

I/R leads to impaired intestinal microcirculation, which was not restored by volume administration in spite of improved CO. In contrast, further volume administration exceeding preload reserves was associated with additional decreases in the intestinal microcirculation. The potentially negative effect of excessive volume resuscitation after I/R injury should encourage further translational research.

Examining the Use of Sodium Nitroprusside in Coronary Artery Bypass Grafting: Is the Benefit Worth the Cost?

Purpose: Sodium nitroprusside is a vasodilator frequently used in the coronary artery bypass grafting (CABG) setting. However, the price of a 50-mg vial of sodium nitroprusside increased from $5.00 in 2003 to up to $900 in 2016. The purpose of this review is to help health systems balance high-quality patient care with economic responsibility. Methods: A MEDLINE literature search was performed using the search terms "nitroprusside" and "coronary artery bypass." All English-language trials in human subjects assessing the use of sodium nitroprusside in the setting of CABG were evaluated. The references of these studies were also reviewed. Results: In the setting of CABG, sodium nitroprusside attenuates conduit vasospasm and reduces the incidence of inflammation, atrial fibrillation, and acute kidney injury after surgery. However, other vasodilators are more effective at maintaining postoperative blood pressure at goal. Conclusions: Despite its cost, sodium nitroprusside may be an appropriate agent to use during CABG operations, but other agents should be considered for treatment of postoperative hypertension.

Antioxidants in experimental ischemia-reperfusion injury of the testis: Where are we heading towards?

Testicular torsion (TT) is a medical emergency that primary affects newborns and young adolescents. It causes testicular injury due to the torsion of the spermatic cord and its components, initially in the venous blood flow and finally in the arterial blood flow. Prompt diagnosis and early surgical management are necessary in managing this urgent situation. The process of the pathophysiological events in ischemia-reperfusion is multifactorial and deals with the perception of the oxidative stress responsible for the consequences of ischemia/reperfusion (I/R) stress following TT. Duration and severity of torsion also play a significant role in the oxidative stress. A detrimental result of the defense system of the testes takes place resulting finally in testicular atrophy and impaired function. Antioxidant factors have been experimentally studied in an effort to front this state. They have been classified as endogenous or exogenous antioxidants. Endogenous antioxidants comprise a structure of enzymic enzymatic and non-enzymic enzymatic particles presented within cytoplasm and numerous other subunits in the cells. Exogenous antioxidants include a variety of natural and pharmaceutical agents that may prevent or ameliorate the harmful effects of I/R injury. In this study we review those factors and their ability to enhance the oxidative status of the testis. A feature insight into where we are heading is attempted.

Acetylsalicylic acid-tris-hydroxymethyl-aminomethane reduces colon mucosal damage without causing gastric side effects in a rat model of colitis

BACKGROUND

We have developed a novel compound from acetylsalicylic acid (ASA) and 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris) precursors with ASA-like anti-inflammatory efficacy and reduced the mucosa-damaging side-effects. Our aim was to examine local and remote consequences of ASA-Tris administration in 2-,4-,6-trinitrobenzene-sulfonic acid (TNBS)-induced colitis as compared to ASA or mesalamine (5-aminosalicylate) treatment.

METHODS

Sprague-Dawley rats were randomized to five groups (n = 6, each), and TNBS enemas were performed. Group 1 was the negative control; group 2 was the untreated colitis group. 12 hour after colitis induction repeated doses of ASA, ASA-Tris (both 0.55 mmol/kg) and mesalamine (0.77 mmol/kg) were given 3 times daily for 3 days to groups 3-5. On day 3 of colitis, the in vivo histology of the colon and stomach was investigated. Tissue xanthine-oxidoreductase, myeloperoxidase, nitrite/nitrate changes, and circulating TNF-alpha levels were measured. In addition, liver mitochondria were examined with high-resolution respirometry to analyze alterations in the electron transport chain.

RESULTS

TNBS enema significantly elevated inflammatory enzyme activities, NO production, TNF-alpha concentration, and induced morphological damage in the colon. ASA-treatment reduced the inflammatory marker levels and mucosal injury in the colon, but gastric tissue damage was present. ASA-Tris- and mesalamine-treatments significantly reduced the cytokine levels, inflammatory enzyme activities, and colonic mucosal damage without inducing gastric injury. Also, ASA significantly reduced the Complex IV-linked respiration of liver mitochondria, which was not observed after ASA-Tris-treatment.

CONCLUSION

As compared to ASA, ASA-Tris conjugation provides significant protection against the colonic injury and cytokine-mediated progression of inflammatory events in experimental colitis without influencing the gastric epithelial structure.

Redox-Dependent Calpain Signaling in Airway and Pulmonary Vascular Remodeling in COPD

The calcium-dependent cytosolic, neutral, thiol endopeptidases, calpains, perform limited cleavage of their substrates thereby irreversibly changing their functions. Calpains have been shown to be involved in several physiological processes such as cell motility, proliferation, cell cycle, signal transduction, and apoptosis. Overactivation of calpain or mutations in the calpain genes contribute to a number of pathological conditions including neurodegenerative disorders, rheumatoid arthritis, cancer, and lung diseases. High concentrations of reactive oxygen and nitrogen species (RONS) originated from cigarette smoke or released by numerous cell types such as activated inflammatory cells and other respiratory cells cause oxidative and nitrosative stress contributing to the pathogenesis of COPD. RONS and calpain play important roles in the development of airway and pulmonary vascular remodeling in COPD. Published data show that increased RONS production is associated with increased calpain activation and/or elevated calpain protein level, leading to epithelial or endothelial barrier dysfunction, neovascularization, lung inflammation, increased smooth muscle cell proliferation, and deposition of extracellular matrix protein. Further investigation of the redox-dependent calpain signaling may provide future targets for the prevention and treatment of COPD.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

Editor's Choice- Inside the cold heart: A review of therapeutic hypothermia cardioprotection

Targeted temperature management has been originally used to reduce neurological injury and improve outcome in patients after out-of-hospital cardiac arrest. Myocardial infarction remains a major cause of death in the world and several investigators are studying the effect of mild therapeutic hypothermia during an acute cardiac ischemic injury. A search on MEDLINE, Scopus and EMBASE databases was conducted to obtain data regarding the cardioprotective properties of therapeutic hypothermia. Preclinical studies have shown that therapeutic hypothermia provides a cardioprotective effect in animals. The proposed pathways for the cardioprotective effects of therapeutic hypothermia include stabilization of mitochondrial permeability, production of nitric oxide, equilibration of reactive oxygen species, and calcium channels homeostasis. Clinical trials in humans have yielded controversial results. Current trials are therefore seeking to combine therapeutic hypothermia with other treatment modalities in order to improve the outcomes of patients with acute ischemic injury. This article provides a review of the hypothermia effects on the cardiovascular system, from the basic science of physiological changes in the human body and molecular mechanisms of cardioprotection to the bench of clinical trials with therapeutic hypothermia in patients with acute ischemic injury.

Delayed coronary reperfusion is ineffective at impeding the dynamic increase in cardiac efferent sympathetic nerve activity following myocardial ischemia

Acute myocardial infarction (MI) is associated with an adverse and sustained increase in cardiac sympathetic nerve activity (SNA), triggering potentially fatal ventricular arrhythmias. While myocardial reperfusion undoubtedly improves patient prognosis, it remains unknown whether reperfusion therapy also attenuates the dangerous increase in SNA. This study aimed to investigate the effect of time-dependent coronary reperfusion therapy on cardiac SNA following acute MI. Electrophysiological recordings of cardiac efferent SNA were performed in urethane-anaesthetized rats following ligation of the left anterior descending coronary artery (i.e., MI) for either 15 or 45 min, followed by 'early' or 'delayed' reperfusion, respectively. Another group of rats had permanent ischemia with no reperfusion. Forty-five minutes of ischemia induced a 55 % increase in efferent SNA. Subsequent 'delayed' reperfusion was ineffective at ameliorating further increases in SNA (maximal 153 % increase), so that MI-induced increases in SNA mirrored that observed in rats with permanent MI. Although SNA did not increase during 15 min of ischemia, it did significantly increase, albeit delayed, during the subsequent reperfusion period (max. 75 % increase). Importantly, however, this increase in SNA, which tended to be lower in the 'early'-reperfusion group, was matched with a lower incidence of arrhythmias and mortality rate, compared to the 'delayed'-reperfusion and permanent-MI groups. These results highlight that 'prompt' coronary reperfusion, before SNA becomes activated, may provide a crucial window of opportunity for improving outcome. Further research is essential to identify the mechanisms that underpin, not only sympathetic activation, but also importantly sympathetic deactivation as a potential therapeutic target for MI.

Differences in ward-to-cath lab systolic blood pressure predicts long-term adverse outcomes after drug-eluting stent implantation

We sought to investigate the effect of ward-to-cath lab blood pressure (BP) differences on long-term clinical outcomes in patients undergoing percutaneous coronary intervention (PCI) with drug-eluting stent (DES). There are limited data available on the association between PCI with DES and BP differences on long-term clinical outcomes. This study enrolled 994 patients who underwent PCI with DES from March 2003 to August 2007. Resting BP was measured in a ward environment before transfer to the cardiac catheterization lab (cath lab), and again when the patient was laid down on the cath lab table. Patients were divided into two groups according to the difference in ward-to-cath lab systolic BP. Large difference group (n = 383) was defined as the absolute systolic difference of >20 mmHg and small difference group (n = 424) as the absolute systolic difference of ≤20 mmHg. The primary endpoints were all-cause mortality, cardiac death, nonfatal myocardial infarction and stroke. A total of 807 patients (mean age 60 ± 10 years, 522 males) received follow-up for 5.1 ± 2.4 years. The rate of all-cause mortality was significantly higher in the large difference group compared to the small difference group (6.6 vs. 2.8 %; adjusted hazard ratio (HR) 2.43; 95 % confidence interval (CI) 1.22-4.83; p = 0.012). There were higher cardiac deaths seen in the large difference group compared to the small difference group (3.9 vs. 1.4 %; adjusted HR 2.84; 95 % CI 1.1-7.31; p = 0.031). Stroke (2.4 vs. 1.2 %, p = 0.125) and TVR (3.7 vs. 1.7 %, p = 0.051) had higher trends in the large difference group compared to the small difference group. The composite of primary endpoints (all-cause mortality, cardiac death, nonfatal MI and stroke) occurred more frequently in the large difference group compared to the small difference group (10.0 vs. 6.4 %; adjusted HR 1.71; 95 % CI 1.04-2.81; p = 0.033). A difference in ward-to-cath lab systolic BP of >20 mmHg may contribute to increased adverse outcomes in the form of all-cause mortality and cardiac deaths in patients undergoing PCI with DES.

Hypercholesterolemia: its impact on ischemia-reperfusion injury

Ischemic diseases are a leading cause of death worldwide. It is becoming increasingly appreciated that atherosclerosis is a major cause of ischemia reperfusion. Hypercholesterolemia is a major risk factor for the development of atherosclerosis, and is associated with an increased incidence of ischemia reperfusion. Furthermore, elevated cholesterol levels exacerbate the vascular responses to ischemia-reperfusion, which intensifies the resulting organ dysfunction. One of the underlying features of both ischemia-reperfusion injury and hypercholesterolemia is the proinflammatory and prothrombogenic phenotype invoked in the microvasculature. This is manifested as an endothelial dysfunction, characterized by leukocyte and platelet recruitment, oxidative stress and angiotensin II receptor Type 1a activation. These common pathways of inflammation offer attractive targets for the development of drugs to combat cardiovascular disease and the associated ischemic disorders.

Role of reactive oxygen and nitrogen species in the vascular responses to inflammation

Inflammation is a complex and potentially life-threatening condition that involves the participation of a variety of chemical mediators, signaling pathways, and cell types. The microcirculation, which is critical for the initiation and perpetuation of an inflammatory response, exhibits several characteristic functional and structural changes in response to inflammation. These include vasomotor dysfunction (impaired vessel dilation and constriction), the adhesion and transendothelial migration of leukocytes, endothelial barrier dysfunction (increased vascular permeability), blood vessel proliferation (angiogenesis), and enhanced thrombus formation. These diverse responses of the microvasculature largely reflect the endothelial cell dysfunction that accompanies inflammation and the central role of these cells in modulating processes as varied as blood flow regulation, angiogenesis, and thrombogenesis. The importance of endothelial cells in inflammation-induced vascular dysfunction is also predicated on the ability of these cells to produce and respond to reactive oxygen and nitrogen species. Inflammation seems to upset the balance between nitric oxide and superoxide within (and surrounding) endothelial cells, which is necessary for normal vessel function. This review is focused on defining the molecular targets in the vessel wall that interact with reactive oxygen species and nitric oxide to produce the characteristic functional and structural changes that occur in response to inflammation. This analysis of the literature is consistent with the view that reactive oxygen and nitrogen species contribute significantly to the diverse vascular responses in inflammation and supports efforts that are directed at targeting these highly reactive species to maintain normal vascular health in pathological conditions that are associated with acute or chronic inflammation.

The impact of hypertension and diabetes on outcome in patients undergoing percutaneous coronary intervention

OBJECTIVE

Information relating the outcome of percutaneous coronary intervention to diabetes mellitus or hypertension is limited. The study objective was to describe the outcome in patients undergoing percutaneous coronary intervention in relation to diabetes and hypertension.

METHODS

Data were extracted from 5 national registers: the Swedish Coronary Angiography and Angioplasty Register (all percutaneous coronary interventions), the Prescribed Drug Registry (all prescribed pharmaceuticals purchased in Swedish pharmacies), the Swedish Hospital Discharge Register (data on myocardial infarction, revascularization, stroke, and congestive heart failure from in-hospital and specialist health care), and the National Population Register and Cause of Death Register (data on death). We included all "first percutaneous coronary interventions" between January 1, 2006, and December 31, 2008 (n=44,268; followed an average of 1.9 [± 0.9] years).

RESULTS

Mortality was 6.4% and highest in patients with diabetes plus hypertension. Hypertension per se did not increase mortality or the risk for repeat intervention, but carried a 10% increased risk for subsequent myocardial infarction, increasing to a 4-fold increase when combined with diabetes. Stroke occurred in 2%; the importance of hypertension was evident in nondiabetic patients, but even stronger in diabetic patients. Congestive heart failure caused hospital admission in 8%, with a negative influence from hypertension with and without diabetes.

CONCLUSION

After percutaneous coronary intervention and with modern pharmacotherapy, diabetes had a negative effect on the outcome, especially when combined with hypertension. Hypertension per se was not associated with increased mortality but with an increased risk for myocardial infarction, stroke, and congestive heart failure, probably related to widespread coronary artery disease. Improved diabetes care might improve the prognosis.

Effects of disturbed flow on vascular endothelium: pathophysiological basis and clinical perspectives

Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.

Cytomegalovirus infection leads to microvascular dysfunction and exacerbates hypercholesterolemia-induced responses

Cytomegalovirus (CMV) persistently infects more than 60% of the worldwide population. In immunocompetent hosts, it has been implicated in several diseases, including cardiovascular disease, possibly through the induction of inflammatory pathways. Cardiovascular risk factors promote an inflammatory phenotype in the microvasculature long before clinical disease is evident. This study determined whether CMV also impairs microvascular homeostasis and synergizes with hypercholesterolemia to exaggerate these responses. Intravital microscopy was used to assess endothelium-dependent and -independent arteriolar vasodilation and venular leukocyte and platelet adhesion in mice after injection with either mock inoculum or murine CMV (mCMV). Mice were fed a normal (ND) or high-cholesterol (HC) diet beginning at 5 weeks postinfection (p.i.), or a HC diet for the final 4 weeks of infection. mCMV-ND mice exhibited impaired endothelium-dependent vasodilation versus mock-ND at 9 and 12 weeks and endothelium-independent arteriolar dysfunction by 24 weeks. Transient mild leukocyte adhesion occurred in mCMV-ND venules at 7 and 21 weeks p.i. HC alone caused temporary arteriolar dysfunction and venular leukocyte and platelet recruitment, which were exaggerated and prolonged by mCMV infection. The time of introduction of HC after mCMV infection determined whether mCMV+HC led to worse venular inflammation than either factor alone. These findings reveal a proinflammatory influence of persistent mCMV on the microvasculature, and suggest that mCMV infection enhances microvasculature susceptibility to both inflammatory and thrombogenic responses caused by hypercholesterolemia.

Diannexin treatment decreases ischemia-reperfusion injury at the endothelial cell level of the microvascular bed in muscle flaps

Ischemia-reperfusion injury (IRI) is a common and serious complication of reperfusion following vascular occlusion. We present a novel interpretation of the pathogenesis of IRI. According to this hypothesis, anoxia resulting from ischemia allows translocation of phosphatidylserine to the surface of endothelial cells (ECs), providing an attachment site for leukocytes and platelets. This attachment impedes blood flow through the microvasculature. During IRI mediators of increased vascular permeability are produced, resulting in edema. We have developed a recombinant homodimer of human Annexin V, Diannexin, to attenuate IRI. Annexin V (36 kDa) rapidly passes from the circulation into the urine. In Diannexin 2 annexin V molecules are joined by a short peptide linker to produce a 73 kDa protein, which exceeds the renal filtration threshold. Diannexin has a half-life of about 2.5 hours in the human circulation. Diannexin also has a higher affinity for phosphatidylserine on cell surfaces than the monomer has. Such binding inhibits leukocyte attachment to ECs, and inflammatory mediator formation, during IRI. The aim of the study now reported was to ascertain the effects of Diannexin on IRI in the rat cremaster muscle flap, as revealed by intravital microscopy. During IRI there was increased attachment of leukocytes to ECs, reduced blood flow and augmented vascular permeability. Administration of Diannexin before or just after ischemia prevented these effects. Diannexin inhibited transmigration of leukocytes during IRI. Edema complicates peripheral vascular surgery, stroke, and other clinical conditions. Diannexin has proven to be safe when administered to patients after major surgical operations, and it may be useful to prevent IRI associated with peripheral vascular surgery.

Clevidipine in the treatment of perioperative hypertension: assessing safety events in the ECLIPSE trials

Clevidipine is an arterial, selective, dihydropyridine calcium channel blocker with an ultrashort half-life. In this prospective, randomized, open-label, parallel-comparison trial series, the safety and efficacy of intravenous clevidipine with nitroglycerin, sodium nitroprusside and nicardipine in hypertensive patients during cardiac surgery were compared. No differences in the incidences of myocardial infarction, stroke or renal dysfunction were observed between treatment groups. Mortality was similar between the clevidipine-nitrogylcerine- and clevidipine-nicardipine-treated groups, whereas mortality appeared to be greater in the sodium nitroprusside group compared to clevidipine (p = 0.04 in a univariant analysis). Clevidipine was significantly more effective in blood pressure control compared with nitroglycerin (p = 0.0006) or sodium nitroprusside (p = 0.003) and was associated with fewer blood pressure excursions compared with nicardipine as a predetermined blood pressure range was narrowed.

Diabetes mellitus as a predictor of retinopathy associated with acute myocardial infarction

BACKGROUND

A unique transient retinopathy characterized by soft exudates around the optic disc after percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) has been reported, so in the present study the risk factors for retinopathy associated with AMI (RAMI) were investigated.

METHODS AND RESULTS

The study group comprised 62 patients with their first AMI who underwent successful PCI within 24 h of onset (48 men, 14 women; age 63 +/-10 years). The fundus of each eye was assessed on days 3-5, and again at 4 weeks after AMI onset. New soft exudates developed in 29 patients (47%) at 4 weeks. The frequency of diabetes mellitus (DM), and the hemoglobin A(1c) and peak creatine kinase concentrations were higher in patients with than in those without RAMI (55% vs 21%, P=0.008; 7.0 +/-2.0% vs 5.9 +/-1.4%, P=0.013; and 3,428 +/-2,210 IU/L vs 2,352 +/-1,652 IU/L, P=0.036, respectively). Multivariate analysis identified DM as an independent predictive factor for the occurrence of RAMI (odds ratio, 6.60; 95% confidence interval, 1.68-25.90; P=0.007).

CONCLUSIONS

DM might be a risk factor for RAMI.

The effect of hypoxia, reoxygenation, ischemia, and reperfusion on hydraulic permeability in rat mesenteric venules

Little is known regarding the effects of I/R on hydraulic permeability (Lp). We sought to compare the individual influences of hypoxia, ischemia, reoxygenation, and reperfusion on Lp. We hypothesized that (1) hypoxia increases Lp; (2) reoxygenation further increases Lp; (3) ischemia results in greater increases in Lp compared with hypoxia; (4) reperfusion causes additional increases in Lp compared with hypoxia, ischemia, and reoxygenation; and (5) xanthine oxidase (XO) and white blood cell adherence play important roles in hypoxia, ischemia, and reperfusion. Hydraulic permeability was measured by an in vivo microcannulation technique during hypoxia, reoxygenation, ischemia, and reperfusion in rat mesenteric postcapillary venules. Additional rats were fed a Tungsten-enriched diet to inhibit XO activity, and the studies were repeated. White blood cell adherence was also documented. Hypoxia and ischemia both increased Lp 2-fold from baseline levels (P < 0.001). Reoxygenation did not alter Lp compared with 15 min of hypoxia alone (P > 0.07). Reperfusion after hypoxia increased Lp 6-fold (P < 0.001). Reperfusion after ischemia also increased Lp 6-fold (P < 0.001). Inhibition of XO had no effect on the increase in Lp after both hypoxia and ischemia. However, inhibition of XO attenuated the 6-fold increase in Lp observed during reperfusion after both hypoxia and ischemia by approximately 50% (P < 0.001). White blood cell adherence increased during reperfusion but not hypoxia or ischemia. The complexity of I/R injury makes it a difficult clinical scenario to model for research. We have demonstrated in an in vivo model that hypoxia and ischemia increase Lp similarly, and that reperfusion has a profound deleterious effect on Lp. These changes in Lp seem to be XO and white blood cell dependent.

Investigation of reperfusion injury and ischemic preconditioning in microsurgery

Ischemia/reperfusion (I/R) is inevitable in many vascular and musculoskeletal traumas, diseases, free tissue transfers, and during time-consuming reconstructive surgeries in the extremities. Salvage of a prolonged ischemic extremity or flap still remains a challenge for the microvascular surgeon. One of the common complications after microsurgery is I/R-induced tissue death or I/R injury. Twenty years after the discovery, ischemic preconditioning has emerged as a powerful method for attenuating I/R injury in a variety of organs or tissues. However, its therapeutic expectations still need to be fulfilled. In this article, the author reviews some important experimental evidences of I/R injury and preconditioning-induced protection in the fields relevant to microsurgery.

Insulin reduces cerebral ischemia/reperfusion injury in the hippocampus of diabetic rats: a role for glycogen synthase kinase-3beta

OBJECTIVE

There is evidence that insulin reduces brain injury evoked by ischemia/reperfusion (I/R). However, the molecular mechanisms underlying the protective effects of insulin remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3beta (GSK-3beta). Here, we investigate the role of GSK-3beta inhibition on I/R-induced cerebral injury in a rat model of insulinopenic diabetes.

RESEARCH DESIGN AND METHODS

Rats with streptozotocin-induced diabetes were subjected to 30-min occlusion of common carotid arteries followed by 1 or 24 h of reperfusion. Insulin (2-12 IU/kg i.v.) or the selective GSK-3beta inhibitor TDZD-8 (0.2-3 mg/kg i.v.) was administered during reperfusion.

RESULTS

Insulin or TDZD-8 dramatically reduced infarct volume and levels of S100B protein, a marker of cerebral injury. Both drugs induced phosphorylation of the Ser9 residue, thereby inactivating GSK-3beta in the rat hippocampus. Insulin, but not TDZD-8, lowered blood glucose. The hippocampi of the drug-treated animals displayed reduced oxidative stress at 1 h of reperfusion as shown by the decreased generation of reactive oxygen species and lipid peroxidation. I/R-induced activation of nuclear factor-kappaB was attenuated by both drug treatments. At 24 h of reperfusion, TDZD-8 and insulin significantly reduced plasma levels of tumor necrosis factor-alpha; neutrophil infiltration, measured as myeloperoxidase activity and intercellular-adhesion-molecule-1 expression; and cyclooxygenase-2 and inducible-NO-synthase expression.

CONCLUSIONS

Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats. We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.

The ECLIPSE trials: comparative studies of clevidipine to nitroglycerin, sodium nitroprusside, and nicardipine for acute hypertension treatment in cardiac surgery patients

BACKGROUND

Acute hypertension during cardiac surgery can be difficult to manage and may adversely affect patient outcomes. Clevidipine is a novel, rapidly acting dihydropyridine L-type calcium channel blocker with an ultrashort half-life that decreases arterial blood pressure (BP). The Evaluation of CLevidipine In the Perioperative Treatment of Hypertension Assessing Safety Events trial (ECLIPSE) was performed to compare the safety and efficacy of clevidipine (CLV) with nitroglycerin (NTG), sodium nitroprusside (SNP), and nicardipine (NIC) in the treatment of perioperative acute hypertension in patients undergoing cardiac surgery.

METHODS

We analyzed data from three prospective, randomized, open-label, parallel comparison studies of CLV to NTG or SNP perioperatively, or NIC postoperatively in patients undergoing cardiac surgery at 61 medical centers. Of the 1964 patients enrolled, 1512 met postrandomization inclusion criteria of requiring acute treatment of hypertension based on clinical criteria. The patients were randomized 1:1 for each of the three parallel comparator treatment groups. The primary outcome was the incidence of death, myocardial infarction, stroke or renal dysfunction at 30 days. Adequacy and precision of BP control was evaluated and is reported as a secondary outcome.

RESULTS

There was no difference in the incidence of myocardial infarction, stroke or renal dysfunction for CLV-treated patients compared with the other treatment groups. There was no difference in mortality rates between the CLV, NTG or NIC groups. Mortality was significantly higher, though, for SNP-treated patients compared with CLV-treated patients (P=0.04). CLV was more effective compared with NTG (P=0.0006) or SNP (P=0.003) in maintaining BP within the prespecified BP range. CLV was equivalent to NIC in keeping patients within a prespecified BP range; however, when BP range was narrowed, CLV was associated with fewer BP excursions beyond these BP limits compared with NIC.

CONCLUSIONS

CLV is a safe and effective treatment for acute hypertension in patients undergoing cardiac surgery.

Ischemia-reperfusion injury in rats affects hydraulic conductivity in two phases that are temporally and mechanistically separate

Ischemia-reperfusion (IR) injury is a major insult to postcapillary venules. We hypothesized that IR increases postcapillary venular hydraulic conductivity and that IR-mediated changes in hydraulic conductivity result from temporally and mechanistically separate processes. A microcannulation technique was used to determine hydraulic conductivity (Lp) in rat mesenteric postcapillary venules serially throughout ischemia (45 min) and reperfusion (5 h) induced by superior mesenteric artery occlusion and release. Mesenteric IR resulted in a biphasic increase in Lp. White blood cell (WBC) adhesion slowly increased with maximal adhesion corresponding to the second peak (P < 0.005). After IR, tissue was harvested for RT-PCR analysis of ICAM-1, E-selectin, and P-selectin mRNA. Intercellular adhesion molecule-1 (ICAM-1) mRNA in the gut showed the most significant upregulation. Quantitative real-time PCR revealed that ICAM-1 mRNA was upregulated 60-fold in the gut. An ICAM-1 antibody was therefore used to determine the effect of WBC adhesion on Lp during IR. ICAM-1 inhibition attenuated Lp during the first peak and completely blocked the second peak (P < 0.005). When rats were fed a tungsten diet to inhibit xanthine oxidase and then underwent IR, Lp was dramatically attenuated during the first peak and mildly decreased the second peak (P < 0.005). Inhibition of xanthine oxidase by oxypurinol decreased Lp during IR by over 60% (P < 0.002). Tempol, a superoxide dismutase mimetic, decreased Lp during IR by over 30% (P < 0.01). We conclude that IR induces a biphasic increase in postcapillary hydraulic conductivity. Reactive oxygen species impact both the first transient peak and the sustained second peak. However, the second peak is also dependent on WBC-endothelial cell adhesion. These serial measurements of postcapillary hydraulic conductivity may lead the way for optimal timing of pharmaceutical therapies in IR injury.