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Lance B Becker

Publications and source records attributed to Lance B Becker.

At least 19 recordsLinked to original sources
PubMed2006

Hypothermia-induced cardioprotection using extended ischemia and early reperfusion cooling.

Optimal timing of therapeutic hypothermia for cardiac ischemia is unknown. Our prior work suggests that ischemia with rapid reperfusion (I/R) in cardiomyocytes can be more damaging than prolonged ischemia alone. Also, these cardiomyocytes demonstrate protein kinase C (PKC) activation and nitric oxide (NO) signaling that confer protection against I/R injury. Thus we hypothesized that hypothermia will protect most using extended ischemia and early reperfusion cooling and is mediated via PKC and NO synthase (NOS). Chick cardiomyocytes were exposed to an established model of 1-h ischemia/3-h reperfusion, and the same field of initially contracting cells was monitored for viability and NO generation. Normothermic I/R resulted in 49.7 +/- 3.4% cell death. Hypothermia induction to 25 degrees C was most protective (14.3 +/- 0.6% death, P < 0.001 vs. I/R control) when instituted during extended ischemia and early reperfusion, compared with induction after reperfusion (22.4 +/- 2.9% death). Protection was completely lost if onset of cooling was delayed by 15 min of reperfusion (45.0 +/- 8.2% death). Extended ischemia/early reperfusion cooling was associated with increased and sustained NO generation at reperfusion and decreased caspase-3 activation. The NOS inhibitor N(omega)-nitro-L-arginine methyl ester (200 microM) reversed these changes and abrogated hypothermia protection. In addition, the PKCepsilon inhibitor myr-PKCepsilon v1-2 (5 microM) also reversed NO production and hypothermia protection. In conclusion, therapeutic hypothermia initiated during extended ischemia/early reperfusion optimally protects cardiomyocytes from I/R injury. Such protection appears to be mediated by increased NO generation via activation of protein kinase Cepsilon; nitric oxide synthase.

Animals↗
PubMed2006

Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest.

BACKGROUND: Cardiopulmonary resuscitation (CPR) and electrical defibrillation are the primary treatment options for ventricular fibrillation (VF). While recent studies have shown that providing CPR prior to defibrillation may improve outcomes, the effects of CPR quality remain unclear. Specifically, the clinical effects of compression depth and pauses in chest compression prior to defibrillation (pre-shock pauses) are unknown. METHODS: A prospective, multi-center, observational study of adult in-hospital and out-of-hospital cardiac resuscitations was conducted between March 2002 and December 2005. An investigational monitor/defibrillator equipped to measure compression characteristics during CPR was used. RESULTS: Data were analyzed from 60 consecutive resuscitations in which a first shock was administered for VF. The primary outcome was first shock success defined as removal of VF for at least 5s following defibrillation. A logistic regression analysis demonstrated that successful defibrillation was associated with shorter pre-shock pauses (adjusted odds ratio 1.86 for every 5s decrease; 95% confidence interval 1.10-3.15) and higher mean compression depth during the 30s of CPR preceding the pre-shock pause (adjusted odds ratio 1.99 for every 5mm increase; 95% confidence interval 1.08-3.66). CONCLUSIONS: The quality of CPR prior to defibrillation directly affects clinical outcomes. Specifically, longer pre-shock pauses and shallow chest compressions are associated with defibrillation failure. Strategies to correct these deficiencies should be developed and consideration should be made to replacing current-generation automated external defibrillators that require long pre-shock pauses for rhythm analysis.

Aged↗
PubMed2006

Antioxidant effects of ginsenoside Re in cardiomyocytes.

We have previously demonstrated that American ginseng berry extract exhibited significant protection against oxidant-mediated injury in cardiomyocytes. To extend this work, we sought to investigate the antioxidant effects of Re, a protopanaxatriols-type and single chemical integrant present in American ginseng berry extract, using the same chick cardiomyocyte model of oxidant injury as well as ESR spectroscopy in a cell-free chemical system. In cells exposed to 2 h of H2O2 (0.5 mM), pretreatment with Re (0.05, 0.1, or 0.5 mg/ml for 2 h) significantly attenuated 2',7'-dichlorofluorescein (DCF) fluorescence by 51% (from 1345+/-67 to 658+/-46 a.u., P<0.001), and remarkably reduced cell death (from 51.5+/-3.0% to 11.8+/-1.5%, P<0.001, compared to the control). Similar results were also observed in cells exposed to antimycin A (100 microM), a mitochondrial electron transport chain site III inhibitor which increases endogenous oxidative stress. In the ESR study, however, Re failed to reduce the formation of the superoxide/DMPO adduct and DPPH radicals. These results suggest that ginsenoside Re functions as an antioxidant, protecting cardiomyocytes from oxidant injury induced by both exogenous and endogenous oxidants, and that its protective effects may be mostly attributed to scavenging H2O2 and hydroxyl radicals.

Animals↗
PubMed2006

Therapeutic hypothermia utilization among physicians after resuscitation from cardiac arrest.

OBJECTIVE: We sought to evaluate current physician use of therapeutic hypothermia after cardiac arrest, to ascertain reasons for nonadoption of this treatment, and to determine current cooling techniques employed. DESIGN: Web-based survey. SETTING: International physician cohort in the United States, UK, and Finland. SUBJECTS: Physicians (MD or DO) caring for resuscitated cardiac arrest patients. INTERVENTIONS: An anonymous Web-based survey was distributed to physicians identified through United States-based critical care, cardiology, and emergency medicine directories and critical care networks in the UK and Finland. Recipients were queried regarding use of postresuscitation therapeutic hypothermia. MEASUREMENTS AND MAIN RESULTS: Of the final 13,272 surveys actually distributed to physicians, 2,248 (17%) were completed. Most respondents were attending physicians (82%) at teaching hospitals (76%) who practiced critical care (35%), cardiology (20%), or emergency medicine (22%). Of all replies, 74% of United States respondents and 64% of non-United States respondents had never used therapeutic hypothermia. United States emergency medicine physician adoption of cooling was significantly less than that of United States intensivists (16% vs. 34%, p < .05). The most often cited reasons for nonuse by respondents were "not enough data," "not part of Advanced Cardiac Life Support guidelines," and "too technically difficult to use." Factors associated with increased use included non-United States residence, critical care specialty, and larger hospital size. CONCLUSIONS: Physician utilization of cooling after cardiac arrest remains low. For improved adoption of therapeutic hypothermia, our data suggest that development of better cooling methodology and recent incorporation into resuscitation guidelines may improve use.

Attitude of Health Personnel↗
PubMed2006

Transient and partial mitochondrial inhibition for the treatment of postresuscitation injury: getting it just right.

OBJECTIVE: Within minutes of reperfusing ischemic cardiomyocytes, oxidant stress dramatically increases and is associated with postresuscitation injury. Because mitochondria produce deleterious oxidants and useful metabolic substrates, utilization of electron transport chain inhibitors against reperfusion injury, though promising, must not overly compromise recovery of mitochondrial function. This study sought to further characterize the oxidant source at reperfusion and develop a strategy for therapeutic intervention by manipulation of dose, duration, and the degree of reversibility of mitochondrial inhibition. DESIGN: Comparative laboratory investigation. SETTING: Laboratory of a research university. SUBJECTS: Embryonic chick cardiomyocytes. INTERVENTIONS: Synchronously contracting chick cardiomyocytes were exposed to 1 hr of simulated ischemia and 3 hrs of reperfusion and were monitored for cell viability (propidium iodide) and oxidant generation (dichlorofluorescein). Inhibitors were administered either all course or for the first 15 mins of reperfusion. MEASUREMENTS AND MAIN RESULTS: : Application of diethyldithiocarbamic acid, 2-anthracene-carboxylic acid (rhein tech), and alpha-nicotinamide adenine dinucleotide dehydrogenase (NADH) demonstrated attenuation of the oxidant burst. In addition, diethyldithiocarbamic acid (1 mM), rhein tech (0.1 microM), and alpha-NADH (20 microM) significantly attenuated cell death from a control of 49.7% +/- 6.7% to 15.7% +/- 4.7% (n = 5, p < .01), 26.1% +/- 4.1% (n = 5, p < .01), and 13.8% +/- 1.3% (n = 5, p < .001), respectively. All doses of stigmatellin attenuated reactive oxygen species, but only a 2-20 nM dose during the first 15 mins of reperfusion abrogated cell death from 53.8% +/- 3.5% to 10.8% +/- 2.9% (n = 5, p < .001). Increased doses and durations of stigmatellin abolished reactive oxygen species but augmented injury. Although rotenone (5 microM) attenuated reactive oxygen species, no dose or duration of exposure that ameliorated cell death was found. CONCLUSIONS: Early events of reperfusion are marked by rapid mitochondrial oxidant generation and postresuscitation injury. Electron transport chain blockade provides an effective method of attenuating reactive oxygen species. However, inhibitor administration should be both transient and reversible to necessitate cardioprotection and successful metabolic recovery.

Animals↗
PubMed2006

Therapeutic hypothermia after cardiac arrest: unintentional overcooling is common using ice packs and conventional cooling blankets.

OBJECTIVES: Although therapeutic hypothermia for cardiac arrest survivors has been shown to improve neurologically intact survival, optimal methods to ensure controlled induction and maintenance of cooling are not clearly established. Precise temperature control is important to evaluate because unintentional overcooling below the consensus target range of 32-34 degrees C may place the patient at risk for serious complications. We sought to measure the prevalence of overcooling (<32 degrees C) in postarrest survivors receiving primarily noninvasive cooling. DESIGN: Retrospective chart review of postarrest patients. SETTING: Three large teaching hospitals. PATIENTS: Cardiac arrest survivors receiving therapeutic hypothermia. INTERVENTIONS: Charts were reviewed if primarily surface cooling was used with a target temperature goal between 32 degrees C and 34 degrees C. MEASUREMENTS AND MAIN RESULTS: Of the 32 cases reviewed, overcooling lasting for >1 hr was identified as follows: 20 of 32 patients (63%) reached temperatures of <32 degrees C, 9 of 32 (28%) reached temperatures of <31 degrees C, and 4 of 32 (13%) reached temperatures of <30 degrees C. Of those with overcooling of <32 degrees C, 6 of 20 (30%) survived to hospital discharge, whereas of those without overcooling, 7 of 12 (58%) survived to hospital discharge (p = not significant). CONCLUSIONS: The majority of the cases reviewed demonstrated unintentional overcooling below target temperature. Improved mechanisms for temperature control are required to prevent potentially deleterious complications of more profound hypothermia.

Adolescent↗
PubMed2006

Difficulty of cardiac arrest rhythm identification does not correlate with length of chest compression pause before defibrillation.

OBJECTIVE: Performing high-quality cardiopulmonary resuscitation immediately before electrical defibrillation serves as an important predictor of shock success. Long preshock pauses in cardiopulmonary resuscitation frequently occur, as noted by recent clinical investigations. We sought to determine whether these long pauses were due to difficulties in identifying shockable rhythms or rather due to local factors during resuscitation attempts. DESIGN: Prospective in-hospital study of cardiac arrest resuscitation attempts coupled with a retrospective review of preshock pause rhythms by 12 trained providers. Reviewers scored rhythms by ease of identification using a discrete Likert scale from 1 (most difficult to identify) to 5 (easiest to identify). The resuscitation cohort was organized into preshock pause-duration quartiles for statistical analysis. Resident physicians were then surveyed regarding human factors affecting preshock pauses. RESULTS: A total of 118 preshock pauses from 45 resuscitation episodes were collected. When evaluated by quartiles of preshock pause duration, difficulty of rhythm identification did not correlate with increasing pause time. In fact, the opposite was found (longest preshock pause quartile of 23.8-60.2 secs vs. shortest pause quartile of 1.1-7.9 secs; rhythm difficulty scores, 3.2 vs. 3.0; p = .20). When 29 resident physicians who recently served on resuscitation teams were surveyed, 18 of 29 (62.1%) attributed long pauses to lack of time sense during resuscitation, and 16 of 29 (55.2%) thought that room crowding prevented rapid defibrillation. CONCLUSIONS: Long cardiopulmonary resuscitation pauses before defibrillation are likely due to human factors during the resuscitation and not due to inherent difficulties with rhythm identification. This preliminary work highlights the need for more research and training in the area of team performance and human factors during resuscitation.

Cardiopulmonary Resuscitation↗
PubMed2005

Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest.

BACKGROUND: Recent data highlight a vital link between well-performed cardiopulmonary resuscitation (CPR) and survival after cardiac arrest; however, the quality of CPR as actually performed by trained healthcare providers is largely unknown. We sought to measure in-hospital chest compression rates and to determine compliance with published international guidelines. METHODS AND RESULTS: We developed and validated a handheld recording device to measure chest compression rate as a surrogate for CPR quality. A prospective observational study of adult cardiac arrests was performed at 3 hospitals from April 2002 to October 2003. Resuscitations were witnessed by trained observers using a customized personal digital assistant programmed to store the exact time of each chest compression, allowing offline calculation of compression rates at serial time points. In 97 arrests, data from 813 minutes during which chest compressions were delivered were analyzed in 30-second time segments. In 36.9% of the total number of segments, compression rates were <80 compressions per minute (cpm), and 21.7% had rates <70 cpm. Higher chest compression rates were significantly correlated with initial return of spontaneous circulation (mean chest compression rates for initial survivors and nonsurvivors, 90+/-17 and 79+/-18 cpm, respectively; P=0.0033). CONCLUSIONS: In-hospital chest compression rates were below published resuscitation recommendations, and suboptimal compression rates in our study correlated with poor return of spontaneous circulation. CPR quality is likely a critical determinant of survival after cardiac arrest, suggesting the need for routine measurement, monitoring, and feedback systems during actual resuscitation.

Aged↗
PubMed2005

Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest.

CONTEXT: The survival benefit of well-performed cardiopulmonary resuscitation (CPR) is well-documented, but little objective data exist regarding actual CPR quality during cardiac arrest. Recent studies have challenged the notion that CPR is uniformly performed according to established international guidelines. OBJECTIVES: To measure multiple parameters of in-hospital CPR quality and to determine compliance with published American Heart Association and international guidelines. DESIGN AND SETTING: A prospective observational study of 67 patients who experienced in-hospital cardiac arrest at the University of Chicago Hospitals, Chicago, Ill, between December 11, 2002, and April 5, 2004. Using a monitor/defibrillator with novel additional sensing capabilities, the parameters of CPR quality including chest compression rate, compression depth, ventilation rate, and the fraction of arrest time without chest compressions (no-flow fraction) were recorded. MAIN OUTCOME MEASURE: Adherence to American Heart Association and international CPR guidelines. RESULTS: Analysis of the first 5 minutes of each resuscitation by 30-second segments revealed that chest compression rates were less than 90/min in 28.1% of segments. Compression depth was too shallow (defined as <38 mm) for 37.4% of compressions. Ventilation rates were high, with 60.9% of segments containing a rate of more than 20/min. Additionally, the mean (SD) no-flow fraction was 0.24 (0.18). A 10-second pause each minute of arrest would yield a no-flow fraction of 0.17. A total of 27 patients (40.3%) achieved return of spontaneous circulation and 7 (10.4%) were discharged from the hospital. CONCLUSIONS: In this study of in-hospital cardiac arrest, the quality of multiple parameters of CPR was inconsistent and often did not meet published guideline recommendations, even when performed by well-trained hospital staff. The importance of high-quality CPR suggests the need for rescuer feedback and monitoring of CPR quality during resuscitation efforts.

Adult↗
PubMed2005

Induced hypothermia is underused after resuscitation from cardiac arrest: a current practice survey.

BACKGROUND: Important recent work has demonstrated that the use of induced hypothermia can improve survival and neurologic recovery after cardiac arrest. We wished to ascertain the extent to which physicians were using this treatment, and what opinions are held by clinicians regarding its use. METHODS: An internet-based survey of physicians was conducted, with physicians chosen at random from published directories of the Society for Academic Emergency Medicine, the American Thoracic Society, and the American Heart Association. Physicians were questioned regarding use of therapeutic hypothermia, methods employed, and/or reasons why they had not incorporated hypothermia into their care of cardiac arrest patients. RESULTS: Completed surveys were collected from 265 physicians, including those practicing emergency medicine (41%), critical care (13%), and cardiology (24%). Respondents were geographically well distributed and the majority (94%) were at post-training level. Most respondents (78%) practiced at either larger referral hospitals or academic medical centers. When asked if they had ever used hypothermia following cardiac arrest, 87% said they had not. Among reasons cited for non-use, 49% felt that there were not enough data, 32% mentioned lack of incorporation of hypothermia into advanced cardiovascular life support (ACLS) protocols, and 28% felt that cooling methods were technically too difficult or too slow. CONCLUSION: Despite compelling data supporting its use, hypothermia has yet to be broadly incorporated into physician practice. This highlights the need for improved awareness and education regarding this treatment option, as well as the need to consider hypothermia protocols for inclusion in future iterations of ACLS.

Attitude of Health Personnel↗
PubMed2005

Effectiveness of a 30-min CPR self-instruction program for lay responders: a controlled randomized study.

BACKGROUND: The length of current 4-h classes in cardiopulmonary resuscitation (CPR) is a barrier to widespread dissemination of CPR training. The effectiveness of video-based self-instruction (VSI) has been demonstrated in several studies; however, the effectiveness of this method with older adults is not certain. Although older adults are most likely to witness out-of-hospital cardiac arrests, these potential rescuers are underrepresented in traditional classes. We evaluated a VSI program that comprised a 22-min video, an inflatable training manikin, and an audio prompting device with individuals 40-70 years old. The hypotheses were that VSI results in performance of basic CPR skills superior to that of untrained learners and similar to that of learners in Heartsaver classes. METHODS: Two hundred and eighty-five adults between 40 and 70 years old who had had no CPR training within the past 5 years were assigned to an untrained control group, Heartsaver training, or one of three versions of VSI. Basic CPR skills were measured by instructor assessment and by a sensored manikin. RESULTS: The percentage of subjects who assessed unresponsiveness, called the emergency telephone number 911, provided adequate ventilation, proper hand placement, and adequate compression depth was significantly better (P<0.05) for the VSI groups than for untrained controls. VSI subjects tended to have better overall performance and better ventilation performance than did Heartsaver subjects. CONCLUSIONS: Older adults learned the fundamental skills of CPR with this training program in about half an hour. If properly distributed, this type of training could produce a significant increase in the number of lay responders who can perform CPR.

Adult↗
PubMed2005

Oxidant injury occurs rapidly after cardiac arrest, cardiopulmonary resuscitation, and reperfusion.

OBJECTIVE: Investigations conducted in cellular models show that reperfusion of ischemic tissue is associated with a burst of reactive oxidant species within minutes after reperfusion. Oxidant injury may play a role in the poor outcome typical of people resuscitated from cardiac arrest. The objective of the present study was to determine the presence and timing of oxidant injury in an in vivo model of cardiac arrest. DESIGN: Randomized controlled. SETTING: University medical center laboratory. SUBJECTS: Domestic swine. INTERVENTIONS: We evaluated oxidant injury during and after 8 mins of cardiac arrest using a gas chromatography/mass spectrometry F2-isoprostane assay and compared these results with a matched control group. MEASUREMENTS AND MAIN RESULTS: Baseline mean arterial, venous, and brain tissue F2-isoprostane levels were not significantly different when the cardiac arrest group was compared with the control group. However, in the group subjected to cardiac arrest and cardiopulmonary resuscitation we found significant (p < .0006) two- to three-fold increases in venous and arterial F2-isoprostane levels, which peaked between 15 and 30 mins after reperfusion and returned to baseline within 90 mins (p < .0006). Overall mean (+/- SE) brain tissue F2-isoprostane levels increased significantly to 370 +/- 60 vs. 140 +/- 60 ng/g tissue in the cardiac arrest group compared with the control group (p = .026). CONCLUSION: This study shows that F2-isoprostane measurement could be used to assess oxidant injury in an animal model of cardiac arrest and that oxidant injury occurs rapidly after cardiac arrest and reperfusion.

Animals↗
PubMed2004

Intra-arrest cooling improves outcomes in a murine cardiac arrest model.

BACKGROUND: Recent clinical studies have demonstrated that hypothermia to 32 degrees to 34 degrees C provides significant clinical benefit when induced after resuscitation from cardiac arrest. However, cooling during the postresuscitation period was slow, requiring 4 to 8 hours to achieve target temperatures after return of spontaneous circulation (ROSC). Whether more rapid cooling would further improve survival remains unclear. We sought to determine whether cooling during cardiac arrest before ROSC (ie, "intra-arrest" hypothermia) has survival benefit over more delayed post-ROSC cooling, using a murine cardiac arrest model. METHODS AND RESULTS: A model of potassium-induced cardiac arrest was established in C57BL/6 mice. After 8 minutes of untreated cardiac arrest, resuscitation was attempted with chest compression, ventilation, and intravenous fluid. Mice were randomized to 3 treatment groups (n=10 each): an intra-arrest hypothermia group, in which mice were cooled to 30 degrees C just before attempted resuscitation, and then rewarmed after 1 hour; a post-ROSC hypothermia group, in which mice were kept at 37 degrees C for 20 minutes after successful ROSC and then were cooled to 30 degrees C for 1 hour; and a normothermic control group, in which mice were kept at 37 degrees C. The intra-arrest hypothermia group demonstrated better 72-hour survival than delayed hypothermia and normothermia groups (6/10 versus 1/10 and 1/10 survivors, respectively, P<0.05), with similar differences seen at 6-hour survival and on neurological scoring. CONCLUSIONS: Timing of hypothermia is a crucial determinant of survival in the murine arrest model. Early intra-arrest cooling appears to be significantly better than delayed post-ROSC cooling or normothermic resuscitation.

Animals↗
PubMed2004

Antioxidant effects of American ginseng berry extract in cardiomyocytes exposed to acute oxidant stress.

It is postulated that antioxidant properties of American ginseng root mediate its cardioprotective actions. The antioxidant capabilities of the American ginseng root have been demonstrated previously, however, the berry of the American ginseng has not yet been evaluated. In this study, we tested the American ginseng berry extract (AGBE) for its antioxidant effects in cell-free chemical systems using H(2)O(2)/FeSO(4) to generate hydroxyl radicals which were measured by a fluorescent probe, 2', 7'-dichlorofluorescin diacetate (DCFH/DA). Xanthine/xanthine oxidase was used to generate superoxide anion, which was measured by a fluorescent probe dihydroethidium (DHE). We found that AGBE decreased fluorescence significantly, suggesting that AGBE scavenges oxygen free radicals. We further tested whether AGBE (0.1-1 mg/ml) can protect cardiomyocytes from oxidative injury induced by exogenous or endogenous oxidants. Cells were exposed to either H(2)O(2) or antimycin A (a mitochondrial electron transport chain site III inhibitor that augments mitochondrial oxidant production). The resulting oxidant stress was measured using DCFH/DA and the cell death was assessed using propidium iodide staining. Pretreatment with AGBE (1 mg/ml) significantly attenuated DCF fluorescence by 49% or 85% and reduced cell death by 59% or 63% in cells exposed to H(2)O(2) or antimycin A, respectively. When the effects of extracts from berry and root of American ginseng were compared in cardiomyocytes exposed to antimycin A, we observed that AGBE conferred greater antioxidant protection at the same dose. We conclude that AGBE is a potent antioxidant that protects cardiomyocytes against oxidant-mediated injury and this protection is partly mediated by its free radical scavenging properties.

Animals↗
PubMed2004

Caspase-dependent cytochrome c release and cell death in chick cardiomyocytes after simulated ischemia-reperfusion.

We recently demonstrated that reperfusion rapidly induces the mitochondrial pathway of apoptosis in chick cardiomyocytes after 1 h of simulated ischemia. Here we tested whether ischemia-reperfusion (I/R)-induced apoptosis could be initiated by caspase-dependent cytochrome c release in this model of cardiomyocyte injury. Fluorometric assays of caspase activity showed little, if any, activation of caspases above baseline levels induced by 1 h of ischemia alone. However, these assays revealed rapid activation of caspase-2, yielding a 2.95 +/- 0.52-fold increase (over ischemia only) within the 1st h of reperfusion, whereas activities of caspases-3, -8, and -9 increased only slightly from their baseline levels. The rapid and prominent activation of caspase-2 suggested that it could be an important initiator caspase in this model, and using specific caspase inhibitors given only at the point of reperfusion, we tested this hypothesis. The caspase-2 inhibitor benzyloxycarbonyl-Val-Asp(Ome)-Val-Ala-Asp(Ome)-CH(2)F was the only caspase inhibitor that significantly inhibited cytochrome c release from mitochondria. This inhibitor also completely blocked activation of caspases-3, -8, and -9. The caspase-3/7 inhibitor transiently and only partially blocked caspase-2 activity and was less effective in blocking the activities of caspases-8 and -9. The caspase-8 inhibitor failed to significantly block caspase-2 or -3, and the caspase-9 inhibitor blocked only caspase-9. Furthermore, the caspase-2 inhibitor protected against I/R-induced cell death, but the caspase-8 inhibitor failed to do so. These data suggest that active caspase-2 initiates cytochrome c release after reperfusion and that it is critical for the I/R-induced apoptosis in this model.

Amino Acid Chloromethyl Ketones↗
PubMed2004

New concepts in reactive oxygen species and cardiovascular reperfusion physiology.

Increasingly complex behavior of free radicals and reactive oxygen species (ROS) are noted within biological systems. Classically free radicals and ROS were considered injurious, however current mechanisms describe both protective and deleterious effects. A burst of ROS has been well described with the first moments of reperfusion and is associated with injury. However ROS can also be protective as signal preconditioning protection and induce stress responses that lead to survival. ROS generation is appreciated to occur during ischemia despite the low oxygen tension, from a likely mitochondria source, and ROS-induced ROS release may amplify its signal. The burst of ROS seen during reperfusion may originate from a different cellular source than during ischemia and is not yet fully identified. ROS and cellular redox conditions regulate a large number of vital pathways (energy metabolism, survival/stress responses, apoptosis, inflammatory response, oxygen sensing, etc). While cellular systems may demonstrate reperfusion injury, whole organ and animal models continue to report contradictory results on reperfusion injury and the role of antioxidants as a therapy. Collectively, these data may offer insight into why clinical trials of antioxidants have had such mixed and mostly negative results. Future antioxidant therapies are likely to be effective but they must become: more specific for site of action, not have deleterious effects on other signaling pathways, be targeted to a specific reactive oxygen species or cellular compartment, and be "time sensitive" so they deliver the correct therapy at precisely the correct time in ischemia and reperfusion.

Animals↗