Myosin Heavy Chain as a Novel Key Modulator of Striated Muscle Resting State.

After years of intense research using structural, biological, and biochemical experimental procedures, it is clear that myosin molecules are essential for striated muscle contraction. However, this is just the tip of the iceberg of their function. Interestingly, it has been shown recently that these molecules (especially myosin heavy chains) are also crucial for cardiac and skeletal muscle resting state. In the present review, we first overview myosin heavy chain biochemical states and how they influence the consumption of ATP. We then detail how neighboring partner proteins including myosin light chains and myosin binding protein C intervene in such processes, modulating the ATP demand in health and disease. Finally, we present current experimental drugs targeting myosin ATP consumption and how they can treat muscle diseases.

An endogenous inhibitor of angiogenesis downregulated by hypoxia in human aortic valve stenosis promotes disease pathogenesis.

Aortic valve stenosis is the most common valve disease in the western world. Central to the pathogenesis of this disease is the growth of new blood vessels (angiogenesis) within the aortic valve allowing infiltration of immune cells and development of intra-valve inflammation. Identifying the cellular mediators involved in this angiogenesis is important as this may reveal new therapeutic targets which could ultimately prevent the progression of aortic valve stenosis. Aortic valves from patients undergoing surgery for aortic valve replacement or dilation of the aortic arch were examined both ex vivo and in vitro. We now demonstrate that the anti-angiogenic protein, soluble fms-like tyrosine kinase 1 (sFlt1), a non-signalling soluble receptor for vascular endothelial growth factor, is constitutively expressed in non-diseased valves. sFlt-1 expression was, however, significantly reduced in aortic valve tissue from patients with aortic valve stenosis while protein markers of hypoxia were simultaneously increased. Exposure of primary-cultured valve interstitial cells to hypoxia resulted in a decrease in the expression of sFlt-1. We further reveal using a bioassay that siRNA knock-down of sFlt1 in valve interstitial cells directly results in a pro-angiogenic environment. Finally, incubation of aortic valves with sphingosine 1-phosphate, a bioactive lipid-mediator, increased sFlt-1 expression and inhibited angiogenesis within valve tissue. In conclusion, this study demonstrates that sFlt1 expression is directly correlated with angiogenesis in aortic valves and the observed decrease in sFlt-1 expression in aortic valve stenosis could increase valve inflammation, promoting disease progression. This could be a viable therapeutic target in treating this disease.

Predominant myosin superrelaxed state in canine myocardium with naturally occurring dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a naturally occurring heart failure condition in humans and dogs, notably characterized by a reduced contractility and ejection fraction. As the identification of its underlying cellular and molecular mechanisms remain incomplete, the aim of the present study was to assess whether the molecular motor myosin and its known relaxed conformational states are altered in DCM. For that, we dissected and skinned thin cardiac strips from left ventricle obtained from six DCM Doberman Pinschers and six nonfailing (NF) controls. We then used a combination of Mant-ATP chase experiments and X-ray diffraction to assess both energetic and structural changes of myosin. Using the Mant-ATP chase protocol, we observed that in DCM dogs, the amount of myosin molecules in the ATP-conserving conformational state, also known as superrelaxed (SRX), is significantly increased when compared with NF dogs. This alteration can be rescued by applying EMD-57033, a small molecule activating myosin. Conversely, with X-ray diffraction, we found that in DCM dogs, there is a higher proportion of myosin heads in the vicinity of actin when compared with NF dogs (1,0 to 1,1 intensity ratio). Hence, we observed an uncoupling between energetic (Mant-ATP chase) and structural (X-ray diffraction) data. Taken together, these results may indicate that in the heart of Doberman Pinschers with DCM, myosin molecules are potentially stuck in a nonsequestered but ATP-conserving SRX state, that can be counterbalanced by EMD-57033 demonstrating the potential for a myosin-centered pharmacological treatment of DCM.NEW & NOTEWORTHY The key finding of the present study is that, in left ventricles of dogs with a naturally occurring dilated cardiomyopathy, relaxed myosin molecules favor a nonsequestered superrelaxed state potentially impairing sarcomeric contractility. This alteration is rescuable by applying a small molecule activating myosin known as EMD-57033.

The influence of polygraphs on evaluators' decisions regarding sexually violent persons.

OBJECTIVE: This study examined the degree to which polygraph results affected evaluators' decisions regarding patients committed as sexually violent persons (SVPs) in Wisconsin. Specifically, we examined evaluators' opinions on patients' significant progress in treatment (SPT), suitability for supervised release, and suitability for discharge. HYPOTHESES: We hypothesized that having failed a polygraph during the prior year would predict evaluators' opinions that patients did not meet criteria for SPT, supervised release, and discharge from civil commitment even after analyses controlled for other factors related to evaluators' decision making. Similarly, we hypothesized that patients taking and passing polygraphs in the year before the evaluations would predict positive recommendations for the aforementioned outcomes. METHOD: All patients civilly committed under Wisconsin's SVP statute who had a Treatment Progress Report (TPR) and a Chapter 980.07 evaluation completed by a state-employed forensic evaluator in 2017 were eligible for this study; we selected a random sample of 158 participants. TPR and 980.07 evaluation reports were coded to reflect evaluators' opinions regarding SPT, supervised release, and/or discharge. All polygraph types and outcomes completed within the review period were coded. RESULTS: Results indicated that taking and passing polygraphs significantly predicted favorable evaluator opinions regarding SPT after analyses controlled for other potentially relevant factors. Polygraphs were not significantly predictive of discharge or supervised release recommendations after analyses controlled for other factors. CONCLUSIONS: Some polygraph outcomes may affect specific evaluator opinions regarding treatment progress. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The Validity of the Personality Assessment Inventory-Adolescent in Assessing Callous-Unemotional Traits in At-Risk Adolescents.

This study examines the validity of the Personality Assessment Inventory-Adolescent (PAI-A; Morey) in assessing callous-unemotional (CU) traits within two independent samples of at-risk adolescents from a residential intervention program. The study tests the extent to which CU traits are represented within PAI-A scales with respect to empirically- or theoretically-related indicators, such as antisociality, aggression, low warmth, low social connectedness, and subdued internalizing psychopathology. The PAI-A substantive scales statistically accounted for an average of 55.0% of the variance in total scores on the Inventory of Callous-Unemotional Traits (ICU; Frick) across samples. Broadly, PAI-A substantive scales evinced theoretically-consistent relations with CU traits. Consistent with expectations, CU traits were broadly related to PAI-A-assessed constructs of antisocial features, aggression, low warmth and social disconnection, but not to subdued internalizing symptoms. Moreover, some of the PAI-A clinical, treatment consideration, and interpersonal scales or subscales demonstrated differential relations across the traits. Implications for assessment of CU traits using the PAI framework are discussed. Overall, this research adds to the literature on CU traits in broadband personality assessment and provides a foundation for future research on CU traits using the PAI-A.

How do different dimensions of adolescent narcissism impact the relation between callous-unemotional traits and self-reported aggression?

The current study examined the moderating influence that different aspects of narcissism have on the relation between callous-unemotional (CU) traits and aggression in a sample of 720 adolescents (500 males), ages 16-19 enrolled in a 22-week residential program. Findings from the two studies revealed that psychopathy-linked narcissism as assessed by the Antisocial Process Screening Device (APSD; Frick & Hare, 2001; Antisocial process screening device. Toronto: Multi-Health Systems.) and vulnerable narcissism as assessed using the Pathological Narcissism Inventory (PNI; Pincus et al., 2009; Initial construction and validation of the Pathological Narcissism Inventory. Psychological Assessment, 21, 365-379) significantly moderated the relation between CU traits and aggression in adolescents. Conversely, non-pathological narcissism assessed by the Narcissistic Personality Inventory for Children (NPIC; Barry, Frick, & Killian, 2003; The relation of narcissism and self-esteem to conduct problems in children. Journal of Clinical Child and Adolescent Psychology, 32, 139-152) and PNI grandiose narcissism did not significantly impact this relation. These results suggest that forms of narcissism most closely connected to internalizing problems combined with CU traits are associated with relatively heightened aggression in youth. The implications of these findings are discussed. Aggr. Behav. 43:14-25, 2017. © 2016 Wiley Periodicals, Inc.

Anxiety Symptoms and Coping Motives: Examining a Potential Path to Substance Use-Related Problems in Adolescents With Psychopathic Traits.

BACKGROUND: Although the relation between impulsive-irresponsible psychopathic traits and substance use is well-documented, the path to developing substance use problems is less understood in adolescents with these characteristics. OBJECTIVES: To examine the associations between psychopathy, anxiety, and substance use motives and a mechanism by which anxiety and alcohol and marijuana coping motives mediate the relation between psychopathic traits and substance use-related problems. METHODS: A sample of 185 at-risk adolescent males from a residential military-style program reporting past alcohol or marijuana use (M age = 16.74) participated in the study. RESULTS: Impulsive-Irresponsible psychopathic traits were uniquely and incrementally predictive of alcohol and marijuana use-related problems and anxiety. Anxiety and coping motives appeared to partially explain the association between impulsivity-irresponsibility and substance use-related problems. CONCLUSIONS/IMPORTANCE: Findings suggest that youth expressing impulsive-irresponsible psychopathic traits may engage in problematic substance use at least partly as a function of heightened anxiety and a subsequent desire to alleviate distress by using alcohol or marijuana to cope.

Remodelling of Skeletal Muscle Myosin Metabolic States in Hibernating Mammals.

Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20°C). Upon repeating loaded Mant-ATP chase experiments at 8°C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.

Remodeling of skeletal muscle myosin metabolic states in hibernating mammals.

Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20 °C). Upon repeating loaded Mant-ATP chase experiments at 8 °C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.

Many animals use hibernation as a tactic to survive harsh winters. During this dormant, inactive state, animals reduce or limit body processes, such as heart rate and body temperature, to minimise their energy use. To conserve energy during hibernation, animals can use different approaches. For example, garden dormice undergo periodic states of extremely low core temperatures (down to 4­8^oC); whereas Eurasian brown bears see milder temperature drops (down to 23­25^oC). An important organ that changes during hibernation is skeletal muscle. Skeletal muscle typically uses large amounts of energy, making up around 50% of body mass. To survive, hibernating animals must change how their skeletal muscle uses energy. Traditionally, active myosin ­ a protein found in muscles that helps muscles to contract ­ was thought to be responsible for most of the energy use by skeletal muscle. But, more recently, resting myosin has also been found to use energy when muscles are relaxed. Lewis et al. studied myosin and skeletal muscle energy use changes during hibernation and whether they could impact the metabolism of hibernating animals. Lewis et al. assessed myosin changes in muscle samples from squirrels, dormice and bears during hibernation and during activity. Experiments showed changes in resting myosin in squirrels and dormice (whose temperature drops to 4­8^oC during hibernation) but not in bears. Further analysis revealed that cooling samples from non-hibernating muscle to 4­8^oC increased energy use in resting myosin, thereby generating heat. However, no increase in energy use was found after cooling hibernating muscle samples to 4­8^oC. This suggest that resting myosin generates heat at cool temperatures ­ a mechanism that is switched off in hibernating animals to allow them to cool their body temperature. These findings reveal key insights into how animals conserve energy during hibernation. In addition, the results show that myosin regulates energy use in skeletal muscles, which indicates myosin may be a potential drug target in metabolic diseases, such as obesity.

Super-relaxed myosins contribute to respiratory muscle hibernation in mechanically ventilated patients.

Patients receiving mechanical ventilation in the intensive care unit (ICU) frequently develop contractile weakness of the diaphragm. Consequently, they may experience difficulty weaning from mechanical ventilation, which increases mortality and poses a high economic burden. Because of a lack of knowledge regarding the molecular changes in the diaphragm, no treatment is currently available to improve diaphragm contractility. We compared diaphragm biopsies from ventilated ICU patients (N = 54) to those of non-ICU patients undergoing thoracic surgery (N = 27). By integrating data from myofiber force measurements, x-ray diffraction experiments, and biochemical assays with clinical data, we found that in myofibers isolated from the diaphragm of ventilated ICU patients, myosin is trapped in an energy-sparing, super-relaxed state, which impairs the binding of myosin to actin during diaphragm contraction. Studies on quadriceps biopsies of ICU patients and on the diaphragm of previously healthy mechanically ventilated rats suggested that the super-relaxed myosins are specific to the diaphragm and not a result of critical illness. Exposing slow- and fast-twitch myofibers isolated from the diaphragm biopsies to small-molecule compounds activating troponin restored contractile force in vitro. These findings support the continued development of drugs that target sarcomere proteins to increase the calcium sensitivity of myofibers for the treatment of ICU-acquired diaphragm weakness.

CaMKK2 is not involved in contraction-stimulated AMPK activation and glucose uptake in skeletal muscle.

OBJECTIVE: The AMP-activated protein kinase (AMPK) gets activated in response to energetic stress such as contractions and plays a vital role in regulating various metabolic processes such as insulin-independent glucose uptake in skeletal muscle. The main upstream kinase that activates AMPK through phosphorylation of α-AMPK Thr172 in skeletal muscle is LKB1, however some studies have suggested that Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) acts as an alternative kinase to activate AMPK. We aimed to establish whether CaMKK2 is involved in activation of AMPK and promotion of glucose uptake following contractions in skeletal muscle. METHODS: A recently developed CaMKK2 inhibitor (SGC-CAMKK2-1) alongside a structurally related but inactive compound (SGC-CAMKK2-1N), as well as CaMKK2 knock-out (KO) mice were used. In vitro kinase inhibition selectivity and efficacy assays, as well as cellular inhibition efficacy analyses of CaMKK inhibitors (STO-609 and SGC-CAMKK2-1) were performed. Phosphorylation and activity of AMPK following contractions (ex vivo) in mouse skeletal muscles treated with/without CaMKK inhibitors or isolated from wild-type (WT)/CaMKK2 KO mice were assessed. Camkk2 mRNA in mouse tissues was measured by qPCR. CaMKK2 protein expression was assessed by immunoblotting with or without prior enrichment of calmodulin-binding proteins from skeletal muscle extracts, as well as by mass spectrometry-based proteomics of mouse skeletal muscle and C2C12 myotubes. RESULTS: STO-609 and SGC-CAMKK2-1 were equally potent and effective in inhibiting CaMKK2 in cell-free and cell-based assays, but SGC-CAMKK2-1 was much more selective. Contraction-stimulated phosphorylation and activation of AMPK were not affected with CaMKK inhibitors or in CaMKK2 null muscles. Contraction-stimulated glucose uptake was comparable between WT and CaMKK2 KO muscle. Both CaMKK inhibitors (STO-609 and SGC-CAMKK2-1) and the inactive compound (SGC-CAMKK2-1N) significantly inhibited contraction-stimulated glucose uptake. SGC-CAMKK2-1 also inhibited glucose uptake induced by a pharmacological AMPK activator or insulin. Relatively low levels of Camkk2 mRNA were detected in mouse skeletal muscle, but neither CaMKK2 protein nor its derived peptides were detectable in mouse skeletal muscle tissue. CONCLUSIONS: We demonstrate that pharmacological inhibition or genetic loss of CaMKK2 does not affect contraction-stimulated AMPK phosphorylation and activation, as well as glucose uptake in skeletal muscle. Previously observed inhibitory effect of STO-609 on AMPK activity and glucose uptake is likely due to off-target effects. CaMKK2 protein is either absent from adult murine skeletal muscle or below the detection limit of currently available methods.

Physical activity impacts resting skeletal muscle myosin conformation and lowers its ATP consumption.

It has recently been established that myosin, the molecular motor protein, is able to exist in two conformations in relaxed skeletal muscle. These conformations are known as the super-relaxed (SRX) and disordered-relaxed (DRX) states and are finely balanced to optimize ATP consumption and skeletal muscle metabolism. Indeed, SRX myosins are thought to have a 5- to 10-fold reduction in ATP turnover compared with DRX myosins. Here, we investigated whether chronic physical activity in humans would be associated with changes in the proportions of SRX and DRX skeletal myosins. For that, we isolated muscle fibers from young men of various physical activity levels (sedentary, moderately physically active, endurance-trained, and strength-trained athletes) and ran a loaded Mant-ATP chase protocol. We observed that in moderately physically active individuals, the amount of myosin molecules in the SRX state in type II muscle fibers was significantly greater than in age-matched sedentary individuals. In parallel, we did not find any difference in the proportions of SRX and DRX myosins in myofibers between highly endurance- and strength-trained athletes. We did however observe changes in their ATP turnover time. Altogether, these results indicate that physical activity level and training type can influence the resting skeletal muscle myosin dynamics. Our findings also emphasize that environmental stimuli such as exercise have the potential to rewire the molecular metabolism of human skeletal muscle through myosin.

Adolescent psychopathy, heart rate, and skin conductance.

Researchers have advocated for a greater focus on measuring neurobiological underpinnings of serious psychological conditions such as psychopathy. This has become particularly important to investigate early in the life span, when intervention efforts for psychopathy-related behavior like conduct disorder (CD) are more successful. Given that psychopathy is a complex syndrome, it is also important to investigate physiological processes at a dimensional level. Using a sample of 56 adolescent male offenders (Mage = 15.92; SD = 1.31), this study explored the relationship between the Psychopathy Checklist-Youth Version (Forth, Kosson, & Hare, 2003), heart rate (HR), and skin conductance (SC). A white noise countdown task was used to measure autonomic activity across a baseline, anticipatory (prenoise), and reactivity (postnoise) period. Findings revealed no significant associations between psychopathy and HR activity across the time intervals. However, results revealed a positive association between grandiose-manipulative traits and SC activity and a negative association between callous-unemotional traits and SC activity. The results indicate that autonomic processes may contribute to distinct psychopathic traits in different ways, implicating slightly differential brain functioning. The findings suggest that, in order to better understand and treat youth with CD, future research should continue to examine the biological correlates of psychopathy at the broader construct level but perhaps especially at the component level.

Validity of the Youth Psychopathic Traits Inventory-Short Version in Justice-Involved and At-Risk Adolescents.

The current study examined the reliability and validity of the Youth Psychopathic Traits Inventory-Short Version (YPI-S) in two different samples of at-risk adolescents enrolled in a residential program ( n = 160) and at a detention facility ( n = 60) in the United States. YPI-S scores displayed adequate internal consistency and were moderately associated with concurrent scales on other self-report psychopathy measures and externalizing behaviors. YPI-S scores were moderately related to interviewer-ratings of the construct using the four-factor model of the Psychopathy Checklist: Youth Version. Findings suggest that the YPI-S may be a clinically useful and valid tool for the assessment of psychopathic traits in juvenile settings. This may be particularly true given the differential predictive utility of each of its dimensions.

Thioredoxin reduces post-ischemic myocardial apoptosis by reducing oxidative/nitrative stress.

BACKGROUND AND PURPOSE: Thioredoxin (Trx) is an oxidoreductase that prevents free radical-induced cell death in cultured cells. Here we assessed the mechanism(s) underlying the cardioprotective effects of Trx in vivo. EXPERIMENTAL APPROACH: The effects of myocardial ischemia (30 min) and reperfusion were measured in mice, with assays of myocardial apoptosis, superoxide production, NOx and nitrotyrosine content, and myocardial infarct size. Recombinant human Trx (rhTrx, 0.7-20 mg kg(-1), i.p.) was given 10 min before reperfusion. KEY RESULTS: Treatment with 2 mg kg(-1) rhTrx significantly decreased myocardial apoptosis and reduced infarct size (P<0.01). Nitrotyrosine content of cardiomyocytes was markedly reduced in rhTrx-treated animals (P<0.01). To further identify the mechanisms by which rhTrx may exert its anti-nitrative effect, iNOS expression and production of NOx and superoxide were determined. Treatment with rhTrx had no significant effect on iNOS expression or NOx content in the ischemic/reperfused heart. However, it markedly upregulated mSOD and reduced tissue superoxide content. To further establish a causative link between the anti- peroxynitrite effect and the cardioprotective effect of rhTrx, cultured adult cardiomyocytes were incubated with SIN-1, a peroxynitrite donor, (50 microM for 3 h) resulting in a nitrotyrosine content comparable to that seen in the ischemic/reperfused heart and causing significant cardiomyocyte apoptosis (P<0.01). Treatment with rhTrx markedly decreased SIN-1 induced apoptosis (P<0.01). CONCLUSIONS AND IMPLICATIONS: These results demonstrate that Trx is a novel anti-apoptotic and cardioprotective molecule that exerts its cardioprotective effects by reducing ischemia/reperfusion-induced oxidative/nitrative stress.

Peroxynitrite aggravates myocardial reperfusion injury in the isolated perfused rat heart.

OBJECTIVE: This study examined the effects of peroxynitrite (ONOO-) on cardiac function and cellular injury following ischemia (30 min) and reperfusion (60 min) in isolated perfused rat hearts. METHODS: 3-Morpholinosydnonimine (SIN-1, 0.1 mM), an ONOO- donor, was administered alone or combined with superoxide dismutase (SOD, 300 U/ml) or glutathione (GSH, 1 mM) at the time of reperfusion. RESULTS: Administration of SIN-1 alone significantly aggravated post-ischemic myocardial injury characterized by depressed cardiac function recovery (p < 0.05 vs. vehicle), increased lactic dehydrogenase (LDH) and creatine kinase (CK) release (p < 0.01 vs. vehicle), and enlarged necrotic size (p < 0.01 vs. vehicle). The co-administration of either SOD to decrease the formation of ONOO-, or GSH to increase the detoxification of ONOO-, completely blocked the detrimental effects of SIN-1 and exerted significant cardioprotective effects against reperfusion injury. CONCLUSION: These results suggest that ONOO- may play a significant role in postischemic myocardial injury.

Anti-apoptotic effect of benidipine, a long-lasting vasodilating calcium antagonist, in ischaemic/reperfused myocardial cells.

1. Ischaemia/reperfusion causes intracellular calcium overloading in cardiac cells. Administration of calcium antagonists reduces myocardial infarct size. Recent in vitro studies have demonstrated that calcium plays a critical role in the signal transduction pathway leading to apoptosis. However, whether or not calcium antagonists may reduce myocardial apoptosis induced by ischaemia-reperfusion, and thus decrease myocardial infarction, has not been directly investigated. 2. The present study investigated the effects of benidipine, an L-type calcium channel blocker, on myocardial infarct size, apoptosis, necrosis and cardiac functional recovery in rabbits subjected to myocardial ischaemia/reperfusion (MI/R, 45 min/240 min). Ten minutes prior to coronary occlusion, rabbits were treated with vehicle or benidipine (10 microg x kg(-1) or 3 microg x kg(-1), i.v.). 3. In the vehicle-treated group, MI/R caused cardiomyocyte apoptosis as evidenced by DNA ladder formation and TUNEL positive nuclear staining (12.2+/-1.1%). Treatment with 10 microg x kg(-1) benidipine lowered blood pressure, decreased myocardial apoptosis (6.2+/-0.8%, P<0.01 vs vehicle) and necrosis, reduced infarct size (20+/-2.3% vs 49+/-2.6%, P<0.01), and improved cardiac functional recovery after reperfusion. Administering benidipine at 3 microg x kg(-1), a dose at which no haemodynamic effect was observed, also exerted significant anti-apoptosis effects, which were not significantly different from those observed with higher dose benidipine treatment. However, treatment with this low dose benidipine failed to reduce myocardial necrosis. 4. These results demonstrate that benidipine, a calcium antagonist, exerts significant anti-apoptosis effects, which are independent of haemodynamic changes. Administration of benidipine at a higher dose produced favourable haemodynamic effects and provided additional protection against myocardial necrotic injury and further improved cardiac functional recovery.

Effects of a hydroxylated metabolite of the beta-andrenoreceptor antagonist, carvedilol, on post-ischaemic splachnic tissue injury.

1 Reactive oxygen species have been demonstrated to play a critical role in post-ischaemic tissue injury. The present experiment was designed to evaluate the effects of SB 211475, a hydroxylated metabolite of the new beta-adrenoceptor antagonist, carvedilol, on rat splanchnic ischaemia (SI, 60 min) and reperfusion(R)-induced shock and tissue injury. 2 Administration of SB 211475 two min before R attenuated SI/R injury in a dose-dependent manner. At doses of 0.5 mg kg(-1) and 1.0 mg kg(-1), SB 211475 exerted significant anti-shock and endothelial protective effects, characterized by prolonged survival times, increased survival rates, attenuated increases in tissue myeloperoxidase activity and haematocrits, and preserved endothelium-dependent vasorelaxation. 3 Administration of 1 mg kg(-1) carvedilol attenuated shock-induced tissue injury and endothelial dysfunction. However, administration of 0.5 mg kg(-1) carvedilol had no protective effects on post-ischaemic tissue injury. 4 Previous studies have shown that SB 211475 has virtually no beta-blocking activity but possesses more potent antioxidant activity than carvedilol. In the present study, SB 211475 exerted more potent protective effects than the parent compound, suggesting that this metabolite of carvedilol is superior to carvedilol with regard to its protection against post-ischaemia tissue injury.

Beneficial actions of S-nitroso-N-acetylpenicillamine, a nitric oxide donor, in murine traumatic shock.

We studied the effects of the nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP), in rat traumatic shock characterized by hypotension, increases in plasma free amino-nitrogen (5.3 +/- 0.5 U/ml vs. 2.5 +/- 0.3 U/ml controls) and intestinal myeloperoxidase activities (2.7 +/- 1.0 U/100 mg vs. 0.2 +/- 0.1 U/100 mg controls), and a survival time of 143 +/- 20 min. Moreover, superior mesenteric artery rings isolated from rats in traumatic shock relaxed to the endothelium-dependent vasodilator acetylcholine only 21 +/- 6% of U-46619 induced contraction. Administration of 100 micrograms/kg SNAP 10 min post-trauma followed by 10 micrograms/kg/h infusion prolonged survival time to 273 +/- 18 min (p < .05), attenuated the increases in plasma free amino-nitrogen (3.1 +/- 0.4 U/ml, p < .05) and tissue myeloperoxidase activities (0.6 +/- 0.3 U/100 mg, p < .05). Moreover, SNAP significantly preserved superior mesenteric artery endothelial function; the vasorelaxation to acetylcholine was 54 +/- 4% (p < .01). Protective effects were not seen in traumatic shock rats treated with the non-NO-donating parent compound N-acetylpenicillamine. These results indicate that SNAP affords significant protection in murine traumatic shock which may be achieved through maintenance of systemic blood pressure, preservation of vascular endothelial integrity, and inhibition of neutrophil-endothelial interaction and the resultant reduced microvascular leakiness.