L-NMMA (a nitric oxide synthase inhibitor) is effective in the treatment of cardiogenic shock

Vascular endothelial growth factor secretion and immunosuppression are distinct potency mechanisms of human bone marrow mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are investigated as cellular therapeutics for inflammatory bowel diseases and associated perianal fistula, although consistent efficacy remains a concern. Determining host factors that modulate MSCs' potency including their secretion of angiogenic and wound-healing factors, immunosuppression, and anti-inflammatory properties are important determinants of their functionality. We investigated the mechanisms that regulate the secretion of angiogenic and wound-healing factors and immune suppression of human bone marrow MSCs. Secretory analysis of MSCs focusing on 18 angiogenic and wound-healing secretory molecules identified the most abundancy of vascular endothelial growth factor A (VEGF-A). MSC viability and secretion of other angiogenic factors are not dependent on VEGF-A secretion which exclude the autocrine role of VEGF-A on MSC's fitness. However, the combination of inflammatory cytokines IFNγ and TNFα reduces MSC's VEGF-A secretion. To identify the effect of intestinal microvasculature on MSCs' potency, coculture analysis was performed between human large intestine microvascular endothelial cells (HLMVECs) and human bone marrow-derived MSCs. HLMVECs do not attenuate MSCs' viability despite blocking their VEGF-A secretion. In addition, HLMVECs neither attenuate MSC's IFNγ mediated upregulation of immunosuppressive enzyme indoleamine 2,3-dioxygenase nor abrogate suppression of T-cell proliferation despite the attenuation of VEGF-A secretion. We found that HLMVECs express copious amounts of endothelial nitric oxide synthase and mechanistic analysis showed that pharmacological blocking reverses HLMVEC-mediated attenuation of MSC's VEGF-A secretion. Together these results suggest that secretion of VEGF-A and immunosuppression are separable functions of MSCs which are regulated by distinct mechanisms in the host.

Medical therapy of cardiogenic shock: Contemporary use of inotropes and vasopressors

Cardiogenic shock is a primary cardiac disorder that results in both clinical and biochemical evidence of tissue hypoperfusion and can lead to multi-organ failure and death depending on its severity. Inadequate cardiac contractility or cardiac power secondary to acute myocardial infarction remains the most frequent cause of cardiogenic shock, although its contribution has declined over the past two decades, compared with other causes. Despite some advances in cardiogenic shock management, this clinical syndrome is still burdened by an extremely high mortality. Its management is based on immediate stabilization of haemodynamic parameters so that further treatment, including mechanical circulatory support and transfer to specialized tertiary care centres, can be accomplished. With these aims, medical therapy, consisting mainly of inotropic drugs and vasopressors, still has a major role. The purpose of this article is to review current evidence on the use of these medications in patients with cardiogenic shock and discuss specific clinical settings with indications to their use.

Dysfunctional and Dysregulated Nitric Oxide Synthases in Cardiovascular Disease: Mechanisms and Therapeutic Potential

Nitric oxide (NO) plays an important and diverse signalling role in the cardiovascular system, contributing to the regulation of vascular tone, endothelial function, myocardial function, haemostasis, and thrombosis, amongst many other roles. NO is synthesised through the nitric oxide synthase (NOS)-dependent L-arginine-NO pathway, as well as the nitrate-nitrite-NO pathway. The three isoforms of NOS, namely neuronal (NOS1), inducible (NOS2), and endothelial (NOS3), have different localisation and functions in the human body, and are consequently thought to have differing pathophysiological roles. Furthermore, as we continue to develop a deepened understanding of the different roles of NOS isoforms in disease, the possibility of therapeutically modulating NOS activity has emerged. Indeed, impaired (or dysfunctional), as well as overactive (or dysregulated) NOS activity are attractive therapeutic targets in cardiovascular disease. This review aims to describe recent advances in elucidating the physiological role of NOS isoforms within the cardiovascular system, as well as mechanisms of dysfunctional and dysregulated NOS in cardiovascular disease. We then discuss the modulation of NO and NOS activity as a target in the development of novel cardiovascular therapeutics.

Ammonia detoxification promotes CD8+ T cell memory development by urea and citrulline cycles

Amino acid metabolism is essential for cell survival, while the byproduct ammonia is toxic and can injure cellular longevity. Here we show that CD8⁺ memory T (T_M) cells mobilize the carbamoyl phosphate (CP) metabolic pathway to clear ammonia, thus promoting memory development. CD8⁺ T_M cells use β-hydroxybutyrylation to upregulate CP synthetase 1 and trigger the CP metabolic cascade to form arginine in the cytosol. This cytosolic arginine is then translocated into the mitochondria where it is split by arginase 2 to urea and ornithine. Cytosolic arginine is also converted to nitric oxide and citrulline by nitric oxide synthases. Thus, both the urea and citrulline cycles are employed by CD8⁺ T cells to clear ammonia and enable memory development. This ammonia clearance machinery might be targeted to improve T cell-based cancer immunotherapies.

Basic mechanisms in cardiogenic shock: part 1-definition and pathophysiology

Cardiogenic shock mortality rates remain high despite significant advances in cardiovascular medicine and the widespread uptake of mechanical circulatory support systems. Except for early invasive angiography and percutaneous coronary intervention of the infarct-related artery, the most widely used therapeutic measures are based on low-quality evidence. The grim prognosis and lack of high-quality data warrant further action. Part 1 of this two-part educational review defines cardiogenic shock and discusses current treatment strategies. In addition, we summarize current knowledge on basic mechanisms in the pathophysiology of cardiogenic shock, focusing on inflammation and microvascular disturbances, which may ultimately be translated into diagnostic or therapeutic approaches to improve the outcome of our patients.

A novel evaluation of endothelial dysfunction ex vivo: "Teaching an Old Drug a New Trick"

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Many CVDs begin with endothelium dysfunction (ED), including hypertension, thrombosis, and atherosclerosis. Our assay evaluated ED in isolated murine aorta by quantifying phenylephrine-induced contractions (PE) in the presence of L-NAME, which blocked acetylcholine-induced relaxation (ACh %; >99%). The "L-NAME PE Contraction Ratio" (PECR) was defined as: "PE Tension post-L-NAME" divided by "PE Tension pre-L-NAME." We hypothesized that our novel PE Contraction Ratio would strongly correlate with alterations in endothelium function. Validation 1: PECR and ACh % values of naïve aortas were strongly and positively correlated (PECR vs. ACh %, r2  = 0.91, n = 7). Validation 2: Retrospective analyses of published aortic PECR and ACh % data of female mice exposed to filtered air, propylene glycol:vegetable glycerin (PG:VG), formaldehyde (FA), or acetaldehyde (AA) for 4d showed that the PECR in air-exposed mice (PECR = 1.43 ± 0.05, n = 16) correlated positively with the ACh % (r2  = 0.40) as seen in naïve aortas. Similarly, PECR values were significantly decreased in aortas with ED yet retained positive regression coefficients with ACh % (PG:VG r2  = 0.54; FA r2  = 0.55). Unlike other toxicants, inhaled AA significantly increased both PECR and ACh % values yet diminished their correlation (r2  = 0.09). Validation 3: To assess species-specific dependence, we tested PECR in rat aorta, and found PECR correlated with ACh % relaxation albeit less well in this aged and dyslipidemic model. Because the PECR reflects NOS function directly, it is a robust measure of both ED and vascular dysfunction. Therefore, it is a complementary index of existing tests of ED that also provides insight into mechanisms of vascular toxicity.

Inflammation in Human Heart Failure: Major Mediators and Therapeutic Targets

Inflammation has been recognized as a major pathophysiological contributor to the entire spectrum of human heart failure (HF), including HF with reduced ejection fraction, HF with preserved ejection fraction, acute HF and cardiogenic shock. Nevertheless, the results of several trials attempting anti-inflammatory strategies in HF patients have not been consistent or motivating and the clinical implementation of anti-inflammatory treatments for HF still requires larger and longer trials, as well as novel and/or more specific drugs. The present work reviews the different inflammatory mechanisms contributing to each type of HF, the major inflammatory mediators involved, namely tumor necrosis factor alpha, the interleukins 1, 6, 8, 10, 18, and 33, C-reactive protein and the enzymes myeloperoxidase and inducible nitric oxide synthase, and their effects on heart function. Furthermore, several trials targeting these mediators or involving other anti-inflammatory treatments in human HF are also described and analyzed. Future therapeutic advances will likely involve tailored anti-inflammatory treatments according to the patient's inflammatory profile, as well as the development of resolution pharmacology aimed at stimulating resolution of inflammation pathways in HF.

Vasoactive pharmacologic therapy in cardiogenic shock: a critical review

BACKGROUND

Cardiogenic shock (CS) is an acute complex condition leading to morbidity and mortality. Vasoactive medications, such as vasopressors and inotropes are considered the cornerstone of pharmacological treatment of CS to improve end-organ perfusion by increasing cardiac output (CO) and blood pressure (BP), thus preventing multiorgan failure.

OBJECTIVE

A critical review was conducted to analyze the currently available randomized studies of vasoactive agents in CS to determine the indications of each agent and to critically appraise the methodological quality of the studies.

METHODS

PubMed database search was conducted to identify randomized controlled trials (RCTs) on vasoactive therapy in CS. After study selection, the internal validity of the selected studies was critically appraised using the three-item Jadad scale.

RESULTS

Nine studies randomized 2388 patients with a mean age ranged between 62 and 69 years, were identified. Seven of studies investigated CS in the setting of acute myocardial infarction (AMI). The studies evaluated the comparisons of norepinephrine (NE) vs. dopamine, epinephrine vs. NE, levosimendan vs. dobutamine, enoximone or placebo, and nitric oxide synthase inhibitors (NOSi) vs. placebo. The mean Jadad score of the nine studies was 3.33, with only three studies of a score of 5.

CONCLUSIONS

The evidence from the studies of vasoactive agents in CS carries uncertainties. The methodological quality between the studies is variable due to the inherent difficulties to conduct a study in CS. Vasopressors and inotropes continue to have a fundamental role given the lack of pharmacological alternatives.

Xenocoumacin 2 reduces protein biosynthesis and inhibits inflammatory and angiogenesis-related processes in endothelial cells

Xenocoumacin (Xcn) 1 and 2 are the major antibiotics produced by the insect-pathogenic bacterium Xenorhabdus nematophila. Although the antimicrobial activity of Xcns has been explored, research regarding their action on mammalian cells is lacking. We aimed to investigate the action of Xcns in the context of inflammation and angiogenesis. We found that Xcns do not impair the viability of primary endothelial cells (ECs). Particularly Xcn2, but not Xcn1, inhibited the pro-inflammatory activation of ECs: Xcn2 diminished the interaction between ECs and leukocytes by downregulating cell adhesion molecule expression and blocked critical steps of the NF-κB activation pathway including the nuclear translocation of NF-κB p65 as well as the activation of inhibitor of κBα (IκBα) and IκB kinase β (IKKβ). Furthermore, the synthesis of pro-inflammatory mediators and enzymes, nitric oxide (NO) production and prostaglandin E₂ (PGE₂), inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2), was evaluated in leukocytes. The results showed that Xcns reduced viability, NO release, and iNOS expression in activated macrophages. Beyond these anti-inflammatory properties, Xcn2 effectively hindered pro-angiogenic processes in HUVECs, such as proliferation, undirected and chemotactic migration, sprouting, and network formation. Most importantly, we revealed that Xcn2 inhibits de novo protein synthesis in ECs. Consequently, protein levels of receptors that mediate the inflammatory and angiogenic signaling processes and that have a short half-live are reduced by Xcn2 treatment, thus explaining the observed pharmacological activities. Overall, our research highlights that Xcn2 exhibits significant pharmacological in vitro activity regarding inflammation and angiogenesis, which is worth to be further investigated preclinically.

eNOS-induced vascular barrier disruption in retinopathy by c-Src activation and tyrosine phosphorylation of VE-cadherin

Background

Hypoxia and consequent production of vascular endothelial growth factor A (VEGFA) promote blood vessel leakiness and edema in ocular diseases. Anti-VEGFA therapeutics may aggravate hypoxia; therefore, therapy development is needed.

Methods

Oxygen-induced retinopathy was used as a model to test the role of nitric oxide (NO) in pathological neovascularization and vessel permeability. Suppression of NO formation was achieved chemically using L-NMMA, or genetically, in endothelial NO synthase serine to alanine (S1176A) mutant mice.

Results

Suppression of NO formation resulted in reduced retinal neoangiogenesis. Remaining vascular tufts exhibited reduced vascular leakage through stabilized endothelial adherens junctions, manifested as reduced phosphorylation of vascular endothelial (VE)-cadherin Y685 in a c-Src-dependent manner. Treatment with a single dose of L-NMMA in established retinopathy restored the vascular barrier and prevented leakage.

Conclusions

We conclude that NO destabilizes adheren junctions, resulting in vascular hyperpermeability, by converging with the VEGFA/VEGFR2/c-Src/VE-cadherin pathway.

Funding

This study was supported by the Swedish Cancer foundation (19 0119 Pj ), the Swedish Research Council (2020-01349), the Knut and Alice Wallenberg foundation (KAW 2020.0057) and a Fondation Leducq Transatlantic Network of Excellence Grant in Neurovascular Disease (17 CVD 03). KAW also supported LCW with a Wallenberg Scholar grant (2015.0275). WCS was supported by Grants R35 HL139945, P01 HL1070205, AHA MERIT Award. DV was supported by grants from the Deutsche Forschungsgemeinschaft, SFB1450, B03, and CRU342, P2.

Nitric Oxide and Endothelial Dysfunction

Nitric oxide is a strong vasodilatory and anti-inflammatory signaling molecule that plays diverse roles in maintaining vascular homeostasis. Nitric oxide produced by endothelial cells is a critical regulator of this balance, such that endothelial dysfunction is defined as a reduced capacity for nitric oxide production and decreased nitric oxide sensitivity. This ultimately results in an imbalance in vascular homeostasis leading to a prothrombotic, proinflammatory, and less compliant blood vessel wall. Endothelial dysfunction is central in numerous pathophysiologic processes. This article reviews mechanisms governing nitric oxide production and downstream effects, highlighting the role of nitric oxide signaling in organ system pathologies.

Translational research in retinal vascular disease. An approach

The clinical presentation of the most frequent vision threatening retinal diseases is dominated by lesions indicating that disturbances in retinal blood flow are involved in the pathogenesis of these diseases. The present review describes the experience from a translational strategy pursued to investigate retinal vascular diseases with diabetic retinopathy as the main object. The normal regulation of retinal blood flow is investigated in porcine retinal vessels in vitro and ex vivo. Subsequently, the in vitro findings are translated to clinical studies in normal persons in vivo, and it is investigated whether the mechanisms are disturbed in retinal vascular disease. This is followed by clinical intervention studies on these diseases. The approach has been used to investigate pressure autoregulation, metabolic autoregulation and vasomotion in retinal vessels. The investigations have shown that retinal vascular tone can be regulated by receptor-specific agonists and antagonists to vasoactive compounds such as purines, prostaglandins and nitric oxide synthesis and that the vasoactive effects can be modulated by the concentration and the mode of administration of these compounds. Additionally, it has been shown that retinal precapillary arterioles and capillaries not visible by ophthalmoscopy may play an important role for the pathophysiology of retinal vascular disease and its treatment. Future studies should focus on investigating normal and pathological regulation of retinal blood flow in these smaller vessels.

Endothelial nitric oxide synthase polymorphism and prognosis in systolic heart failure patients

BACKGROUND

The endothelial nitric oxide synthase (eNOS) gene single nucleotide polymorphism G894T is associated with thrombotic vascular diseases. However, its functional significance is controversial and data are scarce concerning its influence in heart failure (HF).

METHODS

We studied 215 patients with chronic systolic HF. DNA was analyzed for eNOS gene G894T polymorphism using PCR and DNA sequencing. Evaluation of clinical characteristics and analysis of factors associated with 2-year mortality were performed for the homozygous G-allele G894T variant (GG), relative to the TT and GT variants.

RESULTS

The genotype distributions of eNOS G894T alleles were: GG 135 patients (63%) and TT/GT 80 (37%). Two-year mortality was significantly higher in the GG variant (48%) than the combined TT/GT group (32%). The usage of nitrates was associated with increased 2-year mortality (HR 2.0, 95% CI 1.28-3.17; p = 0.003), which was most significant in the GG group treated with nitrates (73.5%) in comparison to the TT/GT group not treated with nitrates (34%); HR 2.75, 95% CI 1.57-4.79, P < 0.001.

CONCLUSIONS

Homozygosity for the G allele of the eNOS G894T polymorphism was associated with worse survival in systolic HF patients, especially in those treated with nitrates. ENOS polymorphism may result in different mechanistic interactions in HF than in thrombotic vascular diseases, suggesting that overexpression of NO may be associated with deleterious effects in systolic HF.

Nitrates for acute heart failure syndromes

BACKGROUND

Current drug therapy for acute heart failure syndromes (AHFS) consists mainly of diuretics supplemented by vasodilators or inotropes. Nitrates have been used as vasodilators in AHFS for many years and have been shown to improve some aspects of AHFS in some small studies. The aim of this review was to determine the clinical efficacy and safety of nitrate vasodilators in AHFS.

OBJECTIVES

To quantify the effect of different nitrate preparations (isosorbide dinitrate and nitroglycerin) and the effect of route of administration of nitrates on clinical outcome, and to evaluate the safety and tolerability of nitrates in the management of AHFS.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3), MEDLINE (1950 to July week 2 2011) and EMBASE (1980 to week 28 2011). We searched the Current Controlled Trials MetaRegister of Clinical Trials (compiled by Current Science) (July 2011). We checked the reference lists of trials and contacted trial authors. We imposed no language restriction.

SELECTION CRITERIA

Randomised controlled trials comparing nitrates (isosorbide dinitrate and nitroglycerin) with alternative interventions (frusemide and morphine, frusemide alone, hydralazine, prenalterol, intravenous nesiritide and placebo) in the management of AHFS in adults aged 18 and over.

DATA COLLECTION AND ANALYSIS

Two authors independently performed data extraction. Two authors performed trial quality assessment. We used mean difference (MD), odds ratio (OR) and 95% confidence intervals (CI) to measure effect sizes. Two authors independently assessed and rated the methodological quality of each trial using the Cochrane Collaboration tool for assessing risk of bias.

MAIN RESULTS

Four studies (634 participants) met the inclusion criteria. Two of the included studies included only patients with AHFS following acute myocardial infarction (AMI); one study excluded patients with overt AMI; and one study included participants with AHFS with and without acute coronary syndromes.Based on a single study, there was no significant difference in the rapidity of symptom relief between intravenous nitroglycerin/N-acetylcysteine and intravenous frusemide/morphine after 30 minutes (fixed-effect MD -0.30, 95% CI -0.65 to 0.05), 60 minutes (fixed-effect MD -0.20, 95% CI -0.65 to 0.25), three hours (fixed-effect MD 0.20, 95% CI -0.27 to 0.67) and 24 hours (fixed-effect MD 0.00, 95% CI -0.31 to 0.31). There is no evidence to support a difference in AHFS patients receiving intravenous nitrate vasodilator therapy or alternative interventions with regard to the following outcome measures: requirement for mechanical ventilation, systolic blood pressure (SBP) change after three hours and 24 hours, diastolic blood pressure (DBP) change after 30, 60 and 90 minutes, heart rate change at 30 minutes, 60 minutes, three hours and 24 hours, pulmonary artery occlusion pressure (PAOP) change after three hours and 18 hours, cardiac output (CO) change at 90 minutes and three hours and progression to myocardial infarction. There is a significantly higher incidence of adverse events after three hours with nitroglycerin compared with placebo (odds ratio 2.29, 95% CI 1.26 to 4.16) based on a single study. There was no consistent evidence to support a difference in AHFS patients receiving intravenous nitrate vasodilator therapy or alternative interventions with regard to the following secondary outcome measures: SBP change after 30 and 60 minutes, heart rate change after 90 minutes, and PAOP change after 90 minutes. None of the included studies reported healthcare costs as an outcome measure. There were no data reported by any of the studies relating to the acceptability of the treatment to the patients (patient satisfaction scores).Overall there was a paucity of relevant quality data in the included studies. Assessment of overall risk of bias in these studies was limited as three of the studies did not give sufficient detail to allow assessment of potential risk of bias.

AUTHORS' CONCLUSIONS

There appears to be no significant difference between nitrate vasodilator therapy and alternative interventions in the treatment of AHFS, with regard to symptom relief and haemodynamic variables. Nitrates may be associated with a lower incidence of adverse effects after three hours compared with placebo. However, there is a lack of data to draw any firm conclusions concerning the use of nitrates in AHFS because current evidence is based on few low-quality studies.

Transthyretin aggregates induce production of reactive nitrogen species

BACKGROUND AND OBJECTIVE

Misfolded and aggregated transthyretins (agTTR) contribute to neurodegenerative amyloid diseases such as familial amyloid polyneuropathy and senile systemic amyloidosis. The neurotoxicity mechanisms of agTTR, however, are not well understood. In the current study, the possible contribution of reactive nitrogen species (RNS) to such mechanisms was investigated by examining agTTR-mediated changes in cellular RNS levels.

METHODS AND RESULTS

The production of RNS was assessed through nitrate and nitrite assays in two human cell lines after exposure to agTTR (2.4 µM pre-aggregation concentration). In both epidermoid (A431) and schwannoma (sNF94.3) cell lines, agTTR induced significant increases in RNS (p < 0.05 relative to the same concentration of normal TTR, or no-TTR controls). Redox modulators such as apocynin (1-(4-hydroxy-3-methoxy-phenyl)ethanone) and L-NMMA (N(G)-monomethyl-L-arginine) were tested for their effects on RNS production. These modulators decreased RNS production in both cell lines; although the effects of L-NMMA were statistically significant only in the schwannoma cells. Moreover, cells treated with agTTR exhibited decreases in metabolic activity relative to TTR- or non-TTR-treated cells (p < 0.05) as assessed by reduction of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide).

CONCLUSION

The results provide novel evidence for involvement of RNS in pro-oxidative effects of agTTR in two different human cell lines, and show that agTTR can induce more generalized changes in cellular metabolic activity.

A review of cardiogenic shock in acute myocardial infarction

Cardiogenic shock continues to be the most common cause of death in patients hospitalized with acute myocardial infarction. It has also been frequently associated with ST-segment elevation myocardial infarction (STEMI) and patients with co-morbidities. Cardiogenic shock presents with low systolic blood pressure and clinical signs of hypoperfusion. Rapid diagnosis and supportive therapy in the form of medications, airway support and intra-aortic balloon counterpulsation is required. Initial stabilization can be followed by reperfusion by fibrinolytic therapy, emergent percutaneous intervention (PCI) or coronary artery bypass grafting (CABG). The latter two have been found to decrease mortality in the long term. Research is being carried out on the role of inflammatory mediators in the clinical manifestation of cardiogenic shock. Mechanical support devices also show promise in the future.

Post myocardial infarction cardiogenic shock: a review of current therapies

Cardiogenic shock is often a devastating consequence of acute myocardial infarction (MI) and portends to significant mortality and morbidity. Despite improvements in expediting the time to treatment and enhancements in available medical therapy and reperfusion techniques, cardiogenic shock remains the most common cause of mortality following MI. Post-MI cardiogenic shock most commonly occurs as a consequence of severe left ventricular dysfunction. Right ventricular (RV) MI must also be considered. Mechanical complications including acute mitral regurgitation, ventricular septal rupture, and ventricular free-wall rupture can also lead to cardiogenic shock. Rapid diagnosis of cardiogenic shock and its underlying cause is pivotal to delivering definitive therapy. Intravenous vasoactive agents and mechanical support devices may temporize the patient's hemodynamic status until definitive therapy by percutaneous or surgical intervention can be performed. Despite prompt management, post-MI cardiogenic shock mortality remains high.

Nitric oxide synthase inhibitors in cardiogenic shock: present and future

Cardiogenic shock (CS) accompanying myocardial infarction carries a case fatality rate of 40-50%. Profound myocardial dysfunction is partially reversible, and possibly related to a state of inflammatory storm accompanied by nitric oxide (NO) overproduction. CS survivors enjoy satisfactory longevity and quality of life. The focus of this review is to describe the available data regarding NO synthase (NOS) inhibitors in CS. In view of supportive evidence from mammalian research (inducible-NOS-knockout mice are less susceptible to ischemic and reperfusion injury), therapies mitigating NO overproduction were tested in human CS subjects. Human randomized clinical trials project excellent safety but lack of efficacy. Although the Phase III, multicenter, prospective, randomized, double-blind, placebo-controlled Study to Assess the Safety and Efficacy of Tilarginine Acetate (L-N(G)-monomethyl arginine citrate [L-NMMA]) in CS (TRIUMPH) trial demonstrated lack of clinical benefit of 5-h infusion of L-NMMA in CS, major design issues regarding the optimal timing, dosing, duration and NOS inhibitor need to be addressed prior to rendering this therapy ineffective.

Causes of death and re‐hospitalization in cardiogenic shock

BACKGROUND

In cardiogenic shock, causes of death usually are cardiac. However, a systemic inflammatory response syndrome may influence outcome.

METHODS

SHould we emergently revascularize Occluded Coronaries in cardiogenic shocK? (SHOCK) Trial patients (n = 302) were analyzed regarding cause of death and re-hospitalization.

RESULTS

Deaths (n = 180) occurred < or =30 days in 86% and >30 days in 14%. Known causes of death < or =30 days were cardiac in 88% (37% arrhythmic) and non-cardiac in 12% (29% septic). Non-cardiac deaths < or =30 days occurred later (206 [91,394] versus 41 [15,156] h, P<0.01) and were more frequently associated with signs of inflammation (43 versus 12%, P = 0.01) than cardiac deaths < or =30 days. Known causes of in-hospital death >30 days (n = 19) were cardiac in 58% and non-cardiac in 42%. Among deaths < or =30 days systemic vascular resistance index was higher (2,666+/-1,063 versus 2,090+/-731 dynes.sec.cm(-5) m(2), P = 0.05) than among deaths >30 days. Among the 116 survivors of the initial hospitalization with data available, 52 (45%) were readmitted, most of which due to heart failure (n = 22, 42%) and myocardial ischemia (n = 16, 31%).

CONCLUSIONS

In CS, early deaths < or =30 days are mainly cardiac. Non-cardiac deaths are associated with signs of inflammation. In survivors of the initial hospitalization, re-hospitalizations are due to heart failure and myocardial ischemia.

Post-resuscitation NOS inhibition does not improve hemodynamic recovery of hypoxic newborn pigs

BACKGROUND

Significant improvement in myocardial recovery has been shown previously with interventions to decrease reactive oxygen species after ischemia/hypoxia. We investigated whether co-administration of N-acetylcysteine (NAC, a scavenger for reactive oxygen species) and N (G)-monomethyl-L: -arginine (L-NMMA, a non-selective nitric oxide synthase inhibitor) results in better hemodynamic recovery.

DESIGN

Controlled, block-randomized study.

SETTING

University research laboratory.

SUBJECT

Mixed breed piglets (1-4d, 1.6-2.4 kg).

INTERVENTIONS

Acutely instrumented piglets received normocapnic alveolar hypoxia (10-15% oxygen) for 2 h followed by reoxygenation with 100% oxygen (1 h) then 21% oxygen (3 h). After reoxygenation, hypoxic-reoxygenated piglets were given either saline (controls), NAC [30 mg/kg bolus + 20 mg/(kg h) infusion], NMMA [0.1 mg/kg bolus + 0.1 mg/(kg h) infusion] or NAC + L-NMMA via intravenous infusion in a blinded, randomized fashion (n = 8/group). Sham-operated piglets had no hypoxia-reoxygenation (n = 5).

MEASUREMENTS AND RESULTS

Both cardiac index and stroke volume of hypoxia-reoxygenation controls remained depressed during reoxygenation (vs. normoxic baseline, p < 0.05). Post-resuscitation treatment with L-NMMA alone did not improve systemic hemodynamic recovery, but caused pulmonary hypertension (vs. controls). In contrast, treating the piglets with either NAC or NAC + L-NMMA improved cardiac index and stroke volume, with no effect on heart rate and blood pressure (vs. controls). These treatments also decreased various oxidative stress markers in myocardial tissues (vs. controls). However, there was no significant difference between NAC- and NAC + L-NMMA groups in all examined parameters.

CONCLUSIONS

Post-resuscitation administration of NAC improved cardiac function and reduced oxidative stress in newborn pigs with hypoxia-reoxygenation insult. Low-dose, non-selective inhibitor of nitric oxide synthase activity did not provide any further beneficial effect.

Expert opinion on tilarginine in the treatment of shock

Tilarginine is L-N-monomethyl arginine (L-NMMA) or N(G)-monomethyl-L-arginine HCL, a non-selective inhibitor of nitric oxide synthase (NOS), which has been studied in the treatment of septic shock and cardiogenic shock complicating myocardial infarction. Despite strong evidence that excessive nitric oxide (NO) production plays a pivotal role in the pathogenesis of septic shock and may contribute to the pathogenesis of cardiogenic shock complicating myocardial infarction, outcome studies in these two disorders have proved disappointing. L-NMMA therapy was associated with an excess mortality, particularly at doses > 5 mg/(kg h), in septic shock whereas the effects of a lower dose (1 mg/(kg h)) in cardiogenic shock complicating myocardial infarction were neutral. The excess mortality in patients with septic shock was almost certainly the result of unfavourable haemodynamic changes induced by L-NMMA (decreased cardiac output, increased pulmonary vascular resistance and reduced tissue oxygen delivery) whereas the lack of benefit in patients with cardiogenic shock complicating myocardial infarction may have been because the dose of L-NMMA was too low. Further studies of L-NMMA at doses < 5 mg/(kg h) in conjunction with inotrope support may produce more beneficial results. Conversely, the use of a selective inducible NOS inhibitor to reduce the pathological effects of excessive NO production although leaving the beneficial effects of vascular NO production by endothelial NOS unaltered may prove to be of value.

The evaluation and management of cardiogenic shock

Cardiogenic shock (CS) continues to be the leading cause of death in patients who present to the hospital with acute myocardial infarction (AMI). Mortality in patients with AMI complicated by CS remains extremely high, with 1-month mortality rates ranging from 40% to 60%. Although pump failure is the dominant etiologic feature of CS after AMI, the inflammatory system has been implicated in its pathogenesis. The dominant therapy for treatment of CS is early mechanical revascularization with either percutaneous coronary intervention or coronary artery bypass graft surgery. Supportive measures such as intravenous vasopressors or intra-aortic balloon counterpulsation can complement the benefit of definitive revascularization. Newer therapies are directed at mitigating the inflammatory response or supporting cardiovascular function until either patient recovery or until other destination therapy is available. The strategies in this critical pathway outline the general approach in treating CS after AMI at our institution.

Cardiogenic shock

Cardiogenic shock is the most common cause of death in patients hospitalized with acute myocardial infarction and is associated with a poor prognosis. More than 75% of cases are due to extensive left ventricular infarction and ventricular failure. Other causes include right ventricular infarction and papillary muscle rupture with acute severe mitral regurgitation. Activation of neurohormonal systems and the systemic inflammatory response worsens shock. To improve outcomes, cardiogenic shock needs to be recognized early in its course and its cause needs to be diagnosed rapidly. Treatment strategies using intra-aortic balloon counterpulsation and emergency revascularization by percutaneous coronary interventions or coronary bypass surgery have been shown to improve outcomes. To decrease the incidence of cardiogenic shock, public education regarding early presentation to hospital in the course of acute chest pain is important. Emergency medical transport systems may need to take patients with complicated acute myocardial infarction to hospitals with the capability to perform urgent revascularization.

Mediators of anaphylaxis

Anaphylaxis is a life-threatening condition closely linked to IgE activation of mast cells with subsequent release of preformed mediators, including histamine, neutral proteases (tryptase and chymase), and proteoglycans (eg, heparin) from intracellular granules. These factors participate in the development of classic symptoms involving the skin, respiratory tract, circulation, and gastrointestinal system. Release of these granules is followed quickly by increased synthesis from membrane arachidonic acid of prostaglandins and leukotrienes that have an additional role in clinical symptoms. Thereafter, mast cells release numerous chemokines and cytokines that initiate recruitment and activation of additional inflammatory cells, including basophils, eosinophils, and Th2 cells.

Cardiogenic shock: treatment

The treatment of cardiogenic shock complicating the acute coronary syndromes consists of medical therapy, percutaneous revascularization procedures, cardiac surgery, and the implantation of devices. Medical therapy is limited to different positive inotropic and vasoactive drugs, without any firm evidence of survival benefit using these drugs. Several new pharmacologic compounds are at different stages of clinical research, but are not yet routinely approved for the treatment of cardiogenic shock. The only evidence-based therapy with proven survival benefit is timely revascularization. Intra-aortic balloon pump counterpulsation maintains its central role as supportive treatment in cardiogenic shock patients. Anecdotal evidence is available about the use of ventricular assist devices, cardiac resynchronization therapy, and emergent heart transplantation.

Pathophysiology of cardiogenic shock complicating acute myocardial infarction

Cardiogenic shock is a rapidly progressive, often fatal complication of acute myocardial infarction. A vicious circle of ischemia, decreased cardiac output and reinfarction progress to left ventricular failure and death. The fundamental pathophysiology of this cascade and other mechanisms beyond the classic paradigm of ischemia and dysfunction are discussed in detail.

Nitric oxide synthase inhibitors in post-myocardial infarction cardiogenic shock--an update

Cardiogenic shock (CS) in acute myocardial infarction, after successful coronary angioplasty, still carries a case fatality rate of 50%. These patients succumb to a systemic metabolic storm, superimposed on extensive myocardial necrosis and stunning. Nitric oxide (NO) overproduction contributes to the pathophysiology of this morbid state. Current data regarding the physiologic effects of NO and nitric oxide synthase (NOS) inhibitors on the cardiovascular system are reviewed. Clinical trials assessing the safety and efficacy of NOS inhibitors in CS are summarized.

Methylene blue added to a hypertonic–hyperoncotic solution increases short-term survival in experimental cardiac arrest*

OBJECTIVE

Methylene blue (MB), a free-radical scavenger inhibiting the production and actions of nitric oxide, may counteract excessive vasodilatation induced by nitric oxide during cardiac arrest. Effects of MB in cardiac arrest and cardiopulmonary resuscitation were investigated.

DESIGN

Randomized, prospective, laboratory animal study.

SETTING

University animal research laboratory.

SUBJECTS

A total of 63 piglets of both sexes.

INTERVENTIONS

A pig model of extended cardiac arrest (12 mins of untreated cardiac arrest and 8 mins of cardiopulmonary resuscitation) was employed to assess the addition or no addition of MB to a hypertonic saline-dextran solution. These two groups (MB and hypertonic saline-dextran group [MB group] and hypertonic saline-dextran-only group) of 21 animals were each compared with a group receiving isotonic saline (n = 21).

MEASUREMENTS AND MAIN RESULTS

Although the groups were similar in baseline values, 4-hr survival in the MB group was increased (p = .02) in comparison with the isotonic saline group. Hemodynamic variables were somewhat improved at 15 mins after restoration of spontaneous circulation in the MB group compared with the other two groups. The jugular bulb levels of 8-isoprostane-prostaglandin F2alpha and 15-keto-dihydro-prostaglandin F2alpha (indicators of peroxidation and inflammation) were significantly decreased in the MB group compared with the isotonic saline group. Significant differences were recorded between the three groups in levels of protein S-100beta (indicator of neurologic injury), with lower levels in the MB group compared with the isotonic saline and hypertonic saline-dextran-only groups. Troponin I and myocardial muscle creatine kinase isoenzyme arterial concentrations (indicators of myocardial damage) were also significantly lower in the MB group.

CONCLUSIONS

MB co-administered with a hypertonic-hyperoncotic solution increased 4-hr survival vs. saline in an experimental porcine model of cardiac arrest and reduced oxidative, inflammatory, myocardial, and neurologic injury.

Plasma concentrations of interleukin-6, organ failure, vasopressor support, and successful coronary revascularization in predicting 30-day mortality of patients with cardiogenic shock complicating acute myocardial infarction

OBJECTIVE

Inflammation may play an important role in the pathogenesis, persistence, and prognosis of cardiogenic shock. We analyzed whether elevated plasma concentrations of inflammatory markers are independently associated with an adverse prognosis (increased 30-day mortality rate) in patients with cardiogenic shock.

DESIGN

Retrospective study.

SETTING

Single-center study, eight-bed intensive care unit at a university hospital.

PATIENTS

Retrospective study on stored plasma samples from 38 patients with cardiogenic shock complicating acute myocardial infarction.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thirty-day nonsurvivors (n = 23, 61%) had been less frequently successfully revascularized, exhibited more frequently renal failure, needed higher vasopressor doses, and presented with significantly higher interleukin-6 plasma concentrations on intensive care unit admission than 30-day survivors. Univariate hazard ratios (95% confidence interval) for 30-day mortality were 1.49 (1.24-1.80) for every 50 pg/mL increase in the interleukin-6 plasma concentration (p = .00003), 1.06 (1.02-1.10) for every 0.1 microg x kg x min increase in the total vasopressor dose (p = .007), 1.14 (1.04-1.25) for every mmol/L increase in serum lactate (p = .006), 2.47 (1.06-5.73) for acute renal failure (p = .036), and 0.34 (0.14-0.82) for successful revascularization (p = .016). However, interleukin-6 plasma concentrations were correlated with vasopressor need and were significantly higher in patients with acute renal failure and in patients without or unsuccessful revascularization. In a multivariate Cox-proportional hazard model, interleukin-6 was the only significant predictor of 30-day mortality with a hazard ratio of 1.42 (1.12-1.80, p = .004). Accordingly, interleukin-6 concentrations > or =200 pg/mL (the point of maximum interest by receiver operating characteristic analysis with a specificity of 87% and a sensitivity of 74%) were associated with a significantly increased 30-day mortality rate in both patients with and patients without successful revascularization.

CONCLUSIONS

Interleukin-6 concentrations are an independent predictor of 30-day mortality in patients with acute myocardial infarction complicated by cardiogenic shock.

Effect of pexelizumab on mortality in patients with acute myocardial infarction or undergoing coronary artery bypass surgery: a systematic overview

BACKGROUND

Recent trials evaluating the C5 complement inhibitor, pexelizumab, have shown that modulation of inflammation during ischemia/reperfusion in patients with acute myocardial infarction (MI) or undergoing coronary artery bypass graft (CABG) surgery may improve clinical outcomes.

METHODS

We performed a systematic overview of individual patient data from all completed randomized controlled trials of pexelizumab to evaluate the effect on all-cause mortality at 30 and 180 days after treatment. We used a random effects model and included all 5916 patients randomized in 4 clinical trials. Patients received placebo, pexelizumab bolus only or pexelizumab bolus followed by a 24-hour infusion.

RESULTS

A significant reduction in mortality at 30 days was observed in patients treated with bolus plus infusion (n = 2476) compared with placebo (n = 2492) (2.9% vs 4.2%; relative risk [RR], 0.70; 95% confidence interval [CI], 0.52-0.95; P = .02), with no interaction according to disease state of CABG or acute MI (P for interaction .33). A trend toward a reduction in mortality was observed in patients who received bolus plus infusion or bolus only (n = 3429) compared with placebo (n = 2476) (3.5% vs 4.2%; RR, 0.85; 95% CI, 0.66-1.0975; P = .215), but not in patients who received bolus only (n = 937) compared with placebo (n = 937) (5.2% vs 5.4%; RR, 0.96; 95% CI, 0.66-1.41; P = .918). The mortality benefit with bolus plus infusion compared with placebo persisted through 180 days (P = .05).

CONCLUSIONS

Pexelizumab reduced 30-day mortality in this systematic evaluation. Bolus plus infusion dose is being studied in ongoing trials in acute MI and CABG populations.

Predictors of in-hospital mortality after percutaneous coronary intervention for cardiogenic shock

OBJECTIVES

The mortality of patients with cardiogenic shock (CS) complicating ST elevation acute myocardial infarction (STEMI) remains high, despite early revascularization. Current knowledge of predictors of death is limited.

BACKGROUND

The pathophysiologic understanding of CS after acute myocardial infarction has shifted from a mere hemodynamic disorder to a more complex approach including imbalance in metabolic functions.

METHODS

In 45 consecutive patients (71.4+/-13 years) with CS complicating STEMI treated with primary percutaneous coronary intervention (PCI) serum levels of lactate, glucose and uric acid on coronary care unit (CCU) admission were measured. The end-point was in-hospital death.

RESULTS

The following parameters, on CCU admission, were univariate predictors of in-hospital mortality: serum glucose >200 mg/dl (OR=11.3, p=0.002), serum creatinine >1.5 mg/dl (OR=12.7, p=0.003), uric acid >6.5 mg/dl (OR=6.7, p=0.016), lactate >6.5 mmol/l (OR=54, p<0.0001), age > or =75 years (OR=8.5, p=0.002), history of hypertension (OR=8.3, p=0.003) and TIMI flow post PCI < or = 2 (OR=12.9, p=0.02). At multivariate analysis, after adjustment for sex, age, hypertension and diabetes, lactate >6.5 mmol/l and TIMI flow post PCI < or = 2 were still independent predictors of in-hospital mortality (OR=295, p=0.01; OR=19.5, p=0.04, respectively).

CONCLUSIONS

Hyperlactatemia, hyperglycemia and increased levels of uric acid on CCU admission are univariate predictors of in-hospital death. Moreover, at multivariate analysis, hyperlactatemia (>6.5 mmol/l) is an independent indicator of in-hospital death in CS patients complicating STEMI.

Concerning the mechanism of pexelizumab's benefit in acute myocardial infarction

BACKGROUND

The COMplement inhibition in Myocardial infarction treated with Angioplasty (COMMA) trial previously demonstrated an unexpected dose-dependent reduction in 90-day mortality after bolus/infusion of pexelizumab despite no reduction in the primary end point of myocardial infarction (MI) size. We examined whether the mortality benefit was related to established modulators of clinical benefit such as baseline demographics, time to treatment from symptom onset, myocardial perfusion post-percutaneous coronary intervention (PCI), and extent of ST resolution.

METHODS AND RESULTS

Eight hundred fourteen patients were randomized into 3 groups; (1) placebo, (2) pexelizumab bolus 2.0 mg/kg and placebo infusion for 20 hours, and (3) pexelizumab bolus 2.0 and 0.05 mg/kg per hour infusion for 20 hours commencing 4 hours after the bolus. Subjects presented with ST elevation MI within 6 hours of symptom onset and underwent PCI, creatine kinase (CK), and CK-MB measurements taken sequentially to define CK-MB area under the curve (AUC) and sequential ECG's defined ST resolution and QRS infarct size. Whereas mortality for both placebo and bolus pexelizumab groups rose during later time after presentation, it remained low and did not change appreciably during the 6-hour randomization window when patients received pexelizumab bolus infusion. Amplification of the mortality benefit was evident in patients with the highest quartile of hemodynamic compromise, that is, heart rate > or = 90 beat/min and systolic blood pressure < or = 118 mm Hg (3.2% vs 11.3% P = .004). A significant interaction between treatment assignment and hemodynamic status (P = .013) existed after adjusting for age, race, and MI location. Clinical benefit was not related to infarct size, extent of ST elevation, or evidence of angiographic or electrocardiographic reperfusion.

CONCLUSIONS

These data raise the possibility that the clinical benefit of pexelizumab is mediated through novel pathways such as reduction in apoptosis or other mechanisms.

Update on acute coronary syndromes and ST-elevation myocardial infarction

PURPOSE

The goal of modern therapy of acute myocardial infarction is twofold: to achieve rapid reperfusion of ischemic myocardium and to decrease subsequent remodeling, which can have deleterious effects on ventricular function and prognosis. The current paradigm for treatment of most patients with acute coronary syndromes is the consideration of an 'early invasive' strategy.

RECENT FINDINGS

Studies published this year have reinforced the importance of early reperfusion, solidified the evidence for early institution of aggressive adjunctive treatment, and added newer therapies to the existing armamentarium. This review evaluates published data from the past year encompassing advancements in percutaneous coronary intervention, drug-eluting stents, glycoprotein IIb/IIIa antagonists, thienopyridines, HMG-CoA reductase inhibitors, aldosterone blockade, low-molecular-weight heparins, direct thrombin inhibitors, implantable cardioverter-defibrillators, and beta-blockade in the treatment of acute coronary syndrome and ST-segment elevation myocardial infarction. In addition to patency of the epicardial coronary arteries, the role of the microvascular has become an area of recent interest.

SUMMARY

As novel modalities and approaches are put to the test of clinical trials, evidence-based therapies may help to lessen the adverse effects of myocardial ischemia and reduce future cardiovascular events.

Evolving the concept of regulation of vascular tone in humans

Elucidation of mechanisms regulating microcirculatory vascular tone is a key issue in the knowledge of human pathophysiology. Anandamide is an endogenous lipidic cannabinoid (CB) characterized by potent vasodilator activity acting mainly through the activation of CB receptors, located on the vessel walls, and the vanilloid receptor 1, located on sensory peptidergic nerve endings within the external layers of vessel walls. In humans, cutaneous anandamide administration causes forearm skin vasodilation by activating vanilloid receptor 1 presumably on primary sensory nerves, while intrabrachial infusion of the same compound is devoid of effect on forearm muscle microcirculation. Taken together, these results indicate that, apart from a possible distrectual difference, the effect of anandamide is specific for the abluminal, but not for the endoluminal, part of the vessel wall. Thus, it is conceivable that, at least in the peripheral microcirculation, this compound could act as an autocrine/paracrine agent and not as a circulating hormone. In line with this possibility, it has been demonstrated that anandamide can be produced by macrophages and therefore its biological effect might increase in clinical conditions characterized by augmented activity of this cell line, including cardiogenic, hemorrhagic and endotoxic shock and even in atherosclerosis, inflammation and ischemia. Moreover, increased serum values of anandamide have been found in patients with endotoxic shock. However, decisive information concerning the role of anandamide in humans will be obtained when specific antagonists or inhibitors will be available. In that case, the anandamide system might represent a potential target for the treatment of important cardiovascular conditions, including severe shock.

Management of cardiogenic shock attributable to acute myocardial infarction in the reperfusion era

Cardiogenic shock is the leading cause of death among patients hospitalized with acute myocardial infarction. It is defined as tissue hypoperfusion resulting from ventricular pump failure in the presence of adequate intravascular volume. Rapid assessment and triage of patients presenting in cardiogenic shock followed by appropriate institution of supportive therapies including vasopressor and inotropic agents, mechanical ventilatory support, and intra-aortic balloon pump counterpulsation are critical for effective management of these patients. However, emergency percutaneous coronary intervention or coronary artery bypass graft surgery is required to decrease mortality rates. Novel approaches, including inhibition of nitric oxide synthase and new mechanical support devices, may further decrease mortality rates, which remain high despite reperfusion therapy.

Differential signaling in presynaptic neurotransmitter release

Neuronal communication is tightly regulated by presynaptic signaling, thereby temporarily and locally secreting one or more transmitters in order to exert propagation or modulation of network activity. In the last 2 decades our insight into the molecular regulation of presynaptic transmitter vesicle traffic and fusion has exponentionally grown due to the identification of specific functional interactions between presynaptic proteins involved in these processes. In addition, a plethora of extracellular and intracellular messengers regulate neurotransmitter release, occasionally leading to short- or long-term adaptations of the synapse to altered environmental signals. Important in this respect is the ability of various nerve terminals to diverge their output by differentiation in secretion of co-localized transmitters. This divergence in presynaptic signaling may converge in the postsynaptic target neuron or spread to neighbouring cells. In this review differential presynaptic signaling mechanisms will be related to their potential divergent roles in transmitter release.