Endotoxin-induced myocardial dysfunction: evidence for a role of sphingosine production

Energetic dysfunction in sepsis: a narrative review

Background

Growing evidence associates organ dysfunction(s) with impaired metabolism in sepsis. Recent research has increased our understanding of the role of substrate utilization and mitochondrial dysfunction in the pathophysiology of sepsis-related organ dysfunction. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Main text

Sepsis is characterized by systemic and organ-specific changes in metabolism. Alterations of oxygen consumption, increased levels of circulating substrates, impaired glucose and lipid oxidation, and mitochondrial dysfunction are all associated with organ dysfunction and poor outcomes in both animal models and patients. The pathophysiological relevance of bioenergetics and metabolism in the specific examples of sepsis-related immunodeficiency, cerebral dysfunction, cardiomyopathy, acute kidney injury and diaphragmatic failure is also described.

Conclusions

Recent understandings in substrate utilization and mitochondrial dysfunction may pave the way for new diagnostic and therapeutic approaches. These findings could help physicians to identify distinct subgroups of sepsis and to develop personalized treatment strategies. Implications for their use as bioenergetic targets to identify metabolism- and mitochondria-targeted treatments need to be evaluated in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00893-7.

Evaluation of plasma sphingosine 1-phosphate, hepcidin and cardiovascular damage biomarkers (cardiac troponin I and homocysteine) in rats infected with brucellosis and vaccinated (Rev-1, RB-51)

Brucellosis is known as one of important zoonosis. Studying the histological and biochemical effects of the disease could help to increase our knowledge about it. The aim of the present study was to evaluate changes of plasma parameters after intraperitoneal injection of two species of Brucella (Brucella melitensis and Brucella abortus) and two vaccines (Rev-1, RB-51) in the rat. Forty male rats were divided into five groups (n = 8 in each group). Two groups received suspensions of Brucella abortus and Brucella melitensis and two other groups were injected intraperitoneally with two mentioned vaccines and the last group received only distilled water. The results showed a significant increase in sphingosine 1-phosphate, Malondialdehyde, hepcidin, homocysteine, cardiac troponin I and copper levels and a considerable decrease in the levels of iron and zinc (P ≤ 0.01) in infected groups compared to the control animals. In vaccinated groups, hepcidin was increased but other parameters were not changed in comparison to the control group. It can be concluded that increase of homocysteine and cardiac troponin I in brucellosis could be a warning for cardiac adverse effects. Besides, increase of sphingosine 1-phosphate probably indicates its stimulant and modulatory effects in anti- Brucellosis biochemical pathways of the host.

Lipid mediators of inflammation as novel plasma biomarkers to identify patients with bacteremia

OBJECTIVES

Rapid diagnostic tests for bacteremia are important for early treatment to improve clinical outcome. We sought to identify plasma biomarkers that can identify patients with bacteremia using an untargeted global metabolomic analysis.

METHODS

Plasma metabolomic profiles were analyzed for 145 adult patients with (cases) and without (controls) bacteremia using ultra-high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). All metabolites were compared between cases and controls using a 2-tier filtering approach, and each metabolite underwent receiver operating characteristic (ROC) curve analysis. Individual metabolites that distinguish between cases and controls were characterized. Subgroup analysis was performed to identify metabolites with prognostic significance.

RESULTS

After 2-tier filtering, 128 molecular features were identified to be potential biomarkers that could distinguish cases from controls. Five metabolites had an area under the ROC curve (AUC) of >0.8 in ROC curve analysis, including a sphingolipid, an acylcarnitine, a fatty acid ester, and 2 glycerophosphocholines. These metabolites could distinguish cases from controls in the unsupervised hierarchical clustering analysis. Subgroup analysis of bacteremic patients showed that the level of trans-2,3,4-trimethoxycinnamate was lower in fatal than non-fatal cases.

CONCLUSIONS

Plasma lipid mediators of inflammation can distinguish bacteremia cases from non-bacteremia controls. These biomarkers may be used as targets for rapid test in clinical practice.

Sphingomyelinase promotes oxidant production and skeletal muscle contractile dysfunction through activation of NADPH oxidase

Elevated concentrations of sphingomyelinase (SMase) have been detected in a variety of diseases. SMase has been shown to increase muscle derived oxidants and decrease skeletal muscle force; however, the sub-cellular site of oxidant production has not been elucidated. Using redox sensitive biosensors targeted to the mitochondria and NADPH oxidase (Nox2), we demonstrate that SMase increased Nox2-dependent ROS and had no effect on mitochondrial ROS in isolated FDB fibers. Pharmacological inhibition and genetic knockdown of Nox2 activity prevented SMase induced ROS production and provided protection against decreased force production in the diaphragm. In contrast, genetic overexpression of superoxide dismutase within the mitochondria did not prevent increased ROS production and offered no protection against decreased diaphragm function in response to SMase. Our study shows that SMase induced ROS production occurs in specific sub-cellular regions of skeletal muscle; however, the increased ROS does not completely account for the decrease in muscle function.

Use of insulin to decrease septic shock-induced myocardial depression in a porcine model

Insulin is known to attenuate septic shock-induced myocardial depression. Possible mechanisms include an anti-inflammatory or inotropic effect of insulin. The objective of this study was to determine whether the mechanism of action of insulin in attenuating septic shock-induced myocardial depression is through an immunomodulatory effect. Fourteen pigs were assigned to one of two groups. Both groups received a 4-h infusion of lipopolysaccharide endotoxin from Escherichia coli 0111:B4. Group 2 additionally received insulin at 1.5 U/kg/h with infusions of D50 normal saline and KCl to maintain normal serum glucose and potassium levels. Cardiac function was measured with shortening fraction using transthoracic echocardiogram. Plasma TNF-α, IL-1β, and IL-6 levels were obtained every 30 min. Postmortem cytokine analysis and histomorphology were performed on the heart tissue. Although insulin attenuated septic shock-induced myocardial depression, this was not due to an anti-inflammatory effect and, therefore, likely resulted from an inotropic effect of insulin.

Sepsis-induced cardiomyopathy

Myocardial dysfunction is one of the main predictors of poor outcome in septic patients, with mortality rates next to 70%. During the sepsis-induced myocardial dysfunction, both ventricles can dilate and diminish its ejection fraction, having less response to fluid resuscitation and catecholamines, but typically is assumed to be reversible within 7-10 days. In the last 30 years, It´s being subject of substantial research; however no explanation of its etiopathogenesis or effective treatment have been proved yet. The aim of this manuscript is to review on the most relevant aspects of the sepsis-induced myocardial dysfunction, discuss its clinical presentation, pathophysiology, etiopathogenesis, diagnostic tools and therapeutic strategies proposed in recent years.

Crosstalk between leptin and interleukin-1β abrogates negative inotropic effects in a model of chronic hyperleptinemia

Interleukin 1 beta (IL-1 β) is a proinflammatory cytokine with potent cardiosuppressive effects. Previous studies have shown that leptin blunts the negative inotropic effects of IL-1 β in isolated adult rat cardiac myocytes. However, the interactions between leptin and IL-1 β in the heart have not been examined on a background of chronic hyperleptinemia. To study this interaction, we have chosen the SHHF rat, a model of spontaneous hypertension that ultimately develops congestive heart failure. SHHF that are heterozygous for a null mutation of the leptin receptor (+/ fa cp, HET) are phenotypically lean but chronically hyperleptinemic and develop heart failure earlier than their normoleptinemic true lean (+/+, LN) littermates. Simultaneous cell shortening and calcium transients were measured in isolated ventricular cardiac myocytes from LN and HET SHHF in response to leptin, IL-1 β or IL-1 β following one hour pretreatment with leptin. Despite evidence of metabolic leptin resistance, HET myocytes were sensitive to the negative inotropic effect of leptin, similar to LN. Contractility returned to control levels in myocytes from HET that were pretreated with leptin prior to IL-1 β, while contractility remained depressed compared with control and similar to leptin alone in LN. Chronic hyperleptinemia resulted in altered JAK/STAT signaling in response to leptin and IL-1 β in isolated perfused hearts from HET compared with LN SHHF. Phosphorylated STAT3 (pSTAT3) and STAT5 (pSTAT5) decreased when HET hearts were treated with leptin followed by IL-1 β. While decreases in pSTAT3 and pSTAT5 may be associated with abrogation of the acute negative inotropic effects of IL-1 β in the presence of leptin in HET, long-term consequences remain to be explored. This study demonstrates that the heart remains sensitive to leptin in a hyperleptinemic state. Crosstalk between leptin and IL-1 β can influence cardiac function and cytokine signaling and these interactions are moderated by the presence of long-term hyperleptinemia.

Caspase-dependent protein phosphatase 2A activation contributes to endotoxin-induced cardiomyocyte contractile dysfunction

OBJECTIVE

Several studies report calcium mishandling, sarcomere disarray, and caspase activation during heart failure. Although active caspases have been shown to cleave myofibrillar proteins, little is known regarding their effects on calcium handling proteins. Therefore, we aimed to explore how endotoxin-induced caspase activation disrupts intracellular calcium regulation.

DESIGN

Randomized controlled trial.

SETTING

Small animal research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Sepsis was induced by injection of endotoxin (10 mg/kg, intravenously). Caspase inhibition was achieved by coinjection with zVAD.fmk (3 mg/kg, intravenously). We first isolated adult rat ventricular myocytes from control, endotoxin, and (endotoxin + zVAD)-treated rats to characterize contractile parameters and cellular calcium homeostasis. Underlying molecular mechanisms responsible for calcium mishandling were explored on sarcoplasmic reticulum vesicles and mitochondria prepared from treated animals. All experiments were performed 4 hrs postendotoxin treatment.

MEASUREMENTS AND MAIN RESULTS

zVAD normalized reductions in fractional cell shortening and relaxation rate triggered by endotoxin treatment. Both sarco-/endoplasmic reticulum Ca-ATPase and mitochondria-dependent calcium uptakes were impaired after endotoxin treatment and prevented when myocytes were isolated from zVAD-treated endotoxinic rat hearts. zVAD blocked endotoxin-induced phospholamban dephosphorylation, protein phosphatase 2A activation, and mitochondrial calcium retention capacity reduction. To strengthen these results, control sarcoplasmic reticulum vesicles and mitochondria were incubated with active recombinant caspase-3. Although no effects were observed on mitochondria, caspase-3 directly exerts detrimental effects on sarcoplasmic reticulum calcium uptake capacity by activating protein phosphatase 2A, leading to phospholamban dephosphorylation.

CONCLUSIONS

Caspase inhibition protects from endotoxin-induced sarcoplasmic reticulum calcium uptake capacity reduction and mitochondrial dysfunction.

Truncated human cytidylate-phosphate-deoxyguanylate-binding protein for improved nucleic acid amplification technique-based detection of bacterial species in human samples

A trunk of human cytidylate-phosphate-deoxyguanylate-binding protein/CXXC finger protein 1 (CFP1), immobilized onto an aminohexyl-Sepharose column, can be used as a preanalytical tool for the selective enrichment of bacterial DNA from mixed solutions with high amounts of human background DNA for nucleic acid amplification technique-based detection of pathogens. The transcriptional activator protein exhibits a high affinity for nonmethylated CpG dinucleotide motifs, which are differentially distributed in prokaryotic and higher eukaryotic genomes. The feasibility of the affinity chromatography (AC) step was tested with DNA from severely septic patients. AC using 16S rRNA gene primers substantially increased PCR sensitivity. Approximately 90% of eukaryotic DNA was removed, which significantly increased the signal-to-noise ratio. Threshold cycle values revealed that sensitivity was elevated at least 10-fold. The change in the ratio of bacterial DNA to human DNA increased from 26% to 74% the likelihood of culture-independent PCR-based identification of bacterial presence. Compared to the results seen with blood culture (which is the clinical gold standard for systemic infections, exhibiting 28% positives), the combination of AC and PCR achieves a significant increase in sensitivity and contributes to shortening the time to results for the initiation of guided antibiotic therapy.

Leptin modulates the negative inotropic effect of interleukin-1beta in cardiac myocytes

Interleukin-1beta (IL-1beta) is a potent negative inotrope implicated in the functional abnormalities of heart failure. Because the adipokine, leptin, protects against some of the cardiovascular effects of endotoxin, we hypothesized that leptin may modulate the cardiosuppressive effects of IL-1beta in isolated cardiomyocytes. Ventricular cardiac myocytes isolated from adult male Sprague Dawley rats were analyzed simultaneously for electrically stimulated contractility and calcium transients following 30 min exposure to IL-1beta (10 ng/ml) with or without 60 min pretreatment with leptin (25 ng/ml). IL-1beta decreased cell shortening, depressed maximal velocities of shortening and relengthening, and prolonged the time to 90% relaxation. The change in fura2-AM fluorescence ratio amplitude (Delta[Ca(2+)]) was significantly depressed and the time to return to baseline [Ca(2+)] was prolonged. The negative inotropic effects of IL-1beta were blocked by the neutral sphingomyelinase inhibitor Manumycin A (5 microM) or the ceramidase inhibitor N-oleoyl ethanolamine (1 microM). Prior exposure of myocytes to leptin blocked IL-1beta-induced cardiosuppression in conjunction with a blunting of IL-1beta stimulated ceramide accumulation. These data suggest that leptin may modulate IL-1beta signaling through the sphingolipid signaling pathway in cardiomyocytes.

Mechanisms of sepsis-induced cardiac dysfunction

OBJECTIVES

To review mechanisms underlying sepsis-induced cardiac dysfunction in general and intrinsic myocardial depression in particular.

DATA SOURCE

MEDLINE database.

DATA SYNTHESIS

Myocardial depression is a well-recognized manifestation of organ dysfunction in sepsis. Due to the lack of a generally accepted definition and the absence of large epidemiologic studies, its frequency is uncertain. Echocardiographic studies suggest that 40% to 50% of patients with prolonged septic shock develop myocardial depression, as defined by a reduced ejection fraction. Sepsis-related changes in circulating volume and vessel tone inevitably affect cardiac performance. Although the coronary circulation during sepsis is maintained or even increased, alterations in the microcirculation are likely. Mitochondrial dysfunction, another feature of sepsis-induced organ dysfunction, will also place the cardiomyocytes at risk of adenosine triphosphate depletion. However, clinical studies have demonstrated that myocardial cell death is rare and that cardiac function is fully reversible in survivors. Hence, functional rather than structural changes seem to be responsible for intrinsic myocardial depression during sepsis. The underlying mechanisms include down-regulation of beta-adrenergic receptors, depressed postreceptor signaling pathways, impaired calcium liberation from the sarcoplasmic reticulum, and impaired electromechanical coupling at the myofibrillar level. Most, if not all, of these changes are regulated by cytokines and nitric oxide.

CONCLUSIONS

Integrative studies are needed to distinguish the hierarchy of the various mechanisms underlying septic cardiac dysfunction. As many of these changes are related to severe inflammation and not to infection per se, a better understanding of septic myocardial dysfunction may be usefully extended to other systemic inflammatory conditions encountered in the critically ill. Myocardial depression may be arguably viewed as an adaptive event by reducing energy expenditure in a situation when energy generation is limited, thereby preventing activation of cell death pathways and allowing the potential for full functional recovery.

ROLE OF BACTERIAL ENDOTOXIN IN CHRONIC HEART FAILURE

Proinflammatory cytokines are now thought to play a key role in the pathophysiology of chronic heart failure, driving both symptomatic presentation and disease progression. We propose that this proinflammatory state, in turn, may be sustained through a chronic release of enterically derived bacterial endotoxin. Human trials have indicated that bacterial decontamination of the gut with concomitant decrease in lipopolysaccharide (LPS) has a positive outcome on heart disease patients. Antiendotoxin antibodies may thus represent therapeutic agents in this setting. Previously, antiendotoxin antibodies were targeted to the inner hydrophobic lipid A moiety of endotoxin in an attempt to neutralize its toxicity. These antibodies failed because they lacked specificity and bound to LPS weakly. In contrast, our studies on antiendotoxin antibodies have revealed that antibodies targeted to the hydrophilic oligosaccharides of the endotoxin have the potential to bind specifically with high affinity. Development of immunotherapeutics that can reduce systemic LPS or other agents, such as bactericidal/permeability-increasing protein that can neutralize LPS and limit inflammation safely, will enable the role of LPS in chronic heart failure to be elucidated and may pave the way to develop a new generation of effective therapeutic agents that may be directed to the treatment of chronic heart failure.

Tracking the Microbes in Sepsis: Advancements in Treatment Bring Challenges for Microbial Epidemiology

During the 1980s and 1990s, sepsis research propelled dozens of potential therapeutic candidates into clinical trials without a single novel therapeutic approach entering the clinical arena. After the publication of the landmark PROWESS trial in 2001, which showed survival benefit associated with the use of recombinant activated protein C for treatment of severe sepsis, there have been a series of positive sepsis intervention trials studying intensive glycemic control, low-dose steroid therapy, and early goal-directed therapy. The fact that the efficacy of these interventions is not restricted to certain types of infection should not detract from the importance of a full understanding of the microbial epidemiology of sepsis. Empirical antimicrobial therapy remains the mainstay of sepsis treatment. Furthermore, among a number of promising novel therapies that are in phase II and III clinical trials, several have pathogen-specific modes of action. The optimal targeting of antibiotics and such novel treatments toward the specific patient groups who will benefit represents a major challenge to reducing sepsis mortality. This requires detailed, up-to-date, and local epidemiological data. It is becoming increasingly clear that the nature of the infection underlying sepsis is a major determinant of outcome, and future trials of sepsis interventions, guided by high-quality data on microbial epidemiology, may well have to focus on subgroups of patients with different forms of infection. Finally, with the rapidly increasing challenge of antimicrobial resistance and the paucity of novel antibiotics, particularly for infections with gram-negative pathogens, it is more important than ever that we properly understand the forces that drive changes in the microbial epidemiology of sepsis.

Sphingosine impairs mitochondrial function by opening permeability transition pore

Growing evidence suggest that, in the heart, sphingosine participates to contractile dysfunction by altering calcium transients and mitochondria function. However, mechanisms underlying sphingosine-induced cardiac mitochondria dysfunction are poorly understood. Here, we studied the effects of sphingosine on isolated cardiac mitochondria of either wild-type or Bcl-2 overexpressing transgenic mice. Sphingosine induced reductions in ADP-coupled respiration, membrane potential, mitochondrial cytochrome c content and ATP production, which were partially prevented by cyclosporine A and mitochondrial Bcl-2 overexpression. These data suggest that sphingosine promotes mitochondrial permeability transition pore opening, which may result in uncoupled respiration and participate in cardiac contractile dysfunction.

Endotoxin-induced heart dysfunction in rats: assessment of myocardial perfusion and permeability and the role of fluid resuscitation

OBJECTIVE

The pathophysiology of sepsis-induced myocardial dysfunction is still controversial. Whether microcirculatory hypoperfusion together with capillary leakage can occur in the heart wall also remains a matter of debate. The objective was to evaluate the impact of fluid resuscitation on endotoxin-induced myocardial dysfunction.

DESIGN

Adult rats were given intraperitoneal injection of endotoxin (lipopolysaccharide, Escherichia coli, 10 mg/kg) or phosphate-buffered solution, followed up by echocardiography and acetate micro-positron emission tomography scan imaging, together with final hemodynamic, biochemical, and pathologic evaluations up to 48 hrs.

SETTING

University laboratory.

SUBJECTS

Pathogen-free male Wistar rats (350 g).

INTERVENTIONS

Influence of isovolumic fluid infusion type (saline vs. pentastarch) on these variables was assessed in 11 groups of six animals including an unchallenged control one.

MEASUREMENTS AND MAIN RESULTS

Endotoxin injection induced a) myocardial dysfunction (decrease of approximately 15-20% in left ventricular ejection fraction); b) ventricular enlargement (approximately 1.5- to 1.7-fold increase in left ventricular systolic volume); c) cardiac output increase (10-15%); d) myocardial hypoperfusion ( approximately 1.5- to 2-fold decrease in acetate k1 constant rate); e) increased oxygen consumption (k2); and f) interstitial wall increase. Endotoxin injection also enhanced levels of arterial lactates and troponin I. Colloid (pentastarch) over crystalloid (saline) fluid resuscitation significantly reversed echocardiographic changes, some positron emission tomography imaging alterations, and lactate and troponin I levels without further enhancing interstitial spaces.

CONCLUSION

Endotoxin can induce reversible myocardial alterations with evidence of coronary hypoperfusion and heart wall enlargement/damage, some of which can be prevented by fluid resuscitation. The use of crystalloids is less beneficial than pentastarch.

Role of increased sphingomyelinase activity in apoptosis and organ failure of patients with severe sepsis

Numerous studies support the notion that an activation of sphingomyelinases and a subsequent increase of the concentration of the bioactive lipid mediator ceramide are critical in the concert of inflammatory stimuli and to the induction of apoptosis during inflammation. Here we show that patients with severe sepsis exhibit an enhanced sphingolytic activity in comparison with controls [262 pmol/(mlxh) vs. 123.6 pmol/(mlxh), P<0.005]. During the clinical course, a further increase was paralleled by the severity of illness and by fatal outcome. Moreover, we show that oxidative stress may partially account for the increased activity through posttranslational modification of the enzyme. In a murine endotoxic shock model, administration of a low molecular weight inhibitor diminished the rise in enzymatic activity and improved the survival rate. In liver specimen, inhibition of activity correlated with a reduced rate of hepato-cellular apoptosis. Our data support the concept that activation of the plasmatic isoform of sphingomyelinase may play a critical role in the development of apoptosis and organ failure in sepsis. An inhibition of the secreted isoform of sphingomyelinase should be explored further as a potential target in the complicated puzzle of sepsis.

Endotoxin-induced myocardial dysfunction: effects of macrophage migration inhibitory factor neutralization

The pathophysiology of sepsis-induced myocardial dysfunction still remains controversial. Macrophage migration inhibitory factor (MIF) has recently been identified as a cardiac-derived myocardial depressant factor in septic shock. Putative mechanisms by which MIF affects cardiac function are unknown. In an investigation of possible mechanisms of action, a rat model of endotoxin toxicity was designed using intraperitoneal (I/P) injection of lipopolysaccharides (LPS) with or without coinfusion of neutralizing anti-MIF or isotypic-matched antibodies. Echocardiographic evaluation revealed that MIF neutralization reversed endotoxin-induced myocardial dysfunction at 24 hours after injection. RNase protection assay (RPA) and Western blot established that MIF neutralization prevented LPS-induced mRNA expression and production of heart-derived inflammatory paracrine and autocrine cytokines such as IL-1s and IL-6. Moreover, MIF immunoneutralization increased heart Bcl-2/Bax protein ratio and suppressed endotoxin-induced release of mitochondrial cytochrome-c, as demonstrated by Western blotting. Inhibition of mitochondrial loss of cytochrome-c decreased in heart caspase-3 activity at 6 and 24 hours after injection. MIF neutralization also restored the LPS-induced deficient nuclear translocation of phospho-Akt and consequently the expression of the heart survival nuclear factor GATA-4. The restoration of the translocation/expression of survival factors by MIF inhibition resulted in lowered endotoxin-induced DNA fragmentation at 24 hours, a hallmark of downstream cardiomyocyte apoptosis. Our data indicate that early inactivation of MIF significantly reverses the imbalance of proapoptotic to prosurvival pathways and reduces acute inflammation of the heart thereby improving myocardial dysfunction induced by endotoxin.

Synthesis and Antiapoptotic Activity of a Novel Analogue of the Neutral Sphingomyelinase Inhibitor Scyphostatin

The enantioselective synthesis of an analogue of scyphostatin, a potent inhibitor of the neutral sphingomyelinase, is described. The synthesis starts with cyclohexanone and a protected D-serine derivative. The key step is an asymmetric hydroxylation to access a hydroxycyclohexanone, which is transformed into a substituted hydroxycyclohexenone. This is converted into the scyphostatin analogue 14, a chemically and metabolically stabilised compound lacking the epoxy function of the natural congener and carrying a palmitic acid group instead of the native trienoyl residue. An evaluation of the biological activity of 14 revealed neutral sphingomyelinase inhibition in several in vivo test systems (monocytes, macrophages, hepatocytes) monitoring antiapoptotic effects and the inversion of phorbolester-induced translocation of green fluorescent protein labelled kinase (protein kinase C-alpha).

Mitochondrial proliferation during apoptosis induced by anticancer agents: effects of doxorubicin and mitoxantrone on cancer and cardiac cells

Doxorubicin is one of the most largely prescribed antitumor drug for the treatment of breast, liver and colon cancers as well as leukemia, but the cardiotoxicity of this anthracycline derivative limits its clinical use. Although doxorubicin is toxic to both cancer and cardiac cells, there are evidences suggesting that the mechanism of cell death is different for the two cell types. To investigate further this issue, we have compared the proapoptotic effects of doxorubicin and the functionally related anthracenedione compound mitoxantrone, which is also used in the clinic for the treatment of cancer. After evaluating the toxicity of the two drugs to mammary adenocarcinoma MTLn3 cells and H9C2 cardiomyocytes, we dissected the drug-induced apoptotic machinery by measuring the effects on the cell cycle progression, DNA condensation and fragmentation, production of endogenous peroxides and caspase activation. Both doxorubicin and mitoxantrone are potent inducers of apoptosis in H9C2 cardiomyocytes and MTLn3 breast cancer cells, but there are significant differences between the two cell types in terms of kinetics and order of the events. In particular, flow cytometry measurements of drug-induced changes in mitochondrial transmembrane potential and mitochondrial mass with different fluorescent probes suggested that the two drugs induced a progressive increase in mitochondrial mass in the cancer cells but not in the cardiac cells. The hypothesis was validated by means of electron microscopy, which revealed a significant increase in the number of mitochondria in drug-treated MTLn3 but not in H9C2 cells. The mitochondrial proliferation precedes the nuclear apoptosis in doxorubicin-treated MTLn3 cells. The changes in the architecture and number of mitochondria are linked to the drug-induced perturbation of the cell cycle progression and apoptosis. The proliferation of mitochondria could explain the higher toxicity of doxorubicin to cancer cells compared to cardiac cells and this suggests novel therapeutic opportunities to better control the cardiotoxicity of anthracyclines.

Practice parameters for hemodynamic support of sepsis in adult patients: 2004 update

OBJECTIVE

To provide the American College of Critical Care Medicine with updated guidelines for hemodynamic support of adult patients with sepsis.

DATA SOURCE

Publications relevant to hemodynamic support of septic patients were obtained from the medical literature, supplemented by the expertise and experience of members of an international task force convened from the membership of the Society of Critical Care Medicine.

STUDY SELECTION

Both human studies and relevant animal studies were considered.

DATA SYNTHESIS

The experts articles reviewed the literature and classified the strength of evidence of human studies according to study design and scientific value. Recommendations were drafted and graded levels based on an evidence-based rating system described in the text. The recommendations were debated, and the task force chairman modified the document until <10% of the experts disagreed with the recommendations.

CONCLUSIONS

An organized approach to the hemodynamic support of sepsis was formulated. The fundamental principle is that clinicians using hemodynamic therapies should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis by monitoring a combination of variables of global and regional perfusion. Using this approach, specific recommendations for fluid resuscitation, vasopressor therapy, and inotropic therapy of septic in adult patients were promulgated.