Elucidating the role of reversible protein phosphorylation in sepsis-induced myocardial dysfunction

Post-translational modifications in sepsis-induced organ dysfunction: mechanisms and implications

As a grave and highly lethal clinical challenge, sepsis, along with its consequent multiorgan dysfunction, affects millions of people worldwide. Sepsis is a complex syndrome caused by a dysregulated host response to infection, leading to fatal organ dysfunction. An increasing body of evidence suggests that the pathogenesis of sepsis is both intricate and rapid and involves various cellular responses and signal transductions mediated by post-translational modifications (PTMs). Hence, a comprehensive understanding of the mechanisms and functions of PTMs within regulatory networks is imperative for understanding the pathological processes, diagnosis, progression, and treatment of sepsis. In this review, we provide an exhaustive and comprehensive summary of the relationship between PTMs and sepsis-induced organ dysfunction. Furthermore, we explored the potential applications of PTMs in the treatment of sepsis, offering a forward-looking perspective on the understanding of infectious diseases.

Altered function of the left ventricle and clinical significance of heart-type fatty acid-binding protein in cardiac dysfunction among patients with sepsis

The present study aimed to determine the clinical significance of heart-type fatty acid-binding protein (H-FABP) in patients with sepsis-induced cardiac dysfunction. A total of 30 healthy subjects served as the control group and 80 patients with sepsis were recruited for the present single-center prospective observational study for the final analysis. Among these patients, 50 developed cardiac dysfunction, while no cardiac dysfunction was detected in the remaining 30 patients. Echocardiography was performed on days 1, 3, 7 and 10 of hospitalization. Routine blood biochemistry, serum H-FABP, N-terminal pro-brain natriuretic peptide (NT-proBNP) and troponin I were also analyzed. Alterations in cardiac biomarkers and echocardiography results were compared between patients with sepsis who did and who did not develop any cardiac dysfunction to determine the time of the occurrence of sepsis-induced cardiac dysfunction. Furthermore, the significance of H-FABP in the prediction of the 28-day mortality rate was evaluated using binary logistic regression analysis for sepsis and receiver operating characteristic (ROC) curve analysis. In addition, the specificity and sensitivity of H-FABP in the prediction of sepsis-induced cardiac dysfunction were verified using ROC curve analysis. For patients with cardiac dysfunction, the levels of cardiac output (CO), stroke volume (SV), mitral early diastolic peak velocity to mitral atrial systolic peak velocity ratio (E/A) and left ventricle ejection fraction (LVEF) were relatively decreased, while the levels of H-FABP and NT-proBNP were markedly increased compared with patients with sepsis and without cardiac dysfunction. CO and SV initially increased and subsequently decreased. EF was elevated, and E/A initially decreased and subsequently increased. Furthermore, H-FABP and NT-proBNP decreased in sepsis patients with cardiac dysfunction. The results of the ROC curve and binary logistic regression analyses suggest that H-FABP was associated with the 28-day prognosis for patients with sepsis. An H-FABP level of >35.7 ng/ml was able to predict the 28-day mortality for patients with sepsis, with an area under the curve (AUC) of 0.680. Furthermore, >30.3 ng/ml was the threshold for the prediction of sepsis-induced cardiac dysfunction, and the sensitivity and specificity were 76.27 and 61.76%, respectively, with an AUC of 0.673. In summary, patients with sepsis had an increased risk of cardiac insufficiency on days 7-10 of hospitalization. In addition, H-FABP may serve as an indicator to predict the prognosis of patients with sepsis in the short term, which has a certain significance in the diagnosis of sepsis-induced cardiac dysfunction.

The impact of cardiac dysfunction on acute respiratory distress syndrome and mortality in mechanically ventilated patients with severe sepsis and septic shock: an observational study

PURPOSE

Acute respiratory distress syndrome (ARDS) is associated with significant mortality and morbidity in survivors. Treatment is only supportive, therefore elucidating modifiable factors that could prevent ARDS could have a profound impact on outcome. The impact that sepsis-associated cardiac dysfunction has on ARDS is not known.

MATERIALS AND METHODS

In this retrospective observational cohort study of mechanically ventilated patients with severe sepsis and septic shock, 122 patients were assessed for the impact of sepsis-associated cardiac dysfunction on incidence of ARDS (primary outcome) and mortality.

RESULTS

Sepsis-associated cardiac dysfunction occurred in 44 patients (36.1%). There was no association of sepsis-associated cardiac dysfunction with ARDS incidence (p= 0.59) or mortality, and no association with outcomes in patients that did progress to ARDS after admission. Multivariable logistic regression demonstrated that higher BMI was associated with progression to ARDS (adjusted OR 11.84, 95% CI 1.24 to 113.0, p= 0.02).

CONCLUSIONS

Cardiac dysfunction in mechanically ventilated patients with sepsis did not impact ARDS incidence, clinical outcome in ARDS patients, or mortality. This contrasts against previous investigations demonstrating an influence of nonpulmonary organ dysfunction on outcome in ARDS. Given the frequency of ARDS as a sequela of sepsis, the impact of cardiac dysfunction on outcome should be further studied.

Lipoteichoic acid from Staphylococcus aureus directly affects cardiomyocyte contractility and calcium transients

Lipoteichoic acid (LTA) is the key pathogenic factor of gram-positive bacteria and contributes significantly to organ dysfunction in sepsis, a frequent complication in critical care patients. We hypothesized that LTA directly affects cardiomyocyte function, thus contributing to cardiac failure in sepsis. This study was designed to evaluate the effects of LTA on contractile properties and calcium-transients of isolated adult rat cardiomyocytes. When myocytes were exposed to LTA for 1h prior to analysis, the amplitudes of calcium-transients as well as sarcomere shortening increased to 130% and 142% at 1 Hz stimulation frequency. Relengthening of sarcomeres as well as decay of calcium-transients was accelerated after LTA incubation. Exposure to LTA for 24 h resulted in significant depression of calcium-transients as well as of sarcomere shortening compared to controls. One of the major findings of our experiments is that LTA most likely affects calcium-handling of the cardiomyocytes. The effect is exacerbated by reduced extracellular calcium, which resembles the clinical situation in septic patients. Functionally, an early stimulating effect of LTA with increased contractility of the cardiomyocytes may be an in vitro reflection of early hyperdynamic phases in clinical sepsis. Septic disorders have been shown to induce late hypodynamic states of the contractile myocardium, which is also supported at the single-cell level in vitro by results of our 24h-exposure to LTA.

Resuscitation fluids and endotoxin-induced myocardial dysfunction: is selection a load-independent differential issue?

Along with redistributive shock, myocardial dysfunction is now recognized as highly prevalent in early severe sepsis. Indeed, aside from their distinct loading potency, resuscitation fluids have been poorly investigated as to their specific molecular impact on myocardial dysfunction. The objective of this study was to evaluate the load-independent biological impact of different resuscitation fluids on endotoxin-induced myocardial dysfunction. Adult rats implanted with a central venous catheter were given an intraperitoneal injection of endotoxin (lipopolysaccharides [LPSs], Escherichia coli, 10 mg/kg) or normal saline (sham) and subsequently infused or not with similar "fluid potency" loading resuscitation fluid (normal saline, albumin [Alb], or hypertonic saline solution) for 6 to 24 h, followed by echocardiographic and hemodynamic monitoring together with biochemical and histopathologic evaluation. Intervention was to assess the selective influence of load-independent fluid infusion on the aforementioned parameters in groups of animals challenged or not with LPS. At comparative plasma volumes, Alb improved myocardial homeostasis after LPS challenge by (i) reducing left ventricular relative wall diastolic thickness, interstitial space enlargement, and endogenous Alb content; (ii) limiting cardiac apoptosis and sustaining extracellular signal-regulated mitogen-activated protein kinase activation; and (iii) enhancing the expression pattern of heme-oxygenase 1/inducible nitric oxide synthase. Hypertonic saline solution was also cardioprotective by early prevention of myocardial dysfunction and by reducing cardiac apoptosis. Fluid infusions have distinct load-independent structural/biological impacts on endotoxin-induced myocardial dysfunction. Albumin and hypertonic saline solution are the most pleiotropic fluids in protecting the heart after a "sepsis" hit.

Sequential abundant ion fragmentation analysis (SAIFA): an alternative approach for phosphopeptide identification using an ion trap mass spectrometer

Phosphorylation has been the most studied of all the posttranslational modifications of proteins. Mass spectrometry has emerged as a powerful tool for phosphomapping on proteins/peptides. Collision-induced dissociation (CID) of phosphopeptides leads to the loss of phosphoric or metaphosphoric acid as a neutral molecule, giving an intense neutral loss product ion in the mass spectrum. Dissociation of the neutral loss product ion identifies peptide sequence. This method of data-dependent constant neutral loss (DDNL) scanning analysis has been commonly used for mapping phosphopeptides. However, preferential losses of groups other than phosphate are frequently observed during CID of phosphopeptides. Ions that result from such losses are not identified during DDNL analysis due to predetermined scanning for phosphate loss. In this study, we describe an alternative approach for improved identification of phosphopeptides by sequential abundant ion fragmentation analysis (SAIFA). In this approach, there is no predetermined neutral loss molecule, thereby undergoing sequential fragmentation of abundant peak, irrespective of the moiety lost during CID. In addition to improved phosphomapping, the method increases the sequence coverage of the proteins identified, thereby increasing the confidence of protein identification. To the best of our knowledge, this is the first report to use SAIFA for phosphopeptide identification.

Pediatric sepsis and multiorgan dysfunction syndrome: progress and continued challenges

Sepsis, septic shock, systemic inflammatory response syndrome, and Multiorgan dysfunction syndrome (MODS) remain clinical challenges in pediatric critical care. Understanding of the immune response has increased greatly over the past decade, which has certainly increased the understanding of the pathophysiology and treatment of these conditions. The future promises more exciting discoveries as we understand cellular physiology, immunity, and host responses even better. This article reviews the current knowledge about sepsis and MODS in pediatric patients and discusses the best treatment modalities while highlighting the critical aspects of nursing care for this vulnerable population.