Thrombopoietin modulates cardiac contractility in vitro and contributes to myocardial depressing activity of septic shock serum

A review on the functional characteristics of the c-Myeloproliferative Leukaemia (c-MPL) gene and its isoforms

The c-MPL-TPO axis regulates hematopoiesis by activating various signalling cascades, including JAK/STAT, MAPK/ERK, and PIK3/AKT. Here, we have summarized how TPO is regulated by c-MPL and, how mutations in the c-MPL regulate hematopoiesis. We also focus on its non-hematological regulatory role in diseases like Unstable Angina and pathways like DNA damage repair, skeletal homeostasis, & apoptotic regulation of neurons/HSCs at the embryonic state. We discuss the therapeutic efficiency of c-MPL and, its potential to be developed as a bio-marker for detecting metastasis and development of chemo-resistance in various cancers, justifying the multifaceted nature of c-MPL. We have also highlighted the importance of c-MPL isoforms and their stoichiometry in controlling the HSC quiescent and proliferative state. The regulation of the ratio of different isoforms through gene-therapy can open future therapeutic avenues. A systematic understanding of c-MPL-isoforms would undoubtedly take one step closer to facilitating c-MPL from basic-research towards translational medicine.

Decoding Endothelial MPL and JAK2V617F Mutation: Insight Into Cardiovascular Dysfunction in Myeloproliferative Neoplasms

BACKGROUND

Patients with JAK2V617F-positive myeloproliferative neoplasms (MPNs) and clonal hematopoiesis of indeterminate potential face a significantly elevated risk of cardiovascular diseases. Endothelial cells carrying the JAK2V617F mutation have been detected in many patients with MPN. In this study, we investigated the molecular basis for the high incidence of cardiovascular complications in patients with MPN.

METHODS

We investigated the impact of endothelial JAK2V617F mutation on cardiovascular disease development using both transgenic murine models and MPN patient-derived induced pluripotent stem cell lines.

RESULTS

Our investigations revealed that JAK2V617F mutant endothelial cells promote cardiovascular diseases under stress, which is associated with endothelial-to-mesenchymal transition and endothelial dysfunction. Importantly, we discovered that inhibiting the endothelial TPO (thrombopoietin) receptor MPL (myeloproliferative leukemia virus oncogene) suppressed JAK2V617F-induced endothelial-to-mesenchymal transition and prevented cardiovascular dysfunction caused by mutant endothelial cells. Notably, the endothelial MPL receptor is not essential for the normal physiological regulation of blood cell counts and cardiac function.

CONCLUSIONS

JAK2V617F mutant endothelial cells play a critical role in the development of cardiovascular diseases in JAK2V617F-positive MPNs, and endothelial MPL could be a promising therapeutic target for preventing or ameliorating cardiovascular complications in these patients.

Unlocking the Role of Endothelial MPL Receptor and JAK2V617F Mutation: Insights into Cardiovascular Dysfunction in MPNs and CHIP

Patients with JAK2V617F-positive myeloproliferative neoplasms (MPNs) and clonal hematopoiesis of indeterminate potential (CHIP) are at a significantly higher risk of cardiovascular diseases (CVDs). Endothelial cells (ECs) carrying the JAK2V617F mutation can be detected in many MPN patients. Here, we investigated the impact of endothelial JAK2V617F mutation on CVD development using both transgenic murine models and human induced pluripotent stem cell lines. Our findings revealed that JAK2V617F mutant ECs promote CVDs by impairing endothelial function and undergoing endothelial-to-mesenchymal transition (EndMT). Importantly, we found that inhibiting the endothelial thrombopoietin receptor MPL suppressed JAK2V617F-induced EndMT and prevented cardiovascular dysfunction caused by mutant ECs. These findings propose that targeting the endothelial MPL receptor could be a promising therapeutic approach to manage CVD complications in patients with JAK2V617F-positive MPNs and CHIP. Further investigations into the impact of other CHIP-associated mutations on endothelial dysfunction are needed to improve risk stratification for individuals with CHIP.

Thrombopoietin participates in platelet activation in COVID-19 patients

BACKGROUND

The pathogenesis of coronavirus disease 2019 (COVID-19) is characterized by enhanced platelet activation and diffuse hemostatic alterations, which may contribute to immunothrombosis/thromboinflammation and subsequent development of target-organ damage. Thrombopoietin (THPO), a growth factor essential to megakariocyte proliferation, is known to prime platelet activation and leukocyte-platelet interaction. In addition, THPO concentrations increase in several critical diseases, such as acute cardiac ischemia and sepsis, thus representing a potential diagnostic and prognostic biomarker. Furthermore, several data suggest that interleukin (IL)-6 is one of the most important inflammatory mediators involved in these phenomena, which led to explore the potential therapeutic role of IL-6 inhibitors. In this prospective cohort study, we aimed to study THPO and IL-6 concentrations in COVID-19 patients at the time of first clinical evaluation in the Emergency Department (ED), and to investigate their potential use as diagnostic and prognostic biomarkers. In addition, we sought to explore the role of THPO contained in plasma samples obtained from COVID-19 patients in priming in vitro platelet activation and leukocyte-platelet interaction.

METHODS

We enrolled 66 patients presenting to the ED with symptoms suggestive of COVID-19, including 47 with confirmed COVID-19 and 19 in whom COVID-19 was excluded (Non-COVID-19 patients). As controls, we also recruited 18 healthy subjects. In vitro, we reproduced the effects of increased circulating THPO on platelet function by adding plasma from COVID-19 patients or controls to platelet-rich plasma or whole blood obtained by healthy donors, and we indirectly studied the effect of THPO on platelet activation by blocking its biological activity.

FINDINGS

THPO levels were higher in COVID-19 patients than in both Non-COVID-19 patients and healthy subjects. Studying THPO as diagnostic marker for the diagnosis of COVID-19 by receiver-operating-characteristic (ROC) statistics, we found an area under the curve (AUC) of 0.73, with an optimal cut-off value of 42.60 pg/mL. IL-6 was higher in COVID-19 patients than in healthy subjects, but did not differ between COVID-19 and Non-COVID-19 patients. THPO concentrations measured at the time of diagnosis in the ED were also higher in COVID-19 patients subsequently developing a severe disease than in those with mild disease. Evaluating THPO as biomarker for severe COVID-19 using ROC analysis, we found an AUC of 0.71, with an optimal cut-off value of 57.11 pg/mL. IL-6 was also higher in severe than in mild COVID-19 patients, with an AUC for severe COVID-19 of 0.83 and an optimal cut-off value of 23 pg/ml. THPO concentrations correlated with those of IL-6 (r=0.2963; p=0.043), and decreased 24 h after the administration of tocilizumab, an IL-6 receptor blocking antibody, showing that the increase of THPO levels depends on IL-6-stimulated hepatic synthesis. In vitro, plasma obtained from COVID-19 patients, but not from healthy subjects, primed platelet aggregation and leukocyte-platelet binding, and these effects were reduced by inhibiting THPO activity.

INTERPRETATION

Increased THPO may be proposed as an early biomarker for the diagnosis of COVID-19 and for the identification of patients at risk of developing critical illness. Elevated THPO may contribute to enhance platelet activation and leukocyte-platelet interaction in COVID-19 patients, thus potentially participating in immunothrombosis/thromboinflammation.

FUNDING

This work was supported by Ministero dell'Università e della Ricerca Scientifica e Tecnologica (MURST) ex 60% to GM and EL.

Prognostic Value of Platelet to Lymphocyte Ratio in Sepsis: A Systematic Review and Meta-analysis

The goal of this study was to conduct a systematic review of the literature on the relationship between peripheral blood platelet to lymphocyte ratio (PLR) and mortality in sepsis and to integrate the findings in a meta-analysis. An electronic search of three main databases was performed: PubMed, Embase, and Scopus on 19 December 2021. Finally, 16 studies comprising 2403 septic patients, including 1249 survivors and 1154 nonsurvivors, were included in this meta-analysis. We found that PLR levels were significantly higher in nonsurvivors than in survivors (random effect model: SMD = 0.72, 95% CI; 0.35–1.10, p < 0.001). However, significant heterogeneity was observed across the studies (I² = 94.1%, p < 0.01). So, we used random effect model in our meta-analysis. In the subgroup analysis, according to mortality time, patients deceased during one month after sepsis had elevated levels of PLR compared to survivors (SMD = 1.03, 95% CI = 0.15-1.92, p = 0.22). However, in-hospital mortality was not associated with PLR level (SMD = 0.41, 95% CI = −0.18-0.99, p = 0.175). Our findings support PLR to be a promising biomarker that can be readily integrated into clinical settings to aid in the prediction and prevention of sepsis mortality.

Correlation between thrombopoietin and inflammatory factors, platelet indices, and thrombosis in patients with sepsis: A retrospective study

BACKGROUND

Thrombopoietin (TPO) is a primary regulator of thrombopoiesis in physiological conditions. TPO, in combination with its specific cytokine receptor c-Mpl, drives platelet production by inducing the proliferation and differentiation of megakaryocytes. However, the role of TPO in sepsis is not well determined. The elevated levels of TPO are often accompanied by a decrease of platelet count (PLT) in systemic infected conditions, which is contrary to the view that TPO promotes platelet production under physiological conditions. In addition, whether TPO mediates organ damage in sepsis remains controversial.

AIM

To explore the relationships between TPO and inflammatory factors, platelet indices, and thrombotic indicators in sepsis.

METHODS

A total of 90 patients with sepsis diagnosed and treated at the emergency medicine department of The First People’s Hospital of Foshan between January 2020 and March 2021 were enrolled in this study. In addition, 110 patients without sepsis who came to the emergency medicine department were included as controls. Clinical and laboratory parameters including age, gender, TPO, blood cell count in peripheral blood, platelet indices, inflammatory factors such as high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-21, and IL-6, organ damage indicators, and thrombotic indicators were collected and analyzed by using various statistical approaches.

RESULTS

The results showed that the TPO levels were higher in the sepsis group than in controls [86.45 (30.55, 193.1) vs 12.45 (0.64, 46.09) pg/mL, P < 0.001], but PLT was lower (P < 0.001). Multivariable analysis showed that white blood cell count (WBC) [odds ratio (OR) = 1.32; 95% confidence interval (CI): 1.01-1.722; P = 0.044], TPO (OR = 1.02; 95%CI: 1.01-1.04; P = 0.009), IL-21 (OR = 1.02; 95%CI: 1.00-1.03; P = 0.019), troponin I (OR = 55.20; 95%CI: 5.69-535.90; P = 0.001), and prothrombin time (PT) (OR = 2.24; 95%CI: 1.10-4.55; P = 0.027) were independent risk factors associated with sepsis. TPO levels were positively correlated with IL-21, IL-6, hs-CRP, creatinine, D-dimer, PT, activated prothrombin time, international normalized ratio, fibrinogen, WBC count, and neutrophil count, and negatively correlated with PLT, thrombin time, red blood cell count, and hemoglobin concentration (P < 0.05). Receiver operating characteristic analysis showed that TPO had fair predictive value in distinguishing septic patients and non-septic patients (the area under the curve: 0.788; 95%CI: 0.723-0.852; P < 0.001). With an optimized cutoff value (28.51 pg/mL), TPO had the highest sensitivity (79%) and specificity (65%).

CONCLUSION

TPO levels are independently associated with sepsis. High TPO levels and low PLT suggest that TPO might be an acute-phase response protein in patients with infection.

Na+/K+-ATPase Alpha 2 Isoform Elicits Rac1-Dependent Oxidative Stress and TLR4-Induced Inflammation in the Hypothalamic Paraventricular Nucleus in High Salt-Induced Hypertension

Numerous studies have indicated that a high salt diet inhibits brain Na⁺/K⁺-ATPase (NKA) activity, and affects oxidative stress and inflammation in the paraventricular nucleus (PVN). Furthermore, Na⁺/K⁺-ATPase alpha 2-isoform (NKA α2) may be a target in the brain, taking part in the development of salt-dependent hypertension. Therefore, we hypothesized that NKA α2 regulates oxidative stress and inflammation in the PVN in the context of salt-induced hypertension. Part I: We assessed NKA subunits (NKA α1, NKA α2, and NKA α3), Na⁺/K⁺-ATPase activity, oxidative stress, and inflammation in a high salt group (8% NaCl) and normal salt group (0.3% NaCl). Part II: NKA α2 short hairpin RNA (shRNA) was bilaterally microinjected into the PVN of salt-induced hypertensive rats to knockdown NKA α2, and we explored whether NKA α2 regulates downstream signaling pathways related to protein kinase C γ (PKC γ)-dependent oxidative stress and toll-like receptor 4 (TLR4)-induced inflammation in the PVN to promote the development of hypertension. High salt diet increased NKA α1 and NKA α2 protein expression in the PVN but had no effect on NKA α3 compared to the normal salt diet. Na⁺/K⁺-ATPase activity and ADP/ATP ratio was lower, but NAD(P)H activity and NF-κB activity in the PVN were higher after a high salt diet. Bilateral PVN microinjection of NKA α2 shRNA not only improved Na⁺/K⁺-ATPase activity and ADP/ATP ratio but also suppressed PKC γ-dependent oxidative stress and TLR4-dependent inflammation in the PVN, thus decreasing sympathetic activity in rats with salt-induced hypertension. NKA α2 in the PVN elicits PKC γ/Rac1/NAD (P)H-dependent oxidative stress and TLR4/MyD88/NF-κB-induced inflammation in the PVN, thus increasing MAP and sympathetic activity during the development of salt-induced hypertension.

Bilateral Paraventricular Nucleus Upregulation of Extracellular Superoxide Dismutase Decreases Blood Pressure by Regulation of the NLRP3 and Neurotransmitters in Salt-Induced Hypertensive Rats

Aims: Long-term salt diet induces the oxidative stress in the paraventricular nucleus (PVN) and increases the blood pressure. Extracellular superoxide dismutase (Ec-SOD) is a unique antioxidant enzyme that exists in extracellular space and plays an essential role in scavenging excessive reactive oxygen species (ROS). However, the underlying mechanism of Ec-SOD in the PVN remains unclear. Methods: Sprague-Dawley rats (150-200 g) were fed either a high salt diet (8% NaCl, HS) or normal salt diet (0.9% NaCl, NS) for 6 weeks. Each group of rats was administered with bilateral PVN microinjection of AAV-Ec-SOD (Ec-SOD overexpression) or AAV-Ctrl for the next 6 weeks. Results: High salt intake not only increased mean arterial blood pressure (MAP) and the plasma noradrenaline (NE) but also elevated the NAD(P)H oxidase activity, the NAD(P)H oxidase components (NOX2 and NOX4) expression, and ROS production in the PVN. Meanwhile, the NOD-like receptor protein 3 (NLRP3)-dependent inflammatory proteins (ASC, pro-cas-1, IL-β, CXCR, CCL2) expression and the tyrosine hydroxylase (TH) expression in the PVN with high salt diet were higher, but the GSH level, Ec-SOD activity, GAD67 expression, and GABA level were lower than the NS group. Bilateral PVN microinjection of AAV-Ec-SOD decreased MAP and the plasma NE, reduced NAD(P)H oxidase activity, the NOX2 and NOX4 expression, and ROS production, attenuated NLRP3-dependent inflammatory expression and TH, but increased GSH level, Ec-SOD activity, GAD67 expression, and GABA level in the PVN compared with the high salt group. Conclusion: Excessive salt intake not only activates oxidative stress but also induces the NLRP3-depensent inflammation and breaks the balance between inhibitory and excitability neurotransmitters in the PVN. Ec-SOD, as an essential anti-oxidative enzyme, eliminates the ROS in the PVN and decreases the blood pressure, probably through inhibiting the NLRP3-dependent inflammation and improving the excitatory neurotransmitter release in the PVN in the salt-induced hypertension.

Thrombopoietin Contributes to Enhanced Platelet Activation in Patients with Type 1 Diabetes Mellitus

Atherosclerotic cardiovascular disease is the major cause of morbidity and mortality in patients with type 1 diabetes mellitus (T1DM). Enhanced platelet reactivity is considered a main determinant of the increased atherothrombotic risk of diabetic patients. Thrombopoietin (THPO), a humoral growth factor able to stimulate megakaryocyte proliferation and differentiation, also modulates the response of mature platelets by enhancing both activation and binding to leukocytes in response to different agonists. Increased THPO levels have been reported in different clinical conditions characterized by a generalized pro-thrombotic state, from acute coronary syndromes to sepsis/septic shock, and associated with elevated indices of platelet activation. To investigate the potential contribution of elevated THPO levels in platelet activation in T1DM patients, we studied 28 T1DM patients and 28 healthy subjects. We measured plasma levels of THPO, as well as platelet-leukocyte binding, P-selectin, and THPO receptor (THPOR) platelet expression. The priming activity of plasma from diabetic patients or healthy subjects on platelet–leukocyte binding and the role of THPO on this effect was also studied in vitro. T1DM patients had higher circulating THPO levels and increased platelet–monocyte and platelet–granulocyte binding, as well as platelet P-selectin expression, compared to healthy subjects, whereas platelet expression of THPOR did not differ between the two groups. THPO concentrations correlated with platelet–leukocyte binding, as well as with fasting glucose and Hb1Ac. In vitro, plasma from diabetic patients, but not from healthy subjects, primed platelet–leukocyte binding and platelet P-selectin expression. Blocking THPO biological activity using a specific inhibitor prevented the priming effect induced by plasma from diabetic patients. In conclusion, augmented THPO may enhance platelet activation in patients with T1DM, potentially participating in increasing atherosclerotic risk.

Central Blockade of E-Prostanoid 3 Receptor Ameliorated Hypertension Partially by Attenuating Oxidative Stress and Inflammation in the Hypothalamic Paraventricular Nucleus of Spontaneously Hypertensive Rats

Hypertension, as one of the major risk factors for cardiovascular disease, significantly affects human health. Prostaglandin E2 (PGE2) and the E3-class prostanoid (EP3) receptor have previously been demonstrated to modulate blood pressure and hemodynamics in various animal models of hypertension. The PGE2-evoked pressor and biochemical responses can be blocked with the EP3 receptor antagonist, L-798106 (N-[(5-bromo-2methoxyphenyl)sulfonyl]-3-[2-(2-naphthalenylmethyl) phenyl]-2-propenamide). In the hypothalamic paraventricular nucleus (PVN), sympathetic excitation can be introduced by PGE2, which can activate EP3 receptors located in the PVN. In such a case, the central knockdown of EP3 receptor can be considered as a potential therapeutic modality for hypertension management. The present study examined the efficacy of the PVN infusion of L-798106, by performing experiments on spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKYs). The rats were administered with chronic bilateral PVN infusion of L-798106 (10 μg/day) or the vehicle for 28 days. The results indicated that the SHRs had a higher mean arterial pressure (MAP), an increased Fra-like (Fra-LI) activity in the PVN, as well as a higher expression of gp91phox, mitogen-activated protein kinase (MAPK), and proinflammatory cytokines in the PVN compared with the WKYs. Additionally, the expression of Cu/Zn-SOD in the PVN of the SHRs was reduced compared with the WKYs. The bilateral PVN infusion of L-798106 significantly reduced MAP, as well as plasma norepinephrine (NE) levels in the SHRs. It also inhibited Fra-LI activity and reduced the expression of gp91phox, proinflammatory cytokines, and MAPK, whereas it increased the expression of Cu/Zn-SOD in the PVN of SHRs. In addition, L-798106 restored the balance of the neurotransmitters in the PVN. On the whole, the findings of the present study demonstrate that the PVN blockade of EP3 receptor can ameliorate hypertension and cardiac hypertrophy partially by attenuating ROS and proinflammatory cytokines, and modulating neurotransmitters in the PVN.

Platelets as a prognostic marker for sepsis: A cohort study from the MIMIC-III database

During sepsis, platelets dysfunction contributes to organ dysfunction. Studies on platelets dysfunction in the long-term prognosis of sepsis are lacking. The aim of this study was to assess the role of platelets in the long-term prognosis of sepsis patients.A total of 4576 sepsis patients were extracted from MIMIC III Database. Survival was analyzed by the Kaplan-Meier method. Univariate and multivariate cox analyses were performed to identify prognostic factors. Significant prognostic factors were combined to build a nomogram to predict 1 year overall survival (OS). The discriminative ability and predictive accuracy of the nomogram were evaluated using the receiver operating characteristic curve (ROC) analysis and calibration curves used for sepsis.The more abnormal the platelet level, the worse prognosis of patients. After final regression analysis, age, blood urea nitrogen, platelets, international normalized ratio, partial thromboplastin time, potassium, hemoglobin, white blood cell count, organ failures were found to be independent predictors of 1 year OS of sepsis patient and were entered into a nomogram. The nomogram showed a robust discrimination, with an area under the receiver operating characteristic curve of 0.752. The calibration curves for the probability of the prognosis of sepsis patients showed optimal agreement between the probability as predicted by the nomogram and the actual probability.Platelet was an independent prognostic predictor of 1 year OS for patients with sepsis. Platelet-related nomogram that can predict the 1 year OS of sepsis patients. It revealed optimal discrimination and calibration, indicating that the nomogram may have clinical utility.

Development of a Bioinformatics Framework for Identification and Validation of Genomic Biomarkers and Key Immunopathology Processes and Controllers in Infectious and Non-infectious Severe Inflammatory Response Syndrome

Sepsis is defined as dysregulated host response caused by systemic infection, leading to organ failure. It is a life-threatening condition, often requiring admission to an intensive care unit (ICU). The causative agents and processes involved are multifactorial but are characterized by an overarching inflammatory response, sharing elements in common with severe inflammatory response syndrome (SIRS) of non-infectious origin. Sepsis presents with a range of pathophysiological and genetic features which make clinical differentiation from SIRS very challenging. This may reflect a poor understanding of the key gene inter-activities and/or pathway associations underlying these disease processes. Improved understanding is critical for early differential recognition of sepsis and SIRS and to improve patient management and clinical outcomes. Judicious selection of gene biomarkers suitable for development of diagnostic tests/testing could make differentiation of sepsis and SIRS feasible. Here we describe a methodologic framework for the identification and validation of biomarkers in SIRS, sepsis and septic shock patients, using a 2-tier gene screening, artificial neural network (ANN) data mining technique, using previously published gene expression datasets. Eight key hub markers have been identified which may delineate distinct, core disease processes and which show potential for informing underlying immunological and pathological processes and thus patient stratification and treatment. These do not show sufficient fold change differences between the different disease states to be useful as primary diagnostic biomarkers, but are instrumental in identifying candidate pathways and other associated biomarkers for further exploration.

Platelets and Multi-Organ Failure in Sepsis

Platelets have received increasing attention for their role in the pathophysiology of infectious disease, inflammation, and immunity. In sepsis, a low platelet count is a well-known biomarker for disease severity and more recently authors have focused their attention on the active role of platelets in the pathogenesis of multi-organ failure. Septic shock is characterised by a dysregulated inflammatory response, which can impair the microcirculation and lead to organ injury. Being at the crossroads between the immune system, clotting cascade, and endothelial cells, platelets seem to be an appealing central mediator and possible therapeutic target in sepsis. This review focuses on the pathogenic role of platelets in septic organ dysfunction in humans and animal models.

Sepsis-Induced Cardiomyopathy: Oxidative Implications in the Initiation and Resolution of the Damage

Cardiac dysfunction may complicate the course of severe sepsis and septic shock with significant implications for patient's survival. The basic pathophysiologic mechanisms leading to septic cardiomyopathy have not been fully clarified until now. Disease-specific treatment is lacking, and care is still based on supportive modalities. Septic state causes destruction of redox balance in many cell types, cardiomyocytes included. The production of reactive oxygen and nitrogen species is increased, and natural antioxidant systems fail to counterbalance the overwhelming generation of free radicals. Reactive species interfere with many basic cell functions, mainly through destruction of protein, lipid, and nucleic acid integrity, compromising enzyme function, mitochondrial structure and performance, and intracellular signaling, all leading to cardiac contractile failure. Takotsubo cardiomyopathy may result from oxidative imbalance. This review will address the multiple aspects of cardiomyocyte bioenergetic failure in sepsis and discuss potential therapeutic interventions.

Oxidative-Nitrosative Stress and Myocardial Dysfunctions in Sepsis: Evidence from the Literature and Postmortem Observations

BACKGROUND

Myocardial depression in sepsis is common, and it is associated with higher mortality. In recent years, the hypothesis that the myocardial dysfunction during sepsis could be mediated by ischemia related to decreased coronary blood flow waned and a complex mechanism was invoked to explain cardiac dysfunction in sepsis. Oxidative stress unbalance is thought to play a critical role in the pathogenesis of cardiac impairment in septic patients.

AIM

In this paper, we review the current literature regarding the pathophysiology of cardiac dysfunction in sepsis, focusing on the possible role of oxidative-nitrosative stress unbalance and mitochondria dysfunction. We discuss these mechanisms within the broad scenario of cardiac involvement in sepsis.

CONCLUSIONS

Findings from the current literature broaden our understanding of the role of oxidative and nitrosative stress unbalance in the pathophysiology of cardiac dysfunction in sepsis, thus contributing to the establishment of a relationship between these settings and the occurrence of oxidative stress. The complex pathogenesis of septic cardiac failure may explain why, despite the therapeutic strategies, sepsis remains a big clinical challenge for effectively managing the disease to minimize mortality, leading to consideration of the potential therapeutic effects of antioxidant agents.

Blockade of Thrombopoietin Reduces Organ Damage in Experimental Endotoxemia and Polymicrobial Sepsis

Background and Purpose

Thrombopoietin (TPO), a growth factor primarily involved in thrombopoiesis may also have a role in the pathophysiology of sepsis. In patients with sepsis, indeed, TPO levels are markedly increased, with disease severity being the major independent determinant of TPO concentrations. Moreover, TPO increases and correlates with ex vivo indices of platelet activation in patients with burn injury upon sepsis development, and may contribute to depress cardiac contractility in septic shock. Still, the role of TPO in sepsis pathophysiology remains controversial, given the protective role of TPO in other experimental disease models, for instance in doxorubicin-induced cardiotoxicity and myocardial ischemia/reperfusion injury. The aim of our study was to define the contribution of TPO in the development of organ damage induced by endotoxemia or sepsis, and to investigate the effects of inhibiting TPO in these conditions.

Methods

We synthesized a chimeric protein able to inhibit TPO, mTPOR-MBP, and studied its effect in two murine experimental models, acute endotoxemia and cecal ligation and puncture (CLP) model.

Results

In both models, TPO levels markedly increased, from 289.80±27.87 pg/mL to 465.60±45.92 pg/mL at 3 hours in the LPS model (P<0.01), and from 265.00±26.02 pg/mL to 373.70±26.20 pg/mL in the CLP model (P<0.05), respectively. Paralleling TPO levels, also platelet-monocyte aggregates increased, from 32.86±2.48% to 46.13±1.39% at 3 hours in the LPS model (P<0.01), and from 43.68±1.69% to 56.52±4.66% in the CLP model (P<0.05). Blockade of TPO by mTPOR-MBP administration reduced histological damage in target organs, namely lung, liver, and gut. In particular, neutrophil infiltration and lung septal thickening were reduced from a score of 1.86±0.34 to 0.60±0.27 (P<0.01) and from 1.43±0.37 to 0.40±0.16 (P<0.05), respectively, in the LPS model at 3 hours, and from a score of 1.75±0.37 to 0.38±0.18 (P<0.01) and from 1.25±0.31 to 0.13±0.13 (P<0.001), respectively, in the CLP model. Similarly, the number of hepatic microabscesses was decreased from 14.14±1.41 to 3.64±0.56 in the LPS model at 3 hours (P<0.001), and from 1.71±0.29 to 0.13±0.13 in the CLP model (P<0.001). Finally, the diameter of intestinal villi decreased from 90.69±3.95 μm to 70.74±3.60 μm in the LPS model at 3 hours (P<0.01), and from 74.29±4.29 μm to 57.50±1.89 μm in the CLP model (P<0.01). This protective effect was associated with the blunting of the increase in platelet-monocyte adhesion, and, on the contrary, with increased platelet-neutrophil aggregates in the circulation, which may be related to decreased neutrophil sequestration into the inflamed tissues. Conversely, circulating cytokine levels were not significantly changed, in both models, by mTPOR-MBP administration.

Conclusion

Our results demonstrate that TPO participates in the development of organ damage induced by experimental endotoxemia or polymicrobial sepsis via a mechanism involving increased platelet-leukocyte adhesion, but not cytokine release, and suggest that blocking TPO may be useful in preventing organ damage in patients affected by systemic inflammatory response or sepsis.

Alpha lipoic acid supplementation attenuates reactive oxygen species in hypothalamic paraventricular nucleus and sympathoexcitation in high salt-induced hypertension

AIMS

High salt-induced oxidative stress plays an important role in the development of hypertension. Alpha lipoic acid (ALA) is extensively recognized as having a powerful superoxide inhibitory property. In this study, we determined whether ALA supplementation attenuates oxidative stress in hypothalamic paraventricular nucleus (PVN), decreases the sympathetic activity and arterial pressure in high salt-induced hypertension by cross-talking with renin-angiotensin system (RAS) and pro-inflammatory cytokines (PICs).

METHODS

Male Wistar rats were administered a normal-salt diet (NS, 0.3% NaCl) or a high-salt diet (HS, 8.0% NaCl) for 8 weeks. These rats received ALA (60mg/kg) dissolved in vehicle (0.9% saline) or an equal voleme of vehicle, by gastric perfusion for 9 weeks.

RESULTS

High salt intake resulted in higher renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP). These rats also had higher levels of superoxide, gp91(phox), gp47(phox) (subunits of NAD(P)H oxidase), angiotensin-converting enzyme (ACE), angiotensin II type1 receptor (AT1-R), interleukin-1beta (IL-1β), interleukin-6 (IL-6), and lower levels of interleukin-10 (IL-10) and copper/zinc superoxide dismutase (Cu/Zn-SOD) than control animals. Treatment with ALA significantly attenuated the levels of superoxide, gp91(phox), gp47(phox), ACE, AT1-R, IL-1β and IL-6, increased the levels of IL-10 and Cu/Zn-SOD, and decreased MAP and RSNA compared with high-salt induced hypertensive rats. The mRNA expression of gp47(phox) and gp91(phox) are in accordance with their protein expression.

CONCLUSION

These findings suggest that supplementation of ALA obviously decreases the sympathetic activity and arterial pressure in high salt-induced hypertension by improving the superoxide inhibitory property, suppressing the activation of RAS and restoring the balance between pro- and anti-inflammatory cytokines in the PVN.

Endothelial NOS (NOS3) impairs myocardial function in developing sepsis

Endothelial nitric oxide synthase (NOS)3-derived nitric oxide (NO) modulates inotropic response and diastolic interval for optimal cardiac performance under non-inflammatory conditions. In sepsis, excessive NO production plays a key role in severe hypotension and myocardial dysfunction. We aimed to determine the role of NOS3 on myocardial performance, NO production, and time course of sepsis development. NOS3(-/-) and C57BL/6 wildtype mice were rendered septic by cecum ligation and puncture (CLP). Cardiac function was analyzed by serial echocardiography, in vivo pressure and isolated heart measurements. Cardiac output (CO) increased to 160 % of baseline at 10 h after sepsis induction followed by a decline to 63 % of baseline after 18 h in wildtype mice. CO was unaltered in septic NOS3(-/-) mice. Despite the hyperdynamic state, cardiac function and mean arterial pressure were impaired in septic wildtype as early as 6 h post CLP. At 12 h, cardiac function in septic wildtype was refractory to catecholamines in vivo and respective isolated hearts showed impaired pressure development and limited coronary flow reserve. Hemodynamics remained stable in NOS3(-/-) mice leading to significant survival benefit. Unselective NOS inhibition in septic NOS3(-/-) mice diminished this survival benefit. Plasma NO( x )- and local myocardial NO( x )- and NO levels (via NO spin trapping) demonstrated enhanced NO( x )- and bioactive NO levels in septic wildtype as compared to NOS3(-/-) mice. Significant contribution by inducible NOS (NOS2) during this early phase of sepsis was excluded. Our data suggest that NOS3 relevantly contributes to bioactive NO pool in developing sepsis resulting in impaired cardiac contractility.

Opinion paper on innovative approach of biomarkers for infectious diseases and sepsis management in the emergency department

Sepsis is a leading healthcare problem, accounting for the vast majority of fatal events in critically ill patients. Beyond early diagnosis and appropriate treatment, this condition requires a multifaceted approach for monitoring the severity, the potential organ failure as well as the risk of death. Monitoring of the efficacy of treatment is also a major issue in the emergency department (ED). The assessment of critically ill conditions and the prognosis of patients with sepsis is currently based on some scoring systems, which are, however, inefficient to provide definite clues about organ failure and prognosis in general. The discretionary and appropriate use of some selected biomarkers such as procalcitonin, inducible protein 10 (IP10), Group IV phospholipase A2 type II (PLA2 II), neutrophil gelatinase-associated lipocalin (NGAL), natriuretic peptides, mature adrenomedullin (ADM), mid-regional pro-adrenomedullin (MR-proADM), copeptin, thrombopoietin, Mer receptor and even red blood cell distribution width (RDW) represent thereby an appealing perspective in the diagnosis and management of patients with sepsis. Nevertheless, at the moment, it is not still clear if it is better to use a multimarkers approach or if a single, most appropriate, biomarker exists. This collective opinion paper is aimed at providing an overview about the potential clinical usefulness of some innovative biomarkers of sepsis in its diagnosis and prognosis, but also in the treatment management of the disease. This manuscript represents a synopsis of the lectures of Third Italian GREAT Network Congress, that was hold in Rome, 15–19 October 2012.

Thrombopoietin as biomarker and mediator of cardiovascular damage in critical diseases

Thrombopoietin (TPO) is a humoral growth factor originally identified for its ability to stimulate the proliferation and differentiation of megakaryocytes. In addition to its actions on thrombopoiesis, TPO directly modulates the homeostatic potential of mature platelets by influencing their response to several stimuli. In particular, TPO does not induce platelet aggregation per se but is able to enhance platelet aggregation in response to different agonists (“priming effect”). Our research group was actively involved, in the last years, in characterizing the effects of TPO in several human critical diseases. In particular, we found that TPO enhances platelet activation and monocyte-platelet interaction in patients with unstable angina, chronic cigarette smokers, and patients with burn injury and burn injury complicated with sepsis. Moreover, we showed that TPO negatively modulates myocardial contractility by stimulating its receptor c-Mpl on cardiomyocytes and the subsequent production of NO, and it mediates the cardiodepressant activity exerted in vitro by serum of septic shock patients by cooperating with TNF-α and IL-1β. This paper will summarize the most recent results obtained by our research group on the pathogenic role of elevated TPO levels in these diseases and discuss them together with other recently published important studies on this topic.

NF-κB in the paraventricular nucleus modulates neurotransmitters and contributes to sympathoexcitation in heart failure

Findings from our laboratory indicate that proinflammatory cytokines and their transcription factor, nuclear factor-kappaB (NF-κB), are increased in the hypothalamic paraventricular nucleus (PVN) and contribute towards the progression of heart failure. In this study, we determined whether NF-κB activation within the PVN contributes to sympathoexcitation via interaction with neurotransmitters in the PVN during the pathogenesis of heart failure. Heart failure was induced in rats by left anterior descending coronary artery ligation. Sham-operated control (SHAM) or heart failure rats were treated for 4 weeks through bilateral PVN infusion with SN50, SN50M or vehicle via osmotic minipump. Rats with heart failure treated with PVN vehicle or SN50M (inactive peptide for SN50) had increased levels of glutamate, norepinephrine (NE), tyrosine hydroxylase (TH), superoxide, gp91(phox) (a subunit of NAD(P)H oxidase), phosphorylated IKKβ and NF-κB p65 activity, and lower levels of gamma-aminobutyric acid (GABA) and the 67-kDa isoform of glutamate decarboxylase (GAD67) in the PVN compared with those of SHAM rats. Plasma levels of cytokines, norepinephrine, epinephrine and angiotensin II, and renal sympathetic nerve activity (RSNA) were increased in heart failure rats. Bilateral PVN infusion of SN50 prevented the decreases in PVN GABA and GAD67, and the increases in RSNA and PVN glutamate, norepinephrine, TH, superoxide, gp91(phox), phosphorylated IKKβ and NF-κB p65 activity observed in vehicle or SN50M-treated heart failure rats. A same dose of SN50 given intraperitoneally did not affect neurotransmitters concentration in the PVN and was similar to vehicle-treated heart failure rats. These findings suggest that NF-κB activation in the PVN modulates neurotransmitters and contributes to sympathoexcitation in rats with ischemia-induced heart failure.

Paraventricular nucleus corticotrophin releasing hormone contributes to sympathoexcitation via interaction with neurotransmitters in heart failure

Recent studies indicate that systemic administration of tumor necrosis factor (TNF)-α induces increases in corticotrophin releasing hormone (CRH) and CRH type 1 receptors in the hypothalamic paraventricular nucleus (PVN). In this study, we explored the hypothesis that CRH in the PVN contributes to sympathoexcitation via interaction with neurotransmitters in heart failure (HF). Sprague-Dawley rats with HF or sham-operated controls (SHAM) were treated for 4 weeks with a continuous bilateral PVN infusion of the selective CRH-R1 antagonist NBI-27914 or vehicle. Rats with HF had higher levels of glutamate, norepinephrine (NE) and tyrosine hydroxylase (TH), and lower levels of gamma-aminobutyric acid (GABA) and the 67-kDa isoform of glutamate decarboxylase (GAD67) in the PVN when compared to SHAM rats. Plasma levels of cytokines, NE, ACTH and renal sympathetic nerve activity (RSNA) were increased in HF rats. Bilateral PVN infusions of NBI-27914 attenuated the decreases in PVN GABA and GAD67, and the increases in RSNA, ACTH and PVN glutamate, NE and TH observed in HF rats. These findings suggest that CRH in the PVN modulates neurotransmitters and contributes to sympathoexcitation in rats with ischemia-induced HF.

A novel role of thrombopoietin as a physiological modulator of coronary flow

Thrombopoietin (TPO) is known for its ability to stimulate platelet production. However, little is currently known whether TPO plays a physiological function in the heart. The potential vasodilatory role of TPO was tested on the isolated rat heart. The expression of TPO receptor (c-mpl) and the TPO-dependent eNOS phosphorylation (P(Ser1179)) were studied on Cardiac-derived normal Human Micro Vascular Endothelial Cells (HMVEC-C) by Western blot analysis. While TPO (10-200 pg/mL) did not modify coronary flow (CF) under basal conditions, it reduced the coronary constriction caused by endothelin-1 (ET-1; 10nM) in a dose-dependent manner. This effect was blocked by both Wortmannin (100 nM) and L-NAME (100 nM); on HMVEC-C, TPO induced eNOS phosphorylation through a Wortmannin sensitive mechanism. Taken together, our data suggest a potential role of TPO as a physiological regulator of CF. By acting on specific receptors present on endothelial cells, TPO may induce PI3K/Akt-dependent eNOS phosphorylation and NO release.

The role of mitochondrial K(ATP) channels in cardioprotection

Pro-coagulant and pro-inflammatory intramyocardial (micro)vasculature plays an important role in acute myocardial infarction (AMI). Currently, inhibition of serine protease dipeptidyl peptidase 4 (DPP4) receives a lot of interest as an anti-hyperglycemic therapy in type 2 diabetes patients. However, DPP4 also possesses anti-thrombotic properties and may behave as an immobilized anti-coagulant on endothelial cells. Here, we studied the expression and activity of endothelial DPP4 in human myocardial infarction in relation to a prothrombogenic endothelial phenotype. Using (immuno)histochemistry, DPP4 expression and activity were found on the endothelium of intramyocardial blood vessels in autopsied control hearts (n = 9). Within the infarction area of AMI patients (n = 73), this DPP4 expression and activity were significantly decreased, coinciding with an increase in Tissue Factor expression. In primary human umbilical vein endothelial cells (HUVECs), Western blot analysis and digital imaging fluorescence microscopy revealed that DPP4 expression was strongly decreased after metabolic inhibition, also coinciding with Tissue Factor upregulation. Interestingly, inhibition of DPP4 activity with diprotin A also enhanced the amount of Tissue Factor encountered and induced the adherence of platelets under flow conditions. Ischemia induces loss of coronary microvascular endothelial DPP4 expression and increased Tissue Factor expression in AMI as well as in vitro in HUVECs. Our data suggest that the loss of DPP4 activity affects the anti-thrombogenic nature of the endothelium.