ABSTRACT
BACKGROUND: Infusion of exogenous catecholamines (i.e., norepinephrine [NE] and dobutamine) is a recommended treatment for septic shock with myocardial dysfunction. However, sustained catecholamine infusion is linked to cardiac toxicity and impaired responsiveness. Several pre-clinical and clinical studies have investigated the use of alternative vasopressors in the treatment of septic shock, with limited benefits and generally no effect on mortality. Apelin-13 (APL-13) is an endogenous positive inotrope and vasoactive peptide and has been demonstrated cardioprotective with vasomodulator and sparing life effects in animal models of septic shock. A primary objective of this study was to evaluate the NE-sparing effect of APL-13 infusion in an experimental sepsis-induced hypotension. METHODS: For this goal, sepsis was induced by cecal ligation and puncture (CLP) in male rats and the arterial blood pressure (BP) monitored continuously via a carotid catheter. Monitoring, fluid resuscitation and experimental treatments were performed on conscious animals. Based on pilot assays, normal saline fluid resuscitation (2.5 mL/Kg/h) was initiated 3 h post-CLP and maintained up to the endpoint. Thus, titrated doses of NE, with or without fixed-doses of APL-13 or the apelin receptor antagonist F13A co-infusion were started when 20% decrease of systolic BP (SBP) from baseline was achieved, to restore SBP values ≥ 115 ± 1.5 mmHg (baseline average ± SEM). RESULTS: A reduction in mean NE dose was observed with APL-13 but not F13A co-infusion at pre-determined treatment time of 4.5 ± 0.5 h (17.37 ± 1.74 µg/Kg/h [APL-13] vs. 25.64 ± 2.61 µg/Kg/h [Control NE] vs. 28.60 ± 4.79 µg/Kg/min [F13A], P = 0.0491). A 60% decrease in NE infusion rate over time was observed with APL-13 co-infusion, (p = 0.008 vs NE alone), while F13A co-infusion increased the NE infusion rate over time by 218% (p = 0.003 vs NE + APL-13). Associated improvements in cardiac function are likely mediated by (i) enhanced left ventricular end-diastolic volume (0.18 ± 0.02 mL [Control NE] vs. 0.30 ± 0.03 mL [APL-13], P = 0.0051), stroke volume (0.11 ± 0.01 mL [Control NE] vs. 0.21 ± 0.01 mL [APL-13], P < 0.001) and cardiac output (67.57 ± 8.63 mL/min [Control NE] vs. 112.20 ± 8.53 mL/min [APL-13], P = 0.0036), and (ii) a reduced effective arterial elastance (920.6 ± 81.4 mmHg/mL/min [Control NE] vs. 497.633.44 mmHg/mL/min. [APL-13], P = 0.0002). APL-13 administration was also associated with a decrease in lactate levels compared to animals only receiving NE (7.08 ± 0.40 [Control NE] vs. 4.78 ± 0.60 [APL-13], P < 0.01). CONCLUSION: APL-13 exhibits NE-sparing benefits in the treatment of sepsis-induced shock, potentially reducing deleterious effects of prolonged exogenous catecholamine administration.
ABSTRACT
Sepsis is an archetype of distributive shock and combines different levels of alterations in preload, afterload, and often cardiac contractility. The use of hemodynamic drugs has evolved over the past few years, along with the invasive and non-invasive tools used to measure these components in real time. However, none of them is impeccable, which is why the mortality of septic shock remains too high. The concept of ventriculo-arterial coupling (VAC) allows for the integration of these three fundamental macroscopic hemodynamic components. In this mini review, we discuss the knowledge, tools, and limitations of VAC measurement, along with the evidence supporting ventriculo-arterial uncoupling in septic shock. Finally, the impact of recommended hemodynamic drugs and molecules on VAC is detailed.
ABSTRACT
BACKGROUND: Apelins are potential candidate therapeutic molecules for hemodynamic support. The objective of this study was to assess the hemodynamic impacts of apelin-13 in a neonatal lamb model of septic shock. METHODS: Lambs were randomized to receive apelin-13 or normal saline. Septic shock was induced by injecting a fecal slurry into the peritoneal cavity. Lambs underwent volume repletion (30 mL/kg over 1 h) followed by intravenous administration of 5 incremental doses (D) of apelin-13 (D1 = 0.039 to D5 = 19.5 µg/kg/h) or normal saline. RESULTS: Following fecal injection, mean arterial pressure (MAP) and cardiac index (CI) dropped in both groups (p < 0.05). The MAP decreased non-significantly from D1 to D5 (p = 0.12) in the saline group, while increasing significantly (p = 0.02) in the apelin group (-12 (-17; 12) vs. +15 (6; 23) % (p = 0.012)). Systemic vascular resistances were higher in the apelin-13 group at D5 compared to the saline group (4337 (3239, 5144) vs. 2532 (2286, 3966) mmHg/min/mL, respectively, p = 0.046). The CI increased non-significantly in the apelin-13 group. CONCLUSION: Apelin-13 increased MAP in a neonatal lamb septic shock model. IMPACT: Administration of apelin-13 stabilized hemodynamics during the progression of the sepsis induced in this neonatal lamb model. Systemic vascular resistances were higher in the apelin-13 group than in the placebo group. This suggests ontogenic differences in vascular response to apelin-13 and warrants further investigation. This study suggests that apelin-13 could eventually become a candidate for the treatment of neonatal septic shock.
Subject(s)
Peritonitis , Shock, Septic , Animals , Hemodynamics , Saline Solution/therapeutic use , Sheep , Shock, Septic/drug therapyABSTRACT
We previously reported a series of macrocyclic analogues of [Pyr1]-apelin-13 (Ape13) with increased plasma stability and potent APJ agonist properties. Based on the most promising compound in this series, we synthesized and then evaluated novel macrocyclic compounds of Ape13 to identify agonists with specific pharmacological profiles. These efforts led to the development of analogues 39 and 40, which possess reduced molecular weight (MW 1020 Da vs Ape13, 1534 Da). Interestingly, compound 39 (Ki 0.6 nM), which does not activate the Gα12 signaling pathway while maintaining potency and efficacy similar to Ape13 to activate Gαi1 (EC50 0.8 nM) and ß-arrestin2 recruitment (EC50 31 nM), still exerts cardiac actions. In addition, analogue 40 (Ki 5.6 nM), exhibiting a favorable Gα12-biased signaling and an increased in vivo half-life (t1/2 3.7 h vs <1 min of Ape13), produces a sustained cardiac response up to 6 h after a single subcutaneous bolus injection.
Subject(s)
Apelin/analogs & derivatives , Apelin/pharmacology , GTP-Binding Protein alpha Subunits, G12-G13/drug effects , Heart/drug effects , Signal Transduction/drug effects , Apelin/pharmacokinetics , Apelin Receptors/drug effects , Arrestin/drug effects , HEK293 Cells , Half-Life , Humans , Injections, Subcutaneous , Macrocyclic Compounds/chemical synthesis , Macrocyclic Compounds/pharmacology , Molecular WeightABSTRACT
BACKGROUND: The impact of carotid stenosis (CS) in patients undergoing cardiac surgery remains controversial. The aim of this study was to evaluate the association between carotid stenosis and stroke and/or transient ischemic attack (TIA) in patients undergoing cardiac surgery on cardiopulmonary bypass. METHODS: This was a retrospective cohort study including patients undergoing cardiac surgery on cardiopulmonary bypass from January 2006 to March 2018 at the Québec Heart and Lung Institute. Data of patients' preoperative demographic characteristics, operative and postoperative variables were taken from a computerised database and patients' charts. Univariate and multivariate analyses were performed. RESULTS: A total of 20,241 patients were included in the study. Among those who had received preoperative carotid ultrasound, 516 (2.6% of the total population) had unilateral or bilateral CS ≥ 50%. Categorised levels of CS severity were identified as independent risk factors for postoperative stroke and/or TIA. There was an almost 3-fold increased risk of postoperative neurologic events in 80%-99% CS vs less severe 50%-79% CS (odds ratio 2.91, 95% confidence interval 1.30-6.54), suggesting that the degree of severity of CS is potentially a strong independent predictor of postoperative neurologic events. CONCLUSIONS: CS is an independent risk factor of postoperative stroke and/or TIA. This study suggests for the first time that the risk of stroke increases with the degree of severity of CS, with the greatest risk being for CS of 80%-99%. The strength of this relationship and potential causality effect should be further explored in a prospective study focusing on this population most at risk.
Subject(s)
Cardiac Surgical Procedures/adverse effects , Carotid Stenosis , Ischemic Attack, Transient , Postoperative Complications , Risk Assessment , Severity of Illness Index , Stroke , Aged , Canada/epidemiology , Cardiac Surgical Procedures/methods , Cardiac Surgical Procedures/statistics & numerical data , Cardiopulmonary Bypass/methods , Carotid Stenosis/diagnosis , Carotid Stenosis/epidemiology , Female , Humans , Ischemic Attack, Transient/diagnosis , Ischemic Attack, Transient/epidemiology , Ischemic Attack, Transient/etiology , Male , Outcome and Process Assessment, Health Care , Postoperative Complications/diagnosis , Postoperative Complications/epidemiology , Prognosis , Risk Assessment/methods , Risk Assessment/statistics & numerical data , Risk Factors , Stroke/diagnosis , Stroke/epidemiology , Stroke/etiology , Survival AnalysisABSTRACT
Sepsis is a prevalent life-threatening condition related to a systemic infection, and with unresolved issues including refractory septic shock and organ failures. Endogenously released catecholamines are often inefficient to maintain blood pressure, and low reactivity to exogenous catecholamines with risk of sympathetic overstimulation is well documented in septic shock. In this context, apelinergics are efficient and safe inotrope and vasoregulator in rodents. However, their utility in a larger animal model as well as the limitations with regards to the enzymatic breakdown during sepsis, need to be investigated. The therapeutic potential and degradation of apelinergics in sepsis were tested experimentally and in a cohort of patients. (1) 36 sheep with or without fecal peritonitis-induced septic shock (a large animal experimental design aimed to mimic the human septic shock paradigm) were evaluated for hemodynamic and renal responsiveness to incremental doses of two dominant apelinergics: apelin-13 (APLN-13) or Elabela (ELA), and (2) 52 subjects (33 patients with sepsis/septic shock and 19 healthy volunteers) were investigated for early levels of endogenous apelinergics in the blood, the related enzymatic degradation profile, and data regarding sepsis outcome. APLN-13 was the only one apelinergic which efficiently improved hemodynamics in both healthy and septic sheep. Endogenous apelinergic levels early rose, and specific enzymatic breakdown activities potentially threatened endogenous apelin system reactivity and negatively impacted the outcome in human sepsis. Short-term exogenous APLN-13 infusion is helpful in stabilizing cardiorenal functions in ovine septic shock; however, this ability might be impaired by specific enzymatic systems triggered during the early time course of human sepsis. Strategies to improve resistance of APLN-13 to degradation and/or to overcome sepsis-induced enzymatic breakdown environment should guide future works.
Subject(s)
Apelin/metabolism , Enzymes/metabolism , Hemodynamics , Pancreatic Elastase/metabolism , Proteolysis , Shock, Septic/pathology , Aged , Animals , Apelin/genetics , Case-Control Studies , Catecholamines/metabolism , Feces , Female , Follow-Up Studies , Humans , Male , Middle Aged , Pancreatic Elastase/genetics , Peritonitis/complications , Prognosis , Prospective Studies , Sheep , Shock, Septic/etiology , Shock, Septic/metabolismABSTRACT
Objectives: Arterial hypertension, when exacerbated by excessive dietary salt intake, worsens the morbidity and mortality rates associated with cardiovascular and renal diseases. Stimulation of the apelinergic system appears to protect against several circulatory system diseases, but it remains unknown if such beneficial effects are conserved in severe hypertension. Therefore, we aimed at determining whether continuous infusion of apelinergic ligands (i.e., Apelin-13 and Elabela) exerted cardiorenal protective effects in spontaneously hypertensive (SHR) rats receiving high-salt diet. Methods: A combination of echocardiography, binding assay, histology, and biochemical approaches were used to investigate the cardiovascular and renal effects of Apelin-13 or Elabela infusion over 6 weeks in SHR fed with normal-salt or high-salt chow. Results: High-salt intake upregulated the cardiac and renal expression of APJ receptor in SHR. Importantly, Elabela was more effective than Apelin-13 in reducing high blood pressure, cardiovascular and renal dysfunctions, fibrosis and hypertrophy in high-salt fed SHR. Unlike Apelin-13, the beneficial effects of Elabela were associated with a counter-regulatory role of the ACE/ACE2/neprilysin axis of the renin-angiotensin-aldosterone system (RAAS) in heart and kidneys of salt-loaded SHR. Interestingly, Elabela also displayed higher affinity for APJ in the presence of high salt concentration and better resistance to RAAS enzymes known to cleave Apelin-13. Conclusion: These findings highlight the protective action of the apelinergic system against salt-induced severe hypertension and cardiorenal failure. As compared with Apelin-13, Elabela displays superior pharmacodynamic and pharmacokinetic properties that warrant further investigation of its therapeutic use in cardiovascular and kidney diseases.
ABSTRACT
Side-chain-constrained amino acids are useful tools to modulate the biological properties of peptides. In this study, we applied side-chain constraints to apelin-13 (Ape13) by substituting the Pro12 and Phe13 positions, affecting the binding affinity and signaling profile on the apelin receptor (APJ). The residues 1Nal, Trp, and Aia were found to be beneficial substitutions for Pro12, and the resulting analogues displayed high affinity for APJ (Ki 0.08-0.18 nM vs Ape13 Ki 0.7 nM). Besides, constrained (d-Tic) or α,α-disubstituted residues (Dbzg; d-α-Me-Tyr(OBn)) were favorable for the Phe13 position. Compounds 47 (Pro12-Phe13 replaced by Aia-Phe, Ki 0.08 nM) and 53 (Pro12-Phe13 replaced by 1Nal-Dbzg, Ki 0.08 nM) are the most potent Ape13 analogues activating the Gα12 pathways (53, EC50 Gα12 2.8 nM vs Ape13, EC50 43 nM) known to date, displaying high affinity, resistance to ACE2 cleavage as well as improved pharmacokinetics in vitro (t1/2 5.8-7.3 h in rat plasma) and in vivo.
Subject(s)
Intercellular Signaling Peptides and Proteins/metabolism , Signal Transduction , Amino Acid Sequence , Amino Acid Substitution , Animals , Apelin Receptors/chemistry , Apelin Receptors/metabolism , Blood Pressure/drug effects , GTP-Binding Protein alpha Subunits, G12-G13/chemistry , GTP-Binding Protein alpha Subunits, G12-G13/metabolism , Half-Life , Humans , Intercellular Signaling Peptides and Proteins/chemistry , Intercellular Signaling Peptides and Proteins/pharmacology , Male , Protein Binding , Protein Stability , Rats , Rats, Sprague-Dawley , Signal Transduction/drug effectsABSTRACT
Apelin receptor (APJ) activation by apelin-13 (APLN-13) engages both Gαi proteins and ß-arrestins, stimulating distinct intracellular pathways and triggering physiological responses like enhanced cardiac contractility. Substituting the C-terminal phenylalanine of APLN-13 with α-methyl-l-phenylalanine [(l-α-Me)Phe] or p-benzoyl-l-phenylalanine (Bpa) generates biased analogs inducing APJ functional selectivity toward Gαi proteins. Using these original analogs, we proposed to investigate how the canonical Gαi signaling of APJ regulates the cardiac function and to assess their therapeutic impact in a rat model of isoproterenol-induced myocardial dysfunction. In vivo and ex vivo infusions of either Bpa or (l-α-Me)Phe analogs failed to enhance rats' left ventricular (LV) contractility compared with APLN-13. Inhibition of Gαi with pertussis toxin injection optimized the cardiotropic effect of APLN-13 and revealed the inotropic impact of Bpa. Moreover, both APLN-13 and Bpa efficiently limited the forskolin-induced and PKA-dependent phosphorylation of phospholamban at the Ser16 in neonatal rat ventricular myocytes. However, only Bpa significantly reduced the inotropic effect of forskolin infusion in isolated-perfused heart, highlighting its efficient bias toward Gαi. Compared with APLN-13, Bpa also markedly improved isoproterenol-induced myocardial systolic and diastolic dysfunctions. Bpa prevented cardiac weight increase, normalized both ANP and BNP mRNA expressions, and decreased LV fibrosis in isoproterenol-treated rats. Our results show that APJ-driven Gαi/adenylyl cyclase signaling is functional in cardiomyocytes and acts as negative feedback of the APLN-APJ-dependent inotropic response. Biased APJ signaling toward Gαi over the ß-arrestin pathway offers a promising strategy in the treatment of cardiovascular diseases related to myocardial hypertrophy and high catecholamine levels.NEW & NOTEWORTHY By using more potent Gαi-biased APJ agonists that strongly inhibit cAMP production, these data point to the negative inotropic effect of APJ-mediated Gαi signaling in the heart and highlight the potential protective impact of APJ-dependent Gαi signaling in cardiovascular diseases associated with left ventricular hypertrophy.
Subject(s)
Apelin Receptors/agonists , Apelin/pharmacology , GTP-Binding Protein alpha Subunits/metabolism , Intercellular Signaling Peptides and Proteins/pharmacology , Myocytes, Cardiac/drug effects , Ventricular Dysfunction, Left/prevention & control , Ventricular Function, Left/drug effects , Adenylyl Cyclases/metabolism , Animals , Apelin/analogs & derivatives , Apelin Receptors/metabolism , Calcium-Binding Proteins/metabolism , Cells, Cultured , Cyclic AMP-Dependent Protein Kinases/metabolism , Disease Models, Animal , Isolated Heart Preparation , Isoproterenol , Ligands , Male , Myocytes, Cardiac/metabolism , Phosphorylation , Rats, Sprague-Dawley , Signal Transduction , Ventricular Dysfunction, Left/chemically induced , Ventricular Dysfunction, Left/metabolism , Ventricular Dysfunction, Left/physiopathologyABSTRACT
ELABELA (ELA) is the second endogenous ligand of the apelin receptor (APJ). Although apelin-13 and ELA both target APJ, there is limited information on structure-activity relationship (SAR) of ELA. In the present work, we identified the shortest bioactive C-terminal fragment ELA23-32, which possesses high affinity for APJ (Ki 4.6 nM) and produces cardiorenal effects in vivo similar to those of ELA. SAR studies on conserved residues (Leu25, His26, Val29, Pro30, Phe31, Pro32) show that ELA and apelin-13 may interact differently with APJ. His26 and Val29 emerge as important for ELA binding. Docking and binding experiments suggest that Phe31 of ELA may bind to a tight groove distinct from that of Phe13 of Ape13, while the Phe13 pocket may be occupied by Pro32 of ELA. Further characterization of signaling profiles on the Gαi1, Gα12, and ß-arrestin2 pathways reveals the importance of aromatic residue at the Phe31 or Pro32 position for receptor activation.
Subject(s)
Apelin Receptors/agonists , Peptide Hormones/pharmacology , Amino Acid Sequence , Animals , Apelin Receptors/metabolism , Binding Sites , Blood Pressure/drug effects , Computational Biology , Heart/drug effects , Heart/physiology , Humans , Intercellular Signaling Peptides and Proteins/chemistry , Ligands , Male , Peptide Hormones/chemistry , Rats , Rats, Sprague-Dawley , Structure-Activity RelationshipABSTRACT
BACKGROUND: Hypertonic sodium lactate (HSL) may be of interest during inflammation. We aimed to evaluate its effects during experimental sepsis in rats (cecal ligation and puncture (CLP)). METHODS: Three groups were analyzed (n = 10/group): sham, CLP-NaCl 0.9%, and CLP-HSL (2.5 mL/kg/h of fluids for 18 h after CLP). Mesenteric microcirculation, echocardiography, cytokines, and biochemical parameters were evaluated. Two additional experiments were performed for capillary leakage (Evans blue, n = 5/group) and cardiac hemodynamics (n = 7/group). RESULTS: HSL improved mesenteric microcirculation (CLP-HSL 736 [407-879] vs. CLP-NaCl 241 [209-391] UI/pixel, p = 0.0006), cardiac output (0.34 [0.28-0.43] vs. 0.14 [0.10-0.18] mL/min/g, p < 0.0001), and left ventricular fractional shortening (55 [46-73] vs. 39 [33-52] %, p = 0.009). HSL also raised dP/dtmax slope (6.3 [3.3-12.1] vs. 2.7 [2.0-3.9] 103 mmHg/s, p = 0.04), lowered left ventricular end-diastolic pressure-volume relation (1.9 [1.1-2.3] vs. 3.0 [2.2-3.7] RVU/mmHg, p = 0.005), and reduced Evans blue diffusion in the gut (37 [31-43] vs. 113 [63-142], p = 0.03), the lung (108 [82-174] vs. 273 [222-445], p = 0.006), and the liver (24 [14-37] vs. 70 [50-89] ng EB/mg, p = 0.04). Lactate and 3-hydroxybutyrate were higher in CLP-HSL (6.03 [3.08-10.30] vs. 3.19 [2.42-5.11] mmol/L, p = 0.04; 400 [174-626] vs. 189 [130-301] µmol/L, p = 0.03). Plasma cytokines were reduced in HSL (IL-1ß, 172 [119-446] vs. 928 [245-1470] pg/mL, p = 0.004; TNFα, 17.9 [12.5-50.3] vs. 53.9 [30.8-85.6] pg/mL, p = 0.005; IL-10, 352 [267-912] vs. 905 [723-1243] pg/mL) as well as plasma VEGF-A (198 [185-250] vs. 261 [250-269] pg/mL, p = 0.009). CONCLUSIONS: Hypertonic sodium lactate fluid protects against cardiac dysfunction, mesenteric microcirculation alteration, and capillary leakage during sepsis and simultaneously reduces inflammation and enhances ketone bodies.
Subject(s)
Inflammation , Microcirculation , Sepsis , Sodium Lactate , Animals , Rats , Analysis of Variance , Disease Models, Animal , Echocardiography/methods , Endothelial Growth Factors/analysis , Endothelial Growth Factors/blood , Heart Function Tests/methods , Hypertonic Solutions/therapeutic use , Inflammation/drug therapy , Inflammation/physiopathology , Interleukin-10/analysis , Interleukin-10/blood , Interleukin-1beta/analysis , Interleukin-1beta/blood , Microcirculation/drug effects , Microcirculation/physiology , Prospective Studies , Sepsis/drug therapy , Sepsis/physiopathology , Sodium Lactate/pharmacology , Sodium Lactate/therapeutic use , Syndecan-1/analysis , Syndecan-1/blood , Tumor Necrosis Factor-alpha/analysis , Tumor Necrosis Factor-alpha/bloodABSTRACT
BACKGROUND/AIMS: Apelin and its G protein-coupled receptor APJ (gene symbol Aplnr) are strongly expressed in magnocellular vasopressinergic neurons suggesting that the apelin/APJ system plays a key role at the central level in regulating salt and water balance by counteracting the antiduretic action of vasopressin (AVP). Likewise, recent studies revealed that apelin exerts opposite effects to those of vasopressin induced on water reabsorption via a direct action on the kidney collecting duct. However, the underlying mechanisms of the peripheral action of apelin are not clearly understood. Here, we thus investigated the role of the apelin/APJ system in the regulation of water balance in the kidney, and more specifically its involvement in modulating the function of aquaporin-2 (AQP2) in the collecting duct. METHODS: Mouse cortical collecting duct cells (mpkCCD) were incubated in the presence of dDAVP and treated with or without apelin-13. Changes in AQP2 expression and localization were determined by immunoblotting and confocal immunofluorescence staining. RESULTS: Herein, we showed that the APJ was present in mpkCCD cells. Treatment of mpkCCD with apelin-13 reduced the cAMP production and antagonized the AVP-induced increase in AQP2 mRNA and protein expressions. Immunofluorescent experiments also revealed that the AVP-induced apical cell surface expression of AQP2, and notably its phosphorylated isoform AQP2-pS269, was considerably reduced following apelin-13 application to mpkCCD cells. CONCLUSION: Our data reinforce the aquaretic role of the apelin/APJ system in the fine regulation of body fluid homeostasis at the kidney level and its physiological opposite action to the antiduretic activity of AVP.
Subject(s)
Aquaporin 2/metabolism , Deamino Arginine Vasopressin/pharmacology , Gene Expression Regulation/drug effects , Intercellular Signaling Peptides and Proteins/pharmacology , Protein Transport/drug effects , Animals , Apelin Receptors/metabolism , Aquaporin 2/genetics , Cell Line , Cyclic AMP/metabolism , HEK293 Cells , Humans , Kidney Tubules, Collecting/cytology , Kidney Tubules, Collecting/metabolism , Mice , Phosphorylation/drug effectsABSTRACT
BACKGROUND: Standard clinical imaging of the acute respiratory distress syndrome (ARDS) lung lacks resolution and offers limited possibilities in the exploration of the structure-function relationship, and therefore cannot provide an early and clear discrimination of patients with unexpected diagnosis and unrepair profile. The current gold standard is open lung biopsy (OLB). However, despite being able to reveal precise information about the tissue collected, OLB cannot provide real-time information on treatment response and is accompanied with a complication risk rate up to 25%, making longitudinal monitoring a dangerous endeavor. Intravital probe-based confocal laser endomicroscopy (pCLE) is a developing and innovative high-resolution imaging technology. pCLE offers the possibility to leverage multiple and specific imaging probes to enable multiplex screening of several proteases and pathogenic microorganisms, simultaneously and longitudinally, in the lung. This bedside method will ultimately enable physicians to rapidly, noninvasively, and accurately diagnose degrading lung and/or fibrosis without the need of OLBs. OBJECTIVES AND METHODS: To extend the information provided by standard imaging of the ARDS lung with a bedside, high-resolution, miniaturized pCLE through the detailed molecular imaging of a carefully selected region-of-interest (ROI). To validate and quantify real-time imaging to validate pCLE against OLB. RESULTS: Developments in lung pCLE using fluorescent affinity- or activity-based probes at both preclinical and clinical (first-in-man) stages are ongoing-the results are promising, revealing correlations with OLBs in problematic ARDS. CONCLUSION: It can be envisaged that safe, high-resolution, noninvasive pCLE with activatable fluorescence probes will provide a "virtual optical biopsy" and will provide decisive information in selected ARDS patients at the bedside.
ABSTRACT
The apelinergic pathway has been generating increasing interest in the past few years for its potential as a therapeutic target in several conditions associated with the cardiovascular and metabolic systems. Indeed, preclinical and, more recently, clinical evidence both point to this G protein-coupled receptor as a target of interest in the treatment of not only cardiovascular disorders such as heart failure, pulmonary arterial hypertension, atherosclerosis, or septic shock, but also of additional conditions such as water retention/hyponatremic disorders, type 2 diabetes, and preeclampsia. While it is a peculiar system with its two classes of endogenous ligand, the apelins and Elabela, its intricacies are a matter of continuing investigation to finely pinpoint its potential and how it enables crosstalk between the vasculature and organ systems of interest. In this perspective article, we first review the current knowledge on the role of the apelinergic pathway in the above systems, as well as the associated therapeutic indications and existing pharmacological tools. We also offer a perspective on the challenges and potential ahead to advance the apelinergic system as a target for therapeutic intervention in several key areas.
Subject(s)
Apelin/metabolism , Cardiovascular Diseases/metabolism , Metabolic Diseases/metabolism , Animals , Humans , Proteolysis , Signal TransductionABSTRACT
BACKGROUND: Improving sepsis support is one of the three pillars of a 2017 resolution according to the World Health Organization (WHO). Septic shock is indeed a burden issue in the intensive care units. Hemodynamic stabilization is a cornerstone element in the bundle of supportive treatments recommended in the Surviving Sepsis Campaign (SSC) consecutive biannual reports. MAIN BODY: The "Pandera's box" of septic shock hemodynamics is an eternal debate, however, with permanent contentious issues. Fluid resuscitation is a prerequisite intervention for sepsis rescue, but selection, modalities, dosage as well as duration are subject to discussion while too much fluid is associated with worsen outcome, vasopressors often need to be early introduced in addition, and catecholamines have long been recommended first in the management of septic shock. However, not all patients respond positively and controversy surrounding the efficacy-to-safety profile of catecholamines has come out. Preservation of the macrocirculation through a "best" mean arterial pressure target is the actual priority but is still contentious. Microcirculation recruitment is a novel goal to be achieved but is claiming more knowledge and monitoring standardization. Protection of the cardio-renal axis, which is prevalently injured during septic shock, is also an unavoidable objective. Several promising alternative or additive drug supporting avenues are emerging, trending toward catecholamine's sparing or even "decatecholaminization." Topics to be specifically addressed in this review are: (1) mean arterial pressure targeting, (2) fluid resuscitation, and (3) hemodynamic drug support. CONCLUSION: Improving assessment and means for rescuing hemodynamics in early septic shock is still a work in progress. Indeed, the bigger the unresolved questions, the lower the quality of evidence.
ABSTRACT
Stem cell therapy has shown great promise for organ repair and regeneration. In the context of lung disease, such as radiation-induced lung damage (RILD) in cancer radiotherapy, mesenchymal stem cells (MSCs) have shown the ability to reduce damage possibly due to their immunomodulatory properties and other unknown mechanisms. However, once MSCs are transplanted into the body, little is known as to their localization or their mechanisms of action. In this work, we proposed, implemented, and validated a fluorescence endomicroscopy (FE) imaging technique that allows for the real-time detection and quantification of transplanted pre-labeled MSCs in vivo and tracking in a rat model. This protocol covers aspects related to MSCs extraction, labeling, FE imaging, and image analysis developed in a RILD rat model but applicable to other biological systems. © 2018 by John Wiley & Sons, Inc.
Subject(s)
Lung/cytology , Mesenchymal Stem Cells/cytology , Microscopy, Fluorescence/methods , Animals , Image Processing, Computer-Assisted , Rats, Sprague-Dawley , Video RecordingABSTRACT
The apelinergic system is an important player in the regulation of both vascular tone and cardiovascular function, making this physiological system an attractive target for drug development for hypertension, heart failure and ischemic heart disease. Indeed, apelin exerts a positive inotropic effect in humans whilst reducing peripheral vascular resistance. In this study, we investigated the signaling pathways through which apelin exerts its hypotensive action. We synthesized a series of apelin-13 analogs whereby the C-terminal Phe13 residue was replaced by natural or unnatural amino acids. In HEK293 cells expressing APJ, we evaluated the relative efficacy of these compounds to activate Gαi1 and GαoA G-proteins, recruit ß-arrestins 1 and 2 (ßarrs), and inhibit cAMP production. Calculating the transduction ratio for each pathway allowed us to identify several analogs with distinct signaling profiles. Furthermore, we found that these analogs delivered i.v. to Sprague-Dawley rats exerted a wide range of hypotensive responses. Indeed, two compounds lost their ability to lower blood pressure, while other analogs significantly reduced blood pressure as apelin-13. Interestingly, analogs that did not lower blood pressure were less effective at recruiting ßarrs. Finally, using Spearman correlations, we established that the hypotensive response was significantly correlated with ßarr recruitment but not with G protein-dependent signaling. In conclusion, our results demonstrated that the ßarr recruitment potency is involved in the hypotensive efficacy of activated APJ.
Subject(s)
Antihypertensive Agents/pharmacology , Apelin Receptors/metabolism , Blood Pressure/drug effects , Intercellular Signaling Peptides and Proteins/pharmacology , beta-Arrestins/metabolism , Animals , Antihypertensive Agents/chemistry , Cyclic AMP/metabolism , HEK293 Cells , Humans , Hypotension/drug therapy , Hypotension/metabolism , Intercellular Signaling Peptides and Proteins/chemistry , Male , Rats, Sprague-Dawley , Receptors, G-Protein-Coupled/metabolism , Signal Transduction/drug effectsABSTRACT
The apelin receptor generates increasing interest as a potential target across several cardiovascular indications. However, the short half-life of its cognate ligands, the apelin peptides, is a limiting factor for pharmacological use. In this study, we systematically explored each position of apelin-13 to find the best position to cyclize the peptide, with the goal to improve its stability while optimizing its binding affinity and signaling profile. Macrocyclic analogues showed a remarkably higher stability in rat plasma (half-life >3 h versus 24 min for Pyr-apelin-13), accompanied by improved affinity (analogue 15, Ki 0.15 nM and t1/2 6.8 h). Several compounds displayed higher inotropic effects ex vivo in the Langendorff isolated heart model in rats (analogues 13 and 15, maximum response at 0.003 nM versus 0.03 nM of apelin-13). In conclusion, this study provides stable and active compounds to better characterize the pharmacology of the apelinergic system.
Subject(s)
Azetidines/chemical synthesis , Intercellular Signaling Peptides and Proteins/chemical synthesis , Monoacylglycerol Lipases/chemistry , Positron-Emission Tomography/methods , Radiopharmaceuticals/chemical synthesis , Animals , Azetidines/pharmacokinetics , Brain/diagnostic imaging , Brain/enzymology , Brain/metabolism , Carbon Radioisotopes , Fluorine Radioisotopes , Intercellular Signaling Peptides and Proteins/pharmacokinetics , Macaca mulatta , Male , Mice , Radioactive Tracers , Radiopharmaceuticals/pharmacokinetics , Rats, Sprague-Dawley , Substrate Specificity , Tissue DistributionABSTRACT
Catecholamines, in concert with fluid resuscitation, have long been recommended in the management of septic shock. However, not all patients respond positively and controversy surrounding the efficacy-to-safety profile of catecholamines has emerged, trending toward decatecholaminization. Contextually, it is time to re-examine the "maintaining blood pressure" paradigm by identifying safer and life-saving alternatives. We put in perspective the emerging and growing knowledge on a promising alternative avenue: the apelinergic system. This target exhibits invaluable pleiotropic properties, including inodilator activity, cardio-renal protection, and control of fluid homeostasis. Taken together, its effects are expected to be greatly beneficial for patients in septic shock.
Subject(s)
Apelin Receptors/metabolism , Catecholamines/adverse effects , Shock, Septic/drug therapy , Apelin/metabolism , Apelin/pharmacokinetics , Apelin/therapeutic use , Apelin Receptors/drug effects , Homeostasis/physiology , Humans , Multiple Organ Failure/physiopathology , Multiple Organ Failure/prevention & control , Peptide Hormones/metabolism , Peptide Hormones/pharmacokinetics , Peptide Hormones/therapeutic useABSTRACT
Radiation-induced pulmonary fibrosis (RIPF) is a debilitating side effect of radiation therapy (RT) of several cancers including lung and breast cancers. Current clinical methods to assess and monitor RIPF involve diagnostic computed tomography (CT) imaging, which is restricted to anatomical macroscopic changes. Confocal laser endomicroscopy (CLE) or fluorescence endomicroscopy (FE) in combination with a fibrosis-targeted fluorescent probe allows to visualize RIPF in real-time at the microscopic level. However, a major limitation of FE imaging is the lack of anatomical localization of the endomicroscope within the lung. In this work, we proposed and validated the use of x-ray fluoroscopy-guidance in a rat model of RIPF to pinpoint the location of the endomicroscope during FE imaging and map it back to its anatomical location in the corresponding CT image. For varying endomicroscope positions, we observed a positive correlation between CT and FE imaging as indicated by the significant association between increased lung density on CT and the presence of fluorescent fiber structures with FE in RT cases compared to Control. Combining multimodality imaging allows visualization and quantification of molecular processes at specific locations within the injured lung. The proposed image-guided FE method can be extended to other disease models and is amenable to clinical translation for assessing and monitoring fibrotic damage.