Experimental Shock Research Articles

Alterations in the Renin-Angiotensin System in Experimental Septic Shock.

To analyze dynamic changes in the renin-angiotensin system (RAS) during septic shock, focusing on angiotensin-converting enzyme (ACE) activity and the balance between angiotensin peptides, using a mass spectrometry method. Experimental septic shock model induced by peritonitis in swine. Experimental Laboratory, Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles. Forty time points from eight mechanically ventilated pigs. Septic shock was induced using intraperitoneal instillation of autologous feces, followed by standardized fluid resuscitation, norepinephrine infusion, antibiotic administration, and peritoneal lavage. The induction of sepsis resulted in a significant increase in plasma renin activity and levels of angiotensin I and II, with a significant decrease in ACE activity observed from 4 hours post-resuscitation and a notable rise in the angiotensin I/angiotensin II ratio at 12 hours. Additionally, a shift toward the angiotensin-(1-7) axis was observed, evidenced by an increased angiotensin-(1-7)/angiotensin II ratio. The study highlighted dynamic shifts in the RAS during septic shock, characterized by reduced circulating ACE activity, elevated angiotensin I/II ratio, and a shift toward the angiotensin-(1-7) axis. These findings suggest an adaptive response within the RAS, potentially offering new insights into sepsis management and therapeutic targets.

The performance of interrupted time series designs with a limited number of time points: Learning losses due to school closures during the COVID-19 pandemic.

Interrupted time series (ITS) designs are increasingly used for estimating the effect of shocks in natural experiments. Currently, ITS designs are often used in scenarios with many time points and simple data structures. This research investigates the performance of ITS designs when the number of time points is limited and with complex data structures. Using a Monte Carlo simulation study, we empirically derive the performance-in terms of power, bias and precision- of the ITS design. Scenarios are considered with multiple interventions, a low number of time points and different effect sizes based on a motivating example of the learning loss due to COVID school closures. The results of the simulation study show the power of the step change depends mostly on the sample size, while the power of the slope change depends on the number of time points. In the basic scenario, with both a step and a slope change and an effect size of 30% of the pre-intervention slope, the required sample size for detecting a step change is 1,100 with a minimum of twelve time points. For detecting a slope change the required sample size decreases to 500 with eight time points. To decide if there is enough power researchers should inspect their data, hypothesize about effect sizes and consider an appropriate model before applying an ITS design to their research. This paper contributes to the field of methodology in two ways. Firstly, the motivation example showcases the difficulty of employing ITS designs in cases which do not adhere to a single intervention. Secondly, models are proposed for more difficult ITS designs and their performance is tested.

Inhibition of circulating dipeptidyl-peptidase 3 by procizumab in experimental septic shock reduces catecholamine exposure and myocardial injury

BackgroundDipeptidyl peptidase 3 (DPP3) is a ubiquitous cytosolic enzyme released into the bloodstream after tissue injury, that can degrade angiotensin II. High concentrations of circulating DPP3 (cDPP3) have been associated with worse outcomes during sepsis. The aim of this study was to assess the effect of Procizumab (PCZ), a monoclonal antibody that neutralizes cDPP3, in an experimental model of septic shock.MethodsIn this randomized, open-label, controlled study, 16 anesthetized and mechanically ventilated pigs with peritonitis were randomized to receive PCZ or standard treatment when the mean arterial pressure (MAP) dropped below 50 mmHg. Resuscitation with fluids, antimicrobial therapy, peritoneal lavage, and norepinephrine was initiated one hour later to maintain MAP between 65–75 mmHg for 12 h. Hemodynamic variables, tissue oxygenation indices, and measures of organ failure and myocardial injury were collected. Organ blood flow was assessed using isotopic assessment (99mtechnetium albumin). cDPP3 activity, equilibrium analysis of the renin–angiotensin system and circulating catecholamines were measured. Tissue mRNA expression of interleukin-6 and downregulation of adrenergic and angiotensin receptors were assessed on vascular and myocardial samples.ResultsPCZ-treated animals had reduced cDPP3 levels and required less norepinephrine and fluid than septic control animals for similar organ perfusion and regional blood flow. PCZ-treated animals had less myocardial injury, and higher PaO2/FiO2 ratios. PCZ was associated with lower circulating catecholamine levels; higher circulating angiotensin II and higher angiotensin II receptor type 1 myocardial protein expression, and with lower myocardial and radial artery mRNA interleukin-6 expression.ConclusionsIn an experimental model of septic shock, PCZ administration was associated with reduced fluid and catecholamine requirements, less myocardial injury and cardiovascular inflammation, along with preserved angiotensin II signaling.Graphical

Effects of remote ischemic preconditioning on early markers of intestinal injury in experimental hemorrhage in rats

The maintenance of intestinal integrity and barrier function under conditions of restricted oxygen availability is crucial to avoid bacterial translocation and local inflammation. Both lead to secondary diseases after hemorrhagic shock and might increase morbidity and mortality after surviving the initial event. Monitoring of the intestinal integrity especially in the early course of critical illness remains challenging. Since microcirculation and mitochondrial respiration are main components of the terminal stretch of tissue oxygenation, the evaluation of microcirculatory and mitochondrial variables could identify tissues at risk during hypoxic challenges, indicate an increase of intestinal injury, and improve our understanding of regional pathophysiology during acute hemorrhage. Furthermore, improving intestinal microcirculation or mitochondrial respiration, e.g. by remote ischemic preconditioning (RIPC) that was reported to exert a sufficient tissue protection in various tissues and was linked to mediators with vasoactive properties could maintain intestinal integrity. In this study, postcapillary oxygen saturation (µHbO2), microvascular flow index (MFI) and plasmatic d-lactate concentration revealed to be early markers of intestinal injury in a rodent model of experimental hemorrhagic shock. Mitochondrial function was not impaired in this experimental model of acute hemorrhage. Remote ischemic preconditioning (RIPC) failed to improve intestinal microcirculation and intestinal damage during hemorrhagic shock.

Isotonic hydroxyethyl starch is ineffective in restoring blood pressure during experimental septic shock: Implications for fluid resuscitation strategies

Objectives: The objectives of the study were to evaluate the effect of isotonic or hypertonic hydroxyethyl starch (HES) solutions on blood pressure and to assess the influence of the neurohypophyseal system on this response during experimental septic shock. Male Wistar rats were randomly allocated to undergo either cecal and ligation puncture (CLP) or a simulated surgical procedure (sham). Materials and Methods: Of 6 h post-surgery, either isotonic saline (0.9% sodium chloride, 4 mL/kg), isotonic (HES; at doses of 4, 8 or 16 mL/kg), or hypertonic saline-HES (HS-HES; 4 mL/kg) was administered through the endovenous route, followed by the recording of blood pressure and heart rate. In addition, the levels of sodium, vasopressin, and oxytocin were evaluated after the fluid infusion. Results: The administration of HES did not have a significant effect on blood pressure in our study. However, the HS-HES solution increased plasma osmolality, sodium, vasopressin, and oxytocin levels. Furthermore, the HS-HES induced a transient elevation in blood pressure immediately after infusion, which could be completely blunted by the pre-administration of a V1-vasopressin antagonist. Conclusion: Our results demonstrate that the infusion of an isotonic blood volume expander during experimental septic shock is ineffective in restoring blood pressure due to blood vessel compliance. In contrast, the infusion of a hypertonic solution stimulates vasopressin secretion and can transiently restore blood pressure.

Chemical Kinetic Analysis of High-Pressure Hydrogen Ignition and Combustion toward Green Aviation

In the framework of the “Multidisciplinary Optimization and Regulations for Low-boom and Environmentally Sustainable Supersonic aviation” project, pursued by a consortium of European government and academic institutions, coordinated by Politecnico di Torino under the European Commission Horizon 2020 financial support, the Italian Aerospace Research Centre is computationally investigating the high-pressure hydrogen/air kinetic combustion in the operative conditions typically encountered in supersonic aeronautic ramjet engines. This task is being carried out starting from the zero-dimensional and one-dimensional chemical kinetic assessment of the complex and strongly pressure-sensitive ignition behavior and flame propagation characteristics of hydrogen combustion through the validation against experimental shock tube and laminar flame speed measurements. The 0D results indicate that the kinetic mechanism by Politecnico di Milano and the scheme formulated by Kéromnès et al. provide the best matching with the experimental ignition delay time measurements carried out in high-pressure shock tube strongly argon-diluted reaction conditions. Otherwise, the best behavior in terms of laminar flame propagation is achieved by the Mueller scheme, while the other investigated kinetic mechanisms fail to predict the flame speeds at elevated pressures. This confirms the non-linear and intensive pressure-sensitive behavior of hydrogen combustion especially in the critical high-pressure and low-temperature region which is hard to be described by a single all-encompassing chemical model.

Learning thermodynamically constrained equations of state with uncertainty

Numerical simulations of high energy-density experiments require equation of state (EOS) models that relate a material’s thermodynamic state variables—specifically pressure, volume/density, energy, and temperature. EOS models are typically constructed using a semi-empirical parametric methodology, which assumes a physics-informed functional form with many tunable parameters calibrated using experimental/simulation data. Since there are inherent uncertainties in the calibration data (parametric uncertainty) and the assumed functional EOS form (model uncertainty), it is essential to perform uncertainty quantification (UQ) to improve confidence in EOS predictions. Model uncertainty is challenging for UQ studies since it requires exploring the space of all possible physically consistent functional forms. Thus, it is often neglected in favor of parametric uncertainty, which is easier to quantify without violating thermodynamic laws. This work presents a data-driven machine learning approach to constructing EOS models that naturally captures model uncertainty while satisfying the necessary thermodynamic consistency and stability constraints. We propose a novel framework based on physics-informed Gaussian process regression (GPR) that automatically captures total uncertainty in the EOS and can be jointly trained on both simulation and experimental data sources. A GPR model for the shock Hugoniot is derived, and its uncertainties are quantified using the proposed framework. We apply the proposed model to learn the EOS for the diamond solid state of carbon using both density functional theory data and experimental shock Hugoniot data to train the model and show that the prediction uncertainty is reduced by considering thermodynamic constraints.

Shock and contact interaction with a simple cubic array of particles

Shock-particle interaction is a fundamental pillar of multiphase compressible flows that has been studied at length for many decades. However, little attention has been paid to the interaction of particles with a contact interface that follows a shock in shock tube experiments and applications relating to blast waves. Presently, the phenomenon is studied at the microscale via particle resolved simulations of shock contact systems interacting with a structured array of particles as well as isolated particles. Simulations are conducted at particle volume fractions of 0%, 5%, 10%, 20%, and 40% at three contact Mach numbers. Additionally, the diaphragm position is varied, which controls the timing of the shock arrival time in relation to the contact arrival time. The modification to the drag on these stationary particles by the contact is analyzed and compared to the compressible Maxey–Riley–Gatignol model, which is adequate for the single particle cases but does not account for fluid mediated particle–particle interactions.

Study of IL-4 and IL-6 Levels and Complement Activity Comparatively in Blood and Lymph in Experimental Anaphylactic Shock and Arthus Phenomenon

The levels of interleukins IL-4 and IL-6 and the activity of complement in blood and lymph were studied in experimental anaphylactic shock and the Arthus phenomenon. The experiments were carried out on 27 Winstar rats in two series. The studied parameters of interleukins IL-4 and IL-6 and complement activity in the blood and lymph of intact animals served as control. The results of the study showed that the level of IL-4 in anaphylactic shock increases and IL-6 decreases. On the other hand, with the Arthus phenomenon, the level of IL-6 increases, IL-4 decreases. The titer of complement in atopic reactions sharply decreases, and it indicates the participation of complement together with IgG in the elimination of the allergen. In immunocomplex reactions, the complement titer also decreases.

Identification of Johnson-Cook material model parameters for laser shock peening process simulation for AA2024, Ti–6Al–4V and Inconel 718

This paper addresses the identification of Johnson-Cook material model parameters for the simulation of high strain rate processes such as laser shock peening. A combined numerical and experimental approach is described for the identification of the material parameters for AA2024-T3, Ti–6Al–4V, and Inconel 718 alloys. Validation of the parameters was performed based on depth-resolved residual stress profile evaluation after both experimental and numerical laser shock peening application. However, it has been observed that the strain rate-dependent coefficient identified at low strain rates is insufficient for accurately representing the behavior of the Ti–6Al–4V alloy. Consequently, there is a need to identify and determine the appropriate parameter specifically tailored to the strain rates that are relevant to the intended application of the material. The outcomes of this study provide significant insights into the accurate identification of Johnson-Cook material model parameters for laser shock peening simulations. The findings emphasize the critical importance of considering the strain rate-dependent coefficient C in the Johnson-Cook material model to enhance the accuracy and precision of representing material behavior in simulation efforts.

Neisseria meningitidis accumulate in large organs during meningococcal sepsis.

Neisseria meningitidis (Nm) is the cause of epidemic meningitis and fulminant meningococcal septicemia. The clinical presentations and outcome of meningococcal septic shock is closely related to the circulating levels of lipopolysaccharides (LPS) and of Neisseria meningitidis DNA (Nm DNA). We have previously explored the distribution of Nm DNA in tissues from large organs of patients dying of meningococcal septic shock and in a porcine meningococcal septic shock model. 1) To explore the feasibility of measuring LPS levels in tissues from the large organs in patients with meningococcal septic shock and in a porcine meningococcal septic shock model. 2) To evaluate the extent of contamination of non-specific LPS during the preparation of tissue samples. Plasma, serum, and fresh frozen (FF) tissue samples from the large organs of three patients with lethal meningococcal septic shock and two patients with lethal pneumococcal disease. Samples from a porcine meningococcal septic shock model were included. Frozen tissue samples were thawed, homogenized, and prepared for quantification of LPS by Pyrochrome® Limulus Amoebocyte Lysate (LAL) assay. N. meningitidis DNA and LPS was detected in FF tissue samples from large organs in all patients with meningococcal septic shock. The lungs are the organs with the highest LPS and Nm DNA concentration followed by the heart in two of the three meningococcal shock patients. Nm DNA was not detected in any plasma or tissue sample from patients with lethal pneumococcal infection. LPS was detected at a low level in all FF tissues from the two patients with lethal pneumococcal disease. The experimental porcine meningococcal septic shock model indicates that also in porcinis the highest LPS and Nm DNA concentration are detected in lungs tissue samples. The quantification analysis showed that the highest concentration of both Nm DNA and LPS are in the organs and not in the circulation of patients with lethal meningococcal septic shock. This was also shown in the experimental porcine meningococcal septic shock model. Our results suggest that LPS can be quantified in mammalian tissues by using the LAL assay.

Neutralization of extracellular histones by sodium-Β-O-methyl cellobioside sulfate in septic shock

BackgroundExtracellular histones have been associated with severity and outcome in sepsis. The aim of the present study was to assess the effects of sodium-β-O-Methyl cellobioside sulfate (mCBS), a histone-neutralizing polyanion, on the severity and outcome of sepsis in an experimental model.MethodsThis randomized placebo-controlled experimental study was performed in 24 mechanically ventilated female sheep. Sepsis was induced by fecal peritonitis. Animals were randomized to three groups: control, early treatment, and late treatment (n = 8 each). mCBS was given as a bolus (1 mg/kg) followed by a continuous infusion (1 mg/kg/h) just after sepsis induction in the early treatment group, and 4 h later in the late treatment group. Fluid administration and antimicrobial therapy were initiated 4 h T4 after feces injection, peritoneal lavage performed, and a norepinephrine infusion titrated to maintain mean arterial pressure (MAP) between 65–75 mmHg. The experiment was blinded and lasted maximum 24 h.ResultsDuring the first 4 h, MAP remained > 65 mmHg in the early treatment group but decreased significantly in the others (p < 0.01 for interaction, median value at T4: (79 [70–90] mmHg for early treatment, 57 [70–90] mmHg for late treatment, and 55 [49–60] mmHg for the control group). mCBS-treated animals required significantly less norepinephrine to maintain MAP than controls (p < 0.01 for interaction) and had lower creatinine (p < 0.01), lactate (p < 0.01), and interleukin-6 (p < 0.01) levels, associated with reduced changes in H3.1 nucleosome levels (p = 0.02). Early treatment was associated with lower norepinephrine requirements than later treatment. Two control animals died; all the mCBS-treated animals survived.ConclusionsNeutralization of extracellular histones with mCBS was associated with reduced norepinephrine requirements, improved tissue perfusion, less renal dysfunction, and lower circulating IL-6 in experimental septic shock and may represent a new therapeutic approach to be tested in clinical trials.

Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan

Thermochemical modeling and shock-tube experiments show that shocks applied to N2/CH4 gas mixtures can synthesize organic molecules. Sufficiently large, hypersonic meteoroids entering the atmosphere of Saturn’s moon Titan should therefore drive organic chemistry. To do so meteoroids must be sufficiently large compared to the atmospheric mean free path at a given altitude to generate shocks, and deposit enough energy per path length to produce temperatures high enough to excite and dissociate the relevant molecules. The Cassini spacecraft imaged multiple meteoroid impacts on Saturn’s rings, allowing for the first time an empirical estimate to be made of the flux and size–frequency distributions of meteoroids in the millimeter-to-meter size range. We combine these results with an atmospheric entry model and thermochemical and experimental shock production efficiencies for N2/CH4 atmospheres and calculate the shock production rates for HCN, C2H2, and C2H4 as well as the resulting H2 generation. We find that meteoroids may be producing these molecules at as much as ∼1% the production rate of photochemistry driven by UV photons, and may be depositing more energy than magnetospheric ions and 90–100 nm UV photons. Moreover, these meteoroids produce these organic molecules hundreds of kilometers lower in Titan’s atmosphere than the relevant UV photons and magnetospheric ions penetrate, with peak production occurring between 200 and 500 km altitudes, i.e., at the observed haze layer. Meteoroid-driven shock generation of molecules may therefore be crucial to understanding Titan’s atmospheric chemistry.

Combined Experimental and Numerical Investigation of a Hypersonic Turbulent Boundary Layer by Means of FLDI and Large-Eddy Simulations

This work investigates a hypersonic turbulent boundary layer over a 7° half angle cone at a wall-to-total temperature ratio of 0.1, M∞=7.4 and Re∞m=4.2×106 m−1, in terms of density fluctuations and the convection velocity of density disturbances. Experimental shock tunnel data are collected using a multi-foci Focused Laser Differential Interferometer (FLDI) to probe the boundary layer at several heights. In addition, a high-fidelity, time-resolved Large-Eddy Simulation (LES) of the conical flowfield under the experimentally observed free stream conditions is conducted. The experimentally measured convection velocity of density disturbances is found to follow literature data of pressure disturbances. The spectral distributions evidence the presence of regions with well-defined power laws that are present in pressure spectra. A framework to combine numerical and experimental observations without requiring complex FLDI post-processing strategies is explored using a computational FLDI (cFLDI) on the numerical solution for direct comparisons. Frequency bounds of 160 kHz &lt;f&lt;1 MHz are evaluated in consideration of the constraining conditions of both experimental and numerical data. Within these limits, the direct comparisons yield good agreement. Furthermore, it is verified that in the present case, the cFLDI algorithm may be replaced with a simple line integral on the numerical solution.

Particle-in-cell simulations of collisionless perpendicular shocks driven at a laser-plasma device

Experiments of generation of quasi-perpendicular collisionless shocks driven by laser plasma were performed at the Shenguang-II laser facility with intense lasers. Here, using a 1D particle-in-cell simulation code including protons, carbon ions, and electrons, we investigate the experimental shock formation via the interaction between the laser-ablated piston and ambient plasma magnetized by a large pre-existing magnetic field and the associated ion dynamics in more detail. Simulation results show that, given enough time and space, ambient protons and carbon ions can be reflected at the piston–ambient interface successively, which leads to the formation of corresponding shocks before the piston and interface. Electric fields associated with the initial interaction known as Larmor coupling and the shocks may accelerate ambient protons, carbon ions reflected at the interface or shocks, and piston ones transmitted to the ambient region before shock formation.

Microcirculatory effects of rewarming in experimental hemorrhagic shock.

Rewarming is a recommended therapy during the resuscitation of hypothermic patients with hemorrhagic shock. In experimental models, however, it increases inflammatory response and mortality. Although microcirculation is potential target of inflammation, the microvascular effects of rewarming during the resuscitation of hemorrhagic shock have not been studied. Our goal was to assess the systemic and microcirculatory effects of an increase in core temperature (T°) during the retransfusion of hemorrhagic shock in sheep. Our hypothesis was that rewarming could hamper microcirculation. In anesthetized and mechanically ventilated sheep, we measured systemic, intestinal, and renal hemodynamics and oxygen transport. O2 consumption (VO2) and respiratory quotient were measured by indirect calorimetry. Cortical renal, intestinal villi and sublingual microcirculation were assessed by IDF-videomicroscopy. After basal measurements, hemorrhagic shock was induced and T° was reduced to ~33°C. After 1h of shock and hypothermia, blood was retransfused and Ringer lactate solution was administered to prevent arterial hypotension. In the control group (n=12), T° was not modified, while in the intervention (rewarming) group, it was elevated ~3°C. Measurements were repeated after 1h. During shock, both groups showed similar systemic and microvascular derangements. After retransfusion, VO2 remained decreased compared to baseline in both groups, but was lower in the control compared to the rewarming group. Perfused vascular density has a similar behavior in both groups. Compared to baseline, it remained reduced in peritubular (control vs. rewarming group, 13.8 [8.7-17.5] vs. 15.7 [10.1-17.9] mm/mm2, PNS) and villi capillaries (14.7 [13.6-16.8] vs. 16.3 [14.2-16.9] mm/mm2, PNS), and normalized in sublingual mucosa (19.1 [16.0-20.3] vs. 16.6 [14.7-17.2] mm/mm2, PNS). This is the first experimental study assessing the effect of rewarming on systemic, regional, and microcirculatory perfusion in hypothermic hemorrhagic shock. We found that a 3°C increase in T° neither improved nor impaired the microvascular alterations that persisted after retransfusion. In addition, sublingual mucosa was less susceptible to reperfusion injury than villi and renal microcirculation.

Impact of β3-adrenergic receptor modulation on vascular function during experimental septic shock

Dysautonomia is an adverse event in septic shock (SC) associated with loss of cardiovascular variability. Modulation by β1-blockers is associated with cardiovascular benefits. Unlike β1-adrenergic (AR) receptors, β3-ARs are widely expressed on vascular level and, when stimulated, cause vasorelaxation. We hypothesize that during SC, vascular function could also be mediated by β3-ARs. The aim of the study is to assess the impact of β3-ARs modulation at the level of endothelial cells on vascular function during SC. We developed an inflammatory model using commercial human aortic endothelial cells (HAEC) stimulated with lipopolysaccharides (LPS, 10 μg/mL) to mimic SC conditions. These HAECs were treated 6 h for the transcriptional evaluations (PCR) and 24 h for the protein evaluations (WB). Then, the β3-AR was modulated with an agonist (CL316243, 1 μM) and antagonist (SR59230A, 1 μM) and its impact on different markers was assessed as inflammatory markers (VCAM-1, ICAM-1), expression of other β-ARs, NO synthases (eNOS, iNOS) and cell permeability. Finally, the expression of β3-AR was evaluated using murine vascular tissue samples (thoracic aorta and mesenteric arteries) lysed for PCR and WB detection. The expression of endothelial surface inflammatory markers (VCAM-1, ICAM-1) and the activation of NFκB were increased in LPS condition, validating the inflammatory model. Additionally, LPS induced a decreased transcriptional expression of β1 and 2-AR. In LPS condition, eNOS was decreased, while iNOS as well as cell permeability were increased. However, β3-AR expression was not demonstrated on HEACs, and the addition of agonist or antagonist had not induced any change on the above mentioned markers. Although, we demonstrated the expression of β3-AR in mouse aortic and mesenteric vessels at the genetic and protein level, allowing the study of the modulation of this receptor in vivo. The concept of decatecholamines emerged in order to minimize the use of catecholamines in SC management. Blockade of β-AR is a therapeutic approach aimed at downregulating adrenergic stimulation during SC. While β1-ARs have been widely studied, there are no data on β3-ARs, so characterization of the β3-AR is required and could play a significant role in septic vascular dysfunction.

Enteral protease inhibition reduces systemic enzymatic activity and proteolysis after experimental trauma-hemorrhagic shock

Trauma-hemorrhagic shock (T-HS) is a major cause of multiorgan failure and mortality world-wide. Our previous work demonstrates that uncontrolled proteolysis in T-HS is associated with poor outcomes and that enteral inhibition of proteolytic activity may be beneficial. However, the enzymes involved, their degradation products, and the systemic consequences of protease activity in T-HS are not well understood. Our aim was to identify plasma enzymatic activity and the resulting peptidome in experimental T-HS, and determine the changes in this activity following enteral protease inhibition. Anesthetized male Wistar rats (~400g) were subjected to T-HS via laparotomy followed by blood removal to achieve a mean blood pressure of ~35-40mmHg for 90 min. An orogastric catheter was passed through the mouth into the proximal duodenum and Golytely (Shock-control, n=8) or Golytely+gabexate mesilate, 10mg/kg (GM-treated, n=8) was enterally infused starting 30 minutes into the shock period. Animals were resuscitated with Lactated Ringers solution (LR) and monitored for 120 min after reperfusion. The gabexate mesilate treatment improved mean arterial pressure after reperfusion (57.6±4.3 mmHg) compared to Shock-control group (43.7±4.5mmHg, p&lt;0.0001) requiring significantly less resuscitation fluid (14±3ml vs 25.7±2.3 ml, respectively, p&lt;0.0001). Systemic proteolysis, as measured by the plasma peptidome, increased by 630±212% in the Shock-control group compared to baseline, and was mitigated by treatment with gabexate mesilate to 203±70% (p=0.02). Using tagged fluorescent substrates, trypsin-like activity in plasma increased with T-HS to 937±90% of baseline (p&lt;0.0001) and was reduced by enteral protease inhibition to 321±72% of baseline (p=0.0321 vs. baseline, p=0.0078 vs. Shock-control). The most common proteins to be degraded were structural (myosin, actin, and collagen), coagulation-related (inter-alpha trypsin inhibitor, kininogen, complement C4, and fibrinogen) and metabolic in function (apolipoprotein E, fructose-bisphosphate aldolase, and carbonyl reductase). These proteins were cleaved after T-HS 1.5-4 times more in the Shock-control compared to the GM-treated group. In conclusion, we were able to identify trypsin-like activity in plasma from animals subjected to T-HS. Enteral inhibition of serine proteases was able to significantly decrease this activity and improve outcomes, suggesting that the gut is a driver of uncontrolled proteolysis and resulting morbidity in T-HS. Enteral serine protease inhibition may be an effective clinical strategy for decreasing inappropriate systemic proteolysis and improving outcomes in T-HS. This work was supported by the Office of the Assistant Secretary of Defense for Health Affairs and the Defense Health Agency J9, Research and Development Directorate under Award No. W81XWH-17-2-0047. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Laser absorption study of the N2+ O → NO + N and NO + O → O2+ N Zeldovich reactions in shock-heated N2O mixtures

The fast decomposition of nitrous oxide (N2O) into molecular nitrogen (N2) and atomic oxygen (O) was leveraged to probe the N2 + O and NO + O Zeldovich reactions behind reflected shocks in experiments spanning 2000–6800 K and 0.04–1.67 atm in 1% and 5% N2O diluted in either argon (Ar) or N2, respectively. One infrared (IR) and two ultraviolet (UV) laser absorption diagnostic systems probed N2O and NO. The IR laser system probed N2O in isolation, while the two UV laser systems probed a combination of N2O, NO, and O2 using an online/offline method. The resulting absorbance time-histories were used to infer the NO rotational temperature and the number densities of N2O and NO. The number density time-histories were used to infer (1) the N2O dissociation rate to form N2 and O ( k d N 2 O − [ M ]), (2) the reaction rate of N2O and O to form two NO ( k d N 2 O − O , 1), (3) the NO + O Zeldovich reaction rate ( k z NO − O), and (4) the N2 + O Zeldovich reaction rate ( k z N 2 − O). The experiments were insensitive to the reaction rate of N2O and O to form O2 and N2 ( k d N 2 O − O , 2) at high temperatures. Generally, k d N 2 O − [ M ] was inferred from IR and UV offline data, with k d N 2 O − O , 1, k z NO − O, and k z N 2 − O inferred from UV online data in Ar and N2 dilution. Each inferred reaction rate shows consistency with literature, while extending data to higher temperatures with reduced uncertainty. The reduced uncertainty is sufficient to enable comparisons of the data to various high-temperature quantum chemistry models.

The Protective Effects of Goitrin on LPS-Induced Septic Shock in C57BL/6J Mice via Caspase-11 Non-Canonical Inflammasome Inhibition.

Septic shock is defined as a subset of sepsis, which is associated with a considerably high mortality risk. The caspase-11 non-canonical inflammasome is sensed and activated by intracellular lipopolysaccharide (LPS) leading to pyroptosis, it plays a critical role in septic shock. However, there are few known drugs that can control caspase-11 non-canonical inflammasome activation. We report here that goitrin, an alkaloid from Radix Isatidis, shows protective effects in LPS-induced septic shock and significant inhibitory effect in caspase-11 non-canonical inflammasome pathway. Male C57BL/6J were injected intraperitoneally with LPS (20 mg/kg) to induce experimental septic shock. The results demonstrated that the survival rates of mice pretreated with goitrin or Toll-like receptor 4 (TLR4) inhibitor TKA-242 increased, and LPS-induced hypothermia and lung damage improved by inhibiting inflammatory response. Elucidating the detailed mechanism, we surprisingly found goitrin is really different from TAK-242, it independent of the TLR4 signal activation, but significantly inhibited the activation of caspase-11 non-canonical inflammasome, including cleaved caspase-11 and N-terminal fragment of gasdermin D (GSDMD-NT). Furthermore, with a nonlethal dose of the TLR3 agonist poly(I:C)-primed and subsequently challenged with LPS to induce caspase-11-mediated lethal septic shock, the efficacy of goitrin had been verified. Those results revealed the effect of goitrin in protective against LPS-induced septic shock via inhibiting caspase-11 non-canonical inflammasome, which provided a new therapeutic strategy for clinical treatment of septic shock.