Endotoxin Infusion Research Articles

Hemoadsorption improves kidney microcirculatory oxygenation and oxygen consumption, ameliorates tubular injury, and improves kidney function in a rat model of sepsis-induced AKI

Microcirculatory dysfunction, hypoxia, and inflammation are considered to be central in the pathogenesis of sepsis-induced acute kidney injury (AKI). In this experimental study, we hypothesized that extracorporeal removal of inflammatory cytokines by hemoadsorption (HA) therapy may mitigate renal injury associated with sepsis-induced AKI. To this end, we investigated renal microcirculatory oxygenation and perfusion, oxygen consumption, lactate, systemic hemodynamic variables, tubular cell integrity, inflammatory mediators, and kidney function in a rat model of septic AKI elicited by endotoxin infusion. Three groups of rats were investigated on extracorporeal circulation: HA only, LPS, and LPS + HA. Endotoxin infusion reduced cortex microcirculatory oxygenation and raised creatinine and lactate levels. Renal microcirculatory oxygenation, measured by two independent techniques (phosphorescence (µPO2) and spectrophotometry/Doppler (µHbO2sat and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu \ ext{RBCv}$$\\end{document})), was ameliorated by HA therapy. The renal oxygen consumption, lactate and creatinine levels were restored in the LPS + HA group. A reduced amount of injured tubular cells was found in histological analysis of the kidneys. This experimental study demonstrated an improvement in multiple determinants of kidney oxygenation, damage, and systemic blood perfusion by HA in a clinically relevant rat model of septic AKI. Further studies are needed to optimize and support the clinical use of HA as a renal protective strategy.

Capnodynamic assessment of mixed venous oxygen saturation in a porcine experimental endotoxemic model.

Sepsis continues to be a major cause of death and illness globally, posing significant challenges for healthcare professionals. In the pursuit of more accurate and timely monitoring tools, the concept of capnodynamically derived mixed venous oxygen saturation (Capno-SvO2) has emerged as a promising method. Capno-SvO2 provides a non-invasive way to assess and track SvO2 and could serve as an additional tool alongside more invasive methods like the pulmonary artery catheter. This could potentially be of great value in the care of critically ill patients with sepsis, where alternative minimal invasive monitoring methods may vary in reliability. The aim of the current study was to compare capno-SvO2 against values obtained through pulmonary artery blood sample CO-oximetry and continuous fiberoptic SvO2 monitoring, using a well-established porcine experimental sepsis model. Anesthetized pigs were exposed to a standardized endotoxin infusion sepsis protocol, followed by a series of maneuvers typically applied in sepsis care. Simultaneous recordings were done throughout the experiment for all three monitoring methods. Bland-Altman analysis corrected for repeated measurements was used to assess the agreement of absolute values between the paired recording of CO-oximetry and Capno-SvO2 as well as between CO-oximetry and fiberoptic SvO2. The ability of Capno-SvO2 and fiberoptic SvO2 to track changes was assessed by concordance rate. A total of 10 animals and 275 paired datapoints were included in the study. The majority of the animals displayed pronounced hemodynamical instability in response to endotoxin exposure and subsequent treatment interventions. Analysis of all paired data points showed a bias between Capno-SvO2 and CO-oximetry SvO2 of + 1% with 95% limits of agreement of -14% to + 17%. The corresponding numbers for fiberoptic SvO2 and CO-oximetry SvO2 were -4% and -15% to + 8%. The concordance rate as compared to CO-oximetry, were 97% and 93% for Capno-SvO2 and fiberoptic SvO2, respectively. In this experimental sepsis model, continuous, non-invasive Capno-SvO2 generates average absolute values comparable to the gold standard CO-oximetry albeit with relatively wide limits of agreement. Capno-SvO2 displayed a concordance rate of 97% against CO-oximetry and exhibits better trending ability compared to invasive fiberoptic SvO2.

Abnormalities of Coagulation and Fibrinolysis Assessed by Thromboelastometry in an Endotoxic Shock Model in Piglets Treated with Nitric Oxide and Hydrocortisone.

This is an animal model study to investigate changes in hemostasis during endotoxemic shock and to determine whether the combination of inhaled nitric oxide (iNO) + intravenous hydrocortisone had an effect on clot formation and fibrinolysis. iNO selectively decreases pulmonary artery pressure, without affecting cardiac index or systemic vascular resistance; however, the results of studies on the possible consequences of iNO administration on coagulation are inconsistent and require further research. Thirty-four piglets were included. Administering endotoxin caused severe hypodynamic shock. Half of the animals received iNO (30 ppm) + hydrocortisone, starting 3 h after endotoxin infusion and continuing to the end of the study. All animals developed coagulation disorders, manifested by a tendency to hypocoagulation; at the same time, fibrinolysis was impaired. Coagulation and fibrinolysis disorders persisted after endotoxin infusion was discontinued, with worse severity in the animals that died before the study was terminated. Administering iNO + hydrocortisone did not cause further changes in coagulation and fibrinolysis parameters, either during or after the endotoxin challenge, suggesting that potential therapeutic interventions with iNO to lower pulmonary arterial pressure will not affect hemostasis.

Different Preclinical Animal Models for Sepsis

Sepsis is a significant cause of illness and death, primarily due to the multiple organ dysfunction it can induce. Despite promising results in preclinical studies, most clinical trials testing new treatment strategies for sepsis have failed to show effectiveness. One possible reason for this discrepancy is the misinterpretation of preclinical data, particularly when using animal models that do not adequately mimic human sepsis. This review discusses the potential and limitations of various animal models used in sepsis research, aiming to determine the extent to which these findings are applicable to human sepsis. These animal models encompass different methods such as intravascular infusion of endotoxin or live bacteria, bacterial peritonitis, cecal ligation and perforation, soft tissue infection, pneumonia, and meningitis models. Animal models are crucial in developing new sepsis therapies because they provide essential information about pharmacokinetics, toxicity, and the mechanisms of drug action that cannot be obtained through other means. They offer insights into drugs and initial treatments interact with the body, assess the safety and efficacy of drugs, and investigate the underlying mechanisms of sepsis. However, it is important to acknowledge the limitations of animal models. Animals used in research may not fully replicate the complexity and heterogeneity of human sepsis, leading to differences in treatment response. Ethical considerations also restrict certain invasive procedures in human subjects that can be performed in animal models. These factors contribute to challenges in translating preclinical findings into successful clinical trials.

ACETAMINOPHEN ATTENUATES PULMONARY VASCULAR RESISTANCE AND PULMONARY ARTERIAL PRESSURE AND INHIBITS CARDIOVASCULAR COLLAPSE IN A PORCINE MODEL OF ENDOTOXEMIA.

Acetaminophen (paracetamol) is often used in critically ill patients with fever and pain; however, little is known about the effects of acetaminophen on cardiovascular function during systemic inflammation. Here, we investigated the effect of acetaminophen on changes in the systemic and pulmonary circulation induced by endotoxin (0.5 μg/kg per hour) in anesthetized pigs. Endotoxin infusion led to a rapid increase in pulmonary artery pressure and pulmonary vascular resistance index. Acetaminophen delayed and attenuated this increase. Furthermore, acetaminophen reduced tachycardia and decreased stroke volume, accompanied by systemic inflammation, without affecting inflammatory parameters such as white blood cell count and TNF-α in blood. As a proof of concept, we injected a high dose of endotoxin (100 μg), which induced rapid cardiovascular collapse in pigs. Pigs treated with acetaminophen survived with no obvious hemodynamic instability during the 50-min observation period. In conclusion, acetaminophen attenuates the effects of endotoxin on pulmonary circulation in anesthetized pigs. This may play a role in severe systemic inflammation.

Interleukin-8 and depressive responses to an inflammatory challenge: secondary analysis of a randomized controlled trial

Emerging evidence suggests that interleukin (IL)-8 has a protective role in the context of depression. Higher levels of IL-8 are associated with lower depressive symptom severity among depressed patients, and treatment-related increases in IL-8 correlate with a positive response in depressed patients. This study (a secondary analysis of a completed randomized controlled trial) aimed to examine whether higher levels of IL-8 mitigate increases in depressed mood in response to an experimental model of inflammation induced depression. Given epidemiologic relationships identified between IL-6, tumor necrosis factor (TNF)- α, and subsequent depression, levels of these pro-inflammatory cytokines were also explored as potential moderators of depressed mood response to endotoxin. Secondary analyses were completed on data from healthy adults (n = 114) who completed a double-blind, placebo-controlled randomized trial in which participants were randomly assigned to receive either a single infusion of low-dose endotoxin (derived from Escherichia coli; 0.8 ng/kg of body weight) or placebo (same volume of 0.9% saline). IL-8, as well as IL-6 and TNF- α, were measured at baseline prior to infusion, and depressed mood and feelings of social disconnection were assessed approximately hourly. Baseline levels of IL-8, but not IL-6 or TNF-α, moderated depressed mood (β = − 0.274, p = .03) and feelings of social disconnection (β = − 0.307, p = .01) responses, such that higher baseline IL-8 was associated with less increase in depressed mood and feelings of social disconnection in the endotoxin, but not placebo, condition. IL-8 had threshold effects, in which highest quartile IL-8 (≥ 2.7 pg/mL) attenuated increases in depressed mood in response to endotoxin as compared to lower IL-8 quartiles (p = .02). These findings suggest that IL-8 may be a biological factor that mitigates risk of inflammation-associated depression.Clinical trials registration: ClinicalTrials.gov NCT01671150, registration date 23/08/2012.

Differential Protein Expression among Two Different Ovine ARDS Phenotypes-A Preclinical Randomized Study.

Despite decades of comprehensive research, Acute Respiratory Distress Syndrome (ARDS) remains a disease with high mortality and morbidity worldwide. The discovery of inflammatory subphenotypes in human ARDS provides a new approach to study the disease. In two different ovine ARDS lung injury models, one induced by additional endotoxin infusion (phenotype 2), mimicking some key features as described in the human hyperinflammatory group, we aim to describe protein expression among the two different ovine models. Nine animals on mechanical ventilation were included in this study and were randomized into (a) phenotype 1, n = 5 (Ph1) and (b) phenotype 2, n = 4 (Ph2). Plasma was collected at baseline, 2, 6, 12, and 24 h. After protein extraction, data-independent SWATH-MS was applied to inspect protein abundance at baseline, 2, 6, 12, and 24 h. Cluster analysis revealed protein patterns emerging over the study observation time, more pronounced by the factor of time than different injury models of ARDS. A protein signature consisting of 33 proteins differentiated among Ph1/2 with high diagnostic accuracy. Applying network analysis, proteins involved in the inflammatory and defense response, complement and coagulation cascade, oxygen binding, and regulation of lipid metabolism were activated over time. Five proteins, namely LUM, CA2, KNG1, AGT, and IGJ, were more expressed in Ph2.

Near-Infrared Spectroscopy-Derived Dynamic Cerebral Autoregulation in Experimental Human Endotoxemia-An Exploratory Study.

Cerebral perfusion may be altered in sepsis patients. However, there are conflicting findings on cerebral autoregulation (CA) in healthy participants undergoing the experimental endotoxemia protocol, a proxy for systemic inflammation in sepsis. In the current study, a newly developed near-infrared spectroscopy (NIRS)-based CA index is investigated in an endotoxemia study population, together with an index of focal cerebral oxygenation.Methods: Continuous-wave NIRS data were obtained from 11 healthy participants receiving a continuous infusion of bacterial endotoxin for 3 h (ClinicalTrials.gov NCT02922673) under extensive physiological monitoring. Oxygenated–deoxygenated hemoglobin phase differences in the (very)low frequency (VLF/LF) bands and the Tissue Saturation Index (TSI) were calculated at baseline, during systemic inflammation, and at the end of the experiment 7 h after the initiation of endotoxin administration.Results: The median (inter-quartile range) LF phase difference was 16.2° (3.0–52.6°) at baseline and decreased to 3.9° (2.0–8.8°) at systemic inflammation (p = 0.03). The LF phase difference increased from systemic inflammation to 27.6° (12.7–67.5°) at the end of the experiment (p = 0.005). No significant changes in VLF phase difference were observed. The TSI (mean ± SD) increased from 63.7 ± 3.4% at baseline to 66.5 ± 2.8% during systemic inflammation (p = 0.03) and remained higher at the end of the experiment (67.1 ± 4.2%, p = 0.04). Further analysis did not reveal a major influence of changes in several covariates such as blood pressure, heart rate, PaCO2, and temperature, although some degree of interaction could not be excluded.Discussion: A reversible decrease in NIRS-derived cerebral autoregulation phase difference was seen after endotoxin infusion, with a small, sustained increase in TSI. These findings suggest that endotoxin administration in healthy participants reversibly impairs CA, accompanied by sustained microvascular vasodilation.

Sildenafil in endotoxin-induced pulmonary hypertension: an experimental study

BackgroundSepsis and septic shock still represent great challenges in critical care medicine. Sildenafil has been largely used in the treatment of pulmonary arterial hypertension, but its effects in sepsis are unknown. The aim of this study was to investigate the hypothesis that sildenafil can attenuate endotoxin-induced pulmonary hypertension in a porcine model of endotoxemia. MethodsTwenty pigs were randomly assigned to Control group (n.ß=.ß10), which received saline solution; or to Sildenafil group (n.ß=.ß10), which received sildenafil orally (100.ßmg). After 30.ßminutes, both groups were submitted to endotoxemia with intravenous bacterial lipopolysaccharide endotoxin (LPS) infusion (4.ß..g.kg-1.h-1) for 180.ßminutes. We evaluated hemodynamic and oxygenation functions, and also lung histology and plasma cytokine (TNF.., IL-1.., IL6, and IL10) and troponin I response. ResultsSignificant hemodynamic alterations were observed after 30.ßminutes of LPS continuous infusion, mainly in pulmonary arterial pressure (from Baseline 19.ß...ß2.ßmmHg to LPS30 52.ß...ß4.ßmmHg, p.ß<.ß0.05). There was also a significant decrease in PaO2/FiO2 (from Baseline 411.ß...ß29 to LPS180 334.ß...ß49, p.ß<.ß0.05). Pulmonary arterial pressure was significantly lower in the Sildenafil group (35.ß...ß4.ßmmHg at LPS30, p.ß<.ß0.05). The Sildenafil group also presented lower values of systemic arterial pressure. Sildenafil maintained oxygenation with higher PaO2/FiO2 and lower oxygen extraction rate than Control group but had no effect on intrapulmonary shunt. All cytokines and troponin increased after LPS infusion in both groups similarly. ConclusionSildenafil attenuated endotoxin-induced pulmonary hypertension preserving the correct heart function without improving lung lesions or inflammation.

Platelet dysfunction in a large-animal model of endotoxic shock; effects of inhaled nitric oxide and low-dose steroid

ObjectiveThe role of inhaled nitric oxide in the treatment of shock remains controversial and further translational research is needed. Long-term observation studies using a model of endotoxin-induced shock to assess the effect of inhaled nitric oxide on platelet aggregation have not yet been reported. Approach and resultsThe tests were carried out in an animal model of shock in two 10-h periods. During the first 10 h, endotoxin was infused and the inhibition of platelet aggregation was evaluated; following the termination of endotoxin infusion, the restoration of platelet aggregation was assessed for 10 h. A total of 30 pigs were used (NO group, N = 14; control, N = 16). In the NO group, nitric oxide inhalation (30 ppm) was started 3 h after endotoxin infusion and continued until the end of the study. Treatment with NO selectively decreased pulmonary artery pressure at 4 (p = 0.002) and 8 h (p = 0.05) of the experiment as compared to the control. Endotoxin significantly reduced platelet aggregation, as indicated by the decreased activity of platelet receptors: ASPI, ADP, collagen, and TRAP during the experiment (p < 0.001). Endotoxin had no significant effect on changes in the response of the receptor after ristocetin stimulation. After stopping endotoxin infusion, a significant restoration of receptor activity was observed for collagen and TRAP, while ASPI and ADP remained partially depressed. Inhaled nitric oxide did not cause additional inhibition of platelet aggregation, either during or after endotoxin challenge. ConclusionsA profound reduction in platelet aggregation was observed during endotoxic shock. After stopping endotoxin infusion a restoration of platelet receptor activity was seen. The inhibition of platelet aggregation induced by endotoxin infusion was not intensified by nitric oxide, indicating there was no harmful effect of inhaled nitric oxide on platelet aggregation.

Regional venous\u2013arterial CO2 to arterial\u2013venous O2 content difference ratio in experimental circulatory shock and hypoxia

BackgroundVenous–arterial carbon dioxide (CO2) to arterial–venous oxygen (O2) content difference ratio (Cv-aCO2/Ca-vO2) > 1 is supposed to be both sensitive and specific for anaerobic metabolism. What regional hemodynamic and metabolic parameters determine the ratio has not been clarified.ObjectivesTo address determinants of systemic and renal, spleen, gut and liver Cv-aCO2/Ca-vO2.MethodsPost hoc analysis of original data from published experimental studies aimed to address effects of different fluid resuscitation strategies on oxygen transport, lactate metabolism and organ dysfunction in fecal peritonitis and endotoxin infusion, and from animals in cardiac tamponade or hypoxic hypoxia. Systemic and regional hemodynamics, blood flow, lactate uptake, carbon dioxide and oxygen-derived variables were determined. Generalized estimating equations (GEE) were fit to assess contributors to systemic and regional Cv-aCO2/Ca-vO2.ResultsMedian (range) of pooled systemic Cv-aCO2/Ca-vO2 in 64 pigs was 1.02 (0.02 to 3.84). While parameters reflecting regional lactate exchange were variably associated with the respective regional Cv-aCO2/Ca-vO2 ratios, only regional ratios were independently correlated with systemic ratio: renal Cv-aCO2 /Ca-vO2 (β = 0.148, 95% CI 0.062 to 0.234; p = 0.001), spleen Cv-aCO2/Ca-vO2 (β = 0.065, 95% CI 0.002 to 0.127; p = 0.042), gut Cv-aCO2/Ca-vO2 (β = 0.117, 95% CI 0.025 to 0.209; p = 0.013), liver Cv-aCO2/Ca-vO2 (β = − 0.159, 95% CI − 0.297 to − 0.022; p = 0.023), hepatosplanchnic Cv-aCO2/Ca-vO2 (β = 0.495, 95% CI 0.205 to 0.786; p = 0.001).ConclusionIn a mixed set of animals in different shock forms or during hypoxic injury, hepatosplanchnic Cv-aCO2/Ca-vO2 ratio had the strongest independent association with systemic Cv-aCO2/Ca-vO2, while no independent association was demonstrated for lactate or hemodynamic variables.

Lung-protective ventilation suppresses systemic and hepatic vein levels of cell-free DNA in porcine experimental post-operative sepsis

BackgroundPlasma levels of cell-free DNA (cf-DNA) are known to be elevated in sepsis and high levels are associated with a poor prognosis. Mechanical ventilation affects systemic inflammation in which lung-protective ventilation attenuates the inflammatory response. The aim was to study the effect of a lung protective ventilator regime on arterial and organ-specific venous blood as well as on trans-organ differences in cf-DNA levels in a porcine post-operative sepsis model.MethodOne group of anaesthetised, domestic-breed, 9–12 weeks old, pigs were ventilated with protective ventilation (VT 6 mL x kg− 1, PEEP 10 cmH2O) n = 20. Another group, ventilated with a medium high tidal volume and lower PEEP, served as a control group (VT 10 mL x kg− 1, PEEP 5 cm H2O) n = 10. Blood samples were taken from four sources: artery, hepatic vein, portal vein and, jugular bulb. A continuous endotoxin infusion at 0.25 μg x kg− 1 x h− 1 for 5 h was started following 2 h of laparotomy, which simulated a surgical procedure. Inflammatory cytokines and cf-DNA in plasma were analysed and trans-organ differences calculated.ResultsThe protective ventilation group had lower levels of cf-DNA in arterial (p = 0.02) and hepatic venous blood (p = 0.03) compared with the controls. Transhepatic differences in cf-DNA were lower in the protective group, compared with the controls (p = 0.03). No differences between the groups were noted as regards the transcerebral, transsplanchnic or the transpulmonary cf-DNA differences.ConclusionsProtective ventilation suppresses arterial levels of cf-DNA. The liver seems to be a net contributor to the systemic cf-DNA levels, but this effect is attenuated by protective ventilation.

The aptamer BT200 effectively inhibits von Willebrand factor (VWF) dependent platelet function after stimulated VWF release by desmopressin or endotoxin

Von Willebrand factor (VWF) plays a major role in arterial thrombosis. Antiplatelet drugs induce only a moderate relative risk reduction after atherothrombosis, and their inhibitory effects are compromised under high shear rates when VWF levels are increased. Therefore, we investigated the ex vivo effects of a third-generation anti-VWF aptamer (BT200) before/after stimulated VWF release. We studied the concentration-effect curves BT200 had on VWF activity, platelet plug formation under high shear rates (PFA), and ristocetin-induced platelet aggregation (Multiplate) before and after desmopressin or endotoxin infusions in healthy volunteers. VWF levels increased > 2.5-fold after desmopressin or endotoxin infusion (p < 0.001) and both agents elevated circulating VWF activity. At baseline, 0.51 µg/ml BT200 reduced VWF activity to 20% of normal, but 2.5-fold higher BT200 levels were required after desmopressin administration (p < 0.001). Similarly, twofold higher BT200 concentrations were needed after endotoxin infusion compared to baseline (p < 0.011). BT200 levels of 0.49 µg/ml prolonged collagen-ADP closure times to > 300 s at baseline, whereas 1.35 µg/ml BT200 were needed 2 h after desmopressin infusion. Similarly, twofold higher BT200 concentrations were necessary to inhibit ristocetin induced aggregation after desmopressin infusion compared to baseline (p < 0.001). Both stimuli elevated plasma VWF levels in a manner representative of thrombotic or pro-inflammatory conditions such as arterial thrombosis. Even under these conditions, BT200 potently inhibited VWF activity and VWF-dependent platelet function, but higher BT200 concentrations were required for comparable effects relative to the unstimulated state.

The bioflavonoid quercetin improves pathophysiology in a rat model of preeclampsia

Preeclampsia (PE) is a pregnancy-specific hypertensive syndrome and is a leading risk of thousands of patient and offspring’s deaths worldwide with no effective therapies but early delivery. Quercetin is associated with multiple pathways that link placental dysfunction with the maternal system phenotypes in the pathogenesis of PE, however, whether quercetin can be used to treat preeclampsia is not known. We employed a preeclampsia animal model induced by ultra-low-dose endotoxin infusion and monitored angiogenic factors, inflammatory response and oxidative stress changes after quercetin treatment. We showed that quercetin attenuated multi-pathophysiology changes induced by LPS and ameliorated the symptoms. We concluded that quercetin significantly improved the pathophysiology in PE and could be developed as candidates for preeclampsia treatment.

The impact of the systemic inflammatory response on hepatic bacterial elimination in experimental abdominal sepsis

BackgroundBacterial translocation from the gut has been suggested to induce a systemic inflammatory response syndrome (SIRS) and organ dysfunction. The liver has a pivotal role in eliminating circulating bacteria entering from the gut. We investigated whether pre-existing inflammation affects hepatic bacterial elimination.MethodsFifteen anaesthetised piglets were infused with E. coli in the portal vein for 3 h. The naive group (n = 6) received the bacterial infusion without endotoxin exposure. SIRS (SIRS group, n = 6) was induced by endotoxin infusion 24 h before the bacterial infusion. For effects of anaesthesia, controls (n = 3) received saline instead of endotoxin for 24 h. Bacterial counts and endotoxin levels in the portal and hepatic veins were analysed during bacterial infusion.ResultsThe bacterial killing rate was higher in the naive group compared with the SIRS group (p = 0.001). The ratio of hepatic to portal venous bacterial counts, i.e. the median bacterial influx from the splanchnic circulation, was 0.06 (IQR 0.01–0.11) in the naive group and 0.71 (0.03–1.77) in the SIRS group at 3 h, and a magnitude lower in the naive group during bacteraemia (p = 0.03). Similar results were seen for hepatic endotoxin elimination. Peak log tumour necrosis factor alpha was higher in the naive 4.84 (4.77–4.89) vs. the SIRS group 3.27 (3.26–3.32) mg/L (p < 0.001).ConclusionsOur results suggest that hepatic bacterial and endotoxin elimination is impaired in pigs with pre-existing SIRS while the inflammatory response to bacterial infusion is diminished. If similar mechanisms operate in human critical illness, the hepatic elimination of bacteria from the gut could be impaired by SIRS.

A non-linear mixed effect model for innate immune response: In vivo kinetics of endotoxin and its induction of the cytokines tumor necrosis factor alpha and interleukin-6.

Endotoxin, a component of the outer membrane of Gram-negative bacteria, has been extensively studied as a stimulator of the innate immune response. However, the temporal aspects and exposure-response relationship of endotoxin and resulting cytokine induction and tolerance development is less well defined. The aim of this work was to establish an in silico model that simultaneously captures and connects the in vivo time-courses of endotoxin, tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and associated tolerance development. Data from six studies of porcine endotoxemia in anesthetized piglets (n = 116) were combined and used in the analysis, with purified endotoxin (Escherichia coli O111:B4) being infused intravenously for 1–30 h in rates of 0.063–16.0 μg/kg/h across studies. All data were modelled simultaneously by means of importance sampling in the non-linear mixed effects modelling software NONMEM. The infused endotoxin followed one-compartment disposition and non-linear elimination, and stimulated the production of TNF-α to describe the rapid increase in plasma concentration. Tolerance development, observed as declining TNF-α concentration with continued infusion of endotoxin, was also driven by endotoxin as a concentration-dependent increase in the potency parameter related to TNF-α production (EC50). Production of IL-6 was stimulated by both endotoxin and TNF-α, and four consecutive transit compartments described delayed increase in plasma IL-6. A model which simultaneously account for the time-courses of endotoxin and two immune response markers, the cytokines TNF-α and IL-6, as well as the development of endotoxin tolerance, was successfully established. This model-based approach is unique in its description of the time-courses and their interrelation and may be applied within research on immune response to bacterial endotoxin, or in pre-clinical pharmaceutical research when dealing with study design or translational aspects.

A Comparative Evaluation of Different Treatment Regimens in Endotoxemic Buffalo Calves—A Physio-Pathological Perspective

Fifteen apparently healthy male buffalo calves aged between 6 months to one year with body weight range of 70 - 140 Kg divided into 3 groups of 5 buffalo calves each were used in the present investigation. Endotoxic shock was produced by IV infusion of Escherichia coli endotoxin @ 5 μg/kg BW/hr for 3 hours followed by administration of three different treatment regimens comprising of intravenous infusion of hypertonic saline solution(HSS) @ 4 ml/Kg bw, flunixin meglumine @ 1.1 mg/Kg bw and blood @ 20 ml/Kg bw to group-I, HSS, Dextran-40 and Flunixin meglumine to group-II and HSS, Dextran-40, whole blood and Flunixin meglumine to group-III with the objectives to study the major physio-pathological changes during induced endotoxemia in buffalo calves and to compare the effects of different treatment options to find out the best treatment option out of the three combinations. All the animals were further observed up to day 2 or death whichever was earlier. Endotoxin infusion to all the animals caused symptoms of restlessness, respiratory distress, snoring, diarrhoea, profuse salivation along with the significant hypoproteinemia, hypoalbuminemia, hypoglobulinemia, hypokalemia and hypocalcemia. The treatment with HSS, flunixin meglumine and blood infused as one time infusion to these endotoxemic buffalo calves not only alleviated the above mentioned symptoms but also significantly raised the circulating albumin level at 5.5 hrs and day 2 and Fibrinogen level at day 2 of observation. A significant hypocalcaemia was observed at 4.5 hours along with an increase in Alkaline Phosphatase at 3.5, 4.5 and 6.5 hrs. All the endotoxemic buffalo calves which died were subjected to post mortem and histopathological studies. Epicardial and endocardial haemorrhages, haemorrhages on intestinal mucosa, congestion, haemorrhages, emphysema and fibrinous thrombi in microvasculature of lungs were salient histopathological findings. On comparison with observations of the other treatment regimens tried, it was found that the IV infusion of the combination of HSS, Flunixin meglumine, Dextran-40 and blood was found to be the most effective leading to full recovery of 3 out of 5 buffalo calves of group-III where as only 1 out of 5 animals recovered in group-II. None of the group-I animals recovered and all of these succumbed to shock after day-2.

Blood pressure waveform contour analysis for assessing peripheral resistance changes in sepsis

BackgroundThis paper proposes a methodology for helping bridge the gap between the complex waveform information frequently available in an intensive care unit and the simple, lumped values favoured for rapid clinical diagnosis and management. This methodology employs a simple waveform contour analysis approach to compare aortic, femoral and central venous pressure waveforms on a beat-by-beat basis and extract lumped metrics pertaining to the pressure drop and pressure-pulse amplitude attenuation as blood passes through the various sections of systemic circulation.ResultsValidation encompasses a comparison between novel metrics and well-known, analogous clinical metrics such as mean arterial and venous pressures, across an animal model of induced sepsis. The novel metric Ofe → vc, the direct pressure offset between the femoral artery and vena cava, and the clinical metric, ΔMP, the difference between mean arterial and venous pressure, performed well. However, Ofe → vc reduced the optimal average time to sepsis detection after endotoxin infusion from 46.2 min for ΔMP to 11.6 min, for a slight increase in false positive rate from 1.8 to 6.2%. Thus, the novel Ofe → vc provided the best combination of specificity and sensitivity, assuming an equal weighting to both, of the metrics assessed.ConclusionsOverall, the potential of these novel metrics in the detection of diagnostic shifts in physiological behaviour, here driven by sepsis, is demonstrated.

Moderators for depressed mood and systemic and transcriptional inflammatory responses: a randomized controlled trial of endotoxin.

Activation of the innate immune system is thought to contribute to depression. Multiple social and behavioral factors are also known to instigate depression. Whether these socio-behavioral factors interact with inflammatory stimuli to alter proinflammatory responses and depressed mood is not known. In 115 healthy adults, social, emotional, and behavioral factors were assessed at baseline. A single infusion of endotoxin (Escherichia coli; 0.8 ng/kg of body weight) or placebo (0.9% saline) was administered with hourly assessment of depressed mood and proinflammatory cytokines (interleukin-6 (IL-6); tumor necrosis factor-α (TNF)). Inflammatory gene expression was examined at 30 min after infusion, prior to increase of inflammatory cytokines. As compared to placebo, endotoxin-induced increases of depressed mood were moderated by baseline levels of perceived stress, trait sensitivity to social disconnection, and severity of symptoms of anxiety and depression (all Ps < 0.05) but not early life stress, social status, social support, neuroticism, or sleep disturbance. Anxiety symptoms remained significant in multivariable analyses (P < 0.01). None of these socio-behavioral factors were related to increases in proinflammatory cytokines. Transcriptome profiling analyses indicated that perceived stress, sensitivity to social disconnection, and depressive symptoms were associated with increased activation of pro-inflammatory transcription control pathways (i.e., activator protein-1, nuclear factor-κB) in response to endotoxin (all Ps < 0.05). These results indicate that an array of socio-behavioral factors, which are associated with depression risk, modify vulnerability to inflammation-induced depressed mood. Together, these observations may be used to help target therapeutic interventions to mitigate occurrence of the inflammatory biotype of depression.

Esmolol indirectly stimulates vagal nerve activity in endotoxemic pigs

BackgroundThere is an increasing interest in beta-blockade as a therapeutic approach to sepsis following consistent experimental findings of attenuation of inflammation and improved survival with beta1 selective antagonist. However, the mechanism of these beneficial effects remains very uncertain. Thus, this study is aimed at investigating the effects of a beta-1 selective blockade on sympathetic/parasympathetic activity in endotoxin-challenged pigs using heart rate variability. The hypothesis is that an adrenergic blockade could promote parasympathetic activity. Indeed, the increase of parasympathetic activity is a mechanism recently described as beneficial in septic states.MethodsFifty-one endotoxin-challenged pigs were studied. After 30 min of endotoxin infusion and 30 min of evolution without intervention, the pigs were randomly assigned the placebo or esmolol treatment and were observed for 200 min. Overall heart rate variability was assessed continuously, in the temporal domain by standard deviation of RR intervals (SDNN, ms),and in the frequency domain by spectral powers of low frequency (LF, ms2 × 103/Hz) and high frequency (HF, ms2 × 103/Hz) bands.ResultsVariations of power in these frequency bands were interpreted as putative markers of sympathetic (LF) and parasympathetic (HF) activity. In LPS treated animals, Esmolol did not increase SDNN, but instead decreased LF and increased HF power.ConclusionThese spectral modifications associated to a beta-blocker treatment after an endotoxemic challenge are interpreted as a significant decrease of sympathetic activity and an indirect increase of vagal autonomic tone.