Identifying septic shock subgroups to tailor fluid strategies through multi-omics integration.

Fluid management remains a critical challenge in the treatment of septic shock, with individualized approaches lacking. This study aims to develop a statistical model based on transcriptomics to identify subgroups of septic shock patients with varied responses to fluid strategy. The study encompasses 494 septic shock patients. A benefit score is derived from the transcriptome space, with higher values indicating greater benefits from restrictive fluid strategy. Adherence to the recommended strategy is associated with a hazard ratio of 0.82 (95% confidence interval: 0.64-0.92). When applied to the baseline hospital mortality rate of 16%, adherence to the recommended fluid strategy could potentially lower this rate to 13%. A proteomic signature comprising six proteins is developed to predict the benefit score, yielding an area under the curve of 0.802 (95% confidence interval: 0.752-0.846) in classifying patients who may benefit from a restrictive strategy. In this work, we develop a proteomic signature with potential utility in guiding fluid strategy for septic shock patients.

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

OBJECTIVES: 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. DESIGN: Experimental septic shock model induced by peritonitis in swine. SETTING: Experimental Laboratory, Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles. SUBJECTS: Forty time points from eight mechanically ventilated pigs. INTERVENTIONS: Septic shock was induced using intraperitoneal instillation of autologous feces, followed by standardized fluid resuscitation, norepinephrine infusion, antibiotic administration, and peritoneal lavage. MEASUREMENTS AND MAIN RESULTS: 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. CONCLUSIONS: 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 Modulation of Septic Shock: A Proteomic Approach.

Sepsis poses a significant challenge due its lethality, involving multiple organ dysfunction and impaired immune responses. Among several factors affecting sepsis, monocytes play a crucial role; however, their phenotype, proteomic profile, and function in septic shock remain unclear. Our aim was to fully characterize the subpopulations and proteomic profiles of monocytes seen in septic shock cases and discuss their possible impact on the disease. Peripheral blood monocyte subpopulations were phenotype based on CD14/CD16 expression by flow cytometry, and proteins were extracted from the monocytes of individuals with septic shock and healthy controls to identify changes in the global protein expression in these cells. Analysis using 2D-nanoUPLC-UDMSE identified 67 differentially expressed proteins in shock patients compared to controls, in which 44 were upregulated and 23 downregulated. These proteins are involved in monocyte reprogramming, immune dysfunction, severe hypotension, hypo-responsiveness to vasoconstrictors, vasodilation, endothelial dysfunction, vascular injury, and blood clotting, elucidating the disease severity and therapeutic challenges of septic shock. This study identified critical biological targets in monocytes that could serve as potential biomarkers for the diagnosis, prognosis, and treatment of septic shock, providing new insights into the pathophysiology of the disease.

Evaluating tissue hypoxia and the response to fluid administration in septic shock patients: a metabolic cluster analysis.

BACKGROUND: The selection of adequate indicators of tissue hypoxia for guiding the resuscitation process of septic patients is a highly relevant issue. Current guidelines advocate for the use of lactate as sole metabolic marker, which may be markedly limited, and the integration of different variables seems more adequate. In this study, we explored the metabolic profile and its implications in the response to the administration of a fluid challenge in early septic shock patients. METHODS: Observational study including septic shock patients within 24 h of ICU admission, monitored with a cardiac output estimation system, with ongoing resuscitation. Hemodynamic and metabolic variables were measured before and after a fluid challenge (FC). A two-step cluster analysis was used to define the baseline metabolic profile, including lactate, central venous oxygen saturation (ScvO2), central venous-to-arterial carbon dioxide difference (PcvaCO2), and PcvaCO2 corrected by the difference in arterial-to-venous oxygen content (PcvaCO2/CavO2). RESULTS: Seventy-seven fluid challenges were analyzed. Cluster analysis revealed two distinct metabolic profiles at baseline. Cluster A exhibited lower ScvO2, higher PcvaCO2, and lower PcvaCO2/CavO2. Increases in cardiac output (CO) were associated with increases in VO2 exclusively in cluster A. Baseline isolated metabolic variables did not correlate with VO2 response, and changes in ScvO2 and PcvaCO2 were associated to VO2 increase only in cluster A. CONCLUSIONS: In a population of early septic shock patients, two distinct metabolic profiles were identified, suggesting tissue hypoxia or dysoxia. Integrating metabolic variables enhances the ability to detect those patients whose VO2 might increase as results of fluid administration.

Microbial metabolome in septic shock: Bridging bench to bedside.

Due to its enormous incidence and mortality, sepsis is a huge health priority. In the latest issue of Cell, an innovative approach is provided that addresses the major sepsis hurdles of today, i.e., early recognition, prompt treatment, translation from experimental animals to human patients, and urgent need for novel therapeutics.

Antimicrobial peptide 2K4L inhibits the inflammatory response in macrophages and Caenorhabditis elegans and protects against LPS-induced septic shock in mice.

2K4L is a rationally designed analog of the short α-helical peptide temporin-1CEc, a natural peptide isolated and purified from the skin secretions of the Chinese brown frog Rana chensinensis by substituting amino acid residues. 2K4L displayed improved and broad-spectrum antibacterial activity than temporin-1CEc in vitro. Here, the antibacterial and anti-inflammatory activities of 2K4L in macrophages, C. elegans and mice were investigated. The results demonstrated that 2K4L could enter THP-1 cells to kill a multidrug-resistant Acinetobacter baumannii strain (MRAB 0227) and a sensitive A. baumannii strain (AB 22933), as well as reduce proinflammatory responses induced by MRAB 0227 by inhibiting NF-κB signaling pathway. Similarly, 2K4L exhibited strong bactericidal activity against A. baumannii uptake into C. elegans, extending the lifespan and healthspan of the nematodes. Meanwhile, 2K4L alleviated the oxidative stress response by inhibiting the expression of core genes in the p38 MAPK/PMK-1 signaling pathway and downregulating the phosphorylation level of p38, thereby protecting the nematodes from damage by A. baumannii. Finally, in an LPS-induced septic model, 2K4L enhanced the survival of septic mice and decreased the production of proinflammatory cytokines by inhibiting the signaling protein expression of the MAPK and NF-κB signaling pathways and protecting LPS-induced septic mice from a lethal inflammatory response. In conclusion, 2K4L ameliorated LPS-induced inflammation both in vitro and in vivo.

[2, 6-dimethoxy-1, 4-benzoquinone alleviates septic shock in mice by inhibiting NLRP3 inflammasome activation].

OBJECTIVE: To investigate the mechanism of 2, 6-dimethoxy-1, 4-benzoquinone (DMQ), an active ingredients in fermented wheat germ extract, for inhibiting NLRP3 inflammasome activation and alleviating septic shock in mice. METHODS: Cultured murine bone marrow-derived macrophages (BMDM) stimulated with lipopolysaccharide (LPS) were treated with DMQ, followed by treatment with Nigericin, ATP, and MSU for activating the canonical NLRP3 inflammasome; the noncanonical NLRP3 inflammasome was activated by intracellular transfection of LPS, and AIM2 inflammasome was activated using Poly A: T.In human monocytic THP-1 cells, the effect of Nigericin on inflammasome activation products was examined using Western blotting and ELISA.Co-immunoprecipitation was performed to explore the mechanism of DMQ-induced blocking of NLRP3 inflammasome activation.In a male C57BL/6J mouse model of LPS-induced septic shock treated with 20 and 40 mg/kg DMQ, the levels of IL-1ß and TNF-α in the serum and peritoneal lavage fluid were determined using ELISA, and the survival time of the mice within 36 h was observed. RESULTS: Treatment with DMQ effectively inhibited LPS-induced activation of canonical NLRP3 inflammasome in mouse BMDM and human THP-1 cells and also inhibited non-canonical NLRP3 inflammasome activation in mouse BMDM, but produced no significant effect on AIM2 inflammasome activation.DMQ significantly blocked the binding between ASC and NLRP3.In the mouse models of septic shock, DMQ treatment significantly reduced the levels of IL-1ß in the serum and peritoneal fluid and obviously prolonged survival time of the mice. CONCLUSION: DMQ can effectively block ASC-NLRP3 interaction to inhibit NLRP3 inflammasome activation and alleviate LPSinduced septic shock in mice.

New Insights into Hepatic and Intestinal Microcirculation and Pulmonary Inflammation in a Model of Septic Shock and Veno-Arterial Extracorporeal Membrane Oxygenation in the Rat.

Despite significant efforts toward improving therapy for septic shock, mortality remains high. Applying veno-arterial (V-A) extracorporeal membrane oxygenation (ECMO) in this context remains controversial. Since the cannulation of the femoral artery for V-A ECMO return leads to lower body hyperoxia, this study investigated the impact of V-A ECMO therapy on the intestinal and hepatic microcirculation during septic shock in a rodent model. Thirty male Lewis rats were randomly assigned to receive V-A ECMO therapy with low (60 mL/kg/min) or high (90 mL/kg/min) blood flow or a sham procedure. Hemodynamic data were collected through a pressure-volume catheter in the left ventricle and a catheter in the lateral tail artery. Septic shock was induced by intravenous administration of lipopolysaccharide (1 mg/kg). The rats received lung-protective ventilation during V-A ECMO therapy. The hepatic and intestinal microcirculation was measured by micro-lightguide spectrophotometry after median laparotomy for two hours. Systemic and pulmonary inflammation was detected via enzyme-linked immunosorbent assays (ELISA) of the plasma and bronchoalveolar lavage (BAL), respectively, measuring tumor necrosis factor-alpha (TNF-α), interleukins 6 (IL-6) and 10 (IL-10), and C-X-C motif ligands 2 (CXCL2) and 5 (CXCL5). Oxygen saturation and relative hemoglobin concentration were reduced in the hepatic and intestinal microcirculation during V-A ECMO therapy, independent of the blood flow rate. Further, rats treated with V-A ECMO therapy also presented elevated systolic, diastolic, and mean arterial blood pressure and increased stroke volume, cardiac output, and left ventricular end-diastolic volume. However, left ventricular end-diastolic pressure was only elevated during high-flow V-A ECMO therapy. Blood gas analysis revealed a dilutional anemia during V-A ECMO therapy. ELISA analysis showed an elevated plasma CXCL2 concentration only during high-flow V-A ECMO therapy and elevated BAL CXCL2 and CXCL5 concentrations only during low-flow V-A ECMO therapy. Rats undergoing V-A ECMO therapy exhibited impaired microcirculation of the intestine and liver during septic shock despite increased blood pressure and cardiac output. Increased pulmonary inflammation was detected only during low-flow V-A ECMO therapy in septic shock.

Associations of tissue factor and tissue factor pathway inhibitor with organ dysfunctions in septic shock.

Coagulopathy, microvascular alterations and concomitant organ dysfunctions are hallmarks of sepsis. Attempts to attenuate coagulation activation with an inhibitor of tissue factor (TF), i.e. tissue factor pathway inhibitor (TFPI), revealed no survival benefit in a heterogenous group of sepsis patients, but a potential survival benefit in patients with an international normalized ratio (INR) < 1.2. Since an increased TF/TFPI ratio determines the procoagulant activity specifically on microvascular endothelial cells in vitro, we investigated whether TF/TFPI ratio in blood is associated with INR alterations, organ dysfunctions, disseminated intravascular coagulation (DIC) and outcome in septic shock. Twenty-nine healthy controls (HC) and 89 patients with septic shock admitted to a tertiary ICU were analyzed. TF and TFPI in blood was analyzed and related to organ dysfunctions, DIC and mortality. Patients with septic shock had 1.6-fold higher levels of TF and 2.9-fold higher levels of TFPI than HC. TF/TFPI ratio was lower in septic shock compared to HC (0.003 (0.002-0.005) vs. 0.006 (0.005-0.008), p < 0.001). Non-survivors had higher TFPI levels compared to survivors (43038 (29354-54023) vs. 28041 (21675-46582) pg/ml, p = 0.011). High TFPI levels were associated with acute kidney injury, liver dysfunction, DIC and disease severity. There was a positive association between TF/TFPI ratio and troponin T (b = 0.531 (0.309-0.754), p < 0.001). A high TF/TFPI ratio is exclusively associated with myocardial injury but not with other organ dysfunctions. Systemic TFPI levels seem to reflect disease severity. These findings point towards a pathophysiologic role of TF/TFPI in sepsis-induced myocardial injury.

Discovery of an antivirulence compound that targets the Staphylococcus aureus SaeRS two-component system to inhibit toxic shock syndrome toxin-1 production.

Menstrual toxic shock syndrome (mTSS) is a rare but severe disorder associated with the use of menstrual products such as high-absorbency tampons and is caused by Staphylococcus aureus strains that produce the toxic shock syndrome toxin-1 (TSST-1) superantigen. Herein, we screened a library of 3920 small bioactive molecules for the ability to inhibit transcription of the TSST-1 gene without inhibiting the growth of S. aureus. The dominant positive regulator of TSST-1 is the SaeRS two-component system (TCS), and we identified phenazopyridine hydrochloride (PP-HCl) that repressed the production of TSST-1 by inhibiting the kinase function of SaeS. PP-HCl competed with ATP for binding of the kinase SaeS leading to decreased phosphorylation of SaeR and reduced expression of TSST-1 as well as several other secreted virulence factors known to be regulated by SaeRS. PP-HCl targets the virulence of S. aureus, and it also decreases the impact of TSST-1 on human lymphocytes without affecting the healthy vaginal microbiota. Our findings demonstrate the promising potential of PP-HCl as a therapeutic strategy against mTSS.

SEPTIC SHOCK: LPS TOLERANCE PROTECTS MITOCHONDRIAL BIOGENESIS AND RESPIRATION.

ABSTRACT: Mitochondrial dysfunction is a recognized feature of sepsis, characterized by ultrastructural damage, diminished oxidative phosphorylation, and depletion of mitochondrial antioxidant capacity observed in deceased septic patients. LPS tolerance induces a controlled response to sepsis. This study aimed to evaluate the function of tolerant mitochondria after cecal ligation and puncture (CLP)-induced sepsis. Mytochondrial oxygen consumption was determined using polarography. Extraction and quantification of RNA for the expression of Tfam, Nrf-1, and Ppargc-1α, and respiratory complex activity were measured. CLP-tolerant animals presented preserved respiratory rates of S3 and S4 and a ratio of respiratory control (RCR) compared to CLP-nontolerant animals with reduced oxidative phosphorylation and increased uncoupled respiration. Complex I Vmax was reduced in septic animals; however, CLP animals sustained normal Vmax. Mitochondrial biogenesis was preserved in CLP-tolerant animals compared to the CLP-nontolerant group, likely due to increased TFAM expression. LPS tolerance protected septic animals from mitochondrial dysfunction, favoring mitochondrial biogenesis and preserving mitochondrial respiration and respiratory complex I activity.

New Insights into Hepatic and Intestinal Microcirculation and Pulmonary Inflammation in a Model of Septic Shock and Venovenous Extracorporeal Membrane Oxygenation in the Rat.

Treatment of critically ill patients with venovenous (V-V) extracorporeal membrane oxygenation (ECMO) has gained wide acceptance in the last few decades. However, the use of V-V ECMO in septic shock remains controversial. The effect of ECMO-induced inflammation on the microcirculation of the intestine, liver, and critically damaged lungs is unknown. Therefore, the aim of this study was to measure the hepatic and intestinal microcirculation and pulmonary inflammatory response in a model of V-V ECMO and septic shock in the rat. Twenty male Lewis rats were randomly assigned to receive V-V ECMO therapy or a sham procedure. Hemodynamic data were measured by a pressure-volume catheter in the left ventricle and a catheter in the lateral tail artery. Septic shock was induced by the intravenous infusion of lipopolysaccharide (1 mg/kg). During V-V ECMO therapy, rats received lung-protective ventilation. The hepatic and intestinal microcirculation was assessed by micro-lightguide spectrophotometry after median laparotomy for 2 h. Systemic and pulmonary inflammation was measured by enzyme-linked immunosorbent assays of plasma and bronchoalveolar lavage (BAL), respectively, which included tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), IL-10, C-X-C motif ligand 2 (CXCL2), and CXCL5. Reduced oxygen saturation and relative hemoglobin concentration were measured in the hepatic and intestinal microcirculation during treatment with V-V ECMO. These animals also showed increased systolic, mean, and diastolic blood pressures. While no differences in left ventricular ejection fraction were observed, animals in the V-V ECMO group presented an increased heart rate, stroke volume, and cardiac output. Blood gas analysis showed dilutional anemia during V-V ECMO, whereas plasma analysis revealed a decreased concentration of IL-10 during V-V ECMO therapy, and BAL measurements showed increased concentrations of TNF-α, CXCL2, and CXCL5. Rats treated with V-V ECMO showed impaired microcirculation of the intestine and liver during septic shock despite increased blood pressure and cardiac output. Despite lung-protective ventilation, increased pulmonary inflammation was recognized during V-V ECMO therapy in septic shock.

Anti-inflammatory effect of proanthocyanidins from blueberry through NF-κß/NLRP3 signaling pathway in vivo and in vitro.

BACKGROUND: Systemic inflammatory response syndrome (SIRS) is an uncontrolled systemic inflammatory response. Proanthocyanidins (PC) is a general term of polyphenol compounds widely existed in blueberry fruits and can treat inflammation-related diseases. This study aimed to explore the regulatory effect of PC on lipopolysaccharide (LPS)-induced systemic inflammation and its potential mechanism, providing effective strategies for the further development of PC. METHODS: Here, RAW264.7 macrophages were stimulated with LPS to establish an inflammation model in vitro, while endotoxin shock mouse models were constructed by LPS in vivo. The function of PC was investigated by MTT, ELISA kits, H&E staining, immunohistochemistry, and Western blot analysis. RESULTS: Functionally, PC could demonstrate the potential to mitigate mortality in mice with endotoxin shock, as well as attenuated the levels of inflammatory cytokines (IL-6, TNF-α) and biochemical indicators (AST, ALT, CRE and BUN). Moreover, it had a significant protective effect on lung and kidney tissues damage. Mechanistically, PC exerted anti-inflammatory effects by inhibiting the activation of the NF-κB/NLRP3 signaling pathway. CONCLUSION: PC might have the potential ability of anti-inflammatory effects via modulation of the NF-κB/NLRP3 signaling pathway.

Major endothelial damage markers identified from hemadsorption filters derived from treated patients with septic shock - endoplasmic reticulum stress and bikunin may play a role.

Introduction: In septic patients the damage of the endothelial barrier is decisive leading to circulatory septic shock with disseminated vascular coagulation, edema and multiorgan failure. Hemadsorption therapy leads to rapid resolution of clinical symptoms. We propose that the isolation of proteins adsorbed to hemadsorption devices contributes to the identification of mediators responsible for endothelial barrier dysfunction. Material and methods: Plasma materials enriched to hemadsorption filters (CytoSorb®) after therapy of patients in septic shock were fractionated and functionally characterized for their effect on cell integrity, viability, proliferation and ROS formation by human endothelial cells. Fractions were further studied for their contents of oxidized nucleic acids as well as peptides and proteins by mass spectrometry. Results: Individual fractions exhibited a strong effect on endothelial cell viability, the endothelial layer morphology, and ROS formation. Fractions with high amounts of DNA and oxidized DNA correlated with ROS formation in the target endothelium. In addition, defined proteins such as defensins (HNP-1), SAA1, CXCL7, and the peptide bikunin were linked to the strongest additive effects in endothelial damage. Conclusion: Our results indicate that hemadsorption is efficient to transiently remove strong endothelial damage mediators from the blood of patients with septic shock, which explains a rapid clinical improvement of inflammation and endothelial function. The current work indicates that a combination of stressors leads to the most detrimental effects. Oxidized ssDNA, likely derived from mitochondria, SAA1, the chemokine CXCL7 and the human neutrophil peptide alpha-defensin 1 (HNP-1) were unique for their significant negative effect on endothelial cell viability. However, the strongest damage effect occurred, when, bikunin - cleaved off from alpha-1-microglobulin was present in high relative amounts (>65%) of protein contents in the most active fraction. Thus, a relevant combination of stressors appears to be removed by hemadsorption therapy which results in fulminant and rapid, though only transient, clinical restitution.

GSNOR negatively regulates the NLRP3 inflammasome via S-nitrosation of MAPK14.

Hyperactivation of the NLRP3 inflammasome has been implicated in the pathogenesis of numerous diseases. However, the precise molecular mechanisms that modulate the transcriptional regulation of NLRP3 remain largely unknown. In this study, we demonstrated that S-nitrosoglutathione reductase (GSNOR) deficiency in macrophages leads to significant increases in the Nlrp3 and Il-1ß expression levels and interleukin-1ß (IL-1ß) secretion in response to NLRP3 inflammasome stimulation. Furthermore, in vivo experiments utilizing Gsnor-/- mice revealed increased disease severity in both lipopolysaccharide (LPS)-induced septic shock and dextran sodium sulfate (DSS)-induced colitis models. Additionally, we showed that both LPS-induced septic shock and DSS-induced colitis were ameliorated in Gsnor-/- Nlrp3-/- double-knockout (DKO) mice. Mechanistically, GSNOR deficiency increases the S-nitrosation of mitogen-activated protein kinase 14 (MAPK14) at the Cys211 residue and augments MAPK14 kinase activity, thereby promoting Nlrp3 and Il-1ß transcription and stimulating NLRP3 inflammasome activity. Our findings suggested that GSNOR is a regulator of the NLRP3 inflammasome and that reducing the level of S-nitrosylated MAPK14 may constitute an effective strategy for alleviating diseases associated with NLRP3-mediated inflammation.

INTERPLAY BETWEEN BRAIN OXYGENATION AND THE DEVELOPMENT OF HYPOTHERMIA IN ENDOTOXIC SHOCK.

ABSTRACT: There is evidence to suggest that the hypothermia observed in the most severe cases of systemic inflammation or sepsis is a regulated response with potential adaptive value, but the mechanisms involved are poorly understood. Here, we investigated the interplay between brain oxygenation (assessed by tissue P o2 ) and the development of hypothermia in unanesthetized rats challenged with a hypotension-inducing dose of bacterial LPS (1 mg/kg i.v.). At an ambient temperature of 22°C, oxygen consumption (V̇O 2 ) began to fall only a few minutes after the LPS injection, and this suppression in metabolic rate preceded the decrease in core temperature. No reduction in brain P o2 was observed prior to the development of the hypometabolic, hypothermic response, ruling out the possibility that brain hypoxia served as a trigger for hypothermia in this model. Brain P o2 was even increased. Such an improvement in brain oxygenation could reflect either an increased O 2 delivery or a decreased O 2 consumption. The former explanation seems unlikely because blood flow (cardiac output) was being progressively decreased during the recording period. On the other hand, the decrease in V̇O 2 usually preceded the rise in P o2 , and an inverse correlation between V̇O 2 and brain P o2 was consistently observed. These findings do not support the existence of a closed-loop feedback relationship between brain oxygenation and hypothermia in systemic inflammation. The data are consistent with a feedforward mechanism in which hypothermia is triggered (possibly by cryogenic inflammatory mediators) in anticipation of changes in brain oxygenation to prevent the development of tissue hypoxia.

Blockade of sympathetic ganglia improves vascular dysfunction in septic shock.

Sepsis/septic shock activates the sympathetic nervous system (SNS) to deal with the infection stress. However, an imbalanced or maladaptive response due to excessive or uncontrolled activation characterizes autonomic dysfunction. Our hypothesis was that reducing this excessive activation of the autonomic nervous system would impact positively in sepsis. Using ganglionic blockers as a pharmacological approach, the main aim of the present report was to assess the role of ganglionic transmission in the vascular dysfunction associated with sepsis.Sepsis was induced in rats by cecal ligation and puncture (CLP). One hour after CLP surgery, rats were treated subcutaneously with hexamethonium (15 mg/kg; ganglionic blocker), pentolinium (5 mg/kg; a blocker with a higher selectivity for sympathetic ganglia compared to hexamethonium), or vehicle (PBS). Basal blood pressure and the response to adrenergic agonists were evaluated at 6 and 24 h after CLP surgery. Reactivity to vasoconstrictors, nitric oxide (NO) synthase 2 (NOS-2) expression, IL-1 and TNF plasma levels, and density of α1 adrenergic receptors were evaluated in the aorta 24 h after CLP.Septic shock resulted in hypotension and hyporesponsiveness to norepinephrine and phenylephrine, increased plasma cytokine levels and NOS-2 expression in the aorta, and decreased α1 receptor density in the same vessel. Pentolinium but not hexamethonium recovered responsiveness and α1 adrenergic receptor density in the aorta. Both blockers normalized the in vivo response to vasoconstrictors, and reduced plasma IL-1 and NOx levels and NOS-2 expression in the aorta.Blockade of ganglionic sympathetic transmission reduced the vascular dysfunction in experimental sepsis. This beneficial effect seems to be, at least in part, due to the preservation of α1 adrenergic receptor density and to reduced NOS-2 expression and may lead to adjuvant ways to treat human sepsis.

Dysfunction of the renin-angiotensin-aldosterone system in human septic shock.

Sepsis and septic shock are global healthcare problems associated with mortality rates of up to 40% despite optimal standard-of-care therapy and constitute the primary cause of death in intensive care units worldwide. Circulating biomarkers of septic shock severity may represent a clinically relevant approach to individualize those patients at risk for worse outcomes early in the course of the disease, which may facilitate early and more precise interventions to improve the clinical course. However, currently used septic shock biomarkers, including lactate, may be non-specific and have variable impact on prognosis and/or disease management. Activation of the renin-angiotensin-aldosterone system (RAAS) is likely an early event in septic shock, and studies suggest that an elevated level of renin, the early and committed step in the RAAS cascade, is a better predictor of worse outcomes in septic shock, including mortality, than the current standard-of-care measure of lactate. Despite a robust increase in renin, other elements of the RAAS, including endogenous levels of Ang II, may fail to sufficiently increase to maintain blood pressure, tissue perfusion, and protective immune responses in septic shock patients. We review the current clinical literature regarding the dysfunction of the RAAS in septic shock and potential therapeutic approaches to improve clinical outcomes.

A palmitoylation-depalmitoylation relay spatiotemporally controls GSDMD activation in pyroptosis.

Gasdermin D (GSDMD) is the executor of pyroptosis, which is important for host defence against pathogen infection. Following activation, caspase-mediated cleavage of GSDMD releases an amino-terminal fragment (GSDMD-NT), which oligomerizes and forms pores in the plasma membrane, leading to cell death and release of proinflammatory cytokines. The spatial and temporal regulation of this process in cells remains unclear. Here we identify GSDMD as a substrate for reversible S-palmitoylation on C192 during pyroptosis. The palmitoyl acyltransferase DHHC7 palmitoylates GSDMD to direct its cleavage by caspases. Subsequently, palmitoylation of GSDMD-NT promotes its translocation to the plasma membrane, where APT2 depalmitoylates GSDMD-NT to unmask the C192 residue and promote GSDMD-NT oligomerization. Perturbation of either palmitoylation or depalmitoylation suppresses pyroptosis, leading to increased survival of mice with lipopolysaccharide-induced lethal septic shock and increased sensitivity to bacterial infection. Our findings reveal a model through which a palmitoylation-depalmitoylation relay spatiotemporally controls GSDMD activation during pyroptosis.