Advances in Sepsis Research

Chitin-glucan improves important pathophysiological features of irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is one of the most frequent and debilitating conditions leading to gastroenterological referrals. However, recommended treatments remain limited, yielding only limited therapeutic gains. Chitin-glucan (CG) is a novel dietary prebiotic classically used in humans at a dosage of 1.5-3.0 g/d and is considered a safe food ingredient by the European Food Safety Authority. To provide an alternative approach to managing patients with IBS, we performed preclinical molecular, cellular, and animal studies to evaluate the role of chitin-glucan in the main pathophysiological mechanisms involved in IBS.

AIM

To evaluate the roles of CG in visceral analgesia, intestinal inflammation, barrier function, and to develop computational molecular models.

METHODS

Visceral pain was recorded through colorectal distension (CRD) in a model of long-lasting colon hypersensitivity induced by an intra-rectal administration of TNBS [15 milligrams (mg)/kilogram (kg)] in 33 Sprague-Dawley rats. Intracolonic pressure was regularly assessed during the 9 wk-experiment (weeks 0, 3, 5, and 7) in animals receiving CG (n = 14) at a human equivalent dose (HED) of 1.5 g/d or 3.0 g/d and compared to negative control (tap water, n = 11) and positive control (phloroglucinol at 1.5 g/d HED, n = 8) groups. The anti-inflammatory effect of CG was evaluated using clinical and histological scores in 30 C57bl6 male mice with colitis induced by dextran sodium sulfate (DSS) administered in their drinking water during 14 d. HT-29 cells under basal conditions and after stimulation with lipopolysaccharide (LPS) were treated with CG to evaluate changes in pathways related to analgesia (µ-opioid receptor (MOR), cannabinoid receptor 2 (CB2), peroxisome proliferator-activated receptor alpha, inflammation [interleukin (IL)-10, IL-1b, and IL-8] and barrier function [mucin 2-5AC, claudin-2, zonula occludens (ZO)-1, ZO-2] using the real-time PCR method. Molecular modelling of CG, LPS, lipoteichoic acid (LTA), and phospholipomannan (PLM) was developed, and the ability of CG to chelate microbial pathogenic lipids was evaluated by docking and molecular dynamics simulations. Data were expressed as the mean ± SEM.

RESULTS

Daily CG orally-administered to rats or mice was well tolerated without including diarrhea, visceral hypersensitivity, or inflammation, as evaluated at histological and molecular levels. In a model of CRD, CG at a dosage of 3 g/d HED significantly decreased visceral pain perception by 14% after 2 wk of administration (P < 0.01) and reduced inflammation intensity by 50%, resulting in complete regeneration of the colonic mucosa in mice with DSS-induced colitis. To better reproduce the characteristics of visceral pain in patients with IBS, we then measured the therapeutic impact of CG in rats with TNBS-induced inflammation to long-lasting visceral hypersensitivity. CG at a dosage of 1.5 g/d HED decreased visceral pain perception by 20% five weeks after colitis induction (P < 0.01). When the CG dosage was increased to 3.0 g/d HED, this analgesic effect surpassed that of the spasmolytic agent phloroglucinol, manifesting more rapidly within 3 wk and leading to a 50% inhibition of pain perception (P < 0.0001). The underlying molecular mechanisms contributing to these analgesic and anti-inflammatory effects of CG involved, at least in part, a significant induction of MOR, CB2 receptor, and IL-10, as well as a significant decrease in pro-inflammatory cytokines IL-1b and IL-8. CG also significantly upregulated barrier-related genes including muc5AC, claudin-2, and ZO-2. Molecular modelling of CG revealed a new property of the molecule as a chelator of microbial pathogenic lipids, sequestering gram-negative LPS and gram-positive LTA bacterial toxins, as well as PLM in fungi at the lowesr energy conformations.

CONCLUSION

CG decreased visceral perception and intestinal inflammation through master gene regulation and direct binding of microbial products, suggesting that CG may constitute a new therapeutic strategy for patients with IBS or IBS-like symptoms.

Gramine improves sepsis-induced myocardial dysfunction by binding to NF-κB p105 and inhibiting its ubiquitination

BACKGROUND

Sepsis and its associated heart failure are among the leading causes of death. Gramine, a natural indole alkaloid, can be extracted from a wide variety of raw plants, and it exhibits therapeutic potential in pathological cardiac hypertrophy. However, the effect of gramine on inflammatory cardiomyopathy, particularly sepsis-induced myocardial injury, remains an unexplored area.

PURPOSE

To determine the role of gramine in sepsis-induced myocardial dysfunction and explore its underlying mechanism.

STUDY DESIGN AND METHODS

In mice, sepsis was established by intraperitoneally injecting lipopolysaccharide (LPS, 10 mg/kg). Subsequently, the effects of gramine administration (50 or 100 mg/kg) on LPS-triggered cardiac dysfunction in mice were investigated. For in vitro studies, isolated primary cardiomyocytes were used to assess the effect of gramine (25 or 50 µM) on LPS-induced apoptosis and inflammation. Additionally, molecular docking, co-immunoprecipitation and ubiquitination analyzes were conducted to explore the underlying mechanisms.

RESULTS

Gramine visibly ameliorated sepsis-induced cardiac dysfunction, inflammatory response, and mortality in vivo. Moreover, it significantly alleviated LPS-induced apoptotic and inflammatory responses in vitro. Furthermore, target prediction for gramine using the SuperPred website indicated that the nuclear factor NF-κB p105 subunit was one of the molecules ranked in priority order with a high model accuracy and a high probability score. Molecular docking studies demonstrated that gramine effectively docked to the death domain of NF-κB p105. Mechanistic studies revealed that gramine suppressed the processing of NF-κB p105 to p50 by inhibiting NF-κB p105 ubiquitination. Additionally, the protective effect of gramine on cardiac injury was almost abolished by overexpressing NF-κB p105.

CONCLUSION

Gramine is a promising bioactive small molecule for treating sepsis-induced myocardial dysfunction, which acts by docking to NF-κB p105 and inhibiting NF-κB p105 ubiquitination, thus preventing its processing to NF-κB p50. Therefore, gramine holds potential as a clinical drug for treating myocardial depression during sepsis.

Efficacy of Pretreatment with Lycium barbarum Polysaccharide in Various Doses in Influencing Splenic Immunity and Prognosis of Sepsis in Rats

Objective

Sepsis, showing high mortality, is a lethal dysfunction of organs caused by an infection-induced disorder in the host response. It has complicated pathogenesis, which has not yet been elucidated completely. Recently, the principal factors causing pathogenesis and even death in sepsis patients are imbalance in inflammatory response and immunosuppression occurring when the host is challenged by infection. Previous studies found that Lycium barbarum polysaccharide (LBP) worked well in enhancing immunity. This study aims at exploring the efficacy of pretreatment with LPB in regulating splenic immunity during the pathogenesis of sepsis induced by cecum ligation perforation (CLP) in rats.

Methods

This research established the cecum ligation perforation rat model. Using immunohistochemistry and flow cytometry, the effects of Lycium barbarum polysaccharide in various doses in influencing splenic immunity and prognosis of sepsis induced by cecum ligation perforation in rats were examined.

Results

This study showed that LBP lowered the 72-hour mortality of sepsis rats induced by CLP, relieved systemic inflammation, improved the ratio of T-cell subgroups positive in CD3+, CD4+, or CD8+ and expression of HLA-DR protein, and repaired damage to splenic tissue, implying its efficacy in enhancing the immunity of sepsis rats induced by CLP.

Conclusions

LBP may ameliorate clinical symptoms of rats with cecum ligation perforation, improve cellular immunity in the spleen, and treat sepsis so as to provide a theoretical basis for the pathogenesis and development of sepsis as well as its diagnosis and treatment, and offer scientific proof for the development and utilization of LBP applied to critical diseases.

MiR-125b enhances autophagic flux to improve septic cardiomyopathy via targeting STAT3/HMGB1

We explore the role of miR-125b in septic cardiomyopathy, focusing on miR-125b/STAT3/HMGB1 axis. CLP mouse model and LPS-stimulated primary rat cardiomyocytes (CMs) and H9C2 cell were used as in vivo and in vitro models of septic cardiomyopathy, respectively. qRT-PCR and western blot were performed to measure expression levels of miR-125b, STAT3, HMGB1, and autophagy-related proteins. MTT assay was employed to examine LPS toxicity. Dual luciferase activity assay and CHIP were performed to validate interactions of miR-125b/STAT3 and STAT3/HMGB1 promoter. Immunostaining was used to assess the level of autophagic flux. ROS level was measured by fluorescence assay. Heart functions were examined via intracoronary Doppler ultrasound. miR-125b was diminished while STAT3 and HMGB1 were elevated in the heart tissue following CLP surgery and in LPS-treated H9C2 cells. LPS treatment up-regulated ROS generation and suppressed autophagic flux. Overexpression of miR-125b mimics or knockdown of STAT3 or HMGB1 alleviated LPS-induced hindrance of autophagic flux and ROS production. miR-125b directly targeted STAT3 mRNA and STAT3 bound with HMGB1 promoter. Overexpression of miR-125b mitigated myocardial dysfunction induced by CLP in vivo. Hyperactivation of STAT3/HMGB1 caused by reduced miR-125b contributes to ROS generation and the hindrance of autophagic flux during septic cardiomyopathy, leading to myocardial dysfunction.

Impaired B-Cell Maturation Contributes to Reduced B Cell Numbers and Poor Prognosis in Sepsis

BACKGROUND

Reduced B cell numbers play a critical role in sepsis immunosuppression. The role of B-cell maturation regulated by T follicular helper (Tfh) cells in reduced B cell numbers during sepsis remains unclear. We tested the hypothesis that impaired B-cell maturation contributes to reduced B cell numbers.

DESIGN

Retrospective study and observational prospective cohort study.

SETTINGS

Critical care units.

METHODS

To identify the exact lymphocyte counts that affect the prognosis of sepsis, we first conducted a retrospective study. Then in the prospective cohort study, differences in B-cell maturation, B cell death, and numbers of circulating Tfh (cTfh) cell were compared between 28-day survivors and 28-day non-survivors, mainly by flow cytometry and enzyme-linked immunosorbent assay.

MAIN RESULTS

In retrospective study (n = 123), we found patients with lymphocyte counts less than 0.4 × 10 cells/L had higher mortality than patients with lymphocyte counts above 0.4 × 10 cells/L. In observational prospective cohort study (n = 40), compared with survivors, non-survivors had fewer numbers of mature B cell and circulating Tfh (cTfh) cell (sepsis onset: memory B cells: 3.44% vs. 4.48%, antibody-secreting cells: 4.53% vs. 6.30%, cTfh cells: 3.57% vs. 4.49%; 24 h after sepsis onset: memory B cells: 4.05% vs. 7.20%, antibody-secreting cells: 5.25% vs. 8.78%, cTfh cells: 3.98% vs. 6.15%), while there were no differences in cell death of mature B cells between them. We further noticed the numbers of cTfh cell positively correlated with the numbers of mature B cell and immunoglobulin concentrations.

CONCLUSIONS

Impaired B-cell maturation contributes to reduced B cell numbers, while the numbers of cTfh cell, acting as a warning indicator for sepsis prognosis, may be a new therapeutic target for treating sepsis.

Effects of propranolol and clonidine on brain edema, blood-brain barrier permeability, and endothelial glycocalyx disruption after fluid percussion brain injury in the rat

BACKGROUND

Traumatic brain injury causes a disruption of the vascular endothelial glycocalyx layer that is associated with an overactivation of the sympathoadrenal system. We hypothesized that early and unselective beta-blockade with propranolol alone or in combination with the alfa2-agonist clonidine would decrease brain edema, blood-brain barrier permeability, and glycocalyx disruption at 24 hours after trauma.

METHODS

We subjected 53 adult male Sprague-Dawley rats to lateral fluid percussion brain injury and randomized infusion with propranolol (n = 16), propranolol + clonidine (n = 16), vehicle (n = 16), or sham (n = 5) for 24 hours. Primary outcome was brain water content at 24 hours. Secondary outcomes were blood-brain barrier permeability and plasma levels of syndecan-1 (glycocalyx disruption), cell damage (histone-complexed DNA fragments), epinephrine, norepinephrine, and animal motor function.

RESULTS

We found no difference in brain water content (mean ± SD) between propranolol (80.8 ± 0.3%; 95% confidence interval [CI], 80.7-81.0) and vehicle (81.1 ± 0.6%; 95% CI, 80.8-81.4) (p = 0.668) or between propranolol/clonidine (80.8 ± 0.3%; 95% CI, 80.7-81.0) and vehicle (p = 0.555). We found no effect of propranolol and propranolol/clonidine on blood-brain barrier permeability and animal motor scores. Unexpectedly, propranolol and propranolol/clonidine caused an increase in epinephrine and syndecan-1 levels.

CONCLUSION

This study does not provide any support for unselective beta-blockade with propranolol or the combination of propranolol and the alfa2-agonist clonidine on brain water content. The novel finding of an increase in plasma concentrations of epinephrine and syndecan-1 after propranolol treatment in traumatic brain injury is of unclear significance and should be investigated further.

Apigenin Alleviates Endotoxin-Induced Myocardial Toxicity by Modulating Inflammation, Oxidative Stress, and Autophagy

Apigenin, a component in daily diets, demonstrates antioxidant and anti-inflammatory properties. Here, we intended to explore the mechanism of apigenin-mediated endotoxin-induced myocardial injury and its role in the interplay among inflammation, oxidative stress, and autophagy. In our lipopolysaccharide- (LPS-) induced myocardial injury model, apigenin ameliorated cardiac injury (lactate dehydrogenase (LDH) and creatine kinase (CK)), cell death (TUNEL staining, DNA fragmentation, and PARP activity), and tissue damage (cardiac troponin I (cTnI) and cardiac myosin light chain-1 (cMLC1)) and improved cardiac function (ejection fraction (EF) and end diastolic left ventricular inner dimension (LVID)). Apigenin also alleviated endotoxin-induced myocardial injury by modulating oxidative stress (nitrotyrosine and protein carbonyl) and inflammatory cytokines (TNF-α, IL-1β, MIP-1α, and MIP-2) along with their master regulator NFκB. Apigenin modulated redox homeostasis, and its anti-inflammatory role might be associated with its ability to control autophagy. Autophagy (determined by LAMP1, ATG5, and p62), its transcriptional regulator transcription factor EB (TFEB), and downstream target genes including vacuolar protein sorting-associated protein 11 (Vps11) and microtubule-associated proteins 1A/1B light chain 3B (Map1lc3) were modulated by apigenin. Thus, our study demonstrated that apigenin may lead to potential development of new target in sepsis treatment or other myocardial oxidative and/or inflammation-induced injuries.

Naringin Decreases TNF-α and HMGB1 Release from LPS-Stimulated Macrophages and Improves Survival in a CLP-Induced Sepsis Mice

Naringin, a flavanone glycoside extracted from various plants, has a wide range of pharmacological effects. In the present study, we investigated naringin’s mechanism of action and its inhibitory effect on lipopolysaccharide-induced tumor necrosis factor-alpha and high-mobility group box 1 expression in macrophages, and on death in a cecal ligation and puncture induced mouse model of sepsis. Naringin increased heme oxygenase 1 expression in peritoneal macrophage cells through the activation of adenosine monophosphate-activated protein kinase, p38, and NF-E2-related factor 2. Inhibition of heme oxygenase 1 abrogated the naringin’s inhibitory effect on high-mobility group box 1 expression and NF-kB activation in lipopolysaccharide-stimulated macrophages. Moreover, mice pretreated with naringin (200 mg/kg) exhibited decreased sepsis-induced mortality and lung injury, and alleviated lung pathological changes. However, the naringin’s protective effects on sepsis-induced lung injury were eliminated by zinc protoporphyrin, a heme oxygenase 1 competitive inhibitor. These results revealed the mechanism underlying naringin’s protective effect in inflammation and may be beneficial for the treatment of sepsis.

Regulation of Cellular Immune Responses in Sepsis by Histone Modifications

Severe sepsis, septic shock, and related inflammatory syndromes are driven by the aberrant expression of proinflammatory mediators by immune cells. During the acute phase of sepsis, overexpression of chemokines and cytokines drives physiological stress leading to organ failure and mortality. Following recovery from sepsis, the immune system exhibits profound immunosuppression, evidenced by an inability to produce the same proinflammatory mediators that are required for normal responses to infectious microorganisms. Gene expression in inflammatory responses is influenced by the transcriptional accessibility of the chromatin, with histone posttranslational modifications determining whether inflammatory gene loci are set to transcriptionally active, repressed, or poised states. Experimental evidence indicates that histone modifications play a central role in governing the cytokine storm of severe sepsis, and that aberrant chromatin modifications induced during the acute phase of sepsis may mediate chronic immunosuppression in sepsis survivors. This review will focus on the role of histone modifications in governing immune responses in severe sepsis, with an emphasis on specific leukocyte subsets and the histone modifications observed in these cells during chronic stages of sepsis. Additionally, the expression and function of chromatin-modifying enzymes (CMEs) will be discussed in the context of severe sepsis, as potential mediators of epigenetic regulation of gene expression in sepsis responses. In summary, this review will argue for the use of chromatin modifications and CME expression in leukocytes as potential biomarkers of immunosuppression in patients with severe sepsis.

The Endothelial Glycocalyx: New Diagnostic and Therapeutic Approaches in Sepsis

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. The endothelial glycocalyx is one of the earliest sites involved during sepsis. This fragile layer is a complex network of cell-bound proteoglycans, glycosaminoglycan side chains, and sialoproteins lining the luminal side of endothelial cells with a thickness of about 1 to 3 μm. Sepsis-associated alterations of its structure affect endothelial permeability and result in the liberation of endogenous damage-associated molecular patterns (DAMPs). Once liberated in the circulatory system, DAMPs trigger the devastating consequences of the proinflammatory cascades in sepsis and septic shock. In this way, the injury to the glycocalyx with the consecutive release of DAMPs contributes to a number of specific clinical effects of sepsis, including acute kidney injury, respiratory failure, and septic cardiomyopathy. Moreover, the extent of glycocalyx degradation serves as a marker of endothelial dysfunction and sepsis severity. In this review, we highlight the crucial role of the glycocalyx in sepsis as a diagnostic tool and discuss the potential of members of the endothelial glycocalyx serving as hopeful therapeutic targets in sepsis-associated multiple organ failures.

Cryogenic role of central endogenous hydrogen sulfide in the rat model of endotoxic shock

Thermoregulatory responses to lipopolysaccharide (LPS) are affected by modulators that increase (propyretic) or decrease (cryogenic) body temperature (Tb). We tested the hypothesis that central hydrogen sulfide (H₂S) acts as a thermoregulatory modulator and that H₂S production in the anteroventral preoptic region of the hypothalamus (AVPO) is increased during hypothermia and decreased during fever induced by bacterial lipopolysaccharide (LPS, 2.5mg/kg i.p.) in rats kept at an ambient temperature of 25°C. Deep Tb was recorded before and after pharmacological inhibition of the enzyme cystathionine β-synthase (CBS - responsible for H₂S endogenous production in the brain) combined or not with LPS administration. To further investigate the mechanisms responsible for these thermoregulatory adjustments, we also measured prostaglandin D₂ (PGD₂) production in the AVPO. LPS caused typical hypothermia followed by fever. Levels of AVPO H₂S were significantly increased during hypothermia when compared to both euthermic and febrile rats. Intracerebroventricular (icv) microinjection of aminooxyacetate (AOA, a CBS inhibitor; 100 pmol) neither affected Tb nor basal PGD₂ production during euthermia. In LPS-treated rats, AOA caused increased Tb values during hypothermia, along with enhanced PGD₂ production. We conclude that the gaseous messenger H₂S modulates hypothermia during endotoxic shock, acting as a cryogenic molecule.

Permissive role of AMPK and autophagy in adiponectin deficiency-accentuated myocardial injury and inflammation in endotoxemia

BACKGROUND

Adiponectin (APN), an adipose-derived adipokine, alleviates lipopolysaccharide (LPS)-induced injury in multiple organs including hearts although the underlying mechanism in endotoxemia remains elusive. This study was designed to examine the role of adiponectin in LPS-induced cardiac anomalies and inflammation as well as the underlying mechanism with a focus on autophagy - a conserved machinery for bulk degradation of intracellular components.

METHODS AND RESULTS

Wild-type (WT) and APN(-/-) mice were challenged with LPS (4mg/kg) or saline for 6h. Echocardiography, cardiomyocyte contractile and intracellular Ca(2+) properties were evaluated. Markers of autophagy, apoptosis and inflammation including LC3B, p62, Beclin1, AMPK, mTOR, ULK, Caspase 3, Bcl-2, Bax, TLR4, TRAF6, MyD88, IL-1B, TNFα, HMGB1, JNK and IκB were examined using Western blot or RT-PCR. Our results showed that LPS challenge reduced fractional shortening, compromised cardiomyocyte contractile capacity, intracellular Ca(2+) handling properties, apoptosis and inflammation, which were accentuated by adiponectin ablation. Adiponectin ablation unmasked the LPS-induced cardiac remodeling (left ventricular end systolic diameter) and prolongation of cell shortening. The detrimental effects of adiponectin ablation were associated with dampened autophagy in response to LPS through an AMPK-mTOR-ULK1-dependent mechanism. In vivo administration of AMPK activator AICAR or the autophagy inducer rapamycin effectively attenuated or obliterated LPS-induced and adiponectin deficiency-accentuated responses without affecting TLR4, TRAF6 and MyD88.

CONCLUSIONS

The findings suggest that AMPK and autophagy may play a permissive role in the adiponectin deficiency-exacerbated cardiac dysfunction, apoptosis and inflammation under LPS challenge possibly at the post-TLR4 receptor level.

Clinical significance of plasma levels of brain natriuretic peptide and cardiac troponin T in patients with sepsis

Sepsis is a systemic inflammatory response of the body to an antigen and can become a life-threatening condition by triggering a cascade of changes leading to multiple organ failure such as heart failure. The aim of the present study was to examine the changes of the plasma levels of N-terminal of the prohormone brain natriuretic peptide (NT-proBNP) and cardiac troponin T (cTnT) in patients with sepsis and to analyze their prognostic significance. A total of 38 hospitalized patients with sepsis were included in the present study. The patients were divided into the survival and death groups, based on their prognosis. The plasma levels of NT-proBNP and cTnT for the two groups were measured for all the patients on the 1st, 3rd and 7th day of admission. The plasma levels of NT-proBNP and cTnT between the two groups were compared and their association with prognosis were analyzed. The plasma levels of NT-proBNP and cTnT in the death group were significantly higher than those in the survival group (P<0.05). Additionally, a positive assocciation of the plasma levels of NT-proBNP and cTnT was identified (P<0.05). In conclusion, the plasma levels of NT-proBNP and cTnT may be used as routine clinical biomarkers to assess the prognosis of patients with sepsis.