Reactive oxygen and nitrogen species in sepsis-induced hepatic microvascular dysfunction

Pregnane X Receptor Activation in Liver Macrophages Protects against Endotoxin-Induced Liver Injury

Endotoxemia-related acute liver injury has a poor prognosis and high mortality, and macrophage polarization plays a central role in the pathological process. Pregnane X receptor (PXR) serves as a nuclear receptor and xenosensor, safeguarding the liver from toxic stimuli. However, the effect and underlying mechanism of PXR activation on endotoxemic liver injury remain largely unknown. Here, the expression of PXR is reported in human and murine macrophages, and PXR activation modified immunotypes of macrophages. Moreover, PXR activation significantly attenuated endotoxemic liver injury and promoted macrophage M2 polarization. Macrophage depletion by GdCl3 confirmed the essential of macrophages in the beneficial effects observed with PXR activation. The role of PXR in macrophages is further validated using AAV8-F4/80-Pxr shRNA-treated mice; the PXR-mediated hepatoprotection is impaired, and M2 polarization enhancement is blunted. Additionally, treatment with PXR agonists inhibited lipopolysaccharide (LPS)-induced M1 polarization and favored M2 polarization in BMDM, Raw264.7, and THP-1 cells. Further analyses revealed an interaction between PXR and p-STAT6 in vivo and in vitro. Moreover, blocking Pxr or Stat6 abolished the PXR-induced polarization shift. Collectively, macrophage PXR activation attenuated endotoxin-induced liver injury and regulated macrophage polarization through the STAT6 signaling pathway, which provided a potential therapeutic target for managing endotoxemic liver injury.

Simultaneous Inhibition of Three Major Cytokines and Its Therapeutic Effects: A Peptide-Based Novel Therapy against Endotoxemia in Mice

Three major cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6, mediate endotoxemia-induced liver injury. With the similar structures to the binding domains of the three cytokines to their cognate receptors, the novel peptide KCF18 can simultaneously inhibit TNF-α, IL-1β, and IL-6. We elucidated whether KCF18 can alleviate injury of liver in endotoxemic mice. Adult male mice (BALB/cJ) were intraperitoneally (i.p.) administered lipopolysaccharide (LPS, 15 mg/kg; LPS group) or LPS with KCF18 (LKCF group). Mice in the LKCF group received KCF18 (i.p.) at 2 h (0.6 mg/kg), 4 h (0.3 mg/kg), 6 h (0.3 mg/kg), and 8 h (0.3mg/kg) after LPS administration. Mice were sacrificed after receiving LPS for 24 h. Our results indicated that the binding levels of the three cytokines to their cognate receptors in liver tissues in the LKCF group were significantly lower than those in the LPS group (all p < 0.05). The liver injury level, as measured by performing functional and histological analyses and by determining the tissue water content and vascular permeability (all p < 0.05), was significantly lower in the LKCF group than in the LPS group. Similarly, the levels of inflammation (macrophage activation, cytokine upregulation, and leukocyte infiltration), oxidation, necroptosis, pyroptosis, and apoptosis (all p < 0.05) in liver tissues in the LKCF group were significantly lower than those in the LPS group. In conclusion, the KCF18 peptide–based simultaneous inhibition of TNF-α, IL-1β, and IL-6 can alleviate liver injury in mice with endotoxemia.

Progress in research of liver injury induced by acute biliary pancreatitis

Acute biliary pancreatitis (ABP) not only causes acute inflammation of the pancreas, but also leads to obstruction or infection of the biliary system. Liver injury is one of the most common complications of ABP. The pathological mechanisms mainly include infection and endotoxin, cholestasis, pancreatic enzyme damage, microcirculatory disorders, and oxidative stress, and the research conclusions are mostly derived from animal experiments. On the basis of routine medical treatment of ABP, active anti-infective treatment and rapid relief of biliary obstruction can promote the recovery of ABP-related liver injury.

Acute hyperglycemia increases sepsis related glycocalyx degradation and endothelial cellular injury: A microfluidic study

BACKGROUND

Hyperglycemia promotes vascular inflammation; however its effect on endothelial dysfunction in sepsis is unknown. Microfluidic devices (MFD) may closely mimic the in vivo endothelial cell microenvironment. We hypothesized that stress glucose concentrations would increase sepsis related endothelial injury/activation.

METHODS

Human umbilical vein endothelial cell (HUVEC) monolayers were established in microfluidic channels. TNF was added followed by glucose. Endothelial glycocalyx (EG) integrity was indexed by shedding of the EG components as well as thickness. Endothelial cell (EC) injury/activation was indexed by soluble biomarkers. Intracellular reactive oxygen species (ROS) was by fluorescence.

RESULTS

TNF increased glycocalyx degradation and was associated with biomarkers of EC injury. These vascular barrier derangements were further increased by hyperglycemia. This may be related to increase ROS species generated followed by the combined insults.

CONCLUSION

MFD technology may be a useful platform to study endothelial barrier function and stress conditions and allow preclinical assessment of potential therapies.

Analysis of early-onset bloodstream infection due to Escherichia coli infection in premature babies

In early-onset bacteremia among preterm neonates, Escherichia coli (E. coli) is the main pathogen and can cause a high mortality rate. Thus, the predictive factors of mortality and extended-spectrum β-lactamase (ESBL)-producing E. coli in preterm babies with E. coli early-onset bacteremia were reported.We retrospectively reviewed preterm neonates who had E. coli bacteremia occurring within 3 days after birth between 2004 and 2015. Maternal and perinatal information were collected from their medical records and analyzed by comparing the survival and nonsurvival groups, and also the ESBL-producing and non-ESBL-producing E. coli bacteremia groups. Mann-Whitney U test, Fisher exact test, and multivariate Cox proportional-hazard model were used for statistical analysis.A total of 27 preterm babies had E. coli bacteremia. The overall mortality rate was 55.56% (15 deaths). Five babies had ESBL-producing E. coli. The low systolic blood pressure of <48 mm Hg and low absolute neutrophil count of <2318 cells/mm were the most significant factors in predicting mortality. Moreover, the level of serum alanine aminotransferase was significantly lower in the ESBL-producing E. coli group than that in the non-ESBL-producing E. coli group.Therefore, the lower systolic blood pressure and absolute neutrophil count were the risk factors of mortality in preterm babies with early-onset E. coli bacteremia, and alanine aminotransferase could be a significant factor in predicting ESBL-producing E. coli.

Balancing Innate Immunity and Inflammatory State via Modulation of Neutrophil Function: A Novel Strategy to Fight Sepsis

Sepsis and SIRS (systemic inflammatory response syndrome) belong to a severe disease complex characterized by infection and/or a whole-body inflammatory state. There is a growing body of evidence that neutrophils are actively involved in sepsis and are responsible for both release of cytokines and phagocytosis of pathogens. The neutrophil level is mainly regulated by G-CSF, a cytokine and drug, which is widely used in the septic patient with neutropenia. This review will briefly summarize the role of neutrophils and the therapeutic effect of G-CSF in sepsis. We further suggest that targeting neutrophil function to modulate the balance between innate immunity and inflammatory injury could be a worthwhile therapeutic strategy for sepsis.

Endothelial nitric oxide synthase in the microcirculation

Endothelial nitric oxide synthase (eNOS, NOS3) is responsible for producing nitric oxide (NO)--a key molecule that can directly (or indirectly) act as a vasodilator and anti-inflammatory mediator. In this review, we examine the structural effects of regulation of the eNOS enzyme, including post-translational modifications and subcellular localization. After production, NO diffuses to surrounding cells with a variety of effects. We focus on the physiological role of NO and NO-derived molecules, including microvascular effects on vessel tone and immune response. Regulation of eNOS and NO action is complicated; we address endogenous and exogenous mechanisms of NO regulation with a discussion of pharmacological agents used in clinical and laboratory settings and a proposed role for eNOS in circulating red blood cells.

Platelet hemostasis in patients with metabolic syndrome and type 2 diabetes mellitus: cGMP- and NO-dependent mechanisms in the insulin-mediated platelet aggregation

Patients with metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) have high risk of microcirculation complications and microangiopathies. An increase in thrombogenic risk is associated with platelet hyperaggregation, hypercoagulation, and hyperfibrinolysis. Factors leading to platelet activation in MetS and T2DM comprise insulin resistance, hyperglycemia, non-enzymatic glycosylation, oxidative stress, and inflammation. This review discusses the role of nitric oxide (NO) in the regulation of platelet adhesion and aggregation processes. NO is synthesized both in endotheliocytes, smooth muscle cells, macrophages, and platelets. Modification of platelet NO-synthase (NOS) activity in MetS patients can play a central role in the manifestation of platelet hyperactivation. Metabolic changes, accompanying T2DM, can lead to an abnormal NOS expression and activity in platelets. Hyperhomocysteinemia, often accompanying T2DM, is a risk factor for cardiovascular accidents. Homocysteine can reduce NO production by platelets. This review provides data on the insulin effects in platelets. Decrease in a number and sensitivity of the insulin receptors on platelets in T2DM can cause platelet hyperactivation. Various intracellular mechanisms of anti-aggregating insulin effects are discussed. Anti-aggregating effects of insulin are mediated by a NO-induced elevation of cGMP and upregulation of cAMP- and cGMP-dependent pathways. The review presents data suggesting an ability of platelets to synthesize humoral factors stimulating thrombogenesis and inflammation. Proinflammatory cytokines are considered as markers of T2DM and cardiovascular complications and are involved in the development of dyslipidemia and insulin resistance. The article provides an evaluation of NO-mediated signaling pathway in the effects of cytokines on platelet aggregation. The effects of the proinflammatory cytokines on functional activity of platelets are demonstrated.

The liver in sepsis: patterns of response and injury

PURPOSE OF REVIEW

Sepsis elicits profound changes in the concentrations of plasma proteins synthesized by liver parenchymal cells referred to as acute-phase proteins. Mechanisms controlling this orchestrated response include release of cytokines that induce acute-phase proteins, while other 'house-keeping' genes are downregulated.

RECENT FINDINGS

Although some acute-phase proteins help to control damage, functions of many other acute-phase reactants remain obscure. Changes in acute-phase gene expression are primarily subject to transcriptional regulation and can be comprehensively monitored by array techniques. Emerging evidence from such strategies implies that in addition to a 'common host response' also highly specific pathways are induced in specific disease contexts. Applying a systems biology approach to the integrated response of the hepatocyte to infection would suggest that the reprogramming of metabolic functions occurs in parallel with a severity-dependent disruption of phase I and II biotransformation and canalicular transport, that is, excretory failure. Although traditionally bilirubin serves to monitor excretion, emerging evidence suggests that bile acids indicate liver dysfunction with higher sensitivity and specificity.

SUMMARY

Sepsis induces reprogramming of the hepatic transcriptome. This includes induction of adaptive acute-phase proteins but also repression of phase I, II metabolism and transport with important implications for monitoring and pharmacotherapy.