The contact system proteases play disparate roles in streptococcal sepsis

The role of TLR4/MyD88/NF-κB in the protective effect of ulinastatin on the intestinal mucosal barrier in mice with sepsis

OBJECTIVE

To investigate the effect of the TLR4/MyD88/NF-κB (Toll-like receptor 4/myeloid differentiation factor/nuclear factor kappa B) signalling pathway on the protective effect of ulinastatin on the intestinal mucosal barrier in mice with sepsis.

METHODS

A mouse model of sepsis was established by classical caecal ligation and perforation. Forty-four SPF C57BL/6 mice were randomly divided into the following four groups with 11 mice in each group: the control group (Con group), ulinastatin group (Uti group), Uti + LPS (lipopolysaccharide, LPS) group (Uti + LPS group) and LPS group. Mice in the Con group and Uti group received saline or ulinastatin injected 2 h after modelling; Mice in the Uti + LPS group received LPS injected 0 h after modelling, other procedures were the same as in the Uti group; Mice in the LPS group received LPS only. At 48 h after surgery, the levels of TNF-α (tumour necrosis factor-α, TNF-α), IL-6 (interleukin-6, IL-6) and IL-1β (interleukin-1β, IL-1β) in vein, and the expression of TLR4, MyD88 and NF-κB mRNA in small intestinal mucosa tissues using ELISA and RT‒PCR.

RESULTS

The pathological specimens showed increased inflammatory injury in the Con and LPS groups, while these injuries and changes improved in the Uti group. The scores of intestinal mucosal injury at 48 h of Uti injection were significantly lower than those of the Con group (P < 0.001), while the scores of intestinal mucosal injury of Uti + LPS were significantly higher than those of the Uti group (P = 0.044). The expression of TNF-α, IL-6 and IL-1β in the Uti decreased significantly at 48 h after surgery than that in the Con group (P = 0.001, P = 0.014, P = 0.004), while the expression of TNF-α, IL-6 and IL-1β in the Uti + LPS group increased significantly after surgery than that in the Uti group (P = 0.026, P = 0.040, P = 0.039). The expression of TLR4, MyD88 and NF-κB mRNA in the Uti group decreased significantly compared with that in the Con group (P = 0.001, P = 0.021, P = 0.007), while the expression of TLR4, MyD88 and NF-κB mRNA in the Uti + LPS group was higher than that in the Uti group (P = 0.023, P = 0.040, P = 0.045).

CONCLUSION

These findings indicate that the protective effect of ulinastatin on the intestinal mucosal barrier against sepsis may be mediated through the TLR4/MyD88/NF-κB pathway.

An update on factor XII-driven vascular inflammation

The plasma protein factor XII (FXII) is the liver-derived zymogen of the serine protease FXIIa that initiates an array of proteolytic cascades. Zymogen activation, enzymatic FXIIa activity and functions are regulated by interactions with cell receptors, negatively charged surfaces, other serine proteases, and serpin inhibitors, which bind to distinct protein domains and regions in FXII(a). FXII exerts mitogenic activity, while FXIIa initiates the pro-inflammatory kallikrein-kinin pathway and the pro-thrombotic intrinsic coagulation pathway, respectively. Growing evidence indicates that FXIIa-mediated thrombo-inflammation plays a crucial role in various pathological states besides classical thrombosis, such as endothelial dysfunction. Consistently, increased FXIIa levels are associated with hypercholesterolemia and hypertriglyceridemia. In contrast, FXII deficiency protects from thrombosis but is otherwise not associated with prolonged bleeding or other adverse clinical manifestations. Here, we review current concepts for FXII(a)-driven vascular inflammation focusing on endothelial hyperpermeability, receptor signaling, atherosclerosis and immune cell activation.

The contact system in liver injury

Coagulation is controlled by a delicate balance of prothrombotic and antithrombotic mechanisms, to prevent both excessive blood loss from injured vessels and pathologic thrombosis. The liver plays a pivotal role in hemostasis through the synthesis of plasma coagulation factors and their inhibitors that, in addition to thrombosis and hemostasis, orchestrates an array of inflammatory responses. As a result, impaired liver function has been linked with both hypercoagulability and bleeding disorders due to a pathologic balance of pro- and anticoagulant plasma factors. At sites of vascular injury, thrombus propagation that finally may occlude the blood vessel depends on negatively charged biopolymers, such as polyphosphates and extracellular DNA, that provide a physiological surface for contact activation of coagulation factor XII (FXII). FXII initiates the contact system that drives both the intrinsic pathway of coagulation, and formation of the inflammatory mediator bradykinin by the kallikrein–kinin system. Moreover, FXII facilitates receptor-mediated signalling, thereby promoting mitogenic activities, angiogenesis, and neutrophil stimulation with implications for liver diseases. Here, we summarize current knowledge on the FXII-driven contact system in liver diseases and review therapeutic approaches to target its activities during impaired liver function.

The Diagnostic Value of Fe3+ and Inflammation Indicators in the Death of Sepsis Patients: A Retrospective Study of 428 Patients

Background

Studies have shown that a variety of blood inflammatory markers can be used to assess the criticality of patients with sepsis. In this study, the blood inflammatory factors related to the sepsis survival group and the death group were compared and analyzed, which can be used by clinicians to adjust sepsis patient treatment.

Methods

This study used retrospective methods to analyze the medical records of 428 patients with sepsis. The test of blood samples includes the patient's age, gender, hospital stays, the concentration of procalcitonin (PCT), absolute neutrophil count (ANC), absolute lymphocyte count (ALC), neutrophil-to-lymphocyte ratio (NLR), D-dimer (DD), Fe³⁺, and hemoglobin (Hb) in the venous blood of patients with sepsis. The detection of PCT methods adopts the sandwich immunofluorescence (IF). ROC curve was used for the diagnosis and analysis of various factors of sepsis.

Results

Among all the patients with sepsis, 133 patients died, with a mortality rate of 31.07%. Analysis of related inflammatory indicators and the patient's baseline parameters showed the patients age, the values of PCT, ANC, NLR, and DD in death group were statistically higher than those in survival group (all p values were <0.05). However, the concentration of Fe³⁺ and ALC show an opposite trend between the two groups. Regression analysis results showed the patient's gender, Fe³⁺, PCT, ANC, and DD are all independent prognostic factors for patients with sepsis. The results of the ROC curve of related diagnostic indicators show that DD has the best area under curve (AUC=0.700), the most sensitive index is ANC (74.44), and the most specific index is PCT (89.80). The results of the two-by-two combined diagnosis of the four indicators showed that the PCT+DD group had better AUC (0.748) and specificity (78.23), and the Fe³⁺+DD group had the best sensitivity (75.89).

Conclusion

In this study, the patient's gender and the inflammation-related markers of Fe³⁺, PCT, ANC, and DD can be used as independent risk factors affecting the prognosis of patients with sepsis. The combination of PCT+DD and Fe³⁺+DD has high diagnostic value for patients with sepsis.

Kinins and Their Receptors in Infectious Diseases

Kinins and their receptors have been implicated in a series of pathological alterations, representing attractive pharmacological targets for several diseases. The present review article aims to discuss the role of the kinin system in infectious diseases. Literature data provides compelling evidence about the participation of kinins in infections caused by diverse agents, including viral, bacterial, fungal, protozoan, and helminth-related ills. It is tempting to propose that modulation of kinin actions and production might be an adjuvant strategy for management of infection-related complications.

Kininogen supports inflammation and bacterial spreading during Streptococccus Pyogenes Sepsis

BACKGROUND

High-molecular-weight kininogen is a cofactor of the human contact system, an inflammatory response mechanism that is activated during sepsis. It has been shown that high-molecular-weight kininogen contributes to endotoxemia, but is not critical for local host defense during pneumonia by Gram-negative bacteria. However, some important pathogens, such as Streptococcus pyogenes, can cleave kininogen by contact system activation. Whether kininogen causally affects antibacterial host defense in S. pyogenes infection, remains unknown.

METHODS

Kininogen concentration was determined in course plasma samples from septic patients. mRNA expression and degradation of kininogen was determined in liver or plasma of septic mice. Kininogen was depleted in mice by treatment with selective kininogen directed antisense oligonucleotides (ASOs) or a scrambled control ASO for 3 weeks prior to infection. 24 h after infection, infection parameters were determined.

FINDINGS

Data from human and mice samples indicate that kininogen is a positive acute phase protein. Lower kininogen concentration in plasma correlate with a higher APACHE II score in septic patients. We show that ASO-mediated depletion of kininogen in mice indeed restrains streptococcal spreading, reduces levels of proinflammatory cytokines such as IL-1β and IFNγ, but increased intravascular tissue factor and fibrin deposition in kidneys of septic animals.

INTERPRETATION

Mechanistically, kininogen depletion results in reduced plasma kallikrein levels and, during sepsis, in increased intravascular tissue factor that may reinforce immunothrombosis, and thus reduce streptococcal spreading. These novel findings point to an anticoagulant and profibrinolytic role of kininogens during streptococcal sepsis.

FUNDING

Full details are provided in the Acknowledgements section.

Sepsis Activates the TLR4/MyD88 Pathway in Schwann Cells to Promote Infiltration of Macrophages, Thereby Impeding Neuromuscular Function

INTRODUCTION

Sepsis is a kind of maladjustment response to bacterial infection and activation of coagulation, which can induce neuromuscular dysfunction. However, there is scarce of experimental evidence about the relationship between Schwann cells (SCs) and sepsis in neuromuscular dysfunction. We therefore set out to identify the potential role of SCs in sepsis-induced neuromuscular dysfunction and to explore the underlying molecular mechanism.

METHODS

Primary SCs were isolated from the left hind limb sciatic nerve of sepsis mice, which was constructed by cecal ligation and puncture. Then, the SCs were infected with adenovirus encoding toll-like receptor 4 (TLR4), MyD88, or IL-1R (with lipopolysaccharide stimulation), and the Raw 264.7 macrophages were injected with adenovirus with CCR2 silencing (with mMCP-1 stimulation). Further investigation of the interleukin 1 beta (IL-1β) and macrophage cationic peptide 1 (MCP-1) expressions, we followed reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay techniques, the F4/80 and Ki67 expressions was observed by immunofluorescence staining, while the expressions of CCR2, FAK/p-FAK, nuclear factor-κB (NFκB)/p-NFκB, and ERK1/2/p-ERK1/2 were determined by Western blot analysis. Last, but not the least, the cell migration ability and cell proliferation ability were detected by Transwell assay and Flow cytometry respectively.

RESULTS

Our results showed that in sepsis mice, the TLR4/MyD88/ERK pathway was activated in SCs, which triggered the cells to secrete IL-1β and MCP-1. The secreted IL-1β bound with IL-1β receptor on the surface of SCs, thereby activating the IL-1β/IL-1R/MyD88/ERK pathway and further promoting the secretion of MCP-1 by SCs. MCP-1 was found to bind to CCR2 on the surface of Raw264.7 macrophages to activate the TLR4/MyD88/ERK pathway which caused the inhibition of neuromuscular function.

CONCLUSION

Sepsis significantly promotes the infiltration of macrophages by activating the TLR4/MyD88 pathway in SCs, thereby impeding neuromuscular function. Consistently, our study provides a novel concept in the area of neuromuscular dysfunction therapeutics following sepsis.