Acute phase protein, α - 1- acid glycoprotein (AGP-1), has differential effects on TLR-2 and TLR-4 mediated responses

An Update on Toll-like Receptor 2, Its Function and Dimerization in Pro- and Anti-Inflammatory Processes

While a certain level of inflammation is critical for humans to survive infection and injury, a prolonged inflammatory response can have fatal consequences. Pattern recognition Toll-like receptors (TLRs) are key players in the initiation of an inflammatory process. TLR2 is one of the most studied pattern recognition receptors (PRRs) and is known to form heterodimers with either TLR1, TLR4, TLR6, and TLR10, allowing it to recognize a wide range of pathogens. Although a large number of studies have been conducted over the past decades, there are still many unanswered questions regarding TLR2 mechanisms in health and disease. In this review, we provide an up-to-date overview of TLR2, including its homo- and heterodimers. Furthermore, we will discuss the pro- and anti-inflammatory properties of TLR2 and recent findings in prominent TLR2-associated infectious and neurodegenerative diseases.

Metagenomic next-generation sequencing and proteomics analysis in pediatric viral encephalitis and meningitis

Introduction

Early and accurate identification of pathogens is essential for improved outcomes in patients with viral encephalitis (VE) and/or viral meningitis (VM).

Methods

In our research, Metagenomic next-generation sequencing (mNGS) which can identify viral pathogens unbiasedly was performed on RNA and DNA to identify potential pathogens in cerebrospinal fluid (CSF) samples from 50 pediatric patients with suspected VEs and/or VMs. Then we performed proteomics analysis on the 14 HEV-positive CSF samples and another 12 CSF samples from health controls (HCs). A supervised partial least squaresdiscriminant analysis (PLS-DA) and orthogonal PLS-DA (O-PLS-DA) model was performed using proteomics data.

Results

Ten viruses in 48% patients were identified and the most common pathogen was human enterovirus (HEV) Echo18. 11 proteins overlapping between the top 20 DEPs in terms of P value and FC and the top 20 proteins in PLS-DA VIP lists were acquired.

Discussion

Our result showed mNGS has certain advantages on pathogens identification in VE and VM and our research established a foundation to identify diagnosis biomarker candidates of HEV-positive meningitis based on MS-based proteomics analysis, which could also contribute toward investigating the HEV-specific host response patterns.

A comparative proteomic analysis to define the influencing factors on gingival crevicular fluid using LC-MS/MS

Gingival crevicular fluid (GCF) is a promising biofluid for disease identification and biomarker searching in periodontology. This study aimed to investigate the possible influencing factors, including tooth site, sex and age, on the normal GCF proteome. Forty periodontal healthy adults were randomly divided into a training group and a testing group. In the training group, GCF samples from 12 adults were analyzed using the iTRAQ 2D LC-MS/MS method. The influencing factors, tooth site (including periodontitis-susceptible and -insusceptible tooth sites), sex and age, and related differential proteins were defined and functionally annotated. The important differential proteins from 28 adults in the testing group were then validated by PRM analysis. An average of approximately 5 differential proteins were found between tooth sites of periodontitis-susceptible and -insusceptible sites. Eighty-five differentially expressed proteins were obtained between sexes in the young group, while only 7 sex-associated proteins were found in the old group. A total of 203 and 235 age-associated proteins were found in the male and female groups, respectively. The differential protein functional annotation showed that sex-related proteins were mainly related to immune function and metabolism, and age-related proteins were primarily associated with inflammation, lipid metabolism and immune function. In the testing group, a total of 4 sex-related proteins and 12 age-related proteins were validated by PRM analysis. SIGNIFICANCE: The influences of tooth site, sex and age in GCF proteomics in periodontal health were firstly analyzed using LC-MS/MS. Tooth site showed a small influence on the GCF proteome. The sex effect was significant in young adults, but its influence in old adults is small. Age is an important impact factor for the GCF proteome. These findings enrich the knowledge about the normal GCF proteome and might benefit future disease analyses.

Reversible cross-tolerance to platelet-activating factor signaling by bacterial toxins

Bacterial toxins signaling through Toll-like receptors (TLRs) are implicated in the pathogenesis of many inflammatory diseases. Among the toxins, lipopolysaccharide (LPS) exerts its action via TLR-4 while lipoteichoic acid (LTA) and bacterial lipoproteins such as Braun lipoprotein (BLP) or its synthetic analogue Pam3CSK4 act through TLR-2. Part of the TLR mediated pathogenicity is believed to stem from endogenously biosynthesized platelet-activating factor (PAF)- a potent inflammatory phospholipid acting through PAF-receptor (PAF-R). However, the role of PAF in inflammatory diseases like endotoxemia is controversial. In order to test the direct contribution of PAF in TLR-mediated pathogenicity, we intraperitoneally injected PAF to Wistar albino mice in the presence or absence of bacterial toxins. Intraperitoneal injection of PAF (5 μg/mouse) causes sudden death of mice, that can be delayed by simultaneously or pre-treating the animals with high doses of bacterial toxins- a phenomenon known as endotoxin cross-tolerance. The bacterial toxins- induced tolerance to PAF can be reversed by increasing the concentration of PAF suggesting the reversibility of cross-tolerance. We did similar experiments using human platelets that express both canonical PAF-R and TLRs. Although bacterial toxins did not induce human platelet aggregation, they inhibited PAF-induced platelet aggregation in a reversible manner. Using rabbit platelets that are ultrasensitive to PAF, we found bacterial toxins (LPS and LTA) and Pam3CSK4 causing rabbit platelet aggregation via PAF-R dependent way. The physical interaction of PAF-R and bacterial toxins is also demonstrated in a human epidermal cell line having stable PAF-R expression. Thus, we suggest the possibility of direct physical interaction of bacterial toxins with PAF-R leading to cross-tolerance.

Bacterial lipoproteins in sepsis

Bacterial lipoproteins are membrane proteins derived from both gram-negative and gram-positive bacteria. They seem to have diverse functions not only on bacterial growth, but also play an important role in host's virulence. Bacterial lipoproteins exert their action on host immune cells via TLR2/1 or TLR2/6. Therefore, bacterial lipoproteins also need to be considered while addressing bacterial pathogenicity besides classical bacterial endotoxin like LPS and other microbial associated molecular patterns such as LTA, and peptidoglycans. In this mini-review, we provide an overview of general bacterial lipoprotein biosynthesis and the need to understand the lipoprotein-mediated pathogenicity in diseases like sepsis.

Different glycoforms of alpha-1-acid glycoprotein contribute to its functional alterations in platelets and neutrophils

Alpha-1-acid glycoprotein (AGP-1) is a positive acute phase glycoprotein with uncertain functions. Serum AGP-1 (sAGP-1) is primarily derived from hepatocytes and circulates as 12-20 different glycoforms. We isolated a glycoform secreted from platelet-activating factor (PAF)-stimulated human neutrophils (nAGP-1). Its peptide sequence was identical to hepatocyte-derived sAGP-1, but nAGP-1 differed from sAGP-1 in its chromatographic behavior, electrophoretic mobility, and pattern of glycosylation. The function of these 2 glycoforms also differed. sAGP-1 activated neutrophil adhesion, migration, and neutrophil extracellular traps (NETosis) involving myeloperoxidase, peptidylarginine deiminase 4, and phosphorylation of ERK in a dose-dependent fashion, whereas nAGP-1 was ineffective as an agonist for these events. Furthermore, sAGP-1, but not nAGP-1, inhibited LPS-stimulated NETosis. Interestingly, nAGP-1 inhibited sAGP-1-stimulated neutrophil NETosis. The discordant effect of the differentially glycosylated AGP-1 glycoforms was also observed in platelets where neither of the AGP-1 glycoforms alone stimulated aggregation of washed human platelets, but sAGP-1, and not nAGP-1, inhibited aggregation induced by PAF or ADP, but not by thrombin. These functional effects of sAGP-1 correlated with intracellular cAMP accumulation and phosphorylation of the protein kinase A substrate vasodilator-stimulated phosphoprotein and reduction of Akt, ERK, and p38 phosphorylation. Thus, the sAGP-1 glycoform limits platelet reactivity, whereas nAGP-1 glycoform also limits proinflammatory actions of sAGP-1. These studies identify new functions for this acute phase glycoprotein and demonstrate that the glycosylation of AGP-1 controls its effects on 2 critical cells of acute inflammation.

Integration Analysis of m6A-SNPs and eQTLs Associated With Sepsis Reveals Platelet Degranulation and Staphylococcus aureus Infection are Mediated by m6A mRNA Methylation

Sepsis is a major threat with high mortality rate for critically ill patients. Response to pathogen infection by the host immune system is a key biological process involved in the onset and development of sepsis. Heterogeneous host genome variation, especially single nucleotide polymorphisms (SNPs), has long been suggested to contribute to differences in disease progression. However, the function of SNPs located in non-coding regions remains to be elucidated. Recently, m⁶A mRNA modification levels were revealed to differ at SNPs. As m⁶A is a crucial regulator of gene expression, these SNPs might control genes by changing the m⁶A level on mRNA. To investigate the potential role of m⁶A SNPs in sepsis, we integrated m⁶A-SNP and expression quantitative trait loci (eQTLs) data. Analysis revealed 15,720 m⁶A-cis-eQTLs and 381 m⁶A-trans-eQTLs associated with sepsis. We identified 1321 genes as locations of m⁶A-cis-eQTLs. These were enriched in platelet degranulation and Staphylococcus aureus infection pathways, which are vital for the pathophysiological process of sepsis. We conclude that m⁶A modification of mRNA plays a very important role in sepsis, with m⁶A-cis-eQTLs potentially having the most effect on individual variation in sepsis progression.

α1-Acid glycoprotein and seminal parameter in chronic hemodialysis patients

INTRODUCTION

To find out the changes in seminal quality of hemodialysis chronic renal patients, we investigated the possible relationship between seminal parameter and seminal α1-acid glycoprotein levels in chronic hemodialysis patients.

METHODS

Prospective study of prevalence realized in the Hemodialysis Sector of the University Hospital of the University of Brasília, between July 2016 and December 2016. Men aged 18-60 years grouped into case groups (n = 81) represented by chronic hemodialysis patients and control group (n = 20) of healthy men without clinical or laboratory signs of infection and eugonadic. We performed a spermogram, hormonal profile, and assessment of leukocytes and seminal α1-acid glycoprotein level in the semen. The most appropriate statistical test was applied to verify differences and correlations between the studied variables.

RESULTS

The age in case and control is similar (49.47 ± 5.55 years vs 50.53 ± 4.24 years; p = 0.060). Mean level of α1-acid glycoprotein in human seminal plasma were not significantly different between case and control (48.52 ± 4.90 mg/L vs 46.33 ± 4.29 mg/L; p = 0.10) and between normosperm and oligosperm (47.76 ± 5.15 mg/L vs 49.48 ± 4.49 mg/L; p = 0.19). Mean level of α1-acid glycoprotein in human seminal plasma in the case group, which were classified into severe, moderate, mild, and normosperm, were similar to each other (p = 0.27) and did not correlate (p > 0.05) with the analyzed seminal parameters. All participants presented normal hormonal profile.

CONCLUSION

Results of this study suggest that the seminal α1-acid glycoprotein levels do not help in the initial evaluation of patients with seminal parameter changes.