Thrombomodulin: a multifunctional receptor modulating the endothelial quiescence

Thrombomodulin (TM) is a type 1 receptor best known for its function as an anticoagulant cofactor for thrombin activation of protein C on the surface of vascular endothelial cells. In addition to its anticoagulant cofactor function, TM also regulates fibrinolysis, complement, and inflammatory pathways. TM is a multidomain receptor protein with a lectin-like domain at its N-terminus that has been shown to exhibit direct anti-inflammatory functions. This domain is followed by 6 epidermal growth factor-like domains that support the interaction of TM with thrombin. The interaction inhibits the procoagulant function of thrombin and enables the protease to regulate the anticoagulant and fibrinolytic pathways by activating protein C and thrombin-activatable fibrinolysis inhibitor. TM has a Thr/Ser-rich region immediately above the membrane surface that harbors chondroitin sulfate glycosaminoglycans, and this region is followed by a single-spanning transmembrane and a C-terminal cytoplasmic domain. The structure and physiological function of the extracellular domains of TM have been extensively studied, and numerous excellent review articles have been published. However, the physiological function of the cytoplasmic domain of TM has remained poorly understood. Recent data from our laboratory suggest that intracellular signaling by the cytoplasmic domain of TM plays key roles in maintaining quiescence by modulating phosphatase and tensin homolog signaling in endothelial cells. This article briefly reviews the structure and function of extracellular domains of TM and focuses on the mechanism and possible physiological importance of the cytoplasmic domain of TM in modulating phosphatase and tensin homolog signaling in endothelial cells.

Thrombomodulin Switches Signaling and Protease-Activated Receptor 1 Cleavage Specificity of Thrombin

BACKGROUND

Cleavage of the extracellular domain of PAR1 (protease-activated receptor 1) by thrombin at Arg41 and by APC (activated protein C) at Arg46 initiates paradoxical cytopathic and cytoprotective signaling in endothelial cells. In the latter case, the ligand-dependent coreceptor signaling by EPCR (endothelial protein C receptor) is required for the protective PAR1 signaling by APC. Here, we investigated the role of thrombomodulin in determining the specificity of PAR1 signaling by thrombin.

METHODS

We prepared a PAR1 knockout (PAR1-/-) EA.hy926 endothelial cell line by CRISPR/Cas9 and transduced PAR1-/- cells with lentivirus vectors expressing PAR1 mutants in which either Arg41 or Arg46 was replaced with an Ala. Furthermore, human embryonic kidney 293 cells were transfected with wild-type or mutant PAR1 cleavage reporter constructs carrying N-terminal Nluc (NanoLuc luciferase) and C-terminal enhanced yellow fluorescent protein tags.

RESULTS

Characterization of transfected cells in signaling and receptor cleavage assays revealed that, upon interaction with thrombomodulin, thrombin cleaves Arg46 to elicit cytoprotective effects by a β-arrestin-2 biased signaling mechanism. Analysis of functional data and cleavage rates indicated that thrombin-thrombomodulin cleaves Arg46>10-fold faster than APC. Upon interaction with thrombin, the cytoplasmic domain of thrombomodulin recruited both β-arrestin-1 and -2 to the plasma membrane. Thus, the thrombin cleavage of Arg41 was also cytoprotective in thrombomodulin-expressing cells by β-arrestin-1-biased signaling. APC in the absence of EPCR cleaved Arg41 to initiate disruptive signaling responses like thrombin.

CONCLUSIONS

These results suggest that coreceptor signaling by thrombomodulin and EPCR determines the PAR1 cleavage and signaling specificity of thrombin and APC, respectively.

Genomic investigation unveils colistin resistance mechanism in carbapenem-resistant Acinetobacter baumannii clinical isolates

Colistin resistance in Acinetobacter baumannii is mediated by multiple mechanisms. Recently, mutations within pmrABC two-component system and overexpression of eptA gene due to upstream insertion of ISAba1 have been shown to play a major role. Thus, the aim of our study is to characterize colistin resistance mechanisms among the clinical isolates of A. baumannii in India. A total of 207 clinical isolates of A. baumannii collected from 2016 to 2019 were included in this study. Mutations within lipid A biosynthesis and pmrABC genes were characterized by whole-genome shotgun sequencing. Twenty-eight complete genomes were further characterized by hybrid assembly approach to study insertional inactivation of lpx genes and the association of ISAba1-eptA. Several single point mutations (SNPs), like M12I in pmrA, A138T and A444V in pmrB, and E117K in lpxD, were identified. We are the first to report two novel SNPs (T7I and V383I) in the pmrC gene. Among the five colistin-resistant A. baumannii isolates where complete genome was available, the analysis showed that three of the five isolates had ISAba1 insertion upstream of eptA. No mcr genes were identified among the isolates. We mapped the SNPs on the respective protein structures to understand the effect on the protein activity. We found that majority of the SNPs had little effect on the putative protein function; however, some SNPs might destabilize the local structure. Our study highlights the diversity of colistin resistance mechanisms occurring in A. baumannii, and ISAba1-driven eptA overexpression is responsible for colistin resistance among the Indian isolates.IMPORTANCEAcinetobacter baumannii is a Gram-negative, emerging and opportunistic bacterial pathogen that is often associated with a wide range of nosocomial infections. The treatment of these infections is hindered by increase in the occurrence of A. baumannii strains that are resistant to most of the existing antibiotics. The current drug of choice to treat the infection caused by A. baumannii is colistin, but unfortunately, the bacteria started to show resistance to the last-resort antibiotic. The loss of lipopolysaccharides and mutations in lipid A biosynthesis genes are the main reasons for the colistin resistance. The present study characterized 207 A. baumannii clinical isolates and constructed complete genomes of 28 isolates to recognize the mechanisms of colistin resistance. We showed the mutations in the colistin-resistant variants within genes essential for lipid A biosynthesis and that cause these isolates to lose the ability to produce lipopolysaccharides.

Thrombomodulin Regulates PTEN/AKT Signaling Axis in Endothelial Cells

BACKGROUND

We recently demonstrated that deletion of thrombomodulin gene from endothelial cells results in upregulation of proinflammatory phenotype. In this study, we investigated the molecular basis for the altered phenotype in thrombomodulin-deficient (TM-/-) cells.

METHODS

Different constructs containing deletions or mutations in the cytoplasmic domain of thrombomodulin were prepared and introduced to TM-/- cells. The phenotype of cells expressing different derivatives of thrombomodulin and tissue samples of thrombomodulin-knockout mice were analyzed for expression of distinct regulatory genes in established signaling assays.

RESULTS

The phosphatase and tensin homolog were phosphorylated and its recruitment to the plasma membrane was impaired in TM-/- cells, leading to hyperactivation of AKT (protein kinase B) and phosphorylation-dependent nuclear exclusion of the transcription factor, forkhead box O1. The proliferative/migratory properties of TM-/- cells were enhanced, and cells exhibited hypersensitivity to stimulation by angiopoietin 1 and vascular endothelial growth factor. Reexpression of wild-type thrombomodulin in TM-/- cells normalized the cellular phenotype; however, thrombomodulin lacking its cytoplasmic domain failed to restore the normal phenotype in TM-/- cells. Increased basal permeability and loss of VE-cadherin were restored to normal levels by reexpression of wild-type thrombomodulin but not by a thrombomodulin construct lacking its cytoplasmic domain. A thrombomodulin cytoplasmic domain deletion mutant containing 3-membrane-proximal Arg-Lys-Lys residues restored the barrier-permeability function of TM-/- cells. Enhanced phosphatase and tensin homolog phosphorylation and activation of AKT and mTORC1 (mammalian target of rapamycin complex 1) were also observed in the liver of thrombomodulin-KO mice.

CONCLUSIONS

These results suggest that the cytoplasmic domain of thrombomodulin interacts with the actin cytoskeleton and plays a crucial role in regulation of phosphatase and tensin homolog/AKT signaling in endothelial cells.

Diverse nature of ClpX degradation motifs in Streptococcus mutans

IMPORTANCE

Cytoplasmic Clp-related proteases play a major role in maintaining cellular proteome in bacteria. ClpX/P is one such proteolytic complex that is important for conserving protein homeostasis. In this study, we investigated the role of ClpX/P in Streptococcus mutans, an important oral pathogen. We identified several putative substrates whose cellular levels are regulated by ClpX/P in S. mutans and subsequently discovered several recognition motifs that are critical for degradation. Our study is the first comprehensive analysis of determining ClpX/P motifs in streptococci. We believe that identifying the substrates that are regulated by ClpX/P will enhance our understanding about virulence regulation in this important group of pathogens.

A retrospective analysis of the evolution of ergonomics for environmental sustainability (2011-2021)

Ergonomics for environmental sustainability has been rapidly gaining attention in the scientific community. So far, a large part of the literature has focussed on specific dimensions of ergonomics for environmental sustainability, such as green designs, green buildings, environmental education, and sustainability frameworks. However, there is a necessity for an integrated study that presents the summary of published literature supported by detailed bibliometric characteristics. To address this gap, this study examined 418 articles on ergonomics for environmental sustainability and analysed them through bibliometric and network analysis. Major findings reveal the publication trends in ergonomics for environmental sustainability starting from 2011 to the present, the most productive and influential authors, and the most influential articles. This study also identifies the co-citation structure, bibliographical couplings and keyword co-occurrences among these articles. Findings from this study also provide a summary of the current research and present a robust roadmap for future directions in ergonomics for environmental sustainability.Practitioner summary: This paper presents a bibliometric and network analysis of the academic literature in the domain of ergonomics for environmental sustainability. The study provides comprehensive insights into the relevant literature and identifies global research foci and future scopes. This study can guide practitioners in identifying the specific aspects of ergonomics for environmental sustainability to reduce global environmental impacts.

Phage-based therapy against biofilm producers in gram-negative ESKAPE pathogens

Persistent antibiotic use results in the rise of antimicrobial resistance with limited or no choice for multidrug-resistant (MDR) and extensively drug resistant (XDR) bacteria. This necessitates a need for alternative therapy to effectively combat clinical pathogens that are resistant to last resort antibiotics. The study investigates hospital sewage as a potential source of bacteriophages to control resistant bacterial pathogens. Eighty-one samples were screened for phages against selected clinical pathogens. Totally, 10 phages were isolated against A. baumannii, 5 phages against K. pneumoniae, and 16 phages were obtained against P. aeruginosa. The novel phages were observed to be strain-specific with complete bacterial growth inhibition of up to 6 h as monotherapy without antibiotics. Phage plus colistin combinations reduced the minimum-biofilm eradication concentration of colistin up to 16 folds. Notably, a cocktail of phages exhibited maximum efficacy with complete killing at 0.5-1 μg/ml colistin concentrations. Thus, phages specific to clinical strains have a higher edge in treating nosocomial pathogens with their proven anti-biofilm efficacy. In addition, analysis of phage genomes revealed close phylogenetic relations with phages reported from Europe, China, and other neighbouring countries. This study serves as a reference and can be extended to other antibiotics and phage types to assess optimum synergistic combinations to combat various drug resistant pathogens in the ongoing AMR crisis.

The role of hydrophobic patches of de novo designed MSI-78 and VG16KRKP antimicrobial peptides on fragmenting model bilayer membranes

Antimicrobial peptides (AMPs) with cell membrane lysing capability are considered potential candidates for the development of the next generation of antibiotics. Designing novel AMPs requires an in-depth understanding of the mechanism of action of the peptides. In this work, we used various biophysical techniques including ³¹P solid-state NMR to examine the interaction of model membranes with amphipathic de novo-designed peptides. Two such peptides, MSI-78 and VG16KRKP, were designed with different hydrophobicity and positive charges. The model lipid membranes were constituted by mixing lipids of varying degrees of 'area per lipid' (APL), which directly affected the packing properties of the membrane. The observed emergence of the isotropic peak in ³¹P NMR spectra as a function of time is a consequence of the fragmentation of the membrane mediated by the peptide interaction. The factors such as the charges, overall hydrophilicity of the AMPs, as well as lipid membrane packing, contributed to the kinetics of membrane fragmentation. Furthermore, we anticipate the designed AMPs follow the carpet and toroidal pore mechanisms when lysing the cell membrane. This study highlights the significance of the effect of the overall charges and the hydrophobicity of the novel AMPs designed for antimicrobial activity.

Activated protein C inhibits mesothelial-to-mesenchymal transition in experimental peritoneal fibrosis

BACKGROUND

In addition to its anticoagulant function in downregulating thrombin generation, activated protein C (APC) evokes pleiotropic cytoprotective signaling activities when it binds to endothelial protein C receptor (EPCR) to activate protease-activated receptor 1 (PAR1) in endothelial cells.

OBJECTIVES

To investigate the protective effect of APC in a chlorhexidine gluconate (CG)-induced peritoneal fibrosis model.

METHODS

Peritoneal fibrosis was induced in wild-type as well as EPCR- and PAR1-deficient mice via daily injection of CG (0.2 mL of 0.1% CG in 15% ethanol and 85% saline) for 21 days with or without concomitant injection of recombinant human APC derivatives (50 μg/kg of bodyweight). The expression of proinflammatory cytokines and profibrotic markers as well as collagen deposition were analyzed using established methods.

RESULTS

CG significantly upregulated the expression of transforming growth factor-β1 in peritoneal tissues, which culminated in the deposition of excessive extracellular matrix proteins, thickening of the peritoneal membrane, and mesothelial-to-mesenchymal transition in damaged tissues. APC potently inhibited CG-induced peritoneal fibrosis and downregulated the expression of proinflammatory cytokines, collagen deposition, Smad3 phosphorylation, and markers of mesothelial-to-mesenchymal transition (α-smooth muscle actin, vimentin, and N-cadherin). APC also inhibited transforming growth factor-β1-mediated upregulation of α-smooth muscle actin, Smad3, and fibronectin in human primary mesothelial cells. Employing signaling-selective and anticoagulant-selective variants of APC and mutant mice deficient for either EPCR or PAR1, we demonstrated that the EPCR-dependent signaling function of APC through PAR1 activation was primarily responsible for its antifibrotic activity in the CG-induced peritoneal fibrosis model.

CONCLUSION

APC and signaling-selective variants of APC may have therapeutic potential for preventing or treating pathologies associated with peritoneal fibrosis.

Distribution of two-component signal transduction systems BlpRH and ComDE across streptococcal species

Two-component signal transduction (TCS) systems are important regulatory pathways in streptococci. A typical TCS encodes a membrane-anchored sensor kinase (SK) and a cytoplasmic response regulator (RR). Approximately, 20 different types of TCSs are encoded by various streptococci. Among them, two TCSs, in particular BlpRH and ComDE, are required for bacteriocins production and competence development. The SK component of these two TCSs is highly similar and belongs to the protein kinase-10 (HPK-10) subfamily. While these two TCSs are present in streptococci, no systematic studies have been done to differentiate between these two TCSs, and the existence of these pathways in several species of the genus Streptococcus is also unknown. The lack of information about these pathways misguided researchers for decades into believing that the Streptococcus mutans BlpRH system is a ComDE system. Here, we have attempted to distinguish between the BlpRH and ComDE systems based on the location of the chromosome, genomic arrangement, and conserved residues. Using the SyntTax and NCBI databases, we investigated the presence of both TCS systems in the genome of several streptococcal species. We noticed that the NCBI database did not have proper annotations for these pathways in several species, and many of them were wrongly annotated, such as CitS or DpiB instead of BlpH. Nevertheless, our critical analyses led us to classify streptococci into two groups: class A (only the BlpRH system) and class B (both the BlpRH and ComDE systems). Most of the streptococcal groups, including bovis, pyogenic, mutans, salivarius, and suis, encode only the BlpRH system. In contrast, only in the mitis and anginosus groups were both the TCS systems present. The focus of this review is to identify and differentiate between the BlpRH and ComDE systems, and discuss these two pathways in various streptococci.

Antibody deposition on vascular endothelial cells contributes to localized inflammation in salivary glands

BACKGROUND

Oral and ocular dryness due to reduced saliva and tear production, exocrine gland inflammation, and autoantibodies to multiple cellular proteins are the cardinal features of Sjögren's Disease. Among the autoantibody specificities, anti-Ro52 is linked with higher disease severity. We have previously reported that mice immunized with recombinant Ro52 developed IgG deposits in salivary and lacrimal glands and showed reduced saliva and tear production. Furthermore, passive transfer of sera from Ro52-immunized mice rapidly induced glandular dysfunction without immune cell infiltration in recipient mice.

METHODS

To identify mechanisms driving antibody-mediated salivary gland dysfunction, hyperimmune rabbit antiserum to mouse Ro52 was passively transferred into NZM2758 female mice, pretreated with alum adjuvant. Alum-pretreated mice given hyperimmune rabbit antiserum to maltose-binding protein served as controls. Antibody deposition and its distribution in the salivary glands were studied by immunofluorescence staining for rabbit IgG, nerve fibers, and endothelial cells. The nCounter inflammation panel was used to determine differentially expressed genes in the salivary gland.

RESULTS

Rabbit IgG deposits were detected in salivary glands of anti-Ro52 immune sera recipients. The rabbit IgG was present on the endothelial cells in small blood vessels, and it did not co-localize with nerve fibers. Ingenuity pathway analysis of the gene expression dataset predicted the canonical vascular endothelial growth factor (VEGF) pathway as the most activated and Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) as the most inhibited pathway in the salivary glands of anti-Ro52 sera recipients.

CONCLUSION

Our study suggests that autoantibody deposition on salivary gland endothelial cells might play a critical role in the pathogenesis of Sjögren's Disease.

Genomic Characterization of Mobile Genetic Elements Associated With Carbapenem Resistance of Acinetobacter baumannii From India

With the excessive genome plasticity, Acinetobacter baumannii can acquire and disseminate antimicrobial resistance (AMR) genes often associated with mobile genetic elements (MGEs). Analyzing the genetic environment of resistance genes often provides valuable information on the origin, emergence, evolution, and spread of resistance. Thus, we characterized the genomic features of some clinical isolates of carbapenem-resistant A. baumannii (CRAb) to understand the role of diverse MGEs and their genetic context responsible for disseminating carbapenem resistance genes. For this, 17 clinical isolates of A. baumannii obtained from multiple hospitals in India between 2018 and 2019 were analyzed. AMR determinants, the genetic context of resistance genes, and molecular epidemiology were studied using whole-genome sequencing. This study observed an increased prevalence of bla_OXA–23 followed by dual carbapenemases, bla_OXA–23, and bla_NDM. This study identified three novel Oxford MLST sequence types. The majority of the isolates belonged to the dominant clone, IC2, followed by less prevalent clones such as IC7 and IC8. This study identified variations of AbaR4 and AbGRI belonging to the IC2 lineage. To the best of our knowledge, this is the first study that provides comprehensive profiling of resistance islands, their related MGEs, acquired AMR genes, and the distribution of clonal lineages of CRAb from India.

Clp ATPases differentially affect natural competence development in Streptococcus mutans

In naturally competent bacteria, DNA transformation through horizontal gene transfer is an evolutionary mechanism to receive extracellular DNA. Bacteria need to maintain a state of competence to accept foreign DNA, and this is an energy-driven phenomenon that is tightly controlled. In Streptococcus, competence development is a complex process that is not fully understood. In this study, we used Streptococcus mutans, an oral bacterium, to determine how cell density affects competence development. We found that in S. mutans the transformation efficiency is maximum when the transforming DNA was added at low cell density and incubated for 2.5 h before selecting for transformants. We also found that S. mutans cells remain competent until the mid-logarithmic phase, after which the competence decreases drastically. Surprisingly, we observed that individual components of Clp proteolytic complexes differentially regulate competence. If the transformation is carried out at the early growth phase, both ClpP protease and ClpX ATPase are needed for competence. In contrast, we found that both ClpC and ClpE negatively affect competence. We also found that if the transformation is carried out at the mid-logarithmic growth phase ClpX is still required for competence, but ClpP negatively affects competence. While the exact reason for this differential effect of ClpP and ClpX on transformation is currently unknown, we found that both ClpC and ClpE have a negative effect on transformation, which was not reported before.

Performance of three-echelon supply chain under uncertainty: influence of contract sequence and individual rationality

Purpose

In the paper, the authors study the simultaneous influence of incentive compatibility and individual rationality (IR) on a multi-echelon supply chain (SC) under uncertainty. The authors study the impact of contract sequence on coordination strategies of a serial three-echelon SC consisting of a supplier, a manufacturer and a retailer in an uncertain environment.

Design/methodology/approach

The authors develop a game-theoretic framework of a serial decentralized three-echelon SC. Under a decentralized setting, the supplier and the manufacturer can choose from two contract types namely, wholesale price (WP) and linear two-part tariff (LTT) and it leads to four different cases of contract sequence.

Findings

The study show that SC coordination is possible when both the supplier and the manufacturer choose LTT contract. This study not only identifies the influence of contract sequence on profit distribution among SC agents, but also establishes cut-off policies for all SC agents for each contract sequence. This study also examine the influence of chosen contract sequence on optimal profit distribution among SC agents.

Research limitations/implications

Three-echelon SC coordination under uncertain environment depends upon the contract sequence chosen by SC agents.

Practical implications

This study results will be helpful to managers of various SCs to take operational decisions under uncertain situations.

Originality/value

The main contribution of this study is that it explores the possibility of coordination by supply contracts for three-echelon SC in a fuzzy environment.

Involvement of ClpE ATPase in Physiology of Streptococcus mutans

Streptococcus mutans, a dental pathogen, harbors at least three Clp ATPases (ClpC, ClpE, and ClpX) that form complexes with ClpP protease and participate in regulated proteolysis. Among these, the function of ClpE ATPase is poorly understood. We have utilized an isogenic clpE-deficient strain derived from S. mutans UA159 and evaluated the role of ClpE in cellular physiology. We found that loss of ClpE leads to increased susceptibility against thiol stress but not to oxidative and thermal stress. Furthermore, we found that the mutant displays altered tolerance against some antibiotics and altered biofilm formation. We performed a label-free proteomic analysis by comparing the mutant with the wild-type UA159 strain under nonstressed conditions and found that ClpE modulates a relatively limited proteome in the cell compared to the proteomes modulated by ClpX and ClpP. Nevertheless, we found that ClpE deficiency leads to an overabundance of some cell wall synthesis enzymes, ribosomal proteins, and an unknown protease encoded by SMU.2153. Our proteomic data strongly support some of the stress-related phenotypes that we observed. Our study emphasizes the significance of ClpE in the physiology of S. mutans. IMPORTANCE When bacteria encounter environmental stresses, the expression of various proteins collectively known as heat shock proteins is induced. These heat shock proteins are necessary for cell survival specifically under conditions that induce protein denaturation. A subset of heat shock proteins known as the Clp proteolytic complex is required for the degradation of the misfolded proteins in the cell. The Clp proteolytic complex contains an ATPase and a protease. A specific Clp ATPase, ClpE, is uniquely present in Gram-positive bacteria, including streptococci. Here, we have studied the functional role of the ClpE protein in Streptococcus mutans, a dental pathogen. Our results suggest that ClpE is required for survival under certain antibiotic exposure and stress conditions but not others. Our results demonstrate that loss of ClpE leads to a significantly altered cellular proteome, and the analysis of those changes suggests that ClpE's functions in S. mutans are different from its functions in other Gram-positive bacteria.

Key role of Extracellular RNA in hypoxic stress induced myocardial injury

Myocardial infarction (MI), atherosclerosis and other inflammatory and ischemic cardiovascular diseases (CVDs) have a very high mortality rate and limited therapeutic options. Although the diagnosis is based on markers such as cardiac Troponin-T (cTrop-T), the mechanism of cTrop-T upregulation and release is relatively obscure. In the present study, we have investigated the mechanism of cTrop-T release during acute hypoxia (AH) in a mice model by ELISA & immunohistochemistry. Our study showed that AH exposure significantly induces the expression and release of sterile inflammatory as well as MI markers in a time-dependent manner. We further demonstrated that activation of TLR3 (mediated by eRNA) by AH exposure in mice induced cTrop-T release and Poly I:C (TLR3 agonist) also induced cTrop-T release, but the pre-treatment of TLR3 immuno-neutralizing antibody or silencing of Tlr3 gene or RNaseA treatment two hrs before AH exposure, significantly abrogated AH-induced Caspase 3 activity as well as cTrop-T release. Our immunohistochemistry and Masson Trichrome (MT) staining studies further established the progression of myocardial injury by collagen accumulation, endothelial cell and leukocyte activation and adhesion in myocardial tissue which was abrogated significantly by pre-treatment of RNaseA 2 hrs before AH exposure. These data indicate that AH induced cTrop-T release is mediated via the eRNA-TLR3-Caspase 3 pathway.

Sub-pulmonic stenosis caused by a right ventricular outflow tract vegetation in a children with restricted ventricular septal defect

Infective endocarditis involving the right heart is rarely observed in the pediatric population. Echocardiography plays an important role in its diagnosis, and surgery is indicated in patients with heart failure and persistent sepsis not responding to medical treatment. Here, we report a rare case of restricted ventricular septal defect complicated by a vegetation developed in the right ventricular outflow tract and causing sub-pulmonic stenosis in a 3-year-old male child.

Pulmonary Function, Mental and Physical Health in Recovered COVID-19 Patients Requiring Invasive Versus Non-invasive Oxygen Therapy: A Prospective Follow-Up Study Post-ICU Discharge

Background Survivors of COVID-19 pneumonia may have residual lung injury and poor physical and mental health even after discharge. We hypothesized that COVID-19 severe acute respiratory distress syndrome (ARDS) patients needing mechanical ventilation may be at a greater risk of deterioration in pulmonary function, mental health, and quality of life (QOL). This study analyses the differences in pulmonary function, mental health, and QOL after recovery, in patients having received non-invasive oxygen therapy versus invasive mechanical ventilation during ICU stay. Methods Patients aged >18 years, who had completed 3 months post ICU discharge, with moderate to severe COVID-19 ARDS, were consecutively enrolled from May 1 to July 31, 2021. Patients were allocated into Group A - having required high flow nasal cannula (HFNC)/non-invasive ventilation (NIV) and Group B - having received invasive mechanical ventilation. Pulmonary function tests, 6-minute walk test (6-MWT), and health-related quality of life were compared. Results Of the 145 eligible patients, 31 were lost to follow-up and 21 died. Seventy-four patients were allocated into Groups A (57 patients) and B (17 patients). In Group A, abnormal forced expiratory volume in first second (FEV₁), forced vital capacity (FVC), forced expiratory flow in mid-half of FVC (FEF_25-75), and peak expiratory flow rate (PEFR) values were obtained in 27 (47.37%), 43 (75.44%), 11 (19.3%), and 25 (43.86%) patients, and in Group B, in 13 (76.47%), 17 (100%), 1 (5.88%), and 8 (47%) patients, respectively. No patient had abnormal FEV₁/FVC. All Group B patients had a restrictive pattern in spirometry as compared to 77% in Group A. Group B had a lower arterial partial pressure of oxygen (PaO₂) (p=0.0019), % predicted FVC (p<0.0001), % predicted FEV₁ (p=0.001), and 6-MWT distance (p<0.001). The physical component score in the short-form survey 12 questionnaire was higher in group A, p<0.001, whereas the mental component score was comparable. Conclusions Patients requiring invasive mechanical ventilation (MV) have a greater risk of impaired pulmonary function and reduced QOL post-ICU discharge. This warrants a greater need for following these patients for better rehabilitation.

Extracellular Histones Bind Vascular Glycosaminoglycans and Inhibit the Anti-Inflammatory Function of Antithrombin

BACKGROUND/AIMS

Binding of histones to molecular pattern recognition receptors on endothelial cells and leukocytes provokes proinflammatory responses and promotes activation of coagulation. Histones also bind therapeutic heparins, thereby neutralizing their anticoagulant functions. The aim of this study was to test the hypothesis that histones can interact with the antithrombin (AT)-binding vascular glycosaminoglycans (GAGs) to induce inflammation and inhibit the anti-inflammatory function of AT.

METHODS

We evaluated the heparin-binding function of histones by an AT-dependent protease-inhibition assay. Furthermore, we treated endothelial cells with histones in the absence and presence of AT and monitored cellular phenotypes employing established signaling assays.

RESULTS

Histones neutralized AT-dependent anticoagulant function of heparin in both purified protease-inhibition and plasma-based assays. Histones also disrupted endothelial cell barrier-permeability function by a GAG-dependent mechanism as evidenced by the GAG-antagonist, surfen, abrogating their disruptive effects. Further studies revealed histones and AT compete for overlapping binding-sites on GAGs, thus increasing concentrations of one protein abrogated effects of the other. Histones elicited proapoptotic effects by inducing nuclear localization of PKC-δ in endothelial cells and barrier-disruptive effects by destabilizing VE-cadherin, which were inhibited by AT, but not by a D-helix mutant of AT incapable of interacting with GAGs. Finally, histones induced release of Weibel-Palade body contents, VWF and angiopoietin-2, and promoted expression of cell adhesion molecules on endothelial cells, which were all downregulated by AT but not by D-helix mutant of AT.

CONCLUSION

We conclude that histones and AT compete for overlapping binding sites on vascular GAGs to modulate coagulation and inflammation.

Antithrombin Resistance Rescues Clotting Defect of Homozygous Prothrombin-Y510N Dysprothrombinemia

A patient with hematuria in our clinic was diagnosed with urolithiasis. Analysis of the patient's plasma clotting time indicated that both activated partial thromboplastin time (52.6 seconds) and prothrombin time (19.4 seconds) are prolonged and prothrombin activity is reduced to 12.4% of normal, though the patient exhibited no abnormal bleeding phenotype and a prothrombin antigen level of 87.9%. Genetic analysis revealed the patient is homozygous for prothrombin Y510N mutation. We expressed and characterized the prothrombin-Y510N variant in appropriate coagulation assays and found that the specificity constant for activation of the mutant zymogen by factor Xa is impaired approximately fivefold. Thrombin generation assay using patient's plasma and prothrombin-deficient plasma supplemented with either wild-type or prothrombin-Y510N revealed that both peak height and time to peak for the prothrombin mutant are decreased; however, the endogenous thrombin generation potential is increased. Further analysis indicated that the thrombin mutant exhibits resistance to antithrombin and is inhibited by the serpin with approximately 12-fold slower rate constant. Protein C activation by thrombin-Y510N was also decreased by approximately 10-fold; however, thrombomodulin overcame the catalytic defect. The Na⁺-concentration-dependence of the amidolytic activities revealed that the dissociation constant for the interaction of Na⁺ with the mutant has been elevated approximately 20-fold. These results suggest that Y510 (Y184a in chymotrypsin numbering) belongs to network of residues involved in binding Na⁺. A normal protein C activation by thrombin-Y510N suggests that thrombomodulin modulates the conformation of the Na⁺-binding loop of thrombin. The clotting defect of thrombin-Y510N appears to be compensated by its markedly lower reactivity with antithrombin, explaining patient's normal hemostatic phenotype.

Firm investment decisions for information security under a fuzzy environment: a game-theoretic approach

Purpose

This paper aims to examine optimal decisions for information security investments for a firm in a fuzzy environment. Under both sequential and simultaneous attack scenarios, optimal investment of firm, optimal efforts of attackers and their economic utilities are determined.

Design/methodology/approach

Throughout the analysis, a single firm and two attackers for a “firm as a leader” in a sequential game setting and “firm versus attackers” in a simultaneous game setting are considered. While the firm makes investments to secure its information assets, the attackers spend their efforts to launch breaches.

Findings

It is observed that the firm needs to invest more when it announces its security investment decisions ahead of attacks. In contrast, the firm can invest relatively less when all agents are unaware of each other’s choices in advance. Further, the study reveals that attackers need to exert higher effort when no agent enjoys the privilege of being a leader.

Research limitations/implications

In a novel approach, inherent system vulnerability of the firm, financial benefit of attackers from the breach and monetary loss suffered by the firm are considered, as fuzzy variables in the well-recognized Gordon – Loeb breach function, with the help of fuzzy expectation operator.

Practical implications

This study reports that the optimal breach effort exerted by each attacker is proportional to its obtained economic benefit for both sequential and simultaneous attack scenarios. A set of numerical experiments and sensitivity analyzes complement the analytical modeling.

Originality/value

In a novel approach, inherent system vulnerability of the firm, financial benefit of attackers from the breach and monetary loss suffered by the firm are considered, as fuzzy variables in the well-recognized Gordon – Loeb breach function, with the help of fuzzy expectation operator.

COVID-19 Infection in a 13-year-old Heart Transplant Recipient in Immediate Post Transplant Period - A Case Report

Introduction

Experience regarding course and outcome of Covid-19 infection in heart transplant recipients is limited. Case fatality rate of 25% of covid-19 infection in adult recipients of heart transplant and mild and self-limited disease in young heart transplant patients have been reported in small case series. We describe a case where a 13 year old patient contracted covid-19 infection on 7^th post-operative day after undergoing heart transplant and was subsequently discharged from hospital uneventfully.

Case Report

A 13 year old boy, with dilated cardiomyopathy underwent orthotopic heart transplant surgery. In the immediate pre-operative period, the real-time polymerase chain reaction (RTPCR) of nasopharyngeal swabs of both the recipient and the brain-dead organ donor were negative for severe acute respiratory syndrome coronavirus type 2 (SARS CoV 2). The intraoperative and immediate postoperative periods were uneventful. The recipient got weaned off from mechanical ventilation on the 1^st postoperative day and O₂ support was weaned off on 4^th postoperative day. He was put on immunosuppressive regimen consisting of mycophenolate mofetil, tacrolimus and prednisone. On 7^th postoperative day, he complained of fever, sore throat and dry cough. Nasopharyngeal swab for RTPCR was sent. It reported positive for SARS CoV 2. He was shifted to isolation facility. He maintained more than 94% saturation on pulse oximetry in room air. Immunosuppressive regimen was continued. He was administered 5-day course of remdesivir. Inotropic support was weaned off on 10^th postoperative day. On serial bedside echocardiography, the allograft function was found to be normal throughout. He was kept on prophylactic antimicrobial, antifungal and anti-cytomegaloviral therapy and on prophylactic dose of low molecular weight heparin. There was initial rise in neutrophil lymphocyte ratio (17), C reactive protein (58 mg/l), ferritin (871 ng/ml), D-dimer (1904 ng/ml), Troponin T (227 pg/ml) levels, which gradually came down to within normal limits. He was discharged on 38^th postoperative day to a home isolation facility as his RTPCR for SARS CoV 2 was still positive, although he remained completely asymptomatic for the last 21 days.

Summary

The course of Covid-19 infection in the immediate post-transplant period of this young heart transplant recipient was largely uneventful.

Role of Gly197 in the structure and function of protein C

We previously demonstrated that heterozygous Gly197 to Arg mutation in PROC is associated with venous thrombosis due to the mutation abrogating both zymogenic and enzymatic activities of protein C and activated protein C (APC). In this study, we investigated the role of Gly197 on the structure and function of protein C by replacing it with Ala, Lys and Glu in separate constructs. Characterization of protein C mutants indicated their activation by thrombin is improved ~5-20-fold with the order of PC-G197K > PC-G197E > PC-G197A > PC-WT. Interestingly, the cofactor function of thrombomodulin (TM) in promoting the activation of zymogens by thrombin followed the reverse order of PC-WT > PC-G197A > PC-G197E > PC-G197K. The thrombin-generation inhibitory profiles of zymogens in a tissue factor-mediated thrombin generation assay using protein C-deficient plasma with or without supplementation with TM followed the same order of zymogen activation in the purified system. Evaluation of anticoagulant activities of APC derivatives by prothrombinase and aPTT assays revealed a normal activity for APC-G197A but dramatically impaired activity for the other two mutants. In the endothelial cell permeability assay, APC-G197A exhibited normal antiinflammatory activity, but the other two mutants were nearly inactive. These results suggest that Gly197 plays a key role in TM cofactor-dependent protein C activation by thrombin. It facilitates the recognition of protein C by thrombin in the presence of TM but impedes it in the absence of the cofactor. In APC, a small residue at this position is required for the proper folding/reactivity of the active-site pocket of the protease, a hypothesis supported by structural modeling.

Protective Role of Activated Protein C against Viral Mimetic Poly(I:C)-Induced Inflammation

Activated protein C (APC) is an anticoagulant plasma serine protease which exhibits potent cytoprotective and anti-inflammatory activities. Here, we studied protective effects of APC on the proinflammatory function of polyinosinic:polycytidylic acid [poly(I:C)], a synthetic analog of viral double-stranded RNA, in cellular and animal models. Poly(I:C) induced histone H3 extranuclear translocation via interaction with toll-like receptor 3 in two established endothelial cell lines. Furthermore, poly(I:C) induced histone H3 extranuclear translocation in J774A.1 macrophages and human neutrophils and formation of macrophage and neutrophil extracellular traps (ETs). Mechanistically, poly(I:C) was found to upregulate expression of peptidylarginine deiminase 4 and enhance its interaction with histone H3, thereby leading to increased histone citrullination and neutrophil ET formation. Poly(I:C) elicited proinflammatory signaling responses by inducing nuclear factor kappa B activation and disrupting endothelial cell permeability. In vivo, poly(I:C) enhanced cell surface expression of Mac-1 on neutrophils in mice and facilitated their infiltration to lung tissues. Poly(I:C) also downregulated thrombomodulin expression in mouse tissues and reduced its circulating soluble level in plasma. We demonstrate in this study that APC and a signaling-selective mutant of APC effectively inhibit proinflammatory signaling effects of poly(I:C) in both cellular and animal models. We further demonstrate that unlike the requirement for endothelial protein C receptor on endothelial cells, the integrin Mac-1 is involved in the protease-activated receptor 1-dependent APC inhibition of macrophage ET formation in J774A.1 cells. Taken together, these results support a key role for APC signaling in inhibiting the viral mimetic-induced proinflammatory signaling responses and histone translocation-associated formation of ETs by innate immune cells.

A novel ItrA4 d-galactosyl 1-phosphate transferase is predicted to initiate synthesis of an amino sugar-lacking K92 capsular polysaccharide of Acinetobacter baumannii B8300

The K92 capsular polysaccharide (CPS) from Acinetobacter baumannii B8300 was studied by sugar analysis, Smith degradation, and one- and two-dimensional ¹H and ¹³C NMR spectroscopy. The elucidated CPS includes a branched pentasaccharide repeat unit containing one d-Galp and four l-Rhap residues; an atypical composition given that all A. baumannii CPS structures determined to date contain at least one amino sugar. Accordingly, biosynthesis of A. baumannii CPS types are initiated by initiating transferases (Itrs) that transfer 1-phosphate of either a 2-acetamido-2-deoxy-d-hexose, a 2-acetamido-2,6-dideoxy-d-hexose or a 2-acetamido-4-acylamino-2,4,6-trideoxy-d-hexose to an undecaprenyl phosphate (UndP) carrier. However, the KL92 capsule biosynthesis gene cluster in the B8300 genome sequence includes a gene for a novel Itr type, ItrA4, which is predicted to begin synthesis of the K92 CPS by transferring D-Galp 1-phosphate to the UndP lipid carrier. The itrA4 gene was found in a module transcribed in the opposite direction to the majority of the K locus. This module also includes an unknown open reading frame (orf_KL92), a gtr166 glycosyltransferase gene, and a wzi gene predicted to be involved in the attachment of CPS to the cell surface. Investigation into the origins of orf_KL92-gtr166-itrA4-wzi_KL92 revealed it might have originated from Acinetobacter junii.

High Prevalence of Hypocalcemia in Non-severe COVID-19 Patients: A Retrospective Case-Control Study

Purpose: To compare serum total calcium and phosphate levels in patients with non-severe COVID-19 with age, sex, and serum 25-hydroxyvitamin D level matched healthy adult cohort. Methods: In this retrospective case-control study, medical records of patients (≥18 years) diagnosed as non-severe COVID-19 admitted at and discharged from our tertiary care institution during the period from April 10, 2020 and June 20, 2020 were retrieved. Baseline investigations, notably, serum calcium, phosphate, albumin, magnesium, 25-hydroxyvitamin D, and C-reactive protein (CRP), were performed at admission before any form of calcium or vitamin D supplementation were considered. The biochemical parameters were compared with age, sex, and 25-hydroxyvitamin D matched healthy adult controls (1:1 ratio) derived from the Chandigarh Urban Bone Epidemiological Study (CUBES). Results: After exclusion, 72 patients with non-severe COVID-19 (63 mild and 9 moderate disease) and an equal number of healthy controls were included in the final analysis. Age, sex, serum 25-hydroxyvitamin D, and albumin levels were matched between the 2 groups. Hypovitaminosis D and hypocalcemia were seen in 97 and 67% of the patients, respectively. The patients had lower serum calcium (P value <0.001) and phosphate (P = 0.007) compared with the controls. There was no statistically significant correlation between serum calcium and CRP. Conclusions: Hypocalcemia is highly prevalent even in COVID-19 patients with non-severe disease probably implying that hypocalcemia is intrinsic to the disease. Prospective studies with larger number of patients are required to prove this hypothesis and unravel the underlying pathophysiological mechanisms.

Emergence of Multidrug Resistant Hypervirulent ST23 Klebsiella pneumoniae: Multidrug Resistant Plasmid Acquisition Drives Evolution

Background

In recent years, the emergence of multidrug resistant hypervirulent K. pneumoniae (MDR hvKp) isolates poses severe therapeutic challenge to global public health. The present study used the complete genome sequence of two MDR hvKp isolates belonging to ST23 to characterize the phylogenetic background and plasmid diversity.

Methods

Two hvKp isolates from patients with bacteremia were sequenced using Ion Torrent PGM and Oxford Nanopore MinION platforms and assembled by hybrid genome assembly approach. Comparative genomics approaches were used to investigate the population structure, evolution, virulence, and antimicrobial resistance of MDR hvKp strains.

Results

The study isolates exhibited typical features of hvKp phenotypes associated with ST23. The convergence of multidrug resistance and hypervirulence were attributed by the presence of multiple plasmids including a 216 kb virulence plasmid and MDR plasmids belonging to IncA/C₂, IncFIB, IncX3, and ColKP3 groups. The insertion of catA1 gene into virulence plasmid was observed along with genetic factors such as aerobactin, salmochelin, and rmpA2 that confer hvKp’s hypervirulent phenotype. The core genome single nucleotide polymorphism (SNP) phylogenetic analyses of the isolates showed the evolution of ST23 hvKp was predominantly driven by ICEKp acquisitions.

Conclusion

To the best of our knowledge, this is the first report of MDR hvKp isolates of ST23 with insertion of catA1 gene into the virulence plasmid which presents the possibility of hotspot integration sites on the plasmids to aid acquisition of AMR genes. ST23 is no longer confined to susceptible strains of hvKp. Our findings emphasize the need for more studies on recombinant events, plasmid transmission dynamics and evolutionary process involving hvKp.

Coagulation Disorders in COVID-19: Role of Toll-like Receptors

Coronavirus disease 2019 (COVID-19) has spread rapidly throughout the world. The range of the disease is broad but among hospitalized patients with COVID-19 are coagulation disorders, pneumonia, respiratory failure, and acute respiratory distress syndrome (ARDS). The excess production of early response proinflammatory cytokines results in what has been described as a cytokine storm, leading to an increased risk of thrombosis, inflammations, vascular hyperpermeability, multi-organ failure, and eventually death over time. As the pandemic is spreading and the whole picture is not yet clear, we highlight the importance of coagulation disorders in COVID-19 infected subjects and summarize it. COVID-19 infection could induce coagulation disorders leading to clot formation as well as pulmonary embolism with detrimental effects in patient recovery and survival. Coagulation and inflammation are closely related. In this review, we try to establish an association between virus infections associated with innate immune activation, inflammation and coagulation activation.

Significance of Individual Domains of ClpL: A Novel Chaperone from Streptococcus mutans

ClpL is a member of the HSP100 family of AAA+ chaperones that is widely present in Gram-positive but surprisingly absent in Gram-negative bacteria. ClpL is involved in various cellular processes, including stress tolerance response, long-term survival, virulence, and antibiotic resistance. ClpL is poorly characterized, and its molecular mechanisms of chaperone activity are largely unclear. Here, we biochemically characterized the ClpL protein from Streptococcus mutans, a dental pathogen, to understand its biological functions. ClpL harbors five domains: N-domain, two nucleotide binding domains (NBD-1 and NBD-2), M-domain, and C-domain. NBD-1 and NBD-2 contain distinct Walker A and B motifs for ATP binding and hydrolysis, respectively. We found that ClpL predominantly exists as a trimer in solution; however, upon ATP binding, it rapidly forms a hexameric structure. To study structure-function activity, we constructed several substitution and deletion mutants. We found that mutations in the Walker A and B motifs interfered with ATP hydrolysis and oligomerization. Similarly, deletions of N-, M-, and C-domains abolished both ATPase activity and oligomerization. Because we previously found that ClpL acts as a chaperone, we analyzed the chaperone activity. Surprisingly, we found that the NBD-2 mutants did not display any chaperone activity, indicating that ATP binding and hydrolysis by NBD-2 are essential for the chaperone. However, NBD-1 mutants showed chaperone activities, but the activities were variable depending on the nature of the mutations. Our results indicate that unlike other HSP100 family chaperones, ClpL is a novel chaperone that does not require any additional secondary chaperones for its activity.

Hypoxia induced up-regulation of tissue factor is mediated through extracellular RNA activated Toll-like receptor 3-activated protein 1 signalling

Sterile Inflammation (SI), a condition where damage associated molecular patterns (DAMPs) released from dying cells, leads to TLR (Toll-like receptor) activation and triggers hypoxemia in circulation leading to venous thrombosis (VT) through tissue factor (TF) activation, but its importance under acute hypoxia (AH) remains unexplored. Thus, we hypothesized that eRNA released from dying cells under AH activates TF via the TLR3-ERK1/2-AP1 pathway, leading to VT. Animals were exposed to stimulate hypoxia for 0–24 h at standard temperature and humidity. RNaseA and DNase1 were injected immediately before exposure. TLR3 gene silencing was performed through in vivo injection of TLR3 siRNA. 80 μg/kg BW of isolated eRNA and eDNA were injected 6 h prior to sacrifice. Antigens of TF pathway were determined by ELISA and TF activity by a chromogenic assay. AH exposure significantly induced release of SI markers i.e. eRNA, eDNA, HMGB1 and upregulated TLR3, ERK1/2 (Extracellular signal-regulated kinases), AP1 (Activator Protein-1) and TF, whereas RNaseA pre-treatment diminished the effect of AH, thus inhibiting TF expression as well as activity during AH. Hence, we propose a possible mechanism of AH-induced TF activation and thrombosis where RNaseA can become the novel focal point in ameliorating therapy for AH induced thrombosis.

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Acute hypoxia exposure leads to systemic Sterile Inflammation.

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eRNA regulates upregulation of TF by activation of TLR3 pathway.

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RNase A pre-treatment ameliorates effect of acute hypoxia on coagulation.

Plasmodium falciparum histidine rich protein HRPII inhibits the anti-inflammatory function of antithrombin

BACKGROUND

It has been reported that histidine-rich protein II (HRPII), secreted by the malaria parasite, Plasmodium falciparum (Pf), inhibits the heparin-dependent anticoagulant activity of antithrombin (AT) in vitro and in plasma-based assay systems.

OBJECTIVE

The objective of this study was to test the hypothesis that HRPII may also interact with the AT-binding vascular glycosaminoglycans (GAGs), thereby inhibiting the anti-inflammatory signaling function of the serpin.

METHODS

We expressed HRPII in bacteria, purified it to homogeneity and studied its effect on endothelial cell signaling in the absence and presence of AT employing established signaling assays.

RESULTS

We demonstrate that a low concentration of HRPII potently disrupts the barrier permeability function of endothelial cells. Moreover, HRPII competitively inhibits the protective effect of AT by a concentration-dependent manner. Similarly, AT inhibits the pro-inflammatory activity of HRPII by a concentration-dependent manner. The siRNA knockdown of 3-O-sulfotransferase 1 (3-OST-1), the enzyme responsible for the essential 3-O-sulfation of the AT-binding GAGs, downregulates the pro-inflammatory function of HRPII in endothelial cells, supporting the hypothesis that HRPII competitively inhibits the interaction of AT with 3-OS containing vascular GAGs. Histidine-rich protein II elicits its barrier-disruptive effect by the Src-dependent phosphorylation of vascular endothelial (VE)-cadherin and AT counteracts this effect. We further demonstrate that inorganic polyphosphates bind HRPII with a high affinity to amplify the pro-inflammatory signaling function of HRPII in both cellular and in vivo permeability models.

CONCLUSION

We postulate that Pf-derived HRPII and polyphosphate can contribute to the pathogenesis of malaria infection by downregulating the AT-dependent anti-inflammatory and anticoagulant pathways.

Thr90Ser Mutation in Antithrombin is Associated with Recurrent Thrombosis in a Heterozygous Carrier

Antithrombin (AT) is a serine protease inhibitor that regulates the activity of coagulation proteases of both intrinsic and extrinsic pathways. We identified an AT-deficient patient with a heterozygous Thr90Ser (T90S) mutation who experiences recurrent venous thrombosis. To understand the molecular basis of the clotting defect, we expressed AT-T90S in mammalian cells, purified it to homogeneity, and characterized its properties in established kinetics, binding, and coagulation assays. The possible effect of mutation on the AT structure was also evaluated by molecular modeling. Results demonstrate the inhibitory activity of AT-T90S toward thrombin and factor Xa has been impaired three- to fivefold in both the absence and presence of heparin. The affinity of heparin for AT-T90S has been decreased by four- to fivefold. Kinetic analysis revealed the stoichiometry of AT-T90S inhibition of both thrombin and factor Xa has been elevated by three- to fourfold in both the absence and presence of heparin, suggesting that the reactivity of coagulation proteases with AT-T90S has been elevated in the substrate pathway. The anticoagulant activity of AT-T90S has been significantly impaired as analyzed in the AT-deficient plasma supplemented with AT-T90S. The anti-inflammatory effect of AT-T90S was also decreased. Structural analysis predicts the shorter side-chain of Ser in AT-T90S has a destabilizing effect on the structure of AT and/or the AT-protease complex, possibly increasing the size of an internal cavity and altering a hydrogen-bonding network that modulates conformations of the allosterically linked heparin-binding site and reactive center loop of the serpin. This mutational effect increases the reactivity of AT-T90S with coagulation proteases in the substrate pathway.

Induction of clpP expression by cell-wall targeting antibiotics in Streptococcus mutans

Streptococcus mutans is one of the major bacteria of the human oral cavity that is associated with dental caries. The pathogenicity of this bacterium is attributed to its ability to rapidly respond and adapt to the ever-changing conditions of the oral cavity. The major player in this adaptive response is ClpP, an intracellular protease involved in degradation of misfolded proteins during stress responses. S. mutans encodes a single clpP gene with an upstream region uniquely containing multiple tandem repeat sequences (RSs). Here, we explored expression of clpP with respect to various stresses and report some new findings. First, we found that at sub-inhibitory concentration, certain cell-wall damaging antibiotics were able to induce clpP expression. Specifically, third- and fourth-generation cephalosporins that target penicillin-binding protein 3 (PBP3) strongly enhanced the clpP expression. However, induction of clpP was weak when the first-generation cephalosporins with lower affinity to PBP3 were used. Surprisingly, carbapenems, which primarily target PBP2, induced expression of clpP the least. Second, we found that a single RS element was capable of inducing clpP expression as efficiently as with the wild-type seven RS elements. Third, we found that the RS-element-mediated modulation of clpP expression was strain dependent, suggesting that specific host factors might be involved in the transcription. And finally, we observed that ClpP regulates its own expression, as the expression of clpP-gusA was higher in a clpP-deficient mutant. This suggests that ClpP is involved in the degradation of activator(s) involved in its own transcription.

PKC (Protein Kinase C)-δ Modulates AT (Antithrombin) Signaling in Vascular Endothelial Cells

OBJECTIVE

Native and latent conformers of AT (antithrombin) induce anti-inflammatory and proapoptotic signaling activities, respectively, in vascular endothelial cells by unknown mechanisms. Synd-4 (syndecan-4) has been identified as a receptor that is involved in transmitting signaling activities of AT in endothelial cells. Approach and Results: In this study, we used flow cytometry, signaling assays, immunoblotting and confocal immunofluorescence microscopy to investigate the mechanism of the paradoxical signaling activities of high-affinity heparin (native) and low-affinity heparin (latent) conformers of AT in endothelial cells. We discovered that native AT binds to glycosaminoglycans on vascular endothelial cells via its heparin-binding D-helix to induce anti-inflammatory signaling responses by recruiting PKC (protein kinase C)-δ to the plasma membrane and promoting phosphorylation of the Synd-4 cytoplasmic domain at Ser179. By contrast, the binding of latent AT to endothelial cells to a site(s), which is not competed by the native AT, induces a proapoptotic effect by localizing PKC-δ to the perinuclear/nuclear compartment in endothelial cells. Overexpression of a dominant-negative form of PKC-δ resulted in inhibition of anti-inflammatory and proapoptotic signaling activities of both native and latent AT.

CONCLUSIONS

These results indicate that the native and latent conformers of AT may exert their distinct intracellular signaling effects through differentially modulating the subcellular localization of PKC-δ in endothelial cells.

Ribosomal protein L4 of Lactobacillus rhamnosus LRB alters resistance to macrolides and other antibiotics

Lactobacillus rhamnosus is an important lactic acid bacterium that is predominantly used as a probiotic supplement. This bacterium secretes immunomodulatory and antibacterial peptides that are necessary for the probiotic trait. This organism also occupies diverse ecological niches, such as gastrointestinal tracts and the oral cavity. Several studies have shown that L. rhamnosus is prone to spontaneous genome rearrangement irrespective of the ecological origins. We previously characterized an oral isolate of L. rhamnosus, LRB, which is genetically closely related to the widely used probiotic strain L. rhamnosus LGG. In this study, we isolated a nontargeted mutant that was particularly sensitive to acid stress. Using next generation sequencing, we further mapped the putative mutations in the genome and found that the mutant had acquired a deletion of 75 base pairs in the rplD gene that encodes the large ribosomal subunit L4. The mutant had a growth defect at 37°C and at ambient temperature. Further antibiotic sensitivity analyses indicated that the mutant is relatively more resistant to erythromycin and chloramphenicol; two antibiotics that target the 50S subunit. In contrast, the mutant was more sensitive to tetracycline, which targets the 30S subunit. Thus, it appears that nontargeted mutations could significantly alter the antibiotic resistance profile of L. rhamnosus. Our study raises concern that probiotic use of L. rhamnosus should be carefully monitored to avoid unintended consequences.

Ile73Asn mutation in protein C introduces a new N-linked glycosylation site on the first EGF-domain of protein C and causes thrombosis

Activated protein C exerts its anticoagulant activity by protein S-dependent inactivation of factors Va and VIIIa by limited proteolysis. We identified a venous thrombosis patient who has plasma protein C antigen level of 63% and activity levels of 44% and 23%, as monitored by chromogenic and clotting assays. Genetic analysis revealed the proband carries compound heterozygous mutations (c.344T>A, p.I73N and c.1181G>A, p.R352Q) in PROC. We individually expressed protein C mutations and discovered that thrombin-thrombomodulin activates both variants normally and the resulting activated protein C mutants exhibit normal amidolytic and proteolytic activities. However, while protein S-dependent catalytic activity of activated protein C-R352Q toward factor Va was normal, it was significantly impaired for activated protein C-I73N. These results suggest that the Ile to Asn substitution impairs interaction of activated protein C-I73N with protein S. This conclusion was supported by a normal anticoagulant activity for activated protein C-I73N in protein S-deficient but not in normal plasma. Further analysis revealed Ile to Asn substitution introduces a new glycosylation site on first EGF-like domain of protein C, thereby adversely affecting interaction of activated protein C with protein S. Activated protein C-R352Q only exhibited reduced activity in sub-physiological concentrations of Na⁺ and Ca²⁺, suggesting that this residue contributes to metal ion-binding affinity of the protease, with no apparent adverse effect on its function in the presence of physiological levels of metal ions. These results provide insight into the mechanism by which I73N/R352Q mutations in activated protein C cause thrombosis in proband carrying this compound heterozygous mutation.

Inorganic Polyphosphate Amplifies High Mobility Group Box 1-Mediated Von Willebrand Factor Release and Platelet String Formation on Endothelial Cells

Objective- Inorganic polyphosphate (polyP) is known to modulate coagulation, inflammation, and metabolic pathways. It also amplifies inflammatory responses of HMGB1 (high mobility group box 1) in endothelial cells. The objective of this study was to evaluate the effect of polyP on von Willebrand factor (VWF) release from endothelial cells with or without HMGB1. Approach and Results- EA.hy926 endothelial cells were treated with different concentrations of polyP₇₀ alone or in combination with different concentrations of HMGB1. VWF release was measured by an ELISA assay in the absence or presence of pharmacological inhibitors of the receptor for advanced glycation end products, P2Y₁, and Ca²⁺. A flow chamber assay was used to monitor polyP₇₀-mediated platelet recruitment and VWF-platelet string formation. PolyP₇₀ and HMGB1 induced VWF release from endothelial cells by a concentration-dependent manner. PolyP₇₀ amplified HMGB1-mediated VWF release from endothelial cells. This was also true if boiled platelet releasate was used as the source of polyP. Gene silencing or pharmacological inhibitors of receptor for advanced glycation end products, P2Y₁, and Ca²⁺ significantly inhibited VWF release. PolyP₇₀ and HMGB1 synergistically promoted VWF-platelet string formation in the flow chamber assay, which was inhibited by the anti-GPIbα (glycoprotein Ib alpha) antibody. VWF release by polyP₇₀-HMGB1 complex required phosphorylation of Src and phospholipase C because inhibitors of Src, phospholipase C, and Ca²⁺ signaling significantly decreased VWF secretion. The polyP₇₀-HMGB1 complex also increased angiopoietin-2 release, indicating that Weibel-Palade body exocytosis is involved in the VWF release. Conclusions- PolyP₇₀ can promote thrombotic and inflammatory pathways by inducing VWF release and platelet string formation on endothelial cells.

Characterization of a stress tolerance-defective mutant of Lactobacillus rhamnosus LRB

Lactobacillus rhamnosus is a lactic acid bacterium that survives diverse ecological niches, including the human oral cavity and gastrointestinal tract. L. rhamnosus is an acidogenic bacterium that produces copious amounts of lactic acid. The organism is also considered as aciduric, since it can survive prolonged exposure to an acidic environment. For a probiotic bacterium such as L. rhamnosus, it is necessary to understand how this organism survives acid stress. In this study we used L. rhamnosus LRB to isolate one spontaneous mutant that was sensitive to acid stress. The mutant, which we named RBM1, also displayed sensitivity to a wide range of stresses including osmotic, thermal, and others. Using whole genome sequencing, we mapped the putative mutations in the mutant strain. It appears that three single nucleotide substitutions occurred in the mutant as compared to the wild-type LRB strain. Among those, the most relevant mutation occurred in the ftsH gene that created a single amino acid change in the protein. We performed a comparative proteomic study to understand the molecular basis for stress sensitivity and found that ~15% of the proteome is altered in the mutant strain. Our study suggests that generation of spontaneous mutants during L. rhamnosus colonization could drastically affect bacterial physiology and survival under stress conditions.

Activated protein C inhibits lipopolysaccharide-mediated acetylation and secretion of high-mobility group box 1 in endothelial cells

Essentials APC elicits cytoprotective responses in endothelial cells via EPCR-dependent cleavage of PAR1. APC inhibits LPS-mediated translocation and extracellular secretion of HMGB1 in endothelial cells. Signaling activity of APC inhibits LPS-mediated acetylation of HMGB1 by epigenetic mechanisms. APC inhibits LPS-mediated HMGB1 expression in CD31-positive endothelial cells in cremaster muscle. SUMMARY: Background Activated protein C (APC) inhibits high-mobility group box 1 (HMGB1) signaling and its lipopolysaccharide (LPS)-mediated release by endothelial protein C receptor (EPCR)-dependent activation of protease-activated receptor 1 (PAR1) in endothelial cells. Post-translational acetylation is known to modulate the subcellular localization of HMGB1, and its hyperacetylated form is translocated to the cytoplasm of innate immune cells before being secreted into the extracellular space. Objective To determine whether APC inhibits LPS-mediated HMGB1 secretion from endothelial cells by modulating its acetylation status. Methods The subcellular localization of HMGB1 in LPS-treated endothelial cells was monitored in the absence and presence of APC by western blot analysis of fractionated cell lysates and confocal immunofluorescence microscopy. Results Both western blot and immunofluorescence data indicated that APC effectively inhibits LPS-mediated translocation of HMGB1 from the nucleus to the cytoplasm by EPCR-dependent and PAR1-dependent mechanisms. When EPCR was ligated by the Gla-domain of protein C/APC, thrombin also inhibited LPS-mediated HMGB1 translocation. Further studies revealed that APC inhibits the translocation of HMGB1 from the nucleus to the cytoplasm by inhibiting LPS-mediated hyperacetylation of HMGB1 by (de)acetylating enzymes. Furthermore, the translocated HMGB1 was found to be associated with lysosome-associated membrane protein 1 in LPS-treated endothelial cells. The in vivo relevance of these findings was investigated in the mouse cremaster muscle, and this demonstrated that both wild-type APC and a signaling-selective mutant of APC inhibit LPS-mediated HMGB1 expression and translocation in CD31-positive endothelial cells. Conclusion These results suggest that APC inhibits LPS-mediated cytoplasmic translocation and secretion of HMGB1 in endothelial cells by epigenetic mechanisms.

A Simple Static Biofilm Assay for Acinetobacter baumannii

Acinetobacter baumannii and other Acinetobacter spp. display biofilm formation on abiotic surfaces. The degree of biofilm formation varies considerably depending on the isolates. While culturing, bacteria tend to attach to abiotic surfaces, and some surfaces perform better than others. Numerous methods are available to study in vitro biofilm formation by bacteria under static growth, and they basically rely upon culturing the bacteria in an ampule followed by staining the bacterial growth attached to the abiotic surface with a suitable dye such as crystal violet to visualize the biofilm. Subsequently, the dye is eluted with a suitable solvent, and optical density is measured to quantify the attached bacterial mass. In this chapter, we provide a basic and simple yet a powerful method to study biofilm formation by A. baumannii grown under static conditions.

Targeted Gene Replacement in Acinetobacter baumannii

Acinetobacter baumannii is characterized as a nosocomial, gram-negative, multidrug-resistant bacterium, which has gained increasing attention due to its prevalence in hospital settings and high mortality rates upon infection. Currently, a number of different protocols have been developed in attempts to genetically alter A. baumannii, including multidrug-resistant strains. Although the bacterium has an unusual ability to uptake exogenous DNA in the natural environments, within the laboratory setting, gene manipulation to study virulence properties can be challenging. In this chapter we describe a general protocol for modification of specific genes using homologous recombination and a counterselectable marker.

Immune response against the coiled coil domain of Sjögren's syndrome associated autoantigen Ro52 induces salivary gland dysfunction

OBJECTIVES

The structural domains of Ro52, termed the RING, B-box, coiled coil (CC) and B30.2/SPRY are targets of anti-Ro52 in multiple autoimmune disorders. In Sjögren's syndrome patients, the presence of anti-Ro52 is associated with higher disease severity, and in mice, they induce salivary gland hypofunction. This study was undertaken to investigate whether immune responses against different domains of Ro52, influences salivary gland disease in mice.

METHODS

Female NZM2758 mice were immunised with Ro52 domains expressed as recombinant fusion proteins with maltose binding protein (MBP) [MBP-RING-B-box, MBP-CC, MBP-CC(ΔC19), MBP-B30.2/SPRY]. Sera from immunised mice were studied for IgG antibodies to Ro52 by immunoprecipitation, and to salivary gland cells by immunofluorescence. Pilocarpine-induced saliva production was measured to evaluate salivary gland function. Submandibular glands were investigated by histopathology for inflammation and by immune-histochemistry for IgG deposition.

RESULTS

Mice immunised with different Ro52-domains had comparable reactivity to Ro52 and to salivary gland cells. However, only mice immunised with the CC domain and its C-terminal truncated version CC(ΔC19) showed a significant drop in saliva production. None of the mice developed severe salivary gland inflammation. The salivary gland hypofunction significantly correlated with increased intra-lobar IgG deposits in the submandibular salivary glands.

CONCLUSIONS

Our data demonstrate that epitope specificity of anti-Ro52 antibodies plays a critical role in the induction of glandular dysfunction. Clearly, screening Sjögren's syndrome patients for relative levels of Ro52 domain specific antibodies will be more informative for associating anti-Ro52 with clinical measures of the disorder.

Role of CovR phosphorylation in gene transcription in Streptococcus mutans

Streptococcus mutans, the primary aetiological agent of dental caries, is one of the major bacteria of the human oral cavity. The pathogenicity of this bacterium is attributed not only to the expression of virulence factors, but also to its ability to respond and adapt rapidly to the ever-changing conditions of the oral cavity. The two-component signal transduction system (TCS) CovR/S plays a crucial role in virulence and stress response in many streptococci. Surprisingly, in S. mutans the response regulator CovR appears to be an orphan, as the cognate sensor kinase, CovS, is absent in all the strains. We found that acetyl phosphate, an intracellular phosphodonor molecule known to act in signalling, might play a role in CovR phosphorylation in vivo. We also found that in vitro, upon phosphorylation by potassium phosphoramide (a high-energy phophodonor) CovR formed a dimer and showed altered electrophoretic mobility. As expected, we found that the conserved aspartic acid residue at position 53 (D53) was the site of phosphorylation, since neither phosphorylation nor dimerization was seen when an alanine-substituted CovR mutant (D53A) was used. Surprisingly, we found that the ability of CovR to act as a transcriptional regulator does not depend upon its phosphorylation status, since the D53A mutant behaved similarly to the wild-type protein in both in vivo and in vitro DNA-binding assays. This unique phosphorylation-mediated inhibition of CovR function in S. mutans sheds light on an unconventional mechanism of the signal transduction pathway.