Neutrophils Protect Against Staphylococcus aureus Endocarditis Progression Independent of Extracellular Trap Release.

BACKGROUND: Infective endocarditis (IE) is characterized by an infected thrombus at the heart valves. How bacteria bypass the immune system and cause these thrombi remains unclear. Neutrophils releasing NETs (neutrophil extracellular traps) lie at this interface between host defense and coagulation. We aimed to determine the role of NETs in IE immunothrombosis. METHODS: We used a murine model of Staphylococcus aureus endocarditis in which IE is provoked on inflamed heart valves and characterized IE thrombus content by immunostaining identifying NETs. Antibody-mediated neutrophil depletion and neutrophil-selective PAD4 (peptidylarginine deiminase 4)-knockout mice were used to clarify the role of neutrophils and NETs, respectively. S. aureus mutants deficient in key virulence factors related to immunothrombosis (nucleases or staphylocoagulases) were investigated. RESULTS: Neutrophils releasing NETs were present in infected thrombi and within cellular infiltrates in the surrounding vasculature. Neutrophil depletion increased occurrence of IE, whereas neutrophil-selective impairment of NET formation did not alter IE occurrence. Absence of S. aureus nuclease, which degrades NETs, did not affect endocarditis outcome. In contrast, absence of staphylocoagulases (coagulase and von Willebrand factor binding protein) led to improved survival, decreased bacteremia, smaller infiltrates, and decreased tissue destruction. Significantly more NETs were present in these vegetations, which correlated with decreased bacteria and cell death in the adjacent vascular wall. CONCLUSIONS: Neutrophils protect against IE independent of NET release. Absence of S. aureus coagulases, but not nucleases, reduced IE severity and increased NET levels. Staphylocoagulase-induced fibrin likely hampers NETs from constraining infection and the resultant tissue damage, a hallmark of valve destruction in IE.

PspC domain-containing protein (PCP) determines Streptococcus mutans biofilm formation through bacterial extracellular DNA release and platelet adhesion in experimental endocarditis.

Bacterial extracellular DNA (eDNA) and activated platelets have been found to contribute to biofilm formation by Streptococcus mutans on injured heart valves to induce infective endocarditis (IE), yet the bacterial component directly responsible for biofilm formation or platelet adhesion remains unclear. Using in vivo survival assays coupled with microarray analysis, the present study identified a LiaR-regulated PspC domain-containing protein (PCP) in S. mutans that mediates bacterial biofilm formation in vivo. Reverse transcriptase- and chromatin immunoprecipitation-polymerase chain reaction assays confirmed the regulation of pcp by LiaR, while PCP is well-preserved among streptococcal pathogens. Deficiency of pcp reduced in vitro and in vivo biofilm formation and released the eDNA inside bacteria floe along with reduced bacterial platelet adhesion capacity in a fibrinogen-dependent manner. Therefore, LiaR-regulated PCP alone could determine release of bacterial eDNA and binding to platelets, thus contributing to biofilm formation in S. mutans-induced IE.

Role of the Staphylococcus aureus Extracellular Loop of GraS in Resistance to Distinct Human Defense Peptides in PMN and Invasive Cardiovascular infections.

GraS is a membrane sensor in Staphylococcus aureus that induces mprF and dltABCD expression to alter the surface positive charge upon exposure to cationic human defense peptides (HDPs). The sensing domain of GraS likely resides in the 9-residue extracellular loop (EL). In this study, we assessed a hospital-acquired methicillin-resistant S. aureus (HA-MRSA) strain (COL) for the specific role of two distinct EL mutations: F38G (bulk) and D/35/37/41K (charged inversion). Activation of mprF by polymyxin B (PMB) was reduced in the D35/37/41K mutant versus the D35/37/41G mutant, correlating with reduced surface positive charge; in contrast, these effects were less prominent in the F38G mutant but still lower than those in the parent. These data indicated that both electrostatic charge and steric bulk of the EL of GraS influence induction of genes impacting HDP resistance. Using mprF expression as a readout, we confirmed GraS signaling was pH dependent, increasing as pH was lowered (from pH 7.5 down to pH 5.5). In contrast to PMB activation, reduction of mprF was comparable at pH 5.5 between the P38G and D35/37/41K point mutants, indicating a mechanistic divergence between GraS activation by acidic pH versus cationic peptides. Survival assays in human blood and purified polymorphonuclear leukocytes (PMNs) revealed lower survival of the D35/37/41K mutant versus the F38G mutant, with both being lower than that of the parent. Virulence studies in the rabbit endocarditis model mirrored whole blood and PMN killing assay data described above. Collectively, these data confirmed the importance of specific residues within the EL of GraS in conferring essential bacterial responses for MRSA survival in infections.

The Stringent Response Contributes to Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection Through the Purine Biosynthetic Pathway.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections represent a significant clinical-therapeutic challenge. Of particular concern is antibiotic treatment failure in infections caused by MRSA that are "susceptible" to antibiotic in vitro. In the current study, we investigate specific purine biosynthetic pathways and stringent response mechanism(s) related to this life-threatening syndrome using genetic matched persistent and resolving MRSA clinical bacteremia isolates (PB and RB, respectively), and isogenic MRSA strain sets. We demonstrate that PB isolates (vs RB isolates) have significantly higher (p)ppGpp production, phenol-soluble-modulin expression, polymorphonuclear leukocyte lysis and survival, fibronectin/endothelial cell (EC) adherence, and EC damage. Importantly, an isogenic strain set, including JE2 parental, relP-mutant and relP-complemented strains, translated the above findings into significant outcome differences in an experimental endocarditis model. These observations indicate a significant regulation of purine biosynthesis on stringent response, and suggest the existence of a previously unknown adaptive genetic mechanism in persistent MRSA infection.

Involvement of the phosphoryl transfer network on cardiac energetic metabolism during Staphylococcus aureus infection and its association to disease pathophysiology.

Evidences have suggested that the phosphoryl transfer network by the enzymatic activities of creatine kinase (CK), adenylate kinase (AK), pyruvate kinase (PK), and lactate dehydrogenase (LDH), shows new perspectives to understand some disturbances in the energy metabolism during bacterial infections. Thus, the aim of this study was to evaluate whether Staphylococcus aureus infection in mice could alter serum and cardiac activities of these enzymes and their association to disease pathophysiology. For that, we measured total leukocytes, lymphocytes and neutrophils (just 48 h of infection) that were lower in infected animals after 48 and 72 h in infected mice compared with negative control, while total protein and globulin plasma levels were higher after 72 h of infection. The serum CK activity was higher in infected animals 48 and 72 h post-infection compared to the control group, as well as observed for mitochondrial cardiac CK activity. The serum PK activity was higher in infected animals after 72 h of infection compared to the control group, and lower in the cardiac tissue. The cardiac AK activity was lower in infected animals 48 h and 72 h post-infection compared to the control group, while serum and cardiac LDH activities were higher. Based on these evidences, it is possible to conclude that the stimulation of CK activity exerts a key role as an attempt to maintain the bioenergetic homeostasis by the production of phosphocreatine to avoid a rapid fall on the concentrations of total adenosine triphosphate. In summary, the phosphoryl transfer network can be considered a pathway involved in the improvement on tissue and cellular energy homeostasis of S. aureus-infected mice.

Adjunctive Clavulanic Acid Abolishes the Cefazolin Inoculum Effect in an Experimental Rat Model of Methicillin-Sensitive Staphylococcus aureus Endocarditis.

We tested the ability of clavulanic acid to restore the efficacy of cefazolin against Staphylococcus aureus TX0117, which exhibits the cefazolin inoculum effect (CzIE). In the rat infective endocarditis model, the coadministration of cefazolin plus clavulanic acid resulted in a significant reduction of bacterial counts (7.1 ± 0.5 log10 CFU/g) compared to that with cefazolin alone (2 ± 0.6 log10 CFU/g; P < 0.0001). The addition of a ß-lactamase inhibitor may be a viable strategy for overcoming the CzIE.

Structural Basis for Sialoglycan Binding by the Streptococcus sanguinis SrpA Adhesin.

Streptococcus sanguinisis a leading cause of infective endocarditis, a life-threatening infection of the cardiovascular system. An important interaction in the pathogenesis of infective endocarditis is attachment of the organisms to host platelets.S. sanguinisexpresses a serine-rich repeat adhesin, SrpA, similar in sequence to platelet-binding adhesins associated with increased virulence in this disease. In this study, we determined the first crystal structure of the putative binding region of SrpA (SrpABR) both unliganded and in complex with a synthetic disaccharide ligand at 1.8 and 2.0 Å resolution, respectively. We identified a conserved Thr-Arg motif that orients the sialic acid moiety and is required for binding to platelet monolayers. Furthermore, we propose that sequence insertions in closely related family members contribute to the modulation of structural and functional properties, including the quaternary structure, the tertiary structure, and the ligand-binding site.

Inherited Variation in Cytokine, Acute Phase Response, and Calcium Metabolism Genes Affects Susceptibility to Infective Endocarditis.

Infective endocarditis (IE) is a septic inflammation of the endocardium. Recognition of microbial patterns, cytokine and acute phase responses, hemostasis features, and alterations in plasma lipid and calcium profile all have been reported to affect pathogenesis and clinical course of IE. Having recruited 123 patients with IE and 300 age-, sex-, and ethnicity-matched healthy blood donors, we profiled their genomic DNA for 35 functionally significant polymorphisms within the 22 selected genes involved in the abovementioned pathways, with the further genetic association analysis. We found that the G/A genotype of the rs1143634 polymorphism within the IL1B gene, the G/T genotype of the rs3212227 polymorphism within the IL12B gene, the A/G genotype of the rs1130864 polymorphism within the CRP gene, and the G allele of the rs1801197 polymorphism within the CALCR gene were associated with a decreased risk of IE whereas the T/T genotype of the rs1205 polymorphism within the CRP gene was associated with a higher risk of IE. Furthermore, heterozygous genotypes of the rs1143634 and rs3212227 polymorphisms were associated with the higher plasma levels of IL-1ß and IL-12, respectively. Our results indicate that inherited variation in the cytokine, acute phase response, and calcium metabolism pathways may be linked to IE.

Innate Immunity of Adipose Tissue in Rodent Models of Local and Systemic Staphylococcus aureus Infection.

Background. The role of adipose tissue in systemic inflammation during bacterial infection is unclear. Effects of Staphylococcus aureus infection on adipocytes in rodent models of experimental endocarditis and peritonitis, the impact of S. aureus infection on gene expression in epididymal and subcutaneous adipose tissue, and effects of S. aureus infection on the toll-like receptor-2- (TLR2-) cathelicidin pathway in vivo and in vitro were investigated. Material and methods. The rat model of catheter-induced S. aureus endocarditis and the mouse model of S. aureus-induced peritonitis were used for infection experiments, gene expression profiling in adipose tissue, and measurement of cytokines. 3T3-L1 adipocytes were analyzed for expression of the TLR2-cathelicidin pathway. Results. Upon systemic bacterial infection by S. aureus, there is a shift from anti- to proinflammatory cytokines in serum and in adipose tissue gene expression. The TLR2-cathelicidin pathway is increasingly expressed during adipocyte differentiation in vitro and is induced upon stimulation by synthetic lipopeptides. Conclusions. Systemic infection by Gram-positive bacteria induces proinflammatory transformation of adipose tissue sites distinct from infection sites, documented on the levels of gene expression and secreted mediators. The TLR2-cathelicidine pathway is expressed and highly inducible in adipocytes in vitro. Lipopeptides are important immune-modulators of adipocytes in both gene expression and protein secretion.

Endocarditis pathogen promotes vegetation formation by inducing intravascular neutrophil extracellular traps through activated platelets.

BACKGROUND: Endocarditis-inducing streptococci form multilayered biofilms in complex with aggregated platelets on injured heart valves, but the host factors that interconnect and entrap these bacteria-platelet aggregates to promote vegetation formation were unclear. METHODS AND RESULTS: In a Streptococcus mutans endocarditis rat model, we identified layers of neutrophil extracellular traps interconnecting and entrapping bacteria-platelet aggregates inside vegetation that could be reduced significantly in size along with diminished colonizing bacteria by prophylaxis with intravascular DNase I alone. The combination of activated platelets and specific immunoglobulin G-adsorbed bacteria are required to induce the formation of neutrophil extracellular traps through multiple activation pathways. Bacteria play key roles in coordinating the signaling through spleen tyrosine kinase, Src family kinases, phosphatidylinositol-3-kinase, and p38 mitogen-activated protein kinase pathways to upregulate the expression of P-selectin in platelets, while inducing reactive oxygen species-dependent citrullination in the arm of neutrophils. Neutrophil extracellular traps in turn serve as the scaffold to further enhance and entrap bacteria-platelet aggregate formation and expansion. CONCLUSIONS: Neutrophil extracellular traps promote and expand vegetation formation through enhancing and entrapping bacteria-platelet aggregates on the injured heart valves.

[Optimization of postoperative medical therapy of infective endocarditis in patients with congenital valvular heart disease].

The purpose of this study was to evaluate the effectiveness of combined surgical and medical treatment of infective endocarditis in patients with congenital valvular heart disease when included in a regimen of the drug Reamberin. In this regard, the analysis of the effectiveness of a combination regimen of 74 patients with valvular congenital heart diseases complicated with infective endocarditis. Given the indications for surgical correction operative technique features and possible technical difficulties in carrying out such operations, due to the inflammatory changes and tissue destruction, and ways to overcome them. For the correction of metabolic disorders in the postoperative period, 47 patients (main group) was appointed Reamberin: once, intravenous drip 400 ml/day during the first 5 days after surgery. 27 patients (control group) was conducted infusion therapy depending on the severity of the condition according to the classical scheme. In addition to standard clinical and laboratory examination, to assess the effectiveness of Reamberin was investigated catalase activity of CPK in blood serum in the dynamics of observation (1, 3 and 5 days after surgery). It is revealed that surgical approach, used in complex treatment of patients with valvular congenital heart diseases, including reorganization of the cavities of the heart, increasing the frequency of joints and the use of reinforcing strips of synthetic material that prevents the cutting of sutures through the inflamed tissue has achieved good short-and long-term results. Infective endocarditis and destruction of the valvular annulus fibrosus the use of a frame of strips of polytetrafluoroethylene allows you to restore its integrity and to implant a mechanical prosthesis. The inclusion in the regimen of patients with infective endocarditis complicated by cardiac insufficiency in the early postoperative period the drug Reamberin improves the efficiency of treatment by a more rapid restoration of the normal metabolism of cardiomyocytes and accelerates elimination of signs of heart failure.

Invasion of endothelial cells and arthritogenic potential of endocarditis-associated Corynebacterium diphtheriae.

Although infection by Corynebacterium diphtheriae is a model of extracellular mucosal pathogenesis, different clones have been also associated with invasive infections such as sepsis, endocarditis, septic arthritis and osteomyelitis. The mechanisms that promote C. diphtheriae infection and haematogenic dissemination need further investigation. In this study we evaluated the association and invasion mechanisms with human umbilical vein endothelial cells (HUVECs) and experimental arthritis in mice of endocarditis-associated strains and control non-invasive strains. C. diphtheriae strains were able to adhere to and invade HUVECs at different levels. The endocarditis-associated strains displayed an aggregative adherence pattern and a higher number of internalized viable cells in HUVECs. Transmission electron microscopy (TEM) analysis revealed intracellular bacteria free in the cytoplasm and/or contained in a host-membrane-confined compartment as single micro-organisms. Data showed bacterial internalization dependent on microfilament and microtubule stability and involvement of protein phosphorylation in the HUVEC signalling pathway. A high number of affected joints and high arthritis index in addition to the histopathological features indicated a strain-dependent ability of C. diphtheriae to cause severe polyarthritis. A correlation between the arthritis index and increased systemic levels of IL-6 and TNF-α was observed for endocarditis-associated strains. In conclusion, higher incidence of potential mechanisms by which C. diphtheriae may access the bloodstream through the endothelial barrier and stimulate the production of pro-inflammatory cytokines such as IL-6 and TNF-α, in addition to the ability to affect the joints and induce arthritis through haematogenic spread are thought to be related to the pathogenesis of endocarditis-associated strains.

Release of leukotriene B4, transforming growth factor-beta1 and microparticles in relation to aortic valve calcification.

BACKGROUND AND AIM OF THE STUDY: Aortic stenosis, the most frequent valvulopathy in the Western world, is characterized by an important extracellular matrix (ECM) remodeling and a process of calcification in the aortic valves. One physiopathological assumption is that transforming growth factor-beta1 (TGF-beta1) acts through ECM remodeling and plays a role in calcification, implicating also microparticles (MPs). Another recent notion is the active involvement of inflammatory mediators in the calcification process of aortic stenosis. METHODS: A total of 105 aortic valves was collected from patients suffering from calcified aortic stenosis with either tricuspid valve (AS) or bicuspid aortic valve (BAV), rheumatic aortic stenosis (RA), endocarditis, or aortic regurgitation (AR). Each valve was incubated for 24 h in culture medium and the supernatants (conditioned media) were used to measure the concentrations of leukotriene B4 (LTB4) and TGF-beta1 and to quantify the number of MPs released. Valvular calcification was evaluated using biphotonic absorptiometry. RESULTS: LTB4 concentrations were significantly higher in media conditioned by AS valves compared to those conditioned by RA and endocarditis valves. In addition, LTB4 concentrations correlated significantly with the calcium content of the aortic valves. In contrast, the concentrations of TGF-beta1 and MPs in the conditioned media did not differ significantly between the various groups of valves, and there was no significant correlation between calcification and either TGF-beta1 or the number of MPs released from the aortic valves. CONCLUSION: Taken together, these results indicate that inflammatory signaling through LTB4 may be more closely linked to calcification and aortic stenosis than signaling through TGF-beta1 and MPs.

Interaction between bacteria and cholesterol crystals: Implications for endocarditis and atherosclerosis.

BACKGROUND: The interaction between pathogenic bacteria and cholesterol crystals (CCs) has not been investigated. However, CCs are found extensively in atherosclerotic plaques and sclerotic cardiac valves. Interactions between pathogenic bacteria and CCs could provide insights into destabilization of atherosclerotic plaques and bacterial adhesion to cardiac valves. METHODS: Staphylococcus aureus and Pseudomonas aeruginosa were used to assess in vitro bacterial adhesion to CCs and proliferation in the presence of CCs compared to plastic microspheres and glass shards as controls. Ex vivo studies evaluated bacterial adhesion to atherosclerotic rabbit arteries compared to normal arteries and human atherosclerotic carotid plaques compared to normal carotid arteries. Scanning electron microscopy (SEM) was used to visualize bacterial adhesion to CCs and confocal microscopy was used to detect cholesterol binding to bacteria grown in the presence or absence of CCs. RESULTS: In vitro, S. aureus and P. aeruginosa displayed significantly greater adhesion, 36% (p<0.0001) and 89% (p<0.0001), respectively, and growth upon exposure to CCs compared to microspheres or glass shards. Rabbit and human atherosclerotic arteries contained significantly greater bacterial burdens compared to controls (4× (p<0.0004); 3× (p<0.019), respectively. SEM demonstrated that bacteria adhered and appeared to degrade CCs. Consistent with this, confocal microscopy indicated increased cholesterol bound to the bacterial cells. CONCLUSIONS: This study is the first to demonstrate an interaction between bacteria and CCs showing that bacteria dissolve and bind to CCs. This interaction helps to elucidate adhesion of bacteria to sclerotic valves and atherosclerotic plaques that may contribute to endocarditis and plaque destabilization.

Surgery for Endocarditis in Intravenous Drug Users.

BACKGROUND: Few studies have analyzed outcomes after surgery for endocarditis in intravenous drug users (IVDUs). The aim of this study was to compare survival after surgery for endocarditis in IVDUs versus non-IVDUs. Secondary outcomes were the rates of reoperation, reinfection, and relapse to drug use. METHODS: This population-based, observational cohort study included all patients who had undergone surgery for endocarditis at Karolinska University Hospital between 2002 and 2019. Patient data were collected from the institutional surgical database and medical charts. We used multivariable Cox regression to analyze associations between intravenous drug use and long-term survival. RESULTS: Of the 510 study patients, 55 were IVDUs (11%) and 455 were not (89%). During a mean follow-up of 5.3 years (maximum, 17.1 years), 30 IVDUs (55%) and 133 non-IVDUs (29%) died. The 30-day mortality was 10.9% and 8.5%, respectively, for IVDUs and non-IVDUs (P = .53). Survival in IVDUs versus non-IVDUs at 1, 5, and 8 years was 76% versus 86%, 49% versus 76%, and 35% versus 68%, respectively (adjusted hazard ratio = 4.12; 95% confidence interval, 2.54-6.68; P < .001). The risk for reoperation was higher in IVDUs (adjusted hazard ratio = 3.47; 95% confidence interval, 1.74-6.89; P < .001). Forty-two IVDUs died or were reinfected (76%) and 49 died or returned to drug use (89%). CONCLUSIONS: After surgery for endocarditis, IVDUs had substantially higher mortality and reoperation rates than did non-IVDUs. However, postoperative survival was comparable between groups, indicating that IVDUs manage surgery well. Prevention of relapse to drug use is of utmost importance in these patients.

Identification of the pivotal differentially expressed genes and pathways involved in Staphylococcus aureus-induced infective endocarditis by using bioinformatics analysis.

OBJECTIVE: Infective endocarditis (IE), particularly by Staphylococcus aureus, is an uncommon bacteremia-associated infection of the endocardium and cardiac valves. Herein, we evaluated predictive noninvasive biomarkers for IE caused by S. aureus through bioinformatics analysis. MATERIALS AND METHODS: Staphylococcus aureus-associated and IE-associated differentially expressed genes (DEGs) were identified by bioinformatics analysis of the GSE6269 and GSE29161 Gene Expression Omnibus (GEO) datasets. The DEGs were analyzed with the LIMMA package, and the coregulated genes were chosen as the intersection of DEGs between the two datasets, called common differentially expressed genes (CDEGs). The enrichment study of CDEGs was subsequently performed with the DAVID and KOBAS web resources. Finally, protein-protein interaction (PPI) network, microRNA (miRNA)-transcription factor (TF)-mRNA (messenger RNA) regulatory network, and the network of drug-genes were identified. RESULTS: From GSE6269 and GSE29161, respectively, a total of 201 and 741 DEGs were obtained. Gene Ontology (GO) analysis showed that CDEGs were primarily involved in innate immune response, extracellular exosome, as well as calcium ion binding, while the pathway analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that CDEGs were significantly enriched in the B-cell receptor, IL-17, and NF-kappa B signaling pathways. The hub genes in the PPI network included HP, S100A12, SPI1, CD14, CCR1, S100A9 and so on. In the miRNA-TF-mRNA regulatory network, SPI1 could target miR-361-5p, miR-155-5p, and miR-339-5p in the progression of IE. CONCLUSIONS: Several pivotal genes and pathways were identified in the progression of S. aureus-induced IE, which may have the potential for early detection.

Libman-Sacks endocarditis and associated cerebrovascular disease: The role of medical therapy.

BACKGROUND: Libman-Sacks endocarditis in patients with systemic lupus erythematosus (SLE) is commonly complicated with embolic cerebrovascular disease (CVD) or valve dysfunction for which high-risk valve surgery is frequently performed. However, the role of medical therapy alone for Libman-Sacks endocarditis and associated acute CVD remains undefined. OBJECTIVE: To determine in this cross-sectional and longitudinal study if conventional anti-inflammatory and anti-thrombotic therapy may be an effective therapy in SLE patients with Libman-Sacks endocarditis and associated acute CVD. METHODS AND MATERIALS: 17 SLE patients with Libman-Sacks endocarditis detected by two-and-three-dimensional transesophageal echocardiography (TEE) and complicated with acute CVD [stroke/TIA, focal brain injury on MRI, or cognitive dysfunction] were treated with conventional anti-inflammatory and anti-thrombotic therapy for a median of 6 months and then underwent repeat TEE, transcranial Doppler, brain MRI, and neurocognitive testing for re-assessment of Libman-Sacks endocarditis and CVD. RESULTS: Valve vegetations decreased in number, diameter, and area (all p ≤0.01); associated valve regurgitation significantly improved (p = 0.04), and valve thickening did not progress (p = 0.56). In 13 (76%) patients, valve vegetations or valve regurgitation resolved or improved in number and size or by ≥1 degree, respectively, as compared to 4 (24%) patients in whom vegetations or valve regurgitation persisted unchanged or increased in size or by ≥1 degree (p = 0.03). Also, cerebromicroembolism, lobar and global gray and white matter cerebral perfusion, ischemic brain lesion load, and neurocognitive dysfunction resolved or significantly improved (all p ≤0.04). CONCLUSION: These preliminary data suggest that combined conventional anti-inflammatory and antithrombotic therapy may be an effective treatment for Libman-Sacks endocarditis and its associated CVD and may obviate the need for high-risk valve surgery.

Potential involvement of Streptococcus mutans possessing collagen binding protein Cnm in infective endocarditis.

Streptococcus mutans, a significant contributor to dental caries, is occasionally isolated from the blood of patients with infective endocarditis. We previously showed that S. mutans strains expressing collagen-binding protein (Cnm) are present in the oral cavity of approximately 10-20% of humans and that they can effectively invade human umbilical vein endothelial cells (HUVECs). Here, we investigated the potential molecular mechanisms of HUVEC invasion by Cnm-positive S. mutans. The ability of Cnm-positive S. mutans to invade HUVECs was significantly increased by the presence of serum, purified type IV collagen, and fibrinogen (p < 0.001). Microarray analyses of HUVECs infected by Cnm-positive or -negative S. mutans strains identified several transcripts that were differentially upregulated during invasion, including those encoding the small G protein regulatory proteins ARHGEF38 and ARHGAP9. Upregulation of these proteins occurred during invasion only in the presence of serum. Knockdown of ARHGEF38 strongly reduced HUVEC invasion by Cnm-positive S. mutans. In a rat model of infective endocarditis, cardiac endothelial cell damage was more prominent following infection with a Cnm-positive strain compared with a Cnm-negative strain. These results suggest that the type IV collagen-Cnm-ARHGEF38 pathway may play a crucial role in the pathogenesis of infective endocarditis.

Cholesterol induced heart valve inflammation and injury: efficacy of cholesterol lowering treatment.

BACKGROUND: Heart valves often undergo a degenerative process leading to mechanical dysfunction that requires valve replacement. This process has been compared with atherosclerosis because of shared pathology and risk factors. In this study, we aimed to elucidate the role of inflammation triggered by cholesterol infiltration and cholesterol crystals formation causing mechanical and biochemical injury in heart valves. METHODS: Human and atherosclerotic rabbit heart valves were evaluated. New Zealand White male rabbits were fed an enriched cholesterol diet alone or with simvastatin and ezetimibe simultaneous or after 6 months of initiating cholesterol diet. Inflammation was measured using C-reactive protein (CRP) and RAM 11 of tissue macrophage content. Cholesterol crystal presence and content in valves was evaluated using scanning electron microscopy. RESULTS: Cholesterol diet alone induced cholesterol infiltration of valves with associated increased inflammation. Tissue cholesterol, CRP levels and RAM 11 were significantly lower in simvastatin and ezetimibe rabbit groups compared with cholesterol diet alone. However, the treatment was effective only when initiated with a cholesterol diet but not after lipid infiltration in valves. Aortic valve cholesterol content was significantly greater than all other cardiac valves. Extensive amounts of cholesterol crystals were noted in rabbit valves on cholesterol diet and in diseased human valves. CONCLUSIONS: Prevention of valve infiltration with cholesterol and reduced inflammation by simvastatin and ezetimibe was effective only when given during the initiation of high cholesterol diet but was not effective when given following infiltration of cholesterol into the valve matrix.

Prognostic Value of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Infective Endocarditis.

BACKGROUND: 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is commonly used for the diagnosis of infective endocarditis (IE), but its prognostic value remains unknown. OBJECTIVES: This study sought to assess the prognostic value of 18F-FDG PET/CT in prosthetic valve endocarditis (PVE) and native valve endocarditis (NVE). METHODS: This study prospectively included 173 consecutive patients (109 PVE and 64 NVE) with definite left-sided IE who had an 18F-FDG PET/CT and were followed-up for 1 year. The primary endpoint was a composite of major cardiac events: death, recurrence of IE, acute cardiac failure, nonscheduled hospitalization for cardiovascular indication, and new embolic event. RESULTS: 18F-FDG PET/CT was positive in 100 (58%) patients, 83% (n = 90 of 109) in the PVE, and 16% (n = 10 of 64) in the NVE group. At a mean follow-up of 225 days (interquartile range: 199 to 251 days), the primary endpoint occurred in 94 (54%) patients: 63 (58%) in the PVE group and 31 (48%) in the NVE group. In the PVE group, positive 18F-FDG PET/CT was significantly associated with a higher rate of primary endpoint (hazard ratio [HR]: 2.7; 95% confidence interval [CI]: 1.1 to 6.7; p = 0.04). Moderate to intense 18F-FDG valvular uptake was also associated with worse outcome (HR: 2.3; 95% CI: 1.3 to 4.5; p = 0.03) and to new embolic events in PVE (HR: 7.5; 95% CI: 1.24 to 45.2; p = 0.03) and in NVE (HR: 8.8; 95% CI: 1.1 to 69.5; p = 0.02). In the NVE group, 18F-FDG PET/CT was not associated with occurrence of the primary endpoint CONCLUSIONS: In addition to its good diagnostic performance, 18F-FDG PET/CT is predictive of major cardiac events in PVE and new embolic events within the first year following IE.