Differential induction of inflammatory cytokines and reactive oxygen species in murine peritoneal macrophages and resident fresh bone marrow cells by acute staphylococcus aureus infection: contribution of toll-like receptor 2 (TLR2)

Cellular and microenvironmental cues that promote macrophage fusion and foreign body response

During the foreign body response (FBR), macrophages fuse to form foreign body giant cells (FBGCs). Modulation of FBGC formation can prevent biomaterial degradation and loss of therapeutic efficacy. However, the microenvironmental cues that dictate FBGC formation are poorly understood with conflicting reports. Here, we identified molecular and cellular factors involved in driving FBGC formation in vitro. Macrophages demonstrated distinct fusion competencies dependent on monocyte differentiation. The transition from a proinflammatory to a reparative microenvironment, characterised by specific cytokine and growth factor programmes, accompanied FBGC formation. Toll-like receptor signalling licensed the formation of FBGCs containing more than 10 nuclei but was not essential for cell-cell fusion to occur. Moreover, the fibroblast-macrophage crosstalk influenced FBGC development, with the fibroblast secretome inducing macrophages to secrete more PDGF, which enhanced large FBGC formation. These findings advance our understanding as to how a specific and timely combination of cellular and microenvironmental factors is required for an effective FBR, with monocyte differentiation and fibroblasts being key players.

Extracellular fibrinogen-binding protein released by intracellular Staphylococcus aureus suppresses host immunity by targeting TRAF3

Many pathogens secrete effectors to hijack intracellular signaling regulators in host immune cells to promote pathogenesis. However, the pathogenesis of Staphylococcus aureus secretory effectors within host cells is unclear. Here, we report that Staphylococcus aureus secretes extracellular fibrinogen-binding protein (Efb) into the cytoplasm of macrophages to suppress host immunity. Mechanistically, RING finger protein 114, a host E3 ligase, mediates K27-linked ubiquitination of Efb at lysine 71, which facilitates the recruitment of tumor necrosis factor receptor associated factor (TRAF) 3. The binding of Efb to TRAF3 disrupts the formation of the TRAF3/TRAF2/cIAP1 (cellular-inhibitor-of-apoptosis-1) complex, which mediates K48-ubiquitination of TRAF3 to promote degradation, resulting in suppression of the inflammatory signaling cascade. Additionally, the Efb K71R mutant loses the ability to inhibit inflammation and exhibits decreased pathogenicity. Therefore, our findings identify an unrecognized mechanism of Staphylococcus aureus to suppress host defense, which may be a promising target for developing effective anti-Staphylococcus aureus immunomodulators.

Staphylococcus aureus secrete numerous effectors to evade or inhibit the host immune response, yet the mechanism underlying the effectors ability to manipulate the signalling pathways of macrophages remain unclear. Authors utilise in vitro and in vivo models to explore the role of extracellular fibrinogen-binding protein (Efb) in immune response modulation and pathogenicity.

The Influence of Antibiotic Resistance on Innate Immune Responses to Staphylococcus aureus Infection

Staphylococcus aureus (S. aureus) causes a broad range of infections and is associated with significant morbidity and mortality. S. aureus produces a diverse range of cellular and extracellular factors responsible for its invasiveness and ability to resist immune attack. In recent years, increasing resistance to last-line anti-staphylococcal antibiotics daptomycin and vancomycin has been observed. Resistant strains of S. aureus are highly efficient in invading a variety of professional and nonprofessional phagocytes and are able to survive inside host cells. Eliciting immune protection against antibiotic-resistant S. aureus infection is a global challenge, requiring both innate and adaptive immune effector mechanisms. Dendritic cells (DC), which sit at the interface between innate and adaptive immune responses, are central to the induction of immune protection against S. aureus. However, it has been observed that S. aureus has the capacity to develop further antibiotic resistance and acquire increased resistance to immunological recognition by the innate immune system. In this article, we review the strategies utilised by S. aureus to circumvent antibiotic and innate immune responses, especially the interaction between S. aureus and DC, focusing on how this relationship is perturbed with the development of antibiotic resistance.

Immunoregulation by type I interferons in the peritoneal cavity

The peritoneal cavity, a fluid-containing potential space surrounding the abdominal and pelvic organs, is home to a rich network of immune cells that maintain tissue homeostasis and provide protection against infection. However, under pathological conditions such as peritonitis, endometriosis, and peritoneal carcinomatosis, the peritoneal immune system can become dysregulated, resulting in nonresolving inflammation and disease progression. An enhanced understanding of the factors that regulate peritoneal immune cells under both homeostatic conditions and in disease contexts is therefore required to identify new treatment strategies for these often life-limiting peritoneal pathologies. Type I interferons (T1IFNs) are a family of cytokines with broad immunoregulatory functions, which provide defense against viruses, bacteria, and cancer. There have been numerous reports of immunoregulation by T1IFNs within the peritoneal cavity, which can contribute to both the resolution or propagation of peritoneal disease states, depending on the specifics of the disease setting and local environment. In this review, we provide an overview of the major immune cell populations that reside in the peritoneal cavity (or infiltrate it under inflammatory conditions) and highlight their contribution to the initiation, progression, or resolution of peritoneal diseases. Additionally, we will discuss the role of T1IFNs in the regulation of peritoneal immune cells, and summarize the results of laboratory studies and clinical trials which have investigated T1IFNs in peritonitis/sepsis, endometriosis, and peritoneal carcinomatosis.

Detection of Immune Checkpoint Receptors - A Current Challenge in Clinical Flow Cytometry

Immunological therapy principles are increasingly determining modern medicine. They are used to treat diseases of the immune system, for tumors, but also for infections, neurological diseases, and many others. Most of these therapies base on antibodies, but small molecules, soluble receptors or cells and modified cells are also used. The development of immune checkpoint inhibitors is amazingly fast. T-cell directed antibody therapies against PD-1 or CTLA-4 are already firmly established in the clinic. Further targets are constantly being added and it is becoming increasingly clear that their expression is not only relevant on T cells. Furthermore, we do not yet have any experience with the long-term systemic effects of the treatment. Flow cytometry can be used for diagnosis, monitoring, and detection of side effects. In this review, we focus on checkpoint molecules as target molecules and functional markers of cells of the innate and acquired immune system. However, for most of the interesting and potentially relevant parameters, there are still no test kits suitable for routine use. Here we give an overview of the detection of checkpoint molecules on immune cells in the peripheral blood and show examples of a possible design of antibody panels.

Prevalence of methicillin-resistant Staphylococcus aureus colonization among healthcare workers at a tertiary care hospital in northeastern Brazil

BACKGROUND

Staphylococcus aureus is a human pathogen of clinical importance related to a variety of infections.

AIM

The objective of this study was to analyze the molecular and epidemiological characteristics of S. aureus obtained from healthcare professionals (HCP) of a hospital in southwestern Bahia, Brazil.

METHODS

Samples were collected from hands, nasal cavity, and laboratory coats of 80 HCP. The bacterial isolates recovered from 240 samples were identified as S. aureus, and then analyzed for their antimicrobial resistance profile, genotypic characterization, and pathogenicity.

FINDINGS

178 isolates were identified as S. aureus, being mostly isolated from the nasal cavity. Thirty isolates (16.8%) were characterized as MRSA. The virulence gene frequency varied according to isolate source. All virulence genes were identified in at least one hand isolate. Isolates from laboratory coats did not show seb and pvl. Isolates from the nasal cavity did not exhibit pvl. The SCCmec type I was identified in 56.7% of MRSA isolates. Among MRSA isolates, 14 PFGE pulsotypes were characterized, with profile A being predominant (nine isolates). Clonal complexes CC5, CC45, and CC398 were found. MRSA isolates induced cytokine gene expression in macrophages, with IL-10 and IL-17 being expressed more often.

CONCLUSION

We found a high colonization rate for S. aureus among HCP. Moreover, we observed that MRSA strains presented different virulence factors and could induce cytokine gene expression, indicating an urgent need to control colonization rates of HCP by MRSA isolates in order to protect hospital patients and the general public.

Coating of a Novel Antimicrobial Nanoparticle with a Macrophage Membrane for the Selective Entry into Infected Macrophages and Killing of Intracellular Staphylococci

Internalization of Staphylococcus aureus by macrophages can inactivate bacterial killing mechanisms, allowing intracellular residence and dissemination of infection. Concurrently, these staphylococci can evade antibiotics that are frequently unable to pass mammalian cell membranes. A binary, amphiphilic conjugate composed of triclosan and ciprofloxacin is synthesized that self-assemble through micelle formation into antimicrobial nanoparticles (ANPs). These novel ANPs are stabilized through encapsulation in macrophage membranes, providing membrane-encapsulated, antimicrobial-conjugated NPs (Me-ANPs) with similar protein activity, Toll-like receptor expression and negative surface charge as their precursor murine macrophage/human monocyte cell lines. The combination of Toll-like receptors and negative surface charge allows uptake of Me-ANPs by infected macrophages/monocytes through positively charged, lysozyme-rich membrane scars created during staphylococcal engulfment. Me-ANPs are not engulfed by more negatively charged sterile cells possessing less lysozyme at their surface. The Me-ANPs kill staphylococci internalized in macrophages in vitro. Me-ANPs likewise kill staphylococci more effectively than ANPs without membrane-encapsulation or clinically used ciprofloxacin in a mouse peritoneal infection model. Similarly, organ infections in mice created by dissemination of infected macrophages through circulation in the blood are better eradicated by Me-ANPs than by ciprofloxacin. These unique antimicrobial properties of macrophage-monocyte Me-ANPs provide a promising direction for human clinical application to combat persistent infections.

Baicalin protects mice from infection with methicillin-resistant Staphylococcus aureus via alleviating inflammatory response

Sepsis was redefined as life-threatening organ dysfunction caused by a dysregulated host response to infection in 2016. One of its most common causes is Staphylococcus aureus, especially methicillin-resistant Staphylococcus aureus (MRSA), which leads to a significant increase in morbidity and mortality. Therefore, innovative and effective approaches to combat MRSA infection are urgently needed. Recently, host-directed therapy (HDT) has become a new strategy in the treatment of infectious diseases, especially those caused by antibiotic-resistant bacteria. Baicalin (BAI) is the predominant flavonoid and bioactive compound isolated from the roots of Radix Scutellariae (Huang Qin), a kind of traditional Chinese medicine. It has been reported that BAI exhibits multiple biological properties such as anti-oxidant, antitumor, and anti-inflammatory activities. However, the therapeutic role of BAI in MRSA infection is still unknown. In this study, it is found that BAI treatment inhibited the production of IL-6, TNF-α, and other cytokines from MRSA- or bacterial mimics-stimulated Mϕs and dendritic cells (DCs). BAI played an anti-inflammatory role by inhibiting the activation of ERK, JNK MAPK, and NF-κB pathways. Moreover, the serum level of TNF-α was decreased, whereas IL-10 was increased, in mice injected with MRSA. Furthermore, the bacterial load in livers and kidneys were further decreased by the combination of BAI and vancomycin (VAN), which might account for the amelioration of tissue damage. BAI reduced the high mortality rate caused by MRSA infection. Collectively, the results suggested that BAI may be a viable candidate of HDT strategy against severe sepsis caused by antibiotic-resistant bacteria such as MRSA.

Mechanisms of Blood Brain Barrier Disruption by Different Types of Bacteria, and Bacterial-Host Interactions Facilitate the Bacterial Pathogen Invading the Brain

This review aims to elucidate the different mechanisms of blood brain barrier (BBB) disruption that may occur due to invasion by different types of bacteria, as well as to show the bacteria-host interactions that assist the bacterial pathogen in invading the brain. For example, platelet-activating factor receptor (PAFR) is responsible for brain invasion during the adhesion of pneumococci to brain endothelial cells, which might lead to brain invasion. Additionally, the major adhesin of the pneumococcal pilus-1, RrgA is able to bind the BBB endothelial receptors: polymeric immunoglobulin receptor (pIgR) and platelet endothelial cell adhesion molecule (PECAM-1), thus leading to invasion of the brain. Moreover, Streptococcus pneumoniae choline binding protein A (CbpA) targets the common carboxy-terminal domain of the laminin receptor (LR) establishing initial contact with brain endothelium that might result in BBB invasion. Furthermore, BBB disruption may occur by S. pneumoniae penetration through increasing in pro-inflammatory markers and endothelial permeability. In contrast, adhesion, invasion, and translocation through or between endothelial cells can be done by S. pneumoniae without any disruption to the vascular endothelium, upon BBB penetration. Internalins (InlA and InlB) of Listeria monocytogenes interact with its cellular receptors E-cadherin and mesenchymal-epithelial transition (MET) to facilitate invading the brain. L. monocytogenes species activate NF-κB in endothelial cells, encouraging the expression of P- and E-selectin, intercellular adhesion molecule 1 (ICAM-1), and Vascular cell adhesion protein 1 (VCAM-1), as well as IL-6 and IL-8 and monocyte chemoattractant protein-1 (MCP-1), all these markers assist in BBB disruption. Bacillus anthracis species interrupt both adherens junctions (AJs) and tight junctions (TJs), leading to BBB disruption. Brain microvascular endothelial cells (BMECs) permeability and BBB disruption are induced via interendothelial junction proteins reduction as well as up-regulation of IL-1α, IL-1β, IL-6, TNF-α, MCP-1, macrophage inflammatory proteins-1 alpha (MIP1α) markers in Staphylococcus aureus species. Streptococcus agalactiae or Group B Streptococcus toxins (GBS) enhance IL-8 and ICAM-1 as well as nitric oxide (NO) production from endothelial cells via the expression of inducible nitric oxide synthase (iNOS) enhancement, resulting in BBB disruption. While Gram-negative bacteria, Haemophilus influenza OmpP2 is able to target the common carboxy-terminal domain of LR to start initial interaction with brain endothelium, then invade the brain. H. influenza type b (HiB), can induce BBB permeability through TJ disruption. LR and PAFR binding sites have been recognized as common routes of CNS entrance by Neisseria meningitidis. N. meningitidis species also initiate binding to BMECs and induces AJs deformation, as well as inducing specific cleavage of the TJ component occludin through the release of host MMP-8. Escherichia coli bind to BMECs through LR, resulting in IL-6 and IL-8 release and iNOS production, as well as resulting in disassembly of TJs between endothelial cells, facilitating BBB disruption. Therefore, obtaining knowledge of BBB disruption by different types of bacterial species will provide a picture of how the bacteria enter the central nervous system (CNS) which might support the discovery of therapeutic strategies for each bacteria to control and manage infection.

Dietary Bovine Lactoferrin Reduces Staphylococcus aureus in the Tissues and Modulates the Immune Response in Piglets Systemically Infected with S. aureus

BACKGROUND

Bovine lactoferrin (bLf) reduces Staphylococcus aureus infection in premature infants and promotes the growth of Bifidobacterium infantis, a predominant infant gut species. We hypothesized that bLf in combination with B. infantis would reduce the severity of systemic S. aureus infection.

OBJECTIVE

The aim was to determine the effects of oral administration of bLf and B. infantis on the course of systemic S. aureus infection.

METHODS

Colostrum-deprived piglets were fed formulas containing 4 g whey/L (CON group) or bLf (LF group). One-half of the piglets in each group were gavaged with B. infantis (109 colony-forming units/d), resulting in 2 additional groups (BI or COMB, respectively). On day 7, piglets were intravenously injected with S. aureus. Blood samples were collected preinfection and every 12 h postinfection for immune analyses. Tissue samples were collected on day 12 for analysis of bacterial abundance and gene expression.

RESULTS

Preinfection, LF piglets had lower serum interleukin 10 (IL-10), a higher percentage of lymphocytes, and a lower percentage of neutrophils than BI or COMB piglets. After infection, dietary bLf increased piglet weight gain, reduced staphylococcal counts in the kidneys, and tended to lower staphylococcal counts in the lungs and heart. Dietary bLf also decreased kidney IL-10 and increased lung interferon γ (IFN-γ) mRNA. B. infantis increased splenic IFN-γ expression. Renal Toll-like receptor 2 was upregulated in BI piglets but not in COMB piglets. Postinfection, BI piglets had increased serum IL-10 and decreased memory T cell populations. LF and COMB piglets had fewer circulating monocytes and B cells than CON or BI piglets.

CONCLUSIONS

Dietary bLf and B. infantis produced independent and tissue-specific effects. Piglets fed bLf alone or in combination with B. infantis mounted a more effective immune response and exhibited lower bacterial abundance. This study provides biological underpinnings to the clinical benefits of bLf observed in preterm infants but does not support B. infantis administration during S. aureus infection.

Dried Plum Polyphenolic Extract Combined with Vitamin K and Potassium Restores Trabecular and Cortical Bone in Osteopenic Model of Postmenopausal Bone Loss

Dried plum has unique anabolic effects on bone, but the responsible bioactive components have remained unclear. This study investigated components of dried plum with potential osteoprotective activity utilizing aged, osteopenic Sprague Dawley rats fed diets supplemented with a crude polyphenol extract, potassium, vitamin K or their combination. Whole body and femoral bone mineral density were restored with the polyphenol and combination treatments to a similar extent as the dried fruit. The combination treatment reversed trabecular bone loss in the spine and cortical bone in the femur mid-diaphysis in a similar manner. Biomarkers of bone resorption were reduced by the polyphenol and combination treatments. The polyphenol extract accounted for most of the anabolic effect of dried plum on bone. This study is the first to show the bioactive components in dried plum responsible for restoring bone in vivo.

The Peritoneal Macrophages in Inflammatory Diseases and Abdominal Cancers

Peritoneal macrophages (PMs) are the major cell type of peritoneal cells that participate in multiple aspects of innate and acquired immunity in the peritoneal cavity. PMs have an ability to release a large amount of proinflammatory and anti-inflammatory cytokines and therefore play a critical role in regulating the differentiation of innate immune cells and inflammatory T cells. Accumulating studies demonstrate that the immunological reactions and inflammatory responses of PMs are strongly related to the pathogenic processes of various inflammatory diseases and abdominal cancers. Consequently, the regulation of PM activation has gradually emerged as a promising target for immunotherapy, and better understanding of the distinctly biological function of PMs in individual diseases is crucial for designing specific and effective therapeutic agents. This review covers the characterization and immunological function of PMs in hosts with inflammatory diseases and abdominal cancers.

Expression of CXCR1 (IL-8 receptor A) in splenic, peritoneal macrophages and resident bone marrow cells after acute live or heat killed Staphylococcus aureus stimulation in mice

Literature reveals that interaction with live Staphylococcus aureus (S. aureus) or heat killed S. aureus (HKSA) promotes secretion of CXCL-8 or interleukin-8 (IL-8) from leukocytes, however, the expressions of CXCR1 in murine splenic (SPM), peritoneal macrophages (PM) and resident fresh bone marrow cells (FBMC) have not been identified. Currently, very few studies are available on the functional characterization of CXCR1 in mouse macrophage subtypes and its modulation in relation to acute S. aureus infection. SPM, PM and FBMCs were infected with viable S. aureus or stimulated with HKSA in presence and absence of anti-CXCR1 antibody in this study. We reported here that CXCR1 was not constitutively expressed by macrophage subtypes and the receptor was induced only after S. aureus stimulation. The CXCR1 band was found specific as we compared with human polymorphonuclear neutrophils (PMNs) as a positive control (data not shown). Although, we did not show that secreted IL-8 from S. aureus-infected macrophages promotes migration of PMNs. Blocking of cell surface CXCR1 decreases the macrophage's ability to clear staphylococcal infection, attenuates proinflammatory cytokine production and the increased catalase and decreased superoxide dismutase (SOD) enzymes of the bacteria might indicate their role in scavenging macrophage derived hydrogen peroxide (H₂O₂). The decreased levels of cytokines due to CXCR1 blockade before S. aureus infection appear to regulate the killing of bacteria by destroying H₂O₂ and nitric oxide (NO). Moreover, functional importance of macrophage subpopulation heterogeneity might be important in designing new effective approaches to limit S. aureus infection induced inflammation and cytotoxicity.

Riboflavin along with antibiotics balances reactive oxygen species and inflammatory cytokines and controls Staphylococcus aureus infection by boosting murine macrophage function and regulates inflammation

Background

Macrophages serve as intracellular reservoirs of S. aureus. Recent in vitro studies have confirmed high level resistance by S. aureus to macrophage mediated killing and the intracellular persistence of Staphylococci may play an important role in the pathogenesis. Since this localization protects them from both cell-mediated and humoral immune responses, therefore, a successful anti-staphylococcal therapy should include the elimination of intracellular bacteria, further protecting the host cells from staphylococci-induced cell death. So, only antibiotic therapy may not be helpful, successful therapy needs combination of drugs not only for elimination of pathogen but also for rescuing the host cell for S. aureus induced cell death.

Methods

In keeping with this idea an in vitro study has been done to examine the effect of Riboflavin along with antibiotics on phagocytosis, hydorgen peroxide, superoxide production, antioxidant enzyme levels, and cytokine levels in mouse macrophages for amelioration of the Staphylococcus aureus burden. The immune boosting effects of Riboflavin have been validated through perturbations of redox homeostasis and pro-inflammatory cytokines measurements.

Results

It was observed that the supplementation of Vitamin B-2 (Riboflavin) not only enhances macrophage function as previously reported but also decreases pro-inflammatory responses in Staphylococcus aureus infected macrophages. The observed influence of Riboflavin on enhanced antimicrobial effects such as enhanced phagocytosis of macrophages exposed to S. aureus, hydrogen peroxide or superoxide production when combined with either ciprofloxacin (CIP) or Azithromycin (AZM) and decrease in pro-inflammatory responses of IFN-γ, IL-6, IL-1β. Riboflavin treatment also decreased NO and TNF-α level possibly by inhibiting the NF-κβ pathway. The increased antioxidant enzymes like glutathione reductase, SOD and GSH level helped in maintaining a stable redox state in the cell.

Conclusion

Riboflavin plus antibiotic pretreatment not only enhances macrophage functions but also decreases proinflammatory responses in Staphylococcus aureus infected macrophages indicating better bacterial clearance and regulated inflammation which may be considered as a novel and important therapeutic intervention.

Murine macrophage response from peritoneal cavity requires signals mediated by chemokine receptor CCR-2 during Staphylococcus aureus infection

C-C chemokine receptor-2 (CCR-2) is a cognate receptor for monocyte chemotactic protein-1 (MCP-1), and recent studies revealed that MCP-1-CCR-2 signaling is involved in several inflammatory diseases characterized by macrophage infiltration. Currently, there is no study on the involvement of CCR-2 in the killing of S. aureus by macrophages of Swiss albino mice, and its substantial role in host defense against S. aureus infection in murine macrophages is still unclear. Therefore, the present study was aimed to investigate the functional and interactive role of CCR-2 and MCP-1 in regulating peritoneal macrophage responses with respect to acute S. aureus infection. We found that phagocytosis of S. aureus can serve as an important stimulus for MCP-1 production by peritoneal macrophages, which is dependent directly or indirectly on cytokines, reactive oxygen species and nitric oxide. Neutralization of CCR-2 in macrophages leads to increased production of IL-10 and decreased production of IFN-γ and IL-6. In CCR-2 blocked macrophages, pretreatment with specific blocker of NF-κB or p38-MAPK causes elevation in MCP-1 level and subsequent downregulation of CCR-2 itself. We speculate that CCR-2 is involved in S. aureus-induced MCP-1 production via NF-κB or p38-MAPK signaling. We also hypothesized that unnaturally high level of MCP-1 that build up upon CCR-2 neutralization might allow promiscuous binding to one or more other chemokine receptors, a situation that would not occur in CCR-2 non-neutralized condition. This may be the plausible explanation for such observed Th-2 response in CCR-2 blocked macrophages infected with S. aureus in the present study.

Staphylococcus aureus-mediated blood-brain barrier injury: an in vitro human brain microvascular endothelial cell model

Blood-brain barrier (BBB) disruption constitutes a hallmark event during pathogen-mediated neurological disorders such as bacterial meningitis. As a prevalent opportunistic pathogen, Staphylococcus aureus (SA) is of particular interest in this context, although our fundamental understanding of how SA disrupts the BBB is very limited. This paper employs in vitro infection models to address this. Human brain microvascular endothelial cells (HBMvECs) were infected with formaldehyde-fixed (multiplicity of infection [MOI] 0-250, 0-48 hr) and live (MOI 0-100, 0-3 hr) SA cultures. Both Fixed-SA and Live-SA could adhere to HBMvECs with equal efficacy and cause elevated paracellular permeability. In further studies employing Fixed-SA, infection of HBMvECs caused dose-dependent release of cytokines/chemokines (TNF-α, IL-6, MCP-1, IP-10, and thrombomodulin), reduced expression of interendothelial junction proteins (VE-Cadherin, claudin-5, and ZO-1), and activation of both canonical and non-canonical NF-κB pathways. Using N-acetylcysteine, we determined that these events were coupled to the SA-mediated induction of reactive oxygen species (ROS) within HBMvECs. Finally, treatment of HBMvECs with Fixed-ΔSpA (MOI 0-250, 48 hr), a gene deletion mutant of Staphylococcal protein A associated with bacterial infectivity, had relatively similar effects to Newman WT Fixed-SA. In conclusion, these findings provide insight into how SA infection may activate proinflammatory mechanisms within the brain microvascular endothelium to elicit BBB failure.

Control of Methicillin-Resistant Staphylococcus aureus Pneumonia Utilizing TLR2 Agonist Pam3CSK4

The spread of methicillin-resistant Staphylococcus aureus (MRSA) is a critical health issue that has drawn greater attention to the potential use of immunotherapy. Toll-like receptor 2 (TLR2), a pattern recognition receptor, is an essential component in host innate defense system against S. aureus infection. However, little is known about the innate immune response, specifically TLR2 activation, against MRSA infection. Here, we evaluate the protective effect and the mechanism of MRSA murine pneumonia after pretreatment with Pam3CSK4, a TLR2 agonist. We found that the MRSA-pneumonia mouse model, pretreated with Pam3CSK4, had reduced bacteria and mortality in comparison to control mice. As well, lower protein and mRNA levels of TNF-α, IL-1β and IL-6 were observed in lungs and bronchus of the Pam3CSK4 pretreatment group. Conversely, expression of anti-inflammatory cytokine IL-10, but not TGF-β, increased in Pam3CSK4-pretreated mice. Our additional studies showed that CXCL-2 and CXCL1, which are necessary for neutrophil recruitment, were less evident in the Pam3CSK4-pretreated group compared to control group, whereas the expression of Fcγ receptors (FcγⅠ/Ⅲ) and complement receptors (CR1/3) increased in murine lungs. Furthermore, we found that increased survival and improved bacterial clearance were not a result of higher levels of neutrophil infiltration, but rather a result of enhanced phagocytosis and bactericidal activity of neutrophils in vitro and in vivo as well as increased robust oxidative activity and release of lactoferrin. Our cumulative findings suggest that Pam3CSK4 could be a novel immunotherapeutic candidate against MRSA pneumonia.

Host antioxidant enzymes and TLR-2 neutralization modulate intracellular survival of Staphylococcus aureus: Evidence of the effect of redox balance on host pathogen relationship during acute staphylococcal infection

Staphylococcus aureus is an important pathogen in bone disease and innate immune recognition receptor, TLR-2 is reported to be crucial for inflammatory bone loss. Role of TLR-2 in bacterial clearance and cytokine response to S. aureus infection in murine bone marrow macrophages has been reported but the role of host derived ROS in host-pathogen relationship still remains an obvious question. In the present study, blocking of SOD and catalase in TLR-2 neutralized fresh bone marrow cells (FBMC) with Diethyldithiocarbamic acid (DDC) and 3-Amino-1,2,4-triazole (ATZ), separately, during acute S. aureus infection, produces moderate level of ROS and limits inflammation as compared with only TLR-2 non-neutralized condition and leads to decreased bacterial count compared with only TLR-2 neutralized condition. In summary, host SOD and catalase modulates ROS generation, cytokine levels and TLR-2 expression in FBMCs during acute S. aureus infection which might be useful in the alleviation of S. aureus infection and bone loss.