Staphylococcal lipoteichoic acid inhibits delayed-type hypersensitivity reactions via the platelet-activating factor receptor

Tissue adaptation of CD4 T lymphocytes in homeostasis and cancer

The immune system is traditionally classified as a defense system that can discriminate between self and non-self or dangerous and non-dangerous situations, unleashing a tolerogenic reaction or immune response. These activities are mainly coordinated by the interaction between innate and adaptive cells that act together to eliminate harmful stimuli and keep tissue healthy. However, healthy tissue is not always the end point of an immune response. Much evidence has been accumulated over the years, showing that the immune system has complex, diversified, and integrated functions that converge to maintaining tissue homeostasis, even in the absence of aggression, interacting with the tissue cells and allowing the functional maintenance of that tissue. One of the main cells known for their function in helping the immune response through the production of cytokines is CD4+ T lymphocytes. The cytokines produced by the different subtypes act not only on immune cells but also on tissue cells. Considering that tissues have specific mediators in their architecture, it is plausible that the presence and frequency of CD4+ T lymphocytes of specific subtypes (Th1, Th2, Th17, and others) maintain tissue homeostasis. In situations where homeostasis is disrupted, such as infections, allergies, inflammatory processes, and cancer, local CD4+ T lymphocytes respond to this disruption and, as in the healthy tissue, towards the equilibrium of tissue dynamics. CD4+ T lymphocytes can be manipulated by tumor cells to promote tumor development and metastasis, making them a prognostic factor in various types of cancer. Therefore, understanding the function of tissue-specific CD4+ T lymphocytes is essential in developing new strategies for treating tissue-specific diseases, as occurs in cancer. In this context, this article reviews the evidence for this hypothesis regarding the phenotypes and functions of CD4+ T lymphocytes and compares their contribution to maintaining tissue homeostasis in different organs in a steady state and during tumor progression.

RNA Sequencing Reveals the Regulation Mechanism of Yunnan Baiyao in Treating Skin Infection Caused by Staphylococcus aureus

Yunnan Baiyao is a well-known traditional Chinese medicine that can be formulated into a powder or capsule form. The mechanism by which it exerts its anti-inflammation effect, which is used in skin care products, needs to be further explored. In this study, we established the Staphylococcus aureus-induced mouse skin inflammatory model to investigate the effects of Yunnan Baiyao by the method of RNA-sequencing technology. The mice were randomly assigned to three groups, and those were control, model, and the Yunnan Baiyao-treated (YNtreated) group. Key genes and pathways were identified using bioinformatics analyses. In the study, we obtained 1,053 differentially expressed genes (DEGs) induced by Yunnan Baiyao. The 233 upregulated genes were enriched in 32 GO terms and 5 KEGG pathways, focused on the items, such as wound healing, cell metabolism, and proliferation, indicating the accelerating effects of Yunnan Baiyao on these aspects. The 820 downregulated genes were enriched mainly in the items, including the regulation of inflammation factor production, immune responses, and regulation of structure dermal components. Besides, Yunnan Baiyao reversed the expressions of 277 (201 decreased and 76 increased DEGs, respectively) induced by S. aureus. Ten key regulatory nodes (MMP2, PLK1, CCNB1, TLR4, CDK1, CCNA2, CDC25C, PDGFRA, MYOC, and KNG1) were identified by the construction of the protein interaction network, half of which were related to cell proliferation. VAV1 was another hub node that was affected by Yunnan Baiyao (Top 20). In the study, VAV1 and TLR4 can be considered key module genes in inflammation regulation. In conclusion, this study found that Yunnan Baiyao can significantly relieve inflammatory symptoms by regulating genes and pathways involved in the regulation of inflammation and immune response and also helped to deepen our understanding of the associated molecular mechanisms.

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

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

Keratinocyte-derived microvesicle particles mediate ultraviolet B radiation-induced systemic immunosuppression

A complete carcinogen, ultraviolet B (UVB) radiation (290-320 nm), is the major cause of skin cancer. UVB-induced systemic immunosuppression that contributes to photocarcinogenesis is due to the glycerophosphocholine-derived lipid mediator platelet-activating factor (PAF). A major question in photobiology is how UVB radiation, which only absorbs appreciably in the epidermal layers of skin, can generate systemic effects. UVB exposure and PAF receptor (PAFR) activation in keratinocytes induce the release of large numbers of microvesicle particles (MVPs; extracellular vesicles ranging from 100 to 1000 nm in size). MVPs released from skin keratinocytes in vitro in response to UVB (UVB-MVPs) are dependent on the keratinocyte PAFR. Here, we used both pharmacologic and genetic approaches in cells and mice to show that both the PAFR and enzyme acid sphingomyelinase (aSMase) were necessary for UVB-MVP generation. Our discovery that the calcium-sensing receptor is a keratinocyte-selective MVP marker allowed us to determine that UVB-MVPs leaving the keratinocyte can be found systemically in mice and humans following UVB exposure. Moreover, we found that UVB-MVPs contained bioactive contents including PAFR agonists that allowed them to serve as effectors for UVB downstream effects, in particular UVB-mediated systemic immunosuppression.

New Insights Into the Pathologic Roles of the Platelet-Activating Factor System

Described almost 50 years ago, the glycerophosphocholine lipid mediator Platelet-activating factor (PAF) has been implicated in many pathologic processes. Indeed, elevated levels of PAF can be measured in response to almost every type of pathology involving inflammation and cell damage/death. In this review, we provide evidence for PAF involvement in pathologic processes, with focus on cancer, the nervous system, and in photobiology. Importantly, recent insights into how PAF can generate and travel via bioactive extracellular vesicles such as microvesicle particles (MVP) are presented. What appears to be emerging from diverse pathologies in different organ systems is a common theme where pro-oxidative stressors generate oxidized glycerophosphocholines with PAF agonistic effects, which then trigger more enzymatic PAF synthesis via the PAF receptor. A downstream consequence of PAF receptor activation is the generation and release of MVP which provide a mechanism to transmit PAF as well as other bioactive agents. The knowledge gaps which when addressed could result in novel therapeutic strategies are also discussed. Taken together, an enhanced understanding of the PAF family of lipid mediators is essential in our improved comprehension of the relationship amongst the diverse cutaneous, cancerous, neurologic and systemic pathologic processes.

Enhanced Platelet-Activating Factor Synthesis Facilitates Acute and Delayed Effects of Ethanol-Intoxicated Thermal Burn Injury

Thermal burn injuries in patients who are alcohol-intoxicated result in greater morbidity and mortality. Murine models combining ethanol and localized thermal burn injury reproduce the systemic toxicity seen in human subjects, which consists of both acute systemic cytokine production with multiple organ dysfunction, as well as a delayed systemic immunosuppression. However, the exact mechanisms for these acute and delayed effects are unclear. These studies sought to define the role of the lipid mediator platelet-activating factor in the acute and delayed effects of intoxicated burn injury. Combining ethanol and thermal burn injury resulted in increased enzymatic platelet-activating factor generation in a keratinocyte cell line in vitro, human skin explants ex vivo, as well as in murine skin in vivo. Further, the acute increase in inflammatory cytokines, such as IL-6, and the systemic immunosuppressive effects of intoxicated thermal burn injury were suppressed in mice lacking platelet-activating factor receptors. Together, these studies provide a potential mechanism and treatment strategies for the augmented toxicity and immunosuppressive effects of thermal burn injury in the setting of acute ethanol exposure, which involves the pleotropic lipid mediator platelet-activating factor.

Langerhans cell: exciting developments in health and disease

Langerhans cells (LCs) have been the subject of much research since their discovery in 1868. LCs belong to the subset of leucocytes called dendritic cells. They are present in the epidermis and the pilosebaceous apparatus and monitor the cutaneous environment for changes in homeostasis. During embryogenesis, a wave of yolk sac macrophages seed the fetal skin. Then, fetal liver monocytes largely replace the yolk sac macrophages and comprise the majority of adult LCs. In the presence of skin irritation, LCs process antigen and travel to regional lymph nodes to present antigen to reactive T lymphocytes. Changes in LCs' surface markers during the journey occur under the influence of cytokines. The difference in expression of surface markers and the ability to resist radiation have allowed researchers to differentiate LCs from the murine Langerin-positive dermal dendritic cells. Exciting discoveries have been made recently regarding their role in inflammatory skin diseases, cancer and HIV. New research has shown that antibodies blocking CD1a appear to mitigate inflammation in contact hypersensitivity reactions and psoriasis. While it has been established that LCs have the potential to induce effector cells of the adaptive immune system to counter oncogenesis, recent studies have demonstrated that LCs coordinate with natural killer cells to impair development of squamous cell carcinoma caused by chemical carcinogens. However, LCs may also physiologically suppress T cells and permit keratinocyte transformation and tumorigenesis. Although long known to play a primary role in the progression of HIV infection, it is now understood that LCs also possess the ability to restrict the progression of the disease. There is a pressing need to discover more about how these cells affect various aspects of health and disease; new information gathered thus far seems promising and exciting.

Identification of a serum-induced transcriptional signature associated with metastatic cervical cancer

Objective

Tumor cells that escape local tissue control can convert inflammatory cells from tumor suppressors to tumor promoters. Moreover, soluble immune-modulating factors secreted from the tumor environment can be difficult to identify in patient serum due to their low abundance. We used an alternative strategy to infer a metastatic signature induced by sera of cervical cancer patients.

Methods

Sera from patients with local and metastatic cervical cancer were used to induce a disease-specific transcriptional signature in cultured, healthy peripheral blood mononuclear cells (PBMCs). An empirical Bayesian method, EBarrays, was used to identify differentially expressed (DE) genes with a target false discovery rate of <5%. Ingenuity Pathway Analysis (IPA) software was used to detect the top molecular and cellular functions associated with the DE genes. IPA and in silco analysis was used to pinpoint candidate upstream regulators, including cancer-related microRNAs (miRNAs).

Results

We identified enriched pathways in the metastatic cervical group related to immune surveillance functions, such as downregulation of engulfment, accumulation, and phagocytosis of hematopoietic cells. The predicted top upstream genes were IL-10 and immunoglobulins. In silco analysis identified miRNAs predicted to drive the transcriptional signature. Two of the 4 miRNAs (miR-23a-3p and miR-944) were validated in a cohort of women with local and metastatic cervical cancer.

Conclusions

This study supports the use of a cell-based assay that uses PBMC “reporters” to predict biologically relevant factors in patient serum. Further, disease-specific transcriptional signatures induced by patient sera have the potential to differentiate patients with local versus metastatic disease.

Understanding the connection between platelet-activating factor, a UV-induced lipid mediator of inflammation, immune suppression and skin cancer

Lipid mediators of inflammation play important roles in several diseases including skin cancer, the most prevalent type of cancer found in the industrialized world. Ultraviolet (UV) radiation is a complete carcinogen and is the primary cause of skin cancer. UV radiation is also a potent immunosuppressive agent, and UV-induced immunosuppression is a well-known risk factor for skin cancer induction. An essential mediator in this process is the glyercophosphocholine 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine commonly referred to as platelet-activating factor (PAF). PAF is produced by keratinocytes in response to diverse stimuli and exerts its biological effects by binding to a single specific G-protein-coupled receptor (PAF-R) expressed on a variety of cells. This review will attempt to describe how this lipid mediator is involved in transmitting the immunosuppressive signal from the skin to the immune system, starting from its production by keratinocytes, to its role in activating mast cell migration in vivo, and to the mechanisms involved that ultimately lead to immune suppression. Recent findings related to its role in regulating DNA repair and activating epigenetic mechanisms, further pinpoint the importance of this bioactive lipid, which may serve as a critical molecular mediator that links the environment (UVB radiation) to the immune system and the epigenome.

Topical application of a platelet activating factor receptor agonist suppresses phorbol ester-induced acute and chronic inflammation and has cancer chemopreventive activity in mouse skin

Platelet activating factor (PAF) has long been associated with acute edema and inflammatory responses. PAF acts by binding to a specific G-protein coupled receptor (PAF-R, Ptafr). However, the role of chronic PAF-R activation on sustained inflammatory responses has been largely ignored. We recently demonstrated that mice lacking the PAF-R (Ptafr-/- mice) exhibit increased cutaneous tumorigenesis in response to a two-stage chemical carcinogenesis protocol. Ptafr-/- mice also exhibited increased chronic inflammation in response to phorbol ester application. In this present study, we demonstrate that topical application of the non-hydrolysable PAF mimetic (carbamoyl-PAF (CPAF)), exerts a potent, dose-dependent, and short-lived edema response in WT mice, but not Ptafr -/- mice or mice deficient in c-Kit (c-Kit^W-sh/W-sh mice). Using an ear inflammation model, co-administration of topical CPAF treatment resulted in a paradoxical decrease in both acute ear thickness changes associated with a single PMA application, as well as the sustained inflammation associated with chronic repetitive PMA applications. Moreover, mice treated topically with CPAF also exhibited a significant reduction in chemical carcinogenesis. The ability of CPAF to suppress acute and chronic inflammatory changes in response to PMA application(s) was PAF-R dependent, as CPAF had no effect on basal or PMA-induced inflammation in Ptafr-/- mice. Moreover, c-Kit appears to be necessary for the anti-inflammatory effects of CPAF, as CPAF had no observable effect in c-Kit^W-sh/W-sh mice. These data provide additional evidence that PAF-R activation exerts complex immunomodulatory effects in a model of chronic inflammation that is relevant to neoplastic development.

Chemotherapeutic agents subvert tumor immunity by generating agonists of platelet-activating factor

Oxidative stress suppresses host immunity by generating oxidized lipid agonists of the platelet-activating factor receptor (PAF-R). Because many classical chemotherapeutic drugs induce reactive oxygen species (ROS), we investigated whether these drugs might subvert host immunity by activating PAF-R. Here, we show that PAF-R agonists are produced in melanoma cells by chemotherapy that is administered in vitro, in vivo, or in human subjects. Structural characterization of the PAF-R agonists induced revealed multiple oxidized glycerophosphocholines that are generated nonenzymatically. In a murine model of melanoma, chemotherapeutic administration could augment tumor growth by a PAF-R-dependent process that could be blocked by treatment with antioxidants or COX-2 inhibitors or by depletion of regulatory T cells. Our findings reveal how PAF-R agonists induced by chemotherapy treatment can promote treatment failure. Furthermore, they offer new insights into how to improve the efficacy of chemotherapy by blocking its heretofore unknown impact on PAF-R activation.

To hydrolyze or not to hydrolyze: the dilemma of platelet-activating factor acetylhydrolase

Mounting ambiguity persists around the functional role of the plasma form of platelet-activating factor acetylhydrolase (PAF-AH). Because PAF-AH hydrolyzes PAF and related oxidized phospholipids, it is widely accepted as an anti-inflammatory enzyme. On the other hand, its actions can also generate lysophosphatidylcholine (lysoPC), a component of bioactive atherogenic oxidized LDL, thus allowing the enzyme to have proinflammatory capabilities. Presence of a canonical lysoPC receptor has been seriously questioned for a multitude of reasons. Animal models of inflammation show that elevating PAF-AH levels is beneficial and not deleterious and overexpression of PAF receptor (PAF-R) also augments inflammatory responses. Further, many Asian populations have a catalytically inert PAF-AH that appears to be a severity factor in a range of inflammatory disorders. Correlation found with elevated levels of PAF-AH and CVDs has led to the design of a specific PAF-AH inhibitor, darapladib. However, in a recently concluded phase III STABILITY clinical trial, use of darapladib did not yield promising results. Presence of structurally related multiple ligands for PAF-R with varied potency, existence of multi-molecular forms of PAF-AH, broad substrate specificity of the enzyme and continuous PAF production by the so called bi-cycle of PAF makes PAF more enigmatic. This review seeks to address the above concerns.

Staphylococcus aureus lipoteichoic acid inhibits platelet activation and thrombus formation via the Paf receptor

Impaired healing is common in wounds infected with the major human pathogen Staphylococcus aureus, although the underlying mechanisms are poorly understood. Here, we show that S. aureus lipoteichoic acid (LTA) inhibits platelet aggregation caused by physiological agonists and S. aureus and reduced platelet thrombus formation in vitro. The presence of D-alanine on LTA is necessary for the full inhibitory effect. Inhibition of aggregation was blocked using a monoclonal anti-platelet activating factor receptor (PafR) antibody and Ginkgolide B, a well-defined PafR antagonist, demonstrating that the LTA inhibitory signal occurs via PafR. Using a cyclic AMP (cAMP) assay and a Western blot for phosphorylated VASP, we determined that cAMP levels increase upon platelet incubation with LTA, an effect which inhibits platelet activation. This was blocked when platelets were preincubated with Ginkgolide B. Furthermore, LTA reduced hemostasis in a mouse tail-bleed assay.

Signalling or binding: the role of the platelet-activating factor receptor in invasive pneumococcal disease

Streptococcus pneumoniae (the pneumococcus) is an opportunistic human pathogen, which causes serious invasive disease such as pneumonia, bacteraemia and meningitis. The interaction of the bacteria with host receptors precedes the development of invasive disease. One host receptor implicated in pneumococcal adhesion to, invasion of and ultimately translocation of cell layers is the platelet-activating factor receptor (PAFR). PAFR is a G-protein coupled receptor which binds PAF, a potent phospholipid activator involved in many leucocyte functions, platelet aggregation and inflammation. PAFR has been proposed to bind S. pneumoniae and as such facilitate adhesion to, uptake by and transcytosis of endothelial cells leading to invasive disease. However, there is a shortage of biochemical data supporting direct interaction between PAFR and the bacteria, in addition to conflicting data on its role in development of invasive pneumococcal disease (IPD). In this review, we will discuss current literature on PAFR and S. pneumoniae and other pathogens,including data concerning human PAFR genetic variation related to IPD clinical aspects, to shed light on the importance of PAFR in IPD. Clarification of the role of this receptor in IPD development has the potential to enable the development of novel therapeutic strategies for treating pneumococcal disease by interfering with the PAFR.

Cigarette smoke exposure inhibits contact hypersensitivity via the generation of platelet-activating factor agonists

Previous studies have established that pro-oxidative stressors suppress host immunity because of their ability to generate oxidized lipids with platelet-activating factor receptor (PAF-R) agonist activity. Although exposure to the pro-oxidative stressor cigarette smoke (CS) is known to exert immunomodulatory effects, little is known regarding the role of PAF in these events. The current studies sought to determine the role of PAF-R signaling in CS-mediated immunomodulatory effects. We demonstrate that CS exposure induces the generation of a transient PAF-R agonistic activity in the blood of mice. CS exposure inhibits contact hypersensitivity in a PAF-R-dependent manner as PAF-R-deficient mice were resistant to these effects. Blocking PAF-R agonist production either by systemic antioxidants or treatment with serum PAF-acetyl hydrolase enzyme blocked both the CS-mediated generation of PAF-R agonists and PAF-R-dependent inhibition of contact hypersensitivity (CHS) reactions, indicating a role for oxidized glycerophosphocholines with PAF-R agonistic activity in this process. In addition, cyclooxygenase-2 inhibition did not block PAF-R agonist production but prevented CS-induced inhibition of CHS. This suggests that cyclooxygenase-2 acts downstream of the PAF-R in mediating CS-induced systemic immunosuppression. Moreover, CS exposure induced a significant increase in the expression of the regulatory T cell reporter gene in Foxp3(EGFP) mice but not in Foxp3(EGFP) mice on a PAF-R-deficient background. Finally, regulatory T cell depletion via anti-CD25 Abs blocked CS-mediated inhibition of CHS, indicating the potential involvement of regulatory T cells in CS-mediated systemic immunosuppression. These studies provide the first evidence, to our knowledge, that the pro-oxidative stressor CS can modulate cutaneous immunity via the generation of PAF-R agonists produced through lipid oxidation.

Treatment outcomes of secondarily impetiginized pediatric atopic dermatitis lesions and the role of oral antibiotics

Patients with atopic dermatitis (AD) are predisposed to infection with Staphylococcus aureus, which worsens their skin disease; it has been postulated that the lack of antimicrobial peptides due to aberrant allergic inflammation in skin with AD could mediate this enhanced bacterial susceptibility. We sought to characterize the amounts of S. aureus and biological products found in infected AD lesions and whether treatment with topical corticosteroids and oral cephalexin as the only antimicrobial improved outcomes. Fifty-nine children with clinically and S. aureus-positive impetiginized lesions of AD were enrolled in this study. A lesion was graded clinically using the Eczema Area and Severity Index, and wash fluid was obtained from the lesion for quantitative bacterial culture and antibiotic sensitivities and measurement of bacterial products and cytokines. Subjects were re-evaluated 2 weeks after treatment. Improvement in the clinical and inflammatory characteristics of impetiginized lesions were noted, even in the 15% of lesions infected with Methicillin-resistant S. aureus (MRSA). In a subgroup of subjects whose lesions did not contain S. aureus 2 weeks after initiating treatment, beta-defensin levels were higher at both visits than in normal skin. Treatment of uncomplicated impetiginized pediatric AD with topical corticosteroids and cephalexin results in significant clinical improvement, even in subjects infected with MRSA. We propose that the inhibition of abnormal inflammation by the treatment regimen, resulting in the high levels of defensins, is involved in the improvement of AD and that systemic antibiotics do not appear to be necessary in secondary impetiginized AD.

Platelet-activating factor receptor agonists mediate xeroderma pigmentosum A photosensitivity

To date, oxidized glycerophosphocholines (Ox-GPCs) with platelet-activating factor (PAF) activity produced non-enzymatically have not been definitively demonstrated to mediate any known disease processes. Here we provide evidence that these Ox-GPCs play a pivotal role in the photosensitivity associated with the deficiency of the DNA repair protein xeroderma pigmentosum type A (XPA). It should be noted that XPA-deficient cells are known to have decreased antioxidant defenses. These studies demonstrate that treatment of human XPA-deficient fibroblasts with the pro-oxidative stressor ultraviolet B (UVB) radiation resulted in increased reactive oxygen species and PAF receptor (PAF-R) agonistic activity in comparison with gene-corrected cells. The UVB irradiation-generated PAF-R agonists were inhibited by antioxidants. UVB irradiation of XPA-deficient (Xpa-/-) mice also resulted in increased PAF-R agonistic activity and skin inflammation in comparison with control mice. The increased UVB irradiation-mediated skin inflammation and TNF-α production in Xpa-/- mice were blocked by systemic antioxidants and by PAF-R antagonists. Structural characterization of PAF-R-stimulating activity in UVB-irradiated XPA-deficient fibroblasts using mass spectrometry revealed increased levels of sn-2 short-chain Ox-GPCs along with native PAF. These studies support a critical role for PAF-R agonistic Ox-GPCs in the pathophysiology of XPA photosensitivity.

Loss of the platelet activating factor receptor in mice augments PMA-induced inflammation and cutaneous chemical carcinogenesis

Although platelet-activating factor (PAF) is a well-known acute inflammatory mediator, little is known regarding the role of PAF in chronic inflammation. Phorbol esters are known to stimulate PAF production. Moreover, the ability of repeated applications of phorbol esters to induce a sustained inflammatory response is crucial to their tumorigenic activity. We therefore examined whether PAF acts as a mediator of phorbol ester-induced inflammation and tumorigenesis. While PAF receptor knockout mice (PAFR(-/-)) showed an expected but modest reduction in the acute inflammatory response to phorbol 12-myristate 13-acetate (PMA), these mice exhibited a surprising increase in inflammation following chronic PMA application. This increased inflammation was documented by a number of findings that included: increased skin thickness, increased myeloperoxidase activity and expression and increased expression of known inflammatory mediators. Interestingly, vehicle-treated PAFR(-/-) mice also exhibited modest increases in levels of inflammatory markers. This suggests that the platelet activating factor receptor (PAFR) acts to suppress chronic inflammation in response to other stimuli, such as barrier disruption. The idea that chronic PAFR activation is anti-inflammatory was documented by repetitive topical PAFR agonist administration that resulted in reduced myeloperoxidase activity in skin. We next utilized a 7,12-dimethylbenz(a)anthracene/PMA carcinogenesis protocol to demonstrate that PAFR(-/-) mice exhibit significantly increased tumor formation and malignant progression compared with wild-type control mice. These studies provide evidence for two important, unexpected and possibly interrelated pathological roles for the PAFR: first, the PAFR acts to suppress PMA-induced chronic inflammation; secondly, the PAFR acts to suppress neoplastic development in response to chemical carcinogens.

Encoding a superantigen by Staphylococcus aureus does not affect clinical characteristics of infected atopic dermatitis lesions

BACKGROUND

Bacterial infection with Staphylococcus aureus is a known trigger for the worsening of atopic dermatitis (AD). Staphylococcal superantigens have been theorized to make a potential contribution to this worsening of AD seen with infection.

OBJECTIVES

We sought to assess whether encoding a superantigen by S. aureus affects the inflammatory characteristics of impetiginized AD skin lesions.

METHODS

Fifty-two children with clinically impetiginized lesions of AD which were positive for S. aureus were enrolled in this study. A lesion was graded clinically using the Eczema Area and Severity Index (EASI), and then wash fluid was obtained from the lesion for quantitative bacterial culture, and measurement of bacterial products lipoteichoic acid and staphylococcal protein A and cytokines. The staphylococcal isolate was tested for antibiotic susceptibilities and the presence of a superantigen.

RESULTS

Fifty-four per cent (28 of 52) of the staphylococcal isolates encoded a superantigen. The presence of a superantigen had no significant effect on EASI score, amounts of bacterial products or inflammatory cytokines in the AD lesion.

CONCLUSIONS

These studies suggest that the expression of a superantigen by S. aureus alone does not play an important role in the increased skin inflammation associated with staphylococcal infection in childhood AD.

Dendritic cells produce inflammatory cytokines in response to bacterial products from Staphylococcus aureus-infected atopic dermatitis lesions

Atopic Dermatitis (AD) patients often acquire secondary skin infections resulting in increased inflammation. The increased inflammation occurs through the activation of multiple cell types including dendritic cells (DC). In this study, we investigated the activity of soluble products present in infected AD lesions by measuring the ability of patients' wash fluids from a quantitative culture of lesions to activate DC. We found that wash fluid derived from AD lesions induced cytokine production by murine bone marrow-derived DC, including IL-1β, IL-6, ΙL-10, and tumor necrosis factor-α. The lipoprotein lipoteichoic acid (LTA) from Staphylococcusaureus was implicated as a potent stimulus in the wash fluids as only wash fluid samples that contained LTA exerted this activity, and exogenous LTA triggered similar DC cytokine activation. Wash fluid- and LTA-stimulated DC cytokine production required MyD88, but not the platelet-activating factor receptor (PAF-R), despite the ability of LTA to function through this receptor in keratinocytes. Thus, our results support a role for DC in the worsening of AD inflammation due to secondary bacteria infections.

Ultraviolet B radiation of human skin generates platelet-activating factor receptor agonists

Ultraviolet B radiation (UVB) is a potent stimulator of epidermal cytokine production. In addition to cytokines, such as tumor necrosis factor-alpha (TNF-alpha), UVB generates bioactive lipids including platelet-activating factor (PAF). Our previous in vitro studies in keratinocytes or epithelial cell lines have demonstrated that UVB-mediated production of PAF agonists is due primarily to the pro-oxidative effects of this stimulant, resulting in the nonenzymatic production of modified phosphocholines (oxidized glycerophosphocholines). The current studies use human skin to assess whether UVB irradiation generates PAF-receptor agonists, and the role of oxidative stress in their production. These studies demonstrate that UVB irradiation of human skin results in PAF agonists, which are blocked by the antioxidant vitamin C and the epidermal growth factor receptor inhibitor PD168393. Inasmuch as UVB-generated PAF agonists have been implicated in animal model systems as being involved in photobiologic processes including systemic immunosuppression and cytokine (TNF-alpha) production, these studies indicate that this novel activity could be involved in human disease.

Infected atopic dermatitis lesions contain pharmacologic amounts of lipoteichoic acid

BACKGROUND

Bacterial infection with Staphylococcus aureus is a known trigger for worsening of atopic dermatitis (AD); the exact mechanisms by which bacterial infection worsens dermatitis are unknown.

OBJECTIVE

We sought to characterize the amounts of the biologically active bacterial lipoprotein lipoteichoic acid (LTA) in infected AD lesions.

METHODS

Eighty-nine children with clinically impetiginized lesions of AD were enrolled in this study. A lesion was graded clinically by using the Eczema Area and Severity Index (EASI), wash fluid obtained from the lesion for quantitative bacterial culture, and measurement of LTA and cytokines. The staphylococcal isolate was tested for antibiotic susceptibilities. The patients were treated with a regimen that included topical corticosteroids and systemic antibiotics, and the lesion was reanalyzed after 2 weeks.

RESULTS

S aureus was identified in 79 of 89 children enrolled in the study. The bacterial colony-forming unit (CFU) counts correlated with the EASI lesional score (P = .04). LTA levels as high as 9.8 mug/mL were measured in the wash fluid samples, and the amounts correlated with the lesional EASI scores (P = .01) and S aureus CFU (P < .001). Approximately 30% of clinically impetiginized AD lesions contained greater than 1 mug/mL LTA, amounts that exert effects on various cell types in vitro. Moreover, injection of skin tissue ex vivo with amounts of LTA found in AD lesions resulted in epidermal cytokine gene expression.

CONCLUSION

Pharmacologic levels of LTA are found in many infected atopic dermatitis lesions.

Lipoteichoic acid improves the capability of mast cells in the host defense system against bacteria

OBJECTIVES AND DESIGN

We investigated the effects of microbial components on the uptake of microbes by mast cells (MCs), and studied the change in cytokine production in MCs after bacterial uptake.

MATERIAL OR SUBJECTS

LAD2 human mast cells, cord-blood and peripheral-blood derived MCs were employed to analyze their surface molecule expression and cytokine generation by flow cytometry. Bacterial internalization in these MCs was observed by confocal microscopy and flow cytometry.

RESULTS

Complement receptor 3 expression was augmented by LTA but not by PGN or 3CpG-oligodeoxynucleotide. LTA also enhanced the uptake of opsonized bacteria (over twofold augmentation). After bacterial uptake, MCs augmented the production of chemoattractant cytokines for neutrophils, while Th1 and Th2 cytokine production showed little or no change.

CONCLUSIONS

LTA increases the capability of the MC as a sentinel in the host immune response, and some bacterial components direct human MC function towards innate immunity after pathogen infection.

Ultraviolet B radiation generated platelet-activating factor receptor agonist formation involves EGF-R-mediated reactive oxygen species

Recent studies have implicated the lipid mediator platelet-activating factor (PAF) in UVB-mediated systemic immunosuppression known to be a major cause for skin cancers. Previously, our group has demonstrated that UVB irradiation triggers the production of PAF and oxidized glycerophosphocholines that act as PAF-receptor (PAF-R) agonists. The present studies explored the mechanisms by which UVB generates PAF-R agonists. UVB irradiation of human epidermal KB cells resulted in both increased levels of reactive oxygen species (ROS) and PAF-R agonistic activity. Pretreatment of KB cells with antioxidants vitamin C and N-acetylcysteine or the pharmacological inhibitor PD168393 specific for the epidermal growth factor receptor all inhibited UVB-induced ROS as well as PAF-R agonists, yet had no effect on fMLP-mediated PAF-R agonist production. In addition, in vivo production of PAF-R agonists from UVB-irradiated mouse skin was blocked by both systemic vitamin C administration and topical PD168393 application. Moreover, both vitamin C and PD168393 abolished UVB-mediated but not the PAF-R agonist 1-hexadecyl-2-N-methylcarbamoyl glycerophosphocholine-mediated immunosuppression as measured by the inhibition of delayed type contact hypersensitivity to the chemical dinitrofluorobenzene. These studies suggest that UVB-induced systemic immunosuppression is due to epidermal growth factor receptor-mediated ROS which results in PAF-R agonist formation.

The balance between immunity and tolerance: the role of Langerhans cells

Langerhans cells are immature skin-homing dendritic cells that furnish the epidermis with an immune surveillance system, and translate information between the internal and external milieu. Dendritic cells, in particular Langerhans cells, are gaining prominence as one of the potential principal players orchestrating the decision between immunity and tolerance. Langerhans cells capture aberrant self-antigen and pathogen-derived antigen for display to the efferent immune response. Recent evidence suggests redundancy in the antigen-presenting function of Langerhans cells, with dermal dendritic subsets capable of fulfilling an analogous role. There is mounting evidence that Langerhans cells can cross-prime T cells to recognize antigens. Langerhans cells are proposed to stimulate T regulatory cells, and are implicated in the pathogenesis of cutaneous T cell lymphoma.The phenotype of Langerhans cells, which may be tolerogenic or immunogenic, appears to depend on their state of maturity, inciting immunogen and cytokine environment, offering the potential for manipulation in immunotherapy.

p21-activated kinase regulates mast cell degranulation via effects on calcium mobilization and cytoskeletal dynamics

Mast cells are key participants in allergic diseases via activation of high-affinity IgE receptors (FcepsilonRI) resulting in release of proinflammatory mediators. The biochemical pathways linking IgE activation to calcium influx and cytoskeletal changes required for intracellular granule release are incompletely understood. We demonstrate, genetically, that Pak1 is required for this process. In a passive cutaneous anaphylaxis experiment, W(sh)/W(sh) mast cell-deficient mice locally reconstituted with Pak1(-/-) bone marrow-derived mast cells (BMMCs) experienced strikingly decreased allergen-induced vascular permeability compared with controls. Consistent with the in vivo phenotype, Pak1(-/-) BMMCs exhibited a reduction in FcepsilonRI-induced degranulation. Further, Pak1(-/-) BMMCs demonstrated diminished calcium mobilization and altered depolymerization of cortical filamentous actin (F-actin) in response to FcepsilonRI stimulation. These data implicate Pak1 as an essential molecular target for modulating acute mast cell responses that contribute to allergic diseases.

Dermal dendritic cells, and not Langerhans cells, play an essential role in inducing an immune response

Langerhans cells (LCs) serve as epidermal sentinels of the adaptive immune system. Conventional wisdom suggests that LCs encounter Ag in the skin and then migrate to the draining lymph nodes, where the Ag is presented to T cells, thus initiating an immune response. Platelet-activating factor (PAF) is a phospholipid mediator with potent biological effects. During inflammation, PAF mediates recruitment of leukocytes to inflammatory sites. We herein tested a hypothesis that PAF induces LC migration. Applying 2,4-dinitro-1-fluorobenzene (DNFB) to wild-type mice activated LC migration. In contrast, applying DNFB to PAF receptor-deficient mice or mice injected with PAF receptor antagonists failed to induce LC migration. Moreover, after FITC application the appearance of hapten-laden LCs (FITC+, CD11c+, Langerin+) in the lymph nodes of PAF receptor-deficient mice was significantly depressed compared with that found in wild-type mice. LC chimerism indicates that the PAF receptor on keratinocytes but not LCs is responsible for LC migration. Contrary to the diminution of LC migration in PAF receptor-deficient mice, we did not observe any difference in the migration of hapten-laden dermal dendritic cells (FITC+, CD11c+, Langerin-) into the lymph nodes of PAF receptor-deficient mice. Additionally, the contact hypersensitivity response generated in wild-type or PAF receptor-deficient mice was identical. Finally, dermal dendritic cells, but not LCs isolated from the draining lymph nodes after hapten application, activated T cell proliferation. These findings suggest that LC migration may not be responsible for the generation of contact hypersensitivity and that dermal dendritic cells may play a more important role.

Human mast cell activation by Staphylococcus aureus: interleukin-8 and tumor necrosis factor alpha release and the role of Toll-like receptor 2 and CD48 molecules

The ability of Staphylococcus aureus to invade and survive within host cells is believed to contribute to its propensity to cause persistent and metastatic infections. In addition, S. aureus infections often are associated with atopic diseases such as dermatitis, rhinitis, and asthma. Mast cells, the key cells of allergic diseases, have a pivotal role in innate immunity and have the capacity of phagocytosis, and they can destroy some pathogenic bacteria. However, little is known about the ability of some other bacteria to survive and overcome mast cell phagocytosis. Therefore, we were interested in evaluating the interplay between mast cells and S. aureus. In this study, we show that human cord blood-derived mast cells (CBMC) can be infected by pathogenic S. aureus. S. aureus displayed a high adherence to mast cells as well as invasive and survival abilities within them. However, when infections were performed in the presence of cytochalasin D or when CBMC were preincubated with anti-Toll-like receptor 2 (TLR2) or anti-CD48 antibodies, the invasiveness and the inflammatory response were abrogated, respectively. Furthermore, we observed an increase of TLR2 and CD48 molecules on CBMC after S. aureus infection. The infection of CBMC with S. aureus also caused the release of tumor necrosis factor alpha (TNF-alpha) and interleukin-8 (IL-8). Both live and killed S. aureus organisms were found to trigger TNF-alpha and IL-8 release by CBMC in a time-dependent manner. Cumulatively, these findings suggest that S. aureus internalizes and survives in mast cells. This may play an important role in infections and in atopic diseases associated with S. aureus.

Involvement of platelet-activating factor in ultraviolet B-induced hyperalgesia

Ultraviolet B (UVB) radiation causes cutaneous inflammation. One important clinical consequence of UVB-induced inflammation is increased pain or hyperalgesia, which is likely mediated by enhanced sensitivity of cutaneous sensory neurons. Previous studies have demonstrated that UVB radiation generates the lipid mediator, platelet-activating factor (PAF), as well as oxidized phospholipids that act as PAF-mimetics. These substances exert effects through the PAF receptor (PAF-R). This study was designed to assess whether PAF-R is involved in UVB-induced hyperalgesia. Intradermal injection of carbamoyl PAF (CPAF; 1-hexadecyl-2-N-methylcarbamoyl glycerophosphocholine) resulted in an enhanced response to mechanical stimuli in wild-type mice but not in PAF-R knockout (KO) mice. There was no significant change in paw withdrawal to noxious thermal stimuli in either genotype after intradermal injection of CPAF. Exposure of the hind paw to 1,500 J m(-2) UVB radiation caused an increased sensitivity to both mechanical and thermal stimulation in wild-type mice but not in PAF-R KO mice. The thermal hyperalgesia caused by UVB irradiation was inhibited in mice that lacked PAF-R in bone marrow-derived cells. These data demonstrate that the PAF-R is important for UVB-induced hyperalgesia. Further investigation of the role of PAF-R signaling in UVB-induced hyperalgesia could provide better understanding of the pathological processes initiated by UVB-induced skin damage.

Staphylococcal scalded skin syndrome and toxic shock syndrome after tooth extraction

Staphylococcus aureus may cause cutaneous and systemic infections such as staphylococcal scalded skin syndrome (SSSS) and toxic shock syndrome (TSS). Although exfoliative toxins A and B, which cause SSSS, and TSS toxin-1 may be produced by different strains of S aureus, the two syndromes rarely occur simultaneously. We describe a patient admitted to the intensive care department with an exfoliative generalized erythroderma, signs of shock, and biopsy specimen findings consistent with SSSS. This patient presented after a tooth extraction. Symptoms recurred after dismissal, and he was readmitted. Subsequent test results were positive for exfoliative toxin B and TSS toxin-1, suggesting concurrent SSSS and TSS. For patients with acute, exfoliative, generalized erythroderma, TSS and SSSS should be considered. Although rare, it is possible to see both syndromes present concurrently.

Emerging roles of PAR-1 and PAFR in melanoma metastasis

Melanoma growth, angiogenesis and metastatic progression are strongly promoted by the inflammatory tumor microenvironment due to high levels of cytokine and chemokine secretion by the recruited inflammatory and stromal cells. In addition, platelets and molecular components of procoagulant pathways have been recently emerging as critical players of tumor growth and metastasis. In particular, thrombin, through the activity of its receptor protease-activated receptor-1 (PAR-1), regulates tumor cell adhesion to platelets and endothelial cells, stimulates tumor angiogenesis, and promotes tumor growth and metastasis. Notably, in many tumor types including melanoma, PAR-1 expression directly correlates with their metastatic phenotype and is directly responsible for the expression of interleukin-8, matrix metalloproteinase-2 (MMP-2), vascular endothelial growth factor, platelet-derived growth factor, and integrins. Another proinflammatory receptor–ligand pair, platelet-activating factor (PAF) and its receptor (PAFR), have been shown to act as important modulators of tumor cell adhesion to endothelial cells, angiogenesis, tumor growth and metastasis. PAF is a bioactive lipid produced by a variety of cells from membrane glycerophospholipids in the same reaction that releases arachidonic acid, and can be secreted by platelets, inflammatory cells, keratinocytes and endothelial cells. We have demonstrated that in metastatic melanoma cells, PAF stimulates the phosphorylation of cyclic adenosine monophosphate response element-binding protein (CREB) and activating transcription factor 1 (ATF-1), which results in overexpression of MMP-2 and membrane type 1-MMP (membrane type 1-MMP). Since only metastatic melanoma cells overexpress CREB/ATF-1, we propose that metastatic melanoma cells are better equipped than their non-metastatic counterparts to respond to PAF within the tumor microenvironment. The evidence supporting the hypothesis that the two G-protein coupled receptors, PAR-1 and PAFR, contribute to the acquisition of the metastatic phenotype of melanoma is presented and discussed.

Clinical correlations of recent developments in the pathogenesis of atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease with a steadily increasing prevalence affecting 10-20 of infants and 1-3 of adults globally. It is often the first clinical manifestation of atopic disease preceding asthma and allergic rhinitis. Probably half of the children with atopic dermatitis develop some other form of atopic disease later in life. The pathogenesis involves a complex interplay of factors including genetic predisposition due to altered immune or skin barrier function, interactions with the environment such as food and allergen exposures, and infectious triggers of inflammation. In this review, we summarize the recent advances in understanding the contribution of different factors in the pathophysiology of atopic dermatitis and how insights provide new therapeutic potential for its treatment.

UVB radiation-mediated inhibition of contact hypersensitivity reactions is dependent on the platelet-activating factor system

Through its ability to both induce immunosuppression and act as a carcinogen, UVB radiation plays a major role in cutaneous malignancies. Recent studies have indicated that UVB-mediated inhibition of delayed-type hypersensitivity reactions is mediated, in part, by the lipid mediator platelet-activating factor (PAF). The objective of this study was to further define the mechanism by which UVB inhibits contact hypersensitivity (CHS) reactions. UVB irradiation resulted in an inhibition of subsequent CHS to the chemical DNFB in wild-type, but not in PAF-R-deficient mice. UVB-mediated inhibition of CHS was also blocked by a cyclooxygenase-2 (COX-2) inhibitor or a neutralizing antibody directed against IL-10. UVB irradiation upregulated IL-10 mRNA levels in lymph nodes and spleen only to significant levels in PAF-R-expressing mice. Bone marrow transplantation studies demonstrated that UVB-mediated immunomodulatory effects were dependent on PAF-R-positive bone marrow. These studies suggest that UVB irradiation results in epidermal production of PAF agonists, which then act on PAF-R-positive bone marrow-derived cells to upregulate IL-10 through COX-2-generated prostaglandins.

Lipoteichoic acid is important in innate immune responses to gram-positive bacteria

To define the role of lipoteichoic acid (LTA) in innate immunity to gram-positive bacteria, we investigated the production of tumor necrosis factor alpha (TNF-alpha) by macrophages stimulated with gram-positive bacterial culture supernatants (GPCSs) after their LTA was removed or inactivated. GPCSs were obtained from three gram-positive species (pneumococci, staphylococci, and group B streptococci) during the exponential growth phase (designated early GPCSs) or at the senescent stage (designated late GPCSs). LTA was removed using an anti-LTA antibody or was inactivated by alkaline hydrolysis or platelet-activating factor acetylhydrolase (PAF-AH) treatment. Both early and late GPCSs from the three gram-positive bacteria stimulated macrophages to produce TNF-alpha primarily via Toll-like receptor 2 (TLR2), although late pneumococcal supernatant could stimulate macrophages via TLR4 as well. Following LTA inactivation by both methods, early GPCS lost about 85 to 100% of its activity and late GPCS lost about 50 to 90%. Both early and late culture supernatants from Escherichia coli could be inactivated by alkali hydrolysis but not by PAF-AH. In addition, removal of LTA from an early staphylococcal culture supernatant with a monoclonal antibody reduced about 70 to 85% of its potency. Reconstitution of inactivated early GPCS with a highly purified LTA restored its inflammatory activity, but the restored GPCS had higher activity than the pure LTA alone. These findings indicate that LTA is the primary TLR2 ligand in the early phase of gram-positive bacterial infection and remains a major ligand in the late phase when another TLR2 and TLR4 ligand(s) appears. In addition, our findings suggest that another gram-positive bacterial factor(s) synergizes with LTA in inducing inflammatory responses.

Augmentation of UVB radiation-mediated early gene expression by the epidermal platelet-activating factor receptor

UVB radiation (UVB) is a known inducer of many biological changes in human skin, and triggers the production of glycerophosphocholines that act as platelet-activating factor (PAF) agonists. To gain a better insight into the role of the epidermal PAF receptor (PAF-R) in UVB-mediated gene expression, Affymetrix oligonucleotide microarrays were used to compare mRNA expression in the PAF-R-negative epithelial cell line KB-expressing PAF-Rs (KBP) with that in KB cells transduced with a vector control (KBM). Total RNA was isolated from KB cells 1 hour after treatment with a PAF-R agonist or UVB irradiation. Treatment of KBP with PAF agonist resulted in altered expression of 220 genes, including cytokines and growth factors. UVB irradiation of KB cells resulted in an increased expression of genes in both cell types. A panel of genes including cytokines CCL20 (MIP3alpha) and tumor necrosis factor-alpha (TNF-alpha) were upregulated selectively in KBP cells and are also selectively upregulated in response to PAF agonist. Consistent with these in vitro findings, UVB irradiation resulted in increased levels of epidermal CCL20 and TNF-alpha mRNA in wild-type over PAF-R-deficient mice in vivo. These studies provide evidence that the epidermal PAF-R can modulate UVB-mediated early gene expression.

Soluble proteins produced by probiotic bacteria regulate intestinal epithelial cell survival and growth

BACKGROUND & AIMS

Increased inflammatory cytokine levels and intestinal epithelial cell apoptosis leading to disruption of epithelial integrity are major pathologic factors in inflammatory bowel diseases. The probiotic bacterium Lactobacillus rhamnosus GG (LGG) and factors recovered from LGG broth culture supernatant (LGG-s) prevent cytokine-induced apoptosis in human and mouse intestinal epithelial cells by regulating signaling pathways. Here, we purify and characterize 2 secreted LGG proteins that regulate intestinal epithelial cell antiapoptotic and proliferation responses.

METHODS

LGG proteins were purified from LGG-s, analyzed, and used to generate polyclonal antibodies for immunodepletion of respective proteins from LGG-conditioned cell culture media (CM). Mouse colon epithelial cells and cultured colon explants were treated with purified proteins in the absence or presence of tumor necrosis factor (TNF). Akt activation, proliferation, tissue injury, apoptosis, and caspase-3 activation were determined.

RESULTS

We purified 2 novel proteins, p75 (75 kilodaltons) and p40 (40 kilodaltons), from LGG-s. Each of these purified protein preparations activated Akt, inhibited cytokine-induced epithelial cell apoptosis, and promoted cell growth in human and mouse colon epithelial cells and cultured mouse colon explants. TNF-induced colon epithelial damage was significantly reduced by p75 and p40. Immunodepletion of p75 and p40 from LGG-CM reversed LGG-CM activation of Akt and its inhibitory effects on cytokine-induced apoptosis and loss of intestinal epithelial cells.

CONCLUSIONS

p75 and p40 are the first probiotic bacterial proteins demonstrated to promote intestinal epithelial homeostasis through specific signaling pathways. These findings suggest that probiotic bacterial components may be useful for preventing cytokine-mediated gastrointestinal diseases.

Dietary protein deficiency in pregnant mice and offspring

Previous studies suggest an association between dermal contact hypersensitivity and preterm delivery. We hypothesized that dietary protein deficiency produces cell-mediated immune hypersensitivity in pregnant animals and their offspring akin to those known to produce tissue damage. We compared the effects of feeding a 20% protein diet (controls) to those of feeding a 10% protein (deficient) diet ad libitum to pregnant BALB/c mice. We measured dermal contact sensitivity to 2,4-dinitrofluorobenzene (DNFB) by the increment in ear skin thickness (swelling) 72 h after immunization and parity by the number of viable pups delivered. Dams fed the protein-deficient diet ingested less food, gained less weight and delivered fewer viable pups than the dams fed the control diet. Greater DNFB-stimulated increment in ear skin thickness was found in the protein-deficient mothers and in their offspring than in the control mothers and their offspring. We conclude that dietary protein deficiency limits parity and induces immune hypersensitivity. These findings suggest the potential for dietary protein deficiency to activate a T-cell-mediated branch of the immune response that may put pregnant animals at risk for preterm delivery.

Staphylococcal cutaneous infections: invasion, evasion and aggression

Staphylococcal infections cause a variety of cutaneous and systemic infections, including impetigo, furuncle, subcutaneous abscess, staphylococcal scalded skin syndrome (SSSS), toxic shock syndrome (TSS) and neonatal toxic shock syndrome-like exanthematous disease (NTED), in association with microbial virulence factors. The virulence factors produced by Staphylococcus aureus have a wide array of biological properties, including disruption of the epithelial barrier, inhibition of opsonization by antibody and complement, interference with neutrophil chemotaxis, cytolysis of neutrophils, and inactivation of antimicrobial peptides. Exfoliative toxins (ETs) induce the 'acantholytic' infection of S. aureus due to the disruption of cell-to-cell cohesion, which allows the pathogenic organisms to spread within the epithelium. Furthermore, S. aureus expresses exotoxins with biological properties of superantigens that induce T-cell activation with subsequent anergy and immunosuppression. Of the S. aureus leukotoxins, Panton-Valentine leukocidin (PVL) is involved in the development of multiple furuncles with more intense erythema, particularly in healthy young adults. TSS is an acute life-threatening illness caused by TSS toxin-1 (TSST-1) and is usually classified into two categories; menstrual TSS, originally described in association with tampon use, and nonmenstrual TSS with a variety of clinical settings. NTED is a neonatal disease induced by TSST-1 although clinical symptoms are much milder than those of TSS. In TSS and NTED, the expansion of TSST-1-reactive Vbeta2-positive T cells is observed. The production of pathogenic S. aureus exotoxins and biofilm formation is regulated by the accessory gene regulator (agr) locus in the quorum-sensing signaling pathway. There is no doubt that targeting the quorum-sensing signaling pathway or anti-toxin therapy is a promising therapeutic approach supportive of primary antibiotic therapy.