Molecular basis for the activation of PAF receptor by PAF.

Platelet-activating factor (PAF) is a potent phospholipid mediator crucial in multiple inflammatory and immune responses through binding and activating the PAF receptor (PAFR). However, drug development targeting the PAFR has been limited, partly due to an incomplete understanding of its activation mechanism. Here, we present a 2.9-Å structure of the PAF-bound PAFR-Gi complex. Structural and mutagenesis analyses unveil a specific binding mode of PAF, with the choline head forming cation-π interactions within PAFR hydrophobic pocket, while the alkyl tail penetrates deeply into an aromatic cleft between TM4 and TM5. Binding of PAF modulates conformational changes in key motifs of PAFR, triggering the outward movement of TM6, TM7, and helix 8 for G protein coupling. Molecular dynamics simulation suggests a membrane-side pathway for PAF entry into PAFR via the TM4-TM5 cavity. By providing molecular insights into PAFR signaling, this work contributes a foundation for developing therapeutic interventions targeting PAF signal axis.

Platelet Activating Factor Receptor and Intercellular Adhesion Molecule-1 Expression Increases in the Small Airway Epithelium and Parenchyma of Patients with Idiopathic Pulmonary Fibrosis: Implications for Microbial Pathogenesis.

Background: Idiopathic pulmonary fibrosis (IPF) is an irreversible lung fibrotic disorder of unknown cause. It has been reported that bacterial and viral co-infections exacerbate disease pathogenesis. These pathogens use adhesion molecules such as platelet activating factor receptor (PAFR) and intercellular adhesion molecule-1 (ICAM-1) to gain cellular entry, causing infections. Methods: Immunohistochemical staining was carried out for lung resections from IPF patients (n = 11) and normal controls (n = 12). The quantification of PAFR and ICAM-1 expression is presented as a percentage in the small airway epithelium. Also, type 2 pneumocytes and alveolar macrophages were counted as cells per mm2 of the parenchymal area and presented as a percentage. All image analysis was done using Image Pro Plus 7.0 software. Results: PAFR expression significantly increased in the small airway epithelium (p < 0.0001), type 2 pneumocytes (p < 0.0001) and alveolar macrophages (p < 0.0001) compared to normal controls. Similar trend was observed for ICAM-1 expression in the small airway epithelium (p < 0.0001), type 2 pneumocytes (p < 0.0001) and alveolar macrophages (p < 0.0001) compared to normal controls. Furthermore, the proportion of positively expressed type 2 pneumocytes and alveolar macrophages was higher in IPF than in normal control. Conclusions: This is the first study to show PAFR and ICAM-1 expression in small airway epithelium, type 2 pneumocytes and alveolar macrophages in IPF. These findings could help intervene microbial impact and facilitate management of disease pathogenesis.

PAFR/Stat3 axis maintains the symbiotic ecosystem between tumor and stroma to facilitate tumor malignancy.

Stroma surrounding the tumor cells plays crucial roles for tumor progression. However, little is known about the factors that maintain the symbiosis between stroma and tumor cells. In this study, we found that the transcriptional regulator-signal transducer and activator of transcription 3 (Stat3) was frequently activated in cancer-associated fibroblasts (CAFs), which was a potent facilitator of tumor malignancy, and formed forward feedback loop with platelet-activating factor receptor (PAFR) both in CAFs and tumor cells. Importantly, PAFR/Stat3 axis connected intercellular signaling crosstalk between CAFs and cancer cells and drove mutual transcriptional programming of these two types of cells. Two central Stat3-related cytokine signaling molecules-interleukin 6 (IL-6) and IL-11 played the critical role in the process of PAFR/Stat3 axis-mediated communication between tumor and CAFs. Pharmacological inhibition of PAFR and Stat3 activities effectively reduced tumor progression using CAFs/tumor co-culture xenograft model. Our study reveals that PAFR/Stat3 axis enhances the interaction between tumor and its associated stroma and suggests that targeting this axis can be an effective therapeutic strategy against tumor malignancy.

PAFR/Stat3 axis maintains the symbiotic ecosystem between tumor and stroma to facilitate tumor malignancy

Stroma surrounding the tumor cells plays crucial roles for tumor progression. However, little is known about the factors that maintain the symbiosis between stroma and tumor cells. In this study, we found that the transcriptional regulator-signal transducer and activator of transcription 3 (Stat3) was frequently activated in cancer-associated fibroblasts (CAFs), which was a potent facilitator of tumor malignancy, and formed forward feedback loop with platelet-activating factor receptor (PAFR) both in CAFs and tumor cells. Importantly, PAFR/Stat3 axis connected intercellular signaling crosstalk between CAFs and cancer cells and drove mutual transcriptional programming of these two types of cells. Two central Stat3-related cytokine signaling molecules-interleukin 6 (IL-6) and IL-11 played the critical role in the process of PAFR/Stat3 axis-mediated communication between tumor and CAFs. Pharmacological inhibition of PAFR and Stat3 activities effectively reduced tumor progression using CAFs/tumor co-culture xenograft model. Our study reveals that PAFR/Stat3 axis enhances the interaction between tumor and its associated stroma and suggests that targeting this axis can be an effective therapeutic strategy against tumor malignancy.

Health effects and known pathology associated with the use of E-cigarettes.

In recent years, new nicotine delivery methods have emerged, and many users are choosing electronic cigarettes (e-cigarettes) over traditional tobacco cigarettes. E-cigarette use is very popular among adolescents, with more than 3.5 million currently using these products in the US. Despite the increased prevalence of e-cigarette use, there is limited knowledge regarding the health impact of e-cigarettes on the general population. Based on published findings by others, E-cigarette is associated with lung injury outbreak, which increased health and safety concerns related to consuming this product. Different components of e-cigarettes, including food-safe liquid solvents and flavorings, can cause health issues related to pneumonia, pulmonary injury, and bronchiolitis. In addition, e-cigarettes contain alarmingly high levels of carcinogens and toxicants that may have long-lasting effects on other organ systems, including the development of neurological manifestations, lung cancer, cardiovascular disorders, and tooth decay. Despite the well- documented potential for harm, e-cigarettes do not appear to increase susceptibility to SARS-CoV- 2 infection. Furthermore, some studies have found that e-cigarette users experience improvements in lung health and minimal adverse effects. Therefore, more studies are needed to provide a definitive conclusion on the long-term safety of e-cigarettes. The purpose of this review is to inform the readers about the possible health-risks associated with the use of e-cigarettes, especially among the group of young and young-adults, from a molecular biology point of view.

Correlation of COVID-19 Receptors with Neutrophils and Their Role in the Adherence of Co-Infected Bacteria.

The COVID-19 caused by the SARS-CoV-2 virus has an impact on all aspects of patient care. Since the onset of this disease pandemic in 2019, numerous studies have been published which have attempted to identify virus receptors in the upper respiratory tract, such as nasal, oropharynx, and lung and their role in coinfection of bacterial adherence. In this study, the level of m RNA for platelet-activating factor receptor (PAF-R) and angiotensin-converting enzyme 2 receptor (ACE2-R) were detected in the whole blood of COVID-19 patients and controlled by using real-time reverse transcription-polymerase chain reaction technique. The results of the expression level of the PAF-R gene were higher in patients (43 ± 12.5) than in the healthy control (40 ± 2.1). Moreover, the expression level of ACE2-R was significantly (0.0001) increased in patients (27.5±6.2), compared to the control group. In addition, there was an elevation of neutrophils (79.6±17.6%) and PAF-R level (43%) in COVID-19 patients in comparison to the control (40) with a positive correlation between these factors (r=0.8769, P=0.0001). Nasopharyngeal epithelial cells showed a higher adherence rate (86%) to both bacteria isolates (Streptococcus pneumonia and Staphylococcus aureus) in patients than in the control group. Increased expression of PAF-R and ACE2-R genes in COVID-19 patients and co-infected bacteria disease could be the factors for the SARS-CoV-2 virus to enter the cells of the host.

Multiple Mechanistic Models Reveal the Neuroprotective Effects of Diterpene Ginkgolides against Astrocyte-Mediated Demyelination via the PAF-PAFR Pathway.

Currently, therapies for ischemic stroke are limited. Ginkgolides, unique Folium Ginkgo components, have potential benefits for ischemic stroke patients, but there is little evidence that ginkgolides improve neurological function in these patients. Clinical studies have confirmed the neurological improvement efficacy of diterpene ginkgolides meglumine injection (DGMI), an extract of Ginkgo biloba containing ginkgolides A (GA), B (GB), and K (GK), in ischemic stroke patients. In the present study, we performed transcriptome analyses using RNA-seq and explored the potential mechanism of ginkgolides in seven in vitro cell models that mimic pathological stroke processes. Transcriptome analyses revealed that the ginkgolides had potential antiplatelet properties and neuroprotective activities in the nervous system. Specifically, human umbilical vein endothelial cells (HUVEC-T1 cells) showed the strongest response to DGMI and U251 human glioma cells ranked next. The results of pathway enrichment analysis via gene set enrichment analysis (GSEA) showed that the neuroprotective activities of DGMI and its monomers in the U251 cell model were related to their regulation of the sphingolipid and neurotrophin signaling pathways. We next verified these in vitro findings in an in vivo cuprizone (CPZ, bis(cyclohexanone)oxaldihydrazone)-induced model. GB and GK protected against demyelination in the corpus callosum (CC) and promoted oligodendrocyte regeneration in CPZ-fed mice. Moreover, GB and GK antagonized platelet-activating factor (PAF) receptor (PAFR) expression in astrocytes, inhibited PAF-induced inflammatory responses, and promoted brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF) secretion, supporting remyelination. These findings are critical for developing therapies that promote remyelination and prevent stroke progression.

Critical role of PAFR/YAP1 positive feedback loop in cardiac fibrosis.

Aberrant activation of cardiac fibroblasts is the main cause and character of cardiac fibrosis, and inhibition of cardiac fibrosis becomes a promising treatment for cardiac diseases. Platelet-activating factor (PAF) and Hippo pathway is recently recognized as key signaling mechanisms in cardiovascular diseases. In this study we explored the potential roles of PAF and Hippo signaling pathway in cardiac fibrosis. Myocardial infarction (MI) was induced in mice by left anterior descending artery ligation. After 28 days, the mice were sacrificed, and the hearts were collected for analyses. We showed that PAF receptor (PAFR) and yes-associated protein 1 (YAP1, a key effector in the Hippo pathway) were significantly increased in the heart of MI mice. Increased expression of PAFR and YAP1 was also observed in angiotensin II (Ang II)-treated mouse cardiac fibroblasts. In mouse cardiac fibroblasts, forced expression of YAP1 increased cell viability, resulted in collagen deposition and promoted fibroblast-myofibroblast transition. We showed that PAF induced fibrogenesis through activation of YAP1 and promoted its nuclear translocation via interacting with PAFR, while YAP1 promoted the expression of PAFR by binding to and activating transcription factor TEAD1. More importantly, silencing PAFR or YAP1 by shRNA, or using transgenic mice to induce the conditional deletion of YAP1 in cardiac fibroblasts, impeded cardiac fibrosis and improved cardiac function in MI mice. Taken together, this study elucidates the role and mechanisms of PAFR/YAP1 positive feedback loop in cardiac fibrosis, suggesting a potential role of this pathway as novel therapeutic targets in cardiac fibrosis.

Impact of Phosphorylcholine Expression on the Adherence and Invasion of Streptococcus pyogenes to Epithelial Cells.

Phosphorylcholine (PC) is a structural component of various pathogens and is involved in bacterial adhesion via the platelet-activating factor receptor (PAF-R). In this study, we investigated how PC expression affects cell adhesion and invasion of Streptococcus pyogenes (S. pyogenes). Eight clinical strains of S. pyogenes were cultured, and PC expression was measured using fluorescence-activated cell sorting. Bacterial adherence and invasion were examined using Detroit 562 cells. An anti-PC-specific monoclonal antibody (TEPC-15) was used to inhibit bacterial PC, and a PAF-R antagonist (ABT-491) was used to inhibit cellular PAF-R. The emm gene was amplified by the polymerase chain reaction with the standard primers. The level of PC expressed on the S. pyogenes surfaces differed in each strain and differed even in the same emm genotype. Adherence assay experiments showed a significant negative correlation between TEPC-15 and ABT-491 inhibitory effects and PC expression in S. pyogenes. Similarly, intracellular invasion assay experiments showed a significant negative correlation between TEPC-15 and ABT-491 inhibitory effects and PC expression in S. pyogenes. This study suggests that S. pyogenes is involved in cell adhesion and invasion by PC.

The Platelet-Activating Factor Receptor's Association with the Outcome of Ovarian Cancer Patients and Its Experimental Inhibition by Rupatadine.

The platelet-activating factor receptor (PAFR) and its ligand (PAF) are important inflammatory mediators that are overexpressed in ovarian cancer. The receptor is an important player in ovarian cancer development. In this study, we aimed to evaluate the prognostic value of PAFR in epithelial ovarian cancer (EOC) and the potential use of its antagonist, rupatadine, as an experimental treatment. Tissue microarrays of ovarian cancer patients, most markedly those with a non-mucinous subtype, immunohistochemically overexpressed PAFR. Elevated cytoplasmic PAFR expression was found to significantly and independently impair patients' overall and recurrence-free survival (OS: median 83.48 vs. 155.03 months; p = 0.022; RFS: median 164.46 vs. 78.03 months; p = 0.015). In vitro, the serous ovarian cancer subtypes especially displayed an elevated PAFR gene and protein expression. siRNA knockdown of PAFR decreased cell proliferation significantly, thus confirming the receptor's protumorigenic effect on ovarian cancer cells. The clinically approved PAFR antagonist rupatadine effectively inhibited in vitro cell proliferation and migration of ovarian cancer cells. PAFR is a prognostic marker in ovarian cancer patients and its inhibition through rupatadine may have important therapeutic implications in the therapy of ovarian cancer patients.

A novel Danshensu/tetramethylpyrazine protects against Myocardial Ischemia Reperfusion Injury in rats.

A new Danshensu/tetramethylpyrazine derivative (ADTM) with cardio-protection effects such as antioxidant, arterial relaxation, pro-angiogenesis and antiplatelet activities. Platelet activating factor receptor (PAFR) plays a key role in myocardial ischemia reperfusion (MIR) injury. This study aims to investigate the protective role of ADTM in MIR injury and clarify the potential role of PAFR. We measured the effects of ADTM on MIR injury in rats in vivo and hypoxia re-oxygenation (HR) injury in neonatal rat ventricular myocytes (NRVMs) in vitro. The results show that ADTM can significantly improve the IR-induced decline in heart function as increasing EF and FS, and restore the decreased cardiac hemodynamic parameters (LVSP, ± dp/dt max) and increased the level of LVEDP, decrease the infarct size of damaged myocardium and lactate dehydrogenase (LDH) activity in serum. Additionally, ADTM inhibits cardiomyocytes apoptosis, caspase-3 activity, and inflammatory response as well as down-regulates the MIR-induced IL-1ß and TNFα production. Next, PAFR expression was significantly down-regulated in cardiomyocytes of MIR model in vivo and in vitro after treated with ADTM compare to IR group. At the same time, ADTM and PAFR small interfering RNA (siRNA) could inhibit cardiomyocytes apoptosis and inflammation during HR, while PAF presents the opposite effect. Furthermore, the above effects of PAF in HR induced cardiomyocytes were reversed by co-treatment of ADTM. Our findings demonstrate for the first time that ADTM protects against MIR injury through inhibition of PAFR signaling, which provides a new treatment for MIR.

Porphyromonas gingivalis enhances pneumococcal adhesion to human alveolar epithelial cells by increasing expression of host platelet-activating factor receptor.

Streptococcus pneumoniae causes pneumonia by infecting the alveolar epithelium via binding to host receptors, such as the platelet-activating factor receptor (PAFR). Although chronic periodontitis has been identified as a pneumonia risk factor, how periodontopathic bacteria cause pneumonia is not known. We found that S. pneumoniae adhered to PAFR expressed on A549 human alveolar epithelial cells stimulated by Porphyromonas gingivalis culture supernatant, and this was abrogated by a PAFR-specific inhibitor. Among the major virulence factors of P. gingivalis [lipopolysaccharide (LPS), fimbriae and gingipains (Rgps and Kgp)], PAFR expression and pneumococcal adhesion were executed in an Rgp-dependent manner. LPS and fimbriae did not induce PAFR expression. Hence, our findings suggest that P. gingivalis enhances pneumococcal adhesion to human alveoli by inducing PAFR expression and that gingipains are responsible for this.

Platelet-activating factor induces the stemness of ovarian cancer cells via the PAF/PAFR signaling pathway.

BACKGROUND: Cancer stem cells (CSCs) play an important role in tumor recurrence, metastasis, and chemoresistance. CSCs can shift between non-CSC and CSC states in certain tumor microenvironments. The mechanisms of this shift are not well understood. We previously demonstrated that platelet-activating factor (PAF), a lipid mediator of inflammation in the tumor microenvironment, can promote ovarian cancer progression and induce chemoresistance via PAF/PAFR-mediated inflammatory signaling pathways. Here, we investigated the role of PAF/PAFR signaling in the stemness of ovarian cancer cell. METHODS: The effects of PAF and PAFR antagonists on the stemness of SKOV3 and A2780 cells were evaluated using sphere-formation assays, FACS analysis and real-time PCR in vitro and a SKOV3 tumor-formation experiment in nude mice in vivo. The potential mechanism of the PAF effect on the stemness of ovarian cancer cells was evaluated by human cytokine antibody microarray analysis. RESULTS: PAF can promote spheroid formation and inhibit the transition of quiescent ovarian cancer cells into the cell cycle. The percentage of cancer stem cells increased significantly, and the expression of stemness genes increased in PAF-treated group. These effects could be blocked by PAFR inhibitors. Ginkgolide B (GB) inhibited tumor growth and decreased the CSC percentage in vivo. Human cytokine antibody microarray analysis showed that some stemness-maintaining proteins increased in PAF-treated group. CONCLUSION: Our results suggest that PAF can regulate the stemness of ovarian cancer cells through the PAF/PAFR pathway, suggesting a new target for the treatment of ovarian cancer.

Data showing effects of a PI3K-δ inhibitor on neutrophil superoxide production during FPR2 activation and reactivation.

Reactive oxygen species (ROS) generated by the NADPH oxidase are crucial for antimicrobial host defense and also play a role in the regulation of inflammatory processes. Signals generated by formyl peptide receptor 2 (FPR2) activate the neutrophil ROS generating NADPH oxidase; such signals are mediated when the receptors bind an activating agonist, as well as when agonist desensitized FPR2 are reactivated by the receptor for platelet-activating factor (PAF). We present data on the effects of Idelalisib, a specific inhibitor for the PI3Kδ isoform, on ROS production during FPR2 activation and reactivation by PAF, respectively. Neutrophils were isolated from peripheral blood of healthy adults obtained from the blood bank at Sahlgrenska University Hospital and ROS release was measured using isoluminol-amplified chemiluminescence.

Effect of acyl and alkyl analogs of platelet-activating factor on inflammatory signaling.

Platelet-activating factor (PAF), a bioactive ether phospholipid with significant pro-inflammatory properties, was identified almost half a century ago. Despite extensive study of this autocoid, therapeutic strategies for targeting its signaling components have not been successful, including the recent clinical trials with darapladib, a drug that targets plasma PAF-acetylhydrolase (PAF-AH). We recently provided experimental evidence that the previously unrecognized acyl analog of PAF, which is concomitantly produced along with PAF during biosynthesis, dampens PAF signaling by acting both as a sacrificial substrate for PAF-AH and probably as an endogenous PAF-receptor antagonist/partial agonist. If this is the scenario in vivo, PAF-AH needs to catalyze the selective hydrolysis of alkyl-PAF and not acyl-PAF. Accordingly, different approaches are needed for treating inflammatory diseases in which PAF signaling is implicated. The interplay between acyl-PAF, alkyl-PAF, PAF-AH, and PAF-R is complex, and the outcome of this interplay has not been previously appreciated. In this review, we discuss this interaction based on our recent findings. It is very likely that the relative abundance of acyl and alkyl-PAF and their interactions with PAF-R in the presence of their hydrolyzing enzyme PAF-AH may exert a modulatory effect on PAF signaling during inflammation.

Platelet activating factor receptor acts to limit colitis-induced liver inflammation.

Liver inflammation is a common extraintestinal manifestation in inflammatory bowel disease (IBD), yet, the mechanisms driving gut-liver axis inflammation remain poorly understood. IBD leads to a breakdown in the integrity of the intestinal barrier causing an increase in portal and systemic gut-derived antigens, which challenge the liver. Here, we examined the role of platelet activating factor receptor (PAFR) in colitis-associated liver damage using dextran sulfate sodium (DSS) and anti-CD40-induced colitis models. Both DSS and anti-CD40 models exhibited liver inflammation associated with colitis. Colitis reduced global PAFR protein expression in mouse livers causing an exclusive re-localization of PAFR to the portal triad. The global decrease in liver PAFR was associated with increased sirtuin 1 while relocalized PAFR expression was limited to Kupffer cells (KCs) and co-localized with toll-like receptor 4. DSS activated the NLRP3-inflammasome and increased interleukin (IL)-1ß in the liver. Antagonism of PAFR amplified the inflammasome response by increasing NLRP3, caspase-1, and IL-1ß protein levels in the liver. LPS also increased NLRP3 response in human hepatocytes, however, overexpression of PAFR restored the levels of NLPR3 and caspase-1 proteins. Interestingly, KCs depletion also increased IL-1ß protein in mouse liver after DSS challenge. These data suggest a protective role for PAFR-expressing KCs during colitis and that regulation of PAFR is important for gut-liver axis homeostasis.

Vaping Associated Pulmonary Injury (VAPI) with superimposed Mycoplasma pneumoniae infection.

There is growing evidence that vaping has the potential to cause adverse health effects. Vaping is affecting the younger and healthier population which is a public concern. Mycoplasma pneumoniae pneumonia is a benign condition and is usually underdiagnosed and is managed in an outpatient setting. Here we present a case of fulminant MPP in a young adult probably associated with VAPI. A 24-year-old woman presented to our hospital for severe hypoxic respiratory failure needing intubation and intensive care unit admission. She had a history for vaping for 2 years prior to presentation. She had fever and an elevated white count. Her Chest X-Ray and CT scan of the chest were consistent with bilateral predominantly lower lobe patchy opacities. She had mildly elevated serum LDH and Urine toxicology screen was positive for THC. Serum IgM Mycoplasma level was positive and her BAL fluid analysis showed lipid-laden macrophages. She was diagnosed as a probable case of VAPI per CDC guidelines with superimposed fulminant MPP. Vaping is known to increase the risk of viral and bacterial pneumonia by compromising the respiratory local immune response. Vaping also causes lipoid pneumonia where the alveoli are filled with lipid-laden macrophages with surrounding inflammation. We hypothesize that this patient had fulminant MPP in the setting of background VAPI. The association between vaping and MPP infection has not been established in the literature and this is the first documented report to establish a link between e-cigarettes and fulminant MPP. Further research is needed to confirm this association.

Ginkgolide B enhances gemcitabine sensitivity in pancreatic cancer cell lines via inhibiting PAFR/NF-кB pathway.

Gemcitabine resistance will occur by time after the initial response in pancreatic cancer. Ginkgolide B (GB), a major terpene lactone component of Ginkgo biloba leaves, is a highly selective and competitive inhibitor for platelet-activating factor (PAF) receptor. In the present study, we evaluated the effect of GB on gemcitabine sensitivity in pancreatic cancer cell lines in vitro and in vivo. Cell viability assay, flow cytometry, dual luciferase reporter assay and tumor xenograft model were used to evaluate cell proliferation, apoptosis, nuclear factor kappa b (NF-кB) activity in vitro and tumor growth in vivo. Western blot, immunohistochemistry (IHC) and immunofluorescence were used to shown different protein expression levels. We found the half maximal inhibitory concentration (IC50) of gemcitabine was significantly downregulated by GB in a dose-dependent manner. Furthermore, GB could suppress cell proliferation, increase cell apoptosis and repress tumor growth when combined with gemcitabine, but had no effect when treated alone. Gemcitabine could upregulate PAFR and phosphorylated NF-кB/p65 expression, and increase NF-кB activity, but this was largely suppressed in combination with GB. GB could suppress PAFR expression in a dose-dependent manner. Knockout of PAFR significantly decreased phosphorylated NF-кB/p65 expression, inhibited NF-кB activity, increased gemcitabine sensitivity and cell apoptosis. Besides, GB had no influence on gemcitabine IC50 in IκBα-SR stably expressed BxPC-3 and CAPAN1. Our results suggested that GB could enhance gemcitabine sensitivity in pancreatic cancer cell lines by suppressing PAFR/NF-кB pathway. Thus GB may have therapeutic potential when used in combination with gemcitabine in pancreatic cancer.

Role of phosphorylcholine in Streptococcus pneumoniae and nontypeable Haemophilus influenzae adherence to epithelial cells.

OBJECTIVE: Phosphorylcholine (PC) is a structural component of Streptococcus pneumoniae (Spn) and nontypeable Haemophilus influenzae (NTHi), and is known to be associated with adherence through the platelet activating factor receptor (PAF-R). Furthermore, high PC expression is considered to be involved in Spn and NTHi virulence. In this study, we examined the influence of PC expression on the adherence of Spn and NTHi to epithelial cells in order to clarify the potential effectiveness of a vaccine targeting PC. METHODS: Twenty-seven strains of Spn and twenty-two strains of NTHi were used, cultured overnight, and PC expression was evaluated by fluorescence activated cell sorting; the strains were divided into two groups: PC low expression (PC-low) and PC high expression (PC-high) groups. Bacterial adherence was then examined using Detroit 562 cells and BALB/c mice. Bacterial invasion was then examined in Detroit 562 cells. RESULTS: The adherence of Spn and NTHi and invasion of NTHi in the PC-high group was significantly reduced by pretreatment with a monoclonal anti-PC antibody (TEPC-15), PAF-R antagonist (ABT-491), and PC-keyhole limpet hemocyanin (PC-KLH). However, such findings were not observed in the PC-low group. CONCLUSION: The present study suggests that PC is involved in the mucosal adhesion of Spn and NTHi, and the mucosal invasion of NTHi with PC-high strains, but not PC-low strains. These results suggest that a PC-targeting mucosal vaccine only affects PC-high Spn and NTHi strains and does not disturb commensal bacterial flora in the upper respiratory tract, which comprises nonpathogenic PC-low bacteria.

Systemic Platelet-Activating Factor-Receptor Agonism Enhances Non-Melanoma Skin Cancer Growth.

Platelet-activating factor-receptor (PAF-R) agonists are pleiotropic lipid factors that influence multiple biological processes, including the induction and resolution of inflammation as well as immunosuppression. PAF-R agonists have been shown to modulate tumorigenesis and/or tumor growth in various skin cancer models by suppressing either cutaneous inflammation and/or anti-tumoral adaptive immunity. We have previously shown that a chronic systemic PAF-R agonist administration of mice enhances the growth of subcutaneously implanted melanoma tumors. Conversely, chronic topical applications of a PAF-R agonist suppressed non-melanoma skin cancer (NMSC) in a topical chemical carcinogenesis model (dimethylbenz[a]anthracene/phorbol 12-myristate 13-acetate (DMBA/PMA)) in-part via anti-inflammatory effects. These results indicate that the context of PAF-R agonist exposure via either chronic cutaneous or systemic administration, result in seemingly disparate effects on tumor promotion. To further dissect the contextual role of PAF-R agonism on tumorigenesis, we chronically administered systemic PAF-R agonist, carbamoyl-PAF (CPAF) to mice under a cutaneous chemical carcinogenesis protocol, recently characterized to initiate both NMSC and melanocytic nevus formation that can progress to malignant melanoma. Our results showed that while systemic CPAF did not modulate melanocytic nevus formation, it enhanced the growth of NMSC tumors.