Platelet-activating Factor Receptor mRNA Expression Research Articles

Upregulation of Platelet-Activating Factor Receptor Expression and Lyso-Platelet-Activating Factor Isoforms in Human Nasal Polyp Tissues

Background: The Platelet-Activating Factor (PAF)/receptor (PAFR) system is involved in asthma and allergic rhinitis; however, its role in chronic rhinosinusitis (CRS) is still unclear. This study aimed to assess the expression of PAFR and the concentration of Lyso-PAF isoforms in the nasal polyps (NP) of patients suffering from CRS with/without comorbidities such as asthma and NSAID-exacerbated respiratory disease (N-ERD) compared to healthy nasal mucosa (NM) from control subjects. Methods: NM (n = 8) and NP tissues were obtained from patients undergoing surgery for septal deviation/turbinate hypertrophy or endoscopic sinus surgery, respectively. Three phenotypes were studied: CRSwNP with no asthma (n = 6), CRSwNP with non-steroidal anti-inflammatory drug (NSAID)-tolerant asthma (n = 6), and CRSwNP with NSAID-exacerbated respiratory disease (n = 6). PAFR protein and mRNA were assessed via immunochemistry, immunofluorescence, Western blot, and real-time quantitative PCR. Lyso-PAF isoforms (C16, C18, and C18:1) were quantified via mass spectrometry. Results: PAFR protein was expressed in the NM and NP, concretely in epithelial cells and submucosal glands. Compared to NM, PAFR mRNA expression was higher in all NP phenotypes (p < 0.05) while all Lyso-PAF isoform concentrations were higher in the NP from asthmatic patients (p < 0.05). Lyso-PAF C16 and C18 concentrations were higher in the NP from asthmatic patients than in the NP from patients without asthma. Conclusions: The PAF/PAFR system could play a pathophysiological role in CRSwNP pathogenesis.

New transcriptome and clinical findings of platelet-activating factor in chronic spontaneous urticaria: Pathogenic and treatment relevance.

The objective of the study was to assess the pathogenic and treatment relevance of Platelet Activating factor (PAF) in chronic spontaneous urticaria (CSU). The expression and cellular location of PAF receptor (PAFR) and serum levels of PAF and PAF acetylhydrolase (PAF-AH) in patients with moderate/severe CSU (n=45) and healthy controls (HCs, n=17) were studied. Skin samples from the active wheal (LS-CSU, 13 samples for qPCR and 33 for immunohistochemistry) and non-lesional skin (NLS-CSU, 13 samples) of CSU patients and HCs (13 samples and 5 for immunohistochemistry) were analyzed. Serum PAF and PAF-AH levels were measured by ELISA and compared between HC (10 samples) and CSU patients (25 samples) and, among them, between those refractory and non-refractory to second-generation H1 -antihistamines (sgAH). PAFR mRNA expression was significantly higher in LS-CSU versus HCs (p=0.014). PAFR positive staining in immunohistochemistry was mainly found in the epidermal basal layer in HCs, whereas it was broadly present along the epidermis in LS-CSU samples. Endothelial cells showed PAFR expression exclusively in LS-CSU and NLS-CSU samples. PAFR expression was observed in the nerves of HC, LS-CSU, and NLS-CSU samples. Double PAFR/CD43 expression showed that T-lymphocytes were the main cell type from the wheal inflammatory infiltrate expressing PAFR. A significantly lower PAF-AH/PAF ratio was observed in sgAH non-responders versus responders (6.1 vs. 12.6; p=0.049). Our study confirms that PAF is a mediator of wheal pathogenesis in CSU. The significantly lower PAF-AH/PAF ratio in sgAH non-responders vs responders suggests that PAF could be a potential biomarker of sgAH refractoriness.

Association between changes in the mRNA expression of platelet-activating factor receptor in peripheral blood mononuclear cells and progression of diabetic nephropathy.

Several studies have recently pointed out the role of many inflammatory mediators in the progression of diabetes complications. We had previously demonstrated that mRNA expression of platelet-activating factor receptor (PAFR) in peripheral blood mononuclear cells (PBMCs) was associated with urinary albumin to creatinine ratio (ACR) and forearm flow-mediated dilatation in patients with type 2 diabetes. In an attempt to elucidate this association, patients were followed up for 1year. We recruited 95 patients from the hospital outpatient clinic, among whom 86 were followed up for 1year (normoalbuminuria: 40 patients, microalbuminuria: 25 patients, macroalbuminuria: 21 patients). We then measured their baseline and 12month characteristics and collected blood samples to extract PBMCs and measure gene expressions. Despite higher mRNA expression of PAFR in PBMCs among patients with macroalbuminuria, the rise in its value was not associated with biomarkers of nephropathy, while baseline values were not associated with progression of nephropathy. Moreover, changes in mRNA expression of PAFR were correlated with changes in ACR in all patients (r = 0.225, p = 0.037) and estimated glomerular filtration rate in patients with macroalbuminuria (r = - 0.438, p = 0.047) during the follow-up period. Our findings indicate that even though no causal relationship exists between diabetic nephropathy and elevated expression of PAFR in PBMCs, their close association signifies the presence of another common mechanism that could induce both events. Given these findings, the PAF/PAFR interaction could clarify corresponding mechanisms involved in diabetic complications.

MRNA expression of platelet activating factor receptor (PAFR) in peripheral blood mononuclear cells is associated with albuminuria and vascular dysfunction in patients with type 2 diabetes

AimsRenal dysfunction in addition to diabetes is a serious risk factor for cardiovascular events. We hypothesized that some of the changes in gene expression in blood cells cause renal dysfunction and macrovascular disease through impaired endothelial function. This study aimed to define which changes in gene expression in peripheral blood mononuclear cells (PBMCs) are related to renal function parameters and endothelial function of large arteries in patients with type 2 diabetes mellitus (T2DM). MethodsWe recruited 95 patients with T2DM. After matching for gender, age, BMI and HbA1c levels, the patient cohort included 42 with normoalbuminuria, 28 with microalbuminuria, and 25 with macroalbuminuria. All patients in the three groups were assessed for urinary albumin to creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), flow-mediated dilatation (FMD), and mRNA expression in PBMCs. ResultsThe mRNA expression of platelet activating factor receptor (PAFR) differed most markedly between the three groups and was significantly higher in the macroalbuminuric group (p < 0.001 vs. normoalbuminuric group; p < 0.05 vs. microalbuminuric group). PAFR mRNA expression significantly correlated with log transformed ACR (ρ = 0.424, p < 0.001) but not eGFR. PAFR mRNA expression also had a significant negative correlation with FMD (ρ = −0.379, p < 0.001). Furthermore, the prevalence of macrovascular complications, particularly stroke, was significantly higher in patients with elevated PAFR mRNA expression in PBMCs. ConclusionsPAFR overexpression in PBMCs may link diabetic nephropathy to macroangiopathy through impairment of endothelial function in patients with T2DM.

Exposure to welding fumes and lower airway infection with Streptococcus pneumoniae

Welders are at increased risk of pneumococcal pneumonia. The mechanism for this association is not known. The capacity of pneumococci to adhere to and infect lower airway cells is mediated by host-expressed platelet-activating factor receptor (PAFR). We sought to assess the effect of mild steel welding fumes (MS-WF) on PAFR-dependent pneumococcal adhesion and infection to human airway cells invitro and on pneumococcal airway infection in a mouse model. The oxidative potential of MS-WF was assessed by their capacity to reduce antioxidants invitro. Pneumococcal adhesion and infection of A549, BEAS-2B, and primary human bronchial airway cells were assessed by means of quantitative bacterial culture and expressed as colony-forming units (CFU). After intranasal instillation of MS-WF, mice were infected with Streptococcus pneumoniae, and bronchoalveolar lavage fluid (BALF) and lung CFU values were determined. PAFR protein levels were assessed by using immunofluorescence and immunohistochemistry, and PAFR mRNA expression was assessed by using quantitative PCR. PAFR was blocked by CV-3988, and oxidative stress was attenuated by N-acetylcysteine. MS-WF exhibited high oxidative potential. In A549 and BEAS-2B cells MS-WF increased pneumococcal adhesion and infection and PAFR protein expression. Both CV-3988 and N-acetylcysteine reduced MS-WF-stimulated pneumococcal adhesion and infection of airway cells. MS-WF increased mouse lung PAFR mRNA expression and increased BALF and lung pneumococcal CFU values. In MS-WF-exposed mice CV-3988 reduced BALF CFU values. Hypersusceptibility of welders to pneumococcal pneumonia is in part mediated by the capacity of welding fumes to increase PAFR-dependent pneumococcal adhesion and infection of lower airway cells.

Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease

Bacteria expressing phosphorylcholine (ChoP) co-opt host-expressed platelet-activating factor receptor (PAFR) to adhere to lower airway cells. Cigarette smoke and rhinovirus (RV) infection upregulate PAFR-dependent bacterial adhesion to airway cells in vitro, and in healthy adults smoking increases the proportion of PAFR positive bronchial epithelial cells. To date the effect of chronic obstructive pulmonary disease (COPD) on smoke-induced PAFR is unknown. We therefore sought to test the hypothesis that bronchial PAFR mRNA expression is increased in smokers with chronic obstructive pulmonary disease (COPD), and further increases after RV infection. Endobronchial biopsies were obtained by fibreoptic bronchoscopy from healthy non-smokers, smokers without airway obstruction, and smokers with COPD, before and after infection with rhinovirus (RV) serotype 16. Endobronchial PAFR mRNA expression was assessed by quantitative PCR and expressed as a ratio of glyceraldehyde-3-phosphate dehydrogenase. The distribution of PAFR was assessed by immunohistochemistry. Baseline PAFR mRNA expression was increased (p < 0.05) in smokers (n = 16), and smokers with COPD (n = 14) compared with non-smokers (n = 18). In RV16 infected subjects there was no increase in PAFR mRNA expression in either non-smokers (n = 9), smokers (n = 8), or smokers with COPD (n = 7). PAFR immunoreactivity in all 3 groups was predominately restricted to the bronchial epithelium and submucosal glands. Endobronchial PAFR mRNA is increased in both smokers without airway obstruction and smokers with COPD. We found preliminary evidence that RV16 infection does not increase PAFR mRNA expression in either smokers or smokers with COPD.

Platelet-activating factor synthesis and receptor-mediated signaling are downregulated in ovine newborn lungs: relevance in postnatal pulmonary adaptation and persistent pulmonary hypertension of the newborn.

Platelet-activating factor (PAF) is a phospholipid with a wide range of biological activities. We studied PAF metabolism and PAF receptor (PAFR) signaling in perinatal ovine lungs to understand PAF's role in transition of the perinatal pulmonary hemodynamics and pathophysiology of persistent pulmonary hypertension of the newborn. We hypothesized that downregulation of PAF synthesis with upregulation of PAF catabolism by acetylhydrolase (PAF-Ah) in the newborn lung is needed for fetus-to-newborn pulmonary adaptation. Studies were conducted on fetal and newborn lamb pulmonary arteries (PA), veins (PV) and smooth muscle cells (SMC). PAF metabolism, PAFR binding and cell proliferation were studied by cell culture; gene expression was studied by qPCR. Fetal lungs synthesized 60% more PAF than newborn lungs. Compared with the fetal PVs and SMCs, PAF-Ah activity in newborn was 40-60% greater. PAF-Ah mRNA expression in newborn vessels was different from the expression by fetal PA. PAF-Ah gene clone activity confirmed deletion of hypoxia-sensitive site. PAFR mRNA expression by the PVs and SMC-PV of the fetus and newborn was greater than by corresponding PAs and SMC-PA. Q-PCR study of PAFR expression by the SMC-PV of both groups was greater than SMC-PA. Fetal SMCs bound more PAF than the newborn SMCs. PAFR antagonist, CV-3988, inhibited PAFR binding and DNA synthesis by the fetal SMCs, but augmented binding and DNA synthesis by newborn cells. We show different PAF-PAFR mediated effects in perinatal lungs, suggesting both transcriptional and translational regulation of PAF-Ah and PAFR expression in the perinatal lamb lungs. These indicate that the downregulation of PAF-mediated effects postnatally protects against persistent pulmonary hypertension of the newborn.

Polyinosine‐polycytidylic acid enhances cellular adherence of Streptococcus pneumoniae

Viral upper respiratory tract infections (URIs) are often followed by secondary bacterial infections. To better understand this phenomenon, we examined the impact of the viral agent polyinosine-polycytidylic acid [Poly (I:C)] on the adherence of Streptococcus pneumoniae (Spn) to pharyngeal epithelial cells. In vitro model of cultured human pharyngeal epithelial cells. Detroit 562 cells, a human pharyngeal carcinoma cell line, were pretreated with Poly (I:C). Poly (I:C)-induced expression of platelet-activating factor receptor (PAF-R) was assayed using real-time polymerase chain reaction, flow cytometry, and immunofluorescence microscopy. Bacterial adhesion to these epithelial cells was assessed using immunofluorescence microscopy and colony formation assays. Pretreatment with Poly (I:C) increased mRNA and protein expression of PAF-R in Detroit 562 cells and enhanced the adherence of Spn to these epithelial cells. RNA viral infection can enhance PAF-R expression in epithelial cells and increase the adherence of Spn. These findings might explain in part the mechanisms that underlie the increase in bacterial infection following URIs.

Mechanism and dose-effect of Ginkgolide B on severe acute pancreatitis of rats

To determine the optimal dosage and mechanism of Ginkgolide B (BN52021) on severe acute pancreatitis (SAP) of rats. Seventy male Wistar rats were randomly divided into seven groups (10 for each group). Sham-operation group (SO), SAP model group (SAP), dimethyl sulfoxide (DMSO) contrast group (DMSO), and groups treated with 2.5 mg/kg BN52021 (BN1), 5 mg/kg BN52021 (BN2), 10 mg/kg BN52021 (BN3), and 20 μg/kg Sandostatin (SS). The SAP model was established in Wistar rats by injecting 5% sodium taurocholate retrogradely into the common bilio-pancreatic duct. The rats of SO, DMSO and BN52021 were injected with 0.9% NaCl, 0.5% DMSO and BN52021 through femoral vein 15 min after the operation. The SS group was injected with Sandostatin subcutaneously. All rats were anaesthetized at 6 h after operation, and venous blood was collected to determine the levels of serum amylase and phospholipase A2 (PLA₂), and pancreas tissue was harvested and stained. There was no significant difference between the SAP and DMSO groups in serum amylase level, PLA₂, ascites and pathologic score, but significant difference was found in SAP/DMSO groups compared with those in SO group (P < 0.05) and the levels of serum amylase, PLA₂, ascites, and pathologic score were lower in the BN1, BN2, BN3 and SS groups than in the SAP and DMSO groups (P < 0.05). However, among BN1, BN2, BN3 and SS groups, BN2 had the best effect in decreasing the levels of serum amylase and PLA₂ (P < 0.05). Expression of platelet activating factor (PAF) receptor (PAFR) mRNA and protein showed no significant difference between the SAP and DMSO groups, or among BN1, BN2, BN3 and SS groups, but there was remarkable difference between SAP/DMSO group and SO group (P < 0.05), and expression of PAFR mRNA and protein was higher in the BN1, BN2, BN3 and SS groups than in the SAP and DMSO groups (P < 0.05). PAFR expression was observed in the nucleus and cytoplasm of pancreatic islet cells in Wistar rats by immunohistochemistry. By iv injection, 5 mg/kg of BN52021 is the optimal dosage for SAP rats. BN52021 may inhibit the interaction/binding of PAF with PAFR.

Expression and significance of platelet-acfivating factor in human hepatocellular carcinoma

Objective To investigate the expression of platelet-activating factor(PAF)gene in human hepatocellular carcinoma(hHCC).Methods The samples were obtained from 10 cases of hHCC specimens.Immunohistochemistry and semi-quantitative RT-PCR techniques were used for detecting the PAF positive-staining and PAF receptor mRNA expression in 10 samples and adjacent noncanerous tissues.Results PAF pesitive-staining and PAF receptor mRNA were detected in 90% of hHCC samples and 20% adjacent noncanerous tissues respectively(P ＜ 0.05).Conclusion The PAF expression is increased in middle-advance hHCC,which may play a role in the pathogenesis of hHCC. Key words: Carcinoma; hepatocellular; PAF

Hepatic stellate cells may be potential effectors of platelet activating factor induced portal hypertension

To determine platelet activating factor (PAF) receptor expression in cirrhotic hepatic stellate cells. Hepatic stellate cells, isolated from the livers of control and CCl(4)-induced cirrhotic rats, were placed in serum-free medium after overnight culture. We determined the PAF receptor in hepatic stellate cells by saturation binding technique and semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), and the effects of PAF and its antagonist BN52021 on prostaglandin E(2) (PGE(2)) release by stellate cells. Scatchard analysis indicated the presence of PAF receptor with dissociation constant (Kd) of 4.66 nmol/L and maximum binding capacity (Bmax) of 24.65 fmol/microg in cirrhotic stellate cells. Compared with the control, the maximum PAF binding capacity increased significantly (Bmax: 24.65 +/- 1.96 fmol/microg. DNA, R = 0.982 vs 5.74 +/- 1.55 fmol/microg. DNA, R = 0.93; P < 0.01), whereas receptor affinity had no significant difference (Kd of 4.66 +/- 0.33 nmol/L for the cirrhosis and 3.51 +/- 0.26 nmol/L for the control; P > 0.05). Consistent with the receptor binding data, the mRNA expression of PAF receptor was increased significantly in cirrhotic stellate cells. PAF in a concentration-dependent manner induced PGE(2) synthesis in cirrhotic hepatic stellate cells, but the effects were blocked significantly by BN52021. Cirrhosis sensitizes hepatic stellate cells to PAF by elevating its receptor level and hepatic stellate cells maybe potential effectors of PAF induced portal hypertension.

The Effects of Hantaan Virus on the Expression of Platelet Activating Factor Receptor and on the Activity of Platelet Activating Factor Acetylhydrolase

Background : The central physiological derangement of hemorrhagic fever with renal syndrome (HFRS) caused by hantaan virus (HTNV) is a vascular dysfunction, manifested by hemorrhage, impaired vascular tone and increased vascular permeability. Platelet activating factor (PAF), whose actions are mediated through a specific receptor, is a potent bioactive lipid. PAF has diverse biological functions in the vascular system, such as increasing vascular permeability, adhesion of leukocytes to the endothelium and reduction of cardiac output, which result in hypotension and shock. The goal of the present study was to investigate whether PAF is involved in the pathogenesis of HFRS. For this purpose, we evaluated the effect of HTNV on the expression of PAF receptor (PAF-R) and on the activity of PAF-acetylhydrolase (PAF-AH) instead of PAF because PAF is rapidly degraded by PAF-AH in vivo. Materials and methods : To evaluate the expression of PAF-R, we performed reverse-transcription PCR, western blot and FACS analyses using HTNV-infected human umbilical vein endothelial cells (HUVECs) and non-infected (control) HUVECs. In addition, we measured the activity of plasma PAF-AH in HFRS patients and normal healthy persons. Results : The mRNA and protein expression of PAF-R was increased in HTNV-infected HUVECs compared with control HUVECs at 2 and 3 days post-infection (d.p.i.). FACS analysis showed that HTNV induced the surface expression of PAF-R in HUVECs from 2 d.p.i. The activity of plasma PAF-AH was 2.5-fold lower in HFRS patients than in normal healthy persons. Conclusion : Increased PAF-R expression by HTNV might increase the responsiveness to PAF in endothelial cells. Reduced PAF-AH activity in the blood of HFRS patients might delay PAF degradation. These results suggest that changes in PAF-R and PAF-AH by HTNV might influence to PAF activity and might be involved in the vascular dysfunction of HFRS.

Polyunsaturated Fatty Acid Supplementation Alters Proinflammatory Gene Expression and Reduces the Incidence of Necrotizing Enterocolitis in a Neonatal Rat Model

Although supplementation of preterm formula with polyunsaturated fatty acids (PUFA) has been shown to reduce the incidence of necrotizing enterocolitis (NEC) in animal models and clinical trials, the mechanisms remain elusive. We hypothesized that the protective effect of PUFA on NEC may be due to the ability of PUFA to suppress Toll-like receptor (TLR) 4 and platelet-activating factor receptor (PAFR) gene expression (molecules that are important in the pathogenesis of NEC) in epithelial cells. To investigate the efficacy of different PUFA preparations on NEC in a neonatal rat model, we compared the incidence of NEC among the four PUFA supplemented groups--A: arachidonic acid and docosahexaenoic acid (AA+DHA), B: egg phospholipids (EP), C: DHA, and D: control without PUFA. PUFA supplementation reduced the incidence of NEC and inhibited intestinal PAFR and TLR4 gene expression compared with the controls. To validate the in vivo observations, IEC-6 cells were exposed to PAF after pretreatment with AA or DHA. Both AA and DHA supplementation blocked PAF-induced TLR4 and PAFR mRNA expression in these enterocytes. These results suggest that PUFA modulates gene expression of key factors involved in experimental NEC pathogenesis. These effects might in part explain the protective effect of PUFA on neonatal NEC.

Dual phase regulation of experimental allergic encephalomyelitis by platelet-activating factor

Experimental allergic encephalomyelitis (EAE) serves as a model for multiple sclerosis and is considered to be a CD4+ Th1 cell–mediated autoimmune disease. To investigate the role of platelet-activating factor (PAF) in this disease, PAF receptor (PAFR) KO (PAFR-KO) and wild-type (WT) mice, on a C57BL/6 genetic background, were immunized with myelin oligodendrocyte glycoprotein 35–55. The levels of PAF production and PAFR mRNA expression in the spinal cord (SC) correlated with the EAE symptoms. PAFR-KO mice showed lower incidence and less severe symptoms in the chronic phase of EAE than WT mice. However, no difference was observed in T cell proliferation, Th1-cytokine production, or titer of IgG2a between both genotypes. Before onset, as revealed by microarray analysis, mRNAs of inflammatory mediators and their receptors—including IL-6 and CC chemokine receptor 2—were down-regulated in the SC of PAFR-KO mice compared with WT mice. Moreover, in the chronic phase, the severity of inflammation and demyelination in the SC was substantially reduced in PAFR-KO mice. PAFR-KO macrophages reduced phagocytic activity and subsequent production of TNF-α. These results suggest that PAF plays a dual role in EAE pathology in the induction and chronic phases through the T cell–independent pathways.

Expression and localization of platelet-activating factor receptor in human nasal mucosa

Platelet-activating factor (PAF) has been thought to be a potent mediator of allergic rhinitis because PAF was recovered from the nasal lavage fluid of patients with allergic rhinitis after allergen provocation. Furthermore, PAF receptor antagonist attenuates the antigen-induced increase in nasal airway resistance and nasal vascular permeability in sensitized guinea pigs. To clarify the expression of PAF receptor in human nasal mucosa by investigating PAF receptor messenger RNA (mRNA) expression and its protein localization using polymerase chain reaction (PCR) and immunohistochemical analyses, respectively. Human turbinates were obtained after turbinectomy from 6 patients with nasal obstruction refractory to medical therapy. Total RNA was isolated from human nasal mucosa, and PAF receptor mRNA was detected in these tissues by using reverse transcriptase-PCR analysis. To identify the cells expressing PAF receptor protein, double immunostaining was performed using anti-PAF receptor antibody and monoclonal antileukocyte antibodies. Reverse transcriptase-PCR analysis of total nasal RNA demonstrated the expression of PAF receptor mRNA. The immunohistochemical studies revealed that anti-PAF receptor antibody-labeled eosinophils, macrophages, neutrophils, mast cells, lymphocytes, vascular endothelial cells, epithelial cells, and submucosal glands in nasal mucosa. These results may have important clinical implications for understanding the role of PAF receptor on upper airway diseases such as allergic and nonallergic rhinitis.

Influence of ovarian steroid hormones or platelet-activating factor on mRNA of platelet-activating factor receptor in endometrial explant perfusion cultures from ovariectomized bovine

Platelet-activating factor (PAF) and its receptors are involved in inflammatory-like processes of the uterus associated with increased vascular permeability. PAF is supposed to be influenced by ovarian steroid hormones. The present study was undertaken to examine whether progesterone (P 4), estradiol (E 2) or PAF influence the PAF receptor gene expression in perfused endometrial explants derived from ovariectomized bovine. Furthermore, we identified the cell types in which the PAF receptor gene and protein are expressed. In endometrial explants, applications of 10 nM P 4 or 10 nM P 4 plus 10 nM E 2 for 24 h induced elevated transcript levels of PAF receptor in comparison to the controls or after treatment with 1 nM E 2. When explants were administered 10 nM E 2, a slight decrease in the transcript level was recorded. After treatment of explants with PAF, no significant changes in PAF receptor mRNA expression was observed compared to the control group. We demonstrate that PAF receptor immunoreactivity and mRNA are detected mainly in the luminal epithelium, epithelial cells of the superficial glands and to a lesser degree in stroma. Levels of PAF receptor mRNA in bovine endometrial explants were correlated with PAF receptor protein localization assessed by immunohistochemistry. The regulation of PAF receptor by progesterone in bovine endometrial explants suggests that PAF is involved in the physiological process of reproduction.

Development of tactile allodynia and thermal hyperalgesia by intrathecally administered platelet-activating factor in mice

Platelet-activating factor (PAF) is a potent inflammatory lipid mediator in peripheral tissues. However, its role in mediation of nociception in central nervous system is unknown. In the present study, whether PAF plays some role in pain transduction in the spinal cord was studied in mice. Intrathecal injection of PAF induced tactile pain, tactile allodynia at as low as 10 fg to 1 pg with a peak response at 100 fg, while lyso-PAF was without effect in the range of doses. Tactile allodynia induced by PAF was blocked by a PAF receptor antagonists, TCV-309, WEB 2086 and BN 50739. The expression of PAF receptor mRNA by RT-PCR was observed in DRG and spinal cord in mice. ATP P2X receptor antagonists, pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid and 2′,3′- O-(2,4,6-trinitrophenyl)adenosine 5-triphosphate, NMDA receptor antagonist, MK 801 and nitric oxide synthetase inhibitor, 7-nitroindazole blocked the PAF-induced tactile allodynia. PAF-induced tactile allodynia and thermal hyperalgesia disappeared in neonatally capsaicin-treated adult mice, while tactile allodynia but not thermal hyperalgesia induced by intrathecally injected α,β-methylene ATP, a P2X receptor agonist, was capsaicin-insensitive. The present study demonstrated that PAF is a potent inducer of tactile allodynia and thermal hyperalgesia at the level of the spinal cord. PAF-evoked tactile allodynia is suggested to be mediated by ATP and the following NMDA and NO cascade through capsaicin-sensitive fiber, different from exogenously injected α,β-methylene ATP which is insensitive to capsaicin treatment.

Oxidized low density lipoproteins downregulate LPS-induced platelet-activating factor receptor expression in human monocyte-derived macrophages: implications for LPS-induced nuclear factor-kappaB binding activity.

Monocytes/macrophages play a key role in atherogenesis due to their inflammatory properties including formation of lipid mediators such as platelet-activating-factor (PAF). We investigated the effect of oxidized low-density lipoprotein (oxLDL) on lipopolysaccharide (LPS)-induced PAF receptor (PAF-R) expression in human macrophages and the implication of the nuclear factor (NF)-kappaB in this regulation. LPS-treatment (1 microg.mL(-1)) of macrophages increased PAF binding and PAF-R mRNA expression by 56% (P < 0.05) and twofold (P < 0.01), respectively. In contrast, highly oxidized low-density lipoprotein [ox24hLDL; 100 microg.mL(-1); thiobarbituric acid reacting substances: 31 +/- 3 nmol equiv. malondialdehyde (MDA).mg protein LDL-1] diminished PAF-R expression (-69%; P < 0.05) and mRNA level (- 45%; P < 0.01). LPS pretreatment induced the activated form of p65 in the nuclear compartment of macrophages (detected by Western blotting) and NF-kappaB binding activity (by electrophoretic mobility shift assay). Treatment of macrophages with ox24hLDL suppressed the LPS-induced binding of NF-kappaB to DNA. In addition, treatment of macrophages with lysophosphatidylcholine (2 and 10 microM), a major component of oxLDL, inhibited the LPS-induced NF-kappaB binding to DNA and reduced PAF binding by 30 and 70%, respectively. In conclusion, oxLDL may downregulate PAF-R expression in human macrophages by inhibiting LPS-induced NF-kappaB binding to DNA.

Acid exposure stimulates the adherence of Streptococcus pneumoniae to cultured human airway epithelial cells: effects on platelet-activating factor receptor expression.

To examine the effects of acid exposure on the adherence of Streptococcus pneumoniae to cultured human tracheal epithelial cells, cells were exposed to acid at various pH levels, and various concentrations of S. pneumoniae were added to the culture medium. The number of S. pneumoniae adhering to cultured human tracheal epithelial cells increased after acid exposure. Y-24180, a specific inhibitor of the receptor for the platelet-activating factor (PAF) and PAF itself decreased the number of S. pneumoniae adhering to cultured human tracheal epithelial cells after acid exposure. Acid exposure increased the activation of transcription factor nuclear factor (NF)-kappa B and the expression of protein and messenger RNA (mRNA) of the PAF receptor. The pyrrolidine derivative of dithiocarbamate (PDTC), an inhibitor of NF-kappa B, also decreased the number of S. pneumoniae adhering to the cultured human tracheal epithelial cells after acid exposure. Acid exposure increased the content of interleukin (IL)-1 alpha and IL-1 beta in the culture supernatants, but monoclonal antibodies to IL-1 alpha and IL-1 beta failed to inhibit the increased number of S. pneumoniae adhering to cultured human tracheal epithelial cells after acid exposure. These findings suggest that acid exposure stimulates the adherence of S. pneumoniae to the airway epithelial cells via increases in PAF receptors. Increases in PAF receptor expression may be, in part, mediated via activation of transcription factors and subsequent PAF receptor mRNA expression by acid exposure. Increased adherence of S. pneumoniae may be one of the reasons why pneumonia develops after gastric juice aspiration.

Oxidized low-density lipoprotein and peroxisome-proliferator-activated receptor alpha down-regulate platelet-activating-factor receptor expression in human macrophages.

Regulation of the expression of platelet-activating factor (PAF) receptor by atherogenic lipoproteins might contribute to atherogenesis. We show that progressive oxidation of low-density lipoprotein (LDL) gradually inhibits PAF receptor expression on the macrophage cell surface. We tested the effect of oxidized LDL (oxLDL) on PAF receptor expression in human monocytes that do not contain peroxisome-proliferator-activated receptor gamma (PPARgamma), a nuclear receptor activated by oxLDL. OxLDL decreased by 50% (P < or = 0.001) and by 29% (P < or = 0.05) the binding of PAF and the expression of PAF receptor mRNA respectively. Next we demonstrated that progressive oxidation of LDLs significantly activated PPARalpha-dependent transcription in transfected mouse aortic endothelial cells. Finally we demonstrated, in mature macrophages, that fenofibrate (20 microM), a specific PPARalpha agonist, but not the specific PPARgamma agonist BRL49653 (20 nM), significantly decreased both PAF binding and PAF receptor mRNA expression, by 65% and 40% (P < or = 0.001) respectively. Additionally, another PPARalpha agonist, Wy14,643, decreased PAF receptor promoter activity by 70% (P < or = 0.05) in transfected THP-1 cells, suggesting the involvement of the proximal promoter region (-980 to -500) containing a series of four nuclear factor (NF)-kappaB motifs. Thus PPARalpha might be involved in the down-regulation of PAF receptor gene expression by oxLDLs in human monocytes/macrophages. The oxidation of one or more lipid components of LDLs might result in the formation of natural activators of PPARalpha. It is hypothesized that such activators might modulate inflammation and apoptosis upon atherogenesis by decreasing the expression of PAF receptor.