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Platelet activating factor is a lipid mediator of inflammation, and in recent decades, it has emerged as an important factor in tumor outcomes. Platelet activating factor acts by specific binding to its receptor, which is present in both tumor cells and cells that infiltrate tumors. Pro-tumorigenic effects of platelet activating factor receptor in tumors includes promotion of tumor cell proliferation, production of survival signals, migration of vascular cells and formation of new vessels and stimulation of dendritic cells and macrophages suppressor phenotype. In experimental models, blocking of platelet activating factor receptor reduced tumor growth and increased animal survival. During chemotherapy and radiotherapy, tumor cells that survive treatment undergo accelerated proliferation, a phenomenon known as tumor cell repopulation. Work from our group and others showed that these treatments induce overproduction of platelet activating factor-like molecules and increase expression of its receptor in tumor cells. In this scenario, antagonists of platelet activating factor markedly reduced tumor repopulation. Here, we note that combining chemo- and radiotherapy with platelet activating factor antagonists could be a promising strategy for cancer treatment.
Subject(s)
Animals , Platelet Membrane Glycoproteins/antagonists & inhibitors , Cell Proliferation/drug effects , Cell Proliferation/radiation effects , Neoplasms, Experimental/therapy , Combined Modality Therapy/methods , Cell Line, Tumor , Neoplasms, Experimental/pathology , Neovascularization, Pathologic/drug therapy , Neovascularization, Pathologic/therapyABSTRACT
To study the antagonistic effect of ginkgolide homologues on platelet-activating factor (PAF)-induced platelet aggregation and investigate its neuroprotective effect. PAF was used as a coagulant, and ginkgolides were added to the rabbit blood samples respectively. The inhibitory effect of each compound on platelet aggregation was detected by turbidimetry. In L-glutamate induced primary cortical neuron cell injury model, MTT assay was used to detect cell viability. Intracellular free Ca2+ concentration in neurons was measured by using the fluorescent Ca2+ indicator Fura-2 AM. Morphological observation and Hoechst 33258 staining were used to detect the inhibitory effect of ginkgolide on neuronal apoptosis. The results showed that the inhibitory effect on PAF-induced platelet aggregation activity in ginkgolide homologues was ginkgolide K (GK), ginkgolide B (GB), ginkgolide A (GA), ginkgolide C (GC), ginkgolide M (GM), ginkgolide J (GJ) and ginkgolide (GL) from high to low. GB and GK (1-100 μmol•L ⁻¹) could significantly reduce the cell damage caused by L-glutamate, with survival rate increasing, intracellular calcium concentration reducing and cell morphology restoring. This paper has identified the activities and characteristics of various compounds of ginkgolide homologues on PAF-induced platelet aggregation as well as its neuroprotective effect.
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Objective To investigate the protective effect of prostaglandin E2 (PGE2), cyclooxygenase-2 (COX-2) and platelet activating factor (PAF) receptor antagonist on endotoxin-induced acute gastric mucosal injury in young rats. Methods Eighteen-day old Wistar rats were randomly divided into 4 groups: normal control group, model group (LPS group), PAF antagonist prevention group, and PAF antagonist treatment group. The model of endotoxemia in young rats was reproduced by intraperitoneal injection of endotoxin (5mg/kg of O55:B5 lipopolysaccharide). The rats in PAF prevention and treatment group received PAF antagonist BN52021 (Ginkgolide B, 5mg/kg) 0.5h before or after modeling. The rats in control group were given intraperitoneal injection of same amount of normal saline (1ml/kg). The animals were sacrificed 1.5, 3, 6, 24, 48 and 72h after intraperitoneal injection of endotoxin (8 in each group). The pathologic changes in gastric mucosa were observed after HE staining. The content of PGE2was measured by radioimmunoassay, the expression of COX-2 protein was determined by immunohistochemistry SP method, and the expression of COX-2 mRNA was assessed with RT-PCR method. Results Pathological changes in gastric mucosa were found to be edema of epithelial cells at 1.5h, and hyperemia and edema 3h after intraperitoneal injection of endotoxin in LPS group. The changes were most marked at 6h, including bleeding, karyorrhexis, pyknosis and apoptosis of epithelial cells of gastric mucosa. Exfoliation of the epithelium and neutrophil infiltration were observed at 24h, thinning of mucosa and a decrease in glands were observed at 48h, but no further changes were observed at 72h. However, all the above changes were significantly alleviated in prevention and treatment groups. The PGE2 content of gastric mucosa was lowered at 3h (P<0.05), and it was lowest at 6h (P<0.01) after endotoxin injection in LPS group, and significant difference was found between LPS group and control group. The PGE2 content of gastric mucosa was obviously increased at 3h and 6h in prevention group (P<0.05), and at 6h in treatment group (P<0.05). The differences at 6h were significant (P<0.01) among prevention group, treatment group and LPS group. No expression of COX-2 protein or mRNA was seen in gastric mucosal tissue of control group. In contrast with control group, cytoplasm COX-2 protein of gastric mucosal tissue was seen to express at 6h after endotoxin injection in LPS group, and it was obviously enhanced at 24, 48 and 72h (P<0.01), and the COX-2 mRNA level was also elevated. The expressions of COX-2 protein and mRNA were increased obviously at 6h in PAF antagonist prevention group and treatment group (P<0.01). The expressions of COX-2 protein at 6h and COX-2 mRNA at 24h were obviously elevated in prevention group and treatment group compared with those of LPS group (P<0.01). Conclusion PAF receptor antagonist may up-regulate the expression level of COX-2 protein and mRNA, increase PGE2 content, alleviate acute gastric mucosal injury, and promote the healing of gastric mucosal injury.
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Aim To investigate the effect of ginkgolide B on TLR4 expression in glucose-treated endothelial cells.Methods Human umbilical vein endothelial cells (HUVECs)were stimulated by high concentra-tion of glucose.TLR4,inflammatory protein expression and Akt phosphorylation were analyzed by Western blot.Transcription factor NF-κB nuclear translocation was analyzed by immunofluorescence.Results The expression of TLR4 and PAF receptor was increased in high glucose-treated HUVECs. In contrast, both ginkgolide B and CV3988 dose-dependently decreased TLR4 and PAF receptor expression in high glucose-treated cells,respectively.Ginkgolide B decreased in-flammatory protein ICAM-1 ,VCAM-1 expression.Mo-reover,ginkgolide B potently abolished Akt phospho-rylation and NF-κB p65 nuclear translocation.Conclu-sion Ginkgolide B can reduce TLR4,PAF receptor, ICAM-1 and VCAM-1 expression in high dose of glu-cose-treated HUVECs,the mechanism might be linked to inhibition of Akt phosphorylation and NF-κB activa-tion.
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Platelet-activating factor (PAF; 1-O-Alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is a ubiquitous phospholipid that is implicated in the mediation of a wide variety of reproductive processes. To better understand the role of PAF in bovine reproduction, it was designed experiments to: (a) determine whether bull spermatozoa express receptors for PAF and (b) study the effect of exogenous PAF on in vitro sperm physiology (i.e., capacitation, acrosome reaction, motility, and fertilizing ability). Bull sperm express PAF receptor as determined by two approaches: RT-PCR and immunofluorescence. However, exposure of spermatozoa to different concentrations of exogenous PAF (10-11-10-6 M) did not affect capacitation, acrosome reaction or motility. Consistent with these findings, coculture of gametes in medium containing increasing concentrations of PAF (1 x 10-8-8 x 10-6 M) did not improve in vitro fertilization outcome as measured by percentage of inseminated oocytes reaching 2-cell stage 48 h after fertilization. In contrast, PAF at 8 x 10-6 M concentration significantly inhibited IVF. In conclusion, although bull sperm have PAF receptors, exposure of bull spermatozoa to exogenous PAF failed to enhance the sperm function parameters measured in this study. Additional studies are warranted to elucidate the biological role of PAF on bull spermatozoa.
El factor activador de plaquetas (PAF; del inglés Platelete Activating Factor; 1-O-Alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) es un fosfolípido ampliamente distribuido que participa como mensajero mediador en diferentes procesos reproductivos. Para comprender mejor la participación del PAF en la fisiología espermática bovina se diseñaron experimentos para: (a) determinar si los espermatozoides de toro expresan receptores para PAF y (b) estudiar el efecto del PAF sobre el comportamiento de los espermatozoides bovinos in vitro (capacitación, reacción acrosomal y capacidad fertilizante). De acuerdo a los resultados obtenidos por RT-PCR e inmunofluorescencia, los espermatozoides de toro expresan receptores para PAF. Sin embargo, la exposición de los espermatozoides a concentraciones crecientes de PAF exógeno (10-11-10-6 M) no afectó la capacitación, reacción de acrosoma ni la motilidad. En concordancia con estos hallazgos, el cocultivo de gametas (ovocitos y espermatozoides) en medio al cual se le había adicionado PAF (1 x 10-8-8 x 10-6 M) no mejoró la tasa de fertilización medida como el porcentaje de ovocitos inseminados que alcanzaron el estadio de 2 células 48 hs después de la inseminación. Por el contrario, PAF a una concentración de 8 x 10-6 M inhibió significativamente la tasa de fertilización. En conclusión, a pesar de que los espermatozoides bovinos poseen receptores para PAF, el agregado de PAF al medio de cultivo no mejora las funciones espermáticas examinadas en el presente trabajo. Otros estudios serán necesarios para dilucidar la participación del PAF en la fisiología espermática del toro.
Subject(s)
Cattle , Animals , Spermatozoa/growth & development , Fertilization/physiology , Oocytes/transplantation , Platelet Activating Factor , Insemination , Veterinary MedicineABSTRACT
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.
Subject(s)
Humans , Blood Platelets , Blotting, Western , Capillary Permeability , Cardiac Output , Endothelial Cells , Endothelium , Hantaan virus , Hemorrhage , Hemorrhagic Fever with Renal Syndrome , Human Umbilical Vein Endothelial Cells , Hypotension , Leukocytes , Plasma , Platelet Activating Factor , Platelet Membrane Glycoproteins , Polymerase Chain Reaction , Receptors, G-Protein-Coupled , RNA, Messenger , ShockABSTRACT
Platelet activating factor(PAF), a potent phospholipid mediator of inflammation, has diverse physiological actions and participates in many diseases in vivo . In recent years, it has been revealed that PAF system involve in the expression of keratinocytes function and reaction of skin inflammation. Therefore, PAF system was found closely associated with inflammatory skin disease. Keratinocytes could express functional PAF receptors (PAF R) and involve in the action of epidermis cytokine system. The interaction between PAF system and other inflammatory mediators can lead to skin inflammatory cascade.