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

The Exploration of Novel Pharmacophore Characteristics and Multidirectional Elucidation of Structure-Activity Relationship and Mechanism of Sesquiterpene Pyridine Alkaloids from Tripterygium Based on Computational Approaches

Sesquiterpene pyridine alkaloids are a large group of highly oxygenated sesquiterpenoids, which are characterized by a macrocyclic dilactone skeleton containing 2-(carboxyalkyl) nicotinic acid and dihydro-β-agarofuran sesquiterpenoid, and are believed to be the active and less toxic components of Tripterygium. In this study, 55 sesquiterpene pyridine alkaloids from Tripterygium were subjected to identification of pharmacophore characteristics and potential targets analysis. Our results revealed that the greatest structural difference of these compounds was in the pyridine ring and the pharmacophore model-5 (Pm-05) was the best model that consisted of three features including hydrogen bond acceptor (HBA), hydrogen bond donor (HBD), and hydrophobic (HY), especially hydrophobic group located in the pyridine ring. It was proposed that 2-(carboxyalkyl) nicotinic acid part possessing a pyridine ring system was not only a pharmacologically active center but also a core of structural diversity of alkaloids from Tripterygium wilfordii. Furthermore, sesquiterpene pyridine alkaloids from Tripterygium were predicted to target multiple proteins and pathways and possibly played essential roles in the cure of Alzheimer's disease, breast cancer, Chagas disease, and nonalcoholic fatty liver disease (NAFLD). They also had other pharmacological effects, depending on the binding interactions between pyridine rings of these compounds and active cavities of the target genes platelet-activating factor receptor (PTAFR), cannabinoid receptor 1 (CNR1), cannabinoid receptor 1 (CNR2), squalene synthase (FDFT1), and heat shock protein HSP 90-alpha (HSP90AA1). Taken together, the results of this present study indicated that sesquiterpene pyridine alkaloids from Tripterygium are promising candidates that exhibit potential for development as medicine sources and need to be promoted.

Inflammation-driven vascular dysregulation in chronic rhinosinusitis

BACKGROUND

Altered neovascularity is typically observed in chronic inflammatory diseases with overlapping pathophysiology to that observed in chronic rhinosinusitis (CRS). However, characterization of these inflammatory-induced vascular-mediated changes in CRS is limited. Understanding the underlying vascular changes in CRS will allow for strategic design and development of new drug-delivery technologies that exploit vascular permeability for increased extravasation into the target sinonasal tissues.

METHODS

Patients with CRS with nasal polyps (CRSwNP) and without nasal polyps (CRSsNP) and non-CRS controls were enrolled in this prospective, observational study. The extent of angiogenesis in tissue was characterized using immunohistochemical and multiplex gene expression analyses. Vascular permeability, interendothelial junction structures, and endothelial barrier morphology were evaluated using transmission electron microscopy.

RESULTS

Sinonasal vascularity was increased significantly in CRSsNP and CRSwNP (p < 0.05) when compared with controls, as assessed by enumerating the platelet endothelial cell adhesion molecule (PECAM-1)-positive blood vessels. Pro-angiogenic gene expression, including PECAM1 and platelet-activating factor receptor, was elevated significantly in patients with CRSwNP when compared with controls (p < 0.05). The fenestration sizes between endothelial cells (17-280 nm) were larger in CRSwNP compared with CRSsNP (10-33 nm) patients and controls (4-12 nm). Global thinning of the endothelial cell lining was observed in CRS patients but not in controls.

CONCLUSION

Significant increases in vascularity, the pro-angiogenic gene, and protein expression and blood vessel morphogenesis were observed in CRS patients compared with controls. In addition, fenestration sizes between interendothelial junction structures were larger in CRS patients than in controls, suggesting inflammation-driven vascular dysregulation in CRS pathology.

Thermal Burn Injury Generates Bioactive Microvesicles: Evidence for a Novel Transport Mechanism for the Lipid Mediator Platelet-Activating Factor (PAF) That Involves Subcellular Particles and the PAF Receptor

Thermal burn injuries are an important environmental stressor that can result in considerable morbidity and mortality. The exact mechanism by which an environmental stimulus to skin results in local and systemic effects is an area of active research. One potential mechanism to allow skin keratinocytes to disperse bioactive substances is via microvesicle particles, which are subcellular bodies released directly from cellular membranes. Our previous studies have indicated that thermal burn injury of the skin keratinocyte in vitro results in the production of the lipid mediator platelet-activating factor (PAF). The present studies demonstrate that thermal burn injury to keratinocytes in vitro and human skin explants ex vivo, and mice in vivo generate microvesicle particles. Use of pharmacologic and genetic tools indicates that the optimal release of microvesicles is dependent upon the PAF receptor. Of note, burn injury-stimulated microvesicle particles do not carry appreciable protein cytokines yet contain high levels of PAF. These studies describe a novel mechanism involving microvesicle particles by which a metabolically labile bioactive lipid can travel from cells in response to environmental stimuli.

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.

Acetylsalicylic acid inhibits the growth of melanoma tumors via SOX2-dependent-PAF-R-independent signaling pathway

Acquired resistance to standard therapies remains a serious challenge, requiring novel therapeutic approaches that incorporate potential factors involved in tumor resistance. As cancers including melanoma express inflammatory cyclooxygenases generating prostaglandins implicated in tumor growth, we investigated mechanism of anti-inflammatory drug, acetylsalicylic acid (ASA) which has been shown to inhibit various tumor types, however, its effects against highly aggressive melanoma model are unclear. Given our reports that an activation of platelet-activating factor-receptor (PAF-R) augments the growth and impede efficacies of therapeutic agents in experimental melanoma, we also sought to determine if PAF-R mediates anti-melanoma activity of ASA. The current studies using stably PAF-R-positive (B16-PAFR) and negative (B16-MSCV) murine melanoma cells and PAF-R-expressing and deficient mice, demonstrate that ASA inhibits the in-vitro and in-vivo growth of highly aggressive B16F10 melanoma via bypassing tumoral or stromal PAF-R signaling. Similar ASA-induced effects in-vitro were seen in human melanoma and nasopharyngeal carcinoma cells positive or negative in PAF-R. Mechanistically, the ASA-induced decrease in cell survival and increase in apoptosis were significantly blocked by prostaglandin F2 alpha (PGF2α) agonists. Importantly, PCR array and qRT-PCR analysis of B16-tumors revealed significant downregulation of sry-related high-mobility-box-2 (SOX2) oncogene by ASA treatment. Interestingly, modulation of SOX2 expression by PGF2α agonists and upregulation by fibroblast growth factor 1 (FGF-1) rescued melanoma cells from ASA-induced decreased survival and increased apoptosis. Moreover, PGF2α-receptor antagonist, AL8810 mimics ASA-induced decreased melanoma cells survival which was significantly blocked by PGF2α and FGF-1. These findings indicate that ASA inhibits the growth of aggressive melanoma via SOX2-dependent-PAF-R-indepedent pathway.

Antiplatelet agents for cancer treatment: a real perspective or just an echo from the past?

The association between coagulation and cancer development has been observed for centuries. However, the connection between inflammation and malignancy is also well-recognized. The plethora of evidence indicates that among multiple hemostasis components, platelets play major roles in cancer progression by providing surface and granular contents for several interactions as well as behaving like immune cells. Therefore, the anticancer potential of anti-platelet therapy has been intensively investigated for many years. Anti-platelet agents may prevent cancer, decrease tumor growth, and metastatic potential, as well as improve survival of cancer patients. On the other hand, there are suggestions that antiplatelet treatment may promote solid tumor development in a phenomenon described as "cancers follow bleeding." The controversies around antiplatelet agents justify insight into the subject to establish what, if any, role platelet-directed therapy has in the continuum of anticancer management.

Platelet-inspired medicine for tumor therapy

As the number of patients with tumor increases dramatically recent years, traditional therapies expose more and more problems which can even lead to death. Many researchers and clinicians quest for an efficient drug delivery system to deal with tumor as a result. With the researches further develop, we find that platelet can interact with tumor cells through a variety of ways. So it can be used as a carrier broadly to deliver different anti-tumor drugs for tumor treatment. In the present review, we summarize the interaction of tumor cells and platelet. At the same time, we focus on recent progress on the application of platelet drug-loaded system in the anti-tumor prospects.