BACKGROUND: Formyl peptide receptors (FPRs) play pivotal roles in the regulation of innate immunity and host defense. The FPRs include three family members: FPR1, FPR2/ALX, and FPR3. The activation of FPR1 by its high-affinity ligand, N-formyl-methionyl-leucyl-phenylalanine (fMLF) (a bacterial chemoattractant peptide), triggers intracellular signaling in immune cells such as neutrophils and exacerbates inflammatory responses to accelerate the clearance of microbial infection. Notably, fMLF has been demonstrated to induce intracellular calcium mobilization and chemotaxis in platelets that are known to play significant roles in the regulation of innate immunity and inflammatory responses. Despite a plethora of research focused on the roles of FPR1 and its ligands such as fMLF on the modulation of immune responses, their impact on the regulation of hemostasis and thrombosis remains unexplored.
OBJECTIVE: To determine the effects of fMLF on the modulation of platelet reactivity, hemostasis, and thrombus formation.
METHODS: Selective inhibitors for FPR1 and Fpr1-deficient mice were used to determine the effects of fMLF and FPR1 on platelets using various platelet functional assays.
RESULTS: N-formyl-methionyl-leucyl-phenylalanine primes platelet activation through inducing distinctive functions and enhances thrombus formation under arterial flow conditions. Moreover, FPR1 regulates normal platelet function as its deficiency in mouse or blockade in human platelets using a pharmacological inhibitor resulted in diminished agonist-induced platelet activation.
CONCLUSION: Since FPR1 plays critical roles in numerous disease conditions, its influence on the modulation of platelet activation and thrombus formation may provide insights into the mechanisms that control platelet-mediated complications under diverse pathological settings.
Methods: This study investigated the cytotoxic effect of the venom from Trimeresurus purpureomaculatus, the mangrove pit viper (also known as shore pit viper) which is native in Malaysia, across a panel of human cancer cell lines from breast, lung, colon and prostate as well as the corresponding normal cell lines of each tissue.
Results: The venom exhibited dose-dependent cytotoxic activities on all cell lines tested, with median inhibition concentrations (IC50) ranging from 0.42 to 6.98 µg/mL. The venom has a high selectivity index (SI = 14.54) on breast cancer cell line (MCF7), indicating that it is significantly more cytotoxic toward the cancer than to normal cell lines. Furthermore, the venom was fractionated using C18 reversed-phase high-performance liquid chromatography and the anticancer effect of each protein fraction was examined. Fraction 1 that contains a hydrophilic low molecular weight (approximately 7.5 kDa) protein was found to be the most cytotoxic and selective toward the breast cancer cell line (MCF7). The protein was identified using liquid chromatography-tandem mass spectrometry as a venom disintegrin, termed purpureomaculin in this study.
Conclusion: Taken together, the findings revealed the potent and selective cytotoxicity of a disintegrin protein isolated from the Malaysian T. purpureomaculatus venom and suggested its anticancer potential in drug discovery.
Materials and Methods: The coagulometer for factor VIII assay is Sysmex CS-5100. All data were expressed as mean ± standard deviation (SD).
Results: A total of 135 cases were studied. Of these, 100 cases were of mild hemophilia A diagnosed by molecular genetics and, 15 cases were positive for LAC, which were confirmed by dilute Russell Viper venom test. Clot-based one-stage APTT assay showed 65% sensitivity and 80% specificity in diagnosing mild hemophilia A cases and out of 15 LAC cases, it showed false positivity in five cases. Chromogenic assay showed 85% sensitivity and 90% specificity in diagnosing mild hemophilia cases and was 100% specific in excluding LAC cases.
Conclusions: One-stage APTT assay is the most commonly used test for determining factor VIII levels but chromogenic assay are considered as the gold standard and recommended as the reference method by European Pharmacopoeia and ISTH subcommittee. Mild hemophilia A patients with missense mutations show discrepancy between the one-stage clot-based APTT assay and chromogenic assays for determination of factor VIII level and this can lead to misdiagnosis or misclassification of mild hemophilia A. Therefore, it is recommended that both the assays should be used in the evaluation of mild hemophilia cases.