@article {514, title = {Elucidation of procoagulant mechanism and pathophysiological significance of a new prothrombin activating metalloprotease purified from Daboia russelii russelii venom. (Mass Spectrometry)}, journal = {Toxicon}, volume = {100}, year = {2015}, month = {2015 Jun 15}, pages = {1-12}, abstract = {

The procoagulant proteases present in Russell{\textquoteright}s Viper venom (RVV) are responsible for promoting consumption coagulopathy in victims. In this study, a procoagulant metalloprotease (Rusviprotease) possessing prothrombin activating and α-fibrinogenase properties has been purified and characterized from RVV. Rusviprotease is a 26.8\ kDa glycoprotein which also exists in other multimeric forms. The peptide mass fingerprinting and secondary structure analyses of Rusviprotease revealed its similarity with snake venom prothrombin activators and metalloproteases. Similar to group A prothrombin activators, Rusviprotease cleaved prothrombin independent of any co-factor requirement generating meizothrombin which is further cleaved to form thrombin. The Km and Vmax values of Rusviprotease towards prothrombin were determined to be 1.73\ μM, and 153.5\ nM thrombin generated/min/μmoles of Rusviprotease, respectively. The Km and Vmax values of Rusviprotease towards fibrinogen were calculated to be 3.14\ μM and 78.7\ nmol/min, respectively. Spectrofluorometric study provided the evidence of interaction between Rusviprotease and factor Xa with a Kd value of\ 6.64\ nM. This interaction augmented the prothrombin activating property of the factor Xa-prothrombinase-Rusviprotease complex by 2.5 fold. Intravenous injection of Rusviprotease to BALB/c mice (0.1\ mg/kg) resulted in in\ vivo defibrinogenation rendering the blood incoagulable. In conclusion, Rusviprotease is the first example of a prothrombin activator with fibrinogenolytic property purified from Daboia russelii russelii venom.

}, keywords = {Animals, Blood Coagulation, Blood Platelets, Chemical Fractionation, Coagulants, Erythrocytes, Goats, Metalloproteases, Mice, Inbred BALB C, Plasma, Russell{\textquoteright}s Viper, Toxicity Tests, Acute, Viper Venoms}, issn = {1879-3150}, doi = {10.1016/j.toxicon.2015.03.019}, author = {Thakur, Rupamoni and Chattopadhyay, Pronobesh and Ghosh, Siddharth S and Mukherjee, Ashis K} } @article {516, title = {A new C-type lectin (RVsnaclec) purified from venom of Daboia russelii russelii shows anticoagulant activity via inhibition of FXa and concentration-dependent differential response to platelets in a Ca{\texttwosuperior}$^{+}$-independent manner. (Mass spectrometry)}, journal = {Thromb Res}, volume = {134}, year = {2014}, month = {2014 Nov}, pages = {1150-6}, abstract = {

This is the first report on the characterization of a snaclec (RVsnaclec) purified from Daboia russelii russelii venom. The RVsnaclec is a heterodimer of two subunits, α (15.1 kDa) and β (9 kDa). These subunits are covalently linked to form multimeric (αβ)$_{2}$ and (αβ)$_{4}$ structures. Peptide mass fingerprinting analysis of RVsnaclec via LC-MS/MS demonstrated its similarity to snaclecs purified from other viperid snake venoms. Two tryptic peptide sequences of RVsnaclec revealed the putative conserved domains of C-type lectin (CTL). RVsnaclec dose-dependently increased the Ca-clotting time and prothrombin time of platelet-poor plasma (PPP); however, it did not affect the partial thromboplastin time (APTT) or thrombin time of PPP. The in vitro and in vivo anticoagulant activity of RVsnaclec is correlated to its binding and subsequent uncompetitive inhibition of FXa (Ki = 0.52 μmole) in a Ca(2+)-independent manner; however, supplementation with 0.25 mM Ca(2+) enhanced the Xa binding potency of RVsnaclec. Monovalent or polyvalent antivenom failed to neutralize its anticoagulant potency, and RVsnaclec did not inhibit trypsin, chymotrypsin, thrombin or plasmin. RVsnaclec was devoid of hemolytic activity or cytotoxicity against several human cancer cell lines, demonstrated concentration-dependent aggregation and deaggregation of human platelets, and inhibited the ADP-induced aggregation of platelet. RVsnaclec (5.0 mg/kg body weight) was non-lethal to mice and showed no adverse pharmacological effects, suggesting that it has potential as a lead compound for future therapeutic applications in cardiovascular disorders.

}, keywords = {Animals, Anticoagulants, Blood Coagulation, Blood Platelets, Calcium, Factor Xa, Factor Xa Inhibitors, Goats, Humans, Lectins, C-Type, Mice, Platelet Aggregation, Russell{\textquoteright}s Viper, Viper Venoms}, issn = {1879-2472}, doi = {10.1016/j.thromres.2014.09.009}, author = {Mukherjee, Ashis K and Dutta, Sumita and Mackessy, Stephen P} } @article {517, title = {Two acidic, anticoagulant PLA2 isoenzymes purified from the venom of monocled cobra Naja kaouthia exhibit different potency to inhibit thrombin and factor Xa via phospholipids independent, non-enzymatic mechanism. (Mass Spectrometry - Proteomics)}, journal = {PLoS One}, volume = {9}, year = {2014}, month = {2014}, pages = {e101334}, abstract = {

BACKGROUND: The monocled cobra (Naja kaouthia) is responsible for snakebite fatality in Indian subcontinent and in south-western China. Phospholipase A2 (PLA2; EC 3.1.1.4) is one of the toxic components of snake venom. The present study explores the mechanism and rationale(s) for the differences in anticoagulant potency of two acidic PLA2 isoenzymes, Nk-PLA2α (13463.91 Da) and Nk-PLA2β (13282.38 Da) purified from the venom of N. kaouthia.

PRINCIPAL FINDINGS: By LC-MS/MS analysis, these PLA2s showed highest similarity (23.5\% sequence coverage) with PLA2 III isolated from monocled cobra venom. The catalytic activity of Nk-PLA2β exceeds that of Nk-PLA2α. Heparin differentially regulated the catalytic and anticoagulant activities of these Nk-PLA2 isoenzymes. The anticoagulant potency of Nk-PLA2α was comparable to commercial anticoagulants warfarin, and heparin/antithrombin-III albeit Nk-PLA2β demonstrated highest anticoagulant activity. The anticoagulant action of these PLA2s was partially contributed by a small but specific hydrolysis of plasma phospholipids. The strong anticoagulant effect of Nk-PLA2α and Nk-PLA2β was achieved via preferential, non-enzymatic inhibition of FXa (Ki = 43 nM) and thrombin (Ki = 8.3 nM), respectively. Kinetics study suggests that the Nk-PLA2 isoenzymes inhibit their "pharmacological target(s)" by uncompetitive mechanism without the requirement of phospholipids/Ca(2+). The anticoagulant potency of Nk-PLA2β which is higher than that of Nk-PLA2α is corroborated by its superior catalytic activity, its higher capacity for binding to phosphatidylcholine, and its greater strength of thrombin inhibition. These PLA2 isoenzymes thus have evolved to affect haemostasis by different mechanisms. The Nk-PLA2β partially inhibited the thrombin-induced aggregation of mammalian platelets suggesting its therapeutic application in the prevention of unwanted clot formation.

CONCLUSION/SIGNIFICANCE: In order to develop peptide-based superior anticoagulant therapeutics, future application of Nk-PLA2α and Nk-PLA2β for the treatment and/or prevention of cardiovascular disorders are proposed.

}, keywords = {Anticoagulants, Blood Platelets, Chemical Fractionation, Chromatography, Liquid, Cobra Venoms, Factor Xa, Factor Xa Inhibitors, Isoenzymes, Kinetics, Phospholipases A2, Phospholipids, Sequence Analysis, Protein, Tandem Mass Spectrometry, Thrombin}, issn = {1932-6203}, doi = {10.1371/journal.pone.0101334}, author = {Mukherjee, Ashis K and Kalita, Bhargab and Thakur, Rupamoni} } @article {724, title = {Neutrophil extracellular traps contain mitochondrial as well as nuclear DNA and exhibit inflammatory potential.}, journal = {Cytometry A}, volume = {81}, year = {2012}, month = {2012 Mar}, pages = {238-47}, abstract = {

Neutrophils expel extracellular traps (NETs) to entrap and exterminate the invaded micro-organisms. Acute/chronic inflammatory disorders are often observed with aberrantly enhanced NETs formation and high nitric oxide (NO) availability. Recent study from this laboratory demonstrated release of NETs from human neutrophils following treatment with SNP or SNAP. This study is an extension of our previous finding to explore the extracellular bacterial killing, source of DNA in the expelled NETs, their ability to induce proinflammatory cytokines release from platelets/THP-1 cells, and assessment of NO-mediated free radical formation by using a consistent NO donor, DETA-NONOate. NO-mediated NETs exhibited extracellular bacterial killing as determined by colony forming units. NO-mediated NETs formation was due to the activation of NADPH oxidase and myeloperoxidase. NO- or PMA-mediated NETs were positive for both nuclear and mitochondrial DNA as well as proteolytic enzymes. Incubation of NETs with human platelets enhanced the release of IL-1β and IL-8, while with THP-1 cells, release of IL-1β, IL-8, and TNFα was observed. This study demonstrates that NO by augmenting enzymatic free radical generation release NETs to promote extracellular bacterial killing. These NETs were made up of mitochondrial and nuclear DNA and potentiated release of proinflammatory cytokines.

}, keywords = {Adult, Blood Platelets, DNA, DNA, Mitochondrial, Free Radicals, Humans, Inflammation, Interleukin-1beta, Interleukin-8, Mitochondria, NADPH Oxidases, Neutrophil Activation, Neutrophils, Nitric Oxide, Peroxidase, Tumor Necrosis Factor-alpha}, issn = {1552-4930}, doi = {10.1002/cyto.a.21178}, author = {Keshari, Ravi S and Jyoti, Anupam and Kumar, Sachin and Dubey, Megha and Verma, Anupam and Srinag, Bangalore S and Krishnamurthy, Hanumanthappa and Barthwal, Manoj K and Dikshit, Madhu} }