Carbon monoxide inhibits hemotoxic activity of Elapidae venoms: potential role of heme

Abstract

Envenomation by hemotoxic enzymes continues to be a major cause of morbidity and mortality throughout the world. With regard to treatment, the gold standard to abrogate coagulopathy caused by these venoms is still the administration of antivenom; however, despite antivenom therapy, coagulopathy still occurs and recurs. Of interest, this laboratory has demonstrated in vitro and in vivo that coagulopathy inducing venom derived from snakes of the family Viperidae exposed to carbon monoxide (CO) is inhibited, potentially by an attached heme. The present investigation sought to determine if venoms derived from snakes of the Elapidae family (taipans and cobras) could also be inhibited with CO or with the metheme inducing agent, O-phenylhydroxylamine (PHA). Assessing changes in coagulation kinetics of human plasma with thrombelastography, venoms from Elapidae snakes were exposed in isolation to CO (five species) or PHA (one specie) and placed in human plasma to assess changes in procoagulant or anticoagulant activity. The procoagulant activity of two taipan venoms and anticoagulant activity of three cobra venoms were significantly inhibited by CO. The venom of the inland taipan was also inhibited by PHA. In sum, these data demonstrate indirectly that the biometal heme is likely bound to these disparate venoms as an intermediary modulatory molecule. In conclusion, CO may not just be a potential therapeutic agent to treat envenomation but also may be a potential modulator of heme as a protective mechanism for venomous snakes against injury from their own proteolytic venoms.

Mechanisms Responsible for the Anticoagulant Properties of Neurotoxic Dendroaspis Venoms: A Viscoelastic Analysis

“…While the coagulopathic effects of hemotoxic venoms derived from venomous snakes have been of great scientific interest for several decades [1], it is only recently that investigation has intensified on the effects of neurotoxic venoms on coagulation [2][3][4][5][6][7]. Specifically, utilizing the thrombelastograph, the effects of neurotoxic venoms containing proteolytic and lipolytic enzymes on human plasma-based coagulation or isolated human thrombin-fibrinogen systems have been defined in venoms obtained from snakes within the Elapidae and Viperidae families [2][3][4][5][6][7]. Of interest, the venoms containing neurotoxic phospholipase A 2 (PLA 2 ) that were investigated were found to have their anticoagulant effects inhibited by either specific phospholipase A 2 inhibitors or tricarbonyldichlororuthenium (II) dimer (CORM-2) [3][4][5][6][7].…”

CatroxMP-II: a heme-modulated fibrinogenolytic metalloproteinase isolated from Crotalus atrox venom

“…With regard to the concentration of CatroxMP-II used, the onset of coagulation had to be double and/or the velocity of clot formation half of plasma without CatroxMP-II addition to be acceptable for experimentation. The following elastic modulus-based parameters previously described (Nielsen 2018; Nielsen and Bazzell 2016, 2017; Nielsen et al 2016, 2018a, b; Nielsen and Losada 2017; Nielsen and Matika 2017) were determined: time to maximum rate of thrombus generation (TMRTG): this is the time interval (minutes) observed prior to maximum speed of clot growth; maximum rate of thrombus generation (MRTG): this is the maximum velocity of clot growth observed (dynes/cm 2 /second); and total thrombus generation (TTG, dynes/cm 2 ), the final viscoelastic resistance observed after clot formation. Data were collected for 30 min.…”

“…It has been recently demonstrated that the hemotoxic venom activity of several species of snakes can be inhibited in vitro and in vivo by exposure to carbon monoxide (CO) via thrombelastography (Nielsen 2018; Nielsen and Bazzell 2016, 2017; Nielsen et al 2016, 2018a, b; Nielsen and Losada 2017; Nielsen and Matika 2017). Also of interest, an agent that causes metheme formation (Nielsen et al 2011a) used to identify fibrinogen as a heme binding protein (Nielsen et al 2011b) was demonstrated to decrease the prothrombotic activity of Oxyuranus microlepidotus venom (Nielsen et al 2018a).…”

“…Also of interest, an agent that causes metheme formation (Nielsen et al 2011a) used to identify fibrinogen as a heme binding protein (Nielsen et al 2011b) was demonstrated to decrease the prothrombotic activity of Oxyuranus microlepidotus venom (Nielsen et al 2018a). While it was originally posited that CO may have inhibited snake venom metalloproteinase (SVMP) activity by in some way interacting with the typically zinc metal catalytic center, subsequent inactivation of a snake venom serine protease (SVSP) activity by CO could not be similarly explained (Nielsen and Bazzell 2017).…”

“…Second, a trypsin digest of this purified SVMP had to be analyzed with mass spectroscopy to determine if a mass consistent with heme could be identified. Lastly, it had to be determined if exposure of this heme-bearing SVMP to CO could inhibit its fibrinogenolytic activity in a well-established thrombelastographic assay (Nielsen 2018; Nielsen and Bazzell 2016, 2017; Nielsen et al 2016, 2018a, b; Nielsen and Losada 2017; Nielsen and Matika 2017). …”