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

2018

Hum Exp Toxicol

Venomous snake bite and subsequent coagulopathy is a significant source of morbidity and mortality worldwide. The gold standard to treat coagulopathy caused by these venoms is the administration of antivenom; however, despite this therapy, coagulopathy still occurs and recurs. Of interest, our laboratory has demonstrated in vitro and in vivo that coagulopathy-inducing venom 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 African genera Atheris, Atractaspis, Causus, Cerastes, Echis, and Macrovipera that have no or limited antivenoms available could be inhibited with CO or with the metheme-inducing agent, O-phenylhydroxylamine (PHA). Assessing changes in coagulation kinetics of human plasma with thrombelastography, venoms were exposed in isolation to CO or PHA. Eight species were found to have procoagulant activity consistent with the generation of human thrombin, while one was likely fibrinogenolytic. All venoms were significantly inhibited by CO/PHA with species-specific variation noted. These data demonstrate indirectly that the heme is likely bound to these disparate venoms as an intermediary modulatory molecule. In conclusion, future investigation is warranted to determine if heme could serve as a potential therapeutic target to be modulated during treatment of envenomation by hemotoxic enzymes.

Section: Introductionmentioning

confidence: 99%

Role of heme modulation in inhibition of Atheris, Atractaspis, Causus, Cerastes, Echis, and Macrovipera hemotoxic venom activity

2018

Hum Exp Toxicol

“…Envenomation by hemotoxic enzymes continues to be a major cause of morbidity and mortality worldwide [ 1 ], and these venoms are often complex, containing a myriad of diverse enzymes (metalloproteinases, serine proteases, phospholipase A 2 ), which have been investigated for medicinal and toxinological purposes [ 2 ]. Over the past year, our laboratory has assessed a novel approach to modulating hemotoxic venom activity by directly exposing these substances to carboxyheme and metheme forming agents in insolation [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. These assessments were performed with thrombelastography, and involved several vipers from Africa [ 3 , 4 , 5 ], Asia [ 6 , 7 , 8 , 9 ], and Australia [ 5 , 8 ], as well as some from the Americas [ 6 , 7 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…These assessments were performed with thrombelastography, and involved several vipers from Africa [ 3 , 4 , 5 ], Asia [ 6 , 7 , 8 , 9 ], and Australia [ 5 , 8 ], as well as some from the Americas [ 6 , 7 , 10 , 11 ]. Importantly, by recently demonstrating that heme was bound to an isolated, purified fibrinogenolytic enzyme derived from Crotalus atrox venom that was inhibited by carbon monoxide (CO), our hypothesis that snake venom enzymes may be modulated by heme groups was mechanistically supported [ 12 ]. The pattern observed thus far has been that CO inhibits whole venom activity within a concentration range of 70–700 µM, whereas metheme induction by O -phenylhydroxylamine (PHA) in the 10-30 mM range may inhibit, enhance, or not affect venom hemotoxic effects [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…In cases where primary literature describing the venom was unavailable, the designation of procoagulant or anticoagulant activity was guided by the Clinical Toxinology Resources website ( ), an internationally recognized site on envenomation that is maintained by the University of Adelaide in Australia. In terms of definitions, anticoagulant venom enzymes have been thrombelastographically documented to exert their effects via fibrinogenolytic [ 3 , 6 , 10 , 12 ] or phospholipase [ 32 ] mechanisms, which have not been differentiated with our methodology yet. Procoagulant venoms with thrombin-like activity cause rapid onset of coagulation, but with weak clot strength secondary to lack of engagement of Factor XIII (FXIII) [ 7 , 11 , 31 ].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

De Novo Assessment and Review of Pan-American Pit Viper Anticoagulant and Procoagulant Venom Activities via Kinetomic Analyses

Afshar

2019

Toxins

Self Cite

Snakebite with hemotoxic venom continues to be a major source of morbidity and mortality worldwide. Our laboratory has characterized the coagulopathy that occurs in vitro in human plasma via specialized thrombelastographic methods to determine if venoms are predominantly anticoagulant or procoagulant in nature. Further, the exposure of venoms to carbon monoxide (CO) or O-phenylhydroxylamine (PHA) modulate putative heme groups attached to key enzymes has also provided mechanistic insight into the multiple different activities contained in one venom. The present investigation used these techniques to characterize fourteen different venoms obtained from snakes from North, Central, and South America. Further, we review and present previous thrombelastographic-based analyses of eighteen other species from the Americas. Venoms were found to be anticoagulant and procoagulant (thrombin-like activity, thrombin-generating activity). All prospectively assessed venom activities were determined to be heme-modulated except two, wherein both CO and its carrier molecule were found to inhibit activity, while PHA did not affect activity (Bothriechis schlegelii and Crotalus organus abyssus). When divided by continent, North and Central America contained venoms with mostly anticoagulant activities, several thrombin-like activities, with only two thrombin-generating activity containing venoms. In contrast, most venoms with thrombin-generating activity were located in South America, derived from Bothrops species. In conclusion, the kinetomic profiles of venoms obtained from thirty-two Pan-American Pit Viper species are presented. It is anticipated that this approach will be utilized to identify clinically relevant hemotoxic venom enzymatic activity and assess the efficacy of locally delivered CO or systemically administered antivenoms.

“…Numerous proteins have been found to be heme-bound, and their functions are controlled by the ligand (e.g., oxygen, nitric oxide, CO) that binds to the iron center of the heme group as recently reviewed [ 12 ]. Heme modulation has potential therapeutic applications in the setting of envenomation, and we have recently described a heme group bound to a fibrinogenolytic enzyme obtained from Crotalus atrox venom, and this enzyme was inhibited by CO [ 13 ]. Taken as a whole, the analyses of changes in coagulation kinetics in human plasma mediated by hemotoxic venom can complement the elegant proteomic analyses of these venoms, potentially providing insight into the relative impact of major enzyme types (e.g., snake venom metalloproteinases (SVMP), snake venom serine proteases (SVSP)) on human coagulopathy after envenomation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Heme Modulation on Ovophis and Trimeresurus Venom Activity in Human Plasma

Matika

2018

Toxins

Self Cite

Geographic isolation and other factors result in evolution-driven diversity of the enzymatic composition of venom of pit vipers in the same genus. The present investigation sought to characterize venoms obtained from such genetically diverse Ovophis and Trimeresurus pit vipers utilizing thrombelastographic coagulation kinetic analyses. The coagulation kinetics of human plasma were assessed after exposure to venom obtained from two Ovophis and three Trimeresurus species. The potency of each venom was defined (µg/mL required to equivalently change coagulation); additionally, venoms were exposed to carbon monoxide (CO) or a metheme-inducing agent to modulate any enzyme-associated heme. All venoms had fibrinogenolytic activity, with four being CO-inhibitable. While Ovophis venoms had similar potency, one demonstrated the presence of a thrombin-like activity, whereas the other demonstrated a thrombin-generating activity. There was a 10-fold difference in potency and 10-fold different vulnerability to CO inhibition between the Trimeresurus species. Metheme formation enhanced fibrinogenolytic-like activity in both Ovophis species venoms, whereas the three Trimeresurus species venoms had fibrinogenolytic-like activity enhanced, inhibited, or not changed. This novel “venom kinetomic” approach has potential to identify clinically relevant enzymatic activity and assess efficacy of antivenoms between genetically and geographically diverse species.