Cubozoan Venom-Induced Cardiovascular Collapse Is Caused by Hyperkalemia and Prevented by Zinc Gluconate in Mice

Abstract

Chironex fleckeri (Australian box jellyfish) stings can cause acute cardiovascular collapse and death. We developed methods to recover venom with high specific activity, and evaluated the effects of both total venom and constituent porins at doses equivalent to lethal envenomation. Marked potassium release occurred within 5 min and hemolysis within 20 min in human red blood cells (RBC) exposed to venom or purified venom porin. Electron microscopy revealed abundant ∼12-nm transmembrane pores in RBC exposed to purified venom porins. C57BL/6 mice injected with venom showed rapid decline in ejection fraction with progression to electromechanical dissociation and electrocardiographic findings consistent with acute hyperkalemia. Recognizing that porin assembly can be inhibited by zinc, we found that zinc gluconate inhibited potassium efflux from RBC exposed to total venom or purified porin, and prolonged survival time in mice following venom injection. These findings suggest that hyperkalemia is the critical event following Chironex fleckeri envenomation and that rapid administration of zinc could be life saving in human sting victims.

Chironex fleckeri (Box Jellyfish) Venom Proteins

“…Given that the N-terminal domains of CfTX-like and 3d-Cry toxins are structurally analogous, it is therefore plausible that the CfTX-like toxins are involved in oligomerization and pore formation in cardiocytes, erythrocytes, and other susceptible cells. The for- mation of relatively large ring-shaped pores (12-nm inner diameter/25-nm outer diameter) in human erythrocyte cell membranes following exposure to purified CfTX isoforms (11) provides evidence that toxin oligomerization at the cell surface is integral to pore formation. Furthermore, as demonstrated here and in a previous study (3), the CfTX proteins have a propensity to oligomerize into high molecular mass quaternary structures, implying that although each toxin is individually The functional role(s) of the C-terminal domain in CfTX-like toxins is less clear, but due to its structural similarity (albeit weaker) to Domain II of 3d-Cry toxins, it may be involved in receptor binding and/or toxin specificity.…”

Evolution and diversification of the cnidarian venom system

“…They range in size from the tiny Hydra spp., at less than 1 cm in length, to the massive lion's mane jellyfish, Cyanea capillata with the bell diameter exceeding 2 m [2]. The envenomation hazard to humans also varies widely from non-hazardous to the infamous Chironex fleckeri (Australian box jellyfish), one of the most venomous animal dangerous to humans, as a meter of tentacle contact can provoke immediate cardiovascular collapse and death even within minutes after a sting [3]. The majority of cnidarians live in salt water habitats at different water depths.…”

“…Envenomation syndromes induced by cnidarian animals represent a therapeutic challenge especially to bathers, swimmers and surfers. Envenomation symptoms are painful hemorrhagic skin lesions, systemic reactions (e.g., direct effects on muscle and nerve tissue), long-term immunological responses, and occasionally fatalities due to Chironex fleckeri cardiovascular and pore-forming toxins [3,125,140,215].…”

“…However, in comparison with the vast number of studies conducted on the venoms of other venomous animals such as snakes, cone snails, spiders and scorpions, cnidarian venoms have received scant attention from toxinologists. The principal technical impediment in cnidarian research is the fact that the venom does not exist in a large discrete gland as an aqueous mixture in milligram quantities but instead is distributed in microscopic individual nematocysts, each containing picogram of protein [3]. Venom analysis at the picogram scale presents challenges as cnidarian venom is a complex mixture of bioactive molecules, some of which are aqueous while others are lipidic [3,140].…”

“…The principal technical impediment in cnidarian research is the fact that the venom does not exist in a large discrete gland as an aqueous mixture in milligram quantities but instead is distributed in microscopic individual nematocysts, each containing picogram of protein [3]. Venom analysis at the picogram scale presents challenges as cnidarian venom is a complex mixture of bioactive molecules, some of which are aqueous while others are lipidic [3,140]. As a consequence, a modern proteomics approach based on high-throughput mass spectrometry analysis is ideal [220].…”