Calcium-dependent contractile response of arterial smooth muscle to a jellyfish toxin (pCrTX: Carybdea rastonii)

Raising Awareness on the Clinical and Forensic Aspects of Jellyfish Stings: A Worldwide Increasing Threat

Jellyfish are ubiquitous animals registering a high and increasing number of contacts with humans in coastal areas. These encounters result in a multitude of symptoms, ranging from mild erythema to death. This work aims to review the state-of-the-art regarding pathophysiology, diagnosis, treatment, and relevant clinical and forensic aspects of jellyfish stings. There are three major classes of jellyfish, causing various clinical scenarios. Most envenomations result in an erythematous lesion with morphological characteristics that may help identify the class of jellyfish responsible. In rare cases, the sting may result in delayed, persistent, or systemic symptoms. Lethal encounters have been described, but most of those cases happened in the Indo-Pacific region, where cubozoans, the deadliest jellyfish class, can be found. The diagnosis is mostly clinical but can be aided by dermoscopy, skin scrapings/sticky tape, confocal reflectance microscopy, immunological essays, among others. Treatment is currently based on preventing further envenomation, inactivating the venom, and alleviating local and systemic symptoms. However, the strategy used to achieve these effects remains under debate. Only one antivenom is currently used and covers merely one species (Chironex fleckeri). Other antivenoms have been produced experimentally but were not tested on human envenomation settings. The increased number of cases, especially due to climate changes, justifies further research in the study of clinical aspects of jellyfish envenoming.

Cnidarian Jellyfish: Ecological Aspects, Nematocyst Isolation, and Treatment Methods of Sting

Cnidarians play an important role in ecosystem functioning, in the competition among species, and for possible utilization of several active compounds against cardiovascular, nervous, endocrine, immune, infective, and inflammatory disorders or having antitumoral properties, which have been extracted from these organisms. Nevertheless, notwithstanding these promising features, the main reason for which cnidarians are known is due to their venomousness as they have a serious impact on public health as well as in economy being able to affect some human activities. For this reason a preeminent subject of the research about cnidarians is the organization of proper systems and methods of care and treatment of stinging. This chapter aims to present the data about the morphological, ecological, toxicological, epidemiological, and therapeutic aspects regarding cnidarians with the purpose to summarize the existing knowledge and to stimulate future perspectives in the research on these organisms.

Medusa: A Review of an Ancient Cnidarian Body Form

Medusae (aka jellyfish) have multiphasic life cycles and a propensity to adapt to, and proliferate in, a plethora of aquatic habitats, connecting them to a number of ecological and societal issues. Now, in the midst of the genomics era, affordable next-generation sequencing (NGS) platforms coupled with publically available bioinformatics tools present the much-anticipated opportunity to explore medusa taxa as potential model systems. Genome-wide studies of medusae would provide a remarkable opportunity to address long-standing questions related to the biology, physiology, and nervous system of some of the earliest pelagic animals. Furthermore, medusae have become key targets in the exploration of marine natural products, in the development of marine biomarkers, and for their application to the biomedical and robotics fields. Presented here is a synopsis of the current state of medusa research, highlighting insights provided by multi-omics studies, as well as existing knowledge gaps, calling upon the scientific community to adopt a number of medusa taxa as model systems in forthcoming research endeavors.

β adrenergic receptor/cAMP/PKA signaling contributes to the intracellular Ca2+ release by tentacle extract from the jellyfish Cyanea capillata

Background

Intracellular Ca²⁺ overload induced by extracellular Ca²⁺ entry has previously been confirmed to be an important mechanism for the cardiotoxicity as well as the acute heart dysfunction induced by jellyfish venom, while the underlying mechanism remains to be elucidated.

Methods

Under extracellular Ca²⁺-free or Ca²⁺-containing conditions, the Ca²⁺ fluorescence in isolated adult mouse cardiomyocytes pre-incubated with tentacle extract (TE) from the jellyfish Cyanea capillata and β blockers was scanned by laser scanning confocal microscope. Then, the cyclic adenosine monophosphate (cAMP) concentration and protein kinase A (PKA) activity in primary neonatal rat ventricular cardiomyocytes were determined by ELISA assay. Furthermore, the effect of propranolol against the cardiotoxicity of TE was evaluated in Langendorff-perfused rat hearts and intact rats.

Results

The increase of intracellular Ca²⁺ fluorescence signal by TE was significantly attenuated and delayed when the extracellular Ca²⁺ was removed. The β adrenergic blockers, including propranolol, atenolol and esmolol, partially inhibited the increase of intracellular Ca²⁺ in the presence of 1.8 mM extracellular Ca²⁺ and completely abolished the Ca²⁺ increase under an extracellular Ca²⁺-free condition. Both cAMP concentration and PKA activity were stimulated by TE, and were inhibited by the β adrenergic blockers. Cardiomyocyte toxicity of TE was antagonized by β adrenergic blockers and the PKA inhibitor H89. Finally, the acute heart dysfuction by TE was antagonized by propranolol in Langendorff-perfused rat hearts and intact rats.

Conclusions

Our findings indicate that β adrenergic receptor/cAMP/PKA signaling contributes to the intracellular Ca²⁺ overload through intracellular Ca²⁺ release by TE from the jellyfish C. capillata.

Cytotoxic and cytolytic cnidarian venoms. A review on health implications and possible therapeutic applications

The toxicity of Cnidaria is a subject of concern for its influence on human activities and public health. During the last decades, the mechanisms of cell injury caused by cnidarian venoms have been studied utilizing extracts from several Cnidaria that have been tested in order to evaluate some fundamental parameters, such as the activity on cell survival, functioning and metabolism, and to improve the knowledge about the mechanisms of action of these compounds. In agreement with the modern tendency aimed to avoid the utilization of living animals in the experiments and to substitute them with in vitro systems, established cell lines or primary cultures have been employed to test cnidarian extracts or derivatives. Several cnidarian venoms have been found to have cytotoxic properties and have been also shown to cause hemolytic effects. Some studied substances have been shown to affect tumour cells and microorganisms, so making cnidarian extracts particularly interesting for their possible therapeutic employment. The review aims to emphasize the up-to-date knowledge about this subject taking in consideration the importance of such venoms in human pathology, the health implications and the possible therapeutic application of these natural compounds.

In vivo effects of cnidarian toxins and venoms

Cnidarians (Coelenterates), a very old and diverse animal phylum, possess a wide variety of biologically active substances that can be considered as toxins. Anthozoan toxins can be classified into two chemically very different groups, namely polypeptide toxins isolated from sea anemones and diterpenes isolated from octocorals. Cubozoan and scyphozoan protein toxins have been the most elusive cnidarian toxins to investigate - despite a tremendous effort in the past few decades, very few of these large, relatively unstable protein toxins were isolated, but recently this has been achieved for cubozoan venoms. Hydrozoans mainly contain large proteins with physiological mechanisms of action similar to the sea anemone and jellyfish pore-forming toxins. This article will focus on the in vivo physiological effects of cnidarian toxins and venoms; their actions at the cellular level will only be considered to understand their actions at the organ and whole animal levels. An understanding of mechanisms underlying the in vivo toxic effects will facilitate the development of more effective treatments of cnidarian envenomations.

Australian venomous jellyfish, envenomation syndromes, toxins and therapy

The seas and oceans around Australia harbour numerous venomous jellyfish. Chironex fleckeri, the box jellyfish, is the most lethal causing rapid cardiorespiratory depression and although its venom has been characterised, its toxins remain to be identified. A moderately effective antivenom exists which is also partially effective against another chirodropid, Chiropsalmus sp. Numerous carybdeids, some unidentified, cause less severe illness, including Carybdea rastoni whose toxins CrTX-A and CrTX-B are large proteins. Carukia barnesi, another small carybdeid is one cause of the 'Irukandji' syndrome which includes delayed pain from severe muscle cramping, vomiting, anxiety, restlessness, sweating and prostration, and occasionally severe hypertension and acute cardiac failure. The syndrome is in part caused by release of catecholamines but the cause of heart failure is undefined. The venom contains a sodium channel modulator. Two species of Physalia are present and although one is potentially lethal, has not caused death in Australian waters. Other significant genera of jellyfish include Tamoya, Pelagia, Cyanea, Aurelia and Chyrosaora.

Novel proteinaceous toxins from the box jellyfish (sea wasp) Carybdea rastoni

During summer and autumn, the box jellyfish (sea wasp) Carybdea rastoni is one of the most bothersome stinging pests to swimmers and bathers on the Japanese coast. Two labile but potent hemolytic toxins from the tentacles of Carybdea rastoni were isolated in their active forms using newly developed purification methods. The molecular masses of the isolated C. rastoni toxin-A and toxin-B (CrTX-A and CrTX-B) are 43 and 46 kDa, respectively, as calculated from SDS-PAGE. In the present study, we sequenced the full-length cDNA (1600 bp), which encodes both CrTX-A and CrTX-B. The deduced 450 amino acid sequence of the CrTXs, showed no significant homology with any known protein. This report presents the first complete sequence of a proteinaceous jellyfish toxin. Furthermore, it was revealed that CrTX-A was primarily localized in the nematocyst, whereas CrTX-B was detected only in the tentacle. Because the nematocyst is the organ responsible for the cnidarian sting, the remainder of the study focused on the toxicity of CrTX-A. We found that CrTX-A was fatally toxic to mice at 20 microg/kg (i.v.) and crayfish at 5 microg/kg (i.p.). Subcutaneously injected CrTX-A (0.1 microg) caused inflammation of mouse skin. These results showed that CrTX-A is responsible for the cutaneous inflammation observed in humans stung by C. rastoni.

Multiple vasoactive factors in epidermal secretions of the Arabian Gulf catfish, Arius bilineatus (Valenciennes)

1. The Arabian Gulf catfish produces proteinaceous epidermal secretions when threatened or injured. 2. The soluble fraction of the catfish epidermal secretions (SES) has vasoconstrictor activities on sheep renal arteries, which can be inhibited by several antagonists, including atropine, indomethacin, prazosin, and verapamil. 3. Mepyramine, yohimbine, and ketanserin have negligible effects on SES-induced contraction. 4. SES exhibits a significant tachyphylaxis upon addition of a second (8.4% reduction) and third (47% reduction) dose of SES to the organ bath, which can be partially prevented by addition of a fresh arterial section prior to each addition. 5. A vasoconstricting activity has been partially purified from SES by gel filtration on Fractogel HW-65(F) and appears to be a protein with a pI near 7.3. This activity is affected only by verapamil and prazosin.

Prevention of intimal thickening after endothelial removal by a nonpeptide angiotensin II receptor antagonist, losartan

1. The present experiments were designed to investigate the role of local angiotensin II receptors in the myointimal proliferative response of the vascular wall after endothelial removal, by use of a novel, nonpeptide, angiotensin II receptor antagonist, losartan. 2. When administered 1 week before endothelial removal from the rabbit carotid artery and then continuously until animals were killed 6 weeks later, losartan in a dose of 10 mg kg-1 daily, p.o. had no significant effects on the carotid blood flow (CBF), mean arterial blood pressure (MBP) and heart rate (HR). 3. A full endothelial lining with increased density of regenerated endothelial cells was observed 6 weeks after the endothelial removal. These changes were unaffected by treatment with losartan. 4. Six weeks after endothelial removal, acetylcholine (ACh)- and adenosine diphosphate (ADP)-induced relaxations were greatly reduced though endothelial cells had regenerated. The reduction of the relaxations to these agonists were significantly restored by chronic treatment with losartan. The endothelial-independent, sodium nitroprusside (SNP)-induced relaxation remained unaffected in all groups. 5. There were no differences in the noradrenaline (NA)- and endothelin-1 (ET-1)-induced contractions of the carotid artery strips between vehicle and losartan-treated groups. In contrast, the contractile response of the strips to angiotensin II was significantly decreased in the losartan group, indicating the specific antagonism by chronic losartan against the angiotensin II receptor. 6. Six weeks after endothelial removal, marked myointimal proliferation resulting from new accumulation of proliferating smooth muscle cells and connective tissue was observed in the vehicle group. Losartan treatment greatly suppressed the myointimal proliferative response.7. These results suggest that the local angiotensin II receptors play a role in the myointimal proliferativeresponse of the vascular wall to removal of the endothelium.

Cutaneous reactions caused by experimental exposure to jellyfish, Carybdea rastonii

Dermatitis caused by contact with tentacles of jellyfish was studied on 25 volunteers. Two tentacles cut from a living jellyfish, Carybdea rastonii, were applied on each of the forearms and skin reactions were observed. All volunteers complained of severe pain, which lasted from 10 min to 8 hrs. Erythema and wheal appeared within 3 to 4 min and enlarged for 15 to 20 min. Erythema subsided within 24 hrs to 3 days in all but two individuals. Seven to 13 days after the application, linear erythema and papulo-vesicular lesions with pruritus were observed on the forearms of 15 out of 25 volunteers tested. These flare-up lesions lasted for one week leaving slight pigmentation. Histological findings from the flare-up lesions corresponded to those of allergic contact dermatitis. The lymphocyte response to the jellyfish venom in the subjects who had recurring lesions was greater than that in either the subjects with no recurring lesions or the control group, who was never exposed to jellyfish.

Alpha 1-adrenoceptor antagonist activity of novel pyrimidine derivatives (SHI437 and IK29) in rabbit aorta and trigone of the bladder

1. In the rabbit isolated aorta and trigone of the bladder, noradrenaline, phenylephrine and clonidine elicited concentration-dependent contractions, which may be caused through activation of postsynaptic alpha 1-adrenoceptors. 2. SHI437, IK29, prazosin and yohimbine competitively antagonized the contractile responses induced by noradrenaline in the aorta and trigone. The pA2 values of SHI437, IK29, prazosin and yohimbine were 7.35 +/- 0.09, 7.47 +/- 0.10, 8.55 +/- 0.02 and 6.28 +/- 0.05 in the aorta, and 8.07 +/- 0.04, 8.30 +/- 0.03, 8.22 +/- 0.04 and 6.46 +/- 0.04 in the trigone, respectively. 3. SHI437, IK29, prazosin and yohimbine also possessed competitive alpha 2-adrenoceptor blocking properties, judging from their antagonism of the clonidine-induced inhibitory effect on the twitch responses in the electrically stimulated vas deferens of the rat. The pA2 values of SHI437, IK29, prazosin and yohimbine were determined to be 4.76 +/- 0.02, 4.74 +/- 0.02, 5.06 +/- 0.03 and 7.86 +/- 0.04, respectively. 4. SHI437, IK29 and prazosin inhibited the contractile responses elicited by transmural electrical stimulation without affecting the evoked 3H-overflow from the [3H]-noradrenaline-preloaded rabbit aorta. Yohimbine augmented the contractile responses and 3H-overflow. 5. SHI437 and IK29 at a concentration sufficient to inhibit noradrenaline-induced contraction failed to attenuate the contractile responses of aorta to KCl, 5-hydroxytryptamine and prostaglandin F2 alpha, and of the trigone to acetylcholine and histamine. 6. The present results suggest that SHI437 and IK29 are highly selective alpha 1-adrenoceptor antagonists, especially in the trigone of the bladder.

Contractile and relaxant effects of jellyfish toxin on the vascular and intestinal tissues

A toxic component (pCrTX) of jellyfish Carybdea rastonii (10(-8)-10(-6)g/ml) caused a contraction in both rat aorta and guinea-pig taenia coli which was partially inhibited by indomethacin or aspirin. pCrTX (10(-7)-10(-6)g/ml) relaxed the norepinephrine-induced contraction in rat aorta which was inhibited by removing endothelium or by adding methylene blue. These results suggest that a portion of the pCrTX-induced contraction is due to release of prostaglandin(s) and that the pCrTX-induced relaxation is due to release of an endothelium-derived relaxing factor.

Contractile effects of jellyfish toxin extracted from Carybdea rastonii on isolated rabbit aorta

Effects of the toxic component of jellyfish (Carybdea rastonii) (pCrTX) on the smooth muscle tension of isolated rabbit thoracic aorta were examined. pCrTX, at concentrations higher than 10(-7) g/ml, caused slowly developing tension that reached its maximum after about 1 hr. This contraction was partially inhibited by pretreatment of the tissue with phentolamine (5 X 10(-6) M) or indomethacin (10(-5) M). The contraction induced by pCrTX was partially inhibited by nicardipine (10(-7) M) and markedly augmented by Bay k8644 (10(-6) M). In low-Na+ solution, the rate of rise of the pCrTX-induced contraction was significantly reduced. Removal of external Ca2+ inhibited the pCrTX-induced contraction by about 30%, while chlorpromazine, trifluoperazine, prenylamine and papaverine (10(-4) M) completely inhibited the contraction. pCrTX itself did not cause any contraction in saponin-skinned smooth muscle and had no effect on the Ca2+-induced contractile tension. It has been reported that pCrTX-induced contraction is attributable to the release of endogenous catecholamines and also to the increase in Ca2+ influx in smooth muscle (Azuma et al., 1986). The present results confirmed the previous suggestion and further suggested that a portion of the contraction is due to release of prostaglandin(s) and also to the direct effect on smooth muscle which is not dependent on Ca2+ influx.