An examination of the cardiovascular effects of an ‘Irukandji’ jellyfish, Alatina nr mordens

Differences in Cardiac Effects of Venoms from Tentacles and the Bell of Live Carukia barnesi: Using Non-Invasive Pulse Wave Doppler

Carukia barnesi was the first in an expanding list of cubozoan jellyfish whose sting was identified as causing Irukandji syndrome. Nematocysts present on both the bell and tentacles are known to produce localised stings, though their individual roles in Irukandji syndrome have remained speculative. This research examines differences through venom profiling and pulse wave Doppler in a murine model. The latter demonstrates marked measurable differences in cardiac parameters. The venom from tentacles (CBV_t) resulted in cardiac decompensation and death in all mice at a mean of 40 min (95% CL: ± 11 min), whereas the venom from the bell (CBV_b) did not produce any cardiac dysfunction nor death in mice at 60 min post-exposure. This difference is pronounced, and we propose that bell exposure is unlikely to be causative in severe Irukandji syndrome. To date, all previously published cubozoan venom research utilised parenterally administered venom in their animal models, with many acknowledging their questionable applicability to real-world envenomation. Our model used live cubozoans on anaesthetised mice to simulate normal envenomation mechanics and actual expressed venoms. Consequently, we provide validity to the parenteral methodology used by previous cubozoan venom research.

Efficacy of silver nanoparticles against multidrug resistant clinical Staphylococcus aureus isolates from Nigeria

Multidrug resistant (MDR) S. aureus infections continue to account for excess mortality in hospital and community settings and constitute a rising global health problem. However, data on the efficacy and mechanism of actions of alternative solutions like silver nanoparticles in developing countries are lacking. This study investigated anti-staphylococcal activity of silver nanoparticles (AgNP) against local strains from Nigeria. A total 119 clinical isolates of S. aureus from five Nigerian laboratories categorized as MRSA (n = 52) and MSSA (n = 67) by PCR were studied. The MIC of AgNP produced by chemical reduction method and characterized by surface plasmon resonance absorbance and size equivalence by scanning electron microscopy was determined by microbroth dilution method. Its effect on protease activity and plasmids were also investigated. Baseline characteristics of the isolates revealed MDR phenotype of the isolates, carriage of diverse plasmids (15-32 kb) among the MDR MSSA, and mean extracellular protease activity of 24.8-55.7 U/mL. The chemically synthesized AgNP had a peak absorbance at 400 nm with a size equivalence of 4.58 nm. The MICs of AgNP against the isolates were 4.7 μg/mL and 4.9 μg/mL, respectively, for MRSA and MSSA (P > 0.05). The bactericidal effect of AgNP at 2.5-5 μg/mL on the MSSA and MRSA isolates was observed at 2.7-5.5 h post exposure in vitro. Further analysis revealed plasmid eviction in the MDR MSSA isolates exposed to 5 μg/mL AgNP and dose-dependent reduction in extracellular protease activity by 84.6-93.1%. Hemolysis of human erythrocytes by AgNP was not observed at the MIC range. Conclusion: This study revealed safety and efficacy of AgNP against clinical MDR S. aureus isolates from Nigeria, using plasmid eviction and protease inhibition as mechanisms of action.

Intracellular Ca(2+) overload induced by extracellular Ca(2+) entry plays an important role in acute heart dysfunction by tentacle extract from the jellyfish Cyanea capillata

The exact mechanism of acute heart dysfunction caused by jellyfish venom remains unclear for the moment. In the present study, we examined the problem caused by the tentacle extract (TE) from the jellyfish Cyanea capillata at the levels of whole animal, isolated heart, primarily cultured cardiomyocytes, and intracellular Ca(2+). The heart indexes, including HR, APs, LVPs, and MMLs, were all decreased significantly by TE in both whole animal and Langendorff-perfused isolated heart model. Imbalance of cardiac oxygen supply and demand also took place. In both Ca(2+)-containing and Ca(2+)-free bathing solutions, TE could cause obvious cytoplasmic Ca(2+) overload in NRVMs, but the cytoplasmic Ca(2+) increased faster, Ca(2+) overload peaks arrived earlier, and the morphological changes were more severe under the extracellular Ca(2+)-containing condition. L-type Ca(2+) channel blockers, as well as the inhibitor of ryanodine receptor (ryanodine), could improve the viability of NRVMs. Moreover, diltiazem significantly inhibited the acute heart dysfunction caused by TE in both Langendorff isolated heart model and whole animal. These results suggested that intracellular Ca(2+) overload induced by extracellular Ca(2+) entry plays an important role in acute heart failure by TE from the jellyfish C. capillata. Inhibition of extracellular Ca(2+) influx is a promising antagonistic alternative for heart damage by jellyfish venom.

Biology and ecology of Irukandji jellyfish (Cnidaria: Cubozoa)

Irukandji stings are a leading occupational health and safety issue for marine industries in tropical Australia and an emerging problem elsewhere in the Indo-Pacific and Caribbean. Their mild initial sting frequently results in debilitating illness, involving signs of sympathetic excess including excruciating pain, sweating, nausea and vomiting, hypertension and a feeling of impending doom; some cases also experience acute heart failure and pulmonary oedema. These jellyfish are typically small and nearly invisible, and their infestations are generally mysterious, making them scary to the general public, irresistible to the media, and disastrous for tourism. Research into these fascinating species has been largely driven by the medical profession and focused on treatment. Biological and ecological information is surprisingly sparse, and is scattered through grey literature or buried in dispersed publications, hampering understanding. Given that long-term climate forecasts tend toward conditions favourable to jellyfish ecology, that long-term legal forecasts tend toward increasing duty-of-care obligations, and that bioprospecting opportunities exist in the powerful Irukandji toxins, there is a clear need for information to help inform global research and robust management solutions. We synthesise and contextualise available information on Irukandji taxonomy, phylogeny, reproduction, vision, behaviour, feeding, distribution, seasonality, toxins, and safety. Despite Australia dominating the research in this area, there are probably well over 25 species worldwide that cause the syndrome and it is an understudied problem in the developing world. Major gaps in knowledge are identified for future research: our lack of clarity on the socio-economic impacts, and our need for time series and spatial surveys of the species, make this field particularly enticing.

Direct cardiac toxicity of the tentacle-only extract from the jellyfish Cyanea capillata demonstrated in isolated rat heart

Previous studies in our laboratory have shown that the cardiotoxicity is the main reason for rat death caused by tentacle-only extract from jellyfish Cyanea capillata. However, the direct cardiotoxicity in vitro and its mechanisms of toxic action remain unclear. The current studies were performed by using the Langendorff-perfused isolated heart model, which showed a dose-dependent hemodynamic and electrocardiogram changes. Heart injury-related enzymes increased. Histopathological analysis showed early ischemic damage in the myocardium. The Ca channel blockers nifedipine and verapamil led to a marked improvement in recovery of cardiac function, including heart rate, left ventricular developed pressure, positive and negative first derivatives of intraventricular pressure, coronary flow, left ventricular end-diastolic pressure, and electrocardiogram changes. Tentacle-only extract-induced cardiac dysfunction could be partly improved by the pretreatments of both propranolol and phentolamine, but not by either atropine or neostigmine at all. In conclusion, we have verified the direct cardiotoxicity of tentacle-only extract from jellyfish C. capillata by the Langendorff isolated heart model, which consisted of 3 separate parts: sinoatrial node malfunction, cardiomyocyte injury, and coronary spasm. The potential mechanism might be attributed to the overactivation of L-type Ca channel, β- and α-adrenergic receptors, but not cholinergic receptors.

Australian carybdeid jellyfish causing "Irukandji syndrome"

The Australian carybdeid jellyfish associated with Irukandji syndrome is Carukia barnesi, (Barnes' jellyfish). Other Australian carybdeid jellyfish that may be associated with the syndrome include Carukia shinju, Carybdea xaymacana, Malo maxima, Malo kingi, Alatina mordens, Gerongia rifkinae, and Morbakka fenneri ("Morbakka"). These small jellyfish are difficult to capture and identify. They are located offshore of the coasts of Australian states including Queensland, The Northern Territory, Western Australia and South Australia. The syndromic illness, resulting from a characteristic relatively minor sting, develops after about 30 minutes and consists of severe muscle pains especially of the lower back, muscle cramps, vomiting, sweating, agitation, vasoconstriction, prostration, hypertension and in cases of severe envenomation, acute heart failure. The mechanisms of actions of their toxins are obscure but they appear to include modulation of neuronal sodium channels leading to massive release of endogenous catecholamines (C. barnesi, A. mordens and M. maxima) and thereby to possible stress-induced cardiomyopathy. In addition, pore formation may occur in myocardial cellular membranes (C. xaymacana). In human cases of severe envenomation, systemic hypertension and myocardial dysfunction are associated with membrane leakage of troponin. Clinical management includes parenteral analgesia, antihypertensive therapy, oxygen and mechanical ventilation. No effective first-aid is known. Large knowledge gaps exist in biology of the jellyfish, their distribution, their toxins and mode of actions and in treatment of the Irukandji syndrome.

Target organ identification of jellyfish envenomation using systemic and integrative analyses in anesthetized dogs

Proper treatment of jellyfish envenomed patients can be successfully achieved only from an understanding of the overall functional changes and alterations in physiological parameters under its envenomation. The majority of previous investigations on jellyfish venoms have covered only a couple of parameters at a time. Unlike most other fragmentary jellyfish studies, we employed an integrative toxicological approach, including hemodynamics, clinical chemistry and hematology analyses, using N. nomurai jellyfish venom (NnV) in dogs. After the baseline measurements for mean arterial pressure (MAP), cardiac output (CO) and heart rate (HR), NnV was intravenously administered to the dogs at doses of 0.1 or 0.3mg/kg body weight. The dogs showed significant decreases in MAP (-27.4±3.7 and -48.1±9.9 mmHg), CO (-1.1±0.1 L/min and -1.0±0.2 L/min), and HR (-4.5±0.3 and -9.9±3.1 beats/min) comparing with the respective baseline controls. The onset of systemic hypotension and bradycardia occurred within 1 min of NnV injection and they lasted for 1-35 min, depending on the NnV doses. Interestingly, serum biochemical analyses of envenomed dogs exhibited dramatic increases of alkaline phosphatase (ALP), creatine phosphokinase (CPK), alanine aminotransferase (ALT) and aspartate aminotransferase (AST), indicating its possible target organs. In conclusion, we have demonstrated simultaneously, for the first time, the multiple organ toxicities (cardiotoxic, myotoxic and hepatotoxic) of a scyphozoan jellyfish venom. Based on these results, an integrative toxinological approach using dogs appears to be effective in predicting jellyfish venom toxicities and designing their therapeutic strategies. We expect this method can be applied to other jellyfish venom research as well.

The acute toxicity and hematological characterization of the effects of tentacle-only extract from the jellyfish Cyanea capillata

To investigate the hematologic changes and the activities of jellyfish venoms other than hemolytic and cardiovascular toxicities, the acute toxicity of tentacle-only extract (TOE) from the jellyfish Cyanea capillata was observed in mice, and hematological indexes were examined in rats. The median lethal dose (LD₅₀) of TOE was 4.25 mg/kg, and the acute toxicity involved both heart- and nervous system-related symptoms. Arterial blood gas indexes, including pH, PCO₂, HCO₃⁻, HCO₃std, TCO₂, BEecf and BE (B), decreased significantly. PO₂ showed a slight increase, while SO₂c (%) had no change at any time. Na⁺ and Ca²⁺ decreased, but K⁺ increased. Biochemical indexes, including LDH, CK, CK-MB, ALT, AST and sCr, significantly increased. Other biochemical indexes, including BUN and hemodiastase, remained normal. Lactic acid significantly increased, while glucose, Hct% and THbc showed slight temporary increases and then returned to normal. These results on the acute toxicity and hematological changes should improve our understanding of the in vivo pathophysiological effects of TOE from C. capillata and indicate that it may also have neurotoxicity, liver toxicity and muscular toxicity in addition to hemolytic and cardiovascular toxicities, but no kidney or pancreatic toxicity.

The pharmacology of Malo maxima jellyfish venom extract in isolated cardiovascular tissues: A probable cause of the Irukandji syndrome in Western Australia

The in vitro cardiac and vascular pharmacology of Malo maxima, a newly described jellyfish suspected of causing Irukandji syndrome in the Broome region of Western Australia, was investigated in rat tissues. In left atria, M. maxima crude venom extract (CVE; 1-100μg/mL) caused concentration-dependent inotropic responses which were unaffected by atropine (1μM), but significantly attenuated by tetrodotoxin (TTX; 0.1μM), propranolol (1μM), Mg(2+) (6mM) or calcitonin gene-related peptide antagonist (CGRP(8-37); 1μM). CVE caused no change in right atrial rate until 100μg/mL, which elicited bradycardia. This was unaffected by atropine, TTX, propranolol or CGRP(8-37). In the presence of Mg(2+), CVE 30-100μg/mL caused tachycardia. In small mesenteric arteries CVE caused concentration-dependent contractions (pEC(50) 1.03±0.07μg/mL) that were unaffected by prazosin (0.3μM), ω-conotoxin GVIA (0.1μM) or Mg(2+) (6mM). There was a 2-fold increase in sensitivity in the presence of CGRP(8-37) (3μM). TTX (0.1μM), box jellyfish Chironex fleckeri antivenom (92.6U/mL) and benextramine (3μM) decreased sensitivity by 2.6, 1.9 and 2.1-fold, respectively. CVE-induced maximum contractions were attenuated by C. fleckeri antivenom (-22%) or benextramine (-49%). M. maxima CVE appears to activate the sympathetic, but not parasympathetic, nervous system and to stimulate sensory nerve CGRP release in left atria and resistance arteries. These effects are consistent with the catecholamine excess thought to cause Irukandji syndrome, with additional actions of CGRP release.

Irukandji syndrome case series from Australia's Tropical Northern Territory

STUDY OBJECTIVE

We describe Irukandji syndrome (a painful hypercatecholaminergic condition caused by jellyfish envenoming) in Australia's Northern Territory.

METHODS

We collected prospectively a standardized data set on patients presenting to health facilities in the Northern Territory. Additional cases were identified retrospectively. Data collected included demographic, geographic, seasonal, and environmental features, as well as sting details, clinical manifestations, investigations, management, and outcomes.

RESULTS

From 1990 to 2007, Irukandji syndrome affected 87 people. Age ranged from 1 to 51 years (64% male victims; 41% children [63% indigenous]). Activities associated with stings included snorkeling or scuba diving (35%) and swimming (29%). Stings commonly occurred in water greater than 2 m deep (63%), with fine weather (73%) and still or light breeze (70%). Seasonal variation was bimodal; peaks in May and October corresponded to prevailing offshore winds in the Darwin and Gove areas, respectively. Pain was severe (65%), with rapid onset (<30 minutes in 79%). Sting lesions (visible in 63%) were mild, and nematocysts (detected in 7 cases) had variable morphology. Systemic features were common, including hypertension and ECG abnormalities. Severe complications included troponin-level increases (2 cases) and cardiomyopathy with ventricular tachycardia (1 case), but no fatalities. Management included vinegar as first aid (66%), parenteral opioids (70%) (range 2 to 82.5 mg morphine equivalents in adults), and magnesium sulfate (3 cases). Hospital admission (49%) and aeromedical retrieval (16%) were commonplace.

CONCLUSION

Irukandji syndrome in the Northern Territory was clinically consistent with previous studies but had distinct seasonal, geographic, and environmental features. Indigenous children in remote coastal communities are at risk, and there is room for improvement in prevention and management.