Inactivation of Venom PLA2 Alleviates Myonecrosis and Facilitates Muscle Regeneration in Envenomed Mice: A Time Course Observation

Abstract

Snake venom is a complex cocktail of toxins which induces a series of clinical and pathophysiological manifestations in victims, including severe local tissue damage and systemic alterations. Deinagkistrodon acutus (D. acutus) ranks among the “big four” life-threatening venomous species in China, whose venom possesses strong myotoxicity and hematotoxicity that often lead to permanent disability or muscle atrophy. Varespladib, an inhibitor of mammalian phospholipase A2 (PLA2), has been recently reproposed as an effective antidote against snakebite envenomation. The present study aimed at evaluating the protective role of varespladib on muscle regeneration in envenomed mice. Mice were grouped and subjected to inoculation with D. acutus venom or a mixture of venom and varespladib or control vehicle in the gastrocnemius muscle. Local injuries including hemorrhage, myonecrosis, ulceration, and systemic damages including general dysfunction, visceral failure, and inflammatory responses were observed at 1, 3, 7, 14, and 21 days. The results indicated that most of the muscle myonecrosis and hemorrhage were alleviated by varespladib. Besides, the pretreated mice recovered rapidly with lesser atrophy and muscle fibrosis. In conclusion, the findings of the present study suggested that varespladib is an effective antidote that could neutralize D. acutus venom and allow for earlier and improved rehabilitation outcome.

Coagulotoxic Cobras: Clinical Implications of Strong Anticoagulant Actions of African Spitting Naja Venoms That Are Not Neutralised by Antivenom but Are by LY315920 (Varespladib)

“…Given the observed failure of SAIMR antivenom in this study to neutralise any of the anticoagulant effects of cobra venoms, which is consistent with clinical observations of antivenom ineffectiveness [19], we tested the neutralising potential of LY315920, an anti-inflammatory drug candidate originally designed as an inhibitor of mammalian PLA 2 s. As snake venom PLA 2 s play an important role in morbidity resulting from snakebite (e.g., tissue destruction, haemorrhage, haemolysis) [24], it is important to investigate the possibility of a broad-spectrum PLA 2 inhibitor neutralising venom PLA 2 s. Our results revealed a promising ability of LY315920 to neutralise two different types of anticoagulant venom effects by cobra venoms: thrombin inhibition and inhibition of FXa’s ability to form a prothrombinase complex with FVa. This is consistent with previous work on other venom types which revealed that LY315920 and its variants are effective in preventing myotoxic and neurotoxic venom PLA 2 -driven toxicity [20,25,26,27]. This results in this study are, however, the first time that the ability of LY315920 to prevent potent coagulotoxic effects has been shown.…”

Delayed LY333013 (Oral) and LY315920 (Intravenous) Reverse Severe Neurotoxicity and Rescue Juvenile Pigs from Lethal Doses of Micrurus fulvius (Eastern Coral Snake) Venom

“…In conclusion, our findings suggest that LY315920 and/or LY333013 are likely to be effective in abrogating the main clinical manifestations in envenoming by M. fulvius and could apply to other types of envenoming as well [ 7 , 23 , 24 , 26 ]. Moreover, they support the concept that these drugs may potentiate the therapeutic action of coral snake antivenoms and others [ 26 ].…”

“…Surprisingly, LY315920 and closely related compounds such as the orally-available pro-drug LY333013, are extremely potent inhibitors of 28 medically important venom sPLA2s from snake species of six continents [ 7 ]. These results have been replicated with several venoms both in vitro and in vivo in mice [ 7 , 23 , 24 ]. Both lead compounds have been through extensive human and animal testing, and although they have excellent safety profiles for short-term use, have never gained FDA approval and are now off patent [ 22 , 25 ].…”

“…For the purpose of this study, we stayed within LY333013 dose ranges and schedules previously tested in animals as well as Phase I and II human studies of these compounds that were previously evaluated for indications other than snakebite and never advanced to Food and Drug Administration (FDA) registration due to a lack of efficacy [ 22 ]. The results cannot yet be generalized to the neutralization of a broad range of snake venom sPLA2s and associated pathology but the toxin-specific approach is being increasingly investigated as a treatment for snakebite both alone and in conjunction with antivenom [ 7 , 9 , 10 , 23 , 24 , 26 ]. This was advantageous in guiding these experiments and to allow some reasonable comparison of results [ 30 , 31 , 32 , 33 ].…”

The Search for Natural and Synthetic Inhibitors That Would Complement Antivenoms as Therapeutics for Snakebite Envenoming

“…LY315920 was also effective in inhibiting the cytotoxic effect of the venom on C2C12 myotubes and reducing local myonecrosis induced by crude venoms and myotoxic PLA 2 s from the venoms of two viperids and one elapid, even when administered after venom injection [ 177 ]. Moreover, this inhibitor also reduced the extent of local tissue damage and improved muscle regeneration in experimental envenomings by Deinagkistrodon acutus [ 178 ]. PLA 2 s exert anticoagulant activities owing to the hydrolysis of phospholipids which are required for blood clotting or by directly binding to some clotting factors [ 179 ].…”