Structural Basis for the Inhibition of a Phospholipase A2-Like Toxin by Caffeic and Aristolochic Acids

Abstract

One of the main challenges in toxicology today is to develop therapeutic alternatives for the treatment of snake venom injuries that are not efficiently neutralized by conventional serum therapy. Venom phospholipases A2 (PLA2s) and PLA2-like proteins play a fundamental role in skeletal muscle necrosis, which can result in permanent sequelae and disability. This leads to economic and social problems, especially in developing countries. In this work, we performed structural and functional studies with Piratoxin-I, a Lys49-PLA2 from Bothropspirajai venom, complexed with two compounds present in several plants used in folk medicine against snakebites. These ligands partially neutralized the myotoxic activity of PrTX-I towards binding on the two independent sites of interaction between Lys49-PLA2 and muscle membrane. Our results corroborate the previously proposed mechanism of action of PLA2s-like and provide insights for the design of structure-based inhibitors that could prevent the permanent injuries caused by these proteins in snakebite victims.

PLA2-like proteins myotoxic mechanism: a dynamic model description

“…The following structures, with the Protein Data Bank identification codes in parentheses (PDB id), were used: apo1 BthTX-I (3HZD), apo2 BthTX-I (3I3H), BthTX-I/Zn 2+ (4WTB) 24 , BthTX-I/PEG4k [polyethylene glycol with an average weight of 4000 g/mol) (3IQ3)] 13 , BthTX-I/PEG400 (2H8I) 21 , BthTX-I/α-tocopherol (3CXI), PrTX-I/α-tocopherol (3CYL), apo PrTX-I (2Q2J) 22 , PrTX-I/BPB (2OK9) 37 , PrTX-I/rosmarinic acid+PEG330 (3QNL) 38 , PrTX-I/caffeic acid+PEG4k (4YU7), PrTX-I/aristolochic acid+PEG4k (4YZ7) 39 , PrTX-II/ n -tridecanoic acid (1QLL) 40 , apo BnSP-VII (1PA0) 26 , apo BbTX-II (4K09), MTX-II/PEG4k (4K06) 14 , BaspTX-II/suramin (1Y4L) 41 , BnIV/myristic acid (3MLM) 42 , MjTX-II/stearic acid (1XXS) 43 , MjTX-II/PEG4k (4KF3) 15 , and MjTX-II/suramin+PEG4k (4YV5) 44 . The structures BthTX-I/BPB (3I03), apo BthTX-I (3I3I), apo BnSP-VI (1PC9), apo BaspTX-II (1CLP), and BbTX-II (4DCF) were not included because in the first two, their asymmetric unit (ASU) content is composed of a monomer, and in the others, the resolution was lower than or equal to 2.5 Å.…”

Medicinal Plants for the Treatment of Local Tissue Damage Induced by Snake Venoms: An Overview from Traditional Use to Pharmacological Evidence

“…The mechanism by which medicinal plants neutralize the toxic venom constituents is still unknown, but many hypotheses have been proposed, such as protein precipitation, enzyme inactivation, proteolytic degradation, metal chelation, antioxidant action, and a combination of these mechanisms [ 15 ]. In this context, some improvements in this understanding have been achieved in the last years, through the use of in silico methods (e.g., docking simulations) to analyze the interaction of compounds isolated from plants and certain classes of snake venom toxins such as PLA 2 and SVMP [ 120 – 122 ].…”

Varespladib (LY315920) Appears to Be a Potent, Broad-Spectrum, Inhibitor of Snake Venom Phospholipase A2 and a Possible Pre-Referral Treatment for Envenomation

“…Acetylcholinesterase inhibitors such as neostigmine and edrophonium have been administered intravenously for management of snakebite [ 9 , 10 , 11 , 12 ] yet their use in neurotoxic snakebite remains controversial [ 13 ]. Snake venom metalloproteinases (svMP) and serine protease (SP) inhibitors [ 2 , 14 , 15 , 16 ] have also been proposed with phospholipase A2 inhibitors as potential therapies, but potent, clinically plausible, broad-spectrum examples have not yet been identified with certainty [ 17 , 18 , 19 , 20 , 21 ] and remain elusive [ 22 , 23 , 24 , 25 , 26 ]. Snake venom PLA2s, in particular, play a critical role in early morbidity and mortality from snakebite, causing death by paralysis as well as destruction of tissues and derangement of homeostatic mechanisms critical for regulation of coagulation and oxygen transport [ 27 , 28 , 29 , 30 ].…”

“…Unless given shortly after a bite, antivenom is generally considered ineffective in the setting of neurotoxin-induced pathology because of its inability to penetrate peripheral and central nervous system tissues [ 13 , 31 ]. Additionally, snake venom sPLA2s are not as antigenic as larger, more foreign proteins, such as svMPs [ 22 , 23 , 24 , 25 , 26 ]. Thus, snake venom sPLA2s are as an ideal target for other types of therapeutics, such as small molecule therapeutics [ 2 ].…”