Structural requirements for the edema-inducing and hemolytic activities of mastoparan B isolated from the hornet (Vespa basalis) venom

Unwrapping the structural and functional features of antimicrobial peptides from wasp venoms

The study of wasp venoms has captured attention due to the presence of a wide variety of active compounds, revealing a diverse array of biological effects. Among these compounds, certain antimicrobial peptides (AMPs) such as mastoparans and chemotactic peptides have emerged as significant players, characterized by their unique amphipathic short linear alpha-helical structure. These peptides exhibit not only antibiotic properties but also a range of other biological activities, which are related to their ability to interact with biological membranes to varying degrees. This review article aims to provide updated insights into the structure/function relationships of AMPs derived from wasp venoms, linking this knowledge to the potential development of innovative treatments against infections.

Highly potent antimicrobial peptide derivatives of bovine cateslytin

The antimicrobial activity of bovine cateslytin was optimized in a series of sequential modifications leading to synlytin, a highly potent non-haemolytic antimicrobial peptide.

Discovery of an ultra-short linear antibacterial tetrapeptide with anti-MRSA activity from a structure-activity relationship study

The overuse and misuse of antibiotics has resulted in the emergence of drug-resistant pathogenic bacteria, including meticillin-resistant Staphylococcus aureus (MRSA), the primary pathogen responsible for human skin and soft-tissue infections. Antibacterial peptides are known to kill bacteria by rapidly disrupting their membranes and are deemed plausible alternatives to conventional antibiotics. One advantage of their membrane-targeting mode of action is that bacteria are unlikely to develop resistance as changing their cell membrane structure and morphology would likely involve extensive genetic mutations. However, major concerns in using peptides as antibacterial drugs include their instability towards plasma proteases, toxicity towards human cells due to their membrane-targeting mode of action and high manufacturing cost. These concerns can be mitigated by developing peptides as topical agents, by the judicial selection of amino acids and developing very short peptides respectively. In this preliminary report, we reveal a linear, non-hemolytic tetrapeptide with rapid bactericidal activity against MRSA developed from a structure-activity relationship study based on the antimicrobial hexapeptide WRWRWR-NH2. Our finding opens promising avenues for the development of ultra-short antibacterials to treat multidrug-resistant MRSA skin and soft tissue infections.

Effects of 'casoparan', a peptide isolated from casein hydrolysates with mastoparan-like properties

Casein, a protein found in milk of several species, is divided into different chains from 19 to 25 kDa. Casein is also considered as a source of amino acids and generating peptides with biological activities such as opiate, immunostimulating, antibacterial, peptidase inhibitors, among others. In this work, Sephadex G-10 chromatography followed by high-performance liquid chromatography isolation purified NZCase TT, an industrial culture media for tetanus toxin production. In the first step, four pools were isolated and tested in different assays: isolated smooth muscle assay (guinea pig ileum, rat uterus), phagocytosis in vitro of opsonized sheep red blood cells, and hydrogen peroxide (H2O2) release from mouse peritoneal macrophages. Pool III was the main active pool being able to potentiate bradykinin action in guinea pig ileum, stimulating phagocitic activity by resident macrophages and increasing H2O2 release from macrophages previously activated with bacille Calmette Guérin. Using mass spectra the primary structure of the main peptide from pool III was obtained--INKKI, which corresponds to beta-casein fragment 26-30. The immunostimulating action is probably related to a direct action in macrophage cells.

Venom from the ectoparasitic wasp Nasonia vitripennis increases Na+ influx and activates phospholipase C and phospholipase A2 dependent signal transduction pathways in cultured insect cells

The mode of action of venom from the ectoparasitic wasp Nasonia vitripennis in eliciting cell death was examined using an in vitro approach with BTI-TN-5B1-4 cells, and the cell responses were compared to those evoked by the extensively studied wasp toxin mastoparan. Wasp venom increased plasma membrane permeability to Na+, resulting in cellular swelling and death due to oncosis. When ouabain was used to disable Na+, K+-ATPases, the effects of venom were enhanced. Measurements of intracellular calcium using fluo-4 AM revealed a rearrangement and an increase in cytosolic [Ca+2]i within 30 min after exposure of BTI-TN-5B1-4 cells to venom. This venom-mediated increase in Ca+2 was apparently due to mobilization of intracellular stores since the changes occurred in the absence of extracellular Ca+2. Phospholipase C (PLC) inhibitors, neomycin and U-73122, blocked the venom-induced death temporarily (<3h), but by 24h, all venom-treated cells swelled and lysed. Pre-treatment of cells with caffeine or theophylline but not ryanodine attenuated the induction of oncosis by wasp venom. Anti-inflammatory peptide 1 (antiflammin 1) but not bromophenacyl bromide, agents that block phospholipase A2 (PLA2) activity, abolished the responsiveness of BTI-TN-5B1-4 cells to venom. These results suggest that venom initiates cell death by inducing Ca+2 release from intracellular stores probably via phospholipase C and IP3. A possible mode of action for venom from N. vitripennis requiring dual activation of PLC and PLA2 is discussed and compared to the pathways known to be activated by mastoparan.

Enhancing the hypotensive effect and diminishing the cytolytic activity of hornet mastoparan B by D-amino acid substitution

Mastoparan B (MP-B) is a cationic tetradecapeptide (LKLKSIVSWAKKVL-CONH(2)) isolated from the venom of the Taiwan hornet Vespa basalis. Unlike other vespid mastoparans, the peptide is capable of inducing short-term hypotension and causes hemolysis in animals. This study was aimed to find out MP-B analogs that possess higher hypotensive potency with the least lytic action by D-amino acid substitution, especially at lysine (Lys) residues. The synthetic MP-B isomer in which Lys(2) was replaced by D-Lys showed a significant decrease in both hemolytic and hypotensive activities. Substitution of Lys(4) by D-Lys in MP-B also caused a marked reduction of hemolytic activity, but its hypotensive action was only slightly affected. However, when Lys(11,12) were replaced by D-Lys, the resulting isomer ([D-Lys(11,12)]MP-B) exhibited a higher hypotensive activity with negligible hemolytic activity as compared with the native peptide. The D-antipot of MP-B in which all amino acid residues were replaced by D-isomers showed the highest hypotensive activity with a hemolytic activity about 1/5 that of MP-B. The results reveal that D-Lys substitution at the N-terminus of MP-B (Lys(2,4)) causes decreases in both hypotensive and hemolytic activities, while D-Lys substitution at the C-terminus (Lys(11,12)) leads to a significant increase in hypotensive activity of MP-B with a remarkable decrease in hemolytic activity. The hypotensive effect of [D-Lys(11,12)]MP-B was more prominent on spontaneously hypertensive rats. At a proper dose (0.3mg/kg) the peptide could reduce the high blood pressure (approximately 180 mmHg) of the rat to a normal level (approximately 120 mmHg) for more than 3h. [D-Lys(11,12)]MP-B which possesses a potent hypotensive action with the least cytolytic side effect is the best MP-B analog for studying the mechanism of cardiovascular inhibition by MP-B and could be useful as a hypotensive agent in hypertension crisis.

The role of tryptophan residues in the hemolytic activity of stonustoxin,a lethal factor from stonefish (Synanceja horrida) venom

Stonustoxin (SNTX) is a pore-forming cytolytic lethal factor, isolated from the venom of the stonefish Synanceja horrida, that has potent hemolytic activity. The role of tryptophan residues in the hemolytic activity of SNTX was investigated. Oxidation of tryptophan residues of SNTX with N-bromosuccinimide (NBS) resulted in loss of hemolytic activity. Binding of 8-anilino-1-naphthalenesulphonate (ANS) to SNTX resulted in occlusion of tryptophan residues that resulted in loss of hemolytic activity. Circular dichroism and fluorescence studies indicated that ANS binding resulted in a conformational change of SNTX, in particular, a relocation of surface tryptophan residues to the hydrophobic interior. NBS-modification resulted in oxidised surface tryptophan residues that did not relocate to the hydrophobic interior. These results suggest that native surface tryptophan residues play a pivotal role in the hemolytic activity of STNX, possibly by being an essential component of a hydrophobic surface necessary for pore-formation. This study is the first report on the essentiality of tryptophan residues in the activity of a lytic and lethal factor from a fish venom.

Effects of mastoparan B and its analogs on the phospholipase D activity in L1210 cells

Mastoparan B (MP-B), an amphiphilic alpha-helical peptide isolated from hornet venom, and its Ala-substituted analogs were examined for their effectiveness on phospholipase D (PLD) activity in L1210 cells. PLD activity was determined by measuring phosphatidylethanol produced from [3H]myristate-labelled cells in the presence of ethanol. PLD activity was stimulated by MP-B, 4MP-B (Lys4-->Ala), and 12MP-B (Lys12-->Ala), but not by 3MP-B (Leu3-->Ala) and 9MP-B (Trp9-->Ala). Other MPs including mastoparan 7 also stimulated the PLD activity, but inactive mastoparan 17 did not. The stimulatory effect of various MP analogs could be correlated with their alpha-helical contents. The PLD activity stimulated by MP-B was not affected by G-protein blocking chemicals. The extent of PLD stimulation by various MP-Bs, as well as by digitonin and beta-escin, correlated with the permeability of the membrane to ethidium bromide. These results suggest that the stimulation of PLD activity by MP-B in L1210 cells is probably coupled with membrane perturbation brought about by the peptide.

Structures and biological activities of new wasp venom peptides isolated from the black-bellied hornet (Vespa basalis) venom

The black-bellied hornet (Vespa basalis) is the most dangerous species of vespine wasps found in Taiwan. The hornet possesses a highly toxic venom which is rich in toxin, enzymes and biologically active peptides. Using ultrafiltration to remove the high molecular weight toxin and enzymes followed by reverse-phase HPLC, three bioactive tridecapeptides, designated "HP-1, HP-2 and HP-3" were isolated from the venom. Their amino acid sequences were determined as: HP-1: LFRLIAKTLGSLM, HP-2: LFRLLANTLGKIL, HP-3: IFGLLAKTLGNLF. The primary structures of these peptides appear to be homologous to those of chemotactic peptides isolated from other vespid venoms. However, these peptides show little chemotactic activity on human neutrophils and have distinct tripeptide sequences at the amino and carboxylic terminal sides, as compared with other hornet chemotactic peptides. The lack of Pro3 which is a characteristic structure of vespid chemotactic peptides in their sequences is most distinctive. Circular dichroism spectra of these peptides measured in 20% trifluoroethanol show a high content of alpha-helical conformation. All three peptides provoked local edema in rat hind paw, which could be inhibited by antihistamine (diphenhydramine) and drug with antiserotonin activity (cyproheptadine). These peptides also exhibited a potent hemolytic activity which was potentiated by a non-lytic dose of the hornet lethal protein, suggesting a supporting role of these peptides in the lethal effect of Vespa basalis venom.