Novel phospholipase A2 inhibitors from python serum are potent peptide antibiotics

Proteomic characterization and biological activities of the mucus produced by the zoanthid Palythoa caribaeorum (Duchassaing & Michelotti, 1860)

Mucus, produced by Palythoa caribaeorum has been popularly reported due to healing, anti-inflammatory, and analgesic effects. However, biochemical and pharmacological properties of this mucus remains unexplored. Therefore, the present study aimed to study its proteome profile by 2DE electrophoresis and MALDI-TOF. Furthermore, it was evaluated the cytotoxic, antibacterial, and antioxidant activities of the mucus and from its protein extract (PE). Proteomics study identified14 proteins including proteins involved in the process of tissue regeneration and death of tumor cells. The PE exhibited cell viability below 50% in the MCF-7 and S-180 strains. It showed IC50 of 6.9 μg/mL for the J774 lineage, and also, favored the cellular growth of fibroblasts. Furthermore, PE revealed activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Staphylococcus epidermidis (MIC of 250 μg/mL). These findings revealed the mucus produced by Palythoa caribaeorum with biological activities, offering alternative therapies for the treatment of cancer and as a potential antibacterial agent.

Mapping possible interaction sites for crotoxin in CNF, a gamma PLA2 inhibitor from Crotalus durissus terrificus rattle snake, using SPOT synthesis

Phospholipases A2 (PLA2s) are main components of snake venoms. Several snake species possess endogenous PLA2 inhibitors in their circulating blood, which are generally known as sbPLIs (an acronym for snake blood phospholipase A2inhibitors). The sbPLIs are categorized in three classes (alpha, beta or gamma) depending on the existence of distinguishing protein domains in their structure. The Crotalus durrissus terrificus venom has a highly neurotoxic PLA2 - crotoxin (CTX) - in its composition and the self-protection of the snake is mainly ensured by a sbγPLI named CNF (standing for Crotalusneutralizing factor). In an attempt to find smaller molecules able to inhibit the catalytic activity of CTX, in the present study we used linear peptide arrays to identify CNF segments possibly involved in the interaction with the toxin. Five reacting segments were identified as possible interacting regions. The target peptides were synthesized and located in the in silico CNF structure. Although all of them are exposed to the solvent, high concentrations were needed to inhibit the PLA2 activity of the whole venom or CTX. Limitations of the methodology employed and particular characteristics of CTX inhibition by CNF are discussed.

Purification of PaTx-II from the Venom of the Australian King Brown Snake and Characterization of Its Antimicrobial and Wound Healing Activities

Infections caused by multi-drug-resistant (MDR) bacteria are a global threat to human health. As venoms are the source of biochemically diverse bioactive proteins and peptides, we investigated the antimicrobial activity and murine skin infection model-based wound healing efficacy of a 13 kDa protein. The active component PaTx-II was isolated from the venom of Pseudechis australis (Australian King Brown or Mulga Snake). PaTx-II inhibited the growth of Gram-positive bacteria in vitro, with moderate potency (MICs of 25 µM) observed against S. aureus, E. aerogenes, and P. vulgaris. The antibiotic activity of PaTx-II was associated with the disruption of membrane integrity, pore formation, and lysis of bacterial cells, as evidenced by scanning and transmission microscopy. However, these effects were not observed with mammalian cells, and PaTx-II exhibited minimal cytotoxicity (CC₅₀ > 1000 µM) toward skin/lung cells. Antimicrobial efficacy was then determined using a murine model of S. aureus skin infection. Topical application of PaTx-II (0.5 mg/kg) cleared S. aureus with concomitant increased vascularization and re-epithelialization, promoting wound healing. As small proteins and peptides can possess immunomodulatory effects to enhance microbial clearance, cytokines and collagen from the wound tissue samples were analyzed by immunoblots and immunoassays. The amounts of type I collagen in PaTx-II-treated sites were elevated compared to the vehicle controls, suggesting a potential role for collagen in facilitating the maturation of the dermal matrix during wound healing. Levels of the proinflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and interleukin-10 (IL-10), factors known to promote neovascularization, were substantially reduced by PaTx-II treatment. Further studies that characterize the contributions towards efficacy imparted by in vitro antimicrobial and immunomodulatory activity with PaTx-II are warranted.

Emerging role of biologics for the treatment of melioidosis and glanders

Introduction: Two important pathogenic species within the genus Burkholderia, namely Burkholderia pseudomallei (Bpm) and Burkholderia mallei (Bm), are the causative agents of the life-threatening diseases melioidosis and glanders, respectively. Due to their high mortality rate and potential for aerosolization, they have gained interest as potential biothreat agents and are classified as Tier 1 Select Agents.Areas covered: The manuscript provides an overview of the literature covering the efforts taken in the last 10 years to develop new therapeutics measures against both Bpm and Bm, with attention on novel therapeutic agents.Expert Opinion: As a result of the complicated antibiotic regimens necessary to treat these infections, development of novel therapeutics is needed to treat both diseases. In recent years, the understanding of the pathogenesis of Burkholderia has improved significantly and so have the efforts to develop novel therapeutic agents with high efficacy, either alone, or in combination with conventional antibiotics.

Endogenous phospholipase A2 inhibitors in snakes: a brief overview

The blood plasma of numerous snake species naturally comprises endogenous phospholipase A₂ inhibitors, which primarily neutralize toxic phospholipases A₂ that may eventually reach their circulation. This inhibitor type is generally known as snake blood phospholipase A₂ inhibitors (sbPLIs). Most, if not all sbPLIs are oligomeric glycosylated proteins, although the carbohydrate moiety may not be essential for PLA₂ inhibition in every case. The presently known sbPLIs belong to one of three structural classes – namely sbαPLI, sbβPLI or sbγPLI – depending on the presence of characteristic C-type lectin-like domains, leucine-rich repeats or three-finger motifs, respectively. Currently, the most numerous inhibitors described in the literature are sbαPLIs and sbγPLIs, whereas sbβPLIs are rare. When the target PLA₂ is a Lys49 homolog or an Asp49 myotoxin, the sbPLI is denominated a myotoxin inhibitor protein (MIP). In this brief overview, the most relevant data on sbPLIs will be presented. Representative examples of sbαPLIs and sbγPLIs from two Old World – Gloydius brevicaudus and Malayopython reticulatus – and two New World – Bothrops alternatus and Crotalus durissus terrificus – snake species will be emphasized.

Antimicrobial activity of Tachyplesin 1 against Burkholderia pseudomallei: an in vitro and in silico approach

Burkholderia pseudomallei, the causative agent of melioidosis, is intrinsically resistant to many conventional antibiotics. Therefore, alternative antimicrobial agents such as antimicrobial peptides (AMPs) are extensively studied to combat this issue. Our study aims to identify and understand the mode of action of the potential AMP(s) that are effective against B. pseudomallei in both planktonic and biofilm state as well as to predict the possible binding targets on using in vitro and in silico approaches. In the in vitro study, 11 AMPs were tested against 100 B. pseudomallei isolates for planktonic cell susceptibility, where LL-37, and PG1, demonstrated 100.0% susceptibility and TP1 demonstrated 83% susceptibility. Since the B. pseudomallei activity was reported on LL-37 and PG1, TP1 was selected for further investigation. TP1 inhibited B. pseudomallei cells at 61.69 μM, and membrane blebbing was observed using scanning electron microscopy. Moreover, TP1 inhibited B. pseudomallei cell growth, reaching bactericidal endpoint within 2 h post exposure as compared to ceftazidime (CAZ) (8 h). Furthermore, TP1 was shown to suppress the growth of B. pseudomallei cells in biofilm state at concentrations above 221 μM. However, TP1 was cytotoxic to the mammalian cell lines tested. In the in silico study, molecular docking revealed that TP1 demonstrated a strong interaction to the common peptide or inhibitor binding targets for lipopolysaccharide of Escherichia coli, as well as autolysin, pneumolysin, and pneumococcal surface protein A (PspA) of Streptococcus pneumoniae. Homology modelled B. pseudomallei PspA protein (YDP) also showed a favourable binding with a strong electrostatic contribution and nine hydrogen bonds. In conclusion, TP1 demonstrated a good potential as an anti-B. pseudomallei agent.

Isolation and biochemical characterization of a gamma-type phospholipase A2 inhibitor from Macropisthodon rudis snake serum

A novel phospholipaseA₂ (PLA₂) inhibitory protein (PLI) was purified from the serum of Macropisthodon rudis, a non-venomous snake mainly found in southern China. The molecular mass of the purified PLI was 160 kDa as determined by Superdex 200HR; however, the PLI protein had only one subunit of 25.4 kDa as determined by 12% SDS-PAGE, indicating an oligomeric protein. PLI cDNA obtained by PCR from the liver of Macropisthodon rudis, revealed 549 bps coding for a mature protein of 183 amino acid residues. Based on an amino acid sequence alignment with venomous and non-venomous snakes, this inhibitor was determined to be in the γ type family of PLI. In vitro experiments showed that PLIγ inhibited enzymatic, inflammatory, and antibacterial activities of snake venom PLA₂ isolated from Agkistrodon acutus.

A brief update on potential molecular mechanisms underlying antimicrobial and wound-healing potency of snake venom molecules

Infectious diseases remain a significant cause of morbidity and mortality worldwide. A wide range of diverse, novel classes of natural antibiotics have been isolated from different snake species in the recent past. Snake venoms contain diverse groups of proteins with potent antibacterial activity against a wide range of human pathogens. Some snake venom molecules are pharmacologically attractive, as they possess promising broad-spectrum antibacterial activities. Furthermore, snake venom proteins (SVPs)/peptides also bind to integrins with high affinity, thereby inhibiting cell adhesion and accelerating wound healing in animal models. Thus, SVPs are a potential alternative to chemical antibiotics. The mode of action for many antibacterial peptides involves pore formation and disruption of the plasma membrane. This activity often includes modulation of nuclear factor kappa B (NF-κB) activation during skin wound healing. The NF-κB pathway negatively regulates the transforming growth factor (TGF)-β1/Smad pathway by inducing the expression of Smad7 and eventually reducing in vivo collagen production at the wound sites. In this context, SVPs that regulate the NF-κB signaling pathway may serve as potential targets for drug development.

Identification of synergists that potentiate the action of polymyxin B against Burkholderia cenocepacia

Burkholderia cenocepacia and other members of the Burkholderia cepacia complex (BCC) are highly multidrug-resistant bacteria that cause severe pulmonary infections in patients with cystic fibrosis. A screen of 2686 compounds derived from marine organisms identified molecules that could synergise with polymyxin B (PMB) to inhibit the growth of B. cenocepacia. At 1 μg/mL, five compounds synergised with PMB and inhibited the growth of B. cenocepacia by ≥70% compared with growth in PMB alone. Follow-up testing revealed that one compound from the screen, the aminocoumarin antibiotic novobiocin, synergised with PMB and colistin against tobramycin-resistant clinical isolates of B. cenocepacia and Burkholderia multivorans. In parallel, we show that novobiocin sensitivity is common among BCC species and that these bacteria are even more susceptible to an alternative aminocoumarin, clorobiocin, which also had an additive effect with PMB against B. cenocepacia. These studies support using aminocoumarin antibiotics to treat BCC infections and show that synergisers can be found to increase the efficacy of antimicrobial peptides and polymyxins against BCC bacteria.