The Synthetic Peptide LyeTx I mn∆K, Derived from Lycosa erythrognatha Spider Toxin, Is Active against Methicillin-Resistant Staphylococcus aureus (MRSA) In Vitro and In Vivo

The urgent global health challenge posed by methicillin-resistant Staphylococcus aureus (MRSA) infections demands effective solutions. Antimicrobial peptides (AMPs) represent promising tools of research of new antibacterial agents and LyeTx I mn∆K, a short synthetic peptide based on the Lycosa erythrognatha spider venom, is a good representative. This study focused on analyzing the antimicrobial activities of LyeTx I mn∆K, including minimum inhibitory and bactericidal concentrations, synergy and resensitization assays, lysis activity, the effect on biofilm, and the bacterial death curve in MRSA. Additionally, its characterization was conducted through isothermal titration calorimetry, dynamic light scattering, calcein release, and finally, efficacy in a mice wound model. The peptide demonstrates remarkable efficacy against planktonic cells (MIC 8-16 µM) and biofilms (>30% of inhibition) of MRSA, and outperforms vancomycin in terms of rapid bactericidal action and anti-biofilm effects. The mechanism involves significant membrane damage. Interactions with bacterial model membranes, including those with lysylphosphatidylglycerol (LysylPOPG) modifications, highlight the versatility and selectivity of this compound. Also, the peptide has the ability to sensitize resistant bacteria to conventional antibiotics, showing potential for combinatory therapy. Furthermore, using an in vivo model, this study showed that a formulated gel containing the peptide proved superior to vancomycin in treating MRSA-induced wounds in mice. Together, the results highlight LyeTx I mnΔK as a promising prototype for the development of effective therapeutic strategies against superficial MRSA infections.

Jelleine, a Family of Peptides Isolated from the Royal Jelly of the Honey Bees (Apis mellifera), as a Promising Prototype for New Medicines: A Narrative Review

The jelleine family is a group of four peptides (jelleines I-IV) originally isolated from the royal jelly of honey bee (Apis mellifera), but later detected in some honey samples. These oligopeptides are composed of 8-9 amino acid residues, positively charged (+2 to +3 at pH 7.2), including 38-50% of hydrophobic residues and a carboxamide C-terminus. Jelleines, generated by processing of the C-terminal region of major royal jelly proteins 1 (MRJP-1), play an important biological role in royal jelly conservation as well as in protecting bee larvae from potential pathogens. Therefore, these molecules present numerous benefits for human health, including therapeutic purposes as shown in preclinical studies. In this review, we aimed to evaluate the biological effects of jelleines in addition to characterising their toxicities and stabilities. Jelleines I-III have promising antimicrobial activity and low toxicity (LD50 > 1000 mg/Kg). However, jelleine-IV has not shown relevant biological potential. Jelleine-I, but not the other analogues, also has antiparasitic, healing, and pro-coagulant activities in addition to indirectly modulating tumor cell growth and controlling the inflammatory process. Although it is sensitive to hydrolysis by proteases, the addition of halogens increases the chemical stability of these molecules. Thus, these results suggest that jelleines, especially jelleine-I, are a potential target for the development of new, effective and safe therapeutic molecules for clinical use.

PnPP-15, a Synthetic Peptide Derived from a Toxin from Phoneutria nigriventer Spider Venom, Alleviates Diabetic Neuropathic Pain and Acts Synergistically with Pregabalin in Mice

Diabetic neuropathic pain is one of the complications that affect a wide variety of the diabetic population and is often difficult to treat. Only a small number of patients experience pain relief, which usually comes with onerous side effects and low levels of satisfaction. The search for new analgesic drugs is necessary, given the limitations that current drugs present. Combining drugs to treat neuropathic pain has been attracting interest to improve their efficacy compared to single-drug monotherapies while also reducing dose sizes to minimize side effects. The aim of our study was to verify the antinociceptive effect of a synthetic peptide, PnPP-15, alone and combined with pregabalin, in male Swiss diabetic mice using the von Frey method. PnPP-15 is a synthetic peptide derived from PnPP19, a peptide representing a discontinuous epitope of the primary structure of the toxin PnTx2-6 from the venom of the spider Phoneutria nigriventer. The antinociceptive activity of both compounds was dose-dependent and showed synergism, which was verified by isobolographic analysis. Treatment with PnPP-15 did not cause spontaneous or forced motor changes and did not cause any damage or signs of toxicity in the analyzed organs (pancreas, lung, heart, kidney, brain, or liver). In conclusion, PnPP-15 is a great candidate for an analgesic drug against neuropathic pain caused by diabetes and exerts a synergistic effect when combined with pregabalin, allowing for even more efficient treatment.

Therapeutic Prospection of Animal Venoms-Derived Antimicrobial Peptides against Infections by Multidrug-Resistant Acinetobacter baumannii: A Systematic Review of Pre-Clinical Studies

Infections caused by multidrug-resistant Acinetobacter baumannii (MDR-Ab) have become a public health emergency. Due to the small therapeutic arsenal available to treat these infections, health agencies have highlighted the importance of developing new antimicrobials against MDR-Ab. In this context, antimicrobial peptides (AMPs) stand out, and animal venoms are a rich source of these compounds. Here, we aimed to summarize the current knowledge on the use of animal venom-derived AMPs in the treatment of MDR-Ab infections in vivo. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The eight studies included in this review identified the antibacterial activity of eleven different AMPs against MDR-Ab. Most of the studied AMPs originated from arthropod venoms. In addition, all AMPs are positively charged and rich in lysine residues. In vivo assays showed that the use of these compounds reduces MDR-Ab-induced lethality and bacterial load in invasive (bacteremia and pneumonia) and superficial (wounds) infection models. Moreover, animal venom-derived AMPs have pleiotropic effects, such as pro-healing, anti-inflammatory, and antioxidant activities, that help treat infections. Animal venom-derived AMPs are a potential source of prototype molecules for the development of new therapeutic agents against MDR-Ab.

Antifungal activity of a shortened analogue of the natural peptide LyeTx I isolated from the venom of the spider Lycosa erythrognatha

The increase in the incidence of fungal infections associated with the limited therapeutic arsenal available and the increasing rate of resistance of pathogenic fungi reinforce the need for research of new antifungal agents. Thus, this study aims to evaluate the antifungal activity of the peptide LyeTx I mnΔK, a shortened analogue of the natural peptide LyeTx I derived from spider venom, against Candida species. LyeTx I mnΔK showed potent activity against Candida spp. with minimum inhibitory concentration (MIC) and minimum fungicide concentration (MFC) between 4 and 32 µM. The peptide also completely inhibited the yeast-to-hypha transition (at 2 µM) and broke mature biofilms (67% reduction at 32 µM) of C. albicans. In addition, LyeTx I mnΔK did not induce resistance in C. albicans during 21 days of exposure. Therefore, the LyeTx I mnΔK is a promising prototype for the development of new antifungal agents.

PEGylation of the antimicrobial peptide LyeTx I-b maintains structure-related biological properties and improves selectivity

The biological activity of antimicrobial peptides and proteins is closely related to their structural aspects and is sensitive to certain post-translational modifications such as glycosylation, lipidation and PEGylation. However, PEGylation of protein and peptide drugs has expanded in recent years due to the reduction of their toxicity. Due to their size, the PEGylation process can either preserve or compromise the overall structure of these biopolymers and their biological properties. The antimicrobial peptide LyeTx I-b_cys was synthesized by Fmoc strategy and coupled to polyethylene glycol 2.0 kDa. The conjugates were purified by HPLC and characterized by MALDI-ToF-MS analysis. Microbiological assays with LyeTx I-b_cys and LyeTx I-bPEG were performed against Staphylococcus aureus (ATCC 33591) and Escherichia coli (ATCC 25922) in liquid medium. MIC values of 2.0 and 1.0 µM for LyeTx I-b_cys and 8.0 and 4.0 µM for LyeTx I-bPEG were observed against S. aureus and E. coli, respectively. PEGylation of LyeTx I-b_cys (LyeTx I-bPEG) decreased the cytotoxicity determined by MTT method for VERO cells compared to the non-PEGylated peptide. In addition, structural and biophysical studies were performed to evaluate the effects of PEGylation on the nature of peptide-membrane interactions. Surface Plasmon Resonance experiments showed that LyeTx I-b binds to anionic membranes with an association constant twice higher than the PEGylated form. The three-dimensional NMR structures of LyeTx I-b_cys and LyeTx I-bPEG were determined and compared with the LyeTx I-b structure, and the hydrodynamic diameter and zeta potential of POPC:POPG vesicles were similar upon the addition of both peptides. The mPEG-MAL conjugation of LyeTx I-b_cys gave epimers, and it, together with LyeTx I-bPEG, showed clear α-helical profiles. While LyeTx I-b_cys showed no significant change in amphipathicity compared to LyeTx I-b, LyeTx I-bPEG was found to have a slightly less clear separation between hydrophilic and hydrophobic faces. However, the similar conformational freedom of LyeTx I-b and LyeTx I-bPEG suggests that PEGylation does not cause significant structural changes. Overall, our structural and biophysical studies indicate that the PEGylation does not alter the mode of peptide interaction and maintains antimicrobial activity while minimizing tissue toxicity, which confirmed previous results obtained in vivo. Interestingly, significantly improved proteolytic resistance to trypsin and proteinase K was observed after PEGylation.

From the PnTx2-6 Toxin to the PnPP-19 Engineered Peptide: Therapeutic Potential in Erectile Dysfunction, Nociception, and Glaucoma

The venom of the “armed” spider Phoneutria nigriventer comprises several potent toxins. One of the most toxic components from this venom is the neurotoxin PnTx2-6 (LD50 = ∼ 0.7 μg/mouse, 48 residues, five disulfide bridges, MW = 5,289.31 Da), which slows down the inactivation of various Na+ channels. In mice and rats, this toxin causes priapism, an involuntary and painful erection, similar to what is observed in humans bitten by P. nigriventer. While not completely elucidated, it is clear that PnTx2-6 potentiates erectile function via NO/cGMP signaling, but it has many off-target effects. Seeking to obtain a simpler and less toxic molecule able to retain the pharmacological properties of this toxin, we designed and synthesized the peptide PnPP-19 (19 residues, MW = 2,485.6 Da), representing a discontinuous epitope of PnTx2-6. This synthetic peptide also potentiates erectile function via NO/cGMP, but it does not target Na+ channels, and therefore, it displays nontoxic properties in animals even at high doses. PnPP-19 effectively potentiates erectile function not only after subcutaneous or intravenous administration but also following topical application. Surprisingly, PnPP-19 showed central and peripheral antinociceptive activity involving the opioid and cannabinoid systems, suggesting applicability in nociception. Furthermore, considering that PnPP-19 increases NO availability in the corpus cavernosum, this peptide was also tested in a model of induced intraocular hypertension, characterized by low NO levels, and it showed promising results by decreasing the intraocular pressure which prevents retinal damage. Herein, we discuss how was engineered this smaller active non-toxic peptide with promising results in the treatment of erectile dysfunction, nociception, and glaucoma from the noxious PnTx2-6, as well as the pitfalls of this ongoing journey.

Pegylated LyeTx I-b peptide is effective against carbapenem-resistant Acinetobacter baumannii in an in vivo model of pneumonia and shows reduced toxicity

The World Health Organization (WHO) has been warning about the importance of developing new drugs against superbugs. Antimicrobial peptides are an alternative in this context, most of them being involved in innate immunity, acting in various ways, and some even showing synergism with commercial antimicrobial agents. LyeTx I-b is a synthetic peptide derived from native LyeTx I, originally isolated from Lycosa erythrognatha spider venom. Although LyeTx I-b is active against several multidrug-resistant bacteria, it shows some hemolytic and cytotoxic effects. To overcome this hindrance, in the present study we PEGylated LyeTx I-b and evaluated its toxicity and in vitro and in vivo activities on pneumonia caused by multi-resistant Acinetobacter baumannii. PEGylated LyeTx I-b (LyeTx I-bPEG) maintained the same MIC value as the non- PEGylated peptide, showed anti-biofilm activity, synergistic effect with commercial antimicrobial agents, and did not induce resistance. Moreover, in vivo experiments showed its activity against pneumonia. Additionally, LyeTx I-bPEG reduced hemolysis up to 10 times, was approximately 2 times less cytotoxic to HEK-293 cells and 4 times less toxic to mice in acute toxicity models, compared to LyeTx I-b. Our results show LyeTx I-bPEG as a promising antimicrobial candidate, significantly active against pneumonia caused by multidrug-resistant A. baumannii.

Tityus serrulatus (Scorpion): From the Crude Venom to the Construction of Synthetic Peptides and Their Possible Therapeutic Application Against Toxoplasma gondii Infection

Toxoplasmosis, caused by Toxoplasma gondii, is a major public concern owing to its neurotropic nature and high morbidity and mortality rates in immunocompromised patients and newborns. Current treatment for this disease is inefficient and produces side effects. Inflammatory mediators produced during T. gondii infection (e.g., cytokines and nitric oxide) are crucial in controlling parasite replication. In this context, Tityus serrulatus venom (TsV) induces the production of inflammatory mediators by immune cells. Thus, this study aimed to isolate and identify the components of TsV with potential anti-T. gondii activity. TsV was extracted from scorpions and lyophilized or loaded onto a column to obtain its fractions. TsV subfractions were obtained using chromatography, and its amino acid sequence was identified and applied to peptide design using bioinformatics tools. The C57BL/6 mice and their harvested macrophages were used to test the anti-Toxoplasma activity of TsV components and peptides. TsV and its fraction F6 attenuated the replication of tachyzoites in macrophages and induced nitric oxide and cytokine (IL-12, TNF, and IL-6) production by infected cells, without host cell toxicity. Moreover, Su6-B toxin, a subfraction of F6, demonstrated anti-T. gondii activity. The partially elucidated and characterized amino acid sequence of Sub6-B demonstrated 93% similarity with T. serrulatus 2 toxin (Ts2). Ts2 mimetic peptides (“Pep1,” “Pep2a,” and “Pep2b”) were designed and synthesized. Pep1 and Pep2a, but not Pep2b, reduced the replication of tachyzoites in macrophages. In vivo, treatment of T. gondii-infected mice with Pep1, Pep2a, or Pep2b decreased the number of cerebral cysts and did not induce hepatotoxicity in the animals. Taken together, our data show promising immunomodulatory and antiparasitic activity of TsV that could be explored and applied in future therapies for treating infectious parasitic diseases such as toxoplasmosis.

A short synthetic peptide, based on LyeTx I from Lycosa erythrognatha venom, shows potential to treat pneumonia caused by carbapenem-resistant Acinetobacter baumannii without detectable resistance

The emergence of antibiotic-resistant bacteria, especially carbapenem-resistant Acinetobacter baumannii (CRAB), together with relative stagnation in the development of effective antibiotics, has led to enormous health and economic problems. In this study, we aimed to describe the antibacterial spectrum of LyeTx I mnΔK, a short synthetic peptide based on LyeTx I from Lycosa erythrognatha venom, against CRAB. LyeTx I mnΔK showed considerable antibacterial activity against extensively resistant A. baumannii, with minimum inhibitory and bactericidal concentrations ranging from 1 to 16 µM and 2 to 32 µM, respectively. This peptide significantly increased the release of 260 nm-absorbing intracellular material from CRAB, suggesting bacteriolysis. LyeTx I mnΔK was shown to act synergistically with meropenem and colistin against CRAB. The cytotoxic concentration of LyeTx I mnΔK against Vero cells (CC50 = 55.31 ± 5.00 µM) and its hemolytic activity (HC50 = 77.07 ± 4.00 µM) were considerably low; however, its antibacterial activity was significantly reduced in the presence of human and animal serum and trypsin. Nevertheless, the inhalation of this peptide was effective in reducing pulmonary bacterial load in a mouse model of CRAB infection. Altogether, these results demonstrate that the peptide LyeTx I mnΔK is a potential prototype for the development of new effective and safe antibacterial agents against CRAB.

Synthetic Peptides Derived From Lycosa Erythrognatha Venom: Interaction With Phospholipid Membranes and Activity Against Resistant Bacteria

Superbugs are a public health problem, increasing the need of new drugs and strategies to combat them. Our group has previously identified LyeTxI, an antimicrobial peptide isolated from Lycosa erythrognatha spider venom. From LyeTxI, we synthesized and characterized a derived peptide named LyeTxI-b, which has shown significant in vitro and in vivo activity. In this work, we elucidate the interaction of LyeTxI-b with artificial membranes as well as its effects on resistant strains of bacteria in planktonic conditions or biofilms. Isothermal titration calorimetry revealed that LyeTxI-b interacts more rapidly and with higher intensity with artificial vesicles, showing higher affinity to anionic vesicles, when compared to synthetic LyeTxI. In calcein experiments, LyeTxI-b caused greater levels of vesicle cleavage. Both peptides showed antibacterial activity at concentrations of μmol L⁻¹ against 12 different clinically isolated strains, in planktonic conditions, in a concentration-dependent manner. Furthermore, both peptides elicited a dose-dependent production of reactive oxygen species in methicillin-resistant Staphylococcus aureus. In S. aureus biofilm assay, LyeTxI-b was more potent than LyeTxI. However, none of these peptides reduced Escherichia coli biofilms. Our results show LyeTxI-b as a promising drug against clinically resistant strains, being a template for developing new antibiotics.

Tityus serrulatus scorpion venom as a potential drug source for Chagas' disease: Trypanocidal and immunomodulatory activity

Current chemical therapies for Chagas Disease (CD) lack ability to clear Trypanosoma cruzi (Tc) parasites and cause severe side effects, making search for new strategies extremely necessary. We evaluated the action of Tityus serrulatus venom (TsV) components during Tc infection. TsV treatment increased nitric oxide and pro-inflammatory cytokine production by Tc-infected macrophages (MØ), decreased intracellular parasite replication and trypomastigotes release, also triggering ERK1/2, JNK1/2 and p38 activation. Ts7 demonstrated the highest anti-Tc activity, inducing high levels of TNF and IL-6 in infected MØ. TsV/Ts7 presented synergistic effect on p38 activation when incubated with Tc antigen. KPP-treatment of MØ also decreased trypomastigotes releasing, partially due to p38 activation. TsV/Ts7-pre-incubation of Tc demonstrated a direct effect on parasite decreasing MØ-trypomastigotes releasing. In vivo KPP-treatment of Tc-infected mice resulted in decreased parasitemia. Summarizing, this study opens perspectives for new bioactive molecules as CD-therapeutic treatment, demonstrating the TsV/Ts7/KPP-trypanocidal and immunomodulatory activity during Tc infection.

Neurotoxic and convulsant effects induced by jack bean ureases on the mammalian nervous system

Ureases are microbial virulence factors either because of the enzymatic release of ammonia or due to many other non-enzymatic effects. Here we studied two neurotoxic urease isoforms, Canatoxin (CNTX) and Jack Bean Urease (JBU), produced by the plant Canavalia ensiformis, whose mechanisms of action remain elusive. The neurotoxins provoke convulsions in rodents (LD₅₀ ∼2 mg/kg) and stimulate exocytosis in cell models, affecting intracellular calcium levels. Here, electrophysiological and brain imaging techniques were applied to elucidate their mode of action. While systemic administration of the toxins causes tonic-clonic seizures in rodents, JBU injected into rat hippocampus induced spike-wave discharges similar to absence-like seizures. JBU reduced the amplitude of compound action potential from mouse sciatic nerve in a tetrodotoxin-insensitive manner. Hippocampal slices from CNTX-injected animals or slices treated in vitro with JBU failed to induce long term potentiation upon tetanic stimulation. Rat cortical synaptosomes treated with JBU released L-glutamate. JBU increased the intracellular calcium levels and spontaneous firing rate in rat hippocampus neurons. MicroPET scans of CNTX-injected rats revealed increased ^[18]Fluoro-deoxyglucose uptake in epileptogenesis-related areas like hippocampus and thalamus. Curiously, CNTX did not affect voltage-gated sodium, calcium or potassium channels currents, neither did it interfere on cholinergic receptors, suggesting an indirect mode of action that could be related to the ureases' membrane-disturbing properties. Understanding the neurotoxic mode of action of C. ensiformis ureases could help to unveil the so far underappreciated relevance of these toxins in diseases caused by urease-producing microorganisms, in which the human central nervous system is affected.

Shortened derivatives from native antimicrobial peptide LyeTx I: In vitro and in vivo biological activity assessment

In the continuing search for novel antibiotics, antimicrobial peptides are promising molecules, due to different mechanisms of action compared to classic antibiotics and to their selectivity for interaction with microorganism cells rather than with mammalian cells. Previously, our research group has isolated the antimicrobial peptide LyeTx I from the venom of the spider Lycosa erythrognatha. Here, we proposed to synthesize three novel shortened derivatives from LyeTx I (LyeTx I mn; LyeTx I mnΔK; LyeTx I mnΔKAc) and to evaluate their toxicity and biological activity as potential antimicrobial agents. Peptides were synthetized by Fmoc strategy and circular dichroism analysis was performed, showing that the three novel shortened derivatives may present membranolytic activity, like the original LyeTx I, once they folded as an alpha helix in 2.2.2-trifluorethanol and sodium dodecyl sulfate. In vitro assays revealed that the shortened derivative LyeTx I mnΔK presents the best score between antimicrobial (↓ MIC) and hemolytic (↑ EC50) activities among the synthetized shortened derivatives, and LUHMES cell-based NeuriTox test showed that it is less neurotoxic than the original LyeTx I (EC50 [LyeTx I mnΔK] ⋙ EC50 [LyeTx I]). In vivo data, obtained in a mouse model of septic arthritis induced by Staphylococcus aureus, showed that LyeTx I mnΔK is able to reduce infection, as demonstrated by bacterial recovery assay (∼10-fold reduction) and scintigraphic imaging (less technetium-99m labeled-Ceftizoxime uptake by infectious site). Infection reduction led to inflammatory process and pain decreases, as shown by immune cells recruitment reduction and threshold nociception increment, when compared to positive control group. Therefore, among the three shortened peptide derivatives, LyeTx I mnΔK is the best candidate as antimicrobial agent, due to its smaller amino acid sequence and toxicity, and its greater biological activity.

Antimicrobial Peptides From Lycosidae (Sundevall, 1833) Spiders

Antimicrobial peptides (AMPs) have been found in all organism taxa and may play an essential role as a host defense system. AMPs are organized in various conformations, such as linear peptides, disulfide bond-linked peptides, backbone-linked peptides and circular peptides. AMPs apparently act primarily on the plasma membrane, although an increasing number of works have shown that they may also target various intracellular sites. Spider venoms are rich sources of biomolecules that show several activities, including modulation or blockage of ion channels, anti-insect, anti-cancer, antihypertensive and antimicrobial activities, among others. In spider venoms from the Lycosidae family there are many linear AMPs with a wide range of activities against several microorganisms. Due to these singular activities, some Lycosidae AMPs have been modified to improve or decrease desirable or undesirable effects, respectively. Such modifications, especially with the aim of increasing their antibiotic activity, have led to the filing of many patent applications. This review explores the abundance of Lycosidae venom AMPs and some of their derivatives, and their use as new drug models.

Small cyclic sodium channel inhibitors

Voltage-gated sodium (Na_V) channels play crucial roles in a range of (patho)physiological processes. Much interest has arisen within the pharmaceutical industry to pursue these channels as analgesic targets following overwhelming evidence that Na_V channel subtypes Na_V1.7-Na_V1.9 are involved in nociception. More recently, Na_V1.1, Na_V1.3 and Na_V1.6 have also been identified to be involved in pain pathways. Venom-derived disulfide-rich peptide toxins, isolated from spiders and cone snails, have been used extensively as probes to investigate these channels and have attracted much interest as drug leads. However, few peptide-based leads have made it as drugs due to unfavourable physiochemical attributes including poor in vivo pharmacokinetics and limited oral bioavailability. The present work aims to bridge the gap in the development pipeline between drug leads and drug candidates by downsizing these larger venom-derived Na_V inhibitors into smaller, more "drug-like" molecules. Here, we use molecular engineering of small cyclic peptides to aid in the determination of what drives subtype selectivity and molecular interactions of these downsized inhibitors across Na_V subtypes. We designed a series of small, stable and novel Na_V probes displaying Na_V subtype selectivity and potency in vitro coupled with potent in vivo analgesic activity, involving yet to be elucidated analgesic pathways in addition to Na_V subtype modulation.

Intravitreal injection of peptides PnPa11 and PnPa13, derivatives of Phoneutria nigriventer spider venom, prevents retinal damage

Background:

PnPa11 and PnPa13 are synthetic peptides derived from Phoneutria nigriventer spider venom, which display antinociceptive and neuroprotective properties. In this work, we evaluated the safety of intravitreal use and the neuroprotective effect of these peptides.

Methods:

The cytotoxicity and the antiangiogenic activity of these peptides were evaluated by the sulforhodamine-B method and chicken chorioallantoic membrane (CAM) assay, respectively. The in vivo safety was analyzed in Wistar rats that were intravitreally injected with different doses (0.50; 1.25; 2.50; 3.75 and 5.00 µg/mL) of these peptides (right eye, n = 6). The retinal function was assessed by electroretinography exams (ERG), intraocular pressure (IOP), and histological analyzes. In order to investigate the neuroprotective effect, Wistar rats received intravitreal injections (right eye, n = 6) of peptides at 1.25 µg/mL and then were exposed to blue LED light. In addition, the visual function and the retinal microstructure were verified.

Results:

Cytotoxicity analyses demonstrated that the peptides did not present any toxicity over ARPE-19 (adult retinal pigmented epithelial) cell line and the antiangiogenic study highlighted that the peptides promoted the reduction of blood vessels. The intravitreal injection did not cause major changes, neither induced any irreversible damage. In the retinal degeneration assay, the ERG records demonstrated that the prior treatment with PnPa11 and PnPa13 protected the retina from damage. Morphological analyses confirmed the ERG findings. Immunoblotting analyses revealed that PnPa11 increased Erk1/2, NR2A, and NR2B retinal expression after the light stress model, but did not cause Akt1 activation, while PnPa13 prevented Erk1/2 and Akt1 dephosphorylation.

Conclusions:

The intraocular administration of these peptides was well tolerated and presented protective activity against retinal degeneration, suggesting the potential use of these peptides as neuroprotectors in the ophthalmological field.

GiTx1(β/κ-theraphotoxin-Gi1a), a novel toxin from the venom of Brazilian tarantula Grammostola iheringi (Mygalomorphae, Theraphosidae): Isolation, structural assessments and activity on voltage-gated ion channels

Spider venoms, despite their toxicity, represent rich sources of pharmacologically active compounds with biotechnological potential. However, in view of the large diversity of the spider species, the full potential of their venom molecules is still far from being known. In this work, we report the purification and structural and functional characterization of GiTx1 (β/κ-TRTX-Gi1a), the first toxin purified from the venom of the Brazilian tarantula spider Grammostola iheringi. GiTx1 was purified by chromatography, completely sequenced through automated Edman degradation and tandem mass spectrometry and its structure was predicted by molecular modeling. GiTx1 has a MW of 3.585 Da, with the following amino acid sequence: SCQKWMWTCDQKRPCCEDMVCKLWCKIIK. Pharmacological activity of GiTx1 was characterized by electrophysiology using whole-cell patch clamp on dorsal root ganglia neurons (DRG) and two-electrode voltage-clamp on voltage-gated sodium and potassium channels subtypes expressed in Xenopus laevis oocytes. GiTx1, at 2 μM, caused a partial block of inward (∼40%) and outward (∼20%) currents in DRG cells, blocked rNav1.2, rNav1.4 and mNav1.6 and had a significant effect on VdNav, an arachnid sodium channel isoform. IC₅₀ values of 156.39 ± 14.90 nM for Nav1.6 and 124.05 ± 12.99 nM for VdNav, were obtained. In addition, this toxin was active on rKv4.3 and hERG potassium channels, but not Shaker IR or rKv2.1 potassium channels. In summary, GiTx1 is a promiscuous toxin with multiple effects on different types of ion channels.

PnPP-19 Peptide as a Novel Drug Candidate for Topical Glaucoma Therapy Through Nitric Oxide Release

Purpose

Evaluation of PnPP-19 safety and efficacy in reducing the intraocular pressure (IOP) of animals with healthy (normotensive) and ocular hypertensive eyes. PnPP-19 is a synthetic peptide designed from Phoneutria nigriventer spider toxin PnTx2-6.

Methods

Toxicity tests used chicken chorioallantoic membranes. Electroretinograms (ERGs) were recorded before and after administration of different doses of PnPP-19 on the eyes of Wistar rats. Histological sections of corneas and retinas were prepared. The efficacy of PnPP-19 in reducing IOP was evaluated for normotensive and ocular hypertensive animals using a tonometer. Ocular hypertension was induced in the right eye through injection of hyaluronic acid (HA) into the anterior chamber. ERG was recorded before and after glaucoma induction. The eyes were enucleated, and the corneas and retinas were histologically evaluated.

Results

PnPP-19 showed no toxicity, being safe for ocular application. A single topical instillation of one eye drop of the peptide solution was able to reduce IOP, both in healthy and ocular hypertensive rats, for 24 hours, without eliciting any apparent toxicity. PnPP-19 is a nitric oxide inducer and the results suggest that it may improve the conventional outflow of aqueous humor (AH), preventing the progression of optic nerve degeneration.

Conclusions

PnPP-19 has great potential to emerge as a promising drug for the treatment of ocular hypertension.

Translational Relevance

We regard our findings as exciting progress in translational glaucoma research, combining drug discovery, natural product research, and pharmacology, which may contribute to the establishment of new therapies for the treatment of this disease.

Rate of polymyxin resistance among Acinetobacter baumannii recovered from hospitalized patients: a systematic review and meta-analysis

We conducted a systematic review and meta-analysis to determine the rate of polymyxin resistance among Acinetobacter baumannii isolates causing infection in hospitalized patients around the world during the period of 2010-2019. The systematic review was performed on September 1, 2019, using PubMed/MEDLINE, Scopus, and Web of Science; studies published after January 1, 2010, were selected. The data were summarized in tables, critically analyzed, and treated statistically using the RStudio® Software with Meta package and Metaprop Command. After applying exclusion factors, 41 relevant studies were selected from 969 articles identified on literature search. The overall rate of polymyxin-resistant A. baumannii (PRAB) related to hospitalized patients was estimated to be 13% (95% CI, 0.06-0.27), where a higher rate was observed in America (29%; 95% CI, 0.12-0.55), followed by Europe (13%; 95% CI, 0.02-0.52), and Asia (10%; 95% CI, 0.02-0.32). The extensive use of polymyxins on veterinary to control bacterial infection and growth promotion, as well as the resurgence in prescription and use of polymyxins in the clinics against carbapenem-resistant gram-negative bacteria, may have contributed to the increased incidence of PRAB. The findings of this meta-analysis revealed that the rate of PRAB recovered from hospitalized patients is distinctively high. Thus, action needs to be taken to develop strategies to combat the clinical incidence of PRAB-induced hospital infections.

Biochemical and functional properties of a new l-amino acid oxidase (LAAO) from Micrurus lemniscatus snake venom

This study reports the purification of ML-LAAO, a new LAAO from the venom of Micrurus lemniscatus snake (ML-V), using size exclusion chromatography. ML-LAAO is a 69-kDa glycoprotein that represents ~2.0% of total venom proteins. This enzyme exhibited optimal activity at pH 8.5, displaying high specificity toward hydrophobic l-amino acids. MALDI TOF/TOF and Blast analysis identified internal segments in ML-LAAO that share high sequence identity with homologous snake venom LAAOs. Western blot analysis on two-dimensional SDS-PAGE of ML-V, using anti-LAAO revealed the presence of ML-LAAO isoforms (pI 6.3-8.9). ML-LAAO blocked aggregation induced by collagen on washed platelets in a rather weak manner, it did not, however, inhibit platelet aggregation induced by ADP on platelet-rich plasma. In addition, this enzyme displayed in vitro antibacterial activity against Staphylococcus aureus (MIC/MBC of 0.39 μg/mL) and in vitro leishmanicidal action against Leishmania amazonensis and L. chagasi (IC₅₀ values of 0.14 and 0.039 μg/mL, respectively). These activities were significantly reduced by catalase, suggesting that hydrogen peroxide production is involved in some way. The data presented here revealed that ML-LAAO has bactericidal and leishmanicidal effects, suggesting that it may have therapeutic potential.

Antinociceptive effect of PnTx4(5-5), a peptide from Phoneutria nigriventer spider venom, in rat models and the involvement of glutamatergic system

Background:

The venom of Phoneutria nigriventer spider is a source of numerous bioactive substances, including some toxins active in insects. An example is PnTx4(5-5) that shows a high insecticidal activity and no apparent toxicity to mice, although it inhibited NMDA-evoked currents in rat hippocampal neurons. In this work the analgesic activity of PnTx4(5-5) (renamed Γ-ctenitoxin-Pn1a) was investigated.

Methods:

The antinociceptive activity was evaluated using the paw pressure test in rats, after hyperalgesia induction with intraplantar injection of carrageenan or prostaglandin E₂ (PGE₂).

Results:

PnTx4(5-5), subcutaneously injected, was able to reduce the hyperalgesia induced by PGE₂ in rat paw, demonstrating a systemic effect. PnTx4(5-5) administered in the plantar surface of the paw caused a peripheral and dose-dependent antinociceptive effect on hyperalgesia induced by carrageenan or PGE₂. The hyperalgesic effect observed in these two pain models was completely reversed with 5 µg of PnTx4(5-5). Intraplantar administration of L-glutamate induced hyperalgesic effect that was significantly reverted by 5 μg of PnTx4(5-5) injection in rat paw.

Conclusion:

The antinociceptive effect for PnTx4(5-5) was demonstrated against different rat pain models, i.e. induced by PGE₂, carrageenan or glutamate. We suggest that the antinociceptive effect of PnTx4(5-5) may be related to an inhibitory activity on the glutamatergic system.

Unveiling the Interplay between the TLR4/MD2 Complex and HSP70 in the Human Cardiovascular System: A Computational Approach

While precise mechanisms underlying cardiovascular diseases (CVDs) are still not fully understood, previous studies suggest that the innate immune system, through Toll-like receptor 4 (TLR4), plays a crucial part in the pathways leading to these diseases, mainly because of its interplay with endogenous molecules. The Heat-shock protein 70 family (HSP70-70kDa) is of particular interest in cardiovascular tissues as it may have dual effects when interacting with TLR4 pathways. Although the hypothesis of the HSP70 family members acting as TLR4 ligands is becoming widely accepted, to date no co-crystal structure of this complex is available and it is still unknown whether this process requires the co-adaptor MD2. In this study, we aimed at investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the human cardiovascular system through transcriptomic data analysis and at proposing a putative interaction model between these proteins. We report compelling evidence of correlated expression levels between TLR4 and MD2 with HSP70 cognate family members, especially in heart tissue. In our molecular docking simulations, we found that HSP70 in the ATP-bound state presents a better docking score towards the TLR4/MD2 complex compared to the ADP-bound state (-22.60 vs. -10.29 kcal/mol, respectively). Additionally, we show via a proximity ligation assay for HSP70 and TLR4, that cells stimulated with ATP have higher formation of fluorescent spots and that MD2 might be required for the complexation of these proteins. The insights provided by our computational approach are potential scaffolds for future in vivo studies investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the cardiovascular system.

A New Topical Eye Drop Containing LyeTxI-b, A Synthetic Peptide Designed from A Lycosa erithrognata Venom Toxin, Was Effective to Treat Resistant Bacterial Keratitis

Bacterial keratitis is an ocular infection that can lead to severe visual disability. Staphylococcus aureus is a major pathogen of the eye. We recently demonstrated the strong antimicrobial activity of LyeTxI-b, a synthetic peptide derived from a Lycosa erithrognatha toxin. Herein, we evaluated a topical formulation (eye drops) containing LyeTxI-b to treat resistant bacterial keratitis. Keratitis was induced with intrastromal injection of 4 × 10⁵ cells (4 µL) in New Zealand female white rabbits. Minimum inhibitory concentration (MIC) and biofilm viability were determined. LyeTxI-b ocular toxicity was evaluated through chorioallantoic membrane and Draize tests. One drop of the formulation (LyeTxI-b 28.9 µmol/L +0.5% CMC in 0.9% NaCl) was instilled into each eye four times a day, for a week. Slit-lamp biomicroscopy analysis, corneal histopathological studies and cellular infiltrate quantification through myeloperoxidase (MPO) and N-acetylglucosaminidase (NAG) detection were performed. LyeTxI-b was very effective in the treatment of keratitis, with no signs of ocular toxicity. Planktonic bacteria MIC was 3.6 µmol/L and LyeTxI-b treatment reduced biofilm viability in 90%. LyeTxI-b eliminated bacteria and reduced inflammatory cellular activity in the eyes. Healthy and treated animals showed similar NAG and MPO levels. LyeTxI-b is a potent new drug to treat resistant bacterial keratitis, showing effective antimicrobial and anti-inflammatory activity.

Intravitreal injection of the synthetic peptide LyeTx I b, derived from a spider toxin, into the rabbit eye is safe and prevents neovascularization in a chorio-allantoic membrane model

Background

The great diversity of molecules found in spider venoms include amino acids, polyamines, proteins and peptides, among others. Some of these compounds can interact with different neuronal receptors and ion channels including those present in the ocular system. To study potential toxicity and safety of intravitreal injection in rabbits of LyeTx I b, a synthetic peptide derived from the toxin LyeTx I found in venom from the spider Lycosa eritrognatha and to evaluate the angiogenic activity on a CAM model.

Methods

ARPE-19 cells were treated with LyeTx I b (0.36; 0.54; 0.72; 2.89; 4.34 or 9.06 μM). In this study, New Zealand rabbits were used. LyeTx I b (2.89 μM) labeled with FITC dissolved in PBS, or only PBS, were injected into vitreous humor. Electroretinogram (ERG) was recorded 1 day before injection and at 7, 14 and 28 days post-injection. Clinical examination of the retina was conducted through tonometer and eye fundus after ERG. Eyes were enucleated and retinas were prepared for histology in order to assess retinal structure. CAMs were exposed to LyeTx I b (0.54; 0.72; 2.17 or 2.89 μM).

Results

ARPE-19 cells exposed to LyeTx I b showed cell viability at the same levels of the control. The fluorescence of LyeTx I b labeled with FITC indicated its retinal localization. Our findings indicate ERG responses from rats injected in the eye with LyeTx I b were very similar to the corresponding responses of those animals injected only with vehicle. Clinical examination found no alterations of intraocular pressure or retinal integrity. No histological damage in retinal layers was observed. CAM presented reduced neovascularization when exposed to LyeTx I b.

Conclusions

Intravitreal injection of LyeTx I b is safe for use in the rabbit eye and prevents neovascularization in the CAM model, at Bevacizumab levels. These findings support intravitreal LyeTx I b as a good candidate to develop future alternative treatment for the retina in neovascularization diseases.

Physicochemical Characterization and Skin Permeation of Cationic Transfersomes Containing the Synthetic Peptide PnPP-19

BACKGROUND

PnPP-19 is a 19-amino-acid synthetic peptide previously described as a novel drug for the treatment of erectile dysfunction.

OBJECTIVE

The aim of this work was to evaluate the physicochemical properties of cationic transfersomes containing PnPP-19 and the skin permeation of free PnPP-19 and PnPP-19-loaded transfersomes.

METHODS

Three different liposomal preparation methods were evaluated. Cationic transfersomes contained egg phosphatidyl choline: stearylamine (9:1 w/w) and Tween 20 (84.6:15.4 lipid:Tween, w/w). Lipid concentration varied from 20 to 40 mM. We evaluated the entrapment percentage, mean diameter, zeta potential and stability at 4 °C of the formulations. The skin permeation assays were performed with abdominal human skin using Franz diffusion cell with 3 cm2 diffusion area at 32 °C and a fluorescent derivative of the peptide, containing 5-TAMRA, bound to PnPP-19 C-terminal region, where an extra lysine was inserted.

RESULTS

Our results showed variable entrapment efficiencies, from 6% to 30%, depending on the preparation method and the lipid concentration used. The reverse phase evaporation method using a total lipid concentration equal to 40 mM led to the best entrapment percentage (30.2 + 4.5%). Free PnPP-19 was able to permeate skin at a rate of 10.8 ng/cm2/h. However, PnPP-19 was specifically hydrolyzed by skin proteases, generating a fragment of 15 amino acid residues. Encapsulated PnPP-19 permeated the skin at a rate of 19.8 ng/cm2/h.

CONCLUSION

The encapsulation of PnPP-19 in cationic transfersomes protected the peptide from degradation, favoring its topical administration.

Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating

Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian Na_V-channel isoforms, one insect Na_V channel and one arachnid Na_V channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on Na_V1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac Na_V channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

Ts1 from the Brazilian scorpion Tityus serrulatus: A half-century of studies on a multifunctional beta like-toxin

The Tityus serrulatus scorpion species represents a serious human health threat to in Brazil because it is among the animals that produces the most dangerous venoms for mammals in South America. Its venom has provided several highly selective ligands that specifically interact with sodium and potassium channels. During the past decades, several international groups published an increasing amount of data on the isolation and the chemical, pharmacological and immunological characterisation of its main β-toxin, Ts1. In this review, we compiled the best available past and recent knowledge on Ts1. Aside from its intricate purification, the state-of-the-art understanding concerning its pharmacological activities is presented. Its solved three-dimensional structure is shown, as well as the possible surface areas of contact between Ts1 and its diverse voltage-gated Na⁺ channel targets. Organisations of the gene and the precursor encoding Ts1 are also tackled based on available cDNA clones or on information obtained from polymerase chain reactions of stretches of scorpion DNA. At last, the immunological studies complete with Ts1 to set up an efficient immunotherapy against the Tityus serrulatus venom are summarized.

Hydrophobic Nanoprecipitates of β-Cyclodextrin/Avermectins Inclusion Compounds Reveal Insecticide Activity against Aedes aegypti Larvae and Low Toxicity against Fibroblasts

In the present work, hydrophobic nanoprecipitates (HNPs) of inclusion complexes formed between β-cyclodextrin (βCD) and the avermectins (AVMs) named eprinomectin (EPRI) and ivermectin (IVER) were synthesized and characterized, and their larvicidal activity against Aedes aegypti and human safety against fibroblasts were evaluated. Initially, thermogravimetric analysis/differential thermal analysis data revealed that inclusion increased the thermal stability of AVMs in the presence of βCD. Nuclear magnetic resonance experiments and density functional theory calculations pointed out the inclusion of the benzofuran ring of the two AVMs in the βCD cavity. Isothermal titration calorimetry experiments allowed identification of different binding constants for EPRI/βCD ( K_b = 1060) and βCD/IVER ( K_b = 1700) systems, despite the structural similarity. Dynamic light scattering titrations of AVMs' dimethyl sulfoxide solution in βCD aqueous solution demonstrated that the formed HNPs have lower sizes in the presence of βCD. Finally, the inclusion of EPRI in βCD increased its larval toxicity and reduced its human cytotoxicity, while for IVER/βCD no beneficial effect was observed upon inclusion. These results were rationalized in terms of structural differences between the two molecules. Finally, the EPRI/βCD complex has great potential as an insecticide against A. aegypti larvae with high human safety.

NMR structures in different membrane environments of three ocellatin peptides isolated from Leptodactylus labyrinthicus

The peptides ocellatin-LB1, -LB2 and -F1 have previously been isolated from anurans of the Leptodactylus genus and the sequences are identical from residue 1-22, which correspond to ocellatin-LB1 sequence (GVVDILKGAAKDIAGHLASKVM-NH₂), whereas ocellatin-LB2 carries an extra N and ocellatin-F1 extra NKL residues at their C-termini. These peptides showed different spectra of activities and biophysical investigations indicated a direct correlation between membrane-disruptive properties and antimicrobial activities, i.e. ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. To better characterize their membrane interactions, we report here the detailed three-dimensional NMR structures of these peptides in TFE-d₂:H₂O (60:40) and in the presence of zwitterionic DPC-d₃₈ and anionic SDS-d₂₅ micellar solutions. Although the three peptides showed significant helical contents in the three mimetic environments, structural differences were noticed. When the structures of the three peptides in the presence of DPC-d₃₈ micelles are compared to each other, a more pronounced curvature is observed for ocellatin-F1 and the bent helix, with the concave face composed mostly of hydrophobic residues, is consistent with the micellar curvature and the amphipathic nature of the molecule. Interestingly, an almost linear helical segment was observed for ocellatin-F1 in the presence of SDS-d₂₅ micelles and the conformational differences in the two micellar environments are possibly related to the presence of the extra Lys residue near the peptide C-terminus, which increases the affinity of ocellatin-F1 to anionic membranes in comparison with ocellatin-LB1 and -LB2, as proved by isothermal titration calorimetry. To our knowledge, this work reports for the first time the three-dimensional structures of ocellatin peptides.

Moving pieces in a cryptomic puzzle: Cryptide from Tityus serrulatus Ts3 Nav toxin as potential agonist of muscarinic receptors

Cryptome is as a subset of a given proteome containing bioactive cryptides embedded in larger peptides or proteins. We pinpointed a striking sequence similarity between two peptides from the Tityus serrulatus venom: Ts10 (KKDGYPVEYDRAY) and the N-terminal of Ts3 (KKDGYPVEYDNCAY). Ts3 (former Tityustoxin or TsIV) is an α-neurotoxin acting on voltage-gated sodium channels while Ts10 (former Peptide T) is a bradykinin-potentiating peptide and was originally reported as inhibitor of the angiotensin-converting enzyme (ACEi). Thus, the goal of this study was to evaluate whether such peptide hidden in the N-terminal of Ts3 (Ts3_1-14[C12S]) was able to mimic known effects of Ts10 as well as to expand the current knowledge of the vascular effects and molecular targets of these peptides. Similar to Ts10, Ts3_1-14[C12S] was able to potentiate the hypotensive effect of bradykinin (BK). However, none of these peptides was able to induce a long-lasting BK-potentiating effect, suggesting that this effect may not be their main biological outcome. On the other hand, we report that Ts10 and mainly Ts3_1-14[C12S] induced a strong vasodilation effect depending on the presence of functional endothelium and nitric oxide (NO) production. Unlike previously reported, Ts10 was not able to inhibit ACE activity (similar result was observed for Ts3_1-14[C12S]). On the other hand, we report that Ts3_1-14[C12S] induces vasodilation via the activation of muscarinic acetylcholine receptors (mAChRs) M2 and M3 while only the activation of mAChR M2 seems to be required for Ts10-induced vasodilation.

Ts14 from Tityus serrulatus boosts angiogenesis and attenuates inflammation and collagen deposition in sponge-induced granulation tissue in mice

We have previously described a 25mer anti-hypertensive peptide, previously named TsHpt-I (Tityus serrulatus Hypotensin-I), now Ts14, as an agonist of B2 kinin receptor. Bradykinin is known to play physiological roles in angiogenic, inflammatory, and fibrogenic processes, mostly mediated by B2 receptor. Therefore, we investigated whether Ts14 could modulate key events (neovascularization, inflammatory cell recruitment, and extracellular matrix deposition) of the fibrovascular tissue, induced by polyether-polyurethane sponge implants in mice. Sponges were implanted in the dorsum of 7-week-old C57Bl/6 male mice that received daily intrasponge treatment with Ts14 (27.25μg/sponge/day in 10μL PBS) or vehicle (10μL PBS/sponge/day) and were assessed on day 7 after surgery. Hemoglobin content, blood flow (laser Doppler perfusion imaging), and VEGF levels in the implants, used as indices of vascularization, indicated that Ts14 enhanced angiogenesis in implants relative to the PBS-treated group. Interestingly, Ts14 reduced TNF-α levels and neutrophil infiltration, although stimulated macrophage infiltration into implants, as determined by myeloperoxidase (MPO) and N-acetyl-β-d-glucosaminidase (NAG) enzyme activities, respectively. Regarding the fibrogenic component (soluble collagen content and Sirius-red histological staining), we observed that Ts14 inhibited collagen deposition in the implants. Overall, our results suggest that Ts14 exerts proangiogenic, anti-inflammatory, and anti-fibrogenic activities. These effects may indicate a therapeutical potential of this peptide in conditions where angiogenesis, inflammation, and fibrogenesis contribute to disease progression and chronicity.

Upregulation of p38 pathway accelerates proliferation and migration of MDA-MB-231 breast cancer cells

Tumor cells capture the signaling pathways used by normal tissue to promote their own survival and dissemination and among them, the NF-κB and MAPK pathways (ERK, JNK and p38). MAPK activation has ambiguous effects on tumor cell fate depending on cell type, cancer stage and the engaged MAPK isoforms. A synthetic peptide named LyeTx II, derived from the venom of the Brazilian spider Lycosa erythrognatha, was capable of increasing MDA-MB-231 aggressive breast cancer cell proliferation as indicated by MTT and BrdU (5-bromo-2'-deoxyuridine) incorporation assay and cell migration. A correlation has been established between the accelerated proliferation and migration observed in the presence of LyeTx II and the upregulation of p38 MAPK phosphorylation. The use of the selective inhibitor of p38α/β (SB203580) abrogated the peptide effect in MDA-MB-231 cells. Besides, an augment of the canonical NF-κB pathway activation considered as crucial in cancer progression was noted after cell incubation with LyeTx II. Importantly, activation of p38 and NF-κB pathways was dependent on TAK1 activity. Together, these data suggest that TAK1-p38 pathway may represent an interesting target for treatment of aggressive breast cancers.

Ocellatin peptides from the skin secretion of the South American frog Leptodactylus labyrinthicus (Leptodactylidae): characterization, antimicrobial activities and membrane interactions

Background

The availability of antimicrobial peptides from several different natural sources has opened an avenue for the discovery of new biologically active molecules. To the best of our knowledge, only two peptides isolated from the frog Leptodactylus labyrinthicus, namely pentadactylin and ocellatin-F1, have shown antimicrobial activities. Therefore, in order to explore the antimicrobial potential of this species, we have investigated the biological activities and membrane interactions of three peptides isolated from the anuran skin secretion.

Methods

Three peptide primary structures were determined by automated Edman degradation. These sequences were prepared by solid-phase synthesis and submitted to activity assays against gram-positive and gram-negative bacteria and against two fungal strains. The hemolytic properties of the peptides were also investigated in assays with rabbit blood erythrocytes. The conformational preferences of the peptides and their membrane interactions have been investigated by circular dichroism spectroscopy and liposome dye release assays.

Results

The amino acid compositions of three ocellatins were determined and the sequences exhibit 100% homology for the first 22 residues (ocellatin-LB1 sequence). Ocellatin-LB2 carries an extra Asn residue and ocellatin-F1 extra Asn-Lys-Leu residues at C-terminus. Ocellatin-F1 presents a stronger antibiotic potential and a broader spectrum of activities compared to the other peptides. The membrane interactions and pore formation capacities of the peptides correlate directly with their antimicrobial activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. All peptides acquire high helical contents in membrane environments. However, ocellatin-F1 shows in average stronger helical propensities.

Conclusions

The obtained results indicate that the three extra amino acid residues at the ocellatin-F1 C-terminus play an important role in promoting stronger peptide-membrane interactions and antimicrobial properties. The extra Asn-23 residue present in ocellatin-LB2 sequence seems to decrease its antimicrobial potential and the strength of the peptide-membrane interactions.

Electronic supplementary material

The online version of this article (doi:10.1186/s40409-017-0094-y) contains supplementary material, which is available to authorized users.

A spider derived peptide, PnPP-19, induces central antinociception mediated by opioid and cannabinoid systems

Background

Some peptides purified from the venom of the spider Phoneutria nigriventer have been identified as potential sources of drugs for pain treatment. In this study, we characterized the antinociceptive effect of the peptide PnPP-19 on the central nervous system and investigated the possible involvement of opioid and cannabinoid systems in its action mechanism.

Methods

Nociceptive threshold to thermal stimulation was measured according to the tail-flick test in Swiss mice. All drugs were administered by the intracerebroventricular route.

Results

PnPP-19 induced central antinociception in mice in the doses of 0.5 and 1 μg. The non-selective opioid receptor antagonist naloxone (2.5 and 5 μg), μ-opioid receptor antagonist clocinnamox (2 and 4 μg), δ-opioid receptor antagonist naltrindole (6 and 12 μg) and CB₁ receptor antagonist AM251 (2 and 4 μg) partially inhibited the antinociceptive effect of PnPP-19 (1 μg). Additionally, the anandamide amidase inhibitor MAFP (0.2 μg), the anandamide uptake inhibitor VDM11 (4 μg) and the aminopeptidase inhibitor bestatin (20 μg) significantly enhanced the antinociception induced by a low dose of PnPP-19 (0.5 μg). In contrast, the κ-opioid receptor antagonist nor-binaltorphimine (10 μg and 20 μg) and the CB₂ receptor antagonist AM630 (2 and 4 μg) do not appear to be involved in this effect.

Conclusions

PnPP-19-induced central antinociception involves the activation of CB₁ cannabinoid, μ- and δ-opioid receptors. Mobilization of endogenous opioids and cannabinoids might be required for the activation of those receptors, since inhibitors of endogenous substances potentiate the effect of PnPP-19. Our results contribute to elucidating the action of the peptide PnPP-19 in the antinociceptive pathway.

Antibacterial Effect of Synthetic Peptide LyeTxI and LyeTxI/β-Cyclodextrin Association Compound Against Planktonic and Multispecies Biofilms of Periodontal Pathogens

BACKGROUND

Antimicrobial peptides (AMPs) have shown rapid and potent effect against planktonic bacteria. However, control of periodontopathic biofilms is a challenge even for AMPs. Thus, the present study evaluates in vitro antimicrobial activity of synthetic peptide LyeTxI and association compound LyeTxI/β-cyclodextrin (βCD) against multispecies biofilms.

METHODS

Sensibility to LyeTxI and LyeTxI/βCD was determined for planktonic Gram-negative periodontopathogens. Time-kill kinetic assay was performed at minimum inhibitory concentrations (MICs) in all planktonic strains. Multispecies biofilms were grown on pegs using a biofilm device and studied by scanning electron microscopy at 2, 5, and 10 days. Minimal biofilm eradication concentration (MBEC) was determined for 2- and 4-day multispecies biofilms. Metabolic activity of biofilms was determined by fluorometry study.

RESULTS

Biofilms showed reproducible cell density on pegs of the biofilm device. LyeTxI and LyeTxI/βCD were active against all strains tested at concentrations ≤62.5 μg/mL. Kinetic assays showed rapid bactericidal effect of LyeTxI against all periodontopathogens. MBECs of LyeTxI and LyeTxI/βCD against multispecies 2-day biofilms were two-fold higher than MICs of cells shed from biofilms. LyeTxI was able to reduce multispecies 2-day metabolic activity by 90%. Multispecies 4-day biofilms were tolerant to all agents tested.

CONCLUSIONS

LyeTxI and LyeTxI/βCD are active against periodontopathic bacteria, showing rapid bactericidal effect and may be used to prevent biofilm development. In the future, AMPs could be therapeutic tools for treatment of periodontitis.

Structural and Functional Elucidation of Peptide Ts11 Shows Evidence of a Novel Subfamily of Scorpion Venom Toxins

To date, several families of peptide toxins specifically interacting with ion channels in scorpion venom have been described. One of these families comprise peptide toxins (called KTxs), known to modulate potassium channels. Thus far, 202 KTxs have been reported, belonging to several subfamilies of KTxs (called α, β, γ, κ, δ, and λ-KTxs). Here we report on a previously described orphan toxin from Tityus serrulatus venom, named Ts11. We carried out an in-depth structure-function analysis combining 3D structure elucidation of Ts11 and electrophysiological characterization of the toxin. The Ts11 structure is highlighted by an Inhibitor Cystine Knot (ICK) type scaffold, completely devoid of the classical secondary structure elements (α-helix and/or β-strand). This has, to the best of our knowledge, never been described before for scorpion toxins and therefore represents a novel, 6th type of structural fold for these scorpion peptides. On the basis of their preferred interaction with voltage-gated K channels, as compared to all the other targets tested, it can be postulated that Ts11 is the first member of a new subfamily, designated as ε-KTx.

Synthesis and antimicrobial evaluation of two peptide LyeTx I derivatives modified with the chelating agent HYNIC for radiolabeling with technetium-99m

Background

Current diagnostic methods and imaging techniques are not able to differentiate septic and aseptic inflammation. Thus, reliable methods are sought to provide this distinction and scintigraphic imaging is an interesting option, since it is based on physiological changes. In this context, radiolabeled antimicrobial peptides have been investigated as they accumulate in infectious sites instead of aseptic inflammation. The peptide LyeTx I, from the venom of Lycosa erythrognatha, has potent antimicrobial activity. Therefore, this study aimed to synthesize LyeTx I derivatives with the chelating compound HYNIC, to evaluate their antimicrobial activity and to radiolabel them with ^99mTc.

Methods

Two LyeTx I derivatives, HYNIC-LyeTx I (N-terminal modification) and LyeTx I-K-HYNIC (C-terminal modification), were synthesized by Fmoc strategy and purified by RP-HPLC. The purified products were assessed by RP-HPLC and MALDI-ToF-MS analysis. Microbiological assays were performed against S. aureus (ATCC® 6538) and E. coli (ATCC® 10536) in liquid medium to calculate the MIC. The radiolabeling procedure of LyeTx I-K-HYNIC with ^99mTc was performed in the presence of co-ligands (tricine and EDDA) and reducing agent (SnCl₂^.2H₂O), and standardized taking into account the amount of peptide, reducing agent, pH and heating. Radiochemical purity analysis was performed by thin-layer chromatography on silica gel strips and the radiolabeled compound was assessed by RP-HPLC and radioactivity measurement of the collected fractions. Data were analyzed by ANOVA, followed by Tukey test (p-values < 0.05).

Results

Both LyeTx I derivatives were suitably synthesized and purified, as shown by RP-HPLC and MALDI-ToF-MS analysis. The microbiological test showed that HYNIC-LyeTx I (N-terminal modification) did not inhibit bacterial growth, whereas LyeTx I-K-HYNIC (C-terminal modification) showed a MIC of 5.05 μmol^.L⁻¹ (S. aureus) and 10.10 μmol^.L⁻¹ (E. coli). Thus, only the latter was radiolabeled with ^99mTc. The radiochemical purity analysis of LyeTx I-K-HYNIC-^99mTc showed that the optimal radiolabeling conditions (10 μg of LyeTx I-K-HYNIC; 250 μg of SnCl₂^.2H₂O; pH = 7; heating for 15 min) yielded a radiochemical purity of 87 ± 1 % (n = 3). However, RP-HPLC data suggested ^99mTc transchelation from LyeTx I-K-HYNIC to the co-ligands (tricine and EDDA).

Conclusions

The binding of HYNIC to the N-terminal portion of LyeTx I seems to affect its activity against bacteria. Nevertheless, the radiolabeling of the C-terminal derivative, LyeTx I-K-HYNIC, must be better investigated to optimize the radiolabeled compound, in order to use it as a specific imaging agent to distinguish septic and aseptic inflammation.

Differential effects of the recombinant toxin PnTx4(5-5) from the spider Phoneutria nigriventer on mammalian and insect sodium channels

The toxin PnTx4(5-5) from the spider Phoneutria nigriventer is extremely toxic/lethal to insects but has no macroscopic behavioral effects observed in mice after intracerebral injection. Nevertheless, it was demonstrated that it inhibits the N-methyl-d-aspartate (NMDA) - subtype of glutamate receptors of cultured rat hippocampal neurons. PnTx4(5-5) has 63% identity to PnTx4(6-1), another insecticidal toxin from P. nigriventer, which can slow down the sodium current inactivation in insect central nervous system, but has no effect on Nav1.2 and Nav1.4 rat sodium channels. Here, we have cloned and heterologous expressed the toxin PnTx4(5-5) in Escherichia coli. The recombinant toxin rPnTx4(5-5) was tested on the sodium channel NavBg from the cockroach Blatella germanica and on mammalian sodium channels Nav1.2-1.6, all expressed in Xenopus leavis oocytes. We showed that the toxin has different affinity and mode of action on insect and mammalian sodium channels. The most remarkable effect was on NavBg, where rPnTx4(5-5) strongly slowed down channel inactivation (EC50 = 212.5 nM), and at 1 μM caused an increase on current peak amplitude of 105.2 ± 3.1%. Interestingly, the toxin also inhibited sodium current on all the mammalian channels tested, with the higher current inhibition on Nav1.3 (38.43 ± 8.04%, IC50 = 1.5 μM). Analysis of activation curves on Nav1.3 and Nav1.5 showed that the toxin shifts channel activation to more depolarized potentials, which can explain the sodium current inhibition. Furthermore, the toxin also slightly slowed down sodium inactivation on Nav1.3 and Nav1.6 channels. As far as we know, this is the first araneomorph toxin described which can shift the sodium channel activation to more depolarized potentials and also slows down channel inactivation.

PnPP-19, a Synthetic and Nontoxic Peptide Designed from a Phoneutria nigriventer Toxin, Potentiates Erectile Function via NO/cGMP

PURPOSE

We designed a peptide, PnPP-19, comprising the potential active core of the Phoneutria nigriventer native toxin PnTx2-6. We investigated its role on erectile function, and its toxicity and immunogenicity.

MATERIALS AND METHODS

Erectile function was evaluated by the intracavernous pressure-to-mean arterial pressure ratio during electrical field stimulation on rat pelvic ganglia. Cavernous strips were contracted with phenylephrine and relaxation was induced by electrical field stimulation with or without PnPP-19 (10(-8) M). Activity on sodium channels was evaluated by electrophysiological screening of transfected channels on Xenopus oocytes and dorsal root ganglion cells. Antibodies were detected by indirect enzyme-linked immunosorbent assay in mice previously treated with the peptide. Histopathological studies were performed with mouse organs treated with different doses of PnPP-19.

RESULTS

PnPP-19 was able to potentiate erection at 4 and 8 Hz in vivo and ex vivo. It showed no toxicity and low immunogenicity in mice, and did not affect sodium channels or rat hearts. PnPP-19 increased cyclic guanosine monophosphate levels at 8 Hz. This effect was inhibited by L-NAME (10(-4) M). Erectile function was partially inhibited by 7-nitroindazole (10(-5) M), a selective inhibitor of neuronal nitric oxide synthase.

CONCLUSIONS

PnPP-19 potentiates erection in vivo and ex vivo via the nitric oxide/cyclic guanosine monophosphate pathway. It does not affect sodium channels or rat hearts and shows no toxicity and low immunogenicity. These findings make it a promising candidate as a novel drug in the therapy of erectile dysfunction.

Peptides: β-cyclodextrin inclusion compounds as highly effective antimicrobial and anti-epithelial proliferation agents

BACKGROUND

The use of antimicrobial peptides (AMPs) as therapeutic agents for periodontal infections has great advantages, such as broad spectrum of action, low toxicity, and limited bacterial resistance. However, their practical use is limited because of the large amount of peptide required to exercise the microbicidal function.

METHODS

LyeTxI, LL37f, and KR12 cationic peptides were prepared with β-cyclodextrin (βCD) at 1:1 molar ratios. The susceptibility of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum were assessed in anaerobic conditions. Cytotoxicity assays were performed using osteoblast and Caco-2 epithelial cells, and hemolytic activity was assessed on rabbit erythrocytes at an absorbance of 414 nm. Parameters of surface roughness and electrical charge were established by atomic force microscopy and zeta (ζ) potential, respectively.

RESULTS

AMP/βCDs drastically decreased the peptide concentration required for activity against the bacteria tested. Moreover, AMPs associated with βCD were able to modify cell-surface parameters, such as roughness and ζ potential. On the other hand, AMP/βCD did not alter the degree of hemolysis induced by the pure AMPs. The effective concentration at half-maximum values of the peptides and compounds on osteoblasts were greater than the concentrations required to achieve inhibition of bacterial growth in all the species tested. AMP/βCDs inhibited the proliferation of Caco-2 epithelial cells in a more efficient manner than AMPs alone.

CONCLUSION

AMP/βCD compounds more effectively inhibit periodontopathogenic bacteria than AMPs alone, with the additional ability of inhibiting the proliferation of epithelial cells at concentrations that are non-cytotoxic for osteoblasts and erythrocytes.

Erectile function is improved in aged rats by PnTx2-6, a toxin from Phoneutria nigriventer spider venom

INTRODUCTION

Age-associated erectile dysfunction (ED) involves a decrease in nitric oxide (NO) availability and impaired relaxation. PnTx2-6, a toxin from the Phoneutria nigriventer spider, has been demonstrated to improve erectile function via NO/cyclic guanosine monophosphate (cGMP) pathway. This spider's venom is characterized by several symptoms, including erection. PnTx2-6 has been implicated in this phenomenon. Animal venoms have been postulated as potential drugs to treat ED.

AIM

PnTx2-6 toxin improves erectile function in aged rats via NO/cGMP. We investigated the effect of PnTx2-6 in the erectile function of aged rats.

MAIN OUTCOME MEASURES

ED was evaluated through changes in intracavernosal pressure/mean arterial pressure ratio during electrical field stimulation (EFS) of the pelvic ganglion of aged and adult rats (70 vs. 14 weeks). In functional studies, EFS-induced relaxation of corpus cavernosum (CC) strips were performed with or without PnTx2-6 (10-8M).

RESULTS

The decrease in erectile function associated with age was partially restored 15-20 minutes after injection of PnTx2-6 and further improved by sildenafil. PnTx2-6 enhanced EFS-induced relaxation, as well as cGMP levels in CC, from young and aged rats. Relaxation due to PnTx2-6 was further increased after 30 minutes incubation with Y-27632, a Rho-kinase inhibitor (10-6 M), in aging CC. Nitric oxide synthase (NOS) activity in aged and young cavernosal tissue was increased by incubation with PnTx2-6 (10 minutes). However, this toxin did not modify NOS expression.

CONCLUSION

PnTx2-6 improves penile relaxation in aged rats, via increased NOS activity and NO release, resulting in enhanced cGMP levels.