Block of synaptic transmission in insect CNS by toxins from the venom of the wasp Megascolia flavifrons (Fab.)

Comprehensive Analysis and Biological Characterization of Venom Components from Solitary Scoliid Wasp Campsomeriella annulata annulata

Venoms of solitary wasps are utilized for prey capture (insects and spiders), paralyzing them with a stinger injection to be offered as food for their larvae. Thus, the identification and characterization of the components of solitary wasp venoms can have biotechnological application. In the present study, the venom components profile of a solitary scoliid wasp, Campsomeriella annulata annulata, was investigated through a comprehensive analysis using LC-MS and -MS/MS. Online mass fingerprinting revealed that the venom extract contains 138 components, and MS/MS analysis identified 44 complete sequences of the peptide components. The peptides are broadly divided into two classes: bradykinin-related peptides, and linear α-helical peptides. Among the components of the first class, the two main peptides, α-campsomerin (PRLRRLTGLSPLR) and β-campsomerin (PRLRRLTGLSPLRAP), had their biological activities evaluated. Both peptides had no effects on metallopeptidases [human neprilysin (NEP) and angiotensin-converting enzyme (ACE)] and acetylcholinesterase (AChE), and had no cytotoxic effects. Studies with PC12 neuronal cells showed that only α-campsomerin was able to enhance cell viability, while β-campsomerin had no effect. It is noteworthy that the only difference between the primary structures from these peptides is the presence of the AP extension at the C-terminus of β-campsomerin, compared to α-campsomerin. Among the linear α-helical peptides, annulatin (ISEALKSIIVG-NH2) was evaluated for its biological activities. Annulatin showed histamine releasing activity from mast cells and low hemolytic activity, but no antimicrobial activities against all microbes tested were observed. Thus, in addition to providing unprecedented information on the whole components, the three peptides selected for the study suggest that molecules present in solitary scoliid wasp venoms may have interesting biological activities.

Novel neuroprotective peptides in the venom of the solitary scoliid wasp Scolia decorata ventralis

Background

Solitary wasp venoms may be a rich source of neuroactive substances, since their venoms are used for paralyzing preys. We have been exploring bioactive constituents of solitary wasp venoms and, in this study, the component profile of the venom from a solitary scoliid wasp, Scolia decorata ventralis, was investigated through a comprehensive analysis using LC-MS. Two peptides were synthesized, and their neuroprotective properties were evaluated.

Methods

A reverse-phase HPLC connected to ESI-MS was used for LC-MS analyses. Online mass fingerprinting was performed from TIC, and data-dependent tandem mass spectrometry gave the MS/MS spectra. The sequences of two major peptide components were determined by MALDI-TOF/TOF MS analysis, confirmed by solid phase synthesis. Using the synthetic peptides, biological activities were assessed. Cell integrity tests and neuroprotection analyzes using H₂O₂ as an oxidative stress inducer were performed for both peptides.

Results

Online mass fingerprinting revealed that the venom contains 123 components, and the MS/MS analysis resulted in 33 full sequences of peptide components. The two main peptides, α-scoliidine (DYVTVKGFSPLR) and β-scoliidine (DYVTVKGFSPLRKA), present homology with the bradykinin C-terminal. Despite this, both peptides did not behave as substrates or inhibitors of ACE, indicating that they do not interact with this metallopeptidase. In further studies, β-scoliidine, but not α -scoliidine, showed protective effects against oxidative stress-induced neurotoxicity in PC12 cells through integrity and metabolism cell assays. Interestingly, β-scoliidine has the extension of the KA dipeptide at the C-terminal in comparison with α-scoliidine.

Conclusion

Comprehensive LC-MS and MS/MS analyses from the Scolia decorata ventralis venom displayed the component profile of this venom. β-scoliidine showed an effective cytoprotective effect, probably due to the observed increase in the number of cells. This is the first report of solitary wasp venom peptides showing neuroprotective activity.

Peptide Toxins in Solitary Wasp Venoms

Solitary wasps paralyze insects or spiders with stinging venom and feed the paralyzed preys to their larva. Accordingly, the venoms should contain a variety of constituents acting on nervous systems. However, only a few solitary wasp venoms have been chemically studied despite thousands of species inhabiting the planet. We have surveyed bioactive substances in solitary wasp venoms found in Japan and discovered a variety of novel bioactive peptides. Pompilidotoxins (PMTXs), in the venoms of the pompilid wasps Anoplius samariensis and Batozonellus maculifrons, are small peptides consisting of 13 amino acids without a disulfide bond. PMTXs slowed Na⁺ channel inactivation, in particular against neuronal type Na⁺ channels, and were rather selective to the Nav1.6 channel. Mastoparan-like cytolytic and antimicrobial peptides are the major components of eumenine wasp venoms. They are rich in hydrophobic and basic amino acids, adopting a α-helical secondary structure, and showing mast cell degranulating, antimicrobial and hemolytic activities. The venom of the spider wasp Cyphononyx fulvognathus contained four bradykinin-related peptides. They are hyperalgesic and, dependent on the structure, differently associated with B₁ or B₂ receptors. Further survey led to the isolation of leucomyosuppressin-like FMRFamide peptides from the venoms of the digger wasps Sphex argentatus and Isodontia harmandi. These results of peptide toxins in solitary wasp venoms from our studies are summarized.

Anxiolytic activity and evaluation of potentially adverse effects of a bradykinin-related peptide isolated from a social wasp venom

Anxiety disorders are major health problems in terms of costs stemming from sick leave, disabilities, healthcare and premature mortality. Despite the availability of classic anxiolytics, some anxiety disorders are still resistant to treatment, with higher rates of adverse effects. In this respect, several toxins isolated from arthropod venoms are useful in identifying new compounds to treat neurological disorders, particularly pathological anxiety. Thus, the aims of this study were to identify and characterize an anxiolytic peptide isolated from the venom of the social wasp Polybia paulista. The peptide was identified as Polisteskinin R, with nominal molecular mass [M+H](+)=1301Da and primary structure consisting of Ala-Arg-Arg-Pro-Pro-Gly-Phe-Thr-Pro-Phe-Arg-OH. The anxiolytic effect was tested using the elevated plus maze test. Moreover, adverse effects on the spontaneous behavior and motor coordination of animals were assessed using the open field and rotarod tests. Polisteskinin R induced a dose-dependent anxiolytic effect. Animals treated with the peptide and diazepam spent significantly more time into the open arms when compared to the groups treated with the vehicle and pentylenetetrazole. No significant differences in spontaneous behavior or motor coordination were observed between the groups, showing that the peptide was well tolerated. The interaction by agonists in both known BK receptors induces a variability of physiological effects; Polisteskinin R can act on these receptors, inducing modulatory activity and thus, attenuating anxiety behaviors. The results of this study demonstrated that the compound Polisteskinin R exerted potent anxiolytic effects and its analogues are promising candidates for experimental pharmacology.

Differential Properties of Venom Peptides and Proteins in Solitary vs. Social Hunting Wasps

The primary functions of venoms from solitary and social wasps are different. Whereas most solitary wasps sting their prey to paralyze and preserve it, without killing, as the provisions for their progeny, social wasps usually sting to defend their colonies from vertebrate predators. Such distinctive venom properties of solitary and social wasps suggest that the main venom components are likely to be different depending on the wasps' sociality. The present paper reviews venom components and properties of the Aculeata hunting wasps, with a particular emphasis on the comparative aspects of venom compositions and properties between solitary and social wasps. Common components in both solitary and social wasp venoms include hyaluronidase, phospholipase A2, metalloendopeptidase, etc. Although it has been expected that more diverse bioactive components with the functions of prey inactivation and physiology manipulation are present in solitary wasps, available studies on venom compositions of solitary wasps are simply too scarce to generalize this notion. Nevertheless, some neurotoxic peptides (e.g., pompilidotoxin and dendrotoxin-like peptide) and proteins (e.g., insulin-like peptide binding protein) appear to be specific to solitary wasp venom. In contrast, several proteins, such as venom allergen 5 protein, venom acid phosphatase, and various phospholipases, appear to be relatively more specific to social wasp venom. Finally, putative functions of main venom components and their application are also discussed.

Pharmacological Alternatives for the Treatment of Neurodegenerative Disorders: Wasp and Bee Venoms and Their Components as New Neuroactive Tools

Neurodegenerative diseases are relentlessly progressive, severely impacting affected patients, families and society as a whole. Increased life expectancy has made these diseases more common worldwide. Unfortunately, available drugs have insufficient therapeutic effects on many subtypes of these intractable diseases, and adverse effects hamper continued treatment. Wasp and bee venoms and their components are potential means of managing or reducing these effects and provide new alternatives for the control of neurodegenerative diseases. These venoms and their components are well-known and irrefutable sources of neuroprotectors or neuromodulators. In this respect, the present study reviews our current understanding of the mechanisms of action and future prospects regarding the use of new drugs derived from wasp and bee venom in the treatment of major neurodegenerative disorders, including Alzheimer’s Disease, Parkinson’s Disease, Epilepsy, Multiple Sclerosis and Amyotrophic Lateral Sclerosis.

Antibacterial and proteolytic activity in venom from the endoparasitic wasp Pimpla hypochondriaca (Hymenoptera: Ichneumonidae)

Venom from the endoparasitic wasp, Pimpla hypochondriaca, is composed of a mixture of high and low molecular weight proteins, possesses phenoloxidase activity, has immunosuppressive properties, and induces paralysis in several insect species. In the present study we demonstrate that P. hypochondriaca venom also contains antibacterial and proteolytic activity. Antibacterial activity was detected against the Gram-negative bacteria Escherichia coli and Xanthamonas campestris but not against Pseudomonas syringae nor against two Gram-positive bacteria, Bacillus cereus and Bacillus subtilis. Endopeptidase and aminopeptidase activity in venom was detected using the synthetic fluorogenic substrates N-t-BOC-Phe-Ser-Arg-AMC, Arg-AMC and Leu-Arg. The aminopeptidase activity towards Arg-AMC was sensitive to amastatin (70% inhibition), an aminopeptidase inhibitor. Angiotensin-converting enzyme (ACE)-like enzyme activity was detected, by reverse-phase HPLC using the synthetic tripeptide Hip-His-Leu as a substrate. This activity was sensitive to captopril, an ACE inhibitor (IC(50) 3.8 x 10(-8) M). Using an antiserum raised against recombinant Drosophila melanogaster ACE-like enzyme, (rAnce), Western blot analysis revealed an immunoreactive protein, with a molecular weight estimate of 74 kDa, in P. hypochondriaca venom. The possibility that the endopeptidase, aminopeptidase and ACE are involved in the processing of peptide precursors in the venom sac is discussed.

Wasp venom blocks central cholinergic synapses to induce transient paralysis in cockroach prey

The parasitoid wasp Ampulex compressa induces a set of unique behavioral effects upon stinging its prey, the cockroach. It stings into the first thoracic segment inducing 2 to 3 min of transient flaccid paralysis of the front legs. This facilitates a second sting in the cockroach's head that induces 30 min of excessive grooming followed by a 2 to 5-week long lethargic state. In the present study, we examine the immediate effect of the first sting, which is a transient paralysis of the front legs. Using radiolabeled wasps, we demonstrate that the wasp injects its venom directly into the cockroach's first thoracic ganglion. The artificial injection of milked venom into a thoracic ganglion abolishes spontaneous and evoked responses of the motoneurons associated with leg movements. To investigate the physiological mechanism of action of the venom, we injected venom into the last abdominal ganglion of the cockroach, which houses a well-characterized cholinergic synapse. Injected venom abolishes both sensory-evoked and agonist-evoked postsynaptic potentials recorded in the postsynaptic neuron for 2 to 3 min without affecting action potential propagation. Thus, the venom blocking effect has a postsynaptic component that follows the same time course as the transient paralysis induced by the thoracic sting. Finally, injection of a nicotinic antagonist in the front thoracic ganglion induces paralysis of the front legs. We conclude that the transient paralytic effect of the thoracic sting can be mainly accounted for by the presence of a venom active component that induces a postsynaptic block of central cholinergic synaptic transmission.

Differential sensitivity of two insect GABA-gated chloride channels to dieldrin, fipronil and picrotoxinin

In the central nervous system of both vertebrates and invertebrates inhibitory neurotransmission is mainly achieved through activation of gamma-aminobutyric acid (GABA) receptors. Extensive studies have established the structural and pharmacological properties of vertebrate GABA receptors. Although the vast majority of insect GABA-sensitive responses share some properties with vertebrate GABAA receptors, peculiar pharmacological properties of these receptors led us to think that several GABA-gated chloride channels are present in insects. We describe here the pharmacological properties of two GABA receptor subtypes coupled to a chloride channel on dorsal unpaired median (DUM) neurones of the adult male cockroach. Long applications of GABA induce a large biphasic hyperpolarization, consisting of an initial transient hyperpolarization followed by a slow phase of hyperpolarization that is not quickly desensitized. With GABA, the transient hyperpolarization is sensitive to picrotoxinin, fipronil and dieldrin whereas the slow response is insensitive to these insecticides.When GABA is replaced by muscimol and cis-4-aminocrotonic acid (CACA) a biphasic hyperpolarization consisting of an initial transient hyperpolarization followed by a sustained phase is evoked which is blocked by picrotoxinin and fipronil. Exposure to dieldrin decreases only the early phase of the muscimol and CACA-induced biphasic response, suggesting that two GABA-gated chloride channel receptor subtypes are present in DUM neurones. This study describes, for the first time, a dieldrin resistant component different to the dieldrin- and picrotoxinin-resistant receptor found in several insect species.

Digger wasp versus cricket: mechanisms underlying the total paralysis caused by the predator's venom

The data presented here describe neurophysiological experiments addressing the question of cellular mechanisms underlying the total paralysis of locomotor behavior in crickets occurring after being stung by females of the digger wasp species Liris niger. The Liris venom effects have been studied by both in vivo recordings from identified neurons of the well-described giant fiber pathway and in vitro recordings from cultured neurons isolated from the terminal ganglion of crickets. The total paralysis of the prey is characterized by a general block of action potential generation as well as by a block of synaptic transmission. Intracellular recordings from neurons in intact ganglia under single electrode voltage-clamp conditions, as well as whole-cell patch-clamp recordings from cultured cricket neurons consistently show that the block of action potential generation by the Liris venom is due to a block of voltage-gated sodium inward currents in neurons of the stung ganglia. Furthermore, our data provide evidence that the Liris venom also blocks calcium currents in identified neurosecretory neurons. On the other hand, outward currents are not affected by the Liris venom. The in vitro recordings suggest that the Liris venom contains active venom components, which, at least for the observed block of inward currents, do not require a metabolic modification. Because venom application does not affect the ACh-induced EPSPs in giant interneurons, the Liris venom does not seem to influence the postsynaptic ACh receptors. The possible pre- and postsynaptic sites of venom action and the functional consequences on synaptic transmission within the giant fiber system are discussed.

Digger wasp versus cricket: immediate actions of the predator's paralytic venom on the CNS of the prey

The females of the palaearctic digger wasp species Liris niger hunt crickets (e.g., Acheta domesticus) as food for their future brood. The wasps paralyze the prey by injecting their venom directly into each of the three thoracic ganglia and the suboesophageal ganglion. This study describes the effects produced by the Liris venom at the level of the intact prey animal (by chronic electromyogram) and at the level of a dissected preparation (by extra- and intracellular records) during the immediate action. Natural or artificial injections of the Liris venom into various ganglia revealed that: (a) The venom injection induced an about 15- to 35-s long tonical discharge of the neurons located in the stung ganglion. This discharge is usually accompanied by convulsions of the prey's limbs. (b) Subsequently, the generation and propagation of action potentials are blocked for up to 30 min (total paralysis). (c) During total paralysis, the venom blocks synaptic transmission. (d) The effects of the venom are restricted to the stung ganglion. Responses of mechanoreceptors in the legs can be recorded from the peripheral nerves of the stung ganglion during the whole period of total paralysis. (e) The neurons almost completely recover after this period. The venom does not selectively affect leg motoneurons, but affects any neuron (e.g., internerneurons or neurosecretory neurons) in any part of the central nervous system of the prey where it was released.