Immunomodulation of the inflammatory response induced by Androctonus australis hector neurotoxins: biomarker interactions

Analysis of the effect of the scorpion toxin AaH-II on action potential generation in the axon initial segment

The toxin AaH-II, from the scorpion Androctonus australis Hector venom, is a 64 amino acid peptide that targets voltage-gated Na+ channels (VGNCs) and slows their inactivation. While at macroscopic cellular level AaH-II prolongs the action potential (AP), a functional analysis of the effect of the toxin in the axon initial segment (AIS), where VGNCs are highly expressed, was never performed so far. Here, we report an original analysis of the effect of AaH-II on the AP generation in the AIS of neocortical layer-5 pyramidal neurons from mouse brain slices. After determining that AaH-II does not discriminate between Nav1.2 and Nav1.6, i.e. between the two VGNC isoforms expressed in this neuron, we established that 7 nM was the smallest toxin concentration producing a minimal detectable deformation of the somatic AP after local delivery of the toxin. Using membrane potential imaging, we found that, at this minimal concentration, AaH-II substantially widened the AP in the AIS. Using ultrafast Na+ imaging, we found that local application of 7 nM AaH-II caused a large increase in the slower component of the Na+ influx in the AIS. Finally, using ultrafast Ca2+ imaging, we observed that 7 nM AaH-II produces a spurious slow Ca2+ influx via Ca2+-permeable VGNCs. Molecules targeting VGNCs, including peptides, are proposed as potential therapeutic tools. Thus, the present analysis in the AIS can be considered a general proof-of-principle on how high-resolution imaging techniques can disclose drug effects that cannot be observed when tested at the macroscopic level.

Biological Effects of Animal Venoms on the Human Immune System

Venoms are products of specialized glands and serve many living organisms to immobilize and kill prey, start digestive processes and act as a defense mechanism. Venoms affect different cells, cellular structures and tissues, such as skin, nervous, hematological, digestive, excretory and immune systems, as well as the heart, among other structures. Components of both the innate and adaptive immune systems can be stimulated or suppressed. Studying the effects on the cells and molecules produced by the immune system has been useful in many biomedical fields. The effects of venoms can be the basis for research and development of therapeutic protocols useful in the modulation of the immunological system, including different autoimmune diseases. This review focuses on the understanding of biological effects of diverse venom on the human immune system and how some of their components can be useful for the study and development of immunomodulatory drugs.

Mast Cells Modulate the Immune Response and Redox Status of the Gastrointestinal Tract in Induced Venom Pathogenesis

The pathogenesis of Androctonus autralis hector (Aah) scorpion venom involved cellular and molecular mechanisms resulting in multi-organ dysfunction. However, little is reported about the effects of venom on the gastrointestinal axis. Mast cells (MCs) are known to play a crucial role in modulating immune response of the gut. This study aims to investigate the involvement of this cell type in venom-induced gastric and intestinal disorders in a time course (3 and 24h). The obtained results revealed that Aah scorpion venom induced inflammatory cell infiltration as shown by the increase of the myeloperoxidase and eosinophil peroxidase activities. Overexpression of the c-kit receptor (CD117) severely imbalanced the redox status with depletion of antioxidant systemic accompanied by gastrointestinal tissue damage. Moreover, an increased level of lactate dehydrogenase in the serum was correlated with tissue injuries. Pharmacological inhibition of MCs targeting tyrosine kinase (TK) reduces the generation of reactive oxygen species and normalizes catalase, and gluthation S-transferase activities to their physiological levels. In addition, histopathological alterations were restored after pretreatment with c-kit receptor inhibitor associated with a considerable reduction of MC density. Interestingly, obtained results indicate that MCs might be involved in gastric modulation and intestinal inflammation through c-kit signaling following sub-cutaneous Aah venom injection.

Long-term antibody response and protective effect induced by attenuated scorpion toxins: Involvement of memory plasma cells

In Algeria, Androctonus australis hector scorpion envenomation remains a major problem of public health because of non-efficient therapy. The development of safe vaccine against scorpion venom could be one key strategy for the envenomation prevention. The irradiation of venom by γ-rays develops suitable immunogens which produced effective antivenom and safe vaccine. In this study, we investigated the ability of the irradiated toxic fraction (γ-FtoxG50) to induce long-term memory humoral response in immunized animals (mice and rabbits), by involving the long-lived plasma cells to prevent efficiently the lethality of scorpion envenomation. For this purpose, an appropriate immunization schedule was established in mice and rabbits using three (3) similar doses of γ-FtoxG50 associated with Alum adjuvant. Obtained results indicate that the long-term immunogenicity of γ-FtoxG50 is able to induce the long-term memory humoral response with a high level of specific antibodies. The long-term persistence of antibody levels could depend on bone marrow memory plasma cells. These cells produce continuously antibodies without antigen stimulus. Furthermore, an enhanced memory response was obtained post-repeated envenomation with toxic native venom that leads to improved protection of animals. Together, pre-existing protective antibodies and the activation of memory B-cells could induce a rapid neutralization of scorpion toxins and long-term protection against scorpion envenomation.

Immunomodulatory properties of molecules from animal venoms

The immune system can amplify or decrease the strength of its response when it is stimulated by chemical or biological substances that act as immunostimulators, immunosuppressants, or immunoadjuvants. Immunomodulation is a progressive approach to treat a diversity of pathologies with promising results, including autoimmune disorders and cancer. Animal venoms are a mixture of chemical compounds that include proteins, peptides, amines, salts, polypeptides, enzymes, among others, which produce the toxic effect. Since the discovery of captopril in the early 1980s, other components from snakes, spiders, scorpions, and marine animal venoms have been demonstrated to be useful for treating several human diseases. The valuable progress in fields such as venomics, molecular biology, biotechnology, immunology, and others has been crucial to understanding the interaction of toxins with the immune system and its application on immune pathologies. More in-depth knowledge of venoms' components and multi-disciplinary studies could facilitate their transformation into effective novel immunotherapies. This review addresses advances and research of molecules from venoms that have immunomodulatory properties.

Serotherapy against Voltage-Gated Sodium Channel-Targeting αToxins from Androctonus Scorpion Venom

Because of their venom lethality towards mammals, scorpions of the Androctonus genus are considered a critical threat to human health in North Africa. Several decades of exploration have led to a comprehensive inventory of their venom components at chemical, pharmacological, and immunological levels. Typically, these venoms contain selective and high affinity ligands for the voltage-gated sodium (Na_v) and potassium (K_v) channels that dictate cellular excitability. In the well-studied Androctonus australis and Androctonus mauretanicus venoms, almost all the lethality in mammals is due to the so-called α-toxins. These peptides commonly delay the fast inactivation process of Na_v channels, which leads to increased sodium entry and a subsequent cell membrane depolarization. Markedly, their neutralization by specific antisera has been shown to completely inhibit the venom’s lethal activity, because they are not only the most abundant venom peptide but also the most fatal. However, the structural and antigenic polymorphisms in the α-toxin family pose challenges to the design of efficient serotherapies. In this review, we discuss past and present accomplishments to improve serotherapy against Androctonus scorpion stings.

Differential effect of Androctonus australis hector venom components on macrophage KV channels: electrophysiological characterization

Neurotoxins of scorpion venoms modulate ion channels. Voltage-gated potassium (K_V) channels regulate the membrane potential and are involved in the activation and proliferation of immune cells. Macrophages are key components of the inflammatory response induced by scorpion venom. The present study was undertaken to investigate the effect of Androctonus australis hector (Aah) venom on K_V channels in murine resident peritoneal macrophages. The cytotoxicity of the venom was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) -based assay and electrophysiological recordings were performed using the whole-cell patch clamp technique. High doses of Aah venom (50, 125, 250 and 500 µg/ml) significantly decreased cell viability, while concentrations of 0.1-25 µg/ml were not cytotoxic towards peritoneal macrophages. Electrophysiological data revealed a differential block of K_V current between resting and LPS-activated macrophages. Aah venom significantly reduced K_V current amplitude by 62.5 ± 4.78% (n = 8, p < 0.05), reduced the use-dependent decay of the current, decreased the degree of inactivation and decelerated the inactivation process of K_V current in LPS-activated macrophages. Unlike cloned K_V1.5 channels, Aah venom exerted a similar blocking effect on K_V1.3 compared to K_V current in LPS-activated macrophages, along with a hyperpolarizing shift in the voltage dependence of K_V1.3 inactivation, indicating a direct mechanism of current inhibition by targeting K_V1.3 subunits. The obtained results, demonstrating that Aah venom differentially targets K_V channels in macrophages, suggest differential outcomes for their inhibitions, and that further investigations of scorpion venom immunomodulatory potential are required.

Involvement of Cholinergic and Adrenergic Receptors in Pathogenesis and Inflammatory Response Induced by Alpha-Neurotoxin Bot III of Scorpion Venom

Bot III neurotoxin is the most lethal α neurotoxin purified from Buthus occitanus tunetanus scorpion venom. This toxin binds to the voltage-gated sodium channel of excitable cells and blocks its inactivation, inducing an increased release of neurotransmitters (acetylcholine and catecholamines). This study aims to elucidate the involvement of cholinergic and adrenergic receptors in pathogenesis and inflammatory response triggered by this toxin. Injection of Bot III to animals induces an increase of peroxidase activities, an imbalance of oxidative status, tissue damages in lung parenchyma, and myocardium correlated with metabolic disorders. The pretreatment with nicotine (nicotinic receptor agonist) or atropine (muscarinic receptor antagonist) protected the animals from almost all disorders caused by Bot III toxin, especially the immunological alterations. Bisoprolol administration (selective β1 adrenergic receptor antagonist) was also efficient in the protection of animals, mainly on tissue damage. Propranolol (non-selective adrenergic receptor antagonist) showed less effect. These results suggest that both cholinergic and adrenergic receptors are activated in the cardiopulmonary manifestations induced by Bot III. Indeed, the muscarinic receptor appears to be more involved than the nicotinic one, and the β1 adrenergic receptor seems to dominate the β2 receptor. These results showed also that the activation of nicotinic receptor leads to a significant protection of animals against Bot III toxin effect. These findings supply a supplementary data leading to better understanding of the mechanism triggered by scorpionic neurotoxins and suggest the use of drugs targeting these receptors, especially the nicotinic one in order to counteract the inflammatory response observed in scorpion envenomation.

TNF-alpha modulates adipose macrophage polarization to M1 phenotype in response to scorpion venom

OBJECTIVE

We previously reported that Androctonus australis hector (Aah) venom and its toxic fraction affect adipose tissue metabolism. However, the contribution of immune system and the role of adipose tissue macrophages (ATMs) in the progression of inflammation induced by scorpion venom remain largely unknown.

METHODS

Here we evaluate the capacity of the toxic fraction of Aah venom (FTox-G50) to induce the expression of M1 and M2 markers genes on adipose tissue and isolated stromal vascular cells (SVC). Quantitative real-time PCR was performed on the SVC 24 h after FTox-G50 venom injection to assess the gene expressions of IL12p40, IL23, and other macrophages-associated markers.

RESULTS

We found that ATM from FTox-G50-venom-injected mice markedly increased the expressions of IL-12p40 and IL-23. Furthermore, the expression of nitric oxide synthase 2 (an M1 marker) was up-regulated, but the expression of Arginase1 (an M2 marker) was not. Systemic injection of a chemical inhibitor directed against TNF-α binding reduced the expression of inflammatory M1 macrophage markers and the MAPKpk2 gene, a key mediator of inflammatory signaling.

CONCLUSION

These results indicate that TNF-α is a physiological regulator of inflammation and macrophage activation induced by scorpion venom.

Involvement of Kallikrein-Kinin System on Cardiopulmonary Alterations and Inflammatory Response Induced by Purified Aah I Toxin from Scorpion Venom

Bradykinins are released from kininogen by kallikrein. They increase capillary lung permeability after their binding to β1 and especially β2 receptors before being metabolized by kininase enzyme. This study was performed to evaluate cardiopulmonary damages and inflammatory response on injected rats with Aah I toxin of scorpion venom and the involvement of Kallikrein-Kinin system in this pathogenesis. Obtained results revealed that Aah I toxin induces inflammatory cell infiltration accompanied by cellular peroxidase activities, a release of cytokine levels, pulmonary and myocardial damage, with altered metabolic activities and imbalanced redox status. Administration of aprotinin (bradykinin inhibitor) and especially icatibant (bradykinin β2 receptor antagonist) seemed to be able to protect animals against the toxicity of Aah I; nevertheless, the use of captopril (kininase II inhibitor) reduced partially some cardiac disorders. These findings indicate that the kallikrein-kinin system may contribute to the physiopathological effect and lung edema formation induced by toxin, which suggests a potential use of drugs with significant anti-kinin properties.

Neuropathophysiological effect and immuno-inflammatory response induced by kaliotoxin of androctonus scorpion venom

OBJECTIVE

Kaliotoxin (KTX) is a neurotoxin purified from Androctonus scorpion venom. Purification and pharmacological and immunological characterization of this neurotoxin has been extensively studied, but its biological effects have not. The ability of KTX to induce neuropathophysiological and immuno-inflammatory effects was investigated.

METHODS

NMRI mice were injected with a sublethal dose of KTX (20 ng/20 g of body weight) or saline solution via the intra-cerebro-ventricular route. Tissue damage and immunological biomarkers such as eosinophil peroxidase (EPO), myeloperoxidase (MPO), and nitric oxide (NO) were analyzed in serum, brain, lung, and heart tissue. Protein levels, LDH, and CPK activities were also determined in serum 24 h after injection.

RESULTS

In this study, KTX injection induced severe alterations in the cerebral cortex, myocardium, and pulmonary parenchyma. Tissue damage was correlated with seric increase in creatine kinase and lactate dehydrogenase activities. KTX also induced an immuno-inflammatory response distinguished by cell infiltration characterized by a significant increase in EPO and MPO activities in the brain, heart, and lungs. This infiltration was also associated with an increase in albumin, α-, β-, and γ-globulin fractions, and NO release.

CONCLUSION

KTX binding to its targets in CNS (Kv1.1 and Kv1.3 channels) may induce severe modifications in the structure and function of various organs associated with the activation of immuno-inflammatory reactions.

Apple polyphenol protects against cigarette smoke-induced acute lung injury

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a complex chronic inflammatory disease involving oxidative stress as well as a wide variety of cells activated from smoking cigarettes. There have been disappointingly few therapeutic advances in drug therapy for COPD. Plant polyphenols have been the topic of much research regarding their antioxidant activities and antiinflammatory and immunomodulatory effects. In the present study, we ask whether apple polyphenol provides protection against cigarette smoke (CS)-induced acute lung injury.

METHODS

ICR mice were exposed to CS for 4 d with increasing exposure time for up to 6 h per day to elicit epithelial cells injury. One hour before smoke exposure, mice were treated with apple polyphenol (APP) by gavage; all examinations were performed 18 h after the last CS exposure.

RESULTS

APP at 30, 100, or 300 mg not only significantly dose-dependently reduced the CS-induced accumulation of inflammatory cells and gene/protein expression of proinflammatory factors both in the lung and in bronchoalveolar lavage fluid, but also significantly reversed oxidative stress in the lungs. Additionally, treatment with APP also significantly regulated the CS-induced imbalance of matrix metalloproteinases-9/tissue inhibitor of metalloproteinase-1 expression in the lungs. To investigate further the possible signaling pathway of APP effects, we examined protein expression of p-P38 MAPK by immunohistochemistry that found treatment with APP significantly decreased the CS-induced increases of p-P38 expression in the lungs.

CONCLUSION

Taken together, APP may be a potential dietary nutrient supplement agent to improve quality of life of COPD patients by inhibiting CS-exposed acute lung injury via P38 MAPK signaling pathway.