Maurício Rocha e Silva MD: snake venom, bradykinin and the rise of autopharmacology

Dabsylated Bradykinin Is Cleaved by Snake Venom Proteases from Echis ocellatus

The vasoactive peptide bradykinin (BK) is an important member of the renin-angiotensin system. Its discovery is tightly interwoven with snake venom research, because it was first detected in plasma following the addition of viper venom. While the fact that venoms liberate BK from a serum globulin fraction is well described, its destruction by the venom has largely gone unnoticed. Here, BK was found to be cleaved by snake venom metalloproteinases in the venom of Echis ocellatus, one of the deadliest snakes, which degraded its dabsylated form (DBK) in a few minutes after Pro7 (RPPGFSP↓FR). This is a common cleavage site for several mammalian proteases such as ACE, but is not typical for matrix metalloproteinases. Residual protease activity < 5% after addition of EDTA indicated that DBK is also cleaved by serine proteases to a minor extent. Mass spectrometry-based protein analysis provided spectral proof for several peptides of zinc metalloproteinase-disintegrin-like Eoc1, disintegrin EO4A, and three serine proteases in the venom.

New Insights on Glutathione's Supramolecular Arrangement and Its In Silico Analysis as an Angiotensin-Converting Enzyme Inhibitor

Angiotensin-converting enzyme (ACE) inhibitors are one of the most active classes for cardiovascular diseases and hypertension treatment. In this regard, developing active and non-toxic ACE inhibitors is still a continuous challenge. Furthermore, the literature survey shows that oxidative stress plays a significant role in the development of hypertension. Herein, glutathione's molecular structure and supramolecular arrangements are evaluated as a potential ACE inhibitor. The tripeptide molecular modeling by density functional theory, the electronic structure by the frontier molecular orbitals, and the molecular electrostatic potential map to understand the biochemical processes inside the cell were analyzed. The supramolecular arrangements were studied by Hirshfeld surfaces, quantum theory of atoms in molecules, and natural bond orbital analyses. They showed distinct patterns of intermolecular interactions in each polymorph, as well as distinct stabilizations of these. Additionally, the molecular docking study presented the interactions between the active site residues of the ACE and glutathione via seven hydrogen bonds. The pharmacophore design indicated that the hydrogen bond acceptors are necessary for the interaction of this ligand with the binding site. The results provide useful information for the development of GSH analogs with higher ACE inhibitor activity.

Bradykinin-target therapies in SARS-CoV-2 infection: current evidence and perspectives

Coronavirus disease 2019 (COVID-19) is a potentially fatal disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that preferentially infects the respiratory tract. Bradykinin (BK) is a hypotensive substance that recently emerged as one of the mechanisms to explain COVID-19-related complications. Concerning this, in this review, we try to address the complex link between BK and pathophysiology of COVID-19, investigating the role of this peptide as a potential target for pharmacological modulation in the management of SARS-CoV-2. The pathology of COVID-19 may be more a result of the BK storm than the cytokine storm, and which BK imbalance is a relevant factor in the respiratory disorders caused by SARS-CoV-2 infection. Regarding this, an interesting point of intervention for this disease is to modulate BK signaling. Some drugs, such as icatibant, ecallantide, and noscapine, and even a human monoclonal antibody, lanadelumab, have been studied for their potential utility in COVID-19 by modulating BK signaling. The interaction of the BK pathway and the involvement of cytokines such as IL-6 and IL1 may be key to the use of blockers, even if only as adjuvants. In fact, reduction of BK, mainly DABK, is considered a relevant strategy to improve clinical conditions of COVID-19 patients. In this context, despite the current unproven clinical efficacy, drugs repurposing that block B1 or B2 receptor activation have gained prominence for the treatment of COVID-19 in the world.

Revisiting the potential of South American rattlesnake Crotalus durissus terrificus toxins as therapeutic, theranostic and/or biotechnological agents

The potential biotechnological and biomedical applications of the animal venom components are widely recognized. Indeed, many components have been used either as drugs or as templates/prototypes for the development of innovative pharmaceutical drugs, among which many are still used for the treatment of human diseases. A specific South American rattlesnake, named Crotalus durissus terrificus, shows a venom composition relatively simpler compared to any viper or other snake species belonging to the Crotalus genus, although presenting a set of toxins with high potential for the treatment of several still unmet human therapeutic needs, as reviewed in this work. In addition to the main toxin named crotoxin, which is under clinical trials studies for antitumoral therapy and which has also anti-inflammatory and immunosuppressive activities, other toxins from the C. d. terrificus venom are also being studied, aiming for a wide variety of therapeutic applications, including as antinociceptive, anti-inflammatory, antimicrobial, antifungal, antitumoral or antiparasitic agent, or as modulator of animal metabolism, fibrin sealant (fibrin glue), gene carrier or theranostic agent. Among these rattlesnake toxins, the most relevant, considering the potential clinical applications, are crotamine, crotalphine and gyroxin. In this narrative revision, we propose to organize and present briefly the updates in the accumulated knowledge on potential therapeutic applications of toxins collectively found exclusively in the venom of this specific South American rattlesnake, with the objective of contributing to increase the chances of success in the discovery of drugs based on toxins.

Toxin to medicine and bioisosterism in drug development: a study of the discovery and development of ACE inhibitors from snake venom

The advent of the angiotensin-converting enzyme (ACE) inhibitors is a landmark in drug discovery and a breakthrough in the management of hypertension. Their clinical introduction has led to appreciable increase in the lifespan of hypertensive patients. And their development initiated a new era of structure-based or rational drug design that has subsequently been applied successfully for development of drugs for many other disorders. This paper presents an account of the discovery, design and development of ACE inhibitors from an academic perspective and possibly, as a guide to future research. The paper highlights the milestones and recounts the challenges encountered and the strategies applied in the search for ACE inhibitors. This exposition also expounds some of the concepts and intricacies of drug discovery, design and development. Keywords: drug development, ACE inhibitors, snake venom peptide, bioisosterism, antihypertensive agents

Neuropeptides and oligopeptidases in schizophrenia

Schizophrenia (SCZ) is a complex psychiatric disorder with severe impact on patient's livelihood. In the last years, the importance of neuropeptides in SCZ and other CNS disorders has been recognized, mainly due to their ability to modulate the signaling of classical monoaminergic neurotransmitters as dopamine. In addition, a class of enzymes coined as oligopeptidases are able to cleave several of these neuropeptides, and their potential implication in SCZ was also demonstrated. Interestingly, these enzymes are able to play roles as modulators of neuropeptidergic systems, and they were also implicated in neurogenesis, neurite outgrowth, neuron migration, and therefore, in neurodevelopment and brain formation. Altered activity of oligopeptidases in SCZ was described only more recently, suggesting their possible utility as biomarkers for mental disorders diagnosis or treatment response. We provide here an updated and comprehensive review on neuropeptides and oligopeptidases involved in mental disorders, aiming to attract the attention of physicians to the potential of targeting this system for improving the therapy and for understanding the neurobiology underlying mental disorders as SCZ.

Chemical Intuition in Drug Design and Discovery

The medicinal chemist plays the most important role in drug design, discovery and development. The primary goal is to discover leads and optimize them to develop clinically useful drug candidates. This process requires the medicinal chemist to deal with large sets of data containing chemical descriptors, pharmacological data, pharmacokinetics parameters, and in silico predictions. The modern medicinal chemist has a large number of tools and technologies to aid him in creating strategies and supporting decision-making. Alongside with these tools, human cognition, experience and creativity are fundamental to drug research and are important for the chemical intuition of medicinal chemists. Therefore, fine-tuning of data processing and in-house experience are essential to reach clinical trials. In this article, we will provide an expert opinion on how chemical intuition contributes to the discovery of drugs, discuss where it is involved in the modern drug discovery process, and demonstrate how multidisciplinary teams can create the optimal environment for drug design, discovery, and development.

A Latin American Perspective on G Protein-Coupled Receptors

G protein-coupled receptors are sensors that interact with a large variety of elements, including photons, ions, and large proteins. Not surprisingly, these receptors participate in the numerous normal physiologic processes that we refer to as health and in its perturbations that constitute disease. It has been estimated that a large percentage of drugs currently used in therapeutics target these proteins, and this percentage is larger when illegal drugs are included. The state of the art in this field can be defined with the oxymoron "constant change," and enormous progress has been made in recent years. A group of scientists working in Latin America were invited to contribute minireviews for this special section to present some of the work performed in this geographical region and foster further international collaboration.

Characterisation and mechanisms of bradykinin-evoked pain in man using iontophoresis

Bradykinin (BK) is an inflammatory mediator that can evoke oedema and vasodilatation, and is a potent algogen signalling via the B1 and B2 G-protein coupled receptors. In naïve skin, BK is effective via constitutively expressed B2 receptors (B2R), while B1 receptors (B1R) are purported to be upregulated by inflammation. The aim of this investigation was to optimise BK delivery to investigate the algesic effects of BK and how these are modulated by inflammation. BK iontophoresis evoked dose- and temperature-dependent pain and neurogenic erythema, as well as thermal and mechanical hyperalgesia (P < 0.001 vs saline control). To differentiate the direct effects of BK from indirect effects mediated by histamine released from mast cells (MCs), skin was pretreated with compound 4880 to degranulate the MCs prior to BK challenge. The early phase of BK-evoked pain was reduced in degranulated skin (P < 0.001), while thermal and mechanical sensitisation, wheal, and flare were still evident. In contrast to BK, the B1R selective agonist des-Arg9-BK failed to induce pain or sensitise naïve skin. However, following skin inflammation induced by ultraviolet B irradiation, this compound produced a robust pain response. We have optimised a versatile experimental model by which BK and its analogues can be administered to human skin. We have found that there is an early phase of BK-induced pain which partly depends on the release of inflammatory mediators by MCs; however, subsequent hyperalgesia is not dependent on MC degranulation. In naïve skin, B2R signaling predominates, however, cutaneous inflammation results in enhanced B1R responses.

Receptor-targeting mechanisms of pain-causing toxins: How ow?

Venoms often target vital processes to cause paralysis or death, but many types of venom also elicit notoriously intense pain. While these pain-producing effects can result as a byproduct of generalized tissue trauma, there are now multiple examples of venom-derived toxins that target somatosensory nerve terminals in order to activate nociceptive (pain-sensing) neural pathways. Intriguingly, investigation of the venom components that are responsible for evoking pain has revealed novel roles and/or configurations of well-studied toxin motifs. This review serves to highlight pain-producing toxins that target the capsaicin receptor, TRPV1, or members of the acid-sensing ion channel family, and to discuss the utility of venom-derived multivalent and multimeric complexes.

Cloning and sequence analysis of an Ophiophagus hannah cDNA encoding a precursor of two natriuretic peptide domains

The king cobra (Ophiophagus hannah) is the largest venomous snake. Despite the components are mainly neurotoxins, the venom contains several proteins affecting blood system. Natriuretic peptide (NP), one of the important components of snake venoms, could cause local vasodilatation and a promoted capillary permeability facilitating a rapid diffusion of other toxins into the prey tissues. Due to the low abundance, it is hard to purify the snake venom NPs. The cDNA cloning of the NPs become a useful approach. In this study, a 957 bp natriuretic peptide-encoding cDNA clone was isolated from an O. hannah venom gland cDNA library. The open-reading frame of the cDNA encodes a 210-amino acid residues precursor protein named Oh-NP. Oh-NP has a typical signal peptide sequence of 26 amino acid residues. Surprisingly, Oh-NP has two typical NP domains which consist of the typical sequence of 17-residue loop of CFGXXDRIGC, so it is an unusual NP precursor. These two NP domains share high amino acid sequence identity. In addition, there are two homologous peptides of unknown function within the Oh-NP precursor. To our knowledge, Oh-NP is the first protein precursor containing two NP domains. It might belong to another subclass of snake venom NPs.

A novel natriuretic peptide from the cobra venom

Natriuretic peptides (NPs) play crucial roles in human physiology and pathophysiology through natriuresis, dieresis and vasorelaxation. NPs are also one of the important components of snake venoms. However, the low abundance in snake venom hampered the investigation. Here, a novel natriuretic peptide named Na-NP was purified from the cobra Naja atra venom. Na-NP consists of 45 amino acid residues and its molecular weight is 4618.5 Da. A full-length cDNA encoding Na-NP was obtained from the cDNA library constructed from the venom gland. The open reading frame of cloned Na-NP was composed of 498bp and coded for a 165-amino acid residue protein precursor. The nucleotide and deduced protein sequences of Na-NP were remarkably conserved with other elapid NPs while significant different from the viperid NPs. Na-NP showed weak activity to relax the aortic rings precontracted with phenylephrine. Meanwhile, Na-NP showed cGMP-promotion activity against primary cultured rabbit endocardial endothelial cells, but had no effect on human platelet aggregation. In conclusion, this is the first report of a natriuretic peptide from the cobra N. atra venom. Na-NP might be served as a useful tool for the study of human NPs and the development of novel therapeutic drugs.

Identification of novel bradykinin-potentiating peptides and C-type natriuretic peptide from Lachesis muta venom

The generation of expressed sequence tags (ESTs) from the pit-viper snake Lachesis muta venom glands allowed us to identify two cDNA isoforms which encode the precursors for bradykinin-potentiating peptides (BPPs) and a C-type natriuretic peptide (CNP). The sequence data derived from these cDNAs combined with the venom peptides identification using MALDI-TOF mass spectrometry analysis predicted that these molecules are the precursor protein isoforms that are further processed to produce five novel BPPs and a CNP. They were identified directly in crude venom using MALDI-TOF. The BPPs sequences were further confirmed by MALDI-TOF/TOF de novo sequencing, and an unusual BPP with a residue of tryptophan at the N-terminus (usually it is pyroglutamate) was identified. The putative processing steps required to form the mature BPPs and CNP seem to be similar to those proposed for the ones found in the venom of Bothrops jararaca and Glodyus blomhoffi.

Fast analysis of low molecular mass compounds present in snake venom: identification of ten new pyroglutamate-containing peptides

Characterization of the peptide content in snake venoms can be an important tool for the investigation of new pharmacological lead compounds. For this purpose, single-step analysis of crude venoms has recently been demonstrated using mass spectrometry (MS) techniques. Reproducible profiles of ions in MS and MS/MS spectra may also be used to compare venoms from different species. In this work matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to obtain mass patterns of the major peptides (<8 kDa) found in pooled venoms from the genera Bothrops and Crotalus. Venoms from five different Bothrops species (B. jararaca, B. insularis, B. alternatus, B. jararacussu, and B. neuwiedi) and three Crotalus species (C. viridis, C. adamanteus and C. durissus terrificus) were analyzed. In agreement with other reports, venoms from Bothrops species contained a variety of peptides in the range m/z 1000-1500, and in some samples larger components (m/z 7000-8000) were detected. In the Crotalus species venoms were rich in peptides ranging from m/z 1000-1500 and 4000-5500. MS/MS experiments on the low molecular mass peptides (m/z 1000-1500) confirmed the presence of ten new bradykinin-potentiating peptides among venoms from genera Bothrops and Crotalus. In order to determine whether additional peptides could be identified after partial purification, B. jararaca venom was subjected to size-exclusion chromatography on Sephacryl S-200, and two distinct low molecular mass pools were analyzed further by MALDI-TOFMS. No additional peptides were detected from the pool with masses below 2000 Da but a substantial improvement with better resolution was observed for the pool with masses above 7000 Da, indicating that complex samples such as crude snake venoms can be analyzed for low molecular mass peptides using a single-step procedure.

Unmasking venom gland transcriptomes in reptile venoms

While structural studies of reptile venom toxins can be achieved using lyophilized venom samples, until now the cloning of precursor cDNAs required sacrifice of the specimen for dissection of the venom glands. Here we describe a simple and rapid technique that unmasks venom protein mRNAs present in lyophilized venom samples. To illustrate the technique we have RT-PCR-amplified a range of venom protein transcripts from cDNA libraries derived from the venoms of a hemotoxic snake, the Chinese copperhead (Deinagkistrodon acutus), a neurotoxic snake, the black mamba (Dendroaspis polylepis), and a venomous lizard, the Gila monster (Heloderma suspectum). These include a metalloproteinase and phospholipase A2 from D. acutus, a potassium channel blocker, dendrotoxin K, from D. polylepis, and exendin-4 from H. suspectum. These findings imply that the apparent absence and/or lability of mRNA in complex biological matrices is not always real and paves the way for accelerated acquisition of molecular genetic data on venom toxins for scientific and potential therapeutic purposes without sacrifice of endangered herpetofauna.