Lebetin 2, a Snake Venom-Derived Natriuretic Peptide, Attenuates Acute Myocardial Ischemic Injury through the Modulation of Mitochondrial Permeability Transition Pore at the Time of Reperfusion

Changes in attachment and metabolic activity of rat neonatal cardiomyocytes and nonmyocytes caused by Macrovipera lebetina obtusa venom

The Caucasian viper Macrovipera lebetina obtusa (MLO) is one of the most prevalent and venomous snakes in the Caucasus and the surrounding regions, yet the effects of MLO venom on cardiac function remain largely unknown. We examined the influence of MLO venom (crude and with inhibited metalloproteinases and phospholipase A2) on attachment and metabolic activity of rat neonatal cardiomyocytes (CM) and nonmyocytes (nCM), assessed at 1 and 24 h. After exposing both CM and nCM to varying concentrations of MLO venom, we observed immediate cytotoxic effects at a concentration of 100 μg/ml, causing detachment from the culture substrate. At lower MLO venom concentrations both cell types detached in a dose-dependent manner. Inhibition of MLO venom metalloproteinases significantly improved CM and nCM attachment after 1-hour exposure. At 24-hour exposure to metalloproteinases inhibited venom statistically significant enhancement was observed only in nCM attachment. However, metabolic activity of CM and nCM did not decrease upon exposure to the lower dose of the venom. Moreover, we demonstrated that metalloproteinases and phospholipases A2 are not the components of the MLO venom that change metabolic activity of both CM and nCM. These results provide a valuable platform to study the impact of MLO venom on prey cardiac function. They also call for further exploration of individual venom components for pharmaceutical purposes.

A Review of Rattlesnake Venoms

Venom components are invaluable in biomedical research owing to their specificity and potency. Many of these components exist in two genera of rattlesnakes, Crotalus and Sistrurus, with high toxicity and proteolytic activity variation. This review focuses on venom components within rattlesnakes, and offers a comparison and itemized list of factors dictating venom composition, as well as presenting their known characteristics, activities, and significant applications in biosciences. There are 64 families and subfamilies of proteins present in Crotalus and Sistrurus venom. Snake venom serine proteases (SVSP), snake venom metalloproteases (SVMP), and phospholipases A2 (PLA2) are the standard components in Crotalus and Sistrurus venom. Through this review, we highlight gaps in the knowledge of rattlesnake venom; there needs to be more information on the venom composition of three Crotalus species and one Sistrurus subspecies. We discuss the activity and importance of both major and minor components in biomedical research and drug development.

Inflammatory Bowel Disease Increases the Severity of Myocardial Infarction after Acute Ischemia-Reperfusion Injury in Mice

(1) Background: Increased risk of myocardial infarction (MI) has been linked to several inflammatory conditions, including inflammatory bowel disease (IBD). However, the relationship between IBD and MI remains unclear. Here, we implemented an original mouse model combining IBD and MI to determine IBD's impact on MI severity and the link between the two diseases. (2) Methods: An IBD model was established by dextran sulfate sodium (DSS) administration in drinking water, alone or with oral C. albicans (Ca) gavage. IBD severity was assessed by clinical/histological scores and intestinal/systemic inflammatory biomarker measurement. Mice were subjected to myocardial ischemia-reperfusion (IR), and MI severity was assessed by quantifying infarct size (IS) and serum cardiac troponin I (cTnI) levels. (3) Results: IBD mice exhibited elevated fecal lipocalin 2 (Lcn2) and IL-6 levels. DSS mice exhibited almost two-fold increase in IS compared to controls, with serum cTnI levels strongly correlated with IS. Ca inoculation tended to worsen DSS-induced systemic inflammation and IR injury, an observation which is not statistically significant. (4) Conclusions: This is the first proof-of-concept study demonstrating the impact of IBD on MI severity and suggesting mechanistic aspects involved in the IBD-MI connection. Our findings could pave the way for MI therapeutic approaches based on identified IBD-induced inflammatory mediators.

Snake Venom Components as Therapeutic Drugs in Ischemic Heart Disease

Ischemic heart disease (IHD), especially myocardial infarction (MI), is a leading cause of death worldwide. Although coronary reperfusion is the most straightforward treatment for limiting the MI size, it has nevertheless been shown to exacerbate ischemic myocardial injury. Therefore, identifying and developing therapeutic strategies to treat IHD is a major medical challenge. Snake venoms contain biologically active proteins and peptides that are of major interest for pharmacological applications in the cardiovascular system (CVS). This has led to their use for the development and design of new drugs, such as the first-in-class angiotensin-converting enzyme inhibitor captopril, developed from a peptide present in Bothrops jararaca snake venom. This review discusses the potential usefulness of snake venom toxins for developing effective treatments against IHD and related diseases such as hypertension and atherosclerosis. It describes their biological effects at the molecular scale, their mechanisms of action according to their different pharmacological properties, as well as their subsequent molecular pathways and therapeutic targets. The molecules reported here have either been approved for human medical use and are currently available on the drug market or are still in the clinical or preclinical developmental stages. The information summarized here may be useful in providing insights into the development of future snake venom-derived drugs.

Natriuretic-like Peptide Lebetin 2 Mediates M2 Macrophage Polarization in LPS-Activated RAW264.7 Cells in an IL-10-Dependent Manner

Snake natriuretic peptide (NP) Lebetin 2 (L2) has been shown to improve cardiac function and reduce fibrosis as well as inflammation by promoting M2-type macrophages in a reperfused myocardial infarction (MI) model. However, the inflammatory mechanism of L2 remains unclear. Therefore, we investigated the effect of L2 on macrophage polarization in lipopolysaccharide (LPS)-activated RAW264.7 cells in vitro and explored the associated underlying mechanisms. TNF-α, IL-6 and IL-10 levels were assessed using an ELISA assay, and M2 macrophage polarization was determined by flow cytometry. L2 was used at non-cytotoxic concentrations determined by a preliminary MTT cell viability assay, and compared to B-type natriuretic peptide (BNP). In LPS-activated cells, both peptides reduced TNF-α and IL-6 release compared to controls. However, only L2 increased IL-10 release in a sustained manner and promoted downstream M2 macrophage polarization. Pretreatment of LPS-activated RAW264.7 cells with the selective NP receptor (NPR) antagonist isatin abolished both IL-10 and M2-like macrophage potentiation provided by L2. In addition, cell pretreatment with the IL-10 inhibitor suppressed L2-induced M2 macrophage polarization. We conclude that L2 exerts an anti-inflammatory response to LPS by regulating the release of inflammatory cytokines via stimulating of NP receptors and promoting M2 macrophage polarization through activation of IL-10 signaling.

Age-Dependent Changes in Calcium Regulation after Myocardial Ischemia-Reperfusion Injury

During aging, heart structure and function gradually deteriorate, which subsequently increases susceptibility to ischemia-reperfusion (IR). Maintenance of Ca²⁺ homeostasis is critical for cardiac contractility. We used Langendorff's model to monitor the susceptibility of aging (6-, 15-, and 24-month-old) hearts to IR, with a specific focus on Ca²⁺-handling proteins. IR, but not aging itself, triggered left ventricular changes when the maximum rate of pressure development decreased in 24-month-olds, and the maximum rate of relaxation was most affected in 6-month-old hearts. Aging caused a deprivation of Ca²⁺-ATPase (SERCA2a), Na⁺/Ca²⁺ exchanger, mitochondrial Ca²⁺ uniporter, and ryanodine receptor contents. IR-induced damage to ryanodine receptor stimulates Ca²⁺ leakage in 6-month-old hearts and elevated phospholamban (PLN)-to-SERCA2a ratio can slow down Ca²⁺ reuptake seen at 2-5 μM Ca²⁺. Total and monomeric PLN mirrored the response of overexpressed SERCA2a after IR in 24-month-old hearts, resulting in stable Ca²⁺-ATPase activity. Upregulated PLN accelerated inhibition of Ca²⁺-ATPase activity at low free Ca²⁺ in 15-month-old after IR, and reduced SERCA2a content subsequently impairs the Ca²⁺-sequestering capacity. In conclusion, our study suggests that aging is associated with a significant decrease in the abundance and function of Ca²⁺-handling proteins. However, the IR-induced damage was not increased during aging.

In Silico Study of the Mechanisms Underlying the Action of the Snake Natriuretic-Like Peptide Lebetin 2 during Cardiac Ischemia

Lebetin 2 (L2), a natriuretic-like peptide (NP), exerts potent cardioprotection in myocardial infarction (MI), with stronger effects than B-type natriuretic peptide (BNP). To determine the molecular mechanisms underlying its cardioprotection effect, we used molecular modeling, molecular docking and molecular dynamics (MD) simulation to describe the binding mode, key interaction residues as well as mechanistic insights into L2 interaction with NP receptors (NPRs). L2 binding affinity was determined for human, rat, mouse and chicken NPRs, and the stability of receptor-ligand complexes ascertained during 100 ns-long MD simulations. We found that L2 exhibited higher affinity for all human NPRs compared to BNP, with a rank preference for NPR-A > NPR-C > NPR-B. Moreover, L2 affinity for human NPR-A and NPR-C was higher in other species. Both docking and MD studies revealed that the NPR-C-L2 interaction was stronger in all species compared to BNP. Due to its higher affinity to human receptors, L2 could be used as a therapeutic approach in MI patients. Moreover, the stronger interaction of L2 with NPR-C could highlight a new L2 signaling pathway that would explain its additional effects during cardiac ischemia. Thus, L2 is a promising candidate for drug design toward novel compounds with high potency, affinity and stability.

Therapeutic Peptides to Treat Myocardial Ischemia-Reperfusion Injury

Cardiovascular diseases (CVD) including acute myocardial infarction (AMI) rank first in worldwide mortality and according to the World Health Organization (WHO), they will stay at this rank until 2030. Prompt revascularization of the occluded artery to reperfuse the myocardium is the only recommended treatment (by angioplasty or thrombolysis) to decrease infarct size (IS). However, despite beneficial effects on ischemic lesions, reperfusion leads to ischemia-reperfusion (IR) injury related mainly to apoptosis. Improvement of revascularization techniques and patient care has decreased myocardial infarction (MI) mortality however heart failure (HF) morbidity is increasing, contributing to the cost-intense worldwide HF epidemic. Currently, there is no treatment for reperfusion injury despite promising results in animal models. There is now an obvious need to develop new cardioprotective strategies to decrease morbidity/mortality of CVD, which is increasing due to the aging of the population and the rising prevalence rates of diabetes and obesity. In this review, we will summarize the different therapeutic peptides developed or used focused on the treatment of myocardial IR injury (MIRI). Therapeutic peptides will be presented depending on their interacting mechanisms (apoptosis, necroptosis, and inflammation) reported as playing an important role in reperfusion injury following myocardial ischemia. The search and development of therapeutic peptides have become very active, with increasing numbers of candidates entering clinical trials. Their optimization and their potential application in the treatment of patients with AMI will be discussed.

Snake Venom Components: Tools and Cures to Target Cardiovascular Diseases

Cardiovascular diseases (CVDs) are considered as a major cause of death worldwide. Therefore, identifying and developing therapeutic strategies to treat and reduce the prevalence of CVDs is a major medical challenge. Several drugs used for the treatment of CVDs, such as captopril, emerged from natural products, namely snake venoms. These venoms are complex mixtures of bioactive molecules, which, among other physiological networks, target the cardiovascular system, leading to them being considered in the development and design of new drugs. In this review, we describe some snake venom molecules targeting the cardiovascular system such as phospholipase A2 (PLA2), natriuretic peptides (NPs), bradykinin-potentiating peptides (BPPs), cysteine-rich secretory proteins (CRISPs), disintegrins, fibrinolytic enzymes, and three-finger toxins (3FTXs). In addition, their molecular targets, and mechanisms of action—vasorelaxation, inhibition of platelet aggregation, cardioprotective activities—are discussed. The dissection of their biological effects at the molecular scale give insights for the development of future snake venom-derived drugs.

Natriuretic Peptides as the Basis of Peptide Drug Discovery for Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading global cause of death, accounting for more than 17.6 million deaths per year in 2016, a number that is expected to grow to more than 23.6 million by 2030. While many technologies are currently under investigation to improve the therapeutic outcome of CVD complications, only a few medications have been approved. Therefore, new approaches to treat CVD are urgently required. Peptides regulate numerous physiological processes, mainly by binding to specific receptors and inducing a series of signals, neurotransmissions or the release of growth factors. Importantly, peptides have also been shown to play an important role in the circulatory system both in physiological and pathological conditions. Peptides, such as angiotensin II, endothelin, urotensin-II, urocortins, adrenomedullin and natriuretic peptides have been implicated in the control of vascular tone and blood pressure as well as in CVDs such as congestive heart failure, atherosclerosis, coronary artery disease, and pulmonary and systemic hypertension. Hence it is not surprising that peptides are becoming important therapeutic leads in CVDs. This article will review the current knowledge on peptides and their role in the circulatory system, focusing on the physiological roles of natriuretic peptides in the cardiovascular system and their implications in CVDs.

Aging Attenuates Cardiac Contractility and Affects Therapeutic Consequences for Myocardial Infarction

Cardiac function of the human heart changes with age. The age-related change of systolic function is subtle under normal conditions, but abrupt under stress or in a pathogenesis state. Aging decreases the cardiac tolerance to stress and increases susceptibility to ischemia, which caused by aging-induced Ca2+ transient impairment and metabolic dysfunction. The changes of contractility proteins and the relative molecules are in a non-linear fashion. Specifically, the expression and activation of cMLCK increase first then fall during ischemia and reperfusion (I/R). This change is responsible for the nonmonotonic contractility alteration in I/R which the underlying mechanism is still unclear. Contractility recovery in I/R is also attenuated by age. The age-related change in cardiac contractility influences the therapeutic effect and intervention timepoint. For most cardiac ischemia therapies, the therapeutic result in the elderly is not identical to the young. Anti-aging treatment has the potential to prevent the development of ischemic injury and improves cardiac function. In this review we discuss the mechanism underlying the contractility changes in the aged heart and age-induced ischemic injury. The potential mechanism underlying the increased susceptibility to ischemic injury in advanced age is highlighted. Furthermore, we discuss the effect of age and the administration time for intervention in cardiac ischemia therapies.

NO mediates the effect of the synthetic natriuretic peptide NPCdc on kidney and aorta in nephrectomised rats

NPCdc is a synthetic natriuretic peptide that was originally derived from another peptide, the NP2_Casca, isolated from Crotalus durissus cascavella venom. These molecules share 70% structural homology with natriuretic peptides obtained from different species, including humans. NP2_Casca induces vasorelaxation and increases nitric oxide levels independently of natriuretic peptide receptors A and B. This study aimed to investigate whether NPCdc-induced hypotension in control rats and rats with a reduced kidney mass is associated with effects on the glomerular filtration rate, NADPH oxidase activity and components downstream of natriuretic peptide receptor C (NPR-C). Anaesthetized Wistar rats that were subjected to a sham operation and 5/6 nephrectomy (5/6Nx) were infused with saline (vehicle) or NPCdc (7.5 μg/kg/min) for 70 min. The NPCdc treatment decreased the mean arterial pressure and NADPH oxidase activity while simultaneously increasing the glomerular filtration rate, fractional Na⁺ excretion and nitric oxide level. After 70 min, the levels of p-AKT ^Ser-473, p-eNOS ^Ser-1177, p-nNOS ^Ser-1417 and p-iNOS^Tyr-151 were not affected. However, p-ERK1/2 ^{Thr-202/Tyr-204} levels were altered. Thus, nitric oxide and components of NPR-C signalling mediate the effects of NPCdc. The results suggest a potential therapeutic application of this peptide for cardiorenal syndrome.

Lebetin 2, a Snake Venom-Derived B-Type Natriuretic Peptide, Provides Immediate and Prolonged Protection against Myocardial Ischemia-Reperfusion Injury via Modulation of Post-Ischemic Inflammatory Response

Myocardial infarction (MI) followed by left ventricular (LV) remodeling is the most frequent cause of heart failure. Lebetin 2 (L2), a snake venom-derived natriuretic peptide, exerts cardioprotection during acute myocardial ischemia-reperfusion (IR) ex vivo. However, its effects on delayed consequences of IR injury, including post-MI inflammation and fibrosis have not been defined. Here, we determined whether a single L2 injection exerts cardioprotection in IR murine models in vivo, and whether inflammatory response to ischemic injury plays a role in L2-induced effects. We quantified infarct size (IS), fibrosis, inflammation, and both endothelial cell and cardiomyocyte densities in injured myocardium and compared these values with those induced by B-type natriuretic peptide (BNP). Both L2 and BNP reduced IS, fibrosis, and inflammatory response after IR, as evidenced by decreased leukocyte and proinflammatory M1 macrophage infiltrations in the infarcted area compared to untreated animals. However, only L2 increased anti-inflammatory M2-like macrophages. L2 also induced a higher density of endothelial cells and cardiomyocytes. Our data show that L2 has strong, acute, prolonged cardioprotective effects in post-MI that are mediated, at least in part, by the modulation of the post-ischemic inflammatory response and especially, by the enhancement of M2-like macrophages, thus reducing IR-induced necrotic and fibrotic effects.

Snake Venom Peptides: Tools of Biodiscovery

Nature endowed snakes with a lethal secretion known as venom, which has been fine-tuned over millions of years of evolution. Snakes utilize venom to subdue their prey and to survive in their natural habitat. Venom is known to be a very poisonous mixture, consisting of a variety of molecules, such as carbohydrates, nucleosides, amino acids, lipids, proteins and peptides. Proteins and peptides are the major constituents of the dry weight of snake venoms and are of main interest for scientific investigations as well as for various pharmacological applications. Snake venoms contain enzymatic and non-enzymatic proteins and peptides, which are grouped into different families based on their structure and function. Members of a single family display significant similarities in their primary, secondary and tertiary structures, but in many cases have distinct pharmacological functions and different bioactivities. The functional specificity of peptides belonging to the same family can be attributed to subtle variations in their amino acid sequences. Currently, complementary tools and techniques are utilized to isolate and characterize the peptides, and study their potential applications as molecular probes, and possible templates for drug discovery and design investigations.

Vipers of the Middle East: A Rich Source of Bioactive Molecules

Snake venom serves as a tool of defense against threat and helps in prey digestion. It consists of a mixture of enzymes, such as phospholipase A2, metalloproteases, and l-amino acid oxidase, and toxins, including neurotoxins and cytotoxins. Beside their toxicity, venom components possess many pharmacological effects and have been used to design drugs and as biomarkers of diseases. Viperidae is one family of venomous snakes that is found nearly worldwide. However, three main vipers exist in the Middle Eastern region: Montivipera bornmuelleri, Macrovipera lebetina, and Vipera (Daboia) palaestinae. The venoms of these vipers have been the subject of many studies and are considered as a promising source of bioactive molecules. In this review, we present an overview of these three vipers, with a special focus on their venom composition as well as their biological activities, and we discuss further frameworks for the exploration of each venom.

Isatin, an endogenous nonpeptide biofactor: A review of its molecular targets, mechanisms of actions, and their biomedical implications

Isatin (indole-2,3-dione) is an oxidized indole. It is widely distributed in mammalian tissues and body fluids, where isatin concentrations vary significantly from <0.1 to > 10 µM. Isatin output is increased under conditions of stress. Exogenously administered isatin is characterized by low toxicity, mutagenicity, and genotoxicity in vivo. Cytotoxic effects of isatin on various cell cultures are usually observed at concentrations exceeding 100 µM. Binding of [³ H]isatin to rat brain sections is consistent with its physiological concentrations. Proteomic analysis of mouse and rat brain isatin-binding proteins revealed about 90 individual proteins, which demonstrated significant interspecies differences (rat versus mouse). Certain evidence exist that redox state(s) and possibly other types of posttranslational modifications regulate affinity of target proteins to isatin. Recent data suggest that interacting with numerous intracellular isatin binding proteins, isatin can act as a regulator of complex protein networks in norm and pathology. Physiological concentrations of isatin in vitro inhibit monoamine oxidase B and natriuretic peptide receptor guanylate cyclase, higher (neuroprotective) concentrations (50-400 μM) cause apoptosis of various (including malignant tumor) cell lines and influence expression of certain apoptosis-related genes. Being administered in vivo, isatin exhibits various behavioral effects; it attenuates manifestations of MPTP-induced parkinsonism and tumor growth in experimental animal models. © 2017 BioFactors, 44(2):95-108, 2018.