Monocrotaline

Last updated
Monocrotaline
Monocrotaline.svg
Chemical structure of monocrotaline
Names
IUPAC name
(1R,4R,5R,6R,16R)-5,6-dihydroxy-4,5,6-trimethyl-2,8-dioxa-13-azatricyclo[8.5.1.013,16]hexadec-10-ene-3,7-dione
Other names
  • Crotaline
  • (-)-Monocrotaline
  • Retronecine cyclic 2,3-dihydroxy-2,3,4-trimethylglutarate
Identifiers
3DMet
ChEBI
ECHA InfoCard 100.156.772 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
Properties
C16H23NO6
Molar mass 325.361 g·mol−1
AppearanceCrystalline solid
Melting point 204 °C (399 °F; 477 K)
Slightly soluble
Hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg
H301, H351
P203, P264, P270, P280, P301+P316, P318, P321, P330, P405, P501
Lethal dose or concentration (LD, LC):
66 mg/kg (rat, oral) / 259 mg/kg (mouse) intravenous)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Monocrotaline (MCT) is a pyrrolizidine alkaloid that is present in plants of the Crotalaria genus. These species can synthesise MCT out of amino acids and can cause liver, lung and kidney damage in various organisms. Initial stress factors are released intracellular upon binding of MCT to BMPR2 receptors and elevated MAPK phosphorylation levels are induced, which can cause cancer in Homo sapiens. MCT can be detoxified in rats via oxidation, followed by glutathione-conjugation and hydrolysis.

Contents

Origin

Picture of the Crotalaria spectabilis. Crotalaria juncea Da220020.JPG
Picture of the Crotalaria spectabilis.

MCT occurs in the seeds of certain species of the genus Crotalaria , for example, Crotalaria spectabilis and Crotalaria mucronata . [1] MCT is a chemical with pesticide properties and therefore serves as a defence mechanism to fend off predators. However, it can also lead to the poisoning of mammals and birds. [2]

The butterfly Utetheisa ornatrix also benefits from MCT by using it as protection. The larvae of the butterfly feed almost exclusively on Crotalaria seeds, where MCT is accumulated in their bodies. In this way, they are protected from predators such as spiders for the rest of their lives (even after pupation as butterflies). [3]

Toxicity

MCT is an acute toxic substance. The toxicity of MCT is dose-dependent, and it can harm both organs and genetic material (genotoxicity). The organs that will be targeted are the liver (hepatotoxicity), the kidneys (nephrotoxicity) and the lungs (pneumotoxicity). MCT falls into Category 3 toxicity for oral ingestion and Category 2 toxicity for carcinogenicity according to the European Chemicals Agency (ECHA). [4]

Studies concluded that the ingestion of MCT will cause centrilobular necrosis, pulmonary fibrosis and increase in blood urea nitrogen. These conclusions are based on the models that were used during these studies as these effects were caused in rats instead of humans. During the studies it was also concluded that mice are more resilient to MCT than rats, meaning that more mice survived the experiments than rats. [5] [6] [7]

Biosynthesis of monocrotaline

The biosynthesis of MCT involves condensation of monocrotalic acid (MCA), which is derived from L-isoleucine, and retronecine, which is derived from putrescine.

MCA is formed from L-isoleucine and a synthon for propionate of uncertain origin. [8]

Retronecine is synthesized from L-arginine via a multi-step pathway involving putrescine and spermidine intermediates:

Biosynthesis route of retronecine in plants. Biosynthesis route of retronecine.jpg
Biosynthesis route of retronecine in plants.

Putrescine is converted to spermidine by addition of a propylamino group from decarboxylated S-adenosylmethioninamine (4: spermidine synthase). Spermidine and another molecule of putrescine react to form the symmetric homospermidine with loss of 1,3-diaminopropane (5: homospermidine synthase).

Oxidation (likely catalysed by 6: copper-dependent diamine oxidases) to 4,4’-iminodibutanal results into the cyclization of pyrrolizidine-1-carbaldehyde, which is reduced to 1-hydroxymethyl pyrrolizidine (likely catalysed by 7: alcohol dehydrogenase). To form the final product retronecine, 1-hydroxymethyl pyrrolizidine is desaturated and hydroxylated respectively by unknown enzymes. [9]

MCA and retronecine are then condensed to form MCT via an unknown mechanism:

Biosynthesis of monocrotaline in plants. Biosynthesis of MC.jpg
Biosynthesis of monocrotaline in plants.

Biotransformation of monocrotaline

MCT is detoxified in rats by the liver via divergent biotransformation reactions. These reactions proceed as follows:

Biotransformation route of monocrotaline in rats. Biotransformation of monocrotaline in rats 3.jpg
Biotransformation route of monocrotaline in rats.

In Rats, MCT is first oxidised by the biotransformation enzyme cytochrome P450 (CYP) to form dehydro MCT. In this phase 1 reaction a double carbon-carbon bond is introduced out of a single carbon-carbon bond.

After the phase 1 reaction, the oxidised intermediate can either undergo hydrolysis to form monocrotalic acid and dihydropyrolizine or perform group transfer with glutathione to form MCA and a glutathione-conjugated dihydropyrolizine (GS-conjugation). These metabolites are more hydrophilic than MCT and could therefore be more easily excreted by the kidneys, which results in less exposure from MCT to the liver. The phase 2 reactions are thus classified as the detoxifying reactions during the biotransformation of MCT in rats.

During the phase 2 reactions, dehydro MCT can react with nucleophilic biological macromolecules (NuS) which is a toxic intermediate. Addition of such molecules may result into Cytotoxicity. Dehydro MCT may also undergo further toxification after hydrolysis, as dihydropyrolizine can be further oxidized to 7-dihydro-1-hydroxymethyl-5H-pyrrolizine (DHP). This intermediate can bind to DNA which may cause Genotoxicity. [10]

Note that the biotransformation routes may differ based on the studied organism. [11]

Mechanism of action

MCT aggregates on and activates the calcium-sensing receptor (CaSR) of pulmonary artery endothelial cells to trigger endothelial damage and, ultimately, induces pulmonary hypertension. MCT binds to the extracellular domain of the CaSR (calcium-sensing receptor). Thereby, the assembly of CaSR is enhanced and triggers the mobilisation of calcium signalling, and damages pulmonary artery endothelial cells. In addition, MCT strengthens this effect by binding to the bone morphogenetic protein receptor type II (BMPR2), which is a transmembrane receptor. BMPR2 inhibition occurs which in turn induces a blockade of BMPR1 receptor activation via phosphorylation. Inhibiting this process disturbs cell differentiation processes and ossification. Interference with these receptors induce pulmonary arterial hypertension.

Monocrotaline: schematic mechanism of action. Monocrotaline mechanism of action in organism.png
Monocrotaline: schematic mechanism of action.

MAPK is a mitogen activated protein kinase that gets activated upon BMPR2 activation. The protein kinase in turn phosphorylates p38 via a reinforced cascade of intracellular signals. It also activates p21 which has a regulating role in the cell cycle. However, MCT administration inhibits this process via a blockade of BMPR2. Cytokines such as TNF-α are released which cause activation of inflammation mechanisms, attracting neutrophils among others. Furthermore, inducible nitric oxide synthases (iNOS) are upregulated upon MCT induced cellular stress, whereas endothelial NOS (eNOS) gets downregulated. The cytokine TGF-β (also released by macrophages via chemotaxis during inflammation reactions in a positive feedback loop with TNF-α) is a transforming growth factor that is upregulated as a result of iNOS increasement, contributing to pulmonary artery proliferation. Increased levels of iNOS also stimulate caspase-3 activity which increases apoptosis levels. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Hepatotoxicity</span> Liver damage caused by a drug or chemical

Hepatotoxicity implies chemical-driven liver damage. Drug-induced liver injury is a cause of acute and chronic liver disease caused specifically by medications and the most common reason for a drug to be withdrawn from the market after approval.

<i>Crotalaria</i> Genus of legumes

Crotalaria is a genus of flowering plants in the family Fabaceae commonly known as rattlepods. The genus includes over 700 species of herbaceous plants and shrubs. Africa is the continent with the majority of Crotalaria species, which are mainly found in damp grassland, especially in floodplains, depressions and along edges of swamps and rivers, but also in deciduous bush land, roadsides and fields. Some species of Crotalaria are grown as ornamentals. The common name rattlepod or rattlebox is derived from the fact that the seeds become loose in the pod as they mature, and rattle when the pod is shaken. The name derives from the Ancient Greek κρόταλον, meaning "castanet", and is the same root as the name for the rattlesnakes (Crotalus).

<span class="mw-page-title-main">Pulmonary hypertension</span> Increased blood pressure in lung arteries

Pulmonary hypertension is a condition of increased blood pressure in the arteries of the lungs. Symptoms include shortness of breath, fainting, tiredness, chest pain, swelling of the legs, and a fast heartbeat. The condition may make it difficult to exercise. Onset is typically gradual. According to the definition at the 6th World Symposium of Pulmonary Hypertension in 2018, a patient is deemed to have pulmonary hypertension if the pulmonary mean arterial pressure is greater than 20mmHg at rest, revised down from a purely arbitrary 25mmHg, and pulmonary vascular resistance (PVR) greater than 3 Wood units.

<span class="mw-page-title-main">Spermidine</span> Chemical compound

Spermidine is a polyamine compound found in ribosomes and living tissues and having various metabolic functions within organisms. It was originally isolated from semen.

<span class="mw-page-title-main">Endothelin</span>

Endothelins are peptides with receptors and effects in many body organs. Endothelin constricts blood vessels and raises blood pressure. The endothelins are normally kept in balance by other mechanisms, but when overexpressed, they contribute to high blood pressure (hypertension), heart disease, and potentially other diseases.

<span class="mw-page-title-main">BMPR2</span> Protein-coding gene in the species Homo sapiens

Bone morphogenetic protein receptor type II or BMPR2 is a serine/threonine receptor kinase encoded by the BMPR2 gene. It binds bone morphogenetic proteins, members of the TGF beta superfamily of ligands, which are involved in paracrine signaling. BMPs are involved in a host of cellular functions including osteogenesis, cell growth and cell differentiation. Signaling in the BMP pathway begins with the binding of a BMP to the type II receptor. This causes the recruitment of a BMP type I receptor, which the type II receptor phosphorylates. The type I receptor phosphorylates an R-SMAD, a transcriptional regulator.

<span class="mw-page-title-main">Pyrrolizidine alkaloid</span> Class of chemical compounds

Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Pyrrolizidine alkaloids are produced by plants as a defense mechanism against insect herbivores. More than 660 PAs and PA N-oxides have been identified in over 6,000 plants, and about half of them exhibit hepatotoxicity. They are found frequently in plants in the Boraginaceae, Asteraceae, Orchidaceae and Fabaceae families; less frequently in the Convolvulaceae and Poaceae, and in at least one species in the Lamiaceae. It has been estimated that 3% of the world’s flowering plants contain pyrrolizidine alkaloids. Honey can contain pyrrolizidine alkaloids, as can grains, milk, offal and eggs. To date (2011), there is no international regulation of PAs in food, unlike those for herbs and medicines.

In enzymology, a homospermidine synthase (spermidine-specific) is an enzyme that catalyzes the chemical reaction

Biological functions of nitric oxide are roles that nitric oxide plays within biology.

<span class="mw-page-title-main">Riociguat</span> Chemical compound

Riociguat, sold under the brand name Adempas, is a medication by Bayer that is a stimulator of soluble guanylate cyclase (sGC). It is used to treat two forms of pulmonary hypertension (PH): chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary arterial hypertension (PAH). Riociguat constitutes the first drug of the class of sGC stimulators. The drug has a half-life of 12 hours and will decrease dyspnea associated with pulmonary arterial hypertension.

<span class="mw-page-title-main">Senecionine</span> Chemical compound

Senecionine is a toxic pyrrolizidine alkaloid isolated from various botanical sources. It takes its name from the Senecio genus and is produced by many different plants in that genus, including Jacobaea vulgaris. It has also been isolated from several other plants, including Brachyglottis repanda, Emilia, Erechtites hieraciifolius, Petasites, Syneilesis, Crotalaria, Caltha leptosepala, and Castilleja.

Pyrrolizidine alkaloidosis is a disease caused by chronic poisoning found in humans and other animals caused by ingesting poisonous plants which contain the natural chemical compounds known as pyrrolizidine alkaloids. Pyrrolizidine alkaloidosis can result in damage to the liver, kidneys, heart, brain, smooth muscles, lungs, DNA, lesions all over the body, and could be a potential cause of cancer. Pyrrolizidine alkaloidosis is known by many other names such as "Pictou Disease" in Canada and "Winton Disease" in New Zealand. Cereal crops and forage crops can sometimes become polluted with pyrrolizidine-containing seeds, resulting in the alkaloids contaminating flour and other foods, including milk from cows feeding on these plants.

<i>Crotalaria cunninghamii</i> Species of legume

Crotalaria cunninghamii, also known as green birdflower, birdflower ratulpo, parrot pea or regal birdflower, is a plant of the legume family Fabaceae, named Crotalaria after the Greek word for rattle, because their seeds rattle, and cunninghamii after early 19th century botanist Allan Cunningham. Crotalaria cunninghamii is known as Mangarr to the Nyangumarta Warrarn Indigenous group.

<span class="mw-page-title-main">PRX-08066</span> Chemical compound

PRX-08066 is a drug discovered and developed by Predix Pharmaceuticals [Dale S. Dhanoa et al. Patent US 7,030,240 B2], which acts as a potent and selective antagonist at the serotonin 5-HT2B receptor, with a 5-HT2Bbinding affinity (Ki) of 3.4nM, and high selectivity over the closely related 5-HT2A and 5-HT2C receptors and other receptor targets. PRX-08066 and other selective 5-HT2B antagonists are being researched for the treatment of pulmonary arterial hypertension, following the discovery that the potent 5-HT2B agonist norfenfluramine produces pulmonary arterial hypertension and subsequent heart valve damage. In animal studies, PRX-08066 has been found to reduce several key indicators of pulmonary arterial hypertension and improved cardiac output, with similar efficacy to established drugs for this condition such as bosentan, sildenafil, beraprost and iloprost. It is also being researched for potential anti-cancer applications, due to its ability to inhibit fibroblast activation.

<span class="mw-page-title-main">Riddelliine</span> Chemical compound

Riddelliine is a chemical compound classified as a pyrrolizidine alkaloid. It was first isolated from Senecio riddellii and is also found in a variety of plants including Jacobaea vulgaris, Senecio vulgaris, and others plants in the genus Senecio.

Homospermidine synthase (EC 2.5.1.44) is an enzyme with systematic name putrescine:putrescine 4-aminobutyltransferase (ammonia-forming). This enzyme catalyses the following chemical reaction

<span class="mw-page-title-main">GW0742</span> PPAR β/δ receptor Agonist compound

GW0742 is a PPARδ/β agonist that has been investigated for drug use by GlaxoSmithKline.

<span class="mw-page-title-main">20-Hydroxyeicosatetraenoic acid</span> Chemical compound

20-Hydroxyeicosatetraenoic acid, also known as 20-HETE or 20-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid, is an eicosanoid metabolite of arachidonic acid that has a wide range of effects on the vascular system including the regulation of vascular tone, blood flow to specific organs, sodium and fluid transport in the kidney, and vascular pathway remodeling. These vascular and kidney effects of 20-HETE have been shown to be responsible for regulating blood pressure and blood flow to specific organs in rodents; genetic and preclinical studies suggest that 20-HETE may similarly regulate blood pressure and contribute to the development of stroke and heart attacks. Additionally the loss of its production appears to be one cause of the human neurological disease, Hereditary spastic paraplegia. Preclinical studies also suggest that the overproduction of 20-HETE may contribute to the progression of certain human cancers, particularly those of the breast.

<span class="mw-page-title-main">4-Ipomeanol</span> Chemical compound

4-Ipomeanol (4-IPO) is a pulmonary pre-toxin isolated from sweet potatoes infected with the fungus Fusarium solani. One of the 4-IPO metabolites is toxic to the lungs, liver and kidney in humans and animals. This metabolite can covalently bind to proteins, thereby interfering with normal cell processes.

<span class="mw-page-title-main">Thomas Hartmann (biologist)</span> German pharmaceutical biologist (1937–2017)

Thomas Hartmann,, was a German pharmaceutical biologist and ecologist who was professor in the Department of Pharmaceutical Biology at the Technische Universität Braunschweig. His research focused on the biosynthesis, intracellular transport, and action of quinolizidine and pyrrolizidine alkaloids in fungi and plants and the sequestration of these secondary natural products by insects.

References

  1. Gomez-Arroyo, Jose G.; Farkas, Laszlo; Alhussaini, Aysar A.; Farkas, Daniela; Kraskauskas, Donatas; Voelkel, Norbert F.; Bogaard, Harm J. (2012-02-15). "The monocrotaline model of pulmonary hypertension in perspective". American Journal of Physiology. Lung Cellular and Molecular Physiology. 302 (4): L363–L369. doi:10.1152/ajplung.00212.2011. ISSN   1040-0605. PMID   21964406. S2CID   14342793.
  2. Williams, M. Coburn; Molyneux, Russell J. (1987). "Occurrence, Concentration, and Toxicity of Pyrrolizidine Alkaloids in Crotalaria Seeds". Weed Science. 35 (4): 476–481. doi:10.1017/S0043174500060410. ISSN   0043-1745. S2CID   91434059.
  3. Everist, S. L. (1974). Poisonous plants of Australia (1 ed.). Sydney: Angus & Robertson. ISBN   978-0-207-12773-1.
  4. Suparmi, Suparmi; Wesseling, Sebastiaan; Rietjens, Ivonne M. C. M. (2020-09-01). "Monocrotaline-induced liver toxicity in rat predicted by a combined in vitro physiologically based kinetic modeling approach". Archives of Toxicology. 94 (9): 3281–3295. doi:10.1007/s00204-020-02798-z. ISSN   1432-0738. PMC   7415757 . PMID   32518961.
  5. Suparmi, Suparmi; Wesseling, Sebastiaan; Rietjens, Ivonne M. C. M. (2020-09-01). "Monocrotaline-induced liver toxicity in rat predicted by a combined in vitro physiologically based kinetic modeling approach". Archives of Toxicology. 94 (9): 3281–3295. doi:10.1007/s00204-020-02798-z. ISSN   1432-0738. PMC   7415757 . PMID   32518961.
  6. Molteni, Agostino; Ward, William F.; Ts’ao, Chung-hsin; Solliday, Norman H. (1989-01-01). "Monocrotaline pneumotoxicity in mice". Virchows Archiv B. 57 (1): 149–155. doi:10.1007/BF02899076. ISSN   0340-6075. PMID   2570481. S2CID   29465237.
  7. Roth, R. A.; Dotzlaf, L. A.; Baranyi, B.; Kuo, C. -H.; Hook, J. B. (1981-09-15). "Effect of monocrotaline ingestion on liver, kidney, and lung of rats". Toxicology and Applied Pharmacology. 60 (2): 193–203. doi:10.1016/0041-008X(91)90223-2. ISSN   0041-008X. PMID   6792747.
  8. Robins, David J.; Bale, Nicholas M.; Crout, David H. G. (1974). "Pyrrolizidine alkaloids. Biosynthesis of monocrotalic acid, the necic acid component of monocrotaline". Journal of the Chemical Society, Perkin Transactions 1 (18): 2082–2086. doi:10.1039/p19740002082. PMID   4473457.
  9. Schramm, Sebastian; Köhler, Nikolai; Rozhon, Wilfried (2019-01-30). "Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants". Molecules. 24 (3): 498. doi: 10.3390/molecules24030498 . ISSN   1420-3049. PMC   6385001 . PMID   30704105.
  10. Pitanga, Bruno; Nascimento, Ravena; Silva, Victor Diogenes; Costa, Silvia (2012). "The Role of Astrocytes in Metabolism and Neurotoxicity of the Pyrrolizidine Alkaloid Monocrotaline, the Main Toxin of Crotalaria retusa". Frontiers in Pharmacology. 3: 144. doi: 10.3389/fphar.2012.00144 . ISSN   1663-9812. PMC   3411086 . PMID   22876233.
  11. Szymanski, Edward S.; Little, Nancy A.; Kritchevsky, David (1981). "Phospholipid metabolism in livers of young and old fisher 344 and Sprague-Dawley rats". Experimental Gerontology. 16 (2): 163–169. doi:10.1016/0531-5565(81)90041-3. ISSN   0531-5565. PMID   7286096. S2CID   9094511.
  12. Ahmed, Lamiaa A.; Obaid, Al Arqam Z.; Zaki, Hala F.; Agha, Azza M. (2014-10-01). "Naringenin adds to the protective effect of L-arginine in monocrotaline-induced pulmonary hypertension in rats: Favorable modulation of oxidative stress, inflammation and nitric oxide". European Journal of Pharmaceutical Sciences. 62: 161–170. doi:10.1016/j.ejps.2014.05.011. ISSN   0928-0987. PMID   24878387.