Functional characterization of a Colchicum autumnale L. double-bond reductase (CaDBR1) in colchicine biosynthesis.

MAIN CONCLUSION: An alkenal double-bond reductase enzyme (CaDBR1) was cloned from Colchicum autumnale L. The encoded enzyme catalysed 4-coumaraldehyde to 4-hydroxydihydrocinnamaldehyde (4-HDCA). Its functional characterization increased the understanding of colchicine biosynthesis. As a traditional medical plant, Colchicum autumnale L. is famous for producing colchicine, a widely used drug for alleviating gout attacks. The biosynthetic pathway of colchicine was revealed most recently, and 4-hydroxydihydrocinnamaldehyde (4-HDCA) has been verified as a crucial intermediate derived from L-phenylalanine. However, the functional gene that catalyses the formation of 4-HDCA remains controversial. In this study, the alkenal double-bond reductase (DBR) gene member CaDBR1 was cloned and characterized from C. autumnale. Bioinformatics analysis predicted and characterized the basic physicochemical properties of CaDBR1. Recombinant CaDBR1 protein was heterologously expressed in Escherichia coli and purified by a Ni-NTA column. In vitro enzyme assays indicated that CaDBR1 could catalyse 4-coumaraldehyde to form 4-HDCA but could not generate 4-HDCA by taking cinnamaldehyde as a substrate. Stable transformation into tobacco BY-2 cells revealed that CaDBR1 localized in the cytoplasm, and tissue-specific expression results showed that CaDBR1 had the highest expression in bulbs. All these results verify and confirm the participation and contribution of CaDBR1 in the biosynthesis pathway of 4-HDCA and colchicine alkaloids in C. autumnale.

Colchicine, a microtubule-disassembling drug, in the therapy of cardiovascular diseases.

Colchicum autumnale, from which colchicine has been isolated more than 100 years ago, has been used as a treatment for pain and swelling for thousands of years. It is one of the few drugs known from that time period whose use has survived to modernity. Over the past decades, advances in the knowledge of (i) cytoskeletal microtubules (МТ), and (ii) anti-inflammatory and anti-fibrotic effects of colchicine, a classical MT-disassembling (tubulin-targeting) agent, have led to potential new uses for this very old drug extended beyond acute gouty arthritis and familial Mediterranean fever. Here, in brief, I present the Bulgarian contribution to possible potential of colchicine in the therapy of cardiovascular diseases that has emerged in the early 1970s in the Laboratory of Electron Microscopy, Medical Institute, Varna, Bulgaria, studying the secretory function of vascular smooth muscle cells. From this time onward, low-dose colchicine (0.5-1.0 mg/daily) was increasingly administered orally for therapy of cardiovascular diseases such as acute coronary syndromes, postoperative atrial fibrillation (in cardiac surgery), pericarditis, cardiac hypertrophy-associated heart failure, restenosis after angioplasty, and systemic necrotizing vasculitis. Thus, colchicine might be a new tool in the present therapeutic armamentarium for cardiovascular diseases. It is simply an example of MT-disassembling drugs. Further studies will definitely be required before gaining real confidence in this kind of antitubulin pharmacology and therapy. This may lead to developing new and more specific antitubulins for cardiovascular diseases.

Modeling the Colchicum autumnale Tubulin and a Comparison of Its Interaction with Colchicine to Human Tubulin.

Tubulin is the target for many small-molecule natural compounds, which alter microtubules dynamics, and lead to cell cycle arrest and apoptosis. One of these compounds is colchicine, a plant alkaloid produced by Colchicum autumnale. While C. autumnale produces a potent cytotoxin, colchicine, and expresses its target protein, it is immune to colchicine's cytotoxic action and the mechanism of this resistance is hitherto unknown. In the present paper, the molecular mechanisms responsible for colchicine resistance in C. autumnale are investigated and compared to human tubulin. To this end, homology models for C. autumnale α-ß tubulin heterodimer are created and molecular dynamics (MD) simulations together with molecular mechanics Poisson-Boltzmann calculations (MM/PBSA) are performed to determine colchicine's binding affinity for tubulin. Using our molecular approach, it is shown that the colchicine-binding site in C. autumnale tubulin contains a small number of amino acid substitutions compared to human tubulin. However, these substitutions induce significant reduction in the binding affinity for tubulin, and subsequently fewer conformational changes in its structure result. It is suggested that such small conformational changes are insufficient to profoundly disrupt microtubule dynamics, which explains the high resistance to colchicine by C. autumnale.

Inhibition activities of Colchicum luteum baker on lipoxygenase and other enzymes.

In vitro enzymes inhibition activities of the crude methanolic extract and various fractions of Colchicum luteum Baker (Liliaceae) including chloroform, ethyl acetate, n-butanol and aqueous were carried out against actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease enzymes. A significant enzyme inhibition activity (89%) is shown by the crude methanolic extract and its fractions against lipoxygenase, while low to significant activity (32-75%) was evident against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity (29-61%) against acetylcholinesterase and no activity against urease.

Acute poisoning with autumn crocus (Colchicum autumnale L.).

INTRODUCTION: Colchicum autumnale, commonly known as the autumn crocus or meadow saffron, contains the antimitotic colchicine, which binds to tubulin and prevents it forming microtubules that are part of the cytoskeleton in all cells. CASE REPORT: A 71-year-old woman ate a plant she thought to be wild garlic (Allium ursinum). Ten hours later she arrived at the emergency department complaining of nausea, vomiting and watery diarrhea. Ingestion of a poisonous plant was suspected and she was treated with gastric lavage, oral activated charcoal and an infusion of normal saline. Toxicology analysis with gas chromatography and mass spectrometry revealed colchicine in the patient's gastric lavage, blood (5 microg/l) and urine (30 microg/l). She developed arrhythmias, liver failure, pancreatitis, ileus, and bone marrow suppression with pancytopenia. Alopecia began in the third week. Treatment was supportive only. Five months later she had no clinical or laboratory signs of poisoning. DISCUSSION: The patient mistakenly ingested autumn crocus instead of wild garlic because of their great similarity. Colchicine primarily blocks mitosis in tissues with rapid cell turnover; this results in gastroenterocolitis in the first phase of colchicine poisoning, bone marrow hypoplasia with pancytopenia in the second and alopecia in the third, all of which were present in our patient. Colchicine toxicity in tissues without rapid cell turnover caused arrhythmias, acute liver failure and pancreatitis. CONCLUSION: Colchicine poisoning can result in gastroenterocolitis followed by multi-organ dysfunction syndrome. In unexplained gastroenterocolitis after ingestion of wild plants as a salad or spice, especially when wild garlic is mentioned, we should always consider autumn crocus. Diagnosis could be confirmed only by toxicology analyses. Management of colchicine poisoning is restricted to supportive therapy.