Cardiotoxicity of digitalis

Topical Digitoxigenin for Wound Healing: A Feasibility Study

(1) Background: Cardiotonic steroids have been found to stimulate collagen synthesis and might be potential wound healing therapeutics. The objective of this study was to evaluate the feasibility of digitoxigenin and its topical formulation for wound healing; (2) Methods: In the in vitro study, the human dermal fibroblast cells were treated with digitoxigenin and collagen synthesis was assessed. In the in vivo study, digitoxigenin was applied to excisional full-thickness wounds in rats immediately after wounding and remained for three days, and wound open was evaluated over 10 days. A digitoxigenin formulation for topical administration was prepared, and the in vitro release and in vivo wound healing effect were investigated; (3) Results: The expression of procollagen in human dermal fibroblast was significantly increased with the exposure to 0.1 nM digitoxigenin. Topical application of digitoxigenin in olive oil or alginate solution for three days significantly decreased the wound open in rats. Similarly, topical administration of the developed digitoxigenin formulation for three days also significantly increased wound healing. No wound healing effects were observed at days 7 and 10 after wounding when digitoxigenin was not applied; and, (4) Conclusions: It was possible to deliver digitoxigenin using the developed formulation. However, the wound healing effect of digitoxigenin and its mechanisms need to be further investigated in future studies.

Active ingredients in Chinese medicines promoting blood circulation as Na+/K+ -ATPase inhibitors

The positive inotropic effect of cardiac glycosides lies in their reversible inhibition on the membrane-bound Na(+)/K(+)-ATPase in human myocardium. Steroid-like compounds containing a core structure similar to cardiac glycosides are found in many Chinese medicines conventionally used for promoting blood circulation. Some of them are demonstrated to be Na(+)/K(+)-ATPase inhibitors and thus putatively responsible for their therapeutic effects via the same molecular mechanism as cardiac glycosides. On the other hand, magnesium lithospermate B of danshen is also proposed to exert its cardiac therapeutic effect by effectively inhibiting Na(+)/K(+)-ATPase. Theoretical modeling suggests that the number of hydrogen bonds and the strength of hydrophobic interaction between the effective ingredients of various medicines and residues around the binding pocket of Na(+)/K(+)-ATPase are crucial for the inhibitory potency of these active ingredients. Ginsenosides, the active ingredients in ginseng and sanqi, substantially inhibit Na(+)/K(+)-ATPase when sugar moieties are attached only to the C-3 position of their steroid-like structure, equivalent to the sugar position in cardiac glycosides. Their inhibitory potency is abolished, however, when sugar moieties are linked to C-6 or C-20 position of the steroid nucleus; presumably, these sugar attachments lead to steric hindrance for the entrance of ginsenosides into the binding pocket of Na(+)/K(+)-ATPase. Neuroprotective effects of cardiac glycosides, several steroid-like compounds, and magnesium lithospermate B against ischemic stroke have been accordingly observed in a cortical brain slice-based assay model, and cumulative data support that effective inhibitors of Na(+)/K(+)-ATPase in the brain could be potential drugs for the treatment of ischemic stroke.

Is digitalis compound-induced cardiotoxicity, mediated through guinea-pig cardiomyocytes apoptosis?

Our aim in performing this study was to analyze in vivo the cell death mechanism induced by toxic doses of digitalis compounds on guinea-pig cardiomyocytes. We analyzed three study groups of five male guinea pigs each. Guinea pigs were intoxicated under anesthesia with ouabain or digoxin (at a 50-60% lethal dose); the control group did not receive digitalis. A 5-hours period elapsed before guinea pig hearts were extracted to obtain left ventricle tissue. We carried out isolation of mitochondria and cytosol, cytochrome c and caspase-3 and -9 determination, and electrophoretic analysis of nuclear DNA. TdT-mediated DUTP-X nick end labeling (TUNEL) reaction was performed in histologic preparations to identify in situ apoptotic cell death. Ultrastructural analysis was performed by electron microscopy. Electrophoretic analysis of DNA showed degradation into fragments of 200-400 base pairs in digitalis-treated groups. TUNEL reaction demonstrated the following: in the control group, <10 positive nuclei per field; in the digoxin-treated group, 2-14 positive nuclei per field, while in the ouabain-treated group counts ranged from 9-30 positive nuclei per field. Extracts from ouabain-treated hearts had an elevation of cytochrome c in cytosol and a corresponding decrease in mitochondria; this release of cytochrome c provoked activation of caspase-9 and -3. Electron microscopy revealed presence of autophagic vesicles in cytoplasm of treated hearts. Toxic dosages of digitalis at 50-60% of the lethal dose are capable of inducing cytochrome c release from mitochondria, processing of procaspase-9 and -3, and DNA fragmentation; these observations are mainly indicative of apoptosis, although a mixed mechanism of cell death cannot be ruled out.

The rational pharmacology of digoxin

Although digoxin remains one of the most widely prescribed drugs in the United States, potential pharmacodynamic and pharmacokinetic interactions between this compound and other drugs, diseases, and events commonly encountered in the perioperative period remain largely unappreciated. Furthermore, the therapeutic benefit of discontinuing or initiating digoxin treatment preoperatively remains unclear. We present a basic review of current knowledge regarding digoxin pharmacology and examine those concepts from the perspective of clinical anesthesiologists.