Studies on neuromuscular blockade by boldine in the mouse phrenic nerve-diaphragm

Pharmacology of boldine: summary of the field and update on recent advances

Over the past decade, boldine, a naturally occurring alkaloid found in several plant species including the Chilean Boldo tree, has garnered attention for its efficacy in rodent models of human disease. Some of the properties that have been attributed to boldine include antioxidant activities, neuroprotective and analgesic actions, hepatoprotective effects, anti-inflammatory actions, cardioprotective effects and anticancer potential. Compelling data now indicates that boldine blocks connexin (Cx) hemichannels (HCs) and that many if not all of its effects in rodent models of injury and disease are due to CxHC blockade. Here we provide an overview of boldine's pharmacological properties, including its efficacy in rodent models of common human injuries and diseases, and of its absorption, distribution, pharmacokinetics, and metabolism.

Boldine: a narrative review of the bioactive compound with versatile biological and pharmacological potential

OBJECTIVE

Boldine is a plant-derived bioactive compound that has a beneficial impact on human health. Boldine is an aporphine alkaloid mainly obtained from the leaves and bark of the Chilean Boldo tree (Peumus boldus, Family: Monimiaceae). There are plenty of preclinical evidence supports that boldine exerts its beneficial effects against various diseases. Lumiskin™, a patented and marketed formulation by Revitol Skincare for skin brightening, contains Dicetyl boldine, a boldine derivative.

CONTENT

All the available information on the Chilean boldo tree (P. boldus Molina) species was actualized by systematically searching the scientific databases (PubMed, SciFinder, Web of Science, Google Scholar, Scopus and others) and scientific literature. This article covers the recent advances in pharmacokinetic, toxicological, pharmacological/biological activities, and molecular mechanisms of the bioactive compound to understand health benefits of boldine better.

SUMMARY

Boldine exerts antioxidant, hepatoprotective, anti-atherosclerotic, anti-diabetic, analgesic, antipyretic, anti-inflammatory, anti-epileptic, neuroprotective, nephroprotective, anti-arthritis, anticancer and nootropic effects. Moreover, boldine exhibits its various pharmacological activities by altering antioxidant parameters (MDA, superoxide dismutase, glutathione), peroxynitrite, inflammatory markers apoptotic index, caspase-3, acetyl-cholinesterase, myeloperoxidase, TNF-α (Tumor necrosis factor-α), iNOS, Bcl-2-associated X protein (BAX), ACE-1(Angiotensin-converting enzyme-1), dopamine D2 receptors and nicotinic acetylcholine receptor. Boldine has the potential to modulate a variety of biological networks.

OUTLOOK

Due to its versatile pharmacological effects reported in various experimental animals as well as in randomized clinical trials for the treatment of facial melasma and for treatment of urinary stone lithotripsy in children as a complementary phytotherapy; in the future, this compound might be developed as a novel drug for a different indication.

An Overview of Chemistry, Kinetics, Toxicity and Therapeutic Potential of Boldine in Neurological Disorders

Boldine is an alkaloid obtained from the medicinal herb Peumus boldus (Mol.) (Chilean boldo tree; boldo) and belongs to the family Monimiaceae. It exhibits a wide range of pharmacological effects such as antioxidant, anticancer, hepatoprotective, neuroprotective, and anti-diabetic properties. There is a dearth of information regarding its pharmacokinetics and toxicity in addition to its potential pharmacological activity. Boldine belongs to the aporphine alkaloid class and possesses lipophilic properties which enable its efficient absorption and distribution throughout the body, including the central nervous system. It exhibits potent free radical scavenging activity, thereby reducing oxidative stress and preventing neuronal damage. Through a variety of neuroprotective mechanisms, including suppression of AChE and BuChE activity, blocking of connexin-43 hemichannels, pannexin 1 channel, reduction of NF-κβ mediated interleukin release, and glutamate excitotoxicity which successfully reduces neuronal damage. These results point to its probable application in reducing neuroinflammation and oxidative stress in epilepsy, Alzheimer's disease (AD), and Parkinson's disease (PD). Moreover, its effects on serotonergic, dopaminergic, opioid, and cholinergic receptors were further investigated in order to determine its applicability for neurobehavioral dysfunctions. The article investigates the pharmacokinetics of boldine and reveals that it has a low oral bioavailability and a short half-life, requiring regular dosage to maintain therapeutic levels. The review studies boldine's potential therapeutic uses and mode of action while summarizing its neuroprotective benefits.  Given the favorable results for boldine as a potential neurotherapeutic drug in laboratory animals, more research is required. However, in order to optimise its therapeutic potential, it must be more bioavailable with fewer detrimental side effects.

Blockade of Hemichannels Normalizes the Differentiation Fate of Myoblasts and Features of Skeletal Muscles from Dysferlin-Deficient Mice

Dysferlinopathies are muscle dystrophies caused by mutations in the gene encoding dysferlin, a relevant protein for membrane repair and trafficking. These diseases are untreatable, possibly due to the poor knowledge of relevant molecular targets. Previously, we have shown that human myofibers from patient biopsies as well as myotubes derived from immortalized human myoblasts carrying a mutated form of dysferlin express connexin proteins, but their relevance in myoblasts fate and function remained unknown. In the present work, we found that numerous myoblasts bearing a mutated dysferlin when induced to acquire myogenic commitment express PPARγ, revealing adipogenic instead of myogenic commitment. These cell cultures presented many mononucleated cells with fat accumulation and within 48 h of differentiation formed fewer multinucleated cells. In contrast, dysferlin deficient myoblasts treated with boldine, a connexin hemichannels blocker, neither expressed PPARγ, nor accumulated fat and formed similar amount of multinucleated cells as wild type precursor cells. We recently demonstrated that myofibers of skeletal muscles from blAJ mice (an animal model of dysferlinopathies) express three connexins (Cx39, Cx43, and Cx45) that form functional hemichannels (HCs) in the sarcolemma. In symptomatic blAJ mice, we now show that eight-week treatment with a daily dose of boldine showed a progressive recovery of motor activity reaching normality. At the end of this treatment, skeletal muscles were comparable to those of wild type mice and presented normal CK activity in serum. Myofibers of boldine-treated blAJ mice also showed strong dysferlin-like immunoreactivity. These findings reveal that muscle dysfunction results from a pathophysiologic mechanism triggered by mutated dysferlin and downstream connexin hemichannels expressed de novo lead to a drastic reduction of myogenesis and favor muscle damage. Thus, boldine could represent a therapeutic opportunity to treat dysfernilopathies.

Boldine and its antioxidant or health-promoting properties

The increasing recognition of the participation of free radical-mediated oxidative events in the initiation and/or progression of cardiovascular, tumoural, inflammatory and neurodegenerative disorders, has given rise to the search for new antioxidant molecules. An important source of such molecules has been plants for which there is an ethno-cultural base for health promotion. An important example of this is boldo (Peumus boldus Mol.), a chilean tree whose leaves have been traditionally employed in folk medicine and is now widely recognized as a herbal remedy by a number of pharmacopoeias. Boldo leaves are rich in several aporphine-like alkaloids, of which boldine is the most abundant one. Research conducted during the early 1990s led to the discovery that boldine is one of the most potent natural antioxidants. Prompted by the latter, a large and increasing number of studies emerged, which have focused on characterizing some of the pharmacological properties that may arise from the free radical-scavenging properties of boldine. The present review attempts to exhaustively cover and discuss such studies, placing particular attention on research conducted during the last decade. Mechanistic aspects and structure-activity data are discussed. The review encompasses pharmacological actions, which arise from its antioxidant properties (e.g., cyto-protective, anti-tumour promoting, anti-inflammatory, anti-diabetic and anti-atherogenic actions), as well as those that do not seem to be associated with such activity (e.g., vasorelaxing, anti-trypanocidal, immuno- and neuro-modulator, cholagogic and/or choleretic actions). Based on the pharmacological and toxicological data now available, further research needs and recommendations are suggested to define the actual potential of boldine for its use in humans.