Ambroxol inhibits the release of histamine, leukotrienes and cytokines from human leukocytes and mast cells

A brief review on critical analytical aspects for quantification of ambroxol in biological samples

Ambroxol (AMB) is a member of the expectorant class, widely used as a secreolytic agent in patients to break up secretions. AMB is rapidly and effectively distributed from blood to tissue. The lungs have the highest concentration of AMB; accumulation of AMB in human lung tissue was detected at concentrations 15- to 20-fold greater than those reported in the circulation. Because of its wide range of actions and therapeutic applications may be worth looking into, particularly for respiratory symptoms, antioxidant, anti-inflammatory, influenza, and rhinovirus infections. Though several analytical methodologies have been established and confirmed for the AMB analysis in matrices of pharmaceutical and biological origins, novel sustainable, and economical methods are still to be choice of protocol to increase its sensitivity, reliability, and repeatability. Therefore, the present review offers an overview of critical analytical aspects regarding the HPLC, LC-MS/MS, HPTLC, capillary electrophoresis, spectrophotometry, and electrochemical methods for quantifying AMB in pharmaceutical and biological samples. Furthermore, this review will thoroughly discuss the physicochemical properties, stability, extraction conditions, instrumentation, and operational parameters of the targeted analyte. As a result, for the first time, this review complies with vital background information and an up-to-date interpretation of research undertaken by anticipated methodologies examined and implemented for the pharmaceutical analysis AMB.

Respiratory RNA Viruses: How to Be Prepared for an Encounter with New Pandemic Virus Strains

The characteristics of the biology of influenza viruses and coronavirus that determine the implementation of the infectious process are presented. With provision for pathogenesis of infection possible effects of serine proteinase inhibitors, heparin, and inhibitors of heparan sulfate receptors in the prevention of cell contamination by viruses are examined. It has been determined that chelators of metals of variable valency and antioxidants should be used for the reduction of replicative activity of viruses and anti-inflammatory therapy. The possibility of a pH-dependent impairment of glycosylation of cellular and viral proteins was traced for chloroquine and its derivatives. The use of low-toxicity drugs as part of adjunct therapy increases the effectiveness of synthetic antiviral drugs and interferons and ensures the safety of baseline therapy.

The past, present and future of RNA respiratory viruses: influenza and coronaviruses

Influenza virus and coronaviruses continue to cause pandemics across the globe. We now have a greater understanding of their functions. Unfortunately, the number of drugs in our armory to defend us against them is inadequate. This may require us to think about what mechanisms to address. Here, we review the biological properties of these viruses, their genetic evolution and antiviral therapies that can be used or have been attempted. We will describe several classes of drugs such as serine protease inhibitors, heparin, heparan sulfate receptor inhibitors, chelating agents, immunomodulators and many others. We also briefly describe some of the drug repurposing efforts that have taken place in an effort to rapidly identify molecules to treat patients with COVID-19. While we put a heavy emphasis on the past and present efforts, we also provide some thoughts about what we need to do to prepare for respiratory viral threats in the future.

One-pot, chemoselective synthesis of secondary amines from aryl nitriles using a PdPt–Fe3O4 nanoparticle catalyst

We have developed a new catalytic method for the one-pot, cascade synthesis of unsymmetrical secondary amines via the reductive amination of aryl nitriles with nitroalkanes using a PdPt–Fe₃O₄ nanoparticle (NP) catalyst.

An update on emerging drugs for fibromyalgia treatment

INTRODUCTION

Fibromyalgia (FM) is a chronic disorder whose symptoms of pain, fatigue, sleep disturbances and depression have a devastating effect on patients' lives as it limits their ability to engage in everyday working and social activities, and make it difficult to maintain normal relationships with family, friends and employers. None of the currently available drugs are fully effective against the whole spectrum of symptoms. The aim of this narrative review is to summarise the data relating to the new therapeutic options that have become available over the last few years. Areas covered: Increasing efforts by the pharmaceutical industry have led to the introduction of new investigational drugs and new formulations of older drugs, and studies have been carried out in order to investigate the possibility of using drugs that are currently used for other diseases. Expert opinion: Slight improvements in the health of FM patients treated with drugs targeting a range of molecular mechanisms have been observed, but there is still no single drug that is capable of offering substantial efficacy against all of the characteristic symptoms of FM. The identification of new and improved therapies for FM requires consideration of the heterogeneity of the condition, which suggests the existence of different patient subgroups, a relationship between central and peripheral aspects of the pathophysiology, and the need for combined treatment with drugs targeting multiple molecular mechanisms.

Immunoregulatory effect of mast cells influenced by microbes in neurodegenerative diseases

When related to central nervous system (CNS) health and disease, brain mast cells (MCs) can be a source of either beneficial or deleterious signals acting on neural cells. We review the current state of knowledge about molecular interactions between MCs and glia in neurodegenerative diseases such as Multiple Sclerosis, Alzheimer's disease, Amyotrophic Lateral Sclerosis, Parkinson's disease, Epilepsy. We also discuss the influence on MC actions evoked by the host microbiota, which has a profound effect on the host immune system, inducing important consequences in neurodegenerative disorders. Gut dysbiosis, reduced intestinal motility and increased intestinal permeability, that allow bacterial products to circulate and pass through the blood-brain barrier, are associated with neurodegenerative disease. There are differences between the microbiota of neurologic patients and healthy controls. Distinguishing between cause and effect is a challenging task, and the molecular mechanisms whereby remote gut microbiota can alter the brain have not been fully elucidated. Nevertheless, modulation of the microbiota and MC activation have been shown to promote neuroprotection. We review this new information contributing to a greater understanding of MC-microbiota-neural cells interactions modulating the brain, behavior and neurodegenerative processes.

Ambroxol for the treatment of fibromyalgia: science or fiction?

Fibromyalgia appears to present in subgroups with regard to biological pain induction, with primarily inflammatory, neuropathic/neurodegenerative, sympathetic, oxidative, nitrosative, or muscular factors and/or central sensitization. Recent research has also discussed glial activation or interrupted dopaminergic neurotransmission, as well as increased skin mast cells and mitochondrial dysfunction. Therapy is difficult, and the treatment options used so far mostly just have the potential to address only one of these aspects. As ambroxol addresses all of them in a single substance and furthermore also reduces visceral hypersensitivity, in fibromyalgia existing as irritable bowel syndrome or chronic bladder pain, it should be systematically investigated for this purpose. Encouraged by first clinical observations of two working groups using topical or oral ambroxol for fibromyalgia treatments, the present paper outlines the scientific argument for this approach by looking at each of the aforementioned aspects of this complex disease and summarizes putative modes of action of ambroxol. Nevertheless, at this point the evidence basis for ambroxol is not strong enough for clinical recommendation.

Ambroxol Hydrochloride Combined with Fluconazole Reverses the Resistance of Candida albicans to Fluconazole

In this study, we found that ambroxol hydrochloride (128 μg/mL) exhibits synergistic antifungal effects in combination with fluconazole (2 μg/mL) against resistant planktonic Candida albicans (C. albicans) cells. This combination also exhibited synergistic effects against resistant C. albicans biofilms in different stages (4, 8, and 12 h) according to the microdilution method. In vitro data were further confirmed by the success of this combination in treating Galleria mellonella infected by resistant C. albicans. With respect to the synergistic mechanism, our result revealed that ambroxol hydrochloride has an effect on the drug transporters of resistant C. albicans, increasing the uptake and decreasing the efflux of rhodamine 6G, a fluorescent alternate of fluconazole. This is the first study to investigate the in vitro and in vivo antifungal effects, as well as the possible synergistic mechanism of ambroxol hydrochloride in combination with fluconazole against resistant C. albicans. The results show the potential role for this drug combination as a therapeutic alternative to treat resistant C. albicans and provide insights into the development of antifungal targets and new antifungal agents.

A Reliable Method for the Evaluation of the Anaphylactoid Reaction Caused by Injectable Drugs

Adverse reactions of injectable drugs usually occur at first administration and are closely associated with the dosage and speed of injection. This phenomenon is correlated with the anaphylactoid reaction. However, up to now, study methods based on antigen detection have still not gained wide acceptance and single physiological indicators cannot be utilized to differentiate anaphylactoid reactions from allergic reactions and inflammatory reactions. In this study, a reliable method for the evaluation of anaphylactoid reactions caused by injectable drugs was established by using multiple physiological indicators. We used compound 48/80, ovalbumin and endotoxin as the sensitization agents to induce anaphylactoid, allergic and inflammatory reactions. Different experimental animals (guinea pig and nude rat) and different modes of administration (intramuscular, intravenous and intraperitoneal injection) and different times (15 min, 30 min and 60 min) were evaluated to optimize the study protocol. The results showed that the optimal way to achieve sensitization involved treating guinea pigs with the different agents by intravenous injection for 30 min. Further, seven related humoral factors including 5-HT, SC5b-9, Bb, C4d, IL-6, C3a and histamine were detected by HPLC analysis and ELISA assay to determine their expression level. The results showed that five of them, including 5-HT, SC5b-9, Bb, C4d and IL-6, displayed significant differences between anaphylactoid, allergic and inflammatory reactions, which indicated that their combination could be used to distinguish these three reactions. Then different injectable drugs were used to verify this method and the results showed that the chosen indicators exhibited good correlation with the anaphylactoid reaction which indicated that the established method was both practical and reliable. Our research provides a feasible method for the diagnosis of the serious adverse reactions caused by injectable drugs which could be used in the clinical practice.

Pharmacological treatment options for mast cell activation disease

Mast cell activation disease (MCAD) is a term referring to a heterogeneous group of disorders characterized by aberrant release of variable subsets of mast cell (MC) mediators together with accumulation of either morphologically altered and immunohistochemically identifiable mutated MCs due to MC proliferation (systemic mastocytosis [SM] and MC leukemia [MCL]) or morphologically ordinary MCs due to decreased apoptosis (MC activation syndrome [MCAS] and well-differentiated SM). Clinical signs and symptoms in MCAD vary depending on disease subtype and result from excessive mediator release by MCs and, in aggressive forms, from organ failure related to MC infiltration. In most cases, treatment of MCAD is directed primarily at controlling the symptoms associated with MC mediator release. In advanced forms, such as aggressive SM and MCL, agents targeting MC proliferation such as kinase inhibitors may be provided. Targeted therapies aimed at blocking mutant protein variants and/or downstream signaling pathways are currently being developed. Other targets, such as specific surface antigens expressed on neoplastic MCs, might be considered for the development of future therapies. Since clinicians are often underprepared to evaluate, diagnose, and effectively treat this clinically heterogeneous disease, we seek to familiarize clinicians with MCAD and review current and future treatment approaches.

Mast cell stabilisers

Mast cells play a critical role in type 1 hypersensitivity reactions. Indeed, mast cell mediators are implicated in many different conditions including allergic rhinitis, conjunctivitis, asthma, psoriasis, mastocytosis and the progression of many different cancers. Thus, there is intense interest in the development of agents which prevent mast cell mediator release or which inhibit the actions of such mediators once released into the environment of the cell. Much progress into the design of new agents has been made since the initial discovery of the mast cell stabilising properties of khellin from Ammi visnaga and the clinical approval of cromolyn sodium. This review critically examines the progress that has been made in the intervening years from the design of new agents that target a specific signalling event in the mast cell degranulation pathway to those agents which have been developed where the precise mechanism of action remains elusive. Particular emphasis is also placed on clinically used drugs for other indications that stabilise mast cells and how this additional action may be harnessed for their clinical use in disease processes where mast cells are implicated.

A simple cost-effective modification improves the quality of immunocytochemical staining in cervical scrape samples characterized by presence of excess mucus

Immunocytochemistry (ICC) is a very important tool in a diverse range of biomedical research as well as in diagnostic cytopathology. Smears prepared from cervical scrapes contain a large amount of overlying mucus that interferes with the standard immunocytochemical staining protocol. A modified ICC protocol is described, which involves pretreatment of these smears with 1 mg/ml solution of Ambroxol hydrochloride in methanol for 1 hour. Source of Ambroxol hydrochloride was a 30 mg Mucolite^™ tablet, at a cost of 1.70 rupees (∼3·5 US cents) per tablet. This mucolytic solution effectively clears the mucus, facilitating the accessibility of the antibody to the antigenic determinants. This pretreatment resulted in the increased percentage of positively stained cells as well as staining intensity, leading to improved overall ICC staining and score. This is a novel modification that can be cost-effectively applied in ICC staining protocols for cytology samples characterized by the presence of excess mucus.

Twenty-first century mast cell stabilizers

Mast cell stabilizing drugs inhibit the release of allergic mediators from mast cells and are used clinically to prevent allergic reactions to common allergens. Despite the relative success of the most commonly prescribed mast cell stabilizer, disodium cromoglycate, in use for the preventative treatment of bronchial asthma, allergic conjunctivitis and vernal keratoconjunctivitis, there still remains an urgent need to design new substances that are less expensive and require less frequent dosing schedules. In this regard, recent developments towards the discovery of the next generation of mast cell stabilizing drugs has included studies on substances isolated from natural sources, biological, newly synthesized compounds and drugs licensed for other indications. The diversity of natural products evaluated range from simple phenols, alkaloids, terpenes to simple amino acids. While in some cases their precise mode of action remains unknown it has nevertheless sparked interest in the development of synthetic derivatives with improved pharmacological properties. Within the purely synthetic class of inhibitors, particular attention has been devoted to the inhibition of important signalling molecules including spleen TK and JAK3. The statin class of cholesterol-lowering drugs as well as nilotinib, a TK inhibitor, are just some examples of clinically used drugs that have been evaluated for their anti-allergic properties. Here, we examine each approach under investigation, summarize the test data generated and offer suggestions for further preclinical evaluation before their therapeutic potential can be realized.

Biofilm-dependent airway infections: a role for ambroxol?

Biofilms are a key factor in the development of both acute and chronic airway infections. Their relevance is well established in ventilator associated pneumonia, one of the most severe complications in critically ill patients, and in cystic fibrosis, the most common lethal genetic disease in Caucasians. Accumulating evidence suggests that biofilms could have also a role in chronic obstructive pulmonary disease and their involvement in bronchiectasis has been proposed as well. When they grow in biofilms, microorganisms become multidrug-resistant. Therefore the treatment of biofilm-dependent airway infections is problematic. Indeed, it still largely based on measures aiming to prevent the formation of biofilms or remove them once that they are formed. Here we review recent evidence suggesting that the mucokinetic drug ambroxol has specific anti-biofilm properties. We also discuss how additional pharmacological properties of this drug could be beneficial in biofilm-dependent airway infections. Specifically, we review the evidence showing that: 1-ambroxol exerts anti-inflammatory effects by inhibiting at multiple levels the activity of neutrophils, and 2-it improves mucociliary clearance by interfering with the activity of airway epithelium ion channels and transporters including sodium/bicarbonate and sodium/potassium/chloride cotransporters, cystic fibrosis transmembrane conductance regulator and aquaporins. As a whole, the data that we review here suggest that ambroxol could be helpful in biofilm-dependent airway infections. However, considering the limited clinical evidence available up to date, further clinical studies are required to support the use of ambroxol in these diseases.

Ambroxol inhibits rhinovirus infection in primary cultures of human tracheal epithelial cells

The mucolytic drug ambroxol hydrochloride reduces the production of pro-inflammatory cytokines and the frequency of exacerbation in patients with chronic obstructive pulmonary disease (COPD). However, the inhibitory effects of ambroxol on rhinovirus infection, the major cause of COPD exacerbations, have not been studied. We examined the effects of ambroxol on type 14 rhinovirus (RV14) infection, a major RV group, in primary cultures of human tracheal epithelial cells. RV14 infection increased virus titers and cytokine content in the supernatants and RV14 RNA in the cells. Ambroxol (100 nM) reduced RV14 titers and cytokine concentrations of interleukin (IL)-1β, IL-6 and IL-8 in the supernatants and RV14 RNA in the cells after RV14 infection, in addition to reducing susceptibility to RV14 infection. Ambroxol also reduced the expression of intercellular adhesion molecule-1 (ICAM-1), the receptor for RV14, and the number of acidic endosomes from which RV14 RNA enters the cytoplasm. In addition, ambroxol reduced the activation of the transcription factor nuclear factor kappa B (NF-κB) in the nucleus. These results suggest that ambroxol inhibits RV14 infection partly by reducing ICAM-1 and acidic endosomes via the inhibition of NF-κB activation. Ambroxol may modulate airway inflammation by reducing the production of cytokines in rhinovirus infection.

Ambroxol: a multifaceted molecule with additional therapeutic potentials in respiratory disorders of childhood

INTRODUCTION

Mucoactive drugs are currently used to cleanse the respiratory tract following disturbance of the normal mucociliary clearance due to mucous hyperproduction and/or modification of its physicochemical characteristics. However, in addition to possessing the ability to perform specific actions on airway secretion, these compounds have the capability to modulate the mechanisms involved in abnormal secretions. Indeed, over the years, in the postmarketing phase, a large number of studies have been published showing interesting pharmacological activities in addition to their secretagogue activity.

AREAS COVERED

This article collates available data on ambroxol (2-amino-3,5-dibromo-N-[trans-4-hydroxycyclohexyl]benzylamine), a metabolite of bromhexine, used as a secretagogue in the treatment of childhood airway diseases. This article goes beyond the mucoactive aspects of the drug covering its multiple pharmacological properties.

EXPERT OPINION

The non-mucoactive functions exhibited by the compound may provide beneficial effects on airway structure and function in health and disease. Beyond the mucokinetic and secretagogue effects, ambroxol showed great antioxidant, anti-inflammatory, local anesthetic and surfactant synthesis stimulatory activities. Moreover, some antiviral and antibacterial activities were shown. These findings may better explain the clinical results observed in a variety of airway disorders and suggest additional therapeutic potential. Further studies are needed to better define the clinical relevance of these non-mucolytic activities.

Insufficient endogenous redox buffer capacity may underlie neuronal vulnerability to cerebral ischemia and reperfusion

Reactive oxygen species (ROS) are key players in ischemia-induced neurodegeneration. We investigated whether hippocampal neurons may lack sufficient redox-buffering capacity to protect against ROS attacks. Using organotypic hippocampal slice cultures (OHSCs) transiently exposed to oxygen and glucose deprivation (OGD) and gerbils suffering from a two-vessel occlusion (2VO) as complementary ex vivo and in vivo models, we have elucidated whether the intrinsic redox systems interfere with ischemia-induced neurodegeneration. Cell- type-specific immunohistological staining of hippocampal slice cultures revealed that pyramidal neurons, in contrast to astrocytes and microglia, express free thiols only weakly. In addition, free thiol levels were extensively decreased throughout the hippocampal formation immediately after OGD, but recovered within 24 hr after reperfusion. In parallel, progressive glia activation and proliferation were observed. Increased neuronal exposure to ROS was monitored by dihydroethidium oxidation in hippocampal pyramidal cell layers immediately after OGD. Coadministration of reduction equivalents (α-lipoic acid) and thiol-stimulating agents (enalapril, ambroxol) decreased ischemia-induced neuronal damage in OGD-treated OHSCs and in gerbils exposed to 2VO, whereas single drug applications remained ineffective. In summary, limited redox buffering capacities of pyramidal neurons may underlie their exceptional vulnerability to cerebral ischemia. Consistently, multidrug treatments supporting endogenous redox systems may offer a strategy to promote valid neuroprotection.

Differential modulation of IgE-dependent activation of human basophils by ambroxol and related secretolytic analogues

Ambroxol is a widely used secretolytic agent originally developed from vasicine, a natural alkaloid found in Adhatoda vasica, extracts of which have been used to treat bronchitis, asthma, and rheumatism. We previously reported that ambroxol inhibits IgE-dependent mediator secretion from human mast cells and basophils, key effector cells of allergic inflammation. Here, the mechanisms involved in the inhibitory properties of ambroxol were assessed in comparison to other secretolytic analogues (e.g. vasicine, bromhexine, sputolysin). The results show that, in comparison to ambroxol, which reduced IgE-dependent histamine release from basophils at 10 microM-1 mM, the release of the amine was only moderately reduced by sputolysin and vasicine at 1 mM. In contrast, above 10 microM, bromhexine was found to be toxic to basophils in vitro as evidenced by induction of histamine release and reduced cell viability. In contrast, the inhibitory actions of ambroxol at concentrations below 1 mM were not toxic and entirely reversible. Ambroxol was also more potent than either sputolysin or vasicine in attenuating basophil IL-4 and IL-13 secretions, whereas bromhexine-induced suppression of de novo cytokine synthesis was due to toxic effects. Additionally, ambroxol reduced IgE-dependent p38 MAPK phosphorylation in basophils, unlike bromhexine, sputolysin and vasicine. These results clearly show that ambroxol is both more potent and effective at inhibiting IgE-dependent basophil mediator release and p38 MAPK activity than the other secretolytic analogues employed. The therapeutic potential of ambroxol as an anti-allergic agent is further underlined by these data.

The potential role of natural agents in treatment of airway inflammation

Obstructive airway diseases including asthma, chronic obstructive pulmonary disease and cystic fibrosis present with dyspnea and variety of other symptoms. Physiologically, they are characterized by maximal expiratory flow limitation and pathologically, by inflammation of the airways and the lung parenchyma. Inflammation plays a major role in the gradual worsening of the lung function resulting in worsening symptoms. For many years, scientists focused their efforts in identifying various pathways involved in the chronic inflammation present in these diseases. Further, studies are underway to identify various molecular targets in these pathways for the purpose of developing novel therapeutic agents. Natural agents have been used for thousands of years in various cultures for the treatment of several medical conditions and have mostly proven to be safe. Recent in vivo and in vitro studies show potential anti-inflammatory role for some of the existing natural agents. This review provides an overview of the literature related to the anti-inflammatory effects of some of the natural agents which have potential value in the treatment of inflammatory lung diseases.

Ambroxol: a CNS drug?

For almost three decades ambroxol has been used in the therapy of airway diseases. In 2002, ambroxol lozenges were marketed for the treatment of sore throat making use of its local anesthetic effect. Detailed investigations of ambroxol with modern pharmacological methods yielded additional interesting results: ambroxol has been found to have profound effects on neuronal voltage-gated Na(+), as well as Ca(2+) channels, and to effectively reduce chronic inflammatory and neuropathic pain in rodents. The question was raised whether ambroxol affects the central nervous system (CNS) directly, or whether its effects can be explained solely by a peripheral action. This issue was addressed by re-examining pharmacokinetics, as well as toxicology of ambroxol. It has been concluded that even at the highest clinically used doses ambroxol does not have significant direct effects on the CNS. At clinically relevant plasma concentrations ambroxol either does not penetrate blood-brain barrier, or its brain levels are too low to cause relevant effects. The analgesic effects of ambroxol by either systemic administration to animals, or by topical application in humans can be explained by ambroxol-induced blockade of ion channels in peripheral neurons.

A viscoelastic traction layer model of muco-ciliary transport

A new mathematical model of the transport of mucus and periciliary liquid (PCL) in the airways by cilia is presented. Mucus is represented by a linearly viscoelastic fluid, the mat of cilia is modelled as an 'active porous medium.' The propulsive effect of the cilia is modelled by a time-dependent force acting in a shear-thinned 'traction layer' between the mucus and the PCL. The effects of surface and interface tension are modelled by constraining the mucus free surface and mucus-PCL interface to be flat. It is assumed that the epithelium is impermeable to fluid. Using Fourier series, the system is converted into ODEs and solved numerically. We calculate values for mean mucus speed close to those observed by Matsui et al. [J. Clin. Invest., 102(6):1125-1131, 1998], (approximately 40 microm s(-1)). We obtain more detail regarding the dynamics of the flow and the nonlinear relationships between physical parameters in healthy and diseased states than in previously published models. Pressure gradients in the PCL caused by interface and surface tension are vital to ensuring efficient transport of mucus, and the role of the mucus-PCL interface appears to be to support such pressure gradients, ensuring efficient transport. Mean transport of PCL is found to be very small, consistent with previous analyses, providing insight into theories regarding the normal tonicity of PCL.

Secretory leukoprotease inhibitor and pulmonary surfactant serve as principal defenses against influenza A virus infection in the airway and chemical agents up-regulating their levels may have therapeutic potential

Influenza A virus (IAV) is one of the most common infectious pathogens in humans. Entry of this virus into cells is primarily determined by host cellular trypsin-type processing proteases, which proteolytically activate viral membrane fusion glycoprotein precursors. Human IAV and murine parainfluenza virus type 1 Sendai virus are exclusively pneumotropic, and the infectious organ tropism of these viruses is determined by the susceptibility of the viral envelope glycoprotein to cleavage by proteases in the airway. Proteases in the upper respiratory tract are suppressed by secretory leukoprotease inhibitor, and those in the lower respiratory tract are suppressed by pulmonary surfactant, which by adsorption inhibits the interaction between the proteases and viral membrane proteins. Although the protease activities are predominant over the activities of inhibitory compounds under normal airway conditions, intranasal administration of inhibitors was able to significantly suppress multi-cycles of viral replication in the airway. In addition, we identified chemical agents that could act as defensive factors by up-regulating the levels of the natural inhibitors and immunoglobulin A (IgA) in airway fluids. One of these compounds, ambroxol, is a mucolytic and anti-oxidant agent that stimulates the release of secretory leukoprotease inhibitor and pulmonary surfactant in the early phase, and IgA in the late phase of infection at an optimal dose, i.e. a dose sufficient to inhibit virus proliferation and increase the survival rate of animals after treatment with a lethal dose of IAV. Another agent, clarithromycin, is a macrolide antibiotic that increases IgA levels through augmentation of interleukin-12 levels and mucosal immunization in the airway. In addition to the sialidase inhibitors, which prevent the release of IAV from infected cells, inhibitors of the processing proteases and chemical agents that augment mucosal immunity and/or levels of the relevant defensive compounds may also ultimately prove to be useful as new anti-influenza agents.

In vitro inhibition of human neutrophil histotoxicity by ambroxol: evidence for a multistep mechanism

Neutrophils are major culprits for the protease/antiprotease imbalance during various lung diseases, that is, chronic obstructive pulmonary disease, cystic fibrosis, idiopathic pulmonary fibrosis and adult respiratory distress syndrome. Thus, these cells are presently considered an ideal target for the pharmacologic control of tissue injury during these diseases. This study was planned in order to investigate if ambroxol and its precursor bromhexine are actually capable of preventing alpha-1-antitrypsin (A1AT) inactivation by stimulated neutrophils and possibly to look into the mechanisms underlying this event. Ambroxol inhibited the production of superoxide anion by activated neutrophils, whereas bromhexine had no inhibitory effect. Ambroxol decreased the production of hypochlorous acid (HOCl) from activated neutrophils with high efficiency, whereas bromhexine had a modest activity. Ambroxol and bromhexine were capable of limiting the chlorination of monochlorodimedon by HOCl, displaying the capacity of directly scavenging the oxidant. Ambroxol decreased the release of elastase and myeloperoxidase from activated neutrophils, whereas bromhexine was ineffective. Ambroxol prevented the A1AT inactivation by neutrophils, whereas bromhexine was completely ineffective. Among drugs currently available for in vivo use in humans, ambroxol is unique by virtue of its ability to prevent neutrophil-mediated A1AT inactivation via inhibition of HOCl production as well as HOCl scavenging. Also taking into account its capacity for curbing elastase release, the drug displays the potential to lessen the burden of oxidants/proteases and to increase the antiprotease shield at the site of inflammation. Thus, ambroxol appears to be a good candidate for raising attempts to develop new therapeutic histoprotective approaches to inflammatory bronchopulmonary diseases.

Inhibition of inflammatory responses by ambroxol, a mucolytic agent, in a murine model of acute lung injury induced by lipopolysaccharide

Objective

The aim of this study is to investigate whether ambroxol inhibits inflammatory responses in a murine model of lipopolysaccharide-induced acute lung injury (ALI).

Methods

Mice (n=295) were first intratracheally instilled with lipopolysaccharide (LPS) to induce ALI and then received an intraperitoneal (ip) injection of either normal saline (NS), ambroxol (30 or 90 mg/kg per day) or dexamethasone (2.5 or 5 mg/kg per day) for 7 days. Metabolism (n=10, each), lung morphology (n=5, each) and wet-to-dry lung weight ratio (n=10, each) were studied. The levels of tumor necrosis factor (TNF-α), interleukin-6 (IL-6) and transforming growth factor (TGF-β1) and the protein concentration (n=5 or 7, each) in bronchoalveolar lavage (BAL) were measured.

Results

Mice with LPS-induced ALI that were treated with ambroxol at a dosage of 90 mg/kg per day significantly gained weight compared to the control and dexamethasone-treated groups. Ambroxol and dexamethasone significantly reduced the lung hemorrhage, edema, exudation, neutrophil infiltration and total lung injury histology score at 24 and 48 h. In addition, ambroxol and dexamethasone significantly attenuated the lung wet-to-dry weight ratio at 24 and 48 h (p<0.05). Compared to the control group, TNF-α, IL-6 and TGF-β1 levels in the BAL in both ambroxol- and dexamethasone-treated groups were significantly reduced at 24 and 48 h. The protein in BAL, an index of vascular permeability, was also significantly decreased in the ambroxol- and dexamethasone-treated groups (p<0.05).

Conclusion

Ambroxol inhibited proinflammatory cytokines, reduced lung inflammation and accelerated recovery from LPS-induced ALI.

Simultaneous high-throughput determination of clenbuterol, ambroxol and bromhexine in pharmaceutical formulations by HPLC with potentiometric detection

Potentiometric detection of clenbuterol, ambroxol and bromhexine in marketed pharmaceuticals was described in six isocratic HPLC systems. The podant- and macrocyclic-type neutral ionophores, N,N,N',N'-tetracyclohexyl-oxybis(o-phenyleneoxy)diacetamide (TOPA) and hexakis(2,3,6-tri-O-octyl)-alpha-cyclodextrin (OCD), were applied in poly(vinyl)chloride (PVC)-based liquid membrane electrodes. Both types of neutral ionophores improve the sensitivity for all mentioned drugs when compared with a tetrakis(p-chlorophenyl)borate (BOR)-based electrode as well as with single wavelength UV detection. Detection limits (S/N=3) of 2.6 x 10(-10) mol l(-1) (injected concentration) for the highly hydrophobic bromhexine were achieved with the TOPA-based electrode and a cyano reversed-phase (RP)-HPLC with Uptisphere UP5CN-25QS silica column (250 x 4.6 mm i.d.) eluted with acetonitrile (AcN)-ethanol-perchloric acid (1.66 mM) (60:2:38, v/v/v) (pH* 2.45). Comparable result was obtained with OCD-based electrodes and an XTerra RP18 hybrid silica-polymer column eluted with AcN-phosphoric acid (20 mM) (25:75, v/v) (pH* 2.60). In the mobile phases containing 60-75% v/v AcN or methanol, stable and reproducible response of both types of neutral ionophore-based electrodes was observed for at least 3 days. The results of the validated procedure for reliable simultaneous determination of the drugs in fortified representative samples of pharmaceuticals were also presented.

Environmental polycyclic aromatic hydrocarbons, benzo(a) pyrene (BaP) and BaP-quinones, enhance IgE-mediated histamine release and IL-4 production in human basophils

Polycyclic aromatic hydrocarbons (PAHs) are major components of diesel exhaust particles found in pollutant respirable particles. There is growing evidence that these fossil fuel combustion products exacerbate allergic inflammation. Basophils contribute to allergic inflammation through the release of preformed and granule-derived mediators. To determine whether allergens and PAHs interact, we incubated human basophils with PAHs and measured the release of histamine and IL-4 with and without added antigen. None of the PAHs induced mediator release by itself and none affected total cellular histamine levels. However, several PAHs enhanced histamine release and IL-4 production in response to crosslinking the high-affinity IgE receptor, Fc epsilon RI. The enhancement seen with 1,6-BaP-quinone involved an increase in tyrosine phosphorylation in several different substrates, including the Fc epsilon RI-associated tyrosine kinase, Lyn, and elevated reactive oxygen species (ROS) levels detected by dichlorofluorescein fluorescence and flow cytometry. The PAH-induced enhancement of mediator release and ROS production could be inhibited with the antioxidant N-acetylcysteine. These data provide further evidence that environmental pollutants can influence allergic inflammation through enhanced Fc epsilon RI-coupled mediator release from human basophils.

N-acetyl-L-cysteine inhibits 26S proteasome function: implications for effects on NF-kappaB activation

Ionizing radiation shares with cytokines, such as TNF-alpha, an ability to generate free radicals in cells and activate downstream proinflammatory responses through NF-kappaB-dependent signal transduction pathways. Support for the role of free radicals in triggering such responses comes from the use of free radical scavengers like N-acetyl-L-cysteine (NAC). The nature of the link between free radical generation and NF-kappaB activation is, however, unclear. In this study, we explore the possibility that scavenging of free radicals by NAC might not be the mechanism by which it inhibits NF-kappaB activation, but rather that NAC acts through inhibition of proteasome function. The effect of NAC on the chymotryptic function of the 26s and 20s proteasome complex was measured in extracts from EVC 304 bladder carcinoma cells by assessing degradation of fluorogenic substrates. NAC inhibited 26s but not 20s proteasome activity, suggesting that it interferes with 19s regulatory subunit function. NAC blocked radiation-induced NF-kappaB activity in ECV 304 cells and RAW 264.7 macrophages, as measured by a gel shift assay, at doses that inhibited proteasome activity. This provides a possible mechanism whereby NAC could block NF-kappaB activation and affect the expression of other molecules that are dependent on the ubiquitin/proteasome system for their degradation, other than by scavenging free radicals.

Ambroxol inhibits platelet-derived growth factor production in human monocytic cells

Several growth factors, including platelet-derived growth factor (PDGF), have been implicated in the mechanism of lung and airway remodeling. We investigated the effect of ambroxol, trans-4-[(2-amino-3,5-dibromobenzyl) amino] cyclohexanol hydrochloride, on the lipopolysaccharide-induced PDGF production in human monocytic cells, THP-1. Ambroxol inhibited the lipopolysaccharide-induced PDGF-AB production via PDGF-A mRNA expression. Lipopolysaccharide activated p44/42 extracellular signal-regulated kinase (ERK), and ambroxol attenuated the lipopolysaccharide-induced p44/42 ERK activation. Furthermore, mitogen-activated protein kinase kinase (MEK)-1-specific inhibitor, 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one (PD 98059), blocked the lipopolysaccharide-induced p44/42 ERK activation and PDGF production. These findings indicate that ambroxol inhibits the lipopolysaccharide-induced PDGF production due to the suppression of p44/42 ERK activity.

Mercuric chloride enhances immunoglobulin E-dependent mediator release from human basophils

Mercuric chloride (HgCl2) is an industrial agent known to cause autoimmune disorders and induce IgE synthesis, which plays a crucial role in the manifestation of allergic diseases. In rodents, the immunomodulatory effects of HgCl2 have been shown to involve the enhancement of mast cell-derived IL-4 secretion, which facilitates both Th2-lymphocyte development and IgE production. In humans, rapid allergen-dependent release of IL-4 and the related cytokine IL-13 from histamine-containing cells occurs primarily in basophils, along with other proinflammatory mediators such as histamine and LTC4. In this study, we therefore investigated the effects of HgCl2 on the release of the above basophil mediators, either due to the compound alone or in conjunction with IgE-dependent stimulation. HgCl2 (10(-9) to 10(-6) M) did not induce mediator secretion alone but significantly enhanced the release of histamine, LTC4, IL-4, and IL-13 caused by anti-IgE. Higher concentrations of HgCl2 (10(-5) to 10(-3) M) strikingly reduced cell viability; however, toxicity varied depending on cell density and incubation time. Removal of HgCl2 following a short incubation with basophils did not reverse the potentiating effects on basophil mediator secretion to anti-IgE and the concentration of free mercury in the supernatants significantly diminished by up to 20% after incubation with the cells, indicating irreversible Hg binding to cells. By upregulating IgE-dependent human basophil mediator release, our results clearly indicate that HgCl2 potentially exacerbates allergic disorders and promotes a Th2-cytokine profile.

A possible emerging role of phytochemicals in improving age-related neurological dysfunctions: a multiplicity of effects

It is rare to see a day pass in which we are not told through some popular medium that the population is becoming older. Along with this information comes the "new" revelation that as we enter the next millennium there will be increases in age-associated diseases (e.g., cancer, cardiovascular disease) including the most devastating of these, which involve the nervous system (e.g., Alzheimer's disease [AD] and Parkinson's disease [PD]). It is estimated that within the next 50 years approximately 30% of the population will be aged 65 years or older. Of those between 75 and 84 years of age, 6 million will exhibit some form of AD symptoms, and of those older than 85 years, over 12 million will have some form of dementia associated with AD. What appears more ominous is that many cognitive changes occur even in the absence of specific age-related neurodegenerative diseases. Common components thought to contribute to the manifestation of these disorders and normal age-related declines in brain performance are increased susceptibility to long-term effects of oxidative stress (OS) and inflammatory insults. Unless some means is found to reduce these age-related decrements in neuronal function, health care costs will continue to rise exponentially. Thus, it is extremely important to explore methods to retard or reverse age-related neuronal deficits as well as their subsequent, behavioral manifestations. Fortunately, the growth of knowledge in the biochemistry of cell viability has opened new avenues of research focused at identifying new therapeutic agents that could potentially disrupt the perpetual cycle of events involved in the decrements associated with these detrimental processes. In this regard, a new role in which certain dietary components may play important roles in alleviating certain disorders are beginning to receive increased attention, in particular those involving phytochemicals found in fruits and vegetables.

Essential fatty acids and the brain: possible health implications

Linoleic and alpha-linolenic acid are essential for normal cellular function, and act as precursors for the synthesis of longer chained polyunsaturated fatty acids (PUFAs) such as arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic acids (DHA), which have been shown to partake in numerous cellular functions affecting membrane fluidity, membrane enzyme activities and eicosanoid synthesis. The brain is particularly rich in PUFAs such as DHA, and changes in tissue membrane composition of these PUFAs reflect that of the dietary source. The decline in structural and functional integrity of this tissue appears to correlate with loss in membrane DHA concentrations. Arachidonic acid, also predominant in this tissue, is a major precursor for the synthesis of eicosanoids, that serve as intracellular or extracellular signals. With aging comes a likely increase in reactive oxygen species and hence a concomitant decline in membrane PUFA concentrations, and with it, cognitive impairment. Neurodegenerative disorders such as Parkinson's and Alzheimer's disease also appear to exhibit membrane loss of PUFAs. Thus it may be that an optimal diet with a balance of n-6 and n-3 fatty acids may help to delay their onset or reduce the insult to brain functions which these diseases elicit.