Motor behavior induced by bergamot essential oil in experimental tasks is differentially modulated by pretreatment with metabotropic glutamate receptor 2/3 or 5 antagonists.

Bergamot essential oil shows anxiolytic-relaxant effects devoid of sedative action and motor impairment typical of benzodiazepines. Considering the potential for clinical of these effects, it is important to understand the underlying mechanisms of the phytocomplex. Modulation of glutamate group I and II metabotropic receptors is involved in stress and anxiety disorders, in cognition and emotions and increases locomotor activity and wakefulness. Interestingly, early data indicate that bergamot essential oil modulates glutamatergic transmission in specific manifestations of the central nervous system. The aim of this work is to investigate if selective antagonists of metabotropic glutamate 2/3 and 5 receptors affect behavioral parameters modulated by the phytocomplex. Male Wistar rats were used to measure behavioral parameters to correlate anxiety and motor activity using elevated plus maze (EPM), open field (OF), and rotarod tasks. Bergamot essential oil increases in EPM the time spent in open/closed arms and reduces total number of entries. The essential oil also increases immobility in EPM and OF and not affect motor coordination in rotarod. Pretreatment with the metabotropic glutamate antagonists does not affect the time spent in open/close arms, however, differently affects motor behavior measured after administration of phytocomplex. Particularly, glutamate 2/3 antagonist reverts immobility and glutamate 5 antagonist potentiates this parameter induced by the phytocomplex. Our data show that modulation of both metabotropic glutamate receptors is likely involved in some of behavioral effects of bergamot essential oil.

Preclinical Characterization of Antinociceptive Effect of Bergamot Essential Oil and of Its Fractions for Rational Translation in Complementary Therapy.

Bergamot essential oil (BEO) is endowed with consistent and reproducible antinociceptive and anti-allodynic properties when administered via an inhalation route. However, the effects of its main constituents and of its decolored (DEC) and deterpenated (DET) fractions, which are enriched in limonene or in linalool and linalyl acetate, respectively, on spontaneous motor activity related to anxiety and on formalin-induced licking/biting biphasic behavior have never been investigated before. Therefore, the present research aims to characterize the role of BEO components on an experimental pain model that is relevant to clinical translation. Under our present experimental conditions, a paper filter disc soaked with different volumes of the phytocomplex and of its fractions that was applied at the edge of the observation chamber allowed the effects on the spontaneous motor activity and on the formalin-induced nocifensive response in ddY-strain mice to be studied. The present research demonstrated the effects of the DEC fraction of BEO on motor activity and on formalin-induced licking/biting behavior for the first time, proving that limonene is implicated in reduced motor activity and that it is important for the analgesic effect.

Natural Products: Evidence for Neuroprotection to Be Exploited in Glaucoma.

Glaucoma, a leading cause of irreversible blindness worldwide, is an optic neuropathy characterized by the progressive death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is recognized as the main risk factor. Despite effective IOP-lowering therapies, the disease progresses in a significant number of patients. Therefore, alternative IOP-independent strategies aiming at halting or delaying RGC degeneration is the current therapeutic challenge for glaucoma management. Here, we review the literature on the neuroprotective activities, and the underlying mechanisms, of natural compounds and dietary supplements in experimental and clinical glaucoma.

Impact of nutraceuticals on glaucoma: A systematic review.

BACKGROUND: glaucoma is a remarkable social issue being the leading cause of irreversible blindness worldwide. It is a progressive neuropathy characterized by the death of the retinal ganglion cells, of which the most important risk factor is represented by the increase of intraocular pressure (IOP). The role of nutraceutical supplementations with anti-oxidant activity has been extensively tested in preclinical models of glaucoma. The clinical efficacy of nutraceuticals in glaucoma is still controversial. OBJECTIVES: the aim of this systematic review is to assess the efficacy of nutraceuticals with anti-oxidant activity in glaucoma through the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) rigorous criteria. DATA SOURCES: the literature search has been performed on the electronic databases currently recognized of most relevance for medical scientific literature, i.e. PubMed, MEDLINE, The Cochrane Central Register of Controlled Trials (CENTRAL) with access to EMBASE, ClinicalTrials.gov and Scopus. The date of last search is April 8th, 2020. Study eligibility criteria, participants, and interventions: prospective randomized clinical trials assessing the effects of nutraceuticals and anti-oxidants on IOP and/or visual field in patients with glaucoma. The eligible papers must be published in English and available in full text. STUDY APPRAISAL AND SYNTHESIS METHODS: the evaluation of the eligibility of the studies has been carried out independently by two authors. The selection process has followed the PRISMA flow diagram, assessing the quality of the body of evidence and the risk of bias. RESULTS: the search of literature has retrieved 1615 papers and 2 clinical trials with results, among which only 6 are eligible for inclusion in the present systematic review to address the preset participants, interventions, comparisons, outcomes and study design (PICOS) "are the nutraceuticals effective in glaucoma?". In 5 out of 6 studies the nutraceutical supplementation is effective in providing additional decrease of IOP to current usual therapy, without the occurrence of side effects. However, all the studies present high heterogeneity and some concerns in terms of risk of bias, apart from one trial for which the risk of bias is low. CONCLUSIONS: the evidence of effectiveness of nutraceutical formulations is still uncertain and inconclusive. Therefore, large double-blind randomized clinical trials with adequate design, methodology and statistical power are needed to support the use of nutraceuticals in glaucoma.

Pharmacokinetic Interactions between Herbal Medicines and Drugs: Their Mechanisms and Clinical Relevance.

The therapeutic efficacy of a drug or its unexpected unwanted side effects may depend on the concurrent use of a medicinal plant. In particular, constituents in the medicinal plant extracts may influence drug bioavailability, metabolism and half-life, leading to drug toxicity or failure to obtain a therapeutic response. This narrative review focuses on clinical studies improving knowledge on the ability of selected herbal medicines to influence the pharmacokinetics of co-administered drugs. Moreover, in vitro studies are useful to anticipate potential herbal medicine-drug interactions. In particular, they help to elucidate the cellular target (metabolic or transporter protein) and the mechanism (induction or inhibition) by which a single constituent of the herbal medicine acts. The authors highlight the difficulties in predicting herbal-drug interactions from in vitro data where high concentrations of extracts or their constituents are used and pharmacokinetics are missed. Moreover, the difficulty to compare results from human studies where different kinds of herbal extracts are used is discussed. The herbal medicines discussed are among the best sellers and they are reported in the "Herbal Medicines for Human Use" section of the European Medicinal Agency (EMA).

Inhibition of Neuromuscular Contractions of Human and Rat Colon by Bergamot Essential Oil and Linalool: Evidence to Support a Therapeutic Action.

Bergamot essential oil (BEO) added to food and drink promotes a citrus flavour. Folklore suggests benefits on gastrointestinal functions but with little supporting evidence. BEO and major constituents (linalool, limonene, linalyl acetate) were therefore examined for any ability to influence neuromuscular contractions of human and rat colon. Circular muscle strips (macroscopically-normal human colon obtained following ethical approval at cancer surgery; Sprague-Dawley rats) were suspended in baths (Krebs solution; 37 °C; 5% CO2 in O2) for measurement of neuronally-mediated contractions (prevented by tetrodotoxin or atropine) evoked by electrical field stimulation (5 Hz, 0.5 ms pulse width, 10s/minute, maximally-effective voltage), or contractions evoked by KCl (submaximally-effective concentrations). BEO and each constituent concentration dependently inhibited neuronally-mediated and KCl-induced contractions. In human: apparent pIC50 for BEO (volume/volume Krebs), respectively, 3.8 ± 0.3 and 4.4 ± 0.3; Imax 55.8% ± 4.2% and 37.5% ± 4.2%. For the constituents, the rank order of potency differed in human (linalool > limonene >> linalyl-acetate) and rat colon (linalyl-acetate > limonene = linalool), but rank order of efficacy was similar (linalool >> (BEO) = linalyl-acetate >> limonene). Thus, linalool had high efficacy but greater potency in human colon (Imax 76.8% ± 6.9%; pIC50 6.7 ± 0.2; n = 4) compared with rat colon (Imax 75.3% ± 1.9%; pIC50 5.8 ± 0.1; n = 4). The ability of BEO and linalool to inhibit human colon neuromuscular contractility provides a mechanism for use as complementary treatments of intestinal disorders.

Role of 5-HT1A Receptor in the Anxiolytic-Relaxant Effects of Bergamot Essential Oil in Rodent.

The essential oil obtained by the fresh fruit of Citrus bergamia Risso et Poiteau is used worldwide in aromatherapy to reduce pain, facilitate sleep induction, and/or minimize the effects of stress-induced anxiety. Preclinical pharmacological data demonstrate that bergamot essential oil (BEO) modulates specific neurotransmissions and shows an anxiolytic-relaxant effect not superimposable to that of the benzodiazepine diazepam, suggesting that neurotransmissions, other than GABAergic, could be involved. Several studies on essential oils indicate a role for serotonergic (5-HT) neurotransmission in anxiety. Interestingly, among serotonergic receptors, the 5-HT1A subtype seems to play a key role in the control of anxiety. Here, we report that modulation of the 5-HT1A receptor by selective agonist ((±)8-OH-DPAT) or antagonist (WAY-100635) may influence some of the anxiolytic-relaxant effects of BEO in Open Field and Elevated Plus Maze tests.

Anxiolytic-Like Effects of Bergamot Essential Oil Are Insensitive to Flumazenil in Rats.

Anxiety disorders are one of the most common mental disorders, and benzodiazepines (BDZs), acting on gamma-aminobutyric acid type A (GABA-A) receptor complex, represent the most common antianxiety medications in the world. However, chronic BDZ use elicits several adverse reactions. Reportedly, aromatherapy is safer for the management of anxiety. Bergamot essential oil (BEO) extracted from Citrus bergamia Risso et Poiteau fruit, like other essential oils, is widely used in aromatherapy to relieve symptoms of stress-induced anxiety. Interestingly, preclinical data indicate that BEO induces anxiolytic-like/relaxant effects in animal behavioural tasks not superimposable to those of benzodiazepine diazepam. To better elucidate the involvement of GABAergic transmission, the present study examines the effects of pretreatment with flumazenil (FLZ), a benzodiazepine site antagonist, on BEO effects using open-field task (OFT) in rats. The data yielded show that FLZ does not significantly affect behavioural effects of the phytocomplex. These results demonstrate the lack of overlapping between BEO and BDZ behavioural effects, contributing to the characterization of the neurobiological profile of the essential oil for its rational use in aromatherapy.

Neuropharmacology of the Neuropsychiatric Symptoms of Dementia and Role of Pain: Essential Oil of Bergamot as a Novel Therapeutic Approach.

Aging of the population makes of dementia a challenge for health systems worldwide. The cognitive disturbance is a serious but not the only issue in dementia; behavioral and psychological syndromes known as neuropsychiatric symptoms of dementia remarkably reduce the quality of life. The cluster of symptoms includes anxiety, depression, wandering, delusions, hallucinations, misidentifications, agitation and aggression. The pathophysiology of these symptoms implicates all the neurotransmitter systems, with a pivotal role for the glutamatergic neurotransmission. Imbalanced glutamatergic and GABAergic neurotransmissions, over-activation of the extrasynaptic N-methyl-D-aspartate (NMDA) receptors and alterations of the latter have been linked to the development of neuropsychiatric symptoms experienced by almost the entire demented population. Drugs with efficacy and safety for prevention or long term treatment of these disorders are not available yet. Aromatherapy provides the best evidence for positive outcomes in the control of agitation, the most resistant symptom. Demented patients often cannot verbalize pain, resulting in unrelieved symptoms and contributing to agitation. Bergamot essential oil provides extensive preclinical evidence of analgesic properties. Incidentally, the essential oil of bergamot induces anxyolitic-like effects devoid of sedation, typical of benzodiazepines, with a noteworthy advantage for demented patients. These data, together with the reported safety profile, form the rational basis for bergamot as a neurotherapeutic to be trialed for the control of behavioral and psychological symptoms of dementia.

Neuropharmacological Properties of the Essential Oil of Bergamot for the Clinical Management of Pain-Related BPSDs.

BACKGROUND: Alzheimer's Disease (AD) accounts for approximately 50% of all cases of dementia and, in spite of the great effort for the development of disease-modifying drugs, a definitive treatment of cognitive impairment is not available yet. A perfect adherence to the current therapy of cognitive decline is needed for a better control of the disease and this is proven to reduce, though not completely abolish, the associated Behavioural and Psychological Symptoms of Dementia (BPSDs) from occurring. This cluster of symptoms, remarkably affecting patients' health-related quality of life (HRQL), is tightly associated with pain states. Antipsychotics are the only treatment for BPSDs. However, these drugs are more effective and safer in the short-term (6-12 weeks), they are able to manage aggression but not agitation and they cannot control pain. Aromatherapy with Melissa officinalis and Lavandula officinalis has been employed to handle BPSDs, but it has not provided strong evidence to offer relief from pain. OBJECTIVE: Bergamot Essential Oil (BEO) exerts antinociceptive activity through several pharmacological mechanisms: in particular, it is able to enhance autophagy, a process undergoing derangement in chronic pain. Thus, the sound pharmacological basis for clinical translation of aromatherapy with BEO in the treatment of BPSDs has been pointed out. CONCLUSION: The antinociceptive effects elicited by BEO in experimental pain models make it a possible candidate for the pharmacological management of pain-related BPSDs.

Antinociceptive effect of inhalation of the essential oil of bergamot in mice.

Bergamot essential oil (BEO) has proven wide evidence of pharmacological antinociceptive effectiveness both in nociceptive and in neuropathic pain models. The antinociceptive properties of BEO for inhalation have not been investigated. The purpose of this study is to evaluate the effects of the inhalation of BEO on formalin-induced nociceptive response in mice. Male ddY-strain mice (Japan SLC, Hamamatsu, Japan) of 23-25 g of weight at the time the experiments underwent the formalin test. Twenty µl of formalin (2% in saline) were administered into the plantar surface of the mice hindpaw and the time of licking/biting was observed and recorded at intervals of 5 min. The device for BEO inhalatory delivery consisted in a filter paper disc soaked with known volume of BEO placed on the edge of the cage. Inhalation of BEO exerted antinociceptive activity. In particular, it reduced the formalin-induced licking/biting behaviour in a manner that was dependent on the volume of BEO used in the device for its release and on the time of exposure to the phytocomplex. The results support the use of BEO in aromatherapy for complementary management of chronic pain relief in a stepwise therapeutic programme.

Rational Basis for Nutraceuticals in the Treatment of Glaucoma.

BACKGROUND: Glaucoma, the second leading cause of blindness worldwide, is a chronic optic neuropathy characterized by progressive retinal ganglion cell (RGC) axons degeneration and death. Primary open-angle glaucoma (OAG), the most common type, is often associated with increased intraocular pressure (IOP), however other factors have been recognized to partecipate to the patogenesis of the optic neuropathy. IOP-independent mechanisms that contribute to the glaucoma-related neurodegeneration include oxidative stress, excitotoxicity, neuroinflammation, and impaired ocular blood flow. The involvement of several and diverse factors is one of the reasons for the progression of glaucoma observed even under efficient IOP control with the currently available drugs. METHODS: Current research and online content related to the potential of nutritional supplements for limiting retinal damage and improving RGC survival is reviewed. RESULTS: Recent studies have suggested a link between dietary factors and glaucoma risk. Particularly, some nutrients have proven capable of lowering IOP, increase circulation to the optic nerve, modulate excitotoxicity and promote RGC survival. However, the lack of clinical trials limit their current therapeutic use. The appropriate use of nutraceuticals that may be able to modify the risk of glaucoma may provide insight into glaucoma pathogenesis and decrease the need for, and therefore the side effects from, conventional therapies. CONCLUSION: The effects of nutrients with anti-oxidant and neuroprotective properties are of great interest and nutraceuticals may offer some therapeutic potential although a further rigorous evaluation of nutraceuticals in the treatment of glaucoma is needed to determine their safety and efficacy.

Aromatherapy and Aromatic Plants for the Treatment of Behavioural and Psychological Symptoms of Dementia in Patients with Alzheimer's Disease: Clinical Evidence and Possible Mechanisms.

The treatment of agitation and aggression, typical Behavioural and Psychological Symptoms of Dementia (BPSDs) of Alzheimer's Disease (AD), is one of the most complicated aspects of handling patients suffering from dementia. Currently, the management of these symptoms often associated with an increased pain perception, which notably reduces the patients' quality of life (QoL), relies on the employment of antipsychotic drugs. Unfortunately, the use of these pharmacological agents has some limits: in the long term, they do not result in being equally effective as in the first weeks of treatment and they present important side effects. Therefore, there is growing interest, supported by clinical evidence, in aromatherapy for the control of agitation, aggression, and psychotic symptoms. Some molecular mechanisms have been proposed to explain the behavioural effects of essential oils, as the whole phytocomplex or the single components, but important basic research effort is still needed. For this reason, rigorous preclinical studies are necessary in order to understand the pharmacological basis of aromatherapy in the treatment of BPSDs and to widen the cluster of effective essential oils in pharmacotherapeutic practice.

Bergamot Essential Oil Attenuates Anxiety-Like Behaviour in Rats.

Preclinical studies have recently highlighted that bergamot essential oil (BEO) is endowed with remarkable neurobiolological effects. BEO can affect synaptic transmission, modulate electroencephalographic activity and it showed neuroprotective and analgesic properties. The phytocomplex, along with other essential oils, is also widely used in aromatherapy to minimize symptoms of stress-induced anxiety and mild mood disorders. However, only limited preclinical evidences are actually available. This study examined the anxiolytic/sedative-like effects of BEO using an open field task (OFT), an elevated plus-maze task (EPM), and a forced swimming task (FST) in rats. This study further compared behavioural effects of BEO to those of the benzodiazepine diazepam. Analysis of data suggests that BEO induces anxiolytic-like/relaxant effects in animal behavioural tasks not superimposable to those of the DZP. The present observations provide further insight to the pharmacological profile of BEO and support its rational use in aromatherapy.

Implication of limonene and linalyl acetate in cytotoxicity induced by bergamot essential oil in human neuroblastoma cells.

Bergamot (Citrus bergamia, Risso et Poiteau) essential oil (BEO) is a widely used plant extract showing anxiolytic, analgesic and neuroprotective effects in rodents; also, BEO activates multiple death pathways in cancer cells. Despite detailed knowledge of its chemical composition, the constituent/s responsible for these pharmacological activities remain largely unknown. Aim of the present study was to identify the components of BEO implicated in cell death. To this end, limonene, linalyl acetate, linalool, γ-terpinene, ß-pinene and bergapten were individually tested in human SH-SY5Y neuroblastoma cultures at concentrations comparable with those found in cytotoxic dilutions of BEO. None of the tested compounds elicited cell death. However, significant cytotoxicity was observed when cells were cotreated with limonene and linalyl acetate whereas no other associations were effective. Only cotreatment, but not the single exposure to limonene and linalyl acetate, replicated distinctive morphological and biochemical changes induced by BEO, including caspase-3 activation, PARP cleavage, DNA fragmentation, cell shrinkage, cytoskeletal alterations, together with necrotic and apoptotic cell death. Collectively, our findings suggest a major role for a combined action of these monoterpenes in cancer cell death induced by BEO.

Neuropharmacology of the essential oil of bergamot.

Bergamot (Citrus bergamia, Risso) is a fruit most knowledgeable for its essential oil (BEO) used in aromatherapy to minimize symptoms of stress-induced anxiety and mild mood disorders and cancer pain though the rational basis for such applications awaits to be discovered. The behavioural and EEG spectrum power effects of BEO correlate well with its exocytotic and carrier-mediated release of discrete amino acids endowed with neurotransmitter function in the mammalian hippocampus supporting the deduction that BEO is able to interfere with normal and pathological synaptic plasticity. The observed neuroprotection in the course of experimental brain ischemia and pain does support this view. In conclusion, the data yielded so far contribute to our understanding of the mode of action of this phytocomplex on nerve tissue under normal and pathological experimental conditions and provide a rational basis for the practical use of BEO in complementary medicine. The opening of a wide venue for future research and translation into clinical settings is also envisaged.

Effects of systemic administration of the essential oil of bergamot (BEO) on gross behaviour and EEG power spectra recorded from the rat hippocampus and cerebral cortex.

Bergamot (Citrus bergamia Risso et Poiteau) is a citrus fruit growing almost exclusively in the South of Italy. Its essential oil is obtained by cold pressing of the epicarp and, partly, of the mesocarp of the fresh fruit. Although this phytocomplex has been used for centuries, reputedly effectively, as a traditional medicine, there is very little verified scientific evidence to support this use. This paper reports original data on the systemic effects of the essential oil of bergamot (BEO) on gross behaviour and EEG activity recorded from the hippocampus and cerebral cortex of the rat. The Fast Fourier Transformation (FFT) was used to analyse and quantify the energy in single frequency bands of the EEG spectrum. The results obtained indicate that systemic administration of increasing volumes of BEO produces dose-dependent increases in locomotor and exploratory activity that correlate with a predominant increase in the energy in the faster frequency bands of the EEG spectrum. These data contribute to our understanding of the neurobiological profile of BEO.

The essential oil of bergamot enhances the levels of amino acid neurotransmitters in the hippocampus of rat: implication of monoterpene hydrocarbons.

The effects of bergamot essential oil (BEO) on the release of amino acid neurotransmitters in rat hippocampus have been studied by in vivo microdialysis and by in vitro superfusion of isolated nerve terminals. Intraperitoneal administration of BEO (100microl/kg) significantly elevated the extracellular concentration of aspartate, glycine and taurine in a Ca(2+)-dependent manner. A dose-relation study generated a bell-shaped curve. When perfused into the hippocampus via the dialysis probe (20microl/20min), BEO produced a significant increase of extracellular aspartate, glycine, taurine as well as of GABA and glutamate. The augmentation of all amino acids was Ca(2+)-independent. Focally injected 1:1 diluted BEO preferentially caused extracellular increase of glutamate. Interestingly, this release appeared to be strictly Ca(2+)-dependent. BEO concentration-dependently enhanced the release of [(3)H]D-aspartate from superfused hippocampal synaptosomes. Similar results were obtained by monitoring the BEO-evoked release of endogenous glutamate. At relatively high concentrations, the BEO-induced [(3)H]d-aspartate release was almost entirely prevented by the glutamate transporter blocker dl-threo-beta-benzyloxyaspartic acid (DL-TBOA) and was Ca(2+)-independent. At relatively low concentrations the release of [(3)H]D-aspartate was only in part ( approximately 50%) DL-TBOA-sensitive and Ca(2+)-independent; the remaining portion of release was dependent on extracellular Ca(2+). Interestingly, the monoterpene hydrocarbon-free fraction of the essential oil appeared to be inactive while the bergapten-free fraction superimposed the releasing effect of BEO supporting the deduction that psoralens may not be implicated. To conclude, BEO contains into its volatile fraction still unidentified monoterpene hydrocarbons able to stimulate glutamate release by transporter reversal and/or by exocytosis, depending on the dose administered.