The Effect of (-)-Linalool on the Metabolic Activity of Liver CYP Enzymes in Rats

Natural Compounds in the Battle against Microorganisms-Linalool

The purpose of this article is to present recent studies on the antimicrobial properties of linalool, the mechanism of action on cells and detoxification processes. The current trend of employing compounds present in essential oils to support antibiotic therapy is becoming increasingly popular. Naturally occurring monoterpene constituents of essential oils are undergoing detailed studies to understand their detailed effects on the human body, both independently and in doses correlated with currently used pharmaceuticals. One such compound is linalool, which is commonly found in many herbs and is used to flavor black tea. This compound is an excellent fragrance additive for cosmetics, enhancing the preservative effect of the formulations used in them or acting as an anti-inflammatory on mild skin lesions. Previous studies have shown that it is extremely important due to its broad spectrum of biological activities, i.e., antioxidant, anti-inflammatory, anticancer, cardioprotective and antimicrobial. Among opportunistic hospital strains, it is most active against Gram-negative bacteria. The mechanism of action of linalool against microorganisms is still under intensive investigation. One of the key aspects of linalool research is biotransformation, through which its susceptibility to detoxification processes is determined.

A Practical Perspective on the Use of Botanicals During the COVID-19 Pandemic: From Proven to Potential Interactions

In this review, we examined the top 10 nutraceutical products sold in Italian pharmacies and parapharmacies as well as hypermarkets and supermarkets; in the first, three product categories saw the greatest increase in sales (vitamins and minerals, immunostimulants, and sleep products) for the 12-month period between October 2019 and October 2020 (including first pandemic wave of SARS-CoV-2). We are investigating their respective formulas and isolating the botanicals that are used to make them. Many of these products have undergone preclinical and clinical studies. We performed a systematic literature search in the MEDLINE database using PubMed and Google Scholar from November 15, 2020 to December 15, 2020 (including studies carried out between 1980 and 2020). The search terms that were used included the complete name of the medicinal plant in English or Latin and the terms "cytochrome" or "drug interactions," crossing, respectively, the Latin name and English common names with "cytochrome" and "drug interactions." The search included in vitro and in vivo studies describing the effects of interaction between the plant (extract or botanical medicine) and human cytochromes. Despite their great complexity, there is decidedly limited clinical data on botanical medicine. In fact, of the 28 botanicals that were examined, only 2 (Citrus paradisi and Rhodiola rosea) show in vivo pharmacological interactions in human subjects. On the contrary, for the other botanicals, there is only weak evidence of dubious clinical significance or potential interactions shown in animal models or in vitro without clinical confirmation. This study provides a rational assessment of the most widely used products, including those used in self-medication, to simplify patient management during the COVID-19 health emergency.

Linalool inhibits the angiogenic activity of endothelial cells by downregulating intracellular ATP levels and activating TRPM8

Angiogenesis crucially contributes to various diseases, such as cancer and diabetic retinopathy. Hence, anti-angiogenic therapy is considered as a powerful strategy against these diseases. Previous studies reported that the acyclic monoterpene linalool exhibits anticancer, anti-inflammatory and anti-oxidative activity. However, the effects of linalool on angiogenesis still remain elusive. Therefore, we investigated the action of (3R)-(-)-linalool, a main enantiomer of linalool, on the angiogenic activity of human dermal microvascular endothelial cells (HDMECs) by a panel of angiogenesis assays. Non-cytotoxic doses of linalool significantly inhibited HDMEC proliferation, migration, tube formation and spheroid sprouting. Linalool also suppressed the vascular sprouting from rat aortic rings. In addition, Matrigel plugs containing linalool exhibited a significantly reduced microvessel density 7 days after implantation into BALB/c mice. Mechanistic analyses revealed that linalool promotes the phosphorylation of extracellular signal-regulated kinase (ERK), downregulates the intracellular level of adenosine triphosphate (ATP) and activates the transient receptor potential cation channel subfamily M (melastatin) member (TRPM)8 in HDMECs. Inhibition of ERK signaling, supplementation of ATP and blockade of TRPM8 significantly counteracted linalool-suppressed HDMEC spheroid sprouting. Moreover, ATP supplementation completely reversed linalool-induced ERK phosphorylation. In addition, linalool-induced ERK phosphorylation inhibited the expression of bone morphogenetic protein (BMP)-2 and linalool-induced TRPM8 activation caused the inhibition of β1 integrin/focal adhesion kinase (FAK) signaling. These findings indicate an anti-angiogenic effect of linalool, which is mediated by downregulating intracellular ATP levels and activating TRPM8.

Linalool reverses benzene-induced cytotoxicity, oxidative stress and lysosomal/mitochondrial damages in human lymphocytes

Benzene exposure results in bone marrow suppression, leading to a decrease in the number of circulating white blood cells, an increased risk of chronic lymphocytic leukemia, acute myeloid leukemia and aplastic anemia. Since the mechanism of induction of benzene toxicity is due to active metabolites through cytochrome p450 enzymes and production of reactive oxygen species (ROS), we hypothesized that natural compound such linalool with anti-inflammatory/antioxidant properties could be effective in reducing its toxicity. Lymphocytes isolated from healthy individuals were simultaneously cotreated with different concentrations of LIN (10, 25 and 50 µM) and benzene (50 µM) for 4 h at 37 °C. After incubation, the toxicity parameters such cytotoxicity, ROS formation, lysosomal membrane integrity, mitochondria membrane potential (ΔΨm) collapse, oxidized/reduced glutathione (GSH/GSSG) and malondialdehyde (MDA) were analyzed using biochemical and flow cytometry evaluations. Our data showed that benzene (50 µM) induced a significant increase in cytotoxicity, ROS formation, mitochondrial membrane potential (MMP) collapse, lipid peroxidation and oxidative stress while LIN with antioxidant potential reversed the toxic effects of benzene on isolated human lymphocytes. Our results suggest that LIN reduces and reverses benzene-induced cytotoxicity, oxidative stress and lysosomal/mitochondrial damages in human lymphocyte. This study demonstrated that cotreatment of LIN with benzene can reduce several parameters indicative of oxidative stress. As such, LIN could represent a potential therapeutic agent in reducing certain aspects of benzene-induced toxicity.

Protection of CCl4-induced hepatic and renal damage by linalool

The aim of the current study is to determine the protective and therapeutic effects of linalool against carbon tetrachloride (CCl₄)-induced hepatoxicity and nephrotoxicity. Six-week-old male Wistar rats were divided into five groups: Control group (a regular diet); CCl₄ group (1 ml/kg dissolved in olive oil, intraperitoneally at 14th day); pretreatment group (25 mg/kg linalool daily + CCl₄ 14thday); post-treatment group (25 mg/kg linalool 2, 6, 24, and 48 h after the injection of CCl₄ at 14^th day); and linalool group (25 mg/kg linalool daily, orally). All animals were sacrificed, tissue and blood samples were collected to analysis. Administration of CCl₄ resulted in a marked increase in hepatic (aspartate aminotransferase, alanine transaminase, and alkaline phosphatase) and renal (blood urea nitrogen and creatinine) markers. Also, CCl₄ resulted in pathological damages, a significant increase in the concentration of malondialdehyde , tumor necrosis factor-alpha, and Interleukin 6 , expression of nuclear factor kappa-light-chain-enhancer of activated B cells and a significant decrease in the levels of serum total protein, serum albumin, and antioxidants. However, in pretreatment and post treatment groups, linalool significantly inhibited CCl4- induced hepatic and nephric damages. These results demonstrate that linalool has protective and therapeutic effects in an in vitro model of CCL₄-induced hepatic and nephric damage, proposing linalool as a potential therapeutic agent against chemical and drug induced hepatotoxicity and nephrotoxicity.

History repeats itself: Role of characterizing flavors on nicotine use and abuse

The popularity of e-cigarettes has skyrocketed in recent years, and most vapers use flavored e-cigarette products. Consumption of flavored e-cigarettes exceeds that of combustible cigarettes and other tobacco products among adolescents, who are particularly vulnerable to becoming nicotine dependent. Flavorings have been used by the tobacco industry since the 17th century, but the use of flavors by the e-cigarette industry to create products with "characterizing" flavors (i.e. flavors other than tobacco or menthol) has sparked a public health debate. This review addresses the possibility that characterizing flavors make nicotine more appealing, rewarding and addictive. It also discusses ways in which preclinical and clinical studies could improve our understanding of the mechanisms by which flavors may alter nicotine reward and reinforcement. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

Lavender Products Associated With Premature Thelarche and Prepubertal Gynecomastia: Case Reports and Endocrine-Disrupting Chemical Activities

CONTEXT

Previous case reports associated prepubertal gynecomastia with lavender-containing fragrances, but there appear to be no reports of premature thelarche.

OBJECTIVE

To add to a case series about lavender-fragranced product use and breast growth in children and to measure endocrine-disrupting chemical activity of essential oil components.

DESIGN, SETTING, AND PATIENTS

Patients experiencing premature thelarche or prepubertal gynecomastia with continuous exposure to lavender-fragranced products were evaluated in the pediatric endocrinology departments of two institutions. Mechanistic in vitro experiments using eight components of lavender and other essential oils were performed at National Institute of Environmental Health Sciences.

MAIN OUTCOME MEASURES

Case reports and in vitro estrogen and androgen receptor gene expression activities in human cell lines with essential oils.

RESULTS

Three prepubertal girls and one boy with clinical evidence of estrogenic action and a history of continuous exposure to lavender-containing fragrances were studied. Breast growth dissipated in all patients with discontinuation of the fragranced products. Some of the components tested elicited estrogenic and antiandrogenic properties of varying degrees.

CONCLUSION

We report cases of premature thelarche that resolved upon cessation of lavender-containing fragrance exposure commonly used in Hispanic communities. The precise developmental basis for such conditions could be multifactorial. In vitro demonstration of estrogenic and antiandrogenic properties of essential oil components suggests essential oils in these cases could be considered a possible source and supports a possible link with idiopathic prepubertal breast development. Whether the level of lavender oil estrogenic potency is sufficient to cause these effects is unknown.

Effect of Endocannabinoid Oleamide on Rat and Human Liver Cytochrome P450 Enzymes in In Vitro and In Vivo Models

The endocannabinoid system is important for many physiologic and pathologic processes, but its role in the regulation of liver cytochromes P450 (P450s) remains unknown. We studied the influence of the endocannabinoid oleamide on rat and human liver P450s. Oleamide was administered intraperitoneally to rats at doses of 0.1, 1, and 10 mg/kg per day for 7 days. The content and activity of key P450s were evaluated in rat liver microsomes. Moreover, interactions with nuclear receptors regulating P450 genes and serum levels of their ligands (prolactin, corticosterone, and free triiodothyronine) were tested in in vitro P450 inhibition assays. Decreased protein levels and metabolic activities of CYP1A2, CYP2B, and CYP2C11, along with a drop in metabolic activity of CYP2D2, were observed in animals treated with oleamide (10 mg/kg per day). The activities of CYP2C6, CYP2A, and CYP3A and the levels of hormones were not altered. In vitro, oleamide exhibited a weak inhibition of rat CYP1A2, CYP2D2, and CYP2C6. The activities of rat CYP2A, CYP2B, CYP2C11, and CYP3A and human CYP1A2, CYP2B6, CYP2C9, and CYP3A4 were not altered. Oleamide did not interact with human pregnane X, constitutive androstane, or aryl hydrocarbon receptors in reporter gene experiments and did not regulate their target P450 genes in primary human hepatocytes. Our results indicate that oleamide caused the downregulation of some rat liver P450s, and hormones are not mediators of this effect. In vitro oleamide inhibits mainly rat CYP2C6 and is neither an agonist nor antagonist of major human nuclear receptors involved in the regulation of xenobiotic metabolism.