Anti-inflammatory properties of hemp extracts in human bronchial cells

Inflammatory lung diseases represent one of the most widespread affections associated with morbidity, mortality and health care expenditure in Europe [1]. Chronic Obstructive Pulmonary Disease (COPD) is a respiratory disorder associated to a chronic inflammatory response. Main features are a progressive and irreversible airflow limitation, consequence of inflammatory cells infiltration and alteration in cilia structure and functionality [2-3]. The prescribed therapy consists of inhalation of bronchodilators and glucocorticoids [4], but it is historically adopted the use of traditional herbal remedies for treatment of respiratory diseases [5]. Previously, we evaluated thyme extract, obtained from Thymus vulgaris L., widely used as a spice, as potential remedy for airways affections. Briefly, we studied the effects of thyme extract in an in vitro model of lung inflammation induced by lipopolysaccharide (LPS) in primary human airway (bronchial/tracheal) epithelial cell lines (HBEpC/HTEpC) [6]. Indeed, exposure to LPS increases several pro-inflammatory mediators expression, such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-α), involved in pathogenesis of COPD [7], and mucus production in airway epithelial cells. Results showed that thyme extract was non-cytotoxic for HBEpC/HTEpC cells and was effective in reducing inflammatory markers as NF-kB, IL-1β and IL-8 expression in LPS-treated cells [6]. Subsequently, to further characterize the beneficial use of thyme extract in COPD treatment, it was evaluated its effects in regulating Cilia beating frequency (CBF), that is dramatically impaired in COPD, using a 3D in vitro model of Human Airway Epithelia, using three different bronchial primary cells derived from COPD single donors. Results show that thyme extract is involved in stimulating CBF, through an increase of [Ca2+]i in a TRPV4 channel-dependent manner [8]. Hemp (Cannabis sativa L.) represents a sustainable crop multipurpose with a low environmental impact which can be useful in the agricultural field, phytoremediation and for nutrition, cosmetic, building, and pharmaceutical application. In this regard, the hemp essential oil (EO), which is a mixture of volatile compounds with a lower concentration of the cannabinoid fraction, is gaining interest by pharma companies, for its potential anti-inflammatory properties [9-10]. Despite plant EOs have shown several biological properties, it has been scarcely investigated. On this basis, the aim of this study was to investigate if the EOs obtained from inflorescences of hemp may be useful for airways affection management. For the purpose, we selected two different hemp varieties, namely, USO31 and Carmagnola CS and human normal bronchial cells as model of airway inflammation in vitro. Preliminary results obtained in human bronchial cells show that hemp essential oils displayed a moderate cytotoxic effect in a dose-dependent manner, with an IC50 of 34.2 ± 1.1 μg mL-1 for Carmagnola CS essential oil and 40.62 ± 1.8 μg mL−1 for USO31 essential oil. Then, to evaluate the anti-inflammatory potential of these EOs, we treated bronchial cells with Etoposide that several studies have indicated to trigger cytokines production in human cell lines in vitro [11]. Hemp EOs, used at non-cytotoxic doses, did not cause an inflammatory state but, additionally, were able to revert an inflammatory condition, reducing the release of the cytokines induced by Etoposide. In conclusion, these preliminary results evidenced a potential use of EOs for bronchial inflammatory diseases.