Immunomodulatory Role of IRosmarinus officinalis/I L., IMentha/I x Ipiperita/I L., and ILavandula angustifolia/I L. Essential Oils in Sheep Peripheral Blood Mononuclear Cells

The increasing demand for livestock production with a more sustainable approach to reduce greenhouse emissions offers the opportunity to test essential oils (EOs), as natural treatments, for their effect on rumen activity, as well as the use of antibiotics, for their antimicrobial activities. However, little information is available on the effects of EOs on the proliferative immune response and cytokine production. Therefore, the present paper is aimed at evaluating the effect of the Mentha x piperita L., Rosmarinus officinalis L., and Lavandula angustifolia L. EOs on sheep peripheral blood monocular cells’ bio-response in terms of viability, proliferation, and cytokine secretion. The main results obtained encourage the implementation of these EOs as feed additives, in in vivo studies, to improve the animals’ immune competence, especially those under specific physiological or environmental stressors. Recently, the uses of essential oils (EOs) as rumen modifiers, anti-inflammatory agents, and antioxidants were demonstrated in livestock. In the present study, the role of Mentha x piperita L. (MEO), Rosmarinus officinalis L. (REO), and Lavandula angustifolia L. (LEO) EOs in an in vitro sheep model of inflammation was investigated. With this aim, peripheral blood mononuclear cells (PBMCs) were treated with incremental concentrations (3, 5, 7, and 10%) of each EO to test their effects on cell viability and proliferation and on interleukin (IL)-6, IL-10, and IL-8 secretion. The PBMCs were stimulated by Concanavalin A (ConA) alone or in combination with lipopolysaccharide (LPS) mitogen. The positive and negative controls were represented by PBMCs in the presence or absence, respectively, of mitogens only. The cell viability and proliferation were determined by XTT and BrdU assays, while the cytokines were analyzed by ELISA. The EO treatments did not affect the viability; on the contrary, the PBMC proliferation increased in presence of all the EOs tested, according to the different percentages and mitogens used. The IL-10 secretion was higher in both the REO and the LEO tested at 3% than in the positive control; furthermore, the IL-8 level was influenced differently by the various EOs. The present data demonstrate that EOs may modulate the immune response activated by inflammation.