Inhibition of interferon-γ production and T-bet expression by menthol treatment of human peripheral blood mononuclear cells

Abstract

Context: Mentha longifolia (L.) Huds., has shown anti-inflammatory effects.

Objective: To evaluate the immunomodulatory effects of menthol, the major constituent of Mentha longifolia on T cells as the main cells affecting the inflammatory responses.

Methods: Effect of menthol on: proliferation and viability of the peripheral blood human mononuclear cells (PBMCs) by BrdU and propidium iodide (PI) staining, respectively, interferone (IFN)γ and interleukin (IL)-4 cytokine production in lymphocytes stimulated with phytohemagglutinin (PHA) and phorbol myristate acetate/calcium ionophore (PMA/CI) by ELISA; intracellular staining of CD4⁺ cells for IFNγ expression by flow cytometry and gene expressions of T heper (Th) cell transcription factors was measured using real time-PCR.

Results: Menthol dose-dependently inhibited lymphocytes proliferation from 88.7% at 50 μg/ml to 3.63% at 800 μg/ml (p < .05). According to the results of PI staining, this inhibitory effect was not due to cell death. Menthol dose-dependently decreased IFNγ but not IL-4 production in culture of PHA- and PMA/CI-stimulated lymphocytes to more than 80% at 800 µg/ml. In flow cytometry analysis, menthol reduced the number of IFN-γ-expressing CD4⁺T cells stimulated either with PHA or PMA/CI. Treatment of PBMCs with 800 μg/ml of menthol decreased levels of T-bet from 14.5 ± 2.26 fold in untreated control to 2.76 ± 1.74 fold (p < .001). Foxp-3 expression decreased to nearly half, but GATA3 did not significantly change. Ratios of T-bet to GATA3 and T-bet to Foxp3 gene expressions were dose-dependently declined.

Conclusion: Decreased IFNγ expression plus T-bet down-regulation suggested the inhibitory effect of menthol on Th1 cells differentiation and hence imply its possible therapeutic usefulness in inflammatory diseases.

Keywords:

• Menthol
• Mentha longifolia
• T cells
• IFN-γ

Acknowledgements

This study was extracted from the thesis written by one of the authors, M. Bayat.

Disclosure statement

The authors declare no conflicts of interest.

Additional information

Funding

This study was supported by Shiraz University of Medical Sciences (grant no 16260)