Anti-inflammatory effects of Myrtol standardized and other essential oils on alveolar macrophages from patients with chronic obstructive pulmonary disease

Abstract

Introduction: Myrtol standardized is established in the treatment of acute and chronic bronchitis and sinusitis. It increases mucociliar clearance and has muco-secretolytic effects. Additional anti-inflammatory and antioxidative properties have been confirmed for Myrtol standardized, eucalyptus oil, and orange oil in several in vitro studies.

Objective: The aim of this study was to prove the ability of essential oils to reduce cytokines release and reactive oxygen species (ROS) production derived from ex vivo cultured alveolar macrophages.

Material and methods: Alveolar macrophages from patients with chronic obstructive pulmonary disease (COPD, n=26, GOLD III-IV) were pre-cultured with essential oils (10(3)-10(-8)%) for 1 h and then stimulated with LPS (1 microg/ml). After 4 h and 20 h respectively a) cellular reactive oxygen species (ROS) using 2',7'-dichlorofluorescein (DCF), and b) TNF-alpha, IL-8, and GM-CSF secretion were quantified.

Results: In comparison with negative controls, pre-cultured Myrtol, eucalyptus oil and orange oil (10-4%) reduced in the LPS-activated alveolar macrophages ROS release significantly after 1+20 h as follows: Myrtol -17.7% (P=0.05), eucalyptus oil -21.8% (P<0.01) and orange oil -23.6% (P<0.01). Anti-oxidative efficacy was comparable to NAC (1 mmol/l). Essential oils also induced a TNF-alpha reduction: Myrtol (-37.3%, P<0.001), eucalyptus oil (-26.8%, P<0.01) and orange oil (-26.6%, P<0.01). TNF-a reduction at 1+4 h and 1+20 h did not vary (Myrtol: -31.9% and -37.3% respectively, P= 0.372) indicating that this effect occurs early and cannot be further stimulated. Myrtol reduced the release of GM-CSF by -35.7% and that of IL-8 only inconsiderably.

Conclusions: All essential oils tested have effective antioxidative properties in ex vivo cultured and LPS-stimulated alveolar macrophages. Additionally, Myrtol inhibited TNF-a and GM-CSF release best indicating additional potent anti-inflammatory activity.

Figure 1

Reactive oxygen species (ROS) reduction in LPS (1 μg/ml)-stimulated alveolar macrophages from COPD patients with various essential oils (0.0001% dilution) at 1+20 h incubation time (see text for details). Data presented as means ± SD, NAC - N-acetylcysteine (1 mmol/l), orange - orange oil, eucalyptus - eucalyptus oil. #P < 0.05, *P < 0.01 compared with cell medium/LPS alone, non-significant differences among essential oils and NAC.

Figure 2

Reduction of TNFα release from LPS (1 μg/ml-stimulated alveolar macrophages from COPD patients at 1+20 h incubation time (see text for details). TNFα - tumor necrosis factor alpha, NAC - N-acetylcysteine (1 mmol/l), orange - orange oil, eucalyptus - eucalyptus oil. *P < 0.01 compared with cell medium/LPS alone.

Figure 3

Reduction of TNFα release from LPS (1 μg/ml)-stimulated alveolar macrophages derived from COPD patients. Incubation time: 1 h pre-incubation with myrtol 0.0001% solution, followed by a washing step and 4 h incubation (in RPMI/fetal calf serum/LPS). Differences non-significant between myrtol incubation times, but P < 0.01 (*) compared with cell medium alone. TNFα - tumor necrosis factor alpha.