Exposure to inhomogeneous static magnetic field beneficially affects allergic inflammation in a murine model

Abstract

Previous observations suggest that static magnetic field (SMF)-exposure acts on living organisms partly through reactive oxygen species (ROS) reactions. In this study, we aimed to define the impact of SMF-exposure on ragweed pollen extract (RWPE)-induced allergic inflammation closely associated with oxidative stress. Inhomogeneous SMF was generated with an apparatus validated previously providing a peak-to-peak magnetic induction of the dominant SMF component 389 mT by 39 T m(-1) lateral gradient in the in vivo and in vitro experiments, and 192 mT by 19 T m(-1) in the human study at the 3 mm target distance. Effects of SMF-exposure were studied in a murine model of allergic inflammation and also in human provoked skin allergy. We found that even a single 30-min exposure of mice to SMF immediately following intranasal RWPE challenge significantly lowered the increase in the total antioxidant capacity of the airways and decreased allergic inflammation. Repeated (on 3 consecutive days) or prolonged (60 min) exposure to SMF after RWPE challenge decreased the severity of allergic responses more efficiently than a single 30-min treatment. SMF-exposure did not alter ROS production by RWPE under cell-free conditions, while diminished RWPE-induced increase in the ROS levels in A549 epithelial cells. Results of the human skin prick tests indicated that SMF-exposure had no significant direct effect on provoked mast cell degranulation. The observed beneficial effects of SMF are likely owing to the mobilization of cellular ROS-eliminating mechanisms rather than direct modulation of ROS production by pollen NAD(P)H oxidases.

Keywords: allergic inflammation; oxidative stress; pollen; static magnetic field.

Figure 1.

Experimental protocols for the pilot study (a) and the full test (b). Mice were divided into five groups both in the pilot study (A–E) and in the full test (I–V). Black dots indicate the dates of SMF-exposures and open squares represent the dates of intraperitoneal (i.p.), intranasal (i.n.) administration of RWPE or PBS, or termination of the experiment, respectively.

Figure 2.

SMF-exposure does not affect the sensitization phase of the allergic responses. RWPE- or PBS-challenged, sensitized mice were exposed to SMF or sham field for 30 min daily during sensitization (Group B) or elicitation (Group C) phase only or the whole period of the experiment (Groups A, D and E). Three days after challenge bronchoalveolar lavage (BAL) was performed and lavage samples were examined for eosinophil cell counts. Results are presented as means ± s.e.m. *p < 0.05 versus RWPE-challenged, sensitized mice exposed to sham field.

Figure 3.

Exposure to SMF reduces RWPE-induced allergic airway inflammation. Sensitized mice were challenged with PBS or RWPE and exposed to SMF or sham field. Three days after the challenge, BAL was performed and lavage samples were examined for total (a) and eosinophil (b) cell counts. (c) Haematoxylin and eosin staining of formalin-fixed lung sections. Original magnification 100×. Results are presented as means ± s.e.m. **p < 0.01, ***p < 0.001, ****p < 0.0001 versus RWPE-challenged sensitized mice exposed to sham field. ^###p < 0.001, significant difference between Groups III and IV.

Figure 4.

SMF-exposure decreases mucin levels and epithelial cell metaplasia in the airways of RWPE-challenged sensitized mice. (a) MUC5AC levels in the BAL fluids of RWPE- or PBS-challenged sensitized mice exposed to SMF or sham field. MUC5AC levels were measured by means of ELISA and the results were expressed as endpoint titres (squares) and means (thick horizontal line markers). *p < 0.05, ****p < 0.0001 versus RWPE-challenged, sensitized mice exposed to sham field, ^#p < 0.05, significant difference between Groups III and IV. (b) Periodic acid–Schiff staining of formalin-fixed lung sections. Original magnification 100×.

Figure 5.

SMF-exposure fails to alter the generation of ROS by RWPE in cell-free conditions, while it diminishes the increase in intracellular ROS levels in RWPE-treated epithelial cells. (a) PBS (open bars) or RWPE (filled bars) solutions containing redox-sensitive H₂DCF-DA were exposed to SMF or sham field for 30 min at lower or upper position (see §2.1). Changes in DCF fluorescence intensity were detected by means of fluorimetry. ***p < 0.001 versus RWPE exposed to sham field. (b) A549 cells loaded with H₂DCF-DA were treated with PBS (open bars) or RWPE (filled bars) and immediately after the treatment they were exposed to SMF or sham field for 30 min at lower or upper position. Changes in DCF fluorescence intensity are presented as means ± s.e.m. of three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001 versus RWPE-treated cells exposed to sham field.

Figure 6.

SMF-exposure following intranasal challenge lowers the RWPE-induced increase in total antioxidant capacity of the airways. Naive mice were challenged intranasally with RWPE or PBS and immediately thereafter were exposed to SMF or sham field for 30 min. BAL fluid samples were collected 15 min after SMF- or sham field-exposure. Antioxidant potential was measured spectrophotometrically in the supernatant of the samples and expressed in Trolox equivalents. Data are presented as means ± s.e.m. ***p < 0.001 versus RWPE-challenged, naive mice exposed to sham field.

Figure 7.

SMF-exposure has no significant direct effect on provoked mast cell degranulation. Skin prick tests were performed on healthy volunteers, as described in Material and methods. Immediately after introduction of the identical test materials into the skin of both inner forearms, one forearm of the volunteers was exposed to SMF (filled bars), while the other was exposed to sham field (open bars). The wheal reaction was measured immediately after a 15 min exposure period. Data are presented as means ± s.e.m. ^#p < 0.05.