The putative role of ovary removal and progesterone when considering the effect of formaldehyde exposure on lung inflammation induced by ovalbumin

Abstract

Objective: Formaldehyde exposure during the menstrual cycle is known to affect the course of allergic lung inflammation. Because our previous data demonstrated that formaldehyde combined with an ovariectomy reduced allergic lung inflammation, we investigated the putative role of ovary removal and progesterone treatment when considering the effect of formaldehyde on allergic lung inflammation.

Method: Ovariectomized rats and their matched controls were exposed to formaldehyde (1%, 3 days, 90 min/day) or vehicle, and immediately after exposure, the rats were sensitized to ovalbumin by a subcutaneous route. After 1 week, the rats received a booster by the same route, and after an additional week, the rats were challenged with ovalbumin (1%) by an aerosol route. The leukocyte numbers, interleukin-10 (IL-10) release, myeloperoxidase activity, vascular permeability, ex vivo tracheal reactivity to methacholine and mast cell degranulation were determined 24 h later.

Results: Our results showed that previous exposure to formaldehyde in allergic rats decreased lung cell recruitment, tracheal reactivity, myeloperoxidase activity, vascular permeability and mast cell degranulation while increasing IL-10 levels. Ovariectomy only caused an additional reduction in tracheal reactivity without changing the other parameters studied. Progesterone treatment reversed the effects of formaldehyde exposure on ex vivo tracheal reactivity, cell influx into the lungs and mast cell degranulation.

Conclusion: In conclusion, our study revealed that formaldehyde and ovariectomy downregulated allergic lung inflammation by IL-10 release and mast cell degranulation. Progesterone treatment increased eosinophil recruitment and mast cell degranulation, which in turn may be responsible for tracheal hyperreactivity and allergic lung inflammation.

Figure 1

Protocol of study. The rats were ovariectomized or not and after 7 days submitted or not to FA inhalation. Subsequently the animals were sensitized and challenged with OVA.

Figure 2

The effect of ovariectomy (OVx) and progesterone treatment (P) when considering the results of formaldehyde inhalation on the number of cells recruited in the bronchoalveolar lavage (BAL). Seven days after OVx or Sham-operation (Sham-OVx), the rats were subjected or not to FA inhalation. Subsequently, the rats were sensitized and challenged with OVA. In a parallel study, 7 days after the OVx, the rats were treated with progesterone. Lung inflammation was assessed by quantification of the total number of cells (A) and the total number of differential cells (B and C) present in the BAL 24 h after the OVA challenge. Basal parameters were obtained from non-manipulated rats (naïve). The data are the mean ± SEM of 6 animals per group. *p<0.05 relative to the naïve group; ^θp<0.05 relative to the OVA/OVA Sham-OVx group; δp<0.05 relative to the FA/OVA OVx group. (ANOVA followed by the Student-Newman-Keuls test).

Figure 3

The effect of ovariectomy (OVx) when considering the results of FA exposure on myeloperoxidase activity (MPO) and vascular permeability in the lung tissue. Seven days after the OVx or Sham-OVx, the rats were submitted or not to FA inhalation and then sensitized and challenged with OVA. Either 24 h (A) or immediately after the OVA challenge, the MPO activity and vascular permeability were measured. The data are the mean ± SEM of 5 animals. *p<0.05 relative to the naïve group; ^θp<0.05 relative to the OVA/OVA Sham-OVx group; ^ωp<0.05 relative to the OVA/OVA OVx group. (ANOVA followed by the Student-Newman-Keuls test).

Figure 4

The effect of ovariectomy (OVx) and FA exposure on the synthesis of anti-OVA IgE. Seven days after the OVx or Sham-OVx, the rats were submitted or not to FA inhalation and then sensitized and challenged with OVA. The IgE titers were determined by passive cutaneous anaphylaxis. The data are the mean ± SEM of 5 animals. (ANOVA).

Figure 5

The effect of FA inhalation and OVx on IL-10 release in the lung explants. Seven days after the OVx or Sham-OVx, the rats were submitted or not to FA inhalation and then sensitized and challenged with OVA. In a parallel study, the rats 7 days after the OVx were treated with progesterone (P). IL-10 quantification was performed on lung tissue. The data are the mean ± SEM of 5 animals. *p<0.05 relative to the naïve group; ^θp<0.05 relative to the OVA/OVA Sham-OVx group (ANOVA followed by the Student-Newman-Keuls test).

Figure 6

The effects of OVx and FA exposure on tracheal reactivity in allergic rats. Seven days after the OVx or Sham-OVx, the rats were submitted or not to FA inhalation and then sensitized and challenged with OVA. In parallel, the rats 7 days after the OVx were treated with progesterone 4 h before each inhalation of FA. The dose response curve was constructed by the administration of a cholinergic agonist (methacholine). The data are expressed as the mean ± SEM of 6 animals. *p<0.05 relative to the naïve group; ^θp< 0.05 relative to the OVA/OVA Sham-OVx group; ^δp<0.05 relative to the OVA/OVA OVx group; ^□p<0.05 relative to the FA/OVA Sham-OVx group; ^ωp<0.05 relative to the FA/OVA OVx group. (ANOVA followed by the Student-Newman-Keuls test).