The influence of female sex hormones on lung inflammation after brain death ‐ an experimental study

17β-estradiol and methylprednisolone association as a therapeutic option to modulate lung inflammation in brain-dead female rats

Introduction

Brain death (BD) is known to compromise graft quality by causing hemodynamic, metabolic, and hormonal changes. The abrupt reduction of female sex hormones after BD was associated with increased lung inflammation. The use of both corticoids and estradiol independently has presented positive results in modulating BD-induced inflammatory response. However, studies have shown that for females the presence of both estrogen and corticoids is necessary to ensure adequate immune response. In that sense, this study aims to investigate how the association of methylprednisolone (MP) and estradiol (E2) could modulate the lung inflammation triggered by BD in female rats.

Methods

Female Wistar rats (8 weeks) were divided into four groups: sham (animals submitted to the surgical process, without induction of BD), BD (animals submitted to BD), MP/E2 (animals submitted to BD that received MP and E2 treatment 3h after BD induction) and MP (animals submitted to BD that received MP treatment 3h after BD induction).

Results

Hemodynamics, systemic and local quantification of IL-6, IL-1β, VEGF, and TNF-α, leukocyte infiltration to the lung parenchyma and airways, and adhesion molecule expression were analyzed. After treatment, MP/E2 association was able to reinstate mean arterial pressure to levels close to Sham animals (p<0.05). BD increased leukocyte infiltration to the airways and MP/E2 was able to reduce the number of cells (p=0.0139). Also, the associated treatment modulated the vasculature by reducing the expression of VEGF (p=0.0616) and maintaining eNOS levels (p=0.004) in lung tissue.

Discussion

Data presented in this study show that the association between corticoids and estradiol could represent a better treatment strategy for lung inflammation in the female BD donor by presenting a positive effect in the hemodynamic management of the donor, as well as by reducing infiltrated leukocyte to the airways and release of inflammatory markers in the short and long term.

17β-Estradiol Treatment Protects Lungs Against Brain Death Effects in Female Rat Donor

BACKGROUND

Brain death (BD) affects the viability of lungs for transplantation. A correlation exists between high-lung inflammation after BD and the decrease in female sex hormones, especially estradiol. Therefore, we investigated the effects of 17β-estradiol (E2) treatment on the lungs of female brain dead rats.

METHODS

Female Wistar rats were divided into 4 groups: BD (submitted to BD for 6 h), sham (false operated), E2-T0 (treated with E2 immediately after BD; 50 μg/mL, 2 mL/h), and E2-T3 (treated with E2 after 3 h of BD; 50 μg/mL, 2 mL/h). Lung edema, hemorrhage, and leukocyte infiltration were analyzed. Adhesion molecules were evaluated, and analysis of NO synthase gene and protein expression was performed using real-time PCR and immunohistochemistry, respectively. Release of chemokines and matrix degradation in the lungs was analyzed.

RESULTS

BD increased leukocyte infiltration, as shown by intravital microscopy (P = 0.017), bronchoalveolar lavage cell count (P = 0.016), the release of inflammatory mediators (P = 0.02), and expression of adhesion molecules. BD also increased microvascular permeability and the expression and activity of matrix metalloproteinase-9 in the lungs. E2 treatment reduced leukocyte infiltration, especially in the E2-T3 group, release of inflammatory mediators, adhesion molecules, and matrix metalloproteinase activity in the lungs.

CONCLUSIONS

E2 treatment was successful in controlling the lung inflammatory response in females submitted to BD. Our results suggest that E2 directly decreases the release of chemokines, restraining cell traffic into the lungs. Thus, E2 has a therapeutic potential, and its role in improving donor lung quality should be explored further.

Long-term lung inflammation is reduced by estradiol treatment in brain dead female rats

OBJECTIVES

Lung transplantation is limited by the systemic repercussions of brain death (BD). Studies have shown the potential protective role of 17β-estradiol on the lungs. Here, we aimed to investigate the effect of estradiol on the long-lasting lung inflammatory state to understand a possible therapeutic application in lung donors with BD.

METHODS

Female Wistar rats were separated into 3 groups: BD, subjected to brain death (6h); E2-T0, treated with 17β-estradiol (50 μg/mL, 2 mL/h) immediately after brain death; and E2-T3, treated with 17β-estradiol (50 μg/ml, 2 ml/h) after 3h of BD. Complement system activity and macrophage presence were analyzed. TNF-α, IL-1β, IL-10, and IL-6 gene expression (RT-PCR) and levels in 24h lung culture medium were quantified. Finally, analysis of caspase-3 gene and protein expression in the lung was performed.

RESULTS

Estradiol reduced complement C3 protein and gene expression. The presence of lung macrophages was not modified by estradiol, but the release of inflammatory mediators was reduced and TNF-α and IL-1β gene expression were reduced in the E2-T3 group. In addition, caspase-3 protein expression was reduced by estradiol in the same group.

CONCLUSIONS

Brain death-induced lung inflammation in females is modulated by estradiol treatment. Study data suggest that estradiol can control the inflammatory response by modulating the release of mediators after brain death in the long term. These results strengthen the idea of estradiol as a therapy for donor lungs and improving transplant outcomes.