Anti-inflammatory effect of nestorone in a lipopolysaccharide-induced acute lung injury model through regulation of the TLR-4/Myd88/NF-κB signaling pathway

Progesterone plays a crucial and indispensable role in regulating immunity and attenuating inflammation. Nestorone® (NES, segesterone acetate) is a steroidal progestin and a 19-norprogesterone derivative with no -CH3 group radical at the 6-position. Here, we showed that NES enhanced the viability of lipopolysaccharide (LPS)-stimulated THP-1 cell-derived macrophages, potently inhibiting both arms of the Toll-like receptor 4 (TLR-4) signaling cascade triggered by LPS, especially the TLR-4/MyD88/NF-κB pathway. In addition, NES exerted an anti-inflammatory effect by significantly decreasing the secretion of inflammatory cytokines and chemokines in type II alveolar epithelial A549 cells and THP-1 cell-derived macrophages stimulated by LPS. Furthermore, we evaluated the potential of NES pre-treatment, administered 2 h prior to LPS exposure, to mitigate acute lung injury induced by LPS, using an LPS-induced acute lung injury (ALI) mouse model. In this study, NES alleviated lung inflammation and damage by reducing leukocyte infiltration and inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) and lung tissues of mice. Interestingly, our findings indicate that NES at a dosage of 1 mg/kg (91.67%) was more effective than at dosages of 0.1 mg/kg (70.83%) or 10 mg/kg (87.50%), as well as more effective than dexamethasone (DEX, 5 mg/kg, 83.34%), in extending survival in mice subjected to lethal LPS-induced injury. Additionally, this dosage was more successful in reducing acute lung inflammation and alleviating diffuse alveolar damage in the lungs of C57 mice. Our study indicates that concentration is a critical determinant of the anti-inflammatory efficacy of NES. Consequently, NES emerges as a potentially promising therapeutic agent for the treatment of pulmonary inflammatory conditions through the modulation of TLR-4 signaling pathways.