INTRODUCTION: Spontaneous preterm birth (sPTB) is the leading cause of neonatal morbidity and mortality. Inflammation plays a key role in initiating and maintaining uterine contractions and rupture of fetal membranes. Therefore, blunting the inflammatory response presents a therapeutic opportunity. Polyphenols, bioactive components in plants, exhibit potent anti-inflammatory properties. While epidemiological studies have linked plant-based diets with reduced risk for sPTB, the contribution of polyphenols to these effects are unknown. Thus, this study aimed to investigate the effects of punicalagin on mediators involved in active labor using in vitro and in vivo models of sPTB.
METHODS: Primary human myometrial, amnion mesenchymal, amnion epithelial and decidual cells were treated with or without 10μM punicalagin in the presence of 1ng/ml IL-1B or 10ng/ml TNF (n=6-7 patients/group). Endpoint analysis was assessed by RT-qPCR, ELISA and gelatin zymography. Myometrial cell contractility was determined by collagen gel assay. C57BL/6 mice were injected with 1 mg/kg punicalagin on gestational day (GD)14.5 until GD16.5. On GD16.5, mice were injected with 15µg LPS, sacrificed after 6h, and tissues collected for assessment of intrauterine inflammation. Data was analysed by one-way ANOVA and P<0.05 was considered significant.
RESULTS: Punicalagin treatment significantly suppressed IL-1B/TNF-induced expression and secretion of pro-inflammatory cytokines and chemokines in primary human myometrial, amnion and decidual cells. In myometrial cells, punicalagin significantly decreased IL-1B/TNF-induced secretion of PGF2α, expression of contraction associated proteins, and collagen gel contractility. In amnion and decidual cells, punicalagin significantly suppressed IL-1B/TNF-induced expression and activity of matrix metalloproteinases. In vivo, punicalagin significantly reduced intrauterine inflammation induced by LPS.
CONCLUSION: Using human and murine pre-clinical models of sPTB, we have demonstrated that the pomegranate polyphenol punicalagin suppressed the expression of mediators involved in myometrial contractions and rupture of fetal membranes. Punicalagin may represent a novel therapeutic to prevent sPTB and related sequelae.