Vanillin prevents the growth of endometriotic lesions through anti-inflammatory and antioxidant pathways in a mouse model

Endometriosis is an estrogen-dependent chronic inflammatory gynecological disease defined by the presence of endometrial glands and mesenchyme outside the uterine cavity, named ectopic endometrium. Recent studies showed that endometriosis is associated with hormone imbalance, inflammation and oxidative stress. As the main component of vanilla bean extract, vanillin is widely used as a flavoring agent in the food, pharmaceutical, and cosmetic industries. It is known for its anti-inflammatory, antibacterial, and antitumor properties, but its therapeutic efficacy in endometriosis has not been studied. In this study, we evaluated the roles of vanillin in this disease using an induced endometriotic mouse model. The results showed that vanillin significantly inhibited the growth of endometrial lesions. Compared with the control group, the weight and volume of lesions were reduced considerably in the vanillin-treated group, showing its fantastic ability to inhibit cell proliferation and promote apoptosis. In addition, in the treatment group, mRNA expression of the pro-inflammatory cytokines Tnfa, Infg, Il1b, and Il6 was reduced, the number of macrophages and neutrophils was decreased, and the NF-κB signaling pathway was inhibited, indicating that vanillin suppressed the inflammatory response in the ectopic endometrium. Besides, we found that the intensity of tissue reactive oxygen species (ROS) was significantly lower, and mitochondrial complex IV expression was reduced in the vanillin-treated group. Meanwhile, treatment of the immortalized human endometriotic epithelial cell line (11Z) with vanillin resulted in the downregulation of cyclin genes that drive the cell proliferation process, inhibited cell proliferation, promoted apoptosis, and downregulated the expression of LPS-induced inflammatory cytokines. Most importantly, our data showed that the vanillin treatment had only minimal effects on the eutopic endometrium with respect to the pregnancy process, indicating its safety to be used in treating endometriosis in adults. In conclusion, our data suggest that vanillin has potential therapeutic properties for endometriosis as a regulatory molecule of cell proliferation, apoptosis, inflammation, and oxidative stress.