Sphingosine 1-phosphate elicits a ROS-mediated proinflammatory response in human endometrial stromal cells via ERK5 activation

Sphingosine 1-phosphate signaling axis mediates neuropeptide S-induced invasive phenotype of endometriotic cells

Endometriosis is a chronic gynecological syndrome characterized by endometrial cell invasion of the extra-uterine milieu, pelvic pain and infertility. Treatment relies on either symptomatic drugs or hormonal therapies, even though the mechanism involved in the onset of endometriosis is yet to be elucidated. The signaling of sphingolipid sphingosine 1-phosphate (S1P) is profoundly dysregulated in endometriosis. Indeed, sphingosine kinase (SK)1, one of the two isoenzymes responsible for S1P biosynthesis, and S1P1, S1P3 and S1P5, three of its five specific receptors, are more highly expressed in endometriotic lesions compared to healthy endometrium. Recently, missense coding variants of the gene encoding the receptor 1 for neuropeptide S (NPS) have been robustly associated with endometriosis in humans. This study aimed to characterize the biological effect of NPS in endometriotic epithelial cells and the possible involvement of the S1P signaling axis in its action. NPS was found to potently induce cell invasion and actin cytoskeletal remodeling. Of note, the NPS-induced invasive phenotype was dependent on SK1 and SK2 as well as on S1P1 and S1P3, given that the biological action of the neuropeptide was fully prevented when one of the two biosynthetic enzymes or one of the two selective receptors was inhibited or silenced. Furthermore, the RhoA/Rho kinase pathway, downstream to S1P receptor signaling, was found to be critically implicated in invasion and cytoskeletal remodeling elicited by NPS. These findings provide new information to the understanding of the molecular mechanisms implicated in endometriosis pathogenesis, establishing the rationale for non-hormonal therapeutic targets for its treatment.

Sphingosine-1-phosphate receptor 3 is a non-hormonal target to counteract endometriosis-associated fibrosis

OBJECTIVE

To study the molecular mechanisms responsible for fibrosis in endometriosis by investigating whether the protein expression levels of sphingosine-1-phosphate receptor 3 (S1PR3), one of the five specific receptors of the bioactive sphingolipid sphingosine-1-phosphate (S1P), correlate with fibrosis extent in endometriotic lesions and which are the cellular mechanisms involved in this process.

DESIGN

Case-control laboratory study and cultured endometriotic cells.

SETTING

University research institute and university hospital.

PATIENT(S)

A total of 33 women, with and without endometriosis, were included in the study.

INTERVENTIONS(S)

Endometriotic lesions were obtained from women with endometriosis (ovarian endometrioma, n = 8; deep infiltrating endometriosis, n = 15; [urological n = 5, gastrointestinal n = 6, and posterior n = 4]) and control endometrium from healthy women, n = 10, by means of laparoscopic and hysteroscopic surgery. The expression of S1PR3 was evaluated using immunohistochemistry and the extent of fibrosis was assessed using Masson's trichrome staining. Human-cultured epithelial endometriotic 12Z cells were used to evaluate the mechanisms involved in the profibrotic effect of S1PR3 activation.

MAIN OUTCOME MEASURE(S)

The expression of S1PR3 in endometriotic lesions is positively correlated with endometriosis-associated fibrosis. In addition, S1P induced epithelial-mesenchymal transition (EMT) and fibrosis in epithelial endometriotic cells. Using RNA interference and pharmacological approaches, the profibrotic effect of S1P was shown to rely on S1PR3, thus unveiling the molecular mechanism implicated in the profibrotic action of the bioactive sphingolipid.

RESULT(S)

The protein expression levels of S1PR3 were significantly augmented in the glandular sections of endometrioma and deep infiltrating endometriosis of different localizations with respect to the control endometrium and positively correlated with the extent of fibrosis. Sphingosine-1-phosphate was shown to have a crucial role in the onset of fibrosis in epithelial endometriotic cells, stimulating the expression of EMT and fibrotic markers. Genetic approaches have highlighted that S1PR3 mediates the fibrotic effect of S1P. Downstream of S1PR3, ezrin and extracellular-signal-regulated kinases 1 and 2 signaling were found to be critically implicated in the EMT and fibrosis elicited by S1P.

CONCLUSION(S)

Sphingosine-1-phosphate receptor 3 may represent a possible innovative pharmacological target for endometriosis.