Sex hormone steroidal drugs were reported to have modulating actions on the ion channel TRPM3. Pregnenolone sulphate (PS) presents the most potent known endogenous chemical agonist of TRPM3 and affects several gating modes of the channel. These includes a synergistic action of PS and high temperatures on channel opening and the PS-induced opening of a noncanonical pore in the presence of other TRPM3 modulators. Moreover, human TRPM3 variants associated with neurodevelopmental disease exhibit an increased sensitivity for PS. However, other steroidal sex hormones were reported to influence TRPM3 functions with activating or inhibiting capacity. Here, we aimed to answer how DHEAS, estradiol, progesterone and testosterone act on the various modes of TRPM3 function in the wild-type channel and two-channel variants associated with human disease. By means of calcium imaging and whole-cell patch clamp experiments, we revealed that all four drugs are weak TRPM3 agonists that share a common steroidal interaction site. Furthermore, they exhibit increased activity on TRPM3 at physiological temperatures and in channels that carry disease-associated mutations. Finally, all steroids are able to open the noncanonical pore in wild-type and DHEAS also in mutant TRPM3. Collectively, our data provide new valuable insights in TRPM3 gating, structure-function relationships and ligand sensitivity.

Endometriosis is a prevalent gynecologic disease, defined by dysfunctional endometrium-like lesions outside of the uterine cavity. These lesions are presumably established via retrograde menstruation, i.e., endometrial tissue that flows backwards during menses into the abdomen and deposits on the organs. As ongoing pain is one of the main pain symptoms of patients, an animal model that illuminates this problem is highly anticipated. In the present study, we developed and validated a rat model for ongoing endometriosis-associated pain. First, menstrual endometrial tissue was successfully generated in donor rats, as validated by gross examination, histology and qPCR. Next, endometriosis was induced in recipient animals by intraperitoneal injection of menstrual tissue. This resulted in neuro-angiogenesis as well as established endometriosis lesions, which were similar to their human counterparts, since epithelial and stromal cells were observed. Furthermore, significant differences were noted between control and endometriosis animals concerning bodyweight and posture changes, indicating the presence of ongoing pain in animals with endometriosis. In summary, a rat model for endometriosis was established that reliably mimics the human pathophysiology of endometriosis and in which signs of ongoing pain were detected, thus providing a new research tool for therapy development.

Endometriosis-associated pain has debilitating effects on the quality of life of patients. Despite its high prevalence in reproductive-aged women, the pathophysiology is still unknown, impeding the development of targeted treatment approaches. The prospective ExPAND study proposes the neurosteroids pregnenolone sulphate (PS) and dehydroepiandrosterone sulphate (DHEAS) as potential contributors to endometriosis-associated pain, due to their agonistic action at the pain-related ion channel TRPM3. To this end, endometrium, deep endometriosis lesions, and peritoneal fluid were prospectively collected in four demarcated patient groups, which were characterised based on their pain symptoms, as scored via the WERF-EPHect questionnaire, i.e., (1) control (n = 44), (2) endometriosis patients with no pain symptoms (n = 24), (3) with only severe dysmenorrhea (n = 54), or (4) with both severe dysmenorrhea and non-cyclic pelvic pain (n = 78). Tissue mRNA expression levels of steroidogenic enzymes were investigated and showed significantly increased levels of CYP17A1 in the endometrium of patients with severe pain symptoms compared to control tissue. In addition, liquid chromatography with tandem mass spectrometry (LC-MS/MS) was performed to investigate neurosteroid concentrations in the peritoneal fluid. Both neurosteroids PS and DHEAS were present in the peritoneal fluid at concentrations that are known to stimulate TRPM3 activity in vitro. Finally, using microfluorimetric Ca²⁺ imaging, we demonstrate that both DHEAS and PS stimulate human stem-cell-derived sensory neurons in a TRPM3-dependent manner. Taken together, these data indicate a potential contribution of steroidogenesis and TRPM3 in endometriosis-associated pain.