The Relationship Between α1-Adrenergic Receptors and TRPM8 Channels in Detrusor Overactivity Induced by Cold Stress in Ovariectomized Rats

Effect of menstrual cycle and female hormones on TRP and TREK channels in modifying thermosensitivity and physiological functions in women

Thermoregulation is crucial for human survival at various ambient temperatures. Transient receptor potential (TRP) and TWIK-related K⁺ (TREK) channels expressed in sensory neurons play a role in peripheral thermosensitivity for temperature detection. In addition, these channels have various physiological roles in the skeletal, nervous, immune, vascular, digestive, and urinary systems. In women, the female hormones estradiol (E2) and progesterone (P4), which fluctuate during the menstrual cycle, affect various physiological functions, such as thermoregulation in hot and cold environments. The present review describes the effect of female hormones on TRP and TREK channels and related physiological functions. The P4 decreased thermosensitivity via TRPV1. E2 facilitates temporomandibular joint disease (TRPV1), breast cancer (TRPM8), and calcium absorption in the digestive system (TRPV5 and TRPV6), inhibits the facilitation of vasoconstriction (TRPM3), nerve inflammation (TRPM4), sweetness sensitivity (TRPM5), and menstrual disorders (TRPC1), and prevents insulin resistance (TRPC5) via each channel. P4 inhibits vasoconstriction (TRPM3), sweetness sensitivity (TRPM5), ciliary motility in the lungs (TRPV4), menstrual disorder (TRPC1), and immunity (TRPC3), and facilitates breast cancer (TRPV6) via each channel as indicated. The effects of female hormones on TREK channels and physiological functions are still under investigation. In summary, female hormones influence physiological functions via some TRP channels; however, the literature is not comprehensive and future studies are needed, especially those related to thermoregulation in women.

UCP1 and TRPM8 Expression in the Brown Fat Did Not Affect the Restriction of Menthol-Induced Hyperthermia by Estradiol in Ovariectomized Rats

Estradiol (E₂) modulates the central and peripheral thermoregulatory responses to cold. Menthol is an agonist of transient receptor potential melastatin type 8 (TRPM8), which is a peripheral cold receptor. E₂ suppresses menthol-induced elevation of body temperature (T_b) in ovariectomized rats, but the mechanism is unknown. The aim of the present study is to investigate the effect of E₂ on uncoupling protein 1 (UCP1), a thermogenic gene, and TRPM8 mRNA levels in ovariectomized rats applied menthol. A silastic tube was implanted in ovariectomized rats with and without E₂ underneath the dorsal skin (E₂(+) and E₂(-) groups), and data loggers for T_b measurement into peritoneal cavity. After application of 10% L-menthol or vehicle to the skin of the whole trunk of rats, T_b was measured for 2 h. The interscapular brown adipose tissue (BAT) and spinal ganglia of cervical, thoracic, and lumbar parts were obtained for RT-qPCR assay. In the menthol application, T_b in the E₂(+) group was lower than that in the E₂(-) group. The UCP1 mRNA in the BAT, TRPM8 mRNA in the BAT and spinal ganglia in all areas did not differ between the E₂(+) and E₂(-) groups. In conclusion, the UCP1 and TRPM8 expression in the brown fat did not affect the restriction of the menthol-induced hyperthermia by estradiol in ovariectomized rats.

TRPM8 modulates temperature regulation in a sex-dependent manner without affecting cold-induced bone loss

Trpm8 (transient receptor potential cation channel, subfamily M, member 8) is expressed by sensory neurons and is involved in the detection of environmental cold temperatures. TRPM8 activity triggers an increase in uncoupling protein 1 (Ucp1)-dependent brown adipose tissue (BAT) thermogenesis. Bone density and marrow adipose tissue are both influenced by rodent housing temperature and brown adipose tissue, but it is unknown if TRPM8 is involved in the co-regulation of thermogenesis and bone homeostasis. To address this, we examined the bone phenotypes of one-year-old Trpm8 knockout mice (Trpm8-KO) after a 4-week cold temperature challenge. Male Trpm8-KO mice had lower bone mineral density than WT, with smaller bone size (femur length and cross-sectional area) being the most striking finding, and exhibited a delayed cold acclimation with increased BAT expression of Dio2 and Cidea compared to WT. In contrast to males, female Trpm8-KO mice had low vertebral bone microarchitectural parameters, but no genotype-specific alterations in body temperature. Interestingly, Trpm8 was not required for cold-induced trabecular bone loss in either sex, but bone marrow adipose tissue in females was significantly suppressed by Trpm8 deletion. In summary, we identified sex differences in the role of TRPM8 in maintaining body temperature, bone microarchitecture and marrow adipose tissue. Identifying mechanisms through which cold temperature and BAT influence bone could help to ameliorate potential bone side effects of obesity treatments designed to stimulate thermogenesis.

Seasonal variations in overactive bladder drug prescription rates in women: a nationwide population-based study

PURPOSE

Colder seasons can aggravate lower urinary tract symptoms, especially an overactive bladder (OAB). This aspect has been extensively studied in men and rarely in women. We investigated whether colder seasons influence OAB-drug prescription rates (OAB-DPRs) in women.

METHODS

Women aged > 18 years were selected from the Korean Health Insurance Review and Assessment Service-National Patient Sample data between 2012 and 2016. OAB-DPR was calculated according to age and seasonal groups. The prescription rates in summer (June, July, and August) and winter (January, February, and December) months were compared. Sub-analysis was performed according to age group.

RESULTS

In total, 3,061,343 adult women were included. The overall OAB-DPR was 3.75% (114,940/3,061,343). Overall OAB-DPRs in summer and winter were 1.41% (43,090/3,061,343) and 1.54% (47,038/3,061,343), respectively (p < 0.001). Seasonal variations in OAB-DPRs differed by age group (p < 0.001): OAB-DPRs were significantly lower in winter than in summer months in women aged < 50 years (odds ratio 0.942; 95% confidence interval 0.918-0.967; p < 0.001), but significantly higher in winter than in summer months in women aged ≥ 50 years (odds ratio 1.153; 95% confidence interval 1.135-1.171; p < 0.001).

CONCLUSION

In this study, a correlation was noted between OAB-DPR and seasons. OAB-DPRs were higher in the summer in women aged < 50 years and higher in the winter in women aged ≥ 50 years. Our findings suggest that female hormonal status may be involved in the contradictory effect of seasons on OAB symptoms.

Testosterone-androgen receptor: The steroid link inhibiting TRPM8-mediated cold sensitivity

Recent studies have revealed gender differences in cold perception, and pointed to a possible direct action of testosterone (TST) on the cold-activated TRPM8 (Transient Receptor Potential Melastatin Member 8) channel. However, the mechanisms by which TST influences TRPM8-mediated sensory functions remain elusive. Here, we show that TST inhibits TRPM8-mediated mild-cold perception through the noncanonical engagement of the Androgen Receptor (AR). Castration of both male rats and mice increases sensitivity to mild cold, and this effect depends on the presence of intact TRPM8 and AR. TST in nanomolar concentrations suppresses whole-cell TRPM8-mediated currents and single-channel activity in native dorsal root ganglion (DRG) neurons and HEK293 cells co-expressing recombinant TRPM8 and AR, but not TRPM8 alone. AR cloned from rat DRGs shows no difference from standard AR. However, biochemical assays and confocal imaging reveal the presence of AR on the cell surface and its interaction with TRPM8 in response to TST, leading to an inhibition of channel activity.

Estradiol administration suppresses body temperature elevation induced by application of menthol to ovariectomized rats

The aim of the present study was to investigate the effect of estradiol (E₂) on thermoregulatory responses induced by menthol in ovariectomized rats. Wistar rats were ovariectomized, and implanted with a silastic tube with or without E₂ (E₂(+) and E₂(-) groups). L-menthol (10%) or vehicle was applied to the skin of the whole trunk in selected animals, which were then exposed to 27 °C or 16 °C for 2 h. Continuous body temperature (T_b), tail skin temperature (T_tail), and treatment-associated behaviors were measured. cFos immunoreactive (cFos-IR) cells in the median preoptic area, paraventricular nucleus (PVN), medial preoptic area, posterior hypothalamus, and dorsomedial hypothalamus were counted. At 27 °C, in the E₂(+) and E₂(-) groups, the T_b and T_tail were greater in rats applied menthol than that in rats applied vehicle. In rats applied menthol, the T_b in the E₂(+) group was lower than that in the E₂(-) group. In the E₂(+) and E₂(-) groups, the number of cFos-IR cells in the PVN was greater in rats applied menthol than that in rats applied vehicle. These results suggested that menthol treatment increased T_b in ovariectomized rats with or without E₂ at 27 °C, and that activation of the PVN might be involved in this response. E₂ administration suppresses T_b elevation induced by application of menthol to ovariectomized rats.

Effects of β-estradiol on cold-sensitive receptor channel TRPM8 in ovariectomized rats

Transient receptor potential cation channel subfamily M member 8 (TRPM8) is associated with sensitivity to cold sensation in mammals. A previous study demonstrated that TRPM8 was overexpressed in the skin of ovariectomized (OVX) rats due to the loss of estrogen. In the present study, we investigated whether estrogen replacement restricts overexpression of the TRPM8 channel in the skin of OVX rats. We divided 15 Sprague Dawley rats into three groups: a non-operated group (NON-OPE), an ovariectomy group (OVX), and a group subjected to estrogen replacement during 4 weeks beginning 7 days after ovariectomy (OVX + E2). Five weeks later, TRPM8 channel mRNA and protein in lumbar skin were quantified by real-time RT-PCR, protein ELISA, and immunohistochemistry. The OVX + E2 group exhibited a trend for decreased expression of the TRPM8 channel in the lumbar skin in comparison with the OVX group, whereas ELISA data and immunohistochemistry data and immunohistochemistry graphs relating to TRPM8 protein did not show any obvious differences between the OVX group and the OVX + E2 group. Estrogen replacement may restrict the overexpression of TRPM8 in the dermis of OVX rats.

Ovariectomy May Induce Detrusor Overactivity in Rats: The Therapeutic Role of Rho Kinase Inhibition

OBJECTIVE

To verify the impact of ovariectomy (OVX) on the micturition cycle in conscious rats; to examine the influence of rho kinase (ROCK) inhibition on the bladder detrusor in OVX rats; to assess the effect of the joint administration of the ROCK inhibitor (GSK 269962) and solifenacin succinate (SOL) to these animals.

MATERIALS AND METHODS

The impact of OVX or a single dose of GSK 269962 and/or SOL on the cystometric parameters was assessed 28 days after the procedure.

RESULTS

OVX caused an increase in detrusor overactivity index, amplitude, and frequency of nonvoiding contractions, along with a decrease in voided volume, volume threshold, intercontraction interval, bladder compliance, and volume threshold to elicit nonvoiding contractions. GSK 269962 administered in a dose of 10 mg/kg (but not 5 mg/kg) or SOL in a dose of 0.03 mg/kg (but not 0.015 mg/kg) triggered an increase in voided volume, volume threshold, intercontraction interval, bladder compliance, and volume threshold to elicit nonvoiding contractions, along with a decrease in detrusor overactivity index, amplitude, and frequency of nonvoiding contractions. A combined administration of GSK 269962 (5 mg/kg) and SOL (0.15 mg/kg), in doses ineffective in monotherapy, triggered a reversal in the OVX-induced cystometric changes.

CONCLUSION

It appears that ROCK inhibitors can become an alternative worth considering in overactive bladder syndrome treatment, especially in the light of the findings pointing to the decreased efficiency of antimuscarinic drugs in the overactive bladder syndrome treatment of postmenopausal women.