Investigating the role of MKRN3 in vasomotor symptoms in a mouse model of menopause
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Abstract
BACKGROUND: Menopause is characterized by a decline in estrogen levels, which may be associated with vasomotor symptoms (VMS) that can last for years and can significantly impact women’s lives. Recent studies suggest that neurokinin B (NKB) signaling plays a critical role in VMS development, with increased NKB signaling associated with more thermoregulatory disruptions. Regulation of VMS during menopause remains poorly understood. Preliminary data in our laboratory suggest that makorin ring-finger protein 3 (MKRN3) has regulatory effects on NKB levels in the hypothalamus. Given these data, we are exploring if Mkrn3 can be used as a neuroendocrine target to reduce VMS in a mouse model of menopause.
OBJECTIVE: The first aim is to assess Mkrn3 expression in both intact and ovariectomized (OVX) aging mice. The second aim is to measure Nkb levels, core temperature, and skin temperature after overexpressing Mkrn3 in the hypothalamus, to determine how Mkrn3 can affect VMS in ovariectomized (OVX) mice.
METHODS: Mkrn3 mRNA levels were measured in the mediobasal hypothalamus of intact and OVX mice at ages 3 months, 12 months, 18 months, and 26 months through RT-qPCR. Mkrn3 was overexpressed in 3-month-old mice through viral stereotaxic injections and mice were OVX one month later. Core and skin temperature were measured and recorded for 3 weeks, pre and post OVX. The brains from the mice were collected at the end of the experiment and Nkb was detected by immunohistochemistry and quantified with ImageJ.
RESULTS: Mkrn3 mRNA levels at 3 months, 12 months, and 18 months remained constant but increased significantly after OVX at each age, and at 26 months, which is considered the mouse equivalent of the human post-menopausal state. During the light phase, mice with Mkrn3 overexpression (Mkrn3 mice) had significantly higher core temperatures than control mice; in contrast, during the dark phase, Mkrn3 mice had lower core temperatures than controls. These effects were significant in intact mice, before OVX. Skin temperature was not significantly different between Mkrn3 and control mice in either the light or dark phase. Nkb immunostaining did not differ significantly between Mkrn3 and control mice after OVX.
CONCLUSIONS: This study demonstrated that Mkrn3 mRNA levels remain low during adulthood but, unexpectedly, increased in very old mice, as well as following OVX. These findings may suggest that estrogen (or lack of estrogen) played a regulatory role. In addition, we showed that Mkrn3 overexpression in the ARC influences thermoregulation in a phase dependent manner, with opposite effects during light and dark phases. Those effects were significant mainly before OVX, suggesting a role of estrogen levels. Finally, the hypothesized decrease of Nkb in the presence of Mkrn3 was not seen after OVX. The interactions between Mkrn3, Nkb, and estrogen and how they influence VMS are complex. However, by continuing to elucidate these mechanisms, future studies may contribute to development of improved therapies for menopausal VMS.
Description
2025
License
Attribution-NonCommercial-NoDerivatives 4.0 International