Phytochemical and pharmacological characterization of Lily-Rehmannia Decoction, a classic Chinese herbal formula, for menopausal syndrome in ovariectomized mice : a novel brain-uterus mechanism distinct from estrogen therapy

Abstract

Menopause, also known as climacteric, is the permanent cessation of menstruation due to ovarian failure. In addition to physical symptoms, it is also often associated with a wide range of psychological symptoms. Although estrogen therapy is the mainstay for management of menopause syndrome, a large body of evidence confirms that long-term estrogen therapy increases the risk of breast and ovarian cancer, stroke, and cardiovascular disease. Therefore, a search for alternative therapy particularly from herbal medicine is highly desired.

Lily-Rehmannia Decoction (LRD) is a classic Chinese formula, which has been commonly used for depression, deficient dysphoria, insomnia, etc.. However, there have been no comprehensive experimental investigations of LRD on menopausal syndrome. Hence, we hypothesized that LRD, as well as its components AEBL and AERR (aqueous extract of Bulbus Lilli and Radix Rehmanniae), might ameliorate the menopause-associated psychiatric disorders.

Ovariectomized (OVX) mice were treated with 1.8 g/kg AELB, 2.6 g/kg AERR, 2.3 g/kg LRD or 0.3 mg/kg estradiol for 5 weeks. Uterus and brain were collected for the measurement of neurotransmitters and their related biomarkers, neurotrophins, and estrogen receptors (ERα and ERβ). The results revealed that the three agents showed similar anxiolytic and antidepressant effects with estrogen therapy, which seemed to be achieved via the predominant protection of neurotransmitters, neurotrophins and ERβ receptors in the related brain regions. While estradiol limited OVX-induced weight gains and prevented uterine shrinkage and the drop of serum estrogen level, the three agents had no or minor effects on these indices. Moreover, the three agents might exert a better safety profile than estrogen therapy because they had minor effects on uterine nerve growth factor and ERα expression levels. However, AEBL, not AERR or LRD, exerted similar effects on the OVX-induced cognitive deficit with estrogen therapy, which was possibly associated with the upregulation of cortical ERα.

To further explore the underlying mechanisms of AEBL, its two fractions, total polysaccharides and total saponins (TPBL and TSBL), were separated and purified. We tested the effects of TPBL (50, 100 and 200 mg/kg) and TSBL (12, 24 and 48 mg/kg) on the same model. TPBL and TSBL showed similar anxiolytic, antidepressant and memory-enhancing effects with AEBL and estrogen. The mechanism was also in association with predominant activation of ER receptors, along with the regulation of neurotransmitters and neurotrophins in brain, but with minor effects on uterus. Interestingly, we found that TPBL and TSBL can directly bind to ERα and ERβ. Both TPBL and TSBL showed a higher affinity to ERβ than to ERα, and TSBL had a higher affinity to ERα and ERβ than TPBL. Moreover, the effects of TPBL on neurotransmitters and neurotrophins were verified to be mainly mediated by activation of ERs. Finally, the psychotropic effects of TPBL and TSBL were further confirmed by proteomic analysis via multiple mechanisms distinct from estrogen therapy. E2 had a major effect on epigenetics, while TPBL and TSBL predominately influenced mitochondrial oxidative stress.

Therefore, AEBL, and its two constituents TPBL and TSBL, may be served as novel agents for menopause-associated neuropsychological disorders.