Metabolic alteration of neuroactive steroids and protective effect of progesterone in Alzheimer's disease-like rats

A correlation between metabolic alterations of neuroactive steroids and Alzheimer’s disease remains unknown. In the present study, amyloid beta （Aβ） 25-35 （Aβ25-35） injected into the bilateral campus CA1 region significantly reduced learning and memory. At the biochemical level, hippocampal levels of pregnenolone were significantly reduced with Aβ25-35 treatment. Furthermore, progesterone was considerably decreased in the prefrontal cortex and hippocampus, and 17β-estradiol was signifi-cantly elevated. To our knowledge, this is the first report showing that Aβ25-35, a main etiological factor of Alzheimer’s disease, can alter the level and metabolism of neuroactive steroids in the prefrontal cortex and hippocampus, which are brain regions significantly involved in learning and memory. Aβ25-35 exposure also increased the expression of inflammatory mediators, tumor necrosis factor-αand interleukin-1β. However, subcutaneous injection of progesterone reversed the upregulation of tumor necrosis factor-αand interleukin-1βin a dose-dependent manner. Concomitant with improved cognitive abilities, progesterone blocked Aβ-mediated inflammation and increased the survival rate of hippocampal pyramidal cells. We thus hypothesize that Aβ-mediated cognitive deficits may occur via changes in neuroactive steroids. Moreover, our findings provide a possible therapeutic strategy for Alzheimer’s disease via neuroactive steroids, particularly progesterone.

Progesterone promotes neuronal differentiation of human umbilical cord mesenchymal stem cells in culture conditions that mimic the brain microenvironment

In this study, human umbilical cord mesenchymal stem cells from full-term neonates born by vagina delivery were cultured in medium containing 150 mg/mL of brain tissue extracts from Sprague-Dawley rats （to mimic the brain microenvironment）. Immunocytochemical analysis demonstrated that the cells differentiated into neuron-like cells. To evaluate the effects of progesterone as a neurosteroid on the neuronal differentiation of human umbilical cord mesenchymal stem cells, we cultured the cells in medium containing progesterone （0.1, 1, 10 pM） in addition to brain tissue extracts. Reverse transcription-PCR and flow cytometric analysis of neuron specific enolase-positive cells revealed that the percentages of these cells increased significantly following progesterone treatment, with the optimal progesterone concentration for neuron-like differentiation being 1 tJM. These results suggest that progesterone can enhance the neuronal differentiation of human umbilical cord mesenchymal stem cells in culture medium containing brain tissue extracts to mimic the brain microenvironment.

Changes in neurosteroid levels and steroidogenic enzyme expression in the brain of morphine dependent and withdrawing rats

BACKGROUND： Studies have demonstrated that exogenous neurosteroid treatment prevents the development of morphine tolerance and dependence, and attenuates abstinence behavior in mice. However, there are few studies on whether the levels of endogenous neurosteroids can be changed by morphine dependence and withdrawal. OBJECTIVE： To investigate the levels of various neurosteroids in rat brain following morphine dependence and withdrawal. To evaluate the expressions of steroidogenic enzyme mRNAs and proteins. To identify the relationship between neurosteroids and morphine dependence at the whole animal behavior, neural biochemistry, and molecular levels. DESIGN, TIME AND SETTING： A randomized, controlled study. Experiments were performed at the Department of Pharmacology of Hebei Medical University and Department of Pharmacology of Beathune International Peace Hospital, China, from June 2004 to October 2007. MATERIALS： Morphine hydrochloride injection （Shenyang First Pharmaceutical Factory, China）, naloxone hydrochloride （Hunan Yiqiao Pharmaceutical Co., China） and a gas chromatography-mass spectrometry system （Agilent, CA, USA） were used in this study. METHODS： Healthy adult Sprague Dawley rats were randomly divided into three groups： a morphine dependence group, morphine withdrawal group and control group （n = 20）. The rats in the morphine dependence and morphine withdrawal groups were given increasing doses of morphine （5, 10, 15, 20, 30, 40 and 50 mg/kg, intraperitoneal） to create morphine dependence. The rats in the morphine withdrawal group were injected with 2 mg/kg naloxone to precipitate withdrawal 1 hour after the last morphine injection. Rats in the control group were treated with an equal volume of saline. MAIN OUTCOME MEASURES： Following morphine dependence and withdrawal, brain levels of the neurosteroids pregnenolone, progesterone and allopregnanolone were analyzed using gas chromatography-mass spectrometry. The mRNA expression of two key steroidogenic enzymes, P450 side-chain cleavage enzyme （P450scc） and 3[B-hydroxysteroid dehydrogenase （313-HSD）, were determined in rat brain regions using reverse transcription-polymerase chain reaction. The distribution and expression of P450scc protein were visualized in brain regions associated with addiction by immunohistochemistry. RESULTS： In brain tissue from the morphine dependence group, the levels of pregnenolone and progesterone were decreased by 62% （P 〈 0.01） and 92% （P 〈 0.01 ） respectively, compared with the control group. In the morphine dependence group, the key steroidogenic enzyme P450scc mRNA was decreased in striatum （P 〈 0.05）, while 3-HSD mRNA was decreased in amygdala （P 〈 0.05）, striatum （P 〈 0.05） and frontal cortex （P 〈 0.05） compared with the control group. Morphine withdrawal induced a significant increase in the neurosteroid levels compared with the control group （P 〈 0.01）. However, there was no significant difference in the expressions of P450scc and 36-HSD mRNAs between the morphine withdrawal and control groups （P 〉 0.05）. CONCLUSION： The neurosteroid levels and expressions of steroidogenic enzymes changed similarly in morphine dependent rats, suggesting that the morphine dependence-induced decrease in neurosteroids might depend on local expression of steroidogenic enzymes in the central nervous system. However, the changes in neurosteroids in morphine withdrawal rats were not in accordance with the changes in the expression of steroidogenic enzymes, suggesting that the effects of morphine withdrawal on brain neurosteroid levels may not depend primarily on the local expression of steroidogenic enzymes in the central nervous system.

Elevated Neurosteroids in the Lateral Thalamus Relieve Neuropathic Pain in Rats with Spared Nerve Injury

Neurosteroids are synthesized in the nervous system from cholesterol or steroidal precursors imported from peripheral sources. These compounds are important allosteric modulators of γ-aminobutyric acid A receptors （GABAARs）, which play a vital role in pain modulation in the lateral thalamus, a main gate where somatosensory information enters the cerebral cortex. Using high-perfor mance liquid chromatography/tandem mass spectrometry, we found increased levels of neurosteroids （pregnenolone, progesterone, deoxycorticosterone, allopregnanolone, and tetrahydrodeoxycorticosterone） in the chronic stage of neuropathic pain （28 days after spared nerve injury） in rats.The expression of the translocator protein TSPO, the upstream steroidogenesis rate-limiting enzyme, increased at the same time. In vivo stereotaxic microinjection of neurosteroids or the TSPO activator AC-5216 into the lateral thalamus （AP -3.0 mm, ML 4-3.0 mm, DV 6.0 mm） alleviated the mechanical allodynia in neuropathic pain, while the TSPO inhibitor PK 11195 exacerbated it. The analgesic effects of AC-5216 and neurosteroids were sig- nificantly attenuated by the GABAAR antagonist bicuculline. These results suggested that elevated neurosteroids in the lateral thalamus play a protective role in the chronic stage of neuropathic pain.