Progesterone Exerts a Neuromodulatory Effect on Turning Behavior of Hemiparkinsonian Male Rats: Expression of 3 α -Hydroxysteroid Oxidoreductase and Allopregnanolone as Suggestive of GABAA Receptors Involvement

Cytisine is neuroprotective in female but not male 6-hydroxydopamine lesioned parkinsonian mice and acts in combination with 17-β-estradiol to inhibit apoptotic endoplasmic reticulum stress in dopaminergic neurons

Apoptotic endoplasmic reticulum (ER) stress is a major mechanism for dopaminergic (DA) loss in Parkinson's disease (PD). We assessed if low doses of the partial α4β2 nicotinic acetylcholine receptor agonist, cytisine attenuates apoptotic ER stress and exerts neuroprotection in substantia nigra pars compacta (SNc) DA neurons. Alternate day intraperitoneal injections of 0.2 mg/kg cytisine were administered to female and male mice with 6-hydroxydopamine (6-OHDA) lesions in the dorsolateral striatum, which caused unilateral degeneration of SNc DA neurons. Cytisine attenuated 6-OHDA-induced PD-related behaviors in female, but not in male mice. We also found significant reductions in tyrosine hydroxylase (TH) loss within the lesioned SNc of female, but not male mice. In contrast to female mice, DA neurons within the lesioned SNc of male mice showed a cytisine-induced pathological increase in the nuclear translocation of the pro-apoptotic ER stress protein, C/EBP homologous protein (CHOP). To assess the role of estrogen in cytisine neuroprotection in female mice, we exposed primary mouse DA cultures to either 10 nM 17-β-estradiol and 200 nM cytisine or 10 nM 17-β-estradiol alone. 17-β-estradiol reduced expression of CHOP, whereas cytisine exposure reduced 6-OHDA-mediated nuclear translocation of two other ER stress proteins, activating transcription factor 6 and x-box-binding protein 1, but not CHOP. Taken together, these data show that cytisine and 17-β-estradiol work in combination to inhibit all three arms (activating transcription factor 6, x-box-binding protein 1, and CHOP) of apoptotic ER stress signaling in DA neurons, which can explain the neuroprotective effect of low-dose cytisine in female mice.

Paeonol Protection Against Intrastriatal 6-Hydroxydopamine Rat Model of Parkinson's Disease

Introduction:

Parkinson’s Disease (PD) presentations comprise frequent movement disorders in the elderly with various symptoms consisting of motor and non-motor complications. Paeonol is a phenolic chemical agent that has shown antioxidant and anti-inflammatory effects in different disorders and promising effects on metabotropic glutamate receptors (mGluR)- and GABAA-mediated neurotransmission. In this research, we tried to show the neuroprotective potential of paeonol in rat PD model induced by intrastriatal 6-hydroxydopamine (6-OHDA).

Methods:

Rats with intrastriatal 6-OHDA lesioning received with paeonol at a dosage of 100 mg/kg/d for one week. In the end, some biomarkers of oxidative stress, apoptosis, and astrogliosis in nigral and striatal tissues were evaluated in addition to behavioral and Tyrosine Hydroxylase (TH) immunohistochemical analysis.

Results:

The obtained data showed that paeonol alleviates apomorphine-induced rotations and reduces the delay time to initiate and the total time in the narrow beam test. However, its beneficial behavioral effect vanished after intracerebroventricular administration of mGluR III or GABAA receptor antagonists. Moreover, paeonol significantly restored striatal malondialdehyde, tissue levels of reactive oxygen species, the activity of the protective and vital enzymes consisting of superoxide dismutase and catalase, Glial Fibrillary Acidic Protein (GFAP), DNA fragmentation, phosphor apoptosis signal-regulating kinase 1, and nigral aquaporin 4 with no significant and proper change of nitrite, interleukin-1β, inducible nitric oxide synthase, and angiotensin II. Additionally, paeonol prevented injury and reduced tyrosine hydroxylase-containing neurons in the midbrain nigral tissue.

Conclusion:

These obtained findings evidently designate neuroprotective property of paeonol in 6-OHDA murine model of PD that is exerted via easing of oxidative stress, apoptosis, astrogliosis, and its advantageous effect is to some extent mediated via mGluR III/GABAA pathway.

Allopregnanolone restores the tyrosine hydroxylase-positive neurons and motor performance in a 6-OHDA-injected mouse model

AIMS

It has been reported that allopregnanolone (APα) promotes the neurogenesis of the neural progenitor cells (NPCs) in the subventricular zone (SVZ) and prevents the decrease of dopaminergic neurons in 6-hydroxydopamine (6-OHDA)-treated mice by binding to γ-aminobutyric acid A receptor (GABAAR) and then opening voltage-gated L-type Ca²⁺ channel, but the underlying mechanisms remain elusive. The aim of this study was to explore the possible involvement of GABAAR and calcium/calmodulin-dependent protein kinase II delta 3 (CaMKIIδ3) in this process.

METHODS

6-OHDA-treated mice and primary cultured midbrain cells were administrated with APα and GABAAR antagonist bicuculline (Bic), and the proliferation and differentiation of NPCs, the tyrosine hydroxylase (TH)-positive neurons and their fibers, the expression levels of CaMKIIδ3 and brain-derived neurotrophic factor (BDNF), and motor functions were measured using ELISA, immunohistochemical staining, real-time RT-PCR, Western blot, and behavioral test.

RESULTS

Allopregnanolone significantly promoted the phosphorylation of cytoplasmic CaMKIIδ3 and its nuclear translocation by binding to GABAAR, which, in turn, increased the expression levels of BDNF. This may account for the findings that the exogenous APα enhanced the proliferation and differentiation of NPCs, and ameliorated the nigrostriatal system and behavioral performance in 6-OHDA-treated mice.

CONCLUSIONS

Allopregnanolone may directly activate GABAAR, which, in turn, enhance the proliferation and differentiation of NPCs via upregulating the expression levels of CaMKIIδ3, and finally contribute to the restoration of dopaminergic neurons in 6-OHDA-treated mice.

Targeted Interneuron Depletion in the Dorsal Striatum Produces Autism-like Behavioral Abnormalities in Male but Not Female Mice

BACKGROUND

Interneuronal pathology is implicated in many neuropsychiatric disorders, including autism spectrum disorder (ASD) and Tourette syndrome (TS). Interneurons of the striatum, including the parvalbumin-expressing fast-spiking interneurons (FSIs) and the large cholinergic interneurons (CINs), are affected in patients with TS and in preclinical models of both ASD and TS.

METHODS

To test the causal importance of these neuronal abnormalities, we recapitulated them in vivo in developmentally normal mice using a combination transgenic-viral strategy for targeted toxin-mediated ablation.

RESULTS

We found that conjoint ~50% depletion of FSIs and CINs in the dorsal striatum of male mice produces spontaneous stereotypy and marked deficits in social interaction. Strikingly, these behavioral effects are not seen in female mice; because ASD and TS have a marked male predominance, this observation reinforces the potential relevance of the finding to human disease. Neither of these effects is seen when only one or the other interneuronal population is depleted; ablation of both is required. Depletion of FSIs, but not of CINs, also produces anxiety-like behavior, as has been described previously. Behavioral pathology in male mice after conjoint FSI and CIN depletion is accompanied by increases in activity-dependent signaling in the dorsal striatum; these alterations were not observed after disruption of only one interneuron type or in doubly depleted female mice.

CONCLUSIONS

These data indicate that disruption of CIN and FSI interneurons in the dorsal striatum is sufficient to produce network and behavioral changes of potential relevance to ASD, in a sexually dimorphic manner.