TCF7L2: A potential key regulator of antidepressant effects on hippocampal astrocytes in depression model mice.

Clinical and preclinical studies suggest that hippocampal astrocyte dysfunction is involved in the pathophysiology of depression; however, the underlying molecular mechanisms remain unclear. Here, we attempted to identify the hippocampal astrocytic transcripts associated with antidepressant effects in a mouse model of depression. We used a chronic corticosterone-induced mouse model of depression to assess the behavioral effects of amitriptyline, a tricyclic antidepressant. Hippocampal astrocytes were isolated using fluorescence-activated cell sorting, and RNA sequencing was performed to evaluate the transcriptional profiles associated with depressive effects and antidepressant responses. Depression model mice exhibited typical depression-like behaviors that improved after amitriptyline treatment; the depression group mice also had significantly reduced GFAP-positive astrocyte numbers in hippocampal subfields. Comprehensive transcriptome analysis of hippocampal astrocytes showed opposing responses to amitriptyline in depression group and control mice, suggesting the importance of using the depression model. Transcription factor 7 like 2 (TCF7L2) was the only upstream regulator gene altered in depression model mice and restored in amitriptyline-treated depression model mice. In fact, TCF7L2 expression was significantly decreased in the depression group. The level of TCF7L2 long non-coding RNA, which controls mRNA expression of the TCF7L2 gene, was also significantly decreased in this group and recovered after amitriptyline treatment. The Gene Ontology biological processes associated with astrocytic TCF7L2 included proliferation, differentiation, and cytokine production. We identified TCF7L2 as a gene associated with depression- and antidepressant-like behaviors in response to amitriptyline in hippocampal astrocytes. Our findings could provide valuable insights into the mechanism of astrocyte-mediated antidepressant effects.

Upregulation of carbonic anhydrase 1 beneficial for depressive disorder.

Carbonic Anhydrase 1 (CAR1) is a zinc-metalloenzyme that catalyzes the hydration of carbon dioxide, and the alteration of CAR1 has been implicated in neuropsychiatric disorders. However, the mechanism underlying the role of CAR1 in major depressive disorder (MDD) remains largely unknown. In this study, we report the decreased level of CAR1 in MDD patients and depression-like model rodents. We found that CAR1 is expressed in hippocampal astrocytes and CAR1 regulates extracellular bicarbonate concentration and pH value in the partial hilus. Ablation of the CAR1 gene increased the activity of granule cells via decreasing their miniature inhibitory postsynaptic currents (mIPSC), and caused depression-like behaviors in CAR1-knockout mice. Astrocytic CAR1 expression rescued the deficits in mIPSCs of granule cells and reduced depression-like behaviors in CAR1 deficient mice. Furthermore, pharmacological activation of CAR1 and overexpression of CAR1 in the ventral hippocampus of mice improved depressive behaviors. These findings uncover a critical role of CAR1 in the MDD pathogenesis and its therapeutic potential.

Characterisation of Primary Human Hippocampal Astrocyte Cell Culture Following Exposure to Hypoxia.

Background: The present study aimed to understand the characterisation of human hippocampal astrocyte following hypoxia exposure. Based on the preliminary screening, 15 min was chosen as the time point and the cells were exposed to different oxygen percentages. Methods: The Trypan blue viability assay used to examine cell death. Immunofluorescence assay, glial fibrillary acidic protein (GFAP) was used to portray the morphology of astrocytes. The hypoxia-inducible factor 1 (HIF-1) staining was performed to confirm hypoxia induced cell death and there was a dramatic expression of HIF-1α displayed in exposed astrocyte cells compared to the control. In molecular level, genes were chosen, such as glyceraldehyde 3-phosphate dehydrogenase (GAPDH), GFAP, HIF-1α and B-cell lymphoma 2 (Bcl-2) and ran the reverse transcription-polymerase chain reaction (RT-PCR). Results: Microscope revealed a filamentous and clear nucleus appearance in a control whereas the rupture nuclei with no rigid structure of the cell were found in the 3% oxygen. The control and hypoxia cells were also stained with the annexin V-fluorescein isothiocyanate (annexin V-FITC). Fluorescence microscope reveals astrocyte cells after hypoxia showed higher expression of nuclei but not in control. Merging PI and FITC showed the differences of nuclei expression between the control and hypoxia. In the molecular analysis, there were significant changes of GFAP, HIF-1α and Bcl-2 in hypoxia exposed cells when compared to the control group. Conclusion: Cells that were exposed to hypoxia (3% oxygen for 15 min) clearly showed damage. General view of human hippocampal astrocyte genomic response to hypoxia was obtained.

MicroRNA-367-3p suppresses sevoflurane-induced adult rat astrocyte apoptosis by targeting BCL2L11.

The present study aimed to characterize the effect of microRNA (miR)-367-3p on sevoflurane anesthesia and elucidate the underlying mechanism. A total of 36 4-month-old adult Sprague-Dawley rats were divided into six groups. Sevoflurane was inhaled at concentrations of 0, 1, 2, 4, 8 and 16% for a total of 6 h; the hippocampus of the brain was subsequently minced and digested, and astrocytes were isolated. Various methods, including reverse transcription-quantitative (RT-q)PCR, western blotting and TUNEL staining, were used to determine the expression levels of Bax, BCL-2 and BCL-2-like protein 11 (BCL2L11), as well as the level of apoptosis. The rats were treated with 8% sevoflurane and the astrocytes from the rats were transfected with miR-367-3p or anti-miR-367-3p. The present study demonstrated that sevoflurane promoted astrocytes apoptosis. Western blotting revealed that with an increase of sevoflurane concentration, the expression levels of the apoptotic proteins Bax and BCL2L11 were significantly increased, whereas the protein expression levels of BCL-2 were significantly decreased. However, overexpression of miR-367-3p reversed these effects. TUNEL staining revealed that sevoflurane promoted the apoptosis of astrocytes, while apoptosis was reversed by miR-367-3p overexpression. RT-qPCR demonstrated that sevoflurane inhibited the expression of miR-367-3p. Notably, miR-367-3p reduced the expression of BCL2L11, thereby inhibiting the apoptosis of astrocytes originating from the hippocampal area of adult rats induced by sevoflurane. Therefore, miR-367-3p and BCL2L11 may act as effective targets for the study of anesthesia.

Astrocytic rather than neuronal P2X7 receptors modulate the function of the tri-synaptic network in the rodent hippocampus.

Whole-cell patch clamp recordings demonstrated that in the dentate gyrus (DG) as well as in the CA3 area of mouse hippocampal slices the prototypic P2X7 receptor (R) agonist dibenzoyl-ATP (Bz-ATP) induced inward current responses both in neurons and astrocytes. Whereas the selective P2X7R antagonist A438079 strongly inhibited both neuronal and astrocytic currents, a combination of ionotropic glutamate receptor (CNQX, AP-5) and GABAA-R (gabazine) antagonists depressed the Bz-ATP-induced current responses in the DG (granule cells) and CA3 neurons only. It was concluded that Bz-ATP activated astrocytic P2X7Rs and thereby released glutamate and GABA to stimulate nearby neurons. The residual A438079-resistant current response of astrocytes was suggested to be due to the stimulation of P2XRs of the non-P2X7-type. Further, we searched for presynaptic P2X7Rs at the axon terminals of DG and CA3 pyramidal neurons innervating CA3 and CA1 cells, respectively. Bz-ATP potentiated the frequency of spontaneous postsynaptic currents (sPSCs) in CA1 but not CA3 pyramidal cells. However, the Bz-ATP effect in CA1 cells was inhibited by gabazine or the astrocytic toxin fluorocitrate suggesting stimulation of P2X7Rs at stratum radiatum astrocytes located near to interneurons and synapsing onto CA1 neurons. Our data suggest that functional P2X7Rs are missing at neurons in the tri-synaptic network of the rodent hippocampus, but are present at nearby astrocytes indirectly regulating network activity.

Effects of microRNA-206 and its target gene IGF-1 on sevoflurane-induced activation of hippocampal astrocytes in aged rats through the PI3K/AKT/CREB signaling pathway.

The study aims to explore the effects of microRNA-206 (miR-206) targeting IGF-1 on the activation of hippocampal astrocytes in aged rats induced by sevoflurane through the PI3K/AKT/CREB signaling pathway. Wistar rats and astrocytes were divided into the normal/blank, sham/negative control (NC), sevoflurane (sevo), miR-206 mimics+sevo, miR-206 inhibitors+sevo, miR-206 NC+sevo, IGF-1 shRNA+sevo, and miR-206 inhibitors+IGF-1 shRNA+sevo groups. The Morris water maze test was exhibited to assess the cognitive functions. Glial fibrillary acidic protein (GFAP) expression was detected by immunofluorescence assay. Western blotting and RT-qPCR were used to detect the expression of miR-206, IGF-1, PI3K, AKT, CREB, pPI3K, pAKT, pCREB, cytochrome-c (Cyt-c), and caspase-3. Cell viability and apoptosis were detected by MTT assay and annexin V/PI double staining respectively. Mitochondrial transmembrane potential (MTP) were determined by flow cytometry. The IGF-1 shRNA+sevo group showed reduced miR-206 expression. Compared with the normal/blank group, the sevo, and miR-206 NC+sevo groups showed decreased miR-206 and GFAP expressions, cell viability and MTP but increased expressions of IGF-1, PI3K, AKT, CREB, pPI3K, pAKT, pCREB, Cyt-c and caspase-3, as well as cell apoptosis. Similar trends were observed in the miR-206 inhibitors+sevo group when compared with the sevo group. The study provides evidence that miR-206 alleviates the inhibition of activation of hippocampal astrocytes in aged rats induced by sevoflurane by targeting IGT-1 through suppressing the PI3K/AKT/CREB signaling pathway.

Hippocampal Astrocyte Cultures from Adult and Aged Rats Reproduce Changes in Glial Functionality Observed in the Aging Brain.

Astrocytes are dynamic cells that maintain brain homeostasis, regulate neurotransmitter systems, and process synaptic information, energy metabolism, antioxidant defenses, and inflammatory response. Aging is a biological process that is closely associated with hippocampal astrocyte dysfunction. In this sense, we demonstrated that hippocampal astrocytes from adult and aged Wistar rats reproduce the glial functionality alterations observed in aging by evaluating several senescence, glutamatergic, oxidative and inflammatory parameters commonly associated with the aging process. Here, we show that the p21 senescence-associated gene and classical astrocyte markers, such as glial fibrillary acidic protein (GFAP), vimentin, and actin, changed their expressions in adult and aged astrocytes. Age-dependent changes were also observed in glutamate transporters (glutamate aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1)) and glutamine synthetase immunolabeling and activity. Additionally, according to in vivo aging, astrocytes from adult and aged rats showed an increase in oxidative/nitrosative stress with mitochondrial dysfunction, an increase in RNA oxidation, NADPH oxidase (NOX) activity, superoxide levels, and inducible nitric oxide synthase (iNOS) expression levels. Changes in antioxidant defenses were also observed. Hippocampal astrocytes also displayed age-dependent inflammatory response with augmentation of proinflammatory cytokine levels, such as TNF-α, IL-1ß, IL-6, IL-18, and messenger RNA (mRNA) levels of cyclo-oxygenase 2 (COX-2). Furthermore, these cells secrete neurotrophic factors, including glia-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), S100 calcium-binding protein B (S100B) protein, and transforming growth factor-ß (TGF-ß), which changed in an age-dependent manner. Classical signaling pathways associated with aging, such as nuclear factor erythroid-derived 2-like 2 (Nrf2), nuclear factor kappa B (NFκB), heme oxygenase-1 (HO-1), and p38 mitogen-activated protein kinase (MAPK), were also changed in adult and aged astrocytes and are probably related to the changes observed in senescence marker, glutamatergic metabolism, mitochondrial dysfunction, oxidative/nitrosative stress, antioxidant defenses, inflammatory response, and trophic factors release. Together, our results reinforce the role of hippocampal astrocytes as a target for understanding the mechanisms involved in aging and provide an innovative tool for studies of astrocyte roles in physiological and pathological aging brain.

Signaling mechanisms underlying the glioprotective effects of resveratrol against mitochondrial dysfunction.

Resveratrol, a polyphenol found in grapes and red wine, exhibits antioxidant, anti-inflammatory, anti-aging and, neuroprotective effects. Resveratrol also plays a significant role modulating glial functionality, protecting the health of neuroglial cells against several neuropsychiatric in vivo and in vitro experimental models. Mitochondrial impairment strongly affected astrocyte functions and consequently brain homeostasis. Molecules that promote astrocyte mitochondrial protection are fundamental to maintain brain energy balance and cellular redox state, contributing to brain healthy. Thus, the present study was designed to evaluate some glioprotective mechanisms of resveratrol against mitochondrial damage promoted by azide exposure in hippocampal primary astrocyte cultures. Azide treatment provoked deleterious effects, including the dysfunction of mitochondria, the deterioration of redox homeostasis, the augmentation of pro-inflammatory cytokines and impairment of glutamate uptake activity. However, resveratrol prevented these effects, protecting hippocampal astrocytes against azide-induced cytotoxicity through the heme-oxygenase-1 (HO-1) pathway and inhibiting p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor kappa B (NFκB) activation. Resveratrol also protected astrocytes via phosphatidylinositide 3-kinase (PI3K)/Akt. These results contribute to the comprehension of the mechanisms by which resveratrol mediates hippocampal astrocyte protection against mitochondrial failure and implicate resveratrol as an important glioprotective molecule.

Resveratrol increases antioxidant defenses and decreases proinflammatory cytokines in hippocampal astrocyte cultures from newborn, adult and aged Wistar rats.

Astrocytes are responsible for modulating neurotransmitter systems and synaptic information processing, ionic homeostasis, energy metabolism, maintenance of the blood-brain barrier, and antioxidant and inflammatory responses. Our group recently published a culture model of cortical astrocytes obtained from adult Wistar rats. In this study, we established an in vitro model for hippocampal astrocyte cultures from adult (90 days old) and aged (180 days old) Wistar rats. Resveratrol, a polyphenol found in grapes and red wine, exhibits antioxidant, anti-inflammatory, anti-aging and neuroprotective effects that modulate glial functions. Here, we evaluated the effects of resveratrol on GSH content, GS activity, TNF-α and IL-1ß levels in hippocampal astrocytes from newborn, adult and aged Wistar rats. We observed a decrease in antioxidant defenses and an increase in the inflammatory response in hippocampal astrocytes from adult and aged rats compared to classical astrocyte cultures from newborn rats. Resveratrol prevented these effects. These findings reinforce the neuroprotective effects of resveratrol, which are mainly associated with antioxidant and anti-inflammatory activities.