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Objective To explore the effect of chronic restraint stress (CRS) on the phenotypic transition of hippocampal astrocytes and depression-like behavior in mice. Methods Forty eight male C57BL/6 mice were randomly divided into control groups (control), model groups (CRS) and fluoxetine(FLX) drug intervention groups (CRS+FLX), 16 for each group. The mice of the CRS group were subjected to 3 weeks chronic restraint stress. The mice of CRS + FLX group were treated with fluoxetine by intraperitoneal injection 30 minutes before restraint stress from the day 8 to day 21.
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Objective To study the effect of dexmedetomidine (DEX), an α2- adrenoceptor agonist, on the pain-related anxiety-like and depression-like behaviour induced by complete Freund' s adjuvant (CFA) injection and its possible regulatory mechanism. Methods Thirty-six ICR female mice were randomly divided into normal saline (NS) group, CFA group and DEX + CFA group, n = 12 for each group. Chronic inflammatory pain model was established by subcutaneous injection of 10 μl CFA into the right hind limb of mice. DEX + CFA group mice were injected intraperitoneally with 0.025 mg/kg DEX 30 minutes before nociceptive behavior test, and once a day for 7 days. Von-frey fiber was used to evaluate the threshold of mechanical pain in mice, n = 12 for each group. The anxiety-like behavior of mice were detected by open field test, n = 12 for each group. Sucrose preference, tail suspension test and forced swimming test were used to detected the depression-like behavior of mice, n = 12 for each group. The expression of adrenergic receptor β2 (ADRB2), Brain-derived neurotrophic factor (BDNF), tyrosine kinase B receptor (TrkB), and glutamate receptors 1 (GluR1) and GluR2 were detected by Western blotting, n = 8 for each group. Immunohistochemical staining was used to detect the expression of recombinant doublecortin(DCX), which is a marker of newborn neurons in the hippocampus, n = 4 for each group. Results Compared with the NS group, the mechanical threshold of mice on the 1st, 3rd and 7th day after CFA injection decreased significantly (P 0.05). Compared with the NS group, the time spent in the inner ares (P<0.01), number of entering the central grid area (P<0.01) and distance travelled in the inner area (P<0.01) of CFA group mice reduced significantly, while the time (P<0.01), numbers (P < 0.05) and distance (P < 0.05) of DEX + CFA group mice entering the central grid area enhanced significantly. The result of depression-like behavior tests showed that the sucrose preference percentage (P < 0.05) reduced significantly in CFA group when compared with NS group, and the immobility time increased significantly in tail suspension test (P<0.01) and forced swimming test (P< 0.001) in CFA mice when compared with NS group, while DEX intervention could significantly increase the sucrose preference scores (P<0.05) and decreased the immobility time in tail suspension test (P<0.05) and forced swimming test (P<0.05). The result of Western blotting showed that compared with the NS group, the levels of ADRB2 (P<0.0010), BDNF (P < 0.001), TrkB (P < 0.01), GluR1 (P < 0.001) and GluR2 (P < 0.001) in the hippocampus of CFA group were significantly decreased, while DEX intervention could significantly increase the expression of ADRB2 (P<0.05), BDNF (P < 0.001), TrkB (P < 0.001), GluR1 (P < 0.001) and GluR2 (P < 0.001). Immunohistochemical result showed that compared with the NS group, the average absorbance (AA) of DCX decreased significantly in hippocampus of CFA group (P<0.05), but increased significantly in DEX+CFA group (P < 0.05). Conclusion Dexmedetomidine may promote hippocampal neurogenesis through upregulated the expression of BDNF-TrkB, thus improving CFA-induced anxiety-like and depression-like behaviors in mice.
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Objective To investigate the effect of chronic restraint stress on the expression of N6-methyladenosine (m6A)and related enzymes in the hippocampus of mice. Methods Twenty C57BL/6J male mice were randomly divided into control group and chronic restraint stress (CRS) group, the model group was given for 3 weeks chronic restraint stress to establish a mouse anxiety model. Open field test and elevated plus maze test were used to detect anxiety-like behavior; Immunohistochemistry and m6A RNA methylation assay were used to detect the expression changes of mouse hippocampal m6A; Western blotting and Real-time PCR were used to analyze hippocampal m6A related enzymes expression. Results 1.The behavioral results showed that, compared with the control group, the CRS group showed significantly reduced time spent in the center of the open field(P<0.01), the CRS group showed significantly reduced exploration time in the open arm of elevated plus maze (P<0.0001); 2. Immunohistochemical results showed that, compared with the control group, the hippocampal m6A content in the CRS group reduced significantly (P < 0.001); The results of the m6A RNA methylation assay showed that, compared with the control group, the CRS group showed significantly reduced amount of hippocampal m6A(P<0.05); 3. Real-time PCR results showed that the expression of hippocampal demethylase anaplastic lymphoma kinase B(AlkB) homolog 5(ALKBH5) (P<0.001) and fat mass and obestity associated protein(FTO) (P< 0.05) in the CRS group significantly up-regulated, the expression of methylase Wilms' tumour 1-associating protein (WTAP) (P<0.05) was significantly down-regulated compared with the control group; The expression of m6A methylation binding protein YTH domaincontaining family protein 3 (YTHDF3) (P < 0.05) and YTH domaincontaining protein 2 (YTHDC2) (P < 0.01) was significantly up-regulated. Western blotting result showed that, compared with the control group, the mouse hippocampal demethylase ALKBH5 (P < 0.05) and FTO (P < 0.05) expression in the CRS group significantly up-regulated, the expression of WTAP (P<0.01) was significantly down-regulated; m6A methylation binding protein YTHDF3 (P<0.01) and YTHDC2 (P<0.05) were significantly up-regulated. Conclusion In the anxiety model induced by chronic restraint stress, the expression of m6A in the hippocampus of mice is down-regulated. The mechanism may be related to the up-regulation of the m6A demethylase ALKBH5 and FTO or the down-regulation of the methylase WTAP.
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Objective To explore the expression and role of bromodomain-containing protein 4(BRD4) in spinal cord of mice which suffered inflammatory pain induced by formaldelryde solution. Methods Thirty-two ICR mice were randomly divided into normal saline group and formaldehyde injection 5 minutes, 30 minutes and 60 minutes groups, with 8 mice in each group. The expression of BRD4 protein and mRNA in spinal cord of mice in each group were detected by Western blotting (n = 4/group) and Real-time PCR (n = 4/group); 66 mice were randomly divided into formaldelryde injection group, vehicle (DMSO) plus formaldelryde injection group and 6. 25, 12. 5, 25 and 50 mg/kg JQl injection plus formaldelryde solution group, with 11 mice in each group. The effect of BRD4 inhibitor JQl on spontaneous pain in each group was observed (n= 11/group); Immunohistochemistry (n= 3/group), Real-time PCR (n = 4/group) or Western blotting (n= 4/group) were used to detect the effects of 25 mg/kg JQ1 on the expression of c-fos and glutamate receptor 2 (GluR2) in the spinal cord of model mice. Results The result showed that levels of BRD4 protein (P<0. 01) and mRNA in spinal cord increased significantly 30 min and 60 min after formaldehyde solution injection (P<0. 05). The behavioral test showed that both 25 mg/kg and 50 mg/kg JQf administration could reduce the second phase spontaneous pain compared with the solvent (DMSO) group (P < 0 . 05). Furthennore, immunohistochemistry and Real-time PCR result showed that 25 mg/kg JQf injection could significantly reduce positive numbers (P<0. 01) and high mRNA expression of c-fos in mouse spinal cord induced by formaldehyde solution (P < 0 . 05), and the Western blotting result showed that 25 mg/kg JQf administration could significantly reduce the expression of glutamate receptor GluR2 (P < 0. OOf). Conclusion BRD4 may play an important role in the induction of central sensitization of inflammatory pain, and JQf may alleviate inflammatory pain behavior by inhibiting the formation of central sensitization of pain.
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Objective To investigate the alteration of mood and hippocampal microglia morphology in a mouse model of chronic inflammatory pain induced by complete Freund' s adjuvant (CFA). Methods Thirty-two male ICR mice were randomly divided into two groups, including normal saline control group (NS) and CFA model group (CFA). The pain model was established by right hindpaw intraplantar CFA injection. The change of mechanical pain threshold after CFA injection was measured by von Frey fiber needle, the locomotor activity and anxiety-like behavior were determined by open field test (OFT), the depression-like behavior was determined by sucrose preference test (SPT) and forced swimming test (FST). The expression of microglia marker ionized calcium binding adaptor molecule-1 (IBA-1) in the hippocampus was determined by immunohistochemistry and its morphological change was analyzed by Sholl analysis. Results Compared with the NS group, the mechanical pain threshold of CFA group decreased significantly (P<0.01). The behavior result showed that the CFA group showed remarkably reduced time in the inner area (P<0.01) compared with the NS group in the open field test; In the sucrose preference test, the percentage of sucrose preference (P<0.01) of CFA mice decreased significantly compared with the NS mice, while the immobility time of CFA mice (P<0.01) increased significantly in the forced swimming test compared with the NS mice. The immunohistochemistry showed that the number of microglia in the dentate gyrus (DG) of CFA mice increased significantly compared with the NS mice. The Sholl analysis result showed that compared with the NS mice, the number of intersections of microglia in hippocampal DG decreased significantly in CFA mice. Conclusion Our finding indicates that the negative emotions in CFA-induced chronic inflammatory pain may be related to the morphological changes of hippocampal microglia in the mice.
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<p><b>OBJECTIVE</b>To investigate the involvement of NF-kappaB (NF-kB) regulation of hepcidin gene transcription in acute phase response and its molecular mechanism.</p><p><b>METHODS</b>First, a mouse model of acute phase response was established by intraperitoneal injection of LPS. The relationship between hepcidin expression and dose or time of LPS injection was assessed. Then, electrophoretic mobility shift assay (EMSA) was performed to explore the possibility of the involvement of NF-kB in regulation of hepcidin gene transcription. Next, pAVU6+27-NF-kB, NF-kB p65-specific siRNA expression vector was constructed and transfected into mouse primary hepatocytes using DOTAP liposomal transfection reagents. Hepcidin expression changes after silencing of NF-kB p65 and hepcidin expression after LPS induction were tested.</p><p><b>RESULTS</b>Hepcidin expression showed a time and dose-dependent manner with regard to LPS injection. At 10 h after 50 microg LPS injection, hepcidin expression reached its peak. The result of EMSA exhibited an evident lag band at -53 - -64 bp, indicating regulation of hepcidin gene expression by NF-kB. After mouse primary hepatocytes were transiently transfected with NF-kB p65-specific siRNAs, Western blot showed that inhibition rate of NF-kB expression was 50%-67%. Hepcidin expression of transfected hepatocytes dropped down obviously in comparison with that of untransfected hepatocytes, and could not be induced by LPS.</p><p><b>CONCLUSION</b>Transcription factor NF-kB is likely to be an important molecule in transcription regulation of hepcidin gene. As a key component, p65 subunit binds to hepcidin gene at -53 - -64 bp, and upregulates hepcidin expression.</p>