AIMTo investigate whether NR2B-pERK1/2-pElk-1 signaling contributes to the Y-maze learning and memory of rat brain.

METHODS45 adult male SD rats were divided into 4 groups: (1) Ifenprodil peritoneal injection group (Ifenprodil ip, n = 14); (2) DMSO peritoneal injection group(DMSO ip, n = 15); (3) Ifenprodil cerebral ventricle injection group (Ifenprodil ic, n = 8); (4) DMSO cerebral ventricle injection group(DMSO ic, n = 8). Y-maze training and test were used as an learning and memory enhancing stimulus. Immunohistochemical and Western blotting methods were used for detecting pERK1/2 and pElk-1 expression intensity of different brain regions.

RESULTSCompared with the DMSO ip group, the ifenprodil ip group showed no change on the Y-maze learning score (P > 0.05), but its Y-maze memory score tested 24 after learning decreased (P < 0.05). Ifenprodil peritoneal injection made brain pERK1/2 and pElk-1 expression decreased generally. In hippocampus, marginal division of striatum(MrD), amygdala,these changes were more significant (P < 0.05). Compared with the DMSO ic group, the reconsolidation of Y-maze memory tested 6 hours after ifenprodil injection was impaired in ifenprodil ic group (P < 0.05). The OD value of pERK1/2 and pElk-1 positive bands in ifenprodil ic group attenuated generally. The pElk-1 positive bands of caudate putamen and MrD almost disappeared in ifenprodil ic group.

CONCLUSIONNR2B is essential for the formation of long-term memory, reconsolidation of Y-maze memory. The deactivation of NR2B by ifenprodil will impair these courses. Meanwhile, the deactivation of NR2B attenuates pERK1/2 and pElk-1 expression of learning and memory related regions after Y-maze learning and memory reconsolidation test. In MrD and caudate putamen, the pElk-1 expression are completely blocked by ifenprodil after memory reconsolidation test.

Animals ; Avoidance Learning ; physiology ; Dimethyl Sulfoxide ; pharmacology ; Extracellular Signal-Regulated MAP Kinases ; metabolism ; Male ; Maze Learning ; physiology ; Memory ; physiology ; Piperidines ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; metabolism ; ets-Domain Protein Elk-1 ; metabolism

OBJECTIVETo study the role of extracellular signal-regulated kinase (ERK) in cerebral ischemia and the mechanism of protective effects of U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene) on ischemic brain.

METHODSMice underwent left middle cerebral artery occlusion (MCAO) by introducing a suture in the lumen. U0126 was injected intravenously through the internal jugular vein. The immuno-activity of phosphorylated ERK1/2 (pERK1/2), phosphorylated mitogen activated protein kinase kinase (pMEK), and phosphorylated Elk-1 (pElk-1) was assessed by Western blot analysis and immunohistochemistry. Interleukin (IL)-1beta mRNA level was measured by ribonuclease protection assay.

RESULTSPhosphorylated ERK1/2 in 2 hours MCAO mice was down-regulated after intravenous injection of U0126. The inhibition was dose dependent and treatment time related. pMEK and pElk-1 were also reduced in a similar fashion after U0126 treatment. IL-1beta mRNA increased after 1 and 2 hours of MCAO. After injection of U0126, it was down-regulated during 1 to 4 hours after MCAO.

CONCLUSIONIntravenous administration of the MEK inhibitor U0126 inhibits pMEK, pERK1/2, and pElk-1 up-regulation induced by cerebral ischemia. The protective effect of U0126 against ischemic injury is probably resulted from the reduction of IL-1beta mRNA via the inhibition of ERK pathway.

Animals ; Butadienes ; pharmacology ; DNA-Binding Proteins ; metabolism ; Enzyme Inhibitors ; pharmacology ; Infarction, Middle Cerebral Artery ; metabolism ; Interleukin-1 ; biosynthesis ; genetics ; Male ; Mice ; Mitogen-Activated Protein Kinase 1 ; metabolism ; Mitogen-Activated Protein Kinase Kinases ; antagonists & inhibitors ; metabolism ; Nitriles ; pharmacology ; Phosphorylation ; Proto-Oncogene Proteins ; metabolism ; RNA, Messenger ; biosynthesis ; genetics ; Signal Transduction ; Transcription Factors ; metabolism ; ets-Domain Protein Elk-1

OBJECTIVE: To study the effects of Zuogui Jiangtang Jieyu Formula (ZGJTJYF, the Chinese Medicine) on hippocampal neuron apoptosis in diabetes mellitus complicated with depression (DD). METHODS: The primary cultured hippocampal neurons were treated with high glucose (150 mmol/L) and corticosterone (200 micromol/L) to establish the cell model of DD in vitro. The cultured hippocampal neurons were randomly divided into five groups: blank serum group, normal group, Zuogui Jiangtang Jieyu recipe drug-containing serum group, positive drug (metformin + fluoxetine) drug-containing serum group and model group (three compound holes in each group). The model group and the normal group were given the same amount of culture medium, and the other groups were given the corresponding serum with 10% volume fraction for 18 hours. Hoechst staining, high content cell imaging and RT-PCR were used to detect the apoptosis of hippocampal neurons and the expressions of apoptosis-related ETS-like 1 transcription factor(ELK-1), C-Jun N-terminal kinase(JNK) and c-Fos proteins and genes. RESULTS: Compared with the blank group, the apoptotic number of hippocampal neurons in the model group was increased significantly, and the expression levels of ELK-1, JNK and c-Fos were increased significantly (P＜0.05). Compared with the model group, the local bright spots of hippocampal neurons in the Zuogui Jiangtang Jieyu recipe-containing serum group and the positive drug-containing serum group were decreased significantly, and the number of apoptotic cells was decreased significantly. The expressions of JNK, c-fos protein and mRNA were down-regulated significantly (P＜ 0.05), and the neural network and dendritic junction were improved significantly. CONCLUSION Zuo Gui Jiang Tang Jie Yu Formula can reverse the expressions of ELK-1, JNK and c-Fos signals in hippocampal neurons under DD environment and play an anti-apoptotic effect.
Animals ; Apoptosis ; drug effects ; Depression ; drug therapy ; Diabetes Complications ; drug therapy ; Diabetes Mellitus ; Drugs, Chinese Herbal ; pharmacology ; Hippocampus ; drug effects ; MAP Kinase Kinase 4 ; drug effects ; Neurons ; Proto-Oncogene Proteins c-fos ; drug effects ; Random Allocation ; Rats ; ets-Domain Protein Elk-1 ; drug effects

The early growth response-1 gene (egr-1) encodes a zinc-finger transcription factor Egr-1 and is rapidly inducible by a variety of extracellular stimuli. Anisomycin (ANX), a protein synthesis inhibitor, stimulates mitogen-activated protein kinase (MAPK) pathways and thereby causes a rapid induction of immediate-early response genes. We found that anisomycin treatment of U87MG glioma cells resulted in a marked, time-dependent increase in levels of Egr-1 protein. The results of Northern blot analysis and reporter gene assay of egr-1 gene promoter (Pegr-1) activity indicate that the ANX- induced increase in Egr-1 occurs at the transcriptional level. Deletion of the serum response element (SRE) in the 5'-flanking region of egr-1 gene abolished ANX-induced Pegr-1 activity. ANX induced the phosphorylation of the ERK1/2, JNK, and p38 MAPKs in a time-dependent manner and also induced transactivation of Gal4-Elk-1, suggesting that Elk-1 is involved in SRE-mediated egr-1 transcription. Transient transfection of dominant-negative constructs of MAPK pathways blocked ANX-induced Pegr-1 activity. Furthermore, pretreatment with specific MAPK pathway inhibitors, including the MEK inhibitor U0126, the JNK inhibitor SP600125, and the p38 kinase inhibitor SB202190, completely inhibited ANX-inducible expression of Egr-1. Taken together, these results suggest that all three MAPK pathways play a crucial role in ANX-induced transcriptional activation of Pegr-1 through SRE-mediated transactivation of Elk
p38 Mitogen-Activated Protein Kinases/genetics/metabolism ; ets-Domain Protein Elk-1/genetics/*metabolism ; Trans-Activation (Genetics)/*drug effects ; Serum Response Element ; Protein Kinase Inhibitors/pharmacology ; Protein Biosynthesis/*drug effects ; Promoter Regions (Genetics)/genetics ; *MAP Kinase Signaling System/drug effects ; JNK Mitogen-Activated Protein Kinases/genetics/metabolism ; Humans ; Extracellular Signal-Regulated MAP Kinases/genetics/metabolism ; Early Growth Response Protein 1/genetics/*metabolism ; Cell Line, Tumor ; Anisomycin/*pharmacology