Effect of anaesthesia on cemented hemiarthroplasty -A multicentre retrospective study (TRON study).

INTRODUCTION: This study aimed to investigate the survival rate, postoperative complications, and walking ability in cemented hemiarthroplasty (HA) for displaced femoral neck fractures according to the anaesthesia method. METHODS: We conducted a retrospective study of a multicentre group (the TRON group). Three hundred fifty-eight patients who underwent cemented HA between 2015 and 2019 were selected; 289 patients of ≥75 years of age with no missing data were included. Patient background factors were matched and patients were assigned to spinal anaesthesia (SA) and general anaesthesia (GA) groups. The primary outcome was death at any time during the follow-up period. Secondary outcomes included postoperative complications and walking ability assessed using the Parker mobility score (PMS). Overall survival was evaluated using the Kaplan-Meier method, and differences were compared using the log-rank test. The incidence of each complication and PMS were compared between the two groups using Fisher's exact test. RESULTS: Overall survival during follow-up was significantly higher in the SA group in comparison to the GA group (p = 0.037). In the SA and GA groups, the survival rate at 3 months postoperatively was 98.4% and 95.5%, respectively. The incidence of postoperative pneumonia was significantly higher in the GA (p = 0.012), and PMS at 3 months postoperatively was significantly higher in the SA group (p = 0.016). CONCLUSION: The survival rate of elderly patients who underwent cemented HA was better in the SA group. General anaesthesia in cemented HA may be associated with lower life expectancy, increased incidence of pneumonia, and decreased walking ability.

Comparison of conjoined tendon-preserving posterior approach and conventional posterolateral approach in hemiarthroplasty for femoral neck fracture in the elderly: A multicenter (TRON group) retrospective study.

BACKGROUND: Femoral neck fractures (FNF) are one of the most common traumatic injuries in the elderly. The conjoined tendon-preserving posterior (CPP) approach was developed as a modification of the conventional posterolateral (PL) approach in hemiarthroplasty (HA) for displaced femoral neck fractures (FNF) to reduce postoperative dislocation. We hypothesized that the CPP approach would result in fewer dislocations and similar functional and radiographic outcomes compared to the PL approach. PATIENTS AND METHODS: This was a retrospective multicenter (TRON group) study. We evaluated the rate of complications, and functional and radiographic outcomes for patients aged >65 years who underwent HA via the PL approach or the CPP approach from 2017 to 2019 and followed up for at least 24 months. To adjust for baseline differences between the groups, a propensity score-matching algorithm was used in a 1:1 ratio. RESULTS: We identified 135 patients who underwent HA via the PL approach and 135 patients via the CPP approach. The mean follow-up period was 32.4 ± 14.0 months. The incidence of dislocation was 6 in 135 patients (4.4%) in the PL group and 0 in 135 patients (0%) in the CPP group, and there was significant difference (p = 0.04). Operation time was equivalent between the two groups (73.1 ± 30.4 vs. 71.8 ± 30.0 min; p = 0.72). The rate of varus insertion of stems in the PL group lower than that in the CPP group (19.3% vs. 33.3%; p = 0.01). Postoperative Parker's mobility score was similar between the two groups at 12 months follow-up (6.17 vs. 6.27; p = 0.81). CONCLUSION: The CPP approach showed a significantly lower dislocation rate, similar functional outcome and more varus stem insertions compared with the PL approach in this retrospective study.

[Novel therapeutic approach for the treatment of post-traumatic stress disorder (PTSD): facilitating fear extinction].

Pharmacological agents enhancing fear extinction may be promising tools for the treatment of PTSD. Histone acetylation is involved in memory formation, and histone deacetylase (HDAC) inhibitors increase histone acetylation and subsequently enhance fear extinction. In this study, we examined whether vorinostat, an HDAC inhibitor, facilitated fear extinction, using a contextual fear conditioning (FC) paradigm. We found that vorinostat facilitated fear extinction. Next, the levels of global acetylated histone were measured by Western blotting. We also assessed the effect of vorinostat on the hippocampal levels of NMDA receptor mRNA by real-time quantitative PCR (RT-PCR). The levels of acetylated histone and NR2B mRNA, but not NR1 or NR2A mRNA, were elevated in the hippocampus 2 h after administration of vorinostat. We investigated the levels of acetylated histones and phospho-CREB (p-CREB) binding at the promoter of the NR2B gene using the chromatin immunoprecipitation (ChIP) assay followed by RT-PCR. The levels of acetylated histone and the binding of p-CREB to its binding site at the promoter of the NR2B gene were increased. These findings suggest that vorinostat in conjunction with exposure therapy can be a promising new avenue for the treatment of PTSD.

Inhibitory effects of 2-amino-3H-phenoxazin-3-one on the melanogenesis of murine B16 melanoma cell line.

Hyperpigmentations are a serious concern addressed by both the medical community and the cosmetic industry through the development of agents that block melanin biosynthesis. In this study, we found that 2-amino-3H-phenoxazin-3-one (APO), isolated from extracts of the edible mushroom Agaricus bisporus Imbach, exhibited potent inhibitory effects on melanogenesis in B16 cells, a murine melanoma cell line. APO inhibited melanin biosynthesis at 1,000 times lower concentrations (IC(50)=1.31+/-0.08 microM) than kojic acid (IC(50)=1.31+/-0.13 mM), without causing cellular toxicity. APO did not directly inhibit the enzyme activity of tyrosinase, the rate-limiting melanogenic enzyme. Further study showed that APO inhibited the protein expression of tyrosinase and microphthalmia-associated transcription factor (MITF), a melanogenic transcription factor that regulates the expression of tyrosinase. These results suggest that APO is a promising depigmenting agent with both therapeutic and cosmetic value in preventing melanogenesis.

[Epigenetic mechanism of depression].

Numerous epigenetic studies have revealed that the acetylated status of histone as well as methylated status of cytosine is closely involved in gene transcription. Preclinical and clinical studies demonstrate that changes in levels of various genes in the brain including BDNF, play a role in the pathophysiology of depression. It is well known that the levels of BDNF mRNA and protein in the rat brain, such as frontal cortex and hippocampus, was decreased in response to stress, but the precise mechanism of stress-induced downregulation of BDNF has yet to be characterized. In this context, we examined the influence of a single immobilization stress (SIS) on the levels of total BDNF mRNA with each exon mRNA by real-time PCR and acetylated histone at the promoters of the BDNF gene by chromatin immunoprecipitaion assay in the rat hippocampus. SIS significantly decreased the levels of total BDNF mRNA with significant reduced levels of exon I and IV mRNA. Significant decreases in acetylated histone H3, but not H4, were found at the promoters of exons I, IV, and VI. On the other hand, antidepressant-like effects has been reported with sodium butylate (SB), a histone deacetylase (HDAC) inhibitor, promoting gene transcription. We also found antidepressant-like effect of repeated administration of SB in the forced swim test using rats. In addition, we found that upregulation in transthyretin mRNA in the rat hippocampus is, at least in part, associated with this effect using DNA microarray and real-time PCR. Based on these findings, it is postulated that epigenetic regulation of the BDNF gene by stress and antidepressants may be involved in the pathophysiology of depression.

Maternal postpartum learned helplessness (LH) affects maternal care by dams and responses to the LH test in adolescent offspring.

It is known that the early environment affects the mental development of rodent and human offspring. However, it is not known specifically whether a postpartum depressive state influences the depressive state in offspring. Using learned helplessness (LH) in rats as an animal model of depression, we examined the influence of maternal postpartum LH on responses to the LH test of offspring. Dam rats were judged as LH or non-helpless (nLH) on postnatal days (PN) 2-3, and maternal behavior was recorded during PN2-14. On PN 45-46, offspring were subjected to the LH test. Plasma corticosterone (CORT) levels, hippocampal levels of glucocorticoid receptor (GR) and brain-derived neurotrophic factor (BDNF) mRNA were measured before and after the LH test in offspring. Active nursing in LH dams was significantly lower than that in nLH dams. Susceptibility to LH in the offspring of LH dams was significantly higher than in those of nLH dams, and was negatively correlated with active nursing by LH dams. The GR mRNA levels before and after the LH test were lower in the offspring of LH dams than in those of nLH dams, and the reduced basal GR mRNA and protein might have resulted in the higher CORT response after the LH test. There was no significant difference in BDNF mRNA in the offspring of LH and nLH dams. These findings suggest that early postpartum LH decreased active nursing and increased depression-like behavior in the adolescent offspring via dysfunction of the hypothalamic-pituitary-adrenal axis.

Single prolonged stress: toward an animal model of posttraumatic stress disorder.

Although selective serotonin reuptake inhibitors (SSRIs) are reported to be effective in decreasing posttraumatic stress disorder (PTSD) symptoms, a subgroup of PTSD patients remain chronically symptomatic and maintain conditioned fear responses to traumatic stimuli. In this context, the establishment of an appropriate animal model of PTSD is necessary to promote better understanding of the mechanisms of the disorder and to facilitate the development of more effective therapeutic alternatives to SSRIs. Although no single widely accepted animal model of PTSD has been established to date, the single prolonged stress (SPS) animal model has been partially validated as a model for PTSD. SPS rats mimic the pathophysiological abnormalities and behavioral characteristics of PTSD, such as enhanced anxiety-like behavior and glucocorticoid negative feedback, and they exhibit the expected therapeutic response to paroxetine on enhanced fear memory. In addition, SPS rats exhibit enhanced freezing in response to contextual fear conditioning, and impaired extinction of fear memory, which is alleviated by D-cycloserine. The enhanced consolidation and impaired extinction of fear memory found in SPS rats suggests that this model has additional value because recent studies of PTSD indicate that memory abnormalities are a central feature. In this study, we summarize the behavioral and pathophysiological PTSD-like symptoms in SPS, focusing on memory abnormalities, and evaluate the validity of SPS as an animal model of PTSD.

[A novel therapeutic approach for the treatment of post-traumatic stress disorder (PTSD): enhancing the impaired extinction of fear memory].

Although the impaired extinction of traumatic memory is one of the hallmark symptoms of PTSD, the underlying mechanisms of impaired extinction are unclear and effective pharmacological interventions have not yet been developed. In this study, using rats subjected to single prolonged stress (SPS), an animal model of PTSD, we examined (a) the ability of SPS to impair fear extinction, (b) whether D-cycloserine (DCS) can alleviate impaired fear extinction in SPS rats, and (c) the effect of SPS and/or DCS on the levels of N-methyl-D-aspartate (NMDA) receptor subunit mRNAs in the rat hippocampus during extinction training. SPS rats exhibited impaired fear extinction in the contextual fear test, which was alleviated by the repeated administration of DCS. SPS induced significant upregulation of the levels of NMDA receptor subunit mRNAs before and during the period of extinction training, while repeated administration of DCS eliminated the enhanced mRNA levels of NMDARs, suggesting that DCS, irrespective of its mechanistic involvement in the enhancement of fear extinction, may help to reverse hippocampal plasticity, and thus reverse the NMDA compensatory alterations. Our research indicates that DCS may be a promising tool for the treatment of PTSD.

Effects of single prolonged stress and D-cycloserine on contextual fear extinction and hippocampal NMDA receptor expression in a rat model of PTSD.

Although the impaired extinction of traumatic memory is one of the hallmark symptoms of posttraumatic stress disorder (PTSD), the underlying mechanisms of impaired extinction are unclear and effective pharmacological interventions have not yet been developed. Single prolonged stress (SPS) has been proposed as an animal model of PTSD, since rats subjected to SPS (SPS rats) show enhanced negative feedback of the HPA axis and increased contextual fear, which are characteristics similar to those observed in patients with PTSD. In this study, using SPS rats, we examined (a) the ability of SPS to impair fear extinction, (b) whether D-cycloserine (DCS) can alleviate impaired fear extinction in SPS rats, and (c) the effect of SPS and/or DCS on the levels of N-methyl-D-aspartate (NMDA) receptor subunit mRNAs in the rat hippocampus during extinction training. SPS rats exhibited impaired fear extinction in the contextual fear test, which was alleviated by the repeated administration of DCS. The effect of enhanced extinction, induced by the administration of DCS to SPS rats, was maintained for one week following extinction training. SPS induced significant upregulation of the levels of NMDA receptor subunit mRNAs before and during the period of extinction training, while repeated administration of DCS eliminated the enhanced mRNA levels of NMDARs. Behavioral analyses indicated that SPS is an appropriate animal model of PTSD and that DCS may be effective in the treatment of PTSD. These findings suggest that DCS, irrespective of its mechanistic involvement in the enhancement of fear extinction, may help to reverse hippocampal plasticity, and thus reverse the NMDA compensatory alterations.

The combination of IFN-alpha2 and IFN-alpha8 exhibits synergistic antiproliferative activity on renal cell carcinoma (RCC) cell lines through increased binding affinity for IFNAR-2.

Although there are at least 13 interferon-alpha (IFN-alpha) subtypes in humans, interactions between the subtypes remain unknown. To understand IFN-alpha interactions, we examined the antiproliferative activities and the receptor binding affinities of different combinations of IFN-alpha2 and IFN-alpha8 using six renal cell carcinoma (RCC) cell lines. Although IFN-alpha8 was the more potent subtype, synergistic and antagonistic antiproliferative effects were also observed in certain combinations of IFN-alpha2 and IFN-alpha8. To analyze the interactions between IFN-alpha2 and IFN-alpha8, the receptor-binding kinetics of different combinations of IFN-alpha2 and IFN- alpha8 to the IFN-alpha receptors, IFNAR-1 or IFNAR-2, were measured using a surface plasmon resonance-based biosensor. Unexpectedly, the receptor binding kinetics to IFNAR-2 but not to IFNAR-1 were mutually related to antiproliferative activity and increase in the binding speed (K(a)) for IFNAR-2. Moreover, we observed the increased fluorescence intensity (FI) of biotin-labeled IFN-alpha8 to IFNAR-2 by receptor binding inhibition assay with unlabeled IFN-alpha2 but not the other combinations. These findings indicate that the binding manner of IFN-alpha8 for IFNAR-2 is different from that of IFN-alpha2, suggesting that binding of IFN-alpha8 rather than binding of IFN-alpha2 to IFNAR-2 leads to activation and subsequent antiproliferative activity despite the same antiviral activity in RCC.

Role of p53 in the inhibitory effects of interferon-alpha subtypes on proliferation of hepatocellular carcinoma cells.

While interferon-alpha (IFN-alpha) subtypes share a common specific receptor composed of two subunits, interferon-alpha receptor (IFNAR)-1 and IFNAR-2, their subtype activities are exhibited via several intracellular signaling pathways and thus subsequently show different biological effects. Anti-proliferative effects of single treatment with IFN-alpha subtypes or 5-fluorouracil (FU), and of combined treatment with each IFN-alpha subtype and 5-FU were examined on three hepatocellular carcinoma cell lines, HepG2, HLE and PLC/PRF/5. HepG2 and PLC/PRF/5 cells were susceptible to the combination treatment, but HLE cells were not. Proliferation of PLC/PRF/5 cells was also inhibited by the IFN-alpha subtypes singly. In addition, apoptosis was observed in HepG2 cells upon treatment with 5-FU alone and with the combination treatment, and in PLC/PRF/5 cells after single treatment with the IFN-alpha subtypes and after the combination treatment. IFN-alpha subtypes induced cell cycle arrest in the G2/M phase in HepG2 and PLC/PRF/5. Analyses by Western blotting and immunoprecipitation revealed increased p53 phosphorylation in HepG2 and PLC/PRF/5 cells but not in HLE cells after combined treatment. Single treatment with IFN-alpha subtypes promoted p53 activation only in PLC/PRF/5 cells. These results propose that IFN-alpha subtypes induce cells to undergo apoptosis through p53 activation directly and indirectly, in collaboration with 5-FU, further suggesting the presence of distinct signal pathways for IFN-alpha-induced apoptosis.

The potential use of histone deacetylase inhibitors in the treatment of depression.

Numerous preclinical studies demonstrate that changes in gene expression in the brain occur in animal models of depression using exposure to stress, such as social defeat and leaned helplessness, and that repeated administration of antidepressants ameliorates these stress-induced changes in gene expression. These findings suggest that alteration in gene transcription in the central nervous system in response to stress plays an important role in the pathophysiology of depression. Recent advances in epigenetics have led to the realization that chromatin remodeling mediated by histone deacetylase (HDAC) is closely involved in the regulation of gene transcription. In this context, we first review several preclinical studies demonstrating the antidepressant-like efficacy of HDAC inhibitors. We then suggest the efficacy of HDAC inhibitors in treatment-resistant depression based on the mechanism of action of HDAC. Finally, we discuss the possibility of using HDAC inhibitors in patients with treatment-resistant depression.

Effects of interferon-alpha subtypes on the TH1/TH2 balance in peripheral blood mononuclear cells from patients with hepatitis virus infection-associated liver disorders.

Interferon-alpha (IFN-alpha) has recently been shown to modulate in vitro T helper (Th) 1-driven responses in the peripheral blood mononuclear cells (PBMC) of patients with hepatitis B virus or C virus infection. In this study, we examined the in vitro effects of IFN-alpha subtypes (IFN-alpha1, -alpha2, -alpha5, -alpha8, and -alpha10) on the Th1/Th2 balance in PBMC obtained from patients with hepatitis virus infection-associated liver disorders and chronic hepatitis (CH), in comparison with the effect on healthy control volunteer PBMC. The Th1-type cell percentages and Th1/Th2 ratios were significantly higher in the PBMC of patients when compared with controls both before and after cultivation in vitro, with the IFN-alpha subtypes. The IFNalpha-5 induced an increase in the Th2-type cell percentages in both control and patient PBMC, resulting in that IFN-alpha5 lowered the Th1/Th2 ratio in patients with CH. Furthermore, statistical analysis revealed that IFN-alpha8 significantly promoted an increase in the Th1/Th2 ratios of PBMC from patients with CH and liver cirrhosis (LC) but not that of PBMC from patients with LC-hepatocellular carcinoma (HCC) and HCC. These findings imply that hepatitis virus infection and its disease status modify the effects of IFN-alpha subtypes on Th1 and Th2 immune balance in patients. Our findings should help to elucidate the mechanisms underlying successful IFN therapy for hepatitis virus infection and prevention of hepatocellular carcinogenesis.

Expression profiling of tumor necrosis factor alpha-induced apoptosis-associated genes in human solid tumor cell lines.

BACKGROUND: The induction of genes associated with cellular apoptosis by tumor necrosis factor-alpha (TNF-alpha) in human cancer cell line sof various tissue origins may characterize TNF-alpha responder cell lines/cancers. MATERIALS AND METHODS: Using quantitative real-time polymerase chain reaction (PCR), the comprehensive molecular profiling of genes downstream of the TNF-alpha receptor genes in 91 well-defined human cancer cell lines allowed us to elucidate relationships between TNF-alpha response and the genetic expression profiles of the target cell lines. RESULTS: Among the 52 genes tested, the above average expression of Akt mRNA showed significant correlation with TNF-alpha-induced susceptibility to apoptosis. In addition, multidrug resistance protein 5 (MRP5) and tumor necrosis factor receptor type 1 (TNFR1) mRNA expressions also appear to be possible markers for responsiveness to TNF-alpha. CONCLUSION: These results provide a preliminary basis for the screening for genetic markers that may help to predict a favorable therapeutic outcome, and also to identify patients who may benefit from cytokine therapy.

Different antiviral activities of IFN-alpha subtypes in human liver cell lines: synergism between IFN-alpha2 and IFN-alpha8.

We have studied the antiviral activities of five recombinant interferon-alpha (IFN-alpha) subtypes, namely IFN-alpha1, -alpha2, -alpha5, -alpha8 and -alpha10, in eight human liver cancer cell lines. The relative antiviral activities, expressed in terms of the mean 50% inhibitory concentration (IC50), were different for each cell line. In general, IFN-alpha8 was the most potent, IFN-alpha2, -alpha5, and -alpha10 were intermediately active, and IFN-alpha1 was the least potent in the all cell lines. The observed differences between the IC50s of IFN-alpha1 and -alpha8 ranged from 250- to 2200-fold in these cell lines. Thus, the ranking order of relative antiviral activity was similar but the sensitivity to the subtypes was different among these cell lines. The relative antiviral activities of the subtypes were associated with the induction of 2',5'-oligoadenylate synthetase (2',5'-OAS) in the typical hepatocellular carcinoma cell line HAK-3 but not in the cell line KYN-3. Next, we examined for synergistic antiviral activity induced by IFN-alpha2 and -alpha8 that has been reported for the hepatocellular carcinoma cell line, HepG2. Synergism was observed in three of the eight liver cell lines at an IFN-alpha2 to -alpha8 ratio of 60:40, and is considered to reflect the synergistic induction of 2',5'-OAS.

Vorinostat ameliorates impaired fear extinction possibly via the hippocampal NMDA-CaMKII pathway in an animal model of posttraumatic stress disorder.

RATIONALE: Given that impairment of fear extinction plays a pivotal role in the pathophysiology of posttraumatic stress disorder (PTSD), drugs that facilitate fear extinction may be useful as novel treatments for PTSD. Histone deacetylase (HDAC) inhibitors have recently been shown to enhance fear extinction in animal studies. OBJECTIVES: Using a single prolonged stress (SPS) paradigm, an animal model of PTSD, we examined whether the HDAC inhibitor vorinostat can facilitate fear extinction in rats, and elucidated the mechanism by which vorinostat enhanced fear extinction, focusing on the N-methyl-D-aspartate (NMDA) receptor signals in the hippocampus. METHODS: Seven days after SPS, rats received contextual fear conditioning, followed by 2-day extinction training. Vorinostat was intraperitoneally injected immediately after second extinction training session. Contextual fear response was assessed 24 h after vorinostat injection. Hippocampal tissues were dissected 2 h after vorinostat injection. The levels of mRNA and protein tested were measured by RT-PCR or western blotting, respectively. RESULTS: Systemic administration of vorinostat with extinction training significantly enhanced fear extinction in SPS rats as compared with the controls. Furthermore, vorinostat enhanced the hippocampal levels of NR2B and calcium/calmodulin kinase II (CaMKII) α and ß proteins, accompanied by increases in the levels of acetylated histone H3 and H4. CONCLUSIONS: These findings suggest that vorinostat ameliorated the impaired fear extinction in SPS rats, and this effect was associated with an increase in histone acetylation and thereby enhancement of NR2B and CaMKII in the hippocampus. Our results may provide new insight into the molecular and therapeutic mechanisms of PTSD.

Vorinostat, a histone deacetylase inhibitor, facilitates fear extinction and enhances expression of the hippocampal NR2B-containing NMDA receptor gene.

Histone acetylation, which alters the compact chromatin structure and changes the accessibility of DNA to regulatory proteins, is emerging as a fundamental mechanism for regulating gene expression. Histone deacetylase (HDAC) inhibitors increase histone acetylation and enhance fear extinction. In this study, we examined whether vorinostat, an HDAC inhibitor, facilitates fear extinction, using a contextual fear conditioning (FC) paradigm, in Sprague-Dawley rats. We found that vorinostat facilitated fear extinction. Next, the levels of global acetylated histone H3 and H4 were measured by Western blotting. We also assessed the effect of vorinostat on the hippocampal levels of NMDA receptor mRNA by real-time quantitative PCR (RT-PCR) and protein by Western blotting. 2 h after vorinostat administration, the levels acetylated histones and NR2B mRNA, but not NR1 or NR2A mRNA, were elevated in the hippocampus. The NR2B protein level was elevated 4 h after vorinostat administration. Last, we investigated the levels of acetylated histones and phospho-CREB (p-CREB) binding at the promoter of the NR2B gene using the chromatin immunoprecipitation (ChIP) assay followed by RT-PCR. The ChIP assay revealed increases in the levels of acetylated histones and they were accompanied by enhanced binding of p-CREB to its binding site at the promoter of the NR2B gene 2 h after vorinostat administration. These findings suggest that vorinostat increases the expression of NR2B in the hippocampus by enhancing histone acetylation, and this process may be implicated in fear extinction.

Enhanced hippocampal BDNF/TrkB signaling in response to fear conditioning in an animal model of posttraumatic stress disorder.

Because the majority of patients with posttraumatic stress disorder (PTSD) exhibit long-lasting traumatic fear memory, we hypothesize that enhanced fear memory consolidation is closely involved in the pathophysiology of PTSD. Brain-derived neurotrophic factor (BDNF) and its receptor, tyrosine kinase receptor B (TrkB), are crucial for hippocampal-dependent learning and memory. In particular, differential induction of BDNF gene transcripts mediated by histone acetylation plays a role in the consolidation of fear memory. In the present study, total and exon-specific mRNA and protein levels of BDNF and TrkB in the hippocampus after contextual fear conditioning (FC) were compared between rats subjected to single prolonged stress (SPS) and sham treatment. In addition, we examined the degree of histone acetylation at the promoter of each exon of the BDNF gene by chromatin immunoprecipitation (ChIP). We previously demonstrated a significant increase in contextual freezing in SPS rats. In the present study, SPS rats also showed increased total BDNF mRNA (including exons I, IV) and BDNF protein levels in the hippocampus after FC, accompanied by increased acetylation of histone H3 and H4 at the promoter of exon I and IV relative to sham-treated rats. Furthermore, the TrkB protein levels in the hippocampus of SPS rats were significantly higher than those in sham rats. These findings suggest that the enhanced levels of BDNF as well as TrkB along with epigenetic regulation of the BDNF gene during fear memory consolidation is, at least in part, associated with long-lasting fear memory in patients with PTSD.

Epigenetic regulation of BDNF gene in response to stress.

Neuronal plasticity induced by changes in synaptic morphology and function is well known to play a pivotal role in leaning and memory as well as adaptation to stress. It is suggested that these plastic changes are due to orchestration of alterations in gene expression in the brain. Recent advances in molecular biology have provided evidence that epigenetic mechanisms, such as DNA methylation and histone modification, are crucial to gene transcription in the mammalian brain. Our research group has recently investigated the involvement of histone actylation at the promoter of the brain-derived neurotrophic factor (BDNF) gene in stress-induced reduction in BDNF, as well as in fear conditioning-induced enhancement of BDNF, in the rat hippocampus. The results of the stress study demonstrated that single-immobilization stress significantly reduced the levels of total, exon I, and exon IV BDNF mRNA, and also significantly reduced acetylation levels of histone H3, but not H4, at the promoter of exons I, IV, and VI. The results of the fear conditioning study showed that footshock stress significantly increased the levels of total, exon I, and exon IV BDNF mRNA, with significantly increased acetylation levels of both histone H3 and H4, at the promoter of exons I and IV, followed by enhanced freezing to fear-context exposure. These findings suggest that changes in BDNF transcription in the rat hippocampus in response to stressful stimuli are, at least in part, regulated by histone acetylation status.

Alterations in the hippocampal glycinergic system in an animal model of posttraumatic stress disorder.

Previous studies have demonstrated that rats subjected to single prolonged stress (SPS) exhibit posttraumatic stress disorder (PTSD)-like symptoms, such as enhanced contextual fear in response to trauma-related and trauma-unrelated events. Furthermore, we previously reported that upregulation of hippocampal glycine transporter 1 (GlyT-1) mRNA after context exposure could be the initial mechanism underlying impaired fear extinction in SPS rats. To clarify the involvement of the hippocampal glycinergic system in impaired fear extinction in SPS rats, we measured the time course of changes in the duration of freezing and the hippocampal levels of Gly-T1 mRNA using contextual fear conditioning (FC) and extinction training. We also used in vivo microdialysis to measure the concentration of extracellular glycine in the hippocampus during the time interval between FC and the first context exposure. SPS rats exhibited increased and sustained contextual fear responses. The enhanced contextual fear response in SPS rats was associated with a sustained increase in hippocampal levels of Gly-T1 mRNA after FC relative to sham rats, and by a decrease in the extracellular glycine concentration. GlyT-1 mRNA levels in rats that underwent repeated extinction training were significantly lower than in rats that did not undergo extinction training. These findings indicate that reduced activity of the hippocampal glycinergic system could be closely involved in impaired fear extinction in SPS rats, suggesting that activation of the glycinergic system by d-cycloserine or GlyT-1 inhibitors may ameliorate the impairment of fear extinction.