Distinct encoding and post-encoding representational formats contribute to episodic sequence memory formation.

In episodic encoding, an unfolding experience is rapidly transformed into a memory representation that binds separate episodic elements into a memory form to be later recollected. However, it is unclear how brain activity changes over time to accommodate the encoding of incoming information. This study aimed to investigate the dynamics of the representational format that contributed to memory formation of sequential episodes. We combined representational similarity analysis and multivariate decoding approaches on EEG data to compare whether "category-level" or "item-level" representations supported memory formation during the online encoding of a picture triplet sequence and offline, in the period that immediately followed encoding. The findings revealed a gradual integration of category-level representation during the online encoding of the picture sequence and a rapid item-based neural reactivation of the encoded sequence at the episodic offset. However, we found that only memory reinstatement at episodic offset was associated with successful memory retrieval from long-term memory. These results suggest that post-encoding memory reinstatement is crucial for the rapid formation of unique memory for episodes that unfold over time. Overall, the study sheds light on the dynamics of representational format changes that take place during the formation of episodic memories.

Contextual incongruency triggers memory reinstatement and the disruption of neural stability.

Schemas, or internal representation models of the environment, are thought to be central in organising our everyday life behaviour by giving stability and predictiveness to the structure of the world. However, when an element from an unfolding event mismatches the schema-derived expectations, the coherent narrative is interrupted and an update to the current event model representation is required. Here, we asked whether the perceived incongruence of an item from an unfolding event and its impact on memory relied on the disruption of neural stability patterns preceded by the neural reactivation of the memory representations of the just-encoded event. Our study includes data from two different experiments whereby human participants (N = 33, 26 females and N = 18, 16 females, respectively) encoded images of objects preceded by trial-unique sequences of events depicting daily routine. We found that neural stability patterns gradually increased throughout the ongoing exposure to a schema-consistent episode, which was corroborated by the re-analysis of data from two other experiments, and that the brain stability pattern was interrupted when the encoding of an object of the event was incongruent with the ongoing schema. We found that the decrease in neural stability for low-congruence items was seen at ∼1000 ms from object encoding onset and that it was preceded by an enhanced N400 ERP and an increased degree of neural reactivation of the just-encoded episode. Current results offer new insights into the neural mechanisms and their temporal orchestration that are engaged during online encoding of schema-consistent episodic narratives and the detection of incongruencies.

Gamma amplitude is coupled to opposed hippocampal theta-phase states during the encoding and retrieval of episodic memories in humans.

Computational models and in vivo studies in rodents suggest that the emergence of gamma activity (40-140 Hz) during memory encoding and retrieval is coupled to opposed-phase states of the underlying hippocampal theta rhythm (4-9 Hz).1,2,3,4,5,6,7,8,9,10 However, direct evidence for whether human hippocampal gamma-modulated oscillatory activity in memory processes is coupled to opposed-phase states of the ongoing theta rhythm remains elusive. Here, we recorded local field potentials (LFPs) directly from the hippocampus of 10 patients with epilepsy, using depth electrodes. We used a memory encoding and retrieval task whereby trial unique sequences of pictures depicting real-life episodes were presented, and 24 h later, participants were asked to recall them upon the appearance of the first picture of the encoded episodic sequence. We found theta-to-gamma cross-frequency coupling that was specific to the hippocampus during both the encoding and retrieval of episodic memories. We also revealed that gamma was coupled to opposing theta phases during both encoding and recall processes. Additionally, we observed that the degree of theta-gamma phase opposition between encoding and recall was associated with participants' memory performance, so gamma power was modulated by theta phase for both remembered and forgotten trials, although only for remembered trials the dominant theta phase was different for encoding and recall trials. The current results offer direct empirical evidence in support of hippocampal theta-gamma phase opposition models in human long-term memory and provide fundamental insights into mechanistic predictions derived from computational and animal work, thereby contributing to establishing similarities and differences across species.

Post-encoding Reactivation Is Related to Learning of Episodes in Humans.

Prior animal and human studies have shown that post-encoding reinstatement plays an important role in organizing the temporal sequence of unfolding episodes in memory. Here, we investigated whether post-encoding reinstatement serves to promote the encoding of "one-shot" episodic learning beyond the temporal structure in humans. In Experiment 1, participants encoded sequences of pictures depicting unique and meaningful episodic-like events. We used representational similarity analysis on scalp EEG recordings during encoding and found evidence of rapid picture-elicited EEG pattern reinstatement at episodic offset (around 500 msec post-episode). Memory reinstatement was not observed between successive elements within an episode, and the degree of memory reinstatement at episodic offset predicted later recall for that episode. In Experiment 2, participants encoded a shuffled version of the picture sequences from Experiment 1, rendering each episode meaningless to the participant but temporally structured as in Experiment 1, and we found no evidence of memory reinstatement at episodic offset. These results suggest that post-encoding memory reinstatement is akin to the rapid formation of unique and meaningful episodes that unfold over time.

miR-224 Regulates the Aggressiveness of Hepatoma Cells Through the IL-6/STAT3/SMAD4 Pathway.

BACKGROUND: Previous studies have shown that miR-224 regulates the progression of liver cancer. The aim of this study was to investigate the underlying mechanisms. METHODS: The miR-224, p-STAT3 and SMAD4 expression levels were checked with tissue or/and serum samples of HCC patients by qRT-PCR or IHC methods. The regulatory role of IL-6 in p-STAT3 and SMAD4 was investigated by Western-blot. The targeted gene of miR-224 was verified by both Western-blot and luciferase reporter assay. Furthermore, the carcinogenesis of miR-224 in HCC was investigated by cell experiments in vitro and mouse xenograft model and in vivo imaging in vivo. RESULTS: It was found miR-224 was elevated in both tissue and serum of HCC patients. The p-STAT3 expression was higher but the SMAD4 was lower in the HCC tumor tissues. Moreover, IL-6 can induce the p-STAT3/STAT3 and miR-224 expression in HCC cells and STAT3 played the bridge role between IL-6 and miR-224. Target gene studies found miR-224 targeted the 3'UTR of SMAD4. Finally, the promoting roles of miR-224in the growth, proliferation, invasion and migration of HCC were discovered by in vitro and in vivo studies. CONCLUSION: It implies that miR-224 may potentially represent a new target for developing novel anti-HCC therapeutics.

Mechanistic Investigation on the Regulation of FABP1 by the IL-6/miR-603 Signaling in the Pathogenesis of Hepatocellular Carcinoma.

BACKGROUND: Abnormal lipid metabolism is closely associated with the invasiveness and metastasis of cancer. Fatty acid-binding proteins (FABPs) play essential roles in lipid metabolism, and miRNAs can affect lipid metabolism by targeting FABPs. However, the exact mechanism is unknown. METHODS: FABP1 expression in HCC tissues was analyzed by immunochemistry with tissue microarrays. The lipid content was detected by Oil Red O staining, and the interaction between FABP1 and free fatty acid (FFA) was studied by a labeling and tracking method. miRNA arrays were used to detect the expression of miRNAs in IL-6-stimulated HCC cells. miR-603 expression was verified by qPCR. The proteins were checked by Western blot analysis. Gain and loss function evaluation was assessed by lentivirus and miRNA mimic transfection in Huh-7 cells, while reactive oxygen species (ROS) were detected by fluorescence. RESULTS: FABP1 expression was significantly decreased in approximately 90% (81/90) of HCC patients. FABP1 expression in adjacent tissues was closely associated with overall survival. Meanwhile, lipid was abundant in the adjacent tissues, yet significantly reduced in HCC tissues. FABP1 and FFA can promote each other for being uptaken by Huh-7 cells. FABP1 overexpression induced apoptosis and inhibited the proliferation, migration, invasion, and metastasis of Huh-7 cells. IL-6 treatment affected the expression of miRNAs, and miR-603 was overexpressed in HCC tissues. Also, miR-603 overexpression promoted the proliferation, migration, invasion, and metastasis of Huh-7 cells. Bioinformatic analysis predicted that miR-603 targets the 3'-UTR region of FABP1. However, miR-603 overexpression inhibited the expression of the FABP1 but increased the CPT1A, PPAR-α, and SREBP1 expressions. FABP1 overexpression reduced ROS in HCC cells, while miR-603 can reverse these effects. CONCLUSION: Our results indicate that in the pathogenesis of HCC, IL-6 induces miR-603 expression, which subsequently inhibits FABP1 expression, promotes the lipid metabolism- and synthesis-related proteins, and finally increases the cellular oxidative stress level and leads to the metastasis of HCC.

Behavioural and neurophysiological signatures in the retrieval of individual memories of recent and remote real-life routine episodic events.

Autobiographical memory (AM) has been largely investigated as the ability to recollect specific events that belong to an individual's past. However, how we retrieve real-life routine episodes and how the retrieval of these episodes changes with the passage of time remain unclear. Here, we asked participants to use a wearable camera that automatically captured pictures to record instances during a week of their routine life and implemented a deep neural network-based algorithm to identify picture sequences that represented episodic events. We then asked each participant to return to the lab to retrieve AMs for single episodes cued by the selected pictures 1 week, 2 weeks and 6-14 months after encoding while scalp electroencephalographic (EEG) activity was recorded. We found that participants were more accurate in recognizing pictured scenes depicting their own past than pictured scenes encoded in the lab, and that memory recollection of personally experienced events rapidly decreased with the passing of time. We also found that the retrieval of real-life picture cues elicited a strong and positive 'ERP old/new effect' over frontal regions and that the magnitude of this ERP effect was similar throughout memory tests over time. However, we observed that recognition memory induced a frontal theta power decrease and that this effect was mostly seen when memories were tested after 1 and 2 weeks but not after 6-14 months from encoding. Altogether, we discuss the implications for neuroscientific accounts of episodic retrieval and the potential benefits of developing individual-based AM exploration strategies at the clinical level.

MicroRNA-23b-3p promotes pancreatic cancer cell tumorigenesis and metastasis via the JAK/PI3K and Akt/NF-κB signaling pathways.

MicroRNA (miR)-23b-3p plays an important role in tumor growth, proliferation, invasion and migration in pancreatic cancer (PC). However, the function and mechanistic role of miR-23b-3p in the development of PC remains largely unknown. In the present study, the miR-23b-3p levels in the serum of patients with PC were found to be elevated, and the phosphorylation levels of Janus kinase (JAK)2, PI3K, Akt and NF-κВ were found to be upregulated. In addition, miR-23b-3p was induced in response to interleukin-6 (IL-6), which is known to be involved in the progression of PC. Overexpression of miR-23b-3p, on the other hand, activated the JAK/PI3K and Akt/NF-κB signaling pathways in PC cells, as evidenced by miR-23b-3p-induced upregulation of phosphorylated (p-)JAK2, p-PI3K, p-Akt and p-NF-κВ, as well as the downregulation of PTEN; and these effects were found to be reversible by miR-23b-3p inhibition. Furthermore, miR-23b-3p was found to downregulate PTEN by directly targeting the 3'-untranslated region of PTEN mRNA. Notably, in an in vivo xenograft mouse model, overexpression of miR-23b-3p accelerated PC cell-derived tumor growth, activated the JAK/Akt/NF-κВ signaling pathway and promoted liver metastasis. In contrast, knockdown of miR-23b-3p suppressed tumor growth and metastasis as well as JAK/Akt/NF-κВ signaling activity. In vivo imaging of the mice further confirmed the metastasis promoting role of miR-23b-3p in PC. These results suggested that miR-23b-3p enhances PC cell tumorigenesis and metastasis, at least, partially via the JAK/PI3K and Akt/NF-κB signaling pathways. Therefore, targeting miR-23b-3p or the JAK/PI3K and Akt/NF-κB signalings may be potential therapeutic strategy against PC.

Up-regulation of miR-155 contributes to TNF-mediated hepatocyte apoptosis in acute liver failure.

BACKGROUND/AIMS: Acute liver failure (ALF) is due to severe immune response, resulting in massive apoptosis/necrosis of hepatocytes. The precise mechanism has not been explored yet. MATERIALS AND METHODS: The mouse with ALF model was induced by D-GalN/LPS; the hepatic miRNAs expression profile was evaluated by miRNA microarray and verified by RT-PCR. During the ALF in mice, the miR-155 expression was detected in the liver as well as in spleen. Then the correlation between miR-155 and inflammatory cytokines was evaluated. Furthermore, the miR-155 expression in activated Raw264.7 cells and apoptotic hepatocytes was also studied. Finally, the regulatory roles of miR-155 in TNF expression of apoptotic hepatocytes were shown. RESULTS: It was shown that miRNAs changed in the mice with ALF relating to hepatocytes apoptosis/necrosis; the selected miRNAs were confirmed with RT-PCR. miR-155 was up-regulated, but miR-698, -720, and -329 were down-regulated. Moreover, hepatic miR-155 was up-regulated at all-time points in the liver, but only at 7 h in spleen of mice with ALF. A significant correlation was observed between hepatic miR-155 and TNF/IL-6 in mice with ALF, which was supported by the findings in vitro showing up-regulated miR-155 in Raw264.7 cells and Hepa1-6 cells under LPS or D-GalN+TNF induction, respectively. Moreover, a correlation was observed between miR155 and TNF levels in vivo and in vitro. CONCLUSION: These data demonstrate that miR-155 regulates TNF-mediated hepatocyte apoptosis in ALF, which provides some useful information in both basic and clinical researches.

Upregulated exosomic miR­23b­3p plays regulatory roles in the progression of pancreatic cancer.

Pancreatic cancer (PC) is one of the most lethal malignances. Identification of biomarkers for early diagnosis of PC is a key imperative. MicroRNAs (miRNAs) have been shown to be valuable biomarkers in the context of several cancers. Exosomes refer to vesicles released by the tumor cells at the early stage of disease. Thus, detection of miRNA in exosomes can be used as a potential biomarker for PC. In this study, we profiled serum levels of miRNAs in patients with chronic pancreatitis (CP) and PC; the role of miR­23b­3p in PC progression was assessed in vitro. Additionally, we assessed, the expression of miR­23b­3p in exosomes isolated from serum samples and assessed the correlation between the expression of miR­23b­3p and carbohydrate antigen 19-9 (CA19-9). Three serum samples each were randomly selected from healthy controls (n=20), and patients with CP (n=18) and PC (n=16) for miRNA microarray profiling. The dysregulated miRNAs were confirmed using qRT­PCR. Four dysregulated miRNAs common to patients with CP and PC were identified on miRNA microarray analysis and confirmed by qRT­PCR. miR­23b­3p level was consistently higher in serum samples from PC patients as compared to those from healthy controls and CP patients (p<0.05). Overexpression of miR­23b­3p promoted proliferation, migration, and invasion capability of PC cells in vitro (p<0.05). Furthermore, miR­23b­3p was upregulated in exosomes of PC serum samples and the supernatant of pancreatic cancer cells (PANC­1), and the expression levels of miR­23b­3p were associated with those of serum CA19-9 levels. This study provides insights into the potential role of miR­23b­3p as a novel biomarker and target for treatment of PC.

Profiling of downregulated blood-circulating miR-150-5p as a novel tumor marker for cholangiocarcinoma.

Altered microRNA (miRNA) expression plays a role in cholangiocarcinoma (CCA) development; thus, detection of blood-circulating miRNAs could be useful as CCA markers. This study profiled serum miRNA levels in patients with primary sclerosing cholangitis (PSC) and CCA and then assessed the role of miR-150-5p in CCA progression in vitro. Three samples were randomly selected from each of 50 sera of healthy controls, 30 PSC sera, and 28 CCA sera with matched bile samples for miRNA microarray profiling. The dysregulated miRNAs were confirmed using qRT-PCR, and miR-150-5p was selected for further in vitro and ex vivo studies. The miRNA microarray identified three dysregulated miRNAs in both CCA and PSC samples, while miR-150-5p level was consistently lower in CCA sera, bile, and tissues than in normal control and PSC sera (P < 0.05). Furthermore, levels of miR-150-5p were associated with serum carbohydrate antigen 19-9 (CA19-9) levels and CCA pathological grade. Bioinformatic Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses showed that miR-150-5p could regulate hand-full gene pathways, including cancer pathway (P < 0.01). However, overexpression of miR-150-5p inhibited proliferation, migration, and invasion capability of CCA cells (P < 0.05). Luciferase reporter assay showed that miR-150-5p bound to an oncogene Ets including gene-1 (ELK1), and Western blot data confirmed that miR-150-5p suppressed ELK1 expression in CCA cell lines. These results suggest that reduced miR-150-5p expression could contribute to CCA development and progression due to uncontrolled ELK1 expression. Thus, further study could evaluate miR-150-5p as a novel target and predictor for CCA prevention and treatment.

[Regulatory role of serum miR-224 in invasiveness and metastasis of cholangiocarcinoma].

OBJECTIVE: To investigate the expression profile of serum micro (mi)RNAs in cholangiocarcinoma (CCA) and investigate the regulatory contribution of miRNAs to the invasive and metastasis. METHODS: Microarray analysis was carried out using serum samples collected from 30 patients with CCA, bile duct cancer tissues and the corresponding normal tissues collected from 10 patients, and serum samples from 50 healthy volunteers. The miRNAs identified as dysregulated in CCA were verified by RT-PCR. Focused analysis on miR-224 was carried out using the human CCA cell lines HCCC-9810 and RBE to investigate the role of this miRNA in IL-6 expression (using IL-6 induction), cell growth, invasiveness and metastasis (using miR-224 mimic transfection). The one-way ANOVA test was used for statistical analysis. RESULTS: Forty-three miRNAs were dysregulated in CCA (vs. non-CCA, P<0.01), of which 22 were upregulated and 21 were downregulated. RT-PCR data showed that the miR-224 was significantly upregulated in serum as well as in cancer tissue from CCA patients. Induction of HCCC-9810 and RBE cells with IL-6 showed a time-dependent upregulation of miR-224. Furthermore, the HCCC-9810 and RBE cells transfected with miR-224 mimic showed enhanced cell growth, invasiveness and migratory ability. CONCLUSION: IL-6 may promote the invasive and metastatic properties of CCA through upregulated miR-224. Studies of the differentially expressed serum miRNAs in CCA may help to further elucidate the pathogenic processes of this disease and aid in the development of a novel and effective therapeutic strategy.