A role for the PI-3 kinase signaling pathway in fear conditioning and synaptic plasticity in the amygdala

Behavioral plasticity

Behavioral plasticity allows animals to modulate their behavior based on experience and environmental conditions. Caenorhabditis elegans exhibits experience-dependent changes in its behavioral responses to various modalities of sensory cues, including odorants, salts, temperature, and mechanical stimulations. Most of these forms of behavioral plasticity, such as adaptation, habituation, associative learning, and imprinting, are shared with other animals. The C. elegans nervous system is considerably tractable for experimental studies-its function can be characterized and manipulated with molecular genetic methods, its activity can be visualized and analyzed with imaging approaches, and the connectivity of its relatively small number of neurons are well described. Therefore, C. elegans provides an opportunity to study molecular, neuronal, and circuit mechanisms underlying behavioral plasticity that are either conserved in other animals or unique to this species. These findings reveal insights into how the nervous system interacts with the environmental cues to generate behavioral changes with adaptive values.

Impairment of synaptic plasticity in the primary somatosensory cortex in a model of diabetic mice

Type 1 and type 2 diabetic patients experience alterations in the Central Nervous System, leading to cognitive deficits. Cognitive deficits have been also observed in animal models of diabetes such as impaired sensory perception, as well as deficits in working and spatial memory functions. It has been suggested that a reduction of insulin-like growth factor-I (IGF-I) and/or insulin levels may induce these neurological disorders. We have studied synaptic plasticity in the primary somatosensory cortex of young streptozotocin (STZ)-diabetic mice. We focused on the influence of reduced IGF-I brain levels on cortical synaptic plasticity. Unit recordings were conducted in layer 2/3 neurons of the primary somatosensory (S1) cortex in both control and STZ-diabetic mice under isoflurane anesthesia. Synaptic plasticity was induced by repetitive whisker stimulation. Results showed that repetitive stimulation of whiskers (8 Hz induction train) elicited a long-term potentiation (LTP) in layer 2/3 neurons of the S1 cortex of control mice. In contrast, the same induction train elicited a long-term depression (LTD) in STZ-diabetic mice that was dependent on NMDA and metabotropic glutamatergic receptors. The reduction of IGF-I brain levels in diabetes could be responsible of synaptic plasticity impairment, as evidenced by improved response facilitation in STZ-diabetic mice following the application of IGF-I. This hypothesis was further supported by immunochemical techniques, which revealed a reduction in IGF-I receptors in the layer 2/3 of the S1 cortex in STZ-diabetic animals. The observed synaptic plasticity impairments in STZ-diabetic animals were accompanied by decreased performance in a whisker discrimination task, along with reductions in IGF-I, GluR1, and NMDA receptors observed in immunochemical studies. In conclusion, impaired synaptic plasticity in the S1 cortex may stem from reduced IGF-I signaling, leading to decreased intracellular signal pathways and thus, glutamatergic receptor numbers in the cellular membrane.

Anti-inflammatory effect of Irisin on LPS-stimulated macrophages through inhibition of MAPK pathway

This study aimed to investigate the effect of irisin on LPS-induced inflammation in RAW 264.7 macrophages through inhibition of the mitogen-activated protein kinase (MAPK) pathway. A network pharmacology-based approach, combined with molecular docking and in vitro validation were performed to identify the biological activity, key targets, and potential pharmacological mechanisms of irisin against LPS-induced inflammation. By matching 100 potential genes of irisin with 1893 ulcerative colitis (UC) related genes, 51 common genes were obtained. Using protein-protein interaction networks (PPI) and component-target network analysis,10 core genes of irisin on UC were further identified. The results of gene ontology (GO) enrichment analysis showed that the molecular mechanisms of irisin on UC were mainly related to major enrichment in the categories of response to xenobiotic stimulus, response to the drug, and negative regulation of gene expression. Molecular docking results showed good binding activity for almost all core component targets. More importantly, MTT assay and flow cytometry results showed that LPS-induced cytotoxicity was reversed by irisin, after coincubation with irisin, the level of IL-12 and IL-23 decreased in LPS-stimulated RAW264.7 macrophages. Irisin pretreatment significantly inhibited the phosphorylation of ERK and AKT and increased the expression of PPAR alpha and PPAR gamma. LPS-induced enhancement of phagocytosis and cell clearance were reversed by irisin pretreatment. Irisin ameliorated LPS-induced inflammation by inhibiting cytotoxicity and apoptosis, and this protective effect may be mediated through the MAPK pathway. These findings confirmed our prediction that irisin plays an anti-inflammatory role in LPS-induced inflammation via the MAPK pathway.

TrkC Intracellular Signalling in the Brain Fear Network During the Formation of a Contextual Fear Memory

Learned fear is orchestrated by a brain fear network that comprises the amygdala, hippocampus and the medial prefrontal cortex. Synaptic plasticity within this network is critical for the formation of proper fear memories. Known for their role in the promotion of synaptic plasticity, neurotrophins position as obvious candidates in the regulation of fear processes. Indeed, recent evidence from our laboratory and others associates dysregulated signalling through neurotrophin-3 and its receptor TrkC with the pathophysiology of anxiety and fear-related disorders. Here, we put wild-type C57Bl/6J mice through a contextual fear conditioning paradigm in order to characterize TrkC activation and expression in the main brain regions involved in (learned) fear - amygdala, hippocampus, and prefrontal cortex - during the formation of a fear memory. We report an overall decreased activation of TrkC in the fear network during fear consolidation and reconsolidation. During reconsolidation, hippocampal TrkC downregulation was accompanied by a decrease in the expression and activation of Erk, a critical signalling pathway in fear conditioning. Moreover, we did not find evidence that the observed decrease of TrkC activation was caused by altered expression of dominant negative form of TrkC, neurotrophin-3, or the PTP1B phosphatase. Our results indicate hippocampal TrkC inactivation through Erk signalling as a potential mechanism in the regulation of contextual fear memory formation.

Functional specialization of different PI3K isoforms for the control of neuronal architecture, synaptic plasticity, and cognition

Neuronal connectivity and activity-dependent synaptic plasticity are fundamental properties that support brain function and cognitive performance. Phosphatidylinositol 3-kinase (PI3K) intracellular signaling controls multiple mechanisms mediating neuronal growth, synaptic structure, and plasticity. However, it is still unclear how these pleiotropic functions are integrated at molecular and cellular levels. To address this issue, we used neuron-specific virally delivered Cre expression to delete either p110α or p110β (the two major catalytic isoforms of type I PI3K) from the hippocampus of adult mice. We found that dendritic and postsynaptic structures are almost exclusively supported by p110α activity, whereas p110β controls neurotransmitter release and metabotropic glutamate receptor-dependent long-term depression at the presynaptic terminal. In addition to these separate functions, p110α and p110β jointly contribute to N-methyl-d-aspartate receptor-dependent postsynaptic long-term potentiation. This molecular and functional specialization is reflected in different proteomes controlled by each isoform and in distinct behavioral alterations for learning/memory and sociability in mice lacking p110α or p110β.

The effects of subchronic agmatine on passive avoidance memory, anxiety-like behavior and hippocampal Akt/GSK-3β in mice

Agmatine, a polyamine derived from l-arginine, has been suggested to modulate memory. However, the available evidence regarding the effect of agmatine on the memory of intact animals is contradictory. This study aimed to assess the dose-response effect of subchronic agmatine on passive avoidance memory and anxiety-like parameters of elevated plus maze in adult intact mice. Furthermore, considering the roles of Akt/GSK-3β signaling pathway in memory and Alzheimer's disease, the hippocampal contents of phosphorylated and total forms of Akt and GSK-3β proteins were determined using the western blot technique. Agmatine was administered intraperitoneally at the doses of 10, 20, 30, 40 and 80 mg/kg/daily to adult male NMRI mice for 10 days after which the behavioral assessments were performed. Upon completion of the passive avoidance test, the hippocampi were removed for western blot analysis to detect the phosphorylated and total levels of Akt and GSK-3β proteins. Results showed the biphasic effect of agmatine on passive avoidance memory; in lower doses (10, 20 and 30 mg/kg), agmatine impaired memory whereas in higher ones (40 and 80 mg/kg) improved it. Though, agmatine in none of the doses affected animals' anxiety-like parameters in an elevated plus maze. Moreover, the memory-improving doses of agmatine augmented Akt/GSK-3β pathway. This study showed the biphasic effect of agmatine on passive avoidance memory and an augmentation of hippocampal Akt/GSK-3β signaling pathway following the memory-improving doses of this polyamine.

A PDK-1 allosteric agonist neutralizes insulin signaling derangements and beta-amyloid toxicity in neuronal cells and in vitro

The Alzheimer's brain is affected by multiple pathophysiological processes, which include a unique, organ-specific form of insulin resistance that begins early in its course. An additional complexity arises from the four-fold risk of Alzheimer's Disease (AD) in type 2 diabetics, however there is no definitive proof of causation. Several strategies to improve brain insulin signaling have been proposed and some have been clinically tested. We report findings on a small allosteric molecule that reverses several indices of insulin insensitivity in both cell culture and in vitro models of AD that emphasize the intracellular accumulation of β-amyloid (Aβi). PS48, a chlorophenyl pentenoic acid, is an allosteric activator of PDK-1, which is an Akt-kinase in the insulin/PI3K pathway. PS48 was active at 10 nM to 1 μM in restoring normal insulin-dependent Akt activation and in mitigating Aβi peptide toxicity. Synaptic plasticity (LTP) in prefrontal cortical slices from normal rat exposed to Aβ oligomers also benefited from PS48. During these experiments, neither overstimulation of PI3K/Akt signaling nor toxic effects on cells was observed. Another neurotoxicity model producing insulin insensitivity, utilizing palmitic acid, also responded to PS48 treatment, thus validating the target and indicating that its therapeutic potential may extend outside of β-amyloid reliance. The described in vitro and cell based-in vitro coupled enzymatic assay systems proved suitable platforms to screen a preliminary library of new analogs.

Transcriptome and chromatin alterations in social fear indicate association of MEG3 with successful extinction of fear

Social anxiety disorder is characterized by a persistent fear and avoidance of social situations, but available treatment options are rather unspecific. Using an established mouse social fear conditioning (SFC) paradigm, we profiled gene expression and chromatin alterations after the acquisition and extinction of social fear within the septum, a brain region important for social fear and social behaviors. Here, we particularly focused on the successful versus unsuccessful outcome of social fear extinction training, which corresponds to treatment responsive versus resistant patients in the clinics. Validation of coding and non-coding RNAs revealed specific isoforms of the long non-coding RNA (lncRNA) Meg3 regulated, depending on the success of social fear extinction. Moreover, PI3K/AKT was differentially activated with extinction success in SFC-mice. In vivo knockdown of specific Meg3 isoforms increased baseline activity of PI3K/AKT signaling, and mildly delayed social fear extinction. Using ATAC-Seq and CUT&RUN, we found alterations in the chromatin structure of specific genes, which might be direct targets of lncRNA Meg3.

Molecular and Biochemical Pathways Encompassing Diabetes Mellitus and Dementia

Diabetes mellitus is a major metabolic disorder that has now emerged as an epidemic, and it affects the brain through an array of pathways. Diabetes mellitus patients can develop pathological changes in the brain, which eventually take the shape of mild cognitive impairment progressing to Alzheimer's Disease. A number of preclinical and clinical studies demonstrate this fact, and it comes out to be those molecular pathways such as amyloidogenesis, oxidative stress, inflammation, and impaired insulin signaling are identical in diabetes mellitus and dementia. However, the critical player involved in the vicious cycle of diabetes mellitus and dementia is insulin, whose signaling, when impaired in diabetes mellitus (both type 1 and 2), leads to a decline in cognition, although other pathways are also essential contributors. Moreover, it is not only that diabetes mellitus patients indicate cognitive decline at a later stage; many Alzheimer's Disease patients also reflect symptoms of diabetes mellitus, thus creating a vicious cycle inculcating a web of complex molecular mechanisms and hence categorizing Alzheimer's Disease as 'brain diabetes'. Thus, it is practical to suggest that anti-diabetic drugs are beneficial in Alzheimer's Disease; but only smaller trials, not the larger ones, have showcased positive outcomes mainly because of the late onset of therapy. Therefore, it is extremely important to develop more of such molecules that target insulin in dementia patients along with such methods that diagnose impaired insulin signaling and the associated cognitive decline so that early therapy may be initiated and the progression of the disease be prevented.

The Cellular Mechanisms of Dopamine Modulation on the Neuronal Network Oscillations in the CA3 Area of Rat Hippocampal Slices

Network oscillations at γ frequency band (30-80 Hz), generated by the interaction between inhibitory interneurons and excitatory neurons, have been proposed to be associated with higher brain functions such as learning and memory. Dopamine (DA), one of the major CNS transmitters, modulates hippocampal γ oscillations but the intracellular mechanisms involved remain elusive. In this study, we recorded kainate-induced γ oscillations in the CA3 area of rat hippocampal slices, and found that DA strongly enhanced γ power, which was largely blocked by dopamine receptor 1 (DR1) antagonist SCH23390, receptor tyrosine kinase (RTK) inhibitor UNC569 and ERK inhibitor U0126, partially blocked by D2/3R antagonist raclopride, PKA inhibitor H89 and PI3K inhibitor wortmannin, but not affected by AKT inhibitor TCBN or NMDAR antagonist D-AP5. Our results indicate that DA-mediated γ enhancement is involved in the activation of signaling pathway of DR1/2-RTK-ERK. Our data demonstrate a strong, rapid modulation of DA on hippocampal γ oscillations and provide a new insight into cellular mechanisms of DA-mediated γ oscillations.

Implications of Phosphoinositide 3-Kinase-Akt (PI3K-Akt) Pathway in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the foremost type of dementia that afflicts considerable morbidity and mortality in aged population. Several transcription molecules, pathways, and molecular mechanisms such as oxidative stress, inflammation, autophagy, and immune system interact in a multifaceted way that disrupt physiological processes (cell growth, differentiation, survival, lipid and energy metabolism, endocytosis) leading to apoptosis, tauopathy, β-amyloidopathy, neuron, and synapse loss, which play an important role in AD pathophysiology. Despite of stupendous advancements in pathogenic mechanisms, treatment of AD is still a nightmare in the field of medicine. There is compelling urgency to find not only symptomatic but effective disease-modifying therapies. Recently, phosphoinositide 3-kinase (PI3K) and Akt are identified as a pathway triggered by diverse stimuli, including insulin, growth factors, cytokines, and cellular stress, that link amyloid-β, neurofibrillary tangles, and brain atrophy. The present review aims to explore and analyze the role of PI3K-Akt pathway in AD and agents which may modulate Akt and have therapeutic prospects in AD. The literature was researched using keywords "PI3K-Akt" and "Alzheimer's disease" from PubMed, Web of Science, Bentham, Science Direct, Springer Nature, Scopus, and Google Scholar databases including books. Articles published from 1992 to 2021 were prioritized and analyzed for their strengths and limitations, and most appropriate ones were selected for the purpose of review. PI3K-Akt pathway regulates various biological processes such as cell proliferation, motility, growth, survival, and metabolic functions, and inhibits many neurotoxic mechanisms. Furthermore, experimental data indicate that PI3K-Akt signaling might be an important therapeutic target in treatment of AD.

Investigating the molecular mechanisms of learning and memory using Caenorhabditis elegans

Learning is an essential biological process for survival since it facilitates behavioural plasticity in response to environmental changes. This process is mediated by a wide variety of genes, mostly expressed in the nervous system. Many studies have extensively explored the molecular and cellular mechanisms underlying learning and memory. This review will focus on the advances gained through the study of the nematode Caenorhabditis elegans. C. elegans provides an excellent system to study learning because of its genetic tractability, in addition to its invariant, compact nervous system (~300 neurons) that is well-characterised at the structural level. Importantly, despite its compact nature, the nematode nervous system possesses a high level of conservation with mammalian systems. These features allow the study of genes within specific sensory-, inter- and motor neurons, facilitating the interrogation of signalling pathways that mediate learning via defined neural circuits. This review will detail how learning and memory can be studied in C. elegans through behavioural paradigms that target distinct sensory modalities. We will also summarise recent studies describing mechanisms through which key molecular and cellular pathways are proposed to affect associative and non-associative forms of learning.

Molecular and cellular pathways contributing to brain aging

Aging is the leading risk factor for several age-associated diseases such as neurodegenerative diseases. Understanding the biology of aging mechanisms is essential to the pursuit of brain health. In this regard, brain aging is defined by a gradual decrease in neurophysiological functions, impaired adaptive neuroplasticity, dysregulation of neuronal Ca2+ homeostasis, neuroinflammation, and oxidatively modified molecules and organelles. Numerous pathways lead to brain aging, including increased oxidative stress, inflammation, disturbances in energy metabolism such as deregulated autophagy, mitochondrial dysfunction, and IGF-1, mTOR, ROS, AMPK, SIRTs, and p53 as central modulators of the metabolic control, connecting aging to the pathways, which lead to neurodegenerative disorders. Also, calorie restriction (CR), physical exercise, and mental activities can extend lifespan and increase nervous system resistance to age-associated neurodegenerative diseases. The neuroprotective effect of CR involves increased protection against ROS generation, maintenance of cellular Ca2+ homeostasis, and inhibition of apoptosis. The recent evidence about the modem molecular and cellular methods in neurobiology to brain aging is exhibiting a significant potential in brain cells for adaptation to aging and resistance to neurodegenerative disorders.

Polyamines: Functions, Metabolism, and Role in Human Disease Management

Putrescine, spermine, and spermidine are the important polyamines (PAs), found in all living organisms. PAs are formed by the decarboxylation of amino acids, and they facilitate cell growth and development via different cellular responses. PAs are the integrated part of the cellular and genetic metabolism and help in transcription, translation, signaling, and post-translational modifications. At the cellular level, PA concentration may influence the condition of various diseases in the body. For instance, a high PA level is detrimental to patients suffering from aging, cognitive impairment, and cancer. The levels of PAs decline with age in humans, which is associated with different health disorders. On the other hand, PAs reduce the risk of many cardiovascular diseases and increase longevity, when taken in an optimum quantity. Therefore, a controlled diet is an easy way to maintain the level of PAs in the body. Based on the nutritional intake of PAs, healthy cell functioning can be maintained. Moreover, several diseases can also be controlled to a higher extend via maintaining the metabolism of PAs. The present review discusses the types, important functions, and metabolism of PAs in humans. It also highlights the nutritional role of PAs in the prevention of various diseases.

Targeting PI3K-AKT/mTOR signaling in the prevention of autism

PI3K-AKT/mTOR signaling pathway represents an essential signaling mechanism for mammalian enzyme-related receptors in transducing signals or biological processes such as cell development, differentiation, cell survival, protein synthesis, and metabolism. Upregulation of the PI3K-AKT/mTOR signaling pathway involves many human brain abnormalities, including autism and other neurological dysfunctions. Autism is a neurodevelopmental disorder associated with behavior and psychiatric illness. This research-based review discusses the functional relationship between the neuropathogenic factors associated with PI3K-AKT/mTOR signaling pathway. Ultimately causes autism-like conditions associated with genetic alterations, neuronal apoptosis, mitochondrial dysfunction, and neuroinflammation. Therefore, inhibition of the PI3K-AKT/mTOR signaling pathway may have an effective therapeutic value for autism treatment. The current review also summarizes the involvement of PI3K-AKT/mTOR signaling pathway inhibitors in the treatment of autism and other neurodegenerative disorders.

PI3K-Akt Signaling in the Basolateral Amygdala Facilitates Traumatic Stress Enhancements in Fear Memory

BACKGROUND

A core symptom of posttraumatic stress disorder is persistent fear memory, which can be defined as fear memory that is resistant to updating, inhibition, or extinction. posttraumatic stress disorder emerges after traumatic stress exposure, but neurobiological mechanisms via which traumatic stress leads to persistent fear memory are not well defined. Akt signaling within the amygdala (Amy) is enhanced with traumatic stress, and phosphatidylinositol kinase 3 (PI3K) activation of Akt within the basolateral Amy (BLA) has been implicated as critical to fear memory formation. These findings raise the possibility that traumatic stress enhances PI3K→Akt signaling in the BLA, which leads to persistent fear memory.

METHODS

To test this hypothesis, rats were exposed to traumatic stress using the single prolonged stress model, and changes in Akt phosphorylation were assayed in the Amy at 0 and 30 minutes after fear conditioning (FC). In a separate experiment, we inhibited PI3K→Akt signaling in the BLA prior to FC and observed the effect this had on acquisition, expression, and extinction of FC in stressed and control rats.

RESULTS

Enhanced Akt phosphorylation in the Amy at both time points was observed in stressed rats, but not in control rats. PI3K→Akt inhibition in the BLA had no effect on freezing in control rats but decreased freezing during extinction training and testing in stressed rats.

CONCLUSION

These findings suggest that PI3K→Akt signaling in the BLA could be a mechanism via which traumatic stress leads to fear memory that is resistant to extinction.

Spermidine-induced improvement of memory consolidation involves PI3K/Akt signaling pathway

Spermidine (SPD) is an endogenous polyamine that plays a facilitatory role in memory acquisition and consolidation. Memory consolidation occurs immediately after learning and again around 3-6 hours later. Current evidence indicates that the polyamine binding site at the NMDA receptor (NMDAr) mediates the effects of SPD on memory. While NMDAr activation increases brain-derived neurotrophic factor (BDNF) release, no study has investigated whether BDNF-activated signaling pathways, such as the phosphatidylinositol 3-kinase (PI3K)/Akt pathway play a role in SPD-induced improvement of memory consolidation. Therefore, the aim of the current study was to evaluate whether the TrkB receptor and the PI3K/Akt pathway are involved in the facilitatory effect of SPD on memory consolidation. Male Wistar rats were trained in the contextual conditioned fear task. SPD, ANA-12 (TrkB antagonist), and LY294002 (PI3K inhibitor) were administered immediately after training. The animals were tested 24 h after training. We found that SPD improved fear memory consolidation and that both ANA-12 and LY294002 prevented the facilitatory effect of SPD on memory. These results suggest that SPD-induced improvement of memory consolidation involves the activation of the TrkB receptor and PI3K/Akt pathway.

PTEN Is Required for The Anti-Epileptic Effects of AMPA Receptor Antagonists in Chronic Epileptic Rats

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is one of the ligand-gated ion channels for glutamate, which is an important player in the generation and spread of seizures. The efficacy of AMPAR functionality is regulated by the trafficking, synaptic targeting, and phosphorylation. Paradoxically, AMPAR expression and its phosphorylation level are decreased in the epileptic hippocampus. Therefore, the roles of AMPAR in seizure onset and neuronal hyperexcitability in ictogenesis remain to be elucidated. In the present study, we found that AMPAR antagonists (perampanel and GYKI 52466) decreased glutamate ionotropic receptor AMPA type subunit 1 (GRIA1) surface expression in the epileptic rat hippocampus. They also upregulated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression and restored to basal levels the upregulated phosphoinositide 3-kinase (PI3K)/AKT1 phosphorylations. Dipotassium bisperoxovanadium(pic) dihydrate (BpV(pic), a PTEN inhibitor) co-treatment abolished the anti-epileptic effects of perampanel and GYKI 52466. Therefore, our findings suggest that PTEN may be required for the anti-epileptic effects of AMPAR antagonists.

The physiological modulation by intracellular kinases of hippocampal γ-oscillation in vitro

Hippocampal network oscillations at gamma frequency band (γ-oscillation, 20-80 Hz) are synchronized synaptic activities generated by the interactions between the excitatory and inhibitory interneurons and are associated with higher brain function such as learning and memory. Despite extensive studies about the modulation of intracellular kinases on synaptic transmission and plasticity, little is known about the effects of these kinases on γ-oscillations. In this study, we examined the effects of several critical intracellular kinases such as cyclic AMP-dependent protein kinase (PKA), protein kinase B (PKB)/Akt, protein kinase C (PKC), extracellular-regulated protein kinases (ERK) and AMP-activated protein kinase (AMPK), known to regulate synaptic transmission, on hippocampal γ-oscillations in vitro. We found that AMPK inhibitor but not PKA, PKC, or ERK inhibitor, strongly enhanced the power of γ-oscillation (γ-power) and that Akt inhibitor weakly increased γ-power. Western blot analysis confirmed that AMPK inhibitor reduced the expression of p-AMPK but not total AMPK. By using the slice whole cell voltage-clamp technique, we found that AMPK inhibitor increased the frequency but not amplitude of spontaneous inhibitory postsynaptic currents (sIPSC) and had no effect on either frequency or amplitude of spontaneous excitatory postsynaptic currents (sEPSC). Therefore, AMPK activation negatively modulates hippocampal γ-oscillation via modulation of the inhibitory neurons.

PI3K activation within ventromedial prefrontal cortex regulates the expression of drug-seeking in two rodent species

Phosphatidylinositide 3-kinases (PI3Ks) are intracellular signal transducer enzymes that recruit protein kinase B (aka Akt) to the cell membrane, the subsequent activation of which regulates many cellular functions. PI3K/Akt activity is up-regulated within mesocorticolimbic structures in animal models of alcoholism, but less is known regarding PI3K/Akt activity in animal models of cocaine addiction. Given that prefrontal cortex (PFC) is grossly dysregulated in addiction, we studied how cocaine affects protein indices of PFC PI3K/Akt activity in rat and mouse models and examined the relevance of PI3K activity for cocaine-related learning. Immunoblotting of mouse medial PFC at 3 weeks withdrawal from a cocaine-sensitization regimen (seven injections of 30 mg/kg, intraperitoneal [IP]) revealed increased kinase activity, as did immunoblotting of tissue from the ventral PFC of rats with a history of long-access intravenous cocaine self-administration (0.25 mg/0.1 mL infusion; 10 days of 6 h/d cocaine access). Interestingly, increased Akt phosphorylation was observed in rat ventromedial PFC at both 3- and 30-day withdrawal only in animals re-exposed to cocaine-associated cues. A conditioned place-preference paradigm in mice and a cue-elicited drug-seeking test in rats were conducted to determine the functional relevance for elevated PI3K activity for addiction-related behavior. In both cases, an intra-PFC infusion of the PI3K inhibitor wortmannin (50μM) reduced drug-seeking behavior. Taken together, this cross-species, interdisciplinary, study provides convincing evidence that cocaine history produces an enduring increase in PI3K/Akt-dependent signaling within the more ventral aspect of the PFC that is relevant to behavioral reactivity to drug-associated cues/contexts. As such, PI3K inhibitors may well serve as an effective strategy for reducing drug cue reactivity and craving in cocaine addiction.

Metformin reverses the schizophrenia-like behaviors induced by MK-801 in rats

Schizophrenia is known to be a complex and disabling psychiatric disorder. Dopamine receptor antagonists have a significant therapeutic effect in improving the positive symptoms that are associated with the illness. Therefore, dopamine receptor antagonists are commonly used in the treatment of schizophrenia; however, they do not achieve satisfactory results in improving negative symptoms and cognitive impairment. Metformin, widely known as an antidiabetic drug, has been found to enhance spatial memory formation and improve anxiety-like behaviors in rodents. Metformin's neuroprotective effect has been well documented in several neurological disorders including Alzheimer's disease, Parkinson's disease, strokes, Huntington's disease, and seizures. In the present study, we used a rat model to explore the effect of metformin on schizophrenia-like behaviors induced by MK-801 (dizocilpine), an N-methyl-D-aspartate (NMDA) receptor antagonist. We found that the pre-pulse inhibition (PPI) deficit caused by MK-801 could be alleviated by metformin. The hyperlocomotion in the open field test induced by chronic treatment of MK-801 was reversed by administration of metformin. Metformin has no effect on the baseline level of anxiety in normal naive rats, while metformin could relieve the anxiety-like behaviors in MK-801-treatment rats, though this effect is not reaching a significant level. Additionally, metformin could significantly ameliorate working memory impairments induced by MK-801. Moreover, the increased level of phosphorylation of Akt and GSK3β in the frontal cortex induced by MK-801 was normalized by metformin. In conclusion, our results demonstrate that metformin improved schizophrenia-like symptoms in rats, and is therefore a potential agent for the treatment of schizophrenia.

Kinase and Phosphatase Engagement Is Dissociated Between Memory Formation and Extinction

Associative long-term memories (LTMs) support long-lasting behavioral changes resulting from sensory experiences. Retrieval of a stable LTM by means of a large number of conditioned stimulus (CS) alone presentations produces inhibition of the original memory through extinction. Currently, there are two opposing hypotheses to account for the neural mechanisms supporting extinction. The unlearning hypothesis posits that extinction affects the original memory trace by reverting the synaptic changes supporting LTM. On the contrary, the new learning hypothesis proposes that extinction is simply the formation of a new associative memory that inhibits the expression of the original one. We propose that detailed analysis of extinction-associated molecular mechanisms could help distinguish between these hypotheses. Here we will review experimental evidence regarding the role of protein kinases and phosphatases (K&P) on LTM formation and extinction. Even though K&P regulate both memory processes, their participation appears to be dissociated. LTM formation recruits kinases, but is constrained by phosphatases. Memory extinction presents a more diverse molecular landscape, requiring phosphatases and some kinases, but also being constrained by kinase activity. Based on the available evidence, we propose a new theoretical model for memory extinction: a neuronal segregation of K&P supports a combination of time-dependent reversible inhibition of the original memory [CS-unconditioned stimulus (US)], with establishment of a new associative memory trace (CS-noUS).

Mechanisms of fear learning and extinction: synaptic plasticity-fear memory connection

RATIONALE

The ability to memorize threat-associated cues and subsequently react to them, exhibiting escape or avoidance responses, is an essential, often life-saving behavioral mechanism that can be experimentally studied using the fear (threat) conditioning training paradigm. Presently, there is substantial evidence supporting the Synaptic Plasticity-Memory (SPM) hypothesis in relation to the mechanisms underlying the acquisition, retention, and extinction of conditioned fear memory.

OBJECTIVES

The purpose of this review article is to summarize findings supporting the SPM hypothesis in the context of conditioned fear control, applying the set of criteria and tests which were proposed as necessary to causally link lasting changes in synaptic transmission in corresponding neural circuits to fear memory acquisition and extinction with an emphasis on their pharmacological diversity.

RESULTS

The mechanisms of synaptic plasticity in fear circuits exhibit complex pharmacological profiles and satisfy all four SPM criteria-detectability, anterograde alteration, retrograde alteration, and mimicry.

CONCLUSION

The reviewed findings, accumulated over the last two decades, provide support for both necessity and sufficiency of synaptic plasticity in fear circuits for fear memory acquisition and retention, and, in part, for fear extinction, with the latter requiring additional experimental work.

PI3K Signaling in Neurons: A Central Node for the Control of Multiple Functions

Phosphoinositide 3-kinase (PI3K) signaling contributes to a variety of processes, mediating many aspects of cellular function, including nutrient uptake, anabolic reactions, cell growth, proliferation, and survival. Less is known regarding its critical role in neuronal physiology, neuronal metabolism, tissue homeostasis, and the control of gene expression in the central nervous system in healthy and diseased states. The aim of the present work is to review cumulative evidence regarding the participation of PI3K pathways in neuronal function, focusing on their role in neuronal metabolism and transcriptional regulation of genes involved in neuronal maintenance and plasticity or on the expression of pathological hallmarks associated with neurodegeneration.

PI3K-AKT-GSK3β-CREB signaling pathway regulates anxiety-like behavior in rats following alcohol withdrawal

BACKGROUND

Alcohol abuse and anxiety disorders often occur concurrently, but their underlying cellular mechanisms remain unclear. Neuroadaptation within the medial prefrontal cortex (mPFC) have been implicated in the molecular mechanisms underlying alcohol drinking behavior and withdrawal.

METHODS

A chronic alcohol exposure rat model (35 consecutive days of 10% alcohol intake and 48 h of withdrawal) was established, then, wortmannin (0.5 µg/side) was injected bilaterally into the mPFC. The elevated plus maze (EPM) and open field test (OFT) were used to assess anxiety-like behavior. Western blot assays were used to assess protein levels.

RESULTS

We found that anxiety-like behavior peaked approximately 6 h after alcohol withdrawal. However, wortmannin greatly decreased alcohol intake and attenuated anxiety-like behavior in the alcohol exposure rats. Moreover, the PI3K-AKT-GSK3β signaling pathway was activated after alcohol withdrawal, and phosphorylation of the downstream cAMP response element-binding protein (CREB) was increased. Wortmannin uniformly reversed PI3K-AKT-GSK3β-CREB pathway phosphorylation.

LIMITATIONS

The downstream GSK3β activity was not intervened and a single dose level of wortmannin was used.

CONCLUSION

Our results suggest that activating the PI3K-AKT-GSK3β-CREB pathway in the mPFC is an important contributor to the molecular mechanisms underlying alcohol withdrawal. PI3K signaling pathway inhibitors are thus potential candidates for treating alcohol abuse.

Dietary polyphenols promote resilience against sleep deprivation-induced cognitive impairment by activating protein translation

Previous evidence has suggested that dietary supplementation with a bioactive dietary polyphenol preparation (BDPP) rescues impairment of hippocampus-dependent memory in a mouse model of sleep deprivation (SD). In the current study, we extend our previous evidence and demonstrate that a mechanism by which dietary BDPP protects against SD-mediated cognitive impairment is via mechanisms that involve phosphorylation of the mammalian target of rapamycin complex 1 and its direct downstream targets, including the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) and the ribosomal protein S6 kinase β-1 (p70S6K). In additional mechanistic studies in vitro, we identified the brain bioavailable phenolic metabolites derived from the metabolism of dietary BDPP that are responsible for the attenuation of SD-mediated memory impairments. On the basis of high-throughput bioavailability studies of brain bioavailable metabolites after dietary BDPP treatment, we found that select polyphenol metabolites [ e.g., cyanidin-3'- O-glucoside and 3-(3'-hydroxyphenyl) propionic acid] were able to rescue mTOR and p70S6K phosphorylation in primary cortico-hippocampal neuronal cultures, as well as rescue 4E-BP1 phosphorylation in response to treatment with 4EGI-1, a specific inhibitor of eIF4E-eIF4G interaction. Our findings reveal a previously unknown role for dietary polyphenols in the rescue of SD-mediated memory impairments via mechanisms involving the promotion of protein translation.-Frolinger, T., Smith, C., Cobo, C. F., Sims, S., Brathwaite, J., de Boer, S., Huang, J., Pasinetti, G. M. Dietary polyphenols promote resilience against sleep deprivation-induced cognitive impairment by activating protein translation.

Secreted amyloid precursor protein alpha activates neuronal insulin receptors and prevents diabetes-induced encephalopathy

Secreted amyloid precursor protein alpha (sAPPα) is a potent neurotrophin in the CNS but a dedicated receptor has not been found. However, protein interactions involving amyloid beta (Aβ), a peptide cleaved from the same parent peptide as sAPPα, indicate that insulin receptors (IRs) could be a target of amyloid peptides. In this study, in vitro analysis of cortical neuronal cultures revealed that exogenous sAPPα increased IR phosphorylation in the absence of insulin. Furthermore, in an APP overexpressing mouse model, sAPPα bound IRs in the cortex with significantly greater binding in hypoinsulinemic animals. To further examine the effects of sAPPα on the diabetic brain, we next rendered sAPPα overexpressing mice insulin depleted and found that sAPPα blocked aberrant tau phosphorylation (T231) in cortical tissue after 16 weeks diabetes. sAPPα overexpression also prevented hyperphosphorylation of AKT/GSK3 and activation of the unfolded protein response (UPR). In total, these data show sAPPα binds and activates neuronal IRs and that sAPPα has a protective effect on diabetic brain tissue.

Peptides Acting as Cognitive Enhancers

The aim of this paper is to present an overview of three peptides that, by improving synaptic function, enhance learning and memory in laboratory rodents. We summarize their structure, their mechanisms of action, and their effects on synaptic and cognitive function. First we describe FGL, a peptide derived from the neural cell adhesion molecule which improves cognition by the activation of the PKC pathway that triggers an activity-dependent delivery of AMPA receptors to the synapses. Then we describe PTD4-PI3KAc peptide that by activating PI3K signaling pathway it promotes synapse and spine formation and enhances hippocampal dependent memory. Lastly, we describe a new peptide derived from the well-known tumor suppressor PTEN that prevents pathological interactions between PTEN and PDZ proteins at synapses during exposure to Amyloid beta. This action prevents memory deterioration in mouse model of Alzheimer's disease. Together, this review indicates how learning and memory can be improved by manipulating synaptic function and number through pharmacological treatment with peptides, and it establishes synaptic function as a valid target for cognitive enhancement.

Insulin signaling: An opportunistic target to minify the risk of Alzheimer's disease

Alzheimer's disease (AD) is progressive neurodegenerative disorder characterized by accumulation of senile plaques, neurofibrillary tangles (NFT) and neurodegeneration. The diabetes mellitus (DM) is one of the risk factors for AD pathogenesis by impairment in insulin signaling and glucose metabolism in central as well as peripheral system. Insulin resistance, impaired glucose and lipid metabolism are leading to the Aβ (Aβ) aggregation, Tau phosphorylation, mitochondrial dysfunction, oxidative stress, protein misfolding, memory impairment and also mark over Aβ transport through central to peripheral and vice versa. Several pathways, like enzymatic degradation of Aβ, forkhead box protein O1 (FOXO) signaling, insulin signaling shared common pathological mechanism for both AD and DM. Recent evidence showed that hyperinsulinemia and hyperglycemia affect the onset and progression of AD differently. Some researchers have suggested that hyperglycemia influences vascular tone, while hyperinsulinemia may underlie mitochondrial deficit. The objective of this review is to determine whether existing evidence supports the concept that impairment in insulin signaling and glucose metabolism play an important role in pathogenesis of AD. In the first part of this review, we tried to explain the interconnecting link between AD and DM, whereas the second part includes more information on insulin resistance and its involvement in AD pathogenesis. In the final part of this review, we have focused more toward the AD treatment by targeting insulin signaling like anti-diabetic, antioxidant, nutraceuticals and dietary supplements. To date, more researches should be done in this field in order to explore the pathways in insulin signaling, which might ameliorate the treatment options and reduce the risk of AD due to DM.

Opisthorchiasis in Western Siberia: Epidemiology and distribution in human, fish, snail, and animal populations

Opisthorchiasis is a widespread helminth infection in Russia. The largest opisthorchiasis endemic focus in the world is the Ob river watershed in Western Siberia. The main causative agent of this condition is the liver fluke, Opisthorchis felineus. In addition, another liver fluke species in the Opisthorchiidae family, Metorchis bilis, causes a symptomatically similar disease, metorchiasis. Despite a long research history going back to 1927, opisthorchiasis remains a serious problem in Russia, and numerous questions related to the epidemiology of these liver fluke infections and their patterns of distribution in Western Siberia, the causes of high prevalence in different populations, and the prognosis of the epidemiological situation remain to be answered. In this review, we first briefly describe the life cycle of O. felineus and then summarize the available published data on the epidemiological aspects of O. felineus infection among populations in Western Siberia. Additionally, the geographical distribution and rates of infection with the two major small liver flukes, O. felineus and M. bilis, in the intermediate (Bithyniidae snails and cyprinid fish) and definitive (humans, wild and domestic carnivorous animals and birds) hosts are described to assess their role in the transmission cycle. Moreover, species in the genus Opisthorchis and the genus Metorchis that have been reported in carnivorous mammals and birds in Western Siberia are listed and their potential to serve as the agents of opisthorchiasis transmission is discussed.

PI3-kinase cascade has a differential role in acquisition and extinction of conditioned fear memory in juvenile and adult rats

The basolateral amygdala (BLA), medial prefrontal cortex (mPFC) circuit, plays a crucial role in acquisition and extinction of fear memory. Extinction of aversive memories is mediated, at least in part, by the phosphoinositide-3 kinase (PI3K)/Akt pathway in adult rats. There is recent interest in the neural mechanisms that mediate fear and extinction in juvenile animals and whether these mechanisms are distinctive from those in adult animals. In the present study, we examined (1) changes in phosphorylation of Akt in the BLA and mPFC after fear conditioning and extinction in juvenile and adult rats and (2) the effect of BLA and mPFC localized inhibition of the PI3K following acquisition and extinction of contextual fear memory. Our results show that Akt phosphorylation is increased following acquisition of contextual fear learning in the BLA but not in the mPFC in adult and juvenile rats. Extinction learning was not associated with changes in Akt phosphorylation. Although there were no differences in the pattern of phosphorylation of Akt either in adult or juvenile rats, microinjection of the PI3K inhibitor, LY294002, into the BLA or mPFC elicited differential effects on fear memory acquisition and extinction, depending on the site and timing of the microinjection, as well as on the age of the animal. These results suggest that PI3K/Akt has a differential role in formation, retrieval, and extinction of contextual fear memory in juvenile and adult animals, and point to developmental differences between adult and juvenile rats in mechanisms of extinction.

15-Deoxy-Δ12,14-prostaglandin J2 induced neurotoxicity via suppressing phosphoinositide 3-kinase

15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) induces neuronal cell death via apoptosis independently of its receptors. 15d-PGJ₂ inhibits growth factor-induced cell proliferation of primary astrocytes via down-regulating phosphoinositide 3-kinase (PI3K)-Akt pathway. Although 15d-PGJ₂-reduced cell viability is accompanied with attenuation of the PI3K signaling in neuroblastoma, it has not been sufficiently clarified how 15d-PGJ₂ induces cell death in primary neurons. Here, we found that 15d-PGJ₂ exhibited neurotoxicity via inhibiting the PI3K signaling in the primary culture of rat cortical neurons. A PI3K inhibitor induced neuronal cell death regardless serum throughout maturation, confirming that PI3K is required for neuronal cell survival. The inhibitor disrupted neuronal cell bodies, shortened neurites thinly, damaged plasma membranes and activated caspase-3 similarly to 15d-PGJ₂. Little additive or synergistic neurotoxicity was detected between 15d-PGJ₂ and the PI3K inhibitor. A PI3K activator prevented neurons from undergoing the 15d-PGJ₂-induced cell death in vitro. In vivo, the PI3K signaling is required for contextual memory retrieval, which was impaired by bilateral injection of 15d-PGJ₂ into hippocampus. The activator suppressed the 15d-PGJ₂-impaired memory retrieval significantly. In neurons as well as primary astrocytes and neuroblastomas, 15d-PGJ₂ exhibited cytotoxicity via suppressing the PI3K-Akt pathway in vivo and in vitro.

Traumatic stress causes distinctive effects on fear circuit catecholamines and the fear extinction profile in a rodent model of posttraumatic stress disorder

Central catecholamines regulate fear memory across the medial prefrontal cortex (mPFC), amygdala (AMYG), and hippocampus (HPC). However, inadequate evidence exists to address the relationships among these fear circuit areas in terms of the fear symptoms of posttraumatic stress disorder (PTSD). By examining the behavioral profile in a Pavlovian fear conditioning paradigm together with tissue/efflux levels of dopamine (DA) and norepinephrine (NE) and their reuptake abilities across the fear circuit areas in rats that experienced single prolonged stress (SPS, a rodent model of PTSD), we demonstrated that SPS-impaired extinction retrieval was concomitant with the changes of central DA/NE in a dissociable manner. For tissue levels, diminished DA and increased NE were both observed in the mPFC and AMYG. DA efflux and synaptosomal DA transporter were consistently reduced in the AMYG/vHPC, whereas SPS reduced NE efflux in the infralimbic cortex and synaptosomal NE transporter in the mPFC. Furthermore, a lower expression of synaptosomal VMAT2 was observed in the mPFC, AMYG, and vHPC after SPS. Finally, negative correlations were observed between retrieval freezing and DA in the mPFC/AMYG; nevertheless, the phenomena became invalid after SPS. Our results suggest that central catecholamines are crucially involved in the retrieval of fear extinction in which DA and NE play distinctive roles across the fear circuit areas.

The ethanolic extract of the Eclipta prostrata L. ameliorates the cognitive impairment in mice induced by scopolamine

ETHNOPHARMACOLOGICAL RELEVANCE

Eclipta prostrata L. (Asteraceae) has been prescribed for whole body nourishment and nervine tonic in Asia. However, the effects of E. prostrata in learning and memory have not been fully explored.

AIM OF THE STUDY

To scientifically elucidate the effects of E. prostrata on cognitive functions, we examined whether E. prostrata could ameliorate a cholinergic blockade-induced memory impairment, and we also investigated the effects of E. prostrata on the synaptic plasticity in the hippocampus.

MATERIALS AND METHODS

Memory impairment was induced by scopolamine, a cholinergic muscarinic receptor antagonist. The anti-amnesic effects of the ethanolic extract of Eclipta prostrata L. (EEEP) were measured in mice by the passive avoidance, Y-maze and Morris water maze tasks. To test the effects of EEEP on synaptic plasticity, we measured long-term potentiation (LTP) in the hippocampus. We also studied several signaling molecules related to learning and memory, such as phosphorylated protein kinase B (Akt) or phosphorylated glycogen synthase kinase-3β (GSK-3β).

RESULTS

In the passive avoidance task, EEEP (50 or 100mg/kg, p.o.) significantly ameliorated the shortened step-through latency induced by scopolamine. EEEP (100mg/kg, p.o.) also showed significant increase in alternation behavior during the Y-maze task. In the Morris water maze task, scopolamine-induced a decrease in both the swimming time within the target zone and the number of crossings where the platform had been placed were significantly reversed by EEEP (50 or 100mg/kg, p.o.). Moreover, EEEP (100μg/ml) significantly enhanced hippocampal LTP without affecting basal synaptic transmission. The administration of EEEP (100mg/kg) increased the phosphorylation levels of Akt and GSK-3β in the hippocampal region.

CONCLUSION

These results suggest that EEEP has memory-ameliorating activity against scopolamine-induced cognitive impairment and facilitates LTP in the hippocampus. This could be, at least in part, mediated by the activation of the Akt-GSK-3β signaling pathway.

Brain-Derived Neurotrophic Factor in Amygdala-Dependent Learning

The neurotrophin brain-derived neurotrophic factor (BDNF) has recently emerged as a possible molecular mediator of activity-dependent synaptic plasticity underlying learning and memory. Long-term potentiation (LTP) within the hippocampus and hippocampally dependent behaviors has been the primary model for examining the role of BDNF in learning and memory. However, these studies are limited by an incomplete understanding of the complex behavioral function of hippocampal circuitry, making it difficult to unravel the molecular machinery responsible for the formation and storage of these memories. In contrast, the amygdala and its role in Pavlovian fear conditioning promise to provide us with new insights into the mechanisms of BDNF-mediated synaptic plasticity during the learning and memory process. This article reviews the different levels of research on BDNF in learning and memory. The focus is primarily on the use of Pavlovian fear conditioning as a learning model that allows for the examination of the role of BDNF in the amygdala, following a single learning session and within a well-understood neural circuit.

Membrane-tethered AKT kinase regulates basal synaptic transmission and early phase LTP expression by modulation of post-synaptic AMPA receptor level

The serine/threonine kinase AKT/PKB plays a fundamental role in a wide variety of neuronal functions, including neuronal cell development, axonal growth, and synaptic plasticity. Multiple evidence link AKT signaling pathways to regulation of late phase long-term synaptic plasticity, synaptogenesis, and spinogenesis, as well as long-term memory formation. Nevertheless, the downstream effectors mediating the effects of AKT on early phase long-term potentiation (eLTP) are currently unknown. Here we report that using different regimes of pharmacological activation and inhibition of AKT activity in acute hippocampal slices, we found that AKT regulates the post-synaptic expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA) receptors affecting solely the expression of eLTP, with no effect on its induction and maintenance. We further show that both maintenance of basal synaptic activity and expression of eLTP require plasma membrane tethering by activated AKT and that basal synaptic activity may be regulated via the direct effects of AKT1 on the expression level of post-synaptic AMPA receptors bypassing the canonical AKT signaling. Finally, we establish that eLTP expression requires the involvement of both the canonical AKT signaling pathways and the direct effect of AKT1 on AMPA receptor activity/expression in the post-synaptic membrane. © 2016 Wiley Periodicals, Inc.

Impairing autophagy in retinal pigment epithelium leads to inflammasome activation and enhanced macrophage-mediated angiogenesis

Age-related decreases in autophagy contribute to the progression of age-related macular degeneration (AMD). We have now studied the interaction between autophagy impaired in retinal pigment epithelium (RPE) and the responses of macrophages. We find that dying RPE cells can activate the macrophage inflammasome and promote angiogenesis. In vitro, inhibiting rotenone-induced autophagy in RPE cells elicits caspase-3 mediated cell death. Co-culture of damaged RPE with macrophages leads to the secretion of IL-1β, IL-6 and nitrite oxide. Exogenous IL-6 protects the dysfunctional RPE but IL-1β causes enhanced cell death. Furthermore, IL-1β toxicity is more pronounced in dysfunctional RPE cells showing reduced IRAK3 gene expression. Co-culture of macrophages with damaged RPE also elicits elevated levels of pro-angiogenic proteins that promote ex vivo choroidal vessel sprouting. In vivo, impaired autophagy in the eye promotes photoreceptor and RPE degeneration and recruitment of inflammasome-activated macrophages. The degenerative tissue environment drives an enhanced pro-angiogenic response, demonstrated by increased size of laser-induced choroidal neovascularization (CNV) lesions. The contribution of macrophages was confirmed by depletion of CCR2⁺ monocytes, which attenuates CNV in the presence of RPE degeneration. Our results suggest that the interplay between perturbed RPE homeostasis and activated macrophages influences key features of AMD development.

Expression of phosphatidylinositol-3 kinase and effects of inhibitor Wortmannin on expression of tumor necrosis factor-α in severe acute pancreatitis associated with acute lung injury

BACKGROUND

Acute lung injury (ALI) is a common and serious complication of severe acute pancreatitis (SAP). The study aimed to investigate the protective effect and mechanism of phosphatidylinositol-3 kinase (PI3K) inhibitor Wortmannin in SAP associated with ALI.

METHODS

Ninety rats were randomly divided into three groups: sham operation (SO) group (n=30), SAP group (n=30), and SAP+Wortmannin (SAP+W) group (n=30). SAP model was induced by retrograde injection of 4% sodium taurocholate into the biliopancreatic duct of rats. The rate of lung water content, myeloperoxidase (MPO), matrix metalloproteinase 9 (MMP-9), protein kinase B (PKB), abdphosphorylation of protein kinase B (P-PKB) activity in the lung tissue were evaluated.

RESULTS

In the SAP group, the p-PKB expression in the lung tissue began to rise at 3 hours after modeling, and peaked at 12 hours (P<0.05); the rate of lung water content, MPO and TNF-α activity were also gradually increased, and the degree of lung lesion gradually increased (P<0.05). In the SAP+Wortmannin group, the p-PKB expression in the lung tissue began to rise at 3 hours after modeling, and peaked at 12 hours; it was higher than that in the SO group (P<0.05), but significantly lower than that in the SAP group (P<0.05). The rest indicators in the SAP+Wortmannin group were also significantly decreased as compared with the SAP group (P<0.05).

CONCLUSIONS

The expression of phosphatidylinositol-3 kinase/protein kinase B was elevated in severe pancreatitis rats with lung injury. This suggested that PI3K signal transduction pathway is involved in the control and release of proinflammatory cytokines TNF-α, which may play an important role in the pathogenesis of severe acute pancreatitis associated with lung injury. This finding indicated that Wortmannin can block the PI3K signal transduction pathway, and inhibit the release of inflammatory factor TNF-α.