Influence of mTOR signaling pathway on ketamine-induced injuries in the hippocampal neurons of rats

Histidine modulates amyloid-like assembly of peptide nanomaterials and confers enzyme-like activity

Amyloid-like assembly is not only associated with pathological events, but also leads to the development of novel nanomaterials with unique properties. Herein, using Fmoc diphenylalanine peptide (Fmoc-F-F) as a minimalistic model, we found that histidine can modulate the assembly behavior of Fmoc-F-F and induce enzyme-like catalysis. Specifically, the presence of histidine rearranges the β structure of Fmoc-F-F to assemble nanofilaments, resulting in the formation of active site to mimic peroxidase-like activity that catalyzes ROS generation. A similar catalytic property is also observed in Aβ assembled filaments, which is correlated with the spatial proximity between intermolecular histidine and F-F. Notably, the assembled Aβ filaments are able to induce cellular ROS elevation and damage neuron cells, providing an insight into the pathological relationship between Aβ aggregation and Alzheimer's disease. These findings highlight the potential of histidine as a modulator in amyloid-like assembly of peptide nanomaterials exerting enzyme-like catalysis.

Molecular mechanisms of rapid-acting antidepressants: New perspectives for developing antidepressants

Major depressive disorder (MDD) is a chronic relapsing psychiatric disorder. Conventional antidepressants usually require several weeks of continuous administration to exert clinically significant therapeutic effects, while about two-thirds of the patients are prone to relapse of symptoms or are completely ineffective in antidepressant treatment. The recent success of the N-methyl-D-aspartic acid (NMDA) receptor antagonist ketamine as a rapid-acting antidepressant has propelled extensive research on the action mechanism of antidepressants, especially in relation to its role in synaptic targets. Studies have revealed that the mechanism of antidepressant action of ketamine is not limited to antagonism of postsynaptic NMDA receptors or GABA interneurons. Ketamine produces powerful and rapid antidepressant effects by affecting α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors, adenosine A1 receptors, and the L-type calcium channels, among others in the synapse. More interestingly, the 5-HT2A receptor agonist psilocybin has demonstrated potential for rapid antidepressant effects in depressed mouse models and clinical studies. This article focuses on a review of new pharmacological target studies of emerging rapid-acting antidepressant drugs such as ketamine and hallucinogens (e.g., psilocybin) and briefly discusses the possible strategies for new targets of antidepressants, with a view to shed light on the direction of future antidepressant research.

Effects of recurrent ketamine exposure on brain histopathology in juvenile rats

BACKGROUND

Ketamine (KET) is a commonly used anesthetic agent. However, several previous studies reported that KET leads to neuronal damage in neurodevelopmental stages and has neuroprotective effects. The present experimental study aimed to determine the undesirable histopathological effects of KET in the cerebral cortex, striatum, and hippocampus after recurrent KET administration in juvenile rats.

METHODS

After ethical approval was obtained, 32 juvenile male Wistar Albino rats were randomized into four groups: 1 mg/kg serum saline intraperitoneally (i.p.), 5 mg/kg KET i.p., 20 mg/kg KET i.p., and 50 mg/kg KET i.p. KET was administered for three consecutive days at three-h intervals in three doses. Ten days after the last KET dose, the rats were sacrificed. Cerebral hemispheres were fixed. Hematoxylin and eosin stain was used for morphometric analysis. Hippocampi were evaluated by immunohistochemistry with anticleaved caspase-3 antibodies. Statistical analysis was conducted with SPSS 21 software using the ANOVA test and Bonferroni post hoc analysis method.

RESULTS

The experimental study findings revealed no difference between the groups' cell counts or sizes in cortical morphometry. No degenerative changes were observed in pyramidal and granular cells in the striatum. Mild gliosis was observed in the 20 mg/kg and 50 mg/kg KET administration groups. Immuno-histo-chemical analysis was conducted to determine apoptosis in the CA1 region of the hippocampus and revealed that caspase-3 positivity increased with the KET dose. However, there was no statistical difference between the groups. While it was lower than the control group in the 5 mg/kg KET group, it was similar to the control group in the 20 mg/kg KET group and higher in the 50 mg/kg KET group (p > 0.05).

DISCUSSION

: Repetitive KET exposure did not significantly affect juvenile cerebral morphology and apoptosis in hippocampal cells.

Hydrogen Sulfide Attenuates High-Fat Diet-Induced Obesity: Involvement of mTOR/IKK/NF-κB Signaling Pathway

Obesity has become a public health epidemic worldwide and is associated with many diseases with high mortality including hypertension, diabetes, and heart disease. High-fat diet (HFD)-induced energy imbalance is one of the primary causes of obesity, but the underlying mechanisms are not fully elucidated. Our study showed that HFD reduced the level of hydrogen sulfide (H₂S) and its catalytic enzyme cystathionine β-synthase (CBS) in mouse hypothalamus and plasma. We found that HFD activated mTOR, IKK/NF-κB, the main pathway regulating inflammation. Activation of inflammatory pathway promoted the production of pro-inflammatory cytokines including IL-6, IL-1β, and TNF-α, which caused cell damage and loss in the hypothalamus. The disturbance of the hypothalamic neuron circuits resulted in body weight gain in HFD-induced mice. Importantly, we also showed that restoration of H₂S level with NaHS or activation of CBS with SAMe attenuated HFD-induced activation of mTOR, IKK/NF-κB signaling, which reduced the inflammation and the neuronal cell loss in the hypothalamus, and also inhibited body weight gain in mice. The same effects were obtained by inhibiting mTOR or NF-κB, which suggested that mTOR and NF-κB were the critical molecular factors involved in hypothalamic inflammation. Taken together, this study identified that HFD-induced hypothalamus inflammation plays a critical role in the development of obesity. Moreover, the inhibition of hypothalamic inflammation by regaining H₂S level could be a potential therapeutic to prevent the development of obesity.

Dysregulation of adult hippocampal neuroplasticity in major depression: pathogenesis and therapeutic implications

Major depressive disorder (MDD) was previously hypothesized to be a disease of monoamine deficiency in which low levels of monoamines in the synaptic cleft were believed to underlie depressive symptoms. More recently, however, there has been a paradigm shift toward a neuroplasticity hypothesis of depression in which downstream effects of antidepressants, such as increased neurogenesis, contribute to improvements in cognition and mood. This review takes a top-down approach to assess how changes in behavior and hippocampal-dependent circuits may be attributed to abnormalities at the molecular, structural, and synaptic level. We conclude with a discussion of how antidepressant treatments share a common effect in modulating neuroplasticity and consider outstanding questions and future perspectives.

Synergistic Effect and Mechanism of Apoptosis Induction by Morphine and the HIV-1gp120V3 Loop in Hippocampal Neurons

HIV-associated neurocognitive disorders (HAND) are a collective name for neurological disorders associated with HIV-1 infection. The incidence and severity of HAND are increased by concomitant opioid use disorder, such as heroin and morphine abuse. Our previous study showed that the HIV-1 envelope protein gp120 and morphine synergistically induce apoptosis in rat hippocampal neurons. However, the underlying mechanism remains unclear. We hypothesized that morphine and gp120 activated the neuronal apoptosis signaling pathway via their typical membrane receptors. If they shared key signaling molecules, their induction of neuronal apoptosis could be inhibited by blocking these targets. We found that morphine and gp120V3 loop synergistically induced hippocampal neuron apoptosis, mediated by activating the extracellular signal-regulated kinase (ERK) pathway, increasing the intracellular Ca2 + concentration and expression of caspase-, and reducing the mitochondrial membrane potential. The ERK inhibitor PD98509 and the phosphatidylinositol 3-kinase activator IGF-1 blocked this effect. These results indicate that ERK plays a crucial role in the apoptosis of hippocampal neurons in HAND.

Ketamine: Neuroprotective or Neurotoxic?

Ketamine, a non-competitive N-methyl-D-aspartate receptor (NMDAR) antagonist, has been employed clinically as an intravenous anesthetic since the 1970s. More recently, ketamine has received attention for its rapid antidepressant effects and is actively being explored as a treatment for a wide range of neuropsychiatric syndromes. In model systems, ketamine appears to display a combination of neurotoxic and neuroprotective properties that are context dependent. At anesthetic doses applied during neurodevelopmental windows, ketamine contributes to inflammation, autophagy, apoptosis, and enhances levels of reactive oxygen species. At the same time, subanesthetic dose ketamine is a powerful activator of multiple parallel neurotrophic signaling cascades with neuroprotective actions that are not always NMDAR-dependent. Here, we summarize results from an array of preclinical studies that highlight a complex landscape of intracellular signaling pathways modulated by ketamine and juxtapose the somewhat contrasting neuroprotective and neurotoxic features of this drug.

Autophagy Alters Bladder Angiogenesis and Improves Bladder Hyperactivity in the Pathogenesis of Ketamine-Induced Cystitis in a Rat Model

Simple Summary

Long-term ketamine abuse may increase urinary frequency, nocturia, urgency, bladder pain, dysuria, and sometimes hematuria. Evaluation of the pathophysiological mechanism of bladder voiding dysfunction in ketamine-induced cystitis (KIC) patients is a critical step for therapy. This study uses autophagy inducer (rapamycin, mTOR inhibitor) and inhibitor (wortmannin, PI3K-III inhibitor) to identify the role of autophagy in bladder angiogenesis alteration and bladder hyperactivity improvement.

Abstract

The present study attempts to elucidate whether autophagy alters bladder angiogenesis, decreases inflammatory response, and ameliorates bladder hyperactivity—thereby influencing bladder function in ketamine-induced cystitis (KIC). In our methodology, female Sprague-Dawley (S-D) rats were randomly divided into the control group, the ketamine group, the ketamine+rapamycin group, and the ketamine+wortmannin group. The bladder function, contractile activity of detrusor smooth muscle, distribution of autophagosome and autolysosome, total white blood cells (WBCs) and leukocyte differential counts, the expressions of autophagy-associated protein, angiogenesis markers, and signaling pathway molecules involved in KIC were tested, respectively. The data revealed that treatment with ketamine significantly results in bladder overactivity, enhanced interstitial fibrosis, impaired endothelium, induced eosinophil-mediated inflammation, swelling, and degraded mitochondria and organelles, inhibited angiogenesis, and elevated the phosphorylation of Akt. However, treatment with rapamycin caused an inhibitory effect on vascular formation, removed ketamine metabolites, decreased the eosinophil-mediated inflammation, and ameliorated bladder hyperactivity, leading to improve bladder function in KIC. Moreover, wortmannin treatment reduced basophil-mediated inflammatory response, improved bladder angiogenesis by increasing capillary density and VEGF expression, to reverse antiangiogenic effect to repair KIC. In conclusion, these findings suggested that autophagy could modulate inflammatory responses and angiogenesis, which improved bladder function in KIC.

Ketamine induces endoplasmic reticulum stress in rats and SV-HUC-1 human uroepithelial cells by activating NLRP3/TXNIP aix

Many clinical studies have been conducted on ketamine-associated cystitis. However, the underlying mechanisms of ketamine-associated cystitis still remain unclear. Bladder tissues of rats were stained by Hematoxylin and Eosin (HE). The viability of human uroepithelial cells (SV-HUC-1 cells) was determined by cell counting kit-8 (CCK-8). Apoptosis and reactive oxygen species (ROS) were examined by flow cytometry. Additionally, the expressions of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β and IL-18 were respectively determined by reverse transcription quantitative (RTq)-PCR and enzyme-linked immunosorbent assay (ELISA). The mRNA and protein levels of B-cell lymphoma/leukemia-2 (Bcl2), Bcl-2-associated X protein (Bax), cleaved caspase 3, glucose-regulated protein 78 (GRP78), CCAAT/enhancer binding protein homologous protein (CHOP), NOD-like receptor 3 (NLRP3), thioredoxin-interacting protein (TXNIP), Catalase and MnSOD were examined by RT-qPCR and Western blot. Small interfering RNA target TXNIP transfection was performed using Lipofectamine™ 2000. We found that ketamine effectively damaged bladder tissues of rats and promoted apoptosis through regulating the expression levels of GRP78, CHOP, Bcl-2, Bax and cleaved Caspase-3 proteins in vivo and in vitro. NLRP3 inflammatory body and TXNIP were activated by ketamine, which was supported by the changes in TNF-α, IL-6, IL-1 and IL-18 in vivo and in vitro. Furthermore, knocking down TXNIP reversed the effects of ketamine on apoptosis and NLRP3 inflammatory body in SV-HUC-1 cells. Meanwhile, the changes of Catalase and MnSOD showed that ROS was enhanced by ketamine, however, such an effect was ameliorated by down-regulation of TXNIP in SV-HUC-1 cells. Ketamine promoted cell apoptosis and induced inflammation in vivo and in vitro by regulating NLRP3/TXNIP aix.

Crocin promotes osteogenesis differentiation of bone marrow mesenchymal stem cells

Crocin has plentiful pharmacological effects, but its role in osteogenesis differentiation of bone marrow mesenchymal stem cells (BMSCs) is unexplored. This study explored the effect of crocin on osteogenesis differentiation, in order to provide evidence for its clinical application. In cell experiments, human BMSCs (hBMSCs) were induced by osteogenesis differentiation medium or crocin. In animal experiments, steroid-induced osteonecrosis of the femoral head (SANFH) rat models was established using lipopolysaccharide (LPS) plus methylprednisolone (MPS), and then treated with crocin. The osteogenesis differentiation capacity of hBMSCs was analyzed by alkaline phosphatase (ALP) and alizarin red S staining. Histopathological changes in rat femoral head tissues were observed by hematoxylin and eosin (H&E) staining. The expression levels of RUNX2, COL1A1, OCN, and GSK-3β in hBMSCs and rat femoral head tissues were measured by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot (WB) analysis. ALP and alizarin red S staining demonstrated that LAP activity and calcium nodules were increased in hBMSCs treated with crocin. From H&E staining results, femoral head tissues of SANFH models showed typical osteonecrosis, which could be ameliorated by crocin. WB and qRT-PCR assays detected that the expression levels of RUNX2, COL1A1, and OCN in hBMSCs and femoral head tissues of models were obviously increased after crocin treatment, while GSK-3β phosphorylation was reduced. In general, the action of crocin was concentration-dependent. Crocin might be beneficial to the recovery of SANFH through accelerating osteogenesis differentiation of BMSCs, which might be a novel therapy for related diseases.

Neonatal ketamine exposure-induced hippocampal neuroapoptosis in the developing brain impairs adult spatial learning ability

Ketamine exposure can lead to selective neuroapoptosis in the developing brain. p66ShcA, the cellular adapter protein expressed selectively in immature neurons, is a known pro-apoptotic molecule that triggers neuroapoptosis when activated. Sprague-Dawley rats at postnatal day 7 were subcutaneously injected in the neck with ketamine 20 mg/kg, six times at 2-hour intervals. At 0, 1, 3, and 6 hours after final injection, western blot assay was used to detect the expression of cleaved caspase-3, p66ShcA, and phosphorylated p66ShcA. We found that the expression of activated p66ShcA and caspase-3 increased after ketamine exposure and peaked at 3 hours. The same procedure was performed on a different group of rats. At the age of 4 weeks, spatial learning and memory abilities were tested with the Morris water maze. Latency to find the hidden platform for these rats was longer than it was for control rats, although the residence time in the target quadrant was similar. These findings indicate that ketamine exposure resulted in p66ShcA being activated in the course of an apoptotic cascade during the neonatal period. This may have contributed to the deficit in spatial learning and memory that persisted into adulthood. The experimental protocol was approved by the Institutional Animal Care and Use Committee at the University of Texas at Arlington, USA (approval No. A13.008) on January 22, 2013.

SNGH16 regulates cell autophagy to promote Sorafenib Resistance through suppressing miR-23b-3p via sponging EGR1 in hepatocellular carcinoma

OBJECTIVE

Tumor cells could acquire drug resistance through cell autophagy. This study aimed to explore the role of SNHG16 in sorafenib-resistant HCC cells and its mechanism with miR-23b-3p.

METHODS

The sorafenib-resistant Hep3B cell model was established. The SNHG16 and miR-23b-3p gene expressions were determined in normal HCC and sorafenib-resistant HCC tissues. Detection of the expression of SNHG16 and miR-23b-3p and its respective correlation with survival rate were performed. Target genes to SNHG16 and miR-23b-3p were predicted, and verified by dual-fluorescent reporter assay. The effects of SNHG16 and miR-23b-3p on SNHG16, miR-23b-3p, EGR1 expression, viability, apoptosis as well as LC3II/LC3 expression in Hep3B and Hep3B/So cells were detected by qRT-PCR, CCK-8, flow cytometry, and western blot. In in vivo studies, the NOD/SCID mice model was established to explore the effects of Hep3B and Hep3B/So cells with inhibited SNHG16 or miR-23b-3p on tumor size, EGR1 expression, and autophagy.

RESULTS

High SNHG16 expression in HCC-resistant tissues and low miR-23b-3p expression in all HCC tissues were detected, and the two were negatively correlated. Low SNHG16 and high miR-23b-3p were related to a high survival rate of HCC patients. Moreover, SNHG16 overexpression promoted Hep3B/So cell viability and autophagy, suppressed apoptosis by inhibiting miR-23b-3p expression through up-regulating EGR1, however, the effect of si-SNHG16 was opposite. In in vivo studies, miR-23b-3p inhibitor suppressed the high sorafenib sensitivity in Hep3B/So cells caused by SNHG16 silencing through promoting viability, autophagy, and suppressing apoptosis.

CONCLUSION

SNHG16 promotes Hep3B/So cell viability, autophagy, and inhibits apoptosis to maintain its resistance to sorafenib through regulating the expression of miR-23b-3p via sponging EGR1.

mTOR Expression in Hippocampus and Prefrontal Cortex Is Downregulated in a Rat Model of Schizophrenia Induced by Chronic Administration of Ketamine

Schizophrenia is a severe chronic neuropsychiatric disorder, and it negatively affects individuals' quality of life, but the pathogenesis of schizophrenia remains unclear. This study aimed to explore whether the administration of ketamine in rats causes changes in mTOR (mechanistic/mammalian target of rapamycin) expression in the hippocampus and prefrontal cortex. Ketamine was used to establish an animal model of schizophrenia. Rats were randomly divided into four groups: control group (normal saline), low-dose group (15 mg/kg ketamine), middle-dose group (30 mg/kg ketamine), and high-dose group (60 mg/kg ketamine). The rats were intraperitoneally injected with ketamine or normal saline twice a day (9 AM and 9 PM) for 7 consecutive days. Immunohistochemistry was used to detect mTOR protein expression in the hippocampus and prefrontal cortex from rats at 13 h after the last treatment. Using immunohistochemistry, the expression of the mTOR protein was localized exclusively in the CA3 region of the hippocampus and in the Cg1 region of the prefrontal cortexes. Ketamine at 60 mg/kg decreased the expression of mTOR protein in the brain of rats. Ketamine successfully established a rat model of schizophrenia. This study helps elucidate the mechanisms of ketamine-induced schizophrenia and provides novel insights for drug discovery and development.