Element-binding Protein Pathway Research Articles

Tetramethylpyrazine induces the release of BDNF from BM-MSCs through activation of the PI3K/AKT/CREB pathway.

Compelling evidences suggest that transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) can be therapeutically effective for central nervous system (CNS) injuries and neurodegenerative diseases. The therapeutic effect of BM-MSCs mainly attributes to their differentiation into neuron-like cells which replace injured and degenerative neurons. Importantly, the neurotrophic factors released from BM-MSCs can also rescue injured and degenerative neurons, which plays a biologically pivotal role in enhancing neuroregeneration and neurological functional recovery. Tetramethylpyrazine (TMP), the main bioactive ingredient extracted from the traditional Chinese medicinal herb Chuanxiong, has been reported to promote the neuronal differentiation of BM-MSCs. This study aimed to investigate whether TMP regulates the release of neurotrophic factors from BM-MSCs. We examined the effect of TMP on brain-derived neurotrophic factor (BDNF) released from BM-MSCs and elucidated the underlying molecular mechanism. Our results demonstrated that TMP at concentrations of lower than 200 μM increased the release of BDNF in a dose-dependent manner. Furthermore, the effect of TMP on increasing the release of BDNF from BM-MSCs was blocked by inhibiting the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT)/cAMP-response element binding protein (CREB) pathway. Therefore, we concluded that TMP could induce the release of BDNF from BM-MSCs through activation of the PI3K/AKT/CREB pathway, leading to the formation of neuroprotective and proneurogenic microenvironment. These findings suggest that TMP possesses novel therapeutic potential to promote neuroprotection and neurogenesis through improving the neurotrophic ability of BM-MSCs, which provides a promising nutritional prevention and treatment strategy for CNS injuries and neurodegenerative diseases via the transplantation of TMP-treated BM-MSCs.

Ganoderic Acid A-Mediated Modulation of Microglial Polarization is Involved in Depressive-Like Behaviors and Neuroinflammation in a Rat Model of Post-Stroke Depression

BackgroundPost-stroke depression (PSD) is a common complication after stroke. Ganoderic acid A (GAA), one of the main bioactive Ganoderma triterpenoids, exerts preventive and therapeutic effects in many diseases. However, the function of GAA in PSD has not been well studied.MethodsPSD model was established via stimulating rats with chronic unpredictable mild stress stimulations (CUMS) after middle cerebral artery occlusion (MCAO). Rats were treated with GAA before CUMS. Depressive-like behaviors were investigated by body weight alteration, open field test (OFT), and sucrose preference test (SPT). Neuronal damage was evaluated by hematoxylin and eosin (HE) staining and Western blotting. Inflammation was detected by enzyme-linked immunosorbent assay (ELISA) and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Microglial polarization was analyzed via qRT-PCR and Western blotting. The extracellular signal-regulated kinase (ERK)/cAMP-response element-binding protein (CREB) pathway was analyzed by Western blotting, and inactivated by the inhibitor PD98059 (PD).ResultsGAA attenuated PSD-induced depressive-like behaviors in rats. GAA mitigated PSD-induced neuronal damage and reduced BDNF and NGF levels in the cerebral hippocampus. GAA weakened PSD-induced inflammatory response in the cerebral hippocampus. GAA prevented pro-inflammatory (M1) polarization and promoted anti-inflammatory (M2) polarization, as indicated by decreased iNOS and CD86 levels and increased Arg-1 and CD206 levels. GAA restored the PSD-induced inactivation of the ERK/CREB pathway. GAA regulated M1/M2 microglial polarization by activating the ERK/CREB pathway.ConclusionGAA alleviated the depressive-like behaviors and brain inflammation in PSD rats, indicating its potential for PSD therapy.

Repeated oxytocin prevents central sensitization by regulating synaptic plasticity via oxytocin receptor in a chronic migraine mouse model

BackgroundCentral sensitization is one of the characters of chronic migraine (CM). Aberrant synaptic plasticity can induce central sensitization. Oxytocin (OT), which is a hypothalamic hormone, plays an important antinociceptive role. However, the antinociceptive effect of OT and the underlying mechanism in CM remains unclear. Therefore, we explored the effect of OT on central sensitization in CM and its implying mechanism, focusing on synaptic plasticity.MethodsA CM mouse model was established by repeated intraperitoneal injection of nitroglycerin (NTG). Von Frey filaments and radiant heat were used to measure the nociceptive threshold. Repeated intranasal OT and intraperitoneal L368,899, an oxytocin receptor (OTR) antagonist, were administered to investigate the effect of OT and the role of OTR. The expression of calcitonin gene-related peptide (CGRP) and c-fos were measured to assess central sensitization. N-methyl D-aspartate receptor subtype 2B (NR2B)-regulated synaptic-associated proteins and synaptic plasticity were explored by western blot (WB), transmission electron microscope (TEM), and Golgi-Cox staining.ResultsOur results showed that the OTR expression in the trigeminal nucleus caudalis (TNC) of CM mouse was significantly increased, and OTR was colocalized with the postsynaptic density protein 95 (PSD-95) in neurons. Repeated intranasal OT alleviated the NTG-induced hyperalgesia and prevented central sensitization in CM mouse. Additionally, the OT treatment inhibited the overexpression of phosphorylated NR2B and synaptic-associated proteins including PSD-95, synaptophysin-1 (syt-1), and synaptosomal-associated protein 25 (snap25) in the TNC of CM mouse and restored the abnormal synaptic structure. The protective effect of OT was prevented by L368,899. Furthermore, the expression of adenylyl cyclase 1 (AC1)/ protein kinase A (PKA)/ phosphorylation of cyclic adenosine monophosphate response element-binding protein (pCREB) pathway was depressed by OT and restored by L368,899.ConclusionsOur findings demonstrate that repeated intranasal OT eliminates central sensitization by regulating synaptic plasticity via OTR in CM. The effect of OT has closely associated with the down-regulation of AC1/PKA/pCREB signaling pathway, which is activated in CM model. Repeated intranasal OT may be a potential candidate for CM prevention.

Research advances of studies on involvement of the anterior cingulate cortex involved in acupuncture-induced amelioration treatment of affective pain

As an unpleasant subjective feeling and emotional experience, pain has a negative impact on the physical and mental health of patients. In the early years, the research concerning pain mostly focused on the sensory-discriminative component. With the development of modern medicine, people found that the generation of affective-emotional component of pain has its unique physiological mechanism, and thus carried out a lot of in-depth research. The anterior cingulate cortex (ACC) is the main brain area activated by affective pain, and the regulation of acupuncture on pain aversion is mainly related to it. The mechanism includes various signal pathways, such as extracellular regulated protein kinases-mitogen activated protein kinase-cAMP-response element binding protein pathway, adenylate cyclase 1 protein kinase Mζ- glutamate receptor 1 pathway, contains many biomolecules, such as opioid receptors, neuropeptide S and its receptor, and refers to microglia at the cellular level. This article reviewed the neural mechanism of ACC involved in affective pain and the role of acupuncture played in this process.

New Benzimidazothiazolone Derivatives as Tyrosinase Inhibitors with Potential Anti-Melanogenesis and Reactive Oxygen Species Scavenging Activities.

Thirteen (Z)-2-(substituted benzylidene)benzimidazothiazolone analogs were synthesized and evaluated for their inhibitory activity against mushroom tyrosinase. Among the compounds synthesized, compounds 1–3 showed greater inhibitory activity than kojic acid (IC50 = 18.27 ± 0.89 μM); IC50 = 3.70 ± 0.51 μM for 1; IC50 = 3.05 ± 0.95 μM for 2; and IC50 = 5.00 ± 0.38 μM for 3, and found to be competitive tyrosinase inhibitors. In silico molecular docking simulations demonstrated that compounds 1–3 could bind to the catalytic sites of tyrosinase. Compounds 1–3 inhibited melanin production and cellular tyrosinase activity in a concentration-dependent manner. Notably, compound 2 dose-dependently scavenged ROS in B16F10 cells. Furthermore, compound 2 downregulated the protein kinase A (PKA)/cAMP response element-binding protein (CREB) and mitogen-activated protein kinase (MAPK) signaling pathways, which led to a reduction in microphthalmia-associated transcription factor (MITF) expression, and decreased tyrosinase, tyrosinase related protein 1 (TRP1), and TRP2 expression, resulting in anti-melanogenesis activity. Hence, compound 2 may serve as an anti-melanogenic agent against hyperpigmentation diseases.

Alteration of the PKA-CREB cascade in the mPFC accompanying prepulse inhibition deficits: evidence from adolescent social isolation and chronic SKF38393 injection during early adolescence.

Prepulse inhibition (PPI) refers to the inhibition of the startle reflex that occurs when the startling stimulus is preceded by a weak prestimulus. Altered adolescent mPFC circuitry induced by early-life adversity might be a key source of PPI deficits. The current study focused on variations in the cyclic AMP (cAMP)/protein kinase A (PKA)-cAMP-response element-binding protein (CREB) pathway in the medial prefrontal cortex (mPFC). We found a negative relationship between PPI and the PKA-CREB cascade during adolescence by employing both developmental and pharmacologic manipulations. Experiment 1, with the early adolescent social isolation model [postnatal days (PNDs), 21-34), displayed a disrupted PPI at PND 35 and significantly altered PKA, phosphorylated CREB (p-CREB) and the ratio of p-CREB to CREB. In particular, the level of p-CREB was negatively related to PPI performance. In Experiment 2, SKF38393, a well-characterized activator of adenylate cyclase and cAMP/PKA, was chronically injected during early adolescence (PNDs 28-34). We sought to mimic potential biochemical changes, particularly PKA activation, which is possibly altered by adolescent social isolation, and to determine if PPI was disrupted, similar to the disruption associated with adolescent social isolation. On PND 35, PPI deficits were detected, as well as increased PKA, marginally increased CREB and no change occurred in p-CREB or the ratio of p-CREB to CREB. In particular, PKA activity was negatively related to PPI performance. Although these results are limited in suggesting a causal link between PPI deficits and PKA-CREB signaling, they may help to elucidate the role played by PKA-CREB in the mPFC in regulating PPI.

Structural basis for sterol sensing by Scap and Insig.

The sterol regulatory element-binding protein (SREBP) pathway monitors the cellular cholesterol level through sterol-regulated association between the SREBP cleavage-activating protein (Scap) and the insulin-induced gene (Insig). Despite structural determination of the Scap and Insig-2 complex bound to 25-hydroxycholesterol, the luminal domains of Scap remain unresolved. In this study, combining cryogenic electron microscopy (cryo-EM) analysis and artificial intelligence-facilitated structural prediction, we report the structure of the human Scap/Insig-2 complex purified in digitonin. The luminal domain loop 1 and a co-folded segment in loop 7 of Scap resemble those of the luminal/extracellular domain in NPC1 and related proteins, providing clues to the cholesterol-regulated interaction of loop 1 and loop 7. An additional luminal interface is observed between Scap and Insig. We also show that Scap(D428A), which inhibits SREBP activation even under sterol depletion, exhibits an identical conformation with the wild-type protein when complexed with Insig-2, and its constitutive suppression of the SREBP pathway may also involve a later step in protein trafficking.

ADNOC and Petronas ink deal to explore collaboration opportunities

Currently, an increasing proportion of adolescent ketamine users simultaneously consume alcohol. However, the potential behavioural and neurological alterations induced by such a drug combination and the underlying mechanisms have not been systematically examined. Therefore, in the present study, the behavioural and morphological changes and the underlying mechanisms were studied in adolescent rats after repeated alcohol and/or ketamine treatment. This study provided the first evidence that co-administration of alcohol (2 and 4 g/kg, i.g.) in adolescent rats significantly potentiated the neurotoxic properties of repeated ketamine (30 mg/kg, i.p.) treatments over 14 days, manifesting as increased locomotor activity, stereotypic behaviour, ataxia and morphological changes. This potentiation was associated with the enhancement by alcohol of ketamine-induced glutamate (Glu) and dopamine (DA) release in the cortex and hippocampus. Further mechanistic study demonstrated that alcohol potentiated ketamine-induced neurotoxicity through down-regulation of Akt (a serine/threonine kinase or protein kinase, PKB), protein kinase A (PKA), calmodulin-dependent kinase IV (CaMK-IV)-mediated cyclic AMP-responsive element binding protein (CREB) pathways and induction of neuronal apoptosis in the cortex and hippocampus of the adolescent rats. As this study provides strong evidence that repeated alcohol and ketamine co-exposure may cause serious neurotoxicity, attention needs to be drawn to the potential risk of this consumption behaviour, especially for adolescents.

A preliminary study on the mechanism of the neurosteroid-mediated ionotropic receptor dysfunction in neurodevelopmental toxicity induced by decabromodiphenyl ether

The mechanism of neurodevelopmental toxicity of decabromodiphenyl ether (BDE209) remains unclear. Recent evidence suggests that neurosteroids disorders play a vital role in BDE209 induced-neurodevelopmental toxicity. To explore the mechanism of it, pregnant ICR mice were orally gavaged with 0, 225, and 900 mg kg−1 BDE209 for about 42 days. Spatial learning and memory abilities of offspring were tested on postnatal day (PND) 21. Offspring were euthanized at PND26, the neuronal structure, neurosteroids level, and related proteins including neurosteroids synthase, ionotropic receptors and cAMP-response element binding protein (CREB) pathway were evaluated, as well as Ca2+ concentration and the mitochondrial membrane potential (Mmp). Our results showed that BDE209 impaired learning and memory abilities and disrupted neuronal structure. Meanwhile, BDE209 decreased the pregnenolone (PREG), dehydroepiandrosterone (DHEA), progesterone (PROG) and allopregnanolone (ALLO) levels in the serum and brain, as well as the mRNA and protein levels of cholesterol-side-chain cleavage enzyme (P450scc), steroid 17α-hy-droxylase (P450C17), 3β-hydroxysteroid dehydrogenase (3β-HSD) and steroid 5α-reductase of type I (5α-R) in the hippocampi. Also, BDE209 suppressed mRNA and protein levels of NR1, NR2A and NR2B subunits of the N-methyl-D-aspartic acid receptor (NMDAR) and α1 subunit of the Gamma-amino butyric acid A receptor (GABAAR), but increased the levels of β2 and γ2 subunits of the GABAAR in the hippocampi. Moreover, BDE209 increased the Ca2+ concentration and phosphorylation extracellular regulated protein kinases (P-ERK) 1/2 level, but decreased the P-CREB and Mmp level in the hippocampi. These results indicate that BDE209 exposure during pregnancy and lactation is possible to affect learning and memory formation of offspring by the neurosteroid-mediated ionotropic receptors dysfunction.

Impact of high fat diet on the sterol regulatory element-binding protein 2 cholesterol pathway in the testicle.

Male fertility has been shown to be dependent on cholesterol homeostasis. This lipid is essential for testosterone synthesis and spermatogenesis, but its levels must be maintained in an optimal range for proper testicular function. In particular, sperm cells' development is very sensitive to high cholesterol levels, noticeably during acrosomal formation. The aim of this work was to study whether the molecular pathway that regulates intracellular cholesterol, the sterol regulatory element-binding protein (SREBP) pathway, is affected in the testicles of animals under a fat diet. To investigate this, we took advantage of the non-obese hypercholesterolemia (HC) model in New Zealand rabbits that displays poor sperm and seminal quality. The testicular expression of SREBP isoform 2 (SREBP2) and its target molecules 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) and low-density lipoprotein receptor (LDLR) were studied under acute (6 months) and chronic (more than 12 months) fat intake by RT-PCR, western blot and immunofluorescence. Our findings showed that fat consumption promoted down-regulation of the SREBP2 pathway in the testicle at 6 months, but upregulation after a chronic period. This was consistent with load of testicular cholesterol, assessed by filipin staining. In conclusion, the intracellular pathway that regulates cholesterol levels in the testicle is sensitive to dietary fats, and behaves differently depending on the duration of consumption: it has a short-term protective effect, but became deregulated in the long term, ultimately leading to a detrimental situation. These results will contribute to the understanding of the basic mechanisms of the effect of fat consumption in humans with idiopathic infertility.

Sex-specific effects of in vitro fertilization on adult metabolic outcomes and hepatic transcriptome and proteome in mouse.

Although in vitro fertilization (IVF) is associated with adverse perinatal outcomes, there is increasing concern about the long-term and sex-specific health implications. Augmenting our IVF mouse model to longitudinally investigate metabolic outcomes in offspring from optimal neonatal litter sizes, we found sex-specific metabolic outcomes in IVF offspring. IVF-conceived females had higher body weight and cholesterol levels compared to naturally conceived females, whereas IVF-conceived males had higher levels of triglycerides and insulin, and increased body fat composition. Through adult liver transcriptomics and proteomics, we identified sexually dimorphic dysregulation of the sterol regulatory element-binding protein (SREBP) pathways that are associated with the sex-specific phenotypes. We also found that global loss of DNA methylation in placenta was linked to higher cholesterol levels in IVF-conceived females. Our findings indicate that IVF procedures have long-lasting sex-specific effects on metabolic health of offspring and lay the foundation to utilize the placenta as a predictor of long-term outcomes.

CREB: A Multifaceted Target for Alzheimer's Disease.

Alzheimer's disease (AD) is a persistent neuropathological stipulation manifested in the form of neuronal/synapse demise, the formation of senile plaques, hyperphosphorylated tau tangles, neuroinflammation, and apoptotic cell death. The absence of a therapeutic breakthrough for AD has continued the quest to find a suitable intervention. Apart from various candidates, the cyclic AMPprotein kinase A-cAMP response element-binding protein (cAMP/PKA/CREB) pathway is the most sought-after drug target AD as the bulk of quality literature documents that there is downregulation of cAMP signaling and CREB mediated transcriptional cascade in AD. cAMP signaling is evolutionarily conserved and can be found in all species. cAMP response element-binding protein (CREB) is a ubiquitous and integrally articulated transcription aspect that regulates neuronal growth, neuronal differentiation/ proliferation, synaptic plasticity, neurogenesis, maturation of neurons, spatial memory, longterm memory formation as well as ensures neuronal survival. CREB is a central part of the molecular machinery that has a role in transforming short-term memory to long-term. Besides AD, impairment of CREB signaling has been well documented in addiction, Parkinsonism, schizophrenia, Huntington's disease, hypoxia, preconditioning effects, ischemia, alcoholism, anxiety, and depression. The current work highlights the role and influence of CREB mediated transcriptional signaling on major pathological markers of AD (amyloid β, neuronal loss, inflammation, apoptosis, etc.). The present work justifies the continuous efforts being made to explore the multidimensional role of CREB and related downstream signaling pathways in cognitive deficits and neurodegenerative complications in general and AD particularly. Moreover, it is reaffirmed that cyclic nucleotide signaling may have vast potential to treat neurodegenerative complications like AD.

BAY 73-6691 Alters Neuron Plasticity and Phosphorylation of Tau Through Regulation of Cyclic Guanosine Monophosphate/Protein Kinase G/Cyclic Adenosine Monophosphate Response Element-Binding Protein Pathway

Alzheimer’s disease (AD) is one of neurodegenerative diseases characterized by cognitive and memory decline, accompanying with neurofibrillary tangles (NFTs) made of hyperphosphorylated tau protein and senile plaques (SP) accumulated by β-amyloid protein (Aβ). BAY 73-6691, an inhibitor of phosphodiesterase-9 (PDE-9), can improve learning and memory of elderly rats. However, the effects of BAY 73-6691 on neuroapoptotic and neuroinflammatory events, as well as synaptic plasticity of differentiated PC12 cells are remain unclear. In this work, we screened apoptotic cells induced by Aβ25-35 via flow cytometry. TNF-α, IL-1β, IL-6 secreted by PC12 cells were estimated by ELISA kits. The levels of cGMP, PKG and CREB mediated by BAY 73-6691 were assessed. Moreover, we conducted western blots analysis to evaluate the phosphorylation of tau and synaptic related proteins. Results showed that BAY 73-6691 could reduce Aβ25-35-triggered neuroapoptosis and neuroinflammation. Phosphorylation of tau was inhibited by BAY 73-6691, whereas sildenafil citrate (SC, an inhibitor of cGMP) partially weakened the effect of BAY 73-6691. Additionally, synaptic plasticity restored by BAY 73-6691 was also suppressed via SC. Taken together, BAY 73-6691 exhibited neuro protective effects, and altered tau phosphorylation as well as synaptic related proteins through cGMP/PKG/CREB pathway.

Metformin Resensitizes Sorafenib-Resistant HCC Cells Through AMPK-Dependent Autophagy Activation.

Despite the activation of autophagy may enable residual cancer cells to survive and allow tumor relapse, excessive activation of autophagy may eventually lead to cell death. However, the details of the association of autophagy with primary resistance in hepatocellular carcinoma (HCC) remain less clear. In this study, cohort analysis revealed that HCC patients receiving sorafenib with HBV had higher mortality risk. We found that high epidermal growth factor receptor (EGFR) expression and activity may be linked to HBV-induced sorafenib resistance. We further found that the resistance of EGFR-overexpressed liver cancer cells to sorafenib is associated with low activity of AMP-activated protein kinase (AMPK) and CCAAT/enhancer binding protein delta (CEBPD) as well as insufficient autophagic activation. In response to metformin, the AMPK/cAMP-response element binding protein (CREB) pathway contributes to CEBPD activation, which promotes autophagic cell death. Moreover, treatment with metformin can increase sorafenib sensitivity through AMPK activation in EGFR-overexpressed liver cancer cells. This study suggests that AMPK/CEBPD-activated autophagy could be a potent strategy for improving the efficacy of sorafenib in HCC patients.

Metformin Resensitizes Sorafenib-Resistant HCC Cells Through AMPK-Dependent Autophagy Activation

Despite the activation of autophagy may enable residual cancer cells to survive and allow tumor relapse, excessive activation of autophagy may eventually lead to cell death. However, the details of the association of autophagy with primary resistance in hepatocellular carcinoma (HCC) remain less clear. In this study, cohort analysis revealed that HCC patients receiving sorafenib with HBV had higher mortality risk. We found that high epidermal growth factor receptor (EGFR) expression and activity may be linked to HBV-induced sorafenib resistance. We further found that the resistance of EGFR-overexpressed liver cancer cells to sorafenib is associated with low activity of AMP-activated protein kinase (AMPK) and CCAAT/enhancer binding protein delta (CEBPD) as well as insufficient autophagic activation. In response to metformin, the AMPK/cAMP-response element binding protein (CREB) pathway contributes to CEBPD activation, which promotes autophagic cell death. Moreover, treatment with metformin can increase sorafenib sensitivity through AMPK activation in EGFR-overexpressed liver cancer cells. This study suggests that AMPK/CEBPD-activated autophagy could be a potent strategy for improving the efficacy of sorafenib in HCC patients.

4-Acetylantrocamol LT3 Inhibits Glioblastoma Cell Growth and Downregulates DNA Repair Enzyme O6-Methylguanine-DNA Methyltransferase.

Glioblastoma multiforme (GBM) is a deadly malignant brain tumor that is resistant to most clinical treatments. Novel therapeutic agents that are effective against GBM are required. Antrodia cinnamomea has shown antiproliferative effects in GBM cells. However, the exact mechanisms and bioactive components remain unclear. Thus, the present study aimed to investigate the effect and mechanism of 4-acetylantrocamol LT3 (4AALT3), a new ubiquinone from Antrodia cinnamomeamycelium, in vitro. U87 and U251 cell lines were treated with the indicated concentration of 4AALT3. Cell viability, cell colony-forming ability, migration, and the expression of proteins in well-known signaling pathways involved in the malignant properties of glioblastoma were then analyzed by CCK-8, colony formation, wound healing, and western blotting assays, respectively. We found that 4AALT3 significantly decreased cell viability, colony formation, and cell migration in both in vitro models. The epidermal growth factor receptor (EGFR), phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR), Hippo/yes-associated protein (YAP), and cAMP-response element binding protein (CREB) pathways were suppressed by 4AALT3. Moreover, 4AALT3 decreased the level of DNA repair enzyme O6-methylguanine-DNA methyltransferase and showed a synergistic effect with temozolomide. Our findings provide the basis for exploring the beneficial effect of 4AALT3 on GBM in vivo.

Glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide dual receptor agonist DA-CH5 is superior to exendin-4 in protecting neurons in the 6-hydroxydopamine rat Parkinson model.

Patients with Parkinson's disease (PD) have impaired insulin signaling in the brain. Incretin hormones, including glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), can re-sensitize insulin signaling. In a recent phase II clinical trial, the first GLP-1 mimic, exendin-4, has shown reliable curative effect in patients with PD. DA-CH5 is a novel GLP-1/GIP receptor unimolecular co-agonist with a novel peptide sequence added to cross the blood-brain barrier. Here we showed that both exendin-4 and DA-CH5 protected against 6-hydroxydopamine (6-OHDA) cytotoxicity, inhibited apoptosis, improved mitogenesis and induced autophagy flux in SH-SY5Y cells via activation of the insulin receptor substrate-1 (IRS-1)/alpha serine/threonine-protein kinase (Akt)/cAMP response element-binding protein (CREB) pathway. We also found that DA-CH5 (10 nmol/kg) daily intraperitoneal administration for 30 days post-lesion alleviated motor dysfunction in rats and prevented stereotactic unilateral administration of 6-OHDA induced dopaminergic neurons loss in the substantia nigra pars compacta. However, DA-CH5 showed curative effects in reducing the levels of α-synuclein and the levels of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β). It was also more effective than exendin-4 in inhibiting apoptotic process and protecting mitochondrial functions. In addition, insulin resistance was largely alleviated and the expression of autophagy-related proteins was up-regulated in PD model rats after DA-CH5 treatment. These results in this study indicate DA-CH5 plays a therapeutic role in the 6-OHDA-unilaterally lesioned PD rat model and is superior to GLP-1 analogue exendin-4. The study was approved by the Animal Ethics Committee of Shanxi Medical University of China.

Nimodipine promotes neurite outgrowth and protects against neurotoxicity in PC12 cells.

Nimodipine is an L-type voltage-dependent calcium channel (VDCC) antagonist. However, the actions of nimodipine except calcium blocking are poorly understood. This study aimed to investigate the effect of nimodipine on neurite outgrowth and neuroprotection in vitro. After PC12 cells were treated with different concentrations of nimodipine, neurite outgrowth was estimated using the ImageJ software. Neuroprotective effects of nimodipine against H2O2 and calcium ionophore-induced neurotoxicity were investigated using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In addition, the activation of extracellular signal-regulated kinase (ERK) and cyclic AMP-response element-binding protein (CREB) pathway was investigated for clarifying the action mechanism of nimodipine. Nimodipine treatment at doses of higher than 10 µM induced neurite outgrowth in the cells. Additionally, VDCC knockdown by siRNA significantly suppressed the nimodipine-induced neurite outgrowth in PC12 cells, suggesting that the drug promotes neurite outgrowth by binding to VDCC. H2O2 and calcium ionophore induce oxidative and calcium stress in PC12 cells. Nimodipine exhibited neuroprotective effects against H2O2- and calcium ionophore-induced neurotoxicity by increasing the mRNA expression levels of neurotrophic factors, calcium-binding proteins, and antioxidants that are transcribed by CREB activation. This is the first report that nimodipine induces neurite outgrowth and exerts its neuroprotective activity through the ERK/CREB signaling pathway in PC12 cells.

Role of the Sterol Regulatory Element Binding Protein Pathway in Tumorigenesis.

Metabolic changes are a major feature of tumors, including various metabolic forms, such as energy, lipid, and amino acid metabolism. Sterol regulatory element binding proteins (SREBPs) are important modules in regulating lipid metabolism and play an essential role in metabolic diseases. In the previous decades, the regulatory range of SREBPs has been markedly expanded. It was found that SREBPs also played a critical role in tumor development. SREBPs are involved in energy supply, lipid supply, immune environment and inflammatory environment shaping in tumor cells, and as a protective umbrella to support the malignant proliferation of tumor cells. Natural medicine and traditional Chinese medicine, as an important part of drug therapy, demonstrates the multifaceted effects of SREBPs regulation. This review summarizes the core processes in the involvement of SREBPs in tumors and provides a comprehensive understanding of the pathways through which natural drugs target the SREBP pathway and regulate tumor progression.

CD13 Induces Autophagy to Promote Hepatocellular Carcinoma Cell Chemoresistance Through the P38/Hsp27/CREB/ATG7 Pathway.

The chemoresistance of hepatocellular carcinoma (HCC) is a serious problem that directly hinders the effect of chemotherapeutic agents. We previously reported that Aminopeptidase N (CD13) inhibition can enhance the cytotoxic efficacy of chemotherapy agents. In the present study, we use liver cancer cells to explore the molecular mechanism accounting for the relationship between CD13 and chemoresistance. We demonstrate that CD13 overexpression activates the P38/heat shock protein 27/cAMP response element-binding protein (CREB) signaling pathway to limit the efficacy of cytotoxic agents. Moreover, blockade of P38 or CREB sensitizes HCC cells to 5-fluorouracil. Then we reveal that CREB binds to the autophagy related 7 (ATG7) promoter to induce autophagy and promote HCC cell chemoresistance. CD13 inhibition also downregulates the expression of ATG7, autophagy, and tumor cell growth in vivo. Overall, the combination a CD13 inhibitor and chemotherapeutic agents may be a potential strategy for overcoming drug resistance in HCC. SIGNIFICANCE STATEMENT: Our study demonstrates that Aminopeptidase N (CD13) promotes hepatocellular carcinoma (HCC) cell chemoresistance via the P38/heat shock protein 27/cAMP response element-binding protein (CREB) pathway. CREB regulates autophagy related 7 transcription and expression to induce autophagy. Our results collectively suggest that CD13 may serve as a potential target for overcoming HCC resistance.