β-Amyloid peptide (Aβ) deposition in the brain is an important pathological change in Alzheimer\'s disease (AD). Insulin-degrading enzyme (IDE), which is regulated transcriptionally by peroxisome proliferator-activated receptor γ (PPARγ), is able to proteolyze Aβ. One of the members of the MAPK family, ERK, is able to mediate the phosphorylation of PPARγ at Ser112, thereby inhibiting its transcriptional activity. Ginsenoside Rg1 is one of the active ingredients in the natural medicine ginseng and has inhibitory effects on Aβ production. The present study was designed to investigate whether ginsenoside Rg1 is able to affect the regulation of PPARγ based on the expression of its target gene, IDE, and whether it is able to promote Aβ degradation via inhibition of the ERK/PPARγ phosphorylation pathway. In the present study, primary cultured rat hippocampal neurons were treated with Aβ1-42, ginsenoside Rg1 and the ERK inhibitor PD98059, and subsequently TUNEL staining was used to detect the level of neuronal apoptosis. ELISA was subsequently employed to detect the intra- and extracellular Aβ1-42 levels, immunofluorescence staining and western blotting were used to detect the translocation of ERK from the cytoplasm to the nucleus, immunofluorescence double staining was used to detect the co-expression of ERK and PPARγ, and finally, western blotting was used to detect the phosphorylation of PPARγ at Ser112 and IDE expression. The results demonstrated that ginsenoside Rg1 or PD98059 were able to inhibit primary cultured hippocampal neuron apoptosis induced by Aβ1-42 treatment, reduce the levels of intra- and extraneuronal Aβ1-42 and inhibit the translocation of ERK from the cytoplasm to the nucleus. Furthermore, administration of ginsenoside Rg1 or PD98059 resulted in attenuated co-expression of ERK and PPARγ, inhibition of phosphorylation of PPARγ at Ser112 mediated by ERK and an increase in IDE expression. In addition, the effects when PD98059 to inhibit ERK followed by treatment with ginsenoside Rg1 were found to be more pronounced than those when using PD98059 alone. In conclusion, ginsenoside Rg1 was demonstrated to exert neuroprotective effects on AD via inhibition of the ERK/PPARγ phosphorylation pathway, which led to an increase in IDE expression, the promotion of Aβ degradation and the decrease of neuronal apoptosis. These results could provide a theoretical basis for the clinical application of ginsenoside Rg1 in AD.

To investigate the mechanism of shear stress on endothelial cell dysfunction for providing a theoretical basis for the reduction of arteriovenous fistula dysfunction. The in vitro parallel plate flow chamber was used to form different forces and shear stress to mimic the hemodynamic changes in human umbilical vein endothelial cells, and the expression and distribution of krüppel-like factor 2 (KLF2), caveolin-1 (Cav-1), p-extracellular regulated protein kinase (p-ERK), and endothelial nitric oxide synthase (eNOS) were detected by immunofluorescence and real-time quantitative polymerase chain reaction. With the prolongation of the shear stress action time, the expression of KLF2 and eNOS increased gradually, while the expression of Cav-1 and p-ERK decreased gradually. In addition, after cells were exposed to oscillatory shear stress (OSS) and low shear stress, the expression of KLF2, Cav-1, and eNOS decreased and the expression of p-ERK increased. The expression of KLF2 increased gradually with the prolongation of action time, but it was still obviously lower than that of high shear stress. Following the block of Cav-1 expression by methyl β-cyclodextrin, eNOS expression decreased, and KLF2 and p-ERK expression increased. OSS may lead to endothelial cell dysfunction by Cav-1-mediated KLF2/eNOS/ERK signaling pathway.

OBJECTIVE: Cardiac remodeling is a common pathological change in various cardiovascular diseases and can ultimately result in heart failure. Thus, there is an urgent need for more effective strategies to aid in cardiac protection. Our previous work found that sphingosine-1-phosphate (S1P) could ameliorate cardiac hypertrophy. In this study, we aimed to investigate whether S1P could prevent cardiac fibrosis and the associated mechanisms in cardiac remodeling.
METHODS: Eight-week-old male C57BL/6 mice were randomly divided into a sham, transverse aortic constriction (TAC) or a TAC+S1P treatment group.
RESULTS: We found that S1P treatment improved cardiac function in TAC mice and that the cardiac fibrosis ratio in the TAC+S1P group was significantly lower and was accompanied by a decrease in α-smooth muscle actin (α-SMA) and collagen type I (COL I) expression compared with the TAC group. We also found that one of the key S1P enzymes, sphingosine kinase 2 (SphK2), which was mainly distributed in cytoblasts, was downregulated in the cardiac remodeling case and recovered after S1P treatment in vivo and in vitro. In addition, our in vitro results showed that S1P treatment activated extracellular regulated protein kinases (ERK) phosphorylation mainly through the S1P receptor 2 (S1PR2) and spurred p-ERK transposition from the cytoplasm to cytoblast in H9c2 cells exposed to phenylephrine.
CONCLUSIONS: These findings suggest that SphK2 and the S1PR2/ERK pathway may participate in the anti-remodeling effect of S1P on the heart. This work therefore uncovers a novel potential therapy for the prevention of cardiac remodeling.

The gut microbiota is a complex group of microorganisms that is not only closely related to intestinal immunity but also affects the whole immune system of the body. Antimicrobial peptides and reactive oxygen species participate in the regulation of gut microbiota homeostasis in invertebrates. However, it is unclear whether nitric oxide, as a key mediator of immunity that plays important roles in antipathogen activity and immune regulation, participates in the regulation of gut microbiota homeostasis. In this study, we identified a nitric oxide synthase responsible for NO production in the shrimp Marsupenaeus japonicus. The expression of Nos and the NO concentration in the gastrointestinal tract were increased significantly in shrimp orally infected with Vibrio anguillarum. After RNA interference of Nos or treatment with an inhibitor of NOS, L-NMMA, NO production decreased and the gut bacterial load increased significantly in shrimp. Treatment with the NO donor, sodium nitroprusside, increased the NO level and reduced the bacterial load significantly in the shrimp gastrointestinal tract. Mechanistically, V. anguillarum infection increased NO level via upregulation of NOS and induced phosphorylation of ERK. The activated ERK phosphorylated the NF-κB-like transcription factor, dorsal, and caused nuclear translocation of dorsal to increase expression of antimicrobial peptides (AMPs) responsible for bacterial clearance. In summary, as a signaling molecule, NOS-produced NO regulates intestinal microbiota homeostasis by promoting AMP expression against infected pathogens via the ERK-dorsal pathway in shrimp.

Ferroptosis, a new type of programmed cell death discovered in recent years, plays an important role in many neurodegenerative diseases. N2L is a novel lipoic acid-niacin dimer regulating lipid metabolism with multifunction, including antioxidant effect. It also exerts neuroprotective effects against glutamate- or β-amyloid (Aβ) -induced cell death. Because reactive oxygen species (ROS) play an essential role in ferroptosis, we hypothesize that N2L might protect cells from ferroptosis. Here, we investigated the protective effect of N2L and the underlying mechanism(s) under RAS-selective lethality 3 (RSL3) treatment in HT22 cells. RSL3 decreased the cell viability and induced excessive accumulation of ROS in HT22 cells. N2L pretreatment effectively protected HT22 cells against lipid peroxidation. What\'s more, N2L recovered glutathione peroxidase 4 (GPX4) expression and blocked the increase of Cyclooxygenase-2 (cox-2) and acyl-CoA synthetase long-chain family member 4 (ACSL4) protein expressions. Moreover, N2L also significantly prevented Ferritin Heavy Chain 1 (FTH1) from downregulation and maintained iron homeostasis. Finally, N2L pretreatment could decrease c-Jun N-terminal kinase (JNK) / extracellular regulated protein kinases (ERK) activation induced by RSL3. Taken together, our results showed that N2L could protect HT22 cells from RSL3-induced ferroptosis through decreasing lipid peroxidation and JNK/ERK activation. And N2L could be a ferroptosis inhibitor for the therapy of ferroptosis-related diseases, such as Alzheimer\'s disease.

Gold nanoparticles (AuNPs) are extensively utilized in biomedical fields. However, their potential interaction with host cells has not been comprehensively elucidated. In this study, we demonstrated a size-dependent effect of AuNPs to synergize with bacterial lipopolysaccharide (LPS) in promoting neutrophil extracellular traps (NETs) release in human peripheral neutrophils. Mechanistically, LPS was more efficient to contact with 10 nm AuNPs and promote their uptake in neutrophils compared to 40 and 100 nm AuNPs, leading to a synergistic upregulation of class A scavenger receptor (SRA) which mediated AuNPs uptake and triggered activation of extracellular regulated protein kinase (ERK) and p38. Blocking SRA or inhibiting ERK and p38 activation remarkably abrogated the effect of AuNPs and LPS to induce NETs formation. Further experiments demonstrated that AuNPs and LPS augmented the production of cytosolic reactive oxygen species (ROS) in p38 and ERK dependent manner, through upregulating and activating NADPH oxidase 2 (NOX2). Accordingly, scavenging of ROS or inhibiting the NOX2 dampened NETs release induced by combined AuNPs and LPS treatment. AuNPs and LPS also synergized to upregulate reactive oxygen species modulator 1 (ROMO1) via activating ERK, thereby increasing mitochondrial ROS generation and promoting the release of NETs. In summary, we provide new evidences about the synergy of AuNPs and LPS to augment cellular responses in neutrophils, which implicates the need to consider the amplifying effect by pathogenic stimuli when utilizing nanomaterials in infectious or inflammatory conditions.

BACKGROUND: The development of novel treatment strategies to reverse or impede cognitive dysfunction associated with mild cognitive impairment (MCI) has gained attention in recent times. Meanwhile, hyperbaric oxygen (HBO) has been widely used as a neuroprotective therapy that can promote recovery of damaged neurons. The aim of this study was to investigate the effects of HBO on cognitive function in rats with MCI and to clarify the associated mechanisms.
METHODS: We established a D-galactose-induced MCI rat model and evaluated the role of extracellularregulated kinase (ERK) signaling in HBO therapy for cognitive function using a specific inhibitor, U0126. All Rats were randomly assigned to four groups with 12 rats per group: normal control group; D-gal model group (group MCI); D-gal + HBO group (group HBO); D-gal + HBO + U0126 group (group U0126). We evaluated cognitive function by Morris water maze and pathological changes by hematoxylin and eosin (HE) staining of hippocampal slices. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of caspase 3, while total ERK1/2 and phospho-ERK1/2 were assessed by Western blotting.
RESULTS: Shorter escape latency was observed in the HBO group as compared to the MCI group, which was to some extent reversed by U0126. Similarly, the HBO group showed the highest number of platform crossings as compared to the MCI and U0126 groups. Pathological analysis also showed less apoptosis and better hippocampal cell morphology in the HBO group. Caspase 3 levels also differed significantly, with lowest expression in the HBO group as compared to the MCI and U0126 groups. The levels of total ERK1/2 and p-ERK1/2 were more elevated in the HBO group as compared to the MCI group.
CONCLUSIONS: This study found that HBO treatment has a protective effect on early cognitive dysfunction in rats with MCI. HBO therapy may act through ERK signaling, which inhibits apoptosis and protects cognitive function.

Heparanase cleaves the extracellular matrix by degrading heparan sulfate that ultimately leads to cell invasion and metastasis; a condition that causes high mortality among cancer patients. Many of the anticancer drugs available today are natural products of plant origin, such as hinokitiol. In the previous report, it was revealed that hinokitiol plays an essential role in anti-inflammatory and anti-oxidation processes and promote apoptosis or autophagy resulting to the inhibition of tumor growth and differentiation. Therefore, this study explored the effects of hinokitiol on the cancer-promoting pathway in mouse melanoma (B16F10) and breast (4T1) cancer cells, with emphasis on heparanase expression. We detected whether hinokitiol can elicit anti-metastatic effects on cancer cells via wound healing and Transwell assays. Besides, mice experiment was conducted to observe the impact of hinokitiol in vivo. Our results show that hinokitiol can inhibit the expression of heparanase by reducing the phosphorylation of protein kinase B (Akt) and extracellular regulated protein kinase (ERK). Furthermore, in vitro cell migration assay showed that heparanase downregulation by hinokitiol led to a decrease in metastatic activity which is consistent with the findings in the in vivo experiment.

Levo-tetrahydropalmatine (l-THP) is an alkaloid purified from the Chinese herbs Corydalis and Stephania and has been used in many traditional Chinese herbal preparations for its sedative, analgesic and hypnotic properties. Previous studies demonstrated that l-THP has antagonistic activity on dopamine receptors; thus, it may have potential therapeutic effects on drug abuse. However, whether l-THP affects ketamine-induced conditioned place preference (CPP) remains unclear. Therefore, the present study was designed to evaluate the effects of l-THP on the rewarding behavior of ketamine through CPP. Results revealed that ketamine (5, 10 and 15mg/kg) induced CPP in rats. Furthermore, Ketamine (10mg/kg) promoted the phosphorylation of extracellular-regulated kinase (ERK) and cAMP responsive element binding protein (CREB) in the hippocampus (Hip) and caudate putamen (CPu), but not in the prefrontal cortex (PFc). l-THP (20mg/kg) co-administered with ketamine during conditioning inhibited the acquisition of ketamine-induced CPP in rats. Furthermore, l-THP (20mg/kg) prevented the enhanced phosphorylation of ERK and CREB in CPu and Hip. These results suggest that l-THP has potential therapeutic effects on ketamine-induced CPP. The underlying molecular mechanism may be related to its inhibitory effect on ERK and CREB phosphorylation in Hip and CPu. The present data supports the potential use of l-THP for the treatment of ketamine addiction.

Opioid receptors, members of the G-protein-coupled receptor superfamily, appear to be involved in cancer progression. However, the expression and significance of opioid receptors in esophageal squamous cell carcinoma (ESCC) remain unclear. In this study, we demonstrated by flow cytometry that μ, δ, and κ-opioid receptors (MOR, DOR, and KOR) are expressed to various degrees in ESCC cell lines. The KOR protein was further examined by several methods in ESCC cell lines and tissues. Immunocytochemical staining localized KOR to the cell membrane in KYSE180 cells and the nucleus in EC109 cells, whereas no signal or weak staining of the cytoplasm was observed in KYSE150 cells. The expression of KOR was confirmed in ESCC cells by Western blotting. Furthermore, immunohistochemistry staining showed that KOR was up-regulated in ESCC tissues compared with nontumorous esophageal epithelium (P = .004, χ(2) test). Moreover, high nuclear KOR expression was significantly correlated with lymph node metastasis in 256 ESCC cases (R = 0.144; P = .030, Kendall τB test). Patients with high nuclear KOR expression in ESCC had a significantly poorer prognosis (P = .001, log-rank test). Multivariate Cox analysis revealed that KOR in the nucleus was an independent prognostic factor (hazard ratio, 1.789; 95% confidence interval, 1.177-2.720; P = .006). Our results suggest that KOR is involved in the carcinogenesis or progression of ESCC and that nuclear KOR may be indicative of prognosis.