Extracellular Signal-regulated Kinase Research Articles

The general glycan profiling of Dendrobium officinale and their protective effects on MIN6 cells via ERK signaling pathway

Based on structural elucidation of natural and hydrolyzed glycans, the general glycans profiling of D. officinale were unequivocally established for the first time as follows: [Display omitted] The results indicated that the structure of D. officinale glycans with low degree of polymerization (DP ≤ 22) was linear α-D-1,4-glucan, whereas the structure of glycans with high degree of polymerization (DP > 24) was linear acetylated 1,4-glucomannan. The content of acetyl groups and mannose to glucose (M/G) ratio increased with the degree of polymerization of D. officinale glycans. In addition, this study showed that natural D. officinale glycans protected pancreatic β-cell damage induced by glucotoxicity through the extracellular signal–regulated kinase (ERK)1/2 pathway.

Thymol as adjuvant in oncology: molecular mechanisms, therapeutic potentials, and prospects for integration in cancer management.

Cancer remains a global health challenge, prompting a search for effective treatments with fewer side effects. Thymol, a natural monoterpenoid phenol derived primarily from thyme (Thymus vulgaris) and other plants in the Lamiaceae family, is known for its diverse biological activities. It emerges as a promising candidate in cancer prevention and therapy. This study aims to consolidate current research on thymol's anticancer effects, elucidating its mechanisms and potential to enhance standard chemotherapy, and to identify gaps for future research. A comprehensive review was conducted using databases like PubMed/MedLine, Google Scholar, and ScienceDirect, focusing on studies from the last 6years. All cancer types were included, assessing thymol's impact in both cell-based (in vitro) and animal (in vivo) studies. Thymol has been shown to induce programmed cell death (apoptosis), halt the cell division cycle (cell cycle arrest), and inhibit cancer spread (metastasis) through modulation of critical signaling pathways, including phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), extracellular signal-regulated kinase (ERK), mechanistic target of rapamycin (mTOR), and Wnt/β-catenin. It also enhances the efficacy of 5-fluorouracil (5-FU) in colorectal cancer treatments. Thymol's broad-spectrum anticancer activities and non-toxic profile to normal cells underscore its potential as an adjunct in cancer therapy. Further clinical trials are essential to fully understand its therapeutic benefits and integration into existing treatment protocols.

Parecoxib inhibits tumorigenesis and angiogenesis in hepatocellular carcinoma through ERK-VEGF/MMPs signaling pathway.

Parecoxib, a well-recognized nonsteroidal anti-inflammatory drug, has been reported to possess anticancer properties in various tumor types. In this work, we aimed to investigate the potential anticancer effects of parecoxib on hepatocellular carcinoma (HCC) cells. To assess the impact of parecoxib on HCC cell proliferation, we employed Cell Counting Kit-8, colony formation, and 5-ethynyl-2'-deoxyuridine assays. Hoechst/propidium iodide (PI) double staining and flow cytometry were performed to evaluate apoptosis and cell cycle analysis. Wound healing and transwell assays were utilized to assess cell migration and invasion. Tube formation assay was employed to analyze angiogenesis. Protein levels were determined using western blotting, and mRNA expression levels were assessed using quantitative real-time polymerase chain reaction (PCR). A xenograft mouse model was used to confirm the antitumor effects of parecoxib on HCC tumors in vivo. Our data demonstrated that parecoxib effectively inhibited the proliferation of HCC cells in a dose- and time-dependent manner. In addition, parecoxib induced cell cycle arrest in the G2 phase and promoted apoptosis. Moreover, parecoxib hindered tumor migration and invasion by impeding the epithelial-mesenchymal transition process. Further investigation showed that parecoxib could significantly suppress angiogenesis through the inhibition of extracellular signal-regulated kinase (ERK)-vascular endothelial growth factor (VEGF) axis. Notably, treatment with the ERK activator phorbol myristate acetate upregulated the expression of matrix metalloproteinase (MMP)-2, MMP-9, and VEGF and reversed the function of parecoxib in HCC cells. Besides, parecoxib displayed its antitumor efficacy in vivo. Collectively, our results suggest that parecoxib ameliorates HCC progression by regulating proliferation, cell cycle, apoptosis, migration, invasion, and angiogenesis through the ERK-VEGF/MMPs signaling pathway.

Toll-like receptor 2-mediated ERK activation significantly upregulates interleukin-6 expression in M2-polarized macrophages

Abstract Objectives M2-polarized macrophages and interleukin (IL)-6 significantly alter the tumor microenvironment and promote the malignant behaviors of tumor cells. This study aimed to establish M2-type macrophages from THP-1 cells, which are human leukemia monocytes, and investigate the significance of toll-like receptor 2 (TLR2) signaling in IL-6 production. Methods THP-1 cells were treated with phorbol 12-myristate 13-acetate, IL-4, and IL-13 to stimulate their differentiation into M2 macrophages. Cell differentiation was confirmed by cytokine production, marker expression, and morphological alterations. Treatment with TLR agonists induced TLR stimulation in M2 macrophages. Subsequently, secretion and expression levels of IL-6 in M2 macrophages were measured using enzyme-linked immunosorbent assay, quantitative reverse transcription-polymerase chain reaction, and western blotting. Results Myeloid differentiation factor 88, tumor necrosis factor-associated factor 6, and IL-1 receptor-associated kinase-1/4 signaling pathways contributed to IL-6 production upon TLR2 activation in M2 macrophages. While both TLR2 and TLR4 activated NF-κB in M2 macrophages, IL-6 production was mainly dependent on TLR2, not TLR4, suggesting the involvement of major mechanisms other than NF-κB in IL-6 production. Notably, TLR2-stimulated extracellular signal-regulated kinase (ERK) was necessary for abundant IL-6 production, indicating that TLR2-mediated ERK signaling plays an essential role in M2 macrophages. Conclusions These results highlight the significance of TLR2 signaling in IL-6 production by M2 macrophages and provide insights into the underlying regulatory mechanisms.

Bay 11-7082, an NF-κB Inhibitor, Prevents Post-Inflammatory Hyperpigmentation Through Inhibition of Inflammation and Melanogenesis.

Post-inflammatory hyperpigmentation (PIH) is a very common disorder of cutaneous hyperpigmentation, which poses a persistent management challenge in the fields of dermatology and esthetics. This study was designed to explore the anti-melanogenic and anti-inflammatory effects of Bay 11-7082, an NF-κB inhibitor, using small-molecule screening, to determine its potential application for PIH prevention. The molecular mechanisms were investigated invitro and exvivo in epidermis-humanized mice using melanin content, RT-PCR, and immunoblotting. Bay 11-7082 suppressed proinflammatory cytokines and ameliorated 2,4-dinitrofluorobenzene (DNFB)-induced contact dermatitis on day 15. The suppression of melanin synthesis by Bay 11-7082 was attributed to the reduction of MITF, which was induced by extracellular signal-regulated kinase activation. Bay 11-7082 reduced epidermal melanin accumulation in UVB-stimulated exvivo human epidermis as well as in the ear and tail skin of K14-stem cell factor (SCF) transgenic mice. Topical administration of Bay 11-7082 improved PIH on day 35 in the post-DNFB dorsal skin of K14-SCF transgenic mice. In conclusion, Bay 11-7082 can be considered a promising candidate for the development of a preventive topical agent for PIH.

Research progress on the mechanism of acupuncture on depression based on signaling pathway regulation

Depression is high in prevalence rate, recurrence rate and disability rate. Acupuncture is effective on depression. The paper reviewed the regulatory effect of acupuncture on five prominent signaling pathways, i.e. mitogen activated protein kinase (MAPK), Wnt/β-catenin, Notch, adenyl ate cyclase/cyclic adenosine phosphate/protein kinase (AC/cAMP/PKA) and NO/cyclic guanosine monophosphate (cGMP)； and elaborated the structure of each signaling pathway, the association with depression onset, and the relevant research progress of acupuncture in treatment of depression. In view of the regulation of signal pathways, acupuncture can up-regulate AC/cAMP/PKA and extracellular signal-regulated kinase (ERK), promote the expression of neurotrophic factors or Bcl-2, prevent from and repair neuronal damage, advance neurogenesis and improve synaptic plasticity； it can modulate the Wnt/β-catenin and Notch signal pathways to protect neurons and increase cell proliferation； and down-regulate JNK and up-regulate NO/cGMP signal pathways to inhibit stress that leads to abnormal apoptosis of neurosis and attenuate neurotoxicity and neuronal damage so that anti-depression of acupuncture is obtained. This review provides a new approach to the mechanism research of acupuncture in treatment of depression through regulating the relevant single pathways.

"Osteo-Organogenesis Niche" Hyaluronic Acid Engineered Materials Directing Re-Osteo-Organogenesis via Manipulating Macrophage CD44-MAPK/ERK-ETV1/5-MRC1 Axis.

The strategy of re-organogenesis provides an optimal framework for restoring complex organ structures and functions in adult damage. While the focus has often been on restoring organogenesis stem cells, there is limited investigations of reverting the environmental niche to support this approach. The guiding principle of "Nature selects the fittest to survive" drives the intricate dynamic changes in cellular events within the niche environment, especially through immune surveillance. The extracellular matrix (ECM) serves as the "self-associated molecular patterns" of the niche, containing extensive data on cell-niche reaction data and acting as the active tuner of immune surveillance. In this study, hyaluronic acid (HA) is identified as a unique component of the ECM in cranial osteo-organogenesis. Mechanistically, HA activates the Cluster of Differentiation 44 (CD44)-Mitogen-Activated Protein Kinase (MAPK)/Extracellular Signal-Regulated Kinase (ERK)-Ets Variant 1/5 (ETV1/5)- Mannose Receptor C-Type 1 (MRC1) axis in macrophages, establishing a distinct immune surveillance during osteo-organogenesis. Furthermore, HA is utilized as a novel engineered material for an "Osteo-organogenesis niche", restoring immune surveillance and synergistically regulating stem cells to achieve re-osteo-organogenesis in cranial defects of rats. Taken together, the study unveils a previously unknown strategy for leveraging re-organogenesis by utilizing "organogenesis niche" ECM engineered materials to manipulate immune surveillance, thereby comprehensively regulating stem cells and other tissue cells effectively for re-organogenesis.

EIF4F controls ERK MAPK signaling in melanomas with BRAF and NRAS mutations

The eIF4F translation initiation complex plays a critical role in melanoma resistance to clinical BRAF and MEK inhibitors. In this study, we uncover a function of eIF4F in the negative regulation of the rat sarcoma (RAS)/rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) signaling pathway. We demonstrate that eIF4F is essential for controlling ERK signaling intensity in treatment-naïve melanoma cells harboring BRAF or NRAS mutations. Specifically, the dual-specificity phosphatase DUSP6/MKP3, which acts as a negative feedback regulator of ERK activity, requires continuous production in an eIF4F-dependent manner to limit excessive ERK signaling driven by oncogenic RAF/RAS mutations. Treatment with small-molecule eIF4F inhibitors disrupts the negative feedback control of MAPK signaling, leading to ERK hyperactivation and EGR1 overexpression in melanoma cells in vitro and in vivo. Furthermore, our quantitative analyses reveal a high spare signaling capacity in the ERK pathway, suggesting that eIF4F-dependent feedback keeps the majority of ERK molecules inactive under normal conditions. Overall, our findings highlight the crucial role of eIF4F in regulating ERK signaling flux and suggest that pharmacological eIF4F inhibitors can disrupt the negative feedback control of MAPK activity in melanomas with BRAF and NRAS activating mutations.

Emodin Inhibited MUC5AC Mucin Gene Expression via Affecting EGFR-MAPK-Sp1 Signaling Pathway in Human Airway Epithelial Cells.

The aim of this study was to evaluate emodin, a natural trihydroxyanthraquinone compound found in the roots and barks of several plants including rhubarb and buckthorn, might attenuate epidermal growth factor (EGF)-induced airway MUC5AC mucin gene expression. The human pulmonary mucoepidermoid NCI-H292 cells were pretreated with for 30 min and then stimulated with EGF for the following 24 h. The effect of emodin on EGF-induced mitogen-activated protein kinase (MAPK) signaling pathway was examined. As a result, emodin blocked the expression of MUC5AC mucin mRNA and production of mucous glycoprotein via suppressing the phosphorylation of EGF receptor (EGFR), phosphorylation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) 1 and 2 (MEK1/2), phosphorylation of p38 MAPK, phosphorylation of ERK 1/2 (p44/42), and the nuclear expression of specificity protein-1 (Sp1). These findings imply that emodin has a potential to mitigate EGF-stimulated mucin gene expression by inhibiting the EGFR-MAPK-Sp1 signaling pathway, in NCI-H292 cells.

Inhibition of phosphodiesterase 10A mitigates neuronal injury by modulating apoptotic pathways in cold-induced traumatic brain injury

Brain injury develops from a complex series of pathophysiological phases, resulting in acute necrotic or delayed apoptotic cell death after traumatic brain injury (TBI). Inhibition of apoptotic cell death is critical for the treatment of acute neurodegenerative disorders, such as TBI. Here, we investigated the role of phosphodiesterase 10A (PDE10A) in the development of neuronal injury, particularly in apoptotic cell death. Using the PDE10A inhibitor TAK-063, we found that PDE10A inhibition is associated with decreased brain injury, brain swelling, and blood brain barrier disruption 48 h after cold-induced TBI. Furthermore, a particularly notable result was observed with 3 mg/kg TAK-063, which reduced disseminated neuronal injury. Protein abundance analysis revealed that PDE10A inhibition activates survival kinases AKT and ERK-1/-2, which were associated with the decreased activation of MMP-9 and PTEN. Additionally, iNOS and nNOS levels significantly reduced in the TAK-063 group, playing roles in inflammation and apoptosis. A planar surface immunoassay was performed for in-depth analyses of the apoptotic signaling pathways. We observed that inhibition of PDE10A resulted in the decreased expression of TNFRSF1A, TNFRSF10B, and TNFRSF6 receptors, particularly inducing apoptotic cell death. Moreover, these findings correlated with reduced levels of pro-apoptotic proteins, including PTEN, p27, Cytochrome-c, cleaved Caspase-3, Bad, and p53. Interestingly, TAK-063 treatment reduced levels of anti-apoptotic proteins or enzymes, including XIAP, Claspin, and HIF1α, without affecting Bcl-x, MCL-1, SMAC, HO-1, HO-2, HSP27, HSP60, and HSP70. The findings suggest that PDE10A regulates cellular signaling predominantly pro-apoptotic pathways, and inhibition of this protein is a promising approach for the treatment of acute brain injury.

Anti-nociceptive effect of STW 5-II in rodent models of stress and post-inflammatory visceral hypersensitivity

AimsVisceral hypersensitivity is a therapy-resistant hallmark of irritable bowel syndrome (IBS). Many IBS patients’ symptoms develop following an acute colitis, and most report that stress worsens symptoms. STW 5-II, a combination of six herbal extracts, is a clinically proven treatment for IBS, but the mechanism is uncertain. Here, we employ two well-characterized rodent models to test the hypothesis that STW 5-II attenuates chronic colonic hypersensitivity. Main methodsSeparate cohorts of male rats were used for each model of colonic hypersensitivity. The first model used repeated water avoidance stress (1hr/day for 10 days), while the second model used intracolonic trinitrobenzene sulfonic acid to induce a short-lived colitis followed by post-inflammatory visceral hypersensitivity. Both models used sham treatment controls. Colonic sensitivity was quantified as the number of abdominal contractions to graded pressures (20–60 mmHg) of isobaric colorectal distension (CRD). Phosphorylation of extracellular signal-regulated kinase (pERK) was assessed via immunohistochemistry in the brain, spinal cord, and dorsal root ganglion (DRG). STW 5-II (10 ml/kg, p.o.) or vehicle (p.o.) was administered for 7 days, prior to CRD and pERK expression. Key findingsRats exposed to either model developed significant colonic hypersensitivity. Both models enhanced CRD-evoked pERK in DRGs, spinal cord, and brain. STW 5-II decreased colonic hypersensitivity and reduced CRD-evoked brain, spinal, and DRG pERK. SignificanceBoth models induced colonic hypersensitivity and enhanced pERK expression. STW 5-II inhibited colonic hypersensitivity and decreased noxious neuronal activation in both models, which could explain its clinically proven efficacy in relieving visceral hypersensitivity-related symptoms in IBS.

Conditional Pten inactivation in pituitary results in sex-specific prolactinoma formation

Pituitary tumors, including prolactinomas, present significant clinical challenges that require a deeper understanding of their molecular roots for improved diagnostics and therapies. Here, we investigate the role of the phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinase (PI3K) pathway in pituitary tumorigenesis using a mouse model. Conditional knockout of Pten in all pituitary cell lineages resulted in prolactinoma formation exclusively in female mice, demonstrating the critical role of PTEN in pituitary homeostasis. While Pten inactivation induced Akt activation in all pituitary cells, only prolactin-producing cells exhibited tumorigenic changes, suggesting specific cell-type effects. Histological and molecular analyses of prolactinomas revealed similarities with human pituitary tumors, such as decreased vascularization and cell adhesion proteins and increased accumulation of cell cycle proteins. Notably, prolactinomas displayed diminished levels of phosphorylated extracellular signal-regulated kinase (ERK), implicating downregulation of ERK in tumorigenesis. Finally, we analyzed PTEN/PI3K activation in a collection of human pituitary tumors. Overall, our study delineates the intricate interplay between the PTEN and ERK signaling pathways, providing insights into sex-specific mechanisms of pituitary tumorigenesis and potential therapeutic strategies for prolactinomas.

Molecular Mechanisms of Skatole-Induced Inflammatory Responses in Intestinal Epithelial Caco-2 Cells: Implications for Colorectal Cancer and Inflammatory Bowel Disease.

Inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), in intestinal epithelial cells significantly contribute to inflammatory bowel disease (IBD) and colorectal cancer (CRC). Given our previous findings that TNF-α is upregulated in intestinal epithelial Caco-2 cells induced by skatole, a tryptophan-derived gut microbiota metabolite, the present study aimed to explore the relationship between skatole and IL-6, alongside TNF-α. Skatole elevated the promoter activity of IL-6 as well as TNF-α, and increased IL-6 mRNA expression and protein secretion. In addition to activating NF-κB, the NF-κB inhibitor BAY 11-7082 reduced skatole-induced cell survival and the mRNA expression of IL-6 and TNF-α. NF-κB activation was attenuated by the extracellular signal-regulated kinase (ERK) pathway inhibitor U0126 and the p38 inhibitor SB203580, but not by the c-Jun N-terminal kinase (JNK) inhibitor SP600125. U126 and SB203580 also decreased the skatole-induced increase in IL-6 expression. When skatole-induced AhR activation was inhibited by CH223191, in addition to promoting NF-κB activation, IL-6 expression was enhanced in a manner similar to that previously reported for TNF-α. Taken together, these results suggest that skatole-elicited NF-κB activation induces IL-6 and TNF-α expression, although AhR activation partially suppresses this process. The ability of skatole to increase the expression of IL-6 and TNF-α may significantly affect the development and progression of these diseases. Moreover, the balance between NF-κB and AhR activation appears to govern the skatole-induced increases in IL-6 and TNF-α expression. Therefore, the present findings provide new insights into the mechanisms linking tryptophan-derived gut microbiota metabolites with colorectal disease.

Gintonin Stimulates Glucose Uptake in Myocytes: Involvement of Calcium and Extracellular Signal-Regulated Kinase Signaling.

Ginseng has anti-hyperglycemic effects. Gintonin, a glycolipoprotein derived from ginseng, also stimulates insulin release from pancreatic beta cells. However, the role of gintonin in glucose metabolism within skeletal muscle is unknown. Here, we showed the effect of gintonin on glucose uptake, glycogen content, glucose transporter (GLUT) 4 expression, and adenosine triphosphate (ATP) content in C2C12 myotubes. Gintonin (3-30 μg/mL) dose-dependently stimulated glucose uptake in myotubes. The expression of GLUT4 on the cell membrane was increased by gintonin treatment. Treatment with 1-3 μg/mL of gintonin increased glycogen content in myotubes, but the content was decreased at 30 μg/mL of gintonin. The ATP content in myotubes increased following treatment with 10-100 μg/mL gintonin. Gintonin transiently elevated intracellular calcium concentrations and increased the phosphorylation of extracellular signal-regulated kinase (ERK). Gintonin-induced transient calcium increases were inhibited by treatment with the lysophosphatidic acid receptor inhibitor Ki16425, the phospholipase C inhibitor U73122, and the inositol 1,4,5-trisphosphate receptor antagonist 2-aminoethoxydiphenyl borate. Gintonin-stimulated glucose uptake was decreased by treatment with U73122, the intracellular calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester, and the ERK inhibitor PD98059. These results show that gintonin plays a role in glucose metabolism by increasing glucose uptake through transient calcium increases and ERK signaling pathways. Thus, gintonin may be beneficial for glucose metabolism control.

Evaluation of Echinacea purpurea Extracts as Immunostimulants: Impact on Macrophage Activation.

Echinacea purpurea has been traditionally used to strengthen the immune system. Therefore, herein, we investigated the potential of E. purpurea aqueous extracts (AEs) obtained from flowers (F), leaves (L), or roots (R) as an immune booster in human primary monocyte-derived macrophages (hMDMs). Additionally, to identify the main class of compounds (phenolic/carboxylic acids vs. alkylamides) responsible for the bioactivity, the three AEs were fractioned by semi-preparative high-performance liquid chromatography (HPLC). The AEs and the isolated phenolic/carboxylic acidic fractions were not cytotoxic for hMDMs for all tested concentrations, as confirmed by the metabolic activity and DNA content assays. Moreover, AE drastically induced the production of the interleukin (IL)-6 and tumor necrosis factor (TNF)-α, with a minimal effect on IL-1β and prostaglandin E2 (PGE2), supporting their potential for macrophage activation. Interestingly, in the presence of the phenolic/carboxylic acidic fractions, this efficacy considerably decreased, suggesting a complementary effect between compounds. AE also triggered the phosphorylation of the extracellular signal-regulated kinase (ERK) 1/2 and p38 signaling pathways and upregulated the cyclooxygenase (COX)-2 expression in hMDMs. Overall, AE-F was demonstrated to be the most powerful immunostimulant extract that can be related to their higher number in identified bioactive compounds compared to AE-L and AE-R. These results highlight the efficiency of E. purpurea AE to enhance the function of a key cell type of the immune system and their potential as immunostimulant formulations for patients with a compromised immune system due to certain diseases (e.g., acquired immunodeficiencies) and treatments (e.g., chemotherapy).

Hypoxia activates FGF-23-ERK / MAPK signaling pathway in ischemia-reperfusion induced acute kidney injury.

Both hypoxia and fibroblast growth factor-23 (FGF-23) are key factors in ischemia-reperfusion (I/R)-induced acute kidney injury (AKI). This study aimed to explore the relationship between hypoxia and FGF-23 in AKI. An I/R-AKI animal model was established using male BALB/c mice. HK-2 cells, a part of the human proximal tubular epithelial cell line, were subjected to hypoxia/reoxygenation (H/R). qPCR was used to measure FGF-23 and HIF-1α, ELISA was used to measure inflammatory and oxidative stress cytokines. Western blotting used to measure the phosphorylation of ERK level. In I/R mice, the levels of interleukin-6 (IL-6), tumor necrosis factor (TNF-α), malondialdehyde (MDA), and the phosphorylation of extracellular signal-regulated kinase (ERK) were increased, whereas the levels of interleukin-10 (IL-10), superoxide dismutase (SOD), glutathione peroxidase (GPx), and klotho were decreased, compared to the sham operated mice. Silencing the FGF-23 expression in I/R mice normalized the levels of IL-6, IL-10, TNF-α, MDA, SOD, Gpx, and ERK phosphorylation (p-ERK). In HK-2 cells, hypoxia-reperfusion (H/R) elevated the levels of IL-6, TNF-α, MDA, and ERK phosphorylation, but reduced IL-10, SOD, GPx, and klotho levels. Hypoxia induced apoptosis in HK-2 cells but silencing of FGF-23 expression blocked the effects of hypoxia on cell apoptosis, proinflammatory factors levels, oxidative stress response, and p-ERK levels. FGF-23 is a key molecule in AKI, and hypoxia plays a crucial role in AKI by inducing cell apoptosis; however, its role is regulated by FGF-23. FGF-23 affects oxidative stress and the inflammatory response of kidney tissues by activating the ERK/mitogen-activated protein kinase (MAPK) signaling pathway.

Follistatin drives neuropathic pain in mice through IGF1R signaling in nociceptive neurons.

Neuropathic pain is a debilitating chronic condition that lacks effective treatment. The role of cytokine- and chemokine-mediated neuroinflammation in its pathogenesis has been well documented. Follistatin (FST) is a secreted protein known to antagonize the biological activity of cytokines in the transforming growth factor-β (TGF-β) superfamily. The involvement of FST in neuropathic pain and the underlying mechanism remain largely unknown. Here, we report that FST was up-regulated in A-fiber sensory neurons after spinal nerve ligation (SNL) in mice. Inhibition or deletion of FST alleviated neuropathic pain and reduced the nociceptive neuron hyperexcitability induced by SNL. Conversely, intrathecal or intraplantar injection of recombinant FST, or overexpression of FST in the dorsal root ganglion (DRG) neurons, induced pain hypersensitivity. Furthermore, exogenous FST increased neuronal excitability in nociceptive neurons. The biolayer interferometry (BLI) assay and coimmunoprecipitation (co-IP) demonstrated direct binding of FST to the insulin-like growth factor-1 receptor (IGF1R), and IGF1R inhibition reduced FST-induced activation of extracellular signal-regulated kinase (ERK) and protein kinase B (AKT), as well as neuronal hyperexcitability. Further co-IP analysis revealed that the N-terminal domain of FST exhibits the highest affinity for IGF1R, and blocking this interaction with a peptide derived from FST attenuated Nav1.7-mediated neuronal hyperexcitability and neuropathic pain after SNL. In addition, FST enhanced neuronal excitability in human DRG neurons through IGF1R. Collectively, our findings suggest that FST, released from A-fiber neurons, enhances Nav1.7-mediated hyperexcitability of nociceptive neurons by binding to IGF1R, making it a potential target for neuropathic pain treatment.

Low shear stress protects chondrocytes from IL-1β-induced apoptosis by activating ERK5/KLF4 signaling and negatively regulating miR-143-3p

ObjectiveThis study investigated the protective effects of low fluid shear stress (FSS ≤ 2 dyn/cm²) against interleukin-1β (IL-1β)-induced chondrocyte apoptosis and explored the underlying molecular mechanisms.MethodsChondrocytes were cultured under four conditions: control, IL-1β stimulation, low FSS, and combined low FSS + IL-1β stimulation. Apoptosis was assessed using Hoechst staining and flow cytometry. Western blotting determined the expression of caspase-3 (CASP3), caspase-8 (CASP8), and NF-κB p65. Quantitative real-time PCR measured miR-143-3p expression. The roles of miR-143-3p and the extracellular signal-regulated kinase 5 (ERK5)/Krüppel-like factor 4 (KLF4) signaling pathway were further investigated using miR-143-3p mimics and inhibitors, an ERK5 inhibitor, and a KLF4 overexpression vector.ResultsIL-1β induced significant chondrocyte apoptosis, which was markedly inhibited by low FSS. Mechanistically, low FSS suppressed miR-143-3p expression, thereby enhancing ERK5 signaling. This activated ERK5 subsequently upregulated KLF4 expression, further mitigating IL-1β-induced damage. Importantly, miR-143-3p overexpression under low FSS conditions exacerbated IL-1β-induced apoptosis, while miR-143-3p inhibition attenuated it. Consistent with this, ERK5 inhibition augmented IL-1β-induced apoptosis, whereas KLF4 overexpression suppressed it.ConclusionLow FSS protects chondrocytes from IL-1β-induced apoptosis by suppressing miR-143-3p and activating the ERK5/KLF4 signaling pathway. This study reveals a novel mechanism by which mechanical stimulation protects cartilage.

MC-LR disrupts dopamine synthesis in the substantia nigra of midbrain by enhancing the chaperone-mediated autophagy pathway through direct binding to ERK2

Microcystins are environmental toxins produced by freshwater cyanobacteria. Microcystin-LR (MC-LR) is one of the most abundant and harmful isomers. MC-LR poses a serious threat to human health. MC-LR could penetrate the blood-brain barrier of mice and accumulate in the substantia nigra (SN) of the midbrain, leading to a reduction in dopamine levels and Parkinson's disease (PD)-like motor dysfunction in mice. The reduction in dopamine levels is a key factor contributing to movement disorders in humans with PD. Dopamine is synthesized in the dopaminergic neurons of the SN by the actions of tyrosine hydroxylase (TH) and dihydroxyphenylalanine decarboxylase (DDC). In this study, we found that MC-LR could enter dopaminergic neurons in the SN and directly bound to extracellular signal-regulated kinase 2 (ERK2), enhancing ERK2 stability. ERK2 further enhanced the transcriptional activity of Heat Shock Protein Family A Member 8 (HSPA8) and promoted the expression of Heat shock cognate 71 kDa protein (HSC70), which in turn amplified the chaperone-mediated autophagy (CMA) pathway and accelerated the degradation of TH and DDC. This affected the dopamine synthesis process, resulting in a significant reduction in dopamine levels. The study is the first to reveal that ERK2 was a direct target of MC-LR, and further enhanced CMA affecting dopamine synthesis, which has important theoretical and practical significance for environmental safety management.

Reduction of endocytosis and EGFR signaling is associated with the switch from isolated to clustered apoptosis during epithelial tissue remodeling in Drosophila.

Epithelial tissues undergo cell turnover both during development and for homeostatic maintenance. Removal of cells is coordinated with the increase in number of newly dividing cells to maintain barrier function of the tissue. In Drosophila metamorphosis, larval epidermal cells (LECs) are replaced by adult precursor cells called histoblasts. Removal of LECs must counterbalance the exponentially increasing adult histoblasts. Previous work showed that the LEC removal accelerates as endocytic activity decreases throughout all LECs. Here, we show that the acceleration is accompanied by a mode switching from isolated single-cell apoptosis to clustered ones induced by the endocytic activity reduction. We identify the epidermal growth factor receptor (EGFR) pathway via extracellular-signal regulated kinase (ERK) activity as the main components downstream of endocytic activity in LECs. The reduced ERK activity, caused by the decrease in endocytic activity, is responsible for the apoptotic mode switching. Initially, ERK is transiently activated in normal LECs surrounding a single apoptotic LEC in a ligand-dependent manner, preventing clustered cell death. Following the reduction of endocytic activity, LEC apoptosis events do not provoke these transient ERK up-regulations, resulting in the acceleration of the cell elimination rate by frequent clustered apoptosis. These findings contrasted with the common perspective that clustered apoptosis is disadvantageous. Instead, switching to clustered apoptosis is required to accommodate the growth of neighboring tissues.