Activation Of P38 MAPK Signaling Research Articles

A comprehensive review on p38MAPK signaling as a potent radioprotector in testis.

Previous studies have shown that the activation of p38MAPK signaling plays a crucial role in regulating gonadal cell fate decisions in both mouse and human. Excessive activation of p38MAPK by radiation significantly causes testicular damage and negatively affects the male reproductive function. Therefore, fine-tuned regulation of p38MAPK signaling is critical in both physiological and pathological conditions. This review summarizes the impact of p38MAPK signaling on testicular germ cells and microenvironment under normal condition. The relationship between radiation, reactive oxygen species (ROS), and p38MAPK is summarized. In conclusion, radiation exposure triggers the overactivation of p38MAPK, which is regulated by ROS, resulting in testicular damage. Various p38MAPK-targeting agents are discussed, providing guidance for developing new strategies.

Suppressing MTERF3 inhibits proliferation of human hepatocellular carcinoma via ROS-mediated p38 MAPK activation

Mitochondrial transcription termination factor 3 (MTERF3) negatively regulates mitochondrial DNA transcription. However, its role in hepatocellular carcinoma (HCC) progression remains elusive. Here, we investigate the expression and function of MTERF3 in HCC. MTERF3 is overexpressed in HCC tumor tissues and higher expression of MTERF3 positively correlates with poor overall survival of HCC patients. Knockdown of MTERF3 induces mitochondrial dysfunction, S-G2/M cell cycle arrest and apoptosis, resulting in cell proliferation inhibition. In contrast, overexpression of MTERF3 promotes cell cycle progression and cell proliferation. Mechanistically, mitochondrial dysfunction induced by MTERF3 knockdown promotes ROS accumulation, activating p38 MAPK signaling pathway to suppress HCC cell proliferation. In conclusion, ROS accumulation induced by MTERF3 knockdown inhibits HCC cell proliferation via p38 MAPK signaling pathway suggesting a promising target in HCC patients.

Oxidative stress promotes liver fibrosis by modulating the microRNA-144 and SIN3A-p38 pathways in hepatic stellate cells.

Background & Aims: Reactive oxygen species (ROS) act as modulators triggering cellular dysfunctions and organ damage including liver fibrosis in which hepatic stellate cell (HSC) activation plays a key role. Previous studies suggest that microRNA-144 (miR-144) acts as a pro-oxidant molecule; however, whether and how miR-144 affects HSC activation and liver fibrosis remain unknown. Methods: Carbon tetrachloride (CCl4) and bile duct ligation (BDL)-induced experimental liver fibrosis models were used. Hepatic miR-144 expression was analyzed by miRNA in situ hybridization with RNAscope probe. The in vivo effects of silencing or overexpressing miR-144 were examined with an adeno-associated virus 6 (AAV6) carrying miR-144 inhibitor or mimics in fibrotic mouse experimental models. Results: In this study, we demonstrated that ROS treatment significantly upregulated miR-144 in HSCs, which further promoted HSC activation in vitro. Interestingly, miR-144 was preferentially elevated in HSCs of experimental liver fibrosis in mice and in human liver fibrotic tissues. Furthermore, in vivo loss or gain-of-function experiments via AAV6 carrying miR-144 antagomir or agomir revealed that blockade of miR-144 in HSCs mitigated, while overexpression of miR-144 in HSCs accelerated the development of experimental liver fibrosis. Mechanistically, SIN3 transcription regulator family member A (SIN3A), a transcriptional repressor, was identified to be the target of miR-144 in HSCs. MiR-144 downregulated Sin3A, and in line with this result, specific knockdown of Sin3a in HSCs remarkedly activated p38 MAPK signaling pathway to promote HSC activation, eventually exacerbating liver fibrosis. Conclusions: Oxidative stress-driven miR-144 fuels HSC activation and liver fibrogenesis by limiting the SIN3A-p38 axis. Thus, a specific inhibition of miR-144 in HSCs could be a novel therapeutic strategy for the treatment of liver fibrosis.

Role and mechanism of esketamine in improving postoperative cognitive dysfunction in aged mice through the TLR4/MyD88/p38 MAPK pathway.

Postoperative cognitive dysfunction (POCD) is a significant concern for the elderly population worldwide. This study explored the effects of esketamine on aged mice with POCD and investigate its mechanism of action involving the TLR4/MyD88/MAPK pathway. We administrated esketamine, along with lipopolysaccharide or anisomycin, to the aged POCD mouse models. We assessed their cognitive function using the Morris water maze test. Additionally, we evaluated histopathological changes/neuronal apoptosis in the mouse hippocampal CA1 area through HE/TUNEL stainings. Furthermore, we measured IL-1β/IL-6/TNF-α/TLR4/MyD88/MAPK (p-p38/p38) levels in mouse hippocampal tissues using ELISA/RT-qPCR/Western blotting. Lastly, we analyzed the interaction between TLR4 and MyD88 using a co-immunoprecipitation assay. Our findings showed that esketamine effectively mitigated POCD in aged mice. This was evident from the improved cognitive performance observed in the Morris water maze test, characterized by reduced escape latency/increased number of platform crossing/a higher percentage of time spent in the target quadrant. Furthermore, esketamine exhibited a protective effect against neuronal apoptosis and reduced the levels of inflammatory factors. These findings suggest that esketamine exerts an anti-inflammatory effect by downregulating TLR4/MyD88, thereby attenuating the inflammatory response associated with POCD. Additionally, esketamine suppressed the p38 MAPK pathway by inhibiting the TLR4/MyD88 signaling cascade. Esketamine demonstrated its efficacy in improving postoperative inflammation and cognitive impairment in aged mice by inhibiting the TLR4/MyD88 pathway. The activation of p38 MAPK signaling diminished the beneficial effects of esketamine in aged POCD mice. Collectively, the underlying mechanism of esketamine in mitigating POCD in aged mice involves the suppression of the TLR4/MyD88/p38 MAPK pathway.

Loss of ESRP2 Activates TAK1-MAPK Signaling through the Fetal RNA-Splicing Program to Promote Hepatocellular Carcinoma Progression.

Tumors usually display fetal-like characteristics, and many oncofetal proteins have been identified. However, fetal-like reprogramming of RNA splicing in hepatocellular carcinoma (HCC) is poorly understood. Here, it is demonstrated that the expression of epithelial splicing regulatory protein 2 (ESRP2), an RNA splicing factor, is suppressed in fetal hepatocytes and HCC, in parallel with tumor progression. By combining RNA-Seq with splicing analysis, it is identified that ESRP2 controls the fetal-to-adult switch of multiple splice isoforms in HCC. Functionally, ESRP2 suppressed cell proliferation and migration by specifically switching the alternative splicing (AS) of the TAK1 gene and restraining the expression of the fetal and oncogenic isoform, TAK1_ΔE12. Notably, aberrant TAK1 splicing led to the activation of p38MAPK signaling and predicted poor prognosis in HCC patients. Further investigation revealed that TAK1_ΔE12 protein interacted closely with TAB3 and formed liquid condensation in HCC cells, resulting in p38MAPK activation, enhanced cell migration, and accelerated tumorigenesis. Loss of ESRP2 sensitized HCC cells to TAK1 kinase inhibitor (TAK1i), promoting pyroptotic cell death and CD8+ T cell infiltration. Combining TAK1i with immune checkpoint therapy achieved potent tumor regression in mice. Overall, the findings reveal a previously unexplored onco-fetal reprogramming of RNA splicing and provide novel therapeutic avenues for HCC.

A2BR facilitates the pathogenesis of H. pylori-associated GU by inducing oxidative stress through p38 MAPK phosphorylation

Gastric ulcers significantly impact the quality of life of patients, the pathogenesis of which is closely associated with Helicobacter pylori (HP) infection. Oxidative stress is involved in the pathological mechanism of gastric ulcers. Recently, adenosine A2B Receptor (A2BR) was reported to activate the p38MAPK pathway. However, the role of A2BR in gastric ulcers remains unknown. In the present study, the biological function of A2BR in HP-induced gastric ulcers was investigated to explore novel targets for gastric ulcers. GES-1 cells were infected with HP, followed by incubation with 10 μM BAY60-6583 (A2BR agonist) and 25 nM PSB1115 (A2BR antagonist). In HP-infected GES-1 cells, an increased apoptotic rate, enhanced migration ability, excessive release of reactive oxygen species (ROS), increased malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) activity were observed, accompanied by the activation of p38MAPK signaling, which were dramatically aggravated by BAY60-6583 and alleviated by PSB1115. In animal experiments, rats were treated with 2 mg/kg BAY60-6583 and 10 mg/kg PSB1115, followed by gastric ulcer modeling 30 min later. In HP-infected rats, increased ulcer area, elevated pepsin activity, increased hematoxylin and eosin (HE) pathological scores, increased MDA levels, and decreased SOD activity were observed, which were further aggravated by BAY60-6583 and ameliorated by PSB1115. Finally, the effects of A2BR activation on apoptosis, migration, oxidative stress, and p38MAPK signaling in HP-infected GES-1 cells were reversed by an inhibitor of the p38MAPK pathway. Collectively, A2BR facilitated the pathogenesis of HP-induced gastric ulcers by inducing oxidative stress through p38MAPK activation.

Effects of hydrostatic compression on milk production-related signaling pathways in mouse mammary epithelial cells

Mammary epithelial cells (MECs) secrete milk into the mammary alveolar lumen during lactation. The secreted milk accumulates in the alveolar lumen until milk ejection occurs, and excess milk accumulation downregulates milk production in alveolar MECs. Intramammary hydrostatic pressure also increases in the alveolar lumen in a manner dependent on milk accumulation. In this study, we investigated whether high hydrostatic compression directly affects lactating MECs, using a commercial compression device and a lactation culture model of MECs, which have milk production ability and less permeable tight junctions. High hydrostatic compression at 100 kPa for 8 h decreased β-casein and increased claudin-4 levels concurrently with inactivation of STAT5 and glucocorticoid receptor signaling pathways. In addition, high hydrostatic compression for 1 h inactivated STAT5 and activated p38 MAPK signaling. Furthermore, repeated rises and falls of the hourly hydrostatic compression induced activation of positive (Akt, mTOR) and negative (STAT3, NF-κB) signaling pathways for milk production concurrently with stimulation of casein and lactoferrin production in MECs. These results indicate that milk production-related signaling pathways in MECs change in response to hydrostatic compression. Hydrostatic compression of the alveolar lumen may directly regulate milk production in the alveolar MECs of lactating mammary glands.

Obesity exacerbates influenza-induced respiratory disease via the arachidonic acid-p38 MAPK pathway.

Obesity is a risk factor for severe influenza, and asthma exacerbations caused by respiratory viral infections. We investigated mechanisms that increase the severity of airway disease related to influenza in obesity using cells derived from obese and lean individuals, and in vitro and in vivo models. Primary human nasal epithelial cells (pHNECs) derived from obese compared with lean individuals developed increased inflammation and injury in response to influenza A virus (IAV). Obese mice infected with influenza developed increased airway inflammation, lung injury and elastance, but had a decreased interferon response, compared with lean mice. Lung arachidonic acid (AA) levels increased in obese mice infected with IAV; arachidonic acid increased inflammatory cytokines and injury markers in response to IAV in human bronchial epithelial (HBE) cells. Obesity in mice, and AA in HBE cells, increased activation of p38 MAPK signaling following IAV infection; inhibiting this pathway attenuated inflammation, injury and tissue elastance responses, and improved survival. In summary, obesity increases disease severity in response to influenza infection through activation of the p38 MAPK pathway in response to altered arachidonic acid signaling.

T-2 mycotoxin Induces male germ cell apoptosis by ROS-mediated JNK/p38 MAPK pathway

T-2 mycotoxin, a type A trichothecene toxin that, specifically, causes male and female reproductive toxicity. We evaluated T-2 toxin toxicity in testes from neonatal testes after in vitro tissue cultured. Additionally, current study focuses on the molecular mechanism of toxicity and germ cell damage in GC-1 spermatogonial cells. Mouse testicular fragments were subjected to T-2 toxin (0–20 nM) during days 5 of in vitro culture. Testicular germ cell number were reduced and downregulated the expression of corresponding markers depending on the exposure concentration of T-2 toxin; however, Sertoli cell markers and steroidogenic enzyme expression increased when treated with 20 nM T-2 toxin. The cell viability decreased, apoptosis increased, and pro-apoptotic protein expression increased in 5–20 nM T-2 toxin–exposed spermatogonia. Moreover, T-2 toxin generated reactive oxygen species (ROS) and induced mitochondrial dysfunction, indicating that activation of p38 MAPK signaling triggered by ROS is involved in the apoptotic molecular mechanism of T-2 toxin. T-2 toxin induced the phosphorylation of ERK1/2, c-Jun, JNK/SAPK, p38, and p53, and the subsequent inhibition of AKT phosphorylation. The upregulation of genes related to apoptosis and MAPK/JNK signaling was consistently observed in cells exposed to T-2 toxin. These results indicate that T-2 toxin triggers apoptotic cell death in germ cells through the triggering of ROS-mediated JNK/p38-MAPK signaling pathways.

Fibroblast growth factor 8 facilitates cell-cell communication in chondrocytes via p38-MAPK signaling

Gap junction intercellular communication (GJIC) is essential for regulating the development of the organism and sustaining the internal environmental homeostasis of multi-cellular tissue. Fibroblast growth factor 8 (FGF8), an indispensable regulator of the skeletal system, is implicated in regulating chondrocyte growth, differentiation, and disease occurrence. However, the influence of FGF8 on GJIC in chondrocytes is not yet known. The study aims to investigate the role of FGF8 on cell-cell communication in chondrocytes and its underlying biomechanism. We found that FGF8 facilitated cell-cell communication in living chondrocytes by the up-regulation of connexin43 (Cx43), the major fundamental component unit of gap junction channels in chondrocytes. FGF8 activated p38-MAPK signaling to increase the expression of Cx43 and promote the cell-cell communication. Inhibition of p38-MAPK signaling impaired the increase of Cx43 expression and cell-cell communication induced by FGF8, indicating the importance of p38-MAPK signaling. These results help to understand the role of FGF8 on cell communication and provide a potential cue for the treatment of cartilage diseases.

Systems analysis of Alzheimer’s disease pathway dysregulation in human subjects is recapitulated in 3d cellular models to reveal P38 MAPK as a therapeutic target that mitigates tau pathology

AbstractBackground3D human neural cell culture models of Alzheimer’s disease (AD) are valuable resources for studying AD pathogenesis mechanisms. Although our 3D models capture cellular heterogeneity and key pathogenic cascades in AD, including β‐amyloid (Aβ) accumulation and Aβ‐induced tau pathology, it is not known to what extent 3D models functionally reflect human AD pathogenesis. We address this gap by capturing functionally active AD pathways in human brain through a granular systems approach that accurately recapitulates the activity of disease‐associated pathways from afflicted brain tissues in 3D models.MethodsWe leveraged transcriptomic data to precisely determine the activity dynamics of biological pathways. We assembled transcriptomic data from AD brains and compared them with a battery of 3D models displaying a broad range of disease‐associated characteristics. Our approach discovered pathways showing concordant dysregulation patterns between human brain and disease models. We prioritized the most consistent AD‐pathways for in‐vitro therapeutic screening.ResultsOne of our 3D models has transmembrane domain APP mutations, but not PS1 mutations and exhibits an elevated Aβ42/40 ratio. It best recapitulated dysregulated AD‐pathways found in both human prefrontal and temporal cortices. Multiple pathways indicated activation of p38 MAPK signaling, coupled with broad transcriptional inactivation in AD. Cellular and biochemical validations demonstrated elevated phosphorylated‐p38 (p‐tau)/total‐p38 ratios. Treatment with a p38 MAPK inhibitor resulted in significant reduction in the total amount of tau, significant reduction in the amount of p‐tau, and suggestive reduction in p‐tau/tau ratio. Our results strongly support a critical role for p38 MAPK signaling in mediating Ab‐induced tau pathology.ConclusionsUsing human brain transcriptomes, we have introduced a broadly‐applicable systems biology approach to rapidly discover therapeutic targets in 3D models. The approach provides a granular determination of the degree to which cellular models accurately reflect dysregulated molecular pathways in afflicted brains. We have detected, validated, and targeted the activated p38 MAPK pathway in AD. We have diminished tau pathology by inhibiting p38 MAPK signaling in cellular models, suggesting that the p38 MAPK pathway is a potent human‐derived target to combat tau pathology.PNY and SSK are co‐first‐authors.RT, WH, and DYK jointly supervised this project.

Prostacyclin receptor agonists induce DUSP1 to inhibit pulmonary artery smooth muscle cell proliferation

AimsUpregulated p38MAPK signaling is implicated in the accelerated proliferation of pulmonary artery smooth muscle cells (PA-SMCs) and the pathogenesis of pulmonary artery remodeling observed in pulmonary arterial hypertension (PAH). Previously, we reported that after endothelin-1 (ET-1) pretreatment, bone morphogenetic protein 2 (BMP2) activates p38MAPK signaling and accelerates PA-SMC proliferation. The activity of p38MAPK signaling is tightly regulated by the inactivation of dual-specificity phosphatase 1 (DUSP1). Activated p38MAPK induces DUSP1 expression, forming a negative feedback loop. Prostacyclin IP receptor agonists (prostacyclin and selexipag) are used to treat PAH. In this study, we aimed to verify whether IP receptor agonists affect DUSP1 expression and accelerate the proliferation of PA-SMCs. Main methodsPA-SMCs were treated with BMP2, ET-1, prostacyclin, and MRE-269, an active metabolite of selexipag, either alone or in combination. We quantified mRNA expressions using real-time quantitative polymerase chain reaction. Pulmonary artery specimens and PA-SMCs were obtained during lung transplantation in patients with PAH. Key findingsBoth prostacyclin and MRE-269 increased DUSP1 expression. Combined treatment with BMP2 and ET-1 induced cyclin D1 and DUSP1 expression and increased PA-SMC proliferation. MRE-269 attenuated BMP2/ET-1-induced cell proliferation. ET-1 increased DUSP1 expression in PA-SMCs from control patients but not in PA-SMCs from patients with PAH. SignificanceThis study showed that the p38MAPK/DUSP1 negative feedback loop is impaired in PAH, contributing to unregulated p38MAPK activation and PA-SMC hyperplasia. IP receptor agonist MRE-269 increases DUSP1 expression and inhibit p38MAPK-mediated PA-SMC proliferation. Future elucidation of the detailed mechanism underlying reduced DUSP1 expression would be informative for PAH treatment.

Quercetin Induces Cell Cycle Arrest and Apoptosis in YD10B and YD38 Oral Squamous Cell Carcinoma Cells.

Oral squamous cell carcinoma (OSCC) exhibits the highest lethality among head and neck cancers. Treatment for OSCC is limited due to diverse side effects. Quercetin is a natural flavonoid compound found in many kinds of plants and foods. Quercetin has been reported to be a modulator of proliferation and survival in various types of cancers due to its cytotoxic effects. We aimed to investigating chemopreventative roles of quercetin in YD10B and YD38 OSCC cells. For our study, two different types of OSCC cells were used. YD10B cells are tongue SCC cells with the p53 mutation and YD38 cells are lower gingiva SCC cells without the p53 mutation, respectively. The anticancer effects of quercetin were examined by cell viability, cell cycle, annexin-PI staining, and western blot. Our results showed that quercetin decreased cell viability and induced G1 cell cycle arrest in YD10B and YD38 OSCC cells. Moreover, quercetin remarkably decreased the expression of cell cycle upregulating proteins and increased the expression of a CDK inhibitor. Quercetin also significantly increased the number of annexin-V-positive cells in a dose-dependent manner in both types of OSCC cells. This apoptotic potential of quercetin triggered cleavage of PARP followed by activation of p38 MAPK signaling pathway. In conclusion, this study demonstrates that quercetin shows different anti-cancer responses in OSCC with and without p53 mutation, respectively. Despite different p53 status in OSCC cells, quercetin led to apoptotic signals in both cells. Quercetin repressed cell proliferation with G1 cell cycle arrest and apoptosis by activating the p38 signaling pathway in two OSCC cells with different p53 status. These findings might provide new strategy for OSCC therapy by quercetin.

Photothermal lipolysis accelerates ECM production via macrophage-derived ALOX15-mediated p38 MAPK activation in fibroblasts.

Skin and subcutaneous tissue tightening is usually treated by noninvasive photothermal treatment for medical esthetics purpose, while the underlying mechanism remains to be elucidated. Here, we hypothesized that adipocyte injury, as a stimulator, may regulate extracellular matrix (ECM) production by increasing ALOX15 in macrophages, which could lead to fibroblast activation. In this study, we show that lipolysis was induced by laser heating (45°C for 15 min) in patients and rats, and adipocyte thermal injury stimulates the ECM production in fibroblasts by ALOX15 that was increased in cocultured macrophages. These phenomena were evidenced by the ALOX15 knockdown. In addition, ALOX15 metabolite 12(S)-HETE activated p38 MAPK signaling pathway that mediated the production of ECM in fibroblast. In summary, the results of this study demonstrate that the mechanisms of adipose photothermal injury-induced skin and/or subcutaneous tissue tightening may have clinical relevance for noninvasive or minimally invasive photothermal therapeutics.

HIV Tat-Conjugated Histone H3 Peptides Induce Tumor Cell Death Via Cellular Stress Responses.

Histone H3 is a nucleosome scaffold protein that is involved in a variety of intracellular processes. Aberrant modification of H3 is important in carcinogenesis. In contrast, free histones in cells can act as stimuli to trigger cellular immune responses and cell death. In this study, we linked cell-penetrating peptide HIV Tat to a histone H3 fragment to achieve intracellular delivery in tumor cells. We found that Tat-conjugated histone polypeptides localized to nuclei of lung and breast cancer cells and caused cell death. A trans-configured Tat sequence displayed dramatically improved peptide half-life and cytotoxicity. Mechanistic studies demonstrated that treatment with the peptides significantly elevated mitogen-activated protein kinase (MAPK) signaling, reactive oxygen species (ROS) production, as well as levels of stress-inducible transcription factor ATF3 (activating transcription factor 3) and AP-1 (activating protein-1). Cytotoxicity of the peptide was significantly reduced by inhibition of AP-1 activity and ROS production. These results suggest the potential of Tat-conjugated H3 peptides as antitumor agents to induce cell death via increased cellular stress response by activating p38-MAPK signaling and intracellular ROS production.

2, 2′, 4, 4′-tetrabromodiphenyl ether induces placental toxicity via activation of p38 MAPK signaling pathway in vivo and in vitro

2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) is one of the most important polybrominated diphenyl ethers (PBDEs) congeners, and epidemiological studies have shown that it can cause adverse pregnancy outcomes. The aim of our study was to investigate the role of placental injury in BDE-47-induced adverse pregnancy outcomes through in vivo and in vitro models. From day 0.5 to day 16.5 of pregnancy of ICR mice, BDE-47 oral doses of 0, 25, 50 and 100mg/kg/day were administered. Immunohistochemical staining found that BDE-47 inhibited the expression of CD34 in mouse placenta, and ELISA results showed that BDE-47 reduced the levels of VEGF and PlGF in the serum of pregnant mice. Western blot assays found that the expression levels of VEGF-A and invasion-related factors were decreased in the placentas of BDE-47-treated group, which indicated that BDE-47 could impair placental angiogenesis. Furthermore, BDE-47 inhibited proliferation, increased apoptosis and autophagy, and activated p38 MAPK signaling pathway in mouse placental tissue. In vitro, HTR-8/SVneo cells were treated with 0, 5, 10, 20μM BDE-47 for 24h. Wound healing assays and Transwell assays showed that BDE-47 inhibited the migration and invasion ability of HTR-8/SVneo cells. We also found that BDE-47 inhibited the proliferation of HTR-8/SVneo cells and increased apoptosis and autophagy. BDE-47 activated p38 MAPK signaling pathway in HTR-8/SVneo cells, and inhibition of p38 MAPK signaling pathway in HTR-8/SVneo cells restored the effects caused by BDE-47. In conclusion, BDE-47 impairs placental angiogenesis by inhibiting cell migration and invasion, and induces placental toxicity by inhibiting proliferation, increasing apoptosis and autophagy. In vitro, activation of p38 MAPK signaling pathway is involved in the processes of placental injury by BDE-47.

RhoB affects colitis through modulating cell signaling and intestinal microbiome

BackgroundThe pathogenesis of inflammatory bowel diseases (IBD) is multifactorial, and diagnostic and treatment strategies for IBD remain to be developed. RhoB regulates multiple cell functions; however, its role in colitis is unexplored.ResultsHere, we found RhoB was dramatically increased in colon tissues of ulcerative colitis (UC) patients and mice with DSS-induced colitis. Compared with wild type mice, RhoB+/− and RhoB−/− mice developed milder DSS-induced colitis and increased goblet cell numbers and IEC proliferation. Decreased RhoB promoted goblet cell differentiation and epithelial regeneration through inhibiting Wnt signaling pathway and activating p38 MAPK signaling pathway. Moreover, increased SCFA-producing bacteria and SCFA concentrations were detected in intestinal microbiome of both RhoB+/− and RhoB−/− mice and upregulated SCFA receptor expression was also observed.ConclusionsTaken together, a higher level of RhoB is associated with UC, which also contributes to UC development through modulating cell signaling and altering intestinal bacterial composition and metabolites. These observations suggest that RhoB has potential as a biomarker and a treatment target for UC.4JidcymkrD7_Rm_WNvnQpDVideo

Phosphorylation of the small heat shock protein HspB1 regulates cytoskeletal recruitment and cell motility.

The small heat shock protein HspB1, also known as Hsp25/27, is a ubiquitously expressed molecular chaperone that responds to mechanical cues. Uniaxial cyclic stretch activates the p38 mitogen-activated protein kinase (MAPK) signaling cascade and increases the phosphorylation of HspB1. Similar to the mechanosensitive cytoskeletal regulator zyxin, phospho-HspB1 is recruited to features of the stretch-stimulated actin cytoskeleton. To evaluate the role of HspB1 and its phosphoregulation in modulating cell function, we utilized CRISPR/Cas9-edited HspB1-null cells and determined they were altered in behaviors such as actin cytoskeletal remodeling, cell spreading, and cell motility. In our model system, expression of WT HspB1, but not nonphosphorylatable HspB1, rescued certain characteristics of the HspB1-null cells including the enhanced cell motility of HspB1-null cells and the deficient actin reinforcement of stretch-stimulated HspB1-null cells. The recruitment of HspB1 to high-tension structures in geometrically constrained cells, such as actin comet tails emanating from focal adhesions, also required a phosphorylatable HspB1. We show that mechanical signals activate posttranslational regulation of the molecular chaperone, HspB1, and are required for normal cell behaviors including actin cytoskeletal remodeling, cell spreading, and cell migration.

Chenodeoxycholic acid suppresses AML progression through promoting lipid peroxidation via ROS/p38 MAPK/DGAT1 pathway and inhibiting M2 macrophage polarization

PurposeBile acids are steroid synthesized in liver, which are essential for fat emulsification, cholesterol excretion and gut microbial homeostasis. However, the role of bile acids in leukemia progression remains unclear. We aim at exploring the effects and mechanisms of chenodeoxycholic acid (CDCA), a type of bile acids, on acute myeloid leukemia (AML) progression. ResultsHere, we found that CDCA was decreased in feces and plasma of AML patients, positively correlated with the diversity of gut microbiota, and negatively associated with AML prognosis. We further demonstrated that CDCA suppressed AML progression both in vivo and in vitro. Mechanistically, CDCA bound to mitochondria to cause mitochondrial morphology damage containing swelling and reduction of cristae, decreased mitochondrial membrane potential and elevated mitochondrial calcium level, which resulted in the production of excessive reactive oxygen species (ROS). Elevated ROS further activated p38 MAPK signaling pathway, which collaboratively promoted the accumulation of lipid droplets (LDs) through upregulating the expression of the diacylglycerol O-acyltransferase 1 (DGAT1). As the consequence of the abundance of ROS and LDs, lipid peroxidation was enhanced in AML cells. Moreover, we uncovered that CDCA inhibited M2 macrophage polarization and suppressed the proliferation-promoting effects of M2 macrophages on AML cells in co-cultured experiments. ConclusionOur findings demonstrate that CDCA suppresses AML progression through synergistically promoting LDs accumulation and lipid peroxidation via ROS/p38 MAPK/DGAT1 pathway caused by mitochondrial dysfunction in leukemia cells and inhibiting M2 macrophage polarization.

Abstract 723: Dual inhibition of MDM2 and p38 MAPK signaling is a potential therapeutic strategy in esophageal squamous cell carcinoma

Abstract Background: Esophageal squamous cell carcinoma (ESCC) is one of the most common lethal malignancies. Despite recent advances in treatment, the overall 5-year survival rate remains low, primarily due to late diagnosis, acquired resistance to therapy, and distant metastases. Hence, development of novel therapeutic strategies is required to improve patient outcomes. The MDM2 gene is amplified in some patients with ESCC, frequently decreasing the tumor suppressive function of p53. In addition, 40-60% of ESCC tumors exhibit p53 mutations. Missense mutations within the p53 gene cause its overexpression and subsequent activation of p38 MAPK signaling. In this study, we aimed to investigate the effect of combining a p38 MAPK inhibitor and an MDM2 antagonist as a potential therapeutic strategy in ESCC. Methods: To determine the synergistic anti-tumor activity of the MDM2 antagonist siremadlin (HDM-201) and the p38 MAPK inhibitor Ralimetinib dimesylate (LY2228820), we performed cell viability, colony formation, apoptosis, and cell cycle analysis in ESCC cell lines. Next, we evaluated the anti-tumor activity of HDM-201 and LY2228820 in a xenograft mouse model. Finally, we performed siRNA mediated silencing of p53 to assess its functional role in the MDM2 antagonist-induced activation of p38 MAPK signaling and its ability to modulate the DNA damage response (DDR) by measuring ROS status and phosphorylation of H2AX. Results: HDM-201 exerted cytotoxic effects in p53-mutated ESCC cells in a dose-dependent manner and activated the p38 MAPK signaling pathway. These results prompted us to combine the p38 MAPK inhibitor LY2228820 with HDM-201 and evaluate this novel treatment strategy in a p53-mutant pre-clinical model of ESCC. We observed that HDM-201 and LY2228820 acted synergistically to decrease cell viability (p<0.01) and colony formation (p<0.01), as well as induction of apoptosis (p<0.01) and G2/M phase cell cycle arrest (p<0.01). The xenograft animal model confirmed our in vitro findings wherein the combined treatment exerted more potent anti-tumor activity (p<0.05). We also observed that silencing of p53 promoted resistance towards the MDM2 antagonist and did not induce apoptosis, highlighting that a functional p53 is required for inducing apoptosis after combined treatment. Furthermore, we observed that the combined treatment promoted ROS induced oxidative stress (p<0.01) and promoted DNA double strand breaks (DSBs) as evidenced by increased phosphorylation of H2AX (p<0.01), highlighting its potential as an effective therapeutic strategy. Conclusion: We provide novel pre-clinical evidence that inhibition of p38 MAPK signaling can augment the anti-tumor activity of an MDM2 antagonist in p53-mutant human tumor models of ESCC. Citation Format: Souvick Roy, Rachana Garg, David Wang, Ajay Goel. Dual inhibition of MDM2 and p38 MAPK signaling is a potential therapeutic strategy in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 723.