P38-specific Inhibitor SB203580 Research Articles

Increased Expression of CD95 in CD4+ Effector Memory T Cells Promotes Th17 Response in Patients with Myasthenia Gravis.

Emerging data have revealed that CD95 can evoke non-apoptotic signals, thereby promoting pro-inflammatory functions that link to the severity of autoimmune disorders. Here, we reported that the expression of CD95 in CD4+ effector memory T (CD4+ TEM) cells was increased in myasthenia gravis (MG) patients. We also found increased expression of CD95 in CD4+ TEM cells from MG patients correlated positively with clinical severity scores (QMGs), serum IL-17 levels and plasma cells (PCs) frequencies. Conventional treatment, such as glucocorticoid, could down-regulate the expression of CD95 in CD4+ TEM cells, QMGs, serum IL-17 levels and PCs frequencies from MG patients. In vitro, low-dose of agonistic anti-CD95 mAb could promote Th17 cell development. This effect was reversed by CD95 siRNA. Moverover, CD95 stimulation induced the phosphorylation of p38 and Erk1/2 and Th17 cell differentiation, and p38 specific inhibitor SB203580 or Erk1/2 specific inhibitor PD98059 could induce opposite changes. However, SB203580 or PD98059 do not abrogate the increase of CCR6+IL-17A+ cells, ROR-γt and IL-17 expression induced by CD95 triggering relatively to each corresponding control. This suggests that p38 and Erk1/2 MAPK pathway plays a role in expression of CCR6+IL-17A+ cells, ROR-γt and IL-17, but not in their increase induced by CD95 triggering. Taken together, this study revealed that increased expression of CD95 in CD4+ TEM cells promotes Th17 response under the microenvironment of MG.

IL6 Receptor Facilitates Adipogenesis Differentiation of Human Mesenchymal Stem Cells through Activating P38 Pathway.

Background and ObjectivesMesenchymal stem cells (MSCs) have the multipotent capacity to differentiate into multiple tissue lineages as well as to self-renew, which is the main origin of adipocytes. IL6/IL6R pathway exerts a significant role in tissue regeneration and cell differentiation. Whereas, the underlying mechanism between IL6/IL6R pathway and MSCs adipogenesis differentiation remains elusive.MethodsMSCs from healthy donors were cultured in adipogenesis differentiation medium for 0∼14 days, during which their adipogenesis differentiation degree was evaluated by Oil Red O staining. The expression of IL6R was detected in MSCs during adipogenesis differentiation. Knockdown and overexpression of IL6R were respectively performed using siRNA and lentivirus to investigate its effect on MSCs adipogenesis differentiation. The adipogenesis marker genes expression and MAPK pathway activation were detected by Western blotting. The role of P38 pathway in the adipogenesis differentiation of MSCs was determined using the specific inhibitor SB203580.ResultsThe expression of IL6 and IL6R increased during adipogenesis differentiation in MSCs, which were positively correlated with Oil Red O quantification result. Knockdown and overexpression experiments demonstrated a positive correlation between the expressions of IL6R and MSCs adipogenesis differentiation, accompanied by same trend of P38 phosphorylation. Besides, the specific P38 inhibitor SB203580 markedly inhibited the adipogenesis differentiation potential of MSCs.ConclusionsThis study reveals IL6R facilitates the adiogenesis differentiation of MSCs via activating P38 pathway.

P38-Mediated Cellular Senescence in Conjunctivochalasis Fibroblasts.

Conjunctivochalasis (CCH) is a common ocular disease and has received extensive attention recently. However, its exact pathogenesis remains largely unknown. Owing to the high morbidity of CCH in older people, this study aimed to investigate whether cellular senescence contributes to CCH progression and the underlying mechanism. Loose conjunctival tissues from CCH patients (n = 13) and normal conjunctival tissues from age-matched persons (n = 12) were obtained and the fibroblasts were separately induced and obtained. Cellular senescence, and the expression of senescence-associated genes (p53 and p21) and p38 in CCH conjunctival tissues and normal controls, were determined by senescence-associated β-galactosidase (SA-β-Gal) staining and quantitative (q)RT-PCR, respectively. To explore the effects of p38 on cellular senescence in CCH fibroblasts, small interfering RNA (siRNA) targeting p38 (siP38) and p38-specific inhibitor SB203580 was performed in CCH fibroblasts. Then, cellular senescence, cell viability, reactive oxygen species (ROS) production, and gene expression were detected according to the corresponding methods. CCH conjunctival tissues had significantly more senescent cells, evidenced by more SA-β-Gal-positive cells, and higher expression of senescence-associated genes (p53 and p21) and p38. CCH fibroblasts transfected with siP38 or treated with SB203580 had obviously reduced numbers of senescent cells, decreased ROS production, and increased cell viability, as well as reduced expression of senescence-associated genes. Meanwhile, blocking p38 signaling decreased the expression of p53 and p21. Therefore, these findings indicate that cellular senescence might be a causative factor for CCH. P38 signaling might play an important role in the progress of cellular senescence in CCH fibroblasts via manipulation of p53/p21 signaling.

Acetyl-macrocalin B suppresses tumor growth in esophageal squamous cell carcinoma and exhibits synergistic anti-cancer effects with the Chk1/2 inhibitor AZD7762

Natural products derived from herbal medicines have become a major focus of anti-cancer drug discovery studies. Acetyl-macrocalin B (A-macB) is an ent-diterpenoid isolated from Isodon silvatica. This study aimed to examine the effect and molecular action of A-macB in esophageal squamous cell carcinoma (ESCC) and explore possible drug synergistic modalities. A-macB induced cellular reactive oxygen species (ROS) generation, initiated the p38 mitogen-activated protein kinase (MAPK) signaling pathway, and triggered the caspase-9-dependent apoptosis cascade in ESCC cells. The ROS scavenger N-acetylcysteine (NAC) and the specific p38 inhibitor SB203580 reversed the effects of A-macB on the p38 network and thus rescued ESCC cells from apoptosis. The cellular ROS increase was at least partially due to the suppression of glutathione-S-transferase P1 (GSTP1) by A-macB. A-macB also upregulated the Chk1/Chk2-Cdc25C/Cdc2/Cyclin B1 axis to induce G2/M phase arrest. The cell growth inhibition induced by A-macB was further enhanced by AZD7762, a specific Chk1/Chk2 inhibitor, with a combination index (CI) of <1. Moreover, A-macB efficiently suppressed xenograft growth without inducing significant toxicity, and AZD7762 potentiated the effects of A-macB in the suppression of tumor growth in vivo. Taken together, A-macB is a promising lead compound for ESCC and exerts synergistic anti-cancer effects with AZD7762.

CD137-CD137L interaction induced the calcification of mouse smooth muscle cells via P38 MAPK signaling

Objective: To explore whether CD137-CD137L interaction could induce mouse vascular smooth muscle cells(VSMCs) calcification via P38 MAPK signaling. Methods: (1) Mouse VSMCs obtained from 8-week old male C57 mice were cultured by using method of tissue piece inoculation.The cells from 3 to 8 passage were divided into 4 groups: control group, agonist-CD137 group(recombinant CD137L protein), anti-P38 group(agonist-CD137 group+P38 inhibitor), single anti-P38 group(P38 inhibitor). The calcification was induced by adding a mixture of 10 mmol/L β-glycerophosphate+10(-8) mol/L dexamethasone+10(-7) mol/L insulin in the culture medium.Immunofluorescence was used to observe the changes of VSMCs markers(α-SMA and OPN).Real time-PCR was used to observe the mRNA expression of OPN and RUNX-2. Western blot was used to observe the protein expression of p-P38, OPN and RUNX-2. The level of cell calcification was observed by detecting alkaline phosphatase activity and calcium concentration. (2) The degeree of local calcium deposition was also tested on Von Kossa staining and Alizarin red staining methods in following 5 mouse VSMCs groups: control group, agonist-CD137 group(recombinant CD137L protein), anti-P38 group (agonist-CD137 group+P38 inhibitor), anti-CD137 group (agonist-CD137 group+CD137 inhibitor),agonist-P38 group(anti-CD137 group+P38 agonist). Results: (1) Compared with the control group, the fluorescence intensity of α-SMA was lower in the agonist-CD137 group(2.79±0.25 vs. 5.42±0.47,P<0.05), while the fluorescence intensity of OPN was higher(4.91±0.23 vs. 1.63±0.26, P<0.05). The fluorescence intensity of α-SMA was partly recovered after adding P38 inhibitor(4.48±0.27 vs. 2.79±0.25,P<0.05),but it was still lower than the control group (4.48±0.27 vs. 5.42±0.47, P<0.05),the fluorescence intensity of OPN decreased(2.66±0.15 vs. 4.91±0.23,P<0.05),but it was still higher than that in the control group (2.66±0.15 vs. 1.63±0.26,P<0.05).The fluorescence intensity of α-SMA and OPN(5.32±0.67 vs. 5.42±0.47,1.82±0.30 vs.1.63±0.26,both P>0.05) was similar between the control group and single anti-P38 group.(2) Compared with the control group, the protein level of p-P38(4.15±0.24 vs. 3.48±0.26, P<0.05), OPN(2.43±0.21 vs. 1.53±0.08, P<0.05), RUNX-2(3.20±0.23 vs. 1.13±0.10, P<0.05) was significantly increased in agonist-CD137 group,the above effects were blocked by adding specific P38 inhibitor SB203580(1.16±0.12 vs. 4.15±0.24, 0.50±0.02 vs. 2.43±0.21,and 1.74±0.14 vs. 3.20±0.23,all P<0.05);the protein level of p-P38(2.93±0.60 vs. 3.48±0.26,P>0.05),OPN (1.4±0.64 vs. 1.53±0.08,P>0.05),RUNX-2(1.26±0.26 vs.1.13±0.10, P>0.05) was similar between single anti-P38 group and the control group. (3) Compared with the control group, the mRNA level of OPN (1.51±0.34 vs. 1, P<0.05) and RUNX-2(2.67±0.19 vs. 1, P<0.05) was significantly upregulated in agonist-CD137 group, and these effects were blocked by adding specific P38 inhibitor SB203580(0.33±0.14 vs. 1 and 0.45±0.03 vs. 1,P<0.05);the mRNA level of OPN (1.05±0.09 vs. 1, P>0.05) and RUNX-2(1.18±0.10 vs. 1, P>0.05) was similar between the single anti-P38 group and the control group.(4) Compared with the control group,the ALP activity and calcium concentration(2.40±0.25 vs. 1.40±0.21,5.51±0.33 vs. 3.15±0.31,both P<0.05) were significantly increased in agonist-CD137 group,while the effects could be blocked by adding specific P38 inhibitor SB203580((1.99±0.07) king unit/gprot vs. (2.40±0.25) king unit/gprot, (3.74±0.20) mmol/gprot vs. (5.51±0.33) mmol/gprot, both P<0.05).The ALP activity and calcium concentration was similar between single anti-P38 group and the control group((1.60±0.25) king unit/gprot vs. (1.40±0.21)king unit/gprot, (2.66±0.28) mmol/gprot vs. (3.15±0.31) mmol/gprot, both P>0.05). (5) Compared with the control group,the calcification of VSMCs in the agonist-CD137 group was significantly increased,while the calcification in the anti-P38 group was significantly reduced.Compared with the agonist-CD137 group,the level of calcification in the anti-CD137 group was obviously increased,and the calcification in the agonist-P38 group was significantly higher than that in the anti-CD137 group and the control group. Conclusion: These findings suggest that CD137-CD137L signaling may regulate VSMCs calcification via modulating P38 pathway.

TXNIP knockdown alleviates hepatocyte ischemia reperfusion injury through preventing p38/JNK pathway activation

Hepatic ischemia and reperfusion (I/R) injury is a major cause of liver damage during liver transplantation, resection surgery, shock, and trauma. It has been reported that TXNIP expression was upregulated in a rat model of hepatic I/R injury. However, the role of TXNIP in the hepatic I/R injury is little known. In our study, we investigated the biological role of TXNIP and its potential molecular mechanism in the human hepatic cell line (HL7702 cells). Using oxygen-glucose deprivation and reoxygenation (OGD/R) to create a cell model of hepatic I/R injury, we found that the mRNA and protein expression levels of TXNIP were upregulated in HL7702 cells exposed to OGD/R. TXNIP overexpression remarkably promoted OGD/R-induced cell apoptosis and lactate dehydrogenase (LDH) release, both of which were significantly decreased by TXNIP knockdown. The production of malondialdehyde (MDA) was also increased by TXNIP overexpression, but was reduced by TXNIP knockdown. Moreover, TXNIP overexpression significantly upregulated the phosphorylation of p38 and JNK, which was remarkably inhibited by TXNIP knockdown. Additionally, p38-specific inhibitor SB203580 abrogated the effect of TXNIP overexpression on OGD/R-induced cell injury. Taken together, these results indicated that TXNIP knockdown alleviated hepatocyte I/R injury through preventing p38/JNK pathway activation. Thus, TXNIP might offer a novel potential therapeutic target for the treatment of hepatic I/R injury.

Acetyl-macrocalin B, an ent-kaurane diterpenoid, initiates apoptosis through the ROS-p38-caspase 9-dependent pathway and induces G2/M phase arrest via the Chk1/2-Cdc25C-Cdc2/cyclin B axis in non-small cell lung cancer

ABSTRACTNon-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide, and novel effective drugs against NSCLC are urgently needed. Isodon species are rich in ent-kaurane diterpenoids that have been reported to have antitumor bioactivity. Acetyl-macrocalin B (A-macB) is a novel ent-kaurane diterpenoid isolated from Isodon silvatica, and its antitumor efficacy against NSCLC and the underlying mechanisms were scrutinized in depth. The viability of cells treated with A-macB was detected by CCK-8 and colony formation assays. Apoptosis and cell cycle distribution were analyzed by flow cytometry. The mechanisms were investigated by detecting ROS and performing western blotting and verification experiments with specific inhibitors. The in vivo effect of A-macB was explored in a nude mouse xenograft model. A-macB effectively inhibited H1299 and A549 cell viability, triggered apoptosis and delayed cells in the G2/M phase. A-macB induced cellular ROS production and then activated the p38 MAPK-mediated, caspase 9-dependent apoptotic pathway. Both the ROS scavenger NAC and the specific p38 inhibitor SB203580 inactivated the function of p38 induced by A-macB, thus preventing cells from apoptosis. A-macB activated the Chk1/2-Cdc25C-Cdc2/cyclin B1 axis to induce G2/M phase arrest. AZD7762 abrogated the function of Chk1/2, abolished the G2/M delay and enhanced the cytotoxicity of A-macB. Moreover, A-macB efficiently suppressed tumor growth in a mouse xenograft model without noticeable toxicity to normal tissues. Having both efficacy and relative safety, A-macB is a potential lead compound that is worthy of further exploration for development as an anticancer agent.

Juglone induces apoptosis and autophagy via modulation of mitogen-activated protein kinase pathways in human hepatocellular carcinoma cells

Juglone (JG), a naturally-occurring naphthoquinone of Manchurian walnut (Juglans mandshurica) was shown to inhibit proliferation in various tumor types. However, the molecular mechanisms of JG on the induction of apoptosis and autophagy in HepG2 cells have not been examined. Herein, we investigated that JG could inhibit cell proliferation by induction of G2/M phase arrest. Also, occurrence of apoptosis was closely related with loss of mitochondrial membrane potential, the changes of apoptosis-related proteins after treatment with JG. In addition, we found that JG caused autophagy, as evidenced by increased expressions of LC3-II and Beclin-1. Interestingly, inhibition of JG-induced autophagy by 3-methyladenine (3-MA) and wortmannin (WT) significantly decreased apoptosis, whereas the apoptosis inhibitor z-VAD-fmk slightly enhanced autophagy. Furthermore, the induction of autophagy and apoptosis was associated with activation of MAPK family members (p38 and JNK) and production of reactive oxygen species (ROS). Both JNK inhibitor (SP600125) and ROS scavenger (N-acetylcysteine, NAC) could attenuate JG-induced autophagy and apoptosis. However, the p38-specific inhibitor SB203580 enhanced autophagic and apoptotic death. Moreover, the ROS scavenger NAC prevented phosphorylation of both p38 and JNK. Collectively, our data revealed that JG induced G2/M phase arrest, apoptosis, and autophagy through the ROS-dependent signaling pathway.

Upregulation of glutamate metabolism by BYHWD in cultured astrocytes following oxygen-glucose deprivation/reoxygenation in part depends on the activation of p38 MAPK.

Recent studies have demonstrated that Buyang Huanwu Decoction (BYHWD) decreased glutamate levels subsequent to cerebral ischemia. Glutamate transporter-1 (GLT-1) and glutamine synthetase (GS), which are located in astrocytes, mainly contribute to glutamate transportation, thus reducing glutamate concentration. BYHWD has previously been demonstrated to upregulate GLT-1 and GS following ischemia in vivo. However, whether BYHWD can directly influence astrocytic GLT-1/GS levels remains unknown. In the present study, the effect of BYHWD containing serum (BYHWD-CS) on GLT-1/GS levels in astrocytes following oxygen-glucose deprivation/reoxygenation (OGD/R) was investigated. The results revealed that BYHWD-CS enhanced the expression levels of GLT-1 and GS in cultured astrocytes, which reduced glutamate concentration in the culture medium. Meanwhile, increased p38 mitogen-activated protein kinase (p38 MAPK) was phosphorylated (activation form) by BYHWD-CS in cultured astrocytes, and the specific p38 inhibitor SB203580 blocked the increase of GLT-1/GS accompanied by decreased cell viability. Furthermore, SB203580 suppressed the effect of BYHWD-CS on the level of glial fibrillary acidic protein (an astrocytic marker), thus confirming that astrocytes are directly involved in the protective role of BYHWD after OGD/R. These findings suggest that BYHWD upregulates GLT-1 and GS via p38 MAPK activation, and protects cultured astrocytes from death caused by OGD/R (typical in vitro model), which complemented the role of astrocytes in the protective effect of BYHWD.

The tripartite motif-containing protein3 on the proliferation and cytokine secretion of rheumatoid arthritis fibroblast-like synoviocytes.

Recent studies have revealed fibroblast-like synoviocytes (FLS) as a pivotal effector cell in the inflamed joint of rheumatoid arthritis (RA) patients. FLS exhibit high proliferation rates and constitutive expression of cytokines, contributing to the pathogenesis of RA. In this study, we found that the expression of tripartite motif-containing protein 3 (TRIM3), a candidate tumor suppressor gene, was lower in synovial tissue samples of RA patients than in that of healthy controls. We then investigated the role of TRIM3 on the proliferation and cytokine secretion of primary cultured FLS from RA patients. Enforced expression of TRIM3 in RA FLS led to significantly decreased cell proliferation as indicated by Cell Counting Kit-8 assay, reduced secretion of tumor necrosis factor-α (TNF)-α, interleukin (IL)-1β and IL-6 as indicated by enzyme-linked immunosorbent assays, and decreased p38 phosphorylation as assessed by western blot analysis. The proteins promoting cell cycles (cyclin D1 and PCNA) were downregulated and the protein negatively regulating cell cycle progression (p53 and p21) was upregulated after TRIM3 overexpression. Importantly, TRIM3 knockdown had reverse effects on cell proliferation, which was suppressed by the p38-specific inhibitor SB203580. In conclusion, the current results demonstrated the downregulation of TRIM3 expression in RA synovial tissues. Importantly, TRIM3 exerted an anti-proliferation role in RA FLS via p38 signaling pathway.

TGF-β1 contributes to CD8+ Treg induction through p38 MAPK signaling in ovarian cancer microenvironment

CD8+ regulatory T cells (Tregs) contribute to cancer progression and immune evasion. We previously reported that CD8+ Tregs could be induced in vitro by co-culture of CD8+ T cells with the OC cell lines SKOV3/A2780. Here, we described the role of TGF-β1 in CD8+ Treg induction by the OC microenvironment. OC patients expressed high levels of TGF-β1, as did the co-culture supernatant from CD8+ T cells and SKOV3. Additionally, TGF-β1 levels were positively correlated with CD8+ Treg percentages in OC. Neutralization experiments, cytokine studies and proliferation assays revealed that the in vitro-induced CD8+Tregs depended at least partially on up-regulated expression of TGF-β1 to exert their suppressive function. CD8+ T cells cultured with SKOV3 exhibited marked activation of p38 MAPK than CD8+ T cells cultured alone, which could be inhibited by TGF-β1-neutralizing antibody. Moreover, the p38 specific inhibitor SB203580 dose-dependently blocked the TGF-β1 activated conversion of CD8+ T cells into CD8+ Tregs. These data suggested that in vitro-induction of CD8+ Tregs depended in part on TGF-β1 activation of p38 MAPK signaling. Therefore, p38 MAPK could be a therapeutic target in OC anti-tumor immunotherapy.

Geraniin induces apoptosis of human breast cancer cells MCF-7 via ROS-mediated stimulation of p38 MAPK

Geraniin, a typical ellagitannin isolated from Phyllanthus urinaria Linn, has been found to possess a range of bioactive properties. In the present study, we found that Geraniin showed potent anti-proliferative effects on human breast cancer MCF-7 cells. The IC50 values were 9.94, 17.98 and 42.32 µM after 72-, 48- and 24-h treatment, respectively. Meanwhile, Geraniin could remarkably disrupt mitochondrial membrane potential and arrest S phase cell cycle. Western-blot analysis showed that Geraniin induced phosphorylation of the anti-apoptotic Bcl-2, and the cleavage of poly (ADP-ribose) polymerase (PARP) and caspase-3 in MCF-7 cells. Moreover, Geraniin treatment activated p38 mitogen-activated protein kinase (p38 MAPK) and the effect was blunted in MCF-7 cells with the treatment of a specific p38 inhibitor SB203580. Geraniin could generate intracellular reactive oxygen species (ROS), activate p38 MAPK then induce the apoptosis in MCF-7 cells, such phenomena was abrogated by pretreatment with N-acetyl-l-cysteine. In general, these results support the conclusion that Geraniin-induced apoptosis is mediated via ROS-mediated stimulation of p38 MAPK signaling.

Activation of Type 4 Metabotropic Glutamate Receptor Attenuates Oxidative Stress-Induced Death of Neural Stem Cells with Inhibition of JNK and p38 MAPK Signaling.

Promoting both endogenous and exogenous neural stem cells' (NSCs) survival in the hostile host environments is essential to cell replacement therapy for central nervous system (CNS) disorders. Type 4 metabotropic glutamate receptor (mGluR4), one of the members of mGluRs, has been shown to protect neurons from acute and chronic excitotoxic insults in various brain damages. The present study investigated the preventive effects of mGluR4 on NSC injury induced by oxidative stress. Under challenge with H2O2, loss of cell viability was observed in cultured rat NSCs, and treatment with selective mGluR4 agonist VU0155041 conferred protective effects against the loss of cellular viability in a concentration-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Pretreatment of VU0155041 (30 μM) also inhibited the excessive NSC death induced by H2O2, and group III mGluRs antagonist (RS)-a-methylserine-O-phosphate (MSOP) or gene-targeted knockdown abolished the protective action of mGluR4, indicated by propidium iodide-Hoechst and terminal deoxynucleotidyl transferase-mediated UTP nick end labeling (TUNEL) staining. Western blot assay demonstrated that mGluR4 activation reversed the decreased procaspase-8/9/3and the destructed Bcl-2/Bax expressing balance, and likewise, MSOP and mGluR4 knockdown abrogated the action of mGluR4 activity. Furthermore, inhibition of JNK and p38 mitogen-activated protein kinases (MAPKs) were observed after mGluR4 activation, and as paralleling control, JNK-specific inhibitor SP600125 and p38-specific inhibitor SB203580 significantly rescued the H2O2-mediated NSC apoptosis and cleavage of procaspase-3. We suggest that activation of mGluR4 prevents oxidative stress-induced NSC death and apoptotic-associated protein activities with involvement of inhibiting the JNK and p38 pathways in cell culture. Our findings may help to develop strategies for enhancing the resided and transplanted NSC survival after oxidative stress insult of CNS.

Piperlongumine induces apoptotic and autophagic death of the primary myeloid leukemia cells from patients via activation of ROS-p38/JNK pathways.

To investigate the effects of piperlongumine (PL), an anticancer alkaloid from long pepper plants, on the primary myeloid leukemia cells from patients and the mechanisms of action. Human BM samples were obtained from 9 patients with acute or chronic myeloid leukemias and 2 patients with myelodysplastic syndrome (MDS). Bone marrow mononuclear cells (BMMNCs) were isolated and cultured. Cell viability was determined using MTT assay, and apoptosis was examined with PI staining or flow cytometry. ROS levels in the cells were determined using DCFH-DA staining and flow cytometry. Expression of apoptotic and autophagic signaling proteins was analyzed using Western blotting. PL inhibited the viability of BMMNCs from the patients with myeloid leukemias (with IC50 less than 20 μmol/L), but not that of BMMNCs from a patient with MDS. Furthermore, PL (10 and 20 μmol/L) induced apoptosis of BMMNCs from the patients with myeloid leukemias in a dose-dependent manner. PL markedly increased ROS levels in BMMNCs from the patients with myeloid leukemias, whereas pretreatment with the antioxidant N-acetyl-L-cysteine abolished PL-induced ROS accumulation and effectively reduced PL-induced cytotoxicity. Moreover, PL markedly increased the expression of the apoptotic proteins (Bax, Bcl-2 and caspase-3) and autophagic proteins (Beclin-1 and LC3B), and phosphorylation of p38 and JNK in BMMNCs from the patients with myeloid leukemias, whereas pretreatment with the specific p38 inhibitor SB203580 or the specific JNK inhibitor SP600125 partially reversed PL-induced ROS production, apoptotic/autophagic signaling activation and cytotoxicity. Piperlongumine induces apoptotic and autophagic death of the primary myeloid leukemia cells from patients via activation of ROS-p38/JNK pathways.

Induction of GADD45α protects M17 neuroblastoma cells against MPP*.

Growth arrest and DNA-damage-inducible protein 45α (GADD45α) is an important member of the family of growth arrest and DNA damage-inducible (GADD) proteins. The expression patterns and possible roles of GADD45α in Parkinson's disease (PD) are so far less understood. In this study, we found that 1-methyl-4-phenylpyridinium (MPP+) treatment up-regulates the expression of GADD45α in both a time-dependent manner and a dose-dependent manner in human dopamine neuroblastoma M17 cells. The up-regulation of GADD45α was abolished by pretreatment with the c-Jun N-terminal kinases (JNK) inhibitor SP600125 but not the p38 specific inhibitor SB203580. Further study revealed that c-Jun silencing abolished the effects of MPP+ on the expression of GADD45α. Important, ChIP studies verified the ability of c-Jun to bind to the GADD45 promoter. In addition, we found that inhibition of GADD45α by small RNA interference exacerbates the impaired cell viability, LDH release, and apoptosis induced by MPP+. Correspondingly, silence of GADD45 exacerbated Caspase-3 activation induced by MPP+. These data suggested a neuroprotective effect of GADD45α against MPP+ neurotoxicity.

Polygalasaponin F inhibits secretion of inflammatory cytokines via NF-κB pathway regulation

To study the anti-neuroinflammatory mechanisms of polygalasaponin F (PS-F), ELISA method was used to detect the secretion of inflammatory cytokines. Western blot was used to detect the protein expression and phosphorylation levels. Immunofluorescence assay was used to observe the NF-κB nuclear translocation. PS-F could inhibit the release of inflammatory cytokines TNF-α and NO induced by lipopolysaccharides (LPS) and reduce the expression of inducible nitric oxide synthases (iNOS). As for MAPK-signaling pathway, PS-F could only inhibit the phosphorylation levels of p38 MAPK, but did not significantly affect the phosphorylation levels of JNK and ERK1/2 protein kinases. PS-F could inhibit NF-κB nuclear translocation in a dose-dependent manner. The results of Western blot assay were consistent with immunofluorescence assays. Meanwhile, p38-specific inhibitor SB203580 (20 μM) and p65-specific inhibitor PDTC (100 μM) were, respectively, administered as a positive control. In addition, PS-F could significantly inhibit the cytotoxicity of conditioned medium prepared by LPS-stimulated BV-2 microglia (LPS conditioned media) to neuronal PC12 cells and improve cell viability. PS-F inhibits the secretions of neuroinflammatory cytokines by the regulation of NF-κB-signaling pathway.

P38α subtype is a potential target to inhibit eNOS activity and NO production in human endothelial cells

Human endothelial nitric oxide synthase (eNOS) activity is important for maintaining blood pressure homeostasis and vascular integrity through nitric oxide (NO).The in vitro study aimed at investigating a role of p38α signaling in modulating NO production in human umbilical vein endothelial cell-12 (HUVEC-12). Consistent with the stimulation of lipopolysaccharide (LPS) or tumor necrosis factor (TNF)-α, the over-expression of p38α markedly down-regulated the eNOS promoter activity in HUVEC-12, which could be reversed by its negative mutant p38α (AF) or p38-specific inhibitor SB203580. Compared to the stimulation of LPS or TNF-α, p38α-targeting siRNA decreased the expressions of phosphorylated and non-phosphorylated p38α, and increased the promoter activity, an eNOS mRNA level and a phosphorylated eNOS protein expression with the enhancement of NO, which could be abrogated by the scrambled siRNA. The in situ eNOS protein expression in the cells treated by p38α-targeting siRNA was also higher than that of the control, following the corresponding attenuation of a p38 level, and mainly localized in the inner membrane and cytoplasm. These results indicate that the p38α subtype may be a potential target to down-regulate the eNOS activity and NO production in human endothelial cells.

P38 signaling in titanium particle‐induced MMP‐2 secretion and activation in differentiating MC3T3‐E1 cells

The periprosthetic osteolysis induced by wear particles contributes to aseptic loosening after joint arthroplasty. The molecular mechanism underlying osteolysis remains to be described. In this study, cultured MC3T3-E1 cells were incubated with titanium particles. We investigated the role of p38 mitogen-activated protein kinase in the expression of MMP-2 in response to wear particles. Our results demonstrated MC3T3-E1 cells exposed to titanium particles had significantly increased levels of MMP-2 and MT1-MMP mRNA, whereas the TIMP-2 mRNA level was unchanged. In MC3T3-E1 cells, the protein expression of MMP-2, MT1-MMP, and active p38 was also elevated after titanium particle exposure, as detected by Western blot and Biotrak activity analyses. Inhibition studies showed that the specific p38 inhibitor SB203580 completely abrogated the increase in MMP-2 and MT1-MMP production induced by the titanium particles. Moreover, our results revealed that conditioned media-stimulated osteoclast formation was related to the MMP-2 activity of osteoblasts that were challenged with Ti particles. This study demonstrated that p38 signaling is required for MMP-2 activity in osteoblasts under wear particle-induced conditions. MMP-2 could act as a catabolic element or a proinflammatory factor contributing to periprosthetic osteolysis. Therefore, the p38 pathway and MMP-2 may play a critical role in the development of aseptic loosening.

Saikosaponin D disrupts platelet-derived growth factor-β receptor/p38 pathway leading to mitochondrial apoptosis in human LO2 hepatocyte cells: A potential mechanism of hepatotoxicity

Herbal hepatotoxicity has been increasingly reported in clinical context, but the underlying mechanisms are poorly understood. Saikosaponin D (SSD) is a major component of saikosaponins isolated from Bupleurum falactum, a herb that has been linked to hepatotoxicity. Our current study was to examine the toxic effect of SSD on human hepatocyte LO2 cells and explore the possible mechanism. The results demonstrated that SSD reduced cell viability and led to dramatic morphological alterations in LO2 cells. Hoechst staining and flow cytometry analyses showed that SSD stimulated hepatocyte apoptosis. SSD-treated cells exhibited apparent nuclear condensation and fragmentation, and the apoptotic cells were increased by SSD dose-dependently. Subsequent experiments showed that SSD decreased mitochondrial membrane potential and downregulated Bcl-2 but upregulated Bax. Moreover, caspase-9 and caspase-3 were activated in SSD-treated LO2 cells. These data consistently indicated that SSD stimulated mitochondrial apoptosis in hepatocytes. Mechanistic investigations showed that SSD disrupted p38 signaling and that p38 specific inhibitor SB203580 mimicked the pro-apoptotic effect of SSD. In addition, platelet-derived growth factor-β receptor (PDGF-βR) blocker imatinib reduced p38 phosphorylation and also mimicked the pro-apoptotic effect of SSD in LO2 cells. These data collectively indicated that SSD induced apoptosis by interrupting PDGF-βR/p38 pathway in LO2 hepatocytes.

Gene Expression Analysis to Evaluate the Effect of p38 Specific Inhibitor SB203580 on SEB‐Induced Apoptosis Related Pathways

Staphylococcal enterotoxin B (SEB) is an enterotoxin that has been thoroughly investigated. However, little is known about the cascades of signaling events that explain the pathomechanism of SEB. This research involves the pathogenic nature of Staphylococcal aureus, the bacterium responsible for the production of the superantigen SEB which can cause death in human peripheral blood mononuclear cells (PBMC). Since SEB is known to induce multiple signal transduction pathways, we have identified a crucial pathway inter‐connector (p38) that may have an inhibitory effect in unwanted, SEB induced cellular activities. This study is focused on obstructing signaling pathways with the use of the inhibitor 4‐[5‐(4‐Fluorophenyl)‐2‐[4‐(methylsulfonyl)phenyl]‐ 1‐H‐imidazol‐4‐yl]pyridine (SB203580), followed by analyzing alterations to known expression patterns of genes associated with apoptosis. Some of these genes include Caspase 1, 3, 6–10, Heparanase precursor (HEP), genes associated with retinoid‐interferon‐ induced mortality (GRIM)‐19, and CASP2 and RIPK1 domain containing adaptor with death domain (CRADD). These effects will be further confirmed through a set of protein expression analyses. As our experimental design specifically targets pathway inter‐connector p38, we believe the target is unique and has the ability to sustain longer lasting inhibitory effects. We are also confident that inhibiting such a component will have a maximum effect on a cell module, terminating the “leaking effect,” which may benefit a number of experimental modules focused on disease prevention and rapid diagnostics.