The mechanism by which MEK/ERK regulates JNK and p38 activity in polyamine depleted IEC-6 cells during apoptosis

Role of in vitro two-dimensional (2D) and three-dimensional (3D) cell culture systems for ADME-Tox screening in drug discovery and development: a comprehensive review

Drug discovery and development have become a very time-consuming and expensive process. Preclinical animal models have become the gold standard for studying drug pharmacokinetic and toxicity parameters. However, the involvement of a huge number of animal subjects and inter-species pathophysiological variations between animals and humans has provoked a lot of debate, particularly because of ethical concerns. Although many efforts are being established by biotech and pharmaceutical companies for screening new chemical entities in vitro before preclinical trials, failures during clinical trials are still involved. Currently, a large number of two- dimensional (2D) in vitro assays have been developed and are being developed by researchers for the screening of compounds. Although these assays are helpful in screening a huge library of compounds and have shown perception, there is a significant lack in predicting human Absorption, Distribution, Metabolism, Excretion and Toxicology (ADME-Tox). As a result, these assays cannot completely replace animal models. The recent inventions in three-dimensional (3D) cell culture-based assays like organoids and micro-physiological systems have shown great potential alternative tools for predicting the compound pharmacokinetic and pharmacodynamic fate in humans. In this comprehensive review, we have summarized some of the most commonly used 2D in vitro assays and emphasized the achievements in next-generation 3D cell culture-based systems for predicting the compound ADME-Tox.

Protective effects of dietary icariin on lipopolysaccharide-induced acute oxidative stress and hepatopancreas injury in Chinese mitten crab, Eriocheir sinensis

To investigate the effects of dietary icariin (ICA) supplementation on acute oxidative stress and hepatopancreatic injury induced by lipopolysaccharide (LPS) injection in Eriocheir sinensis, an 8-week feeding trial of crabs was conducted using 4 diets with different supplementation levels of ICA (0, 50, 100, and 200 mg/kg diet weight, respectively), and then challenged with LPS of 400 μg/kg body weight for 6 h. Results showed that 100 mg/kg ICA supplementation increased the antioxidant capacity, reduced the stress-related indicators in haemolymph, strengthen the mitochondrial membrane potential, and reduce apoptosis compared to the single LPS-treated crabs. The expressions of apoptosis-related genes and proteins were also evaluated to further understand the effects of dietary ICA pretreatment on LPS-induced cell apoptosis. As a result, dietary 100 mg/kg diet weight ICA pre-addition significantly down-regulated the expression of HSP60, HSP70, Caspase 3c, Caspase 8, Caspase 3, Caspase 9, P38, and Bax (P < 0.05), and alleviated the suppressed expression of PI3K, AKT, MEK, and Bcl-2 (P < 0.05) in crabs challenged with LPS. Overall, this research reveals that ICA supplementation of 100 mg/kg diet weight could enhance the resistance to oxidative damage and apoptosis in E. sinensis facing LPS challenge.

Signaling through the S1P-S1PR Axis in the Gut, the Immune and the Central Nervous System in Multiple Sclerosis: Implication for Pathogenesis and Treatment

Sphingosine 1-phosphate (S1P) is a signaling molecule with complex biological functions that are exerted through the activation of sphingosine 1-phosphate receptors 1–5 (S1PR1–5). S1PR expression is necessary for cell proliferation, angiogenesis, neurogenesis and, importantly, for the egress of lymphocytes from secondary lymphoid organs. Since the inflammatory process is a key element of immune-mediated diseases, including multiple sclerosis (MS), S1PR modulators are currently used to ameliorate systemic immune responses. The ubiquitous expression of S1PRs by immune, intestinal and neural cells has significant implications for the regulation of the gut–brain axis. The dysfunction of this bidirectional communication system may be a significant factor contributing to MS pathogenesis, since an impaired intestinal barrier could lead to interaction between immune cells and microbiota with a potential to initiate abnormal local and systemic immune responses towards the central nervous system (CNS). It appears that the secondary mechanisms of S1PR modulators affecting the gut immune system, the intestinal barrier and directly the CNS, are coordinated to promote therapeutic effects. The scope of this review is to focus on S1P−S1PR functions in the cells of the CNS, the gut and the immune system with particular emphasis on the immunologic effects of S1PR modulation and its implication in MS.

DUSP1 regulates hippocampal damage in epilepsy rats via ERK1/2 pathway

OBJECTIVE

To investigate the effects of DUSP1 on the hippocampal injury of young rats with epilepsy (EP) through mediating ERK1/2 signaling pathway.

METHODS

Young SD rats were selected and divided into Control, EP, EP + LV-GFP, EP + LV-DUSP1, EP + LV-siDUSP1, and EP + LV-siDUSP1 + U0126 groups. Morris Water Maze Test was used to detect the spatial learning and memory. Nissl staining and TUNEL staining were conducted and the inflammatory factors and oxidative stress-related indicators were also measured. Western blotting was utilized to detect the expression of DUSP1 and ERK1/2 pathway. EP cell model was constructed in vitro to verify the in vivo results.

RESULTS

Compared with Control group, young rats in EP group had decreased spatial learning and memory abilities and increased apoptotic rate and decreased number of Nissl positive cells. Besides, the up-regulated levels in inflammatory factors (IL-1β, IL-6), MDA content, and p-ERK1/2/ERK1/2 protein expression, as well as the down-regulated levels in DUSP1 protein expression and SOD content were also observed in EP rats. The EP rats treated with LV-DUSP1 showed obvious improvements regarding the above indicators, while those treated with LV-siDUSP1 had aggravated injury. But the effect of LV-siDUSP1 can be reversed by the treatment with ERK1/2 pathway inhibitor U0126. Further in vitro investigation verified the in vivo results.

CONCLUSION

DUSP1 may ameliorate the oxidative stress and inflammatory injury, as well as improve spatial learning and memory abilities via inhibiting ERK1/2 pathway, eventually playing protective roles in hippocampal injury of young rats with EP.

DGCR5 Promotes Gallbladder Cancer by Sponging MiR-3619-5p via MEK/ERK1/2 and JNK/p38 MAPK Pathways

Gallbladder cancer (GBC) is a highly aggressive malignant cancer with poor prognosis. Long noncoding RNA (lncRNA) DiGeorge syndrome critical region gene (DGCR5) has been reported to participate in various types of cancers, but its role in GBC remains largely unknown. This study aimed to explore the functions and mechanisms of DGCR5 in GBC. Here, we found that DGCR5 was upregulated in GBC tissues and cell lines. Through functional experiments, it was demonstrated that silence of DGCR5 significantly suppressed the cell proliferation, migration, invasion, and induced apoptosis and cell cycle arrest in GBC cells. In addition, miR-3619-5p was predicted and further verified as the target of DGCR5. Moreover, miR-3619-5p was observed downregulated in GBC tissues and cell lines, and miR-3619-5p mimics repressed the GBC cell proliferation, migration, invasion and could be rescued by DGCR5 overexpression. Mechanistically, it was found that DGCR5 knockdown and miR-3619-5p mimics inactivated the MEK/ERK1/2 and JNK/p38 MAPK pathways. In addition, rescue experiments indicated that inhibition of MEK/ERK1/2 and JNK/p38 MAPK pathways could reverse the effects of DGCR5 overexpression on cell proliferation, migration and invasion. Finally, xenograft model assay was used to validate that knockdown of DGCR5 suppressed GBC via regulating MEK/ERK1/2 and JNK/p38 MAPK pathways in vivo. Taken together, it was uncovered in our study that DGCR5 exerts an oncogenic role by sponging miR-3619-5p and activating MEK/ERK1/2 and JNK/p38 MAPK pathways in GBC progression.

Mitogen-Activated Protein Kinase Inhibitors and T-Cell-Dependent Immunotherapy in Cancer

Mitogen-activated protein kinase (MAPK) signaling networks serve to regulate a wide range of physiologic and cancer-associated cell processes. For instance, a variety of oncogenic mutations often lead to hyperactivation of MAPK signaling, thereby enhancing tumor cell proliferation and disease progression. As such, several components of the MAPK signaling network have been proposed as viable targets for cancer therapy. However, the contributions of MAPK signaling extend well beyond the tumor cells, and several MAPK effectors have been identified as key mediators of the tumor microenvironment (TME), particularly with respect to the local immune infiltrate. In fact, a blockade of various MAPK signals has been suggested to fundamentally alter the interaction between tumor cells and T lymphocytes and have been suggested a potential adjuvant to immune checkpoint inhibition in the clinic. Therefore, in this review article, we discuss the various mechanisms through which MAPK family members contribute to T-cell biology, as well as circumstances in which MAPK inhibition may potentiate or limit cancer immunotherapy.

Using high-throughput sequencing to explore the anti-inflammatory effects of α-mangostin

Lipopolysaccharide (LPS) causes an inflammatory response, and α-mangostin (α-MG) is an ingredient of a Chinese herbal medicine with anti-inflammatory effects. We investigated the mechanism by which α-MG reduces LPS-stimulated IEC-6 cells inflammation. A genome-wide examination of control, LPS-stimulated, and α-MG-pretreated cells was performed with the Illumina Hiseq sequencing platform, and gene expression was verified with quantitative real-time PCR (qPCR). Among the 37,199 genes profiled, 2014 genes were regulated in the LPS group, and 475 genes were regulated in the α-MG group. GO enrichment and KEGG pathway analyses of the differentially expressed genes (DEGs) showed that they were mainly related to inflammation and oxidative stress. Based on the transcriptomic results, we constructed a rat model of inflammatory bowel disease (IBD) with LPS and investigated the effects of α-MG on NLRP3 inflammasomes. After LPS stimulation, the rat intestinal villi were significantly detached, with congestion and hemorrhage; the intestinal epithelial cell nuclei were deformed; and the mitochondria were swollen. However, after pretreatment with α-MG, the intestinal villus congestion and hemorrhage were reduced, the epithelial nuclei were rounded, and the mitochondrial morphology was intact. qPCR and western blotting were used to detect NLRP3, caspase 1, interleukin (IL)-18, and IL-1β expression at the gene and protein levels. Their expression increased at both the transcript and protein levels after LPS stimulation, whereas it decreased after pretreatment with α-MG. This study provides new methods and ideas for the treatment of inflammation. α-MG may have utility as a drug for intestinal inflammation.

Alpha-1 Adrenergic Receptor Agonist Phenylephrine Inhibits Sepsis-Induced Cardiomyocyte Apoptosis and Cardiac Dysfunction via Activating ERK1/2 Signal Pathway

It was demonstrated that α1 adrenergic receptor (α1-AR) activation by phenylephrine (PE) attenuated cardiac dysfunction in lipopolysaccharide (LPS)-challenged mice. However, it is unclear whether PE suppresses sepsis-induced cardiomyocyte apoptosis. Here, we investigated the effects of PE on cardiomyocyte apoptosis in LPS-treated adult rat ventricular myocytes (ARVMs) and septic rats induced by cecal ligation and puncture. Cardiomyocyte apoptosis and caspase activity were detected by TUNEL and spectrophotometrical assay, respectively. Bax, Bcl-2 and cytochrome c (Cyt c) levels as well as IκBα, ERK1/2, p38 MAPK, JNK and cardiac troponin I (cTnI) phosphorylation were analyzed by Western blotting, and TNF-α concentration was analyzed by ELISA. PE inhibited LPS-induced caspase-3 activation in ARVMs, which was reversed by prazosin (a membrane permeable α1-AR antagonist), but not by CGP12177A (a membrane impermeable α1-AR antagonist). PE upregulated phosphorylated ERK1/2 and Bcl-2 contents, decreased TNF-α and Bax levels, Cyt c release, caspase-8/-9 activities as well as IκBα, p38MAPK and JNK phosphorylation in LPS-treated ARVMs, all of which were abolished by prazosin. Treatment with U0126 (a specific ERK1/2 inhibitor) reversed the effects of PE on IκBα, p38MAPK and JNK phosphorylation as well as caspase-3/-8/-9 activation in LPS-treated ARVMs. In septic rats, PE not only inhibited myocardial apoptosis as well as IκBα, p38MAPK, and JNK phosphorylation, but also upregulated myocardial phosphorylated ERK1/2. Furthermore, PE inhibited myocardial cTnI phosphorylation and improved cardiac function in septic rats. Taken together, our data suggest that α1-AR activation by PE inhibits sepsis-induced cardiomyocyte apoptosis and cardiac dysfunction via activating ERK1/2 signal pathway.

Dioscin inhibits colon cancer cells' growth by reactive oxygen species-mediated mitochondrial dysfunction and p38 and JNK pathways

Dioscin is a natural steroid saponin derived from several plants that shows potent anticancer effects against a variety of cancer cells. Here, we investigated the antitumor effect of dioscin against human colon cancer cells and evaluated the molecular mechanism involved in this process. The cell cytotoxicity was studied by the MTT assay and BrdU incorporation. The proapoptotic mechanism of dioscin was characterized by flow cytometry analysis. A western blot and an immunofluorescence staining were used to investigate how dioscin induces apoptosis in vitro. In our study, dioscin could significantly inhibit the growth of colon cancer cells in a time-dependent and dose-dependent manner. Dioscin induces apoptosis and reactive oxygen species (ROS) generation, promoting the disruption of mitochondrial membrane potential, Bax translocation to the mitochondria, cytochrome C release to cytosol, activations of caspase-9/3, PARP cleavage, and subsequent apoptosis. Dioscin-induced apoptosis was accompanied by sustained phosphorylation of JNK, p38-MAPK. N-acetyl-L-cysteine, a scavenger of ROS, significantly reversed dioscin-induced cell death and activation of JNK and p38. Collectively, the data indicate that the induction of apoptosis by dioscin is mediated through ROS proteins, which are critical upstream signals for JNK/p38-MAPK activation.

Nonmineralized and Mineralized Collagen Scaffolds Induce Differential Osteogenic Signaling Pathways in Human Mesenchymal Stem Cells

The instructive capabilities of extracellular matrix components in progenitor cell differentiation have recently generated significant interest in the development of bioinspired materials for regenerative applications. Previously, a correlation was described between the osteogenic capabilities of nanoparticulate mineralized collagen glycosaminoglycan scaffolds (MC-GAG) and an autogenous activation of small mothers against decapentaplegic ( Smad1/5) in the canonical bone morphogenetic protein receptor (BMPR) pathway with a diminished extracellular signal regulated kinase 1/2 (ERK1/2) activation when compared to nonmineralized collagen glycosaminoglycan scaffolds (Col-GAG). This work utilizes a canonical BMPR inhibitor (dorsomorphin homologue 1, DMH1) and an inhibitor of the mitogen activated protein kinase/ERK kinase (MEK)/(ERK) cascade (PD98059) to characterize the necessity of each pathway for osteogenesis. While DMH1 inhibits runt-related transcription factor 2 (Runx2) and bone sialoprotein II (BSPII) gene expression of primary human mesenchymal stem cells (hMSCs) on MC-GAG, PD98059 inhibits BSPII expression on Col-GAG independent of Runx2 expression. DMH1 inhibits mineralization on both Col-GAG and MC-GAG, however, PD98059 only inhibits mineralization on Col-GAG. DMH1 inhibits both Smad1/5 phosphorylation and Runx2 protein expression, whereas PD98059 inhibits ERK1/2 and c-Jun amino-terminal kinase 1/2 (JNK1/2) phosphorylation without affecting Runx2. Thus, activation of the canonical BMPR signaling is necessary for osteogenic differentiation and mineralization of hMSCs on Col-GAG or MC-GAG. The MEK/ERK cascade, intimately tied to JNK activation, is necessary for Runx2-independent osteogenesis on Col-GAG, while completely dispensable in osteogenesis on MC-GAG.

ERK2 and JNK1 contribute to TNF-α-induced IL-8 expression in synovial fibroblasts

Tumor necrosis factor α (TNF-α) induces the expression and secretion of interleukin 8 (IL-8), which contributes to synovitis in rheumatoid arthritis (RA). To elucidate the mechanism of the onset of RA, we used synovial fibroblasts without autoimmune inflammatory diseases and investigated MAPK signaling pathways in TNF-α-induced IL-8 expression. Synovial fibroblasts isolated from healthy dogs were characterized by flow cytometry, which were positive for the fibroblast markers CD29, CD44, and CD90 but negative for the hematopoietic cell markers CD14, CD34, CD45, and HLA-DR. TNF-α stimulated the secretion and mRNA expression of IL-8 in a time- and dose-dependent manner. ERK and JNK inhibitors attenuated TNF-α-induced IL-8 expression and secretion. TNF-α induced the phosphorylation of ERK1/2 and JNK1/2. TNF-α-induced IL-8 expression was attenuated both in ERK2- and JNK1-knockdown cells. TNF-α-induced ERK1/2 or JNK1/2 was observed in ERK2- or JNK1-knockdown cells, respectively, showing that there is no crosstalk between ERK2 and JNK1 pathways. These observations indicate that the individual activation of ERK2 and JNK1 pathways contributes to TNF-α-induced IL-8 expression in synovial fibroblasts, which appears to be involved in the progress in RA.

JNK activation is essential for activation of MEK/ERK signaling in IL-1β-induced COX-2 expression in synovial fibroblasts

The proinflammatory cytokine interleukin 1β (IL-1β) induces prostaglandin E₂ (PGE₂) production via upregulation of cyclooxygenase-2 (COX-2) expression in synovial fibroblasts. This effect of IL-1β is involved in osteoarthritis. We investigated MAPK signaling pathways in IL-1β-induced COX-2 expression in feline synovial fibroblasts. In the presence of MAPK inhibitors, IL-1β-induced COX-2 expression and PGE₂ release were both attenuated. IL-1β induced the phosphorylation of p38, JNK, MEK, and ERK1/2. A JNK inhibitor prevented not only JNK phosphorylation but also MEK and ERK1/2 phosphorylation in IL-1β-stimulated cells, but MEK and ERK1/2 inhibitors had no effect on JNK phosphorylation. A p38 inhibitor prevented p38 phosphorylation, but had no effect on MEK, ERK1/2, and JNK phosphorylation. MEK, ERK1/2, and JNK inhibitors had no effect on p38 phosphorylation. We also observed that in IL-1β-treated cells, phosphorylated MEK, ERK1/2, and JNK were co-precipitated with anti-phospho-MEK, ERK1/2, and JNK antibodies. The silencing of JNK1 in siRNA-transfected fibroblasts prevented IL-1β to induce phosphorylation of MEK and ERK1/2 and COX-2 mRNA expression. These observations suggest that JNK1 phosphorylation is necessary for the activation of the MEK/ERK1/2 pathway and the subsequent COX-2 expression for PGE₂ release, and p38 independently contributes to the IL-1β effect in synovial fibroblasts.

The effect of quercetin delivery system on osteogenesis and angiogenesis under osteoporotic conditions

Bone regeneration under osteoporotic conditions with impaired angiogenesis, osteogenesis and remodeling represents a great challenge.

Growth Hormone Releasing Peptide-2 Attenuation of Protein Kinase C-Induced Inflammation in Human Ovarian Granulosa Cells

Cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) are two important inflammatory mediators in ovulation. Ghrelin may modulate inflammatory signaling via growth hormone secretagogue receptors. We investigated the role of ghrelin in KGN human ovarian granulosa cells using protein kinase C (PKC) activator phorbol 12, 13-didecanoate (PDD) and synthetic ghrelin analog growth hormone releasing peptide-2 (GHRP-2). GHRP-2 attenuated PDD-induced expression of protein and mRNA, the promoter activity of COX-2 and IL-8 genes, and the secretion of prostaglandin E2 (PGE₂) and IL-8. GHRP-2 promoted the degradation of PDD-induced COX-2 and IL-8 proteins with the involvement of proteasomal and lysosomal pathways. PDD-mediated COX-2 production acts via the p38, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways; PDD-mediated IL-8 production acts via the p38, JNK and ERK pathways. GHRP-2 reduced the PDD-induced phosphorylation of p38 and JNK and activator protein 1 (AP-1) reporter activation and PDD-induced NF-κB nuclear translocation and reporter activation. The inhibitors of mitogen-activated protein kinase phosphatase-1 (MKP-1) and protein phosphatase 2 (PP2A) reduced the inhibitory effect of GHRP-2 on PDD-induced COX-2 and IL-8 expression. Our findings demonstrate an anti-inflammatory role for ghrelin (GHRP-2) in PKC-mediated inflammation of granulosa cells, at least in part, due to its inhibitory effect on PKC-induced activation of p38, JNK and NF-κB, possibly by targeting to MKP-1 and PP2A.

Regulation of mitogen-activated protein kinase by protein kinase C and mitogen-activated protein kinase phosphatase-1 in vascular smooth muscle

Vascular smooth muscle contraction is primarily regulated by phosphorylation of myosin light chain. There are also modulatory pathways that control the final level of force development. We tested the hypothesis that protein kinase C (PKC) and mitogen-activated protein (MAP) kinase modulate vascular smooth muscle activity via effects on MAP kinase phosphatase-1 (MKP-1). Swine carotid arteries were mounted for isometric force recording and subjected to histamine stimulation in the presence and absence of inhibitors of PKC [bisindolylmaleimide-1 (Bis)], MAP kinase kinase (MEK) (U0126), and MKP-1 (sanguinarine) and flash frozen for measurement of MAP kinase, PKC-potentiated myosin phosphatase inhibitor 17 (CPI-17), and caldesmon phosphorylation levels. CPI-17 was phosphorylated in response to histamine and was inhibited in the presence of Bis. Caldesmon phosphorylation levels increased in response to histamine stimulation and were decreased in response to MEK inhibition but were not affected by the addition of Bis. Inhibition of PKC significantly increased p42 MAP kinase, but not p44 MAP kinase. Inhibition of MEK with U0126 inhibited both p42 and p44 MAP kinase activity. Inhibition of MKP-1 with sanguinarine blocked the Bis-dependent increase of MAP kinase activity. Sanguinarine alone increased MAP kinase activity due to its effects on MKP-1. Sanguinarine increased MKP-1 phosphorylation, which was inhibited by inhibition of MAP kinase. This suggests that MAP kinase has a negative feedback role in inhibiting MKP-1 activity. Therefore, PKC catalyzes MKP-1 phosphorylation, which is reversed by MAP kinase. Thus the fine tuning of vascular contraction is due to the concerted effort of PKC, MAP kinase, and MKP-1.

The apoptotic effect and the plausible mechanism of microwave radiation on rat myocardial cells

Microwaves may exert adverse biological effects on the cardiovascular system at the integrated system and cellular levels. However, the mechanism underlying such effects remains poorly understood. Here, we report a previously uncharacterized mechanism through which microwaves damage myocardial cells. Rats were treated with 2450 MHz microwave radiation at 50, 100, 150, or 200 mW/cm(2) for 6 min. Microwave treatment significantly enhanced the levels of various enzymes in serum. In addition, it increased the malondialdehyde content while decreasing the levels of antioxidative stress enzymes, activities of enzyme complexes I-IV, and ATP in myocardial tissues. Notably, irradiated myocardial cells exhibited structural damage and underwent apoptosis. Furthermore, Western blot analysis revealed significant changes in expression levels of proteins involved in oxidative stress regulation and apoptotic signaling pathways, indicating that microwave irradiation could induce myocardial cell apoptosis by interfering with oxidative stress and cardiac energy metabolism. Our findings provide useful insights into the mechanism of microwave-induced damage to the cardiovascular system.

Akermanite bioceramics promote osteogenesis, angiogenesis and suppress osteoclastogenesis for osteoporotic bone regeneration

It is a big challenge for bone healing under osteoporotic pathological condition with impaired angiogenesis, osteogenesis and remodeling. In the present study, the effect of Ca, Mg, Si containing akermanite bioceramics (Ca2MgSi2O7) extract on cell proliferation, osteogenic differentiation and angiogenic factor expression of BMSCs derived from ovariectomized rats (BMSCs-OVX) as well as the expression of osteoclastogenic factors was evaluated. The results showed that akermanite could enhance cell proliferation, ALP activity, expression of Runx2, BMP-2, BSP, OPN, OCN, OPG and angiogenic factors including VEGF and ANG-1. Meanwhile, akermanite could repress expression of osteoclastogenic factors including RANKL and TNF-α. Moreover, akermanite could activate ERK, P38, AKT and STAT3 signaling pathways, while crosstalk among these signaling pathways was evident. More importantly, the effect of akermanite extract on RANKL-induced osteoclastogenesis was evaluated by TRAP staining and real-time PCR assay. The results showed that akermanite could suppress osteoclast formation and expression of TRAP, cathepsin K and NFATc1. The in vivo experiments revealed that akermanite bioceramics dramatically stimulated osteogenesis and angiogenesis in an OVX rat critical-sized calvarial defect model. All these results suggest that akermanite bioceramics with the effects of Mg and Si ions on osteogenesis, angiogenesis and osteoclastogenesis are promising biomaterials for osteoporotic bone regeneration.

MytiLec, a Mussel R-Type Lectin, Interacts with Surface Glycan Gb3 on Burkitt's Lymphoma Cells to Trigger Apoptosis through Multiple Pathways

MytiLec; a novel lectin isolated from the Mediterranean mussel (Mytilus galloprovincialis); shows strong binding affinity to globotriose (Gb3: Galα1-4Galβ1-4Glc). MytiLec revealed β-trefoil folding as also found in the ricin B-subunit type (R-type) lectin family, although the amino acid sequences were quite different. Classification of R-type lectin family members therefore needs to be based on conformation as well as on primary structure. MytiLec specifically killed Burkitt's lymphoma Ramos cells, which express Gb3. Fluorescein-labeling assay revealed that MytiLec was incorporated inside the cells. MytiLec treatment of Ramos cells resulted in activation of both classical MAPK/ extracellular signal-regulated kinase and extracellular signal-regulated kinase (MEK-ERK) and stress-activated (p38 kinase and JNK) Mitogen-activated protein kinases (MAPK) pathways. In the cells, MytiLec treatment triggered expression of tumor necrosis factor (TNF)-α (a ligand of death receptor-dependent apoptosis) and activation of mitochondria-controlling caspase-9 (initiator caspase) and caspase-3 (activator caspase). Experiments using the specific MEK inhibitor U0126 showed that MytiLec-induced phosphorylation of the MEK-ERK pathway up-regulated expression of the cyclin-dependent kinase inhibitor p21, leading to cell cycle arrest and TNF-α production. Activation of caspase-3 by MytiLec appeared to be regulated by multiple different pathways. Our findings, taken together, indicate that the novel R-type lectin MytiLec initiates programmed cell death of Burkitt's lymphoma cells through multiple pathways (MAPK cascade, death receptor signaling; caspase activation) based on interaction of the lectin with Gb3-containing glycosphingolipid-enriched microdomains on the cell surface.

Non-Hematopoietic β-Arrestin1 Confers Protection Against Experimental Colitis

β-Arrestins are multifunctional scaffolding proteins that modulate G protein-coupled receptor (GPCR)-dependent and -independent cell signaling pathways in various types of cells. We recently demonstrated that β-arrestin1 (β-arr1) deficiency strikingly attenuates dextran sodium sulfate (DSS)-induced colitis in mice. Since DSS-induced colitis is in part dependent on gut epithelial injury, we examined the role of β-arr1 in intestinal epithelial cells (IECs) using a colon epithelial cell line, SW480 cells. Surprisingly, we found that knockdown of β-arr1 in SW480 cells enhanced epithelial cell death via a caspase-3-dependent process. To understand the in vivo relevance and potential cell type-specific role of β-arr1 in colitis development, we generated bone marrow chimeras with β-arr1 deficiency in either the hematopoietic or non-hematopoietic compartment. Reconstituted chimeric mice were then subjected to DSS-induced colitis. Similar to our previous findings, β-arr1 deficiency in the hematopoietic compartment protected mice from DSS-induced colitis. However, consistent with the role of β-arr1 in epithelial apoptosis in vitro, non-hematopoietic β-arr1 deficiency led to an exacerbated colitis phenotype. To further understand signaling mechanisms, we examined the effect of β-arr1 on TNF-α-mediated NFκB and MAPK pathways. Our results demonstrate that β-arr1 has a critical role in modulating ERK, JNK and p38 MAPK pathways mediated by TNF-α in IECs. Together, our results show that β-arr1-dependent signaling in hematopoietic and non-hematopoietic cells differentially regulates colitis pathogenesis and further demonstrates that β-arr1 in epithelial cells inhibits TNF-α-induced cell death pathways.

Investigating the potential of Shikonin as a novel hypertrophic scar treatment

Background

Hypertrophic scarring is a highly prevalent condition clinically and results from a decreased number of apoptotic fibroblasts and over-abundant production of collagen during scar formation following wound healing. Our previous studies indicated that Shikonin, an active component extracted from Radix Arnebiae, induces apoptosis and reduces collagen production in hypertrophic scar-derived fibroblasts. In the study reported here, we further evaluate the potential use of Shikonin as a novel scar remediation therapy by examining the effects of Shikonin on both keratinocytes and fibroblasts using Transwell® co-culture techniques. The underlying mechanisms were also revealed. In addition, effects of Shikonin on the expression of cytokines in Transwell co-culture “conditioned” medium were investigated.

Results

Our results indicate that Shikonin preferentially inhibits cell proliferation and induces apoptosis in fibroblasts without affecting keratinocyte function. In addition, we found that the proliferation-inhibiting and apoptosis-inducing abilities of SHI might be triggered via MAPK and Bcl-2/Caspase 3 signalling pathways. Furthermore, SHI has been found to attenuate the expression of TGF-β1 in Transwell co-cultured “conditioned” medium.

Conclusions

The data generated from this study provides further evidence that supports the potential use of Shikonin as a novel scar remediation therapy.

Mitogen-activated protein kinase phosphatase-1 prevents lipopolysaccharide-induced apoptosis in immature rat intestinal epithelial cells

BACKGROUND

Necrotizing enterocolitis is characterized by intestinal inflammation and epithelial barrier dysfunction. Mitogen-activated protein kinase (MAPK) phosphatase (MKP)-1 plays a pivotal role in the feedback control of MAPK signaling, which regulates inflammation and apoptosis. We hypothesized that MKP-1 prevents lipopolysaccharide (LPS)-induced apoptosis in intestinal epithelial cells.

METHODS

Western blot analysis and qPCR were used to assess MKP-1, MAPK (p38, extracellular signal-regulated kinase (ERK), and c-Jun N terminal kinases (JNK)), caspase 3, caspase 9, tumor necrosis factor (TNF)-α, and cyclooxygenase (COX)-2 expression levels in rIEC-6 enterocytes. MKP-1 expression was inhibited using small interfering RNA (siRNA) methodology. Viable cell number was determined using trypan blue exclusion.

RESULTS

LPS stimulation led to activation of p38, JNK, and ERK, and induction of MKP-1 mRNA and protein expression. The induction of MKP-1 was associated with a decrease in p38 phosphorylation, and knockdown of MKP-1 prolonged p38 phosphorylation. While LPS stimulation significantly attenuated proliferation of rIEC-6 cells transfected with scramble siRNA, LPS stimulation resulted in a net decrease in viable cell number in cells transfected with MKP-1 siRNA. Following LPS stimulation, MKP-1 knockdown resulted in greater caspase 3 and 9 activities and greater proinflammatory cytokine (TNF-α, COX-2) expression than in cells transfected with scramble siRNA.

CONCLUSION

Our results demonstrate that MKP-1 has a central role in preventing inflammation-induced apoptosis in rIEC-6 enterocytes.

The Effect of Quercetin on the Osteogenesic Differentiation and Angiogenic Factor Expression of Bone Marrow-Derived Mesenchymal Stem Cells

Bone marrow-derived mesenchymal stem cells (BMSCs) are widely used in regenerative medicine in light of their ability to differentiate along the chondrogenic and osteogenic lineages. As a type of traditional Chinese medicine, quercetin has been preliminarily reported to promote osteogenic differentiation in osteoblasts. In the present study, the effects of quercetin on the proliferation, viability, cellular morphology, osteogenic differentiation and angiogenic factor secretion of rat BMSCs (rBMSCs) were examined by MTT assay, fluorescence activated cell sorter (FACS) analysis, real-time quantitative PCR (RT-PCR) analysis, alkaline phosphatase (ALP) activity and calcium deposition assays, and Enzyme-linked immunosorbent assay (ELISA). Moreover, whether mitogen-activated protein kinase (MAPK) signaling pathways were involved in these processes was also explored. The results showed that quercetin significantly enhanced the cell proliferation, osteogenic differentiation and angiogenic factor secretion of rBMSCs in a dose-dependent manner, with a concentration of 2 μM achieving the greatest stimulatory effect. Moreover, the activation of the extracellular signal-regulated protein kinases (ERK) and p38 pathways was observed in quercetin-treated rBMSCs. Furthermore, these induction effects could be repressed by either the ERK inhibitor PD98059 or the p38 inhibitor SB202190, respectively. These data indicated that quercetin could promote the proliferation, osteogenic differentiation and angiogenic factor secretion of rBMSCs in vitro, partially through the ERK and p38 signaling pathways.

Venlafaxine protects methylglyoxal-induced apoptosis in the cultured human brain microvascular endothelial cells

It was reported that venlafaxine protects microvascular endothelial cells injury in several models. But the mechanisms of venlafaxine protects cell injury still poor understanding. Here, we shows that in the cultured human brain microvascular endothelial cells (HBMEC), we found that venlafaxine protects methylglyoxal (MGO)-induced cell injury, and the venlafaxine significant reduction in the level of reactive oxygen species, down-regulated expression of pro-apoptotic activated caspase-3 and Bax, increased BDNF release and expression of anti-apoptotic Bcl-2 in the cultured HBMEC. Furthermore, we found that venlafaxine inhibits MGO-induced phosphorylation of JNK. Moreover, venlafaxine increased AKT phosphorylation and the protective effects of venlafaxine was inhibited by PI3K/AKT inhibitor. These findings suggest that venlafaxine protects MGO-induced HBMEC injury through PI3K/AKT and JNK pathway as the potential underlying mechanisms of HBMEC injury in diabetes.