Monolayer versus aggregate balance in survival process for EGF-induced apoptosis in A431 carcinoma cells: Implication of ROS-P38 MAPK-integrin alpha2beta1 pathway

CRS induces depression-like behavior after MCAO in rats possibly by activating p38 MAPK

Post-stroke depression (PSD) is a common neuropsychiatric complication of stroke, which seriously affects the quality of life and prognosis of patients. Nevertheless, the pathogenesis of PSD remains unclear. In our study, a PSD rat model was established by chronic restraint stress (CRS) combined with middle cerebral artery occlusion (MCAO). Depressive and anxiety-like behaviors were tested, as well as Neuronal loss and Apoptosis. The expression of synapse and p38 MAPK signaling pathway -relevant proteins was detected. Our data indicated that CRS combined with MCAO could induce depression-like and anxiety-like behaviors, which led to neuronal damage, apoptosis, and cellular loss in the left parietal cortex and left hippocampus. Furthermore, CRS combined with MCAO decreased synaptic plasticity in the parietal cortex and left hippocampus. We found that CRS combined with MCAO had activated the p38 MAPK signaling pathway, and decreased the expression of pathway-related proteins MKK6 and MKK3. These results suggested that CRS combined with MCAO could lead to depression-like behavior via neuronal damage, apoptosis and reduced synaptic plasticity, which might be related to the activation of the p38 MAPK pathway. Therefore, it provides novel ideas for the research on the intervention and prevention mechanisms of PSD.

p38MAPK Signaling Pathway in Osteoarthritis: Pathological and Therapeutic Aspects

Osteoarthritis (OA) is an aging-related joint disease, pathologically featured with degenerated articular cartilage and deformation of subchondral bone. OA has become the fourth major cause of disability in the world, imposing a huge economic burden. At present, the pathogenesis and pathophysiology of OA are still unclear. Complex regulating networks containing different biochemical signaling pathways are involved in OA pathogenesis and progression. The p38MAPK signaling pathway is a member of the MAPK signaling pathway family, which participates in the induction of cellular senescence, the differentiation of chondrocytes, the synthesis of matrix metalloproteinase (MMPs) and the production of pro-inflammatory factors. In recent years, studies on the regulating role of p38MAPK signaling pathway and the application of its inhibitors have attracted growing attention, with an increasing number of in vivo and in vitro studies. One interesting finding is that the inhibition of p38MAPK could suppress chondrocyte inflammation and ameliorate OA, indicating its therapeutic role in OA treatment. Based on this, we reviewed the mechanisms of p38MAPK signaling pathway in the pathogenesis of OA, hoping to provide new ideas for future research and OA treatment.

Antitumor activity of alantolactone in lung cancer cell lines NCI-H1299 and Anip973

Alantolactone is a sesquiterpene lactone extracted from Inula helenium L. plants possessing many biological activities, including anti-inflammatory, antiproliferation, and antimicrobial. The inhibitory effects and the underlying mechanisms of alantolactone on lung cancer cells NCI-H1299 and Anip973 were investigated in this study. The results showed that alantolactone could decrease cell viability and induce cell apoptosis of NCI-H1299 and Anip973. After the cells were treated with alantolactone, the expression of Bcl-2 decreased, while the expression of Bax increased, the expression of MMP-9, MMP-7, and MMP-2 gradually decreased after alantolactone treatment. Furthermore, results showed that alantolactone could activate p38 MAPK pathway and suppress NF-κB pathway, which are involving in lung cancer development. These results indicated that alantolactone was a potential agent for lung cancer treatment. PRACTICAL APPLICATIONS: Lung cancer is one of the most common contributors of cancer death in the world. Chemoprevention and chemotherapy with natural substances are prospective methods for lung cancer treatment. In recent years, the anti-cancer activity of various sesquiterpene lactones has attracted a great deal of interest. Alantolactone is the major active sesquiterpene lactones isolated from Inula helenium L, which is used as a medicine in ancient Romans due to wide range of pharmacological activities. The results obtained from this study revealed the inhibitory effects of alantolactone on lung cancer cells and might provide some experimental basis for prevention and treatment of lung cancer with alantolactone.

RAC2-P38 MAPK-dependent NADPH oxidase activity is associated with the resistance of quiescent cells to ionizing radiation

Our recent study showed that quiescent G0 cells are more resistant to ionizing radiation than G1 cells; however, the underlying mechanism for this increased radioresistance is unknown. Based on the relatively lower DNA damage induced in G0 cells, we hypothesize that these cells are exposed to less oxidative stress during exposure. As a catalytic subunit of NADPH oxidase, Ras-related C3 botulinum toxin substrate 2 (RAC2) may be involved in the cellular response to ionizing radiation. Here, we show that RAC2 was expressed at low levels in G0 cells but increased substantially in G1 cells. Relative to G1 cells, the total antioxidant capacity in G0 phase cells increased upon exposure to X-ray radiation, whereas the intracellular concentration of ROS and malondialdehyde increased only slightly. The induction of DNA single- and double-stranded breaks in G1 cells by X-ray radiation was inhibited by knockdown of RAC2. P38 MAPK interaction with RAC2 resulted in a decrease of functional RAC2. Increased phosphorylation of P38 MAPK in G0 cells also increased cellular radioresistance; however, excessive production of ROS caused P38 MAPK dephosphorylation. P38 MAPK, phosphorylated P38 MAPK, and RAC2 regulated in mutual feedback and negative feedback regulatory pathways, resulting in the radioresistance of G0 cells.

Treatment dilemmas of cetuximab combined with chemotherapy for metastatic colorectal cancer

Although monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) have largely enriched the available therapeutic choices for colorectal cancer (CRC), the understanding and management of their associated clinical toxicities are limited. In addition, the combined strategies of administering EGFR mAbs and traditional cytotoxic agents, such as 5-fluorouracil, oxaliplatin and irinotecan, have resulted in a more complicated management of CRC treatment-related side effects compared with EGFR mAb monotherapy. We believe that a thorough recognition of the toxicities of EGFR mAb drugs is essential for physicians to increase the therapeutic index in the treatment of CRC. This review aims to summarize the existing information regarding the treatment dilemmas of cetuximab combined with chemotherapy in the management of metastatic CRC.

Alpha2beta1 integrin in cancer development and chemoresistance

Extracellular matrix, via its receptors the integrins, has emerged as a crucial factor in cancer development. The α2β1 integrin is a major collagen receptor that is widely expressed and known to promote cell migration and control tissue homeostasis. Growing evidence suggests that it can be a key pathway in cancer. Recent studies have shown that α2β1 integrin is a regulator of cancer metastasis either by promoting or inhibiting the dissemination process of cancer cells. The α2β1 integrin signaling can also enhance tumor angiogenesis. Emerging evidence supports a role for α2β1 integrin in cancer chemoresistance especially in hematological malignancies originating from the T cell lineage. In addition, α2β1 integrin has been associated with cancer stem cells. In this review, we will discuss the complex role of α2β1 integrin in these processes. Collagen is a major matrix protein of the tumor microenvironment and thus, understanding how α2β1 integrin regulates cancer pathogenesis is likely to lead to new therapeutic approaches and agents for cancer treatment.

Cellular Adhesion Promotes Prostate Cancer Cells Escape from Dormancy

Dissemination of prostate cancer (PCa) cells to the bone marrow is an early event in the disease process. In some patients, disseminated tumor cells (DTC) proliferate to form active metastases after a prolonged period of undetectable disease known as tumor dormancy. Identifying mechanisms of PCa dormancy and reactivation remain a challenge partly due to the lack of in vitro models. Here, we characterized in vitro PCa dormancy-reactivation by inducing cells from three patient-derived xenograft (PDX) lines to proliferate through tumor cell contact with each other and with bone marrow stroma. Proliferating PCa cells demonstrated tumor cell-cell contact and integrin clustering by immunofluorescence. Global gene expression analyses on proliferating cells cultured on bone marrow stroma revealed a downregulation of TGFB2 in all of the three proliferating PCa PDX lines when compared to their non-proliferating counterparts. Furthermore, constitutive activation of myosin light chain kinase (MLCK), a downstream effector of integrin-beta1 and TGF-beta2, in non-proliferating cells promoted cell proliferation. This cell proliferation was associated with an upregulation of CDK6 and a downregulation of E2F4. Taken together, our data provide the first clinically relevant in vitro model to support cellular adhesion and downregulation of TGFB2 as a potential mechanism by which PCa cells may escape from dormancy. Targeting the TGF-beta2-associated mechanism could provide novel opportunities to prevent lethal PCa metastasis.

Mosapride protects against clopidogrel-induced gastric mucosal epithelium cell damage via the p38 MAPK signaling pathway

AIM: To investigate whether mosapride has a protective effect against clopidogrel-induced gastric mucosal epithelium cells (GES-1) damage and to explore the underlying mechanisms.

METHODS: GES-1 cells were cultured in vitro and divided into control group, clopidogrel group (treated with clopidogrel at a concentration of IC50, 0.36 mmol/L) and clopidogrel plus mosapride groups (treated with clopidogrel and 0.4, 0.5, or 0.6 µmol/L of mosapride). MTT assay and flow cytometry were used to detect the proliferation and apoptosis of cells of each group. The expression of phosphorylated P38 (p-P38), occludin and ZO-1 proteins in GES-1 cells was detected by Western blot.

RESULTS: Compared to the control group, p-P38 expression was significantly up-regulated in the clopidogrel group (P < 0.05). The expression of p-P38 in the clopidogrel plus mosapride groups was significantly lower than that in the clopidogrel group (all P < 0.05). With the decrease in p-P38 expression, the expression of occludin and ZO-1 were gradually increased.

CONCLUSION: Mosapride exerts a protective effect against clopidogrel-induced GES-1 cell damage probably by inhibiting p38/MAPK phosphorylation and up-regulating the expression of tight junction proteins occludin and ZO-1.

p38 MAP kinase enhances EGF-induced apoptosis in A431 carcinoma cells by promoting tyrosine phosphorylation of STAT1

While epidermal growth factor (EGF) is a well known mitogen, high doses of EGF result in a paradoxical apoptotic response in the cells that overexpress EGF receptor such as A431 epidermoid carcinoma cells. EGF-induced apoptosis in A431 cells is dependent upon activation of transcription factor STAT1. In this study, we demonstrate that p38 MAP kinase is another important mediator of EGF-dependent pro-apoptotic response in A431 cells. By utilizing p38 MAP kinase inhibitors, SB203580 and BIRB0796, we significantly reduced the integral growth-inhibiting as well as pro-apoptotic effects of EGF. Moreover, we observed that inhibition of p38 MAP kinase markedly decreased phosphorylation of tyrosine 701 in STAT1, while neither EGF-induced accumulation nor serine phosphorylation of STAT1 was decreased. We propose that p38 MAP kinase mediates STAT1 tyrosine phosphorylation, thereby enforcing EGF-induced apoptosis.

P38 MAPK signaling pathway: biological functions, roles in the pathogenesis of liver fibrosis and common research methods

The activation and proliferation of hepatic stellate cells (HSC) are the key events in hepatic fibrogenesis. Now the research about the mechanisms of action of HSC-related signal transduction has become a hot topic. This article reviews the biological functions of the p38 MAPK signaling pathway and its roles in the pathogenesis of liver fibrosis and summarizes common research methods for this signaling pathway.

Assessment of redox changes to hydrogen peroxide-sensitive proteins during EGF signaling

Hydrogen peroxide acts as a second messenger in growth factor signaling where it can oxidize and modify the function of redox-sensitive proteins. While selective thiol oxidation has been measured, there has been no global assessment of protein oxidation following growth factor activation. Significant changes to the abundant and widely distributed redox sensitive thiol proteins were observed in A431 epidermoid carcinoma cells exposed to hydrogen peroxide, but no changes were observed following treatment with epidermal growth factor (EGF). This included members of the peroxiredoxin family, which were also monitored in the presence of the thioredoxin reductase inhibitor auranofin to limit their capacity to recycle to the reduced form. We conclude that widespread thiol oxidation does not occur in cells during EGF signaling, and that hydrogen peroxide must act in a highly localized or selective manner.

Detection of single-molecule H2O2 signalling from epidermal growth factor receptor using fluorescent single-walled carbon nanotubes

An emerging concept in cell signalling is the natural role of reactive oxygen species such as hydrogen peroxide (H2O2) as beneficial messengers in redox signalling pathways. The nature of H2O2 signalling is confounded, however, by difficulties in tracking it in living systems, both spatially and temporally, at low concentrations. Here, we develop an array of fluorescent single-walled carbon nanotubes that can selectively record, in real time, the discrete, stochastic quenching events that occur as H2O2 molecules are emitted from individual human epidermal carcinoma cells stimulated by epidermal growth factor. We show mathematically that such arrays can distinguish between molecules originating locally on the cell membrane from other contributions. We find that epidermal growth factor induces 2 nmol H2O2 locally over a period of 50 min. This platform promises a new approach to understanding the signalling of reactive oxygen species at the cellular level.

Modulation of cellular redox state underlies antagonism between oxaliplatin and cetuximab in human colorectal cancer cell lines

BACKGROUND AND PURPOSE

Oxaliplatin is the first platinum-based compound effective in the treatment of colorectal cancer. Oxaliplatin combined with cetuximab for metastatic colorectal cancer is under evaluation. The preliminary results seem controversial, particularly for the use of cetuximab in K-Ras mutated patients. K-Ras mutation is known to affect redox homeostasis. Here we evaluated how the efficacy of oxaliplatin alone or combined with cetuximab varied according to the Ras mutation and redox status in a panel of colorectal tumour cell lines.

EXPERIMENTAL APPROACH

Viability was evaluated by methylthiazoletetrazolium assay, reactive oxygen species production by DCFDA and lucigenin on HT29-D4, Caco-2, SW480 and SW620 cell lines.

KEY RESULTS

Combination of oxaliplatin and cetuximab was less cytotoxic than oxaliplatin alone in colorectal cells harbouring wild-type Ras and membrane expression of receptors for epidermal growth factor receptor (EGFR), such as HT29-D4 and Caco-2 cells. In contrast, cetuximab did not affect oxaliplatin efficiency in cells harbouring K-Ras(V12) mutation, irrespective of membrane EGFR expression (SW620 and SW480 cells). Transfection of HT29-D4 with K-Ras(V12) decreased oxaliplatin IC(50) and impaired cetuximab sensitivity, without affecting expression of membrane EGFR compared with HT29-D4 control. Oxaliplatin efficacy relies on endogenous production of H(2)O(2). Cetuximab inhibits H(2)O(2) production inhibiting the EGFR/Nox1 NADPH oxidase pathway. Oxaliplatin efficacy was impaired by short hairpin RNA for Nox1 and by catalase (H(2)O(2) scavenger).

CONCLUSIONS AND IMPLICATIONS

Cetuximab limited oxaliplatin efficiency by affecting the redox status of cancer cells through Nox1. Such combined therapy might be improved by controlling H(2)O(2) elimination.

The inhibition of the epidermal growth factor (EGF) pathway enhances TGF-beta-induced apoptosis in rat hepatoma cells through inducing oxidative stress coincident with a change in the expression pattern of the NADPH oxidases (NOX) isoforms

Transforming growth factor-beta (TGF-beta) induces apoptosis in hepatocytes, through a mechanism mediated by reactive oxygen species (ROS) production. Numerous tumoral cells develop mechanisms to escape from the TGF-beta-induced tumor suppressor effects. In this work we show that in FaO rat hepatoma cells inhibition of the epidermal growth factor receptor (EGFR) with the tyrphostin AG1478 enhances TGF-beta-induced cell death, coincident with an elevated increase in ROS production and GSH depletion. These events correlate with down-regulation of genes involved in the maintenance of redox homeostasis, such as gamma-GCS and MnSOD, and elevated mitochondrial ROS. Nonetheless, not all the ROS proceed from the mitochondria. Emerging evidences indicate that ROS production by TGF-beta is also mediated by the NADPH oxidase (NOX) system. TGF-beta-treated FaO cells induce nox1 expression. However, the treatment with TGF-beta and AG1478 greatly enhanced the expression of another family member: nox4. NOX1 and NOX4 targeted knock-down by siRNA experiments suggest that they play opposite roles, because NOX1 knockdown increases caspase-3 activity and cell death, whilst NOX4 knock-down attenuates the apoptotic process. This attenuation correlates with maintenance of GSH and antioxidant enzymes levels. In summary, EGFR inhibition enhances apoptosis induced by TGF-beta in FaO rat hepatoma cells through an increased oxidative stress coincident with a change in the expression pattern of NOX enzymes.

Nox enzymes, ROS, and chronic disease: an example of antagonistic pleiotropy

Reactive oxygen species (ROS) are considered to be chemically reactive with and damaging to biomolecules including DNA, protein, and lipid, and excessive exposure to ROS induces oxidative stress and causes genetic mutations. However, the recently described family of Nox and Duox enzymes generates ROS in a variety of tissues as part of normal physiological functions, which include innate immunity, signal transduction, and biochemical reactions, e.g., to produce thyroid hormone. Nature's "choice" of ROS to carry out these biological functions seems odd indeed, given its predisposition to cause molecular damage. This review describes normal biological roles of Nox enzymes as well as pathological conditions that are associated with ROS production by Nox enzymes. By far the most common conditions associated with Nox-derived ROS are chronic diseases that tend to appear late in life, including atherosclerosis, hypertension, diabetic nephropathy, lung fibrosis, cancer, Alzheimer's disease, and others. In almost all cases, with the exception of a few rare inherited conditions (e.g., related to innate immunity, gravity perception, and hypothyroidism), diseases are associated with overproduction of ROS by Nox enzymes; this results in oxidative stress that damages tissues over time. I propose that these pathological roles of Nox enzymes can be understood in terms of antagonistic pleiotropy: genes that confer a reproductive advantage early in life can have harmful effects late in life. Such genes are retained during evolution despite their harmful effects, because the force of natural selection declines with advanced age. This review discusses some of the proposed physiologic roles of Nox enzymes, and emphasizes the role of Nox enzymes in disease and the likely beneficial effects of drugs that target Nox enzymes, particularly in chronic diseases associated with an aging population.

EGF-induced apoptosis in A431 cells is dependent on STAT1, but not on STAT3

EGF in high concentrations has a growth-inhibitory effect on human epidermoid carcinoma cells A431. The transcription factor STAT1 is the most probable candidate for mediating this effect. In the present study, we demonstrated a strong reduction of the expression level of STAT1 in EGF-resistant sub-clones of A431 cells. EGF resistance was reversed by introducing wild-type STAT1, but not its Y701F mutant. Moreover, blocking the activity of Src family kinases reduced tyrosine phosphorylation of STAT1 and STAT3 and protected A431 cells from the EGF-induced growth inhibition. To further elucidate roles of STATs in A431 cell growth and survival, clones of A431 cells expressing short hairpin RNA (shRNA) against STAT1 or STAT3 were generated. Neither STAT1 nor STAT3 knockdown exerted any effect on growth rate or apoptotic death of A431 cells in the absence of EGF. However, upon EGF treatment A431 cells with knocked down STAT1 continued to grow and demonstrated a significantly lower level of apoptosis as compared to A431 cells. The knockdown of STAT3 did not alter cell growth or apoptosis. Taken together, our experiments prove the essential role of tyrosine phosphorylated STAT1, but not of STAT3, in EGF-induced apoptosis in A431 cells.

The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology

For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the phagocyte NADPH oxidase itself (NOX2/gp91(phox)), the homologs are now referred to as the NOX family of NADPH oxidases. These enzymes share the capacity to transport electrons across the plasma membrane and to generate superoxide and other downstream reactive oxygen species (ROS). Activation mechanisms and tissue distribution of the different members of the family are markedly different. The physiological functions of NOX family enzymes include host defense, posttranlational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. NOX enzymes also contribute to a wide range of pathological processes. NOX deficiency may lead to immunosuppresion, lack of otoconogenesis, or hypothyroidism. Increased NOX activity also contributes to a large number or pathologies, in particular cardiovascular diseases and neurodegeneration. This review summarizes the current state of knowledge of the functions of NOX enzymes in physiology and pathology.

Das anti-inflammatorische Potential von Padma 28 – Übersicht experimenteller Daten zur antiatherogenen Wirkung und Diskussion des Vielstoffkonzepts

BACKGROUND

The Tibetan remedy Padma 28 has been used in Europe for decades and has proved to be effective in inflammatory and atherosclerotic conditions. Beyond clinical trials, a large number of in vitro and ex vivo studies report various properties and biochemical activities of this complex herbal multicompound.

OBJECTIVE

To give an overview of the complex efficacy profile of Padma 28, to review available data, to relate findings to the development of atherosclerosis and thus to discuss the antiatherogenic potential of Padma 28.

METHODS

Published non-clinical original papers on Padma 28 were collected and classified according to the studied mechanisms of action. Results were correlated to the briefly described sequences of atherogenesis and various mechanisms of action were elaborated, laying particular emphasis on more recent articles.

RESULTS

The complex activity profile of Padma 28 spans mainly direct and indirect anti-inflammatory proper-ties as well as further categories of biochemical actions. These can be related to the complex processes of atherogenesis.

CONCLUSIONS

The described mechanisms support the therapeutic field of application of Padma 28, i.e. peripheral circulatory disorders as well as chronic inflammatory disorders. Moreover, the numerous effects as well as the diversity of sites of action allow to draw first conclusions on the conceptual design of this multicomponent formula.

cDNA microarray analysis of isogenic paclitaxel- and doxorubicin-resistant breast tumor cell lines reveals distinct drug-specific genetic signatures of resistance

cDNA microarray analysis is a highly useful tool for the classification of tumors and for prediction of patient prognosis to specific cancers based on this classification. However, to date, there is little evidence that microarray approaches can be used to reliably predict patient response to specific chemotherapy drugs or regimens. This is likely due to an inability to differentiate between genes affecting patient prognosis and genes that play a role in response to specific drugs. Thus, it would be highly useful to identify genes whose expression correlates with tumor cell sensitivity to specific chemotherapy agents in a drug-specific manner. Using cDNA microarray analysis of wildtype MCF-7 breast tumor cells and isogenic paclitaxel-resistant (MCF-7(TAX)) or doxorubicin-resistant (MCF-7(DOX)) derivative cell lines, we have uncovered drug-specific changes in gene expression that accompany the establishment of paclitaxel or doxorubicin resistance. These changes in gene expression were confirmed by quantitative reverse transcription polymerase chain reaction and immunoblotting experiments, with a confirmation rate of approximately 91-95%. The genes identified may prove highly useful for prediction of response to paclitaxel or doxorubicin in patients with breast cancer. To our knowledge this is the first report of drug-specific genetic signatures of resistance to paclitaxel or doxorubicin, based on a comparison of gene expression between isogenic wildtype and drug-resistant tumor cell lines. Moreover, this study provides significant insight into the wide variety of mechanisms through which resistance to these agents may be acquired in breast cancer.