Doxorubicin (Dox) is a chemotherapeutic agent that causes significant cardiotoxicity. We showed previously that Dox activates p53 and induces apoptosis in mouse hearts. This study was designed to elucidate the molecular events that lead to p53 stabilization, to examine the pathways involved in Dox-induced apoptosis, and to evaluate the effectiveness of pifithrin-α (PFT-α), a p53 inhibitor, in blocking apoptosis of rat H9c2 myoblasts. H9c2 cells that were exposed to 5 μM Dox had elevated levels of p53 and phosphorylated p53 at Ser15. Dox also triggered a transient activation of p38, p42/p44ERK, and p46/p54JNK MAP kinases. Caspase activity assays and Western blot analysis showed that H9c2 cells treated with Dox for 16 h had marked increase in the levels of caspases-2, -3, -8, -9, -12, Fas, and cleaved poly(ADP ribose) polymerase (PARP). There was a concomitant increase in p53 binding activity, cytochrome c release, and apoptosis. These results suggest that Dox can trigger intrinsic, extrinsic, and endoplasmic reticulum-associated apoptotic pathways. Pretreatment of cells with PFT-α followed by Dox administration attenuated Dox-induced increases in p53 levels and p53 binding activity and partially blocked the activation of p46/p54JNK and p42/p44ERK. PFT-α also led to decreased levels of caspases-2, -3, -8, -9, -12, Fas, PARP, cytochrome c release, and apoptosis. Our results suggest that p53 stabilization is a focal point of Dox-induced apoptosis and that PFT-α interferes with multiple steps of Dox-induced apoptosis.

Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 86 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Virginia, 2008. / Title from title page. Includes bibliographical references. Also available online through Digital Dissertations.

The c-Jun NH2-terminal kinase (JNK) group and the p38 group of mitogen-activated protein kinases (MAPK) are stress-activated protein kinases that regulate cell proliferation, differentiation, development, and apoptosis. These protein kinases are involved in a signal transduction cascade that includes a MAP kinase (MAPK), a MAP kinase kinase (MAP2K), and a MAP kinase kinase kinase (MAP3K). MAPK are phosphorylated and activated by the MAP2K, which are phosphorylated and activated by various MAP3K. The work presented in this dissertation focuses on understanding the regulation and function of the JNK and p38 MAPK pathways. Two different strategies were utilized. First, I used molecular and biochemical techniques to examine how MAP2K and MAP3K mediate signaling specificity and to define their role in the MAPK pathway. Second, I used gene targeted disruption studies to determine the in vivo role ofMAP2K and MAP3K in MAPK activation. I specifically used these approaches to examine: (1) docking interactions between p38 MAPK and MAP2K [MKK3 and MKK6 (Chapter II)]; (2) the differential activation of p38 MAPK by MAP2K [MKK3, MKK4, and MKK6 (Chapter III)]; and (3) the selective involvement of the mixed lineage kinase (MLK) group of MAP3K in JNK and p38 MAPK activation (Chapter IV and Appendix). In addition, I analyzed the role of the MKK3 and MKK6 MAP2K in cell proliferation and the role of the MLK MAP3K in adipocyte differentiation (Chapter III and Chapter IV). Together, these data provide insight into the regulation and function of the stress-activated MAPK signal transduction pathways.

Yung, Lai Hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 93-115). / Abstract also in Chinese. / Declaration --- p.i / Acknowledgements --- p.ii / Abbreviations --- p.iii / Abstract in English --- p.v / Abstract in Chinese --- p.ix / Contents --- p.xi / Chapter Chapter I - --- Introduction / Chapter 1.1) --- Endothelial cells function --- p.1 / Chapter 1.2) --- Oxidative stress in the vascular wall --- p.2 / Chapter 1.2.1) --- Sources of ROS --- p.3 / Chapter 1.2.2) --- Actions of ROS --- p.3 / Chapter 1.2.2.1) --- Impaired endothelium-dependent vasodilatation --- p.3 / Chapter 1.2.2.2) --- VSMC migration --- p.4 / Chapter 1.2.2.3) --- Programmed cell death (cell apoptosis) --- p.4 / Chapter 1.3) --- Endothelial cell apoptosis --- p.7 / Chapter 1.3.1) --- Apoptosis and cardiovascular diseases --- p.7 / Chapter 1.3.2) --- Mechanisms of endothelial cells apoptosis --- p.7 / Chapter 1.3.2.1) --- What are caspases? --- p.8 / Chapter 1.3.2.2) --- Death receptor-mediated apoptosis --- p.9 / Chapter 1.3.2.3) --- Mitochondria-dependent pathway --- p.9 / Chapter 1.3.3) --- Regulations of endothelial cells apoptosis --- p.10 / Chapter 1.3.3.1) --- Oxidative stress --- p.10 / Chapter 1.3.3.2) --- Shear Stress --- p.11 / Chapter 1.3.3.3) --- Growth factors --- p.12 / Chapter 1.3.3.4) --- NO --- p.12 / Chapter 1.3.3.5) --- Inflammatory mediators --- p.13 / Chapter 1.4) --- Mitogen activated kinases signaling in apoptosis --- p.15 / Chapter 1.5) --- Bone morphogenic proteins (BMPs) --- p.17 / Chapter 1.5.1) --- BMPs functions and cardiovascular system --- p.17 / Chapter 1.5.2) --- BMPs signaling pathways --- p.18 / Chapter 1.5.2.1) --- Smad-dependent pathway --- p.18 / Chapter 1.5.2.2) --- MAPKs and SAPKs pathways --- p.19 / Chapter 1.5.2.3) --- Antagonists of BMPs signaling --- p.20 / Chapter 1.5.3) --- BMP4 and cardiovascular diseases --- p.20 / Chapter 1.6) --- "Justification, long-term significance and objectives of the present project" --- p.23 / Chapter Chapter II - --- Methods and Materials / Chapter 2.1) --- Animal handling --- p.24 / Chapter 2.2) --- Endothelial cell isolation and culture --- p.24 / Chapter 2.2.1) --- Primary culture of rat endothelial cells --- p.24 / Chapter 2.2.2) --- Culture of human umbilical cord vein endothelial cells… --- p.25 / Chapter 2.3) --- Apoptosis assessment --- p.25 / Chapter 2.3.1) --- Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay --- p.25 / Chapter 2.3.2) --- Cell death detection ELISA kit --- p.26 / Chapter 2.3.3) --- Flow cytometry --- p.27 / Chapter 2.4) --- Western blot analysis --- p.28 / Chapter 2.4.1) --- Sample preparation --- p.28 / Chapter 2.4.2) --- SDS-PAGE and transfer --- p.28 / Chapter 2.5) --- DHE fluorescence --- p.29 / Chapter 2.6) --- "Drugs, chemicals and other reagents" --- p.30 / Chapter 2.6.1) --- Drugs and chemicals used in the present experiments --- p.30 / Chapter 2.6.2) --- Reagents for Western blot analysis --- p.30 / Chapter 2.6.3) --- Primary antibodies --- p.33 / Chapter 2.7) --- Small interfering RNA experiment --- p.34 / Chapter 2.8) --- Statistical analysis --- p.34 / Chapter Chapter III - --- BMP4 induces endothelial cell apoptosis in ROS related p38 MAPK and JNK mediated caspase-3 dependent pathway / Chapter 3.1) --- Introduction --- p.35 / Chapter 3.2) --- Methods and materials --- p.39 / Chapter 3.2.1) --- Isolation and culture of endothelial cells --- p.39 / Chapter 3.2.2) --- Drugs treatment --- p.39 / Chapter 3.2.3) --- Assay for cell apoptosis --- p.40 / Chapter 3.2.3.1) --- Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay --- p.40 / Chapter 3.2.3.2) --- Cell death detection ELISA kit --- p.41 / Chapter 3.2.3.3) --- Flow cytometric analysis --- p.41 / Chapter 3.2.4) --- Western blot analysis --- p.41 / Chapter 3.2.5) --- Dihydroethidium (DHE) staining --- p.42 / Chapter 3.2.6) --- Statistical analysis --- p.42 / Chapter 3.3) --- Results --- p.43 / Chapter 3.3.1) --- Dose- and time-dependent effect of BMP4 --- p.43 / Chapter 3.3.2) --- Role of caspases in apoptosis of RAECs and HUVECs --- p.43 / Chapter 3.3.3) --- Roles of BMP4 and ROS in endothelial cell apoptosis --- p.44 / Chapter 3.3.3.1) --- Noggin antagonism of BMP4-induced effect --- p.44 / Chapter 3.3.3.2) --- NAD(P)H oxidase-mediated ROS production --- p.44 / Chapter 3.3.3.3) --- Inhibition of endothelial cell apoptosis by ROS scavengers --- p.45 / Chapter 3.3.4) --- Roles of MAPKs/SAPKs in BMP4-induced endothelial cell apoptosis --- p.45 / Chapter 3.3.5) --- Relationship between ROS and MAPKs/SAPKs --- p.46 / Chapter 3.3.6) --- Relationship between p38 MAPK and JNK --- p.46 / Chapter 3.4) --- Discussion --- p.82 / Chapter 3.4.1) --- Caspase-dependent pathways --- p.82 / Chapter 3.4.2) --- Oxidative stress --- p.85 / Chapter 3.4.3) --- Role of MAPKs activation in BMP4-induced endothelial cell apoptosis --- p.87 / Chapter 3.4.4) --- ROS mediates BMP4-induced activation of MAPKs --- p.88 / Chapter 3.4.5) --- Role of p38 MAPK in the activation of JNK 1 --- p.89 / Chapter 3.5) --- Concluding remarks --- p.91 / References --- p.93 / Publications and Awards --- p.116

Thesis (Ph. D.)--University of Virginia, 2007. / Includes bibliographical references. Also available online through Digital Dissertations.

p38 mitogen-activated protein (MAP) kinases represent a subgroup of MAP kinases that respond to environmental stress and inflammatory cytokines. p38 MAPK is activated by two upstream kinases, MKK3 and MKK6, by dual phosphorylation on threonine and tyrosine in conserved kinase subdomain VII. Until recently the relative roles of MKK3 and MKK6 have remained unclear. I have undertaken two strategies in an effort to understand the importance of MKK3 as a p38 MAPK activator. First, I cloned and characterized the murine mkk3 gene and determined the structure of the 5'-terminus. Comparison of the murine and human mkk3 genes revealed that the mouse gene encodes a single MKK3 isoform, MKK3b, and the human gene encodes two isoforms, MKK3a and MKK3b. Comparison of the mouse and human mkk3 genes suggests that expression of MKK3a and MKK3b is regulated from different promotors. Analysis of the mkk3 promoter demonstrates that muscle specific expression of murine MKK3b is controlled, in part, by the transcription factors MEF2 and MyoD. Second, I have utilized a gene targeting strategy to disrupt the murine mkk3 gene and to examine the effect on p38 MAPK signaling. I found that there is a p38-specific signaling defect in MKK3 deficient primary mouse embryo fibroblasts (MEF) which correlates with deficits in interleukin (IL)-1 and IL-6 production in response to tumor necrosis factor-α (TNFα) stimulation. In addition there is a defect in TNFα mediated expression of TNFα and macrophage inflammatory proteins (MIP) 1α, MIP1β and MIP2. p38 MAPK-specific signaling defects were also observed in lipopolysaccharide (LPS) stimulated mkk3 (-/-) macrophages. Additionally, mkk3 (-/-) macrophages exhibit defects in LPS and CD40-ligand (CD40L) stimulated IL-12 biosynthesis. Similar data were obtained from CD40L-stimulated mkk3 (-/-) dendritic cells. I also observe that interferon (Ifn)-γ production is diminished during T-helper-1 (TH1) differentiation of CD4+ T-cells derived from mkk3 (-/-) mice. Taken together these data demonstrate a crucial role for p38 MAPK activation by MKK3 in response to the inflammatory cytokine, TNFα and during a TH1 inflammatory response.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Introduction: Cancer is an emerging health problem in South Africa, with breast cancer being one of the leading cancers affecting women globally. Therefore, there is a need to find novel targets to improve the therapeutic options for these patients. A recently proposed target is the mitogen-activated protein kinase phosphatase-1 (MKP-1). Studies have suggested that mitogen-activated protein kinase phosphatases are involved in the development of cancer and play an important role in the response of cancer cells to chemotherapy. Additionally, numerous studies have indicated that there is increased expression of MKP-1 in breast cancers where its over-expression is proposed to be a significant mediator in chemo-resistance. We propose that inhibition of MKP-1 will increase the cytotoxic effect of doxorubicin in breast cancer cells, thus making the cells more responsive to treatment leading to increased cell death through autophagy and apoptosis. Methods: In MDA-MB231 cells, MKP-1 was inhibited using sanguinarine or MKP-1 siRNA and this was compared to a known inducer of MKP-1, dexamethasone. MDA-MB231 cells were treated with doxorubicin alone or in combination with MKP-1 inhibitors or an inducer. Following treatment, cell death was determined by trypan blue and a caspase glo assay as well as with western blotting. Autophagy was determined by western blotting and flow cytometry. LC3 and p62 were used as markers of autophagy and caspase 3 and PARP as apoptosis markers. Likewise, the level of MKP-1 expression under conditions of MKP-1 induction, inhibition or silencing was evaluated by means of western blotting. C57BL6 tumour bearing mice was used to analyse apoptosis and autophagy in vivo under conditions of MKP-1 inhibition, using sanguinarine, together with doxorubicin treatment. Western blotting was used to determine levels of caspase 3, LC3, p62 and MKP-1 expression. Results and discussion: A concentration and time curve indicated that 5 μM doxorubicin reduced cell viability in the MDA-MB231 cells significantly after 24 hours of treatment. MKP-1 expression was significantly reduced with sanguinarine and MKP-1 siRNA. Furthermore, our results indicate a significant increase in apoptosis in MDA-MB231 cells when treated with doxorubicin, under conditions of MKP-1 inhibition or MKP-1 silencing. Also, an increase in autophagic activity was observed following treatment with doxorubicin in combination with sanguinarine. Whole excised tumours of C57BL6 mice also showed an increase in apoptosis and autophagy following treatment with sanguinarine in combination with doxorubicin. This indicates that the inhibition of MKP-1 with sanguinarine sensitized the MDA-MB231 cells and E0771 cell tumours to doxorubicin-induced-apoptosis through a mechanism involving autophagy. Conclusion: This is an encouraging finding that could hopefully be used in future studies to overcome doxorubicin-resistance in breast cancer cells overexpressing MKP-1. Targeting MKP-1 can have potential therapeutic benefits for breast cancer patients by making chemotherapy more effective. Sanguinarine thus has potential to be developed as a clinically relevant inhibitor of MKP-1 which could provide a novel avenue for therapeutic intervention in combination with chemotherapy in breast cancer patients. / AFRIKAANSE OPSOMMING: Inleiding: Kanker is 'n vinnig groeiende gesondheidsprobleem in Suid-Afrika, met borskanker as een van die vernaamste kankers wat vroue wêreldwyd raak. Daar is dus 'n behoefte aan nuwe terapeutiese opsies vir hierdie pasiënte en mitogeen-geaktiveerde proteïenkinase fosfatase-1 (MKP-1) is onlangs voorgestel as ‘n moontlike teiken. Verskeie studies toon dat mitogeen-geaktiveerde proteïenkinase fosfatases betrokke is by die ontwikkeling van kanker en ook belangrike rolspelers is in die reaksie van kanker op chemoterapie. Daarbenewens toon talle studies dat daar verhoogde MKP-1 uitdrukking in borskanker is, asook dat dit ‘n belangrike bemiddelaar is vir die weerstand wat borskanker teen chemoterapie bied. Ons het dus voorgestel dat die inhibisie van MKP-1 die sitotoksiese effek van doxorubicin op borskanker selle sal verhoog; sodoende sal die kanker selle beter reageer op behandeling en dit sal dus lei tot verhoogde seldood deur autofagie en apoptose. Metodes: MKP-1 is geïnhibeer met behulp van sanguinarine of MKP-1 siRNA in MDA-MB231 selle en dit is vergelyk met 'n bekende MKP-1 induseerder, dexamethasone. MDA-MB231 selle is met doxorubicin alleen behandel of in kombinasie met MKP-1 inhibeerders of ‘n induseerder. Seldood is bepaal deur middel van ‘n trypan blou en kaspase toetsingsmetode, asook met die westelike kladtegniek. Autofagie is bepaal deur westelike kladtegniek en vloeisitometrie. LC3 en p62 is gebruik as merkers van autofagie en kaspase 3 en PARP is as apoptose merkers gebruik. MKP-1 uitdrukking is geëvalueer deur middel van westelike kladtegniek. C57BL6 muise met kankeragtige gewasse is gebruik om apoptose en autofagie in vivo te ondersoek. MKP-1 is geïnhibeer met sanguinarine en die muise is behandel met ‘n kombinasie van sanguinarine en doxorubicin. Kaspase 3, LC3, p62 en MKP-1 uitdrukking is bepaal deur middel van die westelike kladtegniek. Resultate en bespreking: ‘n Konsentrasie en tyd kurwe het aangedui dat 5 μM doxorubicin die MDA-MB231 selle se lewensvatbaarheid aansienlik verminder het na 24 uur. MKP-1 uitdrukking is ook aansienlik verminder met sanguinarine en MKP-1 siRNA. Verder dui die resultate op 'n beduidende toename in apoptose in MDA-MB231 selle na behandeling met doxorubicin onder toestande van MKP-1 inhibisie. 'n Toename in autofagiese aktiwiteit is waargeneem na behandeling met doxorubicin en sanguinarine. Die kankeragtige gewasse van die C57BL6 muise toon ook 'n toename in apoptose en autofagie na behandeling met sanguinarine en doxorubicin. Hierdie resultate dui daarop dat die inhibisie van MKP-1 met sanguinarine die MDA-MB231 selle en E0771 sel gewasse gesensitiseer het tot doxorubicin-geïnduseerde apoptose deur middel van ‘n meganisme wat autofagie insluit. Gevolgtrekking: Hierdie bevinding kan hopelik in toekomstige studies gebruik word om doxorubicin weerstand te oorkom in borskanker selle waar MKP-1 verhoog is. Deur MKP-1 te teiken, kan dit lei tot potensiële terapeutiese voordele vir borskanker pasiënte en sodoende kan dit chemoterapie meer effektief maak. Sanguinarine het dus die potensiaal om ontwikkel te word as ‘n klinies relevante inhibeerder van MKP-1 wat sodoende kan dien as terapeutiese intervensie in kombinasie met chemoterapie vir borskanker pasiënte.

published_or_final_version / abstract / Biochemistry / Master / Master of Philosophy

published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Philosophy