Aurimas Stulpinas

Stem cell death and survival in heart regeneration and repair.

Cardiovascular diseases are major causes of mortality and morbidity. Cardiomyocyte apoptosis disrupts cardiac function and leads to cardiac decompensation and terminal heart failure. Delineating the regulatory signaling pathways that orchestrate cell survival in the heart has significant therapeutic implications. Cardiac tissue has limited capacity to regenerate and repair. Stem cell therapy is a successful approach for repairing and regenerating ischemic cardiac tissue; however, transplanted cells display very high death percentage, a problem that affects success of tissue regeneration. Stem cells display multipotency or pluripotency and undergo self-renewal, however these events are negatively influenced by upregulation of cell death machinery that induces the significant decrease in survival and differentiation signals upon cardiovascular injury. While efforts to identify cell types and molecular pathways that promote cardiac tissue regeneration have been productive, studies that focus on blocking the extensive cell death after transplantation are limited. The control of cell death includes multiple networks rather than one crucial pathway, which underlies the challenge of identifying the interaction between various cellular and biochemical components. This review is aimed at exploiting the molecular mechanisms by which stem cells resist death signals to develop into mature and healthy cardiac cells. Specifically, we focus on a number of factors that control death and survival of stem cells upon transplantation and ultimately affect cardiac regeneration. We also discuss potential survival enhancing strategies and how they could be meaningful in the design of targeted therapies that improve cardiac function.

Daunorubicin induces cell death via activation of apoptotic signalling pathway and inactivation of survival pathway in muscle-derived stem cells

Daunorubicin (as well as other anthracyclines) is known to be toxic to heart cells and other cells in organism thus limiting its applicability in human cancer therapy. To investigate possible mechanisms of daunorubicin cytotoxicity, we used stem cell lines derived from adult rabbit skeletal muscle. Recently, we have shown that daunorubicin induces apoptotic cell death in our cell model system and distinctly influences the activity of MAP kinases. Here, we demonstrate that two widely accepted antagonistic signalling pathways namely proapoptotic JNK and prosurvival PI3K/AKT participate in apoptosis. Using the Western blot method, we observed the activation of JNK and phosphorylation of its direct target c-Jun along with inactivation of AKT and its direct target GSK in the course of programmed cell death. By means of small-molecule kinase inhibitors and transfection of cells with the genes of the components of these pathways, c-Jun and AKT, we confirm that JNK signalling pathway is proapoptotic, whereas AKT is antiapoptotic in daunorubicin-induced muscle cells. These findings could contribute to new approaches which will result in less toxicity and fewer side effects that are currently associated with the use of daunorubicin in cancer therapies.

Role of MAP kinases in nitric oxide induced muscle-derived adult stem cell apoptosis.

Apoptosis in heart failure has been intensively investigated in vitro and in vivo. Stem cells have therapeutic value in the direct treatment of diseases, including cardiovascular disease. The main drawback of stem cell therapy is their poor survival in the diseased tissues. Since intracellular mitogen‐activated protein kinases (MAPKs) actively participate in the regulation of cell survival and of proapoptotic signals, the ability to manipulate the mechanisms of MAPKs activation in myogenic stem cells might increase the survival of transplanted stem cells. Our results clearly demonstrate sustained activation of all three MAPKs, ERK, JNK and p38 in myogenic stem cells after exposure to the NO inducer, NOC‐18. Inhibition of MAPKs phosphorylation by specific inhibitors revealed the anti‐apoptotic role of MAPKs in myogenic stem cells.

Long‐term muscle‐derived cell culture: multipotency and susceptibility to cell death stimuli

Improvement in the yield of adult organism stem cells, and the ability to manage their differentiation and survival potential are the major goals in their application in regenerative medicine and in the adult stem cell research. We have demonstrated that adult rabbit muscle‐derived cell lines with an unlimited proliferative potential in vitro can differentiate into myogenic, osteogenic, adipogenic and neurogenic lineages. Studies of cell survival in vitro showed that differentiated cells, except neurogenic ones, are more resistant to apoptosis inducers compared to proliferating cells. Resistance to death signals correlated with the level of protein kinase AKT phosphorylation. Skeletal muscle‐derived cell lines can be multipurpose tools in therapy. Enhanced resistance of differentiated cells to certain types of damage shows their potential for long‐term survival and maintenance in an organism.

Study of Bioreductive Anticancer Agent RH-1-Induced Signals Leading the Wild-Type p53-Bearing Lung Cancer A549 Cells to Apoptosis

UNLABELLED Aziridinylquinone RH-1 (2,5-diaziridinyl-3-hydroxymethyl-6-methyl-cyclohexa-2,5-diene-1,4-dione) is a potential anticancer agent. RH-1 action is associated with NAD(P)H quinone oxidoreductase (NQO1) which reduces this diaziridinylbenzoquinone into DNA-alkylating hydroquinone and is overexpressed in many tumors. Another suggested mechanism of RH-1 toxicity is the formation of reactive oxygen species (ROS) arising from its redox cycling. In order to improve anticancer action of this and similar antitumor quinones, we investigated the involvement of different signaling molecules in cytotoxicity induced by RH-1 by using wild-type tumor suppressor p53 bearing nonsmall cell lung carcinoma A549 cells as a model. Gradual and prolonged increase of mitogen-activated protein kinases (MAPK) ERK, P38, and JNK phosphorylation was observed during 24-h RH-1 treatment. In parallel, activation of DNA damage-sensing ATM kinase, upregulation, and phosphorylation of TP53 (human p53) took place. Inhibition studies revealed that RH-1-induced A549 apoptosis involved the NQO1-ATM-p53 signaling pathway and ROS generation. TP53 participated in ROS- and DNA damage-induced cell death differently. Moreover, MAP kinase JNK was another TP53 activator and death inducer in A549 cells. At the same time, rapid and prolonged activation of AKT kinase during RH-1 treatment was found, and it proved to be antiapoptotic kinase in our model system. Therefore, we identified that different and opposite cell death regulating signaling pathways, which may counteract one another, are induced in cancer cells during chemotherapeutic RH-1 treatment.

MAPK signalling in skeletal muscle-derived stem cells after daunorubicin treatment@@@MAPK vaidmuo apsaugant raumeninės kilmės kamienines ląsteles nuo daunorubicino poveikio

To shed some light on the cytoxicity of anthracyclines, we developed muscle-derived myogenic stem cell lines (Myo) from different rabbits and examined their susceptibility to various doses of daunorubicin in vitro. We have found that myogenic cells after daunorubicin treatment die by apoptosis, a programmed cell death. Stem cells residing in the tissue, after various damages might be protected and even regenerate the damaged organs. With this in mind, we have tested the involvement of MAPKs – ERK, JNK and p38 – in determination of Myo cell fate. We ascertained the gradual and sustained phosphorylation of JNK and p38 by daunorubicin in Myo cells. To evaluate their role in stem cell survival after daunorubicin treatment, we targeted MAP kinases with specific inhibitors. As a result, the JNK inhibitor SP600125 significantly increased cell viability, showing its proapoptotic mode of action. The other MAP kinase, p38, exhibited an antiapoptotic action, while ERK did not show a significant effect on regulating the fate of cells. Therefore, we propose that JNK inhibitors might be used in combination with the chemotherapeutic drug daunorubicin as a complex treatment increasing stem cell survival and preventing the cardiotoxicity of daunorubicin in cancer patients.

Adult Stem Cells and Anticancer Therapy

Abstract This chapter first describes the potential of stem cells in diverse biopharmaceutical applications, such as replacement therapy, disease modeling, and drug development. On the other hand, stem cells can become the targets of various potential toxicities in the body. In this context, an overview of stem cells as objects in toxicology as well as various experimental approaches to analyze the effects of toxic substances including anticancer drugs is presented, single-cell methods and natural microenvironment-mimicking models among them. Further, anticancer drugs (both conventional and targeted) and their molecular targets are described, with advances and challenges in their use as well as current directions in their combination and development. Then, recent knowledge about adult stem cell response to anticancer therapy is presented, paying attention to the molecular mechanisms of cell death induction and resistance, and uncovering the possible role of stem cell differentiation state during the anticancer treatment. Finally, various ideas, suggestions, and experimental data to protect adult stem cells during cancer therapy are presented.

Effective Agents Targeting the Mitochondria and Apoptosis to Protect the Heart

A wide variety of agents have been traditionally used in cardiovascular medicine worldwide and their precise mechanisms of action have been demonstrated to be largely related to the cardiomyocyte mitochondria and apoptosis. Abnormalities in the structure and function of the mitochondria and mutations in mitochondrial DNA can decrease energy production, alter the redox system, impair calcium homeostasis, and induce the mitochondrial permeability transition pore (MPTP), causing cell death. All of these data provide evidence of mitochondrial signaling pathways as targets to downregulate cardiac cell apoptosis and thus to prevent and treat cardiovascular diseases. This review focuses on the protective roles of various agents, mostly natural compounds, which express beneficial effects on mitochondrial function and suspend the apoptotic signaling mechanisms by modulating the activity of mitogen-activated protein kinases (MAPKs). Examining cellular and molecular targets of these agents offers essential experimental information for future pharmacological studies, drug discovery, clinical trials and applications.