Heinrich Sauer

Reactive Oxygen Species as Intracellular Messengers During Cell Growth and Differentiation

Reactive oxygen species (ROS) are generated following ligand-receptor interactions and function as specific second messengers in signaling cascades involved in cell proliferation and differentiation. Although ROS are generated intracellularly by several sources, including mitochondria, the primary sources of ROS involved in receptor-mediated signaling cascades are plasma membrane oxidases, preferentially NADPH oxidases, with a rapid kinetics of activation and inactivation. This allows a tight up- and downregulation of intracellular ROS levels within the short time required for the transduction of signals from the plasma membrane to the cell nucleus. The mode of action of ROS may involve direct interaction with specific receptors, and/or redox-activation of members of signaling pathways such as protein kinases, protein phosphatases, and transcription factors. Furthermore, ROS act in concert with intracellular Ca2+ in signaling pathways which regulate the balance of cell proliferation versus cell cycle arrest and cell death. The delicate intracellular interplay between oxidizing and reducing equivalents allows ROS to function as second messengers in the control of cell proliferation and differentiation.

On the validity of the Beck Depression Inventory. A review.

The present review discusses validity aspects of the Beck Depression Inventory (BDI) on the basis of meta-analyses of studies on the psychometric properties. Shortcomings of the BDI are its high item difficulty, lack of representative norms, and thus doubtful objectivity of interpretation, controversial factorial validity, instability of scores over short time intervals (over the course of 1 day), and poor discriminant validity against anxiety. Advantages of the inventory are its high internal consistency, high content validity, validity in differentiating between depressed and nondepressed subjects, sensitivity to change, and international propagation. The present paper outlines agreements and contradictions between the various studies on the BDI and discusses the potential factors (composition of the subject sample, statistical procedures, point in time of measurement) accounting for the variance in their results.

Effect of rivastigmine on delay to diagnosis of Alzheimer's disease from mild cognitive impairment: the InDDEx study

OBJECTIVE To assess the effect of rivastigmine in patients with mild cognitive impairment (MCI) on the time to clinical diagnosis of Alzheimers disease (AD) and the rate of cognitive decline. METHODS The study was a double-blind, randomised, placebo-controlled trial of up to 48 months. All patients had MCI operationally defined by having cognitive symptoms, a global clinical dementia rating stage of 0.5, a score of less than 9 on the New York University delayed paragraph recall test, and by not meeting the diagnostic criteria for AD. Primary efficacy variables were time to clinical diagnosis of AD, and change in performance on a cognitive test battery. This study is registered with the US National Institutes of Health clinical trials database (ClinicalTrials.gov), number NCT00000174. FINDINGS Of 1018 study patients enrolled, 508 were randomly assigned to rivastigmine and 510 to placebo; 17.3% of patients on rivastigmine and 21.4% on placebo progressed to AD (hazard ratio 0.85 [95% CI 0.64-1.12]; p=0.225). There was no significant difference between the rivastigmine and placebo groups on the standardised Z score for the cognitive test battery measured as mean change from baseline to endpoint (-0.10 [95% CI -0.63 to 0.44], p=0.726). Serious adverse events were reported by 141 (27.9%) rivastigmine-treated patients and 155 (30.5%) patients on placebo; adverse events of all types were reported by 483 (95.6%) rivastigmine-treated patients and 472 (92.7%) placebo-treated patients. The predominant adverse events were cholinergic: the frequencies of nausea, vomiting, diarrhoea, and dizziness were two to four times higher in the rivastigmine group than in the placebo group. INTERPRETATION There was no significant benefit of rivastigmine on the progression rate to AD or on cognitive function over 4 years. The overall rate of progression from MCI to AD in this randomised clinical trial was much lower than predicted. Rivastigmine treatment was not associated with any significant safety concerns.

Cardiac specific differentiation of mouse embryonic stem cells

Embryonic stem (ES) cells may represent an alternative source of functionally intact cardiomyocytes for the causal treatment of cardiovascular diseases. However, this requires cardiac-specific differentiation of stem cells and the selection of pure lineages consisting of early embryonic cardiomyocytes. Therefore, an understanding of the basic mechanisms of heart development is essential for selective differentiation of embryonic stem cells into cardiac cells. The development of cardiac cells from embryonic stem cells is regulated by several soluble factors and signalling molecules together with cardiac specific transcription factors such as the zinc-finger GATA proteins and Nkx-2.5. GATA-4 and Nkx-2.5 seem to be essential for heart development. The use of enhanced green fluorescent protein (EGFP) under the control of cardiac-specific promoters in combination with the ES cell system has allowed for the functional characterisation of cardiac precursor cells. Embryonic stem cell-derived cardiomyocytes developmentally express similar cardiac-specific proteins, ion channels and signalling molecules to that of adult cardiomyocytes. Furthermore, identification of growth factors and signalling molecules under cell culture conditions is crucial for the selective cardiac differentiation of embryonic stem cells. Therefore, serum-free culture conditions have to be established in order to examine the influence of different growth factors and signalling molecules on cardiac development and/or formation from ES cells. Although significant progress has been made in generating cardiac cell lineage by the combination of genetically manipulative methods with selective culture conditions for cell transplantation therapy, one of the remaining future challenges for transplantation in humans is the immunological rejection of the engrafted cardiomyocytes.

Embryonic stem cells utilize reactive oxygen species as transducers of mechanical strain-induced cardiovascular differentiation

Growing stem cells are subjected to mechanical forces, which may initiate differentiation programs. Mechanical strain stimulated cardiovascular differentiation of mouse embryonic stem (ES) cells as evaluated by quantification of contracting cardiac foci and capillary areas, respectively. Mechanical strain rapidly elevated intracellular reactive oxygen species (ROS). After 24 h up‐regulation of NADPH oxidase subunits p22‐phox, p47‐phox, p67‐phox, and Nox‐4 as well as Nox‐1 and Nox‐4 mRNA was observed. In parallel, mechanical strain increased hypoxia‐inducible factor‐1α (HIF‐1α) and vascular endothelial growth factor (VEGF) mRNA and protein as well as MEF2C and GATA‐4 mRNA, which are involved in cardiovascular development. Furthermore, phosphorylation of extracellular‐regulated kinase 1,2 (ERK1,2), p38, and c‐jun N‐terminal kinase (c‐Jun NH2‐terminal kinase (JNK)) was observed. Stimulation of cardiovascular commitment, HIF‐1α, VEGF, and MEF2C expression as well as MAPK activation were abolished by free radical scavengers, whereas GATA‐4 expression was increased. Cardiomyogenesis was inhibited by the p38 inhibitor SB203580, the ERK1,2 inhibitor UO126, and the JNK inhibitor SP600125. Vasculogenesis/angiogenesis was blunted following inhibition of ERK1,2 and JNK, whereas p38 inhibition was ineffective. Our data outline a role of ROS as mechanotransducing molecules in mechanical strain‐stimulated cardiovascular differentiation of ES cells, and point toward a microenvironment of elevated ROS required for signaling cascades initiating cardiovascular differentiation programs.—Schmelter, M., Ateghang, B., Helmig, S., Wartenberg, M., Sauer, H. Embryonic stem cells utilize reactive oxygen species as transducers of mechanical strain‐induced cardiovascular differentiation. FASEB J. 20, E294–E306 (2006)

Role of reactive oxygen species and phosphatidylinositol 3-kinase in cardiomyocyte differentiation of embryonic stem cells.

Cardiotypic development in embryonic stem cell‐derived embryoid bodies may be regulated by reactive oxygen species (ROS). ROS were generated by a NADPH oxidase‐like enzyme which was transiently expressed during the time course of embryoid body development. Incubation with either H2O2 or menadione enhanced cardiomyogenesis, whereas the radical scavengers trolox, pyrrolidinedithiocarbamate and N‐acetylcysteine exerted inhibitory effects. The phosphatidylinositol 3‐kinase (PI‐3‐kinase) inhibitors LY294002 and wortmannin abolished cardiac commitment and downregulated ROS in embryoid bodies. Coadministration of LY294002 with prooxidants resumed cardiomyocyte differentiation, indicating a role for PI‐3‐kinase in the regulation of the intracellular redox state.

Cortical inefficiency in patients with unipolar depression: an event-related FMRI study with the Stroop task.

BACKGROUND The present study is aimed to examine the neuronal correlates of Stroop interference in medication-free patients with major depressive disorder. METHODS Sixteen patients fulfilling Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for unipolar depression and 16 healthy control subjects matched for age, gender, and education were included. All subjects underwent an event-related functional magnetic resonance imaging (fMRI) design with an adapted version of the Stroop task including congruent and incongruent task conditions. The fMRI experiment was conducted on a 1.5 T magnetic resonance (MR) scanner, and item responses were given manually by the subjects. RESULTS With regard to behavioral performance, patients revealed no differences in both reaction time and accuracy relative to control subjects. With regard to brain activations, direct comparison of patients with control subjects in the interference condition revealed hyperactivity in rostral anterior cingulate gyrus (rACG) and left dorsolateral prefrontal cortex (DLPFC) in depressive patients, which correlated strongly with the Stroop interference. CONCLUSIONS The study provides new evidence for the functioning and dissociation of the anterior cingulate in depressed patients. The greater prefrontal activation may reflect a cortical inefficiency due to hyperactivity in rACG enhancing the cognitive interferences from the emotional state.

Regulation of the multidrug resistance transporter P-glycoprotein in multicellular tumor spheroids by hypoxia-inducible factor (HIF-1) and reactive oxygen species

Hypoxia in tumors is generally associated with chemoresistance and radioresistance. However, the correlation between the heterodimeric hypoxia‐inducible factor‐1 (HIF‐1) and the multidrug resistance transporter P‐glycoprotein (P‐gp) has not been investigated. Herein, we demonstrate that with increasing size of DU‐145 prostate multicellular tumor spheroids the pericellular oxygen pressure and the generation of reactive oxygen species decreased, whereas the α‐subunit of HIF‐1 (HIF‐1α) and P‐gp were up‐regulated. Furthermore, P‐gp was up‐regulated under experimental physiological hypoxia and chemical hypoxia induced by either cobalt chloride or desferrioxamine. The pro‐oxidants H2O2 and buthionine sulfoximine down‐regulated HIF‐1α and P‐gp, whereas up‐regulation was achieved with the radical scavengers dehydroascorbate, N‐acetylcysteine, and vitamin E. The correlation of HIF‐1α and P‐gp expression was validated by the use of hepatoma tumor spheroids that were either wild type (Hepa1) or mutant (Hepa1C4) for aryl hydrocarbon receptor nuclear translocator (ARNT), i.e., HIF‐1β. Chemical hypoxia robustly increased HIF‐1α as well as P‐gp expression in Hepa1 tumor spheroids, whereas no changes were observed in Hepa1C4 spheroids. Hence, our data demonstrate that expression of P‐gp in multicellular tumor spheroids is under the control of HIF‐1.

Effects of electrical fields on cardiomyocyte differentiation of embryonic stem cells

The effects of electromagnetic fields (EMFs) on the differentiation of cardiomyocytes in embryoid bodies derived from pluripotent embryonic stem (ES) cells were investigated. A single direct current (DC) field pulse was applied to 4‐day‐old embryoid bodies. The electrical field induced a hyperpolarization of the anode‐facing side of embryoid bodies and a depolarization at the cathode‐facing side. Significant effects of a single electrical field pulse applied for 90 s on cardiomyocyte differentiation were achieved with field strengths of 250 and 500 V/m, which increased both the number of embryoid bodies differentiating beating foci of cardiomyocytes and the size of the beating foci. The 500‐V/m electrical field increased intracellular reactive oxygen species (ROS), but not [Ca2+]i and activated nuclear factor kappa B (NF‐κB). A comparable increase in the number of beating embryoid bodies was achieved by an incubation for 1 h with H2O2 (1–10 nM), indicating that the electrical field effect was transduced via the intracellular generation of ROS. Because the radical scavengers dehydroascorbate and pyrrolidinedithiocarbamate (APDC) and the NF‐κB antagonist N‐tosyl‐L‐phenylalanine chloromethyl ketone (TPCK) inhibited cardiac differentiation, we assume that ROS and NF‐κB may play a role in early cardiac development. J. Cell. Biochem. 75:710–723, 1999.

Pain perception in major depression depends on pain modality.

&NA; One frequently described feature of depression is an increased vulnerability to pain complaints, and chronic pain is frequently accompanied by symptoms of depression. In contrast to this, a decreased sensitivity to experimental pain has been described in major depression. The physiological basis of this phenomenon is yet elusive. We investigated 30 patients suffering from a major depressive disorder and matched controls. Pain testing (threshold and tolerance) was performed on both sides of the body and included assessment of thermal, electrical and ischemic pain. While confirming hypoalgesia to heat and electrical pain in comparison to controls, we found hyperalgesia to ischemic muscle pain. Furthermore, thermal pain tolerance and electrical pain tolerance were significantly increased on the right hand side confirming previous results of a lateralized perception of pain in depression. Our main finding suggests that painful stimuli are processed differentially depending on the localization of pain induction in depression. This knowledge may enable us to understand and ultimately treat pain complaints more appropriately in depressed patients.