No abstract

Moderate levels of reactive oxygen species (ROS) are now recognized as redox signalling molecules. However, thus far, only mitochondria and NADPH oxidases have been identified as cellular sources of ROS in signalling. Here we identify a globin (GLB-12) that produces superoxide, a type of ROS, which serves as an essential signal for reproduction in C. elegans. We find that GLB-12 has an important role in the regulation of multiple aspects in germline development, including germ cell apoptosis. We further describe how GLB-12 displays specific molecular, biochemical and structural properties that allow this globin to act as a superoxide generator. In addition, both an intra- and extracellular superoxide dismutase act as key partners of GLB-12 to create a transmembrane redox signal. Our results show that a globin can function as a driving factor in redox signalling, and how this signal is regulated at the subcellular level by multiple control layers.

Transplantation of mesenchymal stem cells (MSCs) into injured or diseased tissue-for the in situ delivery of a wide variety of MSC-secreted therapeutic proteins-is an emerging approach for the modulation of the clinical course of several diseases and traumata. From an emergency point-ofview, allogeneic MSCs have numerous advantages over patient-specific autologous MSCs since "off-the-shelf" cell preparations could be readily available for instant therapeutic intervention following acute injury. Although we confirmed the in vitro immunomodulatory capacity of allogeneic MSCs on antigen-presenting cells with standard coculture experiments, allogeneic MSC grafts were irrevocably rejected by the host's immune system upon either intramuscular or intracerebral transplantation. In an attempt to modulate MSC allograft rejection in vivo, we transduced MSCs with an interleukin-13 (IL13)-expressing lentiviral vector. Our data clearly indicate that prolonged survival of IL13-expressing allogeneic MSC grafts in muscle tissue coincided with the induction of an alternatively activated macrophage phenotype in vivo and a reduced number of alloantigenreactive IFNc-and/or IL2-producing CD8 1 T cells compared to nonmodified allografts. Similarly, intracerebral IL13-expressing MSC allografts also exhibited prolonged survival and induction of an alternatively activated macrophage phenotype, although a peripheral T cell component was absent. In summary, this study demonstrates that both innate and adaptive immune responses are effectively modulated in vivo by locally secreted IL13, ultimately resulting in prolonged MSC allograft survival in both muscle and brain tissue. STEM CELLS 2016;34:1971-1984 SIGNIFICANCE STATEMENTBriefly, this manuscript elaborates on the clinical applicability of allogeneic mesenchymal stem cell (MSC) transplantation as a tool for long-term therapeutic protein delivery in vivo, which, despite the presumed immune privileged status of MSCs, is hindered by the host's capacity to induce graft-specific immunity. Here, we established that genetic engineering of allogeneic MSCs with interleukin-13 can modulate graft-directed innate and adaptive host immune responses, evidenced by the in vivo induction of M2a macrophages and the reduced induction of graft-specific CD8 1 T cells, with prolonged MSC allograft survival as a result.

After its discovery in 2000, the notion grew that neuroglobin, a neuronal specific heme protein, is involved in cytoprotection. To date, neuroglobin levels have been positively correlated with a beneficial outcome in a plethora of neurotoxic insults, e.g., ischemic and traumatic brain injuries and Alzheimer's disease. The first part of this review goes further into these changes of neuroglobin expression upon different neuronal insults as well as the underlying regulation. In the second part, we shed light on the mechanisms by which neuroglobin contributes to neuroprotection, being (i) the scavenging and detoxification of reactive oxygen/nitrogen species, (ii) the augmentation of the threshold for apoptosis initiation, (iii) its contribution to an anti-inflammatory milieu, and (iv) tissue regeneration. We also consider different neuroglobin models to address as yet unanswered questions. Based on the recent findings and progress in the field, we invigorate the avenues of neuroglobin in neurological ailments to increase in the coming years.

Neuroglobin (Ngb) is an evolutionary conserved member of the globin family with a primary expression in neurons of which the exact functions remain elusive. A plethora of in vivo and in vitro model systems has been generated to this day to determine the functional biological roles of Ngb. Here, we provide a comprehensive overview and discussion of the different Ngb models, covering animal and cellular models of both overexpression and knockout strategies. Intriguingly, an in-depth literature search of available Ngb expression models revealed crucial discrepancies in the outcomes observed in different models. Not only does the level of Ngb expression—either physiologically, overexpressed, or downregulated—alter its functional properties, the experimental setup, being in vitro or in vivo, does impact the functional outcome as well and, hence, whether or not a physiological and/or therapeutic role is ascribed to Ngb. These differences could highlight either technical or biological adaptations and should be considered until elucidation of the Ngb biology.

The true function of neuroglobin (Ngb) and, particularly, human Ngb (NGB) has been under debate since its discovery 15 years ago. It has been expected to play a role in oxygen binding/ supply, but a variety of other functions have been put forward, including NO dioxygenase activity. However, in vitro studies that could unravel these potential roles have been hampered by the lack of an Ngb-specific reductase. In this work, we used electrochemical measurements to investigate the role of an intermittent internal disulfide bridge in determining NO oxidation kinetics at physiological NO concentrations. The use of a polarized electrode to efficiently interconvert the ferric (Fe 3؉ ) and ferrous (Fe 2؉ ) forms of an immobilized NGB showed that the disulfide bridge both defines the kinetics of NO dioxygenase activity and regulates appearance of the free ferrous deoxy-NGB, which is the redox active form of the protein in contrast to oxy-NGB. Our studies further identified a role for the distal histidine, interacting with the hexacoordinated iron atom of the heme, in oxidation kinetics. These findings may be relevant in vivo, for example, in blocking apoptosis by reduction of ferric cytochrome c, and gentle tuning of NO concentration in the tissues. Neuroglobin (Ngb)2 is the vertebrate globin that has been hypothesized to be involved in, e.g. O 2 binding/supply, the metabolism of reactive nitrogen and oxygen species, apoptosis through different pathways, intracellular signaling, and cell protection during hypoxia and ischemia (1-6). Besides the central and peripheral nervous system and retina, Ngb is also expressed in endocrine tissues, hematopoietic stem cells, the gastrointestinal tract, and cancer cells (7,8). Although the first publication on the subject was in 2000, the in vivo role of Ngb is still uncertain. Studies on Ngb knock-out mice and regional gene expression did not clarify it further (3, 9 -13), but most of the reports in the topic supported its neuroprotective function at least under conditions of neuroglobin overexpression (11,14,15). Some histological data additionally indicated that Ngb can be involved in regulation of the circadian rhythm (sleep-wake cycle) (12, 16) and protection of neurons from neurodegenerative disorders, such as Alzheimers disease (17)(18)(19). Obviously, further in vivo and in vitro studies of Ngb are necessary to clarify its molecular mechanisms of action.As other globins, e.g. myoglobin and hemoglobin, Ngb displays the three-over-three ␣-helical sandwich structure. However, Ngb structurally differs somewhat from myoglobin and hemoglobin, suggesting a different functional destination for Ngb compared with the classic globins (20). Both its weak O 2 binding affinity under physiological conditions (21) and its hexacoordinated structure of the iron atom of the heme leading to a possible intrinsic binding competition with external gaseous ligands such as O 2 , CO, and NO, support the hypothesis that Ngb is not constructed to transport or store O 2 (22). The unclear mechanism of actio...

Neuroglobin (NGB) is an oxygen-binding protein that is mainly expressed in nervous tissues where it is considered to be neuroprotective during ischemic brain injury. Interestingly, transgenic mice overexpressing NGB reveal cytoprotective effects on tissues lacking endogenous NGB, which might indicate a therapeutic role for NGB in a broad range of ischemic conditions. In the present study, we investigated the effect of NGB overexpression on survival as well as on the size and occurrence of myocardial infarctions (MI) in a mouse model of acute MI (AMI) and a model of advanced atherosclerosis (ApoE Fbn1 mice), in which coronary plaques and MI develop in mice being fed a Western-type diet. Overexpression of NGB significantly enhanced post-AMI survival and reduced MI size by 14% 1 week after AMI. Gene expression analysis of the infarction border showed reduction of tissue hypoxia and attenuation of hypoxia-induced inflammatory pathways, which might be responsible for these beneficial effects. In contrast, NGB overexpression did not affect survival or occurrence of MI in the atherosclerotic mice although the incidence of coronary plaques was significantly reduced. In conclusion, NGB proved to act cytoprotectively during MI in the acute setting while this effect was less pronounced in the atherosclerosis model.

In the quest to unravel its functional significance, neuroglobin (Ngb), a brain-specific neuroprotective protein, has recently been proposed as an actor in neurodevelopment. As neural stem cells (NSCs) are fundamental during brain development, the present study aimed at investigating the role of Ngb in the growth and proliferation of NSCs by comparing an Ngb-floxed (Ngb-)NSC line, equivalent to the wild-type cellular situation, with an in-house created Ngb knockout (Ngb-)NSC line. Ngb-NSCs were characterized by an increased growth and proliferation capacity in vitro, supported by RNA sequencing and western blot results reporting the downregulation of Cdkn1a and the upregulation of Cdk6, both enhancing the cell cycle. Based on additional gene ontology enrichment and pathway analyses, we hypothesize that the loss of Ngb affects multiple cellular signaling pathways with the most important being the Akt-Tp53 axis.