Neuroglobin Overexpression in Cultured Human Neuronal Cells Protects Against Hydrogen Peroxide InsultviaActivating Phosphoinositide-3 Kinase and Opening the Mitochondrial K_ATPChannel

Abstract

Cultured neurons tolerate low H(2)O(2) concentrations (< or =50 microM) through the activity of constitutive antioxidant response elements (ARE). At H(2)O(2) levels (> or =100 microM), neurons increase expression of the gene encoding for inducible hemoxygenase-1 while superoxide dismutase-2 and catalase remain unchanged. Despite this adaptive response, the endogenous antioxidant systems are overwhelmed, leading to decreased viability. Elevating the neuronal cell content of human neuroglobin (Ngb) prior to insult with 100 or 200 microM H(2)O(2) enhanced cell viability and this resulted in a significant decrease in oxidative stress and an increase in the intracellular ATP concentration, whereas in parental cells exposed to the same H(2)O(2)-insult, oxidative stress and ATP increased and decreased, respectively. The mechanism for this increase in ATP involves sustained activation of the mito-K(ATP) channel and an increase in phosphoinositide-3 kinase (PI3K)-mediated phosphorylation of Akt. Pharmacological inhibitors directed toward PI3K (wortmannin and LY294002), or the mito-K(ATP) channel (glybenclamide) inhibited the H(2)O(2)-mediated increase in ATP in cells overexpressing human Ngb and consequently cell viability decreased. Neuroglobin's ability to bolster the intracellular pool of ATP in response to added H(2)O(2) is central to the preservation of cytoskeletal integrity and cell viability.

Combined Antiapoptotic and Antioxidant Approach to Acute Neuroprotection for Stroke in Hypertensive Rats

“…However, Ngb directly activates the PI3K/AKT/mTOR (phosphatidylinositide 3-kinase/ AKT/ mammalian target of rapamycin) pathway of cell survival. 33 Furthermore, JNK may be involved in prooxidant pathways because the N-terminal Von Hippel-Lindau recognition site of hypoxia inducible factor-1a contains a JNK-binding domain. 34 Notably, translation to an in vivo stroke model confirmed that combined Ngb upregulation and JNK inhibition was better than single treatment using infarct size and neurologic deficit as outcome measures (Figures 4-6).…”

Neuroglobin, a Novel Intracellular Hexa-Coordinated Globin, Functions as a Tumor Suppressor in Hepatocellular Carcinoma via Raf/MAPK/Erk

“…In the present study, we also demonstrated that Ngb suppressed H 2 O 2 -induced Erk activation in HepG2 cells. These evidences support an important role of Ngb in oxidative stress, probably as an oxidative stress sensor or ROS scavenger (Herold et al, 2004;Brunori et al, 2005;Burmester and Hankeln, 2009;Antao et al, 2010). Oxidative stress is a critical mechanism in HCC genesis or development.…”

“…Neuroglobin (Ngb), a newly discovered intracellular respiratory globin with a hexa-coordinated heme (Burmester et al, 2000;Trent et al, 2001), plays an important role in protecting brain cells from ischemic (Sun et al, 2001;Chen et al, 2005b) or oxidative stress (Ye et al, 2009;Antao et al, 2010). Because Ngb shows a higher binding affinity to oxygen and nitric oxide (NO), it is hypothesized that the Ngb may function as the oxygen carrier, NO/ROS scavenger, or oxygen/ ROS sensor (Trent et al, 2001;Herold et al, 2004;Brunori et al, 2005;Burmester and Hankeln, 2009).…”

A role for human neuroglobin in apoptosis

“…Experimentally, in cultured cells, over expression of neuroglobin protects against amyloid beta, hydrogen peroxide, paraquat, and HA14-1 (a Bcl-2 inhibitor) induced cell death, as well as from oxygen and glucose deprivation (16)(17)(18)(19)(20)(21). In vitro, knockdown of endogenous neuroglobin renders cortical neurons more susceptible to hypoxia (16), and decreases viability of neuroblastoma cells under oxidative stress (22).…”

“…Following the reduction of cytochrome c, the ferric form of neuroglobin also produced will bind to the G a subunit of the GPCR (6) inhibiting IP3 production (7) and so further suppressing potential calcium rise in the cytosol (45). The other product of the reaction of ferric neuroglobin with the GPCR namely the G bc subunit will then activate PI3K and Akt (21,66) leading to phosphorylation of 14-3-3 and hence suppression of the calcium-stimulated action of the Bcl-2 family protein Bad (8). Neuroglobin can also inhibit RacGTPase and Pak1 (9) preventing the rearrangement of the cytoskeleton necessary for the execution of apoptosis (67).…”