Abstract
The sex steroid hormone 17β-estradiol (E2) upregulates the levels of neuroglobin (NGB), a new neuroprotectant globin, to elicit its neuroprotective effect against H2O2-induced apoptosis. Several mechanisms could be proposed to justify the NGB involvement in E2 prevention of stress-induced apoptotic cell death. Here, we evaluate the ability of E2 to modulate the intracellular NGB localization and the NGB interaction with mitochondrial cytochrome c following the H2O2-induced toxicity. Present results demonstrate that NGB is expressed in the nuclei, mitochondria, and cytosol of human neuroblastoma SK-N-BE cells. E2, but not H2O2 treatment of SK-N-BE cells, reallocates NGB mainly at the mitochondria and contemporarily reduces the number of apoptotic nuclei and the levels of cleaved caspase-3. Remarkably, the E2 treatment strongly increases NGB–cytochrome c association into mitochondria and reduces the levels of cytochrome c into the cytosol of SK-N-BE cells. Although both estrogen receptors (ERα and ERβ) are expressed in the nucleus, mitochondria, and cytosol of SK-N-BE cells, this E2 effect specifically requires the mitochondrial ERβ activity. As a whole, these data demonstrate that the interception of the intrinsic apoptotic pathway into mitochondria (i.e., the prevention of cytochrome c release) is one of the pivotal mechanisms underlying E2-dependent NGB neuroprotection against H2O2 toxicity.
Highlights
During the past decade, several experimental works suggested that NGB overexpression is protective against hypoxic/ischemic injury in the brain.[1,9] In human neuroblastoma cell lines, SH-SY5Y, NGB overexpression enhanced cell survival under the condition of anoxia or glucose deprivation.[6,10] in transgenic rodents, increased levels of NGB significantly protect the brain tissues from hypoxic insult, whereas decreased NGB levels lead to the exacerbation of the tissue death.[11,12,13] As a whole these data sustain a neuroprotective role of high NGB levels in neural tissues and neural-derived cell lines
The first direct experimental evidence that NGB can interrupt the process of apoptosis at the level of cytochrome c reduction derived from a model system consisting of a cell lysate, free of mitochondria, where exogenous cytochrome c was added in the absence and in presence of NGB
In this system it was shown by computer modeling that NGB in the presence of ferric cytochrome c drastically lowers the enzymatic activity of caspase-9.18 if this process occurs the in cytosol or in the mitochondria, where NGB could prevent the onset of apoptosis directly sequestering cytochrome c, could not be ruled out
Summary
Several experimental works suggested that NGB overexpression is protective against hypoxic/ischemic injury in the brain.[1,9] In human neuroblastoma cell lines, SH-SY5Y, NGB overexpression enhanced cell survival under the condition of anoxia or glucose deprivation.[6,10] in transgenic rodents, increased levels of NGB significantly protect the brain tissues from hypoxic insult, whereas decreased NGB levels lead to the exacerbation of the tissue death.[11,12,13] As a whole these data sustain a neuroprotective role of high NGB levels in neural tissues and neural-derived cell lines. Neuroglobin–cytochrome c interaction into mitochondria E De Marinis et al reactions of NGB, it has been hypothesized that NGB could react with the oxidized cytochrome c released from the mitochondria.[15,17,19] The first direct experimental evidence that NGB can interrupt the process of apoptosis at the level of cytochrome c reduction derived from a model system consisting of a cell lysate, free of mitochondria, where exogenous cytochrome c was added in the absence and in presence of NGB In this system it was shown by computer modeling that NGB in the presence of ferric cytochrome c drastically lowers the enzymatic activity of caspase-9.18 if this process occurs the in cytosol or in the mitochondria, where NGB could prevent the onset of apoptosis directly sequestering cytochrome c, could not be ruled out. The aim of this work is to evaluate this hypothesis by assessing the interaction between NGB and cytochrome c in the presence of H2O2 as pro-apoptotic factor and E2 as a survival agent in SK-N-BE neuroblastoma cell line
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
