Endoplasmic reticulum pathology and stress response in neurons precede programmed necrosis after neonatal hypoxia-ischemia. Issue 48 (February 2016)

• Record Type: Journal Article
• Authors: Chavez-Valdez, Raul; Flock, Debbie L.; Martin, Lee J.; Northington, Frances J.
• Is Part Of: International journal of developmental neuroscience. Issue 48(2016:Feb.)
• Page Start: 58
• Page End: 70
• Publication Date: 2016-02
• Subjects: ATF activation transcription factor -- CHOP CCAAT/-enhancer-binding protein homologous protein -- EIF eukaryotic initiation factor -- EM electron microscopy -- ER endoplasmic reticulum -- GADD growth arrest and DNA damage-inducible protein -- GRP78 78 kd glucose regulated protein (also known as BiP and HSP5a) -- HI hypoxia-ischemia -- IQR interquartile range -- IRE inositol-requiring enzyme -- Nec-1 necrostatin-1 -- p postnatal day -- PERK protein kinase RNA-like endoplasmic reticulum kinase -- UPR unfolded protein response -- XBP X-box protein; Endoplasmic reticulum stress -- Programmed necrosis -- Unfolded protein response -- Neonatal hypoxia-ischemia -- Cell death -- Cytoplasmic shedding -- Macrozeiosis; Developmental neurobiology -- Periodicals; Neurology -- Periodicals; Neurologie du développement -- Périodiques; Developmental neurobiology; Periodicals; 612.8
• DOI: 10.1016/j.ijdevneu.2015.11.007
• Languages: English
• ISSNs: 0736-5748

Abstract

Highlights: Biochemical markers of ER stress precede disruption in ER morphology after HI. HI induces progressive ER dilation to maintain homeostasis as mitochondria swell. When ER fails, nuclear pathology proceeds toward a form of programmed necrosis. In areas of severe HI injury, calreticulin expression within the ER dissipates. Necrostatin blocks biochemical ER stress and microstructural ER disruption after HI. Abstract: The endoplasmic reticulum (ER) is tasked, among many other functions, with preventing excitotoxicity from killing neurons following neonatal hypoxia-ischemia (HI). With the search for delayed therapies to treat neonatal HI, the study of delayed ER responses becomes relevant. We hypothesized that ER stress is a prominent feature of delayed neuronal death via programmed necrosis after neonatal HI. Since necrostatin-1 (Nec-1), an inhibitor of programmed necrosis, provides delayed neuroprotection against neonatal HI in male mice, Nec-1 is an ideal tool to study delayed ER responses. C57B6 male mice were exposed to right carotid ligation followed by exposure to FiO2 = 0.08 for 45 min at p7. Mice were treated with vehicle or Nec-1 (0.1 μl of 8 μmol) intracerebroventricularly with age-matched littermates as controls. Biochemistry assays at 3 and 24 h and electron microscopy (EM) and immunohistochemistry at 96 h after HI were performed. EM showed ER dilation and mitochondrial swelling as apparent early changes in neurons. With advanced neurodegeneration, large cytoplasmic fragments containing dilated ER "shed" into the surrounding neuropil and calreticulin immunoreactivity was lost concurrent with nuclear features suggestive of programmed necrosis. Nec-1 attenuated biochemical markers of ER stress after neonatal HI, including PERK and eIF2α phosphorylation, and unconventional XBP-1 splicing, consistent with the mitigation of later ER pathology. ER pathology may be an indicator of severity of neuronal injury and potential for recovery characterized by cytoplasmic shedding, distinct from apoptotic blebbing, that we term neuronal macrozeiosis. Therapies to attenuate ER stress applied at delayed stages may rescue stressed neurons after neonatal HI.