Decreased vulnerability of hippocampal neurons after neonatal hypoxia–ischemia in bis‐deficient mice

Abstract

The Bcl-2-interacting death suppressor (Bis) protein is involved in antiapoptosis and antistress pathways. However, its roles after neonatal hypoxia-ischemia remain obscure. Therefore, we investigated the effects of Bis deletion on hippocampal cell death following neonatal hypoxia-ischemia. We transected the right common carotid artery of bis(+/+) and bis(-/-) mice at postnatal Day 7 and subjected them to hypoxia for 35 min. Cresyl violet staining showed that hypoxia-ischemia induced progressive cell death in the hippocampi of bis(+/+) mice. Moreover, Bis was expressed in astrocytes, not microglia, in sham-manipulated hippocampi of bis(+/+) mice, and was markedly enhanced after hypoxia-ischemia. Immunoblotting showed that Bis expression significantly increased 3 and 7 days following hypoxia-ischemia. Unexpectedly, 7 days after hypoxia-ischemia, the number of hippocampal NeuN-positive cells was higher in the bis(-/-) mice than in the bis(+/+) mice. We subsequently performed transcriptomic analysis and quantitative real time polymerase chain reaction to search for the underlying genes responsible for resistance to hypoxia-ischemia in the bis(-/-) hippocampus. These studies showed that 6 h after hypoxia-ischemia, galectin 3 and filamin C levels increased to a lesser extent in the bis(-/-) hippocampi compared with the bis(+/+) hippocampi. Finally, our in vitro hypoxia-ischemia model, using A172 glioma cells and primary astrocytes, showed that downregulation of Bis blocked the enhanced expression of galectin 3 after oxygen-glucose deprivation. This study demonstrated that Bis was upregulated in the astrocytes after hypoxia-ischemia. In addition, we showed that hippocampal neurons are less vulnerable to hypoxia-ischemia in mice lacking Bis, possibly because of the modulation of galectin 3 induction.

Imaging neurodegeneration in the mouse hippocampus after neonatal hypoxia–ischemia using oscillating gradient diffusion MRI

“…We found early changes in D f ADC contrasts in the Py cell layer of the hippocampal CA1 region (at 24 h post-HI), with relatively delayed onset of changes observed in the GrDG layer. HI has been previously shown to lead to selective cell death of CA1 pyramidal neurons and granule cells in the dentate gyrus in the neonatal mouse brain, at 24-72 h following injury (9,41,42). In our study, compared with the Py region, significant differences in D f ADC measurements between the ipsilateral and contralateral GrDG regions were first detected at day 4 after HI-injury.…”

TRPM7 inhibitor carvacrol protects brain from neonatal hypoxic-ischemic injury

“…The neonatal hypoxic-ischemic brain injury model used in this study was adapted from the method described by Rice et al [ 25 ], with minor modifications. It is a widely used neonatal stroke model, and has been employed to explore drug intervention targets for neonatal hypoxic-ischemic brain injury [ 26 , 27 ]. We have established this HI model to study the neuroprotective effects of a volume-regulated anion channel blocker [ 28 ] and hypoxic preconditioning [ 29 ].…”

Bis is Induced by Oxidative StressviaActivation of HSF1

“…We, and other groups, have reported that Bis expression is increased by oxidative stress or pro-oxidants, both in vivo and in vitro [ 20 , 27 , 28 ]. The physiological significance of Bis induction upon PDTC or HNE was verified by the knockdown of HSF1 [ 20 , 21 ], showing that HSF1-mediated Bis expression confers cellular protection from pro-apoptotic and inflammatory stress.…”

“…Thus, a HSF1 deficiency or inactivation may result in a significant impairment in the antioxidant system, through the modulation of Bis expression and subsequent SOD. However, the survival of neuronal cells of the hippocampus following neonatal hypoxia-reperfusion was higher in bis-deleted (bis -/- ) mice than in the wild type (bis +/+ ) mice, possibly because of the modulation of galectin 3 levels [ 28 ]. Taken together, these results suggest that the modulation of Bis expression resulted in diverse effects related to cell survival depending on the cellular contexts.…”

“…In a previous study, we reported that Bis expression was increased by ischemia-reperfusion in reactive astrocytes in vivo [ 27 , 28 ]. An in vitro study using C6 glioma cells demonstrated that oxygen-glucose deprivation significantly enhanced Bis protein expression, and Bis knockdown resulted in an increase in ROS levels and cell death upon oxygen-glucose deprivation (OGD), concomitant with an impairment in the induction of superoxide dismutase (SOD) activity [ 29 ].…”