Apoptotic Cells In Hippocampus Research Articles

Blockage of calcium-sensing receptor improves chronic intermittent hypoxia-induced cognitive impairment by PERK-ATF4-CHOP pathway

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is involved in cognitive impairment of children. Chronic intermittent hypoxia (CIH) is considered as the critical pathophysiological mechanism of OSAHS. Calcium sensitive receptor (CaSR) mediated apoptosis in many neurological disease models by endoplasmic reticulum stress (ERS)-related pathway. However, little is known about the role of CaSR in OSAHS-induced cognitive dysfunction. In this study, we explored the effect of CaSR on CIH-induced cognitive impairment and possible mechanisms on regulation of PERK-ATF4-CHOP pathway in vivo and in vitro. CIH exposed for 9 h in PC12 cells and resulted in the cell apoptosis, simulating OSAHS-induced neuronal injury. CIH upregulated the level of CaSR, p-PERK, ATF4 and CHOP, contributing to the cell apoptosis. Treated with CaSR inhibitor (NPS-2143) or p-PERK inhibitor (GSK2656157) before CIH exposure, CIH-induced PC12 cell apoptosis was alleviated via inhibition of CaSR by downregulating p-PERK, ATF4 and CHOP. In addition, we established CIH mice model. With CIH exposure for 4 weeks in mice, more spatial memory errors were observed during 8-arm radial maze test. CIH significantly increased apoptotic cells in hippocampus via upregulating cleaved Caspase-3 and downregulating ratio of Bcl-2 to Bax. Besides, treatment of CaSR inhibitor alleviated the hippocampal neuronal apoptosis following CIH with downregulated p-PERK, ATF4 and CHOP, suggesting that CaSR contributed to CIH-induced neuronal apoptosis in hippocampus via ERS pathway. Sum up, our results demonstrated that CaSR accelerated hippocampal apoptosis via PERK-ATF4-CHOP pathway, holding a critical function on CIH-mediated cognitive impairment. Conversely, inhibition of CaSR suppressed PERK-ATF4-CHOP pathway and alleviated cognitive impairment.

Protective effects of m-(tert-butyl) trifluoroacetophenone, a transition state analogue of acetylcholine, against paraoxon toxicity and memory impairments

m-(Tert-butyl) trifluoroacetophenone (TFK), a slow-binding inhibitor of acetylcholinesterase (AChE), a transition state analog of acetylcholine, was investigated as a potential neuroprotectant of central and peripheral AChE against organophosphate paraoxon (POX) toxicity. Acute toxicity and pharmacological effects of TFK were investigated on mice and rats. Intraperitoneal administered TFK has low acute toxicity in mice (LD50 ≈ 19 mg/kg). Effects on motor function as investigated by rotarod and open field tests showed that TFK up to 5 mg/kg did not alter motor coordination and stereotypical exploration behavior of mice. Passive avoidance test showed that 1 or 5 mg/kg TFK restored memory impairment in scopolamine-induced Alzheimer's disease-like dementia in rats. Pretreatment of mice with 5 mg/kg TFK, 2–3 h before challenge by 2xLD50 POX provided a modest and short protection against POX toxicity. Futhermore, analysis of POX-induced neuronal degeneration by using fluoro-jade B staining showed that TFK pretreatment, at the dose 5 mg/kg before POX challenge, significantly reduced the density of apoptotic cells in hippocampus and entorhinal cortex of mice. Thus, TFK is capable of reducing POX-induced neurotoxicity.

Effect of Early Normobaric Hyperoxia on Blast-Induced Traumatic Brain Injury in Rats.

Blast-induced traumatic brain injury (bTBI) is a leading cause of disability and mortality in soldiers during the conflicts in Iraq and Afghanistan. Although substantial clinical and animal studies have investigated the pathophysiology and treatments of bTBI, few effective therapies have been found, especially for the early rescue in the battlefield. The aim of this study is to evaluate neuroprotective effects of early normobaric hyperoxia (NBO) on bTBI. We established a rat model of bTBI caused by explosion in the cabin. It exhibited typical changes of mild bTBI, like impaired neurological function, brain edema, minor intracranial hemorrhage and neuron necrosis. The rats were divided into 4 groups (n = 12): Sham, Vehicle, hyperbaric oxygen(HBO)and NBO. Neurological function of the rats was assessed by the Neurological Severity Scores (NSS) at 24h and 72h after explosion. Serum interleukin-6 (IL-6), neuron specific enolase (NSE)andtauprotein were measured at 24h and 72h after explosion. Brain water content was measured and Aquaporin-4 (AQP4) immunostaining was performed. Neuronal apoptosis was analyzed by TUNEL staining. NBO demonstrated curative effects on protecting the neurological function. Serum levels of NSEandtauprotein were reduced at 24hand72h after explosion. But the levels of IL-6 were not reduced significantly at both time points. Cerebral edema was alleviated. Simultaneously, AQP4 immunostaining of the hippocampus showed remarkably decreased expression after treatment. The number of apoptotic cells in hippocampus was also decreased. Compared with HBO, NBO is simple and convenient, and can be administered in remote areas. It may be a promising therapy for early rescue of bTBI in the battlefield.

The Protective Effect of Remote Renal Preconditioning Against Hippocampal Ischemia Reperfusion Injury: Role of KATP Channels.

Remote ischemic preconditioning (RIPC), which consists of several brief ischemia/reperfusion applied at the remote site of lethal ischemia reperfusion, can, through activating different mechanisms, increase the ability of the body's endogenous protection against prolonged ischemia/reperfusion. Recent studies have shown that RIPC has neuroprotective effects, but its mechanisms are not well elucidated. The present study aimed to determine whether activation of KATP channels in remote renal preconditioning decreases hippocampus damage induced by global cerebral ischemia. RIPC was induced by ischemia of the left renal artery (IPC); 24 h later, global cerebral ischemia reperfusion (IR) was induced by common carotid arteries occlusion. 5hydroxydecanoate (5HD) and glibenclamide (Gli) were injected before of IPC. The levels of malondialdehyde (MDA) and catalase (CAT) activity were assessed in hippocampus. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) was assessed to detect apoptotic cells in hippocampus. RIPC inhibited apoptosis by decreasing positive TUNEL cells (P < 0.05). KATP channels blocking with 5HD and Gli markedly increased apoptosis in hippocampal cells in RIPC group (P < 0.001). RIPC decreased MDA level and increased CAT activity in ischemic hippocampus (P < 0.01). Also, 5HD and Gli inhibited the effect of RIPC on MDA level and CAT activity (P < 0.05). The present study shows that RIPC can effectively attenuate programmed cell death, increase activity of CAT, and reduce MDA levels. Blocking of KATP channels inhibited the protective effects of RIPC.

Neuroprotective effect of nicorandil through inhibition of apoptosis by the PI3K/Akt1 pathway in a mouse model of deep hypothermic low flow

ObjectiveNicorandil exerts a protective effect on ischemia–reperfusion (I/R) injury in the brain and kidney through anti-apoptotic mechanisms. However, the mechanism by which nicorandil protects against I/R injury induced by deep hypothermic low flow (DHLF) remains unclear. MethodsWe used a cerebral I/R model induced by DHLF to determine the neuroprotective effects and possible mechanisms of nicorandil. ResultsHematoxylin–eosin (HE) staining and in situ terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL) assay were used to detect changes in cell morphology and the number of apoptotic cells in hippocampus, respectively. The apoptotic regulators including Bcl-2, Bax, Akt, and p-Akt (the active, phosphorylated form of Akt) were examined by Western blot (WB). Histopathological findings showed that nicorandil significantly alleviated morphological damage in hippocampal and reduced the number of TUNEL-positive nuclei induced by DHLF. Nicorandil also increased the expression of Bcl-2 and decreased the expression of Bax, while increasing p-Akt level. Consistent with these results, nicorandil-mediated neuroprotection was reduced in the Akt1+/− mutant mice and inhibited by LY294002, a PI3K inhibitor. ConclusionsThese findings showed that nicorandil provides a neuroprotective role in DHLF-induced I/R injury by inhibiting apoptosis via activation of the PI3K/Akt1 signaling pathway.

Isoflurane Damages the Developing Brain of Mice and Induces Subsequent Learning and Memory Deficits through FASL-FAS Signaling.

Background. Isoflurane disrupts brain development of neonatal mice, but its mechanism is unclear. We explored whether isoflurane damaged developing hippocampi through FASL-FAS signaling pathway, which is a well-known pathway of apoptosis. Method. Wild type and FAS- or FASL-gene-knockout mice aged 7 days were exposed to either isoflurane or pure oxygen. We used western blotting to study expressions of caspase-3, FAS (CD95), and FAS ligand (FASL or CD95L) proteins, TUNEL staining to count apoptotic cells in hippocampus, and Morris water maze (MWM) to evaluate learning and memory. Result. Isoflurane increased expression of FAS and FASL proteins in wild type mice. Compared to isoflurane-treated FAS- and FASL-knockout mice, isoflurane-treated wild type mice had higher expression of caspase-3 and more TUNEL-positive hippocampal cells. Expression of caspase-3 in wild isoflurane group, wild control group, FAS/FASL-gene-knockout control group, and FAS/FASL-gene-knockout isoflurane group showed FAS or FASL gene knockout might attenuate increase of caspase-3 caused by isoflurane. MWM showed isoflurane treatment of wild type mice significantly prolonged escape latency and reduced platform crossing times compared with gene-knockout isoflurane-treated groups. Conclusion. Isoflurane induces apoptosis in developing hippocampi of wild type mice but not in FAS- and FASL-knockout mice and damages brain development through FASL-FAS signaling.

Effects of escitalopram on the expression of glial cell line-derived neurotrophic factor and apoptosis related factors in hippocampus of depression model rats

Objective To explore the effects and mechanisms of escitalopram on the expression of glial cell line-derived neurotrophic factor(GDNF) in hippocampus of depression model rats. Methods 40 male SD rats were randomly divided into four groups: control group(group A), control+ escitalopram group (group B), depressive group(group C), and depressive+ escitalopram group(group D). Chronic mild unpredicted stress(CUMS)with solitary condition was taken to establish rat depression model. And the group B and D were treated with intragastric admistration of escitalopram(10 mg·kg-1·d-1), the group A and C with sodium chloride.The open-field test and sucrose consumption were used to evaluate the depression behaviors of rats. The apoptotic hippocampal cells were detected by TUNEL.And the expression of GDNF, Bax, Bcl-2 and Caspase3 mRNA were detected by real-time RT-PCR. Results ① Compared with group A(12.0±1.83), the number of apoptotic cells in hippocampus was significantly increased in group C(19.3±1.77)(P 0.05). Compared with group C, the group D(12.7±1.77) had a significant reduction in the number of apoptotic cells (P<0.01). ②Compared with group A, GDNF and Bcl-2 mRNA expression was decreased (P<0.01), but Bax and Caspase3 mRNA expression was both increased significantly in group C(P<0.01); while in group D, GDNF and Bcl-2 mRNA expression was higher (P<0.01), but Bax and Caspase3 mRNA expression was lower than that in group C(P<0.01). Conclusion Escitalopram can improve depressive behaviors and reduce hippocampal apoptosis, which maybe associate with increasing GDNF protein and mRNA expression, and promoting the regeneration of neurons, up-regulating of mRNA Bcl-2 expression, and down-regulating of mRNA Bax and Caspase3 expression.Finally it may prevent the neuronal apoptosis in hippocampal and play the role of cerebral protection. Key words: Escitalopram; Depression; Hippocampus; Glial cell line-derived neurotrophic factor; Apoptosis

Systemic inflammation induces apoptosis with variable vulnerability of different brain regions

During severe sepsis several immunological defence mechanisms initiate a cascade of inflammatory events leading to multi-organ failure including septic encephalopathy and ultimately death. To assess the reaction and participation of parenchymal brain cells during endotoxaemia, the present study evaluates micro- and astroglial activation, expression of the inducible nitric oxide synthase (iNOS) pro- and antiapoptotic protein levels Bax and Bcl-2, and apoptosis. Male Wistar rats received 10 mg/kg lipopolysaccharide (LPS) or vehicle intraperitoneally and were sacrificed for brain collection at 4, 8 or 24 h after induction of experimental sepsis. One group of animals received 10 mg/kg of the NOS inhibitor N-monomethyl- l-arginine ( l-NMMA) intraperitoneally 1 day before and during the experiment. Immunohistochemical evaluation revealed a sepsis-induced, time-dependent increase in the immunoreactivity of iNOS, glial fibrillary acidic protein (GFAP) and activated microglia (ED-1), paralleled by a time-dependent increase of apoptotic brain cells marked by terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL), an increase of Bax-positive cells and a decrease of Bcl-2-positive cells. Evaluation of different brain regions revealed that the hippocampus is the most vulnerable region during experimental sepsis. iNOS-inhibition with l-NMMA significantly reduced the number of apoptotic cells in hippocampus, midbrain and cerebellum. In addition, it reduced the increase of the proapoptotic protein Bax in all examined brain regions and reduced the decrease of Bcl-2-positive cells in the hippocampus. We therefore conclude, that peripheral inflammation leads to a profound glial activation, the generation of nitric oxide and changes of Bax and Bcl-2 protein regulation critical for apoptosis.

Dantrolene protects neurons against kainic acid induced apoptosis in vitro and in vivo.

Apoptotic cell death induced by kainic acid (KA) in cultures of rat cerebellar granule cells (CGC) and in different brain regions of Wistar rat pups on postnatal day 21 (P21) was studied. In vitro, KA (100-500 microM) induced a concentration-dependent loss of cell viability in MTT assay and cell death had apoptotic morphology as studied by chromatin staining with propidium iodide (PI). In vivo, twenty-four hours after induction of status epilepticus (SE) by an intraperitoneal KA injection (5 mg/kg) we quantified apoptotic cells in hippocampus (CA1 and CA3), parietal cortex and cerebellum using PI staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) technique. We report that dantrolene, a specific ryanodine receptor antagonist, was able to significantly reduce the apoptotic cell death in CGC cultures and in hyppocampal CA1 and parietal cortex regions. Our finding can be valuable for neuroprotective therapy strategies in patients with repeated generalized seizures or status epilepticus.

Appearance and alteration of TUNEL positive cells through epileptogenesis in amygdaloid kindled rat

To evaluate the role of neural cell death during and after kindling epileptogenesis, apoptotic cells were analyzed in amygdaloid kindled rat using TUNEL staining as a marker of programmed cell death. TUNEL positive cells (TPC) were stained and counted as apoptotic cells in hippocampus, white matter, diencephalon, and cortex at three stages; C0 (before kindling), C3 (during kindling) and C5 (fully kindled). The animals were studied 2 h after the last stimulation. In all regions except cortex, apoptotic cells in stage C3 were significantly increased as compared to those in stage C0. Especially, in white matter significantly more apoptotic cells in stage C3 were detected than in stage C5. The present data showed that in the course of getting the epileptogenesis, apoptosis had already occurred and this type of cell death may play a significant role in reaching stage C5 through kindling.