Comparison of the Immunoreactivity of Trx2/Prx3 Redox System in the Hippocampal CA1 Region Between the Young and Adult Gerbil Induced by Transient Cerebral Ischemia

Enhanced autophagy interacting proteins negatively correlated with the activation of apoptosis-related caspase family proteins after focal ischemic stroke of young rats

Background

Neuronal injury induced in young rats by cerebral ischemia reperfusion (CIR) is known to differ substantially from that in adult rats. In the present study, we investigated the specific differences in neuronal injury induced by focal CIR between young and adult rats.

Results

2, 3, 5-triphenyl tetrazolium chloride (TTC) staining revealed a gradual increase in the infarct volume of both young and adult rats in accordance with I/R times and was significantly lower in young rats than in adult rats under the same conditions. The number of cells in the cortex showing immunoreactivity for neuronal nuclei (NeuN) gradually decreased in both young and adult rats in accordance with I/R times; these numbers were significantly higher in young rats than in adult rats under the same conditions. Similarly, as the duration of I/R increased, the degree of glial activation in the cortex penumbra region became more severe in both young and adult groups; however, glial activation was significantly lower in the cortex penumbra region of young rats when compared with that in adult rats. In addition, the expression of Beclin-1 was significantly higher in the infarct penumbra of young rats than adult rats and was more frequently co-expressed with neurons. The levels of autophagy-related proteins increased significantly in the penumbra region after I/R in both young and adult groups, this increase was more pronounced in young rats than in adult rats. Following CIR, analysis revealed significantly lower levels of pro-apoptosis-related factors and significantly higher levels of anti-apoptosis-related proteins in the young rats than in adult rats.

Conclusions

Collectively, the present results suggest that the the reduced levels of neuronal death after CIR in young rats were closely related to enhanced levels of autophagy and reduced levels of pro-apoptosis in neurons.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-022-00740-w.

Targeting the Erk1/2 and autophagy signaling easily improved the neurobalst differentiation and cognitive function after young transient forebrain ischemia compared to old gerbils

The hippocampal neurogenesis occurs constitutively throughout adulthood in mammalian species, but declines with age. In this study, we overtly found that the neuroblast proliferation and differentiation in the subgranular zone and the maturation into fully functional and integrated neurons in the granule-cell layer in young gerbils following cerebral ischemia/reperfusion was much more than those in old gerbils. The neurological function and cognitive and memory-function rehabilitation in the young gerbils improved faster than those in the old one. These results demonstrated that, during long term after cerebral ischemia/reperfusion, the ability of neurogenesis and recovery of nerve function in young animals were significantly higher than that in the old animals. We found that, after 14- and 28-day cerebral ischemia/reperfusion, the phosphorylation of MEK1/2, ERK1/2, p90RSK, and MSK1/2 protein levels in the hippocampus of young gerbils was significantly much higher than that of old gerbils. The levels of autophagy-related proteins, including Beclin-1, Atg3, Atg5, and LC3 in the hippocampus were effectively maintained and elevated at 28 days after cerebral ischemia/reperfusion in the young gerbils compared with those in the old gerbils. These results indicated that an increase or maintenance of the phosphorylation of ERK1/2 signal pathway and autophagy-related proteins was closely associated with the neuroblast proliferation and differentiation and the process of maturation into neurons. Further, we proved that neuroblast proliferation and differentiation in the dentate gyrus and cognitive function were significantly reversed in young cerebral ischemic gerbils by administering the ERK inhibitor (U0126) and autophagy inhibitor (3MA). In brief, following experimental young ischemic stroke, the long-term promotion of the neurogenesis in the young gerbil’s hippocampal dentate gyrus by upregulating the phosphorylation of ERK signaling pathway and maintaining autophagy-related protein levels, it overtly improved the neurological function and cognitive and memory function.

Less hippocampal neuronal death in young gerbils following transient global cerebral ischemia is associated with long‑term maintenance of insulin‑like growth factor 1 and its receptors in the hippocampal CA1 region

Insulin-like growth factor 1 (IGF-1) is a well-known growth factor with well-defined neuroprotective effects against cerebral ischemia. However, the age‑dependent differences in the expression of IGF‑1 and its receptor (IGF‑1R) in the brain following transient cerebral ischemia (TCI) have not been elucidated. In the present study, the differences in IGF‑1 and IGF‑1R in the gerbil hippocampal CA1 region of young and adult gerbils 5 min following TCI were determined. Seven days following TCI, the neuronal death in the hippocampal CA1 region of young gerbils was significantly less than that observed in adult gerbils. In addition, the immunoreactivity, and levels of IGF‑1 and IGF‑1R in the CA1 region of the normal young were higher than those in the normal adult. Four days following TCI, the immunoreactivity, and protein levels of IGF‑1 and IGF‑1R were markedly decreased in the adult group. By contrast, in the young group, the immunoreactivity and expression levels were much greater than those in the adult group. However, 7 days following TCI, all immunoreactivity and expression levels were markedly decreased when compared with those in the normal adult and young groups. In addition, the immunoreactivity and expression levels in the young groups were significantly higher than those of the adult groups. In conclusion, the present study demonstrated that the higher and sustained expression of IGF‑1 and IGF‑1R in the young gerbil hippocampal CA1 region following TCI may be associated with the reduced neuronal death compared to that in the adults.

Differences in Reperfusion-Induced Mitochondrial Oxidative Stress and Cell Death Between Hippocampal CA1 and CA3 Subfields Are Due to the Mitochondrial Thioredoxin System

AIMS

The susceptibility of CA1 over CA3 to damage from cerebral ischemia may be related to the differences in reactive oxygen species (ROS) production/removal between the two hippocampal subfields. We aimed to measure CA1/CA3 differences in net ROS production in real time in the first 30 min of reperfusion in pyramidal cells. We aimed to determine the underlying cause of the differential vulnerability of CA1 and CA3.

RESULTS

Real-time determinations of mitochondrial H₂O₂ and, independently, glutathione (GSH) redox status from roGFP-based probes in individual pyramidal cells in organotypic hippocampal cultures during oxygen-glucose deprivation (OGD)-reperfusion (RP) demonstrate a significantly more oxidizing environment during RP in CA1 than CA3 mitochondria. Protein levels (immunohistochemistry and Western blots), roGFP2-based probe measurements during controlled mitochondrial production of ROS, and thioredoxin reductase (TrxR) inhibition by auranofin are consistent with a more effective mitochondrial thioredoxin (Trx) system in CA3. Inhibition of TrxR eliminates the differences in redox status and cell death between the regions. Overexpression of cytosolic Trx1 does not influence mitochondrial H₂O₂ production.

INNOVATION

Real-time changes of mitochondrial H₂O₂ and GSH in tissue cultures during early RP, and also during controlled production of superoxide and peroxide, reveal significant differences between CA1 and CA3. The mitochondrial Trx system is responsible for the observed differences during RP as well as for delayed cell death 18 h afterward.

CONCLUSION

Greater mitochondrial Trx efficacy in CA3 pyramidal cells results in less vulnerability to ischemia/reperfusion because of the less oxidizing environment in CA3 mitochondria during RP. Antioxid. Redox Signal. 27, 534-549.

Antioxidant peroxiredoxin 3 expression is regulated by 17beta-estradiol in rat white adipose tissue

Peroxiredoxin 3 (PRX3) plays a role as a regulator of the adipocyte mitochondrial function due to its antioxidant activity. We have previously reported the existence of a sexual dimorphism in the mitochondrial oxidative stress status of many rat tissues such as white (WAT) and brown (BAT) adipose tissues. The aim was to elucidate whether sex hormones may play a role in PRX3 expression in the adipose tissues of rats. In in vivo experiments, male and female standard diet fed rats, high fat diet (HFD) fed rats and rosiglitazone-supplemented HFD (HDF+Rsg) fed rats, as well as ovariectomized (OVX) and 17beta-estradiol-supplemented OVX (OVX+E2) female rats were used. 3T3-L1 adipocytes and brown adipocyte primary culture were used to study the roles of both E2 and testosterone in in vitro experiments. PRX3 levels were greater in the WAT of female rats than in males. This sexual dimorphism disappeared by HFD feeding but was magnified with Rsg supplementation. PRX3 sexual dimorphism was not observed in BAT, and neither HFD nor ovariectomy modified PRX3 levels. Rsg increased Prx3 expression in the BAT of both sexes. In vitro studies supported the results obtained in vivo and confirmed the contribution of E2 to sex differences in WAT Prx3 expression. Finally, we reported an E2 upregulation of both PRX3 and thioredoxin 2 (TRX2) in WAT but not in BAT that could play a key role in the sex dimorphism reported in the antioxidant defence of WAT in order to palliate the detrimental effect of the oxidative stress.

Transient Cerebral Ischemia Alters GSK-3β and p-GSK-3β Immunoreactivity in Pyramidal Neurons and Induces p-GSK-3β Expression in Astrocytes in the Gerbil Hippocampal CA1 Area

Glycogen synthase kinase 3β (GSK-3β) is a key downstream protein in the PI3K/Akt pathway. Phosphorylation of serine 9 of GSK-3β (GSK-3β activity inhibition) promotes cell survival. In this study, we examined changes in expressions of GSK-3β and phosphorylation of GSK-3β (p-GSK-3β) in the gerbil hippocampal CA1 area after 5 min of transient cerebral ischemia. GSK-3β immunoreactivity in the CA1 area was increased in pyramidal cells at 6 h after ischemia-reperfusion. It was decreased in CA1 pyramidal cells from 12 h after ischemia-reperfusion, and hardly detected in the CA1 pyramidal cells at 5 days after ischemia-reperfusion. p-GSK-3β immunoreactivity was slightly decreased in CA1 pyramidal cells at 6 and 12 h after ischemia-reperfusion. It was significantly increased in these cells at 1 and 2 days after ischemia-reperfusion. Five days after ischemia-reperfusion, p-GSK-3β immunoreactivity was hardly found in CA1 pyramidal cells. However, p-GSK-3β immunoreactivity was strongly expressed in astrocytes primarily distributed in strata oriens and radiatum. In conclusion, GSK-3β and p-GSK-3β were significantly changed in pyramidal cells and/or astrocytes in the gerbil hippocampal CA1 area following 5 min of transient cerebral ischemia. This finding indicates that GSK-3β and p-GSK-3β are closely related to delayed neuronal death.

Differences in the protein expression levels of Trx2 and Prx3 in the hippocampal CA1 region between adult and aged gerbils following transient global cerebral ischemia

The thioredoxin (Trx) and peroxiredoxin (Prx) redox system is associated with neuronal damage and neuroprotective effects via the regulation of oxidative stress in brain ischemia. In the present study, ischemia-induced changes in the protein expression levels of Trx2 and Prx3 in the stratum pyramidale (SP) of the hippocampal CA1 region were investigated in adult and aged gerbils, subjected to 5 min of transient global cerebral ischemia, using immunohistochemistry and western blot analysis. In the adult ischemia-group, minimal Trx2 immunoreactivity was detected in the SP 2 days after ischemia-reperfusion. In the aged animals, the Trx2 immunoreactivity in the sham-group was marginally lower compared with that in the adult sham-group. In the aged ischemia-group, Trx2 immunoreactivity in the SP was significantly higher 1, 2 and 4 days post-ischemia, compared with that in the adult ischemia-group and, in the 5 days post-ischemia group, Trx2 immunoreactivity was significantly decreased in the SP. Prx3 immunoreactivity in the SP of the adult ischemia-group was significantly decreased from 4 days after ischemia-reperfusion. In the aged animals, Prx3 immunoreactivity in the sham-group was also marginally lower compared with that in the adult sham-group. Prx3 immunoreactivity in the aged ischemia-group was also significantly higher 1, 2 and 4 days post-ischemia, compared with the adult ischemia-group; however, the Prx3 immunoreactivity was significantly decreased 5 days post-ischemia. The western blot analyses revealed that the pattern of changes in the protein levels of Trx2 and Prx3 in the adult and aged hippocampal CA1 region following ischemic damage were similar to the results obtained in the immunohistochemical data. These findings indicated that cerebral ischemia lead to different protein expression levels of Trx2 and Prx3 in the hippocampal CA1 region between adult and aged gerbils, and these differences may be associated with more delayed neuronal death in the aged gerbil hippocampus following transient global cerebral ischemia.

Differences in neuronal damage and gliosis in the hippocampus between young and adult gerbils induced by long duration of transient cerebral ischemia

Response to cerebral ischemia in young animals was very different from that in the adult. The aim of this study was to investigate differences in neuronal death and gliosis in the hippocampal CA1 region (CA1) between adult and young gerbils following 5 and 15 min of transient cerebral ischemia. Delayed neuronal death (DND) of pyramidal cells occurred in the CA1 was similar in all the adult gerbils after 5 and 15 min of ischemia: the DND occurred 4 days after ischemia. In the young groups, DND of pyramidal cells in the CA1 region occurred 7 and 3 days after 5 and 15 min of ischemia, respectively. On the other hand, the activation of GFAP-immunoreactive ((+)) astrocytes and Iba-1(+) microglia was different in the young groups from the adult groups after ischemia. The change pattern of GFAP immunoreactivity in the adult groups was similar in both the adult groups after ischemia; in the young groups, the activation of GFAP(+) astrocytes after 5 min of ischemia was much delayed than that after 15 min of ischemia. Activated Iba-1(+) microglia were aggregated in the stratum pyramidale 4 days after ischemia in all the adult ischemia-operated groups; in the young groups, activated Iba-1(+) microglia were aggregated in the stratum pyramidale 7 days after 5 min of ischemia and 3 days after 15 min of ischemia. These observations indicate that DND in young animals is very different from the adult according to different duration of transient cerebral ischemia and glial activation is very different in young animals after different duration of transient ischemia.

Differences of calcium binding proteins immunoreactivities in the young hippocampal CA1 region from the adult following transient ischemic damage

It has been reported that the young were much more resistant to transient cerebral ischemia than in the adult. In the present study, we examined that about 90% of CA1 pyramidal cells in the adult gerbil hippocampus died at 4days after ischemia-reperfusion; however, in the young hippocampus, about 56% of them died at 7days after ischemia-reperfusion. We compared immunoreactivities and levels of calcium binding proteins (CBPs), such as calbindin 28k (CB-D28k), calretinin (CR) and parvalbumin (PV). The immunoreactivities and protein levels of all the CBPs in the young sham were higher than those in the adult sham. In the adult, the immunoreactivities and protein levels of all the CBPs were markedly decreased at 4days after ischemia-reperfusion, however, in the young, they were apparently maintained. At 7days after ischemia-reperfusion, they were decreased in the young, however, they were much higher than those in the adult. In brief, the immunoreactivities and levels of CBPs were not decreased in the ischemic CA1 region of the young 4days after transient cerebral ischemia. This finding indicates that the longer maintenance of CBPs may contribute to a less and more delayed neuronal death/damage in the young.

Comparison of the immunoreactivities of NMDA receptors between the young and adult hippocampal CA1 region induced by experimentally transient cerebral ischemia

Young gerbils are much more resistant to transient cerebral ischemia than the adult. In the present study, we observed that about 90% of CA1 pyramidal cells in the adult hippocampus died 4days post-ischemia; however, about 56% of them in the young hippocampus died at 7days post-ischemia. To compare excitotoxicity between them, we carried out immunoreactivities of NMDA receptor 1 (NMDAR1) and NMDAR2A/B in the hippocampal CA1 region (CA1) induced by 5min of transient cerebral ischemia in the young and adult gerbils. Their immunoreactivities and protein levels in the young sham-group were much lower than those in the adult sham-group. Four days after ischemia-reperfusion, they were significantly decreased in the adult ischemia-group; however, in the young ischemia-group, they were much higher than those in the adult. Seven days after ischemia-reperfusion, NMDAR1 immunoreactivity and its level in the young were much higher than those in the adult; NMDAR2A/B immunoreactivity and its level in the young were lower than in the adult. In brief, the immunoreactivities of NMDARs were not decreased in the ischemic CA1 region of the young 4days after transient cerebral ischemia. This finding indicates that longer maintenance of NMDARs may contribute to less and more delayed neuronal death/damage in the young CA1.