Effects of remote ischemic preconditioning on the deformability and aggregation of red blood cells in a rat endotoxemia model

BACKGROUND

The prevention of rheologic alterations in erythrocytes may be important for reducing sepsis-associated morbidity and mortality. Remote ischemic preconditioning (RIPC) has been shown to prevent tissue damage caused by severe ischemia and mortality resulting from sepsis. However, the effect of RIPC on erythrocytes in sepsis is yet to be determined.

OBJECTIVE

To investigate the effect of RIPC on rheologic alterations in erythrocytes in sepsis.

METHODS

Thirty male Sprague-Dawley rats were used in this study. An endotoxin-induced sepsis model was established by intraperitoneally injecting 20 mg/kg LPS (LPS group). RIPC was induced in the right hind limb using a tourniquet, with three 10-minute of ischemia and 10 min of reperfusion cycles immediately before the injection of LPS (RIPC/LPS group) or phosphate-buffered saline (RIPC group). The aggregation index (AI), time to half-maximal aggregation (T1/2), and maximal elongation index (EImax) of the erythrocytes were measured 8 h after injection.

RESULTS

The AI, T1/2, and EImax values in the LPS and RIPC/LPS groups differed significantly from those in the RIPC group, but there were no differences between the values in the LPS and RIPC/LPS groups.

CONCLUSIONS

RIPC did not prevent rheologic alterations in erythrocytes in the rat model of LPS-induced endotoxemia.

A 2-Min Transient Ischemia Confers Cerebral Ischemic Tolerance in Non-Obese Gerbils, but Results in Neuronal Death in Obese Gerbils by Increasing Abnormal mTOR Activation-Mediated Oxidative Stress and Neuroinflammation

A brief episode of transient ischemia (TI) can confer cerebral ischemic tolerance against a subsequent severer TI under standard condition. The brain under obesity’s conditions is more sensitive to ischemic injury. However, the impact of a brief episode of TI under obesity’s conditions has not been fully addressed yet. Thus, the objective of this study was to determine the effect of a brief TI in the hippocampus of high-fat diet (HFD)-induced obese gerbils and related mechanisms. Gerbils were maintained on HFD or normal diet (ND) for 12 weeks and subjected to 2 min TI. HFD gerbils were heavier, with higher blood glucose, serum total cholesterol, triglycerides, and leptin levels. Massive loss of pyramidal neurons occurred in the hippocampal cornu ammonis 1 (CA1) field of HFD animals at 5 days after 2 min of TI, but 2 min of TI did not elicit death of pyramidal neurons in ND gerbils. The HFD group showed significantly increased levels of oxidative stress indicators (dihydroethidium and 4-hydroxynonenal) and proinflammatory cytokines (tumor necrosis factor-α and interleukin-1β) and microglial activation in pre- and/or post-ischemic phases compared to the ND group. Levels of mammalian target of rapamycin (mTOR) and phosphorylated-mTOR in the CA1 field of the HFD group were also significantly higher than the ND group. On the other hand, inhibition of mTOR activation by rapamycin (an allosteric mTOR inhibitor) significantly attenuated neuronal death induced by HFD, showing reduction of HFD-induced increases of oxidative stress indicators and proinflammatory cytokines, and microglia activation. Taken together, a brief episode of TI can evoke neuronal death under obesity’s conditions. It might be closely associated with an abnormal increase of mTOR activation-mediated, severe oxidative stress and neuroinflammation in pre- and/or post-ischemic phases.

Protective Effects of Nucleobinding-2 After Cerebral Ischemia Via Modulating Bcl-2/Bax Ratio and Reducing Glial Fibrillary Acid Protein Expression

Introduction

Nucleobinding-2 (NUCB2) or nesfatin-1, a newly identified anorexigenic peptide, has antioxidant, anti-inflammatory, and anti-apoptotic properties. Brain ischemiareperfusion induces irreversible damages, especially in the hippocampus area. However, the therapeutic effects of NUCB2 have not been well investigated in cerebral ischemia. This study was designed for the first time to investigate the protective effects of NUCB2/Nesfatin-1 on the expression of apoptosis-related proteins and reactive astrogliosis level in the CA1 area of hippocampus in an experimental model of transient global cerebral ischemia.

Methods

The male Wistar rats were randomly allocated into 4 groups (sham, NUCB2, ischemia-reperfusion, and ischemia-reperfusion+NUCB21) (n =7). The model of cerebral ischemia was prepared by common carotid arteries occlusion for 20 minutes. Nesfatin-1 (20 μg/kg) and saline (as a vehicle) were injected (intraperitoneally) at the beginning of the reperfusion period. The assessment of the protein expression levels was performed by immunofluorescence and immunohistochemical staining.

Results

NUCB2 significantly reduced the Bax and GFAP protein levels in the CA1 area after ischemia (P<0.05). Also, NUCB2 increased Bcl-2 protein level (P<0.05). NUCB2 exerted protective effects against ischemic injury by the inhibition of astrocytes activation as an inflammatory response and decreased neuronal cell apoptosis.

Conclusion

The present study provides the possible neuroprotective view of nesfatin-1 in the treatment of ischemia injury model in rat hippocampus.

Brain ischemic preconditioning protects against moderate, not severe, transient global cerebral ischemic injury

Ischemic preconditioning (IPC) in the brain increases ischemic tolerance to subsequent ischemic insults. In this study, we examined whether IPC protects neurons and attenuates microgliosis or not in the hippocampus following severe transient global cerebral ischemia (TCI) in gerbils. Gerbils were assigned to 8 groups; 5- and 15-min sham operated groups, 5-min and 15-min TCI operated groups, IPC plus 5- and 15-min sham operated groups, and IPC plus 5- and 15-min TCI operated groups. IPC was induced by subjecting animals to 2-min transient ischemia 1 day before 5-min TCI for a typical transient ischemia and 15-min TCI for severe transient ischemia. Neuronal damage was examined by cresyl violet staining and Fluoro-Jade B histofluorescence staining. In addition, microglial activation was examined using immunohistochemistry for Iba-1 (a marker for microglia). Delayed neuronal death and microgliosis was found in the CA1 alone in the 5-min TCI operated group at 5 days post-ischemia, and, in the 15-min TCI operated group, neuronal death and microgliosis was shown in all CA areas (CA1-3) and the dentate gyrus. IPC displayed neuroprotection and attenuated microglial activation in the 5-min TCI operated group. However, in the 15-min TCI operated group, IPC did not show neuroprotection and not attenuate microglial activation. Our present findings indicate that IPC hardly protect against severe transient cerebral ischemic injury.

Tumor necrosis factor receptor 2 is required for ischemic preconditioning-mediated neuroprotection in the hippocampus following a subsequent longer transient cerebral ischemia

Tumor Necrosis Factor-α (TNF-α) is a proinflammatory cytokine implicated in neuronal damage in response to cerebral ischemia. Ischemic preconditioning (IPC) provides neuroprotection against a subsequent severer or longer transient ischemia by ischemic tolerance. Here, we focused on the role of TNF-α in IPC-mediated neuroprotection against neuronal death following a subsequent longer transient cerebral ischemia (TCI). Gerbils used in this study were randomly assigned to eight groups; sham group, TCI operated group, IPC plus (+) sham group, IPC + TCI operated group, sham + etanercept (an inhibitor of TNF-a) group, TCI + etanercept group, IPC + sham + etanercept group, and IPC + TCI + etanercept group. IPC was induced by a 2-min sublethal transient ischemia, which was operated 1 day prior to a longer (5-min) TCI. A significant death of neurons was found in the stratum pyramidale (SP) in the CA1 area (CA1) of the hippocampus 5 days after TCI; however, IPC protected SP neurons from TCI. We found that TNF-α immunoreactivity was significantly increased in CA1 pyramidal neurons in the TCI and IPC + TCI groups compared to the sham group. TNF-R1 expression in CA1 pyramidal neurons of the TCI group was also increased 1 and 2 days after TCI; however, in the IPC + TCI group, TNF-R1 expression was significantly lower than that in the TCI group. On the other hand, we did not detect TNF-R2 immunoreactivity in CA1 pyramidal neurons 1 and 2 days after TCI; meanwhile, in the IPC + TCI group, TNF-R2 expression was significantly increased compared to TNF-R2 expression at 1 and 2 days after TCI. In addition, in this group, TNF-R2 was newly expressed in pericytes, which are important cells in the blood brain barrier, from 1 day after TCI. When we treated etanercept to the IPC + TCI group, IPC-induced neuroprotection was significantly weakened. In brief, this study indicates that IPC confers neuroprotection against TCI by TNF-α signaling through TNF-R2 and suggests that the enhancement of TNF-R2 expression by IPC may be a legitimate strategy for a therapeutic intervention of TCI.