Minimally invasive surgery for ICH evacuation followed by rosiglitazone infusion therapy increased perihematomal PPARγ expression and improved neurological outcomes in rabbits

PPARγ/RAD21 alleviates peripheral secondary brain injury in rat cerebral hemorrhage model through promoting M2 polarization of microglial cells

BACKGROUND

PPARγ has been reported to participate in intracerebral hemorrhage (ICH) progression, and recruit RAD21 through binding DNA. Our study aimed to explore the roles of PPARγ/RAD21 in ICH and their related mechanisms.

METHODS

ICH models in vitro and in vivo were established using thrombin and autologous blood injection, respectively. After that, rosiglitazone (RSG), GW9662, and RAD21 knockdown/overexpression plasmids were used to treat the ICH models. The cell apoptosis, the related inflammatory cytokines levels, and the neurological function of the rats were examined. Real-time quantitative PCR (RT-qPCR), western blot and immunofluorescence were employed to determine the expression of the M1/M2 polarization-related markers. Finally, the interaction of PPARγ and RAD21 in microglial cells was observed using double labeled immunofluorescence and co-immunoprecipitation.

RESULTS

After thrombin induction, the cell apoptosis, and TNF-α, IL-1β and IL-10 contents were all significantly increased (P < 0.05); whereas RSG and RAD21 overexpression evidently inhibited the apoptosis of thrombin-caused microglial cells, reduced TNF-α and IL-1β contents, further increased IL-10 content (P < 0.05). The combination of RAD21 and PPARγ was enhanced by RSG and RAD21 overexpression. In vivo experiments showed that RSG and RAD21 overexpression decreased neurological deficit score, brain water content and hematoma volume. Additionally, RSG and RAD21 overexpression up-regulated the expression of PPARγ, RAD21, Arg1, KLF4, and TGF-β, whereas down-regulated iNOS and CD32 expression. The actions of GW9662 and RAD21 knockdown were opposite to those of RSG and RAD21 overexpression.

CONCLUSION

PPARγ/RAD21 may alleviate ICH progression through promoting M2-type polarization of microglial cells and inhibiting inflammatory response.

Mechanism of neuroprotective effect of stevioside on cerebral ischemia-reperfusion injury via PPAR-γ activation

OBJECTIVE

The aim of this work was to explore the possible protective effects and its mechanism of stevioside on cerebral ischemia reperfusion (CIR) induced neuron damages.

METHODS

Middle cerebral artery occlusion/reperfusion (MCAO/R) rat models were constructed. The rats were treated with stevioside treatment, PPAR-γ antagonist GW9662, PPAR-γ activator pioglitazone or PI3K/AKT inhibitor LY294002 before neurological deficits were assessed using modified Neurological Severity Scale (mNSS) scores. The infarct size, brain injury, apoptotic cells, inflammatory cytokines in neurons extracted from MCAO/R rats were determined by TTC staining, H&E staining, TUNEL staining, qRT-PCR and Western blot, respectively.

RESULTS

Stevioside attenuates MCAO/R-induced neuronal apoptosis and inflammation by regulating PPAR-γ expression. Besides, PPAR-γ activates PI3K/AKT signaling pathway. Moreover, PPAR-γ antagonist GW9662 or PI3K/AKT inhibitor LY294002 abrogated the anti-apoptosis and anti-inflammatory effects of stevioside on MCAO/R rats.

CONCLUSION

Stevioside alleviates MCAO/R-induced neuronal apoptosis and inflammation by upregulating PPAR-γ to activate PI3K/AKT signaling pathway.

Is the CT Blend Sign Composed of Two Parts of Blood with Different Age?

BACKGROUND

Blend sign on initial computed tomography (CT) is associated with poor outcome in patients with intracerebral hemorrhage (ICH). However, the mechanisms underlying the blend sign formation are poorly understood. The present study aimed to explore the possible mechanism of the CT blend sign in patients with ICH.

METHODS

Seventy healthy rabbits were selected to prepare an ICH model. The animals were assigned to a whole blood group + whole blood group (ww group, 50 rabbits), a whole blood + plasma group (wp group, 10 rabbits) or a whole blood + serum group (ws group, 10 rabbits). The animals of the ww group were allocated to five subgroups based on the interval between the first infusion of blood and the second one. The subgroups included ww 1 h group (with an interval of 1 h), ww 2 h group, ww 3 h group, ww 4 h group and ww 5 h group. The rabbits from each group received first infusion of 0.3 mL of whole blood into the basal ganglia area to form a hematoma. Then, they received a second infusion of the same amount of whole blood, plasma or serum into the brain to form another hematoma adjacent to the first one.

RESULTS

A hematoma with two densities on brain CT could be formed in each group after a second infusion of blood into the brain. A significant difference in CT attenuation values was observed between the hyperattenuation and the hypoattenuation in all the groups. However, only the morphological features of the hematoma in the ww group was in accordance with the CT blend sign observed in humans. The CT attenuation values in the hypodensity area of the ww 4 h group or the ww 5 h group were decreased compared with the ww 1 h group to the ww 3 h group.

CONCLUSIONS

The CT blend sign observed in humans might be composed of two parts of blood with different ages. The hypodense area might be blood with older age and the hyperdense area might be new bleeding.

miR-331-3p Inhibits Inflammatory Response after Intracerebral Hemorrhage by Directly Targeting NLRP6

Background

The mechanism of inflammatory reaction after intracerebral hemorrhage remains unclear, which to some extent restrains the therapeutic development of hemorrhagic stroke. The present study attempts to verify whether NLRP6 plays an important role in inflammatory reaction after intracerebral hemorrhage and identify the critical microRNA during the process.

Methods

Suitable simulated cerebral hemorrhage environments were established in vitro and in vivo. BV2 cells were treated with hemin to induce cell damage. Collagenase was used to establish a model of mouse cerebral hemorrhage. The relationship among NLRP6, miR-331-3p, and the corresponding inflammatory expression was closely observed during this process. Techniques, such as western blot, real-time quantitative PCR, immunofluorescence, and immunocytochemistry, were used to detect the expression of relative genes and molecules in the in vitro and in vivo models.

Results

Downregulated miR-331-3p increased the expression of NLRP6 and alleviated the expression of TNF-α and IL-6. The neurological function recovery of mice was promoted after intracerebral hemorrhage.

Conclusion

miR-331-3p regulated the inflammatory response after cerebral hemorrhage by negatively regulating the expression of NLRP6.

Zafirlukast protects blood-brain barrier integrity from ischemic brain injury

Stroke has been considered the second leading cause of death worldwide, and ischemic stroke accounts for the vast majority of stroke cases. Some of the main features of ischemic stroke are increased brain permeability, ischemia/reperfusion injury, oxidative stress, and acute inflammation. Antagonism of cysLT1R has been shown to provide cardiovascular and neural benefits. In the present study, we investigated the effects of the cysLT1R antagonist zafirlukast both in vivo and in vitro using a middle cerebral artery occlusion (MCAO) mouse model and human brain microvascular endothelial cells (HBMVECs). In vivo, we found that zafirlukast pretreatment could reduce MCAO-induced increased brain permeability by rescuing the expression levels of the tight junction proteins occludin and ZO-1. In vitro, we found that zafirlukast could suppress the increase in endothelial monolayer permeability induced by OGD/R via rescue of occludin and ZO-1 expression; additionally, we found that zafirlukast prevented OGD/R-induced degradation of the extracellular matrix via inhibition of MMP-2 and MMP-9 expression. Finally, we found that zafirlukast could also inhibit OGD/R-induced activation of the critical proinflammatory regulator NF-κB by preventing phosphorylation and nuclear translocation of p65 protein. Together, our findings demonstrate a promising role for zafirlukast in preventing damage induced by ischemic stroke and reperfusion injury.

1, 25-D3 Protects From Cerebral Ischemia by Maintaining BBB Permeability via PPAR-γ Activation

The blood-brain barrier (BBB) is a physical and biochemical barrier that maintains cerebral homeostasis. BBB dysfunction in an ischemic stroke, results in brain injury and subsequent neurological impairment. The aim of this study was to determine the possible protective effects of 1, 25-dihydroxyvitamin D3 [1, 25(OH)2D3, 1, 25-D3, vit D] on BBB dysfunction, at the early stages of an acute ischemic brain injury. We analyzed the effects of 1, 25-D3 on BBB integrity in terms of histopathological changes, the neurological deficit, infarct size and the expression of brain derived neurotrophic factor (BDNF), in a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model. BBB permeability and the expression of permeability-related proteins in the brain were also evaluated by Evans blue (EB) staining and Western blotting respectively. To determine the possible mechanism underlying the role of 1, 25-D3 in BBB maintenance, after MCAO/R, the rats were treated with the specific peroxisome proliferator-activated receptor gamma (PPARγ) inhibitor GW9662. Supplementation with 1, 25-D3 markedly improved the neurological scores of the rats, decreased the infarct volume, prevented neuronal deformation and upregulated the expression of the tight junction (TJ) and BDNF proteins in their brains. Furthermore, it activated PPARγ but downregulated neuro-inflammatory cytokines such as nuclear factor kappa-B (NF-κB) and tumor necrosis factor-α (TNF-α), after MCAO/R. Taken together, 1, 25-D3 protects against cerebral ischemia by maintaining BBB permeability, upregulating the level of BDNF and inhibiting PPARγ-mediated neuro-inflammation.

Alternative activation-skewed microglia/macrophages promote hematoma resolution in experimental intracerebral hemorrhage

Microglia/macrophages (MMΦ) are highly plastic phagocytes that can promote both injury and repair in diseased brain through the distinct function of classically activated and alternatively activated subsets. The role of MMΦ polarization in intracerebral hemorrhage (ICH) is unknown. Herein, we comprehensively characterized MMΦ dynamics after ICH in mice and evaluated the relevance of MMΦ polarity to hematoma resolution. MMΦ accumulated within the hematoma territory until at least 14days after ICH induction. Microglia rapidly reacted to the hemorrhagic insult as early as 1-1.5h after ICH and specifically presented a "protective" alternatively activated phenotype. Substantial numbers of activated microglia and newly recruited monocytes also assumed an early alternatively activated phenotype, but the phenotype gradually shifted to a mixed spectrum over time. Ultimately, markers of MMΦ classic activation dominated at the chronic stage of ICH. We enhanced MMΦ alternative activation by administering intraperitoneal injections of rosiglitazone, and subsequently observed elevations in CD206 expression on brain-isolated CD11b⁺ cells and increases in IL-10 levels in serum and perihematomal tissue. Enhancement of MMΦ alternative activation correlated with hematoma volume reduction and improvement in neurologic deficits. Intraventricular injection of alternative activation signature cytokine IL-10 accelerated hematoma resolution, whereas microglial phagocytic ability was abolished by IL-10 receptor neutralization. Our results suggest that MMΦ respond dynamically to brain hemorrhage by exhibiting diverse phenotypic changes at different stages of ICH. Alternative activation-skewed MMΦ aid in hematoma resolution, and IL-10 signaling might contribute to regulation of MMΦ phagocytosis and hematoma clearance in ICH.