Dataset Information

Microglia as target for anti-inflammatory approaches to prevent secondary brain injury after subarachnoid hemorrhage (SAH).

ABSTRACT:

Background

Microglia-driven cerebral spreading inflammation is a key contributor to secondary brain injury after SAH. Genetic depletion or deactivation of microglia has been shown to ameliorate neuronal cell death. Therefore, clinically feasible anti-inflammatory approaches counteracting microglia accumulation or activation are interesting targets for SAH treatment. Here, we tested two different methods of interference with microglia-driven cerebral inflammation in a murine SAH model: (i) inflammatory preconditioning and (ii) pharmacological deactivation.

Methods

7T-MRI-controlled SAH was induced by endovascular perforation in four groups of C57Bl/6 mice: (i) Sham-operation, (ii) SAH naïve, (iii) SAH followed by inflammatory preconditioning (LPS intraperitoneally), and (iv) SAH followed by pharmacological microglia deactivation (colony-stimulating factor-1 receptor-antagonist PLX3397 intraperitoneally). Microglia accumulation and neuronal cell death (immuno-fluorescence), as well as activation status (RT-PCR for inflammation-associated molecules from isolated microglia) were recorded at day 4 and 14. Toll-like receptor4 (TLR4) status was analyzed using FACS.

Results

Following SAH, significant cerebral spreading inflammation occurred. Microglia accumulation and pro-inflammatory gene expression were accompanied by neuronal cell death with a maximum on day 14 after SAH. Inflammatory preconditioning as well as PLX3397-treatment resulted in significantly reduced microglia accumulation and activation as well as neuronal cell death. TLR4 surface expression in preconditioned animals was diminished as a sign for receptor activation and internalization.

Conclusions

Microglia-driven cerebral spreading inflammation following SAH contributes to secondary brain injury. Two microglia-focused treatment strategies, (i) inflammatory preconditioning with LPS and (ii) pharmacological deactivation with PLX3397, led to significant reduction of neuronal cell death. Increased internalization of inflammation-driving TLR4 after preconditioning leaves less receptor molecules on the cell surface, providing a probable explanation for significantly reduced microglia activation. Our findings support microglia-focused treatment strategies to overcome secondary brain injury after SAH. Delayed inflammation onset provides a valuable clinical window of opportunity.

SUBMITTER: Heinz R

PROVIDER: S-EPMC7847606 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Publications

Microglia as target for anti-inflammatory approaches to prevent secondary brain injury after subarachnoid hemorrhage (SAH).

Heinz Rebecca R Brandenburg Susan S Nieminen-Kelhä Melina M Kremenetskaia Irina I Boehm-Sturm Philipp P Vajkoczy Peter P Schneider Ulf C UC

Journal of neuroinflammation 20210130 1

<h4>Background</h4>Microglia-driven cerebral spreading inflammation is a key contributor to secondary brain injury after SAH. Genetic depletion or deactivation of microglia has been shown to ameliorate neuronal cell death. Therefore, clinically feasible anti-inflammatory approaches counteracting microglia accumulation or activation are interesting targets for SAH treatment. Here, we tested two different methods of interference with microglia-driven cerebral inflammation in a murine SAH model: (i ...[more]

PMID: 33516246

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Project description:Aneurysmal subarachnoid hemorrhage (SAH) is associated with high morbidity and mortality. Devastating post-SAH complications, such as cerebral vasospasm (CVS), delayed cerebral ischemia or seizures to mention a few, are mainly responsible for the poor clinical outcome. Inflammation plays an indispensable role during early brain injury (EBI) and delayed brain injury (DBI) phases over which these complications arise. T helper cells are the major cytokine secreting cells of adaptive immunity that can polarize to multiple functionally unique sub-populations. Here, we investigate different CD4+ T cell subsets during EBI and DBI phases after SAH, and their dynamics during post-SAH complications. Peripheral venous blood from 15 SAH patients during EBI and DBI phases, was analyzed by multicolour flowcytometry. Different subsets of CD3+ CD4+ T cells were characterized by differential cell surface expression of CXCR3 and CCR6 into Th1, Th2, Th17, whereas Tregs were defined by CD25hiCD127lo. The analysis of activation states was done by the expression of stable activation markers CD38 and HLA-DR. Interestingly, compared to healthy controls, Tregs were significantly increased during both EBI and DBI phases. Different activation states of Tregs showed differential significant increase during EBI and DBI phases compared to controls. HLA-DR- CD38+ Tregs were significantly increased during DBI phase compared to EBI phase in SAH patients developing CVS, seizures and infections. However, HLA-DR- CD38- Tregs were significantly reduced during EBI phase in patients with cerebral ischemia (CI) compared to those without CI. HLA-DR- CD38- Th2 cells were significantly increased during EBI phase compared to controls. A significant reduction in Th17/Tregs and HLA-DR- CD38+ Th17/Tregs ratios was observed during both EBI and DBI phases compared to controls. While HLA-DR- CD38- Th17/Tregs and HLA-DR- CD38- Th1/Th2 ratios were impaired only during EBI phase compared to controls. In conclusion, CD4+ T cell subsets display dynamic and unique activation patterns after SAH and during the course of the manifestation of post-SAH complications, which may be helpful for the development of precision neurovascular care. However, to claim this, confirmatory studies with larger patient cohorts, ideally from different ethnic backgrounds, are required. Moreover, our descriptive study may be the grounds for subsequent lab endeavors to explore the underlying mechanisms of our observations.

Project description:The SOCS1/JAK2/STAT3 axis is strongly associated with tumor growth and progression, and participates in cytokine secretion in many diseases. However, the effects of the SOCS1/JAK2/STAT3 axis in experimental subarachnoid hemorrhage remain to be studied. A subarachnoid hemorrhage model was established in rats by infusing autologous blood into the optic chiasm pool. Some rats were first treated with JAK2/STAT3 small interfering RNA (Si-JAK2/Si-STAT3) or overexpression plasmids of JAK2/STAT3. In the brains of subarachnoid hemorrhage model rats, the expression levels of both JAK2 and STAT3 were upregulated and the expression of SOCS1 was downregulated, reaching a peak at 48 hours after injury. Simultaneously, the interactions between JAK2 and SOCS1 were reduced. In contrast, the interactions between JAK2 and STAT3 were markedly enhanced. Si-JAK2 and Si-STAT3 treatment alleviated cortical neuronal cell apoptosis and necrosis, destruction of the blood-brain barrier, brain edema, and cognitive functional impairment after subarachnoid hemorrhage. This was accompanied by decreased phosphorylation of JAK2 and STAT3 protein, decreased total levels of JAK2 and STAT3 protein, and increased SOCS1 protein expression. However, overexpression of JAK2 and STAT3 exerted opposite effects, aggravating subarachnoid hemorrhage-induced early brain injury. Si-JAK2 and Si-STAT3 inhibited M1-type microglial conversion and the release of pro-inflammatory factors (inducible nitric oxide synthase, interleukin-1β, and tumor necrosis factor-α) and increased the release of anti-inflammatory factors (arginase-1, interleukin-10, and interleukin-4). Furthermore, primary neurons stimulated with oxyhemoglobin were used to simulate subarachnoid hemorrhage in vitro, and the JAK2 inhibitor AG490 was used as an intervention. The in vitro results also suggested that neuronal protection is mediated by the inhibition of JAK2 and STAT3 expression. Together, our findings indicate that the SOCS1/JAK2/STAT3 axis contributes to early brain injury after subarachnoid hemorrhage both in vitro and in vivo by inducing inflammatory responses. This study was approved by the Animal Ethics Committee of Anhui Medical University and the First Affiliated Hospital of University of Science and Technology of China (approval No. LLSC-20180202) on March 1, 2018.

Dataset Information

Microglia as target for anti-inflammatory approaches to prevent secondary brain injury after subarachnoid hemorrhage (SAH).

Background

Methods

Results

Conclusions

Publications

Microglia as target for anti-inflammatory approaches to prevent secondary brain injury after subarachnoid hemorrhage (SAH).

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