CCL17 exerts neuroprotection through activation of CCR4/mTORC2 axis in microglia after subarachnoid haemorrhage in rats

Background and purpose: C-C motif chemokine ligand 17 (CCL17) presents an important role in immune regulation, which is critical in the pathophysiology of brain injury after subarachnoid haemorrhage (SAH). There is rare evidence to illustrate the function of CCL17 towards SAH. In this study, we try to reveal the therapeutic effects of CCL17 and its underlying mechanism in rat SAH model.

Methods: SAH rat models were assigned to receive recombinant CCL17 (rCCL17) or phosphate buffer saline (PBS). AZD2098 and JR-AB2-011 were applied to investigate the C-C motif chemokine receptor 4 (CCR4)/mammalian target of rapamycin complex 2 (mTORC2) axis in CCL17-mediated neuroprotection. To elucidate the underlying mechanism, the in vitro kinase assay was performed in primary microglia. Microglial-specific Rictor knockdown was administered via intracerebroventricular injection of adenovirus-associated virus. Brain water content, short-term neurobehavioural evaluation, western blot analysis, quantitative RT-PCR and histological staining were performed.

Results: The expression of CCL17 was increased and secreted from neurons after oxyhaemoglobin stimulation. Exogenous rCCL17 significantly alleviated neuronal apoptosis, and alleviated short-term neurofunction after SAH in rats. In addition, rCCL17 increased M2-like polarisation of microglia in rats post-SAH and in primary microglia culture. The neuroprotection of rCCL17 was abolished via inhibition of either CCR4 or mTORC2.

Conclusion: CCL17 activated the CCR4/mTORC2 axis in microglia, which can alleviate SAH-induced neurological deficits by promoting M2-like polarisation of microglia.

 

Comments:

Your study seems to explore the role of CCL17 in the context of subarachnoid hemorrhage (SAH) and its potential therapeutic effects. Here's a breakdown of your methods and findings:

### Background:
- CCL17 is crucial in immune regulation and likely plays a significant role in the pathology of brain injury following SAH.
- Despite limited evidence, your study aims to investigate the function of CCL17 in SAH and its therapeutic potential.

### Methods:
- **SAH Rat Model:** Used recombinant CCL17 (rCCL17) or phosphate buffer saline (PBS) in SAH rat models.
- **Chemical Modulators:** AZD2098 and JR-AB2-011 used to explore the CCR4/mTORC2 axis involvement in CCL17-mediated neuroprotection.
- **In vitro Kinase Assay:** Conducted in primary microglia to understand the underlying mechanism.
- **Rictor Knockdown:** Administered via intracerebroventricular injection of adenovirus-associated virus to study the role of microglial-specific Rictor in SAH.
- **Analysis Methods:** Brain water content, neurobehavioral evaluation, western blot analysis, RT-PCR, and histological staining were performed.

### Results:
- **CCL17 Expression:** Increased in neurons following oxyhemoglobin stimulation.
- **Therapeutic Effects:** Exogenous rCCL17 reduced neuronal apoptosis and improved short-term neurofunction after SAH in rats.
- **Microglia Polarization:** rCCL17 promoted M2-like polarization of microglia both in rats post-SAH and in primary microglia culture.
- **Mechanism:** The neuroprotective effect of rCCL17 was nullified by inhibiting either CCR4 or mTORC2.

### Conclusion:
- **CCL17 Role:** Activated the CCR4/mTORC2 axis in microglia, leading to the alleviation of SAH-induced neurological deficits by promoting M2-like polarization of microglia.

Your study demonstrates that CCL17 could potentially be a therapeutic target in SAH, acting via modulation of microglial polarization through the CCR4/mTORC2 axis. This insight could pave the way for new treatment strategies for SAH-related brain injury.

Related Products

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E1151	JR-AB2-011	JR-AB2-011 is a potent inhibitor of mTOR-mLST8-mSIN1-Rictor complex (mTORC2) which can block mTORC2 signaling and Rictor association with mTOR at lower effective concentrations.

Related Targets

mTOR