PVN Oxytocin Neurons Suppress Microglial CXCL3 via OXTR-ERK Pathway, Reducing Ischemic Brain Injury
Background
In ischemic stroke, secondary brain injury is largely driven by neuroinflammation, primarily through the overactivation of microglia. Current treatments often fall short in effectively modulating this inflammatory cascade. Oxytocin (OXT), a neuropeptide synthesized in the paraventricular nucleus (PVN) of the hypothalamus, has shown promise in mitigating inflammation in various conditions. However, the specific role of PVNOXT neurons in modulating neuroinflammation and its impact on ischemic stroke outcomes remains an underexplored therapeutic avenue, representing a critical gap in understanding OXT's neuroprotective potential.
Study Design
Researchers induced transient middle cerebral artery occlusion (tMCAO) in mice to model ischemic stroke. They measured endogenous OXT levels in the peri-infarct cortex, serum, and cerebrospinal fluid (CSF), and assessed OXTR expression in the peri-infarct cortex post-tMCAO. To investigate the therapeutic potential, PVNOXT neurons were selectively activated using chemogenetic approaches in OXT-Cre mice. Following activation, neurological function, infarct volume, and blood-brain barrier integrity were evaluated. Mechanistic insights were gained through RNA sequencing of the ipsilateral ischemic hemisphere, followed by flow cytometry, molecular assays, and Transwell migration experiments to validate downstream signaling pathways and cellular responses.
Results
Following tMCAO, endogenous OXT levels were significantly reduced in the peri-infarct cortex, serum, and CSF, while OXTR expression increased in the peri-infarct cortex. Chemogenetic activation of PVNOXT neurons successfully increased OXT levels in both the brain and circulation. This activation led to a reduced infarct volume and improved neurological outcomes in the stroke model. Transcriptomic analysis identified CXCL3 as one of the most significantly downregulated chemokines after PVNOXT neuron activation, which was associated with reduced neutrophil chemotaxis. Further in vivo and in vitro studies elucidated the underlying mechanism: > PVNOXT neurons inhibit microglial CXCL3 expression via the OXTR-ERK signaling pathway, thereby attenuating neuroinflammation and subsequent brain injury.
Key Findings
- Endogenous OXT levels significantly reduced in brain, serum, and CSF after tMCAO.
- OXTR expression increased in the peri-infarct cortex post-ischemic stroke.
- Chemogenetic activation of PVNOXT neurons increased OXT levels in brain and circulation.
- PVNOXT neuron activation reduced infarct volume and improved neurological outcomes.
- PVNOXT neurons inhibit microglial
CXCL3expression via theOXTR-ERKsignaling pathway.
Why It Matters
This research provides compelling evidence that targeting PVN oxytocin neurons could be a novel therapeutic strategy for ischemic stroke. By activating these neurons, it's possible to modulate the detrimental microglial-mediated neuroinflammation that exacerbates brain injury. While this study is preclinical, it identifies a specific mechanism (OXTR-ERK pathway on CXCL3) that could be leveraged for future drug development. For biohackers and clinicians, this suggests a potential pathway for neuroprotection, though direct OXT administration protocols for this specific effect are not yet established. Further research is needed to translate chemogenetic activation into a clinically viable intervention, but the findings highlight the therapeutic relevance of endogenous OXT systems in brain injury.
oxytocin
ischemic-stroke
neuroinflammation
microglia
cxcl3
erk