Blocking cerebral lymphatic system reduces central and peripheral inflammatory response in ischemic stroke
Lingfei Yang, Qingsheng Li, Kaixin Wang, Huimin Liu, Xuan Yang, Yudi Xu, Yufei Chen, Junfang Teng, Zhe Gong, Yanjie Jia
Abstract
• This study examines the role of the cerebral lymphatic system in determining the response, both centrally and peripherally, following ischemic stroke. • We used a rat model involving middle cerebral artery occlusion, along with removal of the deep cervical lymph nodes, to obstruct drainage from the meningeal lymphatic system. • We found that blocking drainage from meningeal lymphatic vessels, significantly reduced the infarct area and infiltration by inflammatory cells, and inhibited activation of microglia and astrocytes. • We also observed accompanying changes in the levels of plasma inflammatory factors such as IL-6, IL-10 and TNF-α. • Blockage of cerebral lymphatic drainage was associated with reduced functional deficits. • We believe that our study makes a significant contribution to the literature because our findings suggest that the cerebral lymphatic system may trigger systemic inflammation after ischemic stroke. Reduced blood supply to the brain activates the intracranial inflammatory response, a key contributor to secondary brain damage in ischemic stroke. Post-stroke, activation of peripheral immune cells leads to systemic inflammatory responses. Using in vivo approaches, we investigated meningeal lymphatics’ role in central immune cell infiltration and peripheral immune cell activation. The bilateral deep cervical lymph nodes (dCLNs) were removed 7 days before right middle cerebral artery occlusion in Sprague Dawley (SD) rats. At 3, 24, and 72 h post-intervention, brain immune cell infiltration and microglial and astrocyte activation were measured, while immune cells were classified in the spleen and blood. Inflammatory factor levels in peripheral blood were analyzed. Simultaneously, reverse verification was conducted by injecting AAV-vascular endothelial growth factor C (AAV-VEGFC) adenovirus into the lateral ventricle 14 days before middle cerebral artery occlusion (MCAO) induction to enhance meningeal lymph function. Blocking meningeal LVs in MCAO rats significantly reduced infarct area and infiltration, and inhibited microglia and pro-inflammatory astrocytes activation. After removing dCLNs, CD4 + T lymphocytes, CD8 + T lymphocytes, B lymphocytes, macrophages, and neutrophils in the spleen and blood of MCAO rats decreased significantly at different time points. The levels of inflammatory factors IL-6, IL-10, IL-1β, and TNF-α in plasma decreased significantly. Tests confirmed the results, and AAV-VEGFC-induced MCAO rats provided reverse validation.