The Regulatory Role and Mechanism of Circadian Rhythm in Hemoglobin Co-cultured Neurovascular Unit.

Objective: Intracranial hemorrhage (ICH), the second most common subtype of stroke, exacerbates the disruption of the blood-brain barrier (BBB), leading to vasogenic edema, plasma protein extravasation, and infiltration of neurotoxic substances. The clearance capacity of the brain plays a crucial role in maintaining BBB homeostasis and facilitating patient recovery after hemorrhage. This study aimed to investigate the effect of circadian rhythms on BBB function, neuronal damage, and clearance capabilities.

Methods: The transwell model and hemoglobin were co-cultured to simulate the BBB environment after ICH. After intervention with different light groups, neuronal apoptosis was determined, glial phagocytosis was analyzed, the expression of endogenous clearing-related proteins aquaporin 4 (AQP4) and low-density lipoprotein receptor-related protein 1 (LRP1) was detected by western blotting and immunofluorescence dual standard method, and the expression of the tight junction protein occludin and melatonin receptor 1A (MTNR1A) was quantitatively analyzed.

Results: Circadian rhythms play a key role in maintaining the integrity of the BBB, reducing oxidative stress-induced neuronal damage, and improving microglial phagocytosis. Meanwhile, the expression of occludin and MTNR1A in neurovascular unit (NVU) co-cultured with hemoglobin improved the expression of AQP4 and LRP1, the key proteins in the NVU's endogenous brain clearance system.

Conclusion: Circadian rhythm (alternating black and white light) protects the NVU BBB function after ICH, promotes the expression of proteins related to the clearance of the hematoma, provides new evidence for the clinical treatment of patients recovering from ICH, and improves the circadian rhythm to promote brain metabolism and hematoma clearance.