309 High Glutamine Associated With the Risk of Stroke by Inducing Endothelial to Mesenchymal Transition Through ITGB4 MAPK-ERK Smad in Moyamoya Disease

INTRODUCTION: Previous studies have suggested potential association between glutamine and stroke. The role of glutamine in moyamoya disease (MMD) manifestation and pathological process remains unknown. METHODS: A prospective cohort of 360 adult MMD patients between September 2020 to December 2021 was established. Human brain microvascular endothelial cells (HBMECs) were utilized for rt-qPCR, western blot, immunofluorescence, and functional assays including CCK8, Edu for proliferation and wound healing for migration. HBMECs were transfected with ITGB4 adenovirus, ITGB4 siRNA or Smad4 siRNA to explore the downstream alterations. Atorvastatin was used to treat HBMECs and the mechanism was explored. Finally, the expression of ITGB4 was validated in databases and immunofluorescence staining of superficial temporal artery in MMD patients. RESULTS: After fully adjusted, the risk of stroke increased with each increment of glutamine level (OR = 1.599, 95% CI = 1.071 – 2.387, p = 0.022). Consistently, compared with patients in the lower tertiles of serum glutamine levels, a significantly higher risk of complete stroke was found in those in highest glutamine tertile (OR = 2.752, 95% CI = 1.556 – 4.868, p = 0.001). After treated with glutamine, HBMECs showed increased proliferation, migration, and endothelial-mesenchymal transition (EndMT) which was reversed by ITGB4 knockdown. In ITGB4-transfected HBMECs, MAPK-ERK-TGF-β/BMP pathway was activated and Smad4 knockdown could reverse the EndMT. Atorvastatin alleviated the EndMT by inhibiting Smad2/3 phosphorylation in ITGB4-transfected HBMECs. The upregulated ITGB4 expression was validated in the superficial temporal artery of MMD patients. CONCLUSIONS: High glutamine was independently associated with the risk of stroke in MMD. Glutamine promotes the proliferation, migration, and EndMT by ITGB4 through MAPK-ERK-TGFβ/BMP-Smad pathway. Atorvastatin could alleviate the EndMT by inhibiting Smad2/3 phosphorylation and promoting Smad4 ubiquitination and thus may be a potential drug for MMD patients.