Abstract T MP109: Tocotrienol Induces TIMP1 Expression and Pro-arteriogenic Remodeling of Cerebrovascular Collaterals

Abstract

Introduction: Tocotrienols (TCT), lesser-known vitamin E family members, improve perfusion to brain tissue and attenuate stroke injury. Mechanisms underlying TCT improvement of collateral perfusion during ischemic stroke, however, remain unclear. Arteriogenesis is defined by the growth of functional collaterals in brain tissue where tissue inhibitor of metalloproteinase-1 (TIMP1) is believed to play a key role in extracellular matrix remodeling. Objective/Hypothesis: We tested the effect of prophylactic TCT on arteriogenesis by measuring collateral diameter and quantity in stroke-affected brain. Gene and protein expression of TIMP1 was queried in isolated collaterals as a key regulator of arteriogenesis. We hypothesize that TCT increases collateral size and number, and induces TIMP1 expression in collaterals of stroke-affected brain. Methods: C57/BL6 mice (male, 5 wks) were orally gavaged daily with 50mg/kg body weight of TCT or volume matched placebo (n=12) for 10 wks prior to middle cerebral artery occlusion (MCAO). During MCAO, cerebral perfusion was monitored using laser speckle flowmetry. While ischemia persisted, mice were perfused with FITC-conjugated lectin to identify patent collaterals in the MCA territory of the stroke-affected hemisphere. Collaterals size (diameter) and number were quantified as CD31+/FITC-lectin+ arterioles in stroke-affected S1 cortex and collected by laser capture microdissection. TIMP1 gene and protein expression in laser-captured collaterals was determined by RT-PCR and Western blot. Results: Compared to placebo, TCT treatment significantly increased perfusion (38.7%, p<0.05), collateral size (21.2%, p<0.05), and collateral number (5.7-fold, p<0.05) during MCAO. Prophylactic TCT supplementation significantly induced TIMP1 expression 9.6-fold (p<0.05) in laser-captured collaterals as compared to placebo controls. Conclusions: TCT induced expression of TIMP1 in brain collaterals and enabled arteriogenic remodeling for functional collateral growth and protection against ischemic stroke. As TCT is a safe, natural nutrient, proposal outcomes may quickly translate toward clinical applications for high-risk stroke patients, such as those who suffer a transient ischemic attack (TIA).