The Protective Effect And Mechanism Of Agmatine On Blood-brain Barrier Permeability In Diabetic Cerebral Ischemic

Preface Ischemic stroke is a leading cause of death and disability, which accounts for 80% of the world strokes.Diabetes is an important risk factor for ischemic stroke. Diabetes augments the response of inflammation and oxidative stress, which is induced by the ischemia-reperfusion. AQP-4 mainly expresses in the brain, and is closely associated with cerebral edema induced by cerebral ischemia. Some reports confirmed that in the edematous rodent brain, the expressions of AQP-4 and AQP-9 were shown to be markedly enhanced succeeding to the lesion of ischemic?Agmatine, which can be synthesized by the decarboxylation of L-arginine in the mammalian tissues. Recently, agmatine has been known to be a nerve protection material against transient focal cerebral ischemia in rodents.Objective In this study, we use rat model (by middle cerebral artery occlusion, MCAO) and astrocytes model (in vitro oxygen deprivation) to study changes of blood-brain barrier (BBB) permeability and pharmaceutical effect of agmatine in diabetic cerebral ischemic rats.Methods Diabetic rats, generated by feeding high-fat and high-glucose diet followed by streptozocine induction, were subjected to ischemic reperfusion injury. The cerebral edema was examined by dry-wet weight ratios, and BBB permeability was detected by Evans blue dye and the blood glucose was detected.The infarct size was detected by TTC staining and the expression of AQP-4 and AQP-9 was examined through western blot analysis. Also, the ultra-structure of infarction organization was observed with electron microscopy. Culture primary astrocytes and prepare insulin resistance and oxygen deprivation model in vitro. Cell viability was detected by MTT, the expression of AQP-4 and AQP-9 was observed by immunofluorescence double staining. And the expression of AQP-4 and AQP-9 changed after inhibition of PKA and PKC through Western blotting detection.Results The infarct size and edema were reduced in agmatine treated diabetic rats with ischemic injury. Under the electron microscope, the ultrastructures of brain tissues in diabetic rats with ischemic injury were destroyed seriously, but were improved after agmatine treatment. The expression of AQP-4 and AQP-9 in diabetic rats with ischemic injury significantly decreased in agmatine treatment group. Compared with the group without agmatine treatment, the cell viability in insulin resistance and oxygen deprivation group with agmatine treatment got improved. The location of expression of AQP-4 and AQP-9 coincided with astrocyte. After the inhibition of PKA and PKC, the expression of AQP-4 and AQP-9 in astrocytes was reduced. Conclusion Agmatine has a protective effect on the diabetic cerebral ischemia, which maybe related to the reduction of blood glucose and down-regulation of AQP-4 and AQP-9 expression by PKA and PKC.