Sariipek, N. E. | Search bioRxiv

bioRxiv2020

Vasa vasorum lumen narrowing in brain vascular hyalinosis in systemic hypertension patients with ischemic stroke

Ischemic stroke is a major cause of death among patients with systemic hypertension. The narrowing of the lumen of the brain vasculature contributes to the increased incidence of stroke. While hyalinosis represents the major pathological lesions contributing to the vascular lumen narrowing and stroke, the pathogenic mechanism of brain vascular hyalinosis has not been well characterized. Thus, the present study examined the postmortem brain vasculature of human patients who died of ischemic stroke due to systemic hypertension. Hematoxylin and eosin staining and immunohistochemistry showed the occurrence of brain vascular hyalinosis with infiltrated plasma proteins along with the narrowing of vasa vasorum and oxidative stress. Transmission electron microscopy revealed the endothelial cell bulge protrusion into the vasa vasorum lumen and the occurrence of endocytosis in the vasa vasorum endothelium. The treatment of cultured microvascular endothelial cells with adrenaline also promoted the formation of the bulge as well as endocytic vesicles. siRNA knockdown of sortin nexin-9 (a mediator of clathrin-mediated endocytosis) inhibited the adrenaline-induced endothelial cell bulge formation. Adrenaline promoted protein-protein interactions between sortin nexin-9 and neural Wiskott-Aldrich Syndrome protein (a regulator of actin polymerization). We propose that endocytosis-depending endothelial cell bulge narrows the vasa vasorum, resulting in ischemic oxidative damage to the cerebral vessels, the formation of hyalinosis, the occurrence of ischemic stroke, and death in systemic hypertension patients.

pathology↗

bioRxiv2020

Tau protein in smooth muscle cells and tissues

Tau is a microtubule-associated protein and plays a critical role in the pathophysiology of neurons. However, whether tau protein is expressed in smooth muscle cells is unknown. Here, we report that tau protein is expressed and is constitutively phosphorylated at threonine 181 in various smooth muscle cell types, including human cerebral artery smooth muscle cells, human pulmonary artery smooth muscle cells, and human bronchial airway smooth muscle cells. We also detected the expression of tau protein in the vascular smooth muscle of brain tissues from patients with systemic hypertension who died of ischemic stroke. Immunofluorescence staining revealed that phosphorylated tau at threonine 181 is more organized in the cell than does total tau protein. A protein phosphatase inhibitor, calyculin A induced the formation of higher molecular weight species of phosphorylated tau as visualized by Western blotting, indicating the occurrence of tau aggregation. Immunofluorescence also showed that calyculin A caused the aggregation of phosphorylated tau and disrupted the cytoskeletal organization. These results demonstrate the existence of tau protein in smooth muscle cells and tissues and that smooth muscle tau is susceptible to protein phosphorylation and aggregation.

cell biology↗