# Streptozotocin Causes Blood–Brain Barrier and Astrocytic Dysfunction In Vitro

## TL;DR

Streptozotocin (STZ) can damage the blood-brain barrier and astrocytes in lab models, which may explain some of its neurotoxic effects.

## Contribution

This study is the first to show that STZ directly affects brain endothelial cells and astrocytes, leading to blood-brain barrier dysfunction.

## Key findings

- STZ reduces transendothelial electrical resistance and increases albumin leakage in brain endothelial-like cells.
- STZ decreases tight junction proteins and GLUT-1 in brain endothelial-like cells.
- STZ reduces GFAP and cell numbers in astrocytes, indicating toxicity.

## Abstract

Streptozotocin (STZ) is an alkylating agent that has neurotoxic effects when injected into the cerebral ventricles (ICV) and also models many other features of Alzheimer’s disease. However, the mechanisms of STZ neurotoxicity are not well understood. In this study, we hypothesized that some of the neurotoxic effects of STZ could be due to direct activities on brain endothelial cells and astrocytes, which are key in forming and supporting the functions of the blood–brain barrier (BBB), respectively. To test this hypothesis, we characterized the changes induced by STZ either in cultures of human-induced pluripotent stem cell (iPSC)-derived brain endothelial-like cells (iBECs), which form an in vitro BBB model, or in primary human astrocytes. We found that STZ at a dosage of 5 mM caused a delayed reduction in the transendothelial electrical resistance (TEER) of iBECs at 7–11 days post-treatment, indicating induction of BBB leakage. Additionally, we observed significant increases in albumin leakage across the monolayer, altered iBEC morphology, and reductions in tight junction proteins, suggesting that STZ causes BBB disruption. We further found that the BBB glucose transporter GLUT-1 was reduced in iBECs, as was the total number of iBECs. In astrocytes, the 5 mM dose of STZ reduced the GFAP signal and total number of cells, suggesting that STZ has anti-proliferative and/or toxic effects on astrocytes. Together, these data support that STZ’s neurotoxic effects could be due, in part, to its direct toxic activities on brain endothelial cells and astrocytes.