The in vitro Effect of the Neuroinflammation Inducer on Brain Neurovascular Unit Components

A close relationship between the brain capillaries and the functional load of neurons and glial cells allows considering them as a single structural and functional complex, a neurovascular unit (NVU). The effects of lipopolysaccharide (LPS, 5-30 mu g/mL, 24h) on nitric oxide (NO) production and of menadione (5-50 mu M, 24 h) on cell viability in cultures of granule neurons, cerebrovascular endothelial cells and astrocytes, as well as the state of mitochondria (Mt) in different NVU cell types, were assessed. It was found that the application of 5 mu g/mL of LPS caused an intense NO production in cell cultures. The largest effect was shown for astrocytes, in which LPS caused a significant increase in NO production by more than 8-fold. In cultures of granule neurons, this exposure caused an almost 5-fold increase in NO production. The weakest response to the stimulation of NO production was shown for endotheliocytes, 1.7-fold. To induce oxidative damage, menadione was introduced into a culture medium. In neuronal cultures, 10 mu M of menadione was already enough to cause complete death of granule neurons. Damage to endotheliocytes and astrocytes was only observed when the menadione concentration increased up to 50 mu M. Since menadione-induced oxidative stress is mediated by mitochondria, the state of the Mt was assessed in intact cells. In astrocytes and endotheliocytes, Mt were numerous and represented long curved strands, whereas in granule neurons, these organelles are much smaller in size and have a rounded shape. Thus, in the NVU, astrocytes are the main NO producers during neuroinflammation, while neurons are the most sensitive to oxidative stress despite relatively poor development of the mitochondrial network; cerebrovascular endothelial cells demonstrated a minimum contribution to NO production.

Automated summary

There is a close relationship between brain capillaries and neurons and glial cells, forming a neurovascular unit. The study found that astrocytes are the main producers of nitric oxide during neuroinflammation, while neurons are the most sensitive to oxidative stress.