# Circadian misalignment potentiates blood-brain barrier disruption and mitochondria dysregulation in Zika virus infection

## TL;DR

This study shows that disrupted circadian rhythms worsen the effects of Zika virus on the brain's protective barrier and mitochondria.

## Contribution

The novel finding is that circadian misalignment exacerbates Zika virus-induced blood-brain barrier and mitochondrial dysfunction.

## Key findings

- Zika virus infection disrupts blood-brain barrier integrity by affecting tight junction proteins.
- Circadian rhythm disruption, via Bmal1 silencing, worsens Zika virus effects on endothelial cells and mitochondria.
- Bmal1 knockout mice showed reduced expression of key barrier and mitochondrial proteins after ZIKV infection.

## Abstract

Zika virus (ZIKV) is a mosquito-borne Flavivirus with a strong affinity for the central nervous system (CNS). After infection, ZIKV can cross the blood-brain barrier (BBB) and reach the CNS, causing potential harm to both adult and developing brains.

The current study aims to evaluate how dysregulated circadian rhythms can affect brain infection by ZIKV, as biorhythms regulate essential physiological processes and disrupted circadian clock can contribute to the pathogenesis of multiple disorders. Both ZIKV infection and circadian rhythm alterations have been related to the disruption of the BBB integrity by modulating the expression of the tight junction (TJ) proteins, however, the input of circadian misalignment on ZIKV infection has never been studied in the literature.

Infection of brain endothelial cells with ZIKV selectively impacted endothelial permeability and dysregulated the expression of TJ and mitochondrial proteins. Importantly, these effects were potentiated by silencing Bmal1, a critical circadian rhythm gene. These results were then confirmed in vivo in Bmal1 endothelial cell-specific knockout mice, which were infected with ZIKV at 105 PFU (plaque-forming unit) by retro-orbital infusion. ZIKV infection resulted in a marked decrease in claudin-5, occludin, JAM-3, and ZO-1 expression levels in these mice. In addition, ZIKV affected the expression of FIS1 protein levels and the respiratory complexes of II, III, and IV in mice lacking Bmal1 expression in endothelial cells.

Findings from this study contribute to a better understanding of the impact of circadian misalignment on the pathology of ZIKV infection in the adult brain.

Endothelial cells and endothelial cell-specific Bmal1 knock-out mice were subjected to Zika virus infection. Bmal-1 expression deficiency potentiated the severity ZIKV infection and contributed to endothelial barrier dysfunction and dysregulation of mitochondrial proteins.