The effect of hyperglycemia on neurovascular coupling and cerebrovascular patterning in zebrafish

Abstract

Neurovascular coupling (through which local cerebral blood flow changes in response to neural activation are mediated) is impaired in many diseases including diabetes. Current preclinical rodent models of neurovascular coupling rely on invasive surgery and instrumentation, but transgenic zebrafish coupled with advances in imaging techniques allow non-invasive quantification of cerebrovascular anatomy, neural activation, and cerebral vessel haemodynamics. We therefore established a novel non-invasive, non-anaesthetised zebrafish larval model of neurovascular coupling, in which visual stimulus evokes neuronal activation in the optic tectum that is associated with a specific increase in red blood cell speed in tectal blood vessels. We applied this model to the examination of the effect of glucose exposure on cerebrovascular patterning and neurovascular coupling. We found that chronic exposure of zebrafish to glucose impaired tectal blood vessel patterning and neurovascular coupling. The nitric oxide donor sodium nitroprusside rescued all these adverse effects of glucose exposure on cerebrovascular patterning and function. Our results establish the first non-mammalian model of neurovascular coupling, offering the potential to perform more rapid genetic modifications and high-throughput screening than is currently possible using rodents. Furthermore, using this zebrafish model, we reveal a potential strategy to ameliorate the effects of hyperglycemia on cerebrovascular function.

Sodium nitroprusside prevents the detrimental effects of glucose on the neurovascular unit and behaviour in zebrafish

“…Glucose exposure impaired both vascular NO production and vascular mural cell number, which builds on our previous work showing that tectal endothelial patterning is impaired by glucose exposure (Chhabria et al, 2018). These effects were also associated with reduced endothelial klf2a expression, which is known to promote vascular inflammatory gene expression, thrombosis, and atherosclerosis (SenBanerjee et al, 2004a;Lin et al, 2005).…”

“…Previous studies have linked hyperglycemia and pharmacologically induced diabetes to reductions in cerebral blood flow (Dandona et al, 1978;Stevens et al, 2000). A recent study demonstrated rescuing effects of the NO donor, SNP, on hyperglycemia induced neurovascular uncoupling (Chhabria et al, 2018). Using the same protocol as described in (Chhabria et al, 2018) to induce hyperglycemia in larval zebrafish, we have now described multiple effects of hyperglycemia on cellular markers of the NVU, essential for regulation of CBF and on zebrafish behaviour.…”

“…Glucose, mannitol and SNP (Sigma) were prepared in E3 medium to final concentrations of 20mM (glucose and mannitol) or 0.1mM SNP (Chhabria et al, 2018). Zebrafish larvae for in vivo imaging or immunostaining were incubated in E3 medium containing glucose/mannitol from 4-9 days post fertilization (dpf) and SNP from 8-9 dpf (Chhabria et al, 2018).…”

“…Acquired 3D image stacks were converted to 2D maximum intensity projections and the tectal vasculature was segmented out. Tectal vascular length was extracted (Chhabria et al, 2018).…”

“…We recently established a novel zebrafish larval model of NVC in which incubation of larvae in 20mM glucose impaired NVC. We found the NO donor sodium nitroprusside (SNP) rescued this effect (Chhabria et al, 2018) although the mechanism for this is unclear. We therefore wish to better understand the mechanism and consequences of NVU dysfunction induced by glucose.…”