The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) pathway regulates developmental cerebral-vascular stability via prenylation-dependent signalling pathway

Abstract

Spontaneous intracranial hemorrhage is a debilitating form of stroke, often leading to death or permanent cognitive impairment. Many of the causative genes and the underlying mechanisms implicated in developmental cerebral-vascular malformations are unknown. Recent in vitro and in vivo studies in mice have shown inhibition of the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) pathway to be effective in stabilizing cranial vessels. Using a combination of pharmacological and genetic approaches to specifically inhibit the HMGCR pathway in zebrafish (Danio rerio), we demonstrate a requirement for this metabolic pathway in developmental vascular stability. Here we report that inhibition of HMGCR function perturbs cerebral-vascular stability, resulting in progressive dilation of blood vessels, followed by vessel rupture, mimicking cerebral cavernous malformation (CCM)-like lesions in humans and murine models. The hemorrhages in the brain are rescued by prior exogenous supplementation with geranylgeranyl pyrophosphate (GGPP), a 20-carbon metabolite of the HMGCR pathway, required for the membrane localization and activation of Rho GTPases. Consistent with this observation, morpholino-induced depletion of the β-subunit of geranylgeranyltransferase I (GGTase I), an enzyme that facilitates the post-translational transfer of the GGPP moiety to the C-terminus of Rho family of GTPases, mimics the cerebral hemorrhaging induced by the pharmacological and genetic ablation of HMGCR. In embryos with cerebral hemorrhage, the endothelial-specific expression of cdc42, a Rho GTPase involved in the regulation of vascular permeability, was significantly reduced. Taken together, our data reveal a metabolic contribution to the stabilization of nascent cranial vessels, requiring protein geranylgeranylation acting downstream of the HMGCR pathway.

Disruption of ldlr causes increased LDL-c and vascular lipid accumulation in a zebrafish model of hypercholesterolemia

“…In mammals, HMGCR catalyzes the rate-limiting step in de novo cholesterol synthesis and is targeted and inhibited by statins (52)(53)(54)(55)(56). The zebrafi sh homolog has been identified and mainly explored in the context of its role in migration of cells during development ( 57-61 ), though its potential to mediate cholesterol synthesis has been recently confi rmed ( 62 ). To assess the possibility of LDL-c reduction by statin administration, we treated control or ldlr SB MO embryos, on either diet, with 50 M…”

A Call for Rigorous Study of Statins in Resolution of Cerebral Cavernous Malformation Pathology

“…32,33 Waterborne exposure to statins (atorvastatin and cerivastatin) and morpholino-mediated depletion of embryonic HMGCR transcripts in zebrafish have been shown to induce intracerebral hemorrhage in both embryos and larvae due likely to impaired prenylation-dependent processes. [34][35][36] Surprisingly, though, there exist no experimental or anecdotal studies to suggest statin-induced enhancement of vascular permeability in mice or other mammalian studies, which could suggest species-specific physiological differences. There have also been no studies, to date, to suggest that statins disrupt vascular stability in murine models of aging, hypertensive and amyloid angiopathies.…”

Genetic and Chemical Dissection of BloodBrain Barrier Development in Zebrafish

“…CNS brain hemorrhage in zebrafish after statin treatment has also been reported by other groups and helps validate this hit from our independent screen 150,151 . These groups suggest the brain hemorrhages were due to a modification in protein prenylation.…”

“…While a developmental time course of statin treatment had not been performed in the zebrafish, other groups have previously demonstrated brain hemorrhage induced by statins during the time we were performing our FDA screen 150,151 . These groups suggested hemorrhage was due to inhibition of protein prenylation and absence of Coenzyme Q10.…”