Dose–Response Effects of 7-Dehydrocholesterol Reductase Inhibitors on Sterol Profiles and Vesicular Stomatitis Virus Replication

Abstract

Cholesterol is ubiquitous in cells; it plays a critical role in membrane structure and transport as well as in intracellular trafficking processes. There are suggestions that cholesterol metabolism is linked to innate immunity with inhibitors of DHCR7, the last enzyme in the cholesterol pathway, suggested to have potential as viral therapeutics nearly a decade ago. In fact, there are a number of highly prescribed pharmaceuticals that are off-target inhibitors of DHCR7, causing increased cellular levels of 7-dehydrodesmosterol (7-DHD) and 7-dehydrocholesterol (7-DHC). We report here dose–response studies of six such inhibitors on late-stage cholesterol biosynthesis in Neuro2a cells as well as their effect on infection of vesicular stomatitis virus (VSV). Four of the test compounds are FDA-approved drugs (cariprazine, trazodone, metoprolol, and tamoxifen), one (ifenprodil) has been the object of a recent Phase 2b COVID trial, and one (AY9944) is an experimental compound that has seen extensive use as a DHCR7 inhibitor. The three FDA-approved drugs inhibit replication of a GFP-tagged VSV with efficacies that mirror their effect on DHCR7. Ifenprodil and AY9944 have complex inhibitory profiles, acting on both DHCR7 and DHCR14, while tamoxifen does not inhibit DHCR7 and is toxic to Neuro2a at concentrations where it inhibits the Δ7−Δ8 isomerase of the cholesterol pathway. VSV itself affects the sterol profile in Neuro2a cells, showing a dose–response increase of dehydrolathosterol and lathosterol, the substrates for DHCR7, with a corresponding decrease in desmosterol and cholesterol. 7-DHD and 7-DHC are orders of magnitude more vulnerable to free radical chain oxidation than other sterols as well as polyunsaturated fatty esters, and the effect of these sterols on viral infection is likely a reflection of this fact of Nature.

Inhibition of 7-dehydrocholesterol reductase prevents hepatic ferroptosis under an active state of sterol synthesis

“…To exclude the possibility that these enzymes are involved in the suppression of ferroptosis by AY9944, we evaluated accumulation of their substrates, 14-dehydro zymostenol (14DZyme) and zymostenol (Zyme). As reported previously 18 , low dose AY9944 treatment (10–100 nM) selectively increased 7-DHC, whereas high dose AY9944 treatment (300–1000 nM) also increased 14DZyme, a substrate for DHCR14 (Supplementary Fig. 8b and c).…”

Chronic Aripiprazole and Trazodone Polypharmacy Effects on Systemic and Brain Cholesterol Biosynthesis

“…Yet, it appears that in two other conditions and life stages, 7-DHC has beneficial effects. First, inhibiting DHCR7 protects mice from various viral infections [ 65 , 66 ]. Furthermore, ARI at low doses acts as an antimicrobial agent, inhibits biofilm formation, and impedes yeast-to-hyphal transition and flocculation [ 67 ].…”

Lipid Rafts: The Maestros of Normal Brain Development

“… Antiviral drugs: Some antiviral drugs, such as entry inhibitors [ 211 ], target lipid rafts as part of their mechanism of action. Some of those drugs aim to prevent viral entry into host cells by interfering with ACE2 receptors located in lipid rafts [ 212 , 213 ]. 25-hydroxycholesterol has been shown to interfere with cholesterol in the membrane, making the bilayer less rigid and affecting the composition of lipid rafts [ 214 ].…”