Modified versions of a compound already used in Gaucher disease research are more selective and potent blockers of the key beta-glucosidase (GBA) enzyme and can be used to create superior Gaucher models in zebra fish, according to a study.
The study, “Functionalized Cyclophellitols Are Selective Glucocerebrosidase Inhibitors and Induce a Bona Fide Neuropathic Gaucher Model in Zebrafish,” appeared in the Journal of the American Chemical Society.
Prior animal models of Gaucher have been hampered by lack of selectivity of the compounds used to block GBA, the enzyme whose inherited deficiency causes this disease, and by a narrow and variable therapeutic window.
However, a research team from the Netherlands and the U.K. had shown that derivatives of one of these compounds, called cyclophellitol, are potent and have high selectivity for monitoring GBA activity. In particular, introducing a specific chemical group at the C8 carbon atom of cyclophellitol led to a more efficient and specific inactivation of GBA but not the related enzyme, GBA2.
The investigators generated a GBA-deficient zebra fish model using this approach. They first designed two compounds — biphenyl-cyclophellitol and adamantyl-cyclophellitol, both derivatives of cyclophellitol — based on data from previous studies in a bacterial enzyme similar to human GBA2.
In both cases, a hydrophobic part — meaning that it does not interact with water and does not have an electrical charge — was bound to an also hydrophobic pocket in cyclophellitol.
Researchers found that both compounds were able to inhibit a human form of GBA with a 4,000 times greater potency than conduritol B epoxide (CBE), a compound close in structure to cyclophellitol and previously used to generate models of Gaucher.
Biphenyl-cyclophellitol and adamantyl-cyclophellitol were 4,000 times and 200 times more selective than CBE, respectively. In addition, neither compound was active toward GBA2 and alpha-glucosidase, or GAA.
Experiments in zebra fish embryos again confirmed the higher potency and selectivity of either compound compared with that of CBE and two other cyclophellitol derivatives. They increased the amount of glucosylsphingosine, the fat molecule that builds up in Gaucher, at much lower concentrations (1,000–10,000 times lower) than with CBE.
Then, the researchers found that adamantyl-cyclophellitol selectively blocked GBA in the liver, spleen, and brain of adult zebra fish after being delivered in the food.
According to the researchers, adamantyl-cyclophellitol outperforms the other compounds in inducing GBA deficiency in zebra fish. Its activity in the brain makes it a suitable candidate “to create zebrafish models for neuropathic Gaucher.”