Zinc-chelating BET bromodomain inhibitors equally target islet endocrine cell types

We report the synthesis of a novel, Zn2+-chelating derivative of the pan-BETi (+)-JQ1, (+)-JQ1-DPA, in which (+)-JQ1 was conjugated to dipicolyl amine (DPA). As controls, we synthesized (+)-JQ1-DBA, a non-Zn2+-chelating derivative, and (-)-JQ1-DPA, an inactive enantiomer that chelates Zn2+. Molecular modeling and biophysical assays showed that (+)-JQ1-DPA and (+)-JQ1-DBA retain potent binding to BET bromodomains in vitro. Cellular assays demonstrated (+)-JQ1-DPA attenuated NF-ĸB target gene expression in β-cells stimulated with the pro-inflammatory cytokine interleukin 1β. To assess β-cell selectivity, we isolated islets from a mouse model that expresses green fluorescent protein in insulin-positive β-cells and mTomato in insulin-negative cells (non-β-cells). Surprisingly, Zn2+-chelation did not confer β-cell selectivity as (+)-JQ1-DPA was equally effective in both β- and α-cells; however, (+)-JQ1-DPA was less effective in macrophages, a non-endocrine islet cell type. Intriguingly, the non-Zn2+-chelating derivative (+)-JQ1-DBA displayed the opposite selectivity, with greater effect in macrophages compared to (+)-JQ1-DPA, suggesting potential as a macrophage-targeting molecule. These findings suggest that Zn2+-chelating small molecules confer endocrine cell selectivity rather than β-cell selectivity in pancreatic islets and provide valuable insights and techniques to assess Zn2+-chelation as an approach to selectively target small molecules to pancreatic β-cells.PMI...
Source: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology - Category: Physiology Authors: Source Type: research