A Clinically Applicable Positive Allosteric Modulator of GABA Receptors Promotes Human β-Cell Replication and Survival as well as GABA's Ability to Inhibit Inflammatory T Cells

A major goal of T1D research is to develop new approaches to increase β-cell mass and control autoreactive T cell responses. GABA(A)-receptors (GABA(A)-Rs) are promising drug targets in both those regards due to their abilities to promote β-cell replication and survival, as well as inhibit autoreactive T cell responses. We previously showed that positive allosteric modulators (PAMs) of GABA(A)-Rs could promote rat β-cell line INS-1 and human islet cell replication in vitro. Here, we assessed whether treatment with alprazolam, a widely prescribed GABA(A)-R PAM, could promote β-cell survival and replication in human islets after implantation into NOD/scid mice. We observed that alprazolam treatment significantly reduced human islet cell apoptosis following transplantation and increased β-cell replication in the xenografts. Evidently, the GABA(A)-R PAM works in conjunction with GABA secreted from β-cells to increase β-cell survival and replication. Treatment with both the PAM and GABA further enhanced human β-cell replication. Alprazolam also augmented the ability of suboptimal doses of GABA to inhibit antigen-specific T cell responses in vitro. Thus, combined GABA(A)-R agonist and PAM treatment may help control inflammatory immune responses using reduced drug dosages. Together, these findings suggest that GABA(A)-R PAMs represent a promising drug class for safely modulating islet cells toward beneficial outcomes to help prevent or reverse T1D and, together with a GABA(A)-R agonist, may have broader applications for ameliorating other disorders in which inflammation contributes to the disease process.