Phenylbutyric Acid Modulates Apoptosis and ER Stress-Related Gene Expression in Glycogen Storage Disease Type Ib In Vitro Model.

Introduction: Chronic endoplasmic reticulum (ER) stress and increased apoptosis are involved in the pathogenesis of glycogen storage disease Ib (GSD Ib), whereas small molecule phenylbutyrate (4-PBA) showed the capability of reducing ER stress-induced apoptosis. The objective was to generate an in vitro system in which capability of small molecules (SMs) to influence ER stress and apoptosis could be screened at the expression level.

Methods: G6PT-deficient FlpInHEK293 cell line was created and validated using the CRISPR/Cas9 knockout method. Molecular markers of unfolded protein response (ATF4, DDIT3, HSPA5, XBP1s), and apoptosis (BCL2/BAX, CASP3, CASP7) in G6PT-deficient cells were analyzed using RT-qPCR method before and upon the treatment with 4-PBA.

Results: Treatment with the most effective dose of 1 mM 4-PBA reduced the expression of UPR markers and executioner caspases, while increased BCL2/BAX ratio in G6PT-deficient cells. Our results proved the concept that 4-PBA could alleviate markers of ER stress detected in the GSD Ib in vitro model system and prevent cell death.

Conclusion: This cost-effective in vitro model screens the therapeutic potential of SMs affecting ER stress and apoptosis in G6PT-deficient kidney cells, offering a first-line screening assay for promising compounds. 4-PBA's potential repurposing for GSD Ib patients opens new research directions.