Background: Cystitis glandularis (CG) is a proliferative lesion of the bladder mucosa, and the incidence rate of CG has increased year by year. Considering the potential function of β-sitosterol in CG, we aim to fathom its effect and mechanism of CG.

Methods: Primary human cells isolated from CG patients and following transfection as needed, were treated with different concentrations of β-sitosterol. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and transwell assay was used to test the cell migration. Meanwhile, co-immunoprecipitation was employed to evaluate the interaction between 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and NLR family pyrin domain containing 3 (NLRP3). Additionally, pyroptosis-associated proteins and HMGCR expressions were tested using western blot or quantitative real-time reverse transcription polymerase chain reaction.

Results: β-sitosterol suppressed cell viability and migration, enhanced cell pyroptosis, and upregulated expressions of NLRP3, Cleaved Caspase-1, interleukin-1β (IL-1β), gasdermin D-N-terminal domain (GSDMD-N), and HMGCR in CG primary cells (p < 0.05). HMGCR silencing promoted cell viability and migration, inhibited cell pyroptosis, and downregulated expressions of NLRP3, Cleaved Caspase-1, IL-1β, and GSDMD-N in β-sitosterol-affected CG primary cells (p < 0.05). HMGCR interacted with NLRP3.

Conclusions: β-sitosterol alleviates the proliferation and migration of CG-associated cells by targeting HMGCR to induce NLRP3-dependent pyroptosis. These findings confirmed the therapeutic effect of β-sitosterol on treating CG.