Iterative exposure of clonal BRIN-BD11 cells to ninhydrin enables selection of robust toxin-resistant cells but with decreased gene expression of insulin secretory function

Objectives: Prevention of pancreatic beta-cell destruction combined with preservation of insulin secretory function is an important goal for cell-based diabetes therapy. This study describes the generation and characteristics of toxin-resistant beta-cells. Methods: By using iterative exposures to ninhydrin, a new class of robust ninhydrin-tolerant insulin-secreting BRIN-BD11 ninhydrin-tolerant (BRINnt) cells was generated. Low- and high-passage BRINnt cells were used to evaluate beta-cell function and tolerance against toxins in comparison with native BRIN-BD11 cells. Differences in viability, gene expression, insulin secretory function, antioxidant enzyme activity, DNA damage, and DNA repair efficiency were compared. Results: BRIN-BD11 ninhydrin-tolerant cells exhibited resistance toward ninhydrin and hydrogen peroxide but not streptozotocin (STZ). Both total superoxide dismutase (SOD) and catalase enzyme activities of BRINnt cells were significantly enhanced, and ninhydrin-induced DNA damage was decreased. BRIN-BD11 ninhydrin-tolerant cells also exhibited enhanced DNA repair efficiency. However, this was accompanied by loss of secretagogue-induced insulin release, decreased cellular insulin content, and deficits in insulin and glucose transporter 2 gene expression. Prolonged culture of BRINnt cells in the absence of ninhydrin reversed the degenerated function of BRINnt cells but restored ninhydrin susceptibility. Conclusions: These data illustrate dissociation between beta-cell toxin resistance and secretory function, indicating difficulties in generation of robust and well-functioning cells using this approach.