Thapsigargin-induced autophagic flux impairment and inflammation are potentiated by CLN3 deficiency and alleviated by 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) in human ARPE-19 cells

Juvenile neuronal lipofuscinosis (JNCL) is a rare disease caused by mutations in the CLN3 gene. It leads to early vision loss mediated by retinal degeneration. Impaired autophagosomal-lysosomal degradation is a major hallmark of JNCL pathology, and neuroinflammation has also been postulated to play a role in its pathogenesis. Thapsigargin, a selective inhibitor of sarco/endoplasmic reticulum Ca 2+ -ATPase, inhibits autophagy, leading to an accumulation of autophagosomes/autophagophores in cells. Cells with defective CLN3 protein function have been found to be particularly sensitive to the anti-autophagic effects of thapsigargin. Here, we characterized the effects of thapsigargin on inflammatory cytokines and autophagic markers in ARPE-19 cells using ELISA and western blotting. We further examined these effects in cells deficient in CLN3 function by exposing the cells to CLN3 siRNA and testing whether the effects of thapsigargin could be modulated by the well-known autophagy activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR). Thapsigargin induced the accumulation of LC3 and p62/SQSTM1, consistent with impaired autophagic flux in ARPE-19 cells. Additionally, we observed that thapsigargin possessed pro-inflammatory potential, as it induced the release of IL-6 in ARPE-19 cells, no inflammasome activation was detected. Both effects were enhanced by CLN3 siRNA and alleviated by AICAR. In conclusion, thapsigargin-induced impaired autophagic flux and the accompanying inflammatory response are more pronounced in CLN3-deficient ARPE-19 cells, indicating that loss of CLN3 function affects both autophagy and inflammatory signaling.