ALA-PDT promotes IL-1 secretion from human SZ95 sebocytes via activation of the NLRP3 inflammasome

Background: 5-Aminolevulinic acid photodynamic therapy (ALA-PDT) is an effective treatment for pilosebaceous inflammatory diseases, such as acne vulgaris. In this study, we explored ALA-PDT's mechanisms against acne in vitro. Methods: We treated human SZ95 sebocytes with ALA (0.2 mM) and subjected them to varied PDT doses (0, 5, 10, 20 J/cm2) over 12 h. We assessed cell viability post-treatment using the Annexin V FITC/PI apoptosis kit. ROS accumulation in the sebocytes was detected with a DCFDA probe. We quantified NLRP3 and caspase-1 mRNA via quantitative PCR and determined IL-1 beta release following ALA-PDT by ELISA. Western blotting helped identify the levels of proteins associated with pyroptosis (NLRP3, caspase-1, and IL-1 beta). To elucidate the mechanisms, we re-evaluated these parameters after administering various concentrations of NAC antioxidants (0, 0.4, 2, 10 mM) and the caspase inhibitor Z-VAD-FMK (0, 5, 10, 20 mu M). Results: Increasing PDT dose inversely affected SZ95 sebocyte survival, with a corresponding rise in ROS and pyroptosis-related proteins (NLRP3, caspase-1, and IL-1 beta). Furthermore, NAC and Z-VAD-FMK modulated the expression and secretion of these molecules in a dose-responsive manner. Conclusion: Our findings suggest ALA-PDT's potential mechanism of action on sebaceous glands could involve ROS induction, leading to NLRP3 inflammasome assembly, thereby heightening caspase-1 activation and IL-1 beta secretion. This cascade may amplify the local inflammatory response to break chronic inflammation in acne vulgaris treatment.