Figure 4.

Bilirubin suppresses senescence and mitochondrial dysfunction in cultured primary fibroblasts. Rat primary fibroblasts were cultured for 18 passages in complete media with added bilirubin and then assayed for (a) senescence-associated β-galactosidase staining identified with inverted microscope; (b) whole cell respiration measured with respirometry; (c) mitochondrial DNA copy number per cell as a marker of mitochondrial abundance; (d) cellular production of H₂O₂ as a marker of ROS homeostasis; (e) lactate secretion to media as a marker of mitochondrial dysfunction; (f) intracellular ratio of 2-hydroxyglutarate/2-oxoglutarate as a marker of mitochondrial dysfunction. Data in panels (a, d, e, and f) expressed as % of controls, n = 4–8, overall significance measured with ANOVA, and p < 0.05 in each panel; pairwise comparison with t-test or Mann-Whitney rank sum test; ^∗significantly different from 0 μM; p < 0.05.