Fig. 2. Caffeine blocks SREBP2 activation in hepatocytes.

A The effect of caffeine (CF; 200 µM) on SREBP2 and SREBP1 mRNA expression was examined in primary mouse hepatocytes (PMH) in the presence and absence of thapsigargin (TG; 100 nM), an established activator of SREBPs. The downstream product of SREBP2 transcriptional activity, HMGR, was also examined. B, C The inhibitory effect of CF on SREBP2 was also examined in primary human hepatocytes (PHH) and HepG2 cells. D CF-mediated SREBP1 inhibition was also examined in PMH (*p < 0.05). E–G HuH7 cells were transfected with a reporter construct encoding a sterol-regulatory element-driven green fluorescent protein (SRE-GFP; green color). Cells were subsequently treated with CF (200 µM) and/or TG (100 nM) 24 h later. GFP and nuclear (n)SREBP2 expression were examined via immunoblot analysis. GFP expression was also assessed via immunofluorescent staining, which was quantified using ImageJ. H The cellular localization of SREBP2 (green color) in CF- and TG-treated HuH7 cells was also examined via immunofluorescent staining. Nuclei containing activated SREBP2 are indicated by white arrows. For all data in this figure, n = 5 biologically independent samples per group; data presented are mean ± s.d). Scale bars; G 100 µm; H 20 µm. Statistical comparisons between two groups were conducted using unpaired two-tailed Student’s t-tests, while comparisons between multiple groups were compared using one-way ANOVAs with the Tukey HSD post-hoc test (*p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001). Source data are provided as a Source Data file.