Fig. 3

Curcumin down-regulates mtDNA and POLG to inhibit cellular bioenergetics. a & b Effects of curcumin (10 μg/ml) on mtDNA copy number and proteins of the respiration complex in SGC-7901 orBGC-823 cells determined by quantitative real-time PCR and Western blot analysis, respectively; shown is representative blot of the respiration complex proteins with β-actin as loading control; curcumin = cur; c & d Similar Western blot and Q-PCR analyses were made from SGC-7901 or BGC-823 cells with siRNA-mediated POLG (DNA polymerase γ) knockdown; shown is representative Western blot analysis of respiration proteins; Effects of POLG knockdown in BGC-823 cells on mitochondrial respiration as determined by real-time mitochondrial oxygen consumption rate (OCR), n = 6 (e) and aerobic glycolysis as determined by extracellular acidification rate (ECAR), n = 6 (f); arrows indicate sequential injection of respiration complex modifiers as described in Fig. 2. Effects of POLG siRNA-mediated knock-down in BGC-823 cells on g basal and h maximal respiration as determined by mitochondrial OCR, as well as on i ATP production; n = 6. Effects of POLG siRNA-mediated knock-down in BGC-823 cells on j the basal and k spared glycolytic rates, n = 6. l Shown is representative Western blot analysis of POLG in BGC-823 cells treated N-acetylcysteine (NAC; 10 mM for 4 h) alone or combined with curcumin (cur; 10 μg/ml for 24 min), β-actin as loading control. m Effects of NAC (10 mM for 4 h) on the curcumin-induced changes in BGC-823 mitochondrial respiration (OCR), n = 6 and n aerobic glycolysis (ECAR), n = 6; arrows indicate sequential injection of respiration complex modifiers as described Fig. 2. For a, c-k, m-n, data are shown as mean ± SD