Effects of melatonin on cell viability in NARP cybrids and 143B cells in response to H/RO.

(A) MTT assay. After H/RO (H: 6h, RO: 2h), apoptotic death was noted in NARP cybrids and 143B cells (death ratio: NARP > 143B) (column 2). Adding melatonin 100μm during H/RO significantly reduced NARP-augmented cell death (column 4). (B) Trypan blue exclusion test of cell viability. Addition of 100 μm melatonin during H/RO treatment reduced the percentage of cell death in both 143B and NARP cells (columns 2 and 4). (C) MTT assay. Administering melatonin 100μm during H₂O₂ 5 mM-augmented H/RO improved cell survival in both NARP cybrids and 143B cells (column 4 and 5). (D) Trypan blue exclusion test of cell viability. Addition of melatonin during H/RO treatment reduced the percentage of cell death in 143B and NARP cybrids in response to H₂O₂-augmented H/RO insults (columns 4 and 5). Each value represents the mean ± S.E. of three independent determinations. P-values representing statistically significant differences between NARP and 143B cells upon H/RO; without melatonin and with melatonin during H/RO (both in the groups with and without secondary H₂O₂ stress) are indicated (*). Mln: melatonin.