CAT and major depressive disorder: ↑ Nrf2, Keap1, NF-κB, MnSOD, CuZnSOD, and CAT in MDD vs. HC in PBMC cytoplasm; ≈GPx and GLR between MDD and HC, but ↓GLR/GPx in MDD; MnSOD, CuZnSOD, and CAT levels correlated directly with Nrf2 levels, while MnSOD and CuZnSOD correlated with NF-κB levels