Fig. 1. Illustration of the possible biological effects of hydrogen. Hydrogen exerts antioxidant activity by directly neutralizing ·OH, upregulating Nrf2, HO-1, SOD, CAT, and MPO, and scavenging ONOO - ; hydrogen exerts anti-inflammatory activity by inhibiting NF-κB and the pro-inflammatory factors (TNF-α, IL-1β, IL-6, and HMGB-1), inhibiting MIP-1α, MIP-2, G-CSF, and ICAM-1, and increasing the expression of the anti-inflammatory factor IL-10; hydrogen modulates autophagy including Parkin/PINK1-mediated mitophagy, alleviates inflammation and NLRP3-mediated pyroptosis; hydrogen inhibits apoptosis by modulating apoptosis-related proteins and signaling pathways, but it promotes apoptosis in cancer cells; hydrogen has anti-aging effects by reducing oxidative DNA damage, decreasing the expression of the aging-related proteins β-galactosidase, p53, and p21, and upregulating Sirt3 expression. + refers to activate; - refers to inhibit. RNS: reactive nitrogen species; ROS: reactive oxygen species; NF-κB: nuclear factor-κB; JNK: c-Jun N-terminal kinase; ·OH: hydroxyl free radical; ONOO - : peroxynitrite anion; HO-1: heme oxygenase-1; SOD: superoxide dismutase; CAT: catalase; MPO: myeloperoxidase; NLRP3: nucleotide-binding domain and leucine-rich repeat protein 3; PINK: phosphatase and tensin homolog (PTEN)-induced kinase; TNF-α: tumor necrosis factor-α; G-CSF: granulocyte colony-stimulating factor; ICAM-1: intercellular cell adhesion molecule-1; IL: interleukin; HMGB-1: high-mobility group box 1; MIP: macrophage inflammatory protein; Sirt3: sirtuins 3; Nrf2: nuclear factor erythroid 2-related factor 2.
