Figure 2.

Hypothetical schematic of therapeutic effects of hydrogen for COVID-19. When the SARS-CoV-2 invades the bronchus, the immune defense response is activated, immune cells, such as monocytes and lymphocytes, infiltrate into the alveoli from small vessels, they secrete excessive cytokines IL-6, TNF-α, etc., resulting in cytokine storms and alveolar epithelial cell damage. After hydrogen administration, on the one hand, inflammation can be suppressed by inhibiting NF-κB transcription to reduce activated immune cells, especially macrophages. On the other hand, hydrogen entering alveolar epithelial cells buffers oxidative stress or regulates Nrf2 transcription and inhibits apoptosis. Furthermore, hydrogen can improve dyspnea by inhibiting the secretion of mucus in bronchiole and assisting oxygen diffusion.