Objective   To investigate the regulatory function and mechanism of β-hydroxybutyrate (β-OHB), a ketone body, on the mitochondrial oxidative stress of inflammatory human umbilical vein endothelial cells (HUVECs).

  Methods   Lipopolysaccharide (LPS) and adenosine triphosphate (ATP) were used to induce macrophages to release proinflammatory factors, and the culture supernatant was collected as a macrophage-conditioned medium (MCM) to culture HUVECs. A total of 7 groups of cells were used in the study: ①control group, or normal cultured HUVECs; ②MCM group, or the MCM-cultured HUVECs; groups ③ to ⑦ were all HUVECs co-cultured with different reagents, including ③MCM+β-OHB group, ④MCM+N-acetylcysteine (NAC) group, ⑤MCM+β-OHB+NAC group, ⑥MCM+β-OHB+histone deacetylase agonist ITSA1 group, and ⑦MCM+β-OHB+histone deacetylase inhibitor Entinostat group. MitoSOX immunofluorescence staining was conducted to analyzes the mitochondrial superoxide levels, real-time fluorescent quantitative polymerase chain reaction (RT-qPCR) was performed to examine the mRNA expression of antioxidant genes, and Seahorse mitochondrial energy analyzer was used to measure mitochondrial aerobic respiration capacity.

  Results   Compared with the control group, mitochondrial superoxide production was significantly increased in the MCM cultured HUVECs cells, while β-OHB treatment significantly inhibited mitochondrial superoxide production, which was accompanied by an increase in the mRNA expression of antioxidant genes, and significant increase in the basal mitochondrial oxygen consumption rate and respiratory reserve capacity. NAC treatment did not further enhance the protective effect of β-OHB on mitochondrial functions. In addition, ITSA1 treatment could completely offset the antioxidant and mitochondrial protective effects of β-OHB, and these stated effects were still maintained after Entinostat treatment.

  Conclusion   The ketone body β-OHB attenuates the mitochondrial oxidative stress of vascular endothelial cells through activating the antioxidant pathway and inhibiting histone deacetylase activity.