Effect of butyrate, a bacterial by‐product, on the viability and ICAM‐1 expression/production of human vascular endothelial cells: Role in infectious pulpal/periapical diseases

Aim To investigate the effects of butyric acid (BA), a metabolic product generated by pulp and root canal pathogens, on the viability and intercellular adhesion molecule‐1 (ICAM‐1) production of endothelial cells, which are crucial to angiogenesis and pulpal/periapical wound healing. Methodology Endothelial cells were exposed to butyrate with/without inhibitors. Cell viability, apoptosis and reactive oxygen species (ROS) were evaluated using an MTT assay, PI/annexin V and DCF fluorescence flow cytometry respectively. RNA and protein expression was determined using a polymerase chain reaction assay and Western blotting or immunofluorescent staining. Soluble ICAM‐1 (sICAM‐1) was measured using an enzyme‐linked immunosorbent assay. The quantitative results were expressed as mean ± standard error (SE) of the mean. The data were analysed using a paired Student's t‐test where necessary. A p‐value ≤0.05 was considered to indicate a statistically significant difference between groups. Results Butyrate (>4 mM) inhibited cell viability and induced cellular apoptosis and necrosis. It inhibited cyclin B1 but stimulated p21 and p27 expression. Butyrate stimulated ROS production and hemeoxygenase‐1 (HO‐1) expression as well as activated the Ac‐H3, p‐ATM, p‐ATR, p‐Chk1, p‐Chk2, p‐p38 and p‐Akt expression of endothelial cells. Butyrate stimulated ICAM‐1 mRNA/protein expression and significant sICAM‐1 production (p