Lipopolysaccharides and hydrogen peroxide induce contrasting pathological conditions in dental pulpal cells

Aim To determine the effects of lipopolysaccharides (LPS), hydrogen peroxide (H2O2), and both combined on cell proliferation/differentiation, inflammation, mitochondrial dynamics as indicated by mitochondrial fission/fusion, antioxidants as indicated by superoxide dismutase 2 (SOD2), and apoptosis of human dental pulpal cells (HDPCs). Methodology Pulpal tissues from eight healthy subjects (n = 8) were collected from Faculty of Dentistry, Chiang Mai University. Isolated HDPCs from healthy donors were divided into four experimental groups: vehicle, 20 mu g/ml LPS, 400 mu M H2O2, and the two combined. All experimental groups were investigated to assess cell proliferation, mineralization, differentiation, inflammation, mitochondrial dynamics, antioxidants, and apoptosis. Results H2O2 and combined agents decreased cell proliferation of HDPCs equally. LPS, H2O2, and both combined decreased mineralization and differentiation with an increase in tumour necrosis factor-alpha (TNF-alpha) levels. Surprisingly, LPS and combined agents increased SOD2 expression and caused an imbalance in mitochondrial dynamics. A significant increase in apoptosis was observed in the case of H2O2 and combined agents. Conclusions These findings suggest that LPS induced inflammation, imbalanced mitochondrial dynamics, and reduced cell differentiation without altering apoptosis and cell proliferation. However, H2O2 decreased cell proliferation, and differentiation, and increased inflammation, and apoptosis without interfering with mitochondrial dynamics. Based on our findings, combining LPS and H2O2 could be potentially used as the inducers in in vitro study to mimic the clinical pulpitis.