Essential Amino Acid Starvation-Induced Oxidative Stress Causes DNA Damage and Apoptosis in Murine Osteoblast-like Cells.

Intracellular nutrient metabolism, particularly the metabolism of essential amino acids (EAAs), is crucial for cellular functions, including energy production and redox homeostasis. An EAA deficiency can lead to cellular dysfunction and oxidative stress. This study explores the mechanisms underlying cellular responses to EAA starvation, focusing on ROS-induced DNA damage and apoptosis. MC3T3-E1 cells were subjected to EAA starvation, and various assays were conducted to assess cell proliferation, survival, DNA damage, and apoptosis. The antioxidant N-acetylcysteine (NAC) was employed to block ROS formation and mitigate cellular damage. Gene expression and Western blot analyses were performed to elucidate molecular pathways. EAA starvation-induced ROS generation, DNA damage, and apoptosis in MC3T3-E1 cells. NAC administration effectively reduced DNA damage and apoptosis, highlighting the pivotal role of ROS in mediating these cellular responses during EAA deficiency. This study demonstrates that EAA starvation triggers ROS-mediated DNA damage and apoptosis, offering insights into the intricate interplay between nutrient deficiency, oxidative stress, and programmed cell death. NAC emerges as a potential therapeutic intervention to counteract these adverse effects.

Photodynamic reactions using high-intensity red LED promotes gingival wound healing by ROS induction.

Photodynamic therapy is a treatment that combines a light source with a photosensitizer. LEDs have attracted considerable attention in clinical dentistry because they are inexpensive and safe to use. Although the interaction between photosensitizers and LEDs in dental practice is effective for treating periodontal disease by killing periodontopathic bacteria, little is known about the effects of LEDs on human gingival fibroblasts (HGnFs), which play an important role in gingival wound healing. In this study, we investigated the effects of high-intensity red LED irradiation on HGnFs after the addition of methylene blue (MB), one of the least harmful photosensitizers, on wound healing and reactive oxygen species (ROS) production induced by photodynamic reactions. We found that irradiation of MB with high-intensity red LED at controlled energy levels promoted cell proliferation, migration, and production of wound healing factors. Furthermore, ROS production by a photodynamic reaction enabled the translocation of phosphorylated Grb2-associated binder-1, activating Extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase signals. Our findings suggest that proper control of ROS production has a beneficial effect on gingival fibroblasts, which constitute periodontal tissue, from the perspective of gingival wound healing.

Glucose Starvation-Caused Oxidative Stress Induces Inflammation and Autophagy in Human Gingival Fibroblasts.

Gingival tissue experiences an environment of nutrient shortage, such as low glucose conditions, after periodontal surgery. Our previous studies found that this low glucose condition inhibits normal gingival cell functions. However, the mechanism by which this glucose-deficient environment causes cellular damage to human gingival fibroblasts (HGnFs) remains unclear. This study aimed to investigate the biological effects of ROS induction on HGnFs under low glucose conditions. ROS levels and cellular anti-ROS ability of HGnFs under different glucose concentrations were evaluated by measuring ROS formation and the expression of superoxide dismutase and heme oxygenase 1. Changes in cellular viability were investigated using 5-bromo-2'-deoxyuridine assay and cell survival detection, and the cellular damage was evaluated by the expression of inflammatory cytokines and changes in the expression of autophagy-related protein. ROS formation was then blocked using N-acetyl-L-cysteine (NAC), and the effects of ROS on HGnFs under low glucose conditions were investigated. Low glucose conditions induced ROS accumulation, reduced cellular activity, and induced inflammation and autophagy. After NAC application, the anti-ROS capacity increased, cellular activity improved, and inflammation and autophagy were controlled. This can be effectively controlled by the application of antioxidants such as NAC.

High-Intensity Red Light-Emitting Diode Irradiation Suppresses the Inflammatory Response of Human Periodontal Ligament Stem Cells by Promoting Intracellular ATP Synthesis.

Periodontitis is an inflammatory lesion in the periodontal tissue. The behavior of human periodontal ligament stem cells (hPDLSCs), which play an important role in periodontal tissue regeneration, is restricted by the influence of inflammatory mediators. Photobiomodulation therapy exerts anti-inflammatory effects. The purpose of this study was to investigate the effects of light-emitting diode (LED) irradiation on the inflammatory responses of hPDLSCs. The light source was a red LED (peak wavelength: 650 nm), and the total absolute irradiance was 400 mW/cm2. The inflammatory response in hPDLSCs is induced by tumor necrosis factor (TNF)-α. Adenosine triphosphate (ATP) levels and pro-inflammatory cytokine (interleukin [IL]-6 and IL-8) production were measured 24 h after LED irradiation, and the effects of potassium cyanide (KCN) were investigated. LED irradiation at 6 J/cm2 significantly increased the ATP levels and reduced TNF-α-induced IL-6 and IL-8 production. Furthermore, the inhibitory effect of LED irradiation on the production of pro-inflammatory cytokines was inhibited by KCN treatment. The results of this study showed that high-intensity red LED irradiation suppressed the TNF-α-stimulated pro-inflammatory cytokine production in hPDLSCs by promoting ATP synthesis. These results suggest that high-intensity red LED is a useful tool for periodontal tissue regeneration in chronically inflamed tissues.