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

Involvement of oxidative stress in orofacial mechanical pain hypersensitivity following neonatal maternal separation in rats

Patients with persistent pain have sometimes history of physical abuse or neglect during infancy. However, the pathogenic mechanisms underlying orofacial pain hypersensitivity associated with early-life stress remain unclear. The present study focused on oxidative stress and investigated its role in pain hypersensitivity in adulthood following early-life stress. To establish an early-life stress model, neonatal pups were separated with their mother in isolated cages for 2 weeks. The mechanical head-withdrawal threshold (MHWT) in the whisker pad skin of rats received maternal separation (MS) was lower than that of non-MS rats at postnatal week 7. In MS rats, the expression of 8-hydroxy-deoxyguanosine, a marker of DNA oxidative damage, was enhanced, and plasma antioxidant capacity, but not mitochondrial complex I activity, decreased compared with that in non-MS rats. Reactive oxygen species (ROS) inactivation and ROS-sensitive transient receptor potential ankyrin 1 (TRPA1) antagonism in the whisker pad skin at week 7 suppressed the decrease of MHWT. Corticosterone levels on day 14 increased in MS rats. Corticosterone receptor antagonism during MS periods suppressed the reduction in antioxidant capacity and MHWT. The findings suggest that early-life stress potentially induces orofacial mechanical pain hypersensitivity via peripheral nociceptor TRPA1 hyperactivation induced by oxidative stress in the orofacial region.

Glucose Improves the Efficacy of Photobiomodulation in Changing ATP and ROS Levels in Mouse Fibroblast Cell Cultures

In this study, we tested the idea that photobiomodulation-the application of red to near infrared light (~λ = 600-1300 nm) to body tissues-is more effective in influencing cell metabolism when glucose is readily available. To this end, we used a mouse fibroblast (L-929) cell culture model and had two sets of conditions: non-stressed (10% FBS (foetal bovine serum)) and stressed (1% FBS), both either with or without glucose. We treated (or not) cells with photobiomodulation using an 810 nm laser at 15 mW/cm2 (~7.2 J/cm2). Our results showed that photobiomodulation was neither cytotoxic nor effective in enhancing measures of cell viability and proliferation, together with protein levels in any of the cell cultures. Photobiomodulation was, however, effective in increasing adenosine triphosphate (ATP) and decreasing reactive oxygen species (ROS) levels and this was-most importantly-only in conditions where glucose was present; corresponding cultures that did not contain glucose did not show these changes. In summary, we found that the benefits of photobiomodulation, in particular in changing ATP and ROS levels, were induced only when there was glucose available. Our findings lay a template for further explorations into the mechanisms of photobiomodulation, together with having considerable experimental and clinical implications.

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.

Essential amino acid starvation induces cell cycle arrest, autophagy, and inhibits osteogenic differentiation in murine osteoblast

This study investigates the effects of essential amino acid (EAA) starvation on murine osteoblasts cells and the underlying mechanisms. We performed and observed the cell proliferation, autophagy, and osteogenic differentiation under deprivation of EAA in vitro. The results showed that EAA starvation resulted in cell cycle arrest via phosphorylation of the MAPK signaling pathway, leading to inhibition of cell proliferation and osteogenic differentiation. Additionally, the LKB1-AMPK signaling pathway was also found to be phosphorylated, inducing autophagy. These findings highlight the significant role of EAA in regulating cellular processes. Furthermore, this study contributes to our understanding of the effects of nutrient deprivation on cellular physiology and may aid in the development of novel therapeutic strategies for diseases associated with amino acid metabolism.

SIRT3/GLUT4 signaling activation by metformin protect against cisplatin-induced ototoxicity in vitro

Cisplatin is highly effective for killing tumor cells. However, as one of its side effects, ototoxicity limits the clinical application of cisplatin. The mechanisms of cisplatin-induced ototoxicity have not been fully clarified yet. SIRT3 is a deacetylated protein mainly located in mitochondria, which regulates a variety of physiological processes in cells. The role of SIRT3 in cisplatin-induced hair cell injury has not been founded. In this study, primary cultured cochlear explants exposed to 5 μM cisplatin, as well as OC-1 cells exposed to 10 μM cisplatin, were used to establish models of cisplatin-induced ototoxicity in vitro. We found that when combined with cisplatin, metformin (75 μM) significantly up-regulated the expression of SIRT3 and alleviated cisplatin-induced apoptosis of hair cells. We regulated the expression of SIRT3 to explore the role of SIRT3 in cisplatin-induced auditory hair cell injury. Overexpression of SIRT3 promoted the survival of auditory hair cells and alleviated the apoptosis of auditory hair cells. In contrast, knockdown of SIRT3 impaired the protective effect of metformin and exacerbated cisplatin injury. In addition, we found that the protective effect of SIRT3 may be achieved by regulating GLUT4 translocation and rescuing impaired glucose uptake caused by cisplatin. Our study confirmed that upregulation of SIRT3 may antagonize cisplatin-induced ototoxicity, and provided a new perspective for the study of cisplatin-induced ototoxicity.