Caffeic acid (CA) is a naturally occurring phenolic compound known for its strong antioxidant and cytoprotective properties.Particulate matter (PM) with an aerodynamic diameter of 2.5 μm (PM2.5) or less is a major atmospheric pollutant that induces excessive oxidative stress and apoptosis in human skin cells, contributing to various adverse effects on the skin. In this study, we investigated the protective role of CA against PM2.5-induced cellular injury in human HaCaT keratinocytes. CA reduced PM2.5-induced reactive oxygen species (ROS) accumulation and mitigated oxidative damage, including lipid peroxidation, protein carbonyl formation, mitochondrial membrane depolarization, and intracellular calcium overload. In addition, CA attenuated PM2.5-induced apoptosis by upregulating B-cell lymphoma 2 (Bcl-2) and suppressing Bcl-2-associated X protein (Bax), caspase-3, caspase-9, and phosphorylated c-Jun N-terminal kinase (phospho-JNK). Collectively, these findings demonstrate that CA protects HaCaT keratinocytes from PM2.5-induced oxidative stress and apoptosis by regulating the Bcl-2/Bax axis and inhibiting JNK-mediated apoptotic signaling, highlighting its potential as a therapeutic candidate for preventing pollutant-induced skin damage.

Connecting peptide (C-peptide), a byproduct of insulin biosynthesis, has diverse cellular and biological functions. Particulate mat-ter 2.5 (PM2.5 ) adversely affects human skin, leading to skin thickening, wrinkle formation, skin aging, and inflammation. This study aimed to investigate the protective effects of C-peptide against PM2.5 -induced damage to skin cells, focusing on oxidative stressas a key mechanism. C-peptide mitigated NADPH oxidation and intracellular reactive oxygen species (ROS) production inducedby PM2.5 . It also suppressed PM2.5 -induced NADPH oxidase (NOX) activity and alleviated PM2.5 -induced NOX1 and NOX4 expression. C-peptide protected against PM2.5 -induced DNA damage, lipid peroxidation, and protein carbonylation. Additionally, C-peptide mitigated PM2.5 -induced apoptosis by inhibiting intracellular ROS production. In summary, our findings suggest that C-peptide mitigates PM2.5 -induced apoptosis in human HaCaT keratinocytes by inhibiting intracellular ROS production and NOX activity.

γ-Radiation resistance is a major obstacle to the success of radiotherapy in colorectal cancer. Antioxidant-related factors contribute to resistance to radiation therapy and, therefore, are targets for improving the therapeutic response. In this study, we evaluated the molecular mechanisms underlying γ-radiation resistance using the colorectal cancer cell line SNUC5 and γ-radiation-resistant variant SNUC5/RR, including analyses of the role of nuclear factor erythroid 2-related factor 2 (NRF2), a transcription factor that regulates antioxidant enzymes, and related epigenetic regulators. Reactive oxygen species (ROS) levels, antioxidant enzyme expression, NRF2 expression, and nuclear translocation were higher in SNUC5/RR cells irradiated with or without 8 Gy than in SNUC5 cells. The DNA demethylase ten-eleven translocation 1 (TET1) expression and TET1 binding to the NRF2 promoter in SNUC5/RR cells were stronger than those in SNUC5 cells, indicating lower methylation of CpG islands in the NRF2 promoter.TET1 knockdown in SNUC5/RR cells suppressed NRF2 expression significantly. Additionally, histone mixed-lineage leukemia (MLL), a histone methyltransferase, was upregulated, leading to increased trimethylation of histone H3 lysine 4, whereas enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, was downregulated, leading to decreased trimethylation of histone H3 lysine 27. Histone deacetylase (HDAC) and histone acetyltransferase (HAT) levels were lower and higher in SNUC5/RR cells than in SNUC5 cells, respectively. MLL and HAT knockdown in SNUC5/RR cells irradiated with or without 8 Gy decreased levels of NRF2 and heme-oxygenase 1, resulting in enhanced γ-radiation sensitivity. These findings support NRF2 as a target for improving the response to radiotherapy in patients with colorectal cancer.

Connecting peptide (C-peptide), a byproduct of insulin biosynthesis, has diverse cellular and biological functions. Particulate mat-ter 2.5 (PM2.5 ) adversely affects human skin, leading to skin thickening, wrinkle formation, skin aging, and inflammation. This study aimed to investigate the protective effects of C-peptide against PM2.5 -induced damage to skin cells, focusing on oxidative stressas a key mechanism. C-peptide mitigated NADPH oxidation and intracellular reactive oxygen species (ROS) production inducedby PM2.5 . It also suppressed PM2.5 -induced NADPH oxidase (NOX) activity and alleviated PM2.5 -induced NOX1 and NOX4 expression. C-peptide protected against PM2.5 -induced DNA damage, lipid peroxidation, and protein carbonylation. Additionally, C-peptide mitigated PM2.5 -induced apoptosis by inhibiting intracellular ROS production. In summary, our findings suggest that C-peptide mitigates PM2.5 -induced apoptosis in human HaCaT keratinocytes by inhibiting intracellular ROS production and NOX activity.

γ-Radiation resistance is a major obstacle to the success of radiotherapy in colorectal cancer. Antioxidant-related factors contribute to resistance to radiation therapy and, therefore, are targets for improving the therapeutic response. In this study, we evaluated the molecular mechanisms underlying γ-radiation resistance using the colorectal cancer cell line SNUC5 and γ-radiation-resistant variant SNUC5/RR, including analyses of the role of nuclear factor erythroid 2-related factor 2 (NRF2), a transcription factor that regulates antioxidant enzymes, and related epigenetic regulators. Reactive oxygen species (ROS) levels, antioxidant enzyme expression, NRF2 expression, and nuclear translocation were higher in SNUC5/RR cells irradiated with or without 8 Gy than in SNUC5 cells. The DNA demethylase ten-eleven translocation 1 (TET1) expression and TET1 binding to the NRF2 promoter in SNUC5/RR cells were stronger than those in SNUC5 cells, indicating lower methylation of CpG islands in the NRF2 promoter.TET1 knockdown in SNUC5/RR cells suppressed NRF2 expression significantly. Additionally, histone mixed-lineage leukemia (MLL), a histone methyltransferase, was upregulated, leading to increased trimethylation of histone H3 lysine 4, whereas enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, was downregulated, leading to decreased trimethylation of histone H3 lysine 27. Histone deacetylase (HDAC) and histone acetyltransferase (HAT) levels were lower and higher in SNUC5/RR cells than in SNUC5 cells, respectively. MLL and HAT knockdown in SNUC5/RR cells irradiated with or without 8 Gy decreased levels of NRF2 and heme-oxygenase 1, resulting in enhanced γ-radiation sensitivity. These findings support NRF2 as a target for improving the response to radiotherapy in patients with colorectal cancer.

Connecting peptide (C-peptide), a byproduct of insulin biosynthesis, has diverse cellular and biological functions. Particulate mat-ter 2.5 (PM2.5 ) adversely affects human skin, leading to skin thickening, wrinkle formation, skin aging, and inflammation. This study aimed to investigate the protective effects of C-peptide against PM2.5 -induced damage to skin cells, focusing on oxidative stressas a key mechanism. C-peptide mitigated NADPH oxidation and intracellular reactive oxygen species (ROS) production inducedby PM2.5 . It also suppressed PM2.5 -induced NADPH oxidase (NOX) activity and alleviated PM2.5 -induced NOX1 and NOX4 expression. C-peptide protected against PM2.5 -induced DNA damage, lipid peroxidation, and protein carbonylation. Additionally, C-peptide mitigated PM2.5 -induced apoptosis by inhibiting intracellular ROS production. In summary, our findings suggest that C-peptide mitigates PM2.5 -induced apoptosis in human HaCaT keratinocytes by inhibiting intracellular ROS production and NOX activity.

γ-Radiation resistance is a major obstacle to the success of radiotherapy in colorectal cancer. Antioxidant-related factors contribute to resistance to radiation therapy and, therefore, are targets for improving the therapeutic response. In this study, we evaluated the molecular mechanisms underlying γ-radiation resistance using the colorectal cancer cell line SNUC5 and γ-radiation-resistant variant SNUC5/RR, including analyses of the role of nuclear factor erythroid 2-related factor 2 (NRF2), a transcription factor that regulates antioxidant enzymes, and related epigenetic regulators. Reactive oxygen species (ROS) levels, antioxidant enzyme expression, NRF2 expression, and nuclear translocation were higher in SNUC5/RR cells irradiated with or without 8 Gy than in SNUC5 cells. The DNA demethylase ten-eleven translocation 1 (TET1) expression and TET1 binding to the NRF2 promoter in SNUC5/RR cells were stronger than those in SNUC5 cells, indicating lower methylation of CpG islands in the NRF2 promoter.TET1 knockdown in SNUC5/RR cells suppressed NRF2 expression significantly. Additionally, histone mixed-lineage leukemia (MLL), a histone methyltransferase, was upregulated, leading to increased trimethylation of histone H3 lysine 4, whereas enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, was downregulated, leading to decreased trimethylation of histone H3 lysine 27. Histone deacetylase (HDAC) and histone acetyltransferase (HAT) levels were lower and higher in SNUC5/RR cells than in SNUC5 cells, respectively. MLL and HAT knockdown in SNUC5/RR cells irradiated with or without 8 Gy decreased levels of NRF2 and heme-oxygenase 1, resulting in enhanced γ-radiation sensitivity. These findings support NRF2 as a target for improving the response to radiotherapy in patients with colorectal cancer.

Rosmarinic acid (RA) is a phenolic ester that protects human keratinocytes against oxidative damage induced by ultraviolet B (UVB) exposure, however, the mechanisms underlying its effects remain unclear. This study aimed to elucidate the cell signaling mechanisms that regulate the antioxidant activity of RA and confirm its cyto-protective role. To explore the signaling mechanisms, we used the human keratinocyte cell line HaCaT and SKH1 hairless mouse skin. RA enhanced glutamate-cysteine ligase catalytic subunit (GCLC) and glutathione synthetase (GSS) expression in HaCaT cells in a dose- and time-dependent manner. Moreover, RA induced nuclear factor erythroid-2-related factor 2 (NRF2) nuclear translocation and activated the signaling kinases protein kinase B (AKT) and extracellular signal-regulated kinase (ERK). Treatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, the ERK inhibitor U0126, and small interfering RNA (siRNA) gene silencing suppressed RA-enhanced GCLC, GSS, and NRF2 expression, respectively. Cell viability tests showed that RA significantly prevented UVB-induced cell viability decrease, whereas the glutathione (GSH) inhibitors buthionine sulfoximine, LY294002, and U0126 significantly reduced this effect. Moreover, RA protected against DNA damage and protein carbonylation, lipid peroxidation, and apoptosis caused by UVB-induced oxidative stress in a concentration-dependent manner in SKH1 hairless mouse skin tissues. These results suggest that RA protects against UVB-induced oxidative damage by activating AKT and ERK signaling to regulate NRF2 signaling and enhance GSH biosynthesis. Thus, RA treatment may be a promising approach to protect the skin from UVB-induced oxidative damage.

Specific sensitivity of the skin to ultraviolet B (UVB) rays is one of the mechanisms responsible for widespread skin damage. This study tested whether 1,3,5-trihydroxybenzene (THB), a compound abundant in marine products, might inhibit UVB radiationinduced NADPH oxidase 4 (NOX4) in both human HaCaT keratinocytes and mouse dorsal skin and explore its cytoprotective mechanism. The mechanism of action was determined using western blotting, immunocytochemistry, NADP + /NADPH assay, reactive oxygen species (ROS) detection, and cell viability assay. THB attenuated UVB-induced NOX4 expression both in vitro and in vivo, and suppressed UVB-induced ROS generation via NADP + production, resulting in increased cell viability with decreased apoptosis. THB also reduced the expression of UVB-induced phosphorylated AMP-activated protein kinase (AMPK) and phosphorylated c-Jun N-terminal kinase (JNK). THB suppressed UVB-induced NOX4 expression and ROS generation by inhibiting AMPK and JNK signaling pathways, thereby inhibiting cellular damage. These results showed that THB could be developed as a UV protectant.