Reactive oxygen species (ROS), products of oxidative stress, contribute to the initiation and progression of the pathogenesis of various diseases. Glutathione is a major antioxidant that can help prevent the process through the removal of ROS. The aim of this study was to evaluate the protective effect of glutathione on ROS-mediated DNA damage and apoptosis caused by hydrogen peroxide, H₂O₂, in RAW 264.7 macrophages and to investigate the role of the nuclear factor erythroid 2-related factor-2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. The results showed that the decrease in the survival rate of RAW 264.7 cells treated with H₂O₂ was due to the induction of DNA damage and apoptosis accompanied by the increased production of ROS. However, H₂O₂-induced cytotoxicity and ROS generation were significantly reversed by glutathione. In addition, the H₂O₂-induced loss of mitochondrial membrane potential was related to a decrease in adenosine triphosphate (ATP) levels, and these changes were also significantly attenuated in the presence of glutathione. These protective actions were accompanied by a increase in the expression rate of B-cell lymphoma-2 (Bcl-2)/Bcl-2-associated X protein (Bax) and poly(ADP-ribose) polymerase cleavage by the inactivation of caspase-3. Moreover, glutathione-mediated cytoprotective properties were associated with an increased activation of Nrf2 and expression of HO-1; however, the inhibition of the HO-1 function using an HO-1 specific inhibitor, zinc protoporphyrin IX, significantly weakened the cytoprotective effects of glutathione. Collectively, the results demonstrate that the exogenous administration of glutathione is able to protect RAW 264.7 cells against oxidative stress-induced mitochondria-mediated apoptosis along with the activity of the Nrf2/HO-1 signaling pathway.

We examined the anti-cancer effect of genistein, a soy-derived isoflavone, in human bladder transitional cell carcinoma T24 cells. According to our data, genistein induced G2/M phase arrest of the cell cycle and apoptosis. Genistein down-regulated the levels of cyclin A and cyclin B1, but up-regulated the levels of p21WAF1/CIP1, cyclin-dependent kinase (Cdk) inhibitor, that was complexed with Cdc2 and Cdk2. Furthermore, genistein induced the activation of caspases (caspase-3, -8 and -9), and cleavage of poly (ADP-ribose) polymerase cleavage. However, genistein-induced apoptosis was significantly inhibited by a pan-caspase inhibitor, indicating that the induction of apoptosis by genestein was caspase-dependent. In addition, genistein increased the cytosolic release of cytochrome c by increasing the Bax/Bcl-2 ratio and destroying mitochondria integrity. Moreover, genistein inactivated the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway, while LY294002, a PI3K/Akt inhibitor, increased the apoptosis-inducing effect of genistein. Genistein further increased the accumulation of reactive oxygen species (ROS), which was significantly suppressed by N-acetyl cysteine (NAC), a ROS scavenger, and in particular, NAC prevented genistein-mediated inactivation of PI3K/Akt signaling, G2/M arrest and apoptosis. Therefore, the present results indicated that genistein promoted apoptosis induction in human bladder cancer T24 cells, which was associated with G2/M phase cell cycle arrest via regulation of ROS-dependent PI3K/Akt signaling pathway.

The present study investigated the immunomodulatory activity of reduced glutathione (GSH) by assessment of the macrophage polarization (MP)-mediated immune response in RAW 264.7 cells. Furthermore, we identified the signal pathway associated with immune regulation by GSH. The expressions of MP-associated cytokines and chemokines were assessed using cytokine array, nCounter Sprit platform, ELISA and immunoblotting. Phagocytosis activity and intracellular reactive oxygen species (ROS) generation were measured using fluorescence-activated cell sorter. As results of the cytokine array and nCounter gene array, GSH not only up-regulated pro-inflammatory cytokines, including interleukins and tumor necrosis factor-α, but also overexpressed neutrophil-attracting chemokines. Furthermore, GSH significantly stimulated the production of immune mediators, including nitric oxide and PGE₂, as well as phagocytosis activity through nuclear factor kappa B activation. In addition, GSH significantly decreased LPS-induced ROS generation, which was associated with an activation of nuclear factor erythroid-derived 2-related factor 2 (Nrf2)/ heme oxygenease-1 (HO-1) signaling pathway. Our results suggest that GSH has potential ROS scavenging capacity via the induction of Nrf2-mediated HO-1, and immune-enhancing activity by regulation of M1-like macrophage polarization, indicating that GSH may be a useful strategy to increase the human defense system.

Phloroglucinol (PG) is a component of phlorotannins, which are abundant in marine brown alga species. Recent studies have shown that PG is beneficial in protecting cells from oxidative stress. In this study, we evaluated the protective efficacy of PG in HaCaT human skin keratinocytes stimulated with oxidative stress (hydrogen peroxide, H₂O₂). The results showed that PG significantly inhibited the H₂O₂-induced growth inhibition in HaCaT cells, which was associated with increased expression of heme oxygenase-1 (HO-1) by the activation of nuclear factor erythroid 2-related factor-2 (Nrf2). PG remarkably reversed H₂O₂-induced excessive ROS production, DNA damage, and apoptosis. Additionally, H₂O₂-induced mitochondrial dysfunction was related to a decrease in ATP levels, and in the presence of PG, these changes were significantly impaired. Furthermore, the increases of cytosolic release of cytochrome c and ratio of Bax to Bcl-2, and the activation of caspase-9 and caspase-3 by the H₂O₂ were markedly abolished under the condition of PG pretreatment. However, the inhibition of HO-1 function using zinc protoporphyrin, a HO-1 inhibitor, markedly attenuated these protective effects of PG against H₂O₂. Overall, our results suggest that PG is able to protect HaCaT keratinocytes against oxidative stress-induced DNA damage and apoptosis through activating the Nrf2/HO-1 signaling pathway.

The present study investigated possible mechanisms on the apoptosis induction of human leukemic cells by fucoidan, a sulfated polysaccharide found in marine algae. Fucoidan treatment of cells resulted in inhibition of growth and induction of apoptosis, as measured by 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyl-tetrazolium (MTT) assay, fluorescence microscopy, DNA fragmentation, and flow cytometry analysis. The increase in apoptosis was associated with the proteolytic activation of caspases, Bid cleavage, insertion of pro-apoptotic Bax into the mitochondria, release of cytochrome c from mitochondria to cytosol, and loss of mitochondria membrane potential (MMP) in U937 cells. However, apoptosis induced by fucoidan was attenuated by caspase inhibitors, indicating that fucoidan-induced apoptosis was dependent on the activation of caspases. Furthermore, fucoidan treatment effectively activated the p38 mitogen-activated protein kinase (MAPK) and p38 MAPK inhibitor, SB203580, and significantly reduced fucoidan-induced apoptosis through inhibition of Bax translocation and caspases activation, suggesting that the activation of p38 MAPK may play a key role in fucoidan-induced apoptosis. In addition, the authors found fucoidan-induced significantly attenuated in Bcl-2 overexpressing U937 cells, and pretreatment with fucoidan and HA 14-1, a small-molecule Bcl-2 inhibitor, markedly increased fucoidan-mediated apoptosis in Bcl-2 overexpressing U937 cells. Our findings imply that we may attribute some of the biological functions of p38 MAPK and Bcl-2 to their ability to inhibit fucoidan-induced apoptosis.