α-Lipoic Acid Inhibits Apoptosis by Suppressing the Loss of Ku Proteins in Helicobacter pylori-Infected Human Gastric Epithelial Cells

Alpha-lipoic acid supplementation reverses the declining quality of oocytes exposed to cyclophosphamide

Cyclophosphamide (CY) is a chemotherapeutic drug that is commonly used to treat malignancies of the ovary, breast, and hematology, as well as autoimmune disorders. As a cofactor of mitochondrial multienzyme complexes, alpha lipoic acid (ALA) is well known for its antioxidant characteristics, which operate directly on the scavenging of reactive oxygen species (ROS) and indirectly on the intracellular recycling of other antioxidants. However, the underlying mechanisms through which CY exerts its toxic effects on meiosis and oocyte quality, as well as a viable approach for protecting oocyte quality and preserving fertility, remain unknown. In present study, immunostaining and fluorescence intensity quantification were applied to assess the effects of CY and ALA supplementation on the key processes during the oocyte meiotic maturation. Our results show that supplementing oocytes with ALA, a well-known antioxidant and free radical scavenger, can reverse CY-induced oocyte meiotic maturation failure. Specifically, we found that CY exposure caused oocyte meiotic failure by disrupting meiotic organelle dynamics and arrangement, as well as a prominently impaired cytoskeleton assembly. In addition, CY caused an abnormal distribution of mitochondrion and cortical granules, two indicators of oocyte cytoplasmic maturation. More importantly, we show that ALA supplementation effectively reverses CY-induced meiotic failure and oocyte quality decline by suppressing oxidative stress-induced DNA damage and apoptosis in oocytes. Collectively, our data reveal that ALA supplementation is a feasible approach to protect oocytes from CY-exposed deterioration, providing a better understanding of the mechanisms involved in chemotherapy-induced meiotic failure.

Astaxanthin Inhibits Oxidative Stress-Induced Ku Protein Degradation and Apoptosis in Gastric Epithelial Cells

Oxidative stress induces DNA damage which can be repaired by DNA repair proteins, such as Ku70/80. Excess reactive oxygen species (ROS) stimulate the activation of caspase-3, which degrades Ku 70/80. Cells with decreased Ku protein levels undergo apoptosis. Astaxanthin exerts antioxidant activity by inducing the expression of catalase, an antioxidant enzyme, in gastric epithelial cells. Therefore, astaxanthin may inhibit oxidative stress-induced DNA damage by preventing Ku protein degradation and thereby suppressing apoptosis. Ku proteins can be degraded via ubiquitination and neddylation which adds ubiquitin-like protein to substrate proteins. We aimed to determine whether oxidative stress decreases Ku70/80 expression through the ubiquitin–proteasome pathway to induce apoptosis and whether astaxanthin inhibits oxidative stress-induced changes in gastric epithelial AGS cells. We induced oxidative stress caused by the treatment of β-D-glucose (G) and glucose oxidase (GO) in the cells. As a result, the G/GO treatment increased ROS levels, decreased nuclear Ku protein levels and Ku-DNA-binding activity, and induced the ubiquitination of Ku80. G/GO increased the DNA damage marker levels (γ-H2AX; DNA fragmentation) and apoptosis marker annexin V-positive cells and cell death. Astaxanthin inhibited G/GO-induced alterations, including Ku degradation in AGS cells. MLN4924, a neddylation inhibitor, and MG132, a proteasome inhibitor, suppressed G/GO-mediated DNA fragmentation and decreased cell viability. These results indicated that G/GO-induced oxidative stress causes Ku protein loss through the ubiquitin–proteasome pathway, resulting in DNA fragmentation and apoptotic cell death. Astaxanthin inhibited oxidative stress-mediated apoptosis via the reduction of ROS levels and inhibition of Ku protein degradation. In conclusion, dietary astaxanthin supplementation or astaxanthin-rich food consumption may be effective for preventing or delaying oxidative stress-mediated cell damage by suppressing Ku protein loss and apoptosis in gastric epithelial cells.