Dissecting the Mechanisms of Doxorubicin and Oxidative Stress-Induced Cytotoxicity: The Involvement of Actin Cytoskeleton and ROCK1.

We have recently reported that ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has superior anti-apoptotic and pro-survival effects than antioxidants against doxorubicin, a chemotherapeutic drug. Although oxidative stress is the most widely accepted mechanism, our studies suggest that ROCK1-dependent actin cytoskeleton remodeling plays a more important role in mediating doxorubicin cytotoxicity on MEFs. To further explore the contributions of ROCK1-dependent actin cytoskeleton remodeling in response to stress, this study investigates the mechanistic differences between the cytotoxic effects of doxorubicin versus hydrogen peroxide (H2O2), with a focus on cytoskeleton alterations, apoptosis and necrosis induction. We found that both types of stress induce caspase activation but with different temporal patterns and magnitudes in MEFs: H2O2 induces the maximal levels (2 to 4-fold) of activation of caspases 3, 8, and 9 within 4 h, while doxorubicin induces much higher maximal levels (15 to 25-fold) of caspases activation at later time points (16-24 h). In addition, necrosis induced by H2O2 reaches maximal levels within 4 h while doxorubicin-induced necrosis largely occurs at 16-24 h secondary to apoptosis. Moreover, both types of stress induce actin cytoskeleton remodeling but with different characteristics: H2O2 induces disruption of stress fibers associated with cytosolic translocation of phosphorylated myosin light chain (p-MLC) from stress fibers, while doxorubicin induces cortical F-actin formation associated with cortical translocation of p-MLC from central stress fibers. Furthermore, N-acetylcysteine (an antioxidant) is a potent suppressor for H2O2-induced cytotoxic effects including caspase activation, necrosis, and cell detachment, but shows a much reduced inhibition on doxorubicin-induced changes. On the other hand, ROCK1 deficiency is a more potent suppressor for the cytotoxic effects induced by doxorubicin than by H2O2. These results support the notion that doxorubicin induces caspase activation, necrosis, and actin cytoskeleton alterations largely through ROCK1-dependent and oxidative stress-independent pathways.

The Utility of Commonly Used Laboratory Tests to Screen for Excessive Alcohol Use in Clinical Practice.

BACKGROUND: This current study was undertaken to carefully assess the accuracy of routinely used laboratory tests in detecting excessive/recent alcohol use. We also determined the kinetics of these markers in subjects who underwent an intensive alcohol rehabilitation program. METHODS: The study cohort consisted of 210 nonexcessive drinkers, 272 excessive drinkers, and 76 with alcoholic cirrhosis. To determine the kinetics of these markers during alcohol abstinence, we followed 45 subjects with history of excessive alcohol use for 12 weeks during the intensive alcohol treatment program. RESULTS: Percentage of carbohydrate deficient transferrin (%CDT) provided the highest diagnostic performance (area under the curve [AUC] 0.77) followed by gamma-glutamyl transferase (GGT) (AUC 0.68) to detect excessive drinkers. The percentage of excessive drinkers with aspartate aminotransferase:alanine aminotransferase (AST:ALT) > 2 was only 2%, whereas 51% of subjects with alcoholic cirrhosis had AST:ALT > 2. In the multivariate analysis, the levels of GGT and %CDT were associated with the level of alcohol consumed during the past 30 days. The levels of GGT, mean corpuscular volume (MCV), and %CDT were significantly lower compared to those at baseline before alcohol rehabilitation, whereas the AST, ALT, and AST:ALT ratio were unchanged. The percent reduction was ~2.7% (for MCV), 19% (for GGT), and 43% (for %CDT) at the end of the 12-week follow-up compared to the baseline. CONCLUSIONS: %CDT are useful markers to screen for excessive alcohol use and for follow-up of abstinence. Most subjects with excessive alcohol use do not have a high AST:ALT ratio. Rather, the AST:ALT > 2 is suggestive of alcoholic cirrhosis. The performance of the %CDT to screen for heavy alcohol use is still not ideal. Further research to identify the noninvasive marker(s) (i.e., using proteomic or metabolomics approach) should be considered.