Alaa-Eldin Salah-Eldin

An association of Bcl-2 phosphorylation and Bax localization with their functions after hyperthermia and paclitaxel treatment.

Apoptosis is induced by many kinds of therapy‐related inducers, such as hyperthermia and chemotherapeutic agents. However, differences in apoptotic pathways between these inducers remain unclear, although knowing the differences is important to map out a therapeutic strategy. Therefore, we focused on the localization and phosphorylation of Bcl‐2 and Bax, key mediators of the apoptotic pathway, after hyperthermia and paclitaxel treatment of PC‐10 squamous cell carcinoma cells that excessively expressed Bcl‐2 and Bax in the cytoplasm. Paclitaxel treatment markedly induced qualitative changes in Bcl‐2, whereas hyperthermia did only quantitative changes in Bax. The levels of Bax increased gradually with the duration of hyperthermia, whereas Bcl‐2 levels slightly decreased. On the other hand, paclitaxel treatment induced dose‐ and time‐dependent phosphorylation of Bcl‐2. Interestingly, phosphorylated Bcl‐2 was observed in the specific subcellular sites, mitochondria‐ and lysosome‐rich fractions. Both treatments disturbed the heterodimerization of Bax with Bcl‐2. Hyperthermia, but not paclitaxel treatment, induced a gradual Bax translocation from the cytoplasm to the nucleus. Although both treatments induced a prominent cell cycle disturbance in the G2M phase, paclitaxel treatment induced typical apoptosis, and hyperthermia hardly induced apoptosis. Our results suggest that the subcellular redistribution of Bax and the phosphorylation of Bcl‐2 depend on the type of apoptosis inducers, such as hyperthermia and paclitaxel, and Bcl‐2 has a central role in the decision of apoptotic outcome. Our data may afford new insights in apoptosis from the aspect of an association of Bcl‐2 phosphorylation with intracellular Bax localization.

Butyrate regulates leptin expression through different signaling pathways in adipocytes

Leptin is an adipocytokine that regulates body weight, and maintains energy homeostasis by promoting reduced food intake and increasing energy expenditure. Leptin expression and secretion is regulated by various factors including hormones and fatty acids. Butyrate is a short-chain fatty acid that acts as source of energy in humans. We determined whether this fatty acid can play a role in leptin expression in fully differentiated human adipocytes. Mature differentiated adipocytes were incubated with or without increasing concentrations of butyrate. RNA was extracted and leptin mRNA expression was examined by Northern blot analysis. Moreover, the cells were incubated with regulators that may affect signals which may alter leptin expression and analyzed with Northern blotting. Butyrate stimulated leptin expression, and stimulated mitogen activated protein kinase (MAPK) and phospho-CREB signaling in a time-dependent manner. Prior treatment of the cells with signal transduction inhibitors as pertusis toxin, Gi protein antagonist, PD98059 (a MAPK inhibitor), and wortmannin (a PI3K inhibitor) abolished leptin mRNA expression. These results suggest that butyrate can regulate leptin expression in humans at the transcriptional level. This is accomplished by: 1) Gi protein-coupled receptors specific for short-chain fatty acids, and 2) MAPK and phosphatidylinositol-3-kinase (PI3K) signaling pathways.

Abnormal Intracellular Localization of Bax with a Normal Membrane Anchor Domain in Human Lung Cancer Cell Lines

Proapoptotic Bax is a member of the Bcl‐2 family proteins, which have a key role in regulating programmed cell death. The intracellular localization and redistribution of Bax are important in promoting apoptosis. Bax contains a BH3 domain heterodimerizing with Bcl‐2 and a hydrophobic transmembrane segment to be inserted in specified organelle membranes. In this study, Bcl‐2 showed cytoplasmic localization in all of ten human lung cancer cell lines tested. Interestingly, Bax was localized in the nucleus in 7 cell lines, although Bax lacks nuclear import signals. This may allow cancer cells to escape from apoptosis. Why Bax is able to exist in the nucleus is still unclear. We hypothesized that mutation in the BH3 domain and/or transmembrane segment of Bax possibly causes intracellular Bax distribution. We analyzed the sequence of the bax gene in these cell lines and found only a silent point mutation at codon 184 (TCG → TCA) in the transmembrane segment in all cell lines. This finding indicates that changes in cellular localization of Bax in lung cancer cell lines do not depend on bax mutation and that Bax is possibly translocated into the nucleus without any mutation. This is the first report showing that Bax with the normal amino acid sequence can be localized in the nucleus in established lung cancer cell lines without any treatment of the cells.

Histone deacetylase inhibitors sensitize lung cancer cells to hyperthermia: involvement of Ku70/SirT-1 in thermo-protection.

This study describes the sensitization mechanism to thermal stress by histone deacetylase inhibitors (HDACIs) in lung cancer cells and shows that Ku70, based on its acetylation status, mediates the protection of lung cancer from hyperthermia (42.5°C, 1-6 hrs). Ku70 regulates apoptosis by sequestering pro-apoptotic Bax. However, its role in thermal stress is not fully understood. The findings showed that, pre-treating lung cancer cells with HDACIs, nicotinamide (NM) or Trichostatin A (TsA) or both significantly enhanced hyperthermia-induced Bax-dependent apoptosis in PC-10 cells. We found that hyperthermia induces SirT-1, Sirtuin, upregulation but not HDAC6 or SirT-3, therefore transfection with dominant negative SirT-1 (Y/H) also eliminated the protection and resulted in more cell death by hyperthermia, in H1299 cells through Bax activation. Hyperthermia alone primed lung cancer cells to apoptosis without prominent death. After hyperthermia Bax was upregulated, Bcl-2 was downregulated, the Bax/Bcl-2 ratio was inversed and Bax/Bcl-2 heterodimer was dissociated. Although hyperthermia did not affect total Ku70 expression level, it stimulated Ku70 deacetylation, which in turn could bind more Bax in the PC-10 cells. These findings suggest an escape mechanism from hyperthermia-induced Bax activation. To verify the role of Ku70 in this protection mechanism, Ku70 was silenced by siRNA. Ku70 silencing significantly sensitized the lung cancer cells to hyperthermia. The Ku70 KD cells underwent cytotoxic G1 arrest and caspase-dependant apoptosis when compared to scrambled transfectants which showed only G2/M cytostatic arrest in the cell lines investigated, suggesting an additional cell cycle-dependent, novel, role of Ku70 in protection from hyperthermia. Taken together, our data show a Ku70-dependent protection mechanism from hyperthermia. Targeting Ku70 and/or its acetylation during hyperthermia may represent a promising therapeutic approach for lung cancer.

Chronic effects of soft drink consumption on the health state of Wistar rats: A biochemical, genetic and histopathological study

The present study was performed to examine the effects of chronic soft drink consumption (SDC) on oxidative stress, biochemical alterations, gene biomarkers and histopathology of bone, liver and kidney. Free drinking water of adult male Wistar rats was substituted with three different soft drinks: Coca-Cola, Pepsi and 7-Up, for three consecutive months. The serum and organs were collected for examining the biochemical parameters associated with bone, liver and kidney functions. Semi-quantitative reverse transcription polymerase chain reaction was used to observe the changes in the expression of genes in the liver and kidney, which are associated with oxidative stress resistance. Histopathological investigations were performed to determine the changes in bone, liver and kidney tissues using hematoxylin and eosin stains. SDC affected liver, kidney and bone function biomarkers. Soft drinks increased oxidative stress, which is represented by an increase in malondialdehyde and a decrease in antioxidant levels. SDC affected serum mineral levels, particularly calcium and phosphorus. Soft drinks downregulated the expression levels of glutathione-S-transferase and super oxide dismutase in the liver compared with that of control rats. Rats administered Coca-Cola exhibited a hepatic decrease in the mRNA expression of α2-macroglobulin compared with rats administered Pepsi and 7-Up. On the other hand, SDC increased the mRNA expression of α1-acid glycoprotein. The present renal studies revealed that Coca-Cola increased the mRNA expression levels of desmin, angiotensinogen and angiotensinogen receptor compared with the other groups, together with mild congestion in renal histopathology. Deleterious histopathological changes were reported predominantly in the bone and liver of the Coca-Cola and Pepsi groups. In conclusion, a very strict caution must be considered with SDC due to the increase in oxidative stress biomarkers and disruption in the expression of certain genes associated with the bio-vital function of both the liver and kidney.