Expression Of Antiapoptotic Protein Bcl-X Research Articles

Protective effect of Salacia oblonga against tobacco smoke-induced DNA damage and cellular changes in pancreatic β-cells

Context: Tobacco smoking generates a tremendous amount of free radicals that induce oxidative stress (OS) in diabetics (pancreatic islet cells are defective). Salacia oblonga Wall. (Celastraceae) is a proven antioxidant and antidiabetic plant whose mechanism of action is yet to be explored.Objective: The present study focuses on the protective ability of S. oblonga in tobacco smoke-induced oxidatively stressed pancreatic β-cell line.Materials and methods: The RINm5f cell line was exposed to tobacco smoke concentrate (TSC) (0.5–10%, 24 h), plant extract (1–75 µg/ml, 3 h), and their combinations. Cell viability was determined through MTT assay. Microscopic analysis was carried out in unstained and nonyl acridine orange-stained cells. The effect of toxic doses of TSC on DNA integrity was analyzed through DNA fragmentation assay. The TSC-induced nitric oxide generation was determined spectrophototmetrically. The expression of anti-apoptotic protein Bcl-X under the above treatment conditions was carried out through RT-PCR.Results: The LD50 dose for TSC was found to be 1% TSC. Salacia oblonga extracts (10 and 15 µg/ml) were found to be optimum safe doses that significantly increased cell viability and decreased the nitric oxide production in TSC-treated cells. Pre-treatment with plant extract suppressed apoptosis through probable increase in the expression of anti-apoptotic protein Bcl-X in TSC-treated cells. Thus, the overall efficiency of plant extract in recovering cellular damage was proven.Discussion and conclusion: The results suggest that TSC-induced cellular alterations are related to rise in nitric oxide and Bcl-X mRNA expression and propose that S. oblonga may confer significant cytoprotection against OS-mediated injury in β-cells.

Synthesis, characterization, DNA interaction, antioxidant and anticancer activity studies of ruthenium(II) polypyridyl complexes

Two new Ru(II) polypyridyl complexes [Ru(phen)2(adppz)](ClO4)2 (1) and [Ru(dip)2(adppz)](ClO4)2 (2) have been synthesized and characterized. The DNA-binding constants were determined to be 6.54±0.42×105 and 7.65±0.20×105M−1 for complexes 1 and 2. DNA binding experiments indicated that complexes 1 and 2 interact with DNA through intercalative mode. Antioxidant activity shows that the complexes have significant hydroxyl radical scavenging activity. Cytotoxic activities suggest that the complex 2 exhibits higher cytotoxic activity against BEL-7402, MG-63 and SKBR-3 cells than complex 1 under identical conditions. Complexes 1 and 2 can induce apoptosis of BEl-7402 cells. We have identified several cellular mechanisms induced by 1 and 2 in BEL-7402 cells, including the level detection of ROS, activation of procaspase 3, caspase 7, the expression of antiapoptotic proteins Bcl-x, Bcl-2, proapoptotic proteins Bad, Bax, Bid and cell cycle arrest. Thus, complexes 1 and 2 inhibit growth of BEL-7402 cells through induction of apoptotic cell death, enhancement of ROS levels and S-phase and G0/G1 cell cycle arrest. Further investigations have shown that complex 2 induces apoptosis by regulating the expression of Bcl-2 family proteins.

Fusion tyrosine kinases: a result and cause of genomic instability

Reciprocal chromosomal translocations may arise as a result of unfaithful repair of spontaneous DNA double-strand breaks, most probably induced by oxidative stress, radiation, genotoxic chemicals and/or replication stress. Genes encoding tyrosine kinases are targeted by these mechanisms resulting in the generation of chimera genes encoding fusion tyrosine kinases (FTKs). FTKs display transforming activity owing to their constitutive kinase activity causing deregulated proliferation, apoptosis, differentiation and adhesion. Moreover, FTKs are able to facilitate DNA repair, prolong activation of G(2)/M and S cell cycle checkpoints, and elevate expression of antiapoptotic protein Bcl-X(L), making malignant cells less responsive to antitumor treatment. FTKs may also stimulate the generation of reactive oxygen species and enhance spontaneous DNA damage in tumor cells. Unfortunately, FTKs compromise the fidelity of DNA repair mechanisms, which contribute to the accumulation of additional genetic abnormalities leading to the resistance to inhibitors such as imatinib mesylate and malignant progression of the disease.