cytochrome-c-t and orientin

Colorectal carcinoma is one of the utmost diagnosed cancer with a steep increase in mortality rate. The incidence has been increasing in developing countries like India due to a westernization life style. Flavonoids have been explored widely for its various pharmacological activity including antitumor activity. Orientin, an analogue of luteolin (citrus flavonoid) isolated from rooibos and tulsi leaves is also expected to deliver significant antitumor activity similar to that of luteolin. The present study anticipates exploring the antitumor activity of orientin against colorectal carcinoma cells (HT29). Orientin exhibited remarkable cytotoxicity and antiproliferative activity against HT29 cells, which is clearly evident from tetrazolium based cytotoxicity and lactate dehydrogenase release assays. Orientin induce G0/G1 cell cycle arrest and regulates cyclin and cyclin-dependent protein kinases in order to prevent the entry of the cell cycle to the S phase. Annexin V-FITC (V-Fluorescein Isothiocyanate) dual staining reveals the apoptotic induction ability of orientin. The Bcl-2 family proteins along with the inhibitor of apoptotic proteins were regulated and the tumor suppressor p-53 expression have been decreased. In conclusion, our results proposed that orientin could be a potent chemotherapeutic agent against colorectal cancer after ascertaining their molecular mechanisms.

Topics: Antineoplastic Agents; Apoptosis; Colorectal Neoplasms; Cyclin-Dependent Kinase Inhibitor p21; Cytochromes c; DNA Damage; Flavonoids; G1 Phase Cell Cycle Checkpoints; Glucosides; HT29 Cells; Humans; Mitochondria; Oligopeptides; Poly(ADP-ribose) Polymerases; Proto-Oncogene Proteins c-bcl-2; Reactive Oxygen Species

In this study, we provide new evidence that orientin from bamboo leaves (Phyllostachys nigra) protect H9c2 cardiomyocytes against ischemia/reperfusion (I/R) injury through the mitochondrial apoptotic pathway. A previous work has identified that orientin could protect myocardium against ischemia/reperfusion injury. Mitochondria are both critical determinants of cardioprotection and crucial targets of cardioprotective signaling. Their role during reperfusion is conspicuously critical because the conditions promote apoptosis through the mitochondrial pathway and necrosis though irreversible damage to mitochondria, which is in association with mitochondrial permeability transition (MPT). After myocardial ischemia, opening of the mPTP is a critical determinant of cell death. The relationship of orientin and mPTP in mediating reperfusion-induced cardiomyocytes injury is still elusive. Here, our results indicate that the protective effect of orientin in H9c2 cells subjected to I/R injury is associated with depression of the mPTP opening, resultant mitochondrial dysfunction, and apoptosis. Further investigation of cellular mechanisms revealed that these effects were associated with inhibition of reactive oxygen species (ROS) generation, repolarization of mitochondrial membrane potential (Δψ(m)), suppression of mitochondrial cytochrome C release, enhancement of the Bcl-2 level, and inhibition of Bax and Smac/DIABLO levels. Furthermore, these beneficial effects of orientin were blocked by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, and orientin could enhance Akt phosphorylation. In summary, we demonstrate that orientin protects H9c2 cardiomytocytes against I/R-induced apoptosis by modulating the mPTP opening, and this role of orientin may involve the PI3K/Akt signaling pathway.

Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; bcl-2-Associated X Protein; Carrier Proteins; Cell Line; Cytochromes c; Cytosol; Flavonoids; Glucosides; Membrane Potential, Mitochondrial; Mitochondria, Heart; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Mitochondrial Proteins; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Permeability; Phosphatidylinositol 3-Kinase; Phosphorylation; Protective Agents; Protein Transport; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Rats; Reactive Oxygen Species; Signal Transduction