Chatchai Chaotham

Silymarin selectively protects human renal cells from cisplatin-induced cell death

Context: Cisplatin-induced nephrotoxicity has been accepted as an important obstacle for efficient cisplatin-based chemotherapy. Silymarin from seeds of milk thistle [Silybum marianum L. (Asteraceae)] has been shown to possess various potential pharmacological properties; however, whether or not this agent selectively protects renal cells from cisplatin-induced cell death with no interfering effect on cancer cells is not clear. Objective: Potential of silymarin in protection of cisplatin-induced renal cell death without compromising effect on anticancer activity of cisplatin was demonstrated in this study. Materials and methods: Cisplatin-induced cell death was evaluated in human proximal tubular HK-2, lung carcinoma H460, and melanoma G361 cells using MTT, Hoechst 33342, and propidium iodide assays. Results: Cisplatin induced both apoptosis and necrosis in HK-2 cells and caused a decrease in cell viability by ~40% and 60% at the doses of 25 and 100 µM, respectively. Pretreatment with 25–200 µM of silymarin significantly protected against cisplatin-induced cell death in a dose-dependent manner. In contrast, pretreatment of silymarin (25–100 µM) caused no significant change on cisplatin-induced cell death in H460 cells but significantly potentiated cisplatin-induced apoptosis in G361 cells. Discussion and conclusion: These findings reveal the selectivity of silymarin in protection of renal cells from cisplatin-induced cell death and could be beneficial for the development of this considerately safe compound as a renoprotective agent.

Protective effect of Glycine max and Chrysanthemum indicum extracts against cisplatin-induced renal epithelial cell death

Although cisplatin is one of the most efficient chemotherapeutic agents for the treatment of solid tumors, frequently observed nephrotoxicity has limited its use in several patients. Materials and methods: The protective effect of Glycine max (GM) and Chrysanthemum indicum (CM) extracts on cisplatin-induced apoptosis in human proximal tubular HK-2 cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Hoechst 33342, and propidium iodide assays. Reactive oxygen species (ROS) were determined by flow cytometry with 2,7-dichlorofluorescein diacetate (DCFH2-DA). Results: Cisplatin-induced renal cell toxicity through the induction of hydrogen peroxide (H2O2•−) and hydroxyl radical (OH). CM extract protected cisplatin-induced apoptosis by its anti-oxidant activity against H2O2 and OH•−, while GM extract scavenged only H2O2. Furthermore, GM and CM extracts protect renal cells without significant interfering effect on cisplatin toxicity in lung cancer H460 and melanoma G361 cells. Conclusion: GM and CM extracts exhibited a promising protective effect on cisplatin-induced nephrotoxicity which could benefit the development for nephroprotective approaches.

α-Lipoic acid sensitizes lung cancer cells to chemotherapeutic agents and anoikis via integrin β1/β3 downregulation

Chemotherapeutic failure and metastasis are the main causes of high mortality rate in lung cancer. Alteration of cellular redox status in response to endogenous stimuli or exogenous compounds has a significant impact on cell signaling and behavior. Herein we divulge for the first time that lung cancer cells exposed to α-lipoic acid (LA) resulted in a higher level of cellular superoxide anion (O2·-) and hydrogen peroxide (H2O2), and such an increase of the specific reactive oxygen species (ROS) downregulated integrin β1 and β3, the integrins known for potentiating aggressive behavior and metastasis. The LA-treated cells exhibited significant decrease in their abilities to survive in detached condition and grow in anchorage-independent soft agar assay. Furthermore, LA sensitized the cells to cisplatin, etoposide and paclitaxel-induced apoptosis. For underlying mechanism, we found that the treatment of the cells with LA significantly decreased integrin β1 and β3, while had no effect on integrin α5 and αv. Interestingly, survival protein p-AKT and anti-apoptotic protein Bcl-2 were reduced in an association to such integrin modulations. Using ROS probes and selective anti-oxidants, we have shown that H2O2 and O2·- induced by LA are key players for the decrease of β1 and β3 integrins, respectively. These findings indicate a novel effect of LA as well as specific ROS, O2·- and H2O2 in integrin regulation, anoikis and chemotherapeutic sensitizations.

Peptides extracted from edible mushroom: Lentinus squarrosulus induces apoptosis in human lung cancer cells

Abstract Context: Lentinus squarrosulus Mont. (Polyporaceae) is an interesting source of diverse bioactive compounds. Objective: This is the first study of the anticancer activity and underlying mechanism of peptides extracted from Lentinus squarrosuls. Materials and methods: Peptides were isolated from the aqueous extract of L. squarrosulus by employing solid ammonium sulphate precipitation. They were further purified by ion-exchange chromatography on diethylaminoethanol (DEAE)-cellulose and gel filtration chromatography on Sephadex G25. Anticancer activity was investigated in human lung cancer H460, H292 and H23 cells cultured with 0–40 μg/mL of peptide extracts for 24 h. Cell viability and mode of cell death were evaluated by MTT and nuclear staining assay, respectively. Western blotting was used to investigate the alteration of apoptosis-regulating proteins in lung cancer cells treated with peptide extracts (0–20 μg/mL) for 24 h. Results: The cytotoxicity of partially-purified peptide extracts from L. squarrosulus was indicated with IC50 of ∼26.84 ± 2.84, 2.80 ± 2.14 and 18.84 ± 0.30 μg/mL in lung cancer H460, H292 and H23 cells, respectively. The extracts at 20 μg/mL induced apoptosis through the reduction of anti-apoptotic Bcl-2 protein (∼0.5-fold reduction) and up-regulation of BAX (∼4.5-fold induction), a pro-apoptotic protein. Furthermore, L. squarrosulus peptide extracts (20 μg/mL) also decreased the cellular level of death receptor inhibitor c-FLIP (∼0.6-fold reduction). Conclusions and discussion: This study provides the novel anticancer activity and mechanism of L. squarrosulus peptide extracts, which encourage further investigation and development of the extracts for anticancer use.

Acute and Chronic Oral Toxicity of a Partially Purified Plaunotol Extract from Croton stellatopilosus Ohba

Plaunotol, an acyclic diterpenoid with highly effective antigastric ulcer properties, has been commercially isolated from leaves of Croton stellatopilosus Ohba. This Thai medicinal plant was traditionally used in the form of crude extracts, suggesting that it is possible to administer these plaunotol-containing extracts without toxicity. To confirm its safety, the oral toxicity of a partially purified plaunotol extract (PPE) was evaluated in vivo. The PPE was simply prepared by 95% ethanol reflux extraction followed by hexane partition. The obtained extract was analyzed and found to contain 43% w/w of plaunotol and another compound, likely a fatty acid-plaunotol conjugate that is considered a major impurity. Oral administration of PPE to ICR mice and Wistar rats was conducted to evaluate acute and chronic toxicity of the plaunotol extract, respectively. The acute toxicity study demonstrated that PPE was practically nontoxic based on its high median lethal dose value (LD50 = 10.25 g/kg). The chronic toxicity studies also showed the absence of mortality and clinical symptoms in all rats treated with 11–1,100 mg/kg/day of PPE during a 6-month period. Histopathological and hematological analyses revealed that altered liver and kidney function and increased blood platelet number, but only at the high doses (550–1,100 mg/kg/day). These results suggest that PPE is potentially safe for further development as a therapeutic agent in humans.

Cytoplasmic p21 Mediates 5-Fluorouracil Resistance by Inhibiting Pro-Apoptotic Chk2

The oncogenic cytoplasmic p21 contributes to cancer aggressiveness and chemotherapeutic failure. However, the molecular mechanisms remain obscure. Here, we show for the first time that cytoplasmic p21 mediates 5-Fluorouracil (5FU) resistance by shuttling p-Chk2 out of the nucleus to protect the tumor cells from its pro-apoptotic functions. We observed that cytoplasmic p21 levels were up-regulated in 5FU-resistant colorectal cancer cells in vitro and the in vivo Chorioallantoic membrane (CAM) model. Kinase array analysis revealed that p-Chk2 is a key target of cytoplasmic p21. Importantly, cytoplasmic form of p21 mediated by p21T145D transfection diminished p-Chk2-mediated activation of E2F1 and apoptosis induction. Co-immunoprecipitation, immunofluorescence, and proximity ligation assay showed that p21 forms a complex with p-Chk2 under 5FU exposure. Using in silico computer modeling, we suggest that the p21/p-Chk2 interaction hindered the nuclear localization signal of p-Chk2, and therefore, the complex is exported out of the nucleus. These findings unravel a novel mechanism regarding an oncogenic role of p21 in regulation of resistance to 5FU-based chemotherapy. We suggest a possible value of cytoplasmic p21 as a prognosis marker and a therapeutic target in colorectal cancer patients.