H2O2-induced Cellular Damage Research Articles

Hypoglycemic and beta cell protective effects of andrographolide analogue for diabetes treatment

BackgroundWhile all anti-diabetic agents can decrease blood glucose level directly or indirectly, few are able to protect and preserve both pancreatic beta cell mass and their insulin-secreting functions. Thus, there is an urgent need to find an agent or combination of agents that can lower blood glucose and preserve pancreatic beta cells at the same time. Herein, we report a dual-functional andrographolide-lipoic acid conjugate (AL-1). The anti-diabetic and beta cell protective activities of this novel andrographolide-lipoic acid conjugate were investigated.MethodsIn alloxan-treated mice (a model of type 1 diabetes), drugs were administered orally once daily for 6 days post-alloxan treatment. Fasting blood glucose and serum insulin were determined. Pathologic and immunohistochemical analysis of pancreatic islets were performed. Translocation of glucose transporter subtype 4 in soleus muscle was detected by western blot. In RIN-m cells in vitro, the effect of AL-1 on H2O2-induced damage and reactive oxidative species production stimulated by high glucose and glibenclamide were measured. Inhibition of nuclear factor kappa B (NF-κB) activation induced by IL-1β and IFN-γ was investigated.ResultsIn alloxan-induced diabetic mouse model, AL-1 lowered blood glucose, increased insulin and prevented loss of beta cells and their dysfunction, stimulated glucose transport protein subtype 4 (GLUT4) membrane translocation in soleus muscles. Pretreatment of RIN-m cells with AL-1 prevented H2O2-induced cellular damage, quenched glucose and glibenclamide-stimulated reactive oxidative species production, and inhibited cytokine-stimulated NF-κB activation.ConclusionWe have demonstrated that AL-1 had both hypoglycemic and beta cell protective effects which translated into antioxidant and NF-κB inhibitory activity. AL-1 is a potential new anti-diabetic agent.

Optimisation of accelerated solvent extraction for screening of the health benefits of plant food materials

The development of a rapid, robust and reliable method for extracting plant food materials is important for screening a wide range of plant bioactives for their health benefits. In this study, extractions of bioactive polyphenolic com-pounds from fruits and vegetables were per-formed using a pressurised solvent extraction technique. Variables including solvent, extrac-tion temperature and time, and number of ex-traction cycles, were optimised to develop a rapid and efficient extraction protocol. The re-sulting extracts were then analysed for antioxi-dant capacity, total phenolic content and com-position. The optimal parameters found were 19:1 methanol/water (95% methanol) as solvent and three extraction cycles, of 10 minutes at 40ºC or 2 minutes at 100ºC. High performance liquid chromatography mass spectrometry did not detect any difference in extract composition between low and high temperatures. Extraction at 100°C generally gave a moderately higher yield of polyphenolics for some fruit and vege-table extracts but appeared to reduce the anti-oxidant activity particularly for turnip leaf, el-derberry and sour cherry extracts as measured by oxygen radical absorbance capacity assay. We found that all 40°C extracts were better at protecting cells from H2O2-induced cellular damage than their 100°C counterparts. The 40°C apple puree and elderberry extracts were about 2 fold and 1.7 fold more effective, respectively, than extracts prepared at 100°C. Our results demonstrated that pressurised solvent extrac-tion technique with careful parameter selection can be used as a quick method for screening the health benefits of plant food materials.

Response of Lens Epithelial Cells to Hydrogen Peroxide Stress and the Protective Effect of Caloric Restriction

Hydrogen peroxide (H2O2) has been reported to be present at significant levels in the lens and aqueous humor in some cataract patients and suggested as a possible source of chronically inflicted damage to lens epithelial (LE) cells. We measured H2O2effects on bovine and mouse LE cells and determined whether LE cells from old calorically restricted mice were more resistant to H2O2-induced cellular damage than those of same age ad libitum fed (AL) mice. Bovine lens epithelial cells were exposed to H2O2at 40 or 400 μM for 2 h and then allowed to recover from the stress. The cells were assayed for DNA damage, DNA synthesis, cell viability, cell morphology, response to growth stimuli, and proliferation potential. Hydrogen peroxide-treated cells showed an increased DNA unwinding 50% greater than that for untreated controls. These DNA strand breaks appeared to be almost completely rejoined by 30 min following removal of the cells from a 2-h exposure. The 40 μM exposure did not produce a significantly lower DNA synthesis rate than the control, it responded to growth factor stimuli, and it replicated as did the control cells after removal of H2O2. The 400 μM H2O2severely affected DNA synthesis and replication, as shown by increased cell size and by markedly reduced clonal cell growth. The cells did not respond to growth stimulation by serum or growth factors and lost irreversibly the capacity to proliferate. The responses of LE cells from old adlib diet (AL) and calorically restricted (CR) mice to H2O2were significantly different. Exposure of LE cells to 20, 40, or 100 μM H2O2for 1 h induces a significant loss of cellular proliferation in cells from old AL mice. LE cells from long-term CR mice of the same strain and age were more resistant to oxidative damage at all three concentrations of H2O2than those of both old and young AL mice and showed a significantly higher proliferation potential following treatment. It is concluded that CR results in superior resistance to reactive oxygen radicals in the lens epithelium.