Effect of CDA-II on cell viability, lipid peroxidation, glutathione concentration and its related enzyme activities in primary rat hepatocytes

Enzymatic modification of native chitin and chitin oligosaccharides by an alkaline chitin deacetylase from Microbacterium esteraromaticum MCDA02

In this study, chitin deacetylase from Microbacterium esteraromaticum MCDA02 (MeCDA) was purified by ammonium sulfate precipitation, anion exchange chromatography, and superdex column chromatography. The molecular weight of purified MeCDA was approximately 26 kDa. The optimum pH and temperature of purified MeCDA were 8.0 and 30 °C, respectively. The enzyme activity is enhanced by metal ions K⁺ and Sr⁺ and inhibited by Co²⁺, Cd²⁺, and EDTA. The degree of deacetylation through enzymatic modification of MeCDA was removed an average of 32.75% of the acetyl groups for ɑ-chitin by acid-base titration. Meanwhile, MeCDA can catalyze the hydrolytic cleavage of the acetamido bond in GlcNAc units within chitin oligomers and polymers. Hence, the MeCDA is a potent chitin decomposer to catalyze chitin and chitin oligosaccharides deacetylation to prepare chitosan and chitosan oligosaccharide. This is a value-added utilization of chitin based biological resources.

Human Urine Extract Cell Differentiation Agent 2 Protects PC12 Cells from Serum Deprivation-Induced Apoptosis Accompanied with Priming of Extracellular Signal-Regulated Kinase Activation and Differentiation Induction

OBJECTIVE

To investigate the potential neuroprotective effect of human urine extract cell differentiation agent 2 (CDA-2) by the model of serum deprivation-induced apoptosis of PC12 cells and study the underlying molecular mechanisms.

METHODS

Apoptosis of PC12 cells was induced by serum deprivation. CDA-2 at doses of 0.5-4 mg/mL was used to treat the serum-deprived PC12 cells. The cellular viability was measured by sulforhodamine B binding assay and the cell apoptosis was determined by flow cytometer. Western blot was used to analyze the expression of differentiation markers and activity of extracellular signal-regulated kinase (ERK). The cellular morphology was examined under an inverted microscope.

RESULTS

CDA-2 inhibited apoptotic cell death of serum-deprived PC12 cells in a dose-dependent manner. Expression of low- and mid-sized neurofilaments was observed in serum-deprived PC12 cells treated with CDA-2 or nerve growth factor (NGF). However, CDA-2 did not induce proliferation of these cells like NGF. The morphology of CDA-2 treated cells was changed from rounded to neuron-like flat polygonal shape in contrast to the extensive neurite outgrowth induced by NGF. CDA-2 transiently induced the phosphorylation of ERK in serum deprived-PC12 cells and the expression of neurofilaments induced by CDA-2 was attenuated by mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor PD98059.

CONCLUSIONS

Human urine extract CDA-2 showed a potential neuroprotective activity which may correlate with ERK activation and differentiation induction.

Lipid peroxides and glutathione status in human progenitor mononuclear (U937) cells following exposure to low doses of nickel and copper

Effects of Cu(2+), Ni(2+) or Cu(2+) + Ni(2+) on lipid peroxide and glutathione (GSH) levels in U937 cells were investigated. Cells were treated with 0, 5, 10, and 20 µM of Cu(2+) and/or Ni(2+) and H(2)O(2) (0.01 mM) and incubated for 24 hours at 37°C. Lipid peroxides were measured by the thiobarbituric acid assay (TBA). GSH intracellular levels were assayed by the GSH assay kit from EMD/Calbiochem (San Diego, California, USA). Cu(2+) or Ni(2+) significantly (P < 0.01) increased lipid peroxides in a dose-dependent manner, compared to controls. The effect was more pronounced for Cu(2+), compared to the Ni(2+)-treated samples. Cu(2+) + Ni(2+) increased lipid peroxides in a significant (P < 0.001), dose-dependent manner, compared to Cu(2+) or Ni(2+) alone (i.e., ratio of 2.5:1-fold for combined versus single treatments, respectively). Cu(2+) or Ni(2+) significantly decreased GSH levels in U937 cells, with the effect being pronounced for Cu(2+). Cu(2+) + Ni(2+) metal ions significantly (P < 0.001) depleted cells of GSH in a dose-dependent manner. Ethylene diamine tetraacetic acid (EDTA) at 50 or 100 µM moderately reduced the Cu(2+)- or Ni(2+)-induced effects on GSH levels. Interestingly, GSH levels generally decreased to half (except for the combined metal dose of 20 µM at 100 µM EDTA) of its level at the highest metal concentration tested for both the single or combined treatments. In conclusion, multiple exposures of cells to metal ions may be lethal to cells, compared to their single treatments.

Inhibitory effect of CDA-II, a urinary preparation, on aflatoxin B(1)-induced oxidative stress and DNA damage in primary cultured rat hepatocytes

The effects of CDA-II (cell differentiation agent II; a urinary preparation) on both aflatoxin B(1) (AFB(1))-induced cell injury and DNA damage were investigated using cultured rat hepatocytes. CDA-II was able to suppress both the lipid peroxidation and lactate dehydrogenase leakage induced by AFB(1). Glutathione (GSH) depletion by AFB(1) was replenished by CDA-II treatment. Under these experimental conditions, CDA-II enhanced the activity of GSH peroxidase, but not GSH S-transferase. By evaluation of unscheduled DNA synthesis, CDA-II reduced AFB(1)-induced DNA damage in hepatocyte cultures. These findings suggest that CDA-II can inhibit cytotoxicity of AFB(1) through enhancing the activity of GSH peroxidase and preventing GSH depletion.

In vitro exposure to quercetin and genistein alters lipid peroxides and prevents the loss of glutathione in human progenitor mononuclear (U937) cells

The effects of flavonoids quercetin and genistein were investigated according to their potency to inhibit the oxidation of U937 cells via Fenton's pathway through the analysis of lipid peroxides and glutathione (GSH) levels. Human leukemia (U937) cells from the American Type Culture Collection were maintained at 37 degrees C for 24 h under 5% CO2 tension in RPMI-1640 medium containing 10% fetal bovine serum and 50 units ml(-1) each of penicillin and streptomycin. Cells were oxidized with iron 50 microM) or copper (50 microM) in H2O2 (0.01 mM) without or with a flavonoid sample (10 or 20 microM) for the lipid peroxidation studies. The GSH levels were measured (GSH Kit) before and after oxidation as above with different concentrations of flavonoids (0-40 microM). Lipid peroxide was measured by the thiobarbituric acid assay. Both quercetin and genistein at either the 10 or 20 microM level decreased lipid peroxidation significantly compared with their respective controls (P < 0.01). Lipid peroxides by Fe compared to the Cu-treated samples did not differ significantly from each other. However, the combination of flavonoids at the doses tested significantly (P < 0.001) decreased lipid peroxides, the effect being the same for both metal ions. The GSH levels increased significantly before exposure to the metal ions (for the different doses for the differences between the flavonoid samples and their respective untreated levels). For quercetin and genistein the increases in GSH above their untreated levels were 4.5, 8.3, 11.7 and 15 and 3.8, 7.9, 12.5 and 14.6 nmol 10(-6) cells, respectively, for the 5-40 microM levels tested for each flavonoid. Following the exposure to the metal ions, GSH levels remained almost the same for the different concentrations for each of the flavonoids tested but significantly above all of the controls and same for those of the untreated samples. The results indicate that both flavonoids inhibited lipid peroxides and the inhibition may be attributed to the prevention of loss of intracellular GSH levels in U937 cells.