Jason Y. Chang

Oxidative stress causes ERK phosphorylation and cell death in cultured retinal pigment epithelium: Prevention of cell death by AG126 and 15-deoxy-delta 12, 14-PGJ2

BackgroundThe retina, which is exposed to both sunlight and very high levels of oxygen, is exceptionally rich in polyunsaturated fatty acids, which makes it a favorable environment for the generation of reactive oxygen species. The cytotoxic effects of hydrogen peroxide (H2O2) induced oxidative stress on retinal pigment epithelium were characterized in this study.MethodsThe MTT cell viability assay, Texas-Red phalloidin staining, immunohistochemistry and Western blot analysis were used to assess the effects of oxidative stress on primary human retinal pigment epithelial cell cultures and the ARPE-19 cell line.ResultsThe treatment of retinal pigment epithelial cells with H2O2 caused a dose-dependent decrease of cellular viability, which was preceded by a significant cytoskeletal rearrangement, activation of the Extracellular signal-Regulated Kinase, lipid peroxidation and nuclear condensation. This cell death was prevented partially by the prostaglandin derivative, 15d-PGJ2 and by the protein kinase inhibitor, AG126.Conclusion15d-PGJ2 and AG126 may be useful pharmacological tools in the future capable of preventing oxidative stress induced RPE cell death in human ocular diseases.

Manganese potentiates nitric oxide production by microglia

Manganese toxicity has been associated with clinical symptoms of neurotoxicity which are similar to the symptoms observed in Parkinsons disease. Earlier reports indicated that reactive microglia was present in the substantia nigra of patients with Parkinsons disease. Using N9 microglial cells, the current study was designed to determine whether high levels of manganese were associated with microglial activation. Results indicated that manganese significantly increased the bacterial lipopolysaccharide-induced nitric oxide production. This potent activity of manganese was not shared by other transition metals tested, including iron, cobalt, nickel, copper and zinc. Immunohistochemical staining and Western blot analysis indicated that manganese increased the cellular production of inducible nitric oxide synthase. Northern blot analysis indicated that manganese likely increased iNOS gene transcription since this agent increased the mRNA level of the inducible nitric oxide synthase. In contrast to other transition metals tested, manganese did not appear to be cytotoxic to microglial cells. These results suggested that manganese could induce sustained production of neurotoxic nitric oxide by activated microglial cells, which might cause detrimental consequences to surrounding neurons.

A Pilot Cluster-Randomized Trial of a 20-Week Tai Chi Program in Elders With Cognitive Impairment and Osteoarthritic Knee: Effects on Pain and Other Health Outcomes

CONTEXT Because Tai Chi (TC) is beneficial to elders without cognitive impairment (CI), it also may benefit elders with CI. But elders with CI have generally been excluded from TC studies because many measurement tools require verbal reports that some elders with CI are unable to provide. OBJECTIVES To test the efficacy of a TC program in improving pain and other health outcomes in community-dwelling elders with knee osteoarthritis (OA) and CI. METHODS This pilot cluster-randomized trial was conducted between January 2008 and June 2010 (ClinicalTrials.gov Identifier: NCT01528566). The TC group attended Sun style TC classes, three sessions a week for 20 weeks; the control group attended classes providing health and cultural information for the same length of time. Measures included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, physical function and stiffness subscales; the Get Up and Go test; the Sit-to-Stand test; and the Mini-Mental State Examination (MMSE), administered at baseline, every four weeks during the intervention and at the end of the study (post-test). RESULTS Eight sites participated in either the TC group (four sites, 28 participants) or control group (four sites, 27 participants). The WOMAC pain (P = 0.006) and stiffness scores (P = 0.010) differed significantly between the two groups at post-test, whereas differences between the two groups in the WOMAC physical function score (P = 0.071) and the MMSE (P = 0.096) showed borderline significance at the post-test. WOMAC pain (P = 0.001), physical function (P = 0.021), and stiffness (P ≤ 0.001) scores improved significantly more over time in the TC group than in controls. No adverse events were found in either group. CONCLUSION Practicing TC can be efficacious in reducing pain and stiffness in elders with knee OA and CI.

Methylmercury causes oxidative stress and cytotoxicity in microglia: Attenuation by 15-deoxy-delta 12, 14-Prostaglandin J2

Methylmercury (MeHg) causes severe neurological disorders in the central nervous system. This study focused on the effects of MeHg on microglia, macrophage-like cells that reside in the CNS important in neuro-immune interactions. The murine N9 microglial cell line was used in this set of study. MeHg caused reactive oxygen species generation, mitochondrial depolarization and aconitase inactivation, all of which were signs of cellular oxidative stress. MeHg greatly increased microglial IL-6 secretion despite the fact that it severely inhibited protein synthesis. The concentration that caused 50% cell death in 24 h was approximately 9 microM. Pretreatment of microglia with the prostaglandin derivative, 15-deoxy-delta 12, 14-Prostaglandin J2 attenuated MeHg induced cell death. The saving effect did not appear to be mediated through activation of peroxisome proliferator activated receptors (PPAR) since other agonists of these receptors did not prevent MeHg induced microglial death.

Catecholamines inhibit microglial nitric oxide production

Viral infection in the central nervous system can induce nitric oxide production, which serves as a major host defense against viral infection. Under stress, catecholamine secretion is enhanced and immune responses are diminished in animals. Using N9 microglial cells, this study tested the effect of catecholamines on microglial nitric oxide production. Results indicated that each member of the catecholamine family (dopamine, norepinephrine and epinephrine) was a potent inhibitor of the microglial nitric oxide production. In contrast, dopa, the immediate precursor of the catecholamine biosynthesis pathway, was a weak inhibitor, except at very high concentrations. The inhibitory effect of catecholamines was mimicked by an alpha-adrenergic receptor agonist (phenylephrine) and by a beta-adrenergic receptor agonist (isoproterenol), but not by forskolin or analogs of cyclic adenosine monophosphate. Western blot analysis indicated that catecholamines caused a slight decrease in the formation of inducible nitric oxide synthase. These results suggest that catecholamines have the ability to block nitric oxide production by microglia, which could partially explain the impaired immune protection against viral infection in the central nervous system in stressed animals.

Methylmercury causes glial IL-6 release

Methylmercury (MeHg) is an environmental toxin that causes severe neurological complications in humans and experimental animals. MeHg caused IL-6 release from the rat C6 glioma cells, the human U251HF glioma cells and the human retina pigment epithelial (ARPE-19) cells. These results plus those we reported earlier using mouse N9 microglia cells indicate that IL-6 induction may be a general property of MeHg among various glial cell types across species. MeHg caused a concentration-dependent increase of cellular oxidation with a maximal level reached by approximately 10 microM MeHg, which was similar to that caused by 30 microM H2O2 or t-butyl hydroperoxide (tBH). The ability of MeHg to induce IL-6 release was not affected by exogenously added H2O2 or t-butyl hydroperoxide. Furthermore, IL-6 release was not accompanied by other cytokine release. Given the reports by others that IL-6 could modulate neuronal survival, glia may affect MeHg neurotoxicity by their IL-6 release when exposed to this neurotoxin.

Neurotoxicity of cholesterol oxides on cultured cerebellar granule cells.

Cultured rat cerebellar granule cells were used to determine the potential neurotoxicity of cholesterol oxides. The cholesterol oxides tested included: 7-beta-OH-, 7-keto-, 19-OH-, 22(R)-OH-, 22(S)-OH- and 25-OH- cholesterol. Among them, 7-beta-OH- and 7-keto-cholesterol were the most efficacious in causing neuronal death such that 20 microg/ml (50 microM) of these agents killed more than 80% of cells in 2 days. 7-beta-OH-cholesterol at this concentration killed 50% of cells in approximately 7 h. A number of pharmacological agents were tested for their abilities to prevent neuronal death induced by cholesterol oxides. Among them, aurintricarboxylic acid, vitamin E and methyl-beta-cyclodextrin were able to prevent cholesterol oxide-induced neurotoxicity in a dose-dependent manner. These results suggest that, in addition to causing pathological changes in cells directly involved in atherosclerosis, cholesterol oxides may induce toxicity in neurons of the central nervous system.

15-deoxy-delta 12, 14-Prostaglandin J2 prevents reactive oxygen species generation and mitochondrial membrane depolarization induced by oxidative stress

BackgroundWith the use of cultured human retinal pigment epithelial cells, we have previously described a number of cellular responses to oxidative stress caused by H2O2. We also demonstrated that the cytotoxicity caused by H2O2 could be prevented by the prostaglandin derivative, 15-deoxy-delta 12, 14-Prostaglandin J2 (15d-PGJ2).ResultsFurther characterization of the experimental system indicated that the half-life of H2O2 in cultures was ~1 hour. At a fixed H2O2 concentration, the cytotoxicity was dependent on the volume of H2O2 solution used in the culture, such that higher volume caused more cytotoxicity. Most cells were committed to die if the culture was treated for 2 hours with a cytotoxic concentration of H2O2. The prostaglandin derivative, 15d-PGJ2, could prevent oxidative damage caused by t-butyl hydroperoxide, in addition to H2O2. Further studies indicated that both H2O2 and tBH caused an increase in reactive oxygen species and depolarization of mitochondrial membrane potential. Pretreatment of cells with 1 μM 15d-PGJ2 led to a modest decrease in reactive oxygen species generation, and a significant restoration of mitochondrial membrane potential.ConclusionThis agent may be used in the future as a pharmacological tool for preventing cellular damage caused by oxidative stress.

Stress Management–Augmented Behavioral Weight Loss Intervention for African American Women A Pilot, Randomized Controlled Trial

The relationship between chronic stress and weight management efforts may be a concern for African American (AA) women, who have a high prevalence of obesity, high stress levels, and modest response to obesity treatment. This pilot study randomly assigned 44 overweight/obese AA women with moderate to high stress levels to either a 12-week adaptation of the Diabetes Prevention Program Lifestyle Balance intervention augmented with stress management strategies (Lifestyle + Stress) or Lifestyle Alone. A trend toward greater percentage of baseline weight loss at 3-month data collection was observed in Lifestyle + Stress (−2.7 ± 3.6%) compared with Lifestyle Alone (−1.4 ± 2.3%; p = .17) and a greater reduction in salivary cortisol (Lifestyle + Stress: −0.2461 ± 0.3985 ng/mL; Lifestyle Alone: −0.0002 ± 0.6275 ng/mL; p = .20). These promising results suggest that augmenting a behavioral weight control intervention with stress management components may be beneficial for overweight/obese AA women with moderate to high stress levels and merit further investigation with an adequately powered trial.

Neurotoxicity of 25-OH-Cholesterol on NGF-Differentiated PC12 Cells

PC12 cells induced to differentiate with nerve growth factor were used to study the neurotoxicity of 25-OH-cholesterol. This agent induced a dose- and time-dependent cell death in neuronal PC12 cells. Cells treated with this agent showed condensed nuclei, a morphology similar to that of cells dying of programmed cell death. However, agents known to prevent neuronal programmed cell death (cyclic AMP, KCl, aurintricarboxylic acid, and cycloheximide) failed to prevent the 25-OH-cholesterol-mediated cytotoxicity. On the other hand, cell death induced by 25-OH-cholesterol was prevented by treatment with vitamin E and methyl-beta-cyclodextrin. In contrast to observations made in other cell types, whole-cell patch clamp recording of neuronal PC12 cells revealed that treatment with 25-OH-cholesterol did not significantly alter calcium influx through voltage-dependent channels. These results provide the first characterization of the toxicity of cholesterol oxides toward neuronal PC12 cells, which should be useful in future studies on the interactions between cholesterol oxides and cells from the nervous system.