Paraquat Induces Cell Death Through Impairing Mitochondrial Membrane Permeability.

Paraquat (PQ) as a Parkinsonian mimetic has been demonstrated to impair dopaminergic (DAergic) neurons and is highly correlated with the etiology of Parkinson's disease (PD) where the death of DAergic neurons has been mainly attributed to impaired mitochondrial functioning. In this study, PQ-induced cytotoxicity focusing on mitochondrial membrane permeability (MMP), which has been implicated to play a part in neurodegeneration, was investigated. Primarily, PQ-induced cytotoxicity and reactive oxygen species (ROS) were inhibited by an inhibitor of NADPH oxidase (NOX), indicating the toxic effect of PQ redox cycling. Further, dibucaine and cyclosporin A which respectively inhibit mitochondrial apoptosis-induced channels (MAC) and mitochondrial permeability transition pores (mPTP) were used and found to prevent PQ-induced mitochondrial dysfunction, such as decreased mitochondrial membrane potential and increased MMP, mitochondrial ROS, and pro-apoptotic factor release. Knockdown of bax and/or bak blocked PQ-induced mitochondrial clusterization of Bax and/or Bak and cytotoxicity, demonstrating the significance of MAC which is composed of Bax and/or Bak. This clusterization coincided with the release of mitochondrial apoptotic factors before there was an increase in inner MMP, indicating that MAC may precede mPTP formation. Besides, NOX inhibitor but not dibucaine attenuated the earlier PQ-induced cytosolic ROS formation or Bax and/or Bak clusterization indicating PQ redox cycling may account for MAC formation. In this model, we have resolved for the first that PQ cytotoxicity through redox cycling may sequentially result in increased outer (MAC) and inner (mPTP) MMP and suggested MMP could be implicated as a therapeutic target in treating neurodegenerative diseases like PD.

Inhibitory effects of resveratrol on PDGF-BB-induced retinal pigment epithelial cell migration via PDGFRß, PI3K/Akt and MAPK pathways.

PURPOSE: In diseases such as proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy, and age-related macular degeneration, retinal pigment epithelial (RPE) cells proliferate and migrate. Moreover, platelet-derived growth factor (PDGF) has been shown to enhance proliferation and migration of RPE cells in PVR. Even resveratrol can suppress the migration and adhesion of many cell types, its effects on RPE cell migration and adhesion remain unknown. In this study, we investigated the inhibitory effects of resveratrol on RPE cell migration induced by PDGF-BB, an isoform of PDGF, and adhesion to fibronectin, a major ECM component of PVR tissue. METHODS: The migration of RPE cells was assessed by an electric cell-substrate impedance sensing migration assay and a Transwell migration assay. A cell viability assay was used to determine the viability of resveratrol treated-cells. The cell adhesion to fibronectin was examined by an adhesion assay. The interactions of resveratrol with PDGF-BB were analyzed by a dot binding assay. The PDGF-BB-induced signaling pathways were determined by western blotting and scratch wound healing assay. RESULTS: Resveratrol inhibited PDGF-BB-induced RPE cell migration in a dose-dependent manner, but showed no effects on ARPE19 cell adhesion to fibronectin. The cell viability assay showed no cytotoxicity of resveratrol on RPE cells and the dot binding assay revealed no direct interactions of resveratrol with PDGF-BB. Inhibitory effects of resveratrol on PDGF-BB-induced platelet-derived growth factor receptor ß (PDGFRß) and tyrosine phosphorylation and the underlying pathways of PI3K/Akt, ERK and p38 activation were found; however, resveratrol and PDGF-BB showed no effects on PDGFRα and JNK activation. Scratch wound healing assay demonstrated resveratrol and the specific inhibitors of PDGFR, PI3K, MEK or p38 suppressed PDGF-BB-induced cell migration. CONCLUSIONS: These results indicate that resveratrol is an effective inhibitor of PDGF-BB-induced RPE cell migration via PDGFRß, PI3K/Akt and MAPK pathways, but has no effects on the RPE cell adhesion to fibronectin.

Ile/Ile homozygosity at codon 655 of HER2 in schwannoma.

PURPOSE: This study aimed to determine the genetic role of HER2, one of the epidermal growth factor receptor (EGFR) family, in schwannoma. The latter is a neogrowth of myelin-producing Schwann cells in peripheral nerves, inducible by N-nitrosoethylurea in animals with mutation in the neu gene (homologous gene of human HER2 protein). METHODS: In this study we obtained genomic DNA samples from tissue blocks of schwannoma, initially by xylene treatment and alcohol extraction, followed by use of the DNA extraction kit. Evaluation of this genetic polymorphism in our subjects was conducted by direct nucleotide sequencing or restriction enzyme analyses after PCR work. RESULTS: There were thirty extracted DNA samples from tissue blocks of schwannoma, and all were Ile/Ile homozygotes after genotype analyses. Two individuals received the leukocyte DNA extraction after peripheral blood sampling, both showing Ile/Ile homozygosity. This study gave the impression of an association of the HER2 polymorphism at codon 655 with tumorigenesis of schwannoma. Although the majority of the Taiwanese showed Ile/Ile homozygosity (about 83%), the present study revealed a 100% carriage rate among the tissue blocks from our subjects with schwannoma. CONCLUSION: Ile/Ile homozygosity at codon 655 of HER2 in schwannoma may imply some role in tumorigenesis of Ile655Val allele of HER2 in this nerve tumor.