Screening for DJ-1 mutations in early onset autosomal recessive parkinsonism

The DJ-1 gene was identified as responsible for early onset autosomal recessive parkinsonism in two families (PARK7). In this study, after excluding mutations in the parkin gene, the authors screened a large series of early onset autosomal recessive parkinsonism families and consanguineous isolated patients of diverse geographic origins for DJ-1 mutations. No mutations were found. This indicates that PARK7 is not a common locus for early onset autosomal recessive parkinsonism, and that one or more new loci remains to be identified.     

Preferential megalin-mediated transcytosis of low-hormonogenic thyroglobulin: a control mechanism for thyroid hormone release

Hormone secretion by thyrocytes occurs by fluid phase uptake and lysosomal degradation of the prohormone thyroglobulin (Tg). However, some Tg internalized by megalin bypasses lysosomes and is transcytosed across cells and released into the bloodstream. Because the hormone content of Tg is variable, we investigated whether this affects transcytosis. We found that rat Tg with a low hormone content [low-hormonogenic rat Tg (low-horm-rTg)] is transcytosed by megalin across thyroid FRTL-5 cells to a greater extent than rat Tg with a high hormone content [hormonogenic rat Tg (horm-rTg)]. In immunoprecipitation experiments, the Tg sequence Arg-2489-Lys-2503 (required for binding to megalin and heparan sulfate proteoglycans) was found to be more exposed in low-horm-rTg, which accounted for its preferential transcytosis. Thus, removal of surface heparan sulfate proteoglycans from FRTL-5 cells or blocking of 2489-2503 reduced transcytosis of low-horm-rTg to a greater extent than that of horm-rTg. Preferential transcytosis of low-horm-rTg affected hormone release. Thus, the increase in hormone release from horm-rTg in FRTL-5 cells determined by megalin blocking (due to reduced transcytosis and enhanced Tg degradation) was rescued by low-horm-rTg, suggesting that megalin is required for effective hormone release. This finding was confirmed in a small number of megalin-deficient mice, which had serological features resembling mild hypothyroidism. Reduced hormone formation within Tg in vivo, due to treatment of rats with aminotriazole or of patients with Graves' disease with methimazole, resulted in increased Tg transcytosis via megalin, in confirmation of results with FRTL-5 cells. Our study points to a major role of megalin in thyroid homeostasis with possible implications in thyroid diseases.     

Vaccinia virus encodes a previously uncharacterized mitochondrial-associated inhibitor of apoptosis

To circumvent apoptotic death, many viruses encode Bcl-2 homologous proteins that function at the mitochondria. Vaccinia virus, the prototypic member of the Poxviridae family, does not encode a Bcl-2 homolog but inhibits the mitochondrial arm of the apoptotic cascade by an unknown mechanism. We now report that F1L, a previously unidentified protein in vaccinia virus, is responsible for the inhibition of apoptosis. Cells infected with vaccinia virus are resistant to staurosporine-mediated cleavage of poly(ADP-ribose) polymerase, caspases 3 and 9, and release of cytochrome c. In contrast, a vaccinia virus deletion mutant, VV811, was unable to inhibit apoptosis; however, the antiapoptotic function was restored by expression of the F1L ORF, which is absent in VV811. Although F1L displays no homology to members of the Bcl-2 family, it localizes to the mitochondria through a C-terminal hydrophobic domain. We show that expression of F1L interferes with apoptosis by inhibiting the loss of the inner mitochondrial membrane potential and the release of cytochrome c.     

S100A8 induction in keratinocytes by ultraviolet A irradiation is dependent on reactive oxygen intermediates

Cutaneous exposure to ultraviolet (UV) A (320-400 nm) results in the formation of damaging reactive oxygen intermediates, which are implicated as mediators of DNA damage, apoptosis, and photoaging. S100A8 is a low-molecular-weight calcium-binding protein, highly sensitive to oxidation. In this study, UVA-induced S100A8 expression by keratinocytes was investigated. UVA (50-100 kJ per m2) strongly induced S100A8 in differentiated keratinocytes in the epidermis of BALB/c mice. Similarly, S100A8 mRNA and monomeric protein were significantly upregulated in PAM212 cells (a murine keratinocyte cell line) in response to 10 kJ per m2 UVA 24 h after irradiation. Although S100A9 associates with S100A8 in neutrophils and abnormally differentiated keratinocytes (human psoriasis), in this study it was not coinduced with keratinocyte S100A8. Dorsal application of 4-hydroxy-tempo (a superoxide dismutase-mimicking agent) to mice concentration-dependently reduced UVA-induced S100A8 expression. Incubation of PAM212 cells with superoxide dismutase and catalase during UVA irradiation also abrogated S100A8 induction. These results suggest that UVA-induced S100A8 is expressed by keratinocytes in response to generation of reactive oxygen intermediates.     

Aspartate aminotransferase activity in gingival crevicular fluid during orthodontic treatment. A controlled short-term longitudinal study

BACKGROUND: During orthodontic tooth movement, the early response of periodontal tissues to mechanical stress involves an acute inflammatory response, with a sequence characterized by periods of activation, resorption, reversal, and formation in both tension and compression sites. This study used a longitudinal design to examine aspartate aminotransferase (AST) activity in gingival crevicular fluid (GCF) in order to assess whether AST in GCF has potential as a possible diagnostic aid to monitor tooth movement and tissue response during orthodontic treatment. METHODS: Eighteen patients (mean age, 16.1 years) participated in the study. An upper first molar from each patient undergoing treatment for distal movement served as the test tooth (TT), with its contralateral (CC) and antagonist (AC) first molars used as controls. The CC was included in the orthodontic appliance, but was not subjected to the orthodontic force; the AC was free from any orthodontic appliance. The GCF around the experimental teeth was collected from both mesial and distal tooth sites immediately before appliance activation, 1 hour after, and weekly over the following 4 weeks. Clinical gingival condition was evaluated at baseline and at the end of the experimental period. AST activity was determined spectrophotometrically at 30 degrees C, and the results were expressed as total AST activity (mU/sample). RESULTS: Throughout the experiment, AST levels were significantly elevated in all sites from the TT and CC groups compared to the AC group where, conversely, AST activity remained at the baseline level. However, enzyme levels in the TT group were significantly greater than in the CCs at tension sites on day 14, and in compression sites on days 7 and 14. Moreover, AST activity from the TT group was significantly greater in compression sites than in tension sites on day 7; this was not observed for the CCs. CONCLUSIONS: Our results suggest that AST levels in GCF reflect the biological activity which occurs in the periodontium during controlled occlusal trauma and, therefore, should be further evaluated as a diagnostic tool for monitoring correct orthodontic tooth movement in clinical practice.     

Human enamel dissolution in citric acid as a function of pH in the range 2.30< or =pH< or =6.30--a nanoindentation study

The objective of this study was to investigate the dissolution of human enamel in citric acid solutions over a wide range of pH. The in vitro conditions are considered to be relevant to soft drink-induced enamel erosion. Nanoindentation was used to investigate changes in the nanomechanical properties of polished enamel surfaces after exposure to citric acid solutions. Solutions used had 38.1 mmol l-1 citric acid and pH greater than 2.3 but less than 6.3 (2.30 < or = pH < or = 6.30). Samples were exposed to rapidly stirred, constant composition solutions for 120 s. Statistically significant changes in enamel hardness and reduced elastic modulus were observed after exposure to all solutions. There was an approximately linear dependence of enamel hardness on solution pH for 2.90 < or = pH < or = 6.30. Below pH 2.90, enamel is thought to have reached the lowest possible hardness value. The reduction in enamel dissolution caused by an increase in pH of a soft drink is likely to be small. Product modification to reduce the erosive potential of drinks may require additional methods such as addition of calcium salts.