Caspase-8 deficiency in epidermal keratinocytes triggers an inflammatory skin disease

Expression of enzymatically inactive caspase-8, or deletion of caspase-8 from basal epidermal keratinocytes, triggers chronic skin inflammation in mice. Unlike similar inflammation resulting from arrest of nuclear factor κB activation in the epidermal cells, the effect induced by caspase-8 deficiency did not depend on TNF, IL-1, dermal macrophage function, or expression of the toll-like receptor adapter proteins MyD88 or TRIF. Both interferon regulatory factor (IRF) 3 and TANK-binding kinase were constitutively phosphorylated in the caspase-8–deficient epidermis, and knockdown of IRF3 in the epidermis-derived cells from these mice abolished the expression of up-regulated genes. Temporal and spatial analyses of the alterations in gene expression that result from caspase-8 deficiency reveal that the changes are initiated before birth, around the time that cornification develops, and occur mainly in the suprabasal layer. Finally, we found that caspase-8–deficient keratinocytes display an enhanced response to gene activation by transfected DNA. Our findings suggest that an enhanced response to endogenous activators of IRF3 in the epidermis, presumably generated in association with keratinocyte differentiation, contributes to the skin inflammatory process triggered by caspase-8 deficiency

Induction of cell proliferation and beta-catenin expression in rat utricles in vitro.

peer reviewedLimited regenerative response occurs in mammalian vestibular epithelia, although vestibular hair cell regeneration in mammals has been demonstrated under a variety of experimental conditions. Beta-catenin is known to play an important role in both cell-cell adhesion and signal transduction associated with cell proliferation. This study evaluated cell proliferation activity in mammalian vestibular epithelia in organotypic culture and examined the involvement of beta-catenin in cell proliferation in vestibular epithelia. After 72 h of culture, utricles with or without induction of cell proliferation were examined. Cell proliferation was induced by brief exposure to forskolin and supplementation with fetal bovine serum. Cell proliferation activity was assessed by bromodeoxyuridine (BrdU) labeling. Immunohistochemistry was employed for analysis of cellular distribution of beta-catenin. In utricles cultured without induction of cell proliferation. BrdU labeling was not found in vestibular epithelia. Expression of beta-catenin was found in the area corresponding to the distribution of adherens junctions in vestibular epithelia. However, BrdU labeling was identified in sensory epithelia of utricles following induction of cell proliferation, although the number of BrdU-positive cells in sensory epithelia was very limited. Accumulation of beta-catenin was occasionally found in proliferating cells in sensory epithelia; however, it was not always found in BrdU-positive cells. The present findings suggest that beta-catenin may play a role in the induction of cell proliferation in mammal vestibular epithelia

Thy1-positive bone marrow stem cells express liver-specific genes in vitro and can mature into hepatocytes in vivo

The bone marrow contains stem cells that have the potential to differentiate into a variety of organ-specific mature cells, including the liver and the pancreas. Recently, the origin of hepatic progenitors and hepatocytes was identified to be the bone marrow. However, evidence that describes which cells, among all bone marrow cells, differentiate into hepatocytes, has not yet been presented. Based on recent reports, hematopoietic and hepatic stem cells share characteristic markers such as CD34, c-kit, and Thy1. In particular, both hematopoietic and hepatic stem cells express the Thy1 antigen. We investigated whether rat Thy1-positive bone marrow cells express liver-specific genes in vitro, and whether transplanted Thy1 BM cells differentiate into mature hepatocytes in vivo. For collection of Thy1 cells from bone marrow, FITC-conjugated anti-Thy1.1 monoclonal antibody was used with a Fluorescence-Activated Cell Sorter system. A coculture system of 2 separate layers was used for culture of Thy bone marrow cells. Cultured Thy1 cells expressed albumin protein, which was analyzed by immunofluorescent staining. Thy1 bone marrow cells obtained from wild-type dipeptidyl peptidase IV (DPPIV(+)) male rat were directly transplanted into the injured liver of DPPIV mutant (DPPIV(−)) Fisher 344 female rats and differentiated into mature hepatocytes in recipient liver on 60 days. Donor-derived hepatocytes were confirmed by DPPIV staining and Y-chromsome in situ hybridization. Our results suggest that Thy1-positive bone marrow cells have the potential to generate liver-specific genes in vitro and can differentiate into mature hepatocytes in adult liver in vivo. Thy1-positive bone marrow stem cells may represent preexisting hepatocyte-specific stem cells

Specific Triazine Herbicides Induce Amyloid-beta(42) Production

Proteolytic cleavage of the amyloid-beta protein precursor (A beta PP) ecretases leads to extracellular release of amyloid-beta (A beta) peptides. Increased production of A beta(42) over A beta(40) and aggregation into oligomers and plaques constitute an Alzheimer's disease (AD) hallmark. Identifying products of the 'human chemical exposome' (HCE) able to induce A beta(42) production may be a key to understanding some of the initiating causes of AD and to generate non-genetic, chemically-induced AD animal models. A cell model was used to screen HCE libraries for A beta(42) inducers. Out of 3500+ compounds, six triazine herbicides were found that induced a beta- and gamma-secretases-dependent, 2-10 fold increase in the production of extracellular A beta(42) in various cell lines, primary neuronal cells, and neurons differentiated from human-induced pluripotent stem cells (iPSCs). Immunoprecipitation/mass spectrometry analyses show enhanced production of A beta peptides cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and lower, a characteristic of AD. Neurons derived from iPSCs obtained from a familialAD(FAD) patient (A beta PP K724N) produced more A beta(42) versus A beta(40) than neurons derived from healthy controls iPSCs (A beta PP WT). Triazines enhanced A beta(42) production in both control and AD iPSCs-derived neurons. Triazines also shifted the cleavage pattern of alcadein alpha, another gamma-secretase substrate, suggesting a direct effect of triazines on gamma-secretase activity. In conclusion, several widely used triazines enhance the production of toxic, aggregation prone A beta(42)/A beta(43) amyloids, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in late-onset AD.112sciescopu

Specific Triazine Herbicides Induce Amyloid-beta(42) Production

Proteolytic cleavage of the amyloid-beta protein precursor (A beta PP) ecretases leads to extracellular release of amyloid-beta (A beta) peptides. Increased production of A beta(42) over A beta(40) and aggregation into oligomers and plaques constitute an Alzheimer's disease (AD) hallmark. Identifying products of the 'human chemical exposome' (HCE) able to induce A beta(42) production may be a key to understanding some of the initiating causes of AD and to generate non-genetic, chemically-induced AD animal models. A cell model was used to screen HCE libraries for A beta(42) inducers. Out of 3500+ compounds, six triazine herbicides were found that induced a beta- and gamma-secretases-dependent, 2-10 fold increase in the production of extracellular A beta(42) in various cell lines, primary neuronal cells, and neurons differentiated from human-induced pluripotent stem cells (iPSCs). Immunoprecipitation/mass spectrometry analyses show enhanced production of A beta peptides cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and lower, a characteristic of AD. Neurons derived from iPSCs obtained from a familialAD(FAD) patient (A beta PP K724N) produced more A beta(42) versus A beta(40) than neurons derived from healthy controls iPSCs (A beta PP WT). Triazines enhanced A beta(42) production in both control and AD iPSCs-derived neurons. Triazines also shifted the cleavage pattern of alcadein alpha, another gamma-secretase substrate, suggesting a direct effect of triazines on gamma-secretase activity. In conclusion, several widely used triazines enhance the production of toxic, aggregation prone A beta(42)/A beta(43) amyloids, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in late-onset AD