Development of ichthyosiform skin compensates for defective permeability barrier function in mice lacking transglutaminase 1.

Transglutaminase 1 (TGase 1) is one of the genes implicated in autosomal recessive congenital ichthyosis. Skin from TGase 1(-/-) mice, which die as neonates, lacks the normal insoluble cornified envelope and has impaired barrier function. Characterization of in situ dye permeability and transepidermal water loss revealed defects in the development of the skin permeability barrier in TGase 1(-/-) mice. In the stratum corneum of the skin, tongue, and forestomach, intercellular lipid lamellae were disorganized, and the corneocyte lipid envelope and cornified envelope were lacking. Neonatal TGase 1(-/-) mouse skin was taut and erythrodermic, but transplanted TGase 1(-/-) mouse skin resembled that seen in severe ichthyosis, with epidermal hyperplasia and marked hyperkeratosis. Abnormalities in those barrier structures remained, but transepidermal water loss was improved to control levels in the ichthyosiform skin. From these results, we conclude that TGase 1 is essential to the assembly and organization of the barrier structures in stratified squamous epithelia. We suggest that the ichthyosiform skin phenotype in TGase 1 deficiency develops the massive hyperkeratosis as a physical compensation for the defective cutaneous permeability barrier required for survival in a terrestrial environment.

Nox1 is involved in angiotensin II-mediated hypertension: a study in Nox1-deficient mice.

BACKGROUND: Increased production of reactive oxygen species (ROSs) by angiotensin II (Ang II) is involved in the initiation and progression of cardiovascular diseases. NADPH oxidase is a major source of superoxide generated in vascular tissues. Although Nox1 has been identified in vascular smooth muscle cells as a new homolog of gp91phox (Nox2), a catalytic subunit of NADPH oxidase, the pathophysiological function of Nox1-derived ROSs has not been fully elucidated. To clarify the role of Nox1 in Ang II-mediated hypertension, we generated Nox1-deficient (-/Y) mice. METHODS AND RESULTS: No difference in the baseline blood pressure was observed between Nox1(+/Y) and Nox1(-/Y). Infusion of Ang II induced a significant increase in mean blood pressure, accompanied by augmented expression of Nox1 mRNA and superoxide production in the aorta of Nox1(+/Y), whereas the elevation in blood pressure and production of superoxide were significantly blunted in Nox1(-/Y). Conversely, the infusion of pressor as well as subpressor doses of Ang II did elicit marked hypertrophy in the thoracic aorta of Nox1(-/Y) similar to Nox1(+/Y). Administration of a nitric oxide synthase inhibitor (L-NAME) to Nox1(+/Y) did not affect the Ang II-mediated increase in blood pressure, but it abolished the suppressed pressor response to Ang II in Nox1(-/Y). Finally, endothelium-dependent relaxation and the level of cGMP in the isolated aorta were preserved in Nox1(-/Y) infused with Ang II. CONCLUSIONS: A pivotal role for ROSs derived from Nox1/NADPH oxidase was suggested in the pressor response to Ang II by reducing the bioavailability of nitric oxide.

Knocking-in the R142C mutation in transglutaminase 1 disrupts the stratum corneum barrier and postnatal survival of mice.

BACKGROUND: Mutations in the gene encoding transglutaminase 1 (TG1) are responsible for various types of autosomal recessive congenital ichthyosis (ARCI), such as lamellar ichthyosis (LI), congenital ichthyosiform erythroderma (CIE) and some minor variants of ARCI. A point mutation of R143C in the ß-sandwich domain of TG1 has been often identified in patients with LI or CIE. OBJECTIVE: To elucidate the effect of that point mutation on skin barrier structures and functions, we generated mice with a point mutation of R142C, which corresponds to the R143C mutation in human TG1. METHODS: A mouse line with the R142C point mutation in TG1 was established using a gene targeting technique and the Cre-loxP system. The skin phenotypes were analyzed in homozygous mutant Tgm1(R142C/R142C) mice. RESULTS: In the skin of Tgm1(R142C/R142C) mice, expression of the mutant transcripts was comparable with wild-type or Tgm1(+/R142C) mice. However, the amount of mutated protein in the skin was markedly decreased in Tgm1(R142C/R142C) mice, and the TG1 activity of Tgm1(R142C/R142C) keratinocytes was almost lost. Tgm1(R142C/R142C) mice exhibited morphological and functional skin barrier defects and neonatal lethality. The stratum corneum of those mice lacked cornified envelopes, and loricrin, the major structural component, failed to assemble at the corneocyte cell periphery. Tgm1(R142C/R142C) mice showed a marked increase in transepidermal water loss and their skin was easily permeable to toluidine blue dye. The intercellular lipid lamellar structures of the stratum corneum were irregular and the 13-nm periodic X-ray diffractions from the stratum corneum lipid molecules were lost in vivo. CONCLUSION: From these results, we suggest that the R142C mutation of TG1 reduces the enzyme stability which is indispensable for development of the stratum corneum and skin barrier function and for postnatal survival of mice.

Mice lacking the kf-1 gene exhibit increased anxiety- but not despair-like behavior.

KF-1 was originally identified as a protein encoded by human gene with increased expression in the cerebral cortex of a patient with Alzheimer's disease. In mouse brain, kf-1 mRNA is detected predominantly in the hippocampus and cerebellum, and kf-1 gene expression is elevated also in the frontal cortex of rats after chronic antidepressant treatments. KF-1 mediates E2-dependent ubiquitination and may modulate cellular protein levels as an E3 ubiquitin ligase, though its target proteins are not yet identified. To elucidate the role of kf-1 in the central nervous system, we generated kf-1 knockout mice by gene targeting, using Cre-lox recombination. The resulting kf-1(-/-) mice were normal and healthy in appearance. Behavioral analyses revealed that kf-1(-/-) mice showed significantly increased anxiety-like behavior compared with kf-1(+/+) littermates in the light/dark transition and elevated plus maze tests; however, no significant differences were observed in exploratory locomotion using the open field test or in behavioral despair using the forced swim and tail suspension tests. These observations suggest that KF-1 suppresses selectively anxiety under physiological conditions probably through modulating protein levels of its unknown target(s). Interestingly, kf-1(-/-) mice exhibited significantly increased prepulse inhibition, which is usually reduced in human schizophrenic patients. Thus, the kf-1(-/-) mice provide a novel animal model for elucidating molecular mechanisms of psychiatric diseases such as anxiety/depression, and may be useful for screening novel anxiolytic/antidepressant compounds.

Effect of 14-membered-ring macrolides on production of interleukin-8 mediated by protease-activated receptor 2 in human keratinocytes.

The production of interleukin-8 induced by the activation of protease-activated receptor 2 and its synergism with interleukin-1beta were modulated by 14-membered-ring macrolides, namely, roxithromycin, erythromycin, and clarithromycin, in cultured normal human epidermal keratinocytes. Those macrolides may attenuate the protease-activated receptor 2-interleukin-8 axis and thereby modulate proinflammatory responses in the skin.