Molecular mechanism of kallikrein-related peptidase 8/neuropsin-induced hyperkeratosis in inflamed skin.

BACKGROUND: Hyperkeratosis and acanthosis occur in inflamed skin. Proliferation and differentiation of keratinocytes are important processes during epidermal repair after inflammation. Neuropsin and its human homologue kallikrein-related peptidase 8 (KLK8) have been reported to be involved in epidermal proliferation and differentiation, but the involved molecular mechanisms are obscure. OBJECTIVES: To explore the molecular mechanism of KLK8/neuropsin-induced hyperkeratosis and acanthosis in inflamed skin. METHODS: The molecular mechanism involved in KLK8/neuropsin-induced hyperkeratosis and acanthosis in inflamed skin was investigated both in vivo and in vitro using neuropsin knockout mice and KLK8 knockdown human keratinocytes. Neuropsin-related genes were identified by differential gene display. The localization and functional relationship of the molecules affected downstream of KLK8/neuropsin in normal and inflamed skin were analysed by in situ hybridization and immunohistochemistry. RESULTS: Hyperkeratosis and acanthosis in sodium lauryl sulphate-stimulated skin were markedly inhibited in neuropsin knockout mice. Knockdown of KLK8/neuropsin increased transcription factor activator protein-2α (AP-2α) expression and decreased keratin 10 expression in human keratinocytes and mouse skin, respectively. AP-2α has been reported to inhibit epidermal proliferation and keratin 10 expression. Distributional analysis showed that KLK8/neuropsin was expressed in the stratum spinosum, AP-2α was expressed in the stratum basale and the lower part of the stratum spinosum, and keratin 10 was expressed throughout the stratum spinosum. CONCLUSIONS: The above findings suggest the following mechanism of events underlying KLK8/neuropsin-induced hyperkeratosis: (i) skin inflammation increases KLK8/neuropsin expression in the stratum spinosum; (ii) the released KLK8/neuropsin inhibits AP-2α expression in the cells of the stratum basale and stratum spinosum; (iii) the decrease in AP-2α results in cell proliferation in the stratum basale and cell differentiation in the stratum spinosum, with an increase in keratin 10 expression.

Total protein concentration in selectively collected secretions from the middle and inferior meatus of the nose.

To clarify the characteristics of nasal secretions, a method for collecting human nasal secretion was devised. Total protein concentration in selectively collected secretions from the nasal cavity was determined using biochemical techniques. Dry absorbent cotton was inserted in each middle and inferior meatus of the nasal cavity for 30 min, and put in a test tube with a plastic sieve for centrifugation. After centrifugation at 5,000 rpm for 20 min, 10 microliters were obtained to measure the protein concentration the nasal secretions was made using spectrophotometry. The amount of nasal secretion samples collected was 50 to 400 microliters per site. Nasal secretions collected from the right middle and inferior meatus contained 80 to 2,450 mg/dl and 260 to 3,270 mg/dl of protein, respectively, while those from the left middle and inferior meatus contained 80 to 2,200 mg/dl and 175 to 3,050 mg/dl, respectively. It was concluded that this new method was clinically useful for collecting nasal secretions, and it permitted selective collection from predetermined sites in the nasal cavity. The total protein concentration level of nasal secretions collected by this method was higher in the inferior meatus than in the middle meatus of the nose, with statistical significance.

Transient expression of Xpn, an XLMR protein related to neurite extension, during brain development and participation in neurite outgrowth.

KIAA2022 has been implicated as a gene responsible for expressing X-linked mental retardation (XLMR) proteins in humans. However, the functional role of KIAA2022 in the human brain remains unclear. Here, we revealed that depletion of Kiaa2022 inhibits neurite outgrowth of PC12 cells, indicating that the gene participates in neurite extension. Thus, we termed Kiaa2022 as an XLMR protein related to neurite extension (Xpn). Using the mouse brain as a model and ontogenetic analysis of Xpn by real-time PCR, we clearly demonstrated that Xpn is expressed transiently during the late embryonic and perinatal stages. In situ hybridization histochemistry further revealed that Xpn-expressing neurons could be categorized ontogenetically into three types. The first type showed transient expression of Xpn during development. The second type maximally expressed Xpn during the late embryonic or perinatal stage. Thereafter, Xpn expression in this type of neuron decreased gradually throughout development. Nevertheless, a significant level of Xpn expression was detected even into adulthood. The third type of neurons initiated expression of Xpn during the embryonic stage, and continued to express the gene throughout the remaining developmental stages. Subsequent immunohistochemical analysis revealed that Xpn was localized to the nucleus and cytoplasm throughout brain development. Our findings indicate that Xpn may participate in neural circuit formation during developmental stages via nuclear and cytoplasmic Xpn. Moreover, disturbances of this neuronal circuit formation may play a role in the pathogenesis of mental retardation.