Allergic inflammation triggered by exposure of an allergen frequently leads to the onset of chronic inflammatory diseases such as atopic dermatitis (AD) and bronchial asthma. The mechanisms underlying chronicity in allergic inflammation remain unresolved. Periostin, a recently characterized matricellular protein, interacts with several cell surface integrin molecules, providing signals for tissue development and remodeling. Here we show that periostin is a critical mediator for the amplification and persistence of allergic inflammation using a mouse model of skin inflammation. Th2 cytokines IL-4 and IL-13 stimulated fibroblasts to produce periostin, which interacted with α v integrin, a functional periostin receptor on keratinocytes, inducing production of proinflammatory cytokines, which consequently accelerated Th2-type immune responses. Accordingly, inhibition of periostin or α v integrin prevented the development or progression of allergen-induced skin inflammation. Thus, periostin sets up a vicious circle that links Th2-type immune responses to keratinocyte activation and plays a critical role in the amplification and chronicity of allergic skin inflammation.

CLP1 is a RNA kinase involved in tRNA splicing. Recently, CLP1 kinase-dead mice were shown to display a neuromuscular disorder with loss of motor neurons and muscle paralysis. Human genome analyses now identified a CLP1 homozygous missense mutation (p.R140H) in five unrelated families, leading to a loss of CLP1 interaction with the tRNA splicing endonuclease (TSEN) complex, largely reduced pre-tRNA cleavage activity, and accumulation of linear tRNA introns. The affected individuals develop severe motor-sensory defects, cortical dysgenesis and microcephaly. Mice carrying kinase-dead CLP1 also displayed microcephaly and reduced cortical brain volume due to the enhanced cell death of neuronal progenitors that is associated with reduced numbers of cortical neurons. Our data elucidate a novel neurological syndrome defined by CLP1 mutations that impair tRNA splicing. Reduction of a founder mutation to homozygosity illustrates the importance of rare variations in disease and supports the clan genomics hypothesis.

Recently, DNA methylation and reduced expression of the suppressor of the cytokine signaling-3 (SOCS3) gene in human hepatocellular carcinoma (HCC) patients have been reported. However, the roles of SOCS3 in HCC development in vivo have not been clarified. Using RT-PCR analysis and Western blotting, we confirmed that SOCS3 expression was reduced in HCC patients. However, reduced expression of SOCS3 occurred not only in HCC but also in nontumor regions, and this reduction was stronger as the fibrosis grade increased. Furthermore, SOCS3 levels were inversely correlated with signal transducers and activators of transcription-3 (STAT3) activation as well as transforming growth factor (TGF)-b1 levels in the non-HCC region. To define the molecular consequences of SOCS3 silencing/STAT3 hyperactivation and liver fibrosis, we examined liverspecific SOCS3-deficient mice. We demonstrated that SOCS3 deletion in the liver resulted in hyperactivation of STAT3 and promoted ConA-and chemical-induced liver fibrosis. The expression of TGF-b1, a mediator of fibrosis, was enhanced by SOCS3 gene deletion, but suppressed by the overexpression of a dominant-negative STAT3 or SOCS3 both in vivo and in vitro. These data suggest that TGF-b1 is a target gene of STAT3 and could be one of the mechanisms for enhanced fibrosis in SOCS3-deficient mice. Thus, our present study provides a novel role of SOCS3 and STAT3 in HCC development: in addition to the previously characterized oncogenic potentials, STAT3 enhances hepatic fibrosis through the upregulation of TGF-b1 expression, and SOCS3 prevents this process.

Idiopathic interstitial pneumonias (IIPs) are histopathologically classified into several types, including usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP) and cryptogenic organising pneumonia (COP). We investigated whether periostin, a matrix protein, could be used as a biomarker to assess histopathological types of IIPs.We performed immunohistochemical analyses in each histopathological type of IIP, examined serum levels of periostin in IIP patients and analysed the relationship between serum levels of periostin and the pulmonary functions in patients with idiopathic pulmonary fibrosis (IPF).Periostin was strongly expressed in lungs of UIP and fibrotic NSIP patients, whereas expression of periostin was weak in the lungs of cellular NSIP and COP patients, as well as in normal lungs. Serum levels of periostin in IPF were significantly higher than those of healthy subjects and COP patients. Furthermore, periostin levels in IPF patients were inversely correlated with their pulmonary functions.Thus, we have found that periostin is a novel component of fibrosis in IIP. Periostin may be a potential biomarker to distinguish IIP with fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually fatal form of interstitial lung disease (ILD). The precise molecular mechanisms of IPF remain poorly understood. However, analyses of mice receiving bleomycin (BLM) as a model of IPF established the importance of preceding inflammation for the formation of fibrosis. Periostin is a recently characterized matricellular protein involved in modulating cell functions. We recently found that periostin is highly expressed in the lung tissue of patients with IPF, suggesting that it may play a role in the process of pulmonary fibrosis. To explore this possibility, we administered BLM to periostin-deficient mice, and they subsequently showed a reduction of pulmonary fibrosis. We next determined whether this result was caused by a decrease in the preceding recruitment of neutrophils and macrophages in the lungs because of the lower production of chemokines and proinflammatory cytokines. We performed an in vitro analysis of chemokine production in lung fibroblasts, which indicated that periostin-deficient fibroblasts produced few or no chemokines in response to TNF-α compared with control samples, at least partly explaining the lack of inflammatory response and, therefore, fibrosis after BLM administration to periostin-deficient mice. In addition, we confirmed that periostin is highly expressed in the lung tissue of chemotherapeutic-agent-induced ILD as well as of patients with IPF. Taking these results together, we conclude that periostin plays a unique role as an inducer of chemokines to recruit neutrophils and macrophages important in the process of pulmonary fibrosis in BLM-administered model mice. Our results suggest a therapeutic potential for periostin in IPF and drug-induced ILD.

Hepatocellular carcinomas (HCCs) mainly develop from liver cirrhosis and severe liver fibrosis that are established with long-lasting inflammation of the liver. Silencing of the suppressor of the cytokine signaling-1 (SOCS1) gene, a negative regulator of cytokine signaling, by DNA methylation has been implicated in development or progress of HCC. However, how SOCS1 contributes to HCC is unknown. We examined SOCS1 gene methylation in >200 patients with chronic liver disease and found that the severity of liver fibrosis is strongly correlated with SOCS1 gene methylation. In murine liver fibrosis models using dimethylnitrosamine, mice with haploinsufficiency of the SOCS1 gene (SOCS1−/+ mice) developed more severe liver fibrosis than did wild-type littermates (SOCS1+/+ mice). Moreover, carcinogen-induced HCC development was also enhanced by heterozygous deletion of the SOCS1 gene. These findings suggest that SOCS1 contributes to protection against hepatic injury and fibrosis, and may also protect against hepatocarcinogenesis.

Accumulation of unfolded proteins induces endoplasmic reticulum (ER) stress. Excessive and prolonged stresses lead cells to apoptosis. However, the precise molecular mechanisms of ER stress-induced apoptosis have not been fully elucidated. We investigated the involvement of the apoptosome in ER stress-induced cell death pathway using mouse embryonic fibroblasts (MEFs) and mice deficient for Apaf-1. Apaf-1-deficient MEFs showed more resistance to ER stress-inducing reagents as compared with wild type cells. Despite comparable induction of ER stress in both wild type and Apaf-1-deficient cells, activation of caspase-3 was only observed in wild type, but not Apaf-1-deficient, MEFs. Under ER stress conditions, BAX translocated to mitochondria and cytochrome c was released from mitochondria. We also demonstrated that caspase-12 was processed downstream of Apaf-1 and caspase-3, and neither overexpression nor knockdown of caspase-12 affected susceptibility of the cells to ER stress-induced cell death. Furthermore, in the kidneys of Apaf-1-deficient mice, apoptosis induced by in vivo administration of tunicamycin was remarkably suppressed as compared with wild type mice. These data collectively demonstrated that Apaf-1 and the mitochondrial pathway of apoptosis play significant roles in ER stress-induced apoptosis.

Cutaneous wound repair is a highly ordered and wellcoordinated process involving various cell lineages and many molecular effectors. Cell-matrix interactions through integrin molecules provide key signals important for wound repair. Periostin is a matricellular protein that may provide signals important during tissue development and remodelling by interacting with several integrin molecules, via the phosphatidylinositol 3-kinase ⁄ Akt and MAP kinase pathways. In this study, we examined the role of periostin in the process of cutaneous wound repair using periostin-deficient mice and by analysing the effects of periostin on dermal fibroblasts. We first determined the expression profile and localization of periostin in a well-characterized wound repair model mice. Periostin was robustly deposited in the granulation tissues beneath the extended epidermal wound edges and at the dermal-epidermal junctions in wounded mice. Moreover, periostin-deficient mice exhibited delayed in vivo wound repair, which could be improved by direct administration of exogenous periostin. In vitro analyses revealed that loss of periostin impaired proliferation and migration of dermal fibroblasts, but exogenous supplementation or enforced periostin expression enhanced their proliferation. Combined, these results demonstrate that periostin accelerates the process of cutaneous wound repair by activating fibroblasts.