In psoriasis lesions, a diverse mixture of cytokines is up-regulated that influence each other generating a complex inflammatory situation. Although this is the case, the inhibition of IL-17A alone showed unprecedented clinical results in patients, indicating that IL-17A is a critical inducer of psoriasis pathogenesis. To elucidate IL-17A-driven keratinocyte-intrinsic signaling pathways, we treated monolayers of normal human epidermal keratinocytes in vitro with a mixture of six cytokines (IL-17A, TNF-α, IL-17C, IL-22, IL-36γ and IFN-γ) involved in psoriasis to mimic the inflammatory milieu in psoriasis lesions. Microarray and gene set enrichment analysis revealed that this cytokine mixture induced similar gene expression changes with the previous transcriptome studies using psoriasis lesions. Importantly, we identified a set of IL-17A-regulated genes in keratinocytes, which recapitulate typical psoriasis genes exemplified by DEFB4A, S100A7, IL19 and CSF3, based on the differences in the expression profiles of cells stimulated with six cytokines versus cells stimulated with only five cytokines lacking IL-17A. Furthermore, a specific IL-17A-induced gene, NFKBIZ, which encodes IκB-ζ, a transcriptional regulator for NF-κB, was demonstrated to have a significant role for IL-17A-induced gene expression. Thus, we present novel in vitro data from normal human keratinocytes that would help elucidating the IL-17A-driven keratinocyte activation in psoriasis.
Abstract: The authors report a female patient with congenital pulmonary alveolar proteinosis (PAP). She had two brothers who died from the same disease. BAL did not improve her progressive respiratory failure. After intravenous immunoglobulin G (IVIG) administration for complicated hypogammaglobulinemia, she recovered from respiratory failure. The efficacy of IVIG was confirmed by recovery from deterioration in respiratory status and improvement in chest CT findings on two separate occasions. Subsequently, the patient remains free from respiratory symptoms for more than 3 years on an ongoing regimen of monthly IVIG. She had no surfactant protein (SP) B deficiency. Alveolar macrophages (AM) obtained from her BAL fluid were small and showed decreased phagocytotic activity. Immunostaining revealed weak expression of PU.1 in her AM, a key protein in AM maturation. All nucleotide sequences of granulocyte‐macrophage colony stimulating factor (GM‐CSF), GM‐CSF‐receptor and PU.1 were normal. Endotoxin‐induced GM‐CSF release from peripheral mononuclear cells (PMNC), and proliferation of PMNC in response to GM‐CSF were normal. In addition, an antibody against GM‐CSF, as seen in adult patients with idiopathic PAP, was not detected in the serum or BAL fluid. Although the patient's PMNC secreted only small amounts of IgG and IgM, an EB virus‐derived cell line of her B cells secreted IgM as much as normal control cells. In a flow cytometric study, IgM was expressed on the cell surface. In conclusion, an abnormality in a single gene may have decreased secretion of immunoglobulin from the B cells and the AM phagocytotic activity in the patient.
Daxx has been shown to play an essential in type I interferon (IFN‐α/β)‐mediated suppression of B cell development and apoptosis. Recently, we demonstrated that Tyk2 is directly involved in IFN signaling for the induction and nuclear translocation of Daxx, which may result in growth arrest and/or apoptosis of B lymphocyte progenitors. To clarify the mechanism of Daxx‐mediated apoptosis signaling in B lymphocyte progenitors, here we introduced an efficient suicide switch in a murine pro‐B cell line, BAF3, by expressing FK506‐binding protein‐fused Fas intracellular domain (FKBP‐Fas) and Daxx. It allows us to monitor Fas/Daxx‐mediated signal by induction of Fas dimerization with the dimerizer drug AP20187. AP20187‐mediated Fas dimerization induced not only apoptosis but also Jun N‐terminal kinase (JNK) activation. However, AP20187 had no effect on cells expressing either Fas or Daxx only. Furthermore, expression of a JNK inhibitor, the JNK‐binding domain of JIP‐1, resulted in resistance to AP20187‐mediated apoptosis in cells expressing FKBP‐Fas and Daxx. These results imply that our novel suicide switch system may provide a powerful tool to delineate or identify the signaling molecules for Daxx‐mediated apoptotic machinery in B lymphocyte progenitors through JNK activation.
Abstract Cytokine IL-17A (IL-17) acts on various cell types, including epidermal keratinocytes, and induces antimicrobial peptide and chemokine production to elicit antibacterial and antifungal defense responses. Excess IL-17 leads to inflammatory skin diseases such as psoriasis. The IκB family protein IκB-ζ mediates IL-17–induced responses. However, the mechanism controlling IκB-ζ expression in IL-17–stimulated cells remains elusive. In this study, we showed that JAK kinase TYK2 positively regulates IL-17–induced IκB-ζ expression. TYK2-deficient mice showed reduced inflammation and concomitant reduction of IκB-ζ mRNA compared with wild-type mice in imiquimod-induced skin inflammation. The analysis of the IκB-ζ promoter activity using human cell lines (HaCaT and HeLa) revealed that catalytic activity of TYK2 and its substrate transcription factor STAT3, but not IL-17, is required for IκB-ζ promoter activity. In contrast, IL-17–induced signaling, which did not activate STAT3, posttranscriptionally stabilized IκB-ζ mRNA via its 3′-untranslated region. IL-17 signaling protein ACT1 was required to counteract constitutive IκB-ζ mRNA degradation by RNase Regnase-1. These results suggested that transcriptional activation by TYK2–STAT3 pathway and mRNA stabilization by IL-17–mediated signals act separately from each other but complementarily to achieve IκB-ζ induction. Therefore, JAK/TYK2 inhibition might be of significance in regulation of IL-17–induced inflammatory reactions.
In extremely low birth weight (ELBW) infants, systemic hypotension is associated with poor neurological outcomes as a result of cerebral hypoperfusion. Treatment with arginine vasopressin (AVP) has been shown to increase blood pressure (BP) and urine output in ELBW infants suffering from refractory hypotension. The purpose of this study was to clarify whether low doses of AVP increased renal blood flow (RBF) in ELBW infants. We retrospectively analyzed data from the medical charts describing nine AVP infusions at 0.3-0.8 mU/kg/min in four ELBW infants. The median gestational age was 23 (22.5-23.5, interquartile range) weeks, and the median birth weight was 466 (414-563) g. Changes in the heart rate, BP, urine output, and RBF velocity patterns in response to the AVP infusions were compared using statistical analyses. The AVP infusion caused significant increases in systolic BP from 44 (41.0-47.0) to 50 (42.5-55.5) mmHg, diastolic BP from 17 (15.0-26.5) to 31 (28.5-33.0) mmHg, mean BP from 26 (24.5-30.5) to 36 (34.5-40.5) mmHg, and urine output from 1.4 (0.2-2.5) to 2.8 (1.0-8.6) mL/kg/hr. We also observed significant decreases in the resistance index from 1.0 (0.96-1.0) to 0.8 (0.71-0.91) and peak systolic flow velocity in the renal artery from 40 (27.2-50.6) to 28 (16.0-28.9) cm/s after AVP infusions. AVP infusions at 0.3-0.8 mU/kg/min in ELBW infants appeared to significantly increase the RBF by inducing renal vascular dilation and increasing the BP. Increasing the RBF most likely induces an increase in the glomerular filtration rate, resulting in the diuretic effect of AVP.
