L-PGDS-derived PGD2 attenuates acute lung injury by enhancing endothelial barrier formation

Acute lung injury (ALI) is caused by various stimuli such as acid aspiration and infection, resulting in severe clinical outcomes with high mortality. Prostaglandin D₂ (PGD₂) is a lipid mediator produced in the lungs of patients with ALI. There are two prostaglandin D synthases (PGDS), namely, lipocalin-type PGDS (L-PGDS) and hematopoietic PGDS (H-PGDS). We previously reported the anti-inflammatory role of H-PGDS-derived PGD₂ in an endotoxin-induced murine ALI model. Therefore, in this study, we investigated the role of L-PGDS-derived PGD₂ in ALI in comparison to H-PGDS-derived PGD₂. Intratracheal administration of HCl caused lung inflammation accompanied by tissue edema and neutrophil accumulation in mouse lungs. The deficiency of both L-PGDS and H-PGDS exacerbated HCl-induced lung dysfunction to a similar extent. Furthermore, a detailed investigation revealed that L-PGDS-derived PGD₂ inhibited lung edema, while H-PGDS-derived PGD₂ inhibited neutrophil infiltration. Immunostaining showed that inflamed endothelial/epithelial cells express L-PGDS, while macrophages and neutrophils express H-PGDS. Hematopoietic reconstitution with WT bone marrow did not rescue the exacerbated lung edema in L-PGDS deficient mice, indicating the importance of nonhematopoietic endothelial/epithelial cell-expressing L-PGDS for protection against ALI. A modified Miles assay showed that L-PGDS deficiency accelerated vascular hyper-permeability in the inflamed lung, which was suppressed by the stimulation of D prostanoid (DP) receptor, a PGD₂ receptor. In vitro, DP agonism enhanced the barrier function of endothelial cells but not epithelial cells. Taken together, our results suggest that in the HCl-induced murine ALI model PGD₂ was produced locally by inflamed endothelial and epithelial L-PGDS and this enhanced the endothelial barrier through the DP receptor. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Potential function of TGF-β isoforms in maturation-stage ameloblasts

Objectives

To investigate potential functions of transforming growth factor-beta (TGF-β) isoforms in maturation-stage ameloblasts during amelogenesis.

Relative levels of mRNA encoding enamel proteins in enamel organ epithelia and odontoblasts

Amelogenin, enamelin, sheathlin (ameloblastin/ amelin), enamelysin (MMP-20), and KLK4 (EMSP-1) are the major structural proteins and proteinases in developing tooth enamel. Recently, odontoblasts were reported to express amelogenin, the most abundant enamel protein. In this study, we hypothesized that odontoblasts express all enamel proteins and proteases, and we measured their relative mRNA levels in enamel organ epithelia and odontoblasts associated with porcine secretory- and maturation-stage enamel by RT-PCR, using a LightCycler instrument. The results showed that amelogenin mRNA in secretory-stage EOE is 320-fold higher than in odontoblasts beneath secretory-stage enamel, and over 20,000-fold higher than in odontoblasts under maturation-stage enamel. Similar results were obtained for enamelin and sheathlin. Enamelysin mRNA levels were equivalent in these two tissues, while KLK4 mRNA was higher in odontoblasts than in secretory-stage EOE. These results support the conclusion that odontoblasts are involved in the formation of the enamel layer adjacent to enamel-dentin junction.