Secretoglobin 3A2 Exhibits Anti-Fibrotic Activity in Bleomycin-Induced Pulmonary Fibrosis Model Mice

Objective

Secretoglobin (SCGB) 3A2 is a novel lung-enriched cytokine, previously shown to exhibit anti-inflammatory, growth factor, and anti-fibrotic activities. The latter activity was demonstrated using exogenously-administered recombinant SCGB3A2 in the bleomycin (BLM)-induced pulmonary fibrosis model. Whether SCGB3A2 exhibits anti-fibrotic activity in vivo is not known.

Methods

Mice null for the Scgb3a2 gene were subjected to the BLM-induced pulmonary fibrosis model, and the severity of pulmonary fibrosis determined using histological and biochemical methods.

Results

BLM treatment caused weight loss of both Scgb3a2-null and wild-type mice, however, the loss was far more pronounced in BLM-treated Scgb3a2-null than wild-type mice, and the weight of day 21 of BLM-treated Scgb3a2-null mice was about half of that of BLM-treated wild-type mice. Hematoxylin & Eosin, Masson Trichrome, and Sirius Red staining of lung sections, Ashcroft fibrosis scores, hydroxyproline contents, and the levels of mRNAs encoding various collagens demonstrated that BLM-treated Scgb3a2-null mouse lungs had more severe fibrosis than those of wild-type mouse lungs. Total and differential inflammatory cell numbers in bronchoalveolar lavage fluids, and levels of lung mRNAs including those encoding Th2 cytokines such as IL-4 and profibrotic cytokines such as TGFβ were higher in BLM-treated Scgb3a2-null mouse lungs as compared to those of wild-type mouse lungs. In contrast, mRNAs encoding surfactant proteins A, B, C, and D, and SCGB1A1 did not differ between BLM-treated Scgb3a2-null and wild-type mouse lungs.

Conclusion

The role of SCGB3A2 in fibrosis was revisited using Scgb3a2-null mice and littermate controls in the BLM-induced pulmonary fibrosis model. The pulmonary fibrosis in the Scgb3a2-null mice was more severe than the wild-type controls, thus establishing that SCGB3A2 has anti-fibrotic activity in vivo. Importantly, surfactant proteins and SCGB1A1 appear not to be involved in the susceptibility of Scgb3a2-null mice to BLM-induced pulmonary fibrosis.     

MicroRNAs Regulate Pituitary Development,and MicroRNA 26b Specifically Targets Lymphoid Enhancer Factor 1 (Lef-1), Which Modulates Pituitary Transcription Factor 1 (Pit-1) Expression

To understand the role of microRNAs (miRNAs) in pituitary development, a group of pituitary-specific miRNAs were identified, and Dicer1 was then conditionally knocked out using the Pitx2-Cre mouse, resulting in the loss of mature miRNAs in the anterior pituitary. The Pitx2-Cre/Dicer1 mutant mice demonstrate growth retardation, and the pituitaries are hypoplastic with an abnormal branching of the anterior lobe, revealing a role for microRNAs in pituitary development. Growth hormone, prolactin, and thyroid-stimulating hormone β-subunit expression were decreased in the Dicer1 mutant mouse, whereas proopiomelanocortin and luteinizing hormone β-subunit expression were normal in the mutant pituitary. Further analyses revealed decreased Pit-1 and increased Lef-1 expression in the mutant mouse pituitary, consistent with the repression of the Pit-1 promoter by Lef-1. Lef-1 directly targets and represses the Pit-1 promoter. miRNA-26b (miR-26b) was identified as targeting Lef-1 expression, and miR-26b represses Lef-1 in pituitary and non-pituitary cell lines. Furthermore, miR-26b up-regulates Pit-1 and growth hormone expression by attenuating Lef-1 expression in GH3 cells. This study demonstrates that microRNAs are critical for anterior pituitary development and that miR-26b regulates Pit-1 expression by inhibiting Lef-1 expression and may promote Pit-1 lineage differentiation during pituitary development.     

Developmental expression and localization of IA-2 mRNA in mouse neuroendocrine tissues

Islet antigen (IA)-2 is a novel autoantigen of insulin-dependent diabetes mellitus (IDDM), and belongs to a new class within the receptor-type protein tyrosine phosphatase (PTP) family characterized by lack of PTP enzymatic activity with conventional substrates. Its expression is restricted primarily to the pancreas, pituitary, and brain with the highest level in the brain. IA-2 mRNA expressions in the brain, pituitary and pancreas of 1-, 4-, and 8-week-old mice were examined. In situ hybridization of the brain revealed that IA-2 mRNA was expressed in the cerebral cortex, hippocampus, thalamus, choroid plexus, hypothalamus, Purkinje cells, and granular layer of the cerebellum. In the pituitary, IA-2 mRNA was located in the anterior and posterior pituitary by in situ hybridization. The pattern of IA-2 mRNA expression in normal male mouse brain at 1, 4, and 8 weeks of age by the Northern blot analysis was similar to that in the pituitary by RT-PCR analysis. The expression level was higher at 4 weeks and lower at 1 week of age. In the pancreas, IA-2 mRNA expressions detected by RT-PCR were highest at 8 weeks of age. These results indicated that the amount of mRNA expression increased in accordance to development in brain, pituitary, and pancreas.     

DISTRIBUTION OF BIOGENIC AMINES AND RELATED ENZYMES IN THE RAT PITUITARY GLAND

Abstract— Biogenic amines and related enzymes were quantitatively measured in the pituitary gland of the rat. The sensitivity of the assays used allows the determinations to be performed in single pituitary lobes. Relatively high values of histamine and serotonin were found in all three lobes, with higher amounts in the posterior and intermediate lobes. Highest catecholamine concentrations were detected in the posterior lobe, and only very low amounts of dopamine were measured in the anterior lobe. Throughout the gland, norepinephrine concentrations were low, about one-tenth that of dopamine. Tryptamine could not be detected. High levels of A and B monoamine oxidase were found in all three pituitary lobes. Tyrosine hydroxylase activity was measured in the posterior and intermediate lobes, but was not detected in the anterior lobe. Tryptophan hydroxylase was present in all three pituitary lobes. A relatively low catechol- O -methyltransferase activity was found in the anterior lobe, and none was detected in the intermediate and posterior lobe. Choline acetyltransferase, dopamine-β-hydroxylase and phenylethanolamine- N -methyltransferase activities could not be detected.