Skin inflammation in <i>Grhl1</i>^−/− mice.

<p>(A) Blood levels of TSLP in <i>Grhl1</i>^+/+ (gray bar) and <i>Grhl1</i>^−/− mice (blue bar), measured with ELISA kit. (B) Levels of expression of antimicrobial peptides S100A8 and S100A9 in the epidermis of <i>Grhl1</i>^+/+ (gray bar) and <i>Grhl1</i>^−/− mice (blue bar), measured with Q-RT-PCR. (C) Representative skin sections of <i>Grhl1</i>^+/+ (top panel) and <i>Grhl1</i>^−/− mice (bottom panel) stained with toluidine blue to visualize dermal mast cells (purple cells). Scale bars represent 200 µm. (D) Quantification of skin infiltration with mast cells for <i>Grhl1</i>^+/+ (gray bar) and <i>Grhl1</i>^−/− mice (blue bar), estimated as numbers of stained cells per 1 mm² area of 10 µm thick skin section (using ImageJ software). (A, B, D) Significance (Student’s t-test, p-value) is shown above bars.</p

Histological analysis of the skin of <i>Grhl1</i>^−/− mice (right panels) in comparison to wild type littermates <i>Grhl1</i>^+/+ (left panels).

<p>Scale bars represent 25 µm. (A–B) Hematoxylin and eosin (H&E) staining of epidermis of <i>Grhl1</i>^+/+ and <i>Grhl1</i>^−/− mice; red arrows point to keratinocytes from granular layer of epidermis. (C–L) Immunohistochemical analysis of markers of epidermal differentiation in the epidermis of <i>Grhl1</i>^+/+ and <i>Grhl1</i>^−/− mice: marker of basal layer – keratin 5 (C, D, black arrows indicate suprabasal keratinocytes expressing keratin 5), marker of early terminal differentiation – keratin 10 (E, F, red arrows point to keratinocytes from the granular layer of epidermis), markers of late terminal differentiation – involucrin (G, H), filaggrin (I, J), loricrin (K, L). (M, N) Immunofluorescence staining of proliferation marker Ki67 in <i>Grhl1</i>^+/+ (M) and <i>Grhl1</i>^−/− (N) mice.</p

List of some of the genes that are upregulated in the <i>Grhl1</i>^−/− skin.

<p>Full list of genes with fold changes higher than 2 is provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089247#pone.0089247.s003" target="_blank">Table S2</a>.</p

Discovery of OATD 01 , a First in Class Chitinase Inhibitor as Potential New Therapeutics for Idiopathic Pulmonary Fibrosis

Chitotriosidase CHIT1 and acidic mammalian chitinase AMCase are the enzymatically active chitinases that have been implicated in the pathology of chronic lung diseases such as asthma and interstitial lung diseases ILDs , including idiopathic pulmonary fibrosis IPF and sarcoidosis. The clinical and preclinical data suggest that pharmacological inhibition of CHIT1 might represent a novel therapeutic approach in IPF. Structural modification of an advanced lead molecule 3 led to the identification of compound 9 OATD 01 , a highly active CHIT1 inhibitor with both an excellent PK profile in multiple species and selectivity against a panel of other off targets. OATD 01 given orally once daily in a range of doses between 30 and 100 mg kg showed significant antifibrotic efficacy in an animal model of bleomycin induced pulmonary fibrosis. OATD 01 is the first in class CHIT1 inhibitor, currently completed phase 1b of clinical trials, to be a potential treatment for IP

Inhibition of CHIT1 as a novel therapeutic approach in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and eventually fatal lung disease with a complex etiology. Approved drugs, nintedanib and pirfenidone, modify disease progression, but IPF remains incurable and there is an urgent need for new therapies. We identified chitotriosidase (CHIT1) as new driver of fibrosis in IPF and a novel therapeutic target. We demonstrate that CHIT1 activity and expression are significantly increased in serum (3-fold) and induced sputum (4-fold) from IPF patients. In the lungs CHIT1 is expressed in a distinct subpopulation of profibrotic, disease-specific macrophages, which are only present in patients with ILDs and CHIT1 is one of the defining markers of this fibrosis-associated gene cluster. To define CHIT1 role in fibrosis, we used the therapeutic protocol of the bleomycin-induced pulmonary fibrosis mouse model. We demonstrate that in the context of chitinase induction and the macrophage-specific expression of CHIT1, this model recapitulates lung fibrosis in ILDs. Genetic inactivation of Chit1 attenuated bleomycin-induced fibrosis (decreasing the Ashcroft scoring by 28%) and decreased expression of profibrotic factors in lung tissues. Pharmacological inhibition of chitinases by OATD-01 reduced fibrosis and soluble collagen concentration. OATD-01 exhibited anti-fibrotic activity comparable to pirfenidone resulting in the reduction of the Ashcroft score by 32% and 31%, respectively. These studies provide a preclinical proof-of-concept for the antifibrotic effects of OATD-01 and establish CHIT1 as a potential new therapeutic target for IPF