biomedicines Article Acetylated Diacylglycerol 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol in Autoimmune Arthritis and Interstitial Lung Disease in SKG Mice Doo-Ho Lim 1,† , Eun-Ju Lee 2,† , Hee-Seop Lee 3 , Do Hoon Kim 4 , Jae-Hyun Lee 4 , Mi Ryeong Jeong 4 , Seokchan Hong 4 , Chang-Keun Lee 4 , Bin Yoo 4 , Jeehee Youn 5 and Yong-Gil Kim 4,6, *   Citation: Lim, D.-H.; Lee, E.-J.; Lee, H.-S.; Kim, D.H.; Lee, J.-H.; Jeong, M.R.; Hong, S.; Lee, C.-K.; Yoo, B.; Youn, J.; et al. Acetylated Diacylglycerol 1-palmitoyl-2- linoleoyl-3-acetyl-rac-glycerol in Autoimmune Arthritis and Interstitial Lung Disease in SKG Mice. Biomedicines 2021, 9, 1095. https:// doi.org/10.3390/biomedicines9091095 Academic Editor: Alberto Ricci Received: 30 July 2021 Accepted: 25 August 2021 Published: 27 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Division of Rheumatology, Department of Internal Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan 44033, Korea; dlaengh@hanmail.net 2 Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Korea; krys72@hanmail.net 3 Department of Nutrition and Food Science, College of Agriculture and Natural Resources, University of Maryland, College Park, MD 20742, USA; hslee123@umd.edu 4 Division of Rheumatology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; alakzam41@naver.com (D.H.K.); clesote@hanmail.net (J.-H.L.); mi-ryeong@naver.com (M.R.J.); medivineluke@gmail.com (S.H.); cklee@amc.seoul.kr (C.-K.L.); byoo@amc.seoul.kr (B.Y.) 5 Department of Anatomy and Cell Biology, College of Medicine, Hanyang University, Seoul 04763, Korea; jhyoun@hanyang.ac.kr 6 Convergence Medicine Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Korea * Correspondence: bestmd2000@amc.seoul.kr; Tel.: +82-2-3010-3279; Fax: +82-2-3010-6969 † These authors have contributed equally to this work. Abstract: Acetylated diacylglycerol 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) is a lipid molecule from the antlers of sika deer that might reduce inflammation by effectively controlling neutrophil infiltration, endothelial permeability and inflammatory chemokine production. Therefore, we evaluated the modulatory effect of PLAG on arthritis and interstitial lung disease (ILD) in an autoimmune arthritis model. We injected curdlan into SKG mice and PLAG was orally administered every day from 3 weeks to 20 weeks after the curdlan injection. The arthritis score was measured every week after the curdlan injection. At 20 weeks post-injection, the lung specimens were evaluated with H&E, Masson’s trichrome and multiplexed immunofluorescent staining. Serum cytokines were also analyzed using a Luminex multiple cytokine assay. PLAG administration decreased the arthritis score until 8 weeks after the curdlan injection. However, the effect was not sustained thereafter. A lung histology revealed severe inflammation and fibrosis in the curdlan-induced SKG mice, which was attenuated in the PLAG-treated mice. Furthermore, immunofluorescent staining of the lung tissue showed a GM-CSF + neutrophil accumulation and a decreased citrullinated histone 3 expression after PLAG treatment. PLAG also downregulated the levels of IL-6 and TNF-α and upregulated the level of sIL-7Rα, an anti-fibrotic molecule. Our results indicate that PLAG might have a preventative effect on ILD development through the resolution of NETosis in the lung. Keywords: interstitial lung disease; PLAG; NETosis; arthritis; autoimmune 1. Introduction Interstitial lung disease (ILD) is one of the most serious pulmonary complications in autoimmune diseases and is a major cause of morbidity and mortality [1]. In general, the five major autoimmune diseases with ILD are known as systemic sclerosis, rheumatoid arthritis (RA), polymyositis-dermatomyositis, systemic lupus erythematosus and primary Sjögren syndrome [1]. Among these, RA is the most common autoimmune disease and affects approximately 1% of the population [2] and is characterized by systemic inflam- mation resulting in peripheral arthritis and various pulmonary manifestations [3]. The Biomedicines 2021, 9, 1095. https://doi.org/10.3390/biomedicines9091095 https://www.mdpi.com/journal/biomedicines