Inflammasome-Independent and Atypical Processing of IL-1Β
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Inflammasome-Independent and Atypical Processing of IL-1 β Contributes to Acid Aspiration−Induced Acute Lung Injury This information is current as Yoshiko Mizushina, Tadayoshi Karasawa, Kenichi Aizawa, of September 23, 2021. Hiroaki Kimura, Sachiko Watanabe, Ryo Kamata, Takanori Komada, Naoko Mato, Tadashi Kasahara, Shinichiro Koyama, Masashi Bando, Koichi Hagiwara and Masafumi Takahashi J Immunol published online 20 May 2019 Downloaded from http://www.jimmunol.org/content/early/2019/05/17/jimmun ol.1900168 http://www.jimmunol.org/ Why The JI? Submit online. • Rapid Reviews! 30 days* from submission to initial decision • No Triage! 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Published May 20, 2019, doi:10.4049/jimmunol.1900168 The Journal of Immunology Inflammasome-Independent and Atypical Processing of IL-1b Contributes to Acid Aspiration–Induced Acute Lung Injury Yoshiko Mizushina,*,†,‡ Tadayoshi Karasawa,* Kenichi Aizawa,x Hiroaki Kimura,* Sachiko Watanabe,* Ryo Kamata,* Takanori Komada,* Naoko Mato,† Tadashi Kasahara,* Shinichiro Koyama,‡ Masashi Bando,† Koichi Hagiwara,† and Masafumi Takahashi* Inflammation plays a pivotal role in the pathophysiology of gastric aspiration–induced acute lung injury (ALI). However, its mechanism remains unclear. In this study, we investigated the role of NLRP3 inflammasome–driven IL-1b production in a mouse model of acid aspiration–induced inflammation and ALI. Acid aspiration–induced inflammatory responses and ALI in wild-type mice were significantly attenuated in IL-1b2/2 mice, but not NLRP32/2 mice. In vitro experiments revealed that severe acidic stress (pH 1.75) induced the processing of pro–IL-1b into its 18-kDa mature form (p18–IL-1b), which was different from the caspase-1–processed 17-kDa form (p17–IL-1b), in human THP-1 macrophages and primary murine macrophages. Deficiency of Downloaded from NLRP3 and caspase-1 had no effect on acidic stress–produced IL-1b. The production of IL-1b by severe acidic stress was prevented by inhibitors of serine proteases [4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride], but not of cysteine proteases (E-64), cathepsin G, or inflammasome. The cathepsin D inhibitor pepstatin A inhibited IL-1b production induced by mild acidic stress (pH 6.2) or lactic acid, but not severe acidic stress. Using mass spectrometry and processing-site mutants of pro–IL-1b,we identified D109 as a novel cleavage site of pro–IL-1b in response to severe acidic stress and calculated the theoretical molecular mass of the mature form to be 18.2 kDa. The bioactivity of acidic stress–produced IL-1b was confirmed by its ability to promote http://www.jimmunol.org/ p38 phosphorylation and chemokine upregulation in alveolar epithelial cells. These findings demonstrate a novel mechanism of acid-induced IL-1b production and inflammation independent of NLRP3 inflammasome and provide new insights into the therapeutic strategies for aspiration pneumonitis and ALI. The Journal of Immunology, 2019, 203: 000–000. astric aspiration pneumonitis is defined as an acute lung role in the progression of acid aspiration–induced ALI (1, 2). Be- injury (ALI) following the inhalation of gastric contents cause gastric fluid is highly acidic, it is considered that gastric as- G and is associated with significant morbidity and mor- piration triggers sterile inflammation and injury in the lung. tality (1, 2). Aspiration pneumonitis commonly occurs as a com- Recent evidence indicates that sterile inflammation is mediated by guest on September 23, 2021 plication of general anesthesia and in patients with altered levels of through the nucleotide-binding oligomerization domain-like re- consciousness due to trauma, cerebral vascular ischemia, or meta- ceptor (NLR) family pyrin domain containing 3 (NLRP3) inflam- bolic encephalopathies. The inhalation of highly acidic gastric fluid masome, an intracellular, large, multiple-protein complex that and/or particulate food matter promotes chemical pneumonitis and regulates the processing of a potent proinflammatory cytokine IL-1b the development of ALI, which can frequently be complicated by (5, 6). NLRP3 inflammasome contains NLRP3, an adaptor mole- subsequent bacterial pneumonia. Previous studies have demon- cule apoptosis-associated, speck-like protein containing a caspase strated that aspirated acid induces dysfunction of alveolar epithelial recruitment domain (ASC), and cysteine protease caspase-1, which fluid transport, followed by alveolar epithelial cell injury and neu- induces caspase-1 activation. Because caspase-1 is known to be an trophil infiltration in the lung (3, 4). However, the mechanisms that IL-1b–converting enzyme (7), its activation processes pro–IL-1b underline acid aspiration–induced ALI are unclear, because acid into its mature form and induces IL-1b production, thereby lead- itself is rapidly neutralized by proteins and bicarbonate systems (4). ing to an inflammatory response and tissue injury. Indeed, we re- Recent investigations have shown that inflammation plays a pivotal cently demonstrated that NLRP3 inflammasome was involved in the *Division of Inflammation Research, Center for Molecular Medicine, Jichi Medical performed liquid chromatography–tandem mass spectrometry and analyzed the data. University, Shimotsuke, Tochigi 329-0498, Japan; †Division of Pulmonary Medicine, N.M., T. Kasahara, S.K., M.B., and K.H. discussed the data and provided scientific Department of Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, advice. Y.M. and M.T. wrote the manuscript. Japan; ‡Department of Pulmonary Medicine, Jichi Medical University, Saitama Medical x Address correspondence and reprint requests to Prof. Masafumi Takahashi, Division of Center, Saitama 330-8503, Japan; and Division of Clinical Pharmacology, Department Inflammation Research, Center for Molecular Medicine, Jichi Medical University, 3311-1 of Pharmacology, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan Yakushiji, Shimotsuke, Tochigi 329-0498, Japan. E-mail address: [email protected] ORCIDs: 0000-0002-7441-0382 (H.K.); 0000-0002-6110-9603 (S.W.); 0000-0001- Abbreviations used in this article: AEBSF, 4-(2-aminoethyl)benzenesulfonyl 6970-9657 (R.K.); 0000-0003-3360-3185 (T. Komada); 0000-0001-7687- fluoride hydrochloride; ALI, acute lung injury; BALF, bronchoalveolar lavage 5477 (T. Kasahara); 0000-0003-2716-7532 (M.T.). fluid; CGI, cathepsin G inhibitor I; HCl, hydrochloric acid; 4-HNE, 4-hydroxy- Received for publication February 8, 2019. Accepted for publication April 17, 2019. 2-nonenal; IL-1Ra, IL-1R antagonist; NLR, nucleotide-binding oligomerization domain-like receptor; NLRP3, NLR family pyrin domain containing 3; ROS, This work was supported by grants from the Japan Society for the Promotion of Science reactive oxygen species; sgRNA, single-guide RNA; UBSS, unbuffered balanced through Grants-in-Aid for Scientific Research 16H07151 (to Y.M.) and 18K08112 (to M.T.), salt solution; WT, wild-type. the Private University Research Branding Project (to M.T.), the Agency for Medical Research and Development-Core Research for Evolutional Science and Technology Ó (18gm0610012h0105 to M.T.), the Takeda Science Foundation (to M.T.), and a Jichi Medical Copyright 2019 by The American Association of Immunologists, Inc. 0022-1767/19/$37.50 University Graduate Student Start-Up Award and Student Research Award (to Y.M.). Y.M. and M.T. designed the study concept and experiments. Y.M., T. Karasawa, H.K., S.W., R.K., and T. Komada performed the experiments and analyzed the data. K.A. www.jimmunol.org/cgi/doi/10.4049/jimmunol.1900168 2 IL-1b PROCESSING IN ACID-INDUCED INFLAMMATION pathogenesis of sterile inflammation-related diseases (8–12). In using a Takara TP960 PCR Thermal Cycler Dice Real Time System terms of acidic stress, a mild acidic environment (pH 6–6.5) (Takara Bio, Shiga, Japan) to detect mRNA. The primers (antisense and 9 frequently occurs at sites of inflammation and ischemia (13, 14). sense, respectively) were as follows: Il1b:5-TGAAGTTGACGGACCC- CAAA-39 and 59-TGATGTGCTGCTGTGAGATT-39, Ccl2:59-GGCTCAG- Several studies have suggested that an inflammatory response is CCAGATGCAGTTAAC-39 and 59-GCCTACTCATTGGGATCATCTTG-39, influenced under mild acidic conditions. However, the role of Cxcl1:59-GCTGGGATTCACCTCAAGAA-39 and 59-TCTCCGTTACTTG- NLRP3 inflammasome under such mild acidic conditions re- GGGACAC-39,18SrRNA(Rn18s): 59-GTAACCCGTTGAACCCCATT-39 9 9 9 mains controversial. For instance, Rajamaki et al. (15) recently and 5 -CCATCCAATCGGTAGTAGCG-3 , CCL2:5-CAGCCAGATGCA- ATCAATGCC-39and 59-TGGAATCCTGAACCCACTTCT-39,CXCL1:59-GGAAC- demonstrated that mild acidic stress triggered NLRP3 inflam- AGAAGAGGAAAGAGAGAC-39 and 59-TAGGACAGTGTGCAGGTAGA-39, + masome activation and IL-1b production through K efflux in and 18S rRNA (RNA18S5): 59-GTAACCCGTTGAACCCCATT-39