title: Dysregulated expression of arginine metabolic enzymes in human intestinal tissues of necrotizing enterocolitis and response of CaCO2 cells to bacterial components.
abstract: The small intestine is the exclusive site of arginine synthesis in neonates. Low levels of circulating arginine have been associated with the occurrence of necrotizing enterocolitis (NEC) but the mechanism of arginine dysregulation has not been fully elucidated. We aimed to investigate (i) expressional changes of arginine synthesizing and catabolic enzymes in human intestinal tissues of NEC, spontaneous intestinal perforation (SIP) and noninflammatory surgical conditions (Surg-CTL) and to investigate the (ii) mechanisms of arginine dysregulation and enterocyte proliferation upon stimulation by bacterial components, arginine depletion, ARG1 overexpression and nitric oxide (NO) supplementation. Our results showed that expressions of arginine synthesizing enzymes ALDH18A1, ASL, ASS1, CPS1, GLS, OAT and PRODH were significantly decreased in NEC compared with Surg-CTL or SIP tissues. Catabolic enzyme ARG1 was increased (>100-fold) in NEC tissues and histologically demonstrated to be expressed by infiltrating neutrophils. No change in arginine metabolic enzymes was observed between SIP and Surg-CTL tissues. In CaCO2 cells, arginine metabolic enzymes were differentially dysregulated by lipopolysaccharide or lipoteichoic acid. Depletion of arginine reduced cell proliferation and this phenomenon could be partially rescued by NO. Overexpression of ARG1 also reduced enterocyte proliferation. We provided the first expressional profile of arginine metabolic enzymes at the tissue level of NEC. Our findings suggested that arginine homeostasis was severely disturbed and could be triggered by inflammatory responses of enterocytes and infiltrating neutrophils as well as bacterial components. Such reactions could reduce arginine and NO, resulting in mucosal damage. The benefit of arginine supplementation for NEC prophylaxis merits further clinical evaluation.
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Kam Tong
authors.initials: KT
authors.lastname: Leung
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Kathy Yuen Yee
authors.initials: KY
authors.lastname: Chan
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Terence Ping Yuen
authors.initials: TP
authors.lastname: Ma
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Jasmine Wai Sum
authors.initials: JW
authors.lastname: Yu
authors.affiliation: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Joanna Hung Man
authors.initials: JH
authors.lastname: Tong
authors.affiliation: Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Yuk Him
authors.initials: YH
authors.lastname: Tam
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Hon Ming
authors.initials: HM
authors.lastname: Cheung
authors.affiliation: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Ka Fai
authors.initials: KF
authors.lastname: To
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Hugh Simon
authors.initials: HS
authors.lastname: Lam
authors.affiliation: Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Kim Hung
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Karen
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong. Electronic address: pakcheungng@cuhk.edu.hk.
authors.forename: Pak Cheung
authors.initials: PC
authors.lastname: Ng
mesh_terms: D001119:Arginase / Q000235:genetics; D001120:Arginine / Q000096:biosynthesis / Q000378:metabolism*; D018938:Caco-2 Cells; D020345:Enterocolitis, Necrotizing / Q000201:enzymology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007422:Intestines / Q000201:enzymology* / Q000382:microbiology; D008297:Male
chemical_list: D001120:Arginine; D001119:Arginase
keywords: ARG1; Arginine metabolism; NEC; Nitric oxide; SIP