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TL1A Aggravates Cytokine-Induced Acute Gut Inflammation and Potentiates Infiltration of Intraepithelial Natural Killer Cells in Mice

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Background
The tumor necrosis factor alpha (TNFα)–homologous cytokine TL1A is emerging as a major player in intestinal inflammation. From in vitro experiments on human lymphocytes, TNF-like molecule 1A (TL1A) is known to activate a highly inflammatory lymphoid response in synergy with interleukin (IL)-12 and IL-18. Carriers of specific genetic polymorphisms associated with IL-12, IL-18, or TL1A signaling have increased Crohn’s disease risk, and all 3 cytokines are upregulated during active disease. The study aim was to investigate whether the type 1–polarizing cytokines IL-12 and IL-18 could directly initiate intestinal pathology in mice and how TL1A would influence the resulting inflammatory response.

Methods
Conventional barrier-bred and germ-free mice were randomly allocated to different groups and injected twice with different combinations of IL-12, IL-18, and TL1A, and killed 3 days after the first injection. All treatment groups were co-housed and fed a piroxicam-supplemented chow diet.

Results
Intestinal pathology was evident in IL-12- and IL-18-treated mice and highly exacerbated by TL1A in both the colon and ileum. The cytokine-induced intestinal inflammation was characterized by epithelial damage, increased colonic levels of TNFα, IL-1β, IFN-γ, and IL-6, and various chemokines along with gut microbiota alterations exhibiting high abundance of Enterobacteriaceae. Furthermore, the inflamed ileum and colon exhibited a TL1A-specific increased infiltration of intraepithelial natural killer cells co-expressing NKG2D and IL-18Ra and a higher frequency of unconventional T cells in the colonic epithelium. Upon cytokine injection, germ-free mice exhibited similar intraepithelial lymphoid infiltration and increased colonic levels of IFNγ and TNFα.

Conclusions
This study demonstrates that TL1A aggravates IL-12- and IL-18-induced intestinal inflammation in the presence and absence of microbiota.
OriginalsprogEngelsk
TidsskriftInflammatory Bowel Diseases
Vol/bind25
Udgave nummer3
Sider (fra-til)510-523
ISSN1078-0998
DOI
StatusUdgivet - 2019

ID: 215358470