G protein-coupled receptor kinase 6 controls chronicity and severity of dextran sodium sulphate-induced colitis in mice.
BACKGROUND
Infiltration of inflammatory cells into the colon plays an important role in the onset and course of inflammatory bowel disease. G-protein-coupled receptor kinase 6 (GRK6) is an intracellular kinase that regulates the sensitivity of certain G-protein-coupled receptors, including those involved in the migration of inflammatory cells. Therefore, it is hypothesised that GRK6 plays a role in determining the course of inflammation.


OBJECTIVE
To analyse the role of GRK6 in the course of dextran sodium sulphate (DSS)-induced colitis.


METHODS
Colitis was induced by administering 1% DSS in drinking water to GRK6(-/-), GRK6(+/-) and wild-type (WT) mice for 6 days. The severity of colitis was assessed on the basis of clinical signs, colon length and histology. Moreover, keratinocyte-derived chemokine (KC) levels, granulocyte infiltration, interleukin 1beta (IL1beta), CD4, CD8 and forkhead box protein P3 (FoxP3) expression in the colon were determined. In addition, regulatory T cell function in WT and GRK6(-/-) mice was analysed. The chemotactic response of granulocytes to colon culture supernatants was assessed using a transendothelial migration assay.


RESULTS
The severity of colitis was increased in GRK6(-/-) and GRK6(+/-) mice and was accompanied by increased KC levels and increased granulocyte infiltration. Moreover, the chemotactic response of GRK6(-/-) granulocytes to supernatants of colon cultures was enhanced. Interestingly, the WT mice completely recovered from colitis, whereas the GRK6(-/-) and GRK6(+/-) mice developed chronic colitis, which was accompanied by increased IL1beta and CD4 expression and decreased FoxP3 expression. Moreover, regulatory T cell function was impaired in the GRK6(-/-) mice.


CONCLUSIONS
The intracellular level of GRK6 is an important factor in determining the onset, severity and chronicity of DSS-induced colitis.
Eijkelkamp
Niels
N
Laboratory for Psychoneuroimmunology, University Medical Center Utrecht, Lundlaan 6, Room KC 03.063.0, 3584 EA Utrecht, The Netherlands.
Heijnen
Cobi J
CJ
Lucas
Ayscha
A
Premont
Richard T
RT
Elsenbruch
Sigrid
S
Schedlowski
Manfred
M
Kavelaars
Annemieke
A
D000208:Acute Disease; D000818:Animals; D002634:Chemotaxis, Leukocyte; D002908:Chronic Disease; D003092:Colitis / Q000139:chemically induced / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D016264:Dextran Sulfate; D004195:Disease Models, Animal; D047209:Eosinophil Peroxidase / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D054768:G-Protein-Coupled Receptor Kinases; D006098:Granulocytes / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009195:Peroxidase / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012720:Severity of Illness Index; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D046509:Tissue Culture Techniques
D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D016264:Dextran Sulfate; D047209:Eosinophil Peroxidase; D009195:Peroxidase; D017346:Protein Serine-Threonine Kinases; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6