Hyperosmolarity causes inflammation through the methylation of protein phosphatase 2A.
OBJECTIVE
We evaluated the role of the osmolarity in the pro-inflammatory responses of epithelial cells.


METHODS
Twenty-five female Wistar rats and colorectal (HT-29) and bladder (T24) cell lines were used.


METHODS
Rats and cells were exposed for 48 hours to hyperosmotic solutions.


METHODS
Interleukin-8 (IL-8) production was measured by Enzyme Linked ImmunoSorbent Assay, mRNA transcription of pro-inflammatory cytokines by microarrays or RNase Protection Assay. Nuclear factor-kappa B (NF-kappaB) pathway and Protein Phosphatase 2A (PP2A) activations were measured. Myeloperoxydase (MPO) activation and Macrophage-Inflammatory Protein-2 (MIP-2) transcription were monitored.


RESULTS
The exposure to hyperosmotic solutions enhanced the production of IL-8 and induced pro-inflammatory cytokines transcription. In vivo, MPO enhanced activity accompanied by an increased MIP-2 transcription was observed. In vitro, NF-kappaB activation is accompanied by an inhibitor of kappa B-alpha degradation and inhibitor of kappa B kinase (IKK gamma) activation. We demonstrated the induction of IKK gamma after methylation and activation of PP2A. Cytokine induction was inhibited by okadaic acid and calyculin A and stimulated by xylitol.


CONCLUSIONS
Hyperosmolarity can induce pro-inflammatory cytokine responses in colorectal and bladder epithelial cells. Inflammation appears to be the simple consequence of a shift of methylation of PP2A which in turn activates NF-kappaB.
Abolhassani
M
M
BCG department, Pasteur Institute of Iran, Tehran, 13164 Iran.
Wertz
X
X
Pooya
M
M
Chaumet-Riffaud
P
P
Guais
A
A
Schwartz
L
L
D000818:Animals; D045744:Cell Line, Tumor; D018925:Chemokines / Q000096:biosynthesis; D016207:Cytokines / Q000096:biosynthesis; D004847:Epithelial Cells / Q000276:immunology; D005260:Female; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007249:Inflammation / Q000209:etiology*; D008745:Methylation; D016328:NF-kappa B / Q000378:metabolism; D009994:Osmolar Concentration; D009195:Peroxidase / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
D018925:Chemokines; D016207:Cytokines; D016328:NF-kappa B; D012333:RNA, Messenger; D009195:Peroxidase; D051550:I-kappa B Kinase; D054648:Protein Phosphatase 2