BACKGROUNDNuclear factor-kappa B (NF-kappaB) is elevated in regulating transcription of many cytokines and inflammatory mediators. The purpose of this study was to investigate the activation and the significance NF-kappaB in lipopolysaccharide (LPS) induced keratitis.

METHODSLPS induced keratitis model was based on Wistar rats. At 0.5, 1, 3, 6, 12, 24 or 72 hours after LPS treatment, the rat corneas were observed with a slit lamp microscope, then the rats were sacrificed and their corneas were excised for routine histological analysis. The expression of NF-kappaB was detected with immunohistochemical staining. The change of tumour necrosis factors-alpha (TNF-alpha) mRNA expression was identified by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTSHistological findings demonstrated that LPS treated corneas showed significant changes in corneal structure. Corneal edema, pronounced inflammatory cells infiltration and inordinate collagen fibres were observed. Immunohistochemical results showed that the expression of NF-kappaB and its activation obviously increased after LPS treatment compared with the normal group and control group. Positive cells could be observed at 0.5 hour and peak expression of NF-kappaB was observed between 3 hours and 12 hours after infection, but returned to or approached normal level by 72 hours. RT-PCR showed that the level of TNF-alpha mRNA began to increase 0.5 hour after LPS treatment, peaked at 6 hours and then subsided by 72 hours. NF-kappaB had a positive correlation with the expression of TNF-alpha mRNA (r = 0.964, P < 0.01), both NF-kappaB and TNF-alpha had a strong positive correlation with the degree of inflammatory response in LPS treated corneas (r = 0.929, P < 0.01; r = 0.587, P < 0.05, respectively).

CONCLUSIONSThe activation of NF-kappaB was increased in LPS treated corneas and was elevated in LPS induced keratitis by promoting overexpression of TNF-alpha mRNA. NF-kappaB may play an important role in the pathogenesis of LPS-associated keratitis in rats.