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Differential expression of Kir4.1 and aquaporin 4 in the retina from endotoxin-induced uveitis rat.

ABSTRACT: PURPOSE: The inwardly rectifying potassium channel protein Kir4.1 and the water channel protein aquaporin-4 (AQP4) have been suggested to play essential roles in the potassium and water homeostasis of the retina. In this study, we investigated the expression of Kir4.1 and AQP4 in the retina during endotoxin-induced uveitis (EIU) in rats. METHODS: EIU was induced in male Wistar rats by intravitreal injection of lipopolysaccharide (LPS). The severity of the EIU was evaluated by clinical and histopathological examination. The expression of Kir4.1 and AQP4 in the retina was detected by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemical staining. RESULTS: In the animal model of EIU, the clinical changes correlated well with the histopathological findings. The inflammation peaked at 24 h and resolved by seven day. After an intravitreal LPS injection, the expression of Kir4.1 in the retina showed a significant decline at both the protein and mRNA levels. In the early stages of EIU, the expression of Kir4.1 mRNA decreased sharply, reaching a minimum at 12 h (31%, p<0.001). It then increased gradually and had partially recovered 14 days after LPS injection (92%, p>0.05). The expression of Kir4.1 protein decreased significantly, reaching a minimum at three days after the LPS injection (43%, p<0.001). Thereafter, it increased slightly but was maintained at a low level until 14 days after LPS injection (64%, p<0.001). In contrast, the expression of AQP4 mRNA remained almost unchanged after LPS treatment (p>0.05). The expression of AQP4 protein was only slightly reduced at one day (82%, p>0.05) after LPS injection and then increased gradually and had nearly recovered to the basal level at 14 days after LPS injection. CONCLUSIONS: EIU differently alters the expression of Kir4.1 and AQP4 in the retina. The differential expression of Kir4.1 and AQP4 during EIU implies a disturbance of water and potassium transport in the retina, which may contribute to the retinal edema during ocular inflammation.

SUBMITTER: Liu XQ

PROVIDER: S-EPMC2642914 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature

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Differential expression of Kir4.1 and aquaporin 4 in the retina from endotoxin-induced uveitis rat.

Liu Xiao-Qiang XQ Kobayashi Hideyuki H Jin Zi-Bing ZB Wada Akihiko A Nao-I Nobuhis N

Molecular vision 20070301

<h4>Purpose</h4>The inwardly rectifying potassium channel protein Kir4.1 and the water channel protein aquaporin-4 (AQP4) have been suggested to play essential roles in the potassium and water homeostasis of the retina. In this study, we investigated the expression of Kir4.1 and AQP4 in the retina during endotoxin-induced uveitis (EIU) in rats.<h4>Methods</h4>EIU was induced in male Wistar rats by intravitreal injection of lipopolysaccharide (LPS). The severity of the EIU was evaluated by clinic ...[more]

PMID: 17356517

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Project description:Background and purposeCannabinoid CB2 receptors mediate immunomodulation. Here, we investigated the effects of CB2 receptor ligands on leukocyte-endothelial adhesion and inflammatory mediator release in experimental endotoxin-induced uveitis (EIU).Experimental approachEIU was induced by intraocular injection of lipopolysaccharide (LPS, 20?ng·?L(-1) ). Effects of the CB2 receptor agonist, HU308 (1.5% topical), the CB2 receptor antagonist, AM630 (2.5?mg·kg(-1) i.v.), or a combination of both compounds on leukocyte-endothelial interactions were measured hourly for 6?h in rat iridial vasculature using intravital microscopy. Anti-inflammatory actions of HU308 were compared with those of clinical treatments for uveitis - dexamethasone, prednisolone and nepafenac. Transcription factors (NF-?B, AP-1) and inflammatory mediators (cytokines, chemokines and adhesion molecules) were measured in iris and ciliary body tissue.Key resultsLeukocyte-endothelium adherence was increased in iridial microvasculature between 4-6?h after LPS. HU308 reduced this effect after LPS injection and decreased pro-inflammatory mediators: TNF-?, IL-1?, IL-6, CCL5 and CXCL2. AM630 blocked the actions of HU-308, and increased leukocyte-endothelium adhesion. HU-308 decreased levels of the transcription factors NF-?B and AP-1, while AM630 increased levels of NF-?B. Topical treatments with dexamethasone, prednisolone or nepafenac, failed to alter leukocyte adhesion or mitigate LPS-induced increases in inflammatory mediators during the 6?h of EIU.Conclusion and implicationsActivation of CB2 receptors was anti-inflammatory in a model of acute EIU and involved a reduction in NF-?B, AP-1 and inflammatory mediators. CB2 receptors may be promising drug targets for the development of novel ocular anti-inflammatory agents.Linked articlesThis article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

Dataset Information

Differential expression of Kir4.1 and aquaporin 4 in the retina from endotoxin-induced uveitis rat.

Publications

Differential expression of Kir4.1 and aquaporin 4 in the retina from endotoxin-induced uveitis rat.

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