Abstract
Purpose: :
Chemokines may induce neuron cell death either indirectly through activation of microglia killing mechanism or directly through activation of neuronal chemokine receptors.Our previous study showed that chemokine expression and microglial activation were involved in the retinal degeneration of rd mice. In the present study, localization of chemokines and chemokine receptors in the specific retinal cell types was further investigated.
Methods: :
Localization of chemokines MCP–1 and RANTES in the rd retinas at postnatal day (P) 8, P10, P12, P14, P16 and P18 was examined by in situ hybridization and immunohistochemical studies. Expression of chemokine receptors including CCR1,CCR2,CCR3 and CCR5 in the rd retina at different ages was determined by reverse transcription–polymersase chain reaction (RT–PCR) assay and immunolabeling. Photoreceptor apoptosis in the rd mice was detected by TUNEL. Retinal Muller cells, microglia , horizontal cells, bipolar cells and amacrine cells were identified by GFAP, glutamate synthetase, CD11b, calbindin , PKC α, and calretinin antibodies respectively. Co–localization of chemokine and chemokine receptors with specific retinal cell types was determined by double immunolabeling.
Results: :
Expression of chemokine MCP–1 and RANTES was noted in the inner retinal layers, particularly in the bipolar cells, Muller cells, microglial cells and ganglion cells. The levels of mRNA expression of CCR1, CCR2, CCR3, CCR5 were increased in the retina of the rd mice from P10–P18 compared with controls. Immunostain of above chemokine receptors were observed in the outer nuclear layers, labeling photoreceptor cells, activated microglia or processes of Muller cells. Some of the CCR1, CCR2 and CCR3 were noted in the apoptotic photoreceptor cells. Immunolabling of CCR1, CCR2, CCR3, CCR5 were also observed in the horizontal cells, amacrine cells and ganglion cells.
Conclusions: :
Chemokines MCP–1 and RANTES participated in the retinal degenerative process of rd mice via activation of microglia, stimulation of Muller cells or activation of photoreceptor chemokine receptors.
Keywords: retinal degenerations: cell biology • inflammation • receptors