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Azza B. El-Remessy, Mohammed M. Al-Gayyar, Mohammed A. Abdelsaid, Suraporn Matragoon, Bindu A. Pillai, H Uri Saragovi; ProNGF Stimulates Retinal Inflammation Via Activation of p75NTR. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1001. doi: https://doi.org/.
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We have previously shown significant accumulation of the pro-form of nerve growth factor (proNGF) and its receptor p75NTR in diabetic rat retinas and Muller cells. The purpose of this study is to elucidate the role of proNGF/p75NTR axis in sustaining glial activation, and expression of inflammatory mediators in vitro and in vivo.
Overexpression of proNGF in SD rats was achieved by intravitreal injection of the GFP-proNGF plasmid (20 µg) expressing the protease cleavage resistant proNGF construct. Expression of p75NTR was silenced using co-intravitreal injection of siRNA for 1-week or shRNA for 4-weeks. Expression of proNGF, TNF-alpha, IL-1-beta and NFkB were quantified by immunohistochemistry and Western-Blot. As an ex vivo correlate, Muller rMC-1 cells were cultured in high glucose and stimulated with proNGF in the presence or absence of p75NTR inhibitor.
Overexpression of proNGF in rat retina induced expression of p75NTR, activated glial Muller cells as indicated by GFAP staining, and upregulated the pro-inflammatory transcription factor NFkB. After 1-week, proNGF induced expression of TNF-alpha and IL-1-beta, and this was blocked by p75NTR siRNA. After 4-weeks, proNGF sustained the expression of itself, TNF-alpha and IL-1-beta, and this was blocked by p75NTR shRNA. In high glucose maintained rMC-1 cultures, proNGF induced expression of p75NTR, release of its ICD, and upregulation of of NFkB, which resulted in sustained expression proNGF as well as TNF-alpha. These effects were blunted by the selective p75NTR antagonist.
Similar to diabetes, overexpression of proNGF in normal rat retina induced up-regulation of p75NTR and NFkB expression leading to inflammatory cascades. These effects were associated with induction and sustaining expression of proNGF, TNF-alpha and IL-1B that were blocked by inhibiting p75NTR expression. Thus, inhibiting p75NTR may be an effective strategy in diabetic retinopathy.
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