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A chimeric Cfh transgene leads to increased retinal oxidative stress, inflammation, and accumulation of activated subretinal microglia in mice.

ABSTRACT: Variants of complement factor H (Cfh) affecting short consensus repeats (SCRs) 6 to 8 increase the risk of age-related macular degeneration. Our aim was to explore the effect of expressing a Cfh variant on the in vivo susceptibility of the retina and RPE to oxidative stress and inflammation, using chimeric Cfh transgenic mice (chCfhTg).The chCfhTg and age-matched C57BL/6J (B6) mice were subjected to oxidative stress by either normal aging, or by exposure to a combination of oral hydroquinone (0.8% HQ) and increased light. Eyes were collected for immunohistochemistry of RPE-choroid flat mounts and of retinal sections, ELISA, electron microscopy, and RPE/microglia gene expression analysis.Aging mice to 2 years led to an increased accumulation of basal laminar deposits, subretinal microglia/macrophages (MG/M?) staining for CD16 and for malondialdehyde (MDA), and MDA-modified proteins in the retina in chCfhTg compared to B6 mice. The chCfhTg mice maintained on HQ diet and increased light showed greater deposition of basal laminar deposits, more accumulation of fundus spots suggestive of MG/M?, and increased deposition of C3d in the sub-RPE space, compared to controls. In addition, chCfhTg mice demonstrated upregulation of NLRP3, IP-10, CD68, and TREM-2 in the RNA isolates from RPE/MG/M?.Expression of a Cfh transgene introducing a variant in SCRs 6 to 8 was sufficient to lead to increased retinal/RPE susceptibility to oxidative stress, a proinflammatory MG/M? phenotype, and a proinflammatory RPE/MG/M? gene expression profile in a transgenic mouse model. Our data suggest that altered interactions of Cfh with MDA-modified proteins may be relevant in explaining the effects of the Cfh variant.

SUBMITTER: Aredo B

PROVIDER: S-EPMC4464010 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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A chimeric Cfh transgene leads to increased retinal oxidative stress, inflammation, and accumulation of activated subretinal microglia in mice.

Aredo Bogale B Li Tao T Chen Xiao X Zhang Kaiyan K Wang Cynthia Xin-Zhao CX Gou Darlene D Zhao Biren B He Yuguang Y Ufret-Vincenty Rafael L RL

Investigative ophthalmology & visual science 20150601 6

<h4>Purpose</h4>Variants of complement factor H (Cfh) affecting short consensus repeats (SCRs) 6 to 8 increase the risk of age-related macular degeneration. Our aim was to explore the effect of expressing a Cfh variant on the in vivo susceptibility of the retina and RPE to oxidative stress and inflammation, using chimeric Cfh transgenic mice (chCfhTg).<h4>Methods</h4>The chCfhTg and age-matched C57BL/6J (B6) mice were subjected to oxidative stress by either normal aging, or by exposure to a comb ...[more]

PMID: 26030099

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Project description:Mitochondrial oxidative stress is associated with many neurodegenerative diseases, such as traumatic brain injury (TBI). Targeted delivery of antioxidants to mitochondria has failed to translate into clinical success due to their nonspecific cellular localization, poor transport properties across multiple biological barriers, and associated side effects. These challenges, coupled with the complex function of the mitochondria, create the need for innovative delivery strategies. Methods: Neutral hydroxyl-terminated polyamidoamine (PAMAM) dendrimers have shown significant potential as nanocarriers in multiple brain injury models. N-acetyl cysteine (NAC) is a clinically used antioxidant and anti-inflammatory agent which has shown significant potency when delivered in a targeted manner. Here we present a mitochondrial targeting hydroxyl PAMAM dendrimer-drug construct (TPP-D-NAC) with triphenyl-phosphonium (TPP) for mitochondrial targeting and NAC for targeted delivery to mitochondria in injured glia. Co-localization and mitochondrial content of mitochondria-targeted and unmodified dendrimer were assessed in microglia and macrophages in vitro via immunohistochemistry and fluorescence quantification. Therapeutic improvements of TPP-D-NAC over dendrimer-NAC conjugate (D-NAC) and free NAC were evaluated in vitro in microglia under oxidative stress challenge. In vivo neuroinflammation targeting was confirmed in a rabbit model of TBI. Results: TPP-conjugated dendrimer co-localized significantly more with mitochondria than unmodified dendrimer without altering overall levels of cellular internalization. This targeting capability translated to significant improvements in the attenuation of oxidative stress by TPP-D-NAC compared to D-NAC and free NAC. Upon systemic administration in a rabbit TBI model, TPP-conjugated dendrimer co-localized specifically with mitochondria in activated microglia and macrophages in the white matter of the ipsilateral/injured hemisphere, confirming its BBB penetration and glial targeting capabilities. Conclusion: D-NAC has shown promising efficacy in many animal models of neurodegeneration, and this work provides evidence that modification for mitochondrial targeting can further enhance its therapeutic efficacy, particularly in diseases where oxidative stress-induced glial cell death plays a significant role in disease progression.

Dataset Information

A chimeric Cfh transgene leads to increased retinal oxidative stress, inflammation, and accumulation of activated subretinal microglia in mice.

Publications

A chimeric Cfh transgene leads to increased retinal oxidative stress, inflammation, and accumulation of activated subretinal microglia in mice.

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