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Protein Citrullination: A Proposed Mechanism for Pathology in Traumatic Brain Injury.

Lazarus RC, Buonora JE, Flora MN, Freedy JG, Holstein GR, Martinelli GP, Jacobowitz DM, Mueller GP - Front Neurol (2015)

Bottom Line: The present investigation addressed this gap by examining the effects of TBI on the distribution of protein citrullination and on the specific cell types involved.This response was exclusively seen in astrocytes; no such effects were observed on the status of protein citrullination in neurons, oligodendrocytes or microglia.Further, proteomic analyses demonstrated that the effects of TBI on citrullination were confined to a relatively small subset of neural proteins.

View Article: PubMed Central - PubMed

Affiliation: Program in Neuroscience, Uniformed Services University of the Health Sciences , Bethesda, MD , USA.

ABSTRACT
Protein citrullination is a calcium-driven post-translational modification proposed to play a causative role in the neurodegenerative disorders of Alzheimer's disease, multiple sclerosis (MS), and prion disease. Citrullination can result in the formation of antigenic epitopes that underlie pathogenic autoimmune responses. This phenomenon, which is best understood in rheumatoid arthritis, may play a role in the chronic dysfunction following traumatic brain injury (TBI). Despite substantial evidence of aberrations in calcium signaling following TBI, there is little understanding of how TBI alters citrullination in the brain. The present investigation addressed this gap by examining the effects of TBI on the distribution of protein citrullination and on the specific cell types involved. Immunofluorescence revealed that controlled cortical impact in rats profoundly up--regulated protein citrullination in the cerebral cortex, external capsule, and hippocampus. This response was exclusively seen in astrocytes; no such effects were observed on the status of protein citrullination in neurons, oligodendrocytes or microglia. Further, proteomic analyses demonstrated that the effects of TBI on citrullination were confined to a relatively small subset of neural proteins. Proteins most notably affected were those also reported to be citrullinated in other disorders, including prion disease and MS. In vivo findings were extended in an in vitro model of simulated TBI employing normal human astrocytes. Pharmacologically induced calcium excitotoxicity was shown to activate the citrullination and breakdown of glial fibrillary acidic protein, producing a novel candidate TBI biomarker and potential target for autoimmune recognition. In summary, these findings demonstrate that the effects of TBI on protein citrullination are selective with respect to brain region, cell type, and proteins modified, and may contribute to a role for autoimmune dysfunction in chronic pathology following TBI.

No MeSH data available.


Related in: MedlinePlus

Specificity of anti-protein citrulline immunolabeling by mAb 6B3. (A,B) show immunofluorescent signals from mAb 6B3 anti-protein citrulline labeling of the injured cerebral cortex (A) and ipsilateral hippocampus (B). (C,D) shows immunolabeling of equivalent sections with mAb 6B3 that was preadsorbed with citrullinated protein standards. The control and immunoneutralized preparations of mAb 6B3 were treated identically, with the exception of the presence or absence of neutralizing citrullinated proteins. Data are representative of two independent experiments. Scale bar: 200 μm.
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Figure 2: Specificity of anti-protein citrulline immunolabeling by mAb 6B3. (A,B) show immunofluorescent signals from mAb 6B3 anti-protein citrulline labeling of the injured cerebral cortex (A) and ipsilateral hippocampus (B). (C,D) shows immunolabeling of equivalent sections with mAb 6B3 that was preadsorbed with citrullinated protein standards. The control and immunoneutralized preparations of mAb 6B3 were treated identically, with the exception of the presence or absence of neutralizing citrullinated proteins. Data are representative of two independent experiments. Scale bar: 200 μm.

Mentions: The specificity of mAb 6B3 labeling of citrullinated proteins in TBI brain was confirmed by immunoneutralization. As shown in Figure 2, preabsorption of the mAb 6B3 with citrullinated protein standard effectively eliminated the labeling of cells in the cerebral cortex and hippocampus of CCI brain. In this experiment, the active labeling condition utilized mAb 6B3 that had been exposed to the identical absorption procedures as the neutralized mAb 6B3, except that the neutralizing proteins were not citrullinated under the control condition. Additionally, a secondary-only control was also conducted and further confirmed the specificity of the anti-citrullinated protein labeling (not shown).


Protein Citrullination: A Proposed Mechanism for Pathology in Traumatic Brain Injury.

Lazarus RC, Buonora JE, Flora MN, Freedy JG, Holstein GR, Martinelli GP, Jacobowitz DM, Mueller GP - Front Neurol (2015)

Specificity of anti-protein citrulline immunolabeling by mAb 6B3. (A,B) show immunofluorescent signals from mAb 6B3 anti-protein citrulline labeling of the injured cerebral cortex (A) and ipsilateral hippocampus (B). (C,D) shows immunolabeling of equivalent sections with mAb 6B3 that was preadsorbed with citrullinated protein standards. The control and immunoneutralized preparations of mAb 6B3 were treated identically, with the exception of the presence or absence of neutralizing citrullinated proteins. Data are representative of two independent experiments. Scale bar: 200 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585288&req=5

Figure 2: Specificity of anti-protein citrulline immunolabeling by mAb 6B3. (A,B) show immunofluorescent signals from mAb 6B3 anti-protein citrulline labeling of the injured cerebral cortex (A) and ipsilateral hippocampus (B). (C,D) shows immunolabeling of equivalent sections with mAb 6B3 that was preadsorbed with citrullinated protein standards. The control and immunoneutralized preparations of mAb 6B3 were treated identically, with the exception of the presence or absence of neutralizing citrullinated proteins. Data are representative of two independent experiments. Scale bar: 200 μm.
Mentions: The specificity of mAb 6B3 labeling of citrullinated proteins in TBI brain was confirmed by immunoneutralization. As shown in Figure 2, preabsorption of the mAb 6B3 with citrullinated protein standard effectively eliminated the labeling of cells in the cerebral cortex and hippocampus of CCI brain. In this experiment, the active labeling condition utilized mAb 6B3 that had been exposed to the identical absorption procedures as the neutralized mAb 6B3, except that the neutralizing proteins were not citrullinated under the control condition. Additionally, a secondary-only control was also conducted and further confirmed the specificity of the anti-citrullinated protein labeling (not shown).

Bottom Line: The present investigation addressed this gap by examining the effects of TBI on the distribution of protein citrullination and on the specific cell types involved.This response was exclusively seen in astrocytes; no such effects were observed on the status of protein citrullination in neurons, oligodendrocytes or microglia.Further, proteomic analyses demonstrated that the effects of TBI on citrullination were confined to a relatively small subset of neural proteins.

View Article: PubMed Central - PubMed

Affiliation: Program in Neuroscience, Uniformed Services University of the Health Sciences , Bethesda, MD , USA.

ABSTRACT
Protein citrullination is a calcium-driven post-translational modification proposed to play a causative role in the neurodegenerative disorders of Alzheimer's disease, multiple sclerosis (MS), and prion disease. Citrullination can result in the formation of antigenic epitopes that underlie pathogenic autoimmune responses. This phenomenon, which is best understood in rheumatoid arthritis, may play a role in the chronic dysfunction following traumatic brain injury (TBI). Despite substantial evidence of aberrations in calcium signaling following TBI, there is little understanding of how TBI alters citrullination in the brain. The present investigation addressed this gap by examining the effects of TBI on the distribution of protein citrullination and on the specific cell types involved. Immunofluorescence revealed that controlled cortical impact in rats profoundly up--regulated protein citrullination in the cerebral cortex, external capsule, and hippocampus. This response was exclusively seen in astrocytes; no such effects were observed on the status of protein citrullination in neurons, oligodendrocytes or microglia. Further, proteomic analyses demonstrated that the effects of TBI on citrullination were confined to a relatively small subset of neural proteins. Proteins most notably affected were those also reported to be citrullinated in other disorders, including prion disease and MS. In vivo findings were extended in an in vitro model of simulated TBI employing normal human astrocytes. Pharmacologically induced calcium excitotoxicity was shown to activate the citrullination and breakdown of glial fibrillary acidic protein, producing a novel candidate TBI biomarker and potential target for autoimmune recognition. In summary, these findings demonstrate that the effects of TBI on protein citrullination are selective with respect to brain region, cell type, and proteins modified, and may contribute to a role for autoimmune dysfunction in chronic pathology following TBI.

No MeSH data available.


Related in: MedlinePlus