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Increased expression of cystine/glutamate antiporter in multiple sclerosis.

Pampliega O, Domercq M, Soria FN, Villoslada P, Rodríguez-Antigüedad A, Matute C - J Neuroinflammation (2011)

Bottom Line: In addition, xCT expression is also increased in EAE and in the disease proper.In the later, high expression of xCT occurs both in the central nervous system (CNS) and in peripheral blood cells.Together, these results reveal that increased expression of the cystine/glutamate antiporter system x(c)⁻ in MS provides a link between inflammation and excitotoxicity in demyelinating diseases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Neurotek-UPV/EHU, Parque Tecnológico de Bizkaia, Zamudio, Bizkaia, Spain.

ABSTRACT

Background: Glutamate excitotoxicity contributes to oligodendrocyte and tissue damage in multiple sclerosis (MS). Intriguingly, glutamate level in plasma and cerebrospinal fluid of MS patients is elevated, a feature which may be related to the pathophysiology of this disease. In addition to glutamate transporters, levels of extracellular glutamate are controlled by cystine/glutamate antiporter x(c)⁻, an exchanger that provides intracellular cystine for production of glutathione, the major cellular antioxidant. The objective of this study was to analyze the role of the system x(c)⁻ in glutamate homeostasis alterations in MS pathology.

Methods: Primary cultures of human monocytes and the cell line U-937 were used to investigate the mechanism of glutamate release. Expression of cystine glutamate exchanger (xCT) was quantified by quantitative PCR, Western blot, flow cytometry and immunohistochemistry in monocytes in vitro, in animals with experimental autoimmune encephalomyelitis (EAE), the animal model of MS, and in samples of MS patients.

Results and discussion: We show here that human activated monocytes release glutamate through cystine/glutamate antiporter x(c)⁻ and that the expression of the catalytic subunit xCT is upregulated as a consequence of monocyte activation. In addition, xCT expression is also increased in EAE and in the disease proper. In the later, high expression of xCT occurs both in the central nervous system (CNS) and in peripheral blood cells. In particular, cells from monocyte-macrophage-microglia lineage have higher xCT expression in MS and in EAE, indicating that immune activation upregulates xCT levels, which may result in higher glutamate release and contribution to excitotoxic damage to oligodendrocytes.

Conclusions: Together, these results reveal that increased expression of the cystine/glutamate antiporter system x(c)⁻ in MS provides a link between inflammation and excitotoxicity in demyelinating diseases.

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Related in: MedlinePlus

xCT expression is enhanced in CD68+ cells from MS spinal cord. A. Triple immunofluorescence staining for xCT (green), CD68 (red) and Hoechst 33258 (blue) in spinal cord of control (left) and MS patients (right). A high expression of xCT was detected in CD68+ infiltrating macrophages (arrows) associated with blood vessels, which are virtually absent in controls. Note that overall xCT expression is enhanced in MS tissue. B. CD68+ cells (arrows) show enhanced xCT expression in MS patients as compared to controls. CD68+ macrophages are round shaped and form clusters in MS patients, whereas in controls, CD68+ cells appear isolated and long shaped. Scale bar = 50 μm.
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Figure 5: xCT expression is enhanced in CD68+ cells from MS spinal cord. A. Triple immunofluorescence staining for xCT (green), CD68 (red) and Hoechst 33258 (blue) in spinal cord of control (left) and MS patients (right). A high expression of xCT was detected in CD68+ infiltrating macrophages (arrows) associated with blood vessels, which are virtually absent in controls. Note that overall xCT expression is enhanced in MS tissue. B. CD68+ cells (arrows) show enhanced xCT expression in MS patients as compared to controls. CD68+ macrophages are round shaped and form clusters in MS patients, whereas in controls, CD68+ cells appear isolated and long shaped. Scale bar = 50 μm.

Mentions: Finally, we performed double immunofluorescence analysis of xCT expression in the spinal cord of MS patients and controls. Overall, we observed a higher expression of xCT in the CNS of MS patients than in controls. In particular, infiltrating CD68+ macrophages revealed higher xCT expression in MS patients than in controls (Figure 5). Thus, CD68+ cells located in blood vessels (Figure 5A) or nearby, and usually forming clusters, showed a clear xCT overexpression in MS patients (Figure 5B). These results are consistent with the increase of xCT expression in EAE animals, and suggest that altered xCT expression may have a pathophysiological role in MS disease.


Increased expression of cystine/glutamate antiporter in multiple sclerosis.

Pampliega O, Domercq M, Soria FN, Villoslada P, Rodríguez-Antigüedad A, Matute C - J Neuroinflammation (2011)

xCT expression is enhanced in CD68+ cells from MS spinal cord. A. Triple immunofluorescence staining for xCT (green), CD68 (red) and Hoechst 33258 (blue) in spinal cord of control (left) and MS patients (right). A high expression of xCT was detected in CD68+ infiltrating macrophages (arrows) associated with blood vessels, which are virtually absent in controls. Note that overall xCT expression is enhanced in MS tissue. B. CD68+ cells (arrows) show enhanced xCT expression in MS patients as compared to controls. CD68+ macrophages are round shaped and form clusters in MS patients, whereas in controls, CD68+ cells appear isolated and long shaped. Scale bar = 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117706&req=5

Figure 5: xCT expression is enhanced in CD68+ cells from MS spinal cord. A. Triple immunofluorescence staining for xCT (green), CD68 (red) and Hoechst 33258 (blue) in spinal cord of control (left) and MS patients (right). A high expression of xCT was detected in CD68+ infiltrating macrophages (arrows) associated with blood vessels, which are virtually absent in controls. Note that overall xCT expression is enhanced in MS tissue. B. CD68+ cells (arrows) show enhanced xCT expression in MS patients as compared to controls. CD68+ macrophages are round shaped and form clusters in MS patients, whereas in controls, CD68+ cells appear isolated and long shaped. Scale bar = 50 μm.
Mentions: Finally, we performed double immunofluorescence analysis of xCT expression in the spinal cord of MS patients and controls. Overall, we observed a higher expression of xCT in the CNS of MS patients than in controls. In particular, infiltrating CD68+ macrophages revealed higher xCT expression in MS patients than in controls (Figure 5). Thus, CD68+ cells located in blood vessels (Figure 5A) or nearby, and usually forming clusters, showed a clear xCT overexpression in MS patients (Figure 5B). These results are consistent with the increase of xCT expression in EAE animals, and suggest that altered xCT expression may have a pathophysiological role in MS disease.

Bottom Line: In addition, xCT expression is also increased in EAE and in the disease proper.In the later, high expression of xCT occurs both in the central nervous system (CNS) and in peripheral blood cells.Together, these results reveal that increased expression of the cystine/glutamate antiporter system x(c)⁻ in MS provides a link between inflammation and excitotoxicity in demyelinating diseases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Neurotek-UPV/EHU, Parque Tecnológico de Bizkaia, Zamudio, Bizkaia, Spain.

ABSTRACT

Background: Glutamate excitotoxicity contributes to oligodendrocyte and tissue damage in multiple sclerosis (MS). Intriguingly, glutamate level in plasma and cerebrospinal fluid of MS patients is elevated, a feature which may be related to the pathophysiology of this disease. In addition to glutamate transporters, levels of extracellular glutamate are controlled by cystine/glutamate antiporter x(c)⁻, an exchanger that provides intracellular cystine for production of glutathione, the major cellular antioxidant. The objective of this study was to analyze the role of the system x(c)⁻ in glutamate homeostasis alterations in MS pathology.

Methods: Primary cultures of human monocytes and the cell line U-937 were used to investigate the mechanism of glutamate release. Expression of cystine glutamate exchanger (xCT) was quantified by quantitative PCR, Western blot, flow cytometry and immunohistochemistry in monocytes in vitro, in animals with experimental autoimmune encephalomyelitis (EAE), the animal model of MS, and in samples of MS patients.

Results and discussion: We show here that human activated monocytes release glutamate through cystine/glutamate antiporter x(c)⁻ and that the expression of the catalytic subunit xCT is upregulated as a consequence of monocyte activation. In addition, xCT expression is also increased in EAE and in the disease proper. In the later, high expression of xCT occurs both in the central nervous system (CNS) and in peripheral blood cells. In particular, cells from monocyte-macrophage-microglia lineage have higher xCT expression in MS and in EAE, indicating that immune activation upregulates xCT levels, which may result in higher glutamate release and contribution to excitotoxic damage to oligodendrocytes.

Conclusions: Together, these results reveal that increased expression of the cystine/glutamate antiporter system x(c)⁻ in MS provides a link between inflammation and excitotoxicity in demyelinating diseases.

Show MeSH
Related in: MedlinePlus