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A role for hemopexin in oligodendrocyte differentiation and myelin formation.

Morello N, Bianchi FT, Marmiroli P, Tonoli E, Rodriguez Menendez V, Silengo L, Cavaletti G, Vercelli A, Altruda F, Tolosano E - PLoS ONE (2011)

Bottom Line: In the current study, we found that the expression of the Myelin Basic Protein along with the density of myelinated fibers in the basal ganglia and in the motor and somatosensory cortex of Hx- mice were strongly reduced starting at 2 months and progressively decreased with age.Finally, in vitro experiments showed that Hx promotes OL differentiation.Thus, Hx may be considered a novel OL differentiation factor and the modulation of its expression in CNS may be an important factor in the pathogenesis of human neurodegenerative disorders.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biotechnology Center, University of Turin, Turin, Italy.

ABSTRACT
Myelin formation and maintenance are crucial for the proper function of the CNS and are orchestrated by a plethora of factors including growth factors, extracellular matrix components, metalloproteases and protease inhibitors. Hemopexin (Hx) is a plasma protein with high heme binding affinity, which is also locally produced in the CNS by ependymal cells, neurons and glial cells. We have recently reported that oligodendrocytes (OLs) are the type of cells in the brain that are most susceptible to lack of Hx, as the number of iron-overloaded OLs increases in Hx- brain, leading to oxidative tissue damage. In the current study, we found that the expression of the Myelin Basic Protein along with the density of myelinated fibers in the basal ganglia and in the motor and somatosensory cortex of Hx- mice were strongly reduced starting at 2 months and progressively decreased with age. Myelin abnormalities were confirmed by electron microscopy and, at the functional level, resulted in the inability of Hx- mice to perform efficiently on the Rotarod. It is likely that the poor myelination in the brain of Hx- mice was a consequence of defective maturation of OLs as we demonstrated that the number of mature OLs was significantly reduced in mutant mice whereas that of precursor cells was normal. Finally, in vitro experiments showed that Hx promotes OL differentiation. Thus, Hx may be considered a novel OL differentiation factor and the modulation of its expression in CNS may be an important factor in the pathogenesis of human neurodegenerative disorders.

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Reduction of MBP protein production in Hx−/−                            brain.A) Western blot analysis of MBP expression in brain extracts                            of wild-type and Hx−/− mice. Cerebral cortex and                            basal ganglia region lysates were analyzed at two and twelve months of                            age. Representative experiments are shown. B) Band                            intensities were measured by densitometry and normalized to actin                            expression (AU: Arbitrary Unit). The overall MBP production was obtained                            by summing the relative intensities of the four isoforms recognized by                            the antibody (indicated by arrows in scanned gels). Densitometry data                            represent mean ± SEM; n = 3 for each                            genotype. *  =  P<0.05. Results shown are                            representative of three independent experiments.
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pone-0020173-g001: Reduction of MBP protein production in Hx−/− brain.A) Western blot analysis of MBP expression in brain extracts of wild-type and Hx−/− mice. Cerebral cortex and basal ganglia region lysates were analyzed at two and twelve months of age. Representative experiments are shown. B) Band intensities were measured by densitometry and normalized to actin expression (AU: Arbitrary Unit). The overall MBP production was obtained by summing the relative intensities of the four isoforms recognized by the antibody (indicated by arrows in scanned gels). Densitometry data represent mean ± SEM; n = 3 for each genotype. *  =  P<0.05. Results shown are representative of three independent experiments.

Mentions: We have already demonstrated that OLs are more susceptible than other cell types to lack of Hx as they accumulate heme-derived iron [17]. As iron availability may affect the state of myelination [21], we posed the question whether iron load in OLs of Hx−/− mice impairs their ability to form myelin and therefore analyzed the expression of MBP, one of the major myelin proteins [25], in two distinct regions of Hx−/− mouse brains: cerebral cortex (motor and somatosensory areas) and basal ganglia, at two and twelve months of age. Immunoblot analysis on samples from two month-old mice showed a slight, but significant reduction in MBP content in the cortex of Hx−/− mice compared to wild-type animals. In twelve month-old mice the reduction of MBP in Hx−/− mice was more evident in both cerebral cortex and basal ganglia (Figure 1). The anti-MBP antibody revealed signals for all four bands of MBP, representing MBP splice variants and, in Hx−/− mice, reduced expression affected all isoforms. Particularly, the less abundant 21.5 KDa isoform showed a reduction of about 60% in the cortex of 2 month-old mice, and of 40–50% in the cortex and basal ganglia of 12 month-old animals, whereas the other isoforms, 18.5, 17 and 14 KDa, showed a similar reduction of about 30–40% both in the cortex at 2 months and in the cortex and basal ganglia at 12 months of age (not shown).


A role for hemopexin in oligodendrocyte differentiation and myelin formation.

Morello N, Bianchi FT, Marmiroli P, Tonoli E, Rodriguez Menendez V, Silengo L, Cavaletti G, Vercelli A, Altruda F, Tolosano E - PLoS ONE (2011)

Reduction of MBP protein production in Hx−/−                            brain.A) Western blot analysis of MBP expression in brain extracts                            of wild-type and Hx−/− mice. Cerebral cortex and                            basal ganglia region lysates were analyzed at two and twelve months of                            age. Representative experiments are shown. B) Band                            intensities were measured by densitometry and normalized to actin                            expression (AU: Arbitrary Unit). The overall MBP production was obtained                            by summing the relative intensities of the four isoforms recognized by                            the antibody (indicated by arrows in scanned gels). Densitometry data                            represent mean ± SEM; n = 3 for each                            genotype. *  =  P<0.05. Results shown are                            representative of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3102107&req=5

pone-0020173-g001: Reduction of MBP protein production in Hx−/− brain.A) Western blot analysis of MBP expression in brain extracts of wild-type and Hx−/− mice. Cerebral cortex and basal ganglia region lysates were analyzed at two and twelve months of age. Representative experiments are shown. B) Band intensities were measured by densitometry and normalized to actin expression (AU: Arbitrary Unit). The overall MBP production was obtained by summing the relative intensities of the four isoforms recognized by the antibody (indicated by arrows in scanned gels). Densitometry data represent mean ± SEM; n = 3 for each genotype. *  =  P<0.05. Results shown are representative of three independent experiments.
Mentions: We have already demonstrated that OLs are more susceptible than other cell types to lack of Hx as they accumulate heme-derived iron [17]. As iron availability may affect the state of myelination [21], we posed the question whether iron load in OLs of Hx−/− mice impairs their ability to form myelin and therefore analyzed the expression of MBP, one of the major myelin proteins [25], in two distinct regions of Hx−/− mouse brains: cerebral cortex (motor and somatosensory areas) and basal ganglia, at two and twelve months of age. Immunoblot analysis on samples from two month-old mice showed a slight, but significant reduction in MBP content in the cortex of Hx−/− mice compared to wild-type animals. In twelve month-old mice the reduction of MBP in Hx−/− mice was more evident in both cerebral cortex and basal ganglia (Figure 1). The anti-MBP antibody revealed signals for all four bands of MBP, representing MBP splice variants and, in Hx−/− mice, reduced expression affected all isoforms. Particularly, the less abundant 21.5 KDa isoform showed a reduction of about 60% in the cortex of 2 month-old mice, and of 40–50% in the cortex and basal ganglia of 12 month-old animals, whereas the other isoforms, 18.5, 17 and 14 KDa, showed a similar reduction of about 30–40% both in the cortex at 2 months and in the cortex and basal ganglia at 12 months of age (not shown).

Bottom Line: In the current study, we found that the expression of the Myelin Basic Protein along with the density of myelinated fibers in the basal ganglia and in the motor and somatosensory cortex of Hx- mice were strongly reduced starting at 2 months and progressively decreased with age.Finally, in vitro experiments showed that Hx promotes OL differentiation.Thus, Hx may be considered a novel OL differentiation factor and the modulation of its expression in CNS may be an important factor in the pathogenesis of human neurodegenerative disorders.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biotechnology Center, University of Turin, Turin, Italy.

ABSTRACT
Myelin formation and maintenance are crucial for the proper function of the CNS and are orchestrated by a plethora of factors including growth factors, extracellular matrix components, metalloproteases and protease inhibitors. Hemopexin (Hx) is a plasma protein with high heme binding affinity, which is also locally produced in the CNS by ependymal cells, neurons and glial cells. We have recently reported that oligodendrocytes (OLs) are the type of cells in the brain that are most susceptible to lack of Hx, as the number of iron-overloaded OLs increases in Hx- brain, leading to oxidative tissue damage. In the current study, we found that the expression of the Myelin Basic Protein along with the density of myelinated fibers in the basal ganglia and in the motor and somatosensory cortex of Hx- mice were strongly reduced starting at 2 months and progressively decreased with age. Myelin abnormalities were confirmed by electron microscopy and, at the functional level, resulted in the inability of Hx- mice to perform efficiently on the Rotarod. It is likely that the poor myelination in the brain of Hx- mice was a consequence of defective maturation of OLs as we demonstrated that the number of mature OLs was significantly reduced in mutant mice whereas that of precursor cells was normal. Finally, in vitro experiments showed that Hx promotes OL differentiation. Thus, Hx may be considered a novel OL differentiation factor and the modulation of its expression in CNS may be an important factor in the pathogenesis of human neurodegenerative disorders.

Show MeSH
Related in: MedlinePlus