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Sphingosine-1-phosphate enhances satellite cell activation in dystrophic muscles through a S1PR2/STAT3 signaling pathway.

Loh KC, Leong WI, Carlson ME, Oskouian B, Kumar A, Fyrst H, Zhang M, Proia RL, Hoffman EP, Saba JD - PLoS ONE (2012)

Bottom Line: These changes include early and profound induction of the gene encoding the S1P biosynthetic enzyme SphK1, followed by induction of the catabolic enzyme sphingosine phosphate lyase (SPL) 3 days later.STAT3 activation resulted in p21 and p27 downregulation in a S1PR2-dependent fashion in myoblasts.Our findings suggest that S1P promotes SC progression through the cell cycle by repression of cell cycle inhibitors via S1PR2/STAT3-dependent signaling and that SPL inhibition may provide a therapeutic strategy for MD.

View Article: PubMed Central - PubMed

Affiliation: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.

ABSTRACT
Sphingosine-1-phosphate (S1P) activates a widely expressed family of G protein-coupled receptors, serves as a muscle trophic factor and activates muscle stem cells called satellite cells (SCs) through unknown mechanisms. Here we show that muscle injury induces dynamic changes in S1P signaling and metabolism in vivo. These changes include early and profound induction of the gene encoding the S1P biosynthetic enzyme SphK1, followed by induction of the catabolic enzyme sphingosine phosphate lyase (SPL) 3 days later. These changes correlate with a transient increase in circulating S1P levels after muscle injury. We show a specific requirement for SphK1 to support efficient muscle regeneration and SC proliferation and differentiation. Mdx mice, which serve as a model for muscular dystrophy (MD), were found to be S1P-deficient and exhibited muscle SPL upregulation, suggesting that S1P catabolism is enhanced in dystrophic muscle. Pharmacological SPL inhibition increased muscle S1P levels, improved mdx muscle regeneration and enhanced SC proliferation via S1P receptor 2 (S1PR2)-dependent inhibition of Rac1, thereby activating Signal Transducer and Activator of Transcription 3 (STAT3), a central player in inflammatory signaling. STAT3 activation resulted in p21 and p27 downregulation in a S1PR2-dependent fashion in myoblasts. Our findings suggest that S1P promotes SC progression through the cell cycle by repression of cell cycle inhibitors via S1PR2/STAT3-dependent signaling and that SPL inhibition may provide a therapeutic strategy for MD.

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Dystrophic mice are characterized by an S1P-deficient state.Gene expression of eMHC, a marker of regenerating muscle, and key enzymes involved in S1P metabolism were examined by qRT-PCR in C57BL10/J and mdx (C57BL/10J background) mouse muscles under basal conditions. Data are means ± SD, n = 5/group; * indicates P<0.05. A) eMHC (Myh3) gene expression. B) Sphk1 gene expression. C) Sphk2 gene expression. D) Sgpp1 gene expression. E) Sgpl1 gene expression. F) SPL protein expression. G) Plasma S1P levels. Data are means ± SD, n = 4–5/group for plasma S1P; * indicates p≤0.05. Gene expression levels for qRT-PCR were normalized to GAPDH.
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pone-0037218-g004: Dystrophic mice are characterized by an S1P-deficient state.Gene expression of eMHC, a marker of regenerating muscle, and key enzymes involved in S1P metabolism were examined by qRT-PCR in C57BL10/J and mdx (C57BL/10J background) mouse muscles under basal conditions. Data are means ± SD, n = 5/group; * indicates P<0.05. A) eMHC (Myh3) gene expression. B) Sphk1 gene expression. C) Sphk2 gene expression. D) Sgpp1 gene expression. E) Sgpl1 gene expression. F) SPL protein expression. G) Plasma S1P levels. Data are means ± SD, n = 4–5/group for plasma S1P; * indicates p≤0.05. Gene expression levels for qRT-PCR were normalized to GAPDH.

Mentions: In consideration of our finding that S1P signaling is induced after muscle injury, we suspected that S1P signaling might also be altered in dystrophic muscles. To examine this possibility, we evaluated the levels of S1P and S1P-related gene expression in the dystrophic muscles of mdx mice, which harbor a point mutation in the murine dystrophin gene and are a rodent model for human DMD, in comparison to C57BL/10J control muscles [37]. Under basal conditions, eMHC mRNA was elevated in dystrophic muscles of mdx mice compared to control muscles, reflecting a state of continual degeneration/regeneration characteristic of dystrophic muscle (Figure 4A). No differences were observed between the two lines in gene expression levels of Sphk1 and Sphk2, which suggests that S1P biosynthesis is not likely to be impaired in mdx mice (Figures 4B and C). In contrast, the gene expression of S1P catabolic enzymes Sgpp1 and Sgpl1 were elevated compared to control muscles (Figures 4D and E). Consistent with this finding, SPL protein levels were elevated in mdx muscles compared to control muscles (Figure 4F). Importantly, circulating S1P levels of mdx mice were significantly lower than resting WT control plasma (Figure 4G). In fact, mdx S1P levels were similar to levels observed in SphK1 KO mice. These important findings reveal that dystrophic mdx mice exist in a state of S1P deficiency that is comparable to the S1P-deficient state of SphK1 KO mice and, thus, could have an impact on SC functions and muscle regeneration. However, unlike SphK1 KO mice, the mdx S1P deficiency appears to be due to enhanced S1P catabolism, rather than impaired biosynthesis.


Sphingosine-1-phosphate enhances satellite cell activation in dystrophic muscles through a S1PR2/STAT3 signaling pathway.

Loh KC, Leong WI, Carlson ME, Oskouian B, Kumar A, Fyrst H, Zhang M, Proia RL, Hoffman EP, Saba JD - PLoS ONE (2012)

Dystrophic mice are characterized by an S1P-deficient state.Gene expression of eMHC, a marker of regenerating muscle, and key enzymes involved in S1P metabolism were examined by qRT-PCR in C57BL10/J and mdx (C57BL/10J background) mouse muscles under basal conditions. Data are means ± SD, n = 5/group; * indicates P<0.05. A) eMHC (Myh3) gene expression. B) Sphk1 gene expression. C) Sphk2 gene expression. D) Sgpp1 gene expression. E) Sgpl1 gene expression. F) SPL protein expression. G) Plasma S1P levels. Data are means ± SD, n = 4–5/group for plasma S1P; * indicates p≤0.05. Gene expression levels for qRT-PCR were normalized to GAPDH.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3351440&req=5

pone-0037218-g004: Dystrophic mice are characterized by an S1P-deficient state.Gene expression of eMHC, a marker of regenerating muscle, and key enzymes involved in S1P metabolism were examined by qRT-PCR in C57BL10/J and mdx (C57BL/10J background) mouse muscles under basal conditions. Data are means ± SD, n = 5/group; * indicates P<0.05. A) eMHC (Myh3) gene expression. B) Sphk1 gene expression. C) Sphk2 gene expression. D) Sgpp1 gene expression. E) Sgpl1 gene expression. F) SPL protein expression. G) Plasma S1P levels. Data are means ± SD, n = 4–5/group for plasma S1P; * indicates p≤0.05. Gene expression levels for qRT-PCR were normalized to GAPDH.
Mentions: In consideration of our finding that S1P signaling is induced after muscle injury, we suspected that S1P signaling might also be altered in dystrophic muscles. To examine this possibility, we evaluated the levels of S1P and S1P-related gene expression in the dystrophic muscles of mdx mice, which harbor a point mutation in the murine dystrophin gene and are a rodent model for human DMD, in comparison to C57BL/10J control muscles [37]. Under basal conditions, eMHC mRNA was elevated in dystrophic muscles of mdx mice compared to control muscles, reflecting a state of continual degeneration/regeneration characteristic of dystrophic muscle (Figure 4A). No differences were observed between the two lines in gene expression levels of Sphk1 and Sphk2, which suggests that S1P biosynthesis is not likely to be impaired in mdx mice (Figures 4B and C). In contrast, the gene expression of S1P catabolic enzymes Sgpp1 and Sgpl1 were elevated compared to control muscles (Figures 4D and E). Consistent with this finding, SPL protein levels were elevated in mdx muscles compared to control muscles (Figure 4F). Importantly, circulating S1P levels of mdx mice were significantly lower than resting WT control plasma (Figure 4G). In fact, mdx S1P levels were similar to levels observed in SphK1 KO mice. These important findings reveal that dystrophic mdx mice exist in a state of S1P deficiency that is comparable to the S1P-deficient state of SphK1 KO mice and, thus, could have an impact on SC functions and muscle regeneration. However, unlike SphK1 KO mice, the mdx S1P deficiency appears to be due to enhanced S1P catabolism, rather than impaired biosynthesis.

Bottom Line: These changes include early and profound induction of the gene encoding the S1P biosynthetic enzyme SphK1, followed by induction of the catabolic enzyme sphingosine phosphate lyase (SPL) 3 days later.STAT3 activation resulted in p21 and p27 downregulation in a S1PR2-dependent fashion in myoblasts.Our findings suggest that S1P promotes SC progression through the cell cycle by repression of cell cycle inhibitors via S1PR2/STAT3-dependent signaling and that SPL inhibition may provide a therapeutic strategy for MD.

View Article: PubMed Central - PubMed

Affiliation: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.

ABSTRACT
Sphingosine-1-phosphate (S1P) activates a widely expressed family of G protein-coupled receptors, serves as a muscle trophic factor and activates muscle stem cells called satellite cells (SCs) through unknown mechanisms. Here we show that muscle injury induces dynamic changes in S1P signaling and metabolism in vivo. These changes include early and profound induction of the gene encoding the S1P biosynthetic enzyme SphK1, followed by induction of the catabolic enzyme sphingosine phosphate lyase (SPL) 3 days later. These changes correlate with a transient increase in circulating S1P levels after muscle injury. We show a specific requirement for SphK1 to support efficient muscle regeneration and SC proliferation and differentiation. Mdx mice, which serve as a model for muscular dystrophy (MD), were found to be S1P-deficient and exhibited muscle SPL upregulation, suggesting that S1P catabolism is enhanced in dystrophic muscle. Pharmacological SPL inhibition increased muscle S1P levels, improved mdx muscle regeneration and enhanced SC proliferation via S1P receptor 2 (S1PR2)-dependent inhibition of Rac1, thereby activating Signal Transducer and Activator of Transcription 3 (STAT3), a central player in inflammatory signaling. STAT3 activation resulted in p21 and p27 downregulation in a S1PR2-dependent fashion in myoblasts. Our findings suggest that S1P promotes SC progression through the cell cycle by repression of cell cycle inhibitors via S1PR2/STAT3-dependent signaling and that SPL inhibition may provide a therapeutic strategy for MD.

Show MeSH
Related in: MedlinePlus