title: Cycling exercise affects the expression of apoptosis-associated microRNAs after spinal cord injury in rats.
abstract: There are two major aspects to a spinal cord injury (SCI): an acute, primary mechanical trauma and a progressive phase of secondary tissue damage provoked by inflammation, excitotoxicity, apoptosis, and demyelination. MicroRNAs (miRs) are small, ~22 nucleotide, non-protein-coding RNAs that function at the post-transcriptional level to regulate gene expression. They have important roles in homeostatic processes such as cell proliferation and programmed cell death. In the injured rat spinal cord we performed an expression analysis of miRs and their downstream targets involved in apoptotic pathways and used post-injury cycling exercise to test for activity-dependent plasticity of miR expression. We show that SCI results in increased expression of miR Let-7a and miR16 while exercise leads to elevated levels of miR21 and decreased levels of miR15b. These changes in miR expression are correlated with changes in expression of their target genes: pro-apoptotic (decreased PTEN, PDCD4, and RAS mRNA) and anti-apoptotic (increased Bcl-2 mRNA) target genes. This is accompanied by a down-regulation of mRNA for caspase-7 and caspase-9 and reduced levels of caspase-7 protein. These results indicate possible beneficial effects of exercise through action on multiple miRs and their targets that contribute to the functional regulation of apoptosis after SCI.
authors.affiliation: Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Keeler
authors.forename: Victoria
authors.initials: V
authors.lastname: Zhukareva
authors.forename: John D
authors.initials: JD
authors.lastname: Houlé
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis*; D015153:Blotting, Western; D020169:Caspases / Q000096:biosynthesis; D005260:Female; D006614:Hindlimb / Q000502:physiology; D035683:MicroRNAs / Q000096:biosynthesis*; D009416:Nerve Regeneration / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013119:Spinal Cord Injuries / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; D035683:MicroRNAs; D020169:Caspases
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