Relation of nNOS isoforms to mitochondrial density and PGC-1alpha expression in striated muscles of mice

Baum, Oliver and Aaldijk, Dea and Engeli, Anna Lena and Spree, Matthias and Summermatter, Serge and Handschin, Christoph and Zakrzewicz, Andreas. (2018) Relation of nNOS isoforms to mitochondrial density and PGC-1alpha expression in striated muscles of mice. Nitric Oxide: Biology and Chemistry, 77. pp. 35-43.

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Official URL: https://edoc.unibas.ch/64314/

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The expression of neuronal NO synthase (nNOS) alpha- and beta-isoforms in skeletal muscle is well documented but only little information is available about their regulation/functions. Using different mouse models, we now assessed whether the expression of nNOS-isoforms in muscle fibers is related to mitochondria content/activity and regulated by peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha). Catalytic histochemistry revealed highest nNOS-concentrations to be present in type-2 oxidative muscle fibers. Differences in mitochondrial density between nNOS-KO-mice and WT-littermates established by morphometry after transmission electron microscopy were significant in the oxidative portion of the tibialis anterior muscle (TA) but not in rectus femoris muscle (RF) indicating an nNOS-dependent mitochondrial pool in TA. Quantitative immunoblotting displayed the nNOS alpha-isoform to preponderate in those striated muscles of C57BL/6-mice that comprise of many type-2 oxidative fibers, e.g. TA, while roughly even levels of the two nNOS-isoforms were expressed in those muscles that mainly consist of type-2 glycolytic fibers, e.g. RF. Differences in citrate synthase-activity in muscle homogenates between nNOS-KO-mice and WT-littermates were positively related to nNOS alpha-isoform levels. In transgenic-mice over-expressing muscular PGC-1alpha compared to WT-littermates, immunoblotting revealed a significant shift in nNOS-expression in favor of the alpha-isoform in six out of eight striated muscles (exceptions: soleus muscle and tongue) without consistent relationship to changes in the expression of mitochondrial markers. In summary, our study demonstrated the nNOS alpha-isoform expression to be related to mitochondrial content/activity and to be up-regulated by up-stream PGC-1alpha in striated muscles, particularly in those enriched with type-2 oxidative fibers implying a functional convergence of the two signaling systems in these fibers.
Faculties and Departments:03 Faculty of Medicine > Departement Biomedizin > Associated Research Groups > Pharmakologie (Handschin)
05 Faculty of Science > Departement Biozentrum > Growth & Development > Growth & Development (Handschin)
UniBasel Contributors:Handschin, Christoph
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:08 Feb 2020 14:58
Deposited On:10 Aug 2018 13:52

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