TY - JOUR
T1 - Sphingomyelinase depresses force and calcium sensitivity of the contractile apparatus in mouse diaphragm muscle fibers
AU - Ferreira, Leonardo F.
AU - Moylan, Jennifer S.
AU - Stasko, Shawn
AU - Smith, Jeffrey D.
AU - Campbell, Kenneth S.
AU - Reid, Michael B.
PY - 2012/5/1
Y1 - 2012/5/1
N2 - Diseases that result in muscle weakness, e.g., heart failure, are characterized by elevated sphingomyelinase (SMase) activity. In intact muscle, SMase increases oxidants that contribute to diminished muscle force. However, the source of oxidants, specific processes of muscle contraction that are dysfunctional, and biochemical changes underlying the weakness elicited by SMase remain unknown. We tested three hypotheses: 1) SMase-induced depression of muscle force is mediated by mitochondrial reactive oxygen species (ROS), 2) SMase depresses force and calcium sensitivity of the contractile apparatus, and 3) SMase promotes oxidation and phosphorylation of myofibrillar proteins. Our experiments included intact muscle bundles, permeabilized single fibers, and isolated myofibrillar proteins. The mitochondrial-targeted antioxidant D-Arg-2′,6′-dimethyl-Tyr-Lys-Phe-NH 2, decreased cytosolic oxidants and protected intact muscle bundles from weakness stimulated by SMase. SMase depressed maximal calcium-activated force by 20% in permeabilized single fibers (in kN/m 2: control 117 ± 6; SMase 93 ± 8; P < 0.05). Calcium sensitivity of permeabilized single fibers decreased from 5.98 ± 0.03 (control) to 5.91 ± 0.02 (SMase; P < 0.05). Myofibrillar protein nitrotyrosines, carbonyls, and phosphorylation were unaltered by SMase. Our study shows that the fall in specific force of intact muscle elicited by SMase is mediated by mitochondrial ROS and can be attributed largely to dysfunction of the contractile apparatus.
AB - Diseases that result in muscle weakness, e.g., heart failure, are characterized by elevated sphingomyelinase (SMase) activity. In intact muscle, SMase increases oxidants that contribute to diminished muscle force. However, the source of oxidants, specific processes of muscle contraction that are dysfunctional, and biochemical changes underlying the weakness elicited by SMase remain unknown. We tested three hypotheses: 1) SMase-induced depression of muscle force is mediated by mitochondrial reactive oxygen species (ROS), 2) SMase depresses force and calcium sensitivity of the contractile apparatus, and 3) SMase promotes oxidation and phosphorylation of myofibrillar proteins. Our experiments included intact muscle bundles, permeabilized single fibers, and isolated myofibrillar proteins. The mitochondrial-targeted antioxidant D-Arg-2′,6′-dimethyl-Tyr-Lys-Phe-NH 2, decreased cytosolic oxidants and protected intact muscle bundles from weakness stimulated by SMase. SMase depressed maximal calcium-activated force by 20% in permeabilized single fibers (in kN/m 2: control 117 ± 6; SMase 93 ± 8; P < 0.05). Calcium sensitivity of permeabilized single fibers decreased from 5.98 ± 0.03 (control) to 5.91 ± 0.02 (SMase; P < 0.05). Myofibrillar protein nitrotyrosines, carbonyls, and phosphorylation were unaltered by SMase. Our study shows that the fall in specific force of intact muscle elicited by SMase is mediated by mitochondrial ROS and can be attributed largely to dysfunction of the contractile apparatus.
KW - Mitochondria
KW - Oxidative stress
KW - Single fiber
KW - Skeletal muscle
KW - Sphingolipids
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U2 - 10.1152/japplphysiol.01269.2011
DO - 10.1152/japplphysiol.01269.2011
M3 - Article
C2 - 22362402
AN - SCOPUS:84862058399
SN - 8750-7587
VL - 112
SP - 1538
EP - 1545
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 9
ER -