Project description:Background: Niemann-Pick disease type A (NPDA), a disease caused by mutations in acid sphingomyelinase (ASM), involves severe neurodegeneration and early death. Intracellular lipid accumulation and plasma membrane alterations are implicated in the pathology. ASM is also linked to the mechanism of plasma membrane repair, so we investigated the impact of ASM deficiency in skeletal muscle, a tissue that undergoes frequent cycles of injury and repair in vivo. Methods: Utilizing the NPDA/B mouse model ASM−/− and wild type (WT) littermates, we performed excitation- contraction coupling/Ca2+ mobilization and sarcolemma injury/repair assays with isolated flexor digitorum brevis fibers, proteomic analyses with quadriceps femoris, flexor digitorum brevis, and tibialis posterior muscle and in vivo tests of the contractile force (maximal isometric torque) of the quadriceps femoris muscle before and after eccentric contraction-induced muscle injury. Results: ASM−/− flexor digitorum brevis fibers showed impaired excitation-contraction coupling compared to WT, a defect expressed as reduced tetanic [Ca2+]i in response to electrical stimulation and early failure in sustaining [Ca2+]i during repeated tetanic contractions. When injured mechanically by needle passage, ASM−/− flexor digitorum brevis fibers showed susceptibility to injury similar to WT, but a reduced ability to reseal the sarcolemma. Proteomic analyses revealed changes in a small group of skeletal muscle proteins as a consequence of ASM deficiency, with downregulation of calsequestrin occurring in the three different muscles analyzed. In vivo, the loss in maximal isometric torque of WT quadriceps femoris was similar immediately after and 2 min after injury. The loss in ASM−/− mice immediately after injury was similar to WT, but was markedly larger at 2 min after injury. Conclusions: Skeletal muscle fibers from ASM−/− mice have an impairment in intracellular Ca2+ handling that results in reduced Ca2+ mobilization and a more rapid decline in peak Ca2+ transients during repeated contraction-relaxation cycles. Isolated fibers show reduced ability to repair damage to the sarcolemma, and this is associated with an exaggerated deficit in force during recovery from an in vivo eccentric contraction- induced muscle injury. Our findings uncover the possibility that skeletal muscle functional defects may play a role in the pathology of NPDA/B disease.

Project description:Mice were subjected to 50 eccentric contractions (EC) or 50 isometric contractions (IC) using a non-invasive model, and then sacrificed 48 hours later. RNA from the tibialis anterior of 4 animals were pooled and then split into two groups for hybridization onto two separate Affymetrix MGU74Av2 chips. Control samples were contralateral to the exercised legs, and were only subjected to enough contractions to measure isometric torque. Eccentric contractions (ECs), in which a muscle is forced to lengthen while activated, result in muscle injury and, eventually, muscle strengthening and prevention of further injury. Although the mechanical basis of eccentric contraction-induced injury has been studied in detail, muscle's biological response is less well characterized. This study presents the development of a minimally-invasive model of EC injury in the mouse, follows the time course of torque recovery after an injurious bout of ECs, and uses Affymetrix microarrays to compare the gene expression profile 48 hours after ECs to both isometrically stimulated muscles and contralateral muscles. Torque dropped by about 55% immediately after the exercise bout, and recovered to initial levels 7 days later. 36 known genes were upregulated after ECs compared to contralateral and isometrically stimulated muscles, including five muscle specific genes: muscle LIM protein (MLP), Muscle Ankyrin Repeat Proteins (MARP 1 and 2; also known as cardiac ankyrin repeat protein and Arpp/Ankrd2, respectively), Xin, and Myosin Binding Protein H. The time courses of MLP and MARP expression after the injury bout (determined by quantitative real-time polymerase chain reaction) indicate that these genes are rapidly induced, reaching a peak expression level of 6-11 times contralateral values 12-24 hours after the EC bout and returning to baseline within 72 hours. Very little gene induction was seen after either isometric activation or passive stretch, indicating that the MLP and MARP genes may play an important and specific role in the biological response of muscle to EC-induced injury. Keywords = mouse tibialis anterior eccentric contraction muscle

Project description:Mice were subjected to 50 eccentric contractions (EC) or 50 isometric contractions (IC) using a non-invasive model, and then sacrificed 48 hours later. RNA from the tibialis anterior of 4 animals were pooled and then split into two groups for hybridization onto two separate Affymetrix MGU74Av2 chips. Control samples were contralateral to the exercised legs, and were only subjected to enough contractions to measure isometric torque. Eccentric contractions (ECs), in which a muscle is forced to lengthen while activated, result in muscle injury and, eventually, muscle strengthening and prevention of further injury. Although the mechanical basis of eccentric contraction-induced injury has been studied in detail, muscle's biological response is less well characterized. This study presents the development of a minimally-invasive model of EC injury in the mouse, follows the time course of torque recovery after an injurious bout of ECs, and uses Affymetrix microarrays to compare the gene expression profile 48 hours after ECs to both isometrically stimulated muscles and contralateral muscles. Torque dropped by about 55% immediately after the exercise bout, and recovered to initial levels 7 days later. 36 known genes were upregulated after ECs compared to contralateral and isometrically stimulated muscles, including five muscle specific genes: muscle LIM protein (MLP), Muscle Ankyrin Repeat Proteins (MARP 1 and 2; also known as cardiac ankyrin repeat protein and Arpp/Ankrd2, respectively), Xin, and Myosin Binding Protein H. The time courses of MLP and MARP expression after the injury bout (determined by quantitative real-time polymerase chain reaction) indicate that these genes are rapidly induced, reaching a peak expression level of 6-11 times contralateral values 12-24 hours after the EC bout and returning to baseline within 72 hours. Very little gene induction was seen after either isometric activation or passive stretch, indicating that the MLP and MARP genes may play an important and specific role in the biological response of muscle to EC-induced injury. Keywords = mouse tibialis anterior eccentric isometric contraction muscle Keywords: other

Dataset Information

Isometric contractions in skeletal muscle of adult mice

Publications

Preconditioning of skeletal muscle against contraction-induced damage: the role of adaptations to oxidants in mice.

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