Contractile function, sarcolemma integrity, and the loss of dystrophin after skeletal muscle eccentric contraction-induced injury

Abstract

Lovering, Richard M., and Patrick G. De Deyne. Contractile function, sarcolemma integrity, and the loss of dystrophin after skeletal muscle eccentric contraction-induced injury. Am J Physiol Cell Physiol 286: C230-C238, 2004. First published October 1, 2003 10.1152/ajpcell.00199.2003.-The purpose of this study was to evaluate the integrity of the muscle membrane and its associated cytoskeleton after a contraction-induced injury. A single eccentric contraction was performed in vivo on the tibialis anterior (TA) of male SpragueDawley rats at 900°/s throughout a 90°-arc of motion. Maximal tetanic tension (Po) of the TAs was assessed immediately and at 3, 7, and 21 days after the injury. To evaluate sarcolemmal integrity, we used an Evans blue dye (EBD) assay, and to assess structural changes, we used immunofluorescent labeling with antibodies against contractile (myosin, actin), cytoskeletal (␣-actinin, desmin, dystrophin, ␤-spectrin), integral membrane (␣-and ␤-dystroglycan, sarcoglycan), and extracellular (laminin, fibronectin) proteins. Immediately after injury, P0 was significantly reduced to 4.23 Ϯ 0.22 N, compared with 8.24 Ϯ 1.34 N in noninjured controls, and EBD was detected intracellularly in 54 Ϯ 22% of fibers from the injured TA, compared with 0% in noninjured controls. We found a significant association between EBD-positive fibers and the loss of complete dystrophin labeling. The loss of dystrophin was notable because organization of other components of the subsarcolemmal cytoskeleton was affected minimally (␤-spectrin) or not at all (␣-and ␤-dystroglycan). Labeling with specific antibodies indicated that dystrophin's COOH terminus was selectively more affected than its rod domain. Twenty-one days after injury, contractile properties were normal, fibers did not contain EBD, and dystrophin organization and protein level returned to normal. These data indicate the selective vulnerability of dystrophin after a single eccentric contraction-induced injury and suggest a critical role of dystrophin in force transduction. muscle injury; dystrophin; cytoskeleton; sarcolemma SKELETAL MUSCLE INJURY is characterized by an immediate loss of the ability to produce force. The cause of this force loss has been attributed to such factors as a defect in excitationcontraction (EC) coupling (55), disruption or loss of forcegenerating structures such as actin and myosin (49), and disruption or loss of force-transmitting structures, such as desmin (6,31). Perhaps the best evidence that disruption of force-bearing structures contributes to strength loss after injury comes from single-fiber studies, where reduction in single-fiber maximal force is observed immediately after eccentric injury (32,33). Although the totality of injury is likely the result of many factors, the purpose of this study was to assess structural defects of the sarcolemma, dystrophin, and dystrophin-associated proteins after a single traumatic muscle injury and to relate these observations to contractile properties.The sarcolemma transmits force and is s...

Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults

“…Because contraction-induced injury to the muscle tissue has been proposed to originate at the level of the sarcomere (Proske and Morgan 2001;Morgan 1990), the present approach reveals novel information about how the injury process is initiated in different populations of muscle cells from elderly adults. A potential limitation of our chemically skinned fiber preparation is that it bypasses mechanisms of cell activation that are known to be sensitive to eccentric contractile activity (Warren et al 1993;Balnave and Allen 1995;Ingalls et al 1998), eliminates the role of extracellular ion influx on the damage process (Zhang et al 2008), and may remove strain-sensitive membrane-imbedded proteins involved in transmission of force across the sarcolemma to the extracellular matrix (Lovering and De Deyne 2004). Additional caution must be exercised when generalizing the present findings to the responses of fibers in intact organisms.…”

Noninvasive monitoring of therapeutic gene transfer in animal models of muscular dystrophies

“…The two diseases investigated here are characterized by perturbation of the DGC, an important complex which protects the sarcolemma from contraction-induced stresses. [33][34][35] It has been shown that deficiency in these proteins makes the membrane vulnerable and renders it prone to tears during contraction. [36][37][38] This membrane leakage induces abnormal calcium influx followed by activation of the ubiquitous calpains, leading to an excess of unwanted and untimely proteolysis, and finally necrosis of the muscle fiber.…”

Enhanced activity of eccentric contraction induces alterations in <i>in vitro</i> sarcoplasmic reticulum Ca²⁺ handling in rat hindlimb muscles

“…It is well known that the structural distortions that are produced by mechanical stress lead to membrane damage 28) . The ECC-induced decline of the Na + -K + -ATP pump contributed to impaired sarcolemmal excitability and excitation-contraction coupling in rat fast muscle 31) , which may explain the decline of Na + -K + -ATPase activity immediately after repeated ECC that was observed in this study.…”

“…Previous studies reported ECCinduced abnormalities at the ultrastructural level 2,3) . It seems that the sarcolemma-associated muscle cytoskeleton after repeated ECC is susceptible to damage, which may be the basis for excitation-contraction uncoupling 31) . Mechanical stress in ECC-induced overstretched muscle fibers elicited damage in the triad junction of the t-tubule system 2) .…”

“…In addition, approximately 50% of all the Na + -K + pumps, which play a role in maintaining Na + and K + gradients across the sarcolemma and t-tubules, are located in the intracellular junctions between the SR and t-tubule invaginations of the plasma membrane 36) . As ECC would overstretch sarcomeres, it seems that the myofibrils, t-tubules, and SR in the overstretched regions are susceptible to damage 2,31) . Therefore, these observations could explain, at least in part, the reduction in Na + -K + -ATP pump function in this study.…”