The lumbrical muscle: a novel in situ system to evaluate adult skeletal muscle proteolysis and anticatabolic drugs for therapeutic purposes

Abstract

Bergantin LB, Figueiredo LB, Godinho RO. The lumbrical muscle: a novel in situ system to evaluate adult skeletal muscle proteolysis and anticatabolic drugs for therapeutic purposes. J Appl Physiol 111: 1710 -1718, 2011. First published September 15, 2011 doi:10.1152/japplphysiol.00586.2011.-The molecular regulation of skeletal muscle proteolysis and the pharmacological screening of anticatabolic drugs have been addressed by measuring tyrosine release from prepubertal rat skeletal muscles, which are thin enough to allow adequate in vitro diffusion of oxygen and substrates. However, the use of muscle at accelerated prepubertal growth has limited the analysis of adult muscle proteolysis or that associated with aging and neurodegenerative diseases. Here we established the adult rat lumbrical muscle (4/hindpaw; 8/rat) as a new in situ experimental model for dynamic measurement of skeletal muscle proteolysis. By incubating lumbrical muscles attached to their individual metatarsal bones in Tyrode solution, we showed that the muscle proteolysis rate of adult and aged rats (3-4 to 24 mo old) is 45-25% of that in prepubertal animals (1 mo old), which makes questionable the usual extrapolation of proteolysis from prepubertal to adult/senile muscles. While acute mechanical injury or 1-to 7-day denervation increased tyrosine release from adult lumbrical muscle by up to 60%, it was reduced by 20 -28% after 2-h incubation with ␤-adrenoceptor agonists, forskolin or phosphodiesterase inhibitor IBMX. Using inhibitors of 26S-proteasome (MG132), lysosome (methylamine), or calpain (E64/leupeptin) systems, we showed that ubiquitin-proteasome is accountable for 40 -50% of total lumbrical proteolysis of adult, middle-aged, and aged rats. In conclusion, the lumbrical model allows the analysis of muscle proteolysis rate from prepubertal to senile rats. By permitting eight simultaneous matched measurements per rat, the new model improves similar protocols performed in paired extensor digitorum longus (EDL) muscles from prepubertal rats, optimizing the pharmacological screening of drugs for anticatabolic purposes.

Differential gene expression in small and large rainbow trout derived from two seasonal spawning groups

“…However, with DDBP1 its associated substrate ligand is linked to the degradation of a cell cycle inhibitor [74], and thus up-regulation of this gene would be expected to increase cell growth. Inhibition of 26s proteasome promotes muscle growth in rats [75] and therefore higher activation in smaller fish may be coupled to decreased growth which is consistent with our findings.…”

Contribution of the Extracellular cAMP-Adenosine Pathway to Dual Coupling of β2-Adrenoceptors to Gsand GiProteins in Mouse Skeletal Muscle

“…8 provides a negative feedback loop, which may limit stimulatory G protein-coupled receptor response and possible harmful exacerbation of muscle contraction. In fact, considering the increased generation of extracellular adenosine during muscle contraction (Lynge et al, 2001), the extracellular cAMP-adenosine pathway may influence many other aspects of muscle physiology via activation of postsynaptic adenosine receptors, including those associated with the regulation of skeletal muscle carbohydrate metabolism (Hespel and Richter, 1998) and muscle proteolysis (Gissel, 2005;Bergantin et al, 2011). Thus, in skeletal muscle, the extracellular cAMP-adenosine pathway may function as a feedback mechanism able to modulate the cAMP signaling events initiated by other endogenous substances through activation of G-protein-coupled receptors, such as adrenoceptors or calcitonin gene-related peptide, are able to induce the efflux of cAMP (Godinho and Costa, 2003).…”

Contribution of the autophagy-lysosomal and ubiquitin-proteasomal proteolytic systems to total proteolysis in rainbow trout (Oncorhynchus mykiss) myotubes

“…Inhibition of proteasome activity in mammalian muscle tissue or muscle-derived cell culture using proteasome-specific inhibitors reduced rates of protein degradation by ϳ40 -50% (6,60), although reductions of up to 90% are reported in other cell types (45). These findings suggest that this pathway is responsible for the majority of protein degradation in muscle.…”