Pharmacological interventions improve myosin-actin cross-bridge function in mice with advanced chronic kidney disease.

Abstract

Skeletal muscle fiber force production in adult mice with late-stage chronic kidney disease (CKD) is significantly impaired, although by different myofilament and myosin-actin cross-bridge disease responses in the various fiber types. To reverse some of the CKD-induced contractile deficits, we examined the effects of the ATP analog, 2-deoxyadenosine triphosphate (dATP), to enhance cross-bridge kinetics and the troponin sensitizer, Tirasemtiv (2 µM), to increase cross-bridge formation. Single fiber force production, myosin-actin interactions and myofilament properties were measured at 25°C in fibers from soleus and extensor digitorum longus muscles of 16-week-old CKD mice (N=5) and controls (N=5). Late-stage CKD was induced by 0.2% adenine diet for 8 weeks. dATP in myosin heavy chain (MHC) I and IIA fibers with CKD increased cross-bridge kinetics, returning them to control values or faster, leading to more strongly bound cross-bridges for maximal Ca2+-activation (pCa 4.5, pH 7.0, 5 mM Phosphate) and fatiguing (pCa 4.5, pH 6.2, 30 mM Phosphate) conditions. Specific tensions in CKD were also improved 12-21% under maximal and fatiguing conditions, except in maximally Ca2+-activated MHC I fibers, but fell short of control values. Notably, other studies have found that improvements of 13-25% in knee extensor strength in CKD patients improved their physical function, suggesting changes of this magnitude are clinically meaningful. At submaximal Ca2+-activation (pCa 6.0), Tirasemtiv in MHC IIB fibers with CKD increased myofilament stiffness 520%, number of strongly bound cross-bridges 705%, and specific tension 370%, returning specific tension back to control values. This study provides evidence that cellular and molecular contractile function in CKD may be enhanced through use of dATP or Tirasemtiv, which should be tested to potentially improve physical function and overall quality of life in late-stage CKD patients.