Diltiazem improves contractile properties of skeletal muscle in dysferlin-deficient BLAJ mice, but does not reduce contraction-induced muscle damage.

Morium Begam,Alyssa F Collier,Sujay S Galen,Joseph A Roche,Amber L Mueller,Renuka Roche

doi:10.14814/phy2.13727

Abstract

B6.A‐Dysf prmd/GeneJ (BLAJ) mice model human limb‐girdle muscular dystrophy 2B (LGMD2B), which is linked to mutations in the dysferlin (DYSF) gene. We tested the hypothesis that, the calcium ion (Ca2+) channel blocker diltiazem (DTZ), reduces contraction‐induced skeletal muscle damage, in BLAJ mice. We randomly assigned mice (N = 12; 3–4 month old males) to one of two groups – DTZ (N = 6) or vehicle (VEH, distilled water, N = 6). We conditioned mice with either DTZ or VEH for 1 week, after which, their tibialis anterior (TA) muscles were tested for contractile torque and susceptibility to injury from forced eccentric contractions. We continued dosing with DTZ or VEH for 3 days following eccentric contractions, and then studied torque recovery and muscle damage. We analyzed contractile torque before eccentric contractions, immediately after eccentric contractions, and at 3 days after eccentric contractions; and counted damaged fibers in the injured and uninjured TA muscles. We found that DTZ improved contractile torque before and immediately after forced eccentric contractions, but did not reduce delayed‐onset muscle damage that was observed at 3 days after eccentric contractions.

Highlights

Dysferlin-linked muscular dystrophies (a.k.a. dysferlinopathies) are a group of inherited diseases that cause progressive skeletal muscle weakness and wasting, with onset in the late-teen years (Urtizberea et al 2008; Harris et al 2016)
We found that DTZ improved contractile torque before and immediately after forced eccentric contractions, but did not reduce delayed-onset muscle damage that was observed at 3 days after eccentric contractions
The torque-frequency data collected at Day 3 postMSFEE indicate that, except for the 10 Hz stimulation frequency, there was no difference in contractile torque between the DTZ and VEH groups (Fig. 2D, Table S3)

Summary

Introduction

Dysferlin-linked muscular dystrophies (a.k.a. dysferlinopathies) are a group of inherited diseases that cause progressive skeletal muscle weakness and wasting, with onset in the late-teen years (Urtizberea et al 2008; Harris et al 2016). The Ca2+ channel blocker diltiazem (DTZ), mitigates stress-induced changes in Ca2+ signaling, and protects dysferlin-deficient A/J mouse muscle fibers from stress-induced cell damage, both in vitro and in vivo (Kerr et al 2013). The in vivo data on the protective effect of DTZ against stressinduced muscle fiber damage are of particular translational value, since dysferlin-deficient A/J mice sustain severe delayed-onset muscle damage, following injurious large-strain eccentric contractions (large-strain injury, LSI) to the tibialis anterior (TA) muscle (Roche et al 2010, 2012, 2015). It has been reported that, dysferlin-deficient B6.ADysfprmd/GeneJ (BLAJ) mice (developed by introgressing the A/J dysferlin mutation into the B6 mouse background) do not show as much delayed-onset muscle damage as A/J mice, at 3 days after LSI (Lostal et al 2010; Roche et al 2012). The studies described here, were designed to test the hypothesis that diltiazem protects dysferlin-deficient BLAJ mouse muscle against contraction-induced muscle damage

Methods

Results

Conclusion