Administration of Recombinant Heat Shock Protein 70 Delays Peripheral Muscle Denervation in the SOD1^G93AMouse Model of Amyotrophic Lateral Sclerosis

Abstract

A prominent clinical feature of ALS is muscle weakness due to dysfunction, denervation and degeneration of motoneurons (MNs). While MN degeneration is a late stage event in the ALS mouse model, muscle denervation occurs significantly earlier in the disease. Strategies to prevent this early denervation may improve quality of life by maintaining muscle control and slowing disease progression. The precise cause of MN dysfunction and denervation is not known, but several mechanisms have been proposed that involve potentially toxic intra- and extracellular changes. Many cells confront these changes by mounting a stress response that includes increased expression of heat shock protein 70 (Hsp70). MNs do not upregulate Hsp70, and this may result in a potentially increased vulnerability. We previously reported that recombinant human hsp70 (rhHsp70) injections delayed symptom onset and increased lifespan in SOD1G93A mice. The exogenous rhHsp70 was localized to the muscle and not to spinal cord or brain suggesting it modulates peripheral pathophysiology. In the current study, we focused on earlier administration of Hsp70 and its effect on initial muscle denervation. Injections of the protein appeared to arrest denervation with preserved large myelinated peripheral axons, and reduced glial activation.

Vitamin D and/or calcium deficient diets may differentially affect muscle fiber neuromuscular junction innervation

“…A lack of Csp interaction with SNAP‐25 leads to abnormal synaptic vesicle turnover and impaired synaptic function . Increased Hsp70 levels in muscles of mutated super oxide dismutase‐1 mice help to slow NMJ denervation over time . In our study, higher gene and protein levels of Csp , Hsc70 , and Hsp70 , along with higher SNAP‐25 protein levels in the soleus (Figs.…”

“…Innervated neuromuscular junctions (NMJs) were defined as the histologic colocalization of the presynaptic marker synaptophysin and the AChR marker α‐BTX . The percentage of innervated NMJs from each diet group was determined by counting at least 100 NMJs from each animal in each diet group …”

Glycoprotein nonmetastatic melanoma protein B ameliorates skeletal muscle lesions in a SOD1G93A mouse model of amyotrophic lateral sclerosis

“…In the present study, denervation declined remarkably, and innervated neuromuscular junctions were maintained in SOD1 G93A /GPNMB mice compared with SOD1 G93A mice. Denervation occurs earlier than motor neuronal degeneration in patients with ALS, SOD1 G93A mice, and zebrafish that overexpress SOD1 G93A and is referred to as the dying‐back mechanism of motor neuronal degeneration in ALS (Frey et al, ; Fischer et al, ; Gifondorwa et al, ; Sakowski et al, ). Therefore, the working hypothesis guiding the present study is that preventing denervation might maintain muscular function and slow disease progression.…”

“…To determine the numbers of innervated and denervated neuromuscular junctions, gastrocnemius muscles were analyzed by immunohistochemistry, as reported previously (Gifondorwa et al, 2007(Gifondorwa et al, , 2012Wong and Martin, 2010;Wootz et al, 2010;Sunyach et al, 2012). Mice were perfused with saline, and the gastrocnemius muscle was extracted.…”

Molecular Changes at the Post-Synapse and Improved Motor Function Suggest Accelerated Recovery with SARM Treatment in an Androgen-Depleted Animal Model of Nerve Injury

“…Innervated Neuromuscular Junctions (NMJs) were defined as the histologic colocalization of the presynaptic marker synaptophysin and the AChR marker aBTX [30]. The percentage of innervated NMJs from each diet group was determined by counting at least 100 NMJs from each animal in each diet group [29][30][31].…”