Activation of α7 Nicotinic Acetylcholine Receptor Decreases On-site Mortality in Crush Syndrome through Insulin Signaling-Na/K-ATPase Pathway.

Bo-Shi Fan,Miao Wu,Ding-Feng Su,Jin-Min Guo,Xia Liu,En-Hui Zhang,Jian-Guang Yu

doi:10.3389/fphar.2016.00079

Abstract

On-site mortality in crush syndrome remains high due to lack of effective drugs based on definite diagnosis. Anisodamine (Ani) is widely used in China for treatment of shock, and activation of α7 nicotinic acetylcholine receptor (α7nAChR) mediates such antishock effect. The present work was designed to test whether activation of α7nAChR with Ani decreased mortality in crush syndrome shortly after decompression. Sprague-Dawley rats and C57BL/6 mice with crush syndrome were injected with Ani (20 mg/kg and 28 mg/kg respectively, i.p.) 30 min before decompression. Survival time, serum potassium, insulin, and glucose levels were observed shortly after decompression. Involvement of α7nAChR was verified with methyllycaconitine (selective α7nAChR antagonist) and PNU282987 (selective α7nAChR agonist), or in α7nAChR knockout mice. Effect of Ani was also appraised in C2C12 myotubes. Ani reduced mortality and serum potassium and enhanced insulin sensitivity shortly after decompression in animals with crush syndrome, and PNU282987 exerted similar effects. Such effects were counteracted by methyllycaconitine or in α7nAChR knockout mice. Mortality and serum potassium in rats with hyperkalemia were also reduced by Ani. Phosphorylation of Na/K-ATPase was enhanced by Ani in C2C12 myotubes. Inhibition of tyrosine kinase on insulin receptor, phosphoinositide 3-kinase, mammalian target of rapamycin, signal transducer and activator of transcription 3, and Na/K-ATPase counteracted the effect of Ani on extracellular potassium. These findings demonstrated that activation of α7nAChR could decrease on-site mortality in crush syndrome, at least in part based on the decline of serum potassium through insulin signaling-Na/K-ATPase pathway.

Highlights

Crush injury is defined as compression of the extremities or other parts of the body, resulting in muscle swelling and/or neurological disturbances in the affected areas of the body (Oda et al, 1997)
The major findings of the present study include: (i) activation of α7 nicotinic acetylcholine (ACh) receptor (α7nAChR) with Ani decreases on-site mortality in crush syndrome; (ii) such effect of activating α7nAChR is partially due to decline of serum potassium; (iii) Ani decreases serum potassium through insulin signaling-Na/K-ATPase pathway
The on-site causes of death in crush syndrome are cardiac arrest caused by hyperkalemia or hypovolemic shock caused by bleeding or fluid redistribution (Ashkenazi et al, 2005)

Summary

Introduction

Crush injury is defined as compression of the extremities or other parts of the body, resulting in muscle swelling and/or neurological disturbances in the affected areas of the body (Oda et al, 1997). Safe and effective drugs to reduce on-site mortality in crush syndrome are clinically vacant, due to lack of definite diagnosis (Sever and Vanholder, 2013). Our previous studies found that activation of α7 nicotinic acetylcholine (ACh) receptor (α7nAChR) is involved in the antishock effect of Ani (Liu et al, 2009). We speculated that Ani could reduce mortality in crush syndrome shortly after decompression through activation of α7nAChR. The effect of insulin on serum potassium has been attributed to activation of Na/KATPase (Chibalin et al, 2001; Al-Khalili et al, 2004; Benziane and Chibalin, 2008). We speculated that activation of α7nAChR with Ani could decrease serum potassium through elevation of insulin sensitivity

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