Marked Effects of Tachykinin in Myositis Both in the Experimental Side and Contralaterally: Studies on NK-1 Receptor Expressions in an Animal Model

Yafeng Song,Per S Stål,Sture Forsgren,Jiguo Yu

doi:10.1155/2013/907821

Abstract

Muscle injury and inflammation (myositis) in a rabbit model of an unilateral muscle overuse were examined. It is unknown if the tachykinin system has a functional role in this situation. In this study, therefore, the neurokinin-1 receptor (NK-1R) expression patterns were evaluated. White blood cells, nerve fascicles, fine nerve fibers, and blood vessel walls in myositis areas showed NK-1R immunoreaction. NK-1R mRNA reactions were observable for white blood cells and blood vessel walls of these areas. NK-1R immunoreaction and NK-1R mRNA reactions were also seen for muscle fibers showing degenerative and regenerative features. There were almost no NK-1R immunoreactions in normal muscle tissue. Interestingly, marked NK-1R expressions were seen for myositis areas of both the experimental side and the contralateral nonexperimental side. EIA analyses showed that the concentration of substance P in the muscle tissue was clearly increased bilaterally at the experimental end stage, as compared to the situation for normal muscle tissue. These observations show that the tachykinin system is very much involved in the processes that occur in muscle injury/myositis. The effects can be related to proinflammatory effects and/or tissue repair. The fact that there are also marked NK-1R expressions contralaterally indicate that the tachykinin system has crossover effects.

Highlights

The tachykinins conform to a group of neuropeptides with marked functional roles
The neurokinin-1 receptor (NK-1R) can play an important role in the modulation of the accumulation of white blood cells that occurs in inflammatory processes [8]
Via evaluations of the NK-1R reaction pattern, the present study indicates that tachykinins are highly involved functionally in the myositis and muscle affection process in our rabbit model of muscle overuse

Summary

Introduction

The tachykinins conform to a group of neuropeptides with marked functional roles. The neuropeptide which is most well known in the group is substance P (SP). SP has pronounced pro-inflammatory effects, including the promotion of extravasation and accumulation of leukocytes at sites of injury [1]. SP is on the whole known to have autocrine/paracrine effects [5]. SP has a high affinity for the neurokinin-1 receptor (NK1R), having its major functions via this receptor [6]. The NK1R has 407 amino acids and belongs to the G-protein-coupled group of receptors [7]. The NK-1R can play an important role in the modulation of the accumulation of white blood cells that occurs in inflammatory processes [8]

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Conclusion