Chemokines are regulatory proteins that play an important role in muscle cell migration and proliferation. In this study, C2C12 cells treated with lysophosphatidic acid (LPA) showed an increase in endogenous monocyte chemotactic protein-1 (MCP-1) expression and secretion. LPA is a naturally occurring bioactive lysophospholipid with hormone- and growth-factor-like activities. LPA is produced by activated platelets, cytokine-stimulated leukocytes, and possibly by other cell types. However, the LPA analog cyclic phosphatidic acid (cPA) had no effect on the expression and secretion of MCP-1. LPA, although similar in structure to cPA, had potent inducing effects on MCP-1 expression in C2C12 cells. In this study, we showed that LPA enhanced MCP-1 mRNA expression and protein secretion in a dose-dependent manner. Taken together, these results suggest that LPA enhances MCP-1 secretion in C2C12 cells and thus may play an important role in cell proliferation. 1. Introduction Chemokines are a large family of structurally related proteins that play an essential role in leukocyte migration and differentiation [1]. They exert different functions under physiological conditions such as development and tissue repair [2]. Chemokines are small soluble molecules that are important in the communication between different cells [3, 4]. In recent years, significant advances have been made in understanding the molecular mechanisms involved in the regulation of skeletal muscle cell proliferation. Muscle cells are involved as targets in different pathological conditions such as autoimmune muscle disorders [5, 6]. Skeletal muscle cells are capable of producing and releasing a variety of molecules, including cytokines and chemokines [7]. Recently, chemokines have been considered to play important roles in skeletal muscle regeneration [8]. In response to a number of stimuli, myoblasts become activated, start to proliferate, and differentiate into multinucleated myotubes [9]. In the present study, we used a cytokine protein array to screen for the induction of different cytokines and chemokines. LPA, although similar in structure to cPA, had potent inducing effects on Monocyte chemotactic protein 1 (MCP-1) expression in C2C12 cells. MCP-1 is a chemokine that recruits monocytes to areas of vessel injury [10]. MCP-1 is a relatively basic protein of 8.7？kDa and is a heparin-binding C–C chemokine produced by monocytes. It is expressed in various tissues, including endothelial, bronchial, epithelial, and smooth muscle cells [11]. To identify MCP-1 that play a role in myogenesis, we
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