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Mechanisms of the lysophosphatidic acid-induced increase in [Ca(2+)](i) in skeletal muscle cells.

Xu YJ, Tappia PS, Goyal RK, Dhalla NS - J. Cell. Mol. Med. (2008)

Bottom Line: The present study was therefore undertaken to examine the effect of LPA on the [Ca(2+)](i) in C2C12 cells.The LPA effect was also attenuated by ethylene glycolbis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA), an extracellular Ca(2+) chelator, Ni(2+) and KB-R7943, inhibitors of the Na(+)-Ca(2+) exchanger; the receptor operated Ca(2+) channel (ROC) blockers, 2-aminoethoxydiphenyl borate and SK&F 96365.However, the L-type Ca(2+) channel blockers, verapamil and diltiazem; the store operated Ca(2+) channel blockers, La(3+) and Gd(3+); a sarcoplasmic reticulum calcium pump inhibitor, thapsigargin; an inositol trisphosphate receptor antagonist, xestospongin and a phospholipase C inhibitor, U73122, did not prevent the increase [Ca(2+)](i) due to LPA.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada.

ABSTRACT
Although lysophosphatidic acid (LPA) is known to increase intracellularfree calcium concentration ([Ca(2+)](i)) in different cell types, the effect of LPA on the skeletal muscle cells is not known. The present study was therefore undertaken to examine the effect of LPA on the [Ca(2+)](i) in C2C12 cells. LPA induced a concentration and time dependent increase in [Ca(2+)](i), which was inhibited by VPC12249, VPC 32183 and dioctanoyl glycerol pyrophosphate, LPA1/3 receptor antagonists. Pertussis toxin, a G(i) protein inhibitor, also inhibited the LPA-induced increase in [Ca(2+)](i). Inhibition of tyrosine kinase activities with tyrphostin A9 and genistein also prevented the increase in [Ca(2+)](i) due to LPA. Likewise, wortmannin and LY 294002, phosphatidylinositol 3-kinase (PI3-K) inhibitors, inhibited [Ca(2+)](i) response to LPA. The LPA effect was also attenuated by ethylene glycolbis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA), an extracellular Ca(2+) chelator, Ni(2+) and KB-R7943, inhibitors of the Na(+)-Ca(2+) exchanger; the receptor operated Ca(2+) channel (ROC) blockers, 2-aminoethoxydiphenyl borate and SK&F 96365. However, the L-type Ca(2+) channel blockers, verapamil and diltiazem; the store operated Ca(2+) channel blockers, La(3+) and Gd(3+); a sarcoplasmic reticulum calcium pump inhibitor, thapsigargin; an inositol trisphosphate receptor antagonist, xestospongin and a phospholipase C inhibitor, U73122, did not prevent the increase [Ca(2+)](i) due to LPA. Our data suggest that the LPA-induced increase in [Ca(2+)](i) might occur through G(i)-protein coupled LPA(1/3) receptors that may be linked to tyrosine kinase and PI3-K, and may also involve the Na(+)-Ca(2+) exchanger as well as the ROC. In addition, LPA stimulated C2C12 cell proliferation via PI3-K. Thus, LPA may be an important phospholipid in the regulation of [Ca(2+)](i) and growth of skeletal muscle cells.

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Related in: MedlinePlus

Schematic representation of the hypothetical mechanisms involved in lysophosphatidic acid-induced increase in intracellular calcium in C2C12 cells. LPA: lysophosphatidic acid, PI3-K: phosphatidylinositol 3-kinase, ROCs: receptor operated channels, [Ca2+]i: intracellular calcium concentration.
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fig07: Schematic representation of the hypothetical mechanisms involved in lysophosphatidic acid-induced increase in intracellular calcium in C2C12 cells. LPA: lysophosphatidic acid, PI3-K: phosphatidylinositol 3-kinase, ROCs: receptor operated channels, [Ca2+]i: intracellular calcium concentration.

Mentions: Several lines of evidence indicate that LPA is a lipid mediator, abundantly present in the blood, with a diverse range of biological actions including the regulation of [Ca2+]i and proliferation in different cell types [2, 3, 17–20, 27, 38–41]. In fact, Ca2+ is considered to play a critical role in the activation of signal transduction mechanisms involved in cell proliferation [27]. However, there is no information in the literature regarding the effects of LPA on [Ca2+]i in skeletal muscle. We are the first to report that LPA induces an increase in [Ca2+]i in a concentration and time dependent manner in C2C12 cells. The LPA-induced increase in [Ca2+]i was significantly inhibited three LPA1/3 receptor antagonists, as well as with PTX, genistein and tyrphostin A9, suggesting that the LPA-induced increase in [Ca2+]i is mediated by LPA1/3 receptors that may be coupled to Gi protein and tyrosine kinase (Fig. 7). Similar mechanisms of LPA-induced increase in [Ca2+]i have also been reported in VSMCs and T cells [32, 33]. Exogenous LPA has also been reported to activate PI3-K in cardiomyocytes [21]. PI3-K has been demonstrated to regulate Ca2+ signalling in T cells [17]. In the present study, pre-treatment of C2C12 cells with PI 3K inhibitors wortaminnin and LY 294002, significantly attenuated the Ca2+ response to LPA in C2C12 cells, indicating that PI3-K may be involved in Ca2+ mobilization in skeletal muscle. In view of the reported activation of PI3-K through Gi-protein in leukotriene β-induced degranulation in rat basophilic leukaemic cells [42], it is possible that the LPA1/3 receptor may transduce its signal to PI3-K via Gi-protein in skeletal muscle. However, an interaction between tyrosine kinase and PI3-K cannot be excluded and therefore warrants further investigation (Fig. 7). The partial inhibition observed with LPA1/3 receptor antagonists is suggestive of an involvement of other LPA receptors in the increase in [Ca2+]i in response to LPA. Our preliminary data have revealed that higher concentrations of DGPP (50 and 100 μM) did not abolish the LPA-induced increase in [Ca2+]i, indicating that indeed other LPA receptor subtypes could be involved in the LPA response.


Mechanisms of the lysophosphatidic acid-induced increase in [Ca(2+)](i) in skeletal muscle cells.

Xu YJ, Tappia PS, Goyal RK, Dhalla NS - J. Cell. Mol. Med. (2008)

Schematic representation of the hypothetical mechanisms involved in lysophosphatidic acid-induced increase in intracellular calcium in C2C12 cells. LPA: lysophosphatidic acid, PI3-K: phosphatidylinositol 3-kinase, ROCs: receptor operated channels, [Ca2+]i: intracellular calcium concentration.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4401138&req=5

fig07: Schematic representation of the hypothetical mechanisms involved in lysophosphatidic acid-induced increase in intracellular calcium in C2C12 cells. LPA: lysophosphatidic acid, PI3-K: phosphatidylinositol 3-kinase, ROCs: receptor operated channels, [Ca2+]i: intracellular calcium concentration.
Mentions: Several lines of evidence indicate that LPA is a lipid mediator, abundantly present in the blood, with a diverse range of biological actions including the regulation of [Ca2+]i and proliferation in different cell types [2, 3, 17–20, 27, 38–41]. In fact, Ca2+ is considered to play a critical role in the activation of signal transduction mechanisms involved in cell proliferation [27]. However, there is no information in the literature regarding the effects of LPA on [Ca2+]i in skeletal muscle. We are the first to report that LPA induces an increase in [Ca2+]i in a concentration and time dependent manner in C2C12 cells. The LPA-induced increase in [Ca2+]i was significantly inhibited three LPA1/3 receptor antagonists, as well as with PTX, genistein and tyrphostin A9, suggesting that the LPA-induced increase in [Ca2+]i is mediated by LPA1/3 receptors that may be coupled to Gi protein and tyrosine kinase (Fig. 7). Similar mechanisms of LPA-induced increase in [Ca2+]i have also been reported in VSMCs and T cells [32, 33]. Exogenous LPA has also been reported to activate PI3-K in cardiomyocytes [21]. PI3-K has been demonstrated to regulate Ca2+ signalling in T cells [17]. In the present study, pre-treatment of C2C12 cells with PI 3K inhibitors wortaminnin and LY 294002, significantly attenuated the Ca2+ response to LPA in C2C12 cells, indicating that PI3-K may be involved in Ca2+ mobilization in skeletal muscle. In view of the reported activation of PI3-K through Gi-protein in leukotriene β-induced degranulation in rat basophilic leukaemic cells [42], it is possible that the LPA1/3 receptor may transduce its signal to PI3-K via Gi-protein in skeletal muscle. However, an interaction between tyrosine kinase and PI3-K cannot be excluded and therefore warrants further investigation (Fig. 7). The partial inhibition observed with LPA1/3 receptor antagonists is suggestive of an involvement of other LPA receptors in the increase in [Ca2+]i in response to LPA. Our preliminary data have revealed that higher concentrations of DGPP (50 and 100 μM) did not abolish the LPA-induced increase in [Ca2+]i, indicating that indeed other LPA receptor subtypes could be involved in the LPA response.

Bottom Line: The present study was therefore undertaken to examine the effect of LPA on the [Ca(2+)](i) in C2C12 cells.The LPA effect was also attenuated by ethylene glycolbis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA), an extracellular Ca(2+) chelator, Ni(2+) and KB-R7943, inhibitors of the Na(+)-Ca(2+) exchanger; the receptor operated Ca(2+) channel (ROC) blockers, 2-aminoethoxydiphenyl borate and SK&F 96365.However, the L-type Ca(2+) channel blockers, verapamil and diltiazem; the store operated Ca(2+) channel blockers, La(3+) and Gd(3+); a sarcoplasmic reticulum calcium pump inhibitor, thapsigargin; an inositol trisphosphate receptor antagonist, xestospongin and a phospholipase C inhibitor, U73122, did not prevent the increase [Ca(2+)](i) due to LPA.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada.

ABSTRACT
Although lysophosphatidic acid (LPA) is known to increase intracellularfree calcium concentration ([Ca(2+)](i)) in different cell types, the effect of LPA on the skeletal muscle cells is not known. The present study was therefore undertaken to examine the effect of LPA on the [Ca(2+)](i) in C2C12 cells. LPA induced a concentration and time dependent increase in [Ca(2+)](i), which was inhibited by VPC12249, VPC 32183 and dioctanoyl glycerol pyrophosphate, LPA1/3 receptor antagonists. Pertussis toxin, a G(i) protein inhibitor, also inhibited the LPA-induced increase in [Ca(2+)](i). Inhibition of tyrosine kinase activities with tyrphostin A9 and genistein also prevented the increase in [Ca(2+)](i) due to LPA. Likewise, wortmannin and LY 294002, phosphatidylinositol 3-kinase (PI3-K) inhibitors, inhibited [Ca(2+)](i) response to LPA. The LPA effect was also attenuated by ethylene glycolbis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA), an extracellular Ca(2+) chelator, Ni(2+) and KB-R7943, inhibitors of the Na(+)-Ca(2+) exchanger; the receptor operated Ca(2+) channel (ROC) blockers, 2-aminoethoxydiphenyl borate and SK&F 96365. However, the L-type Ca(2+) channel blockers, verapamil and diltiazem; the store operated Ca(2+) channel blockers, La(3+) and Gd(3+); a sarcoplasmic reticulum calcium pump inhibitor, thapsigargin; an inositol trisphosphate receptor antagonist, xestospongin and a phospholipase C inhibitor, U73122, did not prevent the increase [Ca(2+)](i) due to LPA. Our data suggest that the LPA-induced increase in [Ca(2+)](i) might occur through G(i)-protein coupled LPA(1/3) receptors that may be linked to tyrosine kinase and PI3-K, and may also involve the Na(+)-Ca(2+) exchanger as well as the ROC. In addition, LPA stimulated C2C12 cell proliferation via PI3-K. Thus, LPA may be an important phospholipid in the regulation of [Ca(2+)](i) and growth of skeletal muscle cells.

Show MeSH
Related in: MedlinePlus