Lysophosphatidylcholine, a component of atherogenic lipoproteins, induces the change of calcium mobilization via TRPC ion channels in cultured human corporal smooth muscle cells

Abstract

Hypercholesterolemia is a major risk factor for erectile dysfunction. To understand the mechanism(s) of hypercholesterolemia-induced erectile dysfunction, we studied the effect of lysophosphatidylcholine (LPC) on the membrane conductance of corporal smooth muscle cells. We used cultured human corporal smooth muscle cells. The intracelluar Ca 2 þ concentration ([Ca 2 þ ] i ) and the influx of divalent cation was monitored by the ratio of fura-2 fluorescence (F 340/380 ) and by the Mn 2 þ -induced quenching rate of fura-2, respectively. The LPC-induced membrane current was characterized by the whole-cell patch-clamp technique and the molecular identity of suspected channels was probed by RT-PCR. LPC (20 lM) induced a statistically significant increase in F 340/380 to 119.973.9% of initial control (n ¼ 6) in corporal smooth muscle cells. The addition of 20 lM LPC accelerated the quenching rate of F 360 by 59.5711.8% (n ¼ 5). LPC activated nonselective cationic current (I LPC ), similar to the known effects of phenylephrine in corporal myocytes. The size of I LPC at À60 mV was À55.376.3 pA (n ¼ 8). The transcript of transient receptor potential channel 6 (TRPC6) was detected in human corporal myocytes. We also found one splicing variant of TRPC6, TRPC6a. In conclusion, the present study suggests that the LPC, a major component of oxidized lowdensity lipoprotiens, increases calcium in corporal smooth muscle cells probably through activation of a TRPC6 channel and the increased [Ca 2 þ ] i by LPC via TRP channels is one of mechanisms for hypercholesterolemia-induced erectile dysfunction.

Ca2+-independent phospholipase A2 enhances store-operated Ca2+ entry in dystrophic skeletal muscle fibers

“…Interestingly, a greatly increased total PLA 2 activity has been found in muscles from DMD patients (Lindahl et al, 1995). Since numerous PLA 2 products have been shown to be activators of cationic/SOC channels (Martinez and Moreno, 2005;Rzigalinski et al, 1999;Smani et al, 2004;So et al, 2005;Terasawa et al, 2002), enhanced production of the hydrolysis products of PLA 2 could be responsible for the enhanced Ca 2+ entry observed in mdx 5cv fibers, as proposed in Fig. 9.…”

“…The resulting PLA 2 hydrolysis products would then be responsible for the stimulation of SOC (Smani et al, 2004). Indeed, it has been demonstrated that lysophospholipids or arachidonic acid and some metabolites of the latter can activate cationic channels such as SOC (Rzigalinski et al, 1999;Smani et al, 2004;So et al, 2005;Terasawa et al, 2002;Watanabe et al, 2003).…”

Rho kinase is involved in Ca2+ entry of rat penile small arteries

“…TRPC6 is highly expressed in vascular smooth muscle cells and has been suggested to be the molecular correlate of the ␣ 1 -adrenoceptoractivated nonselective cation channel in rabbit portal vein (1,12) and mesenteric artery (11) myocytes. Moreover, TRPC6 and one of its splicing variant (TRPC6␣) are expressed in corporal myocytes from human CC (27), and, therefore, this TRPC subtype could be a molecular candidate for the nonselective cation channel activated by ␣ 1 -adrenoceptors and regulated by Rho kinase in penile arteries. However, TRPC proteins can form heteromeric and homomeric channels (8), and, therefore, specific molecular and functional studies are needed to clarify the expression of the various TRPC subunits, its possible contribution to ROC entry, and its specific regulation by Rho kinase in penile arteries.…”

Elucidation of a TRPC6-TRPC5 Channel Cascade That Restricts Endothelial Cell Movement

“…LysoPC activated TRPC5 channels in HEK cells overexpressing TRPC5 (Flemming et al, 2006) and increased [Ca 2ϩ ] i in smooth muscle cells that have endogenous TRPC6 channels (So et al, 2005). Because TRPC5 and TRPC6 are expressed in bovine ECs (Yip et al, 2004) and can be store-independent (Nilius and Droogmans, 2003;Zeng et al, 2004) and because TRPC6 plays a role in vascular endothelial growth factor-mediated microvessel permeability and thrombin-induced EC shape change (Pocock et al, 2004;Singh et al, 2007), we explored This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E07-08 -0765) on May 21, 2008. the role of TRPC5 and TRPC6 in lysoPC-induced calcium influx and subsequent inhibition of EC migration.…”