Minimally modified LDL upregulates endothelin type B receptors in rat coronary artery via ERK1/2 MAPK and NF-κB pathways

Abstract

Minimally modified low density lipoprotein (mmLDL) is a well-known risk factor for coronary artery disease. Upregulation of vascular endothelin type B (ET B ) receptors on the vascular smooth muscle cells is predicted to be the molecular mechanism that leads to cardiovascular pathogenesis. The objective of the present study was to examine the hypothesis that mmLDL upregulates ET B receptors in rat coronary artery. The contractile responses to sarafotoxin 6c (ET B receptor agonist) were studied using a sensitive myograph. ETB receptor mRNA and protein expression was determined using real-time PCR and Western blot analysis.The results showed that organ culture increased the contractile responses induced by sarafotoxin 6c and the levels of ET B receptor mRNA and protein. This increase was further enhanced by the addition of mmLDL (10 μg/mL). Specific ERK1/2 inhibitors (SB386023 and U0126) and an NF-κB inhibitor (wedelolactone) attenuated the mmLDL-increased ET B receptor-mediated contraction and ET B receptor mRNA and protein levels. Wedelolactone significantly attenuated the mmLDL-decreased IκBα protein expression. Consistent with this result, IκBα protein expression was significantly decreased by culture withmmLDL compared to the level of expression in the organ culture group. However, the JNK inhibitor, SP600125 or p38 pathway inhibitor, SB203580 did not inhibit mmLDL-enhanced effects. The PKC inhibitor, staurosporine attenuated only culture-alone-increased effects. In conclusion, mmLDL upregulates the ETB receptors in rat coronary arterial smooth muscle cells, mainly via activation of the ERK1/2 MAPK and the downstream transcriptional factor NF-κB.

Low density lipoprotein induces upregulation of vasoconstrictive endothelin type B receptor expression

“…It acts on two types of G protein-coupled receptors named the The upregulation of vasoconstrictive ET B receptor expression with increased vasoconstriction are seen in coronary artery infarction (Wackenfors et al, 2004) and experimental ischemic stroke (Stenman et al, 2002). This increased vasoconstrictive ET B receptor-mediated vasoconstriction are also found in the arterial segments treated with the risk factors such as cigarette smoke particles (Xu et al, 2008) or minimally modified low density lipoprotein (mmLDL) (Jie et al, 2012;Li et al, 2012). Blockage of extracellular signal-regulated kinases 1 and 2 (ERK1/2) mitogen-activated protein kinase (MAPK) signal pathways using Raf inhibitors has demonstrated that in cigarette smoke-exposed rats and in rat experimental subarachnoid hemorrhage model (Ansar et al, 2011), the upregulation of vasoconstrictive ET B receptor expression is associated with activation of Raf/ERK/MAPK signal pathways.…”

“…Taken all together, this suggests although mmLDL is still recognized by LDL receptor (Berliner et al, 1990), it has different effects from LDL on regulation of vasoconstrictive ET B and ET A receptor expressions in the arterial smooth muscle cells. One explanation for the lack effects of LDL at concentration of 2.2 mg protein/L (Jie et al, 2012;Li et al, 2013a;Li et al, 2012) is due to far low concentration of LDL used in the experiments.…”

“…However, the circulating oxLDL is only about 0.25% of total LDL in patients with acute myocardial infarction (Ehara et al, 2001). For the first time, the present study was designed to investigate if LDL at concentrations of 11, 22 and 44 mg protein/L has similar effects as mmLDL (2.2 mg protein/L) on the regulation of vasoconstrictive ET B receptor expression (Jie et al, 2012;Li et al, 2012) and if ERK1/2 and p38 MAPK signal pathways are involved in this process.…”

“…Blockage of extracellular signal-regulated kinases 1 and 2 (ERK1/2) mitogen-activated protein kinase (MAPK) signal pathways using Raf inhibitors has demonstrated that in cigarette smoke-exposed rats and in rat experimental subarachnoid hemorrhage model (Ansar et al, 2011), the upregulation of vasoconstrictive ET B receptor expression is associated with activation of Raf/ERK/MAPK signal pathways. Previously, we have reported that mmLDL upregulates vasoconstrictive ET B (Jie et al, 2012) and ET A (Li et al, 2013a) receptors in rat coronary arterial smooth muscle cells mainly via activation of protein kinase C (PKC), ERK1/2 and the downstream nuclear factor-kappaB (NF-κB) signal pathways. However, at the same concentration (2.2 mg protein/L), low density lipoprotein (LDL) without modification has no such effects (Jie et al, 2012;Li et al, 2013a).…”

“…Previously, we have reported that mmLDL upregulates vasoconstrictive ET B (Jie et al, 2012) and ET A (Li et al, 2013a) receptors in rat coronary arterial smooth muscle cells mainly via activation of protein kinase C (PKC), ERK1/2 and the downstream nuclear factor-kappaB (NF-κB) signal pathways. However, at the same concentration (2.2 mg protein/L), low density lipoprotein (LDL) without modification has no such effects (Jie et al, 2012;Li et al, 2013a). Taken all together, this suggests although mmLDL is still recognized by LDL receptor (Berliner et al, 1990), it has different effects from LDL on regulation of vasoconstrictive ET B and ET A receptor expressions in the arterial smooth muscle cells.…”