Minimally modified LDL upregulates endothelin type B receptors in rat basilar artery.

ABSTRACT

Minimally modified low density lipoprotein (mmLDL) is a well-known risk factor for cerebral vascular diseases and upregulation of endothelin type B (ET(B)) receptors plays key roles in the pathogenesis. The present study was designed to examine if mmLDL upregulated endothelin ET(B) receptors in basilar artery and its possible intracellular signaling molecular mechanisms. Rat basilar arteries were cultured for 24h in the presence of mmLDL with specific inhibitors. The artery contractile responses and receptor expressions of mRNA and protein were investigated using myograph system, real-time PCR and Western blot techniques, respectively. Results showed that ET(B) receptor agonist, sarafotoxin 6c induced a weak contraction in fresh basilar artery segments. After organ culture the contraction curve mediated by ET(B) receptor was shifted towards the left with an increased E(max) of 88 ± 6%. The mmLDL 10 µg/mL further shifted the concentration-contractile curves towards the left with an increased E(max) of 116 ± 12%. The organ culture significantly increased ET(B) receptor mRNA and protein levels from fresh arteries, which was further enhanced by mmLDL. The staurosporine (PKC inhibitor), both SB386023 and U0126 (extracellular signal related kinases 1 and 2 inhibitor), and wedelolactone (NF-κB inhibitor) almost totally abolished organ culture-increased and mmLDL-increased contraction and expressions of endothelin ET(B) receptor. SP600125 (C-jun terminal kinase inhibitor) and SB203580 (p38 inhibitor) attenuated both organ cultured-induced and mmLDL-induced upregulation of endothelin ET(B) receptors. In conclusion, mmLDL upregulates ET(B) receptors of cerebral basilar artery via the PKC, MAPK and NF-κB signal pathways.