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Occlusive vascular disease is a widespread abnormality leading to lethal or debilitating outcomes such as myocardial infarction and stroke. It is part of atherosclerosis and is evoked by clinical procedures including angioplasty and grafting of saphenous vein in bypass surgery. A causative factor is the switch in smooth muscle cells to an invasive and proliferative mode, leading to neointimal hyperplasia. Here we reveal the importance to this process of TRPC1, a homolog of Drosophila transient receptor potential. Using 2 different in vivo models of vascular injury in rodents we show hyperplasic smooth muscle cells have upregulated TRPC1 associated with enhanced calcium entry and cell cycle activity. Neointimal smooth muscle cells after balloon angioplasty of pig coronary artery also express TRPC1. Furthermore, human vein samples obtained during coronary artery bypass graft surgery commonly exhibit an intimal structure containing smooth muscle cells that expressed more TRPC1 than the medial layer cells. Veins were organ cultured to allow growth of neointimal smooth muscle cells over a 2-week period. To explore the functional relevance of TRPC1, we used a specific E3-targeted antibody to TRPC1 and chemical blocker 2-aminoethoxydiphenyl borate. Both agents significantly reduced neointimal growth in human vein, as well as calcium entry and proliferation of smooth muscle cells in culture. The data suggest upregulated TRPC1 is a general feature of smooth muscle cells in occlusive vascular disease and that TRPC1 inhibitors have potential as protective agents against human vascular failure.

The reactivity of the vascular wall to endothelin-1 (ET-1) is influenced by cholesterol, which is of possible importance for the progression of atherosclerosis. To elucidate signaling steps affected, the cholesterol acceptor methyl-β-cyclodextrin (mβcd, 10 mmol/L) was used to manipulate membrane cholesterol and disrupt caveolae in intact rat arteries. In endothelium-denuded caudal artery, contractile responsiveness to 10 nmol/L ET-1 (mediated by the ET A receptor) was reduced by mβcd and increased by cholesterol. Neither ligand binding nor colocalization of ET A and caveolin-1 was affected by mβcd. Ca 2+ inflow via store-operated channels after depletion of intracellular Ca 2+ stores was reduced in mβcd-treated caudal arteries, as shown by Mn 2+ quench rate and intracellular [Ca 2+ ] response. Expression of TRPC1, 3, and 6 was detected by reverse transcriptase–polymerase chain reaction, and colocalization of TRPC1 with caveolin-1 was reduced by mβcd, as seen by immunofluorescence. Part of the contractile response to ET-1 was inhibited by Ni 2+ (0.5 mmol/L) and by a TRPC1 blocking antibody. In the basilar artery, exhibiting less store-operated channel activity than the caudal artery, ET-1–induced contractions were insensitive to the TRPC1 blocking antibody and to mβcd. Increased store-operated channel activity in basilar arteries after organ culture correlated with increased sensitivity of ET-1 contraction to mβcd. These results suggest that cholesterol influences vascular reactivity to ET-1 by affecting the caveolar localization of TRPC1.

Recent studies have established that the immune system plays an important role in the development of atherosclerosis. However, its role in regulating the arterial response to mechanical injury is less well studied. Arterial injury is associated with local accumulation of antibodies, and mice lacking functional T and B cells exhibit increased neointima formation, indicating that adaptive immune responses to neoantigens in the damaged tissue modulate the vascular repair process. To study the role of lipid antigen presentation in the arterial response to injury, we analyzed neointima formation in mice deficient in the lipid antigen-presenting molecule CD1d using a carotid collar model. As compared with control mice, neointima formation was reduced by >60% ( P −/− mice. Moreover, carotid injury of wild-type C57BL/6 mice was associated with expansion of CD1d-restricted natural killer T cells in the spleen and accumulation of natural killer T cells in the periadventitial space of injured arteries. The results suggest that presentation of lipid antigens through the CD1d–natural killer T cell pathway modulates vascular repair responses.