Pharmacologic treatment of atherosclerosis: beyond lipid-lowering therapy

On the antiatherogenity of calcium channel blockers: studies in proliferating vascular smooth muscle cells on age sensitivity, dose dependent inhibitory effect, and time of action

We study the effect of diltiazem on cultured vascular smooth muscle cells from humans and rats, paying special attention to its activity in relation to the concentrations applied, incubation times after addition and the capacity to act against the mitogenic activity of insulin and insulin-like growth factor 1 (IGF-1). The mitotic activity was measured by means of bromodeoxyuridine DNA incorporation. Smooth muscle cells from old individuals showed a dose-dependent regression of the inhibitory level but not those from the young subjects, which showed a remarkable inhibition of mitosis at all concentrations tested. Around 8 h after addition, diltiazem inhibited cell proliferation at all concentrations tested. The inhibition exerted by 10(-7) M rapidly disappeared, reaching values higher than those initially registered and returning to basal rates after 72 h. The inhibition by 10(-6) and 10(-5) M remained after 30 and 72 h, respectively. Insulin (100 nM) or IGF-1 (1 nM) did not counteract the inhibitory effect of diltiazem (10(-5) M). Despite differences related to doses and age of cells, we conclude that diltiazem--as an L-type calcium channels blocker--is a potent inhibitor of vascular smooth muscle cell proliferation.

Novel Vascular Biology of Third-Generation L-Type Calcium Channel Antagonists

Calcium channel blockers (CCBs) were developed as vasodilators, and their use in cardiovascular disease treatment remains largely based on that mechanism of action. More recently, with the evolution of second- and third-generation CCBs, pleiotropic effects have been observed, and at least some of CCBs’ benefit is attributable to these mechanisms. Understanding these effects has contributed greatly to elucidating disease mechanisms and the rationale for CCB use. Furthermore, this knowledge might clarify why drugs are useful in some disease states, such as atherosclerosis, but not in others, such as heart failure. Although numerous drugs used in the treatment of vascular disease, including statins and angiotensin-converting–enzyme inhibitors, have well-described pleiotropic effects universally accepted to contribute to their benefit, little attention has been paid to CCBs’ potentially similar effects. Accumulating evidence that at least 1 CCB, amlodipine, has pharmacologic actions distinct from L-type calcium channel blockade prompted us to investigate the pleiotropic actions of amlodipine and CCBs in general. There are several areas of research; foci here are (1) the physicochemical properties of amlodipine and its interaction with cholesterol and oxidants; (2) the mechanism by which amlodipine regulates NO production and implications; and (3) amlodipine’s role in controlling smooth muscle cell proliferation and matrix formation.

Carboxyl-terminal basic amino acids in the X domain are essential for the nuclear import of phospholipase C δ1

BACKGROUND

Although phospholipase C (PLC)delta1 containing a functional nuclear export signal (NES) is normally localized at the plasma membrane and in the cytoplasm, it shuttles between the nucleus and the cytoplasm. Since nucleocytoplasmic shuttling of a molecule is generally regulated by a balance between its NES and the nuclear localization signal (NLS), we examined whether PLCdelta1 contains an NLS sequence.

RESULTS

A region corresponding to the C terminus of the X domain and the XY-linker, which contains clusters of basic amino acid residues, was essential for the nuclear import of PLCdelta1 in Madin-Darby canine kidney cells. A series of point mutations on lysine residues in this region revealed that K432 and K434 in combination were important for the nuclear import. A short synthetic peptide corresponding to residues 429-442, however, was not able to function as an NLS sequence when they were injected into the cytoplasm in a carrier-conjugated form. Neither a longer peptide equivalent to PLCdelta1 412-498 fused to a protein tag consisting of glutathione S-transferase and green fluorescent protein was imported to the nucleus after microinjection into the cytoplasm.

CONCLUSION

The nuclear import of PLCdelta1 requires the C-terminus of the X domain, particularly the amino acid residues K432 and K434, and the XY-linker. The region alone, however, cannot serve as a functional NLS. The machinery for nuclear transport may require additional structural component(s) of the enzyme.

Arterial calcification: a review of mechanisms, animal models, and the prospects for therapy

The causes of arterial calcification are beginning to be elucidated. Macrophages, mast cells, and smooth muscle cells are the primary cells implicated in this process. The roles of a variety of bone-related proteins including bone morphogenetic protein-2 (BMP-2), matrix Gla protein (MGP), osteoprotegerin (OPG), osteopontin, and osteonectin in regulating arterial calcification are reviewed. Animals lacking MGP, OPG, smad6, carbonic anhydrase isoenzyme II, fibrillin-1, and klotho gene product develop varying extents of arterial calcification. Hyperlipidemia, vitamin D, nicotine, and warfarin, alone or in various combinations, produce arterial calcification in animal models. MGP has recently been discovered to be an inhibitor of bone morphogenetic protein-2, the principal osteogenic growth factor. Many of the forces that induce arterial calcification may act by disrupting the essential post-translational modification of MGP, allowing BMP-2 to induce mineralization. MGP requires gamma-carboxylation before it is functional, and this process uses vitamin K as an essential cofactor. Vitamin K deficiency, drugs that act as vitamin K antagonists, and oxidant stress are forces that could prevent the formation of GLA residues on MGP. The potential role of arterial apoptosis in calcification is discussed. Potential therapeutic options to limit the rate of arterial calcification are summarized.