Lactosylceramide stimulates aortic smooth muscle cell proliferation

Area of Science:

• Biochemistry
• Cell Biology
• Vascular Biology

Background:

• Sphingolipids play critical roles in cellular processes.
• Aortic smooth muscle cell proliferation is implicated in cardiovascular diseases.
• The specific role of lactosylceramide in aortic smooth muscle cells is not fully understood.

Purpose of the Study:

• To investigate the effects of sphingolipids, particularly lactosylceramide, on aortic smooth muscle cell proliferation.
• To identify the key enzyme involved in lactosylceramide-mediated proliferation.
• To determine the cell-type specificity of lactosylceramide's effects.

Main Methods:

• Cell viability assays (viable cell counting, lactate dehydrogenase release).
• DNA synthesis measurement ([3H] thymidine incorporation).
• Enzyme activity assays for UDP-galactose: GlcCer $eta$-4 galactosyltransferase (GalT-2).
• Inhibition studies using antibodies and D-/L-PDMP.

Main Results:

• Lactosylceramide (LacCer) stimulated aortic smooth muscle cell proliferation up to 5-fold.
• Antibody against LacCer blocked proliferation; GbOse3Cer antibody had no effect.
• LacCer decreased aortic endothelial cell viability but not pulmonary endothelial cells.
• D-PDMP inhibited GalT-2 activity and proliferation, while L-PDMP stimulated both.
• Antibody against GalT-2 inhibited cell proliferation.

Conclusions:

• Activation of GalT-2 increases LacCer levels.
• Increased LacCer is involved in aortic smooth muscle cell proliferation.
• This mechanism is specific to aortic smooth muscle cells.