Protective role of clusterin in preserving endothelial function in AL amyloidosis

Abstract

Misfolded immunoglobulin light chain proteins (LC) in light chain amyloidosis (AL) are toxic to vascular tissues. We tested the hypothesis that chaperone protein clusterin preserves endothelial function and cell survival during LC exposure.

Methods: LC (20 μg/mL) were given to human aortic endothelial cells (EC) for 24-h and clusterin protein/gene expression and secretion were measured. DNA fragmentation was measured with/without recombinant clusterin (Clu, 300 ng/mL). Adipose arterioles (non-AL subjects) were tested for dilator responses to acetylcholine/papaverine at baseline and after 1-h of LC ± Clu.

Results: LC reduced EC clusterin secretion, protein and gene expression while increasing DNA fragmentation. Clu attenuated LC-induced DNA fragmentation and restored dilator response to acetylcholine (logEC50: control -7.05 ± 0.2, LC + Clu -6.53 ± 0.4, LC -4.28 ± 0.7, p < 0.05 versus control, LC + Clu).

Conclusions: LC induced endothelial cell death and dysfunction while reducing clusterin protein/gene expression and secretion. Exogenous clusterin attenuated LC toxicity. This represents a new pathobiologic mechanism and therapeutic target for AL amyloidosis.

Figure 1

Endothelial cell clusterin. A. LC reduced precursor/secreted clusterin production (insert is Western blot), clusterin mRNA production (B) and secreted clusterin (C). D. LC increased EC cell death that was attenuated with clusterin co-treatment.

Figure 2

Light chain proteins and arterioles. A–B. LC impaired dilator response to acetylcholine and papaverine. Co-treatment with clusterin attenuated adverse effect of LC and restored acetylcholine EC50. L-NAME blunted the protective effect of clusterin. C–D. LC reduced 30-minute NO production and increased peroxynitrite production in arterioles; clusterin protected against these changes.