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In vitro modulation of AL-amyloid formation by human mesangial cells exposed to amyloidogenic light chains
J Isaac1, J D Kerby, W J Russell
1Department of Pathology, Louisiana State University Medical Center, Shreveport, LA 71130, USA.
Abstract:
We have shown in vitro AL-amyloid formation by human mesangial cells (HMCs). AL-amyloid formation may require lysosomal processing of the light chains (LCs) by HMCs for amyloidogenesis to occur. Chloroquine inhibits lysosomal activity. TGF-beta mediates extracellular matrix formation in many glomerulopathies. Thrombospondin (TSP) has been proposed as a mediator of cell proliferation and a marker of early fibrosis. We investigated amyloid formation by HMCs exposed to AL-LCs in the absence of amyloid enhancing factor (AEF). The effects of TGF-beta, TSP and chloroquine on in vitro amyloid formation were studied. HMCs were incubated with two AL-LCs, a light chain deposition disease (LCDD)-LC, or one of two tubulopathic LCs (T-LCs). Additional cells were treated with an AL-LC and chloroquine, TGF-beta, or TSP. Amyloid formation was evaluated microscopically using hematoxylin and eosin, Congo red and Thioflavin-T stains, as well as ultrastructurally. Amyloid was formed only when HMCs were incubated with AL-LCs. Addition of TSP significantly enhanced amyloid formation. In contrast, exogenous TGF-beta and chloroquine significantly attenuated amyloid formation. These findings show that some AL-LCs do not require AEF for amyloidogenesis to occur, and that chloroquine, TGF-beta and sTSP modulate in vitro AL-amyloidosis.
Insights
Certain AL-light chains (LCs) can form amyloid in vitro without amyloid-enhancing factor. Thrombospondin (TSP) promotes this formation, while chloroquine and TGF-beta inhibit it, revealing modulators of AL-amyloidosis.
Area of Science:
- Nephrology
- Cell Biology
- Biochemistry
Background:
- In vitro amyloid formation by human mesangial cells (HMCs) has been demonstrated.
- Lysosomal processing of light chains (LCs) by HMCs may be crucial for AL-amyloidogenesis.
- Factors like chloroquine (inhibits lysosomal activity), TGF-beta (mediates extracellular matrix formation), and thrombospondin (TSP) (mediates proliferation and fibrosis) are implicated in related cellular processes.
Purpose of the Study:
- To investigate in vitro AL-amyloid formation by HMCs exposed to AL-LCs without amyloid-enhancing factor (AEF).
- To determine the effects of TGF-beta, TSP, and chloroquine on this in vitro amyloid formation process.
Main Methods:
- HMCs were incubated with specific light chain deposition disease (LCDD)-LC or tubulopathic LCs (T-LCs).
- Additional HMCs were treated with AL-LCs combined with chloroquine, TGF-beta, or TSP.
- Amyloid formation was assessed using microscopic (H&E, Congo red, Thioflavin-T) and ultrastructural evaluations.
Main Results:
- Amyloid formation occurred exclusively when HMCs were incubated with AL-LCs.
- TSP significantly enhanced in vitro amyloid formation.
- Exogenous TGF-beta and chloroquine significantly attenuated amyloid formation.
Conclusions:
- Some AL-LCs can undergo amyloidogenesis in vitro independently of AEF.
- Soluble TSP (sTSP) acts as a potent enhancer of in vitro AL-amyloid formation.
- Chloroquine and TGF-beta significantly inhibit in vitro AL-amyloid formation, suggesting their potential roles in modulating AL-amyloidosis.