Background: Atherogenesis is associated with elevated levels of low–density lipoprotein (LDL) and its oxidized form, oxLDL, a proinflammatory, immunogenic and cytotoxic agent. Liver sinusoidal endothelial cells (LSEC) remove... [ view full abstract ]
Background: Atherogenesis is associated with elevated levels of low–density lipoprotein (LDL) and its oxidized form, oxLDL, a proinflammatory, immunogenic and cytotoxic agent. Liver sinusoidal endothelial cells (LSEC) remove circulating oxLDLs, but given their toxicity, we investigated their effects on cultured rat LSEC. After oxLDL challenge we assayed LSEC function/viability, and used direct stochastic optical reconstruction microscopy (dSTORM), structured illumination microscopy (SIM) and scanning electron microscopy (SEM) to study LSEC morphology.
Methods: LDL was oxidized with CuSO4 for 3/6/24h then added to cultured LSEC at 10/40/80 mg/ml. LSEC were then assessed for viability and scavenging ability. Parallel cultures were examined for morphological changes using dSTORM/SIM/SEM.
Results: oxLDL challenge had minimal/moderate effects on LSEC viability/function as judged by LDH release and ligand endocytosis/degradation, with effects becoming more pronounced with increasing oxLDL oxidation/concentration. The effects of oxLDL on fenestration morphology were, however, rather more dramatic. With increasing oxLDL oxidation/concentration: i) sieve plates were lost and (in some cells) the entire cell surface became perforated with fenestrations or ii) fenestrations within sieve plates were destroyed, leaving gaping trans–cytoplasmic holes of 2–8 mm diameter in LSEC. Interestingly, some LSEC appeared to be more resistant to oxLDL challenge.
Conclusions: Despite the presence of oxLDL, LSEC largely remained viable and able to scavenge. However, oxLDL causes major morphological changes to LSEC in vitro, suggesting that oxLDL is detrimental for liver health in vivo. Super-resolution optical microscopy on LSEC will further facilitate the study of these detrimental morphological effects and elucidate mechanisms behind these processes.
