Manipulating fenestrations in young and old liver sinusoidal endothelial cells

Area of Science:

• Liver biology
• Endothelial cell physiology
• Pharmacology

Background:

• Fenestrations in liver sinusoidal endothelial cells (LSECs) are crucial for nutrient and lipoprotein transport.
• Age-related reduction in fenestrations (pseudocapillarization) impairs liver function and is linked to metabolic diseases.
• Existing understanding suggests vascular endothelial growth factor and nitric oxide (NO) pathways regulate fenestrations via actin cytoskeleton and lipid raft remodeling.

Purpose of the Study:

• To investigate the effects of various drugs on LSEC fenestrations in young and aged mice.
• To determine if pharmacological interventions can reverse age-related fenestration loss.
• To elucidate the roles of NO-dependent and independent pathways in fenestration regulation.

Main Methods:

• Isolated LSECs from young and old mice were treated with drugs including 7-ketocholesterol, NMN, sildenafil, amlodipine, TRAIL, cytochalasin D, bosentan, and DOI.
• Fenestrations were quantified using scanning electron microscopy (SEM).
• Actin and NO synthase were examined using direct stochastic optical reconstruction microscopy (dSTORM).

Main Results:

• 7-ketocholesterol increased fenestration porosity, diameter, and frequency in both age groups.
• NMN, sildenafil, amlodipine, TRAIL, and cytochalasin D increased fenestration porosity and/or frequency.
• Bosentan and DOI specifically increased fenestrations in old mice.
• Actin cytoskeleton modifications were observed with fenestration-increasing agents; NO synthase was elevated by sildenafil, amlodipine, and TRAIL.

Conclusions:

• Pharmacological agents targeting NO, actin, or lipid rafts can modulate LSEC fenestrations.
• Fenestration regulation involves both NO-dependent and independent mechanisms.
• Age-related defenestration is pharmacologically reversible, suggesting therapeutic potential for dyslipidemia and insulin resistance.