Effects of lysosomotropic agents on lipogenesis

Area of Science:

• Biochemistry
• Cell Biology
• Pharmacology

Background:

• Lysosomotropic agents, including chloroquine, quinine, and ammonium chloride (NH4Cl), are known to inhibit lysosomal function by increasing intralysosomal pH.
• Understanding the cellular lipid metabolism and the impact of lysosomal function is crucial in various physiological and pathological contexts.

Purpose of the Study:

• To investigate the effect of lysosomotropic agents on lipogenesis in cultured human skin fibroblasts.
• To determine the relationship between lysosomal function impairment and lipid synthesis stimulation.

Main Methods:

• Human skin fibroblasts were preincubated with lysosomotropic agents (chloroquine, quinine, NH4Cl) under serum-free conditions.
• Lipogenesis was assessed by measuring the incorporation of radiolabeled precursors (3H2O, [14C]acetate, [14C]pyruvate, [14C]palmitate, [14C]choline) into cellular lipids.
• The role of protein synthesis was evaluated using cycloheximide, an inhibitor of protein synthesis.

Main Results:

• Lysosomotropic agents induced a significant, dose- and time-dependent stimulation of lipogenesis, up to 10-fold.
• Stimulation of lipid synthesis correlated with impaired lysosomal function.
• Both lipogenesis and cholesterogenesis were stimulated, with most acetate incorporated into phospholipids.
• The stimulatory effect was reversible and dependent on active cellular protein synthesis, as it was abolished by cycloheximide.

Conclusions:

• Lysosomotropic agents enhance lipogenesis and cholesterogenesis in human fibroblasts by increasing intralysosomal pH.
• This lipid synthesis stimulation is dependent on active protein synthesis and is reversible.
• The findings highlight a novel link between lysosomal function and cellular lipid metabolism.