The synthetic TRPML1 agonist ML-SA1 mitigates intracellular lipid accumulation induced by antipsychotics in vitro by stimulating release of extracellular microvesicles

Abstract

Antipsychotics drugs disrupt lipid homeostasis by inhibiting cholesterol biosynthesis and impairing intracellular cholesterol trafficking, leading to lipid accumulation in endolysosomes. Moreover, transient receptor potential mucolipin 1 (TRPML1) cation channels of the endolysosomal membrane facilitate calcium (Ca²⁺) efflux. In the present work, we characterized the mechanism of action of the TRPML1 agonist ML-SA1 to reduce intracellular lipid accumulation and the potential to relieve the antipsychotic-induced endolysosomal lipid accumulation by enhancing the secretion of extracellular microvesicles (EVs) in Huh7 hepatocytes. We show that ML-SA1 increased the secretion of EVs, thus reducing lipid overload and lysosomal size in cells treated with clozapine or risperidone. ML-SA1 likely increased ceramide and dihydroceramide levels via ceramide synthesis de novo, through ML-SA1-induced upregulation of genes that code for enzymes involved in ceramide synthesis. Treatment with the Ca²⁺ chelator BAPTA-AM prevented decreased intracellular lipid accumulation and increased ceramide levels and secretion of EVs, indicating that intracellular Ca²⁺ mediated the effects of the TRPML1 agonist ML-SA1. These results show the potential of TRPML1 activation to alleviate pathological conditions characterized by accumulation of undigested substrates and overloaded dysfunctional endolysosomes.