The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform

Paul M. Tulkens - One of the best experts on this subject based on the ideXlab platform.

  • modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids
    Chemistry and Physics of Lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Mariepaule Mingeotleclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1Phospholipase A1 towards phosphatidylcholine, while the change in lipid hydration or in fluidity of membrane are less critical. These observations may have physiological implications with respect to the rate of degradation of cellular membranes after their lysosomal segregation.

  • Modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids.
    Chemistry and physics of lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Marie-paule Mingeot-leclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1

  • Cocaine induces a mixed lysosomal lipidosis in cultured fibroblasts, by inactivation of acid sphingomyelinase and inhibition of Phospholipase A1.
    Toxicology and applied pharmacology, 2004
    Co-Authors: Marie-cécile Nassogne, Chantal Lizarraga, Francisca N'kuli, Françoise Van Bambeke, Roger Van Binst, Pierre Wallemacq, Paul M. Tulkens, Marie-paule Mingeot-leclercq, Thierry Levade, Pierre J. Courtoy
    Abstract:

    This paper reports that cocaine may induce a lysosomal storage disorder. Indeed, culture of Rat-1 fibroblasts with 250-500 microM cocaine induced after 2-3 days a major accumulation in lysosomes of electron-dense lamellar structures. By subcellular fractionation, this was reflected by a selective decrease of the buoyant density of several lysosomal enzymes, indicating lysosomal lipid overload. Biochemical analysis confirmed an increased cellular content of major phospholipids and sphingomyelin, but not of cholesterol. Cocaine, a membrane-permeant weak base, is concentrated by acidotropic sequestration, because its accumulation was abrogated by the proton ionophore, monensin and the vacuolar ATPase inhibitor, bafilomycin A1. At its estimated lysosomal concentration, cocaine almost completely inhibited Phospholipase A1 activity on liposomes. Cell incubation with cocaine, but not with its inactive metabolite, benzoylecgonine, rapidly inactivated acid sphingomyelinase, as reflected by a 10-fold decrease in Vmax with identical Km. Acid sphingomyelinase inactivation was fully prevented by the thiol proteinases inhibitors, leupeptin and E64, indicating that cocaine induces selective sphingomyelinase proteolysis. Upon cocaine removal, acid sphingomyelinase activity was rapidly restored, pointing to its fast turnover. In contrast, the cellular content of several other lysosomal hydrolases was increased up to 2-fold. Together, these data show that acidotropic accumulation of cocaine in lysosomes rapidly inhibits acid Phospholipase A1 and inactivates acid sphingomyelinase, which can explain induction of a mixed lysosomal lipidosis.

  • Effect of substrate organization on the activity and on the mechanism of gentamicin-induced inhibition of rat liver lysosomal Phospholipase A1.
    Biochemical pharmacology, 1992
    Co-Authors: Jocelyne Piret, Bellamkonda K. Kishore, Paul M. Tulkens
    Abstract:

    Aminoglycoside antibiotics, such as gentamicin, induce a lysosomal phospholipidosis in the kidney cortex of experimental animals and humans. In vitro, gentamicin binds to negatively charged phospholipids, such as phosphatidylinositol, and decreases the activity of lysosomal Phospholipases towards a neutral phospholipid (phosphatidylcholine) included in lipid vesicles. The mechanism of such an inhibition was not unequivocally established. On one hand Mingeot-Leclercq et al. (Biochem Pharmacol 37: 591-599, 1988) observed that the activity of Phospholipase A1 is modulated by the negative charges of the bilayer and that the inhibitory potency of gentamicin is inversely related to the phosphatidylinositol content of the vesicles, and therefore proposed that inhibition is due to charge neutralization. On the other hand, Hostetler and Jellison (J Pharmacol Exp Ther 254: 188-191, 1990) observed that the activity of Phospholipase A1 is not modulated by the negative charges of the vesicles and that the inhibitory potency of gentamicin is directly related to the phosphatidylinositol content of the bilayer, and therefore proposed that inhibition is due to substrate depletion. However, the experimental designs of these two models differed in several respects such as the source (liver versus kidney) and nature of the enzyme (native lysosomal extract versus purified delipidated Phospholipase A1), and the composition of lipid vesicles (those containing constant amounts of phosphatidylcholine and cholesterol, and inversely varying amounts of phosphatidylinositol and sphingomyelin versus those containing inversely related amounts of phosphatidylcholine and phosphatidylinositol only). In order to assess the nature of the differences between these models, we compared the activity of Phospholipase A1 and its inhibition by gentamicin using only one source of enzyme, the rat liver lysosomal extract, and the two types of lipid vesicles as used in the above models. Our results showed that both models are true within the frame work of their respective experimental designs. However, since the composition of the lipid vesicles as well as the nature of the enzyme preparation (whole lysosomal extract) in the "charge neutralization" model is closer to in vivo conditions, we suggest that this model may be more relevant to the in vivo situation.

Jocelyne Piret - One of the best experts on this subject based on the ideXlab platform.

  • Modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids.
    Chemistry and physics of lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Marie-paule Mingeot-leclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1

  • modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids
    Chemistry and Physics of Lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Mariepaule Mingeotleclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1Phospholipase A1 towards phosphatidylcholine, while the change in lipid hydration or in fluidity of membrane are less critical. These observations may have physiological implications with respect to the rate of degradation of cellular membranes after their lysosomal segregation.

  • Effect of substrate organization on the activity and on the mechanism of gentamicin-induced inhibition of rat liver lysosomal Phospholipase A1.
    Biochemical pharmacology, 1992
    Co-Authors: Jocelyne Piret, Bellamkonda K. Kishore, Paul M. Tulkens
    Abstract:

    Aminoglycoside antibiotics, such as gentamicin, induce a lysosomal phospholipidosis in the kidney cortex of experimental animals and humans. In vitro, gentamicin binds to negatively charged phospholipids, such as phosphatidylinositol, and decreases the activity of lysosomal Phospholipases towards a neutral phospholipid (phosphatidylcholine) included in lipid vesicles. The mechanism of such an inhibition was not unequivocally established. On one hand Mingeot-Leclercq et al. (Biochem Pharmacol 37: 591-599, 1988) observed that the activity of Phospholipase A1 is modulated by the negative charges of the bilayer and that the inhibitory potency of gentamicin is inversely related to the phosphatidylinositol content of the vesicles, and therefore proposed that inhibition is due to charge neutralization. On the other hand, Hostetler and Jellison (J Pharmacol Exp Ther 254: 188-191, 1990) observed that the activity of Phospholipase A1 is not modulated by the negative charges of the vesicles and that the inhibitory potency of gentamicin is directly related to the phosphatidylinositol content of the bilayer, and therefore proposed that inhibition is due to substrate depletion. However, the experimental designs of these two models differed in several respects such as the source (liver versus kidney) and nature of the enzyme (native lysosomal extract versus purified delipidated Phospholipase A1), and the composition of lipid vesicles (those containing constant amounts of phosphatidylcholine and cholesterol, and inversely varying amounts of phosphatidylinositol and sphingomyelin versus those containing inversely related amounts of phosphatidylcholine and phosphatidylinositol only). In order to assess the nature of the differences between these models, we compared the activity of Phospholipase A1 and its inhibition by gentamicin using only one source of enzyme, the rat liver lysosomal extract, and the two types of lipid vesicles as used in the above models. Our results showed that both models are true within the frame work of their respective experimental designs. However, since the composition of the lipid vesicles as well as the nature of the enzyme preparation (whole lysosomal extract) in the "charge neutralization" model is closer to in vivo conditions, we suggest that this model may be more relevant to the in vivo situation.

Bellamkonda K. Kishore - One of the best experts on this subject based on the ideXlab platform.

  • Modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids.
    Chemistry and physics of lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Marie-paule Mingeot-leclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1

  • modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids
    Chemistry and Physics of Lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Mariepaule Mingeotleclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1Phospholipase A1 towards phosphatidylcholine, while the change in lipid hydration or in fluidity of membrane are less critical. These observations may have physiological implications with respect to the rate of degradation of cellular membranes after their lysosomal segregation.

  • Effect of substrate organization on the activity and on the mechanism of gentamicin-induced inhibition of rat liver lysosomal Phospholipase A1.
    Biochemical pharmacology, 1992
    Co-Authors: Jocelyne Piret, Bellamkonda K. Kishore, Paul M. Tulkens
    Abstract:

    Aminoglycoside antibiotics, such as gentamicin, induce a lysosomal phospholipidosis in the kidney cortex of experimental animals and humans. In vitro, gentamicin binds to negatively charged phospholipids, such as phosphatidylinositol, and decreases the activity of lysosomal Phospholipases towards a neutral phospholipid (phosphatidylcholine) included in lipid vesicles. The mechanism of such an inhibition was not unequivocally established. On one hand Mingeot-Leclercq et al. (Biochem Pharmacol 37: 591-599, 1988) observed that the activity of Phospholipase A1 is modulated by the negative charges of the bilayer and that the inhibitory potency of gentamicin is inversely related to the phosphatidylinositol content of the vesicles, and therefore proposed that inhibition is due to charge neutralization. On the other hand, Hostetler and Jellison (J Pharmacol Exp Ther 254: 188-191, 1990) observed that the activity of Phospholipase A1 is not modulated by the negative charges of the vesicles and that the inhibitory potency of gentamicin is directly related to the phosphatidylinositol content of the bilayer, and therefore proposed that inhibition is due to substrate depletion. However, the experimental designs of these two models differed in several respects such as the source (liver versus kidney) and nature of the enzyme (native lysosomal extract versus purified delipidated Phospholipase A1), and the composition of lipid vesicles (those containing constant amounts of phosphatidylcholine and cholesterol, and inversely varying amounts of phosphatidylinositol and sphingomyelin versus those containing inversely related amounts of phosphatidylcholine and phosphatidylinositol only). In order to assess the nature of the differences between these models, we compared the activity of Phospholipase A1 and its inhibition by gentamicin using only one source of enzyme, the rat liver lysosomal extract, and the two types of lipid vesicles as used in the above models. Our results showed that both models are true within the frame work of their respective experimental designs. However, since the composition of the lipid vesicles as well as the nature of the enzyme preparation (whole lysosomal extract) in the "charge neutralization" model is closer to in vivo conditions, we suggest that this model may be more relevant to the in vivo situation.

Marie-paule Mingeot-leclercq - One of the best experts on this subject based on the ideXlab platform.

  • Modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids.
    Chemistry and physics of lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Marie-paule Mingeot-leclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1

  • Cocaine induces a mixed lysosomal lipidosis in cultured fibroblasts, by inactivation of acid sphingomyelinase and inhibition of Phospholipase A1.
    Toxicology and applied pharmacology, 2004
    Co-Authors: Marie-cécile Nassogne, Chantal Lizarraga, Francisca N'kuli, Françoise Van Bambeke, Roger Van Binst, Pierre Wallemacq, Paul M. Tulkens, Marie-paule Mingeot-leclercq, Thierry Levade, Pierre J. Courtoy
    Abstract:

    This paper reports that cocaine may induce a lysosomal storage disorder. Indeed, culture of Rat-1 fibroblasts with 250-500 microM cocaine induced after 2-3 days a major accumulation in lysosomes of electron-dense lamellar structures. By subcellular fractionation, this was reflected by a selective decrease of the buoyant density of several lysosomal enzymes, indicating lysosomal lipid overload. Biochemical analysis confirmed an increased cellular content of major phospholipids and sphingomyelin, but not of cholesterol. Cocaine, a membrane-permeant weak base, is concentrated by acidotropic sequestration, because its accumulation was abrogated by the proton ionophore, monensin and the vacuolar ATPase inhibitor, bafilomycin A1. At its estimated lysosomal concentration, cocaine almost completely inhibited Phospholipase A1 activity on liposomes. Cell incubation with cocaine, but not with its inactive metabolite, benzoylecgonine, rapidly inactivated acid sphingomyelinase, as reflected by a 10-fold decrease in Vmax with identical Km. Acid sphingomyelinase inactivation was fully prevented by the thiol proteinases inhibitors, leupeptin and E64, indicating that cocaine induces selective sphingomyelinase proteolysis. Upon cocaine removal, acid sphingomyelinase activity was rapidly restored, pointing to its fast turnover. In contrast, the cellular content of several other lysosomal hydrolases was increased up to 2-fold. Together, these data show that acidotropic accumulation of cocaine in lysosomes rapidly inhibits acid Phospholipase A1 and inactivates acid sphingomyelinase, which can explain induction of a mixed lysosomal lipidosis.

Françoise Van Bambeke - One of the best experts on this subject based on the ideXlab platform.

  • modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids
    Chemistry and Physics of Lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Mariepaule Mingeotleclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1Phospholipase A1 towards phosphatidylcholine, while the change in lipid hydration or in fluidity of membrane are less critical. These observations may have physiological implications with respect to the rate of degradation of cellular membranes after their lysosomal segregation.

  • Modulation of the in vitro activity of lysosomal Phospholipase A1 by membrane lipids.
    Chemistry and physics of lipids, 2005
    Co-Authors: Jocelyne Piret, Françoise Van Bambeke, Paul M. Tulkens, André Schanck, Sylvie Delfosse, Bellamkonda K. Kishore, Marie-paule Mingeot-leclercq
    Abstract:

    Lysosomal Phospholipases play a critical role for degradation of cellular membranes after their lysosomal segregation. We investigated the regulation of lysosomal Phospholipase A1 by cholesterol, phosphatidylethanolamine, and negatively-charged lipids in correlation with changes of biophysical properties of the membranes induced by these lipids. Lysosomal Phospholipase A1 activity was determined towards phosphatidylcholine included in liposomes of variable composition using a whole-soluble lysosomal fraction of rat liver as enzymatic source. Phospholipase A1 activity was then related to membrane fluidity, lipid phase organization and membrane potential as determined by fluorescence depolarization of DPH, 31P NMR and capillary electrophoresis. Phospholipase A1 activity was markedly enhanced when the amount of negatively-charged lipids included in the vesicles was increased from 10 to around 30% of total phospholipids and the intensity of this effect depended on the nature of the acidic lipids used (ganglioside GM1

  • Cocaine induces a mixed lysosomal lipidosis in cultured fibroblasts, by inactivation of acid sphingomyelinase and inhibition of Phospholipase A1.
    Toxicology and applied pharmacology, 2004
    Co-Authors: Marie-cécile Nassogne, Chantal Lizarraga, Francisca N'kuli, Françoise Van Bambeke, Roger Van Binst, Pierre Wallemacq, Paul M. Tulkens, Marie-paule Mingeot-leclercq, Thierry Levade, Pierre J. Courtoy
    Abstract:

    This paper reports that cocaine may induce a lysosomal storage disorder. Indeed, culture of Rat-1 fibroblasts with 250-500 microM cocaine induced after 2-3 days a major accumulation in lysosomes of electron-dense lamellar structures. By subcellular fractionation, this was reflected by a selective decrease of the buoyant density of several lysosomal enzymes, indicating lysosomal lipid overload. Biochemical analysis confirmed an increased cellular content of major phospholipids and sphingomyelin, but not of cholesterol. Cocaine, a membrane-permeant weak base, is concentrated by acidotropic sequestration, because its accumulation was abrogated by the proton ionophore, monensin and the vacuolar ATPase inhibitor, bafilomycin A1. At its estimated lysosomal concentration, cocaine almost completely inhibited Phospholipase A1 activity on liposomes. Cell incubation with cocaine, but not with its inactive metabolite, benzoylecgonine, rapidly inactivated acid sphingomyelinase, as reflected by a 10-fold decrease in Vmax with identical Km. Acid sphingomyelinase inactivation was fully prevented by the thiol proteinases inhibitors, leupeptin and E64, indicating that cocaine induces selective sphingomyelinase proteolysis. Upon cocaine removal, acid sphingomyelinase activity was rapidly restored, pointing to its fast turnover. In contrast, the cellular content of several other lysosomal hydrolases was increased up to 2-fold. Together, these data show that acidotropic accumulation of cocaine in lysosomes rapidly inhibits acid Phospholipase A1 and inactivates acid sphingomyelinase, which can explain induction of a mixed lysosomal lipidosis.