Lipid accumulation in liver, spleen, lungs and kidneys of miniature-pigs after chloroquine treatment

Lysosomal inhibition attenuates peroxisomal gene transcription via suppression of PPARA and PPARGC1A levels

Lysosomes influence dynamic cellular processes such as nutrient sensing and transcriptional regulation. To explore novel transcriptional pathways regulated by lysosomes, we performed microarray analysis followed by qPCR validation in a mouse hepatocyte cell line, AML12, treated with bafilomycin A₁ (lysosomal v-type H⁺-translocating ATPase inhibitor). Pathway enrichment analysis revealed significant downregulation of gene sets related to peroxisomal biogenesis and peroxisomal lipid oxidation upon lysosomal inhibition. Mechanistically, pharmacological inhibition of lysosomes as well as genetic knockdown of Tfeb led to downregulation of the peroxisomal master regulator PPARA and its coactivator PPARGC1A/PGC1α. Consistently, ectopic induction of PPARA transcriptional activity rescues the effects of lysosomal inhibition on peroxisomal gene expression. Collectively, our results uncover a novel metabolic regulation of peroxisomes by lysosomes via PPARA-PPARGC1A transcriptional signalling. Abbreviations: Acox1: acyl-Coenzyme A oxidase 1, palmitoyl; Acot: acyl-CoA thioesterase; ACAA: acetyl-Coenzyme A acyltransferase; ABCD3/PMP70: ATP-binding cassette, sub-family D (ALD), member 3; BafA1: bafilomycin A₁; Crot: carnitine O-octanoyltransferase; CTSB: cathepsin B; Decr2: 2-4-dienoyl-Coenzyme A reductase 2, peroxisomal; Ech1: enoyl coenzyme A hydratase 1, peroxisomal; Ehhadh: enoyl-Coenzyme A, hydratase/3-hydroxyacyl Coenzyme A dehydrogenase; FDR: false discovery rate; Hsd17b4: hydroxysteroid (17-beta) dehydrogenase 4; NES: normalized enrichment score; NOM: nominal; Pex: peroxin; PPARA: peroxisome proliferator activated receptor alpha; PPARGC1A: peroxisome proliferator activated receptor, gamma, coactivator 1 alpha; TFEB: transcription factor EB.

Screening for the drug-phospholipid interaction: correlation to phospholipidosis

Phospholipid bilayers represent a complex, anisotropic environment fundamentally different from bulk oil or octanol, for instance. Even "simple" drug association to phospholipid bilayers can only be fully understood if the slab-of-hydrocarbon approach is abandoned and the complex, anisotropic properties of lipid bilayers reflecting the chemical structures and organization of the constituent phospholipids are considered. The interactions of drugs with phospholipids are important in various processes, such as drug absorption, tissue distribution, and subcellular distribution. In addition, drug-lipid interactions may lead to changes in lipid-dependent protein activities, and further, to functional and morphological changes in cells, a prominent example being the phospholipidosis (PLD) induced by cationic amphiphilic drugs. Herein we briefly review drug-lipid interactions in general and the significance of these interactions in PLD in particular. We also focus on a potential causal connection between drug-induced PLD and steatohepatitis, which is induced by some cationic amphiphilic drugs.

Secondary lipid accumulation in lysosomal disease

Lysosomal diseases are inherited metabolic disorders caused by defects in a wide spectrum of lysosomal and a few non-lysosomal proteins. In most cases a single type of primary storage material is identified, which has been used to name and classify the disorders: hence the terms sphingolipidoses, gangliosidoses, mucopolysaccharidoses, glycoproteinoses, and so forth. In addition to this primary storage, however, a host of secondary storage products can also be identified, more often than not having no direct link to the primary protein defect. Lipids - glycosphingolipids and phospholipids, as well as cholesterol - are the most ubiquitous and best studied of these secondary storage materials. While in the past typically considered nonspecific and nonconsequential features of these diseases, newer studies suggest direct links between secondary storage and disease pathogenesis and support the view that understanding all aspects of this sequestration process will provide important insights into the cell biology and treatment of lysosomal disease.

Abnormal cholesterol metabolism in imipramine-treated fibroblast cultures. Similarities with Niemann-Pick type C disease

Addition of low-density lipoprotein (LDL) to cholesterol-deprived human skin fibroblast cultures treated by imipramine at a 20 microM concentration induced a significant intracellular accumulation of unesterified cholesterol. Intracytoplasmic inclusions were already visible by histochemical filipin staining after 2 h of LDL uptake and were progressively mobilized towards the perinuclear region within 24 h. At this concentration of the drug, the rate of proteolytic 125I-LDL hydrolysis was similar in treated and untreated cells. Treated cells maintained in lipoprotein-deficient medium showed no abnormality, indicating the exogenous origin of the accumulated sterol. Further, the drug induced a drastic dose-dependent impairment of LDL-stimulated cholesterol esterification, not related to an inhibition of acyl CoA:cholesterol acyltransferase, and a significant delay in down-regulation of de novo cholesterol synthesis. However, imipramine did not affect 25-hydroxycholesterol-mediated regulation of the two latter processes. These results resemble those observed in Niemann-Pick type C disease and suggest an impaired mobilization of LDL-derived cholesterol in imipramine-treated cells.

Effect of chloroquine on the activity of some lysosomal enzymes involved in ganglioside degradation

Chronic chloroquine treatment of miniature pigs resulted in increased activity of several lysosomal enzymes of the liver and brain. The most affected enzyme was alpha-fucosidase which showed a 3-fold increase in liver (P less than 0.001) and a 2-fold increase in the brain (P less than 0.01). The increased activity of the other lysosomal enzymes was generally slightly more pronounced in the liver, in which beta-hexosaminidase, alpha-mannosidase and acid phosphatase were also significantly (P less than 0.01) increased. In contrast, chloroquine added in vitro reduced the activity of the lysosomal enzymes. Three of these, alpha-fucosidase, beta-hexosaminidase and acid phosphatase, were further investigated, and at a drug concentration of 15 mM and optimum pH for each respective enzyme, the activity was reduced to 20-30% of the initial value. Kinetic analyses revealed that this inhibition was non-competitive with regard to beta-hexosaminidase but competitive with regard to alpha-fucosidase. These results indicate that there is a multifactorial effect of chloroquine on the lysosomal enzymes, and that the inhibitory effect of alpha-fucosidase and beta-hexosaminidase might well explain the ganglioside storage found in liver and brain.

Comparison of receptors for cholera and Escherichia coli enterotoxins in human intestine

Extraction of lipids from human small intestinal epithelial cells or brush borders removed specific binding sites for cholera toxin completely, but only about 50% of the receptor sites for Escherichia coli heat-labile enterotoxin. Both cholera toxin and E. coli heat-labile enterotoxin bound strongly to ganglioside GM1 in the lipid extract and, to a lesser extent, to another monosialoganglioside and to GD1b. The results suggest that E. coli heat-labile enterotoxin binds to both ganglioside and glycoprotein receptor sites of the human small intestinal epithelium, whereas cholera toxin binding was restricted to the ganglioside receptors.

Systematically applied chemicals that damage lung tissue

A large, and increasing number of drugs and chemicals have been found which are toxic to lung following systemic administration. These agents damage lung tissue specifically, or in addition to damage to other tissues. Mechanisms explaining the pulmonary damage produced by some lung toxins have been uncovered. These include concentration of the agent within lung, the absence of adequate pulmonary detoxication systems, and bioactivation to a toxic species within specific lung cells or at distant sites followed by transport to the lung. The basic biochemical lesions underlying lung damage, responses of individual lung cells and pulmonary repair processes to the toxic agent, and species and age differences in susceptibility to lung damage have not, however, been well defined for most lung toxins. This review describes the information available on pulmonary biochemical and pathological changes associated with some of these lung-toxic agents. In addition, mechanisms proposed to explain the lung damage are discussed. The agents covered include: paraquat, the thioureas, butylated hydroxytoluene, the trialkylphosphorothioates, various lung-toxic furans and antineoplastic agents, the pyrrolizidine alkaloids, metals and organometallic compounds, amphiphilic agents, hydrocarbons, oleic acid, 3-methylindole, and diabetogenic agents. Detailed reviews on the overall toxicity of many of these agents have been published elsewhere. This review concentrates on their pulmonary toxicity. Information is presented as an overview to illustrate both the extensive literature that is available and the important questions that remain to be answered about systemic chemicals that damage lung tissue.

Pulmonary and generalized lysosomal storage induced by amphiphilic drugs

Administration of amphiphilic drugs to experimental animals causes formation of myelinoid bodies in many cell types, accumulation of foamy macrophages in pulmonary alveoli and pulmonary alveolar proteinosis. These changes are the result of an interaction between the drugs and phospholipids which leads to an alteration in physicochemical properties of the phospholipids. Impairment of the digestion of altered pulmonary secretions in phagosomes of macrophages results in accumulation of foam cells in pulmonary alveoli. Impairment of the metabolism of altered phospholipids removed by autophagy induces an accumulation of myelinoid bodies. The administration of amphiphilic compounds thus causes pulmonary intra-alveolar histiocytosis which is a part of a drug-induced lysosomal storage or generalized lipidosis. The accumulation of drug-lipid complexes in myelinoid bodies and in pulmonary foam cells may lead to alteration of cellular functioning and to clinical disease. Currently over 50 amphiphilic drugs are known. Unique pharmacological properties necessitate clinical use of some of these drugs. The occurrence and severity of potential clinical side effects depend on the nature of each drug, dosage and duration of treatment, simultaneous administration of other drugs and foods, individual metabolic pattern of the patient and other factors. Further studies on factors preventing and potentiating adverse effects of amphiphilic drugs are indicated.

Influence of acute injection of chloroquine on the biliary secretion of lipids and lysosomal enzyme on rats

Phospholipids and cholesterol combine with a protein fraction (IgA and an acid polypeptide) in bile to form the bile lipoprotein complex. We wished to determine whether lysosomes participated only on IgA secretion or if their secretory role also involved the lipid components of the bile complex. This aspect was studied with a single acute injection of chloroquine, a lysosomotropic drug. The results show that a nonnegligible quantity of IgA travels through the lysosomes. In addition, phospholipid and cholesterol levels undergo a significant (P less than 0.05) decrease 1 hr after injection before increasing to normal levels. In contrast to the total inhibition of protein secretion (beta-glucuronidase, acid phosphatase), a transitory decrease of the secretion of bile lipids takes place that suggest secretory mechanisms involving organelles other than lysosomes.

Biochemical studies in Niemann-Pick disease. I. Major sphingolipids of liver and spleen

In liver and spleen specimens of 12 patients with Niemann-Pick disease types A or B, sphingomyelin was increased 15-45-fold, total phospholipids 4-10-fold and cholesterol 3-6-fold over the normal values. The storage pattern was qualitatively similar in both types but the degree of accumulation was less in type B. In Niemann-Pick disease type C (16 cases), sphingomyelin was increased 3.5-fold in liver and 6-fold in spleen. In all forms of Niemann-Pick disease, bis(monoacylglycero)phosphate was markedly elevated. Glycosphingolipids were studied in six cases with type C, three cases with type B and two cases with type A. Glucosylceramide showed the largest increase from the normal pattern in all types of Niemann-Pick disease. Highest values were recorded in type C, 14- and 35-fold normal concentrations in liver and spleen, respectively. Other neutral glycosphingolipids, particularly lactosylceramide, were also elevated, and a 2-4-fold increase of ganglioside GM3 occurred. The fatty acid profiles of the sphingolipids showed only minor alterations. In contrast to the largely dominating sphingomyelin storage found in liver and spleen of Niemann-Pick disease types A and B, the major characteristic of the lipid storage in Niemann-Pick disease type C was the absence of any prevailing accumulation and, thus, the concept of this disorder as a primary sphingomyelin storage disease is not founded.