Knockdown of iPLA2γ enhances cisplatin-induced apoptosis by increasing ROS-dependent peroxidation of mitochondrial phospholipids in bladder cancer cells.

Cisplatin (CDDP) is a platinum-based drug with anti-cancer activity and is widely used as a standard therapy for bladder cancer. It is well known that CDDP causes cell death by increasing the generation of reactive oxygen species (ROS) and lipid peroxidation, but the mechanism of its anti-cancer effects has not been fully elucidated. There are still some problems such as chemoresistance in CDDP therapy. In the present study, we found the expression of Ca2+-independent phospholipase A2γ (iPLA2γ), which has been reported to regulate cellular redox homeostasis by inhibiting lipid peroxide accumulation, in human bladder cancer tissues. Thus, we investigated the effect of iPLA2γ knockdown on CDDP-induced bladder cancer cell death. As a result, we found that iPLA2γ knockdown significantly enhanced CDDP-induced apoptosis, intracellular and mitochondrial ROS production, cytochrome c release and caspase activation in bladder cancer cells. Moreover, mitochondrial membrane potential was decreased and peroxidation of mitochondrial phospholipids was increased by iPLA2γ knockdown. It was also shown that co-treatment of bromoenol lactone, an iPLA2 inhibitor, increased CDDP-induced apoptosis. These results indicated that iPLA2γ plays an important role in protecting bladder cancer cells from CDDP-induced apoptosis, and that iPLA2γ inhibitors might represent a novel strategy in CDDP-based multi-drug therapy.

Generation of induced pluripotent stem cell line LNDWCHi001-A from a patient with early-onset Parkinson's disease carrying the homozygous c.1898C > T (p. A633V) mutation in the PLA2G6 gene.

A variant of the phospholipase A2 group VI gene (PLA2G6, PARK14) has been found to cause early-onset Parkinson's disease (EOPD). In this study, we reprogrammed peripheral blood mononuclear cells from a 39-year-old patient with EOPD carrying a homozygous PLA2G6 mutation c.1898C > T (p. A633V) to generate the human induced pluripotent stem cell line LNDWCHi001-A. This cell line was identified based on pluripotent markers and displayed differentiation capacity, providing an essential model for studying the pathogenesis of EOPD and drug screening.

Exploring therapeutic strategies for infantile neuronal axonal dystrophy (INAD/PARK14).

Infantile neuroaxonal dystrophy (INAD) is caused by recessive variants in PLA2G6 and is a lethal pediatric neurodegenerative disorder. Loss of the Drosophila homolog of PLA2G6, leads to ceramide accumulation, lysosome expansion, and mitochondrial defects. Here, we report that retromer function, ceramide metabolism, the endolysosomal pathway, and mitochondrial morphology are affected in INAD patient-derived neurons. We show that in INAD mouse models, the same features are affected in Purkinje cells, arguing that the neuropathological mechanisms are evolutionary conserved and that these features can be used as biomarkers. We tested 20 drugs that target these pathways and found that Ambroxol, Desipramine, Azoramide, and Genistein alleviate neurodegenerative phenotypes in INAD flies and INAD patient-derived neural progenitor cells. We also develop an AAV-based gene therapy approach that delays neurodegeneration and prolongs lifespan in an INAD mouse model.

Dietary Inulin Supplementation Affects Specific Plasmalogen Species in the Brain.

Plasmalogens (Pls) are glycerophospholipids that play critical roles in the brain. Evidence supports the role of diet and that of the gut microbiota in regulating brain lipids. We investigated the impact of dietary intake of inulin-a soluble fiber used as prebiotic-on the Pl content of the cortex in mice. No global modification in the Pl amounts was observed when evaluated by gas chromatographic analysis of dimethyl acetals (DMAs). However, the analysis of individual molecular species of Pls by liquid chromatography revealed a reduced abundance of major species of ethanolamine Pls (PlsEtn)-PE(P-18:0/22:6) and PE(P-34:1)-in the cortex of mice fed a diet supplemented with inulin. DMA and expression levels of genes (Far-1, Gnpat, Agps, Pla2g6 and Tmem86b) encoding key enzymes of Pl biosynthesis or degradation were not altered in the liver and in the cortex of mice exposed to inulin. In addition, the fatty acid profile and the amount of lyso forms derived from PlsEtn were not modified in the cortex by inulin consumption. To conclude, inulin affects the brain levels of major PlsEtn and further investigation is needed to determine the exact molecular mechanisms involved.

Genome sequencing reveals novel noncoding variants in PLA2G6 and LMNB1 causing progressive neurologic disease.

Neurodegenerative disorders and leukodystrophies are progressive neurologic conditions that can occur following the disruption of intricately coordinated patterns of gene expression. Exome sequencing has been adopted as an effective diagnostic tool for determining the underlying genetic etiology of Mendelian neurologic disorders, however genome sequencing offer advantages in its ability to identify and characterize copy number, structural, and sequence variants in noncoding regions. Genome sequencing from peripheral leukocytes was performed on two patients with progressive neurologic disease of unknown etiology following negative genetic investigations including exome sequencing. RNA sequencing from peripheral blood was performed to determine gene expression patterns in one of the patients. Potential causative variants were matched to the patients' clinical presentation. The first proband was found to be heterozygous for a likely pathogenic missense variant in PLA2G6 (c.386T>C; p.Leu129Pro) and have an additional deep intronic variant in PLA2G6 (c.2035-926G>A). RNA sequencing indicated this latter variant created a splice acceptor site leading to the incorporation of a pseudo-exon introducing a premature termination codon. The second proband was heterozygous for a 261 kb deletion upstream of LMNB1 that included an enhancer region. Previous reports of copy number variants spanning this region of cis-acting regulatory elements corroborated its pathogenicity. When combined with clinical presentations, these findings led to a definitive diagnosis of autosomal recessive infantile neuroaxonal dystrophy and autosomal dominant adult-onset demyelinating leukodystrophy, respectively. In patients with progressive neurologic disease of unknown etiology, genome sequencing with the addition of RNA analysis where appropriate should be considered for the identification of causative noncoding pathogenic variants.

Vitamin E prevents lipid peroxidation and iron accumulation in PLA2G6-Associated Neurodegeneration.

BACKGROUND: PLA2G6-Associated Neurodegeneration (PLAN) is a rare neurodegenerative disease with autosomal recessive inheritance, which belongs to the NBIA (Neurodegeneration with Brain Iron Accumulation) group. Although the pathogenesis of the disease remains largely unclear, lipid peroxidation seems to play a central role in the pathogenesis. Currently, there is no cure for the disease. OBJECTIVE: In this work, we examined the presence of lipid peroxidation, iron accumulation and mitochondrial dysfunction in two cellular models of PLAN, patients-derived fibroblasts and induced neurons, and assessed the effects of α-tocopherol (vitamin E) in correcting the pathophysiological alterations in PLAN cell cultures. METHODS: Pathophysiological alterations were examined in fibroblasts and induced neurons generated by direct reprograming. Iron and lipofuscin accumulation were assessed using light and electron microscopy, as well as biochemical analysis techniques. Reactive Oxygen species production, lipid peroxidation and mitochondrial dysfunction were measured using specific fluorescent probes analysed by fluorescence microscopy and flow cytometry. RESULTS: PLAN fibroblasts and induced neurons clearly showed increased lipid peroxidation, iron accumulation and altered mitochondrial membrane potential. All these pathological features were reverted with vitamin E treatment. CONCLUSIONS: PLAN fibroblasts and induced neurons reproduce the main pathological alterations of the disease and provide useful tools for disease modelling. The main pathological alterations were corrected by Vitamin E supplementation in both models, suggesting that blocking lipid peroxidation progression is a critical therapeutic target.

Parkinson's Disease-Related Genes and Lipid Alteration.

Parkinson's disease (PD) is a complex and progressive neurodegenerative disorder with a prevalence of approximately 0.5-1% among those aged 65-70 years. Although most of its clinical manifestations are due to a loss of dopaminergic neurons, the PD etiology is largely unknown. PD is caused by a combination of genetic and environmental factors, and the exact interplay between genes and the environment is still debated. Several biological processes have been implicated in PD, including mitochondrial or lysosomal dysfunctions, alteration in protein clearance, and neuroinflammation, but a common molecular mechanism connecting the different cellular alterations remains incompletely understood. Accumulating evidence underlines a significant role of lipids in the pathological pathways leading to PD. Beside the well-described lipid alteration in idiopathic PD, this review summarizes the several lipid alterations observed in experimental models expressing PD-related genes and suggests a possible scenario in relationship to the molecular mechanisms of neuronal toxicity. PD could be considered a lipid-induced proteinopathy, where alteration in lipid composition or metabolism could induce protein alteration-for instance, alpha-synuclein accumulation-and finally neuronal death.

iPLA2ß-mediated lipid detoxification controls p53-driven ferroptosis independent of GPX4.

Here, we identify iPLA2ß as a critical regulator for p53-driven ferroptosis upon reactive oxygen species (ROS)-induced stress. The calcium-independent phospholipase iPLA2ß is known to cleave acyl tails from the glycerol backbone of lipids and release oxidized fatty acids from phospholipids. We found that iPLA2ß-mediated detoxification of peroxidized lipids is sufficient to suppress p53-driven ferroptosis upon ROS-induced stress, even in GPX4-null cells. Moreover, iPLA2ß is overexpressed in human cancers; inhibition of endogenous iPLA2ß sensitizes tumor cells to p53-driven ferroptosis and promotes p53-dependent tumor suppression in xenograft mouse models. These results demonstrate that iPLA2ß acts as a major ferroptosis repressor in a GPX4-independent manner. Notably, unlike GPX4, loss of iPLA2ß has no obvious effect on normal development or cell viability in normal tissues but iPLA2ß plays an essential role in regulating ferroptosis upon ROS-induced stress. Thus, our study suggests that iPLA2ß is a promising therapeutic target for activating ferroptosis-mediated tumor suppression without serious toxicity concerns.

The Impact of the Ca2+-Independent Phospholipase A2ß (iPLA2ß) on Immune Cells.

The Ca2+-independent phospholipase A2ß (iPLA2ß) is a member of the PLA2 family that has been proposed to have roles in multiple biological processes including membrane remodeling, cell proliferation, bone formation, male fertility, cell death, and signaling. Such involvement has led to the identification of iPLA2ß activation in several diseases such as cancer, cardiovascular abnormalities, glaucoma, periodontitis, neurological disorders, diabetes, and other metabolic disorders. More recently, there has been heightened interest in the role that iPLA2ß plays in promoting inflammation. Recognizing the potential contribution of iPLA2ß in the development of autoimmune diseases, we review this issue in the context of an iPLA2ß link with macrophages and T-cells.

Phospholipase iPLA2ß averts ferroptosis by eliminating a redox lipid death signal.

Ferroptosis, triggered by discoordination of iron, thiols and lipids, leads to the accumulation of 15-hydroperoxy (Hp)-arachidonoyl-phosphatidylethanolamine (15-HpETE-PE), generated by complexes of 15-lipoxygenase (15-LOX) and a scaffold protein, phosphatidylethanolamine (PE)-binding protein (PEBP)1. As the Ca2+-independent phospholipase A2ß (iPLA2ß, PLA2G6 or PNPLA9 gene) can preferentially hydrolyze peroxidized phospholipids, it may eliminate the ferroptotic 15-HpETE-PE death signal. Here, we demonstrate that by hydrolyzing 15-HpETE-PE, iPLA2ß averts ferroptosis, whereas its genetic or pharmacological inactivation sensitizes cells to ferroptosis. Given that PLA2G6 mutations relate to neurodegeneration, we examined fibroblasts from a patient with a Parkinson's disease (PD)-associated mutation (fPDR747W) and found selectively decreased 15-HpETE-PE-hydrolyzing activity, 15-HpETE-PE accumulation and elevated sensitivity to ferroptosis. CRISPR-Cas9-engineered Pnpla9R748W/R748W mice exhibited progressive parkinsonian motor deficits and 15-HpETE-PE accumulation. Elevated 15-HpETE-PE levels were also detected in midbrains of rotenone-infused parkinsonian rats and α-synuclein-mutant SncaA53T mice, with decreased iPLA2ß expression and a PD-relevant phenotype. Thus, iPLA2ß is a new ferroptosis regulator, and its mutations may be implicated in PD pathogenesis.

Type 1 interferon-dependent repression of NLRC4 and iPLA2 licenses down-regulation of Salmonella flagellin inside macrophages.

Inflammasomes have been implicated in the detection and clearance of a variety of bacterial pathogens, but little is known about whether this innate sensing mechanism has any regulatory effect on the expression of stimulatory ligands by the pathogen. During infection with Salmonella and many other pathogens, flagellin is a major activator of NLRC4 inflammasome-mediated macrophage pyroptosis and pathogen eradication. Salmonella switches to a flagellin-low phenotype as infection progresses to avoid this mechanism of clearance by the host. However, the host cues that Salmonella perceives to undergo this switch remain unclear. Here, we report an unexpected role of the NLRC4 inflammasome in promoting expression of its microbial ligand, flagellin, and identify a role for type 1 IFN signaling in switching of Salmonella to a flagellin-low phenotype. Early in infection, activation of NLRC4 by flagellin initiates pyroptosis and concomitant release of lysophospholipids which in turn enhance expression of flagellin by Salmonella thereby amplifying its ability to elicit cell death. TRIF-dependent production of type 1 IFN, however, later represses NLRC4 and the lysophospholipid biosynthetic enzyme iPLA2, causing a decline in intracellular lysophospholipids that results in down-regulation of flagellin expression by Salmonella These findings reveal a previously unrecognized immune-modulating regulatory cross-talk between endosomal TLR signaling and cytosolic NLR activation with significant implications for the establishment of infection with Salmonella.

PLA2G6 guards placental trophoblasts against ferroptotic injury.

The recently identified ferroptotic cell death is characterized by excessive accumulation of hydroperoxy-arachidonoyl (C20:4)- or adrenoyl (C22:4)- phosphatidylethanolamine (Hp-PE). The selenium-dependent glutathione peroxidase 4 (GPX4) inhibits ferroptosis, converting unstable ferroptotic lipid hydroperoxides to nontoxic lipid alcohols in a tissue-specific manner. While placental oxidative stress and lipotoxicity are hallmarks of placental dysfunction, the possible role of ferroptosis in placental dysfunction is largely unknown. We found that spontaneous preterm birth is associated with ferroptosis and that inhibition of GPX4 causes ferroptotic injury in primary human trophoblasts and during mouse pregnancy. Importantly, we uncovered a role for the phospholipase PLA2G6 (PNPLA9, iPLA2beta), known to metabolize Hp-PE to lyso-PE and oxidized fatty acid, in mitigating ferroptosis induced by GPX4 inhibition in vitro or by hypoxia/reoxygenation injury in vivo. Together, we identified ferroptosis signaling in the human and mouse placenta, established a role for PLA2G6 in attenuating trophoblastic ferroptosis, and provided mechanistic insights into the ill-defined placental lipotoxicity that may inspire PLA2G6-targeted therapeutic strategies.

Rescue of Hepatic Phospholipid Remodeling Defectin iPLA2ß-Null Mice Attenuates Obese but Not Non-Obese Fatty Liver.

Polymorphisms of group VIA calcium-independent phospholipase A2 (iPLA2ß orPLA2G6) are positively associated with adiposity, blood lipids, and Type-2 diabetes. Theubiquitously expressed iPLA2ß catalyzes the hydrolysis of phospholipids (PLs) to generate a fattyacid and a lysoPL. We studied the role of iPLA2ß on PL metabolism in non-alcoholic fatty liverdisease (NAFLD). By using global deletion iPLA2ß-null mice, we investigated three NAFLD mousemodels; genetic Ob/Ob and long-term high-fat-diet (HFD) feeding (representing obese NAFLD) aswell as feeding with methionine- and choline-deficient (MCD) diet (representing non-obeseNAFLD). A decrease of hepatic PLs containing monounsaturated- and polyunsaturated fatty acidsand a decrease of the ratio between PLs and cholesterol esters were observed in all three NAFLDmodels. iPLA2ß deficiency rescued these decreases in obese, but not in non-obese, NAFLD models.iPLA2ß deficiency elicited protection against fatty liver and obesity in the order of Ob/Ob > HFD ¼MCD. Liver inflammation was not protected in HFD NAFLD, and that liver fibrosis was evenexaggerated in non-obese MCD model. Thus, the rescue of hepatic PL remodeling defect observedin iPLA2ß-null mice was critical for the protection against NAFLD and obesity. However, iPLA2ßdeletion in specific cell types such as macrophages may render liver inflammation and fibrosis,independent of steatosis protection.

Gene Deletion of Calcium-Independent Phospholipase A2γ (iPLA2γ) Suppresses Adipogenic Differentiation of Mouse Embryonic Fibroblasts.

Adipogenic differentiation is a complex process by which fibroblast-like undifferentiated cells are converted into cells that accumulate lipid droplets. We here investigated the effect of gene deletion of calcium-independent phospholipase A2γ (iPLA2γ), a membrane-bound PLA2 enzyme, on adipogenic differentiation in mice. Since iPLA2γ knockout (KO) mice showed reduced fat volume and weight, we prepared mouse embryonic fibroblasts (MEF) from wild-type (WT) and iPLA2γ KO mice and examined the effect of iPLA2γ deletion on in vitro adipogenic differentiation. iPLA2γ increased during adipogenic differentiation in WT mouse-derived MEFs, and the differentiation was partially abolished in iPLA2γ KO-derived MEFs. In KO-derived MEFs, the inductions of peroxisome proliferator activator receptor γ (PPARγ) and CAAT/enhancer-binding protein α (C/EBPα) were also reduced during adipogenic differentiation, and the reductions in PPARγ and C/EBPα expressions and the defect in adipogenesis were restored by treatment with troglitazone, a PPARγ ligand. These results indicate that iPLA2γ might play a critical role in adipogenic differentiation by regulating PPARγ expression.

12-LOX catalyzes the oxidation of 2-arachidonoyl-lysolipids in platelets generating eicosanoid-lysolipids that are attenuated by iPLA2γ knockout.

The canonical pathway of eicosanoid production in most mammalian cells is initiated by phospholipase A2-mediated release of arachidonic acid, followed by its enzymatic oxidation resulting in a vast array of eicosanoid products. However, recent work has demonstrated that the major phospholipase in mitochondria, iPLA2γ (patatin-like phospholipase domain containing 8 (PNPLA8)), possesses sn-1 specificity, with polyunsaturated fatty acids at the sn-2 position generating polyunsaturated sn-2-acyl lysophospholipids. Through strategic chemical derivatization, chiral chromatographic separation, and multistage tandem MS, here we first demonstrate that human platelet-type 12-lipoxygenase (12-LOX) can directly catalyze the regioselective and stereospecific oxidation of 2-arachidonoyl-lysophosphatidylcholine (2-AA-LPC) and 2-arachidonoyl-lysophosphatidylethanolamine (2-AA-LPE). Next, we identified these two eicosanoid-lysophospholipids in murine myocardium and in isolated platelets. Moreover, we observed robust increases in 2-AA-LPC, 2-AA-LPE, and their downstream 12-LOX oxidation products, 12(S)-HETE-LPC and 12(S)-HETE-LPE, in calcium ionophore (A23187)-stimulated murine platelets. Mechanistically, genetic ablation of iPLA2γ markedly decreased the calcium-stimulated production of 2-AA-LPC, 2-AA-LPE, and 12-HETE-lysophospholipids in mouse platelets. Importantly, a potent and selective 12-LOX inhibitor, ML355, significantly inhibited the production of 12-HETE-LPC and 12-HETE-LPE in activated platelets. Furthermore, we found that aging is accompanied by significant changes in 12-HETE-LPC in murine serum that were also markedly attenuated by iPLA2γ genetic ablation. Collectively, these results identify previously unknown iPLA2γ-initiated signaling pathways mediated by direct 12-LOX oxidation of 2-AA-LPC and 2-AA-LPE. This oxidation generates previously unrecognized eicosanoid-lysophospholipids that may serve as biomarkers for age-related diseases and could potentially be used as targets in therapeutic interventions.

Extract of Danggui-Shaoyao-San ameliorates cognition deficits by regulating DHA metabolism in APP/PS1 mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The traditional Chinese medicine formula Danggui-Shaoyao-San (DSS) has been reported to show therapeutic effect on alleviating the symptoms of Alzheimer's disease (AD). AIM OF THE STUDY: The present study aims to investigate the relation between DSS treatment of AD and DHA metabolism and evaluates its neuroprotective effect on cognitive in APP/PS1 mice. MATERIAL AND METHODS: DSS (1.6, 3.2, 6.4 g/kg/day) or Aricept (3 mg/kg/day) was orally administered (i.g.) to APP/PS1 mice, and saline was orally administered to Wild-type (WT) male mice as control group. Then, the Morris water maze (MWM) test, Y-maze spontaneous alternation test, open filed test and fear conditioning test were conducted for evaluation of learning and memory abilities. The DHA content was assessed by HPLC-MS/MS. Physiological indices were determined, including triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), ROS level, activity of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), PEG2, TXB2 and LTB4. The expressions of COX-1, COX-2, cPLA2, iPLA2, 15-LOX, and were assessed by Western blot. RESULTS: APP/PS1 mice showed serious cognitive impairment in behavioral tests. However, treatment of DSS extract significantly ameliorated the cognitive deficits of APP/PS1 mice. Biochemical measurements showed the increases in TG, TC, LDL-c and the decrease in HDL-c in APP/PS1 mice compared with WT mice, and DSS extract significantly retarded these changes. Low content of DHA, low expression of iPLA2 and 15-LOX were observed both in hippocampus and cortex of APP/PS1 mice, while DSS extract significantly restored these changes. Additionally, the abnormal activity of SOD and ROS level, the decreased levels of MDA and GSH were observed in APP/PS1 mice, while DSS extract prominently lessened these changes. Moreover, DSS extract decreased the level of PEG2, TXB2 and LTB4 and also attenuated the expression of cPLA2, COX-1 and COX-2 in hippocampus as well as cortex of APP/PS1 mice. CONCLUSIONS: Based on these results, we suggest that DSS play a positive effective role in increasing DHA content by up-regulating iPLA2 and 15-LOX, resulting in ameliorating oxidative stress and inflammation and finally ameliorating cognition deficits in APP/PS1 mice.

Alzheimer's disease: The derailed repair hypothesis.

A lot of research has been done on Alzheimer's disease, especially focused on factors like amyloid beta, ApoE and tau-protein. However, a complete theory on the disease mechanism of AD, including and connecting all known pathological elements of AD in a conceivable context and order of occurrence, is still lacking. In this article I describe a hypothesis on the entire pathophysiology of Alzheimer's disease, based on the most wellknown pathological elements in AD, filling the gaps with hypothetical mechanisms. This proposed mechanism of derailed repair starts with an insufficiently increased level of injury signalling in the axon by ApoE, DLK, APP, BACE-1, Aß and iPLA2ß, followed by an excessive repair response induced by opening of the mitochondrial permeability transition pore, release of mitochondrial CoA and activation of palmitoylation and massive endocytosis. Excessive compounds, associated with injury signalling and repair, start to accumulate, adding to axonal injury. This increased activation of the repair mechanism causes exhaustion of the repair response by lack of mitochondrial CoA. A vicious circle of increased injury signalling and insufficient repair ensues. Based on this hypothesis, I propose possible markers for early diagnosis and disease-modifying treatments for Alzheimer's disease.

Generation of induced pluripotent stem cells from a young-onset Parkinson's disease patient carrying the compound heterozygous PLA2G6 p.D331Y/p.M358IfsX mutations.

Mutations in PLA2G6 gene cause PLA2G6-associated neurodegeneration, including recessive familial type 14 of Parkinson's disease (PARK14). Previously, we identified PARK14 patients with compound heterozygous c.991G > T/c.1077G > A (p.D331Y/p.M358IfsX) mutations. The c.1077G > A mutation led to a four base-pairs deletion and frameshift mutation (p.M358IfsX) of PLA2G6 mRNA. We established induced pluripotent stem cells (iPSCs) from peripheral blood mononuclear cells of a female patient with compound heterozygous c.991G > T/c.1077G > A (p.D331Y/ p.M358IfsX) mutations by using Sendai-virus delivery system. The iPSCs exhibited pluripotency and in vivo differentiation potential. The iPSCs can be used for studying the molecular pathogenic mechanism of PARK14.

Parkinson's disease-associated iPLA2-VIA/PLA2G6 regulates neuronal functions and α-synuclein stability through membrane remodeling.

Mutations in the iPLA2-VIA/PLA2G6 gene are responsible for PARK14-linked Parkinson's disease (PD) with α-synucleinopathy. However, it is unclear how iPLA2-VIA mutations lead to α-synuclein (α-Syn) aggregation and dopaminergic (DA) neurodegeneration. Here, we report that iPLA2-VIA-deficient Drosophila exhibits defects in neurotransmission during early developmental stages and progressive cell loss throughout the brain, including degeneration of the DA neurons. Lipid analysis of brain tissues reveals that the acyl-chain length of phospholipids is shortened by iPLA2-VIA loss, which causes endoplasmic reticulum (ER) stress through membrane lipid disequilibrium. The introduction of wild-type human iPLA2-VIA or the mitochondria-ER contact site-resident protein C19orf12 in iPLA2-VIA-deficient flies rescues the phenotypes associated with altered lipid composition, ER stress, and DA neurodegeneration, whereas the introduction of a disease-associated missense mutant, iPLA2-VIA A80T, fails to suppress these phenotypes. The acceleration of α-Syn aggregation by iPLA2-VIA loss is suppressed by the administration of linoleic acid, correcting the brain lipid composition. Our findings suggest that membrane remodeling by iPLA2-VIA is required for the survival of DA neurons and α-Syn stability.

Amorphous solid dispersion of Berberine mitigates apoptosis via iPLA2ß/Cardiolipin/Opa1 pathway in db/db mice and in Palmitate-treated MIN6 ß-cells.

Aims: Berberine (BBR) improves beta-cell function in Type 2 diabetes (T2D) because of its anti-apoptotic activity, and our laboratory developed a new preparation named Huang-Gui Solid Dispersion (HGSD) to improve the oral bioavailability of BBR. However, the mechanism by which BBR inhibits beta-cell apoptosis is unclear. We hypothesized that the Group VIA Ca2+-Independent Phospholipase A2 (iPLA2ß)/Cardiolipin(CL)/Opa1 signaling pathway could exert a protective role in T2D by regulating beta-cell apoptosis and that HGSD could inhibit ß-cell apoptosis through iPLA2ß/CL/Opa1 upregulation. Methods: We examined how iPLA2ß and BBR regulated apoptosis and insulin secretion through CL/Opa1 in vivo and in vitro. In in vitro studies, we developed Palmitate(PA)-induced apoptotic cell death model in mouse insulinoma cells (MIN6). iPLA2ß overexpression and silencing technology were used to examine how the iPLA2ß/CL/Opa1 interaction may play an important role in BBR treatment. In in vivo studies, db/db mice were used as a diabetic animal model. The pancreatic islet function and morphology, beta-cell apoptosis and mitochondrial injury were examined to explore the effects of HGSD. The expression of iPLA2ß/CL/Opa1 was measured to explore whether the signaling pathway was damaged in T2D and was involved in HGSD treatment. Results: The overexpression of iPLA2ß and BBR treatment significantly attenuated Palmitate- induced mitochondrial injury and apoptotic death compared with Palmitate-treated MIN6 cell. In addition, iPLA2ß silencing could simultaneously partly abolish the anti-apoptotic effect of BBR and decrease CL/Opa1 signaling in MIN6 cells. Moreover, HGSD treatment significantly decreased beta-cell apoptosis and resulted in the upregulation of iPLA2ß/CL/Opa1 compared to those of the db/db mice. Conclusion: The results indicated that the regulation of iPLA2ß/CL/Opa1 by HGSD may prevent beta-cell apoptosis and may improve islet beta-cell function in Type 2 diabetic mice and in palmitate-treated MIN6 cells.