Independent Phospholipase Research Articles

Differential lipid signaling from CD4+ and CD8+ T cells contributes to type 1 diabetes development.

We reported that Ca2+-independent phospholipase A2β (iPLA2β)-derived lipids (iDLs) contribute to type 1 diabetes (T1D) onset. As CD4+ and CD8+ T cells are critical in promoting β-cell death, we tested the hypothesis that iDL signaling from these cells participates in T1D development. CD4+ and CD8+ T cells from wild-type non-obese diabetic (NOD) and NOD.iPLA2β+/- (NOD.HET) mice were administered in different combinations to immunodeficient NOD.scid. In mice receiving only NOD T cells, T1D onset was rapid (5 weeks), incidence 100% by 20 weeks, and islets absent. In contrast, onset was delayed 1 week and incidence reduced 40%-50% in mice receiving combinations that included NOD.HET T cells. Consistently, islets from these non-diabetic mice were devoid of infiltrate and contained insulin-positive β-cells. Reduced iPLA2β led to decreased production of proinflammatory lipids from CD4+ T cells including prostaglandins and dihydroxyeicosatrienoic acids (DHETs), products of soluble epoxide hydrolase (sEH), and inhibition of their signaling decreased (by 82%) IFNγ+CD4+ cells abundance. However, only DHETs production was reduced from CD8+ T cells and was accompanied by decreases in sEH and granzyme B. These findings suggest that differential select iDL signaling in CD4+ and CD8+ T cells contributes to T1D development, and that therapeutics targeting such signaling might be considered to counter T1D.

Selective Reduction of Ca2+-Independent Phospholipase A2β (iPLA2β)-Derived Lipid Signaling from Macrophages Mitigates Type 1 Diabetes Development.

Type 1 diabetes (T1D) is a consequence of autoimmune destruction of β-cells and macrophages (MΦ) have a central role in initiating processes that lead to β-cell demise. We reported that Ca2+-independent phospholipase A2β (iPLA2β)-derived lipid (iDL) signaling contributes to β-cell death. As MΦ express iPLA2β, we assessed its role in T1D development. We find that selective reduction of myeloid-iPLA2β in spontaneously diabetes-prone nonobese diabetic (NOD) mice (a) deceases proinflammatory eicosanoid production by MΦ, (b) favors anti-inflammatory (M2-like) MΦ phenotype, and (c) diminishes activated CD4+ and CD8+ T-cells phenotype in the pancreatic infiltrate, prior to T1D onset. These outcomes are associated with a significant reduction in T1D. Further, inhibition of select proinflammatory lipid signaling pathways reduces M1-like MΦ polarization and adoptive transfer of M2-like MΦ reduces NOD T1D incidence, suggesting a mechanism by which iDLs impact T1D development. These findings identify MΦ-iPLA2β as a critical contributor to TID development and potential target to counter T1D onset.

Reactive oxygen species in endothelial signaling in COVID-19: Protective role of the novel peptide PIP-2.

Recent research suggests that endothelial activation plays a role in coronavirus disease 2019 (COVID-19) pathogenesis by promoting a pro-inflammatory state. However, the mechanism by which the endothelium is activated in COVID-19 remains unclear. To investigate the mechanism by which COVID-19 activates the pulmonary endothelium and drives pro-inflammatory phenotypes. The "inflammatory load or burden" (cytokine storm) of the systemic circulation activates endothelial NADPH oxidase 2 (NOX2) which leads to the production of reactive oxygen species (ROS) by the pulmonary endothelium. Endothelial ROS subsequently activates pro-inflammatory pathways. The inflammatory burden of COVID-19 on the endothelial network, was recreated in vitro, by exposing human pulmonary microvascular endothelial cells (HPMVEC) to media supplemented with serum from COVID-19 affected individuals (sera were acquired from patients with COVID-19 infection that eventually died. Sera was isolated from blood collected at admission to the Intensive Care Unit of the Hospital of the University of Pennsylvania). Endothelial activation, inflammation and cell death were assessed in HPMVEC treated with serum either from patients with COVID-19 or from healthy individuals. Activation was monitored by measuring NOX2 activation (Rac1 translocation) and ROS production; inflammation (or appearance of a pro-inflammatory phenotype) was monitored by measuring the induction of moieties such as intercellular adhesion molecule (ICAM-1), P-selectin and the NLRP3 inflammasome; cell death was measured via SYTOX™ Green assays. Endothelial activation (i.e., NOX2 activation and subsequent ROS production) and cell death were significantly higher in the COVID-19 model than in healthy samples. When HPMVEC were pre-treated with the novel peptide PIP-2, which blocks NOX2 activation (via inhibition of Ca2+-independent phospholipase A2, aiPLA2), significant abrogation of ROS was observed. Endothelial inflammation and cell death were also significantly blunted. The endothelium is activated during COVID-19 via cytokine storm-driven NOX2-ROS activation, which causes a pro-inflammatory phenotype. The concept of endothelial NOX2-ROS production as a unifying pathophysiological axis in COVID-19 raises the possibility of using PIP-2 to maintain vascular health.

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.

Involvement of the Mitochondrial Ca2+-Independent Phospholipase iPLA2 in the Induction of Mitochondrial Permeability Transition Pore by Long-Chain Acylcarnitines

Involvement of the Mitochondrial Ca2+-Independent Phospholipase iPLA2 in the Induction of Mitochondrial Permeability Transition Pore by Long-Chain Acylcarnitines

Structural and Functional Diversity of the Peroxiredoxin 6 Enzyme Family.

Significance: Peroxiredoxins (Prdxs) with a single peroxidative cysteine (CP) in a conserved motif PXXX(T/S)XXCP within its thioredoxin fold, have been classified as the peroxiredoxin 6 (Prdx6 ) family. All Prdxs can reduce H2O2 and short chain hydroperoxides while Prdx6 in addition, can reduce phospholipid hydroperoxides (PLOOH) due to its ability to interact with peroxidized phospholipid substrate. The single CP of Prdx6 uses various external electron donors including glutathione thioredoxin, and ascorbic acid for resolution of its peroxidized state and, therefore, its peroxidase activity. Prdx6 proteins also exhibit Ca2+-independent phospholipase A2 (PLA2), lysophosphatidylcholine acyltransferase (LPCAT), and chaperone activities that depend on cellular localization and the oxidation and oligomerisation states of the protein. Thus, Prdx6 is a "moonlighting" enzyme. Recent Advance: Physiologically, Prdx6s have been reported to play an important role in protection against oxidative stress, repair of peroxidized cell membranes, mammalian lung surfactant turnover, activation of some NADPH oxidases, the regulation of seed germination in plants, as an indicator of cellular levels of reactive O2 species through Nrf-Klf9 activation, and possibly in male fertility, regulation of cell death through ferroptosis, cancer metastasis, and oxidative stress-related signalling pathways. Critical Issues: This review outlines Prdx6 enzyme unique structural features and explores its wide range of physiological functions. Yet, existing structural data falls short of fully revealing all of human Prdx6 multifunctional roles. Further endeavour is required to bridge this gap in its understanding. Although there are wide variations in both the structure and function of Prdx6 family members in various organisms, all Prdx6 proteins show the unique a long C-terminal extension that is also seen in Prdx1, but not in other Prdxs. Future Directions: As research data continues to accumulate, the potential for detailed insights into the role of C-terminal of Prdx6 in its oligomerisation and activities. There is a need for thorough exploration of structural characteristics of the various biological functions. Additionally, uncovering the interacting partners of Prdx6 and understanding its involvement in signalling pathways will significantly contribute to a more profound comprehension of its role.

1488-P: Reduced iPLA2b Expression in T-Lymphocytes Decreases Proinflammatory Eicosanoid Production and Cytokine Secretion Delaying Type 1 Diabetes Development in NOD Mice

Type 1 diabetes (T1D) is characterized by the destruction of insulin-producing pancreatic islet β-cells, but the causes of this process remain unclear. We find that Ca2+-independent phospholipase A2β (iPLA2β), which hydrolyzes membrane phospholipids at the sn-2 substituent to yield iPLA2β-derived lipids (iDLs), is induced under a diabetic milieu and mitigation of iPLA2β activity attenuates β-cell death. Several iDLs are pro-inflammatory and have been studied in different diseases but are not understood in diabetes. We investigated the role of immune-cell iDLs by utilizing T-cell adoptive transfer. Isolated CD4+/8+ T-cells from splenocytes prepared from donor female NOD and NOD. iPLA2β+/− (HET) mice, were transferred i.p. to NOD.scid recipient mice. We observed T1D onset for all T-cell recipient groups between 10-12 weeks of age. However, reduction of iPLA2β in CD4/8 T-cells delayed 50% incidence by 10 weeks in NOD4/HET8-recipient mice and HET4/NOD8 T-cell recipients compared to “matched” T-cell recipients. Furthermore, reduced insulitis and increased β-cell preservation was detected in HET4/NOD8-recipients compared to NOD4/8 recipients. The immune cell composition between our genotypes revealed no difference suggesting iDL signaling contributes to the observed incidence. Lipidomic analyses revealed a decrease in pro-inflammatory eicosanoids (PGs, DHETs and HETEs) in nondiabetic recipient mice, compared to diabetic counterparts. In addition, by targeting select eicosanoid signaling (PGE2 and DHET) utilizing chemical inhibitors (i.e., Grapiprant (EP4 receptor antagonist) and EC5026 (soluble epoxide hydrolase inhibitor)), we observed decreased IFN-γ production by Th1 helper cells in HET donors compared to NOD. These findings suggest that iPLA2β in T-cells is a critical contributor to the production of pro-inflammatory iDLs and could be a potential target in reducing T1D development. Disclosure T. White: None. S. Ramanadham: None. T.P. DiLorenzo: None. C.E. Chalfant: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK069455); National Institute of Allergy and Infectious Diseases (R21AI146743, R21AI169214); JDRF (2-SRA-2022-1210-S-B); University of Alabama at Birmingham (5T32GM8111-34)

32-OR: Reduction of Macrophage-iPLA2ß–Derived Proinflammatory Lipids Inhibit Type 1 Diabetes Development

Type 1 diabetes (T1D) is a consequence of autoimmune-mediated destruction of pancreatic β-cells, but the leading causes for this process remain elusive. Our lab revealed that Ca2+-independent phospholipase A2β (iPLA2β) modulates the polarization of macrophages (MΦ). Recently, we showed that selective iPLA2β-derived lipid signals (iDLs) produced by MΦ from spontaneous-T1D prone mice (NOD) is high during the pre-diabetic phase. Therefore, we examined the impact of bone marrow-derived macrophages (BMD-MΦ)-iDLs on T1D development by generating NOD mice with conditional reduction in MΦ-iPLA2β (NOD. cM Φ iPLA2𝛽;-/- and NOD. cM Φ iPLA2𝛽;+/-). Our data show that BMD-MΦ from NOD. cM Φ iPLA2𝛽;-/- or NOD. cMΦiPLA2𝛽;+/- are skewed towards an M2 anti-inflammatory phenotype, compared with NOD BMD-MΦ. Also, BMD-MΦ from NOD.cMΦiPLA2𝛽;-/- and NOD.cMΦiPLA2𝛽;+/- have significantly less proinflammatory lipids (PGs, DHETs, and TXB2), compared to NOD BMD-MΦ. Moreover, selective inhibition of PGE2 (EP4 antagonist) or DHET (TPPU) signaling inhibits NOD BMD-MΦ polarization towards an M1 proinflammatory phenotype, as reflected by reductions in M1 markers (Arg2, CXCL10, STAT1, and TNFα) and increases in M2 markers (Arg1, RELA, STAT6, and MRC1). Furthermore, pancreata from NOD.cMΦiPLA2𝛽;-/- and NOD.cMΦiPLA2𝛽;+/- have significantly reduced immune cell (CD4, CD8 and, CD19) infiltration and a higher abundance of M2 anti-inflammatory macrophages relative to NOD pancreata. These outcomes were associated with improved glucose tolerance and significant reduction of T1D incidence in the NOD.cMΦiPLA2𝛽;-/- and NOD.cMΦiPLA2𝛽;+/-, as compared with the incidence in the NOD mice. In summary, reduction of select proinflammatory iDLs production by BMD-MΦ favors M2 anti-inflammatory phenotype, reduced T1D pathogenesis, and T1D incidence. We conclude that MΦ-iDLs contribute to T1D onset and that inhibition of selected macrophages-derived iDLs production can be targeted to counter T1D development Disclosure A.Almutairi: None. Y.Gai: None. J.Nadler: None. C.E.Chalfant: None. S.Ramanadham: None.

The Lysophospholipase PNPLA7 Controls Hepatic Choline and Methionine Metabolism.

The in vivo roles of lysophospholipase, which cleaves a fatty acyl ester of lysophospholipid, remained unclear. Recently, we have unraveled a previously unrecognized physiological role of the lysophospholipase PNPLA7, a member of the Ca2+-independent phospholipase A2 (iPLA2) family, as a key regulator of the production of glycerophosphocholine (GPC), a precursor of endogenous choline, whose methyl groups are preferentially fluxed into the methionine cycle in the liver. PNPLA7 deficiency in mice markedly decreases hepatic GPC, choline, and several metabolites related to choline/methionine metabolism, leading to various symptoms reminiscent of methionine shortage. Overall metabolic alterations in the liver of Pnpla7-null mice in vivo largely recapitulate those in methionine-deprived hepatocytes in vitro. Reduction of the methyl donor S-adenosylmethionine (SAM) after methionine deprivation decreases the methylation of the PNPLA7 gene promoter, relieves PNPLA7 expression, and thereby increases GPC and choline levels, likely as a compensatory adaptation. In line with the view that SAM prevents the development of liver cancer, the expression of PNPLA7, as well as several enzymes in the choline/methionine metabolism, is reduced in human hepatocellular carcinoma. These findings uncover an unexplored role of a lysophospholipase in hepatic phospholipid catabolism coupled with choline/methionine metabolism.

Bilateral varicocele leads to ferroptosis, pyroptosis and necroptosis of human spermatozoa and affects semen quality in infertile men.

Purpose: This study explored the effects of bilateral varicocele on male semen quality in infertile men and the molecular mechanisms involving ferroptosis, pyroptosis and necroptosis signaling pathways. Methods: Totally, 20 healthy males and 26 patients with bilateral varicocele receiving infertility treatment were enrolled. Semen samples were collected. Basic semen parameters, acrosome integrity and membrane integrity, mitochondrial membrane potential (MMP) and apoptosis rate were compared. Levels of reactive oxygen species (ROS), iron, glutathione (GSH), total superoxide dismutase (T-SOD), and, Catalase (CAT), were detected in human seminal plasma. Relative mRNA expression of Ca 2+-independent phospholipases A2 beta (iPLA 2β), P53, Zinc finger E-box binding homeobox 1 (ZEB1) and GSH-dependent peroxidase 4 (GPX4) were evaluated. Relative protein expression was determined for GPX4, receptor interacting serine/threonine kinase 1 (RIPK1) and receptor interacting serine/threonine kinase 3 (RIPK3), as well as pyroptosis markers of Gasdermin E (GSDME) and heat shock protein 90 (HSP 90). Results: The results revealed that the bilateral varicocele group had significantly higher abnormalities (sperm progressive rate and sperm motility) compared to the control group. Meanwhile, compared to control group, GSH, T-SOD, and CAT levels were reduced in the bilateral varicocele group (p < 0.05). However, the level of ROS and iron were significantly increased (p < 0.05). Relative mRNA expression of P53, iPLA 2β, ZEB1, and GPX4 were reduced. In addition, ROS exposure activated ferroptosis-related signal pathways. RIPK1, RIPK3, GSDME and HSP 90 were increased in bilateral varicocele group. ROS exposure affected signaling pathways related to ferroptosis, necrosis and pyroptosis in human spermatozoa. Conclusion: Bilateral varicocele leads to ferroptosis, pyroptosis and necroptosis of human spermatozoa and affects semen quality in infertile men.

Peroxiredoxin 6 Regulates Glia Toxicity in Tau Mediated Neurodegeneration

AbstractBackgroundIn Alzheimer’s disease (AD) neurons, which accumulate hyperphosphorylated tau (p‐tau) are associated with neurodegenerative phenotype microglia (MGnD) and A1 neurotoxic astrocytes. MGnD display reduced ability to phagocytose p‐tau aggregates and neuronal remnants, while their pro‐inflammatory character furthers p‐tau accumulation and neuronal demise. Likewise, A1 astrocytes lose their neuron‐supporting function and promote neurodegeneration. Importantly, MGnD and A1 astrocytes reciprocally stimulate their pathological phenotypes. Factors protecting astrocytes form A1 phenotype transformation are unknown. In this work we explored the role of peroxiredoxin (PRDX) 6 in tau mediated neurodegeneration. PRDX6 is an enzymatic protein which in the CNS is unique to astrocytes. It possesses independent glutathione peroxidase and phospholipase 2 enzymatic activities, which confer ability to repair oxidatively damaged cell membranes and cell‐to‐cell signaling.Method MAPT P301S mutant mice (PS19/Prdx6 +/+) were once crossed to Prdx6 ‐/‐ mice and mice homozygous for the knock‐in of the Prdx6 129X1/SvJ allele overexpressing wild‐type PRDX6 to generate novel PS19/Prdx6 +/‐ and PS19/Prdx6 Tg lines, respectively. Eight weeks old PS19/Prdx6 +/‐, PS19/Prdx6 +/+, and PS19/Prdx6 Tg animals show 0.4:1:2 ratio of Prdx6 brain mRNA level, while levels of hTau and Gfap mRNA remain unchanged. Male mice were neuropathologically characterized at the age of 9.5 months.Result PS19/Prdx6 +/‐ mice feature increased hippocampal atrophy and ventricular enlargement and greater p‐tau accumulation compared to PS19/Prdx6 +/+ mice. Contrariwise, PS19/Prdx6 Tg animals show attenuated brain atrophy and p‐tau accumulation. The GFAP+ load used as a marker of global astrocytic activation and the C3+/GFAP+ ratio, used as a surrogate A1 phenotype marker, vary inversely with the Prdx6 gene dose. Likewise, the load of IBA1+ microglia vary inversely with the Prdx6 gene dose, while the CD68+/IBA1+ index, which determines relative microglia phagocytic activity, directly correlates with the Prdx6 expression.ConclusionExacerbation of the pathological phenotype in PS19/Prdx6 +/‐ mice reveals a neuroprotective effect of PRDX6 in tau mediated neurodegeneration, while attenuation of pathology in PS19/Prdx6 Tg mice suggests a merit of therapeutic PRDX6 upregulation. PRDX6 endows astrocytes with resistance to A1 phenotype transition. Astrocytic PRDX6 also reprograms microglia by downregulating their global activation level and selectively promoting phagocytic properties. Comparative analysis of astrocytic and microglia transcriptomic markers across PS19/Prdx6 +/‐, PS19/Prdx6 +/+, and PS19/Prdx6 Tg genotypes is underway.

76-OR: Macrophage-Derived Proinflammatory Lipids Play a Role in the Development of Type 1 Diabetes

Type 1 diabetes (T1D) is a consequence of autoimmune-mediated destruction of pancreatic β-cells, but the leading causes for this process remain elusive. We revealed that Ca2+-independent phospholipase A2β (iPLA2β) , which hydrolyzes membrane phospholipids at the sn-2 position to generate bioactive lipids, modulates polarization of macrophages (MΦ) . Several of the iPLA2β-derived lipid signals (iDLs) are proinflammatory and can initiate immune cell infiltration and β-cell damage. Recently, we showed that production of MΦ- proinflammatory lipids (i.e., PGs, DHETs, LTB4) from spontaneous-T1D prone nonobese diabetic mice (NOD) is high during the pre-diabetic phase. Herein, we examined the impact of bone marrow-derived macrophages (BMD-MΦ) -iDLs on T1D development by generating NOD mice with a conditional reduction in MΦ-iPLA2β (NOD.cMΦ iPLA2 &amp;#120573;; -/- and NOD.cMΦ iPLA2 &amp;#120573;; +/- ) . Our findings reveal that (1) BMD-MΦ from NOD.cMΦiPLA2 &amp;#120573;; -/- or NOD.cMΦiPLA2 &amp;#120573;; +/- are skewed towards an M2 (anti-inflammatory) phenotype, in comparison with NOD BMD-MΦ (2) production of proinflammatory lipids (PGs, DHETs, and TXB2) is significantly decreased in BMD-MΦ from NOD.cMΦiPLA2 &amp;#120573;; -/- and NOD.cMΦiPLA2 &amp;#120573;; +/- (3) selective inhibition of PGE2 or DHETs signaling inhibits NOD BMD-MΦ polarization towards a proinflammatory phenotype M1 (4) selective decrease of iPLA2β in MΦ significantly reduces leukocytes infiltration into the pancreas of NOD mice (5) pancreata from NOD.cMΦiPLA2 &amp;#120573;; -/- and NOD.cMΦiPLA2 &amp;#120573;; +/- mice have significantly higher M2 macrophages and less activated T cells (6) importantly, selective decrease of iPLA2β in MΦ (NOD.cMΦiPLA2 &amp;#120573;; -/- and NOD.cMΦiPLA2 &amp;#120573;; +/- ) significantly reduces T1D incidence in NOD mice. The overall reduced macrophages-proinflammatory lipids is associated with increased M2 macrophages and less T1D diabetes pathogenesis in selective decrease of MΦ-iPLA2β NOD mice. And inhibition of selective macrophages-derived iDLs production can be targeted to counter T1D. Disclosure A.Almutairi: None. T.White: None. D.Stephenson: None. Y.Gai: None. E.Ubil: None. C.Chalfant: None. S.Ramanadham: None. Funding NIH/NIAID R21 (AI 146743) NIH/NIDDK (R01DK110292) Cell, Developmental, &amp; Integrative Biology (CDIB) , the University of Alabama at BirminghamUAB Comprehensive Diabetes CenterKing Saud bin Abdulaziz University for Health Sciences/ Saudi Arabian Cultural Mission

74-OR: Adoptively Transferred T Lymphocytes with Reduced iPLA2b Expression Delays Type 1 Diabetes Development in NOD Mice

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease characterized by the destruction of insulin-producing pancreatic islet β-cells. An understudied area is the role lipid signaling plays in this process. We find that the Ca2+-independent phospholipase A2β (iPLA2β) is induced under a diabetic milieu and mitigation of iPLA2β activity attenuates β-cell death. iPLA2β, a member of the PLA2 family, hydrolyzes the sn-2 substituent from glycerophospholipid substrates to yield a free fatty acid. When the fatty acid is arachidonic acid, it can be metabolized to eicosanoids, many of which are pro-inflammatory. To address our overarching hypothesis that iPLA2β-derived lipids (iDLs) contribute to T1D development, we investigated the role of immune cell-iDLs by utilizing a T-cell adoptive transfer. We isolated CD4+/8+ T-cells from splenocytes prepared from 11-week-old donor female NOD and NOD.iPLA2 β +/- (HET) . These were transferred i.p. to 4-week-old NOD.scid recipient mice. We find that NOD4/8-recipient mice develop T1D between 14-16 weeks of age. In contrast, T1D onset in HET4/8-recipient mice is delayed by 12 weeks and this was associated with better glucose tolerance, compared to NOD4/8 T-cell recipients. This finding is also supported by histology analysis of the pancreatic islet, which revealed less islet infiltration, more islet abundance, and the frequency of CD4 T cells were increased in the pancreas of HET4/8-recipient mice compared to NOD4/8 recipients. Further, lipidomics analyses revealed that HET donor T-cell production of proinflammatory lipids (i.e., PGE2 and DHETs) is decreased, relative to NOD T-cells. These findings suggest that pro-inflammatory iDLs generated by CD4 T-cells are critical contributors T1D development and can be targeted to counter T1D onset. Disclosure T.White: None. C.Chalfant: None. T.P.Dilorenzo: None. S.Ramanadham: None. D.Stephenson: None. Funding Training Program in Cell, Molecular, and Developmental Biology (5T32GM008111-34) NIH/NIDDK (R01DK110292) NIH/NIAID R21 (AI 146743) Cell, Developmental, &amp; Integrative Biology (CDIB) , the University of Alabama at Birmingham

Cellular concentrations of plasmalogen species containing a polyunsaturated fatty acid significantly increase under hypoxia in human colorectal cancer, Caco2 cells

Plasmalogen localized in the raft of mammalian cell membranes plays a role in the storage of polyunsaturated fatty acid (PUFA), and exists to a higher extent in malignant cells that survive, and even grow in hypoxic conditions. The biosynthesis of plasmalogen in mammalian cells has been reported to depend on aerobic conditions. Using liquid chromatography-tandem mass spectrometry, we found that the intracellular concentration of plasmalogen species containing a PUFA at the sn-2-position did not change for two days from the start of hypoxic culture in human colorectal cancer-derived Caco2 cells. At the third day of hypoxia, Caco2 cells showed the average increase rate of 2.6 times in ethanolamine plasmalogen and 2.9 times in choline plasmalogen depending on the molecular species compared with those in the second day of hypoxia. In normoxic culture, there was little quantitative change in any species of both ethanolamine and choline plasmalogens for three days. The up-regulations of mRNA of Ca2+-independent phospholipase A2β and cytoplasmic phospholipase A2γ as well as the down-regulation of lysoplasmalogenase observed in hypoxia were suggested to be responsible for the increase of plasmalogen in Caco2 cells under hypoxia.

Molecular Characterization of Two Genes Encoding Novel Ca2+-Independent Phospholipase A2s from the Silkworm, Bombyx mori

Eicosanoids are crucial downstream signals in the insect immune responses. Phospholipase A2 (PLA2) catalyzes phospholipids, the initial step in eicosanoid biosynthesis. In mammals, the biological roles of Ca2+-independent Phospholipase A2 (iPLA2) have been extensively studied; however, only a few studies have attempted to explore iPLA2 functions in insects. In this study, we identified two iPLA2 genes (designated as BmiPLA2A and BmiPLA2B) in the silkworm, Bombyx mori. BmiPLA2A had a 2427 base pair (bp) open reading frame (ORF) that coded for a protein with 808 amino acids. In contrast, BmiPLA2B had a 1731 bp ORF that coded for a protein with 576 amino acids. Domain analysis revealed that BmiPLA2A had six ankyrin repeat domains, but BmiPLA2B lacks these domains. BmiPLA2A and BmiPLA2B were transcribed widely in various tissues and developmental stages with different expression patterns. The administration of 20-hydroxyecdysone increased their expression levels in the epidermis and hemocytes. Furthermore, challenged with virus, fungus, Gram-negative bacteria, and Gram-positive bacteria induced the expression of BmiPLA2A and BmiPLA2B with variable degrees along with different time points. Our findings imply that BmiPLA2A and BmiPLA2B may have important biological roles in the development and innate immunity of B. mori.

Peroxiredoxin 6 Peroxidase and Ca2+-Independent Phospholipase A2 Activities Are Essential to Support Male-Mouse Fertility.

Human infertility is an important health problem that affects one in six couples worldwide. Half of these cases are due to male infertility. Oxidative stress is a common culprit of male infertility, promoting lipid peroxidation and the oxidation of proteins and DNA in spermatozoa, thereby impairing motility, capacitation and fertilization. Peroxiredoxin 6 (PRDX6) possesses peroxidase and Ca2+-independent-phospholipase-A2 (iPLA2) activities that scavenge ROS and repair oxidized sperm membranes, respectively. PRDX6 protects spermatozoa against oxidative stress. Infertile men’s spermatozoa have impaired motility, elevated lipid peroxidation levels and DNA damage due to low PRDX6 levels. A lack of PRDX6 is associated with male-mouse infertility. Here, we determined the impact of the absence of PRDX6 peroxidase or iPLA2 activities on male-mouse fertility. Two-month-old male C57Bl6/J (wild-type), Prdx6−/−, C47S and D140A knock-in (peroxidase- and iPLA2-deficient, respectively) male mice were challenged with an in vivo oxidative stress triggered by tert-butyl hydroperoxide (t-BHP). C47S and D140A males produced smaller litters compared to wild-type controls. The t-BHP treatment promoted a lower number of pups, high levels of lipid peroxidation, tyrosine nitration, and DNA oxidation in all mutant spermatozoa compared to wild-type controls. All mutant spermatozoa had impaired capacitation and motility. In summary, both PRDX6 peroxidase and iPLA2 activities are essential to support male-mouse fertility.

Antioxidant Role and Cardiolipin Remodeling by Redox-Activated Mitochondrial Ca2+-Independent Phospholipase A2γ in the Brain.

Mitochondrial Ca2+-independent phospholipase A2γ (iPLA2γ/PNPLA8) was previously shown to be directly activated by H2O2 and release free fatty acids (FAs) for FA-dependent H+ transport mediated by the adenine nucleotide translocase (ANT) or uncoupling protein 2 (UCP2). The resulting mild mitochondrial uncoupling and consequent partial attenuation of mitochondrial superoxide production lead to an antioxidant effect. However, the antioxidant role of iPLA2γ in the brain is not completely understood. Here, using wild-type and iPLA2γ-KO mice, we demonstrate the ability of tert-butylhydroperoxide (TBHP) to activate iPLA2γ in isolated brain mitochondria, with consequent liberation of FAs and lysophospholipids. The liberated FA caused an increase in respiratory rate, which was fully inhibited by carboxyatractyloside (CATR), a specific inhibitor of ANT. Employing detailed lipidomic analysis, we also demonstrate a typical cleavage pattern for TBHP-activated iPLA2γ, reflecting cleavage of glycerophospholipids from both sn-1 and sn-2 positions releasing saturated FAs, monoenoic FAs, and predominant polyunsaturated FAs. The acute antioxidant role of iPLA2γ-released FAs is supported by monitoring both intramitochondrial superoxide and extramitochondrial H2O2 release. We also show that iPLA2γ-KO mice were more sensitive to stimulation by pro-inflammatory lipopolysaccharide, as reflected by the concomitant increase in protein carbonyls in the brain and pro-inflammatory IL-6 release in the serum. These data support the antioxidant and anti-inflammatory role of iPLA2γ in vivo. Our data also reveal a substantial decrease of several high molecular weight cardiolipin (CL) species and accumulation of low molecular weight CL species in brain mitochondria of iPLA2γ-KO mice. Collectively, our results support a key role of iPLA2γ in the remodeling of lower molecular weight immature cardiolipins with predominantly saturated acyl chains to high molecular weight mature cardiolipins with highly unsaturated PUFA acyl chains, typical for the brain.

Ca2+-independent phospholipase A2β-derived PGE2 contributes to osteogenesis

Bone modeling can be modulated by lipid signals such as arachidonic acid (AA) and its cyclooxygenase 2 (COX2) metabolite, prostaglandin E2 (PGE2), which are recognized mediators of optimal bone formation. Hydrolysis of AA from membrane glycerophospholipids is catalyzed by phospholipases A2 (PLA2s). We reported that mice deficient in the Ca2+- independent PLA2beta (iPLA2β), encoded by Pla2g6, exhibit a low bone phenotype, but the cause for this remains to be identified. Here, we examined the mechanistic and molecular roles of iPLA2β in bone formation using bone marrow stromal cells and calvarial osteoblasts from WT and iPLA2β-deficient mice, and the MC3T3-E1 osteoblast precursor cell line. Our data reveal that transcription of osteogenic factors (Bmp2, Alpl, and Runx2) and osteogenesis are decreased with iPLA2β-deficiency. These outcomes are corroborated and recapitulated in WT cells treated with a selective inhibitor of iPLA2 β (10 μM S-BEL), and rescued in iPLA2β-deficient cells by additions of 10 μM PGE2. Further, under osteogenic conditions we find that PGE2 production is through iPLA2β activity and that this leads to induction of Runx2 and iPLA2β transcription. These findings reveal a strong link between osteogenesis and iPLA2β-derived lipids and raise the intriguing possibility that iPLA2β-derived PGE2 participates in osteogenesis and in the regulation of Runx2 and also iPLA2β.

Brain Derived Neurotrophic Factor Deficiency is Associated with Cognitive Impairment and Elevated Phospholipase A2 Activity in Plasma of Mice

Decreased levels of Brain-Derived Neurotrophic Factor (BDNF) are a common finding in schizophrenia. Another well-documented protein linked to schizophrenia is intracellular Ca2+-independent Phospholipase (PLA2). However, the potential association between PLA2 and BDNF with regard to schizophrenia has yet to be examined.In the present study, male and female BDNF knockout mice, a possible genetic model of schizophrenia, were exposed to prenatal stress and tested in the nest test, open field test and T-maze. Following behavioral tests, whole brain and plasma samples were harvested to measure the activity of PLA2. BDNF knockout mice showed cognitive deficits in the T-maze. Furthermore, there was a quadratic association of PLA2 with performance in the open field test. Moreover, BDNF deficiency and female sex were associated with elevated plasma PLA2 levels. The cognitive impairment of BDNF heterozygous mice as well as their increased PLA2 activity in plasma is consistent with findings in schizophrenia patients. The particular elevation of PLA2 activity in females may partly explain sex differences of clinical symptoms in schizophrenia (e.g. age of onset, severity of symptoms). Additionally, PLA2 was significantly correlated with body and adrenal weight after weaning, whereby the latter emphasizes the possible connection of PLA2 with steroidogenesis.

Alterations in β-Cell Sphingolipid Profile Associated with ER Stress and iPLA2β: Another Contributor to β-Cell Apoptosis in Type 1 Diabetes.

Type 1 diabetes (T1D) development, in part, is due to ER stress-induced β-cell apoptosis. Activation of the Ca2+-independent phospholipase A2 beta (iPLA2β) leads to the generation of pro-inflammatory eicosanoids, which contribute to β-cell death and T1D. ER stress induces iPLA2β-mediated generation of pro-apoptotic ceramides via neutral sphingomyelinase (NSMase). To gain a better understanding of the impact of iPLA2β on sphingolipids (SLs), we characterized their profile in β-cells undergoing ER stress. ESI/MS/MS analyses followed by ANOVA/Student’s t-test were used to assess differences in sphingolipids molecular species in Vector (V) control and iPLA2β-overexpressing (OE) INS-1 and Akita (AK, spontaneous model of ER stress) and WT-littermate (AK-WT) β-cells. As expected, iPLA2β induction was greater in the OE and AK cells in comparison with V and WT cells. We report here that ER stress led to elevations in pro-apoptotic and decreases in pro-survival sphingolipids and that the inactivation of iPLA2β restores the sphingolipid species toward those that promote cell survival. In view of our recent finding that the SL profile in macrophages—the initiators of autoimmune responses leading to T1D—is not significantly altered during T1D development, we posit that the iPLA2β-mediated shift in the β-cell sphingolipid profile is an important contributor to β-cell death associated with T1D.