1-O-alkylglycerols improve boar sperm motility and fertility

Comparison between commercial media and TRIS-egg yolk extender in the refrigerated storage of collared peccary semen at 17°C

To assist in the conservation of collared peccary, it is important to strengthen semen processing protocols. The aim of this study was to compare the effects of different commercial extenders (BTS; NUTRIXcell+ and PRIMXcell Ultra) and TRIS + egg yolk on the functional and morphological aspects of collared peccary semen stored at 17 °C for 48 hours. Ten ejaculates obtained by electroejaculation were divided into 4 aliquots and diluted in the respective extenders, then stored in a biological incubator at 17 °C for 12, 24, 36, and 48 hours. The samples were evaluated for kinetic parameters, membrane functionality, membrane integrity, mitochondrial activity, morphology, and sperm-binding capacity. At the end of storage (48 h), promising results were found for motility parameters, with TRIS + egg yolk (71.0 ± 4.6%) being more efficient than NUTRIXcell+ (38.9 ± 10.9%) (P < 0.05) and similar to BTS (42.9 ± 11.9%) and PRIMXcell Ultra (46.8 ± 10.8%). The results for membrane integrity and mitochondrial activity were around ∼30-50%, with TRIS being the only extender to preserve both parameters (58.9 ± 5.3 and 59.2 ± 5.6%) for up to 48 hours, respectively (P < 0.05). Finally, the extenders could guarantee 60% membrane functionality and ∼ 60-70% normal sperm morphology, as well as similar binding capacity among the groups. In conclusion, TRIS + egg yolk is effective in preserving the sperm parameters of collared peccary semen at 17 °C for 48 hours, while PRIMXcell Ultra and BTS are viable alternatives for this purpose.

1-O-Alkylglycerol Ethers from the Marine Sponge Guitarra abbotti and Their Cytotoxic Activity

The cytotoxicity-bioassay-guided fractionation of the ethanol extract from the marine sponge Guitarra abbotti, whose 1-O-alkyl-sn-glycerol ethers (AGEs) have not been investigated so far, led to the isolation of a complex lipid fraction containing, along with previously known compounds, six new lipids of the AGE type. The composition of the AGE fraction as well as the structures of 6 new and 22 previously known compounds were established using ¹H and ¹³C NMR, GC/MS, and chemical conversion methods. The new AGEs were identified as: 1-O-(Z-docos-15-enyl)-sn-glycerol (1), 1-O-(Z-docos-17-enyl)-sn-glycerol (2), 1-O-(Z-tricos-15-enyl)-sn-glycerol (3), 1-O-(Z-tricos-16-enyl)-sn-glycerol (4), 1-O-(Z-tricos-17-enyl)-sn-glycerol (5), and 1-O-(Z-tetracos-15-enyl)-sn-glycerol (6). The isolated AGEs show weak cytotoxic activity in THP-1, HL-60, HeLa, DLD-1, SNU C4, SK-MEL-28, and MDA-MB-231 human cancer cells. A further cytotoxicity analysis in JB6 P⁺ Cl41 cells bearing mutated MAP kinase genes revealed that ERK2 and JNK1 play a cytoprotective role in the cellular response to the AGE-induced cytotoxic effects.

A gatekeeper helix determines the substrate specificity of Sjögren-Larsson Syndrome enzyme fatty aldehyde dehydrogenase

Mutations in the gene coding for membrane-bound fatty aldehyde dehydrogenase (FALDH) lead to toxic accumulation of lipid species and development of the Sjögren-Larsson Syndrome (SLS), a rare disorder characterized by skin defects and mental retardation. Here, we present the crystallographic structure of human FALDH, the first model of a membrane-associated aldehyde dehydrogenase. The dimeric FALDH displays a previously unrecognized element in its C-terminal region, a 'gatekeeper' helix, which extends over the adjacent subunit, controlling the access to the substrate cavity and helping orientate both substrate cavities towards the membrane surface for efficient substrate transit between membranes and catalytic site. Activity assays demonstrate that the gatekeeper helix is important for directing the substrate specificity of FALDH towards long-chain fatty aldehydes. The gatekeeper feature is conserved across membrane-associated aldehyde dehydrogenases. Finally, we provide insight into the previously elusive molecular basis of SLS-causing mutations.

Orphan enzymes in ether lipid metabolism

Ether lipids are an emerging class of lipids which have so far not been investigated and understood in every detail. They have important roles as membrane components of e.g. lens, brain and testis, and as mediators such as platelet-activating factor. The metabolic enzymes for biosynthesis and degradation have been investigated to some extent. As most involved enzymes are integral membrane proteins they are tricky to handle in biochemical protocols. The sequence of some ether lipid metabolising enzymes has only recently been reported and other sequences still remain obscure. Defined enzymes without assigned sequence are known as orphan enzymes. One of these enzymes with uncharacterised sequence is plasmanylethanolamine desaturase, a key enzyme for the biosynthesis of one of the most abundant phospholipids in our body, the plasmalogens. This review aims to briefly summarise known functions of ether lipids, give an overview on their metabolism including the most prominent members, platelet-activating factor and the plasmalogens. A special focus is set on the description of orphan enzymes in ether lipid metabolism and on the successful strategies how four previous orphans have recently been assigned a sequence. Only one of these four was characterised by classical protein purification and sequencing, whereas the other three required alternative strategies such as bioinformatic candidate gene selection and recombinant expression or development of an inhibitor and multidimensional metabolic profiling.

Platelet-activating factor in Iberian pig spermatozoa: receptor expression and role as enhancer of the calcium-induced acrosome reaction

Platelet-activating factor (PAF) is a phospholipid involved in reproductive physiology. PAF receptor is expressed in some mammalian spermatozoa species where it plays a role in these germ-cell-specific processes. The aim of this study is to identify PAF receptor in Iberian pig spermatozoa and to evaluate PAF's effects on motility, viability and acrosome reaction. Semen samples from Iberian boars were used. PAF receptor identification was performed by Western blotting. Spermatozoa motility was analysed by computer-assisted sperm analysis system, whereas spermatozoa viability and acrosome reaction were evaluated by flow cytometry. Different PAF concentrations added to non-capacitating medium during 60 min have no effect on any spermatozoa motility parameter measured. Acrosome reaction was rapid and potently induced by 1 μm calcium ionophore A23187 showing an effect at 60 min and maximum at 240 min. PAF added to a capacitating medium is not able to induce spermatozoa acrosome reaction at any time studied. However, PAF, in the presence of A23187, significantly accelerates and enhances the calcium-induced acrosome reaction in a concentration-dependent manner in Iberian boar spermatozoa. Exogenous PAF does not affect at all spermatozoa viability, whereas slightly exacerbated the A23187-induced loss in viability. This work demonstrates that PAF receptor is expressed in Iberian pig spermatozoa and that its stimulation by PAF regulates the calcium-induced acrosome reaction. This work contributes to further elucidate the physiological regulation of the most relevant spermatozoa functions for successful fertilization: acrosome reaction.

Ether lipids

The naturally occurring 1-O-alkyl-sn-glycerols and their methoxylated congeners, 1-O-(2'-methoxyalkyl)-sn-glycerols, are biologically active compounds, ubiquitously found in nature as diacyl glyceryl ether lipids and phosphoether lipids. The chief objective of this article is to provide a comprehensive and up to date review on such ether lipids. The occurrence and distribution of these compounds in nature are extensively reviewed, their chemical structure and molecular variety, their biosynthesis and chemical synthesis and, finally, their various biological effects are described and discussed. An unprecedented biosynthesis of the 2'-methoxylated alkylglycerols is proposed. The first synthesis of enantiopure (Z)-(2'R)-1-O-(2'-methoxyhexadec-4'-enyl)-sn-glycerol, the most prevalent 2'-methoxylated type alkylglycerol present in cartilaginous fish, is described. It was accomplished by a highly convergent five step process.

An update on the therapeutic role of alkylglycerols

Scandinavian folk medicine used shark liver oil for the treatment of cancers and other ailments based on the rarity of tumors in sharks and their ability to resist infections. Shark liver oil is a source of alkylglycerols which have been studied as anti-cancer agents in several clinical trials. Moreover, alkylglycerols have been investigated for the treatment of radiation induced side effects and for their ability to boost the immune system. Several experimental studies have shown the ability of alkylglycerols to open the blood brain barrier to facilitate the access of therapeutic drugs to the central nervous system. This review covers the most important studies of alkylglycerols in both animals and humans.

Multiple beneficial health effects of natural alkylglycerols from shark liver oil

Alkylglycerols (alkyl-Gro) are ether lipids abundant in the liver of some elasmobranch fish species such as ratfishes and some sharks. Shark liver oil from Centrophorus squamosus (SLO), or alkyl-Gro mix from this source, have several in vivo biological activities including stimulation of hematopoiesis and immunological defences, sperm quality improvement, or anti-tumor and anti-metastasis activities. Several mechanisms are suggested for these multiple activities, resulting from incorporation of alkyl-Gro into membrane phospholipids, and lipid signaling interactions. Natural alkyl-Gro mix from SLO contains several alkyl-Gro, varying by chain length and unsaturation. Six prominent constituents of natural alkyl-Gro mix, namely 12:0, 14:0, 16:0, 18:0, 16:1 n-7, and 18:1 n-9 alkyl-Gro, were synthesized and tested for anti-tumor and anti-metastatic activities on a model of grafted tumor in mice (3LL cells). 16:1 and 18:1 alkyl-Gro showed strong activity in reducing lung metastasis number, while saturated alkyl- Gro had weaker (16:0) or no (12:0, 14:0, 18:0) effect. Multiple compounds and mechanisms are probably involved in the multiple activities of natural alkyl-Gro.

Acute and repeated dose (28 days) oral safety studies of an alkoxyglycerol extract from shark liver oil in rats

Shark liver oil has been used for over 50 years as both a therapeutic and preventive agent. The active ingredients in shark liver oil have been found to be a group of ether-linked glycerols known as alkoxyglycerols. Despite its popularity, there is little published toxicology data on alkoxyglycerols. The toxicity of a supercritical fluid extract of shark liver oil (AKG-1 extract) has been evaluated in acute and repeated dose (28 days) oral toxicity studies in rats at doses of 200 and 100 times the maximum recommended dose by supplement manufacturers in humans, respectively. The AKG-1 extract administered in a single oral gavage dose of 2000 mg kg(-1) of body weight resulted in no adverse events or mortality. The AKG-1 extract administered as a daily dose of 1000 mg kg(-1) of body weight for 28 days by gavage resulted in no adverse effects or mortality. For both studies, no abnormal clinical signs, behavioral changes, body weight changes, or change in food and water consumption occurred. There were no changes in hematological and serum chemistry values, organ weights, or gross or histological characteristics. It is concluded that the AKG-1 extract is well tolerated in rats at an acute dose of 2000 mg kg(-1) and at a subchronic (28 days) dose of 1000 mg kg(-1).

Which alkylglycerols from shark liver oil have anti-tumour activities?

Alkylglycerols (alkyl-Gro) are ether lipids abundant in shark liver oil (SLO), and oral SLO or alkyl-Gro mix from this source have several in vivo biological activities including stimulation of haematopoiesis an immunological defences, or anti-tumour and anti-metastasis activities in vivo. Composition of natural alkyl-Gro mix contains several alkyl-Gro varying by chain length and unsaturation, and individual anti-tumour activity of each molecule present in natural mix remained unknown. We synthesized six prominent constituents of natural alkyl-Gro mix, namely 12:0, 14:0 16:0, 18:0, 16:1 n-7, and 18:1 n-9 alkyl-Gro. Using an in vivo model of grafted tumour in mice (3LL cells), we studied and compared the oral anti-tumour and anti-metastasis activities of each of these 6 alkyl-Gro. 16:1 and 18:1 alkyl-Gro showed strong activity in reducing lung metastasis number, while saturated alkyl-Gro had weaker (16:0) or no (12:0, 14:0, 18:0) effect. Spleen weights at day 20 after graft were also measured and showed tremendous variations depending on the treatment. Tumour graft resulted in a raise in spleen weight in control group, this raise was nearly abolished in 16:1 and 18:1 alkyl-Gro-treated mice, and was reduced in 14:0 and 16:0 alkyl-Gro-treated mice. Conversely, 18:0 alkyl-Gro-treated mice showed spleen weigh raise as compared with untreated grafted mice. These new data demonstrate a prominent role of unsaturation in the anti-tumour activities of alkyl-Gro.

Effect of chronic supplementation with shark liver oil on immune responses of exercise-trained rats

Previous studies have reported that chronic supplementation with shark liver oil (SLO) improves immune response of lymphocyte, macrophage and neutrophil in animal models and humans. In a similar manner, exercise training also stimulates the immune system. However, we are not aware of any study about the association of exercise and SLO supplementation on immune response. Thus, our main goal was to investigate the effect of chronic supplementation with SLO on immune responses of exercise-trained rats. Male Wistar rats were divided into four groups: sedentary with no supplementation (SED, n = 20), sedentary with SLO supplementation (SEDslo, n = 20), exercised (EX, n = 17) and exercised supplemented with SLO (EXslo, n = 19). Rats swam for 6 weeks, 1.5 h/day, in water at 32 +/- 1 degrees C, with a load of 6.0% body weight attached to the thorax of rat. Animals were killed 48 h after the last exercise session. SLO supplementation did not change phagocytosis, lysosomal volume, superoxide anion and hydrogen peroxide production by peritoneal macrophages and blood neutrophils. Thymus and spleen lymphocyte proliferation were significantly higher in SEDslo, EX, and EXslo groups compared with SED group (P < 0.05). Gut-associated lymphocyte proliferation, on the other hand, was similar between the four experimental groups. Our findings show that SLO and EX indeed are able to increase lymphocyte proliferation, but their association did not induce further stimulation in the adaptive immune response and also did not modify innate immunity.

Humoral defence improvement and haematopoiesis stimulation in sows and offspring by oral supply of shark-liver oil to mothers during gestation and lactation

Shark-liver oil (SLO) contains two bioactive lipids: alkylglycerols andn-3 PUFA. Alkylglycerols have immunostimulating and haematopoietic properties, whilen-3 PUFA are essential for optimal neonatal development. We investigated the beneficial effects of dietary supplementation with 32g SLO/d to twelve pregnant and then lactating sows (from day 80 of pregnancy to weaning) on the growth and immune status of their offspring, compared with a control group. Sows were vaccinated against Aujeszky's disease 21d before term. Blood samples were collected from sows before treatment, on delivery and 14d later, and from five piglets per litter on days 2, 21 and 36 after birth; colostrum and milk samples were collected 12h, 14 and 28d postpartum. Compared with controls, supplemented sows had higher levels of both erythrocytes and Hb in their blood, and higher concentrations of IgG, alkylglycerols andn-3 PUFA in their mammary secretions. In piglets from supplemented sows, leucocytes and IgG were higher. Supplementation with SLO resulted in an increase in Aujeszky antibodies in both blood and colostrum of sows after vaccination, together with an increase in Aujeszky antibodies in piglet blood. Our findings demonstrate that improvement of both passive and active immune status in piglets is related to the consumption of alkylglycerols associated withn-3 PUFA in the sow diet. The overall improvement in offspring health status by SLO supplementation to the mother could be of interest for optimisation of the lipid diet during and after pregnancy.

Shedding off specific lipid constituents from sperm cell membrane during cryopreservation

Membrane damage is one of the main reasons for reduced motility and fertility of sperm cells during cryopreservation. Using a model system of sperm cryopreservation developed in our laboratory, we have investigated the detailed changes due to cryopreservation in the plasma membrane lipid composition of the goat epididymal sperm cells. Total lipid and its components, i.e., neutral lipids, glycolipids and phospholipids decreased significantly after cryopreservation. Among neutral lipids sterols, steryl esters and 1-O-alkyl-2,3-diacyl glycerols decreased appreciably, while among phospholipids, major loss was observed for phosphatidyl choline and phosphatidyl ethanolamine. Unsaturated fatty acids bound to the phospholipids diminished while the percentage of saturated acids increased. The cholesterol:phospholipid ratio enhanced and the amount of hydrocarbon, which was unusually high, increased further on cryopreservation. The data indicates that profound increase of the hydrophobicity of the cell membrane is one of the major mechanisms by which spermatozoa acquire potential to resist or combat stress factors like cryodamage. The results are compatible with the view that for survival against cryodamage, sperm cells modulate the structure of their outer membrane by shedding off preferentially some hydrophilic lipid constituents of the cell membrane.

Platelet-activating factor acetylhydrolase activity affects sperm motility and serves as a decapacitation factor

OBJECTIVE

To determine the relationship between platelet-activating factor acetylhydrolase (PAFah) content in semen and sperm motility.

DESIGN

The PAFah levels in semen were measured and correlated with sperm motility.

SETTING

Clinical laboratory in a private assistant reproductive technology clinic.

PATIENT(S)

Three hundred and twelve men seeking diagnosis and treatment of infertility.

INTERVENTION(S)

Semen samples were collected from 312 healthy mature men seeking infertility treatment. Sperm motility and PAFah activity were measured in seminal plasma. Data was analyzed by Student's t test and regression analysis.

MAIN OUTCOME MEASURE(S)

PAFah activity and sperm motility.

RESULT(S)

Seminal PAFah content ranged from a low of 179 IU/L to a high of 2,457 IU/L. The overall mean PAFah content in semen was 780.59 IU/L. Linear regression analysis revealed a significant (R2 = 0.655) and negative relationship between PAFah content in semen and sperm motility. Semen specimens with high percent motility (> or = 50%) had significantly lower PAFah concentrations (442.03 +/- 14.37 IU/L) than those with the lower percent sperm motility (< 50%) (882.16 +/- 18.45 IU/L).

CONCLUSION(S)

The data confirm the presence of PAFah in human semen and that activity is significantly and negatively correlated with sperm motility. The PAFah is proven to be a candidate for sperm decapacitation factors, whereas PAF is qualified to be a candidate for sperm capacitation factors.

Oral intake of shark liver oil modifies lipid composition and improves motility and velocity of boar sperm

The natural ether-lipids 1-O-alkylglycerols (alkyl-Gro) from shark liver oil improve boar sperm motility and fertility in vitro. We examined the effects of oral shark liver oil on motility and velocity parameters of sperm together with modifications of lipid composition. Eleven boars were used as control and 11 were fed with 40 g/day for 28 days and sperm was collected on Days 0, 14 and 28 in control and treated groups. After 28 days treatment, sperm motility was improved by 2.9% as well as velocity parameters (curvilinear velocity +10.75%, progressive velocity +18.8% and average path velocity +13.5%) and sperm lipid composition was modified as follows: alkyl-Gro with saturated chains were increased (C16:0 +40.1%, C18:0 +87.2%) while alkyl-Gro with unsaturated chains remained absent, as in the control group, despite the prominence of C18:1 and C16:1 in shark liver oil. The treatment also resulted in an overall increase in the proportion of n - 3 and n - 6 polyunsaturated fatty acids in sperm lipids with a prominent increase of docosahexaenoic acid over time (18.9 +/- 1.34% at Day 0 to 25.7 +/- 1.11% at Day 28) and compared to control (25.7 +/- 1.11% for treated versus 16.1 +6/- 0.81 % for control at Day 28, respectively). These data demonstrate the influence of lipid intake on boar sperm composition and functions and suggest that oral intake of shark liver oil might improve reproduction.

Natural 1-O-alkylglycerols reduce platelet-activating factor-induced release of [3H]-serotonin in rabbit platelets

Natural 1-O-alkylglycerols have multiple biological activities with distinct mechanisms. In THP-1 monocytes, they amplify platelet-activating factor production. In endothelial cells, they participate in the production of 1-O-alkyl-2-acyl-sn-glycerol, a PKC inhibitor. Since PAF as well as PKC may interfere with platelet functions, we studied the effect of natural alkylglycerols purified from shark liver oil on [3H]-serotonin release from rabbit platelets in vitro. [3H]-alkylglycerols (1 microM) were consistently incorporated into platelet lipids and after a 2-h incubation, they were metabolised into phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, which represented 53.5+/-1.7%, 36.3+/-1.8%, 5.3+/-0.5% of metabolised [3H]-alkylglycerols, respectively. Alkylglycerols (10 microM) had no effect on spontaneous [3H]-serotonin release. However, alkylglycerols partially inhibited PAF-induced [3H]-serotonin release while they did not modify thrombin-induced release. These data show that alkylglycerols inhibit partially and specifically PAF-induced platelet stimulation and suggest that this effect could result from interfering with PAF receptors.

Regulation of calcium signalling by 1-O-alkylglycerols in human Jurkat T lymphocytes

We studied the role of natural occurring 1-O-alkylglycerols on the calcium signalling in Jurkat T-cells. Alkylglycerols evoked an increase in free intracellular calcium concentration [Ca2+]i, in a dose-dependent manner. When the experiments were performed in calcium-free buffer, the alkylglycerol response on the rise of [Ca2+]i was wholly abolished compared with the one in calcium-containing buffer, suggesting that these etherlipids induce a calcium influx by the opening of Ca2+ channels. We further employed inhibitors of voltage-gated calcium channels. We observed that omega-conotoxin, a blocker of N-type voltage-activated Ca2+ channels, but not verapamil, a blocker of L-type voltage-activated Ca2+ channels, curtailed significantly the calcium rise evoked by the lipid agents. Alkylglycerols also induced plasma membrane depolarisation, known to be involved in the opening of the voltage-gated calcium channels. Our study shows that alkylglycerols increase [Ca2+]i influx in human Jurkat T-cells possibly by modulating the permeability of calcium channels.

Inactivation of a testis-specific Lis1 transcript in mice prevents spermatid differentiation and causes male infertility

Lis1 protein is the non-catalytic component of platelet-activating factor acetylhydrolase 1b (PAF-AH 1B) and associated with microtubular structures. Hemizygous mutations of the LIS1 gene cause type I lissencephaly, a brain abnormality with developmental defects of neuronal migration. Lis1 is also expressed in testis, but its function there has not been determined. We have generated a mouse mutant (LIS1GT/GT) by gene trap integration leading to selective disruption of a Lis1 splicing variant in testis. Homozygous mutant males are infertile with no other apparent phenotype. We demonstrate that Lis1 is predominantly expressed in spermatids, and spermiogenesis is blocked when Lis1 is absent. Mutant spermatids fail to form correct acrosomes and nuclei appear distorted in size and shape. The tissue architecture in mutant testis appears severely disturbed displaying collapsed seminiferous tubules, mislocated germ cells, and increased apoptosis. These results provide evidence for an essential and hitherto uncharacterized role of the Lis1 protein in spermatogenesis, particularly in the differentiation of spermatids into spermatozoa.

Sperm preparation for ART

The onset of clinical assisted reproduction, a quarter of a century ago, required the isolation of motile spermatozoa. As the indication of assisted reproduction shifted from mere gynaecological indications to andrological indications during the years, this urged andrological research to understand the physiology of male germ cell better and develop more sophisticated techniques to separate functional spermatozoa from those that are immotile, have poor morphology or are not capable to fertilize oocytes. Initially, starting from simple washing of spermatozoa, separation techniques, based on different principles like migration, filtration or density gradient centrifugation evolved. The most simple and cheapest is the conventional swim-up procedure. A more sophisticated and most gentle migration method is migration-sedimentation. However, its yield is relatively small and the technique is therefore normally only limited to ejaculates with a high number of motile spermatozoa. Recently, however, the method was also successfully used to isolate spermatozoa for intracytoplasmic sperm injection (ICSI). Sperm separation methods that yield a higher number of motile spermatozoa are glass wool filtration or density gradient centrifugation with different media. Since Percoll as a density medium was removed from the market in 1996 for clinical use in the human because of its risk of contamination with endotoxins, other media like IxaPrep, Nycodenz, SilSelect, PureSperm or Isolate were developed in order to replace Percoll. Today, an array of different methods is available and the selection depends on the quality of the ejaculates, which also includes production of reactive oxygen species (ROS) by spermatozoa and leukocytes. Ejaculates with ROS production should not be separated by means of conventional swim-up, as this can severely damage the spermatozoa. In order to protect the male germ cells from the influence of ROS and to stimulate their motility to increase the yield, a number of substances can be added to the ejaculate or the separation medium. Caffeine, pentoxifylline and 2-deoxyadenosine are substances that were used to stimulate motility. Recent approaches to stimulate spermatozoa include bicarbonate, metal chelators or platelet-activating factor (PAF). While the use of PAF already resulted in pregnancies in intrauterine insemination, the suitability of the other substances for the clinical use still needs to be tested. Finally, the isolation of functional spermatozoa from highly viscous ejaculates is a special challenge and can be performed enzymatically to liquefy the ejaculate. The older method, by which the ejaculate is forcefully aspirated through a narrow-gauge needle, should be abandoned as it can severely damage spermatozoa, thus resulting in immotile sperm.

Previously uncharacterized roles of platelet-activating factor acetylhydrolase 1b complex in mouse spermatogenesis

Platelet-activating factor (PAF) has been shown to affect sperm motility and acrosomal function, thereby altering fertility. PAF acetylhydrolase 1b (PAFAH1B) hydrolyzes PAF and is composed of three subunits [the lissencephaly (LIS1) protein and alpha1 and alpha2 subunits] and structurally resembles a GTP-hydrolyzing protein. Besides the brain, transcripts for Lis1, alpha1, and alpha2 are localized to meiotic and early haploid germ cells. Here, we report disruptions of the alpha2 (Pafah1b2) and alpha1 (Pafah1b3) genes in mice. Male mice homozygous null for alpha2(alpha2-/-) are infertile, and spermatogenesis is disrupted at mid- or late pachytene stages of meiosis or early spermiogenesis. Whereas mice homozygous mutant for alpha1(alpha1-/-) have normal fertility and normal spermatogenesis, those with disruptions of both alpha1 and alpha2 (alpha1-/-alpha2-/-) manifest an earlier disturbance of spermatogenesis with an onset at preleptotene or leptotene stages of meiosis. Testicular Lis1 protein levels are up-regulated in the alpha2-/- and alpha1-/-alpha2-/- mice. Lowering Lis1 levels by inactivating one allele of Lis1 in alpha2 null or alpha1/alpha 2 null genetic backgrounds (i.e., alpha2-/-Lis1+/- or alpha1-/-alpha2-/-Lis1+/- mice) restored spermatogenesis and male fertility. Our data provide evidence for unique roles of the PAFAH1B complex and, particularly, the lissencephaly protein Lis1 in spermatogenesis.

Modulation of endothelial permeability by 1-O-alkylglycerols

Regulation of endothelial barrier function often occurs through signalling involving phospholipase C activation which produces diacylglycerol (DAG), a lipidic second messenger activator of protein kinase C (PKC). Therefore, modification of lipidic composition of endothelial cell membranes might modify DAG production and, as a result, alter regulation of endothelial permeability. We investigated the in vitro effects of natural 1-O-alkylglycerols on porcine aortic endothelial cell permeability to dye-labelled albumin. [3H]-1-O-alkylglycerols (10 microm) were substantially incorporated into phosphatidylcholine (6.6%) and phosphatidylethanolamine (4.4%). Stimulation of endothelial cell monolayer with phorbol-myristate-acetate or with the calcium ionophore A23187 resulted in a raise in permeability to albumin. Pre-treatment with 1-O-alkylglycerols (10 microm, 24 h) had no effect on basal albumin permeability but totally inhibited the effect of phorbol-myristate-acetate, and brought the permeability of A23187-stimulated endothelial cell monolayers below control. After incubation of cells with [3H]-1-O-alkylglycerols (10 microm, 24 h), we detected the production of the analogue of DAG, and PKC inhibitor, [3H]-1-O-alkyl-2-acyl-glycerol, in resting cells. This production was increased by 58% under A23187 stimulation while phorbol-myristate-acetate had no effect. Our data demonstrate that natural 1-O-alkylglycerols modify endothelial permeability, and suggest that this effect could be mediated through alteration of lipidic signalling.