A turn in the road: How studies on the pharmacology of glucosylceramide synthase inhibitors led to the identification of a lysosomal phospholipase A 2 with ceramide transacylase activity

A series of inhibitors of glucosylceramide synthesis, the PDMP based family of compounds, has been developed as a tool for the study of sphingolipid biochemistry and biology. During the course of developing more active glucosylceramide synthase inhibitors, we identified a second site of inhibitory activity for PDMP and its structural homologues that accounted for the ability of the inhibitors to raise cell and tissue ceramide levels. This inhibitory activity was directed against a previously unknown pathway for ceramide metabolism, viz . the formation of 1- O -acylceramide. In this pathway the addition of a fatty acyl group to the primary hydroxyl of ceramide occurs through a transacylation with either phosphatidylethanolamine or phosphatidylcholine as a substrate. However, both in the absence and presence of ceramide, water serves as an acceptor for the fatty acid. Thus the enzyme may be considered to be a phospholipase A 2 . The enzyme is unique in that it has an acidic pH optimum and is localized to lysosomes by cell fractionation. More recently, the 1- O -acylceramide synthase has been purified, sequenced, and cloned. This phospholipase A 2 was discovered to be structurally homologous to lecithin cholesterol acyltransferase (LCAT). However, this phospholipase A 2 does not recognize cholesterol and lacks the defined lipoprotein-binding domain present in LCAT. We now refer to this enzyme as lysosomal phospholipase A 2 (LPLA 2 ). Although acidic phospholipase A 2 activities have been previously identified, LPLA 2 appears to be the first lysosomal PLA 2 to have been sequenced. This new phospholipase A 2 lacks an obvious and proven biological function. Published in 2004.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45762/1/10719_2004_Article_5257241.pd

Cadherin activity is required for activity-induced spine remodeling

Neural activity induces the remodeling of pre- and postsynaptic membranes, which maintain their apposition through cell adhesion molecules. Among them, N-cadherin is redistributed, undergoes activity-dependent conformational changes, and is required for synaptic plasticity. Here, we show that depolarization induces the enlargement of the width of spine head, and that cadherin activity is essential for this synaptic rearrangement. Dendritic spines visualized with green fluorescent protein in hippocampal neurons showed an expansion by the activation of AMPA receptor, so that the synaptic apposition zone may be expanded. N-cadherin-venus fusion protein laterally dispersed along the expanding spine head. Overexpression of dominant-negative forms of N-cadherin resulted in the abrogation of the spine expansion. Inhibition of actin polymerization with cytochalasin D abolished the spine expansion. Together, our data suggest that cadherin-based adhesion machinery coupled with the actin-cytoskeleton is critical for the remodeling of synaptic apposition zone

Sonication-induced formation of size-controlled self-assemblies of amphiphilic Janus-type polymers as optical tumor-imaging agents.

In this study, amphiphilic Janus-type polymers were synthesized via ring-opening metathesis polymerization (ROMP), multiple vicinal diol formation, and grafting of poly(ethylene glycol) monomethyl ether (mPEG). These amphiphilic polymers formed self-assemblies, which were a mixture of micelles and multimicellar aggregates, in water. By choosing suitable Janus-type polymers and irradiating an aqueous solution of polymers using a sonicator, either small micelles or large multimicellar aggregates were obtained selectively. Hydrophobic substituents controlled the aggregation-disaggregation behavior, leading to the formation of metastable self-assemblies by sonication. The formation of self-assemblies with a uniform size was affected by ultrasonic frequency, rather than power. In vivo optical tumor imaging revealed that the large-size multimicellar aggregates persisting for a long time in blood circulation slowly accumulated in tumor tissues. In contrast, the tumor site was rapidly, clearly visualized using the small-size micelles

Acute Retinal Necrosis Associated with Epstein-Barr Virus in a Patient Undergoing Immunosuppressive Therapy

Acute retinal necrosis (ARN) is a rapidly progressive and severe retinitis resulting in a poor visual outcome. Infections caused by herpes viruses such as herpes simplex virus (HSV) types 1 and 2 or the varicella zoster virus (VZV) are known to be implicated in the development of ARN. In the present study, an 80-year-old female with ARN was examined. She had been affected with rheumatoid arthritis and had taken methotrexate for over 10 years. Her right eye showed clinical features of ARN, and her left eye showed mild retinitis. The genomic DNA in the aqueous humor and vitreous fluid from her right eye were analyzed by a comprehensive polymerase chain reaction (PCR) assay to screen infectious pathogens including viruses. The Epstein-Barr virus (EBV) was detected from both specimens, but neither HSV or VZV nor cytomegalovirus was detected. She underwent intraocular surgery following systemic corticosteroid and acyclovir applications. However, although the retinitis of her right eye was extinguished, the final visual outcome was blindness due to optic nerve atrophy. There are few reports indicating that EBV is associated with ARN development. The present findings suggest that EBV alone can be the causative agent of ARN

Systemic Cyclosporine Therapy for Scleritis: A Proposal of a Novel System to Assess the Activity of Scleritis

In the present study, two female patients with unilateral scleritis without systemic complications were examined. Both patients were suffering from ocular pain and received corticosteroid therapy. The first patient, a 45-year-old woman, was diagnosed with scleritis and iritis in her right eye. Topical corticosteroid treatment could eradicate the iritis but not the scleritis. Oral corticosteroid administration and corticosteroid pulse therapy were applied with little effect. The application of systemic cyclosporine had a satisfactory effect in controlling the scleritis. The other patient, a 60-year-old woman, was suffering from scleritis and lid swelling in her right eye. Not only did topical and systemic corticosteroid therapy prove insufficient, they also resulted in the elevation of her intraocular pressure. After termination of corticosteroid therapy, the systemic cyclosporine was applied orally. Subsequently, the patient's scleritis improved without any severe side effects. Scleritis is a painful and destructive inflammatory disease of the sclera that causes congestion of the scleral venous plexus. In this study, we have established a new grading system for assessing activity in scleritis that can score the extent of ocular pain and the area of congestion. This system provides a practical method for following the clinical course and monitoring the outcome of therapy. We report two cases of unilateral scleritis that were resistant to corticosteroid therapy but responsive to systemic administration of cyclosporine. Findings from these cases indicate that cyclosporine is an effective drug for controlling severe scleritis

Association of Cryptogenic Organizing Pneumonia in Bilateral Anterior Uveitis

Two female patients with histories of cancer who showed cryptogenic organizing pneumonia (COP) complications and bilateral anterior uveitis with hypopyon were examined. Both patients had suffered from COP and received intermitted systemic corticosteroid administration (SCA). The first patient, a 65-year-old woman with a history of breast cancer, showed bilateral uveitis with hypopyon. The topical corticosteroid treatment was ineffective. After SCA for the treatment of COP was started, the hypopyon gradually dissipated. Upon termination of SCA, uveitis relapses were controlled by renewed SCA. The other patient, a 69-year-old woman with a history of ovarian cancer, showed bilateral anterior uveitis with hypopyon. Her intraocular outcome did not improve by the topical corticosteroid administration, but SCA that was applied to treat COP led to remission of uveitis. Imaging examinations, biochemical analysis, symptoms or HLA-B27 antigen screenings in either patient did not explain the development of uveitis. Bilateral anterior uveitis is commonly related to autoimmune disease or systemic syndrome. We report two cases with COP that developed bilateral anterior uveitis with hypopyon resistant to topical administration but responsive to systemic administration of corticosteroid. These findings suggest that COP can be associated with the etiology of anterior uveitis