Phospholipase A2 activities in skin physiology and pathology.

Skin inflammatory diseases are most commonly treated with corticosteroids, especially topical preparations, benefitting from high potency and unparalleled formulation flexibility. However, these benefits are limited due to side effects, especially under long-term use. Non-steroidal anti-inflammatory drugs (NSAIDs) which block the COX pathways have been used as safer alternatives to corticosteroids, and much effort and resources have been invested in developing COX inhibitors. However, synthetic NSAIDs are less potent than steroids, have limited formulation flexibility and have their own safety issues, thereby yielding unsatisfactory results, with some high-profile drugs (e.g., the COX-2 inhibitors Vioxx, Celebrex) being withdrawn from the market due to safety concerns. The potency and safety challenges of NSAIDs are related to inter-eicosanoid dynamics, pertaining to their pro-versus anti-inflammatory action, homeostatic functions and tissue-specific activities. Instead, the upstream control of phospholipase A2 (PLA2) enzymatic activity, which hydrolyzes cell membrane phospholipids to initiate the eicosanoid production, has been considered for inhibiting eicosanoid activation while maintaining the intricate balance needed for their homeostatic functions. Yet, PLA(2) inhibitors have hardly been tested for treating skin inflammatory/allergic conditions. In this article we review the involvement of PLA(2)s in skin physiology and pathology, and discuss the prospect of PLA(2) inhibition for the treatment of dermatological diseases.

Screening for active small molecules in mitochondrial complex I deficient patient's fibroblasts, reveals AICAR as the most beneficial compound.

Congenital deficiency of the mitochondrial respiratory chain complex I (CI) is a common defect of oxidative phosphorylation (OXPHOS). Despite major advances in the biochemical and molecular diagnostics and the deciphering of CI structure, function assembly and pathomechanism, there is currently no satisfactory cure for patients with mitochondrial complex I defects. Small molecules provide one feasible therapeutic option, however their use has not been systematically evaluated using a standardized experimental system. In order to evaluate potentially therapeutic compounds, we set up a relatively simple system measuring different parameters using only a small amount of patient's fibroblasts, in glucose free medium, where growth is highly OXPOS dependent. Ten different compounds were screened using fibroblasts derived from seven CI patients, harboring different mutations.5-Aminoimidazole-4-carboxamide ribotide (AICAR) was found to be the most beneficial compound improving growth and ATP content while decreasing ROS production. AICAR also increased mitochondrial biogenesis without altering mitochondrial membrane potential (Δψ). Fluorescence microscopy data supported increased mitochondrial biogenesis and activation of the AMP activated protein kinase (AMPK). Other compounds such as; bezafibrate and oltipraz were rated as favorable while polyphenolic phytochemicals (resverastrol, grape seed extract, genistein and epigallocatechin gallate) were found not significant or detrimental. Although the results have to be verified by more thorough investigation of additional OXPHOS parameters, preliminary rapid screening of potential therapeutic compounds in individual patient's fibroblasts could direct and advance personalized medical treatment.

2-Hydroxylated sphingomyelin profiles in cells from patients with mutated fatty acid 2-hydroxylase.

Fatty acid 2-hydroxylase (FA2H) is the enzyme responsible for the hydroxylation of free fatty acids prior to their incorporation into 2-hydroxylated sphingolipids, which are the major constituents of the myelin leaflet. Mutated FA2H has been associated with neurodegenerative diseases. Decreased FA2H activity was demonstrated only in vitro, but not in patient tissues. In this study we characterized the 2-hydroxylated sphingomyelin (SM) profiles in blood and fibroblasts from patients harboring a deleterious FA2H mutatation, and found that hydroxylated fatty acid sphingomyelin is present in normal amounts in patient lymphocytes, but decreased to a different extent in fibroblasts and erythrocytes.

The interplay between SUCLA2, SUCLG2, and mitochondrial DNA depletion.

SUCLA2-related mitochondrial DNA (mtDNA) depletion syndrome is a result of mutations in the ß subunit of the ADP-dependent isoform of the Krebs cycle succinyl-CoA synthase (SCS). The mechanism of tissue specificity and mtDNA depletion is elusive but complementation by the GDP-dependent isoform encoded by SUCLG2, and the association with mitochondrial nucleoside diphosphate kinase (NDPK), is a plausible link. We have investigated this relationship by studying SUCLA2 deficient fibroblasts derived from patients and detected normal mtDNA content and normal NDPK activity. However, knockdown of SUCLG2 by shRNA in both patient and control fibroblasts resulted in a significant decrease in mtDNA amount, decreased NDPK and cytochrome c oxidase activities, and a marked growth impairment. This suggests that, SUCLG2, to a higher degree than SUCLA2, is crucial for mtDNA maintenance and that mitochondrial NDPK is involved. Although results pertain to a cell culture system, the findings might explain the pathomechanism and tissue specificity in mtDNA depletion caused by defective SUCLA2.

Extracellular phospholipase A2 inhibitors suppress central nervous system inflammation.

Phospholipase A2 (PLA2) plays a key role in the production of proinflammatory mediators, namely the arachidonic acid-derived eicosanoids, lysophospholipids, and platelet-activating factor, and indirectly influences the generation of cytokines, nitric oxide (NO), and free radicals. Accordingly, regulation of its activity is important in the treatment of inflammation. Since the main site of PLA2 action in inflammatory processes is the cell membrane, we synthesized extracellular PLA2 inhibitors (ExPLIs) composed of N-derivatized phosphatidyl-ethanolamine linked to polymeric carriers. These membrane-anchored lipid conjugates do not penetrate the cell and interfere with vital phospholipid metabolism or cell viability. The ExPLIs markedly inhibited central nervous system inflammation. This was reflected by the suppressed production and secretion of lipopolysaccharide-induced sPLA2, prostaglandin E2, and NO by glial cells and by the amelioration of experimental autoimmune encephalomyelitis in rats and mice.