Summary Metabolic disorders including obesity and insulin resistance have their basis in dysregulated lipid metabolism and low-grade inflammation. In a microarray search of unique lipase-related genes whose expressions are associated with obesity, we found that two secreted phospholipase A2s (sPLA2s), PLA2G5 and PLA2G2E, were robustly induced in adipocytes of obese mice. Analyses of Pla2g5−/− and Pla2g2e−/− mice revealed distinct and previously unrecognized roles of these sPLA2s in diet-induced obesity. PLA2G5 hydrolyzed phosphatidylcholine in fat-overladen low-density lipoprotein to release unsaturated fatty acids, which prevented palmitate-induced M1 macrophage polarization. As such, PLA2G5 tipped the immune balance toward an M2 state, thereby counteracting adipose tissue inflammation, insulin resistance, hyperlipidemia and obesiy. PLA2G2E altered minor lipoprotein phospholipids, phosphatidylserine and phosphatidylethanolamine, and moderately facilitated lipid accumulation in adipose tissue and liver. Collectively, the identification of “metabolic sPLA2s” adds this gene family to a growing list of lipolytic enzymes that act as metabolic coordinators.

Among the many mammalian secreted phospholipase A 2 (sPLA 2 ) enzymes, PLA2G3 (group III secreted phospholipase A 2 ) is unique in that it possesses unusual N-and C-terminal domains and in that its central sPLA 2 domain is homologous to bee venom PLA 2 rather than to other mammalian sPLA 2 s. To elucidate the in vivo actions of this atypical sPLA 2 , we generated transgenic (Tg) mice overexpressing human PLA2G3. Despite marked increases in PLA 2 activity and mature 18-kDa PLA2G3 protein in the circulation and tissues, PLA2G3 Tg mice displayed no apparent abnormality up to 9 months of age. However, alterations in plasma lipoproteins were observed in PLA2G3 Tg mice compared with control mice. In vitro incubation of low density (LDL) and high density (HDL) lipoproteins with several sPLA 2 s showed that phosphatidylcholine was efficiently converted to lysophosphatidylcholine by PLA2G3 as well as by PLA2G5 and PLA2G10, to a lesser extent by PLA2G2F, and only minimally by PLA2G2A and PLA2G2E. PLA2G3-modified LDL, like PLA2G5-or PLA2G10-treated LDL, facilitated the formation of foam cells from macrophages ex vivo. Accumulation of PLA2G3 was detected in the atherosclerotic lesions of humans and apoE-deficient mice. Furthermore, following an atherogenic diet, aortic atherosclerotic lesions were more severe in PLA2G3 Tg mice than in control mice on the apoE-null background, in combination with elevated plasma lysophosphatidylcholine and thromboxane A 2 levels. These results collectively suggest a potential functional link between PLA2G3 and atherosclerosis, as has recently been proposed for PLA2G5 and PLA2G10.

Although lipid metabolism is thought to be important for the proper maturation and function of spermatozoa, the molecular mechanisms that underlie this dynamic process in the gonads remains incompletely understood. Here, we show that group III phospholipase A 2 (sPLA 2 -III), a member of the secreted phospholipase A 2 (sPLA 2 ) family, is expressed in the mouse proximal epididymal epithelium and that targeted disruption of the gene encoding this protein (Pla2g3) leads to defects in sperm maturation and fertility. Although testicular spermatogenesis in Pla2g3 -/-mice was grossly normal, spermatozoa isolated from the cauda epididymidis displayed hypomotility, and their ability to fertilize intact eggs was markedly impaired. Transmission EM further revealed that epididymal spermatozoa in Pla2g3 -/-mice had both flagella with abnormal axonemes and aberrant acrosomal structures. During epididymal transit, phosphatidylcholine in the membrane of Pla2g3 +/+ sperm underwent a dramatic shift in its acyl groups from oleic, linoleic, and arachidonic acids to docosapentaenoic and docosahexaenoic acids, whereas this membrane lipid remodeling event was compromised in sperm from Pla2g3 -/-mice. Moreover, the gonads of Pla2g3 -/-mice contained less 12/15-lipoxygenase metabolites than did those of Pla2g3 +/+ mice. Together, our results reveal a role for the atypical sPLA 2 family member sPLA 2 -III in epididymal lipid homeostasis and indicate that its perturbation may lead to sperm dysfunction.

Although perturbed lipid metabolism can often lead to skin abnormality, the role of phospholipase A 2 (PLA 2 ) in skin homeostasis is poorly understood. In the present study we found that group X-secreted PLA 2 (sPLA 2 -X) was expressed in the outermost epithelium of hair follicles in synchrony with the anagen phase of hair cycling. Transgenic mice overexpressing sPLA 2 -X (PLA2G10-Tg) displayed alopecia, which was accompanied by hair follicle distortion with reduced expression of genes related to hair development, during a postnatal hair cycle. Additionally, the epidermis and sebaceous glands of PLA2G10-Tg skin were hyperplasic. Proteolytic activation of sPLA 2 -X in PLA2G10-Tg skin was accompanied by preferential hydrolysis of phosphatidylethanolamine species with polyunsaturated fatty acids as well as elevated production of some if not all eicosanoids. Importantly, the skin of Pla2g10-deficient mice had abnormal hair follicles with noticeable reduction in a subset of hair genes, a hypoplasic outer root sheath, a reduced number of melanin granules, and unexpected up-regulation of prostanoid synthesis. Collectively, our study highlights the spatiotemporal expression of sPLA 2 -X in hair follicles, the presence of skin-specific machinery leading to sPLA 2 -X activation, a functional link of sPLA 2 -X with hair follicle homeostasis, and compartmentalization of the prostanoid pathway in hair follicles and epidermis.Hair follicle morphogenesis is regulated by interactions between epidermal keratinocytes committed to hair follicle differentiation and dermal fibroblasts committed to form the dermal papilla of the developing hair follicles (1-3). These epithelialmesenchymal interactions culminate in the formation of the hair shaft, which is surrounded by the multilayered inner root sheath (IRS) 3 and outer root sheath (ORS), the latter being the outermost concentric layer of epithelial cells. Hair follicles undergo repeated cycles of growth (anagen), regression (catagen), and rest (telogen) during their life span. Distinct signaling pathways and transcription factors control hair follicle morphogenesis, postnatal hair growth, and hair cycling in a coordinated manner. Accordingly, disturbance in the expression or function of these genes by point mutations, transgenic (Tg) overexpression, or targeted disruption often culminates in a hairless phenotype. Because hair loss due to various factors, such as diseases, hormonal imbalance, and drug regimens, affects a large population worldwide, there are compelling reasons to understand the fundamentals of hair biology.Current evidence suggests that, in addition to a variety of cytokines and growth factors (4, 5), lipids also play important roles in hair follicle homeostasis (6, 7). The PGE 2 receptors EP3 and EP4 are expressed in the dermal papilla and ORS of hair follicles (8, 9). COX-2 displays a trend of hair cycle-synchronized expression in the ORS of hair follicles (9), and skin-specific Tg overexpression of COX-2 leads to delayed emergence of hair shafts, reduced hair fo...

Although the secreted phospholipase A 2 (sPLA 2 ) family has been generally thought to participate in pathologic events such as inflammation and atherosclerosis, relatively high and constitutive expression of group X sPLA 2 (sPLA 2 -X) in restricted sites such as reproductive organs, the gastrointestinal tract, and peripheral neurons raises a question as to the roles played by this enzyme in the physiology of reproduction, digestion, and the nervous system. Herein we used mice with gene disruption or transgenic overexpression of sPLA 2 -X to clarify the homeostatic functions of this enzyme at these locations. Our results suggest that sPLA 2 -X regulates 1) the fertility of spermatozoa, not oocytes, beyond the step of flagellar motility, 2) gastrointestinal phospholipid digestion, perturbation of which is eventually linked to delayed onset of a lean phenotype with reduced adiposity, decreased plasma leptin, and improved muscle insulin tolerance, and 3) neuritogenesis of dorsal root ganglia and the duration of peripheral pain nociception. Thus, besides its inflammatory action proposed previously, sPLA 2 -X participates in physiologic processes including male fertility, gastrointestinal phospholipid digestion linked to adiposity, and neuronal outgrowth and sensing.

PLA2 (phospholipase A2) group III is an atypical sPLA2 (secretory PLA2) that is homologous with bee venom PLA2 rather than with other mammalian sPLA2s. In the present paper, we show that endogenous group III sPLA2 (PLA2G3) is expressed in mouse skin and that Tg (transgenic) mice overexpressing human PLA2G3 spontaneously develop skin inflammation. Pla2g3-Tg mice over 9 months of age frequently developed dermatitis with hyperkeratosis, acanthosis, parakeratosis, erosion, ulcer and sebaceous gland hyperplasia. The dermatitis was accompanied by infiltration of neutrophils and macrophages and by elevated levels of pro-inflammatory cytokines, chemokines and prostaglandin E2. In addition, Pla2g3-Tg mice had increased lymph aggregates and mucus in the airway, lymphocytic sialadenitis, hepatic extramedullary haemopoiesis, splenomegaly with increased populations of granulocytes and monocytes/macrophages, and increased serum IgG1. Collectively, these observations provide the first demonstration of spontaneous development of inflammation in mice with Tg overexpression of mammalian sPLA2.

Phospholipase A2 (PLA2) is a group of enzymes that hydrolyze the sn-2 position of glycerophospholipids to yield fatty acids and lysophospholipids. Of many PLA2s or related enzymes identified to date, secreted PLA2s (sPLA2s) comprise the largest family that contains 10 catalytically active isozymes. Besides arachidonic acid released from cellular membranes for eicosanoid synthesis, several if not all sPLA2s have recently been implicated in hydrolysis of phospholipids in lipoprotein particles. The sPLA2-processed low-density lipoprotein (LDL) particles contain a large amount of lysophospholipids and exhibit the property of “small-dense” or “modified” LDL, which facilitates foam cell formation from macrophages. Transgenic overexpression of these sPLA2s leads to development of atherosclerosis in mice. More importantly, genetic deletion or pharmacological inhibition of particular sPLA2s significantly attenuates atherosclerosis and aneurysm. In this article, we will give an overview of current understanding of the role of sPLA2s in atherosclerosis, with recent lipidomics data showing the action of a subset of sPLA2s on lipoprotein phospholipids.

Introduction Early discontinuation and poor adherence are common limitations of conventional preventive migraine medications that limit their long-term efficacy. Therefore, a migraine preventive medication with favorable long-term safety is warranted. Objective This study aimed to evaluate the long-term safety and tolerability of fremanezumab for the preventive treatment of chronic or episodic migraine in Japanese patients. Methods In this 52-week, randomized, open-label, parallel-group study, fremanezumab monthly or quarterly was administered in newly enrolled Japanese patients with chronic migraine or episodic migraine. Safety was assessed by monitoring of treatment-emergent adverse events, including injection-site reactions, laboratory and vital sign assessments. Newly enrolled patients and rollover patients from previous phase IIb/III trials who did not receive fremanezumab in this study were included in the immunogenicity testing cohort (n = 587). Efficacy outcomes included changes from baseline in the average monthly migraine days and headache days of at least moderate severity. Other efficacy outcomes included changes in disability scores. Results A total of 50 patients were enrolled with chronic migraine (monthly, n = 17; quarterly, n = 17) or episodic migraine (monthly, n = 8; quarterly, n = 8). The most commonly reported treatment-emergent adverse events were nasopharyngitis (64.0%) and injection-site reactions (erythema, 24.0%; induration, 10.0%; pain, 8.0%; pruritus, 6.0%). The discontinuation rate was low (4.0% from adverse events, 2.0% from a lack of efficacy) and no deaths were reported. The incidence of antidrug antibody development was low (2.4%). Fremanezumab reduced monthly migraine days and headache days of at least moderate severity from 1 month after initial administration, and this effect was maintained with no worsening throughout 12 months. Fremanezumab also led to sustained reductions in any acute headache medication use and headache-related disability at 12 months. Conclusions Fremanezumab administered monthly and quarterly was well tolerated in patients with chronic migraine and episodic migraine and led to sustained improvements in monthly migraine days and headache days of at least moderate severity throughout 12 months. Clinical Trial Registration ClinicalTrials.gov Identifier: NCT03303105.