The impact of cyclooxygenase inhibitor use on urinary prostaglandin metabolites in preterm infants

BACKGROUND

There is limited evidence on the association between the clinical course of patent ductus arteriosus (PDA) and prostaglandin (PG) metabolites. This study aimed to determine the influence of PDA treatment on urinary PG metabolite excretion in very-low-birth-weight (VLBW) infants.

METHODS

Urine samples were collected from 25 VLBW infants at 1, 3, and 7 days of age. Infants were separated into two groups: a PDA-treated group that received a cyclooxygenase-2 (COX) inhibitor (n = 12) and a control group that did not receive a COX inhibitor during the first 7 days after birth (n = 13). Urinary PG metabolite tetranor prostaglandin E2 metabolite (t-PGEM) and tetranor prostaglandin D2 metabolite (t-PGDM) levels were analyzed using liquid chromatography-tandem mass spectrometry.

RESULTS

Urinary t-PGEM excretion levels were not significantly different between the groups at 1, 3, and 7 days of age. Urinary t-PGDM excretion levels at 1 day of age were higher in PDA-treated infants than in control infants (median [interquartile range]: 5.5 [2.6, 12.2] versus 2.1 [1.0, 3.9] ng/mg creatinine; p = 0.017); however, among PDA-treated infants, the levels were significantly lower at 3 and 7 days than at 1 day of age (5.5 [2.6, 12.2] versus 3.4 [1.7, 4.5] and 4.0 [1.7, 5.3] ng/mg creatinine, respectively; p < 0.05). The urinary t-PGDM excretion level in the control group did not significantly differ among the time points.

CONCLUSION

PDA and COX inhibitor administration affected PG metabolism in VLBW infants. Our results indicated that urinary t-PGDM excretion was significantly associated with PDA-treatment in preterm infants.

Robust and Objective Evaluation of Superficial Punctate Keratopathy in a Murine Dry Eye Model

Purpose

To establish a robust and objective method to evaluate (SPK) superficial punctate keratopathy in a murine dry eye model by developing a reliable photographic system.

Design

Experimental study.

Subjects

A murine dry eye model was generated by exorbital lacrimal gland excision. Sham-operated mice were used as healthy controls. For the sham operation, an incision was made without touching the gland.

Methods

A photographic system was constructed, consisting of an LED lamp and a digital camera fitted with a zoom lens and sharp cut filter. SPK was detected by applying fluorescein solution. To validate the system, SPK was compared between dry eye mice and healthy control mice, and diquafosol (DIQUAS ophthalmic solution 3%; Santen Pharmaceutical Co., Ltd.) or cyclosporine (PAPILOCK Mini ophthalmic solution 0.1%; Santen Pharmaceutical Co., Ltd.) was used to dry eye mice.

Main Outcome Measures

SPK was evaluated using the parameters of fluorescence score and fluorescein-stained area.

Results

The photographs clearly indicated SPK in dry eye mice. A fluorescence score of 0 to 9 could be easily assessed, and the fluorescein-stained area was quantifiable. The fluorescein-stained area correlated with fluorescence score (correlation coefficient: 0.98), with good interobserver reliability (intraclass correlation coefficient: 0.999). The fluorescein-stained area increased significantly in dry eye mice compared with that of healthy controls (P < 0.0001). Both types of therapeutic eye drops decreased the fluorescein-stained area relative to saline-treated mice (P < 0.05 in diquafosol vs. saline; P < 0.01 in cyclosporine vs. saline).

Conclusions

This newly developed system is a robust alternative for quantitative evaluation of SPK in a murine dry eye model.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Development of sexual dimorphism of skeletal muscles through the adrenal cortex, caused by androgen-induced global gene suppression

The zona fasciculata (zF) in the adrenal cortex contributes to multiple physiological actions through glucocorticoid synthesis. The size, proliferation, and glucocorticoid synthesis characteristics are all female biased, and sexual dimorphism is established by androgen. In this study, transcriptomes were obtained to unveil the sex differentiation mechanism. Interestingly, both the amount of mRNA and the expressions of nearly all genes were higher in females. The expression of Nr5a1, which is essential for steroidogenic cell differentiation, was also female biased. Whole-genome studies demonstrated that NR5A1 regulates nearly all gene expression directly or indirectly. This suggests that androgen-induced global gene suppression is potentially mediated by NR5A1. Using Nr5a1 heterozygous mice, whose adrenal cortex is smaller than the wild type, we demonstrated that the size of skeletal muscles is possibly regulated by glucocorticoid synthesized by zF. Taken together, considering the ubiquitous presence of glucocorticoid receptors, our findings provide a pathway for sex differentiation through glucocorticoid synthesis.

Bicarbonate signalling via G protein-coupled receptor regulates ischaemia-reperfusion injury

Homoeostatic regulation of the acid-base balance is essential for cellular functional integrity. However, little is known about the molecular mechanism through which the acid-base balance regulates cellular responses. Here, we report that bicarbonate ions activate a G protein-coupled receptor (GPCR), i.e., GPR30, which leads to Gq-coupled calcium responses. Gpr30-Venus knock-in mice reveal predominant expression of GPR30 in brain mural cells. Primary culture and fresh isolation of brain mural cells demonstrate bicarbonate-induced, GPR30-dependent calcium responses. GPR30-deficient male mice are protected against ischemia-reperfusion injury by a rapid blood flow recovery. Collectively, we identify a bicarbonate-sensing GPCR in brain mural cells that regulates blood flow and ischemia-reperfusion injury. Our results provide a perspective on the modulation of GPR30 signalling in the development of innovative therapies for ischaemic stroke. Moreover, our findings provide perspectives on acid/base sensing GPCRs, concomitantly modulating cellular responses depending on fluctuating ion concentrations under the acid-base homoeostasis.

FTY720 requires vitamin B12-TCN2-CD320 signaling in astrocytes to reduce disease in an animal model of multiple sclerosis

Vitamin B12 (B12) deficiency causes neurological manifestations resembling multiple sclerosis (MS); however, a molecular explanation for the similarity is unknown. FTY720 (fingolimod) is a sphingosine 1-phosphate (S1P) receptor modulator and sphingosine analog approved for MS therapy that can functionally antagonize S1P1. Here, we report that FTY720 suppresses neuroinflammation by functionally and physically regulating the B12 pathways. Genetic and pharmacological S1P1 inhibition upregulates a transcobalamin 2 (TCN2)-B12 receptor, CD320, in immediate-early astrocytes (ieAstrocytes; a c-Fos-activated astrocyte subset that tracks with experimental autoimmune encephalomyelitis [EAE] severity). CD320 is also reduced in MS plaques. Deficiency of CD320 or dietary B12 restriction worsens EAE and eliminates FTY720's efficacy while concomitantly downregulating type I interferon signaling. TCN2 functions as a chaperone for FTY720 and sphingosine, whose complex induces astrocytic CD320 internalization, suggesting a delivery mechanism of FTY720/sphingosine via the TCN2-CD320 pathway. Taken together, the B12-TCN2-CD320 pathway is essential for the mechanism of action of FTY720.

The leukotriene B4 receptors BLT1 and BLT2 as potential therapeutic targets

Leukotriene B4 (LTB4 ) was recognized as an arachidonate-derived chemotactic factor for inflammatory cells and an important drug target even before the molecular identification of its receptors. We cloned the high- and low-affinity LTB4 receptors, BLT1 and BLT2, respectively, and examined their functions by generating and studying gene-targeted mice. BLT1 is involved in the pathogenesis of various inflammatory and immune diseases, including asthma, psoriasis, contact dermatitis, allergic conjunctivitis, age-related macular degeneration, and immune complex-mediated glomerulonephritis. Meanwhile, BLT2 is a high-affinity receptor for 12-hydroxyheptadecatrienoic acid, which is involved in the maintenance of dermal and intestinal barrier function, and the acceleration of skin and corneal wound healing. Thus, BLT1 antagonists and BLT2 agonists are promising candidates in the treatment of inflammatory diseases.

Deficiency of leukotriene B4 receptor type 1 ameliorates ovalbumin-induced allergic enteritis in mice

Leukotriene B4 receptor type 1 (BLT1), a high-affinity receptor for leukotriene B4 (LTB4), plays an important role in inflammatory responses, including allergic airway inflammation. In this study, we examined the effect of genetic BLT1 deletion (BLT1KO) on ovalbumin (OVA)-induced allergic enteritis in mice to determine the pathogenic role of LTB4/BLT1 in allergic enteritis, a gastrointestinal form of food allergy. Repeated oral OVA challenges after sensitization with OVA and aluminium potassium sulphate induced allergic enteritis, characterized by systemic allergic symptoms (scratching, immobility and swelling), diarrhoea, colonic oedema and colonic goblet cell hyperplasia, accompanied by increased colonic peroxidase activity, colonic inflammatory cytokine expression and increased serum OVA-specific IgE levels. The severity of enteritis was significantly attenuated in BLT1KO mice compared with wild-type (WT) mice, without an increase in serum OVA-specific IgE levels. The accumulation of neutrophils, eosinophils, M2-macrophages, dendritic cells, CD4+ T cells and mast cells was observed in the colonic mucosa of allergic enteritis, and such accumulation was significantly lower in BLT1KO mice than in WT mice. BLT1 expression was upregulated and colocalized mostly in neutrophils and partly in eosinophils and dendritic cells in the colonic mucosa of allergic enteritis. These findings indicate that BLT1 deficiency ameliorates OVA-induced allergic enteritis in mice and that LTB4/BLT1 contributes to neutrophil and eosinophil accumulation in the allergic colonic mucosa. Therefore, BLT1 is a promising drug target for treating food allergies.

GWAS-identified bipolar disorder risk allele in the FADS1/2 gene region links mood episodes and unsaturated fatty acid metabolism in mutant mice

Large-scale genome-wide association studies (GWASs) on bipolar disorder (BD) have implicated the involvement of the fatty acid desaturase (FADS) locus. These enzymes (FADS1 and FADS2) are involved in the metabolism of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are thought to potentially benefit patients with mood disorders. To model reductions in the activity of FADS1/2 affected by the susceptibility alleles, we generated mutant mice heterozygously lacking both Fads1/2 genes. We measured wheel-running activity over six months and observed bipolar swings in activity, including hyperactivity and hypoactivity. The hyperactivity episodes, in which activity was far above the norm, usually lasted half a day; mice manifested significantly shorter immobility times on the behavioral despair test performed during these episodes. The hypoactivity episodes, which lasted for several weeks, were accompanied by abnormal circadian rhythms and a marked decrease in wheel running, a spontaneous behavior associated with motivation and reward systems. We comprehensively examined lipid composition in the brain and found that levels of certain lipids were significantly altered between wild-type and the heterozygous mutant mice, but no changes were consistent with both sexes and either DHA or EPA was not altered. However, supplementation with DHA or a mixture of DHA and EPA prevented these episodic behavioral changes. Here we propose that heterozygous Fads1/2 knockout mice are a model of BD with robust constitutive, face, and predictive validity, as administration of the mood stabilizer lithium was also effective. This GWAS-based model helps to clarify how lipids and their metabolisms are involved in the pathogenesis and treatment of BD.

The leukotriene B4 /BLT1-dependent neutrophil accumulation exacerbates immune complex-mediated glomerulonephritis

Crescent formation is the most important pathological finding that defines the prognosis of nephritis. Although neutrophils are known to play an important role in the progression of crescentic glomerulonephritis, such as anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, the key chemoattractant for neutrophils in ANCA-associated glomerulonephritis has not been identified. Here, we demonstrate that a lipid chemoattractant, leukotriene B₄ (LTB₄ ), and its receptor BLT1 are primarily involved in disease pathogenesis in a mouse model of immune complex-mediated crescentic glomerulonephritis. Circulating neutrophils accumulated into glomeruli within 1 h after disease onset, which was accompanied by LTB₄ accumulation in the kidney cortex, leading to kidney injury. LTB₄ was produced by cross-linking of Fc gamma receptors on neutrophils. Mice deficient in BLT1 or LTB₄ biosynthesis exhibited suppressed initial neutrophil infiltration and subsequent thrombotic glomerulonephritis and renal fibrosis. Depletion of neutrophils before, but not after, disease onset prevented proteinuria and kidney injury, indicating the essential role of neutrophils in the early phase of glomerulonephritis. Administration of a BLT1 antagonist before and after disease onset almost completely suppressed induction of glomerulonephritis. Finally, we found that the glomeruli from patients with ANCA-associated glomerulonephritis contained more BLT1-positive cells than glomeruli from patients with other etiologies. Taken together, the LTB₄ -BLT1 axis is the key driver of neutrophilic glomerular inflammation, and will be a novel therapeutic target for the crescentic glomerulonephritis.

The UFM1 system regulates ER-phagy through the ufmylation of CYB5R3

Protein modification by ubiquitin-like proteins (UBLs) amplifies limited genome information and regulates diverse cellular processes, including translation, autophagy and antiviral pathways. Ubiquitin-fold modifier 1 (UFM1) is a UBL covalently conjugated with intracellular proteins through ufmylation, a reaction analogous to ubiquitylation. Ufmylation is involved in processes such as endoplasmic reticulum (ER)-associated protein degradation, ribosome-associated protein quality control at the ER and ER-phagy. However, it remains unclear how ufmylation regulates such distinct ER-related functions. Here we identify a UFM1 substrate, NADH-cytochrome b5 reductase 3 (CYB5R3), that localizes on the ER membrane. Ufmylation of CYB5R3 depends on the E3 components UFL1 and UFBP1 on the ER, and converts CYB5R3 into its inactive form. Ufmylated CYB5R3 is recognized by UFBP1 through the UFM1-interacting motif, which plays an important role in the further uyfmylation of CYB5R3. Ufmylated CYB5R3 is degraded in lysosomes, which depends on the autophagy-related protein Atg7- and the autophagy-adaptor protein CDK5RAP3. Mutations of CYB5R3 and genes involved in the UFM1 system cause hereditary developmental disorders, and ufmylation-defective Cyb5r3 knock-in mice exhibit microcephaly. Our results indicate that CYB5R3 ufmylation induces ER-phagy, which is indispensable for brain development.

Identification and characterization of bioactive metabolites of 12-hydroxyheptadecatrienoic acid, a ligand for leukotriene B4 receptor 2

12(S)-hydroxyheptadecatrienoic acid (12-HHT) is a bioactive fatty acid synthesized from arachidonic acid via the cyclooxygenase pathway and serves as an endogenous ligand for the low-affinity leukotriene B4 receptor 2 (BLT2). Although the 12-HHT/BLT2 axis contributes to the maintenance of epithelial homeostasis, 12-HHT metabolism under physiological conditions is unclear. In this study, 12-keto-heptadecatrienoic acid (12-KHT) and 10,11-dihydro-12-KHT (10,11dh-12-KHT) were detected as 12-HHT metabolites in the human megakaryocytic cell line MEG01s. We found that 12-KHT and 10,11dh-12-KHT are produced from 12-HHT by 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and prostaglandin reductase 1 (PTGR1), key enzymes in the degradation of prostaglandins, respectively. The 15-PGDH inhibitor SW033291 completely suppressed the production of 12-KHT and 10,11dh-12-KHT in MEG01s cells, resulting in a 9-fold accumulation of 12-HHT. 12-KHT and 10,11dh-12-KHT were produced in mouse skin wounds, and the levels were significantly suppressed by SW033291. Surprisingly, the agonistic activities of 12-KHT and 10,11dh-12-KHT on BLT2 were comparable to that of 12-HHT. Taken together,12-HHT is metabolized into 12-KHT by 15-PGDH, and then 10,11dh-12-KHT by PTGR1 without losing the agonistic activity.

Role of leukotriene B4 (LTB4)-LTB4 receptor 1 signaling in post-incisional nociceptive sensitization and local inflammation in mice

Leukotriene B4 (LTB4) is a potent lipid mediator involved in the recruitment and activation of neutrophils, which is an important feature of tissue injury and inflammation. The biological effects of LTB4 are primarily mediated through the high-affinity LTB4 receptor, BLT1. Postoperative incisional pain is characterized by persistent acute pain at the site of tissue injury and is associated with local inflammation. Here, we compared the role of LTB4-BLT1 signaling in postoperative incisional pain between BLT1-knockout (BLT1KO) and wild-type (BLT1WT) mice. A planter incision model was developed, and mechanical pain hypersensitivity was determined using the von Frey test before and after incision. Local infiltration of neutrophils and inflammatory monocytes was quantified by flow cytometry. Inflammatory cytokine levels in the incised tissue were also determined. Mechanical pain hypersensitivity was significantly reduced in BLT1KO mice compared to BLT1WT mice at 2, 3, and 4 days after incision. LTB4 levels in the tissue at the incision site peaked 3 hours after the incision. Infiltrated neutrophils peaked 1 day after the incision in both BLT1KO and BLT1WT mice. The accumulation of inflammatory monocytes increased 1-3 days after the incision and was significantly more reduced in BLT1KO mice than in BLT1WT mice. In BLT1KO mice, Interleukin-1β and Tumor Necrosis Factor-α levels 1 day after the incision were significantly lower than those of BLT1WT mice. Our data suggest that LTB4 is produced and activates its receptor BLT1 in the very early phase of tissue injury, and that LTB4-BLT1 signaling exacerbates pain responses by promoting local infiltration of inflammatory monocytes and cytokine production. Thus, LTB4-BLT1 signaling is a potential target for therapeutic intervention of acute and persistent pain induced by tissue injury.

Omega-6 highly unsaturated fatty acids in Leydig cells facilitate male sex hormone production

Highly unsaturated fatty acids (HUFAs) are fatty acids with more than three double bonds in the molecule. Mammalian testes contain very high levels of omega-6 HUFAs compared with other tissues. However, the metabolic and biological significance of these HUFAs in the mammalian testis is poorly understood. Here we show that Leydig cells vigorously synthesize omega-6 HUFAs to facilitate male sex hormone production. In the testis, FADS2 (Fatty acid desaturase 2), the rate-limiting enzyme for HUFA biosynthesis, is highly expressed in Leydig cells. In this study, pharmacological and genetic inhibition of FADS2 drastically reduces the production of omega-6 HUFAs and male steroid hormones in Leydig cells; this reduction is significantly rescued by supplementation with omega-6 HUFAs. Mechanistically, hormone-sensitive lipase (HSL; also called LIPE), a lipase that supplies free cholesterol for steroid hormone production, preferentially hydrolyzes HUFA-containing cholesteryl esters as substrates. Taken together, our results demonstrate that Leydig cells highly express FADS2 to facilitate male steroid hormone production by accumulating omega-6 HUFA-containing cholesteryl esters, which serve as preferred substrates for HSL. These findings unveil a previously unrecognized importance of omega-6 HUFAs in the mammalian male reproductive system.

Leydig cells highly express FADS2 to facilitate male steroid hormone production by accumulating omega-6 HUFA-containing cholesteryl esters, which serve as preferred substrates for hormone-sensitive lipase

Lysophosphatidic acid receptor1/3 antagonist inhibits the activation of satellite glial cells and reduces acute nociceptive responses

Lysophosphatidic acid (LPA) exerts various biological activities through six characterized G protein-coupled receptors (LPA_1-6 ). While LPA-LPA₁  signaling contributes toward the demyelination and retraction of C-fiber and induces neuropathic pain, the effects of LPA-LPA₁  signaling on acute nociceptive pain is uncertain. This study investigated the role of LPA-LPA₁  signaling in acute nociceptive pain using the formalin test. The pharmacological inhibition of the LPA-LPA₁ axis significantly attenuated formalin-induced nociceptive behavior. The LPA₁  mRNA was expressed in satellite glial cells (SGCs) in dorsal root ganglion (DRG) and was particularly abundant in SGCs surrounding large DRG neurons, which express neurofilament 200. Treatment with LPA_1/3 receptor (LPA_1/3 ) antagonist inhibited the upregulation of glial markers and inflammatory cytokines in DRG following formalin injection. The LPA_1/3 antagonist also attenuated phosphorylation of extracellular signal-regulated kinase, especially in SGCs and cyclic AMP response element-binding protein in the dorsal horn following formalin injection. LPA amounts after formalin injection to the footpad were quantified by liquid chromatography/tandem mass spectrometry, and LPA levels were found to be increased in the innervated DRGs. Our results indicate that LPA produced in the innervated DRGs promotes the activation of SGCs through LPA₁ , increases the sensitivity of primary neurons, and modulates pain behavior. These results facilitate our understanding of the pathology of acute nociceptive pain and demonstrate the possibility of the LPA₁ on SGCs as a novel target for acute pain control.

Sphingosine 1-Phosphate (S1P) in the Peritoneal Fluid Skews M2 Macrophage and Contributes to the Development of Endometriosis

Sphingosine 1-phosphate (S1P), an inflammatory mediator, is abundantly contained in red blood cells and platelets. We hypothesized that the S1P concentration in the peritoneal cavity would increase especially during the menstrual phase due to the reflux of menstrual blood, and investigated the S1P concentration in the human peritoneal fluid (PF) from 14 non-endometriosis and 19 endometriosis patients. Although the relatively small number of samples requires caution in interpreting the results, S1P concentration in the PF during the menstrual phase was predominantly increased compared to the non-menstrual phase, regardless of the presence or absence of endometriosis. During the non-menstrual phase, patients with endometriosis showed a significant increase in S1P concentration compared to controls. In vitro experiments using human intra-peritoneal macrophages (MΦ) showed that S1P stimulation biased them toward an M2MΦ-dominant condition and increased the expression of IL-6 and COX-2. An in vivo study showed that administration of S1P increased the size of the endometriotic-like lesion in a mouse model of endometriosis.

Biosynthetic Crossover of 5-Lipoxygenase and Cyclooxygenase-2 Yields 5-Hydroxy-PGE2 and 5-Hydroxy-PGD2

The biosynthetic crossover of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) enzymatic activities is a productive pathway to convert arachidonic acid into unique eicosanoids. Here, we show that COX-2 catalysis with 5-LOX derived 5-hydroxy-eicosatetraenoic acid yields the endoperoxide 5-hydroxy-PGH2 that spontaneously rearranges to 5-OH-PGE2 and 5-OH-PGD2, the 5-hydroxy analogs of arachidonic acid derived PGE2 and PGD2. The endoperoxide was identified via its predicted degradation product, 5,12-dihydroxy-heptadecatri-6E,8E,10E-enoic acid, and by SnCl2-mediated reduction to 5-OH-PGF2α. Both 5-OH-PGE2 and 5-OH-PGD2 were unstable and degraded rapidly upon treatment with weak base. This instability hampered detection in biologic samples which was overcome by in situ reduction using NaBH4 to yield the corresponding stable 5-OH-PGF2 diastereomers and enabled detection of 5-OH-PGF2α in activated primary human leukocytes. 5-OH-PGE2 and 5-OH-PGD2 were unable to activate EP and DP prostanoid receptors, suggesting their bioactivity is distinct from PGE2 and PGD2.

The c-terminal region of BLT2 restricts its localization to the lateral membrane in a LIN7C-dependent manner

Leukotriene B₄ receptor type 2 (BLT2) is a G protein-coupled receptor (GPCR) mainly expressed in epithelial cells, where it enhances barrier function. A unique characteristic of BLT2 is its restricted localization to the lateral membrane. However, the molecular mechanism underlying the localization of BLT2 to the lateral membrane and the physiological roles of laterally localized BLT2 are unknown. BLT1 is the most homologous GPCR to BLT2 and localizes to both the apical and lateral membranes. In this study, we generated chimeric receptors of BLT2 and BLT1 as well as deletion mutants of BLT2 to determine the region(s) of BLT2 responsible for its localization. Chimeric receptors containing the C-terminal domain of BLT2 localized only to the lateral membrane, and the C-terminal deletion mutant of BLT2 accumulated at the Golgi apparatus. Furthermore, the middle and C-terminal regions of BLT2 were important for maintaining epithelial barrier function. Proteomics analysis using the chimeric BLT-ascorbate peroxidase 2 biotinylation method showed that some proteins involved in intracellular protein transport, cell-cell junctions, and actin filament binding were located very close to the C-terminal domain of BLT2. Knockdown of lin-7 homolog C (LIN7C), a membrane trafficking protein, led to accumulation of BLT2 in the Golgi apparatus, resulting in diminished epithelial barrier function. These results suggest that the C-terminal region of BLT2 plays an important role in the transport of BLT2 from the Golgi apparatus to the plasma membrane in a LIN7C-dependent manner.

Eicosanoid profiling in patients with complete form of pachydermoperiostosis carrying SLCO2A1 mutations

Pachydermoperiostosis (PDP) is a genetic disease characterized by digital clubbing, periostosis, and pachydermia caused by mutated HPGD or SLCO2A1. Plasma prostaglandin (PG)E₂ levels are increased in these patients. However, other eicosanoids have not been quantitated. We aimed to quantitate plasma eicosanoid levels in four patients carrying SLCO2A1 mutations by high-performance liquid chromatography-tandem mass spectrometry. PGE₂ level was elevated in all patients; PGD₂ and 11β-PGF₂ α levels were also increased in some patients, whereas eicosapentaenoic acid, docosahexaenoic acid, and arachidonic acid levels were decreased in all patients. Our data indicate a dysfunctional eicosanoid homeostasis and varied levels of PG in patients with a complete form of PDP carrying SLCO2A1 mutations. PGE₂ levels seem to mostly affect the symptoms, with other eicosanoids possibly having a minor effect.

Expression of leukotriene B4 receptor 1 defines functionally distinct DCs that control allergic skin inflammation

Leukotriene B4 (LTB4) receptor 1 (BLT1) is a chemotactic G protein-coupled receptor expressed by leukocytes, such as granulocytes, macrophages, and activated T cells. Although there is growing evidence that BLT1 plays crucial roles in immune responses, its role in dendritic cells remains largely unknown. Here, we identified novel DC subsets defined by the expression of BLT1, namely, BLT1hi and BLT1lo DCs. We also found that BLT1hi and BLT1lo DCs differentially migrated toward LTB4 and CCL21, a lymph node-homing chemoattractant, respectively. By generating LTB4-producing enzyme LTA4H knockout mice and CD11c promoter-driven Cre recombinase-expressing BLT1 conditional knockout (BLT1 cKO) mice, we showed that the migration of BLT1hi DCs exacerbated allergic contact dermatitis. Comprehensive transcriptome analysis revealed that BLT1hi DCs preferentially induced Th1 differentiation by upregulating IL-12p35 expression, whereas BLT1lo DCs accelerated T cell proliferation by producing IL-2. Collectively, the data reveal an unexpected role for BLT1 as a novel DC subset marker and provide novel insights into the role of the LTB4-BLT1 axis in the spatiotemporal regulation of distinct DC subsets.

Ablation of fatty acid desaturase 2 (FADS2) exacerbates hepatic triacylglycerol and cholesterol accumulation in polyunsaturated fatty acid-depleted mice

Deficiency of polyunsaturated fatty acids (PUFAs) is known to induce hepatic steatosis. However, it is not clearly understood which type of PUFA is responsible for the worsening of steatosis. This study observed a marked accumulation of hepatic triacylglycerol and cholesterol in fatty acid desaturase 2 knockout (FADS2^-/- ) mice lacking both C18 and ≥ C20 PUFAs that were fed a PUFA-depleted diet. Hepatic triacylglycerol accumulation was associated with enhanced sterol regulatory element-binding protein (SREBP)-1-dependent lipogenesis and decreased triacylglycerol secretion into the plasma via very-low-density lipoprotein (VLDL). Furthermore, upregulation of cholesterol synthesis contributed to increased hepatic cholesterol content in FADS2^-/- mice. These results suggest that ≥ C20 PUFAs synthesized by FADS2 are important in regulating hepatic triacylglycerol and cholesterol accumulation during PUFA deficiency.

Development of a liquid chromatography-electrospray ionization tandem mass spectrometric method for the simultaneous analysis of free fatty acids

Fatty acids (FAs) play important roles in several physiological and pathophysiological processes, functioning as both non-esterified free FAs (FFAs) and components of other lipid classes. Although many lipid classes are readily measured using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), the measurement of FFAs by this method is not straightforward because of inconsistent fragmentation behaviors. In this study, we describe a strategy to measure FFAs using conventional reverse-phase LC-ESI-MS/MS, without derivatization. The strategy combines three key methods: 1) an isocratic LC separation with a high organic solvent ratio, 2) post-column base addition, and 3) pseudo-multiple reaction monitoring. The method facilitates the measurement of ultra-long-chain FAs, the accumulation of which is a common biochemical abnormality in peroxisomal disorders. This study delivers a broad strategy that measures a wide spectrum of FFA species in complex biological samples.

Inhibition of Both Cyclooxygenase-1 and -2 Promotes Epicutaneous Th2 and Th17 Sensitization and Allergic Airway Inflammation on Subsequent Airway Exposure to Protease Allergen in Mice

INTRODUCTION

Epicutaneous (e.c.) allergen exposure is an important route of sensitization toward allergic diseases in the atopic march. Allergen sources such as house dust mites contain proteases that involve in the pathogenesis of allergy. Prostanoids produced via pathways downstream of cyclooxygenases (COXs) regulate immune responses. Here, we demonstrate effects of COX inhibition with nonsteroidal anti-inflammatory drugs (NSAIDs) on e.c. sensitization to protease allergen and subsequent airway inflammation in mice.

METHODS

Mice were treated with NSAIDs during e.c. sensitization to a model protease allergen, papain, and/or subsequent intranasal challenge with low-dose papain. Serum antibodies, cytokine production in antigen-restimulated skin or bronchial draining lymph node (DLN) cells, and airway inflammation were analyzed.

RESULTS

In e.c. sensitization, treatment with a nonspecific COX inhibitor, indomethacin, promoted serum total and papain-specific IgE response and Th2 and Th17 cytokine production in skin DLN cells. After intranasal challenge, treatment with indomethacin promoted allergic airway inflammation and Th2 and Th17 cytokine production in bronchial DLN cells, which depended modestly or largely on COX inhibition during e.c. sensitization or intranasal challenge, respectively. Co-treatment with COX-1-selective and COX-2-selective inhibitors promoted the skin and bronchial DLN cell Th cytokine responses and airway inflammation more efficiently than treatment with either selective inhibitor.

CONCLUSION

The results suggest that the overall effects of COX downstream prostanoids are suppressive for development and expansion of not only Th2 but also, unexpectedly, Th17 upon exposure to protease allergens via skin or airways and allergic airway inflammation.

Correction: A novel mutation in the SLCO2A1 gene, encoding a prostaglandin transporter, induces chronic enteropathy

[This corrects the article DOI: 10.1371/journal.pone.0241869.].

Eicosanoids in Skin Wound Healing

Wound healing is an important process in the human body to protect against external threats. A dysregulation at any stage of the wound healing process may result in the development of various intractable ulcers or excessive scar formation. Numerous factors such as growth factors, cytokines, and chemokines are involved in this process and play vital roles in tissue repair. Moreover, recent studies have demonstrated that lipid mediators derived from membrane fatty acids are also involved in the process of wound healing. Among these lipid mediators, we focus on eicosanoids such as prostaglandins, thromboxane, leukotrienes, and specialized pro-resolving mediators, which are produced during wound healing processes and play versatile roles in the process. This review article highlights the roles of eicosanoids on skin wound healing, especially focusing on the biosynthetic pathways and biological functions, i.e., inflammation, proliferation, migration, angiogenesis, remodeling, and scarring.

Levels of phospholipids and triacylglycerol-containing omega 3 fatty acids in myocardial tissue of patients with myocardial infarction: analyzed by a lipidomics profiling method

Objective

According to population-based studies, low omega 3 fatty acid (omega3FA) intake and high levels of serum triacylglycerol (TAG) are associated with cardiovascular diseases. Recent advances in mass spectrometry allow molecular lipid (lipidomics) profiling, which may enhance cardiovascular risk prediction. In this study, we assessed the levels of omega3FA-containing phospholipids (PL) and TAG in myocardial tissues of patients with and without myocardial infarction (MI) using a lipidomics profiling method.

Methods

We performed lipidomics profiling of human left atrial appendage (LAA) tissue of 29 consecutive patients receiving off-pump coronary bypass surgery with standard LAA resection. The patients were divided into the MI group (n=7) and an age- and gender-matched non-MI group (n=7).

Results

Lipidomics profiling revealed that the MI group tended to have low levels of phosphatidylcholines (PC), phosphatidylethanolamine (PE), lysophosphatidylethanolamine (LPE), and plasmalogen, and high levels of TAG species. Individual molecular species containing omega3FA, such as PC (18:0/20:5; 3,200±1,200 vs. 4,500±910 pmol/g tissue, p=0.04) and plasmalogen (18:1/20:5; 57,000±21,000 vs. 91,000±28,000 pmol/g tissue, p=0.02), were significantly lower in the MI group than in the non-MI group.

Conclusions

To our knowledge, this is the first study to determine the levels of omega3FA-containing PL and TAG in myocardial tissue using lipidomics profiling. We discovered that lower levels of omega3FA-containing PL and higher levels of TAG existed in myocardial tissues of patients with MI than in those of patients without MI. Accordingly, the lipidomics profiling method for human myocardial tissue may be useful for developing therapy targets for cardiovascular diseases.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): MEXT/JSPS KAKENHI Grant

Combined use of irinotecan and p53 activator enhances growth inhibition of mesothelioma cells

Malignant mesothelioma (MM) is an aggressive malignant neoplasm which rapidly invades pleural tissues and has a poor prognosis. Here, we explore enhancement of the effect of irinotecan [camptothecin-11 (CPT-11)] by the p53-dependent induction of carboxylesterase 2 (CES2), a CPT-11-activating enzyme, in MM. The level of CES2 mRNA was greatly increased on treatment with nutlin-3a. A combination of CPT-11 and nutlin-3a inhibited the growth of MM cells more effectively than either drug alone. Knocking down CES2 in MM cells reduced the effect of the drug combination, and its forced expression in MESO4 cells enhanced the growth inhibitory activity of CPT-11 in the absence of nutlin-3a. Enhancement of the growth inhibitory activity of CPT-11 by nutlin-3a suggests a possible new combinatorial MM chemotherapy regimen.

Trimebutine attenuates high mobility group box 1-receptor for advanced glycation end-products inflammatory signaling pathways

We previously identified papaverine as an inhibitor of receptor for advanced glycation end-products (RAGE) and showed its suppressive effect on high mobility group box 1 (HMGB1)-mediated responses to inflammation. Here, we found trimebutine to be a 3D pharmacophore mimetics of papaverine. Trimebutine was revealed to have more potent suppressive effects on HMGB1-induced production of pro-inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-α in macrophage-like RAW264.7 cells and mouse bone marrow primarily differentiated macrophages than did papaverine. However, the inhibitory effect of trimebutine on the interaction of HMGB1 and RAGE was weaker than that of papaverine. Importantly, mechanism-of-action analyses revealed that trimebutine strongly inhibited the activation of RAGE downstream inflammatory signaling pathways, especially the activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), which are mediator/effector kinases recruited to the intracellular domain of RAGE. Consequently, the activation of Jun amino terminal kinase, which is an important effector kinase for the up-regulation of pro-inflammatory cytokines, was inhibited. Taken together, these results suggest that trimebutine may exert its suppressive effect on the HMGB1-RAGE inflammatory signal pathways by strongly blocking the recruitment of ERK1/2 to the intracellular tail domain of RAGE in addition to its weak inhibition of the extracellular interaction of HMGB1 with RAGE. Thus, trimebutine may provide a unique scaffold for the development of novel dual inhibitors of RAGE for inflammatory diseases.

Leukotriene A4 hydrolase deficiency protects mice from diet-induced obesity by increasing energy expenditure through neuroendocrine axis

Obesity is a health problem worldwide, and brown adipose tissue (BAT) is important for energy expenditure. Here, we explored the role of leukotriene A₄ hydrolase (LTA₄ H), a key enzyme in the synthesis of the lipid mediator leukotriene B₄ (LTB₄ ), in diet-induced obesity. LTA₄ H-deficient (LTA₄ H-KO) mice fed a high-fat diet (HFD) showed a lean phenotype, and bone-marrow transplantation studies revealed that LTA₄ H-deficiency in non-hematopoietic cells was responsible for this lean phenotype. LTA₄ H-KO mice exhibited greater energy expenditure, but similar food intake and fecal energy loss. LTA₄ H-KO BAT showed higher expression of thermogenesis-related genes. In addition, the plasma thyroid-stimulating hormone and thyroid hormone concentrations, as well as HFD-induced catecholamine secretion, were higher in LTA₄ H-KO mice. In contrast, LTB₄ receptor (BLT1)-deficient mice did not show a lean phenotype, implying that the phenotype of LTA₄ H-KO mice is independent of the LTB₄ /BLT1 axis. These results indicate that LTA₄ H mediates the diet-induced obesity by reducing catecholamine and thyroid hormone secretion.

Aging exacerbates high-fat diet-induced steatohepatitis through alteration in hepatic lipid metabolism in mice

BACKGROUND AND AIM

Aging is an independent risk factor for the progression of non-alcoholic steatohepatitis. Here, we investigated the role of age-related alterations in fatty acid metabolism in dietary steatohepatitis using lipidomics analysis.

METHODS

Male 8-week and 55-week-old C57BL/6 J mice were fed a high-fat diet (HFD) for 8 weeks. The quality and quantity of lipid molecular species in the liver were evaluated using the lipidomics approach.

RESULTS

Elder mice fed an HFD developed more severe steatohepatitis than young mice. Oxidative stress and inflammatory cytokines in the liver were exacerbated following HFD feeding in elder mice compared with young mice. In elder mice, de novo fatty acid synthesis was promoted, whereas β oxidation was blunted following HFD feeding, and lipid secretion from the liver was reduced. The expression of sirtuin 1 was not only reduced with age as expected but also significantly decreased due to intake of HFD. In the lipidomics analysis, the concentrations of diacylglycerol and TAG molecular species containing monounsaturated fatty acids were markedly increased following HFD feeding in elder mice compared with young mice. In contrast, the concentration of phosphatidylethanolamine and phosphatidylcholine molecular species containing polyunsaturated fatty acids were remarkably decreased following HFD feeding in elder mice compared with young mice, and the expression of fatty acid desaturase was blunted.

CONCLUSIONS

Aging-dependent alterations in lipid metabolism under excessive lipid supply most likely enhance hepatic lipotoxicity, thereby exacerbating metabolic steatohepatitis in elderly.

Leukotriene B4 receptors as therapeutic targets for ophthalmic diseases

Leukotriene B₄ (LTB₄) is an inflammatory lipid mediator produced from arachidonic acid by multiple reactions catalyzed by two enzymes 5-lipoxygenase (5-LOX) and LTA₄ hydrolase (LTA₄H). The two receptors for LTB₄ have been identified: a high-affinity receptor, BLT1, and a low-affinity receptor, BLT2. Our group identified 12(S)-hydroxy-5Z,8E,10E-heptadecatrienoic acid (12-HHT) as a high-affinity BLT2 ligand. Numerous studies have revealed critical roles for LTB₄ and its receptors in various systemic diseases. Recently, we also reported the roles of LTB₄, BLT1 and BLT2 in the murine ophthalmic disease models of mice including cornea wound, allergic conjunctivitis, and age-related macular degeneration. Moreover, other groups revealed the evidence of the ocular function of LTB₄. In the present review, we introduce the roles of LTB₄ and its receptors both in ophthalmic diseases and systemic inflammatory diseases. LTB₄ and its receptors are putative novel therapeutic targets for systemic and ophthalmic diseases.

The PDK1-FoxO1 signaling in adipocytes controls systemic insulin sensitivity through the 5-lipoxygenase-leukotriene B4 axis

Although adipocytes are major targets of insulin, the influence of impaired insulin action in adipocytes on metabolic homeostasis remains unclear. We here show that adipocyte-specific PDK1 (3'-phosphoinositide-dependent kinase 1)-deficient (A-PDK1KO) mice manifest impaired metabolic actions of insulin in adipose tissue and reduction of adipose tissue mass. A-PDK1KO mice developed insulin resistance, glucose intolerance, and hepatic steatosis, and this phenotype was suppressed by additional ablation of FoxO1 specifically in adipocytes (A-PDK1/FoxO1KO mice) without an effect on adipose tissue mass. Neither circulating levels of adiponectin and leptin nor inflammatory markers in adipose tissue differed between A-PDK1KO and A-PDK1/FoxO1KO mice. Lipidomics and microarray analyses revealed that leukotriene B4 (LTB4) levels in plasma and in adipose tissue as well as the expression of 5-lipoxygenase (5-LO) in adipose tissue were increased and restored in A-PDK1KO mice and A-PDK1/FoxO1KO mice, respectively. Genetic deletion of the LTB4 receptor BLT1 as well as pharmacological intervention to 5-LO or BLT1 ameliorated insulin resistance in A-PDK1KO mice. Furthermore, insulin was found to inhibit LTB4 production through down-regulation of 5-LO expression via the PDK1-FoxO1 pathway in isolated adipocytes. Our results indicate that insulin signaling in adipocytes negatively regulates the production of LTB4 via the PDK1-FoxO1 pathway and thereby maintains systemic insulin sensitivity.

Leukotriene B4 receptor 1 exacerbates inflammation following myocardial infarction

Leukotriene B₄ receptor 1 (BLT1), a high-affinity G-protein-coupled receptor for leukotriene B4 (LTB₄ ), is expressed on various inflammatory cells and plays critical roles in several inflammatory diseases. In myocardial infarction (MI), various inflammatory cells are known to be recruited to the infarcted area, but the function of BLT1 in MI is poorly understood. Here, we investigated the role of BLT1 in MI and the therapeutic effect of a BLT1 antagonist, ONO-4057, on MI. Mice with infarcted hearts showed increased BLT1 expression and LTB₄ levels. BLT1-knockout mice with infarcted hearts exhibited attenuated leukocyte infiltration, proinflammatory cytokine production, and cell death, which led to reduced mortality and improved cardiac function after MI. Bone-marrow transplantation studies showed that BLT1 expressed on bone marrow-derived cells was responsible for the exacerbation of inflammation in infarcted hearts. Furthermore, ONO-4057 administration attenuated the inflammatory responses in hearts surgically treated for MI, which resulted in reduced mortality and improved cardiac function after MI. Our study demonstrated that BLT1 contributes to excessive inflammation after MI and could represent a new therapeutic target for MI.

The leukotriene receptors as therapeutic targets of inflammatory diseases

Leukotrienes (LTs) are inflammatory mediators derived from arachidonic acid. LTs include the di-hydroxy acid LT (LTB4) and the cysteinyl LTs (CysLTs; LTC4, LTD4 and LTE4), all of which are involved in both acute and chronic inflammation. We and other groups identified a high-affinity LTB4 receptor, BLT1; the LTC4 and LTD4 receptors, CysLT1 and CysLT2; and the LTE4 receptor, GPR99. Pharmacological studies have shown that BLT1 signaling stimulates degranulation, chemotaxis and phagocytosis of neutrophils, whereas CysLT1 and CysLT2 signaling induces airway inflammation by increasing vascular permeability and the contraction of bronchial smooth muscle. Recently, we and other groups suggested that the LTB4-BLT1 axis and the cysteinyl LTs-CysLT1/2 axis are involved in chronic inflammatory diseases including asthma, atopic dermatitis, psoriasis, atherosclerosis, arthritis, obesity, cancer and age-related macular degeneration using animal models for disease and gene knockout mice. This review describes the classical and novel functions of LTs and their receptors in several inflammatory diseases and discusses the potential clinical applications of antagonists for LT receptors and inhibitors of LT biosynthesis.

Leukotriene B4 Receptor Type 2 Accelerates the Healing of Intestinal Lesions by Promoting Epithelial Cell Proliferation

Leukotriene B₄ receptor type 2 (BLT2) is a low-affinity leukotriene B₄ receptor that is highly expressed in intestinal epithelial cells. Previous studies demonstrated the protective role of BLT2 in experimentally induced colitis. However, its role in intestinal lesion repair is not fully understood. We investigated the role of BLT2 in the healing of indomethacin-induced intestinal lesions in mice. There was no significant different between wild-type (WT) and BLT2-deficient (BLT2KO) mice in terms of the development of indomethacin-induced intestinal lesions. However, healing of these lesions was significantly impaired in BLT2KO mice compared with WT mice. In contrast, transgenic mice with intestinal epithelium-specific BLT2 overexpression presented with superior ileal lesion healing relative to WT mice. An immunohistochemical study showed that the number of Ki-67-proliferative cells was markedly increased during the healing of intestinal lesions in WT mice but significantly attenuated in BLT2KO mice. Exposure of cultured mouse intestinal epithelial cells to CAY10583, a BLT2 agonist, promoted wound healing and cell proliferation in a concentration-dependent manner. Nevertheless, these responses were abolished under serum-free conditions. The CAY10583-induced proliferative effect was also negated by Go6983, a protein kinase C (PKC) inhibitor, U-73122, a phospholipase C (PLC) inhibitor, LY255283, a BLT2 antagonist, and pertussis toxin that inhibits G protein-coupled receptor signaling via G_i/o proteins. Thus, BLT2 plays an important role in intestinal wound repair. Moreover, this effect is mediated by the promotion of epithelial cell proliferation via the G_i/o protein-dependent and PLC/PKC signaling pathways. The BLT2 agonists are potential therapeutic agents for the treatment of intestinal lesions. SIGNIFICANCE STATEMENT: The healing of indomethacin-induced Crohn's disease-like intestinal lesions was impaired in mice deficient in low-affinity leukotriene B₄ receptor type 2 (BLT2). They presented with reduced epithelial cell proliferation during the healing. In contrast, healing was promoted in mice overexpressing intestinal epithelial BLT2. In cultured intestinal epithelial cells, the BLT2 agonist CAY10583 substantially accelerated wound repair by enhancing cell proliferation rather than migration. Thus, BLT2 plays an important role in the intestinal lesions via acceleration of epithelial cell proliferation.

n-3 Fatty Acid and Its Metabolite 18-HEPE Ameliorate Retinal Neuronal Cell Dysfunction by Enhancing Müller BDNF in Diabetic Retinopathy

Diabetic retinopathy (DR) is a widespread vision-threatening disease, and neuroretinal abnormality should be considered as an important problem. Brain-derived neurotrophic factor (BDNF) has recently been considered as a possible treatment to prevent DR-induced neuroretinal damage, but how BDNF is upregulated in DR remains unclear. We found an increase in hydrogen peroxide (H₂O₂) in the vitreous of patients with DR. We confirmed that human retinal endothelial cells secreted H₂O₂ by high glucose, and H₂O₂ reduced cell viability of MIO-M1, Müller glia cell line, PC12D, and the neuronal cell line and lowered BDNF expression in MIO-M1, whereas BDNF administration recovered PC12D cell viability. Streptozocin-induced diabetic rats showed reduced BDNF, which is mainly expressed in the Müller glia cell. Oral intake of eicosapentaenoic acid ethyl ester (EPA-E) ameliorated BDNF reduction and oscillatory potentials (OPs) in electroretinography (ERG) in DR. Mass spectrometry revealed an increase in several EPA metabolites in the eyes of EPA-E-fed rats. In particular, an EPA metabolite, 18-hydroxyeicosapentaenoic acid (18-HEPE), induced BDNF upregulation in Müller glia cells and recovery of OPs in ERG. Our results indicated diabetes-induced oxidative stress attenuates neuroretinal function, but oral EPA-E intake prevents retinal neurodegeneration via BDNF in Müller glia cells by increasing 18-HEPE in the early stages of DR.

Prostaglandin E2 and its receptor EP2 trigger signaling that contributes to YAP-mediated cell competition

Cell competition is a biological process by which unfit cells are eliminated from “cell society.” We previously showed that cultured mammalian epithelial Madin‐Darby canine kidney (MDCK) cells expressing constitutively active YAP were eliminated by apical extrusion when surrounded by “normal” MDCK cells. However, the molecular mechanism underlying the elimination of active YAP‐expressing cells was unknown. Here, we used high‐throughput chemical compound screening to identify cyclooxygenase‐2 (COX‐2) as a key molecule triggering cell competition. Our work shows that COX‐2‐mediated PGE₂ secretion engages its receptor EP2 on abnormal and nearby normal cells. This engagement of EP2 triggers downstream signaling via an adenylyl cyclase‐cyclic AMP‐PKA pathway that, in the presence of active YAP, induces E‐cadherin internalization leading to apical extrusion. Thus, COX‐2‐induced PGE₂ appears a warning signal to both abnormal and surrounding normal cells to drive cell competition.

Loss of autophagy impairs physiological steatosis by accumulation of NCoR1

Lipid droplets (LDs) are dynamic organelles that store neutral lipids during times of energy excess, such as after a meal. LDs serve as an energy reservoir during fasting and have a buffering capacity that prevents lipotoxicity. Autophagy and the autophagic machinery have been proposed to play a role in LD biogenesis, but the underlying molecular mechanism remains unclear. Here, we show that when nuclear receptor co-repressor 1 (NCoR1), which inhibits the transactivation of nuclear receptors, accumulates because of autophagy suppression, LDs decrease in size and number. Ablation of ATG7, a gene essential for autophagy, suppressed the expression of gene targets of liver X receptor α, a nuclear receptor responsible for fatty acid and triglyceride synthesis in an NCoR1-dependent manner. LD accumulation in response to fasting and after hepatectomy was hampered by the suppression of autophagy. These results suggest that autophagy controls physiological hepatosteatosis by fine-tuning NCoR1 protein levels.

Volatile anesthetics isoflurane and sevoflurane directly target and attenuate Toll-like receptor 4 system

General anesthesia has been the requisite component of surgical procedures for over 150 yr. Although immunomodulatory effects of volatile anesthetics have been growingly appreciated, the molecular mechanism has not been understood. In septic mice, the commonly used volatile anesthetic isoflurane attenuated the production of 5-lipoxygenase products and IL-10 and reduced CD11b and intercellular adhesion molecule-1 expression on neutrophils, suggesting the attenuation of TLR4 signaling. We confirmed the attenuation of TLR4 signaling in vitro and their direct binding to TLR4-myeloid differentiation-2 (MD-2) complex by photolabeling experiments. The binding sites of volatile anesthetics isoflurane and sevoflurane were located near critical residues for TLR4-MD-2 complex formation and TLR4-MD-2-LPS dimerization. Additionally, TLR4 activation was not attenuated by intravenous anesthetics, except for a high concentration of propofol. Considering the important role of TLR4 system in the perioperative settings, these findings suggest the possibility that anesthetic choice may modulate the outcome in patients or surgical cases in which TLR4 activation is expected.-Okuno, T., Koutsogiannaki, S., Hou, L., Bu, W., Ohto, U., Eckenhoff, R. G., Yokomizo, T., Yuki, K. Volatile anesthetics isoflurane and sevoflurane directly target and attenuate Toll-like receptor 4 system.

The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction

Sepsis remains a significant health care burden, with high morbidities and mortalities. Patients with sepsis often require general anesthesia for procedures and imaging studies. Knowing that anesthetic drugs can pose immunomodulatory effects, it would be critical to understand the impact of anesthetics on sepsis pathophysiology. The volatile anesthetic sevoflurane is a common general anesthetic derived from ether as a prototype. Using a murine sepsis model induced by cecal ligation and puncture surgery, we examined the impact of sevoflurane on sepsis outcome. Different from volatile anesthetic isoflurane, sevoflurane exposure significantly improved the outcome of septic mice. This was associated with less apoptosis in the spleen. Because splenic apoptosis was largely attributed to the apoptosis of neutrophils, we examined the effect of sevoflurane on FasL-induced neutrophil apoptosis. Sevoflurane exposure significantly attenuated apoptosis. Sevoflurane did not affect the binding of FasL to the extracellular domain of Fas receptor. Instead, in silico analysis suggested that sevoflurane would bind to the interphase between Fas death domain (DD) and Fas-associated DD (FADD). The effect of sevoflurane on Fas DD-FADD interaction was examined using fluorescence resonance energy transfer (FRET). Sevoflurane attenuated FRET efficiency, indicating that sevoflurane hindered the interaction between Fas DD and FADD. The predicted sevoflurane binding site is known to play a significant role in Fas DD-FADD interaction, supporting our in vitro and in vivo apoptosis results.-Koutsogiannaki, S., Hou, L., Babazada, H., Okuno, T., Blazon-Brown, N., Soriano, S. G., Yokomizo, T., Yuki, K. The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction.

The Role of Leukotrienes as Potential Therapeutic Targets in Allergic Disorders

Leukotrienes (LTs) are lipid mediators that play pivotal roles in acute and chronic inflammation and allergic diseases. They exert their biological effects by binding to specific G-protein-coupled receptors. Each LT receptor subtype exhibits unique functions and expression patterns. LTs play roles in various allergic diseases, including asthma (neutrophilic asthma and aspirin-sensitive asthma), allergic rhinitis, atopic dermatitis, allergic conjunctivitis, and anaphylaxis. This review summarizes the biology of LTs and their receptors, recent developments in the area of anti-LT strategies (in settings such as ongoing clinical studies), and prospects for future therapeutic applications.

Abstract 989: The relationship between TP53 gene status and carboxylesterase 2 expression in human gastric cancer

Carboxylesterases are serine hydrolases that are involved in the metabolisms of various endogenous and exogenous compounds. They are also required for activation of many anti-cancer prodrugs. For example, irinotecan (CPT-11), an anti-cancer prodrug that has been approved for the treatment of many types of solid tumors including gastric cancer, is converted by the carboxylesterase CES2 to its active metabolite 7-ethyl-10-hydroxycamptothesin (SN-38), a very potent topoisomerase I inhibitor. Among carboxylesterase isozymes, CES2 is most highly expressed in the gastrointestinal tract. Thus, the expression of CES2 may play an important role in local (i.e., intratumoral) activation of anti-cancer prodrugs such as irinotecan in the gut. Recent studies with cultured cancer cell lines have shown that CES2 expression is regulated by the tumor suppressor protein p53. However, whether CES2 expression is affected by the presence of p53 mutation in clinical cancer samples still remains unclear. In this study, we focused on the regulatory mechanism of CES2 expression in gastric cancer. First, we examined the relationship between TP53 gene status and CES2 expression using gastric cancer cell lines. Several gastric cancer cell lines expressing wild-type p53 (AGS, NUGC4, MKN74, and HSC58) were treated with nutlin-3a, a drug that inhibits the interaction between p53 and the E3 ubiquitin ligase MDM2 and thereby directly activates p53 signaling without genotoxic side effects. The expression of p21, a downstream target of p53, was increased following nutlin-3a treatment in two p53 wild-type cell lines NUGC4 and HSC58. The expression of CES2 was also upregulated by nutlin-3a in three p53 wild-type cell lines AGS, NUGC4, and HSC58. As expected, the expression levels of p21 and CES2 were not largely affected by nutlin-3a in gastric cancer cell lines with TP53 mutations. These results indicate that CES2 expression is positively regulated by the p53 pathway in most gastric cancer cells. We also investigated the relationship between TP53 gene status and CES2 expression in human gastric cancer samples. Our results may provide useful information for predicting the efficacy of anti-cancer prodrugs that are activated by CES2 in gastric cancer.

Note: This abstract was not presented at the meeting.

Citation Format: Yoshinori Kohira, Hyeon-Cheol Lee, Momoko Ishimine, Hajime Orita, Toshiyuki Kobayashi, Koichi Sato, Takehiko Yokomizo, Tetsu Fukunaga. The relationship between TP53 gene status and carboxylesterase 2 expression in human gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 989.

Autophagy regulates lipid metabolism through selective turnover of NCoR1

Selective autophagy ensures the removal of specific soluble proteins, protein aggregates, damaged mitochondria, and invasive bacteria from cells. Defective autophagy has been directly linked to metabolic disorders. However how selective autophagy regulates metabolism remains largely uncharacterized. Here we show that a deficiency in selective autophagy is associated with suppression of lipid oxidation. Hepatic loss of Atg7 or Atg5 significantly impairs the production of ketone bodies upon fasting, due to decreased expression of enzymes involved in β-oxidation following suppression of transactivation by PPARα. Mechanistically, nuclear receptor co-repressor 1 (NCoR1), which interacts with PPARα to suppress its transactivation, binds to the autophagosomal GABARAP family proteins and is degraded by autophagy. Consequently, loss of autophagy causes accumulation of NCoR1, suppressing PPARα activity and resulting in impaired lipid oxidation. These results suggest that autophagy contributes to PPARα activation upon fasting by promoting degradation of NCoR1 and thus regulates β-oxidation and ketone bodies production.

Defective autophagy has been associated with metabolic disorders. Here Saito et al. show that autophagy promotes the selective degradation of NCoR1, a repressor of lipid metabolism regulator PPARα, in response to starvation, and thus induces the expression of enzymes involved in lipid oxidation and the production of ketone bodies.

Papaverine identified as an inhibitor of high mobility group box 1/receptor for advanced glycation end-products interaction suppresses high mobility group box 1-mediated inflammatory responses

The interaction of high mobility group box 1 (HMGB1), which is secreted from immune and dying cells during cellular infection and injury, and receptor for advanced glycation end-products (RAGE) appears to be critical for acute and chronic inflammatory disorders. Here we designed a unique cyclic β-hairpin peptide (Pepb2), which mimics the predicted RAGE-binding domain of HMGB1. Pepb2 competitively inhibited HMGB1/RAGE interaction. We then identified papaverine as a Pepb2 mimetic by in silico 3D-structural similarity screening from the DrugBank library. Papaverine was found to directly inhibit HMGB1/RAGE interaction. It also suppressed the HMGB1-mediated production of pro-inflammatory cytokines, IL-6 and TNF-α, in mouse macrophage-like RAW264.7 cells and bone marrow-derived macrophages. In addition, papaverine attenuated mortality in cecal ligation puncture-induced sepsis model mice. Taken together, these findings indicate that papaverine could become a useful therapeutic against HMGB1/RAGE-mediated sepsis and other inflammatory diseases.