Lipocalin-type Prostaglandin D Synthase Research Articles

Early predictive value of lipocalin-type prostaglandin D synthase for 28-day mortality in cardiac arrest patients: study protocol for a prospective study

IntroductionPublic training in cardiopulmonary resuscitation and treatment in emergency and intensive care unit have made tremendous progress. However, cardiac arrest remains a major health burden worldwide, with brain damage being...

Astrocyte atrophy induced by L-PGDS/PGD2/Src signaling dysfunction in the central amygdala mediates postpartum depression

BackgroundPostpartum depression (PPD) is a serious psychiatric disorder that has significantly adverse impacts on maternal health. Metabolic abnormalities in the brain are associated with numerous neurological disorders, yet the specific metabolic signaling pathways and brain regions involved in PPD remain unelucidated. MethodsWe performed behavioral test in the virgin and postpartum mice. We used mass spectrometry imaging (MSI) and targeted metabolomics analyses to investigate the metabolic alternation in the brain of GABAAR Delta-subunit-deficient (Gabrd−/−) postpartum mice, a specific preclinical animal model of PPD. Next, we performed mechanism studies including qPCR, Western blot, immunofluorescence staining, electron microscopy and primary astrocyte culture. In the specific knockdown and rescue experiments, we injected the adeno-associated virus into the central amygdala (CeA) of female mice. ResultsWe identified that prostaglandin D2 (PGD2) downregulation in the CeA was the most outstanding alternation in PPD, and then validated that lipocalin-type prostaglandin D synthase (L-PGDS)/PGD2 downregulation plays a causal role in depressive behaviors derived from PPD in both wild-type and Gabrd−/− mice. Furthermore, we verified that L-PGDS/PGD2 signaling dysfunction-induced astrocytes atrophy is mediated by Src phosphorylation both in vitro and in vivo. LimitationsL-PGDS/PGD2 signaling dysfunction may be only responsible for the depressive behavior rather than maternal behaviors in the PPD, and it remains to be seen whether this mechanism is applicable to all depression types. ConclusionOur study identified abnormalities in the L-PGDS/PGD2 signaling in the CeA, which inhibited Src phosphorylation and induced astrocyte atrophy, ultimately resulting in the development of PPD in mice.

Lipocalin-type prostaglandin D synthase: a glymphopathy marker in idiopathic hydrocephalus.

Idiopathic normal pressure hydrocephalus in elderly people is considered a form of glymphopathy caused by malfunction of the waste clearance pathway, called the glymphatic system. Tau is a representative waste material similar to amyloid-β. During neurodegeneration, lipocalin-type prostaglandin D synthase (L-PGDS), a major cerebrospinal fluid (CSF) protein, is reported to act as a chaperone that prevents the neurotoxic aggregation of amyloid-β. L-PGDS is also a CSF biomarker in idiopathic normal pressure hydrocephalus and significantly correlates with tau concentration, age, and age-related brain white matter changes detected by magnetic resonance imaging. To investigate this glymphopathy, we aimed to analyze white matter changes and contributing factors in vivo and their interactions ex vivo. Cerebrospinal tap tests were performed in 60 patients referred for symptomatic ventriculomegaly. Patients were evaluated using an idiopathic normal pressure hydrocephalus grading scale, mini-mental state examination, frontal assessment battery, and timed up-and-go test. The typical morphological features of high convexity tightness and ventriculomegaly were measured using the callosal angle and Evans index, and parenchymal white matter properties were evaluated with diffusion tensor imaging followed by tract-based spatial statistics. Levels of CSF biomarkers, including tau, amyloid-β, and L-PGDS, were determined by ELISA, and their interaction, and localization were determined using immunoprecipitation and immunohistochemical analyses. Tract-based spatial statistics for fractional anisotropy revealed clusters that positively correlated with mini-mental state examination, frontal assessment battery, and callosal angle, and clusters that negatively correlated with age, disease duration, idiopathic normal pressure hydrocephalus grading scale, Evans index, and L-PGDS. Other parameters also indicated clusters that correlated with symptoms, microstructural white matter changes, and L-PGDS. Tau co-precipitated with L-PGDS, and colocalization was confirmed in postmortem specimens of neurodegenerative disease obtained from the human Brain Bank. Our study supports the diagnostic value of L-PGDS as a surrogate marker for white matter integrity in idiopathic normal pressure hydrocephalus. These results increase our understanding of the molecular players in the glymphatic system. Moreover, this study indicates the potential utility of enhancing endogenous protective factors to maintain brain homeostasis.

Roles of lipocalin-type and hematopoietic prostaglandin D synthases in mouse retinal angiogenesis

Normal angiogenesis is essential for retinal development and maintenance of visual function in the eye, and its abnormality can cause retinopathy and other eye diseases. Prostaglandin D2 is an anti-angiogenic lipid mediator produced by lipocalin-type PGD synthase (L-PGDS) or hematopoietic PGD synthase (H-PGDS). However, the exact role of these PGD synthases remains unclear. Therefore, we compared the roles of these synthases in murine retinal angiogenesis under physiological and pathological conditions. On postnatal day (P) 8, the WT murine retina was covered with an elongated vessel. L-PGDS deficiency, but not H-PGDS, reduced the physiological vessel elongation with sprouts increase. L-PGDS expression was observed in endothelial cells and neural cells. In vitro, L-PGDS inhibition increased the hypoxia-induced vascular endothelial growth factor expression in isolated endothelial cells, inhibited by a prostaglandin D2 metabolite, 15-deoxy-Δ12,14 -PGJ2 (15d-PGJ2) treatment. Pericyte depletion, using antiplatelet-derived growth factor receptor-β antibody, caused retinal hemorrhage with vessel elongation impairment and macrophage infiltration in the WT P8 retina. H-PGDS deficiency promoted hemorrhage but inhibited the impairment of vessel elongation, while L-PGDS did not. In the pericyte-depleted WT retina, H-PGDS was expressed in the infiltrated macrophages. Deficiency of the D prostanoid receptor also inhibited the vessel elongation impairment. These results suggest the endogenous role of L-PGDS signaling in physiological angiogenesis and that of H-PGDS/D prostanoid 1 signaling in pathological angiogenesis.

Preparation and Application of Monoclonal Antibodies for an Immune Complex Transfer Enzyme Immunoassay of an Egg White Allergen, Lipocalin-Type Prostaglandin D Synthase.

We have previously reported that lipocalin-type prostaglandin D synthase (L-PGDS) in egg white reacts with IgE antibodies from children with egg allergies. However, antibodies against chicken L-PGDS are not commercially available, and the amount of L-PGDS in egg white is unclear. In this study, we prepared four monoclonal antibodies against chicken L-PGDS and developed a sandwich enzyme-linked immunosorbent assay (ELISA) and a highly sensitive immune complex transfer enzyme immunoassay (ICT-EIA) to quantify L-PGDS in hen egg whites. The detection sensitivity of ICT-EIA for L-PGDS (0.01 ng/mL) was 2,000-fold higher than that of ELISA, which could not be adapted to determine the amount of L-PGDS in egg white. Thus, ICT-EIA is a better method for quantification of trace allergens and expected to be applied to the quantification of other food allergens. Hen eggs (white-shelled eggs from Julia Lite hens, brown-shelled eggs, and iodine-enriched eggs from Boris Brown hens) were purchased from markets in Kochi City, Japan, and the amounts of L-PGDS in them were determined by ICT-EIA. The amounts of L-PGDS per hen egg white were: brown-shelled eggs, 1,179.3±214.3 μg/egg; iodine-enriched eggs, 607.7±126.1 μg/egg; and white-shelled eggs, 350.0±74.1 μg/egg. These results show that the amount of L-PGDS in hen eggs varies depending on the hen lineage; it could also be affected to some extent by other factors, such as feeds and breeding environment.

Structural and interaction analysis of human lipocalin-type prostaglandin D synthase with the poorly water-soluble drug NBQX.

Lipocalin-type prostaglandin D synthase (L-PGDS) is a secretory lipid-transporter protein that was shown to bind a wide variety of hydrophobic ligands in vitro. Exploiting this function, we previously examined the feasibility of using L-PGDS as a novel delivery vehicle for poorly water-soluble drugs. However, the mechanism by which human L-PGDS binds to poorly water-soluble drugs is unclear. In this study, we determined the solution structure of human L-PGDS and investigated the mechanism of L-PGDS binding to 6-nitro-7-sulfamoyl-benzo[f]quinoxalin-2,3-dione (NBQX), an α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor antagonist. NMR experiments showed that human L-PGDS has an eight-stranded antiparallel β-barrel structure that forms a central cavity, a short 310 -helix, and two α-helices. Titration with NBQX was monitored using 1 H-15 N HSQC spectroscopy. At higher NBQX concentrations, some cross-peaks of the protein exhibited fast-exchanging shifts with a curvature, indicating at least two binding sites. These residues were located in the upper portion of the cavity. Singular value decomposition analysis revealed that human L-PGDS has two NBQX binding sites. Large chemical shift changes were observed in the H2-helix and A-, B-, C-, D-, H-, and I-strands and H2-helix upon NBQX binding. Calorimetric experiments revealed that human L-PGDS binds two NBQX molecules with dissociation constants of 46.7 μM for primary binding and 185.0 μM for secondary binding. Molecular docking simulations indicated that these NBQX binding sites are located within the β-barrel. These results provide new insights into the interaction between poorly water-soluble drugs and human L-PGDS as a drug carrier.

Thermodynamic stability of human lipocalin-type prostaglandin D synthase under various pH conditions.

Lipocalin-type prostaglandin D synthase (L-PGDS) binds various hydrophobic small molecules. Since we aim to use human L-PGDS as a carrier in a drug delivery system (DDS) for poorly water-soluble drugs, quality control of the protein is indispensable. In this study, we investigated the thermodynamic stability of human L-PGDS under various pH conditions. Differential scanning calorimetry revealed that the thermal unfolding of L-PGDS was an almost-reversible two-state transition between the native and unfolded states over the pH range from 2.5 to 7.4. The linear relationship of ΔH(Tm) to Tm in this pH range gave a heat capacity change (ΔCp) of 4.76kJ/(K·mol), which was small compared to those commonly found in globular proteins. The temperature-dependent free energy of unfolding, ΔG(T), specified by Tm, ΔH(Tm) and ΔCp, showed a pH dependence with the highest value at pH7.4 closest to the isoelectric point of 8.3. The small value of Cp resulted in a large value of ΔG(T), which contributed to the stability of the protein. Taken together, these results demonstrated that human L-PGDS is sufficiently thermostable for storage and practical use and can be useful as a delivery vehicle of protein-based DDS.

Lipid nanoparticles for antisense oligonucleotide gene interference into brain border-associated macrophages.

A colloidal synthesis' proof-of-concept based on the Bligh-Dyer emulsion inversion method was designed for integrating into lipid nanoparticles (LNPs) cell-permeating DNA antisense oligonucleotides (ASOs), also known as GapmeRs (GRs), for mRNA interference. The GR@LNPs were formulated to target brain border-associated macrophages (BAMs) as a central nervous system (CNS) therapy platform for silencing neuroinflammation-related genes. We specifically aim at inhibiting the expression of the gene encoding for lipocalin-type prostaglandin D synthase (L-PGDS), an anti-inflammatory enzyme expressed in BAMs, whose level of expression is altered in neuropsychopathologies such as depression and schizophrenia. The GR@LNPs are expected to demonstrate a bio-orthogonal genetic activity reacting with L-PGDS gene transcripts inside the living system without interfering with other genetic or biochemical circuitries. To facilitate selective BAM phagocytosis and avoid subsidiary absorption by other cells, they were functionalized with a mannosylated lipid as a specific MAN ligand for the mannose receptor presented by the macrophage surface. The GR@LNPs showed a high GR-packing density in a compact multilamellar configuration as structurally characterized by light scattering, zeta potential, and transmission electronic microscopy. As a preliminary biological evaluation of the mannosylated GR@LNP nanovectors into specifically targeted BAMs, we detected in vivo gene interference after brain delivery by intracerebroventricular injection (ICV) in Wistar rats subjected to gene therapy protocol. The results pave the way towards novel gene therapy platforms for advanced treatment of neuroinflammation-related pathologies with ASO@LNP nanovectors.

Oral exposure to DEHP may stimulate prostatic hyperplasia associated with upregulation of COX-2 and L-PGDS expressions in male adult rats

Di-(2-ethylhexyl) phthalate (DEHP), a typical environmental endocrine disruptor (EED), can disrupt estrogen and androgen secretion and metabolism process, thus inducing dysfunctional reproduction such as impaired gonadal development and spermatogenesis disorder. Prostaglandin synthases (PGS) catalyze various prostaglandins biosynthesis, involved in inflammatory cascade and tumorigenesis. Yet, little is known about how PGS may impact prostatic hyperplasia development and progression. This study concentrates predominantly on the potential prostatic toxicity of DEHP exposure and the mediating role of PGS. In vivo study, adult male rats were administered via oral gavage 30 μg/kg/d, 90 μg/kg/d, 270 μg/kg/d, 810 μg/kg/d DEHP or vehicle for four weeks. The results elucidated that low-dose DEHP may cause the proliferation of the prostate with an increased PCNA/TUNEL ratio. Given the importance of estrogens and androgens in prostatic hyperplasia, our first objective was to evaluate the levels of sex hormones. DEHP improved the ratio of estradiol (E2)/testosterone (T) in a dose-dependent manner and upregulated estrogen receptor alpha (ERα) and androgen receptor (AR) expressions. Prostaglandin synthases, including cyclooxygenase-2 (COX-2) and lipocalin-type prostaglandin D synthase (L-PGDS), were significantly upregulated in the ventral prostate. COX-2 and L-PGDS might mediate the tendency of prostatic hyperplasia induced by low-dose DEHP through estradiol/androgen regulation and imbalance between proliferation and apoptosis in vivo. These findings provide the first evidence that prostaglandin synthases contribute to the tendency toward benign prostatic hyperplasia induced by DEHP. Further investigations will have to be performed to facilitate an improved understanding of the role of prostaglandin synthases in DEHP-induced prostatic lesions.

L-PGDS Attenuates Acute Lung Injury by Prostaglandin D2 in Both Dependent and Independent Ways.

Lipocalin-type PG D synthase (L-PGDS) has two roles: it can be a PGD synthase, or it can be a carrier protein of hydrophobic small molecules. In this study, we investigated the dual roles of L-PGDS in acute lung injury by using L-PGDS-deficient and point-mutated mice, which lack PGD2 producibility but maintain lipocalin ability. Hydrochloride (HCl) administration (0.1 M intratracheally for 6 h) caused hemorrhage and dysfunction in the wild-type (WT) mouse lung. These symptoms were accompanied by an increase in PGD2 production. Both deficiency and point mutation of L-PGDS aggravated the HCl-induced hemorrhage and dysfunction. Although both the gene modifications decreased PGD2 production, only L-PGDS-deficient mice, but not point mutation mice, lacked protein expressions of L-PGDS in the lungs. In the WT mice, HCl administration caused pulmonary edema, indexed as an increase in lung water content and protein leakage in bronchoalveolar lavage fluid. L-PGDS deficiency and point mutation similarly aggravated edema formation. HCl administration also stimulated mucin production and bronchoalveolar lavage fluid leukocyte infiltration in the WT mouse lungs. Of interest, L-PGDS deficiency, but not point mutation, exacerbated these manifestations. Consistently, only L-PGDS deficiency increased the mRNA expression of IL-33, which stimulates mucin production in the inflamed lung. These results show that L-PGDS attenuated HCl-induced acute lung injury progresses in two different ways: L-PGDS produced PGD2, which inhibited pulmonary edema formation, whereas its lipocalin ability decreased mucin formation and inflammatory cell infiltration in the inflamed lung.

Lipocalin‐Type Prostaglandin d Synthase Conjugates as Magnetic Resonance Imaging Contrast Agents for Detecting Amyloid β‐Rich Regions in the Brain of Live Alzheimer's Disease Mice

With a significant proportion of the global population growing older (>60 years), the low success rates of current diagnoses for early neurodegeneration signs are disappointing. Early detection of Alzheimer's disease (AD) can improve acclimatization and quality of life for patients in their later years. Endogenous proteins, such as the most abundant secreted protein in cerebrospinal fluid, lipocalin‐type prostaglandin d synthase (L‐PGDS), can bind the early toxic oligomers of amyloid β (Aβ) peptides implicated in AD and prevent their aggregation. Herein, the utility of L‐PGDS for detection of amyloids is demonstrated. L‐PGDS is conjugated with different iron‐oxide magnetic nanoparticles for contrast‐enhanced visualization using magnetic resonance imaging (MRI). These conjugates inhibit amyloid aggregation in vitro and improve viability in neuronal cells incubated with amyloid fibrils, showing a potential neuroprotective function. L‐PGDS‐ferritin conjugates, when administered intraventricularly, localize to AD‐associated amyloid‐rich regions in mice brain imaged using MRI and histological stains. As a proof‐of‐concept, it is demonstrated that L‐PGDS conjugates could reach the brain regions through non‐invasive intranasal administration. These conjugates are developed as the first entirely protein‐based nanoprobes for early detection of brain amyloids. The results of this study open a wider avenue for study of endogenous proteins as potential theranostics for AD.

Indomethacin Disrupts the Formation of β-Amyloid Plaques via an α2-Macroglobulin-Activating lrp1-Dependent Mechanism.

Epidemiological studies have implied that the nonsteroidal anti-inflammatory drug (NSAID) indomethacin slows the development and progression of Alzheimer’s disease (AD). However, the underlying mechanisms are notably understudied. Using a chimeric mouse/human amyloid precursor protein (Mo/HuAPP695swe) and a mutant human presenilin 1 (PS1-dE9) (APP/PS1) expressing transgenic (Tg) mice and neuroblastoma (N) 2a cells as in vivo and in vitro models, we revealed the mechanisms of indomethacin in ameliorating the cognitive decline of AD. By screening AD-associated genes, we observed that a marked increase in the expression of α2-macroglobulin (A2M) was markedly induced after treatment with indomethacin. Mechanistically, upregulation of A2M was caused by the inhibition of cyclooxygenase-2 (COX-2) and lipocalin-type prostaglandin D synthase (L-PGDS), which are responsible for the synthesis of prostaglandin (PG)H2 and PGD2, respectively. The reduction in PGD2 levels induced by indomethacin alleviated the suppression of A2M expression through a PGD2 receptor 2 (CRTH2)-dependent mechanism. Highly activated A2M not only disrupted the production and aggregation of β-amyloid protein (Aβ) but also induced Aβ efflux from the brain. More interestingly, indomethacin decreased the degradation of the A2M receptor, low-density lipoprotein receptor-related protein 1 (LRP1), which facilitated the brain efflux of Aβ. Through the aforementioned mechanisms, indomethacin ameliorated cognitive decline in APP/PS1 Tg mice by decreasing Aβ production and clearing Aβ from the brains of AD mice.

Substrate-induced product-release mechanism of lipocalin-type prostaglandin D synthase

Prostaglandin D2 (PGD2), an endogenous somnogen, is a unique PG that is secreted into the cerebrospinal fluid. PGD2 is a relatively fragile molecule and should be transported to receptors localized in the basal forebrain without degradation. However, it remains unclear how PGD2 is stably carried to such remote receptors. Here, we demonstrate that the PGD2-synthesizing enzyme, Lipocalin-type prostaglandin D synthase (L-PGDS), binds not only its substrate PGH2 but also its product PGD2 at two distinct binding sites for both ligands. This behaviour implys its PGD2 carrier function. Nevertheless, since the high affinity (Kd = ∼0.6 μM) of PGD2 in the catalytic binding site is comparable to that of PGH2, it may act as a competitive inhibitor, while our binding assay exhibits only weak inhibition (Ki = 189 μM) of the catalytic reaction. To clarify this enigmatic behavior, we determined the solution structure of L-PGDS bound to one substrate analog by NMR and compared it with the two structures: one in the apo form and the other in substrate analogue complex with 1:2 stoichiometry. The structural comparisons showed clearly that open or closed forms of loops at the entrance of ligand binding cavity are regulated by substrate binding to two sites, and that the binding to a second non-catalytic binding site, which apparently substrate concentration dependent, induces opening of the cavity that releases the product. From these results, we propose that L-PGDS is a unique enzyme having a carrier function and a substrate-induced product-release mechanism.

Lipocalin-type Prostaglandin D Synthase Concentration Gradients in the Cerebrospinal Fluid in Normal-tension Glaucoma Patients with Optic Nerve Sheath Compartmentation.

ObjectiveTo report on the lipocalin-type prostaglandin D synthase (L-PGDS) concentrations in the cerebrospinal fluid (CSF) of the perioptic and lumbar subarachnoid space (SAS) in patients with radiologically proven optic nerve (ON) sheath compartmentation presenting as normal-tension glaucoma (NTG).MethodsRetrospective biochemical analysis of CSF in thirteen patients with ON sheath compartmentation presenting as NTG (four females, mean age 70±8 years). CSF was sampled from the SAS of the ON during ON sheath fenestration for ON sheath compartmentation and from the lumbar SAS at the time of lumbar puncture. Nephelometry was used for the quantification of L-PGDS and albumin concentration. Albumin was measured in order to assess the amount of contamination with serum in the CSF samples taken from the ON SAS. Main outcome measures were L-PGDS concentrations in the CSF of the perioptic and lumbar SAS.ResultsMean L-PGDS concentration was 24±8 mg/L in the lumbar SAS compared to 33±27 mg/L without correction of serum contamination and 45±39 mg/L after correction of serum contamination in the perioptic SAS. The difference between the lumbar and the perioptic SAS was statistically significant (P=0.0047 without correction of serum contamination, P=0.0002 with correction of serum contamination; Mann–Witney U-test).ConclusionThis study demonstrates a concentration gradient of L-PGDS levels within the CSF with a statistically significant higher concentration in the compartmentalized perioptic SAS compared to that in the lumbar SAS. Biochemical changes in the perioptic SAS might be involved in the pathophysiology in NTG patients with ON sheath compartmentation.

Lipocalin-type prostaglandin D synthase levels increase in patients with narcolepsy and idiopathic hypersomnia.

Excessive daytime sleepiness (EDS) is a frequent cause for consultation and a defining symptom of narcolepsy and idiopathic hypersomnia (IH). The associated mechanisms remain unclear. Lipocalin-type prostaglandin D synthase (LPGDS) is a plausible sleep-inducing candidate. This study is to compare cerebral spinal fluid (CSF) and serum LPGDS levels in patients group with hypersomnia of central origin, including those with narcolepsy type 1 (NT1) and type 2 (NT2) and IH, to those in healthy controls (Con). Serum LPGDS, CSF LPGDS, and CSF hypocretin-1(Hcrt-1) levels were measured by ELISA in 122 narcolepsy patients (106 NT1 and 16 NT2), 27 IH, and 51Con. LPGDS levels in CSF (p = 0.02) and serum (p < 0.001) were 22%-25% lower in control subjects than in patients with EDS complaints, including NT1, NT2, and IH. In contrast to significant differences in CSF Hcrt-1 levels, CSF L-PGDS levels and serum L-PGDS were comparable among NT1, NT2, and IH (p > 0.05), except for slightly lower serum LPGDS in IH than in NT1 (p = 0.01). Serum L-PGDS correlated modestly and negatively to sleep latency on MSLT (r = -0.227, p = 0.007) in hypersomnia subjects. As a somnogen-producing enzyme, CSF/serum LPGDS may serve as a new biomarker for EDS of central origin and imply a common pathogenetic association, but would complement rather than replaces orexin markers.

Dexamethasone Suppresses Radicular Pain Through Targeting the L-PGDS/PI3K/Akt Pathway in Rats With Lumbar Disc Herniation.

Lumbar disc herniation (LDH) is a frequently occurring disease with unknown etiology, which makes treatment a challenge. The aim of this study was to analyze the effects of dexamethasone on LDH and elucidate the underlying mechanisms. An LDH rat model was established by nucleus pulposus implantation. The activity of the lipocalin type prostaglandin D synthase (L-PGDS)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) axis was evaluated by Western blotting. Paw withdrawal threshold and paw withdrawal latency were assessed by the Von Frey hairs method and the thermal dolorimeter of Hargreaves, respectively. The 21-point Basso-Beattie-Bresnahan scale was used to assess the locomotor function of rats. Pathological changes in the affected region were analyzed by hematoxylin-eosin staining. Immunofluorescence was used to measure the expression of microtubule-associated protein (MAP-2). Lumbar disc herniation markedly increased thermo-mechanical allodynia and induced dorsal root ganglion (DRG) degeneration by inactivating the L-PGS/PI3K/Akt pathway. Dexamethasone restored the L-PGDS/PI3K/Akt pathway and relieved LDH-induced thermo-mechanical allodynia. Furthermore, overexpression and knockdown of L-PGDS respectively attenuated and worsened LDH-triggered thermo-mechanical allodynia and tissue degeneration by modulating the PI3K/Akt pathway. Pretreatment with dexamethasone partially abrogated the effect of L-PGDS knockdown through PI3K/Akt activation. Dexamethasone relieves LDH-mediated radicular pain by exerting anti-inflammatory effects and reducing the suppression of L-PGDS induced by LDH. Meanwhile, the activity of the PI3K/Akt pathway was decreased, possibly due to the attenuated inflammation induced by dexamethasone. Our results revealed the underlying mechanism of dexamethasone, which might be helpful in reducing the side effects of dexamethasone and provide more focused therapy in LDH.

The prostaglandin synthases, COX-2 and L-PGDS, mediate prostate hyperplasia induced by low-dose bisphenol A

This study aimed to identify prostaglandin synthases (PGS) that mediate bisphenol A (BPA)-induced prostatic hyperplasia and explore their underlying mechanisms. In an in vivo study, male adult Sprague–Dawley rats were treated with different concentrations of BPA (10, 30, 90, or 270 μg/kg, i.g., daily), or with vehicle for 4 weeks. Results revealed that low-dose BPA induced prostatic hyperplasia with increased PCNA/TUNEL ratio. It significantly upregulated the expression of cyclooxygenase-2 (COX-2) and NF-κB in the dorsolateral prostate (P < 0.05) and the expression of lipocalin-type prostaglandin D synthase (L-PGDS) in ventral prostate (P < 0.05). The level of estradiol (E2)/testosterone (T) and expression of androgen receptor (AR) and estrogen receptor α (ERα) were also altered. In vitro studies showed that low-dose BPA (0.1–10 nM) promoted the proliferation of human prostate fibroblasts and epithelial cells, and significantly upregulated the expression of COX-2 and L-PGDS in the cells. The two types of cell proliferation induced by BPA were inhibited by COX-2 inhibitor (NS398) and L-PGDS inhibitor (AT56), with increased apoptosis level. These findings suggested that COX-2 and L-PGDS could mediate low-dose BPA-induced prostatic hyperplasia through pathways involved in cell proliferation and apoptosis, which might be related to the functions of ERα and AR. The role of COX-2/NF-κB pathway in dorsolateral prostate requires further research.

Role of Lipocalin-Type Prostaglandin D Synthase in Experimental Osteoarthritis.

Lipocalin-type prostaglandin D synthase (L-PGDS) catalyzes the formation of prostaglandin D2 (PGD2 ), which has important roles in inflammation and cartilage metabolism. We undertook this study to investigate the role of L-PGDS in the pathogenesis of osteoarthritis (OA) using an experimental mouse model. Experimental OA was induced in wild-type (WT) and L-PGDS-deficient (L-PGDS-/- ) mice (n = 10 per genotype) by destabilization of the medial meniscus (DMM). Cartilage degradation was evaluated by histology. The expression of matrix metalloproteinase 13 (MMP-13) and ADAMTS-5 was assessed by immunohistochemistry. Bone changes were determined by micro-computed tomography. Cartilage explants from L-PGDS-/- and WT mice (n = 6 per genotype) were treated with interleukin-1α (IL-1α) ex vivo in order to evaluate proteoglycan degradation. Moreover, the effect of intraarticular injection of a recombinant adeno-associated virus type 2/5 (rAAV2/5) encoding L-PGDS on OA progression was evaluated in WT mice (n = 9 per group). Compared to WT mice, L-PGDS-/- mice had exacerbated cartilage degradation and enhanced expression of MMP-13 and ADAMTS-5 (P< 0.05). Furthermore, L-PGDS-/- mice displayed increased synovitis and subchondral bone changes (P< 0.05). Cartilage explants from L-PGDS-/- mice showed enhanced proteoglycan degradation following treatment with IL-1α (P< 0.05). Intraarticular injection of rAAV2/5 encoding L-PGDS attenuated the severity of DMM-induced OA-like changes in WT mice (P< 0.05). The L-PGDS level was increasedin OA tissues of WT mice (P< 0.05). Collectively, these findings suggest a protective role of L-PGDS in OA, and therefore enhancing levels of L-PGDS may constitute a promising therapeutic strategy.

Anticholinergic Drugs Interact With Neuroprotective Chaperone L-PGDS and Modulate Cytotoxicity of Aβ Amyloids.

Anticholinergic drugs can be used as a treatment for many diseases. However, anticholinergic drugs are also known for their cognition-related side effects. Recently, there has been an increasing number of reports indicating a positive association between exposure to anticholinergic drugs and Alzheimer's disease (AD). Our novel study provides evidence of interactions between two representative anticholinergic drugs [Chlorpheniramine (CPM), a common antihistamine, and Trazodone (TRD), an antidepressant] with neuroprotective amyloid-beta (Aβ) chaperone, lipocalin-type prostaglandin D synthase (L-PGDS) and the amyloid beta-peptide (1–40). Here, we demonstrate that CPM and TRD bind to L-PGDS with high affinity where chlorpheniramine exhibited higher inhibitory effects on L-PGDS as compared to Trazodone. We also show that the interactions between the drug molecules and Aβ(1–40) peptides result in a higher fibrillar content of Aβ(1–40) fibrils with altered fibril morphology. These altered fibrils possess higher cytotoxicity compared to Aβ(1–40) fibrils formed in the absence of the drugs. Overall, our data suggest a mechanistic link between exposure to anticholinergic drugs and increased risk of Alzheimer's disease via inhibition of the neuroprotective chaperone L-PGDS and direct modification of Aβ amyloid morphology and cytotoxicity.

Amyloid β chaperone — lipocalin-type prostaglandin D synthase acts as a peroxidase in the presence of heme

The extracellular transporter, lipocalin-type prostaglandin D synthase (L-PGDS) binds to heme and heme metabolites with high affinity. It has been reported that L-PGDS protects neuronal cells against apoptosis induced by exposure to hydrogen peroxide. Our study demonstrates that when human WT L-PGDS is in complex with heme, it exhibits a strong peroxidase activity thus behaving as a pseudo-peroxidase. Electron paramagnetic resonance studies confirm that heme in the L-PGDS–heme complex is hexacoordinated with high-spin Fe(III). NMR titration of heme in L-PGDS points to hydrophobic interaction between heme and several residues within the β-barrel cavity of L-PGDS. In addition to the transporter function, L-PGDS is a key amyloid β chaperone in human cerebrospinal fluid. The presence of high levels of bilirubin and its derivatives, implicated in Alzheimer's disease, by binding to L-PGDS may reduce its chaperone activity. Nevertheless, our ThT binding assay establishes that heme and heme metabolites do not significantly alter the neuroprotective chaperone function of L-PGDS. Guided by NMR data we reconstructed the heme L-PGDS complex using extensive molecular dynamics simulations providing a platform for mechanistic interpretation of the catalytic and transporting functions and their modulation by secondary ligands like Aβ peptides and heme metabolites.