Dipeptidase 1 promotes ferroptosis in renal tubular epithelial cells in diabetic nephropathy via inhibition of the GSH/GPX4 axis.

Renal tubular injury is an important pathological change associated with diabetic nephropathy (DN), in which ferroptosis of renal tubular epithelial cells is critical to its pathogenesis. Inhibition of the glutathione/glutathione peroxidase 4 (GSH/GPX4) axis is the most important mechanism in DN tubular epithelial cell ferroptosis, but the underlying reason for this is unclear. Our biogenic analysis showed that a zinc-dependent metalloproteinase, dipeptidase 1 (DPEP1), is associated with DN ferroptosis. Here, we investigated the role and mechanism of DPEP1 in DN tubular epithelial cell ferroptosis. DPEP1 upregulation was observed in the renal tubular epithelial cells of DN patients and model mice, as well as in HK-2 cells stimulated with high glucose. Furthermore, the level of DPEP1 upregulation was associated with the degree of tubular injury in DN patients and HK-2 cell ferroptosis. Mechanistically, knocking down DPEP1 expression could alleviate the inhibition of GSH/GPX4 axis and reduce HK-2 cell ferroptosis levels in a high glucose environment. HK-2 cells with stable DPEP1 overexpression also showed GSH/GPX4 axis inhibition and ferroptosis, but blocking the GSH/GPX4 axis could mitigate these effects. Additionally, treatment with cilastatin, a DPEP1 inhibitor, could ameliorate GSH/GPX4 axis inhibition and relieve ferroptosis and DN progression in DN mice. These results revealed that DPEP1 can promote ferroptosis in DN renal tubular epithelial cells via inhibition of the GSH/GPX4 axis.

N2-Acetylornithine deacetylase functions as a Cys-Gly dipeptidase in the cytosolic glutathione degradation pathway in Arabidopsis thaliana.

Glutathione (GSH) is required for various physiological processes in plants, including redox regulation and detoxification of harmful compounds. GSH also functions as a repository for assimilated sulfur and is actively catabolized in plants. In Arabidopsis, GSH is mainly degraded initially by cytosolic enzymes, γ-glutamyl cyclotransferase, and γ-glutamyl peptidase, which release cysteinylglycine (Cys-Gly). However, the subsequent enzyme responsible for catabolizing this dipeptide has not been identified to date. In the present study, we identified At4g17830 as a Cys-Gly dipeptidase, namely cysteinylglycine peptidase 1 (CGP1). CGP1 complemented the phenotype of the yeast mutant that cannot degrade Cys-Gly. The Arabidopsis cgp1 mutant had lower Cys-Gly degradation activity than the wild type and showed perturbed concentrations of thiol compounds. Recombinant CGP1 showed reasonable Cys-Gly degradation activity in vitro. Metabolomic analysis revealed that cgp1 exhibited signs of severe sulfur deficiency, such as elevated accumulation of O-acetylserine (OAS) and the decrease in sulfur-containing metabolites. Morphological changes observed in cgp1, including longer primary roots of germinating seeds, were also likely associated with sulfur starvation. Notably, At4g17830 has previously been reported to encode an N2-acetylornithine deacetylase (NAOD) that functions in the ornithine biosynthesis. The cgp1 mutant did not show a decrease in ornithine content, whereas the analysis of CGP1 structure did not rule out the possibility that CGP1 has Cys-Gly dipeptidase and NAOD activities. Therefore, we propose that CGP1 is a Cys-Gly dipeptidase that functions in the cytosolic GSH degradation pathway and may play dual roles in GSH and ornithine metabolism.

The amino-dipeptidyl peptidases DPP8 and DPP9: Purification and enzymatic assays.

Proline residues highly impact protein stability when present either in the first or second N-terminal position. While the human genome encodes for more than 500 proteases, only few proteases are capable of hydrolyzing a proline-containing peptide bond. The two intra-cellular amino-dipeptidyl peptidases DPP8 and DPP9 are exceptional as they possess the rare ability to cleave post-proline. By removing N-terminal Xaa-Pro dipeptides, DPP8 and DPP9 expose a neo N-terminus of their substates, which can consequently alter inter- or intra-molecular interactions of the modified protein. Both DPP8 and DPP9 play key roles in the immune response and are linked to cancer progression, emerging as attractive drug targets. DPP9 is more abundant than DPP8 and is rate limiting for cleavage of cytosolic proline-containing peptides. Only few DPP9 substrates have been characterized; these include Syk, a central kinase for B-cell receptor mediated signaling; Adenylate Kinase 2 (AK2) which is important for cellular energy homeostasis; and the tumor suppressor Breast cancer type 2 susceptibility protein (BRCA2) that is critical for repair of DNA double strand breaks. N-terminal processing of these proteins by DPP9 triggers their rapid turn-over by the proteasome, highlighting a role for DPP9 as upstream components of the N-degron pathway. Whether N-terminal processing by DPP9 leads to substrate-degradation in all cases, or whether additional outcomes are possible, remains to be tested. In this chapter we will describe methods for purification of DPP8 and DPP9 as well as protocols for biochemical and enzymatic characterization of these proteases.

Dexamethasone sensitizes to ferroptosis by glucocorticoid receptor-induced dipeptidase-1 expression and glutathione depletion.

Dexamethasone is widely used as an immunosuppressive therapy and recently as COVID-19 treatment. Here, we demonstrate that dexamethasone sensitizes to ferroptosis, a form of iron-catalyzed necrosis, previously suggested to contribute to diseases such as acute kidney injury, myocardial infarction, and stroke, all of which are triggered by glutathione (GSH) depletion. GSH levels were significantly decreased by dexamethasone. Mechanistically, we identified that dexamethasone up-regulated the GSH metabolism regulating protein dipeptidase-1 (DPEP1) in a glucocorticoid receptor (GR)-dependent manner. DPEP1 knockdown reversed the phenotype of dexamethasone-induced ferroptosis sensitization. Ferroptosis inhibitors, the DPEP1 inhibitor cilastatin, or genetic DPEP1 inactivation reversed the dexamethasone-induced increase in tubular necrosis in freshly isolated renal tubules. Our data indicate that dexamethasone sensitizes to ferroptosis by a GR-mediated increase in DPEP1 expression and GSH depletion. Together, we identified a previously unknown mechanism of glucocorticoid-mediated sensitization to ferroptosis bearing clinical and therapeutic implications.

The relationship between serum prolidase activity and histone H3 protein levels and fibromyalgia.

OBJECTIVE: Fibromyalgia (FM) is a clinical syndrome characterized by prominent physical and psychological impairment and widespread pain on both sides of the body, above and below the waist, and along the axial skeleton. It often causes sleep difficulties, memory impairment, mood changes, irritable bowel syndrome, and fatigue. Our study aimed to investigate the relationship between FM and prolidase (peptidase D) and histone H3 protein levels by comparing a patient group with a healthy control group. PATIENTS AND METHODS: In total, 176 people were examined in our study, 88 of whom were healthy and 88 of whom had FM. Serum level was measured by ELISA. Then the results were analyzed using SPSS. All p < 0.05 were considered statistically significant. RESULTS: A significant increase in the levels of prolidase was observed in the patient group compared with the control group (6.28-4.68, p <0.001). Histone H3 protein values were not significantly different between the patient and control groups (p=0.184). The ROC analysis indicated that prolidase was statistically significant in disease prediction (p<0.001, AUC: 0.795 (0.697-0.893), while histone H3 protein was statistically insignificant in predicting disease. CONCLUSIONS: The results of the study show that prolidase activity may play a role in diagnosing FM. In addition, since no study like ours has been performed before, it can bring a new perspective to the literature.

Loss of peptidase D binding restores the tumor suppressor functions of oncogenic p53 mutants.

Tumor suppressor p53, a critical regulator of cell fate, is frequently mutated in cancer. Mutation of p53 abolishes its tumor-suppressing functions or endows oncogenic functions. We recently found that p53 binds via its proline-rich domain to peptidase D (PEPD) and is activated when the binding is disrupted. The proline-rich domain in p53 is rarely mutated. Here, we show that oncogenic p53 mutants closely resemble p53 in PEPD binding but are transformed into tumor suppressors, rather than activated as oncoproteins, when their binding to PEPD is disrupted by PEPD knockdown. Once freed from PEPD, p53 mutants undergo multiple posttranslational modifications, especially lysine 373 acetylation, which cause them to refold and regain tumor suppressor activities that are typically displayed by p53. The reactivated p53 mutants strongly inhibit cancer cell growth in vitro and in vivo. Our study identifies a cellular mechanism for reactivation of the tumor suppressor functions of oncogenic p53 mutants.

Carnosine dipeptidase II (CNDP2) protects cells under cysteine insufficiency by hydrolyzing glutathione-related peptides.

The knockout (KO) of the cystine transporter xCT causes ferroptosis, a type of iron-dependent necrotic cell death, in mouse embryonic fibroblasts, but this does not occur in macrophages. In this study, we explored the gene that supports cell survival under a xCT deficiency using a proteomics approach. Analysis of macrophage-derived peptides that were tagged with iTRAQ by liquid chromatography-mass spectrometry revealed a robust elevation in the levels of carnosine dipeptidase II (CNDP2) in xCT KO macrophages. The elevation in the CNDP2 protein levels was confirmed by immunoblot analyses and this elevation was accompanied by an increase in hydrolytic activity towards cysteinylglycine, the intermediate degradation product of glutathione after the removal of the γ-glutamyl group, in xCT KO macrophages. Supplementation of the cystine-free media of Hepa1-6 cells with glutathione or cysteinylglycine extended their survival, whereas the inclusion of bestatin, an inhibitor of CNDP2, counteracted the effects of these compounds. We established CNDP2 KO mice by means of the CRISPR/Cas9 system and found a decrease in dipeptidase activity in the liver, kidney, and brain. An acetaminophen overdose (350 mg/kg) showed not only aggravated hepatic damage but also renal injury in the CNDP2 KO mice, which was not evident in the wild-type mice that were receiving the same dose. The aggravated renal damage in the CNDP2 KO mice was consistent with the presence of abundant levels of CNDP2 in the kidney, the organ prone to developing ferroptosis. These collective data imply that cytosolic CNDP2, in conjugation with the removal of the γ-glutamyl group, recruits Cys from extracellular GSH and supports redox homeostasis of cells, particularly in epithelial cells of proximal tubules that are continuously exposed to oxidative insult from metabolic wastes that are produced in the body.

Platelet-Rich Plasma Promotes the Proliferation of Human Keratinocytes via a Progression of the Cell Cycle. A Role of Prolidase.

Although the role of platelet-rich plasma (PRP) in tissue regeneration has been confirmed in many studies, the mechanism of this process is still not fully understood. Human keratinocytes (HaCaT) cells were used as an experimental model for studies on the effects of PRP on cell proliferation, migration, collagen biosynthesis, prolidase activity, and its expression and anabolic signaling. The activation of epidermal growth factor receptor (EGFR), ß1-integrin, and insulin-like growth factor-1 receptor (IGF-1R) by PRP were investigated by western blot and immunocytochemistry. It has been found that PRP induced keratinocytes migration and proliferation through activation of cell cycle progression and EGFR downstream signaling. Similar biological effects were achieved by an addition to the culture medium of prolidase (PEPD), a ligand of EGFR (PRP is a rich source of PEPD-2 ng/mL). PRP-dependent stimulation of collagen biosynthesis was accompanied by an increase in the expression of NF-κß, IGF-1R-downstream signaling proteins, and PEPD activity. The data suggest that PRP activates a complex of growth factors and adhesion receptors that stimulate cell proliferation, migration, and collagen biosynthesis. PRP induces PEPD-dependent human keratinocyte proliferation through activation of the EGFR receptor. Our study provides a novel mechanism of PRP-dependent wound healing.

Extracellular Prolidase (PEPD) Induces Anabolic Processes through EGFR, ß1-integrin, and IGF-1R Signaling Pathways in an Experimental Model of Wounded Fibroblasts.

The role of prolidase (PEPD) as a ligand of the epidermal growth factor receptor (EGFR) was studied in an experimental model of wound healing in cultured fibroblasts. The cells were treated with PEPD (1-100 nM) and analysis of cell viability, proliferation, migration, collagen biosynthesis, PEPD activity, and the expressions of EGFR, insulin-like growth factor 1 (IGF-1), and ß1-integrin receptor including downstream signaling proteins were performed. It has been found that PEPD stimulated proliferation and migration of fibroblasts via activation of the EGFR-downstream PI3K/Akt/mTOR signaling pathway. Simultaneously, PEPD stimulated the expression of ß1-integrin and IGF-1 receptors and proteins downstream to these receptors such as FAK, Grb2, and ERK1/2. Collagen biosynthesis was increased in control and "wounded" fibroblasts under PEPD treatment. The data suggest that PEPD-induced EGFR signaling may serve as a new attempt to therapy wound healing.

Prolidase - A protein with many faces.

Prolidase is a metal-dependent peptidase specialized in the cleavage of dipeptides containing proline or hydroxyproline on their C-termini. Prolidase homologues are found in all kingdoms of life. The importance of prolidase in human health is underlined by a rare hereditary syndrome referred to as Prolidase Deficiency. A growing number of studies highlight the importance of prolidase in various other human conditions, including cancer. Some recent studies link prolidase's activity-independent regulatory role to tumorigenesis. Furthermore, the enzyme or engineered variants have some applications in biotechnology. In this short review, we aim to highlight different aspects of the protein the importance of which is increasingly recognized over the last years.

Grape seed procyanidins suppress the apoptosis and senescence of chondrocytes and ameliorates osteoarthritis via the DPP4-Sirt1 pathway.

Osteoarthritis (OA) is a complicated pathological condition affecting thousands of people around world, many with substantial unmet medical care needs and without any effective therapies. Previous study has indicated that glucagon-like peptide-1 (GLP-1) is involved in the pathological progress of osteoarthritis; however, the role of dipeptidase-4 (DPP4), which regulates the degradation of GLP-1, still remains unclear in osteoarthritis. Herein, after comparing normal mouse cartilage tissues with OA mouse cartilage tissues by histological analysis, we found out that DPP4 was highly expressed in OA cartilage tissues. To investigate the role of DPP4 in osteoarthritis, the apoptosis and senescence of chondrocytes were found to be decreased in vitro when DPP4 was downregulated by siRNA in chondrocytes. Further study showed that the inhibition of DPP4 by procyanidins, a grape seed extract, attenuated apoptosis and senescence of chondrocytes in vitro. Furthermore, the results showed that DPP4 inhibition protects cartilage by activating Sirt1, which has been reported to be associated with many pathophysiological processes, particularly in age-related diseases, such as neurodegenerative disorders and osteoarthritis. In addition, animal experiment results demonstrated that procyanidins were capable of ameliorating the progression of osteoarthritis through the inhibition of DPP4. This study provides a competitive target for the therapeutic treatment of osteoarthritis, and procyanidins were shown to be a potential medicine for the restoration of the effects of osteoarthritis.

DPEP1 promotes the proliferation of colon cancer cells via the DPEP1/MYC feedback loop regulation.

DPEP1 is highly expressed in the colorectal carcinoma tissues and colon cancer cells. However, the function and underlying mechanism of DPEP1 in the colon cancer cells are still poorly understood. Here, we found that transcription factor MYC could occupy on the DPEP1 promoter and activate its activities, and DPEP1 was up-regulated by MYC proteins in mRNA and protein levels in a dose-dependent manner in colon cancer cells. The expression levels of DPEP1 were positively correlated with that of MYC in colorectal tumor tissues. Moreover, Laser confocal images and Co-immunoprecipitation (Co-IP) revealed that DPEP1 and MYC proteins could bind to each other in the colon cancer cells. In turn, DPEP1 could enhance the stability of MYC proteins by extending the half-life of MYC proteins in colon cancer cells. Thus, DPEP1 and MYC proteins might form a positive feedback loop to maintain their high expression levels in colon cancer cells. In function, the MTT, EdU, Clone Formation assays and xenograft tumors assays demonstrated that DPEP1 could boost the proliferation of colon cancer cells through the DPEP1/MYC positive feedback loop in vitro and in vivo. Theoretically, DPEP1 may serve as a colon cancer biomarker and a novel target of colorectal carcinogenesis therapy.

Current Understanding of the Emerging Role of Prolidase in Cellular Metabolism.

Prolidase [EC 3.4.13.9], known as PEPD, cleaves di- and tripeptides containing carboxyl-terminal proline or hydroxyproline. For decades, prolidase has been thoroughly investigated, and several mechanisms regulating its activity are known, including the activation of the ß1-integrin receptor, insulin-like growth factor 1 receptor (IGF-1) receptor, and transforming growth factor (TGF)-ß1 receptor. This process may result in increased availability of proline in the mitochondrial proline cycle, thus making proline serve as a substrate for the resynthesis of collagen, an intracellular signaling molecule. However, as a ligand, PEPD can bind directly to the epidermal growth factor receptor (EGFR, epidermal growth factor receptor 2 (HER2)) and regulate cellular metabolism. Recent reports have indicated that PEPD protects p53 from uncontrolled p53 subcellular activation and its translocation between cellular compartments. PEPD also participates in the maturation of the interferon α/ß receptor by regulating its expression. In addition to the biological effects, prolidase demonstrates clinical significance reflected in the disease known as prolidase deficiency. It is also known that prolidase activity is affected in collagen metabolism disorders, metabolic, and oncological conditions. In this article, we review the latest knowledge about prolidase and highlight its biological function, and thus provide an in-depth understanding of prolidase as a dipeptidase and protein regulating the function of key biomolecules in cellular metabolism.

Loss of CNDP causes a shorter lifespan and higher sensitivity to oxidative stress in Drosophila melanogaster.

Increasing oxidative stress seems to be the result of an imbalance between free radical production and antioxidant defenses. During the course of aging, oxidative stress causes tissue/cellular damage, which is implicated in numerous age-related diseases. Carnosinase (CN or CNDP) is dipeptidase, which is associated with carnosine and/or glutathione (GSH) metabolism, those are the most abundant naturally occurring endogenous dipeptide and tripeptides with antioxidant and free radical scavenger properties. In the present study, we generated Drosophila cndp (dcndp) mutant flies using the CRISPR/Cas9 system to study the roles of dcndp in vivo. We demonstrate that dcndp mutant flies exhibit shorter lifespan and increased sensitivity to paraquat or hydrogen peroxide (H2O2) induced oxidative stress. These results suggest that dcndp maintains homeostatic conditions, protecting cells and tissues against the harmful effects of oxidative stress in the course of aging.

Structure of human DPEP3 in complex with the SC-003 antibody Fab fragment reveals basis for lack of dipeptidase activity.

Dipeptidase 3 (DPEP3) is one of three glycosylphosphatidylinositol-anchored metallopeptidases potentially involved in the hydrolytic metabolism of dipeptides. While its exact biological function is not clear, DPEP3 expression is normally limited to testis, but can be elevated in ovarian cancer. Antibody drug conjugates targeting DPEP3 have shown efficacy in preclinical models with a pyrrolobenzodiazepine conjugate, SC-003, dosed in a phase I clinical trial (NCT02539719). Here we reveal the novel atomic structure of DPEP3 alone and in complex with the SC-003 Fab fragment at 1.8 and 2.8 Å, respectively. The structure of DPEP3/SC-003 Fab complex reveals an eighteen-residue epitope across the DPEP3 dimerization interface distinct from the enzymatic active site. DPEP1 and DPEP3 extracellular domains share a conserved, dimeric TIM (ß/α)8-barrel fold, consistent with 49% sequence identity. However, DPEP3 diverges from DPEP1 and DPEP2 in key positions of its active site: a histidine to tyrosine variation at position 269 reduces affinity for the ß zinc and may cause substrate steric hindrance, whereas an aspartate to asparagine change at position 359 abolishes activation of the nucleophilic water/hydroxide, resulting in no in vitro activity against a variety of dipeptides and biological substrates (imipenem, leukotriene D4 and cystinyl-bis-glycine). Hence DPEP3, unlike DPEP1 and DPEP2, may require an activating co-factor in vivo or may remain an inactive, degenerate enzyme. This report sheds light on the structural discriminants between active and inactive membrane dipeptidases and provides a benchmark to characterize current and future DPEP3-targeted therapeutic approaches.

Lysis of a Lactococcus lactis Dipeptidase Mutant and Rescue by Mutation in the Pleiotropic Regulator CodY.

Lactococcus lactis subsp. cremoris MG1363 is a model for the lactic acid bacteria (LAB) used in the dairy industry. The proteolytic system, consisting of a proteinase, several peptide and amino acid uptake systems, and a host of intracellular peptidases, plays a vital role in nitrogen metabolism and is of eminent importance for flavor formation in dairy products. The dipeptidase PepV functions in the last stages of proteolysis. A link between nitrogen metabolism and peptidoglycan (PG) biosynthesis was underlined by the finding that deletion of the dipeptidase gene pepV (creating strain MGΔpepV) resulted in a prolonged lag phase when the mutant strain was grown with a high concentration of glycine. In addition, most MGΔpepV cells lyse and have serious defects in their shape. This phenotype is due to a shortage of alanine, since adding alanine can rescue the growth and shape defects. Strain MGΔpepV is more resistant to vancomycin, an antibiotic targeting peptidoglycan d-Ala-d-Ala ends, which confirmed that MGΔpepV has an abnormal PG composition. A mutant of MGΔpepV was obtained in which growth inhibition and cell shape defects were alleviated. Genome sequencing showed that this mutant has a single point mutation in the codY gene, resulting in an arginine residue at position 218 in the DNA-binding motif of CodY being replaced by a cysteine residue. Thus, this strain was named MGΔpepVcodYR218C Transcriptome sequencing (RNA-seq) data revealed a dramatic derepression in peptide uptake and amino acid utilization in MGΔpepVcodYR218C A model of the connections among PepV activity, CodY regulation, and PG synthesis of L. lactis is proposed.IMPORTANCE Precise control of peptidoglycan synthesis is essential in Gram-positive bacteria for maintaining cell shape and integrity as well as resisting stresses. Although neither the dipeptidase PepV nor alanine is essential for L. lactis MG1363, adequate availability of either ensures proper cell wall synthesis. We broaden the knowledge about the dipeptidase PepV, which acts as a linker between nitrogen metabolism and cell wall synthesis in L. lactis.

CNDP2 Acts as an Activator for Human Ovarian Cancer Growth and Metastasis via the PI3K/AKT Pathway.

INTRODUCTION: The mechanism of tumorigenesis and metastasis of ovarian cancer has not yet been elucidated. This study aimed to investigate the role and molecular mechanism of cytosolic nonspecific dipeptidase 2 in tumorigenesis and metastasis. METHODS: Cytosolic nonspecific dipeptidase 2 expression in human ovarian cancer tissues and cell lines was assessed with methyl thiazolyl tetrazolium (MTT), clone formation, and transwell assays performed to evaluate the ability of ovarian cancer cells to proliferate and migrate. Nude mice tumor formation experiments were also performed by subcutaneously injecting cells with stable cytosolic nonspecific dipeptidase 2 knockdown and control SKOV3 cells into BALB/c female nude mice to detect changes in PI3K/AKT pathway-related proteins by Western blotting. RESULTS: Cytosolic nonspecific dipeptidase 2 was highly expressed in human ovarian cancer tissues, with its expression associated with pathological data, including ovarian cancer metastasis. A cytosolic nonspecific dipeptidase 2 stable knockdown or ectopic expression ovarian cancer cell model was established and demonstrated that cytosolic nonspecific dipeptidase 2 could promote the proliferation of ovarian cancer cells. Transwell cell migration and invasion assays confirmed that cytosolic nonspecific dipeptidase 2 enhanced cell metastasis in ovarian cancer. Furthermore, in vivo xenograft experiments demonstrated that cytosolic nonspecific dipeptidase 2 can promote the development and progression of ovarian cancer, increasing the expression of phosphorylated PI3K and AKT. CONCLUSIONS: Cytosolic nonspecific dipeptidase 2 promotes the occurrence and development of ovarian cancer through the PI3K/AKT signaling pathway.

Dipeptidase-1 Is an Adhesion Receptor for Neutrophil Recruitment in Lungs and Liver.

A hallmark feature of inflammation is the orchestrated recruitment of neutrophils from the bloodstream into inflamed tissue. Although selectins and integrins mediate recruitment in many tissues, they have a minimal role in the lungs and liver. Exploiting an unbiased in vivo functional screen, we identified a lung and liver homing peptide that functionally abrogates neutrophil recruitment to these organs. Using biochemical, genetic, and confocal intravital imaging approaches, we identified dipeptidase-1 (DPEP1) as the target and established its role as a physical adhesion receptor for neutrophil sequestration independent of its enzymatic activity. Importantly, genetic ablation or functional peptide blocking of DPEP1 significantly reduced neutrophil recruitment to the lungs and liver and provided improved survival in models of endotoxemia. Our data establish DPEP1 as a major adhesion receptor on the lung and liver endothelium and identify a therapeutic target for neutrophil-driven inflammatory diseases of the lungs.

Roles of cysteinyl leukotrienes and their receptors in immune cell-related functions.

The cysteinyl leukotrienes (cys-LTs), leukotriene C4, (LTC4), LTD4, and LTE4, are lipid mediators of inflammation. LTC4 is the only intracellularly synthesized cys-LT through the 5-lipoxygenase and LTC4 synthase pathway and after transport is metabolized to LTD4 and LTE4 by specific extracellular peptidases. Each cys-LT has a preferred functional receptor in vivo; LTD4 to the type 1 cys-LT receptor (CysLT1R), LTC4 to CysLT2R, and LTE4 to CysLT3R (OXGR1 or GPR99). Recent studies in mouse models revealed that there are multiple regulatory mechanisms for these receptor functions and each receptor plays a distinct role as observed in different mouse models of inflammation and immune responses. This review focuses on the integrated host responses to the cys-LT/CysLTR pathway composed of sequential ligands with preferred receptors as seen from mouse models. It also discusses potential therapeutic targets for LTC4 synthase, CysLT2R, and CysLT3R.

Epistasis between ADIPOQ rs1501299 and PON1 rs662 polymorphisms is potentially associated with the development of knee osteoarthritis.

Overweight produces oxidative stress (OS) on the articular cartilage, with the subsequent risk of developing knee osteoarthritis (OA). Associations between genetic polymorphisms related to OS and OA have been reported, but it is currently unknown whether there exist interactions among them that affect OA development. To identify and evaluate interactions between multiple SNPs related to OS in Mexican knee OA patients. Ninety-two knee OA patients were included in the study, which were compared to 147 healthy controls. Nine variants of six genes (PEPD, AGER, IL6, ADIPOQ, PON1, and CA6) related to OS were genotyped in both study groups through the OpenArray system. Epistasis was analyzed with the multifactor dimensionality reduction (MDR) method. The MDR analysis revealed a significant interaction (p = 0.0107) between polymorphisms rs1501299 (ADIPOQ) and rs662 (PON1), with an entropy value of 9.84%; in addition, high and low risk genotypes were identified between these two polymorphisms. The effect of the interaction between rs1501299 (ADIPOQ) and rs662 (PON1) polymorphisms seems to play an important role in OA pathogenesis; so the epistasis analysis may provide an excellent tool for identifying individuals at high risk for developing OA.