ABSTRACT
Extremely preterm infants are at risk of developing retinopathy of prematurity (ROP), characterized by neovascularization and neuroinflammation leading to blindness. Polyunsaturated fatty acid (PUFA) supplementation is recommended in preterm infants to lower the risk of ROP, however, with no significant improvement in visual acuity. Reasonably, this could be as a result of the non-consideration of PUFA metabolizing enzymes. We hypothesize that abnormal metabolism of the arachidonic acid (AA) pathway may contribute to severe stages of ROP. The present study investigated the AA-metabolizing enzymes in ROP pathogenesis by a targeted gene expression analysis of blood (severe ROP = 70, No/Mild = 56), placenta (preterm placenta = 6, full term placenta = 3), and human primary retinal cell cultures and further confirmed at the protein level by performing IHC in sections of ROP retina. The lipid metabolites were identified by LC-MS in the vitreous humor (VH; severe ROP = 15, control = 15). Prostaglandins D2 (p = 0.02), leukotrienes B5 (p = 0.0001), 11,12-epoxyeicosatrienoic acid (p = 0.01), and lipid-metabolizing enzymes of the AA pathway such as CYP1B1, CYP2C8, COX2, and ALOX15 were significantly upregulated while EPHX2 was significantly (0.04) downregulated in ROP cases. Genes involved in hypoxic stress, angiogenesis, and apoptosis showed increased expression in ROP. An increase in the metabolic intermediates generated from the AA metabolism pathway further confirmed the role of these enzymes in ROP, while metabolites for EPHX2 activity were low in abundance. Inflammatory lipid intermediates were higher compared to anti-inflammatory lipids in VH and showed an association with enzyme activity. Both the placenta of preterm infants who developed ROP and hypoxic retinal cultures showed a reduced expression of EPHX2. These findings suggested a strong involvement of EPHX2 in regulating retinal neovascularization and inflammation. The study results underscore the role of arachidonic acid metabolism in the development of ROP and as a potential target for preventing vision loss among preterm-born infants.
ABSTRACT
Inflammation plays a key role in the pathogenesis of retinal vascular diseases. We have shown earlier an increase in the activity of matrix metalloproteinases in the vitreous and tears of preterm born babies with retinopathy of prematurity (ROP) compared to those with no-ROP leading to a shift in the balance of angiogenic (vascular endothelial growth factor [VEGF], matrix metalloproteinase [MMPs], complement component [C3]) and anti-angiogenic (opticin, thrombospondin) in ROP eyes. We now confirmed that tear MMP levels in premature infants perfectly correlates with disease severity. Next, we demonstrated that a reduced opticin levels in ROP vitreous are regulated by MMPs secreted by activated microglia. Upon exposing the human microglia cell line (CHME3) to hypoxia, an increased expression of inflammatory proteins (MMP9, VEGF) was noticed while opticin reduced significantly (p = 0.005). Further, the reduced opticin's expression by microglial cells under hypoxia could be rescued by inhibiting the MMP activity using doxycycline and EDTA. The inhibition of MMP activity altered the expression of other key signaling molecules under hypoxia. Our study clearly explains that increased activity of MMPs under hypoxia regulates the expression of opticin as seen in the vitreous humor of ROP and could serve as a potential target for ROP management.
Subject(s)
Extracellular Matrix Proteins/metabolism , Hypoxia/metabolism , Matrix Metalloproteinase 9/metabolism , Microglia/metabolism , Proteoglycans/metabolism , Retina/metabolism , Stress, Physiological , Case-Control Studies , Computer Simulation , Doxycycline/metabolism , Extracellular Matrix/drug effects , Extracellular Matrix/metabolism , Gene Expression Regulation/drug effects , Humans , Infant , Infant, Newborn , Ligands , Matrix Metalloproteinase Inhibitors/pharmacology , Microglia/drug effects , Models, Biological , Protein Binding/drug effects , Retina/drug effects , Retinopathy of Prematurity/genetics , Retinopathy of Prematurity/metabolism , Retinopathy of Prematurity/pathology , Signal Transduction/drug effects , Stress, Physiological/drug effects , Tissue Inhibitor of Metalloproteinase-2/metabolismABSTRACT
Purpose: To investigate the presence and level of 35 distinct cytokines in the tear fluid obtained from patients with primary acquired nasolacrimal duct obstruction (PANDO) and compare it with controls in an effort to understand the disease etiopathogenesis.Methods: Standard protocols were used for collecting tears from 60 eyes (20 diseased eyes and 20 healthy fellow eyes of unilateral PANDO, 20 control eyes of healthy subjects). A total of 35 analytes involved in inflammation, angiogenesis and wound healing were assessed by multiplex ELISA. Alterations in the tear levels of cytokines in PANDO and their comparison with the levels in the non-diseased fellow eye and healthy volunteers were noted. STRING analysis was used to assess the involved biological pathways of the altered cytokines. Linear mixed effect model was used for statistical analysis. A P value of <0.05 was considered significant.Results: There was significant upregulation of 10 pro-inflammatory cytokines in tears from diseased eyes of PANDO patients in comparison with the non-diseased controls and include matrix metalloproteinase 9 (MMP 9), serpin E1, Interleukin-6 (IL-6), hepatocyte growth factor (HGF), vascular endothelial growth factor-A and R2 (VEGF-A, VEGF R2), platelet-endothelial cell adhesion molecule (PECAM-1), c-reactive protein (CRP), chemokine ligand 2 (CCL2) and platelet-derived growth factor- AA (PDGF-AA). Amongst the anti-inflammatory cytokines, three were significantly upregulated in diseased eyes of PANDO patients in comparison with the non-diseased controls and include granulocyte-colony stimulating factor (G-CSF), retinol binding protein 4 (RBP4) and tissue inhibitor of metalloproteinases -1 (TIMP-1). There were no significant differences between the control eyes of the diseased patient and control eyes of healthy subjects. Based on the significantly altered cytokines, string analysis revealed that the biological pathways involved in the etiopathogenesis of PANDO include inflammation, angiogenesis, negative regulation of apoptosis, cellular proliferation and hormonal regulation.Conclusions: In cases of PANDO, dysregulation of certain cytokines was disease specific. Biological pathways reflect a possible link and interaction between the inflammatory cytokines with vasculature and hormonal microenvironments of the lacrimal drainage system, which in a way is bringing three promising candidates in the PANDO etiopathogenesis on a common ground.
Subject(s)
Cytokines/biosynthesis , Lacrimal Duct Obstruction/metabolism , Nasolacrimal Duct/metabolism , Tears/metabolism , Biomarkers/metabolism , Case-Control Studies , Female , Humans , Lacrimal Duct Obstruction/etiology , MaleABSTRACT
Metabolomics refers to the systematic identification and quantification of the small molecule metabolites (the metabolome) of a biological system in a given space (cell, tissue, organ, biological fluid, or organism) and time. Global metabolic profiling provides broad range of coverage for most of the analytes present in any tissue. Human retina is metabolically highly active, and retinal vascular diseases such as age-related macular degeneration (AMD), diabetic retinopathy (DR), retinal vein occlusion (RVO), central retinal artery occlusion, and retinopathy of prematurity (ROP) are often associated with the disruptions in metabolic activities. A systematic study of total retinal metabolites from human diseased retina is a major challenge owing to the nonavailability of tissue specimens. Therefore, vitreous humor being very proximal to retina could be used as surrogate for retinal metabolomic analysis. As the extraction method adopted for such analysis determines the type of metabolites, two different types of solvent (methanol and chloroform)-based extraction methods could be used for retinal vascular patient samples (vitreous humor). Metabolites obtained from both the extraction methods are then subjected to LC-MS/MS for detection and identification.
Subject(s)
Metabolomics/methods , Retinal Diseases/pathology , Vitreous Body/metabolism , Chemical Fractionation/methods , Chloroform/chemistry , Chromatography, High Pressure Liquid/methods , Humans , Methanol/chemistry , Retina/metabolism , Solvents/chemistry , Tandem Mass Spectrometry/methodsABSTRACT
AIM: Retinopathy of prematurity (ROP) is a vasoproliferative eye disease in preterm infants. Based on its phenotypic similarities with familial exudative vitreo retinopathy (FEVR), the present study was conducted to screen the Norrin signalling pathway genes (already been implicated in FEVR) for understanding their involvement among Indian patients with ROP. METHODS: The study cohort consisted of patients with ROP (n=246) and controls (n=300) that included full term (n=110) and preterm babies devoid of ROP (n=190). Screening of the NDP, FZD4, TSPAN12 genes were accomplished by resequencing the entire coding and untranslated regions (UTR). The genotype data of the patients with ROP were analysed in the background of their clinical manifestations and further analysed in conjunction with other available data on these genes worldwide. RESULTS: Two novel variants in intron 1 (IVS1 +16A>G) and 3'UTR (c.5 22T>C) along with a previously reported change in the 5'UTR (c.395_409del14bp) were observed in the NDP gene in three patients with ROP. Screening of the FZD4 revealed four heterozygous variants, p.(Pro33Ser), p.(Pro168Ser), p.(Ile192Ile) and p.(Ile360Val), a compound heterozygous (p.(Pro33Ser)/p.(Pro168Ser)) and a 3'UTR (c*G>T) variants in the study cohort. Variants p.(Pro33Ser) and p.(Pro168Ser) were found to be significantly associated with ROP. A heterozygous variant p.(Leu119Arg) in TSPAN12 gene was observed in a patient with threshold ROP. However, a formal genotype-phenotype correlation could not be established due to the low frequencies of the variant alleles in these genes. CONCLUSIONS: This is a first study that revealed association of few variants in Norrin signalling genes among Indian patients with ROP that warrants further detailed investigation worldwide.
Subject(s)
Eye Proteins/genetics , Frizzled Receptors/genetics , Genetic Association Studies/methods , Mutation , Nerve Tissue Proteins/genetics , Retinopathy of Prematurity/genetics , Tetraspanins/genetics , Cohort Studies , DNA Mutational Analysis , Eye Proteins/metabolism , Female , Frizzled Receptors/metabolism , Humans , India/epidemiology , Infant , Infant, Newborn , Male , Nerve Tissue Proteins/metabolism , Pedigree , Retinopathy of Prematurity/epidemiology , Retinopathy of Prematurity/metabolism , Retrospective Studies , Tetraspanins/metabolismABSTRACT
Retinopathy of prematurity (ROP) is a neurovascular complication in preterm babies, leading to severe visual impairment, but the underlying mechanisms are yet unclear. The present study aimed at unraveling the molecular mechanisms underlying the pathogenesis of ROP. A comprehensive screening of candidate genes in preterms with ROP (n = 189) and no-ROP (n = 167) was undertaken to identify variants conferring disease susceptibility. Allele and genotype frequencies, linkage disequilibrium and haplotypes were analyzed to identify the ROP-associated variants. Variants in CFH (p = 2.94 × 10-7), CFB (p = 1.71 × 10-5), FBLN5 (p = 9.2 × 10-4), CETP (p = 2.99 × 10-5), and CXCR4 (p = 1.32 × 10-8) genes exhibited significant associations with ROP. Further, a quantitative assessment of 27 candidate proteins and cytokines in the vitreous and tear samples of babies with severe ROP (n = 30) and congenital cataract (n = 30) was undertaken by multiplex bead arrays and further validated by western blotting and zymography. Significant elevation and activation of MMP9 (p = 0.038), CFH (p = 2.24 × 10-5), C3 (p = 0.05), C4 (p = 0.001), IL-1ra (p = 0.0019), vascular endothelial growth factor (VEGF) (p = 0.0027), and G-CSF (p = 0.0099) proteins were observed in the vitreous of ROP babies suggesting an increased inflammation under hypoxic condition. Along with inflammatory markers, activated macrophage/microglia were also detected in the vitreous of ROP babies that secreted complement component C3, VEGF, IL-1ra, and MMP-9 under hypoxic stress in a cell culture model. Increased expression of the inflammatory markers like the IL-1ra (p = 0.014), MMP2 (p = 0.0085), and MMP-9 (p = 0.03) in the tears of babies at different stages of ROP further demonstrated their potential role in disease progression. Based on these findings, we conclude that increased complement activation in the retina/vitreous in turn activated microglia leading to increased inflammation. A quantitative assessment of inflammatory markers in tears could help in early prediction of ROP progression and facilitate effective management of the disease, thereby preventing visual impairment.