Proteomics reveals ablation of PlGF increases antioxidant and neuroprotective proteins in the diabetic mouse retina

High-throughput mRNA sequencing of human placenta shows sex differences across gestation

INTRODUCTION

Fetal sex affects fetal and maternal health outcomes in pregnancy, but this connection remains poorly understood. As the placenta is the route of fetomaternal communication and derives from the fetal genome, placental gene expression sex differences may explain these outcomes.

OBJECTIVES

We utilized next generation sequencing to study the normal human placenta in both sexes in first and third trimester to generate a normative transcriptome based on sex and gestation.

STUDY DESIGN

We analyzed 124 first trimester (T1, 59 female and 65 male) and 43 third trimester (T3, 18 female and 25 male) samples for sex differences within each trimester and sex-specific gestational differences.

RESULTS

Placenta shows more significant sexual dimorphism in T1, with 94 T1 and 26 T3 differentially expressed genes (DEGs). The sex chromosomes contributed 60.6% of DEGs in T1 and 80.8% of DEGs in T3, excluding X/Y pseudoautosomal regions. There were 6 DEGs from the pseudoautosomal regions, only significant in T1 and all upregulated in males. The distribution of DEGs on the X chromosome suggests genes on Xp (the short arm) may be particularly important in placental sex differences. Dosage compensation analysis of X/Y homolog genes shows expression is primarily contributed by the X chromosome. In sex-specific analyses of first versus third trimester, there were 2815 DEGs common to both sexes upregulated in T1, and 3263 common DEGs upregulated in T3. There were 7 female-exclusive DEGs upregulated in T1, 15 female-exclusive DEGs upregulated in T3, 10 male-exclusive DEGs upregulated in T1, and 20 male-exclusive DEGs upregulated in T3.

DISCUSSION

This is the largest cohort of placentas across gestation from healthy pregnancies defining the normative sex dimorphic gene expression and sex common, sex specific and sex exclusive gene expression across gestation. The first trimester has the most sexually dimorphic transcripts, and the majority were upregulated in females compared to males in both trimesters. The short arm of the X chromosome and the pseudoautosomal region is particularly critical in defining sex differences in the first trimester placenta. As pregnancy is a dynamic state, sex specific DEGs across gestation may contribute to sex dimorphic changes in overall outcomes.

Mass spectrometry-based retina proteomics

A subfield of neuroproteomics, retina proteomics has experienced a transformative growth since its inception due to methodological advances in enabling chemical, biochemical, and molecular biology techniques. This review focuses on mass spectrometry's contributions to facilitate mammalian and avian retina proteomics to catalog and quantify retinal protein expressions, determine their posttranslational modifications, as well as its applications to study the proteome of the retina in the context of biology, health and diseases, and therapy developments.

Downregulated HDAC3 or up-regulated microRNA-296-5p alleviates diabetic retinopathy in a mouse model

Objective

It has been demonstrated the efficacy of histone deacetylase 3 (HDAC3) in diabetes. Nevertheless, the function of HDAC3 in diabetic retinopathy (DR) remained largely obscure. Here, we investigated the HDAC3 effects in DR mice through the microRNA (miR)-296-5p/G protein subunit alpha i2 (GNAI2) axis.

Methods

The mice diabetes model was established. HDAC3, GNAI2 and miR-296-5p levels in retina tissues of DR mice were evaluated. The weight, blood glucose, Evans blue leakage in DR mice, apoptosis of retinal ganglion cells, vascular endothelial growth factor (VEGF) and malondialdehyde (MDA) contents and superoxide dismutase (SOD) activity in DR mice were detected after miR-296-5p elevation or HDAC3 depletion. The relations among HDAC3, miR-296-5p and GNAI2 were validated.

Results

HDAC3 and GNAI2 expressed at a high level while miR-296-5p expressed at a low level in retina tissues of DR mice. Restoring miR-296-5p or depleting HDAC3 reduced Evans blue leakage in DR mice, attenuated apoptosis of retinal ganglion cells, reduced VEGF and MDA, and enhanced SOD activity in serum and retinal tissues of DR mice. HDAC3 repressed miR-296-5p expression by binding to its promoter region, thereby enhancing GNAI2 expression.

Conclusion

Depleting HDAC3 or restoring miR-296-5p suppresses apoptosis of retinal ganglion cells of DR mice via down-regulating GNAI2.

Direct modulation of microglial function by electrical field

Non-invasive electric stimulation (ES) employing a low-intensity electric current presents a potential therapeutic modality that can be applied for treating retinal and brain neurodegenerative disorders. As neurons are known to respond directly to ES, the effects of ES on glia cells are poorly studied. A key question is if ES directly mediates microglial function or modulates their activity merely via neuron-glial signaling. Here, we demonstrated the direct effects of ES on microglia in the BV-2 cells—an immortalized murine microglial cell line. The low current ES in a biphasic ramp waveform, but not that of rectangular or sine waveforms, significantly suppressed the motility and migration of BV-2 microglia in culture without causing cytotoxicity. This was associated with diminished cytoskeleton reorganization and microvilli formation in BV-2 cultures, as demonstrated by immunostaining of cytoskeletal proteins, F-actin and β-tubulin, and scanning electron microscopy. Moreover, ES of a ramp waveform reduced microglial phagocytosis of fluorescent zymosan particles and suppressed lipopolysaccharide (LPS)-induced pro-inflammatory cytokine expression in BV-2 cells as shown by Proteome Profiler Mouse Cytokine Array. The results of quantitative PCR and immunostaining for cyclooxygenase-2, Interleukin 6, and Tumor Necrosis Factor-α corroborated the direct suppression of LPS-induced microglial responses by a ramp ES. Transcriptome profiling further demonstrated that ramp ES effectively suppressed nearly half of the LPS-induced genes, primarily relating to cellular motility, energy metabolism, and calcium signaling. Our results reveal a direct modulatory effect of ES on previously thought electrically “non-responsive” microglia and suggest a new avenue of employing ES for anti-inflammatory therapy.

The attenuation effect of potassium 2-(1-hydroxypentyl)-benzoate in a mouse model of diabetes-associated cognitive decline: The protein expression in the brain

Aims

dl‐PHPB (potassium 2‐(1‐hydroxypentyl)‐benzoate) has been shown to have neuroprotective effects against acute cerebral ischemia, vascular dementia, and Alzheimer's disease. The aim of this study was to investigate the effects of dl‐PHPB on memory deficits and preliminarily explore the underlying molecular mechanism.

Methods

Blood glucose and behavioral performance were evaluated in the KK‐A^y diabetic mouse model before and after dl‐PHPB administration. Two‐dimensional difference gel electrophoresis (2D‐DIGE)‐based proteomics was used to identify differentially expressed proteins in brain tissue. Western blotting was used to study the molecular mechanism of the related signaling pathways.

Results

Three‐month‐old KK‐A^y mice were given 150 mg/kg dl‐PHPB by oral gavage for 2 months, which produced no effect on the level of serum glucose. In the Morris water maze test, KK‐A^y mice treated with dl‐PHPB showed significant improvements in spatial learning and memory deficits compared with vehicle‐treated KK‐A^y mice. Additionally, we performed 2D‐DIGE to compare brain proteomes of 5‐month KK‐A^y mice treated with and without dl‐PHPB. We found 14 altered proteins in the cortex and 11 in the hippocampus; two of the 25 altered proteins and another four proteins that were identified in a previous study on KK‐A^y mice were then validated by western blot to further confirm whether dl‐PHPB can reverse the expression levels of these proteins. The phosphoinositide 3‐kinase/protein kinase B/glycogen synthase kinase‐3β (PI3K/Akt/GSK‐3β) signaling pathway was also changed in KK‐A^y mice and dl‐PHPB treatment could reverse it.

Conclusions

These results indicate that dl‐PHPB may play a potential role in diabetes‐associated cognitive impairment through PI3K/Akt/GSK‐3β signaling pathway and the differentially expressed proteins may become putative therapeutic targets.

Transcriptome-wide analysis reveals core sets of transcriptional regulators of sensome and inflammation genes in retinal microglia

BACKGROUND

Retinal microglial cells (RMCs) play crucial roles in maintaining normal visual functions in a healthy eye. However, the underlying mechanisms of RMCs over-activation manifesting the alterations of sensome profile and inflammation state, which contribute to various retinal neurodegenerative diseases, remain elusive. Here, we aimed to identify the core set of sensome and pro-inflammatory genes and their regulators using transcriptome and data mining approaches.

METHODS

We performed paired-end RNA-sequencing in primary microglial cell cultures treated with TNFα/IFNϒ (10 ng/ml for 12 h) and PBS as a control. Gene enrichment analysis and hierarchical clustering for the differentially expressed transcripts highlight functional pathways and network perturbations. We examined overlaps of the mouse microglial gene expression profiles with the data-mined human sensome and pro-inflammatory marker genes. The core sets of sensome and pro-inflammatory genes were selected and predicted for transcription factors (TFs). The identified TFs in RNA-Seq are validated by the quantitative PCR method.

RESULTS

TNFα/IFNϒ induced 668 differentially expressed transcripts in retinal microglial cells relative to the control. Furthermore, gene enrichment analysis and the gene expression network revealed activated microglial genes, biological, molecular and inflammatory pathways. The overlapping analysis of the TNFα/IFNϒ-activated microglia genes and the data-mined human gene sets revealed 22 sensome and 61 pro-inflammatory genes. Based on network analysis, we determined 10 genes as the core sets of sensome and pro-inflammatory genes and predicted the top ten TFs that regulate them. The SP110, IRF1, FLI1, SP140 (sensome) and RELB, BATF2, NFKB2, TRAFD1, SP100, NFKB1 (inflammation) are differentially expressed between the TNFα/IFNϒ activated and the non-activated microglia which were validated by quantitative PCR. The outcomes indicate that these transcriptional regulators are highly expressed and may regulate the sensome and inflammatory genes of RMCs and switch them to over-activation.

CONCLUSION

Our results comprise a powerful, cross-species functional genomics resource for sensome and inflammation of RMCs, which may provide novel therapeutic approaches to prevent retinal neurodegenerative diseases.

MiR-133b Modulates the Osteoblast Differentiation to Prevent Osteoporosis Via Targeting GNB4

MiR-133b is considered to be lowly expressed in osteoporosis patients. This study aimed to probe the role and in-depth mechanism of miR-133b in modulating osteoblast biological behavior and differentiation. The differential expressions of miR-133b and GNB4 in patients with osteoporosis and healthy control were analyzed based on the GEO database. Osteoblastic differentiation of hFOB 1.19 cells was induced in the culture medium containing 10 mM β-glycerophosphate, 50 nm dexamethasone, and 100 μg/ml ascorbic acid. The level of GNB4 was detected using quantitative real-time PCR (qRT-PCR) and Western blot. Cell viability and apoptosis were measured by Cell Counting Kit-8 (CCK-8) and flow cytometry assays, respectively. Western blot was also utilized to measure the levels of osteoblast-related proteins, including ALP, Runx2, Osterix, and OPN. GNB4 was identified and confirmed as a downstream target gene of miR-133b. The expression of miR-133b was declined while the expression of GNB4 was increased in osteoporosis patients. Importantly, up-regulation of miR-133b caused the increase of cell viability and the decrease of apoptosis, which could be blocked by overexpression of GNB4. Also, up-regulation of miR-133b promoted osteoblasts differentiation, as shown by the increase in the expression of ALP, Runx2, Osterix, and OPN. Similarly, this promoting impact resulted from miR-133b overexpression can be reversed via up-regulation of GNB4. These findings revealed that miR-133b can promote the viability and differentiation of osteoblasts by targeting GNB4, hoping to lay a feasible theoretical foundation for the clinical treatment of osteoporosis.

RNA-Seq reveals placental growth factor regulates the human retinal endothelial cell barrier integrity by transforming growth factor (TGF-β) signaling

Placental growth factor (PlGF or PGF) is a member of the VEGF (vascular endothelial growth factor) family. It plays a pathological role in inflammation, vascular permeability, and pathological angiogenesis. The molecular signaling by which PlGF mediates its effects in non-proliferative diabetic retinopathy (DR) remains elusive. This study aims to characterize the transcriptome changes of human retinal endothelial cells (HRECs) with the presence and the absence of PlGF signaling. Primary HRECs were treated with the PlGF antibody (ab) to block its activity. The total RNA was isolated and subjected to deep sequencing to quantify the transcripts and their changes in both groups. We performed transcriptome-wide analysis, gene ontology, pathway enrichment, and gene-gene network analyses. The results showed that a total of 3760 genes were significantly differentially expressed and were categorized into cell adhesion molecules, cell junction proteins, chaperone, calcium-binding proteins, and membrane traffic proteins. Functional pathway analyses revealed that the TGF-β pathway, pentose phosphate pathway, and cell adhesion pathway play pivotal roles in the blood-retina barrier and antioxidant defense system. Collectively, the data provide new insights into the molecular mechanisms of PlGF's biological functions in HRECs relevant to DR and diabetic macular edema (DME). The newly identified genes and pathways may act as disease markers and target molecules for therapeutic interventions for the patients with DR and DME refractory to the current anti-VEGF therapy.

Synergistic interactions of PlGF and VEGF contribute to blood-retinal barrier breakdown through canonical NFκB activation

To investigate the role of placental growth factor/vascular endothelial growth factor (PlGF-VEGF) heterodimers are involved in the blood-retinal barrier (BRB) breakdown and the associated mechanism, human retinal endothelial cells (HRECs) were treated with recombinant human (rh)PlGF-VEGF heterodimers and rhPlGF and studied in normal and high-glucose conditions. HREC barrier function was evaluated by the measurement of trans-endothelial electrical resistance (TEER). Adeno-Associated Virus Type 5 (AAV5) vectors overexpressed PlGF in the retina by intravitreal injection into the C57BL6 mouse eye. AAV5-GFP vector and naïve animals were used as controls. Immunofluorescence (IF) and western blots examined the protein expression of PlGF-VEGF heterodimers, VEGF, PlGF, NFκB, p-IκBα, ZO-1, and VE-cadherin in HREC and mouse retina. PlGF-VEGF heterodimers were detected predominantly in the HREC cell nuclei based on IF and cytoplasmic and nuclear fractionation experiments. High glucose treatment increased PlGF-VEGF nuclear abundance. Dot immunoblotting demonstrated a strong affinity of the 5D11D4 antibody to PlGF-VEGF heterodimers. rhPlGF-VEGF disrupted the barrier function of HREC, which was prevented by the neutralization of PlGF-VEGF by the 5D11D4 antibody. Stimulation of HRECs with rhPlGF also led to an increase in the nuclear signals for PlGF-VEGF, p-IκBα, and colocalization of NFκB p65 and PlGF-VEGF in the nuclei. The selective IKK2 inhibitor IMD0354 disrupted the nuclear colocalization. Treatment with IMD0354 restored the barrier function of HREC, as indicated by the ZO-1 and VE-cadherin expression. In the mouse retinas, PlGF overexpression by AAV5 vector reduced ZO-1 expression and increased abundance of pIκBα. PIGF/VEGF heterodimers mediate BRB breakdown potentially through the canonical NFκB activation.

Pericyte-Endothelial Interactions in the Retinal Microvasculature

Retinal microvasculature is crucial for the visual function of the neural retina. Pericytes and endothelial cells (ECs) are the two main cellular constituents in the retinal microvessels. Formation, maturation, and stabilization of the micro-vasculatures require pericyte-endothelial interactions, which are perturbed in many retinal vascular disorders, such as retinopathy of prematurity, retinal vein occlusion, and diabetic retinopathy. Understanding the cellular and molecular mechanisms of pericyte-endothelial interaction and perturbation can facilitate the design of therapeutic intervention for the prevention and treatment of retinal vascular disorders. Pericyte-endothelial interactions are indispensable for the integrity and functionality of retinal neurovascular unit (NVU), including vascular cells, retinal neurons, and glial cells. The essential autocrine and paracrine signaling pathways, such as Vascular endothelial growth factor (VEGF), Platelet-derived growth factor subunit B (PDGFB), Notch, Angipointein, Norrin, and Transforming growth factor-beta (TGF-β), have been well characterized for the regulation of pericyte-endothelial interactions in the neo-vessel formation processes (vasculogenesis and angiogenesis) during embryonic development. They also play a vital role in stabilizing and remodeling mature vasculature under pathological conditions. Awry signals, aberrant metabolisms, and pathological conditions, such as oxidative stress and inflammation, can disrupt the communication between pericytes and endothelial cells, thereby resulting in the breakdown of the blood-retinal barrier (BRB) and other microangiopathies. The emerging evidence supports extracellular exosomes' roles in the (mis)communications between the two cell types. This review summarizes the essential knowledge and updates about new advancements in pericyte-EC interaction and communication, emphasizing the retinal microvasculature.

Stabilization of HIF-1α in Human Retinal Endothelial Cells Modulates Expression of miRNAs and Proangiogenic Growth Factors

Retinal hypoxia is one of the causative factors of diabetic retinopathy and is also one of the triggers of VEGF release. We hypothesized that specific dysregulated miRNAs in diabetic retinopathy could be linked to hypoxia-induced damage in human retinal endothelial cells (HRECs). We investigated in HRECs the effects of chemical (CoCl₂) hypoxia on the expression of HIF-1α, VEGF, PlGF, and of a focused set of miRNAs. We found that miR-20a-5p, miR-20b-5p, miR-27a-3p, miR-27b-3p, miR-206-3p, miR-381-3p correlated also with expression of TGFβ signaling pathway genes in HRECs, challenged with chemical hypoxic stimuli. In conclusion, our data suggest that retinal angiogenesis would be promoted, at least under HIF-1α activation, by upregulation of PlGF and other factors such as miRNAs, VEGFA, and TGFβ1.

Transcriptome-Wide Analysis of CXCR5 Deficient Retinal Pigment Epithelial (RPE) Cells Reveals Molecular Signatures of RPE Homeostasis

Age-related macular degeneration (AMD) is the most common cause of irreversible blindness in the elderly population. In our previous studies, we found that deficiency of CXCR5 causes AMD-like pathological phenotypes in mice, characterized by abnormalities and dysfunction of the retinal pigment epithelium (RPE) cells. The abnormalities included abnormal cellular shape and impaired barrier function. In the present study, primary RPE cells were derived separately from CXCR5 knockout (KO) mice and from C57BL6 wild type (WT). The isolated primary cells were cultured for several days, and then total RNA was isolated and used for library preparation, sequencing, and the resultant raw data analyzed. Relative to the WT, a total of 1392 differentially expressed genes (DEG) were identified. Gene ontology analysis showed various biological processes, cellular components, and molecular functions were enriched. Pathway enrichment analysis revealed several pathways, including the PI3K-Akt signaling, mTOR signaling, FoxO, focal adhesion, endocytosis, ubiquitin-mediated proteolysis, TNFα-NF-kB Signaling, adipogenesis genes, p53 signaling, Ras, autophagy, epithelial–mesenchymal transition (EMT), and mitochondrial pathway. This study explores molecular signatures associated with deficiency of CXCR5 in RPE cells. Many of these signatures are important for homeostasis of this tissue. The identified pathways and genes require further evaluation to better understand the pathophysiology of AMD.

Placental growth factor regulates the pentose phosphate pathway and antioxidant defense systems in human retinal endothelial cells

The molecular mechanisms whereby placental growth factor (PlGF) mediates its effects in nonproliferative diabetic retinopathy (DR) are unknown. To better understand the role of PlGF in DR, we used tandem mass tags (TMT)-labeled quantitative proteomics to human retinal endothelial cells (HRECs), treated anti-PlGF antibody, and PBS as a control. Functional annotation and pathway enrichments were performed, which suggested that the differentially expressed proteins (DEPs) were involved in key metabolic processes, protein binding, and membrane, pentose phosphate pathway (PPP) and adherens junction. We conducted integrated gene profiles of our previously published transcriptomic data to the TMT-labeled proteomics data. The results showed the sixty genes were found to be changed at the proteome level. The functional annotation conducted for the sixty proteins suggested that 58.3% of proteins were involved in PPP, 25% of proteins were in interleukin-12 singling and 16.7% of proteins were involved in glycolysis and gluconeogenesis pathway. Mass spectrometry results were validated by transendothelial electrical resistance measurement by an electrical cell-impedance sensing (ECIS) and western blot analysis of VE-cadherin, G6PD. These findings suggest that the PPP proteins and antioxidants may act as a downstream target of PlGF and may play a decisive role in HREC biological functions in DR. SIGNIFICANCE: PlGF (Placental growth factor) is known to play a pivotal role in pathological angiogenesis and inflammation by stimulating endothelial cell migration and by recruiting pericytes and inflammatory cells such as microglia and macrophages. Despite the well-defined pathophysiological roles of PlGF, the underlying molecular and cellular mechanisms are not completely understood, especially the exact relationships between biochemical events and molecular pathways regulated by PlGF, whose inhibition exhibits a protective role in DR. This study provides new insights into protein expression patterns and enables the identification of many attractive candidates for investigation of PPP pathway role in the activation of the antioxidant defense system in DR. Our findings suggest that the PPP proteins and antioxidants (PRDX6, HMOX1, NQO1 and YES1) may act as downstream targets of PlGF and may play a decisive role in HREC biological functions in DR.

RNA-Seq reveals differential expression profiles and functional annotation of genes involved in retinal degeneration in Pde6c mutant Danio rerio

BACKGROUND

Retinal degenerative diseases affect millions of people and represent the leading cause of vision loss around the world. Retinal degeneration has been attributed to a wide variety of causes, such as disruption of genes involved in phototransduction, biosynthesis, folding of the rhodopsin molecule, and the structural support of the retina. The molecular pathogenesis of the biological events in retinal degeneration is unclear; however, the molecular basis of the retinal pathological defect can be potentially determined by gene-expression profiling of the whole retina. In the present study, we analyzed the differential gene expression profile of the retina from a wild-type zebrafish and phosphodiesterase 6c (pde6c) mutant.

RESULTS

The datasets were downloaded from the Sequence Read Archive (SRA), and adaptors and unbiased bases were removed, and sequences were checked to ensure the quality. The reads were further aligned to the reference genome of zebrafish, and the gene expression was calculated. The differentially expressed genes (DEGs) were filtered based on the log fold change (logFC) (±4) and p-values (p < 0.001). We performed gene annotation (molecular function [MF], biological process [BP], cellular component [CC]), and determined the functional pathways Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway for the DEGs. Our result showed 216 upregulated and 3527 downregulated genes between normal and pde6c mutant zebrafish. These DEGs are involved in various KEGG pathways, such as the phototransduction (12 genes), mRNA surveillance (17 genes), phagosome (25 genes), glycolysis/gluconeogenesis (15 genes), adrenergic signaling in cardiomyocytes (29 genes), ribosome (20 genes), the citrate cycle (TCA cycle; 8 genes), insulin signaling (24 genes), oxidative phosphorylation (20 genes), and RNA transport (22 genes) pathways. Many more of all the pathway genes were down-regulated, while fewer were up-regulated in the retina of pde6c mutant zebrafish.

CONCLUSIONS

Our data strongly indicate that, among these genes, the above-mentioned pathways' genes as well as calcium-binding, neural damage, peptidase, immunological, and apoptosis proteins are mostly involved in the retinal and neural degeneration that cause abnormalities in photoreceptors or retinal pigment epithelium (RPE) cells.

17β-Estradiol Delivered in Eye Drops: Evidence of Impact on Protein Networks and Associated Biological Processes in the Rat Retina through Quantitative Proteomics

To facilitate the development of broad-spectrum retina neuroprotectants that can be delivered through topical dosage forms, this proteomics study focused on analyzing target engagements through the identification of functional protein networks impacted after delivery of 17β-estradiol in eye drops. Specifically, the retinae of ovariectomized Brown Norway rats treated with daily eye drops of 17β-estradiol for three weeks were compared to those of vehicle-treated ovariectomized control animals. We searched the acquired raw data against a composite protein sequence database by using Mascot, as well as employed label-free quantification to detect changes in protein abundances. Our investigation using rigorous validation criteria revealed 331 estrogen-regulated proteins in the rat retina (158 were up-regulated, while 173 were down-regulated by 17β-estradiol delivered in eye drops). Comprehensive pathway analyses indicate that these proteins are relevant overall to nervous system development and function, tissue development, organ development, as well as visual system development and function. We also present 18 protein networks with associated canonical pathways showing the effects of treatments for the detailed analyses of target engagements regarding potential application of estrogens as topically delivered broad-spectrum retina neuroprotectants. Profound impact on crystallins is discussed as one of the plausible neuroprotective mechanisms.

Placental growth factor negatively regulates retinal endothelial cell barrier function through suppression of glucose-6-phosphate dehydrogenase and antioxidant defense systems

We report that placental growth factor (PlGF) negatively affects the endothelial cell (EC) barrier function through a novel regulatory mechanism. The PlGF mAb promotes (but recombinant protein disrupts) EC barrier function, thus affecting the barrier-forming protein levels, membrane distribution, and EC monolayer impedance by the electrical cell-impedance sensing system, Western blot, and immunofluorescence staining. RNA sequencing-based transcriptome analysis identified the up-regulation of the pentose phosphate pathway (PPP) and the antioxidant defense protein by PlGF blockade. The PlGF and PlGF/VEGF dimers (but not VEGF-A) down-regulated the protein expression of glucose-6-phosphate dehydrogenase (G6PD) and peroxiredoxin (PRDX). G6PD inhibition and gene silencing (small interfering RNA) abolished the beneficial effects of PlGF inhibition on EC barrier function and PRDX3/6 protein expression. VEGF receptor (VEGFR)1 or VEGFR2 blockade prevented the inhibitory effect of PlGF on G6PD protein expression and EC barrier function. The PRDX6 played dual roles in EC barrier function through glutathione peroxidase and phospholipase A₂ activity. In sum, PlGF negatively regulates EC barrier function through the activation of VEGFR1 and VEGFR2 and the suppression of the G6PD/PPP and the antioxidant pathways.-Huang, H., Lennikov, A., Saddala, M. S., Gozal, D., Grab, D. J., Khalyfa, A., Fan, L. Placental growth factor negatively regulates endothelial cell barrier function through suppression of glucose-6-phosphate dehydrogenase and antioxidant defense systems.

The Placental Growth Factor Pathway and Its Potential Role in Macular Degenerative Disease

There is growing evidence that placental growth factor (PlGF) is an important player in multiple pathologies, including tumorigenesis, inflammatory disorders and degenerative retinopathies. PlGF is a member of the vascular endothelial growth factor (VEGF) family and in the retina, binding of this growth factor to specific receptors is associated with pathological angiogenesis, vascular leakage, neurodegeneration and inflammation. Although they share some receptor signalling pathways, many of the actions of PlGF are distinct from VEGF and this has revealed the enticing prospect that it could be a useful therapeutic target for treating early and late stages of diabetic retinopathy (DR) and neovascular age-related macular degeneration (AMD). Recent research suggests that modulation of PlGF could also be important in the geographic atrophy (GA) form of late AMD by protecting the outer retina and the retinal pigment epithelium (RPE). This review discusses PlGF and its signalling pathways and highlights the potential of blocking the bioactivity of this growth factor to treat irreversible visual loss due to the two main forms of AMD.

Identification of differentially expressed genes, associated functional terms pathways, and candidate diagnostic biomarkers in inflammatory bowel diseases by bioinformatics analysis

Inflammatory bowel diseases (IBDs), including ulcerative colitis (UC) and Crohn's disease (CD), are chronic inflammatory disorders caused by genetic influences, the immune system and environmental factors. However, the underlying pathogenesis of IBDs and the pivotal molecular interactions remain to be fully elucidated. The aim of the present study was to identify genetic signatures in patients with IBDs and elucidate the potential molecular mechanisms underlying IBD subtypes. The gene expression profiles of the GSE75214 datasets were obtained from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified in UC and CD patients compared with controls using the GEO2R tool. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of DEGs were performed using DAVID. Furthermore, protein-protein interaction (PPI) networks of the DEGs were constructed using Cytoscape software. Subsequently, significant modules were selected and the hub genes were identified. In the GO and KEGG pathway analysis, the top enriched pathways in UC and CD included Staphylococcus aureus infection, rheumatoid arthritis, complement and coagulation cascades, PI3K/Akt signaling pathway and osteoclast differentiation. In addition, the GO terms in the category biological process significantly enriched by these genes were inflammatory response, immune response, leukocyte migration, cell adhesion, response to molecules of bacterial origin and extracellular matrix (ECM) organization. However, several other biological processes (GO terms) and pathways (e.g., ‘chemotaxis’, ‘collagen catabolic process’ and ‘ECM-receptor interaction’) exhibited significant differences between the two subtypes of IBD. The top 10 hub genes were identified from the PPI network using respective DEGs. Of note, the hub genes G protein subunit gamma 11 (GNG11), G protein subunit beta 4 (GNB4), Angiotensinogen (AGT), Phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3) and C-C motif chemokine receptor 7 (CCR7) are disease-specific and may be used as biomarkers for differentiating UC from CD. Furthermore, module analysis further confirmed that common significant pathways involved in the pathogenesis of IBD subtypes were associated with chemokine-induced inflammation, innate immunity, adapted immunity and infectious microbes. In conclusion, the present study identified DEGs, key target genes, functional pathways and enrichment analysis of IBDs, enhancing the understanding of the pathogenesis of IBDs and also advancing the clarification of the underlying molecular mechanisms of UC and CD. Furthermore, these results may provide potential molecular targets and diagnostic biomarkers for UC and CD.