Pigment epithelium-derived factor induces pro-survival genes through cyclic AMP-responsive element binding protein and nuclear factor kappa B activation in rat cultured cerebellar granule cells: Implication for its neuroprotective effect

Functional Roles of Pigment Epithelium-Derived Factor in Retinal Degenerative and Vascular Disorders: A Scoping Review

Purpose

This review explores the role of pigment epithelium-derived factor (PEDF) in retinal degenerative and vascular disorders and assesses its potential both as an adjunct to established vascular endothelial growth factor inhibiting treatments for retinal vascular diseases and as a neuroprotective therapeutic agent.

Methods

A comprehensive literature review was conducted, focusing on the neuroprotective and anti-angiogenic properties of PEDF. The review evaluated its effects on retinal health, its dysregulation in ocular disorders, and its therapeutic application in preclinical models. Advances in drug delivery, including gene therapy, were also examined.

Results

PEDF, initially identified for promoting neuronal differentiation, is also a potent endogenous angiogenesis inhibitor. Strong anti-angiogenic and neuroprotective effects are observed in preclinical studies. It has pro-apoptotic and antiproliferative effects on endothelial cells thereby reducing neovascularization. Although promising, clinical development is limited with only a single conducted phase I clinical trial for macular neovascularization. Development of PEDF-derived peptides enhances potency and specificity, and emerging gene therapy approaches offer sustained PEDF expression for long-term treatment. However, questions regarding dosage, durability, and efficacy remain, particularly in large animal models.

Conclusions

PEDF shows significant therapeutic potential in preclinical models of retinal degeneration and vascular disorders. Despite inconclusive evidence on PEDF downregulation as a primary disease driver, many studies highlight its therapeutic benefits and favorable safety profile. Advances in gene therapy could enable long-acting PEDF-based treatments, but further research is needed to optimize dosage and durability, potentially leading to clinical trials and expanding treatment options for retinal disorders.

In vitro heterochronic parabiosis identifies pigment epithelium-derived factor as a systemic mediator of rejuvenation by young blood

Several decades of heterochronic parabiosis (HCPB) studies have demonstrated the restorative impact of young blood, and deleterious influence of aged blood, on physiological function and homeostasis across tissues, although few of the factors responsible for these observations have been identified. Here we develop an in vitro HCPB system to identify these circulating factors, using replicative lifespan (RLS) of primary human fibroblasts as an endpoint of cellular health. We find that RLS is inversely correlated with serum donor age and sensitive to the presence or absence of specific serum components. Through in vitro HCPB, we identify the secreted protein pigment epithelium-derived factor (PEDF) as a circulating factor that extends RLS of primary human fibroblasts and declines with age in mammals. Systemic administration of PEDF to aged mice reverses age-related functional decline and pathology across several tissues, improving cognitive function and reducing hepatic fibrosis and renal lipid accumulation. Together, our data supports PEDF as a systemic mediator of the effect of young blood on organismal health and homeostasis and establishes our in vitro HCPB system as a valuable screening platform for the identification of candidate circulating factors involved in aging and rejuvenation.

Current progression in application of extracellular vesicles in central nervous system diseases

Early diagnosis and pharmacological treatment of central nervous system (CNS) diseases has been a long-standing challenge for clinical research due to the presence of the blood-brain barrier. Specific proteins and RNAs in brain-derived extracellular vesicles (EVs) usually reflect the corresponding state of brain disease, and therefore, EVs can be used as diagnostic biomarkers for CNS diseases. In addition, EVs can be engineered and fused to target cells for delivery of cargo, demonstrating the great potential of EVs as a nanocarrier platform. We review the progress of EVs as markers and drug carriers in the diagnosis and treatment of neurological diseases. The main areas include visual imaging, biomarker diagnosis and drug loading therapy for different types of CNS diseases. It is hoped that increased knowledge of EVs will facilitate their clinical translation in CNS diseases.

Polarized RPE Secretome Preserves Photoreceptors in Retinal Dystrophic RCS Rats

Retinal degenerative diseases, including age-related macular degeneration (AMD) and retinitis pigmentosa, lack effective therapies. Conventional monotherapeutic approaches fail to target the multiple affected pathways in retinal degeneration. However, the retinal pigment epithelium (RPE) secretes several neurotrophic factors addressing diverse cellular pathways, potentially preserving photoreceptors. This study explored human embryonic stem cell-derived, polarized RPE soluble factors (PRPE-SF) as a combination treatment for retinal degeneration. PRPE-SF promoted retinal progenitor cell survival, reduced oxidative stress in ARPE-19 cells, and demonstrated critical antioxidant and anti-inflammatory effects for preventing retinal degeneration in the Royal College of Surgeons (RCS) rat model. Importantly, PRPE-SF treatment preserved retinal structure and scotopic b-wave amplitudes, suggesting therapeutic potential for delaying retinal degeneration. PRPE-SF is uniquely produced using biomimetic membranes for RPE polarization and maturation, promoting a protective RPE secretome phenotype. Additionally, PRPE-SF is produced without animal serum to avoid immunogenicity in future clinical development. Lastly, PRPE-SF is a combination of neurotrophic factors, potentially ameliorating multiple dysfunctions in retinal degenerations. In conclusion, PRPE-SF offers a promising therapeutic candidate for retinal degenerative diseases, advancing the development of effective therapeutic strategies for these debilitating conditions.

Potential therapeutic role for pigment epithelium-derived factor in post-menopausal breast cancer bone metastasis

OBJECTIVES

This review discusses key oestrogens associated with the circulating pre- and post-menopausal milieu and how they may impact intratumoral oestrogen levels and breast cancer (BC) metastasis. It also identifies critical steps in BC metastasis to bone from the viewpoint of pigment epithelium-derived factor (PEDF) function, and discusses the role of several associated pro-metastatic biomarkers in BC bone metastasis.

KEY FINDINGS

PEDF is regulated by oestrogen in a number of oestrogen-sensitive tissues. Changes in circulating oestrogen levels associated with menopause may enhance the growth of BC bone metastases, leading to the establishment of a pre-metastatic niche. The establishment of such a pre-metastatic niche is driven by several key mediators, with pro-osteoclastic and pro-metastatic function which are upregulated by BC cells. These mediators appear to be regulated by oestrogen, as well as differentially affected by menopausal status. PEDF interacts with several pro-metastatic, pro-osteoclastic biomarkers, including C-X-C motif chemokine receptor 4 (CXCR4) and nuclear factor kappa B (NFκB) in BC bone metastasis.

CONCLUSION

Mediators such as CXCR4 and MT1-MMP underpin the ability of PEDF to function as an antimetastatic in other cancers such as osteosarcoma, highlighting the possibility that this serpin could be used as a therapeutic against BC metastasis in future.

MiR-186-5p Dysregulation Leads to Depression-like Behavior by De-repressing SERPINF1 in Hippocampus

Diagnosis of major depressive disorder (MDD) is perplexing due to its multifactorial etiologies. Here, we isolated exosomes from the peripheral blood of MDD patients and healthy control subjects for mass spectrometry-based label-free quantitative proteomics. We identified that SERPINF1 is significantly diminished in the peripheral blood-derived exosomes of MDD patients compared to the healthy control subjects. Through RNA immunoprecipitation and luciferase reporter assays, we validated that SERPINF1 is a target of miR-186-5p that is upregulated in MDD patients' blood. In vivo studies in the chronic unpredictable mild stress (CUMS) mice further demonstrated that SERPINF1 in hippocampus is suppressed by miR-186-5p. Inhibiting the microRNA significantly restores the hippocampal SERPINF1 mRNA and protein expression, and ameliorates the depressive-like behaviors including sucrose preference and extended immobility time in the forced swim test. Instead, overexpressing miR-186-5p through tail intravenous injection of the mimics molecularly and behaviorally phenocopies the CUMS mice in wild-type mice. Our results indicate that the exosomal SERPINF1 in peripheral blood could serve as a reliable biomarker indicating MDD development, and miR-186-5p is a potential therapeutic target for the disease.

Signaling Mechanisms Involved in PEDF-Mediated Retinoprotection

Pigment epithelium-derived factor (PEDF) is involved in signal transduction cascades necessary for protection of the retina. The interaction between PEDF and retinal cells elicits neuroprotective effects in vitro and in vivo. The direct substrates and signaling mechanisms involved in the survival response derived from such interaction are beginning to be revealed. It is of interest to elucidate cell death pathways that are crucial for the retinoprotective response of PEDF for the identification of targets that interfere with retina degeneration with potential therapeutic value. Here we review the molecular pathways triggered by PEDF that are involved in retinal survival activity.

Proteomics in the Diagnosis of Inborn Encephalopathies of Unknown Origin: A Myth or Reality

Synaptopathy underlies a great variety of neurological or neurodevelopmental disorders, including neurodegenerative diseases and the highly complex neuropsychiatric syndromes. Standard diagnostic assays in the majority of synaptopathies are insufficient to make an appropriate and fast diagnosis, which has spurred a search for more accurate diagnostic methods using recent technological advances. As synaptopathy phenotypes strictly depend on genetics and environmental factors, the best way to approach these diseases is the investigation of entire sets of protein characteristics. Thus, proteomics has emerged as a mainstay in the studies on synaptopathies, with mass spectrometry as a technology of choice. This review is an update on the proteomic methods and achievements in the understanding, diagnostics, and novel biomarkers of synaptopathies. The article also provides a critical point of view and future perspectives on the application of neuroproteomics in clinical practice.

Mechanisms of PEDF-mediated protection against reactive oxygen species damage in diabetic retinopathy and neuropathy

Pigment epithelium-derived factor (PEDF) is a pluripotent glycoprotein belonging to the serpin family. PEDF can stimulate several physiological processes such as angiogenesis, cell proliferation, and survival. Oxidative stress plays an important role in the occurrence of diabetic retinopathy (DR), which is the major cause of blindness in young diabetic adults. PEDF plays a protective role in DR and there is accumulating evidence of the neuroprotective effect of PEDF. In this paper, we review the role of PEDF and the mechanisms involved in its antioxidative, anti-inflammatory, and neuroprotective properties.

Induction of serpinb1a by PACAP or NGF is required for PC12 cells survival after serum withdrawal

PC12 cells are used to study the signaling mechanisms underlying the neurotrophic and neuroprotective activities of pituitary adenylate cyclase-activating polypeptide (PACAP) and nerve growth factor (NGF). Previous microarray experiments indicated that serpinb1a was the most induced gene after 6 h of treatment with PACAP or NGF. This study confirmed that serpinb1a is strongly activated by PACAP and NGF in a time-dependent manner with a maximum induction (~ 50-fold over control) observed after 6 h of treatment. Co-incubation with PACAP and NGF resulted in a synergistic up-regulation of serpinb1a expression (200-fold over control), suggesting that PACAP and NGF act through complementary mechanisms. Consistently, PACAP-induced serpinb1a expression was not blocked by TrkA receptor inhibition. Nevertheless, the stimulation of serpinb1a expression by PACAP and NGF was significantly reduced in the presence of extracellular signal-regulated kinase, calcineurin, protein kinase A, p38, and PI3K inhibitors, indicating that the two trophic factors share some common pathways in the regulation of serpinb1a. Finally, functional investigations conducted with siRNA revealed that serpinb1a is not involved in the effects of PACAP and NGF on PC12 cell neuritogenesis, proliferation or body cell volume but mediates their ability to block caspases 3/7 activity and to promote PC12 cell survival.

PEDF is a novel oligodendrogenic morphogen acting on the adult SVZ and corpus callosum

Pigment epithelium-derived factor (PEDF) is a serine protease inhibitor (serpin) protein with well established neuroprotective and anti-angiogenic properties. Recent studies have also shown that PEDF enhances renewal of adult subventricular zone (SVZ) neural precursors. In neurosphere cultures prepared from the SVZ of adult mice, we found that addition of recombinant PEDF to the medium enhanced expressions of oligodendroglial lineage markers (NG2 and PDGFrα) and transcription factors (Olig1, Olig2, and Sox10). Similarly, continuous PEDF administration into the lateral ventricles of adult glial fibrillary acidic protein:green fluorescent protein (GFAP:GFP) transgenic mice increased the proportions of GFAP:GFP+ and GFAP:GFP- SVZ neural precursors coexpressing oligodendroglial lineage markers and transcription factors. Notably, PEDF infusion also resulted in an induction of doublecortin- and Sox10 double-positive cells in the adult SVZ. Immunoreactive PEDF receptor was detectable in multiple cell types in both adult SVZ and corpus callosum. Furthermore, PEDF intracerebral infusion enhanced survival and maturation of newly born oligodendroglial progenitor cells in the normal corpus callosum, and accelerated oligodendroglial regeneration in lysolecithin-induced corpus callosum demyelinative lesions. Western blot analysis showed a robust upregulation of endogenous PEDF in the corpus callosum upon lysolecithin-induced demyelination. Our results document previously unrecognized oligodendrotrophic effects of recombinant PEDF on the adult SVZ and corpus callosum, demonstrate induction of endogenous CNS PEDF production following demyelination, and make PEDF a strong candidate for pharmacological intervention in demyelinative diseases.

Cerebrospinal fluid biomarkers for major depression confirm relevance of associated pathophysiology

Individual characteristics of pathophysiology and course of depressive episodes are at present not considered in diagnostics. There are no biological markers available that can assist in categorizing subtypes of depression and detecting molecular variances related to disease-causing mechanisms between depressed patients. Identification of such differences is important to create patient subgroups, which will benefit from medications that specifically target the pathophysiology underlying their clinical condition. To detect characteristic biological markers for major depression, we analyzed the cerebrospinal fluid (CSF) proteome of depressed vs control persons, using two-dimensional polyacrylamide gel electrophoresis and time-of-flight (TOF) mass spectrometry peptide profiling. Proteins of interest were identified by matrix-assisted laser desorption ionization TOF mass spectrometry (MALDI-TOF-MS). Validation of protein markers was performed by immunoblotting. We found 11 proteins and 144 peptide features that differed significantly between CSF from depressed patients and controls. In addition, we detected differences in the phosphorylation pattern of several CSF proteins. A subset of the differentially expressed proteins implicated in brain metabolism or central nervous system disease was validated by immunoblotting. The identified proteins are involved in neuroprotection and neuronal development, sleep regulation, and amyloid plaque deposition in the aging brain. This is one of the first hypothesis-free studies that identify characteristic protein expression differences in CSF of depressed patients. Proteomic approaches represent a powerful tool for the identification of disease markers for subgroups of patients with major depression.

Antiapoptotic actions of exendin-4 against hypoxia and cytokines are augmented by CREB

Islets isolated from cadaveric donor pancreas are functionally viable and can be transplanted in diabetic patients to reduce insulin requirements. This therapeutic approach is less efficient because a significant portion of functional islets is lost due to oxidative stress, inflammation, and hypoxia. Exendin-4, a glucagon-like peptide-1 receptor agonist, is known to improve islet survival through activation of the transcription factor, cAMP response element binding protein (CREB). However, isolated human islets are exposed to several stresses known to down-regulate CREB. The objective of the present study was to determine whether the cytoprotective actions of exendin-4 in human islets can be augmented by increasing the levels of CREB. Simulation of ischemia/reperfusion injury and exposure to hypoxic conditions in cultured human islets resulted in decreased CREB activation and induction of apoptosis. Islets were transduced with adenoviral CREB followed by exposure to exendin-4 as a strategy for improving their survival. This combination increased the levels of several proteins needed for β-cell survival and function, including insulin receptor substrate-2, Bcl-2, and baculoviral IAP repeat-containing 3, and suppressed the expression of proapoptotic and inflammatory genes. A combination of CREB and exendin-4 exerted enhanced antiapoptotic action in cultured islets against hypoxia and cytokines. More significantly, transplantation of human islets transduced with adenoviral CREB and treated with exendin-4 showed improved glycemic control over a 30-d period in diabetic athymic nude mice. These observations have significant implications in the therapeutic potential of exendin-4 and CREB in the islet transplantation setting as well as in preserving β-cell mass of diabetic patients.

Pigment epithelium-derived factor (PEDF) protects cortical neurons in vitro from oxidant injury by activation of extracellular signal-regulated kinase (ERK) 1/2 and induction of Bcl-2

Mitigating oxidative stress-induced damage is critical to preserve neuronal function in diseased or injured brains. This study explores the mechanisms contributing to the neuroprotective effects of pigment epithelium-derived factor (PEDF) in cortical neurons. Cultured primary neurons are exposed to PEDF and H₂O₂ as well as inhibitors of phosphoinositide-3 kinase (PI3K) or extracellular signal-regulated kinase 1/2 (ERK1/2). Neuronal survival, cell death and levels of caspase 3, PEDF, phosphorylated ERK1/2, and Bcl-2 are measured. The data show cortical cultures release PEDF and that H₂O₂ treatment causes cell death, increases activated caspase 3 levels and decreases release of PEDF. Exogenous PEDF induces a dose-dependent increase in Bcl-2 expression and neuronal survival. Blocking Bcl-2 expression by siRNA reduced PEDF-induced increases in neuronal survival. Treating cortical cultures with PEDF 24 h before H₂O₂ exposure mitigates oxidant-induced decreases in neuronal survival, Bcl-2 expression, and phosphorylation of ERK1/2 and also reduces elevated caspase 3 level and activity. PEDF pretreatment effect on survival is blocked by inhibiting ERK or PI3K. However, only inhibition of ERK reduced the ability of PEDF to protect neurons from H₂O₂-induced Bcl-2 decrease and neuronal death. These data demonstrate PEDF-mediated neuroprotection against oxidant injury is largely mediated via ERK1/2 and Bcl-2 and suggest the utility of PEDF in preserving the viability of oxidatively challenged neurons.

NF-kappaB balances vascular regression and angiogenesis via chromatin remodeling and NFAT displacement

Extracellular factors control the angiogenic switch in endothelial cells (ECs) via competing survival and apoptotic pathways. Previously, we showed that proangiogenic and antiangiogenic factors target the same signaling molecules, which thereby become pivots of angiogenic balance. Here we show that in remodeling endothelium (ECs and EC precursors) natural angiogenic inhibitors enhance nuclear factor-kappaB (NF-kappaB) DNA binding, which is critical for antiangiogenesis, and that blocking the NF-kappaB pathway abolishes multiple antiangiogenic events in vitro and in vivo. NF-kappaB induction by antiangiogenic molecules has a dual effect on transcription. NF-kappaB acts as an activator of proapoptotic FasL and as a repressor of prosurvival cFLIP. On the FasL promoter, NF-kappaB increases the recruitment of HAT p300 and acetylated histones H3 and H4. Conversely, on cFLIP promoter, NF-kappaB increases histone deacetylase 1 (HDAC1), decreases p300 and histone acetylation, and reduces the recruitment of NFAT, a transcription factor critical for cFLIP expression. Finally, we found a biphasic effect, when HDAC inhibitors (HDACi) were used to test the dependence of pigment epithelial-derived factor activity on histone acetylation. The cooperative effect seen at low doses switches to antagonistic as the concentrations increase. Our study defines an interactive transcriptional network underlying angiogenic balance and points to HDACi as tools to manipulate the angiogenic switch.

Pigment epithelium-derived factor inhibits lysosomal degradation of Bcl-xL and apoptosis in HepG2 cells

Pigment epithelium-derived factor (PEDF) has several biological actions on tumor cells, but its effects are cell-type dependent. The aim of this study was to examine the pathophysiological role of PEDF in hepatocellular carcinoma (HCC). PEDF expression was examined in various hepatoma cell lines and human HCC tissues, and was seen in various hepatoma cell lines including HepG2 cells. In human HCC tissues, PEDF expression was higher than in adjacent non-HCC tissues. In addition, serum PEDF levels were higher in HCC patients than in non-HCC patients, and curative treatment of HCC caused significant reductions in serum PEDF levels compared with pretreatment levels. In vitro experiments, camptothecin (CPT) was used to induce apoptosis and the effect of PEDF was investigated by knockdown of the PEDF gene in CPT-treated HepG2 cells. Knockdown of the PEDF gene enhanced CPT-induced apoptosis, simultaneously down-regulating Bcl-xL expression in HepG2 cells. Expression of apoptosis-related molecules and effects of bafilomycin A1 on CPT-induced apoptosis were also examined in PEDF gene knockdown HepG2 cells. Treatment with bafilomycin A1 suppressed CPT-induced decreases in Bcl-xL expression and increases in apoptosis in PEDF gene knockdown HepG2 cells. PEDF may, therefore, exert anti-apoptotic effects through inhibition of lysosomal degradation of Bcl-xL in CPT-treated HepG2 cells.

Inhibition of nuclear translocation of apoptosis-inducing factor is an essential mechanism of the neuroprotective activity of pigment epithelium-derived factor in a rat model of retinal degeneration

Photoreceptor apoptosis is a critical process of retinal degeneration in retinitis pigmentosa (RP), a group of retinal degenerative diseases that result from rod and cone photoreceptor cell death and represent a major cause of adult blindness. We previously demonstrated the efficient prevention of photoreceptor apoptosis by intraocular gene transfer of pigment epithelium-derived factor (PEDF) in animal models of RP; however, the underlying mechanism of the neuroprotective activity of PEDF remains elusive. In this study, we show that an apoptosis-inducing factor (AIF)-related pathway is an essential target of PEDF-mediated neuroprotection. PEDF rescued serum starvation-induced apoptosis, which is mediated by AIF but not by caspases, of R28 cells derived from the rat retina by preventing translocation of AIF into the nucleus. Nuclear translocation of AIF was also observed in the apoptotic photoreceptors of Royal College of Surgeons rats, a well-known animal model of RP that carries a mutation of the Mertk gene. Lentivirus-mediated retinal gene transfer of PEDF prevented the nuclear translocation of AIF in vivo, resulting in the inhibition of the apoptotic loss of their photoreceptors in association with up-regulated Bcl-2 expression, which mediates the mitochondrial release of AIF. These findings clearly demonstrate that AIF is an essential executioner of photoreceptor apoptosis in inherited retinal degeneration and provide a therapeutic rationale for PEDF-mediated neuroprotective gene therapy for individuals with RP.

Changes in pigment epithelium-derived factor expression following kainic acid induced cerebellar lesion in rat

Pigment epithelium-derived factor (PEDF) is a potent and broad-acting neurotrophic factor that protects various types of cultured neurons against glutamate excitotoxicity and induced apoptosis. The expression pattern and functions of PEDF in the central nervous system (CNS) remain largely undetermined. In this study, we analyzed the spatial and temporal expression of PEDF in normal and kainic acid (KA)-induced lesioned rat cerebellum using immunoblotting, immunohistochemistry and fluorescent in situ hybridization techniques. In normal rat cerebellum, PEDF protein and mRNA were mostly confined and co-localized with calbindin-positive cells in the Purkinje cell layer of the cerebellum, but not with glial fibrillary acidic protein (GFAP)-, 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase)-, and isolectin B4-positive cells. Injection of KA into the right cellebellum caused severe loss of calbindin-positive Purkinje neurons, and an increased number of GFAP-positive astrocytes and isolectin B4-positive microglia was observed on the ipsilateral side of the lesioned cerebellum. Although the PEDF level on the ipsilateral side of the cerebellum was dramatically decreased 2 days after KA treatment, significantly elevation of PEDF levels was observed at 7 days. In agreement with these results, PEDF protein and PEDF mRNA expression were co-localized with GFAP-positive reactive astrocytes in the ipsilateral side 7 days after KA treatment. Although the mechanism by which PEDF is induced in reactive astrocytes remains unclear, the increase in PEDF expression in injured brain may form part of a compensation mechanism against neuronal degeneration.

Pigment epithelium-derived factor inhibits oxidative stress-induced cell death by activation of extracellular signal-regulated kinases in cultured retinal pigment epithelial cells

Oxidative stress-induced retinal pigment epithelial (RPE) cell death is involved in the pathogenesis of age-related macular degeneration (AMD). Pigment epithelium-derived factor (PEDF) is an anti-angiogenic/neurotropic dual functional factor, and recently it was also shown to mediate anti-oxidative action. In the present study, the influence of PEDF in hydrogen peroxide (H(2)O(2))-induced RPE cell death was investigated using nontransformed human RPE cell line (ARPE-19). The recombinant PEDF was purified from E. coli. The MTT cell viability assay showed that PEDF rescued ARPE-19 from H(2)O(2)-induced cell death in a dose- and time-dependent manner. Western blot analysis revealed that PEDF stimulated the extracellular signal-regulated kinases (ERK1/2) phosphorylation. The PEDF cytoprotective effect was significantly attenuated by the ERK1/2 inhibitor PD98059. In this study, we demonstrate that PEDF induces ERK1/2 phosphorylation and we further suggest that the ERK signal cascade contributes to RPE cell's cytoprotection against oxidative stress.

NFkappaB in neurons? The uncertainty principle in neurobiology

Nuclear factor kappaB (NFkappaB) is a dynamically modulated transcription factor with an extensive literature pertaining to widespread actions across species, cell types and developmental stages. Analysis of NFkappaB in a complex environment such as neural tissue suffers from a difficulty in simultaneously establishing both activity and location. Much of the available data indicate a profound recalcitrance of NFkappaB activation in neurons, as compared with most other cell types. Few studies to date have sought to distinguish between the various combinatorial dimers of NFkappaB family members. Recent research has illuminated the importance of these problems, as well as opportunities to move past them to the nuances manifest through variable activation pathways, subunit complexity and target sequence preferences.

Variable phosphorylation states of pigment-epithelium-derived factor differentially regulate its function

The pigment epithelium-derived factor (PEDF) belongs to the family of noninhibitory serpins. Although originally identified in the eye, PEDF is widely expressed in other body regions including the plasma. This factor can act either as a neurotrophic or as an antiangiogenic factor, and we previously showed that the 2 effects of PEDF are regulated through phosphorylation by PKA and CK2. Here, we studied the interplay between the PKA and CK2 phosphorylation of PEDF, and found that a PEDF mutant mimicking the CK2-phosphorylated PEDF cannot be phosphorylated by PKA, while the mutant mimicking the PKA-phosphorylated PEDF is a good CK2 substrate. Using triple mutants that mimic the PKA- and CK2-phosphorylated and nonphosphorylated PEDF, we found that PEDF can induce several distinct cellular activities dependent on its phosphorylation. The mutant mimicking the accumulative PKA plus CK2 phosphorylation exhibited the strongest antiangiogenic and neurotrophic activities, while the mutants mimicking the individual phosphorylation site mutants had either a reduced activity or only one of these activities. Thus, differential phosphorylation induces variable effects of PEDF, and therefore contributes to the complexity of PEDF action. It is likely that the triple phosphomimetic mutant can be used to generate effective antiangiogenic or neurotrophic drugs.

Beta-adrenergic receptor activation in immortalized human urothelial cells stimulates inflammatory responses by PKA-independent mechanisms

Background

Interstitial cystitis (IC) is a debilitating disease characterized by chronic inflammation of the urinary bladder, yet specific cellular mechanisms of inflammation in IC are largely unknown. Multiple lines of evidence suggest that β-adrenergic receptor (AR) signaling is increased in the inflamed urothelium, however the precise effects of these urothelial cell signals have not been studied. In order to better elucidate the AR signaling mechanisms of inflammation associated with IC, we have examined the effects of β-AR stimulation in an immortalized human urothelial cell line (UROtsa). For these studies, UROtsa cells were treated with effective concentrations of the selective β-AR agonist isoproterenol, in the absence or presence of selective inhibitors of protein kinase A (PKA). Cell lysates were analyzed by radioimmunoassay for generation of cAMP or by Western blotting for induction of protein products associated with inflammatory responses.

Results

Radioligand binding demonstrated the presence of β-ARs on human urothelial UROtsa cell membranes. Stimulating UROtsa cells with isoproterenol led to concentration-dependent increases of cAMP production that could be inhibited by pretreatment with a blocking concentration of the selective β-AR antagonist propranolol. In addition, isoproterenol activation of these same cells led to significant increases in the amount of phosphorylated extracellular signal-regulated kinase (pERK), inducible nitric oxide synthase (iNOS) and the induced form of cyclooxygenase (COX-2) when compared to control. Moreover, preincubation of UROtsa cells with the selective PKA inhibitors H-89 or Rp-cAMPs did not diminish this isoproterenol mediated phosphorylation of ERK or production of iNOS and COX-2.

Conclusion

Functional β-ARs expressed on human urothelial UROtsa cell membranes increase the generation of cAMP and production of protein products associated with inflammation when activated by the selective β-AR agonist isoproterenol. However, the increased production of iNOS and COX-2 by isoproterenol is not blocked when UROtsa cells are preincubated with inhibitors of PKA. Therefore, UROtsa cell β-AR activation significantly increases the amount of iNOS and COX-2 produced by a PKA-independent mechanism. Consequently, this immortalized human urothelial cell line can be useful in characterizing potential AR signaling mechanisms associated with chronic inflammatory diseases of the bladder.