Achilleas Gravanis

University of Crete | UOC · Laboratory of Pharmacology

Neuronal cell fate is predominantly controlled by the effects of growth factors, such as neurotrophins, and the activation of a variety of signaling pathways acting through neurotrophin receptors, namely Trk and p75 (p75NTR). Despite their beneficial effects on brain function, their therapeutic use is compromised, due to their polypeptidic nature a...

Background Loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) underlines much of the pathology of Parkinson’s disease (PD), but the existence of an endogenous neurogenic system that could be targeted as a therapeutic strategy has been controversial. BNN-20 is a synthetic, BDNF-mimicking, microneurotrophin that we previously s...

Inflammatory Bowel Disease (IBD), including Crohn’s disease (CD) and Ulcerative Colitis (UC), is a disease associated with dysbiosis, resulting in compromised intestinal epithelial barrier and chronic mucosal inflammation. Patients with IBD present with increased incidence of psychiatric disorders and cognitive impairment. Hippocampus is a brain re...

Purpose Diabetic retinopathy (DR) is a complex eye disease associated with diabetes mellitus. It is characterized by three pathophysiological components, namely microangiopathy, neurodegeneration, and inflammation. We recently reported that intraperitoneal administration of BNN27, a novel neurosteroidal microneurotrophin, reversed the diabetes-indu...

Neuroinflammation is a physiological protective response in the context of infection and injury. However, neuroinflammation, especially if chronic, may also drive neurodegeneration. Neurodegenerative diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD) and traumatic brain injury (TBI), display inflammatory a...

Consistent experimental evidence supports an important role of the glutamatergic system in the etiopathogenesis of schizophrenia. Numerous studies propose that blockade of the NMDA receptor by its antagonist ketamine impairs cognition and can mimic certain aspects of positive and negative symptoms of schizophrenia in rodents. Neuroactive steroids,...

Microglia, the parenchymal immune cells of the central nervous system, orchestrate neuroinflammation in response to infection or damage, and promote tissue repair. However, aberrant microglial responses are integral to neurodegenerative diseases and critically contribute to disease progression. Thus, it is important to elucidate how microglia - med...

Retinal detachment (RD) leads to photoreceptor cell death secondary to the physical separation of the retina from the underlying retinal pigment epithelium. Intensifying photoreceptor survival in the detached retina could be remarkably favorable for many retinopathies in which RD can be seen. BNN27, a blood-brain barrier (BBB)-permeable, C17-spiroe...

Family B of G-protein-coupled receptors (GPCRs) and their ligands play a central role in a number of homeostatic mechanisms in the endocrine, gastrointestinal, skeletal, immune, cardiovascular and central nervous systems. Alterations in family B GPCR-regulated homeostatic mechanisms may cause a variety of potentially life-threatening conditions, si...

The gut-brain axis is a bidirectional communication system that integrates neural, immune and hormonal signals between the brain and the gut. Alterations in this axis are thought to be implicated in the pathophysiology of several brain disorders, including depression and anxiety. Although, accumulating evidence support a clear association between g...

BNN27, a C17-spiroepoxy derivative of DHEA, was shown to have anti-apoptotic properties via mechanisms involving the NGF receptors (TrkA/ p75NTR). In this study we examined the effects of BNN27 on neural/glial cell function, apoptosis and inflammation in the experimental rat streptozotocin (STZ)-model of diabetic retinopathy (DR). The ability of BN...

Dehydroepiandrosterone (DHEA) is the most abundant circulating steroid hormone in humans, produced by the adrenals, the gonads and the brain. DHEA was previously shown to bind to the nerve growth factor receptor, tropomyosin-related kinase A (TrkA), and to thereby exert neuroprotective effects. Here we show that DHEA reduces microglia-mediated infl...

BNN27, a member of a chemical library of C17-spiroepoxy derivatives of the neurosteroid DHEA, has been shown to regulate neuronal survival through its selective interaction with NGF receptors (TrkA and p75(NTR) ), but its role on glial populations has not been studied. Here, we present evidence that BNN27 provides trophic action (rescue from apopto...

Neurotrophic factors are among the most promising treatments aiming at slowing or stopping and even reversing Parkinson's disease (PD). However, in most cases, they cannot readily cross the human blood-brain-barrier (BBB). Herein, we propose as a therapeutic for PD the small molecule 17-beta-spiro-[5-androsten-17,2'-oxiran]-3beta-ol (BNN-20), a syn...

Blood-brain-barrier permeable 17-spiro-steroid derivatives bind to and activate neurotrophin receptors, protecting various neurons against apoptosis, in vitro, ex vivo and in vivo in animal models of neurodegenerative diseases. These synthetic microneurotrophins offer a new pharmacological tool to develop non-toxic, blood-brain-barrier permeable ne...

Background: The corticotropin releasing factor (CRF) family of neuropeptides, CRF and the Urocortins, and their receptors are present not only within the central nervous system but also in the periphery at various locations and at the sites of inflammation where they influence its progress in a complex local / paracrine manner. Objective and meth...

Neurotrophin receptors mediate a plethora of signals affecting neuronal survival. The p75 pan-neurotrophin receptor controls neuronal cell fate after its selective activation by immature and mature isoforms of all neurotrophins. It also exerts pleiotropic effects interacting with a variety of ligands in different neuronal or non-neuronal cells. In...

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease caused by loss of motor neurons. ALS patients experience rapid deterioration in muscle function with an average lifespan of 3–5 years after diagnosis. Currently, the most effective therapeutic only extends lifespan by a few months, thus highlighting the need for new and improved the...

Nerve growth factor (NGF) holds a pivotal role in brain development and maintenance, been also involved in the pathophysiology of neurodegenerative diseases. Here, we provide evidence that a novel C17-spiroepoxy steroid derivative, BNN27, specifically interacts with and activates the TrkA receptor of NGF, inducing phosphorylation of TrkA tyrosine r...

Fingolimod (FTY720) was the first per os administered disease-modifying agent approved for the treatment of relapsing–remitting multiple sclerosis. It is thought that fingolimod modulates the immune response by activating sphingosine-1 phosphate receptor type 1 (S1P1) on lymphocytes following its in vivo phosphorylation. In addition to its immune-r...

The application of multispectral imaging to discriminate myelinated and demyelinated areas of neural tissue is herein presented. The method is applied through a custom-made, multispectral imaging monochromator, coupled to a commercially available microscope. In the present work, a series of spinal cord sections were analysed derived from mice with...

POSTER MO21. Objectives: Diabetes is increasing in the population worldwide leading to an increase of other diseases, including diabetic retinopathy (DR). DR causes apoptotic events in retinal ganglion, amacrine and glial cells in the first step of the disease, prior to neovascularization. Dehydroepiandrosterone (DHEA) has neuroprotective and anti-...

Objectives: Diabetic retinopathy (DR) is a neovascular, inflammatory and neurodegenerative disease. Available therapeutics target only the neovascular component. Early pathological findings in the diabetic retina include amacrine and ganglion cell death and elevated levels of inflammatory cytokines. The neurosteroid Dehydroepiandrosterone (DHEA) af...

This article contains data related to the research article entitled "Laser fabricated discontinuous anisotropic microconical substrates as a new model scaffold to control the directionality of neuronal network outgrowth" in the Biomaterials journal [1]. Scanning electron microscopy (SEM) analysis is performed to investigate whether Schwann cells an...

Purpose: Diabetic Retinopathy (DR) is an important cause of blindness in people who suffer chronically from diabetes. The eye endures proliferative formation of new blood vessels and impairment of retinal neurons such as retinal ganglion and amacrine cells, leading to apoptotic processes (Lieth et al., 2000). The neovascularization component of DR...

Patterning of neuronal outgrowth in vitro is important in tissue engineering as well as for the development of neuronal interfaces with desirable characteristics. To date, this has been achieved with the aid of micro- and nanofabrication techniques giving rise to various anisotropic topographies, either in the form of continuous or discontinuous st...

Diabetic retinopathy (DR) is a neovascular, inflammatory and neurodegenerative disease. The neovascular component is treatable but no therapeutic agents are available for the other two components. Early changes in the diabetic retina include neuronal death of amacrine and retinal ganglion cells (RGC)(Barber et al., J Clin Invest,1998), and elevated...

Purpose: Diabetic retinopathy (DR) is characterized by a neovascular and a neurodegenerative component. While available treatments target the neovascular aspects of the disease, no therapy exists for the neurodegenerative component. Dehydroepiandrosterone (DHEA) and its spiro-epoxy derivative BNN27 were shown to have antiapoptotic activity [Caloger...

Purpose: Diabetic Retinopathy (DR) is a concomitant disease of both type I and type II Diabetes Mellitus, and it is responsible for visual impairment and blindness [1]. DR is the result of the combined actions of neovascularization and neurodegeneration processes [2]. While there are therapeutics available for the neovascularization component [3],...

Dehydroepiandosterone (DHEA), the most abundant steroid in humans, affects multiple cellular functions of the endocrine, immune and nervous systems. However, up to quite recently no receptor has been described specifically for it while most of its physiological actions have been attributed to its conversion to either androgens or estrogens. DHEA in...

Purpose To investigate the effect of the intravitreal administration of a synthetic analog of DHEA on retinal anatomy and function of the rabbit eye. Methods All experiments complied with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. We injected 0.6mg/0.1ml of a synthetic DHEA analog in the right eye of 9 pigmented ra...

Early actin cytoskeleton reorganization is an important regulatory step of membrane-initiated, non-genomic steroid hormone actions. Specific intracellular signaling cascades control the rapid alterations of actin polymerization in a variety of cell models. Moreover, actin remodeling is a decisive component in the signaling of hormone-induced early...

Fingolimod (FTY720; Gilenya™,Novartis Pharma AG) is a recently developed Sphingosine-1-Phosphate (S1P) analogue, orally administered as a new therapeutic agent in Multiple Sclerosis (MS) (Brinkmann V. et al. 2010). S1P receptors (S1PRs) are expressed in various sites in the CNS including the subventricular zone (Waeber C. et al. 1999; Choi J.W. et...

Tumor growth is fostered by inhibition of cell death, which involves the receptiveness of tumor to growth factors and hormones. We have recently shown that testosterone exerts proapoptotic effects in prostate and colon cancer cells through a membrane-initiated mechanism. In addition, we have recently reported that dehydroepiandrosterone (DHEA) can...

The control of the outgrowth of neuronal cultured cells is of critical importance in a wide spectrum of neuroscience applications including tissue engineering scaffolds and neural electrodes. However, the study of neuron cell outgrowth on more complex topographies remains limited. Phenotype alteration of stem cells and differentiated neuronal cells...

Structural determinants underlying signaling specificity in the tumor necrosis factor receptor superfamily (TNFRSF) are poorly characterized, and it is unclear whether different signaling outputs can be genetically dissociated. The p75 neurotrophin receptor (p75(NTR)), also known as TNFRSF16, is a key regulator of trophic and injury responses in th...

The neurosteroid dehydroepiandrosterone (DHEA) exerts a portion of its neuroprotective effects by directly interacting with the nerve growth factor (NGF) receptors TrkA and p75(NTR) to induce prosurvival signaling. DHEA is an intermediate in the biosynthesis of estrogens and androgens that affects the endocrine system and potentially increases the...

The TNF superfamily ligands APRIL and BAFF bind with different affinity to two receptors, BCMA and TACI, and induce cell survival and/or proliferation, whereas BAFF also binds specifically to BAFFR. These molecules were considered specific for the immune system. Recently, however, they were also found in epithelial and mesenchymal noncancerous and...

The biological effects of the Corticotropin-releasing factor (CRF) family of neuropeptides are mediated by mobilization of [Ca(2+)]. Aim of the current work was to examine if the calcineurin/NFAT (nuclear factor of activated T-cells) signaling pathway is involved in the effect of CRF peptides in catecholamine synthesis and secretion from PC12 rat p...

There is a need in autoimmune diseases to uncover the mechanisms involved in the natural resolution of inflammation. In this article, we demonstrate that granulocytic myeloid-derived suppressor cells (G-MDSCs) abundantly accumulate within the peripheral lymphoid compartments and target organs of mice with experimental autoimmune encephalomyelitis p...

Purpose To evaluate the neuroprotective activity of a new synthetic analogue of Dehydroepiandrosterone (DHEA) in an experimental model of retinal detachment (RD). Methods Sprague Dawley rats underwent a retinal detachment in their right eye under deep anesthesia while the left eye was served as a control. Animals were dived into three groups and in...

Purpose To evaluate the retinal bioavailability of a synthetic Dehydroepiandrosterone (DHEA) analog, a molecule with potential anti‐apoptotic action, after systemic administration. Methods 25 Sprague Dawley rats were injected intraperitoneally with 10 mg of the analog in1 ml of an ethanol/Water For Injection (WFI) solution. The synthetic neurostero...

Corticotropin-releasing hormone, or factor, (CRH or CRF) exerts important biological effects in multiple peripheral tissues via paracrine/autocrine actions. The aim of our study was to assess the effects of endogenous CRH in the biology of mouse and human skin fibroblasts, the primary cell type involved in wound healing. We show expression of CRH a...

[3H]-DHEA saturation binding assays and Scatchard blots in HEK293 cells, transfected with the plasmid cDNAs of TrkA and p75NTR receptors. Fifty µl of cell membrane suspension in triplicate were incubated overnight at 4°C with 1–30 nM [3H]-DHEA in the presence or absence of 500-fold molar excess of DHEA. (TIF)

RT-PCR of androgen receptors (AR) mRNA in HEK23 cells, transfected with the plasmid cDNAs of TrkA and p75NTR receptors. Total RNA was extracted from LNCaP and naïve HEK293 cells or HEK293 cells transfected with the plasmid cDNAS of TrkA, p75NTR, or both plasmids, by using the Trizol Reagent (InVitrogen). One microgram of total RNA was reverse trans...

Effects of PTX, DHEAS, and testosterone on TrkA phosphorylation in HEK293TrkA cells. HEK293TrkA transfectants cultured in serum free conditions were exposed for 10 min to 100 nM of DHEA or 100 ng/ml of NGF, in the absence or the presence of 100 ng/ml PTX, or to 100 nM of DHEAS or testosterone. Cell lysates were then immunoprecipitated overnight at...

DHEA regulates the levels of TrkA and p75NTR receptors, mimicking NGF. Serum deprived PC12 cells were exposed to 100 nM of DHEA or 100 ng/ml of NGF for 12, 14, and 48 h. TrkA and p75NTR protein levels were measured in cell lysates with immunoblotting, using specific antibodies, and were normalized against GAPDH (* p<0.01 versus control-Serum Free,...

Representative curves of [3H]-DHEA displacement experiments. The selectivity of DHEA binding to HEK293TrkA and HEK293p75NTR cell membranes was examined by performing heterologous [3H]-DHEA displacement experiments using a number of non-labeled steroids or NGF. Membranes (at a final concentration of 2 mg protein/ml) isolated from HEK293 cells transf...

The neurosteroid dehydroepiandrosterone (DHEA), produced by neurons and glia, affects multiple processes in the brain, including neuronal survival and neurogenesis during development and in aging. We provide evidence that DHEA interacts with pro-survival TrkA and pro-death p75(NTR) membrane receptors of neurotrophin nerve growth factor (NGF), actin...

Amyloid-β protein precursor (AβPP) is a ubiquitously expressed glycoprotein, which under physiological conditions can be cleaved following two alternative routes; the non-amyloidogenic and the amyloidogenic pathway. Shift of AβPP processing in favor of the amyloidogenic pathway is a key event in the pathogenesis of Alzheimer's disease (AD). Among t...

Incubation of isolated rat hepatocytes under conditions known to induce cell swelling caused several alterations in microtubule physiology. As shown by immunofluorescence microscopy experiments in the absence and presence of triethyllead or colchicine (two well-established microtubule inhibitors), an apparent stabilization of the microtubule networ...

Purpose Many retinopathies that lead to visual loss and blindness are characterized by neovascularization and neural retinal defects, such as a marked loss in retinal neurons and an increase in apoptosis. There are no therapeutic agents for the treatment of the neurodegenerative component of retinal disease. Immunohistochemistry and western blot me...

Purpose The aim of the present study was to investigate whether DHEA and NGF could protect retinal cells from cell death in an in vivo model of AMPA excitotoxicity. Methods Male and female Sprague‐Dawley rats (250‐300g) were administered intravitreally: AMPA (42 nmol per eye) or AMPA and DHEA (10‐6,10‐7M) or NGF (60pg/eye) or vehicle. A TrkA inhibi...

Corticotropin-releasing factor (CRF) is the principal regulator of the stress response. In addition to mediating the neural control of pituitary adrenocorticotropin (ACTH) secretion, CRF and its close related urocortins are produced by the immune cells, and modulate the inflammatory response various tissues. Newly synthesized non-peptide CRF antago...

DHEA analogues with modifications at positions C3 or C17 were synthesized and evaluated for neuroprotective activity against the neural-crest-derived PC12 cell model of serum deprivation-induced apoptosis. The most potent compounds were the spiro-epoxy derivatives 17beta-spiro[5-androstene-17,2'-oxiran]-3beta-ol (20), (20S)-3beta,21-dihydroxy-17bet...

Although the epidermis is importantly affected by steroid hormones, little is known about the effects of dehydroepiandrosterone (DHEA) on human keratinocytes, in spite of its abundance in human serum. Here, we demonstrate for the first time a protective role of DHEA against apoptosis in keratinocytes, using non-cancerous immortalized human HaCaT ce...

SNP-typing strategies involve an exponential amplification step, an allele discrimination reaction and detection of the products. Usually, allele discrimination is performed after amplification. Tetra-primer PCR allows allele discrimination during the amplification step, thereby avoiding additional genotyping reactions. However, to date, electropho...

Upon binding of the corticotropin-releasing factor (CRF) analog sauvagine to the type 1 CRF receptor (CRF(1)), the amino-terminal portion of the peptide has been shown to lie near Lys257 in the receptor's second extracellular loop (EL2). To test the hypothesis that EL2 residues play a role in the binding of sauvagine to CRF(1) we carried out an ala...

Dehydroepiandrosterone (DHEA) protects neural crest-derived PC12 cells from serum deprivation-induced apoptosis via G protein-associated specific plasma membrane-binding sites (mDBS). Here, we studied the signaling pathways involved in the pro-survival effects of DHEA-mediated activation of the mDBS binding sites. Membrane impermeable DHEA-bovine s...