Competitive ELISA for the identification of 35-55 myelin oligodendrocyte glycoprotein immunodominant epitope conjugated with mannan.

Analogs of immunodominant myelin peptides involved in multiple sclerosis (MS: the most common autoimmune disease) have been extensively used to modify the immune response over the progression of the disease. The immunodominant 35-55 epitope of myelin oligodendrocyte glycoprotein (MOG35-55 ) is an autoantigen appearing in MS and stimulates the encephalitogenic T cells, whereas mannan polysaccharide (Saccharomyces cerevisiae) is a carrier toward the mannose receptor of dendritic cells and macrophages. The conjugate of mannan-MOG35-55 has been extensively studied for the inhibition of chronic experimental autoimmune encephalomyelitis (EAE: an animal model of MS) by inducing antigen-specific immune tolerance against the clinical symptoms of EAE in mice. Moreover, it presents a promising approach for the immunotherapy of MS under clinical investigation. In this study, a competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect the MOG35-55 peptide that is conjugated to mannan. Intra- and inter-day assay experiments proved that the proposed ELISA methodology is accurate and reliable and could be used in the following applications: (i) to identify the peptide (antigen) while it is conjugated to mannan and (ii) to adequately address the alterations that the MOG35-55 peptide may undergo when it is bound to mannan during production and stability studies.

Characterization of Asparagine Deamidation in Immunodominant Myelin Oligodendrocyte Glycoprotein Peptide Potential Immunotherapy for the Treatment of Multiple Sclerosis.

Mannan (polysaccharide) conjugated with a myelin oligodendrocyte glycoprotein (MOG) peptide, namely (KG)5MOG35-55, represents a potent and promising new approach for the immunotherapy of Multiple Sclerosis (MS). The MOG35-55 epitope conjugated with the oxidized form of mannan (poly-mannose) via a (KG)5 linker was found to inhibit the symptoms of MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) in mice using prophylactic and therapeutic vaccinated protocols. Deamidation is a common modification in peptide and protein sequences, especially for Gln and Asn residues. In this study, the structural solution motif of deaminated peptides and their functional effects in an animal model for MS were explored. Several peptides based on the MOG35-55 epitope have been synthesized in which the Asn53 was replaced with Ala, Asp, or isoAsp. Our results demonstrate that the synthesized MOG peptides were formed to the deaminated products in basic conditions, and the Asn53 was mainly modified to Asp. Moreover, both peptides (wild type and deaminated derivative) conjugated with mannan (from Saccharomyces cerevisiae) independently inhibited the development of neurological symptoms and inflammatory demyelinating spinal cord lesions in MOG35-55-induced EAE. To conclude, mannan conjugated with a deamidated product did not affect the efficacy of the parent peptide.

Recovery and quantification of a myelin oligodendrocyte glycoprotein peptide from rat plasma after protein precipitation.

The recovery of high molecular weight peptides from complex biological samples is a challenging task. Herein, a reliable, cost effective and rapid methodology was developed for the recovery and quantification of a myelin oligodendrocyte glycoprotein epitope namely (LysGly)5MOG35-55, from rat plasma. Removal of plasma proteins before quantification of the peptide was achieved after precipitation by an acetonitrile/water/formic acid solution. Using the developed protocol, average recoveries of the peptide from plasma ranged between 83.3 and 90.3%.

Cyclic citrullinated MBP87-99 peptide stimulates T cell responses: Implications in triggering disease.

Amino acid mutations to agonist peptide epitopes of myelin proteins have been used to modulate immune responses and experimental autoimmune encephalomyelitis (EAE, animal model of multiple sclerosis). Such amino acid alteration are termed, altered peptide ligands (APL). We have shown that the agonist myelin basic protein (MBP) 87-99 epitope (MBP87-99) with crucial T cell receptor (TCR) substitutions at positions 91 and 96 (K91,P96 (TCR contact residues) to R91,A96; [R91,A96]MBP87-99) results in altered T cell responses and inhibits EAE symptoms. In this study, the role of citrullination of arginines in [R91,A96]MBP87-99 peptide analog was determined using in vivo experiments in combination with computational studies. The immunogenicity of linear [Cit91,A96,Cit97]MBP87-99 and its cyclic analog - cyclo(87-99)[Cit91,A96,Cit97]MBP87-99 when conjugated to the carrier mannan (polysaccharide) were studied in SJL/J mice. It was found that mannosylated cyclo(87-99)[Cit91,A96,Cit97]MBP87-99 peptide induced strong T cell proliferative responses and IFN-gamma cytokine secretion compared with the linear one. Moreover, the interaction of linear and cyclic peptide analogs with the major histocompatibility complex (MHC II, H2-IAs) and TCR was analyzed using molecular dynamics simulations at the receptor level, in order to gain a better understanding of the molecular recognition mechanisms that underly the different immunological profiles of citrullinated peptides compared to its agonist native counterpart MBP87-99 epitope. The results demonstrate that the citrullination of arginine in combination with the backbone conformation of mutated linear and cyclic analogs are significant elements for the immune response triggering the induction of pro-inflammatory cytokines.

Conjugation of a peptide to mannan and its confirmation by tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

The conjugation of polysaccharides to peptides is essential for antigen delivery and vaccine development. Herein, we show that tricine SDS-PAGE in combination with Coomassie Blue staining was adequate to determine the conjugation efficacy of a peptide (epitope 35-55 of myelin oligodendrocyte glycoprotein) to mannan. In addition, tricine SDS-PAGE and periodic acid-Schiff stains were able to monitor the redox state of mannan. Using the described protocol, more than 99.9% of a peptide containing five lysines at its N-terminus was confirmed conjugated to mannan.

Use of the 2-chlorotrityl chloride resin for microwave-assisted solid phase peptide synthesis.

A fast and efficient microwave (MW)-assisted solid-phase peptide synthesis protocol using the 2-chlorotrityl chloride resin and the Fmoc/tBu methodology, has been developed. The established protocol combines the advantages of MW irradiation and the acid labile 2-chlorotrityl chloride resin. The effect of temperature during the MW irradiation, the degree of resin substitution during the coupling of the first amino acids and the rate of racemization for each amino acid were evaluated. The suggested solid phase methodology is applicable for orthogonal peptide synthesis and for the synthesis of cyclic peptides.

Insights into AT1 receptor activation through AngII binding studies.

This study investigates the binding of angiotensin II (AngII) to the angiotensin II type 1 receptor (AT1R), taking into consideration several known activation elements that have been observed for G-protein-coupled receptors (GPCRs). In order to determine the crucial interactions of AngII upon binding, several MD simulations were implemented using AngII conformations derived from experimental data (NMR ROEs) and in silico flexible docking methodologies. An additional goal was to simulate the induced activation mechanism and examine the already known structural rearrangements of GPCRs upon activation. Performing MD simulations to the AT1R - AngII - lipids complex, a series of dynamic changes in the topology of AngII and the intracellular part of the receptor were observed. Overall, the present study proposes a complete binding profile of AngII to the AT1R, as well as the key transitional elements of the receptor and the agonist peptide upon activation through NMR and in silico studies.

Facile and efficient syntheses of a series of N-benzyl and N-biphenylmethyl substituted imidazole derivatives based on (E)-urocanic acid, as angiotensin II AT1 receptor blockers.

In the present work, a facile and efficient route for the synthesis of a series of N-substituted imidazole derivatives is described. Docking studies have revealed that N-substituted imidazole derivatives based on (E)-urocanic acid may be potential antihypertensive leads. Therefore, new AT1 receptor blockers bearing either the benzyl or the biphenylmethyl moiety at the N-1 or N-3 position, either the (E)-acrylate or the propanoate fragment and their related acids at the C-4 position as well as a halogen atom at the C-5 position of the imidazole ring, were synthesized. The newly synthesized analogues were evaluated for binding to human AT1 receptor. The biological results showed that this class of molecules possesses moderate or no activity, thus not always confirming high docking scores. Nonetheless, important conclusions can be derived for their molecular basis of their mode of action and help medicinal chemists to design and synthesize more potent ones. An aliphatic group as in losartan seems to be important for enhancing binding affinity and activity.

Maturation of circulating Ly6ChiCCR2+ monocytes by mannan-MOG induces antigen-specific tolerance and reverses autoimmune encephalomyelitis.

Autoimmune diseases affecting the CNS not only overcome immune privilege mechanisms that protect neural tissues but also peripheral immune tolerance mechanisms towards self. Together with antigen-specific T cells, myeloid cells are main effector cells in CNS autoimmune diseases such as multiple sclerosis, but the relative contributions of blood-derived monocytes and the tissue resident macrophages to pathology and repair is incompletely understood. Through the study of oxidized mannan-conjugated myelin oligodendrocyte glycoprotein 35-55 (OM-MOG), we show that peripheral maturation of Ly6ChiCCR2+ monocytes to Ly6ChiMHCII+PD-L1+ cells is sufficient to reverse spinal cord inflammation and demyelination in MOG-induced autoimmune encephalomyelitis. Soluble intradermal OM-MOG drains directly to the skin draining lymph node to be sequestered by subcapsular sinus macrophages, activates Ly6ChiCCR2+ monocytes to produce MHC class II and PD-L1, prevents immune cell trafficking to spinal cord, and reverses established lesions. We previously showed that protection by OM-peptides is antigen specific. Here, using a neutralizing anti-PD-L1 antibody in vivo and dendritic cell-specific Pdl1 knockout mice, we further demonstrate that PD-L1 in non-dendritic cells is essential for the therapeutic effects of OM-MOG. These results show that maturation of circulating Ly6ChiCCR2+ monocytes by OM-myelin peptides represents a novel mechanism of immune tolerance that reverses autoimmune encephalomyelitis.

Design, synthesis and biological evaluation of non-peptide PAR1 thrombin receptor antagonists based on small bifunctional templates: arginine and phenylalanine side chain groups are keys for receptor activity.

In the present study, we report the synthesis and biological evaluation of a series of new non-peptide PAR(1) mimetic receptor antagonists, based on conformational analysis of the S(42)FLLR(46) tethered ligand (TL) sequence of PAR(1). These compounds incorporate the key pharmacophore groups in the TL sequence, guanidyl, amino and phenyl, which are essential for triggering receptor activity. Compounds 5 and 15 (50-100 microM) inhibited both TFLLR-amide (10 microM) and thrombin-mediated (0.5 and 1 U/ml; 5 and 10 microM) calcium signaling in a cultured human HEK cell assay.

An efficient synthesis of a rationally designed 1,5 disubstituted imidazole AT(1) angiotensin II receptor antagonist: reorientation of imidazole pharmacophore groups in losartan reserves high receptor affinity and confirms docking studies.

A new 1,5 disubstituted imidazole AT(1) Angiotensin II (AII) receptor antagonist related to losartan with reversion of butyl and hydroxymethyl groups at the 2-, 5-positions of the imidazole ring was synthesized and evaluated for its antagonist activity (V8). In vitro results indicated that the reorientation of butyl and hydroxymethyl groups on the imidazole template of losartan retained high binding affinity to the AT(1) receptor concluding that the spacing of the substituents at the 2,5- positions is of primary importance. The docking studies are confirmed by binding assay results which clearly show a comparable binding score of the designed compound V8 with that of the prototype losartan. An efficient, regioselective and cost effective synthesis renders the new compound as an attractive candidate for advanced toxicological evaluation and a drug against hypertension.

Gonadotropin-Releasing Hormone and GnRH Receptor: Structure, Function and Drug Development.

BACKGROUND: Gonadotropin-Releasing Hormone (GnRH) is a key element in sexual maturation and regulation of the reproductive cycle in the human organism. GnRH interacts with the pituitary cells through the activation of the Gonadotropin Releasing Hormone Receptors (GnRHR). Any impairments/dysfunctions of the GnRH-GnRHR complex lead to the development of various cancer types and disorders. Furthermore, the identification of GnRHR as a potential drug target has led to the development of agonist and antagonist molecules implemented in various treatment protocols. The development of these drugs was based on the information derived from the functional studies of GnRH and GnRHR. OBJECTIVE: This review aims at shedding light on the versatile function of GnRH and GnRH receptor and offers an apprehensive summary regarding the development of different agonists, antagonists and non-peptide GnRH analogues. CONCLUSION: The information derived from these studies can enhance our understanding of the GnRH-GnRHR versatile nature and offer valuable insight into the design of new more potent molecules.

Mannan-MOG35-55 Reverses Experimental Autoimmune Encephalomyelitis, Inducing a Peripheral Type 2 Myeloid Response, Reducing CNS Inflammation, and Preserving Axons in Spinal Cord Lesions.

CNS autoantigens conjugated to oxidized mannan (OM) induce antigen-specific T cell tolerance and protect mice against autoimmune encephalomyelitis (EAE). To investigate whether OM-peptides treat EAE initiated by human MHC class II molecules, we administered OM-conjugated murine myelin oligodendrocyte glycoprotein peptide 35-55 (OM-MOG) to humanized HLA-DR2b transgenic mice (DR2b.Ab°), which are susceptible to MOG-EAE. OM-MOG protected DR2b.Ab° mice against MOG-EAE by both prophylactic and therapeutic applications. OM-MOG reversed clinical symptoms, reduced spinal cord inflammation, demyelination, and neuronal damage in DR2b.Ab° mice, while preserving axons within lesions and inducing the expression of genes associated with myelin (Mbp) and neuron (Snap25) recovery in B6 mice. OM-MOG-induced tolerance was peptide-specific, not affecting PLP178-191-induced EAE or polyclonal T cell proliferation responses. OM-MOG-induced immune tolerance involved rapid induction of PD-L1- and IL-10-producing myeloid cells, increased expression of Chi3l3 (Ym1) in secondary lymphoid organs and characteristics of anergy in MOG-specific CD4+ T cells. The results show that OM-MOG treats MOG-EAE in a peptide-specific manner, across mouse/human MHC class II barriers, through induction of a peripheral type 2 myeloid cell response and T cell anergy, and suggest that OM-peptides might be useful for suppressing antigen-specific CD4+ T cell responses in the context of human autoimmune CNS demyelination.

Myelin Oligodendrocyte Glycoprotein and Multiple Sclerosis.

BACKGROUND: Myelin oligodendrocyte glycoprotein (MOG) is located on the external surface of myelin, a membranous component of the central nervous system (CNS) that forms the insulating lipid layer around neurons. The major MOG splicing variant (a1 transcript) encodes a transmembrane protein with an extracellular domain of an Ig variable (IgV) fold. MOG IgV domains from the same or different cells dimerize and contribute to the organization and maintenance of the myelin sheath in neurons. The encepalitogenic T cells recognize MOG and its immunodominant epitopes (epitopes 1-22, 35-55 and 92-106 located at the dimer interface) as foreign antigens and cause the destruction of myelin (demyelination) leading to the clinical condition known as multiple sclerosis (MS). Recognition of the antigen takes place in the context of the trimolecular complex formed by HLA, MOGpeptides and TCR. OBJECTIVE: Understanding the role of MOG in MS. METHOD/RESULTS: We have reviewed herein, the genomic organization of the human MOG gene, the structural characteristics of the MOG protein, the involvement of MOG in MS and clinical studies for the treatment of MS based on MOG peptide analogues. CONCLUSION: Conjugates of antigenic MOG peptides to mannan and combinations of antigenic MOG and other peptides chemically linked to cells of the immune system may modify the immune response, alleviating in some cases the symptoms of MS.

Chloride Intracellular Channel 4 Overexpression in the Proximal Tubules of Kidneys from the Spontaneously Hypertensive Rat: Insight from Proteomic Analysis.

BACKGROUND: Hypertensive nephropathy, a leading cause of declining kidney function, is a multifactorial process not well understood. In order to elucidate biological processes and identify novel macromolecular components crucially involved in the process of kidney damage, the application of system biology approaches, like proteomics, is required. METHODS: Proteomic studies were performed using the renal parenchyma of spontaneously hypertensive rats (SHR) and their normotensive Wistar Kyoto controls. Animals were sacrificed at early time intervals (6, 13, and 20 weeks after birth), the renal tissue extract was subjected to two-dimensional gel electrophoresis, differential expressed proteins were identified, and altered pathways were evaluated. One specific protein, chloride intracellular channel 4 (CLIC4), not implicated so far in the development of hypertension and nephrosclerosis, was further studied by Western blotting, immunohistochemistry and immunofluorescence. RESULTS: Proteomic analysis identified several pathways/processes and organelles (mitochondria) as being affected from the early stages of hypertension. CLIC4 was overexpressed in SHR at all 3 time intervals examined. This finding was confirmed by Western blotting and by immunohistochemistry and immunofluorescence; these morphological techniques demonstrated that CLIC4 was almost exclusively localized at the apical surface of the proximal tubular epithelial cells. CONCLUSIONS: Our studies provide evidence that major changes occur in the renal parenchyma from early stages of the development of hypertension. The overexpression of CLIC4 suggests that alterations in the proximal tubular compartment during hypertension should be further examined and that CLIC4 may be a useful early marker of renal tubular alterations due to elevated blood pressure.

Transdermal Delivery of AT1 Receptor Antagonists Reduce Blood Pressure and Reveal a Vasodilatory Effect on Kidney Blood Vessels.

BACKGROUND: The Renin Angiotensin System (RAS) is pharmacologically targeted to reduce blood pressure, and patient compliance to oral medications is a clinical issue. The mechanisms of action of angiotensin receptor blockers (ARBs) in reducing blood pressure are not well understood and are purported to be via a reduction of angiotensin II signaling. OBJECTIVE: We aimed to develop a transdermal delivery method for ARBs (losartan potassium and valsartan) and to determine if ARBs reveal a vasodilatory effect of the novel RAS peptide, alamandine. In addition, we determined the anti-hypertensive effects of the transdermal delivery patch. METHODS: In vitro and in vivo experiments were performed to develop an appropriate therapeutic system, promising an alternative and more effective therapy in the treatment of hypertension. A variety of penetration enhancers were selected such as isopropyl myristate, propylene glycol, transcutol and dimenthyl sulfoxide to obtain a constant release of drugs through human skin. Small resistance vessels (kidney interlobar arteries) were mounted in organ baths and incubated with an ARB. Vasodilatory curves to alamandine were constructed. RESULTS: The in vivo studies demonstrate that systemic absorption of valsartan and losartan potassium using the appropriate formulations provide a steady state release and anti-hypertensive effect even after 24 hours of transdermal administration. No apparent skin irritations (erythema, edema) were observed with the tested formulations. We also show that blocking the AT1 receptor of rabbit interlobar arteries in vitro reveals a vasodilatory effect of alamandine. CONCLUSION: This study reveals the potential mechanism of AT1 receptor blockade via alamandine, and is an important contribution in developing a favorable, convenient and painless antihypertensive therapy of prolonged duration through transdermal delivery of AT1 blockers.

Multiple Sclerosis: Immunopathology and Treatment Update.

The treatment of multiple sclerosis (MS) has changed over the last 20 years. All immunotherapeutic drugs target relapsing remitting MS (RRMS) and it still remains a medical challenge in MS to develop a treatment for progressive forms. The most common injectable disease-modifying therapies in RRMS include ß-interferons 1a or 1b and glatiramer acetate. However, one of the major challenges of injectable disease-modifying therapies has been poor treatment adherence with approximately 50% of patients discontinuing the therapy within the first year. Herein, we go back to the basics to understand the immunopathophysiology of MS to gain insights in the development of new improved drug treatments. We present current disease-modifying therapies (interferons, glatiramer acetate, dimethyl fumarate, teriflunomide, fingolimod, mitoxantrone), humanized monoclonal antibodies (natalizumab, ofatumumb, ocrelizumab, alentuzumab, daclizumab) and emerging immune modulating approaches (stem cells, DNA vaccines, nanoparticles, altered peptide ligands) for the treatment of MS.

Mannosylated Linear and Cyclic Single Amino Acid Mutant Peptides Using a Small 10 Amino Acid Linker Constitute Promising Candidates Against Multiple Sclerosis.

Multiple sclerosis (MS) is a serious autoimmune demyelinating disease leading to loss of neurological function. The design and synthesis of various altered peptide ligands of immunodominant epitopes of myelin proteins to alter the autoimmune response, is a promising therapeutic approach for MS. In this study, linear and cyclic peptide analogs based on the myelin basic protein 83-99 (MBP83-99) immunodominant epitope conjugated to reduced mannan via the (KG)5 and keyhole limpet hemocyanin (KLH) bridge, respectively, were evaluated for their biological/immunological profiles in SJL/J mice. Of all the peptide analogs tested, linear MBP83-99(F(91)) and linear MBP83-99(Y(91)) conjugated to reduced mannan via a (KG)5 linker and cyclic MBP83-99(F(91)) conjugated to reduce mannan via KLH linker, yielded the best immunological profile and constitute novel candidates for further immunotherapeutic studies against MS in animal models and in human clinical trials.