Harnessing The Glucocorticoid Receptor To Treat Inflammation Biology Essay

Glucocorticoids ( GC ) are endocrines synthesised in response to emphasize which maintain the homeostatic mechanisms. This consequence on the organic structure is mediated by adhering of the glucocorticoid endocrine to a ligand regulated written text factor known as the glucocorticoid receptor ( GR ) . GRs are expressed in every cell of the organic structure and are really of import, as they regulate cistrons which control critical mechanisms of the organic structure like metamorphosis, immune response and development.

GCs are active therapeutics for the intervention of assorted inflammatory upsets and malignant neoplastic diseases. However, due to their side effects, their usage is limited. Therefore, designation of mechanisms of GR sensitiveness and opposition is important for development of new curative attacks and betterment of bing interventions.

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The possible ground for such opposition arises from deregulating of the GR tract. This can cut down the figure of GR, alter DNA binding or increase the look of written text factors such as AP-1, STAT and NF-A?B which have negative effects on GR map. One ground for the GR opposition could perchance be the deficiency of specific and dependable biomarkers of steroid opposition. Observations show that the presence of interleukins 2 and 4 ( IL 2/4 ) , reduces sensitiveness of T-cells to GCs.

Our purpose here is to discourse and depict the function of the GR in redness and how this can be used to place biomarkers, isolated from T lymph cells treated with IL 2/4 and glucocorticoids that can be targeted for therapy.

Section 1: Introduction

Glucocorticoid endocrine

Steroids are biochemical elements that are of course present in the organic structure and modulate physiological, metabolic and immune procedures. Glucocorticoid is a type of steroid endocrine secreted by the adrenal secretory organ and is present in about every craniate animate being cell ( So et al, 2009 ) . GCs modulate a assortment of physiological maps and keep stress- related homeostasis. They raise blood glucose degrees by the dislocation of fats and proteins, inhibit bone formation and raise blood force per unit area. They are widely used due to their anti-inflammatory and immune-modulation belongingss and therefore hold clinical applications. GC ‘s are widely prescribed for the intervention of inflammatory marks and symptoms ( Campagnolo et al, 2008 ) . Most of the glucocorticoid activity in mammals is from hydrocortisone ( Fig.1 ; Miner et Al, 2007 ) .

Fig.1: The chemical construction of hydrocortisone ( a GC )

Glucocorticoids are the most effectual mediators for stamp downing redness. They act via the glucocorticoid receptor.

Dexamethasone ( Fig.3 ) is a category of man-made glucocorticoids which has 20-30 times more authority to handle redness as compared to other categories of GCs.

In our research we will therefore be utilizing Decadron as stimulation, along with IL 2 and 4, after the isolation of T-lymphocytes from human blood.

Glucocorticoid receptor

GR is a cytoplasmatic, ligand dependent written text factor. The human GR cistron is present on chromosome 5 and consists of 9 coding DNAs. Exon 1 contains 5’UTR, coding DNAs 2-9 contain the cryptography sequences and exon 9 the 3’UTR. It is besides known as NR3C1 which explains that GR belongs to the Nuclear Receptor subfamily 3, group C, member 1 ( Charmandari et al, 2004 ) . The receptor exhibits different effects in different parts of the organic structure. Its primary action is to modulate cistron written text on adhering to GCs. Like other steroid endocrine receptors, GRs are besides intracellular receptors ( IRs ) as they are found in the cytosol of cells. These receptors are transcription factors. Heat daze proteins ( hsp ) are found bound to the receptor until the endocrine is present.

Fig.3: Spheres of the glucocorticoid receptor.

( Beginning: Wikipedia )

The construction of GR consists of a Deoxyribonucleic acid adhering sphere ( DBD ) and a Ligand binding sphere ( LBD ) ( Fig.3 ) edge to dexamethasone and TIF2 co-activator protein. The glucocorticoid endocrine entirely can non demo any consequence ( Buckingham, 2009 ) . Its effects are expressed through the GR ( Fig.4 ) .

Fig.4: Binding of the endocrine to the glucocorticoid receptor.

( Beginning: hypertext transfer protocol: //home.fuse.net/apoptosis/GIA02.html )

The figure 4 shows how GC binds to the receptor with the remotion of certain heat-shock proteins that act like chaperones. The ensuing GC-GR complex Acts of the Apostless as a homodimer coactivator and diffuses into the karyon.

Degrees of control of the Glucocorticoid Receptor map:

To find the anti-inflammatory belongingss of glucocorticoids, it is of import to cognize the factors that could impact the glucocorticoid receptor map and therefore cut down its proposed anti-inflammatory belongingss.

3.1. Ligand and DNA binding of the Glucocorticoid Receptor:

GR is structurally similar to the androgen and Lipo-Lutin receptors that contain a Deoxyribonucleic acid adhering sphere and a ligand adhering sphere. The proper control of written text relies on the assembly of GR regulative composites at promoter-proximal site of mark cistron response elements ( Luecke and Yamamoto, 2005 ) .

3.1.1. Transactivation

GC binds to the GR in the cytosol and translocates to the karyon where it binds to DNA as a homodimer at consensus sites, termed Glucocorticoid Response Elements ( GREs ) , normally located in the cis-regulatory part of mark cistrons. The GR modulates the look of legion mark cistrons depending on the cell type and booster context. The magnitude and way of GR-mediated transcriptional activity is determined by the GRE sequence, balance between co-activators and co-repressors and post-translational alterations ( Liberman et al, 2009 ) . The GR edge to the endocrine binds to GRE upstream of the mark cistron and novices written text ( Fig.5 ) .

Fig.5: Transactivation by the GR.

( Lovinger D.M. , 2008 )

3.1.2. Transrepression

Alternatively, GR can quash written text by adhering to written text factors like NF-A?B and AP-1, and assorted other co-activators. This attributes to the anti-inflammatory consequence of GC as it suppresses the action of inflammatory and immune modulating mark cistrons. GR affects the activity of other written text factors like activator protein-1 ( regulates homeostasis in response to viral and bacterial infections and emphasis ) , STAT ( Signal Transducer and Activator of Transcription which regulates cell growing, distinction and endurance ) and NF-A?B ( a written text factor commanding cellular response to emphasis ) . These effects may be attributed due to a figure of different mechanisms like the competition between GR and the camp response component adhering protein ( CBP ) for the written text factors stated above. The GR to binding of written text factors such as NF-A?B, leads to the loss of DNA adhering capableness of the GR ( Muzikar et al, 2009 ) .

Transrepression of the GR is considered to bring forth positive curative consequence as it shows an anti-inflammatory action. Transactivation of cistrons is considered to demo negative curative effects due to its side effects.

Cofactors: Co-activators and co-repressors

Activation of GR is a complex procedure and involves a figure of stairss which includes the ability of the receptor to adhere the endocrine and so translocate into nucleus to place mark cistrons. Transcription factors are proteins that bind to DNA regulative sequences of mark cistrons to modify the rate of cistron written text. The tract of these factors might affect multiple intracellular signal transductions or may straight be activated by ligands ( for illustration GCs ) or be activated within the cytol. Thus these factors are able to change over environmental signals at the cell surface into long-run alterations in cistron written text ( Adcock, 2000 ; Frego and Davidson, 2006 ) .

Co-activator molecules are big proteins that bind written text factors to basal written text setup and therefore act as planimeters of cistron written text. GR interacts with heat daze proteins ( hsp90 ) as shown in Fig.4 above, and co-activators like Cyclic Adenosine Mono Phosphate ( camp ) response component adhering protein ( CBP ) and p300. Hsp90 maintains the GR in a place that it is able to adhere to the endocrine and besides plays an of import function in the translocation of the GR composite to the karyon ( Ricketson et al, 2007 ) . The p300-CBP complex interacts with a figure of written text factors and mediates the look of mark cistrons ( Fig.6 ) .

Interactions between coactivators and GR are still under probes and a few coactivators have been identified which are BRGA 1 ( SWIA /SNF ) composite, theA P/CAFA ( ADA/SAGA ) composite, A CBP/p300, the p160 coactivators and constituents of theA DRIPA ( TRAP/ARC ) composite ( Fig.6 ; Jenkins et Al, 2001 ; Chaudhuri, 2008 ) .

Co-repressors on the other manus are proteins that bind to a written text factor which contains a Deoxyribonucleic acid adhering sphere and diminish the look of the GR mark cistrons. They interact via receptor interaction spheres ( RIDs ) in the carboxyl terminal half of the ligand adhering sphere of the GR ( Lee at Al, 2000 ) .

Fig.6: Consequence of coactivators and corepressors on DNA written text.

The identified corepressors are NCoR1 ( Nuclear Receptor Corepressor 1 ) , which assists atomic receptors in down ordinance of DNA look, e.g. : Thyroid endocrine and Retinoic Acid receptor Co-repressor 1 ( TRAC-1 ) , and NCoR2 ( Nuclear Receptor Corepressor 2 ) , which fixes histone deacetylases to DNA booster parts ( Wang and Simons, 2005 ) , e.g. : SMRT ( Hushing Mediator of Retinoid and Thyroid endocrine receptor ) ( Fig.6 ) .

Post-translational alterations of the Glucocorticoid Receptor

Glucocorticoid signalling pathway needs to be tightly regulated to guarantee the anti-inflammatory belongings of glucocorticoids. The map of GR can besides be affected by different station translational alterations like phosphorylation, ubiquitination, sumoylation, acetylation and methylation ( Kumar and Calhoun, 2008 ) .

3.3.1. Phosphorylation

The human GR has five phosphorylation sites at serines 113, 141, 203, 211 and 226. These serines are normally followed by a proline and are therefore called proline-directed consensus sequences ( Galliher-Beckley and Cidlowski, 2009 ) . The phosphorylation on serines is normally dependent on the ligand adhering to GR. These sites can be phosphorylated by Cyclin Dependent Kinase ( CDK ) , Mitogen Protein Kinases ( MAPK ) , and Glycogen Synthase Kinase-3 ( GSK-3 ) ( Krstic et al, 1997 ) .

Phosphorylation has two major effects on the GR map. First, it effects the subcellular localisation of the receptor and secondly, it alters the ability of the receptor to modulate mark cistron written text. It has besides been suggested that hyper-phosphorylation of the GR may be the ground for the development of GR opposition in the organic structure due to the reduced binding of GR to its mark sites ( Duma D. et Al, 2006 ) .

3.3.2. Ubiquitination

The covalent binding of ubiquitin, a multi-protein composite, to the GR consequences in its ‘ debasement by proteasome. The ubiquitin-proteasome mediated tract standardises the GC signalling system by commanding the debasement rates of GR. This is of import as it degrades both short lived and regulative proteins involved in cell rhythm patterned advance, cell surface receptor action, transition of ion channels and antigen presentation. Therefore, phosphorylation could ensue in the loss of proteins in the glucocorticoid receptor. It has been observed that mutant of all phosphorylated sites in GR increased the half life of the receptor and eliminated downregulation ( Duma D. et Al, 2006 ) .

3.3.3. SUMOylation

Addition of a Small Ubiquitin related Modifier-1 ( SUMO-1 ) is another of import station translational mechanism which can modulate GR map. Proteins like written text factors, chromatin remodelling proteins and co-regulators which are involved in cistron ordinance are marks for SUMO. In sumoylation the SUMO-1 gets attached to the lysine residues of the mark proteins and regulates protein stableness, localisation and activity of transcriptional regulators ( Davies et al, 2008 ) .

The protein acknowledgment and SUMO linkage is a dynamic procedure and is catalysed by an enzyme named Ubc9. The glucocorticoid receptor has three SUMO fond regard sites K277, K293 and K703. The first two fond regard sites reside in the N-terminal transactivation part while the 3rd attachment site resides in the ligand-ligand adhering sphere of the receptor because of which sumoylation might hold a greater consequence on the operation of the receptor ( Duma D. et Al, 2006 ) .

3.3.4. Acetylation and methylation

Acetylation and methylation can besides modulate protein map. Even though less grounds is available in support of this, some studies provide indicants for this instance. Surveies show that histones can be methylated and these alterations regulate cistron written text through chromatin rearrangements. Very small is known about the transcriptional activity mediated by histone methylation. Methylation of GR coactivators like p300 can modulate GR signalling by suppressing the interaction between p300 and GR Interacting Protein ( GRIP1 ) ( Duma D. et Al, 2006 ) .

Acetylation is a really of import characteristic as old surveies show that acetylation occurs in the Deoxyribonucleic acid adhering sphere ( DBD ) of GR on aminic acids 492-495. Studies show that the glucocorticoid receptor is acetylated after Decadron binding. The acetylation negatively regulates Decadron induced repression of NF-A?B dependent cistron look ( Ito K. Et Al, 2005 ) .

Section 2: Inflammation PROPERTIES

Inflammation

Inflammation is described as “ the sequence of alterations which occurs in a life tissue when it is injured provided that the hurt is non of such a grade as to at one time destruct its construction and verve ” or “ the reaction to hurt of the life microcirculation and related tissues ” ( Punchard et al, 2004 ) . Harmonizing to World Health Organisation ( WHO ) 2007 study, redness and redness related unwellnesss are the biggest challenge in current medical specialty as about 500 million people suffer from them ( Beck et al, 2009 ) .

Until the nineteenth century redness was regarded as an unwanted response that was harmful to the host. However, surveies subsequently suggested that redness is a organic structure ‘s ain defensive and mending procedure. Typical marks of redness are as follows:

Inflammation is accompanied by a ruddy visual aspect which is due to the accretion of many red blood cells in the country,

Heat esthesis is caused due to the increased motion of blood through dilated vass,

Swelling can be seen due to infiltration of cells into the damaged country, and

Pain is ever felt in the damaged country which could be either due to the harm caused, or due to the inflammatory response and even due to the stretching of nervousnesss due to swelling.

The inflammatory response of the organic structure could be of great value, every bit good as endangering. The inflammatory response to weave harm is of great value as it isolates the damaged country, immobilizes effecter cells to the site and encourages mending. Sometimes, immune response causes more harm to the organic structure than the agent itself and the conditions are described as allergic reactions and autoimmune diseases like asthma, arthritic arthritis, induration, etc. These diseases are debilating and incurable.

The implicit in genetic sciences and molecular biological science forms the footing, to analyze and place inclination of inflammatory diseases, and pharmalogical surveies aim to develop fresh interventions to handle these diseases. Therefore, research into different ways of forestalling inflammatory diseases in an effectual manner, with no side effects, is an of import portion of the industry.

The function of glucocorticoid receptor in redness

One of the most of import pharmacological functions of glucocorticoids is their anti-inflammatory and immunosuppressive activity. The anti-inflammatory effects of glucocorticoids are mediated through negative interaction with NF-A?B and AP1, which are good characterized inducers of proinflammatory cytokine look ( Tait et al, 2008 ; McMaster and Ray, 2008 ) .

5.1. Mechanisms of Glucocorticoid action

The glucocorticoid receptor has multiple isoforms that arise due to alternate splice and translational events of the cistron NR3C1.

GRE‘-A: binds ligand and mediates GC action. The cell types that show negligible look of GRE‘-A show minimal consequence of glucocorticoids.

GRI? and GR-P: do non adhere ligand and intercede GRE‘-A activity.

Fig.7: Structural administration of the human glucocorticoid receptor E‘ protein ( Beginning: Smoak and Cidlowski, 2004 ) .

The figure shows three major spheres viz. the N-terminal transactivation sphere which consists of AF-1 activation sphere and helps transcriptional sweetening and its association with the basal written text machinery ( BTM ) . The Deoxyribonucleic acid adhering sphere is necessary for receptor dimerization and mark binding. The C-terminal sphere is a binding site for hsp, coactivators and the ligand dependent activation map sphere ( AF-2 ) ( Dey et al, 2001 ) .

NF-A?B hostility mechanism

The engagement of NF-A?B in redness has been established good in both in vivo and in vitro systems. The omnipresent written text factor is made up of p65, p52 in combination with p100, p50 in combination with p105, c-Rel and RelB. The p65 and p50 combination is involved in the transcriptional activation procedure. NF-A?B exists in the cytol interacting with the inhibitor IA?B ( Beck et al, 2009 ) . This interaction prevents DNA binding as atomic translocation of NF-A?B is inhibited ( Fig. 8 )

Fig.8: Mechanisms of NF-A?B hostility ( Smoak and Cidlowski, 2004 ) .

GRE‘ represses the transcriptional activity of NF-A?B by interacting with p65 fractional monetary unit as show in the figure above.

Another proposed mechanism is the competition ( common hostility ) of GRE‘ and NF-A?B for common co-factors such as camp response component adhering protein ( CREB ) -binding protein ( CBP ) and steroid receptor co-activator ( SRC-1 ) . CBP and SRC-1 are required for maximal written text activity of NF-A?B and GRE‘ ( Bosscher et al, 2009 ) . It is besides required for GRE‘ and CBP to p65 to adhere to the same part of CBP.

Surveies besides show that the GR interferes with the phosphorylation of RNA pol II C-terminal sphere ( CTD ) as a consequence of which NF-A?B is non able to adhere written text elongation factor ( P-TEFb ) , therefore suppressing written text ( Luecke and Yamamoto, 2005 ) .

Therefore a assortment of mechanisms are likely to be involved in the mutual hostility between GRE‘ and NF-A?B ( Fig. 8 ) .

AP-1 hostility mechanism

AP-1 is an of import regulator in the cistron look of many cytokine cistrons and is besides in commanding programmed cell death or programmed cell decease ( Johnson and Lapadat, 2002 ) .

Fig.9: AP-1 repression mechanisms by GRE‘ ( Smoak and Cidlowski, 2004 ) .

GRE‘ represses AP-1 activity by interacting with c-Jun and prevents adhering of DNA in the karyon in a manner more or less similar to the NF-A?B repression mechanism. AP-1 interacts with a dimer composed of a Jun household member like c-Jun and a Fos protein like c-Fos. This dimer regulates cistron written text by adhering to the GR. When edge to GRE‘ at the site of inflammatory cistron boosters they repress written text because they do non let AP-1 to adhere DNA ( Smoak and Cidlowski, 2004 ; Kassel and Herrlich, 2007 ) .

Another mechanism shows that GRE‘ facilitates the look of MPK-1 cistron which encodes for MAP kinase and prevents the activation of c-Jun N-terminal Kinases ( JNK ) , extracellular signal-regulated kinases ( ERK ) and p38 in the cytol which are kinases of import for inflammatory responses which consequences in the destabilization of the proinflammatory cytokines such as Cox ( COX-2 ) ( Smoak and Cidlowski, 2004 ) .

Because of the strong anti-inflammatory effects of GC ‘s, they are used to handle a assortment of conditions like arthritis, allergic reactions, tegument upsets, malignant neoplastic disease, pneumonic upsets, transplant rejection and even spinal cord hurt ( Hardy et al, 2008 ) . Glucocorticoid as a drug has been used for over 50 old ages now to handle chronic inflammatory diseases despite their side effects like suppression of the activity of the hypothalamus, pituitary and adrenal ( HPA ) glands ( Silverman and Sternberg,2008 ) , increased serum glucose, altered electrolyte balance, insomnia, induction of osteoporosis and glaucoma and behavioral alterations. The presently used drugs with generic name Decadron are Decadron which is marketed by Merck and Co. , Hexadrol, Dexasone and Maxidex.

GCs are besides known to be a portion of the intervention of some malignant neoplastic diseases. For illustration, GCs in combination with ketoconazole or chemotherapy are used in prostatic malignant neoplastic disease therapy ( Keith, 2008 ) .

GCs have intense immune modulating belongingss, and man-made glucocorticoids are the most powerful anti-inflammatory agents presently available. However, fluctuations in response to these drugs is of import, as there have been incidences of side effects like osteoporosis which are normally irreversible and can take to considerable morbidity. No clear grounds supports how this fluctuation exerts these effects. Microarray engineering allows cistron profiling to be done to place accurate cistron look degrees within an single and so leads to the designation of genome response to different concentrations of glucocorticoids ( Donn et al, 2007 ) . In our experiments we will be utilizing cistron microarray experiments to find unsimilarities in GC dependent cistron look webs taking topographic point in T cells. We besides plan to insulate RNA from blood givers that will be processed by the Affymetrix GeneChip engineering available in the nucleus installation at the University of Manchester. Labelled marks derived from the messenger RNA of an experimental sample will be hybridised to nucleic acerb investigations attached to the solid support. System analysis will so be used to place relevant alterations in the cistron look profiles.

Decision

The increased apprehension of how glucocorticoids act has given new penetrations into the pathophysiology of inflammatory diseases such as arthritis and has besides opened new doors for the development of new anti-inflammatory interventions. Development of glucocorticoids with an improved curative consequence is now a major focal point. GCs are important for anti-inflammatory therapy. Previous attempts of planing of glucocorticoid constructions with an increased curative activity have been concentrating on transcriptional ways of disassociating anti-inflammatory transcriptional repression from their side effects or by the combination of drugs like Pediapred and dipyridamole ( an antithrombotic drug ) in order to show a dissociated activity profile without the side effects. None of the plants so far have shown full success. The constriction in translational research into glucocorticoid opposition is the deficiency of specific and dependable biomarkers that can be obtained from blood samples. Alternatively, it has been observed that in the presence of interleukins 2 and 4 ( IL2/4 ) , T cells show decreased sensitiveness to glucocorticoids. In our experiments we will therefore be analyzing GC induced transcriptome response in IL 2/4 treated T cells in order to insulate biomarkers of opposition that can be targeted for therapy.

AIMS AND OBJECTIVES

Our purpose is to seek and insulate a biomarker of steroid opposition, utilizing ex-vivo cistron look profiling of lymph cells from healthy human voluntaries and to analyze GC induced transcriptome response in IL 2/4 treated T-lymphocytes to aim them for therapy and facilitate development of better drugs with lower side effects.

Plan OF INVESTIGATION

T lymph cells would foremost be isolated from blood samples taken from a lower limit of five healthy voluntaries. These T lymph cells would so be stimulated with IL 2 and IL 4 for 48 hours and so with man-made glucocorticoid Decadron for 6 hours. Gene look profiling would so be carried out on these samples utilizing cistron microarray experiments.

FUTURE WORK

Future probes would affect the usage of consequences obtained in the present experiment, to construct new hypothesis with identified overlapping set of cistron webs. The function of MAPK tract in IL 2/4 induced opposition to glucocorticoids would besides be determined. The cognition obtained from translational research and the development of cost effectual simple checks, will let the development of better apprehension and interventions of opposition to glucocorticoids and possibly facilitate isolation of compounds that will aim the identified tracts and consequence in the switch to GC sensitiveness.