Signal Transducer &Activator of Signal Transducer &Activator of Transcription( STAT)-3 & T Transcription( STAT)-3 & T Helper (Th) 17 Cell in Psoriasis Helper (Th) 17 Cell in Psoriasis ImmunopathogenesisImmunopathogenesis

DR M.YOUSRY ABDEL-MAWLA,MDDR M.YOUSRY ABDEL-MAWLA,MDZAGAZIG FACULTY OF MEDICINE,EGYPTZAGAZIG FACULTY OF MEDICINE,EGYPT

SignalSignal transducerstransducers andand activatorsactivators ofof transcriptiontranscription) ) Stat) FamilyStat) Family

StatsStats areare latentlatent inin thethe cytoplasmcytoplasm untiluntil theythey areare activatedactivated byby extracellularextracellular signalingsignaling ligandsligands, , includingincluding cytokinescytokines, , growthgrowth factorsfactors andand hormones.hormones.Binding of these extracellular ligands to the Binding of these extracellular ligands to the specific receptors leads to activation of specific receptors leads to activation of various various tyrosine kinases (TKs). tyrosine kinases (TKs). They include JAKs, receptor TKs, and non-They include JAKs, receptor TKs, and non-receptor TKs such as Src and ABL, which can receptor TKs such as Src and ABL, which can directly phosphorylate Stat proteins in the directly phosphorylate Stat proteins in the absence of ligand-induced receptor signaling absence of ligand-induced receptor signaling

STAT3 ActivationSTAT3 ActivationStat3 is activated by cytokines of the IL-6 Stat3 is activated by cytokines of the IL-6 family such as IL-6, IL-11, leukemia inhibitory family such as IL-6, IL-11, leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), factor (LIF), ciliary neurotrophic factor (CNTF), oncostatin M and cardiotropin I .oncostatin M and cardiotropin I .Stat3 is the major signal transducer Stat3 is the major signal transducer downstream of gp130-like receptorsdownstream of gp130-like receptors . .Other extracellular signaling ligands such as Other extracellular signaling ligands such as IL-10 family members, epidermal growth factor IL-10 family members, epidermal growth factor (EGF), platelet derived growth factor (PDGF), (EGF), platelet derived growth factor (PDGF), hepa- tocyte growth factor (HGF), granulocyte hepa- tocyte growth factor (HGF), granulocyte colony- stimulating factor (G-CSF) and colony- stimulating factor (G-CSF) and leptin have also known to activate Stat3. leptin have also known to activate Stat3.

Mechanism of Stat3 signalingMechanism of Stat3 signaling

Different tyrosine kinases (TKs) can induce Stat3 activation. Growth factors such as Different tyrosine kinases (TKs) can induce Stat3 activation. Growth factors such as EGF bind to receptor tyrosine kinases (RTKs), followed by phosphorylation of Stat3 EGF bind to receptor tyrosine kinases (RTKs), followed by phosphorylation of Stat3 through activation of intermediary kineases of the SRC and JAK families. Cytokines through activation of intermediary kineases of the SRC and JAK families. Cytokines such as IL-6 family members bind to gp130, a common receptor subunit, thereby JAK such as IL-6 family members bind to gp130, a common receptor subunit, thereby JAK families and subsequent Stat3 are activated. Non-receptor TKs such as SRC families and subsequent Stat3 are activated. Non-receptor TKs such as SRC and ABL can directly phophorylate Stat3 in the absence of ligand-dependent and ABL can directly phophorylate Stat3 in the absence of ligand-dependent receptor signaling. In any pathway, two tyrosine phosphorylated Stat3 proteins form receptor signaling. In any pathway, two tyrosine phosphorylated Stat3 proteins form dimers, enter the nucleus and bind DNA to activate transcription of the target genesdimers, enter the nucleus and bind DNA to activate transcription of the target genes

PsoriasisPsoriasis

PsoriasisPsoriasis

Psoriasis is a chronic inflammatory skin Psoriasis is a chronic inflammatory skin disease characterized by excessive disease characterized by excessive proliferation, abnormal differentiation of proliferation, abnormal differentiation of epidermal keratino- cytes, vascular epidermal keratino- cytes, vascular proliferation, and leukocyte infiltration in the proliferation, and leukocyte infiltration in the dermis and epidermis .dermis and epidermis . It has been considered that psoriasis results It has been considered that psoriasis results from complex, aberrant relationships between from complex, aberrant relationships between the skin and immune system the skin and immune system as well as as well as genetic predisposition and environmental factorsgenetic predisposition and environmental factors

Psoriasis Clinical PresentationPsoriasis Clinical Presentation

Psoriasis as an immune Psoriasis as an immune disorderdisorder

Prepsoriasis StatePrepsoriasis State

Prepsoriasis StatePrepsoriasis State

Development of PsoriasisDevelopment of Psoriasis

Immunopathology of PsoriasisImmunopathology of Psoriasis

T-Cell in PsoriasisT-Cell in Psoriasis

T helper 1 versus 2 in T helper 1 versus 2 in psoriasispsoriasis

Psoriasis is an inflammatory skin disorder characterized by increased Psoriasis is an inflammatory skin disorder characterized by increased activation of CD4+ T lymphocytes, and systemic and local activation of CD4+ T lymphocytes, and systemic and local overexpression of pro-inflammatory cytokines such as interleukin 2 (IL-overexpression of pro-inflammatory cytokines such as interleukin 2 (IL-2), gamma interferon (IFN-), IL-6 and tumour necrosis factor alpha, 2), gamma interferon (IFN-), IL-6 and tumour necrosis factor alpha, indicating that immunopathogenesis of the disease is T helper 1 (Th1) indicating that immunopathogenesis of the disease is T helper 1 (Th1) mediated. mediated. T helper cell precursors (Thp) can be skewed towards mutually T helper cell precursors (Thp) can be skewed towards mutually exclusive Th1, Th2, Th17 and T regulatory cell (Treg) phenotypes on exclusive Th1, Th2, Th17 and T regulatory cell (Treg) phenotypes on the basis of the cytokine environmentthe basis of the cytokine environment..  Several studies suggest a pivotal role of bacterial superantigens in the Several studies suggest a pivotal role of bacterial superantigens in the initiation and/or exacerbation of this illness. In contrast to controls, initiation and/or exacerbation of this illness. In contrast to controls, psoriasis patients in the early course of disease were characterized by psoriasis patients in the early course of disease were characterized by significantly increased expression of the pro-inflammatory cytokine significantly increased expression of the pro-inflammatory cytokine IFN-, whilst a shift towards IL-10 secretion (Th2 response) was IFN-, whilst a shift towards IL-10 secretion (Th2 response) was observed in those presenting with increased duration of disease. observed in those presenting with increased duration of disease. These observations suggest a possible shift from a Th1 to a Th2 These observations suggest a possible shift from a Th1 to a Th2 cytokine response with superantigen-associated progression for the cytokine response with superantigen-associated progression for the duration of psoriasis, perhaps as an adaptive process by the immune duration of psoriasis, perhaps as an adaptive process by the immune system in an attempt to downregulate abnormal inflammatory Th1 system in an attempt to downregulate abnormal inflammatory Th1 immune responsesimmune responses ( (Jain etal 2009 Jain etal 2009 J Med Microbiol J Med Microbiol 5858 :180-184). :180-184).

Psoriasis shares immunologic and genetic Psoriasis shares immunologic and genetic features with other human autoimmune features with other human autoimmune inflammatory conditions such as inflammatory conditions such as inflammatory bowel disease, rheumatoid inflammatory bowel disease, rheumatoid arthritis, and multiple sclerosis. arthritis, and multiple sclerosis. Novel CD4 T-helper (Th) cells, called Th17 Novel CD4 T-helper (Th) cells, called Th17 cells, are important in the pathogenesis of cells, are important in the pathogenesis of psoriasispsoriasis..

T helper cell precursors being skewed towards Th1, Th2, Th17 and T T helper cell precursors being skewed towards Th1, Th2, Th17 and T

regulatory cell (Treg) phenotypes on the basis of the cytokine environmentregulatory cell (Treg) phenotypes on the basis of the cytokine environment. . 

PSORIASIS IS A PSORIASIS IS A Th17 Th17 DISEASE :A HypothesisDISEASE :A Hypothesis

An initiating event such as trauma or skin surface An initiating event such as trauma or skin surface microbes triggers IL-23 production by keratinocytes microbes triggers IL-23 production by keratinocytes and resident dendritic cells, which in turn stimulates and resident dendritic cells, which in turn stimulates proliferation of CCR4 and CCR6proliferation of CCR4 and CCR6 Th17Th17 cells found within skin. These activated cells found within skin. These activated Th17Th17 cells secrete Th17 cytokines including cells secrete Th17 cytokines including IL-22IL-22 and and IL-IL-17A17A, which cause keratinocyte growth and , which cause keratinocyte growth and activation, respectively. activation, respectively. Th17 Th17 cytokines also induce CCL20 production by cytokines also induce CCL20 production by keratinocytes, which fosters additional chemotaxis keratinocytes, which fosters additional chemotaxis of CCR6++of CCR6++Th17Th17 cells and CCR6 dendritic cells from cells and CCR6 dendritic cells from blood into skin. Cytokines released by these newly blood into skin. Cytokines released by these newly recruited cells maintain psoriatic recruited cells maintain psoriatic inflammationinflammation((Fitch et al.Fitch et al. Current Rheumatology Reports 2007, 9:461–467)Current Rheumatology Reports 2007, 9:461–467)

PSORIASIS IS A PSORIASIS IS A Th17 Th17 DISEASEDISEASE

T helper (Th) 17 cells, a novel T-cell subset, have been T helper (Th) 17 cells, a novel T-cell subset, have been implicated in the pathogenesis of psoriasis and other implicated in the pathogenesis of psoriasis and other autoimmune inflammatory diseases. autoimmune inflammatory diseases. Interleukin (IL)-23 stimulates survival and proliferation of Interleukin (IL)-23 stimulates survival and proliferation of Th17 cells, and thus serves as a key master cytokine Th17 cells, and thus serves as a key master cytokine regulator for these diseases. regulator for these diseases. In psoriasis, IL-23 is overproduced by dendritic cells and In psoriasis, IL-23 is overproduced by dendritic cells and keratinocytes, and this cytokine stimulates Th17 cells keratinocytes, and this cytokine stimulates Th17 cells within dermis to make IL-17A and IL-22. IL-22, in within dermis to make IL-17A and IL-22. IL-22, in particular, drives keratinocyte hyperproliferation in particular, drives keratinocyte hyperproliferation in psoriasis. psoriasis. Future targeting of these key cytokines is likely to lead to Future targeting of these key cytokines is likely to lead to dramatic clinical improvement in patients with psoriasis.dramatic clinical improvement in patients with psoriasis.

Microbial Antigens & Th 17 Microbial Antigens & Th 17 ResponseResponse

Helper T cell (Th) commitment to Th1, Th17 and T regulatory cell (Treg) phenotypes Helper T cell (Th) commitment to Th1, Th17 and T regulatory cell (Treg) phenotypes following encounter with antigen. Production of transforming growth factor (TGF)-β by following encounter with antigen. Production of transforming growth factor (TGF)-β by naturally occurring Tregs leads to lineage commitment of precursornaturally occurring Tregs leads to lineage commitment of precursor 

ACTIVATION of T h 17 ACTIVATION of T h 17 &STAT3&STAT3

TH17 responses in mice are also TH17 responses in mice are also restrained byCD4+ regulatory T cells (Tregs)restrained byCD4+ regulatory T cells (Tregs) This suppression was lost upon Treg-specific This suppression was lost upon Treg-specific ablation of ablation of Stat3Stat3, a transcription factor critical , a transcription factor critical for for TH17 TH17 differentiation, and resulted in the differentiation, and resulted in the development of a fatal intestinal inflammation. development of a fatal intestinal inflammation. These findings suggest that Tregs adapt to their These findings suggest that Tregs adapt to their environment by engaging distinct effector environment by engaging distinct effector response–specific suppression modalities upon response–specific suppression modalities upon activation of STAT proteins that direct activation of STAT proteins that direct the corresponding class of the immune the corresponding class of the immune response(Chaudhryresponse(Chaudhry et al,2009 et al,2009 ScienceScience 13  13 326326. . no. 5955, : 986 – 991no. 5955, : 986 – 991)) ..

STAT3 REGULATION of CYTOKINE-STAT3 REGULATION of CYTOKINE-MEDIATED GENERATION of TH 17MEDIATED GENERATION of TH 17

IL-6 functions to up-regulate IL-23R and that IL-23 synergized IL-6 functions to up-regulate IL-23R and that IL-23 synergized with IL-6 in promoting THi (TH17)generation. with IL-6 in promoting THi (TH17)generation. STAT3, activated by both IL-6 and IL-23, plays a critical role in STAT3, activated by both IL-6 and IL-23, plays a critical role in THi development. A hyperactive form of STAT3 promoted THi THi development. A hyperactive form of STAT3 promoted THi development, whereas this differentiation process was greatly development, whereas this differentiation process was greatly impaired in STAT3-deficient T cells. Moreover, STAT3 regulated impaired in STAT3-deficient T cells. Moreover, STAT3 regulated the expression of retinoic acid receptor-related orphan receptor the expression of retinoic acid receptor-related orphan receptor IL-17 -T (RORt), a THi-specific transcriptional regulator. IL-17 -T (RORt), a THi-specific transcriptional regulator. STAT3 deficiency impaired ROR t expression and led to elevated STAT3 deficiency impaired ROR t expression and led to elevated expression of T-box expressed in T cells (T-bet) and Forkhead expression of T-box expressed in T cells (T-bet) and Forkhead box P3 (Foxp3). box P3 (Foxp3). There is a pathway whereby cytokines regulate THi There is a pathway whereby cytokines regulate THi differentiation through a selective STAT transcription factor that differentiation through a selective STAT transcription factor that functions to regulate lineage-specific gene expression (functions to regulate lineage-specific gene expression (Yang et Yang et al.,2007 J.Biol Chem.,282,13:9358al.,2007 J.Biol Chem.,282,13:9358).).

Proinflammatory Effects of Proinflammatory Effects of IL17IL17

Stat3 links activated keratinocytes and Stat3 links activated keratinocytes and immunocytes required for development of immunocytes required for development of

psoriasispsoriasis Epidermal keratinocytes in psoriatic lesions are characterized Epidermal keratinocytes in psoriatic lesions are characterized by activated Stat3. by activated Stat3. Transgenic mice with keratinocytes expressing a constitutively Transgenic mice with keratinocytes expressing a constitutively active Stat3 (active Stat3 (K5.Stat3C miceK5.Stat3C mice) develop a skin phenotype either ) develop a skin phenotype either spontaneously, or in response to wounding, that closely spontaneously, or in response to wounding, that closely resembles psoriasis.resembles psoriasis.Keratinocytes from K5.Stat3C mice show upregulation of Keratinocytes from K5.Stat3C mice show upregulation of several molecules linked to the pathogenesis of psoriasis.several molecules linked to the pathogenesis of psoriasis. In addition, the development of psoriatic lesions in K5.Stat3C In addition, the development of psoriatic lesions in K5.Stat3C mice requires cooperation between Stat3 activation in mice requires cooperation between Stat3 activation in keratinocytes and activated T cells. keratinocytes and activated T cells. Finally, abrogation of Stat3 function by a decoy oligonucleotide Finally, abrogation of Stat3 function by a decoy oligonucleotide inhibits the onset and reverses established psoriatic lesions in inhibits the onset and reverses established psoriatic lesions in K5.Stat3C mice. K5.Stat3C mice. Thus, targeting Stat3Thus, targeting Stat3 may be potentially may be potentially therapeutic in the treatment of psoriasis.therapeutic in the treatment of psoriasis.

Blocking the function ofBlocking the function of STAT3STAT3 using antisense oligo-using antisense oligo-nucleotides inhibited the onset of, and reversed, established nucleotides inhibited the onset of, and reversed, established psoriatic lesionspsoriatic lesions. . Further analysis revealed a dual requirement of both activated Further analysis revealed a dual requirement of both activated STAT3 in keratinocytes as well as in T cells, indicating that the STAT3 in keratinocytes as well as in T cells, indicating that the pathogenesis of psoriasis is rooted in a co-operative process pathogenesis of psoriasis is rooted in a co-operative process involving STAT3-regulated genes in both skin cells and the involving STAT3-regulated genes in both skin cells and the immune system .immune system .Phosphatyrosyl peptides block STAT3-mediated DNA binding Phosphatyrosyl peptides block STAT3-mediated DNA binding activity, gene regulation and cell transformation. activity, gene regulation and cell transformation.

((VaradwajVaradwaj et al 2010 et al 2010 EgyptianEgyptian Dermatology Dermatology Online Journal 6 (1Online Journal 6 (1) ) ))

A positive feedback mechanism for A positive feedback mechanism for Th1/Th17 inflammationTh1/Th17 inflammation..

Th1 cells, but,not Th2 cells, produce an endogenous ligand Th1 cells, but,not Th2 cells, produce an endogenous ligand for Toll-like receptor (TLR) 4, namely extradomain A+ for Toll-like receptor (TLR) 4, namely extradomain A+ fibronectin containing extra type III domain A (FnEDA+).fibronectin containing extra type III domain A (FnEDA+).As TLR4 stimulation leads to production of As TLR4 stimulation leads to production of proinflammatory cytokines that recruit (via altered proinflammatory cytokines that recruit (via altered endothelial adhesion molecule expression and chemokine endothelial adhesion molecule expression and chemokine production) more Th1/Th17 cells, a positive feedback production) more Th1/Th17 cells, a positive feedback mechanism for Th1/Th17 inflammation exists .mechanism for Th1/Th17 inflammation exists .FnEDA+ positive feedback loops are a potential driver of FnEDA+ positive feedback loops are a potential driver of Th1/Th17 Th1/Th17 ininflammation flammation (John (John P. McFadden et al Clinics in P. McFadden et al Clinics in Dermatology (2011) 29, 257–265).Dermatology (2011) 29, 257–265).

Skin trauma is one of the best-known stimuli for psoriasis Skin trauma is one of the best-known stimuli for psoriasis plaque formation (the Koebner phenomenon). plaque formation (the Koebner phenomenon). After wound injury, TGF-β upregulates FnEDA+ and α5β1 After wound injury, TGF-β upregulates FnEDA+ and α5β1 integrin expres-macrophages) stimulation by FnEDA+ can lead integrin expres-macrophages) stimulation by FnEDA+ can lead to production of IL-1β, TNF-α, IL-6, IL-12, and IL-23.to production of IL-1β, TNF-α, IL-6, IL-12, and IL-23.These cytokines will in turn lead to endothelial expression of These cytokines will in turn lead to endothelial expression of intercellular adhesion molecule-1, E-selectin, and vascular intercellular adhesion molecule-1, E-selectin, and vascular cellular adhesion molecule-1, with augmentation of T-cell cellular adhesion molecule-1, with augmentation of T-cell recruitment into the lesional skin.recruitment into the lesional skin.Such cytokine produc- tion should lead to promotion of Th1 Such cytokine produc- tion should lead to promotion of Th1 and Th17 cell activation; and psoriasis is indeed characterized and Th17 cell activation; and psoriasis is indeed characterized by such a cytokine and T-cell profile.by such a cytokine and T-cell profile.

FnEDA+ will cause keratinocytes from psoriatic FnEDA+ will cause keratinocytes from psoriatic individuals (but not nonpsoriatic) to proliferate.individuals (but not nonpsoriatic) to proliferate.Hyperprolifer-ating keratinocytes produce Hyperprolifer-ating keratinocytes produce proliferative keratins such as keratins 6, 16, and proliferative keratins such as keratins 6, 16, and 17.17.The observation of close homology between The observation of close homology between proliferative keratin and streptococcal M proliferative keratin and streptococcal M protein31 lead to the proposal that T cells that protein31 lead to the proposal that T cells that recognize epitopes in both proteins are involved recognize epitopes in both proteins are involved in an autoimmune reaction in psoriasis.in an autoimmune reaction in psoriasis.

Such an autoimmune reaction will lead to Such an autoimmune reaction will lead to proinflammatory cytokine release, which in proinflammatory cytokine release, which in turn will lead to recruitment of Th1 and turn will lead to recruitment of Th1 and Th17 cells. Th1 cells will produce Th17 cells. Th1 cells will produce FnEDA+, completing the positive feedback FnEDA+, completing the positive feedback loop.loop.It remains to be established whether T It remains to be established whether T cells within psoriasis lesions react to cells within psoriasis lesions react to keratin, so the akeratin, so the autoimmune loop remains as a utoimmune loop remains as a hypothetic possibility, hypothetic possibility,

Multiple genes/candidate genes variants Multiple genes/candidate genes variants have been associated with psoriasis.have been associated with psoriasis.Many of these genes can be accommodated Many of these genes can be accommodated onto a model of psoriasis based on multiple onto a model of psoriasis based on multiple FnEDA+ loops .FnEDA+ loops .Multiple FnEDA+ loops are operative in Multiple FnEDA+ loops are operative in psoriasis and override regulatory attempts to psoriasis and override regulatory attempts to switch off cutaneous inflammation, which switch off cutaneous inflammation, which may explain why psoriatic inflammatory may explain why psoriatic inflammatory plaques have the potential to persist plaques have the potential to persist indefinitely.indefinitely.

New InformationsNew Informations

Do Other Therapies Work Within This Do Other Therapies Work Within This Framework?Framework?

Anti–T-cell agents could affect Th17 Anti–T-cell agents could affect Th17 cells as they would other T cells, but cells as they would other T cells, but this needs to be clarified this needs to be clarified Anti-TNF agents could decrease Anti-TNF agents could decrease activity of Th17 cells or work directly activity of Th17 cells or work directly on keratinocyte responseson keratinocyte responses

Studies on Stat 3 in PsoriasisStudies on Stat 3 in Psoriasis

Stat 3 in PsoriasisStat 3 in Psoriasis

New Prospectives &DirectionsNew Prospectives &Directions

Manipulation of PsorasisManipulation of Psorasis

Fitch et al.

Therapeutic Targets (Therapeutic Targets (FitchFitch et alet al, , Current Current

Rheumatology ReportsRheumatology Reports 2007, 2007, 9:9:461–467461–467))

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Stat3 is Key intracellular signaling Stat3 is Key intracellular signaling molecule important in Th17 molecule important in Th17 development and mediates IL-22–development and mediates IL-22–induced keratinocyte hyperproliferation.induced keratinocyte hyperproliferation.Blocking of stat3 pathway is good-to-Blocking of stat3 pathway is good-to-excellent (similar to TNF-a inhibitors): excellent (similar to TNF-a inhibitors): major signaling pathway inhibition major signaling pathway inhibition may have expected good clinical may have expected good clinical results in psoriasis .results in psoriasis .

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