MODULO 2: infiammazione e immunità innata Lezione 2

MODULO 2: infiammazione e immunità innata
Lezione 2-9:
mediatori chimici dell’infiammazione
•  proteine plasmatiche
•  mediatori di origine cellulare
Dott.ssa Chiara Porta:
[email protected] Tel 0321-375883
Chemical mediators of inflamma2on Derivazione plasma2ca (come precursori): complemento, chinine, coagulazione Kininasi: ina8vano bradykinin Proteine regolatrici del complemento: Frammentano e degradano componen2 a8va2 del complemento Derivazione cellulare: da granuli (istamina dei mastoci2), sintesi ex novo (prostaglandine, citochine) An2ossidan2: ina8vano ROS, NOS EC = endothelial cell Proteine plasma4che •  Sistema del complemento (permeabilità vascolare, chemiotassi e fagocitosi) •  Sistema delle chinine (permeabilità vascolare, vasodilatazione, dolore) •  Sistema della coagulazione (trombina espressione di molecole di adesione, e mediatori dell’infiammazione di derivazione cellulare) The ac2va2on and func2ons of the complement system Ac4va4on of complement by different pathways leads to cleavage of C3. The func4ons of the complement system are mediated by breakdown products of C3 and other complement proteins, and by the membrane aJack complex (MAC). (LPS, complessi polisaccaridici) C3a e C5a (anafilotossine) s4molano il rilascio di istamina (vasodilatazione a aumento della permeabilità vascolare) da parte dei mastoci4 e la via lipossigenasica dell’ac. arachidonico in neutrofili e monoci4 FASI PRECOCI -‐the classical pathway, which is ac4vated by certain isotypes of an4bodies bound to an4gens -‐the alterna4ve pathway, which is ac4vated on microbial cell surfaces in the absence of an4body -‐the lec4n pathway, which is ac4vated by a plasma lec4n that binds to mannose residues on microbes via alterna4va: -‐C3 riconosce struJure microbiche -‐microbi non esprimono le proteine inibitorie che impediscono la deposizione del C3b Bb prodoJo di degradazione del faJore B C3b-‐Bb = C3 convertasi C3 convertase-‐C3b = C5 convertasi via classica: -‐IgG, IgM -‐C1q èC1r, C1s (serin proteasi) C4b2b = C3 convertasi via leWnica: -‐colleWne e ficoline -‐MASP1, MASP2 (serin proteasi) C4b2b = C3 convertasi The C5 convertase cleaves C5 to begin the late steps of complement ac2va2on FASI TARDIVE Late steps of complement ac2va2on and forma2on of the MAC. A schema4c view of the cell surface events leading to forma4on of the MAC is shown. Cell-‐associated C5 convertase cleaves C5 and generates C5b, which becomes bound to the convertase. C6 and C7 bind sequen4ally, and the C5b,6,7 complex becomes directly inserted into the lipid bilayer of the plasma membrane, followed by stable inser4on of C8. Up to 15 C9 molecules may then polymerize around the complex to form the MAC, which creates pores in the membrane and induces cell lysis. C5a released on proteolysis of C5 s4mulates inflamma4on. Sistemi di regolazione dell’a8vazione del complemento •  regolazione della C3 e della C5 convertasi favorendo la dissociazione del complesso (Decay accelera4ng factor, DAF) o degradando il C3b (faJore I) •  inibitore di C1 (C1INH) blocca l’aWvazione delle serin proteasi associate a C1q •  proteine che inibiscono la formazione di MAC (es CD59) patologie associate a un’alterata a8vazione del complemento •  deficit di C3 porta a un aumento della susceWbilità alle infezioni (infezioni baJeriche ricorren4 e spesso letali) •  deficit di MAC aumentata susceWbilità a un gruppo ristreJo di baJeri (Neisseria) •  deficit di DAF e CD59 = emoglobinuria parossisis4ca noJurna (emolisi intravascolare disseminata provocata dalla lisi degli eritroci4 mediata dal complemento) •  deficit di C1INH = edema angioneuro4co ereditario (edema a livello di cute, ar4 mucosee laringea e intes4nale in risposta a stress emo4vi o traumi) Sistema delle chinine amplificazione autocatali4ca dello s4molo iniziale (prekallikrein ac4vator) Kininase INCREASES: vascular permeability, causes contrac;on of smooth muscle, dila;on of blood vessels, and pain The kinin system generates vasoac4ve pep4des Bradykinin from plasma proteins, called kininogens, by the ac4on of specific proteases called kallikreins. Bradykinin (vasoac4ve nonapep4de) increases: vascular permeability and causes contrac4on of smooth muscle, dila4on of blood vessels, and pain when injected into the skin. These effects are similar to those of histamine. The cascade that produces kinins is triggered by ac2va2on of Hageman factor (factor XII of the intrinsic cloWng pathway) upon contact with nega2vely charged surfaces, such as collagen and basement membranes. A fragment of factor XII (prekallikrein ac4vator, or factor XIIa) is produced, and this converts plasma prekallikrein into an ac4ve proteoly4c form, the enzyme kallikrein. The laJer cleaves a plasma glycoprotein precursor, high-‐
molecular-‐weight kininogen, to produce bradykinin. High-‐molecular-‐weight kininogen also acts as a cofactor or catalyst in the ac4va4on of Hageman factor. The ac4on of bradykinin is short-‐lived because it is quickly inac4vated by an enzyme called kininase. Any remaining kinin is inac2vated during passage of plasma through the lung by angiotensin-‐conver2ng enzyme Sistema della coagulazione trombina induce •  reclutamento di leucoci4 (mobilizzazione della (PAR-‐1) P seleWna, chemochine, ligandi delle integrin) •  sintesi di mediatori di derivazione cellulare (COX2-‐
PGE2, PAF, NO) The clo8ng system is divided into two pathways that converge, culmina4ng in the ac2va2on of thrombin and the forma2on of fibrin. The intrinsic cloWng pathway is a series of plasma proteins that can be ac4vated by Hageman factor (factor XII), a protein synthesized by the liver that circulates in an inac4ve form un4l it encounters collagen or basement membrane or ac4vated platelets (as occurs at the site of endothelial injury). Thrombin is the enzyme that cleaves circula2ng soluble fibrinogen to generate an insoluble fibrin clot and is the major coagula4on protease. It binds to receptors that are called protease-‐
ac;vated receptors (PARs) because they bind mul4ple trypsin-‐like serine proteases in addi4on to thrombin. PARs are seven-‐transmembrane G protein-‐coupled receptors that are expressed on platelets, endothelial and smooth muscle cells, and many other cell types. Engagement of the so-‐called type 1 receptor (PAR-‐1) by proteases, par4cularly thrombin, triggers several responses that induce inflamma4on. Sistema fibrinoli2co è il quarto sistema di mediatori plasma2ci innescato dal fa]ore XII (Hageman factor) At the same 4me that factor XIIa is inducing cloWng, it can also ac4vate the fibrinoly2c system. This cascade counterbalances cloWng by cleaving fibrin, thereby solubilizing the fibrin clot. The fibrinoly4c system contributes to the vascular phenomena of inflamma4on in several ways. Plasminogen ac2vator (released from endothelium, leukocytes, and other 4ssues) cleaves plasminogen, a plasma protein that binds to the evolving fibrin clot to generate plasmin, a mul2func2onal protease. Plasmin is important in lysing fibrin clots, but in the context of inflamma4on it also cleaves C3 to produce C3 fragments, and it degrades fibrin to form fibrin split products, which may have permeability-‐
inducing proper4es. Plasmin can also ac4vate Hageman factor, which can trigger mul4ple cascades, amplifying the response. Mediatori di derivazione cellulare • 
• 
• 
• 
• 
• 
• 
• 
Amine vasoaWve FaJore aWvante le piastrine citochine e chemochine ossido nitrico cos4tuen4 lisosomiali dei leucoci4 radicali liberi dell’ossigeno neuropep4di Metaboli4 dell’acido arachidonico Amine vasoa8ve: istamina e serotonina • 
• 
Istamina (preformata in mastoci4, basofili e piastrine circolan4): secreta per degranulazione in risposta a vari s4moli: -‐fisici: traumi, freddo o calore, -‐Reazioni immunitarie (interazione an4corpo-‐mastocita) -‐anafilatossine: C3a e C5a -‐proteine leucocitarie -‐neuropep4di -‐citochine (IL-‐1, IL-‐8) Causa dilatazione delle arterie, aumento permeabilità delle venule (ma costrizione delle grandi arterie). Agisce interagendo con i receJori istaminici H1 sulle cellule endotelial Serotonina (5-‐idrossitriptamina, 5-‐HT): mediatore vasoaWvo con azioni simili all’istamina. Presente nelle: piastrine, cellule enterocromaffini nell’apparato gastrointes4nale Rilascio s4molato dall’aggregazione delle piastrine: (avviene in seguito a contaJo con collagene, trombina, ADP, e complessi an4gene-‐an4corpo). Anche in risposta a PAF rilasciato da mastoci4 (reazioni IgE-‐mediate) Fa]ore A8vante le Piastrine (PAF) rilasciato da basofili e mastoci4 s4mola4 dal legame di an4geni alle IgE prodoJo da basofili, mastoci4, piastrine neutrofili, monoci4/macrofagi, cellule endoteliali lega un receJore specifico accoppiato a proteine G: •  AWvazione piastrinica •  vasocostrizione e broncocostrizione •  a concentrazioni estramemente basse vasodilatazione e aumento della permeabilità vascolare •  promuove il reclutamento (chemiotassi) e aWva i leucoci4 (s4mola la sintesi di eicosanoidi e altri mediatori infiammazione) Major effects of interleukin-‐1 (IL-‐1) and tumor necrosis factor alpha (TNF) in inflamma4on Ossido nitrico (NO) E’ un gas con emivita molto breve (pochi secondi) agisce in modo paracrino inducendo GMP ciclico. NOS, Ossido nitrico sintetasi: esistono 3 diverse isoforme: eNOS (endoteliale) , nNOS (neuronale), iNOS (inducibile fagoci4) NO plays an important role in the vascular and
cellular components of inflammatory responses. NO
is a potent vasodilator by virtue of its actions on vascular
smooth muscle. In addition, NO reduces platelet
aggregation and adhesion, inhibits several features
of mast cell-induced inflammation, and serves as an
endogenous regulator of leukocyte recruitment.
Blocking NO production under normal conditions
promotes leukocyte rolling and adhesion in postcapillary
venules, and delivery of exogenous NO reduces
leukocyte recruitment. Thus, production of NO is an
endogenous compensatory mechanism that reduces
inflammatory responses. Abnormalities in endothelial
production of NO occur in atherosclerosis, diabetes, and
hypertension
NO and its derivatives are microbicidal, and thus NO is
also a mediator of host defense against infection.
Evidence supporting the importance of this antimicrobial
activity of NO includes the following: (1) reactive
nitrogen intermediates derived from NO possess
antimicrobial activity; (2) interactions occur between NO
and reactive oxygen intermediates, leading to the
formation of multiple antimicrobial metabolites; (3)
production of NO is increased during host responses to
infection; and (4) genetic inactivation of iNOS enhances
microbial replication in experimental animal models.
High levels of NO production by a variety of cells appear
to limit the replication of bacteria, helminths, protozoa,
and viruses (as well as tumor cells).
NO causes vasodila2on, and NO free radicals are toxic to microbial and mammalian cells. Opsonizzazione aumenta efficienza fagocitosi: An4corpi-‐IgG C3b (C3b receptor=CR1) Lec4ne plasma4che-‐MBL Radicali liberi dell’ossigeno RICONOSCIUTI: Residui di fucosio e mannosio di glicoproteine e glicolipidi (microbi) fagocitosi aumenta: consumo di O2 gliconeogenesi produzione ROI NON RICONOSCIUTI: glicoproteine e glicolipidi di mammiferi hanno Acido sialico e la N-‐ace4lgalaJosammina Lipoproteine ossidate a bassa densità
pseudopodi azzurrofili Lec4na macrofagica Rid dismutazione spontanea 7 proteine anione superossido alogenazione o ossidazione di proteine e lipidi Rid H2O e O2 Dopo uccisione del patogeno le idrolasi acide all’interno dei fago-‐lisosomi degradano il microbo. Il pH scende 4-‐5, oWmale per ques4 enzimi NADPH: nico2nammide adenina dinucleo2de fosfato Polimerizzazione dei filamen4 di ac4na ROS possono danneggiare l’ospite: 1) lesioni alle cellule endoteliali (aumento della permeabilità vascolare) e parenchimali 2) inaWvazionedi proteasi (es alpha-‐an4tripsina) quindi danni al livello della matrice extracellulare meccanismi an4ossidan4: ceruloplasmina e la transferrina (plasma) superossido dismutasi, catalasi, gluta4one perossidasi (cellule)

Download Report