School of Medicine, School of Medicine, UCDHSCUCDHSCDisease & Defense BlockDisease & Defense BlockFebruary 1February 1stst, 2008, 2008

Chemical Mediators of Chemical Mediators of InflammationInflammation

Francisco G. La Rosa, MDFrancisco.LaRosa@uchsc.eduAssistant Professor, Department of Pathology

University of Colorado at Denver Health Science Center, Denver, Colorado

Leukocyte activation.Leukocyte activation. Different classes of cell surface receptors of Different classes of cell surface receptors of leukocytes recognize different stimuli. The receptors initiate leukocytes recognize different stimuli. The receptors initiate

responses that mediate the functions of the leukocytes.responses that mediate the functions of the leukocytes.Only some receptors are depicted.Only some receptors are depicted.

Click for Movie

NECROSIS:A white blood cell dies after a meal

Ingesting “leukotoxic”Streptococcus pyogenes

1.1. Reactions are similar irrespective of tissue Reactions are similar irrespective of tissue or type of injuryor type of injury

2. Reactions occur in absence of nervous 2. Reactions occur in absence of nervous connectionsconnections

““Chemical substances mediate all phasesChemical substances mediate all phasesof acute inflammation”of acute inflammation”

Thomas, Lewis (1913-1993)

Chemical mediators of inflammation (EC: endothelial cells)Chemical mediators of inflammation (EC: endothelial cells)

Vasodilatation:Vasodilatation:• HistamineHistamine• ProstaglandinsProstaglandins• Nitric oxideNitric oxide

Increased vascular permeability:Increased vascular permeability:• HistamineHistamine• Anaphylatoxins C3a and C5aAnaphylatoxins C3a and C5a• KininsKinins• Leukotrienes C, D, and ELeukotrienes C, D, and E• PAFPAF• Substance PSubstance P

Chemotaxis:Chemotaxis:• Complement fragment C5aComplement fragment C5a• Lipoxygenase products, Lipoxygenase products,

lipoxins & leukotrines (LTB4)lipoxins & leukotrines (LTB4)• ChemokinesChemokines

Tissue DamageTissue Damage• Lysosomal productsLysosomal products• Oxygen-derived radicalsOxygen-derived radicals• Nitric OxydeNitric Oxyde

Events in Acute InflammationEvents in Acute Inflammation

Prostaglandins :Prostaglandins :• VasodilationVasodilation• PainPain• FeverFever• Potentiating edemaPotentiating edema

IL-1 and TNF:IL-1 and TNF:• Endothelial-leukocyte interactionsEndothelial-leukocyte interactions• Leukocyte recruitmentLeukocyte recruitment• Production of acute-phase reactantsProduction of acute-phase reactants

Diversity of Effects of Chemical MediatorsDiversity of Effects of Chemical Mediators

VASODILATATIONVASODILATATION

Basophils & Mast CellsBasophils & Mast Cells

HistamineHistamine

Adipose tissue showing Adipose tissue showing mast cells around blood vesselsmast cells around blood vessels and in the interstitial space. and in the interstitial space.Stained with metachromatic stain to identify the mast cell granules (dark blue or purple).Stained with metachromatic stain to identify the mast cell granules (dark blue or purple).

The red structures are fat globules stained with fat stain (oil red)The red structures are fat globules stained with fat stain (oil red)

Mast Cells & AllergyMast Cells & Allergy

Ultrastructure and contents of Ultrastructure and contents of neutrophil granulesneutrophil granules, stained for , stained for peroxidase activity. The large peroxidase-containing granules peroxidase activity. The large peroxidase-containing granules

are the azurophil granules; the smaller peroxidase-negative are the azurophil granules; the smaller peroxidase-negative ones are the specific granules (SG). N, portion of nucleus.ones are the specific granules (SG). N, portion of nucleus.

LEUKOTRINES & PROSTAGLANDINSLEUKOTRINES & PROSTAGLANDINS

Leukotrienes and ProstaglandinsLeukotrienes and Prostaglandins: Potent mediators of inflammation: Potent mediators of inflammation

Derived from Arachidonic acid (AA): 20-carbon, unsaturated fatty acid Derived from Arachidonic acid (AA): 20-carbon, unsaturated fatty acid produced from membrane phospholipids. produced from membrane phospholipids.

Principal pathways:Principal pathways:• 5-lipoxygenase: Produces a collection of leukotrienes (LT)5-lipoxygenase: Produces a collection of leukotrienes (LT)

• Cyclooxygenase (COX): Produces prostaglandin H2 (PGH2)Cyclooxygenase (COX): Produces prostaglandin H2 (PGH2)

PGH2 serves as substratePGH2 serves as substrate for two enzymatic pathways:for two enzymatic pathways:

• Prostaglandins (PG)Prostaglandins (PG)• Thromboxanes (Tx). Thromboxanes (Tx).

Biosynthesis of Biosynthesis of leukotrienesleukotrienes and and lipoxinslipoxins by cell-cell interaction. by cell-cell interaction.AA: arachidonic acid –derived; LTA4: Leukotriene A4; LTC4: Leukotriene C4AA: arachidonic acid –derived; LTA4: Leukotriene A4; LTC4: Leukotriene C4

NITRIC OXIDENITRIC OXIDE

Functions of Functions of nitric oxide (NO)nitric oxide (NO) in blood vessels and macrophages, produced by in blood vessels and macrophages, produced by two NO synthase enzymes. NO causes vasodilation, and NO free radicals are two NO synthase enzymes. NO causes vasodilation, and NO free radicals are

toxic to microbial and mammalian cells. NOS: nitric oxide synthase.toxic to microbial and mammalian cells. NOS: nitric oxide synthase.

IL-1 & Tumor Necrosis Factor (TNF)IL-1 & Tumor Necrosis Factor (TNF)

Major effects of interleukin-1 (IL-1) and tumor necrosis factor (TNF) in inflammationMajor effects of interleukin-1 (IL-1) and tumor necrosis factor (TNF) in inflammation

COMPLEMENTCOMPLEMENT

Complement Activation PathwaysComplement Activation Pathways

The activation and functions of the The activation and functions of the complement systemcomplement system. Activation of . Activation of complement by different pathways leads to cleavage of C3. The functions of complement by different pathways leads to cleavage of C3. The functions of

the complement system are mediated by breakdown products of C3 and other the complement system are mediated by breakdown products of C3 and other complement proteins, and by the membrane attack complex (MAC)complement proteins, and by the membrane attack complex (MAC)

OXYGEN FREE RADICALSOXYGEN FREE RADICALS

Production of microbicidal reactive oxygen Production of microbicidal reactive oxygen intermediates within phagocytic vesicles.intermediates within phagocytic vesicles.

OXIDATIVE BURST:Neutrophils kill microbes

by producing reactive oxygen species,demonstrated here with the dye

nitroblue tetrazolium (NBT)

Click for Movie

Interrelationships between the four plasma mediator systems triggered by Interrelationships between the four plasma mediator systems triggered by activation of factor XII (Hageman factor). Note that thrombin induces inflammation activation of factor XII (Hageman factor). Note that thrombin induces inflammation

by binding to protease-activated receptors (principally PAR-1) on platelets, by binding to protease-activated receptors (principally PAR-1) on platelets, endothelium, smooth muscle cells, and other cells.endothelium, smooth muscle cells, and other cells.

VasodilatationVasodilatation ProstaglandinsProstaglandinsNitric oxideNitric oxideHistamineHistamine

Increased vascular permeabilityIncreased vascular permeability Vasoactive aminesVasoactive aminesC3a and C5a (through liberating amines)C3a and C5a (through liberating amines)BradykininBradykininLeukotrienes C4, D4, E4Leukotrienes C4, D4, E4PAFPAFSubstance PSubstance P

Chemotaxis,Chemotaxis,leukocyte recruitment and activationleukocyte recruitment and activation

C5aC5aLeukotriene B4Leukotriene B4ChemokinesChemokinesIL-1, TNFIL-1, TNFBacterial productsBacterial products

FeverFever IL-1, TNFIL-1, TNFProstaglandinsProstaglandins

PainPain ProstaglandinsProstaglandinsBradykininBradykinin

Tissue damageTissue damage Neutrophil and macrophage lysosomal Neutrophil and macrophage lysosomal enzymesenzymesOxygen metabolitesOxygen metabolitesNitric oxideNitric oxide

Role of Mediators in Different Reactions of InflammationRole of Mediators in Different Reactions of Inflammation

Summary of Mediators of Acute Inflammation  ACTION

Mediator Source Vascular Leakage Chemotaxis Other

Histamine and serotonin

Mast cells, platelets + -  

Bradykinin Plasma substrate + - Pain

C3a Plasma protein via liver + - Opsonic fragment (C3b)

C5a Macrophages + +Leukocyte adhesion,

activation

ProstaglandinsMast cells, from

membrane phospholipids

Potentiate other mediators

- Vasodilatation, pain, fever

Leukotriene B4 Leukocytes - +Leukocyte adhesion,

activation

LeukotrienesC4 D4 E4

Leukocytes, mast cells + -Bronchoconstriction,

vasoconstriction

Platelet Activating Factor

(PAF) Leukocytes, mast cells + +

Bronchoconstriction, leukocyte priming

IL-1 and TNF Macrophages, other - +Acute-phase reactions, endothelial activation

Chemokines Leukocytes, others - + Leukocyte activation

Macrophages, endothelium

+ + Vasodilatation, cytotoxicity

Generation of Generation of arachidonic acid metabolitesarachidonic acid metabolites and their roles in inflammation. and their roles in inflammation.The molecular targets of some The molecular targets of some anti-inflammatory drugsanti-inflammatory drugs are indicated by a red X. are indicated by a red X.

COX, cyclooxygenase; HETE, hydroxyeicosatetraenoic acid;COX, cyclooxygenase; HETE, hydroxyeicosatetraenoic acid;HPETE, hydroperoxyeicosatetraenoic acid.HPETE, hydroperoxyeicosatetraenoic acid.

Prostaglandin Arachidonic acid Eicosanoid Eicosanoids Leukotriene Prostacyclin Thromboxane Thromboxane-A synthase Essential fatty acid interactions Leukotriene B4 Leukotriene E4 Prostacyclin synthase Leukotriene A4 Leukotriene D4 Leukotriene C4 Thromboxane A2 Arachidonate 5-lipoxygenase Prostaglandin H2 Prostaglandin E synthase Arachidonic acid 5-hydroperoxide Leukotriene C4 synthase

GLOSSARYGLOSSARY abscess abscess acute inflammation acute inflammation adhesion molecules adhesion molecules chemokinesis chemokinesis chemotactic agent chemotactic agent chemotaxis chemotaxis chronic inflammation chronic inflammation contact inhibition contact inhibition degranulation degranulation empyema empyema emigration emigration eosinophil eosinophil erosion erosion exudate exudate fibrin/fibrinous fibrin/fibrinous fibrinogen fibrinogen fibrous/fibrosis fibrous/fibrosis free radicalsfree radicalsgranulation tissue granulation tissue granuloma granuloma hyperemiahyperemiainfectioninfectionkeloid keloid left shift left shift

leukocyte leukocyte leukemoid reaction leukemoid reaction leukocytosis leukocytosis lymphocyte lymphocyte lysosomes lysosomes macrophage (AKA...) macrophage (AKA...) margination margination myeloperoxidase myeloperoxidase neutrophil neutrophil neutrophilia neutrophilia opsonization opsonization organization organization phagocytosis phagocytosis plasma cell plasma cell pseudomembrane pseudomembrane purulent purulent pus pus regeneration regeneration resolution resolution scar scar suppurate suppurate transudate transudate ulcerulcer