inflamamtion - final new

8/13/2019 Inflamamtion - Final New

1/88

IN L MM TION

1


2/88

CONTENTS

INTRODUCTION

HISTORICAL HIGHLIGHTSDEFINITION AND CAUSES

ACUTE INFLAMMATION

-VASCULAR CHANGES

-LEUKOCYTE CELLULAR EVENTS

CHEMICAL MEDIATORS

CHRONIC INFLAMMATION

SYSTEMIC EFFECTS OF INFLAMMATION

2


3/88

Introduction

War is the metaphor for inflammation. Both are necessaryevils

3


4/88

The word inflammation is derived from the state of being

inflammed.

To inflamme means to set afire which conjurs up the

color red , a sense of heat and often pain

The word is derived from the latin word enflammare

4


5/88

DEFINITION AND CAUSES

DEFINITION: Inflammation is defined as the local response

of living mammalian tissues to injury due to any agent. Itis body defense reaction in order to eliminate or limit the

spread of injurious agent.

Inflammation is defined as a complex reaction toinjurious agents such as microbes and damaged, usuallynecrotic cells, that consists of vascular responses,migration and activation of leukocytes, and systemicreactions (Robins)

5


6/88

Purpose of inflammation

It is a body defense reaction to eliminate or limit the

spread of an injurious agent as well as to remove theconsequent necrosed cells and tissues.

It is the channel which the immune system uses, both theinnate and adaptive immune responses

Innate immunity -inherent nonspecific antimicrobialresponse on exposure to a pathogen. Eg. Phagocytosis

Adaptive immunity- lymphocytes specifically recognizeeach pathogen and retains memory , and are able to combatit on reexposure to antigen.

6


7/88

Historical Perspectives

The English word inflammation carries the same

association with heat

The earliest reference to inflammation in ancient medicalliterature is in the Smith Papyrus from around 1650 B.C.Egypt.

The use of a symbol of a flame as the determinant showsthat the ancient Egyptians associated inflammation withheat.

7


8/88

HISTORICAL PERSPECTIVES

Ancient Greeks usedthe term flegmonh to

mean inflammation,

also indicating a hot

thing(flegein to burn).

The Greek term

persists in our word

phlegmon, used todescribe certain

internal inflammatory

lesions

8


9/88

FOUR CARDINAL SIGNS

RUBOR(redness)

TUMOR(swelling)

CALOR(heat)

DOLOR(pain)

Signs of inflammation were first described in the Egyptian papyrus in 3000BC

9


10/88

Fifth Cardinal Sign of Inflammation

Redness andSwelling with Heat

and Pain

...and Loss ofFunction

was added by the

famous 19th century

pathologist RudolfVirchow

...et Functio lsa

10


11/88

The Cellular Theory of Inflammation

was advancedduring the mid-19th centurythrough works ofexperimentalistsJulius Cohnheim,who firstobserved

vasomotor effectsand leukocyteemigration in sitesof inflammation

and Elie11


12/88

Contemporaneously, the

work of Paul Ehrlichdefining the role of

complements and

antibodies in hostdefenses gave rise to a.

Humoral Theory of

Inflammation Modern understanding

of inflammation admits

important roles for both

cellular and soluble12

Th t f t d h i


13/88

The components of acute and chronic

inflammatory responses

13


14/88

ACUTE INFLAMMATION

Acute inflammation is the immediate and early response to

injury,Short duration, lasting from a few minutes up to a few

days

Characterized by fluid and plasma protein exudation and

by a predominantly neutrophillic leukocyte accumulation.

It has three major components

a) Alteration in vascular caliber

b)Structural changes in microvasculature

c)Emigration of the leucocytes

These changes account for five classical signs of acute

inflammation. 14


15/88

Signs of inflammation

Redness (rubor) caused by

hyperaemia

Swelling (tumor) caused by fluid

exudation

Heat (calor)caused by hyperaemia

Pain (dolor) resulting from release of

bradykinin and PGE2

Loss of function- due to combined

effects of the above

15


16/88

16


17/88

STIMULI FOR ACUTE INFLAMMATION

Infections (bacterial, viral, parasitic) and microbial

toxins

Trauma(blunt and penetrating)

Physical and chemical agents (thermal injury, e.g.,

burns or frostbite; irradiation; some environmentalchemicals)

Tissue necrosis (from any cause)

Foreign bodies (splinters, dirt, sutures)

Immune reactions (also called hypersensitivity

reactions)

17


18/88

TERMINOLOGIES

The escape of fluid, proteins, and blood cells from the

vascular system into the interstitial tissue or body cavitiesis known as exudation.

Anexudateis an inflammatory extravascular fluid that has

a high protein concentration, cellular debris, and a specificgravity above 1.020.

Transudate is a fluid with low protein content (most of

which is albumin) and a specific gravity of less than 1.012.

18


19/88

Edema denotes an excess of fluid in the interstitial or

serous cavities; it can be either an exudate or a transudate.

Pus,a purulent exudate, is an inflammatory exudate rich in

leukocytes (mostly neutrophils), the debris of dead cells

and, in many cases, microbes.

19


20/88

20

VASCULAR CHANGES


21/88

VASCULAR CHANGES

CHANGES IN VASCULAR FLOW AND CALIBER

Transient vasoconstriction(seconds)

Vasodilatation involving arteriole first

Local increase in blood flow

redness and warmth(erythema)

Increased permeability resulting in exudation of protein rich fluid into the extra vascular

tissues

Red blood cells become concentrated increasing the viscosity and slowing the

circulation(process called STASIS)

Leucocytes (neutrophils) accumulate along the vascular endothelial surface(process calledMARGINATION)21


22/88

After adhering to endothelial cells the leucocytes squeeze between

them and migrate through the vascular wall into interstitialtissue(process called emigration)

22


23/88

23


24/88

INCREASED VASCULAR PERMEABILITY

In earliest phase, vasodilatation and increased blood flow increase intra vascular

hydrostatic pressure

in filtration of fluid from the capillaries called Transudate.

flow of protein rich fluid and cells called Exudate into the interstitium

( reduces the intravascular osmotic pressure, while increasing the osmotic

pressure of the interstitial fluid.)

Net result is out flow of water and ions into the extra vascular tissues ,accumulation is

called Edema.

How does the normally non penetratable endothelial layer become leaky during acute

inflammation ? 24


25/88

25


26/88

FIVE MECHANISM ARE KNOWN

Endothelial cellcontraction

-Immediate transient response

- Lasts for (15-30 min)

-Capillaries and arterioles are

unaffected

26


27/88

Junctional retraction

-reversible mechanism

-occurs 4-6 hr after initial stimulus

-persists for 24 hr or more

-structural reorganization of cytoskeleton

-induced by cytokine mediator(TNF&IL-1)

27


28/88

Direct endothelial injury

-vascular leakage by causing endothelial cell necrosis anddetachment

- reaction is called immediate sustained response

-direct injury may also induce a delayed prolonged leakage,

begins after a delay of 2-12hr.lasts for several hours or even days

-Attributed to apoptosis, and actions of cytokines.

28


29/88

Leukocyte dependent endothelial injury

-due to leukocyte accumulation during inflammatory response

-leukocyte may be activated, releasing toxic oxygen species and proteolytic enzymes

which cause endothelial injury or detachment

-injury restricted to sites where leukocytes can adhere to the endothelium(venules,and

pulmonary capillaries)

29


30/88

Increased transcytosis

-via an vesiculovacuolar pathway-augments venular permeability,f ollowing exposure to certain

mediators (vascular endothelial growth factor VEGF)

30


31/88

Leakage from new blood vessels

31


32/88

I n acute inf lammation, fluid loss from vessels with

increased permeabil i ty occurs in distinct phases: (1) an immediate transient response lasting for 30

minutes or less, mediated mainly by the actions of

histamine and leukotrienes on endothelium;

(2) a delayed response starting at about 2 hours and

lasting for about 8 hours, mediated by kinins, complement

products, and other factors; and

(3) a prolonged response that is most noticeable after

direct endothelial injury,for example, after burns.

32

LEUKOCYTE CELLULAR EVENTS


33/88

LEUKOCYTE CELLULAR EVENTS

Extravasation of leukocytes from vascular lumen to extravascular space is divided into

Margination and rolling

Adhesion and transmigration between endothelial cells

Miagration in interstial tissue toward a chemotactic stimulus

33


34/88

MARGINATION AND ROLLING

In normal blood flow red and white blood cells travel along the central axis

As vascular permeability increases, fluid exits the vascular lumen and blood flowslows

As a result leukocytes settle out of central column, marginating to vessel periphery

Subsequently they tumble on the endothelium, transiently sticking along the way, a

process called rolling.

34

Th lti t f l k t i ti


35/88

The multistep process of leukocyte migration

through blood vessels, for neutrophils

35

L k t Adh i d T i ti


36/88

Leukocyte Adhesion and Transmigration

Regulated largely by the binding of complementary

adhesion molecules on the leukocyte and endothelialsurfaces,

chemical mediators chemoattractants and certain

cytokinesaffect these processes by modulating the

surface expression or avidity of such adhesion molecules.

The adhesion receptors involved belong to four molecular

families

theselectins,

the immunoglobulin superfamily, the integrins,

and mucin-like glycoproteins.

36


37/88

37


38/88

Selectins

E-selectin (on endothelium) P-selectin (on endothelium & platelets; is preformed and

stored in Weibel Palade bodies)

L-selectin (leukocytes) Ligands for E-and P-Selectinsare sialylated glycoproteins (e.g

Sialylated Lewis X) Ligands for L-Selectin are Glycan-bearing molecules such as

GlyCam-1, CD34, MadCam-1

38


39/88

39

E selectin(ELAM 1)


40/88

E-selectin(ELAM-1)-

Identified as cytokine-inducible

endothelial glycoprotein that binds toboth neutrophils and monocytes

Not found in uninflammed endothelium

Expressed within 30 mins of stimulation

Peak concn. - 2 - 4 hrs

Expressed for about 24 hrs.

Induced by IL-1 and TNF secreted by

macrophages

40


41/88

P-SELECTIN

Platelet activation dependent granule to external membraneprotein (PADGEM)

P-selectin contains the largest number of complement

binding protein like sequences

P-selectin is found in platelets upon activation withthrombin, histamine etc and in activated endothelium.

Ligand lacto-n-fucopentaose III- sialyl LewisX

Bind to neutrophils and monocytes

Expressed within 10- 30 mins

41

L-SELECTIN


42/88

L SELECTIN

Leukocytes use it to interact with carbohydrate moleculescalled vascular addressins sialomucin CD34) on the luminalsurface of the endothelial cells. SYNONYMS: Lectin adhesion molecule-1 and Leu8 and is

believed to be intimately associated with lymphocyte binding

to endothelium

This molecule contains only 2 complement-bindingextracellular domains and is found on lymphocytes, PMNs,

and monocytes

The expression of this molecule is associated with leukocytecell activation and rolling.

42


43/88

Following adhesion to endothelial cells

the expression of L-selectin isdiminished and other leukocytic

integrins that help in transendothelial

migration are increased

43


44/88

44


45/88

45


46/88

46


47/88

INTEGRINS

Family of transmembrane glycoprotein cell surface receptor

adhesins with one alpha and one beta subunit Three domains- large extracellular domain

6 types of beta subunits and 11 different alpha subunits = 16

integrins

Beta 2 subunit is most important in leukocyte adhesion Other functions include helping in diapedesis, leukocyte

migration, T-cell macrophage interactions, clot formation,epithelial cell migration

47


48/88

48


49/88

Integrins- and factors controlling their

expression in adhesion

C5a induces increased surface

expression of LFA-1, Mac-1 and P150-

95 (CD11/18) integrin complex on the

surface of leukocytes.

The ligand on endothelial cells for LFA

and MAC-1

is ICAM-1 molecule on endothelium.

49


50/88

IL-1 stimulates leukocyte adhesion by

inducing synthesis or increasedsurface expression of adhesive

proteins onendothelialcells which can

then bind to receptors on leukocytes- anendothelium dependent defect.

TNF affects expression of both

leukocyte and endothelial molecules.

50


51/88

Integrins(a+bchain)

Heterodimeric molecules VLA-4(b1 integrin) binds to VCAM-1

LFA1 and MAC1 (CD11/CD18) = b2

integrin bind to ICAM

Expressed on leukocytes

51

Endothelial adhesion Receptor on leukocyte Function


52/88

Endothelial adhesion

molecule

Receptor on leukocyte Function

ELAM-1 Sialyl Lewis X PMN adhesion

ICAM-1 Integrins LFA-1

Mac -1 (CD-

11a,b/CD18)

Neutrophil,

Lymphocyte

adhesion

VCAM-1 Integrin VLA-4 Lymphocyte and

monocyte adhesion

52


53/88

Immunoglobulin family

Are expressed on activated

endotheliumLigands are integrins on leukocytes

Induction ICAM-1- 4-6hrs, max. 24hrs

Leukocytes binds to ICAM- flatten over

epithelium

ICAM-1 (intercellular adhesion

molecule 1)

VCAM-1 (vascular adhesion molecule

1)

ICAM-253


54/88

ICAM-2-

33kd, binds to leukocyte integrin a12and a22

ICAM-1,2-localizes leukocytes to the site

of injury

ICAM-3-

87 kd, 5 domains forms Head-tail

arrangement

For T cell activation

VCAM-1 is induced on endothelial cells

b several inflammator c tokines54


55/88

PECAM-1 (CD31)

cell surface glycoprotein of 130kdfound on platelets, endothelial cells,

monocytes and neutrophils and some T-

cell subsets Localized at endothelial cell junctions-

may provide means by which

endothelial cells may lose theiradhesiveness and permit emigration

Ligand is aVb3 integrin55

M i lik l t i


56/88

Mucin-like glycoproteins

Heparan sulfate (endothelium)

Ligands for CD44 on leukocytes

Bind chemokines

56


57/88

Rolling leukocytes become activated by

chemokinessuch as monocyte chemoattractant

protein 1 and RANTES, presented by

the activated endothelial surface. The activated leukocytes can bind to

other endothelial adhesion molecules,

such as ICAM-2, and starttransmigrating into the vascular intima.

Prolonged endothelial stimulation

results in more of ICAM-157

Diapedesis


58/88

p

Neutrophils and monocytes create a passage between the

endothelial cells.

Diapedesis typically occurs in venules and is mediated by

PECAM-1(CD31)

A leukocyte leading edge process rich in F-actin, catenin

and LFA-1 interacts with endothelial cell surface in

creating this channel

The endothelial zonula adherens junction undergoes rapid

assembly and disassembly during the process

58

Emigration


59/88

g

Adherent neutrophils throw out cytoplasmic pseudopodsand cross the basement membrane by damaging it with

secreted collagenases and escapes into the extravascularspace.

First 24 hours- PMNs escape

24-48 hours- monocytes and macrophages

Neutrophils are shortlived.

Monocyte migration is sustained

Chemotactic factors for neutrophils and monocytes areactivated at different phases of the response

59

I t ti ith ll f i t ll l t i


60/88

Interaction with cells of intercellular matrix

After crossing endothelium leukocytes have to interact

with cells of intercellular matrix using VLA molecules of

the 1 integrin group

VLA-2,3 for collagen

VLA-3,6 for laminin

VLA-3,4,5 for fibronectin

60


61/88

61

CHEMOTAXIS AND ACTIVATION


62/88

After extravasation leukocyte emigrate toward the site of injury along

a chemical gradient in a process called chemotaxis

Both endogenous and exogenous substances can act as chemotactic

agent for leukocyte including:

-soluble bacterial products, paricularly peptides with N-formyl

methionine termini-components of complement system, particularly C5a

-products of lipoxygenase pathway of arachidonic acid

(AA)metabolism, leukotrieneB4 (LTB4)

-cytokines

62

Leukocyte activation


63/88

Leukocyte activation

63

Biochemical events in leukocyte activation


64/88

Biochemical events in leukocyte activation

64

PHAGOCYTOSIS


65/88

PHAGOCYTOSIS

Process of engulfment of solid particulate material by the

cells of the size visible to light microscope

Cells performing phagocytosis are microphages (PMN)

and macrophages

Results in the eventual containment of the pathogen in a

within a membrane- delimited structure -phagosome

65

Timed sequential events in the formation of


66/88

a phagosome

66

STEPS


67/88

STEPS

Recognition and attachment

(opsonisation) Engulfment stage

Secretion (degranulation)

Digestion (degradation)

67



68/88


Phagocytes are recognized and attracted to bacteria by

chemokines released by bacteria and tissue proteins

Opsonized by serum complement, immunoglobulin (C3b,

Fc portion of IgG)

Corresponding receptors on leukocytes (FcR, CR1, 2, 3)

leads to binding

Microorganisms get coated with opsonins from the serum

to make a bond between bacteria and cell membrane of the

phagocytes as phagocyte possesses receptor for opsonin

68

O i i


69/88

Opsonization- coating the pathogen with a few recognizableligands which enable the pathogen to bind to and ingest the pathogen

69

OPSONINS


70/88

OPSONINS

IgG-Fc fragments

C3bgenerated by complement pathway

Lectins-carbohydrate binding proteins in

plasma

binding to bacterial cell wall

70


71/88

The activation of the neutrophils makes

them more efficient at phagocytosis andkilling. Opsonisation of bacteria by

complement and immunoglobulins

renders them more readilyphagocytosed.

This entire process is orchestrated by a

plethora of chemical mediators derivedfrom injured tissues, bacteria, plasma

proteins and leucocytes

71

Engulfment stage


72/88

Engulfment stage

Opsonized particles bonded to the

phagocyte is engulfed by formation ofcytoplasmic pseudopods around the

particle due to activation of actin

filaments beneath the cell wall,enveloping it in a phagocytic vacuole.

72


73/88

73


74/88

74

Degranulation stage


75/88

Degranulation stage

Preformed granule stored products of PMN

azurophilic granules are fused to phagosomes phagocytosistriggers an oxidative burst engulfment and formation of

vacuole which fuses with lysosomal granule membrane

(phagolysosome)

Granules discharge within phagolysosome and

extracellularly (degranulation)

Lysosomes discharged into intercellular space

75

Killing/degradation


76/88

Killing/degradation

Killing byHydrolytic

enzymes

Oxygen-

DependentBactericidal

enzymes

Oxygen-

independentBactericidal

enzymes

Nitric oxide

Mechanismsenzymes

After the

microorganisms are

killed by antibacterial

substances they are

degraded by

hydrolytic enzymes

76

Oxygen-dependent bactericidal mechanisms


77/88

Require oxygen & redox potential of -160mv

Within seconds of stimulation the neutrophils sharplyincrease their oxygen uptake (RESPIRATORY BURST)

because of two biochemical events-

One electron reduction of molecular oxygen to superoxideradical

oxidation of glucose via HMP shunt with resultantproduction of NADPH and reduced glutathionine (GSH)

A respiratory burst oxidase is activated that catalyzes thetransfer of electrons from NADPH to oxygen through anelectron transport chain consting of a flavin and

cytochrome 558 to create superoxide.

77


78/88

Extracellular superoxide is also converted to hydrogenperoxide using plasma protein ceruloplasmin

H2O2 diffuses across cell membranes and is utilized byMPO enzyme as substrate with halide ions to form HOClions

Microbicidal activity by forming toxic, reduced oxygenmetabolites such as superoxide anion O2- & H2O2.iscomparitively weaker than that of HOCl.

78


79/88

Detoxification of hydrogen peroxide

Reduced glutathionine(GSH) is acted upon byenzyme glutathione peroxidase to detoxify H2O2.

It is also detoxified in the cytoplasm by catalase to

water and oxygen.

79

Oxygen-Independent Antimicrobial Activity


80/88

Oxygen Independent Antimicrobial Activity

Bactericidal permeability increasing protein (BPI) causes

phospholipase activation, phospholipid degradation and

increased membrane permeability

Lysozyme causes degradation of bacterial coat

oligosaccharides

Major basic protein (MBP) is cytotoxic component of

eosinophil granules- parasites

Defensinsare pore-forming antibacterials. alpha defensins

are small antimicrobial peptides( eg.HNP-1,2,3) ,rendering

them susceptibile to cathepsins and ROS esp. for bacteria

and fungi.

80


81/88

81


82/88

Inhibition of locomotion--- serum of certain patients,

drugs- corticosteroids and phenylbutazone.

Deficiencies in generation of chemotactic signals---

complement system

Disorders of phagocytosis- Opsonin deficiencies

complement or IgG sickle cell disease failure of

alternate pathway activation.

Defects of engulfment- morphine analogues, diabetic

ketoacidosis

Disorders of lysosomal fusion steroids, colchicine,

Chediak-Higashi syndrome

82

Chemical Mediators


83/88

Mediators- in plasma or at local site of inflammation

Induce effect by binding to specific receptors on target

cells.

Stimulate target cells secondary effector molecules

amplify a particular response or have an opposing

function Act on only one or very few targets, or widespread

activity.

Function is tightly regulated

Quickly decay-----AA metabolites Eliminated -------antioxidants scavenge toxic O2

metabolites

Inhibited------complement inhibitory proteins.83

Chemical mediators of inflammation


84/88

84

Vasoactive amines


85/88

Histamine- tissues- in mast cells adjacent to vessels

( basophils, platelets)

85


86/88

Neuropeptides

small peptides, such as substance P andneurokinin A,

Transit pain signals, regulate vessel tone and

modulate vascular permeability

Nerve fibres secrete neuropeptides

Commonly seen in lung & GIT

86


87/88

Plasma proteases

Three interrelated plasma derived factors- kinins,clotting system, complement activation of

Hageman factor

87


88/88

Increased vascular permeability

and leukocyte emigration

Increased

permeabili

ty,

arteriolar

dilation,

leukocyte adhesion

vascular

permeability and

inflamamtion - final new

Documents