Case 7- inflammation

Question 1

Why is acute inflammation important

Answer 1

A precursor for the repair processes in damaged tissue. It brings the host’s defence mechanism from circulation to the sites they are needed. They remove necrotic cells and tissues and promote healing and reconstruction of damaged tissure

Question 2

What triggers inflammation

Answer 2

PAMPS (found on the outside of pathogens) and DAMPS (due to localised tissue injury) trigger inflammation.

Question 3

Characteristics of acute inflammation

Answer 3

Rapid onset, short duration, mainly Neutrophils and prominent characteristic response.

Question 4

Characteristics of chronic inflamation

Answer 4

Slow onset (days), long duration (weeks, months), involves Monocytes/ Macrophages/ Lymphocytes, there is a less characteristic response.

Question 5

Cardinal symptoms of inflammation

Answer 5

Redness (rubor), Heat (calor), Swelling (tumor), Pain (dalor) and loss of function.

Question 6

Acute inflammation- vasodilation of small vessels (neurotransmitter)

Answer 6

Relaxation of smooth muscle cells within the vessel walls leading to slowed blood flow. Histamine drives this by binding to H1 receptors, there is decreased blood flow. There will be pooling of blood at the site causing heat and redness.

Question 7

Acute inflammation- increased vascular permeability of the microvasculature

Answer 7

This enables plasma proteins and leukocytes to leave the circulation and enter the interstitial space. Occurs primarily via endothelial cell retraction via the breakdown of adjacent cell gap Junctions. Can also occur indirectly via leukocyte mediated damage, the leukocytes become over excited and attack the endothelial cells, or direct endothelial cell injury (such as burns and trauma). Vascular permeability is driven by Histamine binding to H1 receptors. Causes swelling and pain, the pain is due to the dissociation of the gap junctions and the swelling.

Question 8

Acute inflammation- emigration of leukocytes

Answer 8

Leukocytes move from the circulation to the site of injury and infection. Is a multi-step process. Vasodilation and increased vascular permeability encourages stasis where the blood slows down, so leukocytes can leave the blood

Question 9

Transudate

Answer 9

When the fluid leaves the vasculature but the proteins and Leukocytes dont. Less oncotic then exudate

Question 10

Exudate

Answer 10

The fluid that moves from the vasculature to the interstitial space, contains high protein and Leukocyte levels. More oncotic then transudate

Question 11

Pus

Answer 11

When the fluid leaves the vasculature to the interstitial space containing high protein levels and Leukocytes, in pus the Leukocytes are dead (mainly neutrophils)

Question 12

The multistep process of the Emigration of Leukocytes

Answer 12

1) Margination
2) Rolling
3) Stable adhesion
4) Emigration/ Transmigration/ Diapedesis
5) Chemotaxis

Question 13

The multistep process of the Emigration of Leukocytes- Margination

Answer 13

Leukocytes move from the central part of the blood vessel to the peripheral zone of the blood vessel, directly engaging with the endothelial cells. It is mediated by stasis (slowed blood flow)

Question 14

The multistep process of the Emigration of Leukocytes- Rolling

Answer 14

Leukocytes rolling along the surface of the endothelial layer. Slowed by selectin/glycoprotein and integrin/integrin ligand interactions, which are fragile and easily break. The leukocytes express glycoproteins and the endothelia cells selectins. This slows down the movement of the Leukocyte along the endothelial layer

Question 15

The multistep process of the Emigration of Leukocytes- stable adhesion

Answer 15

Cytokines released from the site of injury increase integrin and integrin receptor binding (affinity) – this stops the leukocyte at site of infection / injury

Question 16

The multistep process of the Emigration of Leukocytes- emigration/ transmigration/ diapedesis

Answer 16

Leukocytes extend their pseudopodia downwards and squeezes through endothelial gap junctions, they are made larger by increased vascular permeability. Emigration is mediated by a protein called PCAM1

Question 17

The multistep process of the Emigration of Leukocytes- Chemotaxis

Answer 17

Leukocytes follow a chemokine gradient to find and locate pathogens –complement proteins C3a & C5a are potent chemokines. They move down the chemotaxic gradient to the site of infection.

Question 18

The white blood cells which you find in acute inflammation

Answer 18

Presence of neutrophils (6-24 hours) which are replaced by Macrophages (24-48 hours). This because Neutrophils have the highest amount of Glycoproteins so they bind the easiest to the endothelial layer.

Question 19

Causes of chronic inflammation

Answer 19

• Persistent infection- which the body cant get rid of.
• Hypersensitivity disease- auto antigens (rheumatoid arthritis), microbes (inflammatory bowel disease), allergic disease.
• Prolonged exposure to toxic agents- exogenous exposure (dust, asbestos particles), can be endogenous like atherosclerosis

Question 20

The 3 major components of inflammation

Answer 20

• Infiltration with mononuclear cells
• Tissue destruction, can be due to the presence of a microbial threat. Necrosis is mediated by the continued presence and activation of mononuclear immune cells and inflammatory chemical mediators.
• Attempts at healing- collagen deposition and fibrosis mediated by fibroblasts.

Question 21

Cellular mediators of chronic inflammation

Answer 21

The two main cellular mediators of chronic inflammation are Macrophages and Lymphocytes. The Macrophages initiate Phagocytosis to get rid of the offending agent, they then initiate tissue repair by secreting growth factors and cytokines which recruit other cellular mediators. The Macrophages activate the Lymphocytes via antigen presentation on the MHC2 complex. The T Lymphocytes then secrete Cytokines/ Chemokines. It also stimulates B cells to secrete antibodies. This then propagates chronic inflammation.

Question 22

The two complication of chronic inflammation?

Answer 22

Granulomatous and Fibrosis

Question 23

Granulomatous inflammation

Answer 23

Cellular attempt to contain an offending agent that is difficult to eradicate. Mediated by Macrophages which differentiate into specialised epithelioid cells which form a “cage” around the offending agent with a necrotic centre.

Question 24

Types of Granulomatous

Answer 24

Depends on the substance which induces granulomatous inflammation:
Immune granulomas- infectious organisms like bacteria and fungi
Foreign body granulomas- foreign objects and suture fragments

Question 25

Diseases caused by Granulomatous inflammation

Answer 25

Tuberculosis, leprosy, sarcoidosis and syphilis

Question 26

Why does fibrosis occur

Answer 26

When the tissue injury is severe or repetitive you get irreversible collagen deposition. Normally the collagen deposited is removed but not in fibrosis. Due to dysregulation of the wound-healing response

Question 27

Fibrosis

Answer 27

Fibrosis is due to the excessive accumulation of fibrous connective tissue (components of the extracellular matrix (ECM) such as collagen and fibronectin) in and around inflamed or damaged tissue, which can lead to permanent scarring → organ malfunction → death. ECM deposition is driven by fibroblasts

Question 28

Fibrosis mechanism of action

Answer 28

1) A persistent stimulus which chronic inflammation 2) Continued Activation of Macrophages and Lymphocytes leads to the secretion of Cytokines (TNF, IL-1, IL-4) and Growth Factors (TGF-b, FGF) 3) This promotes proliferation of Resident Fibroblasts & Recruitment of Bone Marrow Fibroblasts 4) Leading to the excessive synthesis and deposition of ECM Proteins (Collagen) 5) Production of these cytokines leads to a reduction in the breakdown of collagen via Inhibition of MMPs (Matrix metallopeptidase) 6) Continued failure to adequately contain or eliminate the inciting factors can exacerbate the inflammatory response and lead to a chronic wound-healing response, with continued tissue damage, repair and regeneration, ultimately resulting in fibrosis.

Question 29

Serous inflammation

Answer 29

The slow movement of cell fluid into spaces created by cell injury or into body cavities. The fluid is not infected and does not contain a large number of leukocytes. For example, a skin blister from a burn or viral infection. The fluid will be within or immediately beneath the damaged epidermis

Question 30

Fibrinous inflammation

Answer 30

The passage of fibrinogen out of the blood and into the extracellular space after an increase in vascular permeability or procoagulant stimuli (i.e. cancer cells). Appears as an eosinophilic (bright pink) meshwork or amorphous coagulum. Can occur in serous cavities where there is the conversion of fibrinous exudate into a scar between the serous membranes.

Question 31

Purulent inflammation

Answer 31

Characterised by the production of pus consisting of neutrophils, liquefied cellular debris and edema fluid. Commonly due to pyogenic (pus producing) bacterial infections that cause liquefactive tissue necrosis such as Staphylococci. Abscesses are localised collections of purulent inflammatory tissue with a central mass of necrotic leukocytes and tissue cells surrounded by preserved neutrophils. The pus is enclosed by surrounding tissue.

Question 32

Ulcers

Answer 32

A local defect or excavation of the surface of an organ or tissue that is produced by the sloughing (shedding) of inflamed necrotic tissue. Occurs when tissue necrosis and resultant inflammation is on or near a surface. It is most commonly encountered in the mucosa of the mouth, stomach, intestines, or genitourinary tract, and the skin and subcutaneous tissue of the lower extremities in older persons who have circulatory disturbances that predispose them to extensive ischemic necrosis.

Question 33

Histamine inflammation table

Answer 33

Mast cell/ basophil Vasodilation Increased permeability

Question 34

Plasma proteins inflammation table

Answer 34

Liver Vasodilation Increased permeability Leukocyte recruitment

Question 35

Prostaglandins

Answer 35

Mast cell/ basophil/ Nuetrophil Vasodilation Increased permeability

Question 36

Leukotrienes

Answer 36

Mast cell/ basophil/ neutrophil Increased permeability Increased Leukocyte recruitment

Question 37

Cytokines

Answer 37

Mast cells/ Macrophages Vasodilation Increased permeability Leukocyte recruitment

Question 38

Chemokines

Answer 38

Mast cell / Macrophages | Leukocyte recruitment

Question 39

Bradykinin

Answer 39

Made from kininogens (plasma proteins) produced by the liver. It increases vascular permeability by gap junction dissociation and increased histamine release from mast cells. It increases local endothelial eicosanoid production

Question 40

Eicosanoids

Answer 40

Prostaglandins and Leukotrienes. Made from oxidation of Arichodonic acid

Question 41

How are Prostaglandins and Thromboxane's produced

Answer 41

Membrane phospholipids -> Arachidonic acid using the enzyme Phosphilpase A2. Arachidonic acid -> Prostglandins and Thromboxanes using the enzyme Cyclooxygenase

Question 42

How is Leukotriene A4 produced

Answer 42

Membrane phospholipids -> Arachidonic acid using the enzyme Phospholipase A2. Arachidonic acid -> Leukotriene A4 using the enzyme 5-lipoxygenase and FLAP

Question 43

How is Leukotriene B4 produced

Answer 43

Membrane phospholipids -> Arachidonic acid using the enzyme Phosphilpase A2. Arachidonic acid -> Leukotriene A4 using the enzyme 5-lipoxygenase and FLAP. Leukotriene A4 -> Leukotriene B4 using the enzyme Epoxide hydrolase.

Question 44

How is Leukotriene C4 produced

Answer 44

Membrane phospholipids -> Arachidonic acid using the enzyme Phosphilpase A2. Arachidonic acid -> Leukotriene A4 using the enzyme 5-lipoxygenase and FLAP. Leukotriene A4 -> Leukotriene C4 using the enzyme Leukotriene C4 synthase

Question 45

The main systemic effects of inflammation

Answer 45

1) Fever (pyrexia) 2) Increase in acute phase proteins. 3) Increase in Leukocyte cell number 4) Sepsis

Question 46

What causes fever in inflammation

Answer 46

It is mediated by pyrogenic microorganisms and the Prostaglandin E2 production

Question 47

Pyrogens

Answer 47

Components from microorganisms that induce fever, i.e. LPS which is found on the outside of gram negative bacteria. They act like pathogen-associated molecular patterns (PAMP) and bind to Toll-Like Receptors

Question 48

Pyrogen mediated mechanism of action of fever

Answer 48

1) Pyrogens on the surface of Gram Negative Bacteria, bind to the PRR on macrophages 2) Pyrogen/PRR binding results in the production and secretion of cytokines IL-6, IL-1b , TNF-a into the blood 3) These cytokines migrate to the Blood Brain Barrier and bind to receptors on Brain Endothelial Cells 4) This activates Prostaglandin E2 Synthesis. Phospholipids in the membrane of blood brain barrier endothelial cells → Arachidonic acid (by the enzyme Phospholipase A2) → Prostaglandin E2 (PGE2) Synthesis (by Cyclooxygenase). 5) PGE2 enters the brain vasculature and binds to receptors in the hypothalamus, which raises the body temperature.

Question 49

Why is a fever useful?

Answer 49

Bacteria work best at the bodies normal temperature, so by increasing the temperature you reduce bacteria reproduction. A high temperature also causes hyperproliferation of leukocytes i.e. Macrophages. You can treat fever by blocking the enzymes from working.

Question 50

What causes the increase in acute phase proteins in inflammation?

Answer 50

Mediated by cytokine released by macrophages (IL1, and IL6, and TNFα) which stimulate the Liver to produce acute phase proteins like C-reactive proteins.

Question 51

Why is the increase in acute phase proteins useful in inflammation?

Answer 51

C-reactive protein (CRP) can bind to bacterial and fungal cell envelopes. This can cause opsonisation (attracting phagocytic Macrophages). It can also promote the classical complement activation which drives the recruitment of other phagocytic leukocytes and drives the destruction of bacteria and fungi using the membrane attack complex.

Question 52

Clinical blood biomarkers of inflammation?

Answer 52

↑ C-Reactive Protein (CRP) ↑ Fibrinogen- relies on the use of the Erythrocyte Sedimentation rate test (ESR), the more inflammation there is the higher ESR is because there is more fibrinogen

Question 53

Inflammation- increase in cell number

Answer 53

Caused by micro-organism exposure (PAMP/PRR binding). This causes increased Cytokine production by macrophages (IL-1, IL-6, IL-8) which stimulate haematopoietic stems cells in the bone marrow to proliferate and differentiate into leukocytes, usually neutrophils. The Leukocytes are then released into circulation and increased white cell count (WCC). Typically rises to 20,000 cells per ml and up to 100,000 cells per ml.

Question 54

Why do you get s drop in blood pressure in sepsis?

Answer 54

Sustained and increasing microbiological stimulus can lead to continued activation of macrophages and other immune cells (PAMP / Toll like receptors binding). It can lead to a hyperinflammatory response leading to the production of inflammatory cytokines (cytokine storm). The cytokines and ROS from phagocytic leukocytes drives the damage of endothelial vasculature. This can increase vascular permeability, causing the efflux of blood plasma out of the circulation and into the interstitial space.

Question 55

Sepsis- clots

Answer 55

In sepsis you get disseminated intravascular coagulation (DIC) where blood clots form throughout the body, blocking small blood vessels. This is caused by the hypersecretion of acute phase proteins.

Question 56

Local factors that effect wound healing

Answer 56

Type, size location of wound Infection and contamination Growth factors and cellular mediators Local blood flow, effected by co-morbidities

Question 57

Systemic factors that effect wound healing

Answer 57

Increasing age Nutritional status (especially vitamin C) Co-morbidities, especially diabetes or CV disease Drug treatments, especially chronic glucocorticoids

Question 58

Wound healing- extent and location if injury

Answer 58

There are two main types of wound healing, primary intention and secondary intention. In both types, there are four stages which occur; haemostasis (process to prevent and stop bleeding), inflammation, proliferation, and remodelling.

Question 59

Healing by primary intention

Answer 59

Less collagen deposition and more epithelialisation. Occurs in small traumatic and surgical wounds (scalpel incision) where the dermal edges are close together. There will be clearance of the injurious stimuli as well as mediators and neutrophils

Question 60

Healing by secondary intention

Answer 60

More collagen deposition less epithelialisation. Typical in larger traumatic wounds (dog bite) and occurs when the sides of the wound are not opposed, therefore healing must occur from the bottom of the wound upwards. There may be connective tissue replacement and loss of function

Question 61

Wound healing- infection

Answer 61

Persistent infections and failure to remove the offending agents impairs wound healing

Question 62

Wound healing- production of local growth factors

Answer 62

* Transforming Growth Factor (TGF) Beta – Activates fibroblast to deposit collagen * Vascular Endothelial Growth Factor (VEGF) – Neoangiogenesis (new blood vessels) * Fibroblast Growth Factor (FGF)– Fibroblast proliferation * Epidermal Growth Factor – Epithelization

Question 63

Wound healing old age

Answer 63

The inflammatory response is decreased or delayed, as is the proliferative response. Remodelling occurs, but to a lesser degree, and the collagen formed is qualitatively different.

Question 64

Wound healing- nutrients

Answer 64

Poor nutrient status will compromised the patient's ability to heal and prolong wound healing. Vitamin C play an important role in collagen synthesis and is required for collagen deposition and scar formation.

Question 65

Wound healing- diabetes mellitus

Answer 65

Causes the peripheral vasculature to become stiff and rigid, impairing local blood flow throughout the small vessels at the surface of the wound. It inhibits leukocyte recruitment and activation at the site of infection. Can lead to gangrene and amputation. This is due to impaired NO signalling which is needed in vasodilation. The narrowing of the blood vessels leads to a higher blood pressure which limits circulation to the lower extremities.

Question 66

Wound healing- chronic glucocorticoid treatment

Answer 66

Suppresses inflammation. Glucocorticoid receptors and nuclear hormone receptors produce proteins which inhibit the inflammatory response. Inhibits TGF beta which is the main growth factor for stimulating fibroblast secretion of collagen. It also destroys the collagen which is already there

Question 67

The mechanism in which Glucocorticoid inhibits the inflammatory response

Answer 67

1) Production of Lipocortin which inhibits Phospholipase A2 – ultimately inhibiting the production of proinflammatory mediators prostaglandin and leukotrienes 2) Directly and indirectly Inhibits the transcription factor NFKB – which serves to inhibits toll like receptor signaling and cytokine production in macrophages 3) Inhibits the recruitment and activation of leukocytes

Question 68

How is tissue repaired?

Answer 68

It is either regenerated or the scar formation/collagen deposition

Question 69

Regeneration- Labile tissue

Answer 69

The tissue is continuously dividing so it regenerates rapidly after injury. I.e. mucous membranes (easily damaged as exposed to outside environment), Lymphoid cells and Haematopoietic cells.

Question 70

Regeneration- stable tissue

Answer 70

Long lifespan, “capable” of rapid division following injury when they receive the correct growth factors. (Smooth muscle cell, kidney, lung, fibroblasts and endothelial cells).

Question 71

Regeneration- permanent tissuse

Answer 71

Very limited regenerative ability - may regenerate portions of the cell (neurons, cardiac muscle cells, Lens epithlium).

Question 72

How the extent of tissue injury effect tissue regeneration?

Answer 72

The integrity of the extracellular matrix and underlying basement membrane is important in regenerative capacity. The basement membrane is needed for growth factor production which allows the cells to progress through the cell cycle and proliferate. There are also stem cells within the basal layer which are in direct contact with the basement membrane. If the basement membrane is damaged, stem cells cant be stimulated to divide impairing regenerative capacity

Question 73

Why is the Liver so good at regeneration?

Answer 73

The Liver is able to regenerate due to proliferation of remaining hepatocytes (triggered by cytokines and growth factors) and repopulation from progenitor cells which occurs when hepatocyte proliferation is impaired.

Question 74

Why does collagen deposition occur?

Answer 74

Occurs when regeneration isn't possible because the basement membrane is damaged and the stem cell niche is destroyed. Instead there is proliferation of resident and bone marrow fibroblasts which make the collagen and connective tissue. This provides tensile strength to the damaged tissue

Question 75

Regeneration- acute inflammatory phase

Answer 75

Removes injurious agents by recruitment of phagocytic leukocytes (neutrophils), limiting tissue damage. Prepares the wound environment for repair – Macrophages produce Cytokines and Growth Factors (such as TGF beta which tells the fibroblast to produce collagen). The Cytokines and growth factors also cause cellular recruitment and proliferation of fibroblasts from the bone marrow.

Question 76

Stages in tissue regeneration

Answer 76

1) A tissue injury 2) Acute inflammatory response 3) Proliferative phase 4) Remodelling phase

Question 77

Tissue regeneration- Proliferative phase

Answer 77

1) Angiogenesis 2) Granulocyte tissue formation 3) Epithelialisation

Question 78

Tissue regeneration- Granulocyte tissue formation

Answer 78

* TGFb is secreted from Macrophages, this promotes resident fibroblast activation and bone marrow fibroblast recruitment * The fibroblasts are stimulated by TGF-beta to start synthesising and laying down collagen to fill the wound. This forms loose connective tissue. * Granulation tissue is pink, soft and very fragile. Intermediate stage before scar tissue formation. * Macrophages also produce fibroblast growth factor (FGF) which promotes fibroblast proliferation.

Question 79

Tissue regeneration- Epithelialisation

Answer 79

Cells surrounding the injury release epidermal growth factors (EGF) which stimulates epithelial cell growth to close the wound

Question 80

Tissue regeneration- Remodelling phase

Answer 80

Maturation & reorganisation of connective tissue by Matrix Metalloproteinases (enzymes which breakdown collagen). The blood vessels which were produced are now destroyed, this is called avascularisation. The scar increases in tensile strength over the next 3-6 months and the wound balances due to avascularisation (regression of new blood vessels formed during the proliferative phase). The Leukocyte’s and fibroblasts depart, those that remain become inactive.