inflammation and tissue repair pt 1

Immunity Lines of defense

Immunity Lines of defense

• First line: innate (natural/native) immunity = physical/mechanical/biochemical barrier. {ex. blink reflex, enzymes in tears, lashes}

• Second line: innate (inflammation) {ex. inflammatory mechanisms are activated, vasodilation, increased permeability, phagocytes move into engulf substance}

• Third line: adaptive (acquired/specific) immunity {ex. immune response activated, immune cells recognize and destroy substance} adequate response = resolution inadequate response = disease spread

Innate= happens the same way every time

inflammation

is an immunologic defence against tissue injury, infection, or allergy.

Virus caused inflammation

Don’t have cell walls (bundle of MRNA) viruses enter human cells, multiply, rupture the cell, and with that rupture release chemical mediators such as histamine, which initiate the inflammatory process. Harder for immune cells to destroy as they are in host cells. High lymphocyte counts mean a viral infection.

Bacteria caused inflammation

Bacteria has cell walls, so they can’t enter cells but use the host body for resources to multiply. As they multiply they damage native cells as they release endotoxins. This initiates a inflammatory response as cells are injured. If a bacterial infection reaches the blood stream it’s known as sepsis. High neutrophil counts means bacterial infection.

non viral/bacterial inflammation causing

physical trauma, foreign objects, burns, radiation, necrosis, and chemicals such as (acids, alkalis, & oxidizing agents). Stress from environmental or psychological stressors.

Excessive ineffective inflammatory responses

local tissue damage from compression, developing chronic inflammation, systemic pathology (atherosclerosis, chronic renal disease, neurological disorders).

Acute Inflammation

Warmth, swelling, redness, shows response is working. Good kind of inflammation.

Steps in Acute inflammation

1. Tissue is injured and releases chemical mediators

2. Vasodilation and increased blood flow

3. swelling and retraction of activated endothelial cells

4. Increased vascular permeability and leakage of small plasma proteins

5. “walling off” damage isn’t spread (fibrin clots)

6. Movement of immune response cells to the site of injury

7. Exudate forms

8. movement of glucose and oxygen to the site of injury requiring repair

9)Release of chemical repair factors from activated endothelial cells

Goals of Inflammatory process

1. limit and control inflammatory process

2. prevent and limit infection and further damage

3)To alert products of healing through cellular response

4. removal of injured tissue and preparation of healing

Stage of Acute Inflammation

1. Vascular stage

chemical mediators are released from damaged cells, this triggers dilation and increased blood flow, and permeability, and cells within the bloodstream flood into the area of damaged tissue. This allows for dilution and phagocytosis to engulf harmful substances.

2. Cellular stage

also regulated by chemical mediators

Three steps:

• Chemostaxis (movement of different cells)

• cellular adherence (attaches circulating leukocytes to the area of damaged tissue)

• cellular migration/diapedesis (leukocyte squeezes between endothelial cells to get to area of injury) & phagocytosis

Cell derived inflammatory mediators

inside of cells, when released trigger inflammatory process

• Histamine (vasoactive, found in mast cells, basophils, and platelets)

• serotonin (vasoactive, found in platelets)

• cytokines (Tumour necrosis factor & interleukin 1) TNF & IL_1 (produced by WBC’s = lymphocytes, monocytes, macrophages), & endothelial, epithelial cells. (very important for the regulation of inflammation)

• chemokines (chemotactic = draws other cells) are chemo-attractants that recruit leukocytes. (both pro-inflammatory and anti-inflammatory = regulation of inflammation.

• Platelet-activating factor (generated from the phospholipid layer of all IM cells, activates platelets, and stimulates other cells involved in the inflammatory process, enhancing serotonin release and causing changes in vascular permeability, enhancing leukocyte adhesion, chemotaxis, and formation of other IM’s

• Arachidonic acid (found in phospholipids of the cell membrane, release initiates a process resulting in the production of IM’s {ex. prostaglandins, leukotrienes)

Plasma derived inflammatory mediators

outside of cells circulating within the bloodstream, help enhance effects of chemical mediators, inactive until stimulated.

• complement system : proteins that activate a cascade of inflammatory mediators (IM’s)

• Clotting system: promotes and surpasses clotting, formation of fibrin mesh (walling-off), clotting factors produce and release IM’s

• Kinin system: potent vasoactive IM, trigger other IM’s (synthesized in the liver and then circulated in plasma in high concentrations)

Cytokines TNF & IL-1

Local effects:

Inflammation

• (Vascular endothelium) expression of leukocyte adhesion molecules, production of IL-1 chemokine

• (Leukocytes) activation, production of cytokines

  Repair

• (fibroblasts) proliferation, collagen synthesis

  Systemic effects:

• fever

• leukocytosis = increased production of wbc

• lowers appetite

• increases sleep

• increases acute phase proteins

Prostaglandin

• a hormone of lipid autacoids derived from arachidonic acid by the action of cyclooxyrgenase (COX) isoenzymes

• not secreted from a gland, created directly from area of injury.

• their presences bothers nerves causing pain

• stimulates blood clot formation and contraction of vessel wall when bleeding

• Fever occurs when production of prostaglandin is in the central nervous system (anterior hypothalamus)

Local inflammation manifestation

• erythema (redness)

• swelling (edema)

• pain

• heat

• loss of function

• possible lymphodentitis (lymph node enlargement)

Systemic inflammation manifestation

• pyrexia (fever)

• Leukocytosis (increased production of WBC’s)

• fatigue

• weight loss

• increased plasma proteins

Neutrophils (WBC)

• first white blood cell (leukocyte) to enter the site of injury

• high concentration = bacterial infection

• known as the workhorse

• monocytes arrive after

• chemotactic = attracts other cells

Lymphocytes

• high concentration = viral infection

• Main cells for chronic inflammation/ immune response

Monocytes > macrophages

• largest circulating leukocytes

• circulate as monocytes and once in the tissue area will become macrophages

• Produces potent vasoactive mediators

• also associated with chronic infection

• cell of inflammation

• engulf bacteria and dead cells, clear area for new cells

• Arrive within 72hrs of injury and remain for weeks after

• arrive after neutrophils

Masts cells

• leukocyte (WBCs)

• comes from marrow, matures in tissue

• has +++ granules

• When activated release granules containing histamine and heparin

• Trigger other mediators prostaglandin, leukotriene, and platelet-activating factor

• Cell of inflammation

Endothelial cells

• cell of inflammation

• lines vessels (shrinks to increase permeability to tissue)

• allows adhesion and migration of leukocytes to area of injury

• controls clotting mechanisms (to allow fibrin, and continued blood flow)

• Regulate immune cell proliferation through secretion of CSF (colony-stimulating factors)

Leukocytes (wbc)

• neutrophils

• eosinophils

• mast cells

• basophils (contain & activate inflammatory mediators histamine, leyukotrine, & prostaglandin)

Lymphatic system

• drain all exudate and extracellular fluid with waste to lymph nodes

• lymphangitis = inflamed node due to bacteria or virus in the node

• once area is clear healing starts

Normal Microbiome

formally known as “flora” the microorganisms that colonize the body's surface. Doesn’t normally cause disease and is a commensal relationship. (to benefit one and not affect the other).

Opportunistic Microorganisms

can cause disease if their is a break in the defences

Three Plasma protein systems

1. complement system (releases IM that create a cascade)

• Classical pathway

• Alternative pathway

• Lectin pathway

2. Clotting system (promotes the formation of clots through fibrin produced by fiborblats and create a clot by binding platelets)

• Extrinsic pathway

• Intrinsic pathway

• common pathway

3. Kinin system (coverts kinin into active form of bradykin which is a inflammatory mediator)

Chemokine

A family of cytokines which are chemotactic and attract leukocytes to areas of inflammation

Chemotaxis (cellular response)

directional movement of cells along a chemical gradient created by chemotactic factors.

Leukotrienes

cause: vascular permeability, muscle contraction

Types of exudate

• Serous: thin, clear, yellow = proper healing

• Hemorrhagic sanguineous: bloody = normal after surgery

• serosanguineous: blood tinge, yellow, pink = expected after trauma

• Purulent: thin, cloudy, foul-smelling = indicates infection

• Catarrhal: thin, clear mucous = respiratory infection

Diapedesis/ emigration (cellular response)

going through junctions in the endothelial tissue in response to inflammatory mediators.

Adrenal Cortex

Creates two types of Corticosteroids, a steroid created from cholesterol. The outer part of the adrenal gland

• Glucocorticoids (inner layer/zona fasciculata) suppresess inflammatory response. Stabilizes cell membranes of lysosomes (inflammatory cells), decreasing permeability, decreasing migration of white blood cells into tissue, and increases blood sugar.

• Mineralocorticoids (outer layer/zona glomerulosa) regulate mineral salts (electrolytes) in the bloodstream. The most important is aldosterone (regulates sodium levels in blood/Ph,

Adrenal Medulla

The inner layer of adrenal gland. Releases to hormones

• Epinephrine:

• Norepinephrine:

Cushings syndrome

Hyper secretion of glucocorticoids redistribution of fat from peripheral locations (arms), to central areas (face). “moon face”

Addison’s disease

hypo secretion adrenocortical hormones. Dehydration, hyperpigmentation, nausea, vomiting, anorexia.

Tissue Regernation vs Tissue Repair

• Tissue Regeneration:

Occurs in less severe wounds and when damaged tissue is replaced with healthy tissue, ending in resolution.

• Tissue Repair:

Occurs when extreme damage has occurred, and destroyed tissue is replaced with scar tissue derived from collagen. Strength is restored but the function is not.

Wound healing process

• (1) Fill in: (epithelialization)

• (2) Seal:

• (3) Shrinking of wound: (contraction)

Wound healing options

• (1) Primary Intention: Minimal tissue loss, & close tissue proximity (ex. sutures, staples, paper cut) epithelialization & contraction periods are shorter

• (2) Secondary intention: open wound, extensive tissue loss, leads to scaring and longer epithelialization and contraction periods.

• (3) Tertiary intention: open for a few days due to inflammation and then sutured closed

Wound healing phases (overlapping)

• (1) Inflammation: includes coagulation and hemostasis, and the infiltration of cells. Fibrin mesh acts as a platform for new cells. Platelets clot as they degranulate and release new growth factors for undamaged cells to prolificate. Neutrophils initially clear wound of debris. Macrophages take over phagocytosis as inflammation transitions into healing. They clear debris and release healing mediators.

• (2) Proliferation & Tissue Formation: Occurs 3-4 days after injury. Fibrin is replaced by new tissue or scar tissue. Fill-in (epithelialization), Seal, & Shrinking of wound (contraction) occurs.

• (3) Remodelling & maturation: Begins several weeks after injury, may take up to 2yrs. Continuation of cellular differentiation. Fibroblasts are the major cell of this phase, as they deposited collagen. Tissue regeneration and contraction continue. For wounds that scar maturation happens and its avascular with 2/3 of its strength

Angiogenesis

Formation of new blood supply, promoted by macrophages

Hemostasis

Bodies natural reaction to stopping of bleeding during injury

Dysfunctional wound healing

• ischemia (lack of blood flow)

• excessive bleeding

• obesity

• excessive fibrin deposits

• disorder such as diabetes

• wound infection

• inadequate nutrients

• multiple medications

• tobacco smoke

Hypertonic Scar

a scar that is raised but remains within original boundaries

Keloid scar

a raised scar not within original boundaries, invades surrounding tissue. Will recur if surgically removed

Dehiscence

When a wound pulls apart at the suture line. Occurs 5-12 days after suturing. When collagen synthesis is at its peak.

Collagen synthesis

Occurs from fibroblasts both intracellularly and extracellularly. Collagen is deposited in injury.

Fibroblasts

Cells recruited and stimulated to proliferate by macrophages. They lay down collagen within wounds and preform collagen synthesis.

Cellular Response

• Chemotaxis: moving cells to injury site, inflammatory mediators (chemotactic factors) are activated which attract the cells.

• Cellular adherence: inflammatory mediators attract cells to site of injury and then receptors bind the leukocytes to the endothelial cells.

• Cellular migration: Moving across endothelial cells into tissue where injury occurred.

Lymphadenitis

Enlargement of lymph node

Leukocytosis

Increase in the number of white blood cells due to infection

Cardinal signs

• Erythema (redness)

• Edema (swelling)

• Heat

• Pain

• Loss of function

RICE for inflammation

• rest

• ice

• compress

• elevate

Scab is known as a

Thrombus

WBC differentials

• Neutrophils (bacterial infection)

• Bands - immature neutrophils (prolonged bacterial infection)

• Eosinophils (chronic infection, allergies & parasites)

• Basophils - acts like a mast cell but inhabits bloodstream instead of tissue (blood stream infection)

• Lymphocytes (viral infection)

• Monocyte > Macrophage (general)

Inflammatory Stress

Is caused by chronic inflammation.

• innate immune system can’t tell between self and none self

• increase oxygen radicals

• increased inflammatory mediators

Cortisol

is the stress hormone. It activates glucose storage release, inhibits insulin release. Which results in norepinephrine release. Resulting in blood vessels restricting and low levels of inflammation will continue.

Common blood tests for inflammation

• Erythrocyte sedimentation rate: how fast red blood cells settle. RBCs will clump together if there is inflammation and fall faster, measuring this rate can determine if there is inflammation present. Child/woman/male differences

• Prothrombin time: (the time it takes to clot)

• Fibrinogen: (makes a fibrin clot) lower in newborns

• C-reactive protein: (if not related to injury, it indicates chronic inflammation)

• Complement activity: (indicates inflammation)

Types of Exudate

• Serosanguineous: Blood + plasma

• Sanguineous/Hemorrhagic: Blood (pink)

• Serous: plasma + lymphatic fluid

• Purulent: dead cells (thin, cloudy, foul smelling, maybe thick = infection)

• Catarrhal: thin clear mucous

viral strep = no exudate / Bacterial strep = exudate

Granuloma formulation

Happens due to an excessive inflammatory process that is too difficult to manage as usual.

• Macrophages group together to form a large nodular lesion that operates as a phagocyte engulfing substances.

• Form of walling off that leaves scar tissue.

(tuberculosis & RA)

Macrophages producing: Proteinases & Fibroblasts

• Proteinases: an enzyme that breaks down dead tissue. Does not discriminate from healthy tissue so long-term chronic infection can cause damage.

• Fibroblasts: Responsible for collagen development

• scaring leads to loss of function

Chronic Inflammation

• monocytes, macrophages, lymphocytes more involved

• Formation of fibrosis, granulomas and scarring occur

• Contributing factors: unrelenting injury, persistent infection, autoimmunity

• Prolonged > 6 months

What are pattern recognition receptors?

Receptors used in the innate immune response to identify antigens

1. Pattern 1: molecules expressed by infectious agent

2. Pattern 2: Products of cellular damage

What are cytokines? How do they promote inflammation?

They are signalling molecules that come from mast cells. Binding to cells causes synthesis of other products. Cytokine storms is when a immune system isn't regulating properly and the production of cytokines results in a amplified immune response which can be deadly.

What do mast cells release during inflammation and what are their effects?

Most important inflammatory activating factor. They reside in the tissue near blood vessels. They contain granules. When stimulated mast cells go through degranulation (release of contents from mast cells). And synthesis (new production of mediators). This results in the release of histamines, cytokines, and chemotactic factors to begin the inflammatory response.

What 2 phagocytic cells are involved in acute inflammation? What are their roles?

(granulocytes)

• Neutrophils: first on scene, removal of debris/dead cells = sterile lesions (burns)

Destruction of bacteria = non sterile lesions

• Monocytes/Macrophages:

• 5 steps in phagocytosis?

1. Recognition & adherence of the phagocyte to its target

2. Engulfment (ingestion/ endocytosis)

3. Formation of a phagosome

4. Fusion of phagosome with lysosomal granules within the phagocyte

5. Destruction of target

Why are innate immunity and inflammation known as "non-specific?”

The response occurs in a similar way every time even when the same action has already happened (ex. getting burned)

What are the 5 cardinal signs of inflammation and how are they related to the process?

1. (Rubor) Redness - due to increased blood flow/ viscous blood {erythema}

2. (Calor) Heat - due to increased blood flow & increased cell activity

3. (Tumor) Swelling - due to increased extracellular fluid {exudate}

4. (Dolor) Pain - due to chemical mediators triggering nerves

5. (Functio laesa) Loss of function - due to pain or swelling affecting nerves and mobility

What are the benefits of inflammation?

1} Prevents infection and further damage by invading microorganisms 2} Prepares the site for healing/repair 3} Limits and controls inflammatory process 4} Interacts with parts of adaptive immunity with a goal to have a more specific response in future cases

Three components of complement system?

1. Classical pathway (Bacteria) antibodies from immune system needed to activate

2. Alternative pathway (Bacteria/yeast) doesn’t need antibodies, activated by substances on surface of infectious agent.

3. Lectin pathway (fungi/bacteria/virus) Independent from antibodies

How is coagulation cascade activated? How is it related to plasma kinin cascade?

1. Release of collagen, plasmin ect, endotoxin released from bacteria.

2. They interact closely together, factor 12 converted into 12a activates both the clotting and kinin systems. Kinin produces bradykinin causing dilation, works with prostaglandins to produce pain, smooth muscle cell contraction, increase vascular permeability.

What factors control the plasma protein system of inflammation?

1. Mast cells {activator} 2) Dendritic cells {connect innate & acquired immune responses}

• Plasma enters tissue and has enzymes which destroy mediators of inflammation

• The Liver synthesises the proteins

The differences between acute & chronic inflammation and similarities?

• Acute: self-limiting, 8-10 days,

• Chronic: if inflammatory response is inadequate, 2 weeks or longer,

• Granuloma: excessive chronic inflammation (try's to contain) walls off issue (cyst)

Types of exudate released during inflammation?

• Serous Exudate: (early/mild inflammation) watery, few plasma proteins {blisters}

• Fibrinous Exudate: (server/advanced) thick, clotted {lung infection}

• Purulent/suppurative Exudate: pus, large amount of leukocytes from bacterial infection, walled off {cyst, abscess)

• Hemorrhagic Exudate: exudate containing erythrocytes (blood)

How does regeneration of tissue and repair of tissue differ?

• Regeneration is the replacement of damaged tissue with healthy tissue. The restoration of the tissue is known as __resolution__and may take up to two years. May not be possible if extensive damage is present.

• If to extensive and the presence  of abscesses, granuloma formation or fibrin persist repair occurs. Repairing is the replacement of destroyed tissue with scar tissue. Collagen is the main component, and fills the lesion. It repairs the strength but not the function.

What does it mean to heal by primary intention?

When a wound is sutured/stapled closed and not left open to heal.

What is the role of fibroblasts in wound healing?

They are cells that secrete collagen and other connective tissue properties. Macrophages stimulate fibroblast proliferation and migration to the lesion of a debrided area and start depositing about 6 days after entering.

Describe ways in which wound healing maybe dysfunctional?

• (1) Ischemia (Low blood flow/poor oxygenation) (2) excessive bleeding (3) obesity (4) excessive fibrin deposition (5) disorder such as diabetes (6) wound infection (7) inadequate nutrients (8) numerous medications (10) smoking tobacco

Acute vs chronic inflammation

Acute:

• resolved in weeks

• Neutrophils are the main phagocytic cell

• minimal scaring

Chronic

• prolonged period > 6 months

• monocytes, lymphocytes

• granuloma formation, scaring, fibrosis

Granuloma Formation

• Macrophages form together to incase substance and forms a inflammatory nodular lesion

• when injury is to difficult to handle normally

• Happens with RA & TB

Adrenal drugs (glucocorticoids)

A type of corticosteroid produces by the adrenal cortex

Prednisolone: most commonly used for anti-inflammatory and respiratory exacerbations, doesn’t manage adrenocortical insufficiency (Addison’s)

• When to take: given in the morning, same time every day with food to limit GI upset, with no caffeine, alcohol, aspirin, NSAIDS. Should never stop suddenly will cause adrenal crisis. If used inhaler wash mouth out not to cause thrush.

• Interactions: Don’t pair with NSAIDS will cause GI tract effects, diabetes (raises blood glucose), glaucoma, ulcers, avoid if you have infections expect with meningitis to stop swelling of CNS

• Adverse Effects: effects the whole body, May cause Cushing’s, Adison’s, electrolyte imbalances, heart failure, hyperkalemia, vertigo

Mechanism of action:

• use effects to modify enzyme activity

• suppresses prostaglandin synthesis (causes pain), and leukotrienes

• Inhibits inflammatory cellular activity such as epeithial cellular adhesion, chemotaxis, phagocytosis

NSAIDs

• Effects: analgesic, anti-inflammatory, antipyretic, (Aspirin = anti-platelet)

Types of NSAIDs:

• Salicylates: (aspirin/ASA)

• Acetic acid derivatives: (Voltaren)

• COX-2 inhibitors; (Celebrex)

• Propionic acid derivatives: (ibuprofen)

Mechanism of Action:

• inhibits leukotriene or prostaglandin pathway or both

• Blocking the chemical activity of COX

~ COX-1 maintains GI tract

~ COX-2 promotes synthesis of prostaglandins involved in the inflammatory process

Adverse effects:

• Heart burn, GI upset

• acute kidney injury

• pulmonary edema

• Tinnitus, hearing loss

Fibrosis

thickening of tissue caused by scarring

Free Radical

• unstable molecules that are made during normal cell metabolism. They can build up and effect the DNA of the cell and causes risks for cancer formation

Antioxidant

• they provide extra electrons to free radicals to prevent them from causing damage to the body’s cells

Treatment of inflammation when it’s beyond helpful

Want to minimize tissue damage and promote healing

• reduce blood flow to local area

• decrease swelling

• block action of chemical mediators

• decrease pain