Learn the basics of Inflammation - a response to injured tissue
Can't Live with it, Can't live without it!
Inflammation is a response to injured tissue
Damage can be caused by pathogens (E.g. bacteria,
viruses, fungi, parasites), toxins/chemicals (E.g. air particulates,
allergens),
physical injury, burns,
or by an overzealous immune system.
Without inflammation, infections would go unchecked and wounds (E.g. trauma,
surgery, burns, damage inflicted by a saber-tooth tiger!) would never heal.
An example of inflammation is when you "catch" a cold
(actually a viral infection) - your throat becomes
sore, your eyes water, and your sinuses are congested. These are the physical signs of inflammation as fluid and cells build up, as a
result of the immune system's fight against a hostile invader.
Inflammation is characterized by increased blood
flow to the tissue
The inflammation process begins when
cells resident in tissue (E.g. mast
cells and macrophages) detect a problem and
release inflammation mediators .
These mediators include:
• Histamines and lipid signaling factors
(E.g.
eicosanoids : leukotrienes and prostaglandins) - which instruct bloods
vessels to dilate;
•
Chemoattractants (E.g. chemokines, cytokines) - which
attract leukocytes to the "scene of the crime".
Roman doctor / scientist, Celsus, noted these signs of inflammation: "tumor, dolor, rubor, and calor ",
better known today as:-
• Swelling.
As
blood vessels leak fluid containing large quantities of leukocytes and also serum proteins into surrounding tissues.
• Pain / Tenderness. Resulting from
swollen / stretching tissue and also release of eicosanoid lipid signaling
factors (E.g. prostaglandin D2, and leukotrienes).
• Redness. A
consequence of dilated blood vessels, which enhance delivery of leukocytes and
serum proteins to troubled location.
• Heat. An additional
consequence of dilated blood vessels.
Inflammation is categorized as either ACUTE or CHRONIC
Acute (short-term) inflammation
Acute Inflammation is the result of an immediate,
necessary and appropriate response to injury or infection
ACUTE inflammation
Chronic low-level inflammation (CLLI)
A chronic low-level inflammatory response occurs if
an infection/ injury continues without being resolved.
CLLI is a common factor in most health problems of today
CHRONIC Low Level inflammation
Health problems
linked with
Chronic Low level Inflammation
Many lifestyle choices today are causing chronic low level inflammation
Causes include stress, exposure to toxins, consuming too
much dairy / meat, too many carbs and damaging fats and not enough healthy fats:
Causes of Chronic Low level
Inflammation
Mast cells are key players in initiating
inflammatory process
Found in tissues
Their surface is coated
with a variety of receptors. When engaged by the appropriate
ligand (E.g. LPS/Endotoxin of Gram-negative
bacteria , peptodoglycan of
Gram-positive
bacteria ), it triggers release of granules (by exocytosis), some discharging their
inflammatory mediators immediately, others later.
Mast cell cytoplasm
is loaded with granules containing potent mediators of inflammation.
Dozens of
these are released when stimulated by the immune system,
which
recruit all types of white blood cells to the site, many of which
are activated to produce their own inflammatory mediators.
• Monocytes. They
become macrophages ("big eaters") when they leave the blood and enter the tissue
• Neutrophils. Squeeze through capillary walls and into infected tissue to kill invaders and
then engulf the remnants by phagocytosis;
• Antigen-presenting dendritic cells .
Main function is to process antigen material and present it on the
cell
surface
to the immune system's T-cells ,
thereby acting as messengers between the innate and the adaptive immune
systems).
• All kinds of lymphocytes:
Natural Killer (NK) cells.
Specialized to kill certain types of target cells (esp.
virally infected or cancerous host cells) in innate (1st line of
defense) immunity
B-cells and T-cells. These cells lead to an adaptive immune response
(2nd line of defense);
• Eosinophils.
Blood levels increase sharply with parasitic worm infections. Eosinophils
release the cytoxic contents of their granules on the invader.
Some of the better known inflammatory mediators
released by mast cells
(which either initiate inflammation or deal with the damage)
Histamine
• Released from mast cell granules in nearby
connective tissues
• Increases blood flow to the area and the
leakage of fluid, pathogen-fighting WBCs and proteins from the blood into the
tissue space
• Produces redness, warmth and swelling
Serotonin
Bradykinin
• Produced from an inactive precursor always
circulating in the blood
• Dilates blood vessels /lowers blood pressure
(by stimulating
NITRIC OXIDE ), and
increases blood vessel permeability.
To allow needed blood components
to enter the tissue space; ACE inhibitor drugs reduce blood pressure by
increasing bradykinin
• Contracts airway smooth muscle, is a
potent bronchial vasodilator, stimulates mucus secretion and coughing.
Bradykinin activates release of neuropeptides from sensory nerves in airways,
leading to reflex bronchoconstriction, coughing and neurogenic inflammation
Fuller RW, Dixon
CM, Cuss
FM, Barnes
PJ. Bradykinin-induced bronchoconstriction in humans. Mode of action.
Am Rev Respir Dis. 1987 Jan;135(1):176-80.
PubMed
• Like histamine, effects produce redness,
warmth and swelling
• Involved in pain mechanism
• Stimulates phospholipase.
Increases the production of
prostaglandins
(local "hormones")
Prostaglandins, Leukotrienes
• Potent mediators of inflammation.
These
hormone-like messengers are derived from specific dietary
essential fats (EFAs)
in local cell membrane phospholipids.
Consuming a balance of both inflammatory (most
omega-6
fats) and anti-inflammatory
(omega-3 EPA and DHA , and
omega-6 GLA ) fatty acids will
ensure a balanced response when dealing with injured tissue;
EFAs ==> Local Hormones - First Response Team
Tumor Necrosis Factor-alpha (TNF-α)
• Large amounts released by stimulated mast
cells
• TNF-α used to regulate immune cells.
Induce fever, apotosis (natural cell death),
sepsis (via IL1 & IL6 production),
cachexia, inflammation and to inhibit tumorigenesis and viral replication
Reactive Oxygen Species (ROS)
• All inflammatory cells have receptors for TNF-α and are activated by
it to synthesize more on their own. This positive feedback quickly amplifies the
response.
• Produced by activated phagocytes:
macrophages and neutrophils
Interleukin-1
(IL-1)
• Toxic to microorganisms, but can also lead
to tissue injury
• This cytokine is released by macrophages,
monocytes and activated platelets
• Has paracrine effects on cells in the
local vicinity:
▪ Causes cells to
produce tissue factor to trigger blood clotting;
▪ Stimulates
synthesis/secretion of other interleukins
▪ Helps activate
T-cells in the adaptive (2nd line of defense) immune response;
• Has endocrine
(hormonal) effects via the blood:
▪ Decreases blood
pressure
▪ Induces fever
(stimulates prostaglandin release,
which affect hypothalamic temperature control);