The appearance of inflammatory processes in response to the action of a pathological factor is an adequate reaction of the body. Inflammation is a complex process that develops at the local or general level that occurs in response to the action of foreign agents. The main task of the development of the inflammatory reaction is aimed at eliminating the pathological effect and restoring the body. Inflammatory mediators are mediators that are directly involved in these processes.
Briefly about the principles of inflammatory reactions
The immune system is a guardian of human health. When necessary, she enters the battle and destroys bacteria, viruses, fungi. However, with the intensified activation of the work, the process of combating microorganisms can be seen visually or to feel the appearance of the clinical picture. It is in such cases that inflammation develops as a protective response of the body.
There are acute process of inflammatory reaction and its chronic course. The first occurs as a result of the sudden action of an irritating factor (trauma, damage, allergic effect, infection). Chronic inflammation has a protracted nature and less pronounced clinical signs.
In the case of a local response of the immune system in the area of injury or injury, the following signs of an inflammatory reaction appear:
- soreness;
- swelling, swelling;
- hyperemia of the skin ;
- functional impairment;
- hyperthermia (temperature rise).
Stages of inflammation
The process of inflammation is based on the simultaneous interaction of protective factors of the skin, blood and immune cells. Immediately after contact with a foreign agent, the body responds with local vasodilation in the area of direct trauma. There is an increase in the permeability of their walls and increased local microcirculation. Together with a blood stream, humoral defense cells come here.
In the second stage, immune cells begin to fight with microorganisms that are at the site of damage. A process called phagocytosis begins. Neutrophil cells change their shape and absorb pathological agents. Next, special substances are allocated aimed at the destruction of bacteria and viruses.
In parallel with microorganisms, neutrophils also destroy old dead cells located in the area of inflammation. Thus, the development of the third phase of the reaction of the organism begins. The focus of inflammation is, as it were, protected from the whole organism. Sometimes a ripple can be felt in this place. Cellular inflammatory mediators begin to be produced by mast cells, which allows you to clean the injured area from toxins, toxins and other substances.
General Concepts of Plectrum
Inflammatory mediators are active substances of biological origin, the release of which is accompanied by the main phases of alteration. They are responsible for the occurrence of manifestations of inflammatory reactions. For example, increased permeability of the walls of blood vessels or a local temperature increase in the area of trauma.
The main inflammatory mediators are distinguished not only during the development of the pathological process. Their development is ongoing. It is aimed at regulating body functions at the tissue and cellular levels. Depending on the direction of action, modulators have the effect of:
- additive (incremental);
- synergistic (potentiating);
- antagonistic (weakening).
When damage occurs or at the site of action of microorganisms, the mediator link controls the processes of interaction of inflammatory effectors and the change of the characteristic phases of the process.
Types of inflammatory mediators
All inflammatory modulators are divided into two large groups, depending on their origin:
- Humoral: kinins, complement derivatives, coagulation factors of the blood.
- Cellular: vasoactive amines, derivatives of arachidonic acid, cytokines, lymphokines, lysosomal factors, active oxygen metabolites, neuropeptides.
Humoral inflammatory mediators are in the human body before exposure to a pathological factor, that is, the body has a supply of these substances. Their deposition occurs in cells in an inactive form.
Vasoactive amines, neuropeptides and lysosomal factors are also preexisting modulators. The remaining substances belonging to the group of cellular mediators are produced directly in the process of the development of the inflammatory reaction.
Derivatives of Complement
Derivatives of inflammation include compliment derivatives. This group of biologically active substances is considered the most important among humoral modulators. Derivatives include 22 different proteins, the formation of which occurs upon complement activation (the formation of an immune complex or immunoglobulins).
- The C5a and C3a modulators are responsible for the acute phase of inflammation and are the liberators of histamine produced by mast cells. Their action is aimed at increasing the level of vascular cell permeability, which is carried out directly or indirectly through histamine.
- The modulator C5a des Arg increases the permeability of venules at the site of the inflammatory reaction and attracts neutrophilic cells.
- C3b promotes phagocytosis.
- The C5b-C9 complex is responsible for the lysis of microorganisms and pathological cells.
This group of mediators is produced from plasma and tissue fluid. Due to entry into the pathological zone, exudation processes occur. Interleukin, neurotransmitters, leukotrienes, prostaglandins, and platelet activating factors are released with complement derivatives.
Kinins
This group of substances is a vasodilator. They are formed in tissue fluid and plasma from specific globulins. The main representatives of the group are bradykinin and callidine, the effect of which is manifested as follows:
- participate in muscle contraction of smooth groups;
- due to the reduction of vascular endothelium, they enhance the processes of permeability of the wall;
- contribute to an increase in arterial and venous pressure;
- dilate small vessels;
- cause pain and itching;
- contribute to the acceleration of regeneration and collagen synthesis.
The action of bradykinin is aimed at opening the access of blood plasma to the focus of inflammation. Kinins are mediators of inflammation pain. They irritate local receptors, causing discomfort, pain, itching.
Prostaglandins
Cell mediators of inflammation are prostaglandins. This group of substances relates to derivatives of arachidonic acid. Sources of prostaglandins are macrophages, platelets, granulocytes and monocytes.
Prostaglandins are inflammatory mediators with the following activity:
- pain receptor irritation;
- vasodilation;
- an increase in exudative processes;
- increased hyperthermia in the lesion;
- acceleration of the movement of leukocytes in the pathological zone;
- increased swelling.
Leukotrienes
Biologically active substances related to newly formed mediators. That is, in the body at rest of the immune system, their number is not enough to immediately respond to an irritating factor.
Leukotrienes provoke an increase in the permeability of the vascular wall and give leukocytes access to the pathology zone. They matter in the genesis of inflammatory pain. Substances can be synthesized in all blood cells, except for red blood cells, as well as in adventitia of lung, vascular and mast cells.
In the case of the development of the inflammatory process in response to bacteria, viruses or allergic factors, leukotrienes cause bronchospasm, causing the development of swelling. The effect is similar to the action of histamine, but more prolonged. The target organ for active substances is the heart. Standing out in large numbers, they act on the heart muscle, slow down coronary blood flow and increase the level of inflammatory response.
Thromboxanes
This group of active modulators is formed in spleen tissues, brain cells, lungs and blood cells, platelets. They have a spastic effect on blood vessels, enhance the processes of thrombosis during cardiac ischemia, and promote platelet aggregation and adhesion.
Biogenic amines
The primary mediators of inflammation are histamine and serotonin. Substances are provocateurs of initial microcirculation disorders in the pathology zone. Serotonin is a neurotransmitter that is produced in mast cells, enterochromaffins and platelets.
The action of serotonin varies depending on its level in the body. Under normal conditions, when the amount of mediator is physiological, it enhances vasospasm and increases their tone. With the development of inflammatory reactions, the number increases dramatically. Serotonin becomes a vasodilator, increasing the permeability of the vascular wall and dilating the vessels. Moreover, its action is a hundred times more effective than the second neurotransmitter of biogenic amines.
Histamine is a mediator of inflammation that has a versatile effect on blood vessels and cells. Acting on one group of histamine-sensitive receptors, the substance expands the arteries and inhibits the movement of leukocytes. When exposed to another, it narrows the veins, causes an increase in intracapellary pressure and, conversely, stimulates the movement of leukocytes.
Acting on neutrophilic receptors, histamine limits their functionality, on monocyte receptors it stimulates the latter. Thus, the neurotransmitter can have an inflammatory anti-inflammatory effect at the same time.
The vasodilating effect of histamine is enhanced under the influence of a complex with acetylcholine, bradykinin and serotonin.
Lysosomal enzymes
Mediators of immune inflammation are produced by monocytes and granulocytes at the site of the pathological process during stimulation, emigration, phagocytosis, damage and cell death. Proteinases, which are the main component of lysosomal enzymes, have the effect of antimicrobial protection, lysing foreign destroyed pathological microorganisms.
In addition, the active substances increase the permeability of the vascular walls, modulate leukocyte infiltration. Depending on the amount of enzymes isolated, they can enhance or weaken the processes of migration of leukocyte cells.
The inflammatory reaction develops and lasts for a long time due to the fact that lysosomal enzymes activate the complement system, release cytokines and limokines, activate coagulation and fibrinolysis.
Cationic proteins
Inflammatory mediators include proteins contained in neutrophilic granules and having high microbicidal activity. These substances act directly on a foreign cell, disrupting its structural membrane. This causes the death of the pathological agent. Next, the process of destruction and cleavage of lysosomal proteinases occurs.
Cationic proteins promote the release of the histamine neurotransmitter, increase vascular permeability, and accelerate the adhesion and migration of leukocyte cells.
Cytokines
These are cellular inflammatory mediators produced by the following cells:
- monocytes;
- macrophages;
- neutrophils;
- lymphocytes;
- endothelial cells.
Acting on neutrophils, cytokines increase the level of permeability of the vascular wall. They also stimulate leukocyte cells to kill, absorb and destroy alien settled microorganisms, enhance the phagocytosis process.
After the killing of pathological agents, cytokines stimulate the restoration and proliferation of new cells. Substances interact with representatives from their group of mediators, prostaglandins, neuropeptides.
Active oxygen metabolites
A group of free radicals, which, due to the presence of unpaired electrons, are able to interconnect with other molecules, taking a direct part in the development of the inflammatory process. The oxygen metabolites that are part of mediators include:
- hydroxyl radical;
- hydroperoxide radical;
- superoxide anion radical.
The source of these active substances is the outer layer of arachidonic acid, a phagocytic explosion upon stimulation, and the oxidation of small molecules.
Oxygen metabolites increase the ability of phagocytotic cells to destroy foreign agents, cause oxidation of fats, damage to amino acids, nucleic acids, carbohydrates, which increases vascular permeability. As modulators, metabolites can increase inflammation or have an anti-inflammatory effect. Of great importance in the development of chronic diseases.
Neuropeptides
This group includes calcitonin, neurokinin A and substance P. These are the most famous modulators of neuropeptides. The effect of substances is based on the following processes:
- the involvement of neutrophils in the focus of inflammation;
- increased vascular permeability;
- help with the action of other groups of neurotransmitters on sensitive receptors;
- increased sensitivity of neutrophils to venous endothelium;
- participation in the formation of pain in the inflammatory process.
In addition to all of the above, acetylcholine, adrenaline and norepinephrine are also active mediators. Acetylcholine takes part in the process of formation of arterial hyperemia, dilates blood vessels in the focus of pathology.
Norepinephrine and adrenaline act as modulators of inflammation, inhibiting the growth of vascular permeability.
The development of an inflammatory reaction is not a violation on the part of the body. On the contrary, it is an indicator that the immune system is coping with its tasks.