Respiratory burst
Encyclopedia
Respiratory burst is the rapid release of reactive oxygen species
(superoxide radical
and hydrogen peroxide
) from different types of cells
.
Usually it denotes the release of these chemicals from immune cells, e.g., neutrophil
s and monocyte
s, as they come into contact with different bacteria or fungi
. They are also released from the ovum
of higher animals after the ovum has been fertilized. These substances can also be released from plant cell
s.
Respiratory burst plays an important role in the immune system
. It is a crucial reaction that occurs in phagocyte
s to degrade internalized particles and bacteria
.
NADPH oxidase
, an enzyme
family in the vasculature (in particular, in vascular disease
), produces superoxide
, which spontaneously recombines with other molecule
s to produce reactive free radicals. The superoxide reacts with NO
, resulting in the formation of peroxynitrite
, reducing the bioactive NO
needed to dilate terminal arteriole
s, feed arteries
and resistance arteries. Superoxide anion, peroxynitrite, and other reactive oxygen
species also lead to pathology
via peroxidation
of protein
s and lipid
s, and via activation of redox sensitive signaling cascades and protein nitrosylation
. NADPH oxidase activation has been suggested to depend on prior PKC
activation. Myeloperoxidase
uses the reactive oxygen species hydrogen peroxide
to produce hypochlorous acid
. Many vascular stimuli, including all those known to lead to insulin resistance
, activate NADPH oxidase via both increased gene expression
and complex activation mechanisms
.
To combat infections, immune cells use NADPH oxidase to reduce O2 to oxygen free radical and then H2O2. Neutrophils and monocytes utilize myeloperoxidase
to further combine H2O2 with Cl- to produce hypochlorite
, which plays a role in destroying bacteria. Absence of NADPH oxidase will prevent the formation of reactive oxygen species and will result in chronic granulomatous disease
.
Reactive oxygen species
Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....
(superoxide radical
Superoxide
A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...
and hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
) from different types of cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
.
Usually it denotes the release of these chemicals from immune cells, e.g., neutrophil
Neutrophil granulocyte
Neutrophil granulocytes are the most abundant type of white blood cells in mammals and form an essential part of the innate immune system. They are generally referred to as either neutrophils or polymorphonuclear neutrophils , and are subdivided into segmented neutrophils and banded neutrophils...
s and monocyte
Monocyte
Monocytes are a type of white blood cell and are part of the innate immune system of vertebrates including all mammals , birds, reptiles, and fish. Monocytes play multiple roles in immune function...
s, as they come into contact with different bacteria or fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
. They are also released from the ovum
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
of higher animals after the ovum has been fertilized. These substances can also be released from plant cell
Plant cell
Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic organisms. Their distinctive features include:...
s.
Respiratory burst plays an important role in the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. It is a crucial reaction that occurs in phagocyte
Phagocyte
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek phagein, "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek kutos, "hollow vessel". They are...
s to degrade internalized particles and bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
.
NADPH oxidase
NADPH oxidase
The NADPH oxidase is a membrane-bound enzyme complex. It can be found in the plasma membrane as well as in the membrane of phagosome.-Subunits:It is made up of six subunits...
, an enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
family in the vasculature (in particular, in vascular disease
Vascular disease
Vascular disease is a form of cardiovascular disease primarily affecting the blood vessels.Some conditions, such as angina and myocardial ischemia, can be considered both vascular diseases and heart diseases .Cigarette smoking is the major risk factor....
), produces superoxide
Superoxide
A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...
, which spontaneously recombines with other molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s to produce reactive free radicals. The superoxide reacts with NO
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
, resulting in the formation of peroxynitrite
Peroxynitrite
Peroxynitrite is the anion with the formula ONOO−. It is an unstable structural isomer of nitrate, NO3−, which has the same formula but a different structure. Although peroxynitrous acid is highly reactive, its conjugate base peroxynitrite is stable in basic solution...
, reducing the bioactive NO
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
needed to dilate terminal arteriole
Arteriole
An arteriole is a small diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.Arterioles have muscular walls and are the primary site of vascular resistance...
s, feed arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
and resistance arteries. Superoxide anion, peroxynitrite, and other reactive oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
species also lead to pathology
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
via peroxidation
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
of protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s and lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s, and via activation of redox sensitive signaling cascades and protein nitrosylation
Nitrosylation
Nitrosylation is a protein modification in which a nitrosyl group is post-translationally added to a protein.There is a range of enzymes that produce nitric oxide, and the frequent consequence of this production is nitrosylation....
. NADPH oxidase activation has been suggested to depend on prior PKC
Protein kinase C
Protein kinase C also known as PKC is a family of enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and threonine amino acid residues on these proteins. PKC enzymes in turn are activated by signals such as increases in...
activation. Myeloperoxidase
Myeloperoxidase
Myeloperoxidase is a peroxidase enzyme that in humans is encoded by the MPO gene. Myeloperoxidase is most abundantly expressed in neutrophil granulocytes . It is a lysosomal protein stored in azurophilic granules of the neutrophil...
uses the reactive oxygen species hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
to produce hypochlorous acid
Hypochlorous acid
Hypochlorous acid is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor...
. Many vascular stimuli, including all those known to lead to insulin resistance
Insulin resistance
Insulin resistance is a physiological condition where the natural hormone insulin becomes less effective at lowering blood sugars. The resulting increase in blood glucose may raise levels outside the normal range and cause adverse health effects, depending on dietary conditions. Certain cell types...
, activate NADPH oxidase via both increased gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
and complex activation mechanisms
Activation
Activation in chemical sciences generally refers to the process whereby something is prepared or excited for a subsequent reaction.- Chemistry :...
.
To combat infections, immune cells use NADPH oxidase to reduce O2 to oxygen free radical and then H2O2. Neutrophils and monocytes utilize myeloperoxidase
Myeloperoxidase
Myeloperoxidase is a peroxidase enzyme that in humans is encoded by the MPO gene. Myeloperoxidase is most abundantly expressed in neutrophil granulocytes . It is a lysosomal protein stored in azurophilic granules of the neutrophil...
to further combine H2O2 with Cl- to produce hypochlorite
Hypochlorite
The hypochlorite ion, also known as chlorate anion is ClO−. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1.Hypochlorites are the salts of hypochlorous acid...
, which plays a role in destroying bacteria. Absence of NADPH oxidase will prevent the formation of reactive oxygen species and will result in chronic granulomatous disease
Chronic granulomatous disease
Chronic granulomatous disease is a diverse group of hereditary diseases in which certain cells of the immune system have difficulty forming the reactive oxygen compounds used to kill certain ingested pathogens...
.