Podcast
Questions and Answers
What role do reactive oxygen species play in neutrophils and macrophages?
What role do reactive oxygen species play in neutrophils and macrophages?
- They contribute to energy production.
- They help in nutrient absorption.
- They are involved in cellular respiration.
- They are part of the bactericidal activity. (correct)
Which enzyme is responsible for generating nitric oxide in phagocytes?
Which enzyme is responsible for generating nitric oxide in phagocytes?
- NADPH oxidase
- Superoxide dismutase
- Cyclooxygenase
- Inducible nitric oxide synthase (iNOS) (correct)
Which statement correctly describes the production of reactive species in neutrophils and macrophages?
Which statement correctly describes the production of reactive species in neutrophils and macrophages?
- Macrophages produce more nitric oxide than neutrophils. (correct)
- Both produce equal amounts of reactive oxygen species.
- Neutrophils produce more nitric oxide than macrophages.
- Neither cell type produces reactive species.
What is the NADPH phagocyte oxidase primarily responsible for?
What is the NADPH phagocyte oxidase primarily responsible for?
How are NADPH oxidase and iNOS regulated in phagocytes?
How are NADPH oxidase and iNOS regulated in phagocytes?
What is a primary characteristic of free radicals?
What is a primary characteristic of free radicals?
Which radical is primarily considered a mitochondrial source?
Which radical is primarily considered a mitochondrial source?
Which of the following is a mechanism by which free radicals can cause damage?
Which of the following is a mechanism by which free radicals can cause damage?
What role do antioxidants like Vitamin E and C play regarding free radicals?
What role do antioxidants like Vitamin E and C play regarding free radicals?
Which of the following is considered a free radical?
Which of the following is considered a free radical?
What process is lipid peroxidation primarily associated with?
What process is lipid peroxidation primarily associated with?
Nrf2 is primarily involved in which of the following processes?
Nrf2 is primarily involved in which of the following processes?
Which of the following describes hydrogen peroxide?
Which of the following describes hydrogen peroxide?
What percentage of O2 consumed is reduced to water during aerobic respiration?
What percentage of O2 consumed is reduced to water during aerobic respiration?
Which reactive oxygen species are primarily produced by mitochondria?
Which reactive oxygen species are primarily produced by mitochondria?
The process where a small fraction of O2 is reduced to O2.– is known as what?
The process where a small fraction of O2 is reduced to O2.– is known as what?
What is the primary process associated with the consumption of O2 in mitochondria?
What is the primary process associated with the consumption of O2 in mitochondria?
Which of the following represents a minor percentage of O2 consumed during aerobic metabolism?
Which of the following represents a minor percentage of O2 consumed during aerobic metabolism?
What is the consequence of the electron leak process in mitochondria?
What is the consequence of the electron leak process in mitochondria?
What is the major end product of O2 reduction in aerobic respiration?
What is the major end product of O2 reduction in aerobic respiration?
Which of the following is NOT a reactive oxygen species produced in mitochondria?
Which of the following is NOT a reactive oxygen species produced in mitochondria?
What is the overall efficiency of O2 reduction by mitochondria under normal conditions?
What is the overall efficiency of O2 reduction by mitochondria under normal conditions?
During oxidative phosphorylation, what is the percentage range of O2 that leaks univalently to form O2.–?
During oxidative phosphorylation, what is the percentage range of O2 that leaks univalently to form O2.–?
Which transition metal is specifically mentioned as catalyzing the Fenton reaction?
Which transition metal is specifically mentioned as catalyzing the Fenton reaction?
What is the product of the Fenton reaction alongside hydroxyl radical (HO.)?
What is the product of the Fenton reaction alongside hydroxyl radical (HO.)?
What is the initial reactant involved in the Fenton reaction?
What is the initial reactant involved in the Fenton reaction?
How are reactive oxygen species (ROS) primarily generated in cells?
How are reactive oxygen species (ROS) primarily generated in cells?
What role do superoxides (O2.–) play in the context of oxidative stress?
What role do superoxides (O2.–) play in the context of oxidative stress?
What is one cellular source of reactive oxygen species mentioned?
What is one cellular source of reactive oxygen species mentioned?
In the Haber-Weiss reaction, which substance is produced as a result of superoxide and hydrogen peroxide reaction?
In the Haber-Weiss reaction, which substance is produced as a result of superoxide and hydrogen peroxide reaction?
Which enzyme is NOT listed as a source of reactive oxygen species?
Which enzyme is NOT listed as a source of reactive oxygen species?
What is the final product of the dismutation of superoxide?
What is the final product of the dismutation of superoxide?
What is suggested as a mechanism by which oxidants mediate cellular damage?
What is suggested as a mechanism by which oxidants mediate cellular damage?
What is the primary role of NADPH oxidase in phagocytic cells?
What is the primary role of NADPH oxidase in phagocytic cells?
Which component is essential for the respiratory burst in phagocytes?
Which component is essential for the respiratory burst in phagocytes?
What characterizes the process of NETosis?
What characterizes the process of NETosis?
Which molecule is associated with both macrophage polarization and inflammation?
Which molecule is associated with both macrophage polarization and inflammation?
What is the function of inducible Nitric Oxide Synthase (iNOS) in macrophages?
What is the function of inducible Nitric Oxide Synthase (iNOS) in macrophages?
Which of the following is a key component involved in inflammasome activation?
Which of the following is a key component involved in inflammasome activation?
Which pathway leads to the expression of inflammatory cytokines IL-1b and IL-18?
Which pathway leads to the expression of inflammatory cytokines IL-1b and IL-18?
What role does mitochondrial DNA (mtDNA) play in the immune response?
What role does mitochondrial DNA (mtDNA) play in the immune response?
Which factor contributes to the antimicrobial activity of Neutrophil Extracellular Traps?
Which factor contributes to the antimicrobial activity of Neutrophil Extracellular Traps?
What is the main purpose of using reactive species in inflammation?
What is the main purpose of using reactive species in inflammation?
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Study Notes
Phagocytosis and Intracellular Killing
- Phagocytosis is part of the innate immune response.
- The NADPH phagocyte oxidase (phox or nox) is responsible for O2.– generation.
- The inducible nitric oxide synthase (iNOS) is responsible for the generation of NO.
- Neutrophils and macrophages both express NADPH oxidase and iNOS.
- Neutrophils produce more O2.– than macrophages, while macrophages generally produce more NO than neutrophils.
- NADPH oxidase and iNOS are separate enzyme complexes with independent regulation.
NADPH Oxidase
- NADPH oxidase is responsible for generating superoxide radical (O2.–).
- The enzyme system is also called phox or nox.
- The reaction is: NADPH + O2 ® NADP+ + O2.–
- The complex uses NADPH and oxygen to produce superoxide.
- NADPH oxidase is a multi-component enzyme complex.
- Several components of NADPH oxidase regulate its activity:
- cytosolic component p47phox and p67phox
- membrane-associated components p22phox and gp91phox
- During phagocytosis, these components assemble onto a membrane-bound oxidase complex that initiates the respiratory burst (burst of superoxide radical production) and promotes bactericidal activity.
- NADPH oxidase is upregulated and its activity is increased during infection and inflammation, producing a burst of superoxide radicals.
- gp91phox is crucial for the respiratory burst; it is the catalytic component of NADPH oxidase.
Respiratory burst
- Respiratory burst refers to the rapid production of reactive oxygen species (ROS) such as superoxide radical (O2.–) that occurs in phagocytic cells, such as neutrophils and macrophages.
- It is triggered by the engulfment of microbes (phagocytosis).
- The burst is critical for the destruction of ingested microbes, by generating the superoxide radical.
Role of Superoxide radical
- Superoxide radical (O2.–) produced by NADPH oxidase is essential for killing bacteria and other pathogens.
- O2.– is produced in the phagosome where bacteria are trapped.
- O2.– can also be generated by mitochondria.
- O2.– is involved in signaling pathways.
Inducible Nitric Oxide Synthase (iNOS)
- Inducible nitric oxide synthase (iNOS) is a calcium-independent enzyme that is induced in macrophages (and other cell types) in response to inflammatory stimuli.
- iNOS is responsible for the generation of nitric oxide (NO).
- iNOS also uses arginine, NADPH, and oxygen for the reaction: Arginine + NADPH + O2 ® Citrulline + NADP+ + NO.
- Nitric oxide production is crucial for defense against bacterial and parasitic infections.
- NO reacts with superoxide (O2.–), forming peroxynitrite (ONOO–).
- Peroxynitrite is a highly reactive molecule that damages microbial DNA and proteins.
- It is thought to contribute to the antimicrobial activity of phagocytes, but also plays a role in inflammation and tissue damage.
- NO has a variety of roles in the body, including vasodilation, neurotransmission, and immune regulation.
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