Chemical Mediators of Inflammation — MCQs
All are sources of free radicals except -
First mediator of inflammation to be released is
Cyclooxygenase plays a role in which pathway?
Fever occurs due to which of the following mechanisms?
Elaboration of which of the following mediators will be most beneficial in preventing further ischemic injury to the cerebral cortex?
Which mediators are involved in the resolution of inflammation?
Rolling of leucocytes on endothelial cells is mediated by which of the following proteins?
Arrange the following cellular events of inflammation in the correct sequence: 1. Rolling 2. Cytokine-mediated integrin activation 3. Adhesion 4. Migration
Most important for diapedesis is
A male patient is not responding to oxygen therapy and has been diagnosed with ARDS (Acute Respiratory Distress Syndrome). What is the role of IL-8 in ARDS?
Chemical Mediators of Inflammation Indian Medical PG Practice Questions and MCQs
Question 1: All are sources of free radicals except -
- A. Glutathione (Correct Answer)
- B. Nitric oxide
- C. Myeloperoxidase
- D. Fenton's reaction
Explanation: ***Glutathione*** - **Glutathione** is a powerful **antioxidant** that helps to neutralize free radicals, not produce them. - It plays a crucial role in protecting cells from **oxidative damage**. *Nitric oxide* - **Nitric oxide (NO)** is a free radical itself, containing an unpaired electron. - It can lead to the formation of other reactive nitrogen species, contributing to **oxidative stress**. *Myeloperoxidase* - **Myeloperoxidase (MPO)** is an enzyme primarily found in neutrophils that produces powerful free radicals like **hypochlorous acid (HOCl)**, a highly reactive oxidant. - This process is essential for the immune system's ability to kill invading pathogens. *Fenton's reaction* - **Fenton's reaction** is a key chemical process that generates highly reactive **hydroxyl radicals (•OH)** from hydrogen peroxide in the presence of ferrous iron (Fe2+). - This reaction is a significant source of oxidative damage in biological systems.
Question 2: First mediator of inflammation to be released is
- A. Nitric oxide
- B. PAF
- C. Histamine (Correct Answer)
- D. IL-1
Explanation: ***Histamine*** - Histamine is the **first mediator of inflammation released** by mast cells and basophils during an allergic or inflammatory response [1][3]. - It promotes **vasodilation** and increased vascular permeability, leading to typical symptoms of inflammation [1][2]. *PAF* - Platelet-activating factor (PAF) is released later in the inflammatory process and is primarily involved in **amplifying** the response rather than initiating it. - It plays a role in **platelet aggregation** and acting on vascular smooth muscle but is not the first released mediator. *Nitric oxide* - Nitric oxide is produced by endothelial cells and plays a role in **vascular relaxation and inflammation**, but it is not among the first mediators released. - It is involved in more **regulatory functions** in the inflammatory response rather than the initial trigger. *IL-1* - Interleukin-1 (IL-1) is a cytokine that is important for the **inflammatory response**, but it is produced after the initial release of mediators like histamine [2]. - It is primarily secreted by **activated macrophages** and contributes to the **amplification** of the immune response [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-94.
Question 3: Cyclooxygenase plays a role in which pathway?
- A. Leukotriene
- B. Vitamin K
- C. Krebs cycle
- D. Prostaglandin (Correct Answer)
Explanation: ***Prostaglandin*** - **Cyclooxygenase (COX)** enzymes specifically catalyze the conversion of **arachidonic acid** into **prostaglandins**, **prostacyclins**, and **thromboxanes**. - This pathway is crucial for mediating **inflammation**, **fever**, and **pain** responses in the body. *Leukotriene* - **Leukotrienes** are synthesized via the **lipoxygenase** pathway, not the cyclooxygenase pathway. - They are primarily involved in **allergic reactions** and **asthma**, causing bronchoconstriction and increased vascular permeability. *Vitamin K* - **Vitamin K** is a fat-soluble vitamin essential for the synthesis of **blood clotting factors** and does not involve cyclooxygenase enzymes. - It acts as a cofactor for the enzyme **gamma-glutamyl carboxylase**. *Krebs cycle* - The **Krebs cycle (citric acid cycle)** is a central metabolic pathway for **cellular respiration**, producing ATP, NADH, and FADH2. - It takes place in the **mitochondria** and is involved in the breakdown of carbohydrates, fats, and proteins for energy, unrelated to cyclooxygenase.
Question 4: Fever occurs due to which of the following mechanisms?
- A. Endorphin
- B. Enkephalin
- C. Histamine
- D. IL-1 (Correct Answer)
Explanation: ***IL1*** - Interleukin-1 (IL-1) is a **proinflammatory cytokine** that plays a key role in the immune response and is a primary mediator of fever [1]. - It stimulates the **hypothalamus** to increase body temperature set-point, thus inducing fever. *Enkephalin* - Enkephalins are **opioid peptides** involved in pain modulation, not in the fever response. - They primarily act in the **central nervous system** and do not directly influence thermoregulation. *Endorphin* - Endorphins, like enkephalins, are also **opioid peptides** related to pain relief and mood regulation, with no significant role in fever induction. - Their main function is to provide **analgesic** effects rather than influencing body temperature. *Histamine* - Histamine is predominantly involved in **allergic responses** and inflammation but is not a direct mediator of fever. - It causes **vasodilation** and increases vascular permeability, but does not raise the body temperature set-point like IL-1 does. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 110-111.
Question 5: Elaboration of which of the following mediators will be most beneficial in preventing further ischemic injury to the cerebral cortex?
- A. Nitric oxide (Correct Answer)
- B. Bradykinin
- C. Leukotriene E4
- D. Platelet-activating factor
Explanation: ***Nitric oxide*** - Increased production of **nitric oxide** leads to **vasodilation**, improving blood flow to ischemic areas and potentially preventing further neuronal damage. - As a **vasodilator**, nitric oxide can help restore oxygen and nutrient supply to the cerebral cortex affected by ischemia. *Bradykinin (involved in vasodilation and vascular permeability)* - While bradykinin causes **vasodilation**, it also significantly increases **vascular permeability**, which can lead to **cerebral edema** in the context of ischemic injury, worsening patient outcomes. - The increased vascular permeability associated with Bradykinin causes **fluid leakage** into the brain tissue, potentially increasing intracranial pressure and exacerbating secondary injury. *Leukotriene E4 (involved in inflammatory responses)* - **Leukotriene E4** is a potent mediator of **inflammation** and **vasoconstriction**, which would further restrict blood flow and worsen ischemic injury rather than prevent it. - Its pro-inflammatory actions contribute to the **secondary injury cascade** following ischemia, exacerbating tissue damage. *Platelet-activating factor (contributes to inflammation and thrombosis)* - **Platelet-activating factor (PAF)** promotes **platelet aggregation** and **inflammation**, leading to further thrombosis and exacerbating vascular occlusion, thereby worsening ischemia. - Its role in **thrombosis** would directly counteract efforts to restore blood flow to the ischemic cerebral cortex.
Question 6: Which mediators are involved in the resolution of inflammation?
- A. TNF Alfa, IL-1, and CRP
- B. IL-10, IL-1 receptor antagonist, and TGF-β
- C. Interferon-gamma and IL-12
- D. Resolvins, protectins, and lipoxins (Correct Answer)
Explanation: ***Resolvins, protectins, and lipoxins*** - These are **specialized pro-resolving mediators (SPMs)** derived from omega-3 and omega-6 polyunsaturated fatty acids that actively promote the resolution phase of inflammation. - **Lipoxins** (from arachidonic acid) inhibit neutrophil chemotaxis and promote macrophage-mediated clearance of apoptotic cells. - **Resolvins** (from EPA and DHA) actively terminate inflammatory signals, reduce neutrophil infiltration, and enhance bacterial clearance. - **Protectins** promote resolution by limiting neutrophil recruitment and enhancing clearance of inflammatory debris. - These mediators represent the **endogenous "stop signals"** that actively resolve inflammation rather than simply suppressing it. *IL-10, IL-1 receptor antagonist, and TGF-β* - While these have **anti-inflammatory** effects, they are not classified as primary resolution mediators. - **IL-10** inhibits pro-inflammatory cytokine synthesis and suppresses immune responses (immunosuppressive rather than pro-resolving). - **IL-1 receptor antagonist (IL-1Ra)** blocks IL-1 signaling, preventing inflammation amplification. - **TGF-β** promotes tissue repair and has immunosuppressive functions. - These are **anti-inflammatory mediators** that prevent or dampen inflammation, distinct from specialized pro-resolving mediators that actively orchestrate the resolution process. *TNF-alpha, IL-1, and CRP* - **TNF-alpha** and **IL-1** are classic **pro-inflammatory cytokines** that initiate and amplify inflammation. - **CRP (C-reactive protein)** is an acute-phase reactant and biomarker of inflammation, not a mediator of resolution. *Interferon-gamma and IL-12* - **IFN-γ** and **IL-12** promote **Th1 immune responses** and cellular immunity. - These are pro-inflammatory mediators involved in host defense against intracellular pathogens, not resolution of inflammation.
Question 7: Rolling of leucocytes on endothelial cells is mediated by which of the following proteins?
- A. Integrins
- B. Transferrin
- C. PECAM-1
- D. Selectins (Correct Answer)
Explanation: **Selectins** - **Selectins** mediate the initial, weak and transient adhesion of **leukocytes** to the **endothelial cells** lining blood vessels [1]. - This interaction slows down the leukocytes, causing them to **roll** along the vascular endothelium as a prerequisite for **extravasation** [1]. *Integrins* - **Integrins** are responsible for the **firm adhesion** of leukocytes to endothelial cells, but not the rolling [1]. - They bind to **ICAM-1 (intercellular adhesion molecule-1)** on endothelial cells, leading to stable arrest of the leukocyte [1]. *PECAM-1* - **PECAM-1 (Platelet Endothelial Cell Adhesion Molecule-1)** plays a role in **diapedesis** or **transmigration**, the movement of leukocytes *through* the endothelial cell junctions [1]. - It facilitates the passage of the leukocyte by interacting with PECAM-1 on the endothelial cells, but does not mediate rolling [1]. *Transferrin* - **Transferrin** is an iron-binding protein found in blood plasma that regulates free **iron levels** in the body. - It is crucial for **iron transport** and metabolic processes but has no direct role in leukocyte adhesion or rolling on endothelial cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89.
Question 8: Arrange the following cellular events of inflammation in the correct sequence: 1. Rolling 2. Cytokine-mediated integrin activation 3. Adhesion 4. Migration
- A. 1,2,3,4 (Correct Answer)
- B. 3,4,1,2
- C. 2,1,4,3
- D. 4,1,2,3
Explanation: ***1,2,3,4*** - The correct sequence of cellular events for leukocyte recruitment during inflammation begins with **rolling** [1], followed by **cytokine-mediated integrin activation** [2], then firm **adhesion** to the endothelium [1], and finally **migration** (diapedesis) into the tissues [3]. - This step-by-step process ensures effective targeting of leukocytes to the site of injury or infection [1]. *3,4,1,2* - This sequence is incorrect as **adhesion** cannot occur before **rolling**, and **migration** is the final step after adhesion, not an early one. - **Cytokine-mediated integrin activation** must precede firm adhesion [1]. *2,1,4,3* - This order is incorrect because **rolling** (1) is the initial interaction that allows leukocytes to slow down on the endothelium [2], and it occurs before **cytokine-mediated integrin activation** (2) which strengthens the binding. - **Migration** (4) is also misplaced as it should be the last step after firm adhesion (3). *4,1,2,3* - This sequence is incorrect as **migration** (4) is the last step in the process, not the first. - **Rolling** (1) initiates the process by transiently interacting with endothelial cells, followed by activation and adhesion. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 87. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Migration in the tissues toward a chemotactic stimulus, pp. 86-87. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89.
Question 9: Most important for diapedesis is
- A. PECAM (Correct Answer)
- B. Selectins
- C. Mucin like glycoprotein
- D. Integrins
Explanation: ***Platelet Endothelial Cell Adhesion Molecule (PECAM)*** - PECAM plays a crucial role in the process of **diapedesis**, allowing white blood cells to pass through the endothelial barrier [1]. - It is specifically involved in **intercellular junctions**, facilitating the migration of leukocytes during **inflammation** [1]. *Selectins* - Selectins are important for **rolling** of leukocytes on the endothelium but do not directly mediate **diapedesis**. - They are crucial for initial attachment but do not promote the passage through the endothelial cell junctions. *Mucin like glycoprotein* - While mucin like glycoproteins can facilitate **cell adhesion**, they primarily contribute to the **rolling phase** rather than diapedesis itself. - They are not as directly involved in the **transmigration** across the endothelium as PECAM. *Integrins* - Integrins are involved in **firm adhesion** of leukocytes, but do not directly enable **diapedesis** across the endothelium. - They support the binding to the endothelium but play a lesser role compared to PECAM in the actual process of migration. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89.
Question 10: A male patient is not responding to oxygen therapy and has been diagnosed with ARDS (Acute Respiratory Distress Syndrome). What is the role of IL-8 in ARDS?
- A. Endothelial cell activation
- B. Recruitment of neutrophils (Correct Answer)
- C. Macrophage activation
- D. Promote surfactant production
Explanation: Recruitment of neutrophils - **Interleukin-8 (IL-8)**, also known as **CXCL8**, is a powerful **chemotactic cytokine** that primarily attracts and activates neutrophils [3]. - In **ARDS**, this recruitment leads to an influx of neutrophils into the pulmonary interstitium and alveolar spaces, contributing to inflammation and lung injury [1]. *Endothelial cell activation* - While other **cytokines** and inflammatory mediators can activate **endothelial cells** in ARDS [2], IL-8's primary role is not direct endothelial activation but rather **neutrophil chemotaxis** [3]. - **Endothelial cell activation** leads to increased vascular permeability and leukocyte adherence, which is often a consequence of overall inflammation, not solely IL-8 [4]. *Macrophage activation* - **Macrophages** are activated by various stimuli and other **cytokines**, such as **TNF-alpha** and **IFN-gamma**, as part of the inflammatory response. - While macrophages produce IL-8, its main function is not to activate macrophages themselves but to attract **neutrophils**. *Promote surfactant production* - **Surfactant production** is primarily regulated by **Type II pneumocytes** and is often impaired in ARDS due to damage to these cells [1]. - IL-8 is a **pro-inflammatory cytokine** and plays no direct role in promoting surfactant synthesis; in fact, its inflammatory effects can indirectly worsen surfactant dysfunction. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 681. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 679. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Migration in the tissues toward a chemotactic stimulus, pp. 86-87.
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