surfactant homeostasis

Definition

Target type: biologicalprocess

Any process involved in the maintenance of a steady-state level of a surface-active agent that maintains the surface tension of a liquid. [PMID:23708874, PMID:9751757]

Surfactant homeostasis is a complex and tightly regulated process that ensures the proper functioning of the lungs, specifically the alveoli. Surfactant, a mixture of phospholipids, proteins, and carbohydrates, lines the alveoli, reducing surface tension and preventing them from collapsing during expiration. This delicate balance is crucial for normal breathing and gas exchange.

**Production and Secretion:**

* Type II pneumocytes within the alveoli synthesize and secrete surfactant.
* This process involves the synthesis of phospholipids, primarily dipalmitoylphosphatidylcholine (DPPC), which is the main component responsible for reducing surface tension.
* Other key surfactant proteins (SP-A, SP-B, SP-C, and SP-D) are also produced and play important roles in regulating surfactant function and immunity.
* The production and secretion of surfactant are influenced by various factors, including stretch of the alveoli, hormonal signals, and inflammation.

**Surfactant Turnover:**

* Surfactant is constantly being recycled within the alveoli to maintain its optimal concentration and function.
* Surfactant phospholipids are internalized by type II pneumocytes and other alveolar cells through endocytosis.
* These phospholipids are then processed and re-secreted back into the alveoli, ensuring a continuous supply of surfactant.

**Regulation of Surfactant Homeostasis:**

* **Mechanical Stretch:** Stretching of the alveoli during inspiration stimulates the release of surfactant.
* **Hormones:** Hormones like cortisol and catecholamines can regulate surfactant production.
* **Inflammation:** Inflammatory mediators can influence surfactant production and function.
* **Surfactant Proteins:** SP-A, SP-B, and SP-C are crucial for surfactant function. SP-A helps with the formation of surfactant films and clearance of foreign substances, while SP-B and SP-C aid in the spreading and stability of the surfactant layer.

**Consequences of Surfactant Dysfunction:**

* **Respiratory Distress Syndrome (RDS):** Premature infants often lack sufficient surfactant, leading to RDS.
* **Lung Injury:** Surfactant dysfunction can contribute to lung injury in various conditions, including pneumonia and sepsis.
* **Alveolar Collapse:** Reduced surfactant levels can cause the alveoli to collapse during expiration, leading to respiratory distress.

**Clinical Relevance:**

* Surfactant replacement therapy is a crucial intervention for infants with RDS, providing the necessary surfactant to improve lung function.
* Understanding surfactant homeostasis is essential for developing new therapies to treat various lung diseases and conditions.'
"

Proteins (5)

Compounds (264)