The respiratory system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
The etiology of newborn respiratory distress syndrome differs considerably from that of the adult. Respiratory distress in the newborn is most commonly caused by a lack of surfactant by the lungs. Pulmonary surfactant is a mixture of lipids and proteins and is produced by type II cells of the alveoli. A thin layer of surfactant covers the surface of the alveoli and provides surface tension that keeps the thin-walled alveoli from collapsing. Surfactant also moistens the alveolar surfaces to facilitate gas exchange. Respiratory distress syndrome of the newborn occurs most commonly in infants who are born premature and whose lungs have not developed to the point where they are producing adequate surfactant. Clinical manifestations become evident immediately at birth and can be rapidly fatal if not treated.
The Biology of the Surfactant-Associated Proteins
Jacques R. Bourbon in Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
Pulmonary surfactant is a lipoprotein substance that is synthesized and secreted by the pulmonary alveolar type II cell.1 Surfactant is stored within the type II cell in lamellar bodies, organelles that are released by exocytosis into the alveolar lumen (Figure 1). The secreted surfactant then lines the alveolus and, by reducing the surface tension of the aqueous-lining layer, prevents the collapse of alveoli during the expiratory phase of respiration. Surfactant deficiency in the newborn can lead to the development of respiratory distress syndrome (RDS), the leading cause of death in premature newborns in the U.S.2 Another disease, adult respiratory distress syndrome (ARDS), may also be caused by deficiency or inactivation of pulmonary surfactant.3 Recently, in several clinical trials, it has been shown that surfactant replacement can be an effective therapy for diseases characterized by surfactant deficiency or inactivity.4,5 Further progress in the treatment of these diseases will depend on a better understanding of the synthesis, secretion, and metabolism of pulmonary surfactant.6
Medicines in neonates
Evelyne Jacqz-Aigrain, Imti Choonara in Paediatric Clinical Pharmacology, 2021
Pulmonary surfactant is a complex mixture of phospholipids, neutral lipids and specific proteins. It lowers surface tension at the air-liquid interface of the lung to prevent alveolar collapse at end-expiration [1]. The major cause of neonatal respiratory distress syndrome (RDS) is a primary deficiency of surfactant [2], and surfactant replacement therapy has had a major impact in improving the outcome of this disorder in preterm infants [3]. Surfactants were the first drugs designed primarily for use in the newborn, and those licensed for treatment or prevention of RDS fall into 2 broad categories: synthetic and natural. Synthetic surfactants are composed mainly of phospholipids (usually dipalmitoylphosphatidylcholine, DPPC, also known as colfosceril palmitate) but do not contain surfactant proteins. Natural surfactants are derived from animal lungs, and they contain both phospholipids and surfactant proteins B and C [4].
Could Vitamin C Protect Against Mercuric Chloride Induced Lung Toxicity In The Offspring Rat: A Histological And Immunohistochemical Study
Published in Ultrastructural Pathology, 2021
Omnia I. Ismail, Manal M.S. El-Meligy
We have suggested that the damage in the type II pneumocytes led to produce insufficient pulmonary surfactant, which trigger a rise in the surface tension, therefore the collapse of alveoli was detected in our work. It was known that the pulmonary surfactant serves to reduce the surface tension of the alveolar lining and to keep the alveoli patent enabling efficient ventilation.26 We hypothesized that prenatal mercury exposure may promote the neonatal death owing to respiratory distress syndrome generating from deficient pulmonary surfactant. Additionally, other function of the type II pneumocyte acts as a progenitor for the type I pneumocyte, which is responsible for the gas exchange and lung maintenance. This mechanism plays a critical role in injury repair and regeneration. As during pulmonary injury, the type II pneumocyte proliferates and then differentiates into the type I pneumocyte that replaces the injured one and restores the structure of alveoli.27 Therefore, we proposed that the type II pneumocyte lost their proliferative and regenerative properities and the integration between both types of pneumocytes in the present work due to HgCl2 exposure.
Ultrastructural analysis of the intracellular surfactant in lungs of healthy and ovalbumin sensitized and challenged Brown Norway rats
Published in Experimental Lung Research, 2023
Andreas Schmiedl, Stefanie Frank, Thomas Tschernig, Jens M. Hohlfeld
Pulmonary surfactant (surface active agent) stabilizes alveolar walls and prevents alveolar collapse during exhalation by a surface area depending reduction of alveolar surface tension.1–3 Surfactant can be subdivided in an intra-alveolar pool and an intracellular compartment.4,5 The intra-alveolar pool is represented by the active and inactive surfactant subtypes in the alveolar hypophase of the lining layer covering the alveolar epithelium.6–10 The intracellular surfactant is found in type II alveolar epithelial cells (AEII), which synthesize, store, secrete and recycle surfactant.11 The phospholipids are synthesized in the endoplasmic reticulum and stored in so-called immature lamellar bodies (Lb).12 Mature Lb are formed by fuzing immature Lb with SP-B and -C containing multivesicular bodies (mvb).13,14 SP-B and SP-C containing Lb are secreted by controlled exocytosis, SP-A and SP-D containing mvb by constitutive exocytosis.15,16
Inhalation of titanium dioxide (P25) nanoparticles to rats and changes in surfactant protein (SP-D) levels in bronchoalveolar lavage fluid and serum
Published in Nanotoxicology, 2019
Takami Okada, Byeong Woo Lee, Akira Ogami, Takako Oyabu, Toshihiko Myojo
Pulmonary surfactants are components of the lining fluid of lung alveoli and the first contact points of inhaled particles in the respiratory system. The surfactant secreted into the alveolar space is a lipoprotein complex produced in type II alveolar epithelial cells and Club cells. The major components of pulmonary surfactant are phospholipids and about 10% of the surfactant consists of proteins, four of which have been defined: SP-A, SP-B, SP-C and SP-D (Schleh et al. 2009; Wright 2005). Serum SP-D tests are conducted on patients with pulmonary diseases in hospitals. In our previous studies of rats administered crystalline silica, nickel oxide and multiwall carbon nanotubes by intratracheal instillation and inhalation, the pulmonary surfactants in BALF were effective biomarkers for assessing the hazardous property of these substances, allowing us to clarify the role of pulmonary surfactants in inflammation (Kuroda et al. 2006; Kadoya et al. 2012; Lee et al. 2013; Kadoya et al. 2016). Phospholipids, total protein, SP-D and BALF surface tension all correlated significantly with the polimorphonuclear neutrophils (PMNs) counts in BALF (Kadoya et al. 2016). If SP-D concentration in serum samples has any correlation with that in BALF samples, it will be feasible to analyze the SP-D level in serum samples of workers exposed to nanoparticles as a biomarker of the exposure.
Related Knowledge Centers
- Adsorption
- Dipalmitoylphosphatidylcholine
- Lung Compliance
- Phospholipid
- Protein
- Pulmonary Surfactant
- Atelectasis
- Surfactant
- Pulmonary Alveolus
- Health System