Lung Surfactant Protein D (SP-D) Response and Regulation During Acute and Chronic Lung Injury

Abstract

Background Surfactant protein D (SP-D) is a collection that plays important roles in modulating host defense functions and maintaining phospholipid homeostasis in the lung. The aim of current study was to characterize comparatively the SP-D response in bronchoalveolar lavage (BAL) and serum in three murine models of lung injury, using a validated ELISA technology for estimation of SP-D levels. Methods Mice were exposed to lipopolysaccharide, bleomycin, or Pneumocystis carinii (Pc) and sacrificed at different time points. Results In lipopolysaccharide-challenged mice, the level of SP-D in BAL increased within 6 h, peaked at 51 h (4,518 ng/ml), and returned to base level at 99 h (612 ng/ml). Serum levels of SP-D increased immediately (8.6 ng/ml), peaked at 51 h (16 ng/ml), and returned to base levels at 99 h (3.8 ng/ml). In a subacute bleomycin inflammation model, SP-D levels were 4,625 and 367 ng/ml in BAL and serum, respectively, 8 days after exposure. In a chronic Pc inflammation model, the highest level of SP-D was observed 6 weeks after inoculation, with BAL and serum levels of 1,868 and 335 ng/ml, respectively. Conclusions We conclude that serum levels of SP-D increase during lung injury, with a sustained increment during chronic inflammation compared with acute inflammation. A quick upregulation of SP-D in serum in response to acute airway inflammation supports the notion that SP-D translocates from the airways into the vascular system, in favor of being synthesized systemically. The study also confirms the concept of using increased SP-D serum levels as a biomarker of especially chronic airway inflammation.

Airway Surfactant Protein D Deficiency in Adults With Severe Asthma

“…22 Furthermore, acute lung injury in animals, which induces airway inflammation, enhances spillage of SP-D molecules into the systemic circulation and increases serum SP-D concentrations. 23 The increase in serum SP-D concentration in COPD is associated with a risk of exacerbation and is reduced by high-dose oral steroid therapy. 24 Glucocorticoids upregulate the expression of surfactant proteins, including SP-D, both in vivo and in vitro.…”

Influence of Concomitant Arterial Hypertension on Activity of Inflammatory Process in Patients With Community-Acquired Pneumonia

“…Higher SP-D rates were also determined in patients with multiple lesion of the lung on the one hand, indicating a marked increase in the area of lung tissue damage and bacterial infiltration and the relationship between pathological changes in the body in which the violation occurs as a consequence of primary changes in their own turn, reinforce each other [22].…”

p120-Catenin Expressed in Alveolar Type II Cells Is Essential for the Regulation of Lung Innate Immune Response

“…Sp-D plays a protective role against lung infection, allergy, asthma, and inflammation by modulating host defense and inflammation. 23,45,46 Sp-D can bind to bacteria, viruses, and dead cells to enhance uptake by macrophages. 47 It can also modulate the production of inflammatory mediators by binding to cell surface receptors, including SP-A receptor 210, TLR2, TLR4, and signal-inhibitory protein.…”