Degradation of surfactant protein D by alveolar macrophages

1998 ◽  
Vol 274 (1) ◽  
pp. L97-L105 ◽  
Author(s):  
Qun Dong ◽  
Jo Rae Wright
Keyword(s):  
Alveolar Macrophages ◽  
Pulmonary Surfactant ◽  
Degradation Products ◽  
Surfactant Protein ◽  
Surfactant Protein D ◽  
Alveolar Type ◽  
Clara Cells ◽  
Temperature Dependent ◽  
A Cell

Surfactant protein (SP) D is a pulmonary surfactant-associated protein that may function in lung host defense. SP-D is produced by alveolar type II cells and nonciliated bronchiolar epithelial (Clara) cells of the airway and is secreted into the air space. Here we investigated whether alveolar macrophages degraded SP-D in vitro. We also examined the effects of SP-A and lipids on SP-D metabolism. The results showed that alveolar macrophages bound and degraded SP-D in a time- and temperature-dependent fashion. After 100 min of incubation, the formation of trichloroacetic acid-soluble degradation products increased 4-fold in the medium and 30-fold in the cells. The degradation of SP-D was via a cell-associated process because SP-D was not degraded when incubated in medium previously conditioned by alveolar macrophages. Gel autoradiography of cell lysate samples after incubation with 125I-labeled SP-D demonstrated an increase in degradation products, further confirming the degradation of SP-D by alveolar macrophages. In addition, the degradation of SP-D was not affected by coincubation with SP-A or surfactant-like liposomes containing either phosphatidylglycerol or phosphatidylinositol. In conclusion, alveolar macrophages rapidly degrade SP-D and may play an important role in SP-D turnover and clearance.

scholarly journals Immunocytochemical localization of surfactant protein D (SP-D) in type II cells, Clara cells, and alveolar macrophages of rat lung.

1992 ◽  
Vol 40 (10) ◽  
pp. 1589-1597 ◽  
Author(s):  
W F Voorhout ◽  
T Veenendaal ◽  
Y Kuroki ◽  
Y Ogasawara ◽  
L M van Golde ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Alveolar Macrophages ◽  
Surfactant Protein ◽  
Surfactant Protein D ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Clara Cells ◽  
Double Labeling

We investigated the cellular and subcellular distribution of surfactant protein D (SP-D) by immunogold labeling in lungs of adult rats that had been given bovine serum albumin coupled to 5-nm gold (BSAG) for 2 hr to visualize the endocytotic pathway. Specific gold labeling for SP-D was found in alveolar Type II cells, Clara cells, and alveolar macrophages. In Type II cells abundant labeling was observed in the endoplasmic reticulum, whereas the Golgi complex and multivesicular bodies were labeled to a limited extent only. Lamellar bodies did not seem to contain SP-D. Gold labeling in alveolar macrophages was restricted to structures containing endocytosed BSAG. In Clara cells labeling was found in the endoplasmic reticulum, the Golgi complex, and was most prominent in granules present in the apical domain of the cell. Double labeling experiments with anti-surfactant protein A (SP-A) showed that both SP-A and SP-D were present in the same granules. However, SP-A was distributed throughout the granule contents, whereas SP-D was confined to the periphery of the granule. The Clara cell granules are considered secretory granules and not lysosomes, because they were not labeled for the lysosomal markers cathepsin D and LGP120, and they did not contain endocytosed BSAG.

Differential susceptibilities of isolated hamster lung cell types to amiodarone toxicity

1998 ◽  
Vol 76 (7-8) ◽  
pp. 721-727 ◽  
Author(s):  
M W Bolt ◽  
W J Racz ◽  
J F Brien ◽  
T M Bray ◽  
T E Massey
Keyword(s):  
Alveolar Macrophages ◽  
Gradient Centrifugation ◽  
Cell Types ◽  
Clara Cell ◽  
Blue Dye ◽  
Alveolar Type ◽  
Specific Cell ◽  
Type Ii ◽  
Clara Cells

Treatment of cardiac dysrhythmias with the iodinated benzofuran derivative amiodarone (AM) is limited by pulmonary toxicity. The susceptibilities of different lung cell types of male Golden Syrian hamsters to AM-induced cytotoxicity were investigated in vitro. Bronchoalveolar lavage and protease digestion to release cells, followed by centrifugal elutriation and density gradient centrifugation, resulted in preparations enriched with alveolar macrophages (98%), alveolar type II cells (75-85%), and nonciliated bronchiolar epithelial (Clara) cells (35-50%). Alveolar type II cell and Clara cell preparations demonstrated decreased viability (by 0.5% trypan blue dye exclusion) when incubated with 50 µM AM for 36 h, and all AM-treated cell preparations demonstrated decreased viability when incubated with 100 or 200 µM AM. Based on a viability index ((viability of AM-treated cells ÷ viability of controls) × 100%), the Clara cell fraction was significantly (p < 0.05) more susceptible than all of the other cell types to 50 µM AM. However, AM cytotoxicity was greatest (p < 0.05) in alveolar macrophages following incubation with 100 or 200 µM AM. There was no difference between any of the enriched cell preparations in the amount of drug accumulated following 24 h of incubation with 50 µM AM, whereas alveolar macrophages accumulated the most drug during incubation with 100 µM AM. Thus, the most susceptible cell type was dependent on AM concentration. AM-induced cytotoxicity in specific cell types may initiate processes leading to inflammation and pulmonary fibrosis.Key words: amiodarone, susceptibility, alveolar macrophage, accumulation.

scholarly journals Noncapsulated Klebsiella pneumoniae Bearing Mannose-Containing O Antigens Is Rapidly Eradicated from Mouse Lung and Triggers Cytokine Production by Macrophages following Opsonization with Surfactant Protein D

2005 ◽  
Vol 73 (12) ◽  
pp. 8282-8290 ◽  
Author(s):  
Elena Kostina ◽  
Itzhak Ofek ◽  
Erika Crouch ◽  
Rotem Friedman ◽  
Lea Sirota ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Alveolar Macrophages ◽  
Cytokine Production ◽  
Human Monocyte ◽  
Surfactant Protein ◽  
Mouse Lung ◽  
Surfactant Protein D ◽  
O Antigens

ABSTRACT To better understand the relationship between the surface polysaccharides of pulmonary pathogens and components of the lung innate immune system, we employed selected serotypes of Klebsiella pneumoniae expressing distinct capsular polysaccharides and/or O antigen in a murine model of K. pneumoniae infection. In addition, we examined the effect of surfactant protein D (SP-D) on the cytokine response of human monocyte-derived macrophages to these serotypes in vitro. Noncapsulated mannose-containing O3 serotypes (K50/n and K55/n), which react efficiently with SP-D in vitro, triggered high levels of interleukin-1β (IL-1β) and IL-6 production. In vivo, they were more efficiently cleared from the lungs of mice but not from macrophage-depleted mice. They also were more efficiently internalized by alveolar macrophages in vivo. In contrast, galactose-containing O1 serotypes (K2/n and K21a/n), which interact poorly with SP-D, exhibited significantly lower cytokine production and less efficient pulmonary clearance and were ineffectively internalized by alveolar macrophages. These findings are consistent with in vitro results showing that production of IL-1β and IL-6 mRNA and IL-6 protein by human macrophages exposed to mannose-bearing Klebsiella O serotypes is significantly increased by SP-D. Thus, survival of inhaled bacteria in the lung depends partially on the lipopolysaccharide structure of the bacteria and their interactions with innate immunity components. We speculate that an imbalance of host SP-D and therefore cytokine levels may result in high susceptibility of the host to the pathogen.

Metabolism of phosphatidylglycerol by alveolar macrophages in vitro

2000 ◽  
Vol 279 (2) ◽  
pp. L399-L407 ◽  
Author(s):  
Omar A. Quintero ◽  
Jo Rae Wright
Keyword(s):  
Alveolar Macrophages ◽  
Isotope Ratio ◽  
Animal Studies ◽  
Surfactant Protein ◽  
Dependent Manner ◽  
Phospholipase Activity ◽  
Temperature Dependent ◽  
Isolated Rat

In whole animal studies, it has been shown that turnover of surfactant dipalmitoylphosphatidylglycerol (DPPG) is faster than that of dipalmitoylphosphatidylcholine (DPPC). The goal of this investigation was to characterize the metabolism of DPPG by alveolar macrophages and to determine whether they contribute to the faster alveolar clearance of DPPG. Isolated rat alveolar macrophages were incubated with liposomes colabeled with [3H]DPPG and [14C]DPPC. Macrophages internalized both lipids in a time- and temperature-dependent manner. The uptake of both lipids was increased by surfactant protein (SP) A and by adherence of the macrophages to plastic slides. The isotope ratio of DPPC to DPPG internalized by macrophages in suspension in the absence of SP-A was significantly lower than the isotope ratio in liposomes, suggesting that macrophages preferentially internalize DPPG when SP-A is absent. Phospholipase activity in macrophage homogenate was higher toward sn-2-labeled DPPG than toward sn-2-labeled DPPC. These studies show that alveolar macrophages play an important role in catabolizing surfactant lipids and may be partially responsible for the relatively faster clearance of DPPG from the lung.

scholarly journals Surfactant Protein D-Mediated Aggregation of Pneumocystis carinii Impairs Phagocytosis by Alveolar Macrophages

2003 ◽  
Vol 71 (4) ◽  
pp. 1662-1671 ◽  
Author(s):  
Suk-Joong Yong ◽  
Zvezdana Vuk-Pavlovic ◽  
Joseph E. Standing ◽  
Erika C. Crouch ◽  
Andrew H. Limper
Keyword(s):  
Alveolar Macrophages ◽  
Animal Studies ◽  
Pneumocystis Carinii ◽  
Lavage Fluid ◽  
Surfactant Protein ◽  
Molecular Forms ◽  
Surfactant Protein D ◽  
Lectin Domain

ABSTRACT Pneumocystis carinii remains an important and potentially fatal cause of opportunistic pneumonia. Animal studies reveal that substantial quantities of surfactant protein D (SP-D) accumulate in the airspaces during P. carinii pneumonia and are particularly abundant in aggregates of organisms. Due to the multimeric structure of SP-D, we hypothesized that SP-D mediates aggregation of the organism. From previous clinical studies it is known that aggregated organisms are conspicuous in sections of lung tissue and bronchoalveolar lavage (BAL) fluids of humans with active P. carinii pneumonia. Herein, we observe that SP-D levels increased at least fourfold in BAL fluids of patients with P. carinii pneumonia. Next, a spectrophotometric sedimentation assay was developed to assess the aggregation of P. carinii in vitro by SP-D. P. carinii organisms were first stripped with glutathione to remove bound SP-D and subsequently incubated in the presence of SP-D and 2 mM calcium. P. carinii incubated with natural SP-D (10 μg/ml) containing dodecamers and higher-order forms exhibited aggregation and enhanced sedimentation compared to that of glutathione-stripped P. carinii. Aggregation was also enhanced by the concentrated supernatant of rat BAL fluid, and this effect was abolished by the selective removal of SP-D from the lavage fluid. P. carinii aggregation was reduced by maltose, mannose, and EDTA, consistent with the role of the SP-D C-type lectin domain (CRD) in the aggregation event. Comparisons of different molecular forms of SP-D showed that dodecamers—but not trimeric subunits—mediate optimal aggregation of P. carinii. Aggregation of P. carinii by SP-D was shown to be responsible for the impaired phagocytosis of the organisms by alveolar macrophages. Thus, SP-D-mediated aggregation of P. carinii may represent one means by which the organism avoids elimination by the host.

Surfactant protein-D regulates the postnatal maturation of pulmonary surfactant lipid pool sizes

2009 ◽  
Vol 106 (5) ◽  
pp. 1545-1552 ◽  
Author(s):  
Machiko Ikegami ◽  
Shawn Grant ◽  
Thomas Korfhagen ◽  
Ronald K. Scheule ◽  
Jeffrey A. Whitsett
Keyword(s):  
Pulmonary Surfactant ◽  
Surfactant Protein ◽  
Pool Size ◽  
Surfactant Protein D ◽  
Type Ii Cells ◽  
Type Ii ◽  
Postnatal Maturation ◽  
Lipid Pool ◽  
Surfactant Lipid

Surfactant protein (SP)-D plays an important role in host defense and pulmonary surfactant homeostasis. In SP-D-deficient ( Sftpd−/−) mice, the abnormal large surfactant forms seen at the ultrastructural level are taken up inefficiently by type II cells, resulting in an over threefold increase in the surfactant pool size. The mechanisms by which SP-D influences surfactant ultrastructure are unknown. We hypothesized that SP-D binds to surfactant immediately after being secreted and influences surfactant ultrastructure conversion. In newborn and adult sheep lungs, immunogold-labeled SP-D was associated with both lamellated membranous lipid structures of newly secreted surfactant and with small aggregate surfactant but not with tubular myelin. Since SP-D preferentially binds to phosphatidylinositol (PI) in vitro, the postnatal changes in PI were assessed. PI content in the bronchoalveolar lavage fluid increased after birth and peaked at 2–5 days of age, a time of rapid conversion of surfactant forms that is associated with the peak of surfactant lipid pool size. SP-D selectively interacted with PI-rich liposomes in vitro, causing their lysis. Similarly, the abnormal surfactant ultrastructure in Sftpd−/− mice was corrected by the addition of SP-D or melittin, and both peptides caused lysis of lipid vesicles. The normal conversion of surfactant ultrastructure requires SP-D that preferentially interacts with PI-rich, newly secreted surfactant, causing lysis of surfactant lipid membranes, converting the lipid forms into smaller surfactant lamellated structures that are critical for surfactant uptake by type II cells and normal surfactant homeostasis. SP-D regulates the dramatic decreases in the surfactant pool size that occurs in the newborn period.

Surfactant protein D influences surfactant ultrastructure and uptake by alveolar type II cells

2005 ◽  
Vol 288 (3) ◽  
pp. L552-L561 ◽  
Author(s):  
Machiko Ikegami ◽  
Cheng-Lun Na ◽  
Thomas R. Korfhagen ◽  
Jeffrey A. Whitsett
Keyword(s):  
Surfactant Protein ◽  
Surfactant Protein D ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Defense Proteins ◽  
Conditional Expression ◽  
Pool Sizes

Surfactant protein D (SP-D) is a member of the collectin family of the innate host defense proteins. In the lung, SP-D is expressed primarily by type II cells. Gene-targeted SP-D-deficient [SP-D(−/−)] mice have three- to fivefold higher surfactant lipid pool sizes. However, surfactant synthesis and secretion by type II cells and catabolism by alveolar macrophages are normal in SP-D(−/−) mice. Therefore, we hypothesized that SP-D might regulate surfactant homeostasis by influencing surfactant structure, thereby altering its uptake by type II cells. Large (LA) and small aggregate (SA) surfactant were isolated from bronchoalveolar lavage fluid (BALF) from SP-D(−/−), wild-type [SP-D(+/+)], and transgenic mice in which SP-D was expressed under conditional control of doxycycline in alveolar type II cells. Uptake of both LA and SA isolated from SP-D(-/-) mice by normal type II cells was decreased. Abnormally dense lipid forms were observed by electron microscopy of LA from SP-D(−/−) mice. SA from SP-D(−/−) mice consisted of atypical multilamellated small vesicles. Abnormalities in surfactant uptake by type II cells and in surfactant ultrastructure were corrected by conditional expression of SP-D in vivo. Preincubation of BALF from SP-D(−/−) mice with SP-D changed surfactant ultrastructure to be similar to that of SP-D(+/+) mice in vitro. The rapid changes in surfactant structure, increased uptake by type II cells, and decreased pool sizes normally occurring in the postnatal period were not seen in SP-D(−/−) mice. SP-D regulates uptake and catabolism by type II cells and influences the ultrastructure of surfactant in the alveolus.

Interactions of recombinant human pulmonary surfactant protein D and SP-D multimers with influenza A

1996 ◽  
Vol 271 (5) ◽  
pp. L753-L762 ◽  
Author(s):  
K. Hartshorn ◽  
D. Chang ◽  
K. Rust ◽  
M. White ◽  
J. Heuser ◽  
...  
Keyword(s):  
Pulmonary Surfactant ◽  
Influenza A ◽  
Culture Medium ◽  
Chinese Hamster ◽  
Surfactant Protein ◽  
Surfactant Protein D ◽  
Major Fraction ◽  
Viral Hemagglutinin ◽  
And Function

To further study the structure and function of surfactant protein D (SP-D), recombinant human SP-D (rhSP-D) was isolated from the culture medium of Chinese hamster ovary (CHO)-K1 cells stably transfected with a full-length hSP-D cDNA. Although a significant fraction of the secreted rhSP-D was recovered as dodecamers similar to recombinant rat SP-D (rrSP-D), a major fraction accumulated as multimers of dodecamers indistinguishable from human proteinosis SP-D. As previously shown for the rat protein, rhSP-D agglutinated specific strains of influenza A virus (IAV), inhibited viral hemagglutinin activity, and protected neutrophils (PMN) from deactivation by IAV. However, the potency of rhSP-D multimers was severalfold greater than for purified dodecamers, comparable to natural, proteinosis hSP-D. Although rhSP-D multimers were also more potent than the serum collectins in mediating viral aggregation and protection of PMN, they were less potent than conglutinin in inhibiting infectivity in vitro. These studies establish that the propensity of hSP-D to form multimers of dodecamers is determined by its primary structure and demonstrate carbohydrate recognition domain valency-dependent interactions of SP-D with IAV.

Degradation of pulmonary surfactant disaturated phosphatidylcholines by alveolar macrophages

1988 ◽  
Vol 64 (6) ◽  
pp. 2474-2481 ◽  
Author(s):  
P. R. Miles ◽  
J. Y. Ma ◽  
L. Bowman
Keyword(s):  
Alveolar Macrophages ◽  
Pulmonary Surfactant ◽  
Specific Activity ◽  
Extracellular Fluid ◽  
Temperature Dependent ◽  
Physical Form ◽  
Other Information ◽  
Cell Fragments

Experiments were performed to determine whether rat pulmonary surfactant disaturated phosphatidylcholines (DSPC) are degraded by alveolar macrophages in vitro. When [3H]choline-labeled surfactant materials are incubated with unlabeled alveolar macrophages, approximately 40% of the labeled DSPC is broken down in 6 h. There is just a slight decrease in the specific activity of DSPC, which suggests that most products of degradation are not reincorporated into DSPC, at least during the 6-h incubation period. There is a time- and temperature-dependent association of surfactant DSPC with alveolar macrophages, and some of the cell-associated materials are released from the cell fragments after sonication. Association of surfactant with the cells precedes degradation. The breakdown of surfactant DSPC by intact alveolar macrophages lags behind that produced by sonicated cell preparations with disrupted cell membranes. These data and other information suggest that the surfactant materials are internalized by the cells, before the breakdown. The products of degradation probably include free choline and fatty acids, most of which appear in the extracellular fluid. The breakdown processes do not seem to depend on the physical form of the surfactant or on the presence of surfactant apoproteins. Incubation of the cells alone also results in disappearance of intracellular DSPC, some of which may be surfactant phospholipid taken up by the cells in vivo. These results indicate that alveolar macrophages can degrade surfactant DSPC and suggest that these cells may be involved in catabolism of pulmonary surfactant materials.

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