These data provide new in vivo evidence for an antiinflammatory role for SP-D in response to noninfectious, subacute lung injury via modulation of oxidative-nitrative stress.

Surfactant protein-D (SP-D), a member of the "collectin" family, has been shown to play a role in innate immunity through modulation of inflammation and clearance of organisms. The role of SP-D in host defense against Pneumocystis carinii pneumonia was assessed using SP-D knockout (KO) mice. When inoculated with P. carinii, both wild-type (wt) and SP-D KO mice required CD4 cell depletion to develop infection. In CD4 cell-depleted models, 2 weeks after infection with P. carinii, SP-D KO mice developed increased intensity of infection, compared with wt mice, despite higher lung-inflammation scores and increased amounts of alveolar inflammatory cells. The increased inflammation seen in SP-D KO mice was accompanied by increases in lung weight, expression of inducible nitric oxide (NO) synthase, total NO levels, and 3-nitrotyrosine levels in lung tissue. These results indicate that SP-D plays a role in host defense against P. carinii in vivo by modulating clearance of organisms, lung inflammation, and metabolism of NO.

Surfactant protein D (SP-D)-deficient (SP-D−/−) mice exhibit early development of emphysema. Previously we have shown that SP-D deficiency results in increased production and activity of inducible NO synthase (iNOS). In this study, we examined whether treatment with the iNOS inhibitor 1400W could inhibit the inflammatory phenotype. Mice were treated with 1400W systemically for 7 wk from 3 wk of age. Treatment reduced total lung NO synthase activity to 14.7 ± 6.1% of saline-treated 10-wk-old SP-D−/− littermates. Long-term administration of 1400W reduced lung inflammation and cellular infiltration; and significantly attenuated the increased levels of matrix metalloproteinases 2 and 9, chemokines (KC, TARC), and cytokines (IFN-γ) seen in bronchoalveolar lavage (BAL) of SP-D−/− mice. Abrogation of these levels was associated with decreasing BAL chemotactic activity for RAW cells. Two weeks of treatment with 1400W reduced total lung NO synthase (NOS) activity to 12.7 ± 6.3% of saline-treated SP-D−/− mice. Short-term iNOS inhibition resulted in attenuation of pulmonary inflammation within SP-D−/− mice as shown by decreases in total BAL cell count (63 ± 6% of SP-D−/− control), macrophage size (>25 μm) within the BAL (62 ± 10% of SP-D−/− control), and a percentage of BAL macrophages producing oxidants (76 ± 9% of SP-D−/− control). These studies showed that s.c. delivery of 1400W can be achieved in vivo and can attenuate the inflammatory processes within SP-D deficiency. Our results represent the first report linking defects in the innate immune system in the lung with alterations in NO homeostasis.

, SP-D OE mice exposed to 80% O 2 demonstrated substantially increased survival accompanied by significant reductions in wet to dry lung ratios and bronchoalveolar lavage (BAL) protein. Although SP-D OE and WT mice exhibited a twofold increase in total BAL cells and neutrophilia in response to hyperoxia, the SP-D OE group had lower levels of BAL proinflammatory cytokines and chemokines, including IL-6, tumor necrosis factor-a, and monocyte chemotactic protein-1; increased mRNA levels of the transcription factor NF-E2 related factor-2 (NRF-2) and phase 2 antioxidants hemoxygenase-1 (HO-1), glutathione peroxidase-2 (GPx-2) and NAD(P)H quinone oxidoreductase-1 (Nqo-1); and decreases in lung tissue thiobarbituric acid-reactive substances. As proof of principle, the protective role of SP-D on hyperoxic injury was confirmed as SP-D Dox-on mice exposed to 85% O 2 demonstrated increased mortality upon withdrawal of doxycycline. Conclusions: Local expression of SP-D protects against hyperoxic lung injury through modulation of proinflammatory cytokines and antioxidant enzymatic scavenger systems.

surfactant protein D; inflammation; alveolar macrophages; collectin AS A BYPRODUCT OF THE USE of high oxygen (O 2 ) concentrations often required in management of patients with respiratory failure, reactive oxygen species produced during hyperoxic exposure can adversely affect the lung. It has been proposed that the balance between oxygen radical production and antioxidant capacities can modulate oxygen-mediated injury. The lung responds to hyperoxia by enhancing the expression of cytoprotective proteins including antioxidants (65), DNA repair enzymes (55), and regulators of cell survival. In addition, elevated expression of certain surfactant components occurs in lungs of adult (54) and neonatal rats (64) during adaptation to both sublethal (85%) and lethal (95%) oxygen (1).Surfactant protein D (SP-D), an airway epithelial secretory product, belongs to the superfamily of mammalian C-type (Ca 2ϩ -binding) lectins (collectins), which also includes SP-A and serum mannose-binding lectin. Like all collectins, monomeric SP-D is distinguished by the presence of an NH 2 -terminal cysteine-rich domain, a collagen domain, a coiled-coil neck domain, and a lectin domain with calcium-dependent regulatory elements. SP-D monomers associate through their collagenous domains to form a basic functional trimer, which then associates into higher order multimers. This oligomeric assembly provides high avidity, affinity, and specificity to SP-D ligand recognition. In the lung, SP-D ligands include allergens, particles, bacterial cell wall components, and viral envelope proteins (26). SP-D is also known to be chemotactic for neutrophils and mononuclear phagocytes (25) and to modulate alveolar type II (61) and macrophage function in vitro (39).SP-D is produced primarily by alveolar type II cells and nonciliated bronchiolar cells in the lung (24) and is constitutively secreted into the alveoli where it influences surfactant homeostasis (40), effector cell functions, and host defense. It is upregulated in a variety of inflammatory and infectious conditions including Pneumocystis pneumonia (5), asthma (2), and bleomycin injury (17). Mice or rats exposed to hyperoxic challenge also have increases in SP-D (13), suggesting that it may have a role in protection from this insult.Targeted disruption of the SP-D gene in vivo in two genetically different backgrounds has been shown to result in mice with increased alveolar and cellular pools of surfactant phospholipid, accelerated development of age-related emphysema, and large, foamy macrophages (14,40). These SP-D null mice (SP-D Ϫ/Ϫ ) also exhibit an increase in the baseline level of inflammation in the lung, increases in metalloproteinase activity, and biochemical evidence of enhanced oxidative-nitrative stress (4, 63). In addition, SP-D deficiency also confers susceptibility to specific bacterial (45) and viral infections (46).We have previously reported modulation of bleomycininduced lung injury by SP-D. In SP-D Ϫ/Ϫ mice, we showed increased susceptibility to bleomycin and evidence of oxida...