SP-D loaded PLGA nanoparticles as drug delivery system for prevention and treatment of premature infant's lung diseases.

Preterm infants, particularly those who born between 23 and 28 weeks' gestation, suffer from a very high incidence of respiratory distress syndrome (RDS) related to pulmonary immaturity and inability to make Pulmonary Surfactant (PS). These infants are supported by the use of oxygen, ventilators, and routine administration of surfactant replacement. The currently commercial surfactant replacement therapies do not contain hydrophilic surfactant proteins such as Surfactant Protein D (SP-D). These proteins have a key role in the innate lung host defense, thus the development of a sustained release vehicle that provides SP-D for long periods in preterm infants' lungs would exploit the therapeutic potential of SP-D and other pulmonary medications. The proposed SP-D delivery system is based on nanoparticles (NPs) composed of poly (lactic acid-co-glycolic acid) (PLGA), a biodegradable, FDA approved biopolymer. The resulted NPs were spherical with high Zeta potential value, were not toxic to A-549 lungs cells, and did not induce any inflammatory response in mouse's lungs for short and long-term periods. Moreover, SP-D released from NPs showed biological activity for several days and in vivo release experiment of SP-D loaded NPs revealed that SP-D was released from NPs in mouse lungs with different NPs delivery doses.

Role of viral hemagglutinin glycosylation in anti-influenza activities of recombinant surfactant protein D.

BACKGROUND: Surfactant protein D (SP-D) plays an important role in innate defense against influenza A viruses (IAVs) and other pathogens. METHODS: We tested antiviral activities of recombinant human SP-D against a panel of IAV strains that vary in glycosylation sites on their hemagglutinin (HA). For these experiments a recombinant version of human SP-D of the Met11, Ala160 genotype was used after it was characterized biochemically and structurally. RESULTS: Oligosaccharides at amino acid 165 on the HA in the H3N2 subtype and 104 in the H1N1 subtype are absent in collectin-resistant strains developed in vitro and are important for mediating antiviral activity of SP-D; however, other glycans on the HA of these viral subtypes also are involved in inhibition by SP-D. H3N2 strains obtained shortly after introduction into the human population were largely resistant to SP-D, despite having the glycan at 165. H3N2 strains have become steadily more sensitive to SP-D over time in the human population, in association with addition of other glycans to the head region of the HA. In contrast, H1N1 strains were most sensitive in the 1970s-1980s and more recent strains have become less sensitive, despite retaining the glycan at 104. Two H5N1 strains were also resistant to inhibition by SP-D. By comparing sites of glycan attachment on sensitive vs. resistant strains, specific glycan sites on the head domain of the HA are implicated as important for inhibition by SP-D. Molecular modeling of the glycan attachment sites on HA and the carbohydrate recognition domain of SPD are consistent with these observations. CONCLUSION: Inhibition by SP-D correlates with presence of several glycan attachment sites on the HA. Pandemic and avian strains appear to lack susceptibility to SP-D and this could be a contributory factor to their virulence.

Protective effects of a recombinant fragment of human surfactant protein D in a murine model of pulmonary hypersensitivity induced by dust mite allergens.

Lung surfactant protein D (SP-D) is a carbohydrate pattern recognition immune molecule. It can interact with a range of pathogens, stimulate immune cells and manipulate cytokine profiles during host's immune response. SP-D has also been shown to interact, via its carbohydrate recognition domains, with glycoprotein allergens of house dust mite (Dermatophagoides pteronyssinus, Derp), inhibiting specific IgE isolated from mite-sensitive asthmatic patients from binding these allergens, and blocking subsequent histamine release from sensitized basophils. In the present study, we have examined the protection offered by various doses of intranasal administration of a recombinant fragment of human SP-D (rhSP-D) in a murine model of pulmonary hypersensitivity to Derp allergens which showed characteristic high levels of specific IgE antibodies, peripheral blood eosinophilia, pulmonary infiltrates and a Th2 cytokine response. Treatment of Derp mice with rhSP-D led to significant reduction in Derp-specific IgE levels, blood eosinophilia and pulmonary cellular infiltration. The levels of IL-4 and IL-5 were decreased, while those of IL-12 and IFN-gamma were raised in the supernatant of the cultured splenocytes, indicating a Th2 to Th1 polarization. These results suggest that SP-D has a protective role in the modulation of allergic sensitization and in the development of allergic reactions to Derp allergens and highlight potential of the rhSP-D as a therapeutic for pulmonary hypersensitivity.

Biodistribution of inhaled gold nanoparticles in mice and the influence of surfactant protein D.

BACKGROUND: The pulmonary route is very promising for drug delivery by inhalation. In this regard, nanoparticulate drug delivery systems are discussed, and one very promising nano carrier example is gold nanoparticles (Au NP). Directly after their deposition, inhaled Au NP come into contact with pulmonary surfactant protein D (SP-D). SP-D can agglomerate Au NP in vitro, and this may influence the clearance as well as the systemic translocation in vivo. The aim of the present study was to investigate the clearance and translocation of Au NP at a very early time point after inhalation, as well as the influence of SP-D. METHODS: Aerosolized 20-nm radioactively labeled Au NP were inhaled by healthy adult female mice. One group of mice received dissolved 10 µg of SP-D by intratracheal instillation prior to the Au NP inhalation. After a 2-hr Au NP inhalation period, the mice were killed immediately, and the clearance and translocation to the blood stream were investigated. RESULTS: The highest amount of Au NP was associated with the lung tissue. In the bronchoalveolar lavage fluid (BALF), more Au NP remained free compared with the amount associated with the BALF cells. The amount of Au NP cleared by the mucociliary escalator was low, probably because of this very early time point. Instillation of SP-D prior to Au NP inhalation had no statistically significant effect on the biodistribution of the Au NP. CONCLUSION: Our data show that inhaled Au NP are retained in the mouse lungs and are translocated after a short time, and that SP-D has only a minor effect on Au NP translocation and clearance at a very early time point.

Surfactant protein d deficiency in mice is associated with hyperphagia, altered fat deposition, insulin resistance, and increased basal endotoxemia.

Pulmonary surfactant protein D (SP-D) is a host defence lectin of the innate immune system that enhances clearance of pathogens and modulates inflammatory responses. Recently it has been found that systemic SP-D is associated with metabolic disturbances and that SP-D deficient mice are mildly obese. However, the mechanism behind SP-D's role in energy metabolism is not known.Here we report that SP-D deficient mice had significantly higher ad libitum energy intake compared to wild-type mice and unchanged energy expenditure. This resulted in accumulation but also redistribution of fat tissue. Blood pressure was unchanged. The change in energy intake was unrelated to the basal levels of hypothalamic Pro-opiomelanocortin (POMC) and Agouti-related peptide (AgRP) gene expression. Neither short time systemic, nor intracereberoventricular SP-D treatment altered the hypothalamic signalling or body weight accumulation.In ad libitum fed animals, serum leptin, insulin, and glucose were significantly increased in mice deficient in SP-D, and indicative of insulin resistance. However, restricted diets eliminated all metabolic differences except the distribution of body fat. SP-D deficiency was further associated with elevated levels of systemic bacterial lipopolysaccharide.In conclusion, our findings suggest that lack of SP-D mediates modulation of food intake not directly involving hypothalamic regulatory pathways. The resulting accumulation of adipose tissue was associated with insulin resistance. The data suggest SP-D as a regulator of energy intake and body composition and an inhibitor of metabolic endotoxemia. SP-D may play a causal role at the crossroads of inflammation, obesity, and insulin resistance.

Surfactant protein (SP)-A and SP-D as antimicrobial and immunotherapeutic agents.

Surfactant protein (SP)-A and SP-D belong to the "Soluble C-type Lectin" family of proteins and are collectively known as "Collectins". Based on their ability to recognize pathogens and to regulate the host defense, SP-A and SP-D have been recently categorized as "Secretory Pathogen Recognition Receptors". SP-A and SP-D were first identified in the lung; the expression of SP-A and SP-D has also been observed at other mucosal surfaces, such as lacrimal glands, gastrointestinal mucosa, genitourinary epithelium and periodontal surfaces. Since the role of these proteins is not fully elucidated at other mucosal surfaces, the focus of this article is on lung-SP-A and SP-D. It has become clear from research studies performed over a number of years that SP-A and SP-D are critical for the maintenance of lung homeostasis and the regulation of host defense and inflammation. However, none of the surfactant preparations available for clinical use have SP-A or SP-D. A review is presented here on SP-A- and SP-D-deficiencies in lung diseases, the importance of the administration of SP-A and SP-D, and recent patents and research directions that may lead to the design of novel SP-A- or SP-D-based therapeutics and surfactants.

Susceptibility of mice genetically deficient in the surfactant protein (SP)-A or SP-D gene to pulmonary hypersensitivity induced by antigens and allergens of Aspergillus fumigatus.

Lung surfactant protein A (SP-A) and D (SP-D) are innate immune molecules which are known to interact with allergens and immune cells and modulate cytokine and chemokine profiles during host hypersensitivity response. We have previously shown therapeutic effects of SP-A and SP-D using a murine model of lung hypersensitivity to Aspergillus fumigatus (Afu) allergens. In this study, we have examined the susceptibility of SP-A (AKO) or SP-D gene-deficient (DKO) mice to the Afu allergen challenge, as compared with the wild-type mice. Both AKO and DKO mice exhibited intrinsic hypereosinophilia and several-fold increase in levels of IL-5 and IL-13, and lowering of IFN-gamma to IL-4 ratio in the lungs, suggesting a Th2 bias of immune response. This Th2 bias was reversible by treating AKO or DKO mice with SP-A or SP-D, respectively. The AKO and DKO mice showed distinct immune responses to Afu sensitization. DKO mice were found more susceptible than wild-type mice to pulmonary hypersensitivity induced by Afu allergens. AKO mice were found to be nearly resistant to Afu sensitization. Intranasal treatment with SP-D or rhSP-D (a recombinant fragment of human SP-D containing trimeric C-type lectin domains) was effective in rescuing the Afu-sensitized DKO mice, while SP-A-treated Afu-sensitized AKO mice showed several-fold elevated levels of IL-13 and IL-5, resulting in increased pulmonary eosinophilia and damaged lung tissue. These data reaffirm an important role for SP-A and SP-D in offering resistance to pulmonary allergenic challenge.

Intranasal delivery of a truncated recombinant human SP-D is effective at down-regulating allergic hypersensitivity in mice sensitized to allergens of Aspergillus fumigatus.

C57BL/6 mice were sensitized to Aspergillus fumigatus 1-week culture filtrate, which is rich in the non-glycosylated allergen Asp f1, a major allergen in allergic bronchopulmonary aspergillosis (ABPA). A comparison of the effect of treatment of allergen challenged mice by intranasal administration of a 60-kDa truncated recombinant form of human SP-D (rfhSP-D) or recombinant full length SP-A (rhSP-A) was undertaken. Treatment with rfhSP-D produced significant reduction in IgE, IgG1 and peripheral blood eosinophilia and treatment with rfhSP-D, but not rhSP-A resulted in a significant reduction in airway hyperresponsiveness as measured by whole body plethysmography. Lung histology revealed less peribronchial lymphocytic infiltration in mice treated with rfhSP-D. Intracellular cytokine staining of spleen homogenates showed increases in IL-12 and IFN-gamma and decrease in IL-4. The level of endogenous mouse SP-D was elevated sixfold in the lungs of sensitized mice and was not affected by treatment with rfhSP-D. Taken with our previous studies, with a BALB/c mouse model of ABPA using a 3-week A. fumigatus culture filtrate, the present results show that rfhSP-D can suppress the development of allergic symptoms in sensitized mice independent of genetic background and using a different preparation of A. fumigatus allergens.