Recombinant expression of the precursor of rat lung surfactant protein B in Escherichia coli and its antibacterial mechanism

Bacterial expression, purification and folding of exceptionally hydrophobic and essential protein: Surfactant Protein-B (SP-B)

Lung Surfactant Protein B (SP-B) is essential for life. It is thus striking that, to this point, no method for making the full-length protein has been published and consequently we lack detailed understanding of SP-B's basic structure-function relationships, as well as an inability to make it for clinical use. The major challenge in producing SP-B lies with its exceptionally hydrophobic nature. In this work, we present a method to produce recombinant SP-B in bacteria that can be used to make the full-length protein as well as the product focused on here, which is a construct lacking the N-terminal 7 residues, rSP-B (Δ7NTC48S-SP-B-6His). The construct is produced as a fusion to Staphylococcus nuclease A (SN) in Escherichia coli C43 cells, a strain known to promote production of toxic and membrane recombinant proteins. After cleavage from SN, rSP-B is folded on column and then exchanged into the lipid or detergent system of choice. rSP-B prepared in this way exhibits the correct secondary structure and demonstrates surface activity. The yield obtained is 0.3 mg of purified rSP-B (Δ7NTC48S-SP-B-6His) per liter of initial bacterial culture. We expect this method for producing SP-B will be valuable in enabling basic research into SP-B's mechanisms, as well as possibly facilitating the inclusion of SP-B in lung surfactant formulations to treat common and frequently fatal lung conditions and in lung surfactant-based drug delivery.

The dual antimicrobial and immunomodulatory roles of host defense peptides and their applications in animal production

Host defense peptides (HDPs) are small molecules with broad-spectrum antimicrobial activities against infectious bacteria, viruses, and fungi. Increasing evidence suggests that HDPs can also indirectly protect hosts by modulating their immune responses. Due to these dual roles, HDPs have been considered one of the most promising antibiotic substitutes to improve growth performance, intestinal health, and immunity in farm animals. This review describes the antimicrobial and immunomodulatory roles of host defense peptides and their recent applications in animal production.

Down-regulated surfactant protein B in obese asthmatics

BACKGROUND

Obesity is a common comorbid condition in adult asthmatics and known as a feature of asthma severity. However, the molecular mechanism under obesity-induced inflammation has not yet been fully understood.

OBJECTIVE

Considering the essential role of hydrophobic surfactant protein B (SP-B) in lung function, SP-B was targeted to examine its involvement in the development of obesity-induced airway inflammation in asthmatics.

METHODS

The aim was to examine an alteration in circulating SP-B according to obesity in adult asthmatics, 129 asthmatics were enrolled and classified into 3 groups (obese, overweight and normal-weight groups) according to body mass index (BMI). Circulating SP-B levels were determined by enzyme-linked immunosorbent assay. Four single nucleotide polymorphisms of SFTPB gene were genotyped. Serum ceramide levels were measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Significantly lower serum SP-B levels were noted in the obese group than in the overweight or normal-weight group (p = .002). The serum SP-B level was significantly correlated with serum levels of C18:0 ceramide and transforming growth factor beta 1 as well as BMI (r = -0.200; r = -0.215; r = -0.332, p < .050 for all). An inverse correlation was noted between serum SP-B and fractional exhaled nitric oxide levels in female asthmatics (r = -0.287, p = .009). Genetic predisposition of the SFTPB gene at 9306 A>G to the obese and overweight groups was noted.

CONCLUSION

Obesity altered ceramide metabolism leading to pulmonary surfactant dysfunction and impaired resolution of airway inflammation, finally contributing to the phenotypes of obese asthmatics.