Calcitonin gene-related peptide down-regulates the inflammatory response induced by lipopolysaccharide of Klebsiella pneumoniae
Objective 
To investigate the effects of calcitonin gene-related peptide (CGRP) on the inflammatory response induced by lipopolysaccharide (LPS) of Klebsiella pneumoniae. 
 
 
Methods 
Klebsiella pneumoniae was cultured in vitro to extracted LPS. Different concentrations of LPS were used to stimulate BEAS-2B cells. The activation of human β defensin 2 (hBD-2) in these cells was detected by immunofluorescence assay before and after adding different concentrations of CGRP. MTT assay and flow cytometry were respectively used to detect the proliferation and apoptosis of BEAS-2B cells after LPS stimulation with and without CGRP treatment. Neutrophil granules released in the cells after CGRP treatment were detected using neutrophil gelatinase-related apolipoprotein (NGAL) as the marker. 
 
 
Results 
Immunofluorescence assay results showed that LPS at different concentrations could significantly increase the relative expression of hBD-2 in BEAS-2B cells, which was significantly inhibit by CGRP intervention. LPS at 50 ng/ml, 100 ng/ml and 200 ng/ml had no significant effect on the activity of BEAS-2B cells, while treatment with 400 ng/ml of LPS for 24 h could significantly reduce the activity and promote the apoptosis of BEAS-2B cells. In addition, remarkedly increased cell activity and suppressed cell apoptosis were induced when BEAS-2B cells were treated with 10 nmol/L of CGRP in combination with LPS. LPS at different concentrations could induce the release of neutrophil-specific granules, while the LPS-induce release could be significantly inhibited by 10 nmol/L of CGRP. 
 
 
Conclusions 
CGRP could inhibit the expression of hBD-2, promote cell proliferation and reduce the degranulation of neutrophils to down-regulate the inflammatory response induced by LPS of Klebsiella pneumoniae. 
 
 
Key words: 
Klebsiella pneumoniae; Calcitonin gene-related peptide; βdefensin; Inflammatory response