Defensin beta 118
innate immune response
Expression and Functional Characterization of a Novel Antimicrobial Peptide: Human Beta-Defensin 118.
<h4>Purpose</h4><i>β</i>-Defensin 118 (DEFB118) is a novel host defense peptide (HDP) identified in humans. To evaluate its potentials for future utilization, the DEFB118 gene was expressed in <i>Escherichia coli</i> (<i>E. coli</i>) and the recombinant protein was fully characterized.<h4>Methods</h4>The DEFB118 protein was obtained by heterologous expression using <i>E. coli</i> Rosetta (DE3). Antibacterial activity of DEFB118 was determined by using various bacterial strains. IPEC-J cells challenged by <i>E. coli</i> K88 were used to determine its influences on inflammatory responses.<h4>Results</h4>The <i>E. coli</i> transformants yielded more than 250 <i>μ</i>g/mL DEFB118 protein after 4 h induction by 1.0 mM IPTG. The DEFB118 was estimated by SDS-PAGE to be 30 kDa, and MALDI-TOF analysis verified that it is a human <i>β</i>-defensin 118. Importantly, the DEFB118 showed antimicrobial activities against both Gram-negative bacteria (<i>E. coli K88</i> and <i>E. coli DH5α</i>) and Gram-positive bacteria (<i>S. aureus</i> and <i>B. subtilis</i>), with a minimum inhibitory concentration (MIC) of 4 <i>μ</i>g/mL. Hemolytic assays showed that DEFB118 had no detrimental impact on cell viability. Additionally, DEFB118 was found to elevate the viability of IPEC-J2 cells upon <i>E. coli</i> K88 challenge. Moreover, DEFB118 significantly decreased cell apoptosis in the late apoptosis phase and downregulated the expression of inflammatory cytokines such as IL-1<i>β</i> and TNF-<i>α</i> in IPEC-J2 cell exposure to <i>E. coli</i> K88.<h4>Conclusions</h4>These results suggested a novel function of the mammalian defensins, and the antibacterial and anti-inflammatory properties of DEFB118 may allow it as a potential substitute for conventionally used antibiotics or drugs.