Hemoglobin and its derived peptides may play a role in the antibacterial mechanism of the vagina.
BACKGROUND
Hemoglobin is a precursor of antibacterial peptides. Our aim was to identify an antibacterial peptide in human endometrium. We tested the antimicrobial activities of hemoglobin and a derived peptide in vitro and in vivo in rats.


METHODS
Samples (n = 3) were scraped from the surface of endometrium. Acid-soluble proteins underwent electrophoresis followed by gel overlay assay and reversed-phase high-performance liquid chromatography. Antibacterial activities were determined by agar radial diffusion assay. Purified peptides were further characterized by electrophoresis, mass spectrometry, N-terminal amino acid (AA) sequencing and protein structure analysis. A rat model was used to test the inhibitory activity of human hemoglobin on vaginal infection with Escherichia coli, using one experimental group (intravaginal hemoglobin, n = 9) and three control groups (n = 14). Vaginal histology was studied.


RESULTS
The purified peptide exhibited potent antibacterial activities against E. coli ML-35P. The N-terminal AA sequence was F L S F P T T K T Y, identical to AA 32-41 of the human hemoglobin alpha chain, and it had the same mass (m/z = 6776.8) as the alpha chain 32-93 AA fragment, with at least three alpha-helices. Histology indicated that the hemoglobin group changed significantly compared with the matrix control group (no treatment after infection): the surface layer of stratified squamous epithelium was smoother, inflammatory cell infiltration was relieved in the lamina propria and congestion pattern was decreased.


CONCLUSIONS
These results suggest that erythrocytes from endometrium are another source of the antimicrobial molecules. Hemoglobin and its derived peptides may play a role in the host defense against pathogens in human vagina.
Deng
Luxia
L
Research Unit of Infection and Immunity, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, People's Republic of China.
Pan
Xiaoling
X
Wang
Yi
Y
Wang
Lili
L
Zhou
Xin E
XE
Li
Ming
M
Feng
Yun
Y
Wu
Qi
Q
Wang
Boyao
B
Huang
Ning
N
D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology* / Q000627:therapeutic use; D002851:Chromatography, High Pressure Liquid; D004717:Endometrium / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000188:drug therapy; D030762:Estrous Cycle; D005260:Female; D006454:Hemoglobins / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D008826:Microbial Sensitivity Tests; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use; D051381:Rats; D017208:Rats, Wistar; D014599:Uterus / Q000473:pathology; D014621:Vagina / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology
D000900:Anti-Bacterial Agents; D006454:Hemoglobins; D010455:Peptides