Author Interviews, Case Western, Diabetes, Infections, PLoS / 14.08.2015
Compromised Antimicrobial Response Tied to Infections in Diabetes
MedicalResearch.com Interview with:
Wesley M. Williams, PhD
Cell molecular biologist
Department of Biological Sciences
Case Western Reserve University School of Dental Medicine
MedicalResearch.com: What is the background for this study? What are the main findings?
Dr. Williams: Individuals with uncontrolled blood sugar levels frequently present with higher than normal rates of infection and protracted wound healing. The beta-defensin family of antimicrobial peptides responds to bacterial, fungal and viral invasion. As part of the innate immune system, these cationic peptides normally expressed by epithelial cells are important early responders that, together with other components of the innate immune response, act to inhibit microbial infection. Our initial observations led us to question whether glucose or a metabolite of glucose could contribute to antimicrobial peptide dysfunction, and thus compromise control of infection. Elevated levels of glucose result in increased production of dicarbonyls, a class of molecule that can selectively react with proteins having an unusually high content of cationic amino acids, such as arginine and lysine. We first investigated the effects of two well-characterized dicarbonyls, methylglyoxal (MGO) and glyoxal (GO) on recombinant beta-defensin 2 (rHBD-2) structure using MALDI TOF and LC/MS/MS mass spectral analysis of the recombinant peptide. We found MGO to be particularly reactive with the rHBD-2 peptide as it readily and irreversibly adducted to two arginine residues and the N-terminal glycine. Next we tested in vitro for the effects of adducted rHBD-2 on antimicrobial and chemotactic functions, both essential to an effective innate and adaptive immune response in vivo. Through radial diffusion testing on gram-negative E. coli and P. aeruginosa, and gram-positive S. aureus, and a chemotaxis assay for CEM-SS cells, we found that both antimicrobial and chemotactic functions of rHBD-2 were significantly compromised by MGO.
(more…)