Role of processed peptides of the basement membrane component laminin in skin barrier function
Final Report Abstract
Expression and processing of laminins in skin are tightly regulated. Processing of laminins to generate smaller peptide fragments have a critical function in innate skin immune response and wound healing. In a recent study, we showed that (1) human skin and skin-derived cells process and secrete biologically active peptides from the LG4-5 module of the laminin α3, α4 and α5 chains in vitro and in vivo, (2) expression of laminin α3 is increased in human keratinocytes by proinflammatory cytokines and growth factors, (3) expression and processing of laminin α3 are increased in chronic wounds and in human keratinocytes after bacterial infection, (4) bacterial and neutrophil-derived proteases are able to further process the laminin α3 LG4-5 module and (5) laminin LG4 module-derived peptides from the α3, α4 and α5 chains display antimicrobial activity and potent chemotactic activity on immune cells and further promote wound healing by increasing keratinocyte proliferation and migration. In a detailed study on processed peptides we used recombinant laminin α3 LG4-5 and incubated with wound fluid. As a result we get post-processed peptides of the LG4-5 tandem module. At least one of these generated peptides showed potent antibacterial activity against gram negative bacteria. However, further studies are needed to investigate the role of the newly identified peptides in promoting wound healing or other interactions. In a previously unpublished study, we analyzed the effect of UV A exposure to skin, which can leads to impaired wound healing, infections, wrinkling, decreased elasticity etc. In our study we focused on LM-332 as an important regulator of epidermal cell-BM interactions. We observed slight increase of intracellular LM-332 expression in irradiated keratinocytes. This observation was also confirmed on human skin sections, which were irradiated with UV A and analyzed by immunohistochemistry. At the same time, we can demonstrate decreased secretion to cell supernatant of LM α3 and LG4-5 in a dose-dependent manner. In our study, we could show that this effect was protease-independent. However, LM-511 another laminin which can be found in human skin, shows dose-dependent decreased synthesis after irradiation. We believe that irradiation of skin with UV A leads to reorganisation of ECM and as a protective mechanism to increased synthesis of intracellular LM-332 and decreased secretion of LG4-5 tandem module.
