Low molecular weight proteins secreted by peritoneal macrophages obtained from 2,3,7,8-tetrabromodibenzo-p-dioxin-treated NMRI mice

Lipocalin-type prostaglandin D synthase in milk: a new biomarker for bovine mastitis

The whey protein pattern of milk from animals affected by mastitic inflammation was resolved by two-dimensional gel electrophoresis (2D-PAGE) and compared to milk from unaffected cows. Inflammation caused the appearance of four spots aligned at a molecular weight level of 26 kDa and over a pH-region of 5.0 to 6.4. The spots excised from 2D gels were treated with chymotrypsin and the resulting peptides analyzed by MALDI-TOF mass spectrometry and RP-HPLC. All four spots yielded highly similar chymotryptic peptide mass fingerprints as well as chromatographic peak patterns. A database search could identify the four spots as isoforms of the bovine prostaglandin D synthase (PGD-S). In one of the isoforms a defined cysteine residue was shown to be oxidized to a sulfonic acid.

In vitro model system for the identification and characterization of proteins involved in inflammatory processes

An in vitro model featuring important inflammatory cellular states was established, based on the murine monocyte/macrophage cell line RAW 264.7. Macrophages are key players in chronic inflammation, and major parts of the biochemical reactions taking place in vivo, e.g., the production of proinflammatory cytokines, can be triggered in vitro by stimulation of the cells with bacterial lipopolysaccharide (LPS). A mastergel, representing a synthetic image of the expressed basic set of cellular proteins, was designed by a computer-assisted overlay of a statistically significant number of two-dimensional electrophoresis (2-DE) gels of unstimulated RAW 264.7 cells. This image served as a reference for qualitative and quantitative changes in the protein pattern induced by stimulation of the macrophages with LPS. The optimal conditions for LPS stimulation were evaluated by monitoring the expression and secretion of the proinflammatory cytokine tumor necrosis factor-alpha(TNF-alpha). The comparison of the mastergel with the 2-DE gels of LPS-stimulated cells revealed several changes in the protein pattern. In order to prove the relevance of the presented model system, we focused on two low molecular weight proteins, which showed significant changes in the apparent concentration in a 2-DE pattern. These proteins were further characterized by microsequencing of internal peptides. A comparison of the obtained sequences with protein databases identified them as cofilin and keratinocyte lipid-binding protein.