No abstract

Broad-spectrum inhibitors of HDACs are therapeutic in many inflammatory disease models but exacerbated disease in a mouse model of atherosclerosis. HDAC inhibitors have anti- and proinflammatory effects on macrophages in vitro. We report here that several broad-spectrum HDAC inhibitors, including TSA and SAHA, suppressed the LPS-induced mRNA expression of the proinflammatory mediators Edn-1, Ccl-7/MCP-3, and Il-12p40 but amplified the expression of the proatherogenic factors Cox-2 and Pai-1/serpine1 in primary mouse BMM. Similar effects were also apparent in LPS-stimulated TEPM and HMDM. The pro- and anti-inflammatory effects of TSA were separable over a concentration range, implying that individual HDACs have differential effects on macrophage inflammatory responses. The HDAC1-selective inhibitor, MS-275, retained proinflammatory effects (amplification of LPS-induced expression of Cox-2 and Pai-1 in BMM) but suppressed only some inflammatory responses. In contrast, 17a (a reportedly HDAC6-selective inhibitor) retained anti-inflammatory but not proinflammatory properties. Despite this, HDAC6(-/-) macrophages showed normal LPS-induced expression of HDAC-dependent inflammatory genes, arguing that the anti-inflammatory effects of 17a are not a result of inhibition of HDAC6 alone. Thus, 17a provides a tool to identify individual HDACs with proinflammatory properties.

BACKGROUND AND PURPOSEMany cells express proteinase activated receptor 2 (PAR2) on their plasma membrane. PAR2 is activated by proteolytic enzymes, such as trypsin and tryptase that cleave the receptor N-terminus, inititating signalling to intracellular G proteins. Studies on PAR2 have relied heavily upon activating effects of proteases and peptide agonists that lack stability and bioavailability in vivo. EXPERIMENTAL APPROACHA novel small molecule agonist GB110 and an antagonist GB88 were characterized in vitro against trypsin, peptide agonists, PAR2 antibody, PAR1 agonists and flow cytometry,in seven cell lines using intracellular Ca 2+ mobilization and examined in vivo against PAR2-and PAR1-induced rat paw oedema. KEY RESULTSGB110 is a potent non-peptidic agonist activating PAR2-mediated Ca 2+ release in HT29 cells (EC50~200 nM) and six other human cell lines, inducing PAR2 internalization. GB88 is a unique PAR2 antagonist, inhibiting PAR2 activated Ca 2+ release (IC50 2 mM) induced by native (trypsin) or synthetic peptide and non-peptide agonists. GB88 was a competitive and surmountable antagonist of agonist 2f-LIGRLO-NH2, a competitive but insurmountable antagonist of agonist GB110, and a non-competitive insurmountable antagonist of trypsin. GB88 was orally active and anti-inflammatory in vivo, inhibiting acute rat paw oedema elicited by agonist GB110 and proteolytic or peptide agonists of PAR2 but not by corresponding agonists of PAR1 or PAR4. CONCLUSIONS AND IMPLICATIONSThe novel PAR2 agonist and antagonist modulate intracellular Ca 2+ and rat paw oedema, providing novel molecular tools for examining PAR2-mediated diseases.

Lysine acetylation is becoming increasingly appreciated as a key post-translational modification in the endogenous regulation of protein function. The so-called histone acetyl transferases (HATs) and histone deacetylases (HDACs), best known for their roles in controlling chromatin remodeling via histone acetylation/deacetylation, are now known to modify a large number of non-histone proteins to control diverse cell processes. In relation to inflammation, acetylation modulates the activity or function of cytokine receptors, nuclear hormone receptors, intracellular signaling molecules and transcription factors. Small molecule inhibitors of HDACs have been found to trigger both pro- and anti-inflammatory effects in a range of inflammation-relevant cell types. Although their inflammatory profiles have only just begun to be elucidated, some HDAC inhibitors are already showing therapeutic promise in animal models of inflammatory diseases such as arthritis, inflammatory bowel diseases, septic shock, ischemia-reperfusion injury, airways inflammation and asthma, diabetes, age-related macular degeneration, cardiovascular diseases, multiple sclerosis and other CNS and neurodegenerative diseases. This article describes those HDAC inhibitors which have been most examined to date for their potentially beneficial effects on inflammatory cells or in animal models of inflammatory disease.

Copper resistance is a key virulence trait of the uropathogen Proteus mirabilis. Here we show that P. mirabilis ScsC (PmScsC) contributes to this defence mechanism by enabling swarming in the presence of copper. We also demonstrate that PmScsC is a thioredoxin-like disulfide isomerase but, unlike other characterized proteins in this family, it is trimeric. PmScsC trimerization and its active site cysteine are required for wild-type swarming activity in the presence of copper. Moreover, PmScsC exhibits unprecedented motion as a consequence of a shape-shifting motif linking the catalytic and trimerization domains. The linker accesses strand, loop and helical conformations enabling the sampling of an enormous folding landscape by the catalytic domains. Mutation of the shape-shifting motif abolishes disulfide isomerase activity, as does removal of the trimerization domain, showing that both features are essential to foldase function. More broadly, the shape-shifter peptide has the potential for ‘plug and play’ application in protein engineering.