A systematic identification of anti-inflammatory active components derived from Mu Dan Pi and their applications in inflammatory bowel disease.

Mu Dan Pi (MDP), also known as Moutan Cortex Radicis, is a traditional Chinese medicine used to treat autoimmune diseases. However, the impact of MDP and its principal active compounds on inflammatory bowel disease (IBD) is uncertain. This study therefore systemically assessed the anti-inflammatory effects of MDP and its known active compounds in IBD. The anti-inflammatory activities of water extract and individual compounds were screened by NF-κB and interferon regulatory factor (IRF) reporter assays in THP-1 cells induced with either Toll-like receptor or retinoic acid inducible gene I/melanoma differentiation-associated gene 5 activators and further verified in bone marrow-derived macrophages. MDP water extract significantly inhibited the activation of NF-κB and IRF reporters, downstream signaling pathways and the production of IL-6 and TNF-α, in a dose-dependent manner. Among 5 known active components identified from MDP (1,2,3,4,6-penta-O-galloyl-ß-d-glucose [PGG], gallic acid, methyl gallate, paeoniflorin, and paeonol), PGG was the most efficient at inhibiting both reporters (with an IC50 of 5-10 µM) and downregulating IL-6 and TNF-α. Both MDP powder for clinical use and MDP water extract, but not PGG, reduced colitis and pathological changes in mice. MDP and its water extract show promise as a novel therapy for IBD patients.

Glutathione peroxidase 8 negatively regulates caspase-4/11 to protect against colitis.

Human caspase-4 and its mouse homolog caspase-11 are receptors for cytoplasmic lipopolysaccharide. Activation of the caspase-4/11-dependent NLRP3 inflammasome is required for innate defense and endotoxic shock, but how caspase-4/11 is modulated remains unclear. Here, we show that mice lacking the oxidative stress sensor glutathione peroxidase 8 (GPx8) are more susceptible to colitis and endotoxic shock, and exhibit reduced richness and diversity of the gut microbiome. C57BL/6 mice that underwent adoptive cell transfer of GPx8-deficient macrophages displayed a similar phenotype of enhanced colitis, indicating a critical role of GPx8 in macrophages. GPx8 binds covalently to caspase-4/11 via disulfide bonding between cysteine 79 of GPx8 and cysteine 118 of caspase-4 and thus restrains caspase-4/11 activation, while GPx8 deficiency leads to caspase-4/11-induced inflammation during colitis and septic shock. Inhibition of caspase-4/11 activation with small molecules reduces the severity of colitis in GPx8-deficient mice. Notably, colonic tissues from patients with ulcerative colitis display low levels of Gpx8 and high caspase-4 expression. In conclusion, these results suggest that GPx8 protects against colitis by negatively regulating caspase-4/11 activity.

NagZ is required for beta-lactamase expression and full pathogenicity in Xanthomonas campestris pv. campestris str. 17.

Xanthomonas campestris pv. campestris expresses a chromosomally encoded class A ß-lactamase Blaxc. Basal expression and induction of blaxc require the transcriptional factor AmpRxc and the peptidoglycan-monomers permease AmpGxc. NagZ is a ß-GlcNAcase which cleaves GlcNAc-anhMurNAc peptides (peptidoglycan-monomers) to generate anhMurNAc-peptides. In many bacteria, anhMurNAc-peptides act as activation ligands for AmpR. Nevertheless, the role of NagZ in ß-lactamase induction differs among species. In this paper, we studied the roles of nagZxc in the regulation of blaxc and pathogenicity in X. campestris pv. campestris. Our data showed that cells lacking nagZxc dramatically reduced the basal expression and induction of blaxc, suggesting that anhMurNAc-peptides, products of NagZxc, are required for blaxc expression regardless of the presence or absence of inducers. Expression of blaxc is regulated via an ampG-nagZ-ampR pathway. Pathogenicity assay demonstrated that an ampGxc mutant excited more severe symptoms than the wild-type; on the contrary, the nagZxc mutant became less virulent. To our knowledge, this is the first demonstration of a link between the ampG or nagZ defects and the pathogenicity in a plant pathogen.

AmpG is required for BlaXc beta-lactamase expression in Xanthomonas campestris pv. campestris str. 17.

The chromosomal ampR(Xc) -bla(Xc) module is essential for the ß-lactam resistance of Xanthomonas campestris pv. campestris. Bla(Xc) ß-lactamase is expressed at a high basal level in the absence of an inducer and its expression can be further induced by ß-lactam. In enterobacteria, ampG encodes an inner membrane facilitator involved in the recycling of murein degradation compounds. An isogenic ampG mutant (XcampG) of X. campestris pv. campestris str. 17 (Xc17) was constructed to investigate the link between murein recycling and bla(Xc) expression. Our data demonstrate that (1) XcampG is susceptible to ß-lactam antibiotics; (2) AmpG(Xc) is essential for expression of bla(Xc) ; (3) AmpGs of Xc17, Stenotrophomonas maltophilia KJ (SmKJ) and Escherichia coli DH5α can complement the defect of XcampG; (4) overexpression of AmpG(X) (c) significantly increased bla(Xc) expression; and (5) AmpG(Xc) from Xc17 is able to restore ß-lactamase induction of the ampN(Xc) -ampG(Xc) double mutant of SmKJ. In Xc17, ampG(Xc) can be expressed from the promoter residing in the intergenic region of ampN(Xc) -ampG(Xc) and the expression is independent of ß-lactam induction. AmpN, which is required for ß-lactamases induction in SmKJ, is not required for the ß-lactam antibiotic resistance of Xc17.