IFN-gamma down-regulates TGF-beta1-induced IgA expression through Stat1 and p300 signaling

Plumbagin protects liver against fulminant hepatic failure and chronic liver fibrosis via inhibiting inflammation and collagen production

Plumbagin is a quinonoid constituent extracted from Plumbago genus, and it exhibits diverse pharmacological effects. This study thoroughly investigated the effects of plumbagin on thioacetamide-induced acute and chronic liver injury. Results shown that plumbagin increased survival rate, reduced liver congestion and inflammation, and decreased macrophages and neutrophils in the fulminant hepatic failure model, and remarkably diminished liver fibrosis and inflammation in the chronic liver injury model. Furthermore, plumbagin significantly suppress the HSCs/myofibroblasts activation by reduced expression of markers α-SMA and COL-1/3, and reduced macrophage in liver. In the in vitro study, plumbagin induced apoptosis and suppressed the proliferation of LX-2 cells (human HSCs). Plumbagin treatment increased AMPK phosphorylation and attenuated NF-κB, STAT3, and Akt/mTOR signals in LX-2 cells, while SMAD2 phosphorylation was not changed. Noticeably, plumbagin promoted AMPK binding to p300 which is a cofactor of SMAD complex, this may further competitively decreases the p300/SMAD complex initiated transcription of COL-1/3 and α-SMA. Additionally, plumbagin hampered inflammation related NF-κB signal in RAW 264.7 cells. In conclusion, these findings indicate that plumbagin may be a powerful drug candidate to protect the liver from acute and chronic damage by inhibiting inflammation and collagen production.

Protein tyrosine phosphatase non-receptor type 2 and inflammatory bowel disease

Genome wide association studies have associated single nucleotide polymorphisms within the gene locus encoding protein tyrosine phosphatase non-receptor type 2 (PTPN2) with the onset of inflammatory bowel disease (IBD) and other inflammatory disorders. Expression of PTPN2 is enhanced in actively inflamed intestinal tissue featuring a marked up-regulation in intestinal epithelial cells. PTPN2 deficient mice suffer from severe intestinal and systemic inflammation and display aberrant innate and adaptive immune responses. In particular, PTPN2 is involved in the regulation of inflammatory signalling cascades, and critical for protecting intestinal epithelial barrier function, regulating innate and adaptive immune responses, and finally for maintaining intestinal homeostasis. On one hand, dysfunction of PTPN2 has drastic effects on innate host defence mechanisms, including increased secretion of pro-inflammatory cytokines, limited autophagosome formation in response to invading pathogens, and disruption of the intestinal epithelial barrier. On the other hand, PTPN2 function is crucial for controlling adaptive immune functions, by regulating T cell proliferation and differentiation as well as maintaining T cell tolerance. In this way, dysfunction of PTPN2 contributes to the manifestation of IBD. The aim of this review is to present an overview of recent findings on the role of PTPN2 in intestinal homeostasis and the impact of dysfunctional PTPN2 on intestinal inflammation.

SUMO Proteins are not Involved in TGF-β1-induced, Smad3/4-mediated Germline α Transcription, but PIASy Suppresses it in CH12F3-2A B Cells

TGF-β induces IgA class switching by B cells. We previously reported that Smad3 and Smad4, pivotal TGF-β signal-transducing transcription factors, mediate germline (GL) α transcription induced by TGF-β1, resulting in IgA switching by mouse B cells. Post-translational sumoylation of Smad3 and Smad4 regulates TGF-β-induced transcriptional activation in certain cell types. In the present study, we investigated the effect of sumoylation on TGF-β1-induced, Smad3/4-mediated GLα transcription and IgA switching by mouse B cell line, CH12F3-2A. Overexpression of small ubiquitin-like modifier (SUMO)-1, SUMO-2 or SUMO-3 did not affect TGF-β1-induced, Smad3/4-mediated GLα promoter activity, expression of endogenous GLα transcripts, surface IgA expression, and IgA production. Next, we tested the effect of the E3 ligase PIASy on TGF-β1-induced, Smad3/4-mediated GLα promoter activity. We found that PIASy overexpression suppresses the GLα promoter activity in cooperation with histone deacetylase 1. Taken together, these results suggest that SUMO itself does not affect regulation of GLα transcription and IgA switching induced by TGF-β1/Smad3/4, while PIASy acts as a repressor.

Decreased IgA+ plasma cells and IgA expression in acute liver necrosis mice

AIM: To investigate the number of intestinal immunoglobulin A (IgA+) plasma cells and expression of intestinal IgA in mice with acute liver necrosis.

METHODS: A model of acute liver necrosis was established by intraperitoneal injection of galactosamine (GalN) and lipopolysaccharide (LPS). Sixty mice were randomly divided into one of 4 equal groups: normal control, acute liver necrosis, LPS, or GalN. Hematoxylin and eosin staining, immunohistochemistry, and an enzyme-linked immunosorbent assay were employed to assess liver and intestinal injury, count intestinal IgA+ plasma cells, and measure the expression level of IgA and interferon γ (IFN-γ) in the small intestinal mucosa of mice.

RESULTS: Injured intestinal mucosa was observed in the acute liver necrosis group but not in the normal, LPS or GalN groups. Compared with the normal group, intestinal IgA+ plasma cells were slightly decreased in the LPS and GalN groups [429 ± 20 per high power field (HPF), 406 ± 18/HPF, respectively], whereas they were markedly decreased in the acute liver necrosis group (282 ± 17/HPF vs 495 ± 26/HPF in normal group, P < 0.05). The expression of intestinal IgA was also slightly decreased in LPS and GalN groups, but was markedly reduced in the acute liver necrosis group as determined by enzyme-linked immunosorbent assay (P < 0.05). In contrast, the level of IFN-γ was slightly increased in LPS, GalN and acute liver necrosis groups, but with no statistical significance (P > 0.05).

CONCLUSION: Intestinal IgA+ plasma cells and IgA expression levels indicating that mucosal immune barrier dysfunction, does exist in acute liver necrosis.