A preliminary report on the thymidine labeling indices and kinetics of cell proliferation in selected Morris hepatomas

Impaired IFN-γ-dependent STAT3 Activation Is Associated With Dysregulation of Regulatory and Inflammatory Signaling in Monocytes of Ulcerative Colitis Patients

BACKGROUND

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) inhibitor tofacitinib has been recently approved for the treatment of ulcerative colitis (UC) but not Crohn's disease (CD). Systematic analysis of the JAK/STAT pathway in inflammatory bowel disease is still missing. The aim of this study was to investigate JAK/STAT activation and adjacent signaling in monocytes of patients with inflammatory bowel diseases, which are key players in inflammatory responses.

METHODS

Blood samples of active UC (n = 28) and CD patients (n = 28) and healthy controls (n = 22) were collected for primary monocyte investigation. STAT phosphorylation (pSTAT), cytokine secretion, and surface marker expression ± prior tofacitinib blockade in addition to Th-17 and regulatory T cell induction in cocultures were analyzed upon interferon (IFN)-γ timulation.

RESULTS

Baseline frequencies of pSTAT1+ and pSTAT3+ monocytes were significantly higher in UC, whereas IFN-γ-associated crosstalk induction of pSTAT3+ monocytes was missing in UC-derived monocytes compared with controls and CD. This coincided with decreased interleukin (IL)-10 and cluster of differentiation (CD)39 levels, diminished regulatory T cell (Treg) induction, and increased IL-12 and IL-23 secretion compared with controls, which was not observed in CD monocytes. Tofacitinib induced stronger inhibition of inflammatory cytokine release (IL-6, TNFα, IL-12, IL-23) in UC compared with CD monocytes.

CONCLUSIONS

In UC monocytes, IFN-γ-associated activation of the JAK/STAT pathway is impaired with an imbalance between STAT1 and STAT3, coinciding with stronger induction of inflammatory monocytes by IFN-γ compared with controls or CD. The fact that tofacitinib had stronger regulatory impact on UC than on CD monocytes further underlines a stronger inflammatory involvement of the JAK/STAT pathway in UC pathogenesis, which might result from missing STAT3 activation to counteract STAT1-induced inflammation.

A permeabilized cell system for studying regulation of aryl hydrocarbon hydroxylase: NADPH as rate limiting factor in benzo(a)pyrene metabolism

The disadvantage of a whole cell system for studying the metabolism of xenobiotics is that some substrates and regulatory molecules do not readily cross the cell membrane. The present study describes a technique to permeabilize H-4-II-E rat hepatoma cells for the study of benzo(a)pyrene metabolism. NADPH is an essential cofactor in the in vitro microsomal metabolism of benzo(a)pyrene and has been shown by indirect measurement to be a rate limiting factor in mixed function oxidase activity in whole liver perfusion systems. The role of NADPH has not been directly demonstrated in an intact cell system. Using this permeabilized whole cell system it is possible to directly demonstrate that NADPH is rate limiting in the mixed function oxidation of benzo(a)pyrene.