The JAK inhibitor ruxolitinib reduces inflammation in an ILC3-independent model of innate immune colitis

Therapeutic inhibition of the JAK-STAT pathway in the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) encompasses a group of non-specific chronic intestinal inflammatory conditions of unclear etiology. The current treatment and long-term management primarily involve biologics. Nevertheless, some patients experience treatment failure or intolerance to biologics [1], making these patients a primary focus of IBD research. The Janus kinase (JAK)-Signal Transducers and Activator of Transcription (STAT) signal transduction pathway is crucial to the regulation of immune and inflammatory responses [2], and plays an important role in the pathogenesis of IBD. JAK inhibitors alleviate IBD by suppressing the transmission of JAK-STAT signaling pathway. As the first small-molecule oral inhibitor for IBD, JAK inhibitors greatly improved the treatment of IBD and have demonstrated significant efficacy, with tofacitinib and upadacitinib being approved for the treatment of ulcerative colitis (UC) [3]. JAK inhibitors can effectively alleviate intestinal inflammation in IBD patients who have failed to receive biologics, which may bring new treatment opportunities for refractory IBD patients. This review aims to elucidate the crucial roles of JAK-STAT signal transduction pathway in IBD pathogenesis, examine its role in various cell types within IBD, and explore the research progress of JAK inhibitors as therapeutic agents, paving the road for new IBD treatment strategies.

Retinoid orphan receptor gamma t (rorγt) promotes inflammatory eosinophilia but is dispensable for innate immune-mediated colitis

Inflammatory bowel diseases (IBD) result from uncontrolled inflammation in the intestinal mucosa leading to damage and loss of function. Both innate and adaptive immunity contribute to the inflammation of IBD and innate and adaptive immune cells reciprocally activate each other in a forward feedback loop. In order to better understand innate immune contributions to IBD, we developed a model of spontaneous 100% penetrant, early onset colitis that occurs in the absence of adaptive immunity by crossing villin-TNFAIP3 mice to RAG1-/- mice (TRAG mice). This model is driven by microbes and features increased levels of innate lymphoid cells in the intestinal mucosa. To investigate the role of type 3 innate lymphoid cells (ILC3) in the innate colitis of TRAG mice, we crossed them to retinoid orphan receptor gamma t deficient (Rorγt-/-) mice. Rorγt-/- x TRAG mice exhibited markedly reduced eosinophilia in the colonic mucosa, but colitis persisted in these mice. Colitis in Rorγt-/- x TRAG mice was characterized by increased infiltration of the intestinal mucosa by neutrophils, inflammatory monocytes, macrophages and other innate cells. RNA and cellular profiles of Rorγt-/- x TRAG mice were consistent with a lack of ILC3 and ILC3 derived cytokines, reduced antimicrobial factors, increased activation oof epithelial repair processes and reduced activation of epithelial cell STAT3. The colitis in Rorγt-/- x TRAG mice was ameliorated by antibiotic treatment indicating that microbes contribute to the ILC3-independent colitis of these mice. Together, these gene expression and cell signaling signatures reflect the double-edged sword of ILC3 in the intestine, inducing both proinflammatory and antimicrobial protective responses. Thus, Rorγt promotes eosinophilia but Rorγt and Rorγt-dependent ILC3 are dispensable for the innate colitis in TRAG mice.

Double-edged sword of JAK/STAT signaling pathway in viral infections: novel insights into virotherapy

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) is an intricate signaling cascade composed of various cytokines, interferons (IFN, growth factors, and other molecules. This pathway provides a delicate mechanism through which extracellular factors adjust gene expression, thereby acting as a substantial basis for environmental signals to influence cell growth and differentiation. The interactions between the JAK/STAT cascade and antiviral IFNs are critical to the host's immune response against viral microorganisms. Recently, with the emergence of therapeutic classes that target JAKs, the significance of this  cascade has been recognized in an unprecedented way. Despite the functions of the JAK/STAT pathway in adjusting immune responses against viral pathogens, a vast body of evidence proposes the role of this cascade in the replication and pathogenesis of viral pathogens. In this article, we review the structure of the JAK/STAT signaling cascade and its role in immuno-inflammatory responses. We also highlight the paradoxical effects of this pathway in the pathogenesis of viral infections. Video Abstract.

Identification of Gene Expression Profiles Associated with an Increased Risk of Post-Operative Recurrence in Crohn's Disease

BACKGROUND AND AIMS

Ileocolonic resection is frequently needed in the course of Crohn's disease [CD] treatment and post-operative recurrence is extremely common. Our main objective was to analyse gene expression in the mucosa of CD patients at the time of surgery and at post-operative endoscopy, in order to identify predictors and mechanisms of early endoscopic recurrence.

METHODS

We conducted transcriptome analyses on ileal mucosa samples collected from inflamed sections of the surgical specimens [n = 200], from ileal resection margins [n = 149] and in the neo-terminal ileum 6 months after surgery [n = 122]; these were compared with non-inflammatory bowel disease controls [n = 25]. The primary endpoint was post-operative endoscopic recurrence at 6 months. We applied regression models to identify gene signatures predicting endoscopic recurrence.

RESULTS

Chronic inflammation was associated with strong expression of inflammatory genes [IL-6, IL-8, IL-1B] and decreased expression of genes involved in metabolic processes, but with a high inter-individual heterogeneity. Gene signatures associated with early endoscopic recurrence were mainly characterized by upregulation of TNFα, IFNγ, IL23A and IL17A. Pathway analyses showed that upregulation of mitochondrial dysfunction within the inflamed sections and JAK/STAT at the ileal margin were predictive of post-operative recurrence. A combined model integrating these top pathway signatures improved the prediction of endoscopic recurrence [area under the curve of 0.79]. STAT3 phosphorylation at the surgical ileal margin was associated with severe recurrence at 6 months.

CONCLUSION

We identified several biological pathways in surgical ileal mucosa specimens associated with an increased risk of disease recurrence. Integration of the JAK/STAT and mitochondrial dysfunction pathways in the clinical model improved the prediction of post-operative recurrence.

Affecting the effectors: JAK inhibitors modulation of immune cell numbers and functions in patients with rheumatoid arthritis

INTRODUCTION

The Janus kinase family includes four members - JAK1, JAK2, JAK3, TYK2 that are selectively associated with type I and II cytokine receptors. Jak-inhibitors (Jakinibs) are a new class of drugs for treating inflammatory diseases. Five Jakinibs are currently available for Rheumatoid Arthritis (RA): tofacitinib, baricitinib, upadacitinib, filgotinib and peficitinib. Considering the role of cytokines and growth factors in immune cell survival and activation, the anti-proliferative and suppressive effects of Jakinibs on these cells are predictable.

AREAS COVERED

This review summarizes Jakinibs' effects of on immune populations in vitro and in vivo. In vitro, Jakinibs affected T and B lymphocytes, monocytes, neutrophils and dendritic cell proliferation. T helper, B cell differentiation and cytokine secretion was impaired. Accordingly, changes in the number of lymphocytes, natural killer (NK) cells and neutrophils have been reported during the randomized clinical trials with all the Jakinibs, reverting after drug withdrawal.

EXPERT OPINION

In vitro and in vivo studies showed that the numbers and the function of immune cells are influenced by Jakinibs. Nonetheless, their effects do not seem to represent a major safety issue as these changes do not correlate with the onset of serious infection despite the increased rates of herpes zoster reactivation.

Ruxolitinib attenuates secondary injury after traumatic spinal cord injury

Excessive inflammation post-traumatic spinal cord injury (SCI) induces microglial activation, which leads to prolonged neurological dysfunction. However, the mechanism underlying microglial activation-induced neuroinflammation remains poorly understood. Ruxolitinib (RUX), a selective inhibitor of JAK1/2, was recently reported to inhibit inflammatory storms caused by SARS-CoV-2 in the lung. However, its role in disrupting inflammation post-SCI has not been confirmed. In this study, microglia were treated with RUX for 24 hours and then activated with interferon-γ for 6 hours. The results showed that interferon-γ-induced phosphorylation of JAK and STAT in microglia was inhibited, and the mRNA expression levels of pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β, interleukin-6, and cell proliferation marker Ki67 were reduced. In further in vivo experiments, a mouse model of spinal cord injury was treated intragastrically with RUX for 3 successive days, and the findings suggest that RUX can inhibit microglial proliferation by inhibiting the interferon-γ/JAK/STAT pathway. Moreover, microglia treated with RUX centripetally migrated toward injured foci, remaining limited and compacted within the glial scar, which resulted in axon preservation and less demyelination. Moreover, the protein expression levels of tumor necrosis factor-α, interleukin-1β, and interleukin-6 were reduced. The neuromotor function of SCI mice also recovered. These findings suggest that RUX can inhibit neuroinflammation through inhibiting the interferon-γ/JAK/STAT pathway, thereby reducing secondary injury after SCI and producing neuroprotective effects.

Altered microbial biogeography in an innate model of colitis

Changes in the spatial organization, or biogeography, of colonic microbes have been observed in human inflammatory bowel disease (IBD) and mouse models of IBD. We have developed a mouse model of IBD that occurs spontaneously and consistently in the absence of adaptive immunity. Mice expressing tumor necrosis factor-induced protein 3 (TNFAIP3) in intestinal epithelial cells (villin-TNFAIP3) develop colitis when interbred with Recombination Activating 1-deficient mice (RAG1^-/-). The colitis in villin-TNFAIP3 × RAG1^-/- (TRAG) mice is prevented by antibiotics, indicating a role for microbes in this innate colitis. We therefore explored the biogeography of microbes and responses to antibiotics in TRAG colitis. Laser capture microdissection and 16S rRNA sequencing revealed altered microbial populations across the transverse axis of the colon as the inner mucus layer of TRAG, but not RAG1^-/-, mice was infiltrated by microbes, which included increased abundance of the classes Gammaproteobacteria and Actinobacteria. Along the longitudinal axis differences in the efficacy of antibiotics to prevent colitis were evident. Neomycin was most effective for prevention of inflammation in the cecum, while ampicillin was most effective in the proximal and distal colon. RAG1^-/-, but not TRAG, mice exhibited a structured pattern of bacterial abundance with decreased Firmicutes and Proteobacteria but increased Bacteroidetes along the proximal to distal axis of the gut. TRAG mice exhibited increased relative abundance of potential pathobionts including <i>Bifidobacterium animalis</i> along the longitudinal axis of the gut whereas others, like <i>Helicobacter hepaticus</i> were increased only in the cecum. Potential beneficial organisms including <i>Roseburia</i> were decreased in the proximal regions of the TRAG colon, while <i>Bifidobacterium pseudolongulum</i> was decreased in the TRAG distal colon. Thus, the innate immune system maintains a structured, spatially organized, gut microbiome along the transverse and longitudinal axis of the gut, and disruption of this biogeography is a feature of innate immune colitis.

Network medicine for disease module identification and drug repurposing with the NeDRex platform

Traditional drug discovery faces a severe efficacy crisis. Repurposing of registered drugs provides an alternative with lower costs and faster drug development timelines. However, the data necessary for the identification of disease modules, i.e. pathways and sub-networks describing the mechanisms of complex diseases which contain potential drug targets, are scattered across independent databases. Moreover, existing studies are limited to predictions for specific diseases or non-translational algorithmic approaches. There is an unmet need for adaptable tools allowing biomedical researchers to employ network-based drug repurposing approaches for their individual use cases. We close this gap with NeDRex, an integrative and interactive platform for network-based drug repurposing and disease module discovery. NeDRex integrates ten different data sources covering genes, drugs, drug targets, disease annotations, and their relationships. NeDRex allows for constructing heterogeneous biological networks, mining them for disease modules, prioritizing drugs targeting disease mechanisms, and statistical validation. We demonstrate the utility of NeDRex in five specific use-cases.

Priming of microglia with IFN-γ impairs adult hippocampal neurogenesis and leads to depression-like behaviors and cognitive defects

Neuroinflammation driven by interferon-gamma (IFN-γ) and microglial activation has been linked to neurological disease. However, the effects of IFN-γ-activated microglia on hippocampal neurogenesis and behavior are unclear. In the present study, IFN-γ was administered to mice via intracerebroventricular injection. Mice received intraperitoneal injection of ruxolitinib to inhibit the JAK/STAT1 pathway or injection of minocycline to inhibit microglial activation. During a 7-day period, mice were assessed for depressive-like behaviors and cognitive impairment based on a series of behavioral analyses. Effects of the activated microglia on neural stem/precursor cells (NSPCs) were examined, as was pro-inflammatory cytokine expression by activated microglia. We showed that IFN-γ-injected animals showed long-term adult hippocampal neurogenesis reduction, behavior despair, anhedonia, and cognitive impairment. Chronic activation with IFN-γ induces reactive phenotypes in microglia associated with morphological changes, population expansion, MHC II and CD68 up-regulation, and pro-inflammatory cytokine (IL-1β, TNF-α, IL-6) and nitric oxide (NO) release. Microglia isolated from the hippocampus of IFN-γ-injected mice suppressed NSPCs proliferation and stimulated apoptosis of immature neurons. Inhibiting of the JAK/STAT1 pathway in IFN-γ-injected animals to block microglial activation suppressed microglia-mediated neuroinflammation and neurogenic injury, and alleviated depressive-like behaviors and cognitive impairment. Collectively, these findings suggested that priming of microglia with IFN-γ impairs adult hippocampal neurogenesis and leads to depression-like behaviors and cognitive defects. Targeting microglia by modulating levels of IFN-γ the brain may be a therapeutic strategy for neurodegenerative diseases and psychiatric disorders.