Mucosal Epithelial Jak Kinases in Health and Diseases

Ruxolitinib attenuates microglial inflammatory response by inhibiting NF-κB/MAPK signaling pathway

Neuroinflammation is involved in the physiological and pathological processes of numerous neurological diseases, and its inhibition seems to be a promising therapeutic direction for these diseases. Ruxolitinib is a classical Janus kinase (JAK) inhibitor that is oral, highly potent and bioavailable, which has recently gained approval from the US Food and Drug Administration (FDA) for the treatment of inflammatory disorders. The potential inhibitory effect of ruxolitinib on neuroinflammation has not been fully studied. In the lipopolysaccharide (LPS) induced neuroinflammatory cell model, we observed that ruxolitinib reduced the levels of IL-1β, IL-6 and tumor necrosis factor-α (TNF-α) expression, and neuroinflammation by inhibiting the Mitogen-Activated Protein Kinase/Nuclear factor-κ B (MAPK/NF-κB) signaling pathway. Similarly, mice injected intracerebroventricular with ruxolitinib exhibited significantly reduced LPS-stimulated activation of microglia and astrocytes, and expression of proinflammatory cytokine IL-1β, TNF-α and IL-6. These results demonstrate that ruxolitinib attenuates the neuroinflammatory responses both in vivo and in vitro, at least in part by inhibiting MAPK/NF-κB signaling pathway. Our findings suggest that ruxolitinib may serve as a potential drug for the treatment of microglia-mediated neuroinflammation.

Vaccination with Toxoplasma lysate antigen or its encapsulated niosomes form immunomodulates adjuvant-induced arthritis through JAK3 downregulation

BACKGROUND

Inflammatory autoimmune arthritis like that present in rheumatoid arthritis (RA) is treated by medications with many side effects. This study was a trial to benefit from Toxoplasma immune-modulatory effects on its host to treat arthritis in rat model resembling joints affection of RA. To avoid hazards of infection, Toxoplasma lysate antigen (TLA) was given instead of the whole infection, in addition to giving its encapsulated niosomes form, assuming that it would enhance the effect of TLA alone, to compare effects of both on disease activity with that of prednisolone.

METHODS

Swiss albino rats were divided into 6 groups: normal control group and the remaining 5 groups were injected by CFA adjuvant to induce arthritis; one of those groups was the untreated model. Each of the other groups received one of the following (TLA, TLA-encapsulated niosomes, prednisolone or niosomes) for comparison of their results. Inflammatory markers measured at the end of the experiment were: interleukin 17 (IL-17), IL-10 and CRP by ELISA technique; histopathological assessment of the biopsied hind paw joints was done and also, Janus kinase 3 (JAK3) expression was assessed by immunohistochemistry.

RESULTS

TLA and TLA-encapsulated niosomes both mitigated the signs of clinical and histopathological arthritis and were having anti-inflammatory effects (decreased CRP, IL-17 and JAK3 expressions, while increased IL-10 levels) with better effects in TLA-encapsulated niosomes-treated RA group, both groups' results were comparable to prednisolone. Niosomes also gave some anti-inflammatory effects but were mild in comparison to TLA and TLA-encapsulated niosomes.

CONCLUSION

Vaccination with both TLA and TLA-encapsulated niosomes for the first time in adjuvant-induced arthritis ameliorated the disease through diversion of immune system and JAK3 downregulation. Both vaccinations should be further tested to evaluate the possibility of their introduction for disease treatment and in other autoimmune diseases.

The gut ecosystem and immune tolerance

The gastrointestinal tract is home to the largest microbial population in the human body. The gut microbiota plays significant roles in the development of the gut immune system and has a substantial impact on the maintenance of immune tolerance beginning in early life. These microbes interact with the immune system in a dynamic and interdependent manner. They generate immune signals by presenting a vast repertoire of antigenic determinants and microbial metabolites that influence the development, maturation and maintenance of immunological function and homeostasis. At the same time, both the innate and adaptive immune systems are involved in modulating a stable microbial ecosystem between the commensal and pathogenic microorganisms. Hence, the gut microbial population and the host immune system work together to maintain immune homeostasis synergistically. In susceptible hosts, disruption of such a harmonious state can greatly affect human health and lead to various auto-inflammatory and autoimmune disorders. In this review, we discuss our current understanding of the interactions between the gut microbiota and immunity with an emphasis on: a) important players of gut innate and adaptive immunity; b) the contribution of gut microbial metabolites; and c) the effect of disruption of innate and adaptive immunity as well as alteration of gut microbiome on the molecular mechanisms driving autoimmunity in various autoimmune diseases.

Inhibition of T-cell activity in alopecia areata: recent developments and new directions

Alopecia areata (AA) is an autoimmune disease that has a complex underlying immunopathogenesis characterized by nonscarring hair loss ranging from small bald patches to complete loss of scalp, face, and/or body hair. Although the etiopathogenesis of AA has not yet been fully characterized, immune privilege collapse at the hair follicle (HF) followed by T-cell receptor recognition of exposed HF autoantigens by autoreactive cytotoxic CD8+ T cells is now understood to play a central role. Few treatment options are available, with the Janus kinase (JAK) 1/2 inhibitor baricitinib (2022) and the selective JAK3/tyrosine kinase expressed in hepatocellular carcinoma (TEC) inhibitor ritlecitinib (2023) being the only US Food and Drug Administration-approved systemic medications thus far for severe AA. Several other treatments are used off-label with limited efficacy and/or suboptimal safety and tolerability. With an increased understanding of the T-cell-mediated autoimmune and inflammatory pathogenesis of AA, additional therapeutic pathways beyond JAK inhibition are currently under investigation for the development of AA therapies. This narrative review presents a detailed overview about the role of T cells and T-cell-signaling pathways in the pathogenesis of AA, with a focus on those pathways targeted by drugs in clinical development for the treatment of AA. A detailed summary of new drugs targeting these pathways with expert commentary on future directions for AA drug development and the importance of targeting multiple T-cell-signaling pathways is also provided in this review.

Effect of Janus Kinase 3 Inhibitor on Sebaceous Gland Regeneration during Skin Wound Healing

BACKGROUND

Janus kinase (Jak) 3 has recently been shown as a beneficial target for the treatment of chronic inflammatory diseases, such as psoriasis and alopecia areata. The role of Jak3 in tissue repair and remodeling is emerging.

OBJECTIVE

This study aimed to investigate the role of Jak3 signaling in the remodeling of the sebaceous gland (SG) during skin wound repair, and the development of in vitro SGs.

METHODS

Mouse skin tissue (ICR mouse) was obtained from the recovered skin eight days after a 4 mm biopsy punch wound. To observe the role of Jak3, the selective inhibitors WHI-p131 and PF06651600 was administered. Formation of in vitro SG was examined using primary sebocyte cultures obtained postnatally from 3-day-old mice.

RESULTS

The data showed that SGs showed highly positive signals with anti-isolectin B4, which also used for detection of angiogenetic vessels and the basal epidermis. Isolectin B4 could be a good indicator of SGs. The Jak3 inhibitors significantly reduced the area and volume of SG remodeling with reduced expression of p-Jak3. In addition, the area of cultured intact SG in vitro was significantly decreased in a concentration-dependent manner by Jak3 inhibition.

CONCLUSION

These data showed that Jak3 signaling is a potent regulator to develop SGs. Jak3 inhibition did not decrease the number of sebocytes in SGs but decreased the area and volume of SG remodeling. Therefore, Jak3 inhibition may be a potential target for the treatment of SG hyperplasia and associated skin diseases.

Mechanistic Role of Jak3 in Obesity-Associated Cognitive Impairments

Background and Aims: A compromise in intestinal mucosal functions is associated with several chronic inflammatory diseases. Previously, we reported that obese humans have a reduced expression of intestinal Janus kinase-3 (Jak3), a non-receptor tyrosine kinase, and a deficiency of Jak3 in mice led to predisposition to obesity-associated metabolic syndrome. Since meta-analyses show cognitive impairment as co-morbidity of obesity, the present study demonstrates the mechanistic role of Jak3 in obesity associated cognitive impairment. Our data show that high-fat diet (HFD) suppresses Jak3 expression both in intestinal mucosa and in the brain of wild-type mice. Methodology: Recapitulating these conditions using global (Jak3-KO) and intestinal epithelial cell-specific conditional (IEC-Jak3-KO) mice and using cognitive testing, western analysis, flow cytometry, immunofluorescence microscopy and 16s rRNA sequencing, we demonstrate that HFD-induced Jak3 deficiency is responsible for cognitive impairments in mice, and these are, in part, specifically due to intestinal epithelial deficiency of Jak3. Results: We reveal that Jak3 deficiency leads to gut dysbiosis, compromised TREM-2-functions-mediated activation of microglial cells, increased TLR-4 expression and HIF1-α-mediated inflammation in the brain. Together, these lead to compromised microglial-functions-mediated increased deposition of β-amyloid (Aβ) and hyperphosphorylated Tau (pTau), which are responsible for cognitive impairments. Collectively, these data illustrate how the drivers of obesity promote cognitive impairment and demonstrate the underlying mechanism where HFD-mediated impact on IEC-Jak3 deficiency is responsible for Jak3 deficiency in the brain, reduced microglial TREM2 expression, microglial activation and compromised clearance of Aβ and pTau as the mechanism during obesity-associated cognitive impairments. Conclusion: Thus, we not only demonstrate the mechanism of obesity-associated cognitive impairments but also characterize the tissue-specific role of Jak3 in such conditions through mucosal tolerance, gut–brain axis and regulation of microglial functions.

Null Function of Npr1 Disturbs Immune Response in Colonic Inflammation During Early Postnatal Stage

Natriuretic peptide receptor 1 (NPR1) is conventionally known as a regulator of vascular homeostasis. Here, we generated an Npr1 knockout mouse model with CRISPR/Cas9 technology and found that homozygous mice (Npr1^−/−) exhibited weight loss and poor survival rate during early postnatal stage. Careful examination revealed unexpectedly that Npr1^−/− mice developed colitis characterized by shortened colon, evident colonic mucosal damage, increased histopathological score, and higher colonic expression of proinflammatory cytokines interleukin-1B (IL1B) and -6 (IL6). RNA-sequencing analysis revealed that differentially expressed genes were prominently enriched in the biological pathways related to immune response in both spleen and colon of Npr1^−/− mice. Cytofluorimetric analysis demonstrated that leukocytes in the spleen were significantly increased, particularly, the populations of neutrophil and CD3⁺ T cell were elevated but CD4⁺ T cells were decreased in Npr1^−/− mice. Administration of 8-Br-cGMP, a downstream activator of NPR1, restored these immune-cell populations disturbed in Npr1^−/− mice and lessened the colitis-related phenotypes. To validate the involvement of Npr1 in colitis, we examined another mouse model induced by dextran sodium sulfate (DSS) and found a decreased Npr1 expression and shifted immune-cell populations as well. Importantly, 8-Br-cGMP treatment exhibited a similar effect in the restoration of immune-cell populations and attenuation of colonic inflammation in DSS mice. Our data indicate that loss of Npr1 possibly interrupts immune response, which is critical to the pathogenesis of colitis in the early life.

Chicken-Specific Kinome Analysis of Early Host Immune Signaling Pathways in the Cecum of Newly Hatched Chickens Infected With Salmonella enterica Serovar Enteritidis

Poultry is a major source of human foodborne illness caused by broad host range Salmonella serovars (paratyphoid), and developing cost-effective, pre-harvest interventions to reduce these pathogens would be valuable to the industry and consumer. Host responses to infectious agents are often regulated through phosphorylation. However, proteomic mechanisms of Salmonella acute infection biology and host responses to the bacteria have been limited concentrating predominately on the genomic responses of the host to infection. Our recent development of chicken-specific peptide arrays for kinome analysis of host phosphorylation-based cellular signaling responses provided us with the opportunity to develop a more detailed understanding of the early (4-24 h post-infection) host-pathogen interactions during the initial colonization of the cecum by Salmonella. Using the chicken-specific kinomic immune peptide array, biological pathway analysis showed infection with S. Enteritidis increased signaling related to the innate immune response, relative to the non-infected control ceca. Notably, the acute innate immune signaling pathways were characterized by increased peptide phosphorylation (activation) of the Toll-like receptor and NOD-like receptor signaling pathways, the activation of the chemokine signaling pathway, and the activation of the apoptosis signaling pathways. In addition, Salmonella infection induced a dramatic alteration in the phosphorylation events of the JAK-STAT signaling pathway. Lastly, there is also significant activation of the T cell receptor signaling pathway demonstrating the initiation of the acquired immune response to Salmonella infection. Based on the individual phosphorylation events altered by the early Salmonella infection of the cecum, certain conclusions can be drawn: (1) Salmonella was recognized by both TLR and NOD receptors that initiated the innate immune response; (2) activation of the PPRs induced the production of chemokines CXCLi2 (IL-8) and cytokines IL-2, IL-6, IFN-α, and IFN-γ; (3) Salmonella infection targeted the JAK-STAT pathway as a means of evading the host response by targeting the dephosphorylation of JAK1 and TYK2 and STAT1,2,3,4, and 6; (4) apoptosis appears to be a host defense mechanism where the infection with Salmonella induced both the intrinsic and extrinsic apoptotic pathways; and (5) the T cell receptor signaling pathway activates the AP-1 and NF-κB transcription factor cascades, but not NFAT.

JAK2-Mediated Phosphorylation of Stress-Induced Phosphoprotein-1 (STIP1) in Human Cells

Stress-induced phosphoprotein-1 (STIP1)—a heat shock protein (HSP)70/HSP90 adaptor protein—is commonly overexpressed in malignant cells, where it controls proliferation via multiple signaling pathways, including JAK2/STAT3. We have previously shown that STIP1 stabilizes the protein tyrosine kinase JAK2 in cancer cells via HSP90 binding. In this study, we demonstrate that STIP1 may act as a substrate for JAK2 and that phosphorylation of tyrosine residues 134 and 152 promoted STIP1 protein stability, induced its nuclear-cytoplasmic shuttling, and promoted its secretion into the extracellular space. We also found that JAK2-mediated STIP1 phosphorylation enhanced cell viability and increased resistance to cisplatin-induced cell death. Conversely, interference STIP1 with JAK2 interaction—attained either through site-directed mutagenesis or the use of cell-penetrating peptides—decreased JAK2 protein levels, ultimately leading to cell death. On analyzing human ovarian cancer specimens, JAK2 and STIP1 expression levels were found to be positively correlated with each other. Collectively, these results indicate that JAK2-mediated phosphorylation of STIP-1 is critical for sustaining the JAK2/STAT3 signaling pathway in cancer cells.