Molecular dissection of Janus kinases as drug targets for inflammatory diseases

BCR-ABL: The molecular mastermind behind chronic myeloid leukemia

The chromosomal translocation t(9;22)(q34;q11), known as the Philadelphia (Ph) chromosome, results in the BCR-ABL gene fusion which gives rise to Chronic Myeloid Leukemia (CML), a slowly progressing hematopoietic cancer that begins in the bone marrow of the patient. Making up about 15 % of all new leukemia cases, CML remains a critical focus of cancer research and treatment due to its distinctive genetic hallmark, the BCR-ABL fusion gene. The BCR-ABL fusion protein is a constitutively active tyrosine kinase which signals to multiple pathways including the Ras/MAPK, PI3K/AKT, JAK/STAT and NF-kappaB pathways which promote uncontrolled cell proliferation and survival. While multiple tyrosine kinase inhibitors (TKIs) are used to specifically target the fusion in the treatment of CML, new therapies are becoming available to overcome the resistance that occurs during TKI treatments of the disease. The discovery of the Philadelphia chromosome and the subsequent elucidation of the BCR-ABL fusion protein have since become a paradigm for understanding the genetic basis of cancer and developing precision medicine approaches. This review highlights the etiology and historical discovery of the BCR-ABL fusion, recent advances in understanding its regulatory mechanisms, and emerging strategies for its therapeutic targeting.

Modified expression of JAK-STAT pathway genes in an in vivo rheumatoid arthritis model: A preclinical study to explore genetic insights

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterised by inflammatory synovial tissue, joint deterioration, and effects on systems other than the joints. The biological process underlying the progression of the disease remains unknown, however cell-mediated immunity plays an important part in the onset of RA. The current study investigated the involvement of the JAK-STAT pathway genes (JAK-1, IL-6, and SOCS-2) in the pathogenesis of RA (Rheumatoid arthritis).

METHODOLOGY

The study was carried out on thirty male Albino Wistar rats categorised in to the three groups. The AIA (Adjuvant induced animal) model was utilised to study the disease pathogenesis. The haematoxylin and Eosin (H and E) was performed followed by ELISA and expression analyses by RT-q-PCR. The obtained data was analysed using one-way ANOVA (Analysis of Variance).

RESULTS

Histopathology confirmed that diseased group appeared to be severely impaired, demonstrating manifestations of inflammation with chronic as well as cartilage degenerative changes. Furthermore, chronic inflammation was also noticed in the intertrabecular area. The significant increased levels of JAK1, IL-6 and TYK-2 were recorded among RA group. The gene expression assessment indicated that higher expression of JAK-1 and IL-6 was linked to the further development of RA in the disease group. The SOSC2 (a negative regulator of the JAK-STAT pathway) was significantly (p < 0.01) downregulated. Moreover, SOCS2 may be unable to suppress the transcription of the related JAKs (IL-6 and JAK-1), resulting in the constant release of immune mediators and contributing to the pathophysiology of RA.

CONCLUSIONS

The JAK-STAT pathway may serve as the target for diagnosing and treating inflammatory and autoimmune disorders (RA). The findings may enhance therapeutic possibilities by investigating the possible implications of JAK-STAT pathway genes as candidates for progressive rheumatoid arthritis therapies.

Computational insights of deucravacitinib's selectivity for TYK2 pseudokinase vs. JAK kinase domain via molecular modeling studies

Deucravacitinib (Sotyktu) stands out as a novel and highly specific oral inhibitor targeting tyrosine kinase 2 (TYK2). Its mechanism of action involves an allosteric binding, to catalytically inactive pseudokinase domain of TYK2, this stabilizes an inhibitory contact between the catalytic and regulatory domains. This inhibition of Janus kinase (JAK) is associated with suppression of cytokine signaling using diverse molecules defining wide importance in current research. In our recent investigation, we examined the selectivity of the TYK2JH2 inhibitor, deucravacitinib, against four JAK kinases (JAK1, JAK2, JAK3, TYK2) and TYK2 pseudokinases utilizing a merged approach involving molecular docking, molecular dynamics analysis (300 ns), and binding free energy calculation through the molecular mechanics Poisson - Boltzmann surface area (MM-PBSA) scheme. The results obtained indicate that deucravacitinib effectively interacts with the ATP-binding site of four JAK kinases and TYK2 pseudokinase through hydrogen bond formation, electrostatic attraction, and notably, van der Waals interaction. We found the calculated binding affinity demonstrates a reduction in the TYK2JH2-deucravacitinib complex due to an increased favorable intermolecular electrostatic contribution. Consequently, deucravacitinib exhibits greater selectivity for the TYK2 pseudokinase domain compared to the other four JAKs. Moreover, the interaction with DPG motif residues and the hinge region contributed to the stabilization of deucravacitinib through robustly formed hydrogen bonds. The interaction with the hydrophobic catalytic region caused the ATP-binding site to adopt a closed conformation, thereby minimizing protein movement at the glycine loop of the JAK pseudokinase protein. In summary, our study holds significant potential for informing the strategic design of TYK2 inhibitors with enhanced affinity.

[Small Molecule Therapy for Inflammatory Bowel Disease: JAK Inhibitors and S1PR Modulators]

Small molecules, including Janus kinase (JAK) inhibitors and sphingosine-1-phosphate receptor modulators (S1PRMs), are promising new treatments for inflammatory bowel disease (IBD). Small molecules exhibit more predictable pharmacokinetics than biologics, are less likely to induce immune responses, and can be administered orally. JAK inhibitors function by blocking the activity of JAK enzymes, which prevents the subsequent phosphorylation and activation of signal transducer and activator of transcription (STAT) proteins. Tofacitinib and filgotinib are approved for treating ulcerative colitis (UC), while upadacitinib is approved for UC and Crohn's disease. Nevertheless, JAK inhibitors can increase the risk of herpes zoster, cancer, major adverse cardiovascular events, and venous thromboembolism. S1PRMs bind to S1PRs, particularly S1PR1, on lymphocytes. This interaction inhibits lymphocytes from exiting the lymph nodes and migrating to the gut, thereby reducing inflammation and the immune response in the intestinal mucosa. Ozanimod and etrasimod are S1PRMs approved for the treatment of UC, but they can cause side effects such as bradycardia, conduction disorder, and macular edema. Overall, JAK inhibitors and S1PRMs offer significant benefits in managing IBD, although their potential side effects require careful monitoring.

Atopic dermatitis: treatment and innovations in immunotherapy

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by itching and skin barrier dysfunction. Moderate to severe AD is often refractory to first-line topical treatments, and systemic immunosuppressants have been shown to be effective but have significant adverse effects. The paucity of basic treatments has contributed to the development of targeted topical and systemic immunotherapies based on the use of small molecules and biologic drugs which can directly interact with AD pathogenetic pathways. They represent a new era of therapeutic innovation. Additional new treatments are desirable since AD is a heterogeneous disease marked by different immunological phenotypes. This manuscript will review the mechanism of action, safety profile, and efficacy of promising new systemic immunological treatments for AD. Since moderate to severe AD can result in poor quality of life, the development of targeted and well-tolerated immunomodulators is a crucial purpose. The introduction of new pharmacological agents may offer new therapeutic options. However, there is the need to evaluate how "narrow-acting" agents, such as individual interleukin inhibitors, will perform under the safety and efficacy profiles compared with "broad-acting" agents, such as JAK inhibitors.

Terpenoid-Mediated Targeting of STAT3 Signaling in Cancer: An Overview of Preclinical Studies

Cancer has become one of the most multifaceted and widespread illnesses affecting human health, causing substantial mortality at an alarming rate. After cardiovascular problems, the condition has a high occurrence rate and ranks second in terms of mortality. The development of new drugs has been facilitated by increased research and a deeper understanding of the mechanisms behind the emergence and advancement of the disease. Numerous preclinical and clinical studies have repeatedly demonstrated the protective effects of natural terpenoids against a range of malignancies. Numerous potential bioactive terpenoids have been investigated in natural sources for their chemopreventive and chemoprotective properties. In practically all body cells, the signaling molecule referred to as signal transducer and activator of transcription 3 (STAT3) is widely expressed. Numerous studies have demonstrated that STAT3 regulates its downstream target genes, including Bcl-2, Bcl-xL, cyclin D1, c-Myc, and survivin, to promote the growth of cells, differentiation, cell cycle progression, angiogenesis, and immune suppression in addition to chemotherapy resistance. Researchers viewed STAT3 as a primary target for cancer therapy because of its crucial involvement in cancer formation. This therapy primarily focuses on directly and indirectly preventing the expression of STAT3 in tumor cells. By explicitly targeting STAT3 in both in vitro and in vivo settings, it has been possible to explain the protective effect of terpenoids against malignant cells. In this study, we provide a complete overview of STAT3 signal transduction processes, the involvement of STAT3 in carcinogenesis, and mechanisms related to STAT3 persistent activation. The article also thoroughly summarizes the inhibition of STAT3 signaling by certain terpenoid phytochemicals, which have demonstrated strong efficacy in several preclinical cancer models.

Immune Responses Induced at One Hour Post Cataract Surgery Wounding of the Chick Lens

While the lens is an avascular tissue with an immune-privileged status, studies have now revealed that there are immune responses specifically linked to the lens. The response to lens injury, such as following cataract surgery, has been shown to involve the activation of the resident immune cell population of the lens and the induction of immunomodulatory factors by the wounded epithelium. However, there has been limited investigation into the immediate response of the lens to wounding, particularly those induced factors that are intrinsic to the lens and its associated resident immune cells. Using an established chick embryo ex vivo cataract surgery model has made it possible to determine the early immune responses of this tissue to injury, including its resident immune cells, through a transcriptome analysis. RNA-seq studies were performed to determine the gene expression profile at 1 h post wounding compared to time 0. The results provided evidence that, as occurs in other tissues, the resident immune cells of the lens rapidly acquired a molecular signature consistent with their activation. These studies also identified the expression of many inflammatory factors by the injured lens that are associated with both the induction and regulation of the immune response.

Drug Retention Rates of Janus Kinase Inhibitors in Rheumatoid Arthritis Patients with Therapy-Induced Lymphopenia

OBJECTIVES

To determine whether drug-induced lymphocytopenia is associated with drug retention rates of JAKi (tofacitinib or baricitinib) in rheumatoid arthritis (RA) patients.

METHODS

Patients with RA who were initiated with tofacitinib (n = 38) or baricitinib (n = 74) between July 2015 and July 2022 and continued for at least 4 months were enrolled in this study. Absolute lymphocyte count (ALC) value was obtained pre-treatment and monthly after initiation of JAKi (up to 4 months). Associations between ALC nadir at an early phase (up to 4 months) from JAKi initiation and drug retention rates were analysed.

RESULTS

112 patients (87 females; age, 71.2 ± 14.0 years; disease duration, 9.2 ± 10.5 months; DAS28-CRP, 3.60 ± 1.12; DAS28-ESR, 4.43 ± 1.29; CDAI, 17.9 ± 12.9; C-reactive protein, 3.07 ± 3.43 mg/dL; and lymphocyte count, 1361.9 ± 538.7 per μL) treated with tofacitinib or baricitinib were retrospectively analysed. Lymphocytopenia (>10% decline in lymphocyte count to pre-treatment basal levels) was observed in a quarter of RA patients treated with JAKi (tofacitinib; 16 baricitinib; 14). RA patients with lymphopenia were associated with the lower drug retention rates of tofacitinib compared to those without lymphocytopenia. The reduced drug retention rates in patients with lymphocytopenia were attributed to the discontinuation of tofacitinib due to AEs. Whereas lymphocytopenia was not associated with lower drug retention rates of baricitinib. Pre-treatment absolute lymphocyte counts did not affect the drug retention rates of JAKi in patients with RA.

CONCLUSIONS

These findings suggest that lymphopenia during the first 4 months from the initiation of JAKi is associated with reduced drug retention rates in patients with RA due to AEs, which is exclusively associated with the use of tofacitinib.