Inhibition of JAK3 and PKC via Immunosuppressive Drugs Tofacitinib and Sotrastaurin Inhibits Proliferation of Human B Lymphocytes In Vitro

JAK Inhibitors in Rheumatoid Arthritis: Immunomodulatory Properties and Clinical Efficacy

Rheumatoid arthritis (RA) is a highly prevalent autoimmune disorder. The pathogenesis of the disease is complex and involves various cellular populations, including fibroblast-like synoviocytes, macrophages, and T cells, among others. Identification of signalling pathways and molecules that actively contribute to the development of the disease is crucial to understanding the mechanisms involved in the chronic inflammatory environment present in affected joints. Recent studies have demonstrated that the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway regulates the behaviour of immune cells and contributes to the progression of RA. Several JAK inhibitors, such as tofacitinib, baricitinib, upadacitinib, and filgocitinib, have been developed, and their efficacy and safety in patients with RA have been comprehensively investigated in a number of clinical trials. Consequently, JAK inhibitors have been approved and registered as a treatment for patients with RA. In this review, we discuss the involvement of JAK/STAT signalling in the pathogenesis of RA and summarise the potential beneficial effects of JAK inhibitors in cells implicated in the pathogenesis of the disease. Moreover, we present the most important phase 3 clinical trials that evaluated the use of these agents in patients.

Protein kinase C isoforms mediate the formation of neutrophil extracellular traps

Neutrophils release extracellular traps (NETs) in response to numerous pathogenic microbes as the last suicidal resource (NETosis) in the fight against infection. Apart from the host defense function, NETs play an essential role in the pathogenesis of various autoimmune, inflammatory and malignant diseases. Therefore, understanding the molecular mechanisms of NETosis is important for regulating the aberrant or excessive NET release. Protein kinase C (PKC) is a serine/threonine kinase which is involved in various neutrophil functions, however, little is known about its implication in NETosis activated by various physiological and pharmacological stimuli. Since there are conventional, novel and atypical PKC isoforms (α, βI, βII, δ, and ζ) found in human neutrophils, we investigated their impact in NETosis, oxidative burst and spreading applying pharmacological approach. Using specific inhibitors of PKC isoforms, we showed that PKCβ, PKCδ, and PKCζ are involved in the oxidative burst, spreading and NETosis activated by calcium ionophore A23187, while only PKCβ is implicated in these functions activated by phorbol 12-myristate 13-acetate (PMA). The data obtained in our study might help in the development of new drugs useful for the treatment of autoimmune and inflammatory diseases associated with NETs.

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.

Activators and Inhibitors of Protein Kinase C (PKC): Their Applications in Clinical Trials

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinase, is classed into three subfamilies based on their structural and activation characteristics: conventional or classic PKC isozymes (cPKCs; α, βI, βII, and γ), novel or non-classic PKC isozymes (nPKCs; δ, ε, η, and θ), and atypical PKC isozymes (aPKCs; ζ, ι, and λ). PKC inhibitors and activators are used to understand PKC-mediated intracellular signaling pathways and for the diagnosis and treatment of various PKC-associated diseases, such as cancers, neurological diseases, cardiovascular diseases, and infections. Many clinical trials of PKC inhibitors in cancers showed no significant clinical benefits, meaning that there is a limitation to design a cancer therapeutic strategy targeting PKC alone. This review will focus on the activators and inhibitors of PKC and their applications in clinical trials.

B Cells in Rheumatoid Arthritis：Pathogenic Mechanisms and Treatment Prospects

Rheumatoid arthritis (RA) is a common, chronic, systemic autoimmune disease, and its clinical features are the proliferation of joint synovial tissue, the formation of pannus and the destruction of cartilage. The global incidence of RA is about 1%, and it is more common in women. The basic feature of RA is the body’s immune system disorders, in which autoreactive CD4⁺T cells, pathogenic B cells, M1 macrophages, inflammatory cytokines, chemokines and autoantibodies abnormally increase in the body of RA patients B cell depletion therapy has well proved the important role of B cells in the pathogenesis of RA, and the treatment of RA with B cells as a target has also been paid more and more attention. Although the inflammatory indicators in RA patients receiving B-cell depletion therapy have been significantly improved, the risk of infection and cancer has also increased, which suggests that we need to deplete pathogenic B cells instead of all B cells. However, at present we cannot distinguish between pathogenic B cells and protective B cells in RA patients. In this review, we explore fresh perspectives upon the roles of B cells in the occurrence, development and treatment of RA.

JAK Inhibitors and Modulation of B Cell Immune Responses in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, systemic immune-mediated inflammatory disease that can lead to joint destruction, functional disability and substantial comorbidity due to the involvement of multiple organs and systems. B cells have several important roles in RA pathogenesis, namely through autoantibody production, antigen presentation, T cell activation, cytokine release and ectopic lymphoid neogenesis. The success of B cell depletion therapy with rituximab, a monoclonal antibody directed against CD20 expressed by B cells, has further supported B cell intervention in RA development. Despite the efficacy of synthetic and biologic disease modifying anti-rheumatic drugs (DMARDs) in the treatment of RA, few patients reach sustained remission and refractory disease is a concern that needs critical evaluation and close monitoring. Janus kinase (JAK) inhibitors or JAKi are a new class of oral medications recently approved for the treatment of RA. JAK inhibitors suppress the activity of one or more of the JAK family of tyrosine kinases, thus interfering with the JAK-Signal Transducer and Activator of Transcription (STAT) signaling pathway. To date, there are five JAK inhibitors (tofacitinib, baricitinib, upadacitinib, peficitinib and filgotinib) approved in the USA, Europe and/ or Japan for RA treatment. Evidence from the literature indicates that JAK inhibitors interfere with B cell functions. In this review, the main results obtained in clinical trials, pharmacokinetic, in vitro and in vivo studies concerning the effects of JAK inhibitors on B cell immune responses in RA are summarized.

Use of De Novo mTOR Inhibitors in Hypersensitized Kidney Transplant Recipients: Experience From Clinical Practice

BACKGROUND

It is commonly believed that mTOR inhibitors (mTORi) should not be used in high-immunological risk kidney transplant recipients due to a perceived increased risk of rejection. However, almost all trials that examined the association of optimal-dose mTORi with calcineurin inhibitor (CNI) have excluded hypersensitized recipients from enrollment.

METHODS

To shed light on this issue, we examined 71 consecutive patients with a baseline calculated panel reactive antibody (cPRA) ≥50% that underwent kidney transplantation from June 2013 to December 2016 in our unit. Immunosuppression was based on CNI (tacrolimus), steroids and alternatively mycophenolic acid (MPA; n = 38), or mTORi (either everolimus or sirolimus, n = 33, target trough levels 3-8 ng/mL).

RESULTS

Demographic and immunological risk profiles were similar, and almost 90% of patients in both groups received induction with lymphocyte-depleting agents. Cox-regression analysis of rejection-free survival revealed better results for mTORi versus MPA in terms of biopsy-proven acute rejection (hazard ratio [confidence interval], 0.32 [0.11-0.90], P = 0.031 at univariable analysis and 0.34 [0.11-0.95], P = 0.040 at multivariable analysis). There were no differences in 1-year renal function, Banff chronicity score at 3- and 12-month protocol biopsy and development of de novo donor-specific antibodies. Tacrolimus trough levels along the first year were not different between groups (12-mo levels were 8.72 ± 2.93 and 7.85 ± 3.07 ng/mL for MPA and mTORi group respectively, P = 0.277).

CONCLUSIONS

This single-center retrospective cohort analysis suggests that in hypersensitized kidney transplant recipients receiving tacrolimus-based immunosuppressive therapy similar clinical outcomes may be obtained using mTOR inhibitors compared to mycophenolate.