Tocilizumab promotes corneal allograft survival in rats by modulating Treg-Th17 balance

Suppressive Role of Pigment Epithelium-derived Factor in a Rat Model of Corneal Allograft Rejection

BACKGROUND

Immunological rejection is the most common reason for corneal transplantation failure. The importance of T cells in corneal allograft rejection is well demonstrated. Recent studies highlight that pigment epithelium-derived factor (PEDF) plays an immunoregulatory role in ocular diseases by enhancing the suppressive phenotype of regulatory T cells besides its other functions in neurotrophy and antiangiogenesis.

METHODS

The effects of PEDF on immune rejection were examined in rat models of corneal transplantation using slit-lamp microscope observation, immunohistochemistry, flow cytometry, and Western blot. In vitro, we demonstrated PEDF reduced alloreactive T-cell activation using real-time polymerase chain reaction, flow cytometry, and Western blot.

RESULTS

Topical administration of PEDF provided corneal transplantation rats with an improved graft survival rate of corneal allografts, reduced hemangiogenesis, and infiltration of immune cells in corneas, in particular, type 17 T helper cells while increased regulatory T cells. Moreover, nerve reinnervation within grafts was promoted in PEDF-treated recipient rats. In vitro, PEDF inhibited alloreactive T-cell activation via the c-Jun N-terminal kinase/c-Jun signaling pathway and upregulated the expressions of interleukin-10 and transforming growth factor-β, emphasizing the suppressive role of PEDF on immune responses.

CONCLUSIONS

Our results underscore the feasibility of PEDF in alleviating corneal allograft rejection and further illustrate its potential in managing immune-related diseases.

Impact of interleukin-6 on T cells in kidney transplant recipients

Interleukin-6 (IL-6), a multifunctional proinflammatory cytokine, plays a key role in T cell activation, survival, and differentiation. Acting as a switch that induces the differentiation of naïve T cells into Th17 cells and inhibits their development into regulatory T cells, IL-6 promotes rejection and abrogates tolerance. Therapies that target IL-6 signaling include antibodies to IL-6 and the IL-6 receptor and inhibitors of janus kinases; several of these therapeutics have demonstrated robust clinical efficacy in autoimmune and inflammatory diseases. Clinical trials of IL-6 inhibition in kidney transplantation have focused primarily on its effects on B cells, plasma cells, and HLA antibodies. In this review, we summarize the impact of IL-6 on T cells in experimental models of transplant and describe the effects of IL-6 inhibition on the T cell compartment in kidney transplant recipients.

miR-151-5p alleviates corneal allograft rejection by activating PI3K/AKT signaling pathway and balancing Th17/Treg after corneal transplantation via targeting IL-2Rɑ

Background

Worldwide, corneal transplantation (CT) is the most common type of tissue replacement and the increased rate of corneal graft rejection (CGR) after CT is a critical problem. Corneal endothelium cells (CECs) are often targets of the immune response mediated by graft-attacking effector T cells. However, the molecular mechanism underlying CGR remains poorly understood.

Methods

The differentially expressed microRNAs (miRNAs) and mRNA of graft-fail corneas were measured by transcriptome sequencing (RNA-Seq). real-time quantitative polymerase chain reaction was used to measure gene expression levels. Western blot and immunofluorescence staining were used to measure protein expression levels. Kaplan-Meier survival curves were constructed to assess corneal graft survival. Hematoxylin and eosin staining was used for histopathological examination. CCK-8 and ELISA staining were used to detect cell viability and inflammatory cytokines levels, respectively. Flow cytometry was used to detect cell apoptosis and the population of Treg and Th17. Transwell migration and wound-healing assays were used to measure cell migration.

Results

We identified 453 miRNAs and 4,279 mRNAs aberrant expression in the corneas showing CGR. The differentially expressed miR-151-5p and its potential target gene [interleukin 2 receptor subunit alpha (IL-2Rɑ)] were selected from the RNA-Seq microarrays. The levels of miR-151-5p and IL-2Rɑ were respectively downregulated and upregulated in the CGR. The luciferase activity assay suggested that IL-2Rɑ is a target of miR-151-5p in 293 T cells. In addition, the miR-151-5p inhibitor, si-IL-2Rɑ, and oe-IL-2Rɑ transfection tests in CECs further confirmed that miR-151-5p downregulation and IL-2Rɑ overexpression promoted apoptosis of CECs and inhibited CEC migration, tight junction-related protein ZO-1 and Claudin-5 expression, and PI3K/AKT signaling pathway activity; however, downregulation of IL-2Rɑ abolished the inhibitor effect of miR-151-5p. Similarly, upregulation of miR-151-5p alleviated CGR via activation of the PI3K/AKT signaling pathway and balancing of Th17/Treg, and upregulation of IL-2Rɑ abolished the alleviating effect of miR-151-5p.

Conclusions

Upregulation of miR-151-5p alleviated CGR by activating the PI3K/AKT signaling pathway and balancing Th17/Treg via targeting of IL-2Rɑ, which contributes to improving the results of CT.

Effect of systemic steroid therapy in Graves' orbitopathy on regulatory T cells and Th17/Treg ratio

PURPOSE

Glucocorticoids are a mainstay treatment for Graves' orbitopathy, yet their exact mechanisms of action remain unclear. We aimed to determine whether the therapeutic effects of systemic steroid therapy in Graves' orbitopathy are mediated by changes in regulatory T lymphocytes (Tregs) and T helper 17 lymphocytes (Th17).

METHODS

We assessed Treg and Th17 levels in the peripheral blood of 32 patients with active, moderate-to-severe Graves' orbitopathy who received 12 weekly pulses of methylprednisolone, and determined their association with disease severity, disease activity, and treatment outcomes. The acute orbitopathy phase was confirmed based on clinical evaluation and magnetic resonance imaging, and assessed using the clinical activity score (CAS). The severity of the disease was classified according to ETA/EUGOGO guidelines, and quantified based on the total eye score. Treatment response was determined based on specific criteria (e.g., changes in CAS score, diplopia grade, visual acuity, etc.). Treg and Th17 cells were identified using flow cytometry.

RESULTS

Methylprednisolone treatment improved the activity of the disease and altered the Th17/Treg balance (i.e., the percentage of Tregs decreased while the number of Th17 cells remained unchanged). There was no association between the Treg/Th17 ratio and the activity and severity of the disease or the treatment response.

CONCLUSIONS

Therapeutic effects of steroid therapy in Graves' orbitopathy are not mediated by Treg and Th17 alterations in the peripheral blood. The decrease in peripheral Treg percentage is likely a consequence of the non-specific effects of steroids and does not impact clinical outcome.