Inflammatory cytokine TNF-α promotes corneal endothelium apoptosis via upregulating TIPE2 transcription during corneal graft rejection

Topical application of calcitonin gene-related peptide as a regenerative, antifibrotic, and immunomodulatory therapy for corneal injury

Calcitonin gene-related peptide (CGRP) is a multifunctional neuropeptide abundantly expressed by corneal nerves. Using a murine model of corneal mechanical injury, we found CGRP levels in the cornea significantly reduced after injury. Topical application of CGRP as an eye drop accelerates corneal epithelial wound closure, reduces corneal opacification, and prevents corneal edema after injury in vivo. CGRP promotes corneal epithelial cell migration, proliferation, and the secretion of laminin. It reduces TGF-β1 signaling and prevents TGF-β1-mediated stromal fibroblast activation and tissue fibrosis. CGRP preserves corneal endothelial cell density, morphology, and pump function, thus reducing corneal edema. Lastly, CGRP reduces neutrophil infiltration, macrophage maturation, and the production of inflammatory cytokines in the cornea. Taken together, our results show that corneal nerve-derived CGRP plays a cytoprotective, pro-regenerative, anti-fibrotic, and anti-inflammatory role in corneal wound healing. In addition, our results highlight the critical role of sensory nerves in ocular surface homeostasis and injury repair.

cGAS-STING pathway in ischemia-reperfusion injury: a potential target to improve transplantation outcomes

Transplantation is an important life-saving therapeutic choice for patients with organ or tissue failure once all other treatment options are exhausted. However, most allografts become damaged over an extended period, and post-transplantation survival is limited. Ischemia reperfusion injury (IRI) tends to be associated with a poor prognosis; resultant severe primary graft dysfunction is the main cause of transplant failure. Targeting the cGAS-STING pathway has recently been shown to be an effective approach for improving transplantation outcomes, when activated or inhibited cGAS-STING pathway, IRI can be alleviated by regulating inflammatory response and programmed cell death. Thus, continuing efforts to develop selective agonists and antagonists may bring great hopes to post-transplant patient. In this mini-review, we reviewed the role of the cGAS-STING pathway in transplantation, and summarized the crosstalk between this pathway and inflammatory response and programmed cell death during IRI, aiming to provide novel insights into the development of therapies to improve patient outcome after transplantation.

TIPE2 knockout reduces myocardial cell damage by inhibiting IFN-γ-mediated ferroptosis

Acute rejection of the transplanted heart is mediated by oxidative programmed cell death through the synergistic effects of the innate and adaptive immune systems. However, the role of ferroptosis, a newly discovered form of oxidative cell death, has not been widely evaluated. Tumor necrosis factor-α-induced protein-8 like 2 (TNFAIP8L2), also known as TIPE2, is required for maintaining immune homeostasis. To characterize the role of TIPE2 in mediating heart allografts, BALB/c hearts were transplanted into C57BL/6 wild-type (WT) and TIPE2^-/- recipient mice. In TIPE2^-/- recipient mice, allograft injury in BALB/c allograft hearts was significantly reduced through the inhibition of allograft ferroptosis. On day 3 and day 6 post-transplantation, the numbers of CD3⁺, CD4⁺, and CD8⁺ cells among splenocytes and draining lymph node cells were significantly decreased, and the activation of CD4⁺ and CD8⁺ cells in grafts was decreased in TIPE2^-/- recipient mice compared with WT mice. Moreover, CD4⁺ and CD8⁺ T cells in TIPE2^-/- recipient mice were characterized by deficient capacities for interferon-γ (IFN-γ) production through the TBK1 signaling axis and increased glutathione peroxidase 4 (GPX4). In cell experiments, treatment with IFN-γ enhanced ferroptosis-specific lipid peroxidation in myocardial cells and correlated inversely with GPX4 expression. Mechanistically, IFN-γ administration decreased the expression of GPX4 by inhibiting MEK/ERK phosphorylation. In summary, our findings demonstrated that TIPE2 deficiency inhibits T-cell production of IFN-γ to reduce ferroptosis in allografts by restraining lipid peroxidation.

Genome-wide analysis of RNA-binding proteins co-expression with alternative splicing events in mitral valve prolapse

Objectives

We investigated the role and molecular mechanisms of RNA-binding proteins (RBPs) and their regulated alternative splicing events (RASEs) in the pathogenesis of mitral valve prolapse (MVP).

Methods

For RNA extraction, we obtained peripheral blood mononuclear cells (PBMCs) from five patients with MVP, with or without chordae tendineae rupture, and five healthy individuals. High-throughput sequencing was used for RNA sequencing (RNA-seq). Differentially expressed genes (DEGs) analysis, alternative splicing (AS) analysis, functional enrichment analysis, co-expression of RBPs, and alternative splicing events (ASEs) analysis were conducted.

Results

The MVP patients exhibited 306 up-regulated genes and 198 down-regulated genes. All down- and up-regulated genes were enriched in both Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Furthermore, MVP was closely associated with the top 10 enriched terms and pathways. In MVP patients, 2,288 RASEs were found to be significantly different, and four suitable RASEs (CARD11 A3ss, RBM5 ES, NCF1 A5SS, and DAXX A3ss) were tested. We identified 13 RNA-binding proteins (RBPs) from the DEGs and screened out four RBPs (ZFP36, HSPA1A, TRIM21, and P2RX7). We selected four RASEs based on the co-expression analyses of RBPs and RASEs, including exon skipping (ES) of DEDD2, alternative 3' splice site (A3SS) of ETV6, mutually exclusive 3'UTRs (3pMXE) of TNFAIP8L2, and A3SS of HLA-B. Furthermore, the selected four RBPs and four RASEs were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and showed high consistency with RNA sequencing (RNA-seq).

Conclusion

Dysregulated RBPs and their associated RASEs may play regulatory roles in MVP development and may therefore be used as therapeutic targets in the future.

Lead Nitrate Induces Inflammation and Apoptosis in Rat Lungs Through the Activation of NF-κB and AhR Signaling Pathways

Lead (Pb) is one of the most frequent hazardous air contaminants, where the lungs are particularly vulnerable to its toxicity. However, the Pb distribution and its impact on lung inflammation/apoptosis and particularly the involvement of nuclear factor kappa B (NF-κB) and aryl hydrocarbon receptor (AhR) signaling pathways in Pb-induced lung toxicity have not yet been fully investigated. Adult male Wistar albino rats were exposed to Pb nitrate 25, 50, and 100 mg/kg b.w. orally for 3 days. The histopathological changes of several rat organs were analyzed using hematoxylin and eosin staining. The concentrations of Pb ion in different organ tissues were quantified using inductive coupled plasma mass spectrometry, while gas chromatography-mass spectrometry was used to identify organic compounds. The changes in the mRNA and protein expression levels of inflammatory and apoptotic genes in response to Pb exposure were quantified by using RT-PCR and Western blot analyses, respectively. Treatment of rats with Pb for three consecutive days significantly increased the accumulation of Pb in lung tissues causing severe interstitial inflammation. Pb treatment also increased the percentage of lung apoptotic cells and modulated apoptotic genes (Bc2, p53, and TGF-α), inflammatory markers (IL-4, IL-10, TNF-α), and oxidative stress biomarkers (iNOS, CYP1A1, EphX) in rat lung tissues. These effects were associated with a significant increase in organic compounds, such as 3-nitrotyrosine and myeloperoxidase, and some inorganic elements, such as selenium. Importantly, the Pb-induced lung inflammation and apoptosis were associated with a proportional increase in the expression of NF-κB and AhR mRNAs and proteins. These findings clearly show that Pb induces severe inflammation and apoptosis in rat lungs and suggest that NF-κB and AhR may play a role in Pb-induced lung toxicity.

Long-term observation after transplantation of cultured human corneal endothelial cells for corneal endothelial dysfunction

Background

Corneal transplantation is the only way to treat serious corneal diseases caused by corneal endothelial dysfunction. However, the shortage of donor corneal tissues and human corneal endothelial cells (HCECs) remains a worldwide challenge. We cultivated HCECs by the use of a conditioned medium from orbital adipose-derived stem cells (OASC-CM) in vitro. Then the HCECs were used to treat animal corneal endothelial dysfunction models via cell transplantation. The purpose of this study was to conduct a long-term observation and evaluation after cell transplantation.

Methods

Orbital adipose-derived stem cells (OASCs) were isolated to prepare the conditioned medium (CM). HCECs were cultivated and expanded by the usage of the CM (CM-HCECs). Then, related corneal endothelial cell (CEC) markers were analyzed by immunofluorescence. The cell proliferation ability was also tested. CM-HCECs were then transplanted into monkey corneal endothelial dysfunction models by injection. We carried out a 24-month postoperative preclinical observation and verified the long-term effect by histological examination and transcriptome sequencing.

Results

CM-HCECs strongly expressed CEC-related markers and maintained polygonal cell morphology even after 10 passages. At 24 months after cell transplantation, there was a CEC density of more than 2400 cells per square millimeter (range, 2408–2685) in the experimental group. A corneal thickness (CT) of less than 550 μm (range, 490–510) was attained. Gene sequencing showed that the gene expression pattern of CM-HCECs was similar to that of transplanted cells and HCECs.

Conclusions

Transplantation of CM-HCECs into monkey corneal endothelial dysfunction models resulted in a transparent cornea after 24 months. This research provided a promising prospect of cell-based therapy for corneal endothelial diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02889-x.

TIPE2-modified human amnion-derived mesenchymal stem cells promote the efficacy of allogeneic heart transplantation through inducing immune tolerance

Background

Immune rejection of heart transplantation has been regarded as the biggest challenge encountered by a patient suffering from end-stage heart disease. The transplantation of human amnion-derived mesenchymal stem cells (hAD-MSCs) has exhibited promising application prospects in organ transplantation. However, its persistent unsatisfactory tolerance has limited the widespread application of this technology. We aim to investigate the role of tumor necrosis factor-α-induced protein-8 like-2 (TIPE2)-mediated hAD-MSCs in immune tolerance in heart transplantation and its molecular regulatory mechanisms.

Methods

This project detected the effect of TIPE2 on immune tolerance by constructing an allogeneic heart transplantation mouse model through which TIPE2-overexpressed hAD-MSCs were injected into recipients. The fluorescence distribution of TIPE2-hAD-MSCs in mice was observed by a small animal in vivo imaging system. Pathological changes of the transplanted heart were detected by hematoxylin and eosin (HE) staining. Flow cytometry was performed to detect the content of cardiac lymphocytes. The expression of immune-induced related factors was measured by quantitative real-time PCR (qRT-PCR) and western blot assays.

Results

TIPE2-hAD-MSCs protected myocardial tissue structures, reduced the spleen and thymus indexes in recipient mice, minimized the content of cardiac lymphocytes, reduced expressions of ERK, p38, and IFN-γ, and elevated expressions of both IL-10 and TGF-β, markedly improving the survival time and survival rates of recipient mice.

Conclusions

TIPE2-hAD-MSCs induce immune tolerance and improve the survival rates of allogeneic heart transplantation in mice. This study is expected to offer an ideal source and target of cells for organ transplantation.

Comparison of early changes in ocular surface markers and tear inflammatory mediators after femtosecond lenticule extraction and FS-LASIK

AIM

To compare the short-term impacts of femtosecond lenticule extraction (FLEx) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) on ocular surface measures and tear inflammatory mediators.

METHODS

This prospective comparative nonrandomized clinical study comprised 75 eyes (75 patients). Totally 20 male and 15 female patients (age 21.62±3.25y) with 35 eyes underwent FLEx, and 26 male and 14 female patients (age 20.18±3.59y) with 40 eyes underwent FS-LASIK. Central corneal sensitivity, noninvasive tear breakup time, corneal fluorescein staining, Schirmer I test, tear meniscus height, and ocular surface disease index were evaluated in all patients. Tear concentrations of nerve growth factor (NGF), interleukin-1α (IL-1α), transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and matrix metalloproteinase-9 (MMP-9) were assessed by multiplex antibody microarray. All measurements were performed preoperatively, and 1d, 1wk, and 1mo postoperatively.

RESULTS

Patients who underwent FLEx exhibited a more moderate reduction in central corneal sensation and less corneal fluorescein staining than those in the FS-LASIK group 1wk after the procedure (P<0.01). NGF was significantly higher 1d and 1wk after surgery in the FS-LASIK group than in the FLEx group (P<0.01). By contrast, compared to those in the FLEx group, higher postoperative values and slower recovery of tear TGF-β1, IL-1α, and TNF-α concentrations were observed in the FS-LASIK group (P<0.01). Tear concentrations of NGF, TGF-β1, TNF-α, and IL-1α were correlated with ocular surface changes after FLEx or FS-LASIK surgery.

CONCLUSION

There is less early ocular surface disruption and a reduced inflammatory response after FLEx than after FS-LASIK. NGF, TGF-β1, TNF-α, and IL-1α may contribute to the process of ocular surface recovery.

Effects of ROCK Inhibitors on Apoptosis of Corneal Endothelial Cells in CMV-Positive Posner-Schlossman Syndrome Patients

Purpose

To examine the role of aqueous tumor necrosis factor α (TNF-α)–RhoA–Rho kinase (ROCK) signaling in cytomegalovirus (CMV)-induced apoptosis and the barrier function of cultured human corneal endothelial cells (hCECs) in CMV-positive Posner–Schlossman syndrome (CMV+/PSS) patients.

Methods

Aqueous levels of TNF-α, IL-8, IL-10, and several other cytokines in 19 CMV+/PSS patients and 20 healthy control subjects were quantitated using a multiplex assay. The expression of active RhoA in hCECs post-CMV infection was determined using western blotting (WB). The expression levels of TNF-α and nuclear factor kappa B (NF-κB) in CMV-infected hCECs were examined by immunocytochemistry (ICC) and WB with and without ROCK inhibitors. The apoptotic rate and barrier integrity in CMV-infected hCECs were also examined.

Results

The expression levels of TNF-α, monocyte chemoattractant protein-1 (MCP-1), IL-8, and IL-10 were upregulated in the aqueous humor of CMV+/PSS patients, and among these upregulated cytokines aqueous TNF-α was negatively correlated with the number of corneal endothelial cells. In CMV-infected hCECs, upregulation of TNF-α and NF-κB was determined by WB and ICC. In hCECs, CMV infection induced apoptosis and significantly impaired cell–cell contacts, effects that were attenuated by treatment with a ROCK inhibitor.

Conclusions

Aqueous TNF-α was upregulated in CMV+/PSS patients, which may have triggered corneal endothelial cell loss. Modulation of TNF-α, including its downstream Rho–ROCK signaling, could serve as a novel treatment modality for corneal endothelial cell loss in CMV+/PSS patients.

Regulatory Roles of Tumor Necrosis Factor-α-Induced Protein 8 Like-Protein 2 in Inflammation, Immunity and Cancers: A Review

Tumor necrosis factor-alpha (TNF-α)-induced protein 8 (TNFAIP8/TIPE) family, including TNFAIP8 (TIPE), TNFAIP8 like-protein 1 (TNFAIP8L1/TIPE1), TNFAIP8 like-protein 2 (TNFAIP8L2/TIPE2), and TNFAIP8 like-protein 3 (TNFAIP8L3/TIPE3), plays a vital role in regulating inflammatory responses, immune homeostasis, and cancer development. Over the last decade, studies have shown that TIPE2 protein is differentially expressed in diverse cells and tissues. The dysregulation of TIPE2 protein can lead to dysregulation of inflammatory responses and immune homeostasis, and change the basic characteristics of cancers. In consideration of the immeasurable values of TIPE2 in diagnosis, treatment, and prognosis of various human diseases, this review will focus on the expression pattern, structure, and regulatory roles of TIPE2 in inflammation, immunity, and cancers.

TIPE2 Suppresses Pseudomonas aeruginosa Keratitis by Inhibiting NF-κB Signaling and the Infiltration of Inflammatory Cells

Background

The role of tumor necrosis factor α (TNF-α) induced protein 8-like-2 (TIPE2) in Pseudomonas aeruginosa (PA) keratitis was explored.

Methods

Eight-week-old TIPE2 knockout (TIPE2−/−) C57BL/6 mice and their wild-type (WT) littermates were used. Corneal disease was graded at 1, 2, and 3 days postinfection, and slit lamp, clinical score, histopathology, and immunostaining were performed in the infected corneas. The corneas were harvested, and messenger ribonucleic acid (mRNA) levels of TNF-α, interleukin-1β (IL-1β), and interleukin-6 (IL-6) were tested. Enzyme-linked immunosorbent assay (ELISA) determined the protein levels, and nuclear factor κ-light-chain-enhancer of activated B cell (NF-κB) signaling molecules were tested by Western blot. In vitro human corneal epithelial cells (HCECs) were used to determine the relationship between TIPE2 and TAK1. The HCECs were treated with TIPE2 short hairpin ribonucleic acid (shRNA) and lipopolysaccharide (LPS) to test the NF-κB signaling molecules by Western blot.

Results

Pseudomonas aeruginosa infection induced a decreased expression of TIPE2 in mouse corneas 2 days postinfection. Compared with the control group, TIPE2-deficient mice were susceptible to infection with PA and showed increased corneal inflammation. Reduced NF-κB signaling and inflammatory cell infiltration were required in the TIPE2-mediated immune modulation.

Conclusions

TIPE2 promoted host resistance to PA infection by suppressing corneal inflammation via regulating TAK1 signaling negatively and inhibiting the infiltration of inflammatory cells.