Thrombospondin-1/CD47 Interaction Regulates Th17 and Treg Differentiation in Psoriasis

Advances in RNA therapy for the treatment of autoimmune diseases

Autoimmune diseases (ADs) are a group of complex, chronic conditions characterized by disturbance of immune tolerance, with examples including systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, and psoriasis. These diseases have unclear pathogenesis, and traditional therapeutic approaches remain limited. However, advances in high-throughput histology technology and scientific discoveries have led to the identification of various pathogenic factors contributing to ADs. Coupled with improvements in RNA nucleic acid-based drug synthesis, design, and delivery, RNA-based therapies have been extensively investigated for their potential in treating ADs. This paper reviews the progress in the use of miRNAs, lncRNAs, circRNAs, siRNAs, antisense oligonucleotides (ASOs), aptamers, mRNAs, and other RNA-based therapies in ADs, focusing on their therapeutic potential and application prospects, providing insights for future research and clinical treatment of autoimmune diseases.

Deciphering the role of CD47 in cancer immunotherapy

BACKGROUND

Immunotherapy has emerged as a novel strategy for cancer treatment following surgery, radiotherapy, and chemotherapy. Immune checkpoint blockade and Chimeric antigen receptor (CAR)-T cell therapies have been successful in clinical trials. Cancer cells evade immune surveillance by hijacking inhibitory pathways via overexpression of checkpoint genes. The Cluster of Differentiation 47 (CD47) has emerged as a crucial checkpoint for cancer immunotherapy by working as a "don't eat me" signal and suppressing innate immune signaling. Furthermore, CD47 is highly expressed in many cancer types to protect cancer cells from phagocytosis via binding to SIRPα on phagocytes. Targeting CD47 by either interrupting the CD47-SIRPα axis or combing with other therapies has been demonstrated as an encouraging therapeutic strategy in cancer immunotherapy. Antibodies and small molecules that target CD47 have been explored in pre- and clinical trials. However, formidable challenges such as the anemia and palate aggregation cannot be avoided because of the wide presentation of CD47 on erythrocytes.

AIM OF VIEW

This review summarizes the current knowledge on the regulation and function of CD47, and provides a new perspective for immunotherapy targeting CD47. It also highlights the clinical progress of targeting CD47 and discusses challenges and potential strategies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of targeting CD47 in cancer immunotherapy, it also augments the concept of combination immunotherapy strategies by employing both innate and adaptive immune responses.

Emerging functions of thrombospondin-1 in immunity

Thrombospondin-1 is a secreted matricellular glycoprotein that modulates cell behavior by interacting with components of the extracellular matrix and with several cell surface receptors. Its presence in the extracellular matrix is induced by injuries that cause thrombospondin-1 release from platelets and conditions including hyperglycemia, ischemia, and aging that stimulate its expression by many cell types. Conversely, rapid receptor-mediated clearance of thrombospondin-1 from the extracellular space limits its sustained presence in the extracellular space and maintains sub-nanomolar physiological concentrations in blood plasma. Roles for thrombospondin-1 signaling, mediated by specific cellular receptors or by activation of latent TGFβ, have been defined in T and B lymphocytes, natural killer cells, macrophages, neutrophils, and dendritic cells. In addition to regulating physiological nitric oxide signaling and responses of cells to stress, studies in mice lacking thrombospondin-1 or its receptors have revealed important roles for thrombospondin-1 in regulating immune responses in infectious and autoimmune diseases and antitumor immunity.

Splenocytes with fucosylation deficiency promote T cell proliferation and differentiation through thrombospondin-1 downregulation

Fucosylation plays a critical role in cell-to-cell interactions and disease progression. However, the effects of fucosylation on splenocytes and their interactions with T cells remain unclear. In this study, we aimed to explore the transcriptome profiles of splenocytes deficient in fucosyltransferase (FUT) 1, an enzyme that mediates fucosylation, and investigate their impact on the proliferation and differentiation of T cells. We analysed and compared the transcriptomes of splenocytes isolated from Fut1 knockout (KO) mice and those from wild-type (WT) mice using RNA-seq. Additionally, we examined the effects of Fut1 KO splenocytes on CD4 T cell proliferation and differentiation, in comparison to WT splenocytes, and elucidated the mechanisms involved. The comparative analysis of transcriptomes between Fut1 KO and WT splenocytes revealed that thrombospondin-1, among the genes related to immune response and inflammation, was the most highly downregulated gene in Fut1 KO splenocytes. The reduced expression of thrombospondin-1 was further confirmed using qRT-PCR and flow cytometry. In coculture experiments, Fut1 KO splenocytes promoted the proliferation of CD4 T cells and drove their differentiation toward Th1 and Th17 cells, compared with WT splenocytes. Moreover, the levels of IL-2, IFN-γ and IL-17 were increased, while IL-10 was decreased, in T cells cocultured with Fut1 KO splenocytes compared with those with WT splenocytes. These effects of Fut1 KO splenocytes on T cells were reversed when thrombospondin-1 was replenished. Taken together, our results demonstrate that splenocytes with Fut1 deficiency promote CD4 T cell proliferation and Th1/Th17 differentiation at least in part through thrombospondin-1 downregulation.

The TSP1-CD47-SIRPα interactome: an immune triangle for the checkpoint era

The use of treatments, such as programmed death protein 1 (PD1) or cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) antibodies, that loosen the natural checks upon immune cell activity to enhance cancer killing have shifted clinical practice and outcomes for the better. Accordingly, the number of antibodies and engineered proteins that interact with the ligand-receptor components of immune checkpoints continue to increase along with their use. It is tempting to view these molecular pathways simply from an immune inhibitory perspective. But this should be resisted. Checkpoint molecules can have other cardinal functions relevant to the development and use of blocking moieties. Cell receptor CD47 is an example of this. CD47 is found on the surface of all human cells. Within the checkpoint paradigm, non-immune cell CD47 signals through immune cell surface signal regulatory protein alpha (SIRPα) to limit the activity of the latter, the so-called trans signal. Even so, CD47 interacts with other cell surface and soluble molecules to regulate biogas and redox signaling, mitochondria and metabolism, self-renewal factors and multipotency, and blood flow. Further, the pedigree of checkpoint CD47 is more intricate than supposed. High-affinity interaction with soluble thrombospondin-1 (TSP1) and low-affinity interaction with same-cell SIRPα, the so-called cis signal, and non-SIRPα ectodomains on the cell membrane suggests that multiple immune checkpoints converge at and through CD47. Appreciation of this may provide latitude for pathway-specific targeting and intelligent therapeutic effect.

Platelet activation: a promoter for psoriasis and its comorbidity, cardiovascular disease

Psoriasis is a chronic inflammatory skin disease with a prevalence of 0.14% to 1.99%. The underlying pathology is mainly driven by the abnormal immune responses including activation of Th1, Th17, Th22 cells and secretion of cytokines. Patients with psoriasis are more likely to develop cardiovascular disease (CVD) which has been well recognized as a comorbidity of psoriasis. As mediators of hemostasis and thromboinflammation, platelets play an important part in CVD. However, less is known about their pathophysiological contribution to psoriasis and psoriasis-associated CVD. A comprehensive understanding of the role of platelet activation in psoriasis might pave the path for more accurate prediction of cardiovascular (CV) risk and provide new strategies for psoriasis management, which alleviates the increased CV burden associated with psoriasis. Here we review the available evidence about the biomarkers and mechanisms of platelet activation in psoriasis and the role of platelet activation in intriguing the common comorbidity, CVD. We further discussed the implications and efficacy of antiplatelet therapies in the treatment of psoriasis and prevention of psoriasis-associated CVD.

Dysregulated thrombospondin 1 and miRNA-29a-3p in severe COVID-19

Although nearly a fifth of symptomatic COVID-19 patients suffers from severe pulmonary inflammation, the mechanism of developing severe illness is not yet fully understood. To identify significantly altered genes in severe COVID-19, we generated messenger RNA and micro-RNA profiling data of peripheral blood mononuclear cells (PBMCs) from five COVID-19 patients (2 severe and 3 mild patients) and three healthy controls (HC). For further evaluation, two publicly available RNA-Seq datasets (GSE157103 and GSE152418) and one single-cell RNA-Seq dataset (GSE174072) were employed. Based on RNA-Seq datasets, thrombospondin 1 (THBS1) and interleukin-17 receptor A (IL17RA) were significantly upregulated in severe COVID-19 patients' blood. From single-cell RNA-sequencing data, IL17RA level is increased in monocytes and neutrophils, whereas THBS1 level is mainly increased in the platelets. Moreover, we identified three differentially expressed microRNAs in severe COVID-19 using micro-RNA sequencings. Intriguingly, hsa-miR-29a-3p significantly downregulated in severe COVID-19 was predicted to bind the 3'-untranslated regions of both IL17RA and THBS1 mRNAs. Further validation analysis of our cohort (8 HC, 7 severe and 8 mild patients) showed that THBS1, but not IL17RA, was significantly upregulated, whereas hsa-miR-29a-3p was downregulated, in PBMCs from severe patients. These findings strongly suggest that dysregulated expression of THBS1, IL17RA, and hsa-miR-29a-3p involves severe COVID-19.

Discrete Correlation Summation Clustering Reveals Differential Regulation of Liver Metabolism by Thrombospondin-1 in Low-Fat and High-Fat Diet-Fed Mice

Thrombospondin-1 (TSP1) is a matricellular protein with many important roles in mediating carcinogenesis, fibrosis, leukocyte recruitment, and metabolism. We have previously shown a role of diet in the absence of TSP1 in liver metabolism in the context of a colorectal cancer model. However, the metabolic implications of TSP1 regulation by diet in the liver metabolism are currently understudied. Therefore Discrete correlation summation (DCS) was used to re-interrogate data and determine the metabolic alterations of TSP1 deficiency in the liver, providing new insights into the role of TSP1 in liver injury and the progression of liver pathologies such as nonalcoholic fatty liver disease (NAFLD). DCS analysis provides a straightforward approach to rank covariance and data clustering when analyzing complex data sets. Using this approach, our previous liver metabolite data was re-analyzed by comparing wild-type (WT) and Thrombospondin-1 null (Thbs1-/-) mice, identifying changes driven by genotype and diet. Principal component analysis showed clustering of animals by genotype regardless of diet, indicating that TSP1 deficiency alters metabolite handling in the liver. High-fat diet consumption significantly altered over 150 metabolites in the Thbs1-/- livers versus approximately 90 in the wild-type livers, most involved in amino acid metabolism. The absence of Thbs1 differentially regulated tryptophan and tricarboxylic acid cycle metabolites implicated in the progression of NAFLD. Overall, the lack of Thbs1 caused a significant shift in liver metabolism with potential implications for liver injury and the progression of NAFLD.

CD47 interactions with exportin-1 limit the targeting of m7G-modified RNAs to extracellular vesicles

CD47 is a marker of self and a signaling receptor for thrombospondin-1 that is also a component of extracellular vesicles (EVs) released by various cell types. Previous studies identified CD47-dependent functional effects of T cell EVs on target cells, mediated by delivery of their RNA contents, and enrichment of specific subsets of coding and noncoding RNAs in CD47+ EVs. Mass spectrometry was employed here to identify potential mechanisms by which CD47 regulates the trafficking of specific RNAs to EVs. Specific interactions of CD47 and its cytoplasmic adapter ubiquilin-1 with components of the exportin-1/Ran nuclear export complex were identified and confirmed by coimmunoprecipitation. Exportin-1 is known to regulate nuclear to cytoplasmic trafficking of 5'-7-methylguanosine (m7G)-modified microRNAs and mRNAs that interact with its cargo protein EIF4E. Interaction with CD47 was inhibited following alkylation of exportin-1 at Cys528 by its covalent inhibitor leptomycin B. Leptomycin B increased levels of m7G-modified RNAs, and their association with exportin-1 in EVs released from wild type but not CD47-deficient cells. In addition to perturbing nuclear to cytoplasmic transport, transcriptomic analyses of EVs released by wild type and CD47-deficient Jurkat T cells revealed a global CD47-dependent enrichment of m7G-modified microRNAs and mRNAs in EVs released by CD47-deficient cells. Correspondingly, decreasing CD47 expression in wild type cells or treatment with thrombospondin-1 enhanced levels of specific m7G-modified RNAs released in EVs, and re-expressing CD47 in CD47-deficient T cells decreased their levels. Therefore, CD47 signaling limits the trafficking of m7G-modified RNAs to EVs through physical interactions with the exportin-1/Ran transport complex.

The matricellular protein thrombospondin-1 in lung inflammation and injury

Matricellular proteins comprise a diverse group of molecular entities secreted into the extracellular space. They interact with the extracellular matrix (ECM), integrins, and other cell-surface receptors, and can alter matrix strength, cell attachment to the matrix, and cell-cell adhesion. A founding member of this group is thrombospondin-1 (TSP-1), a high molecular-mass homotrimeric glycoprotein. Given the importance of the matrix and ECM remodeling in the lung following injury, TSP-1 has been implicated in a number of lung pathologies. This review examines the role of TSP-1 as a damage controller in the context of lung inflammation, injury resolution, and repair in noninfectious and infectious models. This review also discusses the potential role of TSP-1 in human diseases as it relates to lung inflammation and injury.

CD47 as a promising therapeutic target in oncology

CD47 is ubiquitously expressed on the surface of cells and plays a critical role in self-recognition. By interacting with SIRPα, TSP-1 and integrins, CD47 modulates cellular phagocytosis by macrophages, determines life span of individual erythrocytes, regulates activation of immune cells, and manipulates synaptic pruning during neuronal development. As such, CD47 has recently be regarded as one of novel innate checkpoint receptor targets for cancer immunotherapy. In this review, we will discuss increasing awareness about the diverse functions of CD47 and its role in immune system homeostasis. Then, we will discuss its potential therapeutic roles against cancer and outlines, the possible future research directions of CD47- based therapeutics against cancer.

Fasciola hepatica Fatty Acid Binding Protein 1 Modulates T cell Polarization by Promoting Dendritic Cell Thrombospondin-1 Secretion Without Affecting Metabolic Homeostasis in Obese Mice

Background

The parasitic trematode Fasciola hepatica evades host immune defenses through secretion of various immunomodulatory molecules. Fatty Acid Binding Proteins (fhFABPs) are among the main excreted/secreted proteins and have been shown to display anti-inflammatory properties. However, little is currently known regarding their impact on dendritic cells (DCs) and their subsequent capacity to prime specific CD4+ T cell subsets.

Methodology/Principal Findings

The immunomodulatory effects of both native F. hepatica extracts and recombinant fhFABPs were assessed on monocyte-derived human DCs (moDCs) and the underlying mechanism was next investigated using various approaches, including DC-allogenic T cell co-culture and DC phenotyping through transcriptomic, proteomic and FACS analyses. We mainly showed that fhFABP1 induced a tolerogenic-like phenotype in LPS-stimulated moDCs characterized by a dose-dependent increase in the cell-surface tolerogenic marker CD103 and IL-10 secretion, while DC co-stimulatory markers were not affected. A significant decrease in secretion of the pro-inflammatory cytokines IL-12p70 and IL-6 was also observed. In addition, these effects were associated with an increase in both Th2-on-Th1 ratio and IL-10 secretion by CD4+ T cells following DC-T cell co-culture. RNA sequencing and targeted proteomic analyses identified thrombospondin-1 (TSP-1) as a non-canonical factor highly expressed and secreted by fhFABP1-primed moDCs. The effect of fhFABP1 on T cell skewing was abolished when using a TSP-1 blocking antibody during DC-T cell co-culture. Immunomodulation by helminth molecules has been linked to improved metabolic homeostasis during obesity. Although fhFABP1 injection in high-fat diet-fed obese mice induced a potent Th2 immune response in adipose tissue, it did not improved insulin sensitivity or glucose homeostasis.

Conclusions/Significance

We show that fhFABP1 modulates T cell polarization, notably by promoting DC TSP-1 secretion in vitro, without affecting metabolic homeostasis in a mouse model of type 2 diabetes.

Delivery of CD47 blocker SIRPα-Fc by CAR-T cells enhances antitumor efficacy

Background

Chimeric antigen receptor (CAR) T cell therapy has been successfully applied in treating lymphoma malignancies, but not in solid tumors. CD47 is highly expressed on tumor cells and its overexpression is believed to inhibit phagocytosis by macrophages and dendritic cells. Given the antitumor activity against preclinical model of CD47-blocking to induce the innate and adaptive immune system in the tumor microenvironment, here we developed a CAR-T cell secreting CD47 blocker signal regulatory protein α (SIRPα)-Fc fusion protein (Sirf CAR-T) to boost CAR-T cell therapeutic effect in solid tumor therapy.

Methods

Murine T cells were transduced to express a conventional anti-Trop2 CAR and Sirf CAR. The expression of SIRPα-Fc fusion protein in the supernatant of CAR-T cells and its effect on macrophage phagocytosis were tested in vitro. In vivo antitumor efficacy of CAR-T cells was evaluated in immunocompetent mice and analysis of the tumor microenvironment in the tumor-bearing mice was performed.

Results

We found that Sirf CAR-T cells dramatically decreased tumor burden and significantly prolonged survival in several syngeneic immunocompetent tumor models. Furthermore, we found that Sirf CAR-T cells induced more central memory T cells (T_CM) and improved the persistence of CAR-T cells in tumor tissue, as well as decreased PD-1 expression on the CAR-T cell surface. In addition, we demonstrated that Sirf CAR-T cells could modulate the tumor microenvironment by decreasing myeloid-derived stem cells as well as increasing CD11c⁺ dendritic cells and M1-type macrophages in tumor tissue.

Conclusions

In summary, our findings indicate that CD47 blocker SIRPα-Fc enhances the antitumor efficacy of CAR-T cells and propose to block CD47/SIRPα signaling effect on CAR-T cells function, which could provide a new strategy for successful cancer immunotherapy by rationalizing combination of CD47 blocker and CAR-T cell therapy.

Tissue Tregs and Maintenance of Tissue Homeostasis

Regulatory T cells (Tregs) specifically expressing Forkhead box P3 (Foxp3) play roles in suppressing the immune response and maintaining immune homeostasis. After maturation in the thymus, Tregs leave the thymus and migrate to lymphoid tissues or non-lymphoid tissues. Increasing evidence indicates that Tregs with unique characteristics also have significant effects on non-lymphoid peripheral tissues. Tissue-resident Tregs, also called tissue Tregs, do not recirculate in the blood or lymphatics and attain a unique phenotype distinct from common Tregs in circulation. This review first summarizes the phenotype, function, and cytokine expression of these Tregs in visceral adipose tissue, skin, muscle, and other tissues. Then, how Tregs are generated, home, and are attracted to and remain resident in the tissue are discussed. Finally, how an increased understanding of these tissue Tregs might guide clinical treatment is discussed.

Targeting TSP-1 decreased periodontitis by attenuating extracellular matrix degradation and alveolar bone destruction

An important factor in periodontitis pathogenesis relates to a network of interactions of various cytokines. Thrombospondin-1 (TSP-1) is upregulated in several inflammatory diseases. We previously found that Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS)-induced TSP-1 production, and that TSP-1 simultaneously and effectively elevated inflammatory cytokines in THP-1 macrophages. This suggests that TSP-1 plays an important role in the pathology of periodontitis. However, the function of TSP-1 on oral cells is largely unknown. This study aimed to elucidate the underlying molecular mechanisms of TSP-1 in human periodontal fibroblasts (hPDLFs). We demonstrated that TSP-1 is highly expressed in the gingival crevicular fluid of patients with chronic periodontitis and in the inflammatory gingival tissues of rats. TSP-1 overexpression or treatment with recombinant human TSP-1(rTSP-1) promoted the expression of MMP-2, MMP-9 and RANKL/OPG in hPDLFs, while anti-TSP-1 inhibited cytokines production from P. gingivalis LPS-treated hPDLFs. Additional experiments showed that SB203580 (a special p38MAPK inhibitor) inhibited MMP-2, MMP-9 and RANKL/OPG expression induced by rTSP-1. Thus, TSP-1 effectively promoted P. gingivalis LPS-induced periodontal tissue (extracellular matrix (ECM) and alveolar bone) destruction by the p38MAPK signalling pathway, indicating that it may be a potential therapeutic target against periodontitis.

Recent Advancements in CD47 Signal Transduction Pathways Involved in Vascular Diseases

Cardiovascular and cerebrovascular diseases caused by atherosclerosis have a high disability rate and reduce the quality of life of the population. Therefore, understanding the mechanism of atherosclerosis and its control may interfere with the progression of atherosclerosis and thus control the occurrence of diseases closely related to atherosclerosis. TSP-1 is a factor that has been found to have an antiangiogenic effect, and CD47, as the receptor of TSP-1, can participate in the regulation of antiangiogenesis of atherosclerosis. VEGF is an important regulator of angiogenesis, and TSP-1/CD47 can cause VEGF and its downstream expression. Therefore, the TSP-1/CD47/VEGF/VEGFR2 signal may have an important influence on atherosclerosis. In addition, some inflammatory factors, such as IL-1 and NLRP3, can also affect atherosclerosis. This review will be expounded focusing on the pathogenesis and influencing factors of atherosclerosis.