Jun-Ho Lee

Background: Parkinson’s disease (PD) is characterized by a progressive decline in dopaminergic neurons within the substantia nigra (SN). Although its underlying cause has yet to be fully elucidated, accumulating evidence suggests that neuroinflammation contributes substantially to disease development. Treatment strategies targeting neuroinflammation could improve PD outcomes. Monocyte-derived tolerogenic dendritic cells (tolDCs) modulate immune responses and induce regulatory T cells (Tregs) during various inflammatory diseases. However, the mechanisms underlying tolDC-mediated immunoregulation in PD remain unclear. Methods: We investigated the immune modulatory role of tolDCs by analyzing gene expression patterns and identified that the C-type lectin domain family 5 member A (Clec5a) was highly induced in tolDCs. To assess its function, we generated Clec5a-knockdown tolDCs and measured cytokine production, including interleukin (IL)-10 and IL-6, forkhead box protein P3 (Foxp3)+ Treg induction, and nuclear factor kappa B (NF-κB) signaling activity. Furthermore, we evaluated the therapeutic effects of Clec5a-expressing dendritic cells (DCs) in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. Dopaminergic neuron survival, α-synuclein (α-syn) accumulation, neuroinflammatory markers, and locomotor behavior were analyzed following DC administration. Results: Clec5a-knockdown tolDCs exhibited reduced immunomodulatory function and IL-10 levels but enhanced IL-6 levels. In addition, these cells induced fewer Foxp3+ Tregs and showed significantly enhanced NF-κB signaling activity. In the MPTP-induced PD model, administration of Clec5a-expressing DCs ameliorated dopaminergic neuron loss and α-syn accumulation. Furthermore, Clec5a-expressing DCs reduced the number of CD45highCD11b+CD86+ macrophages in the brain, reduced brain inflammatory cytokine expression, and improved locomotor activity. Conclusions: These findings suggest that Clec5a plays a critical role in the immunomodulatory function of tolDCs. The administration of Clec5a-expressing DCs effectively reduced neuroinflammation and protected dopaminergic neurons in an MPTP-induced PD model. Therefore, Clec5a-expressing tolDCs may demonstrate therapeutic potential by managing PD symptoms by suppressing inflammatory responses associated with neurodegeneration.

The newly synthesized compound TGF-β signaling agonist (T74) is a small molecule associated with the TGF-β receptor signaling pathway. Tolerogenic dendritic cells (tDCs) have been used to examine immunosuppressive and anti-inflammatory effects in multiple autoimmune disease models. The aim of this study was to investigate whether treatment of DCs with T74 has an antirheumatic effect in a mouse model of collagen-induced arthritis (CIA). Bone marrow-derived cells were obtained from DBA/1J mice and differentiated into DCs. T74-treated DCs (T74-DCs) were generated by treating bone marrow-derived DCs with LPS, type II collagen, and T74. T74-DCs expressed lower levels of surface molecules and inflammatory cytokines associated with antigen presentation and T cell stimulation. The ability of T74-DCs to differentiate effector T cells was lower than that of T74-untreated DCs (NT-DCs), but T74-DCs increased the regulatory T (Treg) cell differentiation in vitro. DBA/1J mice received two subcutaneous (s.c.) injections of type II collagen to establish CIA. Mice then received two s.c. injections of T74-DCs or NT-DCs. Joint inflammation was ameliorated in the paws of T74-DC-treated mice. Additionally, Treg populations in T74-DC-treated mice were higher than in NT-DC-treated or PBS-treated CIA mice. Taken together, these results demonstrate that T74 induces tolerance in DCs, and that T74-mediated DCs exert antirheumatic effects via induction of Tregs.

Mitophagy is a selective form of autophagy that removes damaged mitochondria. Increasing evidence indicates that dysregulated mitophagy is implicated in numerous autoimmune diseases, but the role of mitophagy in rheumatoid arthritis (RA) has not yet been reported. The aim of the present study was to determine the roles of mitophagy in patient-derived RA synovial fibroblasts (RASFs) and in the collagen antibody-induced arthritis mouse model. We measured the mitophagy marker PTEN-induced putative kinase 1 (PINK1) in RASFs treated with tumor necrosis factor-α (TNF-α) using Western blotting and immunofluorescence. Arthritis was induced in PINK1^−/− mice by intraperitoneal injection of an anti-type II collagen antibody cocktail and lipopolysaccharide. RA severity was assessed by histopathology. PINK1 expression and damaged mitochondria increased in TNF-α treated RASFs via increased intracellular levels of reactive oxygen species. PINK1 knockdown RASFs decreased cellular migration and invasion functions. In addition, PINK1^−/− mice with arthritis exhibited markedly reduced swelling and inflammation relative to wild-type mice with arthritis. Taken together, these findings suggest that regulation of PINK1 expression in RA could represent a potential therapeutic and diagnostic target for RA.

Enpp2 is an enzyme that catalyzes the conversion of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), which exhibits a wide variety of biological functions. Here, we examined the biological effects of Enpp2 on dendritic cells (DCs), which are specialized antigen-presenting cells (APCs) characterized by their ability to migrate into secondary lymphoid organs and activate naïve T-cells. DCs were generated from bone marrow progenitors obtained from C57BL/6 mice. Enpp2 levels in DCs were regulated using small interfering (si)RNA or recombinant Enpp2. Expression of Enpp2 in LPS-stimulated mature (m)DCs was high, however, knocking down Enpp2 inhibited mDC function. In addition, the migratory capacity of mDCs increased after treatment with rmEnpp2; this phenomenon was mediated via the RhoA-mediated signaling pathway. Enpp2-treated mDCs showed a markedly increased capacity to migrate to lymph nodes in vivo. These findings strongly suggest that Enpp2 is necessary for mDC migration capacity, thereby increasing our understanding of DC biology. We postulate that regulating Enpp2 improves DC migration to lymph nodes, thus improving the effectiveness of cancer vaccines based on DC.

Chimeric antigen receptor (CAR)-T cells are effective in the treatment of hematologic malignancies but have shown limited efficacy against solid tumors. Here, we demonstrated an approach to inhibit recurrence of B cell lymphoma by co-expressing both a human anti-CD19-specific single-chain variable fragment (scFv) CAR (CD19 CAR) and a TGF-β/IL-7 chimeric switch receptor (tTRII-I7R) in T cells (CD19 CAR-tTRII-I7R-T cells). The tTRII-I7R was designed to convert immunosuppressive TGF-β signaling into immune-activating IL-7 signaling. The effect of TGF-β on CD19 CAR-tTRII-I7R-T cells was assessed by western blotting. Target-specific killing by CD19 CAR-tTRII-I7R-T cells was evaluated by Eu-TDA assay. Daudi tumor-bearing NSG (NOD/SCID/IL2Rγ^-/-) mice were treated with CD19 CAR-tTRII-I7R-T cells to analyze the in vivo anti-tumor effect. In vitro, CD19 CAR-tTRII-I7R-T cells had a lower level of phosphorylated SMAD2 and a higher level of target-specific cytotoxicity than controls in the presence of rhTGF-β1. In the animal model, the overall survival and recurrence-free survival of mice that received CD19 CAR-tTRII-I7R-T cells were significantly longer than in control mice. These findings strongly suggest that CD19 CAR-tTRII-I7R-T cell therapy provides a new strategy for long-lasting, TGF-β-resistant anti-tumor effects against B cell lymphoma, which may lead ultimately to increased clinical efficacy.

Background: The immune and inflammatory responses play a considerable role in left ventricular remodeling after myocardial infarction (MI). Binding of AhR (aryl hydrocarbon receptor) to its ligands modulates immune and inflammatory responses; however, the effects of AhR in the context of MI are unknown. Therefore, we evaluated the potential association between AhR and MI by treating mice with a nontoxic endogenous AhR ligand, ITE (2‐[1’H‐indole‐3’‐carbonyl]‐thiazole‐4‐carboxylic acid methyl ester). We hypothesized that activation of AhR by ITE in MI mice would boost regulatory T‐cell differentiation, modulate macrophage activity, and facilitate infarct healing. Methods and Results: Acute MI was induced in C57BL/6 mice by ligation of the left anterior descending coronary artery. Then, the mice were randomized to daily intraperitoneal injection of ITE (200 µg/mouse, n=19) or vehicle (n=16) to examine the therapeutic effects of ITE during the postinfarct healing process. Echocardiographic and histopathological analyses revealed that ITE‐treated mice exhibited significantly improved systolic function ( P P + (forkhead box protein P3‐positive) regulatory T cells and tolerogenic dendritic cell populations. Conclusions: Activation of AhR by a nontoxic endogenous ligand, ITE, improves cardiac function after MI. Post‐MI mice treated with ITE have a significantly lower risk of developing advanced left ventricular systolic dysfunction than nontreated mice. Thus, the results imply that ITE has a potential as a stimulator of cardiac repair after MI to prevent heart failure.

Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs) and inducers of T cell-mediated immunity. Although DCs play a central role in promoting adaptive immune responses against growing tumors, they also establish and maintain peripheral tolerance. DC activity depends on the method of induction and/or the presence of immunosuppressive agents. Tolerogenic dendritic cells (tDCs) induce immune tolerance by activating CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells and/or by producing cytokines that inhibit T cell activation. These findings suggest that tDCs may be an effective treatment for autoimmune diseases, inflammatory diseases, and infertility.