Yoon Kyung Park

Protective potential of resveratrol against oxidative stress and apoptosis in Batten disease lymphoblast cells

Batten disease (BD) is the most common form of a group of disorders called neuronal ceroid lipofuscinosis, which are caused by a CLN3 gene mutation. A variety of pathogenic lysosomal storage disorder mechanisms have been suggested such as oxidative stress, endoplasmic reticulum (ER) stress, and altered protein trafficking. Resveratrol, a stilbenoid found in red grape skin, is a potent antioxidant chemical. Recent studies have suggested that resveratrol may have a curative effect in many neurodegenerative diseases. Therefore, we investigated the activities of resveratrol at the levels of oxidative and ER stress and apoptosis factors using normal and BD lymphoblast cells. We report that the BD lymphoblast cells contained low-levels of superoxide dismutase-1 (SOD-1) due to the long-term stress of reactive oxygen species. However, when we treated the cells with resveratrol, SOD-1 increased to levels observed in normal cells. Furthermore, we investigated the expression of glucose-regulated protein 78 as an ER stress marker. BD cells underwent ER stress, but resveratrol treatment resolved the ER stress in a dose-dependent manner. We further demonstrated that the levels of apoptosis markers such as apoptosis induce factor, cytochrome c, and cleavage of poly (ADP)-ribose polymerase decreased following resveratrol treatment. Thus, we propose that resveratrol may have beneficial effects in patients with BD.

Regulation of Secondary Antigen-Specific CD8+ T-Cell Responses by Natural Killer T Cells

The physiologic function of natural killer T (NKT) cells in adaptive immunity remains largely unknown because most studies have used NKT cell agonists. In the present study, the role of NKT cells during the secondary effector phase was investigated separately from the primary immunization phase via adoptive transfer of differentiated effector T cells into naive recipients. We found that secondary antitumor CD8(+) T-cell responses were optimal when NKT cells were present. Tumor-specific CD8(+) effector T cells responded less strongly to tumor cell challenge in NKT cell-deficient recipients than in recipients with intact NKT cells. NKT cell-mediated enhancement of the secondary antitumor CD8(+) T-cell response was concurrent with increased number and activity of tumor-specific CD8(+) T cells. These findings provide the first demonstration of a direct role for NKT cells in the regulation of antigen-specific secondary T-cell responses without the use of exogenous NKT cell agonists such as alpha-galactosylceramide (alpha-GalCer). Furthermore, forced activation of NKT cells with alpha-GalCer during the secondary immune response in suboptimally immunized animals enhanced otherwise poor tumor rejection responses. Taken together, our findings strongly emphasize the importance of NKT cells in secondary CD8(+) T-cell immune responses.

Natural killer T cells promote collagen-induced arthritis in DBA/1 mice

The role of NKT cells in the pathogenesis of collagen-induced arthritis (CIA) remains unclear since most studies have used C57BL/6 (B6) mice, which are less susceptible to CIA than mice with a DBA/1 background. To clarify the immunological functions of NKT cells in CIA, it is necessary to analyze in detail the effects of NKT cell deficiency on CIA development in DBA/1 mice. The incidence and severity of CIA were significantly exacerbated in DBA/1CD1d(+/-) mice as compared to DBA/1CD1d(-/-) mice. In DBA/1CD1d(+/-) mice, antigen-specific responses of B and T cells against CII were remarkably increased and inflammatory cytokine levels were also increased in vivo and in vitro. The number of IL-17-producing NKT cells significantly increased in DBA/1CD1d(+/-) mice as the disease progressed. Our results clearly show that NKT cells are involved not only in accelerating the severity and incidence of CIA but also in perpetuating the disease progression.

The presence of CD8+ invariant NKT cells in mice

Invariant natural killer T (iNKT) cells develop in the thymus upon recognition of CD1d expressed on developing thymocytes. Although CD4 and CD8 coreceptors are not directly involved in the interaction between CD1d and the T cell receptors (TCRs) of iNKT cells, a conspicuous lack of CD8+ iNKT cells in mice raised the question of whether CD8+ iNKT cells are excluded due to negative selection during their thymic development, or if there is no lineage commitment for the development of murine CD8+ iNKT cells. To address this question, we analyzed iNKT cell-specific TCR Vα14+ transgenic mice, where the Vα14 transgene forces the generation of iNKT cells. This allows detailed study of the iNKT cell repertoire. We were able to identify CD8+ iNKT cells which respond to the NKT cell-specific glycolipid ligand α-galactosylceramide. Unlike conventional iNKT cells, CD8+ iNKT cells produce predominantly IFN-γ but not IL-4 upon antigen stimulation. We also confirmed the presence of CD8+ iNKT cells in wild type mice. Our results suggest that CD8+ NKT cells do exist in mice, although their population size is quite small. Their Th1-skewed phenotype might explain why the population size of this subtype needs to be controlled tightly.

Mutation of a Positively Charged Cytoplasmic Motif within CD1d Results in Multiple Defects in Antigen Presentation to NKT Cells

CD1d is an MHC class I-like molecule that presents glycolipid Ags to types I and II NKT cells. The YxxI motif in the cytoplasmic tail of CD1d contributes to its intracellular localization to the endolysosomal compartment and is important for Ag presentation to type I NKT cells. In this study, we identified the 327–329RRR motif in CD1d and showed that it is critical for the control of CD1d intracellular trafficking and Ag presentation. The replacement of the arginines in this motif with alanines resulted in the extensive accumulation of CD1d in lysosomes but did not affect the cell surface expression. The defect in its cellular localization was accompanied by defects in Ag presentation to both type I and type II NKT cells. These results demonstrated that the 327–329RRR motif of CD1d is required for proper cellular distribution of CD1d and optimal Ag presentation to both type I and type II NKT cells.

The requirement of natural killer T-cells in tolerogenic APCs-mediated suppression of collagen-induced arthritis

TGF-β-induced tolerogenic-antigen presenting cells (Tol-APCs) could induce suppression of autoimmune diseases such as collagen-induced arthritis (CIA) and allergic asthma. In contrast, many studies have shown that NKT cells are involved in the pathogenesis of Th1-mediated autoimmune joint inflammation and Th2-mediated allergic pulmonary inflammation. In this study, we investigated the effect of CD1d-restricted NKT cells in the Tol-APCs-mediated suppression of autoimmune disease using a murine CIA model. When CIA-induced mice were treated with Tol-APCs obtained from CD1d+/- or CD1d-/- mice, unlike CD1d+/- APCs, CD1d-/- Tol-APCs failed to suppress CIA. More specifically, CD1d-/- Tol-APCs failed to suppress the production of inflammatory cytokines and the induction of Th2 responses by antigen-specific CD4 T cells both in vitro and in vivo. Our results demonstrate that the presence of CD1d-restricted NKT cells is critical for the induction of Tol-APCs-mediated suppression of CIA.

Induction of tolerance against the arthritogenic antigen with type-II collagen peptide-linked soluble MHC class II molecules.

In murine collagen-induced arthritis (CIA), self-reactive T cells can recognize peptide antigens derived from type-II collagen (CII). Activation of T cells is an important mediator of autoimmune diseases. Thus, T cells have become a focal point of study to treat autoimmune diseases. In this study, we evaluated the efficacy of recombinant MHC class II molecules in the regulation of antigen-specific T cells by using a self peptide derived from CII (CII260-274; IAGFKGEQGPKGEPG) linked to mouseI-Aq in a murine CIA model. We found that recombinant I-Aq/CII260-274 molecules could be recognized by CII-specific T cells and inhibit the same T cells in vitro. Furthermore, the development of CIA in mice was successfully prevented by in vivo injection of recombinant I-Aq/CII260-274 molecules. Thus, treatment with recombinant soluble MHC class II molecules in complex with an immunodominant self-peptide might offer a potential therapeutic for chronic inflammation in autoimmune disease such as rheumatoid arthritis. [BMB Reports 2016; 49(6): 331-336