Academic Background

Inflammatory Bowel Disease (IBD) is a chronic, relapsing autoimmune disorder primarily comprising Crohn’s Disease (CD) and Ulcerative Colitis (UC). The exact pathogenesis of IBD remains unclear, but it is known that abnormal immune responses play a critical role in its development, particularly the imbalance of CD4+ T cells. The balance between Th17 cells and regulatory T cells (Treg cells) is especially important in the progression of IBD. Th17 cells play a vital role in defending against extracellular pathogens, but their dysfunction is closely associated with chronic inflammatory diseases such as IBD, multiple sclerosis, and rheumatoid arthritis. Conversely, Treg cells, which express Foxp3, inhibit inflammatory responses and protect against autoimmune diseases. The imbalance between Th17 and Treg cells is closely linked to the persistence of intestinal inflammation, making the regulation of this balance a potential therapeutic strategy for IBD.

Additionally, metabolism plays a crucial role in immune cell function, with glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) being the primary energy pathways in cells. The differentiation and pathogenicity of Th17 cells depend on OXPHOS, and inhibiting OXPHOS can suppress Th17 cell differentiation while promoting Treg cell function, offering a new approach to IBD treatment.

Mitochondrial protease ClpP (Caseinolytic Protease P), located in the mitochondrial matrix, regulates the degradation of mitochondrial proteins. Chemical activation of ClpP can affect the function of mitochondrial respiratory chain complexes, thereby modulating OXPHOS. Previous studies have shown that ClpP activation can inhibit OXPHOS by degrading mitochondrial respiratory chain-related proteins, leading to tumor cell death. However, the role of ClpP in immune cells, particularly CD4+ T cells, remains poorly understood. Therefore, this study aims to explore the role of ClpP in IBD and to treat IBD by chemically activating ClpP to modulate the energy metabolism of CD4+ T cells.

Source of the Paper

This paper was co-authored by Jiangnan Zhang, Yunhan Jiang, Dongmei Fan, and others from the State Key Laboratory of Biotherapy and the Institute of Immunology and Inflammation at West China Hospital, Sichuan University. The paper was published on December 17, 2024, in Cell Reports Medicine, titled Chemical Activation of Mitochondrial ClpP to Modulate Energy Metabolism of CD4+ T Cell for Inflammatory Bowel Diseases Treatment.

Research Process and Results

1. Aberrant Expression of ClpP in IBD

The study first examined the expression levels of ClpP in colon tissues from IBD patients and colitis model mice using immunohistochemistry and Western blotting. The results showed that ClpP expression was significantly upregulated in the colon tissues of IBD patients and colitis model mice, particularly in CD4+ T cells. Additionally, single-cell data analysis revealed that ClpP expression was significantly upregulated in various immune cell subsets under inflammatory conditions, suggesting that ClpP may influence the course of IBD by modulating immune responses.

2. Correlation Between ClpP Expression and Colitis Progression

To investigate the impact of ClpP expression on colitis, the research team knocked down or overexpressed ClpP in mice using adeno-associated viruses (AAV) and observed the development of DSS (Dextran Sulfate Sodium)-induced colitis. The results showed that ClpP knockdown exacerbated colitis symptoms, while ClpP overexpression enhanced the mice’s tolerance to DSS stimulation and alleviated colitis symptoms. This suggests that the upregulation of ClpP may be an adaptive response to inflammation, and ClpP supplementation could be a therapeutic strategy for IBD.

3. Effects of NCA029 on Apoptosis and Differentiation of CD4+ T Cells

The research team developed a small molecule compound, NCA029, as a chemical activator of ClpP. In vitro experiments demonstrated that NCA029 significantly inhibited OXPHOS in CD4+ T cells and induced apoptosis. Additionally, NCA029 reduced Th17 cell differentiation and promoted Treg cell differentiation by inhibiting the STAT3 signaling pathway. These results indicate that NCA029 exerts anti-inflammatory effects by modulating the metabolism and differentiation of CD4+ T cells.

4. Therapeutic Effects of NCA029 in DSS and IL-10 KO Models

In DSS-induced acute colitis models and IL-10 knockout (KO) chronic colitis models, oral administration of NCA029 significantly alleviated colitis symptoms, including intestinal inflammation and the restoration of intestinal barrier function. NCA029 also modulated the gut microbiota, reducing inflammatory responses. Furthermore, NCA029 demonstrated favorable safety and pharmacokinetic properties during treatment.

5. NCA029 Relieves IBD Symptoms by Targeting CD4+ T Cells

Through cell transfer experiments, the research team further confirmed that NCA029 alleviates IBD symptoms by targeting ClpP in CD4+ T cells. CD4+ T cells with ClpP knockdown could not be effectively inhibited by NCA029, indicating that the therapeutic effect of NCA029 depends on its activation of ClpP.

6. NCA029 Modulates the Metabolism of CD4+ T Cells

Proteomic analysis revealed that NCA029 inhibited OXPHOS in CD4+ T cells by modulating the expression of mitochondrial respiratory chain complexes, reducing ATP production. Additionally, NCA029 reduced the number of Th17 cells and increased the number of Treg cells by modulating their metabolic pathways.

Conclusions and Significance

This study reveals the important role of ClpP in IBD and develops a novel ClpP activator, NCA029, which alleviates IBD symptoms by modulating the energy metabolism of CD4+ T cells, inhibiting Th17 cell differentiation, and promoting Treg cell function. The significant therapeutic effects of NCA029 in DSS and IL-10 KO models suggest that activating ClpP may be an effective strategy for treating IBD. Moreover, the favorable safety and pharmacokinetic properties of NCA029 provide a foundation for its further clinical development.

Research Highlights

1. Key Findings: ClpP expression is significantly upregulated in IBD patients and colitis models, and its activation can alleviate IBD symptoms by modulating the metabolism and differentiation of CD4+ T cells.
2. Innovation: This study is the first to develop a novel ClpP activator, NCA029, and experimentally validate its potential in IBD treatment.
3. Application Value: As a novel therapeutic agent for IBD, NCA029 exhibits favorable safety and pharmacokinetic properties, offering a new treatment option for IBD patients.

Other Valuable Information

The limitations of this study include the use of only male animal models, and future research should validate the effects of NCA029 in female animals. Additionally, the study did not delve into the epigenetic mechanisms underlying immunometabolism and T cell differentiation. Future research could further explore these mechanisms to fully understand the action mechanisms of NCA029.