Inhibition of inosine metabolism of the gut microbiota decreases testosterone secretion in the testis.

Growing evidence indicates that gut microbiota is involved in the regulation of the host's sex hormone levels, such as through interfering with the sex hormone metabolism in the intestine. However, if gut microbiota or its metabolites directly influence the sex hormone biosynthesis in the gonad remains largely unknown. Our previous study showed that colistin, as a narrow-spectrum antibiotic, can significantly downregulate the serum testosterone levels and thus enhance the antitumor efficiency of anti-PD-L1 in male mice; however, the underlying mechanism for the regulation of the host's testosterone levels remains uninvestigated. In the present study, we analyzed the impact of colistin on the immune microenvironment of the testis as well as the composition and metabolism of gut microbiota in male mice. Our results showed that colistin has an impact on the immune microenvironment of the testis and can downregulate serum testosterone levels in male mice through inhibition of Akkermansia, leading to destroyed inosine metabolism. Supplement with inosine can restore testosterone secretion probably by prompting the recovery of the intestinal mucus barrier and the serum lipopolysaccharides levels. All these findings reveal a new pathway for the regulation of the host's sex hormone levels by gut microbiota.IMPORTANCEThis study demonstrates that exposure to even narrow-spectrum antibiotics may affect the host's testosterone levels by altering the gut microbiota and its metabolites. Our findings provide evidence that some specific gut bacteria have an impact on the sex hormone biosynthesis in the testis.

CXCL1-CXCR2 axis mediates inflammatory response after sciatic nerve injury by regulating macrophage infiltration.

Macrophages play a crucial role in the inflammatory response following sciatic nerve injury. Studies have demonstrated that C-X-C motif chemokine (CXCL) 1 recruit macrophages by binding to C-X-C chemokine receptor (CXCR) 2 and participates in the inflammatory response of various diseases. Based on these findings, we aimed to explore the role of the CXCL1-CXCR2 axis in the repair process after peripheral nerve injury. Initially, we simulated sciatic nerve injury and observed an increased expression of CXCL1 and CXCR2 in the nerves of the injury group. Both in vivo and in vitro experiments confirmed that the heightened CXCL1 expression occurs in Schwann cells and is secreted, while the elevated CXCR2 is expressed by recruited macrophages. In addition, in vitro experiments demonstrated that the binding of CXCL1 to CXCR2 can activate the NLRP3 inflammasome and promote the production of interleukin-1 beta (IL-1ß) in macrophages. However, after mice were subjected to sciatic nerve injury, the number of macrophages and the expression of inflammatory factors in the sciatic nerve were reduced following treatment with the CXCR2 inhibitor SB225002. Simultaneously, we evaluated the sciatic nerve function index, the expression of p75 neurotrophic factor receptor (p75NTR), and myelin proteins, and all of these results were improved with the use of SB225002. Thus, our results suggest that after sciatic nerve injury, the CXCL1-CXCR2 axis mediates the inflammatory response by promoting the recruitment and activation of macrophages, which is detrimental to the repair of the injured nerves. In contrast, treatment with SB225002 promotes the repair of injured sciatic nerves.

Pathogenic Th17 cell-mediated liver fibrosis contributes to resistance to PD-L1 antibody immunotherapy in hepatocellular carcinoma.

Understanding the mechanisms of resistance of hepatocellular carcinoma (HCC) to targeted therapies and immune checkpoint blockade is critical for the development of new combination therapies and improving patient survival. Here, we found that in HCC, anti-programmed cell death 1 ligand 1 (PD-L1) therapy reduces liver cancer growth, but the tumors eventually become resistant to continued therapy. Experimental analyses shows that the infiltration of pathogenic T helper 17 (pTh17) cells increases in drug-resistant HCC, and pTh17 cells secrete interleukin-17A (IL-17A), which promotes the expression of PD-L1 on the surface of HCC cells and produces resistance to anti-PD-L1 therapy. Anti-IL-17A combined with PD-L1 blockade significantly increased the infiltration of cytotoxic CD8+ T cells expressing high levels of interferon-γ and reduced treatment resistance in HCC. These results support the combination of anti-PD-L1 and anti-IL-17A as a novel strategy to induce effective T cell-mediated anti-tumor immune responses.

Management of the designed risk level of urban drainage system in the future: Evidence from haining city, China.

The design of urban drainage infrastructure is mainly based on historical conditions. Under global warming, more intense precipitation extremes will pose severe risk to current infrastructure. The evaluation of where and by how much design standards need to change, is urgently needed to help maintain well-functioning drainage systems. In this study, we used climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and InfoWorks Integrated Catchment Modeling (ICM) to simulate urban flooding. According to the latest design standard of urban drainage infrastructure, we assess the risk of future urban flooding, and evaluate the effect and benefit of drainage infrastructure adaptation measures. The results showed that, under the shared socioeconomic pathway (SSP) 5-8.5 scenario, a 35% increase in extreme rainfall would be expected. Under a 1-in-30-year precipitation event, the maximum depth would increase by 5.59%, and the withdrawal time would rise by 2.94% in the future period, relative to the baseline level. After the enlargement of drainage infrastructure in local areas, 10% pipe enlargement has a better effect to reduce risk and higher benefits than 5% pipe enlargement. These findings provide valuable insights for policymakers in enhancing the drainage system and adapting to climate change.

IL-17A functions and the therapeutic use of IL-17A and IL-17RA targeted antibodies for cancer treatment.

Interleukin 17A (IL-17A) is a major member of the IL-17 cytokine family and is produced mainly by T helper 17 (Th17) cells. Other cells such as CD8+ T cells, γδ T cells, natural killer T cells and innate lymphoid-like cells can also produce IL-17A. In healthy individuals, IL-17A has a host-protective capacity, but excessive elevation of IL-17A is associated with the development of autoimmune diseases and cancer. Monoclonal antibodies (mAbs) targeting IL-17A (e.g., ixekizumab and secukinumab) or IL-17A receptor (IL-17RA) (e.g., brodalumab) would be investigated as potential treatments for these diseases. Currently, the application of IL-17A-targeted drugs in autoimmune diseases will provide new ideas for the treatment of tumors, and its combined application with immune checkpoint inhibitors has become a research hotspot. This article reviews the mechanism of action of IL-17A and the application of anti-IL-17A antibodies, focusing on the research progress on the mechanism of action and therapeutic blockade of IL-17A in various tumors such as colorectal cancer (CRC), lung cancer, gastric cancer and breast cancer. Moreover, we also include the results of therapeutic blockade in the field of cancer as well as recent advances in the regulation of IL-17A signaling.

The CXCL12-CXCR4-NLRP3 axis promotes Schwann cell pyroptosis and sciatic nerve demyelination in rats.

Studies have shown that the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome is detrimental to the functional recovery of the sciatic nerve, but the regulatory mechanisms of the NLRP3 inflammasome in peripheral nerves are unclear. C-X-C motif chemokine 12 (CXCL12) can bind to C-X-C chemokine receptor type 4 (CXCR4) and participate in a wide range of nerve inflammation by regulating the NLRP3 inflammasome. Based on these, we explore whether CXCL12-CXCR4 axis regulates the NLRP3 inflammasome in the peripheral nerve. We found that CXCR4/CXCL12, NLRP3 inflammasome-related components, pyroptosis-related proteins and inflammatory factors in the sciatic nerve injured rats were markedly increased compared with the sham-operated group. AMD3100, a CXCR4 antagonist, reverses the activation of NLRP3 inflammasome, Schwann cell pyroptosis and sciatic nerve demyelination. We further treated rat Schwann cells with LPS (lipopolysaccharide) and adenosine triphosphate (ATP) to mimic the cellular inflammation model of sciatic nerve injury, and the results were consistent with those in vivo. In addition, both in vivo and in vitro experiments demonstrated that AMD3100 treatment reduced the phosphorylation of nuclear factor κB (NF-κB) and the expression of thioredoxin interacting protein (TXNIP), which contributes to activating NLRP3 inflammasome. Therefore, our findings suggest that, after sciatic nerve injury, CXCL12-CXCR4 axis may promote Schwann cell pyroptosis and sciatic nerve demyelination through activating NLRP3 inflammasome and slow the recovery process of the sciatic nerve.

Enhancing therapeutic effects of murine cancer vaccine by reshaping gut microbiota with Lactobacillus rhamnosus GG and jujube powder.

Cancer vaccines have gained widespread attention in recent years as an emerging treatment for tumors. However, most therapeutic cancer vaccines have failed in phase III clinical trials due to faint clinical benefits. In this study, we funded that a specific synbiotic composing Lactobacillus rhamnosus GG (LGG) and jujube powder significantly enhanced the therapeutic effects of whole cells cancer vaccine in MC38 cancer cells bearing-mouse. The utilization of LGG increased the abundance of Muribaculaceae, which is conductive to an enhanced anti-tumor effect, but reduced microbial α-diversity. The use of jujube nursed probiotic microorganisms in Lachnospiaceae and enriched microbial diversity, as indicated by increased Shannon and Chao index. The reshaped gut microbiota by this synbiotic improved lipid metabolism conductive to intensified infiltration of CD8+ T cells in the tumor microenvironment and enhanced the potency of above-mentioned cancer vaccine. These encouraging findings are helpful for further efforts towards enhancing the therapeutic effects of cancer vaccines through nutritional intervention.

The role of CXCL1/CXCR2 axis in neurological diseases.

The C-X-C chemokine ligand (CXCL) 1 and its receptor C-X-C chemokine receptor (CXCR) 2 are widely expressed in the peripheral nervous systems (PNS) and central nervous systems (CNS) and are involved in the development of inflammation and pain after various nerve injuries. Once a nerve is damaged, it affects not only the neuron itself but also lesions elsewhere in its dominant site. After the CXCL1/CXCR2 axis is activated, multiple downstream pathways can be activated, such as c-Raf/MAPK/AP-1, p-PKC-µ/p-ILK/NLRP3, JAK2/STAT3, TAK1/NF-κB, etc. These pathways in turn mediate cellular motility state or cell migration. CXCR2 is expressed on the surface of neutrophils and monocytes/macrophages. These cells can be recruited to the lesion through the CXCL1/CXCR2 axis to participate in the inflammatory response. The expression of CXCR2 in neurons can activate some pathways in neurons through the CXCL1/CXCR2 axis, thereby causing damage to neurons. CXCR2 is also expressed in astrocytes, and when CXCR2 activated, it increases the number of astrocytes but impairs their function. Since inflammation can occur at almost any site of injury, elucidating the mechanism of CXCL1/CXCR2 axis' influence on inflammation may provide a favorable target for clinical treatment. Therefore, this article reviews the research progress of the CXCL1/CXCR2 axis in neurological diseases, aiming to provide a more meaningful theoretical basis for the treatment of neurological diseases.

PKC-ζ mediated reduction of the extracellular vesicles-associated TGF-ß1 overcomes radiotherapy resistance in breast cancer.

BACKGROUND: Radiotherapy is widely applied in breast cancer treatment, while radiotherapy resistance is inevitable. TGF-ß1 has been considered to be an endogenous factor for the development of radiotherapy resistance. As a large portion of TGF-ß1 is secreted in an extracellular vesicles-associated form (TGF-ß1EV), particularly in radiated tumors. Thus, the understanding of the regulation mechanisms and the immunosuppressive functions of TGF-ß1EV will pave a way for overcoming the radiotherapy resistance in cancer treatment. METHODS: The superoxide-Zinc-PKC-ζ-TGF-ß1EV pathway in breast cancer cells was identified through sequence alignments of different PKC isoforms, speculation and experimental confirmation. A series of functional and molecular studies were performed by quantitative real-time PCR, western blot and flow cytometry analysis. Mice survival and tumor growth were recorded. Student's t test or two-way ANOVA with correction was used for comparisons of groups. RESULTS: The radiotherapy resulted in an increased expression of the intratumoral TGF-ß1 and an enhanced infiltration of the Tregs in the breast cancer tissues. The intratumoral TGF-ß1 was found mainly in the extracellular vesicles associated form both in the murine breast cancer model and in the human lung cancer tissues. Furthermore, radiation induced more TGF-ß1EV secretion and higher percentage of Tregs by promoting the expression and phosphorylation of protein kinase C zeta (PKC-ζ). Importantly, we found that naringenin rather than 1D11 significantly improved radiotherapy efficacy with less side effects. Distinct from TGF-ß1 neutralizing antibody 1D11, the mechanism of naringenin was to downregulate the radiation-activated superoxide-Zinc-PKC-ζ-TGF-ß1EV pathway. CONCLUSIONS: The superoxide-zinc-PKC-ζ-TGF-ß1EV release pathway was elucidated to induce the accumulation of Tregs, resulting in radiotherapy resistance in the TME. Therefore, targeting PKC-ζ to counteract TGF-ß1EV function could represent a novel strategy to overcome radiotherapy resistance in the treatment of breast cancer or other cancers. TRIAL REGISTRATION: The using of patient tissues with malignant Non-Small Cell Lung Cancer (NSCLC) was approved by the ethics committees at Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (NCC2022C-702, from June 8th, 2022).

The role of the sex hormone-gut microbiome axis in tumor immunotherapy.

Accumulating evidence suggested that both gut microbiome and sex play a critical role in the efficacy of immune checkpoint blockade therapy. Considering the reciprocal relationship between sex hormones and gut microbiome, the sex hormone-gut microbiome axis may participate in the regulation of the response to immune checkpoint inhibitors (ICIs). In this review, it was attempted to summarize the current knowledge about the influences of both sex and gut microbiome on the antitumor efficacy of ICIs and describe the interaction between sex hormones and gut microbiome. Accordingly, this review discussed the potential of enhancing the antitumor efficacy of ICIs through regulating the levels of sex hormones through manipulation of gut microbiome. Collectively, this review provided reliable evidence concerning the role of the sex hormone-gut microbiome axis in tumor immunotherapy.

Investigating relationships between landscape patterns and surface runoff from a spatial distribution and intensity perspective.

Rapid urbanization changes landscape patterns and results in frequent urban waterlogging issues, which affect citizens' daily lives and cause economic loss. Understanding the spatial patterns and impact factors associated with urban waterlogging under different rainfall intensities has significant implications for mitigating this hazard. In this study, the runoff depth calculated according to the Storm Water Management Model (SWMM) simulation results was used to investigate the spatial characteristics of urban waterlogging. Multiple scenario-based designs, a correlation analysis, and a stepwise regression model were employed to detect the relationship between surface runoff depth and landscape patterns under different rainfall intensities. The results show that when the rainfall intensity reached 12.5 mm/12 h, the conversion rate of rainfall to runoff increased significantly, indicating an increased waterlogging risk. Areas with impervious surface proportions of 25-50% and 75-100% were shown to require more attention due to the strong sensitivity of the surface runoff depth to an increase in the impervious surface. It is most cost-effective to maintain the original high-density vegetation or increase the vegetation density from 0-25% to 25-50% for urban green space. Additionally, the landscape configuration also affects the surface runoff depth. The fragmented, scattered, or regular shape of impervious surface patches can reduce surface runoff effectively; larger and less fragmented green space was also shown to have a surface runoff controlling. The adjusted R2 values were greater than 0.6 for all stepwise regression models, indicating that the landscape variables selected in the study can effectively predict the surface runoff depth. These models also showed that the landscape composition had a more profound contribution than the landscape configuration on runoff depth. These findings provide meaningful insights and perspectives for urban waterlogging hazard mitigation, quantitative landscape planning, and risk management. The method proposed by this study provides a referable framework for future studies on urban waterlogging and its response to the landscape in the context of global climate change.

Promoting intestinal IgA production in mice by oral administration with anthocyanins.

While recent years have witnessed ever-growing evidence on the prebiotic attributes of anthocyanins for treatment of microbiota-associated diseases, the complex interplay between anthocyanin uptake, the gut microbiota, and the intestinal mucosal immune system remains poorly understood. Here, we investigate the effects of bilberry anthocyanins on the gut microbiota composition and metabolism, and the intestinal mucosal immune system of mice. We observed an increased proportion of IgA-producing plasma cells in the mesenteric lymph nodes (MLNs) and an enhanced secretion of secretory immunoglobulin A (sIgA) and antimicrobial peptides in the small intestine. Small intestine transcriptome analysis further suggested that anthocyanins influenced IgA production. We found that oral administration of anthocyanins altered the gut microbiota through maintaining the anaerobic intestinal environment, promoting the secretion of sIgA and antimicrobial peptides, and downregulating cell motility and mobile genetic elements of commensal bacteria. These observations suggest that the oral administration of anthocyanins helps in maintaining intestinal homeostasis and thus it may find applications in immunotherapy and related fields.

Research progress of targeting NLRP3 inflammasome in peripheral nerve injury and pain.

Nerve injury and nerve pain are common diseases caused by neuroinflammation. Numerous studies have shown that the activation of NLRP3 (nod-like receptor family, pyrin domain-containing 3) inflammasome is involved in a various inflammatory response, such as Alzheimer's disease, diabetes, nerve damage and other diseases. The NLRP3 inflammasome is a complex containing NLRP3 protein, ASC (apoptosis-associated speckle-like protein), and pro-caspase-1, which is highly expressed and activated to promote the secretion of IL-1ß and IL-18 in response to the stimulation of danger-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) in immune cells such as macrophages and dendritic cells. The activation of NLRP3 inflammasome can cause cell death through caspase-1-mediated cell pyroptosis and plays an important role in the development of nervous system injury and inflammation-related diseases. This discussion aims to summarize the mechanisms of nerve damage and pain caused by excessive activation of the NLRP3 inflammasome.

Sex-Biased Immune Responses to Antibiotics during Anti-PD-L1 Treatment in Mice with Colon Cancer.

Colitis is a frequently occurred side effect of immune checkpoint inhibitors (ICIs), which are increasingly used in cancer treatment, whereas antibiotics are widely used to treat colitis, their effectiveness in ICI-associated colitis remains controversial. In this study, we firstly assessed the effectiveness of several commonly used antibiotics and antibiotic cocktails in alleviating of dextran sulfate sodium- (DSS-) induced colitis. We observed that two narrow-spectrum antibiotics, neomycin and metronidazole, were more effective in alleviating colitis, as evidenced by the remission of loss of the body weight, enlargement of the spleen, shortening of the colon, secretion of proinflammatory cytokines, and histological score of the colon tissue. Moreover, these two antibiotics resulted in better relief of colitis symptoms in the MC38 tumor-bearing male mice receiving the anti-PD-L1 mAb (αPD-L1) treatment, compared to the females. In the meantime, an enhanced response to αPD-L1 efficiency against mice colon cancer was observed in the male mouse group upon the application of these two antibiotics. In contrast, both neomycin and metronidazole showed destructive effects on the antitumor efficiency of αPD-L1 in female mice, despite relief from colitis. We found that antibiotic treatment attenuated the increased infiltration of granulocytes and myeloid cells in colon tissue induced by DSS in female mice, while reducing the proportion of Th17 cells in male mice. These differences were further associated with the sex-biased differences in the gut microbiota. These findings indicated that sex-dependent alterations in the gut microbiota should be considered when applying antibiotics for the treatment of ICI-associated colitis.

Urban Inundation under Different Rainstorm Scenarios in Lin'an City, China.

Under the circumstances of global warming and rapid urbanization, damage caused by urban inundation are becoming increasingly severe, attracting the attention of both researchers and governors. The accurate simulation of urban inundation is essential for the prevention of inundation hazards. In this study, a 1D pipe network and a 2D urban inundation coupling model constructed by InfoWorks ICM was used to simulate the inundation conditions in the typical urbanized area in the north of Lin'an. Two historical rainfall events in 2020 were utilized to verify the modeling results. The spatial-temporal variation and the causes of urban inundation under different designed rainfalls were studied. The results were as follows: (1) The constructed model had a good simulation accuracy, the Nash-Sutcliffe efficiency coefficient was higher than 0.82, R2 was higher than 0.87, and the relative error was ±20%. (2) The simulation results of different designed rainfall scenarios indicated that the maximum inundation depth and inundation extent increased with the increase in the return period, rainfall peak position coefficient, and rainfall duration. According to the analysis results, the urban inundation in Lin'an is mainly affected by topography, drainage network (spatial distribution and pipe diameter), and rainfall patterns. The results are supposed to provide technical support and a decision-making reference for the urban management department of Lin'an to design inundation prevention measures.

Downregulating testosterone levels enhance immunotherapy efficiency.

Low response rates to certain tumor types remain a major challenge for immune checkpoint blockade therapy. In this study, we first conducted an integrated biomarker evaluation of bladder cancer patients from confirmatory cohorts (IMvigor210) and found that no significant differences exist between sexes before acceptance of anti-PD-L1 treatment, whereas male patients showed a better response. Thus, we then focused on sex-related changes post anti-PD-L1 treatment and found no obvious impact on the gut microbiota in male mice but a significant decrease in the sex hormone levels. Further, castration dramatically enhanced the antitumor efficacy against murine colon adenocarcinoma in male mice. Moreover, a narrow-spectrum antibiotic, colistin was innovatively used for deregulation of testosterone levels to enhance the immunotherapy efficiency in male mice. These findings indicate that the impact on the sex hormone levels in males may contribute to the sexual dimorphism in response and provide a promising way to enhance immunotherapy efficiency.

Jujube Powder Enhances Cyclophosphamide Efficiency against Murine Colon Cancer by Enriching CD8+ T Cells While Inhibiting Eosinophilia.

Cyclophosphamide (CTX) is widely applied in cancer treatment. However, the outcome is often compromised by lymphopenia, myelosuppression, and gut dysbiosis. Here, we used jujube powder to enhance CTX efficiency through nurturing gut microbiota in order to facilitate favorable metabolisms. It was observed that the oral administration of jujube powder enriched CD8+ T cells in mouse MC38 colon tumor microenvironment and increased the diversity of gut microbiota and the abundance of Bifidobacteriales, which is helpful to the production of butyrate in the cecum content. The application of jujube powder also stimulated the production of white blood cells, especially CD8+ T cells in peripheral and bone marrow, while inhibiting the growth of eosinophils in peripheral blood and the production of IL-7 and GM-CSF in serum. All these are conductive to the significant inhibition of the tumor growth, suggesting the high potential of nurturing gut microbiota with natural products for improving the efficiency of chemotherapy.

Ultrafine Jujube Powder Enhances the Infiltration of Immune Cells during Anti-PD-L1 Treatment against Murine Colon Adenocarcinoma.

Whereas dietary intervention with natural nutrients plays an important role in activating the immune response and holds unprecedented application potential, the underpinning mechanism is poorly understood. The present work was dedicated to comprehensively examine the effects of ultrafine jujube powder (JP) on the gut microbiota and, consequentially, the effects associated with the response rate to anti-PD-L1 treatment against murine colon adenocarcinoma. A murine colon adenocarcinoma model with anti-PD-L1 immunotherapy was established to evaluate how dietary interventions affect the microbiota. In vitro and in vivo experiments confirmed the role of SCFAs in the immune response. Oral administration of JP greatly improves the response of anti-PD-L1 treatment against murine colon adenocarcinoma. Such an improvement is associated with the alteration of gut microbiota which leads to an increased abundance of Clostridiales, including Ruminococcaceae and Lachnospiraceae, an elevated SCFA production, and an intensified infiltration of CD8+ T cells to the tumor microenvironment. This work demonstrates that JP is particularly effective in modulating the gut microbiota for an improved immune checkpoint blockage therapy by boosting cytotoxic CD8+ T cells in tumor-infiltrating lymphocytes. The experimental findings of the present study are helpful for the development of dietary intervention methods for cancer immunotherapy using natural nutrients.

Optimal combination treatment regimens of vaccine and radiotherapy augment tumor-bearing host immunity.

A major obstacle to immunotherapy is insufficient infiltration of effector immune cells into the tumor microenvironment. Radiotherapy greatly reduces tumor burden but relapses often occur. Here we show that the immunosuppressive tumor microenvironment was gradually established by recruiting Tregs after radiation. Despite tumors being controlled after depletion of Tregs in the irradiated area, improvement of mice survival remained poor. A much better antitumor effect was achieved with vaccination followed by radiation than other treatments. Vaccination followed by radiation recruited more effector T cells in tumor regions, which responded to high levels of chemokines. Sequential combination of vaccination and radiotherapy could elicit distinct host immune responses. Our study demonstrated that optimal combination of irradiation and vaccination is required to achieve effective antitumor immune responses. We propose a combination regimen that could be easily translated into the clinic and offer an opportunity for rational combination therapies design in cancer treatment.

PPARα Inhibition Overcomes Tumor-Derived Exosomal Lipid-Induced Dendritic Cell Dysfunction.

Dendritic cells (DCs) orchestrate the initiation, programming, and regulation of anti-tumor immune responses. Emerging evidence indicates that the tumor microenvironment (TME) induces immune dysfunctional tumor-infiltrating DCs (TIDCs), characterized with both increased intracellular lipid content and mitochondrial respiration. The underlying mechanism, however, remains largely unclear. Here, we report that fatty acid-carrying tumor-derived exosomes (TDEs) induce immune dysfunctional DCs to promote immune evasion. Mechanistically, peroxisome proliferator activated receptor (PPAR) α responds to the fatty acids delivered by TDEs, resulting in excess lipid droplet biogenesis and enhanced fatty acid oxidation (FAO), culminating in a metabolic shift toward mitochondrial oxidative phosphorylation, which drives DC immune dysfunction. Genetic depletion or pharmacologic inhibition of PPARα effectively attenuates TDE-induced DC-based immune dysfunction and enhances the efficacy of immunotherapy. This work uncovers a role for TDE-mediated immune modulation in DCs and reveals that PPARα lies at the center of metabolic-immune regulation of DCs, suggesting a potential immunotherapeutic target.