Targeting SERT promotes tryptophan metabolism: mechanisms and implications in colon cancer treatment

1, 8-Cineole Ameliorated Staphylococcus aureus-Induced Pneumonia through Modulation of TRP-KYN and Arginine-NO Reprogramming

1, 8-Cineole (Cin), a cyclic monoterpenoid derived from tea trees and eucalyptus species, exhibits diverse pharmacological properties. Yet, its therapeutic impact and underlying mechanism against Staphylococcus aureus (S. aureus) pneumonia remain to be elucidated. In this study, metabolomics based on UPLC-MS/MS was integrated with network pharmacology, molecular biology, and molecular docking to investigate the effects of Cin. The findings demonstrated that Cin markedly reduced mortality and lung bacterial load, lessened pulmonary damage while suppressing the levels of proinflammatory factors, including tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in the bronchoalveolar lavage fluid (BALF) of infected mice. Additionally, 19 metabolites, primarily involved in tryptophan metabolism and arginine biosynthesis, were notably modified by Cin via suppressing the enzymatic activity of indoleamine 2, 3-dioxygenase 1 (IDO1) and inducible nitric oxide synthase (iNOS), thereby attenuating the inflammatory response. Notably, knockdown of IDO1 or iNOS significantly diminished the anti-inflammation effect of Cin. In conclusion, our study validates the therapeutic potential of Cin against S. aureus pneumonia via anti-inflammation by downregulating IDO1 and iNOS. Our results provide a theoretical basis of natural substances applied in bacterial pneumonia treatment.

New insights into tryptophan metabolism in cancer

Tryptophan (Trp) is an essential amino acid and key intermediate in a range of biological processes. Early studies identified altered Trp utilization in cancer cells favoring cancer survival and growth. Seminal findings linking Trp metabolism and suppression of immunity led to an explosion of interest ultimately culminating in clinical trials targeting these pathways in melanoma. The failure of these trials led to a clinical retreat in this approach; however, recent insights into the complex interplay of the various Trp circuits and between tumor cells, immune cells, and the microbiota have shown that reconsideration of Trp metabolism is needed. Here, we discuss recent developments in our understanding of Trp metabolism and apparent contradictions in the field. We also discuss adaptations that occur when Trp pathways are manipulated, which may impact therapy responses.

Repurposing of nervous system drugs for cancer treatment: recent advances, challenges, and future perspectives

The nervous system plays a critical role in developmental biology and oncology, influencing processes from ontogeny to the complex dynamics of cancer progression. Interactions between the nervous system and cancer significantly affect oncogenesis, tumor growth, invasion, metastasis, treatment resistance, inflammation that promotes tumors, and the immune response. A comprehensive understanding of the signal transduction pathways involved in cancer biology is essential for devising effective anti-cancer strategies and overcoming resistance to existing therapies. Recent advances in cancer neuroscience promise to establish a new cornerstone of cancer therapy. Repurposing drugs originally developed for modulating nerve signal transduction represent a promising approach to target oncogenic signaling pathways in cancer treatment. This review endeavors to investigate the potential of repurposing neurological drugs, which target neurotransmitters and neural pathways, for oncological applications. In this context, it aims to bridge the interdisciplinary gap between neurology, psychiatry, internal medicine, and oncology. By leveraging already approved drugs, researchers can utilize existing extensive safety and efficacy data, thereby reducing both the time and financial resources necessary for the development of new cancer therapies. This strategy not only promises to enhance patient outcomes but also to expand the array of available treatments, thereby enriching the therapeutic landscape in oncology.

Reciprocal tumor-platelet interaction through the EPHB1-EFNB1 axis in the liver metastatic niche promotes metastatic tumor outgrowth in pancreatic ductal adenocarcinoma

BACKGROUND

The interaction between the metastatic microenvironment and tumor cells plays an important role in metastatic tumor formation. Platelets play pivotal roles in hematogenous cancer metastasis through tumor cell-platelet interaction in blood vessels. Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy distinguished by its notable tendency to metastasize to the liver. However, the role of platelet in the liver metastatic niche of PDAC remains elusive. This study aimed to elucidate the role of platelets and their interactions with tumor cells in the liver metastatic niche of PDAC.

METHODS

An mCherry niche-labeling system was established to identify cells in the liver metastatic niche of PDAC. Platelet depletion in a liver metastasis mouse model was used to observe the function of platelets in PDAC liver metastasis. Gain-of-function and loss-of-function of erythropoietin-producing hepatocellular receptor B1 (Ephb1), tumor cell-platelet adhesion, recombinant protein, and tryptophan hydroxylase 1 (Tph1)-knockout mice were used to study the crosstalk between platelets and tumor cells in the liver metastatic niche.

RESULTS

The mCherry metastatic niche-labeling system revealed the presence of activated platelets in the liver metastatic niche of PDAC patients. Platelet depletion decreased liver metastatic tumor growth in mice. Mechanistically, tumor cell-expressed EPHB1 and platelet-expressed Ephrin B1 (EFNB1) mediated contact-dependent activation of platelets via reverse signaling-mediated AKT signaling activation, and in turn, activated platelet-released 5-HT, further enhancing tumor growth.

CONCLUSION

We revealed the crosstalk between platelets and tumor cells in the liver metastatic niche of PDAC. Reciprocal tumor-platelet interaction mediated by the EPHB1-EFNB1 reverse signaling promoted metastatic PDAC outgrowth via 5-HT in the liver. Interfering the tumor-platelet interaction by targeting the EPHB1-EFNB1 axis may represent a promising therapeutic intervention for PDAC liver metastasis.

Nervous system in colorectal cancer

A malignant tumor is a complex systemic disease involving the nervous system, which regulates nerve signals. Cancer neuroscience is a field that explores the interactions between tumors and the nervous system. The gastrointestinal tract is a typical peripheral organ with abundant neuroregulation and is regulated by the peripheral, enteric, and central nervous systems (PNS, ENS, and CNS, respectively). The physiological functions of the gastrointestinal tract are maintained via complex neuromodulation. Neuroregulatory imbalance is the primary cause of gastrointestinal diseases, including colorectal cancer (CRC). In CRC, there is a direct interaction between the nervous system and tumor cells. Moreover, this tumor-nerve interaction can indirectly regulate the tumor microenvironment, including the microbiota, immunity, and metabolism. In addition to the lower nerve centers, the stress response, emotion, and cognition represented by the higher nerve centers also participate in the occurrence and progression of CRC. Herein, we review some basic knowledge regarding cancer neuroscience and elucidate the mechanism underlying tumor-nerve interactions in CRC.

Amitriptyline revitalizes ICB response via dually inhibiting Kyn/Indole and 5-HT pathways of tryptophan metabolism in ovarian cancer

Reprogramming tryptophan metabolism (TRP) may be able to overcome immunosuppression and restore the immune checkpoint blockade (ICB) response in patients with epithelial ovarian cancer (EOC) resistant to ICB therapy because TRP metabolism is involved in the kynurenine/indole and serotonin pathways of tryptophan metabolism. Herein, employing amitriptyline (AMI), an antagonist of TLR4 and serotonin transporter (SERT), we revealed that AMI remodels the immunological landscape of EOC. In particular, AMI lowered the expression of IDO1, IL-4I1, and PD-L1, the quantity of KYN and indoles, and the level of immunosuppressive immune cells MDSC, Tregs, and CD8+CD39+/PD-1+ T cell. AMI boosted the killing potential of anti-PD-1-directed CD8+T cells and worked in concert with PD-1 inhibitors to suppress tumor growth and to prolong the survival of EOC-bearing mice. This work highlights AMI as an effective regulator of ICB response by manipulating EOC cell TRP metabolism, indicating it could be a potential strategy for improving EOC ICB therapy.

KLF7 Promotes Hepatocellular Carcinoma Progression Through Regulating SLC1A5-Mediated Tryptophan Metabolism

Krüppel-like factor 7 is a transcriptional activator and acts as an oncogene in human cancers, including hepatocellular carcinoma (HCC). Tryptophan metabolism is important for HCC cell proliferation, metastasis, and invasion. It is unclear whether KLF7 could regulate Trp metabolism in HCC. In this study, we found that Trp metabolism was suppressed in HCC cells with KLF7 knockdown. The mRNA and protein levels of SLC1A5, SLC7A5, and TPH1, as well as the content of Trp and serotonin, were reduced after KLF7 knockdown, and were potentiated following KLF7 overexpression. Increasing the content of serotonin could restore the malignancy of tumour cells in vitro and tumour growth in vivo. Conversely, decreasing the content of serotonin suppressed HCC cell proliferation. The binding activity of KLF7 was on the promoter of SLC1A5, and KLF7 positively regulated the expression of SLC1A5. KLF7 contributed to the proliferation and migration of HCC cells by up-regulation of SLC1A5. Collectively, KLF7 promotes the progression of HCC through regulating Trp metabolism. The newly identified axis of KLF7/ SLC1A5 in HCC could represent a potential target for HCC therapy.

Molecular mechanisms and therapeutic significance of Tryptophan Metabolism and signaling in cancer

Tryptophan (Trp) metabolism involves three primary pathways: the kynurenine (Kyn) pathway (KP), the 5-hydroxytryptamine (serotonin, 5-HT) pathway, and the indole pathway. Under normal physiological conditions, Trp metabolism plays crucial roles in regulating inflammation, immunity, and neuronal function. Key rate-limiting enzymes such as indoleamine-2,3-dioxygenase (IDO), Trp-2,3-dioxygenase (TDO), and kynurenine monooxygenase (KMO) drive these metabolic processes. Imbalances in Trp metabolism are linked to various cancers and often correlate with poor prognosis and adverse clinical characteristics. Dysregulated Trp metabolism fosters tumor growth and immune evasion primarily by creating an immunosuppressive tumor microenvironment (TME). Activation of the KP results in the production of immunosuppressive metabolites like Kyn, which modulate immune responses and promote oncogenesis mainly through interaction with the aryl hydrocarbon receptor (AHR). Targeting Trp metabolism therapeutically has shown significant potential, especially with the development of small-molecule inhibitors for IDO1, TDO, and other key enzymes. These inhibitors disrupt the immunosuppressive signals within the TME, potentially restoring effective anti-tumor immune responses. Recently, IDO1 inhibitors have been tested in clinical trials, showing the potential to enhance the effects of existing cancer therapies. However, mixed results in later-stage trials underscore the need for a deeper understanding of Trp metabolism and its complex role in cancer. Recent advancements have also explored combining Trp metabolism inhibitors with other treatments, such as immune checkpoint inhibitors, chemotherapy, and radiotherapy, to enhance therapeutic efficacy and overcome resistance mechanisms. This review summarizes the current understanding of Trp metabolism and signaling in cancer, detailing the oncogenic mechanisms and clinical significance of dysregulated Trp metabolism. Additionally, it provides insights into the challenges in developing Trp-targeted therapies and future research directions aimed at optimizing these therapeutic strategies and improving patient outcomes.

SSRI antidepressant citalopram reverses the Warburg effect to inhibit hepatocellular carcinoma by directly targeting GLUT1

Selective serotonin reuptake inhibitors (SSRIs) have shown promise in cancer therapy, particularly for hepatocellular carcinoma (HCC), but their molecular targets and mechanisms remain unclear. Here, we show that SSRIs exhibit significant anti-HCC effects independent of their classical target, the serotonin reuptake transporter (SERT). Using global inverse gene expression profiling, drug affinity responsive target stability assays, and in silico molecular docking, we demonstrate that citalopram targets glucose transporter 1 (GLUT1), resulting in reduced glycolytic flux. A mutant GLUT1 variant at the citalopram binding site (E380) diminishes the drug's inhibitory effects on the Warburg effect and tumor growth. In preclinical models, citalopram dampens the growth of GLUT1high liver tumors and displays a synergistic effect with anti-PD-1 therapy. Retrospective analysis reveals that SSRI use correlates with a lower risk of metastasis among patients with HCC. Our study describes a role for SSRIs in cancer metabolism, establishing a rationale for their repurposing as potential anti-cancer drugs for HCC.

Revealing the association between East Asian oral microbiome and colorectal cancer through Mendelian randomization and multi-omics analysis

BACKGROUND

Colorectal cancer (CRC) poses a global health threat, with the oral microbiome increasingly implicated in its pathogenesis. This study leverages Mendelian Randomization (MR) to explore causal links between oral microbiota and CRC using data from the China National GeneBank and Biobank Japan. By integrating multi-omics approaches, we aim to uncover mechanisms by which the microbiome influences cellular metabolism and cancer development.

METHODS

We analyzed microbiome profiles from 2017 tongue and 1915 saliva samples, and GWAS data for 6692 CRC cases and 27178 controls. Significant bacterial taxa were identified via MR analysis. Single-cell RNA sequencing and enrichment analyses elucidated underlying pathways, and drug predictions identified potential therapeutics.

RESULTS

MR identified 19 bacterial taxa significantly associated with CRC. Protective effects were observed in taxa like RUG343 and Streptococcus_umgs_2425, while HOT-345_umgs_976 and W5053_sp000467935_mgs_712 increased CRC risk. Single-cell RNA sequencing revealed key pathways, including JAK-STAT signaling and tyrosine metabolism. Drug prediction highlighted potential therapeutics like Menadione Sodium Bisulfite and Raloxifene.

CONCLUSION

This study establishes the critical role of the oral microbiome in colorectal cancer development, identifying specific microbial taxa linked to CRC risk. Single-cell RNA sequencing and drug prediction analyses further elucidate key pathways and potential therapeutics, providing novel insights and personalized treatment strategies for CRC.

Serotonin signalling in cancer: Emerging mechanisms and therapeutic opportunities

BACKGROUND

Serotonin (5-hydroxytryptamine) is a multifunctional bioamine serving as a neurotransmitter, peripheral hormone and mitogen in the vertebrate system. It has pleiotropic activities in central nervous system and gastrointestinal function via an orchestrated action of serotonergic elements, particularly serotonin receptor-mediated signalling cascades. The mitogenic properties of serotonin have garnered recognition for years and have been exploited for repurposing serotonergic-targeted drugs in cancer therapy. However, emerging conflicting findings necessitate a more comprehensive elucidation of serotonin's role in cancer pathogenesis.

MAIN BODY AND CONCLUSION

Here, we provide an overview of the biosynthesis, metabolism and action modes of serotonin. We summarise our current knowledge regarding the effects of the peripheral serotonergic system on tumourigenesis, with a specific emphasis on its immunomodulatory activities in human cancers. We also discuss the dual roles of serotonin in tumour pathogenesis and elucidate the potential of serotonergic drugs, some of which display favourable safety profiles and impressive efficacy in clinical trials, as a promising avenue in cancer treatment.

KEY POINTS

Primary synthesis and metabolic routes of peripheral 5-hydroxytryptamine in the gastrointestinal tract. Advanced research has established a strong association between the serotonergic components and carcinogenic mechanisms. The interplay between serotonergic signalling and the immune system within the tumour microenvironment orchestrates antitumour immune responses. Serotonergic-targeted drugs offer valuable clinical options for cancer therapy.

Akkermansia muciniphila inhibits tryptophan metabolism via the AhR/β-catenin signaling pathway to counter the progression of colorectal cancer

Akkermansia muciniphila (A. muciniphila), a gram-negative anaerobic bacterium, is selectively decreased in the fecal microbiota of patients with colorectal cancer (CRC), but its molecular mechanism in CRC development remains inconclusive. In this study, we first confirmed the inhibitory effect of A. muciniphila on CRC formation and analyzed the metabolic role of intestinal flora in human Polyps, A-CRA (advanced colorectal adenoma) and CRC samples. To better clarify the role of A. muciniphila in CRC development, a pseudo-germ-free (GF) azoxymethane (AOM)/dextran sulfate sodium (DSS) mouse model was established, followed by infection with or without A. muciniphila. Metabolomic analysis and RNA-seq analysis showed tryptophan-mediated aryl hydrocarbon receptor (AhR) was significantly down-regulated in A. muciniphila-infected CRC mice. Then, mice with intestinal specific AhR deficiency (AhRfl/fl Cre) were generated and were used in 2 murine models: AOM/DSS treatment as a model of carcinogen-induced colon cancer and a genetically induced model using ApcMin/+ mice. Notably, AhR deficiency inhibited CRC growth in the AOM/DSS and ApcMin/+ mouse model. Moreover, AhR deficiency inhibited, rather than enhanced, tumor formation and tumor-derived organoids in Apc-deficient cells both in vivo and in vitro by activating Wnt/β-catenin signaling and TCF4/LEF1-dependent transcription. Furthermore, the antitumor effectiveness of A. muciniphila was abolished either in a human colon cancer tumor model induced by subcutaneous transplantation of AhR-silenced CRC cells, or AhR-deficienty spontaneous colorectal cancer model. In conclusion, supplementation with A. muciniphila. protected mice from CRC development by specifically inhibiting tryptophan-mediated AhR/β-catenin signaling.

Metabolic reprogramming in colorectal cancer: regulatory networks and therapy

With high prevalence and mortality, together with metabolic reprogramming, colorectal cancer is a leading cause of cancer-related death. Metabolic reprogramming gives tumors the capacity for long-term cell proliferation, making it a distinguishing feature of cancer. Energy and intermediate metabolites produced by metabolic reprogramming fuel the rapid growth of cancer cells. Aberrant metabolic enzyme-mediated tumor metabolism is regulated at multiple levels. Notably, tumor metabolism is affected by nutrient levels, cell interactions, and transcriptional and posttranscriptional regulation. Understanding the crosstalk between metabolic enzymes and colorectal carcinogenesis factors is particularly important to advance research for targeted cancer therapy strategies via the investigation into the aberrant regulation of metabolic pathways. Hence, the abnormal roles and regulation of metabolic enzymes in recent years are reviewed in this paper, which provides an overview of targeted inhibitors for targeting metabolic enzymes in colorectal cancer that have been identified through tumor research or clinical trials.

Nerves in gastrointestinal cancer: from mechanism to modulations

Maintenance of gastrointestinal health is challenging as it requires balancing multifaceted processes within the highly complex and dynamic ecosystem of the gastrointestinal tract. Disturbances within this vibrant environment can have detrimental consequences, including the onset of gastrointestinal cancers. Globally, gastrointestinal cancers account for ~19% of all cancer cases and ~22.5% of all cancer-related deaths. Developing new ways to more readily detect and more efficiently target these malignancies are urgently needed. Whereas members of the tumour microenvironment, such as immune cells and fibroblasts, have already been in the spotlight as key players of cancer initiation and progression, the importance of the nervous system in gastrointestinal cancers has only been highlighted in the past few years. Although extrinsic innervations modulate gastrointestinal cancers, cells and signals from the gut's intrinsic innervation also have the ability to do so. Here, we shed light on this thriving field and discuss neural influences during gastrointestinal carcinogenesis. We focus on the interactions between neurons and components of the gastrointestinal tract and tumour microenvironment, on the neural signalling pathways involved, and how these factors affect the cancer hallmarks, and discuss the neural signatures in gastrointestinal cancers. Finally, we highlight neural-related therapies that have potential for the management of gastrointestinal cancers.

In silico analysis of a SLC6A4 G100V mutation in lung cancers

SLC6A4 is a serotonin re-uptake transporter which has been a target for anti-depressant therapies but recently some mutations have been described in cancer cells. Here, we characterize mutations in SLC6A4 that appear in cancer cells. We employed several validated computational and artificial intelligence algorithms to characterize the mutations. We identified a previously uncharacterized G100V mutation in lung cancers. In sillico structural analysis reveals that this mutation may affect SLC6A4 ligand binding and subsequently its function. We also identified several other mutations that may affect the structure of the protein. This preliminary analysis highlights the role of SLC6A4 in human cancers.

Sertraline inhibits stress-induced tumor growth through regulating CD8+ T cell-mediated anti-tumor immunity

Chronic stress has been reported to be associated with tumor initiation and progression. But the underlying mechanism and the specific role of tumor immunity in this process are still unknown. Herein, we applied the repeated restrain stress model in C57BL/6J mice and found that the tumor growth in stressed mice was accelerated compared with that in control mice. In addition, serotonin, also called 5-hydroxytryptamine (5-HT), in the serum of stressed mice was also elevated. Sertraline, a selective serotonin reuptake inhibitor used in the clinic, can restore the serum 5-HT level in stressed mice and restrain tumor growth. We further explored the distribution of major immune cells, including B lymphocytes cells, T lymphocytes, natural killer cells, dendritic cells, tumor-associated macrophages (TAM) and regulatory T cells (Treg). We found that the infiltration of CD8+ T cells in the tumor microenvironment (TME) decreased significantly in stressed mice. And the extra 5-HT treatment could further decrease the infiltration of CD8+ T cells in the TME. The expression of IFN-γ and Granular enzyme B (GzmB) in CD8+ T cells were also dropped in the stressed mice group, whereas the expression of programmed cell death protein 1 (PD-1) on CD8+ T cells was increased. The T cell deficiency induced by stress can be reversed by sertraline, indicating its promising role in strengthening the efficacy of anti-PDL1/PD-1 immunotherapy. The present study provides new mechanistic insights into the impact of chronic stress on antitumor immunity and implicates a novel combined immunotherapy strategy for cancer patients with chronic stress.

Action Mechanism of Zhuang Medicine Jin-mu Granules Against Chronic Pelvic Inflammatory Disease Explored Using Comprehensive Network Pharmacology and Metabolomics

Zhuang Medicine Jin-mu Granules (ZMJG) are prescriptions derived from the Zhuang nationality, which is the largest minority among 56 ethnic groups in China. They have been widely used in the treatment of chronic pelvic inflammatory disease (CPID) in Guangxi Zhuang Autonomous Region for clearing away heat and toxins, removing dampness and poisoning. CPID is a common gynecological disease of female reproductive organs and surrounding tissues and is characterized by persistent and recurrent symptoms, causing serious physical and psychological damage to the patient. Preliminary research found that ZMJG have beneficial effects on CPID model rats, but the metabolic mechanism underlying their protective effects is unclear. In this study, we used the strategy of combining network pharmacology, pharmacodynamic, and metabolomic approaches to investigate the molecular mechanisms and potential targets of ZMJG for the treatment of CPID. First, a network diagram of “medicinal materials-components-targets-pathways” based on network pharmacology was constructed to obtain a preliminary understanding of the biologically active compounds and related targets of ZMJG and clarify their molecular mechanism in CPID. Subsequently, the in vivo efficacy of ZMJG was verified in a rat model. Furthermore, we analyzed the corresponding metabolomics profile to explore the differentially induced metabolic markers and elucidate the metabolic mechanism by which ZMJG treat CPID. The results show that the therapeutic effect of ZMJG on CPID is mediated through multiple pathways, metabolic pathways, and multi-component multi-target modes, providing a detailed theoretical basis for the development and clinical application of ZMJG and a new research idea for the treatment of CPID in Chinese medicine.

Metabolism and polarization regulation of macrophages in the tumor microenvironment

The occurrence and development of tumors depend on the tumor microenvironment (TME), which consists of various types of cellular and acellular components. Tumor-associated macrophages (TAMs) are the most abundant stromal cell types in the TME. The competition for nutrients between tumor cells and macrophages leads to a limited supply of nutrients, such as glucose, lipids, and amino acids, to immune cells, which affects the differentiation and function of macrophages. Other factors in the TME, such as cytokines, chemokines, and immune checkpoints, also affect the polarization and function of macrophages. Remodeling the tumor microenvironment induces changes in macrophage nutrient uptake and polarization status, which enhance anti-tumor immunity and oxidative stress resistance and suppress immune escape. This review summarizes the influence factors on tumor progression and immune function under different conditions of macrophages. It also demonstrates the metabolic heterogeneity and phenotypic plasticity of macrophages, which provides novel strategies for anti-tumor treatment.

Disruption of autophagy by increased 5-HT alters gut microbiota and enhances susceptibility to experimental colitis and Crohn's disease

Autophagy, an essential intracellular recycling process, is linked to the pathogenesis of various diseases including Crohn’s disease (CD). Factors that lead to the development of impaired autophagy during intestinal inflammation remain largely unexplored. Here, we report the impact of the interaction between serotonin [5-hydroxytryptamine;(5-HT)] and autophagy in colitis in mouse and human studies. In mice, increased gut 5-HT inhibited autophagy and led to enhanced colitis susceptibility. Reciprocally, mice with reduced 5-HT exhibited up-regulated autophagy via the mammalian target of rapamycin pathway, which resulted in significantly decreased colitis. Deletion of autophagy gene, Atg7, in an epithelial-specific manner, in concert with reduced 5-HT, promoted the development of a colitogenic microbiota and abolished the protective effects conferred by reduced 5-HT. Notably, in control and patient peripheral blood mononuclear cells, we uncovered that 5-HT treatment inhibited autophagy. Our findings suggest 5-HT as a previously unidentified therapeutic target in intestinal inflammatory disorders such as CD that exhibits dysregulated autophagy.