Synbindin deficiency inhibits colon carcinogenesis by attenuating Wnt cascade and balancing gut microbiome

Lycopene from tomatoes and tomato products exerts renoprotective effects by ameliorating oxidative stress, apoptosis, pyroptosis, fibrosis, and inflammatory injury in calcium oxalate nephrolithiasis: the underlying mechanisms

Several mechanisms underlying nephrolithiasis, one of the most common urological diseases, involve calcium oxalate formation, including oxidative stress, inflammatory reactions, fibrosis, pyroptosis, and apoptosis. Although lycopene has strong antioxidant activity, its protective effects against CaOx-induced injury have not yet been reported. This study aimed to systematically investigate the protective effects of lycopene and explore its mechanisms and molecular targets. Crystal deposition, renal function, oxidative stress, inflammatory response, fibrosis, pyroptosis, and apoptosis were assessed to evaluate the renoprotective effects of lycopene against crystal formation in a CaOx rat model and oxalate-stimulated NRK-52E and HK-2 cells. Lycopene markedly ameliorated crystal deposition, restored renal function, and suppressed kidney injury by reducing oxidative stress, apoptosis, inflammation, fibrosis, and pyroptosis in the rats. In cell models, lycopene pretreatment reversed reactive oxygen species increase, apoptotic damage, intracellular lactate dehydrogenase release, cytotoxicity, pyroptosis, and extracellular matrix deposition. Network pharmacology and proteomic analyses were performed to identify lycopene target proteins under CaOx-exposed conditions, and the results showed that Trappc4 might be a pivotal target gene for lycopene, as identified by cellular thermal shift assay and surface plasmon resonance analyses. Based on molecular docking, molecular dynamics simulations, alanine scanning mutagenesis, and saturation mutagenesis, we observed that lycopene directly interacts with Trappc4 via hydrophobic bonds, which may be attributed to the PHE4 and PHE142 residues, preventing ERK1/2 or elevating AMPK signaling pathway phosphorylation events. In conclusion, lycopene might ameliorate oxalate-induced renal tubular epithelial cell injury via the Trappc4/ERK1/2/AMPK pathway, indicating its potential for the treatment of nephrolithiasis.

Acetylation increases expression, interaction with TRAPPC4 and surface localization of PD-L1

PD-L1 is an immune checkpoint inhibitor, whose surface expression may be exploited by cancer cells to escape T cell-mediated immune recognition. PD-L1 expression and nuclear localization can be affected by epigenetic modifications, such as acetylation. In this study, we showed that VPA, a class I/IIa HDAC inhibitor, upregulated PD-L1 expression on the surface of pancreatic cancer cells. To this effect contributed the increased transcription, in correlation with histone acetylation of the PD-L1 gene and the acetylation of PD-L1 protein, which led to an increased interaction with TRAPPC4, molecule involved in PD-L1 recycling to the cell membrane. Interestingly, the BRD4 inhibitor JQ-1, counteracted PD-L1 transcription and reduced its surface expression, suggesting that such a combination could improve the outcome of VPA treatment, also because it increased the cytotoxic effect of VPA. Also considering that this HDACi did not upregulate PD-L2 and that the supernatant of VPA-treated cancer cells did not increase PD-L1 expression on the surface of macrophages exposed to it.

FADS1-arachidonic acid axis enhances arachidonic acid metabolism by altering intestinal microecology in colorectal cancer

Colonocyte metabolism shapes the microbiome. Metabolites are the main mediators of information exchange between intestine and microbial communities. Arachidonic acid (AA) is an essential polyunsaturated fatty acid and its role in colorectal cancer (CRC) remains unexplored. In this study, we show that AA feeding promotes tumor growth in AOM/DSS and intestinal specific Apc^-/- mice via modulating the intestinal microecology of increased gram-negative bacteria. Delta-5 desaturase (FADS1), a rate-limiting enzyme, is upregulated in CRC and effectively mediates AA synthesis. Functionally, FADS1 regulates CRC tumor growth via high AA microenvironment-induced enriched gram-negative microbes. Elimination of gram-negative microbe abolishes FADS1 effect. Mechanistically, gram-negative microbes activate TLR4/MYD88 pathway in CRC cells that contributes FADS1-AA axis to metabolize to prostaglandin E2 (PGE2). Cumulatively, we report a potential cancer-promoting mechanism of FADS1-AA axis in CRC that converts raising synthesized AA to PGE2 via modulating the intestinal microecology of gram-negative.

Synbindin restrains proinflammatory macrophage activation against microbiota and mucosal inflammation during colitis

OBJECTIVE

As a canonical membrane tethering factor, the function of synbindin has been expanding and indicated in immune response. Here, we investigated the role of synbindin in the regulation of toll-like receptor 4 (TLR4) signalling and macrophage response to microbiota during colitis.

DESIGN

Three distinct mouse models allowing global, myeloid-specific or intestinal epithelial cell-specific synbindin heterozygous deletion were constructed and applied to reveal the function of synbindin during dextran sodium sulfate (DSS) colitis. Effects of synbindin on TLR4 signalling and macrophage activation in response to bacterial lipopolysaccharide (LPS) or Fusobacterium nucleatum were evaluated. The colocalisation and interaction between synbindin and Rab7b were determined by immunofluorescence and coimmunoprecipitation. Synbindin expression in circulating monocytes and intestinal mucosal macrophages of patients with active IBD was detected.

RESULTS

Global synbindin haploinsufficiency greatly exacerbated DSS-induced intestinal inflammation. The increased susceptibility to DSS was abolished by gut microbiota depletion, while phenocopied by specific synbindin heterozygous deletion in myeloid cells rather than intestinal epithelial cells. Profoundly aberrant proinflammatory gene signatures and excessive TLR4 signalling were observed in macrophages with synbindin interference in response to bacterial LPS or Fusobacterium nucleatum. Synbindin was significantly increased in intestinal mucosal macrophages and circulating monocytes from both mice with DSS colitis and patients with active IBD. Interleukin 23 and granulocyte-macrophage colony-stimulating factor were identified to induce synbindin expression. Mechanistic characterisation indicated that synbindin colocalised and directly interacted with Rab7b, which coordinated the endosomal degradation pathway of TLR4 for signalling termination.

CONCLUSION

Synbindin was a key regulator of TLR4 signalling and restrained the proinflammatory macrophage activation against microbiota during colitis.

TRAPPC4 regulates the intracellular trafficking of PD-L1 and antitumor immunity

Tumor cells evade T cell-mediated immunosurveillance via the interaction between programmed death-1 (PD-1) ligand 1 (PD-L1) on tumor cells and PD-1 on T cells. Strategies disrupting PD-1/PD-L1 have shown clinical benefits in various cancers. However, the limited response rate prompts us to investigate the molecular regulation of PD-L1. Here, we identify trafficking protein particle complex subunit 4 (TRAPPC4), a major player in vesicular trafficking, as a crucial PD-L1 regulator. TRAPPC4 interacts with PD-L1 in recycling endosomes, acting as a scaffold between PD-L1 and RAB11, and promoting RAB11-mediated recycling of PD-L1, thus replenishing its distribution on the tumor cell surface. TRAPPC4 depletion leads to a significant reduction of PD-L1 expression in vivo and in vitro. This reduction in PD-L1 facilitates T cell-mediated cytotoxicity. Overexpression of Trappc4 sensitizes tumor cells to checkpoint therapy in murine tumor models, suggesting TRAPPC4 as a therapeutic target to enhance anti-tumor immunity.

Chemoprevention of DMH-Induced Early Colon Carcinogenesis in Male BALB/c Mice by Administration of Lactobacillus Paracasei DTA81

We evaluated the effects of the probiotic candidate Lactobacillus paracasei DTA81 (DTA81) on liver oxidative stress, colonic cytokine profile, and gut microbiota in mice with induced early colon carcinogenesis (CRC) by 1,2-dimethylhydrazine (DMH). Animals were divided into four different groups (n = 6) and received the following treatments via orogastric gavage for 8 weeks: Group skim milk (GSM): 300 mg/freeze-dried skim milk/day; Group L. paracasei DTA81 (DTA81): 3 × 10⁹ colony-forming units (CFU)/day; Group Lactobacillus rhamnosus GG (LGG): 3 × 10⁹ CFU/day; Group non-intervention (GNI): 0.1 mL/water/day. A single DMH dose (20 mg/kg body weight) was injected intraperitoneally (i.p), weekly, in all animals (seven applications in total). At the end of the experimental period, DTA81 intake reduced hepatic levels of carbonyl protein and malondialdehyde (MDA). Moreover, low levels of the pro-inflammatory cytokines Interleukin-6 (IL-6) and IL-17, as well as a reduced expression level of the proliferating cell nuclear antigen (PCNA) were observed in colonic homogenates. Lastly, animals who received DTA81 showed an intestinal enrichment of the genus Ruminiclostridium and increased concentrations of caecal acetic acid and total short-chain fatty acids. In conclusion, this study indicates that the administration of the probiotic candidate DTA81 can have beneficial effects on the initial stages of CRC development.

Clostridium butyricum, a butyrate-producing probiotic, inhibits intestinal tumor development through modulating Wnt signaling and gut microbiota

Gut microbiota dysbiosis is closely involved in intestinal carcinogenesis. A marked reduction in butyrate-producing bacteria has been observed in patients with colorectal cancer (CRC); nevertheless, the potential benefit of butyrate-producing bacteria against intestinal tumor development has not been fully investigated. We found that Clostridium butyricum (C. butyricum, one of the commonly used butyrate-producing bacteria in clinical settings) significantly inhibited high-fat diet (HFD)-induced intestinal tumor development in Apc^min/+ mice. Moreover, intestinal tumor cells treated with C. butyricum exhibited decreased proliferation and increased apoptosis. Additionally, C. butyricum suppressed the Wnt/β-catenin signaling pathway and modulated the gut microbiota composition, as demonstrated by decreases in some pathogenic bacteria and bile acid (BA)-biotransforming bacteria and increases in some beneficial bacteria, including short-chain fatty acid (SCFA)-producing bacteria. Accordingly, C. butyricum decreased the fecal secondary BA contents, increased the cecal SCFA quantities, and activated G-protein coupled receptors (GPRs), such as GPR43 and GPR109A. The anti-proliferative effect of C. butyricum was blunted by GPR43 gene silencing using small interfering RNA (siRNA). The analysis of clinical specimens revealed that the expression of GPR43 and GPR109A gradually decreased from human normal colonic tissue to adenoma to carcinoma. Together, our results show that C. butyricum can inhibit intestinal tumor development by modulating Wnt signaling and gut microbiota and thus suggest the potential efficacy of butyrate-producing bacteria against CRC.

Wnt Signaling: Pathogen Incursion and Immune Defense

Wnt ligands interact with the transmembrane cell surface receptors Frizzled and ROR/RYK to initiate complex signaling cascades that are crucial for cell physiology and the proper functioning of the immune system. Wnt signaling is instrumental in maintaining immune surveillance and during infections by pathogenic microbes helps mount host resistance to infection. Some pathogens, however, utilize Wnt signaling to build a niche for their survival. The goal of this review is to summarize current and developing concepts about the tug of war between Wnt signaling and pathogens for deployment of host resources, focusing mostly on macrophages and cytoskeletal actin dynamics. An additional objective is to outline the interrelation between Wnt signaling and the host microbiota, which is vital for immune defense, discussing in the same perspective, how Wnt signaling could be differentiating pathogen from non-pathogen.