Oroxylin A-induced Trained Immunity Promotes LC3-associated Phagocytosis in Macrophage in Protecting Mice Against Sepsis.

Sepsis is defined as a dysregulated host response to infection that leads to multiorgan failure. Innate immune memory, i.e., "trained immunity", can result in stronger immune responses and provide protection against various infections. Many biological agents, including ß-glucan, can induce trained immunity, but these stimuli may cause uncontrolled inflammation. Oroxylin A (OA) is an active flavonoid compound that is derived from Scutellaria baicalensis. OA is an agonist for inducing trained immunity in vivo and in vitro, and ß-glucan was used as a positive control. The protective effects of OA-induced trained immunity were evaluated in mouse models that were established by either lipopolysaccharide (LPS) administration or caecal ligation and puncture (CLP). The expression of inflammatory factors and signaling pathway components involved in trained immunity was evaluated in vitro using qRT‒PCR, western blotting (WB) and enzyme-linked immunosorbent assay (ELISA). Flow cytometry and confocal microscopy were used to examine reactive oxygen species (ROS) levels and phagocytosis in trained macrophages. A PCR array was used to screen genes that were differentially expressed in trained macrophages. Here, we revealed that OA alleviated sepsis via trained immunity. OA-treated macrophages displayed increased glycolysis and mTOR phosphorylation, and mTOR inhibitors suppressed OA-induced trained immunity by effectively reprogramming macrophages. The PCR array revealed key genes in the mTOR signaling pathway in OA-treated macrophages. Furthermore, OA targeted the Dectin-1-syk axis to promote LC3-associated phagocytosis (LAP) by trained macrophages, thereby enhancing the ability of these macrophages to protect against infection. This ability could be transferred to a new host via the adoptive transfer of peritoneal macrophages. This study is the first to provide new insights into the potential of OA-induced trained immunity to be used as a strategy to protect mice against sepsis by promoting LAP by macrophages.

Low expression of m6A reader YTHDC1 promotes progression of ovarian cancer via PIK3R1/STAT3/GANAB axis.

Background: N6-Methyladenosine (m6A) is considered to be the most prevalent and abundant internal modification observed in mRNA between viruses and mammals. As a reversible epigenetic modification, m6A controls gene expression in diverse physiological and pathological processes. Accumulating evidence in recent years reveals that aberrant expression of m6A reader proteins may have tumor-suppressing or carcinogenic functions. However, the biological role and mechanism of m6A reader YTH Domain Containing 1 (YTHDC1) in ovarian cancer progression remain inadequately understood. Methods: Quantitative RT-PCR, immunohistochemistry, Western blot, and bioinformatics analyses were undertaken for studying the YTHDC1 expression in ovarian cancer. In vitro and in vivo models were used to examine the role of YTHDC1. RNA sequencing, RNA immunoprecipitation sequencing, m6A-modified RNA immunoprecipitation, actinomycin-D assay, chromatin immunoprecipitation, and Western blot were used in the investigation the regulatory mechanisms among YTHDC1, Signal Transducer and Activator of Transcription 3 (STAT3), Phosphoinositide-3-Kinase Regulatory Subunit 1 (PIK3R1), and Glucosidase II Alpha Subunit (GANAB). Results: Here, we found that YTHDC1 expression is decreased in ovarian cancer. Overexpression of YTHDC1 inhibited ovarian cancer development both in vivo and in vitro. Mechanistically, PIK3R1 was identified to be the direct target for YTHDC1. YTHDC1 enhanced PIK3R1 stability in an m6A-dependent manner, which subsequently inhibited GANAB expression in the N-glycan biosynthesis via the STAT3 signaling. Conclusions: Our findings unveil YTHDC1 as a tumor suppressor in the progression of ovarian cancer and as a potential prognostic biomarker that could serve as a target in ovarian cancer treatment.

C. tropicalis promotes CRC by down-regulating tumor cell-intrinsic PD-1 receptor via autophagy.

Background: The programmed cell death 1 (PD-1) receptor is an immune checkpoint molecule that induces immune tolerance and mediates the immune escape of tumor cells. It is mainly expressed in immune cells such as T cells, B cells and monocytes. In recent years, studies have shown that tumor cell-intrinsic PD-1 plays different roles in the development of melanoma, Liver cancer and lung cancer. However, the expression and function of PD-1 in colon cancer cells has not been reported. Our previous studies have found that Candida tropicalis (C. tropicalis) can promote CRC tumor growth and chemotherapy resistance to oxaliplatin by regulating mismatch repair system. Whether C. tropicalis participates in the progression of CRC and immunotherapy resistance through regulating the tumor cell-intrinsic PD-1 remains to be further elucidated. Methods & Results: In this study, we first found that high concentrations of C. tropicalis promote tumor growth in cell cultures and xenografts. In addition, we proved that colon cancer cell lines express PD-1 receptors. Knockdown of PD-1 enhanced SW480 viability in-vitro, while overexpression of PD-1 diminished cell viability. Moreover, blocking antibody against PD-1 promotes tumor growth both in SW480 cells and mice CRC xenografts in an adaptive immune-independent manner. We also demonstrated that high concentrations of C. tropicalis can down-regulate tumor cell-intrinsic PD-1 expression in colon cancer cells. CRC cell growth induced by C. tropicalis is partially offset in the presence of PD-1 overexpression. This shows that C. tropicalis promotes CRC progression via controlling the expression of tumor cell-intrinsic PD-1. Mechanistically, we found that C. tropicalis modulates the expression of PD-1 via increasing the autophagy traffic in colon cancer cells. Combining autophagy inhibitor with C. tropicalis treatment partly blocked the CRC tumor growth and reversed the downregulation of PD-1. Conclusion: This study shows that PD-1 is a tumor suppressor in CRC. C. tropicalis can down-regulate tumor cell-intrinsic PD-1 expression via enhancing tumor cells autophagy levels to promote CRC progression. It may provide a new idea and mechanism for answering why the immune monoclonal antibody treatment is ineffective in cancer patients.

Candida tropicalis induces NLRP3 inflammasome activation via glycogen metabolism-dependent glycolysis and JAK-STAT1 signaling pathway in myeloid-derived suppressor cells to promote colorectal carcinogenesis.

Our previous studies showed that Candida tropicalis promoted colorectal cancer (CRC) by activating the function of MDSCs. However, underlying molecular mechanisms remains to be further investigated. In the present study, we indicated that C. tropicalis induced NLRP3 inflammasome activation through Dectin-3 in myeloid-derived suppressor cells (MDSCs). Mechanistically, we identified that C. tropicalis significantly enhanced the levels of glycolysis dependent on glycogen metabolism in MDSCs, which was required for NLRP3 inflammasome activation. C. tropicalis-induced NLRP3 inflammasome activation of MDSCs required the first priming signal and the second activation signal. For one thing, C. tropicalis promoted transcription of Nlrp3, Pro-caspase-1 and IL-1ß genes through activation of JAK-STAT1 signaling pathway. For another, mtROS as the second activation signal mediated C. tropicalis-induced activation of NLRP3 inflammasome. Pharmacological inhibition of NLRP3 inflammasome activation abolished the pro-tumorigenic effect of C. tropicalis in an AOM/DSS-induced CAC mice model and significantly reduced C. tropicalis-promoted infiltration of MDSCs in colon tumors. Finally, in human CRC samples, the expression of STAT1, p-STAT1 and NLRP3 was elevated in MDSCs infiltrated by CRC. Collectively, these findings shed light on a previously unidentified mechanism by which C. tropicalis induces NLRP3 inflammasome activation in MDSCs to contribute to the progression of CRC. And STAT1-NLRP3 axis might represent a prospective therapeutic target for the treatment of CRC.