The effect of glucose-dependent insulinotropic polypeptide (GIP) on cells under oxidative stress induced by glutamate, a neurotransmitter, and the underlying molecular mechanisms were assessed in the present study. We found that in the pre-treatment of HT-22 cells with glutamate in a dose-dependent manner, intracellular ROS were excessively generated, and additional cell damage occurred in the form of lipid peroxidation. The neurotoxicity caused by excessive glutamate was found to be ferroptosis and not apoptosis. Other factors (GPx-4, Nrf2, Nox1 and Hspb1) involved in ferroptosis were also identified. In other words, it was confirmed that GIP increased the activity of sub-signalling molecules in the process of suppressing ferroptosis as an antioxidant and maintained a stable cell cycle even under glutamate-induced neurotoxicity. At the same time, in HT-22 cells exposed to ferroptosis as a result of excessive glutamate accumulation, GIP sustained cell viability by activating the mitogen-activated protein kinase (MAPK) signalling pathway. These results suggest that the overexpression of the GIP gene increases cell viability by regulating mechanisms related to cytotoxicity and reactive oxygen species production in hippocampal neuronal cell lines.

Oral cancer (OC) has been attracted research attention in recent years as result of its high morbidity and mortality. Costunolide (CTD) possesses potential anticancer and bioactive abilities that have been confirmed in several types of cancers. However, its effects on oral cancer remain unclear. This study investigated the potential anticancer ability and underlying mechanisms of CTD in OC in vivo and in vitro. Cell viability and anchorage-independent colony formation assays were performed to examine the antigrowth effects of CTD on OC cells; assessments for migration and invasion of OC cells were conducted by transwell; Cell cycle and apoptosis were investigated by flow cytometry and verified by immunoblotting. The results revealed that CTD suppressed the proliferation, migration and invasion of oral cancer cells effectively and induced cell cycle arrest and apoptosis; regarding the mechanism, CTD bound to AKT directly by binding assay and repressed AKT activities through kinase assay, which thereby downregulating the downstream of AKT. Furthermore, CTD remarkably promotes the generation of reactive oxygen species by flow cytometry assay, leading to cell apoptosis. Notably, CTD strongly suppresses cell-derived xenograft OC tumor growth in an in vivo mouse model. In conclusion, our results suggested that costunolide might prevent progression of OC and promise to be a novel AKT inhibitor.

LETM1 domain–containing protein 1 (LETMD1), also known as HCCR-1, is a mitochondrial protein and is known to regulate p53 and STAT3 activities in cancer cells. In this study, we present, for the first time (to our knowledge), data indicating that LETMD1 suppresses multiple immune responses in monocyte/macrophage lineage cells and mouse primary macrophages. Attenuation of LETMD1 expression with specific small interfering RNA and short hairpin RNA constructs enhanced LPS-induced expressions of inflammatory mediators in macrophages. In addition, LETMD1 attenuation caused potentiation of phagocytosis as well as migration in a macrophage-like cell line, U937. These enhancing effects were associated with altered activation of signaling adaptors (such as NF-κB, MAPKs, p53, and JAK-STAT) involved in TLR4 signaling. Especially, LETMD1 selectively regulated TLR4-induced NF-κB activation via MyD88 but not via TIR-domain–containing adapter-inducing IFN-β (TRIF). Attenuation of LETMD1 expression caused mitochondrial hyperpolarization and subsequent decrease in ATP production and increase in mitochondrial/cellular reactive oxygen species (ROS) and intracellular calcium levels. LETMD1 attenuation also enhanced LPS-induced expression of NADPH oxidase (NOX) 2, the main producer of cellular ROS in phagocytes, through augmenting IFN regulatory factor 1. Accordingly, treatment with ROS scavenger, NOX2 suppressing agents, or calcium chelators resulted in suppression of LPS-induced cytokine production as well as NF-κB activation in cells with LETMD1 attenuation. These findings reveal a previously unknown function of LETMD1 and provide evidences showing LETMD1 negatively regulates macrophage functions by modulating mitochondrial function, subsequent ROS generation, and NF-κB activation.

Jiwon Ko, Soyoung Jang, Soyeon Jang, Song Park, Junkoo Yi, Dong Kyu Choi, Seonggon Kim, Myoung Ok Kim, Su-Geun Lim & Zae Young Ryoo. BMB Reports 2024;57:417-23. https://doi.org/10.5483/BMBRep.2024-0067

Long intergenic noncoding (LINC)01270 is a 2278 bp transcript belonging to the intergenic subset of long noncoding (lnc)RNAs. Despite increased reports of LINC01270’s involvement in different diseases, evident research on its effects on inflammation is yet to be achieved. In the present study, we investigated the potential role of LINC01270 in modulating the inflammatory response in the human monocytic leukemia cell line THP-1. Lipopolysaccharide treatment upregulated LINC01270 expression, and siRNA-mediated suppression of LINC01270 enhanced NF-κB activity and the subsequent production of cytokines IL-6, IL-8, and MCP-1. Interestingly, the knockdown of LINC01270 downregulated expression of leucine zipper downregulated in cancer 1 (LDOC1), a novel NF-κB suppressor. An analysis of the LINC01270/micro-RNA (miRNA)/protein interactome profile identified miR-326 as a possible mediator. Synthetic RNA agents that perturb the interaction among LINC01270, miR-326, and LDOC1 mRNA mitigated the changes caused by LINC01270 knockdown in THP-1 cells. Additionally, a luciferase reporter assay in HEK293 cells further confirmed that LINC01270 knockdown enhances NF-κB activation, while its overexpression has the opposite effect. This study provides insight into LINC01270’s role in modulating inflammatory responses to lipopolysaccharide stimulation in THP-1 cells via the miR-326/LDOC1 axis, which negatively regulates NF-κB activation.