Pyk2 inhibitor prevents epithelial hyperpermeability induced by HMGB1 and inflammatory cytokines in Caco-2 cells

Mettl3/Ythdf2 regulate macrophage inflammation and ROS generation by controlling Pyk2 mRNA stability

As one of the most prevalent modifications on RNA, N6-methyladenosine (m6A) has been recently found implicated in various pathological processes. Emerging studies have demonstrated the role of m6A and its writer Mettl3 in fine-tuning the immune response, which now becomes a research hotspot owing to its potential therapeutic value. However, the results are inconsistent and even contradictory, suggesting that there might be multiple Mettl3 target genes involved in different pathways. To delve deeper into the function of Mettl3 in the cellular inflammatory response, we first conducted bioinformatics analysis using RNA-seq in Mettl3 ablation macrophages, and found that Mettl3 might attenuate LPS-induced proinflammatory pathways and reactive oxygen species (ROS) generation process. Mettl3 knockdown significantly increased the LPS-induced IL-6, TNF-α, NOXs (Nox1, Nox2, Ncf1, and Ncf2) expression, ROS generation, and the phosphorylation of MAPKs and AKT signaling. Combining the results of RNA-seq and m6A mapping, we found that Pyk2 might be the target gene of Mettl3 affecting the inflammatory response. Mettl3 and Ythdf2 depletion increased the expression and mRNA stability of Pyk2, and RIP-PCR showed that Ythdf2 directly targeting Pyk2 was Mettl3 dependent. Moreover, the upregulated expression of TNF-α, IL-6, NOXs, ROS generation, and the phosphorylation of MAPKs and AKT signaling were downregulated by Pyk2 inhibitor in Mettl3 knockdown cells. All of these results suggest that Mettl3 regulates the mRNA stability and expression of Pyk2 in a Ythdf2-dependent way, which consequently triggers the activation of MAPKs and AKT signaling and upregulation of NOXs, thus promoting the generation of proinflammatory cytokines and ROS.

Recent progress on FAK inhibitors with dual targeting capabilities for cancer treatment

Focal adhesion kinase (FAK, also known as PTK2) is a tyrosine kinase that regulates integrin and growth factor signaling pathways and is involved in the migration, proliferation and survival of cancer cells. FAK is a promising target for cancer treatment. Many small molecule FAK inhibitors have been identified and proven in both preclinical and clinical studies to be effective inhibitors of tumor growth and metastasis. There are many signaling pathways, such as those involving FAK, Src, AKT, MAPK, PI3K, and EGFR/HER-2, that provide survival signals in cancer cells. Dual inhibitors that simultaneously block FAK and another factor can significantly improve efficacy and overcome some of the shortcomings of single-target inhibitors, including drug resistance. In this review, the antitumor mechanisms and research status of dual inhibitors of FAK and other targets, such as Pyk2, IGF-IR, ALK, VEGFR-3, JAK2, EGFR, S6K1, and HDAC2, are summarized, providing new ideas for the development of effective FAK dual-target preparations.

IL-1β is a key inflammatory cytokine that weakens lactation-specific tight junctions of mammary epithelial cells

In lactating mammary glands, alveolar mammary epithelial cells (MECs) produce milk and form less-permeable tight junctions (TJs). However, alveolar TJs are weakened with a reduction in milk production in mammary glands due to mastitis or weaning in the presence of high levels of IL-1β, IL-6, or TNF-α. In this study, using in vitro cultured model of MECs with milk-producing ability and lactation-specific TJs, we investigated whether the aforementioned cytokines affect MEC TJs. The results showed that TNF-α, IL-1β, and IL-6 affected lactation-specific TJs in different ways. In particular, upon activation of p38 and JNK signalling, IL-1β caused rapid disruption of TJs at tricellular contact points. IL-1β treatment led to decreased CLDN3, CLDN4, and OCLN levels and a weakened TJ barrier. The adverse effects of IL-1β on TJs were mimicked by anisomycin, which is an activator of p38 and JNK signalling, and were blocked by MEC pretreatment with a p38 inhibitor but not a JNK inhibitor. The mislocalization of tricellulin at tricellular contact areas was confirmed in MECs treated with IL-1β or anisomycin. These results indicate that IL-1β is a key cytokine that adversely affects the TJs between MECs by activating p38.

Dysfunction of epithelial permeability barrier induced by HMGB1 in 2.5D cultures of human epithelial cells

Airway and intestinal epithelial permeability barriers are crucial in epithelial homeostasis. High mobility group box 1 (HMGB1), increased by various stimuli, is involved in the induction of airway inflammation, as well as the pathogenesis of inflammatory bowel disease. HMGB1 enhances epithelial hyperpermeability. Two-and-a-half dimensional (2.5D) culture assays are experimentally convenient and induce cells to form a more physiological tissue architecture than 2D culture assays for molecular transfer mechanism analysis. In 2.5D culture, treatment with HMGB1 induced permeability of FITC-dextran into the lumen formed by human lung, nasal and intestinal epithelial cells. The tricellular tight junction molecule angulin-1/LSR is responsible for the epithelial permeability barrier at tricellular contacts and contributes to various human airway and intestinal inflammatory diseases. In this review, we indicate the mechanisms including angulin-1/LSR and multiple signaling in dysfunction of the epithelial permeability barrier induced by HMGB1 in 2.5D culture of human airway and intestinal epithelial cells.