TLR4 signaling plays key roles in the innate immune response to microbial infection. Innate immune cells encounter different mechanical cues in both health and disease to adapt their behaviors. However, the impact of mechanical sensing signals on TLR4 signal-mediated innate immune response remains unclear. Here we show that TLR4 signalling augments macrophage bactericidal activity through the mechanical sensor Piezo1. Bacterial infection or LPS stimulation triggers assembly of the complex of Piezo1 and TLR4 to remodel F-actin organization and augment phagocytosis, mitochondrion-phagosomal ROS production and bacterial clearance and genetic deficiency of Piezo1 results in abrogation of these responses. Mechanistically, LPS stimulates TLR4 to induce Piezo1-mediated calcium influx and consequently activates CaMKII-Mst1/2-Rac axis for pathogen ingestion and killing. Inhibition of CaMKII or knockout of either Mst1/2 or Rac1 results in reduced macrophage bactericidal activity, phenocopying the Piezo1 deficiency. Thus, we conclude that TLR4 drives the innate immune response via Piezo1 providing critical insight for understanding macrophage mechanophysiology and the host response.

Reactive oxygen species (ROS) production in phagocytes is a major defense mechanism against pathogens. However, the cellular self-protective mechanism against such potential damage from oxidative stress remains unclear. Here we show that the kinases Mst1 and Mst2 (Mst1/2) sense ROS and maintain cellular redox balance by modulating the stability of antioxidant transcription factor Nrf2. Site-specific ROS release recruits Mst1/2 from the cytosol to the phagosomal or mitochondrial membrane, with ROS subsequently activating Mst1/2 to phosphorylate kelch like ECH associated protein 1 (Keap1) and prevent Keap1 polymerization, thereby blocking Nrf2 ubiquitination and degradation to protect cells against oxidative damage. Treatment with the antioxidant N-acetylcysteine disrupts ROS-induced interaction of Mst1/2 with phagosomes or mitochondria, and thereby diminishes the Mst-Nrf2 signal. Consistently, loss of Mst1/2 results in increased oxidative injury, phagocyte ageing and death. Thus, our results identify the Mst-Nrf2 axis as an important ROS-sensing and antioxidant mechanism during an antimicrobial response.

The spleen, the largest lymphatic organ, comprises a diverse array of immunocytes in approximately one quarter of the body, including T cells, B cells, natural killer cells, and myeloid cells (such as dendritic cells, neutrophils, myeloid-derived suppressor cells, and macrophages). These immune cells undergo dynamic transitions and mobilization, enabling the spleen to execute a wide range of immunological functions. The spleen's structural organization and multicellular composition, along with its reservoir of lymphocytes, facilitate the capture and clearance of blood-borne antigens while also orchestrating both innate and adaptive immune responses. Additionally, the spleen plays critical roles in hematopoiesis and the removal of aged or damaged red blood cells. Despite being innervated by sympathetic (catecholaminergic) nerve fibers, the spleen lacks parasympathetic (vagal or cholinergic) innervation. The neuroimmune axis, particularly the interplay between sympathetic and parasympathetic nervous system immune circuits, significantly influences disease onset and progression. Extensive research employing physical, genetic, and pharmacological approaches has sought to directly modulate splenic immunocytes and activate neuroimmune interactions to restore immune homeostasis and counteract disease. Two primary mechanisms underlie these immunomodulatory interventions: (1) the cholinergic anti-inflammatory pathway, wherein norepinephrine released by splenic catecholaminergic fibers binds to β2-adrenergic receptors on CD4⁺ T cells, triggering acetylcholine secretion, which in turn suppresses inflammatory cytokine production in macrophages via α7 nicotinic acetylcholine receptor signaling, and (2) direct immunomodulation of splenic immunocytes, which regulates key genes and signaling pathways, alters cytokine secretion, and modulates ion flux to influence cellular functions. Among various therapeutic strategies, physical methods, particularly electrical stimulation and splenic ultrasound stimulation, have demonstrated the greatest promise for clinical applications in splenic immunomodulation and disease management.

Macrophage plasticity, critical for immune response, is often dysregulated in various infectious and inflammatory diseases. While ion channels have been implicated in immune cell modulation, how they influence macrophage polarization remains poorly understood. Here, it is demonstrated that ectosomes carrying the ion channel Calhm6 effectively suppress severe inflammation triggered by LPS. These Calhm6‐bearing ectosomes, secreted by macrophages, facilitate M2‐like polarization, elicit an anti‐inflammatory response, and foster immune tolerance. Conversely, Calhm6 deficiency leads to suppressed Creb1 activity, which in turn augments M1‐like macrophage polarization, enhancing bactericidal activity and the secretion of pro‐inflammatory cytokines. Mechanistically, Chp1 serves as a scaffold protein and undergoes phosphorylation by CaMK4. This phosphorylation enhances the localization of the Calhm6‐Chp1‐CaMK4 complex to the cell membrane, promoting Creb1 activation and M2‐like macrophage polarization calcium‐dependently. Moreover, the M1‐like polarization inducers LPS and IFNγ enhance the binding of Irf1 to the Calhm6 promoter, upregulating its expression and stimulating ectosome formation. Conversely, Stat6, activated by IL‐4, competes with Irf1 for binding to the Calhm6 promoter, thereby suppressing its expression. In summary, our findings unravel the intricate interplay between ion channels, ectosomes, and macrophage polarization, revealing that ectosomal‐Calhm6 can serve as a novel therapeutic agent to modulate inflammatory responses and facilitate tissue repair.

Purpose: HOX cluster-embedded long noncoding RNAs (HOX-lncRNAs) have been shown to be tightly related to hepatocellular carcinoma (HCC). However, the potential biological roles and underlying molecular mechanism of HOX-lncRNAs in HCC largely remains to be elucidated. Methods: The expression signature of eighteen HOX-lncRNAs in HCC cell lines were measured by qRT-PCR. HOXD-AS2 expression and its clinical significance in HCC was investigated by bioinformatics analysis utilizing the TCGA data. Subcellular localization of HOXD‐AS2 in HCC cells was observed by RNA-FISH. Loss‑of‑function experiments in vitro and in vivo were conducted to probe the roles of HOXD-AS2 in HCC. Potential HOXD-AS2-controlled genes and signaling pathways were revealed by RNA-seq. Rescue experiments were performed to validate that SMYD3 mediates HOXD-AS2 promoting HCC progression. The positive feedback loop of HOXD-AS2 and SMYD3 was identified by luciferase reporter assay and ChIP-qPCR. Results: HOXD-AS2 was dramatically elevated in HCC, and its up-regulation exhibited a positive association with aggressive clinical features (T stage, pathologic stage, histologic grade, AFP level, and vascular invasion) and unfavorable prognosis of HCC patients. HOXD-AS2 was distributed both in the nucleus and the cytoplasm of HCC cells. Knockdown of HOXD-AS2 restrained the proliferation, migration, invasion of HCC cells in vitro, as well as tumor growth in subcutaneous mouse model. Transcriptome analysis demonstrated that SMYD3 expression and activity of MEK/ERK pathway were impaired by silencing HOXD-AS2 in HCC cells. Rescue experiments revealed that SMYD3 as downstream target mediated oncogenic functions of HOXD-AS2 in HCC cells through altering the expression of cyclin B1, cyclin E1, MMP2 as well as the activity of MEK/ERK pathway. Additionally, HOXD-AS2 was uncovered to be positively regulated at transcriptional level by its downstream gene of SMYD3. Conclusion: HOXD-AS2, a novel oncogenic HOX-lncRNA, facilitates HCC progression by forming a positive feedback loop with SMYD3 and activating the MEK/ERK pathway.

Background: Splenic immunomodulation triggered by ultrasound shows a significant anti-inflammatory effect against various inflammatory diseases, whose mechanism is mainly attributable to the activation of cholinergic anti-inflammatory pathway (CAP). However, the potential role and underlying mechanism of splenic ultrasound stimulation in cancer management have been rarely reported and superficially defined. Methods: Following optimization of ultrasonic parameters, this study evaluated the anti-tumor efficacy of splenic sonication across multiple tumor models (eg, orthotopic H22 hepatocellular carcinoma (HCC), orthotopic Hepa1-6 HCC, and subcutaneous 4T1 breast cancer), and applied flow cytometry to quantify dynamic alterations in immune cell populations. Furthermore, in orthotopic H22 HCC models, this study employed fluorescence-activated cell sorting, RNA sequencing, splenic nerve blockade via absolute ethanol ablation, and in vitro Ca²⁺ flux assays to delineate the mechanisms underlying ultrasound-mediated splenic anti-tumor immunity. Results: This study first assessed the therapeutic effect of focused ultrasound precisely targeting the spleen (FUS sti. spleen) on various tumors at specific ultrasonic doses. It fully demonstrated that FUS directly stimulated splenic immune cell proliferation and activation (especially NK and CD8 T cells) rather than CAP excitation to modulate splenic immune function. Particularly, NK cells are much more indispensable and important in responding to FUS stimulation for cancer suppression than CD8 T cells. RNA sequencing of NK and CD8 T cells, as well as in vitro experiments revealed that FUS firstly regulated calcium-related signaling pathways to further modulate others, such as PI3K-AKT, Rap1, and Hippo pathways to promote immune cell proliferation, migration and activation to suppress cancer cell deterioration. Particularly, FUS sti. spleen and FUS intervention on the tumor synergistically induced the best tumor suppression than each of the two taken individually. Conclusion: FUS sti. spleen facilitated immunocyte proliferation and activation through altering calcium-dependent signaling rather than CAP excitation to modulate anti-tumor immunity, indicating substantial clinical translation potential.