Multiple sclerosis (MS) is a chronic autoimmune disease in the central nervous system. Forskolin (FSK) is a plant-derived diterpene with excellent immunomodulatory properties and has not been systematically reported for treating MS. This study investigated the therapeutic effects of FSK on cellular and animal MS models and preliminarily explored related mechanisms. The results showed that FSK suppressed the inflammatory response, reduced the expression of STEAP4, and relieved iron deposition in BV-2 cells pretreated by LPS at the cellular level. Meanwhile, at the animal level, FSK treatment halted the progression of experimental autoimmune encephalomyelitis (EAE), alleviated the damage at the lesion sites, reduced the concentration of proinflammatory factors in peripheral blood, and inhibited the immune response of peripheral immune organs in EAE mice. Besides, FSK treatment decreased the expression of STEAP4 in the spinal cord and effectively restored the iron balance in the brain, spinal cord, and serum of EAE mice. Further investigation showed that FSK can reduce IL-17 expression, prevent the differentiation of TH17 cells, and inhibit the calcium signaling pathway. Thus, these results demonstrate that FSK may have the potential to treat MS clinically.

Asthma comprises one of the most common chronic inflammatory conditions, yet still lacks effective diagnostic markers and treatment targets. To gain deeper insights, we comprehensively analyzed microarray datasets of airway epithelial samples from asthmatic patients and healthy subjects in the Gene Expression Omnibus database using three machine learning algorithms. Our investigation identified a pivotal gene, STEAP4. The expression of STEAP4 in patients with allergic asthma was found to be reduced. Furthermore, it was found to negatively correlate with the severity of the disease and was subsequently validated in asthmatic mice in this study. A ROC analysis of STEAP4 showed the AUC value was greater than 0.75. Functional enrichment analysis of STEAP4 indicated a strong correlation with IL-17, steroid hormone biosynthesis, and ferroptosis signaling pathways. Subsequently, intercellular communication analysis was performed using single-cell RNA sequencing data obtained from airway epithelial cells. The results revealed that samples exhibiting low levels of STEAP4 expression had a richer MIF signaling pathway in comparison to samples with high STEAP4 expression. Through both in vitro and in vivo experiments, we further confirmed the overexpression of STEAP4 in airway epithelial cells resulted in decreased expression of MIF, which in turn caused a decrease in the levels of the cytokines IL-33, IL-25, and IL-4; In contrast, when the STEAP4 was suppressed in airway epithelial cells, there was an upregulation of MIF expression, resulting in elevated levels of the cytokines IL-33, IL-25, and IL-4. These findings suggest that STEAP4 in the airway epithelium reduces allergic asthma Th2-type inflammatory reactions by inhibiting the MIF signaling pathway.

Iron homeostasis is crucial for optimal cardiac function. Iron deficiency and overload have been linked to the development of cardiomyopathy and heart failure (HF) via intricate mechanisms. Although the crucial role of SLC40A1 in iron metabolism by facilitating the efflux of cellular iron has been confirmed, its specific molecular functions in cardiovascular diseases remain poorly understood. In this study, we generated mice with inducible cardiomyocyte-specific overexpression of SLC40A1 for the first time. The overexpression of SLC40A1 in the cardiomyocytes of adult mice resulted in significant iron deficiency, leading to mitochondrial dysfunction, oxidative stress, and apoptosis, subsequently resulting in the development of fatal HF. Notably, SLC40A1 upregulation was observed in the ischemic region during the initial phase of myocardial infarction (MI), contributing to iron loss in the cardiomyocytes. Conversely, the cardiomyocyte-specific knockdown of SLC40A1 improved cardiac dysfunction after MI by enhancing mitochondrial function, suppressing oxidative stress, and reducing cardiomyocytes apoptosis. Mechanistically, Steap4 interacted with SLC40A1, facilitating SLC40A1-mediated iron efflux from cardiomyocytes. In short, our study presents evidence for the involvement of SLC40A1 in the regulation of myocardial iron levels and the therapeutic benefits of cardiomyocyte-specific knockdown of SLC40A1 in MI in mice.

Ferroptosis, characterized by iron-dependent cell death, has recently emerged as a critical defense mechanism against microbial infections. The present study aims to investigate the involvement of exosomes in the induction of ferroptosis and the inhibition of bacterial infection in crustaceans. Our findings provide compelling evidence for the pivotal role of exosomes in the immune response of crustaceans, wherein they facilitate intracellular iron accumulation and activate the ferroptotic pathways. Using RNA-seq and bioinformatic analysis, we demonstrate that cytochrome P450 (CYP) can effectively trigger ferroptosis. Moreover, by conducting an analysis of exosome cargo proteins, we have identified the participation of six-transmembrane epithelial antigen of prostate 4 in the regulation of hemocyte ferroptotic sensitivity. Subsequent functional investigations unveil that six-transmembrane epithelial antigen of prostate 4 enhances cellular Fe2+ levels, thereby triggering Fenton reactions and accelerating CYP-mediated lipid peroxidation, ultimately culminating in ferroptotic cell death. Additionally, the Fe2+-dependent CYP catalyzes the conversion of arachidonic acid into 20-hydroxyeicosatetraenoic acid, which activates the peroxisome proliferator-activated receptor. Consequently, the downstream target of peroxisome proliferator-activated receptor, cluster of differentiation 36, promotes intracellular fatty acid accumulation, lipid peroxidation, and ferroptosis. These significant findings shed light on the immune defense mechanisms employed by crustaceans and provide potential strategies for combating bacterial infections in this species.

Endothelial dysfunction is a common complication of diabetes mellitus (DM) and contributes to the high incidence and mortality of cardiovascular and cerebrovascular diseases. Aberrant epigenetic regulation under diabetic conditions, including histone modifications, DNA methylation, and non-coding RNAs (ncRNAs) play key roles in the initiation and progression of diabetic vascular complications. ASH2L, a H3K4me3 regulator, triggers genetic transcription, which is critical for physiological and pathogenic processes. In this study we investigated the role of ASH2L in mediating diabetic endothelial dysfunction. We showed that ASH2L expression was significantly elevated in vascular tissues from diabetic db/db mice and in rat aortic endothelial cells (RAECs) treated with high glucose medium (11 and 22 mM). Knockdown of ASH2L in RAECs markedly inhibited the deteriorating effects of high glucose, characterized by reduced oxidative stress and inflammatory responses. Deletion of endothelial ASH2L in db/db mice by injection of an adeno-associated virus (AAV)-endothelial specific system carrying shRNA against Ash2l (AAV-shAsh2l) restored the impaired endothelium-dependent relaxations, and ameliorated DM-induced vascular dysfunction. We revealed that ASH2L expression activated reductase STEAP4 transcription in vitro and in vivo, which consequently elevated Cu(I) transportation into ECs by the copper transporter CTR1. Excess copper produced by STEAP4-mediated copper uptake triggered oxidative stress and inflammatory responses, resulting in endothelial dysfunction. Our results demonstrate that hyperglycemia triggered ASH2L-STEAP4 axis contributes to diabetic endothelial dysfunction by modulating copper uptake into ECs and highlight the therapeutic potential of blocking the endothelial ASH2L in the pathogenesis of diabetic vascular complications.

BACKGROUND: The study was aimed to find promising targets for cancer therapy involved in the tumorigenesis of hepatocellular carcinoma (HCC).
METHODS: Identification of STEAP4 in HCC between GSE54503 and TCGA datasets by performing RNA-seq. The STEAP4 mRNA expression level was determined by qRT-PCR. DNA methylation was measured by MSP and BSP. Besides, the effect of STEAP4 tumorigenesis was determined by in vivo experiments. The function of STEAP4 on methylation was further assessed by 5-Aza‑dC, a demethylating agent.
RESULTS: Reduced STEAP4 expression was found in HCC tissues. Promoter region methylation correlated with the downregulated expression of STEAP4. STEAP4 inhibited the proliferation and metastasis of HCC cells. Re-expression of STEAP4 was induced 5-Aza‑dC. STEAP4 mediated the biological effects of HCC cells through PI3K/AKT/mTOR pathway inhibition.
CONCLUSIONS: Our findings indicate that STEAP4 functions as a suppressor gene in HCC, and hypermethylation is a driving factor in cancer progression.

OBJECTIVE: Nonalcoholic fatty liver disease (NAFLD) has become a global epidemic, but its pathogenesis is unclear. STEAP4, a member of six transmembrane protein family, integrates inflammatory and metabolic responses. Our present aim is to explore the roles of STEAP4 in maintaining cellular homeostasis and improving high-fat-diet (HFD)-caused oxidative stress in hepatocytes.
METHODS: NAFLD model was established by HFD-feeding mice. The effects of over-nutrition on liver were detected by serum biochemical analysis and bulk RNA-seq. The levels of gene expression were measured by QPCR and Western Blot. Immunofluorescent staining was applied to determine the localization of STEAP4. AMPK agonist was employed to investigate the link between STEAP4 and AMPK pathway.
RESULTS: Sus scrofa STEAP4 (sSTEAP4) relieved oxidative stress and rescued the viability of hepatocytes. sSTEAP4 increased AKT phosphorylation and SOD2 level in hepatocytes, whether or not treated with H2O2, suggesting sSTEAP4 has regulatory effects on insulin signaling and antioxidant pathways. However, sSTEAP4 inhibited AMPK phosphorylation and Beclin1/LC3 expression under H2O2-deficiency situation, but the results were conversed with H2O2 stimulation. The cellular ER stress was aggravated with the increased energy during oxidative stress, indicating that sSTEAP4 might regulate the energetic communication between ER and mitochondria by intervening mitochondrial energy production. In addition, sSTEAP4 was demonstrated to localize in the membranes of plasma and ER in HepG2 hepatocytes.
CONCLUSIONS: Our results reveal that sSTEAP4 based on the needs of cell itself to improve hepatic oxidative stress and HFD-caused NAFLD, which might provide a new therapeutic scheme for NAFLD.

UNASSIGNED: Sepsis is a systemic disease characterized by extensive inflammatory responses and impaired organ function, which are characteristics that make it easily missed and complex to treat. A large number of laboratory and clinical studies on the diagnosis and treatment of sepsis have been continuously carried out, confirming the importance of mitochondrial function during the development of sepsis. STEAP4 is an important metalloreductase in mitochondria, which is involved in the biogenesis and respiratory chain of mitochondria. The role of STEAP4 in inflammation remains controversial. Research in this field may contribute to the development of new diagnostic and treatment options for sepsis.
UNASSIGNED: The expression of STEAP4 was measured in the peripheral blood of patients with severe sepsis and compared with healthy controls. Cell and mouse inflammatory models were established to detect the expression of STEAP4 and other inflammatory cytokines.
UNASSIGNED: (I) The expression of STEAP4 in the peripheral blood of patients with severe sepsis is higher than that of healthy volunteers (P<0.01), which is related to the SOFA score and transaminase. (II) STEAP4 has a certain predictive effect on the outcome of patients [area under curve (AUC) =0.696, P<0.05, 95% CI: 0.528 to 0.833]. (III) Inflammation led to increased expression of STEAP4 gene in RAW264.7 cells and mouse liver tissue.
UNASSIGNED: The expression of STEAP4 is elevated in the early stage of sepsis and the degree of its elevation can be used to predict the clinical outcome of sepsis patients.

Six-transmembrane epithelial antigen of prostate 4 (STEAP4) is involved in the development of human cancers. However, the role of STEAP4 in prostate cancer remains largely unknown. The purpose of this research is to explore the role and action mechanism of STEAP4 in prostate cancer development under lipopolysaccharide (LPS)-induced inflammatory microenvironment. STEAP4 expression was analyzed by Gene Expression Profiling Interactive Analysis (GEPIA), UALCAN and Cancer Cell Line Encyclopedia (CCLE), and its prognostic value was analyzed by LinkedOmics. STEAP4-correlated genes were analyzed by LinkedOmics and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. STEAP4 level was detected by Western blotting or qRT-PCR. Proliferation was investigated by CCK-8 and EdU staining. Inflammatory cytokine levels were detected by ELISA. The cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway was detected by ELISA and Western blotting. STEAP4 level was increased in prostate cancer tissues, and high expression of STEAP4 was associated with the poor overall survival. LPS promoted cell viability and STEAP4 expression. STEAP4 knockdown attenuated LPS-induced inflammation in prostate cancer cells. STEAP4 downregulation mitigated LPS-induced tumorigenesis by decreasing cell proliferation. STEAP4 silencing reversed LPS-induced inactivation of the cGMP-PKG pathway. Inhibition of the cGMP-PKG pathway using inhibitor KT5823 relieved STEAP4 silencing-mediated suppression of cell proliferation and inflammation in LPS-stimulated cells. In conclusion, STEAP4 silencing inhibits LPS-induced proliferation of prostate cancer cells by activating the cGMP-PKG pathway.

The six-transmembrane protein of prostate 2 (Stamp2) acts as an anti-inflammatory protein in macrophages by protecting from overt inflammatory signaling and Stamp2 deficiency accelerates atherosclerosis in mice. Herein, we describe an unexpected role of Stamp2 in polymorphonuclear neutrophils (PMN) and characterize Stamp2\'s protective effects in myocardial ischemic injury. In a murine model of ischemia and reperfusion (I/R), echocardiography and histological analyses revealed a pronounced impairment of cardiac function in hearts of Stamp2-deficient- (Stamp2-/- ) mice as compared to wild-type (WT) animals. This difference was driven by aggravated cardiac fibrosis, as augmented fibroblast-to-myofibroblast transdifferentiation was observed which was mediated by activation of the redox-sensitive p38 mitogen-activated protein kinase (p38 MAPK). Furthermore, we observed increased production of reactive oxygen species (ROS) in Stamp2-/- hearts after I/R, which is the likely cause for p38 MAPK activation. Although myocardial macrophage numbers were not affected by Stamp2 deficiency after I/R, augmented myocardial infiltration by polymorphonuclear neutrophils (PMN) was observed, which coincided with enhanced myeloperoxidase (MPO) plasma levels. Primary PMN isolated from Stamp2-/- animals exhibited a proinflammatory phenotype characterized by enhanced nuclear factor (NF)-κB activity and MPO secretion. To prove the critical role of PMN for the observed phenotype after I/R, antibody-mediated PMN depletion was performed in Stamp2 -/- mice which reduced deterioration of LV function and adverse structural remodeling to WT levels. These data indicate a novel role of Stamp2 as an anti-inflammatory regulator of PMN and fibroblast-to-myofibroblast transdifferentiation in myocardial I/R injury.