Glucocorticoid receptor-mediated Nr1d1 chromatin circadian misalignment in stress-induced irritable bowel syndrome

Toxic effects and mechanisms of monometallic bismuth nanoparticles on early stages of zebrafish (Danio rerio)

Bismuth nanoparticles (Bi NPs) have shown great potential in the fields of biomedical applications due to their favourable properties. However, the impacts and toxic mechanisms of monometallic Bi NPs on vertebrates remain poorly explored. In the present study, we utilised zebrafish (Danio rerio) as a model to evaluate the toxic effects of acute exposure to Bi NPs on early life stages. Bi NPs-treated embryos exhibited an increase in the number of malformations and decreased hatching. Exposure to 5 mg/L Bi NPs induced embryonic developmental abnormalities, including lipid transport, behavioural, and craniofacial deformities. Moreover, exposure to 25 mg/L Bi NPs caused embryonic developmental defects, including behavioural dysfunction, skeletal deformity, cardiac teratogenesis, and ocular abnormalities. Based on transcriptomics, we identified a total of 859 differentially expressed genes. Of these, 338 upregulated genes are mainly related to skeletal system development, circadian rhythm, and oxidative stress, while 519 downregulated genes are associated with visual perception and heart contraction. Furthermore, the carbon metabolism and peroxisome proliferator-activated receptor (PPAR) signalling pathways, which are essential for embryonic development, were significantly dysregulated by exposure to Bi NPs. This study innovatively focused on evaluating the embryonic developmental toxicities of monometallic Bi NPs on zebrafish and unveiled the underlying toxic mechanisms, highlighting the potential hazard and risk posed by Bi NPs and raising concerns regarding adverse impacts on aquatic organisms.

Stress triggers gut dysbiosis via CRH-CRHR1-mitochondria pathway

Stress can lead to gut dysbiosis in brain-gut axis disordered diseases as irritable bowel syndrome (IBS), yet the mechanisms how stress transfer from the brain to the gut and disrupt gut microbiota remain elusive. Here we describe a stress-responsive brain-to-gut axis which impairs colonocytes' mitochondria to trigger gut dysbiosis. Patients with IBS exhibit significantly increased facultative anaerobes and decreased obligate anaerobes, related to increased serum corticotropin-releasing hormone (CRH) level and defected colonocytes' mitochondria ultrastructure. Mice exposed to acute stress experienced enhanced CRH-CRH receptor type 1 (CRHR1) signaling, which impaired mitochondria and epithelium hypoxia in the colon, subsequently triggered gut dysbiosis. Antagonizing CRHR1 expression to inhibit cAMP/Ras/MAPK signaling or activating mitochondria respiration conferred resilience against stress-induced mitochondria damaging and epithelium hypoxia impairment, ultimately improving gut dysbiosis. These results suggest that the CRH-CRHR1-mitochondria pathway plays a pivotal role in stress-induced gut dysbiosis that could be therapeutically targeted for stress-induced gastrointestinal diseases. Yiming Zhang et.al report that psychological stress activated Corticotropin-releasing hormone (CRH)-CRH receptor type 1 (CRHR1)-mitochondria pathway to trigger gut dysbiosis and reveal CRHR1 upregulation damages mitochondria via cAMP/Ras/MAPK signaling in colonocytes.

A Ctnnb1 enhancer transcriptionally regulates Wnt signaling dosage to balance homeostasis and tumorigenesis of intestinal epithelia

The β-catenin-dependent canonical Wnt signaling is pivotal in organ development, tissue homeostasis, and cancer. Here, we identified an upstream enhancer of Ctnnb1 - the coding gene for β-catenin, named ieCtnnb1 (intestinal enhancer of Ctnnb1), which is crucial for intestinal homeostasis. ieCtnnb1 is predominantly active in the base of small intestinal crypts and throughout the epithelia of large intestine. Knockout of ieCtnnb1 led to a reduction in Ctnnb1 transcription, compromising the canonical Wnt signaling in intestinal crypts. Single-cell sequencing revealed that ieCtnnb1 knockout altered epithelial compositions and potentially compromised functions of small intestinal crypts. While deletion of ieCtnnb1 hampered epithelial turnovers in physiologic conditions, it prevented occurrence and progression of Wnt/β-catenin-driven colorectal cancers. Human ieCTNNB1 drove reporter gene expression in a pattern highly similar to mouse ieCtnnb1. ieCTNNB1 contains a single-nucleotide polymorphism associated with CTNNB1 expression levels in human gastrointestinal epithelia. The enhancer activity of ieCTNNB1 in colorectal cancer tissues was stronger than that in adjacent normal tissues. HNF4α and phosphorylated CREB1 were identified as key trans-factors binding to ieCTNNB1 and regulating CTNNB1 transcription. Together, these findings unveil an enhancer-dependent mechanism controlling the dosage of Wnt signaling and homeostasis in intestinal epithelia.

Discovery of novel ocotillol derivatives modulating glucocorticoid receptor/NF-κB signaling for the treatment of sepsis

Glucocorticoids (GCs) have been used in the treatment of sepsis because of their potent anti-inflammatory effects. However, their clinical efficacy against sepsis remains controversial because of glucocorticoid receptor (GR) downregulation and side effects. Herein, we designed and synthesized 30 ocotillol derivatives and evaluated their anti-inflammatory activities. Ocotillol 24(R/S) differential isomers were stereoselective in their pharmacological action. Specifically, 24(S) derivatives had better anti-inflammatory activity than their corresponding 24(R) derivatives. Compound 20 most effectively inhibited NO release (85.97% reduction), and it exerted dose-dependent inhibitory effects on interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) levels. Mechanistic studies revealed that compound 20 reduces the degradation of GR mRNA and GR protein. Meanwhile, compound 20 inhibited the activation of nuclear factor-κB (NF-κB) signaling, thereby inhibiting the nuclear translocation of p65 and attenuating the inflammatory response. In vivo studies revealed that compound 20 attenuated hepatic, pulmonary, and renal pathology damage in mice with sepsis and suppressed the production of inflammatory mediators. These results indicated that compound 20 is a promising lead compound for designing and developing anti-sepsis drugs.

Melatonin restores hepatic lipid metabolic homeostasis disrupted by blue light at night in high-fat diet-fed mice

Artificial light at night (ALAN) is an emerging environmental pollutant that threatens public health. Recently, ALAN has been identified as a risk factor for obesity; however, the role of ALAN and its light wavelength in hepatic lipid metabolic homeostasis remains undetermined. We showed that chronic dim (~5 lx) ALAN (dLAN) exposure significantly promoted hepatic lipid accumulation in obese or diabetic mice, with the most severe effect of blue light and little effect of green or red light. These metabolic phenotypes were attributed to blue rather than green or red dLAN interfering with hepatic lipid metabolism, especially lipogenesis and lipolysis. Further studies found that blue dLAN disrupted hepatic lipogenesis and lipolysis processes by inhibiting hepatic REV-ERBs. Mechanistically, feeding behavior mediated the regulation of dLAN on hepatic REV-ERBs. In addition, different effects of light wavelengths at night on liver REV-ERBs depended on the activation of the corticosterone (CORT)/glucocorticoid receptor (GR) axis. Blue dLAN could activate the CORT/GR axis significantly while other wavelengths could not. Notably, we demonstrated that exogenous melatonin could effectively inhibit hepatic lipid accumulation and restore the hepatic GR/REV-ERBs axis disrupted by blue dLAN. These findings demonstrate that dLAN promotes hepatic lipid accumulation in mice via a short-wavelength-dependent manner, and exogenous melatonin is a potential therapeutic approach. This study strengthens the relationship between ALAN and hepatic lipid metabolism and provides insights into directing ambient light.