Neuropeptide substance P attenuates colitis by suppressing inflammation and ferroptosis via the cGAS-STING signaling pathway.

Neuropeptide substance P (SP) belongs to a family of bioactive peptides and regulates many human diseases. This study aims to investigate the role and underlying mechanisms of SP in colitis. Here, activated SP-positive neurons and increased SP expression were observed in dextran sodium sulfate (DSS)-induced colitis lesions in mice. Administration of exogenous SP efficiently ameliorated the clinical symptoms, impaired intestinal barrier function, and inflammatory response. Mechanistically, SP protected mitochondria from damage caused by DSS or TNF-α exposure, preventing mitochondrial DNA (mtDNA) leakage into the cytoplasm, thereby inhibiting the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway. SP can also directly prevent STING phosphorylation through the neurokinin-1 receptor (NK1R), thereby inhibiting the activation of the TBK1-IRF3 signaling pathway. Further studies revealed that SP alleviated the DSS or TNF-α-induced ferroptosis process, which was associated with repressing the cGAS-STING signaling pathway. Notably, we identified that the NK1R inhibition reversed the effects of SP on inflammation and ferroptosis via the cGAS-STING pathway. Collectively, we unveil that SP attenuates inflammation and ferroptosis via suppressing the mtDNA-cGAS-STING or directly acting on the STING pathway, contributing to improving colitis in an NK1R-dependent manner. These findings provide a novel mechanism of SP regulating ulcerative colitis (UC) disease.

Activation of GABA receptor attenuates intestinal inflammation by modulating enteric glial cells function through inhibiting NF-κB pathway.

AIMS: Emerging research indicates that γ-aminobutyric acid (GABA) provides substantial benefits during enteritis. Nevertheless, GABA signaling roles on enteric glial cells (EGCs) remain unknown. The study's objective was to evaluate the underlying mechanisms of GABA signaling on EGCs in vitro and in vivo. MAIN METHODS: We established LPS-induced mouse models and stimulated EGCs with LPS to mimic intestinal inflammation, and combined GABA, GABAA receptor (GABAAR) or GABAB receptor (GABABR) agonists to explore the exact mechanisms of GABA signaling. KEY FINDINGS: EGCs were immunopositive for GAD65, GAD67, GAT1, GABAARα1, GABAARα3, and GABABR1, indicating GABAergic and GABAceptive properties. GABA receptor activation significantly inhibited the high secretions of proinflammatory factors in EGCs upon LPS stimulation. Interestingly, we found that EGCs express immune-related molecules such as CD16, CD32, CD80, CD86, MHC II, iNOS, Arg1, and CD206, thus establishing their characterization of E1 and E2 phenotype. EGCs exposed to LPS mainly acted as E1 phenotype, whereas GABABR activation strongly promoted EGCs polarization into E2 phenotype. Transcriptome analysis of EGCs indicated that GABA, GABAAR or GABABR agonists treatment participated in various biological processes, however all of these treatments exhibit inhibitory effects on NF-κB pathway. Notably, in LPS-induced mice, activation of GABABR mitigated intestinal damage through modulating inflammatory factors expressions, strengthening sIgA and IgG levels, inhibiting NF-κB pathway and facilitating EGCs to transform into E2 phenotype. SIGNIFICANCE: These data demonstrate that the anti-inflammatory actions of GABA signaling system offer in enteritis via regulating EGCs-polarized function through impeding NF-κB pathway, thus providing potential targets for intestinal inflammatory diseases.

Inhibition of GABAAR or Application of Lactobacillus casei Zhang Alleviates Ulcerative Colitis in Mice: GABAAR as a Potential Target for Intestinal Epithelial Renewal and Repair.

Emerging evidence indicates that the gamma-aminobutyric acid type A receptor (GABAAR) and Lactobacillus casei Zhang regulate colitis in a variety of ways, such as by participating in host immune and inflammatory responses, altering the gut microbiota, and influencing intestinal barrier function. However, not much is known about the mechanisms by which GABAAR and L. casei affect colon epithelial cell renewal and the interaction between GABAAR and L. casei during this process. To elucidate this, we established a dextran sulfate sodium (DSS)-induced model and measured the mouse body weights, colon length, the disease activity index (DAI), and histological scores. Our results indicated that inhibition of GABAAR alleviated the DSS-induced colitis symptoms, resulting in less weight loss and more intact colon tissue. Moreover, treatment with bicuculline (Bic, a GABAAR inhibitor) increased the levels of PCNA, ß-catenin, and TCF4 in mice with colitis. Interestingly, open field test performances showed that inhibition of GABAAR also attenuated colitis-related anxiety-like behavior. By 16S RNA gene sequencing analysis, we showed that inhibition of GABAAR partially reversed the gut dysbacteriosis of DSS-induced mice and increased the abundance of beneficial bacteria. Additionally, L. casei Zhang supplementation inhibited the expression of GABAAR in mice with colitis, promoted the proliferation and renewal of colon epithelial cells, and alleviated anxiety-like behavior and intestinal microflora disorder in mice. Thus, GABAAR plays a key role in the beneficial effects of L. casei on DSS-induced colitis in mice.

Leonurine Reduces Oxidative Stress and Provides Neuroprotection against Ischemic Injury via Modulating Oxidative and NO/NOS Pathway.

Leonurine (Leo) has been found to have neuroprotective effects against cerebral ischemic injury. However, the exact molecular mechanism underlying its neuroprotective ability remains unclear. The aim of the present study was to investigate whether Leo could provide protection through the nitric oxide (NO)/nitric oxide synthase (NOS) pathway. We firstly explored the effects of NO/NOS signaling on oxidative stress and apoptosis in in vivo and in vitro models of cerebral ischemia. Further, we evaluated the protective effects of Leo against oxygen and glucose deprivation (OGD)-induced oxidative stress and apoptosis in PC12 cells. We found that the rats showed anxiety-like behavior, and the morphology and number of neurons were changed in a model of photochemically induced cerebral ischemia. Both in vivo and in vitro results show that the activity of superoxide dismutase (SOD) and glutathione (GSH) contents were decreased after ischemia, and reactive oxygen species (ROS) and malondialdehyde (MDA) levels were increased, indicating that cerebral ischemia induced oxidative stress and neuronal damage. Moreover, the contents of NO, total NOS, constitutive NOS (cNOS) and inducible NOS (iNOS) were increased after ischemia in rat and PC12 cells. Treatment with L-nitroarginine methyl ester (L-NAME), a nonselective NOS inhibitor, could reverse the change in NO/NOS expression and abolish these detrimental effects of ischemia. Leo treatment decreased ROS and MDA levels and increased the activity of SOD and GSH contents in PC12 cells exposed to OGD. Furthermore, Leo reduced NO/NOS production and cell apoptosis, decreased Bax expression and increased Bcl-2 levels in OGD-treated PC12 cells. All the data suggest that Leo protected against oxidative stress and neuronal apoptosis in cerebral ischemia by inhibiting the NO/NOS system. Our findings indicate that Leo could be a potential agent for the intervention of ischemic stroke and highlighted the NO/NOS-mediated oxidative stress signaling.

Lactobacillus casei protects intestinal mucosa from damage in chicks caused by Salmonella pullorum via regulating immunity and the Wnt signaling pathway and maintaining the abundance of gut microbiota.

Dysfunction of the intestinal mucosal barrier of chicks caused by Salmonella pullorum is of great harm to the poultry industry. Probiotics are recognized for their beneficial health-promoting properties, promoting maintenance of bowel epithelial integrity and host immune system homeostasis. Our previous research showed that Lactobacillus casei protects jejunal mucosa from injury in chicks infected with S. pullorum. However, the specific mechanisms underlying its protective properties are still not fully understood. In the present study, we aimed to explore the mechanisms underlying the protective effects of L. casei on the intestinal mucosal barrier of chicks infected with S. pullorum through histological, immunological, and molecular biology methods. The results indicated that L. casei significantly reduced the diarrhea rate, increased the daily weight gain, and maintained normal levels of IgA, IgM, and IgG in the serum of chicks infected with S. pullorum. Furthermore, we found that L. casei markedly improved the immunity of gut mucosa by regulating cytokine and chemokine receptor balance, elevating the number of intraepithelial lymphocytes, and hence effectively restraining bowel inflammation. Strikingly, feeding of infected chicks with L. casei notably boosted interleukin-22 expression to activate the Wingless-Int pathway, moderated diamine oxidase and D-lactic acid levels, diminished the generation of myosin light chain kinase, and expanded tight junction protein levels (Zonulin-1 and Claudin-1), strengthening the function of the gut mucosal epithelium. In addition, experiments using 16S rDNA sequencing also demonstrated that L. casei immensely weakened the adhesion of S. pullorum, mainly manifesting as improved diversity of the intestinal microbiota in the V4 area of infected chicks. Taken together, these results show that the application of L. casei may be a good strategy to regulate the intestinal inflammatory response of chicks infected with S. pullorum, providing new perspectives in producing antibiotic substitutes in poultry farms.

Decreased GABAergic signaling, fewer parvalbumin-, somatostatin- and calretinin-positive neurons in brain of a rat model of simulated transport stress.

Transport stress (TS) in animals lead to change in blood composition, brain structure, and the endocrine system as well as behavior. γ-aminobutyric acid (GABA), a major inhibitory neurotransmitter in the mammalian central nervous system (CNS), influences many physiological functions and plays a significant role in coping with stress. This study aimed to explore the effect of stress on behavior, HPA axis, GABA transmitters and the distribution of GABAergic interneurons in the prefrontal cortex (PFC) and striatum of the brain by a rat model of simulated transport stress (STS). Thirty-six male Sprague Dawley rats were randomly divided into a control group (n = 12, no stress), a TS1d group (n = 12, 2 h stress for 1 d) and a TS7d group (n = 12, 2 h stress each day for 7 d). After STS, the rats were subjected to open-field testing (OFT) followed by serologic analysis, colorimetry, Western blot and immunohistochemistry. The total score of the OFT showed the similar profile with serum concentrations of corticosterone (CORT) and norepinephrine (NE), which in the TS7d group were all higher than the TS1d group but lower than the control group. STS also reduced GABA, glutamate decarboxylase 67 (GAD67) and GABA transporter 1 (GAT1) expression in the TS1d and these markers were increased in the TS7d, suggesting that GABA was related to hypothalamic-pituitary-adrenal (HPA) axis activation under stress. The number of parvalbumin (PV)-, somatostatin (SOM)-, and calretinin (CR)- positive cells were decreased with stress increase. Our findings revealed that STS affected the behavior of rats, synthesis and release of GABA by altering the HPA axis.