Dragon's Blood Regulates Rac1-WAVE2-Arp2/3 Signaling Pathway to Protect Rat Intestinal Epithelial Barrier Dysfunction Induced by Simulated Microgravity

Loureirin C extracted from Dracaena cochinchinensis S.C. Chen prevents rotaviral diarrhea in mice by inhibiting the intestinal Ca2+-activated Cl- channels

ETHNOPHARMACOLOGICAL RELEVANCE

Resina Draconis (RD) is the red resin of Dracaena cochinchinensis (Lour.) S.C. Chen and most used as a hemostatic drug in traditional Chinese medicine. Recent studies have reported that RD has a therapeutic effect on gastrointestinal diseases. Loureirin A, B, and C (LA, LB, and LC) are dihydrochalcone compounds isolated from RD.

AIM OF THE STUDY

Dehydration is the primary cause of death in rotaviral diarrhea. Inhibition of Ca2+-activated Cl- channels (CaCCs)-mediated Cl- secretion significantly reduced fluid secretion in rotaviral diarrhea. RD was used to treat digestive diseases such as diarrhea and abdominal pain; however, the pharmacological mechanism remains unclear. This study investigated the effects of RD and loureirin on intestinal Cl- channels and their therapeutic effects on rotavirus-induced diarrhea, aiming to reveal RD's molecular basis, targets, and mechanisms for treating rotaviral diarrhea.

MATERIALS AND METHODS

Cell-based fluorescence quenching assays were used to examine the effect of RD and loureirin on Cl- channels activity. Electrophysiological properties were tested using short-circuit current experiments in epithelial cells or freshly isolated mouse intestinal tissue. Fecal water content, intestinal peristalsis rate, and smooth muscle contraction were measured in neonatal mice infected with SA-11 rotavirus before and after LC treatment or adult mice.

RESULTS

RD, LA, LB, and LC inhibited CaCCs-mediated Cl- current in HT-29 cells and colonic epithelium. The inhibitory effect of LC on CaCCs was primarily on the apical side in epithelial cells, which may be partially produced by affecting cytoplasmic Ca2+ levels. LC significantly inhibited TMEM16A-mediated Cl- current. Characterization studies revealed that LC inhibited basolateral K+ channel activity without affecting Na+/K+-ATPase activity in the colonic epithelium. Although LC activated the cystic fibrosis transmembrane regulator in epithelial cells, its effect was not apparent in colonic epithelium. In vivo, LC significantly reduced the fecal water content, intestinal peristalsis rate, and smooth muscle contraction of mice infected with rotavirus.

CONCLUSION

RD and its active compound LC inhibit intestinal CaCCs activity, which might mediate the anti-rotaviral diarrheal effect of RD.

Rac1: A Regulator of Cell Migration and A Potential Target for Cancer Therapy

Cell migration is crucial for physiological and pathological processes such as morphogenesis, wound repair, immune response and cancer invasion/metastasis. There are many factors affecting cell migration, and the regulatory mechanisms are complex. Rac1 is a GTP-binding protein with small molecular weight belonging to the Rac subfamily of the Rho GTPase family. As a key molecule in regulating cell migration, Rac1 participates in signal transduction from the external cell to the actin cytoskeleton and promotes the establishment of cell polarity which plays an important role in cancer cell invasion/metastasis. In this review, we firstly introduce the molecular structure and activity regulation of Rac1, and then summarize the role of Rac1 in cancer invasion/metastasis and other physiological processes. We also discuss the regulatory mechanisms of Rac1 in cell migration and highlight it as a potential target in cancer therapy. Finally, the current state as well as the future challenges in this area are considered. Understanding the role and the regulatory mechanism of Rac1 in cell migration can provide fundamental insights into Rac1-related cancer progression and further help us to develop novel intervention strategies for cancer therapy in clinic.

Simulated Microgravity Alters P-Glycoprotein Efflux Function and Expression via the Wnt/β-Catenin Signaling Pathway in Rat Intestine and Brain

The drug efflux transporter permeability glycoprotein (P-gp) plays an important role in oral drug absorption and distribution. Under microgravity (MG), the changes in P-gp efflux function may alter the efficacy of oral drugs or lead to unexpected effects. Oral drugs are currently used to protect and treat multisystem physiological damage caused by MG; whether P-gp efflux function changes under MG remains unclear. This study aimed to investigate the alteration of P-gp efflux function, expression, and potential signaling pathway in rats and cells under different simulated MG (SMG) duration. The altered P-gp efflux function was verified by the in vivo intestinal perfusion and the brain distribution of P-gp substrate drugs. Results showed that the efflux function of P-gp was inhibited in the 7 and 21 day SMG-treated rat intestine and brain and 72 h SMG-treated human colon adenocarcinoma cells and human cerebral microvascular endothelial cells. P-gp protein and gene expression levels were continually down-regulated in rat intestine and up-regulated in rat brain by SMG. P-gp expression was regulated by the Wnt/β-catenin signaling pathway under SMG, verified by a pathway-specific agonist and inhibitor. The elevated intestinal absorption and brain distribution of acetaminophen levels also confirmed the inhibited P-gp efflux function in rat intestine and brain under SMG. This study revealed that SMG alters the efflux function of P-gp and regulates the Wnt/β-catenin signaling pathway in the intestine and the brain. These findings may be helpful in guiding the use of P-gp substrate drugs during spaceflight.

Xue-Jie-San restricts ferroptosis in Crohn's disease via inhibiting FGL1/NF-κB/STAT3 positive feedback loop

Crohn's disease (CD) is an incurable inflammatory bowel disease due to unclear etiology and pathogenesis. Accumulating evidences have shown the harmful role of ferroptosis in CD onset and development. Additionally, fibrinogen-like protein 1 (FGL1) has been verified to be a potential therapeutic target of CD. Xue-Jie-San (XJS) is an effective prescription for treating CD. However, its therapeutic mechanism has not been fully elucidated. This study aimed to determine whether XJS alleviating CD via regulating ferroptosis and FGL1 expression. A colitis rat model was induced by 2,4,6-trinitrobenzene sulfonic acid and treated with XJS. The disease activity indices of the colitis rats were scored. Histopathological damage was assessed using HE staining. ELISA was performed to examine inflammatory cytokines. Transmission electron microscopy was utilized to observe ultrastructure changes in intestinal epithelial cells (IECs). Iron load was evaluated by examining iron concentrations, the expressions of FPN, FTH and FTL. Lipid peroxidation was investigated through detecting the levels of ROS, 4-HNE, MDA and PTGS2. Furthermore, the SLC7A11/GSH/GPX4 antioxidant system and FGL1/NF-κB/STAT3 signaling pathway were examined. The results showed that colitis was dramatically ameliorated in the XJS-treated rats as evidenced by relief of clinical symptoms and histopathological damages, downregulation of pro-inflammatory cytokines IL-6, IL-17 and TNF-α, and upregulation of anti-inflammatory cytokine IL-10. Furthermore, XJS administration led to ferroptosis inhibition in IECs by reducing iron overload and lipid peroxidation. Mechanistically, XJS enhanced the SLC7A11/GSH/GPX4 antioxidant system negatively regulated by the FGL1/NF-κB/STAT3 positive feedback loop. In conclusion, XJS might restrain ferroptosis in IECs to ameliorate experimental colitis by inhibition of FGL1/NF-κB/STAT3 positive feedback loop.

Semen Ziziphi Spinosae attenuates blood-brain barrier dysfunction induced by lipopolysaccharide by targeting the FAK-DOCK180-Rac1-WAVE2-Arp3 signaling pathway

Semen Ziziphi Spinosae (SZS) has been extensively used in the daily diet as a functional food for neuroprotective health-benefit in China for many years. However, the neuroprotective mechanism of SZS associated with blood–brain barrier (BBB) integrity remains unexplored. The present study suggests SZS could protect against lipopolysaccharide (LPS)-induced BBB dysfunction. Proteomics indicate that 135 proteins in rat brain are significantly altered by SZS. These differentially expressed proteins are mainly clustered into cell–cell adhesion and adherens junctions, which are closely related with BBB integrity. SZS reversed LPS-induces BBB breakdown by activating the FAK-DOCK180-Rac1-WAVE2-Arp3 pathway. Molecular docking between signaling pathway proteins and identified SZS components in rat plasma reveals that 6”‘-feruloylspinosin, spinosin, and swertisin strongly binds to signaling proteins at multiple amino acid sites. These novel findings suggest a health benefit of SZS in prevention of cerebral diseases and contributes to the further application of SZS as a functional food.

Functions of Arp2/3 Complex in the Dynamics of Epithelial Tissues

Epithelia are sheets of cells that communicate and coordinate their behavior in order to ensure their barrier function. Among the plethora of proteins involved in epithelial dynamics, actin nucleators play an essential role. The branched actin nucleation complex Arp2/3 has numerous functions, such as the regulation of cell-cell adhesion, intracellular trafficking, the formation of protrusions, that have been well described at the level of individual cells. Here, we chose to focus on its role in epithelial tissue, which is rising attention in recent works. We discuss how the cellular activities of the Arp2/3 complex drive epithelial dynamics and/or tissue morphogenesis. In the first part, we examined how this complex influences cell-cell cooperation at local scale in processes such as cell-cell fusion or cell corpses engulfment. In the second part, we summarized recent papers dealing with the impact of the Arp2/3 complex at larger scale, focusing on different morphogenetic events, including cell intercalation, epithelial tissue closure and epithelial folding. Altogether, this review highlights the central role of Arp2/3 in a diversity of epithelial tissue reorganization.

Antifungal and wound healing promotive compounds from the resins of Dracaena cochinchinensis

Five new compounds (xuejieins A-E), including three new phenolic glycosides (1, 2, and 5) and two new flavonoids (10 and 11), together with six known compounds were isolated from the resins of Dracaena cochinchinensis (Chinese dragon's blood). The structures of the new compounds were confirmed by extensive spectroscopic methods and electronic circular dichroism (ECD) data analysis. Especially, the absolute configurations of the sugar moieties in compounds 1, 2, and 5 were clarified by GC analysis after acid hydrolysis. All isolated compounds have been tested for antifungal and wound healing promoting activities, The results showed that compound 9 shows significant antifungal activities against Botrytis cinerea, Magnaporthe grisea, Penicillium digitatum, and Sclerotinia sclerotiorum. In addition, compound 4 could significantly stimulate human keratinocytes (HaCAT) proliferation, mobility, and human umbilical vein vascular endothelial cells (HUVECs) tube formation at 40 μM.