The quorum sensing (QS) circuit plays a role in the precise regulation of genes controlling virulence factors and biofilm formation in Pseudomonas aeruginosa. QS-controlled biofilm formation by Pseudomonas aeruginosa in clinical settings has remained controversial due to emerging drug resistance; therefore, screening diverse compounds for anti-biofilm or anti-QS activities is important. This study demonstrates the ability of sub-minimum inhibitory concentrations (sub-MICs) of baicalin, an active natural compound extracted from the traditional Chinese medicinal Scutellaria baicalensis, to inhibit the formation of Pseudomonas aeruginosa biofilms and enhance the bactericidal effects of various conventional antibiotics in vitro. In addition, baicalin exerted dose-dependent inhibitory effects on virulence phenotypes (LasA protease, LasB elastase, pyocyanin, rhamnolipid, motilities and exotoxin A) regulated by QS in Pseudomonas aeruginosa. Moreover, the expression levels of QS-regulatory genes, including lasI, lasR, rhlI, rhlR, pqsR and pqsA, were repressed after sub-MIC baicalin treatment, resulting in significant decreases in the QS signaling molecules 3-oxo-C12-HSL and C4-HSL, confirming the ability of baicalin-mediated QS inhibition to alter gene and protein expression. In vivo experiments indicated that baicalin treatment reduces Pseudomonas aeruginosa pathogenicity in Caenorhabditis elegans. Greater worm survival in the baicalin-treated group manifested as an increase in the LT50 from 24 to 96 h. In a mouse peritoneal implant infection model, baicalin treatment enhanced the clearance of Pseudomonas aeruginosa from the implants of mice infected with Pseudomonas aeruginosa compared with the control group. Moreover, the combination of baicalin and antibiotics significantly reduced the numbers of colony-forming units in the implants to a significantly greater degree than antibiotic treatment alone. Pathological and histological analyses revealed mitigation of the inflammatory response and reduced cell infiltration in the peritoneal tissue surrounding the implants after baicalin treatment. Measurement of the cytokine levels in the peritoneal lavage fluid of mice in the baicalin treatment group revealed a decrease in IL-4, an increase in interferon γ (IFN-γ), and a reversed IFN-γ/IL-4 ratio compared with the control group, indicating that baicalin treatment activated the Th1-induced immune response to expedite bacterial load clearance. Based on these results, baicalin might be a potent QS inhibitor and anti-biofilm agent for combating Pseudomonas aeruginosa biofilm-related infections.

Perihematomal edema (PHE) occurs within hours after intracerebral hemorrhage (ICH), leading to secondary injury manifested by impaired blood–brain barrier (BBB) integrity and destruction of adjacent tissue. To dissect the mechanisms underlying PHE formation, we profiled human and mouse perihematomal tissues and identified natural killer (NK) cells as the predominant immune cell subset that outnumbers other infiltrating immune cell types during early stages of ICH. Unbiased clustering of single-cell transcriptional profiles revealed two major NK cell subsets that respectively possess high cytotoxicity or robust chemokine production features in the brain after ICH, distinguishing them from NK cells of the periphery. NK cells exacerbate BBB disruption and brain edema after ICH via cytotoxicity toward cerebral endothelial cells and recruitment of neutrophils that augment focal inflammation. Thus, brain-bound NK cells acquire new features that contribute to PHE formation and neurological deterioration following ICH.

Directed differentiation of bone‐marrow‐derived stem cells (BMSCs) toward chondrogenesis has served as a predominant method for cartilage repair but suffers from poor oriented differentiation tendency and low differentiation efficiency. To overcome these two obstacles, an injectable composite hydrogel that consists of collagen hydrogels serving as the scaffold support to accommodate BMSCs and cadmium selenide (CdSe) quantum dots (QDs) is constructed. The introduction of CdSe QDs considerably strengthens the stiffness of the collagen hydrogels via mutual crosslinking using a natural crosslinker (i.e., genipin), which simultaneously triggers photodynamic provocation (PDP) to produce reactive oxygen species (ROS). Experimental results demonstrate that the intensified stiffness and augmented ROS production can synergistically promote the proliferation of BMSCs, induce cartilage‐specific gene expression and increase secretion of glycosaminoglycan. As a result, this approach can facilitate the directed differentiation of BMSCs toward chondrogenesis and accelerate cartilage regeneration in cartilage defect repair, which routes through activation of the TGF‐β/SMAD and mTOR signaling pathways, respectively. Thus, this synergistic strategy based on increased stiffness and PDP‐mediated ROS production provides a general and instructive approach for developing alternative materials applicable for cartilage repair.

Alzheimer’s disease (AD) is a neurodegenerative disorder, characterized by progressive loss of memory and cognitive function, and is associated with the deficiency of synaptic acetylcholine, as well as chronic neuroinflmmation. Tacrine, a potent acetylcholinesterase (AChE) inhibitor, was previously a prescribed clinical therapeutic agent for AD, but it was recently withdrawn because it caused widespread hepatotoxicity. Hydrogen sulfide (H2S) has neuroprotective, hepatoprotective, and anti-inflammatory effects. In this study, we synthesized a new compound, a tacrine–H2S donor hybrid (THS) by introducing H2S-releasing moieties (ACS81) to tacrine. Subsequently, pharmacological and biological evaluations of THS were conducted in the aluminum trichloride (AlCl3)-induced AD mice model. We found that THS (15 mmol/kg) improved cognitive and locomotor activity in AD mice in the step-through test and open field test, respectively. THS showed strong AChE inhibitory activity in the serum and hippocampus of AD mice and induced increased hippocampal H2S levels. Furthermore, THS reduced mRNA expression of the proinflammatory cytokines, TNF-α, IL-6, and IL-1β and increased synapse-associated proteins (synaptophysin and postsynaptic density protein 95) in the hippocampus of AD mice. Importantly, THS, unlike tacrine, did not increase liver transaminases (alanine transaminase and aspartate transaminase) or proinflammatory cytokines, indicating THS is much safer than tacrine. Therefore, the multifunctional effects of this new hybrid compound of tacrine and H2S indicate it is a promising compound for further research into the treatment of AD.

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