TLR4 Activation Research Articles

Forodesine Enhances Immune Responses through Guanosine-Mediated TLR7 Activation while Preventing Graft-versus-Host Disease.

Recent evidence indicates that specific types of nuclear acids, including guanosine and its derivatives, act as natural ligands for TLR7. This led us to hypothesize that purine nucleoside phosphorylase inhibitors not only can induce apoptosis of T cells but also can lead to TLR7 activation by accumulation of guanine nucleosides, in particular under systemic inflammation, where damaged tissues release a large amount of nucleotides. We demonstrate in the present study that a purine nucleoside phosphorylase inhibitor, forodesine, can reduce the disease severity and prolong the survival in a xenogeneic mouse model of graft-versus-host disease (GVHD). Guanine nucleosides were undetectable in mice during GVHD but increased significantly following forodesine treatment. Our invitro experiments showed that forodesine enhanced guanosine-mediated cytokine production from APCs, including alveolar macrophages and plasmacytoid dendritic cells, through TLR7 signaling. Forodesine also enhanced Ag-presenting capacity, as demonstrated by increased CD8+ T cell proliferation and higher secretion of IFN-γ and IL-12p40 in an MLR with plasmacytoid dendritic cells. Furthermore, forodesine stimulated IFN-γ production from activated T cells in the presence of a low concentration of guanosine while inhibiting their proliferation and inducing apoptotic cell death. Although forodesine ameliorated GVHD severity, mice treated with forodesine showed significantly higher levels of multiple proinflammatory cytokines and chemokines in plasma, suggesting invivo upregulation of TLR7 signaling. Our study suggests that forodesine may activate a wide range of immune cells, including T cells, through TLR7 stimulation while inhibiting GVHD by inducing apoptosis of T cells, after allogeneic hematopoietic stem cell transplant.

Toll-like receptor 9 signaling in chronic lymphocytic leukemia cell lines.

Chronic lymphocytic leukemia (CLL) is a prototypic neoplasia in which malignant cells strongly depend on microenvironmental stimulations in the lymphoid tissues where they accumulate; leukemic cells are exposed to interaction with bystander and accessory cells, as well as inflammatory soluble mediators. Cell lines are frequently used to model the pathobiology of this disease; however, they do not always recapitulate leukemic cell growth and response to stimulation, and no data are available on Toll-like receptors (TLR) signaling in CLL cell lines. To address this gap, we analyzed HG3, MEC2, and PCL12 cell lines, before and after CpG stimulation, by RNA-sequencing followed by bioinformatic analyses and validation experiments. We identified NFKBIZ mRNA and the corresponding IkBz protein as robust markers of TLR9 activation in both MEC2 and PCL12, but not in HG3 cells. Next, we compared our current results with previous results obtained with primary CLL patient samples and were able to conclude that MEC2 is most similar to the patients' cells in terms of global responsiveness to TLR stimulation; in particular, MEC2 better resembles the samples of patients, as it is characterized by high expression levels of IkBz, but with a lower number of genes regulated.

Behavioural responses to TLR activation are underpinned by a sexually dimorphic shift in metabolism

Behavioural responses to TLR activation are underpinned by a sexually dimorphic shift in metabolism

Improvement on renal interstitial fibrosis in rats with renal failure via TLR4/NF-κB signaling pathway by means of panax notoginseng saponins

Panax notoginseng saponins (PNS) have excellent effects on treating cardiovascular and cerebrovascular diseases, tumors and organ interstitial diseases. This study assessed the effect of PNS on renal interstitial fibrosis (RIF). Four groups of models were firstly created, which included; renal failure model, healthy group, model group, PNS group, and then established TLR4 inhibitor group (TAK-242 group), TLR4 activator group (LPS group), combined PNS and TLR4 inhibitor group (PNS+ TAK-242 group) and combined PNS and TLR4 agonist (PNS+LPS group). TLR4/NF-κB signaling pathway and regulatory mechanism for PNS were observed along with analysis of TGF-β1, α-SMA, Collagen I and FN expressions in kidney tissues. The PNS significantly inhibited changes of renal interstitial fibrosis in rats with renal failure, and this process was related to decreased expressions of TLR4 and NF-κB. The PNS also inhibited the expression of TLR4, and expressions of TGF-β1, α-SMA, Collagen I and FN were down-regulated in kidney cells after using TAK-242, especially in the PNS+TAK-242 group. The PNS can thus significantly inhibit the process of renal fibrosis, and this process is due to the fact that, PNS inhibits the activity of TLR4/NF-κB signaling pathway to down-regulate the expressions of fibrosis-related factors TGF-β1, α-SMA, etc., in exerting its effects.

Signaling pathways regulating the extracellular digestion of lipoprotein aggregates by macrophages.

The interaction between aggregated low-density lipoprotein (agLDL) and macrophages in arteries plays a major role in atherosclerosis. Macrophages digest agLDL and generate free cholesterol in an extracellular, acidic, hydrolytic compartment known as the lysosomal synapse. Macrophages form a tight seal around agLDL through actin polymerization and deliver lysosomal contents into this space in a process termed digestive exophagy. Our laboratory has identified TLR4 activation of MyD88/Syk as critical for digestive exophagy. Here we use pharmacological agents and siRNA knockdown to characterize signaling pathways downstream of Syk that are involved in digestive exophagy. Syk activates Bruton's tyrosine kinase (BTK) and phospholipase Cγ2 (PLCγ2). We show that PLCγ2 and to a lesser extent BTK regulate digestive exophagy. PLCγ2 cleaves PI(4,5)P2 into diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3). Soluble IP3 activates release of Ca2+ from the endoplasmic reticulum (ER). We demonstrate that Ca2+ release from the ER is upregulated by agLDL and plays a key role in digestive exophagy. Both DAG and Ca2+ activate protein kinase Cα (PKCα). We find that PKCα is an important regulator of digestive exophagy. These results expand our understanding of the mechanisms of digestive exophagy, which could be useful in developing therapeutic interventions to slow development of atherosclerosis.

TLR7 activation of age-associated B cells mediates disease in a mouse model of primary Sjögren's disease.

Primary Sjögren's disease (pSD) (also referred to as Sjögren's syndrome) is an autoimmune disease that primarily occurs in women. In addition to exocrine gland dysfunction, pSD patients exhibit B cell hyperactivity. B cell-intrinsic TLR7 activation is integral to the pathogenesis of systemic lupus erythematosus, a disease that shares similarities with pSD. The role of TLR7-mediated B cell activation in pSD, however, remains poorly understood. We hypothesized that age-associated B cells (ABCs) were expanded in pSD and that TLR7-stimulated ABCs exhibited pathogenic features characteristic of disease. Our data revealed that ABC expansion and TLR7 expression were enhanced in a pSD mouse model in a Myd88-dependent manner. Splenocytes from pSD mice showed enhanced sensitivity to TLR7 agonism as compared with those derived from control animals. Sort-purified marginal zone B cells and ABCs from pSD mice showed enhanced inflammatory cytokine secretion and were enriched for antinuclear autoantibodies following TLR7 agonism. Finally, IgG from pSD patient sera showed elevated antinuclear autoantibodies, many of which were secreted preferentially by TLR7-stimulated murine marginal zone B cells and ABCs. These data indicate that pSD B cells are hyperresponsive to TLR7 agonism and that TLR7-activated B cells contribute to pSD through cytokine and autoantibody production. Thus, therapeutics that target TLR7 signaling cascades in B cells may have utility in pSD patients.

Chitosan-coated artesunate protects against ulcerative colitis via STAT6-mediated macrophage M2 polarization and intestinal barrier protection

Oral delivery of chitosan-coated artesunate (CPA) has been proven to be effective at preventing ulcerative colitis (UC) in mice. However, the anti-inflammatory mechanism is not fully understood. STAT6 is a key transcription factor that promotes anti-inflammatory effects by inducing M2 and Th2 dominant phenotypes, therefore we hypothesized STAT6 might play a key role in the process. To prove it, a STAT6 gene knockout macrophage cell line (STAT6−/− RAW264.7, by CRISPR/Cas9 method), and its corresponding Caco-2/RAW264.7 co-culture system combined with the STAT6 inhibitor (AS1517499, AS) in a mouse UC model were established and studied. The results showed that CPA remarkably suppressed the activation of TLR-4/NF-κB pathway and the mRNA levels of proinflammatory cytokines, while increased the IL-10 levels in RAW264.7. This effect of CPA contributed to the protection of the ZO-1 in Caco-2 which was disrupted upon the stimulation to macrophages. Simultaneously, CPA reduced the expression of CD86 but increase the expression of CD206 and p-STAT6 in LPS-stimulated RAW264.7 cells. However, above alterations were not obvious as in STAT6−/− RAW264.7 and its co-culture system, suggesting STAT6 plays a key role. Furthermore, CPA treatment significantly inhibited TLR-4/NF-κB activation, intestinal macrophage M1 polarization and mucosal barrier injury induced by DSS while promoted STAT6 phosphorylation in the UC mouse model, but this effect was also prominently counteracted by AS. Therefore, our data indicate that STAT6 is a major regulator in the balance of M1/M2 polarization, intestinal barrier integrity and then anti-colitis effects of CPA. These findings broaden our understanding of how CPA fights against UC and imply an alternative treatment strategy for UC via this pathway.

Expression of Toll-like Receptors in Stem Cells of the Apical Papilla and Its Implication for Regenerative Endodontics.

Regenerative therapies to replace cells and tissues damaged due to trauma and dental infections require temporal and spatial controlled recruitment and the differentiation of progenitor/stem cells. However, increasing evidence shows microbial antigens can interfere with this process. Toll-like receptors (TLRs) are crucial in recognizing pathogen-associated molecular patterns. Stem cells of the apical papilla (SCAP) are required for normal dental development and are intimately involved in the reparative and regenerative capacity of developing teeth. We hypothesized that TLRs are expressed in SCAP and that the activation of TLR2/TLR4 or TLR3 by different ligands results in differential cellular fate, impacting their differentiation into a mineralizing phenotype. We found that most TLRs are expressed as detected by PCR except TLR7 and TLR8; exposure to heat-killed E. coli results in upregulating TLR2 and TLR4 and reducing mineralization capacity. In addition, bacterial exposure resulted in the upregulation of 11 genes, of which 9 were chemokines whose proteins were also upregulated and released, promoting in vitro macrophage migration. On the other hand, TLR3 activation resulted in increased proliferation and a dramatic inhibition of osteogenic and odontoblastic differentiation, which was reversed by inhibition or the knockdown of TLR3 expression. The profound effects of TLR activation resulting in different cell fates that are ligand and receptor-specific warrants further evaluation and represents an important therapeutic target to make regenerative approaches more predictable following dental infections.

Hematopoietic stem cells undergo a lymphoid to myeloid switch in early stages of emergency granulopoiesis.

Emergency granulopoiesis is the enhanced and accelerated production of granulocytes that occurs during acute infection. The contribution of hematopoietic stem cells (HSCs) to this process was reported; however, how HSCs participate in emergency granulopoiesis remains elusive. Here, using a mouse model of emergency granulopoiesis we observe transcriptional changes in HSCs as early as 4 h after lipopolysaccharide (LPS) administration. We observe that the HSC identity is changed towards a myeloid-biased HSC and show that CD201 is enriched in lymphoid-biased HSCs. While CD201 expression under steady-state conditions reveals a lymphoid bias, under emergency granulopoiesis loss of CD201 marks the lymphoid-to-myeloid transcriptional switch. Mechanistically, we determine that lymphoid-biased CD201+ HSCs act as a first response during emergency granulopoiesis due to direct sensing of LPS by TLR4 and downstream activation of NF-κΒ signaling. The myeloid-biased CD201- HSC population responds indirectly during an acute infection by sensing G-CSF, increasing STAT3 phosphorylation, and upregulating LAP/LAP* C/EBPβ isoforms. In conclusion, HSC subpopulations support early phases of emergency granulopoiesis due to their transcriptional rewiring from a lymphoid-biased to myeloid-biased population and thus establishing alternative paths to supply elevated numbers of granulocytes.

Total Flavonoids from Camellia oleifera Alleviated Mycoplasma pneumoniae-Induced Lung Injury via Inhibition of the TLR2-Mediated NF-κB and MAPK Pathways.

Mycoplasma pneumoniae (M. pneumoniae) is an atypical bacterial pathogen responsible for community-acquired pneumonia primarily among school-aged children and young adults. Camellia oleifera (C. oleifera) has been used as a medicinal and edible plant in China for centuries, the constituents from which possessed various bioactivities. Notably, flavonoids existing in residues of C. oleifera defatted seeds exhibited significant anti-inflammatory activities. In the present study, we investigated the impact of total flavonoids from C. oleifera (TFCO) seed extract on M. pneumoniae pneumonia. TFCO was obtained using multiple column chromatography methods and identified as kaempferol glycosides via UPLC-HRESIMS. In a M. pneumoniae pneumonia mouse model, TFCO significantly reduced the lung damage, suppressed IL-1β, IL-6, and TNF-α production, and curbed TLR2 activation triggered by M. pneumoniae. Similarly, in RAW264.7 macrophage cells stimulated by lipid-associated membrane proteins (LAMPs), TFCO suppressed the generation of proinflammatory cytokines and TLR2 expression. Moreover, TFCO diminished the phosphorylation of IκBα, JNK, ERK, p38, and p65 nuclear translocation in vitro. In conclusion, TFCO alleviated M. pneumoniae-induced lung damage via inhibition of TLR2-mediated NF-κB and MAPK pathways, suggesting its potential therapeutic application in M. pneumoniae-triggered lung inflammation.

Dictyophora polysaccharides alleviate intestinal-hepatic injury exposed to low-arsenic by regulating the imbalance of gut microbiota and LPS/TLR4 pathway in rats

Intestinal and liver damage caused by low arsenic exposure exists in worldwide, but the pathogenic mechanism is not clear at present.Dictyophora is a characteristic edible and medicinal fungus in China, and research has shown that its polysaccharides have good prebiotic effects.Therefore,we explored whether volva polysaccharide from Dictyophora has a certain therapeutic effect and its mechanism on intestinal and hepatic injury caused by low arsenic exposure.Firstly,we constructed the SD rat model of enteritis caused by low arsenic-induced.Then, from the perspectives of inflammatory responses capacity,histological alterations and serum biochemical levels of rats by arsenic-exposed with DIP intervention are analyzes the possible mechanism of intestinal and liver injury.Besides, the caecal microbiomes patterns were analysed using 16 S rDNA amplicon sequencing.Results showed that dictyophora polysaccharide increased the abundance of beneficial bacteria such as Turicibacter, Oscillospiraceae_UCG-005,and reduced the abundance of Desulfovibrionia and Lachnospiraceae_NK4A136_group proinflammatory bacteria.After dictyophora polysaccharide intervention, the pathological changes of liver and colon were alleviated,and the levels of triglyceride, total cholesterol,and lipopolysaccharide in hepatic portal vein, total arsenic contents in the liver and colon tissues were reduced. Finally,we also found after dictyophora polysaccharide intervention,the gene and protein expression of Toll-like receptor 4 was returned to normal level,and the expression levels of pro-inflammatory factors in liver and colon were reduce. In summary, our study found that dictyophora polysaccharide alleviated intestinal and hepatic injury in rats exposed to low arsenic by regulated intestinal microbiota and reduced TLR4 activation, which inhibited downstream proteins MyD88 to reduce the nuclear translocation of the NF-κB p65 genes and protein.

TLR4 signalling protects Sertoli cells from cell stress via reprogramming inflammasome and autophagy pathways in MAPK1/ERK2 dependent way

Sertoli cells constitutively maintain the spermatogonial stem cell niche and blood-testis barrier via impenetrable tight junctions under hormonal, growth factor and cytokine control. Immature Sertoli cell proliferation and survival benefit from FSH, NF-κB, and IL-1α-dependent signalling effective via the MAPK family of pathways and related to p38 MAPK dependent Ca2+ and K+ fluxes. Little is known about how the NF-κB and MAPK axis interact with pro-inflammatory NOD1/TLR4 and different voltage-gated channels. Silencing MAPK1, we found that MAPK1/ERK2 has a synergistic role with TLR4 in restricting the pro-inflammatory NF-κB/Caspase-1/IL-1β axis while having an antagonistic effect on TLR4 in promoting adult 15 P-1 Sertoli cell line proliferation and migration. In MAPK1/ERK2 absence, there was an unexpected TLR4-NF-κB behaviour, showing a strong NF-κB transactivation, assessed using a pNIFTY-SEAP reporter plasmid, accompanied by significantly activated cell migration and proliferation, as demonstrated by the wound healing assay. Voltage-gated potassium flux, most likely via Kv1.3, was significantly increased after TLR4 and NOD1 challenge in ATP DAMP signal presence, associated with inflammasome activation. TLR4 challenge also activated macroautophagy while inhibiting mitophagy. Thus, TLR4 activation restricted the NF-κB and Caspase-1/IL-1β pro-inflammatory axis, cell migration and proliferation, voltage-gated potassium efflux, and shifted mitophagy to macroautophagy (towards an inflammasome pathway-related cell death), promoting cell survival. MAPK1/ERK2 had a differential effect, as in its absence, TLR4 activation had the opposite effect on NF-κB transactivation and cell migration and proliferation. Thus, TLR4/MAPK1/NF-κB/Kv1.3 interaction provides optimal Sertoli cell maintenance conditions and allows cell death only in extreme circumstances of cumulative DAMP/PAMP signalling stimulation.

THU274 Gluten Free Diet Reduces Systemic Innate Inflammation in Children Genetically Susceptible To Type 1 Diabetes

Abstract Disclosure: A.T. Coren: None. M.F. Roethle: None. L. Zhang: None. A.Y. Pan: None. S. Jia: None. M.J. Hessner: None. S.M. Cabrera: None. While genetic predisposition for type 1 diabetes (T1D) is strongly conferred by HLA-DR3 and/or HLA-DR4, shifting environmental factors that potentiate β-cell autoimmunity are believed responsible for increasing T1D incidence. Evidence suggests that intestinally mediated exposures, such as the Western diet, influence immunity and T1D risk. Gluten is a potential mediator of inflammation. We have described endogenous innate inflammation in individuals with T1D and their healthy siblings and that T1D progresses when this innate state is augmented by additional inflammatory signals prior to development of protective counter-regulatory mechanisms. We hypothesize that, in genetically susceptible hosts, gluten promotes the innate inflammation that potentiates T1D progression and that its removal will abrogate this risk. In an exploratory pilot study, we enrolled healthy children who had a full sibling with T1D to a 4-wk gluten free diet (GFD). Adherence was measured by self-report and fecal gluten peptide. Pre- and post-GFD plasma was analyzed for changes to microbial antigen detection by TLR4 activation, short chain fatty acids (SCFAs), cytokines, and chemokines. Wilcoxon signed rank tests were used to examine paired data. Stool microbial composition was measured by 16s rRNA bacterial gene sequencing and analyzed by generalized linear mixed models with negative binominal distribution. P<0.05 was considered significant. 28 participants completed the study (mean 13 years, range 2.7-22.1, 20 (71%) females, 22 (79%) non-Hispanic white, 9 (32%) pre-pubertal). 21% had a first degree relative with celiac disease and 11 (39%) had HLA-DR3 and/or DR4. At baseline, 50% had inadequate dietary fiber intake. There was no attrition, but 29% admitted to occasional gluten consumption or had detectable fecal gluten peptides. TLR4 activity trended lower post-GFD (p =0.06). Post-GFD, plasma acetate, an anti-inflammatory SCFA, was increased; hexanoate, an inflammatory fatty acid, was decreased (p<0.001). The plasma-to-fecal ratio of acetate, propionate, butyrate, valerate, and hexanoate were increased. Several inflammatory cytokines/chemokines were significantly reduced post-GFD (IFNα, IL-7, MCP-1, CCL5, Eotaxin-2) but IL-1α and TNFβ increased. Fecal 16s rRNA analyses revealed no GFD-driven differences in alpha or beta diversity, but at genus level, post-GFD samples had lower abundances of Roseburia, Faecalibacterium, and Bifidobacterium and higher abundances of Bacteroides. In sum, removal of gluten reduced several markers of systemic inflammation, independent of HLA-DR3/DR4, suggesting gluten may potentiate innate inflammation and T1D progression in those with underlying susceptibility. This may occur by altering gut barrier integrity and/or shifts in microbial taxa/metabolites. These data suggest mechanisms by which gluten may directly and indirectly drive T1D progression. Presentation: Thursday, June 15, 2023

Let-7b-TLR7 Signaling Axis Contributes to the Anesthesia/Surgery-Induced Cognitive Impairment.

Perioperative neurocognitive disorders (PNDs) are severe and common neurological complications among elderly patients following anesthesia and surgery. As the first line of defense of the innate immune system, Toll-like receptors (TLRs) have been found to be involved in the occurrence of neurodegenerative diseases in recent years. However, the role of TLR7 in the pathology and development of PNDs remains largely unclear. In our current study, we hypothesized that increased microRNA let-7b (let-7b) during anesthesia and surgical operation would activate TLR7 signaling pathways and mediate PNDs. Using a mouse model of PNDs, 18-20months wild-type (WT) mice were undergoing unilateral nephrectomy, and increased TLR7 and let-7b expression levels were found in the surgery group compared with the Sham group. Of note, increased TLR7 was found to be co-localized with let-7b in the hippocampal area CA1 in the PNDs model. In addition, TLR7 and let-7b inhibition could improve hippocampus-dependent memory and attenuate the production of inflammatory cytokines. Together, our results indicated that TLR7 activation and up-regulation might be triggered by increased let-7b under stressful conditions and initiated the downstream inflammatory signaling, playing a substantial role in the development of PNDs.

Mitochondrial DNA damage triggers spread of Parkinson’s disease-like pathology

In the field of neurodegenerative diseases, especially sporadic Parkinson’s disease (sPD) with dementia (sPDD), the question of how the disease starts and spreads in the brain remains central. While prion-like proteins have been designated as a culprit, recent studies suggest the involvement of additional factors. We found that oxidative stress, damaged DNA binding, cytosolic DNA sensing, and Toll-Like Receptor (TLR)4/9 activation pathways are strongly associated with the sPDD transcriptome, which has dysregulated type I Interferon (IFN) signaling. In sPD patients, we confirmed deletions of mitochondrial (mt)DNA in the medial frontal gyrus, suggesting a potential role of damaged mtDNA in the disease pathophysiology. To explore its contribution to pathology, we used spontaneous models of sPDD caused by deletion of type I IFN signaling (Ifnb–/–/Ifnar–/– mice). We found that the lack of neuronal IFNβ/IFNAR leads to oxidization, mutation, and deletion in mtDNA, which is subsequently released outside the neurons. Injecting damaged mtDNA into mouse brain induced PDD-like behavioral symptoms, including neuropsychiatric, motor, and cognitive impairments. Furthermore, it caused neurodegeneration in brain regions distant from the injection site, suggesting that damaged mtDNA triggers spread of PDD characteristics in an “infectious-like” manner. We also discovered that the mechanism through which damaged mtDNA causes pathology in healthy neurons is independent of Cyclic GMP-AMP synthase and IFNβ/IFNAR, but rather involves the dual activation of TLR9/4 pathways, resulting in increased oxidative stress and neuronal cell death, respectively. Our proteomic analysis of extracellular vesicles containing damaged mtDNA identified the TLR4 activator, Ribosomal Protein S3 as a key protein involved in recognizing and extruding damaged mtDNA. These findings might shed light on new molecular pathways through which damaged mtDNA initiates and spreads PD-like disease, potentially opening new avenues for therapeutic interventions or disease monitoring.

Lotus Seedpod Oligomeric Procyanidin Nanoliposomes Targeting TLR4/NF-κB Reduce Inflammation and Oxidative Stress in Patients with Traumatic Brain Injury

The inflammatory-immune response secondary to nerve injury is an important mechanism for craniocerebral injury. Procyanidins from lotus seedpods (LSPCs) are one of the main active ingredients isolated from the mature receptacles of the Nymphaeaceae family lotus plant. LSPCs exhibit strong free radical scavenging and antioxidant activities. The objective of this study was to determine the effects of LSPC nanoliposomes on traumatic brain injury (TBI). In a TBI rat model, LSPC nanoliposomes were injected intraperitoneally. Inflammatory factors and oxidative stress molecules were detected with ELISAs and RT-PCR. The TLR4/NF-κB signaling pathway was explored using Western blotting. The modified neurological severity scores (mNSS) increased in the TBI group compared with the scores in the Sham group. The water maze test indicated latency in finding the platform was prolonged and staying time in the platform quadrant and the number of times crossing the platform were reduced in the TBI group. Treatment with LSPCs significantly reduced the mNSS scores in rats with TBI and significantly reduced the time to find the platform, increased the residence time in the platform quadrant, and increased the frequency of crossing the platform during the water maze test. In addition, brain edema was reduced in rats with TBI after intraperitoneal injection of LSPCs. Iba-1, IL-1β, IL-6, and TNF-α levels were reduced after intraperitoneal injection of LSPCs. MDA levels were also reduced, while GSH-Px and SOD levels increased. After intraperitoneal injection of LSPCs, TLR4, MyD88, and pNF-κB p65 were significantly attenuated. Activation of TLR4 prevented the protective effects of LCPCs in rats with TBI. The results of this study demonstrate that LSPCs attenuate activation of the TLR4/NF-κB pathway in rats with TBI, thereby reducing microglia activation, inflammation, and oxidative stress.

The effects of Shikonin on the hypertrophic scar of rabbit ears via the TLR4/NF-κB signaling pathway.

As a traditional Chinese medicine, Zihuang Shengji Ointment has obvious effects on promoting postoperative wound healing and reducing scar formation in clinical application. Shikonin is the major phytochemical in Zihuang Shengji Ointment. As a kind of naphquinone compound with anti-tumor, anti-viral, anti-inflammatory, anti-bacterial and other biological activities extracted from Lithospermum erythrorhizon, shikonin exerts an important role in many diseases. Shikonin has impacts on the development of hypertrophic scars (HS), however, these effects are yet mostly unknown. As a result, we created the Newland white rabbit ear HS model, administered shikonin to it, and then assessed scar hypertrophy using HE and VG staining. The degree of scarring is assessed by HI, NA, as well as AA. The expression levels of collagen I, collagen III, as well as α-SMA as well as fibroblast proliferation, are also measured using real-time PCR, immunohistochemistry, and western blot. TUNEL tests are used to assess fibroblast apoptosis. In our work, HE staining and VG staining showed that the shikonin-treated group had normal bundles of collagen fibers and regular fibroblasts. Shikonin suppresses the production of HS, according to histopathological features, HI, NA, and AA measures. Shikonin also causes fibroblast apoptosis and lowers the production of α-SMA, collagen I, as well as collagen III in the HS rat. Notably, we discover that NF-κB activation and TLR4 activity are inhibited by shikonin. Overall, the results show that the signaling pathway of TLR4/NF-κB is modulated by shikonin's inhibitory effect on scar formation, which represses the levels of collagen I, collagen III, α-SMA, as well as fibroblasts.

Naphthyridine-based neutral fluorescent probes for dynamic monitoring lipid droplet polarity

In this paper, several novel nitrogen-containing heterocycle dyes 1a-c with large conjugated planar structures based on naphthyridine derivatives were designed and synthesized, which had excellent optical properties and biological applications. Optical test showed the maximum absorption wavelengths of 1a-c were in the range of 443–485 nm, while the maximum emission wavelengths located at 523–610 nm in difference solvents. Furthermore, they exhibited polarity related fluorescence intensity changes with high fluorescence quantum yields, even up to 88% (1a in THF). Moreover, the transient absorption spectra revealed the excited-state lifetime of dye 1a became shorter with the increase of solvent polarity. Density functional theory calculations are also used to help explain the effect of the polarity of solvents on their fluorescence properties. Interestingly, the dyes 1a-c were somewhat toxic to cancer cells, while had an obvious growth-promoting effect on normal cells. Additionally, 1a-c with excellent lipid droplet (LD) targeting could be used for long-term observation of targeted cellular lis) hysiological activity and further applied to dynamic monitoring of changes in LDs polarity stimulated by TLR4 activator (LPS) in living cells. Overall, the excellent optical properties and biocompatibility of 1a-c indicate that they can serve as fluorescent probes for biological applications, and the results have important implications for understanding the physiological functions of LDs, especially in terms of morphological and polar changes.

TLR4 sensitizes plasmacytoid dendritic cells for antiviral response against SARS-CoV-2 coronavirus.

Plasmacytoid dendritic cells are a rare subset of dendritic cells that exhibit antiviral functions in response to toll-like receptor 7/8 stimulations. Alternative toll-like receptors such as TLR4 have been known to be active in plasmacytoid dendritic cells for immune regulatory functions. However, it is unclear whether these toll-like receptors differentially activate plasmacytoid dendritic cells as compared with canonical toll-like receptor 7/8 stimulation. Here, we assessed alternative plasmacytoid dendritic cell activation states mediated by toll-like receptors other than endosomal toll-like receptors via the RNA sequencing approach. We found that toll-like receptor 4 stimulation induced a high degree of similarity in gene expression pattern to toll-like receptor 7/8 stimulation in plasmacytoid dendritic cells. Despite high resemblance to toll-like receptor 7/8, we discovered unique genes that were activated under toll-like receptor 4 activation only, as well as genes that were induced at a higher magnitude in comparison to toll-like receptor 7/8 activation. In comparison between toll-like receptor 4-activated plasmacytoid dendritic cells and conventional dendritic cells, we revealed that plasmacytoid dendritic cells and conventional dendritic cells expressed distinct gene sets, whereby conventional dendritic cells mostly favored antigen presentation functions for adaptive immune response regulation while plasmacytoid dendritic cells leaned toward immune response against infectious diseases. Last, we determined that toll-like receptor 4 activation sensitized plasmacytoid dendritic cells against SARS-CoV-2 (COVID-19) single-stranded RNA by enhancing antiviral-related responses and type I interferon production. These findings provided greater insights into the toll-like receptor 4 activation state in plasmacytoid dendritic cells, which can be beneficial for alternative therapeutic interventions involving plasmacytoid dendritic cells for various diseases.

The transcriptome landscape of 3D-cultured placental trophoblasts reveals activation of TLR2 and TLR3/7 in response to low Trypanosoma cruzi parasite exposure.

Vertical transmission of Trypanosoma cruzi (T. cruzi) become a globalized health problem accounting for 22% of new cases of Chagas disease (CD). Congenital infection is now considered the main route of CD spread in non-endemic countries where no routine disease testing of pregnant women is implemented. The main mechanisms that lead to fetal infection by T. cruzi remain poorly understood. Mother-to-child transmission may occur when bloodstream trypomastigotes interact with the syncytiotrophoblasts (SYNs) that cover the placenta chorionic villi. These highly specialized cells function as a physical barrier and modulate immune responses against pathogen infections. To model the human placenta environment, we have previously used a three-dimensional (3D) cell culture system of SYNs that exhibits differentiation characteristics comparable to placental trophoblasts. Further, we have shown that 3D-grown SYNs are highly resistant to T. cruzi infection. In this work, we used RNA sequencing and whole transcriptome analysis to explore the immunological signatures that drive SYNs' infection control. We found that the largest category of differentially expressed genes (DEGs) are associated with inflammation and innate immunity functions. Quantitative RT-PCR evaluation of selected DEGs, together with detection of cytokines and chemokines in SYNs culture supernatants, confirmed the transcriptome data. Several genes implicated in the Toll-like receptors signaling pathways were upregulated in 3D-grown SYNs. In fact, TLR2 blockade and TLR3/7 knockdown stimulated T. cruzi growth, suggesting that these molecules play a significant role in the host cell response to infection. Ingenuity Pathway Analysis of DEGs predicted the activation of canonical pathways such as S100 protein family, pathogen induced cytokine storm, wound healing, HIF1α signaling and phagosome formation after T. cruzi exposure. Our findings indicate that SYNs resist infection by eliciting a constitutive pro-inflammatory response and modulating multiple defense mechanisms that interfere with the parasite's intracellular life cycle, contributing to parasite killing and infection control.