Toll-Like Receptor 4 Promotes NO Synthesis by Upregulating GCHI Expression under Oxidative Stress Conditions in Sheep Monocytes/Macrophages

Tenascin-C fibronectin D domain is involved in the fine-tuning of glial response to CNS injury in vitro

Understanding processes that occur after injuries to the central nervous system is essential in order to gain insight into how the restoration of function can be improved. Extracellular glycoprotein tenascin-C (TnC) has numerous functions in wound healing process depending on the expression time, location, isoform and binding partners which makes it interesting to study in this context. We used an in vitro injury model, the mixed culture of cortical astrocytes and microglia, and observed that without TnC microglial cells tend to populate gap area in greater numbers and proliferate more, whereas astrocytes build up in the border region to promote faster gap closure. Alternatively spliced domain of TnC, fibronectin type III-like repeat D (FnD) strongly affected physiological properties and morphology of both astrocytes and microglia in this injury model. The rate of microglial proliferation in the injury region decreased significantly with the addition of FnD. Additionally, density of microglia also decreased, in part due to reduced proliferation, and possibly due to reduced migration and increased contact inhibition between enlarged FnD-treated cells. Overall morphology of FnD-treated microglia resembled the activated pro-inflammatory cells, and elevated expression of iNOS was in accordance with this phenotype. The effect of FnD on astrocytes was different, as it did not affect their proliferation, but stimulated migration of reactivated astrocytes into the scratched area 48 h after the lesion. Elevated expression and secretion of TNF-α and IL-1β upon FnD treatment indicated the onset of inflammation. Furthermore, on Western blots we observed increased intensity of precursor bands of β1 integrin and appearance of monomeric bands of P2Y12R after FnD treatment which substantiates and clarifies its role in cellular shape and motility changes. Our results show versatile functions of TnC and in particular FnD after injury, mostly contributing to ongoing inflammation in the injury region. Based on our findings, FnD might be instrumental in limiting immune cell infiltration, and promoting astrocyte migration within the injury region, thus influencing spaciotemporal organization of the wound and surrounding area.

Galectin-3 facilitates inflammation and apoptosis in chondrocytes through upregulation of the TLR-4-mediated oxidative stress pathway in TC28a2 human chondrocyte cells

Osteoarthritis (OA) is a common degenerative joint disease. The pathological changes of chondrocytes involve oxidative stress, the pro-inflammatory response, and pro-apoptotic events. Galectin-3 (Gal-3) is a 35 kDa protein with a special chimeric structure. Gal-3 participates in the progression of many diseases, such as cancer metastasis and heart failure. A previous study demonstrated that Gal-3 expression in human cartilage with OA is increased. However, the role of Gal-3 in chondrocyte dysfunction in joints is still unclear. In this study, we applied Gal-3 (5-20 μg/ml) to TC28a2 human chondrocyte cells for 24 h to induce chondrocyte dysfunction. We found that Gal-3 upregulated TLR-4 and MyD88 expression and NADPH oxidase, thereby increasing intracellular ROS in the chondrocytes. Gal-3 increased phosphorylated MEK1/2 and ERK levels, and promoted NF-κB activity. This activation of NF-κB was reduced by silencing TLR-4 and NOX-2. In addition, Gal-3 caused apoptosis of chondrocytes through the mitochondrial-dependent pathway via the TLR-4/NADPH oxidase/MAPK axis. Our study proves the pathogenic role of Gal-3 in Gal-3-induced chondrocyte dysfunction and injuries.

Lactobacillus plantarum FNCC 0137 fermented red Moringa oleifera exhibits protective effects in mice challenged with Salmonella typhi via TLR3/TLR4 inhibition and down-regulation of proinflammatory cytokines

Background

Salmonella typhi is a foodborne pathogenic bacterium that threatens health. S. typhi infection exacerbated the antibiotic resistance problem that needs alternative strategies. Moringa oleifera possesses anti-inflammatory and antimicrobial effects. However, there is a lack of information about the pharmacological value of red M. oleifera. The fermentation of red M. oleifera leaves extract (RMOL) is expected to add to its nutritional value.

Objective

The present study aimed to evaluate non-fermented RMOL (NRMOL) and fermented RMOL (FRMOL) effects on S. typhi infection in mice.

Materials and methods

Female Balb/C mice were randomly divided into eight groups. The treatment groups were orally administered with NRMOL or FRMOL at doses 14, 42, and 84 mg/kg BW during the 28 days experimental period. Then S. typhi was introduced to mice through intraperitoneal injection except in the healthy groups. The NRMOL or FRMOL administration was continued for the next seven days. Cells that expressed CD11b⁺ TLR3⁺, CD11b⁺TLR4⁺, CD11b⁺IL-6⁺, CD11b⁺IL-17⁺, CD11b⁺TNF-a⁺, and CD4⁺CD25⁺CD62L⁺ were assessed by flow cytometry.

Results

Our result suggested that NRMOL and FRMOL extracts significantly reduced (p < 0.05) the expression of CD11b⁺TLR3⁺, CD11b⁺TLR4⁺, CD11b⁺IL-6⁺, CD11b⁺IL-17⁺, and CD11b⁺TNF-α⁺ subsets. In contrast, NRMOL and FRMOL extracts significantly increased (p < 0.05) the expression of CD4⁺CD25⁺CD62L⁺ subsets. NRMOL at dose 14 and 42 mg/kg BW was more effective compared to FRMOL in reducing the expression of CD11b⁺TLR3⁺, CD11b⁺TLR4⁺, and CD11b⁺TNF-α⁺ subsets.

Conclusion

Our findings demonstrated that NRMOL and FRMOL extracts could be promising agents for protection against S. typhi infection via modulation of TLR3/TLR4, regulatory T cells, and proinflammatory cytokines.

Mechanisms of TLR4-Mediated Autophagy and Nitroxidative Stress

Pathogenic infections have badly affected public health and the development of the breeding industry. Billions of dollars are spent every year fighting against these pathogens. The immune cells of a host produce reactive oxygen species and reactive nitrogen species which promote the clearance of these microbes. In addition, autophagy, which is considered an effective method to promote the destruction of pathogens, is involved in pathological processes. As research continues, the interplay between autophagy and nitroxidative stress has become apparent. Autophagy is always intertwined with nitroxidative stress. Autophagy regulates nitroxidative stress to maintain homeostasis within an appropriate range. Intracellular oxidation, in turn, is a strong inducer of autophagy. Toll-like receptor 4 (TLR4) is a pattern recognition receptor mainly involved in the regulation of inflammation during infectious diseases. Several studies have suggested that TLR4 is also a key regulator of autophagy and nitroxidative stress. In this review, we describe the role of TLR4 in autophagy and oxidation, and focus on its function in influencing autophagy-nitroxidative stress interactions.

Methylene Blue Application to Lessen Pain: Its Analgesic Effect and Mechanism

Methylene blue (MB) is a cationic thiazine dye, widely used as a biological stain and chemical indicator. Growing evidence have revealed that MB functions to restore abnormal vasodilation and notably it is implicated even in pain relief. Physicians began to inject MB into degenerated disks to relieve pain in patients with chronic discogenic low back pain (CDLBP), and some of them achieved remarkable outcomes. For osteoarthritis and colitis, MB abates inflammation by suppressing nitric oxide production, and ultimately relieves pain. However, despite this clinical efficacy, MB has not attracted much public attention in terms of pain relief. Accordingly, this review focuses on how MB lessens pain, noting three major actions of this dye: anti-inflammation, sodium current reduction, and denervation. Moreover, we showed controversies over the efficacy of MB on CDLBP and raised also toxicity issues to look into the limitation of MB application. This analysis is the first attempt to illustrate its analgesic effects, which may offer a novel insight into MB as a pain-relief dye.

Overexpression of Toll-like receptor 4 contributes to the internalization and elimination of Escherichia coli in sheep by enhancing caveolae-dependent endocytosis

BACKGROUND

Gram-negative bacterial infections have a major economic impact on both the livestock industry and public health. Toll-like receptor 4 (TLR4) plays a crucial role in host defence against Gram-negative bacteria. Exploring the defence mechanism regulated by TLR4 may provide new targets for treatment of inflammation and control of bacterial infections. In a previous study, we generated transgenic sheep overexpressing TLR4 by microinjection to improve disease resistance. The defence mechanism through which TLR4 overexpression protected these sheep against pathogens is still not fully understood.

RESULTS

In the present study, we used Escherichia coli to infect monocytes isolated from peripheral blood of the animal model. The overexpression of TLR4 strongly enhanced the percentage of endocytosis and capacity of elimination in monocytes during the early stages of infection. This phenomenon was mainly due to overexpression of TLR4 promoting caveolae-mediated endocytosis. Pretreatment of the transgenic sheep monocytes with inhibitors of TLR4, Src signalling, or the caveolae-mediated endocytosis pathway reduced the internalization of bacteria, weakened the ability of the monocytes to eliminate the bacteria, and increased the pH of the endosomes.

CONCLUSION

Together, our results reveal the effects of TLR4 on the control of E. coli infection in the innate immunity of sheep and provide crucial evidence of the caveolae-mediated endocytosis pathway required for host resistance to invading bacteria in a large animal model, providing theoretical support for breeding disease resistance in the future. Furthermore, Src and caveolin 1 (CAV1) could be potentially valuable targets for the control of infectious diseases.

Melatonin Ameliorates Inflammation and Oxidative Stress by Suppressing the p38MAPK Signaling Pathway in LPS-Induced Sheep Orchitis

Gram-negative bacterial infections of the testis can lead to infectious orchitis, which negatively influences steroid hormone synthesis and spermatogenesis. Lipopolysaccharide (LPS), a major component of the Gram-negative bacterial cell wall, acts via toll like receptors 4 (TLR4) to trigger innate immune responses and activate nuclear factor kappa B signaling. The protective mechanisms of melatonin on LPS-induced infectious orchitis have not been reported. Herein, we developed an LPS-induced sheep infectious orchitis model. In this model, the phagocytic activity of testicular macrophages (TM) was enhanced after melatonin treatment. Moreover, we found that melatonin suppressed secretion of TM pro-inflammatory factors by suppressing the p38MAPK pathway and promoting Leydig cell testosterone secretion. Expressions of GTP cyclohydrolase-I and NADPH oxidase-2 were reduced by melatonin while heme oxygenase-1 expression was up-regulated. Thus, melatonin reduced the severity of LPS-induced orchitis by stimulating antioxidant activity. The results of this study provide a reference for the treatment of acute infectious orchitis.

Evaluating the effect of TLR4-overexpressing on the transcriptome profile in ovine peripheral blood mononuclear cells

Background

Toll-like receptor 4 (TLR4) plays an important role in the elimination of Gram-negative bacteria infections and the initiation of antiinflammatory response. Using the technology of pronuclear microinjection, genetically modified (GM) sheep with TLR4 overexpression were generated. Previous studies have shown that these GM sheep exhibited a higher inflammatory response to Gram-negative bacteria infection than wild type (WT) sheep. In order to evaluate the gene expression of GM sheep and study the co-expressed and downstream genes for TLR4, peripheral blood mononuclear cells (PBMC) from TLR4-overexpressing (Tg) and wild type (WT) sheep were selected to discover the transcriptomic differences using RNA-Seq.

Result

An average of 18,754 and 19,530 known genes were identified in the Tg and WT libraries, respectively. A total of 338 known genes and 85 novel transcripts were found to be differentially expressed in the two libraries (p < 0.01). A differentially expressed genes (DEGs) enrichment analysis showed that the GO terms of inflammatory response, cell recognition, etc. were significantly (FDR < 0.05) enriched. Furthermore, the above DEGs were significantly (FDR < 0.05) enriched in the sole KEGG pathway of the Phagosome. Real-time PCR showed the OLR1, TLR4 and CD14 genes to be differentially expressed in the two groups, which validated the DEGs data.

Conclusions

The RNA-Seq results revealed that the overexpressed TLR4 in our experiment strengthened the ovine innate immune response by increasing the phagocytosis in PBMC.

Classical monocyte transcriptomes reveal significant anti-inflammatory statin effect in women with chronic HIV

AIMS

During virally suppressed chronic HIV infection, persistent inflammation contributes to the development of cardiovascular disease (CVD), a major comorbidity in people living with HIV (LWH). Classical blood monocytes (CMs) remain activated during antiretroviral therapy and are a major source of pro-inflammatory and pro-thrombotic factors that contribute to atherosclerotic plaque development and instability.

METHODS AND RESULTS

Here, we identify transcriptomic changes in circulating CMs in peripheral blood mononuclear cell samples from participants of the Women's Interagency HIV Study, selected by HIV and subclinical CVD (sCVD) status. We flow-sorted CM from participants of the Women's Interagency HIV Study and deep-sequenced their mRNA (n = 92). CMs of HIV+ participants showed elevated interleukin (IL)-6, IL-1β, and IL-12β, overlapping with many transcripts identified in sCVD+ participants. In sCVD+ participants LWH, those reporting statin use showed reduced pro-inflammatory gene expression to a level comparable with healthy (HIV-sCVD-) participants. Statin non-users maintained an elevated inflammatory profile and increased cytokine production.

CONCLUSION

Statin therapy has been associated with a lower risk of cardiac events, such as myocardial infarction in the general population, but not in those LWH. Our data suggest that women LWH may benefit from statin therapy even in the absence of overt CVD.

Overexpression of Toll-Like Receptor 4 Affects Autophagy, Oxidative Stress, and Inflammatory Responses in Monocytes of Transgenic Sheep

Toll-like receptor 4 (TLR4) is a critical pattern recognition receptor that plays a critical role in the host innate immune system’s recognition of Gram-negative bacteria. Since it is the lipopolysaccharide (LPS) receptor, it links the activated inflammatory response with autophagy and oxidative stress. Autophagy, or type II programmed cell death, was reported to have defensive functions in response to the production of inflammatory cytokines and oxidative stress. To explore the relationship between autophagy, inflammation, and oxidative stress, a TLR4-enriched transgenic (Tg) animal model (sheep) was generated. Autophagy activity in the Tg blood monocytes was significantly higher than in the wild-type animal under LPS stress, and it returned to normal after transfection of TLR4 siRNA. Pretreatment with 3-methyladenine (3-MA) inhibited autophagy and enhanced oxidative stress and the production of TNF-α. The LPS-induced reactive oxygen species (ROS) level was markedly increased in the Tg group at an early stage before quickly returning to normal values. In addition, suppressing ROS production by N-acetyl-L-cysteine down-regulated the number of intracellular autophagosomes and the expression of Beclin-1, ATG5, and cytokines IL-1β, IL-6, and TNF-α. Further mechanistic investigation suggested that the TLR4-associated p38 mitogen-activated protein kinase (MAPK) signaling pathway was involved in autophagy and oxidative stress. P38 MAPK promotes intracellular autophagy, ROS production, and inflammatory response. Moreover, TLR4 over-expression suppressed oxidative stress and the production of inflammatory cytokines and increased autophagy activity in vivo. Taken together, our results showed that LPS induced autophagy, which was related to TLR4-mediated ROS production through the p38 MAPK signaling pathway. In addition, our study also provided a novel transgenic animal model to analyze the effects of TLR4 on autophagy, oxidative stress, and inflammatory responses.

Roles of Toll-Like Receptors in Nitroxidative Stress in Mammals

Free radicals are important antimicrobial effectors that cause damage to DNA, membrane lipids, and proteins. Professional phagocytes produce reactive oxygen species (ROS) and reactive nitrogen species (RNS) that contribute towards the destruction of pathogens. Toll-like receptors (TLRs) play a fundamental role in the innate immune response and respond to conserved microbial products and endogenous molecules resulting from cellular damage to elicit an effective defense against invading pathogens, tissue injury, or cancer. In recent years, several studies have focused on how the TLR-mediated activation of innate immune cells leads to the production of pro-inflammatory factors upon pathogen invasion. Here, we review recent findings that indicate that TLRs trigger a signaling cascade that induces the production of reactive oxygen and nitrogen species.

Overexpression of Toll-like Receptor 4-linked Mitogen-activated Protein Kinase Signaling Contributes to Internalization of Escherichia coli in Sheep

Escherichia coli is one of the most common causal pathogens of mastitis in milk-producing mammals. Toll-like receptor 4 (TLR4) is important for host recognition of this bacteria. Increased activation of TLR4 can markedly enhance the internalization of E. coli. In this study, the relationship between TLR4 and mitogen-activated protein kinase (MAPK) signaling pathways in mediating E. coli internalization was evaluated in sheep monocytes. Using a TLR4-overexpressing transgenic (Tg) sheep model, we explored the bacterial internalization mechanism in sheep. We found that monocytes of Tg sheep could phagocytize more bacteria and exhibited higher adhesive capacity. The specific inhibition of p38 MAPK or c-Jun N-terminal kinase (JNK) or extracellular signal-regulated kinases (ERKs) reduced TLR4-dependent internalization of bacteria into sheep monocytes. Furthermore, the inhibition of MAPK signaling down-regulated the adhesive capacity of monocytes and the expression of scavenger receptors and adhesion molecules. Taken together, the overexpression of TLR4 in transgenic sheep enhanced the internalization of E. coli via MAPK signaling.

Ablation of Toll-like receptor 4 mitigates central blood pressure response during hyperhomocysteinemia

OBJECTIVE

The objective of this study was to define the mechanisms of homocysteine-induced effects on the aortic wall that promote vascular remodeling and hypertension as well as explore the role of Toll-like receptor 4 in homocysteine-induced effects.

METHOD

Five strains of mice were utilized in this study: C57BL/6J, C3H/HeOuJ, CBS+/-, C3H/HeJ and CBS+/-/C3H. Aorta, heart and blood were collected at the end of the experiments. Blood pressure (BP) was recorded using noninvasive tail cuff method. To determinate effects of vasoactive agent and endothelial-dependent vasodilator on aorta contractility, we performed vascular function measurements. In addition, the expression of mitochondrial fusion and fission proteins, antioxidant markers and collagen fragments were assessed.

RESULTS

BP measurements demonstrated a significant increase in SBP and DBPs in CBS+/- mice compared with other groups. CBS+/- mice aorta had lower response to phenylephrine and acetylcholine compared with other groups; however, CBS+/-/C3H mice response was improved. Dynamin-related protein 1 protein expression was significantly upregulated in CBS+/- mice, whereas C3H mice showed downregulation. In addition, CBS+/- mice showed increased oxidative stress, inflammation and decreased nitric oxide. These effects were normalized in CBS+/-/C3H mice.

CONCLUSION

Our findings demonstrate the dominance of endothelial cell mitochondrial fission over mitochondrial fusion in hyperhomocysteinemia and oxidative stress. This may explain the endothelial cell loss and dysfunction that follows collagen deposition, which contributes to inward aorta remodeling in hypertension.

Human sperm Toll-like receptor 4 (TLR4) mediates acrosome reaction, oxidative stress markers, and sperm parameters in response to bacterial lipopolysaccharide in infertile men

PURPOSE

To study the role of Toll-like receptor 4 (TLR4) in human spermatozoa and to assess sperm parameters, oxidative stress markers, and acrosome reaction in response to the stimulation of TLR4 by its ligand, the lipopolysaccharide (LPS), as a major endotoxin of Gram-negative bacteria.

METHODS

Our study was carried out in 73 sperm samples from patients undergoing semen analysis for couple infertility investigations. The studied patients were divided into three groups: normozoospermic fertile patients (n = 13), patients with abnormal and leukospermic semen (n = 13), and patients with abnormal and non-leukospermic semen (n = 47). TLR4 expression in human spermatozoa was initially analyzed by western blot. Sperm samples were incubated in the presence of LPS (200 ng/ml) for 18 h. Then, sperm motility and vitality were evaluated by microscopic observation and oxidative stress markers as malondialdehyde (MDA) and carbonyl groups (CG) were spectrophotometrically assessed in neat and selected sperm. A triple-stain technique was also performed to evaluate acrosome reaction in 15 sperm samples from infertile patients.

RESULTS

TLR4 expression was confirmed in human spermatozoa with a molecular weight of 69 kDa. In the normozoospermic group, no significant differences in sperm parameters and oxidative stress markers were shown after incubation with LPS in neat and selected sperms. Regarding samples from the non-leukospermic group, LPS reduced spermatozoa motility and vitality rates in selected sperm (P = 0.003; P = 0.004, respectively). A significant increase of MDA and CG levels was also detected (P = 0.01; P = 0.02, respectively). However, only the MDA levels were significantly increased (P = 0.01) in neat LPS-stimulated sperm. The same results were shown within the leukospermic group. The comparison between the two groups, leukospermic and non-leukospermic, in selected sperms showed a more important LPS effect in the leukospermic group significantly on motility and MDA rates (P = 0.006; P = 0.009, respectively). Furthermore, a significant decrease in reacted spermatozoa rate was detected in response to LPS in selected sperm samples from infertile men (P = 0.03).

CONCLUSIONS

These findings indicate that human spermatozoa express TLR4 and respond to LPS stimulation with alterations in viability, motility, and the acrosome reaction implicating reactive oxygen species (ROS) production in sperm samples from infertile patients.

Lack of Fibronectin Extra Domain A Alternative Splicing Exacerbates Endothelial Dysfunction in Diabetes

Glucose-induced changes of artery anatomy and function account for diabetic vascular complications, which heavily impact disease morbidity and mortality. Since fibronectin containing extra domain A (EDA + FN) is increased in diabetic vessels and participates to vascular remodeling, we wanted to elucidate whether and how EDA + FN is implicated in diabetes-induced endothelial dysfunction using isometric-tension recording in a murine model of diabetes. In thoracic aortas of EDA^−/−, EDA^+/+ (constitutively lacking and expressing EDA + FN respectively), and of wild-type mice (EDA^wt/wt), streptozotocin (STZ)-induced diabetes impaired endothelial vasodilation to acetylcholine, irrespective of genotype. However STZ + EDA^−/− mice exhibited increased endothelial dysfunction compared with STZ + EDA^+/+ and with STZ + EDA^wt/wt. Analysis of the underlying mechanisms revealed that STZ + EDA^−/− mice show increased oxidative stress as demonstrated by enhanced aortic superoxide anion, nitrotyrosine levels and expression of NADPH oxidase NOX4 and TGF-β1, the last two being reverted by treatment with the antioxidant n-acetylcysteine. In contrast, NOX1 expression and antioxidant potential were similar in aortas from the three genotypes. Interestingly, reduced eNOS expression in STZ + EDA^+/+ vessels is counteracted by increased eNOS coupling and function. Although EDA + FN participates to vascular remodelling, these findings show that it plays a crucial role in limiting diabetic endothelial dysfunction by preventing vascular oxidative stress.

Repeated lipopolysaccharide exposure causes corticosteroid insensitive airway inflammation via activation of phosphoinositide-3-kinase δ pathway

Corticosteroid resistance is one of major barriers to effective management of chronic inflammatory respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and severe asthma. These patients often experience exacerbations with viral and/or bacterial infection, which may cause continuous corticosteroid insensitive inflammation. In this study, we observed that repeated exposure of lipopolysaccharide (LPS) intranasally attenuated the anti-inflammatory effects of the corticosteroid fluticasone propionate (FP) on neutrophils and CXCL1 levels in bronchoalveolar lavage (BAL) fluid in an in vivo murine model. Histone deacetylase-2 (HDAC2) and NF-E2 related factor 2 (Nrf2) levels in lungs after LPS administration for 3 consecutive days were significantly decreased to 38.9±6.3% (mean±SEM) and 77.5±2.7% of the levels seen after only one day of LPS exposure, respectively. In addition, 3 days LPS exposure resulted in an increase of Akt phosphorylation, indicating activation of the phosphoinositide-3-kinase (PI3K) pathway by 4-fold in lungs compared with 1 day of exposure. Furthermore, combination treatment with theophylline and FP significantly decreased the neutrophil accumulation and CXCL1 concentrations in BAL fluid from 22.5±1.8×10⁴ cells/mL and 214.6±20.6 pg/mL to 7.9±0.5×10⁴ cells/mL and 61.9±13.3 pg/mL, respectively. Combination treatment with IC87114, a selective PI3Kδ inhibitor, and FP also significantly decreased neutrophils and CXCL1 levels from 16.8±0.7×10⁴ cells/mL and 182.4±4.6 pg/mL to 5.9±0.3×10⁴ cells/mL and 71.4±2.7 pg/mL, respectively. Taken together, repeated exposure of LPS causes corticosteroid-insensitive airway inflammation in vivo, and the corticosteroid-resistance induced by LPS is at least partly mediated through the activation of PI3Kδ, resulting in decreased levels of HDAC2 and Nrf2. These findings provide a potentially new therapeutic approach to COPD and severe asthma.

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We first time proposed clinically relevant steroid insensitive exacerbation model.

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LPS caused corticosteroid insensitive airway inflammation via PI3Kδ activation.

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This murine model are useful to discover new therapies for airway inflammation.