A protective Hsp70-TLR4 pathway in lethal oxidant lung injury

Extracellular vesicles promote autophagy in human microglia through lipid raft-dependent mechanisms

Autophagy dysfunction has been closely related with pathogenesis of many neurodegenerative diseases and therefore represents a potential therapeutic target. Extracellular vesicles (EVs) may act as potent anti-inflammatory agents and also modulators of autophagy in target cells. However, the molecular mechanisms by which EVs modulate autophagy flux in human microglia remain largely unexplored. In the present study, we investigated the effects of EVs derived from human oral mucosa stem cells on the autophagy in human microglia. We demonstrate that EVs promoted autophagy and autophagic flux in human microglia and that this process was dependent on the integrity of lipid rafts. Lipopolysaccharide (LPS) also activated autophagy, but combined treatment with EVs and LPS suppressed autophagy response, indicating interference between these signaling pathways. Blockage of Toll-like receptor 4 (TLR4) with anti-TLR4 antibody suppressed EV-induced autophagy. Furthermore, inhibition of the EV-associated heat shock protein (HSP70) chaperone which is one of the endogenous ligands of the TLR4 also suppressed EV-induced lipid raft formation and autophagy. Pre-treatment of microglia with a selective inhibitor of αvβ3/αvβ5 integrins cilengitide inhibited EV-induced autophagy. Finally, blockage of purinergic P2X4 receptor (P2X4R) with selective inhibitor 5-BDBD also suppressed EV-induced autophagy. In conclusion, we demonstrate that EVs activate autophagy in human microglia through interaction with HSP70/TLR4, αVβ3/αVβ5, and P2X4R signaling pathways and that these effects depend on the integrity of lipid rafts. Our findings could be used to develop new therapeutic strategies targeting disease-associated microglia.

Emerging evidence for endogenous neurosteroid modulation of pro-inflammatory and anti-inflammatory pathways that impact neuropsychiatric disease

This mini-review presents emerging evidence that endogenous neurosteroids modulate both pro- and anti-inflammatory signaling by immune cells and brain cells that contribute to depression, alcohol use disorders, and other inflammatory conditions. We first review the literature on pregnenolone and allopregnanolone inhibition of proinflammatory neuroimmune pathways in the periphery and the brain - effects that are independent of GABAergic mechanisms. We follow with evidence for neurosteroid enhancement of anti-inflammatory and protective pathways in brain and immune cells. These studies draw clinical relevance from a large body of evidence that pro-inflammatory immune signaling is dysregulated in many brain disorders and the fact that neurosteroids inhibit the same inflammatory pathways that are activated in depression, alcohol use disorders and other inflammatory conditions. Thus, we describe evidence that neurosteroid levels are decreased and neurosteroid supplementation has therapeutic efficacy in these neuropsychiatric conditions. We conclude with a perspective that endogenous regulation of immune balance between pro- and anti-inflammatory pathways by neurosteroid signaling is essential to prevent the onset of disease. Deficits in neurosteroids may unleash excessive pro-inflammatory activation which progresses in a feed-forward manner to disrupt brain networks that regulate stress, emotion and motivation. Neurosteroids can block various inflammatory pathways in mouse and human macrophages, rat brain and human blood and therefore provide new hope for treatment of intractable conditions that involve excessive inflammatory signaling.

NADPH Oxidase 3: Beyond the Inner Ear

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed.

Neurosteroid [3α,5α]-3-hydroxy-pregnan-20-one enhances IL-10 production via endosomal TRIF-dependent TLR4 signaling pathway

Background

Previous studies demonstrated the inhibitory effect of allopregnanolone (3α,5α-THP) on the activation of inflammatory toll-like receptor 4 (TLR4) signals in RAW264.7 macrophages and the brains of selectively bred alcohol-preferring (P) rats. In the current study, we investigated the impact of 3α,5α-THP on the levels of IL-10 and activation of the TRIF-dependent endosomal TLR4 pathway.

Methods

The amygdala and nucleus accumbens (NAc) of P rats, which exhibit innately activated TLR4 pathways as well as RAW264.7 cells, were used. Enzyme-linked immunosorbent assays (ELISA) and immunoblotting assays were used to ascertain the effects of 3α,5α-THP on the TRIF-dependent endosomal TLR4 pathway and endosomes were isolated to examine translocation of TLR4 and TRIF. Additionally, we investigated the effects of 3α,5α-THP and 3α,5α-THDOC (0.1, 0.3, and 1.0 µM) on the levels of IL-10 in RAW264.7 macrophages. Finally, we examined whether inhibiting TRIF (using TRIF siRNA) in RAW264.7 cells altered the levels of IL-10.

Results

3α,5α-THP administration facilitated activation of the endosomal TRIF-dependent TLR4 pathway in males, but not female P rats. 3α,5α-THP increased IL-10 levels (+13.2 ± 6.5%) and BDNF levels (+21.1 ± 11.5%) in the male amygdala. These effects were associated with increases in pTRAM (+86.4 ± 28.4%), SP1 (+122.2 ± 74.9%), and PI(3)K-p110δ (+61.6 ± 21.6%), and a reduction of TIRAP (-13.7 ± 6.0%), indicating the activation of the endosomal TRIF-dependent TLR4 signaling pathway. Comparable effects were observed in NAc of these animals. Furthermore, 3α,5α-THP enhanced the accumulation of TLR4 (+43.9 ± 11.3%) and TRIF (+64.8 ± 32.8%) in endosomes, with no significant effect on TLR3 accumulation. Additionally, 3α,5α-THP facilitated the transition from early endosomes to late endosomes (increasing Rab7 levels: +35.8 ± 18.4%). In RAW264.7 cells, imiquimod (30 µg/mL) reduced IL-10 while 3α,5α-THP and 3α,5α-THDOC (0.1, 0.3, and 1.0 µM) restored IL-10 levels. To determine the role of the TRIF-dependent TLR4 signaling pathway in IL-10 production, the downregulation of TRIF (-62.9 ± 28.2%) in RAW264.7 cells led to a reduction in IL-10 levels (-42.3 ± 8.4%). TRIF (-62.9 ± 28.2%) in RAW264.7 cells led to a reduction in IL-10 levels (-42.3 ± 8.4%) and 3α,5α-THP (1.0 µM) no longer restored the reduced IL-10 levels.

Conclusion

The results demonstrate 3α,5α-THP enhancement of the endosomal TLR4-TRIF anti-inflammatory signals and elevations of IL-10 in male P rat brain that were not detected in female P rat brain. These effects hold significant implications for controlling inflammatory responses in both the brain and peripheral immune cells.

Bioengineered nanotechnology for nucleic acid delivery

Nucleic acid-based therapy has emerged as a promising therapeutic approach for treating various diseases, such as genetic disorders, cancers, and viral infections. Diverse nucleic acid delivery systems have been reported, and some, including lipid nanoparticles, have exhibited clinical success. In parallel, bioengineered nucleic acid delivery nanocarriers have also gained significant attention due to their flexible functional design and excellent biocompatibility. In this review, we summarize recent advances in bioengineered nucleic acid delivery nanocarriers, focusing on exosomes, cell membrane-derived nanovesicles, protein nanocages, and virus-like particles. We highlight their unique features, advantages for nucleic acid delivery, and biomedical applications. Furthermore, we discuss the challenges that bioengineered nanocarriers face towards clinical translation and the possible avenues for their further development. This review ultimately underlines the potential of bioengineered nanotechnology for the advancement of nucleic acid therapy.

A Nrf2-OSGIN1&2-HSP70 axis mediates cigarette smoke-induced endothelial detachment: implications for plaque erosion

AIMS

Endothelial erosion of plaques is responsible for ∼30% of acute coronary syndromes (ACS). Smoking is a risk factor for plaque erosion, which most frequently occurs on the upstream surface of plaques where the endothelium experiences elevated shear stress. We sought to recreate these conditions in vitro to identify potential pathological mechanisms that might be of relevance to plaque erosion.

METHODS AND RESULTS

Culturing human coronary artery endothelial cells (HCAECs) under elevated flow (shear stress of 7.5 Pa) and chronically exposing them to cigarette smoke extract (CSE) and tumour necrosis factor-alpha (TNFα) recapitulated a defect in HCAEC adhesion, which corresponded with augmented Nrf2-regulated gene expression. Pharmacological activation or adenoviral overexpression of Nrf2 triggered endothelial detachment, identifying Nrf2 as a mediator of endothelial detachment. Growth/Differentiation Factor-15 (GDF15) expression was elevated in this model, with protein expression elevated in the plasma of patients experiencing plaque erosion compared with plaque rupture. The expression of two Nrf2-regulated genes, OSGIN1 and OSGIN2, was increased by CSE and TNFα under elevated flow and was also elevated in the aortas of mice exposed to cigarette smoke in vivo. Knockdown of OSGIN1&2 inhibited Nrf2-induced cell detachment. Overexpression of OSGIN1&2 induced endothelial detachment and resulted in cell cycle arrest, induction of senescence, loss of focal adhesions and actin stress fibres, and disturbed proteostasis mediated in part by HSP70, restoration of which reduced HCAEC detachment. In ACS patients who smoked, blood concentrations of HSP70 were elevated in plaque erosion compared with plaque rupture.

CONCLUSION

We identified a novel Nrf2-OSGIN1&2-HSP70 axis that regulates endothelial adhesion, elevated GDF15 and HSP70 as biomarkers for plaque erosion in patients who smoke, and two therapeutic targets that offer the potential for reducing the risk of plaque erosion.

Heat shock protein 70 protects the lungs from hyperoxic injury in a neonatal rat model of bronchopulmonary dysplasia

Hyperoxia plays a significant role in the pathogenesis of lung injury, such as bronchopulmonary dysplasia (BPD), in premature infants or newborns. BPD management aims to minimize further injury, provide an optimal environment to support growth and recovery. In clinic neonatal care, we need a new therapy for BPD. Heat shock protein 70 (Hsp70) inhibit cell apoptosis and promote cell repair allowing cells to survive lethal injury. We hypothesized that Hsp70 could be used to prevent hyperoxia related BPD in the neonatal rat model through its anti-apoptotic and anti-inflammatory effects. In this study, we explored the effect of Hsp70 on hyperoxia-induced lung injury using neonatal rats. Neonatal Wistar rats were delivered naturally at full term of gestation and were then pooled and randomly assigned to several groups to receive heat stimulation (41°C for 20 min) or room temperature conditions. The Hsp70 group received recombinant Hsp70 intraperitoneally (200 μg/kg, daily). All newborn rats were placed under hyperoxic conditions (85% oxygen) for 21 days. Survival rates in both heat-hyperoxia and Hsp70-hyperoxia groups were higher than those in the hyperoxia group (p < 0.05). Both endogenous and exogenous Hsp70 could reduce early apoptosis of alveolar cells under hyperoxia. Additionally, there were less macrophage infiltration in the lung of the Hsp70 groups (p < 0.05). Heat stress, heat shock proteins, and exogenous recombinant Hsp70 significantly increased the survival rate and reduced pathological hyperoxia induced lung injuries in the development of BPD. These results suggest that treating hyperoxia-induced lung injury with Hsp70 may reduce the risk of developing BPD.

Pathological Roles of Pulmonary Cells in Acute Lung Injury: Lessons from Clinical Practice

Interstitial lung diseases (ILD) are relatively rare and sometimes become life threatening. In particular, rapidly progressive ILD, which frequently presents as acute lung injury (ALI) on lung histopathology, shows poor prognosis if proper and immediate treatments are not initiated. These devastating conditions include acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF), clinically amyopathic dermatomyositis (CADM), epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI)-induced lung injury, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection named coronavirus disease 2019 (COVID-19). In this review, clinical information, physical findings, laboratory examinations, and findings on lung high-resolution computed tomography and lung histopathology are presented, focusing on majorly damaged cells in each disease. Furthermore, treatments that should be immediately initiated in clinical practice for each disease are illustrated to save patients with these diseases.

Trichloroethylene induces immune renal tubular injury through SIRT 1/HSP 70/TLR 4 pathway in BALBc mice

Trichloroethylene (TCE) is a volatile chlorinated solvent widely used for cleaning and degreasing industrial metal parts. Due to the widespread use and improper disposal of TCE, exposure to TCE causes a variety of adverse effects on human and animal health. However, the underlying mechanism of the damage remains unclear. The purpose of this study is to investigate the role of Sirtuin-1 (SIRT 1) in TCE-induced immune renal tubular injury. 6-8-week-old female BALB/c mice were used to construct a TCE sensitized mouse model. SIRT 1 activator, SRT 1720 (0.1 ml, 5 mg/kg) and toll like receptor 4 (TLR 4) inhibitor, TAK-242 (0.1 ml, 3 mg/kg) were used for treatment. Results show that SIRT 1 and heat shock protein 70 (HSP 70) levels are significantly down-regulated in renal tubules, serum and urine HSP 70 levels are significantly increased, and inflammatory cytokines levels are significantly increased in renal tubules in TCE-sensitized positive mice. After SRT 1720 treatment, intracellular HSP 70 level is significantly increased and extracellular HSP 70 level is decreased, and inflammatory cytokines levels get alleviated. In addition, HSP 70 and Toll-like Receptor 4 (TLR 4) proteins exist an interaction that can be significantly attenuated by SIRT 1. Subsequently, inflammation of the renal tubules mediated by SIRT 1 downregulation is attenuated after TAK-242 treatment. In conclusion, SIRT 1 alleviates renal tubular epithelial cells immune injury by inhibiting the release of HSP 70 and thereby weakening interaction with HSP 70 and TLR 4.

TLR4 is required for macrophage efferocytosis during resolution of ventilator-induced lung injury

Mechanical ventilation is a life-sustaining therapy for patients with respiratory failure but can cause further lung damage known as ventilator-induced lung injury (VILI). However, the intrinsic molecular mechanisms underlying recovery of VILI remain unknown. Phagocytosis of apoptotic cells (also known as efferocytosis) is a key mechanism orchestrating successful resolution of inflammation. Here we show the positive regulation of macrophage Toll-like receptor (TLR) 4 in efferocytosis and resolution of VILI. Mice were depleted of alveolar macrophages and then subjected to injurious ventilation (tidal volume, 20 mL/kg) for 4 h. On day 1 after mechanical ventilation, Tlr4^+/+ or Tlr4^-/- bone marrow-derived macrophages (BMDMs) were intratracheally administered to alveolar macrophage-depleted mice. We observed that mice depleted of alveolar macrophages exhibited defective resolution of neutrophilic inflammation, exuded protein, lung edema, and lung tissue injury after ventilation, whereas these delayed responses were reversed by administration of Tlr4^+/+ BMDMs. Importantly, these proresolving effects by Tlr4^+/+ BMDMs were abolished in mice receiving Tlr4^-/- BMDMs. The number of macrophages containing apoptotic cells or bodies in bronchoalveolar lavage fluid was much less in mice receiving Tlr4^-/- BMDMs than that in those receiving Tlr4^+/+ BMDMs. Macrophage TLR4 deletion facilitated a disintegrin and metalloprotease 17 maturation and enhanced Mer cleavage in response to mechanical ventilation. Heat shock protein 70 dramatically increased Mer tyrosine kinase surface expression, phagocytosis of apoptotic neutrophils, and rescued the inflammatory phenotype in alveolar macrophage-depleted mice receiving Tlr4^+/+ BMDMs, but not Tlr4^-/- BMDMs. Our results suggest that macrophage TLR4 promotes resolution of VILI via modulation of Mer-mediated efferocytosis.

HSP70 inhibition suppressed glioma cell viability during hypoxia/reoxygenation by inhibiting the ERK1/2 and PI3K/AKT signaling pathways

Heat shock protein 70 (HSP70) can regulate astrocyte viability under hypoxic and ischemic conditions. However, the protective mechanism involved is not completely clear. This study aimed to investigate whether HSP70 protects U87 glioma cells against hypoxic damage via the extracellular signal-regulated kinases 1/2 (ERK1/2) and phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signaling pathways. Lentivirus-mediated HSP70-siRNA was used for HSP70 silencing. U87 glioma cells with lentiviral infection were exposed to hypoxia for 4, 8, 12, and 24 h, respectively, followed by a 24-h reoxygenation treatment. A Cell-Counting Kit-8 was then used to evaluate the viability of the U87 glioma cells. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting were performed to determine the mRNA and protein levels, respectively. The expression of HSP70, p-ERK1/2, p-AKT, and U87 cell viability were increased after 8 h of hypoxia/24 h of reoxygenation (P < 0.01). However, HSP70 silencing significantly decreased the U87 cell viability after the hypoxia/reoxygenation treatment (P < 0.01). The protein expressions of p-ERK1/2 and p-AKT also decreased in HSP70-silenced U87 cells (P < 0.01). In conclusion, HSP70 inhibition suppressed the viability of U87 glioma cells during hypoxia/reoxygenation (at least partially) by inhibiting the ERK1/2 and PI3K/AKT signaling pathways. This study may help to understand the molecular mechanisms underlying the progression and development of cerebral hypoxia-ischemia.

Hyperoxia and Lungs: What We Have Learned From Animal Models

Although oxygen (O₂) is essential for aerobic life, it can also be an important source of cellular damage. Supra-physiological levels of O₂ determine toxicity due to exacerbated reactive oxygen species (ROS) production, impairing the homeostatic balance of several cellular processes. Furthermore, injured cells activate inflammation cascades, amplifying the tissue damage. The lung is the first (but not the only) organ affected by this condition. Critically ill patients are often exposed to several insults, such as mechanical ventilation, infections, hypo-perfusion, systemic inflammation, and drug toxicity. In this scenario, it is not easy to dissect the effect of oxygen toxicity. Translational investigations with animal models are essential to explore injuring stimuli in controlled experimental conditions, and are milestones in understanding pathological mechanisms and developing therapeutic strategies. Animal models can resemble what happens in critical care or anesthesia patients under mechanical ventilation and hyperoxia, but are also critical to explore the effect of O₂ on lung development and the role of hyperoxic damage on bronchopulmonary dysplasia. Here, we set out to review the hyperoxia effects on lung pathology, contributing to the field by describing and analyzing animal experimentation's main aspects and its implications on human lung diseases.

Selenium Deficiency via the TLR4/TRIF/NF-κB Signaling Pathway Leading to Inflammatory Injury in Chicken Spleen

The aim of the present study was to investigate the effect of selenium (Se) deficiency on the expression of the toll-like receptor (TLR) signal transduction pathway in the spleen of chickens and explore the relationship between the TLR4/TRIF/NF-κB signaling pathway and inflammatory spleen injury. A total of 200 one-day-old healthy broilers were allocated to two groups. The experimental group was fed a self-made low-Se diet (0.004 mg/kg) while the control group was fed a complete formula feed (0.2 mg/kg) for 15, 25, 35, 45, and 55 days, respectively. We observed histopathological changes in the chicken spleens. The messenger RNA(mRNA) expression levels of 8 kinds of ChTLRs, myeloid differential protein-88 (MyD88), toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β (TRIF), nuclear factor-κB (NF-κB), and cytokine (IL-6, TNF-α, IL-2, and IFN-γ) were detected via quantitative real-time PCR. Western blotting was used to detect the protein expression level of TLR4. Then principal component analysis (PCA) was used to analyze the correlation between the ChTLRs, MyD88, TRIF, and NF-κB. The results showed that the boundary between red pulp and white pulp was unclear, the number of lymphocytes decreased, and the nucleus was fragmented and dissolved in the experimental group at 25-55 days. At 15-45 days, the relative expression of TLR4 mRNA was higher than in the control group, and the difference was extremely significant on day 15 (P < 0.01).The relative expression of TRIF mRNA in the experimental group was higher than in the control group at 25-55 days, and the relative expression of NF-κB mRNA in the experimental group was higher than in the control group at 15-45 days. The relative expression of IL-6 mRNA in the experimental group was higher than in the control group at 15-45 days. The protein expression level of TLR4 in the experimental group was higher than in the control group at 15-45 days. The PCA results showed that there was a strong correlation between TLR4, TRIF, and component 1. The results suggest that TLR4 plays an important role in regulating the expression of inflammatory cytokines in the spleens of Se-deficient chickens, and Se deficiency may cause inflammatory injury through the TLR4/TRIF/NF-κB signaling pathway in chicken spleen.

Exosome-mediated protection of auditory hair cells from ototoxic insults

Hearing loss caused by the death of sensory hair cells of the inner ear is an unfortunate side effect for many patients treated with aminoglycoside antibiotics or platinum-containing chemotherapy agents. In animal models, induction of heat shock confers substantial otoprotection against aminoglycoside- and cisplatin-induced hair cell death. In this issue of the JCI, Breglio et al. demonstrate that inner ear tissue released exosomes carrying heat shock protein 70 (HSP70) in response to heat stress. HSP70 acted by a paracrine mechanism that engaged the Toll-like receptor 4 (TLR4) on hair cells to protect them from death. Exosomes and the HSP70/TLR4 pathway could thus provide treatment targets for the protection of hair cells from chemically induced death or from other insults, such as noise.

Alda-1 Attenuates Hyperoxia-Induced Acute Lung Injury in Mice

Acute lung injury (ALI), a milder form of acute respiratory distress syndrome (ARDS), is a leading cause of mortality in older adults with an increasing prevalence. Oxygen therapy, is a common treatment for ALI, involving exposure to a high concentration of oxygen. Unfortunately, hyperoxia induces the formation of reactive oxygen species which can cause an increase in 4-HNE (4-hydroxy 2 nonenal), a toxic byproduct of lipid peroxidation. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) serves as an endogenous shield against oxidative stress-mediated damage by clearing 4-HNE. Alda-1 [(N-(1, 3 benzodioxol-5-ylmethyl)-2, 6- dichloro-benzamide)], a small molecular activator of ALDH2, protects against reactive oxygen species-mediated oxidative stress by promoting ALDH2 activity. As a result, Alda-1 shields against ischemic reperfusion injury, heart failure, stroke, and myocardial infarction. However, the mechanisms of Alda-1 in hyperoxia-induced ALI remains unclear. C57BL/6 mice implanted with Alzet pumps received Alda-1 in a sustained fashion while being exposed to hyperoxia for 48 h. The mice displayed suppressed immune cell infiltration, decreased protein leakage and alveolar permeability compared to controls. Mechanistic analysis shows that mice pretreated with Alda-1 also experience decreased oxidative stress and enhanced levels of p-Akt and mTOR pathway associated proteins. These results show that continuous delivery of Alda-1 protects against hyperoxia-induced lung injury in mice.

Heat Shock Protein-70 Levels Are Associated With a State of Oxidative Damage in the Development of Bronchopulmonary Dysplasia

Background: Heat shock protein-70 (Hsp-70) exhibits cytoprotective effects against oxidative stress-induced airway injury. This study aimed to examine Hsp-70 and 8-hydroxy-2'-deoxyguanosine (8-OHdG) from tracheal aspirates (TA) in very low-birth weight (VLBW) preterm infants to predict the development of bronchopulmonary dysplasia (BPD). Methods: This birth cohort study enrolled 109 VLBW preterm infants, including 32 infants who developed BPD. Hsp-70 and 8-OHdG concentrations from TA were measured by immunoassay. The apoptosis of TA epithelial cells obtained on Day 28 after birth was measured using annexin-V staining assay. Results: Hsp-70 and 8-OHdG levels in TA fluid were persistently increased from Day 1 to Day 28 of life in the BPD group. Multiple linear regression analysis demonstrated that BPD was significantly associated with gestational age, respiratory distress syndrome, and TA Hsp-70 and 8-OHdG levels on post-natal Day 28. The TA Hsp-70 level positively correlated with TA 8-OHdG level on the Day 1 (r = 0.47) and Day 28 of life (r = 0.68). Incubation of recombinant Hsp-70 with primary epithelial cells derived from TA of patients decreased hydrogen peroxide-induced epithelial cell death. Conclusions: Hsp-70 levels are associated with a state of oxidative injury in the development of BPD.

Edaravone-Loaded Macrophage-Derived Exosomes Enhance Neuroprotection in the Rat Permanent Middle Cerebral Artery Occlusion Model of Stroke

Edaravone (Edv) can inhibit tissue damage, cause cerebral edema, and delay neuronal death caused by acute cerebral infarction. Exosomes are considered as cargo carriers for intercellular communication and serve as important regulators in many pathological processes. Here, we developed macrophage-derived exosomes (Exo) containing Edv (Exo + Edv) to improve the bioavailability of Edv and enhance the neuroprotective effects in a rat model of permanent middle cerebral artery occlusion (PMCAO). The results showed that Exo + Edv significantly improved the bioavailability of Edv and prolonged half-life (t_1/2). At the same time, Exo + Edv made Edv more easily reach the ischemic side of rats with PMCAO and was localized with neuronal cells and microglia, thus reducing the death of neuronal cells and promoting the polarization of microglia from M1 to M2. Taken together, Exo + Edv may become a potential clinical treatment option for PMCAO.

Expression of NaV-1.7, TNF-α and HSP-70 in experimental flare-up post-extirpated dental pulp tissue through a neuroimmunological approach

Background

Dental caries continue to represent a major problem which, if left untreated, will cause irreversible pulpitis. Root canal treatment constitutes one potential treatment intended to preserve teeth afflicted with irreversible pulpitis. During root canal treatment, pain or swelling, referred to as flare-ups, can occur at any point in the process.

Aim

To analyze the molecular aspect of the phenomenon of flare-up in vital dental pulp tissue following mechanical and bacterial trauma (extirpation and lipopolysaccharide [LPS] induction respectively) through a neurological approach, based on the expression of NaV-1.7 in neuron cells, and HSP-70, TNF-α in macrophage cells.

Method

This laboratory experimental study was conducted using 15 Spraque Dawley rats as subjects which were divided into three groups of five subjects: a control group, a pulp tissue extirpation group and an LPS induction followed by extirpation of pulp tissue group. Test samples were collected from the apical field of the mandibular incisor and subsequently examined using immunohistochemical methods.

Results

There were significant differences in NaV1.7, HSP70 and TNFα expression between the treatment groups. While a marked increase in the expression of HSP70 occurred, both Nav1.7, and TNFα expression decreased significantly.

Conclusion

Extirpating the dental pulp tissue will induce a more pronounced flare-up response from the molecules of the pulp tissue in vital teeth than those in inflamed vital pulp tissue.

Exosomes mediate sensory hair cell protection in the inner ear

Hair cells, the mechanosensory receptors of the inner ear, are responsible for hearing and balance. Hair cell death and consequent hearing loss are common results of treatment with ototoxic drugs, including the widely used aminoglycoside antibiotics. Induction of heat shock proteins (HSPs) confers protection against aminoglycoside-induced hair cell death via paracrine signaling that requires extracellular heat shock 70-kDa protein (HSP70). We investigated the mechanisms underlying this non-cell-autonomous protective signaling in the inner ear. In response to heat stress, inner ear tissue releases exosomes that carry HSP70 in addition to canonical exosome markers and other proteins. Isolated exosomes from heat-shocked utricles were sufficient to improve survival of hair cells exposed to the aminoglycoside antibiotic neomycin, whereas inhibition or depletion of exosomes from the extracellular environment abolished the protective effect of heat shock. Hair cell-specific expression of the known HSP70 receptor TLR4 was required for the protective effect of exosomes, and exosomal HSP70 interacted with TLR4 on hair cells. Our results indicate that exosomes are a previously undescribed mechanism of intercellular communication in the inner ear that can mediate nonautonomous hair cell survival. Exosomes may hold potential as nanocarriers for delivery of therapeutics against hearing loss.

Diagnostic and prognostic roles of peripheral blood Toll-like receptor-4 and stanniocalcin-1 genes expression in acute lung injury

Acute lung injury (ALI) is an acute inflammatory disorder. Toll-like receptor-4 (TLR-4) and Stanniocalcin -1 (STC-1) had roles in lung endothelial protection. This study aims to assess TLR-4 and SCT-1 genes expressions in peripheral blood of ALI patients. Total RNA was extracted from peripheral blood of 48 subjects (20 healthy controls, 28 ALI patients) and expressions of genes were assessed by real-Time qRT-PCR. The expression levels of TLR-4 and SCT-1 genes were significantly lower in ALI patients compared to controls (P < 0.0001). After 10 days, the expression levels of TLR-4 and SCT-1 were increased compared to their baseline levels (p = 0.012 and 0.024, respectively). SCT-1 has 92.9% sensitivity and 100% specificity in ALI detection. SCT-1 gene expression was negatively correlated with severity score (r= -0.54, p = 0.003). The mortality pattern was higher in ALI patients with lower TLR-4 gene expression (p = 0.014). In conclusion, the peripheral blood expressions of TLR-4 and STC-1 genes were decreased in ALI patients. Both genes expressions were increased with patients' recovery. SCT-1 had higher sensitivity and specificity in ALI diagnosis. The peripheral blood expressions of SCT-1 and TLR-4 genes seem to be diagnostic and prognostic markers in ALI.

Endothelial Stanniocalcin 1 Maintains Mitochondrial Bioenergetics and Prevents Oxidant-Induced Lung Injury via Toll-Like Receptor 4

AIMS

Oxidant-induced endothelial injury plays a critical role in the pathogenesis of acute lung injury (ALI) and subsequent respiratory failure. Our previous studies revealed an endogenous antioxidant and protective pathway in lung endothelium mediated by heat shock protein 70 (Hsp70)-toll-like receptor 4 (TLR4) signaling. However, the downstream effector mechanisms remained unclear. Stanniocalcin 1 (STC1) has been reported to mediate antioxidant responses in tissues such as the lungs. However, regulators of STC1 expression as well as its physiological function in the lungs were unknown. We sought to elucidate the relationship between TLR4 and STC1 in hyperoxia-induced lung injury in vitro and in vivo and to define the functional role of STC1 expression in lung endothelium.

RESULTS

We identified significantly decreased STC1 expression in TLR4 knockout mouse lungs and primary lung endothelium isolated from TLR4 knockout mice. Overexpression of STC1 was associated with endothelial cytoprotection, whereas decreased or insufficient expression was associated with increased oxidant-induced injury and death. An Hsp70-TLR4-nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) signal mediates STC1 induction in the lungs and endothelial cells. We also demonstrated a previously unrecognized role for mitochondrial-associated STC1, via TLR4, in maintaining normal glycolysis, mitochondrial bioenergetics, and mitochondrial calcium levels.

INNOVATION

To date, a physiological role for STC1 in oxidant-induced ALI has not been identified. In addition, our studies show that STC1 is regulated by TLR4 and exerts lung and endothelial protection in response to sterile oxidant-induced lung injury.

CONCLUSIONS

Our studies reveal a novel TLR4-STC1-mediated mitochondrial pathway that has homeostatic as well as oxidant-induced cytoprotective functions in lung endothelium.

Protective Effect of Hesperidin Against Sepsis-Induced Lung Injury by Inducing the Heat-Stable Protein 70 (Hsp70)/Toll-Like Receptor 4 (TLR4)/ Myeloid Differentiation Primary Response 88 (MyD88) Pathway

Background

Sepsis-induced lung injury is associated with high mortality. The present investigation evaluated the protective effect of hesperidin against sepsis-induced lung injury and also postulates the possible mechanism of its action.

Material/Methods

Lung injury was induced by sepsis in all animals, in which sepsis was produced by cecal ligation and puncture (CLP). Animals were treated with hesperidin 10 and 20 mg/kg i.v. 30 min after the surgery. Oxygenation index and lung injury score were determined and levels of pro-inflammatory mediators and markers of oxidative stress were also estimated in the lung tissues. Moreover, expression of caspase-3, B-cell lymphoma (Bcl-2), Toll-like receptor 4 (TLR4), heat-stable protein 70 (Hsp70) and myeloid differentiation primary response 88 (MyD88) protein was estimated by Western blot assay and immunofluorescence assay.

Results

Hesperidin attenuated the partial pressure of arterial oxygen/fraction of inspired oxygen (PaO2/FiO2) ratio and lung injury score in CLP-induced lung injury mice. There was a significant (p<0.01) decrease in the level of pro-inflammatory mediators in the lung tissue of CLP-induced lung injury mice. Moreover, markers of oxidative stress were attenuated in the hesperidin-treated group. Treatment with hesperidin attenuated the expression of caspase-3, Bcl-2, TLR4, Hsp70, and MyD88 protein in the lung tissue of CLP-induced lung injury mice.

Conclusions

Hesperidin protects against lung injury by attenuating the Hsp70/TLR4/MyD88 pathway in CLP-induced lung injury mice.

Induction of suppressor of cytokine signaling 3 via HSF-1-HSP70-TLR4 axis attenuates neuroinflammation and ameliorates postoperative pain

Postoperative pain is a common form of acute pain that, if not managed effectively, can become chronic pain. Evidence has shown that glia, especially microglia, mediate neuroinflammation, which plays a vital role in pain sensitization. Moreover, toll-like receptor 4 (TLR4), the tumor necrosis factor receptor (TNF-R), the interleukin-1 receptor (IL-1R), and the interleukin-6 receptor (IL-6R) have been considered key components in central pain sensitization and neuroinflammation. Therefore, we hypothesized that activation of the body's endogenous "immune brakes" will inhibit these receptors and achieve inflammation tolerance as well as relieve postoperative pain. After searching for potential candidates to serve as this immune brake, we identified and focused on the suppressor of cytokine signaling 3 (SOCS3) gene. To regulate SOCS3 expression, we used paeoniflorin to induce heat shock protein 70 (HSP70)/TLR4 signaling. We found that paeoniflorin significantly induced SOCS3 expression both in vitro and in vivo and promoted the efflux of HSP70 from the cytoplasm to the extracellular environment. Furthermore, paeoniflorin markedly attenuated incision-induced mechanical allodynia, and this effect was abolished by small interfering RNAs targeting SOCS3. These findings demonstrated an effective and safe strategy to alleviate postoperative pain.

Oxidative stress diseases unique to the perinatal period: A window into the developing innate immune response

The innate immune system has evolved to play an integral role in the normally developing lung and brain. However, in response to oxidative stress, innate immunity, mediated by specific cellular and molecular programs and signaling, contributes to pathology in these same organ systems. Despite opposing drivers of oxidative stress, namely hyperoxia in neonatal lung injury and hypoxia/ischemia in neonatal brain injury, similar pathways-including toll-like receptors, NFκB and MAPK cascades-have been implicated in tissue damage. In this review, we consider recent insights into the innate immune response to oxidative stress in both neonatal and adult models to better understand hyperoxic lung injury and hypoxic-ischemic brain injury across development and aging. These insights support the development of targeted immunotherapeutic strategies to address the challenge of harnessing the innate immune system in oxidative stress diseases of the neonate.

Treatment with Geranylgeranylacetone Induces Heat Shock Protein 70 and Attenuates Neonatal Hyperoxic Lung Injury in a Model of Bronchopulmonary Dysplasia

Purpose

Bronchopulmonary dysplasia (BPD) is a respiratory complication characterized by abnormal alveolar development in premature infants. Geranylgeranylacetone (GGA) can induce heat shock protein (HSP) 70, which has cytoprotective effects against various stressors. Here, we investigated whether GGA protected neonatal lungs from hyperoxic stress in a murine BPD model, and measured the serum HSP70 levels in preterm humans treated with oxygen.

Methods

Newborn mice were exposed to >90% oxygen and administered GGA or vehicle alone orally on days 1, 2, and 3 of life. At 2 days of age, HSP70 expression in the lung was determined by western blotting. At 8 days of age, the lungs were processed for histological analysis. Radial alveolar count (RAC) and mean linear intercept (MLI) were measured as parameters of alveolarization. Apoptosis was evaluated by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method and cleaved caspase-3 immunohistochemistry. Serum HSP70 levels in preterm humans treated with oxygen were measured by enzyme-linked immunosorbent assay.

Results

GGA administration enhanced the HSP70 expression to two-fold compared with normoxia-exposed and vehicle-treated mice. Hyperoxia reduced HSP70 expression, whereas GGA abrogated the effects. Hyperoxia-exposed mice exhibited more apoptotic cells in lung parenchyma and a more simplified alveolar structure with less RAC and larger MLI than normoxia-exposed mice. GGA suppressed the increase in apoptotic cells and the structural changes of the lungs induced by hyperoxia. Serum HSP70 levels of preterm human infants gradually decreased with age.

Conclusions

GGA may attenuate hyperoxic injury in neonatal lungs and thereby may prevent the development of BPD.

Saliva initiates the formation of pro-inflammatory macrophages in vitro

OBJECTIVES

Saliva can support oral wound healing, a process that requires a temporary inflammatory reaction. We have reported previously that saliva provokes a strong inflammatory response in oral fibroblasts. Bone marrow cells also give rise to macrophages, a heterogeneous subset of cell population involved in wound healing. Lipopolysaccharide (LPS) and interleukin 4 (IL-4) induce activation of pro-(M1), and anti-(M2) inflammatory macrophages, respectively. Yet, the impact of saliva on programming bone marrow cells into either M1 or M2 macrophages remains unclear .

DESIGN

Herein, we examined whether sterile saliva affects the in vitro process of macrophage polarization based on murine bone marrow cultures and RAW264.7 mouse macrophages.

RESULTS

We report that sterile saliva, similar to lipopolysaccharides, provoked a robust activation of the M1 phenotype which is characterized by a strong increase of the respective genes IL-12 and IL-6, based on a real-time gene expression analysis, and for IL-6 with immunoassay. Arginase-1 and Ym1, both genes characteristic for the M2 phenotype, were not considerably modulated by saliva. Inhibition of TLR4 signaling with TAK-242, blocking NFκB signaling with Bay 11-7085, but also autoclaving saliva greatly reduced the development of the M1 phenotype.

CONCLUSION

These data suggest that saliva activates the TLR4 dependent polarization into pro-inflammatory M1 macrophages in vitro.

Salivary pellets induce a pro-inflammatory response involving the TLR4-NF-kB pathway in gingival fibroblasts

Background

Whole saliva provokes a substantial pro-inflammatory response in gingival fibroblasts. This raises the question whether the salivary pellet, which is used for diagnostic purposes, also has a pro-inflammatory capacity and, if yes, what the underlying mechanisms at the molecular level are.

Methods

We examined the ability of extensively washed salivary pellets to provoke the expression of chemokines in gingival fibroblasts by real-time polymerase chain reaction and immunoassays. Protein composition was determined with proteomic analysis. Endotoxins were analyzed by a Limulus assay and removed by affinity chromatography. The inhibitors TAK-242 and BAY11-7082 were used to determine the involvement of the TLR4 and NF-kB signaling, respectively. Western blot was performed to detect phosphorylated p65.

Results

The experiments show that salivary pellets and the corresponding washing solution contain pro-inflammatory activity without impairing cell viability. Proteomic analysis revealed proteins with a binding capacity for lipopolysaccharides, and the Limulus assay indicated the presence of endotoxin in the salivary pellets. Blocking TLR4 with TAK-242 and depletion of endotoxins both lowered the capacity of salivary pellets to increase chemokine expression and phosphorylation of p65. BAY11-7082 suppressed chemokine expression in response to the salivary pellets. Autoclaving salivary pellets also reduced their pro-inflammatory activity.

Conclusions

The data support the molecular mechanism of a TLR4-NF-kB-dependent pro-inflammatory response of the gingival fibroblasts exposed to preparations of washed salivary pellets. Together, the data indicate that the salivary pellet is rich in endotoxin but it is mainly a heat labile fraction that accounts for the chemokine expression in the bioassay.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-016-0229-5) contains supplementary material, which is available to authorized users.

An Endothelial Hsp70-TLR4 Axis Limits Nox3 Expression and Protects Against Oxidant Injury in Lungs

AIMS

Oxidants play a critical role in the pathogenesis of acute lung injury (ALI). Nox3 is a novel member of the NADPH oxidase (Nox) family of oxidant-generating enzymes, which our laboratory had previously identified to be induced in the lungs of TLR4(-/-) mice. However, the physiologic role of Nox3 induction in lungs and its precise relationship to TLR4 are unknown. Furthermore, the cell compartment involved and the signaling mechanisms of Nox3 induction are unknown.

RESULTS

We identified that Nox3 is regulated by heat shock protein 70 (Hsp70) signaling via a TLR4-Trif-signal transducer and activator of transcription 3 (Stat3) pathway and that Nox3 induction leads to increased oxidant injury and death in mice and lung endothelial cells. We generated Nox3(-/-)/TLR4(-/-) double knockout mice, endothelial-targeting lentiviral silencing constructs, and endothelial-targeted Stat3(-/-) mice to specifically demonstrate that Nox3 induction is responsible for the pro-oxidant, proapoptotic phenotype of TLR4(-/-) mice. We also show that an endothelial Hsp70-TLR4-Trif-Stat3 axis is required to suppress deleterious Nox3 induction.

INNOVATION

To date, a physiologic role for Nox3 in oxidant-induced ALI has not been identified. In addition, we generated unique double knockout mice and endothelial-targeted lentiviral silencing constructs to specifically demonstrate the role of a TLR4 signaling pathway in regulating pro-oxidant generation.

CONCLUSIONS

We identified an endothelial TLR4-Trif antioxidant pathway that leads to the inhibition of a novel NADPH oxidase, Nox3, in lungs and lung endothelial cells. We also identified the role of a TLR4 ligand, Hsp70, in suppressing Nox3 in basal and pro-oxidant conditions. These studies identify potentially new therapeutic targets in oxidant-induced ALI. Antioxid. Redox Signal. 24, 991-1012.

Cathepsin E promotes pulmonary emphysema via mitochondrial fission

Emphysema is characterized by loss of lung elasticity and irreversible air space enlargement, usually in the later decades of life. The molecular mechanisms of emphysema remain poorly defined. We identified a role for a novel cathepsin, cathepsin E, in promoting emphysema by inducing mitochondrial fission. Unlike previously reported cysteine cathepsins, which have been implicated in cigarette smoke-induced lung disease, cathepsin E is a nonlysosomal intracellular aspartic protease whose function has been described only in antigen processing. We examined lung tissue sections of persons with chronic obstructive pulmonary disease, a clinical entity that includes emphysematous change. Human chronic obstructive pulmonary disease lungs had markedly increased cathepsin E protein in the lung epithelium. We generated lung epithelial-targeted transgenic cathepsin E mice and found that they develop emphysema. Overexpression of cathepsin E resulted in increased E3 ubiquitin ligase parkin, mitochondrial fission protein dynamin-related protein 1, caspase activation/apoptosis, and ultimately loss of lung parenchyma resembling emphysema. Inhibiting dynamin-related protein 1, using a small molecule inhibitor in vitro or in vivo, inhibited cathepsin E-induced apoptosis and emphysema. To the best of our knowledge, our study is the first to identify links between cathepsin E, mitochondrial fission, and caspase activation/apoptosis in the pathogenesis of pulmonary emphysema. Our data expand the current understanding of molecular mechanisms of emphysema development and may provide new therapeutic targets.

Geranylgeranylacetone alleviates radiation-induced lung injury by inhibiting epithelial-to-mesenchymal transition signaling

Radiation-induced lung injury (RILI) involves pneumonitis and fibrosis, and results in pulmonary dysfunction. Moreover, RILI can be a fatal complication of thoracic radiotherapy. The present study investigated the protective effect of geranylgeranlyacetone (GGA), an inducer of heat shock protein (HSP)70, on RILI using a C57BL/6 mouse model of RILI developing 6 months subsequent to exposure to 12.5 Gy thoracic radiation. GGA was administered 5 times orally prior and subsequent to radiation exposure, and the results were assessed by histological analysis and western blotting. The results show that late RILI was alleviated by GGA treatment, possibly through the suppression of epithelial‑to‑mesenchymal transition (EMT) marker expression. Based on histological examination, orally administered GGA during the acute phase of radiation injury not only significantly inhibited pro‑surfactant protein C (pro‑SPC) and vimentin expression, but also preserved E‑cadherin expression 6 months after irradiation‑induced injury of the lungs. GGA induced HSP70 and inhibited EMT marker expression in L132 human lung epithelial cells following IR. These data suggest that the prevention of EMT signaling is a key cytoprotective effect in the context of RILI. Thus, HSP70‑inducing drugs, such as GGA, could be beneficial for protection against RILI.

Microvesicles and exosomes: new players in metabolic and cardiovascular disease

The past decade has witnessed an exponential increase in the number of publications referring to extracellular vesicles (EVs). For many years considered to be extracellular debris, EVs are now seen as novel mediators of endocrine signalling via cell-to-cell communication. With the capability of transferring proteins and nucleic acids from one cell to another, they have become an attractive focus of research for different pathological settings and are now regarded as both mediators and biomarkers of disease including cardio-metabolic disease. They also offer therapeutic potential as signalling agents capable of targeting tissues or cells with specific peptides or miRNAs. In this review, we focus on the role that microvesicles (MVs) and exosomes, the two most studied classes of EV, have in diabetes, cardiovascular disease, endothelial dysfunction, coagulopathies, and polycystic ovary syndrome. We also provide an overview of current developments in MV/exosome isolation techniques from plasma and other fluids, comparing different available commercial and non-commercial methods. We describe different techniques for their optical/biochemical characterization and quantitation. We also review the signalling pathways that exosomes and MVs activate in target cells and provide some insight into their use as biomarkers or potential therapeutic agents. In summary, we give an updated focus on the role that these exciting novel nanoparticles offer for the endocrine community.

An endothelial TLR4-VEGFR2 pathway mediates lung protection against oxidant-induced injury

TLR4 deficiency causes hypersusceptibility to oxidant-induced injury. We investigated the role of TLR4 in lung protection, using used bone marrow chimeras; cell-specific transgenic modeling; and lentiviral delivery in vivo to knock down or express TLR4 in various lung compartments; and lung-specific VEGF transgenic mice to investigate the effect of TLR4 on VEGF-mediated protection. C57/BL6 mice were exposed to 100% oxygen in an enclosed chamber and assessed for survival and lung injury. Primary endothelial cells were stimulated with recombinant VEGF and exposed to hyperoxia or hydrogen peroxide. Endothelium-specific expression of human TLR4 (as opposed to its expression in epithelium or immune cells) increased the survival of TLR4-deficent mice in hyperoxia by 24 h and decreased LDH release and lung cell apoptosis after 72 h of exposure by 30%. TLR4 expression was necessary and sufficient for the protective effect of VEGF in the lungs and in primary endothelial cells in culture. TLR4 knockdown inhibited VEGF signaling through VEGF receptor 2 (VEGFR2), Akt, and ERK pathways in lungs and primary endothelial cells and decreased the availability of VEGFR2 at the cell surface. These findings demonstrate a novel mechanism through which TLR4, an innate pattern receptor, interacts with an endothelial survival pathway.

Preinduction of heat shock protein 70 protects mice against post-infection irritable bowel syndrome via NF-κB and NOS/NO signaling pathways

This study aimed to investigate the protective effects of preinduction of heat shock protein 70 (HSP70) on Trichinella spiralis infection-induced post-infectious irritable bowel syndrome (PI-IBS) in mice. Trichinella spiralis infection significantly reduced HSP70 abundance, ileal villus height and crypt depth, expression of tight junctions, serum lysine and arginine concentrations, and ileal SCL7A6 and SCL7A7 mRNA levels, induced inflammatory response, and activated NF-κB signaling pathway. Meanwhile, the heat treatment upregulated HSP70 expression, and then reversed intestinal dysfunction and inflammatory response. Preinduction of HSP70 enhanced serum arginine and intestinal SCL7A7 expression and inhibited NF-κB activation compared with PI-IBS model. Treatment with pyrrolidine dithiocarbamate (PDTC, an NF-κB inhibitor) and N-nitro-L-arginine methyl ester hydrochloride (L-NAME, a nitric oxide synthase inhibitor, NOS) further demonstrated that preinduction of HSP70 might inhibit NF-κB and activated NOS/nitric oxide (NO) signaling pathways. In conclusion, preinduction of HSP70 by heat treatment may confer beneficial effects on Trichinella spiralis infection-induced PI-IBS in mice, and the protective effect of HSP70 may be associated with inhibition of NF-κB and stimulation of NOS/NO signaling pathways.

Plasma exosomes protect the myocardium from ischemia-reperfusion injury

BACKGROUND

Exosomes are nanometer-sized vesicles released from cells into the blood, where they can transmit signals throughout the body. Shown to act on the heart, exosomes' composition and the signaling pathways they activate have not been explored. We hypothesized that endogenous plasma exosomes can communicate signals to the heart and provide protection against ischemia and reperfusion injury.

OBJECTIVES

This study sought to isolate and characterize exosomes from rats and healthy volunteers, evaluate their cardioprotective actions, and identify the molecular mechanisms involved.

METHODS

The exosome-rich fraction was isolated from the blood of adult rats and human volunteers and was analyzed by protein marker expression, transmission electron microscopy, and nanoparticle tracking analysis. This was then used in ex vivo, in vivo, and in vitro settings of ischemia-reperfusion, with the protective signaling pathways activated on cardiomyocytes identified using Western blot analyses and chemical inhibitors.

RESULTS

Exosomes exhibited the expected size and expressed marker proteins CD63, CD81, and heat shock protein (HSP) 70. The exosome-rich fraction was powerfully cardioprotective in all tested models of cardiac ischemia-reperfusion injury. We identified a pro-survival signaling pathway activated in cardiomyocytes involving toll-like receptor (TLR) 4 and various kinases, leading to activation of the cardioprotective HSP27. Cardioprotection was prevented by a neutralizing antibody against a conserved HSP70 epitope expressed on the exosome surface and by blocking TLR4 in cardiomyocytes, identifying the HSP70/TLR4 communication axis as a critical component in exosome-mediated cardioprotection.

CONCLUSIONS

Exosomes deliver endogenous protective signals to the myocardium by a pathway involving TLR4 and classic cardioprotective HSPs.

Heat Shock Protein 70 Prevents Hyperoxia-Induced Disruption of Lung Endothelial Barrier via Caspase-Dependent and AIF-Dependent Pathways

Exposure of pulmonary artery endothelial cells (PAECs) to hyperoxia results in a compromise in endothelial monolayer integrity, an increase in caspase-3 activity, and nuclear translocation of apoptosis-inducing factor (AIF), a marker of caspase-independent apoptosis. In an endeavor to identify proteins involved in hyperoxic endothelial injury, we found that the protein expression of heat-shock protein 70 (Hsp70) was increased in hyperoxic PAECs. The hyperoxia-induced Hsp70 protein expression is from hspA1B gene. Neither inhibition nor overexpression of Hsp70 affected the first phase barrier disruption of endothelial monolayer. Nevertheless, inhibition of Hsp70 by using the Hsp70 inhibitor KNK437 or knock down Hsp70 using siRNA exaggerated and overexpression of Hsp70 prevented the second phase disruption of lung endothelial integrity. Moreover, inhibition of Hsp70 exacerbated and overexpression of Hsp70 prevented hyperoxia-induced apoptosis, caspase-3 activation, and increase in nuclear AIF protein level in PAECs. Furthermore, we found that Hsp70 interacted with AIF in the cytosol in hyperoxic PAECs. Inhibition of Hsp70/AIF association by KNK437 correlated with increased nuclear AIF level and apoptosis in KNK437-treated PAECs. Finally, the ROS scavenger NAC prevented the hyperoxia-induced increase in Hsp70 expression and reduced the interaction of Hsp70 with AIF in hyperoxic PAECs. Together, these data indicate that increased expression of Hsp70 plays a protective role against hyperoxia-induced lung endothelial barrier disruption through caspase-dependent and AIF-dependent apoptotic pathways. Association of Hsp70 with AIF prevents AIF nuclear translocation, contributing to the protective effect of Hsp70 on hyperoxia-induced endothelial apoptosis. The hyperoxia-induced increase in Hsp70 expression and Hsp70/AIF interaction is contributed to ROS formation.

Endothelial CD74 mediates macrophage migration inhibitory factor protection in hyperoxic lung injury

Exposure to hyperoxia results in acute lung injury. A pathogenic consequence of hyperoxia is endothelial injury. Macrophage migration inhibitory factor (MIF) has a cytoprotective effect on lung endothelial cells; however, the mechanism is uncertain. We postulate that the MIF receptor CD74 mediates this protective effect. Using adult wild-type (WT), MIF-deficient (Mif(-/-)), CD74-deficient (Cd74(-/-)) mice and MIF receptor inhibitor treated mice, we report that MIF deficiency or inhibition of MIF receptor binding results in increased sensitivity to hyperoxia. Mif(-/-) and Cd74(-/-) mice demonstrated decreased median survival following hyperoxia compared to WT mice. Mif(-/-) mice demonstrated an increase in bronchoalveolar protein (48%) and lactate dehydrogenase (LDH) (68%) following 72 hours of hyperoxia. Similarly, treatment with MIF receptor antagonist resulted in a 59% and 91% increase in bronchoalveolar lavage protein and LDH, respectively. Inhibition of CD74 in primary murine lung endothelial cells (MLECs) abrogated the protective effect of MIF, including decreased hyperoxia-mediated AKT phosphorylation and a 20% reduction in the antiapoptotic effect of exogenous MIF. Treatment with MIF decreased hyperoxia-mediated H2AX phosphorylation in a CD74-dependent manner. These data suggest that therapeutic manipulation of the MIF-CD74 axis in lung endothelial cells may be a novel approach to protect against acute oxidative stress.

Endothelial PINK1 mediates the protective effects of NLRP3 deficiency during lethal oxidant injury

High levels of inspired oxygen, hyperoxia, are frequently used in patients with acute respiratory failure. Hyperoxia can exacerbate acute respiratory failure, which has high mortality and no specific therapies. We identified novel roles for PTEN-induced putative kinase 1 (PINK1), a mitochondrial protein, and the cytosolic innate immune protein NLRP3 in the lung and endothelium. We generated double knockouts (PINK1(-/-)/NLRP3(-/-)), as well as cell-targeted PINK1 silencing and lung-targeted overexpression constructs, to specifically show that PINK1 mediates cytoprotection in wild-type and NLRP3(-/-) mice. The ability to resist hyperoxia is proportional to PINK1 expression. PINK1(-/-) mice were the most susceptible; wild-type mice, which induced PINK1 after hyperoxia, had intermediate susceptibility; and NLRP3(-/-) mice, which had high basal and hyperoxia-induced PINK1, were the least susceptible. Genetic deletion of PINK1 or PINK1 silencing in the lung endothelium increased susceptibility to hyperoxia via alterations in autophagy/mitophagy, proteasome activation, apoptosis, and oxidant generation.

Bronchoalveolar Lavage Fluid Utilized Ex Vivo to Validate In Vivo Findings: Inhibition of Gap Junction Activity in Lung Tumor Promotion is Toll-Like Receptor 4-Dependent

TLR4 protects against lung tumor promotion and pulmonary inflammation in mice. Connexin 43 (Cx43), a gap junction gene, was increased in Tlr4 wildtype compared to Tlr4-mutant mice in response to promotion, which suggests gap junctional intercellular communication (GJIC) may be compromised. We hypothesized that the early tumor microenvironment, represented by Bronchoalveolar Lavage Fluid (BALF) from Butylated hydroxytoluene (BHT; promoter)-treated mice, would produce TLR4-dependent changes in pulmonary epithelium, including dysregulation of GJIC in the Tlr4-mutant (BALB^Lps-d) compared to the Tlr4-sufficient (BALB; wildtype) mice. BHT (4 weekly doses) was injected ip followed by BALF collection at 24 h. BALF total protein and total macrophages were significantly elevated in BHT-treated BALB^Lps-d over BALB mice, similar to previous findings. BALF was then utilized in an ex vivo manner to treat C10 cells, a murine alveolar type II cell line, followed by the scrape-load dye transfer assay (GJIC), Cx43 immunostaining, and quantitative RT-PCR (Mcp-1, monocyte chemotactic protein 1). GJIC was markedly reduced in C10 cells treated with BHT-treated BALB^Lps-d BALF for 4 and 24 h compared to BALB and control BALF from the respective mice (p < 0.05). Mcp-1, a chemokine, was also significantly increased in the BHT-treated BALB^Lps-d BALF compared to the BALB mice, and Cx43 protein expression in the cell membrane altered. These novel findings suggest signaling from the BALF milieu is involved in GJIC dysregulation associated with promotion and links gap junctions to pulmonary TLR4 protection in a novel ex vivo model that could assist in future potential tumor promoter screening.